JPH097984A - Semiconductor device manufacturing method and polishing apparatus used for the same - Google Patents

Abstract

(57) Abstract: An interlayer insulating film is flattened to a constant thickness by chemical mechanical polishing. SOLUTION: A holding hole 23 of a wafer holding head 20 of a chemical mechanical polishing apparatus 10 has a vent hole 24 connected to an air supply passage 28, a ceramic plate 32 having a fine ventilation passage 33, and a plurality of penetrating holes. An auxiliary pressing device 21 including an elastic material pad 34 having a hole 36 formed therein is mounted. The back surface 8 of the work 1 is brought into contact with the pad and held by the head, and the surface 7 to be polished is rubbed against the polishing material surface 15 of the polishing tool 11. The surface to be polished is mechanically pressed against the surface of the abrasive material, and air pressure is applied to the back side surface of the work through the ceramic plate and the pad to press the surface to be polished against the surface of the abrasive material. [Effect] During the chemical mechanical polishing of the interlayer insulating film, the work is pressed by the head and is also pressed by the action of air pressure, so that the polishing amount of the surface to be polished is uniform and the unevenness of the surface of the interlayer insulating film is reduced. It is flattened to a constant film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing technique, and more particularly to a technique for uniformly planarizing one main surface of a semiconductor wafer (hereinafter referred to as a wafer). In a process, the present invention relates to a technique effectively used to planarize unevenness of an insulating film formed on a main surface of a wafer by chemical mechanical polishing.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, as a polishing apparatus for uniformly polishing a main surface of a wafer, a head for holding a surface to be polished of a wafer, which is a work, in an exposed state, and a polishing material for one main surface. A polishing tool having a surface, and the surface to be polished of the wafer held by the head is one main surface opposite to the polishing material surface of the polishing tool (hereinafter referred to as the back side surface), and the work holding surface of the head. There is a polishing device that relatively moves and polishes while being pressed by a mechanical action force while receiving a reaction force.

In order to uniformly polish the entire surface of the wafer in this polishing apparatus, it is necessary to uniformly press the wafer against the surface of the polishing material. Therefore, in the conventional polishing apparatus, the back surface of the wafer, which is the main surface receiving the reaction force due to the pressing force, is received by the flat work holding surface having high rigidity, so that the surface to be polished of the wafer is It is devised so that it can be pressed uniformly over the entire surface.

However, in a polishing apparatus in which the back side surface of a wafer is received by a flat work holding surface having high rigidity,
When the wafer has a thickness distribution generated in the wafer cutting step and the subsequent grinding step and polishing step, the pressing force concentrates on a portion having a large thickness of the wafer. There is a problem that the polishing amount is uneven.

Further, in order to uniformly polish the surface to be polished,
During the polishing operation, the wafer is revolved or rocked. When the wafer is revolved or oscillated in this way, various forces such as sideways and diagonal directions act on the wafer.
It is difficult to apply a uniform pressing force to the entire surface of the wafer while the back surface of the wafer is received by the flat work holding surface having high rigidity, and the distribution of the polishing amount is high over the entire surface to be polished of the wafer. It is difficult to maintain uniform precision.

As a polishing apparatus that solves the problem of receiving the back side surface of a wafer by a flat work holding surface having high rigidity, a head for holding a wafer is flexibly supported by a spherical joint to polish a wafer to be polished. The surface is configured to follow the polishing material surface in a self-aligning manner, or the head is supported by a copying mechanism equipped with a gyro mechanism to force the polishing surface of the wafer to follow the polishing material surface. Have been developed.

Incidentally, examples of the conventional polishing apparatus of this type are described in JP-A-63-114874, JP-A-6-71558, JP-A-6-8088, and JP-A-5-251411. Japanese Patent Laid-Open No. 6-61202. Japanese Patent Laid-Open No. 63-114874 discloses that
A plurality of wafer support chucks are held on the multiple chuck carrier assembly by vertical polishing force applied by air pressure, liquid pressure or mechanical force so that each sub-carrier can freely accommodate wafers of various thickness and taper. An assembly for processing a possible wafer is disclosed. Japanese Patent Application Laid-Open No. 6-71558 discloses a variable pressure capable of changing the pressing force when the pressurizing means adsorbs the polishing object to the adsorbing surface of the top ring and the pressing force when the polishing object is pressed by the turntable. A functional polishing device is disclosed. JP-A-6-80
Japanese Patent Laid-Open No. 88 discloses a wafer polishing fixing plate that forms a soft resin layer on a wafer suction surface and a hard resin layer on the soft resin layer to suck a wafer in a strain-free state. Japanese Patent Application Laid-Open No. 5-251411 discloses a polishing method and a polishing apparatus in which a wafer is vacuum-sucked until the polishing is started and the wafer is freely rotated after the polishing is started. In Japanese Patent Laid-Open No. 6-61202, a silicone elastic body is formed on the surface of a hard substrate having through holes for vacuum suction, and a hole communicating with the minute holes is formed in the silicone elastic body to hold the wafer by vacuum suction and then to remove the wafer. The method of holding the wafer, which holds the wafer only by the surface adhesiveness of the silicone elastic body during polishing,
It is disclosed.

[0008]

By the way, in a so-called pre-process (hereinafter referred to as a pre-process) in which a semiconductor element is formed on one main surface of a wafer, a main surface (hereinafter, referred to as a table) on which a semiconductor element of a wafer is formed. There is proposed a technique for flattening the unevenness formed on the surface of the insulating film or the metal film by polishing the insulating film or the metal film deposited on the side surface) with a polishing device. Generally, the dimensional accuracy required for each component of the wafer in this pre-process is about 1/10 or less of the design dimension, and an interlayer that is an example of an insulating film or a metal film deposited on the front surface of the wafer. Regarding the film thickness distribution accuracy of the insulating film and the wiring layer film, an accuracy of 0.1 μm or less is required.

However, as described above, a wafer (hereinafter referred to as an unprocessed wafer) in a state of being put into the preceding step from the wafer cutting step and the subsequent grinding step and polishing step has a thickness distribution of about 1 μm. Therefore, when the interlayer insulating film or the wiring layer film deposited on the front surface of the wafer is polished by the above-described conventional polishing apparatus, the thickness distribution of the unprocessed wafer changes to the interlayer insulating film or the wiring layer film. As a result, the accuracy of the film thickness distribution accuracy of the interlayer insulating film or the wiring layer film deposited on the front surface of the wafer cannot be secured to 0.1 μm or less. , Revealed by the present inventor.

Further, even in a polishing apparatus in which the wafer holding head is supported in a floating manner so that the surface to be polished of the wafer follows the surface of the polishing material in a self-aligned or forced manner, the force acting during the polishing operation is Since it is not possible to completely follow fluctuations, the film thickness distribution accuracy of the interlayer insulating film and wiring layer film deposited on the front surface of the wafer is 0.1 μm.
The present inventor has clarified that there is a problem in that accuracy of m or less cannot be ensured.

In short, since the number of wiring layers has been increased with the increase in the integration of semiconductor devices, the unevenness formed on the main surface of the wafer has a step size of 1 μm to several μm. For this reason,
At the time of pattern formation, the depth of focus of lithography cannot correspond to the step, and the processing accuracy deteriorates. Further, the coverage is deteriorated in the metal film formation by the conventional sputtering method. As a countermeasure against this, unevenness on the main surface of the wafer is chemically mechanically polished (Chemical Mechanical Polishing).
Polishing. Hereinafter referred to as CMP. It is proposed that the main surface of the wafer be flattened by polishing with (1). However, if the conventional polishing apparatus is used as it is for the flattening technique by CMP, a predetermined accuracy cannot be obtained.

It is an object of the present invention to provide a semiconductor device manufacturing technique capable of uniformly polishing a surface to be polished of a wafer with high accuracy, regardless of a thickness distribution before processing and a change in a force acting during polishing work. To provide.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

Incidentally, examples in which the CMP is described include JP-A-5-74749, JP-A-6-342778, and JP-A-7-1328. Japanese Patent Laid-Open No. 5-
No. 74749 discloses a device in which a top ring having a lower surface formed by an elastic body in which a pressure fluid is sealed is pressed against a wafer to press a device surface against a polishing cloth, and the polishing cloth and the device surface of the wafer are rubbed against each other. A method and apparatus for planarizing a wafer with a device for planarizing a surface are disclosed. In Japanese Patent Laid-Open No. 6-342778, a change in mechanical vibration generated during CMP is monitored, and a change in vibration generated when polishing of a surface portion having irregularities is completed to control the polishing process. A polishing method, a polishing apparatus, and an object to be polished used therein are disclosed. JP-A-7-132
No. 8 discloses that the lower surface of the top ring in contact with the wafer is formed smooth and the inner diameter of the retaining ring is formed larger than the outer diameter of the wafer, and the outer peripheral surface of the wafer is rotated by the rotation of the turntable. A polishing apparatus and method in which the retaining ring causes the wafer to make a planetary motion as the top ring rotates by contacting the inner peripheral surface,
It is disclosed.

[0015]

The outline of a typical invention among the inventions disclosed in the present application is as follows.

That is, a method of manufacturing a semiconductor device by chemical mechanical polishing for flattening the surface of a multilayer wiring of a semiconductor wafer includes the following steps: (a) a semiconductor wafer for forming a semiconductor device A first-layer insulating film wiring forming step of forming a first-layer wiring on the formed first-layer insulating film; (b) a first layer on the first-layer insulating film and the first-layer wiring. A second insulating film forming step of forming a two-layer insulating film, (c) a back surface of the semiconductor wafer on which the second insulating film is formed is directly or directly attached to a work holding surface of the head. The second layer by being held via a pad and supplying the pressing gas from almost the entire work holding surface of the head in a state in which at least a part of the gas is dissipated from the periphery of the back side surface of the semiconductor wafer to the outside. The surface of the insulating film of Planarizing step of flattening the unevenness of the second-layer insulating film by supplying the abrasive in a quasi-statically pressed state to the surface of the second-layer insulating film, and (d) forming a flattened second-layer insulating film. A hole forming step of forming a through hole or a contact hole, and (e) a second layer wiring forming step of forming a second layer wiring on the second layer insulating film having the holes formed therein.

[0017]

1 shows a chemical mechanical polishing apparatus used in a method of manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 1 (a) is an exploded perspective view of a main part, and FIG. ) Is a partially omitted front view with partial omission. FIG. 2 and subsequent drawings are explanatory views for explaining the planarization process by CMP in the method for manufacturing a semiconductor device according to an embodiment of the present invention.

In the present embodiment, the chemical mechanical polishing apparatus shown in FIG. 1 forms on the surface of an insulating film or a metal film by CMP the insulating film or the metal film deposited on the front surface of the wafer. It is configured as a device that can be used to flatten the formed unevenness. That is, as shown in FIG. 7A, the work 1 of the chemical mechanical polishing apparatus (hereinafter, wafer polishing apparatus) 10 according to the present embodiment has an orientation flat (hereinafter,
Orifla. ) Wafer 2 in which 3 is cut linearly
It has. As shown in FIG. 7B, a memory M, which is an example of a semiconductor element, is formed in the front side region of the substrate of the wafer 2, and an example of a metal film is formed on the front side surface thereof. The wiring 4 formed of the wiring layer film and the interlayer insulating film 5 which is an example of the insulating film are respectively deposited. Since the wiring 4 is formed by a line segment having a thickness, an uneven portion 6 is formed on the front surface of the interlayer insulating film 5 adhered thereon so as to follow the unevenness of the underlying wiring 4. I have. Thus, in the present embodiment, the interlayer insulating film 5 is planarized by polishing and removing a part of the surface of the interlayer insulating film 5 by the wafer polishing apparatus 10. Therefore, the surface to be polished 7 is formed by the surface of the interlayer insulating film 5.

The wafer polishing apparatus 10 comprises a polishing tool and a head. The polishing tool 11 includes a disk-shaped base plate 12 having a radius sufficiently larger than the diameter of the work 1, and the base plate 12 is rotatably supported in a horizontal plane. In the center of the lower surface of the base plate 12, a rotating shaft 1 vertically arranged
3 is fixed, and the base plate 12 is driven to rotate by the rotation shaft 13. A polishing cloth (cloth) 14 is uniformly adhered to the entire upper surface of the base plate 12. The polishing cloth 14 is a polishing material in which fine abrasive grains such as colloidal silica are held in a cloth (cloth) made of a synthetic resin having a pore structure on the surface, and the polishing material surface 15 is formed by the front side surface thereof. During the polishing operation using the polishing cloth 14, an etching solution (a polishing solution called a slurry; hereinafter referred to as a slurry) is used, so that a mechanochemical that enhances the polishing effect in addition to mechanical polishing (polishing) is used. Policing (mechanochemical
polishing) is carried out. Therefore, a slurry supply nozzle 16 for supplying the slurry 17 is piped almost directly above the center line of the polishing tool 11.

On the other hand, the head 20 is constructed so as to hold the work 1 in a state where the work 1 is exposed with the interlayer insulating film 5 side, which is the surface 7 to be polished, facing downward, and the work 1 depends on the gas pressure. Surface 7 to be pressed by pressing force
The auxiliary pressing device 21 is configured to press the abrasive material surface 15 against the abrasive material surface 15. That is, the head 20 is a disk-shaped main body 22 having a diameter slightly larger than the diameter of the work 1.
In the lower surface of the main body 22, circular holding holes 23 having a certain depth are concentrically arranged and recessed. Holding hole 2
The size of 3 is slightly larger than the size of the work 1. A vent hole 24 as a gas flow port is formed at the center of the holding hole 23, and the vent hole 24 is provided in the vent hole 24.
5 is connected. The other end of the air passage 25 is the air pump 2
By being connected to 6, the ventilation passage 25 constitutes a positive pressure supply passage 28 for supplying the air 27 as the positive pressure gas to the ventilation opening 24. Further, the other end of the ventilation path 25 is connected to the vacuum pump 29, so that the ventilation path 25 constitutes a negative pressure supply path 30 for supplying a negative pressure to the ventilation port 24. Therefore, the ventilation passage 25 serves as both the positive pressure supply passage 28 and the negative pressure supply passage 30, and the positive pressure supply passage 28 and the negative pressure supply passage 30 are switched by the switching valve 31 provided midway. Is configured.

Further, a ceramic plate 32 as a distribution member for distributing the gas flowing through the gas flow port to the entire back side surface of the work 1 is laid in the inner space of the holding hole 23 on the inner side. The ceramic plate 32 is made of a ceramic such as alumina having a high rigidity and a small thermal expansion, and is formed into a disk shape having a diameter substantially equal to the diameter of the holding hole 23.
The thickness is set smaller than the depth of the holding hole 23. The ceramic plate 32 as the distribution member is porous and has fine ventilation passages 33 that communicate with each other by the group of the pores.
Are molded so as to be innumerable and uniform over the whole. That is, the ceramic plate 32 is configured so that the positive pressure and the negative pressure can be evenly distributed over the entire surface between the ventilation port 24 side and the opposite side. Further, since the highly rigid ceramic plate 32 is in contact with the bottom surface of the holding hole 23, the lower surface thereof substantially constitutes a work holding surface which receives the reaction force of the work 1.

Further, the pad 3 is provided in the cavity of the holding hole 23.
4 is laid in contact with the lower surface of the ceramic plate 32. The pad 34 has a main body 35.
Is made of rubber or resin, which is an example of an elastic material having appropriate elasticity, and is formed in a disc shape having a diameter substantially equal to the diameter of the holding hole 23. The pad body 35 has a large number of through holes 36 as communication passages for communicating the space on the side of the ceramic plate 32 and the space on the side opposite to the ceramic plate 32. The through holes 36 are evenly arranged over the entire surface so as to penetrate in the thickness direction of the pad body 35. Each of them is opened, and each through hole 36 is formed in a cylindrical shape having a diameter of about 2 mm. Therefore, the density of the opening area formed by the group of through holes 36 is set to be substantially equal over the entire surface of the pad 34.

A guide ring 37 formed in a circular ring shape is attached to the lower end surface of the head body 22 in which the auxiliary pressing device 21 is incorporated so as to surround the opening edge of the holding hole 23. The guide ring 37 is configured to hold the work 1 while exposing the surface 7 to be polished downward from the lower end while preventing the work 1 from jumping out during the polishing operation.

The head 2 constructed as described above
0 is rotatably supported in the horizontal plane around the vent hole 24, and is rotatably driven by a rotary drive device (not shown). The head 20 is configured to be reciprocally moved by a transfer device (not shown) between a station in which the polishing tool 11 is installed and a loading station (not shown) in which the works 1 are dispensed one by one. There is. Further, the head 20 is configured to be fed downward during the polishing operation.

Here, the wafer polishing apparatus 1 having the above structure
The CMP method using 0 will be described. Work 1 is polished surface 7
When inserted into the guide ring 37 of the head 20 with the side facing downward, the switching valve 31 is switched and negative pressure is supplied to the vent hole 24 through the negative pressure supply passage 30.
This negative pressure is applied to the main surface (hereinafter referred to as the back surface) 8 of the work 1 opposite to the surface to be polished 7 through the fine ventilation passages 33 of the ceramic plate 32 and the through holes 36 of the pad 34. The work 1 is in a state of being vacuum-adsorbed and held by the head 20. In this way, the head 20 holding the work 1 is moved right above the polishing tool 11 by the transfer device and then lowered. The head 20 is lowered and the work 1
When the surface 7 to be polished comes into contact with the polishing material surface 15 of the polishing tool 11, the switching valve 31 is switched to supply the air 27 to the ventilation port 24 through the positive pressure supply passage 28.

Subsequently, the polishing tool 11 and the head 20 are respectively rotated, and the head 20 is fed downward to apply a constant mechanical pressing force to the work 1. As a result, the surface 7 to be polished of the work 1 held by the head 20 is rubbed while being pressed against the surface 15 of the polishing tool 11 so that the surface 7 to be polished of the work 1 is polished by the surface 15 of the polishing material. . During this polishing operation, the slurry 17 is supplied from the slurry supply nozzle 16 to the abrasive material surface 15 to perform mechanical polishing (polishing) as well as mechanochemical polishing that enhances the polishing effect.

During this polishing operation, the air 27 is supplied from the positive pressure supply passage 28 to the vent hole 24, so that the surface 7 to be polished of the work 1 is brought into contact with the abrasive surface 15 by the acting force of the supply pressure of the air 27. It will be pressed. That is, the air 27 supplied from the positive pressure supply passage 28 to the ventilation port 24 is supplied to the back side surface 8 of the work 1 through the fine ventilation passages 33 of the ceramic plate 32 and the through holes 36 of the pad 34. The applied pressure of 27 pushes the work 1 downward in the vertical direction. At this time, since the fine ventilation passages 33 of the ceramic plate 32 are evenly opened over the entire surface, the air 27 is evenly distributed over the entire surface of the pad 34. Further, since the through holes 36 of the pad 34 are also uniformly distributed over the whole, the air 27 is evenly supplied over the entire surface of the work 1. Therefore, the work 1 is vertically and uniformly pushed down by the acting force of the air 27, and is quasi-statically pressed against the abrasive material surface 15 of the polishing cloth 14. That is, the air 27
The pushing-down load due to the pressure is a vertical uniform load. By the way, at least a part of the air 27 is the work 1
It will be dissipated to the outside from around the back side of the.

As a result, the surface to be polished 7 of the work 1 is pressed against the abrasive material surface 15 of the polishing tool 11 vertically and uniformly, so that the amount of polishing of the object to be polished 7 by the abrasive material surface 15 is entirely. Becomes uniform over. As a result, the surface portion of the interlayer insulating film 5 forming the surface 7 to be polished of the work 1 is evenly polished over the entire surface, so that the uneven portion 6 is removed over the entire surface and a uniform thickness is formed over the entire surface. The interlayer insulating film 5 exhibiting the above is formed, and extremely excellent planarization can be realized.

Now, the relationship between the arrangement of the through holes 36 of the pad 34 and the distribution of the polishing amount after polishing will be described with reference to FIG. 2 shows a cylindrical through hole 36 having a diameter of about 2 mm (see FIG.
See (g). same as below. ) Are used in the wafer polishing apparatus 10 having the above-mentioned configuration to open the thermal oxide film 9 uniformly formed on the surface of the wafer 2, respectively. FIG. 6 is a schematic plan view showing the relationship between each pad 34 and the form of the remaining thermal oxide film after polishing. In FIG. 2, the mesh portion indicates the residual film portion (the polishing residual portion) of the thermal oxide film 9, and the white background portion indicates the portion where the thermal oxide film 9 is removed (the polished portion). .

First, FIG. 2 (a) shows a pad in which a through hole is not substantially opened, and FIG. 2 (b) shows a thermal oxide film polished by a wafer polishing apparatus using the pad. The residual film distribution in the case is shown. As is clear from FIG. 2B, in this case, the peripheral portion of the wafer is locally polished, and the polishing residue is left in the central portion. The uniformity of the polishing amount (maximum remaining film thickness-minimum remaining film thickness) / (maximum remaining film thickness + minimum remaining film thickness) (%) is >> 100, and the uniformity is extremely poor.

FIG. 2C shows a pad in which a plurality of through holes are centrally formed in the central portion, and FIG.
Shows the residual film distribution when the thermal oxide film is polished by the wafer polishing apparatus using the pad. In this case, polishing residue occurs in the central portion and the peripheral portion. But,
The uniformity of the polishing amount is improved as compared with the case of FIG. 2A, and the uniformity is 23%.

FIG. 2 (e) shows a pad in which a large number of through holes are evenly arranged and opened, and FIG. 2 (f) shows thermal oxidation by a wafer polishing apparatus in which the pad is used. The residual film distribution when the film is polished is shown. In this case, polishing residue occurs in the peripheral portion. However, the uniformity of the polishing amount is further improved as compared with the case of FIG. 2C, and the uniformity is 6.3%.

FIG. 2 (g) shows a pad 3 in which a large number of through holes 36 are evenly arranged over the entire surface.
4B, and FIG. 2H shows the residual film distribution when the thermal oxide film 9 is polished by the wafer polishing apparatus 10 using the pad. In this case, almost no polishing residue occurs. The uniformity of the polishing amount is 3.2%.

By comparing the result (f) in the case of FIG. 2 (e) with the result (h) in the case of FIG. 2 (g), the higher the density of the through holes 36, the more uniform the polishing amount. Is considered to improve.

Next, the relationship between the mechanical pressing force depending on the feed amount of the head 20 and the fluid pressing force depending on the applied pressure of air will be described with reference to FIG. Figure 3 is Figure 2 (g)
The result of investigating the uniformity of the residual film when the thermal oxide film formed on the surface of the wafer is polished by changing the feed amount of the head 20 by the wafer polishing apparatus 10 using the pad 34 shown in FIG. It is a relationship curve shown. In FIG. 3, the vertical axis represents the uniformity of the polishing amount (%), and the horizontal axis represents Pg.
/ Po (%) is taken. Here, Pg is the air 27
Is the applied pressure (g / cm ² ) and Po is the acting force per unit area of the mechanical pressing force that depends on the feed amount of the head 20 (hereinafter referred to as the main pressure, g / cm ² ). Then, by changing the feed amount of the head 20, the main pressure Po is changed from 200 g / cm ² to 500 g / cm ² , and Pg / Po is changed from 0% to 150%.

It can be seen from FIG. 3 that the uniformity gradually increases as Pg / Po increases. When Pg / Po is 50% or more, the uniformity satisfies 10% required in the field of manufacturing semiconductor devices.
Further, it is understood that the change in uniformity is small when Pg / Po exceeds 70%. The X mark in the figure shows the case where the wafer, which is a sample, jumps out from the head 20 during the polishing operation and polishing cannot be performed. Therefore, it is understood that the higher the Pg / Po is, the more the uniformity of the polishing amount is improved, but the wafer popping-out phenomenon occurs when the Pg / Po exceeds 130%.
From the above points, it is considered that adjusting the value of Pg / Po in the range of 50% to 130% is an important condition for ensuring uniform polishing.

By the way, the unprocessed wafer that has been put into the preceding steps from the wafer cutting step and the subsequent grinding step and polishing step may have a thickness distribution of about 1 μm.

FIG. 4A is a schematic view showing a typical thickness distribution of the unprocessed wafer by contour lines. Then, FIG. 9B is a diagram showing a comparison of the film thickness distributions after polishing the thermal oxide film formed on the unprocessed wafer of FIG. In the figure (b), the vertical axis represents the thickness deviation amount (Å), and the horizontal axis represents the distance from the wafer center (mm).
Has been taken. A curve A shows the thickness distribution of the wafer in FIG. 9A, a curve B shows the thickness distribution of the thermal oxide film after being polished by the conventional polishing apparatus, and a curve C shows the wafer polishing apparatus according to this embodiment. The respective thickness distributions of the thermal oxide film after being polished are shown.

According to FIG. 4B, when the polishing is performed by the conventional polishing apparatus, the thermal oxide film after polishing has a thickness distribution corresponding to the thickness distribution of the wafer. When it is polished by the wafer polishing apparatus according to the embodiment,
It is understood that the thickness distribution of the thermal oxide film after polishing is substantially unaffected by the thickness distribution of the wafer and is substantially uniform over the entire surface.

Here, the principle that a difference occurs in the film thickness distribution after polishing will be briefly described with reference to FIG. FIG. 5 (a)
As shown in FIG. 3, according to the conventional polishing apparatus, the wafer 2A having a thickness distribution is strongly pressed against the abrasive surface 15 by the head 20A at a location having a large thickness (as a result of being strongly pushed back from the polishing cloth 14). The interlayer insulating film 5 uniformly formed on the front surface of the wafer 2A
After polishing, as shown in FIG.
The wafer 2 </ b> A having a thickness distribution is thin at a place where the thickness is large and thick at a place where the thickness is small.

On the other hand, according to this embodiment, as shown in FIG.
As shown in (c), the thickness distribution of the wafer 2A having a thickness distribution is absorbed by elastic deformation of the pad body 35 having elasticity. That is, the interlayer insulating film 5 uniformly formed on the front surface of the wafer 2A having a thickness distribution is in a state of being flush (parallel) contacting the entire surface of the polishing material 15 regardless of the thickness distribution. Here, when the pad main body 35 is elastically deformed, an elastic force having a magnitude corresponding to the elastic deformation amount is applied to each portion of the wafer 2A having a thickness distribution, so that the interlayer insulating film 5 formed by the polishing material surface 15 is used. A distribution corresponding to the distribution of the magnitude of the elastic force is generated in the polishing amount. However, the wafer 2A abutting on the pad 34 has the air 27 larger than its elastic force.
Since it is pressed uniformly and vertically over the entire surface in the direction of the abrasive surface 15 by the acting force of the applied pressure Pg, the surface of the interlayer insulating film 5 which is the surface 7 to be polished of the wafer 2A is the pad body 35. The entire surface is pressed uniformly and vertically to the abrasive surface 15 without being affected by the elastic force distribution due to the elastic deformation. In other words, the very slight difference in the elastic force of the pad 34 is almost negligible to the acting force of the air 27 which is much larger than the magnitude of the elastic force. As a result, as shown in FIG. 5D, the interlayer insulating film 5 uniformly formed on the front surface of the wafer 2A having a thickness distribution has a uniform (constant) film thickness after polishing. It will be polished to the state that it has become.

By the way, in the case where the work 1 sent to the flattening step of the method for manufacturing a semiconductor device according to the present embodiment is a wafer 2A having a thickness distribution as shown in FIG. When the interlayer insulating film 5 is polished by the polishing apparatus, as shown in FIG. 5B, the interlayer insulating film 5 becomes too thin and the lower wiring 4 is exposed in a place where the thickness of the wafer 2A is large. Will end up. Therefore, the conventional polishing apparatus cannot be put to practical use for flattening the interlayer insulating film 5.

However, according to the wafer polishing apparatus 10 according to the present embodiment, even the wafer 2A having the thickness distribution has the interlayer insulating film 5 as shown in FIG. 5D.
Is uniformly polished over the entire surface, the interlayer insulating film 5
Can be flattened. That is, according to the present embodiment, as described above, the surface 7 to be polished is uniformly polished over the entire surface regardless of the thickness distribution of the wafer 2A, so that the thickness of the interlayer insulating film 5 is uniformly reduced over the entire surface. It will be. That is, the uneven portion 6 formed on the surface of the interlayer insulating film 5 is removed by polishing, so that the surface of the interlayer insulating film 5 is flattened. On the other hand, since the interlayer insulating film 5 is uniformly deposited over the entire surface, if the polishing amount is uniform over the entire surface, the thickness of the interlayer insulating film 5 after polishing is uniform over the entire surface. Therefore, the polishing amount by the wafer polishing apparatus 10 is
By properly setting the thickness of the interlayer insulating film 5 before polishing, the thickness of the wiring 4 and the relationship between the uneven portions 6, it is possible to flatten the interlayer insulating film 5 without polishing the underlying wiring 4. .

Hereinafter, the planarization step by CMP in the method of manufacturing a semiconductor device according to one embodiment of the present invention will be mainly described.
A case will be described in which the unevenness formed in the interlayer insulating film in the multilayer wiring is flattened by using the wafer polishing apparatus 10 having the above configuration.

As shown in FIG. 6A, CMP
Before being subjected to the planarization step by the above, the first-layer insulating film 5a in the multilayer wiring is formed on the first main surface of the wafer 2, and the first-layer wiring 5a is formed on the first-layer insulating film 5a. 4a is patterned and formed by a metal film deposition process, a lithographic process, and an etching process. In addition,
The wiring 4a of the first layer also includes a word line formed of polysilicon, polycide, or the like.

Thereafter, as shown in FIG. 6B, a second-layer insulating film 5b made of SiO ₂ or Si ₃ N ₄ is formed on the first-layer insulating film 5a of the wafer 2. , The CVD method or the like so as to cover the wiring 4a of the first layer. Since a convex portion corresponding to the thickness of the wiring 4a of the first layer is formed on the surface side of the insulating film 5b of the second layer, an unspecified number of irregular portions 6 are formed on the surface 7 to be polished. It becomes a state.

The wafer 2 in this state is supplied as the work 1 to the wafer polishing apparatus 10 for carrying out the flattening step in the method for manufacturing a semiconductor device according to this embodiment. Then, as described above, the wafer polishing apparatus 10 holds the work 1 in this state by the head 20 and relatively rubs the surface of the second insulating film 5b while supplying the slurry 16 to the polishing tool 11. CMP is performed to flatten the uneven portion 6 of the second insulating film 5b.

By this CMP, the convex portions of the concave-convex portions 6 formed on the second-layer insulating film 5b which is the surface 7 to be polished of the work 1 are removed first, so that the second-layer insulating film 5b of the second-layer insulating film 5b is removed. The surface is gradually flattened. At this time, according to the present embodiment, as described above, the surface 7 to be polished is uniformly polished over the entire surface irrespective of the thickness distribution of the wafer 2.
The thickness of the insulating film 5b of the layer will be uniformly reduced over the whole. That is, the uneven portion 6 formed on the surface of the second-layer insulating film 5b is removed by CMP, so that the surface of the second-layer insulating film 5b is flattened. On the other hand, since the second-layer insulating film 5b was uniformly deposited over the entire surface, if the polishing amount is uniform over the entire surface, the thickness of the second-layer insulating film 5b after the polishing is complete. Is uniform across. Therefore, by appropriately setting the amount of polishing by the wafer polishing apparatus 10 according to the relationship between the thickness of the second-layer insulating film 5b before polishing, the thickness of the second-layer wiring 4a, and the irregularities 6, the second polishing is performed. The second layer insulating film 5b can be planarized without polishing the layer wiring 4a.

As described above, in the state in which the CMP method is completed, the second-layer insulating film 5 which is the surface 7 to be polished of the work 1.
As shown in FIG. 6 (c), the surface of b is flattened with extremely high precision, and the second-layer insulating film 5b is preset just above the first-layer wiring 4a. It is in a state of being left with a certain layer thickness.

The workpiece 1 in this state is the wafer polishing apparatus 10
Is sent to a hole forming step by an unloading device. In the hole forming step, as shown in FIG. 6D, through holes 4c are formed right above the predetermined first-layer wiring 4a in the second-layer insulating film 5b of the work 1. .

Subsequently, in the second-layer wiring forming step, as shown in FIG. 6E, the second-layer wiring 4b is coated with the metal film by the metal-film deposition treatment on the second-layer insulating film 5b. And patterned by lithography and etching. At this time, since the surface of the insulating film 5b of the second layer is flattened with high precision, the wiring 4b of the second layer is patterned with extremely high precision. A part of the metal film deposited on the second-layer insulating film 5b at the time of patterning the second-layer wiring 4b is filled in the through-hole 4c formed in the second-layer insulating film 5b. A through-hole conductor 4d is formed. And the patterned second
A predetermined portion of the layer wiring 4b is electrically connected to the first layer wiring 4a by the through-hole conductor 4d.

Thereafter, the insulating film forming step, the flattening step according to the present invention, the hole forming step and the wiring forming step are repeated to form the multi-layered wiring shown in FIG. 7B. Become. At this time, it goes without saying that the insulating film and the wiring in the layer formed in the previous step correspond to the insulating film and the wiring in the lower layer in the next step. The holes are not limited to through holes, but include contact holes, and the holes are not limited to connecting the wirings of the first layer to the wirings of the second layer, and the wirings of the first layer may be the third layer or the third layer. It may be connected to the wiring of four layers.

FIG. 8 shows a wafer polishing apparatus which is Embodiment 2 of the present invention. (A) is a bottom view thereof, and (b) is a side sectional view taken along line bb of (a). FIG.
(A), (b), (c) is each contour map which shows the film thickness distribution after polish for demonstrating the effect, respectively.

The second embodiment is different from the first embodiment in that the arrangement density of the through holes 36 is small in the region corresponding to the orientation flat 3 of the wafer 2.
By the way, the guide ring 37 is adapted to prevent the work 1 from popping out and to perform positioning in the circumferential direction.

By the way, when the thermal oxide film formed on the surface of the wafer having the orientation flat is polished by the polishing apparatus, the film thickness distribution after polishing exhibits a peculiar distribution in the vicinity of the orientation flat. Was revealed. FIG. 9 (a) shows the film thickness distribution after polishing by a conventional polishing apparatus, showing that the contour lines are extremely dense near the orientation flat and the film thickness distribution is not uniform. Well understood. FIG. 9B shows the film thickness distribution after polishing by the wafer polishing apparatus according to the first embodiment, and it is understood that the contour lines are slightly dense near the orientation flat.

On the other hand, FIG. 9C shows the second embodiment.
It shows the film thickness distribution after polishing by the wafer polishing apparatus according to the above. It is well understood that the contour lines are rough even near the orientation flat and the peculiar thickness distribution near the orientation flat is improved. To be done. Embodiment 2
In the above, the reason why the peculiar film thickness distribution in the vicinity of the orientation flat is improved is that the applied density (Pg) of the air 27 in the vicinity of the orientation flat 3 of the work 1 is set by setting the arrangement density of the through holes 36 group in the pad 34 to be small. It is considered that the pressing force per unit area due to is partially moderately weakened.

FIG. 10 shows a wafer polishing apparatus which is Embodiment 3 of the present invention, (a) is a front sectional view thereof,
(B) is a plane sectional view taken along the line bb of (a).

The difference of the third embodiment from the first embodiment is that an inner ceramic plate 32A, a center ceramic plate 32B, and an outer ceramic plate 32C in which the distribution members are fluidly partitioned from each other and arranged concentrically. It is made up of two different air pressures on each ceramic plate.
7A, 27B, and 27C are applied via a swivel joint 38, respectively.

According to the third embodiment, since different air pressures (Pg) are applied to the work 1 in the radial direction, it is possible to apply different pressing forces to the work 1 in the radial direction. As a result, the uniformity of the polishing amount on the surface to be polished of the work 1 can be further enhanced.
By the way, the magnitude of the pressing force applied to the work 1 is not limited to the radial direction but may be the circumferential direction. In short, the auxiliary pressing device 21 can be configured so that the distribution of the pressing force due to the pressure of gas such as air is different at the portion of the work surface 1 to be polished.

FIG. 11 is a front sectional view showing a wafer polishing apparatus which is Embodiment 4 of the present invention.

The fourth embodiment is different from the first embodiment in that the pad 34 is not provided with a through hole 36 as a communication passage.

FIG. 12 is a front sectional view showing a wafer polishing apparatus which is Embodiment 5 of the present invention.

The fifth embodiment differs from the first embodiment in that the pad 34 is omitted.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the pad, the communication passage that connects the distribution member and the reaction-side main surface (back side surface) of the work is not limited to the through hole formed in the thickness direction of the pad body, but may be formed of foam resin. Alternatively, the pad main body itself may be formed by using a porous material such as a fine porous communication path. The pad body is not limited to being made of rubber, resin, or foamed resin, but may be made of a material having appropriate elasticity such as felt or glass wool.

The means for partially differentiating the density of the opening areas on the work side of the communication passage groups by the through holes or the like is not limited to the different arrangement densities of the through hole groups, but the opening area of each communication passage can be changed. You may make it different.

The distribution member is not limited to be made of porous ceramic, but may be made of foamed resin.

Further, the distribution member may be constructed by forming a large number of through holes in a plate material having rigidity so as to penetrate in the thickness direction. In this distribution member, each through hole can be arranged so as to face each through hole of the pad. Further, an elastic material may be attached to the distribution member by baking, adhesion, or the like to integrally configure the distribution member and the pad.

As the pressing gas of the auxiliary pressing device, not only air is used as the medium, but gas such as nitrogen may be used.

The head is not limited to be disposed on the upper side and the polishing tool is disposed on the lower side, but the head may be disposed on the lower side and the polishing tool may be disposed on the upper side. Further, the head side is not limited to be lowered, and the polishing tool side may be raised.
Further, the head and the polishing tool may be vertically immovable, and the surface to be polished of the work and the abrasive material surface of the polishing tool may be relatively moved in the horizontal direction and simply rubbed.

The negative pressure supply passage 30 is not limited to be used also as the positive pressure supply passage 28, but may be provided separately or may be omitted in some cases.

The work of the wafer polishing apparatus is not limited to the wafer having the surface coated with the metal film and the insulating film, but may be an unprocessed wafer. That is, the wafer polishing apparatus can be used as a wafer grinding apparatus, a polishing apparatus, or the like.

In the above description, the case where the polishing apparatus is applied to polishing a wafer has been described. However, the polishing apparatus is not limited to this, and the polishing apparatus is a plate-shaped object such as a compact disk, a magnetic disk, a liquid crystal panel, a photomask or the like. It can be applied to polishing for polishing the surface.

[0074]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

Even if the wafer has a non-uniform plate thickness, it can be polished with a uniform polishing amount over the entire surface to be polished regardless of the thickness distribution. It is possible to polish the coated film with a uniform thickness over the entire surface.

As a result, in the manufacturing process of the semiconductor device, the surface of the metal film or the insulating film is flattened by uniformly polishing the uneven portions on the surface of the metal film or the insulating film deposited on the surface of the wafer. Therefore, the miniaturization of wiring and high integration can be further promoted.

[Brief description of drawings]

1A and 1B show a chemical mechanical polishing apparatus used in a flattening step in a method for manufacturing a semiconductor device according to an embodiment of the present invention, where FIG. 1A is an exploded perspective view of a main part, and FIG. It is a partially omitted front view.

FIG. 2 is an explanatory diagram for explaining a relationship between an array form of through holes of a pad and a polishing amount distribution after polishing, FIG.
(C), (e), (g) are plan views showing the arrangement of the through holes of the pad, respectively (b), (d), (f),
(H) is a schematic plan view showing a form in which the thermal oxide film remains after polishing.

FIG. 3 is a diagram showing a relationship between a mechanical pressing force depending on a head feed amount and a fluid pressing force depending on an applied pressure of air.

4A is a schematic view showing a typical thickness distribution of a wafer by contour lines, and FIG. 4B is a comparison of film thickness distributions after polishing a thermal oxide film formed on the wafer of FIG. FIG.

5A and 5B are explanatory views for explaining the principle that a difference occurs in the film thickness distribution after polishing, FIG. 5A is a schematic front sectional view showing a polishing state by a conventional polishing apparatus, and FIG. A schematic front sectional view showing a thickness distribution, (c) a schematic front sectional view showing a polishing state by a wafer polishing apparatus according to an embodiment of the present invention, and (d) a front sectional view showing the thickness distribution. .

FIG. 6 is an enlarged partial cross-sectional view for explaining a flattening step of a method for manufacturing a semiconductor device according to an embodiment of the present invention, in which (a) is a wiring forming step for a first layer and (b) is a sectional view. 8A shows a second-layer insulating film forming step, FIG. 8C shows a flattening step, FIG. 8D shows a hole forming step, and FIG. 8E shows a second-layer wiring forming step.

FIG. 7 shows a work, (a) is a plan view, and (b) is a plan view.
Is an enlarged partial sectional view.

FIG. 8 shows a wafer polishing apparatus that is Embodiment 2 of the present invention, in which (a) is a bottom view thereof and (b) is b- of (a).
It is a side surface sectional view which follows a b line.

9A, 9B, and 9C are contour maps showing the film thickness distribution after polishing for explaining the effect.

10A and 10B show a wafer polishing apparatus according to a third embodiment of the present invention, in which FIG. 10A is a front sectional view thereof, and FIG.
FIG. 7 is a plan sectional view taken along line bb of FIG.

FIG. 11 is a front sectional view showing a wafer polishing apparatus that is Embodiment 4 of the present invention.

FIG. 12 is a front sectional view showing a wafer polishing apparatus which is Embodiment 5 of the present invention.

[Description of sign]

1 ... Work, 2 ... Wafer, 2A ... Wafer having thickness distribution, 3 ... Orientation flat (orientation flat), 4
... wiring, 4a ... first layer wiring, 4b ... second layer wiring, 4
c ... through hole, 4d ... through hole conductor, 5 ... interlayer insulating film (insulating film), 5a ... first layer insulating film, 5b ... second
Layer insulating film, 6 ... uneven portion, 7 ... surface to be polished, 8 ... back side surface,
9 ... Thermal oxide film, 10 ... Wafer polishing apparatus (polishing apparatus), 1
1 ... Polishing tool, 12 ... Base plate, 13 ... Rotating shaft,
14 ... Polishing cloth, 15 ... Abrasive material surface, 16 ... Slurry supply nozzle, 17 ... Slurry, 20, 20A ... Head, 21 ...
Auxiliary pressing device, 22 ... Head body, 23 ... Holding hole, 24
... Ventilation port (gas flow port), 25 ... Ventilation path (fluid pressure supply path), 26 ... Air pump, 27, 27A, 27B, 27
C ... Air (gas), 28 ... Positive pressure supply path, 29 ... Vacuum pump, 30 ... Negative pressure supply path, 31 ... Switching valve, 32 ... Ceramic plate (distribution member), 32A ... Inner ceramic plate, 32
B ... Center ceramic plate, 32C ... Outer ceramic plate, 33 ... Fine ventilation passage, 34 ... Pad, 35 ... Pad body, 36 ... Through hole (communication passage), 37 ... Guide ring,
38 ... Swivel joint.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Nakagawa 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division (72) Inventor Yoshio Honma 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi Central (72) Inventor Kikuo Kusugawa 1-280, Higashi Koigokubo, Kokubunji, Tokyo, Hitachi Central Research Laboratory (72) Inventor, Shinichiro Mitani 2326, Imai, Ome, Tokyo Hitachi, Ltd. Device Development Center

Claims (18)

[Claims] 1. A method of manufacturing a semiconductor device by chemical mechanical polishing for flattening the surface of a multi-layer wiring of a semiconductor wafer comprises the steps of: (a) a semiconductor wafer for forming a semiconductor device; A first-layer insulating film wiring forming step of forming a first-layer wiring on the formed first-layer insulating film; (b) a first layer on the first-layer insulating film and the first-layer wiring. A second insulating film forming step of forming a two-layer insulating film;
The back side of the layer on which the insulating film is formed is held directly on the work holding surface of the head or via a pad, and at least a part of the pressing gas is supplied from almost the entire work holding surface of the head to the semiconductor. The surface of the insulating film of the second layer is quasi-statically pressed against the polishing cloth by being supplied to the outside from the periphery of the back surface of the wafer, and the abrasive is relatively moved while supplying the abrasive. A flattening step of flattening the unevenness of the two-layer insulating film, (d) a hole forming step of forming a through hole or a contact hole in the flattened second insulating film, (e) a first hole-forming step A second-layer wiring forming step of forming a second-layer wiring on the two-layer insulating film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a mechanical action force between the head and the polishing cloth is used together in the flattening step. 3. The magnitude of the acting force of the pressing gas in the flattening step is 50% to 13% of the magnitude of the mechanical acting force.
The method for manufacturing a semiconductor device according to claim 2, wherein the value is set to 0%. 4. The method of manufacturing a semiconductor device according to claim 1, wherein a pad having a plurality of communication passages is provided on substantially the entire surface between the work holding surface of the head and the back side surface of the semiconductor wafer. . 5. The method of manufacturing a semiconductor device according to claim 4, wherein the density of the opening area on the semiconductor wafer side of the communication passage group is different in the area of the back side surface of the semiconductor wafer in the planarizing step. 6. A method of manufacturing a semiconductor device by chemical mechanical polishing for flattening the surface of a multi-layer wiring of a semiconductor wafer comprises the steps of: (a) a semiconductor wafer for forming a semiconductor device; A first-layer insulating film wiring forming step of forming a first-layer wiring on the formed first-layer insulating film; (b) a first layer on the first-layer insulating film and the first-layer wiring. A second insulating film forming step of forming a two-layer insulating film;
At least the porous portion of the work holding surface of the head is obtained by holding the back side of the layer on the side where the insulating film is formed, directly or through a pad on the work holding surface in which at least a part of the head is made porous. From the periphery of the back surface of the semiconductor wafer to the outside in a state in which at least a part of the pressing gas is dispersed to the outside by pressing the surface of the insulating film of the second layer against the polishing cloth in a quasi-static manner. A flattening step of flattening irregularities of the second-layer insulating film by relatively moving while supplying an abrasive, (d) a hole for forming a through hole or a contact hole in the flattened second-layer insulating film Forming step, (e) Second-layer wiring forming step of forming second-layer wiring on the second-layer insulating film having holes formed therein. 7. The method of manufacturing a semiconductor device according to claim 6, wherein substantially the entire work holding surface of the head is porous. 8. The mechanical action force between the head and the polishing cloth is used together in the flattening step, and the action force of the pressing gas is 50 times the magnitude of the mechanical action force of the head. 7. The method for manufacturing a semiconductor device according to claim 6, wherein the percentage is set to 100% to 130%. 9. The method of manufacturing a semiconductor device according to claim 6, wherein a pad having a plurality of communication passages is provided on substantially the entire surface between the work holding surface of the head and the back surface of the semiconductor wafer. . 10. The method of manufacturing a semiconductor device according to claim 9, wherein the distribution of the communication passage groups in the flattening step is different in the region of the back side surface of the semiconductor wafer. 11. A semiconductor wafer is held by a head on the back side of the surface to be polished on the work holding surface of the head directly or via a pad, and the pressing gas is supplied from substantially the entire work holding surface of the head. At least a part of the semiconductor wafer is supplied in a state of being scattered to the outside from the back side surface of the semiconductor wafer so that the surface to be polished is quasi-statically pressed against the polishing cloth and the polishing material is relatively moved while being supplied. A method for manufacturing a semiconductor device, which comprises flattening irregularities on a polished surface. 12. A head holding surface of a semiconductor wafer is held by a head on the back side of the surface to be polished, directly or via a pad, on a work holding surface where at least a part of the head is made porous. In a state in which the surface to be polished is quasi-statically pressed against the polishing cloth by supplying a pressing gas from at least a porous portion of the semiconductor wafer in a state in which at least a part of the gas is dissipated from the periphery of the back surface of the semiconductor wafer to the outside. A method of manufacturing a semiconductor device, characterized in that the polishing material is relatively moved while being supplied to flatten the irregularities on the surface to be polished. 13. A head for holding a plate-shaped work in a state where a surface to be polished is exposed, and a polishing tool having an abrasive surface on one main surface, the work being held by the head being polished. In a polishing apparatus in which a surface is rubbed against an abrasive material surface of an abrasive tool to perform polishing, the head distributes a pressing gas to substantially the entire back surface of the workpiece, and a pressing gas to the distributing member. And a gas supply path for supplying the gas. 14. The polishing apparatus according to claim 13, wherein the distribution member is made of porous ceramic or foamed resin. 15. The polishing apparatus according to claim 13, wherein the distribution member is divided into a plurality of sections in the cross section. 16. A polishing tool for a workpiece held by the head, comprising: a head for holding a plate-shaped workpiece with a surface to be polished exposed; and a polishing tool having a polishing material surface on one main surface. In a polishing apparatus in which a surface is rubbed against an abrasive material surface of an abrasive tool to perform polishing, the head distributes a pressing gas to substantially the entire back surface of the workpiece, and the work is made of a material having elasticity. And a gas supply path for supplying a pressing gas to the distribution member. 17. The polishing apparatus according to claim 16, wherein a communication passage communicating with the pad in the thickness direction is opened over substantially the entire surface. 18. The polishing apparatus according to claim 17, wherein the densities of the work-side opening areas of the communication passage groups are different at the back side surface of the work.