JPH09275085A - Semiconductor substrate cleaning method, cleaning apparatus, semiconductor substrate manufacturing film forming method, and film forming apparatus - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To clean a high aspect ratio contact hole or a high step portion without leaving a watermark. SOLUTION: Wet cleaning, vacuum drying and dry cleaning are performed.
Do in this order. Further, after the dry cleaning, the cleanliness of the object to be cleaned is inspected, and if the standard value is not reached, at least part of the cleaning process is re-executed. [Effect] The yield of electronic parts such as semiconductor devices can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning technique for cleaning the surface of a semiconductor substrate such as a semiconductor wafer in a manufacturing process of a semiconductor device, and more particularly to an element having a contact hole with a high aspect ratio or a high step portion. The present invention relates to a cleaning method and a cleaning apparatus that prevent the generation of watermarks that tend to occur during cleaning, and a film forming method and a film forming apparatus using the cleaning method.

[0002]

2. Description of the Related Art In recent years, the degree of integration of integrated circuits formed on the surface of a semiconductor substrate such as a semiconductor wafer has been increasing, and the line width of patterns has been miniaturized. For example, 6
4Mbit DRAM (Dynamic Random Access Memory)
Has a minimum processing size of 0.3 μm and 256 MbitD
The minimum processing size of RAM is 0.2 μm. Therefore, even a slight amount of contamination (contamination of foreign matter / metal, contamination of organic matter, etc.) in the manufacturing process significantly reduces the quality and yield of those products.

For cleaning the semiconductor substrate, for example, as described in RCA Review, Vol. 31, pp. 187-206 (1970), a mixture of ammonia water and hydrogen peroxide water, Cleaning by a method of heating a mixture of hydrochloric acid and hydrogen peroxide solution to about 80 ° C. and immersing the wafer in this (RCA cleaning) is generally performed. Such a cleaning method is called wet cleaning because the surface of the substrate is cleaned by bringing it into contact with a solution. As a method of drying the substrate after wet cleaning,
Spin drying utilizing centrifugal force or vapor drying using alcohol (mainly isopropyl alcohol) is used.

When this wet cleaning method is used, a factor that greatly reduces the yield is a stain after drying called a watermark. The watermark is a natural oxide film formed during drying, or a residue left on the surface of the substrate after the natural oxide film is dissolved in the liquid and dried. For example, when the polysilicon film is etched after cleaning, the watermark cannot be etched because only the watermark part is an oxide film, and thus causes defects in a wide range, which is a major problem in semiconductor cleaning technology. There is. Water marks are considered to be particularly likely to be formed in contact holes and high stepped portions, and various techniques have been made in the prior art, such as shortening the time required to start drying after cleaning and increasing the drying speed. .

Also, unlike wet cleaning, a method of removing contaminants on the surface of the object to be cleaned by reacting active molecules and active atoms excited by plasma, light, heat, etc. with contaminants in the gas phase ( The dry cleaning method) is also used for cleaning the substrate. Although this dry cleaning method is not generally used for mass production of semiconductor substrates yet, it is effective for removing metal contamination, organic contamination, and natural oxide film, and at the research level, some technologies have already been used. Proposed.

For example, with respect to metal contamination, Japanese Patent Laid-Open No. 62-
The cleaning method of irradiating chlorine gas with ultraviolet light, which is described in Japanese Patent No. 42530, has been disclosed in Japanese Patent Application Laid-Open No. Hei 4 (1999) -4
Japanese Patent Laid-Open No. 6-338478 discloses a cleaning method for dry etching with oxygen gas activated by plasma, which is described in JP-A-75324, and a natural oxide film which is a component of a watermark. There are known cleaning methods and the like in which dry etching is performed using nitrogen trifluoride activated by plasma.

[0007]

With the high integration of the substrate, the hole diameter of the contact hole has become as fine as the wiring width, but the hole depth tends to become deeper. The ratio (aspect ratio) is increasing more and more. Further, with the miniaturization of the wiring, it is necessary to increase the height of the wiring in order to reduce the wiring resistance as much as possible, and therefore the high step portion tends to increase.

It is difficult to sufficiently dry the inside of such a contact hole and the high step portion after being immersed in the liquid. Therefore, even if the above-mentioned spin drying or vapor drying is performed after performing wet cleaning, the liquid in the contact hole or in the high step portion cannot be sufficiently dried, and the liquid remains easily. In the case of spin drying, the liquid in the contact hole or the high step portion cannot be ejected by the centrifugal force. Further, in the case of vapor drying using isopropyl alcohol, the liquid in the contact hole or the high step portion cannot be smoothly replaced with alcohol vapor, so that sufficient drying cannot be performed.

Therefore, as a result, long-term natural drying is required. Therefore, when the degree of integration of the substrate becomes higher than the current level, a larger amount of the natural oxide film, that is, the watermark, which is still a big problem than the conventional level, is generated.
It is expected that the yield will be significantly reduced and the manufacture of semiconductor devices will be hindered.

However, since the liquid is not used, it is difficult to remove the contamination due to the minute foreign matter only by the dry cleaning which does not generate the watermark, and in order to remove the foreign matter attached to the substrate surface, the wet method is used. Cleaning cannot be avoided.

Therefore, in order to obtain a clean surface free from watermarks, a technique has been proposed in which after the wet cleaning, the substrate surface is further processed to remove the watermarks. For example, JP-A-61-212375 describes a cleaning method in which dry cleaning is continuously performed after wet cleaning. However, this method cannot completely remove a large amount of watermarks formed in the contact holes of the highly integrated substrate or in the step portion. in this way,
Before the dry cleaning, a large amount of watermarks are formed in the contact hole with a high aspect ratio or in the high step portion, and a considerably violent reaction must be used to completely remove the watermark. However, contact holes are often formed in an insulating film (silicon oxide film), and both the watermark and the insulating film are made of silicon oxide.
The insulating film will be etched.
As described above, if a large amount of watermarks are removed by dry cleaning, the semiconductor element will be damaged by etching the portion other than the watermark (eg, the insulating layer). Therefore, it is not practical to use such a method for a highly integrated substrate.

Therefore, Japanese Patent Laid-Open Nos. 63-45822 and 5-90239 propose a technique of vapor-drying or spin-drying a substrate between wet cleaning and dry cleaning. In the cleaning method described in JP-A-63-45822, after wet cleaning, the substrate is dried by a steam drying method using isopropyl alcohol,
Then, the wafer is heated in a fluorine or hydrogen fluoride gas atmosphere to remove the watermark. Further, in the cleaning method described in JP-A-5-90239,
After wet cleaning, spin drying is performed, and then dry cleaning with vapor of hydrogen fluoride is performed.

However, as described above, it is difficult to sufficiently dry the inside of the contact hole having an aspect ratio of 5 or more by the vapor drying method or the spin drying method. Therefore, even if dry cleaning is performed after performing wet cleaning and drying by these methods, if the aspect ratio of the contact hole becomes high, a large amount of watermarks will remain after drying, and thus it will be removed by dry cleaning. Because I can't
There arises a problem that the watermark remains in the contact hole having an aspect ratio of 7 or more.

Therefore, the present invention solves the above-mentioned problems in the prior art and realizes high cleanliness of a substrate surface, and a cleaning apparatus, and by using the cleaning method,
An object of the present invention is to provide a film forming method and a film forming apparatus for forming a film having good film characteristics.

[0015]

In order to achieve the above object, in the present invention, a wet cleaning step of removing contaminants on the surface of the object to be cleaned by contacting with a cleaning liquid, and decompression of the atmosphere around the object to be cleaned. According to the above, there is provided a semiconductor substrate cleaning method including a drying step of drying the surface of the object to be cleaned and a dry cleaning step of removing contaminants on the surface of the object to be cleaned by dry etching in this order. Furthermore, in the present invention, a cleaning apparatus for cleaning a semiconductor substrate using the cleaning method of the present invention, a film forming method for a semiconductor substrate that forms a film after cleaning by the cleaning method of the present invention, and the film forming method And a film forming apparatus using the same.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the cleaning method of the present invention, a wet cleaning is followed by drying by a vacuum drying method and then a dry cleaning method. As a result of intensive studies on the mechanism of watermark generation and its prevention method, the inventors of the present invention are expected to become a very serious problem in the future by combining wet cleaning, vacuum drying, and dry cleaning in this order. We have found that it is possible to completely prevent the occurrence of watermarks. The present invention is based on this finding.

The vacuum drying method can rapidly dry the liquid remaining in the contact hole having a high aspect ratio or in the high step portion, so that the amount of watermarks can be significantly reduced. However, in the vacuum drying method, the cleaning liquid (or rinse liquid) remaining on the substrate surface in wet cleaning is removed by evaporation, so that the contaminants present in the liquid are deposited as the liquid evaporates and adhere to the substrate surface. I will end up. Therefore, in the present invention, in order to completely remove these contaminations and watermarks, dry cleaning is performed after vacuum drying. In the present invention, perfect cleaning is realized by performing wet cleaning, vacuum drying, and dry cleaning in this order.

Next, the cleaning method of the present invention will be described with reference to FIG. (1) Wet Cleaning Step First, the foreign matter 3 (FIG. 1A) attached to the surface of the object to be cleaned (semiconductor substrate) 100 is removed by wet cleaning (FIG. 1B).

(2) Vacuum drying step After wet cleaning, contact hole 1 with high aspect ratio
The water (cleaning liquid) 4 remaining inside or in the high step portion 2 is dried by vacuum drying. Here, vacuum drying means reducing the pressure of the atmosphere around the object to be cleaned (preferably vacuum),
This is a drying method that promotes evaporation of the liquid, and if the object to be cleaned or the atmosphere is heated during depressurization, it can be dried more efficiently and in a short time. The degree of vacuum is 100 mm
Hg is preferably 10 to 12 mmHg and 10
It is particularly preferable to set it to mmHg to 10-12 mmHg.

(3) Dry Cleaning Step After drying, the watermark 5 and the residue 6 of contamination (metal contamination and organic contamination) contained in the water 4 are removed by dry etching. Specific examples of this dry cleaning step include a step of exposing the substrate to a chlorine-based gas activated by plasma or ultraviolet rays, a step of exposing the substrate to oxygen gas or ozone gas activated by plasma or ultraviolet rays, and a step activated by plasma. And a step of exposing the substrate to a fluorine-based gas activated by plasma, and the like. As the dry cleaning step, any one of these steps may be used, but it is preferable to combine two or more of these steps because the substrate surface can be cleaned more efficiently.

The drying process and the dry cleaning process may be performed in the same chamber. Further, a step of roughly removing the cleaning water remaining on the wafer surface by a conventional method such as steam drying or spin drying may be further provided between the wet cleaning step and the drying step. This is preferable because the time for vacuum (reduced pressure) drying can be shortened.

According to the present invention, it is possible to prevent the formation of a watermark on the inner wall of a contact hole having an aspect ratio of 7 or more, which could not be prevented by the conventional technique. . Therefore,
The cleaning method and the cleaning apparatus of the present invention are particularly suitable for cleaning a semiconductor substrate having a contact hole with an aspect ratio of 7 or more. The film forming method of the present invention is particularly suitable for manufacturing a semiconductor substrate having such a high aspect ratio contact hole. The present invention can be applied to both batch processing and single wafer processing of substrates.

Further, according to the present invention, a method for forming a semiconductor substrate is provided with a cleaning step for cleaning the surface of the substrate by the above-described cleaning method of the present invention and a film forming step for forming a film on the surface in this order. Will be provided. A vapor phase growth method (for example, CVD (chemical vapor deposition) or sputtering) can be used for forming the film. The formed film includes a nitride film, an oxide film, a conductor (for example, aluminum) film, and the like. According to the cleaning method of the present invention, a very clean surface can be obtained. Therefore, according to the film forming method of the present invention in which the surface is cleaned by the cleaning method of the present invention and the film is formed, the yield of film formation can be increased.

A semiconductor substrate is usually manufactured by repeating seven kinds of steps of a cleaning step, an oxidation step, an ion implantation step, a film forming step, an annealing step, a lithography step and an etching step in a predetermined order, The semiconductor element is manufactured by a passivation process and an assembling process for the semiconductor substrate thus obtained. The present invention also provides a method of manufacturing a semiconductor substrate or a semiconductor element using the above-described cleaning method of the present invention in the cleaning step.

Furthermore, the present invention provides a cleaning apparatus used in the above-described cleaning method of the present invention. The cleaning device of the present invention comprises a wet cleaning tank for wet cleaning, a cleaning liquid supply mechanism for supplying a cleaning liquid to the wet cleaning tank,
A drying chamber having a vacuum suction port for sucking the atmosphere in the chamber to reduce the pressure is provided, a dry cleaning chamber for dry cleaning, and an etching mechanism for performing dry etching in the dry cleaning chamber. The etching mechanism includes, for example, a gas supply mechanism that supplies a gas into the dry cleaning chamber and an activation mechanism that generates plasma or ultraviolet rays to activate the gas, or a gas supply mechanism inside the dry cleaning chamber. There is a gas supply mechanism for supplying the gas and a heating mechanism for heating the object to be cleaned held in the dry cleaning chamber.

It should be noted that one chamber may be commonly used as the drying chamber and the dry cleaning chamber. That is, the cleaning apparatus of the present invention includes a wet cleaning tank, a cleaning liquid supply mechanism, a dry cleaning chamber including a vacuum suction port,
An etching mechanism may be provided. Also,
An appropriate transport mechanism may be provided between the wet cleaning tank and the drying chamber and between the drying chamber and the dry cleaning chamber. Since the drying efficiency can be further improved, it is desirable to provide a means for heating the article to be cleaned during the drying.

If the cleaning apparatus of the present invention further includes a monitor mechanism for re-executing at least a part of the cleaning process according to the cleanliness of the substrate surface, the cleanliness of the surface to be cleaned can be kept constant. It is preferable because it can be maintained at the level of.
Examples of the configuration of this monitor mechanism include a sensor that detects the cleanliness of the surface of the object to be cleaned after the dry cleaning process, a return transport unit that returns the object to be cleaned to the dry cleaning tank, and the cleaning detected by the sensor. If the degree does not reach a predetermined value, the return conveying means may include a control means for returning the object to be cleaned to the dry cleaning tank. Instead of the dry cleaning tank, it may be returned to the wet cleaning tank.

Further, the present invention provides a film forming apparatus comprising a film forming mechanism and the cleaning apparatus of the present invention. The film forming mechanism includes a mechanism for forming a film by a vapor phase growth method.
Some include a film forming chamber for forming a film and a mechanism for forming a film on the surface of the substrate in the film forming chamber by a vapor phase growth method. Mechanisms for forming a film on the surface of the substrate by the vapor phase growth method include, for example, a mechanism for forming a film by CVD, a mechanism for forming a film by plasma CVD, and a mechanism for forming a film by sputtering. The film forming chamber of the film forming mechanism and the dry cleaning chamber or the drying chamber of the cleaning device may be realized by sharing one chamber.

It is desirable that this film forming apparatus also includes the above-mentioned monitor mechanism. When the film forming apparatus is provided with a monitor mechanism, a feed / conveyance mechanism is provided between the film forming chamber of the film forming mechanism and the dry cleaning chamber of the cleaning device, and the controller determines the cleaning degree detected by the sensor in advance. If the value does not reach the value, the return conveyance means returns the object to be cleaned to the dry cleaning tank, and if the cleaning degree detected by the sensor has reached a predetermined reference value, the feed conveyance means after cleaning. It is desirable to transfer the substrate to the film forming chamber. When the cleaning degree does not reach the reference value, the object to be cleaned may be returned to the wet cleaning tank instead of the dry cleaning tank.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. In the following examples, the silicon wafer is used as the cleaning object, but the cleaning object of the cleaning method of the present invention is not limited to this.

(Examples 1 to 3) In Examples 1 to 3, FIG.
As shown in (a), a silicon wafer 7 having a diameter of 6 inches having a plurality of contact holes 8 (hole diameter 0.5 μm) having different depths was used as an object to be cleaned, and the following experiment was conducted.

A. Cleaning Device First, the cleaning device used in this embodiment will be described. As shown in FIG. 3, the cleaning apparatus of the present embodiment includes a dry cleaning chamber 10, a gas supply mechanism 13 for supplying gas into the dry cleaning chamber, and an activation mechanism for activating the gas (to generate plasma. The microwave power supply 15 and the ultraviolet lamp 16) for irradiating ultraviolet rays, and the vacuum exhaust device 18 for sucking the atmosphere in the chamber 10 to reduce the pressure.

A sample heating table 12 is provided in the dry cleaning chamber 10. Further, the chamber 10 has a vacuum suction port 18a for reducing the pressure inside and the ultraviolet lamp 1
A quartz window 17 for transmitting the light emitted from No. 6 and a gas introduction port 14a for introducing gas into the chamber are provided. The vacuum suction port 18a communicates with the vacuum exhaust device 18. The gas inlet 14a is in communication with the cavity 14, and the cavity 14 is in communication with the gas supply mechanism 13 and the microwave power supply 15.

In the cleaning apparatus of this embodiment, when the cleaning gas is excited by plasma in dry cleaning,
A cleaning gas may be introduced into the chamber 10 by the gas supply mechanism 13 and plasma may be generated by the cavity 14. When the cleaning gas is excited by ultraviolet rays, the cleaning gas may be introduced into the chamber 10 by the gas supply mechanism 13 and the chamber 16 may be irradiated with ultraviolet rays by the lamp 16.

B. Cleaning Step Next, the cleaning method of this embodiment will be described. First,
The wafer 7 was wet cleaned using a cleaning liquid. That is, 27 wt% ammonia water, 30 wt% hydrogen peroxide water, and water are mixed at a volume ratio of 1: 1: 5,
As a cleaning liquid, the temperature of this cleaning liquid was maintained at 80 ° C., the wafer 7 was immersed in this cleaning liquid for 10 minutes, and then washed in ultrapure water for 10 minutes. The cleaning liquid used in this example is called an RCA cleaning liquid, and is effective in removing foreign matters adhering to the silicon wafer.

Next, the wafer 7 was dipped in a 0.25 wt% hydrofluoric acid aqueous solution for 30 seconds and washed with ultrapure water for 10 minutes to remove the natural oxide film at the bottom of the contact hole. .

Next, the wafer 7 is dried by the spin drying method and immediately placed on the sample heating table 12 of the above-mentioned cleaning device,
The vacuum evacuation device 18 is operated and the chamber 1 is operated for 10 minutes.
After keeping the inside of the vacuum at 0, a cleaning gas is introduced from the gas supply mechanism 13 and plasma is generated by the cavity 14, or ultraviolet light is irradiated by the lamp 16 in accordance with the dry etching method used. The cleaning gas was excited to dry-clean the wafer 7. The chamber atmosphere during vacuum drying and the wafer 7 were not heated at room temperature.

C. Film Forming Step As shown in FIG. 2B, a polysilicon film 9 is formed on the surface of the silicon wafer 7 cleaned by the cleaning method described above by the CVD method and patterned by lithography, and then the contact resistance is measured. . Actually, several contact holes with respective aspect ratios shown in FIG. 2 are formed in the direction perpendicular to the paper surface, and the contact resistance was evaluated from the series resistance thereof.

Table 1 shows the dry etching method used in each example and the measured contact resistance ratio. The contact resistance ratio is the ratio of the aspect ratio 3 to the contact resistance value when vacuum drying and dry cleaning are not performed (Comparative Example 1).

[0040]

[Table 1]

In Examples 1 to 3 in which both vacuum drying and dry cleaning were performed, the contact resistance did not change even in a contact hole having a large aspect ratio, and the effect of the present invention could be demonstrated.

Comparative Example 1 In this comparative example, a silicon wafer provided with the polysilicon film 9 was prepared in the same manner as in Examples 1 to 3 except that vacuum drying and dry cleaning were not performed. That is, in this comparative example, after wet cleaning, the wafer was dried only by spin drying, the polysilicon film 9 was formed as it was, and the contact resistance of the obtained wafer was measured. The results are shown in Table 1.

As can be seen from Table 1, in the wafer of this comparative example, when the aspect ratio of the contact hole was larger than 5, the contact resistance became extremely large. This is because water remains in the contact hole,
This is because a large amount of watermarks are formed with natural drying.

(Comparative Examples 2 to 4) Further, in order to confirm the effect of vacuum drying and dry cleaning independently, Example 1 was carried out except that either vacuum drying or dry cleaning was not performed. A silicon wafer provided with the polysilicon film 9 was prepared in the same manner as in steps 3 to 3. Table 2 shows the vacuum drying time, the dry etching method for dry cleaning, and the experimental results in each comparative example.

[0045]

[Table 2]

From Table 2, in the case of only vacuum drying (Comparative Example 2), contact holes having an aspect ratio of 7 or more gave better values than those of Comparative Example 1, but 10 times as much as those in the case of Aspect Ratio 3. The above high resistance value is shown, and it is understood that a sufficient cleaning effect is not obtained. Further, in the case of only dry cleaning (Comparative Examples 3 and 4), Comparative Example 2 of only vacuum drying
Although the result is better than that of No. 1, the resistance value considerably increases as the aspect ratio increases. From the results of Comparative Examples 2 to 4, it was found that the watermark cannot be completely prevented when the vacuum drying and the dry cleaning are individually performed without combining them.

(Examples 4 to 6) Next, in order to examine the time dependency of vacuum drying, the contact resistance was measured in the same manner as in Example 2 except that the drying time was changed. Table 3 shows the drying time and the obtained results in each example.

[0048]

[Table 3]

As can be seen from Table 3, the longer the drying time, the better the results, but the vacuum drying time was 2.
Even if it is 5 minutes, the contact resistance ratio in the case of the aspect ratio 7 is 1.5, which is a sufficient effect, and if it is 7.5 minutes or more, almost the same good result as in Example 2 is obtained. .

(Examples 7 to 10) In this example, the effect of heating the object to be cleaned during vacuum drying was examined. That is, in this example, the wafer was heated by the sample heating table 12 during vacuum drying and held at 100 ° C.
The cleaning effect was evaluated in the same manner as in Example 6 and Example 2.
The results are shown in Table 4.

[0051]

[Table 4]

As shown in Table 4, it was found from this example that by heating the wafer 7, good results can be obtained in a shorter time than at room temperature. That is, if the wafer 7 is kept at about 100 ° C. during vacuum drying, a very good effect can be obtained even by vacuum drying for 5 minutes or less. Therefore, if the wafer 7 is heated during vacuum drying, the throughput of the cleaning process can be improved.

(Embodiment 11) As shown in FIG. 4, a silicon wafer 7 having a plurality of concave portions 40 each having a square bottom surface of 30 μm in length and width and a step difference of 0.5 μm from the main surface 41 was prepared and carried out. As in Example 1, wet cleaning, spin drying, and vacuum drying were performed in this order, and the surface of the wafer 7 was observed with an electron microscope. No watermark was found at all. Since the watermark is a natural oxide film, it looks up with an electron microscope and looks different from other parts. Therefore, the watermark can be identified based on this difference in appearance.

(Comparative Example 5) A silicon wafer 7 having the same pattern as that used in Example 1 was subjected to wet cleaning and spin drying in the same manner as in Comparative Example 1, and its surface was observed by an electron microscope. A plan view of the observed silicon wafer 7 is shown in FIG. 5A, and a partially enlarged view thereof is shown in FIG.
(B). As shown in FIG. 5B, the watermark 5 was observed on the step portion 2 of the recess 40.

(Examples 12 to 18) In this example, it was confirmed that the cleaning method of the present invention can effectively remove metal contamination or organic contamination. That is, except that the same dry etching method as shown in Table 5 was used after preliminarily contaminating the same silicon wafer 7 as in Example 11, Example 1
In the same manner as in No. 1, each process of wet cleaning, spin drying, and vacuum drying was performed in this order.

Also in the wafer 7 cleaned in this example, the watermark 5 was not observed, as in Example 11. When the amount of contamination on the surface of the wafer 7 after cleaning was measured, as shown in Table 5, almost no contamination was detected. The amount of metal contamination was measured by the total reflection X-ray fluorescence method, and the amount of organic contamination was measured by Auger electron spectroscopy.

[0057]

[Table 5]

Contamination by metal ions is caused by Ni, F
The standard reagents for atomic absorption of e and Cu were used respectively. That is, the wafer 7 was dipped in an aqueous solution adjusted to have a metal amount of 0.1 ppm for 10 minutes, further dipped in ultrapure water for 10 minutes, and then dried by a spinner. Further, the organic matter was polluted by using a 10 ⁻⁴ mol / L aqueous solution of a surfactant (triethanolamine dodecyl sulfate) and similarly scattering it on the wafer 7.

(Comparative Examples 6 to 9) The wafer 7 contaminated in the same manner as in Examples 12 to 18 was wet-cleaned and spin-dried in the same manner as in Comparative Example 5, and then vacuum-dried and dry-cleaned without performing. When the amount of contamination on the surface was measured in the same manner as in Examples 12 to 18, it was found that, as shown in Table 5, the residual amount of contaminant was much higher than that in Examples 12 to 18. It is considered that this is because the cleaning liquid and / or the rinse liquid containing the contaminants remain on the step portion, and the contaminants remain on the wafer 7 as it naturally dries.

(Example 19) In this example, the surface of a silicon wafer was cleaned by single-wafer processing. The cleaning apparatus used in this example is shown in FIG.

The cleaning apparatus used in the present embodiment is the same as the cleaning apparatus used in the first embodiment except that the dry cleaning chamber 1 is used.
0, which is in communication with 0 through a gate valve 23
And an evacuation device 18 for reducing the pressure in the preparation chamber 20.
b, a single-wafer wet cleaning chamber 19 communicating with the preparation chamber 20, a cleaning liquid supply mechanism 60 for supplying a cleaning liquid and a rinse liquid 61 into the single-wafer wet cleaning chamber 19, and a wafer between the chambers 19, 20, and 10. And a transport mechanism (not shown) for transporting 7. The single-wafer wet cleaning chamber 19 includes a spinner 22 inside.

In the cleaning apparatus of this embodiment, as in the apparatus of the first embodiment, when the cleaning gas is excited by plasma in the dry cleaning, the cleaning gas is introduced into the chamber 10 by the gas supply mechanism 13. The plasma may be generated by the cavity 14. When the cleaning gas is excited by ultraviolet rays, the cleaning gas may be introduced into the chamber 10 by the gas supply mechanism 13 and the chamber 16 may be irradiated with ultraviolet rays by the lamp 16.

Next, the cleaning method of this embodiment will be described. First, the wafer 7 is fixed on the mounting table of the spinner 22 of the single-wafer wet cleaning chamber 19, and the cleaning liquid supply mechanism 6
The cleaning liquid and the ultrapure water 61 were sequentially sprayed from 0 to wet-clean the wafer 7. Next, by rotating the mounting table of the spinner 22, the rinse liquid remaining on the surface of the wafer 7 was removed and spin drying was performed.

Next, the wafer 7 is moved into the preparation chamber 20 by the transfer mechanism, the vacuum chamber 18b is operated to evacuate the preparation chamber, the valve 23 is opened, and the wafer 7 is dried in the dry cleaning chamber by the transfer mechanism. The wafer 7 was transferred to the sample heating table 12 in 10 and the vacuum evacuation device 18 was operated while maintaining the wafer 7 at 100 ° C. to increase the degree of vacuum in the chamber 10 and maintain the degree of vacuum.

When the water content in the contact hole of the wafer 7 is sufficiently removed, hydrogen gas is introduced as a cleaning gas by the gas supply mechanism 13 and hydrogen gas for generating plasma is generated by the cavity 14, as in the tenth embodiment. The wafer 7 was excited and dry-cleaned.

When the polysilicon film 9 was formed on the wafer 7 cleaned as described above and the contact resistance was measured, as in the case of Example 10,
Good results were obtained.

(Embodiment 20) In this embodiment, the surface of a silicon wafer is cleaned by batch processing. The cleaning device used in this example is shown in FIG.

The cleaning apparatus used in this embodiment is the same as the cleaning apparatus used in Embodiment 1 except that the dry cleaning chamber 1 is used.
0 through the gate valve 23 in the vacuum drying chamber 2
7, a vacuum evacuation device 18c for reducing the pressure in the vacuum drying chamber 27, a batch wet cleaning chamber 24 in communication with the vacuum drying chamber 27, and a wafer 7 to be transferred between the chambers 24, 27 and 10. Transport mechanism (not shown). The batch wet cleaning chamber 19 has an internal R
A CA cleaning tank 25 and a water washing layer (not shown), a hydrofluoric acid cleaning tank 26 and a water washing layer (not shown), and a transfer mechanism (not shown) for transferring the wafer 7 between the tanks are provided. .

Next, the cleaning method of this embodiment will be described. Before the cleaning, the batch wet cleaning chamber 2
The RCA cleaning tank 25 of No. 4 was filled with the same RCA cleaning solution as in Example 1, and the hydrofluoric acid cleaning tank 26 was filled with hydrofluoric acid (about 0.25).
%), And each washing layer is filled with water.

First, the batch type wet cleaning chamber 24 is made up of a set of 50 wafers (hereinafter referred to as a wafer group).
Of the RCA cleaning tank 25 for 10 minutes, then for 10 minutes in the water washing layer, for 30 seconds in the hydrofluoric acid cleaning tank 26, and then for 30 seconds in the water washing layer. The hydrofluoric acid cleaning may be omitted.

Next, the wafer group is transferred to the vacuum drying chamber 27 by the transfer mechanism, the vacuum evacuation device 18c is operated to evacuate the vacuum drying chamber 27 for 10 minutes, and then the valve 23 is opened to transfer the wafer. The wafer 7 was transferred onto the sample heating table 12 in the dry cleaning chamber 10 by the mechanism, and dry cleaning was performed in the same manner as in Example 19. Note that, also in this embodiment, the dry cleaning is a single-wafer processing, as in the nineteenth embodiment.

When the polysilicon film 9 was formed on the wafer 7 washed as described above and the contact resistance was measured, as in the case of Example 10,
Good results were obtained.

(Embodiment 21) In this embodiment, the surface of a silicon wafer is cleaned and a film is formed by using the film forming apparatus shown in FIG.

The film forming apparatus used in this embodiment includes a load / unload unit 28, a cleaning unit 29, a monitor mechanism 30,
The film forming unit 80. The load / unload unit 28 and the cleaning unit 29, and the cleaning unit 29 and the film forming unit 80 are communicated with each other through the gate valve 23, and a transfer mechanism for transferring the wafer 7 is provided. (Not shown).

The load / unload unit 28 is a chamber for loading and unloading the silicon wafer 7 to be processed. The cleaning unit 29 is a mechanism that performs wet cleaning, vacuum drying, and dry cleaning of the wafer 7 by single-wafer processing.
It has the same structure as the cleaning apparatus of the nineteenth embodiment. The monitor mechanism 30 is attached to the cleaning unit 29 and is a mechanism for keeping the cleanliness of the surface of the wafer 7 after dry cleaning constant.

First, the monitor mechanism 30 in this embodiment will be described. The hardware structure of the monitor mechanism 30 of this embodiment is, as shown in FIG.
And the main memory 101 and the central processing unit (CP
U) 102 and an information processing device 103.

As shown in FIG. 9, the monitor mechanism 30 of this embodiment is connected to a sensor 91 for detecting the cleanliness of the surface of the wafer 7 after dry cleaning and a transfer mechanism 94 of the cleaning section 29 via a line. And a control means 93 for controlling the return transportation means 92 according to the detection result of the sensor. In the present embodiment, the return conveyance means 92 and the control means 9
3 is realized by the CPU 102 executing an instruction previously stored in the main storage device 101. However, the present invention is not limited to this, and may be realized by other means such as a dedicated circuit.

The return transfer means 92 is a means for returning the wafer 7 after dry cleaning onto the spinner 22 in the single wafer wet cleaning chamber 19 by operating the transfer mechanism 94 of the cleaning section 29 in the reverse direction. The dry cleaning may be performed again by returning to the dry cleaning chamber 10 (or the preparation room 20).

The control means 93 is activated at the end of dry cleaning. When the control means 93 is activated as shown in FIG. 11, first, the cleanliness of the surface of the wafer 7 after the dry cleaning is read through the sensor 91 (step 111), and the read cleanliness is a predetermined criterion. The value is compared (step 112). If the cleaning value is equal to or higher than the reference value, the control unit 93 activates the transfer mechanism to the film forming unit 80, sends the wafer 7 to the film forming unit 80, and ends the process (step 1).
13). If it is polluted from the reference value, the control means 93
Causes the return transfer means 92 to return the wafer 7 to the wet cleaning chamber 19 and ends the process (step 11).
4). By this control means 93, the film forming apparatus 3 of the present embodiment
When 0, it is guaranteed that the surface of the wafer used for film formation is always cleaner than the reference value.

Next, the film forming unit 80 of this embodiment will be described. As shown in FIG. 8, the film forming unit 80 of the present embodiment is
The film forming chamber 31, a gas supply mechanism 13a for supplying gas into the chamber 31, a heating lamp 32 for heating the inside of the chamber, and a vacuum exhaust device 18d for depressurizing the inside of the chamber 31 are provided. In the film forming chamber 31,
A sample table 33 is provided.

As a result of the above step 113, the cleaned wafer 7 is placed on the sample stage 33 in the film forming chamber 31 by the transfer mechanism. In response to this, the film forming unit 80 of the present embodiment forms a film on the surface of the substrate by CVD. That is,
After the atmosphere in the chamber 31 is sucked by the vacuum evacuation device 18d, the gas of the film raw material is introduced into the film forming chamber 31 by the gas introducing mechanism 13a and the wafer 7 is heated by the heating lamp 32. Can be formed. Note that a film can be formed by plasma CVD if a mechanism for generating low temperature plasma is provided. In addition, an electrode or microwave power source 15 to which a high voltage can be applied
If a mechanism for generating plasma such as the above and a target holding unit are provided, the film can be formed by sputtering.

[0082]

According to the present invention, the above-mentioned problems in the prior art can be solved, and after wet cleaning, the inside of a contact hole having a high aspect ratio or a high step can be efficiently dried without leaving a watermark. Therefore, a highly clean semiconductor substrate can be obtained. Therefore, according to the present invention, since an element having a high aspect ratio contact hole or a high step portion can be highly cleanly cleaned without a watermark, the yield of electronic parts such as a semiconductor device can be increased and the cost can be kept low. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the cleaning principle of the present invention.

FIG. 2 is a partial cross-sectional view of a silicon wafer for showing a state of a contact hole in Example 1.

FIG. 3 is an explanatory diagram showing a configuration of a cleaning device according to a first embodiment.

FIG. 4 is a partial cross-sectional view of a silicon wafer used in Example 11.

5A and 5B are a plan view and an electron microscope image schematic view showing the surface of a silicon wafer after cleaning in Comparative Example 5.

FIG. 6 is an explanatory diagram showing the structure of a cleaning apparatus according to a nineteenth embodiment.

FIG. 7 is an explanatory diagram showing the structure of a cleaning device according to a twentieth embodiment.

FIG. 8 is an explanatory diagram showing the structure of a cleaning apparatus according to a twenty-first embodiment.

FIG. 9 is a functional configuration diagram of a monitor mechanism according to a twenty-first embodiment.

FIG. 10 is a hardware configuration diagram of a monitor mechanism of Example 21.

FIG. 11 is a flowchart showing the processing of the monitor mechanism of the twenty-first embodiment.

[Explanation of symbols]

1 ... Contact hole, 2 ... High step, 3 ... Foreign matter, 4 ...
Water, 5 ... Water mark, 6 ... Contamination, 7 ... Silicon wafer, 8 ... High aspect ratio contact hole, 9 ... Polysilicon film, 10 ... Dry cleaning chamber, 12 ... Sample heating table, 13, 13a ... Gas supply mechanism, 14 ... cavity,
14a ... Gas introduction port, 15 ... Microwave power source, 16 ... Ultraviolet lamp, 17 ... Quartz window, 18, 18b-d ... Evacuation device, 18a, 18e ... Vacuum suction port, 19 ... Single wafer wet cleaning chamber, 20 ... Preparation room, 22 ... Spinner, 2
3 ... Gate valve, 24 ... Batch wet cleaning chamber, 25 ... RCA cleaning tank, 26 ... Hydrofluoric acid cleaning tank, 27 ...
Vacuum drying chamber 28 ... Load / unload unit, 29 ... Cleaning unit, 30 ... Monitor mechanism, 31 ... Film forming chamber, 32 ... Heating lamp, 33 ... Sample stage, 40 ... Sample recess, 41 ... Sample main surface, 60 ... cleaning liquid supply mechanism, 61 ... cleaning liquid or rinse liquid, 80 ... film forming part, 91 ... sensor, 92 ... return transport means, 93 ... control means, 94 ... transport means, 100 ... semiconductor substrate, 101 ... main memory device, 102 ... Central processing unit, 103 ... Information processing device.

Claims (17)

[Claims] 1. A wet cleaning step of removing contaminants on the surface of the object to be cleaned by contact with a cleaning liquid, and a drying step of drying the surface of the object to be cleaned by reducing the pressure of the atmosphere around the object to be cleaned. A method for cleaning a semiconductor substrate, comprising a dry cleaning step of removing contaminants on the surface of the object to be cleaned by dry etching in this order. 2. The method of cleaning a semiconductor substrate according to claim 1, wherein the drying step includes heating at least one of the object to be cleaned and the atmosphere. 3. The spin drying step of removing liquid existing on the surface of the object to be cleaned by centrifugal force between the wet cleaning step and the drying step, and the surface of the object to be cleaned. A method of cleaning a semiconductor substrate, further comprising at least one of a vapor drying step of azeotropically removing the liquid present in 1. by azeotroping with the vapor of the liquid azeotropic with the liquid. 4. The method for cleaning a semiconductor substrate according to claim 1, wherein in the drying step, the atmosphere around the object to be cleaned is depressurized for 2.5 minutes or more. 5. The method of cleaning a semiconductor substrate according to claim 1, wherein the drying step and the dry cleaning step are performed in the same chamber. 6. The dry cleaning step according to claim 1, wherein the substrate is exposed to a chlorine-based gas activated by plasma or ultraviolet rays, and the substrate is exposed to an oxygen gas activated by plasma or ultraviolet rays. Of the steps of exposing the substrate to ozone gas activated by plasma or ultraviolet rays, exposing the substrate to hydrogen gas activated by plasma, and exposing the substrate to fluorine-based gas activated by plasma. A method for cleaning a semiconductor substrate, comprising at least one step. 7. A film forming method for manufacturing a semiconductor substrate, comprising a cleaning step of cleaning a substrate surface and a film forming step of forming a film on the substrate surface in this order, wherein the cleaning step is an object to be cleaned. Wet cleaning process to remove surface contaminants by contact with cleaning liquid, drying process to dry the surface of the object to be cleaned by reducing the pressure of the atmosphere around the object to be cleaned, and contaminant to the surface of the object to be cleaned And a dry cleaning step of removing by means of dry etching in this order. 8. The film forming method for manufacturing a semiconductor substrate according to claim 7, wherein the film forming step is a step of forming a film on the surface of the substrate by a vapor phase growth method. 9. A method of manufacturing a semiconductor device comprising a step of cleaning a surface of a semiconductor substrate, wherein the cleaning step includes a wet cleaning step of removing contaminants on the surface of the object to be cleaned by contacting with a cleaning liquid, and an object to be cleaned. It is characterized by comprising a drying step of drying the surface of the object to be cleaned by reducing the pressure of the surrounding atmosphere and a dry cleaning step of removing contaminants on the surface of the object to be cleaned by dry etching in this order. Manufacturing method of semiconductor device. 10. The method of manufacturing a semiconductor element according to claim 9, wherein the semiconductor element has a contact hole having an aspect ratio of 7 or more. 11. A wet cleaning tank for wet cleaning, a cleaning solution supply mechanism for supplying a cleaning solution to the wet cleaning tank, a drying chamber having a vacuum suction port for decompressing the inside, and a dry cleaning chamber. An apparatus for cleaning a semiconductor substrate, comprising: a cleaning chamber; and a dry etching mechanism for performing dry etching in the dry cleaning chamber. 12. The semiconductor substrate cleaning apparatus according to claim 11, further comprising a monitor mechanism for re-executing at least a part of the cleaning process according to the cleanliness of the substrate surface. 13. A wet cleaning tank for wet cleaning, a cleaning liquid supply mechanism for supplying a cleaning liquid to the wet cleaning tank, a drying chamber having a vacuum suction port for decompressing the inside, and a dry chamber in the drying chamber. An apparatus for cleaning a semiconductor substrate, comprising: a dry etching mechanism for etching; and a monitor mechanism for re-executing at least a part of the cleaning process according to the cleanliness of the substrate surface. 14. The monitor mechanism according to claim 12, wherein the monitor mechanism includes a sensor for detecting a degree of cleanliness of the surface of the object to be cleaned after the dry cleaning process, and a return conveying means for returning the object to be cleaned to the dry cleaning tank. If the cleaning degree detected by the sensor has not reached a predetermined value, the returning and conveying means includes a control means for returning the object to be cleaned to the dry cleaning tank, and a semiconductor substrate cleaning apparatus. . 15. A film forming apparatus for manufacturing a semiconductor substrate, comprising a cleaning mechanism for cleaning a substrate surface and a film forming mechanism for forming a film on the substrate surface, wherein the cleaning mechanism is wet cleaning for wet cleaning. Bath, a cleaning liquid supply mechanism for supplying a cleaning liquid to the wet cleaning bath, a drying chamber having a vacuum suction port for decompressing the inside, a dry cleaning chamber for dry cleaning, and dry etching in the dry cleaning chamber. A film forming apparatus for manufacturing a semiconductor substrate, comprising: a mechanism for performing the film formation. 16. The mechanism according to claim 15, wherein the film forming mechanism is a mechanism for forming a film on the surface of the substrate by a vapor phase growth method in at least one of the drying chamber and the dry cleaning chamber. A film forming apparatus for manufacturing a semiconductor substrate, further comprising: 17. The film forming apparatus for manufacturing a semiconductor substrate according to claim 15, further comprising a monitor mechanism for re-executing at least a part of the cleaning process according to the cleanliness of the substrate surface.