CN100539000C - Capacitive coupling plasma processing apparatus - Google Patents

Abstract

The present invention provides a capacitively coupled plasma processing apparatus (100), comprising a processing chamber which can be set to have a vacuum atmosphere, and a processing gas supply part (15) for supplying processing gas into the chamber (1). In the chamber (1), the first electrode (2) and the second electrode (18) are arranged facing each other. In order to form a high-frequency electric field in a plasma generation region (R1) between the first and second electrodes, a high-frequency power supply (10) for supplying high-frequency power to the first or second electrodes is arranged. The high-frequency electric field turns the process gas into a plasma. The substrate to be processed (W) is supported by a support member (2) between the first and second electrodes so that the surface to be processed is opposed to the second electrode (18). In a peripheral region (R2) around the plasma generation region (R1), a grounded conductive active surface AS is arranged to spread the plasma, modulated so as to combine substantially direct current with the plasma.

Description

Capacitively coupled plasma processing device

technical field

The present invention relates to, for example, a capacitively coupled plasma processing apparatus used for plasma processing a substrate to be processed in a semiconductor processing system. Here, the term "semiconductor processing" refers to forming semiconductor layers, insulating layers, conductive layers, etc. Layers, etc., and various processes for manufacturing structures including semiconductor devices and wiring, electrodes, etc. connected to the semiconductor devices on the substrate to be processed.

Background technique

For example, in the manufacturing process of semiconductor devices, plasma processing such as etching or sputtering, CVD (Chemical Vapor Deposition), and the like is often used on a semiconductor wafer as a substrate to be processed. As a plasma processing apparatus for performing such plasma processing, various apparatuses are used, and among them, a capacitively coupled parallel plate plasma processing apparatus is the mainstream.

Generally, a capacitively coupled parallel-plate plasma processing apparatus has a pair of parallel-plate electrodes (upper and lower electrodes) arranged in a processing chamber. During processing, a processing gas is introduced into the chamber, and at the same time, high-frequency power is supplied to one electrode, and a high-frequency electric field is formed between the electrodes to generate a high-frequency discharge. Such a high-frequency discharge is used to form a plasma of a process gas to perform plasma etching on a given layer of a semiconductor wafer, for example.

As such a device, for example, there is a form in which high-frequency power is supplied to a lower electrode on which a semiconductor wafer is placed. In this case, the lower electrode acts as a cathode and the upper electrode acts as an anode. In addition, the high-frequency power applied to the lower electrode serves both to generate plasma and to apply a high-frequency bias to the substrate to be processed.

In such a capacitive coupling type parallel plate plasma processing apparatus, components present in the plasma generation region must be prevented from metal contamination and consumption. Therefore, as these members, those coated with insulating ceramics having high plasma resistance such as Y ₂ O ₃ , or those made of quartz are used.

However, in recent years, the design rules in the manufacturing process of semiconductors have become increasingly finer, especially in plasma etching, higher dimensional accuracy is required, and the selection ratio and in-plane uniformity of the etching mask and substrate are required to be further improved. . Due to this, there tends to be a reduced pressure in the processing region within the chamber, reducing ion energy. Therefore, a high frequency of 40 MHz or higher is used, which is an extremely higher frequency than the conventional technology.

However, by lowering the pressure and lowering the ion energy, the resistivity of the plasma increases, making it difficult to control the uniformity of the plasma. Specifically, when the frequency of the high frequency applied to the high frequency application electrode is high, the high frequency supplied from the high frequency power supply to the back of the electrode is transmitted on the surface of the electrode due to the skin effect, and is concentrated on the main surface of the electrode (opposite to the plasma). the center of the face). Because of this, the electric field intensity in the central portion of the main surface of the electrode is higher than that in the outer peripheral portion, and the generated plasma density is also higher in the electrode central portion than in the electrode outer peripheral portion. At the center of the electrode where the plasma density is high, the resistivity of the plasma is low, and the current also concentrates at the center of the electrode in the opposite electrode. Therefore, the plasma density becomes non-uniform and stronger, causing in-plane non-uniformity and charge-up damage in plasma processing such as etching.

In order to solve this problem, it is known to form the central part of the main surface of the high-frequency application electrode with a high-resistance member (Patent Document 1: Japanese Patent Laid-Open No. 2000-323456). With this technique, a high-resistance member is used to form the central portion of the main surface of the high-frequency application electrode, so that more high-frequency power is consumed as Joule heat. In this way, the electric field intensity of the main surface of the high-frequency application electrode is relatively lower in the center of the electrode than in the outer periphery of the electrode, so that the above-mentioned unevenness in plasma density can be corrected. However, when the central portion of the main surface of the high-frequency application electrode is formed of a high-resistance member, high-frequency power consumption (energy loss) due to Joule heat is large, and the efficiency is not good.

Contents of the invention

An object of the present invention is to provide a capacitively coupled plasma processing apparatus that has high in-plane uniformity in plasma processing and is less prone to charge damage.

The capacitively coupled plasma processing apparatus of the first aspect of the present invention includes:

Can be set as a processing chamber with a vacuum atmosphere;

supplying a processing gas to a processing gas supply unit in the chamber;

a first electrode disposed in the chamber;

a second electrode disposed in the chamber opposite to the first electrode;

In order to form a high-frequency electric field in the plasma generation region between the above-mentioned first and second electrodes, high-frequency power is supplied to the high-frequency power supply of the first or second electrode; Integrate (turn into plasma);

a support member that supports the substrate to be processed between the first and second electrodes so that the surface to be processed is opposed to the second electrode;

A conductive active surface arranged in the surrounding area around the plasma generation region and grounded in the chamber can spread the plasma to the outside of the plasma generation region, and can modulate the active surface so that Combined substantially direct current with the aforementioned plasma.

With the apparatus of the first aspect, when plasma is generated in the chamber, current flows from the plasma to the active surface provided around the substrate to be processed. As a result, the plasma spreads outward and the plasma density is made uniform, thereby improving the in-plane uniformity of the plasma treatment and reducing charging damage.

Description of drawings

1 is a cross-sectional view showing a plasma etching apparatus as a plasma processing apparatus according to a first embodiment of the present invention.

2 is a schematic cross-sectional view showing a state in which a high-frequency power source for plasma generation and a high-frequency power source for ion introduction are connected to a support as a lower electrode.

FIG. 3 is a schematic diagram showing a schematic configuration of a conventional plasma etching apparatus.

FIG. 4 is a schematic diagram for explaining the principle of uniformizing plasma density by the plasma etching apparatus shown in FIG. 1 .

FIG. 5 is a schematic diagram showing a modified example of the plasma etching apparatus of the first embodiment.

FIG. 6 is a schematic diagram showing another modified example of the plasma etching apparatus of the first embodiment.

FIG. 7 is a schematic diagram showing still another modified example of the plasma etching apparatus of the first embodiment.

FIG. 8 is a graph showing Vdc values at in-plane positions of the wafer obtained by comparing examples of the first embodiment in which shield members have different heights and comparative examples of the prior art.

FIG. 9 is a graph showing the power dependence of ΔVdc obtained by comparing the example shown in FIG. 8 with the comparative example.

FIG. 10 is a graph showing Vdc values at in-plane positions of the wafer obtained in Examples of the first embodiment in which the position of the exhaust ring is different.

FIG. 11 is a graph showing the power dependence of ΔVdc obtained by the implementation described in FIG. 10 .

12 is a cross-sectional view showing a plasma etching apparatus as a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 13 is a schematic diagram illustrating the principle of uniformizing plasma density by the plasma etching apparatus shown in FIG. 12 .

FIG. 14 is a schematic diagram showing a modified example of the plasma etching apparatus of the second embodiment.

FIG. 15 is a schematic diagram showing another modified example of the plasma etching apparatus of the second embodiment.

FIG. 16 is a schematic view showing a modified example of the ground member used in the plasma etching apparatus shown in FIGS. 14 and 15 .

FIG. 17 is a schematic view showing another modified example of the ground member used in the plasma etching apparatus shown in FIGS. 14 and 15 .

18 is a cross-sectional plan view showing the relationship between the ground member shown in FIG. 17 and the processing chamber.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the following description, elements having substantially the same function and structure are denoted by the same reference numerals, and description will be repeated only when necessary.

(first embodiment)

1 is a cross-sectional view showing a plasma etching apparatus as a plasma processing apparatus according to a first embodiment of the present invention. This device is configured to etch an oxide film (SiO ₂ film) disposed on a semiconductor wafer.

The plasma etching apparatus 100 has an airtight and substantially cylindrical processing chamber 1 . The main body of the chamber 1 is made of metal such as aluminum, and an insulating film such as an oxidized film or a film (such as a sprayed film) made of insulating ceramics such as Y ₂ O ₃ is formed on the inner wall surface. Chamber 1 is grounded.

A support table 2 that horizontally supports a wafer W as a substrate to be processed and functions as a lower electrode is arranged in the chamber 1 . The support table 2 is made of, for example, aluminum whose surface has been oxidized. The annular support part 3 protrudes from the bottom wall of the chamber 1 and corresponds to the outer periphery of the support table 2 . An annular insulating member 4 is disposed on the supporting portion 3 , and the outer edge portion of the supporting table 2 is supported by the insulating member 4 .

On the outer side of the insulating member 4 , a ring-shaped conductive shield member 25 is formed on the support portion 3 . The height position of its upper end is near the upper surface of the wafer W. The shielding part 25 is directly grounded via the chamber 1 or via the exhaust ring 14 and the chamber 1 shown below. A focus ring 5 made of a conductive material (for example, Si, SiC) or the like is arranged on the outer periphery above the support table 2 . A conical exhaust ring 14 is disposed between the lower end of the shield member 25 and the peripheral wall of the chamber 1 . The exhaust ring 14 not only introduces the process gas into the exhaust line, but also functions to define a peripheral area around the plasma generation area as will be described later. An insulating film made of insulating ceramics such as Y ₂ O ₃ is formed on the surface of the exhaust ring 14 . Furthermore, a hollow portion 7 is formed between the support table 2 and the bottom wall of the chamber 1 .

An electrostatic chuck 6 for electrostatically holding wafer W is disposed on a surface portion of support table 2 . This electrostatic chuck 6 is configured by placing an electrode 6a between insulators 6b, and a DC power supply 13 is connected to the electrode 6a through a switch 13a. Then, the semiconductor wafer W is attracted by electrostatic force (for example, Coulomb force) by applying a voltage from the DC power supply 13 to the electrode 6a.

A refrigerant flow path 8a is provided in the support table 2, and a refrigerant line 8b is connected to the refrigerant flow path 8a. An appropriate refrigerant is supplied and circulated to the refrigerant flow path 8a via the refrigerant line 8b by the refrigerant control device 8 . In this way, the support table 2 can be controlled at an appropriate temperature. In addition, a heat transfer gas line 9 a for supplying a heat transfer gas (for example, He gas) for heat transfer is arranged between the surface of the electrostatic chuck 6 and the back surface of the wafer W. The heat transfer gas is supplied from the heat transfer gas supply device 9 to the rear surface of the wafer W through the heat transfer gas line 9 a. In this way, even if the inside of the chamber 1 is evacuated to maintain a vacuum, the heat and cold of the refrigerant circulating in the refrigerant passage 8a can be efficiently transferred to the wafer W, and the temperature controllability of the wafer W can be improved.

A feeder wire 12 for supplying high-frequency power is connected to the approximate center of the support table 2 . The matching unit 11 and the high-frequency power supply 10 are connected to the power supply line 12 . High-frequency power of a predetermined frequency is supplied from the high-frequency power source 10 to the support table 2 .

On the other hand, a shower head 18 (hereinafter referred to as an upper electrode 18 ) also serving as an upper electrode is arranged on the opposite side of the support table 2 . The shower head 18 is embedded in the top wall portion of the chamber 1 . The shower head 18 has a conductive main body 18a, and a plurality of gas outlet holes 18d are formed to penetrate the lower portion of the main body 18a. The gas output hole 18d communicates with the space 18c formed inside the main body 18a and the gas introduction part 18b formed at the upper part. The gas introduction part 18b is connected to a processing gas supply device 15 for supplying a processing gas for etching through a gas supply line 15a.

The upper electrode 18 is grounded through the chamber 1, and forms a pair of parallel plate electrodes together with the support table 2 that supplies high-frequency power and functions as a lower electrode. The support 2 serving as a lower electrode for supplying high-frequency power functions as a cathode, and the grounded upper electrode 18 functions as an anode. Between the upper electrode 18 and the support table 2 is formed a plasma generation region R1 in which the processing gas becomes plasma. In addition, the region up to the exhaust ring 14 around the plasma generation region R1 becomes the peripheral region R2.

The main body 18a of the upper electrode 18 is made of metal, semiconductor (for example, carbon or Si), or the like. In order to prevent wear by metal contamination or plasma, especially damage, the surface of the main body 18a facing the support table 2 is covered with an insulating film (see insulating film 27 described later). The insulating film is formed of an oxidized film or a film made of insulating ceramics such as Y ₂ O ₃ (for example, a thermally sprayed film).

As the processing gas for etching, various gases used in the prior art can be used, for example, halogen elements containing fluorocarbon gas (C _x F _y ) or hydrogen-containing fluorocarbon (C _p H _q F _r ) can be used. gas. In addition, rare gases such as Ar and He, N ₂ gas, O ₂ gas, and the like may be further added. In addition, when used for ashing, O ₂ gas or the like can be used as a processing gas.

Such processing gas is passed from the processing gas supply device 15 to the space 18c in the main body 18a via the gas supply line 15a and the gas introduction part 18b. The processing gas is output from the gas output hole 18d for etching the film formed on the wafer W. As shown in FIG.

The exhaust pipe 19 is connected to the bottom wall of the chamber 1 . An exhaust device 20 including a vacuum pump and the like is connected to the exhaust pipe 19 . Furthermore, by operating the vacuum pump of the exhaust device 20, the inside of the chamber 1 can be depressurized to a predetermined vacuum degree. On the other hand, on the upper side of the side wall of the chamber 1, a gate valve 24 for opening and closing the loading and unloading port 23 of the wafer W is arranged.

On the other hand, two ring magnets 21 a and 21 b are arranged above and below the loading/unloading port 23 of the chamber 1 so as to surround the chamber 1 . A magnetic field is formed around the processing space between the support table 2 and the upper electrode 18 by the ring magnets 21a and 21b. The ring magnets 21a and 21b are rotatable by a rotation mechanism not shown in the figure.

The ring magnets 21a, 21b are a plurality of segment magnets composed of permanent magnets arranged in a ring shape in a multi-pole state. That is, in the ring magnets 21a and 21b, the magnetic pole directions of the plurality of adjacent sector magnets are arranged so as to be opposite to each other. Therefore, the lines of force are formed between adjacent segment magnets, and a magnetic field of 0.02-0.2T (200-2000 Gauss), preferably 0.03-0.045T (300-450 Gauss) is formed only around the processing space. The wafer placement portion is substantially in a magnetic field-free state. In this way, an appropriate plasma confinement effect can be obtained. The so-called substantially non-magnetic field state of the wafer placement portion is not limited to the case where there is no magnetic field at all. For example, this concept also includes a case where a magnetic field is formed in a wafer arrangement portion, but the magnetic field has substantially no influence on plasma processing.

As mentioned above, the conductive shielding member 25 is DC grounded through the chamber 1 or through the exhaust ring 14 and the chamber 1 . The surface of the shield member 25 disposed on the peripheral region R2 functions as a conductive action surface AS for spreading plasma outside the plasma generation region R1. This action surface AS can be adjusted so that it is directly connected to the plasma and arranged concentrically with respect to the wafer W on the support table 2 . Specifically, the shielding member 25 is made of a conductive material such as clean aluminum, aluminum with anodized surface, Si (doped with impurities to make it conductive), SiC, C (carbon), or W. For example, in the case of using aluminum whose surface is anodized, the active surface AS may be covered with an Al ₂ O ₃ film as an insulator. However, since the insulating film is very thin, the active surface AS can be directly connected to the plasma.

On the other hand, the chamber 1, the upper electrode 18, and the exhaust ring 14 are grounded, and the inner wall of the chamber 1, the facing surface of the upper electrode 18, and the surface of the exhaust ring 14 are covered with an insulating film of Y ₂ O ₃ (compared to a shielding member). 25 surface insulation film thickness) coverage. Due to this, the surfaces of these components are bonded to the plasma alternatingly or at high frequency. In addition, the focus ring 5 is connected to a high-frequency power source 10 through the support stand 2 . Therefore, the surface of the constituent elements that distinguishes the plasma generation electrical region R1 from the surrounding region R2 does not include the surface (action surface AS) of the shield member 25 that is modulated by direct current coupling with the plasma.

In order to adjust the plasma density and the ion introduction action, the high-frequency power for generating plasma and the high-frequency power for introducing ions in the plasma may be superimposed. Specifically, as shown in FIG. 2 , in addition to the high-frequency power supply 10 for plasma generation connected to the matching unit 11 , the high-frequency power supply 26 for ion introduction is connected to the matching unit 11 b so as to overlap. In this case, the frequency of the high-frequency power supply 26 for ion introduction is preferably 500 KHz to 27 MHz. In this way, the ion energy can be controlled to further increase the plasma processing rate such as the etching rate.

Each constituent unit of the plasma etching apparatus 100 is connected to and controlled by a control unit (process controller) 50 . Specifically, the refrigerant control device 8, the heat transfer gas supply device 9, the exhaust device 20, the switch 13a of the DC power supply 13 for the electrostatic chuck 6, the high-frequency power supply 10, and the matching device 11 are controlled by the control unit 50. wait.

In addition, a user interface 51 composed of a keyboard for operations such as command input by a project manager to manage the plasma etching apparatus 100, and a display for visually displaying the operation status of the plasma processing apparatus 100 is connected to the control unit 50. .

In addition, a control program for realizing various processes performed by the plasma etching apparatus 100 under the control of the control unit 50, and a program for performing processing on each component of the plasma etching apparatus (that is, a method) according to processing conditions are stored. ) storage unit 52 is connected to the control unit 50. The method may be stored in a hard disk or a semiconductor memory, and may be installed in a predetermined position of the storage unit 52 while stored in a portable storage medium such as a CDROM or DVD.

Furthermore, by calling any method such as an instruction from the user interface 51 from the storage unit 52 and executing it in the control unit 50 as needed, the plasma etching apparatus 100 performs the process under the control of the control unit 50 . treatment of hope.

Next, the processing operation of the plasma etching apparatus configured in this way will be described.

First, the gate valve 24 of the plasma etching apparatus 100 in FIG. 1 is opened, and the wafer W having the layer to be etched is carried into the chamber 1 by the transfer arm, and placed on the support table 2 . Next, the transfer arm is retreated, the gate valve 24 is closed, and the inside of the chamber 1 is evacuated to a predetermined vacuum degree through the exhaust pipe 19 by the vacuum pump of the exhaust device 20 .

Then, a processing gas for etching is introduced into the chamber 1 from the processing gas supply device 15 at a predetermined flow rate, and the chamber 1 is maintained at a predetermined pressure, for example, 0.13-133.3 Pa (1-1000 mTorr). In this way, high-frequency power having a frequency of 40 MHz or higher (for example, 100 MHz) is supplied from the high-frequency power source 10 to the support table 2 while maintaining a predetermined pressure. At this time, a predetermined voltage is applied from the DC power supply 13 to the electrode 6a of the electrostatic chuck 6, and the wafer W is attracted by the Coulomb force.

In this way, by applying high-frequency power to the support table 2 as the lower electrode, a high-voltage plasma is formed in the processing space (plasma generation region) between the shower head 18 as the upper electrode and the support table 2 as the lower electrode. frequency electric field. In this way, the processing gas supplied to the processing space becomes plasma, and the layer to be etched formed on the wafer W is etched by the plasma.

During this etching, a magnetic field is formed around the processing space by the ring magnets 21a and 21b in a multipolar state. In this way, an appropriate plasma confinement effect can be exerted, and the homogenization of plasma can be assisted. In addition, there may be cases where the effect of such a magnetic field is not obtained by using a film. In this case, the segment magnets may be rotated to perform processing without substantially forming a magnetic field around the processing space.

When the above-mentioned magnetic field is formed, the conductive focus ring 5 provided around the wafer W on the support table 2 functions as a lower electrode up to the focus ring region. Because of this, the plasma formation area is extended to the focus ring 5, the plasma processing of the peripheral portion of the wafer W can be facilitated, and the uniformity of the etching rate can be improved.

In addition, the shielding member 25 disposed on the peripheral region R2 around the plasma generation region R1 can provide effects described below.

FIG. 3 is a schematic diagram showing a schematic configuration of a conventional plasma etching apparatus. In the conventional plasma etching apparatus, a shield member 25' having an insulating film 27 of Y ₂ O ₃ or the like formed on the surface is disposed around the support table 2 . Since the insulating film 27 is thick, the surface of the shield member 25' cannot be directly bonded to the plasma. Furthermore, the insulating member 4' protruding from the upper part of the shielding member 25' is arrange|positioned inside the shielding member 25'. In addition, in the chamber 1, other parts that are grounded (for example, the chamber 1, the upper electrode 18, and the exhaust ring 14) are all covered with an insulating film 27 such as a Y ₂ O ₃ thermally sprayed film and the insulating member 4'. Owing to this, the surfaces of these components are combined with the plasma not in direct current but in alternating current (high frequency). Therefore, these components only form a graphic circuit for high-frequency current, and have no effect on correcting the inhomogeneity of the plasma.

FIG. 4 is a schematic diagram for explaining the principle of making plasma density uniform by the plasma etching apparatus shown in FIG. 1 . As described above, the conductive shielding member 25 is DC-grounded, and its surface functions as the action surface AS that is substantially DC-coupled to the plasma. As shown in FIG. 4 , when plasma is generated, current flows from the plasma to the shield member 25 through the action surface AS provided around the wafer W. As shown in FIG. As a result, the plasma spreads outward, thereby making the plasma density uniform. In this way, while improving the in-plane uniformity of the etching process, it is possible to reduce charge damage such as dielectric breakdown of the control electrode oxide film.

Among them, the multi-pole ring magnets 21a and 21b can exert a plasma confinement effect to prevent plasma diffusion in the peripheral edge portion of the plasma generation region R1. That is, the multipole ring magnets 21a and 21b have the opposite function to that of the shielding member 25 having the effect of spreading the plasma in the center. Therefore, when forming a magnetic field using the multi-pole ring magnets 21a and 21b, it is necessary to set conditions so that the effect of shielding member 25 to expand plasma is not hindered.

As described above, the height position of the upper end of the action surface AS of the shield member 25 can be set higher than the height position of the wafer W in order to exert the effect of spreading the plasma and making the plasma density uniform. In this case, the current can be made to flow from the plasma to the shield member 25 more easily.

FIG. 5 is a schematic diagram showing a modified example of the plasma etching apparatus of the first embodiment. In the structure of FIG. 1 , all of the upper end surface and the side surface facing the exhaust path of the shielding member 25 function as the action surface AS directly coupled with the plasma. In contrast, in the modified example of FIG. 5 , the lower portion of the shield member 25 is covered with a thick insulating film 27 . That is, only the surface of the upper portion 25a of the shielding member 25 functions as the action surface AS for direct current coupling with the plasma. In such a structure, the function of spreading the above-mentioned plasma outward and making it uniform can be exhibited.

FIG. 6 is a schematic diagram showing another modified example of the plasma etching apparatus of the first embodiment. In the modified example of FIG. 6, the exhaust ring 14a whose surface is not covered with an insulating film is used. In addition to the shielding member 25, the upper surface of the exhaust ring 14a also functions as an active surface AS directly coupled to the plasma. In this way, the current can flow from the plasma to the outer surface of the wafer W toward the shield member 25 and the exhaust ring 14a, and similarly, the plasma can be spread outward to exert a uniform effect. In this case, when the shield member 25 is covered with a thick insulating film, only the upper surface of the exhaust ring 14 can be made to function as the active surface AS directly coupled with the plasma.

FIG. 7 is a schematic diagram showing still another modified example of the plasma etching apparatus of the first embodiment. In the modified example of FIG. 7 , the exhaust ring 14' is disposed near the bottom of the chamber 1 below the position where the exhaust ring 14 of FIG. 1 is disposed. Therefore, the surrounding area around the plasma generation area expands downward. In addition, the surfaces of the exhaust ring 14' and the shielding member 25 can function as the active surface AS directly coupled with the plasma. In this way, the effect of spreading the plasma outward is improved, and the function of uniformizing the plasma can be further improved. When the shielding member 25 is covered with a thick insulating film, only the upper surface of the exhaust ring 14' can function as the action surface AS directly coupled with the plasma.

Next, experiments for confirming the effects of the first embodiment will be described.

( experiment 1 )

First, plasma processing was performed by changing the height of the shield member 25 using the apparatus having the basic structure of FIG. 1 , and the in-plane variation of the bias voltage Vdc of the plasma itself was grasped. As the shield member 25 , a member having an anodized coating formed on the surface of aluminum was used, and three examples A, B, and C of the first embodiment in which the height of the upper end of the shield member was different were tested. In embodiment A, the height of the upper end of the shielding member is the same as the height of the upper end of the supporting platform (Z=0). In Example B, the height of the upper end of the shielding member is 4.5 mm from the support table, which is approximately the same as the surface height of the wafer (Z=+4.5). In embodiment C, the height of the upper end of the shielding component is above 9.5 mm from the support platform (Z=+9.5). In addition, for comparison, a conventional device (Z=−30) in which a shielding member of a thick insulating film is arranged as shown in FIG. 3 was tested (comparative example D).

In the plasma processing, a 300mm wafer is used as the wafer, and the following conditions are used: the pressure in the chamber is 0.67pa, the processing gas is _O2 gas, the flow rate is 200mL/min, the frequency of the high frequency is 100MHz, and the power of the high frequency is 200W, 500W , 1200W, 1800W, 2400W. The self-bias voltage Vdc at each position on the wafer at this time was measured by a Vdc monitor built in the matching unit, and the in-plane distribution of Vdc was obtained.

The results of the experiments are shown in FIGS. 8 and 9 . FIG. 8 is a graph showing Vdc values at in-plane positions of the wafer obtained from examples of the first embodiment in which shield members have different heights and comparative examples of the prior art. FIG. 9 is a graph showing the power dependence of ΔVdc obtained from the example and the comparative example described in FIG. 8 .

As shown in FIGS. 8 and 9 , in the case of the prior art device (Comparative Example D), Vdc was overall deep, and the value of ΔVdc and the power dependence of ΔVdc were large. On the other hand, in the case of Examples A to C in which the member of the active surface that directly connects the shield member to the plasma is provided, the value of Vdc is small, and the value of ΔVdc and the power dependence of ΔVdc are small. In addition, within the experimental range, the higher the height of the shielding member, the larger the value of Vdc, and the smaller the power dependence of the value of ΔVdc and ΔVdc. In particular, Example C in which the upper end height position of the shield member was higher than the wafer surface gave the best results.

(experiment 2)

Next, check the effect of the exhaust ring. Here, taking the height of the shielding part as Z=0, experiments were carried out on two embodiments E and F using different exhaust rings. In Embodiment E, a conical exhaust ring (height -30 to -110 mm, with insulating film) shown in FIG. 1 is used (same as Example A). In Example F, as shown in FIG. 7 , the exhaust ring is moved downward and placed near the bottom of the chamber as a component that provides an active surface for the exhaust ring and the plasma to be directly connected (exhaust ring The height is -170mm). In the plasma treatment, a 300 mm wafer was used as the wafer, and the same conditions as in Experiment 1 were used. The in-plane distribution of Vdc was obtained by measuring the self-bias voltage Vdc at each position directly above the wafer at this time using a Vdc monitor built in the matching unit.

The results of this experiment are shown in FIGS. 10 and 11 . FIG. 10 is a graph showing the value of Vdc at the in-plane position of the wafer obtained by an example of the first embodiment in which the position of the exhaust ring is different. FIG. 11 is a graph showing the power dependence of ΔVdc obtained from the embodiment described in FIG. 10 .

As shown in these figures, the Vdc value of Example F, in which the exhaust ring is arranged at the bottom and serves as a member providing the action surface, is large, and the value of ΔVdc and the power dependence of ΔVdc are extremely small.

( second embodiment )

12 is a cross-sectional view showing a plasma etching apparatus as a plasma processing apparatus according to a second embodiment of the present invention. This device is configured to etch the Si layer on the semiconductor wafer or the surface of the Si substrate. Since the basic structure of the device shown in FIG. 12 is substantially the same as that shown in FIG. 1 , the following description will focus on the differences.

In the plasma etching apparatus 200 , an annular support portion 3 is formed so as to protrude from the bottom wall of the processing chamber 1 . An annular insulating member 4 is disposed on the supporting portion 3 , and the outer edge of the supporting table 2 is supported by the insulating member 4 . A focus ring 35 made of an insulating material (for example, SiO ₂ ) is arranged on the outer periphery above the support table 2 . The insulating member 4, the upper outer surface of the support portion 3, most of the inner surface of the chamber 1, and the surface of the upper electrode 18 opposite to the support table 2 are covered by insulator covers 36, 37 made of, for example, quartz, respectively. On the other hand, the lower outer surface of the support part 3 and the lower inner surface of the chamber 1 are exposed surfaces 33, 31 exposed from aluminum (conductive material) covered with a thin anodized film, respectively, without a quartz cover. No exhaust ring is provided in the space between the insulator cover 36 and the inner wall of the chamber 1 , and the surrounding region R2 around the plasma generation region R1 extends to the bottom of the chamber 1 along the exhaust path.

Next, the processing operation of the plasma etching apparatus configured in this way will be described.

First, as in the first embodiment, a wafer W having a layer to be etched is loaded into the chamber 1 . Next, the inside of the chamber 1 is evacuated to a predetermined degree of vacuum by the vacuum pump of the exhaust device 20 through the exhaust pipe 19 .

Then, a processing gas for etching is introduced into the chamber 1 at a predetermined flow rate from the processing gas supply device 15, and the inside of the chamber 1 is maintained at a predetermined pressure, for example, 0.13 to 133.3 Pa (1 to 1000 mTorr). In this way, high-frequency power having a frequency of 40 MHz or higher (for example, 100 MHz) is supplied to the support table 2 from the high-frequency power source 10 while maintaining a predetermined pressure. At this time, a predetermined voltage is applied from the DC power supply 13 to the electrode 6a of the electrostatic chuck 6, and the wafer W is attracted by the Coulomb force.

In this way, by applying high-frequency power to the support table 2 as the lower electrode, a high-voltage plasma is formed in the processing space (plasma generation region) between the shower head 18 as the upper electrode and the support table 2 as the lower electrode. frequency electric field. In this way, the processing gas supplied to the processing space is turned into plasma, and the layer to be etched formed on the wafer W is etched by the plasma.

During etching, a magnetic field is formed around the processing space by the ring magnets 21a and 21b in a multi-pole state. In this way, an appropriate plasma confinement effect can be exerted, and uniformization of plasma can be assisted. In addition, there may be cases where there is no effect of such a magnetic field through the membrane. In this case, the sector magnets may be rotated to perform processing without substantially forming a magnetic field around the processing space.

When the above-mentioned magnetic field is formed, the insulating focus ring 35 provided around the wafer W on the support table 2 does not give and receive charges between electrons and ions in the plasma. In this case, the effect of the confinement effect plasma can be increased, and the uniformity of the etching rate can be improved.

Furthermore, the exposed surfaces 31 , 33 arranged in the peripheral region R2 around the plasma generation region R1 provide the effects described below.

As shown with reference to FIG. 3 , in the conventional plasma etching apparatus for Si etching, the surfaces of the conductive components that distinguish the plasma generation region R1 from the surrounding region R2 are all covered with insulator caps. Therefore, these constituent elements constitute only a return circuit for high-frequency current, and do not have the function of correcting the unevenness of plasma.

On the other hand, in the second embodiment, the insulator cover is not provided in the vicinity of the lower end of the peripheral region R2, but the conductive exposed surfaces 31 and 33 that are grounded via the chamber 1 are arranged. These exposed surfaces 31, 33 are covered with a film of _AL2O3 as an insulator; however, since the insulating film is very thin, the exposed surfaces 31, 33 can be directly connected to _the plasma. That is, the exposed surfaces 31 and 33 are directly connected to the plasma, and function as an action surface AS for spreading the plasma outside the plasma generation region R1.

FIG. 13 is a schematic diagram illustrating the principle of uniformizing plasma density by the plasma etching apparatus shown in FIG. 12 . As shown in FIG. 13 , when plasma is generated, it is difficult for current to flow from the plasma to the chamber 1 and the support portion 3 via the action surface AS provided around the wafer W. As a result, the plasma diffuses outward, and the density of the plasma is made uniform. In this way, while improving the in-plane uniformity of the etching process, charge damage such as dielectric breakdown of the control electrode oxide film can be reduced. However, this effect can be obtained even if any one of the exposed surfaces 31 and 33 is used, and the effect of using both is higher.

FIG. 14 is a schematic diagram showing a modified example of the plasma etching apparatus of the second embodiment. FIG. 15 is a schematic diagram showing another modified example of the plasma etching apparatus of the second embodiment. In the modified example of FIG. 14 , a grounding member 38 that functions as AS is disposed on a portion corresponding to the exposed surface 31 . In the modified example of FIG. 15 , grounding members 38 , 39 providing action surfaces AS are arranged on portions corresponding to exposed surfaces 31 , 33 , respectively. In this way, by arranging the ground member providing the action surface AS on the exposed surface, the effect of uniformizing the plasma density can be enhanced.

As such a grounding member, for example, it can be made of high-conductivity non-scaling aluminum. However, from the viewpoint of stability of characteristics and measures against dust, it is preferable to use Si to constitute the grounding member. The grounding part can be formed by digging holes in the middle solid material. However, the cost is high and processing is difficult. In particular, in recent years, since the diameter of the wafer tends to increase, the size of the components has increased, so the above-mentioned problem of using a material with a solid center has become prominent.

FIG. 16 is a schematic view showing a modified example of the ground member used in the plasma etching apparatus shown in FIGS. 14 and 15 . In the modified example of FIG. 16 , the annular ground member 38X may be formed by combining a plurality of conductive segments (eg, segment 41 made of Si (doped with impurities to make it conductive)). With this structure, the above-mentioned cost problems and processing problems can be avoided.

FIG. 17 is a schematic view showing another modified example of the ground member used in the plasma etching apparatus shown in FIGS. 14 and 15 . Fig. 18 is a cross-sectional plan view showing the relationship between the ground member and the chamber shown in Fig. 17 . In the modified example of FIG. 17 , the ring-shaped grounding member 38Y is composed of a plurality of conductive sectors (such as sectors 41 made of Si) and a plurality of insulating sectors (such as sectors 42 made of quartz (SiO ₂ ). ) are composed interactively. For example, as shown in Figure 18. The annular ground member 38Y is divided into 16 parts along the radial direction, and eight Si segments 41 and eight quartz segments 42 are alternately arranged.

Since quartz is cheaper than Si and has high durability, the ground member 38Y can be continued to be used only by replacing the Si segments 41 . In addition, in the structure in which SiO ₂ is partially provided in this way, the same degree of characteristics as in the case of only Si can be exhibited. The division method of alternately combining conductive segments and insulating segments is not limited to the illustrated structure. Among them, SiC can be used instead of Si when stability of characteristics and dust countermeasures are taken into consideration. In addition, the ground member 39 may be configured in the same manner as the ground members 38X and 38Y. Furthermore, the shield member of the first embodiment described above may also be configured in the same manner as the ground members 38X and 38Y.

Hereinafter, experiments for confirming the effects of the second embodiment will be described.

(Experiment 3)

First, a device having the basic structure of FIG. 12 and connecting high-frequency power sources of two frequencies to the lower electrode as shown in FIG. 2 was used. The state of the insulator cap is changed to perform plasma etching of Si, and the etched shape is grasped. Experiments were conducted using two examples G and H of the second embodiment as plasma etching devices. In Embodiment G, only the exposed surface 33 of the outer peripheral lower end portion of the support portion 3 is formed. In Embodiment H, the exposed surface 33 and the exposed surface 31 are formed on the lower outer surface of the support portion 3 and the lower inner surface of the chamber 1, respectively. In addition, for comparison, a conventional device (Comparative Example 1) with no exposed surface was also tested.

In plasma etching, the following conditions are used: the pressure in the chamber is 27Pa, the processing gas is HBr, NF ₃ , SF ₆ , SiF ₄ and O ₂ , the frequency of high frequency is 40MHz, 3.2MHz, and the power of high frequency is 600/700W , forming holes with a depth of 10 μm on a 200 mm Si wafer. Etching is performed at several places from the center of the wafer to the vicinity of the edge, and the bottom CD of each etched hole is measured to obtain the deviation.

As a result, in the case of Comparative Example 1, the variation (ΔBCD) of the bottom CD was 30 nm. The ΔBCD of Example G having only the exposed surface 33 was 21 nm, and the uniformity of etching was improved. In addition, the ΔBCD of Example H having the exposed surface 33 and the exposed surface 31 is 17 nm, and the uniformity of etching is further improved.

However, the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the above-mentioned embodiments, a magnetic field is formed around the processing space by using a plurality of segment magnets made of permanent magnets arranged in a ring shape in a multi-pole state around the chamber to form a magnetic field, but this magnetic field forming device It is not essential, and in the above-mentioned embodiments, the device in the form of applying high-frequency power to the lower electrode was taken as an example. The present invention is also applicable to the formation of applying high-frequency power to the upper electrode, applying high-frequency power for plasma generation to the upper electrode, and applying high-frequency power for ion introduction to the lower electrode. In addition, In the above-mentioned embodiments, a case where the present invention is applied to plasma etching was shown, but it can also be applied to other plasma processes such as plasma CVD and sputtering. In addition, other device structures, materials of the conductive layer, and the like are not limited to the above embodiments, and various structures and materials can be used. In addition, in the above-mentioned embodiments, a case where a semiconductor wafer is used as a substrate to be processed was shown, but the present invention is not limited thereto, and can be applied to other substrates.

Claims (19)

1. A capacitively coupled plasma processing device, characterized in that, comprising: Can be set as a processing chamber with a vacuum atmosphere; supplying a processing gas to a processing gas supply part in the chamber; a first electrode disposed within the chamber; a second electrode disposed within the chamber opposite to the first electrode; In order to form a high-frequency electric field in the plasma generation region between the first and second electrodes, a high-frequency power supply that supplies high-frequency power to the first or second electrode, and utilizes the high-frequency an electric field to plasmatize the process gas; and a support member for supporting the substrate to be processed between the first and second electrodes in such a manner that the surface to be processed is opposed to the second electrode; In the chamber, the plasma generation region and its surrounding area are divided by the inner surface of the chamber including the surface of the grounded conductive constituent element, disposing a grounded conductive active surface in the surrounding area to expand the plasma to the outside of the plasma generation area, The active surface is covered with a first insulating film, the surface of the constituent element is covered with an insulating film thicker than the first insulating film, the active surface is directly connected to the plasma, and the surface of the constituent element is not Directly combined with the plasma. 2. The plasma processing apparatus according to claim 1, characterized in that: The action surface is defined by either the conductive Si layer or the SiC layer. 3. The plasma processing apparatus according to claim 1, characterized in that: The action surface is disposed substantially concentrically with respect to the substrate to be processed supported by the supporting member. 4. The plasma processing apparatus according to claim 1, characterized in that: The action surface is defined by a surface of a conductive member disposed on either one or both of the support member and the chamber. 5. The plasma processing apparatus according to claim 1, characterized in that: The active surface is defined by the surface of any one or both of the conductive part of the support member and the chamber. 6. The plasma processing apparatus according to claim 1, characterized in that: An exhaust passage for exhausting gas from the plasma generation region is formed around the supporting member, and the action surface faces the exhaust passage. 7. The plasma processing apparatus according to claim 6, characterized in that: In the exhaust passage, the action surface is arranged near the bottom of the chamber. 8. The plasma processing apparatus according to claim 1, characterized in that: An annular member is supported by the supporting member or the cavity so as to surround the supporting member, the annular member including a conductive portion having a role as the active surface. 9. The plasma processing apparatus according to claim 8, characterized in that: The annular member has a conductive shield member disposed on a side surface of the support member. 10. The plasma processing apparatus according to claim 8, characterized in that: An exhaust passage for exhausting gas from the plasma generation region is formed around the support member, and the annular member is arranged around the support member so as to divide the exhaust passage, and has a Conductive vent ring with holes for gas passage. 11. The plasma processing apparatus according to claim 8, characterized in that: An exhaust passage for exhausting gas from the plasma generation region is formed around the support member, and the annular member defines a part of an inner surface of the exhaust passage. 12. The plasma processing apparatus according to claim 8, characterized in that: The annular member is formed by combining a plurality of conductive segments. 13. The plasma processing apparatus according to claim 8, characterized in that: The annular member is composed of a combination of a plurality of conductive segments and a plurality of insulating segments. 14. The plasma processing apparatus according to claim 13, characterized in that: The conductive sector is made of any one of Si and SiC having conductivity, and the insulating sector is made of silicon oxide. 15. The plasma processing apparatus according to claim 1, characterized in that: The high-frequency power supply is connected to the first electrode. 16. The plasma processing apparatus according to claim 1, characterized in that: The first electrode is assembled in the support member. 17. The plasma processing apparatus according to claim 1, characterized in that: The high-frequency power has a frequency of 40 MHz or higher. 18. The plasma processing apparatus according to claim 1, characterized in that: The surface of the constituent element is coupled to the plasma in alternating current or high frequency. 19. The plasma processing apparatus according to claim 2, characterized in that: The active surface is arranged in the chamber so as to be located radially outside of a focus ring arranged around the first electrode.

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