JPS6380535A - Plasma processing apparatus - Google Patents

Abstract

PURPOSE:To improve the adhesion property between a substrate to be processed and an electrode surface contacted therewith for improving electrical coupling properties, thermal conductivity and uniformity and to improve the processing efficiency, by providing a conducting resin body on the electrode surface contacted with the substrate. CONSTITUTION:A semiconductor wafer 20 is disposed on a wafer push-up pin 35 by a wafer conveyor and the wafer push-up pin 35 is lowered. As it is, there is a gap between the semiconductor wafer and the periphery of a wafer carrying base 22a whose top face is gradually projected. But this gap is eliminated by lowering a clamp ring 9 for pressing the periphery of the semiconductor wafer 20 against the wafer carrying base 22a. Such gap can not be eliminated completely by conventional wafer fixing mechanisms and the gap causes, in turn, deterioration in electrical coupling properties or thermal conductivity which, in turn, causes ununiform etching or decrease of etching efficiency. According to this embodiment, however, a conductive silicon rubber 33 having high elasticity is mounted on the wafer carrying base 22a so as to provide improved adhesion properties. Thus, the electrical coupling properties and the thermal conductivity between the semiconductor wafer 20 and the wafer carrying base 22a can be improved substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a plasma processing apparatus that processes a semiconductor substrate using plasma.

(Prior Art) In recent years, semi-volatile processing apparatuses that utilize plasma, such as plasma CVD apparatuses, plasma etching apparatuses, and sputtering apparatuses, have become widely used as semiconductor processing apparatuses.

For example, in a plasma etching apparatus, a reactive gas is introduced into an etching tank, the reactive gas is excited to a plasma state, and the generated active component reacts with a target object on a substrate, such as a semiconductor wafer, to perform an etching process. This plasma etching apparatus will be described below as an example of a plasma processing apparatus.

FIG. 7 shows a plasma etching apparatus having parallel plate type electrodes, in which a lower electrode 3, which serves as a mounting table 6 for a semiconductor wafer 2, is placed in an etching bath 1 which maintains airtightness, and a high-frequency etching device is placed opposite to this lower electrode 3. Electric f! 4 is placed. The high frequency electrode 4 has a structure that acts as a reaction gas introduction tube, and a porous member is used for the electrode portion 4a at the lower end thereof.

In such a plasma etching apparatus, the atmosphere inside the etching tank 1 is heated to a high vacuum, e.g.
After setting the pressure to 6 Torr, a reactive gas source 6 is placed in the etching tank 1.
A reactive gas, such as argon gas, is introduced into the etching chamber 1 to maintain the inside of the etching tank 1 at a vacuum level of, for example, 10' to 10@-2 Torr, which is necessary for the etching process.

Next, a high frequency cuff is applied to the high frequency electrode 4 to turn the reactive gas into plasma, and the reactive components of this gas plasma 8 perform an etching process.

By the way, in the plasma etching apparatus as mentioned above,
Since the structure is such that the semiconductor wafer 2 is in direct contact with the lower electrode 3, if the adhesion between the semiconductor wafer 2 and the lower electrode 3 is insufficient, a gap will be created between the semiconductor wafer 2 and the lower electrode 3. There is a risk that electrical connectivity and thermal conductivity will be lowered due to gaps.

A decrease in electrical connectivity causes a decrease in processing efficiency, such as a decrease in etching processing rate (hereinafter referred to as etching rate) and uneven processing in plasma etching equipment.A decrease in thermal conductivity causes a rise in the temperature of the semiconductor wafer, causing the wafer There is a problem in that it softens the photoresist coated on the surface and makes it easier to peel off during the etching process.

Therefore, in conventional plasma etching equipment, the upper surface of the lower electrode is flattened to improve its adhesion to the semiconductor wafer.

(Problem to be solved by the invention) However, a slight amount of distortion occurs in semiconductor wafers during the manufacturing process, and this distortion varies depending on the individual semiconductor wafer. There was a problem in that a considerable gap was created between the wafer and the lower electrode, making it impossible to achieve complete adhesion.

In order to solve this problem, as shown in FIG.
The contact surface 3a with the semiconductor wafer 2 is formed into a gentle convex shape, and a wafer fixing plate whose inner diameter is slightly smaller than the diameter of the semiconductor wafer 2 is provided above and parallel to the lower electrode 3 as a fixing ms for the semiconductor wafer 2. A wafer fixing mechanism is provided in which a ring body (hereinafter referred to as a clamp ring) 9 is movable up and down, and the clamp ring 9 is lowered to press the peripheral edge of the semiconductor wafer 2 against the lower electrode 3 to improve adhesion. be.

However, the above-mentioned wafer fixing mechanism cannot sufficiently cope with the case where the curvature of the distortion of the semiconductor wafer 2 and the curvature of the lower electrode upper surface 3a are significantly different, and the structure in which only the peripheral edge of the semiconductor wafer is pressed by the clamp ring 9 Therefore, when the semiconductor wafer is fixed, stress from the wafer periphery is concentrated in the center, causing the semiconductor wafer 2 to be fixed as shown in FIG.
is warped upward in an arc shape, and a gap 10 is created between the center of the wafer 2 and the lower electrode 2. The semiconductor wafer 2 that has been etched in this state has the following properties as shown in FIG.
The wafer central portion 2a appears blue, and the wafer outer peripheral portion 2b appears green. This indicates that the etching rate of the wafer central portion 2a is lower than that of the wafer outer peripheral portion 2b, and that uniform processing is not performed.

The present invention was made to solve the above-mentioned problems, and by improving the adhesion of the contact surface between the electrode and the substrate to be processed, it improves electrical connectivity and thermal conductivity, and improves uniformity. The object of the present invention is to provide a plasma processing bag that enables plasma processing with good efficiency and high processing efficiency.

[Structure of the Invention] (Means for Solving the Problems) The plasma processing apparatus of the present invention includes an electrode disposed in an airtight container equipped with a plasma generation source, and a substrate to be processed is brought into contact with the electrode surface. The plasma processing apparatus configured to perform plasma processing is characterized in that a conductive resin body is provided on the surface of the electrode that comes into contact with the substrate to be processed.

The conductive resin body is preferably one with excellent heat resistance and flexibility, such as carbon-containing silicone rubber, and the thickness is 0.2 nm.
A value of approximately +n is suitable.

Further, the electrode and the conductive resin body may be attached by adhesion using a conductive adhesive that remains elastic even after curing, thermocompression bonding, or the like.

(Function) The conductive synthetic resin film provided on the contact surface of the electrode that contacts the substrate to be processed greatly improves the adhesion between the substrate to be processed and the electrode, resulting in good electrical connectivity and thermal conductivity. Therefore, uniform and efficient plasma processing becomes possible.

(Example) Hereinafter, an example in which the present invention is applied to a plasma etching apparatus will be described with reference to the drawings.

Figures 1 and 2 show the etching processing section,
This etching processing section is installed in an etching bath which is kept airtight and is not shown in the drawings.

The semiconductor wafer 20 as the substrate to be processed is taken out from the wafer cassette by a transport device (not shown) and transported to the etching processing section 21, where a disk-shaped substructure is formed! f! After being placed on the substrate 22 and subjected to etching treatment there, it is carried out again by the conveyance device.

Above the lower electrode 22, a hollow circular rock-shaped high-frequency electrode 23 connected to a high-frequency power source 40 is disposed oppositely, and at the center of the upper surface of the high-frequency electrode 23, a reactive gas generated by a reactive gas generator 24, such as argon, is placed. An introduction 'Ef 24 for introducing gas into the etching tank 1 is vertically provided.

The lower surface electrode portion 23a of the high-frequency electrode 23 is formed of a porous material, for example, carbon formed in a mesh shape, and the reaction gas introduced from the reaction gas introduction tube 23 passes through this lower surface electrode portion 23a to lower the lower surface electrode portion 23a. The structure is such that it reaches above the semiconductor wafer 20 placed on the electrode 22.

Below the side surface of the lower electrode 22, a reactive gas exhaust pipe 26, which is an annular hollow body with a mouth-shaped cross section, is disposed with a difference in level from the upper surface of the lower electrode 22, and a large number of exhaust holes 27 are provided in the upper surface.
A pipe 29 is provided from a part of the outer periphery of the six reaction gas exhaust pipes 26, which are concentrically bored at regular intervals, to guide the spent reaction gas introduced from the numerous exhaust holes 27 to the vacuum pump 28. It is being

As a semiconductor wafer fixing mechanism, a ring-shaped clamp ring 30 having an inner diameter slightly smaller than the diameter of the semiconductor wafer is arranged above the lower electrode 22, and this clamp ring 30 is arranged along the circumference of the lower electrode 22. It is supported by four clamp ring support rods 31 provided at intervals. The four clamp ring support rods 31 are connected to an air cylinder 32 which is a drive mechanism for lifting and lowering the clamp ring and which is arranged below the lower electrode 22.
2, the clamp ring can be moved up and down.

The lower electrode 22 has a diameter of about 200 IIll and a thickness of about 1011
It has the shape of a disk with a diameter of approximately 1 in the center of its upper surface.
251111, a wafer RE table 22a having a disk-shaped convex portion with a thickness of about 8 nm is formed. This wafer! ! Stand 2
The upper surface of 2a has a smooth convex shape to improve adhesion to the semiconductor wafer 20. As the material of the lower electrode 22, a metal material having excellent electrical conductivity and thermal conductivity, such as aluminum, is used.

On the upper surface of this wafer'mT1 stand 22a is a wafer mounting stand 22.
A carbon-containing conductive silicone rubber 33 having approximately the same diameter as or larger than a and a thickness of about 0.2 nua is attached. Conductive silicone rubber 33 and wafer mounting table 22
In this example, thermocompression bonding with a conductive synthetic resin adhesive which remains elastic even after curing was used as a means of adhering the material.

The surface of the conductive silicone rubber 33 has a grid-like shallow m 33
a is formed, and four holes 33b for raising and lowering the evaporator push-up pin are bored in the central part.

This wafer push-up pin lifting hole 33b is for lifting and lowering the wafer push-up pin 35, which passes through the lower electrode 22 and is connected to an air cylinder 34 serving as a push-up pin vertical drive mechanism. The structure is such that the wafer 20 is pushed up from the lower surface by push-up pins 35 and separated from the conductive silicon rubber 33.

An annular cooling water circulation pipe 36 for cooling the semiconductor wafer 20 during the etching process is buried in a position facing the back surface of the semiconductor wafer 20 of the lower electrode 22. Cooling water at a low temperature, for example, 15° C., is introduced from a cooling water introducing device 37 into the chamber.

The wafer fixing operation of such a plasma etching apparatus will be explained with reference to FIG.

First, the state in which the wafer push-up pin 35 is raised (the third
After the semiconductor wafer 20 is placed on the wafer push-up pin 35 using a wafer transfer device (not shown in FIG. 3C), the wafer push-up pin 35 is lowered (FIG. 3A).
)) In this state, since the upper surface of the wafer mounting table 22a has a gentle convex shape, a gap between the peripheral edge and the semiconductor wafer is created, but the clamp ring 9 descends and places the peripheral edge of the semiconductor wafer 20 on the wafer aZ table. By pressing on 22a, this gap disappears (FIG. 3(b)). At this time, in the conventional wafer fixing mechanism, there is a small amount of space between the semiconductor wafer 20 and the wafer mounting table 22a due to distortion inherent in the semiconductor wafer, processing accuracy problems on the surface of the wafer mounting table 22a, and stress generated in the center of the wafer due to clamping pressure. However, in this example, a conductive silicone rubber 33 with excellent elasticity is used as a wafer. Since it is pasted on the 8W stand 22a, the adhesion is improved and the generation of such a gap is eliminated, and the semiconductor wafer 20 and wafer iZ
The electrical connection and thermal conductivity between the stands 22a are extremely excellent.

Now, after the etching work is finished, the clamp ring 9 is raised, and then the wafer push-up pin 35 is raised to push the semiconductor wafer 20 up from the wafer mounting table 22a (third
Figure (C)). Since the etching process is normally performed in a high temperature environment, the semiconductor wafer 20 is heated to a high temperature, for example, about 100°C, and the semiconductor wafer 20 and the conductive silicone rubber 33
However, in this example, a lattice-shaped shallow groove 33 is formed on the surface of the conductive silicon rubber 33.
However, as shown in FIG. 3(b), this shallow groove 33a is completely crushed when the semiconductor wafer 20 is fixed, so that no gap occurs. It goes without saying that it belongs to

An actual experiment was conducted using the plasma etching apparatus of the above embodiment, which will be explained below.

The experiment was conducted using a device that did not use conductive silicone rubber.
Two types of devices using the carbon-containing conductive silicone rubber of this example were tested. In addition to the equipment structure, the materials and shapes of the electrodes used,
The etching conditions such as the type of reaction gas, power output value, degree of vacuum, etc. were all the same. As the object to be etched was an oxide film, a 380K tan frequency power supply was used as the power supply. Of course, the optimum power supply frequency differs depending on the object to be etched.

An experiment was conducted under the experimental conditions shown in Table 1 below, and the results shown in Table 2 were obtained.

(Leaving space below) Table 1 Experimental conditions Table 2 Experimental results The results of this experiment revealed that: (1) the etching rate was 469 people/min when conductive silicone rubber was used, compared to when it was not used; (2) Si entrainment rate is 1154 people/min (3) Si transition ratio is 6.
3 (4) The upper surface temperature of the semiconductor wafer was improved by about -20°C, clearly showing the effect of the conductive silicon rubber.

Furthermore, the temperature distribution on the upper surface of the semiconductor wafer during etching became almost uniform.

What can be considered from the above experimental results is that as a result of the conductive silicone rubber significantly improving the adhesion between the semiconductor wafer and the lower electrode, (a) the electrical bond between the semiconductor wafer and the lower electrode becomes better and the semiconductor (b) The strength of the electric field between the wafer and the counter electrode is uniform, improving processing efficiency.
Thermal conductivity between the semiconductor wafer and the lower electrode is improved, and the cooling effect is improved. Furthermore, when the semiconductor wafer was separated from the isoelectric silicon rubber after the etching process was completed, no fusion was observed between the semiconductor wafer and the conductive silicon rubber, and there was no difference between the device and the device to which the conductive silicon rubber was not attached. It was still possible to separate easily.

This is because the shallow grooves formed on the conductive silicon rubber prevented fusion with the semiconductor wafer.

By the way, the present inventor also paid attention to the pressing force of the clamp ring against the semiconductor wafer, and conducted experiments to determine the relationship between the change in the pressing force of the clamp ring and the etching rate, which will be described below. The experiment was conducted under the experimental conditions shown in Table 3 below using the apparatus of the above-mentioned Example. Measurements were made at clamp pressures of 10k (If (2.5kgf per clamp ring support rod) and 27kgf (6.75kgf per clamp ring support rod).
gf), 42 kgf (10.5 kgf), and the results are shown in Figure 4.

(Leaving space below) Table 3 Experimental conditions In Figure 4, a, b, and C in X@ represent a point a on the periphery of the semiconductor wafer, a point a on the semiconductor wafer periphery, and a semiconductor wafer on the side opposite to a passing through b. A point provided on the periphery is designated as C, and the etching rate on these lines a→b→C is taken as the Y axis.

The experimental results reveal that (a) the etching rate decreases as the clamp pressure increases, and (b) the etching rate at the center of the semiconductor wafer decreases significantly when the clamp pressure is 27 kgf and 42 k(lf). There is something
(c) The most uniform etching can be achieved when the clamp pressure is 10 kgf.

This is because if the clamping pressure becomes too large, the semiconductor wafer 20 warps upward in an arc, creating a gap between the center of the semiconductor wafer and the conductive silicon rubber 33. Therefore, in the case of a 5-inch wafer with a thickness of 630 μm, it has been found that the most efficient method is to press the periphery with 10 kgf.

By the way, the more flexible the conductive synthetic resin film used in the present invention is, the better the adhesion will be, which is preferable, but when the wafer is fixed, stress is applied to the crumpling press area, that is, the periphery of the conductive synthetic resin film, causing wrinkles. These wrinkles may cause voids to form.

As another embodiment of the present invention, as shown in FIG. 5, a recess 40 is formed in the upper part of the wafer mounting table 22a, with a diameter slightly smaller than that of the semiconductor wafer 20 and a depth approximately equal to that of the conductive synthetic resin film. By attaching the conductive synthetic resin film 41 to this recess 40 (FIG. 5(a)), the stress on the outer circumferential portion of the conductive synthetic resin film 41 when the wafer is fixed is reduced to the wafer mounting table 2.
2a can reduce the appearance of wrinkles (
FIG. 5(b)), The conductive resin body used in the present invention is made of a material having excellent elasticity, thermal conductivity, and electrical conductivity, such as conductive Teflon, conductive silicone rubber, and conductive fluorine rubber. Any item is fine.

Further, the present invention can be applied to any apparatus, such as plasma CVD, ECR etching, and sputtering apparatuses, which have a structure in which an electrode and a substrate to be processed are in contact with each other and a plasma cloud is provided. Further, the plasma atmosphere is not limited to high frequency discharge, and may be formed by microwave discharge or direct current discharge.

[Effects of the Invention] As explained above, according to the plasma processing apparatus of the present invention, the adhesion between the object to be processed and the lower electrode is improved, so electrical coupling and thermal conductivity are improved, and uniformity is improved. It becomes possible to perform plasma processing with high efficiency and low processing efficiency.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an etching processing section of a plasma etching apparatus which is an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of FIG. 1, and FIG. 3 shows the operation of a wafer fixing mechanism. A sectional view, FIG. 4 is a diagram showing the relationship between clamp pressure and etching rate, and FIG. 5 is a wafer fixing aFf of another embodiment.
6 is a sectional view showing the conceptual configuration of a plasma etching device, FIGS. 7 and 8 are sectional views showing a conventional wafer fixing mechanism, and FIG. 9 is a sectional view showing a conventional wafer fixing mechanism. FIG. 3 is a diagram showing a processing state of the surface of a semiconductor wafer. 20... Semiconductor wafer, 21... Etching processing section, 22... Lower electrode, 22a...
... Wafer mounting table, 23 ... Opposing main peak, 3
0... Clamp ring, 31 Clamp ring support rod, 32... Air cylinder, 33...
・Conductive silicon rubber, 33a... Shallow groove, 3
4...Air cylinder, 35...Wafer push-up pin, 40...Concavity, 41...
・Conductive synthetic resin film. Applicant Tokyo Electron Co., Ltd. Agent
Patent Attorney Suyama Sa - Engineering Figure 2 (C1 Figure 3 Figure 4 (a) Figure 5 Figure 8 Figure 9

Claims (5)

[Claims] (1) In a plasma processing apparatus configured to perform plasma processing by placing an electrode in an airtight container equipped with a plasma generation source and bringing the substrate to be processed into contact with the surface of the electrode, the substrate to be processed by the electrode; A plasma processing apparatus characterized in that a conductive resin body is provided on a contact surface with the plasma processing apparatus. (2) The plasma processing apparatus includes an etching electrode on which a substrate to be processed is placed, a conductive synthetic resin film provided on the etching electrode, a counter electrode disposed facing the etching electrode, and the etching electrode. A substrate pressing ring body disposed above and parallel to the electrode, the inner diameter of which is slightly smaller than the outer diameter of the substrate to be processed; and the substrate pressing ring body is raised and lowered, and when lowered, the peripheral edge of the substrate to be processed is pressed against the etching electrode. 2. The plasma processing apparatus according to claim 1, further comprising a substrate pressing ring lifting device for pressing the substrate. (3) The plasma processing apparatus according to claim 1, wherein a rough surface is formed on the surface of the conductive resin body that comes into contact with the substrate to be processed. (4) The plasma processing apparatus according to claim 1, wherein the conductive resin body is adhered to the contact surface of the electrode that comes into contact with the substrate to be processed using a conductive synthetic resin adhesive. . (5) The plasma processing apparatus according to claim 1, wherein the conductive resin body is a conductive silicone rubber.