JPH11162940A - Plasma etching electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation of the electrode even when the temperature of the central part of the electrode become higher due to plasma and improve the uniformity of etching rate by providing the central part of the electrode consisting of single crystal silicon and an outer peripheral part of the electrode consisting of other material. SOLUTION: A plasma etching electrode 1 consists of a central part (the part exposed to plasma) 4 of the electrode consisting of single crystal silicon and a member 5 including the outer peripheral part of the electrode, and both of these are fixed together with a screw 6. A small gas blowout hole 2 is formed in the central part 4 of the electrode exposed to the plasma. A mounting hole 3 is formed in the member 5, including the outer peripheral part of the electrode, for mounting the plasma etching electrode plate to a plasma etching apparatus. In this plasma etching electrode 1, only the central part 4 of the electrode consists of single crystal silicon. Thus, even when the temperature of the central part of the electrode become higher due to plasma, the deformation of the electrode can be prevented and the electrode can easily be manufactured at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching electrode mounted on a plasma etching apparatus used in a process of etching a silicon wafer when manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, electrodes for plasma etching have been manufactured from materials such as single crystal silicon and glassy carbon. Above all, those made of single crystal silicon are frequently used because of their good performance, but they are made of single crystal silicon alone. In the manufacturing method, first, an ingot of single crystal silicon having a required diameter is sliced into a required thickness to obtain a disk. Then, after a gas blowing small hole and a mounting hole are formed in the disk, the surface is polished and washed to form an electrode. FIG. 1 is a sectional view of a typical single-crystal silicon plasma etching electrode. In FIG. 1, a single-crystal silicon disk-shaped electrode 1 for plasma etching is provided with gas blowing small holes 2.
And a mounting hole 3.

This electrode is mounted as an upper electrode in a plasma etching apparatus, and faces the lower electrode on which a wafer is placed. By generating plasma between the upper electrode and the lower electrode, the wafer is etched into a required shape. At this time, the portion of the single-crystal silicon plasma etching electrode exposed to the plasma is consumed at the same time when the wafer is etched. The consumable portion is a range exposed to the plasma and smaller than the outer diameter of the single-crystal silicon plasma etching electrode.

[0004] This electrode is consumed to a certain thickness,
When predetermined etching characteristics (etching rate, uniformity of etching rate, generated foreign matter) are out of specifications, they are replaced. The size of the electrode is larger than the diameter of the silicon wafer to be etched. For example, the size of the electrode used to etch a 6-inch wafer has an outer diameter of 200 mm (8 inches), and the size of the electrode used to etch an 8-inch wafer has an outer diameter of It is 280 mm (11 inches). Further, in order to etch a 12-inch wafer in the future, an electrode having an outer diameter of about 400 mm (15 inches) is considered necessary. As described above, the size of the electrode increases as the diameter of the silicon wafer to be etched increases, and the size must always be larger than the silicon wafer. It is very difficult to obtain single crystal silicon.
In addition, single-crystal silicon requires a technique for its production, and thus has the disadvantage that it is expensive.

[0005] In addition, an integrated large electrode formed of single crystal silicon alone has a plasma generating portion (electrode central portion) at least approximately equivalent to the diameter of a silicon wafer, which has a higher temperature due to plasma than the outer peripheral portion. As a result, temperature unevenness occurs, the electrode is deformed during use, and a gap is formed between the electrode and the back plate to which the electrode is attached. A reaction product due to the etching gas accumulates in the gap, passes through the gas blowing small hole, falls as a foreign substance on the silicon wafer, and has a defect that etching failure occurs. In addition, there is a disadvantage that a difference in etching rate occurs between the central portion and the outer peripheral portion of the wafer due to the non-uniform temperature, which causes a decrease in the uniformity of the etching rate.

[0006]

According to the first and second aspects of the present invention, even if the center of the electrode is heated to a high temperature by the plasma, the electrode is hardly deformed, and the price is low. An object of the present invention is to provide a plasma etching electrode that can be easily manufactured.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a disk-shaped plasma etching electrode comprising a single-crystal silicon electrode central portion and an electrode outer peripheral portion made of another material. About. The present invention also relates to the electrode for plasma etching, wherein the material of the outer peripheral portion of the electrode is glassy carbon, graphite, or aluminum coated with hard alumite.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the disk-shaped plasma etching electrode of the present invention, only the central portion of the electrode, that is, the portion exposed to plasma is made of single crystal silicon. This example is shown in FIGS.
Shown in 2 and 3 are cross-sectional views of the electrode 1 for plasma etching, each of which is composed of a single-crystal silicon electrode central part (part exposed to plasma) 4 and a member 5 including an electrode outer peripheral part. 6. A gas blowing small hole 2 is formed in an electrode central portion 4 exposed to plasma, and a mounting hole 3 for mounting a plasma etching electrode plate to a plasma etching apparatus is formed in a member 5 including an electrode outer peripheral portion. ing.

In the example shown in FIG. 2, the consumable portion at the center of the electrode is made of a single-crystal silicon disk over the entire thickness, and the outer peripheral portion of the electrode is manufactured in a ring shape from other materials, and is manufactured by a method of combining them. Things. As means for assembling, as shown in FIG. 2, a step structure that can be fitted to each other is formed and fitted. Further, if necessary, an assembling screw hole for fixing the both can be formed and screwed and fixed. Further, in the example of FIG. 3, only the exposed portion of the central portion of the electrode exposed to the plasma is a single-crystal silicon disk, and the other portions, that is, the outer peripheral portion and the side of the central portion of the electrode that are not exposed to the plasma are exposed. It is based on a method of forming a member integrally made of another material. In this shape, for example, a counterbore is formed in the center of the disk-shaped member on the side exposed to the plasma, and a single-crystal silicon disk is fitted therein. If necessary, it can be fixed by screwing.

The size of the plasma etching electrode is determined according to the size of the silicon wafer to be etched. When the size of the silicon wafer to be etched is 6 inches to 12 inches, it is preferable that the silicon wafer has an outer diameter of 200 to 400 mm and a thickness of 3 to 10 mm. The size of the central portion of the electrode made of single-crystal silicon is almost the same as the size of the silicon wafer to be etched, or larger in the range of 0 to 50 mm as compared with this, so that the etching can be performed uniformly and the electrode is hardly deformed. In the case of 6 inches to 12 inches, the outer diameter is preferably 150 to 350 mm. It is preferable that the difference between the outer diameter of the central portion of the electrode and the outer diameter of the outer peripheral portion of the electrode is 20 to 100 mm because the electrode is less likely to be deformed. It is preferable that 8 to 24 mounting holes for mounting the electrodes are provided on the outer peripheral portion. The size of the gas blowing hole for dispersing the etching gas in the form of a shower varies depending on the etching conditions and the like.
2.0 mm is preferable, and the number of holes is preferably 100 to 3000.

As the single crystal silicon used in the present invention, one manufactured by a known method such as the Czochralski method can be used. The material used for parts other than the center of the electrode exposed to plasma is made of glassy carbon, graphite, or alumite coated, which makes it relatively easy to manufacture relatively large products and is relatively inexpensive. Aluminum and the like are preferred. The method for producing these materials can be in accordance with a known method.

For example, glassy carbon is produced as follows. Using a phenolic resin, an epoxy resin, an unsaturated polyester resin, a furan resin, a melamine resin, an alkyd resin, a thermoplastic resin such as a xylene resin, or a mixture of these resins as a raw material, and further, if necessary, sulfuric acid as a curing agent , Hydrochloric acid, nitric acid, phosphoric acid and other inorganic acids, p
-Toluenesulfonic acid, organic sulfonic acid such as methanesulfonic acid, acetic acid, trichloroacetic acid, carboxylic acid such as trifluoroacetic acid, etc., preferably 0.0
It is used in an amount of from 01 to 20% by weight, molded by various molding methods according to the desired shape, and then cured. This curing is preferably performed by heat treatment at a temperature of 60 to 200 ° C, more preferably 70 to 100 ° C. After further processing as required, use a highly purified jig and furnace in an inert atmosphere (usually a non-oxidizing gas such as an inert gas such as helium or argon or nitrogen, hydrogen or halogen gas). In an oxygen-free atmosphere composed of at least one kind of gas or under vacuum), preferably 800 to 300
Firing and carbonizing at a temperature of 0 ° C, more preferably 1100 to 2800 ° C. Then, heat treatment is preferably performed at a temperature of 1300 to 3500 ° C. to obtain glassy carbon.

The graphite material is manufactured as follows. A binder such as a pitch and an aggregate such as coke are preferably blended in a weight ratio of aggregate / binder of 7/3 to 5/5 and kneaded by heating (also referred to as kneading). After cooling, it is ground and then molded. There is no particular limitation on the molding method, and a method in which the material is filled into a mold and molded by a uniaxial press, extrusion molding, rubber press (CIP), or the like can be used. Then
A firing step is performed. The firing can be performed using a batch-type furnace, a continuous-type furnace, or the like, preferably at 700 to 1000 ° C. After firing, pitch and the like can be impregnated as necessary, and the above firing can be performed again. After firing, graphitization is performed.
Graphitization is preferably performed at 2400 to 3000 ° C. using a batch type Acheson furnace, induction furnace, continuous type, or the like.

In the present invention, the central portion of the electrode exposed to the plasma is made of single-crystal silicon, and the outer peripheral portion of the electrode is made of a different material. It can be absorbed by the slip at the joint between the central part and the outer peripheral part. From this point, when a screw is used to fix the single crystal silicon to another member, it is preferable that the surface roughness of the counterbore hole to which the screw is attached is Ra 5 μm or less.

[0015]

The present invention will be described below in detail with reference to examples. Example 1 The electrode for plasma etching manufactured in this example has the shape shown in FIG. Disc of single crystal silicon having a resistivity of 10 Ωcm, conductivity type P and crystal face 001 (size: outer diameter φ2
After forming a step structure (outer diameter φ220 mm on the stepped side, step height 2 mm) as shown in FIG. 2 on the outer periphery of 40 mm, thickness 5 mm, a pitch circle diameter (P. C. D) Four counterbore holes 3 (Ra 5 μm or less) are provided on the outer circumference of 230 mm. Further, 633 holes having a diameter of 0.5 mm were formed in the center portion as gas blowing holes at a pitch of 7 mm. This is the electrode center (consumable part)
Used as (Part 1). Next, a bulk density of 1.52,
Glass-like carbon (PXG-3S, Hitachi Chemical Co., Ltd.) having an electrical resistivity of 45 μΩm, a bending strength of 160 MPa and a Shore hardness of 127
Co., Ltd.) has an outer diameter of 280 mm, an inner diameter of 220 mm, and a thickness of 5 mm.
After being formed into a ring shape as described above, P.S. C. Four M3 screw taps were provided at D230 mm, and the inner periphery was a stepped structure to be fitted to the component 1. In addition, a P.I. C. Twelve counterbored holes for mounting were provided at D254 mm. This was defined as an outer peripheral portion (part 2).
Hard anodized aluminum aluminum 6061
A screw No. 3 was manufactured, and parts 1 and 2 were combined using this screw to form an electrode for etching an 8-inch wafer.

Embodiment 2 The electrode for plasma etching manufactured in this embodiment has a shape shown in FIG. Disc of single crystal silicon having a resistivity of 30 Ωcm, conductivity type P type and crystal face 001 (size: outer diameter φ24
0 mm, thickness 3 mm) C. Four M3 taps are provided at D230. Further, 633 holes having a diameter of 0.5 mm were formed at a central portion at a pitch of 7 mm as gas blowing holes. This is used as a central part (consumable part) (part 3). Next, the bulk density was 1.82, and the electrical resistivity was 12 μm.
A high purity isotropic graphite material (PD-600S, manufactured by Hitachi Chemical Co., Ltd.) having a bending strength of 50 Mpa and a Shore hardness of 60 was formed into a disk having an outer diameter of 280 mm and a thickness of 5 mm. A counterbore with a diameter of 240 mm and a depth of 3 mm for inserting C. D230mm was provided with an assembly hole.
Further, a P.O. C. D2
Twelve counterbored holes for attachment were provided at 54 mm. Further, 633 holes having a diameter of 1.0 mm were formed at a central portion at a pitch of 7 mm as gas blowing small holes. This was defined as an outer peripheral portion (part 4). M3 screws are manufactured from aluminum Al6061 + hard anodized products, and parts 3
And component 4 were combined to form an electrode for etching an 8-inch wafer.

COMPARATIVE EXAMPLE 1 A single-crystal silicon disk (size: outer diameter φ280 mm, thickness 5 mm) having a resistivity of 30 Ωcm, conductivity type P, and crystal face 001 has a small hole of φ0.5 as a gas blowing small hole. 7mm hole
633 were opened at the pitch. In addition, a P.I. C. Twelve counterbored holes for mounting were provided at D254 mm. This was used as an electrode for etching an 8-inch wafer.

Evaluation Using the electrodes for plasma etching obtained in Examples 1 and 2 and Comparative Example 1, this electrode plate was set in a plasma etching apparatus, and the reaction gas was methane trifluoride (CHF ₃ ).
And methane tetrafluoride (CF ₄ ), carrier gas: argon (Ar), gas pressure in the reaction chamber: 0.5 Torr,
An oxide film was etched on a silicon wafer having a diameter of 8 inches under the condition of RF power: 800 W. At this time, the number of powder particles of 0.15 μm or more adhering to the surface of the silicon wafer was counted. Table 1 shows the results. Further, the uniformity of the etching rate was measured at a total of 17 points including one point at the center part, eight points at the middle part, and eight points at the outer peripheral part of the wafer, and the maximum point (max) and the minimum point (min) of the etching rate were measured. It was calculated from the value by the following equation.

(Equation 1)

[0019]

[Table 1] As described above, the combined electrode according to the present invention was more effective in the number of foreign particles generated and the uniformity of the etching rate than in the case where the conventional electrode was integrally manufactured.

[0020]

According to the first and second aspects of the present invention, even if the center of the electrode is heated by plasma, the electrode is hardly deformed, and the cost is lower. It can be easily manufactured, has a small number of generated foreign matters, and has excellent etching rate uniformity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a conventional plasma etching electrode.

FIG. 2 is a sectional view showing an example of the electrode for plasma etching of the present invention.

FIG. 3 is a sectional view showing an example of the electrode for plasma etching of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Plasma etching electrode 2 Gas blowing small hole 3 Mounting hole 4 Central part of electrode (part exposed to plasma) 5 Other members including electrode outer peripheral part 6 Screw

Claims (2)

[Claims] 1. A disk-shaped plasma etching electrode comprising a single-crystal silicon electrode central part and an electrode outer peripheral part made of another material. 2. The electrode for plasma etching according to claim 1, wherein the material of the outer periphery of the electrode is glassy carbon, graphite or aluminum coated with hard alumite.