JPH0945669A - Electrode plate for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate, for a plasma etching operation, by which carbon particles which fall onto the surface of a wafer adhere thereto are small in the etching operation, by which the etching operation is performed stably and by which an electrode can be used for many hours. SOLUTION: In an electrode plate for a plasma etching operation, glasslike carbon whose raw material is a mixture of a liquid phenolic resin and a powdery phenolic resin having a number average molecular weight of 250 to 350 and having a viscosity at 25 deg.C of 100 to 350 centipoises is used as a basic material.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to an electrode plate for plasma etching.

[0002]

2. Description of the Related Art Glassy carbon has the properties of ordinary carbon materials such as light weight, heat resistance, corrosion resistance, and electrical conductivity, as well as gas impermeability, high hardness, and low dust generation. Because of its characteristics, it is being used for a wide range of applications in various fields such as the electronics industry, the nuclear industry, and the aviation industry. Recently, JP-A-62-10931
As described in Japanese Unexamined Patent Publication (Kokai) No. 7, utilizing the property that carbon particles do not drop off or adhere, it is considered to be used as an electrode plate for plasma etching of a wafer when manufacturing a semiconductor integrated circuit.

However, the performance of semiconductor integrated circuits in recent years has been improved, and there are problems such as generation of finer particles and unstable etching rate, which have not been problems in the past. The required performance of an electrode plate for plasma etching is becoming more sophisticated, and in particular, an electrode plate having a small number of particles such as carbon particles which drop and adhere to a wafer surface during etching is required.

[0004]

The present invention satisfies the above-mentioned requirements. That is, the invention according to claim 1 provides a plasma-etched electrode plate in which carbon particles that fall onto the wafer surface during etching are small and adhered, stable etching is possible, and the electrode can be used for a long time.
The invention described in claim 2 is to provide a plasma etching electrode plate in which the electrode can be used for a long time in the problem to be solved by the invention described in claim 1. The invention according to claim 3 provides a plasma etching electrode plate capable of particularly stable etching in the problem to be solved by the invention according to claim 1.

[0005]

The present invention has a number average molecular weight of 250 to 350 and a viscosity at 25 ° C. of 100.
The present invention relates to an electrode plate for plasma etching using glassy carbon as a base material, which is made of a mixture of a liquid phenol resin and a powdery phenol resin of about 350 centipoise. The present invention also relates to the above-mentioned electrode plate for plasma etching, wherein the substrate has an apparent density of 1.50 to 1.53 g / cm ³ and an impurity content of 20 ppm or less. Further, the present invention relates to the plasma etching electrode plate, wherein the pore diameter of the substrate is 5 μm or less.

In the present invention, as the glassy carbon base material, a raw material is a mixture of a liquid phenol resin having a number average molecular weight of 250 to 350 and a viscosity at 25 ° C. of 100 to 350 centipoise and a powdery phenol resin. is important. One of them has a drawback that the moldability is lowered. The phenol resin can be obtained by reacting phenol or its derivative, aldehydes such as formaldehyde using an alkali catalyst or an acid catalyst, and a resol type phenol resin reacted under an alkali catalyst is preferable. Here, when the number average molecular weight of the liquid phenol resin is less than 250 or more than 350, there is a drawback that the obtained base material has many pores and particles increase. For the same reason, the preferred number average molecular weight range is 27.
0 to 340, and a more preferable range of the number average molecular weight is 270 to 280. The number average molecular weight can be measured by a liquid chromatography method.

Further, when the viscosity at 25 ° C. is less than 100 centipoise or more than 350 centipoise, pores are generated in the tissue. A preferable range is 110 to 320 centipoise, and a more preferable range is 110 to 250 centipoise in terms of the number of pores. On the other hand, the powdery phenolic resin used in the present invention preferably has good compatibility with the liquid phenolic resin. In order to obtain the powdery phenolic resin, it is preferable to use, for example, a liquid phenolic resin, which is molded and cured so as to suppress the generation of pores and then crushed to a predetermined particle size. Although it varies depending on the raw material used, it is preferable to use the liquid phenol resin as a raw material, which is cured at 70 to 120 ° C. If the resin is cured at a temperature higher than 120 ° C., the compatibility with the liquid resin tends to be lowered, which may cause the generation of pores. Tends to not be obtained. The powdery phenolic resin preferably has a weight average particle size of 10 to 30 μm. 10
If it is less than μm, aggregation of particles tends to increase, and as a result, pores tend to be generated. On the other hand, if it exceeds 30 μm, the liquid phenol resin becomes ubiquitous and pores tend to be generated.

The number average molecular weight is 250 to 350 and 2
The mixing ratio of the liquid phenolic resin having a viscosity of 100 to 350 centipoise at 5 ° C. and the powdery phenolic resin is 10/90 to 90/10 in terms of the weight ratio of the former / the latter in view of the characteristics and moldability of the obtained base material. Is preferred, 20 / 80-
80/20 is more preferable, and 30/70 to 60/40 is further preferable. The obtained resin mixture is molded into a predetermined shape according to the desired shape of the electrode for plasma etching before curing, but is not particularly limited.
After being molded into a predetermined shape, it is cured. Molding and curing can be performed under heating conditions and a heating rate at which condensed water or the like easily escapes to the outside, or by setting an appropriate amount of a catalyst for curing. The heating temperature is preferably 130 to 200 ° C. Further, it is preferable that the temperature is raised at 5 to 30 ° C./hour. Then, in an inert atmosphere (usually an oxygen-free atmosphere consisting of an inert gas such as helium or argon or at least one gas of a non-oxidizing gas such as nitrogen, hydrogen or halogen gas, under reduced pressure or under vacuum) Preferably 8
A temperature of 00 to 1200 ° C, more preferably 900 to 11
It is fired and carbonized at a temperature of 00 ° C. Then preferably 1
Glassy carbon is obtained by high-temperature treatment at a temperature of 500 ° C. or higher, more preferably 1700 ° C. or higher.

The glassy carbon obtained has an impurity content of 2
It is preferably 0 ppm or less. If the impurity content exceeds 20 ppm, the wafer tends to be contaminated during etching. Two
To achieve 0 ppm or less, use a highly purified graphite jig in an inert atmosphere (usually an atmosphere of at least one kind of an inert gas such as helium and argon and a non-oxidizing gas such as nitrogen, or a mixed gas thereof), After firing in a vacuum or the like, a method of using a highly purified graphite jig and a furnace and treating in an inert atmosphere, a vacuum or the like is used. The impurity content can be measured by the graphite ash content measuring method of JIS.

The apparent density of the glassy carbon substrate obtained by the above method is 1.5 in view of reducing the consumption rate.
It is preferably 0 to 1.55 g / cm ³ , and 1.50 to
More preferably, it is 1.53 g / cm ³ . The pore diameter is preferably 5 μm or less in order to reduce the particles, and 3 μm or less is preferable in order to reduce the particles. The pore diameter is obtained by measuring the maximum pore diameter per 1 mm 2 in the product cross section. The electrode plate for plasma etching may be obtained by obtaining a glassy carbon substrate having an unprocessed shape and then processing it into a predetermined shape by electrical discharge machining, ultrasonic machining, or the like.

The plasma etching electrode plate obtained as described above is mounted on a plasma etching apparatus,
Used for etching oxide film on silicon wafer. FIG. 1 shows a schematic diagram of a plasma etching apparatus equipped with an electrode plate for plasma etching. In FIG.
The electrode plate for plasma etching is used for the upper electrode 1. A reaction gas such as CHF ₃ or CF ₄ is introduced through the gas outlet 4 and plasma generated by high frequency etches an oxide film on the silicon wafer 3 placed on the lower electrode 2. The size, shape, etc. of the electrode plate for plasma etching are not particularly limited according to the device to be mounted. An example is shown in FIG. FIG. 2 is a front view of an example of the electrode plate for plasma etching.

[0012]

Embodiments of the present invention will be described below. Example 1 Using ammonia as an alkali catalyst, heating at 70 ° C. for 1 hour, 940 parts by weight of phenol and 3 parts of formaldehyde were used.
By reacting 60 parts by weight, a liquid phenol resin having the physical properties shown in Table 1 was obtained. On the other hand, powdered phenolic resin is prepared by injecting the above resin into a mold for 3 days at 50 ° C, 3 days at 70 ° C, 90 ° C.
After drying and curing for 3 days, the average particle size is 11 μm with a crusher.
It was crushed to obtain. 60 parts by weight of a powdery phenolic resin was added to 40 parts by weight (solid content) of the liquid phenolic resin and mixed while removing the solvent to obtain a molding powder having an average particle diameter of 30 μm. Put this in a mold heated to 80 ° C and
It was molded for 15 minutes with a pressing force of 00 kg / cm ³ to obtain a disk-shaped molded product having a thickness of 4 mm and a diameter of 285 mm. This molded body has a diameter of 0.
After making a large number of 8 mm through small holes at a pitch of 3 mm and processing the shape shown in FIG. 2, the temperature is raised up to 160 ° C. at 5 ° C./hour and held at 160 ° C. for 3 days to carry out a hardening treatment. Then, after putting it in a ring furnace and calcining and carbonizing at a temperature of 1300 ° C. in a nitrogen stream, a high-purity atmosphere furnace was used to carry out 2 in an inert atmosphere.
High temperature treatment was performed at a temperature of 000 ° C. to obtain glassy carbon. The amount of impurities in the obtained glass-like carbon plasma-etched electrode plate was 20 ppm or less.

Next, the obtained electrode plate was attached to the plasma etching apparatus having the structure shown in FIG. 1, and reaction gas: trifluoromethane, carrier gas: argon, gas pressure in the reaction chamber: 1 Torr, power supply frequency: 13.5 MHz. Under the above conditions, a silicon wafer having a diameter of 6 inches was etched with an oxide film. 0.1 attached to the surface of the silicon wafer at this time
The number of powder particles of 5 μm or more was counted. The results are also shown in Table 1 as the number of particles. The number average molecular weight was measured by gel permeation chromatography and determined in terms of standard polystyrene. RI-3H manufactured by Nippon Analytical Industry Co., Ltd. was used as a detection device, and gel packs R420, R430 and R440 (all manufactured by Hitachi Chemical Co., Ltd.) were connected in series as columns.

Example 2 Using ammonia as an alkali catalyst, 940 parts by weight of phenol and 360 parts by weight of formaldehyde were reacted under heating at 80 ° C. for 1.5 hours to obtain a liquid phenol resin having the physical properties shown in Table 1. On the other hand, powdered phenolic resin is injected into the mold with the above resin for 3 days at 50 ° C, 3 days at 70 ° C for 9 days.
After drying and hardening at 0 ° C for 3 days, the average particle size is 27 with a crusher.
It was obtained by crushing to μm. 60 parts by weight of a powdery phenolic resin was added to 40 parts by weight (solid content) of the liquid phenolic resin and mixed while removing the solvent to obtain a molding powder having an average particle diameter of 30 μm. Put this in a mold heated to 80 ° C and
It was molded for 15 minutes with a pressing force of 00 kg / cm ³ to obtain a disk-shaped molded product having a thickness of 4 mm and a diameter of 285 mm. This molded body has a diameter of 0.
After making a large number of 8 mm through small holes at a pitch of 3 mm and processing the shape shown in FIG. 2, the temperature is raised up to 160 ° C. at 5 ° C./hour and held at 160 ° C. for 3 days to carry out a hardening treatment. Then, after putting it in a ring furnace and calcining and carbonizing at a temperature of 1300 ° C. in a nitrogen stream, a high-purity atmosphere furnace was used to carry out 2 in an inert atmosphere.
High temperature treatment was performed at a temperature of 000 ° C. to obtain glassy carbon. The amount of impurities in the obtained glass-like carbon plasma-etched electrode plate was 20 ppm or less.

Next, the obtained electrode plate was attached to the plasma etching apparatus having the structure shown in FIG. 1, and reaction gas: trifluoromethane, carrier gas: argon, gas pressure in the reaction chamber: 1 Torr, power supply frequency: 13.5 MHz. Under the above conditions, a silicon wafer having a diameter of 6 inches was etched with an oxide film. 0.1 attached to the surface of the silicon wafer at this time
The number of powder particles of 5 μm or more was counted. The results are also shown in Table 1 as the number of particles.

Example 3 To 40 parts by weight (solid content) of the resin obtained in Example 1 was added 60 parts by weight of powdered phenolic resin (Bellpearl R-800 manufactured by Kanebo Co., Ltd.) having an average particle size of 19 μm. Mixing was performed while removing the solvent to obtain a molding powder having an average particle diameter of 30 μm. This was placed in a mold heated to 80 ° C. and molded for 15 minutes with a pressing force of 800 kg / cm ³ to obtain a disk-shaped molded body having a thickness of 4 mm and a diameter of 285 mm. A large number of through-holes with a diameter of 0.8 mm were perforated in this molded body at a pitch of 3 mm, and the shape shown in FIG. 2 was processed. After holding and hardening treatment, it was put into an annular furnace and calcined and carbonized at a temperature of 1300 ° C. in a nitrogen stream, and then high-temperature treatment was carried out at a temperature of 2000 ° C. in an inert atmosphere using a high-purity atmosphere furnace to obtain glassy carbon. And The amount of impurities in the obtained glass-like carbon plasma-etched electrode plate was 20.
It was below ppm.

The electrode plate thus obtained was attached to a plasma etching apparatus having the structure shown in FIG. 1, and reaction gas: trifluoromethane, carrier gas: argon, gas pressure in the reaction chamber: 1 Torr, power supply frequency: 13.5 MHz. Under the above conditions, a silicon wafer having a diameter of 6 inches was etched with an oxide film. 0.1 attached to the surface of the silicon wafer at this time
The number of powder particles of 5 μm or more was counted. The results are also shown in Table 1 as the number of particles.

Example 4 To 40 parts by weight (solid content) of the resin obtained in Example 2, 60 parts by weight of a powdery phenolic resin having an average particle diameter of 19 μm (Bellpearl R-800 manufactured by Kanebo Co., Ltd.) was added, Mixing was performed while removing the solvent to obtain a molding powder having an average particle diameter of 30 μm. This was placed in a mold heated to 80 ° C. and molded for 15 minutes with a pressing force of 800 kg / cm ³ to obtain a disk-shaped molded body having a thickness of 4 mm and a diameter of 285 mm. A large number of through-holes with a diameter of 0.8 mm were perforated in this molded body at a pitch of 3 mm, and the shape shown in FIG. 2 was processed. After holding and hardening treatment, it was put into an annular furnace and calcined and carbonized at a temperature of 1300 ° C. in a nitrogen stream, and then high-temperature treatment was carried out at a temperature of 2000 ° C. in an inert atmosphere using a high-purity atmosphere furnace to obtain glassy carbon. And The amount of impurities in the obtained glass-like carbon plasma-etched electrode plate was 20.
It was below ppm.

The electrode plate thus obtained was attached to a plasma etching apparatus having the structure shown in FIG. 1, and reaction gas: trifluoromethane, carrier gas: argon, gas pressure in the reaction chamber: 1 Torr, power supply frequency: 13.5 MHz. Under the above conditions, a silicon wafer having a diameter of 6 inches was etched with an oxide film. 0.1 attached to the surface of the silicon wafer at this time
The number of powder particles of 5 μm or more was counted. The results are also shown in Table 1 as the number of particles.

Comparative Examples 1 to 4 Plasma electrode plates for plasma etching were prepared in the same manner as in Example 1 except that the liquid phenol resin having the physical properties shown in Table 2 prepared from the same raw materials as in Example 1 was used. And evaluated. Table 2 shows the characteristics.

Comparative Example 5 The liquid phenol resin used in Example 1 was used as 100 parts by weight, and the liquid phenol resin was cured without using the powdery phenol resin. Then, the same treatment as in Example 1 was carried out to prepare an electrode plate for plasma etching. evaluated. Table 2 shows the characteristics. Comparative Example 6 As a conventional material, furan resin (Hitafuran VF-303 manufactured by Hitachi Chemical Co., Ltd.) was added to paratoluenesulfonic acid 50% by weight.
Table 2 shows the characteristics of the electrode plate for plasma etching obtained by adding 0.6 part by weight of an aqueous solution and curing the same, and then performing the same treatment as in Example 1.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

EFFECT OF THE INVENTION The plasma etching electrode plate according to claim 1 has a significantly small number of harmful carbon fine particles generated during etching, can be used for a long time, and has stable etching processing without trouble. Can be done. The electrode plate for plasma etching according to claim 2 is the electrode plate according to claim 1.
The effect of the electrode plate for plasma etching described above is exhibited, and the life is particularly excellent. The electrode plate for plasma etching according to the third aspect has the effect of the electrode plate for plasma etching according to the first aspect, and is particularly excellent in stability.

[Brief description of drawings]

FIG. 1 is a schematic view of a plasma etching apparatus equipped with a plasma etching electrode plate of the present invention.

FIG. 2 is a front view of an example of a plasma etching electrode plate of the present invention.

[Explanation of symbols]

 1 ... Electrode plate for plasma etching (upper electrode) 2 ... Lower electrode 3 ... Silicon wafer 4 ... Gas blowout hole

Claims (3)

[Claims] 1. A number average molecular weight of 250 to 350,
An electrode plate for plasma etching using glassy carbon as a base material, which is made of a mixture of a liquid phenol resin having a viscosity of 100 to 350 centipoise at 25 ° C. and a powdery phenol resin. 2. The apparent density of the substrate is 1.50 to 1.55.
The electrode plate for plasma etching according to claim 1, which has g / cm ³ and an impurity content of 20 ppm or less. 3. The electrode plate for plasma etching according to claim 1, wherein the pore diameter of the base material is 5 μm or less.