JP2000021853A - Electrode plate for plasma etching and plasma etching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of discharge foreign matters by preventing removal of a phlorocarbon film generated through creeping of plasma to an electrode rear by constituting an average value of central line average roughness based on JIS B 0601 measured at least at five places at an electrode attaching surface side to be at least a specified value. SOLUTION: An average value of central line average roughness based on JIS B 0601 measured at least at five places at an electrode attaching surface side of a glass-like carbon plasma etching electrode plate 2 with a gas blow out small hole 6 is constituted to be at most 0.5 to 5 μm. Adjustment to such surface roughness is carried out by polishing of a rear of the plasma etching electrode plate 2 through polishing by abrasive grain, polish processing, sand blast treatment, etc. Thereby, it is possible to prevent a phlorocarbon film generated through creeping of plasma to an electrode rear from removing, thus reducing the number of discharge foreign matters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode plate for plasma etching and a plasma etching apparatus. More specifically, in a parallel plate type plasma etching apparatus and an apparatus having an electrode having gas blowing holes for dispersing an etching gas in a shower shape, and an electrode on which a silicon wafer is placed opposite to the electrode. And an electrode to which the high-frequency power is applied.

[0002]

2. Description of the Related Art As shown in FIG. 1, a parallel plate type plasma etching apparatus equipped with a plasma etching electrode plate has an upper electrode (plasma etching electrode plate) 2 and a lower electrode 3 in a vacuum vessel 1. A silicon wafer 4 is placed as an object to be processed on the lower electrode 3 at intervals. The back plate 5 and the plasma etching electrode plate 2 are provided with gas blowing small holes 6 for allowing an etching gas to flow therethrough.

A high-frequency power source 7 applies high-frequency power between the upper electrode 2 and the lower electrode 3 while flowing an etching gas toward the silicon wafer 4 through the gas blowing small holes 6 to form a plasma 9. The silicon wafer 4 is etched by this plasma to form a device having a predetermined pattern. The shield ring 8 is made of an insulating material such as alumina or quartz, and covers an outer peripheral portion of the plasma etching electrode plate 2 to protect mounting screws provided on the outer periphery of the plasma etching electrode plate 2 from plasma. Is installed as follows.

As the plasma etching electrode plate 2 is used, a portion where plasma is generated, that is, a portion having substantially the same area as the opposed silicon wafer 4 is etched and consumed by the plasma. Therefore, when the plasma etching electrode 6 is consumed to some extent and the etching characteristics (for example, foreign particles attached to the silicon wafer 4 during the etching) are out of the standard, the use of the plasma etching electrode plate 2 is stopped, and a new electrode is used. Exchange.

[0005] Recently, as an electrode plate for plasma etching, in addition to having properties such as light weight, heat resistance, corrosion resistance, electric conductivity, and high purity that a general carbon material has, and gas impermeability. Since it has features such as high hardness and low dusting properties, glassy carbon is used, and it is considered to be an excellent electrode plate for plasma etching that does not cause carbon particles to fall off or adhere.

As semiconductor devices become more highly integrated, there is a demand for further reduction of discharge foreign substances.
Some of the discharge foreign substances are caused by a fluorocarbon polymer film generated by a reaction gas used in the process, in addition to carbon fine particles desorbed from the electrode.

The fluorocarbon film is highly used as a side wall protective film for etching an object to be etched with high anisotropy. However, if generated excessively, it adheres to and separates from members in the chamber and causes particles. Become. Although the formation of an excessive fluorocarbon film can be reduced to some extent by optimizing the process conditions such as the composition ratio of the reaction gas, the influence cannot be completely eliminated. Since the electrode plate for plasma etching is mounted so as to face the wafer, if the fluorocarbon film adheres to and separates from the back surface (mounting surface) of the electrode, it falls onto the wafer as particles. If the dropped fluorocarbon film adheres to the wafer and becomes a discharge foreign substance, it causes a reduction in the yield of semiconductor elements. The fluorocarbon film is generated when the ionized etching gas (plasma) collides with a member in the chamber and is deactivated. The fluorocarbon film adhered to the back surface of the electrode plate for plasma etching is generated by inactivating the plasma that has flowed into the back surface of the electrode through the gas blowing small hole.

Therefore, in order to prevent the deposition of the fluorocarbon film on the back surface of the upper electrode, it is effective to devise the shape of the gas blowing small hole provided in the electrode to prevent the plasma from entering the electrode mounting surface. . In addition, even if the plasma wraps around the electrode mounting surface side and the fluorocarbon film is deposited, it is necessary to take measures such as preventing the deposited fluorocarbon film from falling onto the wafer through the gas holes.

In order to prevent the plasma from flowing around, it is effective to increase the flow rates of the etching gas and the carrier gas passing through the gas holes. However, in order to perform the etching process with high anisotropy and stability, it is necessary to keep the gas composition to be supplied and the degree of vacuum in the apparatus constant. It is virtually impossible to change the ratio.

Accordingly, the present inventors have found that even if the plasma wraps around the electrode mounting surface side and the fluorocarbon film is deposited without changing the optimized process gas composition ratio and gas amount, the deposited fluorocarbon film can be removed. Investigate ways to avoid falling onto the wafer through the gas holes, and to prevent the deposited fluorocarbon film from falling off,
The surface roughness of the electrode mounting surface was studied. further,
In order to reduce the adhesion of the fluorocarbon film to the back surface of the electrode, the study was conducted by paying attention to the shape of the gas blowing small hole provided in the electrode.

[0011]

According to the present invention, an electrode plate which satisfies the above-mentioned requirements has been found. That is, the first aspect of the present invention is to provide an electrode plate for plasma etching that prevents the fluorocarbon film from falling off due to the plasma wraparound to the back surface of the electrode, and consequently enables the number of discharge foreign substances to be reduced. It is. In addition, the invention according to claim 2 provides, in addition to the object of the invention according to claim 1, prevention of plasma from flowing to the back surface of the electrode,
It is an object of the present invention to provide an electrode plate for plasma etching which prevents the adhesion of a fluorocarbon film and consequently enables a higher reduction in the number of discharge foreign substances. Further, the invention according to claim 3 is generated by the sneak of the plasma to the back surface of the electrode,
An object of the present invention is to provide a plasma etching apparatus capable of preventing a fluorocarbon film from falling off and consequently reducing the number of discharge foreign substances.

[0012]

Means for Solving the Problems According to the present invention, an average value of Ra according to JIS B 0601 measured at at least five places on the electrode mounting surface side having a gas blowing small hole is 0.5.
The present invention relates to an electrode plate for plasma etching made of glassy carbon having a thickness of about 5 μm. The present invention also provides the above-mentioned glass-like carbon-made plasma etching electrode plate having gas blowing holes having a ratio (X / Y) of 9 or more in thickness (X) of the electrode to diameter (Y) of the gas blowing holes. About. Furthermore, the present invention relates to a plasma etching apparatus having the above-mentioned electrode plate for plasma etching.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a parallel plate type plasma etching apparatus, the shape of an electrode plate for plasma etching is generally disk-shaped, and has gas blowing small holes. Ra (center line average roughness) according to JIS B 0601 measured at least at five places on the back surface of the electrode, that is, on the electrode mounting surface side.
By setting the average value to 0.5 to 5 μm, desorption of the fluorocarbon film deposited on the back surface of the electrode can be prevented. If the average value of Ra on the back surface of the electrode is less than 0.1, the effect of preventing desorption of the fluorocarbon film is not exhibited, and if the average value of Ra exceeds 5 μm, the glassy carbon from the rough surface Many particles are detached, resulting in an increase in discharge foreign substances.

In the present invention, Ra (center line average roughness) is measured by a surface roughness meter according to JIS B 0601, and the cut-off value is 0.5.
0.8mm, 2.0μ
2.5 mm when the length is larger than m and 10.0 μm or less, and the reference length is 4 m when the length is larger than 0.5 μm and 2.0 μm or less.
m, larger than 2.0 μm and smaller than 10.0 μm.
It was measured as 5 mm. In the study of the present invention, Ra was measured at a speed of 0.3 mm / sec by using a surface roughness profile measuring device Surfcom 503B manufactured by Tokyo Seimitsu Co., Ltd., and using a stylus having a tip of R5 μm.

As a method of adjusting the surface roughness as described above, there is a method in which the back surface of the electrode plate for plasma etching is polished with abrasive grains, polished, sandblasted, or the like. The roughness can be arbitrarily reduced within the range of Ra 0.01 to 10 μm.

In the present invention, it is effective to reduce the diameter of the gas blowing small hole and increase the thickness of the electrode in order to prevent the plasma from flowing to the back surface of the electrode. The thickness of the electrode and the diameter of the gas blowing hole were variously combined, and the amount of discharge foreign matter generated was investigated under the same conditions. As a result, as described above, the electrode thickness (X) and the gas blowing hole were determined. Of the diameter (Y) of the (X / Y)
Was found to be more remarkable when the value was 9 or more. In a conventional glass-like carbon plasma etching electrode plate, the ratio (X / Y) of the thickness (X) of the electrode to the diameter (Y) of the gas blowing small hole is used.
Was less than 9.

Here, when the ratio (X / Y) of the thickness (X) of the electrode to the diameter (Y) of the gas blowing small hole is less than 9, the plasma wrap around the back surface of the electrode is large, and Abnormal discharge is generated between the substrate and the back plate, and as a result, the generation of discharge foreign substances tends to increase. On the other hand, as the ratio increases,
The supply of the etching gas becomes non-uniform, and the etching tends to be not performed uniformly. Therefore, the ratio (X / Y) between the thickness (X) of the electrode and the diameter (Y) of the gas blowing small hole is obtained.
Is preferably 9 to 30, and more preferably 10 to 20.

In view of the above-mentioned effects, the gas blowing small holes satisfying the above-mentioned relationship are preferably 50% or more, more preferably 80% or more, of all the gas blowing small holes provided in the electrode plate for plasma etching. Is more preferable, and 100% is very preferable. Further, the number of gas blowing small holes and the diameter of the holes are not particularly limited, and vary depending on the size of the silicon wafer to be etched, etching conditions, and the like, but the hole diameter is preferably 0.3 to 2.0 mm, and the number of holes is preferably 100-3000 pieces are preferred.

The size and shape of the electrode plate for plasma etching of the present invention are not particularly limited, but a disk-shaped one having an outer diameter of 150 to 400 mm and a thickness of 3 to 10 mm is preferable. Further, it is preferable to provide 8 to 24 mounting holes on the outer peripheral portion for mounting the electrodes to the plasma etching apparatus.

The raw material and production method of the glassy carbon used in the present invention are not particularly limited. Examples of the thermosetting resin used as a raw material include a phenol resin, an epoxy resin, an unsaturated polyester resin, a furan resin, a melamine resin, an alkyd resin, a xylene resin, and a polycarbodiimide resin. Also, a mixture of these resins can be used. Among these, a phenol resin or a furan resin is preferred.

A curing agent is used depending on the type of the thermosetting resin. Examples of the curing agent include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid; and carboxylic acids such as acetic acid, trichloroacetic acid, and trifluoroacetic acid. The curing agent is preferably used in an amount of 0.001 to 20% by weight depending on the thermosetting resin.

The thermosetting resin is added with the curing agent as needed, then molded by various molding methods according to the desired shape, and then subjected to a curing treatment. This curing can be carried out by heat treatment at a temperature of preferably from 30 to 200C, more preferably from 70 to 100C.

If necessary, after further performing predetermined processing as an electrode plate for plasma etching, using a highly purified jig and a furnace, an inert gas (usually an inert gas such as helium, argon or the like) is used. Or an atmosphere in which oxygen consisting of at least one of non-oxidizing gases such as nitrogen, hydrogen, halogen gas and the like, or in a vacuum), preferably at 800 to 3000 ° C, more preferably 1100 to 2 ° C.
Carbonization at a temperature of 800 ° C. Then preferably 1
Heat treatment can be performed in a temperature range of 300 to 3000 ° C. to obtain glassy carbon.

The processing for forming the electrode plate for plasma etching and the formation of the gas blowing small holes can also be performed by, for example, electric discharge machining or ultrasonic machining after obtaining glassy carbon. The obtained glassy carbon is preferably made to have an impurity content of 20 ppm or less, more preferably 5 ppm or less, by a purification treatment such as a demineralization treatment with chlorine gas. 2 impurities
If it exceeds 0 ppm, there is a risk of contaminating the wafer. In addition,
The amount of impurities can be measured by the graphite ash measurement method specified in JIS.

The thus obtained electrode plate for plasma etching made of glassy carbon of the present invention has a small amount of desorbed fluorocarbon, and as a result, the number of discharge foreign substances can be reduced. In addition, the amount of plasma wraparound is small, and the amount of fluorocarbon film deposited is small. The plasma etching apparatus on which the above-mentioned electrode plate for plasma etching is mounted is not particularly limited except that the above-mentioned electrode plate for plasma etching is used. One example of such an apparatus is shown and described in FIG.

[0026]

Embodiments of the present invention will be described below. Example 1 A furan resin (Hitafuran VF303, manufactured by Hitachi Chemical Co., Ltd.) was used as a raw material resin, and 1% by weight of p-toluenesulfonic acid (based on the furan resin) was added as a curing agent thereto, followed by stirring and mixing. And φ300 petri dishes.
Molding was performed under heating at 70 ° C. for 10 hours to obtain a resin plate having a thickness of 4 mm. This resin plate is heat-cured at 70 ° C. for 3 days and at 90 ° C. for 3 days, and then carbonized at a heating rate of 1 ° C./min at a maximum of 900 ° C., and then at a heating rate of 5 ° C./min at a maximum of 2800 ° C.
Heat treated at ℃. The obtained glass-like carbon flat plate was formed by electric discharge machining with 600 gas blowing small holes having a diameter of 0.3 mm to obtain a shape of an electrode plate for plasma etching. Then, the thickness of the electrode was reduced to 3 mm by lap polishing. Further, a deashing treatment was performed using chlorine gas. The impurity in the electrode plate for plasma etching after the purification treatment was 3 ppm.

The ratio between the thickness (X) of the electrode plate for plasma etching and the gas blowing small hole (Y) is 10. The mounting surface of the obtained electrode plate for plasma etching made of glassy carbon was blasted using abrasive particles of green silicon carbide having an average particle diameter of 80 μm and blowing pressure of the abrasive particles of 2 kg / cm ² . Ra was measured at five places on the back surface of the obtained electrode, and the average was determined to be 0.5 μm. Each of the above-described electrode plates for high-purity plasma etching was attached to the apparatus, and trifluoromethane and fluorinated methane were used as reaction gases at a flow rate of 20 ml / min and argon gas as a carrier gas, respectively.
The silicon oxide film was etched at a flow rate of 0 ml / min and at a power frequency of 400 KHz and a gas pressure in the reaction chamber of 1.0 Torr. Table 1 shows the evaluation results.

Example 2 Same as Example 1 except that the mounting surface was blasted at a pressure of 4 kg / cm ² using green silicon carbide abrasive grains having an average particle diameter of 100 μm. Thus, an electrode plate for plasma etching was prepared. Ra was measured at five places on the back surface of the obtained electrode, and the average was determined.
It was 5 μm. Each of the above-mentioned electrode plates for high-purity plasma etching was attached to the apparatus, and the silicon oxide film was etched under the same conditions as in Example 1. Table 1 shows the evaluation results.

Example 3 Same as Example 1 except that the mounting surface was blasted at a pressure of 4 kg / cm ² using green silicon carbide abrasive grains having an average particle size of 200 μm. Thus, an electrode plate for plasma etching was prepared. Ra was measured at five places on the back surface of the obtained electrode, and the average was determined.
It was 0 μm. Each of the above-mentioned electrode plates for high-purity plasma etching was attached to the apparatus, and the silicon oxide film was etched under the same conditions as in Example 1. Table 1 shows the evaluation results.

Comparative Example 1 The mounting surface was treated in the same manner as in Example 1 except that green silicon carbide abrasive grains having an average particle diameter of 80 μm were used and blasting was performed at a blowing pressure of 1 kg / cm ^2. Thus, an electrode plate for plasma etching was prepared. Ra was measured at five places on the back surface of the obtained electrode, and the average was calculated.
μm. Each of the above-mentioned electrode plates for high-purity plasma etching was attached to the apparatus, and the silicon oxide film was etched under the same conditions as in Example 1. Table 1 shows the evaluation results.

Comparative Example 2 The mounting surface was treated in the same manner as in Example 1 except that green silicon carbide abrasive grains having an average particle size of 220 μm were used and blasting was performed at a blowing pressure of 5 kg / cm ^2. Thus, an electrode plate for plasma etching was prepared. Ra was measured at five places on the back surface of the obtained electrode, and the average was determined.
It was 4 μm. Each of the above-described electrode plates for high-purity plasma etching was attached to the apparatus, and the silicon oxide film was etched under the same conditions as in Example 1. Table 1 shows the evaluation results.

Comparative Example 3 The mounting surface was treated in the same manner as in Example 1 except that blasting was performed at a pressure of 7 kg / cm ² using green silicon carbide abrasive grains having an average particle size of 220 μm. Thus, an electrode plate for plasma etching was prepared. Ra was measured at five points on the back surface of the obtained electrode, and the average was determined.
It was 5 μm. Each of the above-mentioned electrode plates for high-purity plasma etching was attached to the apparatus, and the silicon oxide film was etched under the same conditions as in Example 1. Table 1 shows the evaluation results.

[0033]

[Table 1]

The Ra was measured at a speed of 0.3 mm / sec using a surface roughness measuring device Surfcom 503B manufactured by Tokyo Seimitsu Co., Ltd., and using a stylus having a tip of R5 μm.

[0035]

According to the first aspect of the present invention, the plasma etching electrode plate prevents the fluorocarbon film from falling off due to the plasma sneaking into the back surface of the electrode, thereby reducing the number of discharge foreign substances. is there. Further, the electrode plate for plasma etching according to the second aspect has the effects of the first aspect of the present invention, and further prevents the plasma from wrapping around the electrode back surface, prevents the fluorocarbon film from adhering, and as a result, is higher. The number of discharge foreign substances can be reduced. According to the third aspect of the present invention, it is possible to prevent the fluorocarbon film from dropping off due to the plasma sneaking into the back surface of the electrode, thereby reducing the number of discharge foreign substances.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a plasma etching apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Upper electrode (electrode plate for plasma etching) 3 Lower electrode 4 Silicon wafer 5 Back plate 6 Gas blowing small hole 7 High frequency power supply 8 Shield ring 9 Plasma 10 Insulation ring

Claims (3)

[Claims] 1. A JIS B 0601 having gas outlet holes and measured at least at five locations on the electrode mounting surface side.
An electrode plate for plasma etching made of glassy carbon having an average value of Ra based on 0.5 to 5 μm. 2. The vitreous carbon plasma according to claim 1, wherein the gas blowout holes have a ratio (X / Y) of 9 or more between the thickness (X) of the electrode and the diameter (Y) of the gas blowout holes. Electrode plate for etching. 3. A plasma etching apparatus comprising the electrode plate for plasma etching according to claim 1.