JP2000040689A - Plasma etching electrode plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce foreign particles such as carbon particles attached to a wafer, by a method wherein the center line average roughness of the wearing surface of a plasma etching electrode plate is measured at prescribed sites on the basis of JIS, and the maximum value of the average roughnesses is set in a specific range. SOLUTION: Etching gas is made to flow toward a silicon wafer 4 through through-holes, and when an electric power is applied between an upper and a lower electrode, 2 and 3, by a high-frequency power supply 8, plasma 11 is generated. The silicon wafer 4 is etched by the plasma 11 whereby a device of prescribed pattern is formed. Through-holes provided to a circular range at the center of a glassy carbon board are subjected to ultrasonic processing. The center line average roughness Ra of the wearing surface of the electrode plate 3 opposed to the wafer 4 is measured, at least, at five sites on the basis of JIS B 0601, and the maximum value of the average roughness Ra is set in a roughness range of 0.008 to 0.097 μm. Measuring sites are located on both the surfaces of the electrode plate 3 and when measurements are taken at a center site and four peripheral sites respectively, the maximum of measurements is in the above specified range.

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 plate made of glassy carbon, which is suitably used for a dry etching apparatus in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Glassy carbon has properties such as light weight, heat resistance, corrosion resistance, and electrical conductivity that general carbon materials have, and has high gas impermeability, high hardness, and low dust generation. Due to its characteristics, the electronics industry,
It is being used in a wide range of applications in various fields such as the nuclear industry and the aviation industry. Recently, it has been used as an electrode plate for plasma etching of a wafer at the time of manufacturing a semiconductor integrated circuit, utilizing the property that carbon particles do not fall off or adhere.

However, in recent years, the performance of semiconductor integrated circuits has been improved, and the required performance of an electrode plate for plasma etching has been further enhanced. In particular, the number of foreign matters such as carbon particles that have fallen and adhered to the wafer surface during etching has been increased. Are required.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an electrode plate for plasma etching made of glassy carbon having a small number of foreign substances such as carbon particles which drop and adhere to a wafer surface during etching of a wafer when manufacturing a semiconductor integrated circuit. The purpose is to provide.

[0005]

According to the present invention, a plasma etching electrode plate having a plurality of small through-holes in the center of a glassy carbon substrate is measured at least at five points on a surface which is consumed by plasma during etching. JIS B
The maximum value of Ra based on 0601 is 0.008 to 0.09.
The present invention relates to an electrode plate for plasma etching characterized by being in the range of μm.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a plasma processing apparatus comprises an upper electrode 2 and a lower electrode 3 in a vacuum vessel 1.
Are provided at intervals, and a silicon wafer 4 is mounted on the lower electrode 3 as a material to be processed. The upper electrode 2 has a back plate 5 and an electrode plate 6, each of which is provided with a small through hole 7 for blowing out an etching gas. The electrode plate 6 has a preferably circular area 12 at the center of a preferably disc-shaped substrate as shown in FIG.
Has a plurality of small through holes. Reference numeral 13 denotes a screw mounting hole for fixing the electrode plate to the upper electrode 2.

When a high frequency power is applied between the upper electrode 2 and the lower electrode 3 by the high frequency power supply 8 while flowing the etching gas toward the silicon wafer 4 through the small through holes 7, a plasma 11 is formed. The wafer 4 is etched to form a device having a predetermined pattern. The shield ring 9 is made of an insulating material such as alumina or quartz.
Is installed so as to cover the outer peripheral portion of the electrode plate 6 in order to protect the electrode plate from plasma.

The size and shape of the electrode plate of the present invention are not particularly limited, but are preferably circular and have an outer diameter of 15 mm.
Those having a thickness of 0 to 400 mm and a thickness of 3 to 10 mm are preferable. The size of the small through-holes provided in the preferably circular region at the center varies depending on the etching conditions and the like, but the hole diameter is preferably 0.3 to 2.0 mm, and the number of holes is 100 to 30.
00 is preferred. Machining, electric discharge machining,
It can be performed by ultrasonic processing or the like.

The electrode plate for plasma etching of the present invention has at least five surfaces that are consumed by plasma during etching.
The maximum value of Ra according to JIS B 0601 measured at three places is in the range of 0.008 to 0.09 μm. Here, the surface of the electrode plate consumed by the plasma refers to the surface facing the wafer and the surface on the opposite side, and the range is a circle circumscribing the outermost small hole in the range where the through small hole is provided. Of a circle having a diameter 10 mm larger than the diameter of the circle. In general, the surface of the electrode plate for plasma etching is almost uniform, so that Ra at least at five places should be measured as described above, and the maximum value should be within the above-mentioned range. It is preferably within. Further, in the present invention, it is preferable that Ra of the inner surface of the perforated small hole is also within the above range in order to reduce the number of foreign substances.

Here, Ra (center line average roughness) defined in JIS B 0601 is a value representing the surface smoothness.
In the present invention, Ra is measured in at least five places,
It is necessary that the maximum value is in the range of 0.008 to 0.09 μm. Here, the cut-off value of Ra is 2.5 μ
m, the measurement length is 2.5 mm. The measurement place is not particularly limited, but the center point and the four peripheral points can be measured on the surface facing the wafer and the opposite surface. When the maximum value of Ra exceeds 0.09 μm, when the part is consumed due to the impact of ions generated by the plasma, the projections on the rough surface are not uniformly consumed, so that the powder particles adhering to the wafer surface may not be consumed. The number increases, which is not preferable. On the other hand, if the maximum value of Ra is smaller than 0.008 μm, deposits adhered to the electrode plate during etching are easily peeled off, and the number of powder particles adhering to the wafer surface increases, which is not preferable. The maximum value of Ra is preferably in the range of 0.01 to 0.08 μm. In addition, JIS B
The maximum value measured at least at 5 points of Rmax based on 0601 is 0.1 to 1.0 μm, more preferably 0.13 μm.
０．９0.96 μm, and similarly R in accordance with JIS B 0601
The maximum value measured at least at five places of z is 0.1 to 1.
It is preferably in the range of 0 μm, more preferably in the range of 0.11 to 0.85 μm. As with Ra, it is more preferred that all measurements are in the above range. Note that Rmax and R
The reference length at z is 2.5 mm. Such a surface smoothness can be obtained by polishing the surface of glassy carbon as a base material by a diamond wrap method, a buff polishing method, or the like. The surface smoothness can be changed by changing the alumina used for polishing and the particle size of the particles. For example, granularity #
The above range can be attained by polishing with 2000 alumina and particles.

An electrode plate for plasma etching made of glassy carbon can be obtained, for example, by molding and curing a liquid thermosetting resin, followed by carbonization in an inert atmosphere and high-temperature treatment.

After molding the thermosetting resin at a predetermined temperature,
The curing treatment is performed at a temperature of 130 to 200 ° C. The thermosetting resin is not particularly limited, and examples thereof include a furan resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, a melamine resin, an alkyd resin, and a xylene resin. Further, a mixture of the above resins may be used. Preferably, it is a phenol resin and / or a furan resin.
The thermosetting resin is molded according to the desired shape, but the molding method is not particularly limited.

Next, after performing a predetermined process for forming a shape of the electrode plate for plasma etching, using a high-purity jig and a furnace in an inert atmosphere (usually, an inert gas such as helium, argon or the like). In an oxygen-free atmosphere consisting of at least one kind of non-oxidizing gas such as nitrogen, hydrogen and halogen gas, under reduced pressure or vacuum),
Baking at a temperature of 0 to 1200C, for example, about 1000C,
Carbonize. Next, high-temperature treatment is preferably performed at a temperature of 1700 ° C. or more to obtain a plasma etching electrode plate made of glassy carbon.

As a method of obtaining an electrode plate for plasma etching, other than the above-described method, after obtaining a glassy carbon plate, it may be processed into a predetermined electrode plate for plasma etching by electric discharge machining or ultrasonic machining. The surface finishing can be performed to a predetermined thickness by a double-side polishing machine, and finally, a predetermined surface smoothness can be obtained by the above-described polishing method.

In the electrode plate for plasma etching made of glassy carbon used in the present invention, the amount of impurities in the electrode plate for plasma etching is preferably 50 ppm or less in order to reduce contamination of the cleaning liquid for the semiconductor wafer such as hydrofluoric nitric acid. More preferably, the content is 20 ppm or less. The impurities can be measured by the graphite ash measurement method of JIS.

[0016]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example Furan resin (VF-303 manufactured by Hitachi Chemical Co., Ltd.) 10
After adding 0.3 parts by weight of paratoluenesulfonic acid to 0 parts by weight and mixing well, the resin was poured into a mold, and the mixture was placed at 50 ° C. for 3 days.
After drying and curing at 0 ° C. for 3 days and at 90 ° C. for 3 days, the temperature is raised to 160 ° C. at a rate of 5 ° C./hour, kept at 160 ° C. for 3 days, and cured, and a circle having a thickness of 5 mm and a side of 285 mm is obtained. A plate-shaped resin molded product was obtained. The compact is placed in a tube furnace and placed in a nitrogen stream for 1 hour.
After firing and carbonizing at a temperature of 000 ° C., high-temperature treatment was performed at a temperature of 2000 ° C. in an inert atmosphere using a high-purity atmosphere furnace to obtain glassy carbon. 0.8m in diameter to the glassy carbon
500 through holes having a diameter of 3 m were formed at a pitch of 3 mm and polished with a diamond wrap machine to a thickness of 4.0 mm to obtain an electrode plate for plasma etching. Next, alumina and particles (# 2000 in Examples 1 to 3, # 2500 in Comparative Example 1, and # 2500 in Comparative Example 2) have various surface smoothness as shown in Table 1 on the entire front and back surfaces of this calcined carbonized product. 1000) using a polishing machine based on a buffing method.

Next, this electrode plate is set in a plasma etching apparatus, and a reaction gas: trifluoromethane (CHF ₃ )
Carrier gas: an argon (Ar) gas pressure in a reaction chamber: 1 Torr, power supply frequency: 13.5 MHz, an oxide film was etched on a silicon wafer having a diameter of 8 inches. At this time, the 0.1.
The number of powder particles (the number of foreign substances) of 3 μm or more was counted. Table 1 shows the results.

From Table 1, the surface smoothness is Ra 0.008 or more.
When the electrode plate of Example of 0.09 μm was used, the number of particles was as small as 4 to 5, whereas the surface smoothness was Ra.
When the electrode plate of Comparative Example smaller than 0.008 μm or larger than Ra 0.09 μm was used, the number of particles was 10
-20, indicating that the present invention greatly improves the performance.

Further, each of the electrode plates of Examples 1 to 3 was cut along the small through-holes, and the Ra of five side walls among the small through-holes appearing on the cut surface was measured.
It was in the range of 0.08 μm.

[0021]

[Table 1] * Using a surface roughness measuring device (tip size: a 5 μm radius sphere, stylus feed rate 0.3 mm / sec), measured at a total of 10 points: the center point of the front and back surfaces of the electrode plate and 4 points around the electrode plate And expressed as its maximum value. In addition, all Ra measured in Examples 1-3 are 0.01-0.08 micrometer,
Rmax is 0.1 to 0.96 μm, and Rz is 0.1 to 0.
It was in the range of 85 μm.

[0022]

According to the electrode plate for plasma etching of the present invention, the number of harmful foreign substances such as harmful carbon fine particles generated at the time of etching can be greatly reduced, and the yield is good and high-precision plasma etching is possible. is there.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a plasma etching apparatus using an electrode plate of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Upper electrode 3 Lower electrode 4 Silicon wafer 5 Back plate 6 Electrode plate 7 Small through hole 8 High frequency power supply 9 Shield ring 10 Mounting screw 11 Plasma 12 Circular range where small through hole exists 13 Screw mounting hole

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takayuki Suzuki 3-3-1 Ayukawacho, Hitachi City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Yamazaki Plant F-term (reference) 5F004 BA06 DA16 DA23 DB03

Claims (1)

[Claims] 1. A plasma etching electrode plate having a plurality of small through holes in the center of a glassy carbon substrate,
An electrode plate for plasma etching, wherein the maximum value of Ra measured in at least five places on the surface consumed by plasma during etching is in the range of 0.008 to 0.09 μm in accordance with JIS B 0601.