JPH09188566A - Production of glass-like carbon member for plasma treatment of silicone wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass-like carbon member improved in the stability and endurance of a plasma by forming a specific fluid polymer after defoaming, curing, burning and purifying. SOLUTION: This glass-like carbon member for a plasma treatment of a silicon wafer having >=2mm thickness, <=1μm maximum pore diameter, <=5ppm impurity content and <=0.2% open pore ratio, is obtained by repeating a process of polymerizing a liquid thermosetting resin by adding an organic sulfonic acid little by little until the total amount of the sulfonic acid reaches an explosion limit to obtain a fluid polymer having 1000-4000cps viscosity, forming the fluid polymer as a disk shape by pouring it into a mold after its defoaming, curing by heating at 1 deg.C/hr temperature elevation rate, then burning and carbonizing under an inert atmosphere at 800-1200 deg.C at 2 deg.C/hr temperature elevation rate up to 1000 deg.C, then purifying at 2000-2500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glassy carbon member for silicon wafer plasma processing.

[0002]

2. Description of the Related Art Generally, a glassy carbon material is obtained by carbonizing a cured product of a liquid thermosetting resin having an insoluble and infusible property in an inert atmosphere. This glassy carbon material is excellent in gas impermeability, has high hardness, and has an isotropic structure. Furthermore, this glassy carbon material has a light weight, heat resistance, high electrical conductivity, corrosion resistance, and
It has high thermal conductivity, excellent mechanical strength and lubricity, as well as homogeneity and the property of not producing carbon powder such as chips when slidingly used.

Recently, attention has been paid to the characteristics of such glassy carbon materials, and utilization of the glassy carbon materials as an electrode plate for plasma etching has been studied.

The glassy carbon currently commercialized is mainly manufactured by the following method.

Thermosetting resin is used as a raw material, and a substrate having a predetermined shape is thinly coated with a brush, spray, centrifugal method or the like, and the resin is thinly applied and then cured.

The aggregate itself is made into a resin powder, which is molded and then fired to obtain glassy carbon.

Conventionally, a graphitizable carbon material using pitch or the like as a raw material is produced by crushing coke to produce a powdery carbon material, and an appropriate binder is added to the powdery carbon material and kneaded. The kneaded material is molded to form a molded body, the molded body is fired, and the fired body is graphitized by heat treatment.

Japanese Unexamined Patent Publication No. 62-252942 discloses an electrode plate for plasma etching, which is made of high-purity glassy carbon. The production method is as follows: Liquid furan-based resin, phenol-based resin, or a mixed resin thereof, or a mixture of curable resin powders of the same kind added and mixed into a flat plate and then cured to form a resin. Make a board, then place the resin board in an inert atmosphere at 80
It is carbonized by firing at 0 ° C., graphitized at 3000 ° C. if necessary, and then subjected to deashing high purity treatment. A large number of through holes having a diameter of 0.8 mm are formed at intervals of 2 mm or the like on the electrode plate manufactured in this manner. The thickness of the electrode plate is 3 mm. The physical characteristics of the electrode plate are that the bulk specific gravity is 1.45 g / c.
m ³ , porosity 3%, Shore hardness 75, bending strength 5
80 kgf / cm ² , elastic modulus 2430 kgf / cm ²
It is.

[0009]

According to the above-mentioned manufacturing method, a large number of pores having a relatively large diameter (about 2 μm) are generated due to voids during molding, dissipation of volatile components during heat treatment, and the like.

Further, the size and distribution of pores differ depending on the size of aggregate particles, the type of binder, the manufacturing process, and the like.
Therefore, the physical properties associated with the pores are very complicated.

When the conventional glass-like carbon electrode plate for plasma etching is observed with an electron microscope, as shown in FIG. 7, there are open pores with a large diameter (about 2 μm) on the surface. In addition, a large diameter (about 2 μm) inside the electrode plate
There are closed pores.

As described above, due to the open pores peculiar to the glassy carbon, the phenomenon that the specific surface area is increased and the oxidation characteristics and the strength are lowered is derived.

If not only open pores but also closed pores are present in the electrode plate, the internal closed pores will appear on the surface and become open pores during polishing, and the same phenomenon as the above problem will occur.

The method described in detail as the prior art has the disadvantage that a large number of open pores and closed pores exist in the laminated portion of the resin after firing. In the method of (1), resin powder is used. There is a grain boundary, and the properties such as mechanical strength and porosity are inferior to those of ordinary glassy carbon, and carbon particles are likely to fall off during use or during mouth washing.

In order to prevent the phenomenon of carbon particles falling off, a method of forming a glassy carbon film or a pyrolytic carbon film on the surface of the electrode plate has been proposed, but the mechanical strength of the film itself is weak and There was a problem of peeling.

It is an object of the present invention to provide a method for producing a glassy carbon member for silicon wafer plasma processing, which has good plasma stability and excellent durability.

[0017]

The gist of the present invention resides in a method for producing a glassy carbon member for silicon wafer plasma treatment as set forth in any one of claims 1 to 6.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A typical example of a carbon member manufactured by the method of the present invention is an electrode plate for plasma etching. It is a plate-like body having a thickness of 2 mm or more, which is made of high-purity glassy carbon, has substantially no grain boundaries on the surface and the internal structure, and has a maximum pore diameter of 1 μm or less.

Preferably, the glassy carbon has an impurity content of 5 ppm or less, an open porosity of 0.2% or less, and a maximum pore diameter of 0.5 μm or less. Further, it is best that the open porosity is 0.01% and the maximum pore diameter is 0.1 μm or less.

[0020]

1 and 2 show an example of an electrode plate for plasma etching made of glassy carbon produced by the present invention. The electrode plate 10 is a circular plate as a whole, and a large number of small through holes 13 (third part
8) is formed, and eight large through holes 14 are formed at regular intervals in the periphery.

The through hole 14 is intended to be attached to a plasma etching apparatus, and has a small diameter portion and a large diameter portion.
It has a two-tiered shape.

Although only a part is shown in FIG. 2, a large number of through holes 13 are densely formed in the entire opening 11. These through holes 13 are for the purpose of uniformly etching the wafer by causing the etching gas to flow uniformly, and as shown in FIG. 3, they are arranged at regular intervals in the vertical and horizontal directions. The three through holes 13 adjacent to each other are located at the vertices of an equilateral triangle.

The outer diameter of the electrode plate 10 is 10 inches, and the diameter of the opening portion 11 is set to 8 inches corresponding to the diameter of the processing wafer (not shown). Of course, other modes may be adopted. For example, the outer diameter of the electrode plate 10 is 1
It may be 2 inches, and the diameter of the opening 11 may be 10 inches. The diameter of the opening 11 is preferably the same as or larger than the diameter of the wafer to be processed.

The arrangement density of the through holes 13 in the opening 11 is preferably about 98 holes / cm ² in the example of FIG. In this example, 1733 through holes 13 are formed in the opening 11 having a diameter of 8 inches. The diameter of each through hole 13 is preferably 0.5 to 1 mm.

Although the arrangement density of the through holes 13 in the illustrated example has a uniform distribution over the entire opening portion 11, the present invention is not limited to this example. For example, the arrangement density is 1
The central part of 1 may be dense and the outer peripheral part may be sparse.

The thickness of the electrode plate 10 is 2 mm or more. The reason is to increase the mechanical strength and the useful life. The electrode plate 10 in the illustrated example has a thickness of 3 mm.

The electrode plate 10 is made of glassy carbon in which the content of impurities is controlled to 1/10 to 1/10 or less (for example, 5 ppm or less) of the conventional content.

The outline of the preferred production method of the present invention will be described below.

The process of adding a small amount of organic sulfonic acid to the liquid thermosetting resin and polymerizing at room temperature is repeated. Then, the polymerized resin is poured into a mold to form a disk, and the temperature is slowly raised to cure the resin. A large number of through holes having a diameter of 0.8 mm are provided at the center of the thus hardened disc. After that, the disc is gradually heated and carbonized at 800 to 1200 ° C. It is surface-treated and further purified at 2000-2500 ° C.

The glassy carbon constituting the electrode plate produced by the method of the present invention is preferably produced by using a fluid liquid thermosetting resin as a starting material. This is because it becomes easy to obtain a glassy carbon material that does not include pores of 1 μm or more and has an open porosity of 0.2% or less.

4 to 8 show the surface texture of the electrode plate observed by an electron microscope.

The electrode plate shown in the electron micrograph of FIG. 4 has only a few open pores of about 0.2 μm or less. The open porosity of this example is 0.1%. When using a fluid thermosetting resin as a starting material,
No grain boundaries occur. When the aggregate itself is made into a resin powder and fired after molding, grain boundaries are likely to exist between the particles, and properties such as mechanical strength and porosity deteriorate.

The liquid thermosetting resin, after being cured, is in an inert atmosphere (an atmosphere containing no oxygen and usually at least one kind of inert gas such as helium, argon, nitrogen, hydrogen and halogen). Carbonization and calcination at a slow temperature rising rate under a reduced pressure, a vacuum, or an atmosphere in which the air is shut off.

The open porosity of the glassy carbon is preferably 0.2% or less. When the open porosity exceeds 0.2 wt%, when glassy carbon is used as an electrode plate for plasma etching, the electrode plate is consumed by etching, the closed pores are exposed, and the surface area becomes large. Particle dropout is accelerated. As a result, life is shortened. Further, when the carbon particles fall off, they adhere to the silicon wafer for semiconductor devices and deteriorate the physical properties of the wafer. As a result, the yield is reduced.

As the liquid thermosetting resin, furan resin,
Phenol resin, epoxy resin, unsaturated polyester resin, urea resin, melamine resin, alkyd resin, xylene resin and the like can be mentioned. Such resins are used alone or by blending or modifying. Among them, modified furan resin is preferable.

Experimental Examples 1 to 3 p-toluenesulfonic acid was added to furfuryl alcohol in an amount of 0.
Polymerize by stirring and mixing until the explosion limit of 4 parts by weight is reached.
A flowable polymer having a viscosity of ~ 4000 cp (centipoise) was obtained.

After defoaming the produced frifryl alcohol polymerization solution, it was molded into a disk having a diameter of 300 mm and a thickness of 10 mm in a mold and cured in a dryer at a temperature rising rate of 1 ° C./hr.

The obtained cured product was heated at 2 ° C./h in a nitrogen atmosphere.
The temperature is raised at a heating rate of up to 1000 ° C and baked, and finally 2
A purification treatment was performed at 300 ° C. to obtain glassy carbon.

Comparative Examples 1 to 3 An acid catalyst of p-toluenesulfonic acid was added to the furan resin, followed by defoaming treatment, and after molding, the temperature was gently raised to 200 ° C. to cure. The cured product thus obtained was pulverized to obtain a resin powder having an average particle size of 30 to 50 μm. A furan resin of the same kind was mixed with this resin powder, and the mixture was subjected to defoaming treatment, shaped into a disk having a diameter of 200 mm and a thickness of 3 mm, and then cured. The obtained cured product was heated to 1000 ° C. at a heating rate of 2 ° C./h in a nitrogen atmosphere and baked, and finally purified at 2300 ° C. to obtain glassy carbon.

Table 1 shows Experimental Examples 1 to 3 and Comparative Examples 1 to 3.
The open porosity, the life and the amount of released gas are shown for the glassy carbon of.

A silicon wafer was placed on a disk-shaped glassy carbon electrode plate, and a mixed gas of CF ₄ , Ar, and O ₂ was caused to flow, and plasma was generated to etch the silicon wafer. At that time, the glassy carbon was also etched and consumed by the flowing oxidizing gas and the generated plasma. The initial thickness of the glassy carbon electrode plate was processed and unified to 3 mm, and the time when the residual thickness became 0.8 mm was defined as the life end.

Further, in Table 1, the amount of released gas is 95
The amount of released gases such as CO ₂ , H ₂ and CO adsorbed on the surface of glassy carbon when heated to 0 ° C. is shown.

As shown in Table 1, the glassy carbon electrode plate of the present invention had a significantly improved life under oxygen-containing conditions as compared with the comparative example.

In this experiment, the thickness of the electrode plate was 3 mm.
Although the life end was reached at 0.8 mm, the glassy carbon electrode plate of the comparative example actually had many open pores, so the glassy carbon electrode plate was not uniformly etched, When observed with an electron microscope, as shown in FIG. Therefore, the plasma generated for etching the silicon wafer becomes unstable, and the etching rate of the silicon wafer is different in each part of the silicon wafer. Therefore, in reality, the life when used as a glassy carbon electrode plate for etching is considered to be shorter than the life shown in Table 1.

Further, in the present small-diameter silicon wafer, the variation in the etching rate is within the specified range. However, when considering the etching process of the large-diameter silicon wafer in the future, the etching rate of the comparative example is Variations are likely to be a huge problem.

Further, when the electrode plate is etched in a concavo-convex shape as shown in FIG. 8, particles are easily generated.
In the current semiconductor industry, the degree of integration has moved from 4M to 16M, and the line width of pattern etching has advanced to submicron. Therefore, the particles that have the largest influence on the yield of silicon wafers are 0.1 to 0.3 μm. Reducing such particles greatly contributes to the yield of silicon wafers. For this reason, the glassy carbon of the comparative example does not cause many problems in the initial stage of use, but as the use time elapses, the surface is etched in an uneven shape, thereby roughening the surface and generating particles.

Further, since the amount of released gas is large, the adsorbed gas is released during use, and the high purity silicon wafer is adversely affected along with the generated plasma.

As shown in the electron micrographs of FIGS. 5 to 6, the electrode plate of the present invention is uniformly etched, and no large unevenness is formed after etching as in the comparative example.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electrode plate for plasma etching manufactured according to the present invention.

2 is a schematic cross-sectional view taken along line 2-2 of FIG.

FIG. 3 is an enlarged plan view showing a part of the opening of FIG.

FIG. 4 is an electron micrograph showing a ceramic structure on the surface of an example of an electrode plate for plasma etching manufactured according to the present invention at a magnification of 1000 times.

FIG. 5 is an electron micrograph showing the ceramic structure of the surface of the electrode plate for plasma etching manufactured by the method of the present invention after plasma etching at a magnification of 1000 times.

FIG. 6 is an electron micrograph showing a ceramic structure on the surface after plasma etching produced by the method of the present invention at a magnification of 15,000 times.

FIG. 7 is an electron micrograph showing the ceramic structure of the surface of the conventional electrode plate for plasma etching before use at a magnification of 1000 times.

FIG. 8 is an electron micrograph showing the ceramic structure of the surface after using the conventional electrode plate for plasma etching at a magnification of 1000 times.

[Explanation of symbols]

 10 Electrode Plate 11 Opening Portion 13 Through Hole 14 Through Hole

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yasumi Sasaki Yasumi Sasaki 378 Oguni, Oguni Town, Nishiokitama-gun, Yamagata Prefecture Oguni Factory, Toshiba Ceramics Co., Ltd. (72) Kazuo Ito 30 Soya, Hadano, Kanagawa Prefecture Toshiba Ceramics Co., Ltd. Central Research Laboratory (72) Inventor, Kazunori Meguro, Oguni Town, Oguni Town, Nishikitama District, Yamagata Prefecture 378 Oguni Town, Toshiba Ceramics Oguni Factory

Claims (6)

[Claims] 1. A process of adding a small amount of organic sulfonic acid to a liquid thermosetting resin and polymerizing the mixture to mix the organic sulfonic acid to form a fluid polymer having a viscosity of 1000 to 4000 centipoise. A method for manufacturing a glass-like carbon member for silicon wafer plasma treatment, which comprises defoaming treatment, shaping into a desired shape, curing, firing and purification treatment successively. 2. The method for producing a glassy carbon member for plasma treatment of a silicon wafer according to claim 1, wherein the liquid thermosetting resin is mixed with the organic sulfonic acid to a total explosion limit. 3. The glass for silicon wafer plasma processing according to claim 1, wherein the liquid thermosetting resin is furfuryl alcohol, and the organic sulfonic acid is p-triene sulfonic acid. Of manufacturing a rectangular carbon member. 4. The glass for silicon wafer plasma processing according to claim 1, wherein the glass-like carbon member for silicon wafer plasma processing is a glass-like carbon electrode plate for plasma etching. Of manufacturing a rectangular carbon member. 5. The method for producing a glassy carbon member for silicon wafer plasma treatment according to claim 1, wherein the curing is performed at a temperature rising rate of 1 ° C./hr. 6. The glassy carbon member for silicon wafer plasma processing according to claim 1, wherein the firing is performed up to 1000 ° C. at a temperature rising rate of 2 ° C./hr. Production method.