JP2000272910A - Dummy wafer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dummy wafer which is scarcely curved and comprises highly pure glassy carbon, by forming a plurality of organic polymer films, laminating the films with an adhesive and then carbonizing the laminate. SOLUTION: This dummy wafer comprising glassy carbon is obtained by forming a plurality of stage B films from a raw material by the use of a forming machine, laminating the arbitrary number of the stage B films with the starting raw material or the like as an adhesive, applying a curing treatment and a pre-carbonization treatment to the obtained laminate having the plurally- layered structure in an air oven, carbonizing the treated laminate in a non- oxidizing atmosphere at 700-2,800 deg.C, and if necessary, further treating the carbonization product in a vacuum atmosphere at 1,400-2,800 deg.C. The carbonization treatment may be carried out in a vacuum atmosphere at 1,400-2,800 deg.C. The raw material comprises one or more resins suitably selected from organic polymers, their monomer.oligomers, tar.pitches, dry-distilled pitches, thermoplastic resins, the prepolymers of thermosetting resins, and the like, has a shape- retaining property, and produces glassy carbon after sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a dummy wafer used in a semiconductor device process and a method of manufacturing the same.

[0002]

2. Description of the Related Art In manufacturing semiconductor devices,
The production line is usually composed of 100 or more steps, and a dummy wafer is used for setting process conditions of various steps and stabilizing the production line. The number of dummy wafers is required to be substantially the same as the number of silicon wafers used for production as products, and inexpensive dummy wafers that can be used repeatedly are expected.

Here, the dummy wafer is used during a device forming process, and a side dummy placed on both ends of the furnace for uniforming the temperature distribution in the furnace, and various conditions for the device forming process are determined. Monitor dummy (also called test dummy) used to evaluate film thickness and particle characteristics, and used as a spacer when the number of prime wafers to be produced is less than the number of furnaces Area dummies. These three types of dummies are collectively called a dummy wafer.

When a silicon wafer itself is used as a dummy wafer in a device process, if a second-class product is used, although it is relatively inexpensive, it is difficult to use repeatedly because silicon is affected by a chemical solution at the time of regeneration. The number of times is limited. As a result, the cost increases.

Therefore, as a substitute for a silicon wafer, a ceramic dummy wafer such as SiC, Si ₃ N ₄ , sapphire, or a glassy carbon dummy wafer has been proposed. However, ceramic substrates such as SiC, Si ₃ N ₄ , sapphire, etc.
Since it becomes translucent, it cannot be used as a monitor dummy, and its use as a dummy wafer is limited. In the case of the sintered type SiC, the color is black and there is no translucency, but the purity is poor and it has problems such that it cannot be used in the device process.

Next, a dummy wafer made of glassy carbon alone is formed mainly by press molding or injection molding of a phenol resin, and after heating and curing, firing in a non-oxidizing atmosphere, and in some cases, hot isostatic pressing ( It is manufactured by performing HIP) processing and the like. However, when manufactured by those methods,
Although the reason is not clear, it has a problem of large warpage and poor purity.

[0007]

Since glassy carbon is a material that cannot be fixed by a magnet, if the dummy wafer to be manufactured has a large warp, it is difficult to fix it with a vacuum chuck used in a work for projecting a flat surface. It was very poor workability. In addition, there is a problem in that a large margin must be taken in order to obtain a flat surface, so that it must be molded into an unnecessarily thick one.

In order to increase the purity of the conventional glassy carbon dummy wafer, it is necessary to react it with chlorine gas at 2000 ° C. or higher for production and purification in a clean room, which may increase the cost. And so on. Therefore, an object of the present invention is to provide a dummy wafer having a small amount of warpage and high purity, and a method of manufacturing the same.

[0009]

Means for Solving the Problems The inventors of the present invention have studied in view of the above points, and as a result, have prepared a B-stage film having a thickness approximately equal to or less than a required thickness of a dummy wafer, using a liquid resin as a starting material. By bonding and curing a plurality of these films, the problem of product warpage and the problem of air bubbles can be solved, and in addition, sufficient purity can be improved by vacuum firing at 1400 ° C or more and 2800 ° C or less. And completed the present invention. The dummy wafer of the present invention is characterized in that the dummy wafer is composed of a plurality of layers in a dummy wafer made of glassy carbon. The method of manufacturing a dummy wafer according to the present invention for manufacturing the dummy wafer is characterized in that a plurality of layers are bonded and then carbonized.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The glassy carbon, which is a dummy wafer of the present invention, is obtained by firing an organic resin material having a shape-forming property and three-dimensionally cross-linking or a natural organic material which solidifies in solid phase. It is. Specifically, one or a mixture of two or more kinds of organic polymer substances and their monomers / oligomers, tar pitches, carbonized pitches, thermoplastic resins, thermosetting resin initial polymers, and the like are fired. It is gained by things.

Here, the organic polymer substance is a substance other than a thermoplastic resin and a thermosetting resin described later,
Lignin, cellulose, gum tragacanth, gum arabic, natural gums and derivatives thereof, sugars, chitin, compounds having condensed polycyclic aromatics such as chitosan in the basic structure of the molecule,
And indanthrene-based vat dyes derived from naphthalene sulfonic acid formalin condensate, dinitronaphthalene, pyrene and the like, and intermediates thereof.

As the thermoplastic resin, polyvinyl chloride,
Polyvinylidene chloride, polyacrylonitrile, post-chlorinated polyvinyl chloride, polyvinyl acetate, and other ordinary thermoplastic resins, and polyphenylene oxide, polyimide, polyamide imide, polybenzimidazole, and other heat-resistant thermoplastic resins, At the time of carbonization, a carbon precursor treatment such as oxidative crosslinking is performed.

As the thermosetting resin, a phenol resin,
Furan resin, epoxy resin, xylene resin, copna resin, etc. are used, flow by heating, and cause intermolecular cross-linking to be three-dimensionally hardened, and high carbon residue yield without special carbon precursor treatment It shows.

The pitches include petroleum pitch, coal tar pitch, asphalt, and pitch-dried pitches of hydrocarbon compounds such as these pitches and synthetic resins, which have been subjected to a non-graphitizing treatment such as an oxidation treatment for crosslinking. It is.

The resin composition and the amount used in the present invention are appropriately selected depending on the physical properties required for the target dummy wafer, particularly the coefficient of thermal expansion and the final surface roughness, and may be used alone or as a mixture of two or more. However, it is particularly preferable to use a composition having a liquid state.

Hereinafter, a method for manufacturing a dummy wafer according to the present invention will be described. First, a resin composition that has the above-described shapeability and becomes a glassy carbon after firing is appropriately selected, and an extrusion molding machine, a vacuum molding machine, and a molding machine used when performing ordinary plastic molding such as an applicator. To make a B-stage film.

Next, an arbitrary number of these B-stage films are adhered to form a composite and integrated, thereby obtaining a multilayer structure composition. The adhesive used here can be a resin solution selected arbitrarily, but it seems that it is preferable to use the starting material itself of the B-stage film. After subjecting the obtained multilayer structure composition to a curing treatment and a carbon precursor treatment in an air oven, the temperature is controlled in a non-oxidizing atmosphere such as nitrogen, argon or the like while controlling the temperature rising rate at 700 ° C. to 2800 ° C. The carbonization is terminated by firing in the above temperature range, and a dummy wafer material having a multilayer structure is obtained. In addition, 140
By baking to about 0 to 2800 ° C., elements that have an adverse effect in the device forming process are removed, and required purity can be secured.

According to the present invention, it is possible to obtain a dummy wafer having a higher strength than a conventional glassy carbon simple substance dummy wafer having no multilayer structure. Further, since it can be manufactured without performing purification treatment using HIP or chlorine gas, a high-performance dummy wafer can be provided at low cost.

[0019]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 First, a B-stage film consisting only of a furan resin (Hitafuran VF-302 manufactured by Hitachi Chemical Co., Ltd.) was prepared using a film forming machine. The obtained two B-stage films were bonded and integrated with a solution obtained by mixing a curing agent in a furan resin, processed into an appropriate disc shape, and then subjected to a heat curing treatment. The obtained multilayer structure composition was carbonized to 1400 ° C. in a nitrogen gas atmosphere to obtain a carbon body. The carbon body thus obtained was further fired under vacuum to 2000 ° C. to obtain a dummy wafer material. The obtained dummy wafer material is ground with a surface grinder (using a vacuum chuck) and the surface roughness is about 1μ.
m (Ra) dummy wafers were obtained. Table 1 shows the amount of warpage of the obtained dummy wafer material. Next, the dummy wafer material was ground with a surface grinder, and the stock removal (one side) from the time when the grinding stone first hit the surface to the entire surface is shown in Table 2. Shown in Further, dummy wafers were placed at intervals of 5 mm between silicon prime wafers having a life time of 540 μsec., And impurities were transferred at 900 ° C. in an argon gas flowing atmosphere (dummy wafers were placed upstream of the flowing gas). Table 3. Lifetime Shown in Table 4 shows the thermal expansion coefficient of the obtained dummy wafer. Table 5 shows the three-point bending strength determined by the three-point bending test. Shown in

(Example 2) A B-stage film made of a mixed resin of a furan resin (Hitafuran VF-302 manufactured by Hitachi Chemical Co., Ltd.) and a phenol resin (no hardener added, manufactured by Gunei Chemical Co., Ltd.) was prepared using a film forming machine. Produced. The obtained two B-stage films are bonded and integrated with a solution obtained by mixing a furan resin / phenol resin mixed resin and a furan resin hardener, and then processed into an appropriate disc shape, followed by heat curing. gave. After that, a dummy wafer was obtained in the same manner as in Example 1. As in Example 1, Table 1. ~ Table 5.
Shows the respective values.

(Example 3) A phenolic resin (without addition of a curing agent, manufactured by Gunei Chemical Co., Ltd.) / Isopropyl alcohol solution was applied using a film forming machine to prepare a B-stage film composed of only a phenolic resin. The two B-stage films thus obtained were bonded and integrated with a solution obtained by mixing a curing agent (hexamine) with a phenol resin / IPA solution, processed into an appropriate disc shape, and then subjected to a heat curing treatment. After that, a dummy wafer was obtained in the same manner as in Example 1. As in Example 1, Table 1. ~ Table 5. Shows the respective values.

Example 4 A xylene resin (without addition of a curing agent, manufactured by Mitsubishi Yuka Co., Ltd.) / Xylene solution was applied using a film forming machine to prepare a B-stage film consisting of only the xylene resin. The obtained two B-stage films were bonded together by bonding with a xylene resin / xylene solution and then pre-cured. After that, it was processed into an appropriate disk shape, and then subjected to a heat curing treatment. After that, a dummy wafer was obtained in the same manner as in Example 1. As in Example 1, Table 1. ~ Table 5. Shows the respective values.

(Comparative Example 1) A powder of a phenolic resin (product added with a curing agent, manufactured by Gunei Chemical Co., Ltd.) was filled in a disk-shaped mold, and then heated and press-molded to be cured. To obtain a dummy wafer material, and ground in the same manner as in Example 1 to obtain a dummy wafer. As in Example 1, Table 1. ~ Table 5. Shows the respective values.

(Comparative Example 2) A powder of a phenolic resin (a product containing a hardener, manufactured by Gunei Chemical Co., Ltd.) was filled in a disk-shaped mold, cured by hot press molding, and then cured in a non-oxidizing atmosphere up to 1400 ° C. To obtain a dummy wafer material,
HIP processing was performed at 0 ° C. and 1900 atm to obtain a dummy wafer material, which was ground in the same manner as in Example 1 to obtain a dummy wafer. As in Example 1, Table 1. ~ Table 5. Shows the respective values.

Comparative Example 3 The dummy wafer material obtained in Comparative Example 2 was subjected to a purification treatment at 2800 ° C. in a chlorine-containing gas atmosphere, and then ground similarly to obtain a dummy wafer. Example 1
Similarly to Table 1. ~ Table 5. Shows the respective values.

[0027]

[0028]

[0029]

[0030]

[0031]

As described above, it can be seen that the dummy wafer material of the present invention has a small warpage and a small allowance for grinding or lapping to a required thickness. Also,
In the measurement of the lifetime (longer indicates higher purity) indicating the transfer characteristics of impurities to the prime wafer,
It can be seen that even if the purification treatment using chlorine gas at a high temperature is not performed, there is no adverse effect on the prime wafer. Thermal expansion coefficient is will differ demand value should be used for any stage of the device process the dummy wafer, typically Si ₃ N
_It is important to be ^able to use ₄ (3.4 × 10 ⁻⁶ ) and d-Si (4.6 × 10 ⁻⁶ ). d-Si is metallic silicon doped with Group III or Group V impurities. However, since it is a metal, the deposited film may be cracked or deposited even if there is a slight difference in thermal expansion coefficient from a dummy wafer serving as a base material. Problems such as peeling of the film and the dummy wafer hardly occur. However, in the case of silicon nitride, since it is a brittle ceramic, peeling or cracking occurs even if the difference in thermal expansion coefficient is small. In severe cases, cracks in the deposited film extend to the dummy wafer, which is the base material, leading to destruction. Destruction of a deposited film or a dummy wafer causes particles, which is a fatal defect in a device process.
The dummy wafer of the present invention has a coefficient of thermal expansion closer to that of silicon nitride than conventional products, can solve these problems, and has the potential to increase the deposited film thickness more than before.
The reason for showing a slightly larger coefficient of thermal expansion than the comparative example,
It seems to include the difference between the manufacturing method and the raw materials,
I'm not sure. Further, with respect to the three-point bending strength, it can be seen that the dummy wafer of the present invention realizes high strength without performing a special treatment such as HIP, and is advantageous in cost.

[0033]

As described above, according to the present invention, a dummy wafer having a small amount of warpage and high purity and a method of manufacturing the same are provided.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshihisa Suda 1091 Tateishi, Fujioka City, Gunma Prefecture Mitsubishi Pencil Co., Ltd. Gunma R & D Center F-term (reference) 4G032 AA07 BA04 GA12 4G046 CA04 CB06 CC01 CC02 CC03

Claims (5)

[Claims] 1. A dummy wafer made of glassy carbon, comprising a plurality of layers. 2. The method for manufacturing a dummy wafer according to claim 1, wherein carbonization is performed after bonding the plurality of layers. 3. The method according to claim 1, wherein the carbonization is performed in a non-oxidizing atmosphere at a temperature of 700.degree.
The method according to claim 2, wherein the method is performed in a temperature range of 2 ° C. to 2800 ° C. 4. 4. The carbonization is performed in a vacuum atmosphere at 1400 ° C.
The method according to claim 2, wherein the method is performed in a temperature range of up to 2800 ° C. 4. 5. After the carbonization, 1400 in a vacuum atmosphere
4. The method for manufacturing a dummy wafer according to claim 3, wherein the further processing is performed in a temperature range of from 2 to 800C.