JP3362062B2 - Ceramic member for semiconductor manufacturing apparatus and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic member for a semiconductor manufacturing apparatus and a method for manufacturing the same, and more specifically,
The present invention relates to a ceramic member for a semiconductor manufacturing apparatus suitable for a semiconductor manufacturing apparatus having an excellent surface which is surface-treated by chemical polishing and has suppressed emission of contaminants, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Ceramic members are used in various fields, but quartz glass or silicon carbide members have been frequently used in the semiconductor manufacturing process. Contamination problem is an important issue in semiconductor manufacturing, and quartz glass and silicon carbide forming conventional members have high purity, and Si, C, and O, which are the same elements as semiconductor silicon wafers, are the main components, and silicon contamination is a problem. This is because there are few. However, recently, plasma-excited CV
D. Due to the progress in lowering the semiconductor manufacturing process technology such as plasma-enhanced etching, unlike the conventional high-temperature operation, in the process in which the degree of contamination due to the emission of impurities from the ceramic member has decreased, alumina, etc. other than the above quartz glass, etc. The use of general inorganic oxide ceramics is rapidly increasing. In addition, conventional inorganic oxide ceramics, which have been used in the semiconductor manufacturing process near room temperature, have the functions of high rigidity, low specific gravity, abrasion resistance, chemical resistance, and oxidation resistance. Has been used a lot.

[0003]

However, in order to use ordinary ceramics as a mechanical member, it is necessary to have high accuracy, and there are cases where the ceramics are used as they are fired, but they are used after being ground by a diamond grinder or the like. Things are increasing. When such a ground ceramic member is used, a contamination problem may occur depending on the conditions even in the low temperature operation step of the semiconductor manufacturing process. For example, gas emission from the ceramic member, particles generated due to wear of contact materials There is a growing problem of pollution such as generation and release of trace contaminants from ceramic members.
It is an object of the present invention to solve the above problems when using a ceramic member formed of general ceramics, and to provide a ceramic member that does not constitute a pollution source even when used in a semiconductor manufacturing apparatus.

[0004]

According to the present invention, there is provided a ceramic member made of alumina or zirconia,
Surface-treated by chemical polishing and contaminated surface layer of alumina ceramic material or zirconia ceramic material and / or
Alternatively, there is provided a ceramic member for a semiconductor manufacturing apparatus, in which the microcrack layer is removed and contaminants in the semiconductor manufacturing process are suppressed.

Further, in the method for producing a ceramic member for a semiconductor manufacturing apparatus, the surface of an alumina ceramic material or a zirconia ceramic material forming the ceramic member for a semiconductor manufacturing apparatus is coated with a non-aqueous liquid mixture containing a flux raw material. A method for manufacturing a ceramic member for a semiconductor manufacturing apparatus, which comprises drying to form a flux-coated film, heating to melt and fluidize the flux, followed by cooling and acid treatment for surface treatment. Will be provided.

[0006]

According to the present invention, the ceramic surface forming the member is coated with a flux, and the flux is melted and fluidized to dissolve the ceramic surface in the melt. After flowing out, further, after cooling, the flux coating is positively cracked, and acid treatment is performed to perform surface treatment by chemical polishing to remove the flux and the ceramics on the member surface dissolved and held in the flux. Therefore, a damaged surface layer having microcracks or sharp protrusions generated during grinding of the surface of the ceramic member is removed together with the melt fluidization of the flux, and a ceramic member having a smooth surface without a damaged layer is formed. can do. Since the ceramic member of the present invention is chemically polished as described above and has a surface with excellent smoothness, when used in a semiconductor manufacturing apparatus, there is no gas emission or particle generation, and contaminants during ceramic firing are There is no release, and there is little risk of semiconductor contamination.

The present invention will be described in more detail below. First, how the inventors arrived at the present invention will be described.
First, the inventors of the present invention cause semiconductor contamination when used as a member in a semiconductor manufacturing process by firing an ordinary ceramic material such as alumina which is formed into a predetermined shape, as-fired or after-fired. I considered the cause. As a result, it was concluded that semiconductor contamination is mainly caused by the surface structure of ceramics and is generated by the interaction between the internal structure of ceramics and the surface.

First, the characteristics of the as-fired ceramic surface produced by the sintering method were considered. The as-fired ceramic surface mainly has the following properties. (1) It has a trace of the surface condition before firing. For example,
If the same ceramic powder etc. adheres before firing,
It burns to form protrusions. (2) There is a dent in the grain boundary part. That is, the surface energy and the grain boundary energy are in a balanced form. (3) There is contamination from the firing atmosphere and the contacted material during firing. For example, in electric furnaces, impurities that evaporate from refractory materials that form heaters and furnace walls, and in gas combustion furnaces, rust in pipes blown into the furnace and from refractory materials that are similar to electric furnaces. The surface of ceramics is often contaminated by impurities. There is also contamination from impurities in the tool material.

Next, the characteristics of the surface obtained by grinding the fired ceramics were considered. Since ceramics has high strength, toughness, and is surface-processed into a complicated shape, it is difficult to polish it smoothly by a mechanical method except for a simple surface such as a flat surface or a cylinder outer periphery. As described above, lapping or polishing using diamond powder, or grinding by a diamond grinder or the like is performed, and the processed surface mainly has the following properties. (1) The surface has a damage layer such as a microcrack caused by grinding. Grinding of ceramics is accomplished by treating with a diamond grinder or the like as described above and generating microcracks and dislocations. This treatment is performed in the manner of cultivating a field by skiing, and microcracks and dislocations generated on the ceramic surface form a so-called processing damage layer on the ceramic surface. In addition, in general, the ceramics produced by the sintering method, except the translucent alumina surface-treated,
It was confirmed that when the ceramics having residual pores and many closed pores were subjected to the above-mentioned grinding, a contamination problem particularly occurred. That is, the generated microcracks make the closed pores existing in the ceramic communicate with the outer surface with a narrow gap. On the other hand, when grinding ceramics, a cooling liquid such as water is applied to cool the tool, so this grinding cooling liquid penetrates into the pores communicating with each other through microcracks and is retained in the cracks and pores. It will be used for the member in the as-deposited state. (2) Fine irregularities are formed by grinding, and the irregularities are formed at a sharp angle. (3) The smoothness is not sufficient.

The inventors next examined the cause of contamination based on the consideration of the above-mentioned ceramic surface properties.
First, the problem of gas generation was examined. As described above, the grinding cooling liquid and the like are retained internally in the pores and cracks of the ceramic member, and since they cannot be removed by ordinary ultrasonic cleaning or the like, they are brought into the semiconductor manufacturing process. For this reason, in a semiconductor manufacturing apparatus under reduced pressure, an operation step at a temperature of room temperature or higher, or an atmospheric pressure, high temperature step, a grinding cooling liquid or the like held in pores or the like, or a dried product thereof is vaporized or the like. Was released into the system and polluted equipment and wafers.

Next, the generation of particles was examined. The grinding surface of wear-resistant ceramics such as alumina ceramics has sharp fine irregularities as described above,
By itself, it behaves like a file, abrading the contact surfaces that come into contact, producing wear debris, which will adhere to the ceramic surface. It has been clarified that these adhered powders are the cause of particle generation in the semiconductor manufacturing process.

Next, the release of trace impurities from ceramics was examined. When the wear rate of the ceramic itself is high, when the temperature is high and impurities or adhered contaminants during firing are easily diffused, and when the electric field or the like causes the impurities and firing contaminants in the ceramic to have a movement driving force. At times, it was discovered that pollution was extremely high.
It has also been clarified that, among the trace impurities and contaminants, the presence of alkali metals such as Na and those that easily influence the silicon characteristics, such as Cu, is particularly problematic.

Based on the above consideration and results, a method of grinding a diamond grinder or the like to remove the ceramic surface in which microcracks have occurred and converting it to a smooth surface without damage, that is, polishing without causing surface damage The damaged layer is removed, and it is possible to form a ceramic having substantially no microcracks and no sharp fine irregularities, and is keen to find a method for forming a ceramic member having such an excellent surface structure. Efforts have been made to arrive at the surface chemically polished ceramic member of the present invention.

The ceramic member for a semiconductor manufacturing apparatus of the present invention can be obtained by applying special chemical polishing as the above-mentioned polishing method. The ceramic member of the present invention can be formed into a desired member shape by using a dense polycrystalline sintered body of a known ceramic such as alumina or zirconia as a raw material. As a member for semiconductor manufacturing equipment, alumina is generally common, and in particular, alumina dense polycrystals having a porosity of about 3% or less are preferable in view of problems such as mechanical strength and contamination.

In the chemical polishing of ceramics according to the present invention, a ceramic member having a flux adhered to its surface is inserted into a furnace which is kept at a predetermined temperature in advance at a predetermined preferable speed to heat the ceramic member. The temperature is higher than the melting point of the flux, and the flux adhering to the surface of the ceramic member is melted, and the flux is melted and fluidized on the surface of the ceramic body for processing. As a result, the surface damage layer having the above-mentioned microcracks on the surface of the ceramic member, the burning contaminant, and the diffusion-exposed contained impurities can be dissolved in the melt. In this case, since the flux melt flows, the melting rate of the ceramics that dissolves in the melt becomes approximately constant, and the convex portions on the ceramic surface are selectively melted, and the irregularities on the ceramic member surface are flattened and smoothed. Becomes After the flux is melted and fluidized, then, the ceramic member in the state where the melted flux is adhered to the surface is taken out from the heating furnace at a predetermined preferable rate, the ceramic member is cooled, and the flux is solidified, and After cooling, the flux coating film is actively cracked due to the difference in thermal expansion coefficient between the ceramic and the solidified flux, and after cooling to room temperature, the flux coating film adhering to the ceramic surface is removed. Dissolve and remove by acid treatment. The ceramic member chemically polished as described above has a smooth surface.

The above chemical polishing is a method developed by the inventors for improving the light transmittance of translucent alumina ceramics, and is proposed in Japanese Patent No. 1,116,172. However, in carrying out the chemical polishing in the present invention, it is necessary to pay particular attention to destruction or cracking of the ceramic body. For example, when a large ceramic member is heated rapidly, a temperature gradient occurs in the ceramic member when the thickness of the ceramic member has a large difference. This temperature gradient in the ceramic member usually occurs in the circumferential direction of the surface and in the thickness direction, which causes thermal stress in the ceramic member, and when it exceeds the fracture limit value of the ceramic, cracks occur in the ceramic and lead to fracture. . Therefore, the heating rate takes into consideration the temperature distribution and maximum temperature in the heating furnace, the shape such as the thickness of the ceramic member, the heat capacity and strength of the ceramics, the melting point of the flux used, the viscosity of the flux melt, and other factors. Then, it may be appropriately selected. Further, in the present invention, in the case of chemically polishing a large-thickness ceramic member, in order to prevent cracks from occurring in the ceramic member, in addition to the control of the heating rate, the ceramic member is allowed to stand in the furnace in advance to raise the temperature or The cooling rate may be controlled. Regarding the large-tube-shaped ceramic member, the inventors have already proposed Japanese Patent Application No. 60-939.
It is also effective to apply the partial heating method proposed in No. 00, etc.

When the chemically polished ceramic member of the present invention is used in a semiconductor manufacturing apparatus, the problems of the conventional method can be solved as follows. (1) Remarkably reduce the gas emission from the ceramic member. Microcracks generated by diamond grinding or the like have a high rate of stopping at grain boundaries of ceramics and have a depth of about 20 μm from the surface at most, and the chemical polishing of the present invention dissolves the ceramic surface in the flux melt. It is a mechanism, and virtually no damage is given to ceramics by removing the damaged surface. Therefore, by the chemical polishing of the present invention, a smooth surface having excellent properties is obtained, microcracks and pores communicating therewith are eliminated, the grinding cooling liquid is not retained, and therefore no gas is generated. (2) The surface of the ceramic is smooth, the contacted surface is not abraded, and particles are not generated. Since the flux flows on the ceramic surface, the convex portions on the ceramic surface are selectively dissolved and removed to smooth the surface. Therefore, even if the silicon wafer comes into contact with or slightly rubs at the time of contact, the wafer is not worn. In particular, ceramics having these smooth surfaces are effective as a jig for wafer transfer.

(3) The release of pollutants and impurities is suppressed.
The chemical polishing of the present invention can remove the impurities contained on the surface of the ceramics and the firing contaminated layer, and can reduce the dielectric loss factor tan δ of the entire ceramics, so that the total emission amount of impurities and contaminants can be reduced. Contribute.
The dielectric loss factor tan δ of ceramics becomes large when there are many alkali metal ions such as contaminants and impurities contained in the ceramics, which are easy to diffuse. When the ceramics are irradiated with electromagnetic waves such as microwaves and high frequencies, the ceramics absorb the electromagnetic waves in proportion to the value of tan δ × dielectric constant and the temperature rises. On the other hand, in a plasma processing step in a semiconductor manufacturing process, for example, a plasma-enhanced etching step, the higher the temperature of the ceramic member, the higher the reaction rate with plasma, so that the etching wear of the ceramic member progresses. Therefore, when the impurity contaminated layer on the ceramic surface is removed by the chemical polishing of the present invention and the alkali metal ion contaminated material is reduced, the dielectric loss factor tan δ becomes small, the temperature rise of the ceramic member is suppressed, and the reaction with plasma occurs. The speed is reduced and the wear of the ceramic member is reduced. This prolongs the service life of the ceramic member and reduces the total amount of impurities and contaminants generated during wear.

Examples of the flux raw material powder used in the chemical polishing of the present invention include anhydrous sodium borate, anhydrous sodium borate containing 5 to 50% by weight of alumina, vanadium pentoxide, potassium pyrosulfate and the like. You can The coating of the flux to the raw material ceramic material is usually the above-mentioned flux raw material powder,
It can be carried out by using a non-aqueous solvent such as acetone to form a slip, coating the surface of the raw material ceramic material, and drying. Further, fluidization of the flux can be performed by heating to a predetermined temperature as described above. If the flux is sodium borate anhydrous, it is about 900 to 1400 ° C, and if it is vanadium pentoxide, it is about 900 to. The temperature is 1300 ° C, and the temperature is about 600 to 900 ° C for potassium pyrosulfate. Further, the acid treatment of the present invention can usually be performed using an aqueous solution of an inorganic acid such as hydrochloric acid.

[0020]

The present invention will be described in more detail based on the following examples. However, the present invention is not limited to the following examples. In addition, in the following examples, unless otherwise specified, the description is based on weight. Example 1 and Comparative Example 1 Flange outer diameter 240 mmφ, hemisphere inner diameter 190 mmφ,
A translucent alumina ceramic bell jar having a height of 120 mm and a wall thickness of 2 mm was chemically polished. Heating furnace has an inner diameter of 50
It is a furnace with a diameter of 0 mm and a heating length of 500 mm, and the maximum temperature is 1.
It is set to 200 ° C. 50 parts of sodium borate powder was dispersed in 100 parts of acetone to form a slip, and the above ceramic bell jar was immersed therein. Then, the ceramic bell jar was immediately taken out in the air to evaporate acetone at room temperature, so that the surface of the ceramic bell jar was coated with sodium borate powder in a thickness of about 1 mm almost uniformly.
The sodium borate-covered bell jar thus obtained was held by an alumina jig and inserted into the above-mentioned furnace, and 120 minutes after 30 minutes.
The temperature was raised to 0 ° C. and heated. Also, during the temperature rising
The jig was rotated once per minute, held at 1200 ° C. for 10 minutes, and then cooled at the same cooling rate. When the entire ceramic bell jar reached room temperature, it was removed from the furnace and jig. Next, the above ceramic bell jar was placed in a 5% hydrochloric acid aqueous solution at 60 ° C. and immersed for 12 hours to dissolve sodium borate.

The alumina ceramic bell jar whose surface was chemically polished as described above was washed with ion-exchanged water and dried. When the wall thickness of this bell jar was measured with a micrometer, it was 50 μm thinner. From this, it was found that the front and back surfaces of the ceramic were removed by about 25 μm. Then, a sample was cut out from the translucent alumina bell jar that had been chemically polished, and trace impurity analysis was performed using secondary ion mass spectrometry (SIMS). As Comparative Example 1, the same measurement was performed on the ceramic as it was after the firing before the chemical polishing. As a result, Na, K, Mg, Si, and Fe were reduced from the surface of the chemically-polished ceramic bell jar by about two orders of magnitude compared to the ceramic surface after firing.

Further, from the outside of the bell jar, a microwave of 1 kW of 2.45 GHz is irradiated to introduce oxygen of 0.1 Torr CF ₄ gas and the same pressure into the bell jar,
This was turned into plasma and the silicon wafer placed in the bell jar was etched with an oxide film. The temperature rise caused by absorbing a part of microwaves was measured for the above-mentioned chemically polished bell jar and the as-fired bell jar by measuring the temperature 10 minutes after irradiation. As a result, the temperature of the chemically polished bell jar was 250 ° C, and the temperature of the as-fired bell jar was 300 ° C. In addition, the amount of wear of the ceramic which was irradiated with microwaves for 30 minutes 100 times was measured. The wear amount of the chemically-polished ceramic bell jar was 0.01 mg / cm ² , whereas the wear amount of the ceramic was 0.2 mg / cm ² in the bell jar without chemical polishing. On the inner surface of the translucent alumina bell jar used as described above, A1F
₃ was formed, but rubbed with sandpaper, this A
When 1F ₃ was removed, the chemically-polished alumina could be completely removed, but it was difficult to remove A1F _{3 at the} grain boundary portion with the as-fired bell jar.

Example 2 and Comparative Examples 2 to 3 Outer diameter 38 mm, inner diameter 35 mmφ, length (height) 120 m
A translucent alumina ceramic tube having a thickness of 1.5 mm and a thickness of 1.5 mm was chemically polished in the same manner as in Example 1. Using this as a CDE (chemical dry etching) tube, the contamination level of the silicon wafer was measured. Further, as Comparative Example 2, an as-fired alumina ceramic tube without chemical polishing,
As Comparative Example 3, a quartz glass tube was used as a CDE tube to similarly measure silicon wafer contamination. The results are shown in Table 1.
It was shown to.

[0024]

[Table 1]

As is clear from the results shown in Table 1, the contamination of the silicon wafer is significantly less when the chemically polished alumina ceramics is used as the CDE tube than when the as-fired alumina ceramics is used as the CDE tube. I understand. Although the quartz glass CDE tube has a small amount of impurities, its wear rate is about 100 times as high as that of alumina ceramics, so its use in a fluorine-based plasma atmosphere has a short life.

Example 3 and Comparative Examples 4 to 5 Using high-purity alumina and translucent alumina having a porosity of 4%, three square rods each having a size of 5 mm × 5 mm × 30 mm were prepared. Comparative Example 4), grinding with a diamond grinder (Comparative Example 5), and chemical polishing after grinding (Example 3) were manufactured as samples.
Each of the square rods was inserted into a furnace under vacuum, heated at 800 ° C., and the amount of released gas was measured by the decrease rate of the vacuum degree,
Moreover, the gas component was measured by the mass spectrometer. The result is
The results are shown in Table 2.

[0027]

[Table 2]

As is clear from the results shown in Table 2, it was confirmed that the amount of gas released was remarkably reduced by chemically polishing the alumina ceramics. Further, since carbon oxides were detected in the alumina ground by the diamond grinder, it is presumed that the organic matter stored and retained in the defects near the surface of the ceramic was decomposed and emerged. Further, it can be seen from these results that even if the surface is ground, these organic substances can be removed and converted into alumina ceramics that does not release gas, by performing the chemical polishing of the present invention.

[0029]

The ceramic member for a semiconductor manufacturing apparatus of the present invention has a uniform and high smoothness by grinding and chemically polishing ceramics having a rough surface with sharp irregularities.
A ceramic member having a low gas adsorbing property, not abrading a contact substance, and having an extremely small amount of impurities and gas emission in a semiconductor manufacturing process,
It can be easily manufactured at low cost and is industrially useful.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Haruji Harada, Inventor Haruka Onuma, Togane-shi, Chiba 1573-8 Inside the Togane Plant, Toshiba Ceramics Co., Ltd. Open 1573-8 Toshiba Ceramics Co., Ltd. Togane Factory (72) Inventor Kazu Ando Inuma, Togane City, Chiba Prefecture Open 1573-8 Toshiba Ceramics Co., Ltd. Togane Factory (56) Reference JP-A-4-260678 (JP, A) JP 2-184589 (JP, A) JP 63-169391 (JP, A) JP 61-132579 (JP, A) JP 63-112481 (JP, A) Kaisha 58-190883 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 41/80-41/91

Claims (2)

(57) [Claims] 1. A canceller <br/> Mick member made of alumina or zirconia, it is surface treated by chemical polishing, an alumina ceramic material or zirconia ceramic
A ceramic member for a semiconductor manufacturing apparatus, wherein a contaminated surface layer and / or a microcrack layer of a material is removed to suppress contaminants in a semiconductor manufacturing process. 2. A ceramic for a semiconductor manufacturing apparatus according to claim 1.
A method of producing a click member, the aluminum constituting the ceramic member for a semiconductor manufacturing device
On the surface of na ceramic material or zirconia ceramic material ,
A non-aqueous liquid mixture containing a flux material is applied and dried to form a flux coating film, which is then heated to melt and fluidize the flux,
Then, a method of manufacturing a ceramic member for a semiconductor manufacturing apparatus, which comprises cooling, acid treatment and surface treatment.