JP3517702B2 - Dummy wafer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dummy wafer used in a process of cleaning the inside of a plasma etching chamber in a semiconductor manufacturing process such as IC and LSI, or a position on the end side where product wafers are arranged in a diffusion furnace or a vertical furnace. And a dummy wafer used for stabilizing the processing properties of the product wafer.

In the plasma etching process, a reactive gas (C,
(Atom-containing gas such as H, F, O) is introduced to discharge by applying high-frequency power between the electrodes, and the generated gas plasma is used to etch the non-photoresist portion with high precision. This is a step of forming a circuit pattern.

When the plasma etching process is repeated, problems arise such that the etched silicon adheres to the electrodes and the wafer holder in the etching chamber, and particles are generated due to the adhered silicon falling off. Therefore, it is necessary to periodically set a dummy wafer instead of the wafer, perform a plasma etching process, and clean the inside of the system. In the oxide film forming process in the diffusion furnace and the nitride film forming process by the low pressure CVD method in the vertical furnace,
It is difficult for the reaction gas flow and temperature distribution to be uniform on the end side in the furnace. Therefore, measures are taken to stabilize the properties of the oxide film and the nitride film formed on the wafer by arranging a dummy wafer at the end side where the product wafers are arranged.

Therefore, the dummy wafer is required to have material characteristics that are difficult to be etched and to have high purity. Quartz, silicon carbide, graphite and the like have been studied as this dummy wafer, but quartz cannot be used because it has no electrical conductivity, and silicon carbide has the disadvantages of poor workability and difficulty in high purification. Graphite has a problem in that particles fall off from the tissue due to its material. There is also a method of using a silicon wafer as a dummy wafer, but it is not practical because the cost increases as the size of the wafer increases.

Therefore, a semiconductor wafer dummy in which the above dummy wafer is made of a glassy carbon material (Japanese Patent Laid-Open No. 7-
No. 240401) is proposed. The glassy carbon material is a hard carbon material with a macroscopically non-porous structure obtained by carbonizing a thermosetting resin, and has excellent strength, low chemical reactivity, gas impermeability, self-lubricating property, robustness, etc. Although it has characteristics such as a small amount of impurities, it has an advantage that fine particles, which cause contamination of the wafer during the plasma etching process, are not easily separated from the tissue. Therefore, the dummy wafer has excellent material characteristics. However, in recent years, the degree of semiconductor integration tends to increase more and more, and therefore, dummy wafers are required to have material performance with low wear and excellent durability. Even dummy wafers made of the above glassy carbon material are required. There are not enough problems.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of diversified research on the material structure of the glassy carbon material used as a dummy wafer, the present inventors have found that the surface property of the glassy carbon material is an argon ion laser having a constant wavelength range. The performance of the dummy wafer when the spectral relative intensity ratio of the two Raman bands specified in the Raman spectrum analysis and the lattice spacing of the graphite hexagonal network plane layer, which is an index of the bulk crystalline property of glassy carbon, satisfy a certain relationship. It has been found that can be effectively improved.

The present invention has been completed based on this knowledge, and its purpose is to clean the inside of a chamber for plasma etching or the like, or to process a product wafer in a diffusion furnace or a vertical furnace. It is an object of the present invention to provide a dummy wafer that consumes less, generates less particles, has less pollution, and can be used stably for a long period of time.

[0008]

A dummy wafer according to the present invention for achieving the above object appears in a band region of 1360 ± 100 cm ⁻¹ in a Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 Å. Spectral intensity (IA) and 1580 ± 100
The relative intensity ratio R (IA / IB) of the spectral intensity (IB) appearing in the band region of cm ^-1 and the average lattice spacing d of the graphite hexagonal network layer
_{The structural characteristic is that 00 2} (unit: angstrom) is made of a glassy carbon material that satisfies the relationship of the following formula (1). R ≧ (d ₀₀₂ −3.344) /0.135 (1)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The dummy wafer of the present invention is premised on that it is made of glassy carbon having a uniform structure obtained by firing and carbonizing a thermosetting resin. A flat plate having a high-purity material having a total sulfur content of 2 ppm or less and a total sulfur content of 30 ppm or less and having a surface smoothness as high as possible is preferable.

This glassy carbon material has a wavelength of 5
1360 ± 10 when analyzed by Raman spectrum using 145 Å argon ion laser beam
Spectral intensity (IA) in the 0 cm ^-1 band region and 1580
The R value, which is the relative intensity ratio (IA / IB) of the spectral intensity (IB) in the ± 100 cm ⁻¹ band region, and the average lattice spacing d _{00 2} (unit: angstrom) of the graphite hexagonal network layer are R
Satisfying the relationship of ≧ (d ₀₀₂ −3.344) /0.135 is a main constituent feature of the present invention.

Of these, the value of the relative intensity ratio R (IA / IB) in the Raman spectrum analysis is preferably in the range of 1.0 to 2.0. When the R value is less than 1.0, the crystal structure is not an amorphous material peculiar to glassy carbon, the etching resistance is lowered, and the wear uniformity is also lowered. On the other hand, when the R value exceeds 2.0, carbonization becomes insufficient and the consumption rate increases, and the preferable R value range is 1.2 to 1.9.

The average lattice plane spacing d _{00 2} of the graphite hexagonal mesh plane layer is obtained from the C (002) diffraction peak by X-ray diffraction. The d ₀₀₂ spacing is in the range of 3.40 to 3.60 angstrom. Preferably there is. The average lattice spacing d _{00 2} is 3.
When it is less than 40 Å, graphitization proceeds and the crystal structure does not exhibit an amorphous structure peculiar to glassy carbon, so that the generation of fine particles from the material structure increases. The average lattice spacing d _{00 2} is 3.60.
If it exceeds angstrom, carbon structure will become insufficient,
As a dummy wafer, the etching resistance is reduced, the consumption is non-uniform, and the degree of consumption is increased.

The degree of wear when the glassy carbon material is used for the dummy wafer depends on the purity of the glassy carbon used,
The crystal structure, surface state, etc. are complicatedly affected and slightly change. In general, Raman spectrum analysis of carbon materials gives 13
Out two peaks in the band area of 60cm ^-1 and 1580 cm ^-1 is present, their relative intensity ratio is known to be related to irregularities in the amount of defects and lattice of crystals contained in the structure of the carbon. For example, in the case of artificial graphite, but the intensity of the 1580 cm ^-1 band is higher than 1360 cm ^-1, a peak of 1360 cm ^-1 band in the reverse increases the glassy carbon.
However, the distribution of peaks and the relative intensity between bands differ depending on the properties of the glassy carbon, and the etching resistance changes. On the other hand, the lattice constant C ₀ obtained by X-ray diffraction of a non-graphitizable carbon material such as glassy carbon is larger than that of a carbon material having a graphite structure with developed graphite network crystals, and at the same time, the average lattice plane is The spacing is also relatively wider than that of the graphite material, but this crystal structure also affects the etching resistance and the generation of fine particles.

R ≧ (d ₀₀₂ −3.344) regulated by the present invention
The relational expression (1) of /0.135 is the two bands in Raman spectrum analysis with respect to the average lattice spacing d _{002 of the} graphite hexagonal net-like layer whose surface texture of the glassy carbon material constituting the dummy wafer is measured by X-ray diffraction. Characterized by having an amorphous carbon crystal structure having a relative intensity ratio R of peaks above a certain level, this property suppresses the consumption rate of the dummy wafer and at the same time does not cause the release of fine particles. Form an organization. Therefore, R ≧ (d ₀₀₂
If a dummy wafer composed of a glassy carbon material satisfying the requirement of −3.344) /0.135 is used, it can be used stably for a long time.

The dummy wafer of the present invention made of the glassy carbon material having the above properties can be manufactured as follows. First, in order to achieve high-density and high-purity materials, phenol-based, furan-based, or polyimide-based or a thermosetting resin having a blending ratio of them, which has been preliminarily refined and has a residual carbon ratio of at least 40% or more, is selected and used as a raw material. . Since these raw material resins are usually in the form of powder or liquid, they are molded into a predetermined plate shape by using an optimum molding means such as molding, injection molding or cast molding depending on the form. The molded body is continuously 100 to 1 in the atmosphere.
Curing treatment is performed at a temperature of 80 ° C. The firing and carbonization treatment is performed by packing the cured resin molded body in a graphite crucible or sandwiching it between graphite plates in an electric furnace maintained in an inert atmosphere of nitrogen, argon, or the like, or a lead hammer furnace.
It is carried out by heating to 000 ° C. Further, the carbonized fired body is placed in a vacuum furnace capable of atmosphere replacement and heated to 2000 ° C. while flowing a halogen-based purified gas to carry out a high-purification treatment.

Then, the surface of the fired body is mechanically polished to improve the smoothness of the surface. The mechanical polishing of the surface can change the structure of only the surface layer portion of the glassy carbon material to a desired property by lapping using various abrasives or polishing such as buffing. Examples of the abrasive grains include metal oxides such as Al ₂ O ₃ abrasive grains and Si.
In addition to carbides such as C abrasive grains, borides such as TiB ₂ abrasive grains, nitrides such as BN ₄ abrasive grains, simple abrasive grains such as diamond are included. It is preferable that the abrasive grains sequentially move from one having a larger grain size to one having a smaller grain size to increase the surface smoothness. When such surface polishing is performed, mechanical energy such as compression, shearing and friction is applied to the surfaces of the abrasive grains and the glassy carbon material, and the temperature rise and compression between the abrasive grains and the glassy carbon material occur. Phenomena such as the generation of force, the accumulation of strain energy, the generation of structural defects, etc. act in combination to induce changes in the surface mechanochemistry. As a result, it becomes possible to convert into a glassy carbon material having a surface texture that satisfies the requirements of the present invention.

This surface polishing treatment may be carried out between the above-mentioned firing carbonization treatment and the high-purification treatment, and the texture property due to the structural change of the surface texture due to the surface polishing improves the wear characteristics of the dummy wafer and causes the generation of particles. Effectively functions to suppress the occurrence. Selection of raw resin purified in this way,
By appropriately controlling the firing carbonization temperature, the temperature condition during the refining treatment, the condition during the surface polishing, and the like, the desired properties of the glassy carbon material can be secured.

[0018]

EXAMPLES Hereinafter, examples of the present invention will be specifically described in comparison with comparative examples, but the embodiments of the present invention are not limited to these examples.

Example 1 Phenol and formalin purified by vacuum distillation were condensed by a conventional method to prepare a phenol resin initial condensate. This raw material resin solution was poured into a 400 mm square polypropylene vat, deaerated for 3 hours under a reduced pressure of 10 Torr or less, and then placed in an electric oven at 80 ° C. and left for a whole day and night to form a plate. The molded plate is taken out of the vat, heated to 180 ° C. at a temperature rising rate of 10 ° C./hr, and
A time hardening process was performed. The molded and cured resin molded plate is sandwiched between high-purity graphite plates and set in an electric furnace. The surrounding area is covered with graphite powder having a total ash content of less than 100 ppm and the temperature is raised to 1000 ° C at a heating rate of 2 ° C / hr. It was heated and subjected to firing carbonization treatment.

The resulting flat glassy carbon plate having a thickness of 3 mm was lapped using SiC abrasive grains as an abrasive in the order of grain size # 800 for 35 minutes and grain size # 2000 for 25 minutes to smooth the surface. I went. Then, it was moved to a vacuum furnace (TP300 manufactured by Tokai High Heat Co., Ltd.) that can replace the atmosphere.
High-purity treatment was performed by raising the temperature to 2000 ° C. while flowing a purified gas of Cl ₂ / He (molar ratio: 5/95) into the furnace at a supply rate of 5 liters / minute. This high-purity processed product was buffed using a SiC abrasive in the order of grain size # 4000 for 25 minutes and grain size # 8000 for 35 minutes, and finally polished to produce a dummy wafer having a diameter of 200 mm.

With respect to the dummy wafer made of the glassy carbon material thus obtained, the X-ray diffraction measurement was performed and the average lattice spacing d ₀₀₂ was measured from the C (002) diffraction pattern. Further, the surface thereof is irradiated with an argon ion laser beam having a wavelength of 5145 angstroms to perform Raman spectrum analysis, and 1360 ± 100 cm ⁻¹ and 1580 ±.
The relative intensity ratio R in both bands at 100 cm ^-1 was calculated. As a result, the characteristic requirements of the present invention were satisfied.

This dummy wafer is set in the wafer loading section of the plasma etching apparatus, and the reaction gas; CF ₄ , carrier gas; Ar, gas pressure in the reaction chamber; 0.5.
Plasma etching was performed for 20 hours under the conditions of Torr and power supply frequency: 13.5 MHz. The amount of reduction in the thickness of the dummy wafer after processing (the amount of consumption) and the amount of particles generated in the chamber at the end of processing of 0.1 μm or more were measured, and the results were compared with the properties of the glassy carbon material. It was shown to.

Example 2 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 2
A dummy wafer made of a glassy carbon material was manufactured under the same conditions as in Example 1 except that the temperature was changed to 100 ° C. The obtained glassy carbon material satisfied the characteristic requirements of the present invention. This dummy wafer was subjected to plasma etching treatment under the same conditions as in Example 1, the performance as a dummy wafer was evaluated, and the results are also shown in Table 1.

Example 3 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 2
A dummy wafer made of a glassy carbon material was manufactured by changing the temperature to 100 ° C., the condition of the surface finish polishing after the high-purity treatment was SiC abrasive grain size # 6000 only for 45 minutes, and all other conditions were the same as in Example 1. . The obtained glassy carbon material satisfied the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Example 4 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 2
A dummy wafer made of a glassy carbon material was manufactured by changing the temperature to 500 ° C., the condition of the surface finish polishing after the high-purity treatment was only the SiC abrasive grain size # 3000 for 45 minutes, and all other conditions were the same as in Example 1. . The obtained glassy carbon material satisfied the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Example 5 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 1
A dummy wafer made of a glassy carbon material was manufactured under the same conditions as in Example 1 except that the temperature was changed to 500 ° C. The obtained glassy carbon material satisfied the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Example 6 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 3
A dummy wafer made of a glassy carbon material was manufactured under the same conditions as in Example 1 except that the temperature was changed to 000 ° C. and the surface finish polishing after the high-purity treatment was changed to SiC abrasive grain size # 3000 for 10 minutes only. The obtained glassy carbon material satisfied the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1,
The results are also shown in Table 1.

Comparative Example 1 In the manufacturing process of Example 1, a SiC abrasive was used under the condition of surface treatment after firing and carbonizing at 1000 ° C., and grain size # 4.
Of the glassy carbonaceous material was manufactured under the same conditions as in Example 1 except that the polishing treatment was performed in the order of 000 for 25 minutes and grain size # 8000 for 35 minutes. . The glassy carbon material obtained did not meet the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1,
The results are also shown in Table 1.

Comparative Example 2 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 1
A dummy wafer made of a glassy carbon material was manufactured under the same conditions as in Example 1 except that the temperature was changed to 200 ° C. The glassy carbon material obtained did not meet the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Comparative Example 3 In the manufacturing process of Example 1, the temperature during high-purity treatment was set to 2
A dummy wafer made of a glassy carbon material was manufactured under the same conditions as in Example 1 except that the temperature was changed to 500 ° C., the finishing polishing after the high-purity treatment was stopped. The glassy carbon material obtained did not meet the characteristic requirements of the present invention. The performance of this dummy wafer was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

[0031]

[Table 1] [Table Note] 1) Relative intensity ratio R. 2) The average lattice plane spacing of the graphite hexagonal mesh plane layer is in Angstrom.

From the results shown in Table 1, the dummy wafers of the examples made of the glassy carbon material satisfying the characteristic requirements of the present invention are smaller in the thickness reduction due to wear than the dummy wafers of the comparative examples, and the number of generated particles is small. It turns out that there are few. Further, the relative strength ratio R of the glassy carbon material
Is in the range of 1.0 to 2.0, and the average lattice spacing d ₀₀₂
Was in the range of 3.40 to 3.60 angstroms, and in Examples 5 and 6 in which the thickness deviates from the range of 3.40 to 3.60 angstroms, the amount of decrease in wall thickness and the number of particles generated tended to increase slightly.

[0033]

As described above, according to the present invention, the value of the relative intensity ratio of the two specific band regions revealed by the Raman spectrum analysis and the average lattice of the graphite hexagonal network plane layer obtained by X-ray diffraction By selecting a glassy carbon material having a specific relationship with the surface spacing d ₀₀₂ , it is possible to provide a dummy wafer that consumes less during etching and that generates less fine particles.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (3)

(57) [Claims] 1. A spectrum intensity (IA) appearing in a band region of 1360 ± 100 cm ⁻¹ and a spectrum intensity (IA) appearing in a band region of 1580 ± 100 cm ⁻¹ in a Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 Å. Glassy carbon satisfying the following relationship (1) between the relative intensity ratio R (IA / IB) of the spectral intensities (IB) and the average lattice spacing d _{00 2} (unit: angstrom) of the graphite hexagonal mesh plane layer. A dummy wafer made of a material. R ≧ (d ₀₀₂ −3.344) /0.135 (1) 2. The relative intensity ratio R (IA / IB) is 1.0 to 2.
The dummy wafer according to claim 1, wherein the dummy wafer is composed of a glassy carbon material in the range of 0. 3. The average lattice plane spacing d _{002 of the} graphite hexagonal mesh plane layer.
3. The dummy wafer according to claim 1 or 2, wherein the dummy wafer is composed of a glassy carbon material in the range of 3.40 to 3.60 angstroms.