JP3465838B2 - Electrode plate for plasma etching - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-like glassy carbon material used for plasma etching a silicon oxide film on a wafer surface in a semiconductor device manufacturing process. The present invention relates to a configured electrode plate for plasma etching. [0002] Plasma etching in an etching apparatus installed a pair of planar electrodes facing up and down, while introducing halogen-based reactive gas such as CF _4, CHF ₃ from the upper electrode between the electrodes A high-frequency power is applied and discharged, and a gas circuit is used to etch a non-photoresisted portion of a wafer mounted on a lower electrode to form a fine circuit pattern with high precision. . The planar electrode used for this plasma etching process needs to have not only excellent conductivity, but also high purity that does not contaminate the wafer and chemical stability that is not easily etched, and currently satisfies these material requirements. For example, an electrode plate made of a glassy carbon material has been useful. A glassy carbon material is a hard carbon material having a macroscopically non-porous three-dimensional network structure obtained by carbonizing a thermosetting resin and having high strength, chemical stability, abrasion resistance, and the like. It has features such as excellent gas impermeability, self-lubricating properties, and robustness, and has few impurities.However, it is particularly advantageous in that fine particles that cause soiling of the wafer during plasma etching are not easily separated from the tissue. There is. However, recently, as the degree of integration of semiconductors has increased, strict material requirements have also been imposed on electrode materials for plasma etching, and a reduction in the level of particles attached to the wafer surface and the degree of wear have been strictly required. . For this reason, there have been many proposals for material improvement for glassy carbon electrodes for plasma etching. [0004] For example, the properties such as purity, porosity, porosity, crystal structure, and the like are to be improved.
0002 to 0.0020%, no crystallite is detected by X-ray diffraction, and a carbon member for a plasma device made of a glassy carbon material having an impurity content of 5 ppm or less (Japanese Patent Laid-Open No.
JP-A-33007), an electrode plate for plasma etching composed of high-purity glassy carbon having a maximum pore diameter of 1 μm or less, an average pore diameter of 0.7 μm or less, and a porosity of 1% or less. Gazette), a plate-like body having a thickness of 2 mm or more made of high-purity glassy carbon, having substantially no grain boundaries on the surface and internal structure, and having a maximum pore diameter of 1
μm or less electrode plate for plasma etching (JP-A-3-28
5086 JP), the following purity characteristics total ash content 5 ppm, metal impurities 2ppm or less, or less total sulfur content 30 ppm, the crystal characteristic lattice spacing d ₀₀₂ 0.0375nm or less, the size of the crystallite is more than 1.3 nm, An electrode plate for plasma etching made of glassy carbon having a material characteristic of specific gravity of 1.50 or more and a bending strength of 1100 kg / cm ² or more (JP-A-5-320955), and a lattice constant C ₀ of 6.990 Å or less. An electrode plate for plasma etching made of glassy carbon having crystals (JP-A-6-128761) has been proposed. [0005] In addition, assuming that the surface property is a target, the surface smoothness of a part consumed by plasma is Rmax.
An electrode plate for plasma etching made of glassy carbon having a diameter of 6 μm or less (Japanese Patent Application Laid-Open No. 6-128762) is disclosed. As a technique for specifying a raw material system of glassy carbon, glass produced using phenol resin and polycarbodiimide resin as raw materials is used. Electrode plate for plasma etching made of glassy carbon material (JP-A-5-347276), electrode plate for plasma etching made of glassy carbon material manufactured using polycarbodiimide resin as a raw material, etc. Has been proposed. The present applicant has examined the relationship between the texture of the glassy carbon constituting the electrode plate for plasma etching and the degree of electrode wear during the etching process, and as a result, has found that the surface of the glassy carbon constituting the electrode plate has been studied. Elucidating the fact that the degree of electrode wear is effectively reduced when the relative intensity of the two Raman bands specified in the Raman spectrum analysis with argon ion laser in a certain wavelength range is within a certain range, In a Raman spectrum using an argon ion laser beam having a wavelength of 5145 angstroms, a formula [R = IA / IB] (where IA is a spectrum intensity in a 1360 ± 100 cm ⁻¹ band region, IB
Indicates the spectral intensity of the 1580 ± 100 cm ^-1 band region), the R value is in the range of 1.0 to 2.0, and the half width of IA is 30 to 90 cm ^-1 and the half width of IB is An electrode plate for plasma etching made of glassy carbon having properties ranging from 40 to 100 cm ^-1 has been proposed (JP-A-8-120471). [0007] Further, the applicant of the present invention disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-1204.
By developing the technology of Japanese Patent Publication No. 71, the relative intensity ratio R (= IA / IB) is obtained as a textured glassy carbon material that suppresses electrode consumption rate during plasma etching and does not cause separation of fine particles. The average lattice spacing d ₀₀₂ of the graphite hexagonal mesh layer is R ≧ (d ₀₀₂ −3.3
An electrode plate for plasma etching made of a glassy carbon material satisfying the relationship of (44) /0.135 was developed and proposed (Japanese Patent Application No. 8-52464). SUMMARY OF THE INVENTION [0008]
According to the electrode plate for plasma etching disclosed in Japanese Patent Application No. 471 and Japanese Patent Application No. 8-52464, electrode consumption and generation of particles can be effectively reduced, and electrode performance can be improved and improved. However, subsequent studies showed that the surface layer of the electrode plate was gradually consumed in the process of plasma etching and the internal structure was exposed, so that the generation of particles increased and the consumption rate tended to increase. This tendency becomes more remarkable as the electrode plate becomes larger and thicker. The present inventor has further studied the relationship between the texture of the glassy carbon material during the etching process and the degree of wear of the electrode plate. In particular, it was confirmed that the difference in the structure between the surface layer portion and the central portion of the cross section greatly affected. The present invention has been completed on the basis of the above findings, and it is an object of the present invention to provide a plasma etching electrode plate made of a sheet-like glassy carbon material, in which the crystal structure of a surface layer portion and an internal structure is improved. By setting the difference in a specific range to homogenize the texture of the structure, and by setting the crystal structure of the internal structure to a property range effective to maintain low resistance to etching wear, a large size exceeding 8 inches An object of the present invention is to provide a plasma etching electrode plate made of a plate-like glassy carbon material which can sufficiently cope with a wafer and can perform a stable etching process for a long period of time. In order to achieve the above object, the present invention provides an electrode plate for plasma etching according to the following formula (1) in Raman spectrum analysis using argon ion laser light having a wavelength of 5145 angstroms. Defines the relative intensity ratio R, and R at the surface layer and the center of the cross section.
Value difference is 0.1 or less, and R
5 m in thickness with a texture in the range of 1.2 to 1.7
It is characterized by being composed of a plate-like glassy carbon material of m or more. R = IA / IB (1) where IA indicates the spectrum intensity in the 1360 ± 100 cm ⁻¹ band region, and IB indicates the spectrum intensity in the 1580 ± 100 cm ⁻¹ band region. DETAILED DESCRIPTION OF THE INVENTION The electrode plate for plasma etching of the present invention is premised on that it is made of glassy carbon having a uniform structure obtained by firing and curing a thermosetting resin. Total ash content 5ppm or less, metal impurities 2pp
m and a total sulfur content of 30 ppm or less, and is preferably a flat plate having as high a surface smoothness as possible. When the glassy carbon plate is used as the electrode plate for plasma etching, the degree of consumption slightly varies due to the complicated influence of the purity, crystal structure, surface state and the like of the glassy carbon used. Generally, the carbon material two peaks out current in the band region of 1360 cm ^-1 and 1580 cm ^-1 when a Raman spectrum analysis, their relative intensity ratio to irregularities of defects and lattice of crystals contained in the structure of the carbon It is known to be involved. For example, in the case of artificial graphite, 1360 cm ^-1
Although the intensity of the 1580 cm ^-1 band is higher than that of glassy carbon, the peak of the 1360 cm ^-1 band is higher in 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. According to the present invention, the surface layer and the center of the cross section of the glassy carbon plate are subjected to Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 angstroms, and the spectral intensity IA in the 1360 ± 100 cm ^-1 band region is obtained. The ratio (IA / IB) to the spectral intensity IB in the 1580 ± 100 cm ^-1 band region is defined as the relative intensity ratio R, and the difference in the value of R between the surface layer portion and the center of the cross section is 0.1 or less. This is the first property requirement. If the difference in R value exceeds 0.1, the difference in texture between the surface layer and the center of the cross section increases, and the consumption rate increases as the internal structure appears due to the wear of the surface layer, and the generation of particles also increases. I do. Further, in the present invention, as a second physical property requirement, the value of the relative intensity ratio R at the center of the cross section needs to be in the range of 1.2 to 1.7. When the R value is less than 1.2, the crystal structure is not amorphous, which is characteristic of glassy carbon, and the etching resistance is reduced.
If it exceeds 7, the carbonization is insufficient, the conductivity and chemical stability are low, the eligibility as an electrode plate is poor, and the etching consumption rate is high. A commercially available micro Raman analyzer can be suitably used for measuring the spectral intensity by Raman spectrum analysis. Further, the surface layer and the center of the cross section of the plate-like glassy carbon material to be measured in the present invention means that the surface layer is near the front surface (the surface facing the wafer) or the back surface of the glassy carbon plate, specifically, 3 from the front and back
The area within 0 μm is defined as the measurement target area. In addition, the glassy carbon plate is cut as the center of the cross-section, and the center position in the thickness direction of the fractured surface, that is, half of the plate thickness as the center position, and the area within 30 μm of the periphery is defined as the measurement target region. I do. The thickness of the sheet-like glassy carbon material is 5 mm.
It is preferable that it is above. The electrode plate for plasma etching of the present invention comprising the plate-like glassy carbon material having the above properties can be manufactured as follows. First, in order to increase the density and purity of the material, a phenol-based, furan-based, or polyimide-based resin with a residual carbon ratio of at least 40% or a thermosetting resin obtained by blending them is selectively used as a raw material. Is done. For example, as a raw material, a phenol and formalin, which have been purified in advance, are subjected to a polycondensation reaction, and have a molecular weight of 100 or more and a gelation time of 5 to 6 hours.
A two-component resin composition having a viscosity of 1 to 100 poise and a resin content of 50% by weight or more is prepared by mixing furan or its derivative compound with a phenol resin precondensate of 0 minutes. As the furan derivative compound, a compound having compatibility with a phenolic resin such as furfuryl alcohol, furfural, and methyl furancarboxylate may be used alone or in combination of two or more. These raw material resins are formed into a predetermined plate shape by an appropriate forming method such as molding or casting, and then the resin molded body is cured by heating in the atmosphere. If the structure of the cured resin molded article is not uniform, the texture of the fired and carbonized glassy carbon material will also be heterogeneous. Is more likely to proceed, so that the heterogeneity of the tissue increases. Therefore, in order for the curing reaction to proceed evenly, it is important to adjust the temperature rise rate during heating and curing to promote the curing reaction slowly, and to increase the temperature rise rate to 10 ° C./hr or less, preferably 5 ° C./hr or less. hr or less, more preferably 2 ° C./hr or less. The final curing temperature varies depending on the composition of the resin, the type and the amount of the curing agent, but is usually 140 to 200 ° C.
The curing reaction is terminated by maintaining the temperature at the final curing temperature for a predetermined time. The cured resin molded product is packed in a graphite crucible or packed in an electric furnace or a lead hammer furnace held in a non-oxidizing atmosphere such as nitrogen or argon while being sandwiched by graphite plates. By heating to a temperature, it is calcined and carbonized to be converted to a glassy carbon material. Since the cured resin molded body has a low thermal conductivity, the carbonization reaction tends to be delayed inside the surface layer in the firing carbonization process. For this reason, the carbonization reaction progresses under tension in the inside as the carbonization reaction progresses in the surface layer portion, so that a difference occurs in the crystal structure of the structure between the surface layer portion and the inside. In order to alleviate such a phenomenon, it is necessary to set the heating rate at the time of calcining and carbonization to be small. However, the rate of heating is set to 4 ° C./hr or less in view of the efficiency of the calcining and carbonizing work. It is desirable. In addition, in the firing carbonization process, the temperature can be maintained for a certain period of time in the temperature range where the carbonization is severe, the temperature where the gas generation is severe, the temperature range where the carbonization reaction ends and the structural change occurs, etc. This is effective in achieving equalization. For example, in each temperature range of 300 to 400 ° C., 400 to 500 ° C., and 500 to 600 ° C., each is maintained for 5 hours or more. In this manner, the curing conditions and the calcination conditions such as the heating rate and the final curing temperature during the heat curing of the resin molded article, the heating rate during the calcination and the final calcination temperature are strictly set and controlled. By doing so, the difference in the relative intensity ratio R between the surface layer portion and the center of the cross section of the plate-like glassy carbon material applied to the electrode plate for plasma etching of the present invention is 0.1 or less, and the R value at the center of the cross section. It is possible to produce a plate-like glassy carbon material having a texture of 1.2 to 1.7 and a thickness of 5 mm or more. The calcined and carbonized glassy carbon plate is placed in a vacuum furnace whose atmosphere can be replaced, and heated to 1500 ° C. or higher while flowing a halogen-based purified gas to be subjected to a high purification treatment. In addition, small gas through holes provided in the electrode plate are drilled in the cured resin molded body in advance in anticipation of the dimensional shrinkage during carbonization, or are drilled in the glassy carbon plate after firing and carbonization by electric discharge machining. Done either way. EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. Examples 1 to 5 and Comparative Examples 1 to 3 (1) Production of an electrode plate for plasma etching Phenol and formalin purified by distillation under reduced pressure were condensed according to a conventional method to give a phenol resin having a molecular weight of 132 and a gelation time of 14 minutes. An initial condensate was obtained. Furfuryl alcohol 3 was added to 100 parts by weight of the phenol resin precondensate.
0 parts by weight were added and mixed to prepare a raw resin composition having a viscosity of 40 poise and a resin content of 55% by weight. Pour this raw resin composition into a 400 mm square polypropylene vat,
After deaeration under reduced pressure of 10 Torr or less for 3 hours, the mixture was placed in an electric oven and cured by changing the heating rate, the final curing temperature, and the time to produce a 7 mm-thick plate-like cured resin molded product. . This plate-shaped cured resin molded product is sandwiched between high-purity graphite plates and set in an electric furnace in a state of being placed in a graphite crucible.
The surroundings were covered with graphite powder having a total ash content of less than 100 ppm, and calcined at different heating rates and different firing temperatures. In the firing process, each of the temperature ranges of 350 ° C., 450 ° C., and 550 ° C. was held for 5 hours. A vacuum furnace capable of replacing the atmosphere of the obtained glassy carbon plate [Tokai Kosen Kogyo Co., Ltd.
TP300], and chlorine gas (Cl
_The mixture was heated to the same temperature as the sintering temperature while passing through a ₂ / He molar ratio of 5/95) to perform a high-purification treatment. In this way, a glassy carbon plate having a smooth surface with a thickness of 5 mm was produced. Then, the surface was subjected to electrical discharge machining to a diameter of 0.5
500 through-holes having a diameter of 7 mm were formed at regular intervals of 7 mm to manufacture an electrode plate for plasma etching for processing an 8-inch wafer. Table 1 shows a comparison between these curing conditions and calcined carbonization conditions. [Table 1] (2) Measurement of Material Properties Regarding the glassy carbon plate manufactured as described above,
The surface layer and the center position in the thickness direction of the cut surface (the center of the cross section) are irradiated with argon ion laser light having a wavelength of 5145 angstroms to perform Raman spectrum analysis, and 1360 ± 100 cm ⁻¹ and 1580 ± 100 cm ^−1. The relative intensity ratio R was calculated by measuring the spectral intensities IA and IB in both bands. Table 2 shows the results. [Table 2] (3) Evaluation of electrode performance These electrode plates were set in a plasma etching apparatus,
The amount of consumption of the electrode plate and the amount of generated particles after the etching time of 10 hours, 100 hours, and 200 hours were measured, and the results are shown in Table 3. Plasma etching treatment is performed using a reaction gas; trichloromethane, a carrier gas; argon, a gas pressure in a reaction chamber;
rr, power supply frequency; 13.5 MHz, for an 8-inch silicon wafer oxide film. The amount of consumption of the electrode plate was determined by measuring the wall thickness of the electrode plate with a micrometer for each processing time, and the amount of reduction in thickness was used as the consumption amount. The number of particles generated was measured in the reaction chamber at each processing time. 3μ
The number of particles is shown as m or more. Table 3 shows the obtained results. [Table 3] From the results shown in Tables 1 to 3, the electrode plate of the embodiment made of the plate-like glassy carbon material satisfying the characteristic requirements of the present invention has a lower material quality than the electrode plate of the comparative example which does not satisfy the characteristic requirements of the present invention. It can be seen that the homogeneity reduces the amount of wear on the electrode plate surface even after long-time etching, thereby suppressing the number of generated particles. As described above, according to the present invention, the 1360 ± 100 cm ⁻¹ band region and the 1
A plate having a homogenous texture in which the ratio of the spectral intensities in the 580 ± 100 cm ^-1 band region is defined as a relative intensity ratio R, and the difference between the R value between the surface layer and the center of the cross section and the R value at the center of the cross section are set to specific ranges. When the electrode plate for plasma etching is made of a glassy carbon material, it is possible to provide an electrode plate in which the consumption of the electrode plate by etching is small and generation of particles is suppressed. Therefore, stable etching is always ensured, and the life of the electrode plate can be significantly extended.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 4/00 C01B 31/02 H01L 21/3065

Claims (1)

(57) [Claims 1] In a Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 angstroms, a relative intensity ratio R is defined by the following equation (1), and the relative intensity ratio R in the surface layer portion and the center portion of the cross section is defined. It is characterized by comprising a plate-like glassy carbon material having a thickness of 5 mm or more and having a texture of a R-value difference of 0.1 or less and a cross-sectional center portion in a range of 1.2 to 1.7. Electrode plate for plasma etching. R = IA / IB (1) Here, IA indicates the spectrum intensity in the 1360 ± 100 cm ⁻¹ band region, and IB indicates the spectrum intensity in the 1580 ± 100 cm ⁻¹ band region.