JP4588379B2 - Method for manufacturing member for semiconductor manufacturing apparatus - Google Patents

Description

The present invention relates to a method for manufacturing a member for a semiconductor manufacturing apparatus comprising a β-sialon sintered body.

Parts made of various ceramic sintered bodies having excellent corrosion resistance and heat resistance are used in semiconductor manufacturing equipment. For example, since high precision is required for a stage that is one of the members for semiconductor manufacturing equipment, silicon nitride (Si ₃ N ₄ ) having high rigidity and low thermal expansion is used. Accordingly, silicon nitride is similarly used for electrostatic chucks and length measuring mirrors in order to match the thermal expansion coefficient of silicon nitride (see, for example, Patent Document 1).

However, the silicon nitride sintered body is hard and has a problem that it is difficult to polish. As a method of solving this problem, a method of selecting another material that can be easily processed can be considered. However, in this case, since the thermal expansion coefficient is different from that of silicon nitride, the characteristics and accuracy of the member for semiconductor manufacturing equipment are reduced. Problem arises. In addition, since it is desired that the diameter of voids appearing on the surface of electrostatic chucks and length measuring mirrors is small, it is necessary to increase the polishing processability by increasing the porosity of the silicon nitride sintered body. However, it is necessary to improve the polishing processability while maintaining the denseness of the structure.
Japanese Patent Laid-Open No. 7-135246

The present invention has been made in view of such circumstances, has a thermal expansion coefficient equivalent to that of silicon nitride, the maximum void diameter is smaller in dense, sialon sintered body workability was higher than silicon nitride It aims at providing the manufacturing method of the member for semiconductor manufacturing apparatuses which becomes .

  As a result of intensive studies on the above problems, the inventors have made β-sialon of silicon nitride, thereby maintaining a thermal expansion coefficient equal to that of silicon nitride, and can be sufficiently used as a member for a semiconductor manufacturing apparatus. The inventors have invented a material having a microstructure and mechanical properties and having good processability.

That is, according to the present invention, beta-sialon consisting of sintered body A method of manufacturing a member for a semiconductor manufacturing apparatus, and ground to a specific surface area of the silicon nitride powder as a starting material is 14m 2 / ^g or more The aluminum oxide powder is added to and mixed with the pulverized silicon nitride powder so that the Z value in the chemical formula Si _6-Z Al _Z O _Z N _8-Z is 2 or more and 3 or less. And is fired at 1600 to 1800 ° C., the relative density is 90% or more, the maximum void diameter is 30 μm or less, the Young's modulus is 250 GPa or more, and the thermal expansion coefficient at room temperature is 1. 4 ×, characterized in that to obtain a ^{10 -6} /℃±0.30×10 ^-6 / member for a semiconductor manufacturing apparatus comprising a certain β- sialon sintered body at ° C., a manufacturing method of a semiconductor manufacturing apparatus for member There is provided.

According to the present invention , the maximum void diameter is small, the Young's modulus is high, the thermal expansion coefficient is the same as that of silicon nitride, and the semiconductor manufacturing apparatus is composed of a β-sialon sintered body excellent in machinability. A member is obtained. For this reason, a high-quality member for a semiconductor manufacturing apparatus can be manufactured at a low processing cost.

The member for a semiconductor manufacturing apparatus according to the present invention comprises a β-sialon sintered body. As is well known, the β-sialon sintered body is a material in which alumina is dissolved in silicon nitride, and its compositional formula is generally represented by Si _6-Z Al _Z O _Z N _8-Z . . Here, the value of Z shown in this composition formula (hereinafter simply referred to as “Z value”) indicates the solid solution amount of alumina. In general, the Z value in the β-sialon sintered body is in the range of 0 <Z <4.2. However, in the sialon sintered body used in the member for a semiconductor manufacturing apparatus of the present invention, the Z value is set to 2.0 ≦ It is preferable to be in the range of Z ≦ 3.0. This is because if the Z value is less than 2.0, the workability deteriorates, whereas if the Z value exceeds 3.0, the Young's modulus is greatly reduced.

The member for a semiconductor manufacturing apparatus according to the present invention has a relative density of 90% or more, a maximum void diameter of 30 μm or less, a Young's modulus of 250 GPa or more, and a thermal expansion coefficient at room temperature of 1.4 × 10 ^−6. / ° C. ± 0.30 × 10 ⁻⁶ / ° C., and a β-sialon sintered body having a predetermined machining speed that is 1.5 times or more that of a predetermined dense silicon nitride sintered body.

If the relative density is smaller than 90% and the maximum void diameter is larger than 30 μm, it becomes a non-dense porous sintered body, which is necessary as a member for semiconductor manufacturing equipment, particularly as an electrostatic chuck or a mirror for length measurement. This is because flatness, surface roughness, and reflectance cannot be obtained. In addition, in the porous sintered body, it is very difficult to suppress particles. Furthermore, when the Young's modulus is less than 250 GPa, it becomes impossible to ensure the mechanical strength characteristics for use as a member for a semiconductor manufacturing apparatus.

Further, nitride used in the thermal expansion coefficient is outside the range of ^{1.4 × 10 -6 /℃±0.30×10 -6 / ℃} , which is one of semiconductor manufacturing equipment member stage at room temperature Since a large difference in expansion from silicon (Si ₃ N ₄ ) occurs, problems such as failure to obtain high accuracy arise. For example, when aluminum oxide having a thermal expansion coefficient of 8.00 × 10 ⁻⁶ / ° C. is used as a length measuring bar mirror together with silicon nitride having a thermal expansion coefficient of 1.40 × 10 ⁻⁶ / ° C. as a stage material. When the temperature is changed by 1 ° C. with both members of 500 mm, the deviation of 700 nm is caused on the end face of the stage using silicon nitride, whereas the deviation of 4 μm is caused on the end face of the bar mirror for length measurement using aluminum oxide. As a result, the length measuring bar mirror is distorted and accurate measurement cannot be performed, or there are problems such as destruction. Furthermore, when the predetermined machining speed is less than 1.5 times the predetermined dense silicon nitride sintered body, the processing cost is increased.

  In general, in the production of a β-sialon sintered body, a sintering aid is used to promote densification during sintering. The β-sialon sintered body constituting the member for a semiconductor manufacturing apparatus according to the present invention preferably contains a rare earth element as a sintering aid component. Specific examples of the rare earth element include lanthanum (La), cerium (Ce), yttrium (Y), yttrium (Yb), erbium (Er), and neodymium (Nd). However, the present invention is not limited to these, and gadolinium (Gd), dysprosium (Dy), samarium (Sm), and europium (Eu) can also be used. Moreover, components other than rare earth elements, for example, magnesium (Mg), aluminum (Al), and the like may be further included.

  In such a sintering aid, the proportion of the sintering aid in the total amount of silicon nitride powder, alumina powder and sintering aid powder (that is, 100 parts by weight) is 0.1 parts by weight or more and 5 parts by weight. It is preferable to be as follows. This is because if the amount of the sintering aid is less than 0.1 parts by weight, densification of the sintered body is difficult to proceed, while if it exceeds 5 parts by weight, the workability described later decreases.

  In addition, the coefficient of thermal expansion of the β-sialon sintered body is not changed by converting the silicon nitride into β-sialon and changing the Z value, and changing the type and amount of the sintering aid. It depends on. As described above, since it is preferable to use a predetermined amount of sintering aid for the production of the β-sialon sintered body, the semiconductor manufacturing apparatus member is made of the silicon nitride sintered body and the β-sialon sintered body. When configured (for example, when a β-sialon measuring mirror is attached to a silicon nitride stage), it is necessary to make the thermal expansion coefficients of the silicon nitride sintered body and the β-sialon sintered body as close as possible. is there. As described above, the addition amount of the sintering aid is 0.1 parts by weight or more and 5 parts by weight or less of the total amount of the silicon nitride powder, the alumina powder, and the sintering aid powder. It also has the effect of bringing the thermal expansion coefficient closer to that of the silicon nitride sintered body.

The manufacturing method of the member for semiconductor manufacturing apparatuses which consists of a beta-sialon sintered compact concerning the present invention is as follows. The silicon nitride powder, the aluminum oxide powder, and the sintering aid component as starting materials are uniformly mixed and pulverized so that the specific surface area (BET value) is 14 m ² / g or more. A powder having a BET value of less than 14 m ² / g generally has a large particle diameter, so that the diameter of voids formed in the β-sialon sintered body tends to be large.

Note that the raw material powder may be pulverized by either a wet method or a dry method. If the specific surface area of the silicon nitride powder as the main component is large and the specific surface area (BET value) in the state where the aluminum oxide powder and the sintering aid powder are combined is 14 m ² / g or more from the beginning, pulverization treatment It is also possible to perform only the mixing process without performing the process. However, in this case, when the BET values of the aluminum oxide powder and the sintering aid powder are extremely small compared to the silicon nitride powder, the aluminum oxide powder and the sintered powder are used from the viewpoint of enhancing the uniformity of the structure. It is preferable to pulverize the auxiliary powder in advance or to mix and pulverize all raw material powders.

  A predetermined amount of binder may be added to the adjusted mixed powder in order to improve moldability. The powder thus obtained is press-molded at a predetermined pressure and fired at 1600 ° C. to 1800 ° C. for a predetermined time in a nitrogen atmosphere. When a binder is added to the powder, the degreasing process is performed at a predetermined temperature before or during the baking process. The press molding of the mixed powder is preferably performed by cold isostatic pressing (CIP) after temporary molding by uniaxial pressing.

  The β-sialon sintered body manufactured in this way is subjected to machining such as cutting and polishing necessary for use as a member for a semiconductor manufacturing apparatus. The β-sialon sintered body produced as described above is excellent in machinability despite having a high Young's modulus. Specifically, in the β-sialon sintered body constituting the member for a semiconductor manufacturing apparatus according to the present invention, the processing speed (that is, the polishing rate) in a general polishing process (lapping process) is a fine density described below. It is 1.5 times or more of the case of the quality silicon nitride sintered body.

Here, a manufacturing method and characteristics of a dense silicon nitride sintered body (hereinafter referred to as a “reference sample”) which serves as a reference for obtaining a polishing rate will be described. Reference sample is first silicon nitride powder (particle size:: 0.2 [mu] m, 90% purity) 90 parts by weight, yttrium oxide 8 parts by weight as a sintering aid _(Y 2 _{O 3)} powder (average particle size : 0.3 μm, purity: 99.9%) and 2 parts by weight of spinel (MgAl ₂ O ₄ ) powder (average particle size: 0.3 μm, purity: 99.9%) were added, Ethanol is added and ball milled using silicon nitride balls. The mixed powder obtained by removing and drying ethanol after such a mixing and pulverizing treatment is press-molded into a prismatic shape of 50 mm × 50 mm × 10 mm at 300 kgf / cm ² (= 29.4 MPa), and this press-molded product is further subjected to 1500 kgf / Cold isostatic pressing at cm ² (= 147.1 MPa). The formed body is heated to 1700 ° C. in a nitrogen atmosphere at a rate of temperature increase of 10 ° C./min and fired for 6 hours. A 10 mm × 10 mm × 5 mm sample piece is cut out from the sintered body thus obtained, and this is used as a reference sample.

The silicon nitride sintered body thus fabricated had a Young's modulus of 315 GPa, a maximum void diameter of 10 μm, and a relative density by Archimedes method of 99% as shown in Comparative Example 1 in Table 1 below. The bulk density is 3.33 × 10 ³ kg / m ³ . Further, this silicon nitride sintered body has an average particle diameter of 1.0 μm, a Vickers hardness of 17.9 GPa, a fracture toughness value of 8.7 MPam ^1/2 , a four-point bending strength of 1100 MPa, and a thermal expansion coefficient by SEM observation. It has a characteristic of 1.4 × 10 ⁻⁶ / ° C.

The polishing process for the reference sample is performed as follows. On the back surface of the plate having a diameter of 100 mmφ, three 10 mm × 10 mm × 5 mm reference samples are fixed with a surface of 10 mm × 10 mm so as to be positioned at the apex of a substantially equilateral triangle. Next, a load of 1 kg / cm ² (= 0.098 MPa) is applied to the plate, and the reference sample is pressed against a lapping machine having a diameter of 200 mmφ made of copper and a casting material. The plate is positioned such that its center is located at a position half the radius of the center of the lapping machine. Then, the lapping machine is rotated at a speed of 30 rpm while spraying a predetermined amount of diamond slurry having a particle diameter of 9 μm on the lapping machine at a predetermined time interval. The plate to which the reference sample is attached is held in a state where it can be freely rotated by friction acting between the reference sample and the lapping machine when the lapping machine is rotated.

  The polishing rate is obtained from the thickness t (μm / min) of the sample polished in a predetermined time by such a polishing process. Polishing treatment of the β-sialon sintered body constituting the member for a semiconductor manufacturing apparatus according to the present invention is similarly performed, and the polishing rate is required.

  The polishing rate by such a polishing treatment of the β-sialon sintered body constituting the member for a semiconductor manufacturing apparatus according to the present invention is 1.5 times or more the polishing rate of the reference sample. As for the reference sample, a diamond wheel is used for the cutting process and the grinding process. However, there is no great difference in the processing time at this time, and therefore the processing cost is also equivalent. However, in such a process for producing a surface having a desired surface roughness by the polishing process, the processing time varies greatly depending on the characteristics of the sintered body, and the processing cost and productivity vary greatly. Since the β-sialon sintered body constituting the member for a semiconductor manufacturing apparatus according to the present invention has a high polishing rate, the productivity is good and the processing cost is kept low.

  Examples of the member for a semiconductor manufacturing apparatus made of the β-sialon sintered body according to the present invention having the above-described characteristics include an electrostatic chuck and various rings. In particular, the relative density is high and the maximum Taking advantage of the fact that the void diameter is small, the thermal expansion coefficient is the same as that of silicon nitride, and the processability of the polishing process for mirror finishing is good, it is preferably used as a length measuring mirror.

(Production method of Comparative Example 1)
Since Comparative Example 1 is a dense silicon nitride sintered body and the manufacturing method thereof is as described above, detailed description thereof is omitted here.

(Production method of β-sialon sintered body (excluding Comparative Example 1))
By weighing silicon nitride powder, alumina powder, oxide powder of the sintering aid component so as to have the composition shown in Table 1, mixing this with ethanol, and performing a ball mill treatment using silicon nitride balls, A homogeneous raw material powder having a BET value shown in Table 1 was produced. Next, the mixed powder obtained by removing and drying ethanol after such a mixing and pulverizing treatment is press-molded into a prismatic shape of 50 mm × 50 mm × 10 mm at 100 kgf / cm ² (= 9.81 MPa), and further this press-molded body the 1200kgf ^/ cm 2 (= 117.68MPa) in 1 min, and cold isostatic process. In addition, the shaping | molding conditions of such raw material powder are common to an Example and a comparative example (except for the comparative example 1).

  The molded body thus produced was heated to each temperature shown in Table 1 at a heating rate of 10 ° C./min in a nitrogen atmosphere, and fired at that temperature for 3 hours. A 10 mm × 10 mm × 5 mm sample piece was cut out from the obtained sintered body and used as a sample for determining the polishing rate.

(Sintered body evaluation method)
In addition, the bulk density and relative density of the produced sintered body are determined by Archimedes method, Young's modulus is determined by resonance method, the maximum void diameter is observed by SEM, and the thermal expansion coefficient is determined by a laser interferometer of low thermal expansion glass (JIS R3251). It was determined by a method for measuring the linear expansion coefficient. The measurement of the polishing rate is as described above.

(Evaluation results)
As shown in Table 1, the thermal expansion coefficient at room temperature of each embodiment according to Example β- sialon sintered body within the range of 1.4 × 10 ^-6 /℃±0.25×10 ^-6 / ℃ and which is in the range of 1.4 × 10 ^-6 /℃±0.30×10 ^-6 / ℃ thermal expansion coefficient at room temperature in relation to the standard silicon nitride sintered body. As described above, in each example, preferable characteristics are obtained when the semiconductor manufacturing apparatus member is configured together with the silicon nitride sintered body. Thermal expansion coefficient at room temperature of Comparative Examples 2 and 3 contrast has become outside the range of ^{1.4 × 10 -6 /℃±0.30×10 -6 / ℃} .

  In addition, as shown in Table 1, the Young's modulus of Comparative Example 1 which is a reference sample is 315 GPa, but the Young's modulus of 250 GPa or more is also secured in Examples 1 to 10 according to the present invention, and semiconductor manufacturing It was confirmed that sufficient characteristics were secured as a device member. In the examples, the relative density is 90% or more, and the maximum void diameter is 30 μm or less. Further, the polishing rate of the example is 160 μm / hr or more, which is 1.5 times or more compared with the polishing rate of 100 μm / hr of Comparative Example 1 as a reference sample. From these things, in each Example, it was confirmed that the outstanding workability was obtained and it was easy to obtain a smooth surface (mirror surface) by polishing.

  On the other hand, in Comparative Examples other than Comparative Example 2 and Comparative Example 3, although the standard of the thermal expansion coefficient at room temperature is satisfied, the maximum void diameter is large or the relative density is low when the polishing rate is high, Or, there is a problem from the viewpoint of mechanical properties when used as a member for a semiconductor manufacturing apparatus such as a low Young's modulus. On the other hand, a material with a low polishing rate can be used as a member for a semiconductor manufacturing apparatus, but there is a problem that the product cost increases.

  The member for a semiconductor manufacturing apparatus of the present invention is suitable for an electrostatic chuck produced by polishing the surface thereof flatly or a length measuring mirror produced by mirror polishing the surface.

Claims (1)

  A method for manufacturing a member for a semiconductor manufacturing apparatus comprising a β-sialon sintered body, wherein silicon nitride powder as a starting material has a specific surface area of 14 m ² / G and crushed silicon nitride powder with chemical formula Si _6-Z Al _Z O _Z N _8-Z The aluminum oxide powder was added and mixed so that the Z value at 2 or more and 3 or less was formed, and the obtained mixed powder was molded at a predetermined pressure and fired at 1600 to 1800 ° C., so that the relative density was 90% or more. The maximum void diameter is 30 μm or less, the Young's modulus is 250 GPa or more, and the thermal expansion coefficient at room temperature is 1.4 × 10 ^-6 /℃±0.30×10 ^-6 A method for producing a member for semiconductor production equipment, comprising obtaining a member for semiconductor production equipment comprising a β-sialon sintered body at / ° C.