JP4132685B2 - Quartz glass and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to quartz glass that is used in semiconductor manufacturing and has excellent plasma corrosion resistance, and a method for manufacturing the same.
[0002]
[Related technologies]
In the manufacture of semiconductors, for example, the manufacture of semiconductor wafers, the processing efficiency is improved by using a plasma reactor in an etching process or the like as the diameter increases in recent years. For example, in a semiconductor wafer etching process, an etching process using a plasma gas, for example, a fluorine (F) plasma gas is performed.
[0003]
However, when conventional quartz glass is placed in, for example, an F-based plasma gas atmosphere, SiO ₂ and F-based plasma gas react on the quartz glass surface to produce SiF ₄ , which has a boiling point of −86 ° C. Therefore, it sublimated easily, and quartz glass was corroded in large quantities, resulting in thinning and surface roughness, and was not suitable for use as a jig in an F-based plasma gas atmosphere.
[0004]
As described above, the conventional quartz glass has a large problem in the corrosion resistance, that is, the plasma corrosion resistance, with respect to the plasma reaction in the semiconductor manufacturing, particularly the etching process using the F-based plasma gas. Therefore, a proposal for improving the plasma corrosion resistance by coating the surface of a quartz glass member with aluminum or an aluminum compound (JP-A-9-95777, JP-A-9-95777, JP-A-10-139480) or quartz glass There has been proposed a plasma corrosion-resistant glass whose plasma corrosion resistance is improved by incorporating aluminum (Japanese Patent Laid-Open No. 11-228172).
[0005]
[Problems to be solved by the invention]
The present inventor has been carrying out various studies to further improve the plasma corrosion resistance of quartz glass. As part of this, quartz glass powder in which 5 wt% of alumina powder is mixed with quartz glass is heated and melted under vacuum to produce quartz glass. The plasma corrosion resistance was investigated. Then, the etching rate was reduced by 40% to 50% as compared with the quartz glass member which was not doped at all.
[0006]
However, microbubbles are confirmed inside and on the surface of the glass body, and in particular, the difference between the corroded part and the non-corroded part is increased in the surface part, and the surface roughness increases. Peeling frequently occurred from the portion, and the generation of fine particles and the generation of particles increased and adhered to the wafer surface, resulting in increased wafer defects. In addition, since these bubbles and dents promote etching, even when the concentration of the doped metal is increased, the etching corrosion resistance is not relatively improved.
[0007]
Because in F-based boiling point 1290 ° C. of AlF ₃ that reacts with the plasma gas, since it is much hotter than the SiF _4, while the SiF ₄ portion is a large amount of corrosion, AlF ₃ portion surface This is presumed to be due to the fact that the difference in etching amount has increased due to less sublimation. In addition, when the doped aluminum is locally concentrated, the energy state is clearly different from the adjacent SiO ₂ part, so the balance is lost and the SiO ₂ is more easily transformed into a low energy crystalline state than there. .
[0008]
This crystal portion is visually confirmed as a fine white foreign substance. Since the formed crystal part has a thermal expansion degree different from that of quartz glass, it easily peels off due to a temperature change. Furthermore, locally concentrated metal element, in itself, since the boiling point is lower than SiO _2, at the time of melting heat of the SiO ₂ to form the foam is a gas. The bubble portion in the vicinity of the surface is easily ruptured by temperature change. All of the above-mentioned causes of particle generation. Further, since the bubbles and the concave portions are likely to increase the etching rate due to the concentration of the plasma gas, the etching amount of the entire glass also increases, and the usable time decreases.
[0009]
The present invention has been made on the basis of the above knowledge, and provides a quartz glass excellent in plasma corrosion resistance, particularly corrosion resistance against F-based plasma gas, and a method for producing the same as a jig material for plasma reaction used in semiconductor manufacturing. For the purpose.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the first aspect of the quartz glass of the present invention is produced by mixing a silica glass powder and a solution in which a predetermined metal element is dissolved to prepare a slurry, and drying and then sintering. The quartz glass powder has a particle size distribution of 0.01 to 1000 μm, a mass ratio of particles of 5 μm or less is 1 wt% to 100 wt%, contains a metal element, and has increased plasma corrosion resistance. The metal element has a higher boiling point when it becomes a fluoride than Si, no granular structure is confirmed inside, the concentration of the metal element is 0.1 to 20 wt%, and the quartz glass body When the content of bubbles and foreign matters in the disk is 350 mmφ × 20 mm (thickness) , the metal element has a projected area per 100 cm ^{3 of} less than 100 mm ² and an internal transmittance of visible light of 50% / cm or more . But Al Al and Y, Al and Nd, Al and Sm, Al and Eu, Al and Yb, Al and Pm, Al and Pr, Al and Ce, Al and Tb, Al and Gd, Al and Tm, Al and Dy, Al and It is Ho or Al and Er, and the quartz glass body has an OH concentration of 100 ppm or less . According to a second aspect of the quartz glass of the present invention, quartz glass powder and a metal compound powder containing a predetermined metal element are mixed, the mixed powder is heated, melted and dropped, and manufactured by the Bernoulli method. It is an oxide, the particle size distribution of the metal oxide is in the range of 0.01 to 50 μm, and the particle size of the quartz glass powder is in the range of 0.01 to 500 μm. An increased quartz glass body, which has a higher boiling point when the metal element becomes a fluoride than Si, a granular structure is not confirmed inside, and the concentration of the metal element is 0.1 to When the disk and the content of bubbles and foreign matter in the quartz glass body are 350 mmφ × 20 mm (thickness), the projected area per 100 cm ^{3 is} less than 100 mm ² and the internal transmittance of visible light is 50%. / cm or more, the gold Elements are Al, Al and Y, Al and Nd, Al and Sm, Al and Eu, Al and Yb, Al and Pm, Al and Pr, Al and Ce, Al and Tb, Al and Gd, Al and Tm, Al And Dy, Al and Ho, or Al and Er, and the OH concentration of the quartz glass body is 100 ppm or less .
The quartz glass body preferably has an OH concentration of 100 ppm or less.
[0011]
Examples of the metal element include Sm, Eu, Yb, Pm, Pr, Nd, Ce, Tb, Gd, Ba, Mg, Y, Tm, Dy, Ho, Er, Cd, Co, Cr, Cs, Zr, Al, In, Cu, Fe, Bi, Ru can be used alone or in combination selected from the group consisting of Ga and Ti.
[0012]
These metal elements have a higher boiling point when they are fluoride than Si, and etching does not proceed. The metal elements are described in the order of the boiling point or the sublimation temperature. For example, the boiling point of SmF is 2427 ° C., and the sublimation temperature of TiF is 284 ° C.
[0013]
Etching proceeds because the boiling point or sublimation temperature of fluorides of metal elements other than these is too low. The content concentration of the metal element is preferably in the range of 0.1 to 20 wt%. If it is less than 0.1 wt%, there is no improvement in etching resistance, and if it exceeds 20 wt%, bubbles and foreign matters frequently occur under any conditions, and it cannot be used as a jig.
[0014]
A first aspect of the method for producing quartz glass according to the present invention is a method for producing the quartz glass according to the first aspect of the present invention described above, in which quartz glass powder and a solution in which a predetermined metal element is dissolved are mixed. In the method for producing a transparent quartz glass body by making a slurry, drying and sintering, the particle size distribution of the quartz glass powder is in the range of 0.01 to 1000 μm, and the mass ratio of the particle group of 5 μm or less is a 1 wt% 100 wt%, the metal element is characterized in der Rukoto having a high boiling point when it becomes fluoride in comparison with Si.
[0015]
A second aspect of the method for producing quartz glass according to the present invention is a method for producing the quartz glass according to the second aspect of the present invention described above, in which quartz glass powder and a metal compound powder containing a predetermined metal element are mixed. In the manufacturing method in which the mixed powder is heated and melted and dropped to prepare a transparent quartz glass body by the Bernoulli method, the metal compound is an oxide, and the particle size distribution of the metal oxide is 0.01 to 50 μm. in the range, and in the range granularity of silica glass powder is 0.01～500Myuemu, and characterized der Rukoto having a high boiling point when the metal element becomes fluoride as compared with Si To do.
[0016]
The heating method in the Bernoulli method is preferably an electric melting method, and an arc flame method or the like is known as the electric melting method. As the quartz glass powder, synthetic quartz glass powder or amorphous quartz glass powder can be used.
[0017]
As one of these metal element doping methods, a method is known in which a metal compound containing a predetermined metal element and quartz glass powder are dissolved in pure water to prepare a slurry, dried, and then heated and melted. . A strong granular structure is observed inside the transparent quartz glass body produced by this method. This granular structure is caused by the concentration variation of the contained metal element. The contained metal element exists around the quartz glass powder and is fixed after melting.
[0018]
For this reason, the distribution of the fixed metal element is affected by the particle size of the quartz glass powder. When the particle size is large, a large distribution variation occurs, and the refractive index varies, and is observed as a granular structure. When the quartz glass body comes into contact with the plasma etching gas and is etched, the grain structure, that is, the variation portion of the metal concentration, is not uniformly etched, resulting in increased surface roughness and causing generation of particles. For this reason, it is preferable that the particle size of the quartz powder is finer, and the weight ratio of the quartz glass powder having a particle size of 5 μm or less is 1 wt% to 100 wt%, and the higher the better, but if it is less than 1 wt%, there is no effect.
[0019]
When the Bernoulli method is employed and an oxide is used as the metal compound, the particle size of the oxide is well dispersed when it is 0.01 to 50 μm, and the particle size of the quartz glass powder is also within the range of 0.01 to 500 μm. The concentration variation of the metal element is reduced. More preferably, the metal oxide particle diameter is 0.01 to 5 μm, and the quartz powder particle diameter is 0.01 to 200 μm.
[0020]
The OH concentration in the quartz glass body is also a cause of increasing the granular structure, but in the case of the Bernoulli method, the OH concentration can be lowered by using an electric melting method as a heating method. When the OH concentration is 100 ppm or less, the effect of reducing the granular structure is remarkable.
[0021]
The content of bubbles and foreign substances in the quartz glass body produced by the method of the present invention is less than 100 mm ^{2 in} a projected area per 100 cm ^{3 and} the internal transmittance of visible light is 50% / cm or more.
[0022]
Moreover, as the quartz glass powder used in the present invention, synthetic quartz glass powder or amorphous quartz glass powder is preferably used. These quartz glass powders are preferred because they have a low softening point and thus increase the fluidity during melting and facilitate the uniform dispersion of metal elements.
[0023]
After heating and melting, the obtained transparent quartz glass body is subjected to processing such as grinding, fire polishing, or dipping in a frost solution so that the surface roughness is in the range of 0.01 to 10 μm. According to these processing methods, since micro cracks and the like on the surface after processing are removed, the generation of initial particles in the plasma etching process can be suppressed.
[0024]
Further, the quartz glass body produced by applying the high temperature of 1000 ° C. or higher by the above method has previously released the occluded gas, and at 1000 ° C. or lower, only 2 mol / m ³ or lower gas is released. Since the etching process is a process in the temperature range of several hundred degrees Celsius, the actual gas release amount is smaller than this, and the phenomenon that the released gas touches the wafer or affects the plasma gas state is suppressed.
[0025]
【Example】
Examples of the present invention will be described below, but it is needless to say that these examples are illustrative and should not be construed in a limited manner.
[0026]
(Example 1)
A slurry is prepared by mixing 6750 g of quartz particles having a particle diameter of 100 to 500 μm, 1800 g of pyrolytic silica particles having a particle diameter of 0.01 to 4 μm, 6300 g of aluminum nitrate, and 13500 g of pure water. The slurry was dried in an atmosphere of 40 ° C. for 8 days, further held at 500 ° C. to obtain a solid, and then subjected to heat treatment at 1800 ° C. and 1 HR in a vacuum atmosphere to obtain a transparent quartz glass body of 380 mmφ × 25 mm. It was.
[0027]
A disc of 350 mmφ × 20 mm (thickness) was cut out from the obtained quartz glass body, and the upper and lower surfaces were ground. The Ra value on the surface was 3.0 μm, and the OH concentration of the disk was 300 ppm. When observed with an optical microscope, no granular structure was observed in the disk. The quartz glass body had a foam and foreign matter content of 20 mm ² in a projected area per 100 cm ^{3 and} an internal transmittance of visible light of 80% / cm.
[0028]
Further, when the qualitative and quantitative determination of the released gas was performed in the temperature range from room temperature to 1000 ° C. with a sample cut out from the same quartz glass molded body, the total amount of CO, H ₂ O, O ₂ , and H ₂ gases was 0. 4 mol / m ^{3 was} generated. When the Al concentration of a sample cut out from the same quartz glass body was measured by fluorescent X-ray analysis, it was 3.0 wt%.
[0029]
Similarly, a sample obtained by cutting 30 mmφ × 3 mm from the same quartz glass body and grinding the surface roughness to Ra 3.0 μm in a plasma gas of 50 sccm, CF ₄ + O ₂ (20%), 30 mtorr, 1 kW, 10 HR. An etching test was performed. The etching rate was calculated from the mass change before and after the test, and a result of 30 nm / min was obtained.
[0030]
Regarding the amount of generated particles, after etching, a Si wafer of the same area is placed on the plasma irradiation surface of the sample, the unevenness of the contact surface of the wafer is detected by laser scattering, and the number of particles of 0.3 μm or more is measured with a particle counter. did. The number of particles was 10.
[0031]
(Example 2)
When a quartz ingot is prepared by mixing 28500 g of quartz particles having a particle size of 0.1 to 100 μm and 1500 g of Al ₂ O ₃ powder having a particle size of 0.01 to 1 μm, and heating and dropping the mixed powder, A 200 mmφ × 400 mm quartz ingot was prepared by melting and dropping onto a target ingot rotating at 1 rpm in an arc flame by an electric melting method at a speed of 50 g / min.
[0032]
The prepared ingot was set in a heat treatment furnace, held at 1800 ° C. for 1 HR under a pressure of 1 kg in an N ₂ atmosphere, and formed into 400 mmφ × 100 mm. The obtained quartz glass molded body was processed into a 350 mmφ × 20 mm (thickness) disk, and the upper and lower surfaces were ground. The Ra value on the surface was 3.0 μm, and the OH concentration of the disk was 30 ppm. When observed with an optical microscope, no granular structure was observed in the disk. The other evaluation results were the same as in Example 1.
[0033]
(Comparative Example 1)
A slurry was prepared by mixing 6000 g of quartz particles having a particle size of 100 to 500 μm, 40 g of pyrolyzed silica particles having a particle size of 0.01 to 4 μm, 4200 g of aluminum nitrate, and 4500 g of pure water. This slurry was dried in the atmosphere of 40 ° C. for 8 days, and further kept at 500 ° C. to obtain a solid, followed by heat treatment at 1800 ° C. and 1 HR in a vacuum atmosphere to obtain a transparent glass body of 380 mmφ × 25 mm. .
[0034]
A disc of 350 mmφ × 20 mm (thickness) was cut out from the obtained glass body, and the upper and lower surfaces were ground. The Ra value on the surface was 3.0 μm, and the OH concentration of the disk was 300 ppm. When observed with an optical microscope, a granular structure was strongly observed in the disk.
[0035]
When the Al concentration was measured by fluorescent X-ray analysis, it was 3.0 wt%. The etching rate was calculated from the mass change before and after the etching test, and a result of 80 nm / min was obtained. The number of particles was 300. The other evaluation results were the same as in Example 1.
[0036]
(Comparative Example 2)
28500 g of quartz particles having a particle size of 600 to 1000 μm and 1500 g of Al ₂ O ₃ powder having a particle size of 60 to 100 μm are mixed, melted and dropped onto a target ingot rotating at 1 rpm at a speed of 50 g / min in an oxyhydrogen flame, A 200 mmφ × 400 mm quartz ingot was prepared.
[0037]
The gas conditions used were H ₂ of 300 liters / min and O ₂ of 100 liters / min. The prepared ingot was set in a heat treatment furnace, held at 1800 ° C. for 1 HR under a pressure of 1 kg in an N ₂ atmosphere, and molded into 400 mmφ × 100 mm.
[0038]
The obtained glass molded body was processed into a disk shape of 350 mmφ × 20 mm (thickness), and the upper and lower surfaces were ground. The Ra value on the surface was 3.0 μm, and the OH concentration of the disk was 300 ppm. When observed with an optical microscope, a granular structure was strongly observed in the disk.
[0039]
The etching rate was calculated from the mass change before and after the etching test, and a result of 80 nm / min was obtained. The number of particles was 300. The other evaluation results were the same as in Example 1.
[0040]
In each of the above Examples and Comparative Examples, when the amount of generated particles is 50 or less, the usable portion of the Si wafer is 90% or more, and when it exceeds 200, the yield is reduced to 50% or less. . When the etching rate is 100 nm / min or more, the etching depth reaches 0.6 mm in about 100 HR usage time and cannot be used as a member. However, when the etching rate is 50 nm / min or less, the usage time is doubled and the effect is increased. It was confirmed that the economic effect became very large especially at 20 nm / min or less.
[0041]
【The invention's effect】
As described above, the quartz glass of the present invention has an effect of being excellent in plasma corrosion resistance, particularly corrosion resistance against F-based plasma gas, as a plasma reaction jig material used in semiconductor manufacturing. Further, the method of the present invention has an advantage that quartz glass excellent in plasma corrosion resistance can be efficiently produced.

Claims (6)

A silica glass powder and a solution in which a predetermined metal element is dissolved are mixed to prepare a slurry, dried and then sintered, and the particle size distribution of the quartz glass powder is within a range of 0.01 to 1000 μm, and 5 μm. The mass ratio of the following particle group is 1 wt% to 100 wt%, and is a quartz glass containing a metal element and having increased plasma corrosion resistance, and has a higher boiling point when the metal element becomes a fluoride than Si. In the disk , the granular structure is not confirmed inside, the concentration of the metal element is 0.1 to 20 wt%, and the content of bubbles and foreign matters in the quartz glass body is 350 mmφ × 20 mm (thickness). When the projected area per 100 cm ^{3 is} less than 100 mm ² and the internal transmittance of visible light is 50% / cm or more , the metal elements are Al, Al and Y, Al and Nd, Al and Sm, Al and Eu, Al and Yb, l and Pm, is Al and Pr, Al and Ce, Al and Tb, Al and Gd, Al and Tm, Al and Dy, Al and Ho, or Al and Er, the following OH concentration of the quartz glass body is 100ppm Quartz glass characterized in that there is. A quartz glass powder and a metal compound powder containing a predetermined metal element are mixed, and the mixed powder is heated, melted and dropped, and manufactured by the Bernoulli method. The metal compound is an oxide, and the particle size distribution of the metal oxide is A quartz glass body having a plasma corrosion resistance within a range of 0.01 to 50 μm and a particle size of the quartz glass powder within a range of 0.01 to 500 μm and containing a metal element, wherein the metal element Has a higher boiling point when it becomes a fluoride than Si, a granular structure is not confirmed inside, the concentration of the metal element is 0.1 to 20 wt%, bubbles and foreign matter in the quartz glass body When the disk has a 350 mmφ × 20 mm (thickness) disk, the projected area per 100 cm ^{3 is} less than 100 mm ² , the visible light internal transmittance is 50% / cm or more , and the metal elements are Al, Al And Y, Al and N Al and Sm, Al and Eu, Al and Yb, Al and Pm, Al and Pr, Al and Ce, Al and Tb, Al and Gd, Al and Tm, Al and Dy, Al and Ho, or Al and Er A quartz glass, wherein the quartz glass body has an OH concentration of 100 ppm or less .   A method for producing a quartz glass according to claim 1, wherein a quartz glass powder and a solution in which a predetermined metal element is dissolved are mixed to form a slurry, dried and then sintered to produce a transparent quartz glass body. In the method, the particle size distribution of the quartz glass powder is in the range of 0.01 to 1000 μm, the mass ratio of the particle group of 5 μm or less is 1 wt% to 100 wt%, and the metal element is fluoride compared to Si. A method for producing quartz glass, which has a high boiling point.   A method for producing quartz glass according to claim 2, wherein the quartz glass powder and a metal compound powder containing a predetermined metal element are mixed, the mixed powder is heated, melted and dropped, and a transparent quartz glass body is formed by Bernoulli method. In the production method to be created, the metal compound is an oxide, the particle size distribution of the metal oxide is in the range of 0.01 to 50 μm, and the particle size of the quartz glass powder is in the range of 0.01 to 500 μm. A method for producing quartz glass, characterized in that the metal element has a higher boiling point when it becomes a fluoride than Si. In the Bernoulli method, the quartz glass powder and the metal compound containing the metal element are mixed, and when the mixed powder is heated and melted and dropped to form a quartz ingot, the quartz ingot is subjected to an arc flame by an electric melting method. The method for producing quartz glass according to claim 4, wherein the method is melted by heating. The method for producing quartz glass according to any one of claims 3 to 5 , wherein the quartz glass powder is a synthetic quartz glass powder or an amorphous quartz glass powder.