JP2002068766A - Plasma resistant quarts glass-made fixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixture reduced in abnormal etching or generation of particles even when used in an apparatus of generating a plasma, and having excellent plasma resistance. SOLUTION: This plasma resistant quarts glass-made fixture used in the apparatus of generating the plasma has a surface roughness Ra of 5-0.05 μm of the quarts glass surface, the number of micro cracks of the surface of 500 pieces/cm2 or less, and H2 molecule concentration of 5×1016 molecules/cm3 or more in the quarts glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass jig having excellent plasma etching resistance and used in an apparatus for generating plasma.

[0002]

2. Description of the Related Art In recent years, processing using plasma has been frequently used for processing the surface of a semiconductor element such as a silicon wafer. As a processing method using this plasma, for example, while introducing a halogen-based corrosive gas such as a fluorine-based gas and a chlorine-based gas into a plasma generation chamber, the halogen-based corrosive gas contained therein by introducing a microwave through a microwave introduction window is used. To process the semiconductor element by converting it into plasma, or a method of depositing an insulating thin film or the like on the surface of the semiconductor element. In any of the processes, an apparatus for generating plasma is used. In addition, many jigs made of quartz glass, such as a window material for introducing microwaves, a bell jar as a plasma generation chamber, a ring for shielding the device, and the like, are used in the device. Conventionally, natural quartz glass has been mainly used as a material for these jigs, and the surface in contact with the plasma has been roughened by mechanical processing to stabilize the etching rate and prevent detachment of attached matter. Was. The surface roughening includes mechanical processing for shaving the surface of quartz glass, such as grinding using a grindstone such as a diamond grindstone, sand blasting using powders such as green carbon powder, silicon dioxide powder, and ceramic powder. However, in mechanical processing, the quartz glass surface was roughened and microcracks occurred at the same time, and radicals generated in the plasma attacked the microcracks, causing microcracks There was a problem in that only the etched portion was etched into an abnormal hole, and in the worst case, the quartz glass jig was broken from that portion. In recent years, it has been confirmed that, in the plasma, the gas emits ions and radicals, and also emits extraordinarily strong ultraviolet rays and electron beams, which deteriorates the surface of the quartz glass jig, and the deteriorated portion is formed. It has also been found that the particles are a source of generation and the generated particles fall down on the surface of the semiconductor element and have a secondary adverse effect.

Further, there is a problem that impurities may be taken into the microcracks formed by the mechanical processing method, and the impurities may be volatilized during the processing of the semiconductor element and contaminate the semiconductor element.

[0004]

In view of the current situation,
The present inventors have conducted extensive studies on a quartz glass jig used in a device that generates plasma, and as a result, the surface roughness Ra of the jig surface was 5 μm to 0.05 μm, and the number of microcracks on the surface was 500 pieces. / Cm ² or less, and the content of hydrogen molecules in the quartz glass is 5 × 10 ¹⁶ molecules /
By setting the cm ³ or more, it is possible to obtain a quartz glass jig that has little deterioration of the jig surface due to etching by plasma, abnormally strong ultraviolet rays or electron beams, and has no adverse effect on silicon wafers due to generation of particles and impurities. Was found. Further, the content of bubbles in the quartz glass is set to 0 or 1 in terms of a bubble class according to DIN, the amount of birefringence of the quartz glass is set to 70 nm / cm or less, and the fictive temperature of the quartz glass is set to a range of 800 to 1200 ° C. In addition, it has been found that a quartz glass jig can be obtained in which etching by plasma and deterioration due to abnormally strong ultraviolet rays and electron beams are further reduced, impurities are less taken up by the opening of bubbles, and semiconductor elements can be processed well. The present invention has been completed. That is,

[0005] The present invention provides a quartz glass jig excellent in plasma etching resistance, which is free from abnormal etching and deterioration of the quartz glass surface even when used in an apparatus for generating plasma, and which is free from contamination of a semiconductor element by a captured impurity. The purpose is to provide.

[0006]

The present invention for achieving the above object is a quartz glass jig used for an apparatus for generating plasma, wherein the quartz glass has a surface roughness Ra of 5 μm.
m to 0.05 μm, the number of microcracks on the surface is 5
The present invention relates to a plasma-resistant quartz glass jig, wherein the number is not more than 00 / cm ² and the concentration of hydrogen molecules in quartz glass is 5 × 10 ¹⁶ molecules / cm ³ or more.

The quartz glass jig of the present invention is a jig made of natural or synthetic quartz glass, and the surface of the jig made of natural or synthetic quartz glass is used for stabilizing the etching rate or preventing the adhered material from peeling off. Surface roughness Ra is 5μ
The jig is roughened to a range of m to 0.05 μm. When the surface roughness Ra exceeds 5 μm, radicals and ions generated in the plasma locally attack the concave portions on the rough surface, and the etching proceeds abnormally. In addition, Ra is 0.0
If it is less than 5 μm, a secondary product (for example, particles) generated by the plasma is likely to peel off from the surface, which may fall on the silicon wafer surface and greatly impair the characteristics of the wafer.

Further, the quartz glass jig of the present invention is a jig in which the number of microcracks on the surface is 500 / cm ² or less. If the number of microcracks on the jig surface exceeds the above range, the progress of etching is further accelerated by the attack by radicals generated in the plasma, the microcracks become large, and in the worst case, quartz glass is broken from that part. Become. The number of the micro cracks is 5
Quartz glass jigs of less than 00 pieces / cm ² are disclosed in
No. 273339 describes a method of immersing a quartz glass jig in a solution of hydrofluoric acid, ammonium fluoride and acetic acid to precipitate microcrystals of ammonium silicofluoride, or JP-A-11-106225. As described, it can be formed by a chemical treatment such as a method of forming a thin film of silicone or the like on the surface of a quartz glass jig and etching with a hydrofluoric acid aqueous solution. In the surface roughening by the chemical treatment, it is important to control the reaction between the etching chemical and the quartz glass. Particularly in the case of synthetic quartz glass, it is important to control the temperature of the chemical.
It is better to control the temperature within the range of ± 2 ° C. When the temperature is out of the temperature range, the surface roughness Ra of the quartz glass surface is 5 μm.
m to 0.05 μm. The number of microcracks on the quartz glass surface is measured by observing a micrograph.

Further, the quartz glass jig of the present invention has a hydrogen molecule concentration of 5 × 10 ¹⁶ molecules / cm ³ or more. By having this hydrogen molecule concentration, the generation of the E 'center absorption band is suppressed, the internal strain in the quartz glass network structure is removed, and the unusually strong ultraviolet and electron beams in the plasma form Si-O bonds. Cutting is reduced, the density of the quartz glass is suppressed, and generation of large microcracks and particles is reduced. The hydrogen molecule concentration can be obtained by adjusting the molecular weight of hydrogen in the flame at the time of quartz glass production, or by treating quartz glass at 100 to 900 ° C. in a hydrogen gas atmosphere under normal pressure or pressure for 1 to 100 hours, The measurement is based on the laser Raman method.

[0010] In addition to the above, the quartz glass jig of the present invention has a bubble content of 0 or 1 in bubble class according to DIN.
And the presence of air bubbles, and the birefringence is preferably as uniform as 70 nm / cm or less. When bubbles containing gas exceeding the above range are contained, the bubbles are eroded by the radicals and ions generated by the plasma and are released, and become a precursor of an abnormal hole. At the same time, particles are generated. DIN
0 or 1 in the foam rating according to DIN (Deuts
Her Industry Norm) 58927 and the total cross-sectional area of the foam present at 100 cm ³ (cm ² )
Is 0 to 0.03 when the grade is 0, and 0.03 to 0.
It means that it is 10. If the amount of birefringence of the quartz glass exceeds the above range, the density of the quartz glass is increased by abnormally strong ultraviolet rays or electron beams applied to the strained portion, and the microcracks are coarsened. In order to effectively prevent the densification of quartz glass due to abnormally strong ultraviolet rays or electron beams, the fictive temperature of quartz glass is set to 800 to 12
It is preferable to set the temperature in the range of 00 ° C. By setting the fictive temperature in the above range, the density of the quartz glass is reduced and the structure is relaxed, and defects are unlikely to be generated even by irradiation of an abnormally strong ultraviolet ray or electron beam, thereby preventing the density from being increased. Preferable examples of the quartz glass having a bubble rating according to DIN of 0 or 1 and a birefringence amount include synthetic quartz glass obtained by hydrolyzing a silicon compound in a gas phase. The setting of the fictive temperature of the quartz glass is performed by heating the quartz glass to 800 to 1200 ° C. for a predetermined time. Measurement of virtual temperature
By laser Raman method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to specific examples. However, these examples are merely illustrative, and the present invention is not limited thereto.

[0012]

EXAMPLE 1 Silicon tetrachloride was hydrolyzed in the gas phase and the hydrogen molecule concentration was 15 ×.
A synthetic quartz glass having 10 ¹⁶ molecules / cm ³ and a bubble rating of 0 in DIN was obtained. Next, a window material for a plasma device was prepared using this quartz glass, and about 50% aqueous hydrogen fluoride solution was used.
4% by mass, about 17% by mass of ammonium fluoride, 100%
Immersion in a frost treatment solution of about 35% by mass of an aqueous acetic acid solution and about 24% by mass of water to precipitate microcrystals of ammonium silicofluoride to form a quartz glass window material having a surface roughness Ra of 0.5 μm and an Rmax of 2 μm. Obtained. FIG. 1 shows a photograph of the frosted quartz glass etched with 5% hydrofluoric acid for 2 hours. Microcracks did not exist in the quartz glass as shown in FIG. Output the obtained window material 1
A silicon wafer was subjected to an etching process by using a microwave introduction window material of a plasma apparatus into which a CF ₄ / O ₂ gas was introduced by KW. Although 10,000 silicon wafers were processed, no abnormal increase in particles could be confirmed.

Comparative Example 1 In Example 1, the concentration of hydrogen molecules was 3 × 10 ¹⁶ molecules / cm.
Except for using the synthetic quartz glass of No. ³ , a quartz glass window material was prepared in the same manner as in Example 1 and the silicon wafer was subjected to an etching treatment. confirmed.

Comparative Example 2 A frost treatment was performed in the same manner as in Example 1 except that natural quartz glass having a bubble class of 2 in DIN was immersed in the frost treatment liquid used in Example 1. When the silicon wafer was etched in the same manner as in Example 1, abnormal generation of particles was confirmed in the processing of 2,000 sheets.

Comparative Example 3 The surface of natural quartz glass having a bubble class of 2 in DIN was
Sandblasted with 180 SiC particles. Microcracks as seen in photograph 2 on the surface of the resulting quartz glass is 10,000 to 100,000 pieces / cm ³ was present. A quartz glass window material was prepared using this quartz glass, and the silicon wafer was etched in the same manner as in Example 1. Particles were generated from the beginning, and the etching process could not be performed.

Example 2 Synthetic quartz glass obtained by hydrolyzing silicon tetrachloride in the gas phase in the same manner as in Example 1 was homogenized at 1000 ° C. to obtain a synthetic quartz glass having a birefringence of 20 nm / cm. Obtained. The synthetic quartz glass was subjected to a hydrogen doping treatment. Next, Example 1
The same frost treatment was performed as described above, and the surface roughness Ra was 0.5 μm.
A synthetic quartz glass having m and Rmax of 2 μm was obtained. A window material was prepared from this synthetic quartz glass, heated at 1100 ° C. for 20 hours, and then gradually cooled. The fictive temperature of the obtained quartz glass window material was 1100 ° C. Using the quartz glass window material, a silicon wafer was etched in a plasma apparatus in which a CF ₄ / O ₂ gas was introduced at an output of 1 KW. Although 7000 silicon wafers were processed, no abnormal increase in particles could be confirmed.

COMPARATIVE EXAMPLE 4 The birefringence and fictive temperature of quartz glass without homogenizing treatment and fictive temperature set in Example 2 were measured. The birefringence was 200 nm / cm and the fictive temperature was 1300 ° C. there were. A window made of quartz glass was prepared using the quartz glass, and CF ₄ was output at 1 KW in the same manner as in Example 1.
The apparatus was equipped with a plasma apparatus into which a / O ₂ gas was introduced, and an etching process was performed on a silicon wafer. When 1,000 silicon wafers were processed, an abnormal increase in particles was confirmed.

[0018]

The quartz glass jig of the present invention has a surface roughness R
a is 5 μm to 0.05 μm, the number of microcracks on the surface is 500 / cm ² or less, and the hydrogen molecule concentration in quartz glass is 5 × 10 ¹⁶ molecules / cm ³ or more. Even when used as a jig for a device that generates such a semiconductor device, abnormal etching and generation of particles are small, and a semiconductor element can be favorably manufactured.

[Brief description of the drawings]

FIG. 1 shows a frosted quartz glass of Example 1
It is a 100 times microscope photograph of the surface after etching with% HF for 2 hours.

FIG. 2 shows a quartz glass which has been subjected to sand blasting and which is made of 5% HF.
4 is a photomicrograph at 100 times magnification of the surface after etching for 2 hours.

Claims (4)

[Claims] 1. A quartz glass jig used for an apparatus for generating plasma, wherein the quartz glass surface has a surface roughness Ra.
Wherein the number of microcracks on the surface is 500 / cm ² or less, and the hydrogen molecule concentration of the quartz glass is 5 × 10 ¹⁶ molecules / cm ³ or more. Utensils. 2. The content of bubbles in quartz glass is 0 or 1 in bubble class according to DIN, and the birefringence of quartz glass is 70 or less.
The plasma-resistant quartz glass jig according to claim 1, wherein the jig is not more than nm / cm. 3. The quartz glass has a virtual temperature of 800 to 1200.
The plasma-resistant quartz glass jig according to claim 1 or 2, wherein the temperature is set in a range of ° C. 4. The plasma-resistant quartz glass jig according to claim 1, wherein the quartz glass is a synthetic quartz glass obtained by hydrolyzing a silicon compound in a gas phase. .