JPH09202630A - Treatment of surface of quartz glass-made jig and surface-treated jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a quartz glass jig by perfectly removing foreign matters and microcracks generated on the production and/or the thermal treatment of the quartz glass jig used for the thermal treatment of semiconductor wafers to clean the surface of the treated jig into a clean state free from a factor causing the deterioration of the strength, capable of preventing the staining of the semiconductor wafers and improving the durability of the treated jig, and further to provide a treating jig therefor. SOLUTION: This method for treating the surface of a quartz glass-made jig for the thermal treatment of semiconductor wafers comprises applying an uneven surface treatment to the surface of the jig by a physical method to remove foreign matters and/or microcracks existing on the surface of the quartz glass jig used for the treatment of the semiconductor wafers. In the method, the surface of the treated jig is subjected to the uneven surface treatment, further to an etching treatment, and furthermore to a surface-heat-melting treatment. The quarts glass jig is to one subjected to the surface treatment by the methods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass for a wafer boat, a square tank, etc., which is used for vapor phase growth film forming processing (hereinafter referred to as CVD processing) of semiconductor wafers, heat treatment such as diffusion, cleaning, and handling. The present invention relates to a surface treatment method for a jig and a jig subjected to the surface treatment.

[0002]

2. Description of the Related Art Conventionally, a CVD process for semiconductor wafers,
A quartz glass jig having high purity and heat resistance is used for heat treatment such as diffusion, cleaning, and handling. The jigs made of quartz glass (hereinafter referred to as processing jigs) used for processing these semiconductor wafers are mainly fixed abrasive grains in the manufacturing process, such as thermal processing by burners and groove processing of wafer boats. Although it is performed by combining grinding processes using a blade having, for example, in the grinding process using a metal bond diamond abrasive grain blade, countless microcracks are generated on the surface of the object to be processed by fine grinding with abrasive grains. To do. These microcracks are
Since it easily becomes a stress concentration source, it has been a cause of lowering the strength of the processing jig against thermal strain and mechanical load during wafer processing.

Further, the microcracks easily accumulate dirt such as cutting chips and cutting oil during grinding on the crack interface,
At the time of processing a semiconductor wafer, contaminants may be released from the processing jig and contaminate the semiconductor wafer. further,
Abrasive grains, bonds (bonding agents), chips, etc. may get stuck into the processed surface due to the processing pressure during the grinding process and may remain as foreign matter. Similarly, the semiconductor wafer may be contaminated during the processing of the semiconductor wafer. .

On the other hand, these processing jigs are also used for CVD processing of semiconductor wafers and the like, but during the heat treatment, the processing jigs come into contact with the reaction gas and react with each other such as a polysilicon film or a silicon oxide film. The product may adhere to the surface as a foreign substance. If this is left unattended, the foreign matter grows and accumulates further, and due to the difference in the physical properties such as the coefficient of thermal expansion and the specific heat between the foreign matter and the quartz glass, cracks are generated on the surface of the foreign matter film and the quartz glass in contact therewith, and the strength is reduced. Alternatively, the particles may be peeled off to become particles, which may adhere to the wafer to be processed and contaminate it, thus lowering the manufacturing yield. Therefore, conventionally, this has been removed by a chemical etching process using a strong acid or gas.

Further, since such foreign matter adheres integrally to the processing jig, the coefficient of thermal expansion and the specific heat between the foreign matter and the quartz glass are returned when the processing jig is returned to room temperature or when the temperature changes during cleaning. Due to the difference in physical properties, etc., microcracks are generated in the processing jig centering on the lower surface of the foreign matter.

However, in the conventional chemical etching process, it takes a long time to completely remove the microcracks and the foreign matters, and the size and shape of the entire processing jig is changed by the consumption due to the etching. Actually, it is difficult to completely remove foreign matter and microcracks, and if the treatment jig is used for several heat treatments, foreign matter is formed or deposited in or on the microcracks,
The tips of the existing microcracks grow deeper and larger, and foreign matter and the surface of the processing jig are peeled off, and particles are again generated. Further, if the number of times of heat treatment is further increased, the treatment jig may be cracked or, in the worst case, may be broken.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances of the prior art, by completely removing foreign matter on the surface of a processing jig that occurs during manufacturing and / or heat treatment, and removing dangerous microcracks. By making the surface of the processing jig clean and free from the cause of strength reduction,
An object of the present invention is to provide a surface treatment method capable of preventing contamination of a semiconductor wafer and improving durability of the treatment jig, and a treatment jig subjected to the treatment.

[0008]

In order to achieve the above object, in the surface treatment method of the treatment jig of the present invention, the surface of the treatment jig is subjected to an uneven treatment by using a physical method such as sandblasting. The foreign matter and microcracks on the surface are removed at the same time, or after the unevenness treatment on the surface, etching treatment and surface melting treatment by a chemical method are further performed.

As a physical surface treatment method for the quartz glass jig of the present invention, sand blasting, loose abrasive polishing, ultrasonic polishing, Any method such as tape wrapping may be used, but sand blasting is used because it is possible to select a part to be processed and perform partial processing and to easily process a jig surface with a complicated shape. Is preferred.

In the surface treatment method by sand blasting used in the present invention, particles having a particle size of 5 μm or more and 500 μm or less account for 80 wt% or more of silicon, silicon compounds, carbon, carbon compounds, boron and boron. Hard fine powder equal to or more than quartz glass such as compound is used, and it is usually jetted through an alumina nozzle or the like toward a surface with foreign matter or microcracks with air or nitrogen pressure of about 3 kg / cm ^2. Then, the surface of the treatment jig is subjected to unevenness treatment. At this time, micro-cracks that are less dangerous may be generated due to the impact of sandblasting. Especially, if the abrasive grains of the hard fine powder of sandblasting contain a large number of particles larger than 500 μm, a large particle size The collision impact of the powder causes new deep microcracks to occur again, reducing the effect of the surface treatment. Also, if the abrasive particles of the hard powder for sandblasting contain a large amount of ultrafine particles of less than 5 μm, the particles will be sandblasted. It is not desirable because it coagulates and adheres to the surface, hinders the effect of blasting other particles, and reduces unevenness and efficiency of the unevenness treatment. Therefore, it is necessary for practical use that the fine powder has particles having a particle diameter of 5 μm or more and 500 μm or less in an amount of 80 wt% or more.

As a spraying device used for sandblasting, a commonly known sandblaster for metal surface treatment can be used. According to a physical method such as sandblasting, the surface of the processing jig in which the foreign matter or the microcracks are generated can be selected and partially performed, so that the processing can be performed in a short time without waste.

Further, in the present invention, the processing jig which has been subjected to the unevenness treatment by the above-mentioned physical method is newly provided with sharp unevenness which is apt to become very fine microcracks and particles due to the physical treatment. Since they may remain, it is preferable to further chemically etch the surfaces thereof to completely remove the microcracks and smooth the sharply-roughened portions to some extent.

However, in this case, since it is an extremely fine microcrack when removing the surface, an unreasonable long-time etching treatment with a strong acid for completely removing foreign matters and microcracks during manufacturing or use (for example, , 50% hydrofluoric acid for 3 to 4 hours is not necessary, and treatment with 20% or less of hydrofluoric acid or an acid containing ammonium fluoride may be performed at 20 ° C. for about 30 minutes. At this time, if the acid is too weak, or if it is for a short period of time, fine microcracks cannot be completely removed, so that 2 is practically used.
% To 10% hydrofluoric acid or an acid solution containing ammonium fluoride is preferably treated at 20 ° C. for 5 minutes or more.
As a result, the uneven surface of the processing jig that has been subjected to the uneven processing has the microcracks and the acute-angled uneven surface removed and smoothed, and the reduction of the strength of the processing jig and the generation of new particles are effectively prevented.

Furthermore, if the fine powder during sandblasting before chemical etching is a powder of silicon dioxide, silicon, or the like, it can be removed by etching in the same manner as quartz glass during chemical etching. It is desirable because the residual powder can be completely removed by etching. At this time, if there are many particles of the residual fine powder having a particle size of more than 500 μm, it takes an extra time to remove them by etching, and
If it is smaller than m, a chemical reaction will occur rapidly, causing heating or sudden blowing of bubbles (bumping), so practically when removing the sandblast residue by etching,
Fine particles that can be etched are particles of 5 μm or more and 500 μm or less in an amount of 80 wt% or more, and relatively less than 5 μm or 5
It is desirable to adjust the number of particles larger than 00 μm to be small.

Further, after the etching treatment, a surface melting treatment is further performed by a flame heating means such as a gas burner of oxygen-hydrogen, oxygen-propane, etc., so that the uneven surface is further smoothed, which is more desirable. . However, if this surface melting treatment is carried out before the etching treatment, only the surface will be melted and microcracks will remain inside, so it is necessary to be after the etching treatment.

As a processing jig to which the surface treatment method for a quartz glass jig of the present invention can be applied, a wafer loading boat (hereinafter referred to as a wafer boat), a boat pedestal, a process tube, a handling jig, a cantilever, and heat insulation. Examples include a cap, a bubbler, and a cleaning liquid tank. Also,
In addition to the above-mentioned foreign matter, the treatment method of the present invention can be applied to devitrification, white turbidity, and so-called dot-like colored foreign matter that occur on the surface during manufacturing of a treatment jig or heat treatment of a wafer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 6 by way of example, using a cleaning liquid tank and a wafer boat as examples. 1 is a perspective view of a liquid tank for cleaning semiconductor wafers, which is immediately after grinding with fixed abrasive before its surface treatment.
FIG. 3 is a partially enlarged cross-sectional view of the thick section of the portion A of the liquid tank of FIG. 1 before surface treatment, and FIG. 3 is a view similar to FIG. 2 after surface treatment of the present invention. Further, FIG. 4 is a perspective view of a wafer boat on which a semiconductor wafer after heat treatment is mounted,
5 is a partially enlarged sectional view of a portion B of the wafer boat of FIG. 4 which has been surface-treated by the method of the present invention, and FIG.
FIG. 6 is a partially enlarged cross-sectional view of the wafer boat before the surface treatment by the method of the present invention, which is similar to FIG.

First, a cleaning liquid tank will be described as an example.
The cleaning liquid tank 1 is ground by fixed abrasive grains of the blade so that the inner and outer surfaces have a uniform thickness, and the inner and outer surfaces of the liquid tank are innumerable micro-particles containing the grinding liquid by this grinding process. Crack 2 has occurred. Further, foreign matter 3 such as abrasive grains and a bonding agent for the abrasive grains is observed to remain on this surface (see FIGS. 1 and 2). If this is left unattended, the strength is reduced due to the microcracks 2. Therefore, when the chemical solution is put into the liquid tank, the weight may damage the bottom portion.

The microcracks 2 and the foreign matter 3 are subjected to a concavo-convex treatment on the surface in the cleaning liquid tank by a physical means such as sandblasting, so that the microcracks 2 are formed.
And foreign matter 3 are removed at the same time. After this surface treatment, chemical etching treatment with an acid is further performed, and by further applying a surface melting treatment with an oxygen-hydrogen flame gas burner, the unevenness provided on the surface of the cleaning liquid tank becomes smooth,
The strength that can withstand the weight of the chemical liquid is obtained (see FIG. 3).

Next, referring to FIGS. 4 to 6, a wafer boat will be described as an example. In the wafer boat 4, semiconductor wafers 6 are placed in the respective receiving grooves 5. As shown in FIG. 6, a reaction product such as a polysilicon film adheres to the wafer boat 6 that has undergone the heat treatment as a foreign matter 13 at a position in contact with the gas at the time of the heat treatment. Innumerable microcracks 12 occur on the surface of the boat 4.

These foreign substances 13 and micro cracks 12
On the other hand, the foreign matter 13 and the microcracks 12 can be removed at the same time by subjecting the surface of the wafer boat 4 to unevenness by a physical method such as sandblasting. The state is obtained. After this surface treatment, chemical etching with a conventionally known acid or the like is further performed, so that the uneven surface provided on the surface of the wafer boat becomes smooth, and the same surface strength as a new product can be obtained.

In the surface treatment method of the present invention, foreign matters and microcracks generated on the surface of the treatment jig by the heat treatment are removed by the physical method such as sand blasting to remove the roots by the unevenness treatment, thus leaving no treatment residue. . Further, unlike the conventional chemical etching method, the surface treatment by this method can be performed by selectively selecting a portion where a foreign substance or the like has occurred, rather than treating the treatment jig as a whole. There is no waste of etching unnecessary parts.

Although the surface of the processing jig is slightly shaved due to the above-mentioned unevenness treatment of the surface, the life of the jig is still the same as that of the conventional case. Compared with the case of being damaged by, it will be longer than it is a problem. Further, if the surface of the treatment jig is subjected to the unevenness treatment and then chemical etching is further performed, the unevenness surface is smoothed and the same strength as that of a new product is obtained.

[0024]

【Example】

Example 1 Diamond abrasive grains (grain size # 1 shown in FIG.
20) Metal-bonded grindstone and light oil coolant are used to grind the outer and inner circumferences to a diameter of 400 mm and height of 400 mm,
The cleaning liquid tank 1 having a wall thickness of 5 mm was subjected to an etching treatment with a 5% hydrogen fluoride solution for 30 minutes in the same manner as the conventional one, and thereafter, particles of less than 10 μm and 500 μm or more were removed by using a sieve to obtain a range of 10 to 500 μm. Of silica glass powder having a particle size of 82 wt% and an average particle size of 20 μm, an air pressure of 3 kg /
After spraying at cm ² , the sand blasting treatment was uniformly performed for 40 minutes to remove foreign matters and microcracks, and then etching treatment was performed for 30 minutes with a 5% hydrogen fluoride solution.

Next, the inner and outer surfaces were subjected to surface melting treatment with an oxygen-hydrogen flame gas burner, and a cleaning liquid tank having a smooth surface free of microcracks and foreign matter was obtained. When 25 liters of hydrogen peroxide solution was added to the obtained cleaning liquid tank and the semiconductor wafer was cleaned in this cleaning liquid for 15 minutes, particles on the surface of the wafer were reduced as compared with those before cleaning. Further, even if the liquid was once drained to increase the amount of the cleaning liquid and 47 liters of hydrogen peroxide solution was added, no damage occurred.

[Comparative Example 1] Similar to Example 1, the cleaning liquid tank 1 having a diameter of 400 mm, a height of 400 mm and a wall thickness of 5 mm shown in FIG. When the cleaning liquid tank 1 was observed after grinding the outer and inner circumferences with a coolant, numerous microcracks and residue of abrasive grains were observed on the surface. This was subjected to an etching treatment for 30 minutes with a 5% hydrogen fluoride solution similar to the conventional one, but microcracks and residual foreign matter were observed.

Next, 25 liters of hydrogen peroxide solution was added as a cleaning liquid, and the semiconductor wafer was cleaned in this cleaning liquid for 15 minutes. As a result, the number of particles on the surface of the wafer was increased and the particles were contaminated. I got it. When the liquid was once drained to increase the amount of the cleaning liquid and 47 liters of hydrogen peroxide solution was added, the joint was broken at the joint between the bottom and the side, and the cleaning liquid leaked to the outside.

[Embodiment 2] Wafer boat 4 shown in FIG.
Then, a semiconductor wafer having an outer diameter of 150 mm was housed therein and subjected to a CVD treatment in silane gas at 900 ° C. for 4 hours. With respect to foreign matter (polysilicon) and microcracks generated on the surface of the wafer boat by this heat treatment, particles of less than 10 μm and particles of 500 μm or more are removed using a sieve,
90% by weight of particles in the range of 500 μm have an average particle size of 15
When silicon carbide powder having a particle size of 0 μm was sprayed at an air pressure of 2 kg / cm ² and subjected to a sandblasting treatment for 10 minutes evenly, foreign matter and microcracks could be completely removed. After that, an etching surface treatment was performed with a hydrogen fluoride solution of 8% at 20 ° C. for 10 minutes. As a result of repeating the surface treatment and the heat treatment, the wafer boat was able to endure the heat treatment about 110 times.

[Comparative Example 2] For comparison, a semiconductor wafer was heat treated using the same wafer boat as above.
The surface treatment after the heat treatment was carried out by conventional chemical etching for 10 minutes with a mixed acid solution of 20 ° C. in which a 10% hydrogen fluoride solution and a nitric acid solution were mixed at a ratio of 1: 1. A crack was seen. As a result of repeating this conventional chemical etching and the above-mentioned heat treatment, after about 15 times of heat treatment, it was confirmed that particles were contaminated and contaminated, which are considered to be foreign matter deposited on the semiconductor wafer. Further, the wafer boat was cracked by the 60th heat treatment and could not be used for the next use.

[0030]

According to the method for treating the surface of the quartz glass jig of the present invention, the surface treatment of the treating jig can be completely performed, so that the semiconductor wafer can be prevented from being contaminated by foreign matters. Further, since it is possible to prevent the growth of microcracks generated by heat treatment during use and remove the microcracks during processing, it is possible to greatly extend the strength and life of the processing jig.

[Brief description of drawings]

FIG. 1 is a perspective view immediately after grinding with fixed abrasives before surface treatment of a liquid tank for cleaning semiconductor wafers.

FIG. 2 is a partially enlarged cross-sectional view of the container inner surface of the thick section of the A portion of FIG. 1 before the surface treatment of the present invention.

FIG. 3 is a partially enlarged cross-sectional view of the container inner surface of the thick section of the portion A of FIG. 1 after the surface treatment of the present invention.

FIG. 4 is a perspective view of a wafer boat.

5 is a partially enlarged cross-sectional view of the portion B of FIG. 4 after the surface treatment of the present invention, taken along a perpendicular line passing through the diameter thereof.

FIG. 6 is a partially enlarged cross-sectional view of the portion B in FIG. 4 taken along a line passing through its diameter before the surface treatment of the present invention.

[Explanation of symbols]

 1 Cleaning Liquid Tank 2, 12 Microcrack 3, 13 Foreign Material 4 Wafer Boat 5 Receiving Groove 6 Semiconductor Wafer

Claims (6)

[Claims] 1. A quartz glass product characterized by removing foreign matter and / or microcracks existing on the surface of a quartz glass jig used for processing a semiconductor wafer by subjecting it to unevenness by a physical method. Jig surface treatment method. 2. The method for surface treatment of a quartz glass jig according to claim 1, wherein the physical method is sandblasting. 3. The abrasive grains used for sandblasting are silicon, a silicon compound, carbon, a carbon compound, boron, and a boron compound, and the grain size in the abrasive grains is 5 μm or more and 500 or more.
The method for surface treatment of a quartz glass jig according to claim 2, wherein the particles having a size of μm or less are 80 wt% or more. 4. A surface treatment method for a quartz glass jig, which comprises subjecting a surface of a quartz glass jig to a concavo-convex treatment by a physical method, and further performing a chemical etching treatment. 5. The surface treatment of the quartz glass jig according to claim 4, wherein after the surface of the quartz glass jig is chemically etched, a surface melting treatment by heat is further performed. Method. 6. A reaction product associated with a grinding process using fixed abrasives or a vapor deposition film forming process of a semiconductor wafer,
A quartz glass jig, which is used for processing a semiconductor wafer after removing foreign matters and / or microcracks generated on the surface of the quartz glass jig by sandblasting and subsequent chemical etching.