JPH03170340A - Production of composite silica glass tube for heat treatment of semiconductor - Google Patents

Abstract

PURPOSE:To obtain the subject composite silica glass tube excellent in heat resistance, uniformity, etc., by inserting a low viscosity glass tube of a prescribed thickness for the inner layer into a high viscosity glass tube for the outer layer, holding the glass tubes in the horizontal position and heating one end thereof while rotating the glass tubes around the common axis and simultaneously pressurizing the inside of the tube for the inner layer. CONSTITUTION:Into a silica glass tube (B) for the outer layer having a higher viscosity than that of a silica glass tube (A) for the inner layer, the silica glass tube (A) for the inner layer having a thickness of 8-40% based on the total thickness of the both tubes is inserted and put on top of the other. The piled-up tubes are then held almost in the horizontal position and rotated around the common axis at a same speed. A compressed air is simultaneously introduced thereinto through a nozzle 3 for pressurization of the inside so as to keep the inside of the glass tube (A) for the inner layer to a pressurized state. The piled-up tubes are then heated while moving a gas burner 5 from one end thereof to the other end and both the piled-up pipes (A) and (B) are drown and unified into one body, thus obtaining the objective composite silica glass tube composed of different silica glasses and used for heat treatment of semiconductors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applicable to heat treatment of semiconductor wafers, for example, 1,
The present invention relates to a method for manufacturing a composite quartz glass tube suitable for use in a furnace core tube, heat retention jig, etc. for heat treatment in a high temperature range of 000 to 1,300°C.

[Conventional technology]

Conventionally, furnace tubes and wafer jigs used in the semiconductor industry are required to have heat resistance that will not deform in the high temperature range of 1,000 to 1,300 degrees Celsius. Along with this, trace contamination of wafers by metal impurities, especially alkali metals, during the heat treatment process has become a major problem.

In line with these requirements, a composite tube with a laminated structure has been proposed, in which the outer layer is made of natural quartz glass with excellent heat resistance, and the inner layer is made of high-purity synthetic quartz glass with a low content of metal impurities. A typical manufacturing method thereof is disclosed in Japanese Patent Application Laid-Open No. 48-92410, for example.
It has been published in the Publication No.

According to the method for manufacturing a quartz glass tube with a laminated structure disclosed therein, a quartz glass tube with a laminated structure is formed by thermally spraying crystal or natural quartz glass powder onto the outer surface of the quartz glass tube. Ru. However, this method has the disadvantage that it is difficult to make the thickness of the sprayed natural quartz glass layer uniform, and that it is easily deformed by heat because it is based on a fused silica glass tube. and poor fitting of the tube to the furnace body due to a decrease in outside diameter accuracy or shaft accuracy.
In particular, the heat treatment temperature distribution on the wafer surface becomes non-uniform, resulting in a serious problem of poor heat treatment.

In addition, a method of manufacturing a laminated composite tube has been proposed in which a small-diameter fused silica glass is inserted inside a natural quartz glass tube and heated and integrated. Many air bubbles remain on the welded surface of the fused quartz glass tube, and during use, these air bubbles may expand and break the glass, or may be deformed due to heating during welding, resulting in failure of the specified outer diameter and wall thickness. There is still room for technical improvement, since it is difficult to obtain thick ones, which leads to the same disadvantages in heat treatment as described above.

[Problem to be solved by the invention]

Therefore, an object or technical problem of the present invention is to provide a homogeneous composite tube having excellent heat resistance and metal contamination prevention properties during heat treatment of semiconductor wafers. Another object of the present invention is to provide a uniformly heat-treated high-quality semiconductor wafer that is industrially advantageous.

[Means to solve the problem]

The present inventors have developed a laminated composite stone that can overcome the above problems.
As a result of repeated research into the effective production of English glass tubes, we have developed a manufacturing method that is highly desirable for practical purposes.

That is, in the production of a composite quartz glass tube in which different quartz glasses are integrated as an inner layer tube and an outer layer tube, the present invention provides a composite quartz glass tube with a higher viscosity than that of the inner layer quartz glass tube, preferably log η = 0. A composite quartz glass tube for the inner layer having a wall thickness of 8 to 40% of the total wall thickness of both tubes is inserted into a quartz glass tube for the outer layer having a viscosity higher than 1 poise and polymerized, and the polymerized tube is held horizontally. The outer heating zone is moved from one end to the other while rotating at the same speed about a common axis, maintaining pressure inside the inner layer tube during this operation, and keeping the inner layer tube under pressure during the operation. The present invention provides a method for manufacturing a composite quartz glass tube for semiconductor heat treatment, which involves stretching and integrating the tubes.

In the composite quartz glass tube formed by the method of the present invention, the outer layer type quartz glass tube to be integrated has a higher viscosity than the inner layer forming quartz glass tube, and the inner layer tube having a lower viscosity is relatively The technical feature is that it has a thin shape. However,
The outer layer tube preferably has a high viscosity that does not substantially cause thermal deformation, particularly in the semiconductor wafer heat treatment temperature range.

Such a material is usually provided by natural quartz glass, but modified synthetic quartz glass can also be used.

Furthermore, as the material for the inner layer tube, fused silica glass of the highest possible purity is used. In the present invention, the heating and melting integration of the inner layer tube and the outer layer tube generally involves the following steps:
The larger the difference in viscosity between the inner layer and outer layer quartz glass tubes, the easier and more effective it is, but considering the ease of composite operation, the viscosity difference η between the two tubes at a temperature of 1,280°C
should be log η=0.1 poise or more, and 0.
It is more preferable that it is 2 poise or more. In this way, the present invention includes [0]. The viscosity η, expressed as og η, is 1,
At a temperature of 280°C.

In addition, it is important that the wall thickness of the synthetic quartz glass tube for the inner layer is approximately 8 to 40% of the total wall thickness of both tubes due to the integration operation and actual usage conditions. Selection is made in relation to the difference in viscosity.

If the wall thickness ratio of the inner layer tube is thinner than 1O%, the ability to prevent contamination of the wafer with alkali metals etc. will be greatly reduced, and if it exceeds 40%, it will be practically difficult to melt and integrate by external heating method. This is not preferable because air bubbles are likely to be trapped and the heat resistance is also lowered.

In general, when the viscosity of the outer layer tube is sufficiently larger than that of the inner layer tube, the wall thickness of the inner layer tube can be made relatively large, but conversely, when the viscosity difference is small, the inner layer tube The wall thickness of the pipe is quite limited.

In the method of the present invention, quartz glass tubes for the outer layer and the inner layer to be melted and integrated in a polymerized manner are prepared in advance, the inner layer tube is inserted into the outer layer tube to polymerize, and this is held horizontally. and rotate both tubes at the same speed about their common axis. During the heat melting and unifying operation, it is important to maintain the inside of the inner layer tube in a moderately pressurized state. This pressurized state is normally maintained by sealing one end of the inner layer tube and introducing an inert gas, such as nitrogen gas, through an open port at the other end. For heating, a gas burner or annular furnace that surrounds the entire circumference of the polymerization tube section is preferably used, and the melting heating area is moved from the sealed end side of the inner layer tube of the polymerization tube toward the other end, while the melting part is heated. A laminated composite tube with a desired outer diameter and wall thickness is prepared by stretching.

Movement of the heating area, such as a burner, can also be achieved by fixing the burner or the like and horizontally moving the polymeric tube.

The speed of rotation and horizontal movement of the tube is selected appropriately depending on the tube diameter, wall thickness, material, capacity of the heating source, etc., and the optimum conditions are:
It can be easily determined by simple experiments depending on each case.

There are no restrictions on the inert gas fed into the inner layer tube as long as it does not adversely affect the heated quartz glass tube, but it is usually a high purity nitrogen gas, argon gas, or a gas with a diameter of 0.2 μm or more. Compressed air filtered with mist particles is conveniently used.

In addition, when heating and melting the polymerized tubes to integrate them, applying vibrations at a frequency of 50Hz or higher to the glass tubes to be integrated will promote fusion between the two tubes and effectively eliminate the formation of minute bubbles. This method is extremely effective, and a good composite quartz glass tube without bubbles can be obtained even if the viscosity difference between the outer layer tube and the inner layer tube is small. This vibration may be applied to both tubes or only to one tube, but a satisfactory effect cannot be expected if the frequency is less than 50 Hz. Furthermore, in the melt-stretching process, it is extremely effective to reduce the pressure in the gap between the polymerized tubes, since the remaining air bubbles on the fused surface are more effectively eliminated.

In addition, the production of composite quartz glass tubes with a laminated structure according to the method of the present invention involves not only a combination of composite quartz glass and heat-resistant quartz glass, but also a combination of quartz glass that imparts different properties to the inner or outer surface of the quartz tube. It can be widely applied to pipe manufacturing, etc.

The method of the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view for explaining the implementation state of the method of the present invention.

The right end of the high-viscosity quartz glass outer layer tube B is fixed to the fixed rotary chuck 1, and a low-viscosity glass tube with the same or slightly shorter length is attached to the inside of the tube B and is integrated with it. Insert the quartz glass inner layer tube A, and fix the same end with a vacuum chamber/clamp jig 2 to clamp and fix both tubes A and B. A stopper 4 attached to the opening of the inner tube provided with the nozzle 3 for internal pressurization is inserted into the fixed end opening of the inner layer tube A and fixed. On the other hand, both polymeric tubes A held horizontally,
A mobile oxygen-hydrogen gas burner 5 is attached to the left end opening periphery of B.
This melt-sealed edge is tightly heat-fused with the open end periphery of a bottomed quartz glass tube 7 with the same diameter as the tenon, which is fixed to a separately prepared movable chuck 6. Unify the outfit.

The operation of fusing and integrating the polymeric tubes A and B is performed by rotating the rotating chuck 1 and the movable chuck 6 synchronously around a common axis to rotate the polymeric tubes at the same predetermined speed. The hydrogen gas burner 5 is slowly moved on the guide rail 8 from the fused portion with the bottomed quartz glass tube 7 toward the fixed chuck at the right end. During this fusion operation, nitrogen gas is continuously blown from the internal heating nozzle 3 to maintain a pressure difference of about 0.5 kg/cd from atmospheric pressure, for example.
Also, depending on the conditions, the decompression chamber and crank jig 2
The gap between the tubes A and B is maintained at a reduced pressure by suction, and furthermore, a vibration with a frequency of 50 Hz or more is applied to the outer layer tube B and/or the inner layer tube A by the vibration jig 9.

By burner 5, typically l, 800-2,
The polymerized tubes heated and melted to a temperature of 000°C are effectively integrated in the heating zone by applying pressure from the inside and reducing the pressure in the gap between the two tubes. Preferably, at the same time, the movable rotary chuck 6 is moved opposite to the burner. The tube is moved to the left and stretched to form a composite quartz glass tube 10 having a predetermined diameter and wall thickness, especially the wall thickness being precisely controlled.

[Effect]

According to the method of the present invention, the quartz glass tube for the outer layer and the quartz glass tube for the inner layer inserted and polymerized inside the outer layer can be easily fused and integrated without leaving any air bubbles on the joint surface, and moreover, the wall thickness can be accurately A composite quartz glass tube with good quality can be obtained effectively and easily.

〔Example〕

Next, the present invention will be explained in more detail using specific examples.

Me114 Sen1ll1 Purified ethyl silicate is hydrolyzed, gelled and dried through a condensation reaction to create a tubular porous gel, and the tubular base material is heated and sintered to produce products with different wall thicknesses using the so-called sol-gel method. The following four types of transparent high-purity aluminum or quartz glass tubes Al, A
2, A3 and A4 were prepared. In addition, for each glass tube]
The viscosity at 280°C was measured by the invagination method, and the measured values are also listed.

Outer diameter (rMn) Wall thickness (mu) Length (IIn) Viscosity (log η poise) Al l40 12
2,000 11.2A2 140
3 2,000 11.3A 3
140 1.5 2,000
11.3A4 140 16 2,00
0 11.2 Part 41 Sho 1 Gan A natural crystal block is melted in an induction heating furnace and extruded into a tubular shape using a molybdenum or shaped jig using a known electric melting method or direct pulling method to produce natural stone of various thicknesses. English glass tube B
1, B2, B3 and B4 were produced.

Outer diameter (un) Wall thickness (Ilwl) Length (-) Viscosity (log η poise) Bl 200 18
1,500 12.6B2 200
17 1,500 12.5B 3
200 28.5 1,500
12.6B4 200 14 1,5
00 12.6 Examples 1 and 2 and Comparative Examples 1 and 2 According to the method shown in the drawings, combinations of the inner layer tube Al and outer layer tube B1, A2 and B2, A-11 3 and B3, and Each polymerized tube, which is a combination of A4 and B4, was heat-fused and integrated.

Table 1 below summarizes the results of investigating the state of bubbles on the fused surface of the inner layer pipe and outer layer pipe, the state of variation in the thickness of the inner layer, and the state of variation in the overall wall thickness in each of these composite pipes. .

1st surface inner and outer layer Inner layer tube wall thickness Total thickness of foam inner layer thickness
Ratio (%) U Uniformity Uniformity Example I AI/B
l Approx. 40 Good Good Good Example 2
A2/B2 Approx. 10 Good Good Good comparative example I A3/B3 Approx. 5 Good Poor
Good 17 2 A4/B4 Approximately 53 Bad Good A1, B1 and A in defective example 1
There are no bubbles at the fused interface in the composite tubes of 2 and B2,
In addition, when the cross section of the composite tubes A1 and B1 was observed using a polarizing microscope, it was found that approximately 1. A uniform inner layer with good wall thickness accuracy of 5 mm+ was confirmed.

As can be understood from Table 1 above, when the wall thickness of the inner layer tube exceeds 50% of the total wall thickness of the inner layer tube and the outer layer tube, many bubbles remain at the interface, resulting in a decrease in the wall thickness. 12 - Dispersion is significant and heat resistance is poor, which is disadvantageous. Further, if the wall thickness of the inner layer tube is about 5%, the variation in the thickness of the inner layer becomes large, which naturally impairs the effect of preventing metal contamination, which is not preferable.

In addition, disregarding the actual situation, we created a tube for the outer layer made of composite quartz glass and a tube for the inner layer made of natural quartz glass, and integrated the polymerized tubes by heat-fusion in the same way. Not only could the welding and integration not be carried out smoothly, but there were many large air bubbles on the welded surface of the resulting composite tube.

Although the uniformity of the thickness of the inner layer of the composite tube was good, the variation in the overall wall thickness was large and poor.

Example 3 By the soot method, purified silicon tetrachloride was hydrolyzed in an oxygen-hydrogen flame to produce a soot body, which was heated and dehydrated for a long time in anhydrous nitrogen gas, and then sintered. Vitrification was performed to produce a transparent high-purity quartz glass tube for inner layer having an outer diameter of 100 ma, a wall thickness of 8 yr, a length of 2,000+ nm, and a viscosity of log η = 11.7 voices at a temperature of 1,280°C. On the other hand, by the Bernoulli method, which produces quartz glass blocks by melting and vitrifying natural quartz powder using an oxygen-hydrogen flame, the outer diameter of 126 mm, the wall thickness of 12+ nm,
A transparent natural quartz glass tube for the outer layer with a length of 2,000 nm and a viscosity at 1,280''C].ogη=12.0 poise was manufactured.

Both tubes (the wall thickness of the inner layer tube is about 40% of the total) were polymerized and integrated by heat fusion in the same manner as in Example 1.

There were substantially no bubbles on the fused surfaces of the inner and outer layer tubes, and a composite tube with a good laminated structure was obtained.

Comparative Example 3 A soot body obtained by the soot method was heated and dehydrated in a nitrogen stream, and then sintered and vitrified at temperatures of 1 and 28.
A transparent natural quartz glass tube for outer layer having an outer diameter of 126 mm, a wall thickness of 17 m, and a length of 2,000 mm and having a viscosity of log η = 11.6 poise at 0°C was prepared.

On the other hand, a strike body similarly obtained by the soot method was subjected to ultra-purification treatment in a high-concentration hydrogen chloride monochlorine gas flow instead of dehydration treatment in a nitrogen gas flow, and then sintered and vitrified.
An outer diameter having a viscosity at a temperature of 280° C. that is substantially the same as that of the outer layer tube, log η = 11.6 poise] 00 mn,
A transparent ultra-high purity quartz glass tube for the inner layer with a wall thickness of 3+nm and a length of 2,000+nm was manufactured.

Polymerize both tubes (the wall thickness of the inner layer tube is 15% of the total wall thickness)
, and were heat-fused and integrated in the same manner as in Example 1.

In the resulting composite quartz glass tube, small bubbles were observed on the fused surface, albeit in some parts.

Example 4 A soot body obtained by the soot method was heated and dehydrated in a nitrogen stream, and then sintered and vitrified to produce a material with an outer diameter of 126 mm and a viscosity of log η = 11.6 poise at a temperature of 1,280°C. Thickness 17+m+, length 2, OOO+nm
A high-purity quartz glass tube for the transparent outer layer was manufactured. on the other hand,
Similarly, the soot body obtained by the soot method was subjected to ultra-purification treatment in a high concentration hydrogen chloride monochlorine gas flow instead of dehydration treatment in a nitrogen gas flow, and then sintered and vitrified to obtain 1,280
A transparent ultra-high-purity quartz glass tube for inner layer having an outer diameter of 10 mm, a wall thickness of 3 + nm, and a length of 2,000 mn and having a viscosity of log η = 11.4 poise at a temperature of °C was manufactured.

These two tubes (the inner layer tube's wall thickness was 15% of the total wall thickness) were polymerized and heated and melted into one piece in the same manner as in Example 1. However, in this operation, the pressure in the gap between the septa is 0.5 below atmospheric pressure.
The test was carried out by hand while maintaining a low vacuum of kg/a#.

The obtained composite quartz glass tube did not contain any air bubbles on its fused surface and exhibited a good laminated structure with uniform inner and outer layers without variations.

In place of the tube for the inner layer, an ultra-high purity quartz glass tube with a viscosity of log η = 11.5 poise at a temperature of 1,280°C was used, and as a result of performing exactly the same composite, extremely fine bubbles were found. However, no particular inconvenience was observed during use.

Example 5 A soot body obtained by the soot method was dehydrated in a nitrogen stream, and then sintered and vitrified to obtain an outer diameter of 1 having a viscosity of log η = 11.6 voice at a temperature of 1,280°C.
26+nn+, wall thickness 17mm+, length 2, OOO+m+
A high-purity quartz glass tube for the transparent outer layer was manufactured. on the other hand,
Similarly, the soot body obtained by the soot method was ultra-purified in a high concentration hydrogen chloride monochlorine stream without dehydration in a nitrogen stream, and then sintered and vitrified to obtain a viscosity lag at a temperature of 1,280°C. 7+ = outer diameter 1 with 11,5 poise
00+nm, -16 A transparent ultra-high purity quartz glass tube for the inner layer with a wall thickness of 3+nm and a length of 2,000 mm was manufactured.

These two tubes (the inner layer tube's wall thickness was 15% of the total wall thickness) were polymerized and heated and melted into one piece in the same manner as in Example 1. However, during this operation, the pressure in the gap between both pipes is maintained at a reduced pressure state of 0.5 kgld lower than atmospheric pressure, and
Vibration at 0 Hz was continued to be applied to the outer layer tube.

The obtained composite quartz glass tube did not contain any air bubbles on its fused surface and exhibited a good laminated structure having uniform inner and outer layers with uniform inner and outer composite layers.

Furthermore, in the composite quartz glass tube obtained by applying vibration at 10 Hz in the composite integration operation described above, there were a few spiral microbubbles that caused no actual damage.

〔Effect of the invention〕

The composite quartz glass tube obtained by the manufacturing method of the present invention has heat resistance desirable as a quartz glass member for semiconductor wafer heat treatment and a layer structure with excellent uniformity, so it can be used repeatedly over a long period of time, and , During the heat treatment, contamination of the wafer by metals such as alkali metals is effectively prevented, which is industrially desirable, and the composite quartz glass tube obtained by the present invention has other properties other than viscosity. Because it is a composite right-handed silica glass tube that combines various properties, it can be widely used as a quartz glass member for wafer heat treatment, and its practical value is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the implementation state of the method of the present invention. Codes in the diagram: A...Inner layer tube B...Outer layer tube 1...Fixed rotary chuck 2...Decompression chamber/clamp 3...Internal pressurization nozzle 4...Bung 5...・Gas burner 19 6... Mobile chuck 7... Bottomed quartz glass tube 8... Guide rail 9... Vibration jig 10... Composite quartz glass tube -20-

Claims (1)

[Scope of Claims] 1. In manufacturing a composite quartz glass tube in which different quartz glasses are integrated as an inner layer tube and an outer layer tube, both quartz glass tubes are combined into an outer layer quartz glass tube having a higher viscosity than the inner layer quartz glass tube. Inserting and polymerizing a quartz glass inner layer tube having a wall thickness of 8 to 40% of the total wall thickness of the tubes, keeping the polymerized tube substantially horizontal and rotating it around a common axis at the same speed, Composite quartz glass for semiconductor heat treatment, characterized in that an external heating area is moved from one end to the other end, the inside of the inner layer tube is kept under pressure during this operation, and the two polymerized tubes are stretched and integrated. Method of manufacturing tubes. 2. The quartz glass tube for the outer layer is larger than the quartz glass tube for the inner layer.
The manufacturing method according to claim 1, which has a viscosity higher than log η = 0.1 poise, preferably 0.2 poise or more. 3. The manufacturing method according to claim 1, in which the pressure is reduced in the gap between the two polymerized tubes. 4. The manufacturing method according to claim 1, wherein vibrations at a frequency of 50 Hz or more are applied to at least one of the polymerized tubes.