JPH0729798B2 - Method for manufacturing composite quartz glass tube for semiconductor heat treatment - Google Patents

Description

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

[Conventional technology]

Conventionally, core tubes and wafer jigs used in the semiconductor industry are required to have heat resistance such that they are not deformed in a high temperature range of 1,000 to 1,300 ° C., and heat treatment is required in accordance with improvement in integration degree of semiconductors. A slight problem is a slight amount of contamination of wafers by metal impurities, especially alkali metals, in the process.

In order to meet such demands, a composite tube having a laminated structure has been proposed in which natural quartz glass having excellent heat resistance is used as an outer layer and high-purity synthetic quartz glass having a low content of metal impurities is used as an inner layer. A typical manufacturing method thereof is disclosed in, for example, Japanese Patent Application Laid-Open No. 48-92410.

According to the method for producing a laminated quartz glass tube disclosed therein, a quartz glass tube having a laminated structure is formed on the outer surface of a synthetic quartz glass tube by thermally spraying powder of quartz or natural quartz glass. However, this method has the drawback that it is difficult to make the thickness of the natural quartz glass layer to be sprayed uniform and that it is easily deformed by heat because it uses a synthetic quartz glass tube as a substrate. Due to the deterioration of the outer diameter accuracy or the shaft accuracy, the tube may be improperly attached to the furnace body.
In particular, the heat treatment temperature distribution on the wafer surface becomes non-uniform, resulting in a serious problem of heat treatment failure.

In addition, a method of manufacturing a laminated composite tube in which a synthetic quartz glass with a small diameter is inserted inside a natural quartz glass tube and heat-integrated was also proposed. A large number of bubbles remain on the fused surface of the quartz glass tube, and these bubbles expand during use, causing damage to the glass, deformation due to heating during fusion, etc. It is difficult to obtain, and therefore there is a disadvantage in the heat treatment similar to the above, and there is still room for technical improvement.

[Problems 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 preventing property in heat treatment of a semiconductor wafer. Another object of the present invention is to industrially provide a high-quality semiconductor wafer that has been uniformly heat-treated.

[Means for Solving the Problems]

The present inventors have conducted extensive research on effective production of a laminated composite quartz glass tube capable of overcoming the above-mentioned problems, and as a result, have developed a practically highly desirable production method.

That is, the present invention, in the production of a composite quartz glass tube formed by integrating different quartz glass as an inner layer tube and an outer layer tube, a higher viscosity than the inner layer quartz glass tube, preferably, a higher viscosity than log η = 0.1 poise Synthetic quartz glass inner layer tube having a wall thickness of 8 to 40% of the total wall thickness of both tubes is inserted and polymerized into the outer layer quartz glass tube, and the polymerized tube is kept almost horizontal and this is common. While rotating at the same speed around the axis, the external heating zone is moved from one end to the other end, and during the operation, the inner layer tube is kept under pressure and the polymerized both tubes are stretched and integrated. A method of manufacturing a composite quartz glass tube for semiconductor heat treatment is provided.

In the composite quartz glass tube formed by the method of the present invention, the integrated outer layer forming quartz glass tube has a higher viscosity than the inner layer forming quartz glass tube, and the inner layer tube having a low viscosity is relatively thin. There is a technical feature in forming it. Then,
The outer layer tube preferably has a high viscosity that does not substantially undergo thermal deformation particularly in the semiconductor wafer heat treatment temperature range. Such materials are usually provided by natural quartz glass, but modified synthetic quartz glass can also be used. In addition, as the material for the inner layer tube, synthetic quartz glass having the highest possible purity is used. The heat-melting integration of the inner layer tube and the outer layer tube in the present invention is generally easier and more effective as the viscosity difference between the inner layer outer tube and the outer layer quartz glass tube is larger, but the ease of the compounding operation is taken into consideration. If so, the viscosity difference η between the two tubes at a temperature of 1,280 ° C. may be log η = 0.1 poise or more, and more preferably 0.2 poise or more. As described above, the viscosity η represented by log η in the present invention is at a temperature of 1,280 ° C.

In addition, it is important that the wall thickness of the synthetic quartz glass tube for the inner layer is about 8 to 40% of the total wall thickness of both tubes in view of the integration operation and the actual use. It is selected in relation to the difference in viscosity. The ratio of the wall thickness of the inner layer pipe is 10
If it is thinner than 40%, the ability to prevent the contamination of the wafer by alkali metal etc. is greatly reduced, and if it exceeds 40%, it is practically difficult to melt and integrate by the external heating method, and it is easy for the air bubbles to be enclosed and the heat resistance is high. Also decreases, which is not preferable.

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

In the method of the present invention, quartz glass tubes for the outer layer and the inner layer to be melt-integrated in a polymerized state are prepared in advance, the tube for the inner layer is inserted into the tube for the outer layer and polymerized, and this is held horizontally. , Rotate both tubes around their common axis at the same speed. It is important to keep the inside of the inner layer tube in a moderately pressurized state during the heating-melting integration operation. This holding of the pressurized state is usually performed by sealing one end of the inner layer tube and feeding an inert gas, for example, nitrogen gas, through the opening at the other end. For heating, a gas burner or an annular furnace that surrounds the entire circumference of the portion of the polymerization tube is preferably used, and the melting heating area is moved from the sealing end side of the inner layer tube of the polymerization tube to the other end, while the melting portion is It is stretched to prepare a laminated composite tube having a desired outer diameter and wall thickness. The heating area of the burner or the like can be moved by fixing the burner or the like and horizontally moving the polymer tube.

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

The inert gas fed into the inner layer tube is not limited as long as it does not adversely affect the heated quartz glass tube, but it is usually high-purity nitrogen gas, argon gas, or 0.2 μm or more. Compressed air or the like with filtered mist particles is conveniently used.

Further, in the heat-melting integration of the polymerization tube, if the glass tube to be integrated is vibrated at a frequency of 50 Hz or more, fusion between both tubes is promoted, and formation of fine bubbles is effectively eliminated. Therefore, it is extremely effective, and a good composite quartz glass tube without bubbles can be obtained even if the difference in viscosity between the outer layer tube and the inner layer tube is small. This vibration may be applied to both tubes or only one tube, but with a frequency of 50
Satisfactory effects cannot be expected with vibrations below Hz. Furthermore, in melt-drawing integration, when the pressure in the gap between the polymerized tubes is reduced, it is extremely effective because the bubbles remaining on the fusion-bonded surface can be more effectively eliminated.

In addition, the production of the composite quartz glass tube having a laminated structure according to the method of the present invention is not limited to the combination of synthetic quartz glass and heat-resistant quartz glass, but a quartz glass tube that imparts different properties to the inner surface or the outer surface of the quartz tube. It can be widely applied to the production of

The method of the present invention will be described more specifically with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view for explaining an 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 a fixed rotary chuck 1, and the low-viscosity synthetic quartz glass inside the tube B has the same length or a slightly short length integrated with it. The inner layer pipe A is inserted, and the same end is fixed by the decompression chamber / clamp jig 2 to clamp both pipes A and B.
Into the fixed end opening of the inner layer pipe A, a plug 4 attached to the opening of the inner pipe provided with the internal pressurizing nozzle 3 is inserted and fixed. On the other hand, the peripheral edges of the left end openings of the polymerized tubes A and B held horizontally are heat-melted by the moving oxygen-hydrogen gas burner 5 to be melt-sealed and integrated, and this heat-sealed edge is moved separately prepared. The bottom end quartz glass tube 7 of approximately the same diameter fixed on the chuck 6 is closely heat-melted and integrated.

The operation of fusing and unifying the polymerized tubes A and B is performed by the rotation chuck 1 described above.
And the movable chuck 6 are synchronously rotated about a common axis to rotate the polymer tube at a predetermined same 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, for example, about 0.5 kg / cm ² with the atmospheric pressure. The space between the pipes A and B is maintained at a reduced pressure by suctioning with the crank jig 2, and the outer layer pipes B and / or
Alternatively, the inner tube A is vibrated by the vibrating jig 9 at a frequency of 50 Hz or higher. Depending on burner 5, usually from 1,800
The polymerizing tube heated and melted to a temperature of 2,000 ° C. is effectively integrated by pressurization from the inside and depressurizing the gap between the tubes in the heating zone, and preferably, the movable rotary chuck 6 and the burner are opposed to each other at the same time. By moving the tube to the left side and stretching the tube, a composite quartz glass tube 10 having a predetermined diameter and wall thickness, particularly the wall thickness controlled with high accuracy, is formed.

[Action]

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 tube are easily fused and integrated without leaving bubbles on the joint surface, and the wall thickness accuracy is high. A good composite quartz glass tube can be obtained effectively and easily.

〔Example〕

 Next, the present invention will be described in more detail with reference to specific examples.

Manufacture of pipe for inner layer Hydrolyze purified ethyl silicate, gelate and dry by condensation reaction to make a tubular porous gel, heat and sinter the tubular base material, and use so-called sol-gel method Different 4 types of transparent high-purity synthetic quartz glass tubes A1, A2, A3
And A4 were prepared. The viscosity of each glass tube at 1,280 ° C was measured by the invagination method, and the measured values are also shown.

Manufacture of outer layer tube A natural quartz glass tube of various thicknesses is prepared by melting a natural crystal ingot in an induction heating furnace and extruding it into a tube using a molybdenum molding jig by a known electric melting method or direct pulling method.
1, B2, B3 and B4 were produced.

Examples 1 and 2 and Comparative Examples 1 and 2 According to the method shown in the drawings, a combination of the inner layer pipe A1 and the outer layer pipe B1, A2 and B2, A3 and B3, and A4 and B4 are formed. Each polymerization tube was integrated by heat fusion.

Table 1 below shows the results of investigations on the state of bubbles on the fusion surfaces of the inner layer pipe and the 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. .

In the composite tube of A1 and B1 and A2 and B2 in Example 1, no bubbles were present at the fusion boundary surface, and when the cross section of the composite tube of A1 and B1 was observed with a polarization microscope, it was found that there was about 1.5 mm of meat. A uniform inner layer with good thickness accuracy was confirmed.

As can be understood from Table 1 above, when the wall thickness of the inner layer pipe to the total wall thickness of the inner layer pipe and the outer layer pipe exceeds 50%, a large number of bubbles remain on the boundary surface, resulting in variations in wall thickness. Is significantly
Moreover, it is inferior in heat resistance, which is inconvenient. Further, when the wall thickness of the inner layer pipe is about 5%, the variation in the inner layer thickness becomes large, and naturally the effect of preventing metal contamination is impaired, which is not preferable.

It should be noted that the actual condition was neglected, and a tube for outer layer of synthetic quartz glass and a tube for inner layer of natural quartz glass were prepared, and the polymerization tube was similarly heat-melted and integrated. Not only the fusion and integration could not be performed smoothly, but also a large number of large bubbles were present on the fusion surface of the obtained composite pipe. The thickness uniformity of the inner layer of the composite pipe was good, but the variation in the overall wall thickness was large and was poor.

Example 3 According to the soot method, purified silicon tetrachloride is hydrolyzed in an oxygen-hydrogen flame to form a soot body, and the soot body is heated and dehydrated in anhydrous nitrogen gas for a long time and then sintered. Vitrified, outer diameter 100 mm, wall thickness 8 mm, length 2,000 mm, temperature
A transparent high-purity quartz glass tube for the inner layer having a viscosity at 1,280 ° C. of log η = 11.7 poise was manufactured. On the other hand, natural quartz powder is melted and vitrified by an oxygen-hydrogen flame, and the Bernoulli method of manufacturing a quartz glass block produces an outer diameter of 126 mm, a wall thickness of 12 mm,
With a length of 2,000 mm, the viscosity at 1,280 ℃ is log η = 12.0
A transparent outer quartz glass tube for Poise was manufactured.

Both pipes (wall thickness of the inner layer pipe was about 40% of the total) were polymerized, and heat fusion integration was performed in the same manner as in Example 1.

The fused surfaces of the inner and outer layer tubes were substantially free of bubbles, and a composite tube having 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, sintered and vitrified, and had a viscosity log η = 11.6 poise at a temperature of 1,280 ° C., an outer diameter of 126 mm, and a wall thickness of 1
A natural quartz glass tube for outer layer of 7 mm and length of 2,000 mm was made.

On the other hand, the soot body obtained in the same manner by the soot method,
Instead of dehydration treatment in a nitrogen stream, high-concentration hydrogen chloride-ultra-blunting treatment in a chlorine stream, then sintered glass,
The viscosity at a temperature of 280 ° C is substantially the same as that of the outer layer tube.
η = 11.6 Poise, outer diameter 100mm, wall thickness 3mm, length 2.00
A 0 mm transparent ultra-high purity quartz glass tube for the inner layer was manufactured.

Polymerize both pipes (wall thickness of inner layer is 15% of total wall thickness),
In the same manner as in Example 1, heat fusion was integrated. In the obtained composite quartz glass tube, a small group of bubbles was observed on the fused surface, although it was a part.

Example 4 A soot body obtained by the soot method was heated and dehydrated in a nitrogen stream and then sintered and vitrified to have a viscosity at a temperature of 1,280 ° C. of log η = 11.6 poise, an outer diameter of 126 mm, a wall thickness of 17 mm, A transparent high-purity quartz glass tube for outer layer having a length of 2,000 mm 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-chlorine stream instead of dehydration treatment in a nitrogen stream, and then sintered and vitrified at a temperature of 1,280 ° C. A transparent ultra-high-purity quartz glass tube for the inner layer with an outer diameter of 100 mm, a wall thickness of 3 mm, and a length of 2,000 mm, having a viscosity log η = 11.4 poise was manufactured.

Both of these tubes (the inner tube has a wall thickness of 15% of the total wall thickness) were polymerized, and heat fusion integration was performed in the same manner as in Example 1. However, in this operation, the pressure in the gap between both tubes is 0.5 kg /
It was carried out by keeping a reduced pressure of a cm ² lower.

The obtained composite quartz glass tube showed a good laminated structure having uniform inner and outer layers with no variation in the fused surface without bubbles.

Instead of the inner layer tube, the viscosity at a temperature of 1,280 ° C is log
As a result of performing the same composite using an ultra-high-purity quartz glass tube with η = 11.5 poise, some extremely fine bubbles were observed, but no inconvenience in use was observed.

Example 5 The soot body obtained by the soot method was dehydrated in a nitrogen stream, then sintered and vitrified, and had a viscosity log η = 11.6 poise at a temperature of 1,280 ° C., an outer diameter of 126 mm, a wall thickness of 17 mm,
A transparent high-purity quartz glass tube with a length of 2,000 mm was manufactured. On the other hand, similarly, the soot body obtained by the soot method was ultra-purified in a high-concentration hydrogen chloride-chlorine stream without dehydration treatment in a nitrogen stream, then sintered and vitrified, and a viscosity at a temperature of 1,280 ° C log η = 100mm outer diameter with 11.5 poise,
A transparent ultra-high-purity quartz glass tube with a wall thickness of 3 mm and a length of 2,000 mm was manufactured.

Both of these tubes (the wall thickness of the inner layer tube is 15% of the total wall thickness) were polymerized, and heat fusion integration was performed in the same manner as in Example 1. However, in this operation, the pressure in the gap between the two tubes was kept at a reduced pressure of 0.5 kg / cm ² lower than the atmospheric pressure during that time, and vibration of 50 Hz was further applied to the outer layer tube.

The obtained composite quartz glass tube had a good laminated structure having no uniform air bubbles in the fused surface and having uniform inner and outer composite layers with uniform inner and outer composite layers.

Further, in the above-mentioned composite integration operation, in the composite quartz glass tube obtained by applying a vibration of 10 Hz, there was a small amount of spiral fine bubbles that did not cause actual damage.

〔The invention's effect〕

The composite quartz glass tube obtained by the production method of the present invention has heat resistance desirable as a quartz glass member for heat treatment of semiconductor wafers, and has a layer structure excellent in uniformity, and thus can be repeatedly used for a long period of time. During the heat treatment, for example, contamination of the wafer with metals such as alkali metals is effectively prevented, which is industrially desirable, and the composite quartz glass tube obtained by the present invention has various properties other than viscosity. Since it is a composite quartz glass tube that combines different properties, it can be widely applied as a quartz glass member for wafer heat treatment, and its practical value is extremely high.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an implementation state of the method of the present invention. Symbols in the figure: A ... Inner layer tube B ... Outer layer tube 1 ... Fixed rotary chuck 2 ... Decompression chamber and clamp 3 ... Internal pressurizing nozzle 4 ... Stopper 5 ... Gas burner 6 ... Movable chuck 7: Bottomed quartz glass tube 8: Guide rail 9: Vibration jig 10: Composite quartz glass tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Kato, Kawamura, Kanaya, Tamura-cho, Koriyama-shi, Fukushima 88 Shin-Etsu Quartz Co., Ltd. Quartz Technology Laboratory (72) Hiroyuki Nishimura, Kawakubo, Kawamura, Tamura-cho, Koriyama-shi, Fukushima 88 Shin-etsu Quartz Co., Ltd. Quartz Technology Laboratory (56) Reference JP-A-63-185838 (JP, A) JP-B-54-5404 (JP, B2)

Claims (4)

[Claims] 1. In the manufacture of a composite quartz glass tube in which different quartz glasses are integrated as an inner layer tube and an outer layer tube, the meat of both tubes is placed in an outer layer quartz glass tube having a higher viscosity than the inner layer quartz glass tube. Inserting and polymerizing a tube for inner layer of quartz glass having a wall thickness of 8 to 40% of the total thickness, keeping the polymerized tube almost horizontal, and rotating it around a common axis at the same speed, Manufacture of a composite quartz glass tube for heat treatment of a semiconductor, characterized in that an external heating zone is moved toward an end, a pressure inside the tube for an inner layer is maintained during the operation, and both the polymerization tubes are stretched and integrated. Method. 2. The method according to claim 1, wherein the quartz glass tube for the outer layer has a viscosity higher than that of the quartz glass tube for the inner layer by log η = 0.1 poise or more, preferably 0.2 poise or more. 3. The method according to claim 1, wherein the gap between the polymerized tubes is reduced. 4. The manufacturing method according to claim 1, wherein vibration of a frequency of 50 Hz or more is applied to at least one of the polymer tubes.