JPH05164472A - Expansible fiber insulation material and high air tight insulation material - Google Patents

Abstract

PURPOSE:To enhance a thermal sealing performance by wrapping a core material which uses a heat expansion material made of ceramic fiber and an inorganic heat expansion substance with fabric made of quartz glass fiber of a specific composition. CONSTITUTION:An amorphous short fiber mainly composed of ceramic fiber, such as SiO2-Al2O3 is formed in the shape of a mat with an organic binder. During this formation process, an inorganic expansion material, such as vermiculite is covered in or mixed so as to form a core material. The surface of the core material is covered with a texture or a knitted article made of quartz glass long fiber having a composition of more than 96 mole % of SiO2 and less than 4 mole % of TiO2. Especially preferable is that the quartz glass fiber is made of quartz single fiber having no fine holes. This construction makes it possible to bring the shrinkage percentage of the quartz long fiber to 0 and hence inhibit the generation of local shrinkage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an expansive fibrous heat insulating material,
In particular, the present invention relates to a heat insulating material for various industrial furnaces, a sealing material, or a packing material, and more particularly to a highly airtight heat insulating packing material for a diffusion furnace and a CVD furnace used for manufacturing semiconductors and integrated circuits.

[0002]

2. Description of the Related Art Generally, heat insulating materials, sealing materials or packing materials for industrial furnaces are made of asbestos, glass fibers, wool of ceramic fibers, and further, these short fiber materials are made of heat-resistant glass or ceramic long fibers. Many types of woven or braided type are used. Insulation material consisting of these material configurations,
Further, it is also widely used in diffusion furnaces and CVD furnaces used for manufacturing semiconductors and integrated circuits in the electronics field.

[0003]

However, the conventional heat insulating material or the inorganic fiber material used as a heat insulating material has a difference in heat resistant practical temperature, but when used for a long time, both are fibrous materials themselves. Has a property of being thermally shrunk, so that there is a drawback that the entire heat insulating material is uniformly or locally shrunk, and the originally required thermal seal is significantly impaired.

For the insulation material of the diffusion furnace CVD furnace used for the production of semiconductors and integrated circuits which require particularly severe soaking zone, such dimensional shrinkage is caused by a low dust level (for example, class 100) clean room. , The airflow flowing to a clean room with high dust level (class 1000 or higher, so-called working room) flows into the space between the heating element of the furnace and the furnace core tube such as the diffusion tube, causing cracks in the furnace core tube. It was causing problems such as causing it. From this point of view, as described in Japanese Patent Publication No. 60-43011 (diffusion tube support collar), it is "fitted tightly to the outer periphery of a predetermined diffusion tube and provided on the wall of the furnace. The support collar, which is designed to fit inside the hole, also fits with the outer circumference of the tube and inside the hole in the wall of the furnace for a long time during operation of the furnace, considering the thermal shrinkage of the material. It cannot be said that it keeps keeping.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a core material using at least a part of ceramic fibers and a heat-expandable material made of an inorganic heat-expandable substance. SiO ₂ is 96 mol% or more and Ti
An expansive fibrous heat insulating material, an industrial furnace heat insulating material, especially a semiconductor, characterized by being wrapped with a woven or braided silica glass long fiber having a composition of O ₂ of 4 mol% or less.
The present invention provides a highly airtight insulation for diffusion furnaces and CVD furnaces used in the manufacture of integrated circuits. In particular, the quartz vitreous continuous fibers are preferably composed of quartz vitreous single fibers having no fine pores.

A heat-expandable material comprising a ceramic fiber and an inorganic heat-expandable substance used as a core material in the present invention will be described according to Example 1. In the present invention, the ceramic fiber is, for example, SiO ₂ —Al ₂ O ₃
Is a sheet formed into a mat shape by using an organic binder with an amorphous short fiber as a main component, and an inorganic heat-expandable substance, for example, mica of a type called vermiculite, is formed in the mat in the molding process of the mat. At least a part of the material obtained by dusting or mixing is used as the core material. Such a heat-expandable material is sold under the trademark Intalum (registered trademark) mat and is easily available. The thickness of this mat-like heat-expandable molded product is about 5 m.
m, and in order to obtain further heat insulation, it is advisable to stack a plurality of mat-shaped molded products.

This heat-expandable molded product has a thickness of 600
It has the characteristic that it expands about 3 times when heated at ℃, and it is a heat-resistant heat-insulating material asbestos that has been used in the past, wool of glass fiber, and a short fiber material composed of SiO ₂ -Al ₂ O ₃ (ceramic fiber). ) Mats etc. are 600
There is a big difference compared with the fact that the shrinkage is several percent to several tens percent in the temperature range of ˜1300 ° C. However, when it is desired to adjust the expansion coefficient of the heat insulating material as a whole or to expand only a specific part, the heat-expandable molded product and these general-purpose fibrous heat insulating materials can be used together.

By the way, in the heat insulating material composed of the short fiber material including the heat-expandable molded article described in the present invention, the scattering and the loss of the fibers and the generation of dust are caused,
It is very inconvenient in actual use.

A feature of the present invention is that the expansive substance is used at least in part as a core material, and the surrounding area is covered with SiO ₂ of 9%.
The silica glass long fibers are preferably wrapped with a woven fabric or a braid composed of silica glass long fibers having a composition of 6 mol% or more and TiO ₂ of 4 mol% or less, and particularly preferably the silica glass long fibers have fine pores. It is characterized by being made of non-quartz vitreous monofilament (hereinafter, a woven fabric or a braid that encloses the core material is referred to as an outer skin material).

As the quartz vitreous long fibers, Reached E obtained by immersing E glass fiber in hydrochloric acid and extracting the alkaline earth metal in the glass to increase the apparent SiO ₂ content.
Some are called glass or high siliceous glass fibers. However, this type of fiber (hereinafter, Reached E) has several Å to several tens of Å micropores formed in the traces of the alkaline earth metal extracted by the acid.
When used in a temperature range from around 00 ° C to a higher temperature, there is a drawback that the length shrinks by 7 to 20%, and the same can be said for Reached E woven fabrics and braids.

Therefore, even if the expandable molded article described in the present invention is used as a core material and the periphery thereof is covered with a woven or braided material having such shrinkability, the core material tends to expand. As the surrounding skin material (woven fabric or braid) is about to shrink, the outer skin material may break or the shape of the heat insulating material may be deformed when used in a high temperature range.
Even the phenomenon that heat leaks from the gap created by it occurs, and it does not function as a heat insulating material. Of course, even if heat-resistant short-fiber materials that have been used in the past are used as core materials instead of heat-expandable core materials, they themselves also have heat-shrinkability. It is clear that the deformation and the gap are easily generated.

Therefore, in the present invention, the woven fabric or braid used as the outer cover material is made of quartz vitreous long fibers having a very small shrinkage ratio or having zero or substantially zero shrinkage (zero expansion). The composition for that is 9
6 mol% or more of SiO ₂ and 4 mol% or less of TiO ₂
It is necessary to be.

Quartz glass having a composition of (96 mol%) SiO _2. (4 mol%) TiO ₂ is generally known as zero expansion glass, but in the present invention, TiO 2 exhibiting such expansion characteristics is obtained. _{Even if} the silica glass filaments containing 2 mol% or less of 4 mol% or less and further the woven fabric or the braid thereof are used at a high temperature of 1000 ° C. or more for a long time, they shrink only within 5% in the length direction. It is provided by finding that. It is extremely difficult to produce fused silica long fibers having such a controlled glass composition by the melting method.

In the sol-gel method using metal alkoxide as the main raw material, Si alkoxide and Ti organometallic compound may be prepared.
It is possible as described in 38914. Once a quartz vitreous long fiber having this composition is obtained, thereafter, it can be twisted into a yarn and processed into a woven fabric or a braid as in the case of a normal glass long fiber. Further, the long glass fiber produced by the sol-gel method is composed of a single fiber having substantially no pores.

A procedure for actually forming a heat insulating material using the thermally expandable core material and the silica glass long fibers having a very small shrinkage ratio as described above will be briefly described.

First, a blanket, mat or sheet-shaped core material is cut into a predetermined size. If the desired shape of the heat insulating material as a whole is a donut shape, it is possible to obtain a thickness by cutting and bending a plurality of strips and further stacking them. Also if bowl shape having a dent at the center in the thickness direction, to the outer diameter may be stacked inside diameter different ring-shaped core material in the same, or by laminating plural ones de _Lee disk shape Alternatively, the central portion may be scraped off to have a predetermined size.

However, as a characteristic of the heat-expandable substance, since it expands only in the thickness direction of the mat, when it is cut into a certain shape, in a direction in which airtightness is required as a heat insulating material,
In other words, the mats must be cut out and laminated so that the thickness direction of the mat is aligned with the direction of expansion. Of course, as described above, a mat of glassy short fibers or ceramic fibers may be cut out separately and laminated with this thermally expandable mat to adjust the coefficient of thermal expansion of the whole core material, or used as a heat insulating material. At this time, the heat-expandable mat may be used only on the high temperature side, and the conventional fibrous heat insulating mat may be used on the low temperature side. The point is that such a heat-expandable mat and a general-purpose fibrous heat-insulating mat can be used in combination to freely design the area where the heat-insulating material expands and the expansion rate.

Next, a woven fabric as a skin material or a sleeve-shaped braid which is cut open is cut into a predetermined size. At this time, what is important is to dimension the outer skin material in consideration of the expansion coefficient with respect to the temperature at which the expansive substance used as the core material is used. In addition, the seam allowance due to the sewing process described below must be expected.

As described above, the small size of the core material in the initial state means that in a furnace in the semiconductor field, a hand is placed in a narrow space inside a stainless box called a scavenger provided on the inlet side for inserting a wafer. The work of thrusting and attaching the heat insulating material to the furnace core tube becomes extremely easy. After sizing, the cut woven fabric or braid is then sewn using a yarn made of quartz vitreous long fibers having the same composition as a sewing thread, and a heat insulating material in which the core material is wrapped with an outer covering material is obtained. It's done. At this stage, since the outer skin material covers the expansion amount of the core material, the outer skin material is in a state in which there is a margin in terms of dimensions with respect to the core material.

[0020]

【Example】

[Example 1] mat having a thermal expansion property (Intaramu ® mat thickness 4.9 mm) and SiO ₂ -Al ₂ O
Ceramic fiber mat mainly composed of ₃ (thickness 6m
m) was prepared. In order to form a donut shape having an inner diameter of 270 mm, an outer diameter of 350 mm and a thickness of 60 mm, each mat was cut into strips with a width of 60 mm and laminated as shown in FIG.

That is, (1) in FIG. 1 is a place where each mat is cut into strips, (2) is where it is bent, (3) is an annular product, and (4) is each mat. It shows that the circular objects are laminated. Further, in (4), 1 indicates an interram mat layer, and 2 indicates a ceramic fiber mat layer.

In this embodiment, since the donut-shaped annular object is expanded inward and outward in the radial direction, the thickness direction of the mat is aligned with the radial direction of the annular object. Layers of the innermost cylinder and the outermost cylinder are used as layers of an interram mat, and the layers of ceramic mats are laminated alternately. There are 4 layers of interram mat and 3 layers of ceramic fiber mat, and the laminated thickness is about 38m.
m.

Next, a sleeve-like braid made of quartz glass long fibers containing 99.88 mol% of SiO ₂ containing 0.12 mol% of TiO ₂ was prepared to cover the mixed core material. FIG. 2 shows the shrinkage ratio of this sleeve-like braid with respect to the heat treatment time at 1100 ° C. in the lengthwise direction. For comparison, the thermal shrinkage of the sleeve-like braid made of Reached E fibers described in Comparative Example 1 below is also shown. The sleeve-like braid has an inner diameter of 90 mm and an outer diameter of 92 mm. Then, the ends of the sleeve-like braid were sewn together with a yarn of quartz vitreous long fibers having the same composition while adjusting the shapes so that the final inner diameter was 270 mm, the final outer diameter was 350 mm, and the thickness was 60 mm.

Next, the ring-shaped heat insulating material was attached to both ends of a SiC core tube of a diffusion furnace for a Si wafer for semiconductors operated in a soaking zone of 1200 ° C., and this was installed in a hole in the furnace body. Inserted. At this stage, the inside of the outer skin is not completely filled with the core material, but when the core material expands, the inside of this hole is filled with the heat insulating material without any gap, and moreover, the outer periphery of the furnace core tube is designed to fit tightly without any gap. I am doing it. Furnace 12
When the temperature was raised to 00 ° C, it was 1100 at the position of the heat insulating material.
C., and the core material therein expanded in length by a factor of 1.5 in the radial direction, and the holes provided in the wall inside the furnace body and the outer circumference of the furnace core tube were completely fitted. Operation temperature 1200 in this state
Although it was operated for about 2 years in a thermal cycle of ℃ and standby temperature of 900 ℃, there was no shrinkage of the heat insulating material, it was possible to always maintain a state where an airtight seal was formed, and there was no disturbance in the soaking zone.

[Comparative Example 1] The core material is SiO ₂ --Al ₂ O ₃
Reached E with ceramic fiber mainly composed of
Example 1 except that a sleeve-like braid made of fibers was used and the core material was also cut and laminated so as to have final dimensions in advance.
I made a heat insulating material of a certain shape as well. Reached E used
The heat shrinkability of the fiber sleeve-like braid is shown in FIG. Thus, it can be seen that at 1100 ° C., linear shrinkage of nearly 15% occurs. When the heat insulating material thus obtained was used in the same diffusion furnace as in Example 1, the soaking zone was 12
Approximately one month after starting operation at 00 ° C, a gap of about 3 mm was suddenly created between the hole in the furnace and the outer circumference of the ring-shaped heat insulating material, and the cold air flow in the clean room caused the heater and SiC to flow.
It flowed between the furnace core tubes and cracked in the furnace core tubes.

[Comparative Example 2] The same material as that used in Example 1 was used, and a heat insulating material having a constant shape was prepared by using a braid made of Reached E fiber as a skin material.
However, the linear shrinkage of the Reached E braid reaches 13%, and in consideration of the expansion rate of the core material, the size of the outer skin material is considerably larger than the core material in the initial state. I had to make it. When this heat insulating material was installed in the same diffusion furnace as in Example 1, since the outer skin material was made with a considerable margin at the time of installation, the outer skin material itself could not form a predetermined shape and large pleats were formed. Has been created. When the temperature was raised so that the soaking zone reached 1200 ° C in that state, the core material inside could not expand uniformly, and the creases that had been formed earlier formed a gap between the holes in the wall of the furnace body. As a result, the soaking zone obtained was only half as long as in Example 1.

[0027]

EFFECTS OF THE INVENTION By using a heat insulating material having a constant shape, which is finally sewn with the material composition according to the present invention, it is possible to use it for a long time in various industrial furnaces, in particular, furnaces used for manufacturing semiconductors or integrated circuits. Even when used at high temperature, heat insulation does not deform, break, or create voids with the furnace wall, stable operation is possible with airtightness maintained, and heat insulation that has shrunk or deteriorated is maintained for a short period of time. It will lead to cost reduction without replacement.

[Brief description of drawings]

1 (1) to (4) are explanatory views showing how to make a core material of a heat insulating material of Example 1. FIG.

FIG. 2 is a graph showing the relationship between the heat treatment time at 1100 ° C. and the linear shrinkage of the sleeve-like braid of Example 1.

[Explanation of symbols]

 1 layer of interram mat 2 layer of mat of ceramic fiber

Claims (3)

[Claims] 1. A material comprising at least a part of a ceramic fiber and a heat-expandable material made of an inorganic heat-expandable material as a core material, the core material comprising SiO ₂ of 96 mol% or more and TiO ₂ of 4 or more. An expansive fibrous heat insulating material, characterized in that it is wrapped with a woven or braided silica glass filament having a composition of less than mol%. 2. The expansive fibrous heat insulating material according to claim 1, wherein the quartz vitreous long fibers are composed of single fibers having no fine pores. 3. A diffusion furnace or a CVD used for manufacturing a semiconductor or an integrated circuit comprising the expansive fibrous heat insulating material according to claim 1.
Highly airtight insulation for furnaces.