Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1999-06-01
2003-04-15
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C264S339000
Reexamination Certificate
active
06548008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for bending Si material that can produce a high-accuracy bend in a single crystal or polycrystal silicon (hereinafter, referred simply to as “Si material”) without contamination of the Si material. The present invention also relates to a core wire member made of Si material for manufacturing a polycrystal Si.
2. Description of the Related Art
In recent years, silicon (Si) has shown a remarkable growth in demand for a semiconductor material. The physical and electrical characteristics of this material as a semiconductor are noticed. In particular, Si used as a bulk material has been frequently used as a substrate for a DRAM (Direct Random Access Memory) and for an MPU (Micro Processor Unit). In addition, Si material is in great demand for wafers. Recently, wafers are being made in larger diameters. This requires that the Si ingots, from which the wafers are sliced, also has grown proportionately. Si ingots now weigh 200 kg or more. The large size and great weight are producing problems in holding and carrying the Si ingot. More specifically, in order to prevent metal contamination of the Si ingot, Si and other materials are frequently used in handling jigs and other manufacturing tools. However, as the weight and diameter of the Si ingot increase, the difficulty in manufacturing such jigs increases.
One approach to solving this problem is machining the Si ingot itself to make it easier to attach jigs for carrying. However, the brittleness of Si material makes it difficult to machine, and also, post-process washing or the like is required. For this reason, according to the aforesaid course, new problems arise such as higher cost and complication of the manufacturing process.
Moreover, in order to produce functioning semiconductors such as, for example, integrated circuits on a silicon wafer, heat treatment at high temperature and film forming are carried out in batch processing. Conventionally, a wafer holding jig used in this case is mainly quartz. Quartz is not ideal since it has different thermal characteristics from the Si material of the wafer, especially at large diameter. For this reason, a single crystal silicon board has been often used for the holding jig because single crystal silicon has the same characteristic as the wafer. Therefore, single crystal silicon is effective in decreasing contamination of the wafer. However, such a board is manufactured by cutting it from a single crystal silicon ingot. This makes such boards expensive in view of the poor mechanical workability of the material. Thus, there is a need for a method for freely bending these components so as to reduce or eliminate the need for machining.
Si is a very brittle material. For this reason, Si is fractured (destroyed) by impact when a great force is applied thereto at ordinary (room) temperature. Moreover, Si material has high strength at high temperature. For these reasons, it has been considered impossible to carry out plastic forming of Si material. In the case of compressive deformation restraining slip deformation, Si is not deformed until just as it reaches its melting point. At its melting point the material is in a transition state between rigidity and being melted. For this reason, it has been considered impossible to bend Si material.
OBJECTS AND SUMMARY OF THE INVENTION.
It is an object of the present invention to provide a bending method for Si material which overcomes the drawbacks of the prior art.
The inventors have achieved the present invention on the basis of the fact that, when a bending moment is applied to a heated portion of Si material heated to a brittle-ductile transition temperature or above, slip deformation is generated. Such slip deformation makes it possible to bend the Si material without contaminating the Si material.
Briefly stated, the present invention provides a method for bending Si material, which have been considered to be very brittle, and hard to bend. The Si material is heated to at least its brittle-ductile transition temperature. A bending moment is applied to a heated portion of the Si material so that a slip deformation is generated. Whereby it is possible to perform bending, and to greatly improve a degree of freedom from machining the Si material. The Si material has a brittle-ductile transition temperature which transfers from a brittle to a ductile state at its brittle-ductile transition temperature. At the transition temperature or more, the Si material is in a state that a slip can to be generated between its crystals in response to a bending torque applied thereto. Thus, when a bending moment is applied to the heated portion of the Si material which is heated to the transition temperature or more, a slip is generated between lattices or between crystal grains in the heated portion, so that the Si material is deformed.
According to an embodiment of the invention, there is provided a bending method for Si material, comprising the following steps of: heating an Si material to at least a brittle-ductile transition temperature to produce a heated portion, and applying a bending moment to said heated portion to produce a slip deformation in said Si material.
According to a feature of the invention, there is provided apparatus for bending a Si material comprising: a rotatable arm, said rotatable arm being rotatable about an axis, a holding portion effective for clamping said Si material, means for applying a thrust to said Si material toward said rotatable arm, whereby said Si material is urged toward said rotatable arm, and said rotatable arm applies a bending moment to said Si material, means for heating said Si material upstream of said holding portion, and said means for applying a thrust including a fluid cylinder having a substantially constant flow rate of fluid fed thereto.
According to a further feature of the invention, there is provided a core wire member made of Si material comprising: first and second core wire portions extending substantially parallel with each other, a connective portion, a first junction connecting a first end of said first core wire portion to a first end of said connective portion, a second junction connecting a first end of said second core wire portion to a second end of said connective portion, and said first and second junctions being formed by bending.
According to a still further feature of the invention, there is provided apparatus for bending an Si material comprising: first means for applying a bending torque to said Si material, second means for applying a longitudinal force to said Si material toward said first means, means for locally heating said Si material between said first and second means, said second means being responsive to a reduction in temperature of said Si material to slow down an advance of said Si material, and responsive to an increase in temperature of said Si material, whereby negative feedback stabilizes bending of said Si material.
More specifically, according to the present invention, the Si material, which have been considered to be very brittle and hard to bend, is heated to a brittle-ductile transition temperature or above, a bending moment is applied to a heated portion of the Si material to generate a slip deformation. This technique permits bending Si material. Thus, it is possible to manufacture a member made of Si material, which has been conventionally manufactured only by machining. Further, it is possible to manufacture a member having a shape which is hard to be manufactured by machining, and thus, the need for machining the Si material is reduced or eliminated.
Referring to
FIG. 10
, a core wire member made of Si material is treated to deposit a polycrystal Si on its surface. Core wire members are arranged in a bell jar into which a silicon-bearing gas such as monosilane or trichlorosilane is introduced. Polycrystal silicon is grown on a surface of the core wire member while it is heated. This technique has the following draw backs. Conventionally, in a core wire member made o
Furukoshi Takayuki
Kuriyama Kazuya
Darby & Darby
Komatsu Ltd.
Tentoni Leo B.
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