JPH0761849B2 - Structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure made of polycrystalline silicon, and particularly to a structure having high purity and mechanical strength required as a jig used when heat treating a semiconductor. Regarding

[Prior art]

From the viewpoint of heat resistance, strength and purity, quartz and silicon carbide have generally been used as the jig for semiconductor heat treatment.

However, structures such as quartz glass heat treatment jigs and transportation jigs may undergo plastic deformation at high temperatures,
Crystallization may occur during long-term use, and the durability is unsatisfactory. Therefore, it has been used by making the structure itself large or by adequately reinforcing it, but there are drawbacks such as its heavy weight making it inconvenient to handle, and complicated structures making it difficult to manufacture. It was

Silicon carbide, which has mechanical strength, is also used, but it is expensive, and it is porous because it is a sintered body itself, and impurities or thin film-forming materials are contained in the pores. Due to the inclusion of parts, it has been difficult to use it as a semiconductor heat treatment jig and a transport heat treatment jig that require high purity. Furthermore, in the case of silicon carbide, improvements have been made such as the method of impregnating silicon and filling the voids to compensate for this drawback, but this is at room temperature →
Since the thermal expansion coefficient of the both is large as the thermal history is repeatedly used from high temperature to room temperature, cracking may occur, which is not sufficient in terms of durability.

[Problems to be solved by the invention]

The present invention has been developed in view of the above problems, a structure having sufficient mechanical strength while maintaining high purity,
In particular, the object is to provide a jig for semiconductor heat treatment.

[Means for solving problems]

The inventors of the present invention are based on the finding that polycrystalline silicon having a specified diameter of crystal grains is extremely excellent in mechanical strength, and is extremely useful as a material for a structure as described above. The present invention provides a structure composed of polycrystalline silicon having crystal grains having a grain size of 50 μm or less. The diameter of the crystal particles in the present invention was determined using a metallurgical microscope.

The polycrystalline silicon referred to in the present invention is a commonly known polycrystalline silicon made up of many crystal grains, each of which is connected through grain boundaries, and the silicon atoms are regularly arranged. It does not include single crystal silicon or amorphous amorphous silicon aligned in the direction. Thus, the polycrystalline silicon used in the structure of the present invention, the maximum diameter of the crystal particles is 50μ or less, preferably 35μ or less, more preferably 20μ or less, to obtain a structure particularly excellent in mechanical strength. Is extremely important for. The specified polycrystalline silicon of the present invention does not have a crystal grain boundary in which the crystal grains include a large number of long and linearly continuous twin boundaries. It is composed of crystal grains that have. Therefore, the polycrystalline silicon used in the present invention has a maximum crystal grain size of 50.
is less than or equal to μ and the maximum length is generally 10
It is preferably not more than double.

In detail, the polycrystalline silicon of the present invention, as the maximum diameter of the crystal particles is reduced to 50μ or less, for example, 900 ~ 1200.
Since the bending strength remarkably increases as a hyperbolic function under a high temperature such as ° C, it is suitable for a structure such as a jig for semiconductor heat treatment. On the other hand, the maximum diameter of crystal particles is 50μ
Larger polycrystalline silicon, or even if the maximum diameter is 50μ or less, the maximum length is greater than 10 times the diameter,
Since the bending strength is smaller than that of quartz glass at high temperature, it is unsuitable as the structure of the present invention. That is, even if the maximum diameter of crystal grains is 50 μm or less, the polycrystalline silicon having long crystal grains and a large number of twin boundaries has a small bending strength at high temperature.

The polycrystalline silicon used in the present invention, in which the maximum diameter and the maximum length of the crystal particles are specified, can be obtained by appropriately selecting the production conditions in a conventionally known production method. For example, in the so-called Siemens method, a core wire is set in a bell jar and generally heated to 900 to 1200 ° C., and a gas phase reaction between trichlorosilane and hydrogen supplied at a predetermined gas concentration and a gas flow rate causes the core wire to be heated. Polycrystalline silicon is deposited and grown very little on the line. In such a production method, by changing the reaction conditions such as the gas concentration, the flow rate, and the reaction temperature, it is possible to increase or decrease the crystal grains of the deposited polycrystalline silicon. Polycrystalline particles of crystalline particles having a specified length can be easily obtained by changing, for example, the reaction temperature among the above-mentioned reaction conditions.

As the structure composed of the specified polycrystalline silicon of the present invention, the polycrystalline silicon is significantly higher in purity than quartz glass, etc., and generally 800 to 1100 as described above.
It is particularly suitable for semiconductor heat treatment jigs because it exhibits high bending strength at high temperatures such as ℃.

By the way, quartz has 15-20 ppm of Al as impurities, and K, Na, Ca, M
Contains 1 to 5 ppm of alkali metals such as g and earth metals, 0.1 to 1 ppm of heavy metals such as Fe, and contains 0.1 to 1 ppm of P and B which are the most disliked electrically active substances for semiconductors. Has been. On the other hand, in the polycrystalline silicon used in the present invention, heavy metals, alkali metals, etc. are 0.01 ppm or less,
B and P are 0.0001 ppm or less. As such a semiconductor heat treatment jig, for example, a wafer boat (or mother boat) used when a semiconductor wafer is placed and subjected to heat treatment in a core tube or a diffusion furnace in which impurity diffusion processing or oxidation processing is performed Further, it is a wafer boat transfer jig for loading and unloading the wafer boat into and out of the process tube. The heat treatment with a wafer board is generally performed at a high temperature of 900 to 1200 ° C,
In the case of quartz, it deforms remarkably at a high temperature such as 1200 ° C and cannot withstand long-term use.

As described above in detail, according to the present invention, a highly reliable structure having high purity and having various effects such as improvement of productivity by solving the problem of strength in a conventionally known material, especially for heat treatment. It is possible to provide a jig.

〔Example〕

Examples will be described below for specifically explaining the present invention, but the present invention is not limited thereto.

Example 1 In the Siemens method, after changing the reaction temperature to obtain polycrystalline silicon (hereinafter also referred to as polycrystalline Si) having different maximum diameters of the crystal particles shown in Table 1,
Three-point bending strength at those temperatures of 900 ° C. was measured.
The maximum length of the crystal particles was 10 times or less than the maximum diameter. In addition, the bending strength test is 4.0 ± width
Create a sample of 0.1 mm, length 40 mm and thickness 3.0 ± 0.1 mm,
It was performed according to JIS R1601-1981.

In addition, the above-mentioned three-point bending strength (Kg / mm ² ) at each temperature shown in Table ² was similarly measured for the polycrystalline silicon having the maximum crystal grain diameters of 10 μ and 50 μ. The results are shown in Table 2.

Further, with respect to the above-mentioned polycrystalline silicon, rigidity and the like (unit: Kg / mm ² ) at high temperature shown in Table 3 were measured. The measurement method was performed according to the measurement of bending strength. The results are shown in Table 3.

From the above results, when the same structure made of polycrystalline silicon and quartz specified by the present invention is manufactured and subjected to a high temperature heat treatment furnace, the structure of polycrystalline silicon is mechanically higher than that of quartz. Heat treatment at 900 to 950 ° C. by using a wafer boat made of the polycrystalline silicon specified in the present invention having the same shape as that of a conventional quartz wafer boat due to its excellent mechanical strength and deformation amount. In comparison with a quartz wafer boat, contact with an adjacent wafer or dropping from the wafer boat is hardly observed in the case of being used for a long time. Further, as a result of repeated use at a temperature of 1200 ° C., the surface of the quartz wafer boat was exfoliated due to crystallization, but almost no abnormalities were observed in the polycrystalline silicon wafer boat of the present invention.

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Claims (3)

[Claims] 1. A structure made of polycrystalline silicon having a maximum crystal grain size of 50 μm or less. 2. The structure according to claim 1, which is a jig for heat treatment of semiconductors or a jig for carrying semiconductors. 3. The structure according to claim 2, wherein the jig for heat treatment of semiconductor is a wafer boat.