JPH06163676A - Wafer boat - Google Patents

Abstract

PURPOSE:To provide excellent strength and the long useful life longevity in comparison with a conventional wafer boat having the equal weight by forming the cross-sectional shape of a supporting member in a substantially triangular shape in the wafer boat having the supporting members for supporting semiconductor wafers. CONSTITUTION:A wafer boat 10 has four rod-shaped supporting members 13. The supporting members 13 are arranged in parallel in the longitudinal direction. The upper and lower end parts of the members are rigidly bonded with an upper plate 11 and a lower plate 12. The cross section of the supporting member 13 has the equilateral triangle shape. The second moment of the area of the triangle is about 1.2 times the second moment of the area of a circle having the same area. The deflecting amount of a beam for (the triangle cross section) is decreased by about 20% in comparison with the circular cross section. The bending strength of the equilateral triangle has the strength of about 1.6 times the strength of the circle. Therefore, the strength is excellent, and the useful life can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer boat provided with a support member for supporting a large number of semiconductor wafers.

[0002]

2. Description of the Related Art A heat treatment process such as oxidation and diffusion in a semiconductor wafer manufacturing process is usually performed using a diffusion furnace. The wafers are loaded on the wafer boat and loaded into and unloaded from the diffusion furnace. There are a horizontal diffusion furnace and a vertical diffusion furnace in the diffusion furnace, and a horizontal wafer boat and a vertical wafer boat are used in accordance with this. The specifications of the wafer boat are determined according to the diffusion furnace.

Wafer boats generally have several rod-shaped support members arranged in parallel. Each supporting member is provided with a large number of grooves, and wafers are loaded in these grooves. In the case of a horizontal boat, the supporting members are arranged in the horizontal direction, and the wafers are loaded in a line in the horizontal direction. In the case of a vertical boat, the supporting members are arranged in the vertical direction, and the wafers are loaded in a line in the vertical direction.
In either case, the wafer is supported by the supporting member.

In recent years, the diameter of wafers has increased, and the diffusion furnace tends to increase in size in order to process a large number of wafers at once. Along with this, wafer boats are also required to be large and have a long service life.

[0005]

Large wafers are heavy and the wafer boat must support such a large load.

In the case of a horizontal boat, the weight of the wafer mainly acts so that the supporting member is bent and deformed. On the other hand, in the vertical boat, the weight of the wafer mainly acts so that the supporting member is buckled and deformed.

In any boat, the strength of the support member affects the life of the boat. Conventionally, a bar member having a circular or rectangular cross section has been used as a supporting member for a wafer boat. In order to increase the strength of the round bar supporting member, the diameter must be increased. However, in that case, the boat itself becomes heavy and inconvenient to handle, and the heat capacity of the boat is large, which is also a negative factor in terms of thermal efficiency. As described above, in the wafer boat using the support member of the round bar, the service life cannot be extended beyond a certain extent.

In view of the above problems of the prior art, it is an object of the present invention to provide a wafer boat which is superior in strength and has a long service life as compared with the conventional wafer boat having the same weight.

[0009]

SUMMARY OF THE INVENTION The present invention is a wafer boat provided with a support member for supporting a large number of semiconductor wafers, wherein the support member has a substantially triangular cross-sectional shape. Is the gist.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a vertical wafer boat according to the present invention. The wafer boat 10 is vertically long,
For example, it is configured to accommodate 125 8-inch Si wafers. The wafer boat 10 is made of high-purity SiC or Si.
Impregnated SiC can be formed as a material.

The wafer boat 10 has four rod-shaped support members 13. The support member 13 is arranged in parallel in the vertical (vertical) direction, and its upper and lower ends are firmly coupled by the upper plate 11 and the lower plate 12. The upper plate 11 and the lower plate 12 are horseshoe-shaped plates.

As shown in FIG. 2, the support member 13 has an equilateral cross section. A large number of grooves 14 are formed in each rod-shaped member,
The groove 14 is arranged so as to face the inside of the wafer boat. The grooves 14 are for accommodating wafers, and are formed at equal intervals on one top of each support member 13. The moment of inertia of area of this triangle is about 1.2 times the moment of inertia of area of a circle of the same area, as will be described later. Note that FIG. 2 shows an example of the dimensions of the support member.

The supporting member shown in FIG. 3 is a conventional example 1 having a rectangular cross section. Also in the case of the support member 23 having a rectangular cross section, one top is arranged so as to face the inside of the wafer boat, and the groove 24 for wafer setting is formed on the top. As will be described later, the geometrical moment of inertia of this rectangle is about 1.1 times the geometrical moment of inertia of a circle of the same area. FIG. 3 also shows an example of the dimensions of the support member.

Next, the horizontal wafer boat will be briefly described. A horizontal wafer boat (not shown) can be configured in the same manner as the vertical wafer boat described above. In the case of a horizontal wafer boat, the rod-shaped members are arranged horizontally (horizontally), and both ends thereof are joined by a frame with legs. Then, if necessary, the legged frame is also arranged in the intermediate portion of the rod-shaped member.

Next, the strength of the horizontal and vertical wafer boats of the present invention will be considered. First, in order to study the strength of a horizontal wafer boat, strength calculation was performed using a simplified model as shown in FIG. Example 1 is a calculation example regarding a beam having an equilateral triangular cross section, which is a model of a horizontal wafer boat having a support member having an equilateral triangular cross section having the dimensions shown in FIG. Conventional Example 1 is also a model corresponding to a support member having a rectangular cross section having the dimensions shown in FIG. Conventional Example 2 is a model of a supporting member having a circular cross section shown in FIG. A groove having a depth of 5 mm is formed in each beam (support member), and the cross-sectional areas of the portions other than the groove are substantially the same.

The calculation conditions are shown below.

L (entire beam): 85.7 cm I (second moment of area) Conventional example 2: 0.125 cm ⁴ Example 1: 0.153 cm ⁴ Conventional example 1: 0.139 cm ⁴ Z (section coefficient) Conventional example 2: 0.201 cm ³ Example 1: 0.319 cm ³ Conventional example 1: 0.232 cm ³ E (modulus of elasticity): 7.78 × 10 ⁵ kg / cm ² Maximum deflection (cm) based on the above conditions. ), Maximum bending moment (kg · cm), maximum bending stress (kg / cm ² ),
The safety factor ratios were calculated and the results are shown in Table 1.

[0019]

[Table 1] Further, the ratio of the amount of bending and the ratio of the safety factor were calculated based on Conventional Example 2 and the results are shown in Table 2.

[0020]

[Table 2] Looking at the above results, the amount of deflection of the beam in Example 1 (triangular cross section) was reduced by about 20% compared to Conventional Example 2 (circular cross section), and that in Conventional Example 1 (rectangular cross section) was reduced by about 10%. I understand. In addition, the bending strength of the beam is that of Example 1 (regular triangle) and that of Conventional Example 2
It was found to be about 1.6 times stronger than the (circular) shape.

Next, in order to study the strength of the vertical wafer boat, strength calculation was performed using a simplified model as shown in FIG. Example 2 is a calculation example regarding a beam having an equilateral triangular section, which is a model of a vertical wafer boat having a support member having an equilateral triangular section having the dimensions shown in FIG. Conventional Example 3 is also a model of a support member having a rectangular cross section, which similarly has the dimensions shown in FIG. Conventional Example 4 is a model of a supporting member having a circular cross section shown in FIG. A groove having a depth of 5 mm is formed in each beam, and the cross-sectional areas of the portions other than the groove are substantially the same. The calculation conditions are shown below.

L (entire beam): 85.7 cm I (second moment of area) Conventional example 4: 0.125 cm ⁴ Example 2: 0.153 cm ⁴ Conventional example 3: 0.139 cm ⁴ E (longitudinal elastic modulus): 7.78 × 10 ⁵ kg / cm ² C (end condition coefficient): 0.25 Based on the above conditions, the buckling load (k
g) was calculated, and the buckling load ratios based on Conventional Example 4 were also found and shown in Table 3.

[0023]

[Table 3] Looking at these results, the buckling load of the beam is about 1.2 times in Example 2 (triangular cross section) and 1.1 times in Conventional Example 3 (rectangular cross section) compared to Conventional Example 4 (circular cross section). It has been found to have strength.

[0024]

In the wafer boat of the present invention, since the supporting member has a substantially triangular cross-sectional shape, the bending amount is reduced in the case of the horizontal boat as compared with the conventional wafer boat having the same weight. The buckling load increases in the case of a vertical boat.
Therefore, the useful life is extended in both horizontal and vertical boats.

The cross-sectional shape is not limited to the equilateral triangular cross-sectional shape of the above embodiment. For example, a triangle other than an equilateral triangle (especially an isosceles triangle is preferable) may be used. The corners of the triangle may be chamfered to some extent. It may be a rounded "Omusubi" shaped triangle.

[Brief description of drawings]

FIG. 1 is a perspective view showing a wafer boat of the present invention.

2 is a cross-sectional view of the support member of FIG.

FIG. 3 is a cross-sectional view showing a conventional example.

FIG. 4 is a cross-sectional view showing a supporting member in a conventional wafer boat.

FIG. 5 is a view showing an assumed model for strength calculation of a support member in a horizontal wafer boat.

FIG. 6 is a diagram showing a buckling load calculation model of a supporting member in a vertical wafer boat.

[Explanation of symbols]

 10 Wafer Boat 11 Upper Plate 12 Lower Plate 13 Supporting Member 14 Groove ◆

Claims (1)

[Claims] 1. A wafer boat provided with a supporting member for supporting a large number of semiconductor wafers, wherein the supporting member has a substantially triangular cross-sectional shape.