JP2000021958A - Sic wafer boat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion strength of wafer supporting bars against end plates by installing grooves into which the end parts of the wafer supporting bars are fitted from outside at the outer peripheral parts of a pair of end plates fixing both ends of the wafer supporting bars. SOLUTION: Four wafer supporting bars 3' are provided on the outer peripheral side of a back semicircle between a top plate 1 and a base plate 2 in a vertical SiC wafer boat 5'. The upper/lower ends of the wafer supporting bars 3' are fixed to the lower face of the top plate 1 and the upper face of the base plate 2. A plurality of wafer supporting grooves 4 into which the outer peripheral part of a semiconductor wafer W is inserted are installed in the respective wafer supporting bars 3' at prescribed intervals. Rectangular grooves 11 into which the upper/lower end parts of the wafer supporting bars 3' are engaged from outside are installed at the outer peripheral parts of the back semicircle fixing the upper/lower ends of the wafer supporting bars 3'. The end of the wafer supporting bars 3', which are made into the same rectangular cross sections, are engaged into the grooves 11 and they are adhered through adhesion layers 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SiC wafer boat for supporting a large number of semiconductor wafers when the semiconductor wafers are heat-treated in a heat treatment furnace.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional SiC wafer boat is provided with two slit-shaped annular end plates, namely, a rear semi-circular outer side between a top plate 1 and a bottom plate 2 so as to be bilaterally symmetric. A total of four wafer support rods 3 are arranged two by two, and the upper and lower ends of the wafer support rod 3 are fixed to the top plate 1 and the bottom plate 2. A large number of wafer support grooves 4 for inserting the outer peripheral portion of the semiconductor wafer are provided.

In order to fix the upper and lower ends of the wafer support bar 3 to the top plate 1 and the bottom plate 2 in the SiC wafer boat 5 having the above configuration, as shown in FIG. A counterbore groove 6 and a counterbore groove 7 are provided at required positions on the upper surface of the bottom plate 2, and paste 8 is applied to the counterbore grooves 6 and 7 as an adhesive layer.
7, and a hole 9 having the same cross-sectional shape as the wafer support rod 3 is cut out at a required position on the top plate 1 and the bottom plate 2 as shown in FIG. The upper and lower ends of the wafer support bar 3 were inserted into the hollow 9 through an adhesive layer 10 and bonded.

By the way, as shown in FIG. 4, a spatula is used to apply paste 8 to counterbore grooves 6 and 7,
At that time, it contains air, which forms a void, which is a defect that weakens the strength of the bonded portion. However, when bonding, the wafer supporting rod 3 is pressed against the counterbore grooves 6, 7 of the top plate 1 and the bottom plate 2 with strong force. If this happens, the air inside will be expelled and the void will be eliminated. However, in practice, since the fitting portion was fitted and bonded without applying too much pressure, the above-mentioned defects were frequently generated, and there was frequent occurrence of a problem of breakage during use. Therefore, bonding is performed using a pressure bonding jig that can apply pressure to the bonded portion, but this is still insufficient, and the bonded portion continues to be frequently damaged thereafter. The cause is that even if pressure is applied to the bonding portion by the pressure bonding jig, if four wafer support rods 3 are used, one of the wafer support rods 3 does not necessarily receive a force.
The reason is that the wafer support bar 3 to which the force is applied is not perfect, and some gaps always remain. On the other hand, as shown in FIG. 5, if the upper and lower ends of the wafer support bar 3 are inserted and bonded to the hollow holes 9 of the top plate 1 and the bottom plate 2 with the bonding layer 10 interposed therebetween, no pressure is applied to the bonding surface. Therefore, the above-mentioned adhesion defect is likely to occur.

The above-mentioned SiC wafer boat 5 shown in FIG.
Then, when the semiconductor wafer is supported and subjected to heat treatment, a tensile stress is generated at a bonding portion between the wafer support rod 3 having a small thermal expansion and the top plate 1 and the bottom plate 2 due to variation in thermal expansion of the four wafer support rods 3. . Since SiC is vulnerable to tensile stress, the probability of breakage increases. Further, the SiC wafer boat 5 shown in FIG.
When the semiconductor wafer is heat-treated while supporting it, a shear stress is generated at the bonding portion between the wafer support bar 3 and the top plate 1 and the bottom plate 2 having a small thermal expansion due to the variation in the thermal expansion of the wafer support bar 3. In the case of the same force and cross-sectional area, the generated stress is half the tensile force in the shearing, but the pressure cannot be applied to the bonding surface as described above, so that the bonding defect is easily generated, and as a result, the strength is deteriorated.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a SiC wafer having a structure in which the bonding strength of the wafer support rod to the end plate can be increased, and pressure can be applied to the bonding surface during bonding, so that bonding defects hardly occur. It is intended to provide a boat.

[0007]

According to a first aspect of the present invention, there is provided a SiC wafer boat, comprising: a pair of end plates for fixing both ends of a wafer support rod; A groove is formed in which the wafer support bar is fitted and bonded at both ends. By fitting and bonding in this manner, the stress applied to the bonding portion becomes a shear stress, and a strength twice or more that of the fitting and bonding (tensile stress) is obtained. This is because the shear strength of SiC (ceramics) is more than twice the tensile strength. Therefore, even if there are some defects in the bonding portion, the bonding portion is hardly damaged. In addition, in the fitting bonding, both ends of the wafer support rod are fitted into the groove from the outside and pressed, so that one surface is necessarily crimped.

In the SiC wafer boat according to the present invention, the shape of the groove into which both ends of the wafer support rod are fitted from the outside is formed as a trapezoid, and at least both ends are formed in the same trapezoidal cross section. It is preferable that both ends of the wafer support rod are press-fitted and bonded. The reason is that, at the time of bonding, pressure is applied to each of the three bonding surfaces of the trapezoidal groove and both ends of the wafer support rod,
This is because adhesion defects can hardly occur.

In each of the above-mentioned SiC wafer boats, it is preferable that the substantial bonded area between one end of each wafer support rod and the groove is 250 to 500 mm ² . The reason is that if the area of the substantially bonded portion is less than 250 mm ² , the strength withstanding the shear stress generated at the bonded portion of the wafer supporting rod having a small thermal expansion becomes insufficient due to the variation in the thermal expansion of the wafer supporting rod. , With a substantial bonding area of 500 m
If m ² is exceeded, the thermal expansion of the wafer support bar is suppressed, the shear stress generated at the bonded portion of the wafer support bar increases, and the bonded portion is easily damaged.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a SiC wafer boat according to the present invention will be described with reference to FIG. 1. Reference numeral 1 denotes a slotted annular top plate, and 2 denotes a slotted bottom plate. Have a diameter. A total of four wafer support rods 3 ′ are disposed symmetrically on the outer side of the rear semicircle between the top plate 1 and the bottom plate 2, and two upper and lower ends of the wafer support rod 3 ′ are placed on the top plate 1. And the upper surface of the bottom plate 2. Each of the wafer support rods 3 'is provided with a large number of wafer support grooves 4 for inserting the outer peripheral portion of the semiconductor wafer W indicated by a one-dot chain line at regular intervals. However, this vertical SiC wafer boat 5 '
In the outer periphery of the rear semicircle that fixes the upper and lower ends of each of the wafer support bars 3 ′ of the top plate 1 and the bottom plate 2, there is provided a rectangular groove 11 into which the upper and lower ends of the wafer support bar 3 ′ are fitted from the outside. Both ends of a wafer support rod 3 ′ having at least both ends having the same rectangular cross section are fitted into this rectangular groove 11, and an adhesive layer 12 is formed.
Glued through.

[0011] The SiC of the embodiment configured as described above
When the wafer boat 5 'supports the semiconductor wafer W and heats it in a heat treatment furnace as shown by the dashed line in FIG. 1, the thermal expansion is small due to the variation in the thermal expansion of the four wafer support rods 3'. Top plate 1 and bottom plate 2 of wafer support rod 3 '
A shear stress is generated on the bonding surface between the top plate 1 and the bottom plate 2.
Is fitted and adhered to the rectangular groove 11 from the outer periphery, so that one surface is always pressed and has high strength.

Another embodiment of the SiC wafer boat of the present invention will be described with reference to FIG. In the SiC wafer boat 5 ″ of this embodiment, the rectangular groove 11 into which both ends of the wafer support bar 3 ′ of the above embodiment are fitted from the outside is formed as a trapezoidal groove 13, and at least this trapezoidal groove 13 is formed. Both ends of a wafer support rod 3 ″ having the same trapezoidal cross section at both ends are press-fitted from the outside, and the other components are the same as those in FIG.

The S of another embodiment configured as described above
The iC wafer boat 5 ″ is provided with a trapezoidal groove 13 at a required position on the outer periphery of the rear semicircle of the top plate 1 and the bottom plate 2, and the groove 13 is provided with both ends of the wafer support rod 3 ″ having the same trapezoidal cross section. Since a large pressure is applied to each of the bonding surfaces of both ends of the wafer support rod 3 ″ and the trapezoidal groove 13, the bonding defects are extremely small and the strength is extremely high.

In particular, when the substantially bonded area between one end of the wafer support rods 3 ', 3' and the groove 11 or 13 of the top plate 1 or the bottom plate 2 is 250 to 500 mm ² , the wafer support rod 3 ' , 3 "can withstand the shear stress generated at the bonding portion of the wafer support rods 3 ', 3" having a small thermal expansion, and the SiC wafer boat 5' or 5 "having sufficient strength can be obtained. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of the SiC wafer boat of the present invention and a conventional example will be described. The top plate shown in Table 1 below,
Example 1 shown in FIG. 1, Example 2 shown in FIG. 2, FIG. 4 of shape of bottom plate, top plate, shape of bonding portion of wafer support rod of bottom plate to top plate and bottom plate, shape and size of wafer support rod The SiC wafer boats of Conventional Example 1 shown in FIG. 1 and Conventional Example 2 shown in FIG. 5 were manufactured.

[0016]

[Table 1]

Each of Si in Examples 1 and 2 and Conventional Examples 1 and 2
When the bonded portion of the wafer support bar in the C wafer boat was inspected, the results shown in Table 2 below were obtained. The calculation of the converted strength in Table 2 was calculated by (adhesive area) × (relative strength). As the relative strength, the strength with respect to the shear stress when completely bonded was set to 1. Therefore, in the following case, the relative intensity is as follows. -When completely bonded, the shear stress: 1-When completely bonded, the tensile stress: 1/2-When the bonded portion has a defect, the shear stress: 1/2-When the bonded portion has a defect, Tensile stress: 1/4 For example, in the case of Example 1, the following calculation is performed. (Area completely adhered) × (Complete adhesion, converted strength of shear stress) + (Area of bonded portion having defect) × (Relative strength of defective, shear stress) = 182 × 1 + 190 ×
1/2 = 277 In the case of Conventional Example 1, the calculation was performed separately for a portion that became tensile and a portion that became sheared. (The counterbore depth was assumed to be 1 mm).

[0018]

[Table 2]

As is clear from the results in Table 2 above, the SiC wafer boats of Conventional Examples 1 and 2 have a completely bonded area of zero, whereas the SiC wafer boats of Examples 1 and 2
It can be seen that the wafer boat has a large area of the completely bonded portion. Further, it can be seen that the SiC wafer boats of Conventional Examples 1 and 2 have a large area of a bonded portion having a defect, whereas the SiC wafer boats of Examples 1 and 2 have a very small area of a bonded portion having a defect. Furthermore, the Si of the conventional examples 1 and 2
It can be seen that the strength of the bonded portion is low in the C wafer boat, whereas the strength of the SiC wafer boats in Examples 1 and 2 is high.

However, in the first and second embodiments and the first and second conventional examples,
The SiC wafer boat No. 2 was placed in a furnace set at 600 ° C. at a rate of 250 mm / min, kept for 1 hour, and then repeatedly removed from the furnace at the same rate to conduct an evaluation experiment of adhesive strength. Was. As a result, the SiC wafer boats of Conventional Examples 1 and 2 were 360 times and 950 times respectively.
At this time, the bonded portion was damaged, and the experiment could not be continued. However, any of the SiC wafer boats of Examples 1 and 2 did not cause any problem even if the above operation was repeated 1,800 times. .

The SiC wafer boats 5 ', 5 "of the above-described embodiments and examples are of a vertical type. However, even in the case of a horizontal type, the SiC wafer boats 5', 5" similarly have the least amount of thermal expansion.
Internal stress (shear stress) generated at both ends of the 3 ″ can be reduced, and adhesion defects can be hardly generated in the bonded portion of the wafer support rods 3 ′, 3 ″. Further, in the SiC wafer boats 5 ', 5 "of the embodiment and the example shown in FIGS. 1 and 2, the cross sections are the same over the entire length of the wafer support rods 3', 3", but are fixed to the top plate 1 and the bottom plate 2. Notches 11 and 13 in the outer peripheral portions of the top plate 1 and the bottom plate 2 only at both ends of the wafer support rods 3 'and 3 "
The cross section may be any shape as long as the cross section can be fitted into the device, and the other portions may be circular or square. Further, the notch grooves 11 and 13 in the outer peripheral portions of the top plate 1 and the bottom plate 2 of the SiC wafer boats 5 ′ and 5 ″ of the above-described embodiment and examples are respectively
, But is not limited to this.
In addition, the SiC wafer boats 5 'of the embodiment and the example,
In the case of 5 ″, the top plate 1, the bottom plate 2, the wafer support rods 3 ′, 3 ″ and the like which are made of SiC are not limited to this, but may be Si-impregnated SiC.

[0022]

As can be seen from the above description, the SiC of the present invention
The wafer boat has a high adhesive strength at both ends of the wafer support bar to the pair of end plates, so that it can withstand the shear stress generated at the time of thermal expansion. Excellent durability and long life.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing another embodiment of the SiC wafer boat of the present invention.

FIG. 3 is a perspective view showing a conventional SiC wafer boat.

FIG. 4 is a longitudinal sectional view showing an example of a structure for fixing a wafer support bar to a top plate and a bottom plate at both upper and lower ends of a conventional SiC wafer boat.

FIG. 5 is a longitudinal sectional view showing another example of a structure for fixing a wafer support bar to the top plate and the bottom plate at both upper and lower ends of a conventional SiC wafer boat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Top plate 2 Bottom plate 3 ', 3 "Wafer support bar 5', 5" SiC wafer boat 11 Rectangular groove for fitting both ends of wafer support bar 13 Trapezoidal groove for fitting both ends of wafer support bar

Continued on the front page (72) Inventor Tomohide Otsuka 378 Oguni-machi, Oguni-machi, Nishiokitama-gun, Yamagata F-term in the Oguni Plant of Toshiba Ceramics Co., Ltd. 5F031 BB07 BC01

Claims (3)

[Claims] In a SiC wafer boat, a groove is provided at an outer peripheral portion of a pair of end plates for fixing both ends of a wafer support rod, into which both ends of the wafer support rod are fitted from outside. SiC wafer boat with both ends fitted and bonded. 2. The SiC wafer boat according to claim 1, wherein the shape of the groove into which both ends of the wafer support rod are fitted from the outside is a trapezoid, and at least both ends of the groove are formed in a trapezoidal cross section. A SiC wafer boat formed by press-fitting both ends of a formed wafer support rod. 3. The SiC wafer boat according to claim 1, wherein the substantially bonded area between one end of each wafer support rod and the groove is 250 to 500 mm ² .