JP2000106349A - Wafer supporter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of slip lines and contact scratches which are caused at the time of heat treatment of wafers by a method wherein a support face of a wafer support part of each support lever is formed to be a spherical curved surface having a radius of curvature in a specified range. SOLUTION: A plurality of support levers 2 form a support lever body 20 composed of silicon or silicon carbide, and there is provided a wafer support part 21 of a plurality of stages so as to project inwardly at respective predetermined intervals between both end parts of the support lever body 20. And, the wafer support part 21 is formed with a projected ball-shaped curve face at a center part of an upper face, i.e., a support face 210. This support face 210 is formed as a curved face with a radius of curvature R1 in the inward longitudinal direction, and forms a spherical curved surface with a radius of curvature R2 in a horizontal direction. The radii of curvature R1 and R2 are set in the range of 10 to 100 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer supporting apparatus for supporting a semiconductor wafer during heat treatment.

[0002]

2. Description of the Related Art A semiconductor wafer is subjected to a heat treatment in order to form an oxide film or the like on its surface. When performing this heat treatment, a wafer support device for holding a large number of semiconductor wafers at predetermined intervals is used. This type of wafer support device includes a so-called horizontal type in which a plurality of wafers are arranged substantially vertically and horizontally to support an outer peripheral edge, and a plurality of wafers are arranged in a vertical direction with a plurality of wafers arranged side by side at a plurality of locations. There are generally used two types of so-called vertical type supported by the above. By the way, this type of wafer supporting apparatus has been shifting from a horizontal type to a vertical type in recent years with the downsizing and easy transportation of the heat treatment furnace and the increase in the diameter of the wafer.

[0003] As a vertical type wafer supporting device,
For example, JP-A-5-267202, JP-A-9-28
No. 3455. The wafer support devices disclosed in these publications include a plurality of support rods having a plurality of stages of wafer support portions provided at a predetermined interval, and an upper end of each support rod at a predetermined interval. An upper support member to be attached and a lower support member to attach the lower ends of the support rods at predetermined intervals are provided, and the outer peripheral portion of the wafer is placed on a plurality of wafer support portions provided on each support rod. It is configured as follows.

[0004]

The wafer is supported by the above-mentioned vertical type wafer supporting device, and the 1200 type wafer supporting device is used.
When heat treatment is performed at a high temperature of about ° C, thermal distortion called a slip line a is generated in the wafer W from the supported portion toward the inside as shown in FIG. This slip line cannot be visually confirmed, but can be confirmed by an X-ray photograph. It is considered that the occurrence of such a slip line is caused by the concentration of stress acting on the supported portion of the wafer W. That is, in the wafer support devices disclosed in the above publications, a plurality of wafer support portions provided on a plurality of support rods are formed on a horizontal plane. Therefore, when the wafer placed on the wafer supporting portion is bent due to its own weight and high temperature, the wafer is supported by the inner edge upper edge and the left and right upper edge of the wafer supporting portion. This causes thermal distortion called a slip line. The above-mentioned slip line tends to be larger and larger as the diameter of the wafer becomes as large as 8 inches or 12 inches. This slip line causes a decrease in the reliability of semiconductor products, for example, an increase in leakage current. Further, as described above, the wafer supporting devices disclosed in the above publications support the wafer at the upper edge at the inner end and the upper edges at the left and right ends of the wafer support portion when the wafer is bent due to its own weight and high temperature, so that the wafer is supported. This may cause a contact flaw in the supported portion of the device.

The present invention has been made in view of the above-mentioned circumstances, and a main technical problem thereof is to provide a wafer support device capable of preventing the occurrence of a slip line and the occurrence of a contact flaw at the time of heat treatment of a wafer. Is to do.

[0006]

According to the present invention, there is provided, in accordance with the present invention, a plurality of support rods having a plurality of wafer support portions provided at predetermined intervals. A wafer support device for mounting and supporting an outer peripheral portion of a wafer on a support surface of each wafer support portion of each support rod, wherein the support surface of the wafer support portion has a spherical shape having a radius of curvature of 10 mm to 100 mm. The wafer support device is formed on the curved surface of the above.

The radius of curvature of the support surface is 20 mm to 50 mm.
mm. Further, it is desirable that the surface roughness Ry (Rmax) of the support surface be a mirror surface of 0.5 μm or less. This mirror surface is formed in the center of the support surface in an area having a diameter of 4 mm to 10 mm.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a wafer supporting apparatus according to an embodiment of the present invention;

FIG. 1 is an exploded perspective view showing a part of a wafer supporting apparatus constructed according to the present invention. The illustrated wafer support device includes a plurality of (three in the illustrated embodiment) support rods 2, an upper support member 3, and a lower support member 4. The three support rods 2 are formed of silicon or silicon carbide, and are provided with a plurality of support rod bodies 20 protruding inward at predetermined intervals between both ends of the support rod body 20. Wafer support 21 of a step (125 steps in the illustrated embodiment)
And hooks 2 provided at both ends of the support rod body 20 respectively.
2 and 22. In the illustrated embodiment, arcuate engagement recesses 23, 23 are formed on the inner surface of the support rod body 20 adjacent to the hooks 22, 22, respectively.

[0010] Wafer support 2 constituting the support rod 2
One embodiment will be described with reference to FIGS. The wafer support 21 in the illustrated embodiment includes:
The upper surface, that is, the support surface 210 is formed by a spherical curved surface having a convex central portion. The support surface 210 is formed into a spherical surface having an inward front-rear direction formed on a curved surface having a radius of curvature R1 as shown in FIG. 3 and a left-right direction formed on a curved surface having a radius of curvature R2 as shown in FIG. It is constituted by. If the radius of curvature R1 and the radius of curvature R2 are small, the contact area of the wafer with the supported surface becomes small and the surface pressure increases, so that stress concentration occurs inside the wafer. On the other hand, when the radius of curvature R1 and the radius of curvature R2 are large, the wafer bends due to its own weight and high temperature, so that the supported surface of the wafer comes into contact with the upper edge of the inner end of the wafer support portion 21 and the upper edge of the left and right ends, At the contact portion, stress concentration occurs inside the wafer. According to the experiment of the present inventor, the radius of curvature R1 and the radius of curvature R2 are preferably in a range of 10 mm to 100 mm, more preferably in a range of 20 mm to 50 mm. Also, the support surface 21
0 is an area 2 having a diameter of 4 mm to 10 mm at the center.
11 is buff-polished and mirror-finished. The buffing is performed, for example, in a thickness of 3 to 5 mm and a diameter of 150 m.
It can be easily performed by a buff grinding device in which a buff substrate of about m is mounted on a power tool. The surface roughness Ry (Rmax) of the mirror-finished region 211 is formed to be 0.5 μm or less in the embodiment. If the surface roughness Ry (Rmax) of the support surface 210 is larger than 0.5 μm, the supported surface of the wafer may be in a point contact state, and the surface pressure is increased to cause stress concentration inside the wafer. The mirror-finished region 211 may be the entire support surface 210, but the polishing cost increases. Therefore, the support surface 210 formed in a spherical curved surface having the above-mentioned radius of curvature has a diameter of 4 mm to 10 mm. Is fine.

Next, an example of a method of forming the wafer support 21 having the support surface 210 formed by the spherical curved surface as described above will be described with reference to FIG. In the embodiment shown in FIG. 5, a rectangular parallelepiped raw material 2 a formed of silicon or silicon carbide is ground using an end mill 5. That is, the end mill 5 whose central portion is depressed with the same radius of curvature as the above-mentioned radius of curvature R1 is rotated in the direction shown by the arrow 5a while rotating in the direction shown by the arrow 5b.
By moving the wafer along the same radius of curvature, the support surface 210 of the wafer support 21 can be formed into a spherical curved surface. Therefore, when the radius of curvature R1 of the depression of the end mill 5 and the radius of curvature R2 of the end mill 5 moved in the direction indicated by the arrow 5b are the same, the support surface 210 is formed into a spherical surface.

FIG. 6 shows another embodiment of the support culm 2, in which a wafer support portion 21a is formed separately, while a fitting groove 201 is provided on the inner surface of the support rod body 20, and Groove 2
The support rod 2 is formed by fitting the outer end mounting portion 213 of the wafer support portion 21a to the support rod 2. The upper surface of the wafer support portion 21a, that is, the support surface 210 is formed by a convex spherical curved surface at the center similarly to the above-described embodiment, and is buffed by an area 211 having a diameter of 4 mm to 10 mm at the center. Polished.

Next, with reference to FIGS. 1 and 7 to 9, the upper support member 3 and the lower support member 4 for mounting the three support rods 2 at predetermined positions and the support rods 2 are assembled. I will explain. The upper support member 3 and the lower support member 4 are formed of silicon or silicon carbide, and are provided with three hooks 22 fitted on both ends of the support rod body 20 on the outer peripheral edge side. Stop holes 31 and 41 are provided, and step portions 32 and 42 are formed on the outer surface of the upper surface and the lower surface, respectively, so as to be continuous with the locking holes 31 and 41, respectively. The upper support member 3 and the lower support member 4 are provided with three shaft holes 33 and 43 inside the three locking holes 31 and 41, respectively. These three shaft holes 33 and 4
A cylindrical boss portion 61 formed to protrude from one surface of the stopper piece 6 is rotatably fitted to the stopper piece 4.
The stopper piece 6 and the boss 61 are integrally formed of silicon or silicon carbide.

The above-described support rod 2 is assembled to the upper support member 3 and the lower support member 4 configured as described above. Since the assembling structure is substantially the same in the upper and lower parts, the upper support member 3 and the support rod 2 are assembled. The connection structure with the upper end will be described with reference to FIGS. When assembling the support rods 2, first, the lower end portions of the three support rods 2 are fitted into the corresponding locking holes 41 with respect to the lower support member 4 to be in the upright state, and the support rods 2 in the upright state are set. The upper support member 3 is placed on the upper end, and the support rod 2 is
The upper end of the is fitted. With the upper and lower ends of the support rods 2 fitted into the locking holes 31 and 41 of the upper support member 3 and the lower support member 4 in this manner, the upper and lower ends of each support rod 2 are slightly outwardly directed. When it is moved, the hooks 22 provided at the upper and lower ends of the support rod 2 become stepped portions 32 and 4 formed on the upper support member 3 and the lower support member 4, respectively.
Engage with 2. Then, as shown in FIG. 8, each stopper piece 6 is rotated so that each distal end engaging portion 62 is engaged with the engaged concave portions 24 and 25 provided on the inner surface of the support rod main body 20. As a result, the movement of the support rod body 20 in the inward direction is restricted, and the hook portions 22 and 22 and the step portion 3 are prevented from moving.
The engagement with the wafer supporting devices 2 and 42 is maintained in a stable state, and the assembly of the wafer supporting device is completed as shown in FIG.

In the wafer support device assembled as shown in FIG. 9, wafers W are mounted on the support surfaces 210 of the wafer support portions 21 of the same level provided on the three support rods 2 respectively. Support surface 21 of wafer support 21
0 is formed by a spherical curved surface as described above, and as shown in FIGS. 10 and 11, the wafer W is placed in the mirror-finished region 21 which is the central portion of the support surface 210.
Supported by 1. Therefore, even if the wafer W is bent due to its own weight and high temperature, the supported portion of the wafer W does not contact the upper edge of the inner end of the wafer support portion 21 and the upper edges of the left and right ends. For this reason, it is possible to prevent stress concentration occurring in the supported portion due to contact with the upper edge of the inner end and the upper edges of the left and right ends of the wafer support portion 21, thereby preventing the occurrence of a slip line and the wafer. By contacting the upper edge of the inner end and the upper edges of the left and right ends of the support portion 21, it is possible to prevent the occurrence of contact flaws generated in the supported portion. Also, since the wafer W is supported by the mirror-finished region 211 which is the center of the support surface 210,
There is no possibility that a point contact state occurs due to the large surface roughness of the support surface 210, and therefore, concentration of stress generated inside the wafer due to an increase in surface pressure between the support surface 210 and the supported portion is prevented. be able to.

[0016]

The wafer supporting and setting apparatus according to the present invention is constructed as described above, and has the following effects.

That is, according to the present invention, since the support surface of the wafer support portion is formed as a spherical curved surface having a radius of curvature of 10 mm to 100 mm, the wafer placed on the support surface is under its own weight and high temperature. Therefore, even if the wafer is bent, the supported portion of the wafer does not contact the upper edge of the inner end and the upper edges of the left and right ends of the wafer support portion. Therefore, it is possible to prevent stress concentration occurring in the supported portion due to the wafer contacting the upper edge of the inner end and the upper edge of the left and right ends of the wafer support portion,
The occurrence of a slip line can be prevented. Also,
As described above, the supported portion of the wafer does not contact the upper edge of the inner end of the wafer support portion and the upper edge of the left and right ends,
By contacting the upper edge of the inner end and the upper edges of the left and right ends of the wafer support portion, it is possible to prevent the occurrence of contact flaws generated in the supported portion.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a wafer support device constructed according to the present invention, with a part thereof disassembled.

FIG. 2 is an enlarged perspective view showing a main part of a support rod constituting the wafer support device shown in FIG.

FIG. 3 is an enlarged side view showing a wafer support portion of the support rod shown in FIG. 2;

FIG. 4 is an enlarged front view showing a wafer support portion of the support rod shown in FIG. 2;

FIG. 5 is a perspective view showing an example of a forming method for forming a wafer support portion on a support rod included in a wafer support device configured according to the present invention.

FIG. 6 is an enlarged perspective view of a main part showing another embodiment of a support rod constituting a wafer support device configured according to the present invention.

FIG. 7 is a cross-sectional view of a main part showing a connection structure between a support rod and an upper support member constituting the wafer support device shown in FIG. 1, showing a state before connection.

FIG. 8 is a cross-sectional view of a main part showing a connection structure between a support rod and an upper support member constituting the wafer support device shown in FIG. 1, showing a connection state.

FIG. 9 is a perspective view of the wafer support device shown in FIG.

FIG. 10 is an enlarged side view showing a state where the wafer is placed on a wafer support portion of a support rod included in the wafer support device shown in FIG. 1;

FIG. 11 is an enlarged front view of a main part showing a state where the wafer is placed on a wafer support portion of a support rod constituting the wafer support device shown in FIG. 1;

FIG. 12 is a plan view for explaining a state of a wafer heat-treated by a conventional wafer support device.

[Explanation of symbols]

 2: Support rod 20: Support rod main body 21: Wafer support 210: Support surface 22: Hook 23: Engagement concave 3: Upper support member 31: Locking hole 32: Step 33: Shaft hole 4: Lower support Member 41: Locking hole 42: Step 43: Shaft hole 5: End mill 6: Stopper piece 61: Boss of stopper piece 62: Engagement part of stopper piece

Claims (4)

[Claims] 1. A plurality of support rods each having a plurality of wafer support portions provided at predetermined intervals, and a peripheral surface of the wafer is provided on a support surface of each wafer support portion of each support rod. A wafer support device for mounting and supporting a portion, wherein the support surface of the wafer support portion is formed as a spherical curved surface having a radius of curvature of 10 mm to 100 mm. 2. The support surface has a radius of curvature of 20 mm to 50 mm.
2. The wafer support device according to claim 1, wherein the distance is in mm. 3. The wafer support device according to claim 1, wherein the support surface is formed as a mirror surface having a surface roughness Ry (Rmax) of 0.5 μm or less. 4. The mirror surface has a diameter of 4 mm at the center of the support surface.
4. The wafer support device according to claim 3, wherein the wafer support device is formed in an area of 10 to 10 mm.