WO2005124848A1

WO2005124848A1 - Heat treatment jig and semiconductor wafer heat treatment method

Info

Publication number: WO2005124848A1
Application number: PCT/JP2005/010486
Authority: WO
Inventors: Takeshi Kobayashi
Original assignee: Shin-Etsu Handotai Co., Ltd.
Priority date: 2004-06-21
Filing date: 2005-06-08
Publication date: 2005-12-29
Also published as: JP2006005271A; JP4826070B2

Abstract

A heat treatment jig is provided to be used in heat treatment wherein a wafer-shaped object to be treated is horizontally supported. The heat treatment jig is provided with a supporting part for supporting the object to be treated and a supporting plane of the supporting part is formed in a convex curve. For instance, the jig is an annular susceptor (41) having the supporting part for supporting the object to be treated along the rear plane peripheral part, and heat treatment is performed by supporting a semiconductor wafer (W) by bringing a boundary part of a chamfered part and the rear plane of the wafer (W) into contact with the supporting plane (46) formed in the convex curve. Thus, the heat treatment jig and the semiconductor wafer heat treatment method which can surely prevent not only slip dislocation but also generation of scratches on the rear plane periphery and the chamfered part in heat treatment of a silicon wafer and the like are provided.

Description

Specification

Heat treatment jig and heat treatment method for semiconductor wafer

Technical field

The present invention relates to a jig suitable for heat-treating a wafer to be processed, particularly a silicon wafer, and a method for heat-treating a semiconductor wafer using the jig. Background art

[0002] When a device is manufactured using a wafer cut from a semiconductor ingot such as a silicon single crystal, a number of steps are involved from the processing of the wafer to the process of forming elements. One of those steps is a heat treatment step. This heat treatment process is a very important process performed for the purpose of forming a defect-free layer on the surface of the wafer, gettering, crystallization, oxide film formation, impurity diffusion, and the like.

[0003] In such a heat treatment process for wafers, for example, a diffusion furnace (oxidation / diffusion device) used for oxidation or impurity diffusion requires a large number of wafers W as shown in FIG. A vertical heat treatment furnace 20 that performs heat treatment while being horizontally supported at predetermined intervals is mainly used. The wafer W in the heat treatment furnace 20 can be heated by a heater 24 provided around the reaction chamber 22. During the heat treatment, a gas is introduced into the reaction chamber 22 via a gas introduction pipe 26, flows downward from above and is discharged outside through a gas exhaust pipe 28. The gas used varies depending on the purpose of the heat treatment, but H, N, O, Ar, etc. are mainly used. In the case of impurity diffusion, these gases are impure.

2 2 2

It is also used as a carrier gas for compound gas.

[0004] When heat treatment is performed on the wafer W using the vertical heat treatment furnace 20, a heat treatment jig for supporting the wafer W is used as a heat treatment jig for horizontally setting a large number of wafers W. (Hereinafter, the boat may be referred to as a boat for heat treatment, a vertical boat, or simply a boat.) FIG. 5A schematically shows a general boat 10 for heat treatment. A pair of plate members (top plate 16a, bottom plate 16b) is connected to both ends of four rod-shaped (column-shaped) columns 14. As shown in FIG. 6 (A), each support 14 has a number of slits (grooves) 11 formed therein. The semicircular projections between the slits 11 act as the support portions 12 of the wafer W.

[0005] The boat 10 for heat treatment in which a large number of grooves 11 (support portions 12) are formed in the columns 14 as described above is generally called a short finger type. At the time of heat treatment, as shown in FIG. 5 (B), the periphery of the back surface (lower surface) of the wafer W is horizontally supported at four locations by the support portions 12 formed at the same height of the columns 14. Will be done.

As for the support portion of the boat, for example, there is a boat in which a rectangular support portion 13 is formed on a square pillar 15 as shown in FIG. 6 (B).

[0006] When the peripheral portion of the back surface of the wafer W is supported as described above, the own weight of the wafer W is concentrated on the supporting portion, so that the resulting stress always acts. When this stress exceeds the critical shear stress, dislocations occur in the wafer. This dislocation spreads to a macroscopic size by the action of stress, and becomes a slip dislocation. It is important to prevent the occurrence of slip dislocations, which greatly reduce the quality of wafers.

[0007] However, in general, in a high-temperature atmosphere, slip dislocations are liable to occur significantly in the wafer. In particular, as semiconductor devices become more highly integrated, the diameter of wafers is increasing in order to increase the device yield per wafer. As a result, the self-weight of the wafer becomes larger, and the stress acting on the wafer tends to increase, and slip dislocations are more easily generated in the wafer. Large diameter silicon wafers with a diameter of 200 mm or more, especially 300 mm, have the problem that during heat treatment, the wafers are radiused and stress is concentrated on the back end of the boat support, causing slip dislocation.

[0008] Various heat treatment jigs have been proposed to prevent the occurrence of slip dislocation, and for example, a jig in which a support surface of a support portion of a vertical boat is inclined so as to correspond to a deflection of an aeha is proposed. (See Japanese Patent Application Laid-Open No. 9-251961). When the supporting surface is tilted at a predetermined angle in this manner, the wafer is supported by the chamfered portion, and when the wafer is radiused during the heat treatment, the back surface of the wafer is in surface contact with the supporting surface. The support alleviates stress concentration and suppresses the occurrence of slip dislocations.

[0009] An annular or arcuate susceptor 31 as shown in FIGS. 7A and 7B has also been proposed (see Japanese Patent Application Laid-Open No. 6-260438). By placing such an annular (arc-shaped) susceptor 31 on the support portion of the boat and passing through the susceptor 31, the wafer W can be moved several meters along the rear edge. The entire circumference or a part can be supported with a width of m to several tens of mm. Therefore, since the wafer W is supported by a wider area and the stress is dispersed, the force S can suppress the occurrence of slip dislocation. The susceptor 31 shown in FIG. 7 is provided with an opening (notch portion) 32 so that the transfer machine can pass when transferring the wafer W.

Further, in order to more effectively prevent the occurrence of slip dislocation, a susceptor having a support surface inclined to cope with the deflection of the wafer has been proposed (see Japanese Patent Application Laid-Open No. 9-251961).

[0010] In a boat or a susceptor in which the support surface is inclined to cope with the deflection of the wafer as described above, during heat treatment, the wafer is in contact with the wafer over a wide area even if the wafer is radiused, and the stress is dispersed. The effect of suppressing the occurrence of dislocation is obtained. However, even when the heat treatment was performed using the susceptor having the inclined support surface, a large number of scratches were sometimes generated on the back surface and the chamfered portion of the A eight. Also, since the radius differs depending on the e-ha, it was not possible to identify scratches inside the back surface, scratches on the chamfered portions, or the location of the scratches.

[0011] In recent years, in particular, as semiconductor devices become more highly integrated, importance has been placed on not only slip dislocations but also scratches generated on the back surface of the wafer. This is because when a pin chuck type stepper is used, there is a concern that defocus (poor focus) may occur when a scratch on the back surface of the wafer is placed on the pin of the pin chuck. Therefore, it is important to suppress the occurrence of backside flaws caused by slip dislocations alone, and the occurrence of backside flaws during heat treatment may be a problem in subsequent device processes, even at the periphery of the backside. . Furthermore, it is said that if the chamfered part of the wafer is scratched, the wafer will be cracked in the subsequent device process. Disclosure of the invention

[0012] In view of such problems, the present invention provides a heat treatment method for heat treatment of silicon wafers or the like, which can surely prevent the occurrence of scratches in the peripheral portion of the back surface or chamfered portion that is not caused only by the slip dislocation. An object of the present invention is to provide a jig and a method for heat treating a semiconductor wafer.

[0013] In order to achieve the above object, according to the present invention, a wafer to be processed is horizontally supported. A jig for heat treatment used when heat treatment is performed, wherein the jig has a support portion for supporting the object to be processed, and a support surface of the support portion is formed in a convex curved shape. A heat treatment jig is provided.

[0014] As described above, if the jig for heat treatment is such that the support surface is formed in a convex curved shape, for example, a silicon wafer is formed with a support surface in which the boundary between the chamfered portion and the back surface is always a convex curved surface. It can be supported so as to be in contact, and the occurrence of back surface scratches can be reliably prevented.

[0015] In this case, the convex curved surface of the support surface is inclined downward toward the inside of the jig.

If the convex curved surface of the support surface is inclined downward toward the inside of the jig as described above, the boundary between the chamfered portion and the back surface of the object to be processed is more easily brought into contact with the support surface, and the occurrence of back surface scratches is further reduced. It can be reliably prevented.

[0016] The convex curved surface of the support surface preferably has a constant or variable radius of curvature in the range of 0.5 to 500 mm.

With a convex curved surface having a radius of curvature within this range, slip dislocation due to stress concentration and scratches are more unlikely to occur, and the scratch generation area can be made smaller.

[0017] The heat treatment jig has a top plate, a bottom plate, and a column fixed between the top plate and the bottom plate, and the vertical column for heat treatment has the support portion provided on the column. Alternatively, an arc-shaped or annular susceptor having a supporting portion for supporting the object to be processed along the peripheral edge of the back surface can be used.

Heat treatment jigs of these forms are often used for heat treatment of semiconductor wafers, and if the supporting surface is a convex curved surface as in the present invention, not only slip dislocations but also back surface scratches and scratches at the chamfered portion are generated. It can be suppressed effectively.

Further, according to the present invention, in the method for heat-treating a chamfered semiconductor wafer, the heat treatment jig is used, and a boundary portion between a chamfered portion and a back surface of the semiconductor wafer is the convex curved surface. A method for heat treating a semiconductor wafer, wherein the heat treatment is performed by supporting the wafer so that the wafer is in contact with the support surface formed in a shape.

If the heat treatment of AA8 is performed as described above using the heat treatment jig according to the present invention,

, Even if the wafer is deformed, it is always supported with the boundary part in contact with the support surface. Therefore, it is possible to prevent the occurrence of scratches in the chamfered portion or the back surface scratch, which is a problem in a device process in which a scratch is not deeply formed inside the chamfered portion or the back surface.

In this case, the semiconductor wafer to be subjected to the heat treatment may be a silicon wafer. As the semiconductor wafer, particularly the silicon wafer has a large diameter and a large weight, a slip dislocation, a back surface flaw or the like is generated. It is often a problem that is easy to do. Therefore, when the heat treatment jig of the present invention is used to heat-treat silicon wafers, not only slip dislocations but also back surface scratches and scratches at the chamfered portions can be reliably suppressed, and the yield can be improved. .

[0020] The heat treatment jig according to the present invention supports the object to be processed by the support surface having a convex curved surface, and reliably prevents the back surface scratch that can be formed only by the slip dislocation and the scratch at the chamfered portion. Power S can. Therefore, for example, when heat-treating a silicon wafer having a diameter of 300 mm that has been chamfered, the boundary between the back surface of the wafer and the chamfered portion is formed using an annular susceptor having a support surface formed in a convex curved shape according to the present invention. By supporting, it is possible to prevent the back surface flaw which may cause defocus or the like in the device process, and to suppress the generation of the flaw in the chamfered portion which may cause the crack, and as a result, the yield can be greatly improved. Brief Description of Drawings

FIG. 1 is a schematic front view showing an example of a vertical boat for heat treatment according to the present invention.

FIG. 2 is a schematic view showing an example of an annular susceptor according to the present invention. (A) Perspective view (B) Cross-sectional view

FIG. 3 is an enlarged schematic view of a support portion.

FIG. 4 is a schematic view showing an example of a vertical heat treatment furnace.

FIG. 5 is a schematic view showing an example of a conventional vertical boat for heat treatment. (A) Front view (B) Cross-sectional view in the transverse direction (with the aewa supported)

FIG. 6 is a schematic perspective view showing a wafer support portion in a conventional heat treatment boat. (A) Semi-circular support (B) Rectangular support

FIG. 7 is a schematic view showing an example of a conventional susceptor having an opening. (A) Plan view ( B) Cross-sectional view (with the e-supported)

FIG. 8 is an enlarged schematic view of a support portion of a susceptor whose support surface is inclined.

FIG. 9 is a schematic sectional view showing another example of the annular susceptor according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Prior to the completion of the present invention, the present inventor investigated the causes of scratches on the back surface and chamfered portions of silicon wafers when silicon wafers were heat-treated using boats and susceptors with inclined support surfaces. The following has been found.

First, when the wafer is deformed during heat treatment, as shown in Fig. 8 (A), the back surface 8 of the wafer W repeatedly contacts the tip of the boat support or the inner corner 37 of the annular susceptor 31a. It was found that many rear surface scratches 9 occurred.

Further, since the back surface 8 of the wafer W is in contact with the support surface 36 with a large area, even if the roughness of the support surface 36 of the susceptor 31b is large as shown in FIG. It was found that the back surface flaw 9 was apt to occur due to the minute unevenness of the surface.

[0023] When the wafer A is supported by a boat or the like in which the support surface 36 is inclined such that the supporting surface 36 is inclined, the eaves are deeply scratched on the inside of the rear surface of the wafer due to the radius, inclination, or chamfer shape of the wafer during heat treatment. (See FIG. 8 (A)) or outside (FIG. 8 (B)), and further, as shown in FIG. 8 (C), the chamfered portion 7 is supported by the susceptor 31c to form a flaw 9c. In some cases.

[0024] If the tip of the support portion of the boat or the inner corner 37 of the susceptor is chamfered and rounded, the generation of the back surface flaw 9 caused by the corner 37 can be suppressed. However, since the peripheral portion of the back surface of the device A8 comes in contact with the support surface with a width of several mm, it is impossible to prevent the back surface flaw 9 due to the surface roughness of the support surface.

Also, it is conceivable that the angle of inclination of the support surface is increased so that the chamfered portion 7 is always supported even when the eaves are radiused. As described above, if the chamfered portion 7 is scratched, There is a possibility that particles may be generated.

[0025] Therefore, the present inventor inevitably has a possibility that some scratches may occur at the contact point with the supporting portion (supporting surface) as long as the wafer is supported. Investigations and studies were carried out, considering that scratches should be made at locations where they would not pose a problem. Then, it was found that if control could be performed so that the boundary area between the chamfered portion of the wafer and the back surface would always be in contact, adverse effects such as reduced yield could be minimized in subsequent device processes.

[0026] Based on these findings, the present inventors have further studied diligently. As a result, in the heat treatment jig for horizontally supporting the wafer when heat-treating the wafer, the supporting surface of the supporting portion was changed to a convex curved surface. In this way, it is possible to reliably support the boundary between the chamfered part and the back surface of the aerial wafer, and to control so that even if a flaw occurs, the flaw is located at the position where the problem is least likely to occur. And found that the present invention was completed.

Hereinafter, as a preferred embodiment, a vertical boat for heat treatment and an annular susceptor according to the present invention used for heat treatment of silicon wafers will be specifically described with reference to the accompanying drawings.

FIG. 1 shows an example of a vertical boat for heat treatment according to the present invention. The heat treatment boat 1 has a top plate 2, a bottom plate 3, and four columns 4, and each column 4 is fixed between the top plate 2 and the bottom plate 3. Each pillar 4 is provided with a support portion 5 at a predetermined interval, and a support surface 6 of the support portion 5 is inclined downward toward the inside of the boat 1 and formed in a convex curved shape. .

On the other hand, FIG. 2 shows an example of an annular susceptor according to the present invention, wherein (A) is a perspective view and (B) is a cross-sectional view. The susceptor 41 has a support portion on the upper side, and, like the vertical boat 1, has a support surface 46 which is inclined downward toward the inside of the susceptor 41 and is formed in a convex curved shape.

[0029] In such a vertical boat 1 or the annular susceptor 41, the support surfaces 6, 46 are formed to have a convexly curved surface inclined in a downward direction. Even if it is deformed in any way, the boundary between the chamfered portion and the back surface is always supported so as to be in contact with the support surfaces 6 and 46.

For example, when an annular susceptor 41 is used, as shown in FIG. 3, a boundary portion 47 between the chamfered portion 7 and the back surface 8 of the wafer W comes into contact with a support surface 46 formed in a convex curved shape. It will be supported by the state. As described above, the boundary 47 between the chamfered portion 7 and the back surface 8 is supported. Then, even if the wafer W is elastically deformed during the heat treatment, the corner 37 shown in FIG. 8 does not exist, so that the contact with the corner 37 can be prevented. Further, even if the roughness of the support surface 46 is somewhat rough, the chamfered portion 7 and the back surface 8 of the wafer W do not contact the support surface 46. That is, the wafer always comes into contact with the support surface 46 at the boundary 47 between the chamfered portion 7 and the back surface 8. Therefore, it is possible to reliably prevent the chamfered portion 7 and the back surface 8 of the wafer W from being scratched.

On the other hand, at the boundary 47 between the chamfered portion 7 and the back surface 8 of the wafer W, that is, at the contact point with the support surface 46, a force S that may cause some scratches, Even if the part 47 has some scratches, there is little problem in the subsequent device processing. In some cases, it is conceivable that some scratches may be made within the range of lmm from the boundary part 47, but within this range the problem is small and the influence can be minimized.

The convex curved surface of the support surface may be appropriately set according to the size (diameter) of the wafer to be heat-treated, the shape of the chamfered portion, and the like.

For example, in the case of a silicon wafer, the width of the chamfered portion of the wafer varies slightly depending on the chamfered shape, specifications, etc., but is generally in the range of about 0.3 to 0.4 mm from the outer peripheral end regardless of the diameter of the wafer. It is. Considering the width and shape of the chamfered portion, a convex curved surface of the support surface should be formed so as to support the boundary between the chamfered portion and the back surface of the wafer to be heat-treated. However, if the radius of curvature of the convex surface is less than 0.5 mm, the contact area is too small and stress concentration occurs, which may cause deep scratches and slip dislocations. It is preferably at least 5 mm.

[0033] On the other hand, when the radius of curvature of the convex surface exceeds 500 mm, the stress concentration is further alleviated because the surface becomes relatively gentle, but the contact area becomes large, and there is a possibility that the scratch generation area becomes large. is there. Therefore, if the radius of curvature that defines the curved surface shape of the support surface is set in the range of 0.5 to 500 mm, the generation of scratches can be more effectively suppressed, and the area in which the scratches are generated should be smaller. Power S can.

Note that the radius of curvature of the convex surface is not limited to a constant one, but may be varied within a range of 0.5 to 500 mm.For example, the radius of curvature of the convex surface is closer to the inside of the boat. It is good also as a support surface which becomes smaller continuously.

[0034] Further, it is preferable that the surface roughness of the support surface is as small as possible. If the surface roughness of the support surface is large, point contact may occur between the wafer and the support surface, and stress may be concentrated to cause relatively deep scratches. The jig for heat treatment of the present invention can support the boundary between the chamfered portion and the back surface of the ゥ A8, so that even if a slight scratch is made at this boundary, it does not cause much problem. It is better to avoid deep scratches and scratches as much as possible. Therefore, it is preferable that the surface roughness of the support surface is sufficiently reduced by etching, mirror polishing, or the like to more effectively prevent the occurrence of kisses and the like.

[0035] The material of the heat treatment jig according to the present invention may be appropriately determined according to the material of the object to be processed and the heat treatment conditions. , SiC or Si can effectively prevent contamination during heat treatment

2

. For example, if the heat treatment boat is made of hard high-purity silicon carbide containing almost no metal impurities, the contamination of silicon wafers is prevented, and heat treatment is performed at a high temperature of 1000 ° C or more, especially 1200 ° C or more. There is also an advantage that it is hardly deformed and can be used for a long time. In particular, a material coated with CVD-SiC is preferable because metal contamination generated during the heat treatment can be further reduced.

Note that the support surface of the heat treatment jig according to the present invention does not necessarily need to be inclined downward toward the inside of the jig as long as the support surface is formed in a convex curved shape. For example, a susceptor 51 having a semi-cylindrical cross section as shown in FIG. 9 (A) or a susceptor 61 having a convex curved surface having a large radius of curvature as a whole as shown in FIG. 9 (B) is also acceptable. ,. Each of these susceptors 51 and 61 has a convexly curved support surface 56 and 66, and can be supported in a state where the boundary between the chamfered portion of the wafer W and the back surface is in contact with the support surfaces 56 and 66. it can.

[0037] The shape other than the support surface is not particularly limited. If the susceptor is not limited to a circular shape, it can be passed through a transfer machine when transferring the wafer W onto the susceptor. It may be an arc-shaped susceptor with an opening (notch) formed on the other hand. On the other hand, if the boat is for heat treatment, the number of columns is not limited to four, but can be increased or decreased. That is, the number may be three or less, or five or more. Further, as for the shape of the supporting portion, it is preferable that the supporting column has an annular or arc-shaped supporting portion similar to the susceptor shown in FIG.

Hereinafter, Examples and Comparative Examples of the present invention will be described.

(Example 1)

An annular susceptor having a support surface as shown in FIG. 2 inclined downward toward the inside and formed in a convex curved surface was prepared. This susceptor is made of SiC, and has an outer diameter of 305 mm and an inner diameter of 290 mm. The convex curved surface of the support surface has a radius of curvature of about 10 to 150 mm, and the radius of curvature is reduced inward toward the inside. did.

Such an annular susceptor was set in a short finger type heat treatment boat. Then, the chamfered silicon wafer having a diameter of 300 mm was placed so that the boundary between the chamfered portion and the back surface was in contact with the support surface of the susceptor.

As described above, 30 silicon wafers were supported on the boat for heat treatment via the annular susceptor having a convexly curved support surface, and were loaded into a heat treatment furnace as shown in FIG. Then, a heat treatment was performed in an oven at 1200 ° C. for 1 hour in an argon atmosphere.

After the heat treatment, the boat was unloaded from the heat treatment furnace, and the back surface of the e-wafer after the heat treatment was visually inspected. No slip dislocation was observed in any of the e-inos, and some scratches on the back surface were found. However, this was within the boundary area between the chamfered portion and the back surface, and was not a problem in the subsequent device process.

(Comparative Example)

A silicon wafer was heat-treated under the same heat treatment conditions as in Example 1 using an annular susceptor whose support surface was flat and inclined as shown in FIG. The susceptor used had an outer diameter of 310 mm, an inner diameter of 260 mm, and a tilt angle of the support surface of 2 °.

When the wafers after the heat treatment were similarly inspected, many small back flaws were generated within 20 mm from the outer peripheral edge of all the wafers. Was confirmed.

Note that the present invention is not limited to the above embodiment. The above embodiment is simple The present invention is not limited to those having substantially the same configuration as the technical idea described in the claims of the present invention, and exhibiting the same operation and effect as those described above. Technical scope.

For example, the object to be heat-treated using the heat treatment jig according to the present invention is not limited to a silicon wafer, and can be applied to a case where another semiconductor wafer or the like is heat-treated.

Claims

The scope of the claims

[1] A heat treatment jig used for horizontally supporting an ae-shaped object to be processed and performing heat treatment, the jig having a support portion for supporting the object to be processed, and a support surface of the support portion, A heat treatment jig characterized by being formed in a convex curved shape.

[2] The heat treatment jig according to claim 1, wherein the convex curved surface of the support surface is inclined downward toward the inside of the jig.

[3] The heat treatment jig according to claim 1 or 2, wherein the convex curved surface of the support surface has a constant or varying radius of curvature within a range of 0.5 to 500 mm. Utensils.

[4] The heat treatment jig has a top plate, a bottom plate, and a column fixed between the top plate and the bottom plate, and the vertical column for heat treatment has the support portion provided on the column. The heat treatment jig according to claim 1, wherein the heat treatment jig is characterized in that:

5. The heat treatment jig according to claim 1, wherein the heat treatment jig is an arc-shaped or annular susceptor having a support portion for supporting the object to be processed along a peripheral edge of a back surface. Or the jig for heat treatment according to item 1.

[6] In a method for heat-treating a semiconductor wafer that has been chamfered, the heat treatment jig according to any one of claims 1 to 5 is used, and the chamfered portion and the back surface of the semiconductor wafer are subjected to heat treatment. A heat treatment method for a semiconductor wafer, wherein the heat treatment is performed while supporting the wafer such that a boundary portion is in contact with the support surface formed in a convex curved shape. 7. The heat treatment method for a semiconductor wafer according to claim 6, wherein the semiconductor wafer to be heat-treated is a silicon wafer.