JP2010283272A - Silicon wafer for heat treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon wafer for heat treatment that simply and inexpensively suppresses the extension of slippage due to a contact with a supporting jig when a wafer is supported by the supporting jig for heat treatment, and to provide a manufacturing method thereof. <P>SOLUTION: In the silicon wafer that is supported by a wafer supporting jig for heat treatment, a groove 11 is formed around a contact portion with a supporting jig for the silicon wafer W so as to suppress the extension of dislocation due to the contact portion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a silicon wafer that is supported by a wafer holding jig and heat-treated in a semiconductor device forming process for forming a semiconductor device on the surface of a silicon wafer.

Silicon wafers produced by slicing silicon single crystals grown mainly by the Czochralski method are used as semiconductor device substrates, but silicon single crystals grown by the Czochralski method are Have a lot of oxygen-induced micro defects.
For this reason, a silicon wafer manufactured from such a silicon single crystal is usually subjected to high-temperature heat treatment in an inert atmosphere or a reducing atmosphere, and by this method, oxygen near the wafer surface is diffused outward. Then, crystal defects due to oxygen are removed, and a device formation region is subjected to defect-free / gettering (DZ-IG; Denuded Zone-Intrinsic Gettering) processing.

However, the outward diffusion of oxygen in the vicinity of the wafer surface by the high-temperature heat treatment as described above can occur not only on the device formation surface but also on the back surface thereof.
In the above-described DZ-IG treatment and the subsequent high-temperature heat treatment, when the wafer back surface and the wafer holding jig whose oxygen concentration has decreased due to the outward diffusion of oxygen come into contact with each other, As a result, slip is likely to occur in the vicinity of the contact portion.

Conventionally, the design rules of semiconductor devices have been relatively loose, and the slight slip that occurs due to the outward diffusion of oxygen as described above has not been a problem.
However, in recent years, stricter design rules have been developed, and even a slight slip as described above has been regarded as a problem as a cause of misalignment in the subsequent lithography process.

In response to this, heat treatment of the wafer is performed by devising the shape of the wafer support surface of the wafer holding jig such as surface roughness and inclination, or by holding the wafer at a specific position and dispersing its own weight. It has been proposed to suppress the occurrence of slip at the time (see, for example, Patent Documents 1 to 3).
In addition, in order to mitigate thermal stress and suppress the movement of dislocations, a method of relaxing a heat treatment sequence and a method of increasing the concentration of a dopant dissolved in a crystal of a silicon wafer have been proposed (for example, patents) Reference 4).
Further, Patent Document 5 describes that an oxide film is formed around or entirely including the edge of the wafer to prevent damage to the silicon crystal in the portion in contact with the wafer support.

Japanese Patent No. 4029611 JP 2008-130838 A JP 2008-98589 A JP 2008-53521 A JP 2002-217205 A

However, although the improvement of the holding jig as described in Patent Documents 1 to 3 is effective for slip suppression, the processing cost of the holding jig is high, and it is difficult to design according to conditions. Had.
On the other hand, the change in the heat treatment sequence as described in Patent Document 4 increases the manufacturing time and increases the manufacturing cost of the wafer.
In addition, increasing the dopant concentration in the silicon crystal improves the effect of suppressing slip elongation, but the resistivity of the wafer required in the semiconductor device manufacturing process is limited depending on various types and applications. there were.

  Further, as described in Patent Document 5, when a silicon wafer on which an oxide film is formed is heat-treated, the surface characteristics of the wafer change due to movement of oxygen in the oxide film or penetration into the silicon crystal. In addition, post-processing for removing the oxide film is necessary, and in this post-processing, the surface of the wafer may be contaminated.

  Therefore, in heat treatment of silicon wafers, there has been a demand for a simple and low-cost means capable of preventing slip extension due to contact stress with the wafer holding jig due to the weight of the wafer.

  The present invention has been made in order to solve the above technical problem. When a heat treatment is performed with a wafer supported on a holding jig, the elongation of slip generated by the contact with the holding jig is simple and low-cost. An object of the present invention is to provide a silicon wafer for heat treatment that can be suppressed by the above.

  The silicon wafer for heat treatment according to the present invention is a silicon wafer that is supported and heat-treated by a wafer holding jig, and the contact portion is formed around the contact portion of the silicon wafer that contacts the holding jig. A groove portion that suppresses the extension of the generated dislocations is formed.

The groove is preferably formed within a range of 2 mm from the outer peripheral edge of the silicon wafer toward the center.
If the groove is formed at such a position, the device formation region of the silicon wafer is not unnecessarily narrowed.

Moreover, it is preferable that the said groove part is formed in the circumferential shape inside the center direction of the said silicon wafer with respect to the said contact part.
With such a shape, it is easy to form a groove, and it is possible to reliably prevent the slip generated by the contact with the wafer holding jig in the outer peripheral portion from extending in the wafer center direction.

Furthermore, the depth of the groove is preferably 1 to 100 μm.
By forming the groove having a depth within the above range, the extension of the slip can be reliably prevented.

When the heat-treating silicon wafer according to the present invention is used, when the heat treatment is performed by supporting the wafer on the holding jig, the holding jig is not formed in a special shape or special heat treatment sequence control is performed. Slip elongation caused by contact with the surface can be suppressed easily and at low cost.
Therefore, according to the present invention, it is possible to ensure a device-forming region of a defect-free layer in the silicon wafer surface after the heat treatment without occurrence of a slip or the like, which can contribute to an improvement in device yield and a reduction in manufacturing cost. .

It is a schematic perspective view of a state in which a silicon wafer is supported on a vertical wafer boat. It is the schematic diagram which showed an example of the back surface of the silicon wafer for heat processing which concerns on this invention. It is the schematic of the state by which the silicon wafer is supported by the susceptor, (a) is a top view, (b) is AA sectional drawing in (a). It is the schematic diagram which showed an example of the back surface of the silicon wafer for heat processing which concerns on this invention. 2 is an observation photograph by an optical microscope in Example 1. FIG. 4 is an observation photograph by an optical microscope in Example 2. FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings.
The silicon wafer for heat treatment according to the present invention is a silicon wafer that is supported and heat-treated by a wafer holding jig, and the contact portion is formed around the contact portion of the silicon wafer that contacts the holding jig. A groove portion that suppresses the extension of the generated dislocations is formed.
Examples of the wafer holding jig include a vertical wafer boat, a horizontal wafer boat, and a ring-shaped susceptor, but the form is not particularly limited. In any case, in the silicon wafer for heat treatment according to the present invention, a groove is formed around the contact portion of the silicon wafer with the holding jig.

  Usually, when a silicon wafer for heat treatment is supported by a vertical wafer boat during heat treatment, it contacts the boat at the outer periphery of the wafer back surface, and when supported by a horizontal wafer boat, it is in a boat shape. Since it is supported so as to lean against the groove, it comes into contact with the boat at the outer peripheral ends of both surfaces of the wafer.

Hereinafter, a case where the silicon wafer for heat treatment is supported by the vertical wafer boat will be described as an example.
FIG. 1 shows a schematic diagram of an example of a vertical wafer boat.
As shown in FIG. 1, the vertical wafer boat 1 generally has a structure in which a plurality of support columns 2 are fixed between a top plate 3 and a bottom plate 4. A large number of slits 2 a are formed in the support column 2. And the wafer W is mounted in the slit 2a of the same height position of each support | pillar 2, and the wafer W is supported horizontally in the state which the back surface of the wafer W and the slit 2a upper surface contacted.

FIG. 2 shows one aspect of the back surface of the silicon wafer for heat treatment according to the present invention when supported by the vertical wafer boat 1 as described above.
The wafer W shown in FIG. 2 has grooves 11 formed at three locations on the outer peripheral portion thereof. These three locations correspond to the positions of the slits 2a of the vertical wafer boat 1, and the groove portions 11 are formed so as to surround the portions in contact with the slits 2a.
By forming such a groove 11, it is possible to prevent the extension of slip generated by the contact with the slit 2 a of the vertical wafer boat 1 at the groove 11 when the silicon wafer W is heat-treated. .
The shape of the groove portion 11 is a curved shape in FIG. 2, but is not particularly limited, and may be various shapes in accordance with the shape of the slit 2a.

Next, the case where the silicon wafer for heat treatment is supported by the susceptor will be described as an example.
FIG. 3 shows a schematic diagram of an example of a susceptor. FIG. 3A is a schematic top view when the wafer W is supported by the susceptor 5, and FIG. 3B is a cross-sectional view taken along the line AA in FIG.
As shown in FIG. 3, the susceptor 5 generally includes a ring-shaped support portion 6 that supports the outer peripheral portion of the back surface of the wafer W, and a through-hole 7 is provided on the inner periphery of the support portion 6. . In FIG. 3, 6 a represents the inner peripheral end of the support portion 6. Then, the wafer W is placed on the support portion 6 of the susceptor 5, and the wafer W is horizontally supported in a state where the back surface of the wafer W and the upper surface of the support portion 6 are in a ring shape.

FIG. 4 shows one aspect of the back surface of the heat-treating silicon wafer according to the present invention when supported by the susceptor 5 as shown in FIG.
The wafer W shown in FIG. 4 has a groove 12 formed on the inner side from the inner peripheral end 6a of the support 6 in contact with the susceptor 5 toward the center of the wafer.
By forming such a groove portion 12, when the silicon wafer W is heat-treated, the slip generated by the contact with the support portion 6 of the susceptor 5 extends in the center direction of the wafer W (device formation region direction). Can be blocked by the groove 12.

In addition, even when the vertical wafer boat 1 shown in FIG. 1 is used, as shown in FIG. 4, the contact portion with the slit 2a is spread over a wide range so as to include the entire outer peripheral portion of the contact portion with the slit 2a. On the other hand, a circumferential groove 12 may be formed inside the silicon wafer in the center direction.
With such a shape, the groove portion 12 can be easily formed, and even if the contact portion with the slit 2a of the vertical wafer boat 1 is displaced due to the rotation of the wafer W, it is generated by the contact. Thus, it is possible to reliably prevent the slip extension.

In addition, the grooves 11 and 12 are formed within a range of 2 mm from the outer peripheral edge of the wafer W toward the center from the viewpoint of preventing the device formation region of the silicon wafer W from being narrowed more than necessary. Is preferred. That is, when using a silicon wafer for heat treatment having a groove 12 as shown in FIG. 4, the ring-shaped groove 12 is inside the center of the silicon wafer with respect to the contact portion with the susceptor 5, And it is preferable to form in the range within 2 mm toward the center from the outer peripheral end of the wafer W.
If the groove is formed at such a position, the extension of the slip generated on the outer periphery of the wafer toward the center of the wafer can be sufficiently suppressed.

The depth of the groove portions 11 and 12 is preferably 1 to 100 μm.
When the depth is less than 1 μm, the groove portion is too shallow to sufficiently suppress the extension of the slip toward the center of the wafer W generated at the outer peripheral portion of the back surface of the wafer.
On the other hand, when the depth of the groove portion exceeds 100 μm, the wafer W may be cracked or chipped in the groove portion.

The heat-treating silicon wafer according to the present invention as described above can be produced by forming a groove at a desired position of a general silicon wafer, and a resist is applied to the silicon wafer other than the portion where the groove is formed. After the application or oxide film is formed, the groove is formed by dry etching or wet etching.
A method of forming a protective film by a resist or an oxide film and performing dry etching or wet etching can be performed by a conventionally performed etching method, and according to such a method, the groove portion as described above can be used. Can be easily formed.
When an oxide film is formed, if the oxide film is not removed even after etching, surface oxygen out-diffusion on the back surface of the wafer W can be prevented, and the occurrence of slip itself can be suppressed.

  The formation of the groove is not limited to the method by etching, but can also be performed by cutting or laser processing. Further, the extension of the slip may be caused by driving a high hardness object around the portion where the groove portions 11 and 12 are formed to form a crack by indentation or forming a groove portion due to mechanical damage. Can be suppressed.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
Example 1
A mirror-polished silicon wafer with a diameter of 300 mm was heat-treated at 1200 ° C. for 1 hour in a hydrogen atmosphere, and then the back surface of the silicon wafer using a micro- Vickers hardness indenter with a pyramid indenter under normal pressure. As a result, an indentation was formed as a slip generation source. At that time, when the periphery of the portion where the indentation was formed was confirmed with an optical microscope, it was confirmed that a crack (groove) was generated.
Thereafter, heat treatment was performed at 850 ° C. for 30 minutes in a nitrogen atmosphere, and the extension of slip dislocation at the portion where the indentation was formed was observed with an optical microscope.
This observation photograph is shown in FIG. In FIG. 5, a portion indicated by α is a portion where an indentation is formed using a quadrangular pyramid indenter, and a region (β) surrounded by a dotted line is a portion where a crack (groove portion) is confirmed by microscopic observation.

  As can be seen from the photomicrograph shown in FIG. 5, the extension of slip dislocation is observed inside the area where the crack is confirmed, but the extension of slip dislocation is observed outside the area where the crack is confirmed. It was.

(Example 2)
A mirror-polished silicon wafer with a diameter of 300 mm was heat-treated at 1200 ° C. for 1 hour in a hydrogen atmosphere, and then the back surface of the silicon wafer using a micro- Vickers hardness indenter with a pyramid indenter under normal pressure. As a result, an indentation was formed as a slip generation source.
Similarly, using a Knoop indenter (elongated rhombus shape) of a micro Vickers hardness measuring device, elongated indentations (grooves) were formed only in a part of the periphery of the indentation.
Thereafter, heat treatment was performed at 850 ° C. for 30 minutes in a nitrogen atmosphere, and the extension of slip dislocation at the portion where the indentation was formed was observed with an optical microscope.
This observation photograph is shown in FIG. In FIG. 6, a portion indicated by α is a portion where an indentation is formed using a quadrangular pyramid indenter, and a portion indicated by γ is a portion where a linear indentation (groove portion) is formed using a Knoop indenter.

  As can be seen from the micrograph shown in FIG. 6, in the downward direction (downward on the paper surface) where the linear indentation is formed by the Knoop indenter, the extension of the slip is suppressed by the indentation by the Knoop indenter. Is recognized. In addition, it was recognized that the slip extended | stretched in the other direction (upper side, right side, left side) of the paper where the impression by the Knoop indenter is not formed.

DESCRIPTION OF SYMBOLS 1 Vertical wafer boat 2 Support | pillar 3 Top plate 4 Bottom plate 5 Susceptor 11, 12 Groove W Silicon wafer

Claims (4)

  A silicon wafer that is supported and heat-treated by a wafer holding jig, and a groove portion that suppresses extension of dislocations caused by the contact portion around the contact portion of the silicon wafer that contacts the holding jig. A silicon wafer for heat treatment characterized by being formed.   2. The silicon wafer for heat treatment according to claim 1, wherein the groove is formed within a range of 2 mm from the outer peripheral edge of the silicon wafer toward the center.   3. The heat treatment silicon wafer according to claim 1, wherein the groove is formed circumferentially inward in the center direction of the silicon wafer with respect to the contact portion.   The silicon wafer for heat treatment according to any one of claims 1 to 3, wherein the groove has a depth of 1 to 100 µm.