JP2007036105A - Silicon wafer susceptor - Google Patents

Abstract

The present invention provides a wafer holding member that eliminates the occurrence of protrusions on the back surface of a wafer and prevents slip dislocation.
A susceptor having a structure that is held by a bevel portion of a wafer, and the inclination angle of the holding portion is within a range of X ° -1 to X ° + 1 when the bevel angle of the wafer is X °. Use a ring shape.
[Selection] Figure 1

Description

  The present invention relates to a susceptor on which a silicon wafer is placed when heat-treating the silicon wafer.

In recent years, vertical furnaces are frequently used in heat treatment processes in semiconductor manufacturing processes. This is because in a vertical furnace, silicon wafers (hereinafter also referred to as wafers unless otherwise specified) can be loaded on a boat at equal intervals and processed at the same time, so that production efficiency is high. The wafer holding part of such a vertical boat is designed to hold the wafer back surface, but in order to prevent slip dislocation from occurring due to stress concentration on the wafer back surface, It is devised so as to be held in contact with a wide range (see, for example, Patent Document 1). Another cause of the occurrence of slip is a temperature difference in the wafer surface. As a countermeasure, in order to make the in-plane temperature distribution uniform during heat treatment, the susceptor is inclined and a counterbore part is provided on the susceptor with the same diameter as the wafer, and the back surface of the wafer is placed on the susceptor to minimize the holding area However, this method does not change that the back surface of the wafer is in contact with the susceptor, and the problem of slip dislocation is still not solved (see, for example, Patent Document 2).
JP 2003-173982 A Japanese Utility Model Publication No. 5-29129

  A susceptor is used to prevent the occurrence of slip dislocation when a wafer is heat-treated in a vertical furnace method. However, if the heat treatment is high temperature, the back surface of the wafer is fused at the contact portion with the susceptor and protrusions are formed. May be generated. Since these protrusions adhere to the wafer and are hard and difficult to crush, they remain until the device manufacturing process, and when they are chucked on the stepper in the lithography process, they interfere with the chuck stage and locally deteriorate flatness. This causes a defective device.

  Therefore, a wafer holding member that eliminates the occurrence of protrusions on the back surface of the wafer and prevents slip dislocation is desired.

Please correct this field according to the following claims.

  According to one aspect of the present invention, there is provided a susceptor that is used when a silicon wafer having a bevel angle of X ° of a bevel portion is placed and heat-treated, and a holding portion that holds the silicon wafer at the bevel portion is formed. In addition, a silicon wafer susceptor is provided in which an inclination angle of the holding portion is in a range of X ° -1 ° or more and X ° + 1 ° or less with respect to a horizontal bottom surface of the susceptor.

  The susceptor preferably has a ring shape in which the holding portion and an edge portion connected to the holding portion are formed.

  Moreover, it is preferable that the material is any one selected from silicon, silicon carbide, and quartz.

  According to the present invention, the protrusions generated on the silicon wafer due to the fusion between the silicon wafer and the vertical boat or the susceptor during the heat treatment can be limited to the bevel portion. It is possible to keep good and to avoid the defocus problem in the lithography process of the device.

  In addition, since the silicon wafer can be held on the entire circumference of the bevel portion by making the shape into a ring shape, it is possible to prevent the occurrence of slip dislocation by dispersing the wafer's own weight.

  The detailed configuration of the susceptor for wafers according to the embodiment of the present invention will be described below. First, a heat treatment boat using a susceptor will be described. FIG. 5 shows an example of a vertical boat for semiconductor heat treatment. The boat 1 is made of silicon, silicon carbide or the like, and a round bar or a cross-sectional column 4 is parallel to each other between the circular lower plate 3 as well as the circular upper plate 2 having a larger diameter than the wafer. Four are arranged. Grooves 5 for mounting the wafer 7 horizontally are formed in each support column 4 at regular intervals. A susceptor 6 is detachably fitted in this groove, and a wafer 7 is moved and mounted on the susceptor 6 in the horizontal direction (arrow A direction).

  In order to increase the production efficiency of wafers, it is desirable to use a vertical furnace method for heat treatment. According to an embodiment of the present invention, when a wafer is heat-treated in a vertical furnace method, the wafer is directly mounted on a vertical boat. Since it is mounted via the susceptor, the support mode with respect to the peripheral edge of the wafer is not a dot but a line or a plane, the support area is increased, and the load applied to the support is reduced and dispersed. Therefore, stress concentration caused by the weight of the wafer can be avoided, and the wafer can be prevented from slipping and supported well.

  FIG. 1 shows a susceptor 6 according to an embodiment of the present invention. An X ° inclined portion (inclined surface) 61 is provided on the inner peripheral side of the circumferential edge (rim portion) to form a ring shape. FIG.1 (b) has shown the YY cross section of Fig.1 (a). The inclined surface 61 is in contact with the bevel portion of the silicon wafer. When the bevel angle of the silicon wafer is X °, the inclined angle of the inclined surface 61 is in the range of X ° -1 ° to X ° + 1 °. It is characterized by that. The width of the rim is R, the thickness of the susceptor is t1, the thickness of the inner peripheral end is t2, and the width of the inclined portion is W.

  The material of the susceptor may be silicon, silicon carbide, quartz, etc., but silicon cut from the same single crystal as the semiconductor silicon wafer is desirable. For example, the same synthetic polysilicon as the raw material of the wafer is melted to form a non-doped single crystal ingot by the CZ pulling method. This single crystal is sliced after being block-cut by the same method as the wafer processing. Then, it is finished into a circular plate with a thickness of several mm or less by grinding. The diameter of the plate varies depending on the diameter of the wafer placed as a susceptor and is not limited, but it is better to increase the diameter of the wafer. For example, when producing a susceptor for a Φ200 mm wafer, it is preferably Φ202 to 280 mm, and for a susceptor for a Φ300 mm wafer, preferably Φ302 to 380 mm. In order to make the susceptor 6 from this disc, the inner periphery is removed leaving 5 to 40 mm from the outer peripheral end, and after processing into a ring shape or a semi-ring shape, grinding, etching, and polishing are performed, and the circumference of the circle is set to a predetermined thickness. At the same time, a portion inclined at the same X ° as the bevel angle of the wafer 7 to be placed is formed on the inner peripheral side.

The range of tilt angles X ° -1 ° to X ° + 1 ° is determined based on the results of measuring the length of the generated slip by placing the wafer on several types of susceptors manufactured with different tilt angles and heat-treating them. did. The results are shown in Tables 1 and 2. Table 1 shows the classification and ranking according to the maximum slip length allowed for heat-treated wafers.

A case where no slip occurred was ranked A, and a case where a slip of 30 mm or more was recognized was classified as rank E and classified into five stages. Table 2 shows the relationship between the tilt angle of the susceptor and the maximum slip length generated in the wafer after annealing when a Φ200 mm wafer having a bevel angle X of 22 ° is used as a sample.

   One batch of wafer was placed on each of six types of susceptors with different inclination angles, and five batches of heat treatment were performed. As shown in Table 1, the most developed slip length among the five wafers was ranked. If the inclination angle of the susceptor is X ° -1 ° or more and X ° + 1 ° or less, where the bevel angle is X °, it was A rank or B rank. If it is A rank or B rank, it is a level which can be fully endured for practical use. Further, even when X ° was changed from 22 ° to 17 ° to 27 °, the tendency of the slip generation was the same as in the case of X ° = 22 °.

   2 to 4 show the positional relationship among the vertical boat, susceptor, and wafer installed in the heat treatment furnace during the heat treatment.

  First, FIG. 2 is a view showing a state where the wafer 7 is placed on the susceptor 6. FIG. 3 is an enlarged view of portion A in FIG. 2, and shows a state where the bevel portion of the wafer is supported by the inclined portion of the susceptor. In FIG. 3, 62 is a susceptor circle periphery, 63 is a susceptor backside (angle formed with the backside is X °), 71 is a bevel top, 72 is a beher taper (bevel angle is X °), 73 is a wafer front side, and 74 is a wafer back side.

   FIG. 4 shows a state in which the wafer 7 is placed on and supported by the susceptor 6 and mounted in the boat groove. The susceptor 6 on which the wafer 7 is placed is inserted into the groove portion 5 of the vertical boat 1.

   According to the embodiment of the present invention, the contact angle with the wafer 7 is limited to the bevel portion by setting the inclination angle of the portion where the susceptor 6 supports the wafer 7 within the range of X ° -1 to X ° + 1. (See FIG. 3). As a result, when the wafer 7 is heat-treated, the portion where the protrusion is generated by being fused with the susceptor 6 can be limited to the bevel portion.

  As another embodiment of the present invention, the susceptor 6 has a ring shape. If the shape of the susceptor 6 is a semi-ring shape, the wafer weight is concentrated on the end of the susceptor, so that the frequency of occurrence of slip dislocation increases, and there is a possibility of forming a protrusion on the back surface of the wafer by fusion. Further, if the susceptor is plate-shaped, the wafer is bent at a high temperature and may be fused to the susceptor even if it is other than the bevel portion, so that a protrusion is generated. Therefore, the susceptor is preferably ring-shaped.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited by the following Example.

  An example in which a ring-shaped susceptor for a Φ200 mm wafer is produced from single crystal silicon according to the present invention will be described.

  If the bevel angle X ° of the wafer to be heat-treated is 20 ° ± 1 °, the end face top width is about 0.28mm, and the bevel inclination width is 1 ± 0.1mm, the inclination angle of the susceptor is adjusted to this specification. X is 20 ° ± 1 ° (see FIG. 1). Furthermore, to support the wafer weight, if the rim thickness (t1) is 2 mm, the inner peripheral end face thickness (t2) is 0.5 mm, and the rim width (R) is 15 mm, the slope width is 5.5 mm and the ring The width is 20.5mm.

  A Φ200mm wafer was loaded on a susceptor with such specifications and heat treated by a vertical furnace method. In accordance with the present invention, the inclination angle designed within the range of X ° -1 to X ° + 1 is designated as [A], and the inclination angle designed outside the range of X ° -1 to X ° + 1 is designated as [B]. After loading the wafers on both sides, they were mounted on a vertical boat. As an example, the inclination angle of [A] is 22 °, and the inclination angle of [B] is 20 °. [A] and [B] The five wafer / susceptor pairs were then heat treated in a vertical furnace at 1200 ° C. for 1 hour. Further, five wafers were directly mounted on the same boat and heat-treated to make a comparative example.

  Thereafter, the maximum height of the protrusions generated on the back surface of the wafer was measured with a fine shape measuring device P-15 manufactured by KLA-Tencor. FIG. 6 shows the result of measuring the height of the protrusion. The case where it was directly installed on the boat and the case where it was placed on the susceptor and installed on the boat were compared. Protrusions with a height of 4.2 to 6.4 μm per wafer were confirmed on the backside of the wafer directly mounted on the heat treatment boat. When susceptor [A] or [B] was used, annealing was performed on the backside of the wafer. No protrusions having a height that appears to have occurred in the above were confirmed.

  FIG. 7 shows the results of evaluation of slip dislocations generated by high-temperature heat treatment by X-ray topography (XRT) manufactured by Rigaku Corporation. The case where it was directly installed on the boat and the case where it was placed on the susceptor and installed on the boat were compared. As a result, it was confirmed that the slip length of the five wafers transferred directly to the heat treatment boat was 25 to 33 mm per wafer, but no slip dislocation occurred when the susceptor [A] was applied. However, when the susceptor [B] was applied, the occurrence of slip dislocation could not be completely suppressed although it was lighter than that directly mounted on the heat treatment boat.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. For example, in the above embodiment, the effect of the susceptor of the present invention was confirmed for a φ200 mm wafer, but it goes without saying that if the diameter of the wafer is not more than φ200 mm, at least the same effect as in the case of a φ200 mm wafer can be obtained. Nor. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a figure which shows the external appearance of the susceptor for wafers which concerns on embodiment of this invention. It is a figure which shows the state which mounted the wafer in the susceptor. It is a figure which shows the state in which the bevel part of a wafer is supported by the inclination part of a susceptor. The figure which shows the state where the wafer was supported by the susceptor and mounted in the boat groove It is a figure which shows an example of the vertical boat used when heat-processing a wafer by a vertical furnace system. It is a figure which shows the measurement result of the protrusion height formed in the wafer, when a wafer is mounted in a vertical boat and heat-processed. It is a figure which shows the measurement result of the slip dislocation length formed in the wafer back surface, when a wafer is mounted in a vertical boat and heat-processed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Boat, 6 ... Susceptor, 7 ... Wafer, 61 ... Inclined part (inclined surface), 72 ... Bevel taper part.

Claims (3)

   A susceptor used for placing and heat-treating a silicon wafer having a bevel angle of X °, wherein a holding portion for holding the silicon wafer is formed at the bevel portion, and an inclination angle of the holding portion is A susceptor for a silicon wafer, wherein the susceptor is in a range of X ° -1 ° or more and X ° + 1 ° or less with respect to a horizontal bottom surface of the susceptor.   The susceptor for a silicon wafer according to claim 1, wherein the susceptor for a silicon wafer has a ring shape in which the holding portion and an edge portion continuous to the holding portion are formed.   The susceptor for a silicon wafer according to claim 1, wherein the material is any one selected from silicon, silicon carbide, and quartz.

Images