JP5470769B2 - Heat treatment method for silicon wafer - Google Patents

Description

  The present invention relates to a heat treatment method for a silicon wafer obtained by slicing a silicon single crystal ingot pulled up by the Czochralski method (hereinafter referred to as CZ method). More specifically, the present invention relates to a silicon wafer heat treatment method capable of preventing or reducing the occurrence of slip dislocation during heat treatment.

  Advances in the technology of semiconductor integrated circuits (LSIs) that play a central role in the development of electronic and communication devices in recent years have greatly contributed. In general, for the manufacture of semiconductor devices such as LSI, silicon wafers formed by slicing, chamfering, etc. on a wafer obtained by slicing a silicon single crystal ingot pulled up by the CZ method are used. .

  In such a device manufacturing process using a silicon wafer or a processing process of the silicon wafer itself, for example, heat treatment may be performed for the purpose of controlling the concentration distribution of oxygen precipitates contained in the wafer. Conventionally, batch-type heat treatment methods have been adopted for heat treatment, but lamp annealing methods using RTA (Rapid Thermal Annealing) equipment, which can complete heat treatment of semiconductor substrates in a shorter time, have become widespread. It's getting on. In the lamp annealing method, the temperature can be raised to a predetermined temperature at a very high speed, and can be rapidly cooled from that temperature, so that the silicon wafer can be heat-treated in a very short time.

  A conventional problem in the heat treatment process of a silicon wafer is that when heat treatment is performed at a high temperature of 1000 ° C. or higher, defects called slip dislocations are generated on the wafer surface. When such slip dislocation occurs, not only the mechanical strength of the wafer decreases but also the device characteristics are adversely affected.

  The occurrence of slip dislocation is considered to be mainly caused by the stress due to its own weight applied to the contact point between the support pins supporting the silicon wafer and the wafer and the thermal stress due to the temperature distribution during the heat treatment. As the diameter increases, the stress due to the weight of the wafer also increases, and therefore slip dislocation tends to occur more easily.

In order to solve the above problems at the time of heat treatment, in a semiconductor wafer manufacturing method including a step of heat-treating a semiconductor wafer at a predetermined temperature by an RTA apparatus, at least a contact portion of the semiconductor wafer with a support jig for supporting the semiconductor wafer A method for manufacturing a semiconductor wafer is disclosed, in which heat treatment is performed in a state in which the temperature is controlled to be 3 to 20 ° C. lower than the temperature at the center of the semiconductor wafer (see, for example, Patent Document 1). .)
JP 2002-164300 A (Claim 1)

  However, in the invention described in Patent Document 1, when heat treatment is performed at a high temperature exceeding 1200 ° C., there is a problem that slip dislocation from the support position by the wafer support jig occurs.

  An object of the present invention is to provide a silicon wafer heat treatment method capable of preventing or reducing the occurrence of slip dislocation from the wafer support position when the silicon wafer is heat treated.

The invention according to claim 1 is a silicon wafer heat treatment method in which a silicon wafer obtained by slicing a silicon single crystal ingot is subjected to heat treatment at a predetermined temperature with rapid temperature rise and fall, wherein the predetermined temperature is 1100 to 1250 ° C. In the heat treatment, the outer periphery of the silicon wafer in the range of 0 to 30 mm in the center direction of the wafer from the outer peripheral edge of the wafer is horizontally supported by three support pins arranged at intervals of 120 degrees in a top view. performed Te, wherein as the temperature of the outer peripheral portion of the silicon wafer increases 1 to 6 ° C. than the temperature of the central portion of the silicon wafer, heat treatment is performed while controlling the temperature distribution within the silicon wafer surface, The temperature difference between the support position of the support pin and its peripheral part due to heat radiation from the support pin is reduced, and It is a heat treatment method for a silicon wafer, comprising a thermal stress acting in the lateral direction of the silicon wafer is reduced to prevent or reduce the occurrence of slip dislocations from the supporting position by the supporting pins of the silicon wafer.

The invention according to claim 2 is the invention according to claim 1, wherein the silicon wafer has a diameter of 300 mm, and the temperature of the outer peripheral portion of the silicon wafer is 3 to 3 times higher than the temperature of the central portion of the silicon wafer. This is a heat treatment method of a silicon wafer that is heat- treated so as to increase the temperature by 4 ° C.

  According to the present invention, by performing heat treatment while controlling the temperature distribution in the silicon wafer surface so that the temperature of the outer peripheral portion of the silicon wafer is 1 to 6 ° C. higher than the temperature of the central portion of the silicon wafer, Since the thermal stress due to the temperature distribution applied to the contact point between the support pins supporting the wafer and the wafer can be reduced, the occurrence of slip dislocation from the support position of the wafer can be prevented or reduced.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
The present invention relates to a heat treatment method for a silicon wafer in which a silicon wafer obtained by slicing a silicon single crystal ingot is subjected to heat treatment at a predetermined temperature accompanied by rapid temperature rise and fall. Here, the heat treatment with rapid temperature increase / decrease specifically includes a temperature rising rate or a temperature decreasing rate of 10 to 250 ° C./second, preferably 30 to 150 ° C./second, more preferably 50 to 70 ° C./second. It refers to heat treatment with rapid heating or rapid cooling. Predetermined temperature refers to a 1100 to 1250 ° C..

And the characteristic structure of the heat treatment method of the silicon wafer of the present invention is that the predetermined temperature is 1100 to 1250 ° C., and the heat treatment is performed in the range from 0 to 30 mm in the wafer center direction from the outer periphery of the wafer. part of the carried out supported horizontally by three support pins arranged in 120 degree intervals in a top view, 1 to 6 ° C. than the temperature of the center portion of the temperature silicon wafer outer peripheral portion of the silicon wafer, preferably 3 It is performed while controlling the temperature distribution in the surface of the silicon wafer so as to be higher by ˜4 ° C. It refers to c Eha center range from the center of the silicon wafer 0~30mm the wafer outer peripheral direction and at this time. Thereby, the occurrence of slip dislocation from the wafer support position can be prevented or reduced, but the technical reason is assumed to be as follows.

  In an RTA apparatus that heat-treats a silicon wafer, the heat treatment is generally performed by horizontally supporting the outer peripheral portion of the silicon wafer with three support pins. FIG. 1 is a diagram for explaining the principle that slip dislocation occurs in a silicon wafer during heat treatment. FIG. 1A is an explanatory diagram when the temperature of the outer peripheral portion of the silicon wafer 40 is higher than the temperature of the central portion, and FIG. 1B conversely, the temperature of the outer peripheral portion of the silicon wafer 40 is centered. It is explanatory drawing when it is lower than the temperature of a part. As shown in FIGS. 1A and 1B, the silicon wafer is supported by the support pins 41 at the outer periphery as shown in FIGS. 1A and 1B. This support position tends to have a lower temperature than its periphery. As for the temperature difference between the support position by the support pin 41 and its peripheral portion, the heat radiation from the support pin increases as the heat treatment temperature increases, and the heat is more likely to escape. The stress 42 due to the weight of the silicon wafer 40 works at the position where the silicon wafer is supported by the support pins 41. However, if there is a large temperature difference between the position supported by the support pins 41 and the peripheral portion thereof, the stress is laterally increased. It is considered that the working thermal stress 43 is increased and the occurrence of slip dislocation is promoted. Therefore, by controlling the temperature of the outer peripheral portion of the silicon wafer to be 1 to 6 ° C. higher than the temperature of the central portion of the silicon wafer and performing heat treatment, the temperature difference between the support position by the support pins 41 and the peripheral portion thereof is increased. It is possible to reduce the thermal stress 43 acting in the lateral direction at the support position. Thus, it is presumed that the occurrence of slip dislocation from the support position by the support pins 41 of the wafer can be prevented or reduced.

  The heat treatment apparatus for carrying out the heat treatment method of the present invention is not particularly limited as long as the above temperature distribution can be controlled. For example, a single wafer RTA apparatus (Mattson 3000 Mattson) is preferably used. FIG. 2 is a schematic cross-sectional view of the RTA apparatus. The RTA apparatus 10 has a chamber 12 made of quartz for performing heat treatment of the silicon wafer 11. A wafer tray 13 is installed in the chamber 12, and a base plate 14 is placed on the wafer tray 13. Three support pins 15 are erected on the base plate 14. The three support pins 15 are arranged at intervals of 120 degrees in a top view in order to support a circular wafer. Further, a plurality of heating lamps 16 are disposed outside the chamber 12. The heating lamp 16 is a halogen lamp, and the output of each heating lamp 16 can be controlled independently. That is, the control of the temperature distribution in the wafer surface is performed by adjusting the output of each heating lamp 16. The chamber 12 is provided with a gas introduction port 17 and a gas exhaust port 18 for injecting an inert gas, a reaction gas, and the like, and an opening 19 for conveying the silicon wafer 11. The opening 19 is covered with an auto shutter (not shown) after the silicon wafer 11 is transferred into the chamber 12. A pyrometer 20 capable of measuring the temperature of the silicon wafer 11 is disposed outside the chamber 12.

  In the heat treatment using this RTA apparatus, first, the silicon wafer 11 is carried into the chamber 12 through the opening 19, placed on the three support pins 15, placed in the chamber 12 in a horizontal state, and then opened into the opening 19. Put the lid on. Next, in order to prevent the silicon wafer 11 from reacting with impurities during the heat treatment, the heat treatment of the silicon wafer 11 is performed by heating the heating lamp 16 while injecting an inert gas or a reaction gas from the gas inlet 17. At this time, the temperature distribution of the central portion and the outer peripheral portion of the silicon wafer 11 is controlled by measuring the temperature of the silicon wafer 11 with a pyrometer 20 installed outside the chamber 12. This is performed by adjusting the individual outputs of the plurality of heating lamps 16 provided in the chamber 12 so as to increase the temperature by 1 to 6 ° C.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
A silicon wafer having a diameter of 300 mm for heat treatment was prepared. As a heat treatment apparatus, a single wafer RTA apparatus (Mattson 3000 manufactured by Mattson) was used.
First, the prepared silicon wafer was carried into the chamber from the opening of the RTA apparatus, placed on three support pins, and placed in a horizontal state in the chamber. After carrying in, oxygen was injected from the gas inlet, the outputs of a plurality of heating lamps installed outside the chamber were adjusted, and heat treatment was performed at a heat treatment temperature of 1200 ° C. for 10 seconds.

  The heat treatment was performed while controlling the temperature distribution in the silicon wafer surface so that the temperature at the outer periphery of the wafer was 3 ° C. higher than the temperature at the center of the wafer. The temperature distribution is controlled by measuring the wafer temperature with a pyrometer and adjusting the temperature distribution in the wafer surface to the minimum by considering the balance between heating from the lamp during heat treatment and heat radiation from the wafer. Based on the lamp power balance, the output of the heating lamp installed on the outer peripheral side of the wafer was increased by 10% from the above standard compared with the output of the heating lamp installed in the wafer center. The temperature in the silicon wafer surface is a value converted from the difference between the thickness of the oxide film formed at each position in the wafer surface and the thickness of the oxide film formed in the center of the wafer. That is, in consideration of the balance with the heat from the lamp during the heat treatment at each heat treatment temperature, the wafer is heat-treated in an oxidizing atmosphere after adjusting the lamp power balance so that the temperature distribution in the wafer surface is minimized. The temperature in the silicon wafer surface is converted from the correlation between the average oxide film thickness in the surface and the heat treatment temperature. The correlation between the average oxide film thickness in the surface of the wafer heat-treated in an oxidizing atmosphere and the heat treatment temperature is as shown in FIG.

<Comparative Example 1>
Installed on the outer peripheral side of the wafer based on the power balance of each lamp adjusted so that the temperature distribution in the wafer surface is minimized in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer The silicon wafer was heat-treated in the same manner as in Example 1 except that the output of the heating lamp was adjusted and controlled to be equal to the output of the heating lamp installed in the center of the wafer. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 1 ° C. lower than the temperature at the center of the wafer.

<Comparative example 2>
Installed on the outer peripheral side of the wafer based on the power balance of each lamp adjusted so that the temperature distribution in the wafer surface is minimized in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer The silicon wafer was heat treated in the same manner as in Example 1 except that the output of the heating lamp was adjusted and controlled to be 10% lower than the above standard compared to the output of the heating lamp installed in the center of the wafer. went. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 2 ° C. lower than the temperature at the center of the wafer.

<Comparison test and evaluation 1>
About the silicon wafer after the heat processing in Example 1 and Comparative Examples 1 and 2, the length of the slip dislocation at the three support positions by the support pins was measured with a microscope. The result is shown in FIG.

  As is apparent from FIG. 3, in Comparative Examples 1 and 2, slip dislocations of about 2 to 4 mm were observed at any of the three support positions by the support pins, whereas heat treatment was performed by the heat treatment method of the present invention. No slip dislocation was observed in the silicon wafer of Example 1 that was performed. From this, it was confirmed that the heat treatment method of the present invention is effective.

<Example 2>
Installed on the outer periphery of the wafer based on the power balance of each lamp adjusted to minimize the temperature distribution in the wafer surface in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer The output of the heating lamp is 20% higher than the above standard compared to the output of the heating lamp installed in the center of the wafer, and the temperature distribution in the silicon wafer surface is controlled as in Example 1, except that The silicon wafer was heat treated. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 6 ° C. higher than the temperature at the center of the wafer. In order to confirm reproducibility, the second wafer was heat-treated under the same conditions.

<Example 3>
Installed on the outer peripheral side of the wafer based on the power balance of each lamp adjusted so that the temperature distribution in the wafer surface is minimized in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer As in Example 1, except that the temperature distribution in the silicon wafer surface was controlled so that the output of the heating lamp was increased by 15% from the above reference in comparison with the output of the heating lamp installed in the wafer center. The silicon wafer was heat treated. At this time, the temperature distribution in the silicon wafer surface was controlled such that the temperature at the outer periphery of the wafer was 4 ° C. higher than the temperature at the center of the wafer.

<Example 4>
Installed on the outer periphery of the wafer based on the power balance of each lamp adjusted to minimize the temperature distribution in the wafer surface in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer The output of the heating lamp is 8% higher than the above standard compared with the output of the heating lamp installed in the wafer central portion, and the temperature distribution in the silicon wafer surface is controlled in the same manner as in Example 1. The silicon wafer was heat treated. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 2 ° C. higher than the temperature at the center of the wafer.

<Example 5>
Considering the balance between heating from the lamp during heat treatment and heat radiation from the wafer, the power balance of each lamp adjusted to minimize the temperature distribution in the wafer surface, and compared with that standard, The output of the heating lamp is set so that the difference becomes 10% by increasing the output of the heating lamp installed on the outer periphery of the wafer and decreasing the output of the heating lamp installed near the radius in the wafer radial direction. The silicon wafer was heat-treated in the same manner as in Example 1 except that the temperature distribution in the silicon wafer surface was controlled. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 2 ° C. higher than the temperature at the center of the wafer. In order to confirm reproducibility, the second wafer was heat-treated under the same conditions.

<Example 6>
Taking the balance between heating from the lamp during heat treatment and heat dissipation from the wafer into consideration, the power balance of each lamp adjusted so that the temperature distribution in the wafer surface is minimized, and further outside the outer periphery of the wafer The heating lamp output is adjusted so that the output of the heating lamp installed at the center of the wafer is 8% higher than the above standard compared with the output of the heating lamp installed in the center of the wafer, and the temperature distribution in the silicon wafer surface The silicon wafer was heat-treated in the same manner as in Example 1 except that the above was controlled. At this time, the temperature distribution in the silicon wafer surface was controlled so that the temperature at the outer periphery of the wafer was 1 ° C. higher than the temperature at the center of the wafer. In order to confirm reproducibility, the second wafer was heat-treated under the same conditions.

<Comparative Example 3>
Installed on the outer periphery of the wafer based on the power balance of each lamp adjusted to minimize the temperature distribution in the wafer surface in consideration of the balance between heating from the lamp during heat treatment and heat radiation from the wafer The output of the heating lamp is 5% higher than the above standard compared with the output of the heating lamp installed in the center of the wafer, and the temperature distribution in the silicon wafer surface is controlled in the same manner as in Example 1. The silicon wafer was heat treated. At this time, the temperature distribution in the silicon wafer surface was such that the temperature at the outer periphery of the wafer was the same as the temperature at the center of the wafer. In order to confirm reproducibility, the second wafer was heat-treated under the same conditions.

<Comparison test and evaluation 2>
Regarding the silicon wafers after heat treatment in Examples 2 to 6 and Comparative Example 3, the relationship between the temperature distribution in the wafer surface in the radial direction from the center of the wafer and the occurrence of slip dislocations at the three support positions by the support pins. evaluated. The results are shown in FIG. 4 and Table 1 below. Moreover, in FIG. 4 and Table 1, the result of Example 1 and Comparative Examples 1-2 is also shown collectively. FIG. 4 is a value obtained by converting the temperature distribution in the wafer surface from the thickness of the oxide film formed in the wafer surface. In Table 1, among the three support positions by the support pins, A is a case where no slip has occurred in all three places, and B is a case where slip dislocation has occurred in one or two places. The case where slip occurred in all the locations was designated as C.

図４及び表１から明らかなように、比較例１〜３に比べ、シリコンウェーハ外周部の温度がウェーハ中心部の温度よりも１〜６℃高くなるように制御して熱処理した実施例１〜６では、支持ピンによる支持位置におけるスリップ転位の発生が抑えられていることが確認された。特に、ウェーハ外周部の温度がウェーハ中心部の温度に比べて３〜４℃高くなるように温度分布を制御して熱処理した実施例１では、３箇所全ての支持位置においてスリップが発生しなかった。このことから、本発明が効果的であることが確認された。

As apparent from FIG. 4 and Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 1 were heat-treated by controlling the temperature of the outer peripheral portion of the silicon wafer to be 1 to 6 ° C. higher than the temperature of the center of the wafer. In No. 6, it was confirmed that the occurrence of slip dislocation at the support position by the support pin was suppressed. In particular, in Example 1 where heat treatment was performed by controlling the temperature distribution so that the temperature at the outer periphery of the wafer was 3 to 4 ° C. higher than the temperature at the center of the wafer, no slip occurred at all three support positions. . From this, it was confirmed that the present invention is effective.

FIG. 1A is a diagram for explaining the principle of slip dislocation generation when the wafer outer periphery temperature is higher than the wafer center temperature, and FIG. It is a figure explaining the principle of slip dislocation generation in the case. It is a schematic sectional drawing which shows an example of an RTA apparatus. It is a graph which shows the result of Example 1 and Comparative Examples 1 and 2. It is a graph which shows the result of Examples 1-6 and Comparative Examples 1-3. It is a graph which shows the correlation with the oxide film thickness in a wafer surface, and temperature.

Explanation of symbols

  40 Silicon wafer

Claims (2)

In a silicon wafer heat treatment method in which a silicon wafer obtained by slicing a silicon single crystal ingot is subjected to heat treatment at a predetermined temperature with rapid temperature rise and fall,
The predetermined temperature is 1100 to 1250 ° C,
The heat treatment is performed by horizontally supporting the outer peripheral portion of the silicon wafer within the range of 0 to 30 mm in the center direction of the wafer from the outer peripheral edge of the wafer with three support pins arranged at an interval of 120 degrees in a top view. ,
By performing heat treatment while controlling the temperature distribution in the silicon wafer surface so that the temperature of the outer peripheral portion of the silicon wafer is 1 to 6 ° C. higher than the temperature of the central portion of the silicon wafer ,
The temperature difference between the supporting position of the supporting pin and its peripheral part due to the thermal radiation from the supporting pin is reduced, and the thermal stress acting in the lateral direction of the silicon wafer at the supporting pin is reduced, and the supporting pin of the silicon wafer is reduced by the supporting pin. A method for heat-treating a silicon wafer, characterized by preventing or reducing occurrence of slip dislocation from a support position . The silicon wafer has a diameter of 300 mm,
The heat treatment method for a silicon wafer according to claim 1 , wherein the heat treatment is performed so that a temperature at an outer peripheral portion of the silicon wafer is 3 to 4 ° C. higher than a temperature at a center portion of the silicon wafer.

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