JP7230661B2 - Evaluation method of resistance to slip dislocation of silicon wafer - Google Patents

Description

The present invention relates to a method for evaluating the slip dislocation resistance of a silicon wafer.

Conventionally, silicon wafers have been widely used as substrates for fabricating semiconductor devices. A silicon wafer is obtained by growing a single crystal silicon ingot by, for example, the Czochralski (CZ) method, and subjecting the obtained single crystal silicon ingot to wafer processing.

Slip dislocations can occur in silicon wafers under various circumstances. For example, in recent years, in MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and power devices, epitaxial wafers, in which an epitaxial layer is formed on a silicon wafer, are used as substrates. In the process of manufacturing an epitaxial wafer, scratches may be formed on the back surface and outer periphery of the silicon wafer due to contact with foreign materials such as susceptors and holders. When thermal stress is applied to a silicon wafer with such scratches, slip dislocations may occur starting from the scratches.

Moreover, in the device formation process, various devices are fabricated on the silicon wafer. For example, a large stress may be generated locally at the edge of an STI (Shallow Trench Isolation) structure of a semiconductor device, and slip dislocations may occur.

Thus, in silicon wafers, slip dislocations can occur at various positions during various processes from the wafer manufacturing process to the device forming process. Since slip dislocations cause overlay defects and leak defects in semiconductor devices, it goes without saying that it is necessary to consider ways to prevent the occurrence of slip dislocations. On the other hand, it is also important to improve the resistance of silicon wafers to slip dislocations (hereinafter also referred to as "slip resistance"), and an evaluation method for this purpose is required.

Against this background, Patent Document 1 discloses that a silicon wafer is subjected to a short-time heat treatment using an RTA apparatus, and the length of slip dislocations generated in the silicon wafer is measured to determine the occurrence of oxygen precipitation and the like. A method for reducing the impact and evaluating the slip resistance of silicon wafers is described.

JP-A-2003-142545

Patent Literature 1 does not specify any particular heating conditions. From this, it is considered that the heat treatment of the silicon wafer using the RTA apparatus is controlled to a conventional heating condition, that is, a condition that makes the temperature distribution in the in-plane direction of the silicon wafer uniform.

However, in the above heat treatment in which the temperature distribution in the in-plane direction of the wafer is uniform, the thermal stress generated in the silicon wafer is relatively small. Therefore, even if the conditions such as the oxygen concentration in the silicon wafer are changed to improve the slip resistance, and then evaluation is performed using this method, the sensitivity to the change in conditions is low, and the evaluation result is difficult to reflect. be.

The present invention has been made in view of the above problems, and an object thereof is to propose a method capable of evaluating the resistance to slip dislocations of a silicon wafer with higher sensitivity than before.

The present invention for solving the above problems is as follows.
[1] A method for evaluating the resistance of a silicon wafer to slip dislocations, comprising:
A first step of forming an indentation at a predetermined position on the surface of a silicon wafer to be evaluated;
a second step of introducing the silicon wafer having the indentations into a single-wafer heat treatment apparatus and heating the silicon wafer for heat treatment;
a third step of evaluating resistance to slip dislocations at the predetermined position of the silicon wafer based on the length of the slip dislocations generated from the indentations;
has
A method for evaluating resistance to slip dislocation of a silicon wafer, wherein the second step is performed so as to provide a temperature difference in a radial direction of the silicon wafer.

[2] The evaluation method according to [1], wherein in the second step, the silicon wafer is heated by varying the outputs of a plurality of heating means in the heat treatment apparatus.

[3] The above-mentioned [2], wherein the plurality of heating means are arranged parallel to each other and parallel to the surface of the silicon wafer on each of the front surface side and the back surface side of the silicon wafer. Evaluation method.

[4] The evaluation method according to the above [2] or [3], wherein the second step is performed by changing only the output of the heating means on one surface side of the silicon wafer among the plurality of heating means. .

[5] The evaluation method according to any one of [1] to [4], wherein the heat treatment device is a device capable of rapid heating and cooling.

[6] Any one of [1] to [5], wherein the second step is performed while rotating the silicon wafer around an axis that passes through the center of the silicon wafer and is perpendicular to the surface of the silicon wafer. or the evaluation method described in paragraph 1.

ADVANTAGE OF THE INVENTION According to this invention, the resistance with respect to the slip dislocation of a silicon wafer can be evaluated with higher sensitivity than before. Moreover, according to the present invention, resistance to slip dislocations can be evaluated for various positions on a silicon wafer.

It is a figure which shows an example of an indentation formation apparatus. It is a figure which shows an example of the optical microscope image of an indentation. It is a schematic diagram which shows the structure of heating means vicinity in an example of a RTA apparatus. It is a figure explaining the formation position of an indentation. FIG. 4 shows the output of a heating lamp; FIG. 5 is a diagram showing the relationship between the output difference of heating lamps and the length of slip dislocations generated from indentations. FIG. 10 is a diagram showing the relationship between the oxygen concentration of a silicon wafer and the length of slip dislocations generated from indentations for invention examples 3 to 7 and conventional examples 1 to 5; FIG. 10 is a diagram showing the oxygen concentration in the wafer radial direction of silicon wafers used in Invention Examples 8 to 10. FIG. It is a diagram showing the length of slip dislocations generated from the indentation for Invention Examples 8 to 10, (a) is an indentation formed at a position 5 mm from the outer peripheral edge of the wafer, and (b) is the outer peripheral edge of the wafer and the center of the wafer. It relates to an indentation formed at the position of the midpoint (R/2) of . FIG. 4 is a diagram showing an output pattern of a heating lamp;

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The method for evaluating the resistance of a silicon wafer to slip dislocations according to the present invention comprises a first step of forming an indentation at a predetermined position on the surface of the silicon wafer to be evaluated; A second step of heating and heat-treating the silicon wafer, and a third step of evaluating the resistance to slip dislocations at the predetermined position of the silicon wafer based on the length of the slip dislocations generated from the indentation. and Here, the second step is characterized in that it is performed so as to give a temperature difference in the radial direction of the silicon wafer. Each step will be described below.

<First step>
First, in the first step, an indentation is formed at a predetermined position on the surface of a silicon wafer to be evaluated. As the silicon wafer, a single crystal silicon ingot is grown by a method such as the CZ method or the floating zone melting method (FZ method), and the obtained single crystal silicon ingot is subjected to wafer processing. be able to.

The conductivity type, diameter, dopant type, resistivity, plane orientation, etc. of the silicon wafer are set appropriately according to the conditions for evaluating the resistance to slip dislocations of the silicon wafer (hereinafter also referred to as "slip resistance"). be able to.

Moreover, as the silicon wafer, an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of the above-described silicon wafer (bulk silicon wafer) can also be used.

The impressions formed on the surface of the silicon wafer are formed as starting points of slip dislocations. The position where the indentation is formed can be any position on the surface of the silicon wafer whose slip resistance is desired to be evaluated.

The number of indentations is not particularly limited, but since the temperature inside the heat treatment apparatus used in the second step described later is not necessarily constant and for the purpose of reducing data variations, a plurality of indentations are provided at equivalent positions on the silicon wafer. It is preferable to provide For example, when using a silicon wafer with a plane orientation of (001), there are four equivalent positions on the surface. Therefore, indentations are preferably formed at a plurality of these four locations, most preferably all four locations, and in the third step described later, the slip dislocation lengths from the plurality of indentations are measured, It is preferable to evaluate slip resistance based on the average value.

Although the shape of the indentation is not particularly limited, it preferably has a shape in which slip dislocations are likely to occur in the <110> direction (including directions equivalent to the <110> direction) from the indentation. Examples of the shape of such an indentation include polygonal shapes such as squares and triangles. Preferably, the bisector is oriented in a direction equivalent to the <110> direction. For example, in the case of a rhombus, it is preferable that the bisector of at least one of the four corners is oriented in the <110> direction. Also, in the case of a triangle, it is preferable that at least one perpendicular bisector of the vertex is oriented in the <110> direction.

The indentation can be formed by any suitable method. For example, it can be formed using a hardness tester such as a Vickers hardness tester or a Rockwell hardness tester. Also, the indentation can be formed using an indentation forming apparatus as shown in FIG. In the indentation forming apparatus shown in FIG. 1, an indenter for forming an indentation via a load cell is provided on the lower surface of a vertically movable support member. When the support member is moved downward to press the indenter against the silicon wafer, the load pressing against the silicon wafer is transmitted to the load cell and displayed on a display (not shown). The impression is formed on the surface of the silicon wafer by moving the support member downward, bringing the indenter into contact with the silicon wafer placed on the wafer installation stage, and then applying a predetermined load. be able to. The load applied to the silicon wafer can be read from a display connected to the load cell.

The load applied to the silicon wafer when forming the indentation is not particularly limited, but it is preferably about the same as the load applied when contact scratches or transport scratches are formed on the outer peripheral portion of the silicon wafer. Specifically, it is preferably about 10 to 2000 gf.

When examining the slip resistance at various positions on the silicon wafer surface, or when examining the slip resistance by changing the conditions such as the oxygen concentration in the silicon wafer, the same load is applied to all indentations. It is preferable to form This makes it possible to quantitatively compare evaluation results.

FIG. 2 shows an example of an optical microscope image of an indentation formed using the apparatus shown in FIG. In the diamond-shaped indentations shown in FIG. 2, cracks are generated from the vertices of the rhombus, and the cracks extend in the <110> direction. When a silicon wafer having such indentations is subjected to thermal stress exceeding the critical shear stress at which slip dislocations occur, slip dislocations are generated and propagate from the tip of the crack.

<Second step>
Next, in the second step, the silicon wafer with the indentation formed thereon is introduced into a single-wafer heat treatment apparatus, and the silicon wafer is heated for heat treatment. Here, it is important to perform the second step so as to provide a temperature difference in the radial direction of the silicon wafer.

As described above, when heat treatment is performed on a silicon wafer using a heat treatment apparatus, the temperature in the in-plane direction of the wafer should be uniform in order to obtain uniform characteristics over the entire silicon wafer. Common.

However, if the silicon wafer is heat treated uniformly in the in-plane direction as described above, the thermal stress generated in the silicon wafer is relatively small. Therefore, even if evaluation is performed by changing the formation position of the indentation or by changing the oxygen concentration in the silicon wafer, the sensitivity to such changes in conditions is low, and it is difficult to reflect them in the evaluation results.

The present inventors have earnestly studied a method for evaluating the slip resistance of silicon wafers with higher sensitivity than before. As a result, they came up with the idea of giving a temperature difference in the radial direction of the silicon wafer to intentionally generate a greater thermal stress in the silicon wafer than in the prior art, and completed the present invention.

By heat-treating the silicon wafer so as to provide a temperature difference in the in-plane direction of the wafer, a larger thermal stress is generated in the silicon wafer than before. Therefore, as shown in Examples to be described later, it is possible to evaluate the slip resistance of a silicon wafer with higher sensitivity than before.

In the present invention, "the second step is performed so as to provide a temperature difference in the radial direction of the silicon wafer" means that the silicon wafer is heated to a temperature of 1°C or more between the central portion and the outer peripheral portion of the silicon wafer. It means to apply heat treatment so as to give a difference. Specifically, in the second step, it means that the silicon wafer is heat-treated so that the difference between the temperature at the center of the silicon wafer and the temperature at a position 1 mm from the outer peripheral edge is 1 ° C. or more. ing. At that time, the temperature of the outer peripheral portion of the wafer is not limited to being measured at a position 1 mm from the outer peripheral edge of the wafer. For example, in the second step, there is a temperature difference of 2°C between the center of the silicon wafer and a position 2 mm from the outer peripheral edge, or a temperature difference of 3°C between the center of the silicon wafer and a position 0.5 mm from the outer peripheral edge. If there is a high probability that there is a temperature difference of 1° C. or more between the center of the silicon wafer and the position 1 mm from the outer peripheral edge of the wafer, the second step is performed so as to provide a temperature difference in the radial direction of the silicon wafer. can be assumed to be

The heat treatment apparatus used in the present invention is not particularly limited as long as it is a single-wafer type that can give a temperature difference in the radial direction of the silicon wafer. A device that can be differentiated is preferred. In addition, the heat treatment apparatus is preferably an apparatus capable of rapid heating and cooling. This makes it possible to evaluate the slip resistance while excluding the effects of oxygen precipitation and the like. An RTA (Rapid Thermal Annealing) apparatus, an epitaxial growth apparatus, and the like can be cited as apparatuses capable of such high-speed heating and cooling.

FIG. 3 shows a schematic diagram of the configuration around the heating means in the RTA apparatus that can be used in the present invention. The heating means illustrated in FIG. 3 is composed of 28 linear heating lamps arranged on the front side and the back side of the silicon wafer, respectively. These heating lamps are arranged parallel to each other, equidistantly, and parallel to the surface of the silicon wafer. A radiation thermometer for controlling the temperature near the center of the silicon wafer and a radiation thermometer for monitoring the temperature near the outer periphery are provided above the heating lamps.

By varying the output of a plurality of heating lamps in the RTA apparatus as described above, a temperature difference occurs in the radial direction of the silicon wafer. As a result, a larger thermal stress can be generated in the silicon wafer than before.

For example, the power of the heating lamps arranged near the center of the silicon wafer is made relatively large, and the power of the heating lamps arranged near the periphery of the silicon wafer is made relatively small. Specifically, when the lamp output for setting the temperature near the center of the silicon wafer to a predetermined temperature is 100%, by setting the lamp output near the outer periphery to 60%, a large thermal stress is applied to the outer periphery of the silicon wafer. can be generated.

Regarding the temperature difference in the radial direction of the silicon wafer, for example, when a temperature difference is given between the wafer center and the wafer outer periphery, the temperature difference between the wafer center and the wafer outer periphery is 4°C or more and 12°C or less. preferably. By setting the temperature difference within this range, the slip resistance of the silicon wafer can be evaluated with higher sensitivity.

When the heat lamps shown in FIG. 3 are used and the heat lamps near the center of the silicon wafer have different outputs from the heat lamps near the outer periphery, the heat lamps extend in the direction perpendicular to the direction in which the heat lamps extend. While there is a temperature difference corresponding to the output difference, there is almost no temperature difference in the extending direction of the heating lamps.

Therefore, it is preferable to arrange the silicon wafer in the heat treatment apparatus so that the line segment connecting the impression formed on the surface of the silicon wafer and the center of the wafer is perpendicular to the extending direction of the heating lamps. Thereby, a large thermal stress can be generated in the area where the indentation is formed.

However, when forming a plurality of indentations, the above measures may not be able to cope. In such a case, by rotating the silicon wafer during the heat treatment, it is possible to uniformly heat the wafer in the circumferential direction, so that a large thermal stress can be applied to all the indentations.

Furthermore, by varying the output of the heating means for either the front surface side or the back surface side of the silicon wafer, a greater thermal stress is generated and the slip dislocation resistance of the silicon wafer is evaluated with higher sensitivity. can do.

As shown in Examples described later, the thermal stress generated in the silicon wafer depends on the output difference of the heating lamps, and the greater the output difference, the greater the thermal stress generated in the silicon wafer. Resistance can be evaluated with higher sensitivity. However, if the output difference between the heating lamps is too large, the stress generated in the silicon wafer will increase, and the heat treatment itself may become an error such as warping, so the output difference between the heating lamps is appropriate. is preferably set to

In addition, as shown in the examples described later, when the output of the heating lamp is changed, the output of the heating lamp is discontinuously and greatly changed in the direction perpendicular to the extending direction of the heating lamp rather than gradually changing the output of the heating lamp. The thermal stress generated in the silicon wafer is greater, the length of the slip dislocation generated from the indentation is longer, and the slip resistance of the silicon wafer can be evaluated with high sensitivity.

The heat treatment of the silicon wafer can also be performed using a single-wafer epitaxial growth apparatus as the heat treatment apparatus. In a single-wafer type epitaxial apparatus (for example, Centura manufactured by Applied Materials Co., Ltd.), elliptical halogen lamps are arranged concentrically (inside and outside in two stages) (for example, Japanese Unexamined Patent Application Publication No. 2015-002286). See Figure 1). Therefore, by making the output of the inner lamp and the output of the outer lamp different, it is possible to give a temperature difference in the wafer radial direction of the silicon wafer.

<Third step>
Subsequently, in the third step, resistance to slip dislocation is evaluated based on the length of slip dislocation generated from the indentation at a predetermined position (indentation formation position) of the silicon wafer. Specifically, it can be evaluated that the shorter the length of the slip dislocation generated from the indentation, the higher the resistance to the slip dislocation. The slip resistance can also be evaluated based on the average length of slip dislocations generated from each indentation.

Thus, the slip dislocation resistance of a silicon wafer can be evaluated with higher sensitivity than before.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Examination of heating conditions>
(Invention Example 1)
First, a silicon wafer (diameter: 300 mm, plane orientation: (001), oxygen concentration: 10.3×10 ¹⁷ atoms/cm ³ (ASTM F121-1979)) to be evaluated was prepared, and the surface was coated with the As shown, indentations were formed at four locations 5 mm from the outer edge of the silicon wafer. At that time, the indentation was formed using the indentation forming apparatus shown in FIG. 1, and the load applied to the silicon wafer was 100 gf.

Next, the silicon wafer having the indentations formed thereon was introduced into an RTA apparatus equipped with linear heating lamps as shown in FIG. 3 to heat-treat the silicon wafer. The atmosphere was Ar. The wafer was rotated at 75 rpm during the heat treatment. The temperature near the center of the silicon wafer was raised to 1250° C. at 50° C./second, held at 1250° C. for 30 seconds, and then lowered to room temperature at 50° C./second. At that time, for the heating lamps on the side where the indentation is formed, as shown in FIG. The lamp power was set at 80%. For the heating lamps on the side where the indentation is not formed, the output of all the heating lamps was set at 100%.

The silicon wafer subjected to the heat treatment was taken out from the RTA apparatus, the length of slip dislocation generated from each indentation was measured using an optical microscope, and the average value was obtained for the four indentations.

(Invention Example 2)
Similar to Invention Example 1, the slip resistance of the silicon wafer was evaluated. However, the output of the 1st to 10th and 19th to 28th heating lamps was set to 60% during the heat treatment of the silicon wafer. All other conditions are the same as in Invention Example 1.

(Invention example 3)
Similar to Invention Example 1, the slip resistance of the silicon wafer was evaluated. However, the output of the 1st to 10th and 19th to 28th heating lamps was set to 30% during the heat treatment of the silicon wafers. All other conditions are the same as in Invention Example 1.

(Comparative example)
Similar to Invention Example 1, the slip resistance of the silicon wafer was evaluated. However, the outputs of the 1st to 10th and 19th to 28th heating lamps were set to 0% during the heat treatment of the silicon wafers. All other conditions are the same as in Invention Example 1.

(Conventional example 1)
Similar to Invention Example 1, the slip resistance of the silicon wafer was evaluated. However, the output of all heating lamps was set to 100% during the heat treatment of the silicon wafer. All other conditions are the same as in Invention Example 1.

FIG. 6 shows the relationship between the output difference of the heating lamps and the length of the slip dislocation generated from the indentation. As is clear from FIG. 6, compared with Conventional Example 1 in which the output of all heating lamps is 100%, by reducing the output of the heating lamps near the outer periphery of the wafer, the length of the slip dislocation generated from the indentation is found to be longer. Further, it can be seen that the longer the length of the slip dislocation, the greater the difference between the output of the heat lamp near the center of the wafer and the output of the heat lamp near the outer periphery of the wafer. In addition, under the conditions of the comparative example, the interlock mechanism of the RTA apparatus was activated and the heat treatment could not be performed. However, if the heat treatment was successful, it is considered that the slip dislocations would be longer than in Invention Example 3.

Regarding the conventional example and invention examples 1 to 3, the temperature difference between the central portion and the outer peripheral portion of the silicon wafer was measured. Specifically, in addition to the radiation thermometer near the center for temperature control, a radiation thermometer for monitoring the outer periphery was provided, and the difference was obtained by reading the respective temperatures. As a result, the temperature difference between the central portion and the outer peripheral portion of the silicon wafer was 0.8°C (conventional example), 4.3°C (invention example 1), 8.6°C (invention example 2), and 11.8°C. (Invention Example 3).

<Evaluation of Silicon Wafers with Different Oxygen Concentrations>
(Invention Example 4)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 5.8×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Invention Example 3.

(Invention example 5)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 8.0×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Invention Example 3.

(Invention example 6)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 11.3×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Invention Example 3.

(Invention Example 7)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 17.1×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Invention Example 3.

(Conventional example 2)
Similar to Conventional Example 1, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 5.8×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Conventional Example 1.

(Conventional example 3)
Similar to Conventional Example 1, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 8.0×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Conventional Example 1.

(Conventional example 4)
Similar to Conventional Example 1, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 11.3×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Conventional Example 1.

(Conventional example 5)
Similar to Conventional Example 1, the slip resistance of the silicon wafer was evaluated. However, the silicon wafer used had an oxygen concentration of 17.1×10 ¹⁷ atoms/cm ³ . All other conditions are the same as in Conventional Example 1.

FIG. 7 shows the relationship between the oxygen concentration of silicon wafers and the length of slip dislocations generated from indentations in invention examples 3-7 and conventional examples 1-5. In both the invention example and the conventional example, the length of the slip dislocation becomes shorter when the oxygen concentration in the silicon wafer increases. This trend reproduces the generally known knowledge that the higher the oxygen concentration in the silicon wafer, the more the diffusion of dislocations is suppressed. However, as for the conventional example, when comparing the conventional example 1 and the conventional example 3, for example, the length of the slip dislocation is almost the same although the oxygen concentration of the silicon wafer is different. Further, when comparing Conventional Example 4 and Conventional Example 5, no slip dislocation occurs in either case (that is, the length of the slip dislocation is zero), although the silicon wafers have different oxygen concentrations. That is, the conventional evaluation method has sufficient sensitivity to evaluate the difference in oxygen concentration between Conventional Examples 1 and 3 and the difference in oxygen concentration between Conventional Examples 4 and 5. do not have. On the other hand, in the invention examples, the length of the slip dislocation monotonously decreases as the oxygen concentration of the silicon wafer increases, so the difference in oxygen concentration between the invention examples is reflected in the evaluation results. From the above, it can be said that the method of the present invention can evaluate the slip resistance of a silicon wafer with higher sensitivity than the conventional method.

<Evaluation of Silicon Wafers with Different Oxygen Concentration Distributions in the Radial Direction>
(Invention Example 8)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, a silicon wafer having an oxygen concentration near the center of 12.0×10 ¹⁷ atoms/cm ³ and an oxygen concentration distribution shown in FIG. 8 was used. In addition, the indentation was formed at a position 5 mm from the outer circumference and at the center between the outer circumference edge and the center (hereinafter, R/2). All other conditions are the same as in Invention Example 3.

(Invention example 9)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, similar to Invention Example 8, the oxygen concentration near the center was 12.0×10 ¹⁷ atoms/cm ³ , but as shown in FIG. . Also, the indentation was formed at 5 mm from the outer circumference and R/2. All other conditions are the same as in Invention Example 3.

(Invention Example 10)
Similar to Invention Example 3, the slip resistance of the silicon wafer was evaluated. However, although the oxygen concentration near the center is 12.0×10 ¹⁷ atoms/cm ³ as in Invention Example 8, the oxygen concentration distribution differs from Invention Examples 8 and 9 as shown in FIG. Wafers were used. Also, the indentation was formed at 5 mm from the outer periphery and R/2. All other conditions are the same as in Invention Example 3.

As shown in FIG. 8, the oxygen concentration varies in the wafer radial direction. For example, at a position 5 mm from the outer peripheral edge, the oxygen concentration is the highest in Inventive Example 10, followed by Inventive Examples 9 and 8 in that order. On the other hand, in R/2, the oxygen concentration is the highest in Inventive Example 9, followed by Inventive Examples 8 and 10 in that order.

FIG. 9 shows the lengths of slip dislocations generated from indentations in Examples 8 to 10 of the invention. Here, (a) is the result of 5 mm from the outer peripheral end, and (b) is the result of R/2. Looking at FIG. 9( a ), the slip dislocation length is the longest in Invention Example 8, followed by Invention Examples 9 and 10 in that order. This is in the reverse order of the height of the oxygen concentration at the position 5 mm from the outer edge shown in FIG. 9(b), the slip dislocation length is the longest in invention example 10, followed by invention examples 8 and 9 in that order. Also in this case, the order of the height of the oxygen concentration at the position R/2 shown in FIG. 8 is reversed. Thus, according to the present invention, it is possible to accurately evaluate the slip resistance of silicon wafers.

<Examination of output pattern of heating lamp>
The relationship between the output pattern of the heating lamp and the length of the slip dislocation generated from the indentation was investigated. Specifically, first, six silicon wafers (diameter: 300 mm, outer peripheral oxygen concentration: 10.2×10 ¹⁷ atoms/cm ³ ) were prepared, and on the surface of each silicon wafer, the concentration shown in FIG. As shown, four indentations were formed at positions 5 mm from the outer edge of the wafer. Then, the six silicon wafers were heat-treated with the six output patterns shown in FIG. After the heat treatment, for each silicon wafer, the length of slip dislocations generated from the indentations was measured using an optical microscope, and the average value of the slip dislocation lengths for the four indentations was obtained. As a result, the average slip dislocation length was 3.7 mm (first pattern), 4.7 mm (second pattern), 7.1 mm (third pattern), 4.9 mm (fourth pattern), 5 0.5 mm (fifth pattern) and 14.9 mm (sixth pattern). Thus, it was found that the length of the slip dislocation was the longest when the output pattern of the heating lamp was the sixth pattern.

According to the present invention, the resistance to slip dislocations of a silicon wafer can be evaluated with higher sensitivity than before, and the resistance to slip dislocations can be evaluated for various positions on the silicon wafer. Useful in the semiconductor wafer manufacturing industry.

Claims (5)

A method for evaluating the resistance of a silicon wafer to slip dislocations, comprising:
A first step of forming an indentation at a predetermined position on the surface of a silicon wafer to be evaluated;
a second step of introducing the silicon wafer having the indentations into a single-wafer heat treatment apparatus, supporting the silicon wafer with quartz support pins, and heating the silicon wafer for heat treatment;
a third step of evaluating resistance to slip dislocations at the predetermined position of the silicon wafer based on the length of the slip dislocations generated from the indentations;
has
In the second step, the temperature difference between the central portion and the outer peripheral portion of the silicon wafer is set to 8.6° C. or more and 11.8° C. or less by varying the output of a plurality of heat lamps in the heat treatment apparatus. A method for evaluating resistance to slip dislocations of a silicon wafer characterized by: 2. The evaluation method according to claim 1 , wherein the plurality of heat lamps are arranged parallel to each other and parallel to the surface of the silicon wafer on each of the front surface side and the rear surface side of the silicon wafer. 3. The evaluation method according to claim 1 or 2 , wherein said second step is performed by changing only the output of said heating lamp on one surface side of said silicon wafer among said plurality of heating lamps . The evaluation method according to any one of claims 1 to 3 , wherein the heat treatment apparatus is an RTA (Rapid Thermal Annealing) apparatus or an epitaxial growth apparatus. 5. The method according to any one of claims 1 to 4 , wherein the second step is performed while rotating the silicon wafer around an axis passing through the center of the silicon wafer and perpendicular to the surface of the silicon wafer. Evaluation method.

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