JP6315285B2 - Epitaxial wafer manufacturing method and vapor phase growth apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing an epitaxial wafer and a vapor phase growth apparatus.

  In an epitaxial layer grown using a vapor phase growth apparatus (epitaxial growth apparatus), the film thickness distribution is one of the most important characteristics. For example, if a semiconductor device having a large-scale circuit is produced based on an epitaxial wafer in which the film thickness distribution of the epitaxial layer varies, it causes defocus in an exposure process for transferring the large-scale circuit. Further, when an epitaxial wafer having such a film thickness distribution is used as a power semiconductor, it causes a variation in the electrical characteristics of the power semiconductor. Therefore, an epitaxial layer having a very high film thickness uniformity is required.

  In order to increase the uniformity of the thickness of the epitaxial layer, it is necessary to make the growth rate of the epitaxial layer uniform. This growth rate is determined by the supply rate at which the source molecule of the epitaxial layer is supplied to the substrate surface on which the epitaxial layer is grown and the reaction rate of the source molecule on the substrate surface. Therefore, a general vapor phase growth apparatus is often configured as follows. For example, the temperature distribution of the substrate can be adjusted by arranging the heating device for heating the substrate in a plurality of regions. Further, the supply port for supplying the source gas of the epitaxial layer is divided into a plurality of regions, so that the supply rate of the source gas can be adjusted for each region.

  Also, in such a vapor phase growth apparatus, a susceptor on which the substrate is placed so that the flow of the source gas is in the same environment at the peripheral portion and the peripheral portion of the substrate (substrate to be processed) on which the epitaxial layer is grown. A recess for accommodating the substrate is formed. The recess is formed by cutting the surface of the susceptor into a shape substantially equal to that of the substrate, and the substrate is usually accommodated in the recess. In a state where the substrate is housed in the recess, the surface of the substrate and the surface of the susceptor located so as to surround the substrate are flush with each other, and the periphery of the substrate and the inside of the periphery (other than the periphery) The environment is such that the flow of the source gas is almost equal.

  The recess formed in the susceptor preferably has the same dimensions as the substrate. However, there are individual differences in the dimensions of the substrate, and errors in the susceptor fabrication also occur in the susceptor dimensions. Even in the transfer robot that transfers the substrate above the susceptor, an error occurs in the stop position of the transfer robot that stops above the susceptor. Further, there is a case where the position of the substrate is shifted on a lift pin that lowers the substrate toward the susceptor while supporting the back surface of the substrate in order to transfer the substrate from the transfer robot to the susceptor. Therefore, in consideration of such circumstances, the concave portion must be made sufficiently larger than the dimensions of the substrate. Therefore, when the concave portion on which the substrate is placed is viewed from above, the center of the concave portion is covered with the substrate, while an annular groove (gap) is formed around the substrate where the concave portion is slightly exposed. .

  In such an apparatus, if the substrate is not placed at the center of the recess, a groove having a non-uniform width is formed around the substrate, and this groove disturbs the flow of the source gas, and the periphery of the substrate. The growth rate of the epitaxial layer in the part is made non-uniform.

  Therefore, when placing the substrate in the recess, it is necessary to place the substrate at a predetermined position (for example, the center of the recess) so that a groove having a uniform width is formed around the substrate. As a method of placing a substrate at a predetermined position, Patent Document 1 discloses a method of placing a substrate that is not placed at a normal position on a normal position. In Patent Document 2, the displacement of the substrate position is evaluated based on the temperature distribution of the substrate, and in Patent Document 3, the displacement of the substrate position is evaluated based on the film thickness distribution of the epitaxial layer grown on the substrate. Patent Documents 2 and 3 disclose a method of placing the substrate on the susceptor after adjusting the position of the transfer robot that stops above the susceptor from the evaluated displacement.

Japanese Patent Laid-Open No. 6-29224 JP 2013-84943 A JP 2014-127595 A

  However, there are a plurality of causes for the displacement of the position of the substrate placed on the susceptor. For example, when a room temperature substrate is carried into a high temperature reactor, the temperature of the substrate is rapidly changed and the substrate is warped, so that the position of the substrate placed on the susceptor is shifted. Further, the position of the substrate placed on the susceptor shifts due to a plurality of causes such as thermal expansion of the substrate, wobbling of a lift pin that moves the substrate from the transfer robot to the susceptor, and acceleration of rotation start of the susceptor. Therefore, the deviation of the position of the substrate placed on the susceptor is poorly reproducible, and even if the substrate is placed again as in Patent Document 1, the substrate does not necessarily approach a predetermined position. Further, even when adjusting the position of the transfer robot by evaluating the positional deviation of the substrate based on a certain element as in Patent Documents 2 and 3, since the reproducibility of the positional deviation of the substrate is poor, The location is not always appropriate.

  An object of the present invention is to provide an epitaxial wafer manufacturing method and a vapor phase growth apparatus capable of appropriately adjusting the position of a substrate placed on a susceptor.

Means for Solving the Problems and Effects of the Invention

The method for producing an epitaxial wafer of the present invention includes:
A calculation step of measuring the mounting position of the substrate placed on the susceptor from each of the plurality of substrates placed on the susceptor, and calculating an average position of the mounting positions from the measured plurality of placement positions;
An adjustment step of adjusting a stop position where the transfer robot stops in order to transfer the substrate from the transfer robot that transfers the substrate toward the susceptor, and
The adjusting step is characterized in that the stop position is adjusted so as to eliminate the difference between the target position where the substrate is to be placed on the susceptor and the average position.

  According to the present invention, the transfer robot calculates an average position, which is an average of the placement positions of the substrates placed on the susceptor, and eliminates the difference between the average position and the target position on which the substrate is placed on the susceptor. Adjust the stop position to stop. In other words, by calculating the average of the substrate placement positions, it is possible to give a certain index to the positional deviation of the substrate with no reproducibility. Therefore, by adjusting the position of the transfer robot based on this index, the position of the transfer robot can be adjusted appropriately.

In an embodiment of the present invention,
The calculation step calculates the average position by measuring the mounting position each time the substrate is mounted on the susceptor.

  According to this, the number of populations for calculating the average position that is the average of the placement positions can be increased, and the accuracy of the average position can be increased.

  In the embodiment of the present invention, the target position is a position where the center of the susceptor and the substrate coincide. More specifically, the susceptor is rotatable about an axis, has a counterbore part on which the substrate is placed, and the target position is a position where the center of the counterbore part and the substrate coincide.

  When an epitaxial layer is grown on a substrate placed at such a target position, it is possible to improve the film thickness distribution of the epitaxial layer grown on the periphery of the substrate. Therefore, when the stop position of the transport robot is adjusted aiming at the target position, the substrate transported from the transport robot can be placed at the target position. As a result, an epitaxial layer having a good film thickness distribution can be grown on the substrate transported on the susceptor.

In an embodiment of the present invention,
The calculation process is
Imaging an area including the gap between the counterbore part and the substrate positioned in the direction from the center of the substrate placed on the counterbore part to the outer periphery as an imaging area, and imaging the gap passing through the imaging area by rotating the susceptor at least once around the axis. An imaging process for capturing an image;
A measurement process for obtaining a variation in the width of the gap in the circumferential direction of the substrate from the captured image and measuring the mounting position based on the variation;
Is provided.

  According to this, by rotating at least one rotation of the susceptor on which the substrate is placed, it is possible to capture an image of the gap located around the substrate, and it is possible to acquire a variation in the width of the gap in the circumferential direction of the substrate from the captured gap. For example, when the center of the substrate coincides with the counterbore part, the width of the gap does not vary in the circumferential direction of the substrate. Therefore, the center position of the substrate relative to the center of the counterbore part can be calculated from the size and period of the gap width varying in the circumferential direction of the substrate, and the mounting position of the substrate placed on the counterbore part can be measured.

In an embodiment of the present invention,
The imaging process rotates the susceptor multiple times to image the gap,
In the measurement step, the variation is acquired every time the susceptor rotates once, and the mounting position is measured based on the average of the plurality of acquired variations.

  According to this, since the placement position is measured from the average of the fluctuations in the width, the measurement accuracy of the placement position can be improved.

In an embodiment of the present invention,
The adjustment step adjusts the stop position when the difference (difference between the average position and the target position) is greater than or equal to a preset threshold value, and does not adjust the stop position when the difference is less than the threshold value.

  According to this, it becomes possible to adjust the stop position of the transfer robot when adjustment is necessary by setting the threshold value.

Moreover, the vapor phase growth apparatus of the present invention comprises:
A susceptor on which a substrate is placed;
A transfer robot for transferring substrates;
A control unit that controls a stop position at which the transfer robot stops in order to transfer the substrate from the transfer robot to the susceptor,
The control unit
A calculating means for measuring a mounting position at which the substrate is mounted on the susceptor from each of the plurality of substrates mounted on the susceptor, and calculating an average position of the mounting positions from the plurality of measured mounting positions;
Adjusting means for adjusting the stop position so as to eliminate the difference between the target position where the substrate should be placed on the susceptor and the average position;
It is characterized by having.

  The present invention is an invention configured as a vapor phase growth apparatus (the above-described invention is an invention configured as an epitaxial wafer manufacturing method). Similar to the above-described invention of the epitaxial wafer manufacturing method, the average position is adopted as an index of the positional deviation of the non-reproducible substrate, and the position of the transfer robot is adjusted based on the average position. It becomes possible to adjust.

In an embodiment of the present invention,
The calculating means measures the mounting position each time the substrate is mounted on the susceptor and calculates the average position.

  According to this, each time the substrate is placed on the susceptor, the placement position is measured, the number of populations for calculating the average position that is the average of the placement positions can be increased, and the accuracy of the average position is increased. be able to.

  In the embodiment of the present invention, the target position is a position where the center of the susceptor and the substrate coincide. More specifically, the susceptor can rotate around the axis, has a counterbore part whose center coincides with the susceptor, the substrate is placed on the counterbore part, and the target position matches the center of the counterbore part and the substrate It is a position to do.

  According to this, when the stop position of the transfer robot is adjusted aiming at the target position, the substrate transferred from the transfer robot can be placed at the target position, and an epitaxial layer having a good film thickness distribution can be grown. Is possible.

In an embodiment of the present invention,
An imaging apparatus including an imaging region that includes a gap between the counterbore portion and the substrate located in a direction from the center of the substrate placed on the counterbore portion toward the outer periphery,
The calculation means is
Imaging means for acquiring from the imaging device a captured image of a gap passing through the imaging region by rotating the susceptor at least once around the axis;
Measuring means for obtaining a variation in the width of the gap from the captured image and measuring the mounting position based on the variation;
Is provided.

  According to this, the gap located around the substrate can be imaged by rotating the susceptor on which the substrate is placed at least once, and the variation in the width of the gap in the circumferential direction of the substrate can be acquired from the imaged gap. Therefore, it is possible to calculate the center of the substrate from the magnitude and cycle of the gap width varying in the circumferential direction of the substrate, and to measure the placement position of the substrate placed on the susceptor.

The schematic cross section which shows an example of the vapor phase growth apparatus of this invention. The schematic plan view which shows an example which mounted the board | substrate in the susceptor of FIG. FIG. 2B is a partially enlarged view of the imaging region shown in FIG. 2A. An example of the picked-up image which imaged the clearance gap between a counterbore part and a board | substrate. The schematic diagram which shows an example of the conveyance robot of the vapor phase growth apparatus of FIG. The block diagram which shows an example of the control part of the vapor phase growth apparatus of FIG. The graph which showed the position of the board | substrate outer periphery located in the direction which goes to the outer periphery of a board | substrate from the center of a board | substrate, and the inner wall position of a counterbore part along the circumferential direction of a board | substrate. The graph which showed the distance with the inner wall position of the counterbore part located in the same direction as the position of the board | substrate outer periphery located in the direction which goes to the outer periphery of a board | substrate from the center of the board | substrate mounted in the susceptor in an Example. 6 is a flowchart showing processing of a calculation program and the like stored in the ROM of FIG. 6 is a flowchart showing processing of a position program and the like stored in the ROM of FIG. The figure which shows the measurement result of the mounting position of the board | substrate measured every time a board | substrate is mounted in a susceptor in an Example (The measurement result of the mounting position which mounted the board | substrate, without adjusting the position of a conveyance robot). The figure of the Example which shows the measurement result of the mounting position of the board | substrate measured every time it mounts a board | substrate on a susceptor after adjusting the position of a conveyance robot based on the average position calculated based on the measurement result of FIG. 10A. Comparison showing the measurement result of the placement position of the substrate placed on the susceptor by adjusting the position of the transfer robot when the substrate is next loaded based on the placement position of the substrate placed on the susceptor immediately before The figure of Example 1. The measurement result of the placement position of the substrate placed on the susceptor in a state where the placement position for placing the substrate on the susceptor is intentionally shifted from the target position, and the measured placement position is far from the target position The figure of the comparative example 2 which shows the measurement result of the mounting position which adjusted the position of the conveyance robot based on the mounting position far away from the thing, and mounted the board | substrate again.

  FIG. 1 shows an example of a vapor phase growth apparatus 1 of the present invention. By the vapor phase growth apparatus 1, for example, a silicon single crystal film (epitaxial layer) is vapor-phase grown on a silicon single crystal wafer (substrate W) serving as a growth substrate, and a silicon epitaxial wafer is manufactured.

  The vapor phase growth apparatus 1 includes a reaction furnace 2 having a top plate 2a made of transparent quartz. A susceptor 3 and a support portion 4 that supports the susceptor 3 are arranged inside the reaction furnace 2, and a drive portion 5 that drives the susceptor 3 is connected to the support portion 4.

  The susceptor 3 is formed in a disc shape, and the surface of the susceptor 3 is provided with a counterbore portion 3a that is recessed in a disc shape larger than the diameter of the substrate W, and is disposed in the reaction furnace 2 so as to be rotatable around an axis O extending in the vertical direction. The As shown in FIG. 2A when the susceptor 3 is viewed from above, the susceptor 3 and the counterbore portion 3a are concentrically positioned with the center C as an axis. The substrate W is placed on the counterbore 3a, and the counterbore 3a has an annular inner wall 3a1 that faces the outer periphery Wa of the substrate W placed. A gap S having a width W1 is formed between the outer periphery Wa and the inner wall 3a1 located in the direction from the center C1 of the substrate W toward the outer periphery Wa in a state where the substrate W is placed on the counterbore 3a. In FIG. 2A, the gap S is formed in an annular shape having a non-uniform width W1 around the substrate W. The susceptor 3 supports the substrate W horizontally or substantially horizontally with a gap S between the counterbore part 3a and the substrate W.

  Returning to FIG. 1, the support portion 4 is disposed so as to support the susceptor 3 horizontally or substantially horizontally from the back side of the susceptor 3. The support unit 4 includes a support column 4 a that extends in the vertical direction and has a tip connected to the susceptor 3, and an angle sensor 4 b that is attached to the support column 4 a and detects the rotation angle of the susceptor 3 that rotates about the axis O. As the angle sensor 4b, for example, a disc having a center located on the axis O and having a slit in the outer peripheral portion is attached to the support column 4a, and the light emitting portion and the light receiving portion are received so as to sandwich the outer peripheral portion of the disc from the front and back of the disc. The parts are arranged. Then, the rotation angle of the susceptor 3 is detected based on the time when the light passes through the slit. For example, a photo interrupter may be used for the light receiving unit and the light emitting unit. In addition, as the angle sensor 4b, for example, the rotation angle of the susceptor 3 may be detected more accurately using a rotary encoder.

  The drive unit 5 is connected to the lower portion of the support column 4a, and is configured as a drive means (for example, a motor) that can move the support column 4a up and down and rotate the support column 4a around the axis O. On the axis O, for example, the center C of the susceptor 3 and the counterbore 3a is located. When the drive unit 5 rotates the support 4a around the axis O, the susceptor 3 rotates around the axis O together with the support 4a. .

  Next, outside the reaction furnace 2, a gas supply pipe 6 and a gas discharge pipe 7 are disposed on the left and right of the reaction furnace 2, and a case 8 that covers the reaction furnace 2 is disposed so as to accommodate the reaction furnace 2. .

  The gas supply pipe 6 is located on one end side (the left side in the figure) of the reaction furnace 2 in the horizontal direction, and supplies various gases into the reaction furnace 2 substantially horizontally. The gas supply pipe 6 has a gas supply port 6 a that serves as an inlet for the gas supplied to the reaction furnace 2. At the time of vapor phase growth, the vapor phase growth gas G is supplied into the reaction furnace 2 from the gas supply port 6a. The vapor growth gas G includes a source gas that is a raw material of the silicon single crystal film (epitaxial layer), a carrier gas that dilutes the source gas, and a dopant gas that imparts conductivity to the single crystal film. A silane-based gas such as trichlorosilane (TCS) is used as a source gas, a hydrogen gas is used as a carrier gas, and a gas containing, for example, boron or phosphorus is supplied as a dopant gas during vapor phase growth.

  The gas discharge pipe 7 is located on the other end side (the right side in the drawing) of the reaction furnace 2 in the horizontal direction, and has a gas discharge port 7 a serving as an outlet for the gas supplied to the reaction furnace 2. Vapor growth gas G, purge gas, and the like that have passed through the substrate W are discharged out of the reaction furnace 2 through the gas discharge port 7a.

  The case 8 is positioned so as to cover the reaction furnace 2 so as to accommodate the reaction furnace 2 therein, and includes a lamp 9, a reflector 10, and an imaging device 11 in a space formed between the case 8 and the reaction furnace 2.

  A plurality of lamps 9 are arranged above and below the reaction furnace 2 and are heat sources that adjust the temperature of the substrate W and the like located in the reaction furnace 2 by heating the inside of the reaction furnace 2 during vapor phase growth.

  The reflector 10 is positioned above and below the reaction furnace 2 so as to surround the lamp 9 and the reaction furnace 2, and guides light from the lamp 9 into the reaction furnace 2. The reflector 10 located in the lower part of the reaction furnace 2 is arranged in an inverted M shape in the figure, and the reflector 10 located in the upper part of the reaction furnace 2 is arranged in an M shape in the figure and from the central part of the M shape. It arrange | positions so that it may protrude above illustration. Further, the inverted M-shaped and M-shaped reflector 10 is formed with an opening 10a penetrating the front and back.

  The imaging device 11 includes a camera 11a that images the inside of the reaction furnace 2 and a protective tube 11b that protects the camera 11a, which is positioned above the illustrated M-shaped reflector 10. The camera 11 a images the inside of the reaction furnace 2 through the opening 10 a of the reflector 10 and the transparent top plate 2 a of the reaction furnace 2. Specifically, as shown in FIG. 2A, a gap S located in the direction from the center C1 of the substrate W placed on the counterbore 3a toward the outer periphery Wa is imaged by the camera 11a. In FIG. 2A, a region R surrounded by a square is an example of an imaging region R imaged by the camera 11a. FIG. 2B shows an enlarged view of the imaging region R, and the width W1 of the gap S is measured by the camera 11a. A possible captured image (moving image or the like) is captured. FIG. 3 shows an example of a captured image. The left side in the figure is the substrate W, the right side in the figure is the susceptor 3, and a gap S (a portion where the counterbore portion 3 a is exposed) is located between the substrate W and the susceptor 3. In order to ensure the accuracy of measuring the distance of the width S1 of the gap S, it is preferable to take an image while setting the average distance of the width W1 of the gap S in the imaging region R to be 10 pixels or more. In addition, a reflective ND filter and an infrared absorption filter may be provided in front of the lens of the camera 11a so that excessive light does not enter the camera 11a.

  Returning to FIG. 1, the protective tube 11b is formed in a cylindrical shape and is positioned so as to surround the camera 11a. The protective tube 11b protects the camera 11a from heat that heats the reaction furnace 2 or the like. In order to prevent the temperature of the camera 11a from rising due to heat or the like that heats the reaction furnace 2, cooling air or nitrogen may be circulated in the protective tube 11b at all times.

  Further, as shown in FIG. 4, the vapor phase growth apparatus 1 includes a transfer robot 12 that loads the substrate W into the reaction furnace 2. The transfer robot 12 includes, for example, a blade 12a on which the substrate W is placed, an arm 12b connected to the blade 12a, a movable mechanism 12c that expands and contracts the arm 12b, and a rotation mechanism 12d that rotates the arm 12b. The blade 12a is formed, for example, in a bifurcated shape, and the substrate W is placed on the upper surface of the blade 12a. The arm 12b can be expanded and contracted in the horizontal direction by the expansion / contraction mechanism 12c, and can be rotated around the axis O1 by the rotation mechanism 12d. The transport robot 12 transports the substrate W placed on the blade 12 a to the upper side of the susceptor 3 by making full use of expansion and contraction and rotation of the arm 12 b.

  As shown in FIG. 5, the angle sensor 4b, the drive unit 5, the camera 11a, and the transport robot 12 are electrically connected to a control unit 13 that controls them. The control part 13 is comprised as the computer 13a for control which controls each said part, for example. As shown in FIG. 5, the computer 13 a includes a CPU 14, a RAM 15, and a ROM 16, which are connected to an I / O port 18 (input / output interface) via a bus 17. Further, the angle sensor 4b, the drive unit 5, the camera 11a, and the transport robot 12 are connected to the I / O port 18.

  The CPU 14 performs overall data processing with the angle sensor 4b, the drive unit 5, the camera 11a, the transport robot 12, and the like, and information processing such as data acquired by data communication. For example, a position signal indicating the rotation angle (position) of the susceptor 3 is output from the angle sensor 4b to the CPU 14 every time the susceptor 3 rotates by a predetermined angle. The RAM 15 is a volatile storage unit that functions as a work area for the CPU 14. The ROM 16 is a nonvolatile storage unit that stores data communication with the angle sensor 4b, the drive unit 5, the camera 11a, the transport robot 12, and the like and data and software (program) necessary for processing the communicated data.

  The ROM 16 stores a drive program 16 a for controlling the drive unit 5 as a program for the drive unit 5 that rotates the susceptor 3. As a program related to the camera 11a, a calculation program 16b for calculating the width W1 of the gap S from a captured image input from the camera 11a is stored in the ROM 16. A position program 16 c for controlling the position of the transfer robot 12 is stored in the ROM 16 as a program related to the transfer robot 12.

  The calculation program 16b changes the width W1 of the gap S in the circumferential direction of the substrate W (the length of the width W1) from a plurality of captured images in which the camera 11a images the gap S passing through the imaging region R with the susceptor 3 rotated. To obtain fluctuations). Specifically, a plurality of captured images as shown in FIGS. 2B and 3 are captured while the susceptor 3 rotates around the axis O. Then, distances L1 and L2 shown in FIGS. 2B and 3 are calculated from the captured image. The distance L1 is a distance from a predetermined position at the left end of the imaging region R (see FIG. 2B) to the inner wall 3a1 of the counterbore 3a, and the distance L2 is a distance from the same predetermined position as the distance L1 to the outer periphery Wa of the substrate W. It is. Therefore, the distance obtained by subtracting the distance L2 from the distance L1 is the width W1 of the gap S. In addition to calculating the distances L1 and L2 from the captured image using the computer 13a, the distances L1 and L2 may be calculated by combining a programmable logic controller and a dedicated image processing system for image processing of the captured image.

  FIG. 6 shows a graph in which the distances L1 and L2 are plotted from a plurality of captured images captured while the susceptor 3 makes one rotation. 6 indicates the lengths of the distances L1 and L2, the distance L1 indicates the position of the inner wall 3a1 of the counterbore portion 3a, and the distance L2 indicates the position of the outer periphery Wa of the substrate W. In addition, the rotation angle on the horizontal axis in FIG. 6 indicates the positions of the outer circumference Wa and the inner wall 3a1 around the center C1 of the substrate W for which the distances L1 and L2 are calculated. In the graph in which the distance L1 is plotted, when the rotation center (axis O) of the susceptor 3 and the center C of the susceptor 3 (bore portion 3a) coincide with each other, a flat straight line graph is obtained. This is a trigonometric graph. In the graph in which the distance L2 is plotted, when the rotation center (axis O) of the susceptor 3 and the center C1 of the substrate W coincide with each other, a flat straight line graph is obtained. It becomes a graph.

  Therefore, the positional deviation between the center C of the susceptor 3 and the center of rotation (axis O) of the susceptor 3 is determined from the amplitude and phase of the graph in which the distance L1 is plotted in the circumferential direction of the substrate W as shown in FIG. Direction). Further, the positional deviation between the center C1 of the substrate W and the rotation center (axis O) of the susceptor 3 can be calculated from the amplitude and phase of the graph plotting the distance L2. Then, as shown in FIG. 7, the positional deviation between the center C1 of the substrate W and the center C of the susceptor 3 can be calculated from a graph in which the distance obtained by subtracting the distance L2 from the distance L1 is plotted as in FIG. Since the graph shown in FIG. 6 can be acquired every time the susceptor 3 rotates once, the susceptor 3 is rotated a plurality of times to acquire a plurality of graphs, and an average graph is generated from the plurality of graphs. The positional deviation can be calculated with high accuracy.

  In the calculation program 16b, the position where the substrate W is placed so that the center C of the susceptor 3 and the center C1 of the substrate W coincide with each other as the target position, and the placement position of the substrate W placed on the susceptor 3 is set as the target position. It is calculated from the positional deviation. That is, the placement position of the substrate W placed on the susceptor 3 is calculated based on the positional deviation between the center C1 of the substrate W and the center C of the susceptor 3 calculated based on the graph shown in FIG. The placement position of the substrate W is measured, for example, every time the substrate W is placed on the susceptor 3, and the average position of the placement positions is calculated from the plurality of placement positions measured by the calculation program 16b. If the target position is easy to understand, the center C of the susceptor 3 and the center C1 of the substrate W coincide with each other in plan view.

  The position program 16c adjusts the stop position at which the transfer robot 12 stops in order to transfer the substrate W from the transfer robot 12 that has entered the reaction furnace 2 while holding the substrate W to the susceptor 3. The transport robot 12 stops above the susceptor 3 when transporting the substrate W placed on the blade 12 a to the susceptor 3. Then, the substrate W is transferred to the lift pin from the blade 12a of the stopped transfer robot 12, and the substrate W is transferred to the susceptor 3 by the lift pin. In the position program 16c, the stop position at which the transfer robot 12 stops above the susceptor 3 is adjusted so that there is no difference between the target position where the substrate W should be placed on the susceptor 3 and the average position calculated by the calculation program 16b. .

  Next, the contents of the aforementioned various programs will be described with reference to the flowcharts of FIGS. The process of FIG. 8 is a process of calculating the placement position of the substrate W and the average position of the placement positions from the substrate W placed on the susceptor 3. This is a process in which the CPU 14 executes the drive program 16a and the calculation program 16b using the work memory of the RAM 15 as a work area.

  When the substrate W is placed on the susceptor 3, the CPU 14 rotates the susceptor 3 around the axis O through the drive unit 5 and causes the camera 11 a to capture a captured image of the gap S passing through the imaging region R (S 1). . The captured image is sequentially transmitted as image data from the camera 11a to the CPU 14, and the CPU 14 stores the transmitted image data in the RAM 15 (S2). The CPU 14 calculates the distances L1 and L2 shown in FIGS. 2B and 3 from each stored image data, and generates a graph in which the distances L1 and L2 are plotted from a plurality of captured images (see FIG. 6). The CPU 14 calculates the distance and direction in which the center C1 of the substrate W is shifted from the center C of the susceptor 3 from the generated graph, and stores position data indicating the placement position of the substrate W placed on the susceptor 3 in the RAM 15 ( S3). When there is already measured position data in the RAM 15 (S4: Yes), an average position that is an average of the placement positions of the substrates W is calculated from the plurality of position data. This process is repeatedly executed, for example, every time the substrate W is placed on the susceptor 3, and the average position is updated each time the placement position is measured and stored in the RAM 15. This process corresponds to the calculation means of the present invention.

  The process of FIG. 9 is a process of adjusting a stop position at which the transfer robot 12 stops in order to transfer the substrate W from the transfer robot 12 to the susceptor 3 when the transfer robot 12 that transfers the substrate W enters the reaction furnace 2. . In this process, the CPU 14 executes the position program 16c and the like using the work memory of the RAM 15 as a work area.

  For example, when the data indicating the average position is stored or updated in the RAM 15 by the process of S5 in FIG. 8, the CPU 14 has a fixed number of times of measurement of the mounting position that is a population for calculating the average position in S11 of FIG. Judge whether it is more than the number of times. If the number of measurements is less than a certain number (S11: No), the processing is terminated because the number of populations when calculating the average is small. On the other hand, if the number of measurements of the placement position is equal to or greater than a certain number (S11: Yes), the difference between the average position stored in the RAM 15 in S12 and the target position of the substrate W to be placed on the susceptor 3 is determined in advance. It is determined whether or not the threshold value is exceeded. If the difference does not reach the threshold value (S12: No), the process is terminated assuming that the average position is close to the target position. When the difference between the average position and the target position is greater than or equal to the threshold value (S12: Yes), the process proceeds to S13. In S13, it is determined whether or not the correction amount for correcting the stop position of the transfer robot 12 is equal to or greater than a predetermined amount so that the difference between the average position of the substrate W and the target position is eliminated. If the correction amount is greater than or equal to the predetermined amount (S13: Yes), the process ends with the correction amount as an abnormal value. On the other hand, if the correction amount is less than the predetermined amount (S13: No), it is determined in S14 whether the integrated correction amount of the correction amount that has corrected the stop position of the transport robot 12 so far is equal to or greater than the predetermined integrated amount. . If the integrated correction amount is greater than or equal to the predetermined integrated amount (S14: Yes), the process ends as an abnormality of the integrated correction amount. On the other hand, if the integrated correction amount is less than the predetermined integrated amount (S14: No), the stop position of the transfer robot 12 is adjusted so that there is no difference between the average position of the substrate W and the target position (S15), and processing Finish.

  The series of processes in FIG. 9 is repeatedly executed every time the average position, which is the average of the placement positions of the substrates W, is updated, for example. Since the position of the transfer robot 12 is not adjusted when the number of times of measurement of the placement position that is the basis of the average position is insufficient, the position of the transfer robot 12 can be adjusted based on an appropriate measurement result. Further, when an abnormal value occurs in the correction amount for adjusting the stop position of the transfer robot 12, adjustment of the position of the transfer robot 12 can be avoided. It is preferable to add a protection algorithm for abnormal values as shown in the process of FIG. This process corresponds to the adjusting means of the present invention.

  When an epitaxial wafer is manufactured by the vapor phase growth apparatus 1 configured as described above, first, the substrate W is loaded into the reaction furnace 2 and placed on the susceptor 3. When the substrate W is placed on the susceptor 3, the driving unit 5 rotates the susceptor 3, and the camera 11 a images the gap S around the substrate W placed on the rotating susceptor 3. The positional deviation between the center C1 of the substrate W and the center C of the counterbore part 3a is calculated from a plurality of captured images captured by the camera 11a, and the placement position of the substrate W is calculated. Then, an epitaxial layer is grown on the substrate W placed on the susceptor 3 to produce an epitaxial wafer. The produced epitaxial wafer is transported from the susceptor 3 to the transport robot 12 by lift pins and transported outside the reaction furnace 2. Thereafter, when a new substrate W is transported into the reaction furnace 2 by the transport robot 12 and the substrate W is placed on the susceptor 3, an average (average position) of the placement position and the placement position is calculated. Then, an epitaxial layer is grown on the substrate W as before. By repeating such a process, an epitaxial layer is grown on the plurality of substrates W accommodated in the transport box, and a plurality of epitaxial wafers are produced.

  The substrate W placed on the susceptor 3 when producing the epitaxial wafer may be placed on the susceptor 3 with a deviation from the target position on the susceptor 3. Various causes such as warpage of the substrate W, thermal expansion of the substrate W, wobbling of the lift pins, and the like can be cited as causes of this displacement. Therefore, the displacement of the substrate W placed on the susceptor 3 has poor reproducibility. Therefore, for example, even when the stop position of the transfer robot 12 is corrected based on the position shift of the substrate W that occurred immediately before, if the cause of the next position shift differs from the cause of the position shift that occurred immediately before, the transfer robot 12 stop positions cannot be adjusted properly.

  Therefore, in this embodiment, the average position which is the average of the placement positions of the placement positions of the substrates W placed on the susceptor 3 is calculated, so that an index is given to the positional deviation of the substrate W without reproducibility. Then, by adjusting the position of the transfer robot 12 based on the average position serving as the index, the position of the transfer robot 12 can be adjusted appropriately.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, these do not limit this invention.

(Example)
In the example, an epitaxial layer was vapor-phase grown on a plurality of substrates W (silicon single crystal substrates having a diameter of 300 mm) housed in a transport box using the vapor phase growth apparatus 1. The threshold value of the difference between the average position for adjusting the stop position of the transfer robot 12 and the target position was set to 0.1 mm. As the camera 11a used in the example, a monochrome CMOS camera having a light receiving element size of ¼ inch and a pixel number of 640 × 480 was employed. The lens of the CMOS camera has a 1/2 inch format, focal length so that a 30 × 20 mm area around the substrate W placed on the susceptor 3 (around the gap S between the outer periphery Wa and the inner wall 3a1) can be imaged. A 25 mm lens was used. At this time, the width W1 of the gap S corresponds to an average of about 20 pixels. A reflection type ND filter having a transmittance of 5% and an infrared absorption filter are provided in front of the lens so that excessive light does not enter the CMOS camera. Further, the protective tube 11b for protecting the CMOS camera was mounted on the CMOS camera (camera 11a) so as to reflect the heat from the lamp 9 as much as possible with a gold-plated mirror-finished outer surface. It should be noted that 15 liters of nitrogen was circulated inside the protective tube 11b to prevent the temperature of the CMOS camera from rising, and the heat of the infrared absorption filter was discharged outside the protective tube 11b.

  FIG. 3 shows a captured image captured by a CMOS camera. While the susceptor 3 made one rotation around the axis O, 60 captured images were acquired, and the distances L1 and L2 were calculated from the respective images. A normal computer 13a was used to calculate the distances L1 and L2, and the outer periphery Wa of the substrate W and the inner wall 3a1 of the counterbore part 3a were detected by a unique algorithm. In the angle sensor 4b for detecting the rotation angle of the susceptor 3, a disk provided with a slit is attached to the support column 4a, the position where the slit is detected by the photo interrupter is set as a reference position, and the time after the reference position is detected Based on this, the rotation angle of the susceptor 3 was detected.

  FIG. 7 is a graph in which data obtained by subtracting the distance L2 from the distance L1 acquired from the substrate W used in the example is plotted with the distance on the vertical axis and the rotation angle on the horizontal axis. From the amplitude and phase of the graph of FIG. 7, the center C1 of the substrate W (placement position of the substrate W) is 0.27 mm away from the center C (target position) of the susceptor 3 in the direction of 44 ° from the reference angle position. Was calculated. FIG. 10A shows the result of measuring the mounting positions of all the plurality of substrates W stored in one transport box in the same manner. In FIG. 10A, the center of the circle drawn with a broken line is the center C (target position) of the susceptor 3, and the same applies to FIGS. 10B, 11 and 12. From FIG. 10A, it is detected that the average position of the substrate W (the average of the center C1 position of the substrate W) is 0.59 mm away from the center C (target position) of the susceptor 3 in the direction of 45 ° from the reference angle position. It was.

  Here, since the distance between the average position and the target position is larger than the threshold value 0.1 mm for adjusting the stop position of the transfer robot 12, the stop position of the transfer robot 12 is set so that the distance between the average position and the target position disappears. Adjusted. And the epitaxial layer was grown on the board | substrate W accommodated in one conveyance box different from the previous using the conveyance robot 12 which adjusted the stop position. FIG. 10B shows the result of measuring the placement position of the substrate W placed on the susceptor 3 (position of the center C1 of the substrate W) after adjusting the stop position. As shown in FIG. 10B, the variation in the position of the center C1 of the substrate W is not substantially different from that before the stop position of the transfer robot 12 is adjusted, whereas the placement position of the center C1 of the substrate W is the position of the center C of the susceptor 3 (target Position). Therefore, it can be seen that the position of the transfer robot 12 is appropriately adjusted.

(Comparative example)
In the comparative example, the following experiment was performed following the example using the same apparatus as the example.

  In Comparative Example 1, after the substrate W (silicon single crystal substrate having a diameter of 300 mm) is loaded into the reaction furnace 2 and placed on the susceptor 3, the positional deviation between the center C1 of the substrate W and the center C of the susceptor 3 is Distance and direction shifted). Next, the substrate W placed on the susceptor 3 is taken out of the reaction furnace 2, and the stop position of the transfer robot 12 that stops above the susceptor 3 is adjusted from the calculated displacement so that the displacement does not occur, and the substrate W is again formed. Was loaded into the reactor 2. Then, the operation of measuring the positional deviation and adjusting the position of the transfer robot 12 was repeated 25 times. FIG. 11 is a diagram illustrating a placement position of the substrate W placed on the susceptor 3 (a center C1 of the substrate W). In FIG. 11, the average position of the placement positions substantially coincides with the center of the susceptor 3. However, in Comparative Example 1 shown in FIG. 11, the stop position of the transfer robot 12 is adjusted based on the average (average position) of the placement positions of the variation in the center C1 position (placement position of the substrate W) of the substrate W. It became larger than the example (FIG. 10B). In Comparative Example 1, the stop position of the transfer robot 12 is adjusted every time the substrate W is loaded into the reaction furnace 2 without averaging the mounting position of the substrate W (the position of the center C1 of the substrate W). When the position of the transfer robot 12 is adjusted based on the immediately preceding placement position as in the comparative example 1, the placement position varies every time the substrate W is placed, and thus the dispersion becomes worse and expands. For example, when the next placement position is shifted in the same direction as the direction in which the previous placement position is corrected, the placement position of the substrate W is shifted synergistically, resulting in an increase in the position shift.

(Comparative Example 2)
In Comparative Example 2, the following experiment was performed following Comparative Example 1 using the same apparatus as Comparative Example 1. The average position of the substrate W (silicon single crystal substrate having a diameter of 300 mm) placed on the susceptor 3 (the average position of the center C1 position of the substrate W placed on the susceptor 3) coincides with the center C of the susceptor 3. Thus, the stop position of the transfer robot 12 was adjusted. From there, the stop position of the transfer robot 12 was adjusted so that the placement position of the substrate W was shifted 0.3 mm to the right and 0.1 mm upward from the center C of the susceptor 3. Then, after carrying the substrate W into the reaction furnace 2 and placing it on the susceptor 3, the operation of calculating the positional deviation (distance from the direction of the distance) between the center C1 of the substrate W and the center C of the susceptor 3 is repeated 25 times. It was. On the way, there were 12 cases where it was calculated that the center C1 of the substrate W was separated from the center C (target position) of the susceptor 3 by 0.4 mm or more. For each 12 times, after the substrate W is taken out of the reaction furnace 2, the stop position of the transfer robot 12 is changed so that the substrate W is placed on the center C of the susceptor 3, and the transfer robot 12 is moved into the reaction furnace 2. Was re-loaded and the displacement was measured. Further, the changed stop position of the transfer robot 12 is restored after the completion of the re-loading.

  This experiment corresponds to Patent Document 1 in which the stop position of the transport robot 12 is adjusted and reloaded only when the placement position deviates from a predetermined range. FIG. 12 shows the mounting position of the substrate W at this time. Only when the placement position is largely deviated without averaging the center C1 position of the substrate W, when the transfer robot 12 is adjusted based on the deviated distance, only data with a large distance is selected, and the transfer robot 12 is stopped. Position adjustment is excessive. Therefore, the variation in the mounting position of the substrate W is enlarged.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the specific description, and the illustrated configurations and the like can be appropriately combined within a technically consistent range. In addition, certain elements and processes may be replaced with known forms. For example, the example in which the counterbore part 3a is formed in a disk shape and the example of the lamp heating type in which the substrate W is heated by the lamp 9 have been described above, but the present invention is not limited to this.

DESCRIPTION OF SYMBOLS 1 Vapor growth apparatus 2 Reactor 3 Susceptor 3a Counterbore part 5 Drive part 6 Gas supply pipe 7 Gas exhaust pipe 9 Lamp 11 Imaging device 12 Transfer robot 13 Control part

Claims (12)

A calculation step of measuring a placement position where the substrate is placed on the susceptor from each of the plurality of substrates placed on the susceptor, and calculating an average position of the placement position from the plurality of measured placement positions;
Adjusting the stop position at which the transfer robot stops to transfer the substrate from the transfer robot that transfers the substrate toward the susceptor, and
The method of manufacturing an epitaxial wafer, wherein the adjusting step adjusts the stop position so as to eliminate a difference between a target position on which the substrate is to be placed on the susceptor and the average position.   2. The method for manufacturing an epitaxial wafer according to claim 1, wherein the calculation step calculates the average position by measuring the mounting position every time the substrate is mounted on the susceptor.   The epitaxial wafer manufacturing method according to claim 1, wherein the target position is a position where a center of the susceptor and the substrate coincide. The susceptor is rotatable about an axis, and has a counterbore part on which the substrate is placed;
The epitaxial wafer manufacturing method according to claim 1, wherein the target position is a position where a center of the counterbore part and the substrate coincides. The calculation step includes
An area including a gap between the counterbore part and the substrate located in a direction from the center of the substrate placed on the counterbore part toward the outer periphery is defined as an imaging area, and the susceptor is rotated about the axis to An imaging step of capturing an image of the gap passing through;
A measurement step of obtaining a variation in the width of the gap in the circumferential direction of the substrate from the captured image, and measuring the placement position based on the variation,
The manufacturing method of the epitaxial wafer of Claim 4 provided with these. In the imaging step, the gap is imaged by rotating the susceptor a plurality of times,
The epitaxial wafer manufacturing method according to claim 5, wherein the measurement step acquires the variation every time the susceptor rotates, and measures the mounting position based on an average of the acquired plurality of variations.   The adjustment step adjusts the stop position when the difference is equal to or greater than a preset threshold value, and does not adjust the stop position when the difference is less than the threshold value. Epitaxial wafer manufacturing method. A susceptor on which a substrate is placed;
A transfer robot for transferring the substrate;
A control unit that controls a stop position at which the transfer robot stops in order to transfer the substrate from the transfer robot to the susceptor,
The controller is
Calculation means for measuring a mounting position where the substrate is mounted on the susceptor from each of the plurality of substrates mounted on the susceptor, and calculating an average position of the previous mounting position from the plurality of measured mounting positions. When,
Adjusting means for adjusting the stop position of the transfer robot so as to eliminate the difference between the target position where the substrate is to be placed on the susceptor and the average position;
A vapor phase growth apparatus comprising:   9. The vapor phase growth apparatus according to claim 8, wherein the calculation unit measures the placement position every time the substrate is placed on the susceptor and calculates the average position.   The vapor phase growth apparatus according to claim 8 or 9, wherein the target position is a position where a center of the susceptor and the substrate coincide. The susceptor is rotatable about an axis, and has a counterbore portion whose center coincides with the susceptor, and the substrate is placed on the counterbore portion,
The vapor phase growth apparatus according to claim 10, wherein the target position is a position where a center of the counterbore part and the substrate coincide. An imaging apparatus having an imaging area that includes a gap between the counterbore part and the substrate located in a direction from the center of the substrate placed on the counterbore part toward the outer periphery;
The calculating means includes
Imaging means for rotating the susceptor around the axis to obtain a captured image of the gap passing through the imaging region from the imaging device;
Measuring means for obtaining a variation in the width of the gap from the captured image and measuring the placement position based on the variation;
The vapor phase growth apparatus according to claim 11.