JP2011171637A - Method of manufacturing epitaxial wafer, and susceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique that can easily and suitably control a thickness of an outer peripheral part of an epitaxial wafer. <P>SOLUTION: A method of manufacturing the epitaxial wafer includes: determining counterbore depth information specifying a counterbore depth from a height position of an outer peripheral part of a susceptor 26 for mounting a wafer W to a position of the susceptor 26 in which the wafer W is mounted when an epitaxial layer is formed (step S1); generating a silicon film in a height direction of the outer peripheral part of the susceptor 26 so that a counterbore depth of the susceptor 26 is equal to the counterbore depth specified by the counterbore depth information (step S4); and mounting the wafer W on the susceptor 26 and generating the epitaxial layer on the wafer W (step S7). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an epitaxial wafer manufacturing method and the like for manufacturing an epitaxial wafer by generating an epitaxial layer on a wafer.

  Conventionally, a deposition reaction apparatus for generating an epitaxial layer on a wafer is known. In the film formation reaction apparatus, for example, by placing a wafer on a disk-shaped susceptor and rotating the susceptor, by flowing a raw material gas for generating an epitaxial layer in a direction substantially parallel to the upper surface of the wafer, An epitaxial layer is formed on the upper surface of the wafer.

In recent years, in order to increase the area that can be used as a device on a wafer, it is required to make the film thickness uniform on the outer periphery of the wafer. As a technique for controlling the film thickness at the outer peripheral portion of the wafer, for example, a method for controlling the concentration of a source gas (for example, SiHCl ₃ (trichlorosilane) gas) and a method for controlling a growth temperature during epitaxial growth are known. It has been. In addition, as another technique for controlling the film thickness at the outer peripheral portion of the wafer, a technique is known in which epitaxial growth is performed using a susceptor whose upper surface is at a height between the upper main surface of the wafer and the wafer thickness center. (For example, refer to Patent Document 1).

JP 2008-71921 A

  According to the technique described in Patent Document 1 described above, a susceptor suitable for a wafer to be vapor-grown is prepared, a vapor-phase growth apparatus is configured, and vapor-phase growth is performed using the vapor-phase growth apparatus. Thereby, the uniformity of the outer peripheral part of a wafer can be improved.

  However, for example, when processing a plurality of types of wafers having different thicknesses, a plurality of susceptors suitable for each of the wafers to be processed must be prepared. Furthermore, depending on the wafer to be processed, it is necessary to incorporate a corresponding susceptor into the vapor phase growth apparatus. For this reason, it is necessary to open the inside of the furnace of the vapor phase growth apparatus, a process for removing the susceptor from the vapor phase growth apparatus, or a process required after the vapor phase growth apparatus is assembled by replacing the susceptor (for example, the apparatus) There is a problem that time and labor are required since a withering process for forming a predetermined film inside must be performed.

  This invention is made | formed in view of the said subject, The objective is to provide the technique which can control the thickness of the epitaxial layer of the outer peripheral part of an epitaxial wafer easily and appropriately.

  In order to achieve the above object, an epitaxial wafer manufacturing method for manufacturing an epitaxial wafer by generating an epitaxial layer on a wafer according to the first aspect of the present invention, wherein the wafer is placed when generating an epitaxial layer. A step of determining counterbore depth information for identifying the counterbore depth from the height position of the outer periphery of the susceptor to a position on which the wafer of the susceptor is placed, and the counterbore depth in the susceptor is determined by the counterbore depth information. A silicon film generation step for generating a silicon film in the height direction of the outer periphery of the susceptor so that the specified counterbore depth is obtained, and a wafer is placed on the susceptor that generated the silicon film, and an epitaxial layer is formed on the wafer. And producing an epitaxial growth step. According to such an epitaxial wafer manufacturing method, a silicon film can be generated to make the counterbore depth in the susceptor a predetermined depth, and an epitaxial layer can be generated on the wafer using the susceptor. For this reason, by adjusting the thickness of the silicon film formed on the outer periphery of the susceptor without preparing different susceptors, a plurality of desired counterbore depths can be easily realized. Thereby, the epitaxial film thickness in the peripheral part of the wafer can be appropriately controlled.

  In the epitaxial wafer manufacturing method, in the silicon film generation step, a dummy wafer may be placed on a susceptor to generate a silicon film, and then the dummy wafer may be removed. According to the epitaxial wafer manufacturing method, generation of a silicon film at a position where the wafer is placed can be appropriately reduced.

  The epitaxial wafer manufacturing method may further include a removal step of removing the silicon film generated on the susceptor before the silicon film generation step. According to the epitaxial wafer manufacturing method, the silicon film generated on the susceptor can be removed. For this reason, when the subsequent silicon film is generated, the thickness of the silicon film can be set to an appropriate thickness.

  In the epitaxial wafer manufacturing method, the removal step, the silicon film generation step, and the epitaxial growth step may be repeatedly performed on different wafers. According to the epitaxial wafer manufacturing method, a plurality of epitaxial wafers can be manufactured efficiently.

  In the epitaxial wafer manufacturing method, the thickness of the silicon film generated in the height direction of the outer peripheral portion of the susceptor may be 1 μm or more and 100 μm or less in the silicon film generation step. According to the epitaxial wafer manufacturing method, the counterbore depth can be adjusted in the range of 1 μm or more and 100 μm or less, and the thickness in the height direction of the outer peripheral portion of the wafer can be controlled in detail.

  In order to achieve the above object, the susceptor according to the second aspect of the present invention is a susceptor for placing a wafer for generating an epitaxial layer, and a silicon film is formed on at least the outer periphery of the susceptor. The counterbore depth from the height position of the outer periphery to the position where the wafer of the susceptor is placed is from the height position of the outer periphery when no silicon film is formed on the susceptor and the position where the wafer is placed. Different from the initial counterbore depth. According to such a susceptor, the counterbore depth between the height position where the thickness of the silicon film is added to the outer periphery of the susceptor and the mounting position of the wafer of the susceptor is the initial in the case where no silicon film is formed. Since this is different from the counterbore depth, the film thickness of the epitaxial layer on the outer periphery of the wafer can be controlled to be different from the case of the initial counterbore depth by using this susceptor.

  In the susceptor, a silicon film may not be generated at a position where the wafer is placed. According to such a susceptor, since the silicon film is not generated at the mounting position, it is possible to appropriately prevent the silicon film from being transferred to the contact portion of the wafer with the susceptor.

It is sectional drawing which shows the principal part of the film-forming reaction apparatus which concerns on one Embodiment of this invention. It is a figure explaining the counterbore depth of the susceptor concerning one embodiment of the present invention. It is a figure explaining the difference in the film thickness of the epitaxial layer by the difference in the counterbore depth concerning one Embodiment of this invention. It is a figure which shows the relationship between the counterbore depth which concerns on one Embodiment of this invention, and edge inclination. It is a flowchart which shows the epitaxial wafer manufacturing process which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. The embodiments described below do not limit the invention according to the claims, and all the elements and combinations described in the embodiments are essential for the solution of the invention. Is not limited.

  First, a film formation reaction apparatus according to an embodiment of the present invention will be described.

  FIG. 1 is a cross-sectional view showing a main part of a film forming reaction apparatus according to an embodiment of the present invention. The film formation reaction apparatus 1 can be used to form an epitaxial layer of a semiconductor material such as silicon on the surface of a semiconductor wafer (wafer) such as a silicon wafer.

  As shown in FIG. 1, the film-forming reaction apparatus 1 includes a reactor 20 having a reaction chamber 20A inside. The shape of the reaction chamber 20A is a flat, generally cylindrical shape. The entire upper surface of the reaction chamber 20 </ b> A is covered with a substantially disk-shaped upper dome 21. That is, the upper dome 21 constitutes the ceiling wall of the reaction chamber 20A. The bottom wall of the reactor 20 is composed of a substantially annular lower liner 24 and a disk-shaped susceptor 26 disposed in a circular opening inside the lower liner 24. The susceptor 26 is formed in a predetermined shape by, for example, using C (carbon) as a base material and covering the periphery thereof with high-purity silicon carbide (SiC).

  The upper liner 22 has a protruding annular portion 22A that protrudes downward on the entire periphery of the peripheral edge thereof. The protruding annular portion 22A of the upper liner 22 is coupled to the peripheral portion 24A of the lower liner 24, and constitutes a side wall of the reaction chamber 20A. A wafer (substrate) W is placed on the susceptor 26. The susceptor 26 is coupled to the susceptor support shaft 30 on the lower surface thereof, and is driven to rotate around the center of the wafer W during the film forming process. For example, the wafer W has a diameter of 200 mm.

  Further, an annular row of a large number of heating lamps 32, 32,... Is arranged above and below the reaction chamber 20A, respectively. The main parts of the upper dome 21 and the lower dome 31 are made of a light-transmitting heat-resistant material such as quartz so that the radiant heat from the lamps 32, 32,... Is transmitted well to the susceptor 26 and the wafer W.

  A gas inlet 20B is formed at one end (left side in the figure) of the reaction chamber 20A. Further, a gas discharge port 20C is formed at the end of the reaction chamber 20A opposite to the gas inlet 20B (right side in the figure). Both the gas inflow port 20B and the gas discharge port 20C are arranged in the vicinity of the outside of the periphery of the wafer W, and extend along the periphery of the wafer W in an arc shape substantially parallel to the periphery. The dimension in the width direction of the gas inlet 20B and the gas outlet 20C (the direction in which the gas inlet 20B and the gas outlet 20C extend along the periphery of the wafer W), that is, the width is the diameter of the wafer W on the susceptor 26. Slightly larger than. The center positions of the gas inlet 20B and the gas outlet 20C in the width direction coincide with the center positions of the wafer W in the same width direction. Accordingly, in the reaction chamber 20A, a strip having a wide width for covering the entire region of the wafer W in the direction from the gas inlet 20B to the gas outlet 20C (direction substantially parallel to the upper surface of the wafer W). A reactive gas stream is formed.

  Specifically, the reaction gas passes through the gas inlet 20B and flows into the reaction chamber 20A as a belt-like gas flow. The strip-shaped gas flow that has flowed into the reaction chamber 20A from the gas inlet 20B passes over the entire area of the surface of the wafer W on the susceptor 26 to form an epitaxial layer on the surface of the wafer W. Thereafter, the reaction gas flow enters the gas discharge port 20 </ b> C, passes through the outlet flange 42, and exits to the gas discharge pipe 44.

  In this film forming reaction apparatus 1, a transfer chamber (not shown) provided with a transfer robot for transferring the wafer W is provided, and the transfer chamber can communicate with the reaction chamber 20A without opening the reaction chamber 20A to the atmosphere. ing. Therefore, the transfer robot in the transfer chamber can place the wafer W on the susceptor 26 and take out the wafer W from the susceptor 26 without opening the reaction chamber 20A to the atmosphere.

  FIG. 2 is a view for explaining the counterbore depth of the susceptor according to the embodiment of the present invention.

  2A shows the counterbore depth (initial counterbore depth) when a silicon film (Si film) is not formed in the height direction of the outer peripheral portion of the susceptor 26 (initial state), and FIG. FIG. 2C shows the counterbore depth when the silicon film is formed on the outer peripheral portion and the silicon film is not formed on the mounting position of the wafer W. FIG. 2C shows the outer peripheral portion of the susceptor 26 and the mounting position of the wafer. The counterbore depth when a silicon film is formed is shown. Here, the outer peripheral portion of the susceptor 26 indicates a portion outside the wafer W when the wafer W is placed on the susceptor 26. The thickness direction of the wafer W (the direction from the bottom to the top in the figure) when the wafer W is placed on the susceptor 26 is referred to as the height direction, and the surface of the wafer W that contacts the susceptor 26 (see FIG. It is assumed that the height increases from the middle surface to the other surface of the wafer W (upper surface in the figure). The position of the highest part of the outer periphery of the susceptor 26 is referred to as the height position of the outer periphery.

  As shown in FIG. 2A, in the susceptor 26, the main body portion 26a on the upper surface of the outer peripheral portion is the highest, and the inner peripheral side (the right side in the drawing) has a concave shape for placing the wafer W thereon. ing. On the inner peripheral side of the susceptor 26, a support portion 26b that supports the wafer W in contact with the outer peripheral portion of the lower surface of the wafer W is formed. In the case shown in FIG. 2A, the height position P1 of the contact position (mounting position) 26c of the supporting portion 26b supporting (mounting) the wafer W and the height of the main body portion 26a on the outer peripheral portion of the susceptor 26 are shown. The distance between the position (the height position of the outer peripheral portion in FIG. 2A) T1 is the counterbore depth (initial counterbore depth).

  In FIG. 2B, in the outer peripheral portion of the susceptor 26, the silicon film 26d is formed on the body portion 26a on the outer periphery (in the height direction), but the silicon film is not formed on the support portion 26b. The counterbore depth in each case is shown. In the case shown in FIG. 2B, the height position P1 of the contact position (mounting position) 26c of the support portion 26b on which the wafer W is mounted and the height of the upper surface 26dt of the silicon film 26d on the outer peripheral portion of the susceptor 26. The distance between the position (height position of the outer peripheral portion in FIG. 2B) T2 is the counterbore depth.

  In FIG. 2C, in the outer peripheral portion of the susceptor 26, the silicon film 26d is formed on the body portion 26a on the outer periphery (in the height direction), and the silicon film 26e is also formed on the support portion 26b. The counterbore depth in the case where In the drawing, an example is shown in which the thickness in the height direction of the silicon film thickness at the outer peripheral portion and the silicon film thickness at the support portion 26b are different. In the case shown in FIG. 2C, the height position P2 of the contact position (mounting position) 26et of the wafer W on the silicon film 26e generated on the support portion 26b on which the wafer W is mounted, and the outer peripheral portion of the susceptor 26 The distance from the height position (the height position of the outer peripheral portion in FIG. 2C) T2 of the upper surface 26dt of the silicon film 26d is the counterbore depth. In this way, by adjusting at least one of the thickness of the silicon film on the outer peripheral portion of the susceptor 26 and the thickness of the silicon film on the support portion 26b of the susceptor 26, the counterbore depth of the susceptor 26 is different from the initial counterbore depth. Can be adjusted to depth.

  Next, the influence on the epitaxial layer thickness due to the difference in the counterbore depth will be described.

  FIG. 3 is a diagram for explaining the difference in the thickness of the epitaxial layer due to the difference in the counterbore depth according to the embodiment of the present invention. FIG. 3 is generated with respect to the distance from the center of the wafer W at a certain position and the average film thickness (average film thickness) of the epitaxial layer of the wafer W when the counterbore depth of the susceptor 26 is changed. The relationship with the film thickness of the epitaxial layer is shown.

  Here, the counterbore depth A is the counterbore depth (initial counterbore depth) when no silicon film is formed on the susceptor 26, and the counterbore depth B is a 100 μm silicon film on the outer periphery of the susceptor 26. Is the counterbore depth when. The figure shows an example in which the diameter of the wafer W is 200 mm.

  As shown in FIG. 3, in the range from 98 mm to 95 mm from the center of the wafer W, that is, in the outer peripheral portion of the wafer W, the counterbore depth A is greater when the counterbore depth is large (deep). It can be seen that the film thickness tends to increase as it approaches the center of the wafer W as compared with the outer peripheral portion. Such a tendency will be further described with reference to FIG.

  FIG. 4 is a diagram showing a relationship between the counterbore depth and the edge inclination according to the embodiment of the present invention. Here, the edge inclination is an index indicating a rate of change in film thickness in a predetermined range (for example, a range from 98 mm to 95 mm from the wafer center) in which the film thickness of the outer peripheral portion of the wafer W is desired to be controlled. In this case, edge inclination = ((film thickness at a position 98 mm from the wafer center) − (film thickness at a position 95 mm from the wafer center) / average film thickness of the wafer). According to this edge inclination, when taking a negative value, it indicates that the film thickness decreases toward the outer periphery of the wafer W, and the decreasing rate increases as the absolute value increases (the value decreases). Indicates.

  As shown in FIG. 4, it can be seen that the edge inclination decreases as the counterbore depth increases (deeper). This shows that the film thickness of the outer peripheral part of the wafer W can be controlled by changing the counterbore depth. For example, when it is desired to suppress the film thickness of the outer peripheral portion of the wafer W and control is performed by the counterbore depth, it is basically understood that the counterbore depth may be increased.

  Next, an epitaxial wafer manufacturing process according to an embodiment of the present invention will be described.

  FIG. 5 is a flowchart showing an epitaxial wafer manufacturing process according to an embodiment of the present invention.

First, optimum control conditions for realizing the specifications of an epitaxial wafer produced by producing an epitaxial layer on the wafer W are determined. In the present embodiment, as one of the control conditions, an optimal counterbore depth is determined in order to obtain an appropriate film thickness, and a silicon film thickness (counterbore depth specifying information) necessary for the counterbore depth is determined. Determine (step S1). In this embodiment, the silicon film thickness is 1 μm or more and 100 μm or less. Here, as a control target for making the epitaxial layer generated on the wafer W have an appropriate film thickness, in addition to the counterbore depth, the concentration of the source gas (for example, SiHCl ₃ gas), the growth temperature of the epitaxial layer, and the like There is. And, as a method for determining these optimum control conditions, the relationship between these controlled objects and the film thickness of the generated epitaxial layer is grasped in advance, and the most suitable for the specification based on these relationships What is necessary is just to detect the combination of control conditions. Various methods are known for detecting the optimum control condition for a plurality of control objects, and thus the description thereof is omitted here.

  Next, in the film formation reaction apparatus 1, hydrogen chloride (HCL) gas is supplied into the reaction chamber 20A to clean the inside of the reaction chamber 20A (step S2). As a result, the silicon film or the like formed on the susceptor 26 is appropriately removed.

  Next, a cover wafer is placed on the susceptor 26 of the film formation reaction apparatus 1 so that a silicon film is not formed at the position where the wafer W is placed on the susceptor 26 (step S3). In step S1, a silicon film having a thickness determined in step S1 is generated on the outer periphery of the susceptor 26 (step S4), and the cover wafer is taken out of the susceptor 26 by a transfer robot (not shown) (step S5). As a result, a silicon film having a desired thickness is formed on the outer periphery of the susceptor 26 as shown in FIG. 2B, and no silicon film is formed by the cover wafer at the mounting position of the wafer W. Therefore, the counterbore depth of the susceptor 26 is an optimal depth determined in advance. As a method of forming a silicon film having an appropriate thickness on the outer periphery of the susceptor 26, a silicon film is formed in advance under various conditions, and the thickness of the silicon film on the outer periphery of the susceptor 26 under each condition is changed. When measuring (or measuring the thickness of the silicon film on the cover wafer considered to be equivalent) and forming the silicon film in step S4, the silicon film is formed according to the conditions under which the film thickness to be formed is obtained. May be formed.

  Next, a wafer W for manufacturing an epitaxial wafer is placed on the susceptor 26 (step S6), and an epitaxial growth process is performed according to the determined control conditions (step S7). Thereby, the wafer W becomes an epitaxial wafer on which an epitaxial layer having a desired thickness is formed.

  Next, the wafer W on the susceptor 26 is taken out by the transfer robot (step S8) and transferred to a predetermined transfer destination.

  Next, the control unit (not shown) of the film formation reaction apparatus 1 determines whether or not the epitaxial growth process for all the wafers to be processed has been completed (step S9), and the process has not been completed for all the wafers W. In (Step S9: NO), while the processing from Step S2 is performed, when the epitaxial growth processing for all the wafers W is finished (Step S9: YES), the epitaxial wafer manufacturing processing is finished. .

  According to the above embodiment, the counterbore depth of the susceptor 26 can be adjusted appropriately, so that the film thickness of the outer peripheral portion of the epitaxial wafer can be controlled appropriately.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not restricted to embodiment mentioned above, It can apply to other various aspects.

  For example, in the above embodiment, the upper surface of the wafer W placed on the susceptor 26 is lower than the height of the outer periphery of the susceptor 26, that is, the thickness of the wafer W is thinner than the counterbore depth of the susceptor 26. However, the present invention is not limited to this, and the upper surface of the wafer W is higher than the height of the outer peripheral portion of the susceptor 26, that is, the thickness of the wafer W may be thicker than the counterbore depth of the susceptor 26. .

  In the above embodiment, when the silicon layer is formed on the susceptor 26, the cover wafer is placed on the susceptor 26 so that the silicon film is not formed on the placement position of the wafer W. However, the present invention is not limited to this, and a silicon film may be formed at the mounting position of the wafer W. In short, the counterbore depth may be adjusted to a desired counterbore depth.

  In the above embodiment, the processing from step S2 shown in FIG. 5 is performed on the subsequent wafer W, and the counterbore depth of the susceptor 26 when processing a plurality of wafers W is the same. The present invention is not limited to this. For example, the film thickness of the silicon film having a different counterbore depth of the susceptor 26 may be determined for each wafer W. In this case, the thickness of the silicon film is completely different. Even when epitaxial growth is performed on one wafer or when epitaxial growth with different specifications is performed on a plurality of wafers, an appropriate epitaxial film thickness can be formed on the wafer W in each process.

DESCRIPTION OF SYMBOLS 1 Film-forming reaction apparatus, 20 reactor, 20A reaction chamber, 20B gas inlet, 20C gas outlet, 24 lower liner, 24A stepped recessed part, 26 susceptor, W wafer

Claims (7)

An epitaxial wafer manufacturing method for manufacturing an epitaxial wafer by generating an epitaxial layer on a wafer,
Determining counterbore depth information for specifying the counterbore depth from the height position of the outer periphery of the susceptor for mounting the wafer to the position for mounting the wafer on the susceptor when generating an epitaxial layer A decision step to
A silicon film generating step for generating a silicon film in a height direction of the outer peripheral portion of the susceptor so that the counterbored depth in the susceptor is a counterbored depth specified by the counterbored depth information;
An epitaxial wafer manufacturing method comprising: an epitaxial growth step of placing the wafer on a susceptor that has generated the silicon film and generating an epitaxial layer on the wafer. The epitaxial wafer manufacturing method according to claim 1, wherein in the silicon film generation step, a cover wafer is placed on the susceptor to generate the silicon film, and then the cover wafer is removed. The epitaxial wafer manufacturing method according to claim 1, further comprising a removing step of removing the silicon film generated on the susceptor before the silicon film generating step. The epitaxial wafer manufacturing method according to claim 3, wherein the removing step, the silicon film generating step, and the epitaxial growth step are repeatedly performed on different wafers. 5. The thickness of the silicon film generated in the height direction of the outer peripheral portion of the susceptor in the silicon film generation step is 1 μm or more and 100 μm or less. 6. Epitaxial wafer manufacturing method. A susceptor for mounting a wafer for generating an epitaxial layer,
A silicon film is formed on at least the outer peripheral portion of the susceptor, and the counterbore depth from the height position of the outer peripheral portion to the position where the wafer is placed on the susceptor is completely formed on the susceptor. The susceptor is different from the height position of the outer peripheral portion when there is not, and the initial counterbore depth to the position where the wafer is placed. The susceptor according to claim 6, wherein the silicon film is not generated at a position where the wafer is placed.

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