JP2019117890A - Manufacturing method of epitaxial wafer and epitaxial wafer - Google Patents

Abstract

A method for manufacturing an epitaxial wafer is provided, which can manufacture an epitaxial wafer having an epitaxial layer with excellent flatness. A method of manufacturing an epitaxial wafer according to the present invention includes a first step (steps S1 to S3) of placing the wafer on a susceptor after supporting the wafer loaded into the chamber with lift pins, and adjusting the temperature inside the chamber. A second step (step S4) of raising the temperature of the wafer, and a third step (steps S5 to S6 ), when the temperature difference becomes 10° C. or less, the wafer is again supported by the lift pins and subsequently placed on the susceptor again (steps S7 and S8), and an epitaxial wafer is obtained by epitaxial growth. 5 steps (step S9). [Selection drawing] Fig. 4

Description

  The present invention relates to an epitaxial wafer manufacturing method and an epitaxial wafer.

  An epitaxial wafer is used when crystal integrity is required or when a multilayer structure with different resistivities is required, and is produced by vapor phase growth (epitaxial growth) of an epitaxial layer on the wafer.

  For example, a single wafer type epitaxial growth apparatus shown in FIG. 1 can be used to manufacture an epitaxial wafer. Referring to FIG. 1, epitaxial growth apparatus 100 has a chamber 10 including an upper dome 11, a lower dome 12 and a dome mount 13, and chamber 10 defines a chamber for forming an epitaxial layer. The chamber 10 is provided with a gas supply port 15 and a gas exhaust port 16 for supplying and discharging a reaction gas at opposite positions on the side surface thereof. In the chamber 10, a susceptor 20 for mounting the wafer W is disposed. The susceptor 20 is supported by the susceptor support shaft 30 from below. The susceptor support shaft 30 includes a main column 31 and three arms 32 (one not shown) extending radially from the main column 31 at equal intervals, and three support pins 33 (one on the tip of the arms). (Not shown) supports the peripheral edge of the lower surface of the susceptor 20. Further, three through holes (one not shown) are formed in the susceptor 20, and one through hole is formed in each of the three arms 32. The lift pins 40 are inserted through the through holes of the arms and the through holes of the susceptor. The lower end of the lift pin 40 is supported by the lift shaft 50.

  The manufacture of an epitaxial wafer can be performed as follows using this epitaxial growth apparatus 100. The wafer W at normal temperature is carried into the chamber 10 preheated to 600 ° C. or more and 900 ° C. or less, and the wafer W is supported by each lift pin 40. Thereafter, the wafer W is mounted on the susceptor 20, and the temperature in the chamber 10 is raised to 1000 ° C. or more and 1200 ° C. or less. Thereafter, by supplying a source gas from the gas supply port 15 to grow an epitaxial layer on the wafer W to obtain an epitaxial wafer, the epitaxial wafer is carried out of the chamber.

  Here, when epitaxial growth is performed with the center of the wafer W and the center of the susceptor 20 shifted, turbulent flow of the source gas occurs at the peripheral portion of the front surface of the wafer W, and a flat epitaxial layer can not be obtained. . As a countermeasure against this, Patent Document 1 describes a technique for reducing the deviation between the center of the wafer and the center of the susceptor (hereinafter, also referred to as the “displacement of the mounting position”) as follows. That is, when the wafer is supported by the lift pins, the lift pins are shaken by the load of the wafer and the like, so that the mounting position is shifted. Then, each lift pin is mutually connected by the auxiliary member, and the shift of a mounting position is reduced by suppressing this wobble.

JP, 2014-220427, A

In patent document 1, although the shift of a mounting position is going to be reduced by suppressing the wobble of a lift pin, the shift of the mounting position resulting from the elastic deformation of the wafer demonstrated below is not considered. That is, when a wafer at normal temperature is carried into a chamber preheated to 600 ° C. or more and 900 ° C. or less and supported by each lift pin 40 as shown in FIG. 5A, the wafer W is convex toward the back surface. Elastically deform. This is because the temperature of the back surface of the wafer W rises due to the radiation heat from the susceptor 20, while the temperature of the front surface of the wafer W does not rise compared to the back surface, so the front surface and the back surface of the wafer W The temperature difference is caused in Then, when the elastically deformed wafer W is placed on the susceptor 20 by raising the susceptor support shaft 30, the center O _{1 of the} wafer W and the center O _{2 of the} susceptor deviate as shown in FIG. 5B. . If the epitaxial growth is performed in such a state, the flatness of the epitaxial layer is reduced.

  Then, an object of the present invention is to provide a manufacturing method of an epitaxial wafer which can manufacture an epitaxial wafer which has an epitaxial layer excellent in flatness in view of the above-mentioned subject.

  In order to solve the above problems, the present inventors wait for the wafer to be supported by each lift pin until the shape of the elastically deformed wafer is restored to the original shape, and then place the wafer on the susceptor. I tried. However, it has been found that this recovery takes a long time, and slip dislocation occurs on the back surface of the wafer due to long contact with each lift pin. Therefore, as a further study, after restoring the shape of the elastically deformed wafer to the original shape on the susceptor, the wafer is supported again by each lift pin, and then the wafer is mounted on the susceptor again, and the slip dislocation is generated. It has been found that the shift of the mounting position can be reduced while preventing the occurrence of “H”, and as a result, an epitaxial wafer having an epitaxial layer excellent in flatness can be obtained.

The present invention has been completed based on the above findings, and the gist configuration is as follows.
(1) a chamber, a susceptor for mounting a wafer in the chamber, a main pillar supporting the susceptor from below and coaxial with the center of the susceptor, and a peripheral portion of the susceptor below the main pillar Method of manufacturing an epitaxial wafer using an epitaxial growth apparatus comprising: a susceptor support shaft having three or more arms extending radially and three or more lift pins inserted through the through hole of the susceptor and the through hole of the arm And
A first step of mounting the wafer on the susceptor by supporting the wafer carried into the chamber with the lift pins and subsequently raising the susceptor support shaft;
A second step of raising the temperature in the chamber;
After the first step, measuring the temperature of the front surface and the back surface of the wafer to confirm whether the temperature difference between the front surface and the back surface is 10 ° C. or less;
When the temperature difference becomes 10 ° C. or less, the susceptor support shaft is lowered to support the wafer again with the lift pins, and subsequently the susceptor support shaft is raised to place the wafer on the susceptor. A fourth step of placing again,
After the fourth step, growing an epitaxial layer on the wafer to obtain an epitaxial wafer;
A method of manufacturing an epitaxial wafer comprising:

  (2) Before the fourth step, hydrogen baking for holding the wafer for 10 seconds or more and 1 minute or less is performed within the temperature range in which the temperature of the front surface is 1100 ° C. or more and 1150 ° C. or less The manufacturing method of the epitaxial wafer as described in 1).

  (3) After the fourth step and before the fifth step, the temperature of the front surface is in the temperature range of 1100 ° C. or more and 1150 ° C. or less for 10 seconds or more and 1 minute The manufacturing method of the epitaxial wafer as described in said (1) which performs hydrogen baking hold | maintained below.

  (4) In the third step, whether or not the temperature difference is 5 ° C. or less is confirmed, and the fourth step is performed when the temperature difference becomes 5 ° C. or less. The manufacturing method of the epitaxial wafer as described in any one of 3).

  (5) The manufacturing method of the epitaxial wafer as described in any one of said (1)-(4) whose time to support the said wafer again with the said lift pin in said 4th process is less than 5 seconds.

(6) The susceptor is formed on the front surface thereof with a counterbore portion on which the wafer is placed;
The front surface is located inside the front surface outermost periphery located around the counterbore and the inner surface outer periphery of the front surface, and forms a part of the front facing surface. A wafer supporting surface which supports the rear surface peripheral portion of the wafer by line contact, and a front surface central portion located inside the wafer supporting surface and constituting the bottom surface of the counterbore portion Including
The manufacturing of the epitaxial wafer according to any one of the above (1) to (5), wherein the angle between the wafer supporting surface and the front surface center portion is 0.5 ° or more and 2.5 ° or less. Method.

(7) An epitaxial wafer having an epitaxial layer formed on the wafer,
In the back surface of the epitaxial wafer, a damaged area consisting of three circular defects is concentrically present at three or more places in a circumferential direction in an annular area of 50% or more and less than 90% of the wafer radius from the center.

  According to the method for manufacturing an epitaxial wafer of the present invention, an epitaxial wafer having an epitaxial layer excellent in flatness can be obtained.

FIG. 1 is a schematic view of an epitaxial growth apparatus 100 that can be used in an embodiment of the present invention. It is a figure which shows the structure of the susceptor 20 of FIG. 1, Comprising: (A) is a top view, (B) is sectional drawing in alignment with the X-X 'line | wire of (A). (A) is an exploded perspective view of the susceptor support shaft 30, (B) is an exploded perspective view of the lift shaft 50. 5 is a flowchart illustrating a method of manufacturing an epitaxial wafer according to an embodiment of the present invention. (A) is a figure which shows the state which supported the wafer W elastically deformed by each lift pin 40, (B) is a figure which shows the state which mounted this wafer W on the susceptor 20. FIG. (A) is a figure which shows the state which supported the wafer W decompress | restored from elastic deformation by each lift pin 40 again, (B) is a figure which shows the state which mounted this wafer W on the susceptor 20 again. It is a graph which each shows the temperature change of the front surface of the wafer W in invention example 1, and a back surface.

(Method of manufacturing epitaxial wafer)
Hereinafter, an embodiment of a method of manufacturing an epitaxial wafer according to the present invention will be described with reference to FIGS. 1 to 6 as appropriate.

[Epitaxial growth equipment]
An epitaxial growth apparatus 100 that can be used in one embodiment of the present invention will be described with reference to FIG. The epitaxial growth apparatus 100 includes a chamber 10, a susceptor 20, a susceptor support shaft 30, three lift pins 40, and a lift shaft 50.

[Chamber]
The chamber 10 includes an upper dome 11, a lower dome 12, and a dome attachment 13, and the chamber 10 defines a chamber for forming an epitaxial layer. The chamber 10 is provided with a gas supply port 15 and a gas exhaust port 16 for supplying and discharging a reaction gas at opposite positions on the side surface thereof.

[Susceptor]
The susceptor 20 is a disk-shaped member on which the wafer W is mounted in the chamber 10. Here, among the surfaces of the susceptor 20, the surface on the upper dome 11 side is taken as the front surface of the susceptor, and the opposite surface is taken as the back surface of the susceptor. Referring also to FIGS. 2A and 2B, on the front surface of susceptor 20, a counterbore 22 on which wafer W is placed is formed. The front surface of the susceptor 20 is a front surface outermost peripheral portion 23, a first vertical wall surface 24, a wafer support surface 25, a second vertical wall surface 26, and a front surface central portion 27. including. The outermost surface 23 is located around the counterbore 22. The first vertical wall surface 24 is a wall surface which continues from the inner peripheral end of the outermost surface outer peripheral portion 23 and which constitutes a part of the counterbore portion 22. The wafer support surface 25 is an inclined surface which is continuous with the first vertical wall surface 24 and which constitutes a part of the counterbore 22, and supports the rear surface peripheral portion of the wafer W by line contact. The second vertical wall surface 26 is a wall surface which continues from the inner peripheral end of the wafer support surface 25 and which constitutes a part of the counterbore 22. The front surface center portion 27 is continuous with the second vertical wall surface 26 and constitutes the bottom surface of the counterbore 22. The radius of the inner diameter of the wafer support surface 25 is 75% or more of the radius of the susceptor 20, 90% or more of the wafer radius, and smaller than the wafer radius. However, the outer diameter and the inner diameter of the wafer support surface 25 are adjusted so that the width of the wafer support surface 25 is 1 to 10 mm. The radius of the outer diameter of the wafer support surface 25 is 75% or more of the radius of the susceptor 20 and larger than the wafer radius. In the present specification, the “peripheral portion of the wafer” means an annular area of 2 mm from the outer peripheral edge of the wafer toward the center thereof. Further, the susceptor 20 has three through holes 21 penetrating the susceptor from the front surface to the back surface at equal intervals of 120 ° in the circumferential direction. Lift pins 40 to be described later are respectively inserted into the through holes 21. Each through hole 21 of the susceptor is concentrically located in a region of 40% or more and less than 80% of the radius of the susceptor from the center O ₂ of the susceptor. The susceptor 20 may be made of carbon graphite (graphite) as a base material and the surface thereof coated with silicon carbide (SiC: Vickers hardness: 2,346 kgf / mm ² ).

[Susceptor support shaft]
Referring also to FIG. 3A, the susceptor support shaft 30 supports the susceptor 20 from below in the chamber 10, and includes a main pillar 31, three arms 32, and three support pins 33. And. The main column 31 is disposed coaxially with the center O _{2 of} the susceptor. The three arms 32 extend radially from the main column 31 below the periphery of the susceptor 20. Each arm 32 has a rectangular shape in cross section perpendicular to the extending direction. Here, among the four surfaces of the arm 32, the surface on the susceptor 20 side is the upper surface of the arm, and the opposite surface is the lower surface of the arm. Each arm 32 has a through hole 34 penetrating the arm from its upper surface to its lower surface. The lift pins 40 are respectively inserted into the through holes 34. In the present specification, the “peripheral portion of the susceptor” means a region 80% or more outside the radius of the susceptor from the center O ₂ of the susceptor. Each support pin 33 directly supports the susceptor 20 at the tip of each arm 32. The susceptor support shaft 30 moves the susceptor 20 up and down by moving up and down along the vertical direction. The susceptor support shaft 30 is preferably made of quartz (with a Vickers hardness of 1,103 kgf / mm ² ), and particularly preferably made of synthetic quartz. However, the tip portion of each support pin 33 is preferably made of the same silicon carbide as the susceptor 20. Although the number of arms 32 in the epitaxial growth apparatus 100 is three, it is not limited thereto.

[Lift pin]
The lift pins 40 are respectively inserted into the through holes 21 of the susceptor and the through holes 34 of the arm. Each lift pin 40 is moved up and down by the lift shaft 50. For each lift pin 40, a carbon graphite base material coated with silicon carbide or quartz is used. Although the number of lift pins 40 in the epitaxial growth apparatus 100 is three, it is not limited thereto.

[Lifting shaft]
Referring also to FIG. 3 (B), lift shaft 50 defines a hollow for accommodating main column 31 of susceptor support shaft 30, and main column 51 of the lift shaft which shares the rotation axis with main column 31; The three columns 52 branched at the tip of the main column 51 of the lift shaft are provided, and the tips of these columns 52 respectively support the lower ends of the lift pins 40. The lift shaft 50 moves up and down the lift pins 40 in the vertical direction by moving up and down along the vertical direction at the time of loading and unloading of the wafer W. It is preferable to use quartz for the elevating shaft 50.

[Heating lamp]
The heating lamps 14 are arranged in the upper and lower regions of the chamber 10. As the heating lamp 14, it is preferable to use a halogen lamp or an infrared lamp, which has a high temperature elevating speed and is excellent in temperature control.

[Upper pyrometer and lower pyrometer]
An upper pyrometer 17 and a lower pyrometer 18 are disposed in the upper and lower regions of the chamber 10, respectively. The upper pyrometer 17 detects the temperature of the front surface of the wafer W. On the other hand, the lower pyrometer 18 detects the temperature of the back surface of the susceptor 20. The temperature of the back surface of the susceptor 20 detected by the lower pyrometer 18 can be regarded as the temperature of the back surface of the wafer W. Further, based on the temperatures detected by the upper pyrometer 17 and the lower pyrometer 18, the output of the heating lamp 14 is adjusted by the power output control means (not shown).

  Below, with reference to FIG. 4, an example of the manufacturing method of the epitaxial wafer which can be performed using the epitaxial growth apparatus 100 mentioned above is demonstrated.

[First step]
Before loading the wafer W into the chamber 10, the susceptor support shaft 30 and the lift shaft 50 are completely lowered, and the lift pins 40 project from the susceptor 20. Then, the wafer W is carried into the chamber 10, which has been preheated to 600 ° C. or more and 900 ° C. or less by the heating lamp 14, using a transfer blade (not shown) (step S1). Thereafter, the susceptor 20 and lift pins 40 are moved upward by raising the susceptor support shaft 30 and the lift shaft 50 so as not to change the relative position of the susceptor 20 and the lift pins 40, as shown in FIG. The wafer W is supported by the lift pins 40 as shown in FIG. From the viewpoint of preventing the occurrence of slip dislocation on the back surface of the wafer, the time for which the wafer W is supported by each lift pin 40 is preferably 10 seconds to 60 seconds. Subsequently, the susceptor support shaft 30 is raised to further move the susceptor 20 upward, and the wafer W is mounted on the susceptor 20 as shown in FIG. 5B (step S3). Here, the temperature of the wafer W at the time of loading is normal temperature (normally, 30 ° C. to 90 ° C.), and when the wafer W at normal temperature is loaded into the heated chamber, the temperature of the back surface of the wafer W is the radiation heat from the susceptor 20 The temperature of the front surface of the wafer W does not rise compared to the back surface. Therefore, a temperature difference occurs between the front surface and the back surface of the wafer W. If the temperature difference exceeds 10 ° C., a temperature difference occurs in the surface non-uniformly between the front and back surfaces of the wafer, and the wafer W faces the front surface. It elastically deforms in a convex shape, or elastically deforms in a convex shape toward the back surface. Then, when the in-plane temperature becomes uniform, as shown in FIG. 5B, the wafer W elastically deforms in a convex shape toward the back surface by its own weight.

[Second step]
Next, the temperature in the chamber 10 is raised to 1000 ° C. or more and 1200 ° C. or less by the heating lamp 14 (step S4). In the process of this temperature rise, the radiant heat of the susceptor 20 is transmitted from the back surface of the wafer W to the front surface, and the temperature of the front surface of the wafer W is raised by the heating lamp 14 disposed in the upper region of the chamber 10 . Therefore, the temperature difference between the front surface and the back surface of the wafer W decreases, and the shape of the elastically deformed wafer is restored to the original shape.

[Third step]
Next, the temperature of the front surface and the back surface of the wafer W is measured by the method described above using the upper pyrometer 17 and the lower pyrometer 18 (step S5), and the measured temperature difference between the front surface and the back surface. It is confirmed whether or not 10 ° C. or less (step S6). Here, the “temperature difference between the front surface and the back surface” in the present embodiment means the absolute value of the difference between the temperature measured by the upper pyrometer 17 and the temperature measured by the lower pyrometer 18.

[Step 4]
Next, if the temperature difference between the front and back surfaces of the wafer W measured in the third step is 10 ° C. or less, the susceptor support shaft 30 is lowered to move the susceptor 20 downward. Then, as shown in FIG. 6A, the wafer W is again supported by the lift pins 40 (step S7). Subsequently, the susceptor support shaft 30 is raised to move the susceptor 20 upward, and the wafer W is placed on the susceptor 20 again as shown in FIG. 6B (step S8). At this time, it is preferable that the height position of the front surface of the wafer W be aligned with the height positions of the gas supply port 15 and the gas discharge port 16. When the temperature difference between the front surface and the back surface of the wafer W is not 10 ° C. or less, the process returns to step S 4, and the temperature difference is 10 ° C. or less by raising the output of the heating lamp 14. The temperature in the chamber 10 may be raised.

Below, the technical significance which employ | adopts a 4th process is demonstrated. When the wafer W at normal temperature is carried into the chamber 10 heated in advance and supported by the lift pins 40, the wafer W elastically deforms as shown in FIG. 5A. When placing the wafer W which has been elastically deformed in the susceptor 20, it is displaced center O ₂ of the center O ₁ and the susceptor wafer as shown in FIG. 5 (B). This is because when the wafer W is placed on the susceptor 20, the elastic deformation energy stored in the wafer becomes kinetic energy with elastic deformation due to the temperature difference between the front surface and the back surface, and the center O _{1 of} the wafer The wafer W moves in a direction deviated from the center O ₂ of the susceptor. Then, if epitaxial growth is performed in such a state, the temperature becomes uneven at the peripheral portion of the wafer W or turbulent flow of the source gas occurs, so that an epitaxial layer having good flatness can not be obtained. However, controlling the elastic deformation itself of the wafer W so that the center O ₁ of the wafer coincides with the center O _{2 of the} susceptor causes the heat absorption coefficient of the wafer to be different depending on the resistivity of the wafer, and the elastic deformation also varies. Difficult. Therefore, in the present embodiment, after the temperature difference between the front surface and the back surface of the wafer W becomes 10 ° C. or less, the wafer W shown in FIGS. 6A and 6B is re-mounted (steps S7 to S8). )I do. If the temperature is 10 ° C. or less, it can be considered that the shape of the elastically deformed wafer W has recovered to the original shape. Thus, the wafer W can be placed again on the susceptor 20 in a state where the kinetic energy caused by the elastic deformation energy is suppressed. That is, as shown in FIG. 6B, on the susceptor 20 having the wafer support surface 25 inclined downward toward the susceptor center O ₂ , the wafer W is suppressed with the influence of the kinetic energy on the wafer W suppressed. Since the wafer W is placed again, the center O _{1 of the} wafer W naturally coincides with the center O ₂ of the susceptor by gravity (hereinafter, this phenomenon is also referred to as “self-alignment function”). As a result, when the epitaxial growth (step S9) described later is performed, an epitaxial wafer having an epitaxial layer excellent in flatness can be obtained. In addition, in the re-loading of the wafer W (steps S7 to S8), it is preferable not to rotate the susceptor 20 and the wafer W.

  From the viewpoint of further improving the flatness, when the temperature difference between the front surface and the back surface of the wafer W becomes 5 ° C. or less, it is preferable to perform the re-loading of the wafer W (steps S7 to S8). In addition, it is preferable to suppress the temperature change in the chamber 10 when the wafer W is re-mounted (steps S7 to S8) to 5 ° C. or less.

  Further, in step S7, the height of the wafer W when each lift pin 40 supports the wafer W again is set such that the wafer W is slightly separated from the susceptor 20 from the viewpoint of stably obtaining the self alignment function. It is preferable from Specifically, it is preferable to set the distance between the back surface of the wafer W and the bottom surface (the surface of the front surface central portion 27) of the counterbore 22 to be 5 mm or less.

  Further, in step S7, it is preferable that the time for which the wafer W is again supported by each lift pin 40 be less than 5 seconds. If it is less than 5 seconds, it is possible to prevent a temperature change from occurring in a region in contact with each lift pin 40 in the back surface of the wafer W, and therefore, there is no possibility that slip dislocation occurs in the back surface of the wafer W.

  Further, from the viewpoint of improving the self alignment function of the wafer W, it is preferable to set the angle θ between the wafer support surface 25 shown in FIG. 2B and the front surface central portion 27 to 0.5 ° or more. Further, from the viewpoint of design, it is preferable to set the θ to 2.5 ° or less.

[Step 5]
Next, a source gas such as trichlorosilane or dichlorosilane is supplied from the gas supply port 15 into the chamber 10. Then, the source gas flows in a laminar flow along the front surface of the wafer W heated to 1000 ° C. or more and 1200 ° C. or less, and an epitaxial layer is grown on the wafer W to obtain an epitaxial wafer (step S9). During the epitaxial growth, the susceptor 20 and the wafer W are rotated by rotating the susceptor support shaft 30 with the main column 31 as a rotation axis.

[Wafer unloading]
Next, the temperature in the chamber 10 is lowered to 1000 ° C. or more and 1200 ° C. or less to 600 ° C. or more and 900 ° C. or less, and the susceptor support shaft 30 is lowered to move the susceptor 20 downward. Is supported by each lift pin 40. Thereafter, the susceptor support shaft 30 and the lift shaft 50 are lowered to move the susceptor 20 and the lift pins 40 downward so that the relative position between the susceptor 20 and the lift pins 40 is not changed. The epitaxial wafer is carried out of the chamber 10 using the drawing) (step S10).

  As mentioned above, although the manufacturing method of the epitaxial wafer of the present invention was explained taking this embodiment as an example, the present invention is not limited to the above-mentioned embodiment, A change can be suitably added within the range of a claim.

  For example, a natural oxide film is usually formed on the surface of the wafer W, and it is preferable to remove the natural oxide film before performing epitaxial growth (step S9). Therefore, the native oxide film is removed by performing hydrogen baking for holding the wafer W for 10 seconds or more and 1 minute or less in a temperature range in which the temperature of the front surface of the wafer W is 1100 ° C. or more and 1150 ° C. or less. During the hydrogen baking, the susceptor 20 and the wafer W are rotated by rotating the susceptor support shaft 30 with the main column 31 as the rotation axis. Below, the suitable conditions of the timing which hydrogen-bakes are demonstrated.

For example, in a p ⁻ wafer having a resistivity of 0.1 Ω · cm or more, infrared light is more likely to be transmitted through the wafer W than in a p ⁺ wafer. It may not be absorbed sufficiently, and it may take time to eliminate the temperature difference between the front and back surfaces of the wafer W. That is, in the case of p ^- wafer, even if the temperature of the front surface of the wafer W reaches 1100 to 1150 ° C., the temperature difference between the front and back surfaces of the wafer W may not fall within 10 ° C. Therefore, it is preferable to perform hydrogen baking before the fourth step (steps S7 to S8) to reduce the temperature difference between the front and back surfaces of the wafer W while removing the oxide film. Then, the fourth step is performed when the temperature of the back surface of the wafer W rises due to the radiant heat from the susceptor 20 and the temperature difference between the front and back surfaces of the wafer is within 10 ° C., more preferably within 5 ° C. preferable.

On the other hand, with p ⁺ wafers with resistivity less than 0.1 Ω · cm, the thermal conductivity is high, so elimination of the temperature difference between the front and back of wafer W is faster than with p ^- wafer. Before the surface temperature reaches the range of 1100 to 1150 ° C., the temperature difference between the front and back surfaces of the wafer W may fall within 10 ° C., more preferably within 5 ° C. In this case, it is preferable to perform hydrogen baking after the fourth step (steps S7 to S8) and before the fifth step (step S9). As described above, the reason why the re-loading (steps S7 to S8) is performed prior to the hydrogen baking is that the wafer W is convex toward the back surface when the back surface of the wafer W is excessively heated by the radiant heat from the susceptor 20 In this case, if the center position of the wafer W is deviated, the back surface of the wafer W and the bottom surface of the counterbore 22 may be in contact with each other to generate scratches and slip dislocations on the back surface of the wafer W. It is because there is. In the present specification, the start time point of the fifth step (epitaxial growth) is assumed to be when the source gas is supplied into the chamber 10.

(Epitaxial wafer)
Below, the epitaxial wafer by which an epitaxial layer is formed on a wafer obtained by the manufacturing method of an epitaxial wafer mentioned above is explained. On the back surface of the epitaxial wafer, three circular defect areas consisting of three circular defects exist concentrically in the circumferential direction in an annular area of 50% or more and less than 90% of the wafer radius from the center. These three circular defects are wear marks (so-called pin marks) generated by the contact between each lift pin 40 and the back surface of the wafer W, and when the wafer W carried into the chamber 10 is supported by each lift pin 40 (step S2), when re-loading the wafer W, when the wafer is supported again by each lift pin 40 (step S7), when unloading the wafer out of the chamber, when the wafer is supported by each lift pin (step S10) , Attached to three times. The number of damaged areas corresponds to the number of lift pins 40.

  As mentioned above, although the epitaxial wafer of the present invention was explained taking the example of this embodiment as an example, the present invention is not limited to the above-mentioned embodiment, and can be suitably changed within the range of a claim.

(Invention Example 1)
Using the epitaxial growth apparatus shown in FIG. 1 having the susceptor shown in FIGS. 2A and 2B, the susceptor support shaft shown in FIG. 3A, and the elevation lift shown in FIG. Twenty-five epitaxial wafers were manufactured according to the procedure of As a wafer on which an epitaxial layer is grown, a silicon wafer having a diameter of 300 mm and a resistivity of 10 Ω · cm was used. Further, referring to FIG. 2 (B), the angle θ between the wafer support surface and the surface center portion is 0.6 °.

Referring also to FIGS. 4 and 5A and 5B, using a transfer blade, a silicon wafer at normal temperature is carried into a chamber preheated to 700 ° C. (step S1), and a susceptor support shaft and an elevating shaft To raise the silicon wafer for 30 seconds with each lift pin as shown in FIG. 5A (step S2). Subsequently, by raising the susceptor support shaft, the silicon wafer was mounted on the susceptor as shown in FIG. 5 (B) (step S3). At this time, as shown in FIG. 7, the temperature of the back surface of the wafer rose to 900 ° C., but the temperature of the front surface was 700 ° C., not rising compared to the back surface. The center O ₂ of the center O ₁ and the susceptor of the silicon wafer is deviated as shown in FIG. 5 (B).

  Next, the temperature in the front surface of the silicon wafer was raised to 1100 ° C. by raising the temperature in the chamber with a heating lamp (step S4). Here, the wafer was heated for 50 seconds. Then, when the temperature of the back surface of the silicon wafer exceeded 1100 ° C., hydrogen baking was performed for 1 minute to remove the natural oxide film formed on the surface of the silicon wafer.

Next, the temperatures of the front surface and the back surface of the wafer were measured by the method described above (step S5), and it was confirmed whether the difference was 5 ° C. or less (step S6), and it was 2 ° C. Therefore, by lowering the susceptor support shaft, as shown in FIG. 6A, the silicon wafer was again supported by each lift pin for 3 seconds (step S7). Here, the distance between the back surface of the wafer W and the bottom surface (the surface of the front surface central portion 27) of the counterbore portion 22 was set to 2 mm. Thereafter, by raising the susceptor support shaft, the silicon wafer was placed again on the susceptor as shown in FIG. 6B (step S8). At this time, the center O ₂ of the center O ₁ and the susceptor of the silicon wafer is coincident as shown in FIG. 6 (B). By setting the mode of the heating lamp to the rated output mode (constant power) during the remounting, as shown in FIG. 7, the temperatures of the front and back surfaces of the silicon wafer are set to 1100 ° C. I kept it.

  Next, as shown in FIG. 7, the temperature of the front surface and the back surface of the silicon wafer is maintained at 1100 ° C., the source gas of trichlorosilane is supplied into the chamber from the gas supply port, and the thickness 4 μm on the silicon wafer. The epitaxial silicon layer was grown to obtain an epitaxial silicon wafer (step S9). Thereafter, the epitaxial silicon wafer was carried out of the chamber by the method described above (step S10).

(Invention Example 2)
Twenty-five epitaxial wafers were manufactured according to the following procedure using the same epitaxial growth apparatus as in the invention example 1. As a wafer on which an epitaxial layer is grown, a silicon wafer having a diameter of 300 mm and a resistivity of 0.02 Ω · cm was used.

  Steps S1 to S3 were performed in the same manner as in the invention example 1.

Next, the temperature in the chamber was raised by a heating lamp to raise the temperature of the front and back surfaces of the silicon wafer (step S4). Here, when the temperature was raised for 60 seconds, the temperatures of the front and back surfaces of the wafer were measured by the method described above (step S5), and it was confirmed whether the difference was 5 ° C. or less (step S6) ). Then, since the temperature difference was 3 ° C., the silicon wafer was supported again by each lift pin for 2 seconds as shown in FIG. 6A by lowering the susceptor support shaft (step S7). Here, the distance between the back surface of the wafer W and the bottom surface (the surface of the front surface central portion 27) of the counterbore portion 22 was set to 2 mm. Thereafter, by raising the susceptor support shaft, the silicon wafer was placed again on the susceptor as shown in FIG. 6B (step S8). At this time, the center O ₂ of the center O ₁ and the susceptor of the silicon wafer is coincident as shown in FIG. 6 (B). The temperature of the front surface and the back surface of the silicon wafer was maintained at 1100 ° C. by setting the mode of the heating lamp to the rated output mode (constant power) during the remounting.

  Next, when the temperature of the back surface of the silicon wafer exceeded 1100 ° C., hydrogen baking was performed for 1 minute to remove the natural oxide film formed on the surface of the silicon wafer.

  Next, step S9 and step S10 were performed in the same manner as in the invention example 1.

(Comparative example 1)
In the comparative example 1, 25 epitaxial silicon wafers were produced by the method similar to the invention example 1 except not performing step S5-S8 shown in FIG.

(Comparative example 2)
In Comparative Example 2, the shape of the elastically deformed silicon wafer was recovered to the original shape by supporting the silicon wafer with each lift pin for 90 seconds in step S2 shown in FIG. Twenty-five epitaxial silicon wafers were manufactured in the same manner as in Comparative Example 1 in the steps after Step S3.

(Comparative example 3)
Twenty-five epitaxial wafers were manufactured according to the following procedure using the same epitaxial growth apparatus as in the invention example 1. As a wafer on which an epitaxial layer is grown, a silicon wafer having a diameter of 300 mm and a resistivity of 10 Ω · cm was used.

  Steps S1 to S3 were performed in the same manner as in the invention example 1.

  Next, the temperature in the front surface of the silicon wafer was raised to 700 ° C. by raising the temperature in the chamber with a heating lamp. Here, the wafer was heated for 20 seconds. Thereafter, by lowering the susceptor support shaft, the silicon wafer was again supported by each lift pin, and hydrogen baking was performed for 1 minute in that state to remove the natural oxide film formed on the surface of the silicon wafer. Then, the silicon wafer was again mounted on the susceptor by raising the susceptor support shaft. In addition, it was 14 degreeC when the temperature difference of front and back of the wafer in hydrogen baking was measured by the method as stated above.

  Next, step S9 and step S10 were performed in the same manner as in the invention example 1.

(Evaluation method)
The flatness, slip dislocation, and throughput of each invention example and comparative example were evaluated by the following methods.

<Evaluation of flatness>
With respect to the epitaxial silicon wafers manufactured in each of the invention examples and the comparative examples, ESFQR range (Edge Site Front least sQuaress Range) and ESFQR max of the front surface are known in a known method using Wafer Sight 2 (manufactured by KLA-Tencor). The flatness of the silicon epitaxial layer was evaluated by measuring. Table 1 shows the average values of ESFQR range and ESFQR max, respectively. The edge exclusion area was 2 mm, the entire circumference of the wafer was divided into 72 at intervals of 5 degrees, and the area in the sector with a sector length of 15 mm was subjected to the measurement. Also, “ESFQR range” is the difference between the maximum value and the minimum value of 72 sectors in one wafer, and “average value of ESFQR range” in Table 1 is the average value of 25 sheets of the difference. is there. Further, “ESFQR max” is the maximum value of 72 sectors in one wafer, and “average value of ESFQR max” in Table 1 is an average value for 25 sheets.

<Evaluation of slip dislocation>
For epitaxial silicon wafers produced in each of the invention examples and comparative examples, the slip dislocation is evaluated by measuring the total length of the slip line on the back surface using SP2 (DCN mode) (manufactured by KLA-Tencor). did. Table 1 shows the average value for 25 sheets.

<Evaluation of throughput>
For each of the invention examples and the comparative examples, the time taken to carry the epitaxial silicon wafer out of the chamber after the silicon wafer was carried into the chamber was measured, and the average time for 25 times was calculated. Table 1 shows relative values when the average time of Comparative Example 1 is 1.00.

<Evaluation of damage area>
About the epitaxial silicon wafer manufactured by the invention examples 1 and 2 and the comparative example 1, the back surface of the wafer is measured in the DCO mode (Dark Field Composite Oblique mode) using a surface inspection apparatus (manufactured by KLA-Tencor: Surfscan SP-2). Were observed, and the number of LPDs (Light Point Defects) having a diameter of 1 μm or more was examined. The measurement results make it possible to evaluate the occurrence of circular defects in the damaged area.

(Explanation of evaluation results)
As shown in Table 1, in the invention examples 1 and 2, the average value of both ESFQR max and range was smaller than that of the comparative example 1, and an epitaxial wafer having an epitaxial layer excellent in flatness was obtained. . This is due to the fact that the epitaxial growth can be performed with the center of the wafer aligned with the center of the susceptor by performing the re-loading of the wafer. Moreover, although the process of re-loading a wafer increased compared with the comparative example 1 in the invention examples 1 and 2, the throughput was comparable with the comparative example 1. FIG.

  In addition, in Comparative Example 2, the wafer was mounted on the susceptor after the shape of the elastically deformed wafer was restored to the original shape by supporting the wafer for a long time by each lift pin, but the average of ESFQR max and range was obtained. Both values were inferior to invention examples 1 and 2. Further, in Comparative Example 2, since the wafer was supported for a long time by each lift pin, slip dislocation occurred and the throughput was also deteriorated.

  In addition, in Comparative Example 3, the remounting and the hydrogen baking are simultaneously performed, and the effect on the flatness of the remounting is obtained because the temperature difference between the front and back of the wafer at that time exceeds 10 ° C. It was not.

  Furthermore, in Inventive Examples 1 and 2, the damage area consisting of three circular defects is circumferentially formed in the annular area of 70% to 80% of the wafer radius from the center of the wafer due to steps S2, S7 and S10. There were three concentric circles along the line. On the other hand, in the comparative example 1 which did not perform step S7, the damage area | region which consists of two circular defects existed in three places concentrically along the circumferential direction.

  According to the method for manufacturing an epitaxial wafer of the present invention, an epitaxial wafer having an epitaxial layer excellent in flatness can be obtained.

DESCRIPTION OF SYMBOLS 100 epitaxial growth apparatus 10 chamber 11 upper dome 12 lower dome 13 dome attachment body 14 heating lamp 15 gas supply port 16 gas exhaust port 17 upper pyrometer 18 lower pyrometer 20 susceptor 21 through hole of susceptor 22 counterbore part 23 front side Outer peripheral portion 24 first vertical wall surface 25 wafer support surface 26 second vertical wall surface 27 front surface central portion 30 susceptor support shaft 31 main column 32 arm 33 support pin 34 arm through hole 40 lift pin 50 lift shaft 51 lift shaft Main column of 52 52 support θ angle between wafer support surface and front surface center O ₁ wafer center O ₂ susceptor center W wafer

Claims (7)

A chamber, a susceptor for mounting a wafer in the chamber, a main pillar supporting the susceptor from below and located coaxially with the center of the susceptor and radially from the main pillar below the peripheral portion of the susceptor A method of manufacturing an epitaxial wafer using an epitaxial growth apparatus, comprising: a susceptor support shaft having three or more arms extending; and three or more lift pins inserted into the through holes of the susceptor and the through holes of the arms. ,
A first step of mounting the wafer on the susceptor by supporting the wafer carried into the chamber with the lift pins and subsequently raising the susceptor support shaft;
A second step of raising the temperature in the chamber;
After the first step, measuring the temperature of the front surface and the back surface of the wafer to confirm whether the temperature difference between the front surface and the back surface is 10 ° C. or less;
When the temperature difference becomes 10 ° C. or less, the susceptor support shaft is lowered to support the wafer again with the lift pins, and subsequently the susceptor support shaft is raised to place the wafer on the susceptor. A fourth step of placing again,
After the fourth step, growing an epitaxial layer on the wafer to obtain an epitaxial wafer;
A method of manufacturing an epitaxial wafer comprising:   The hydrogen baking for holding the wafer for 10 seconds or more and 1 minute or less is performed before the fourth step within the temperature range in which the temperature of the front surface is 1100 ° C. or more and 1150 ° C. or less. Of epitaxial wafer production.   After the fourth step, before the fifth step, the wafer is held for 10 seconds or more and 1 minute or less within a temperature range in which the temperature of the front surface is 1100 ° C. or more and 1150 ° C. or less The manufacturing method of the epitaxial wafer of Claim 1 which hydrogen-bakes.   The third step confirms whether the temperature difference is 5 ° C. or less, and performs the fourth step when the temperature difference becomes 5 ° C. or less. The manufacturing method of the epitaxial wafer as described in a term.   The method for manufacturing an epitaxial wafer according to any one of claims 1 to 4, wherein, in the fourth step, the time for which the wafer is again supported by the lift pins is less than 5 seconds. The susceptor is formed on the front surface thereof with a counterbore on which the wafer is placed;
The front surface is located inside the front surface outermost periphery located around the counterbore and the inner surface outer periphery of the front surface, and forms a part of the front facing surface. A wafer supporting surface which supports the rear surface peripheral portion of the wafer by line contact, and a front surface central portion located inside the wafer supporting surface and constituting the bottom surface of the counterbore portion Including
The method for manufacturing an epitaxial wafer according to any one of claims 1 to 5, wherein an angle between the wafer supporting surface and the center portion of the front surface is 0.5 ° or more and 2.5 ° or less. An epitaxial wafer having an epitaxial layer formed on the wafer, wherein
In the back surface of the epitaxial wafer, a damaged area consisting of three circular defects is concentrically present at three or more places in a circumferential direction in an annular area of 50% or more and less than 90% of the wafer radius from the center.

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