JP5834632B2 - Susceptor, vapor phase growth apparatus using the susceptor, and epitaxial wafer manufacturing method - Google Patents

Description

  The present invention relates to a susceptor, a vapor phase growth apparatus using the susceptor, and an epitaxial wafer manufacturing method, and more particularly to a susceptor capable of manufacturing an epitaxial wafer having high flatness and a vapor phase growth using the susceptor. The present invention relates to an apparatus and a method for manufacturing an epitaxial wafer.

  In general, for silicon wafers, single crystal silicon is grown by the Czochralski method (CZ method), etc., the silicon single crystal is cut into blocks, and then sliced thinly, and then surface grinding (lapping), etching, and mirror polishing. (Polishing) It is obtained by final cleaning after the process. After that, various quality inspections are performed and if no abnormality is confirmed, the product is shipped as a product.

  Here, when higher crystallinity and flatness are required, an epitaxial film is further grown on the silicon wafer to manufacture the epitaxial wafer. Specifically, first, a silicon wafer used as a substrate is introduced into a growth furnace of a vapor phase growth apparatus and placed on a susceptor provided in the furnace, and the substrate temperature is raised to a temperature of 1000 ° C. or higher. A silicon source gas is supplied to grow an epitaxial film having a predetermined thickness.

  In the epitaxial growth of silicon wafers that require high flatness, film thickness uniformity is improved by single wafer processing. However, the thickness of the epitaxial layer tends to decrease toward the peripheral edge of the silicon wafer serving as the substrate, and it is not easy to maintain flatness during the formation of the epitaxial film. In particular, at the peripheral edge of the wafer, an abrupt change in the formation thickness of the epitaxial layer is likely to occur, and it is difficult to planarize the epitaxial film.

  Therefore, Patent Document 1 describes a technique that can adjust the thickness of the epitaxial layer by applying a taper process to the annular bottom surface portion 14 and changing the width of the annular bottom surface portion 14. FIG. 1 shows a cross-sectional view of a conventional susceptor described in Patent Document 1. As shown in FIG. A two-stage counterbore part 11 is formed on the upper surface of the susceptor 100, and the counterbore part 11 has an upper counterbore part 12 that supports the wafer W and a lower counterbore part 13. .

JP 2007-273623 A

  Incidentally, in recent years, an epitaxial wafer having a high-purity epitaxial film has been desired. Therefore, a technique for preventing contamination from the susceptor base material by coating the surface of the susceptor with silicon is being adopted.

  However, as a result of investigation by the inventors, when an epitaxial wafer is manufactured using a susceptor coated with silicon, when the width of the annular bottom surface portion 14 is large, polysilicon deposited on the susceptor during the growth of the epitaxial film is formed. It has been clarified that a phenomenon called so-called mass transfer (mass transfer) occurs in which the film is transferred to the back surface of the silicon wafer W, and a lot of silicon growth (back surface deposition) occurs on the back surface side of the peripheral edge of the wafer.

  Then, the inventor examined the method of suppressing the said back surface deposit, and discovered that it was effective to make the width | variety of the annular bottom face part 14 small. However, if the width of the annular bottom surface portion 14 is made too small, the material source gas wraps around from the notch portion N of the wafer W to the back surface of the wafer, and it is new that the back surface deposition cannot be suppressed in the vicinity of the notch portion N. The problem has become.

  Therefore, an object of the present invention is to suppress a back surface deposition in the vicinity of the notch portion provided in the peripheral portion of the silicon wafer, and to produce an epitaxial wafer having high flatness even in the peripheral region of the notch portion, An object of the present invention is to provide a vapor phase growth apparatus using the susceptor and a method for manufacturing an epitaxial wafer.

  As a result of intensive studies on how to solve the above-mentioned problems, the inventor placed the wafer W on the annular bottom surface portion 14 of the upper counterbore portion 12 and supplied the source gas into the epitaxy apparatus. A part of the inner peripheral wall surface of the lower counterbore part 13 is suppressed from the inner peripheral wall surface of the lower counterbore part 13 to suppress the inflow of the source gas that flows into the lower counterbore part 13 from the notch part N provided in the lower part. In addition, the present inventors have found that it is effective to provide a protruding portion that protrudes inward, and have completed the present invention.

That is, the gist configuration of the present invention is as follows.
(1) A susceptor for mounting a wafer in an epitaxial growth apparatus, wherein a circular concave counterbore portion on which the wafer is mounted is formed on an upper surface, and the counterbore portion has a back surface peripheral portion of the wafer. It comprises a two-stage counterbore part having an upper counterbore part to be supported and a lower counterbore part formed at a lower center side than the upper counterbore part. Suppressing the inflow of the raw material source gas flowing into the lower spot facing portion from a notch portion provided on the peripheral edge portion of the wafer when the wafer is placed and the raw material source gas is supplied into the epitaxy apparatus, A protruding portion is provided on a part of the inner peripheral wall surface of the lower counterbore portion so as to protrude inward from the inner peripheral wall surface of the lower counterbore portion, and the annular bottom surface portion of the upper counterbore portion is the center of the annular bottom surface portion. Facing down Susceptor, characterized in that an inclined surface which is inclined.

(2) The susceptor according to (1), wherein a distance from an inner peripheral wall surface of the lower spot facing portion to a tip of the protruding portion is 1 mm or less .

(3) The radius of the wafer is r1, the radius of the inner peripheral wall of the lower spot facing is r4, the distance from the center of the susceptor to the tip of the protrusion is r5, and the depth of the notch is d1. Then, the susceptor according to (1) or (2) , wherein the following formula (B) is satisfied.
r5 ≦ (r1-d1) <r4 (B)

(4) In any one of the above (1) to (3), a plurality of through holes penetrating the back surface side of the susceptor are provided on the bottom surface of the lower spot facing portion. Susceptor.

(5) The susceptor according to any one of (1) to (4), wherein a surface of the susceptor is covered with a silicon film.

(6) The susceptor according to any one of (1) to (5), wherein the protrusion has an upper surface extending in a horizontal direction from the inner peripheral wall surface.

(7) The wafer surface is epitaxially mounted on the susceptor according to any one of (1) to (6) , with the wafer placed with the position of the notch corresponding to the position of the protrusion. A method of manufacturing an epitaxial wafer, comprising forming a film.

(8) the epitaxial layer is a silicon epitaxial film, the epitaxial wafer of the (7), wherein prior to placing the wafer on the susceptor, characterized in that to keep the surface of the susceptor is coated with silicon film Manufacturing method.

(9) An epitaxial growth apparatus having the susceptor according to any one of (1) to (6) .

  According to the present invention, by providing a protruding portion that protrudes inward from the inner peripheral wall surface of the lower counterbore portion on a part of the inner peripheral wall surface of the lower counterbore portion, the wafer is placed on the annular bottom surface portion of the upper counterbore portion. When the raw material source gas is supplied to the epitaxy apparatus after being placed, it is possible to suppress the inflow of the raw material source gas flowing into the lower counterbore portion from the notch portion provided at the peripheral portion of the wafer. Thus, an epitaxial wafer having high flatness can be obtained even in the peripheral region of the notch portion.

It is sectional drawing of the conventional susceptor. It is (a) top view and (b) sectional drawing of the susceptor by this invention. It is (a) top view and (b) sectional drawing of the susceptor by this invention of the state in which the wafer was mounted. 1 is a top view of a susceptor and a wafer according to the present invention. FIG. It is a figure which shows the positional relationship of a susceptor and a wafer in case the width | variety of a cyclic | annular bottom face part is more than the depth of a notch part. It is a figure which shows the positional relationship of a susceptor and a wafer in case the width | variety of a cyclic | annular bottom face part is smaller than the depth of a notch part. It is a figure which shows the vapor phase growth apparatus to which the susceptor by this invention is applied. It is a figure which shows the site map of the flatness (Site Front last sQare Range, SFQR) with respect to (a) Comparative example 1 and (b) invention example 2. FIG. It is a figure which shows the site map of SFQR of the epitaxial wafer with respect to (a) Comparative example 2 and (b) invention example 2. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
2A and 2B are views showing a susceptor according to the present invention, in which FIG. 2A is a top view and FIG. 2B is a cross-sectional view. Here, the same reference numerals are used for the same components as those of the conventional susceptor 100 shown in FIG. In the susceptor 1 according to the present invention, a circular concave counterbore portion 11 on which a wafer W is placed is formed on the upper surface, and this counterbore portion 11 is an upper counterbore portion 12 that supports the peripheral edge of the back surface of the wafer W. And a counterbore part having two stages having a lower counterbore part 13 formed at a lower stage on the center side than the upper counterbore part 12. The wafer W is placed on the annular bottom surface portion 14 of the upper spot facing portion 12. Here, when the source source gas is supplied into the epitaxy apparatus, the lower seat that suppresses the inflow of the source source gas flowing into the lower spot facing portion 13 from the notch portion N provided at the peripheral portion of the wafer W. It is important to provide a protruding portion 15 that protrudes inward from the inner peripheral wall surface of the lower spot facing portion 13 on a part of the inner peripheral wall surface of the counterbore portion 13.

  3A and 3B are diagrams showing the susceptor 1 in a state where the wafer W is placed, where FIG. 3A is a top view and FIG. 3B is a cross-sectional view. As described above, a notch portion N which is a V-shaped notch is provided in a part of the peripheral portion of the wafer W, and alignment and orientation of the wafer W are performed using the notch portion N. It has been broken. The notch portion N can be formed using, for example, a spindle-shaped grindstone. The shape of such a notch portion N is defined in SEMI (Semiconductor Equipment and Materials International) M1-0707. For example, a V-shaped notch portion N opened at 90 ° on the peripheral edge of a wafer W having a diameter of 300 mm. Are formed so that a pin having a depth of 1 mm and a diameter of 3 mm can be inserted and aligned.

  Here, if the width of the annular bottom surface portion 14 of the susceptor 1 is set too small, the raw material source gas wraps around from the notch portion N of the wafer W to the wafer back surface. It cannot be suppressed. Therefore, by providing the protruding portion 15, the raw material source gas flowing from the front surface side of the wafer W is prevented from flowing from the notch portion N to the back surface side of the wafer W, so that the back surface deposition is suppressed. This makes it possible to obtain a wafer W having high flatness even in the peripheral region. Hereinafter, each structure of the susceptor 1 by this invention is demonstrated.

As a material of the susceptor 1, in order to reduce contamination from the susceptor 1 during the formation of the epitaxial film, it is common to use a carbon substrate surface coated with silicon carbide (SiC). The entire susceptor 1 may be formed of SiC. Alternatively, as long as the surface is coated with SiC, the inside may include other materials.
Further, the surface of the susceptor 1 is preferably covered with a silicon film. Thereby, contamination from the susceptor 1 to the epitaxial film can be prevented.

  The annular bottom surface portion 14 supports the peripheral edge portion of the wafer W. Here, when the annular bottom surface portion 14 is a horizontal surface, the wafer W is supported in surface contact with each other, which is advantageous in suppressing the wraparound of the raw material source gas from the notch portion N. However, since the contact area between the annular bottom surface portion 14 and the wafer W is large, a region where contact scratches are generated is also large. For the wafer W, a product guarantee area in which quality is guaranteed is set, for example, “an area 2 mm from the outer circumference in the entire outer circumference” is set. However, even if contact scratches are formed outside the quality assurance area, if the scratches are scattered, the product cannot be shipped as a defective appearance.

  In order to reduce this contact scratch, it is effective to make the contact area between the annular bottom surface portion 14 and the wafer W as small as possible. For this purpose, it is effective to taper the annular bottom surface portion 14 to form an inclined surface inclined downward toward the center of the annular bottom surface portion 14 so that the back surface of the wafer is supported in line contact. is there. Thereby, the contact between the annular bottom surface portion 14 and the peripheral edge portion of the wafer W becomes a line contact, and the contact area is reduced, so that the generation of contact scratches can be reduced. In addition, since the gap with the wafer back surface is increased by using the inclined surface, the occurrence of back surface deposition due to mass transfer can be reduced.

  By the way, the peripheral portion of the wafer W is usually chamfered. Examples of the shape of the chamfered portion E formed by the chamfering include a round shape, a taper shape, and a non-target chamfered shape in which the taper surface angle is different up and down, and the width of the chamfered portion E is 200 to 500 μm (300 μm). ) Is set within a range. The chamfered portion E is subjected to a mirror polishing process, but the surface property of the chamfered portion E is not uniform in the circumferential direction but has minute irregularities. For this reason, if the chamfered portion E is supported by the annular bottom surface portion 14, there is a possibility that particle generation due to contact support may be caused.

  Further, if the chamfered portion E is to be supported by the tapered surface, the chamfered portion E must be supported with the taper surface angle of the annular bottom surface portion 14 being a considerably acute surface. In this case, the wafer W to be placed is inclined. It tends to occur and it is difficult to grow a uniform epitaxial film over the entire wafer surface.

  Therefore, when the wafer W is supported by the annular bottom surface portion 14 of the upper spot facing portion 12, the wafer back surface is supported without supporting the chamfered portion E of the wafer W. Specifically, the wafer W is preferably supported so that the vicinity of the boundary between the chamfered portion E on the wafer back surface side and the wafer back surface is in contact with the annular bottom surface portion 14. Therefore, it is preferable that the inclination angle of the annular bottom surface portion 14 with respect to the horizontal plane is 2 ° or less.

  The protruding portion 15 is provided on a part of the inner peripheral wall surface of the lower counterbore portion 13 so as to protrude inward from the inner peripheral wall surface of the lower counterbore portion 13. Thus, as described above, when the source gas is supplied into the epitaxy apparatus, the inflow of the source gas that flows into the lower counterbore portion 13 from the notch portion N provided at the peripheral portion of the wafer W is prevented. Can be suppressed.

If the shape and size of the projecting portion 15 are configured to cover at least a part immediately below the notch portion N, the flow of the source gas that flows into the lower counterbore portion 13 from the notch portion N is suppressed. However, as shown in FIG. 3A, when the wafer W is placed on the susceptor 1 with the center of the wafer W aligned with the center of the susceptor 1 and viewed from above, the protrusion 15 is formed. It is preferable to cover the entire area of the notch N.
Further, as will be described later, even when the protrusion 15 does not cover the notch portion N, the same protrusion shape as that when the protrusion 15 covers the notch portion N may be adopted. What is necessary is just to arrange | position the protrusion part 15 on the straight line which connects. In particular, it is preferable that the length of the protrusion 15 in the wafer radial direction does not reach the product guarantee area.

  In this way, a wafer is placed on the annular bottom surface of the upper counterbore part by providing a protruding part that protrudes inward from the inner wall surface of the lower counterbore part on a part of the inner wall surface of the lower counterbore part. When the raw material source gas is supplied into the epitaxy apparatus, it is possible to suppress the inflow of the raw material source gas flowing into the lower spot facing portion from the notch portion provided at the peripheral portion of the wafer. Deposition is suppressed, and as a result, an epitaxial wafer having high flatness can be obtained even in the peripheral region of the notch portion.

  In the susceptor 1 according to the present invention described above, the annular bottom surface portion 14 and the protruding portion 15 of the upper counterbore portion 13 have a diameter of the wafer W that is larger than the boundary line L between the product guarantee area and the product exclusion area set in advance on the wafer W. It is preferable to be located outside in the direction. FIG. 4 is a top view of a state where the wafer W is placed on the susceptor 1 with the center of the wafer W aligned with the center of the susceptor 1. However, for the sake of explanation, the notch portion N of the wafer W and the protruding portion 15 of the susceptor 1 are rotated 180 ° relative to each other.

  Here, since the boundary line L between the product guarantee area and the product exclusion area is set along the outer peripheral shape of the wafer W, the wafer radial direction is closer to the periphery of the notch portion N than the other peripheral edge portion of the wafer W. It will be set inside. The width of the product exclusion area is becoming increasingly demanding for narrowing year by year. In the present situation, the width of the product exclusion area is conventionally about 3 mm, but in recent years it has become 2 mm, and sometimes about 1 mm.

  In the region where the annular bottom surface portion 14 of the upper spot facing portion 12 and the back surface of the wafer are in contact with or close to each other, back surface deposition due to mass transfer is likely to occur. Therefore, the annular bottom surface portion 14 and the protruding portion 15 of the upper counterbore portion 12 are not positioned directly below the product warranty area, in other words, the inner peripheral wall of the lower counterbore portion 13 is directly below the product exclusion area of the wafer W. By setting the position, it is possible to suppress the occurrence of back surface deposition due to mass transfer.

  Here, as described above, the geometrical requirement to prevent the annular bottom surface portion 14 and the protruding portion 15 of the upper counterbore portion 12 from being located immediately below the product warranty area will be considered. As shown in FIG. 4, the radius of the wafer W is r1, the radius of the boundary line L set on the wafer W is r2, the minimum radius of the boundary line L corresponding to the notch N in the boundary line L is r3, and the lower part The radius of the inner peripheral wall of the spot facing portion 13 is r4, and the distance from the center of the susceptor 1 to the tip of the protruding portion 15 is r5. Moreover, the depth of the notch part N is set to d1.

As described above, since the annular bottom surface portion 14 of the upper spot facing portion 12 supports the peripheral edge portion of the wafer W, it is necessary that r4 <r1. In addition, the minimum radius r3 of the boundary line L corresponding to the notch N in the boundary line L is smaller than the distance r5 to the tip of the protrusion 15 so that the protrusion 15 is not located immediately below the product guarantee area. Is preferred. That is, it is preferable to satisfy the relationship r3 <r5. Furthermore, in order to suppress the occurrence of backside deposit in the product guarantee area, the radius r2 of the boundary line L set on the wafer W is preferably smaller than the radius r4 of the inner peripheral wall of the lower spot facing portion 13. That is, it is preferable to satisfy the relationship r2 <r4. From the above, by satisfying the following expression (1), it is possible to suppress the occurrence of the backside deposit in the product guarantee area.
r2 <r4 <r1 and r3 <r5 (1)

  When the wafer W is placed on the susceptor 1 according to the present invention, the positional relationship between the protrusion 15 in the susceptor 1 and the notch N of the wafer W can be roughly divided into the following two. That is, as shown in FIG. 5, the width of the annular bottom surface portion 14 of the upper counterbore portion 12 is not less than the depth d1 of the notch portion N, and the protruding portion 15 does not cover the portion directly below the notch portion N. As shown in FIG. 4, the width of the annular bottom surface portion 14 is smaller than the depth d1 of the notch portion N, and the protruding portion 15 covers at least a part directly below the notch portion N. Here, in FIGS. 5 and 6, the annular bottom surface portion 14 is an inclined surface subjected to a taper process, but may be a horizontal surface.

  In the former case, when the annular bottom surface portion 14 is an inclined surface, the raw material source gas flows into the lower spot facing portion 13 from the notch portion N, but the projecting portion 15 does not cover the portion immediately below the notch portion N. Can not. The same applies to the case where the annular bottom surface portion 14 is a horizontal plane. Although the notch portion N is closed by the annular bottom surface portion 14, microscopically, the source material gas is formed between the wafer W and the annular bottom surface portion 14. Distribution occurs. However, as shown in the examples described later, it has been clarified that the formation of the back surface deposits around the notch N on the back surface of the wafer is suppressed by providing the protrusion 15 as shown in FIG.

  The reason for this is not clear, but it is likely that by providing the protrusion 15, the resistance to the gas flow of the source gas that enters the lower counterbore portion 13 from the notch portion N is reduced. The increase is caused by the increase, the ease of flow of the source gas (conductance) is reduced, and the amount of gas inflow is suppressed.

  On the other hand, in the latter case, when the raw material source gas is supplied into the epitaxy apparatus, the raw material source gas is introduced into the lower spot facing portion 13 from the notch portion N provided at the peripheral portion of the wafer W as described above. Flows in and a backside deposit occurs. Therefore, it is effective to provide the projecting portion 15 so as to cover the area immediately below the opening area of the notch portion N, and it is possible to suppress the inflow of the raw material source gas from the notch portion N and suppress the occurrence of the back surface deposit.

Here, in the latter case, the geometric condition that the susceptor 1 should satisfy is that the width of the annular bottom surface portion 14 is smaller than the depth d1 of the notch portion N in addition to the condition of the above formula (1). It is necessary that (r1-d1) <r4. In addition, since it is effective to provide the protrusion 15 so as to cover the opening region of the notch N, it is desirable to satisfy the relationship r5 ≦ (r1-d1). From the above, by satisfying the following equation (2), it is possible to suppress the inflow of the raw material source gas from the notch portion N and suppress the occurrence of the back surface deposit.
r5 ≦ (r1-d1) <r4 (2)

  Thus, the width of the annular bottom surface portion 14 of the upper counterbore portion 12 is provided by providing the protruding portion 15 on the inner wall surface of the lower counterbore portion 13 on a part of the inner peripheral wall surface of the lower counterbore portion 13. Of course, the width of the annular bottom surface portion 14 of the upper counterbore portion 12 is equal to or greater than the depth d1 of the notch portion N, and the protruding portion 15 does not cover immediately below the notch portion N. Even in this case, the wraparound of the source gas through the notch portion N to the wafer back surface is suppressed, and the occurrence of back surface deposition around the notch N on the wafer back surface can be suppressed.

  Moreover, in the susceptor 1 of the present invention, it is preferable that a plurality of through holes penetrating the back surface side of the susceptor 1 are provided in the bottom surface of the lower counterbore portion 13. That is, when the wafer W is placed on the susceptor 1, the wafer is once placed on lift lift pins (not shown) and placed in the counterbore portion 11 of the susceptor 1 by lowering the lift pins. However, when the lift pins are lowered, there is a problem that the gas existing between the wafer W and the susceptor 1 does not escape quickly, and the position on which the wafer W is placed is likely to shift. In the present invention, it is necessary to place the wafer W by accurately aligning the protrusion 15 and the notch N. Therefore, by providing a plurality of through-holes penetrating the back surface side of the susceptor 1 on the bottom surface of the lower counterbore portion 13, when loading the wafer W onto the annular bottom surface portion 14 of the susceptor 1, Is discharged to the back surface side of the susceptor 1 so that the wafer W can be accurately placed at a predetermined position.

  FIG. 7 shows a vapor phase growth apparatus 2 to which the susceptor 1 according to the present invention is applied. The vapor phase growth apparatus 2 includes an upper liner 21 and a lower liner 22 for maintaining hermeticity, and an epitaxial growth furnace is defined by an upper dome 23 and a lower worm 24. A susceptor 1 for placing the wafer W horizontally is provided inside the epitaxial growth furnace. When manufacturing a large-diameter epitaxial wafer, a single wafer type vapor phase growth apparatus as shown in this figure is generally used.

In order to manufacture an epitaxial wafer using the vapor phase growth apparatus 2, first, the wafer W is placed on the annular bottom surface portion 14 of the susceptor 1. At this time, it is important to arrange the notch portion N formed on the peripheral edge of the wafer W and the protruding portion 15 provided on the susceptor 1 so as to overlap each other. Here, when the protrusion 15 as shown in FIG. 5 does not cover the portion directly below the notch N, the protrusion 15 may be arranged on a straight line connecting the notch N from the wafer center.
Next, the wafer W is heated to a predetermined temperature by a heating mechanism, and a silicon source gas as a raw material source gas is supplied in a horizontal direction along the upper surface of the susceptor 1 while rotating the susceptor 1 by a rotor. An epitaxial wafer can be manufactured by growing an epitaxial film having a predetermined thickness thereon.

  Here, since the notch part N formed in the peripheral part of the wafer W and the protruding part 15 provided in the susceptor 1 are arranged so as to overlap with each other, the lower spot facing from the notch part provided in the peripheral part of the wafer. It is possible to suppress the inflow of the raw material source gas flowing into the portion, to suppress the back surface deposit in the vicinity of the notch portion, and to obtain an epitaxial wafer having high flatness in the peripheral region of the notch portion.

(Invention Example 1)
Examples of the present invention will be described below.
An epitaxial wafer was manufactured using the susceptor 1 shown in FIG. 5, that is, the susceptor 1 in which the width of the annular bottom surface portion 14 is not less than the depth d1 of the notch portion N. Here, as the susceptor 1, the surface of the carbon substrate coated with SiC was used. Further, as a substrate for the epitaxial wafer, a boron-doped silicon wafer W having a diameter of 300 mm was used. The peripheral edge portion of the silicon wafer W is chamfered, and the width d2 of the chamfered portion is 300 μm. The width of the product exclusion area of the silicon wafer W was 2 mm. When the silicon wafer W is placed on the susceptor 1, the distance from the outer peripheral end of the wafer W to the inner peripheral wall position of the lower spot facing portion 13 is 1.5 mm, and the distance from the outer peripheral end of the wafer to the tip of the protruding portion 15 is 2. It was 5 mm.
The epitaxial wafer was manufactured as follows. That is, first, in the vapor phase growth apparatus 2 to which the susceptor 1 was applied, trichlorosilane gas as a source gas was supplied at a temperature of 1150 ° C., and a silicon coat was applied to the surface of the susceptor 1. Next, the silicon wafer W was introduced into the vapor phase growth apparatus 2 and placed on the upper spot facing portion 12 of the susceptor 1. At that time, the protrusion 15 was arranged on a straight line connecting the notch N from the wafer center. Subsequently, hydrogen gas was supplied at 1150 ° C. to perform hydrogen baking, and then an epitaxial wafer of silicon was obtained by growing 4 μm of a silicon epitaxial film at 1150 ° C. Here, trichlorosilane gas was used as the source gas, diborane gas was used as the dopant gas, and hydrogen gas was used as the carrier gas.

(Comparative Example 1)
Similar to Invention Example 1, an epitaxial wafer was manufactured. However, as the susceptor, a conventional susceptor 100 in which the protrusion 15 is not provided is used. All other conditions are the same as in Invention Example 1.

(Evaluation of flatness of epitaxial wafer)
The flatness of the epitaxial wafers of the inventive examples and comparative examples manufactured as described above was evaluated. At that time, the thickness at each position on each epitaxial wafer was measured, and evaluation was performed by obtaining SFQR (Site Front Least SQ Range). SFQR is an index indicating the local flatness of the wafer W. Specifically, it is obtained by calculating the sum of absolute values of the maximum displacement from the reference plane at each position of the wafer W. The obtained result is shown in FIG. Here, (a) is SFQR for the epitaxial wafer of Comparative Example 1 and (b) is Invention Example 1, and the value of each SFQR corresponds to each position of the wafer with the notch portion N disposed below. Yes.

As shown in FIG. 8A, when the conventional susceptor 100 having no protrusion is used, the SFQR value at the position of the notch N is as high as 105 nm. It shows that the flatness of the wafer W is low. On the other hand, as shown in FIG. 8B, when the susceptor 1 according to the present invention is used, the value of SFQR at the position of the notch N is greatly reduced to 29 nm. From this, it can be seen that the back surface deposition is suppressed in the peripheral region of the notch portion N, and high flatness of the epitaxial wafer is obtained including the peripheral region of the notch N.
As described above, by using the susceptor according to the present invention, it is possible to effectively suppress the wraparound of the raw material source gas from the notch portion formed at the wafer peripheral portion to the wafer back surface, in the notch portion peripheral region on the wafer back surface. It can be seen that an epitaxial wafer having high flatness can be obtained by suppressing the growth of the epitaxial film.

(Invention Example 2)
In the same manner as in Example 1, an epitaxial wafer was manufactured. However, as the susceptor 1, the susceptor 1 shown in FIG. 6, that is, the susceptor 1 in which the width of the annular bottom surface portion 14 is smaller than the depth d1 of the notch portion N was used. The width of the product exclusion area of the silicon wafer W was 1 mm. When the silicon wafer W is placed on the susceptor 1, the distance from the outer peripheral edge of the wafer W to the inner peripheral wall position of the lower spot facing portion 13 is 0.5 mm, and the distance from the outer peripheral edge of the wafer to the tip of the protrusion 15 is 1. It was 5 mm.

(Comparative Example 2)
An epitaxial wafer was manufactured in the same manner as in Invention Example 2. However, as the susceptor, a conventional susceptor 100 in which the protrusion 15 is not provided is used. All other conditions are the same as in Invention Example 1.

(Evaluation of flatness of epitaxial wafer)
As in the case of Example 1, in the case of Invention Example 2 and Comparative Example 2, the flatness of the epitaxial wafer was evaluated by measuring the thickness at each position on each epitaxial wafer and obtaining the SFQR. The obtained results are shown in FIG. Here, (a) is the SFQR for Comparative Example 2 and (b) is the invention example 2, and the value of each SFQR corresponds to each position of the wafer in which the notch portion N is disposed below.

  As in the case of the first embodiment, when the conventional susceptor 100 having no protrusion is used, the SFQR value at the position of the notch N is 172 nm as shown in FIG. The flatness of the wafer W in the peripheral region of the notch N is low. On the other hand, when the susceptor 1 according to the present invention is used, as shown in FIG. 9B, the SFQR value at the position of the notch N is greatly reduced to 94 nm. From this, it can be seen that the back surface deposition is suppressed in the peripheral region of the notch portion N, and high flatness of the epitaxial wafer is obtained including the peripheral region of the notch N.

DESCRIPTION OF SYMBOLS 1 Susceptor 2 Vapor phase growth apparatus 11 Counterbore part 12 Upper counterbore part 13 Lower counterbore part 14 Lower bottom face part 15 Projection part 21 Upper liner 22 Lower liner 23 Upper dome 24 Low wardome 100 Conventional susceptor W Wafer N Notch E Chamfer

Claims (9)

A susceptor for mounting a wafer in an epitaxial growth apparatus,
A circular concave counterbore part on which the wafer is placed is formed on the upper surface,
The counterbore part is composed of a two-stage counterbore part having an upper counterbore part that supports the peripheral edge of the back surface of the wafer, and a lower counterbore part formed at a lower center side than the upper counterbore part. And
When the wafer is placed on the annular bottom surface of the upper spot facing portion and the source gas is supplied into the epitaxy apparatus, it flows into the lower spot facing portion from a notch portion provided at the peripheral edge of the wafer. Suppress the inflow of the raw material source gas,
A protruding portion that protrudes inward from the inner peripheral wall surface of the lower counterbore part is provided on a part of the inner peripheral wall surface of the lower counterbore part ,
The susceptor according to claim 1, wherein the annular bottom surface portion of the upper counterbore is an inclined surface inclined downward toward the center of the annular bottom surface portion . The susceptor according to claim 1, wherein a distance from an inner peripheral wall surface of the lower spot facing portion to a tip of the protruding portion is 1 mm or less . The radius of the wafer is r1,
The radius of the inner peripheral wall of the lower spot facing is r4,
The distance from the center of the susceptor to the tip of the protrusion is r5,
When the depth of the notch is d1,
The susceptor according to claim 1 or 2 , wherein the following relational expression (B) is satisfied.
r5 ≦ (r1-d1) <r4 (B) The susceptor according to any one of claims 1 to 3 , wherein a plurality of through-holes penetrating the back surface side of the susceptor are provided on a bottom surface of the lower spot facing portion. The susceptor according to any one of claims 1 to 4, characterized in that the surface of the susceptor is coated with silicon film. The susceptor according to claim 1, wherein the protrusion has an upper surface extending in a horizontal direction from the inner peripheral wall surface. On a susceptor according to any one of claims 1 to 6, the position of the notch portion so as to correspond to the position of the projecting portion in a state of mounting the wafer, to form an epitaxial film on the wafer surface An epitaxial wafer manufacturing method characterized by the above. 8. The method of manufacturing an epitaxial wafer according to claim 7, wherein the epitaxial film is a silicon epitaxial film, and the surface of the susceptor is covered with a silicon film before the wafer is placed on the susceptor. The epitaxial growth apparatus which has a susceptor of any one of Claims 1-8 .

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