Susceptor and epitaxial growth device

Provided is a susceptor, capable of preventing occurrence of scratches on the back surface of a wafer attributable to lift pins, and reducing unevenness of the in-surface temperature distribution of the wafer. A susceptor according to one embodiment of this disclosure has a susceptor main body and a plate-shaped member, and when a wafer is conveyed, the front surface of the plate-shaped member ascended by lift pins supports the central part of the back surface of the wafer by surface contact. A separation space between the plate-shaped member and the susceptor main body, in a state in which the plate-shaped member is placed on the recessed part, enters further into the central side of the plate-shaped member, in a direction from the front surface to the back surface of the susceptor.

TECHNICAL FIELD

This disclosure relates to a susceptor for placing a wafer thereon within an epitaxial wafer growth device, and an epitaxial growth device having the susceptor.

BACKGROUND

An epitaxial wafer is formed by growing an epitaxial film on the surface of a semiconductor wafer by vapor phase growth. For example, when crystal integrity is further required, when a multi-layer structure of different resistivity is needed, or the like, an epitaxial silicon wafer is produced by growing a single crystal silicon thin film on a silicon wafer by vapor phase growth or epitaxial growth.

For epitaxial wafer production, a single wafer type epitaxial growth device (apparatus) is used for example. Here, a typical single wafer type epitaxial growth device will be described with reference toFIG. 10. As illustrated inFIG. 10, an epitaxial growth device200has a chamber10including an upper dome11, a lower dome12, and a dome mounting body13, and the chamber10defines an epitaxial film forming chamber. The chamber10is provided with a gas supply opening15and a gas exhaust opening16for supplying and exhausting a reaction gas at opposing positions on the side surface thereof. Meanwhile, a susceptor20for placing a wafer W thereon is arranged within the chamber10. The susceptor20is supported by a susceptor support shaft50from below. The susceptor support shaft50includes a main column52, and three arms54, including one not illustrated, radially extending from this main column52with an equal distance between them. Three supporting pins58, including one not illustrated, at the tip of the arms are fitted to and support the outer circumferential part of the back surface of the susceptor20. Moreover, three penetration holes, including one not illustrated, are formed in the susceptor20, and a penetration hole is also formed in each of the three arms54. Lift pins44are inserted through these penetration holes of the arms and the susceptor. The lower end of the lift pins44is supported by an ascending/descending shaft60. When the wafer W carried into the chamber10is being supported, when this wafer W is being placed on the susceptor20, and when the epitaxial wafer after vapor phase growth is carried out of the chamber10, by the ascending/descending shaft60ascending and descending, the lift pins44ascend and descend while sliding with the penetration holes of the arms and the penetration holes of the susceptor, and ascend and descend the wafer W at the upper end thereof.

In such an epitaxial growth device, the water W is directly supported and lifted by the lift pins. Therefore, to a part of the back surface of the wafer W abutting against the lift pins, the lift pins ascend and abut, and contact with the upper end of the lift pins is continuously maintained. Thus, there has been a problem that scratches or pin marks occur in the above mentioned part of the back surface of the wafer W.

In response to this problem, JP H11-163102 A (PTL 1) discloses the technique of lifting a wafer directly by a part of a susceptor, instead of supporting and lifting the wafer directly by lift pins. More specifically, FIG. 5 to 8 of PLT 1 disclose a susceptor 19 constituted of a base part 21, and a placement part 20 accommodated in a central recessed part 22 provided in the center of this base part. At the time of vapor phase growth, the wafer is accommodated in a peripheral recessed part 23 formed of the base part and the placement part, and when the wafer is carried out of the chamber, the placement part 20 ascends, and lifts the wafer.

CITATION LIST

Patent Literature

PLT 1: JP H 11-163102 A

SUMMARY

Technical Problem

According to the technique of PLT 1, since the water is, when lifted, supported by a surface as a part of the susceptor, without being locally supported by lift pins, occurrence of scratches on the back surface of the wafer attributable to lift pins can be prevented. However, the inventors have newly recognized that the technique of PLT 1 has a problem as follows.

More specifically, in order to fit the placement part into the base part, generation of a gap between the placement part and the base part, in a state in which the placement part is accommodated in the base part, at the time of vapor phase growth, cannot be avoided. While heat is transmitted from a heated susceptor to a wafer at the time of vapor phase growth, heat from the susceptor is less likely to be transmitted to a wafer part immediately above this gap part as compared to other parts of the wafer, and as a result, the growth rate of an epitaxial film also becomes slow. Thus, the gap generated between the placement part and the base part makes the in-surface temperature distribution of the wafer uneven at the time of vapor phase growth, and as a result, makes the in-surface film thickness distribution of the epitaxial film grown by vapor phase growth uneven. Since a high level of evenness of the in-surface film thickness distribution of epitaxial films has been demanded for epitaxial wafers in recent years, it is necessary to make the in-surface temperature distribution of wafers at the time of vapor phase growth more even.

Therefore, in consideration of the above problem, this disclosure has the purpose of providing a susceptor and an epitaxial growth device, capable of preventing occurrence of scratches on the back surface of a wafer attributable to lift pins and reducing unevenness of the in-surface temperature distribution of the wafer.

Solution to Problem

The brief configuration of this disclosure for solving the above problem is as follows.

1. A susceptor for placing a wafer thereon within an epitaxial growth device, wherein

a counterbore part for placing the wafer thereon is formed on a front surface of the susceptor,

the susceptor has a susceptor main body, and a plate-shaped member placed on a recessed part provided in a central part of a front surface of the susceptor main body,

a bottom surface of the counterbore part is constituted of a front surface of the plate-shaped member, and a part of the front surface of the susceptor main body, located around the recessed part,

the susceptor main body is provided with penetration holes, for lift pins that support a back surface of the plate-shaped member, and ascend and descend the plate-shaped member, to be inserted therethrough,

when the wafer is being placed on the counterbore part and when the wafer is carried out of the counterbore part, the front surface of the plate-shaped member ascended by the lift pins acts as a supporting surface for supporting at least a central part of a back surface of the wafer by surface contact, and

a separation space between the plate-shaped member and the to susceptor main body, in a state in which the plate-shaped member is placed on the recessed part, enters further into a central side of the plate-shaped member, in a direction from the front surface to the back surface of the susceptor.

2. The susceptor according to the above item 1, wherein a periphery of the plate-shaped member and a periphery of the recessed part of the susceptor main body each has an inclined surface that enters further into the central side of the plate-shaped member in a direction from the front surface to the back surface of the susceptor.

3. The susceptor according to the above item 1, wherein

a periphery of the recessed part of the susceptor main body has a stepped part,

the plate-shaped member has a first part with a first radius r1, and a second part with a second radius r2that is larger than r1on the first part, and

the stepped part supports a periphery of the second part.

4. The susceptor according to any one of the above items 1 to 3, wherein the lift pins are fixed to the plate-shaped member.

5. An epitaxial growth device comprising the susceptor according to any one of the above items 1 to 4, and an ascending/descending mechanism for ascending and descending the lift pins by supporting the lower end of the lift pins.

Advantageous Effect

The susceptor and the epitaxial growth device according to this disclosure can prevent occurrence of scratches on the back surface of a wafer attributable to lift pins and reduce unevenness of the in-surface temperature distribution of the wafer.

DETAILED DESCRIPTION

With reference toFIG. 8andFIG. 9, the epitaxial growth device100according to one embodiment of this disclosure will be described. Moreover, with reference toFIG. 1 to 3, the susceptor20according to one embodiment of this disclosure, which is included in this epitaxial growth device100, will be described.

Epitaxial Growth Device

Chamber

The chamber10includes the upper dome11, the lower dome12, and the dome mounting body13, and this chamber10defines the epitaxial film forming chamber. The chamber10is provided with the gas supply opening15and the gas exhaust opening16for supplying and exhausting a reaction gas at opposing positions on the side surface thereof.

Heat Lamp

The heat lamp14is arranged in the upper side region and the lower side region of the chamber10, and generally a halogen lamp or infrared lamp having a high temperature increase/decrease rate, and excellent temperature controllability is used.

Main Configuration of Susceptor

With reference toFIG. 1andFIG. 2, the main configuration of the susceptor20will be described. The susceptor20is a disc-shaped member for placing the wafer W thereon inside the chamber10. For the susceptor20, carbon graphite or graphite as a base material having the surface thereof coated with silicon carbide can be used. With reference toFIGS. 1A and 1B, the counterbore part21for placing the wafer W thereon is formed in the front surface of the susceptor20. The diameter of the counterbore part21at the opening end may be set accordingly in consideration of the diameter of the wafer W, and normally is about 1.0 to 2.0 mm larger than the diameter of the wafer W.

With reference toFIG. 1A to 1C, the susceptor20has the susceptor main body30, and the plate-shaped member40placed on a recessed part31provided in the central part of the front surface of this susceptor main body.

With reference toFIG. 1A to 1CandFIG. 2A, the front surface of the susceptor main body30includes a front surface outermost circumferential part32, a wafer supporting surface32A, a vertical wall surface32B, a front surface middle part33, an inclined surface34, and a front surface central part35. The front surface outermost circumferential part32is located around the counterbore part21illustrated inFIG. 1A. The wafer supporting surface32A is an inclined surface located inside the front surface outermost circumferential part32, supporting the back surface periphery of the wafer W by line contact, and constituting a part of the counterbore part. The vertical wall surface32B is a wall surface continuous from the inner circumferential end of the wafer supporting surface32A, and constituting a part of the counterbore part. The front surface middle part33is continuous from the vertical wall surface32B, and constitutes a part of the bottom surface of the counterbore part21. The front surface central part35is located inside the front surface middle part33, and constitutes the bottom surface of the recessed part31. The inclined surface34is a characteristic part of this embodiment described below, and is located between the front surface middle part33and the front surface central part35. The susceptor main body30is provided with three penetration holes36concentrically located with an equal angle of 120 degrees, and penetrating the front surface central part35and the back surface in the vertical direction. The lift pins44described below are inserted through the three penetration holes36.

With reference toFIG. 1A to 1CandFIG. 2B, the plate-shaped member40is a disc-shaped member that has a front surface41and a back surface42, and that is placed on the recessed part31with a necessary minimum gap or clearance. As illustrated inFIG. 1A, the front surface41constitutes a part of the bottom surface of the counterbore part21, and the back surface42is in contact with and supported by the front surface central part35, or the bottom surface of the recessed part, of the susceptor main body. The periphery connecting the front surface41and the back surface42is an inclined surface43, which is a characteristic part of this embodiment described below. Three lift pins44extend from the back surface42. The three lift pins44are respectively inserted through the three penetration holes36provided in the susceptor main body. The lift pins44can attach and detach the plate-shaped member40and the susceptor main body30, while supporting the back surface42of the plate-shaped member, by being ascended and descended in the vertical direction by the ascending/descending shaft60described below. This motion will be described below. The lift pins44are preferably located in a region separate from the center of the back surface42of the plate-shaped member by not less than 50% of the radius of the back surface. Although the lift pins44are fixed to the plate-shaped member40in this embodiment, the lift pins44may not be fixed to the plate-shaped member40.

As illustrated inFIGS. 1A and 1B, the bottom surface of the counterbore part21is constituted of the front surface41of the plate-shaped member, and a part of the front surface of the susceptor main body, specifically the front surface middle part33, located around the recessed part31. More specifically, in a state in which the plate-shaped member40is placed on the recessed part31, and the wafer W is placed on the counterbore part21, among the surfaces of the counterbore part21, the front surface41of the plate-shaped member, and the front surface meddle part33of the susceptor main body are separate from and opposite to the back surface of the wafer W.

Meanwhile, as illustrated inFIG. 1C, when the wafer W is being placed on the counterbore part21, and when the wafer W is carried out of the counterbore part21, i.e., the wafer W is conveyed, the susceptor main body30and the plate-shaped member40are separate in the vertical direction, and the front surface41of the plate-shaped member ascended by the lift pins44acts as a supporting surface for supporting at least the central part of the back surface of the wafer W by surface contact. Therefore, occurrence of scratches on the back surface of the wafer W attributable to the lift pins can be prevented.

Here in the specification, “the central part of the back surface of the wafer” means a region separate from the wafer center by not more than 50% of the wafer radius in the back surface of the wafer. More specifically, in this embodiment, from the front surface view of the susceptor main body30, the center of the counterhore part21and the center of the recessed part31match, i.e., the recessed part31is not decentered from the counterhore part21. Moreover, the radius of the front surface41of the plate-shaped member is not less than 50% of the wafer radius.

Meanwhile, the radius of the front surface41of the plate-shaped member is preferably not more than 90% of the wafer radius. The wafer W supported by the plate-shaped member40is conveyed out of the chamber, while the back surface outer circumferential part of the wafer W is supported by a wafer supporting part72of a U-shaped conveying blade70inserted from the direction illustrated inFIG. 2B. When the radius of the front surface41is more than 90% of the wafer radius, it is difficult to support the wafer W by the conveying blade70.

The surface part of the plate-shaped member40or the entirety of the plate-shaped member40is preferably made of a soft material such as glassy carbon. It is because occurrence of scratches when the back surface of the wafer W is supported by surface contact can be prevented.

In addition, the bottom of the recessed part31of the susceptor main body and the plate-shaped member40are also preferably porous structures. It is because by promoting hydrogen gas to sneak into the back surface of the wafer W, occurrence of halo or haze on the wafer back surface can be prevented.

Susceptor Support Shaft

With reference toFIG. 7A, the susceptor support shaft50supports the susceptor20from below within the chamber10, and has the main column52, the three arms54, and the three supporting pins58. The main column52is arranged on substantially the same axis as the center of the susceptor. The three arms54radially extend below the periphery of the susceptor20from the main column52, and respectively have penetration holes56penetrating in the vertical direction. Additionally in the specification, “the periphery of the susceptor” means a region outside the susceptor center by not less than 80% of the susceptor radius. The supporting pins58are respectively provided in the tip of the three arms54, and directly support the susceptor20. More specifically, the supporting pins58support the back surface periphery of the susceptor. The three lift pins44are respectively inserted through the three penetration holes56. The susceptor support shaft50is desirable to be constituted of quartz, and is desirable to be constituted particularly of synthetic quartz. However, the tip part of the supporting pins58is preferable to be constituted of silicon carbide, which is the same as the susceptor20.

As illustrated inFIG. 7B, the ascending/descending shaft60as an ascending/descending mechanism has a main column62defining a hollow for accommodating the main column52of the susceptor support shaft and having a shared rotation axis with this main column52, and three support columns64branching from the tip of this main column62. The tip parts66of these support columns64supports the lower end of the lift pins44respectively. The ascending/descending shaft60is preferably constituted of quartz. By the ascending/descending shaft60moving up and down along the main column52of the susceptor support shaft in the vertical direction, the lift pins44can be ascended and descended.

Production Procedure for Epitaxial Wafer

Next, a series of actions of carrying the wafer W into the chamber10, vapor phase growth of an epitaxial film onto the wafer W, and carrying the produced epitaxial wafer out of the chamber10will be described with appropriate reference toFIG. 8andFIG. 9.

The wafer W carried into the chamber10while being supported by the conveying blade70illustrated inFIG. 2Bis temporarily placed on the front surface41of the plate-shaped member40lifted by the lift pins44. The ascending movement of the lift pins44is performed through the ascending movement of the ascending/descending shaft60supporting their lower end.

Then, by ascending the susceptor support shaft50, the susceptor main body30is moved to a position of the plate-shaped member40, and the wafer W is placed on the counterbore part21of the susceptor20. Subsequently, an epitaxial wafer is produced by, while heating the wafer W to a temperature not lower than 1000° C. by the heat lamp14, supplying a reaction gas from the gas supply opening15into the chamber10, and growing an epitaxial film having a predetermined thickness by vapor phase growth. During vapor phase growth, by rotating the susceptor support shaft50using the main column52as a rotation axis, the susceptor20and the wafer W thereon are rotated.

Thereafter, by descending the susceptor support shaft50, the susceptor main body30is descended. This descending is performed until the lift pins44are supported by the ascending/descending shaft60and the plate-shaped member40is separate from the susceptor main body30, and the produced epitaxial wafer is supported by the front surface41of the plate-shaped member40supported by the lift pins44. Then, the conveying blade70is introduced into the chamber10, and the epitaxial wafer is placed on the wafer supporting part72of the conveying blade by descending the lift pins44. Thus, the epitaxial wafer is passed from the plate-shaped member40to the conveying blade70. Subsequently, the epitaxial wafer is carried out of the chamber10along with the conveying blade70.

Configuration of Characteristic Part of Susceptor

Here, separation between the susceptor main body30and the plate-shaped member40, as a characteristic configuration of this disclosure, will be described in detail.

With reference toFIGS. 3A and 3B, in the susceptor20of this embodiment, the periphery of the plate-shaped member40has the inclined surface43that enters further into the central side of the plate-shaped member, in a direction from the front surface to the back surface of the susceptor, i.e., downward vertical direction, and the periphery of the recessed part of the susceptor main body30also has the inclined surface34that enters further into the central side of the plate-shaped member in a direction from the front surface to the back surface of the susceptor. Therefore, a separation space between the plate-shaped member40and the susceptor main body30, or a position of the separation part between the plate-shaped member40and the susceptor main body30in the horizontal direction, in a state in which the plate-shaped member40is placed on the recessed part, enters further into the central side of the plate-shaped member in a direction from the front surface to the back surface of the susceptor, i.e., downward vertical direction.

Technical significance of adopting such a configuration will be described with comparison toFIGS. 6A and 6Billustrating Comparative Example. InFIG. 6, the periphery of the plate-shaped member40is a vertical surface49, and the periphery of the recessed part of the susceptor main body30is also a vertical surface39. Therefore, the separation space between the plate-shaped member40and the susceptor main body30extends straight in the vertical direction, and the above mentioned separation space or gap is present in a large size immediately below the wafer W. This gap makes the in-surface temperature distribution of the wafer W uneven at the time of vapor phase growth, even when it is a minimum distance, e.g., about 0.5 to 1.0 mm, necessary for accommodating the plate-shaped member40in the recessed part31, and as a result, makes the in-surface film thickness distribution of the epitaxial film grown by vapor phase growth uneven.

Contrarily, in this embodiment illustrated inFIG. 3, the separation space between the plate-shaped member40and the susceptor main body30enters further into the central side of the plate-shaped member, in the downward vertical direction. Therefore, the size of the gap located immediately below the wafer W can be made smaller as compared toFIG. 6, and as a result, unevenness of the in-surface temperature distribution of the wafer W can be reduced.

Additionally,FIG. 3Aillustrates a state in which the plate-shaped member40is placed on the susceptor main body30without being decentered with respect thereto, i.e., the distance of the gap between the plate-shaped member40and the susceptor main body30is constant in the circumferential direction, andFIG. 3Bis a vertical section view or I-I section view including the susceptor center in that state. It is also similar forFIG. 6, andFIGS. 4 and 5described below.

Here, a thickness t1of the plate-shaped member40is preferably not less than 0.5 mm to not more than 3.0 mm. It is because, although the thickness t1is preferably smaller from the perspective of making the size of the gap located immediately below the wafer W small, there is a possibility that less than 0.5 mm lacks the strength. Moreover, it is because, when the thickness t1is more than 3.0 mm, it becomes difficult to obtain the strength of the susceptor main body30.

With reference toFIG. 3B, a radius r4of the front surface41of the plate-shaped member is, as mentioned previously, preferable to be not less than 50% and not more than 90% of the wafer radius. Moreover, a radius r3of the back surface42of the plate-shaped member is preferable to be about 1.0 to 5.0 mm smaller than r4.

The inclined surface43and the inclined surface34are preferable to have an equal inclination angle, and the inclination angle with respect to the vertical direction is preferable to be 30 to 45 degrees.

The shape of the periphery of the plate-shaped member40and the shape of the periphery of the recessed part of the susceptor main body30are not limited to the shape illustrated inFIG. 3B, and the effect of this disclosure can be obtained by designing the separation space between the plate-shaped member40and the susceptor main body30to enter further into the central side of the plate-shaped member in the downward vertical direction.

Another embodiment is illustrated inFIGS. 4A and 4B. In this embodiment, the periphery of the plate-shaped member40has a vertical surface45A that is continuous from the front surface41, and an inclined surface45B that is continuous from this vertical surface45A and enters further into the central side of the plate-shaped member in the downward vertical direction. The periphery of the recessed part of the susceptor main body30also has a vertical surface37A that is continuous from the front surface middle part33, and an inclined surface37B that is continuous from this vertical surface37A and enters further into the central side of the plate-shaped member in the downward vertical direction. Also in this case, the size of the gap located immediately below the wafer W can be made smaller as compared toFIG. 6, and as a result, unevenness of the in-surface temperature distribution of the wafer W can be reduced. Additionally, while there is a possibility that the strength is not sufficient due to the tip of the plate-shaped member40tapering to a point in the case ofFIG. 3B, the strength is not lost in the case ofFIG. 4B.

The vertical surface45A and the vertical surface37A are preferable to have a height that is 20 to 50% of the thickness t1of the plate-shaped member40. When it is less than 20%, there is a possibility that the strength is not sufficient, and when it is more than 50%, there is a possibility that the effect of reducing unevenness of the in-surface temperature distribution of the wafer W is not sufficient.

The inclined surface45B and the inclined surface37B are preferable to have an equal inclination angle, and the inclination angle with respect to the vertical direction is preferable to be 30 to 45 degrees similarly toFIG. 3B.

Yet another embodiment is illustrated inFIGS. 5A and 5B. In this embodiment, the periphery of the recessed part of the susceptor main body30has a stepped part formed of a first vertical surface38A that is continuous from the front surface central part35, a horizontal surface38B that is continuous from this first vertical surface38A, and a second vertical surface38C that is continuous from this horizontal surface38B to the front surface middle part33. Meanwhile, the plate-shaped member40has a first part46of a first radius r1, and a second part47of a second radius r2that is larger than r1on this first part. More specifically, the periphery of the plate-shaped member40is composed of a first vertical surface46A that is the outer circumference of the first part, a second vertical surface47A that is the outer circumference of the second part, and a horizontal surface48that is located between them. Moreover, the stepped part supports a second part periphery47B. In other words, the horizontal surface48and the horizontal surface38B are in contact with each other.

Also in this embodiment, since the separation space between the plate-shaped member40and the susceptor main body30gradually enters further into the central side of the plate-shaped member in the downward vertical direction, the size of the gap located immediately below the wafer W can be made smaller as compared toFIG. 6, and as a result, unevenness of the in-surface temperature distribution of the wafer W can be reduced.

The second vertical surface47A of the plate-shaped member and the second vertical surface38C of the susceptor main body are preferable to have the same height, which can be about 20 to 50% of the thickness t1of the plate-shaped member40. Additionally, the first vertical surface46A of the plate-shaped member and the first vertical surface38A of the susceptor main body are also preferable to have the same height.

The radius r2of the second part, i.e., the radius of the front surface41of the plate-shaped member is, as mentioned previously, preferable to be not less than 50% and not more than 90% of the wafer radius. Moreover, the radius r1of the first part, i.e., the radius of the back surface42of the plate-shaped member is preferable to be about 1.0 to 5.0 mm smaller than r2. The width of the stepped part or the horizontal surface38B is preferably equal to r2−r1.

EXAMPLES

Using the susceptor illustrated inFIGS. 1 to 3and the epitaxial growth device illustrated inFIGS. 8 and 9, an epitaxial silicon wafer was produced by following the procedure described above. InFIG. 3B, the radius r3was 120 mm, the radius r4was 123 mm, the thickness t1was 2.0 mm, the thickness t2was 2.3 mm, and the gap distance G was 1.0 mm. As a substrate for the epitaxial wafer, a boron doped silicon wafer having a diameter of 300 mm was used.

Similarly to Example 1 except for using the susceptor illustrated inFIG. 5, an epitaxial silicon wafer was produced. InFIG. 5B, the radius r1was 121 mm, the radius r2was 123 mm, the thickness t1was 2.0 mm, the thickness t2was 2.3 mm, and the gap distance G was 1.0 mm.

Comparative Example

Similarly to Example 1 except for using the susceptor illustrated inFIG. 6, an epitaxial silicon wafer was produced. InFIG. 6B, the thickness t1was 2.0 mm, the thickness t2was 2.3 mm, and the gap distance G was 1.0 mm. The radius of the plate-shaped member was 120 mm.

Vapor Phase Growth Conditions

For producing epitaxial wafers, a silicon wafer was introduced into the chamber, and placed on the susceptor in the previously described method. Then, a hydrogen bake out was performed under a hydrogen gas atmosphere at 1150° C., and a silicon epitaxial film was grown on the silicon wafer surface by 4 μm at 1150° C., to obtain an epitaxial silicon wafer. Here, trichlorosilane gas was used as a raw material source gas, diborane gas as a dopant gas, and hydrogen gas as a carrier gas. Subsequently, by the previously described method, the epitaxial silicon wafer was carried out of the chamber.

Evaluation of Back Surface Quality

The epitaxial wafers produced in Examples and Comparative Example were subject to observation of the back surface region corresponding to the position of lift pins using a surface examination device, manufactured by KLA-Tencor: Surfscan SP-2, in DCO mode, and measurement of the area having a scattering strength not lower than the value set for laser reflection, or pin mark strength, to evaluate scratches on the epitaxial wafer back surface attributable to lift pins. The result was 0 mm2, and no scratch attributable to lift pins was observed on the epitaxial wafer back surface for both Comparative Example, and Examples 1 and 2.

Evaluation of In-Surface Temperature Distribution of Wafer

The epitaxial wafers produced in Examples and Comparative Example were subject to measurement of the haze level using a surface examination device, manufactured by KLA-Tencor: Surfscan SP-2. As the haze level is known to be proportional to the temperature within the wafer surface, the temperature distribution within the wafer surface was calculated from this value, and compared. The result is illustrated inFIG. 11.

As illustrated inFIGS. 11A and 11B, the temperature of the wafer is lower in the outer circumference of the wafer having the gap between the plate-shaped member and the susceptor main body located immediately below, or around the position separate from the wafer center by 120 mm, and the in-surface temperature distribution of the wafer is uneven in Comparative Example. On the contrary, a temperature decrease in the outer circumference of the wafer is prevented, and unevenness of the in-surface temperature distribution of the wafer is reduced in Examples 1 and 2.

INDUSTRIAL APPLICABILITY

The susceptor and the epitaxial growth device according to this disclosure, which can prevent occurrence of scratches on the wafer back surface attributable to lift pins, and reduce unevenness of the in-surface temperature distribution of the wafer, can preferably be applied to epitaxial wafer production.

REFERENCE SIGNS LIST

100Epitaxial growth device

13Dome mounting body

15Gas supply opening

30Susceptor main body

32Front surface outermost circumferential part of susceptor main body

32A Wafer supporting surface

32B Vertical wall surface

33Front surface middle part of susceptor main body

35Front surface central part of susceptor main body (or bottom surface of recessed part)

37A Vertical surface

38A First vertical surface

38B Horizontal surface

38C Second vertical surface

41Front surface of plate-shaped member

42Back surface of plate-shaped member

45A Vertical surface

46A First vertical surface

47A Second vertical surface

47B Second part periphery

50Susceptor support shaft

66Tip part of support column

72Wafer supporting part

W Wafer