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.

