Wafer boat and manufacturing method of the same

Abstract

A wafer boat supporting a silicon wafer to be processed provides a sufficient anchor effect between a deposit film and a SiC coating film formed on a base material, and suppresses generation of particles due to peeling off of the deposit film. The vertical wafer boat includes a plurality of columns, being made of SiC-based material having a SiC coating film on a surface thereof, which contains shelf plate portions for supporting wafers, and a top plate and a bottom plate for fixing upper and lower ends of the columns, wherein a supporting plane which is in contact with an outer peripheral portion of the wafer is provided on an upper surface of the shelf plate portion, and a surface roughness Ra of a lower surface of the shelf plate increases toward a front side of the shelf plate portion from a rear side.

Claims

1. A vertical wafer boat comprising a plurality of columns which is made of SiC-based material with a surface thereof provided with a SiC coating film and includes shelf plate portions for supporting wafers thereon, and a top plate and a bottom plate for fixing upper and lower ends of the columns, wherein the shelf plate portion has an upper surface provided with a supporting plane which is in contact with an outer peripheral portion of the wafer, and the shelf plate portion has a lower surface whose surface roughness Ra increases from a rear side toward a front side of the shelf plate portion.

2. The vertical wafer boat according to claim 1, wherein the surface roughness Ra of the lower surface of the shelf plate portion is in a range of 1.0 m or more to 3.0 m or less.

3. The vertical wafer boat according to claim 2, wherein the top plate and the bottom plate are made of SiC-based material and a SiC coating film is formed on a surface thereof.

4. The vertical wafer boat according to claim 1, wherein the top plate and the bottom plate are made of SiC-based material and a SiC coating film is formed on a surface thereof.

5. A manufacturing method of a vertical wafer boat including a plurality of columns, which is formed of SiC-based material with a surface thereof provided with a SiC coating film and include shelf plate portions for supporting wafers placed thereon, and a top plate and a bottom plate for fixing upper and lower ends of the columns, the method comprising a step of performing a process such that a surface roughness Ra of a lower surface of the shelf plate portion increases toward a front side of the shelf plate portion from a rear side.

6. The manufacturing method of a vertical wafer boat according to claim 5, wherein in the step of performing a roughening process to the lower surface of the shelf plate portion, the roughening process is performed so that the surface roughness Ra is in the range from 1.0 m or more to 3.0 m or less.

7. The manufacturing method of a vertical wafer boat according to claim 6, further comprising a step of performing a smoothing process to an upper surface of the shelf plate portion.

8. The manufacturing method of a vertical wafer boat according to claim 5, further comprising a step of performing a smoothing process to an upper surface of the shelf plate portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a magnified side view illustrating one of a plurality of columns included in a wafer boat according to the present invention;

(2) FIG. 2 is a sectional view from arrows A-A in FIG. 1, illustrating a lower surface side of a shelf plate portion;

(3) FIG. 3A is a sectional view schematically illustrating a manufacturing process for a wafer boat according to the present invention (forming method for column);

(4) FIG. 3B is a sectional view schematically illustrating a manufacturing process for a wafer boat (forming method for column), which is subsequent to FIG. 3A;

(5) FIG. 3C is a sectional view schematically illustrating a manufacturing process for a wafer boat (forming method for column), which is subsequent to FIG. 3B;

(6) FIG. 3D is a sectional view schematically illustrating a manufacturing process for a wafer boat (forming method for column), which is subsequent to FIG. 3C;

(7) FIG. 4 is a sectional view illustrating a conventional vertical low-pressure CVD apparatus;

(8) FIG. 5 is a perspective view illustrating a conventional wafer boat; and

(9) FIG. 6 is a magnified side view illustrating a part of the column of the conventional wafer boat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) Hereinafter, description will be made of an embodiment of a wafer boat and a manufacturing method for the same according to the present invention with reference to the accompanying drawings. The wafer boat according to the present invention is different from the conventional wafer boat described above with reference to FIG. 5 and FIG. 6 only in the structure of the shelf plate portion that supports the silicon wafer, and the detailed description on the same structure is therefore omitted.

(11) FIG. 1 is a magnified side view illustrating one of a plurality of columns included in a wafer boat according to the present invention. FIG. 2 is a sectional view from arrows A-A in FIG. 1, illustrating a lower surface side of the shelf plate portion 2b.

(12) As illustrated in FIG. 1 (and FIG. 5), the column 2 is formed to have a plurality of support grooves 2a at predetermined intervals on the inside along the longitudinal direction of the column 2. By the formation of the support grooves 2a, the plate-shaped shelf plate portions 2b are formed. The silicon wafer W is supported by at the outer peripheral portion and in contact with the supporting plane 2b1 of the shelf plate portion 2b provided for each of the plurality of columns 2 and held by the wafer boat.

(13) Each column 2 has surfaces covered with the SiC coating film by CVD process and the SiC coating film on the upper surface (supporting surface 2b1) of the shelf plate portion 2b is in a smoothed state. With a smoothing process, the generation of the particles from the SiC coating film is suppressed when the wafer W is brought into contact with the supporting plane 2b1 of the shelf plate portion 2b.

(14) On the other hand, a lower surface 2b2 of the shelf plate portion 2b is in the roughened state (preferably, with a surface roughness Ra in a range of 1.0 m or more and 3.0 m or less). In particular, this surface roughening process is performed so that the surface roughness increases from the rear side (column side) of the shelf plate portion 2b toward the front side thereof.

(15) When the heat treatment is performed with holding the wafers W, this roughening process makes it easier for the deposit film to be deposited on the lower surface 2b2 of the shelf plate portion 2b (especially on the front side where peeling off of the deposit film easily occurs); as the deposit film thickness increases, the peeling off of the deposit film, which would generate the particles, can be largely suppressed.

(16) It is desirable that the top plate 3 and the bottom plate 4, as with the column 2, are made of the SiC-based material, the SiC coating film is formed on the surface of the base material, and the surface roughness Ra thereof is in the range of 1.0 m or more and 3.0 m or less.

(17) Next, a manufacturing method for the wafer boat according to the present invention will be described with reference to FIGS. 3A to 3D. FIGS. 3A to 3D are sectional views schematically illustrating a manufacturing method (forming method) for the column 2. For forming the column 2, firstly, a plurality of grooves is formed by using a rotary cutter in parallel to each other in a rod-like SiC-based material 10 along a longitudinal direction thereof. Thus, the column with a plurality of support grooves 2a as illustrated in FIG. 3A is formed. With the support grooves 2a, the plate-shaped shelf plate portions 2b projecting horizontally are formed and the upper surface of the shelf plate portion 2b serves as the supporting plane 2b1.

(18) Next, as illustrated in FIG. 3B, the SiC-based material 10 is processed by a chemical vapor growth method (CVD) at 1100 C. for 15 hours. By this CVD process, a SiC coating layer 11 is formed to have a predetermined film thickness (for example, 60 m) on the surface of the base material.

(19) Next, as illustrated in FIG. 3C, the supporting plane 2b1 of the shelf plate portion 2b with the surface provided with the SiC layer 11 is smoothed by a polishing process.

(20) After the supporting plane 2b1 is polished, the lower surface 2b2 of the shelf plate portion 2b is roughened as illustrated in FIG. 3D. Specifically, silicon carbide powder with a medium size (D50) of approximately 100 m is used to perform a sand blasting process to the lower surface 2b2.

(21) The surface roughness Ra of the lower surface 2b2 is set in the range of 1.0 m or more and 3.0 m or less and is increased toward the front (end) of the shelf plate portion 2b. The surface roughness Ra increasing toward the front (end) of the shelf plate portion 2b is achieved by starting the sand blasting process from the inner surface side (groove side) of the column 2. That is to say, by performing the sand blasting process from the groove side of the column 2, more silicon carbide powder collides with the front (end) of the shelf plate portion 2b and less silicon carbide powder collides with the rear of the shelf plate portion 2b. Thus, the lower surface 2b2 of the shelf plate portion 2b is rougher toward the front side thereof.

(22) The lower surface 2b2 of the shelf plate portion 2b of the SiC-based material before the CVD process may be subjected to the sand blasting process to have a surface roughness Ra in a range of 0.5 m or more and 2.0 m or less and then subjected to the CVD process to have a surface roughness Ra in the range of 1.0 m or more and 3.0 m or less.

(23) The wafer boat and the manufacturing method for the same according to the present invention will be further described with reference to Examples. In Examples, the wafer boat described in the embodiment was manufactured and the performance of the obtained wafer boat was examined.

Example 1

(24) In Example 1, for forming the column, a plurality of support grooves for wafer supporting is formed by a rotary cutter in the SiC based-material and a CVD process was performed at 1100 C. for 15 hours to form the SiC coating film with a thickness of 60 m on the surface of the SiC-based material.

(25) Next, the upper surface (supporting plane) of the shelf plate portion formed by the support groove was polished to be smooth.

(26) In addition, the lower surface of the shelf plate portion was subjected to the sand blasting process (using silicon carbide powder D50 having a diameter of approximately 100 m) so that the roughness of the lower surface increases toward the front thereof. Using this roughening process, roughness Ra (arithmetic average roughness) of the lower surface becomes 2.1 m in an area Ar1 on the front side of the lower surface 2b2, 1.5 m in an area Ar2 at the center, and 1.1 m in an area Ar3 on the deepest side (column side), respectively, as illustrated in FIG. 2.

(27) The obtained column was washed with acid and then washed with pure water and dried; thus, the column was completed. After a necessary number of columns were formed similarly, the top plate and the bottom plate were assembled to columns to finish the assembled vertical wafer boat.

(28) In addition, 50 silicon wafers were set to the vertical wafer boat and heated in the furnace at 750 C. for an hour.

(29) In Example 1, the number of particles (pieces/wafer) attached on the front and rear surfaces of the heated silicon wafer was measured.

Example 2

(30) In Example 2, using the roughening process, roughness Ra (arithmetic average roughness) of the lower surface becomes 3.0 m in an area Ar1 on the front side of the lower surface 2b2, 2.0 m in an area Ar2 at the center, and 1.0 m in an area Ar3 on the deepest side (column side), respectively, as illustrated in FIG. 2.

(31) The other conditions are the same as those of Example 1.

(32) With the manufactured vertical wafer boat, wafers were heated under the same condition as that of Example 1 and the number of particles (pieces/wafer) on the front and rear surfaces of the wafer was measured.

Example 3

(33) In Example 3, using the roughening process, roughness Ra (arithmetic average roughness) of the lower surface becomes 2.1 m in an area Ar1 on the front side of the lower surface 2b2, 1.1 m in an area Ar2 at the center, and 0.5 m in an area Ar3 on the deepest side (column side), respectively, as illustrated in FIG. 2. The other conditions are the same as those of Example 1.

(34) With the manufactured vertical wafer boat, the wafers were heated under the same condition as that of Example 1 and the number of particles (pieces/wafer) on the front and rear surfaces of the wafer was measured.

Example 4

(35) In Example 4, using the roughening process, roughness Ra (arithmetic average roughness) of the lower surface becomes 4.0 m in an area Ar1 on the front side of the lower surface 2b2, 3.1 m in an area Ar2 at the center, and 2.2 m in an area Ar3 on the deepest side (column side), respectively, as illustrated in FIG. 2.

(36) The other conditions are the same as those of Example 1.

(37) With the manufactured vertical wafer boat, the wafers were heated under the same condition as that of Example 1 and the number of particles (pieces/wafer) on the front and rear surfaces of the wafer was measured.

Comparative Example 1

(38) In Comparative Example 1, for forming the column, a plurality of support grooves for supporting wafers was formed by a rotary cutter in the SiC-based material and a CVD process was performed at 1100 C. for 15 hours to form the SiC coating film with a thickness of 60 m on the surface of the SiC-based material.

(39) Next, the upper surface (supporting plane) of the shelf plate portion formed by the support groove was polished to be smooth.

(40) The obtained column was washed with acid and then washed with pure water and dried; thus, the column was completed. After a necessary number of columns were formed similarly, the top plate and the bottom plate were assembled thereto to manufacture the assembled vertical wafer boat.

(41) With the manufactured vertical wafer boat, the wafers were heated under the same condition as that of Example 1 and the number of particles (pieces/wafer) on the front and rear surfaces of the wafer was measured.

(42) Table 1 shows the results from Examples 1 to 4 and Comparative Example 1.

(43) TABLE-US-00001 TABLE 1 Surface Thickness of Number of roughness of deposited film particles lower surface on lower surface with diameter of shelf plate of shelf plate less than portion portion 0.5 m Results Example 1 1.1 to 2.1 m 6.3 m 3 good Example 2 1.0 to 3.0 m 6.9 m 2 good Example 3 0.5 to 2.1 m 3.2 m 6 fair Example 4 2.2 to 4.0 m 4.5 m 5 fair Compar- 2.9 m 13 poor ative Example 1

(44) As shown in Table 1, it has been confirmed that, by setting the surface roughness Ra of the lower surface of the shelf plate portion in the range of 1.0 m or more and 3.0 m or less, the amount of depositions on the lower surface of the shelf plate portion of the wafer boat after the heat treatment increases by 50% or more and the number of particles attached to the wafer decreases by 30% or more because the peeling off was suppressed.