JP6322159B2 - Wafer boat and manufacturing method thereof - Google Patents

Description

  The present invention relates to a wafer boat and a method for manufacturing the same, and more particularly, to a wafer boat for holding a silicon wafer and a method for manufacturing the same in a vertical vacuum CVD apparatus used in a semiconductor device manufacturing process.

  When a film is formed on the surface of a silicon wafer to be processed, a CVD apparatus that performs film formation by chemical vapor deposition is used. FIG. 4 shows a conventional vertical reduced pressure CVD apparatus 30. The CVD apparatus 30 includes a furnace main body 31, a process tube 32 that is accommodated in the furnace main body 31 and contains a plurality of silicon wafers W, and a heater that is disposed between the furnace main body 31 and the process tube 32. I have. The process tube 32 is formed of high-purity quartz or silicon carbide (SiC), and the inside of the process tube 32 is heated to maintain a high temperature state. The process tube 32 is connected to a vacuum pump (not shown) so that the inside of the process tube 32 can be depressurized to a predetermined atmospheric pressure (eg, 1.3 kPa) or less.

  A boat receiver 34 is provided at the center of the base 33 covered with the process tube 32, and a vertical rack-shaped wafer boat 50 is disposed on the boat receiver 34. A plurality of silicon wafers W are held on the wafer boat 50 at predetermined intervals in the vertical direction. Further, a gas introduction pipe 35 for introducing a reaction gas into the furnace is disposed on the side of the wafer boat 50, and a thermocouple protection pipe 36 incorporating a thermocouple for measuring the temperature in the furnace is provided. Is provided.

In such a vertical reduced pressure CVD apparatus 30, a plurality of silicon wafers W are held on the wafer boat 50 and accommodated in the furnace body 31.
Next, the inside of the furnace is depressurized to a predetermined pressure (for example, 133 kPa or less), heated to a high temperature of, for example, 800 to 1200 ° C., and a reactive gas such as SiCl ₄ together with a carrier gas (such as H ₂ ) through the gas introduction pipe 35. By introducing (source gas) into the furnace, a polycrystalline silicon film, a silicon oxide film (SiO ₂ ), or the like is formed on the surface of the silicon wafer W.

  In addition, several dummy wafers DW having the same shape as the silicon wafer W are arranged on the upper and lower portions of the wafer boat 50 for the purpose of maintaining the gas flow and temperature uniformity in the furnace. In addition, a monitor wafer MW is arranged in a mixture with a plurality of arranged silicon wafers W. The monitor wafer MW is arranged for examining the state of particles adhering to the silicon wafer W, the film thickness, and the like.

Conventionally, as shown in FIG. 5, the wafer boat 50 has a pair of upper and lower top plates 51 and a bottom plate 52 having an outer diameter larger than the silicon wafer W to be accommodated, and a plurality of (four in the figure) support columns connecting them. 53. In addition, large openings 51a and 52a are formed in the center of the top plate 51 and the bottom plate 52, respectively, and the top plate 51 and the bottom plate 52 have a ring shape.
The support 53 is provided with a support groove 55 for supporting the silicon wafer W, thereby forming a wafer support 54 protruding from the side of the support. In other words, the silicon wafer W is held by engaging the edge of the silicon wafer W with the wafer support 54 formed on the plurality of columns 53.

By the way, in patent document 1, the thing of the hollow body structure comprised only from the silicon carbide film (SiC film) as the wafer boat 50 is proposed.
The support | pillar 53 of the wafer boat 50 disclosed by patent document 1 is formed as follows. That is, a silicon carbide layer 58 (300 to 1500 μm thick) is deposited on the surface of the carbon substrate 60 shown in FIG. 6A by chemical vapor deposition (FIG. 6B).
Next, the carbon base 60 is removed by incineration to obtain a hollow structure column 53 as shown in FIG.
According to the wafer boat 50 having such a support 53, since the structure is made of only high-purity silicon carbide without the base 60, contamination from impurities from the base 60 can be prevented.

JP 2008-34729 A

The wafer boat 50 disclosed in Patent Document 1 has a hollow structure as described above, and the inside of the wafer support portion 54 (the portion that receives the load) shown in FIG. As shown in (A cross section), the whole becomes a hollow state (thin state).
However, since the wafer boat 50 used in the vertical reduced pressure CVD apparatus 30 is subjected to non-uniform heating or cooling when being carried into and out of the furnace, a large thermal stress is generated. Therefore, there is a problem that the thin wafer support portion 54 is deformed due to insufficient rigidity, causing the occurrence of slipping of the wafer.

Further, as indicated by thin lines in FIG. 8, silicon carbide is deposited (grown) in a direction substantially orthogonal to the surface of the wafer support portion 54 (support groove 55). Therefore, granular silicon carbide is deposited on the surface of the wafer support portion 54 that contacts the silicon wafer W.
For this reason, during the heat treatment, there is a problem that particles (silicon carbide grains) are easily generated from the granular surface in the wafer support portion 54 and adhere to the wafer W.

  The present invention has been made under the circumstances as described above, and in a wafer boat that supports a silicon wafer to be processed, it has sufficient rigidity not to be deformed during heat treatment, and during heat treatment, An object of the present invention is to provide a wafer boat capable of suppressing the generation of particles and a manufacturing method thereof.

A wafer boat according to the present invention, which has been made to solve the above-mentioned problems, includes a top plate and a bottom plate, and a wafer having a plurality of support columns that are connected to each other and are formed with support grooves for holding silicon wafers. The boat is a hollow structure in which at least the support column is formed of silicon carbide deposited by a chemical vapor deposition method, and the support groove formed by cutting is formed on a side surface of a cylindrical rod member. in support groove of the strut, locking surface in contact with the silicon wafer, that have a characteristic that the silicon carbide is deposited in a direction along the engaging surface.
By configuring as this, in the support groove of the strut, the site receiving the wafer weights (protruding portion including a locking surface), since the base end portion is not a hollow structure, provides high rigidity, heat treatment The deformation of holding can be prevented.
In addition, since the locking surface has an opening in the center thereof, the contact area with the wafer can be reduced, and the slip generation rate with heat treatment can be reduced.
Further, since the growth direction of silicon carbide on the locking surface is parallel to the locking surface (that is, parallel to the wafer surface), even if the edge of the silicon wafer contacts the locking surface, Generation of particles can be remarkably suppressed.

Further, in order to solve the above-described problem, a method for manufacturing a wafer boat according to the present invention includes a top plate and a bottom plate, and a plurality of support columns in which support grooves for connecting silicon wafers and holding silicon wafers are formed. A method of manufacturing a wafer boat comprising a step of depositing silicon carbide on a surface of a rod-like carbon substrate by chemical vapor deposition, and removing the carbon substrate to form a cylindrical shape made of silicon carbide. The method includes a step of forming a bar member, and a step of forming the support groove by side cutting on the side surface of the cylindrical bar member to form the support column.
According to such a method, the above-described wafer boat of the present invention can be manufactured.

  According to the present invention, in a wafer boat that supports a silicon wafer to be processed, a wafer boat that has sufficient rigidity not to be deformed during heat treatment and can suppress generation of particles during heat treatment, and The manufacturing method can be obtained.

FIG. 1 is a perspective view of one of a plurality of pillars of a wafer boat according to the present invention as viewed from the inner surface of the boat. 2A to 2D are cross-sectional views schematically showing a method for forming the column in FIG. FIG. 3 is a perspective view showing a locking surface that comes into contact with the edge of the silicon wafer in the plurality of support grooves formed in the support column of FIG. 1. FIG. 4 is a cross-sectional view of a conventional vertical reduced pressure CVD apparatus. FIG. 5 is a perspective view of a conventional wafer boat. FIG. 6 is a cross-sectional view schematically showing a conventional method for forming a support for a wafer boat. FIG. 7 is a perspective view of a support groove (wafer support portion) of a conventional wafer boat. FIG. 8 is a cross-sectional view of a wafer support portion of a conventional wafer boat.

  Hereinafter, embodiments of a wafer boat and a manufacturing method thereof according to the present invention will be described with reference to the drawings. The wafer boat according to the present invention is different from the conventional wafer boat already described with reference to FIGS. 4 to 8 only in the configuration of the pillar having the groove for supporting the silicon wafer. Detailed description of the portion is omitted.

  FIG. 1 is a perspective view of one of a plurality of pillars of a wafer boat according to the present invention as viewed from the inner surface of the boat. As shown in FIG. 1, the support | pillar 1 is formed with the several support groove 2 in the inner side along the longitudinal direction at predetermined intervals. The edge of the silicon wafer is supported by being brought into contact with the locking surface 3 (wafer support portion) of the support groove 2 of the plurality of columns 1 and is held by the wafer boat.

  FIGS. 2A to 2D are cross-sectional views schematically showing a method for forming the column 1. In order to form the column 1, first, as shown in FIG. 2 (a), a straight carbon substrate 10 (for example, isotropic graphite material) is prepared, and chemical vapor deposition is performed at 1500 ° C. for 15 hours. Processing by (CVD) is performed. By this CVD process, the silicon carbide layer 11 is formed on the surface of the substrate until a predetermined film thickness (for example, 3000 to 4000 μm) is reached (FIG. 2B). Here, high rigidity can be ensured by forming the thickness of the silicon carbide layer 11 as thick as 3000 to 4000 μm. The silicon carbide layer 11 is not formed on the upper and lower ends of the base material 10, and the upper and lower end surfaces of the base material 10 are exposed.

Next, they are heated to, for example, 1000 ° C. in an oxygen atmosphere. Thereby, the base material 10 is burned and removed from the exposed upper and lower ends.
When base material 10 is removed, cylindrical silicon carbide layer 11 (rod member) is formed as shown in FIG.
A plurality of grooves are formed in parallel on the side surface of the cylindrical silicon carbide layer 11 along the longitudinal direction using a rotary cutting tool. As a result, as shown in FIG. 2D, the support column 1 having a plurality of support grooves 2 is formed.
Similarly, after the necessary number of support columns 1 are formed, a top plate and a bottom plate (not shown) are assembled to them to manufacture an assembling type vertical wafer boat (not shown). The top plate and the bottom plate may have a conventional shape as shown in FIG.

  FIG. 3 is a perspective view showing the locking surface 3 that contacts the edge of the silicon wafer in the plurality of support grooves 2 formed in the support column 1. Since the support groove 2 is formed by groove processing after silicon carbide is deposited as described above, the growth direction of silicon carbide on the locking surface 3 is indicated by a plurality of thin lines in FIG. Are parallel to the locking surface 3 (that is, parallel to the wafer surface). As a result, the proportion of the silicon carbide grain boundaries in the locking surface is reduced as compared with the prior art. As a result, even if the edge of the silicon wafer abuts on the locking surface 3, Occurrence is greatly reduced.

As described above, according to the embodiment of the present invention, a silicon carbide layer is deposited on a base material, and then the base material is removed to form a hollow structure made of silicon carbide. A pillar 1 having a plurality of support grooves 2 is formed by subjecting the thick silicon carbide layer (bar member) to groove processing in parallel along the longitudinal direction thereof.
According to the structure of this support column 1, the portion that receives the wafer load in the support groove 2 (protruding portion including the locking surface 3) can have high rigidity because the base end portion is not a hollow structure, and can retain heat treatment. Can be prevented from being deformed.
Further, since the locking surface 3 is in an open state at the center, the contact area with the wafer can be reduced, and the occurrence of slippage due to heat treatment can be prevented.
Furthermore, since the growth direction of silicon carbide on the locking surface 3 is parallel to the locking surface 3 (that is, parallel to the wafer surface), even if the edge of the silicon wafer contacts the locking surface 3. Generation of silicon carbide particles can be remarkably suppressed.

  The wafer boat and its manufacturing method according to the present invention will be further described based on examples. In this example, the wafer boat shown in the above embodiment was manufactured, and the performance of the obtained wafer boat was verified.

[Example 1]
In Example 1, a carbon base material (for example, isotropic graphite material) was subjected to CVD treatment at 1500 ° C. for 15 hours to coat silicon carbide with a thickness of 3000 to 4000 μm. Subsequently, the carbon base material was burned and removed in an air atmosphere at 1000 ° C. to obtain a cylindrical member made of only silicon carbide having a hollow structure. The obtained cylindrical member made of silicon carbide was a columnar crystal having a particle size of about 100 μm diameter × 200 μm length. Then, a plurality of support grooves for placing the wafer on the obtained cylindrical member were formed by a rotary cutting tool, and the locking surface 3 in contact with the wafer was mirror-polished. Moreover, after the cylindrical member in which the support groove was formed was acid-washed, it was washed with pure water and dried to obtain a support. Moreover, after forming the required number of support columns in the same manner, the top plate and the bottom plate were assembled to produce an assembly type vertical wafer boat.
Furthermore, 50 silicon wafers were supported by the manufactured vertical wafer boat, and heat treatment was performed in a furnace at 900 ° C. for 1 hour.
In Example 1, the amount of particles (pieces / wafer) adhering to the front and back surfaces of the heat-treated silicon wafer was measured.

[Comparative Example 1]
In Comparative Example 1, a carbon substrate that had been grooved in advance was subjected to a CVD treatment at 1300 ° C. for 10 hours to coat silicon carbide with a thickness of 300 to 1500 μm. Subsequently, the carbon base material was burned and removed in an air atmosphere at 1000 ° C. to obtain a cylindrical member made of only silicon carbide having a hollow structure. Further, the surface of the groove portion on which the wafer was placed was mirror-polished.
Next, the polished hollow member was washed with acid, washed with pure water, and dried to obtain a support.
Moreover, after forming the required number of support columns in the same manner, the top plate and the bottom plate were assembled to produce an assembly type vertical wafer boat.
Further, using the manufactured vertical wafer boat, the wafer was heat-treated under the same conditions as in Example 1, and the amount of particles (pieces / wafer) on the front and back surfaces of the wafer was measured.
The results of Example 1 and Comparative Example 1 are shown in Table 1.

  As shown in Table 1, it was confirmed that by using the wafer boat of the present invention, particles adhering to the wafer after the heat treatment can be greatly reduced.

DESCRIPTION OF SYMBOLS 1 Support | pillar 2 Support groove 3 Locking surface 10 Carbon base material (base material)
11 Silicon carbide layer

Claims (2)

A wafer boat comprising a top plate and a bottom plate, and a plurality of support columns that are connected to each other and are formed with support grooves for holding silicon wafers,
At least the support column is a hollow structure formed of silicon carbide deposited by chemical vapor deposition and having the support groove formed by cutting on the side surface of a cylindrical rod member.
In the support groove of the support column, a silicon boat is deposited on a locking surface in contact with the silicon wafer in a direction along the locking surface. A method for manufacturing a wafer boat comprising a top plate and a bottom plate, and a plurality of support columns that are connected to each other and are formed with support grooves for holding silicon wafers,
Depositing silicon carbide on the surface of the rod-shaped carbon substrate by chemical vapor deposition;
Removing the carbon substrate and forming a cylindrical rod member made of silicon carbide;
Forming the support groove by cutting on a side surface of the cylindrical bar member and forming the support column.

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