JP7431487B2 - Vertical wafer boat and manufacturing method of vertical wafer boat - Google Patents

Description

The present invention relates to a vertical wafer boat and a method for manufacturing a vertical wafer boat, and more particularly, to a vertical wafer boat on which silicon wafers and the like are mounted when heat treating silicon wafers and the like, and a method for manufacturing a vertical wafer boat.

Conventionally, semiconductor wafers (hereinafter simply referred to as wafers) such as silicon wafers have been subjected to various heat treatments in a vertical or horizontal heat treatment furnace having a furnace core tube or the like. These heat treatments are generally carried out by setting the wafer on a support and mounting jig such as a wafer boat, inserting the support and mounting jig into a heated heat treatment furnace, further raising the temperature, and introducing a processing gas. It is being done.

For example, based on FIG. 5, a general vertical heat treatment furnace and its heat treatment will be explained briefly. The vertical heat treatment furnace 50 includes a furnace core tube 51, and a heating member 53 disposed around the outer circumference of the soaking tube 52 for heating the wafer W in the furnace core tube 51; It is equipped with
Further, a heat insulating tube 54 for maintaining uniform temperature at the entrance and exit of the furnace core tube 51, and a gas supply tube 56 for supplying processing gas to the wafer W from the top of the furnace core tube 51 toward the internal space; It is provided with an exhaust pipe 55 for discharging the processing gas in the furnace core tube 51.

A vertical wafer boat 10 loaded with a large number of wafers W to be heat-treated is placed on the upper surface of the heat-insulating cylinder 54. This vertical wafer boat 10 is provided with a plurality of shelf sections 10a for supporting and placing wafers W, and is configured such that a plurality of wafers W can be placed in the vertical direction.

Further, as schematically shown in FIG. 6, the wafers W placed on the vertical wafer boat 10 include a wafer PW to become a product (also referred to as a product wafer), and a product wafer on the upper and lower parts of the product wafer PW. It consists of a so-called dummy wafer DW placed on both sides of PW.

In the vertical heat treatment furnace 50 configured in this way, after the wafer boat 10 loaded with product wafers PW and dummy wafers DW is accommodated in the furnace core tube 51, the inside of the furnace core tube 51 is heated by the heating member 53, and , the processing gas is supplied from above to below through the gas supply pipe 56.
As a result, a high-temperature processing gas atmosphere is created in the furnace core tube 51, and a predetermined heat treatment is performed on the wafer W (product wafer PW, dummy wafer DW).

At this time, the dummy wafer DW controls the gas flow so that the introduced processing gas does not directly hit the product wafer PW to be heat-treated, thereby improving the uniformity of the film thickness formed on the product wafer PW, In addition, its heat insulation effect controls the gas flow to ensure uniform heat inside the furnace.

Various proposals have been made regarding such vertical wafer boats and dummy wafers DW.
For example, in Patent Document 1, in order to perform high-quality substrate processing and improve the uniformity of substrate processing within the substrate surface, the interval at which substrates such as wafers are held by the substrate holding means is set at the center of the substrate holding means. It has been proposed that the spacing between non-product substrates such as dummy wafers placed at both end portions of the substrate holding means be narrower than the spacing between product substrates such as product wafers held in one section.

Furthermore, in Patent Document 2, in order to improve the uniformity of the film thickness between the surfaces of product wafers, a plurality of first substrates (product wafers) each having an uneven surface are stacked and held on a boat. A second substrate (dummy wafer) whose surface is less uneven than the first substrate is held at the upper end or lower end of the substrate, and when processing the first substrate and the second substrate in the processing chamber, the first substrate is It has been proposed to supply a processing gas toward the substrate and the second substrate, and to supply an inert gas toward the second substrate.

Japanese Patent Application Publication No. 2004-221227 Japanese Patent Application Publication No. 2011-249407

By the way, although proposals have been made to improve the film thickness uniformity of product wafers as in Patent Documents 1 and 2, no proposals have been made to solve the technical problems caused by dummy wafers being stuck to vertical boats. Not yet.
For example, product wafers to be deposited are stored in a vertical wafer boat, and when processing is completed, they are taken out from the vertical wafer boat.
On the other hand, the dummy wafers are repeatedly used in the film forming process of product wafers while being mounted on the vertical wafer boat. Therefore, a thick film was deposited on the vertical wafer boat and the dummy wafers mounted on the vertical wafer boat, and the dummy wafers were sometimes stuck to the vertical wafer boat.

If the dummy wafer is stuck to the vertical wafer boat, the dummy wafer may be destroyed and removed during maintenance such as cleaning of the vertical wafer boat.
However, it is difficult to completely remove stuck dummy wafer debris, and if a new dummy wafer is placed with unremoved debris remaining, particles will be generated due to friction between the unremoved debris and the new dummy wafer. There was a technical problem in that it could cause
On the other hand, if dummy wafers are not used continuously and are replaced every time the furnace is operated, there is a technical problem in that manufacturing costs and productivity deteriorate.

The present inventor has discovered that a vertical wafer boat and its boat are capable of preventing dummy wafers from sticking even when a thick film is deposited on the vertical wafer boat and the dummy wafers when the dummy wafers are continuously used while mounted on the vertical wafer boat. The present invention was conceived after intensive research into manufacturing methods.

The present invention has been made under the above-mentioned circumstances, and an object of the present invention is to provide a vertical wafer boat and a method for manufacturing a vertical wafer boat that suppresses the adhesion of dummy wafers to the vertical wafer boat.

A vertical wafer boat according to the present invention, which has been made to solve the above-mentioned problems, is a vertical wafer boat on which a plurality of wafers are placed vertically, and in which the plurality of wafers are placed vertically. a boat support section having a plurality of shelf sections, and a top plate and a bottom plate for holding the boat support section ; It is characterized by a surface roughness greater than the surface roughness Ra of the surface.

As described above, in the vertical wafer boat according to the present invention, the surface roughness Ra of the shelf surface on which the dummy wafers are mounted is larger than the surface roughness Ra of the shelf surface on which the product wafers are mounted. Adhesion to vertical wafer boats is suppressed.

Here, it is desirable that the surface roughness Ra of the shelf surface on which the dummy wafer is mounted is 10 μm or more and 50 μm or less.
When the surface roughness is less than 10 μm, if the dummy wafer is used continuously, there is a risk that the dummy wafer will stick as in the conventional case.
Furthermore, if the surface roughness exceeds 50 μm, the placement position of the dummy wafer on the shelf is likely to shift during heat treatment, and there is a risk that particles may be generated due to friction with the shelf surface.
Therefore, it is preferable that the surface roughness Ra of the shelf surface on which the dummy wafer is mounted is 10 μm or more and 50 μm or less.

Further, it is preferable that the surface roughness Ra of the shelf surface on which the product wafers are mounted is 0.5 μm or more and 3.0 μm or less.
In this way, since the surface roughness Ra of the shelf surface on which the product wafers are mounted is 0.5 μm or more and 3.0 μm or less, it is possible to suppress the occurrence of scratches and slips on the wafers.

Further, it is preferable that the boat support section, the top plate, and the bottom plate are made of a Si--SiC composite material or a SiC material, and a SiC coating layer is formed on the surface thereof.

Further, it is preferable that a SiC coating layer containing SiC powder having a particle size of 10 μm or more and 100 μm or less is formed on the surface of the shelf on which the dummy wafer is mounted.
In this way, by incorporating SiC powder with a particle size of 10 μm or more and 100 μm or less in the SiC coating layer, the surface roughness Ra of the shelf surface on which the dummy wafer is mounted can be made 10 μm or more and 50 μm or less.

A method for manufacturing a vertical wafer boat according to the present invention, which has been made to solve the above-mentioned problems, is a method for manufacturing a vertical wafer boat in which a plurality of wafers are placed vertically, the method comprising: A boat support section having a plurality of vertically arranged shelves on which dummy wafers are placed, and a top plate and a bottom plate for holding the boat support section , and a surface roughness Ra of the surface of the shelf section on which dummy wafers are mounted are provided. , in a method for manufacturing a vertical wafer boat whose surface roughness Ra is greater than the surface roughness Ra of the shelf surface on which product wafers are mounted, the boat support section, top plate, and bottom plate are formed of Si-SiC composite material or SiC material, and the boat After the assembly step, a silicon carbide powder adhesion step of adhering silicon carbide powder with a particle size of 10 μm or more and 100 μm or less to the shelf surface on which the dummy wafer is mounted, and after the silicon carbide powder adhesion step The present invention is characterized in that it includes at least a coating layer forming step of forming a silicon carbide coating layer on the boat surface by a CVD method.

As described above, in the method for manufacturing a vertical wafer boat according to the present invention, SiC powder (silicon carbide powder) having a particle size of 10 μm or more and 100 μm or less is attached to the surface of the shelf on which dummy wafers are mounted. After the adhesion step and the SiC powder (silicon carbide powder) adhesion step, there is a coating layer forming step of forming a SiC (silicon carbide) coating layer on the boat surface by the CVD method, so the shelf section on which the dummy wafer is mounted is provided. The surface roughness Ra of the surface can be easily set to 10 μm or more and 50 μm or less.

According to the present invention, it is possible to obtain a vertical wafer boat and a method for manufacturing a vertical wafer boat in which sticking of dummy wafers to the vertical wafer boat is suppressed.

FIG. 1 is a perspective view showing a schematic configuration of a vertical wafer boat according to the present invention. FIG. 2 is a perspective view of the shelf section on which the product wafers shown in FIG. 1 are mounted. FIG. 3 is a perspective view of the shelf section on which the dummy wafers shown in FIG. 1 are mounted. FIG. 4 is a diagram for explaining a method of manufacturing a vertical wafer boat (shelf portion on which dummy wafers are mounted) according to the present invention. FIG. 5 is a cross-sectional view schematically showing the overall configuration of a vertical heat treatment furnace that accommodates a vertical wafer boat. FIG. 6 is a conceptual diagram showing the arrangement of dummy wafers and product wafers in a vertical wafer boat.

EMBODIMENT OF THE INVENTION Below, one Embodiment concerning this invention is described based on FIG. 1 thru|or FIG. 3. Note that FIG. 1 is a perspective view showing a vertical wafer boat according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part of a shelf section on which product wafers are mounted in the vertical wafer boat shown in FIG. 3 is an enlarged view of the main part of the shelf section on which dummy wafers are mounted in the vertical wafer boat shown in FIG. 1, and FIG. FIG.

As shown in FIG. 1, this vertical wafer boat 1 has a plurality of support columns on which are formed a shelf section 2a for mounting product wafers PW to be subjected to film formation processing and a shelf section 2b for mounting dummy wafers DW. 2, and a top plate 3 and a bottom plate 4 for fixing the upper and lower ends of the support column 2.
The base material constituting the pillars 2, the top plate 3, and the bottom plate 4 is preferably a SiC base material (SiC material). It is preferable to use Si-SiC (Si-SiC composite material) in which a carbon component and a part of Si react to form SiC, and recrystallized SiC obtained by heat-treating a SiC molded body at a high temperature, and a sintering aid are used. Self-sintering SiC added and sintered may also be used.

Further, as shown in FIG. 2, the upper surface portion 2a1 of the shelf portion 2a is a wafer placement portion on which a product wafer PW is placed. A tip chamfered portion 2a2 is formed at the tip of this upper surface portion (wafer placement portion) 2a1, and side chamfered portions 2a3 are formed at the left and right side portions.
Note that although the tip chamfered portion 2a2 and the side chamfered portion 2a3 are shown in a planar shape in the figure, they are not limited to this, and may be formed in a curved shape, a so-called R shape.

Further, the wafer mounting section two a1 is a shelf surface (wafer contact surface) on which the product wafer PW is mounted, and its surface roughness Ra is formed to be 0.5 μm or more and 3.0 μm or less. The top chamfered portion 2a2 and the side chamfered portion 2a3 are also formed to have a surface roughness Ra of 0.5 μm or more and 3.0 μm or less, similarly to the wafer placement portion 2a1. Since the product wafer may come into contact with the tip chamfered portion 2a2 and the side chamfered portion 2a3, it is preferable that the surface roughness Ra be formed to be 0.5 μm or more and 3.0 μm or less.

Here, if the surface roughness Ra of the surface is less than 0.5 μm, slippage may occur when the wafer is placed on the wafer placement portion 2a1, and the product wafer PW may fall when the wafer boat is moved. Alternatively, when the product wafer PW is heat-treated in a high-temperature environment, the product wafer PW may be fused at the contact portion of the boat, which is not preferable.
Furthermore, if the surface roughness Ra exceeds 3.0 μm, scratches or slips may occur on the back surface of the product wafer PW when the wafer is mounted or when a film forming process is performed, which is not preferable.

Further, as shown in FIG. 3, the upper surface portion 2b1 of the shelf portion 2b is a wafer placement portion on which a dummy wafer DW is placed. A top chamfered portion 2b2 is formed at the tip of the upper surface portion (wafer placement portion) 2b1, similar to the shelf portion 2a, and side chamfered portions 2b3 are formed on the left and right side portions.
In addition, although the tip chamfered part 2b2 and the side chamfered part 2b3 are shown in a planar shape in the figure, they may be formed in a curved shape, a so-called R shape, similarly to the shelf part 2a.

Further, the wafer mounting portion 2b1 is a shelf surface (wafer contact surface) on which product wafers are mounted, and has a surface roughness Ra of 10 μm or more and 50 μm or less.
The top chamfered portion 2b2 and the side chamfered portion 2b3 are also formed to have a surface roughness Ra of 10 μm or more and 50 μm or less, similarly to the wafer placement portion 2b1. Since the product wafer may come into contact with the tip chamfered portion 2b2 and the side chamfered portion 2b3, it is preferable that the surface roughness Ra is formed to be 10 μm or more and 50 μm or less.

Here, if the surface roughness is less than 10 μm, if the dummy wafer DW is continuously used, there is a risk that the dummy wafer DW will stick as in the conventional case. Furthermore, if the surface roughness exceeds 50 μm, the placement position of the dummy wafer DW on the shelf 2b is likely to shift during heat treatment, and there is a risk that particles may be generated due to friction with the shelf surface.
Therefore, it is preferable that the surface roughness Ra of the shelf surface on which the dummy wafer is mounted is 10 μm or more and 50 μm or less. Furthermore, since the surface roughness Ra of the shelf surface on which the dummy wafer is mounted is 10 μm or more and 50 μm or less, when the film is attached, the anchoring effect is large and peeling of the film can be more effectively suppressed.

Next, a method for manufacturing a vertical wafer boat according to the present invention will be explained based on FIG. 4.
First, the pillar 2, top plate 3, and bottom plate 4 are machined into a predetermined shape from a SiC base material, and the surfaces of these base materials are polished to produce a member having a predetermined surface roughness. For example, a shelf 2b is formed on the support 2, as shown in FIG. 4(a).

Then, as shown in FIG. 4(b), SiC powder 5 having a particle size of 10 μm or more and 100 μm or less is attached to the surface of the shelf 2b on which the dummy wafer DW is mounted.
This SiC powder 5 is mixed with an ethanol solvent and attached by coating or spraying. Note that the SiC powder 5 is not attached to the surface of the shelf 2a on which the product wafers PW are mounted, since the surface roughness becomes large.

Thereafter, as shown in FIG. 4C, a SiC coating layer 6 is formed on the surface of the vertical wafer boat by CVD. Generally, a SiC coating layer 6 of 20 μm to 100 μm is formed under conditions of high temperature and reduced pressure.
At this time, since SiC powder 5 with a particle size of 10 μm or more and 100 μm or less is attached to the surface of the shelf 2b on which the dummy wafer DW is mounted, the surface roughness Ra of the surface of the shelf 2b on which the dummy wafer DW is mounted is 10 μm. The thickness is formed to be greater than or equal to 50 μm.

On the other hand, the surface roughness Ra of the surface of the shelf section 2b on which the product wafers PW are mounted is set to 0.5 μm or more and 3.0 μm or less since there is no SiC powder with a particle size of 10 μm or more and 100 μm or less. Incidentally, if the surface roughness Ra of the SiC coating layer exceeds 3.0 μm, polishing treatment is performed.

Further, embodiments according to the present invention will be described.
(Example 1)
First, three pillars, a top plate, and a bottom plate made of Si-SiC composite material were manufactured using the reaction sintering method, and the surfaces of these base materials were polished to obtain an arithmetic mean surface roughness Ra (JIS B0601-2001) of A 0.5 μm member was manufactured. These parts were then assembled to create a 6-inch boat.
Next, SiC powder having an average particle size of 60 μm was mixed with an ethanol solvent and applied and adhered to the surface of the shelf on which the dummy wafer was mounted.
Note that the SiC powder was not attached to the surface of the shelf on which the product wafers were mounted, since the surface roughness would become large.

Next, in a CVD furnace under conditions of 70 torr and 1200°C, appropriate amounts of methyltrichlorosilane and _H2 gas were introduced at a flow rate ratio of 3:30 to form the columns, top plate, and bottom plate of the 6-inch boat. A 50 μm thick SiC coating film was formed on the surface.
At this time, the surface roughness Ra of the shelf portion on which the product wafers were mounted was 1.5 μm. The surface roughness Ra of the shelf portion on which the dummy wafer was mounted was 30 μm.

(Example 2)
In Example 2, SiC powder having an average particle size of 20 μm was mixed with an ethanol solvent and applied to the surface of the shelf on which the dummy wafers were mounted in a boat manufactured under the same conditions as in Example 1. The SiC powder was not attached to the surface of the shelf on which the product wafers were mounted, since the surface roughness would become large.

Subsequently, under the same conditions as in Example 1, a SiC coating film with a thickness of 50 μm was formed on the surfaces of the pillars, top plate, and bottom plate constituting the boat.
At this time, the surface roughness Ra of the shelf portion on which the product wafers were mounted was 2.1 μm. The surface roughness Ra of the shelf portion on which the dummy wafer was mounted was 10 μm.

(Example 3)
In Example 3, SiC powder having an average particle size of 100 μm was mixed with an ethanol solvent and applied and adhered to the surface of the shelf on which the dummy wafers were mounted in a boat manufactured under the same conditions as Example 1. The SiC powder was not attached to the surface of the shelf on which the product wafers were mounted, since the surface roughness would become large.

Subsequently, under the same conditions as in Example 1, a SiC coating film with a thickness of 50 μm was formed on the surfaces of the pillars, top plate, and bottom plate constituting the boat.
At this time, the surface roughness Ra of the shelf portion on which the product wafers were mounted was 1.2 μm. The surface roughness Ra of the shelf portion on which the dummy wafer was mounted was 50 μm.

(Comparative example 1)
In Comparative Example 1, SiC powder was not attached to the surface of the shelf on which the dummy wafers were mounted and the surface of the shelf on which the product wafers were mounted, of the boat manufactured under the same conditions as in Example 1.

Subsequently, under the same conditions as in Example 1, a SiC coating film with a thickness of 50 μm was formed on the surfaces of the pillars, top plate, and bottom plate constituting the boat.
At this time, the surface roughness Ra of the shelf on which the dummy wafer was mounted and the surface roughness Ra of the shelf on which the product wafer was mounted were both 1.5 μm.

(Comparative example 2)
In Comparative Example 2, SiC powder having an average particle size of 150 μm was mixed with an ethanol solvent and applied to the surface of the shelf on which the dummy wafers were mounted in a boat manufactured under the same conditions as in Example 1. The SiC powder was not attached to the surface of the shelf on which the product wafers were mounted, since the surface roughness would become large.

Subsequently, under the same conditions as in Example 1, a SiC coating film with a thickness of 50 μm was formed on the surfaces of the pillars, top plate, and bottom plate constituting the boat.
At this time, the surface roughness Ra of the shelf portion on which the product wafers were mounted was 1.8 μm. The surface roughness Ra of the shelf portion on which the dummy wafer was mounted was 80 μm.

Then, product wafers and dummy wafers were placed on all the shelves of the 6-inch wafer boat of Examples 1 to 3, Comparative Example 1, and Comparative Example 2, and these were placed in the LP-CVD apparatus, and a 5 μm thick SiN film was placed on the 6-inch wafer boat. After stacking, the wafer boat is taken out from the LP-CVD apparatus, and product wafers are taken out from the wafer boat.
Furthermore, new product wafers were placed on the wafer boat, dummy wafers were used continuously, and a 5 μm thick SiN film was deposited. Then, the dummy wafer was used 50 times in a row, and the state of adhesion between the dummy wafer and the shelf of the wafer boat was examined.
The adhesion status was evaluated by the presence or absence of pieces of the dummy wafer on the shelf of the wafer boat when the dummy wafer was removed.
The results are shown in Table 1.

As described above, it was confirmed that when the surface roughness Ra of the shelf surface on which the dummy wafer is mounted is 10 μm or more and 50 μm or less, the dummy wafer is prevented from sticking to the vertical wafer boat.

1 Vertical wafer boat 2 Support 2a Shelf section on which product wafers are mounted 2b Shelf section on which dummy wafers are mounted 3 Top plate 4 Bottom plate 5 SiC powder 6 SiC coating film DW Dummy wafer PW Product wafer

Claims (6)

In a vertical wafer boat where multiple wafers are placed vertically,
A boat support section having a plurality of vertically arranged shelves on which the plurality of wafers are placed, and a top plate and a bottom plate that hold the boat support section ,
A vertical wafer boat characterized in that surface roughness Ra of a shelf surface on which dummy wafers are mounted is greater than surface roughness Ra of a shelf surface on which product wafers are mounted. 2. The vertical wafer boat according to claim 1, wherein the surface of the shelf on which the dummy wafers are mounted has a surface roughness Ra of 10 μm or more and 50 μm or less. 3. The vertical wafer boat according to claim 1, wherein the surface of the shelf on which the product wafers are mounted has a surface roughness Ra of 0.5 μm or more and 3 μm or less. The vertical boat according to any one of claims 1 to 3, wherein the boat support section, the top plate, and the bottom plate are made of a Si-SiC composite material or a SiC material, and a SiC coating layer is formed on the surface thereof. type wafer boat. 5. The vertical plane according to claim 1 , wherein a SiC coating layer containing silicon carbide powder having a particle size of 10 μm or more and 100 μm or less is formed on the surface of the shelf on which the dummy wafer is mounted. type wafer boat. A method for manufacturing a vertical wafer boat on which a plurality of wafers are placed vertically, the boat support having a plurality of shelves arranged in the vertical direction on which the plurality of wafers are placed, and the boat support. Manufacturing of a vertical wafer boat comprising a top plate and a bottom plate for holding the wafers, and the surface roughness Ra of the surface of the shelf on which dummy wafers are mounted is larger than the surface roughness Ra of the surface of the shelf on which product wafers are mounted. In the method,
an assembly process of assembling a boat by forming a boat support section, a top plate, and a bottom plate from Si-SiC composite material or SiC material;
After the assembly step, a silicon carbide powder adhesion step of adhering silicon carbide powder with a particle size of 10 μm or more and 100 μm or less on the surface of the shelf on which the dummy wafer is mounted;
After the silicon carbide powder adhering step, a coating layer forming step of forming a silicon carbide coating layer on the boat surface by a CVD method;
A method for manufacturing a vertical wafer boat, comprising at least the following:

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