JP2020077724A - Wafer boat - Google Patents

Abstract

To perform chamfering to a rear end side (root side) of the peripheral edge of a wafer mounting surface to suppress the occurrence of slips and the like due to stress concentration in a wafer boat equipped with a long wafer support portion.SOLUTION: A vertical wafer boat 1 includes a top plate 3, a plurality of columns 2 having one end fixed to the top plate and the other end fixed to a bottom plate 4, and a wafer support portion 2a protruding horizontally from the side surface of the column, and the wafer support portion has a polished wafer mounting surface 2a1, and U-shaped edge portions 2a2 and 2a3 in a plan view formed at the peripheral edge of the wafer mounting surface, and the edge portion is in a state in which chamfering is continuously performed from one end of the U-shape starting from the side surface of the column to the other end ending at the side surface of the column.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer boat, and more particularly to a wafer boat that holds a silicon wafer used for manufacturing a semiconductor device in a heat treatment process.

  In a semiconductor manufacturing process, a silicon wafer (hereinafter referred to as a wafer) is subjected to heat treatment such as oxidation, diffusion, and CVD. The wafer boat used during this heat treatment includes a horizontal wafer boat in which a wafer storage groove is vertically formed with respect to a horizontally-arranged boat support, and a wafer storage groove (wafer) that is horizontally provided in a vertically-arranged boat support. There is a vertical wafer boat having a support portion).

The vertical wafer boat can achieve good temperature uniformity in the furnace, high throughput, and reduction of the floor area of the clean room. Therefore, it is possible to cope with mass production and high integration of wafers, and in recent years, a vertical wafer boat is widely used rather than a horizontal wafer boat.
However, as the diameter of the wafer is increased, the temperature of the heat treatment is improved, and the amount of wafers loaded per boat is increased, the wafer supporting portions and the support columns may be deformed, and the wafer itself may be warped. When the boat is deformed or the wafer is warped, a rubbing condition is created at the contact interface between the wafer and the wafer supporting portion, which causes problems such as slips, surface scratches, and particles.

In order to solve such a problem, in Patent Document 1 (Japanese Patent Laid-Open No. 2002-231726), a SiO ₂ film having a predetermined thickness is applied to the surface of a boat for heat treatment using Si as a base material so that the SiO ₂ film is a buffer material. And a wafer boat that suppresses the occurrence of slip.

However, in recent years, as the wafer processing temperature has increased and the number of wafers loaded has increased, SiC wafer boats have become the mainstream, making it difficult to apply the technique of forming a SiO ₂ film functioning as a cushioning material on the surface thereof. is there.

  Patent Document 2 (JP 2003-059851A) discloses a ring-shaped or horseshoe-shaped wafer support whose main surface is highly flat and has low surface roughness. This wafer support is set in a groove formed in a support of a wafer boat, a wafer is placed on the groove, and is used for heat treatment. The chamfering width of the inner peripheral portion of the wafer support and the surface roughness of the main surface portion have been devised so as to suppress the generation of slips and particles.

  However, in the wafer support disclosed in Patent Document 2, the thickness and size of the wafer support may increase the weight of the wafer boat, reduce the wafer load, and adversely affect the wafer due to the warp of the support. However, it cannot be said that it is an effective measure.

  On the other hand, the applicant of the present invention discloses in Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2018-104737) a vertical wafer boat in which a surface of a SiC substrate is subjected to CVD-SiC coating and a chamfering process is performed on an edge of a wafer supporting portion. Proposing a method.

For the chamfering process, specifically, as shown in the plan views of FIGS. 5A and 5B, a disk-shaped polishing member 50 having a donut-shaped brush 51 arranged at the peripheral edge is used.
First, the brush 51 of the polishing member 50 is arranged at a position in contact with the wafer mounting surface 60a1 of the wafer supporting portion 60a protruding from the support column 60 and the peripheral edge portion 60a2 of the wafer mounting surface 60a1 (FIG. 5). (Position (a)).
Then, while the polishing member 50 is rotated and polished, it is moved toward the front end side of the wafer mounting surface 60a1 as shown in FIG. 5 (b).

  According to this method, the wafer mounting surface 60a1 and the edge portion 60a2 can be simultaneously and uniformly polished, and the R chamfering of the edge portion 60a2 can be performed in a short processing time. As a result, the occurrence of slip due to stress concentration can be prevented. It is also suppressed, and the generation of particles is significantly suppressed.

JP, 2002-231726, A JP, 2003-059851, A JP, 2018-104737, A

However, in the manufacturing method proposed in Patent Document 3, since the polishing member 50 has a disk shape, the brush 51 is provided on the rear end side of the edge portion 60a2 (the portion UnP surrounded by the alternate long and short dash line in FIG. 5B). Does not hit Therefore, as shown in the perspective view of FIG. 6, it was not possible to chamfer the rear end portion UnP of the edge portion 60a2.
When a wafer is heat-treated using such a wafer boat, when the wafer comes into contact with the rear end side portion UnP (edge not chamfered) of the edge portion 60a2, slip occurs due to stress concentration there. I was afraid. Further, the wafer may contact the rear end portion UnP (edge not chamfered) of the edge portion 60a2, and the deposition film may be peeled off to generate particles.

  The present invention has been made under the circumstances as described above, and in a wafer boat provided with a long wafer support portion, up to the rear end side (root side) of the peripheral edge portion of the wafer mounting surface. An object of the present invention is to provide a wafer boat that is chamfered and can suppress the generation of slips and particles due to stress concentration.

The wafer boat according to the present invention, which was made to solve the above-mentioned problems, has a top plate, a plurality of columns whose one end is fixed to the top plate and the other end of which is fixed to a bottom plate, and which is horizontal from the side surface of the column. A wafer boat having a wafer supporting portion projecting in a direction, wherein the wafer supporting portion has a polished wafer mounting surface and a U-shaped edge in plan view formed at a peripheral end of the wafer mounting surface. The edge portion is continuously chamfered from one end of the U-shape starting from the side surface of the column to the other end terminating at the side surface of the column. Have.
The chamfering of the edge portion is preferably R chamfering or C chamfering.
The chamfered edge portion preferably has a surface roughness Ra ≦ 0.4 μm.
Further, in the wafer boat according to the present invention, it is desirable that a SiC coating film is formed on the surface of the SiC base material.

According to the wafer boat of the present invention, in each wafer supporting portion, the wafer mounting surface is smoothed by polishing, and the U-shaped edge portion in plan view is entirely chamfered.
Therefore, when the wafer is placed, there is no risk of the back surface of the wafer coming into contact with the sharp edge, and it is possible to prevent slippage due to stress concentration of the load. Also, due to the heat treatment of the wafer, a deposition film is deposited on the rear end side (root side) of the peripheral edge portion of the wafer mounting surface, but the deposition film does not peel off because there is no sharp edge, and particles are generated. Can be prevented.

  According to the present invention, in a wafer boat provided with an elongated wafer supporting portion, chamfering is performed to the rear end side (root side) of the peripheral edge portion of the wafer mounting surface, and slip and particle generation due to stress concentration. It is possible to obtain a wafer boat capable of suppressing the above.

FIG. 1 is a front view of a vertical wafer boat according to this embodiment. FIG. 2 is an enlarged perspective view showing one of the wafer supporting portions included in the vertical wafer boat shown in FIG. 3A is a plan view of the processing jig, FIG. 3B is a sectional view taken along the line AA of FIG. 3A, and FIG. 3C is B of FIG. 3A. FIG. 6 is a sectional view taken along arrow B. FIG. 4 is a perspective view showing how a polishing process is performed by the processing jig shown in FIG. FIG. 5A and FIG. 5B are plan views showing an example of a conventional polishing method using a polishing member. FIG. 6 is a perspective view showing a chamfered edge portion in a conventional wafer supporting portion.

  Embodiments of a wafer boat according to the present invention will be described below with reference to the drawings. 1 is a front view of the vertical wafer boat according to the present embodiment, and FIG. 2 is an enlarged perspective view of one of the wafer support portions of the vertical wafer boat shown in FIG. is there.

  As shown in FIG. 1, the vertical wafer boat 1 includes two support members 2 arranged on the starting end side in the wafer insertion direction (referred to as the wafer insertion start end side) and the end side in the wafer insertion direction (hereinafter , And one supporting member 2 arranged on the wafer insertion terminal side). The lower end of each support member 2 is erected (fixed) on a disk-shaped bottom plate 4, and the upper end of each support member 2 is supported (fixed) by a disk-shaped top plate 3.

  Each of the supporting members 2 has a plurality of long plate-shaped wafer supporting portions 2a for supporting a large number of wafers. The wafer supporting portion 2a in each supporting member 2 has a thickness of 1 mm or more and 5 mm or less, a length of 10 mm or more and 120 mm or less, and a width of 5 mm or more and 20 mm or less, and is formed in the vertical direction at 50 to 150 pieces at an 8 mm pitch, for example.

  In each of the wafer supporting portions 2a, a portion where the lower surface of the wafer W is in contact or may be in contact is an upper surface wafer mounting surface 2a1 shown in FIG. 2 and a U-shaped edge portion in plan view formed at the peripheral end thereof. Is. The edge portion includes a tip edge portion 2a3 on the tip side and a side edge portion 2a2 on the side surface side.

  The wafer mounting surface 2a1 is polished and smoothed so that the wafer W does not slip. Further, as shown in FIG. 2, the front edge portion 2a3 and the side surface edge portion 2a2 are rounded. The side edge portion 2a2 is chamfered up to the root portion on the rear end side. That is, the edge portion is in a state of being continuously chamfered from one end of the U shape starting from the side surface of the support column 2 to the other end of the U shape starting from the side surface of the support column 2 as the end point. The chamfered edge portion is R1 mm or more and R10 mm or less, and the surface roughness (arithmetic mean roughness) of the edge portion is preferably Ra ≦ 0.4 μm. This is because if the surface roughness Ra> 0.4 μm, a slip may occur due to stress concentration when the wafer W contacts.

  When the wafer W is supported by the wafer supporting portion 2a formed in this way, there is no possibility of contact with an acute-angled edge portion as in the conventional case, and it is possible to suppress slippage due to concentrated load. Further, with the heat treatment of the wafer W, a deposition film is deposited on the rear end side (root side) of the peripheral edge portion 2a2 of the wafer mounting surface 2a1, but the deposition film does not peel off because there is no sharp edge, Generation of particles can be prevented.

Further, the vertical wafer boat 1 preferably has a SiC base material coated with a SiC film. The SiC-based material may be Si—SiC which has been converted to SiC by reaction impregnation of SiC, that is, SiC sintered body containing a carbon component is impregnated with Si, and the carbon component reacts with a part of Si. preferable. Alternatively, recrystallized SiC obtained by heat-treating a molded body of SiC at high temperature, self-sintered SiC obtained by adding a sintering aid and sintering may be used. Further, the SiC film is preferably a CVD SiC film capable of forming a highly pure and crystalline SiC film.
The surface roughness of the chamfered portion on which the SiC film is formed is preferably Ra 0.4 μm or less, whereby the defect prevention effect on the wafer W can be improved.

Further, the chamfering process of the wafer supporting portion 2a having the above-described shape can be performed by using the processing jig 10 shown in FIGS.
3A is a plan view of the processing jig 10, FIG. 3B is a sectional view taken along the line AA of FIG. 3A, and FIG. 3C is a sectional view of FIG. It is a BB arrow sectional view.

  As shown in FIGS. 3A and 3B, the processing jig 10 includes two driven shafts 11 arranged in parallel in the horizontal direction and a shaft for rotating the two driven shafts 11 in the same direction. It has a rotary motor 12 and a belt-shaped polishing belt 13 wound between two driven shafts 11 at a tip end side of the two driven shafts 11 with a predetermined tension. The distance dimension between the two driven shafts 11 is set larger than the width dimension of the wafer supporting portion 2a.

Further, the processing jig 10 has a robot arm 14 that can move an axial rotation motor 12 that holds the driven shaft 11 rotatably in at least three axes in the height direction, the left-right direction, and the front-back direction.
The polishing belt 13 is a ring-shaped (endless) band having polishing abrasive particles adhered to the surface thereof, and when it is wound around two driven shafts, the outer peripheral surface becomes a polishing surface. The size of the abrasive grains is preferably # 100 or more and # 1200 or less. Further, the rotation speed of the driven shaft 11 by the axial rotation motor 12 is preferably 2000 rpm or more and 3000 rpm or less.

Next, a method of manufacturing the wafer boat according to the present invention will be described.
First, a SiC base material is machined into a predetermined shape of the support column 2, the top plate 3, and the bottom plate 4 to be manufactured. After that, the pillar 2, the top plate 3, and the bottom plate 4 are assembled, and a SiC coating film is formed on the surface by the CVD method. At this time, a large number of wafer supporting portions 2a formed on the support columns 2 are not chamfered at the edge portions.
Then, the wafer mounting surface 2a1 of the wafer supporting portion 2a, which is the portion which the wafer W contacts or may contact, and the edge portion which is the peripheral end of the wafer mounting surface 2a1, that is, the side surface edge portion 2a2 and the tip. The edge portion 2a3 is polished by the processing jig 10 to be chamfered.

Specifically, the polishing and the chamfering process will be described. The chamfering process is sequentially performed for each wafer supporting portion 2a.
With respect to each wafer supporting portion 2a, first, the polishing belt 13 is moved by the robot arm 14 above the tip edge portion 2a3. At this time, the polishing belt 13 is arranged so that the rotation direction of the polishing belt 13 (direction extending in a belt-like shape) is orthogonal to the protruding direction of the wafer support portion 2a from the column 2.

  Next, the shaft rotation motor 12 is rotationally driven to rotate the polishing belt 13 in one direction. Further, the polishing belt 13 is lowered by the robot arm 14, and the polishing belt 13 is pressed against the tip edge portion 2a3 with a predetermined pressing force for a predetermined time. When the polishing belt 13 is pressed, the polishing belt 13 polishes while being bent along the tip edge portion 2a3 while rotating, so that the chamfering of the tip edge portion 2a3 is performed.

When the R chamfering of the tip edge portion 2a3 is completed, the robot arm 14 moves the polishing belt 13 rearward along the protruding direction of the wafer support portion 2a, and as shown in the perspective view of FIG. The rotating polishing belt 13 is pressed with a predetermined strength for a predetermined time.
As a result, the wafer mounting surface 2a1 is polished and smoothed. Further, since the polishing belt 13 bends along the side edge portion 2a2, the side edge portion 2a2 is chamfered. As shown in the figure, the polishing belt 13 polishes up to the rear end side (root side) of the side surface edge portion 2a2, so that the entire edge portion is chamfered. The surface roughness of the chamfered edge portion is Ra ≦ 0.4.

As described above, according to the embodiment of the present invention, in each wafer supporting portion 2a of the wafer boat 1, the wafer mounting surface 2a1 is smoothed by polishing, and the tip edge portion 2a3 and the side surface edge portion 2a2 are formed. And R are chamfered, and in particular, the side surface edge portion 2a2 is also chamfered to the root portion on the rear end side.
Therefore, when the wafer W is placed, there is no possibility that the back surface of the wafer W contacts the sharp edge, and it is possible to prevent the occurrence of slips and the generation of particles due to stress concentration of the load.

  In the above embodiment, the chamfering of the leading edge portion 2a3 and the side surface edge portion 2a2 is performed as the R surface, but the present invention is not limited to this configuration. For example, by processing the C-face of the edge portion, it is possible to eliminate the sharp edge, eliminate the concentrated load on the wafer surface, and suppress the occurrence of slip and the like.

  The wafer boat according to the present invention will be further described based on examples. In this example, the wafer boat shown in the above-described embodiment was manufactured, and the performance of the wafer boat was verified by heat-treating the wafer using the obtained wafer boat.

(Experiment 1)
In Experiment 1, the effect of the chamfering state of the leading edge portion and the side edge portion on the wafer supporting portion on the occurrence of slips and particles was verified.
In the first embodiment, as shown in FIG. 2, polishing of the wafer mounting surface in the wafer support portion and chamfering of the leading edge portion and the side surface edge portion are performed, and the leading edge portion and the side surface edge portion are all chamfered. A wafer boat subjected to the above was manufactured. The surface roughness (arithmetic mean roughness) of the leading edge portion and the side surface edge portion was formed to be 0 μm <Ra <0.3 μm.
Using this wafer boat, a plurality of wafers for evaluation were placed and heat treated. After the heat treatment, slip evaluation and particle evaluation were performed on the evaluation wafer.

The furnace used in the experiment was a vertical furnace for φ300 mm, the inner diameter of the core tube was 390 mm × the height of the core tube was 1650 mm, and the outer shape of the wafer boat used was the top plate and the bottom plate diameter of 330 mm × the boat height of 1200 mm.
The conditions of use were such that a wafer boat loaded with 100 wafers at 600 ° C. was put in a furnace, heated to 1200 ° C., held for 1 hour, cooled to 600 ° C., and then taken out. As a gas, 100 liters of argon gas in all steps was flowed at 15 liters per minute.

  The slip evaluation was performed by stacking 100 mirror-finished silicon wafers with a diameter of 300 mm and heat-treating the wafers once under the above-mentioned use conditions. It was evaluated that the in-plane was measured by a line topography and the maximum slip length that was the longest among the observed slips was compared.

  The particle evaluation is the number of particles in a φ300 mm wafer.

In the second embodiment, the surface roughness (arithmetic mean roughness) of the front edge portion and the side surface edge portion of the wafer supporting portion is set to 0.2 μm <Ra ≦ 0.4 μm.
The other conditions are the same as in Example 1.

In Comparative Example 1, the surface roughness (arithmetic mean roughness) of the front edge portion and the side surface edge portion in the wafer supporting portion was formed to be 0.5 μm ≦ Ra ≦ 0.8 μm.
The other conditions are the same as in Example 1.

  In Comparative Example 2, as shown in FIG. 6, a vertical wafer boat was used in which only the root portion on the rear end side of the side surface edge portion was not chamfered. The surface roughness (arithmetic mean roughness) of the chamfered edge portion was Ra ≦ 0.4 μm. The other conditions are the same as in Example 1.

  In Comparative Example 3, the wafer mounting surface was not polished, and the vertical wafer boat in which the front edge portion and the side surface edge portion were not chamfered was used. The other conditions are the same as in Example 1.

The results of Examples 1 and 2 and Comparative Examples 1, 2 and 3 are shown in Table 1.
In Table 1, the judgment index of the slip evaluation is x when the maximum slip length exceeds 30 mm, Δ when the maximum slip length is 10 mm or more and less than 30 mm, and the maximum slip length is less than 10 mm or When the slip itself did not exist, it was divided into 3 categories by the index of ◯ and ranked.
In addition, the judgment index of particle evaluation is divided into 3 categories by an index such that × is 30 or more particles of 0.2 μm or more on a φ300 mm silicon wafer, Δ is 10 or more and less than 30, Δ is less than 10 and is ○. Ranked.

In Examples 1 and 2, the maximum slip length was less than 10 mm or the slip itself did not exist for all the wafers that were heat-treated simultaneously. In addition, almost no particles were generated.
On the other hand, in Comparative Examples 1 and 2, some wafers had slips or particles. In Comparative Example 3, generation of slips or particles was confirmed in more wafers.
From the results of Experiment 1 described above, according to the wafer boat of the present invention, by chamfering up to the rear end side (root side) of the peripheral edge portion of the wafer mounting surface in the elongated wafer supporting portion, It was confirmed that the occurrence of slip can be further suppressed. Further, it was confirmed that the occurrence of slip and particles can be further suppressed by setting the surface roughness of the chamfered edge portion to Ra ≦ 0.4 μm.

1 Wafer Boat 2 Support Member 2a Wafer Support 2a1 Wafer Placement Surface 2a2 Side Edge 2a3 Tip Edge 3 Top Plate 4 Bottom Plate

Claims (4)

A wafer boat having a top plate, a plurality of columns whose one end is fixed to the top plate, and the other end of which is fixed to a bottom plate, and a wafer support portion which horizontally protrudes from a side surface of the column,
The wafer supporting portion has a polished wafer mounting surface and a U-shaped edge portion in a plan view formed at a peripheral end of the wafer mounting surface,
The wafer boat, wherein the edge portion is continuously chamfered from one end of the U-shape starting from the side surface of the support column to the other end ending at the side surface of the support column.   The wafer boat according to claim 1, wherein chamfering of the edge portion is R chamfering or C chamfering.   The wafer boat according to claim 1 or 2, wherein the chamfered edge portion has a surface roughness Ra ≦ 0.4 μm.   The wafer boat according to any one of claims 1 to 3, wherein a SiC coating film is formed on the surface of the SiC base material.

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