JP7269798B2 - Vertical wafer boat and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vertical wafer boat and its manufacturing method, and more particularly to a vertical wafer boat on which silicon wafers are placed, which is used for manufacturing semiconductor devices, and its manufacturing method.

In a semiconductor manufacturing process, heat treatment such as oxidation, diffusion, and CVD is performed on silicon wafers (hereinafter referred to as wafers). As a wafer boat used for this heat treatment, there is a vertical wafer boat in which wafer support portions (wafer storage grooves) extend horizontally from a plurality of (for example, four) vertically erected boat pillars. Are known.
By mounting a wafer on this wafer supporting portion and performing a predetermined heat treatment, high throughput can be achieved and mass production of wafers is attempted.

However, since the wafer support portion is in contact with the wafer, if the surface roughness of the wafer support portion is rough, the wafer and the wafer support portion rub against each other during the heat treatment, and surface scratches called slips and particles are generated on the wafer. There were technical issues.

Therefore, conventionally, it has been considered desirable to uniformly reduce (smoothen) the roughness of the upper surface of the wafer supporting portion that contacts the wafer.
For example, in the vertical wafer boat disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2005-203648), a plate-like support made of silicon is arranged on a wafer support, and the support is positioned on the outer periphery of the back surface of the wafer. is used.
In addition, according to Patent Document 1, the surface roughness of the support that contacts the wafer is suppressed to 0.1 μm or less, thereby reducing the friction between the wafer and preventing damage to the wafer contact surface. is described.

Japanese Patent Application Laid-Open No. 2005-203648

By the way, when a vertical wafer boat containing wafers is housed in a chamber and subjected to heat treatment, the wafers are rapidly heated in the initial stage of the heat treatment (immediately after being placed in a furnace or immediately after the temperature is started to rise). Due to deformation of the boat or the like, the wafer may move from the state placed on the wafer support.
In particular, when the surface roughness Ra of the portion in contact with the wafer is small, as in the wafer boat disclosed in Patent Document 1, the frictional force between the wafer and the wafer support is small, so the movement of the wafer is suppressed. It was difficult.
This movement of the wafer sometimes causes the center of the wafer to move by more than 1 mm, resulting in large friction between the wafer and the wafer support, causing the wafer to slip and particles to occur. There was a technical problem.

The present invention has been made under the circumstances as described above, and provides a vertical wafer boat capable of suppressing the movement of silicon wafers and suppressing the slippage of silicon wafers and the generation of particles in the vertical wafer boat. The object is to provide a manufacturing method.

A vertical wafer boat according to the present invention, which has been made to solve the above problems, comprises a top plate, a plurality of pillars each having one end fixed to the top plate and the other end fixed to a bottom plate, and side surfaces of the pillars. a wafer support projecting horizontally from the top surface of the wafer support on which the silicon wafer rests; and a second region with which the heat-treated silicon wafer contacts, wherein the surface roughness of the first region is formed to be greater than the surface roughness of the second region. .

In addition, in the upper surface of the wafer support portion on which the silicon wafer is placed, the second region is a region extending from the tip of the upper surface of the wafer support portion to the base end of the wafer support portion by 1 to 3 mm. is desirable.
Further, on the upper surface of the wafer supporting portion on which the silicon wafer is placed, the surface roughness Ra of the first region is at least 1.5 μm, and the surface roughness Ra of the second region is at most 1.5 μm. is also preferably 0.4 μm.
Furthermore, the upper surface of the wafer support portion may be formed into a tapered surface that slopes downward from the support side toward the tip.

According to the present invention, in each wafer support portion of the wafer boat, the second region within a predetermined range from the tip of the top surface is made to have a small surface roughness, and the other region, the first region, is the second region. , the surface roughness is greater than that of the region of .
Therefore, in a non-heat-treated state, the outer peripheral portion of the wafer abuts against the first region having a large surface roughness, and movement of the wafer is suppressed.
Then, in the heat treatment state, the wafer is warped and the outermost edge of the wafer is lifted away from the region of large surface roughness. At this time, the outer peripheral portion of the wafer is supported by the smoothed second region, thereby preventing the occurrence of slips and particles.
It should be noted that the non-heat-treated state refers to a state including an initial stage of wafer heating in which the wafer is not yet warped even after being heated from the state after the wafer is placed. The heat treatment state refers to a heated state of the wafer in which the wafer warps due to heat and the outermost edge of the wafer floats.

In addition, a method for manufacturing a vertical wafer boat according to the present invention, which has been made to solve the above problems, is a method for manufacturing a vertical wafer boat, comprising the steps of: forming the wafer support portion on the pillar; forming the surface roughness of the second region to be smaller than the surface roughness of the first region.
The step of forming the surface roughness of the second region to be smaller than the surface roughness of the first region includes, for example, mechanically treating the second region such as polishing to make the surface roughness of the second region smaller than the surface roughness of the first region. can be made smaller.
The first region may be the surface roughness of the substrate, but it is preferable to perform mechanical treatment such as polishing in the same manner as the second region to achieve a predetermined surface roughness. .

According to the present invention, it is possible to obtain a vertical wafer boat and a method of manufacturing the same, which can suppress the movement of silicon wafers and suppress the generation of slips and particles of silicon wafers in a vertical wafer boat provided with a wafer supporting portion. can.

FIG. 1 is a front view of a vertical wafer boat according to this embodiment. FIG. 2 is an enlarged perspective view showing a wafer support portion of the vertical wafer boat shown in FIG. FIG. 3 is a plan view of the wafers showing the peripheral region of the wafers supported by the vertical wafer boat of FIG. FIG. 4A is a side view showing the contact state between the wafer outer periphery and the wafer supporting portion in the initial stage of heat treatment (unheated state), and FIG. 4B is the wafer outer periphery during heat treatment (heated state). It is a side view which shows the contact state of a part and a wafer support part. FIG. 5 shows a modification of the vertical wafer boat according to the present invention, and FIG. 5(a) is a side view showing the state of contact between the outer periphery of the wafer and the wafer support in the initial stage of heat treatment (unheated state). , and FIG. 5B is a side view showing a contact state between the wafer outer peripheral portion and the wafer support portion during heat treatment (heated state).

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the vertical wafer boat which concerns on this invention, and its manufacturing method is described based on drawing. FIG. 1 is a front view of a vertical wafer boat according to this embodiment, and FIG. 2 is an enlarged perspective view of a wafer support portion of the vertical wafer boat shown in FIG. FIG. 3 is a plan view of the silicon wafers showing the peripheral regions of the wafers supported by the vertical wafer boat of FIG.

As shown in FIG. 1, a vertical wafer boat 1 includes two support members 2 arranged on the starting end side in the wafer insertion direction and one support member arranged on the end side (back side) in the wafer insertion direction. A member 2 is provided. 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 .

As shown in FIGS. 1 and 2, each support member 2 is formed with a plurality of plate-like wafer support portions 2a for supporting a large number of silicon wafers W, respectively. The wafer support portions 2a in each support member 2 have a thickness L1 of 2 to 3 mm, a length (depth) L2 of 10 to 20 mm, and a width L3 of 15 to 20 mm. formed.

As shown in FIG. 3, a holdable region W1 (contactable region) of the silicon wafer W by the wafer support member 2a is a so-called wafer peripheral portion, and its radial width d2 is, for example, If the diameter is d1, the length dimension is (d1-d1×0.95)/2.
In other words, the wafer W is in contact with the wafer supporting member 2a with a width of 0.025d1 in the radial direction from one end of the wafer W.

In the present embodiment, the upper surface of each wafer supporting portion 2a is formed such that the surface roughness Ra differs between the tip region (second region) 2a2 and the other region (first region) 2a1. .
Specifically, as shown in FIG. 2, the tip region (second region) 2a2 from the tip of the wafer support portion 2a to the base end of the wafer support portion 2a from the distance L4=1 mm to 3 mm is polished. and the surface roughness Ra is 0.4 μm or less.

On the other hand, the other area (first area) 2a1 is not smoothed and has a rough surface roughness Ra of 1.5 μm or more.
It should be noted that the other region (first region) 2a1 may be left as it is or may be polished to a surface roughness of 1.5 μm or more.

The reason why the upper surface of the wafer support portion 2a is divided into two regions in this way is that in the initial stage (non-heated state) of the heat treatment after the wafer is mounted, the outer peripheral portion of the wafer supports the wafer as shown in FIG. 4(a). It comes into contact with a region (first region) 2a1 having a large surface roughness Ra of the portion 2a, the frictional force between the wafer W and the first region 2a1 is large, and the movement of the wafer W is suppressed.
In addition, when the wafer W warps in the heated state as shown in FIG. 4B, the outermost peripheral edge of the wafer floats away from the area (first area) 2a1 having a large surface roughness Ra, It comes into contact with a region (second region) 2a2 having a small surface roughness Ra.
That is, since the frictional force between the wafer W and the second region 2a2 is small, the friction of the wafer W is suppressed, and slips and particles at the outer peripheral edge of the wafer are suppressed.

Moreover, this vertical wafer boat 1 preferably has a SiC base material coated with a SiC film. The SiC base material may be Si—SiC obtained by impregnating a SiC sintered body containing a carbon component with reaction sintered SiC, that is, SiC by reacting a part of the Si with the carbon component. preferable.
Alternatively, recrystallized SiC obtained by heat-treating a SiC compact at a high temperature, or self-sintered SiC obtained by adding a sintering aid and sintering may be used. Moreover, as the SiC film, a SiC film obtained by CVD is preferable because it can form a highly pure and crystalline SiC film.

Such a vertical wafer boat 1 can be manufactured as follows.
First, the support 2, the top plate 3, and the bottom plate 4 are manufactured by machining the SiC base material into predetermined shapes. After that, the column 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.

Then, first, the surface roughness Ra of the other region 2a1 (first region) is set to 1.5 μm or more by performing a rough polishing treatment for rough grinding.
In addition, when the surface roughness Ra of the substrate of the other area (first area) 2a1 is 1.5 μm or more, the polishing process may not be performed.
After that, the front end region (second region) 2a2 extending from 1 mm to 3 mm from the front end of the upper surface of the wafer support portion 2a toward the base end of the wafer support portion 2a is polished so that the surface roughness Ra is 0.4 μm or less. smoothed as

When the upper surfaces of all the wafer supporting portions 2a are formed so that the tip region (second region) 2a2 and the other region (first region) have different surface roughness Ra as described above, A vertical wafer boat 1 of the present invention is obtained.

As described above, according to the embodiment of the present invention, each wafer support portion 2a of the vertical wafer boat 1 has a tip region (second region) 2a2 on the upper surface thereof with a surface roughness Ra of 0.4 μm or less. , and the other area (first area) 2a1 has a rough surface roughness Ra of 1.5 μm or more.
Therefore, in the initial heat treatment stage (unheated state) after the wafers W are mounted on the vertical wafer boat 1, the outer peripheral portion of the wafer contacts the region (first region) 2a1 having a large surface roughness, and the wafer W movement is suppressed, and in the heat treatment state (heating state), the wafer W is warped and the outermost peripheral edge of the wafer floats away from the large surface roughness region (first region) 2a1. Then, the outer peripheral portion of the wafer is supported in contact with the smoothed front end region (second region) 2a2, thereby preventing the generation of slips and particles.

In the above-described embodiment, as shown in FIG. 4, the wafer supporting portion 2a has a substantially uniform thickness dimension. not to be
For example, as shown in FIGS. 5(a) and 5(b), the upper surface of the wafer supporting portion 2a may be a tapered surface that slopes downward toward the tip.

In that case, for example, as shown in FIG. 5(a), in the initial stage (unheated state) of the heat treatment, the outer peripheral portion of the wafer is in contact with a region (first region) 2a1 having a large surface roughness Ra, and Since the outer peripheral portion of the wafer is held (in a mortar shape) by the tapered surfaces of the wafer support portion 2a from three sides, movement of the wafer is further suppressed.

Further, when the wafer warps during heat treatment, as shown in FIG. The outer peripheral portion of the wafer is supported by the tip region (second region) 2a2 having a small surface roughness Ra.
This can suppress the generation of slips and particles during heat treatment.

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

In this experiment, the boundary position between the front end region (second region) and the other region (first region) in the wafer support portion and the surface roughness Ra of each region were used as conditions, and the wafer moving distance, after heat treatment, was verified for the amount of particles adhering to the wafer.

A vertical boat used for one heat treatment accommodated 50 silicon wafers with a diameter of 300 mm and was heat treated at 800° C. for 1 hour in a furnace.
After the observation wafers placed in the upper, middle and lower parts of the boat were subjected to heat treatment, the change in the distance between the outer periphery of the silicon wafer and the back side of the wafer support portion was measured to obtain the average amount of movement of the wafer.
Also, the number of particles adhering to the wafer surface (the number of particles of 0.2 μm or more adhering to the φ300 mm silicon wafer surface) was measured to obtain the particle adhesion amount.
Furthermore, the occurrence of slips on the back surface of the silicon wafer was observed.

Table 1 shows the conditions and results of this experiment.
In Table 1, the average amount of movement of the wafer as the experimental results is indicated by ◯ when the amount of movement of the center of the wafer is 0.1 mm or less, Δ when more than 0.1 mm and 1 mm or less, and x when more than 1 mm.
Also, the case where no slip occurred was evaluated as ◯, and the case where slip occurred was evaluated as x.
The amount of particles adhering to the wafer is ◯ when no particles of 0.2 μm or more are observed, Δ when the number of particles of 0.2 μm or more is 20 or less, and 0.2 μm or more. When the number of particles exceeded 20, it was marked as x.

As shown in Table 1, the tip region (second region) of the upper surface of the wafer support portion is set to a range of 1.0 to 3.0 mm from the tip, and the surface roughness Ra of the tip region (second region) is By setting the surface roughness Ra to 0.4 μm or less and the surface roughness Ra of the region other than the tip region (first region) to 1.5 μm or more, the movement of the wafer in the initial stage of heat treatment is suppressed, and the generation of slips and particles during heat treatment is suppressed. Confirmed that it can be done.

Reference Signs List 1 wafer boat 2 support member 2a wafer support 2a1 other region (first region)
2a2 tip region (second region)
3 top plate 4 bottom plate W silicon wafer

Claims (5)

A vertical wafer boat comprising a top plate, a plurality of columns each having one end fixed to the top plate and the other end fixed to a bottom plate, and a wafer support portion horizontally protruding from a side surface of the column,
The upper surface of the wafer support portion on which the silicon wafer is placed has a first region with which the silicon wafer in a non-heat-treated state contacts and a second region with which the silicon wafer in a heat-treated state contacts;
with
A vertical wafer boat, wherein the surface roughness of the first region is formed to be greater than the surface roughness of the second region. On the upper surface of the wafer support on which the silicon wafer is placed,
2. The vertical wafer boat according to claim 1, wherein the second area extends from the tip of the upper surface of the wafer support portion toward the base end of the wafer support portion by 1 to 3 mm. On the upper surface of the wafer support on which the silicon wafer is placed,
The surface roughness Ra of the first region is at least 1.5 μm,
3. A vertical wafer boat according to claim 1, wherein said second region has a surface roughness Ra of at most 0.4 [mu]m. 4. The vertical wafer boat according to any one of claims 1 to 3, wherein the upper surface of the wafer support portion is formed into a tapered surface that slopes downward from the support side toward the tip. . The vertical wafer boat manufacturing method according to any one of claims 1 to 4,
forming the wafer support on the pillar;
and forming the surface roughness of the second region to be smaller than the surface roughness of the first region.

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