JPH0627952Y2 - Wafer tray / susceptor / tray pedestal shape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to the shapes of a wafer tray, a cassette, and a fork of a vertical vapor deposition apparatus.

Here, the vertical vapor phase growth apparatus is one in which the flow of gas flows from top to bottom. Among them, here, a vapor phase growth apparatus for horizontally placing a wafer on a susceptor is targeted.

The wafer may be placed directly on the upper surface of the susceptor, but then the growth chamber must be opened for wafer attachment / detachment. Inconvenient to handle. Therefore, it is convenient to put the wafer in a thin flat plate-like container and carry, store, and vapor-phase grow the container together. Such a container is referred to as a wafer tray here.

If some wafer trays are temporarily housed in a vacuum chamber, and the wafer trays are fed one by one onto the susceptor for processing, it is not necessary to break the vacuum in the growth chamber, which is efficient.
The one that holds several wafer trays in this way is called a cassette here.

Further, a portion that supports the tray of the apparatus that conveys the wafer tray between the cassette and the susceptor is called a fork.

(B) Conventional Technology FIG. 12 shows the structure of a wafer tray / susceptor according to a conventional example.

The susceptor 6 has a simple cylindrical shape, and the wafer tray 1 is placed on the susceptor 6. The wafer 11 is fitted in the wafer mounting portion 2 formed on the upper surface of the wafer tray 1. The lower surface of the wafer tray 1 is cut so as to be along a cylinder, and the peripheral edge 4
Since it hits the side surface of the susceptor 6, the wafer tray 1 is prevented from falling sideways from the susceptor.

Inside the peripheral edge 4 is a vertical wall 21. A gap g is formed between the vertical wall 21 and the side surface of the susceptor. Assuming that the diameter of the susceptor is D and the diameter of the spot facing (the recess along the cylinder) on the lower surface of the wafer tray 1 is E, D + 2g = E (1) and D <E must be satisfied.

Thus, since the hole and the side surface of the susceptor are vertical surfaces, the gap g is always required.

Although only the susceptor is drawn here, the cassette has the same shape.

A fork conveys the wafer tray, positions it, and places it on the susceptor or on the tray pedestal of the cassette.

(C) Problem to be solved by the invention The hole on the lower surface of the wafer tray is a vertical wall, and the tray pedestal of the susceptor and the cassette is also a vertical outer peripheral surface. Because of such fitting, it is difficult to carry the wafer tray by the fork and position it when it is placed on the susceptor or tray pedestal.

The positioning is performed by aligning the center of the fork with the center of the susceptor or tray pedestal. However, they do not exactly coincide with each other, and a deviation e always occurs between the center lines.

There is also a positional deviation f between the center of the fork and the center of the wafer tray placed on it.

The fork is moved directly above the susceptor, and the susceptor is raised to insert the susceptor 6 into the spot facing on the lower surface of the wafer tray. For this to be possible, the sum of the centerline deviations e, f must be smaller than g.

e + f <g (2).

The fork is a member that moves horizontally and is cantilevered in a vacuum. In order to reduce the error e at the stop position, the accuracy of the device must be increased. This is not always easy.

f is an amount determined by the displacement of the outer surface of the fork and the wafer tray. When f is made small, mistakes may occur when the wafer tray is lifted by the fork.

For this reason, the amounts of deviation e and f of the center line cannot be made too small. Then, the difference g between the diameter E of the hole of the wafer tray and the diameter D of the susceptor becomes large.

If the gap g is increased, the wafer tray may be placed in a biased position on the susceptor. In this case, the gas flow is not axisymmetric. Therefore, there is a possibility that the thin film formation may be adversely affected.

Assuming that the deviation between the center lines of the wafer tray and the susceptor when the wafer tray is placed on the susceptor is q, q can take any value from 0 to g.

0 ≦ q ≦ g (3) In order to reduce q, g must be reduced. However, e and f cannot be made too small because of mechanical restrictions.

(D) Means for Solving the Problem In the present invention, the inner peripheral surface of the recess on the back surface of the wafer tray is an inclined surface instead of a vertical surface. Further, in accordance with this, a part of the outer peripheral surface above the susceptor and the outer peripheral surface of the tray pedestal are also inclined surfaces rather than vertical surfaces.

The slanted surfaces will be fitted together. By doing this, the widths of the inclined surfaces of the wafer tray, the susceptor, and the tray pedestal are set to a, b,
As c, a positioning margin can be provided by this minimum value. In other words, instead of the condition (2), e + f <min {a, b, c} (4). Further, if the wafer tray is placed on the susceptor, the deviation q between the wafer tray center line and the susceptor center line is completely zero.

q = 0 (5) This will be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing an example of a wafer tray according to the present invention.

The wafer tray 1 is a thin container having a substantially disc shape, and is made of, for example, carbon. The wafer mounting portion 2 is shallowly formed on the upper surface. The wafer is placed here. Although the lower surface of the wafer tray 1 is hollow, the back plate portion 3 is flat, and a peripheral edge 4 extending downward is provided on the outer side thereof. A longitudinal surface connecting the peripheral edge 4 and the back plate portion 3 is an inwardly inclined peripheral surface 5. It is not a vertical wall surface, but an inwardly inclined surface that makes an angle θ with the vertical. Moreover, the shape gradually opens downward.

If the height of the inner inclined peripheral surface 5 is h, the radial width is a, and the inclination angle is θ, then a = htan θ (6).

FIG. 2 is a schematic vertical sectional view of the susceptor. The outer peripheral surface 8 is not only a columnar shape but at least a part of the upper side. The remaining lower half may be the cylindrical peripheral surface 10.
The upper surface portion 7 is a flat surface as in the conventional case.

A susceptor instruction shaft 9 is fixed to the lower surface of the susceptor 6. The susceptor 6 is supported by a shaft 9 so as to be rotatable and vertically movable.

When the height of the outer inclined peripheral surface 8 is k, the width in the radial direction is b, and the inclination angle is θ, b = ktan θ (7).

It is best that the inclination angle of the outer inclined peripheral surface of the susceptor and the inclination angle of the wafer tray are the same. However, there may be some differences. Further, the inclined peripheral surface may not be strictly a part of a cone, and may have a slightly rounded vertical cross section.

FIG. 3 is a schematic vertical sectional view of the tray pedestal.

It is a substantially disk-shaped member having a flat upper surface portion 13 and a lower surface portion 14. A vertical hole 17 is formed in the center. This is a hole for letting the gas out from the space surrounded by the wafer tray 1 and the tray holder 12.

A mounting handle 16 is formed on one side, and is fixed to a tray receiving base plate 19 which is a vertical member.

The side peripheral portion between the upper surface portion 13 and the lower surface portion 14 is the outer inclined peripheral surface 1.
It is 5. Although it is a part of the conical surface, it has a truncated cone shape that is small at the top and large at the bottom.

The inclination angle of the outer inclined peripheral surface 15 is preferably the same as the inclination angle of the wafer tray 1 and the susceptor 6.

When the height of the outer inclined peripheral surface 15 of the tray support 12 is 1, the radial width is c, and the inclination angle is θ, c = l tan θ (8).

(E) Action The inner inclined peripheral surface 5 of the wafer tray 1 is fitted to the outer inclined peripheral surface 8 of the susceptor 6 or the outer inclined peripheral surface 15 of the tray pedestal 12. Since each of them has an inclined peripheral surface that is narrow at the top and wide at the bottom, the wafer tray 1 is positioned at the height where the diameter is the same. At this time, the deviation q between the central axis of the wafer tray and the central axes of the susceptor 6 and the tray pedestal 12 is zero. Since q = 0, strict positioning is automatically performed.

FIG. 4 is a vertical sectional view showing a state where the wafer tray 1 is placed on the susceptor. FIG. 6 is a diagram after the wafer tray 1 is transported by the fork 21 and placed on the upper surface of the susceptor 6.

After fitting, the inner inclined peripheral surface 5 of the wafer tray is in close contact with the outer inclined peripheral surface 8 of the susceptor 6. There is no deviation between the central axes (q = 0).

However, before fitting, the central axis of the wafer tray and the central axis of the susceptor may be slightly deviated. If this deviation is smaller than the smaller one of the widths a and b of the inclined peripheral surface, the inclined peripheral surface is guided and positioned correctly.

There is a slight gap s between the back plate portion 3 of the wafer tray 1 and the upper surface portion 7 of the susceptor 6. If s is finite,
The inner and outer inclined surfaces 5 and 8 are in contact with each other over the entire circumference, so that they are correctly positioned.

If s = 0, the inner and outer inclined surfaces 5 and 8 only partially contact, but in this case as well, the positioning accuracy is higher than that of FIG. In the present invention, s ≠ 0 is desirable, but s = 0
May be It is important that the action of the inclined peripheral surface guides the wafer tray correctly and minimizes the deviation between the central axes.

In other words, if the deviation of the wafer tray on the fork is f and the deviation of the center of the fork and the susceptor is e, and if e + f <min {a, b} (9), then when the susceptor is lifted, The inclined peripheral surface 5 can contact the outer inclined peripheral surface 8 of the susceptor 6. When the susceptor is lifted, it is fitted properly along the inner and outer inclined peripheral surfaces 5 and 8.

FIG. 5 is a vertical cross-sectional view showing the fitted state of the wafer tray 1 and the tray pedestal 12 in the cassette.

The inner inclined peripheral surface 5 of the wafer tray 1 is fitted to the outer inclined peripheral surface 15 of the tray pedestal 12. In this state, the bottom of the peripheral edge 4 of the wafer tray is in contact with the tray holder 12. Here, the weight of the wafer tray is supported.

Strictly speaking, the central axes of the wafer tray 1 and the tray pedestal 12 do not match, but they do not need to strictly match because they are not related to vapor phase growth. However, if the dimensions are appropriately determined, the central axes of the two can be made to substantially coincide with each other.

There is a gap t between the wafer tray 1 and the tray pedestal 12. The hole 17 is for venting gas from this space.

The gap t is significantly wider than the gap s between the susceptor 6 and the wafer tray 1. The reason why the gap t is wide is that the tray holder 12 is thin. The height l of the outer inclined peripheral surface 15 of the tray support 12 is reduced. Since h> l, the gap t becomes wider. If the height l of the outer inclined peripheral surface 15 is reduced, the tray support can be made thinner. Then, more tray receiving trays 12 can be attached due to the limited height of the cassette.

How the wafer tray, susceptor and fork are used will be briefly described with reference to FIGS. 6 and 7. These are a plan view and a vertical cross-sectional view showing the entire vapor phase growth apparatus having a transfer device.

The vapor phase growth apparatus comprises a load lock chamber F, a growth chamber G, and a transfer preliminary chamber H arranged in order. Adjacent spaces are partitioned by gate valves 25 and 26. Each space can be evacuated independently.

The load lock chamber F has a cassette 23. This comprises a tray pedestal base plate 19 provided in the vertical direction and a plurality of tray pedestals 12 attached thereto.
The cassette 23 can be raised and lowered freely.

The growth chamber G is provided with a susceptor 6 which is rotatable and vertically movable.
Raw material gas is introduced from the top. The wafer tray 1 is placed on the susceptor 6, and a thin film is formed on the wafer 11.
A high frequency heating coil 24 is provided to heat the susceptor 6 and the wafer 11.

A transfer device 28 is provided in the transfer preliminary chamber H. This comprises a fork 21 for holding the wafer tray and a straight line introducing machine 27 for horizontally moving the fork 21.

When the gate valves 25 and 26 are opened, the fork 21 can be inserted into the growth chamber G or the load lock chamber F.

The susceptor 6 and the tray pedestal 12 can be raised and lowered, and the fork 21
Since the wafer tray 1 can be moved horizontally,
Thus, it can be transported from the susceptor 6 to the tray pedestal 12 or in the opposite direction.

The wafer tray 1 of the susceptor 6 and the tray pedestal 12 is transferred to the fork 21 as follows. The susceptor and the tray pedestal are raised slightly upward, and the tip of the fork 21 is put under the wafer tray 1. Lower the susceptor and tray pedestal. The wafer tray 1 is lifted up by the fork 21. The fork 21 is moved to the side. The opposite process can be performed from the fork 21 to the susceptor 6 and the tray pedestal 12.

(F) Example An example of the shape of the tray pedestal is shown in FIGS. 8 and 9. In this embodiment, the outer inclined peripheral surface 15 is not uniform and is composed of two surfaces having different inclinations. When viewed from the side, the sloping outer surface is connected by fold lines.

The bottom of the peripheral edge 4 of the wafer tray 1 is placed so as to contact the tray support portion 31 and the attachment handle portion 16. Excluding these,
Only the outer inclined peripheral surface 15 exists on the circumference.

An example of the shape of the fork 21 is shown in FIGS. 10 and 11. It is an annular member having a front opening. The wafer tray 1 can be placed on the step portion 32. The fork is not the subject of the present invention and will not be described in detail. However, when the wafer tray 1 is placed on such a fork 21, it can be seen that the center lines of the two are different from each other. This is because the wafer tray 1 can move in the step portion 32. This shift is described as f.

(G) Advantages of the invention (1) A wafer is mounted on a wafer tray in advance and then transferred. Therefore any material of the wafer can be easily and safely transported.

(2) Since the wafer tray, the susceptor, and the tray pedestal are provided with the inner and outer inclined peripheral surfaces, precise positioning can be easily performed.

(3) If the height l of the inclined peripheral surface of the tray pedestal is made smaller than the height h of the inclined peripheral surface of the wafer tray, a larger number of tray pedestals can be mounted in a narrow space.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a wafer tray according to an example of the present invention. FIG. 2 is a vertical sectional view of a susceptor according to an example of the present invention. FIG. 3 is a vertical sectional view of a tray holder according to an example of the present invention. FIG. 4 is a vertical cross-sectional view of the wafer tray placed on the susceptor. FIG. 5 is a vertical cross-sectional view of the wafer tray placed on the tray holder. FIG. 6 is a plan view showing an example of a vapor phase growth apparatus. FIG. 7 is a vertical sectional view of the same thing. FIG. 8 is a plan view of the tray holder according to the embodiment. FIG. 9 is a front view of the same tray pedestal. FIG. 10 is a plan view of the fork. FIG. 11 is a sectional view taken along the line IX-IX in FIG. FIG. 12 is a vertical cross-sectional view showing a fitted state of a wafer tray and a susceptor according to a conventional example. 1 ... Wafer tray 2 ... Wafer mounting part 3 ... Back plate part 4 ... Edge 5 ... Inner inclined peripheral surface 6 ... Susceptor 7 ... Upper surface 8 ... External inclined peripheral surface 9 ... Susceptor instruction shaft 10 ... Cylindrical peripheral surface 11 ... Wafer 12 ... Tray pedestal 13 ... Upper surface 14 ... Lower surface 15 ... Outer inclined peripheral surface 16 ... Mounting handle 17 ... Hole 19 ... Tray pedestal base Plate 21 ...... Vertical wall 23 ...... Cassette 25, 26 ...... Gate valve 27 …… Straight line introduction machine 28 …… Transfer device F …… Load lock chamber G …… Growth chamber H …… Gate valve s …… Susceptor and wafer tray Gap t …… Gap between tray tray and tray

Claims (2)

[Scope of utility model registration request] 1. A wafer mounting part 2 on which a wafer is to be mounted.
The bottom surface has a hole for inserting into the susceptor.
And a flat back plate 3 and a peripheral edge 4 at the center of the hole.
The wafer tray 1 has an inner inclined peripheral surface 5 that is inclined so that the peripheral surface connecting to the bottom is narrowed upward and widened downward, and the flat upper surface portion 7 and the peripheral surface formed on at least a part of the side peripheral portion It is characterized by comprising a susceptor 6 having a narrow and wide outer inclined peripheral surface 8 so that when the wafer tray 1 is placed on the susceptor 6, both are contacted by the inner and outer inclined peripheral surfaces 5, 8. Wafer tray / susceptor shape. 2. A flat upper surface portion 13, a lower surface portion 14, a mounting handle portion 16, and a peripheral surface connecting the upper surface portion 13 and the lower surface portion 14 and having an outer inclined peripheral surface which inclines so as to narrow upward and wide downward. A tray holder 12 having a number 15 and a wafer holder 2 on which a wafer is to be placed are formed on the upper surface, and a hole for inserting into the tray holder 12 is formed on the lower surface, leaving a peripheral edge 4. The wafer tray 1 is composed of a wafer tray 1 whose inner peripheral peripheral surface 5 is inclined so that the peripheral surface connecting the central flat back plate portion 3 and the bottom portion of the peripheral edge 4 is narrow at the top and wide at the bottom. When the wafer tray 1 is placed on the upper surface of the wafer tray 1,
A shape of a wafer tray / tray pedestal, characterized in that the bottom of the peripheral edge 4 of the wafer tray 1 is brought into contact with the tray support portion 31 and the attachment handle portion 16 by being guided by 15.