JPH113866A - Vertical wafer boat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical wafer boat which can prevent peeling of a ceramic film and whose service life is long. SOLUTION: Supporting rods 4 provided with multiple grooves 3 for packing wafers are symmetrically placed between upper and lower supporting plates 2, two at the front and two at the back. The supporting plates 2 and the supporting rods 4 are made of ceramic substrate and their surface is covered with a high-purity ceramic film. At least grooves 3 for packing wafers of the two supporting rods 4 at the front are placed in a position a head of a center line 5 which is perpendicular to the direction of inserting semiconductor wafers W. The horizontal cross section of the grooves 3 for packing wafers of each supporting rod 4 is a polygon without acute angle less than 90 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical wafer boat for loading and supporting a large number of semiconductor wafers in a furnace during processes such as oxidation, diffusion and vapor phase growth of semiconductor wafers. SiO ₂ film on the surface of the semiconductor wafer,
SiO ₃ N ₄ film or a poly-Si film or the like LP (Low Pres
sure) -related to a vertical wafer boat suitable for forming by a CVD method or the like.

[0002]

2. Description of the Related Art Conventionally, as a vertical wafer boat of this type, a wafer boat described in Japanese Patent Application Laid-Open No. 6-163676 filed by the present applicant has been known. In this wafer boat, as shown in FIGS. 15 and 16, four support rods 34 having a triangular cross section and having a number of wafer loading grooves 33 provided between upper and lower support plates 31 and 32 having a semicircular arc shape. The wafer loading groove 33 provided at one edge of each is disposed so as to point toward the center of a semiconductor wafer (not shown) loaded thereon, and both support plates 31 and each support rod 34
It is made of iC or SiC impregnated with metal Si (Si-SiC). It is also known that the surface of the wafer boat is covered with a high-purity ceramic film in order to purify the wafer boat. This wafer boat has a support rod 34
Has a triangular cross-section, so that the buckling load increases and the service life becomes longer. Also, as shown in FIGS. 17 to 19, a slit 35 in the wafer insertion direction (from right to left in FIG. 18) is provided at the center of the rear portion (left portion in FIG. 18) as a conventional vertical wafer boat. Four support rods 39 having a circular cross section and having a number of wafer loading grooves 38 provided between upper and lower support plates 36 and 37 in the shape of a circular plate.
Are arranged so that the respective wafer mounting grooves 38 are directed toward the center of the semiconductor wafer W to be stacked on each of them, and both the support plates 36 and 37 and the respective support rods 39 are made of a ceramic base material and the surface is high. Each support bar 39 has a chamfer 40 at a horizontal edge portion below the wafer loading groove portion 38, which is covered with a high-purity ceramic film (not shown).
In addition, a projection 42 having a reference surface 41, which is a reference for automatic transfer of the semiconductor wafer W, formed on the lower surface of the front portion (the right portion in FIG. 18) of the lower support plate 37 protrudes. Is what is being done. In this vertical wafer boat, when the semiconductor wafer W is transferred, the required position of the wafer loading groove 38 is determined from the reference surface 41, and the semiconductor wafer W can be automatically transferred.

[0003]

However, in the former vertical wafer boat, the support rod has a triangular cross section. For example, when the surface is covered with a high-purity ceramic film, the vertical edge is The ceramic film of the part is easily broken due to contact with other members at the time of manufacture or use, or thermal stress concentration caused by cooling and heating cycles at the time of use, and in such a case, the release of impurities from the ceramic base is caused. There is a problem that the semiconductor wafer to be processed is adversely affected. In particular, a SiO ₂ film or Si
₃ N ₄ film, if the poly-Si film or the like formed by the LP-CVD method or the like, since the CVD film is formed also on the vertical wafer boat itself not a semiconductor wafer only, the vertical edges and the wafer loading of the support rod The CVD film adhered to the upper and lower horizontal edges of the groove is peeled off at the time of the next wafer loading or heat treatment to become particles, which adversely affects the semiconductor wafer to be processed. In the latter vertical wafer boat, since the support rod has a circular cross section, there is no problem as in the former, but since the vertical edge of the wafer loading groove is acute, the There is a problem that the ceramic film and the CVD film attached to the portion are peeled off. Cleaning of the vertical wafer boat for each process is not usually performed because a reduction in productivity is prevented and a ceramic film that cannot be cleaned is present. Further, since all of the vertical wafer boats have four support rods, the number of supporting positions of the semiconductor wafer is increased, and there is a problem that a large amount of particles are generated. Accordingly, an object of the present invention is to provide a vertical wafer boat that can prevent the peeling of the ceramic film and that has a long service life.

[0004]

In order to solve the above-mentioned problems, a first vertical wafer boat according to the present invention is characterized in that a support rod having a large number of wafer loading grooves provided between upper and lower support plates is symmetrical. Two support plates and two support rods are provided at the front and rear, each of the support plates and each support rod is made of a ceramic base material, and the surface is covered with a high-purity ceramic film. At least the wafer loading grooves of the front left and right support rods are loaded on this. The support rod is provided so as to be located forward of a center line perpendicular to the wafer insertion direction of the semiconductor wafer, and the horizontal cross section of each support rod in the wafer loading groove is 9 mm.
It is characterized by being formed in a polygon having no acute angle portion of 0 ° or less. The second vertical type wafer boat is characterized in that, in the first type, the upper and lower edges of the wafer loading groove of each support bar are chamfered. The third vertical wafer boat is the first or second wafer boat, wherein the two support plates have a circular plate shape in which a slit in the wafer insertion direction is provided at the center of a rear part, and the front and rear left and right support rods are provided. It is characterized in that the horizontal cross-sectional area in the wafer mounting groove is substantially equal. The ratio of the horizontal cross-sectional area of the front and rear left and right support bars in the wafer loading groove is 1:
It is preferably from 0.95 to 1: 1.05. The fourth vertical wafer boat is the first or second wafer boat, wherein the two support plates have a circular plate shape in which a slit in the wafer insertion direction is provided at the center of a rear portion, and one of the left and right support bars is provided. It is characterized in that one is replaced by a reinforcing rod having no wafer loading groove. The fifth vertical wafer boat is the fourth vertical wafer boat.
Wherein the horizontal cross-sectional area of the front left and right support rods in the wafer loading groove, and the horizontal cross-sectional area of the rear support rod in the wafer loading groove and the horizontal cross-sectional area of the reinforcing rod are substantially equal. And The ratio of the horizontal cross-sectional area of the front left and right support rods in the wafer mounting groove and the ratio of the horizontal cross-sectional area of the rear support rod in the wafer mounting groove and the horizontal cross-sectional area of the reinforcing rod are 1: 0.95 to 1: 1. It is preferably 1.05. Here, "before" refers to the side where the semiconductor wafer is taken in and out. As a ceramic base material, SiC impregnated with metal Si (Si-SiC), 0.1 wt.
% B or less as a sintering aid
i ₃ N ₄ or the like is used, and as the high-purity ceramic film, a CVD-SiC film, a CVD-Si ₃ N ₄ film, a CVD
An Al ₂ O ₃ film, a SiO ₂ film formed by heating a SiC or Si ₃ N ₄ substrate in an oxidizing atmosphere, or the like.

If the horizontal cross section of each support rod in the wafer mounting groove has a polygonal shape having an acute angle of 90 ° or less, the ceramic film or the deposited CVD film is peeled off by impact force or thermal stress. The horizontal cross section of the support rod in the wafer loading groove is preferably a polygonal shape in which each corner is an obtuse angle of 100 ° or more. Chamfering is performed by sand blasting or the like, and the surface roughness of the portion is 0.3
To 500 μm, and may be any of C-plane and R-plane. When the ratio of the horizontal cross-sectional area of the support rod in the groove for loading the wafer is out of the range of 1: 0.95 to 1: 1.05, thermal distortion occurs in the upper and lower support plates, and eventually the boat is deformed or damaged. Invite. The reinforcing rods are made of the same ceramic base material as both support plates and each support rod, and the surface is covered with the same high-purity ceramic film.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1, 2 and 3 are a front view showing a first embodiment of a vertical wafer boat according to the present invention, a sectional view taken along line AA of FIG. 1 and a sectional view taken along line BB of FIG. FIG. In the figure, reference numerals 1 and 2 denote upper and lower support plates which are separated from each other. Both support plates 1 and 2 have slits in the direction of insertion into semiconductor wafer W (from bottom to top in FIG. 3) at the rear (in FIG. 3). Upper part) It has the shape of a circular plate provided in the center,
It is made of a Si-SiC ceramic substrate whose surface is covered with a CVD-SiC high-purity ceramic film. A support rod 4 in which a number of wafer loading grooves 3 are provided horizontally at regular intervals in the vertical direction between the upper and lower support plates 1 and 2 directs the wafer loading grooves 3 toward the center of the support plates 1 and 2. And a center line 5 perpendicular to the wafer insertion direction of the loaded semiconductor wafer W.
Front side (lower in FIG. 3) on the wafer insertion side than
And the reinforcing rods 8 having no wafer loading groove 3 and the supporting rods 4 are arranged in a symmetrical manner in the left-right direction (the left-right direction in FIG. 3). It is arranged symmetrically. Each of the support rods 4 and the reinforcing rods 8 has a surface C like the support plates 1 and 2.
Si-S covered with VD-SiC high-purity ceramic film
It is made of an iC ceramic substrate. The front two support rods 4 are formed in the shape of a right triangle in cross section, and the right angle part is located outside the front part. The wall part 12 of the wafer loading groove part 3 is provided substantially parallel to the wafer insertion direction. Is formed so as to have a rectangular cross section, and one side face thereof is opposed to the wafer insertion direction, and the wall 12 of the wafer loading groove 3 is formed along a circle centered on the centers of the support plates 1 and 2. Provided,
The reinforcing rod 8 has a rectangular cross section, and one side surface thereof is provided along the above-mentioned circle centering on the centers of the support plates 1 and 2. As shown in FIGS. 3 and 4, the vertical edges of the support rod 4 and the reinforcing rod 8 (including the vertical edge of the groove for loading a wafer) are chamfered 9 as shown in FIGS. The horizontal cross section of the wafer mounting groove 3 and the horizontal cross section of the reinforcing rod 8 are formed in a polygonal shape having no acute angle portion of 90 ° or less. The wall portion 12 of the wafer loading groove 3 in the support rod 4 has an R shape corresponding to the wafer outer peripheral shape.
The shape may be either linear or straight. The horizontal cross-sectional area of the front left and right support rods 4 in the wafer mounting groove 3 and the horizontal cross-sectional area of the reinforcing rod 8 and the horizontal cross-sectional area of the rear support rod 4 in the wafer mounting groove 3 are determined by the difference in thermal expansion. In order to prevent the plates 1 and 2 from being deformed or damaged, they are provided almost equally so that the ratio of the left and right areas is in the range of 1: 0.95 to 1: 1.05. On the other hand, the upper and lower support plates 1 and 2 are provided with protrusions 7 and 7 'having automatic wafer transfer reference surfaces 6 and 6' on the upper and lower sides of the wafer insertion side.

In the vertical wafer boat having the above structure,
Since the horizontal cross section of the support rod 4 in the wafer loading groove 3 and the horizontal cross section of the reinforcing rod 8 are provided in a polygonal shape having no acute angle portion of 90 ° or less, impact force or thermal stress acts on the edge portion. In this case, the ceramic film and the deposited CVD film are hardly peeled off, the service life can be increased, and the generation of particles can be prevented. The reinforcing rod 8 is a support rod 4
However, when the semiconductor wafer W is inserted into the wafer loading groove 3, the semiconductor wafer W actually comes into contact at substantially three places due to the surface accuracy of the groove 3. Three support rods 4 each having a groove 3 for
The remaining one is a reinforcing rod 8 having no wafer loading groove 3, whereby the strength of the vertical wafer boat 5 can be maintained, so that the other supporting rods 4 can be prevented from being damaged. In addition, since the number of the support rods 4 having the wafer loading groove 3 is reduced by one, the CVD film adhered to the wafer loading groove 3 in the vapor phase growth process of the wafer becomes the wafer loading groove 3 of the semiconductor wafer W. Particles that have been rubbed during the insertion and transfer to the substrate can be reduced by the amount corresponding to one support rod 4. Further, projections 7, 7 'having upper and lower reference surfaces 6, 6' for automatic wafer transfer on the uppermost and lowermost positions on the upper and lower support plates 1, 2 having substantially the same shape, respectively, at the forefront position on the insertion side of the semiconductor wafer W. When the semiconductor wafer is automatically loaded in the wafer loading groove 3 with reference to the lower reference surface 6 'in steps such as oxidation, diffusion and vapor phase growth of the semiconductor wafer, Even if the wafer repeatedly comes into contact with the wafer loading groove 3 and the groove surface is chipped or roughened, resulting in generation of particles or damage to the semiconductor wafer, the life of the wafer boat is reduced. The wafer boat 5 is turned over and the semiconductor wafer is placed in the wafer loading groove 3 with reference to the upper reference surface 6.
When the automatic loading is performed, the life of the vertical wafer boat 5 is greatly increased.

FIGS. 5, 6 and 7 are transverse sectional views showing a second embodiment of the vertical wafer boat according to the present invention, a partially enlarged view of FIG. 5, and a sectional view taken along line A'-A 'of FIG. It is an arrow view.
In this vertical wafer boat, the opening edge of the wafer loading groove 3, that is, the upper and lower horizontal edges are chamfered 10a and 10b by sandblasting, and the surface roughness of the portion is 0.3 to 500 μm. It is. Other configurations are
Since it is the same as that of the first embodiment, the same components and the like are denoted by the same reference numerals and description thereof is omitted.
Therefore, in the above-described vertical wafer boat, in addition to the same operation and effect as those of the first embodiment, the ceramic film and the attached CVD film on the upper and lower horizontal edges of the wafer loading groove 3 have an impact force. And the thermal stress makes it difficult to peel off, the service life can be further increased, and the generation of particles can be prevented.

FIGS. 8, 9 and 10 are a front view showing a third embodiment of the vertical wafer boat according to the present invention, a sectional view taken along line CC of FIG. 8, and a line DD of FIG. It is a line sectional arrow view. The upper and lower support plates 1 and 2 of this vertical wafer boat are provided with semiconductor wafers W as in the first and second embodiments.
In the insertion direction (from bottom to top in FIG. 10), a circular plate with a slit provided at the center of the rear portion (upper portion in FIG. 10), the surface of which is covered with a CVD-SiC high-purity ceramic film. -Consisting of a SiC ceramic substrate. Between the upper and lower support plates 1 and 2, four support rods 4 having a large number of wafer loading grooves 3 horizontally provided at regular intervals in the vertical direction,
A pair of front and rear support rods 4 is provided symmetrically with respect to the wafer loading groove 3 toward the center of the support plates 1 and 2 (left and right in FIG. 10). Are arranged in front of a center line 5 perpendicular to the wafer insertion direction of the semiconductor wafer W to be loaded. Each support rod 4 is made of a Si-SiC ceramic base material whose surface is covered with a high-purity CVD-SiC ceramic film. As shown in FIG. A pentagonal shape is formed, the front side of which faces the center of the support plates 1, 2, and the wall 12 of the wafer loading groove 3 is formed.
Are provided along a circle centered on the centers of the support plates 1 and 2. The support rod 4 is formed such that the peripheral vertical edge and the opening edge of the wafer loading groove 3 shown in FIG. 12, that is, the upper and lower horizontal edges are chamfered by sandblasting.
0, 11, 10a, and 10b are provided, and the horizontal section of the support rod 4 in the wafer loading groove 3 is formed in a polygonal shape having no acute angle of 90 ° or less, and the chamfers 10, 1 are formed.
The surface roughness of the portions 1, 10a, 10b is 0.3 to 500
μm. The horizontal cross-sectional area of the front and rear left and right support rods 4 in the wafer loading groove 3 is set to a ratio of 1 to 1 in order to prevent deformation and breakage of the support plates 1 and 2 due to the difference in thermal expansion of the support rods 4. : 0.95 to 1: 1.05. On the other hand, the upper and lower support plates 1 and 2 have projections 7 and 7 having automatic wafer transfer reference surfaces 6 and 6 'on the upper and lower sides on the wafer insertion side, respectively, as in the first embodiment. 'Is provided.

In the vertical wafer boat having the above structure,
Except that the support rods 4 are all the same, they have the same configuration as that of the second embodiment, and provide substantially the same operation and effect.

FIG. 13 is a cross-sectional view showing a fourth embodiment of the vertical wafer boat according to the present invention. In this vertical wafer boat, one of the two rear support rods 4 is used for the first and second support rods.
In this embodiment, the reinforcing rod 8 is used in the same manner as in the embodiment. The other configuration and operation and effect are the same as those of the third embodiment, and thus the same components and the like are denoted by the same reference numerals and description thereof is omitted.

Here, the vertical wafer boats according to the second and fourth embodiments, and similarly to the vertical wafer boats according to the second and fourth embodiments, the surface of the silicon wafer is covered with a high-purity ceramic film of CVD-SiC.
The support rod 4 is made of a SiC ceramic base material,
As shown in FIG. 4, the vertical wafer boat has an acute angle portion of 90 ° or less at the vertical edge portion and the horizontal edge portion of the wafer forming groove portion 3 is not chamfered, and the vertical wafer boat and the vertical wafer boat according to the embodiment. Similarly, FIG. 15, which is composed of a Si-SiC base material whose surface is covered with a CVD-SiC high-purity ceramic film,
Using a vertical wafer boat shown in FIG. 17, a silicon wafer having a thermal oxide film (SiCO ₂ ) formed on the surface in advance to a thickness of 100 nm is prepared, and 50 silicon wafers are loaded under the following LP-CVD conditions. Formed a 150 nm phosphorus-soaked polysilicon film on the vertical wafer boat.
In the vertical wafer boat, cracks occurred in the CVD-SiC film of the boat 700 times, whereas in the vertical wafer boat, cracks occurred in the CVD-SiC film of the boat 300 times. In the vertical wafer boat, cracks occurred, and the number of particles composed of the poly-Si film increased 500 times, and the CVD-SiC film of the boat cracked 650 times, all of which required replacement of the boat. LP-CVD conditions A. Fifty silicon wafers (100 nm thermal oxide film formed on the surface) are loaded on a boat. B. The boat is inserted into the LP-CVD furnace at normal pressure and 500 ° C. C. The pressure was reduced to 0.3 Torr while purging with N ₂ gas, and the temperature was raised to 650 ° C. D. 80% or more concentration of SiH ₄ (monosilane) gas +
He gas + PH ₃ (hydrogen phosphide) gas is charged, and a P (phosphorus) -doped poly-Si film is
It is formed to a thickness of nm. E. FIG. The supply of SiH ₄ gas, He gas and PH ₃ gas is stopped, and N ₂ gas is purged. F. Return to normal pressure and cool to 500 ° C. G. FIG. Remove the boat from the LP-CVD furnace. Therefore, it can be seen that the vertical wafer boat according to the present invention has an excellent service life.

[0013]

As described above, according to the first vertical wafer boat of the present invention, the horizontal cross section of the support rod in the groove for loading the wafer is formed in a polygonal shape having no acute angle of 90 ° or less. Therefore, even if an impact force or thermal stress acts on the vertical edge portion, the ceramic film or the adhered CVD film is hardly peeled off, the service life can be increased, and the generation of particles can be prevented. According to the second vertical wafer boat, the same function and effect as those of the first wafer boat can be obtained, and since the upper and lower horizontal edges of the wafer loading groove are chamfered, the ceramic film in that portion is chamfered. In addition, the deposited CVD film is less likely to be peeled off, the service life can be further increased, and the generation of particles can be prevented. According to the third vertical wafer boat, the same operation and effect as those of the first and second wafer boats can be obtained, and the difference in thermal expansion between the support rods is reduced, so that deformation and breakage of the support plate are prevented, and the service life is extended. Can be extended. According to the fourth vertical wafer boat, in addition to the same operation and effect as the first or second wafer boat, the strength of the vertical wafer boat can be maintained without affecting the loading and holding of semiconductor wafers at all. In addition, since the number of support rods having a wafer mounting groove serving as a particle generation source is reduced by one, the generation of particles is suppressed and the life is prolonged. Further, according to the fifth vertical wafer boat, the same operation and effect as those of the fourth one can be obtained, and the thermal expansion difference between the support rod and the reinforcing rod is reduced, so that the support plate is prevented from being deformed or damaged, and the service life is improved. Life can be extended.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of a vertical wafer boat according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a cross-sectional view of a support rod having a front wafer loading groove in the vertical wafer boat of FIG. 1;

FIG. 5 is a cross-sectional view showing a second embodiment of the vertical wafer boat according to the present invention.

FIG. 6 is a partially enlarged view of FIG. 5;

FIG. 7 is a sectional view taken along line A′-A ′ of FIG. 6;

FIG. 8 is a front view showing a third embodiment of the vertical wafer boat of the present invention.

FIG. 9 is a sectional view taken along the line CC in FIG. 8;

FIG. 10 is a sectional view taken along line DD in FIG. 8;

11 is a cross-sectional view of a support rod having a groove for loading a wafer in the vertical wafer boat of FIG. 8;

FIG. 12 is a partial longitudinal side view of a wafer loading groove of a support bar in the vertical wafer boat of FIG. 8;

FIG. 13 is a transverse sectional view showing a fourth embodiment of the vertical wafer boat according to the present invention.

FIG. 14 is a cross-sectional view of a support rod in a vertical wafer boat for comparison.

FIG. 15 is a perspective view showing a conventional vertical wafer boat.

FIG. 16 is a partial longitudinal side view of a support rod in the vertical wafer boat of FIG.

FIG. 17 is a perspective view showing another conventional vertical wafer boat.

18 is a sectional view taken along the line EE in FIG. 17;

19 is a partial longitudinal side view of a support bar in the vertical wafer boat of FIG.

[Description of Signs] 1, 2 support plate 3 wafer loading groove 4 support rod 5 center line 8 reinforcing rod 9 chamfer 10 chamfer 10a chamfer 10b chamfer 11 chamfer

Claims (7)

[Claims] 1. A support rod having a plurality of wafer mounting grooves provided between upper and lower support plates is disposed symmetrically left and right, two at a time, and both support plates and each support rod are made of a ceramic base material. The surface is covered with a high-purity ceramic film, and at least the wafer loading grooves of the front left and right support rods are provided so as to be located forward of a center line perpendicular to the wafer insertion direction of the semiconductor wafer loaded thereon, A vertical wafer boat, wherein a horizontal section of a support rod in a wafer loading groove is formed in a polygonal shape having no acute angle portion of 90 ° or less. 2. The vertical wafer boat according to claim 1, wherein the upper and lower edges of the wafer loading groove of each of the support rods are chamfered. 3. The two support plates have a circular plate shape in which a slit in the wafer insertion direction is provided at the center of the rear part, and the horizontal cross-sectional areas of the front and rear left and right support rods in the wafer loading grooves are substantially equal. The vertical wafer boat according to claim 1 or 2, wherein: 4. The ratio of the horizontal cross-sectional area of the front and rear left and right support rods in the wafer mounting groove is 1: 0.95 to 0.95.
The vertical wafer boat according to claim 3, wherein the ratio is 1: 1.05. 5. The two support plates have a circular plate shape in which a slit in the wafer insertion direction is provided at the center of the rear portion, and one of the left and right support bars is replaced with a reinforcing bar having no wafer loading groove. 3. The vertical wafer boat according to claim 1, wherein 6. The horizontal cross-sectional area of the front left and right support rods in the wafer mounting groove, and the horizontal cross-sectional area of the rear support rod in the wafer mounting groove and the horizontal cross-sectional area of the reinforcing rod are substantially equal. The vertical wafer boat according to claim 5, wherein: 7. The ratio of the horizontal cross-sectional area of the front support rod in the wafer mounting portion and the ratio of the horizontal cross-sectional area of the rear support rod in the wafer mounting groove to the horizontal cross-sectional area of the reinforcing rod are 1: 0. 7. The vertical wafer boat according to claim 6, wherein the ratio is from 95 to 1: 1.05.