JPH06112126A - Cylinder type silicon epitaxial-layer growth device - Google Patents

Abstract

PURPOSE:To prevent generation in a substrate of a crack resulting from sticking to a susceptor after the growth of an epitaxial layer by specifying the spaces and height of projections formed in a bilaterally symmetrical manner to a vertical line passing through the center of a pocket in the lower half of the inner circumferential surface of the pocket. CONSTITUTION:Projection sections 4 are formed on the inner circumferential surface 5 of a pocket, and a silicon single crystal substrate 21 is held into a pocket 2 by abutting the circumferential section of the substrate 21 against the projection sections 4. The height of the projection sections 4 is formed so that the outer circumference of the silicon substrate 21 is separated from the inner circumferential surface 5 of the pocket by at least 0.5mm or more. On the other hand, the projection sections 4 are formed in a bilaterally symmetrical manner to a vertical line L passing through the center of the pocket in the lower half of the inner circumference of the pocket, and the space of the projections is set in 1/20-1/5 of the peripheral length of the silicon substrate. Accordingly, when a silicon epitaxial substrate with a silicon epitaxial layer in thickness of 30mum or more is manufactured, no crack is generated in the substrate at a growth rate of 1.5mum/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pocket structure for holding a silicon substrate in a cylinder type silicon epitaxial layer growing apparatus.

[0002]

2. Description of the Related Art The above-mentioned cylinder type silicon epitaxial layer growth apparatus has a structure shown in FIG. 5, and a polygonal truncated pyramid-shaped susceptor 12 is provided in a cylinder type reaction tube 11 made of quartz.
Is rotatably provided, a silicon single crystal substrate (not shown) is installed in a pocket 13 of a circular recess formed on the side wall surface of the susceptor 12, and the reaction tube 11 is heated by the heater 14 to rotate the susceptor 12. At the same time, the epitaxial growth raw material gas 15 is passed through the reaction tube 11 in a downward flow to grow the silicon epitaxial layer.

The susceptor 12 has a carbon base material and S
iC coating is applied, the pocket 13 is formed as a simple circular recess, and no special structure for holding the silicon substrate is provided in the pocket 13. Therefore, the silicon substrate 2 is
As shown in FIGS. 6 and 7, in No. 1, the inner peripheral surface (inner edge) 13a of the lower part of the pocket contacts the tip of the chamfered part of the substrate, while the upper part of the pocket makes contact with the bottom face 13b of the pocket at the back end of the substrate. It is held by.

In recent years, there has been an increasing demand for a silicon epitaxial substrate having a thick epitaxial layer for a high withstand voltage large current element including an IGBT. When using a cylinder type silicon epitaxial growth apparatus to grow an epitaxial layer having a film thickness of 30 μm or more using trichlorosilane as a silicon source, for example, 125 mmφ, C
When the zP type <100> and the thickness = 450 μm are used and the reaction temperature is less than 1100 ° C. and the growth rate of the epitaxial layer exceeds 1.25 μm / min, the adhesion between the susceptor and the substrate is caused after the epitaxial layer growth. That is, a crack (crack, chip) of the silicon substrate occurs. This crack is generated in a portion of the chamfered portion of the silicon substrate which comes into contact with the inner edge of the lower portion of the pocket.

[0005]

The generation of cracks due to the sticking becomes more remarkable as the reaction temperature is lower, the epitaxial layer growth rate is higher, and the epitaxial layer is thicker. Therefore, in order to grow a thick epitaxial layer, a manufacturing method has been generally adopted in which the growth temperature is raised and the growth rate is lowered. However, in this manufacturing method, not only the productivity is lowered, but also any one of the conditions is a reaction condition in which the edge crown increases, so that another problem of occurrence of an edge crown occurs.

The cause of the sticking of the silicon substrate is considered as follows. As described above, in the case of the conventional susceptor, the substrate is prepared as shown in the front view of FIG. 6 and the cross-sectional view of FIG. 7, but when the epitaxial layer is grown on this, the cross-sectional view of FIG. As shown, a silicon layer grows on the substrate 21 and the susceptor 12 (the single crystal silicon layer 31, the susceptor 12 on the substrate 21).
Above is a polycrystalline silicon layer 32). As a result, during the growth of the epitaxial layer, as shown in FIGS. 8 and 9, due to bridging by the polycrystalline silicon 32, sticking occurs at the lower inner edge of the pocket 13 and the chamfered portion of the substrate. The sticking occurs at a position where the distance between the substrate and the inner edge of the pocket is a certain amount or less. When the growth is completed and the cooling process is started, the progress of cooling and the coefficient of thermal expansion of the carbon susceptor and the silicon substrate are different, so that the substrate tries to move in the susceptor pocket. However, this movement is hindered by the sticking over a wide area as shown in FIG. 8 under the substrate. As a result, stress concentrates on the chamfered portion of the substrate at the adhered portion, causing cracks.

The present invention has been made in view of the above points, and an object thereof is to manufacture an epitaxial layer when a silicon epitaxial substrate having a silicon epitaxial layer of 30 μm or more is manufactured using a cylinder type silicon epitaxial layer growth apparatus. It is an object of the present invention to provide a pocket structure of a susceptor that can prevent cracks due to sticking with a susceptor from occurring on a substrate after growth.

[0008]

A cylinder type silicon epitaxial layer growth apparatus of the present invention is an epitaxial growth apparatus in which a susceptor having a pocket for holding a silicon single crystal substrate is provided in a cylinder type reaction tube. A protrusion is provided in the lower half of the inner circumference of the pocket so as to be bilaterally symmetric with respect to a vertical line passing through the center of the pocket. The height of the protrusion toward the center of the pocket is 1/5, and the distance between the outer periphery of the protrusion and the inner periphery of the pocket when the silicon substrate is loaded is at least 0.
It is characterized in that it is selected to be 5 mm or more so that the silicon substrate can be held by the protrusions.

On the other hand, in the lower half of the inner circumference of the pocket, the projection has a sawtooth-like continuation of a saw blade edge symmetrical to a vertical line passing through the center of the pocket, which is 1/20 of the outer peripheral length of the silicon substrate. Selected in the range of ~ 1/5,
The height of the protrusion toward the center of the pocket is selected so that the distance between the outer periphery of the protrusion and the inner periphery of the pocket is at least 0.5 mm when the silicon substrate is loaded, and the protrusion can hold the silicon substrate. It may be the one that has been done.

[0010]

In the present invention, since the silicon substrate charged in the susceptor is held in the pocket by contacting only the protrusions provided in the pocket, sticking after the epitaxial layer growth occurs only in a small portion, As a result, when the substrate tries to move due to the difference in the coefficient of thermal expansion during cooling, cracks occur in the polysilicon of the bridge portion, and no cracks occur in the substrate. Even if a certain amount of stress is concentrated on the chamfered portion of the substrate that is in contact with the protrusion, if the contact portion between the substrate and the protrusion is separated from the orientation flat portion and the circumferential portion of the substrate to some extent, the chamfered portion will be Since it is mechanically strong, the occurrence of dislocations can be suppressed.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows a skeleton of this embodiment, wherein 1 is a hexagonal frustum-shaped carbon susceptor with a SiC coat, 2 is a pocket of circular recesses formed in two upper and lower steps on the side wall surface of this susceptor, 3 Is a bottom surface of the pocket, 4 is a protrusion formed on the inner peripheral surface (inner edge portion) 5 of the pocket, and the silicon single crystal substrate 21 is placed inside the pocket 2 by bringing its peripheral portion into contact with the protrusion 4. Is held. In addition, 1a shows the upper surface of the susceptor. In the pocket 2, the peripheral surface (circumferential portion and orientation flat portion 21 a) of the substrate 21 is in contact only with the protrusion 4, and is not in contact with the arcuate inner peripheral surface of the pocket 2.

The protrusions 4 are made of the same material as the susceptor 1 and coated with SiC. The height of the protrusion 4 is selected so that the outer periphery of the silicon substrate 21 is separated from the inner peripheral surface 5 of the pocket by at least 0.5 mm or more. On the other hand, it is important that the silicon substrate 21 is placed on the protrusion 4 and can be stably held. For that purpose, as shown in FIG. 1, in the lower half of the inner circumference of the pocket, the protrusions 4 are provided so as to be symmetrical with respect to the vertical line L passing through the center of the pocket, and the intervals between the protrusions are equal to the outer peripheral length of the silicon substrate. 1/20
It is good to be 1/5. As a mode of charging the silicon substrate into the pocket, any method may be used as long as the boundary between the orientation flat portion and the substrate circumferential portion does not come into contact with the protrusion.

Next, this embodiment will be described in more detail with reference to FIGS. 2 to 5. In FIGS. 2 and 5, the hexagonal truncated pyramid-shaped susceptor 1 has three inner surfaces as shown in FIG. Surface 5
A pocket 2 having a protrusion 4 is provided on the other side, and a pocket (not shown) having the same shape and size as the pocket 2 is provided on each of the other three surfaces except that no protrusion is provided. The protrusion 4 is formed at the same time when the pocket 2 of the susceptor 1 is formed. Therefore, the base material of the protrusion 4 and the base material of the susceptor 1 are made of the same carbon material, and the SiC coating is performed at the same time. The composition and the film thickness are the same for the protrusion 4 and the susceptor 1.

The sectional shape of the pocket is as shown in FIG. 3, and the pocket inner peripheral surface 5 is provided on the outer peripheral portion of the bottom surface 3 of the pocket.
An annular groove 6 is formed along the ridge with a uniform depth and width. In this case, the susceptor top surface 1a of the pocket bottom surface 3
Is 1.4 mm, the depth of the groove 6 is 1.6 mm with respect to the upper surface 1a of the susceptor, and 0.2 mm with respect to the bottom surface 3 of the pocket.

The planar shape of the protrusion 4 (enlarged part A in FIG. 2) is as shown in FIG. 4, and the upper surface 1a of the susceptor is shown.
Has a shape in which a part thereof is extended between the ends of the grooves 6 and 6 in a substantially semicircular shape, and the extended portion serves as the protrusion 4. As a result, in this embodiment, as is apparent from FIG. 4, the contact between the outer peripheral surface of the silicon substrate 21 and the inner peripheral surface of the pocket 21 is improved from the conventional line contact to the point contact. In FIG. 4, the hatched portion indicates the bottom surface 3 of the pocket, and the dotted portion indicates the susceptor upper surface 1a. As is clear from FIG. 3, the relationship between the heights is: susceptor top surface 1a> pocket bottom surface 3> groove 6.

An experiment was conducted using the above susceptor to grow an epitaxial layer having a thickness of 100 μm. As a silicon single crystal substrate, 125 mmφ, CzP type <100>,
Using a CVD oxide film having a thickness of 450 μm and a thickness of 1000 nm on the back surface (no chamfered portion), 12 sheets per batch were placed in a pocket with the orientation flat portion facing upward. Trichlorosilane was used as the silicon source. The reaction temperature was 1130 ° C., and the growth rate of the epitaxial layer was 1.50 μm / min.
In this way, an epitaxial layer was grown on a total of 120 batches of silicon substrates for a total of 10 batches. When the chamfered portion of the silicon substrate was precisely observed after growth of the epitaxial layer, 54 cracked substrates were present in 60 substrates produced with pockets without protrusions (incidence rate = 90%). However, no cracks were found in the substrate prepared in the pocket with the protrusion (incidence rate =
0%). In addition, the substrate 6 manufactured with a pocket having a protrusion
The size of the edge crowns of all 0 sheets was 7 μm or less on the growth surface of the epitaxial layer, which was not a problematic level. Furthermore, the above 60 substrates are
After immersing in the o liquid for 1 minute and performing etching, the dislocation density of the outer peripheral portion of the substrate was measured. As a result, dislocations were generated only in the vicinity of the chamfered portion which was considered to be in contact with the protrusions, but all 10 ³ /
At a level of cm ² or less, there was no particular problematic level.

According to the experience of the present inventors, the height of the protrusion 4 should be selected so that the outer circumference of the silicon substrate is separated from the inner circumference of the pocket by at least 0.5 mm or more. If there is not a sufficient gap between the outer circumference of the silicon substrate and the inner circumference of the pocket, polycrystalline silicon grows so as to bridge the gaps between them and cracks due to sticking occur at the chamfered portion of the substrate. .

In the above embodiment, the case where two protrusions 4 are provided so as to be bilaterally symmetrical in the lower half of the inner circumference of the pocket has been described. However, the number of protrusions 4 is three or more. Good. In addition, as shown in FIG.
Even if they are further connected to form a saw-toothed blade, the same result as in the above-described embodiment can be obtained.

[0019]

As is apparent from the above description, according to the present invention, by providing the protrusions on the inner surface of the pocket of the susceptor, the silicon substrate is provided with the arc-shaped inner peripheral surface (inner edge portion) of the pocket.
A silicon epitaxial substrate having a silicon epitaxial layer with a thickness of 30 μm or more using a cylinder type silicon epitaxial layer growth apparatus, because the epitaxial layer can be grown by holding it in a pocket while being separated from 1.5 μm when manufacturing
Even at a growth rate of / min, it became possible to prevent the occurrence of substrate cracks due to the sticking of the substrate and the susceptor.

[Brief description of drawings]

FIG. 1 is a schematic front view of a susceptor for explaining the essence of an embodiment of the present invention.

FIG. 2 is a front view of the susceptor according to the first embodiment.

3 is a cross-sectional view taken along line XX of FIG.

FIG. 4 is an enlarged view of part A in FIG.

FIG. 5 is a schematic sectional view of a conventional cylinder type epitaxial layer growth apparatus.

6 is an explanatory front view showing a state in which a silicon substrate is loaded in a pocket of a susceptor in the apparatus shown in FIG.

7 is a cross-sectional view taken along the line YY of FIG.

FIG. 8 is an explanatory front view showing a state where the susceptor and the silicon substrate are attached to each other when the silicon substrate is prepared as shown in FIG.

9 is a sectional view taken along line ZZ of FIG.

FIG. 10 is an explanatory front view of a susceptor having pockets whose protrusions are connected in a sawtooth shape.

[Explanation of symbols]

 1 Susceptor 1a Upper surface 2 Pocket 3 Bottom surface 4 Protrusion 5 Inner peripheral surface (inner edge) 6 Groove 11 Reaction tube 12 Susceptor 13 Pocket 13a Inner peripheral surface (inner edge) 13b Bottom 14 Heater 15 Raw material gas 21 Substrate 21a Orientation flat part 31 Single crystal silicon layer 32 Polycrystal silicon layer L Vertical line

Claims (2)

[Claims] 1. An epitaxial growth apparatus in which a susceptor having a pocket for holding a silicon single crystal substrate is provided in a cylindrical reaction tube, wherein an annular groove is provided at an outer peripheral portion of the bottom surface of the pocket, and a pocket is provided in a lower half of the inner peripheral portion of the pocket. The protrusions are provided so as to be bilaterally symmetrical with respect to a vertical line passing through the center of the protrusion, and the distance between the protrusions is 1/20 to 1/5 of the outer peripheral length of the silicon substrate. A cylinder is selected such that the distance between the outer circumference of the silicon substrate and the inner circumference of the pocket is at least 0.5 mm when the silicon substrate is loaded, and the protrusion can hold the silicon substrate. Type silicon epitaxial layer growth equipment. 2. An epitaxial growth apparatus in which a susceptor having a pocket for holding a silicon single crystal substrate is provided in a cylinder type reaction tube, wherein an annular groove is provided at an outer peripheral portion of the bottom surface of the pocket, and a pocket is provided at a lower half of the inner peripheral portion of the pocket. Saw blade-shaped continuity of protrusions is 1/2 of the outer peripheral length of the silicon substrate so as to be symmetrical with respect to a vertical line passing through the center of
The height of the protrusion toward the center of the pocket is selected such that the distance between the outer periphery of the protrusion and the inner periphery of the pocket is at least 0.5 mm when the silicon substrate is loaded. 2. The cylinder type silicon epitaxial layer growth apparatus according to claim 1, wherein the protrusion can hold the silicon substrate.