JP2008071921A - Susceptor for vapor phase epitaxy, vapor phase epitaxial growth device, and vapor phase epitaxial growth method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a susceptor for vapor phase epitaxy which improves the uniformity of an epitaxial film thickness and the uniformity of flatness at the external periphery of a substrate, and can manufacture high quality epitaxial wafers efficiently. <P>SOLUTION: The susceptor for vapor phase epitaxy to hold the substrate horizontally in a vapor phase epitaxial growth device is characterized in that when the substrate is held by the susceptor, the upper surface of the susceptor is positioned in a height between the upper main plane of the substrate and the center of the substrate thickness, and that a countersink is formed so that at least the whole of the maximum external periphery of the lower main plane of the substrate and a counter-sunk bottom contact with each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a susceptor for vapor phase growth mainly used for manufacturing an epitaxial wafer, a vapor phase growth apparatus including the susceptor, and a vapor phase growth method using the susceptor, and more specifically, holds a target substrate substantially horizontally. The present invention relates to a horizontal disk type vapor phase susceptor, a vapor phase growth apparatus including the same, and a vapor phase growth method.

  Vapor phase epitaxial growth technology is a technology for vapor phase growth of a single crystal thin film layer used in the manufacture of integrated circuits such as bipolar transistors and MOSLSIs. A uniform single crystal layer is formed on a clean semiconductor single crystal substrate in accordance with the crystal orientation of the substrate. This is an extremely important technique because a crystal thin film can be grown and a steep impurity concentration gradient of a junction having a large dopant concentration difference can be formed. As the vapor phase epitaxial growth apparatus, three types are generally used: a vertical type (pancake type), a barrel type (cylinder type), and a horizontal type. The basic principle of these growth apparatuses is common.

  FIG. 5 is a schematic cross-sectional view showing an example of a conventional vertical vapor phase growth apparatus. In this vertical type vapor phase growth apparatus 21, a reaction chamber 4 is formed by mounting a bell-shaped bell jar 3 on a base plate 2. In this reaction chamber 4, a horizontal disk type susceptor 16 for placing a semiconductor substrate (wafer) 5 is disposed horizontally, and a high-frequency heating coil 7 for heating the substrate 5 via the susceptor 16 is disposed on the lower surface thereof. A coil cover 8 is provided. At the time of vapor phase growth, the substrate 5 is placed on a counterbore 19 that is a circular recess provided on the upper surface of the susceptor 16, the source gas is supplied from the gas inlet 10, and is provided on the side surface or upper surface of the nozzle 11. The gas is ejected from the ejection hole 12 introduced into the reaction chamber 4 and discharged from the gas discharge port 13. At this time, since the substrate 5 is heated by the high-frequency heating coil 7, the raw material gas ejected onto the substrate reacts on the substrate surface, and a thin-film epitaxial layer can be vapor-grown on the substrate surface.

  One type of horizontal vapor phase growth apparatus is a single wafer type apparatus. In this apparatus, a substrate is placed on a horizontal disk-type susceptor disposed in a horizontal heating furnace, and the raw material gas is circulated in the horizontal direction in the furnace while rotating the substrate around the vertical axis. An epitaxial layer is formed on the substrate surface. Such an apparatus is frequently used as the substrate has a larger diameter, and is regarded as the mainstream as an apparatus that can handle a substrate having a diameter of 300 mm.

  In these vapor phase growth apparatuses, a circular recess for accommodating the substrate 5 is provided on the top surface of the susceptor 16 as shown in FIG. Then, the substrate 5 is accommodated in this recess called counterbore 19 and epitaxial growth is performed (see, for example, Patent Document 1).

By the way, the flow of the source gas has a great influence on the uniformity of the epitaxial layer.
The first effect is that the deposition rate of the epitaxial layer decreases from the upstream side to the downstream side of the source gas. This occurs because consumption of Si in the raw material gas occurs on the upstream side, and the concentration of the raw material gas decreases toward the downstream side.

As a countermeasure, in the case of a single wafer type apparatus which is a kind of horizontal vapor phase growth apparatus, the substrate itself is rotated to eliminate the upstream and downstream influences of the source gas and to improve the film thickness uniformity of the epitaxial layer. ing.
Also, in the vertical vapor phase growth apparatus (vertical vapor phase reactor), the number and height of the gas outlets installed in the nozzles are adjusted, and the epitaxial film thickness is uneven from upstream to downstream of the source gas. It has been suppressed.

  The second effect is a change in film thickness in the vicinity of the outer periphery of the substrate. As shown in FIG. 3, in the vicinity of the outer peripheral portion (edge) of the counterbore 19, gas stays between the side wall of the counterbore 19 and the side surface of the substrate 5 (stepped portion), which becomes a stagnation region, Accumulation is delayed. As a result, the thickness of the epitaxial layer (epi film thickness) becomes thin near the outer periphery of the substrate. As a method of suppressing this, it is effective to lower the growth rate of the epitaxial layer and strengthen the transport-limited reaction. However, since the growth rate is lowered, there is a problem that productivity is lowered and cost is increased. It was.

Japanese Patent Laid-Open No. 2003-12397

  The present invention has been made in view of such problems, and improves the uniformity of the epitaxial film thickness and the uniformity of the flatness at the outer peripheral portion of the substrate, so that a high-quality epitaxial wafer can be efficiently produced. An object is to provide a growth susceptor, a vapor phase growth apparatus, and a vapor phase growth method.

  In order to achieve the above object, the present invention provides a vapor phase growth susceptor for horizontally holding a substrate in a vapor phase growth apparatus, wherein the susceptor is a top surface of the susceptor when the substrate is held by the susceptor. However, the counterbore is formed so that it is located at the height between the upper main surface of the substrate and the thickness center of the substrate and at least the entire outermost peripheral portion of the lower main surface of the substrate is in contact with the counterbore bottom. A susceptor for vapor phase growth is provided (claim 1).

  Thus, when the substrate is held by the susceptor, the upper surface of the susceptor is positioned at a height between the upper main surface of the substrate and the center of the substrate thickness, and at least the entire outermost peripheral portion of the lower main surface of the substrate By using the susceptor for vapor phase growth in which the counterbore is formed so that the counterbore is in contact with the counterbore bottom, the uniformity of the epitaxial film thickness and the flatness of the outer periphery of the substrate can be improved. At this time, since it is not necessary to lower the epitaxial growth rate, a high-quality epitaxial wafer can be produced efficiently.

  Further, the present invention provides at least the susceptor for vapor phase growth according to the present invention, a reaction chamber for housing the susceptor, a heat source for heating the substrate, and a gas inlet for introducing a source gas into the reaction chamber. And a gas phase growth apparatus comprising a gas discharge port for discharging the source gas from the reaction chamber (claim 2).

  Thus, by using the vapor phase growth apparatus equipped with the susceptor for vapor phase growth of the present invention, the uniformity of the epitaxial film thickness and the flatness uniformity at the outer peripheral portion of the substrate can be improved, and high quality epitaxial can be achieved. Can produce wafers efficiently.

  The present invention is also a method of vapor-phase epitaxial layer growth on a substrate, wherein at least the substrate is held by the susceptor of the present invention, and a source gas is supplied while heating the held substrate. And providing a vapor phase growth method characterized in that an epitaxial layer is vapor-grown on a substrate.

  Thus, if the substrate is held by the susceptor of the present invention and the epitaxial layer is vapor-phase grown on the substrate, the uniformity of the thickness of the epitaxial layer and the uniformity of the flatness at the outer periphery of the substrate can be improved. It is possible to improve and efficiently produce high quality epitaxial wafers.

  As described above, by using the susceptor for vapor phase growth of the present invention at the time of vapor phase growth, the uniformity of the thickness of the epitaxial layer and the uniformity of flatness at the outer peripheral portion of the substrate are improved, and high quality is achieved. Can be produced efficiently.

Hereinafter, the present invention will be described in further detail.
As described above, when a conventional vapor phase growth susceptor is used, gas stays between the counterbore side wall and the side surface of the substrate (stepped portion) near the outer periphery (edge) of the counterbore. As a result, the deposition of the epitaxial layer is delayed, and as a result, the thickness of the epitaxial layer (epi film thickness) is reduced in the vicinity of the outer peripheral portion of the substrate. It sometimes worsened. As a method of suppressing this, conventionally, a method of reducing the growth rate of the epitaxial layer and strengthening the transport-controlled reaction has been taken, but this reduces the growth rate, thereby reducing the productivity and increasing the cost. There was a problem of causing.

  Therefore, the present inventors conducted extensive studies to develop a method for effectively preventing the occurrence of non-uniform epi film thickness on the outer periphery of the substrate without reducing productivity, and holding the substrate with a susceptor. The upper surface of the susceptor (the main surface without the counterbore) should be the same as or lower than the upper main surface of the substrate, and at least the entire outermost periphery of the lower main surface of the substrate and the counterbore If the bottom is in contact, the stagnation region of the source gas in the vicinity of the outer peripheral portion (edge) of the substrate disappears, and the source gas does not wrap around the main surface under the substrate, and the epi film deposition rate decreases, that is, the epi film thickness It was found that the film thickness can be suppressed. On the other hand, if the upper surface of the susceptor is too lower than the upper main surface of the substrate, the substrate jumps out of the counterbore pocket, so-called counterboreening occurs. In order to suppress this, at least the upper surface of the susceptor must be equal to or higher than the substrate thickness center height. Therefore, the present inventors combined these two, and when the substrate is placed on the susceptor, the upper surface of the susceptor is positioned at a height between the upper main surface of the substrate and the thickness center of the substrate, The inventors have conceived that the film thickness can be made uniform and the flatness can be improved at the outer periphery of the substrate without reducing the productivity, and the present invention has been completed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.
FIG. 2 is a schematic cross-sectional view showing an example of counterbore of the susceptor for vapor phase growth according to the present invention. FIG. 2A shows an example in which the counterbore 9 is formed so that the upper surface of the susceptor 6 is positioned at the same height as the upper main surface of the substrate 5 when the substrate 5 is held by the susceptor 6. b) shows an example in which the counterbore 9 is formed such that the upper surface of the susceptor 6 is lower than the upper main surface of the substrate 5 and higher than the height of the substrate thickness center. Thus, in the susceptor of the present invention, when the substrate is held by the susceptor, the counterbore is formed so that the upper surface of the susceptor is positioned at a height between the upper main surface of the substrate and the thickness center of the substrate. .
In addition, the susceptor of the present invention has a counterbore formed so that at least the entire outermost peripheral part of the lower main surface of the substrate is in contact with the counterbore bottom. In the example of FIG. 2, since the counterbore bottom is formed flat, the entire lower main surface of the substrate is in contact with the counterbore bottom. In addition to this, for example, by forming the counterbore bottom in a concave shape, at least a part of the lower main surface of the substrate including the entire outermost peripheral portion of the lower main surface of the substrate can be in contact with the counterbore bottom.

  As described above, the upper surface of the susceptor is made equal to or lower than the height of the upper main surface of the substrate, and at least the entire outermost peripheral portion of the lower main surface of the substrate is in contact with the counterbore bottom, so Thus, it is possible to eliminate the stagnation region of the source gas in the substrate and to suppress the reduction of the epi film deposition rate, that is, the reduction of the epi film thickness, thereby providing an epitaxial wafer having a higher epi film thickness uniformity than in the prior art. On the other hand, by making the upper surface of the susceptor higher than the center thickness of the substrate, it is possible to sufficiently prevent the substrate from coming off. By using such a susceptor, it is possible to improve the film thickness uniformity and flatness near the outer periphery of the substrate without reducing the growth rate, so that efficient epitaxial can be achieved without reducing productivity. Wafer can be manufactured.

  The overall shape of the susceptor for vapor phase growth of the present invention is, for example, a disk type, but is not particularly limited, and one or more counterbore can be formed. The diameter or the like of the counterbore can be appropriately selected according to the size of the substrate to be placed.

Here, FIG. 1 is a schematic sectional view showing an example of the vapor phase growth apparatus of the present invention.
In this vertical type vapor phase growth apparatus 1, a reaction chamber 4 is formed by mounting a bell-shaped bell jar 3 on a base plate 2. A horizontal disk type susceptor 6 on which the substrate 5 is placed is horizontally disposed in the reaction chamber 4, and a high-frequency heating coil 7 is provided on the lower surface of the reaction chamber 4 as a heat source for heating the substrate 5 via the susceptor 6. 8 is provided. Further, this vapor phase growth apparatus includes a gas inlet 10 for introducing a source gas into the reaction chamber 4 and a gas outlet 13 for discharging the source gas from the reaction chamber 4.

The susceptor provided in the vapor phase growth apparatus of the present invention is the susceptor of the present invention, and for example, a susceptor having a counterbore shown in FIG. 2 can be used. By using the vapor phase growth apparatus provided with the susceptor according to the present invention, it is possible to suppress the decrease in the deposition rate of the epi film thickness at the outer peripheral portion of the substrate, and to improve the uniformity of the epi film thickness and the flatness. Therefore, the epitaxial layer can be grown in a vapor phase with high productivity, and it is possible to prevent the source gas from flowing into the main surface under the substrate and autodoping.
The vapor phase growth apparatus of the present invention is not limited to such a vertical type, and may be a horizontal type.

Next, the vapor deposition method of the present invention in which a thin film is vapor-grown on the surface of the substrate will be described by taking as an example the case of using the vapor deposition apparatus of the present invention of FIG.
First, the substrate (wafer) 5 is placed on the counterbore 9 of the susceptor 6 of the present invention and held by the susceptor 6. Then, while the held substrate 5 is heated by the high-frequency heating coil 7, the raw material gas is supplied from the gas introduction port 10, and ejected from the ejection holes 12 provided on the side surface and the upper surface of the nozzle 11 and introduced into the reaction chamber 4. The gas is discharged from the gas outlet 13. At this time, since the substrate 5 is heated by the high-frequency heating coil 7, the ejected raw material gas reacts on the substrate surface, and a thin-film epitaxial layer can be vapor-phase grown on the substrate surface.

  At this time, since the upper surface of the susceptor is equal to or lower than the height of the upper main surface of the substrate, there is no source gas stagnation region near the outer periphery of the counterbore, and at least the entire outermost periphery of the lower main surface of the substrate is in contact with the counterbore bottom. Since the counterbore is formed, the source gas does not circulate to the lower surface of the substrate, the epi film deposition rate does not decrease at the outer periphery of the substrate, and the epitaxial film thickness becomes uniform near the outer periphery of the substrate. Improves flatness. For this reason, it is not necessary to reduce the growth rate, and vapor phase growth can be performed with high productivity.

In addition, examples of the substrate on which the epitaxial layer is vapor-grown while being held by the vapor-phase growth susceptor of the present invention include a silicon wafer, but other semiconductor wafers such as a compound semiconductor may be used, and there is no particular limitation. Not.
Moreover, as an epitaxial layer (thin film) to be vapor-phase grown, for example, a silicon thin film can be exemplified, but other semiconductor thin films such as Si-Ge may be vapor-grown by appropriately selecting a source gas, There is no particular limitation.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, it cannot be overemphasized that this invention is not limited to this.
(Examples 1-4, Comparative Examples 1-3)
The vertical vapor phase growth apparatus shown in FIG. 1 or FIG. 5 was used.
First, a silicon wafer having a diameter of 150 mm and a thickness of 600 μm (0.6 mm) was held by a vapor phase growth susceptor, that is, housed in a counterbore of the vapor phase growth susceptor. Then, an epitaxial layer (silicon thin film) was vapor-phase grown on the silicon wafer by supplying the source gas while heating the held wafer.

At this time, the following seven types of susceptors were used as vapor phase growth susceptors. These susceptors are obtained by changing the height of the upper surface of the susceptor relative to the upper main surface of the substrate by changing the depth of the counterbore. In these susceptors, the bottom of the susceptor is formed flat, and the counterbore is formed so that the entire lower main surface of the substrate is in contact with the bottom of the sagittal.
(1) Counterbore is formed such that the height of the upper surface of the susceptor with respect to the upper main surface of the substrate is ± 0 mm (Example 1).
(2) A counterbore formed so that the height of the upper surface of the susceptor with respect to the upper main surface of the substrate is -0.1 mm (Example 2).
(3) A counterbore formed so that the height of the upper surface of the susceptor with respect to the upper main surface of the substrate is -0.2 mm (Example 3).
(4) A counterbore formed so that the height of the upper surface of the susceptor relative to the upper main surface of the substrate is -0.3 mm (Example 4).
(5) A counterbore formed so that the height of the upper surface of the susceptor with respect to the upper main surface of the substrate is +0.2 mm (Comparative Example 1).
(6) A counterbore formed so that the height of the upper surface of the susceptor with respect to the upper main surface of the substrate is +0.4 mm (Comparative Example 2).
(7) Counterbore formed so that the height of the upper surface of the susceptor relative to the upper main surface of the substrate is -0.4 mm (Comparative Example 3).
The positive value means that the upper surface of the susceptor is located higher than the upper main surface of the substrate, and the negative value means that the upper surface of the susceptor is lower than the upper main surface of the substrate. It means that it is located.

In each of the above examples and comparative examples, epitaxial growth was performed on 30 wafers.
SiHCl ₃ was used as a reaction gas, the growth rate was 1.5 μm / min, the reaction temperature was 1050 ° C., and the growth film thickness was 120 μm.

  Then, the flatness value of the outer peripheral portion of the wafer was investigated for the wafer after the vapor phase growth of the epitaxial layer. The flatness referred to here is LTV, and the average of the LTV of cells located on the outer periphery of the wafer is the flatness of the outer periphery. Note that the flatness of the substrate before vapor phase growth is extremely good, and the flatness changes due to variations in the thickness of the epitaxial layer. Therefore, the uniformity of the film thickness can be evaluated by measuring the flatness.

FIG. 4 is a graph showing the relationship between the height of the upper surface of the susceptor relative to the upper main surface of the substrate and the wafer outer peripheral flatness (LTV) (Examples 1 to 4, Comparative Examples 1 and 2).
As shown in FIG. 4, as the height of the upper surface of the susceptor with respect to the upper main surface of the substrate becomes lower, the flatness of the outer peripheral portion of the substrate becomes better.
On the other hand, in the susceptor of Comparative Example 3 in which the counterbore was formed so that the upper surface of the susceptor was positioned lower than the center of the substrate thickness, it was confirmed that the substrate was frequently counterbored and could not be put into practical use.
In the susceptors of Examples 1 to 4, the counterbore is formed so that the entire lower main surface of the substrate is in contact with the bottom of the counterbore as described above. In these susceptors, it was confirmed that the source gas can be prevented from flowing into the lower main surface of the substrate during vapor phase growth, and autodoping can also be prevented.

  From these results, it is possible to improve the uniformity of the epitaxial film thickness and the flatness at the outer periphery of the substrate, efficiently produce a high quality epitaxial wafer, and under the source gas substrate during vapor phase growth. In order to prevent wraparound to the main surface and auto-doping, the susceptor is positioned so that the upper surface of the susceptor is located at a height between the upper main surface of the substrate and the thickness center of the substrate when the substrate is held by the susceptor. In addition, it is understood that it is desirable that the counterbore is formed so that at least the entire outermost peripheral portion of the lower main surface of the substrate is in contact with the counterbore bottom.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a cross-sectional schematic explanatory drawing which shows an example of the vapor phase growth apparatus of this invention. It is a cross-sectional schematic explanatory drawing of the counterbore of the susceptor for vapor phase growth according to this invention. It is a schematic diagram which shows the flow of the source gas in the board | substrate outer peripheral part vicinity. It is a figure which shows the relationship between the height of the upper surface of a susceptor with respect to the upper main surface of a board | substrate, and the flatness of an outer peripheral part of a board | substrate (Examples 1-4, Comparative Examples 1 and 2). It is a cross-sectional schematic explanatory drawing which shows an example of the conventional vapor phase growth apparatus.

Explanation of symbols

1, 21 ... Vertical vapor phase growth apparatus, 2 ... Base plate, 3 ... Berja,
4 ... reaction chamber, 5 ... substrate, 6, 16 ... susceptor, 7 ... high frequency heating coil,
8 ... Coil cover, 9, 19 ... Counterbore, 10 ... Gas inlet, 11 ... Nozzle,
12 ... ejection hole, 13 ... gas discharge port.

Claims (3)

  A susceptor for vapor phase growth for horizontally holding a substrate in a vapor phase growth apparatus, wherein the susceptor has an upper surface of the susceptor, the upper main surface of the substrate and the thickness of the substrate when the substrate is held by the susceptor. A susceptor for vapor phase growth, characterized in that the counterbore is formed at a height between the centers and so that at least the entire outermost peripheral portion of the lower main surface of the substrate is in contact with the counterbore bottom.   The susceptor for vapor phase growth according to claim 1, a reaction chamber containing the susceptor, a heat source for heating the substrate, a gas inlet for introducing a source gas into the reaction chamber, and a reaction chamber A vapor phase growth apparatus comprising a gas discharge port for discharging a source gas from a gas.   A method for vapor phase growth of an epitaxial layer on a substrate, wherein at least the substrate is held by the susceptor according to claim 1, and the source gas is supplied while heating the held substrate, whereby the substrate is epitaxially grown. A vapor phase growth method characterized by vapor-depositing a layer.

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