JP2008071917A - Susceptor, device, and method for vapor-phase epitaxial growth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor-phase epitaxial growth susceptor capable of improving an epitaxial layer located on the peripheral part of a substrate in the uniformity of a thickness and flatness and manufacturing an epitaxial wafer of high quality with a high yield. <P>SOLUTION: The vapor-phase epitaxial growth susceptor is provided with one or more countersinks where substrates are obliquely placed and supported by their lower ends. The vapor-phase epitaxial growth susceptor is characterized in that the countersink becomes gradually deeper from the upstream to the downstream side of a material gas which is supplied at vapor-phase epitaxial growth. <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, in the vicinity of an outer peripheral portion of a target substrate. The present invention relates to a susceptor for vapor phase growth for improving uniformity of epitaxial layer thickness and flatness, 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. 7 is a schematic cross-sectional view showing an example of a vapor phase growth apparatus. In this barrel type vapor phase growth apparatus, a reaction chamber 9 is formed by placing a seal plate 8 on which a susceptor 2 is suspended in a bell jar 1 fixed in an inverted bell shape. In this reaction chamber 9, a polygonal column type susceptor 2 for placing a semiconductor substrate (wafer) on the side surface is disposed slightly tilted from the vertical direction, and a lamp 3 for heating the wafer is provided outside the reaction chamber. is set up. During vapor phase growth, a wafer is placed on a counterbore 4 that is a circular recess provided on the side surface of the susceptor, a raw material gas is supplied from the gas inlet 5, and is ejected from an ejection hole provided in the jet 6. Then, it is introduced into the reaction chamber 9 and discharged from the gas discharge port 7. At this time, since the wafer is heated by the lamp, the source gas ejected on the wafer reacts on the wafer surface, and a thin film epitaxial layer (epilayer) can be vapor-phase grown on the wafer surface.

  One type of horizontal vapor phase growth apparatus is a single wafer type apparatus. In this apparatus, a wafer 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 it around the vertical axis. An epitaxial layer is formed on the wafer surface. Such an apparatus has been widely used as the diameter of the wafer increases, and is regarded as the mainstream as an apparatus capable of handling a wafer having a diameter of 300 mm.

  In these vapor phase growth apparatuses, a circular recess for accommodating the substrate is provided on the upper surface of the susceptor for the purpose of bringing the source gas into contact only with the upper surface of the substrate on which the epitaxial layer is grown. Then, the epitaxial layer is grown by accommodating the substrate in this recess called counterbore. FIG. 6 is a schematic cross-sectional view showing an example of such counterbore.

  In particular, in the barrel type vapor phase growth apparatus, since it is necessary to place the substrate on the counterbore 4 formed on the side surface of the susceptor so that the substrate does not fall during the reaction, the counterbore depth d is constant and the substrate thickness is kept constant. It is deeper than that. This is because if the counterbore depth d is shallower than the substrate thickness, it will be easy to drop from the counterbore.

By the way, the flow direction of the source gas in such a vapor phase growth apparatus 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 the raw material such as Si in the raw material gas is consumed 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, by rotating the substrate itself, the upstream and downstream influences of the source gas are eliminated, and the film thickness uniformity of the epitaxial layer is improved.
Further, in the barrel type vapor phase growth apparatus (barrel type gas phase reactor), as shown in FIG. 7, the side surface of the susceptor 2 is inclined with respect to the inner wall surface of the bell jar 1 so that the space downstream from the upstream side of the source gas. Is narrowed to increase the linear velocity of the source gas on the downstream side, so that the deposition rate of the epitaxial layer on the downstream side is not easily lowered even if the concentration of the source gas is lowered.

  The second effect is a change in film thickness in the vicinity of the outer peripheral portion (edge) of the substrate. As shown in FIG. 8, on the upstream side, the source gas passes over the susceptor 2 and is supplied to the outer peripheral portion of the substrate 10 via the edge portion of the counterbore 4. On the other hand, on the downstream side, it passes over the substrate 10, is supplied as it is to the outer peripheral portion of the substrate 10, and then flows to the edge of the counterbore 4. As described above, in the barrel type vapor phase growth apparatus, the counterbore depth is relatively deep so that the substrate does not fall from the susceptor. Therefore, in the case of the source gas flow on the upstream side, the gap formed between the upper surface of the susceptor and the substrate becomes a stagnation region, the gas stays, and the deposition of the epitaxial layer is delayed. As a result, the thickness (epi film thickness) of the epitaxial layer becomes thin near the outer periphery of the substrate. On the other hand, since such stagnation does not occur on the downstream side, the epitaxial layer is not thinned. As a result, the film thickness non-uniformity in the circumferential direction of the substrate outer peripheral portion occurs such that the epi film thickness is thin at the upstream substrate outer periphery and the epi film thickness is thicker at the downstream compared to the upstream side. .

In the case of a single wafer type apparatus, the substrate rotation described above eliminates the upstream and downstream influences of the source gas for the second influence, thereby improving the film thickness uniformity of the epitaxial layer.
However, in the case of a barrel-type vapor phase growth apparatus, changes in the epilayer deposition rate over a relatively wide range such as the first effect can be suppressed by optimizing the distance between the susceptor and the inner wall of the bell jar. However, this method could not improve the local deposition rate change in the vicinity of the outer periphery of the substrate as in the second effect.
Conventionally, several methods have been proposed to solve this problem (see, for example, Patent Document 1), but this is not sufficient and there is still room for improvement.

Japanese Patent Laid-Open No. 2003-12397

  The present invention has been made in view of such problems, and can improve the uniformity of the thickness of the epitaxial layer and the uniformity of the flatness at the outer peripheral portion of the substrate, and can produce a high-quality epitaxial wafer with a high yield. It is an object of the present invention to provide a vapor phase 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 in which one or more counterbore is formed by placing a substrate on an inclined surface and supporting it at the lower end. A vapor phase growth susceptor characterized in that the depth increases in the direction from the upstream side to the downstream side of the raw material gas supplied during the growth (claim 1).

  Thus, the counterbore formed in the susceptor for vapor phase growth of the present invention has a depth that increases from the upstream side to the downstream side of the source gas supplied during the vapor phase growth. By using such a vapor phase growth susceptor of the present invention during vapor phase growth, the uniformity of the thickness of the epitaxial layer and the uniformity of the flatness at the outer periphery of the substrate are improved, and a high quality epitaxial wafer is obtained. Can be produced with good yield.

  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).

  As described above, by using the vapor phase growth apparatus including the vapor phase growth susceptor of the present invention, the uniformity of the thickness of the epitaxial layer and the uniformity of the flatness at the outer peripheral portion of the substrate are improved, and the high quality is achieved. Epitaxial wafers can be produced with good yield.

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

  If the substrate is thus placed on 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. And can produce high-quality epitaxial wafers with good yield.

  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. Epitaxial wafers can be produced with good yield.

Hereinafter, the present invention will be described in detail.
As described above, in the case of the barrel type vapor phase growth apparatus, on the upstream side of the counterbore source gas, a gap (stepped portion) formed between the upper surface of the susceptor and the substrate becomes a stagnation region and the gas stays, and the epitaxial layer As a result, there is a problem that the thickness of the epitaxial layer becomes thinner in the vicinity of the outer peripheral portion of the substrate on the upstream side of the source gas as compared with other portions.

  Therefore, the present inventors have intensively studied in order to effectively prevent the occurrence of non-uniform film thickness at the outer peripheral portion of the substrate. On the upstream side of the source gas, the depth of the counterbore is reduced, and the substrate It has been found that by eliminating the stagnation region of the source gas in the vicinity of the outer peripheral portion, it is possible to suppress the reduction of the epi film deposition rate, that is, the reduction of the epi film thickness. On the other hand, on the downstream side of the source gas, it is necessary to deepen the counterbore to some extent so that the substrate does not fall during vapor phase growth. Therefore, the present inventors combine these two, and do not make the depth d of the counterbore upstream and downstream of the source gas the same as in the conventional counterbore 4 in FIG. By making the depth of the counterbore shallow compared to the downstream side of the source gas, it is possible to effectively prevent the occurrence of non-uniform film thickness at the outer periphery along the circumferential direction of the substrate, and troubles such as falling of the substrate. As a result, 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. 1 is an explanatory view showing an example of a susceptor for vapor phase growth according to the present invention, and FIG. 2 is an enlarged schematic sectional view of a counterbore portion of the susceptor.
The susceptor 2 shown in FIG. 1 is a pentagonal column type, and three counterbores 4 are formed on each side surface. At the time of vapor phase growth, the source gas flows from the upstream toward the downstream along the side surface of the susceptor 2. Further, the counterbore 4 of the susceptor 2 is placed with the substrate inclined and supported at the lower end, and as shown in FIG. 2, the direction from the upstream side to the downstream side of the source gas supplied during vapor phase growth is shown. The depth gradually increases toward the.

Thus, the depth d1 of the counterbore of the susceptor is made shallower on the upstream side of the source gas, and the stagnation region of the source gas near the outer periphery of the substrate is eliminated, thereby reducing the epi film deposition rate, that is, reducing the epi film thickness. It becomes possible to suppress. Therefore, by using the susceptor for vapor phase growth in which such counterbore is formed, it is possible to provide an epitaxial wafer with higher epitaxial film thickness uniformity than in the past with high productivity. On the other hand, on the downstream side of the raw material gas, the depth d2 of the counterbore is deeper than that on the upstream side of the raw material gas, so that the substrate can be prevented from dropping during vapor phase growth. Furthermore, since the ease of preparation at the time of substrate preparation is ensured, vapor phase growth can also be performed with high productivity.
The overall shape of the susceptor is, for example, a polygonal column type such as a pentagonal column type, but is not particularly limited, and one or more counterbore can be formed. The diameter and depth of the counterbore can be appropriately selected according to the size of the wafer to be placed.
Moreover, it is preferable to form the counterbore so that d2 / d1 is in the range of 1.2 to 3.0. If d2 / d1 is within this range, the wafer does not fall during vapor phase growth, and an epitaxial wafer with high epitaxial film thickness uniformity can be more reliably manufactured.

  As the vapor phase growth apparatus in which the susceptor of the present invention can be installed, the same apparatus as the conventional one can be applied except for the counterbore of the susceptor as shown in FIG. In this barrel type vapor phase growth apparatus, a reaction chamber 9 for accommodating the susceptor 2 is provided by placing a seal plate 8 on which a susceptor 2 for vapor phase growth is suspended in a bell jar 1 fixed in an inverted bell shape. It is formed. A lamp 3 is installed outside the reaction chamber 9 as a heat source for heating the substrate. The vapor phase growth apparatus further includes a gas inlet 5 for introducing a source gas into the reaction chamber and a gas outlet 7 for discharging the source gas from the reaction chamber.

  The susceptor 2 installed in the vapor phase growth apparatus of the present invention is the susceptor of the present invention. For example, a susceptor in which one or more counterbore shown in FIG. 2 is formed can be used. By using a vapor phase growth apparatus including a susceptor according to the present invention, an epitaxial wafer excellent in epitaxial film thickness uniformity at the outer peripheral portion of the substrate can be manufactured with a high yield.

Next, the vapor phase growth method of the present invention for vapor-depositing a thin film on the surface of the substrate will be described by taking as an example the case where the vapor phase growth apparatus having the susceptor of the present invention is used in the apparatus as shown in FIG. .
First, the substrate is placed on the susceptor 2. Then, while heating the mounted substrate with the lamp 3, the source gas is supplied from the gas introduction port 5, ejected from a gas ejection hole called a jet 6, introduced into the reaction chamber, and discharged from the gas exhaust port 7. At this time, since the substrate is heated by the lamp 3, 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, the counterbore depth is made shallower on the upstream side, and the stagnation region of the source gas in the vicinity of the outer periphery of the substrate is eliminated, thereby suppressing the reduction in the epi film deposition rate in that part, that is, the reduction in the epi film thickness. Therefore, an epitaxial wafer having a higher uniformity of epitaxial film thickness can be provided with a higher yield. On the other hand, on the downstream side, the counterbore can be prevented from dropping during the epi-reaction by increasing the counterbore depth from the upstream, so it is possible to prevent yield loss such as substrate breakage due to dropping, and also to ensure ease of loading during board loading. Therefore, vapor phase growth can be performed with high productivity.

In addition, examples of the substrate on which the epitaxial layer is vapor-grown by being placed on the susceptor for vapor-phase growth of the present invention include a silicon wafer, but other semiconductor wafers such as a compound semiconductor may be used, and the substrate is particularly limited. Not done.
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 are shown and this invention is demonstrated further in detail, it cannot be overemphasized that this invention is not limited to this.
(Example 1, Comparative Examples 1-3)
A barrel type vapor phase growth apparatus shown in FIG. 7 was used.
First, the silicon wafer was placed on 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 a silicon wafer having a diameter of 200 mm and a thickness of 525 μm by supplying a raw material gas while heating the mounted silicon wafer.

At this time, the following four types of susceptors were used as susceptors for vapor phase growth.
(1) A counterbore formed so that the depth gradually increases from the upstream side to the downstream side of the raw material gas. The counterbore depth is 0.8 mm on the upstream side of the raw material gas and 1.2 mm on the downstream side of the raw material gas. Some (Example 1).
(2) A counterbore formed so as to have a constant depth from the upstream side to the downstream side of the raw material gas, and the depth of the counterbore is 1.5 mm both on the upstream side of the raw material gas and on the downstream side of the raw material gas. (Comparative Example 1).
(3) A counterbore formed so as to have a constant depth from the upstream side to the downstream side of the raw material gas, and the depth of the counterbore is 1.0 mm on both the upstream side and downstream side of the raw material gas. (Comparative Example 2).
(4) A counterbore formed so as to have a constant depth from the upstream side to the downstream side of the raw material gas, and the depth of the counterbore is 0.8 mm on both the upstream side and downstream side of the raw material gas. (Comparative Example 3).

Further, SiHCl ₃ was used as a reaction gas (raw material gas), the growth rate was 1.5 μm / min, the reaction temperature was 1050 ° C., and the growth film thickness was 50 μm.

In each of the above examples and comparative examples, epitaxial growth was performed on 30 wafers.
In addition, flatness measurement is performed on the wafer after the vapor phase growth of the epitaxial layer in this way, and the average flatness (LTV) in each cell shown in FIG. Flatness was assumed. Since the flatness of the silicon wafer before the vapor phase growth is very good, the flatness after the vapor phase growth is considered to be due to the variation in the thickness of the epitaxial layer. The film thickness uniformity of the outer periphery of the wafer was evaluated.

  FIG. 5 is a graph showing the relationship between the upstream flatness and the downstream peripheral flatness when using the vapor phase growth susceptors of Comparative Examples 1 to 3, and the counterbore depth. As the counterbore depth becomes shallower on both the upstream side and the downstream side, the outer peripheral flatness value decreases, indicating that the epitaxial film thickness uniformity is improved. It can also be seen that at any counterbore depth, the outer peripheral flatness value is larger on the upstream side, and the film thickness uniformity is not equal between the upstream side and the downstream side. This is because, as described above, on the upstream side, a stagnation region of the source gas is formed in the vicinity of the counterbore side wall and the outer periphery of the wafer, and the deposition of the epi film is inhibited. Thus, in the vapor phase growth apparatus using the conventional vapor phase growth susceptor having the same counterbore depth on the upstream side and downstream side of the source gas, the difference in the outer peripheral flatness value between the upstream side and the downstream side, That is, the uniformity of the epi film thickness was deteriorated.

On the other hand, when the epitaxial layer is vapor-phase grown using the susceptor for vapor-phase growth of Example 1 (depth of counterbore: upstream 0.8 mm, downstream 1.2 mm), as shown in FIG. It can be seen that the outer peripheral flatness level is the same on the upstream side and the downstream side of the source gas, and the uniformity of the epi film thickness is greatly improved.
For comparison, FIG. 4 also shows the outer peripheral flatness level when the vapor phase growth susceptor of Comparative Example 1 (depth of counterbore: 1.5 mm on both upstream and downstream sides) is used.

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 explanatory drawing which shows the susceptor for vapor phase growth according to 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 figure which shows the outer periphery flatness cell site of an upstream in flatness measurement, and the outer periphery flatness cell site of a downstream. In Example 1 and Comparative Example 1, it is a figure which shows the comparison of an upstream outer periphery flatness and a downstream outer periphery flatness. It is a figure which shows the relationship between counterbore depth and outer periphery flatness (Comparative Examples 1-3). It is a cross-sectional schematic explanatory drawing of the counterbore of the conventional vapor phase growth susceptor. It is a cross-sectional schematic explanatory drawing which shows an example of a vapor phase growth apparatus. It is a schematic diagram which shows the flow of the source gas in the board | substrate outer peripheral part vicinity.

Explanation of symbols

1 ... Berja, 2 ... Susceptor, 3 ... Lamp, 4 ... Counterbore, 5 ... Gas inlet,
6 ... jet, 7 ... gas outlet, 8 ... seal plate, 9 ... reaction chamber,
10: Substrate.

Claims (3)

  1. A susceptor for vapor phase growth in which one or more counterbore is formed by tilting a substrate and supported at a lower end, the counterbore of the susceptor being downstream from an upstream side of a source gas supplied during vapor phase growth A susceptor for vapor phase growth characterized in that the depth increases toward the side.   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 placed on the susceptor according to claim 1, and a source gas is supplied while heating the placed substrate. Vapor phase epitaxy of the epitaxial layer.

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