JP4000779B2 - Epitaxial growth equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epitaxial growth apparatus, and more particularly to an epitaxial growth apparatus excellent in film thickness uniformity of a semiconductor film to be grown.
[0002]
[Prior art]
In the field of manufacturing semiconductor wafers such as silicon wafers, so-called epitaxial wafers (hereinafter abbreviated as epi-wafers) in which a silicon epitaxial layer is formed on the surface of a substrate are conventionally known. According to this technique, since a single crystal silicon layer having an arbitrary film thickness and resistivity can be formed on a substrate, a high-performance semiconductor device can be manufactured. For example, in the field of bipolar transistors, the use of epiwafers has been recognized to be extremely effective as a countermeasure for defects such as soft errors and latch-ups for the purpose of speeding up, and in the field of CMOS memories, and the demand is increasing.
[0003]
In this type of epi-wafer, the thickness of the silicon epitaxial layer is usually specified, and the standard-controlled one is shipped. For example, in applications where a thick epitaxial layer is required, the thickness is set to about several μm to 20 μm, and in applications where a thin epitaxial layer is required, it is set to about 1 μm to about several μm.
[0004]
As a technique for forming an epitaxial layer in a manufacturing process of a semiconductor device, a vapor phase epitaxial method is usually used. In the case of a single wafer epitaxial furnace, the epitaxial growth apparatus used for this is a wafer placed on a susceptor in a chamber (furnace), the wafer is heated, and a source gas such as SiH ₄ and H ₂ are placed above the wafer. A Si epitaxial layer is formed on the wafer surface by supplying a mixed gas of carrier gas such as the above.
[0005]
[Problems to be solved by the invention]
By the way, in the field of semiconductor devices, higher integration is progressing year by year, and finer processing is required. At this time, the flatness of the silicon wafer as the device material is required to be high, for example, from the relationship of the depth of focus of the exposure apparatus in the photolithography process. The flatness of the wafer is an important factor for improving the processing accuracy not only in the photolithography process but also in other processes.
[0006]
However, the conventional epitaxial wafer growth method using a single wafer epitaxial furnace has a large film thickness variation in the wafer surface, and the film thickness change is not particularly gentle, and locally thick and thin portions are generated. was there. Therefore, even if the processing accuracy from slicing to polishing is increased to improve the flatness of the underlying wafer in the manufacturing process of the epi wafer, there is an unevenness of the epitaxial layer to be grown on it, resulting in the wafer surface as a result. There was a problem that the flatness of the film deteriorated.
[0007]
The present invention has been made in order to solve the above-described problem, and it is possible to improve the flatness of the wafer as a whole by smoothing the film thickness distribution of the epitaxial layer and eliminating irregularities in the wafer surface. An object is to provide an epitaxial growth apparatus.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an epitaxial growth apparatus of the present invention is an epitaxial growth apparatus that is a single wafer epitaxial furnace for forming a silicon epitaxial layer on the surface of a wafer in the manufacture of a silicon wafer,
A chamber that accommodates the wafer, a susceptor that is rotatably installed in the chamber and supports the wafer, and a gas supply source that supplies a gas containing at least a source gas or a carrier gas from the side to the wafer in the chamber A gas supplied from the gas supply source to flow into the chamber from a plurality of gas outlets and flow toward the wafer on the rotatable susceptor located downstream of the gas outlets. And a straightening member of
The rectifying member is a box-shaped body having a hollow inside, and a planar shape thereof follows the shape of the wafer from the central portion to the peripheral portion of the wafer in a plan view of a side surface facing the peripheral portion of the wafer. A curved surface that is gently curved, the curved surface is provided with a plurality of holes as the gas outlet,
As the distance from the gas outlet to the wafer edge is substantially equal, with the plurality of gas outlet ports are arranged in a row along the shape of the wafer,
The central axis of each gas outlet hole is along the radial direction of the wafer, and the outlet direction of the gas flowing out from each gas outlet port is arranged so as to face the center of the wafer.
Compared to the case where the central axes of the holes of the gas outlets are parallel to each other in the gas flow that has flowed from the gas outlets onto the wafer, the amount of gas that contributes to film formation at the peripheral edge of the wafer is increased. The above-mentioned problems have been solved by making it difficult for the film thickness to become thinner at the peripheral edge of the wafer and making the film thickness distribution of the epitaxial layer in the wafer surface more gentle.
In the epitaxial growth apparatus of the present invention, the rectifying member may be provided with a partition plate for rectifying the gas flow in the internal space.
The epitaxial growth apparatus of the present invention includes a chamber for containing a wafer, a susceptor that is rotatably installed in the chamber and supports the wafer, and a gas supply for supplying a gas containing at least a source gas or a carrier gas into the chamber. And a rectifying member for causing the gas supplied from the gas supply source to flow out into the chamber from the plurality of gas outlets and to flow toward the wafer, and the plurality of gas outlets of the rectifying member are The gas outlet corresponding to the peripheral edge of the wafer in the direction perpendicular to the gas flow direction is arranged to be located downstream of the gas outlet corresponding to the central portion of the wafer in the gas flow direction. And
[0009]
As a result of examining the cause of the large variation in the thickness of the epitaxial layer in the conventional epitaxial growth apparatus, the present inventors have found that the arrangement of the gas inlets in the chamber affects the gas flow velocity and flow rate on the wafer. It was found that the variation in thickness caused the variation in film thickness. That is, in the conventional single wafer type epitaxial growth apparatus, a plurality of gas outlets for supplying gas to the upper space of the wafer placed on the susceptor are provided in the chamber, and these gas outlets are in the gas flow direction. It was arrange | positioned on the straight line along the direction perpendicular | vertical to. However, since a semiconductor wafer is generally circular, when the gas outlet is arranged in a straight line in a direction perpendicular to the gas flow direction, the distance from the gas outlet to the wafer edge varies depending on the location. The distance is long on the peripheral edge side, and the distance is short on the center side of the wafer. With this configuration, the flow rate of the gas that reaches the wafer varies depending on the location in the wafer surface, which causes local unevenness in the epitaxial layer in the wafer surface.
[0010]
On the other hand, in the epitaxial growth apparatus of the present invention, the arrangement of the plurality of gas outlets of the rectifying member is not arranged linearly in the direction perpendicular to the gas flow direction, but the gas flow corresponding to the peripheral edge of the wafer. The outlet is disposed so as to be located on the downstream side in the gas flow direction with respect to the gas outlet corresponding to the central portion of the wafer. According to this configuration, the difference between the distance from the gas outlet to the wafer edge at the peripheral edge of the wafer and the distance from the gas outlet to the wafer edge at the center of the wafer is smaller than that of the conventional apparatus. The difference in the gas flow rate is reduced, and local unevenness in the film thickness of the epitaxial layer can be suppressed as compared with the conventional case.
[0011]
As the positional relationship between the plurality of gas outlets, for example, the positions may be shifted stepwise, but it is desirable that the gas outlets be arranged so as to be gently inclined from the center portion to the peripheral portion of the wafer in plan view if possible. According to this configuration, since the gas flow velocity changes gently between the wafer center and the peripheral portion, the film thickness distribution of the epitaxial layer can be made more gentle. In particular, when a general circular wafer is used, it is optimal to arrange the positions of the gas outlets so as to be curved along the wafer shape in plan view.
[0012]
Further, the direction of the gas outlet may be such that the central axis of the hole of each gas outlet is parallel and the flow direction of the gas flowing out from each gas outlet is parallel. Rather than having the central axes parallel, it is desirable that the outflow direction of the gas flowing out from each gas outlet (that is, the central axis of the hole) be directed to the center of the wafer. When gas flows in parallel, it is inevitable that gas diffuses toward the outside of the wafer at the periphery of the wafer, and the amount of gas that contributes to film formation is reduced compared to the center, and the film thickness tends to be thinner. is there. In contrast, when the gas flows toward the center of the wafer, the amount of gas that contributes to film formation at the wafer periphery increases compared to when the gas flows in parallel, so the film thickness decreases at the wafer periphery. Can hardly occur, and the film thickness distribution in the wafer surface can be made smoother.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
A first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a plan view showing a schematic configuration of an epitaxial growth apparatus according to the present embodiment, which is an example of a so-called single wafer epitaxial furnace. In the figure, reference numeral 2 is a chamber, 3 is a susceptor, 4 is a gas supply source, 5 is a rectifying member, and W is a wafer.
[0014]
In the epitaxial growth apparatus 1 of the present embodiment, as shown in FIG. 1, a susceptor 3 is rotatably installed inside a furnace-like chamber 2, and a wafer W on which an epitaxial layer is to be formed is supported on the susceptor 3. It has become so. Therefore, an epitaxial layer is formed on the surface while the wafer W rotates during film formation. For example, a gas supply source 4 that supplies a mixed gas of a source gas such as SiH ₄ , SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ and a carrier gas such as H ₂ into the chamber 2 is provided, and the source gas and the carrier gas are provided. The mixed gas is introduced into the chamber 2 through the pipe 6. And the front-end | tip of the piping 6 is connected to the base end of the rectification | straightening member 5 installed in the chamber 2, and after mixed gas passes through the piping 6, the upper part of the wafer W in the chamber 2 is passed through the rectification | straightening member 5. It flows into the space.
[0015]
In the case of the present embodiment, the flow regulating member 5 is configured by combining two symmetrical parts. 2 is a plan view of one rectifying member 5, and FIG. 3 is a side view seen from the opening side opposite to the surface on which the gas outlet is formed. As shown in FIGS. 2 and 3, each rectifying member 5 is a hollow box-like body, and the planar shape thereof is such that the side facing the peripheral edge of the wafer W faces the wafer W (that is, the gas flow). It protrudes toward the downstream side in the direction, and has a gently curved shape such that the side facing the center of the wafer W is recessed. Therefore, the side surface 5a on the side facing the wafer W is a curved surface substantially conforming to the shape of the wafer W, and a plurality of (9 in this embodiment) holes are provided on the curved surface. Functions as the gas outlet 7. In the present embodiment, the central axes c of the holes of the gas outlets 7 are parallel to each other, and the flow directions of the gas flowing out from the gas outlets 7 are parallel to each other. Further, the rectifying member 5 is provided with a partition plate 8 for rectifying the gas flow in the internal space.
[0016]
In the epitaxial growth apparatus 1 of the present embodiment, the gas outlet 7 corresponding to the peripheral edge of the wafer is disposed downstream of the gas outlet 7 corresponding to the center of the wafer in the gas flow direction. It is provided on the curved surface 5a along the shape. With this configuration, the distance from the gas outlet 7 to the wafer edge at the peripheral edge of the wafer is almost equal to the distance from the gas outlet 7 to the wafer edge at the center of the wafer, and the difference in gas flow velocity depending on the location on the wafer is small. Therefore, local unevenness in the film thickness of the epitaxial layer can be suppressed, and an epitaxial layer having a gentle film thickness distribution can be formed. As a result, the flatness of the completed wafer can be improved.
[0017]
[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the epitaxial growth apparatus of this embodiment is exactly the same as that of the first embodiment, and the only difference is the configuration of the rectifying member. Therefore, only the rectifying member will be described below with reference to FIG. In FIG. 4, the same reference numerals are given to components common to FIG. 2.
[0018]
Also in this embodiment, the rectifying member is configured by combining two symmetrical parts, and FIG. 4 is a plan view of one rectifying member. As shown in FIG. 4, each of the rectifying members 10 is a box-shaped body having a hollow inside, and the planar shape thereof is substantially the shape of a wafer from the side facing the wafer peripheral part to the side facing the wafer central part. It is the same as that of the first embodiment in that it is gently curved along and a plurality (9) of gas outlets 11 are provided on the curved surface 10a. However. In the present embodiment, the central axes c of the holes of the gas outlets 11 are not parallel as in the first embodiment, but are each along the radial direction of the wafer W, and each gas outlet 11 The outflow direction of the outflowing gas is directed toward the center of the wafer W.
[0019]
When the gas flowing out from each gas outlet 7 flows in parallel as in the first embodiment, the gas diffuses to the outside of the wafer at the peripheral edge of the wafer, and contributes to film formation as compared with the central portion. The amount decreases and the film thickness tends to decrease. On the other hand, when the gas is flowed toward the wafer center as in the present embodiment, the amount of gas contributing to film formation at the wafer peripheral portion is larger than that when flowing in parallel, so the wafer peripheral portion As a result, the situation in which the film thickness becomes thinner is less likely to occur, and the film thickness distribution of the epitaxial layer in the wafer surface can be made gentler than in the first embodiment.
[0020]
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the specific configuration such as the number and shape of the gas outlets provided in the rectifying member can be appropriately changed. The present invention is not limited to the single-wafer type epi-furnace of the above embodiment, but can be applied to other epitaxial growth apparatuses of a type that supplies gas from the side to the surface of the wafer. Moreover, although the example of the silicon wafer has been described in the above embodiment, the present invention can be applied to other semiconductor wafers.
[0021]
【Example】
The results of experiments that demonstrate the effects of the present invention are reported below.
In a direction perpendicular to the gas flow direction, (1) a conventional rectifying member in which the gas outlet is arranged on a straight line, (2) the gas outlet is arranged on a curved surface, and then from each gas outlet. The flow straightening member according to the first embodiment of the present invention in which the gas flow directions are parallel, (3) the gas flow outlets are arranged on the curved surface, and the gas flow direction from each gas flow outlet is the center of the wafer. The rectifying member according to the second embodiment of the present invention facing the above was prepared, and each was installed in a single wafer type epi furnace to form a film. At this time, the other epi-growth conditions such as the number of gas outlets of each rectifying member, the raw material gas and carrier gas flow rates, the rotation speed, and the temperature were made completely the same.
[0022]
The measurement results of the film thickness distribution of the formed epitaxial layer are shown in FIGS. FIG. 5A shows the measurement result of the conventional rectifying member of the above (1), FIG. 5B shows the measurement result of the rectifying member of the first embodiment of the present invention of the above (2), and FIG. ) Is a measurement result in the rectifying member of the second embodiment of the present invention of (3) above. 5A to 5C, the horizontal axis represents the distance (mm) from the wafer center, and the vertical axis represents the film thickness (-) of the silicon epitaxial layer.
[0023]
As shown in FIG. 5 (a), when a conventional rectifying member is used, a convex portion that rises to the periphery is formed in a region of about ± 30 mm from the wafer center, and the convex portion is also located at a position near ± 80 mm. Is seen. Thus, it can be seen that extremely local irregularities are formed on the wafer surface.
[0024]
On the other hand, as shown in FIG. 5B, when the rectifying member according to the first embodiment of the present invention is used, the film on the entire wafer surface is increased by increasing the film thickness at the peripheral edge of the wafer. Although the thickness difference is still slightly large, the local unevenness as shown in FIG. 5A disappeared, and the film thickness distribution became smooth.
[0025]
Further, as shown in FIG. 5C, when the rectifying member according to the second embodiment of the present invention is used, the film thickness distribution becomes smoother, and at the same time, the film thickness difference in the entire wafer surface becomes small. I understood it. From this result, it was demonstrated that the flatness of the wafer is greatly improved by the configuration of the epitaxial growth apparatus of the present invention.
[0026]
【The invention's effect】
As described above in detail, according to the present invention, the gas outlet corresponding to the peripheral edge of the wafer is disposed downstream of the gas outlet corresponding to the center of the wafer in the gas flow direction. Since the difference in gas flow rate is reduced, local unevenness can be suppressed in the thickness of the epitaxial layer, and an epitaxial layer having a gentle thickness distribution can be formed. As a result, the flatness of the wafer can be improved, which is suitable for manufacturing a highly integrated semiconductor device.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of an epitaxial growth apparatus according to a first embodiment of the present invention.
FIG. 2 is a plan view of a rectifying member used in the apparatus.
FIG. 3 is a side view of the flow regulating member viewed from the opening side opposite to the surface on which the gas outlet is formed.
FIG. 4 is a plan view of a rectifying member used in the second embodiment of the present invention.
FIGS. 5A and 5B are diagrams showing a state of film thickness distribution in a wafer according to an embodiment of the present invention, in which FIG. 5A is a measurement result of a conventional rectifying member, and FIG. 5B is a diagram of a first embodiment of the present invention. The measurement result in a rectification | straightening member, (c) The measurement result in the rectification | straightening member of the 2nd Embodiment of this invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Epitaxial growth apparatus 2 Chamber 3 Susceptor 4 Gas supply source 5,10 Rectification member 6 Piping 7,11 Gas outlet 8 Partition plate W Wafer

Claims (2)

An epitaxial growth apparatus that is a single wafer epitaxial furnace that forms a silicon epitaxial layer on the surface of a wafer in the manufacture of a silicon wafer,
A chamber that accommodates the wafer, a susceptor that is rotatably installed in the chamber and supports the wafer, and a gas supply source that supplies a gas containing at least a source gas or a carrier gas from the side to the wafer in the chamber A gas supplied from the gas supply source to flow into the chamber from a plurality of gas outlets and flow toward the wafer on the rotatable susceptor located downstream of the gas outlets. And a straightening member of
The rectifying member is a box-shaped body having a hollow inside, and a planar shape thereof follows the shape of the wafer from the central portion to the peripheral portion of the wafer in a plan view of a side surface facing the peripheral portion of the wafer. A curved surface that is gently curved, the curved surface is provided with a plurality of holes as the gas outlet,
As the distance from the gas outlet to the wafer edge is substantially equal, with the plurality of gas outlet ports are arranged in a row along the shape of the wafer,
The central axis of each gas outlet hole is along the radial direction of the wafer, and the outlet direction of the gas flowing out from each gas outlet port is arranged so as to face the center of the wafer.
Compared to the case where the central axes of the holes of the gas outlets are parallel to each other in the gas flow that has flowed from the gas outlets onto the wafer, the amount of gas that contributes to film formation at the peripheral edge of the wafer is increased. An epitaxial growth apparatus characterized in that a situation in which the film thickness becomes thin at the peripheral edge of the wafer does not easily occur, and the film thickness distribution of the epitaxial layer in the wafer surface is made smoother.   The epitaxial growth apparatus according to claim 1, wherein the rectifying member is provided with a partition plate for rectifying a gas flow in the internal space.

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