Susceptor

Abstract

To provide a susceptor allowing uniform deposition of an epitaxial film on a semiconductor wafer without damage such as scratches, by providing an inclination in a pocket portion of the susceptor where the wafer is placed and by holding the wafer without misalignment.SOLUTION: The susceptor has: a plurality of pockets 1 inclined downward in the radially outward direction on an upper surface of a base 2; and a plurality of protrusions 3 formed on inner walls of the pockets and supporting the outer circumference of semiconductor wafers W, where the protrusions are located on a lower side of the inclined pockets.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a susceptor capable of forming a uniform semiconductor epitaxial film on a semiconductor substrate. [Background technology]

[0002] In recent years, miniaturization of semiconductor devices has led to a demand for reducing crystal defects on wafer surfaces. To meet this demand, a technology is needed to deposit epitaxial films on and near the wafer surface with highly controlled crystal defects.

[0003] An epitaxial wafer is manufactured by vapor-phase growing an epitaxial film EP on the surface of a silicon wafer W placed on a susceptor 52 using a vapor-phase epitaxial growth apparatus 50 as shown in FIG. 9. The silicon wafer W is placed in a circular recess (called a pocket) formed in the center of the upper surface of the susceptor. The pocket consists of a circular bottom wall and surrounding side walls. The bottom wall is flat or slightly curved, and the side walls are formed by cutting the upper surface of the susceptor at a right angle to a predetermined depth. The susceptor 52 and silicon wafer W are then rotated in a predetermined direction around a rotation axis 54. While the silicon wafer W is heated from the outside of the chamber 51 (not shown), a reactive gas G is supplied horizontally from a reactive gas supply pipe 55 to an exhaust pipe 56. In this manner, an epitaxial film EP is vapor-phase grown on the surface of the silicon wafer W.

[0004] Conventionally, various proposals have been made regarding susceptors in order to make the thickness of the epitaxial film formed on the wafer surface uniform and to reduce crystal defects. Patent Document 1 describes a semiconductor vapor phase growth apparatus that epitaxially grows semiconductor crystals on heated substrates by metal organic chemical vapor deposition, in which, as shown in FIG. 10, multiple substrates W are arranged circumferentially on a rotating plate-like susceptor 20, and the center of the susceptor 20 is bulged downward so that the crystal growth surfaces of the substrates W are inclined by θ=5° with respect to the flow direction of the source gas G.

[0005] However, when the substrate is tilted at 5° with respect to the flow direction of the source gas, the growth rate at the center of the susceptor is higher than that at the periphery of the susceptor, making it difficult to produce a uniform epitaxial film. Also, because the pocket on which the wafer is placed is tilted while the bottom of the susceptor is horizontal, the thickness of the susceptor is not constant, resulting in uneven heat conduction and making it difficult to produce a uniform epitaxial film.

[0006] Furthermore, even with the technology of Patent Document 1, there was still a problem in that the region at the periphery of the epitaxial wafer could not be used for semiconductor elements due to variations in film thickness at the periphery of the epitaxial wafer caused by the crystal orientation of the wafer.

[0007] To address this issue, Patent Document 2 discloses a susceptor that can produce a uniform epitaxial film by adjusting the growth rate of the epitaxial film on the wafer at the outer periphery and at the center of the susceptor to be the same by providing an inclination in the pocket portion of the susceptor on which the wafer is placed and tilting the crystal growth surface of the wafer relative to the flow direction of the raw material gas. Specifically, as shown in FIG. 11, the rotating plate-shaped susceptor 30 has pocket portions 31 for arranging multiple semiconductor wafers W in the circumferential direction on its upper surface, and the inclination angle θ of each pocket portion 31 relative to the horizontal direction is 2.5° or more and 3.5° or less, and the bottom surface and top surface of the susceptor 30 are parallel to each other. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-207545 [Patent Document 2] Japanese Patent Application Publication No. 2022-159954 Summary of the Invention [Problem to be solved by the invention]

[0009] As disclosed in Patent Document 2, a pocket portion for arranging a plurality of semiconductor wafers is provided in the circumferential direction on the upper surface of a rotating plate-shaped susceptor, and the inclination angle of each pocket portion with respect to the horizontal direction is set to be 2.5° or more and 3.5° or less, and by making the bottom surface and the upper surface of the susceptor parallel, a uniform epitaxial film can be formed.

[0010] However, in the susceptor disclosed in Patent Document 2, since the pocket portion for arranging the semiconductor wafer is inclined with respect to the horizontal direction, due to the centrifugal force generated by the rotation of the susceptor, the semiconductor wafer slides and is displaced, and there is a problem that the thickness of the epitaxial film varies.

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide a susceptor that can form a uniform epitaxial film without damaging the semiconductor wafer such as scratches while providing an inclination to the pocket portion for placing the wafer of the susceptor and holding the wafer without displacement.

Means for Solving the Problems

[0012] In order to solve the above problems, the susceptor according to the present invention A susceptor for epitaxial film growth having a concave pocket portion for mounting a semiconductor wafer, and a reaction gas is supplied to the semiconductor wafer from a horizontal direction, has a plurality of pocket portions that are inclined downward toward the outer side in the radial direction on the upper surface of the substrate, Composed of a circular bottom wall and an inner wall surrounding it and a plurality of protrusion portions that are formed on the inner wall of the pocket portion and support the outer peripheral portion of the semiconductor wafer. The plurality of protrusion portions Provided upward from the bottom surface of the concave pocket portion, and are arranged on the lower side of the inclined pocket portion , the height e of the protrusion from the bottom surface of the concave pocket portion is within the range of f / 2 < e < f with respect to the thickness f of the semiconductor wafer, and the width dimension c of the protrusion is within the range of (a - b) / 4 < c < (a - b) / 2 with respect to the diameter a of the pocket portion and the diameter b of the semiconductor wafer, and the length g of the protrusion is within the range of c / 2 < g < (a - b) / 2 and are characterized in this regard.

[0013] It is desirable that the protrusion portions formed in the pocket portion are arranged symmetrically with respect to the line connecting the center of the substrate and the center of the pocket portion. Also, it is desirable that the number of protrusion portions formed in the pocket portion is 2 to 6. Also, it is desirable that the width dimension c of the protrusion portion is within the range of (a - b) / 4 < c < (a - b) / 2 with respect to the diameter a of the pocket portion and the diameter b of the semiconductor wafer.

[0014] According to the present invention, since the pocket portion is inclined downward toward the radially outer side, when an epitaxial film is formed on a semiconductor wafer held in the pocket portion, the reactant gas supplied horizontally flows uniformly over the entire semiconductor wafer, thereby reducing the variation in the thickness of the formed epitaxial film. Furthermore, since the semiconductor wafer is supported in the pocket portion by multiple protrusions, the semiconductor wafer does not slip due to the centrifugal force generated by the rotation of the susceptor. In other words, it is possible to prevent the semiconductor wafer from shifting in position due to the inclination of the pocket portion and the centrifugal force. Furthermore, by forming the surface (top surface) of the susceptor on which the pocket portion is formed and the opposite surface (bottom surface) parallel to each other, the heat conduction throughout the susceptor becomes uniform, allowing a uniform epitaxial film to be produced. [Effects of the Invention]

[0015] According to the present invention, a susceptor can be obtained in which the pocket portion of the susceptor on which the wafer is placed is inclined, the wafer is held without being misaligned, and a uniform epitaxial film can be formed on the semiconductor wafer without causing damage such as scratches. [Brief explanation of the drawings]

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0017] Hereinafter, embodiments of the susceptor of the present invention will be described with reference to the drawings. Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not accurately illustrated.

[0018] FIG. 1 is a plan view of a susceptor 10 of the present invention, and FIG. 2 is a cross-sectional view of the susceptor 10 of FIG. 1 taken along line AA. As shown in Fig. 1, the susceptor 10 has a disk-shaped base 2 and a plurality of pockets 1 formed concentrically around the outer periphery of the disk. The pockets 1 are arranged so that the susceptor 10 has rotational symmetry with respect to the rotation axis O. In other words, the susceptor 10 of the present invention is a so-called pancake-type susceptor having a recessed pocket 1 formed on one main surface thereof for placing a semiconductor wafer W (substrate to be processed). The semiconductor wafer W is a silicon wafer or the like.

[0019] The substrate 2 constituting the susceptor 10 is made of a carbon material or a carbon material whose surface is coated with silicon carbide (SiC). The susceptor 10 is obtained either by using the disk-shaped substrate 2 as is, which has a plurality of pockets formed therein and slopes from the center to both sides, or by applying a SiC coating film to the substrate 2 by chemical vapor deposition (CVD).

[0020] 2 represents the angle of inclination from the center of the susceptor 10 to both side surfaces. As shown in the figure, the top surface of the susceptor 10, including the pocket portion 3, is inclined downward radially outward from the horizontal direction. The pocket portion 1 of the susceptor 10 has an inclination angle (θ) of 2.5 to 3.5° relative to the horizontal direction, and the bottom surface is parallel to the inclination of the upper surface and the pocket portion 1. If the inclination angle (θ) is less than 2.5°, the growth rate of the epitaxial film is faster at the outer periphery of the susceptor 10. On the other hand, if the inclination angle (θ) is more than 3.5°, the growth rate of the epitaxial film is faster at the center of the susceptor 10, making it difficult to produce a uniform epitaxial film. When the tilt angle (θ) is within the above range, the growth rate of the epitaxial film becomes approximately the same at the outer periphery and the center of the susceptor 10, and a uniform epitaxial film can be produced. The tilt angle (θ) is more preferably 2.7 to 3.3°.

[0021] The number of pockets 1 is 3 to 10, preferably 5 to 8 (8 in FIG. 1), from the viewpoint of enabling stable rotation of the susceptor 10 and uniform supply of gas to the wafer W. Fig. 3 is an enlarged plan view of one pocket 1, and Fig. 4 is a cross-sectional view of the pocket 1 of Fig. 3. Fig. 5 is a plan view showing a modified example of the pocket 1 of Fig. 3. As shown in Fig. 3, the diameter a of the pocket 1 is 150 to 250 mm, preferably 175 to 225 mm. The diameter a of the pocket 1 is determined depending on the number of pockets 1. 4 is formed to have a depth t0 approximately equal to that of the wafer W to be processed. Specifically, the depth t0 of the pocket 1 is 70 to 100 μm, preferably 75 to 95 μm. The depth t0 is in the range of 0.4 / 10 to 0.8 / 10 of the thickness t of the susceptor 10.

[0022] The diameter a of the pocket 1 is formed slightly larger than the diameter of the wafer W, and a plurality of protrusions 3 are provided along the inner wall of the lower portion of the inclined pocket 1. The lower portion of the pocket refers to the half circumference of the pocket on the outer edge side of the susceptor 10, and as shown in FIG. 1, all of the plurality of protrusions 3 are provided in this range. These protrusions 3 are for supporting the outer periphery of the wafer W. As shown in FIG. 3, the tips of the protrusions 3 protrude in an arc shape in a plan view, for example, a shape that is a semicircle of a perfect circle, and the wafer W is supported by the outer periphery of the wafer W coming into contact with the tips as shown.

[0023] For example, as shown in FIG. 3, the protrusions 3 are arranged on the inner wall of each pocket 1 symmetrically with respect to a line L1 connecting the center of the susceptor 10 (rotation axis O1) and the center O2 of the pocket 1. When there is an odd number of protrusions 3, one protrusion 3 (first protrusion) is positioned at the position farthest from the center of the susceptor 10 (rotation axis O1), and protrusions 3 (second protrusions) are positioned at positions rotated 90° to the left and right from there around the center O2 of the pocket portion 1 (three-point support). Alternatively, as shown in Figure 5, one protrusion 3 (first protrusion) is positioned at the position farthest from the center of the susceptor 10 (rotation axis O1), and protrusions 3 (second protrusion, third protrusion) are positioned at positions rotated 45° to the left and right from there around the center O2 of the pocket portion 1 (five-point support).

[0024] When the number of protrusions 3 is even, they are arranged symmetrically about a line L1 connecting the center of the susceptor 10 (rotation axis O1) and the center of the pocket portion 1. As shown in Fig. 7(a), for example, when there are two protrusions 3, the protrusions 3 are arranged at positions 60° to the left and right of the line L1 connecting the center of the susceptor 10 (rotation axis O1) and the center O2 of the pocket portion 1. Further, as shown in Fig. 7(b), when there are four protrusions 3, the protrusions 3 are arranged at equal intervals of 60° on the lower side in the pocket portion 1. Also, as shown in Fig. 7(c), when there are six protrusions 3, they are arranged at equal intervals of 36° on the lower side in the pocket portion 1. Note that even when there are four or six protrusions 3, they are arranged symmetrically about the line L1 connecting the center of the susceptor 10 (rotation axis O1) and the center O2 of the pocket portion 1. By arranging the protrusions 3 on the lower side in the pocket portion 1 in this way, it is preferable to support the wafer W at two or more and six or less points in the inclined pocket portion 1. By supporting the wafer W at two to six points of the protrusions 3, the wafer W can be supported without being damaged.

[0025] Also, as described above, the tip of the protrusion 3 has a shape in which a perfect circle is a semi-circle in plan view, and is connected to the inner wall of the pocket portion 1 with a width of a circular diameter dimension c (width dimension c of the protrusion 3). Here, as shown in Fig. 3, if the diameter of the pocket portion 1 is a and the diameter of the wafer W is b, it is preferable that (a - b) / 4 < c < (a - b) / 2. By having the width dimension c of the protrusion 3 satisfy (a - b) / 4 < c < (a - b) / 2, the wafer W can be placed in the pocket portion 1, and a uniform epitaxial film can be manufactured without the wafer W slipping during processing.

[0026] Also, as shown in Fig. 3, the length g of the protrusion 3 is preferably within the range of c / 2 < g < (a - b) / 2 with respect to the diameter a of the pocket portion 1, the diameter b of the wafer W, and the width dimension c of the protrusion 3. By having the length g of the protrusion 3 satisfy c / 2 < g < (a - b) / 2, the wafer W can be placed in the pocket portion 1, and a uniform epitaxial film can be manufactured without the wafer W slipping during processing.

[0027] Further, as shown in FIG. 4, the height e of the protrusion 3 is preferably within the range of f / 2 < e < f with respect to the thickness f of the wafer W. When the height e of the protrusion 3 is within the range of f / 2 < e < f, even if the wafer W slides, the wafer W does not ride on the protrusion 3, and a uniform epitaxial film can be manufactured without inhibiting the gas of the epitaxial film.

[0028] Also, the protrusion 3 is preferably made of the same material as the substrate 2 and integrally formed. That is, the protrusion 3 is preferably made of a carbon material or a carbon material whose surface is coated with silicon carbide (SiC). By forming the protrusion 3 of the same material as the substrate 2 and integrally, it is possible to suppress the separation of the protrusion 3 due to a difference in thermal expansion caused by heat during use.

[0029] To form an epitaxial film on the upper surface of the wafer W using the susceptor 10, in a chamber (not shown), the wafer W is placed in the pocket portion 1 of the susceptor 10 as shown in FIG. 6. When each pocket portion 1 has three protrusions 3 as shown in FIG. 3, the wafer W is held by three-point support. Then, while rotating the susceptor 10 and the wafer W at a predetermined speed in a predetermined direction (see FIG. 7), the wafer W is heated by a heater (not shown) provided outside the chamber. Then, it is brought into contact with the reaction gas G introduced horizontally into the chamber, and an epitaxial film is chemically vapor-grown on the wafer W.

[0030] Since the susceptor 10 is inclined from its central portion in both side surface directions, when forming an epitaxial film on the wafer W held in the pocket portion 1, the reaction gas G supplied horizontally flows along the shape of the susceptor as shown in FIG. 6. Thereby, the reaction gas G flows uniformly over the entire wafer W, and the variation in the film thickness of the epitaxial film to be formed is reduced. Also, since the wafer W is supported by a plurality of protrusions 3 in the pocket portion 1, the wafer W does not slide due to the centrifugal force caused by the rotation of the susceptor 10. That is, the inclination of the pocket portion 3 and the displacement of the wafer W due to centrifugal force can be prevented, and the above effects can be obtained.

[0031] Furthermore, it is preferable that the thickness t of the susceptor 10 is constant. In other words, it is preferable that the surface on which the pocket portion 1 is formed and the opposite surface are parallel to each other. By making the thickness t constant, the heat conduction throughout the susceptor 10 becomes uniform, and a uniform epitaxial film can be produced. Furthermore, as shown in FIG. 6, the reaction gas G flows along the upper surface of the susceptor, so that the reaction gas G impinges on the entire upper surface of the susceptor 10, contributing to the uniformity of the thickness of the epitaxial film formed on the wafer W.

[0032] The thickness t of the susceptor 10 is preferably 12 mm or more and 18 mm or less. The diameter d of the susceptor 10 is preferably 600 mm or more and 850 mm or less. When the diameter of the susceptor 10 is d and the thickness is t, the relationship 0.01≦t / d<0.05 is satisfied, preferably 0.02≦t / d≦0.04, and more preferably 0.02≦t / d≦0.03. In other words, when the thickness t of the susceptor 10 is 0.01 times or more and 0.05 times or less the diameter d, an epitaxial film with a uniform film thickness and reduced crystal defects can be formed.

[0033] In the above embodiment, the bottom surface of the susceptor 10 is described as being parallel to the slope of the upper surface and the pocket portion 1 (the thickness t of the susceptor 10 is constant), but the present invention is not limited to this configuration. For example, the upper surface of the susceptor 10 on which the pocket portion 3 is formed may be inclined from the center toward both sides, and the bottom surface of the susceptor 10 may be formed along the horizontal direction. Even in this case, the reaction gas G supplied horizontally flows along the shape of the susceptor when forming an epitaxial film on the wafer W held in the pocket portion 1. This allows the reaction gas G to flow uniformly over the entire wafer W, reducing variations in the thickness of the epitaxial film being formed. [Example]

[0034] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. (Experiment 1)

[0035] In experiment 1, the inclination angle (θ) from the center of the susceptor toward both side surfaces was set to 3.0°, and the positions and number of protrusions 3 provided in the pocket 1 were examined. Basically, when the number of protrusions 3 is an odd number (3, 5, or 7), as shown in Figures 3, 5, and 8, one protrusion 3 is placed at the position farthest from the center of the susceptor (the lowest), and further protrusions 3 are placed at positions rotated a predetermined angle to the left or right around the center of the susceptor as an axis from there. The protrusions 3 placed at the top of the left and right protrusions 3 are positioned 90° from the bottom of the pocket 1 (i.e., the rightmost and leftmost positions), and all of the protrusions 3 are placed at equal intervals on the lower inner wall surface of the pocket 1.

[0036] Also, as shown in Figures 7(a) to (c), when the number of protrusions 3 is an even number (2, 4, or 6), they are arranged symmetrically on the left and right sides of a line L1 connecting the center of the susceptor 10 (rotation axis O1) and the center O2 of the pocket portion 1. Table 1 shows the conditions for Examples 1 to 6 and Comparative Examples 1 to 3. In each example, an epitaxial film was formed on a silicon wafer using the fabricated susceptor, and the state of the film formation was evaluated. The evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1. In Table 1, a difference between the maximum and minimum film thicknesses of the epitaxial film within the wafer surface was marked with ◯ when it was 5 μm or less, × when it was more than 10 μm, and △ when it was more than 5 μm and 10 μm or less. Furthermore, after film formation, when the wafer was removed from the susceptor, a mark of ◯ was given if the wafer was free of scratches, an mark of × was given if the wafer was damaged and unusable, and a mark of △ was given if the wafer was scratched but usable.

[0037] [Table 1]

[0038] As shown in Examples 1 to 6, when the number of protrusions provided in the pocket portion was in the range of 2 to 7, the film formation results on the silicon wafer were good. On the other hand, when no protrusions were provided on the pockets (Comparative Example 1), the silicon wafer slipped and shifted position, and a uniform epitaxial film could not be obtained. Furthermore, when the protrusions were provided around the entire periphery of the pocket (Comparative Examples 2 and 3), the number of contact areas between the protrusions and the silicon wafer increased, causing damage to the outer periphery of the silicon wafer. [Explanation of symbols]

[0039] 1 Pocket 2 Base 3 Protrusion 10 Susceptor EP epitaxial film W wafer (semiconductor wafer)

Claims

1. A susceptor for epitaxial film growth having a recessed pocket for placing a semiconductor wafer thereon, and in which a reactant gas is supplied horizontally to the semiconductor wafer, comprising: a plurality of pockets on the upper surface of the base body, each of which is inclined downward radially outward and is formed of a circular bottom wall and an inner wall surrounding the bottom wall; a plurality of protrusions formed on the inner wall of the pocket portion to support the outer periphery of the semiconductor wafer; the plurality of protrusions are provided above the bottom surface of the concave pocket and are arranged on a lower side of the inclined pocket, a height e of the protrusion from a bottom surface of the concave pocket, where f is a thickness f of the semiconductor wafer, is in a range of f / 2<e<f; a width dimension c of the protrusion is within a range of (a-b) / 4<c<(a-b) / 2, where a is a diameter of the pocket and b is a diameter of the semiconductor wafer; A susceptor characterized in that the length g of the protrusion is within the range of c / 2<g<(ab) / 2.

2. 2. The susceptor according to claim 1, wherein the protrusions formed in the pocket are arranged symmetrically with respect to a line connecting the center of the base and the center of the pocket.

3. 2. The susceptor according to claim 1, wherein the number of protrusions formed in the pocket is two to six.

Images