WO2015068022A1

WO2015068022A1 - Susceptor with arched shape grooves on the substrates support surface

Info

Publication number: WO2015068022A1
Application number: PCT/IB2014/002357
Authority: WO
Inventors: Francesco COREA; Vincenzo Ogliari; Franco Preti; Mario Preti
Original assignee: Lpe S.P.A.
Priority date: 2013-11-11
Filing date: 2014-11-06
Publication date: 2015-05-14
Also published as: CN105705679B; ITCO20130058A1; CN105705679A

Abstract

The present invention relates to a susceptor for an epitaxial growth reactor; it substantially consists of a body (601) having a face (602) which comprises at least one zone (603) adapted to receive a substrate to be subjected to epitaxial growth; the zone (603) either has or is associated with a resting surface (604) for resting said substrate; the resting surface (604) is provided with patterns which comprise at least three pluralities (605A, 605B, 605C) of arch-shaped grooves (606); in particular, the concavity of said grooves (606) faces towards the edge of the resting surface (604).

Description

TITLE

SUSCEPTOR WITH ARCHED SHAPE GROOVES ON A SUBSTRATES SUPPORT SURFACE DESCRIPTION FIELD OF THE INVENTION

The present invention relates to a susceptor with patterns obtained on the resting surface of the substrates to be subjected to "epitaxial growth".

BACKGROUND ART

The epitaxial growth and the reactors for achieving it have been known for many decades; they are based on the technique known as "CVD", i.e. "Chemical Vapor Deposition".

A technical field in which they are used is that of the production of electronic components; the processes and reactors for this application are particular because a very high quality of the deposited layers is required and the quality requirements are still on the rise.

One of the types of epitaxial reactors employs a "susceptor", which is inserted in a reaction chamber and which supports one or more substrates to be subjected to epitaxial growth, placed on resting surfaces inside appropriate recesses (see reference numerals 10 and 1000 in

Fig. 1A); as known, the substrates can be perfectly circular or often have a flat (see substrate

1000 in Fig. IB within a perfectly circular recess).

For high-temperature epitaxial growth (no lower than 800°C, no higher than 2000°C, and generally from 1000°C to 1800°C according to the material to be grown), reactors where the chamber is heated and especially the susceptor obtained by electromagnetic induction or by resistance is heated, are often used.

Most of the prior art (Fig. 1) relates to the epitaxial growth of silicon, with process temperatures generally from 1 100°C to 1200°C, and to the reactors involved; indeed, only recently the electronic components made of silicon carbide have become more widely used. The operations of positioning and resting the substrates have several problems: sticking of the substrate to the resting surface, lateral displacement of the substrate with respect to the resting surface during and/or after the positioning of the substrate, deformation of the substrate placed on the resting surface (the substrate generally tends to become concave), lack of uniformity in heat transmission from the resting surface to the substrate, migration of substances from the resting surface to the substrate.

Therefore, continuous research is being conducted to find increasingly better solutions to these problems. This is also due to the increasingly stringent requirements for the quality of the grown substrates and for the quality and speed of the production processes.

SUMMARY The Applicant thus set the objective to provide a satisfactory solution to these problems. Such an objective is achieved by a susceptor having the technical features set forth in the appended claims, which form an integral part of the present description.

The idea underlying the present invention is that of using arch-shaped grooves as patterns on the substrate resting surface.

In particular, the patterns comprise at least three pluralities of arch-shaped grooves; the grooves of each plurality are typically parallel to one another; each groove of said plurality preferably starts in a first point on the edge of the resting surface and ends in a second point on the edge of the resting surface, said first point and said second point being remote from each other; the resting surface may be surrounded by an annular groove.

In particular, the concavity of the grooves faces towards the edge of the resting surface; more in particular, the concavity of each of the grooves faces towards the edge of the resting surface; even more in particular, the concavity of each of the grooves of each of the at least three pluralities faces towards the edge of the resting surface.

In particular, the concavity of each of the at least three pluralities of grooves is oriented in a different direction.

In particular, the concavity of the grooves is constant (i.e. does not change) over their whole longitudinal extension; more in particular, the concavity of each of the grooves is constant (i.e. does not change) over their whole longitudinal extension; even more in particular, the concavity of each of the grooves of each of the at least three pluralities is constant (i.e. does not change) over their whole longitudinal extension.

According to a preferred embodiment, each groove of said pluralities comprises a first and a second rectilinear end stretch, which are equal to each other and reciprocally inclined, and a third circular intermediate stretch, which joins the first and second rectilinear end stretches. LIST OF DRAWINGS

The present invention will become more apparent from the following detailed description to be considered in conjunction with the accompanying drawings, in which:

Fig. 1 shows a simplified section view and a partial top view of a disc-shaped body of a susceptor according to the prior art, with a substrate inserted in a recess thereof,

Fig. 2 shows a simplified section view of a first disc-shaped body of a susceptor according to the invention, with a substrate resting on a surface of a zone thereof,

Fig. 3 shows a simplified section view of a second disc-shaped body of a susceptor according to the invention, with a substrate resting on a surface of a zone thereof,

Fig. 4 shows a simplified section view of a third disc-shaped body of a susceptor according to the invention in combination with a first supporting element with a substrate resting on a surface of the element,

Fig. 5 shows a simplified section view of a fourth disc-shaped body of a susceptor according to the invention in combination with a first supporting element with a substrate resting on a surface of the element,

Fig. 6 shows a susceptor according to five different partial views, with a resting surface for substrates according to the present invention having patterns according to the present invention,

Fig. 7 shows a simplified section view of a disc-shaped body of a susceptor according to the prior art,

Fig. 8 shows a simplified section view of a fifth disc-shaped body of a susceptor according to the invention,

Fig. 9 shows a simplified section view of a sixth disc-shaped body of a susceptor according to the invention,

Fig. 10 shows a simplified section view of a seventh disc-shaped body of a susceptor according to the invention,

Fig. 1 1 shows a simplified section view of an eighth disc-shaped body of a susceptor according to the invention in combination with a second supporting element with a substrate resting on a surface of the element,

Fig. 12 shows a simplified section view of a ninth disc-shaped body of a susceptor according to the invention in combination with a third supporting element with a substrate resting on a surface of the element,

Fig. 13 shows a simplified section view of a tenth disc-shaped body of a susceptor according to the invention in combination with a fourth supporting element with a substrate resting on a surface of the element,

Fig. 14 shows a simplified section view of an eleventh disc-shaped body of a susceptor according to the invention in combination with a fifth supporting element with a substrate resting on a surface of the element,

Fig. 15 shows a simplified section view of a twelfth disc-shaped body of a susceptor according to the invention in combination with a fifth supporting element with a substrate resting on a surface of the element,

Fig. 16 shows a simplified section view of a thirteenth disc-shaped body of a susceptor according to the invention in combination with a frame and a sixth supporting element with a substrate resting on a surface of the element, and

Fig. 17 shows a simplified section view of a fourteenth disc-shaped body of a susceptor according to the invention in combination with seventh supporting elements with substrates resting on a surface of the elements.

Such a description and such drawings are provided by way of mere example and therefore are non-limiting.

As it can be easily understood, the present invention which is defined in the appended claims with regard to the main advantageous aspects thereof can be practically implemented and applied in various manners.

DETAILED DESCRIPTION

As mentioned, the key element of the present invention is a pattern obtained on the substrate resting surface.

In the example in Fig. 2, susceptor 20 is similar to susceptor 10 in Fig. 1 , is disc-shaped and provided with a circular recess in which substrate 1000 rests; unlike susceptor 10 in Fig. 1 , susceptor 20 in Fig. 2 has a resting surface of the recess with a pattern (indicated by a dashed line) according to the present invention.

Susceptor 30 in Fig. 3 comprises a relief which has a resting surface with a pattern (indicated by a dashed line) according to the present invention; substrate 1000 rests on the relief.

Susceptor 40 in Fig. 4 is similar to susceptor 20; however, its recess is thicker; indeed, a supporting element 41 is stably inserted therein; substrate 1000 rests on a resting surface of the element 41 provided with a pattern (indicated by a dashed line) according to the present invention.

Susceptor 50 in Fig. 5 is similar to susceptor 30; but its raised part is not as thick; indeed, a supporting element 51 is stably mounted thereon; substrate 1000 rests on a resting surface of the element 51 provided with a pattern (indicated by a dashed line) according to the present invention.

These susceptors substantially consist of disc-shaped bodies; their recesses or reliefs (the number of which typically varies from one to ten) may be perfectly circular or circular with a flat.

Elements 41 and 5 1 are thin, perfectly circular discs or circular discs with a flat.

A very advantageous example of this pattern is shown in Fig. 6.

In Fig. 6 (see Fig. 6D in particular), the disc-shaped body of the susceptor is indicated by reference numeral 601 and has a face 602 with a zone 603 adapted to receive a substrate to be subjected to epitaxial growth (not shown in the figure); zone 603 is a recess and has a resting surface 604 for the substrates to rest directly thereon.

In this example, both the recess and the resting surface are perfectly circular (see Fig. 6A in particular); furthermore, the resting surface is slightly concave (see Fig. 6D).

The pattern of surface 604 comprises at least three pluralities 605 A, 605B, 605C of arch- shaped grooves 606; the typical number of pluralities to be used is three or four or five, but the preferable number is three (as shown in Fig. 6A).

Each of the pluralities 605 A, 605B, 605C extends in a different sector 607 A, 607B, 607C of surface 604; the grooves 606 of each plurality 605A, 605B, 605C do not cross one another and the grooves of one plurality (for example 605A) do not cross the grooves of any other plurality (for example 605B and 605C).

In the example in Fig. 6, the concavity of each of the grooves 606 of each plurality 605A, 605B, 605C faces the edge of the resting surface 604; in particular, the concavities of the three pluralities 605A, 605B, 605C are oriented in three different directions.

In the example in Fig. 6, the concavity of each of the grooves 606 of each of the pluralities 605A, 605B, 605C is constant (i.e. does not change) over their whole longitudinal extension. Preferably, the grooves 606 of each of the pluralities 605A, 605B, 605C are substantially parallel to one another.

Typically, all the sectors 607A, 607B, 607C are reciprocally equal.

Each groove 606 starts in a first point (for example, 608 in Fig. 6B) on the edge of the resting surface 604 and ends in a second point (for example, 609 in Fig. 6B) on the edge of surface 604; the first point (for example, 608 Fig. 6B) and the second point (for example, 609 Fig. 6B) are remote and spaced apart from each other.

According to an advantageous embodiment (see Fig. 6A), the shape of grooves 606 comprises a first and a second rectilinear end stretch which are equal to each other and reciprocally inclined (e.g., by an angle of 90° or 120° or 72°, as shown in Fig. 16C) and a third circular intermediate stretch, which joins the first and second rectilinear end stretches. According to this embodiment (see Fig. 6A), the first rectilinear stretches of all the grooves of a plurality of grooves are perfectly parallel to one another; the second rectilinear stretches of a plurality of grooves are perfectly parallel to one another; the third rectilinear stretches of all the grooves of a plurality of grooves are substantially parallel to one another. The curvature radius of the third stretches is very large and its value is similar for all grooves; for example, according to the embodiment, the curvature radius may range from 5% to 20% of the outer radius of the resting surface.

In the example in Fig. 6, grooves 606 correspond to a solid line; however, alternatively but in a substantially equivalent manner, could correspond to a dashed line, for example.

In the example in Fig. 6, grooves 606 correspond to a slightly curved line (sometimes even straight); however, alternatively but in a substantially equivalent manner, they could correspond to a wavy line, for example.

In the example in Fig. 6, all the grooves 606 of the pluralities 605A, 605B, 605C are arch- shaped; however, according to an alternative, pejorative solution, either one or some or all the grooves of the pluralities could be straight; in this case, the resting surface would not be uniformly provided with grooves.

The shape of the groove section is advantageously substantially triangular (in particular with rounded corners, as shown in Fig. 6E); the opening angle of the triangle may be 90°- 150°, for example.

The depth of the grooves may be of 0.1-0.2 mm, for example.

The distance between the adjacent grooves may be of 0.5- 1.0 mm, for example.

In the example shown in Fig. 6, the recess for receiving the substrates comprises two thin cylindrical volumes (as shown in particular in Figs. 6C and 6D); the radius of the upper cylinder is slightly greater than the radius of the lower cylinder to facilitate the operation of handling the substrates (e.g. 2-4 mm); the diameter of the substrates is nearly equal to or slightly smaller than the diameter of the lower cylinder.

In the example shown in Fig. 6, the resting surface is surrounded by a circular groove 610, which is in communication with all the grooves 606 of the pluralities 605 A, 605B, 605C (as shown in Fig. 16C); the width of this circular groove may be of 1 -2 mm, for example.

Alternatively, the groove which surrounds the resting surface may be interrupted in several points and may thus consist of the whole of a plurality (e.g., three or four or five, equal to the number of pluralities of grooves) of circular groove stretches of different, or

advantageously equal, length.

The distance between next, parallel grooves 606 may be variable (see Fig. 6B and Fig. 6E); it may be similar to the width of the grooves themselves, i.e. 1 -2 mm (it is worth noting that it is undulation wave, in theory - in practice such a shape is only theoretical); it may be greater, i.e. 2- 10 mm; it may be much greater, i.e. 10-20 mm; in the latter case, there are flat zones 61 1, which may be advantageously lined or rough or knurled parts.

This pattern has the advantage of discharging the gas around the substrate, in particular in the annular groove; such a gas discharge is gradual as the substrate bulges and sets down on the concave surface on the recess bottom. The arched shape, thus without any type of corners, is particularly advantageous because it does not cause stress or thermal peaks on the SiC layer applied to the C underneath (naturally, the cross section of the groves must also by gradual i.e. without corners, for example neither square nor rectangular); moreover, it allows a very smooth discharging of the gas in all directions and thus minimizes the risk of horizontal movements of the substrate; finally, it collects circumferentially (thus with a large surface) and discharges radially.

In the example in Fig. 6, the pattern concerns the whole resting surface but alternatively the pattern could concern it only partially, for example only an outer annular area.

Fig. 7 shows a body 701 of a disc-shaped susceptor according to the prior art, in which a recess 703 has a slightly concave, smooth and flat resting surface 704.

In the example in Fig. 8, a body 801 of a disc-shaped susceptor comprises a circular recess 803 having a slightly concave resting surface 804; surface 804 is patterned and the figure diagrammatical ly shows one of the plurality of grooves 806 (for example, like the grooves 606) at a constant depth which leads into an annular groove 810, much deeper than the grooves 806.

In the example in Fig. 9, a body 901 of a disc-shaped susceptor comprises a circular recess 903, having a slightly concave resting surface 904; surface 904 is patterned and the figure diagrammatically shows one of the plurality of grooves 906 (for example, like the grooves 606) at a variable depth (in particular, minimum in the center and maximum at the edge) which leads into an annular groove 810; the bottom of the grooves 906 and 910 is on the same level and this may facilitate the patterning of the part.

In the example in Fig. 10, a body 1001 of a disc-shaped susceptor comprises a circular recess 1003 having a slightly a slightly concave resting surface 1004; surface 1004 is patterned and the figure diagrammatically shows one of the plurality of grooves 1006 (for example, like the grooves 606) at a variable depth (in particular, minimum in the center and maximum at the edge) which leads into an annular groove 1010; the bottom of the grooves 1006 and 1010 is on the same level and this may facilitate the patterning of the part; it is worth noting that the depth of groove 1006 is zero (or nearly zero) in the center of recess 1003.

Alternative solutions to those in Fig. 8, Fig. 9, Fig. 10 may comprise a plurality of recesses like those shown in these figures.

The examples in figures from 1 1 to 15, include a susceptor with a disc-shaped body comprising a recess; a supporting element is inserted in the recess; the supporting element has a resting surface provided with a pattern (indicated by a dashed line) according to the present invention; in other words, the recess is simply associated with a resting surface for substrates, but does not possess it directly.

In the example in Fig. 1 1 , the body is indicated by reference numeral 1 101 and the supporting element 1 120 is a disc with a thin raised edge; it thus has a recess for substrate 1000 and the edge surrounds the substrate 1000 and the resting surface. The recess of body 1 101 has a bevel on the edge to facilitate the mechanical gripping of element 1 120.

In the example in Fig. 12, the body is indicated by reference numeral 1201 and the supporting element 1220 is a disc with a thick raised edge; it thus has a recess for substrate 1000 and the edge surrounds the substrate 1000 and the resting surface. In the example in Fig. 13, the body is indicated by reference numeral 1301 and the supporting element 1320 is a disc with a thin raised ring which is recessed with respect to the edge of the disc; it thus has a recess for substrate 1000 and the ring surrounds the substrate 1000 and the resting surface.

In the example in Fig. 14, the body is indicated by reference numeral 1401 and the supporting element 1420 is a disc with a shaped edge which forms an "L"-shape in section; it thus has a recess for substrate 1000 and the edge surrounds the substrate 1000 and the resting surface.

In the example in Fig. 15, the body is indicated by reference numeral 1501 and the supporting element 1520 is identical to the supporting element in Fig. 14. The difference between the solution in Fig. 14 and the solution in Fig. 15 consists in that the recess of body 1401 is complementary to element 1420, while the recess 1501 leaves a gap between the surface of the recess and the surface of element 1520; such a space may be used, for example, to facilitate the operation of handling the supporting element.

It is worth noting that the supporting elements with a patterned resting surface either equal or similar to those shown in figures from 1 1 to 15 may be combined not only with susceptor bodies with one or more recesses, but also with susceptor bodies with one or more reliefs. Furthermore, it is worth noting that the outer shape of supporting elements equal or similar to those shown in the figures from 1 1 to 15 may be perfectly circular or circular with a flat. Finally, it is worth noting that the shape of the recesses of supporting elements equal or similar to those shown in the figures from 1 1 to 15 may be perfectly circular or circular with a flat.

Fig. 16 refers to the application of the present invention to a case in which the susceptor comprises a disc-shaped body and at least one supporting element and a corresponding frame; the solution in Fig. 16 includes just one supporting element and just one frame;

however, alternative solutions may include a plurality (e.g. three or four or five or six) of supporting elements and a corresponding plurality (e.g. three or four or five or six) of frames.

Fig. 16 shows the coupling of a supporting element 1630 and a frame 1640 which surrounds it; in Fig. 16A, such a coupling is shown when inserting the body 1601 of the susceptor in a recess 1603, which susceptor body will then be stably set at the bottom of recess 1603; at the end of the operation, the supporting element 1630 will also be stably set at the bottom of recess 1603; alternatively, the supporting element 1630 could be slightly more spaced apart from the bottom of recess 1603 (e.g. by 0.5 mm).

The supporting element 1630 has a patterned resting surface according to the present invention (indicated by the dashed line) on the upper face thereof, for resting a substrate (the substrate 1000 in the figure, adjacent to element 1630).

Element 1630 is substantially a thick disc, but on the lower face thereof it has a slot for coupling to frame 1640.

Fig. 17 refers to the application of the present invention to a case in which the susceptor comprises a disc-shaped body 1701 and a plurality (e.g. three or four or five or six) of supporting elements 1720.

Body 1701 comprises a plurality of through holes in which elements 1720 are inserted, respectively.

The supporting elements 1 720 have a patterned resting surface according to the present invention (indicated by the dashed line) on the upper face thereof, for resting the substrates (the substrate 1000 in the figure, adjacent to elements 1720).

Elements 1720 are substantially thick discs, but they have a slot on the lower face thereof for coupling to the holes of body 1701.

In Fig. 17, a central recess is shown on the back of the susceptor body, which serves to guide the rotation of the body itself.

Claims

1. A susceptor for an epitaxial growth reactor, consisting of a body (601) having a face (602) which comprises at least one zone (603) adapted to receive a substrate to be subjected to epitaxial growth, wherein said zone (603) either has or is associated with a resting surface (604) for resting said substrate, and wherein said resting surface (604) is provided with patterns,

characterized in that said patterns comprise at least three pluralities (605A, 605B, 605C) of arch-shaped grooves (606).

2. A susceptor according to claim 1 , wherein each plurality (605 A, 605B, 605C) of grooves (606) extends in a different, separate sector (607A, 607B, 607C) of said resting surface (604).

3. A susceptor according to claim 2, wherein the sectors (607A, 607B, 607C) of said resting surface (604) are reciprocally equal.

4. A susceptor according to claim 2 or 3, wherein in each plurality (605A, 605B, 605C), the grooves (606) are separated from one another.

5. A susceptor according to claim 4, wherein the grooves (606) of each plurality (605 A, 605B, 605C) are parallel to one another.

6. A susceptor according to any one of the preceding claims, wherein each groove (606) of said pluralities (605A, 605B, 605C) starts in a first point (608) on the edge of said resting surface (604) and ends in a second point (609) on the edge of said resting surface (604), said first point (608) and said second point (609) being remote from each other.

7. A susceptor according to any one of the preceding claims, wherein said resting surface (604) is surrounded by an annular groove (610).

8. A susceptor according to any one of the preceding claims, wherein each groove (606) of said pluralities (605A, 605B, 605C) comprises a first and a second rectilinear end stretch equal to each other and reciprocally inclined, and a third intermediate circular stretch which joins the first and second rectilinear end stretches.

9. A susceptor according to any one of the preceding claims, wherein the surface (61 1) between two grooves (606) is lined or rough or knurled.

10. A susceptor according to any one of the preceding claims, wherein said resting surface (604) is concave.

1 1. A susceptor according to any one of the preceding claims, wherein said zone is a recess (603) or a relief of said body (601).

12. A susceptor according to any one of the preceding claims from 1 to 1 1 , comprising at least one supporting element for said substrate, wherein said supporting element has said resting surface, and wherein said at least one supporting element is set down on said at least one zone.

13. A susceptor according to any one of the claims from 1 to 1 1 , comprising at least one supporting element for said substrate and at least one frame for said supporting element, wherein said at least one frame comprises a hole, wherein said supporting element has said resting surface, and wherein said at least one frame is set on said at least one zone, and said at least one supporting element is inserted in said hole.

14. An epitaxial growth reactor comprising at least one susceptor for supporting and heating substrates according to any one of the preceding claims.