WO2015092527A1

WO2015092527A1 - Susceptor with curved and concentric grooves on the substrates support

Info

Publication number: WO2015092527A1
Application number: PCT/IB2014/002817
Authority: WO
Inventors: Francesco COREA; Danilo Crippa; Vincenzo Ogliari; Franco Preti; Mario Preti
Original assignee: Lpe S.P.A.
Priority date: 2013-12-19
Filing date: 2014-12-17
Publication date: 2015-06-25
Also published as: CN105814243A; CN105814243B; ITCO20130072A1

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 a plurality of curved groove stretches (606) having their center substantially in the same location (605) as said resting surface (604).

Description

TITLE

SUSCEPTOR WITH CURVED, CONCENTRIC PATTERNS

ON THE SUBSTRATE RESTING SURFACE

DESCRIPTION

FIELD OF THE INVENTION

The present invention mainly 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 where 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 or by radiation is heated, are often used.

Most of the prior art (Fig. 1) relates to the epitaxial growth of silicon, with process temperatures generally from 1000°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, lack of uniformity in heat transmission from the resting surface to the substrate, migration of substances between the resting surface and 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. In the past, it was thought to shape the substrate recess with a deep peripheral annular groove and to provide the resting surface in the groove with a slightly concave shape and with some relatively narrow, short radial notches which lead into the groove and which are used to discharge gas trapped between substrate and resting surface in the groove.

SUMMARY

The Applicant thus set the objective to provide a satisfactory solution to these problems, also because the above-described specific solution is satisfactory but not optimal.

Indeed, the Applicant has observed that the substrates tend to stick to the resting surface, especially in the central area thereof where there are no notches; moreover, the Applicant notices that the few, narrow notches cannot perform the function of discharging the gas which is between the central area of the substrate and the central area of the resting surface when the substrate is placed in the recess (i.e. first lowered and then laid down).

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 a plurality of curved groove stretches as patterns on the substrate resting surface. In particular, the center of the groove stretches is substantially in the same location as the resting surface; such groove stretches are used to mimic a rough surface, and thus they particularly avoid even microscopic movements, e.g. translations of 0.1-1.0 mm, or macroscopic movements, e.g. rotations of

360° or more, during the epitaxial growth processes.

According to a preferred embodiment, the groove stretches are joined to form one or more spirals; additionally, the patterns of the resting surface further comprise a plurality of notches which preferably end in an annular groove which surrounds the resting surface, and which are used to discharge the gas trapped between substrate and resting surface, in particular, in a peripheral annular groove.

It is worth noting that the Applicant has also devised a particularly effective, specific configuration of the notches (in particular, a triangular or substantially triangular shape and/or with variable depth) even without curved groove stretches.

The resting surface may be provided with curved groove stretches in a first patterned area and with notches in a second patterned area; the first and second areas may be mutually different.

According to a first further aspect, the present invention relates to a reactor for epitaxial growth comprising at least one susceptor with patterns comprising a plurality of curved groove stretches having their center substantially in the same location.

According to a second further aspect, the present invention relates to a method for receiving and supporting a substrate in a stable manner (i.e. without either microscopic movements, e.g. translations of 0.1-1.0 mm, or macroscopic movements, e.g. rotations of 360° and more, during the growth process), which substrate is to be subjected to an epitaxial growth process on a susceptor of an epitaxial reactor thus avoiding the substrate from sticking on the susceptor during the epitaxial growth process; according to such a method, a resting surface is provided for resting the substrate on the susceptor, and patterns are provided on the resting surface; the patterns comprise a plurality of curved groove stretches having their center substantially in the same location as the resting surface

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 two 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. 11 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 for stably receiving and supporting a substrate to be subjected to an epitaxial growth process.

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 for stably receiving and supporting a substrate to be subjected to an epitaxial growth process; 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 for stably receiving and supporting a substrate to be subjected to an epitaxial growth process.

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 for stably receiving and supporting a substrate to be subjected to an epitaxial growth process.

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.

The component portion (i.e. the disc-shaped body or the supporting element) which is under the resting surface is a solid body, i.e. does not have holes or cavities.

The supporting elements 41 and 51 are thin, perfectly circular discs or circular discs with a flat.

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

In Fig. 6 (see Fig. 6B 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 603 and the resting surface 604 are perfectly circular (see Fig. 6A in particular) and have center 605 at the intersection of a horizontal axis X and a vertical axis Y; furthermore, the resting surface 604 is slightly concave (see Fig. 6B); in fact, recess 603 is the combination of two thin cylindrical recesses of slightly different diameters placed one under the other (as clearly seen in Fig. 6B).

The pattern of surface 604 comprises a single spiral-shaped groove 606 and the groove has its center in the center 605 of the resting surface 604; thereby, the resting surface is rough. For the purposes of the required technical effect, i.e. of roughness, the single groove 606 may be considered as a plurality of curved groove stretches joined to form a single groove; all such curved groove stretches have their center substantially in the same location which, in the example in Fig. 6, corresponds to the center 605 of the resting surface 604, as well as the center of recess 603 (namely, the centers of the various curved groove stretches are located in a central zone of the resting surface 604 which may have an area of 3-50 mm2, for example).

For example, in order to obtain the required roughness, the groove stretches (either joined or separate) may have a depth from 0.05 mm to 0.30 mm, preferably from 0.05 mm to 0.15 mm. For example, in order to obtain the required roughness, the groove stretches (either joined or separate) may have a substantially triangular (opening angle 90°-150°) or substantially circular (as shown in Fig.6B) cross-section.

For example, in order to obtain the required roughness, the groove stretches (either joined or separate) may have a distance (between adjacent stretches) from 0.5 mm to 3.0 mm, preferably from 0.5 mm to 1.5 mm; Fig.6B shows two groove stretches 606-1 and 606-2 (corresponding to two stretches of the same spiral-shaped groove 606 shown in Fig.6A) adjacent to each other and placed at a given distance. The distance between adjacent grooves is typically constant (as shown in Fig.6A), and thus reference may be made to parallel stretches although they are curved in shape; with reference to the spiral in Fig.6, it would be more correct to say that it has a constant pitch.

According to a minor change to the example shown in Fig.6, the groove stretches could be separate and located at the single spiral shape (from the graphic point of view, the spiral can be seen as drawn with a dashed line).

According to a variant of the example in Fig.6, there could be more than one spiral, e.g. two or three or four, etc., but all having the same center, in particular corresponding to the center

605 of the resting surface 604, as well as the centre of recess 603. Also in this case, the groove stretches could be joined to form the various spirals or be separate.

The spiral shape of the groove, in particular the single spiral shape, is very advantageous because it can be made using a tool with a bit of appropriate shape and size, which bores and turns about the centre of the resting surface following the spiral path.

An alternative solution to spiral(s) consists in using perfectly circular or elliptical grooves; also in this case, the curved stretches have the same center corresponding to the center of the resting surface. Such stretches may be joined to form a plurality of concentric

circumferences or ellipses or be separate.

As mentioned, such groove stretches may be separate; in this case, the distance between two subsequent stretches may typically be from 1 mm to 10 mm.

In the recess 603 of the embodiment in Fig.6, there is a deep (e.g. from 2 to 4 mm) peripheral annular groove 610 which surrounds the resting surface 604; unlike that shown in the figure, some groove stretches (e.g. the spiral(s)) may end in the annular groove.

The patterns of the resting surface 604 further comprise a plurality of notches 607 which preferably end in the annular groove 610.

Such notches may be relatively short, e.g. from 5 to 25 mm; such notches may be radial, such notches may have triangular shape (opening towards the periphery of the resting surface as shown in Fig.6A); the number of such notches may be high, e.g. from 60 to 360; such notches may have a depth from 1 mm to 2 mm (as shown in Fig.6B, because of the resting surface 604 being concave, notch 607 has a variable depth, minimum towards the center and maximum towards the periphery).

In the example in Fig.6, the resting surface 604 is divided into a first circular central area 608 and a second annular peripheral area 609; these two areas are mutually different. In the first area 608, the patterns have curved groove stretches; in the second area 609, the patterns have notches. It is worth noting that in Fig.6, the areas 608 and 609 are adjacent;

alternatively, these two areas may be separated from each other, e.g. by an intermediate annular area in which there are no patterns.

According to an alternative embodiment, such curved groove stretches reach the outer edge of the resting surface, and thus such curved grooves intersect with such notches.

According to simpler embodiments, the patterns are made by means of curved groove stretches or by means of such notches only.

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 diagrammatically 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 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 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 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 11 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. 11, the body is indicated by reference numeral 1101 and the supporting element 1120 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 1101 has a bevel on the edge to facilitate the mechanical gripping of element 1120.

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 11 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 11 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 11 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 1720 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 a plurality of curved groove stretches (606) having their center substantially in the same location (605) as said resting surface (604).

2. A susceptor according to claim 1, wherein said groove stretches (606) are located at least at a spiral.

3. A susceptor according to claim 1, wherein said groove stretches are located at a series of spirals.

4. A susceptor according to claim 1, wherein said groove stretches are located at a plurality of concentric circumferences or ellipses.

5. A susceptor according to any one of the preceding claims, wherein some of said groove stretches (606-1, 606-2) are parallel to one another.

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

7. A susceptor according to claim 6, wherein some of said groove stretches end in said annular groove.

8. A susceptor according to claim 6 or 7, wherein said patterns further comprise a plurality of notches (607) which preferably end in said annular groove (610).

9. A susceptor according to claim 8, wherein said resting surface (604) is provided with curved groove stretch patterns (606) in a first area (608) thereof, and with notch patterns (607) in a second area (609) thereof, said first (608) and second (609) areas being mutually different.

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

11. 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 11, 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 11, 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.

15. A method for stably receiving and supporting a substrate to be subjected to an epitaxial growth process on a susceptor of an epitaxial reactor thus avoiding the substrate from sticking on the susceptor during the epitaxial growth process,

wherein a resting surface is provided for the substrate to rest on the susceptor, and wherein patterns are provided on the resting surface;

characterized in that said patterns comprise a plurality of curved groove stretches having their center substantially in the same locations as the resting surface.