ITCO20130040A1 - COVERED SUSCECTOR - Google Patents

Description

Patent application for industrial invention entitled:

"COVERED BEARER"

DESCRIPTION FIELD OF THE INVENTION

The present invention relates to a susceptor coated with silicon carbide and having at least one zone for receiving substrates to be subjected to "epitaxial growth".

STATE OF THE TECHNIQUE

Epitaxial growth and the reactors to obtain it have been known for many decades; the technique on which they are based is known as "CVD", or "Chemical Vapor Deposition".

A sector of the technique 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 is required for the deposited layers and the quality requirements are constantly increasing.

One of the typologies 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 (see references 10 and 1000 in Fig.lA); as known, the substrates can be perfectly circular or, often, with a "fiat" (see substrate 1000 in Fig.lB).

The present invention relates precisely to such a susceptor, in particular by epitaxial growth of silicon carbide at high temperature (1 550-1750 ° C).

Typically, for the epitaxial growth of silicon carbide at high temperature, reactors with a reaction chamber with hot walls are used; the heating of the chamber and of the susceptor is generally obtained by electromagnetic induction or by resistance.

Much of the known art (Fig. 1) refers to the epitaxial growth of silicon, with process temperatures up to 1,250 ° C, and to the related reactors; in fact, only fairly recently have silicon carbide electronic components become popular.

Initially, that is many decades ago, the susceptor was made entirely of graphite.

However, at that time, graphite was found to contaminate substrates as impurities present in susceptor graphite partially migrated to the overlying substrates during epitaxial growth processes.

At that time, it was thought to cover the susceptor, which was made entirely of graphite, by depositing a thin layer of silicon carbide (in Fig. 1 A, the dashed line indicates the boundary between external silicon carbide and internal graphite); the coating affected the entire surface of the susceptor. This solution has proved to be fully satisfactory for many decades, ie substantially up to the present day.

SUMMARY

Recently, the Applicant has realized, also in the light of the ever increasing quality requirements of the grown substrates and of the quality and speed of the production processes, that, in case of epitaxial growth of silicon carbide at high temperature, the silicon carbide layer of the susceptor in contact with the silicon carbide substrates subjected to epitaxial growth causes problems; a first problem is related to the fact that the substrates tend to adhere to the susceptor; a second problem is linked to the fact that the silicon carbide of the layer tends to migrate towards the overlying substrates (it is assumed that first sublimation and then solidification occurs).

The Applicant has therefore decided to entirely cover the susceptor, entirely in graphite, by means of a thin layer of tantalum carbide instead of silicon carbide.

The use of this material has substantially solved both of the problems mentioned above; however, a new problem arose; during the epitaxial growth processes of silicon carbide, the silicon carbide is deposited not only on the substrates, but also on the face of the susceptor exposed to the flow of precursor gases, ie on the surface of the susceptor adjacent to the substrates; the gradual accumulation (process after process) of silicon carbide on one face of the susceptor causes a slight and progressive curvature of the susceptor; in other words, after a certain number of epitaxial growth processes, the susceptor is somewhat rounded. This change in the shape of the susceptor creates problems both for the functioning of the reactor and for the quality and uniformity of the epitaxial growth processes.

The Applicant has therefore set itself the goal of solving the problems set out above.

This object is substantially achieved thanks to the susceptor having the technical characteristics set out in the attached claims which form an integral part of the present description.

The idea behind the present invention is to cover a graphite susceptor only partially with silicon carbide; to receive the substrates to be subjected to epitaxial growth, at least a specific zone is provided which can be lowered with respect to the part of susceptor that surrounds it or raised or, at the limit, at the same level.

LIST OF FIGURES

The present invention will become clearer from the detailed description which follows to be considered together with the annexed drawings in which:

Fig. 1 shows a simplified sectional view and a partial top view of a discoidal body of a susceptor according to the prior art with a substrate inserted in its recess,

Fig. 2 shows a schematic view (in section) of a discoidal body of a susceptor according to a first example of embodiment of the present invention - this figure is obviously out of scale,

Fig. 3 shows a schematic view (in section) of a discoidal body of a susceptor according to a second example of embodiment of the present invention - this figure is obviously out of scale,

Fig. 4 shows a simplified sectional view of a first example of a substrate support member to be used in combination with a susceptor body,

Fig. 5 shows a simplified sectional view of a second example of a substrate support member to be used in combination with a susceptor body,

Fig. 6 shows a simplified sectional view of a third example of a substrate support member to be used in combination with a susceptor body,

Fig. 7 shows a simplified sectional view of a fourth example of a substrate support member to be used in combination with a susceptor body,

Fig. 8 shows a simplified sectional view of a fifth example of a substrate support member to be used in combination with a susceptor body,

Fig. 9 shows a simplified sectional view and a partial top view of an example of a coupling of a support member and a frame to be used in combination with a susceptor body (the susceptor body is shown partially and in a simplified), Fig. 10 shows a simplified and partial sectional view of a first combination of a susceptor body and a support element for substrates,

Fig. 11 shows a simplified and partial sectional view of a second combination of a susceptor body and a support member for substrates,

Fig. 12 shows a simplified and partial sectional view of a third combination of a susceptor body and a support member for substrates,

Fig. 13 shows a simplified and partial sectional view of a fourth combination of a susceptor body and a support member for substrates,

Fig. 14 shows a simplified and partial sectional view of a fifth combination of a susceptor body and a support member for substrates,

Fig. 15 shows a simplified and partial sectional view of a sixth combination of a susceptor body and a substrate support member, and

Fig. 16 shows a simplified sectional view and a top view of a seventh combination of a susceptor body and support elements for substrates.

Both this description and these drawings are to be considered for illustrative purposes only and therefore not for limitation purposes.

It should be noted that this description considers various innovative concepts (and ways of implementing them in practice) which are independent of each other, but which can be advantageously combined with each other.

As can be easily understood, there are various ways of practicing the present invention which is defined in its main advantageous aspects in the appended claims.

DETAILED DESCRIPTION

Fig.2 and Fig.3 are schematic; in particular, the susceptor bodies have distorted dimensions to highlight their details and have a single area suitable for receiving substrates for simplicity; in reality, the susceptor bodies can have one or more regions suitable for receiving substrates, typically identical to each other.

It is considered useful to clarify that, in many of the figures, there are parts adjacent to each other which are shown as if they were slightly spaced only to allow a better view of their shapes.

Fig. 2 shows a susceptor for an epitaxial growth reactor consisting of a solid discoidal body 20 made entirely of graphite having a first face and a second face. Typically, the body is placed inside a reaction chamber so as to be horizontal and therefore the first face corresponds to the upper face and the second face corresponds to the lower face. The first face comprises a circular recess 21 adapted to receive a substrate to be subjected to epitaxial growth. As will be better understood hereinafter, the recess can receive the substrates directly or indirectly the substrates through, for example, a support element; of course, the size of the withdrawal in the first case is smaller than the size of the withdrawal in the second case. The first face therefore exposes a lowered upper surface 22 corresponding to the bottom of the recess 21 and a raised upper surface 23 surrounding the recess 21, while the second face exposes a lower surface 24.

The raised upper surface 23 is covered with an exposed layer 27 of silicon carbide.

At least part of the lower surface 24 is covered with an exposed layer 28 of silicon carbide; in Fig.2, the layer 28 entirely covers the surface 24 for ease of manufacture.

In this way, it is possible to considerably limit the progressive curvature of the susceptor; in fact, it has been experimentally verified that the deformations due to the silicon carbide layers on the upper and lower surfaces tend to compensate each other; this is true even if, during the use of the susceptor for silicon carbide epitaxial growth processes, further silicon carbide is deposited on the upper surface - of course, a progressive deformation of the susceptor cannot be completely avoided also due to such further deposition.

As regards the problem of material migration from the bottom of recess 21, there are two alternatives.

According to the first alternative (shown in Fig.2), the entire lowered upper surface 22 is covered with an exposed layer of graphite; typically, this layer corresponds to the graphite of the discoidal body. In fact, the evolution of materials has led to being able to obtain excellent quality graphite and therefore any small contamination due to graphite, in particular the impurities contained, is not harmful.

According to the second alternative (not shown in Fig. 2), the entire lowered upper surface is covered with an exposed layer of tantalum carbide. In fact, the sublimation of the tantalum carbide is negligible at the epitaxial growth temperatures of the silicon carbide (1'550-1'750 ° C).

Moreover, it was thought to make susceptors completely in sintered silicon carbide as these could have neither substantial problems of migration of the material towards the overlying substrates nor substantial problems of deformation during use. However, this solution is quite expensive, taking into account the fact that the susceptor must be replaced after a certain period of use.

The dimensions of the discoidal body of the susceptor can be indicative: diameter of 200-400 mm, thickness of 5-10 mm, diameter of the recess 100-200 mm, depth of the recess 1-4 mm, number of recesses from 1 to 10; the dimensions of the silicon carbide substrates (homoepitaxial growths) can be indicative: thickness of 250-500 μ and diameter of 100-200 mm; the epitaxial growth processes of silicon carbide for electronic applications generally foresee depositions of 2-20 μ, however, it is possible to push up to 100 μ and beyond.

In the example of Fig.2, the silicon carbide layer 27 on the upper surface 23 reaches the inner side 25 of the recess 21; in the example of Fig.2, the silicon carbide layer 27 on the upper surface 23 reaches the outer side 26 of the discoidal body 20; typically and as shown in Fig.2, both of these characteristics are realized.

Typically, the lower surface 24 is flat, the raised upper surface 23 is flat, and the lowered surface 22 is perfectly flat or slightly concave.

The lower surface 24 can be covered by an exposed layer of silicon carbide entirely or only in an annular zone or only in a central zone; in fact, what matters is to be able to compensate for the deformations.

On the other hand, as regards the upper surface 23 of the susceptor, a complete covering is much preferable; in this way, in fact, when the susceptor is used for epitaxial growth processes of silicon carbide, silicon carbide is always and only deposited on the underlying silicon carbide. Therefore, it can be expected that, at the top, the thickness of the silicon carbide on the susceptor is uniform (i.e. independent of the horizontal position) and remains uniform throughout the life of the susceptor. Furthermore, the silicon carbide can be expected to have uniform physical characteristics at the top (regardless of horizontal position and vertical position).

The thickness of the silicon carbide layer on the lower surface 24 can be comprised, for example, between 10μ and 100μ throughout the life of the susceptor.

The thickness of the silicon carbide layer on the upper surface 23 can be comprised, for example, between 10μ and 100μ at the beginning of the susceptor life; at the end of the susceptor's life (ie before any maintenance of the same), this thickness can reach and exceed even 1000μ.

In general, the thickness of the silicon carbide layer on the upper surface 23 may be equal to or different from the thickness of the silicon carbide layer on the lower surface 24. However, experiments have been conducted and, probably because the area of the upper layer 27 is smaller than the area of the lower layer 28 due to the presence of the recess 21, better results have been obtained when the thickness of the silicon carbide layer on the upper surface 23 is greater than the thickness of the silicon carbide layer on the lower surface 24. According to one of these experiments, an entirely graphite susceptor was treated directly in the reaction chamber of the epitaxial reactor; first it was degassed for a few minutes at a temperature of about 1650 ° C in hydrogen flow, then a "sacrificial substrate" was placed in the recess, then about 20μ were deposited on the upper surface 23 (and on the "sacrificial substrate") , then the "sacrificial substrate" was removed from the recess, then the susceptor was turned and about 10μ was deposited on the lower surface 24, then the susceptor was turned, the "sacrificial substrate" was placed in the recess and deposited about 20μ on the upper surface 23 (and on the "sacrificial substrate"), finally the "sacrificial substrate" was removed from the recess; such a susceptor has given excellent results from all points of view throughout its life. keep in mind that the properties of the silicon carbide layers made in the initial treatment phase of the susceptor are influenced by the method of manufacture.

Variants of the solution shown schematically in Fig. 2 are possible. The inner side 25 of the recess 21 can be covered with an exposed layer of silicon carbide.

The outer side 26 of the discoidal body 20 can be covered with an exposed layer of silicon carbide.

The lowered upper surface 22, smooth in Fig. 2, can be at least partly rough or rough or knurled.

The recess 21 can house a support element for substrates (see Fig.10, Fig.11, Fig.12, Fig.13, Fig.14) instead of just a substrate; this element can be fixedly laid on the bottom 22 of the recess 21. The recess of the discoidal body of the susceptor may present a radial and annular enlargement above and / or below (see Fig.13 and Fig.14). This enlargement, in particular the upper enlargement, can be used to house a corresponding enlargement of the support element (see Fig.13 and Fig.14); as will be explained later, such enlargement, in particular the lower enlargement, can have other purposes.

The recess 21 can house the combination of a support element for substrates (see reference 91 in Fig. 9) and a frame for the support element (see reference 97 in Fig. 9), instead of just a substrate or only a substrate and a support element; this frame can be inserted in the recess 21 and then settled on the bottom 22 of the recess 21.

Unlike Fig.2, the recess of the susceptor may include, at the limit, a through hole, that is, which extends from one face to the other of the discoid body of the susceptor; this possibility will be better understood in the following when Fig. 16 is described in detail.

Fig. 3 shows a susceptor for an epitaxial growth reactor very different from that of Fig.2. As regards the coating of the graphite body, the susceptor of Fig. 3 is similar (but not identical) to that of Fig. 2 and therefore considerations similar to those already made for the susceptor of Fig. 2 apply.

It consists of a solid discoidal body 30 made entirely of graphite having a first face and a second face. The first face comprises a circular shaped relief 31 adapted to receive a substrate to be subjected to epitaxial growth.

The numerical references in Fig. 3 have the following meaning: the reference 32 corresponds to a raised upper surface of the ridge of the relief 31, the reference 33 corresponds to a lowered upper surface surrounding the relief 31, the reference 34 corresponds to a surface lower, the reference 35 corresponds to an external side of the relief 31, the reference 36 corresponds to the external side of the discoidal body 30, the reference 37 corresponds to a layer of silicon carbide on the upper surface 33, the reference 38 corresponds to a layer of silicon carbide on the lower surface 34. The analogy or duality between the references 20, 21, 22, 23, 24, 25, 26, 27, 28 and the references 30, 31, 32, 33, 34, 35, 36 is evident , 37, 38; it should be noted, however, that while the side 25 is internal and therefore potentially not directly exposed to the precursor gases, the side 35 is external and therefore typically exposed to the precursor gases (unless there are particular measures, for example protection elements external to the susceptor ).

Also the relief 31, like the recess 21, can receive the substrates directly or indirectly the substrates through, for example, a support element (see Fig. 15) or the combination of a support element for substrates and a frame for the support element; this frame can be mounted on the relief 31 and then laid down firmly on the ridge 32 of the relief 31 (see Fig. 15 for similarity).

The relief 31 can have a height, as an indication, between 1 mm and 6 mm.

It is worth pointing out that the surface 32 of the ridge of the relief 31 can be perfectly flat or slightly concave, and smooth or rough or rough or knurled.

The surface 32 can also be more shaped; for example, it could have at least one recess and / or at least one relief to allow a stable mechanical coupling between the susceptor body and the substrate support element (see Fig. 15) or the susceptor body and frame.

Previously, reference was made to supports for substrates to be subjected to epitaxial growth. Such supports are conceived and designed to be used in combination with a susceptor body; this combination constitutes a more complex susceptor than the usual susceptors according to the known art (see Fig.1). The disc-shaped bodies of Fig.2 and Fig.3 are certainly suitable for the purpose, even if the support elements that will be described in detail below can also be used with susceptor bodies other than these.

The susceptor body to be combined with one or more supports is essentially constituted by a discoidal body, typically solid, having a first face and a second face; the first face comprises at least one zone adapted to indirectly receive a substrate, ie a support element for a substrate.

The support element is placed in this area; for example, in the case of a recess, the support element is typically inserted into the recess and then placed on its bottom (see Fig.10, Fig. 11, Fig.12, Fig.13, Fig.14); in the case of a relief, the support element is typically mounted on the relief and then placed on its ridge (see Fig. 15).

In the figures from Fig.4 to Fig.9, a substrate 2000 is also shown for a better understanding of the same; the substrate 2000 is made of silicon carbide because this is the most typical application of the present invention, although the present invention is not limited to silicon carbide substrates; substrate 2000 exhibits a "fiat" because it is typical, although the present invention is not limited to substrates with "fiat".

The support element includes at least one circular disk.

In the case of the example of Fig. 4, the element consists of a flat circular disk 41; the surface of the disc 41 where the substrate 2000 rests can be perfectly flat or slightly concave; the diameter of the disc is typically slightly greater than the diameter of the substrate, for example greater than 1-3 mm; the thickness of the disc 41 can be, by way of example, between 1 mm and 3 mm.

The support element can comprise a circular disc with an annular edge that is raised with respect to the disc; in this way, a recess is defined where substrates can be housed.

In the case of the example of Fig.5, the element consists of a flat circular disk 51 with a raised edge 52; the raised edge has a uniform thickness approximately equal to the thickness of the disc, i.e., as an indication, 1-3 mm, Again as an indication, the overall thickness of the element can be between 2 mm and 4 mm and the depth of the recess can be between 250 μ and 1000 μ.

In the case of the example of Fig.6, the element consists of a flat circular disk 61 with a raised edge 63; the raised edge has a uniform and high thickness, that is, as an indication, 3-10 mm.Also as an indication, the overall thickness of the element can be between 2 mm and 4 mm and the depth of the recess can be between 250 μ and 1000 μ. The raised edge can comprise a lower portion and an upper portion, different from each other; the two portions are adjacent to each other and the lower portion is adjacent to the circular disk.

In the case of the example of Fig.7, there is a flat circular disc 71 and the upper portion 75 of the edge, raised with respect to the disc, protrudes radially outwards with respect to the lower portion 74; moreover, both the portion 74 and the portion 75 are annular. As an indication, the overall thickness of the element can be between 2 mm and 6 mm, the protrusion of the upper portion can be between 3 mm and 10 mm, the thickness of the upper portion can be between 1 mm and 3 mm, and the depth of the recess can be between 250 μ and 1000 μ.

The support element can include a circular disk and a ring; the ring is joined to the circular disc at its upper surface; the ring is able to surround substrates; in this way, a recess is defined where substrates can be housed.

In the case of the example of Fig.8, the element consists of a flat circular disk 81 and a circular ring 86; the ring 86 is joined to the circular disk 81 at its upper surface and is distant from the edge of the disk 81. By way of example, the ring can have a thickness between 1 mm and 3 mm, the distance between the edge of the disk and ring can be between 3 mm and 10 mm, the overall thickness of the element can be between 2 mm and 4 mm, and the depth of the recess can be between 250 μ and 1000 μ.

The diameter of the recess defined within the support element is typically slightly greater than the diameter of the substrate, for example greater than 1-3 mm; the depth of the recess defined within the support element is typically slightly greater than the thickness of the substrate and ranges, for example, between 250 μ and 1000 μ.

The raised edge (for example the edge 52, the edge 63, the edge 74 and 75, and similarly the ring 86) can be circular or shaped, for example shaped in such a way as to be complementary to the external shape of the substrate (see for example Fig.9B).

The support element exposes a support surface for the substrates, for example in graphite or tantalum carbide. This surface can be smooth or, alternatively, at least partly rough or rough or knurled. This surface can be flat or, alternatively, slightly concave.

The support element can be made entirely of graphite or entirely of tantalum carbide or graphite covered with tantalum carbide; here it is worth pointing out that tantalum carbide is an expensive material, much more expensive than graphite.

The solutions in which the entire external surface of the support element is in graphite and / or in tantalum carbide are particularly suitable for cases in which the element is not directly exposed to the precursor gases and therefore, during the epitaxial growth processes, silicon carbide does not settle on it; the example of Fig.4 typically falls among these cases; the example of Fig.5 could fall into these cases if the thin upper thickness of the raised edge 52 is neglected.

Alternatively, the support element can be partially covered with silicon carbide; the eventual covering does not affect the surface where the substrate rests, which is in graphite or tantalum carbide.

These solutions are particularly suitable for cases in which the element is directly exposed to precursor gases and therefore, during the epitaxial growth processes, silicon carbide is deposited on it. The examples of Fig.6, Fig.7 and Fig.8 typically fall within these cases; in the figures from Fig. 11 to Fig. 14, an upper surface of the support can be seen which is directly exposed to the precursor gases; in Fig. 15, it is possible to see an upper surface and an external lateral surface of the support which are directly exposed to the precursor gases (except for particular measures, for example protection elements external to the susceptor).

This partial silicon carbide coating is useful for limiting the progressive curvature of the support element caused by the deposition of silicon carbide. In this regard, the considerations already made in relation to the discoidal body of the susceptor and the silicon carbide layers are valid. Therefore, it is advantageous that all the exposed upper surface (i.e. which does not support a substrate) of the support element is covered with a layer of silicon carbide and that at least part of the lower surface of the support element is covered with a layer of silicon carbide; for example, the lower surface of the circular disk can be covered entirely or only in an annular zone or only in a central zone. In the case of a protruding raised edge (see Fig. 7), a layer of silicon carbide could be located, alternatively or in addition to the back of the disc, on the lower outer side of the edge and / or on the back of the protrusion.

Fig. 9 shows the coupling of a support element 91 and a frame 97 that surrounds it; in Fig.9A, this coupling is shown in the phase of insertion into a recess 99 of the susceptor body 90 and, subsequently, will rest stably on the bottom of the recess 99; at the end of the operation, the support element 91 will also be stably placed on the bottom of the recess 99; alternatively, the support element 91 could be a little distant (for example 0.5 mm) from the bottom of the recess 99. The element 91 of Fig.9 resembles the element 41 of Fig.4, but on the lower face it has a groove for coupling with the frame 97. The element + frame coupling of Fig.9 resembles, as a whole, the support element of Fig.6.

In general, the frame includes a hole and the support element is typically stably inserted in the hole; the frame (together with the element) is placed in correspondence with a special area, for example a recess (as in Fig.9 - see Fig.9A) or a relief, of the susceptor body; typically, it lies stably (as in Fig.9 - see Fig.9A); the hole can be through (as in Fig.9 - see Fig.9A) or blind; the hole can be circular or shaped (as in Fig.9 - see Fig.9B), for example shaped in such a way as to be complementary to the external shape of the substrate.

The frame can advantageously be made of graphite totally or partially covered with silicon carbide. In case of partial covering, it is advantageous to provide a silicon carbide layer which completely covers the upper surface of the frame and a silicon carbide layer which entirely covers the lower surface of the frame for the reasons already explained; the thickness of the two layers can advantageously be the same. The support element can advantageously be made entirely of graphite or entirely of tantalum carbide or graphite coated with tantalum carbide. The differentiation of the material between the frame and the support element is obviously very advantageous.

In general, the support element and / or the frame can advantageously comprise an internal side with a partly cylindrical and partly flat surface (as shown in Fig.9B - this could also apply to figures from Fig. 4 to Fig. .8).

Figures Fig.10, Fig .11, Fig .12, Fig.13, Fig.14, Fig.15 show a series of examples of combinations of a susceptor body and a support element for substrates; other combinations are possible. In the figures Fig. 10, Fig. 11, Fig.12, Fig. 13, Fig. 14, the element is stably placed in correspondence with a recess of the body; the depth of the body recess corresponds to the overall thickness of the support element. In Fig. 15, the element is stably placed in correspondence with a slight relief of the body.

All the bodies advantageously have an external bevel on the upper face of the body at the edge.

In the example of Fig.10, the support element corresponds to the support element of Fig.5; the susceptor body has an internal bevel on the upper face of the body at the recess.

In the example of Fig.11, the support element corresponds to the support element of Fig.6.

In the example of Fig. 12, the support element corresponds to the support element of Fig. 8.

In the example of Fig.13, the support element corresponds to the support element of Fig.7; the recess has a radial and annular enlargement that starts at a certain distance from the bottom of the recess; the shape of the withdrawal is complementary to the external shape of the support element.

In the example of Fig. 14, the support element corresponds to the support element of Fig. 7; the recess has a radial and annular enlargement starting from the bottom of the recess; there is therefore some space between the inner side of the recess and the outer side of the support element; in this example, this space has a triangular section, but, alternatively, other shapes are possible.

In the example of Fig.15, the support element corresponds to the support element of Fig.7; in this example, the diameter of the ridge of the relief corresponds to the diameter of the disk of the support element, even if this is not essential. In Fig.15, the surface of the relief is shaped to obtain stable mechanical couplings; in particular, it has an annular groove in which a ring is inserted that protrudes from the lower surface of the support element so that the body with relief and the support element are well coupled to each other. In Fig.15, the lower face of the susceptor body is also shown; in general, this comprises a seat adapted to receive a pin for guiding the rotation of the susceptor.

In the example of Fig. *** 16, the recess of the susceptor comprises a through hole, that is, which extends from one face to the other of the discoidal body of the susceptor, and the support element is similar to the support element of Fig. 4 ; this example provides for a plurality of recesses, in particular four recesses, and a corresponding plurality of support elements. In this example, both the shape of the recess and the shape of the support element correspond to the shape of the substrate which is, in particular, circular with a "fiat"; the diameter of the recess is slightly greater than the diameter of the substrate. In Fig. 16, the support element differs from that of Fig. 4 in that, on the lower face, it has a groove to couple with the susceptor body, in particular with the bottom of the recess which is simply constituted by a rectangular section ring. In Fig. 16, the lower face of the susceptor body is also shown; in general, this comprises a seat adapted to receive a pin for guiding the rotation of the susceptor.

The use of support elements or element + frame couplings extends the life of the susceptor body; in fact, maintenance (e.g. removal of deposited silicon carbide) and / or replacement focuses on them. For maintenance purposes, the element + frame coupling is advantageous as such a support element, which is always "protected", requires practically no maintenance.

The use of support elements or element + frame couplings provides flexibility; in fact, the shape of the recess or relief of the susceptor body is substantially independent of the shape and / or size of the substrate. Among other things, different support elements can be associated with the same recess or relief of the susceptor body, in particular with recesses of different shape and / or size (for example complementary to the external shape of different substrates). As mentioned, the support surface can advantageously be at least partially rough or rough or knurled. These processes tend to avoid adhesions with the overlying body and / or sliding of the overlying body.

This consideration may apply, depending on how the present invention is carried out, both for the surface of the susceptor on which the substrates rest, and for the surface of the support element on which the substrates rest, and for the surface of the susceptor on which the substrates rest. support the support elements.

Such susceptors simultaneously serve both to support and to heat the substrates that are subject to epitaxial growth.

In the case of epitaxial growth of silicon carbide at high temperature, the susceptor is placed inside a reaction chamber of the hot-walled type; typically, the heating is of the induction type and allows the walls of the chamber and the susceptor to be heated simultaneously. Typically, there is a rather small gap between the bottom wall and the top wall of the chamber; it can be, for example, a parallelepiped of a few centimeters in height; the discoidal body of the susceptor is normally inserted in a recess in the lower wall of the chamber where it can rotate around its axis.

The rotation is generally obtained by means of a suitable gas flow (ie there is no shaft that transmits a rotary motion to the susceptor); for this reason, the horizontal position of the susceptor in the chamber is known with an accuracy of a few millimeters and the horizontal position of the substrate in the recess is known with an accuracy of a few tenths of a millimeter; moreover, in general, neither the angular position of the susceptor nor the angular position of the substrates can be known. Due to these position uncertainties, it is not easy to manipulate substrates, especially when they are in the chamber.

As regards the manipulation of the substrates, the present invention advantageously provides for the possibility of manipulating the support elements and / or the element + frame couplings.

This means that it is no longer necessary to load and unload an entire susceptor, which is bulky and heavy, with substrates.

This also means that it is possible to discharge the substrates (together with the support elements or the element + frame couplings), without damaging them, at rather high temperatures, thus reducing the dead times of the epitaxial reactor. The discharge temperature can, for example, exceed 500 ° C, but it can even reach 800-1,000 ° C; to handle such hot objects it is preferable to use tools made of quartz or silicon carbide.

Basically, there are three ways to automatically unload a support element or an element + frame coupling while the susceptor body is inside the reaction chamber of the epitaxial reactor:

A) by mechanical traction and action from above, for example on an edge,

B) by pneumatic suction and action from above, for example on a flat surface,

C) by mechanical thrust and action from below;

for loading, we proceed, of course, in the opposite direction.

Mode A is suitable for example for the solution shown in Fig.10; the internal chamfer can be used for the mechanical action on the edge of the support element of a suitable tool.

Mode B is suitable for example for the solutions shown in Fig .11 and Fig .12 and Fig. 13; the large upper surface of the edge of the support element can be used for pneumatic action on the support element of a suitable tool.

Mode C is suitable for example for the solutions shown in Fig. 14 and Fig.15; under the protrusion of the edge of the support element, an appropriate tool can act from below. For this purpose, the tool may include, for example, two long fingers which, when translating, slip under the protrusion and then rise by pushing the support element upwards.

As mentioned, for the manipulation of the frames similar considerations apply to those valid for the manipulation of the support elements. For example, the frame of Fig.9 leaves no space between the frame and the recess, but an alternative solution could provide it thanks to a different shape of the frame and / or the recess. For example again, the frame of Fig. 9, or a variant thereof, could be placed on a relief like the one shown in Fig. 15.

Claims (17)

CLAIMS 1. Susector for an epitaxial growth reactor, consisting of a discoidal body made of graphite having a first face and a second face, wherein said first face comprises at least a circular-shaped zone adapted to receive a substrate to be subjected to epitaxial growth, whereby said first face exposes a first upper surface corresponding to said at least one zone and a second upper surface surrounding said at least one zone , wherein said second face exposes a lower surface, characterized in that said second upper surface and said lower surface are covered with a layer of silicon carbide. 2. Susceptor for an epitaxial growth reactor according to claim 1, consisting of a discoidal body made of graphite having a first face and a second face, wherein said first face comprises at least one circular shaped recess adapted to receive a substrate to be subjected to epitaxial growth, whereby said first face exposes a lowered upper surface corresponding to the bottom of said at least one recess and a raised upper surface surrounding said at least a withdrawal, wherein said second face exposes a lower surface, characterized in that said raised upper surface and said lower surface are covered with a layer of silicon carbide. 3. Susceptor according to claim 2, wherein said lower surface is covered by a layer of silicon carbide entirely or only in an annular zone or only in a central zone. The support according to claim 2 or 3, wherein the thickness of the silicon carbide layer on the upper surface is greater than the thickness of the silicon carbide layer on the lower surface. 5. Support according to claim 2 or 3 or 4, wherein said lowered upper surface is covered with a layer of graphite. 6. Support according to claim 2 or 3 or 4, wherein said lowered upper surface is covered with a layer of tantalum carbide. 7. Support according to any one of the preceding claims 1 to 6, wherein said lowered upper surface is rough or rough or knurled. 8. Susector for an epitaxial growth reactor according to claim 1, consisting of a discoidal body made of graphite having a first face and a second face, wherein said first face comprises at least one circular shaped relief adapted to receive a substrate to be subjected to epitaxial growth, whereby said first face exposes a raised upper surface corresponding to the ridge of said at least one relief and a lowered upper surface surrounding said at least a relief, in which said second face exposes a lower surface, characterized in that said lowered upper surface and said lower surface are covered with a layer of silicon carbide. 9. Susceptor according to claim 8, wherein said lower surface is covered by a layer of silicon carbide entirely or only in an annular zone or only in a central zone. Susceptor according to claim 8 or 9, wherein the thickness of the silicon carbide layer on the upper surface is greater than the thickness of the silicon carbide layer on the lower surface. 11. A bearing according to claim 8 or 9 or 10, wherein said raised upper surface is covered with a layer of graphite. 12. Susceptor according to claim 8 or 9 or 10, wherein said raised upper surface is covered with a layer of tantalum carbide. 13. Support according to any one of the preceding claims 8 to 12, wherein said raised upper surface is rough or rough or knurled. A carrier according to any one of the preceding claims from 1 to 13, comprising at least one support element for said substrate, and in which said at least one support element is laid on said at least one zone. Support according to any one of the preceding claims 1 to 13, comprising at least one support element for said substrate and at least one frame for said support element, in which said at least one frame comprises a hole, and in which said at least one frame it is laid on said at least one area, in particular inserted in said at least one recess or mounted on said at least one relief, and said at least one support element is inserted in said hole. 16. Epitaxial growth reactor comprising at least one susceptor for supporting and heating substrates according to any one of the preceding claims. 17. Reactor for epitaxial growth according to claim 16, comprising a reaction chamber of the hot-walled type in which said at least one susceptor is contained, the reactor being of the type for deposition of silicon carbide layers on said substrates and with heating to induction.