Substrate support device for reaction chamber of epitaxial reactor with gas flow rotation, reaction chamber and epitaxial reactor

Abstract

A device (420) for supporting a substrate in a reaction chamber of an epitaxial reactor; the device (420) comprises: a disc-shaped element (422) having a first face (422A) and a second face (422B), the first face (422A) being adapted to be positioned upward when the device (420) is in use, and the second face (422B) being adapted to be positioned downward when the device (420) is in use, the disc-shaped element (422) being adapted to receive a gas flow (F) to rotate the device (420) around its axis (X); a substrate supporting element (424) being coupled to the disc-shaped element (422) and the substrate supporting element (424) being coupled to the substrate supporting element (424). The element (422) is a single piece and is preferably adjacent to the first face (422A); and a shaft (426) which is coaxial with the disk-shaped element (422), is a single piece with the disk-shaped element (422) and has a first end (426A) at the second face (422B), the shaft (426) having at least one protrusion (428A, 428B, 428C) at its second end (426B), and the rotation of the protrusion (428A, 428B, 428C) is suitable for detection by a pyrometer (430) or a thermal imager.

Description

Field of the Invention

[0001] The present invention relates to a substrate supporting device for a reaction chamber of an epitaxial reactor for depositing semiconductor materials on a substrate, and a reaction chamber and an epitaxial reactor using the device.

[0002] In particular, but not exclusively, the invention relates to "hot wall" reaction chambers, i.e., where the walls are intentionally kept hot and are usually particularly heated. In contrast, in "cold wall" reaction chambers, the walls are intentionally kept cool, for example by a cooling gas stream and / or a cooling liquid stream.

[0003] This type of reaction chamber is primarily used for the epitaxial deposition of silicon carbide on a silicon carbide substrate (a "homo-epitaxial" process) or for the epitaxial deposition of silicon carbide on a substrate made of another material (a "heteroepitaxial" process). Prior art

[0004] In order to make the deposited material layer uniform, rotation is often used, among other things: in the reaction chamber, a device is arranged to support a substrate (directly or indirectly), one or more substrates are placed on the device, and at least during deposition, the device is rotated.

[0005] Importantly, at least during deposition, the rotation speed of the apparatus and hence of the substrate is predetermined and constant over time.

[0006] There are reaction chambers, in particular "hot wall" reaction chambers, in which rotation of the substrate support device is achieved by pushing the device through a gas flow (rather than by a rotating shaft mechanically connected to the device); this type of solution is described and disclosed, for example, in the applicant's five international patent applications WO2004053187A1, WO2004053188A1, WO2004053189A1, WO2005121417A1 and WO2015092525A1, which are incorporated herein by reference.

[0007] In this case (i.e., in the case of hydrodynamic rotation), estimates of the rotational speed of the device based on the flow rate of the gas stream are imprecise because there are several factors that affect the rotational speed and cannot be determined or measured. For example, the rotational speed may be affected by deposits that accumulate on the device for supporting the substrate over time and / or by changes in the positioning and orientation of the device for supporting the substrate.

[0008] Obviously, if mechanical rotation is used (i.e. obtained by a motor outside the reaction chamber transmitting rotational motion through a shaft to the device for supporting the substrate), the rotation speed will be precisely known and controlled, but the solution will be more complex both in composition / construction and assembly / disassembly.

[0009] Overview

[0010] A general object of the present invention is to overcome the problem of estimating, in particular estimating with high accuracy, ie determining, the rotation speed of a device for supporting a substrate, in particular in a reaction chamber with gas flow rotation.

[0011] This problem is particularly difficult because the device is located in a reaction chamber, precisely in its central area, which during the process is at very high temperatures; in the case of silicon epitaxial deposition, the temperature can be, for example, 800-1200°C and in the case of silicon carbide epitaxial deposition, the temperature can be, for example, 1600-3000°C.

[0012] This general object and other more specific objects are achieved as a result of what is expressed in the appended claims forming an integral part of the present description.

[0013] An object of the present invention is to provide a substrate supporting device and a reaction chamber and an epitaxial reactor using the same.

[0014] List of Figures

[0015] The present invention will become more apparent from the following detailed description considered in conjunction with the accompanying drawings, in which:

[0016] Figure 1 shows a cross-sectional (schematic) view of a reaction chamber,

[0017] Figure 2 Shows Figure 1 A longitudinal cross-sectional (schematic) diagram of a reaction chamber,

[0018] Figure 3 Shows from Figure 1 An internal (schematic) diagram of a portion of the reaction chamber viewed from above,

[0019] Figure 4 Shows Figure 1 a detailed longitudinal section of a reaction chamber of FIG. 1 , in which an embodiment of a substrate support device according to the invention is clearly visible, and

[0020] Figure 5 Shown by Figure 4 Possible time trends of the electrical signals generated by the pyrometer are shown.

[0021] As can be readily appreciated, there are various ways of actually implementing the invention, the invention being defined in its primary advantageous aspects in the appended claims and not limited to the following detailed description or the appended claims.

[0022] Detailed Description

[0023] The present invention particularly, but not exclusively, relates to a reaction chamber having gas flow rotation.

[0024] The present invention relates particularly, but not exclusively, to a "hot wall" reaction chamber.

[0025] Applicant has worked on reaction chambers of this type and has filed, for example, the five aforementioned International patent applications which are incorporated herein by reference.

[0026] An example of a reaction chamber 1 of this type is Figure 1 and Figure 2 as well as Figure 3 Schematically shown in FIG; the reaction chamber 1 extends uniformly in the longitudinal direction. The reaction chamber 1 comprises a susceptor assembly consisting of four susceptor elements 2, 3, 4 and 5, which define a reaction and deposition zone 10 and are contained in a housing 7 made of thermally insulating material; the housing 7 is inserted in a quartz tube 8. The housing 7 consists of a tube 71, in particular with a circular cross section, and two covers 72 and 73, in particular with a circular shape like the tube cross section. Around the tube 8, an inductor 9 is wound, which is suitable for heating the elements 2, 3, 4 and 5 made of graphite by electromagnetic induction; the inductor 9 is represented by a dotted line, because it is not strictly speaking part of the reaction chamber 1. The elements 4 and 5 are two strips (which can be considered as the walls of the reaction chamber) and constitute the side walls of the zone 10. The elements 2 and 3 are projection solids with a section in the shape of a circle segment and through holes 20 and 30 with a section in the shape of a circle segment; the elements 2 and 3 are therefore composed of planar blanks 21 and 31 (which can be considered as the inner wall of the reaction chamber) and curved blanks 22 and 32 (which can be considered as the outer wall of the reaction chamber); the planar blanks 21 and 31 constitute the upper and lower walls of the area 10, respectively. The lower wall 31 is suitable for housing an assembly 6 comprising, among other things, a support element 61 (rotatable during the deposition process) suitable for supporting at least one substrate 62 to be deposited placed in a recess of the element; according to this example, the support element 61 can be inserted into the area 10 and extracted from the area 10. The two covers 72 and 73 are shown closed; however, covers 72 and 73 have openings, in particular openings in cover 73 for the entry of precursor gases (see black arrows) and openings in cover 72 for the exit of exhaust gases (see black arrows); in addition, as will become more apparent below, there may be openings for tubes suitable for flowing rotating gases and for cables suitable for conducting electrical signals for example from pyrometers and temperature sensors (within the reaction chamber).

[0027] refer to Figure 1 and Figure 2 as well as Figure 3If the inductor 9 is supplied with an alternating current, an alternating current is induced in the susceptor elements 2, 3, 4 and 5, in particular in elements 2 and 3 (it should be noted that elements 4 and 5 can also be made wholly or partly of electrically insulating material and thus contribute less to the heating of the reaction and deposition zone 10). The most typical material for making the susceptor elements is graphite; graphite can be used bare or coated, for example, with silicon carbide or tantalum carbide.

[0028] Figure 1 and Figure 2 as well as Figure 3 The reaction chamber 1 is suitable for many variants, for example: having a cross section of different shapes (polygonal, elliptical, ...), having an upper susceptor element without through holes, having a side susceptor element with through holes, having a substrate support element suitable for directly supporting a certain number of substrates, ...

[0029] exist Figure 1 and Figure 2 In the figure, a dashed box associated with reference numeral 428 is visible to schematically indicate the presence of a substrate support device according to the present invention.

[0030] From the following description and Figure 4 A possible configuration of the component 6 can be clearly seen in FIG.

[0031] It is worth noting that in Figure 4 In the figure, a support element 61 is shown according to its non-limiting embodiment. Conceptually, such an element can be described by a set of parts as follows. Such an element comprises: a plate portion, referred to as "plate" for short, having a circular shape and having a support surface suitable for supporting a substrate; in particular, the support surface has substantially the same shape and size as the substrate and constitutes the bottom of the recess of the element. Such an element also comprises a first portion of the edge, which completely surrounds the plate and extends axially to constitute the side walls of the recess of the element. Such an element finally comprises a second portion of the edge, which completely surrounds the first portion of the edge and extends radially; it can be said that the second portion of the edge is a flange located around the first portion of the edge. The parts disclosed above can be connected to form one or more single pieces. Each of the parts disclosed above can be formed by two or more single pieces mechanically connected between them.

[0032] Although not highlighted in the figure (except Figure 4 ), but the reaction chamber and epitaxial reactor in the figure realize the rotation of the device to support the gas flow substrate.

[0033] As previously mentioned, a general purpose of the present invention is to estimate or even determine the means for supporting a substrate (e.g., Figure 4 The rotation speed of the device (indicated as a whole by the reference numeral 420 in the figure).

[0034] The general idea to achieve this is to use a photothermal device, in particular a thermal imager, or more advantageously a pyrometer (e.g. Figure 4 430 in the figure).

[0035] Indeed, for example and in particular pyrometers (e.g. Figure 4 The element indicated by reference numeral 430 in FIG. 4 may be used to estimate or determine the means for supporting the substrate (e.g., Figure 4 The rotation speed of the element indicated by reference numeral 420 in the epitaxial reactor in the reaction chamber; such use provides:

[0036] As the device rotates, hold the pyrometer in a constant orientation (e.g. Figure 4 433 in the figure), so that the temperature detected by the pyrometer undergoes periodic changes due to the rotation of the device (see, for example, Figure 6-2 , Figure 6-3 and Figure 6-4 ),

[0037] as well as

[0038] The rotation speed is determined by a processing electronics unit (e.g. Figure 4 The element indicated by reference numeral 490 in the figure) is calculated according to the period of the periodic change.

[0039] This concept is advantageously implemented in a reaction chamber with gas flow rotation, in particular in a reaction chamber of the “hot wall” type and / or by epitaxial deposition of silicon carbide.

[0040] The following will refer to Figure 4 Examples are provided herein, but such references should not be considered limiting.

[0041] In order to take advantage of this general idea, the device 420 for supporting the substrate in the reaction chamber of the epitaxial reactor is configured in a specific manner; Figure 4 In the embodiment of the present invention, the device 420 indirectly supports the substrate due to the support element 61; the device 420 specifically includes:

[0042] a disk-shaped element 422 having a first face 422A adapted to be positioned upward when the device 420 is in use and a second face 422B adapted to be positioned downward when the device 420 is in use; the disk-shaped element 422 being adapted to receive an air flow F to rotate the device 420 (exactly or substantially) about its axis X,

[0043] a substrate support element 424 which is integral with the disk-shaped element 422 and is preferably adjacent to the first face 422A,

[0044] A shaft 426 , which is coaxial with the disk-shaped element 422 , is in one piece with said disk-shaped element 422 and has a first end 426A at (at least) said second face 422B.

[0045] The shaft 426 has at least one protrusion 428A, 428B, 428C at its second end 426B, the rotation of which is adapted to be detected by a pyrometer 430 or a thermal imager.

[0046] like Figure 4 As shown, element 422 and element 424 may be integrated to form a single piece.

[0047] like Figure 4 As shown, shaft 426 may be integral with element 422 and element 424 .

[0048] like Figure 4 As shown, the first end 426A of the shaft 426 is located at the element 422 and the element 424. In addition, even if Figure 4 In the example of , element 422 is composed of an almost completely planar disk and has a central hole, alternatively, element 422 may have a central protrusion (e.g., a cylindrical protrusion) suitable for mechanically connecting to shaft 426 in place of the central hole; in this case, the first end 426A of shaft 426 is located at the central protrusion of element 422.

[0049] As described and shown in the five aforementioned international patent applications, the disc-shaped element 422 may have a recess on the back side adapted to receive the airflow F.

[0050] Preferably, the rotation of the at least one protrusion is adapted to be detected by a pyrometer 430 .

[0051] The shaft 426 may have two protrusions or three protrusions at one second end 426B thereof; preferably, the shaft 426 may have three protrusions 428A, 428B, 428C (in particular, arranged radially at 120° from each other); the rotation of these protrusions is suitable for detection by a pyrometer 430 or a thermal imager; such protrusions are preferably equal between them.

[0052] At least one projection may be a plate (particularly rectangular and generally substantially planar) extending perpendicularly to the axis X of the shaft 426 .

[0053] Preferably, device 420 is made entirely of graphite; in particular, elements 422 and 424 and shaft 426 are all made of graphite.

[0054] The shaft 426 may be mechanically fixed directly to the disk-shaped element 422; for example, such fixing may be accomplished by screws, a tongue-and-groove connection, or a snap-fit.

[0055] The at least one projection is mechanically fixed directly to the shaft 426; for example, the at least one projection may be inserted into a shaft hole; or, the at least one projection may be integrated in an element to be screwed onto the shaft.

[0056] The device 420 may include a protection socket (particularly at the hole of the wall 31 of the reaction chamber) around a portion of the shaft 426. Such a socket acts as a low-friction rotatable guide and may be considered a consumable.

[0057] The substrate support device according to the present invention, in particular Figure 4 The device 420 is typically a component of a reaction chamber of an epitaxial reactor (ie, for epitaxially depositing a layer of semiconductor material on a substrate).

[0058] This application is particularly advantageous for reaction chambers equipped with a gas rotation system for substrate support means.

[0059] In this case, the disk-shaped element 422 of the device 420 is rotatably housed in a seat in the chamber wall; Figure 4 In the example of FIG. 4 , the wall 31 has such a seat, in particular the plate blank 414 has such a seat.

[0060] Figure 4 The wall 31 comprises a slab 414 and a covering or lining 412 ; an internal duct 416 is obtained in the slab 414 to flow the rotating gas and guide it to the rear part of the element 422 ; a temperature measuring device 460 connected to an electric cable 465 is also inserted in the slab 414 .

[0061] like Figure 4 As shown, the seat of the wall 31 advantageously has a through hole through which the shaft 426 of the device 420 passes; thus, at least one protrusion 428 can be located in a hole of an element of the reaction chamber (see for example Figure 1 and Figure 2 The hole 30 of the element 3 of the chamber 1 in the chamber).

[0062] Advantageously, the wall of the seat for the substrate support device is an inner wall (see for example Figure 1 The walls 31 of the chamber 1 in the reactor are walls that do not define the outer perimeter of the reaction chamber.

[0063] Advantageously, in use, at least one rotatable protrusion of the shaft 426 of the device 420 is located in the inner cavity of the chamber, in particular between the inner wall of the chamber (i.e. the wall that does not define the outer perimeter of the reaction chamber) and the outer wall (i.e. the wall that at least partially defines the outer perimeter of the reaction chamber); Figure 1 and Figure 4 In the example of , the inner wall is wall 31 and the outer wall is wall 32 .

[0064] As previously mentioned, the present invention requires a thermal imager or preferably a pyrometer, which is oriented to detect the rotation of the shaft of the device, or better yet, to detect the rotation of at least one shaft protrusion; a thermal imager or pyrometer (e.g. Figure 4 430) can be considered as part of the reaction chamber according to the present invention.

[0065] according to Figure 4 4 , which shows some components of an embodiment of an epitaxial reactor according to the invention, the epitaxial reactor comprises a control electronics unit 490 and a thermal imager or preferably a pyrometer 430 of the reaction chamber which are electrically connected (see cable 435) and adapted to estimate or determine the rotation speed of a substrate support 420 of the reaction chamber based on the electrical signals received by the thermal imager or pyrometer 430. It is worth observing that in Figure 4 The light rays appear to leave / enter the pyrometer 430 directly; however, an optical connection of the pyrometer or the thermal imager to an optical fiber cannot be ruled out.

[0066] Furthermore, always follow Figure 4 In an embodiment, the control electronics unit 490 can advantageously be electrically connected (see cable 445) to a regulator of the reaction chamber, in particular a mass flow controller 440, and the control electronics unit 490 is suitable for setting the rotating gas flow based on an estimated or determined rotational speed; obviously, the regulator, in particular the mass flow controller 440, is fluidically connected to the conduit 416, for example via a tube 450.

[0067] According to the invention, in order to determine the rotation speed of the substrate support device, the pyrometer (or possibly the thermal imager) must be appropriately oriented toward the rotatable protrusion or protrusions (if more than one); Figure 4 , the pyrometer 430 must be properly oriented toward the rotatable protrusions 428, specifically, the rotatable protrusions 428 are three in number and are radially arranged at 120° from each other; this is a fixed and predetermined direction setting.

[0068] To understand the concept of "appropriately", please refer to Figure 5 and Figure 6.

[0069] exist Figure 5 , four different directional settings of the pyrometer 430 are illustrated. According to the first directional setting, the pyrometer is oriented toward the point 51 of the cover 72 of the housing 7, and the straight line ( Figure 4 433 in the pyrometer) is never intercepted by the protrusion 428. According to the second direction setting, the pyrometer is oriented toward the point 52 of the cover 72 of the housing 7, and the straight line ( Figure 4433 in the figure) is intercepted by the protrusion 428 at a region of the protrusion 428 that is far away (or very far away) from the axis of rotation. According to the third direction setting, the pyrometer is oriented toward the point 53 of the cover 72 of the housing 7, and the straight line ( Figure 4 433 in the middle area of ​​the protrusion 428) is intercepted by the protrusion 428 at the middle area of ​​the protrusion 428. According to the fourth direction setting, the pyrometer is facing the point 54 of the cover 72 of the housing 7, and the straight line ( Figure 4 433) is intercepted by the protrusion 428 at an area of ​​the protrusion 428 that is close to (or very close to) the axis of rotation.

[0070] In Figure 6, for exemplary purposes, the time trend of the temperature read by the pyrometer 430, i.e. detected (e.g. every 10-100 milliseconds), is shown; we can assume that the protrusion 428 is at a high temperature (e.g. 1200-1600°C) and the cover 72 of the insulating material shell 7 is at a low temperature LT (e.g. 400-800°C). Figure 6-1 The temperature trend over time is shown when the pyrometer is set in a first orientation; it is a straight horizontal line. Figure 6-2 The temperature trend over time is shown when the pyrometer is set in the second orientation; it is a set of long, narrow peaks that are far apart from each other. Figure 6-3 The temperature trend over time is shown for the pyrometer set in the third orientation; it is a sinusoidal-looking line with a large width approximately equal to (HT-LT) / 2. Figure 6-4 The temperature trend over time is shown for the pyrometer set in the fourth orientation; it is a line that looks like a sine curve with a very small width.

[0071] It should be understood that Figure 6-2 , Figure 6-3 and Figure 6-4 The rotation speed of the substrate support device 420 is obtained from the periodic trend of the first direction setting, and the first direction setting does not allow the rotation speed to be estimated or determined. The ideal direction setting for estimating or determining the rotation speed is the third direction setting, that is, when the protrusion 428 rotates, the straight line between the pyrometer 430 and the point 53 is intercepted in a certain time range in the area between the tip of the protrusion 428 (away from the rotation axis) and the base of the protrusion 428 (close to the rotation axis). Estimating or determining the rotation speed (which can be 10-100 rpm, for example) involves estimating or determining the period of the time range of the temperature, and can be estimated or determined by processing the pyrometer signal in a known manner in the time domain or frequency domain and in a digital and / or analog manner.

[0072] As can be seen from the above, in the step of assembling the reaction chamber, the pyrometer preferably needs to adjust its orientation.

[0073] It is important to note that in cases where a thermal imager is used rather than a pyrometer, processing the signal may be much more complex, although the orientation setting may be less critical.

Claims

1. A reaction chamber (1) for an epitaxial reactor, comprising: A susceptor element (3), the susceptor element (3) having a cross section in the shape of a circle segment, the susceptor element (3) being composed of a flat plate blank (31), a curved plate blank (32), and a through hole (30) located between the flat plate blank (31) and the curved plate blank (32); A device (420) for supporting a substrate in the reaction chamber (1), the device (420) comprising: a disc-shaped element (422), the disc-shaped element (422) having a first face (422A) adapted to be positioned upward when the device (420) is in use, and a second face (422B) adapted to be positioned downward when the device (420) is in use, the disc-shaped element (422) being adapted to receive an air flow (F) to rotate the device (420) about its axis (X), and being rotatably received in a seat of the planar blank (31), the seat having a through hole traversed by an axis (426) of the device (420); a substrate support element (424) formed in one piece with the disc-shaped element (422) and adjacent to the first face (422A); the shaft (426), the shaft (426) being coaxial with the disk-shaped element (422), being in one piece with the disk-shaped element (422) and having a first end (426A) at the second face (422B); Pyrometer (430) or thermal imager; wherein the shaft (426) has at least one protrusion (428A, 428B, 428C) at its second end (426B), the rotation of the protrusion being suitable for being detected by the pyrometer (430) or the thermal imager, and the at least one protrusion (428A, 428B, 428C) being located in the through hole (30); and Therein, the planar plate (31) has an internal duct (416) suitable for allowing a gas flow (F) to flow to rotate the device (420).

2. The reaction chamber (1) according to claim 1, wherein: Rotation of the at least one protrusion (428A, 428B, 428C) is adapted to be detected by the pyrometer (430).

3. The reaction chamber (1) according to claim 1 or 2, wherein: The shaft has two or three protrusions (428A, 428B, 428C) or four protrusions at its second end (426B), the rotation of which is suitable for being detected by the pyrometer (430) or the thermal imager.

4. The reaction chamber (1) according to claim 3, wherein: The projections are equal between the projections.

5. The reaction chamber (1) according to any one of claims 1 to 4, wherein: The at least one protrusion (428A, 428B, 428C) is a plate extending perpendicular to the axis (X) of the shaft (426).

6. The reaction chamber (1) according to any one of claims 1 to 5, wherein: The shaft (426) is mechanically fixed to the disc-shaped element (422).

7. The reaction chamber (1) according to any one of claims 1 to 6, wherein: The projections (428A, 428B, 428C) are mechanically fixed to the shaft (426).

8. The reaction chamber (1) according to any one of claims 1 to 7, comprising a protective socket surrounding a portion of the shaft (426).

9. The reaction chamber (1) according to any one of claims 1 to 8, wherein: The flat slab (31) is the inner wall of the reaction chamber (1).

10. The reaction chamber (1) according to any one of claims 1 to 9, wherein: The curved plate blank (32) is the outer wall of the reaction chamber (1).

11. The reaction chamber (1) according to any one of claims 1 to 10, wherein: The device (420) is made entirely of graphite.

12. An epitaxial reactor comprising a reaction chamber (1) according to any one of claims 1 to 11.

13. A method for estimating or determining the rotation speed of the device (420) for supporting a substrate in a reaction chamber (1) according to any one of claims 1 to 11, comprising: (i) allowing a gas flow (F) to flow into the inner conduit (416) of the planar slab (31) to rotate the device (420); (ii) maintaining the pyrometer (430) or the thermal imager in a constant orientation to detect the rotation of the at least one protrusion (428A, 428B, 428C) to detect periodic changes in the temperature signal; as well as (iii) calculating the rotational speed based on the period of the periodic variation by a processing electronic unit (490) electrically connected to the pyrometer or the thermal imager.

14. The method according to claim 13, further comprising the steps of: (iv) setting the airflow (F) for rotating the device (420) based on the rotational speed calculated in step (iii), wherein step (iv) is performed using a regulator.

15. The method of claim 14, wherein the regulator is a mass flow controller (440).

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