Susceptor

Abstract

Provided is a susceptor which, despite having a gas supply hole penetrating through a shaft and a plate thereof, is capable of suppressing generation of an arching in a high-output plasma environment. The susceptor, which is for a film formation apparatus or an etching apparatus, comprises: a ceramic plate having a first surface on which a wafer is to be placed, and a second surface opposing the first surface, in which ceramic plate internal electrodes are embedded; a cylindrical ceramic shaft attached to the second surface of the ceramic plate; a gas supply hole penetrating through the ceramic plate and the ceramic shaft so as to extend from the first surface and through the second surface of the ceramic plate to reach a distal end of the ceramic shaft far from the ceramic plate; and a porous plug embedded in at least a part of the gas supply hole corresponding to the ceramic plate.

Description

[Technical field]

[0001] The present invention relates to a susceptor for a film forming apparatus or an etching apparatus. [Background technology]

[0002] In a film forming apparatus or an etching apparatus for a semiconductor manufacturing process, a susceptor is used to support a wafer. A widely used susceptor includes a ceramic plate on which the wafer is placed and a cylindrical ceramic shaft attached to the ceramic plate.

[0003] A susceptor having a ceramic shaft is known that is provided with a gas supply hole for supplying gas to the surface of the ceramic plate. For example, Patent Document 1 (WO2019 / 187785) discloses an electrostatic chuck heater that includes a disk-shaped ceramic base having an electrostatic electrode and a resistance heating element, a hollow shaft, a convex ring, and a through hole. This electrostatic chuck heater is provided with a through hole that penetrates from the lower end of the peripheral wall of the hollow shaft to a predetermined position on the surface of the ceramic base, thereby making it possible to supply gas from the lower end of the hollow shaft to the space below the wafer surrounded by the ceramic base, the convex ring, and the wafer. By supplying gas to the space below the wafer, it becomes difficult for components that become a conductive film to enter the gap between the convex ring and the wafer, and it becomes difficult for an undesirable conductive film to adhere to the upper surface of the convex ring.

[0004] Meanwhile, a method of providing a porous portion in an electrostatic chuck to prevent arc discharge in a gas introduction passage is known. For example, Patent Document 2 (JP 2020-072262 A) discloses an electrostatic chuck including a ceramic dielectric substrate, a base plate supporting the ceramic dielectric substrate and having a gas introduction passage, and a porous portion provided between the base plate and the ceramic dielectric substrate and facing the gas introduction passage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2019 / 187785 [Patent Document 2] JP 2020-072262 A Summary of the Invention

[0006] In a conventional susceptor having a gas supply hole as disclosed in Patent Document 1, as shown in Fig. 5, the gas supply hole 116 is configured as a through hole that reaches from the distal end 114a (the end assembled to the device) of the ceramic shaft 114 to the surface 112a of the ceramic plate 112. However, in a high-power plasma environment, the insulation distance from the ceramic plate surface 112a to the distal end 114a of the ceramic shaft 114 is insufficient, and there is a concern that arcing may occur. That is, since the distal end 114a of the ceramic shaft 114 is assembled to a metal part 122 constituting the device, abnormal discharge may occur due to insufficient insulation distance between the metal part 122 and the ceramic plate surface 112a exposed to the plasma.

[0007] The inventors have now discovered that in a susceptor having gas supply holes penetrating the shaft and plate, by embedding a porous plug in a specified position of the gas supply hole, the occurrence of arcing can be suppressed in a high-power plasma environment.

[0008] Therefore, an object of the present invention is to provide a susceptor that has gas supply holes penetrating the shaft and the plate, yet is capable of suppressing the occurrence of arcing in a high-output plasma environment.

[0009] According to the present invention, the following aspects are provided. [Aspect 1] A susceptor for a film forming apparatus or an etching apparatus, a ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, and having an internal electrode embedded therein; a cylindrical ceramic shaft attached to the second surface of the ceramic plate; a gas supply hole extending through the ceramic plate and the ceramic shaft from the first surface of the ceramic plate through the second surface of the ceramic plate to a distal end of the ceramic shaft remote from the ceramic plate; a porous plug embedded in at least a portion of the gas supply hole corresponding to the ceramic plate; A susceptor comprising: [Aspect 2] 2. The susceptor of embodiment 1, further comprising a cooling jacket secured to the distal end, the cooling jacket having through holes in communication with the gas supply holes. [Aspect 3] 3. The susceptor of claim 1 or 2, further comprising a ceramic protective tube forming an inner wall of the gas supply hole in a region between a lower end of the porous plug and the distal end. [Aspect 4] 4. The susceptor of claim 3, wherein the protective tube is made of alumina. [Aspect 5] A susceptor according to any one of aspects 1 to 4, wherein the gas supply hole has a small diameter portion within the ceramic plate that is smaller than a diameter of the porous plug, and a step is formed between the small diameter portion and a lower portion of the gas supply hole other than the small diameter portion, and the upper end of the porous plug is restricted by the step so as not to move above the step. [Aspect 6] The susceptor according to any one of aspects 1 to 5, further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole. [Aspect 7] A susceptor as described in any one of aspects 2 to 6, further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole, and a ceramic protective tube forming an inner wall of the gas supply hole in the region between the lower end of the porous plug and the distal end, and the elastic member is interposed between the cooling jacket and the protective tube. [Aspect 8] A susceptor according to any one of aspects 1 to 7, wherein the porous plug is also embedded in a portion of the gas supply hole corresponding to the ceramic shaft. [Aspect 9] A susceptor as described in any one of aspects 2 to 8, further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole, the porous plug also being embedded in a portion of the gas supply hole corresponding to the ceramic shaft, and the elastic member being interposed between the cooling jacket and the porous plug. [Aspect 10] 10. The susceptor according to any one of aspects 6 to 9, wherein the elastic member is a spring. [Aspect 11] 11. The susceptor of any one of aspects 2 to 10, further comprising a clamp ring that engages the distal end of the ceramic shaft and secures the ceramic shaft to the cooling jacket. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of a susceptor according to the present invention. [Diagram 2] FIG. 2 is a schematic top view of the susceptor shown in FIG. [Diagram 3] FIG. 4 is a schematic cross-sectional view showing another example of a susceptor according to the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing another example of a susceptor according to the present invention. [Diagram 5] FIG. 1 is a schematic cross-sectional view showing an example of a conventional susceptor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The susceptor according to the present invention is a platform for supporting a wafer, which is used in a film forming apparatus or an etching apparatus, particularly a film forming apparatus or an etching apparatus for a semiconductor manufacturing process. For example, the susceptor according to the present invention may be a ceramic heater for a semiconductor film forming apparatus, or an electrostatic chuck for a semiconductor etching apparatus. Alternatively, the susceptor may be an electrostatic chuck heater having both a heater function and an electrostatic chuck function. Typical examples of the film forming apparatus include CVD (chemical vapor deposition) apparatuses (e.g., thermal CVD apparatuses, plasma CVD apparatuses, photo CVD apparatuses, and MOCVD apparatuses) and PVD (physical vapor deposition) apparatuses.

[0012] An example of a susceptor is shown in Figs. 1 and 2. The susceptor 10 shown in Figs. 1 and 2 includes a ceramic plate 12, a cylindrical ceramic shaft 14, a gas supply hole 16, and a porous plug 18. An internal electrode 13 is embedded in the ceramic plate 12. The ceramic plate 12 has a first surface 12a on which a wafer (not shown) is placed and a second surface 12b opposite to the first surface 12a, and a ceramic shaft 14 is attached to the second surface 12b. The gas supply hole 16 is configured to penetrate the ceramic plate 12 and the ceramic shaft 14 so as to extend from the first surface 12a of the ceramic plate 12 through the second surface 12b to a distal end 14a of the ceramic shaft 14 remote from the ceramic plate 12. A porous plug 18 is embedded in at least a portion of the gas supply hole 16 corresponding to the ceramic plate 12. In this manner, in a susceptor 10 having gas supply holes 16 penetrating the ceramic shaft 14 and the ceramic plate 12, by embedding porous plugs 18 at predetermined positions of the gas supply holes 16, it is possible to suppress the occurrence of arcing in a high-power plasma environment.

[0013] As described above, in the conventional susceptor 110 having the gas supply holes 116 as through holes as shown in FIG. 5, the insulation distance from the ceramic plate surface 112a to the distal end 114a of the ceramic shaft 114 is insufficient in a high-power plasma environment, and arcing may occur. That is, since the distal end 114a of the ceramic shaft 114 is assembled to the metal part 122 constituting the device, abnormal discharge may occur due to insufficient insulation distance between the metal part 122 and the ceramic plate surface 112a exposed to plasma. In this respect, according to the present invention, the occurrence of arcing can be suppressed by embedding the porous plug 18 at least in the part of the gas supply hole 16 corresponding to the ceramic plate 12. This is because the porous plug 18 closes the gas supply hole 16 in a breathable manner, and the length of the gas passage path can be extremely long. That is, the porous plug 18 has an open pore structure because it has breathable porosity, but the length of the gas passage path brought about by the open pore structure is naturally much longer than the length of the gas supply hole 16. Moreover, since the porous plug 18 is generally made of an insulating material such as ceramic, it has excellent dielectric strength and therefore has excellent arcing suppression effect. Therefore, it is possible to prevent arcing (abnormal discharge) that may occur due to insufficient insulation distance between the distal end 14a of the ceramic shaft 14 and the first surface 12a of the ceramic plate 12. In that sense, the length of the ceramic shaft 14 and the gas supply hole 16 themselves does not need to be changed from the existing ones, and therefore it can be advantageously used in existing film formation equipment and etching equipment without design changes.

[0014] The ceramic plate 12 may have the same structure as a ceramic plate used in a known ceramic susceptor. The main portion of the ceramic plate 12 other than the internal electrode 13 (i.e., the ceramic base) is preferably made of aluminum nitride from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0015] The ceramic plate 12 is preferably in the shape of a disk. However, the shape of the disk-shaped ceramic plate 12 in plan view does not have to be a perfect circle. For example, the shape of the disk-shaped ceramic plate 12 may be an orientation flat. r The ceramic plate 12 may have an incomplete circular shape with a part missing, such as a circular circumferential flat. The size of the ceramic plate 12 is not particularly limited and may be appropriately determined according to the diameter of the wafer to be used, but in the case of a circular shape, the diameter is typically 150 to 450 mm, for example, about 300 mm.

[0016] It is preferable that protrusions (not shown) are provided on the first surface 12a of the ceramic plate 12. The protrusions are intended to contact the rear surface of the wafer to support the wafer and to secure a flow path for gas (for example, heat transfer gas) supplied from the gas supply holes 16, and are preferably arranged at equal intervals on the first surface 12a of the ceramic plate 12. The shape of each protrusion is not particularly limited, but is preferably cylindrical. The diameter of each protrusion is not particularly limited, but is preferably 0.1 to 8 mm, more preferably 0.5 to 5 mm, even more preferably 0.5 to 4 mm, and particularly preferably 0.70 to 2.54 mm. It is preferable that the protrusions are integrally formed with the ceramic plate 12 by embossing or the like. Therefore, like the ceramic plate 12, the protrusions are preferably made of aluminum nitride. The height of the protrusions is not particularly limited, but is preferably 0.001 to 0.1 mm, more preferably 0.005 to 0.08 mm, even more preferably 0.01 to 0.05 mm, and particularly preferably 0.01 to 0.03 mm. The distance between the central axes of adjacent projections is preferably 4 to 30 mm, more preferably 5 to 26 mm, further preferably 7 to 26 mm, and particularly preferably 7 to 15 mm.

[0017] Internal electrodes 13 are embedded in the ceramic plate 12. Preferable examples of the internal electrodes 13 include ESC electrodes, heater electrodes, and RF electrodes. For example, two types of internal electrodes 13a and 13b may be provided as in the illustrated example.

[0018] The internal electrode 13a provided in the region close to the first surface 12a may be an ESC electrode. The ESC electrode is an abbreviation of electrostatic chuck (ESC) electrode, and is also called an electrostatic electrode. The ESC electrode is preferably a circular thin-layer electrode having a diameter slightly smaller than that of the ceramic plate 12, and may be, for example, a mesh-like electrode formed by weaving thin metal wires into a sheet shape. The ESC electrode may be used as a plasma electrode. That is, by applying a high frequency to the ESC electrode, the ESC electrode can also be used as a plasma electrode, and film formation can also be performed by a plasma CVD process. An ESC rod (not shown) is connected to the ESC electrode for power supply, and the ESC rod is connected to an external power source (not shown) via the internal space of the ceramic shaft 14. When a voltage is applied by the external power source, the ESC electrode chucks a wafer placed on the first surface 12a. The chucking force at this time is a force that is generated when the volume resistivity of aluminum nitride that can constitute the main part of the ceramic plate 12 is 1×10 8 ~1×10 13 is the Johnsen-Rahbek force because Ωcm.

[0019] The internal electrode 13b provided in the region close to the second surface 12b may be a heater electrode. The heater electrode is not particularly limited, and may be, for example, a conductive coil wired in a single stroke across the entire surface of the ceramic plate 12. Heater rods (not shown) are connected to both ends of the heater electrode for power supply, and the heater rods are connected to a heater power source (not shown) via the internal space of the ceramic shaft 14. When power is supplied from the heater power source, the heater electrode generates heat and heats the wafer placed on the first surface 12a. The heater electrode is not limited to a coil, and may be, for example, a ribbon (a long, thin plate) or a mesh.

[0020] The ceramic shaft 14 is a cylindrical shaft attached to the second surface 12b of the ceramic plate 12, and may have the same configuration as a ceramic shaft employed in a known ceramic susceptor. The ceramic shaft 14 has an internal space for accommodating rods (not shown) such as an ESC rod and a heater rod. The ceramic shaft 14 is preferably made of the same ceramic material as the ceramic plate 12. Therefore, the ceramic shaft 14 is preferably made of aluminum nitride. The upper end surface of the ceramic shaft 14 is preferably joined to the second surface 12b of the ceramic plate 12 by solid-state bonding or diffusion bonding. The outer diameter of the ceramic shaft 14 is not particularly limited and is, for example, about 40 mm. The inner diameter of the ceramic shaft 14 (diameter of the internal space) is also not particularly limited and is, for example, about 36 mm.

[0021] The gas supply hole 16 is a through hole configured to penetrate the ceramic plate 12 and the ceramic shaft 14 so as to pass from the first surface 12a of the ceramic plate 12 through the second surface 12b to the distal end 14a of the ceramic shaft 14. The presence of the gas supply hole 16 allows gas to be supplied to the first surface 12a of the ceramic plate 12. With this configuration, a wafer is placed on the first surface 12a, and by supplying gas to the back surface of the wafer, heat generated in the ceramic plate 12 (particularly the heater electrode) can be efficiently transferred to the wafer. Therefore, the gas supplied to the gas supply hole 16 is preferably an inert gas with excellent heat conductivity, and particularly preferably He gas.

[0022] The shape of the gas supply hole 16 in plan view may be any shape such as a circle or a polygon, but is preferably a circle. The number of gas supply holes 16 provided in the ceramic plate 12 is preferably 1 to 10, more preferably 2 to 6, and even more preferably 4. Within this range, the effective area of ​​the ceramic plate 12 can be increased while the gas can be sufficiently supplied. The diameter of the gas supply hole 16 is not particularly limited, but is preferably 0.5 to 4.0 mm, more preferably 0.5 to 2.0 mm, and even more preferably 0.9 to 1.1 mm.

[0023] The porous plug 18 is embedded in at least the portion of the gas supply hole 16 that corresponds to the ceramic plate 12. The porous plug 18 is not particularly limited as long as it is a member or part that includes a porous material having gas permeability, but such a porous material is preferably composed of an insulating material such as ceramic from the viewpoint of effectively suppressing the occurrence of arcing. For example, it is made of alumina. In general, a porous plug is known as a porous refractory material that is attached to a tuyere refractory material on the bottom wall of a molten metal container such as a ladle or tundish and has gas permeability for blowing gas into the molten metal, and such a commercially available porous plug can be used. In addition, a porous ceramic member called a porous plug or ceramic plug and used in a gas introduction path of a susceptor such as an electrostatic chuck can also be used as the porous plug 18. The diameter of the porous plug 18 is not particularly limited as long as it can block the gas supply hole 16. That is, a porous plug 18 having a diameter that matches the diameter of the gas supply hole 16 may be selected, or the diameter of the gas supply hole 16 may be set to match the diameter of the porous plug 18 to be adopted. The porous plug 18 is preferably made of high purity ceramic (e.g., alumina) in that high pressure resistance can be ensured. Specifically, the purity of the ceramic (e.g., alumina) constituting the porous plug 18 is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. The higher the purity of the porous plug 18, the more desirable it is, and therefore the upper limit is not particularly limited. The porosity of the porous plug 18 is not particularly limited, but is preferably 30 to 70%, more preferably 35 to 65%, and even more preferably 40 to 60%. Within these ranges, a desired discharge suppression effect can be obtained while adequately ensuring air permeability.

[0024] The length of the porous plug 18 is not particularly limited. Since the porous plug 18 is embedded in at least the portion of the gas supply hole 16 corresponding to the ceramic plate 12 (i.e., the portion penetrating the ceramic plate 12), the length is preferably equal to or greater than the thickness of the ceramic plate 12, but is not limited thereto as long as the occurrence of arcing can be suppressed. In any case, the presence of the porous plug 18 in at least the portion of the gas supply hole 16 corresponding to the ceramic plate 12 has the advantage of improving the dielectric strength between the wafer and the internal electrode 13 such as the ESC or RF electrode where a strong electric field is generated.

[0025] In this way, it is sufficient that the porous plug 18 is disposed at the upper part of the gas supply hole 16, and therefore, the gas supply hole 16 may have a portion where the porous plug 18 is not present. By having a portion where the porous plug 18 is not present, there is no flow resistance due to the porous plug 18 in that portion, so that the gas can flow more smoothly through the gas supply hole 16. In this case, it is preferable that the susceptor 10 further includes a ceramic protective tube 20 that forms the inner wall of the gas supply hole 16 in the region between the lower end of the porous plug 18 and the distal end 14a. By protecting the gas supply hole 16 with the protective tube 20 in this way, it is possible to ensure a flow path while suppressing arcing. In addition, since the lower end of the porous plug 18 can be supported by the upper end of the protective tube 20, there is also an advantage that the porous plug 18 can be reliably held at the upper part of the gas supply hole 16. The protective tube 20 is made of ceramic because of its excellent heat resistance and insulation, and is particularly preferably made of alumina.

[0026] However, as shown in Fig. 3, the porous plug 18 may be embedded not only in the portion of the gas supply hole 16 that corresponds to the ceramic plate 12 but also in the portion of the gas supply hole 16 that corresponds to the ceramic shaft 14. For example, the porous plug 18 may be embedded over the entire length of the gas supply hole 16. In this case, the occurrence of arcing can be more reliably suppressed. In this embodiment, flow resistance due to the porous plug 18 exists over most or the entire length of the gas supply hole 16, but the influence of such a factor can be reduced by using a porous plug 18 with high breathability.

[0027] As shown in FIG. 4, the gas supply hole 16 may have a small diameter portion 16a in the ceramic plate 12 that is smaller than the diameter of the porous plug 18. In this case, the small diameter portion 16a and a lower portion 16b of the gas supply hole 16 other than the small diameter portion form a step 16c, and it is preferable that the upper end of the porous plug 18 is restricted by the step 16c so as not to move above the step 16c. With this configuration, when the porous plug 18 is pressed from the lower part of the ceramic shaft 14 by inserting a member such as the protective tube 20 or the elastic member 26, the porous plug 18 is caught by the step 16c, and thus it is possible to prevent the porous plug 18 from shifting from a predetermined position. That is, the porous plug 18 can be stably held at a predetermined position. The step 16c is preferably provided at an intermediate position between the first surface 12a and the second surface 12b in the ceramic plate 12. It is preferable that the small diameter portion 16a extends from the step 16c toward the first surface 12a or to the first surface 12a. This ensures sufficient strength to restrict the upper end of the porous plug 18.

[0028] The cooling jacket 22 is preferably fixed to the distal end 14a of the ceramic shaft 14. The cooling jacket 22 can effectively cool the ceramic shaft 14 (particularly the lower portion thereof). In this case, the cooling jacket 22 may have a through hole 22a communicating with the gas supply hole 16. This allows gas to be supplied to the gas supply hole 16 through the through hole 22a. The cooling jacket 22 is not particularly limited as long as it is a metal member or part having a configuration capable of cooling the ceramic shaft 14. Since the cooling jacket 22 is made of metal, if the porous plug 18 is not provided, abnormal discharge may occur due to insufficient insulation distance between the cooling jacket 22 and the first surface 12a of the ceramic plate 12 exposed to plasma. However, in the present invention, the porous plug 18 is embedded in the above-mentioned position of the gas supply hole 16, thereby suppressing the occurrence of arcing in a high-power plasma environment.

[0029] The susceptor 10 preferably further includes a clamp ring 24 that engages the distal end 14a of the ceramic shaft 14 and secures the ceramic shaft 14 to the cooling jacket 22. The clamp ring 24 allows the ceramic shaft 14 to be removably and securely secured to the cooling jacket 22.

[0030] A gas-permeable elastic member 26 may be provided at the distal end of the gas supply hole 16. The presence of the elastic member 26 can mitigate the effect of thermal expansion of the porous plug 18 and / or the protective tube 20, thereby improving the durability of the susceptor 10. In addition, if the porous plug 18 and / or the protective tube 20 are displaced, a space may be created and discharge may occur, but the elastic member 26 can reduce such a risk by suppressing the displacement of the porous plug 18 and / or the protective tube 20. Since the elastic member 26 is provided in the gas supply hole 16, it is required to have gas permeability so as not to interfere with the function of the gas supply hole 16. In that sense, a preferred elastic member 26 is a spring.

[0031] 1, when the susceptor 10 includes the cooling jacket 22, the protective tube 20, and the elastic member 26, it is preferable that the elastic member 26 is interposed between the cooling jacket 22 and the protective tube 20. In this configuration, the length of the elastic member 26 is restricted between the cooling jacket 22 and the protective tube 20, so that the thermal expansion of the porous plug 18 and / or the protective tube 20 can be absorbed by the compression of the elastic member 26 within that section, and as a result, loosening of the fixation between the ceramic shaft 14 and the cooling jacket 22 (particularly the fixation by the clamp ring 24) can be avoided.

[0032] 3, when the susceptor 10 further includes a cooling jacket 22 and an elastic member 26 and the porous plug 18 is embedded not only in the portion of the gas supply hole 16 corresponding to the ceramic plate 12 but also in the portion of the gas supply hole 16 corresponding to the ceramic shaft 14, it is preferable that the elastic member 26 is interposed between the cooling jacket 22 and the porous plug 18. In this configuration, the length of the elastic member 26 is restricted between the cooling jacket 22 and the porous plug 18, so that the thermal expansion of the porous plug 18 can be absorbed by the compression of the elastic member 26 within that section, and as a result, loosening of the fixation between the ceramic shaft 14 and the cooling jacket 22 (particularly the fixation by the clamp ring 24) can be avoided.

Claims

1. A susceptor for a film forming apparatus or an etching apparatus, a ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, and having an internal electrode embedded therein; a cylindrical ceramic shaft attached to the second surface of the ceramic plate; a gas supply hole extending through the ceramic plate and the ceramic shaft from the first surface of the ceramic plate through the second surface of the ceramic plate to a distal end of the ceramic shaft remote from the ceramic plate; a porous plug embedded in at least a portion of the gas supply hole corresponding to the ceramic plate; and further comprising a ceramic protective tube forming an inner wall of the gas supply hole in a region between the lower end and the distal end of the porous plug.

2. The susceptor of claim 1 further comprising a cooling jacket secured to said distal end, said cooling jacket having through holes communicating with said gas supply holes.

3. The susceptor of claim 2 , wherein the protective tube is made of alumina.

4. 2. The susceptor of claim 1, wherein the gas supply hole has a small diameter portion in the ceramic plate that is smaller than a diameter of the porous plug, the small diameter portion and a lower portion of the gas supply hole other than the small diameter portion form a step, and the upper end of the porous plug is restricted by the step so as not to move above the step.

5. The susceptor of claim 1 , further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole.

6. The susceptor according to claim 2 , further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole, the elastic member being interposed between the cooling jacket and the protective tube.

7. The susceptor according to claim 1 , wherein the porous plug is also embedded in a portion of the gas supply hole corresponding to the ceramic shaft.

8. 3. The susceptor of claim 2, further comprising a gas-permeable elastic member provided at the distal end of the gas supply hole, the porous plug also being embedded in a portion of the gas supply hole corresponding to the ceramic shaft, and the elastic member being interposed between the cooling jacket and the porous plug.

9. The susceptor of claim 5, 6 or 8, wherein the resilient member is a spring.

10. The susceptor of claim 2 , further comprising a clamp ring that engages the distal end of the ceramic shaft and secures the ceramic shaft to the cooling jacket.

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