SUSCEPTOR AND MANUFACTURING METHOD THEREOF

Abstract

The present invention relates to a susceptor including a substrate including a carbon material and having one main surface on which a silicon water is to be placed, and another main surface facing the one main surface, in which an entire surface of the substrate is covered with a thin film including silicon carbide, the one main surface has an emissivity variation of 3% or less, and a ratio of an average emissivity between the one main surface and the another main surface facing the one main surface is from 1:1 to 1:0.8.

Claims

1. A susceptor comprising a substrate comprising a carbon material and having one main surface on which a silicon wafer is to be placed, and another main surface facing the one main surface, wherein an entire surface of the substrate is covered with a thin film comprising silicon carbide, the one main surface has an emissivity variation of 3% or less, and a ratio of an average emissivity between the one main surface and the another main surface facing the one main surface is from 1:1 to 1:0.8.

2. The susceptor according to claim 1, wherein the another main surface facing the one main surface has an emissivity variation of 3% or less.

3. The susceptor according to claim 1, wherein a ratio of a film thickness of the thin film formed on the another main surface to a film thickness of the thin film formed on the one main surface is 0.7 or more and 1.2 or less, a film thickness difference between a central part and an outer edge part in the one main surface is 40% or less of an average film thickness value of the thin film formed on the one main surface, and a film thickness difference between the maximum film thickness and the minimum film thickness in the outer edge part of the one main surface is 40% or less of the average film thickness value of the thin film formed on the one main surface.

4. The susceptor according to claim 1, wherein the film thickness of the thin film comprising silicon carbide formed on the entire surface of the substrate is at least 60 μm.

5. A method of manufacturing the susceptor according to claim 1, the method comprising: supporting the substrate comprising the carbon material in a chamber while moving a support position to the substrate; and supplying a raw material gas such that a supply direction is parallel to the one main surface of the substrate, thereby forming a thin film comprising silicon carbide on the entire surface of the substrate.

Description

BRIEF DESCRIPTION Of DRAWING

[0027] FIG. 1 is a cross-sectional view of the susceptor according to the present invention.

[0028] FIG. 2 is a partially enlarged cross-sectional view of the susceptor of FIG. 1.

[0029] FIG. 3 is a cross-sectional view schematically illustrating a CVD apparatus used at the time of manufacture of the susceptor of FIG. 1.

[0030] FIG. 4 is a plan view of the CVD apparatus of FIG. 3.

DESCRIPTION OF EMBODIMENTS

[0031] One embodiment of each of the susceptor according to the present invention and the manufacturing method thereof is described below based on FIG. 1 to FIG. 4. The drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the proportions of sizes among portions, etc. are not accurately illustrated.

[0032] As illustrated in FIG. 1, the susceptor 1 includes a disk-shaped carbon substrate 2 composed of a carbon material. The carbon substrate 2 is covered, throughout its surface, with a thin film 3 having a predetermined thickness (for example, 60 μm or more) and being composed of silicon carbide.

[0033] That is, the thin film 3 includes a thin film 3F composed of silicon carbide covering one main surface F1 that is a wafer placing surface of the susceptor 1, a thin film 3B composed of silicon carbide covering another main surface F2 that is a back surface facing the one main surface F1, and a thin film 3S composed of silicon carbide covering the outer peripheral surface of the carbon substrate 2.

[0034] Also, the susceptor 1 is a so-called sheet-type susceptor in which one recessed counterbored portion 4 for placing a semiconductor substrate is formed in the one main surface F1.

[0035] The counterbored portion 4 is formed to have a circular shape in planar view, and a cylindrical concave portion 4a is formed in the center. In addition, the susceptor 1 presents circular symmetry about the axis of rotation L passing through its central part O. Here, denoting as To the depth of the deepest part (central part O) of the counterbored portion 4, the average depth Td is To/2.

[0036] The ratio (T/Td) between the thickness T of the susceptor 1 and the average depth Td is preferably 6≤TTd≤30. The ratio (T/To) between the thickness T of the susceptor 1 and the depth To is preferably 3≤T/To≤13.

[0037] As the counterbored portion 4 is formed such that the ratio (T/Td) between the thickness T of the susceptor 1 and the average depth Td satisfies 6≤T/Td≤30, an effect of preventing warpage can thereby be obtained.

[0038] If the ratio (T/Td) between the thickness T of the susceptor 1 and the average depth Td is less than 6, the counterbore is too deep relative to the thickness of the susceptor 1, and this may disadvantageously result in poor deposition on the wafer outer periphery. Also, if the ratio (T/Td) between the thickness T of the susceptor 1 and the average depth Td exceeds 30, the susceptor is thick-walled, and the influence of rigidity of the carbon substrate 2 cannot be neglected, undesirably making it difficult to control the warpage amount in a thin film.

[0039] As described above, a carbon material applicable as a susceptor for semiconductors is used for the carbon substrate 2, and silicon carbide is used for the thin film 3. The thin film 3 is formed on the entire surface of the carbon substrate 2 and has roles in preventing outward diffusion of dust or impurities from the carbon substrate 2, protecting the entire surface of the carbon substrate 2, and suppressing warpage of the carbon substrate 2.

[0040] Here, the ratio between the average of the film thickness t1 of the thin film 3F formed on the main surface F1 of the susceptor 1 illustrated in FIG. 2 and the average of the film thickness t2 of the thin film 3B formed on the another main surface F2 is preferably from 0.7 to 1.2.

[0041] If the ratio above is smaller than 0.7, a thermal conductivity difference is generated in the epitaxial deposition process using the susceptor, and a uniform epitaxial film may be hardly obtained.

[0042] If the ratio is larger than 1.2, in addition to the thermal conductivity difference attributable to thickness variation of the thin film 3, warpage of the susceptor readily occurs, and the epitaxial film disadvantageously becomes non-uniform.

[0043] In the main surface F1 of the susceptor 1, the film thickness difference d1 between the central part O and the outer edge part F1a is preferably 40% or less of the average of the film thickness 11 of the thin film 3F formed on the main surface F1.

[0044] In addition, in the main surface F1 of the susceptor 1, the film thickness difference d2 between the maximum film thickness and the minimum film thickness in the outer edge part F1a is preferably 40% or less of the average of the film thickness 11 of the thin film 3F formed on the main surface F1.

[0045] When the film thickness difference d1 or d2 is 40% or less of the average of the film thickness t1, the uniformity of thermal conduction in the main surface F1 is improved, and in the epitaxial deposition process using the susceptor, a uniform epitaxial film can be obtained.

[0046] On the other hand, if the film thickness difference is more than 40% of the average of the film thickness t1, an irregularity is likely to occur, and the thermal conduction in the main surface F1 becomes non-uniform, as a result, a uniform epitaxial film may not be obtained.

[0047] The susceptor 1 is formed such that in the temperature range (from 900 to 1,300° C.) during the epitaxial deposition process, the emissivity variation on the wafer placing surface (main surface F1) is within 3% and the ratio of average emissivity between the wafer placing surface and its backside surface (another main surface 12) is from 1:1 to 1:0.8.

[0048] In addition, the susceptor is preferably formed such that on the backside surface (another main surface F2) of the wafer placing surface as well, the emissivity variation in the same plane is within 3%.

[0049] By setting the emissivity of the susceptor 1 in this way, the thermal conductivity variation of the susceptor is suppressed, and temperature irregularity does not occur, so that the temperature of the wafer placed can be made uniform to present the film thickness variation of the epitaxial film.

[0050] The above-described susceptor 1 can be manufactured using, for example, a CVD apparatus 5 illustrated in FIG. 3.

[0051] The CVD apparatus 5 illustrated in FIG. 3 has a chamber 10 for forming a processing space, a gas inflow port 11 provided on the side surface of the chamber 10 for supplying a carrier gas (hydrogen gas) into the chamber 10, and a gas outflow port 12 provided on the opposite-side chamber 10 side surface facing the inflow port 11.

[0052] The apparatus further includes, in the chamber 10, a support portion 20 for supporting the underside of the carbon substrate 2 of the susceptor 1 and a plurality of columnar guard members 13 disposed to surround the carbon substrate 2 and slidably support the lateral periphery (outer periphery) of the carbon substrate 2.

[0053] The support portion 20 has a plurality of support legs 20a to 20d disposed to let a roller 22 provided to be rotatable at a constant speed by a motor 21 rotate along a circumferential direction of the carbon substrate 2. In FIG. 3, the support leg 20c is not shown as it is behind the support leg 20a. The rollers 22 of the support legs 20a to 20d abut on a peripheral edge portion of the backside surface of the carbon substrate 2 and are configured such that each roller 22 unidirectionally rotates and the carbon substrate 2 is thereby rotated on the central part O while being supported. The rotational movements (start of rotation, stop, direction of rotation, rotational speed) of rollers 22 of respective support legs 20a to 20d are controlled to be synchronized with one another by a control unit (not shown).

[0054] In addition, as illustrated in FIG. 3, a heater portion 15 is provided above and below the chamber 10 and thus, the apparatus is configured to enable a temperature rise up to a predetermined temperature in the furnace.

[0055] In the case of manufacturing the susceptor 1 by using the CVD apparatus 5, a carbon substrate 2 composed of a carbon material, where a circular counterbored portion is formed in advance, is disposed on the support legs 20a to 20d in the chamber 10.

[0056] Subsequently, the rollers 22 of the support legs 20a to 20d are caused to start rotating at a predetermined rotational speed by a control unit (not shown). This allows the carbon substrate 2 to rotate on the central part O at a predetermined speed (for example, 0.1 rpm).

[0057] In addition, the temperature inside the chamber 10 is raised, for example, to 500° C. by driving the healer portion 15, and the air inside the chamber 10 is sucked from the gas outflow port 12 to make a vacuum state.

[0058] Next, a carrier gas (H.sub.2) is introduced at a predetermined flow rate into the chamber 10 from the gas inflow port 11. Thereafter, the temperature inside the chamber 10 is raised, for example, to 1,300° C. and raw material gases (SiCl.sub.4, C.sub.3H.sub.8) are introduced together with the carrier gas for a predetermined time. The raw material gas concentration in the chamber 10 at the start of introduction is, for example, from 15% to 20%.

[0059] Here, the raw material gases are caused to flow along the top and bottom surfaces of the carbon substrate 2 by the carrier gas and discharged from the gas outflow port 12.

[0060] Also, since the carbon substrate 2 is rotated on the central portion O by a plurality of rotationally driven rollers 22 provided to support the bottom surface-side peripheral edge portion of the carbon substrate 2, the support position in the bottom surface-side peripheral edge portion of the carbon substrate 2 is not located at the same place (not fixed but changes), and the film thickness uniformity of the film formed is enhanced.

[0061] Raw material gases are supplied into the chamber 10 for a predetermined time (for example, 14 hours) so that the film formed can have a predetermined thickness (for example, 60 μm or more).

[0062] Then the raw material gases are stepwise diluted to a concentration of ½ to ¼ of the normal concentration at a final stage of the raw material gas supply process (for example, a stage of 5 to 60 minutes before the end of the process).

[0063] Consequently, the raw material gases turn into more dilute raw material gases than usual, leading to a lower deposition rate than usual, and are deposited in the state of crystal grains being uniform in size. As a result, the deposition amount in plane is likely to be uniform, and the emissivity in the same plane can be made more constant. Specifically, the emissivity variation on the wafer placing surface (and its back side) is adjusted to be within 3%, and the ratio of average emissivity between the wafer placing surface and its backside surface is adjusted to be from 1:1 to 1:0.8.

[0064] When a pre-set raw material gas supply time has elapsed, the supply of raw material gases is stopped and after the further elapse of a predetermined time (for example, after 1 hour), the rotation of rollers 22 is stopped.

[0065] Through such processing, a thin film 3 composed of silicon carbide is formed on the carbon substrate 2 and in turn, the susceptor 1 of the present invention is manufactured. During exposure of the carbon substrate 2 to raw material gases, the positions supporting the carbon substrate 2 in the chamber 10 are always changed, and therefore, the thin film 3 is formed with high film thickness uniformity. More specifically, the susceptor 1 is formed such that the ratio between the average of the film thickness t1 of the thin film 3F formed on the main surface F1 and the average of the film thickness t2 of the thin film 3B formed on the another main surface F2 is preferably from 0.7 to 1.2. In addition, the susceptor 1 is formed such that in the main surface F1, the film thickness difference d1 between the central part O and the outer edge part F1a and the film thickness difference d2 between the maximum film thickness and the minimum film thickness in the outer edge part F1a are preferably 40% or less of the average of the film thickness t1 of the thin film 3F formed on the main surface F1.

[0066] As described above, according to the embodiments of the present invention, in the susceptor 1, the thin film 3 formed on the carbon substrate 2 is formed with high film thickness uniformity, so that the emissivity variation on the wafer placing surface can be within 3% and the ratio of average emissivity between the wafer placing surface and its backside surface can be from 1:1 to 1:0.8.

[0067] In addition, the susceptor 1 is preferably formed such that the ratio between the average of the film thickness t1 of the thin film 3F formed on the main surface F1 and the average of the film thickness t2 of the thin film 3B formed on the another main surface F2 is from 0.7 to 1.2, and the susceptor 1 is formed such that in the main surface F1, the film thickness difference d1 between the central part O and the outer edge part F1a or the film thickness difference d2 between the maximum film thickness and the minimum film thickness in the outer edge pan F1a is 40% or less of the average of the film thickness t1 of the thin film 3F formed or the main surface F1.

[0068] When these are satisfied, the uniformity of the thin film 3 formed on a surface of the carbon substrate 2 is enhanced, and the uniformity of thermal conduction in the main surface F1 is improved without occurrence of temperature irregularity in the susceptor 1.

[0069] As a result, a uniform epitaxial film can be obtained on a silicon water in the epitaxial deposition process using the susceptor.

[0070] Furthermore, at the time of forming the thin film composed of silicon carbide on the carbon substrate 2 composed of a carbon material by CVD, the support positions with respect to the carbon substrate 2 are not fixed, so that a uniform thin film can be formed on the entire carbon substrate 2. Consequently, unlike a usual case, the carbon substrate 2 need not be taken out from the chamber halfway through the thin film formation, and a single-layer thin film with reduced contamination can be formed.

[0071] In the embodiment above, as the method for suppressing the emissivity variation in the same plane of the wafer placing surface (and backside surface), raw material gases are diluted at a final stage of the raw material gas supply process, but the present invention is not limited to this example.

[0072] Also, in the embodiment above, a susceptor where a counterbored portion is formed is described as an example, but the present invention is not limited to this embodiment and can be applied also to a susceptor having no counterbored portion.

[0073] In addition, in the case of having a counterbored portion, the portion is not limited to the cylindrical counterbored portion illustrated, and the present invention can be applied to a susceptor having, for example, a concavely curved counterbored portion.

[0074] The susceptor according to the present invention and its manufacturing method are further descried based on Examples.

Experiment 1

[0075] In Experiment 1, isotropic graphite was used as the material of the substrate of the susceptor, and a plurality of carbon substrates in which a counterbore is formed were prepared. Using the CVD apparatus illustrated in FIG. 3, a silicon carbide film was formed on a substrate surface under a plurality of film thickness-forming conditions.

[0076] In the CVD apparatus, the carbon substrate was placed in the chamber and after vacuuming, the temperature in the chamber was raised up to 500° C., followed by introduction of a carrier gas (H.sub.2) into the chamber. Subsequently, the temperature in the chamber was raised up to 1,300° C. and while rotating the carbon substrate at a rotational speed of 0.1 rpm with care of not fixing the substrate support positions, raw material gases (SiCl.sub.4C.sub.3H.sub.8) were supplied along the top and bottom surfaces of the carbon substrate. After the elapse of a predetermined time (14 hours), the supply of raw material gases was stopped and after 1 hour, the rotation of the carbon substrate was stopped, thereby forming a 70 μm-thick silicon carbide thin film on the substrate surface.

[0077] Here, out of the raw material gas supply process (14 hours), at a final stage (0.2 hours before the end of the process), the raw material gases were diluted by diluting the concentrations so as to suppress the emissivity variation on the wafer placing surface and its backside surface of the susceptor formed.

[0078] The emissivity variation was set as the conditions of Examples 1 to 4 and Comparative Examples 1 to 3, and the emissivity variation was adjusted by the raw material gas concentrations. Note that the emissivity measurement on the wafer placing surface and its backside surface was performed by a method using FTIR (Fourier transform infrared spectroscopy) manufactured by Thermo Fisher Scientific K.K. and an integrating sphere, at four positions in total, namely, center of the wafer placing surface of the carbon substrate and three positions located, at 120° interval, on the concentric circle having radius of 50% of the wafer placing surface outward from the center. The average emissivity was an average of the four measurement values. The emissivity variation was calculated based on the four measurement values by a formula of ((maximum value)−(minimum value))/(average value). As for the backside surface of the wafer placing surface, the measurement and calculation were performed with the same measurement positions as the wafer placing surface.

[0079] In Example 1, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 1% and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:1.

[0080] In Example 2, the emissivity variation on the wafer placing surface of the carbon substrate was 2%. the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0081] In Example 3, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0082] In Example 4, the emissivity variation on the wafer placing surface of the carbon substrate was 1%. the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0083] In Example 5, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 4%. and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0084] In Comparative Example 1, the emissivity variation on the wafer placing surface of the carbon substrate was 4%, the emissivity variation on the backside surf are of the wafer placing surface was 3%e and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0085] In Comparative Example 2, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.7.

[0086] A processing of forming an epitaxial film on a silicon wafer was performed using the susceptors manufactured in Examples 1 to 5 and Comparative Examples 1 and 2.

[0087] The results of Experiment 1 are shown in Table 1. The evaluation under respective conditions shown in Table 1 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00001 TABLE 1 Film Thickness Example Example Example Example Example Comparative Comparative 70 μm 1 2 3 4 5 Example 1 Example 2 Emissivity 1 2 3 1 2 4 3 variation on front surface (%) Emissivity 1 1 1 3 4 3 3 variation on back surface (%) Ratio of 1:1 1:0.9 1:0.8 1:0.8 1:0.8 1:0.9 1:0.7 emissivity between front and back surfaces Evaluation A A A A B C C

[0088] It was confirmed from the results of Experiment 1 that in the case of forming a 70 μm-thick silicon carbide thin film on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

Experiment 2

[0089] In Experiment 2, evaluation was performed using the same conditions as in Experiment 1 except that the thickness of the silicon carbide thin film on the substrate surface was changed to 30 μm.

[0090] In Example 6, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:1.

[0091] In Example 7, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0092] In Example 8, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0093] In Example 9, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0094] In Example 10, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 4%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0095] In Comparative Example 3, the emissivity variation on the wafer placing surface of the carbon substrate was 4%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0096] In Comparative Example 4, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.7.

[0097] A processing of forming an epitaxial film on a silicon wafer was performed using the susceptors manufactured in Examples 6 to 10 and Comparative Examples 3 and 4.

[0098] The results of Experiment 2 are shown in Table 2. The evaluation under respective conditions shown in Table 2 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00002 TABLE 2 Film Thickness Example Example Example Example Example Comparative Comparative 30 μm 6 7 8 9 10 Example 3 Example 4 Emissivity 1 2 3 1 2 4 3 variation on front surface (%) Emissivity 1 1 1 3 4 3 3 variation on back surface (%) Ratio of 1:1 1:0.9 1:0.8 1:0.8 1:0.8 1:0.9 1:0.7 emissivity between front and back surfaces Evaluation A A A A B C C

[0099] It was confirmed from the results of Experiment 2 shown in Table 2 that in the case of forming a 30 μm-thick silicon carbide thin film on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its back side surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

Experiment 3

[0100] In Experiment 3, evaluation was performed using the same conditions as in Experiment 1 except that the thickness of the silicon carbide thin film on the substrate surface was changed to 60 μm.

[0101] In Example 11, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:1.

[0102] In Example 12, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0103] In Example 13, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0104] In Example 14, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0105] In Example 15, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 4%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0106] In Comparative Example 5, the emissivity variation on the wafer placing surface of the carbon substrate was 4%. the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0107] In Comparative Example 6, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.7.

[0108] A processing of forming an epitaxial film on a silicon wafer was performed using the susceptors manufactured in Examples 11 to 15 and Comparative Examples 5 and 6.

[0109] The results of Experiment 3 are shown in Table 3. The evaluation under respective conditions shown in Table 3 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00003 TABLE 3 Film Thickness Example Example Example Example Example Comparative Comparative 60 μm 11 12 13 14 15 Example 5 Example 6 Emissivity 1 2 3 1 2 4 3 variation on front surface (%) Emissivity 1 1 1 3 4 3 3 variation on back surface (%) Ratio of 1:1 1:0.9 1:0.8 1:0.8 1:0.8 1:0.9 1:0.7 emissivity between front and back surfaces Evaluation A A A A B C C

[0110] It was confirmed from the results of Experiment 3 shown in Table 3 that in the case of forming a 60 μm-thick silicon carbide thin film on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

Experiment 4

[0111] In Experiment 4, evaluation was performed using the same conditions as in Experiment 1 except that the thickness of the silicon carbide thin film on the substrate surface was changed to 140 μm.

[0112] In Example 16, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:1.

[0113] In Example 17, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0114] In Example 18, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0115] In Example 19, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0116] In Example 20, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 4%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0117] In Comparative Example 7, the emissivity variation on the wafer placing surface of the carbon substrate was 4%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0118] In Comparative Example 8, the emissivity variation on the water placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.7.

[0119] A processing of forming an epitaxial film on a silicon wafer was performed using the susceptors manufactured in Examples 16 to 20 and Comparative Examples 7 and 8.

[0120] The results of Experiment 4 are shown in Table 4. The evaluation under respective conditions shown in Table 4 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±1%.

TABLE-US-00004 TABLE 4 Film Thickness Example Example Example Example Example Comparative Comparative 140 μm 16 17 18 19 20 Example 7 Example 8 Emissivity 1 2 3 1 2 4 3 variation on front surface (%) Emissivity 1 1 1 3 4 3 3 variation on back surface (%) Ratio of 1:1 1:0.9 1:0.8 1:0.8 1:0.8 1:0.9 1:0.7 emissivity between front and back surfaces Evaluation A A A A B C C

[0121] It was confirmed from the results of Experiment 4 shown in Table 4 that in the case of forming a 140 μm-thick silicon carbide thin film on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

Experiment 5

[0122] In Experiment 5, evaluation was performed using the same conditions as in Experiment 1 except that the thickness of the silicon carbide thin film on the substrate surface was changed to 200 μm.

[0123] In Example 21, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:1.

[0124] In Example 22, the emissivity variation on the water placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0125] In Example 23, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 1%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0126] In Example 24, the emissivity variation on the wafer placing surface of the carbon substrate was 1%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0127] In Example 25, the emissivity variation on the wafer placing surface of the carbon substrate was 2%, the emissivity variation on the backside surface of the wafer placing surface was 4%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.8.

[0128] In Comparative Example 9, the emissivity variation on the wafer placing surface of the carbon substrate was 4%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.9.

[0129] In Comparative Example 10, the emissivity variation on the wafer placing surface of the carbon substrate was 3%, the emissivity variation on the backside surface of the wafer placing surface was 3%, and the ratio of the average emissivity between the wafer placing surface and the backside surface was 1:0.7.

[0130] A processing of forming an epitaxial film on a silicon wafer was performed using the susceptors manufactured in Examples 21 to 25 and Comparative Examples 9 and 10.

[0131] The results of Experiment 5 are shown in Table 5. The evaluation under respective conditions shown in Table 5 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00005 TABLE 5 Film Thickness Example Example Example Example Example Comparative Comparative 200 μm 21 22 23 24 25 Example 9 Example 10 Emissivity 1 2 3 1 2 4 3 variation on front surface (%) Emissivity 1 1 2 3 4 3 3 variation on back surface (%) Ratio of 1:1 1:0.9 1:0.8 1:0.8 1:0.8 1:0.9 1:0.7 emissivity between front and back surfaces Evaluation A A A A B C C

[0132] It was confirmed from the results of Experiment 5 shown in Table 5 that in the case of forming a 200 μm-thick silicon carbide thin film on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

[0133] From these results of Experiments 1 to 5, it was confirmed that under all conditions of the thickness of the silicon carbide thin film formed on a substrate surface, when the emissivity variation on the wafer placing surface (front surface) is within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface is from 1:1 to 1:0.8, the uniformity of the epitaxial film formed on the silicon wafer is improved.

[0134] It is also confirmed that, more preferably, when the emissivity variation on the susceptor back surface is within 3%, the uniformity of the epitaxial film formed on the silicon wafer is better improved.

Experiment 6

[0135] In Experiment 6, a suitable film thickness of the silicon carbide film formed on a surface of a carbon substrate was examined. In Examples 26 to 33, the film thickness was adjusted by the raw material gas supply time. Furthermore, in Experiment 6, the raw material gases were diluted at a final stage of the raw material gas supply process to adjust the emissivity variation on both the wafer placing surface and the backside surface of the susceptor obtained to fail within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface to (all in the range of 1:1 to 1:0.8.

[0136] Then, an epitaxial deposition processing and a cleaning treatment were repeatedly performed using the susceptor obtained so as to verify whether or not a predetermined life time (continuous operation 4,000 hours) can be achieved.

[0137] In Example 26, the film thickness of the silicon carbide film on the main surface (wafer placing surface) was 42 μm. Also, the film thickness was 55 μm in Example 27, 58 pm in Example 28, 61 μm in Example 29, and 66 μm in Example 30.

[0138] In addition, the film thickness was 70 μm in Example 31, 80 μm in Example 32, and 100 μm in Example 33.

[0139] The results of Experiment 6 are shown in Table 6.

TABLE-US-00006 TABLE 6 Example Example Example Example Example Example Example Example 26 27 28 29 30 31 32 33 Film 42 55 58 61 66 70 80 100 thickness (μm) Results Not Not Not Achieved Achieved Achieved Achieved Achieved achieved achieved achieved

[0140] As shown in Table 6, the susceptors where the thickness of the silicon carbide film is less than 60 μm could not achieve a required life. Accordingly, it was confirmed (hat the thickness of the silicon carbide film is preferably 60 μm or more.

Experiment 7

[0141] In Experiment 7, isotropic graphite was used as the material of the substrate of the susceptor, and a carbon substrate where a counterbored portion is formed was prepared. Using the CVD apparatus illustrated in FIG. 3, a silicon carbide film was formed on a substrate surface under a plurality of film thickness-forming conditions.

[0142] Subsequently, a processing of forming an epitaxial film on a silicon wafer was performed using the susceptors formed under respective conditions.

[0143] In the manufacture of the susceptor, at the time of forming a silicon carbide film on a substrate surface of the susceptor by using the CVD apparatus illustrated in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Furthermore, in Experiment 7, the raw material gases were diluted at a final stage of the raw material gas supply process to adjust the emissivity variation on both the wafer placing surface and backside surface of the susceptor obtained to fall within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface to fall in the range of 1:1 to 1:0.8.

[0144] After the formation of the susceptor, the ratio of the average of the film thickness of the silicon carbide film formed on another main surface (wafer non-placing surface) to the average of the film thickness of the silicon carbide film formed on the main surface (wafer placing surface) was determined. The average values of the film thickness of the silicon carbide film formed on the main surface (wafer placing surface) and the film thickness of the silicon carbide film formed on the another main surface (wafer non-placing surface) were determined by performing measurement at cross sections of positions same as the emissivity measurement positions by optical microscope and calculating average of the measured values.

[0145] As shown in Table 7, the ratio is 0.5 in Example 34, 0.6 in Example 35, 0.7 in Example 36, 0.8 in Example 37, 0.9 in Example 38, and 1.0 in Example 39.

[0146] Also, the ratio is 1.1 in Example 40. 1.2 in Example 41, 1.3 in Example 42, and 1.4 in Example 43.

[0147] In all of Examples 34 to 43, in the main surface (wafer placing surface) of the susceptor, the proportion (%) of the film thickness difference between the center and the outer edge pail to the average of the film thickness of the thin film formed on the main surface was 30%. Furthermore, in all susceptors, in the main surface (wafer placing surface) of the susceptor, the proportion (%) of the film thickness difference between the maximum film thickness and minimum film thickness in the outer edge part to the average of the film thickness of the thin film formed on the main surface was 30%.

[0148] The results of Experiment 7 are shown in Table 7, The evaluation under respective conditions shown in Table 7 was performed using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00007 TABLE 7 Film Thickness Ratio Evaluation Example 34 0.5 B Example 35 0.6 B Example 36 0.7 A Example 37 0.8 A Example 38 0.9 A Example 39 1.0 A Example 40 1.1 A Example 41 1.2 A Example 42 1.3 B Example 43 1.4 B

[0149] It was confirmed from the results of Experiment 7 that when the ratio of the average of the film thickness of the silicon carbide film formed on another main surface (wafer non-placing surface) to the average of the film thickness of the silicon carbide film formed on the main surface (wafer placing surface) of the susceptor is from 0.7 to 1.2, the film thickness uniformity of the epitaxial film is improved.

Experiment 8

[0150] In experiment 8, as with Experiment 7, using the CVD apparatus illustrated in FIG. 3, a silicon carbide film was formed on a substrate surface under a plurality of film thickness-forming conditions.

[0151] Subsequently, a processing of forming an epitaxial film on a silicon wafer was performed using the susceptors formed under respective conditions.

[0152] In the manufacture of the susceptor, at the time of forming a silicon carbide film on a substrate surface of the susceptor by using the CVD apparatus illustrated in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Furthermore, the raw material gases were diluted at a final stage of the raw material gas supply process to adjust the emissivity variation on both the wafer placing surface and backside surface of the susceptor obtained to fall within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface to fall in the range of 1:1 to 1:0.8.

[0153] After the formation of the thin film, in the main surface (wafer placing surface) of the susceptor taken out from the CVD apparatus, the proportion (%) of the film thickness difference between the center and the outer edge part to the average of the film thickness of the thin film formed on the main surface was determined.

[0154] The proportion was 0% in Example 44, 10% in Example 45, 20% in Example 46, 30% in Example 47, and 40% in Example 48.

[0155] Also, the proportion was 50% in Example 49 and 60% in Example 50.

[0156] In all of Examples 44 to 50, the ratio of the average of the film thickness of the silicon carbide film formed on another main surface (wafer non-placing surface) to the average of the film thickness of the silicon carbide film formed on the main surface (wafer placing surface) of the susceptor was 1.0. Furthermore, in all susceptors, in the main surface (wafer placing surface) of the susceptor, the proportion (%) of the film thickness difference between the maximum film thickness and minimum film thickness in the outer edge part to the average of the film thickness of the thin film formed on the main surface was 30%.

[0157] The results of Experiment 8 are shown in Table 8. The evaluation under respective conditions shown in Table 8 was performed, as with Experiment 7, using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00008 TABLE 8 Proportion (%) Evaluation Example 44 0 A Example 45 10 A Example 46 20 A Example 47 30 A Example 48 40 A Example 49 50 B Example 50 60 B

[0158] It was confirmed from the results of Experiment 8 that when in the main surface (wafer placing surface) of the susceptor, the film thickness difference between the center and the outer edge part relative to the average of the film thickness of the thin film formed on the main surface is front 0% to 40%, the film thickness uniformity of the epitaxial film is improved.

Experiment 9

[0159] In Experiment 9, as with Experiment 7, using the CVD apparatus illustrated in FIG. 3, a silicon carbide film was formed on a substrate surface under a plurality of film thickness-forming conditions.

[0160] Subsequently, a processing of forming an epitaxial film on a silicon wafer was performed using the susceptors formed under respective conditions.

[0161] In the manufacture of the susceptor, at the time of forming a silicon carbide film on a substrate surface of the susceptor by using the CVD apparatus illustrated in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Furthermore, the raw material gases w ere diluted at a final stage of the raw material gas supply process to adjust the emissivity variation on both the wafer placing surface and backside surface of the susceptor obtained to fall within 3% and the ratio of the average emissivity between the wafer placing surface and its backside surface to fall in the range of 1:1 to 1:0.8.

[0162] After the formation of the thin film, in the main surface (wafer placing surface) of the susceptor taken out from the CVD apparatus, the proportion (%) of the film thickness difference between the maximum film thickness and minimum film thickness in the outer edge part to the average of the film thickness of the thin film formed on the main surface was determined.

[0163] The proportion was 0% in Example 51, 10% in Example 52, 20% in Example 53, 30% in Example 54, and 40% in Example 55.

[0164] Also, the proportion was 50% in Example 56, and 60% in Example 57.

[0165] In all of Examples 51 to 57, the ratio of the average of the film thickness of the silicon carbide film formed on another main surface (wafer non-placing surface) to the average of the film thickness of the silicon carbide film formed on the main surface (wafer placing surface) of the susceptor was 1.0. Furthermore, in all susceptors, in the main surface (wafer placing surface) of the susceptor, the proportion (%) of the film thickness difference between the center and the outer edge part to the average of the film thickness of the thin film formed on the main surface was 30%.

[0166] The results of Experiment 9 are shown in Table 9. The evaluation under respective conditions shown in Table 9 was performed, as with Experiments 7 and 8, using the uniformity of the epitaxial film formed on the silicon wafer. The uniformity was rated as A when the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, rated as B when more than ±5% to ±7%, and rated as C when more than ±7%.

TABLE-US-00009 TABLE 9 Proportion (%) Evaluation Example 51 0 A Example 52 10 A Example 53 20 A Example 54 30 A Example 55 40 A Example 56 50 B Example 57 60 B

[0167] It was confirmed from the results of Experiment 9 that when in the main surface (wafer placing surface) of the susceptor, the film thickness difference between the maximum film thickness and minimum film thickness in the outer edge part relative to the average of the film thickness of the thin film formed on the main surface is from 0% to 40%, the film thickness uniformity of the epitaxial film is improved.

[0168] Although the present invention has been described in detail and by reference to the specific embodiments, it is apparent to one skilled in the art that various modifications or changes can be made without departing the spirit and scope of the present invention. This application is based on Japanese Patent Application (No. 2021-105175) filed on Jun. 24, 2021 and Japanese Patent Application (No. 2022-071844) filed on Apr. 25,2022, the disclosure of which is incorporated herein by reference.

[0169] 1 Susceptor

[0170] 2 Carbon substrate

[0171] 3 Thin film

[0172] 4 Counterbored portion

[0173] 5 CVD apparatus

[0174] 10 Chamber

[0175] 11 Gas inflow port

[0176] 12 Gas outflow port

[0177] 20 Support portion