Susceptor and method for manufacturing the same

Abstract

To provide a susceptor with reduced contamination, which can improve the uniformity of the film thickness of a silicon carbide film formed on a base material, and suppress variations in thermal conductivity, and is made of a carbon composite material in which the surface of the substrate made of a carbon material is covered with a thin film of silicon carbide (SiC), and a manufacturing method thereof.SOLUTION: In a susceptor 1 having a substrate 2 made of a carbon material and having one main surface on which a silicon wafer is placed and another main surface facing the one main surface, the entire surface of the substrate is covered with a thin film 3 made of silicon carbide, the variation in emissivity in the one main surface is within 3%, and the ratio of the average emissivity of the other main surface facing the one main surface is 1:1 to 1:0.8.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a susceptor and a method for manufacturing the same, and more particularly to a susceptor for holding a wafer in an epitaxial film forming apparatus and a method for manufacturing the same.

Background Art

[0002] In an epitaxial film forming apparatus, which is one of semiconductor manufacturing apparatuses, a carbon composite material in which a carbon material (referred to as a carbon base material) is covered with silicon carbide (SiC) is used as a susceptor, which is a member for holding a silicon wafer. The susceptor has a pancake type, a barrel type, a single wafer type, etc. depending on its shape, and a plurality of types are used depending on the apparatus and the processing method. When manufacturing the susceptor, regardless of the type, it is installed in a predetermined coating furnace in the state of the carbon base material, and silicon carbide (SiC) is deposited on the surface of the carbon base material by the CVD method or the like, whereby a susceptor made of a carbon composite material can be obtained.

[0003] By the way, when forming a thin film of silicon carbide (SiC) on the surface of the carbon base material by the CVD method, a silicon carbide film does not adhere to the contact portion between the jig for supporting the carbon base material and the carbon base material. In response to such a problem, Patent Document 1 describes that after the first film forming process, the carbon base material is taken out of the furnace once, the position where the carbon base material and the jig come into contact is changed, and the film forming process after the second time is performed. By doing so, a carbon composite material entirely covered with silicon carbide (SiC) can be obtained.

[0004] As described above, the multiple film-forming processes with the shifted contact positions are effective means for eliminating the contact traces of the jig. However, once the carbon composite material is taken out of the furnace, the carbon composite material is exposed to the outside air of the furnace. Therefore, there has been a problem that the surface of the silicon carbide film may be contaminated. If it is contaminated, a new silicon carbide film will be laminated on the contaminated layer. When this carbon composite material is used as a susceptor, it will cause contamination of the silicon wafer in the epitaxial process.

[0005] Therefore, in the invention described in Patent Document 1, after first forming a silicon carbide film, in order to eliminate the support traces, the carbon composite material is taken out once to change the support position, and purification treatment (spraying of halogen gas) is performed on the surface of the carbon composite material to reduce surface contamination, and then the silicon carbide film is formed again in the furnace.

Prior Art Document

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the method disclosed in Patent Document 1, since the carbon base material is taken out of the furnace once, the possibility of contamination is not eliminated. In addition, since it is necessary to perform multiple film-forming processes at intervals, there are problems that the man-hours and costs increase, which is not desirable.

[0008] Furthermore, the thickness of the silicon carbide film at the part where the jig holding the carbon base material contacts is thinner than other parts. In the case of film formation twice, it is about half. Therefore, in the epitaxial film formation process, there is a possibility that the carbon as the base material may be exposed due to the consumption of the silicon carbide film. In addition, the non-uniformity of the thickness of the silicon carbide film also causes variations in the film thickness during the epitaxial film formation process on the silicon wafer. When the film thickness of the silicon carbide varies significantly, there is a problem that it is difficult to obtain a uniform epitaxial film because of the different thermal conductivities.

[0009] Moreover, if the silicon carbide film covering the carbon substrate is non-uniform, the emissivity in the temperature range where the susceptor is used varies. When this emissivity varies significantly, temperature spots occur on the susceptor, resulting in variations in the wafer temperature and, consequently, variations in the film thickness of the epitaxial film.

[0010] The present invention has been made under the above circumstances, and in a susceptor made of a carbon composite material in which the surface of a substrate made of a carbon material is covered with a thin film of silicon carbide (SiC), the present invention aims to provide a susceptor with suppressed contamination and a method for manufacturing the same, which can increase the uniformity of the film thickness of the silicon carbide film formed on the substrate and suppress variations in thermal conductivity.

Means for Solving the Problems

[0011] The susceptor according to the present invention made to solve the above problems has a substrate made of a carbon material, and is a susceptor having one main surface on which a silicon wafer is placed and another main surface facing the one main surface, wherein the entire surface of the substrate is covered with a thin film made of silicon carbide, the variation in emissivity on the one main surface is within 3%, and the ratio of the average emissivity of the one main surface to the average emissivity of the other main surface facing the one main surface is 1:1 to 1:0.8. It is desirable that the variation in emissivity of the other main surface facing the one main surface is within 3%. In addition, the ratio of the film thickness of the thin film formed on the other main surface to the film thickness of the thin film formed on the one main surface is 0.7 or more and 1.2 or less. On the one main surface, the film thickness difference between the central portion and the outer edge portion is 40% or less of the average value of the film thickness of the thin film formed on the one main surface, and the film thickness difference between the maximum film thickness and the minimum film thickness of the outer edge portion of the one main surface is 40% or less of the average value of the film thickness of the thin film formed on the one main surface, which is desirable. In addition, it is desirable that the film thickness of the silicon carbide thin film formed on the entire surface of the base material is at least 60 μm.

[0012] According to such a configuration, the uniformity of the thin film formed on the surface of the base material is improved, and the uniformity of heat conduction on one main surface becomes good. As a result, in the epitaxial film formation process on a silicon wafer using the susceptor, a uniform epitaxial film can be obtained.

[0013] In addition, the method for manufacturing a susceptor according to the present invention made to solve the above problems is a method for manufacturing the susceptor, in which a base material made of a carbon material is supported in a chamber while moving the support position with respect to the base material, and the supply direction of the raw material gas is parallel to the one main surface of the base material, and a thin film made of silicon carbide is formed on the entire surface of the base material. According to such a method, the susceptor with suppressed contamination can be obtained.

Effects of the Invention

[0014] According to the present invention, in a susceptor made of a carbon composite material in which the surface of a base material made of a carbon material is covered with a thin film of silicon carbide (SiC), it is possible to provide a susceptor with suppressed contamination and a method for manufacturing the same, which can increase the uniformity of the film thickness of the silicon carbide film formed on the base material and suppress the variation in thermal conductivity.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the susceptor and its manufacturing method according to the present invention will be described with reference to FIGS. 1 to 4. The figures are schematic or conceptual, and the relationships between the thicknesses and widths of the respective parts, the ratios of the sizes between the parts, etc. are not accurately illustrated.

[0017] As shown in FIG. 1, the susceptor 1 has a disk-shaped carbon base material 2 made of a carbon material. The entire surface of this carbon base material 2 is coated with a thin film 3 having a predetermined thickness (for example, 60 μm or more) made of silicon carbide. That is, this thin film 3 is composed of a thin film 3F made of silicon carbide that coats one main surface F1, which is the wafer placement surface of the susceptor 1, a thin film 3B made of silicon carbide that coats the other main surface F2, which is the back surface opposite to the one main surface F1, and a thin film 3S made of silicon carbide that coats the outer peripheral surface of the carbon base material 2.

[0018] Further, this susceptor 1 is a so-called single-wafer type susceptor in which a single concave-shaped counterbore portion 4 for placing a semiconductor substrate is formed on one main surface F1 thereof. The counterbore portion 4 is formed in a circular shape in a plan view, and a cylindrical concave portion 4a is formed at the center. Further, this susceptor 1 has rotational symmetry with a rotation axis L passing through its center O. At this time, if the depth of the deepest part (center O) of the counterbore portion 4 is To, the average depth Td is To / 2.

[0019] Moreover, it is preferable that the ratio (T / Td) of the thickness T of the susceptor 1 to the average depth Td is 6 ≤ T / Td ≤ 30. It is preferable that the ratio (T / To) of the thickness T of the susceptor 1 to the depth To is 3 ≤ T / To ≤ 13. In this way, since the countersink portion 4 is formed such that the ratio (T / Td) of the thickness T of the susceptor 1 to the average depth Td is 6 ≤ T / Td ≤ 30, the effect of suppressing warping can be obtained.

[0020] Here, when the ratio (T / Td) of the thickness T of the susceptor 1 to the average depth Td is less than 6, the countersink may be too deep with respect to the thickness of the susceptor 1, which may cause poor film formation on the outer periphery of the wafer, which is not preferable. Further, when the ratio (T / Td) of the thickness T of the susceptor 1 to the average depth Td exceeds 30, the susceptor becomes thick, and the influence of the rigidity of the carbon base material 2 cannot be ignored, making it difficult to control the warping amount of the thin film, which is not preferable.

[0021] As described above, as the carbon base material 2, a carbon material applicable as a semiconductor susceptor is used, and as the thin film 3, silicon carbide is used. The thin film 3 is formed on the entire surface of the carbon base material 2, and has the role of preventing dust generation and outward diffusion of impurities from the carbon base material 2, protecting the entire surface of the carbon base material 2, and suppressing warping of the carbon base material 2.

[0022] Here, it is preferable that the ratio of the average of the film thickness t2 of the thin film 3B formed on the other main surface F2 to the average of the film thickness t1 of the thin film 3F formed on the main surface F1 of the susceptor 1 shown in FIG. 2 is formed between 0.7 and 1.2. If the ratio is less than 0.7, in the epitaxial film formation process using the susceptor, a difference in thermal conductivity may occur, making it difficult to obtain a uniform epitaxial film, which is not preferable. Moreover, if the ratio is greater than 1.2, in addition to the difference in thermal conductivity caused by the film thickness variation of the thin film 3, warping of the susceptor is likely to occur, resulting in a non-uniform epitaxial film, which is not preferable.

[0023] Further, on the main surface F1 of the susceptor 1, it is preferable that the film thickness difference d1 between the central portion O and the outer edge portion F1a is 40% or less of the average of the film thickness t1 of the thin film 3F formed on the main surface F1. Also, on the main surface F1 of the susceptor 1, it is preferable that the film thickness difference d2 between the maximum film thickness and the minimum film thickness of the outer edge portion F1a is 40% or less of the average of the film thickness t1 of the thin film 3F formed on the main surface F1. If the film thickness difference d1 or d2 is 40% or less of the average of the film thickness t1, the uniformity of heat conduction on the main surface F1 becomes good, and in the epitaxial film formation process using the susceptor, a uniform epitaxial film can be obtained. On the other hand, when the film thickness difference is greater than 40% of the average of the film thickness t1, spots are likely to occur, the heat conduction on the main surface F1 becomes non-uniform, and it may become impossible to obtain a uniform epitaxial film.

[0024] Further, the susceptor 1 is formed such that the variation in emissivity on the wafer placement surface (main surface F1) is within 3% in the temperature range (900 to 1300 °C) in the epitaxial film formation process, and the ratio of the average emissivity of the wafer placement surface to that of its back surface (the other main surface F2) is 1:1 to 1:0.8. Also, it is desirable to form the back surface (the other main surface F2) of the wafer placement surface such that the variation in emissivity within the same plane is within 3%. By setting the emissivity of the susceptor 1 in this way, the variation in the thermal conductivity of the susceptor is suppressed and temperature spots do not occur, so that the temperature of the wafer to be placed can be made uniform and the variation in the film thickness of the epitaxial film can be prevented.

[0025] The above-described susceptor 1 can be manufactured, for example, by using a CVD apparatus 5 as shown in FIG. 3. The CVD apparatus 5 shown in Fig. 3 includes a chamber 10 that forms a processing space, a gas inlet 11 provided on the side surface of the chamber 10 for supplying a carrier gas (hydrogen gas) into the chamber 10, and a gas outlet 12 provided on the opposite side surface of the chamber 10 facing the inlet 11.

[0026] Further, it includes a support portion 20 for supporting the lower surface side of the carbon base material 2 of the susceptor 1 in the chamber 10, and a plurality of columnar guard members 13 arranged around the carbon base material 2 and capable of slidably supporting the side peripheral surface (outer periphery) of the carbon base material 2. The support portion 20 has a plurality of support legs 20a to 20d on which rollers 22 rotatably provided at a constant speed by a motor 21 are arranged along the circumferential direction of the carbon base material 2. The rollers 22 of each support leg 20a to 20d are in contact with the peripheral edge portion of the back side surface of the carbon base material 2, and the carbon base material 2 is configured to rotate about the central portion O while being supported as the rollers 22 rotate in one direction. Incidentally, the rotation operations (rotation start, stop, rotation direction, rotation speed) of the rollers 22 of each support leg 20a to 20d are controlled by a control portion (not shown) so as to be synchronized. Also, as shown in Fig. 3, heater portions 15 are provided above and below the chamber 10, and the inside of the furnace is configured to be heated to a predetermined temperature.

[0027] When manufacturing the susceptor 1 using this CVD apparatus 5, a carbon base material 2 made of a carbon material in which a circular counterbore portion is formed in advance is placed on the support legs 20a to 20d in the chamber 10. Next, the control portion (not shown) starts the rotation of the rollers 22 of the support legs 20a to 20d at a predetermined rotation speed. Thereby, the carbon base material 2 rotates about the central portion O at a predetermined speed (for example, 0.1 rpm).

[0028] Also, the heater portion 15 is driven to heat the inside of the chamber 10 to, for example, 500 °C, and the inside of the chamber 10 is sucked from the gas outlet 12 to be in a vacuum state. Next, carrier gas (H2) is introduced into chamber 10 from gas inlet 11 at a predetermined flow rate. Thereafter, the temperature inside chamber 10 is raised to, for example, 1300 °C, and raw material gases (SiCl4, C3H8) are introduced together with the carrier gas for a predetermined time. The concentration of the raw material gas inside chamber 10 at the start of introduction is, for example, 15% - 20%.

[0029] Here, the raw material gas flows along the upper and lower surfaces of carbon base material 2 by the carrier gas and is discharged from gas outlet 12. Also, since carbon base material 2 rotates about center O by a plurality of rotatably driven rollers 22 provided to support the peripheral portion on the lower surface side, the support positions at the peripheral portion on the lower surface side of carbon base material 2 do not become the same location (not fixed and change), and the uniformity of the film thickness of the formed film is improved.

[0030] The raw material gas is supplied into chamber 10 for a predetermined time (for example, 14 hours) so that the formed film reaches a predetermined thickness (for example, 60 μm or more). Then, at the final stage of the supply process of this raw material gas (for example, the stage 5 - 60 minutes before the end), the concentration of the raw material gas is gradually diluted to 1 / 2 - 1 / 4 of the normal concentration. As a result, the raw material gas becomes a thinner raw material gas than normal, the film formation rate is lower than normal, and the film is formed in a state where the sizes of the crystal grains are uniform. As a result, the film formation amount in the plane tends to be uniform, and the emissivity in the same plane can be made closer to being constant. Specifically, the variation in the emissivity on the wafer placement surface (and its back surface) is within 3%, and the ratio of the average emissivity of the wafer placement surface to that of its back surface is adjusted to 1:1 - 1:0.8. When the preset supply time of the raw material gas has elapsed, the supply of the raw material gas is stopped, and after a further predetermined time has elapsed (for example, 1 hour later), the rotation of rollers 22 is stopped.

[0031] Through these processes, a thin film 3 made of silicon carbide is formed on the carbon base material 2, and the susceptor 1 of the present invention is manufactured. Since the position where the carbon base material 2 is supported in the chamber 10 constantly changes while the carbon base material 2 is exposed to the source gas, the thin film 3 is formed with high film thickness uniformity. That is, in the obtained susceptor 1, the ratio of the average of the film thickness t2 of the thin film 3B formed on the other main surface F2 to the average of the film thickness t1 of the thin film 3F formed on the main surface F1 is formed between 0.7 and 1.2. Further, on the main surface F1 of the susceptor 1, the film thickness difference d1 between the central portion O and the outer edge portion F1a, and the film thickness difference d2 between the maximum film thickness and the minimum film thickness of the outer edge portion F1a are formed to be 40% or less of the average of the film thickness t1 of the thin film 3F formed on the main surface F1.

[0032] As described above, according to the embodiment of the present invention, in the susceptor 1, since the thin film 3 formed on the carbon base material 2 is formed with high film thickness uniformity, the variation in emissivity on the wafer placement surface is within 3%, and the ratio of the average emissivity of the wafer placement surface to the average emissivity of the back surface thereof is set to 1:1 to 1:0.8. Also, the ratio of the average of the film thickness t2 of the thin film 3B formed on the other main surface F2 to the average of the film thickness t1 of the thin film 3F formed on the main surface F1 of the susceptor 1 is formed between 0.7 and 1.2, and on the main surface F1 of the susceptor 1, the film thickness difference d1 between the central portion O and the outer edge portion F1a or the film thickness difference d2 between the maximum film thickness and the minimum film thickness of the outer edge portion F1a is formed to be 40% or less of the average of the film thickness t1 of the thin film 3F formed on the main surface F1. Thereby, the uniformity of the thin film 3 formed on the surface of the carbon base material 2 is improved, no temperature spot occurs in the susceptor 1, and the uniformity of heat conduction on the main surface F1 becomes good. As a result, in the epitaxial film formation process on the silicon wafer using the susceptor, a uniform epitaxial film can be obtained. In addition, when forming a thin film made of silicon carbide on a carbon substrate 2 made of a carbon material by CVD, by not fixing the support position with respect to the carbon substrate 2, a uniform thin film can be formed over the entire carbon substrate 2. Further, thereby, it is not necessary to take out the carbon substrate 2 from the chamber during the formation of the thin film as in the conventional case, and a single-layer thin film with suppressed contamination can be formed.

[0033] In addition, in the above embodiment, as a method for suppressing the variation in emissivity within the same plane of the wafer mounting surface (and the back surface), the source gas was diluted at the final stage of the source gas supply process, but it is not limited to this example. In addition, in the above embodiment, the susceptor having the countersunk portion was described as an example, but in the present invention, it is not limited to this form and can also be applied to a susceptor having no countersunk portion. In addition, when having a countersunk portion, the present invention can be applied not only to a cylindrical countersunk portion as shown in the figure, but also to a susceptor having a countersunk portion curved in a concave shape, for example.

Example

[0034] The susceptor and its manufacturing method according to the present invention will be further described based on examples. [Experiment 1] In Experiment 1, isotropic graphite was used as the material of the substrate of the susceptor, and a plurality of carbon substrates having countersunk portions were prepared. Using the CVD apparatus shown in Fig. 3, a silicon carbide film was formed on the substrate surface under a plurality of film thickness forming conditions. In the CVD apparatus, a carbon substrate was placed in the chamber. After evacuation, the temperature in the chamber was raised to 500 °C, and a carrier gas (H2) was introduced into the chamber. Next, the temperature in the chamber was raised to 1300 °C, and the substrate was rotated at a rotation speed of 0.1 rpm without fixing the support position of the carbon substrate, and source gases (SiCl4, C3H8) were supplied along the front and back surfaces of the carbon substrate. After a lapse of a predetermined time (14 hours), the supply of the source gas was stopped, and after 1 hour, the rotation of the carbon substrate was stopped to form a 70-μm-thick silicon carbide thin film on the substrate surface.

[0035] Here, during the supply process (14 hours) of the raw material gas, the concentration of the raw material gas was diluted and thinned in the final stage (0.2 hours before the end) to suppress the variation in the emissivity of the wafer placement surface of the formed susceptor and the back surface thereof. In addition, the variation in emissivity was set as a condition for Examples 1 to 4 and Comparative Examples 1 to 3, and the variation in emissivity was adjusted according to the raw material gas concentration. In addition, the emissivity of the wafer placement surface and the back surface thereof was measured at four points in total at three locations at 120° intervals on a concentric circle located at the center of the wafer placement surface of the carbon base material and at a position 50% of the radius of the placement surface from the center to the outer peripheral side, by using a Thermo Fisher FTIR (Fourier transform infrared spectroscopy) and an integrating sphere. The average emissivity was the average value of the above four points, and the emissivity variation was calculated by (maximum value - minimum value) ÷ average value at the above four points. Regarding the back surface of the wafer placement surface, the measurement and calculation were also performed at the same measurement positions as those of the wafer placement surface.

[0036] In Example 1, the emissivity variation of the wafer placement surface of the carbon base material was 1%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:1. In Example 2, the emissivity variation of the wafer placement surface of the carbon base material was 2%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.9. In Example 3, the emissivity variation of the wafer placement surface of the carbon base material was 3%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 4, the emissivity variation of the wafer placement surface of the carbon base material was 1%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 5, the emissivity variation of the wafer placement surface of the carbon base material was 2%, the emissivity variation of the back surface of the wafer placement surface was 4%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8.

[0037] In Comparative Example 1, the emissivity variation of the wafer placement surface of the carbon substrate was 4%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.9. In Comparative Example 2, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.7.

[0038] Using the susceptors manufactured in Examples 1 to 5 and Comparative Examples 1 and 2, an epitaxial film was formed on the silicon wafer. The results of Experiment 1 are shown in Table 1. The evaluation of each condition shown in Table 1 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. For the in-plane distribution of the film thickness of the epitaxial film, those with ±5% or less were rated as ○, those exceeding ±5% to 7% were rated as △, and those exceeding ±7% were rated as ×.

[0039]

Table 1

[0040] From the results of Experiment 1 above, when a thin film of silicon carbide with a thickness of 70 μm was formed on the substrate surface, the emissivity variation of the wafer placement surface (front surface) was within 3%, and by setting the ratio of the average emissivity between the wafer placement surface and its back surface to 1:1 to 1:0.8, it was confirmed that the uniformity of the epitaxial film formed on the silicon wafer was good.

[0041] [Experiment 2] In Experiment 2, the thickness of the silicon carbide thin film on the substrate surface was changed to 30 μm, and the evaluation was performed under the same conditions as in Experiment 1.

[0042] In Example 6, the emissivity variation of the wafer placement surface of the carbon substrate was 1%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:1. In Example 7, the emissivity variation of the wafer placement surface of the carbon substrate was 2%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.9. In Example 8, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 9, the emissivity variation of the wafer placement surface of the carbon substrate was 1%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 10, the emissivity variation of the wafer placement surface of the carbon substrate was 2%, the emissivity variation of the back surface of the wafer placement surface was 4%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8.

[0043] In Comparative Example 3, the emissivity variation of the wafer placement surface of the carbon substrate was 4%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.9. In Comparative Example 4, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.7.

[0044] Using the susceptors manufactured in Examples 6 to 10 and Comparative Examples 3 and 4, an epitaxial film was formed on the silicon wafer. The results of Experiment 2 are shown in Table 2. The evaluation of each condition shown in Table 2 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. For the in-plane distribution of the film thickness of the epitaxial film, ○ was used when it was ±5% or less, △ was used when it exceeded ±5% to 7%, and × was used when it exceeded ±7%.

[0045]

Table 2

[0046] According to the results of Experiment 2 shown in Table 2, when a silicon carbide thin film with a thickness of 30 μm was formed on the substrate surface, the variation in the emissivity of the wafer placement surface (surface) was within 3%, and the ratio of the average emissivity between the wafer placement surface and its back surface was 1:1 to 1:0.8, thereby confirming that the uniformity of the epitaxial film formed on the silicon wafer was good.

[0047] [Experiment 3] In Experiment 3, the thickness of the silicon carbide thin film on the substrate surface was changed to 60 μm, and evaluations were carried out under the same conditions as in Experiment 1.

[0048] In Example 11, the variation in the emissivity of the wafer placement surface of the carbon substrate was 1%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:1. In Example 12, the variation in the emissivity of the wafer placement surface of the carbon substrate was 2%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.9. In Example 13, the variation in the emissivity of the wafer placement surface of the carbon substrate was 3%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8. In Example 14, the variation in the emissivity of the wafer placement surface of the carbon substrate was 1%, the variation in the emissivity of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8. In Example 15, the variation in the emissivity of the wafer placement surface of the carbon substrate was 2%, the variation in the emissivity of the back surface of the wafer placement surface was 4%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8.

[0049] In Comparative Example 5, the variation in the emissivity of the wafer placement surface of the carbon substrate was 4%, the variation in the emissivity of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.9. In Comparative Example 6, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.7.

[0050] Using the susceptors manufactured in Examples 11 to 15 and Comparative Examples 5 and 6, an epitaxial film was formed on the silicon wafer. The results of Experiment 3 are shown in Table 3. The evaluation of each condition shown in Table 3 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. For the in-plane distribution of the film thickness of the epitaxial film, those with ±5% or less were rated as ○, those exceeding ±5% to 7% were rated as △, and those exceeding ±7% were rated as ×.

[0051] [Table 3]

[0052] From the results of Experiment 3 shown in Table 3, when a thin film of silicon carbide with a thickness of 60 μm was formed on the substrate surface, the emissivity variation of the wafer placement surface (front surface) was within 3%, and by setting the ratio of the average emissivity between the wafer placement surface and its back surface to 1:1 to 1:0.8, it was confirmed that the uniformity of the epitaxial film formed on the silicon wafer was good.

[0053] [Experiment 4] In Experiment 4, the thickness of the silicon carbide thin film on the substrate surface was changed to 140 μm, and the evaluation was performed under the same conditions as in Experiment 1.

[0054] In Example 16, the emissivity variation of the wafer placement surface of the carbon substrate was 1%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:1. In Example 17, the emissivity variation of the wafer placement surface of the carbon substrate was 2%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.9. In Example 18, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8. In Example 19, the emissivity variation of the wafer placement surface of the carbon substrate was 1%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8. In Example 20, the emissivity variation of the wafer placement surface of the carbon substrate was 2%, the emissivity variation of the back surface of the wafer placement surface was 4%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.8.

[0055] In Comparative Example 7, the emissivity variation of the wafer placement surface of the carbon substrate was 4%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.9. In Comparative Example 8, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.7.

[0056] Using the susceptors manufactured in Examples 16 to 20 and Comparative Examples 7 and 8, an epitaxial film was formed on the silicon wafer. The results of Experiment 4 are shown in Table 4. The evaluation of each condition shown in Table 4 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. For the in-plane distribution of the film thickness of the epitaxial film, those with ±5% or less were rated as ○, those exceeding ±5% to 7% were rated as △, and those exceeding ±7% were rated as ×.

[0057]

Table 4

[0058] According to the results of Experiment 4 shown in Table 4, when a silicon carbide thin film with a thickness of 140 μm was formed on the substrate surface, the variation in the emissivity of the wafer placement surface (front surface) was within 3%, and by setting the ratio of the average emissivity of the wafer placement surface to its back surface to be 1:1 to 1:0.8, it was confirmed that the uniformity of the epitaxial film formed on the silicon wafer was good.

[0059] [Experiment 5] In Experiment 5, the thickness of the silicon carbide thin film on the substrate surface was changed to 200 μm, and the evaluation was carried out under the same conditions as in Experiment 1.

[0060] In Example 21, the variation in the emissivity of the wafer placement surface of the carbon substrate was 1%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:1. In Example 22, the variation in the emissivity of the wafer placement surface of the carbon substrate was 2%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.9. In Example 23, the variation in the emissivity of the wafer placement surface of the carbon substrate was 3%, the variation in the emissivity of the back surface of the wafer placement surface was 1%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 24, the variation in the emissivity of the wafer placement surface of the carbon substrate was 1%, the variation in the emissivity of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8. In Example 25, the variation in the emissivity of the wafer placement surface of the carbon substrate was 2%, the variation in the emissivity of the back surface of the wafer placement surface was 4%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.8.

[0061] In Comparative Example 9, the variation in the emissivity of the wafer placement surface of the carbon substrate was 4%, the variation in the emissivity of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity of the wafer placement surface to the back surface was 1:0.9. In Comparative Example 10, the emissivity variation of the wafer placement surface of the carbon substrate was 3%, the emissivity variation of the back surface of the wafer placement surface was 3%, and the ratio of the average emissivity between the wafer placement surface and the back surface was 1:0.7.

[0062] Using the susceptors manufactured in Examples 21 to 25 and Comparative Examples 9 and 10, an epitaxial film formation process was performed on the silicon wafer. The results of Experiment 5 are shown in Table 5. The evaluation of each condition shown in Table 5 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. For the in-plane distribution of the film thickness of the epitaxial film, those with ±5% or less were rated as ○, those exceeding ±5% to 7% were rated as △, and those exceeding ±7% were rated as ×.

[0063]

Table 5

[0064] From the results of Experiment 5 shown in Table 5, when a thin film of silicon carbide with a thickness of 200 μm was formed on the substrate surface, the emissivity variation of the wafer placement surface (front surface) was within 3%, and by setting the ratio of the average emissivity between the wafer placement surface and its back surface to 1:1 to 1:0.8, it was confirmed that the uniformity of the epitaxial film formed on the silicon wafer was good.

[0065] From the results of the above Experiments 1 to 5, regardless of the conditions of the thickness of the silicon carbide thin film formed on the substrate surface, the emissivity variation of the wafer placement surface (front surface) was within 3%, and by setting the ratio of the average emissivity between the wafer placement surface and its back surface to 1:1 to 1:0.8, it was confirmed that the uniformity of the epitaxial film formed on the silicon wafer was good. Also, more preferably, it was confirmed that by setting the emissivity variation of the back surface of the susceptor to within 3% as well, the uniformity of the epitaxial film formed on the silicon wafer became even better.

[0066] [Experiment 6] In Experiment 6, the suitable film thickness of the silicon carbide film formed on the surface of the carbon substrate was examined. In Examples 26 to 30 and Comparative Examples 11 to 13, the film thickness was adjusted by the supply time of the source gas. Further, in this Experiment 6, in the final stage of the source gas supply process, the source gas was diluted so that the variation in the emissivity of the wafer placement surface and the back surface of the obtained susceptor was within 3% in both cases, and the ratio of the average emissivity of the wafer placement surface to its back surface was adjusted to be in the range of 1:1 to 1:0.8.

[0067] Then, using the obtained susceptor, the epitaxial film formation process and the cleaning process were repeated to verify whether a predetermined lifetime (continuous operation for 4000 hours) could be achieved. In Example 26, the film thickness of the silicon carbide film on the main surface (wafer placement surface) was 42 μm. Also, the film thickness was 55 μm in Example 27, 58 μm in Example 28, 61 μm in Example 29, and 66 μm in Example 30. Also, the film thickness was 70 μm in Example 31, 80 μm in Example 32, and 100 μm in Example 33. The evaluation of Experiment 6 is shown in Table 6.

[0068]

Table 6

[0069] As shown in Table 6, for the susceptor with a silicon carbide film thickness of less than 60 μm, the required lifetime could not be obtained. Therefore, it was confirmed that a silicon carbide film thickness of 60 μm or more is preferable.

[0070] [Experiment 7] In Experiment 7, isotropic graphite was used as the material of the susceptor substrate, and a carbon substrate with a drilled portion was prepared. Using the CVD apparatus shown in Figure 3, a silicon carbide film was formed on the substrate surface under a plurality of film thickness formation conditions. Next, using the susceptors formed under each condition, a process of forming an epitaxial film on a silicon wafer was performed.

[0071] In the production of the susceptor, when forming a silicon carbide film on the surface of the susceptor substrate using the CVD apparatus shown in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Further, in this Experiment 7, in the final stage of the raw material gas supply process, the raw material gas was diluted so that the variations in the emissivity of the wafer placement surface and the back surface of the obtained susceptor were both within 3%, and the ratio of the average emissivity of the wafer placement surface to that of its back surface was adjusted to be in the range of 1:1 to 1:0.8. After forming the susceptor, the ratio of the average film thickness of the silicon carbide film formed on the other main surface (wafer non-placement surface) to the average film thickness of the silicon carbide film formed on the main surface (wafer placement surface) was determined. The average value of the film thickness of the silicon carbide film formed on the main surface (wafer placement surface) and the average film thickness of the silicon carbide film formed on the other main surface (wafer non-placement surface) were measured by using an optical microscope to measure the cross section at the same position as the emissivity measurement location, and their averages were calculated.

[0072] As shown in Table 7, the ratio was 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. Also, in Example 40, the ratio was 1.1, in Example 41 it was 1.2, in Example 42 it was 1.3, and in Example 43 it was 1.4.

[0073] In Examples 34 to 43, on the main surface (wafer placement surface) of the susceptor, the ratio (%) of the film thickness difference between the center and the outer edge portion to the average film thickness of the thin film formed on the main surface was set to 30% in each case. Further, on the main surface (wafer placement surface) of the susceptor, the ratio (%) of the film thickness difference between the maximum film thickness and the minimum film thickness at the outer edge portion to the average film thickness of the thin film formed on the main surface was also set to 30% in each case. The results of Experiment 7 are shown in Table 7. The evaluation of each condition shown in Table 7 was performed based on the uniformity of the epitaxial film formed on the silicon wafer. When the in-plane distribution of the film thickness of the epitaxial film was ±5% or less, it was rated as ○; when it exceeded ±5% to 7%, it was rated as △; and when it exceeded ±7%, it was rated as ×.

[0074]

Table 7

[0075] From the results of Experiment 7, it was confirmed that the epitaxial film thickness uniformity was good if the ratio of the average film thickness of the silicon carbide film formed on the other main surface (wafer non-placement surface) to the average film thickness of the silicon carbide film formed on the main surface (wafer placement surface) of the susceptor was in the range of 0.7 to 1.2.

[0076] [Experiment 8] In Experiment 8, similar to Experiment 7, a silicon carbide film was formed on the surface of the substrate under a plurality of film thickness formation conditions using the CVD apparatus shown in FIG. 3. Next, using the susceptor formed under each condition, an epitaxial film was formed on the silicon wafer.

[0077] In the manufacture of the susceptor, when forming a silicon carbide film on the surface of the susceptor substrate using the CVD apparatus shown in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Then, in the final stage of the raw material gas supply process, the raw material gas was diluted so that the variation in the emissivity of both the wafer placement surface and the back surface of the obtained susceptor was within 3%, and the ratio of the average emissivity of the wafer placement surface to its back surface was adjusted to be in the range of 1:1 to 1:0.8. After the thin film formation was completed, the ratio (%) of the film thickness difference between the center and the outer edge portion to the average film thickness of the thin film formed on the main surface was determined on the main surface (wafer placement surface) of the susceptor taken out from the CVD apparatus.

[0078] The ratio was 0% in Example 44, 10% in Example 45, 20% in Example 46, 30% in Example 47, 40% in Example 48. Also, the ratio was 50% in Example 49 and 60% in Example 50.

[0079] In Examples 44 to 50, the ratio of the average film thickness of the thin film formed on the other main surface (wafer non-placement surface) to the average film thickness of the silicon carbide film formed on the main surface (wafer placement surface) of the susceptor was set to 1.0 in all cases. Further, on the main surface (wafer placement surface) of the susceptor, the ratio (%) of the film thickness difference between the maximum film thickness and the minimum film thickness at the outer edge portion to the average film thickness of the thin film formed on the main surface was set to 30% in all cases. The results of Experiment 8 are shown in Table 8. The evaluation of each condition shown in Table 8 was performed based on the uniformity of the epitaxial film formed on the silicon wafer in the same manner as in Experiment 7. For the in-plane distribution of the film thickness of the epitaxial film, ○ was used when it was ±5% or less, △ was used when it exceeded ±5% to 7%, and × was used when it exceeded ±7%.

[0080] [Table 8]

[0081] From the results of Experiment 8, it was confirmed that on the main surface (wafer placement surface) of the susceptor, when the film thickness difference between the center and the outer edge portion was in the range of 0% to 40% of the average film thickness of the thin film formed on the main surface, the film thickness uniformity of the epitaxial film was improved.

[0082] [Experiment 9] In Experiment 9, using the CVD apparatus shown in FIG. 3 in the same manner as in Experiment 7, a silicon carbide film was formed on the surface of the substrate under a plurality of film thickness formation conditions. Next, using the susceptor formed under each condition, a process of forming an epitaxial film on a silicon wafer was performed.

[0083] In the manufacture of the susceptor, when forming a silicon carbide film on the surface of the susceptor substrate using the CVD apparatus shown in FIG. 3, the film thickness was adjusted by increasing or decreasing the processing time. Then, at the final stage of the raw material gas supply process, the raw material gas was diluted so that the variation in the emissivity of the wafer placement surface and the back surface of the obtained susceptor was within 3% in both cases, and the ratio of the average emissivity of the wafer placement surface to its back surface was adjusted to be in the range of 1:1 to 1:0.8. After the film formation was completed, the ratio (%) of the film thickness difference between the maximum film thickness and the minimum film thickness at the outer edge portion to the average film thickness of the thin film formed on the main surface (wafer mounting surface) of the susceptor taken out from the CVD apparatus was determined.

[0084] The ratio was 0% in Example 51, 10% in Example 52, 20% in Example 53, 30% in Example 54, and 40% in Example 55. Also, the ratio was 50% in Example 56 and 60% in Example 57.

[0085] In Examples 51 to 57, the ratio of the average film thickness of the silicon carbide film formed on the other main surface (wafer non-mounting surface) to the average film thickness of the silicon carbide film formed on the main surface (wafer mounting surface) of the susceptor was set to 1.0 in all cases. Further, regarding the ratio (%) of the film thickness difference between the center and the outer edge portion to the average film thickness of the thin film formed on the main surface of the susceptor, it was set to 30% in all cases. The results of Experiment 9 are shown in Table 9. The evaluation of each condition shown in Table 9 was performed based on the uniformity of the epitaxial film formed on the silicon wafer in the same manner as in Experiments 7 and 8. For the in-plane distribution of the film thickness of the epitaxial film, those with ±5% or less were rated as ○, those exceeding ±5% to 7% were rated as △, and those exceeding ±7% were rated as ×.

[0086]

Table 9

[0087] From the results of Experiment 9, it was confirmed that when the film thickness difference between the maximum film thickness and the minimum film thickness at the outer edge portion on the main surface (wafer mounting surface) of the susceptor was in the range of 0% to 40% of the average film thickness of the thin film formed on the main surface, the film thickness uniformity of the epitaxial film was improved.

Explanation of Reference Numerals

[0088] 1 Susceptor 2 Carbon Substrate 3 Thin Film 4 Counterbore Portion 5 CVD Apparatus 10 Chambers 11 Gas Inlet 12 Gas Outlet 20 Support Leg

Claims

1. A susceptor having a base material made of a carbon material and having one main surface on which a silicon wafer is placed and another main surface facing the one main surface, wherein the entire surface of the base material is coated with a thin film made of silicon carbide, the variation in emissivity on the one main surface is within 3%, and the ratio of the average emissivity of the other main surface facing the one main surface is 1:1 to 1:0.

8. A susceptor characterized by this.

2. The susceptor according to claim 1, characterized in that the variation in emissivity of the other main surface facing the one main surface is within 3%.

3. The ratio of the film thickness of the thin film formed on the other main surface to the film thickness of the thin film formed on the one main surface is 0.7 or more and 1.2 or less. On the one main surface, the film thickness difference between the central portion and the outer edge portion is 40% or less of the average value of the film thickness of the thin film formed on the one main surface, and the film thickness difference between the maximum film thickness and the minimum film thickness of the outer edge portion of the one main surface is 40% or less of the average value of the film thickness of the thin film formed on the one main surface. The susceptor according to claim 1, characterized by this.

4. The susceptor according to claim 1, characterized in that the film thickness of the thin film made of silicon carbide formed on the entire surface of the base material is at least 60 μm.

5. A method for manufacturing the susceptor according to any one of claims 1 to 4, supporting a base material made of a carbon material in a chamber while moving the support position with respect to the base material, supplying a raw material gas in a direction parallel to the supply direction of the raw material gas with respect to the one main surface of the base material, and forming a thin film made of silicon carbide on the entire surface of the base material. A method for manufacturing a susceptor characterized by this.

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