JP4591824B2 - Susceptor - Google Patents

Description

  The present invention relates to a susceptor, and more particularly to an improvement of a susceptor having a plurality of through holes penetrating in the thickness direction in order to reduce an autodoping phenomenon from the back surface of a semiconductor wafer.

In recent years, epitaxial wafers having different dopant concentrations on the front side and the back side have been developed as silicon substrates for MOS devices. This is an epitaxial film in which a dopant having a concentration lower than the dopant concentration of this wafer is formed on the surface of a low resistivity silicon wafer to which a dopant is added at a high concentration. Epitaxial wafers have excellent characteristics such as reduction in parasitic capacitance, prevention of soft errors (malfunction of memory), and high gettering capability as well as an increase in the yield of gate oxide films of MOS devices.
As an apparatus for forming an epitaxial film, for example, a single wafer epitaxial growth apparatus is known. It has a compact reaction chamber and employs a radiant heating system with a halogen lamp. In the case of a single wafer type, it is easy to design soaking conditions and gas flow distribution, and it is possible to improve the uniformity of the epitaxial film. Therefore, the apparatus is suitable for processing a large-diameter silicon wafer.

In recent years, as a quality requirement for an epitaxial wafer, there has been a strong demand for uniform distribution of specific resistance in the plane of the epitaxial film. However, during epitaxial growth, since the epitaxial growth process is performed at a high temperature, the dopant in the wafer diffuses outward from the back surface of the wafer during the epitaxial growth process, and the diffused dopant wraps around the wafer surface and enters the epitaxial film. The phenomenon that is taken in occurs. A so-called auto-doping phenomenon has occurred. For this reason, variation in dopant concentration occurs in the formed epitaxial film surface. In particular, the resistivity at the outer peripheral edge portion of the epitaxial film, which is likely to be affected by auto-doping, is reduced, causing a problem that the resistivity distribution in the plane of the epitaxial film is not uniform.
In particular, when epitaxial growth is performed at a concentration lower than the dopant concentration of the silicon wafer, a phenomenon in which the dopant concentration in the epitaxial film increases at the outer periphery of the wafer is observed. As a result, there is a region where the dopant concentration of the epitaxial film is out of specifications, which may cause a reduction in wafer production yield and characteristics.

As a conventional technique for solving this problem, for example, a susceptor disclosed in Patent Document 1 is known. That is, the through hole is formed on the front side of the susceptor, and the through hole is formed in the outer peripheral region in the susceptor counterbore, the outermost peripheral portion of the bottom wall of the pocket on which the silicon wafer is placed. A method of performing epitaxial growth processing using this is known.
However, in the portion of the wafer facing the through-hole, a minute change (bump) of the epitaxial film occurs. Thereby, the uniformity of the film thickness distribution of the epitaxial film is lowered, and the flatness characteristic of the surface of the epitaxial film is deteriorated. Conventionally, such minute fluctuations have not been regarded as a problem, but with the miniaturization of devices, such slight fluctuations have affected the production yield of wafers and the device yield. This phenomenon is presumed to be due to the fact that the portion of the silicon wafer facing the through hole is locally heated due to thermal conduction, and the growth rate of the epitaxial film is increased compared to other portions.

Therefore, as a conventional technique for solving this problem, for example, a susceptor of Patent Document 2 that employs a method of reducing the diameter of a through hole is known. When the through hole is made smaller (inner diameter is preferably 2 mm or less), the area of the portion of the wafer that is directly heated from the lower side of the reaction chamber through the through hole is reduced. Due to the effect, the in-plane of the epitaxial film is heated more uniformly, so that the partial variation in the epitaxial film plane of the epitaxial film growth rate is suppressed. As a result, the uniformity of the film thickness distribution of the epitaxial film is improved, and the nanotopology of the epitaxial film surface is improved (graph of FIG. 8). Nanotopology is the surface roughness (absolute value of change amount) at the nm level.
Japanese Patent Laid-Open No. 10-223545 JP 2003-229370 A

As described above, it has been found that by reducing the diameter of the through hole, the uniformity of the film thickness distribution of the wafer portion facing the through hole is increased, and the nanotopology of the front and back surfaces of the wafer is improved. However, in reducing the diameter of the through hole in Patent Document 2, there is a problem that the SiC film is not formed in the hole in the case of the small diameter hole. That is, there is a concern about the problem of contamination of the wafer. Therefore, in Patent Document 2, improvement of nanotopology on the epitaxial wafer surface beyond the level realized by the through-hole having a diameter of 0.7 mm cannot be expected.
Further, Patent Document 1 and Patent Document 2 disclose improvement of nanotopology on the surface of the epitaxial wafer, but do not describe any improvement method for nanotopology of the back surface of the epitaxial wafer. Today, wafers used for highly integrated devices have been required to have nano-level quality control not only on the surface side corresponding to the device active region but also on the surface roughness on the back side. However, there has been no strict requirement so far, and Patent Literature 1 and Patent Literature 2 cannot cope with it.

  Although the reduction in the diameter of the through hole is effective in improving the nano-level of the wafer surface (reducing the surface roughness) in this way, it increases the concentration of impurities in the relative region of the epitaxial wafer facing the through hole. . As a result, the electrical characteristics (e.g., lifetime) of the epitaxial wafer have been reduced. The concentration of impurities increases in this way because the through-holes are made finer, so that cleaning of the hole part using a wipe material or the like performed after the formation of the through-holes to the susceptor and subsequent chlorine-based purification treatment are performed. This is because the impurities remaining in the through-holes cannot be sufficiently removed even when the high-purity treatment (about 2000 ° C.) in the gas is performed.

  Therefore, as a result of earnest research, the inventor has improved the nanotopology of the surface of the epitaxial wafer and improved the epitaxial wafer if the opening portion of the through hole of the susceptor has a diameter-enlarged structure (structure in which the area of the opening is enlarged). Thus, the inventors have found that the backside nanotopology can be improved, and that the lifetime characteristics of the epitaxial wafer can be improved at the same time as the through-holes are reduced in diameter, and the present invention has been completed.

  The present invention provides a susceptor that can prevent the auto-doping phenomenon and can simultaneously improve the nanotopology of the front and back surfaces of the epitaxial wafer and the deterioration of the lifetime of the epitaxial wafer due to the reduction in the diameter of the through hole. The purpose is that.

The invention according to claim 1 is a susceptor that is housed in a reaction chamber, a semiconductor wafer is placed on the surface, and a plurality of through holes are formed through the thickness direction. An enlarged opening having a larger opening area than that of the other part of the corresponding through hole is provided at least on the surface side of the front side and the back side of the through hole in communication with the other part. The part and the enlarged opening have a circular cross-sectional shape perpendicular to the length direction over the entire length, and the diameter of the other part of the through hole is 0.7 to 1.5 mm. The diameter of the enlarged opening Is a susceptor that is 1.1 to 3 times the diameter of the corresponding other part .

According to the first aspect of the present invention, the susceptor is formed with a plurality of through holes penetrating in the thickness direction. Therefore, during the epitaxial growth, the dopant diffused outward from the back surface of the semiconductor wafer is discharged to the lower space of the reaction chamber through the through hole without going around to the wafer surface side. As a result, the dopant taken in the epitaxial film due to the auto-doping phenomenon can be suppressed.
Moreover, since the enlarged opening is provided at least on the front surface side and the back surface side of each through hole forming portion, the temperature of the portion of the semiconductor wafer that faces each through hole is suppressed. As a result, not only the nanotopology of the front surface of the epitaxial wafer but also the nanotopology of the back surface is improved.

  Furthermore, the presence of the enlarged opening in the through hole makes it relatively easy to clean the through hole after the through hole is formed in the susceptor manufacturing process even if the through hole is reduced in diameter. Moreover, in the subsequent high-purity processing step of the susceptor, the chlorine-based high-purity processing gas can be sufficiently introduced into the holes. Thereby, the impurities remaining in the small-diameter through hole can be removed satisfactorily. As a result, contamination due to impurities in the through hole in the back surface portion of the semiconductor wafer facing the through hole can be reduced during epitaxial growth. Therefore, it is possible to prevent the deterioration of the lifetime characteristics of the epitaxial wafer due to the diameter reduction of the through hole.

The clear reason why the high temperature of the portion facing each through hole of the semiconductor wafer is suppressed is unknown. Presumably, the opening area of at least the front end of each through hole is enlarged, so the amount of heat radiated from the heat source existing below the reaction chamber to the back surface of the semiconductor wafer through each through hole Is considered to have been reduced.
On the other hand, for the mechanism with improved lifetime, the opening area of the end of each through-hole is thus enlarged, so that when the susceptor is manufactured, a chlorine-based heat treatment gas for purifying the susceptor is passed through the through-hole. This is thought to be because the SiC film formation state was improved because the inner wall of the through hole was highly purified and at least one side was enlarged at the time of SiC film formation.

As the semiconductor wafer, a silicon wafer, a germanium wafer, a SiC wafer, or the like can be employed.
The material of the susceptor is not limited. For example, the surface of a carbon substrate coated with a SiC film is used. The susceptor has a disk shape.
The susceptor may be a simple flat plate shape or may be formed with a pocket for accommodating a semiconductor wafer.

The through hole may be formed in the entire area of the susceptor, or may be a part of the susceptor (for example, the outer peripheral portion).
The enlarged opening may be formed only on the front surface side of the through hole, or may be formed only on the back surface side of the through hole. Moreover, you may form in both the surface side and back surface side of a through-hole .

Further, the diameter of the other portions of the through holes and 0.7 to 1.5 mm, also the diameter of the enlarged opening, 1.1 (0.77 mm) to 3 times the diameter of the corresponding other part (4. 5 mm), the nanotopology of the front and back surfaces of the epitaxial wafer can be further improved.
The other part of the through hole and the enlarged opening may have a circular cross-sectional shape orthogonal to the length direction. For example, it may be a circle having a constant cross-sectional area over the entire length. Further, a part or all of the length direction may have a trumpet shape in which the diameter is gradually increased outward. Furthermore, an enlarged portion and / or a reduced diameter portion having an arbitrary size may exist in a part of the length direction.

If the diameter of the other part of the through hole is less than 0.7 mm, it is difficult to form and form sufficient SiC in the through hole of the susceptor according to the current SiC film forming technology. If the thickness exceeds 1.5 mm, the nanotopology of the front and back surfaces of the epitaxial wafer cannot be improved regardless of the presence or absence of the enlarged opening.
If the diameter of the enlarged opening is less than 1.1 times the diameter of the other part, the effect of the enlarged structure is small, and the nanotopology of the front and back surfaces of the epitaxial wafer is only slightly improved. Moreover, when it exceeds 3 times, the improvement effect of the nanotopology of the front and back of an epitaxial wafer will fall.
A more preferable magnification of the diameter of the enlarged opening with respect to the diameter of the other portion is 1.5 to 2.0 times. Within this range, a more favorable effect of the best combination of nanotopology and lifetime characteristics can be obtained.

  According to the susceptor according to claim 1, since the enlarged opening is present at least on the front surface side and the back surface side of each through hole forming portion, the high temperature of the portion facing each through hole of the semiconductor wafer Is suppressed. As a result, the auto-doping phenomenon can be prevented, and the nanotopology of the front and back surfaces of the epitaxial wafer can be improved. Furthermore, the deterioration of the lifetime characteristic of the epitaxial wafer accompanying the reduction in the diameter of the through hole can be improved at the same time.

In addition, the diameter of the other part of the through hole is 0.7 to 1.5 mm, and the diameter of the enlarged opening is 1.1 to 3 times the diameter of the corresponding other part. The effect of improving the topology is obtained.

  Hereinafter, a susceptor according to Embodiment 1 of the present invention will be described.

  In FIG. 1, 10 is an epitaxial growth apparatus incorporating a susceptor according to Embodiment 1 of the present invention, and this epitaxial growth apparatus 10 has a circular upper dome 3 having a concave surface and a circular lower dome 4 as well. Yes. The upper dome 3 and the lower dome 4 are made of a transparent material such as quartz. The upper dome 3 and the lower dome 4 are disposed so as to face each other in the vertical direction, and both ends thereof are respectively fixed to the upper and lower surfaces of the annular dome attachment body 5. Thereby, the substantially circular reaction chamber 2 is formed in a sealed plan view.

  A plurality of halogen lamps 6 for heating the inside of the reaction chamber 2 are provided above and below the reaction chamber 2 so as to be spaced apart at substantially equal intervals in the circumferential direction. A gas supply port 12 through which gas flows into the reaction chamber 2 in parallel (horizontally) with the surface of the silicon wafer W is provided at a predetermined position of the dome mounting body 5. Further, a gas discharge port 13 for discharging the gas in the reaction chamber 2 to the outside is provided at a position facing the dome mounting body 5 (a position separated from the gas supply port by about 180 °). The gas supply port 12 and the gas discharge port 13 are provided two by two apart from each other in the vertical direction. This is because a gas flow is formed on the front surface side of the silicon wafer W and the back surface side of the susceptor. The silicon wafer W is a p-type single-sided mirror silicon single crystal wafer having a diameter of 200 mm, a thickness of 740 μm, a surface orientation (100), and a specific resistance of 15 mΩcm. A silicon oxide film is not formed on the back surface of the silicon wafer W.

  A susceptor 20 on which the silicon wafer W is placed is provided at an intermediate portion in the height direction of the reaction chamber 2. The reaction chamber 2 is divided into an upper space and a lower space with the susceptor 20 as a partition. As the susceptor 20, a carbon substrate whose surface is coated with a SiC film so as to withstand the high temperature in the reaction chamber 2 is employed. Thereby, the contamination resulting from the susceptor base material to be used, such as carbon contamination from the susceptor base material made of the carbon member, can be prevented. The susceptor 20 has a disk shape with a predetermined thickness.

Further, on the surface side of the susceptor 20, a pocket portion 24 which is a circular recess having a predetermined width on which the silicon wafer W is placed is provided. That is, the radius of the susceptor 20 is larger than that of the silicon wafer W to be placed. The depth of the pocket portion 24 is substantially the same as the thickness of the silicon wafer W.
A large number of through holes 30 penetrating in the thickness direction of the susceptor 20 are formed at a constant pitch in the entire outer peripheral portion of the pocket portion 24 of the susceptor 20. On the surface side of each through hole 30, an enlarged opening (trench) 30b having a larger opening area than the other part 30a of the corresponding through hole 30 is provided in communication with the other part 30a.

The length of each through hole 30 is about 2 mm, which is about the same as the thickness of the bottom wall of the pocket portion 24. The enlarged opening 30b and the other portion 30a in each through-hole 30 are straight body holes each having a constant cross-sectional shape perpendicular to the length direction over the entire length thereof. The diameter d1 of the other portion 30a is 1 mm (opening area 0.785 mm ² ). The diameter d2 of the enlarged opening 30b is 3 mm (opening area 7.065 mm ² ), which is three times the diameter d1 of the corresponding other portion 30a. The depth of the enlarged opening 30b (the thickness of the susceptor 20) is 0.3 mm. Instead of the enlarged opening 30b of the straight body hole, for example, a trumpet-shaped enlarged opening 30c that gradually increases in diameter toward the surface of the susceptor 20 may be employed (FIG. 5). Moreover, you may employ | adopt what formed the enlarged opening part 30d not only on the surface side of the formation part of each through-hole 30 but on the back surface side (FIG. 7). During epitaxial growth, the dopant diffused outward from the back surface of the silicon wafer W passes through each through hole 30 including the enlarged opening 30b and is discharged into the lower space of the reaction chamber 2. In order to increase the discharge power of the reaction gas to the lower space of the reaction chamber 2, the lower space of the reaction chamber 2 is set to a negative pressure than the upper space.

  On the outer periphery of the susceptor 20, an annular preheat ring 60 that heats the reaction gas immediately before coming into contact with the silicon wafer W is disposed with a slight gap around the entire periphery. The preheat ring 60 has an outer peripheral side fixed to the inner peripheral side of the dome mounting body 5. The preheat ring 60 is made of a graphite material coated with silicon carbide. The preheat ring 60 is heated by light irradiated from each halogen lamp 6 through the upper dome 3 and the lower dome 4 having translucency.

The susceptor 20 is supported by a susceptor support member 18, part of which is in contact with the back surface. The susceptor support member 18 is made of quartz, and has a support member 18d at the center and three support members 18a to 18c formed radially at intervals of 120 ° in the circumferential direction. A shaft portion 7 fixed to an output shaft of a rotary motor (not shown) is connected to the lower portion of the susceptor support member 18, whereby the susceptor 20 is rotatably provided with the susceptor support member 18.
The susceptor 20 is provided with three lift pins 9 for lifting the silicon wafer W from below after the epitaxial film formation. Each lift pin 9 is inserted into and held by a hole penetrating the susceptor 20 and the susceptor support member 18.

A lift arm support member 25 is disposed integrally with the shaft portion 7 on the outer periphery of the shaft portion 7. Three lift arms 11 for lifting each lift pin 9 are provided at the upper end of the lift arm support member 25 corresponding to each lift pin 9. The structures and functions of the lift arm 11, the lift arm support member 25 and the lift pin 9 are the same as those of the conventional epitaxial growth apparatus.
As a result, the silicon wafer W reacts with the gas supplied while rotating on the susceptor 20 in the reaction chamber 2, and an epitaxial film having a predetermined thickness is formed on the surface thereof. After film formation, the lift arm 11 is lifted by the lift arm support member 25, and the lift pins 9 inserted and held in the holes of the susceptor 20 are lifted by a predetermined height. As a result, the silicon wafer W is lifted from the pocket portion 24 of the susceptor 20, and the silicon wafer W is discharged from the reaction chamber 2 by a transfer mechanism (not shown).

Next, a method for forming an epitaxial film on the surface of the silicon wafer W using the epitaxial growth apparatus 10 incorporating the susceptor of Example 1 will be described.
First, a silicon wafer W is prepared. Next, the silicon wafer W is placed in the pocket portion 24 of the susceptor 20 in the reaction chamber 2 with its main surface facing upward. This is due to a transfer mechanism (not shown). Thereafter, the reaction chamber 2 is sealed. Then, the shaft portion 7 of the susceptor support member 18 is rotated at a predetermined speed, and the silicon wafer W placed on the susceptor 20 is rotated.

Next, hydrogen gas is first supplied into the reaction chamber 2 in parallel with the surface of the silicon wafer W, and heated to a predetermined temperature by the halogen lamp 6. Thus, hydrogen baking is performed on the silicon wafer W at 1130 ° C. for 20 seconds. Thereafter, a mixed gas obtained by diluting SiHCl ₃ that is a silicon source gas and B ₂ H ₆ that is a boron dopant gas with hydrogen gas is on the upper side, and hydrogen gas is on the lower side from each gas supply port 12 to the upper space of the reaction chamber 2. And the lower space respectively. The flow rate at this time is 10 liters / min to 100 liters / min. At the same time, the gas used for the reaction in the reaction chamber 2 is discharged from the gas discharge port 13.

Next, heat is radiated in the reaction chamber 2 by the halogen lamps 6 provided above and below the reaction chamber 2 to keep the temperature in the reaction chamber 2 at 1100 ° C. As a result, a P-type epitaxial film having a thickness of about 6 μm and a specific resistance of 10 Ω · cm grows uniformly on the surface of the silicon wafer W. At this time, the susceptor 20 holding the silicon wafer W receives the radiant heat uniformly by the lower halogen lamp 6 via the susceptor support member 18.
A large number of through holes 30 are formed in the outer peripheral portion of the pocket 24 of the susceptor 20. Therefore, the dopant diffused outward from the back surface of the silicon wafer W during the epitaxial growth is discharged to the lower space of the reaction chamber 2 through each through hole 30 without going around to the wafer surface side. As a result, the dopant taken in the epitaxial film due to the auto-doping phenomenon can be suppressed. As a result, the variation in the dopant concentration in the epitaxial film surface is reduced, the resistivity of the outer peripheral edge of the epitaxial film is substantially the same as the resistivity in the central part of the epitaxial film, and the resistivity distribution in the epitaxial film surface is reduced. Uniformity increases.
Furthermore, the enlarged opening 30b is communicated with the surface side of the formation part of each through-hole 30. Thereby, the high temperature of the part which opposes each through-hole 30 among the silicon wafers W is suppressed. Therefore, not only the nanotopology of the epitaxial wafer surface but also the nanotopology of the backside of the epitaxial wafer is improved.

In addition, by providing the enlarged opening 30b in the minute through hole 30 in this manner, for example, when the susceptor 20 is manufactured, the effect of removing impurities from the through hole 30 in the cleaning process after drilling can be enhanced. . As a result, it is possible to prevent the back surface portion of the silicon wafer W facing the through hole 30 from being contaminated by impurities during epitaxial growth, and to simultaneously improve the deterioration of the lifetime characteristics of the epitaxial wafer facing the through hole 30.
The reason why the silicon wafer W is prevented from being heated at a high temperature at the portion facing each through hole 30 is not clear. Presumably, the amount of heat radiated from the halogen lamp 6 existing below the reaction chamber 2 to the back surface of the silicon wafer W through each through-hole 30 is considered to be reduced.
On the other hand, the reason why the lifetime has been improved is that the enlarged opening 30b is communicated with the end of the through-hole 30 so that the susceptor 20 can be manufactured after the drilling process using, for example, a wipe material. It is mentioned that the cleaning of the through-hole 30 is relatively easy. Further, in the subsequent high-purity processing step of the susceptor 20, a chlorine-based high-purity processing gas for purifying the susceptor 20 can easily flow into the through-hole 30 through the enlarged opening 30b, whereby the inner wall of the through-hole 30 is It can be considered that it has been highly purified.

Here, referring to FIG. 2, an epitaxial film is formed on the surface of silicon wafer W by using susceptor 20 (FIG. 2a) of Example 1 and susceptor 20A (FIG. 2b) having a conventional straight body hole 30A. We report the result of the test comparing the roughness of the backside of the wafer when each film was deposited.
In the susceptor 20 of Example 1, the roughness (unevenness) of the back surface of the epitaxial wafer was about several nm. On the other hand, in the conventional susceptor 20A, the nanotopology was deteriorated to several tens of nm.

Next, referring to the graph of FIG. 3, when changing the magnification of the diameter of the enlarged opening relative to the diameter of the other part of the through hole, the test results comparing the nanotopologies of the front and back surfaces of the epitaxial wafer Indicates. The epitaxial wafer surface is an epitaxial film surface.
Compared to the case of a straight barrel hole (conventional) of 1.0 times where the diameter of the surface side of the through hole and the other part is the same, 1.1 to 3 times that of the front and back surfaces of the epitaxial wafer In both cases, the nanotopology was improved. The effect was particularly high on the back side of the wafer. At 4.0 times, the nanotopology improvement effect on the front and back surfaces of the epitaxial wafer decreased.

FIG. 4 shows the lifetime characteristics of the portion of the epitaxial wafer facing the through-holes of the conventional straight body when the lifetime characteristics of the portion facing the holeless portion of the susceptor of the epitaxial wafer is 1.0. And the result of the test which compared the lifetime characteristic of the part which opposed the through-hole which has an enlarged opening part (trench part) of this invention is reported.
Two types with different diameters of 0.7 mm (level A) and 1.5 mm (level B) in diameter were tested in the through hole of the straight body. In addition, in the case of the through hole of the present invention, those having the magnification of 1.1 times and those of 3.0 times were tested. The 1.1 times through-hole is based on a level A straight body part (other part). Further, the 3.0 times through hole is based on the level B straight body portion.
As is apparent from the graph of FIG. 4, the lifetime characteristics of the portion facing the through hole of the present invention are more than the lifetime characteristics of the portion facing the straight body hole (conventional) of the epitaxial wafer. It was close to the reference value 1.0.

Here, using the susceptor 20 (FIG. 5) in which the through hole 30 having the trumpet-shaped enlarged opening 30c is formed, the magnification of the diameter of the enlarged opening is changed with respect to the diameter of the other part of the through hole. When it was made to do, the test which compared the nanotopology of the epitaxial wafer front and back is shown (graph of FIG. 6).
As with the test results in the graph of FIG. 3, the nanotopology is improved for both the front and back surfaces of the epitaxial wafer in the case of 1.1 to 3 times that of the conventional straight body hole of 1.0 times. It was done. In particular, the effect was high on the backside of the wafer. At 4.0 times, the nanotopology improvement effect on the front and back surfaces of the epitaxial wafer decreased.

It is a longitudinal cross-sectional view which shows the reaction chamber of the epitaxial growth apparatus incorporating the susceptor based on Example 1 of this invention. It is a graph which shows the principal part expanded sectional view of the use condition of the susceptor which concerns on Example 1 of this invention, and the roughness of the wafer back surface after the epitaxial growth using the susceptor. It is a principal part expanded sectional view of the use condition of the susceptor which concerns on the conventional means, and the graph which shows the roughness of the wafer back surface after the epitaxial growth using the susceptor. It is a graph which shows the relationship between the magnification of the diameter of the enlarged opening part on the basis of the diameter of the other part of a through-hole, and the absolute value of the variation | change_quantity of each roughness of the front and back of an epitaxial wafer. It is a graph which shows the relationship between the lifetime of the non-hole part of a susceptor in an epitaxial wafer, the conventional straight body hole, the part each facing the through-hole of this invention, and. It is a principal part expanded sectional view of the susceptor which concerns on other embodiment of this invention. It is a graph which shows the relationship between the magnification of the diameter of the enlarged opening part with respect to the diameter of the other part of a through-hole, and the absolute value of the variation | change_quantity of each roughness of the front and back of an epitaxial wafer. It is a principal part expanded sectional view of the susceptor which concerns on another embodiment of this invention. It is a graph which shows the relationship between the hole diameter of a through-hole, and the absolute value of the variation | change_quantity of each roughness of the front and back of an epitaxial wafer.

2 reaction chamber,
20 susceptors,
30 through holes,
30a other parts,
30b, 30c enlarged opening,
W Silicon wafer (semiconductor wafer).

Claims (1)

In the susceptor housed in the reaction chamber, the semiconductor wafer is placed on the surface, and a plurality of through holes are formed through the thickness direction.
Of the front and back sides of each through hole forming portion, at least on the front side, an enlarged opening having a larger opening area than the other part of the corresponding through hole is provided in communication with the other part .
The other part of the through-hole and the enlarged opening have a circular cross-sectional shape perpendicular to the length direction over the entire length,
The diameter of the other part of the through hole is 0.7 to 1.5 mm,
The diameter of the enlarged opening is 1.1 to 3 times the diameter of the corresponding other part.

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