TW201715068A - Manufacturing method of an epitaxial silicon wafer - Google Patents

Abstract

The invention provides a manufacturing method of an epitaxial silicon wafer, capable of preventing the back surface of the wafer from being cloudy. The method includes: a hydrogen baking step where a silicon wafer W is placed on a susceptor 20 and undergoes a heat treatment process in an atmosphere including hydrogen, and an epitaxial growth step where an epitaxial layer is formed on the front surface of the silicon wafer W. The susceptor 20 has a pocket 20c formed from a bottom wall 20a and a side wall 20b. A plurality of through holes 20e are formed within an area of the bottom wall 20a which is overlapped with the silicon wafer W in the top view. The silicon wafer W is bended such that the center portion of the silicon wafer W protrudes toward a surface side with respect to the edge portion. The hydrogen baking step is performed under a state that the silicon wafer W is placed on the susceptor 20 in the manner of the other surface side of the silicon wafer W facing the bottom wall 20a.

Description

Method for manufacturing epitaxial wafer

The present invention relates to a method of fabricating an epitaxial germanium wafer.

In recent years, in order to cope with the large diameter of the tantalum wafer, a leaf type epitaxial growth device is mainly used. If such an epitaxial growth apparatus is used to form an epitaxial layer on the surface of the germanium wafer, there is a problem that the back surface of the obtained epitaxial wafer is blurred. The backside blur of the epitaxial wafer is a poor appearance, and it is not good as a product wafer. Also, if the back surface is blurred, an erroneous result may be detected when measuring the particles on the back side.

As a technique for preventing blurring of the back surface of the epitaxial wafer, there is a method (for example, Patent Document 1) is to use a germanium wafer to wash the back surface with a HF-based solution as a hydrophobic surface, and control each during hydrogen baking. Output power (heating ratio) of the upper heater and the lower heater above and below the holder.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2013-123004

However, in the method of Patent Document 1, although the back surface of the tantalum wafer is washed with a HF-based solution as a hydrophobic surface, the back surface of the wafer may be naturally formed before the epitaxial growth is performed after the cleaning. Oxide film. In this case, blurring of the back side of the epitaxial wafer may not be sufficiently prevented.

It is an object of the present invention to provide a method of fabricating an epitaxial germanium wafer that prevents blurring on the back side of the wafer.

The method for manufacturing an epitaxial germanium wafer of the present invention comprises: a hydrogen baking step of performing heat treatment on a germanium wafer placed on a holder in a gas atmosphere containing hydrogen; and an epitaxial growth step in An epitaxial layer is formed on the surface of the germanium wafer at the end of the hydrogen baking step. Wherein the holder has a slightly rounded bottom wall and a pocket formed by the side wall surrounding the bottom wall. The bottom wall is provided with a plurality of through holes in a region overlapping the silicon wafer when viewed from above. The germanium wafer is a bent wafer whose center protrudes toward the one side with respect to the outer edge. The hydrogen baking step is performed in a state where the crucible wafer is placed on the holder and the other side surface of the crucible wafer is directed to the bottom wall. Here, the meandering of the center of the enamel wafer with respect to the outer edge is a curved shape in which the height position based on the outer edge on one side is increased from the outer edge toward the center. In the present invention, the silicon wafer is placed on the holder, and the bent silicon wafer is formed into a convex shape, and a hydrogen baking step is performed.

Fig. 1 is a view showing the steps of manufacturing the epitaxial wafer of the present embodiment. First, the reaction chamber of the epitaxial growth apparatus is filled with an inert gas, and the inside of the reaction chamber is heated by heating with a xenon lamp (S1, S2). Next, the germanium wafer is carried into the reaction chamber of the epitaxial growth apparatus. The loaded crucible wafer is placed on top of the holder in the reaction chamber.

As shown in Fig. 2, the holder 20 has a pocket portion 20c which is composed of a circular bottom wall 20a having a larger diameter than the crucible wafer and a cylindrical side wall 20b surrounding the bottom wall 20a. The wafer is stored and placed on the bag portion 20c. The mounting surface of the holder 20, that is, the bottom surface 20a, is provided from the outer peripheral side toward the inner circumference. The support portion 20d is inclined sideways. Through the support portion 20d, the outer peripheral portion of the crucible wafer is supported in a state of being in line contact. Thereby, when the crucible wafer is placed on the holder 20, a space is formed between the holder 20 and the crucible wafer at the center portion. As a result, hydrogen gas is promoted to flow into the back side of the germanium wafer, and the effect of discharging impurities released from the back surface of the germanium wafer becomes large. Further, a plurality of through holes 20e are formed in the mounting surface of the crucible wafer of the holder 20, that is, the bottom surface 20a, in order to prevent the thickness of the epitaxial layer formed on the surface of the outer peripheral portion of the crucible wafer. Reduces and discharges impurities released from the back side of the germanium wafer. The plurality of through holes 20e are holes that penetrate the thickness direction of the holder 20 (from the upper surface of the bottom wall 20a toward the lower surface of the holder 20).

Returning to Fig. 1, after the temperature rises, hydrogen gas is supplied into the reaction chamber, and the silicon wafer placed on the holder is subjected to a hydrogen baking step (S3). After the hydrogen baking step, the material gas is supplied into the reaction chamber to form an epitaxial layer on the surface of the germanium wafer (S4). After the epitaxial layer having a predetermined film thickness is formed, the supply of the material gas is stopped, and the reaction chamber is cooled (S5). The epitaxial wafer is then removed from the cooled reaction chamber.

As shown in Fig. 3, in the hydrogen baking step, hydrogen gas supplied into the reaction chamber flows along the surface of the crucible wafer W, and the natural oxide film formed on the surface of the crucible wafer W is removed by hydrogen gas. A line gap between the holder 20 and the tantalum wafer W forms a microscopic gap. Therefore, a part of the hydrogen gas flows from this microscopic gap into the space formed between the holder 20 and the crucible wafer W. Then, hydrogen gas reaching a space formed between the holder 20 and the crucible wafer W is discharged from the through hole 20e formed in the bottom wall 20a of the holder 20. At this time, the natural oxide film in the vicinity of the through hole 20e on the back surface of the crucible W is removed by hydrogen gas.

However, as shown in FIG. 3, a germanium wafer having a downwardly convex shape is placed. When hydrogen baking is performed in the state of the holder 20, the space formed between the holder 20 and the crucible wafer W is narrow, so that there is not enough hydrogen gas to reach the field where the through hole 20e is not formed. Therefore, the natural oxide film in the vicinity of the region where the through hole 20e is not formed on the back surface of the tantalum wafer W is not completely removed and remains. These residual natural oxide films are responsible for the backside blurring of the epitaxial wafer. Further, in the case where hydrogen baking is performed in a state where the flat tantalum wafer is placed on the holder 20, the natural oxide film on the back surface remains due to the same mechanism.

On the other hand, according to the present invention, as shown in FIG. 4, the silicon wafer W in which the upwardly convex shape is placed on the holder 20 is subjected to hydrogen baking. In Fig. 4, for the sake of easy understanding, the degree of bending is drawn to be larger than the actual bending degree of the silicon wafer. By placing the germanium wafer W having an upwardly convex shape on the holder 20, the carrier 20 is placed on the holder 20 in comparison with the placement of the downwardly convex shape or the flat germanium wafer W. The space formed between the crucibles W of the holder 20 is enlarged. When hydrogen baking is performed in this state, the amount of space in which hydrogen flows into the space formed between the holder 20 and the crucible wafer W increases. Since the amount of inflow is increased, the field in which the through holes 20e are not formed also has a sufficient amount of hydrogen to be removed to remove the natural oxide film. Therefore, the entire natural oxide film formed on the back surface of the germanium wafer W is uniformly removed. As a result, blurring of the back surface of the epitaxial wafer due to the residual of the natural oxide film is prevented.

Further, in the method for producing an epitaxial germanium wafer of the present invention, the amount of protrusion of the center of the germanium wafer toward the one surface side is more than 0 μm and preferably 15 μm or less. According to the invention, the amount of protrusion of the center of the tantalum wafer toward one surface side with respect to the outer edge exceeds 0 μm and is 15 μm or less. If the amount of protrusion in the above range is placed on the holder, the flat wafer is placed on the flat wafer. In the case of a holder, or in the case where a downwardly convex crucible wafer is placed on a holder, hydrogen flows into the space formed between the holder and the crucible wafer in the hydrogen baking step. The amount increases. Therefore, the entire natural oxide film formed on the back surface of the germanium wafer can be uniformly removed. In addition, if the amount of protrusion exceeds 15 μm, a sliding shift may occur on the wafer during epitaxial growth.

Further, in the production method of the present invention, it is preferred that the back side of the tantalum wafer is treated as a hydrophobic surface in advance. According to the present invention, by pretreating the back side of the germanium wafer into a hydrophobic surface, the germanium wafer provided in the hydrogen baking step and the epitaxial growth step is kept in a state in which the natural oxide film is less exposed to the bare state. The thickness of the natural oxide film at this time is only a relatively small thickness of about several nm, and in the hydrogen baking step, the natural oxide film can be removed to prevent blurring of the back surface of the epitaxial wafer. The treatment of the hydrophobic surface on the back side of the crucible wafer may be carried out by washing with an HF solution or a BHF solution. Further, these HF-based solutions may be combined with O ₃ water (ozone water).

Further, in the manufacturing method of the present invention, it is preferable that the surface of the holder on which the tantalum wafer is placed is formed with a tantalum film. In the epitaxial growth apparatus, in order to prevent metal contamination from the susceptor, a ruthenium film is generally coated on the surface of the susceptor on which at least the ruthenium wafer is placed. When such a retort-covered holder is used and an epitaxial wafer is fabricated by a conventional manufacturing method, blurring occurs on the back surface of the epitaxial wafer.

Fig. 5 is a view showing the mechanism by which the back surface of the wafer is blurred when the enamel-receiving holder is used. In the case of a reticle-coated holder, the specific mechanism for blurring the back side of the epitaxial wafer is as follows. As shown in Fig. 5(A), the holder 20 is coated with a ruthenium film 20f on the surface side on which the ruthenium wafer W is placed. First, as shown in Figure 5(A), when the epitaxial growth is being performed, the germanium wafer W is placed on the epitaxial growth. The mounting surface of the holder 20 provided in the reaction chamber of the apparatus. Further, a natural oxide film W1 is formed on the front and back surfaces of the germanium wafer W.

Next, as shown in Fig. 5(B), a hydrogen baking step is performed. In the hydrogen baking step, hydrogen gas is supplied to the reaction chamber. The supplied hydrogen gas mainly flows along the surface of the crucible wafer W, and the natural oxide film W1 formed on the surface of the crucible wafer W is removed by hydrogen gas. Further, the supplied hydrogen gas does not flow only on the surface side of the tantalum wafer W, and a part of the hydrogen gas flows into the back side of the tantalum wafer W. Then, hydrogen gas reaching a space formed between the holder 20 and the crucible wafer W is discharged from the through hole 20e formed in the bottom wall 20a of the holder 20. At this time, the natural oxide film in the vicinity of the through hole 20e on the back surface of the crucible W is removed by hydrogen gas. On the other hand, in the vicinity of the region where the through hole 20e is not formed, hydrogen gas is hard to reach, or is small even if it is reached. Therefore, the natural oxide film W11 in the vicinity of the region where the through hole 20e is not formed on the back surface of the wafer W is not completely removed and remains.

Next, as shown in Fig. 5(C), an epitaxial growth step is carried out. In the epitaxial growth step, the epitaxial layer W2 is formed on the surface of the germanium wafer W. The tantalum film 20f formed on the holder 20 is a tantalum film in which a gas phase composed of a carbon substrate such as SiC is grown on the surface of the holder. Therefore, this ruthenium film is not composed of single crystal germanium but polycrystalline germanium. Further, the polycrystalline ruthenium film is extremely porous and has a property of absorbing other components into the interior. Therefore, the C1 group or the like in the material gas (SiHCl ₃ , SiH ₂ Cl ₂ , SiCl _{4 ,} etc.) used for the ruthenium film in the polycrystalline ruthenium film of the holder 20 is absorbed into the inside, and other moisture, etc. The possibility of suction being absorbed.

Then, in the epitaxial growth step, the holder is subjected to high-temperature heat treatment, and components (for example, HCl component or Si component) in the ruthenium film on the mounting surface of the holder are transferred (substance movement) to the back surface of the ruthenium wafer. As mentioned above, the end of hydrogen baking A natural oxide film remains on a part of the back surface of the wafer, so the enamel film of the holder is transferred to the remaining natural oxide film. The area transferred to the remaining natural oxide film becomes blurred. It is speculated that the blurring of the back side of the epitaxial wafer is due to such a mechanism.

On the other hand, in the present invention, the silicon wafer is placed in a state in which the tantalum wafer having the upwardly convex shape is placed on the holder. By placing a tantalum wafer having an upwardly convex shape on the holder, the carrier is placed on the holder or the tantalum wafer having the downwardly convex shape is placed on the holder, the holder The space formed between the wafer and the germanium wafer is enlarged. Then, in the hydrogen baking step, when hydrogen gas is supplied into the reaction chamber, the amount of space formed between the hydrogen inlet and the crucible wafer increases in response to the expansion of the space formed between the holder and the crucible wafer. Because of the increase in the amount of inflow, the field in which the through holes are not formed also has a sufficient amount of hydrogen to be removed to remove the natural oxide film. Therefore, the entire natural oxide film formed on the back surface of the germanium wafer is uniformly removed. As a result, even in the epitaxial growth step after the hydrogen baking step, the ruthenium film coated on the mounting surface of the susceptor is transferred to the back surface of the ruthenium wafer, and since the back surface does not have a natural oxide film remaining, it can be prevented. The back side of the epitaxial wafer is blurred.

Further, when an epitaxial wafer is manufactured in the same manner as a conventional manufacturing method using a holder without a ruthenium film, etching unevenness occurs on the back surface of the epitaxial wafer. Fig. 6 is a view for explaining that etching unevenness occurs on the back surface of the wafer when a holder without a crucible is used, and in the case where a holder without a crucible is used, etching is not performed on the back surface of the epitaxial wafer. The specific mechanisms are as follows. First, as shown in Fig. 6(A), while epitaxial growth is being performed, the tantalum wafer W is placed on the mounting surface of the holder 20 provided in the reaction chamber of the epitaxial growth apparatus. Further, a natural oxide film W1 is formed on the front and back surfaces of the germanium wafer W.

Next, as shown in Fig. 6(B), a hydrogen baking step is performed. In the hydrogen baking step, hydrogen gas is supplied to the reaction chamber. The supplied hydrogen gas mainly flows along the surface of the crucible wafer W, and the natural oxide film W1 formed on the surface of the crucible wafer W is removed by hydrogen gas. Further, the supplied hydrogen gas does not flow only on the surface side of the tantalum wafer W, and a part of the hydrogen gas flows into the back side of the tantalum wafer W. Then, hydrogen gas reaching a space formed between the holder 20 and the crucible wafer W is discharged from the through hole 20e formed in the bottom wall 20a of the holder 20. At this time, the natural oxide film in the vicinity of the through hole 20e on the back surface of the crucible W is removed by hydrogen gas. On the other hand, in the vicinity of the region where the through hole 20e is not formed, hydrogen gas is hard to reach, or even if it reaches, it is rarely. Therefore, the natural oxide film W11 in the vicinity of the region where the through hole 20e is not formed on the back surface of the wafer W is not completely removed and remains.

Next, as shown in Fig. 6(C), an epitaxial growth step is carried out. In the epitaxial growth step, the epitaxial layer W2 is formed on the surface of the germanium wafer W. When a holder without a ruthenium film is used, unlike the holder having the above-described enamel film, since the ruthenium film is not coated, the ruthenium film is not transferred to the back surface of the ruthenium wafer W. Therefore, the natural oxide film remaining in the hydrogen baking step is maintained in a residual state. It is speculated that the etching unevenness on the back side of the epitaxial wafer is due to such a mechanism.

On the other hand, in the present invention, since the tantalum wafer having the upwardly convex shape is subjected to hydrogen baking in the state of the holder, the entire natural oxide film formed on the back surface of the tantalum wafer is uniformly removed. As a result, even if a holder having no enamel film is used, it is possible to prevent blurring of the back surface of the epitaxial wafer due to uneven etching without causing uneven etching on the back surface of the epitaxial wafer.

Moreover, in the manufacture of the epitaxial germanium wafer of the present invention, the plural The through hole is disposed in the outer peripheral region of the bottom wall that is outward in the radial direction from the center to the 1/2 distance from the radius, and the through hole is preferably included in at least the bottom wall region on which the tantalum wafer is placed. .

In the past, there has been proposed a method of performing epitaxial growth using a holder of a bottom wall which is formed by a plurality of through holes having a plurality of dispersed dispersions. However, in the case where the bottom wall of the holder has a substantially uniform number of through-holes, the temperature difference between the formed area and the non-formed area of the through-hole may deteriorate the nano-morphology of the surface of the wafer. . Further, the field from the center position of the bottom wall to the radius 1/2 is a measurement field of the epitaxial growth treatment temperature in the epitaxial growth apparatus. Therefore, if a through hole is formed in this field, the measurement of the processing temperature causes a non-uniform deviation, and as a result, the possibility that the epitaxial layer is slipped is improved. According to the present invention, as shown in Fig. 7, the plurality of through holes 20e are disposed in the outer peripheral region on the outer side in the radial direction from the center of the bottom wall 20a to a distance of 1/2 of the radius. Therefore, the above problem can be solved.

Further, when the through hole is formed in the outer peripheral region of the holder that exceeds the diameter of the silicon wafer placed thereon, the through hole is formed. Since the temperature of the outer peripheral portion of the holder is not uniform, sliding displacement to the epitaxial layer is liable to occur. Moreover, the discharge effect of the doping gas discharged from the back surface of the germanium wafer is lowered, and the influence of self-doping cannot be excluded. According to the present invention, since the through hole 20e is provided at least in the field of the bottom wall in which the ruthenium wafer is disposed above, the above problem can be solved.

Further, in the production of the epitaxial germanium wafer of the present invention, it is preferable that the plurality of through holes are arranged such that at least the through hole having the annular array is arranged in the bottom wall region on which the germanium wafer is placed. The through holes arranged in a row in a ring shape can suppress the flaw caused by the temperature difference between the formed area and the non-formed area of the through hole. Deterioration of the nanotopography of the wafer surface.

2‧‧‧Reaction room

3‧‧‧Upper round cover

4‧‧‧Lower side cover

6‧‧‧round cover mounting body

7‧‧‧Axis

8‧‧‧Receiver support components

9‧‧‧Halogen lamp

10‧‧‧ Epitaxial growth device

20‧‧‧Support

20a‧‧‧ bottom wall

20b‧‧‧ side wall

20c‧‧‧ bag department

20d‧‧‧Support Department

20e‧‧‧through hole

20f‧‧‧矽膜

31‧‧‧ gas supply port

32‧‧‧ gas discharge

33‧‧‧ gas supply pipe

34‧‧‧Draining tube

S1‧‧‧ Washing steps

S2‧‧‧ warming step

S3‧‧‧ Hydrogen baking step

S4‧‧‧ epitaxial growth step

W‧‧‧矽 wafer

W1‧‧‧ natural oxide film

W11‧‧‧ natural oxide film

Fig. 1 is a view showing the steps of manufacturing the epitaxial wafer of the present embodiment.

Fig. 2 is a schematic view of a holder of the present embodiment.

Fig. 3 is a hydrogen flow diagram of a crucible wafer in which a downwardly convex shape is placed on a holder for hydrogen baking.

Fig. 4 is a hydrogen flow diagram when a silicon wafer having an upwardly convex shape is placed on a holder for hydrogen baking.

Fig. 5 is a view for explaining the mechanism of blurring on the back side of the wafer when a retort-coated holder is used.

Fig. 6 is a view for explaining a mechanism for causing uneven etching on the back surface of the wafer when a holder without a ruthenium film is used.

Figure 7 is a plan view of the holder of the present embodiment.

Fig. 8 is a schematic view showing a leaf type epitaxial growth apparatus of the present embodiment.

A method of manufacturing the epitaxial germanium wafer of this embodiment will be described below. First, the configuration of the epitaxial growth apparatus will be described.

[Configuration of epitaxial growth device]

Fig. 8 is a schematic view showing a leaf type epitaxial growth apparatus of the present embodiment. As shown in Fig. 8, the leaf type epitaxial growth apparatus 10 includes a circular upper side dome 3 having a concave surface and a lower circular lower side cover 4 having the same circular shape. The upper dome 3 and the lower dome 4 are formed of a transparent material such as quartz. Then, the upper dome 3 and the lower dome 4 are placed upside down so that their end portions are respectively fixed to the annular shape The upper cover of the dome cover body 6. Thereby, a slightly circular closed reaction chamber 2 is formed under the above viewing. Above and below the reaction chamber 2, a plurality of halogen lamps 9 for heating the reaction chamber 2 are separately provided at equal intervals in the circumferential direction.

The reactor 20 on which the silicon wafer W is mounted is horizontally disposed in the reaction chamber 2. The holder 20 is made of a carbon substrate such as SiC which can withstand the high temperature in the reaction chamber 2. In this embodiment, the surface of the carbon substrate covers the ruthenium film. As shown in Fig. 2, the holder 20 has a pocket portion 20c composed of a circular bottom wall 20a having a larger diameter than the tantalum wafer W and a cylindrical side wall 20b surrounding the bottom wall 20a. . The wafer W is stored and placed on the bag portion 20c. The depth of the pocket portion 20c, that is, the height from the upper surface of the bottom wall 20a of the holder 20 to the upper end of the side wall 20b is formed to be slightly the same as the thickness of the crucible wafer W. The bottom wall 20a is provided with a support portion 20d that is inclined downward from the outer peripheral side toward the inner peripheral side. Further, the bottom wall 20a is formed with a plurality of through holes 20e in a region overlapping the meandering wafer W as viewed from above. Specifically, the plurality of through holes 20e are disposed in the outer peripheral region of the bottom wall 20a on the outer side in the radial direction from the center to the radius 1/2. Further, the plurality of through holes 20e are disposed such that the through holes are included in at least the region of the bottom wall on which the silicon wafer W is placed. Further, the plurality of through holes 20e are arranged such that at least one of the through holes arranged in a ring shape is included in the field of the bottom wall on which the silicon wafer W is placed.

Returning to Fig. 8, the backrest side (lower side) of the holder 20 is provided with a holder supporting member 8 that supports the holder 20. Below the holder support member 8, a shaft portion 7 is fixedly disposed. The shaft portion 7 is rotatably provided by a rotating mechanism (not shown), and as a result, the holder supporting member 8 and the holder 20 are also rotatably provided at a predetermined speed on a horizontal surface. Further, the shaft portion 7 is provided to be vertically movable in the axial direction by an up-and-down mechanism (not shown), and as a result, the cylinder The shape of the holder support member 8 and the holder 20 are also provided to be movable up and down.

Then, a predetermined position of the dome mounting body 6 of the reaction chamber 2 is provided with a gas supply port 31 through which gas flows into the reaction chamber 2. Further, a discharge port 32 for discharging the gas of the reaction chamber 2 to the outside is provided at an opposing position of the dome mounting body 6 (a position separated from the gas supply port 31 by 180°). The material gas or the like is supplied from the gas supply pipe 33 to the reaction chamber 2 through the gas supply port 31, and is discharged from the gas discharge port 32 through the discharge pipe 34 through the surface of the crucible wafer W in the reaction chamber 2.

[Method of manufacturing epitaxial wafer]

Next, a method of manufacturing the epitaxial germanium wafer of the present embodiment using the leaflet epitaxial growth apparatus 10 of Fig. 8 will be described.

<矽 wafer>

First, a bent silicon wafer is prepared such that the central position of one face side protrudes relative to the outer edge. Specifically, a bent silicon wafer is prepared, and the central position of one surface side thereof is more than 0 μm with respect to the outer edge protruding amount of 15 μm or less. When the tantalum wafer cut out from the single crystal rod is bent to the above range, it can be used as it is. Further, the tantalum wafer bent to the above range can be obtained by the following manufacturing steps.

First, the surface of the thin disk-shaped germanium wafer is adsorbed and held on the table top, and the back surface of the silicon wafer is ground and polished. In this back surface processing, the back surface of the germanium wafer is ground or polished while tilting the substrate on which the germanium wafer is adsorbed and held at a desired angle. By this back surface processing, a convex wafer having an increased thickness from the outer periphery of the wafer toward the center of the wafer is produced. Next, the convex back surface of the germanium wafer is adsorbed and held on the table top, thereby utilizing the elastic deformation shape. In the state in which the center of the surface side protrudes, the surface is ground and polished. In this surface treatment, unlike the above-described back surface treatment, the state in which the table top of the wafer is adsorbed and held at a desired angle is returned to the horizontal state, and then the surface of the wafer is ground or polished to flatten the surface. After the surface treatment is completed, the adsorption holding of the germanium wafer is released, whereby the germanium wafer is restored by elasticity, and a bent germanium wafer is obtained, and the center position of one side of the germanium wafer is protruded with respect to the outer edge. The amount of protrusion.

The prepared crucible wafer was washed with an HF solution, and the back side was previously treated to a hydrophobic surface.

<washing step S1>

In the washing step, an inert gas is supplied into the reaction chamber 2 of the epitaxial growth apparatus 10 to make the reaction chamber an inert gas atmosphere.

<heating step S2>

In the temperature rising step, the temperature in the reaction chamber 2 of the epitaxial growth apparatus 10 is raised from the room temperature to the target temperature by irradiation with the halogen lamp 9. The target temperature is set to 1050 ° C ~ 1280 ° C. After the temperature in the reaction chamber 2 is raised to a desired temperature in the temperature increasing step, the silicon wafer W is carried into the reaction chamber 2 of the epitaxial growth apparatus 10. The loaded silicon wafer W is placed on the upper surface of the holder 20 in the reaction chamber 2 so as to be convex upward, that is, the other surface side of the silicon wafer W faces the bottom wall.

<Hydrogen baking step S3>

Next, in order to remove the natural oxide film or particles present on the surface of the wafer W, hydrogen baking is performed. In the hydrogen baking step, only hydrogen gas is supplied from the gas supply port 31 into the reaction chamber 2 by a gas supply source (not shown), and the halogen lamp 9 maintains the silicon wafer W at 1,100 ° C for about 70 seconds. This embodiment As shown in FIG. 4, since the germanium wafer is placed on the holder 20, the germanium wafer W is formed into a convex shape, and the germanium wafer is placed on the holder or the lower convex shaped wafer is placed on the holder. In the case where a flat crucible wafer is placed on the holder, the space formed between the holder 20 and the crucible wafer W is enlarged. Therefore, the amount of inflow of hydrogen into the space formed between the holder 20 and the crucible wafer W is increased, so that the natural oxide film formed on the entire back surface of the crucible wafer W can be uniformly removed.

<Elobite growth step S4>

Next, an epitaxial growth step for forming an epitaxial layer is performed. First, a reaction gas in which a carrier gas, a source gas, a doping gas, or the like is mixed is supplied from the gas supply port 31 into the reaction chamber 2 by a gas supply source (not shown). The carrier gas may be a gas such as H ₂ , N ₂ or Ar. Examples of the material gas include ruthenium tetrachloride (SiCl ₄ ), cesium methane (SiH ₄ ), cesium trichloride (SiHCl ₃ ), and dichloroindoline (SiH ₂ Cl ₂ ). Examples of the doping gas include boron boride (B ₂ H ₆ ), phosphine (PH ₃ ), and the like. Then, heat radiation is performed by the halogen lamp 9 provided above and below the reaction chamber 2, and the temperature of the silicon wafer W is heated to about 1,100 °C. Thereby, the material gas can react on the surface of the germanium wafer, and the epitaxial layer is grown on the surface of the germanium wafer W. In the present embodiment, the natural oxide film formed on the back surface of the tantalum wafer W is uniformly removed by the above-described hydrogen baking. Therefore, in the epitaxial growth step, even if the tantalum film 20f coated on the mounting surface of the holder 20 is transferred to the back surface of the tantalum wafer W, since the natural oxide film remains on the back surface, it is possible to prevent the natural oxidation due to the remaining The blurring of the back side of the epitaxial wafer caused by the film is generated.

<cooling step S5>

After the epitaxial layer is formed to a desired film thickness, the supply of the material gas is stopped, and the reaction chamber is cooled. Then, the epitaxial enthalpy is removed from the cooled reaction chamber. Wafer. By the above method, it is possible to manufacture an epitaxial wafer which prevents blurring of the back surface.

[Other implementations]

The present invention is not limited to the above-described embodiments, and various modifications and changes in design may be made without departing from the scope of the invention. In the above embodiment, the plurality of through holes are formed by the outer periphery of the bottom wall. However, it is also possible to use a through hole having at least one annular row in the bottom wall region on which the tantalum wafer is placed. Adapter. Further, in the above-described embodiment, a holder in which a plurality of through holes are formed on the outer circumference of the bottom wall is used. However, a holder in which a plurality of through holes are formed in a substantially entire bottom wall may be used. Further, in the above embodiment, a holder covering the diaphragm is used, but a holder not covering the diaphragm may be used. Moreover, the specific steps, structures, and the like in the practice of the present invention may be other structures or the like within the scope in which the object of the present invention can be achieved.

[Examples]

Next, the present invention will be described in more detail by way of examples and comparative examples, but the invention is not limited to these examples.

[Examples 1 to 4, Comparative Examples 1 to 4]

Prepare a 300 mm tantalum wafer of the shape shown in Table 1 below. In Table 1, the positive amount of protrusion indicates that the wafer W is placed on the holder 20 in a convex shape. Further, a negative value indicates that the silicon wafer W is placed in the lower convex shape when it is placed on the holder 20. Then, the crucible wafers of the respective levels shown in Table 1 below were transferred to an epitaxial growth apparatus (manufactured by Applied Materials Co., Ltd.), and after performing a hydrogen baking treatment at a temperature of 1150 ° C for 30 seconds in the apparatus, hydrogen was used as Carrier gas, using trichlorohydroquinone as a source gas, using phosphine as a doping gas, at a growth temperature of 1000 to 1150 ° C Next, an epitaxial layer of germanium was grown on the germanium wafer by a CVD method to fabricate an epitaxial germanium wafer according to the present invention.

The back surface of the epitaxial wafer obtained by optical observation was observed, and the presence or absence of blur on the back surface was confirmed. The results are shown in Table 1.

It can be confirmed from Table 1 that if the amount of protrusion of the germanium wafer placed on the holder exceeds 0 μm, the back surface of the epitaxial wafer is not blurred.

20‧‧‧Support

20a‧‧‧ bottom wall

20b‧‧‧ side wall

20c‧‧‧ bag department

20d‧‧‧Support Department

20e‧‧‧through hole

W‧‧‧矽 wafer

Claims (6)

A method for manufacturing an epitaxial germanium wafer, comprising: a hydrogen baking step of performing heat treatment on a germanium wafer placed on a holder in a gas atmosphere containing hydrogen; and an epitaxial growth step in the hydrogen baking The surface of the germanium wafer at the end of the baking step forms an epitaxial layer, wherein the holder has a slightly rounded bottom wall and a pocket formed by the side wall surrounding the bottom wall, the bottom wall being located when viewed from above A plurality of through holes are provided in a field overlapping the germanium wafer, and the germanium wafer is a bent wafer, and a center thereof protrudes toward one side with respect to the outer edge, and the germanium wafer is placed on the support The hydrogen baking step is performed in a state where the other side surface of the silicon wafer is directed to the bottom wall. The method of manufacturing an epitaxial germanium wafer according to claim 1, wherein the center of the germanium wafer protrudes toward the one surface side with respect to the outer edge by more than 0 μm and not more than 15 μm. The method of manufacturing an epitaxial wafer according to claim 1 or 2, wherein the back side of the germanium wafer is previously processed into a hydrophobic surface. The method of manufacturing an epitaxial wafer according to any one of claims 1 to 3, wherein a surface of the holder on which the tantalum wafer is placed is formed with a tantalum film. The method for manufacturing an epitaxial germanium wafer according to any one of claims 1 to 4, wherein the plurality of through holes are disposed on the bottom wall and are more radially than the center to the radius of 1/2 Outside the outer perimeter area, and at least A through hole is included in the bottom wall region on which the tantalum wafer is placed. The method for manufacturing an epitaxial germanium wafer according to claim 5, wherein the plurality of through holes are disposed such that at least the bottom wall in which the germanium wafer is placed includes a through hole that is annularly arranged in a row .