JP6507573B2 - Lift pin, epitaxial growth apparatus using the lift pin and method of manufacturing epitaxial wafer - Google Patents

Description

  The present invention relates to a lift pin, an epitaxial growth apparatus using the lift pin, and a method of manufacturing an epitaxial wafer, and more particularly to a lift pin for realizing an epitaxial growth apparatus suitable for manufacturing an epitaxial wafer with good crystallinity.

  In general, a silicon wafer grows single crystal silicon by the Czochralski method (CZ method) or the like, cuts the silicon single crystal into blocks, and then thinly slices it into a flat surface grinding (lapping) process, etching process and mirror polishing It can be obtained by final cleaning through the (polishing) step. After that, if various quality inspections are performed and no abnormality is confirmed, the product is shipped.

Here, when crystal integrity is more required or when a multilayer structure with different resistivities is required, a single crystal silicon thin film is vapor phase grown (epitaxial growth) on the silicon wafer to form an epitaxial wafer. Manufacture.
For example, a single wafer type epitaxial growth apparatus is used to manufacture an epitaxial wafer. Here, a general single wafer type epitaxial growth apparatus will be described with reference to FIG. As shown in FIG. 1, the epitaxial growth apparatus 1 has an epitaxial film forming chamber 2 surrounded by an upper dome 11, a lower dome 12 and a dome mounting body 13. The epitaxial film formation chamber 2 is provided with a gas supply port 31 and a gas discharge port 32 for supplying and discharging a reaction gas at opposite positions on the side surface. On the other hand, a susceptor 4 on which a silicon wafer W is to be mounted is disposed in the epitaxial film formation chamber 2. The outer periphery of the lower surface of the susceptor 4 is supported by the susceptor support shaft 41 connected to the susceptor rotating unit 40 so as to rotate together with the susceptor support shaft 41. Further, through holes 42 through which lift pins 5 for moving the silicon wafer W up and down pass are formed in the susceptor 4. Further, the lift pin 5 is raised and lowered while being supported by the raising and lowering shaft 6 at its base end.

  That is, the silicon wafer W introduced into the epitaxial film forming chamber 2 moves the lift pins 5 inserted into the through holes 42 of the susceptor 4 toward the upper side of the susceptor 4, and shows around the through holes 41 of the susceptor 4 in FIG. As described above, the head 50 of the lift pin 5 is brought into contact with the back surface of the silicon wafer W, and the silicon wafer W is temporarily supported by the lift pin 5. Here, the upward movement of the lift pin 5 is performed through the upward movement of a lift shaft 6 supporting the proximal end of the lift pin 5.

  Then, the support shaft 41 supporting the susceptor 4 is raised to move the susceptor 4 to the position of the silicon wafer W, and the silicon wafer W is mounted on the susceptor 4. In this state, the head 50 of the lift pin 5 is accommodated in the through hole 40 of the susceptor 4. As described above, the silicon wafer W is placed on the susceptor 4 and heated to a temperature of 1000 ° C. or more by, for example, a plurality of heating lamps 14 disposed above and below the susceptor 4 while forming an epitaxial film. A reaction gas is supplied into the chamber 2 to grow an epitaxial film of a predetermined thickness to manufacture an epitaxial wafer.

  Thereafter, the susceptor 4 is lowered by lowering the support shaft 41. This lowering is performed to a position where the lift pins 5 are supported by the lift shaft 6 and protrude from the susceptor 4, and the silicon wafer W is supported by the lift pins 5. Then, a transfer blade (not shown) is introduced into the epitaxial film forming chamber 2 and the lift pins 5 are lowered to place the silicon wafer W on the transfer blade, thereby delivering the silicon wafer W from the lift pins 5 to the transfer blade. Thereafter, the silicon wafer W is withdrawn from the growth apparatus 1 together with the transfer blade.

  In the epitaxial wafer manufacturing process described above, the process of placing the silicon wafer W introduced into the growth apparatus 1 on the susceptor 4 and the process of delivering the silicon wafer W after epitaxial growth from the susceptor 4 to the transfer blade Then, the silicon wafer W is supported in contact with the lift pins 5. The portion of the back surface of the silicon wafer on which the lift pin 5 abuts is hit while the lift pin 5 ascends, and since the contact of the head is maintained, the generation of wrinkles in this portion is caused.

  Furthermore, it is essential to lift and lower the lift pin 5 in the above process and before and after that, but as the lift pin 5 slides on the wall surface around the through hole 40 of the susceptor 4 in lifting and lowering operation of the lift pin 5 I was dusting. This dust is in the form of particles and adheres to the surface of the epitaxial layer to reduce the quality of the silicon wafer.

  Patent Document 1 proposes that the surface of the lift pin in contact with the substrate be a material layer having a surface hardness lower than that of the substrate. As this material layer, glassy carbon is shown, but since the base material of the lift pin is silicon carbide (SiC) and adhesion of the glassy carbon to SiC is weak, the base material and the material are made of different materials. It is difficult to avoid partial peeling of the material layer due to the thermal expansion difference with the layer, and it is difficult to guarantee wafer wrinkling over a long period of time.

  Patent Document 2 proposes a lift pin including a sheath made of SiC and a head of glassy carbon embedded in the sheath. Here, in order to fit the head into the sheath, the inset may be broken due to the difference in thermal expansion due to the difference in the material of the head and sheath due to the high heat treatment at the time of the epitaxial growth process. is there. Furthermore, the problem of dust generation when sliding around the through hole of the susceptor as the lift pin moves up and down is not solved.

  Patent Document 3 proposes lift pins for use in a plasma CVD apparatus, in which the support portion is made of a material having a surface hardness lower than that of the wafer in order to suppress scratch defects of the wafer due to the support portion of the wafer. The lift pins are applied to a plasma CVD apparatus which is grown at low temperature, and the main body is anodized aluminum, aluminum oxide, titanium or titanium nitride, but these materials are susceptors (SiC made of epitaxial growth apparatus) ) Softer. For this reason, dust generation can not be avoided when sliding around the through hole of the susceptor as the lift pin moves up and down, which is problematic for application to an epitaxial growth apparatus. In addition, since the thermal conductivity of the main body is lower than that of the susceptor material (SiC), the temperature is lowered at the position where the lift pins are located, the temperature distribution in the wafer surface is largely broken, and the thickness distribution of the formed epitaxial layer is deteriorated. It is expected to do. Furthermore, in the configuration in which the support is bonded to the main body by thermocompression bonding, the side peripheral surface of the support is also lower in hardness than the wafer, so that dusting when sliding with the susceptor becomes more noticeable.

JP 2011-505691 Publication JP 2003-142407 A Japanese Patent Application Publication No. 2011-519393

  Therefore, it is an object of the present invention to prevent the occurrence of the sticking of the back surface of the silicon wafer by the lift pins and to suppress the dust generation due to the lift pins sliding against the wall surface around the through hole of the susceptor. It is to give to the lift pin.

  The inventors of the present invention have intensively studied the solution to the above problems, and when the base material of the lift pin is SiC, the contact surface of the pin head with the silicon wafer is a coating layer of fine ceramic. And, it has been found that it is effective to control the surface roughness of the pin straight body sliding with the susceptor, and the present invention has been accomplished.

That is, the gist configuration of the present invention is as follows.
(1) The inside of the through hole of the susceptor installed in the epitaxial vapor phase growth apparatus is movably inserted in the penetrating direction, and the silicon wafer is advanced and retracted with respect to the susceptor while supporting the silicon wafer mounted on the susceptor Lift pins that
The head portion coming into contact with the silicon wafer and the straight body portion inserted into the through hole, the head portion and the straight body portion being made of a base material having a surface hardness lower than the surface hardness of the silicon wafer, The lift pin which is a coating layer which has the surface hardness higher than the surface hardness of the wall surface which divides the said through-hole, and the surrounding surface of the said straight body part.

(2) The lift pin according to (1), wherein the covering layer is diamond like carbon.

(3) The lift pin according to (1) or (2), wherein the covering layer has a surface roughness of 0.2 μm or less in arithmetic average roughness.

(4) The lift pin according to any one of (1) to (3), wherein the substrate is any of glassy carbon, aluminum nitride, forsterite, cordierite, yttria and steatite.

(5) The lift pin according to any one of (1) to (4), wherein the thickness of the covering layer is 0.1 to 200 μm.

(6) An epitaxial growth apparatus having the lift pin according to any one of (1) to (5).

(7) A method of manufacturing an epitaxial wafer, wherein an epitaxial film is grown on the wafer using the epitaxial growth apparatus described in (6).

  By applying the lift pin of the present invention to an epitaxial vapor phase growth apparatus, it is possible to suppress the occurrence of the sticking of the back surface of the silicon wafer by the lift pin and the dust generation accompanying the elevation of the lift pin. Therefore, by performing epitaxial growth in the epitaxial vapor phase growth apparatus using the lift pins of the present invention, it becomes possible to manufacture a high quality epitaxial wafer with less wafer back surface wrinkle and less particle adhesion.

It is sectional drawing of an epitaxial growth apparatus. It is sectional drawing which shows the surroundings of the through-hole of the susceptor in epitaxial growth apparatus. FIG. 5 is a partial cross-sectional view showing a lift pin according to the present invention.

Hereinafter, lift pins of the present invention will be described in detail with reference to the drawings.
FIG. 8 is a view showing a lift pin according to the present invention, which has a rod-like straight body portion 50 inserted into the through hole 40 of the susceptor 4 shown in FIG. 7 and a diameter larger than the straight body portion 50 and the through hole 40. And a head 51. The shape of the lift pin is not limited as long as the lift pin has a head directly supporting a silicon wafer at the tip of a rod-like straight body, and thus is not limited to the illustrated shape.

Here, the straight body portion 50 and the head portion 51 are made of a base material having a surface hardness lower than the surface hardness of the silicon wafer W, and the circumferential surface of the straight body portion is the surface of the wall surface defining the through hole. It is necessary that the covering layer 52 has a surface hardness higher than the hardness.
That is, the lift pins are made of a substrate having a surface hardness lower than that of the silicon wafer W because the contact surface of the head portion 51 with the silicon wafer W is the substrate itself. In order to prevent this, it is necessary for the base material that constitutes the contact surface to have a surface hardness lower than the surface hardness of the silicon wafer W.

  That is, the surface hardness of this base material is less than the surface hardness of silicon wafer: 1081 Hv. The lift pins are required to have a strength that can endure repeated contact with the silicon wafer in the epitaxial growth apparatus, so it is preferable to secure a surface hardness of 400 HV or more.

  For the substrate, for example, glassy carbon, aluminum nitride, forsterite, cordierite, yttria and steatite are suitable. Because these materials have heat resistance to withstand use in epitaxial growth equipment (maximum temperature of about 1200 ° C.), they are also resistant to HCl used as etching gas, and furthermore, they are epitaxial. It is because the element which forms an active level in a wafer is not contained.

Incidentally, the surface hardness of the above-mentioned material is as follows. Both are less than the surface hardness of 1081 HV of a silicon wafer.
· Glassy carbon (GC): 440 HV
・ Aluminum nitride: 1060 HV
Forsterite: 744 HV
-Cordierite: 734 HV
・ Yttria: 612 HV
Steatite: 591 HV

  Among them, glassy carbon is well suited to the covering layer 52 because it is easy to obtain uniform heat uniformity within the surface of a silicon wafer due to the construction of the epitaxial growth apparatus.

  Next, the circumferential surface of the straight body portion 50 is made to be a coating layer 52 having a surface hardness higher than the surface hardness of the wall surface which divides the through hole 40. It is effective to control dust generation at the time of For example, when the susceptor 4 is made of SiC, the coating layer 52 has a surface hardness higher than the surface hardness: 2300 HV. In this case, diamond like carbon (DLC) having a surface hardness of 3000 HV or more is suitable. This is because when the covering layer 52 is formed by the ionized deposition method, a dense film can be obtained, and the straight body 50 can slide against the wall surface defining the through hole 40 under low friction. is there.

  Furthermore, the covering layer 52 preferably has a surface roughness of 0.2 μm or less in arithmetic mean roughness. This is because the resistance when the straight body portion 50 slides around the through hole 40 becomes smaller as the lift pin 5 moves up and down as described above, and the abrading area with the wall surface defining the through hole 40 decreases. This is because dust generation is suppressed and it becomes possible to manufacture an epitaxial wafer without the influence of particle adhesion.

  The regulation of the surface roughness of the coating layer 52 means that the surface roughness of at least a region of the coating layer 52 sliding around the through holes 40 should be 0.2 μm Ra or less. The surface roughness may be 0.2 μm Ra or less. In the present invention, "surface roughness" means arithmetic mean roughness Ra defined in JIS B 0601 (2001).

  The covering layer 52 is preferably formed by a chemical vapor deposition method (CVD method). This is because the desired surface roughness can be easily obtained, and a coating layer excellent in adhesion and uniformity can be formed.

  The covering layer 52 is preferably formed to a thickness of 0.1 to 200 μm. That is, if the thickness is less than 0.1 μm, it is difficult to sufficiently exhibit the hardness of the material in the coating layer, while if it exceeds 200 μm, the adhesion of the coating layer is reduced to cause peeling from the substrate. .

  Although the covering layer 52 is formed on the peripheral surface of the straight body portion 50 in the illustrated example, the covering layer is provided on the side peripheral surface and the lower surface of the head 51, that is, the surface other than the contact surface with the silicon wafer W. May be This form is effective for suppressing dust generation due to the sliding between the head 51 and the susceptor 4.

Hereinafter, examples of the present invention will be described.
Various lift pins having the specifications shown in Table 1 were applied to the epitaxial chemical vapor deposition apparatus 1 shown in FIG. 1, and an epitaxial wafer was manufactured according to the above-described procedure.
Here, the susceptor 1 used was a carbon substrate coated with SiC. In addition, as a substrate of the epitaxial wafer, a silicon wafer W having a diameter of 300 mm and doped with boron was used.
In the manufacture of an epitaxial wafer, first, trichlorosilane gas as a source gas was supplied at a temperature of 1150 ° C., and a silicon coat was applied to the surface of the susceptor 1. Next, the silicon wafer W was introduced into the vapor phase growth apparatus 2 and mounted on the susceptor 4 using lift pins. Subsequently, hydrogen gas was supplied at 1150 ° C. and hydrogen baking was performed, and then an epitaxial silicon film was grown to 4 μm at 1150 ° C. to obtain an epitaxial silicon wafer. Here, trichlorosilane gas was used as a source gas, diborane gas was used as a dopant gas, and hydrogen gas was used as a carrier gas.

  Various lift pins were applied to produce the above epitaxial wafer. With respect to the epitaxial wafer thus obtained, the quality of the front and back surfaces and the adhesion of the coating layer of the pin head were evaluated. In addition, each evaluation method is as follows,

[Surface quality]
The density of 0.25 μmL PD generation was measured for the obtained epitaxial wafer. That is, with respect to the manufactured epitaxial wafer, a surface defect (LPD: Light Point Defect) of a size of 0.25 μm or more observed on the surface of the epitaxial layer using a wafer surface inspection apparatus (SP-2 manufactured by KEL Atencor Co., Ltd.) Was evaluated. Based on this measurement result, it is possible to evaluate the generation state of particles due to dust generation.

[Back side quality]
For the obtained epitaxial wafer, scattering of the laser reflection setting value or more in the lift pin contact area is performed using a wafer surface inspection device (SP-2 manufactured by KEL Aitcor Co., Ltd.) as the pin mark strength of the lift pin contact portion. The area of the area having the strength was measured to evaluate wrinkles caused by lift pins on the back surface of the wafer.

In addition, when the material of the coating layer was changed to aluminum nitride, forsterite, cordierite, steatite and the same test was conducted, No. 1 in Table 1 was obtained. Similar results were obtained with the 4 to 6 Y ₂ O ₃ coated layer.

Reference Signs List 1 epitaxial growth apparatus 2 epitaxial film forming chamber 4 susceptor 5 lift pin 6 lift shaft W silicon wafer 11 upper dome 12 lower dome 13 dome mounting body 40 susceptor rotating portion 41 susceptor support shaft 42 through hole 50 head 51 straight body portion 52 covering layer

Claims (3)

A lift pin is movably inserted in the penetration direction in the through hole of the susceptor installed in the epitaxial vapor phase growth apparatus, and supports the silicon wafer mounted on the susceptor while advancing and retracting the silicon wafer with respect to the susceptor There,
The head portion coming into contact with the silicon wafer and the straight body portion inserted into the through hole, the head portion and the straight body portion being made of a base material having a surface hardness lower than the surface hardness of the silicon wafer, the circumferential surface of the straight body portion, Ri coating layer der having a surface hardness higher than surface hardness of the walls partitioning the through-holes,
The substrate is any of glassy carbon, aluminum nitride, forsterite, cordierite, yttria and steatite,
The coating layer is a diamond-like carbon has a surface roughness of not more than 0.2μm in arithmetic average roughness, thickness of Ru 0.1~200μm der lift pins. An epitaxial growth apparatus having the lift pin according to claim 1 . A method of manufacturing an epitaxial wafer, wherein an epitaxial film is grown on the wafer using the epitaxial growth apparatus according to claim 2 .

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