JP6520050B2 - 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 JP 2011-519393 gazette

  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) A lift pin which is movably inserted in the penetration direction in the through hole of the susceptor installed in the epitaxial growth apparatus and supports the silicon wafer mounted on the susceptor while advancing and retracting the silicon wafer with respect to the susceptor There,
And a straight body portion inserted into the through hole, the head portion and the straight body portion being made of a base material of SiC, and at least the straight body portion having an arithmetic mean roughness A lift pin having a surface roughness of 0.2 μm or less, and a contact surface of the head with the silicon wafer being a coating layer of fine ceramic having a surface hardness lower than that of the silicon wafer.

(2) The lift pin according to (1), wherein the covering layer is any of aluminum nitride, forsterite, cordierite, yttria and steatite.

(3) The lift pin according to (1) or (2), wherein the covering layer has a thickness of 0.1 to 200 μm.

(4) The epitaxial growth apparatus which has a lift pin in any one of said (1) to (3).

(5) A method of manufacturing an epitaxial wafer, wherein an epitaxial film is grown on a silicon wafer using the epitaxial growth apparatus described in (4).

  By applying the lift pin of the present invention to an epitaxial 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 growth apparatus using the lift pins of the present invention, it is 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. 3 is a view showing the lift pin 5 according to the present invention, and the rod-like straight body portion 50 inserted into the through hole 42 of the susceptor 4 shown in FIG. And the head 51 of the The shape of the lift pin 5 is not limited as long as the lift pin 5 has a head directly supporting a silicon wafer at the tip of a rod-like straight body, and therefore, the shape is not limited to the illustrated shape.

Here, the straight body 50 and the head 51 are made of a base material of SiC, and at least the straight body 50 has a surface roughness of 0.2 μm or less in arithmetic average roughness, and the silicon wafer W of the head 51 is It is necessary that the contact surface thereof be the covering layer 52 of fine ceramic having a surface hardness lower than the surface hardness of the silicon wafer W.
That is, to make the base material of the lift pin 5 be SiC, first, it is satisfied to have a surface hardness equivalent to that of the susceptor 4 and to have good adhesion with a coating layer of fine ceramic described later. It is.

  In particular, when the base material of the lift pins 5 is SiC, it is important that the surface roughness of the straight body 50 sliding around the through holes 40 of the susceptor 4 be 0.2 μm or less in arithmetic average roughness. is there. This is because, by setting the surface roughness to 0.2 μm Ra or less, dusting is suppressed when the straight barrel 50 slides around the through hole 40 as the lift pin 5 moves up and down. It is possible to manufacture an epitaxial wafer free from adhesion effects.

  Note that regulating the surface roughness of the straight body portion 50 means that the surface roughness of at least a region of the straight body portion 50 that slides around the through hole 40 should be 0.2 μm Ra or less, and the straight body portion The surface roughness of the entire 50 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).

In addition, the reason why the coating layer 52 is made of fine ceramic is that the coating layer applied to the SiC substrate has higher adhesion than, for example, glassy carbon.
As the fine ceramics, any of aluminum nitride, forsterite, cordierite, yttria and steatite is suitable. Each of these ceramics has a surface hardness lower than the surface hardness of the silicon wafer W, and is compatible with the epitaxial vapor phase growth atmosphere. That is, although the epitaxial vapor phase growth atmosphere uses HCl as an etching gas at a maximum temperature of 1200 ° C., the ceramic is resistant to this atmosphere.

Incidentally, the surface hardness of the above-mentioned ceramics is as follows. Both are less than the surface hardness of 1081 HV of a silicon wafer.
・ Aluminum nitride: 1060 HV
Forsterite: 744 HV
-Cordierite: 734 HV
・ Yttria: 612 HV
Steatite: 591 HV

  Among them, yttria is a material suitable for plasma CVD processing that can obtain high adhesion, and has a surface hardness suitable for preventing the silicon wafer from being scratched, so it is well compatible with the covering layer 52.

  In addition, it is necessary to limit and provide the coating layer 52 in the contact surface with the silicon wafer W of the head 51, as shown in FIG. That is, when the covering layer 52 is provided on the side peripheral surface or the lower surface of the head portion 51 which may come in contact with the periphery of the through hole 40 of the susceptor 4, it contacts the susceptor 4 harder than the covering layer 52 to cause dust generation. It is necessary to prevent this because

  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. .

Hereinafter, examples of the present invention will be described.
Various lift pins having specifications shown in Table 1 were applied to the epitaxial growth 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 the epitaxial wafer, first, trichlorosilane gas which is a source gas was supplied at a temperature of 1150 ° C., and the surface of the susceptor 1 was coated with silicon. Next, the silicon wafer W was introduced into the 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.

[Cover layer adhesion]
The ratio between the coating layer formation amount on the lift pin head before attaching to the susceptor and the coating layer remaining amount of the lift pin head after performing the contact support operation on the wafer backside actually attached to the susceptor repeatedly 100 times It was used as a sex indicator. The thickness of the coating layer is measured by FIB processing using a Ga ion beam after cutting the covering layer in the thickness direction of the lift pin head in contact with the back surface of the wafer, and then cutting the cut section with a scanning electron microscope (SEM: Scanning Electron Microscope) The thickness of the coating layer was measured by observation and evaluation using

  In addition, when the material of the coating layer was changed to forsterite, cordierite, steatite and the same test was conducted, No. 1 in Table 1 was obtained. Similar results were obtained with the 4 and 5 AlN coatings.

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 which is movably inserted in the through direction in a through hole of a susceptor installed in an epitaxial growth apparatus and supports the silicon wafer mounted on the susceptor while advancing and retracting the silicon wafer relative to the susceptor.
And a straight body portion inserted into the through hole, the head portion and the straight body portion being made of a base material of SiC, and at least the straight body portion having an arithmetic mean roughness in having a surface roughness of less than 0.2 [mu] m, the contact surface between the silicon wafer of the head, Ri coating layer der of fine ceramics having a surface hardness lower than the surface hardness of the silicon wafer,
The covering layer is any of aluminum nitride, forsterite, cordierite, yttria and steatite,
The coating layer, that have a thickness of 0.1~200μm 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 a silicon wafer using the epitaxial growth apparatus according to claim 2 .

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