JP2016163007A - Cleaning method and dummy wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the cleaning of a holder for holding a wafer sufficiently.SOLUTION: A cleaning method includes a step of carrying a dummy wafer into a reaction chamber where a holder having a plurality of supports for supporting the wafer from below formed on the upper surface thereof is placed, and forming an epitaxial film on the wafer surface while holding the wafer on the holder, a step of mounting the dummy wafer so as to be in non-contact with at least a part of the upper surface of the support, and a step of supplying an etching gas into the reaction chamber, and cleaning the holder. Consequently, the reaction by-products adhering to the supports in contact with the wafer and the vicinity thereof can be removed effectively, at the time of etching.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a cleaning method and a dummy wafer.

  In recent years, along with demands for lowering the cost and higher performance of semiconductor devices, there has been a demand for higher quality such as improvement in film thickness uniformity as well as high productivity in wafer film forming processes. In order to satisfy such a requirement, a single wafer type vapor phase growth apparatus is used. By using a single-wafer type vapor phase growth apparatus, for example, a process gas is supplied into the reaction chamber while rotating the wafer at a high speed of 900 rpm or more in the reaction chamber, and the wafer is heated from the back side using a heater. Thus, an epitaxial film can be grown on a wafer such as Si.

  When an epitaxial film is grown in the reaction chamber, reaction byproducts generated by the chemical reaction of the process gas are deposited not only on the wafer but also on the surface of a holder that holds the wafer. Since the deposited reaction by-product becomes, for example, particles, cleaning is periodically performed to remove the reaction by-product attached to the holder.

  At this time, the holder can be etched to perform cleaning without releasing the reaction chamber. At that time, in order to protect a heater element or the like located below the holder, a dummy wafer having the same shape as the wafer is set in the holder and the holder is cleaned (see, for example, Patent Document 1).

JP2013-51350A

  By setting a dummy wafer when cleaning, the heater element and the like can be protected from the etching gas. However, when a dummy wafer is set in the holder, the etching gas may not be sufficiently distributed in the vicinity of the portion where the holder and the dummy wafer are in contact. In this case, the cleaning of the portion in contact with the wafer and the vicinity thereof may be insufficient.

  The present invention has been made under the circumstances described above, and an object thereof is to sufficiently clean a holder for holding a wafer to be formed.

  In the cleaning method of the present invention, a dummy wafer is disposed in a reaction chamber in which a holder having a plurality of support portions formed on the upper surface for supporting the wafer from below is disposed, and the wafer is held on the holder to form an epitaxial film on the wafer surface. , A step of placing a dummy wafer so as not to be in contact with at least a part of the upper surface of the support portion, and a step of supplying an etching gas into the reaction chamber and cleaning the holder.

  A dummy wafer according to a first aspect of the present invention is a dummy wafer placed on a holder when cleaning a reaction by-product deposited on a holder having a plurality of support portions that support the wafer from below. The dummy wafer has a plurality of cutouts that are not in contact with at least a part of the upper surfaces of the plurality of support portions at positions corresponding to the plurality of support portions when placed on the holder.

  A dummy wafer according to a second aspect of the present invention is a dummy wafer placed on a holder when cleaning a reaction byproduct deposited on a holder having a plurality of support portions that support the wafer from below. Then, the dummy wafer has a plurality of convex contact areas in contact with a part of the upper surfaces of the plurality of support portions at positions corresponding to the plurality of support portions when being placed on the holder.

  According to the present invention, since the region where the holder support portion and the dummy wafer are not in contact with each other is formed, the support portion formed on the holder can be sufficiently cleaned.

It is a figure which shows the structure of the epitaxial vapor phase growth apparatus which concerns on this embodiment. It is a perspective view of a ring and a wafer holder. It is a perspective view which expands and shows a part of wafer holder. It is a perspective view which expands and shows a part of wafer holder. 1 is a plan view of a dummy wafer according to a first embodiment. It is a perspective view which shows the dummy wafer mounted in the wafer holder. It is a perspective view which expands and shows a part of wafer holder. It is a top view of the dummy wafer which concerns on 2nd Embodiment. It is a perspective view which expands and shows a part of dummy wafer. It is sectional drawing which shows the dummy wafer mounted in the wafer holder. It is a top view of the dummy wafer which concerns on 3rd Embodiment. It is a perspective view which expands and shows a part of dummy wafer. It is a fragmentary top view which shows the dummy wafer mounted in the wafer holder. It is sectional drawing which shows the dummy wafer mounted in the wafer holder.

<< First Embodiment >>
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. In the description, an XYZ coordinate system including an X axis, a Y axis, and a Z axis orthogonal to each other is used as appropriate.

  FIG. 1 is a cross-sectional view of an epitaxial vapor phase growth apparatus 10 according to this embodiment. The epitaxial vapor deposition apparatus 10 is an apparatus for forming an epitaxial film on the surface of a wafer by supplying a process gas to the wafer W accommodated in the reaction chamber 11 and heating it while rotating it. As the wafer W, for example, a single crystal silicon wafer having a diameter of 200 mm can be used.

  The epitaxial vapor phase growth apparatus 10 includes a reaction chamber 11, a gas supply mechanism 12, a gas discharge mechanism 13, a rectifying plate 14, a heater element 15, a rotation mechanism 20, a wafer holder 30, and a rotation control device 24.

The gas supply mechanism 12 is connected to a gas supply port 12 a provided in the upper part of the reaction chamber 11. For example, when film formation is performed on the wafer from the gas supply mechanism 12, a process gas obtained by diluting dichlorosilane (SiH ₂ Cl ₂ ) with hydrogen (H ₂ ) to a predetermined concentration is supplied from the gas supply port 12a to the reaction chamber 11. Supply inside. Further, when the gas supply mechanism 12 removes reaction by-products deposited on, for example, the wafer holder 30 installed in the reaction chamber 11 by etching, hydrogen chloride (HCl) is predetermined with hydrogen (H ₂ ). An etching gas diluted to a concentration is supplied into the reaction chamber 11 from the gas supply port 12a.

  The rectifying plate 14 is installed inside the reaction chamber 11. When the gas supplied from the gas supply mechanism 12 passes through the rectifying plate 14, the gas is supplied onto the wafer W in a rectified state.

  The gas discharge mechanism 13 is connected to a gas discharge port 13 a provided in the lower part of the reaction chamber 11. The gas discharge mechanism 13 discharges, from the reaction chamber 11, a gas containing a reaction byproduct generated by the reaction of the process gas and the etching gas in the reaction chamber 11, and a surplus of the process gas and the etching gas.

  The rotation mechanism 20 includes a rotation shaft 21, a base plate 22 fixed to the upper end portion of the rotation shaft 21, a ring 23 fixed to the upper surface of the base plate 22, and a rotation control device 24 that rotates the rotation shaft. Yes.

  The rotating shaft 21 is a cylindrical member whose longitudinal direction is the Z-axis direction. The rotating shaft 21 is supported so as to be rotatable about a vertical axis (Z axis) in a state where the upper end portion is inserted into the reaction chamber 11 from below the reaction chamber 11.

  The base plate 22 is a circular plate member. A circular opening having an inner diameter equal to the inner diameter of the rotary shaft 21 is formed at the center of the base plate 22. The base plate 22 is fixed to the upper end of the rotary shaft 21 with the center thereof coinciding with the rotation center of the rotary shaft 21.

  FIG. 2 is a perspective view of the ring 23 and the wafer holder 30 attached to the ring 23. As shown in FIG. 2, the ring 23 is a cylindrical member, and a heater element 15 having a predetermined heater pattern is provided therein. The ring 23 is fixed to the upper surface of the base plate 22 with its center coinciding with the rotation center of the rotary shaft 21.

  The heater element 15 is a heating element made of, for example, silicon carbide. As shown in FIG. 2, the heater element 15 is patterned so that the heater circuit meanders.

  The heater element 15 is supported inside the ring 23 so as to be substantially parallel to the wafer W held by the wafer holder 30. As shown in FIG. 1, the heater element 15 is connected to an electrode bar 19 that is drawn to the outside via a rotating shaft 21. The heater element 15 generates heat when electric power is supplied from an external power source through the electrode rod 19. Thereby, the wafer W located above the heater element 15 is heated.

  The rotation control device 24 includes a motor, an inverter, and the like. The rotation control device 24 rotates the rotating shaft 21 at a predetermined number of rotations. Thereby, the base plate 22, the ring 23, and the wafer holder 30 are rotated around the vertical axis together with the rotating shaft 21. As a result, the wafer W held by the wafer holder 30 rotates.

  The wafer holder 30 is an annular member fixed to the upper end of the ring 23. FIG. 3A shows a part of the wafer holder 30. As shown in FIG. 2 and FIG. 3A, the wafer holder 30 has an L-shaped cross section, and has an outermost frame portion 31 and an extending portion 32 provided inside the frame portion 31. The inner diameter of the frame portion 31 is slightly larger than the outer diameter of the wafer W, and the inner diameter of the extending portion 32 is smaller than the outer diameter of the wafer W. A projecting portion 31 a that projects inward is formed on the inner wall surface of the frame portion 31.

  The upper surface of the extending portion 32 is flat. As shown in FIG. 2, eight support portions 33 shaped in a rectangular shape are provided on the upper surface of the extending portion 32 along the inner wall surface of the frame portion 31 at equal intervals. As shown in FIG. 3A, the extending portion 32 has a width D1 of about 1.5 mm, a height D2 of about 0.1 mm, and a depth D3 of about 4 mm. The upper surfaces of the eight extending portions 32 are located in the same plane parallel to the horizontal plane. A plurality of protruding portions 31 a can be provided on the inner wall surface of the frame portion 31 to prevent the wafer W from sticking. The shape of the protrusion 31a is not particularly limited as long as it can make point contact with the wafer. For example, the protrusion 31a may have a triangular shape as shown in FIG. 2, or a semicircular shape as shown in FIG. 3B. There may be. Moreover, as shown in FIG. 3B, it may be formed on the extended portion 32, or may be formed at a position different from the extended portion 32 as shown in FIG. 2.

  Using such an epitaxial vapor phase growth apparatus 10, an epitaxial film is formed on the wafer W as follows. First, the wafer W is loaded into the reaction chamber 11 and placed on the wafer holder 30. The rotation control device 24 is driven to rotate the wafer W at, for example, about 900 rpm, apply a predetermined voltage to the heater element 15 to heat the wafer W to about 1100 ° C., and the gas supply mechanism 12 A process gas containing a silicon source gas such as dichlorosilane is supplied onto the wafer W. At this time, the gas discharge mechanism 13 discharges a gas containing excess process gas and reaction by-products in the reaction chamber 11 and controls the reaction chamber to a predetermined pressure. In this way, a silicon epitaxial film is formed on the surface of the wafer W.

  As described above, when the epitaxial vapor phase growth apparatus 10 is used to form a film on the wafer W, reaction by-products adhere to the wafer holder 30 or the like that holds the wafer W. Therefore, it is necessary to periodically perform cleaning to remove reaction by-products. In order to release the reaction chamber 11, it is necessary to lower the temperature in the reaction chamber 11 to room temperature. However, the wafer holder 30 can be cleaned without releasing the reaction chamber 11 by performing an etching process on the wafer holder 30 by supplying an etching gas to the reaction chamber 11. When performing this cleaning, the dummy wafer DW 1 is placed on the wafer holder 30 instead of the wafer W.

  FIG. 4 is a plan view of the dummy wafer DW1. As the dummy wafer DW1, for example, a wafer formed by sintering silicon carbide (SiC) is used. The dummy wafer DW1 has a thickness of 1 mm and a diameter equal to that of the wafer W, for example, 200 mm. As shown in FIG. 4, eight notches 92 are formed in the dummy wafer DW1 at equal intervals along the outer edge of the dummy wafer DW1. The notch 92 has a semicircular shape with a radius of 4 mm, and is formed from the lower surface of the dummy wafer DW1 to the upper surface. These notches 92 can be formed using, for example, a circular end mill.

  As shown in FIG. 5, the dummy wafer DW1 is placed on the wafer holder 30 so that the position of the notch 92 and the position of the support portion 33 of the wafer holder 30 coincide. Therefore, as shown in FIG. 6, the support portion 33 of the wafer holder 30 is located in the notch 92 of the dummy wafer DW1, and the dummy wafer DW1 is supported on the upper surface of the extending portion 32 provided in the wafer holder 30. It becomes a state.

  In the etching process, when the dummy wafer DW1 is loaded into the reaction chamber 11 and placed on the wafer holder 30, the rotation control device 24 is driven to rotate the wafer W at a predetermined number of rotations, and a predetermined voltage is applied to the heater element 15. And the temperature of the wafer holder 30 is raised to about 1130 to 1150 ° C., for example, and the etching gas is supplied into the reaction chamber 11 by the gas supply mechanism 12. At this time, the gas discharge mechanism 13 discharges a gas containing excess process gas and reaction by-products in the reaction chamber 11 and controls the reaction chamber to a predetermined pressure. As a result, as shown by an arrow a1 in FIG. 5, the etching gas is supplied to the upper surface and outer edge of the support portion 33 of the wafer holder 30, and adheres to the support portion 33 exposed from the notch 92 of the dummy wafer DW1 and the periphery thereof Cleaning of the reaction by-product is performed.

  As described above, in the present embodiment, as shown in FIG. 5, when the dummy wafer DW1 is placed on the wafer holder 30, the support portion 33 of the wafer holder 30 is exposed from the notch 92 of the dummy wafer DW1. For this reason, the reaction by-product adhering to the support part 33 which contact | connects the wafer W, or its vicinity can be removed effectively. Thereby, it is possible to avoid adhesion of reaction by-products to the wafer W where vapor phase growth is performed.

  In the present embodiment, when the dummy wafer DW 1 is placed on the wafer holder 30, the dummy wafer DW 1 is supported on the upper surface of the extending portion 32 of the wafer holder 30. As a result, the ring 23 is almost closed by the dummy wafer DW1. For this reason, the amount of the etching gas that penetrates into the ring 23 can be reduced. Therefore, damage to the heater element 15 and the like disposed inside the ring 23 due to the etching gas can be suppressed.

  In the present embodiment, reaction by-products can be effectively removed from the wafer holder 30. Therefore, the product yield can be improved. In addition, the wafer holder 30 can be used for a long time. Therefore, the running cost of the epitaxial vapor phase growth apparatus 10 can be suppressed.

<< Second Embodiment >>
Next, the dummy wafer DW2 according to the second embodiment will be described. About the same or equivalent structure as 1st Embodiment, while using the same code | symbol, the description is abbreviate | omitted.

  FIG. 7 is a plan view showing a dummy wafer DW2 according to the second embodiment. This dummy wafer DW2 is different from the dummy wafer DW1 according to the first embodiment in that a notch 93 is formed on the lower surface side of the dummy wafer DW2.

  As shown in FIG. 7, eight notches 93 are formed at equal intervals along the outer edge of the dummy wafer DW2 on the lower surface (the surface on the −Z side) of the dummy wafer DW2. The notch 93 has a semicircular shape with a radius of 4 mm.

  FIG. 8 is an enlarged perspective view showing the notch 93 of the dummy wafer DW2. As shown in FIG. 8, the notch 93 is formed from the lower surface side to the middle of the dummy wafer DW2, and the depth D4 is about 0.5 mm.

  FIG. 9 is a cross-sectional view showing a state in which the dummy wafer DW2 is placed on the wafer holder 30. As shown in FIG. As shown in FIG. 9, when the dummy wafer DW <b> 2 is placed on the wafer holder 30, the support portion 33 of the wafer holder 30 is accommodated without interfering with the inside of the notch 93. The dummy wafer DW2 is supported on the upper surface of the extending portion 32 of the wafer holder 30. The notch 93 is formed from the outer edge of the dummy wafer DW2 toward the center of the dummy wafer DW2. For this reason, the internal space of the notch 93 communicates with the space on the upper surface side of the dummy wafer DW2.

  When the etching process is performed in a state where the dummy wafer DW2 is placed on the wafer holder 30, as shown by an arrow a2 in FIG. 9, an etching gas flows into the notch 93 from between the outer edge of the dummy wafer DW2 and the wafer holder 30. And flows through the inside of the notch 93 as indicated by the broken line. Thereby, the reaction by-product adhering to the support part 33 formed in the wafer holder 30 and its vicinity is removed.

  As described above, in this embodiment, as shown in FIG. 9, when the dummy wafer DW2 is placed on the wafer holder 30, the internal space of the notch 93 of the dummy wafer DW2 is the same as the space on the upper surface side of the dummy wafer DW2. As a result, the etching gas flows around the support portion 33 as indicated by a broken line. Therefore, the support portion 33 formed on the wafer holder 30 can be cleaned while the upper portion of the ring 23 is closed with the dummy wafer DW2.

  Therefore, while protecting the heater element 15 and the like disposed inside the ring 23, the reaction by-product adhering to the support portion 33 in contact with the wafer W and the vicinity thereof can be effectively removed.

<< Third Embodiment >>
Next, the dummy wafer DW3 according to the third embodiment will be described. About the same or equivalent structure as 1st Embodiment, while using the same code | symbol, the description is abbreviate | omitted.

  FIG. 10 is a plan view showing a dummy wafer DW3 according to the third embodiment. The dummy wafer DW3 is different from the dummy wafers DW1 and DW2 according to the above-described embodiment in that a notch is not formed at a position corresponding to the support portion 33 of the wafer holder 30.

  As shown in FIG. 10, eight concave portions 95 are formed at equal intervals along the outer periphery of the dummy wafer DW2 on the lower surface (the surface on the −Z side) of the dummy wafer DW3 via the convex contact region 94. ing.

  FIG. 11 is an enlarged perspective view showing the concave portion 95 of the dummy wafer DW3. As shown in FIG. 11, the recess 95 is formed from the lower surface side to the middle of the dummy wafer DW3, and the depth D5 is about 0.5 mm. Each recess 95 can be formed using a circular end mill. Further, the width D6 of the convex contact region 94 is smaller than the width D1 of the support portion 33 provided in the wafer holder 30 shown in FIG. 3A.

  FIG. 12 is a partial top view of the dummy wafer DW3 placed on the wafer holder 30, and FIG. 13 is a cross-sectional view taken along the line A-A 'of FIG. As shown in FIGS. 12 and 13, when the dummy wafer DW <b> 3 is placed on the wafer holder 30, the convex contact area 94 of the dummy wafer DW <b> 3 is supported by the support portion 33 of the wafer holder 30.

  The width D6 of the convex contact region 94 is smaller than the width D1 of the support portion 33 provided in the wafer holder 30. For this reason, as shown in FIGS. 12 and 13, the outer edge portion of the support portion 33 does not interfere with the convex contact region 94. The recess 95 is formed from the outer edge of the dummy wafer DW3 toward the inside of the dummy wafer DW3. For this reason, the internal space of the recessed part 95 is in a state communicating with the space on the upper surface side of the dummy wafer DW3.

  When the etching process is performed in a state where the dummy wafer DW3 is placed on the wafer holder 30, as shown by an arrow a3 in FIGS. 12 and 13, an etching gas flows from between the dummy wafer DW3 and the wafer holder 30 to the wafer holder 30. It enters a space defined by the upper surface of the extending portion 32 and the inner wall surface of the recess 95. Then, the etching gas flows through the space as shown by the broken line in FIG. Thereby, the reaction by-product adhering to the support part 33 of the wafer holder 30 or its vicinity is removed.

  As described above, in the present embodiment, as shown in FIG. 12, when the dummy wafer DW3 is placed on the wafer holder 30, it is defined by the upper surface of the extending portion 32 of the wafer holder 30 and the inner wall surface of the recess 95. This space is communicated with the space on the upper surface side of the dummy wafer DW3. Further, the outer edge portion of the support portion 33 does not interfere with the convex contact region 94. Therefore, the outer edge of the support portion 33 formed on the wafer holder 30 can be cleaned while the upper portion of the ring 23 is closed with the dummy wafer DW2. Therefore, while protecting the heater element 15 arranged inside the ring 23, the reaction by-product attached to the outer edge of the support portion 33 in contact with the wafer W and the vicinity thereof can be effectively removed.

  According to the above embodiments, the wafer holder 30 can be effectively cleaned while protecting the heater element 15 and the like. For this reason, it is possible to stably form the epitaxial film on the wafer W with high productivity. As a result, the yield of the wafer is improved and the yield of the semiconductor device formed on the wafer can be improved. In particular, in a power semiconductor device such as a power MOSFET or IGBT, a thick film of 40 μm or more is formed in an N-type base region, a P-type base region, an insulating isolation region, and the like. In such a case, the dummy wafer according to the present embodiment can be effectively applied. By applying the dummy wafer according to the present embodiment to a vapor phase growth apparatus used for manufacturing these power semiconductor devices, a semiconductor device having good element characteristics can be obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited by the said embodiment. For example, in the above-described embodiment, a case has been described in which a process gas containing dichlorosilane (SiH ₂ Cl ₂ ) is supplied to the surface of a silicon single crystal wafer to form a silicon epitaxial film. For example, the dummy wafer according to the present embodiment can also be used for a vapor phase growth apparatus that forms an epitaxial film of a compound semiconductor, a polysilicon layer, or the like.

In this embodiment, a gas generated by diluting hydrogen chloride (HCl) with hydrogen (H ₂ ) is used as the etching gas. The etching gas is not limited to this, and for example, an etching gas mainly containing chlorine trifluoride (ClF ₃ ) may be used.

  In the present embodiment, the wafer W is a single crystal silicon wafer having a diameter of 200 mm. The size of the wafer W is not limited to this, and wafers of various sizes can be used.

  In the present embodiment, the holder cleaning method and the dummy wafer used for cleaning when the wafer W is supported by a support portion on an annular holder having an opening and vapor phase growth is performed have been described. However, the present invention is not limited to this, and the present invention can be applied even when vapor phase growth is performed by being supported by a support portion on a disc-shaped holder (susceptor) in which no opening is provided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Epitaxial vapor phase growth apparatus 11 Reaction chamber 12 Gas supply mechanism 12a Gas supply port 13 Gas discharge mechanism 13a Gas discharge port 14 Current plate 15 Heater element 19 Electrode rod 20 Rotation mechanism 21 Rotation shaft 22 Base plate 23 Ring 24 Rotation control device 30 Wafer holder 31 Frame portion 31a Projection portion 32 Extension portion 33 Support portion 92, 93 Notch 94 Convex contact area 95 Concavity DW1 to DW3 Dummy wafer W Wafer

Claims (5)

A step of carrying a dummy wafer into a reaction chamber in which a holder having a plurality of support portions formed on the upper surface for supporting the wafer from below is disposed, holding the wafer on the holder and forming an epitaxial film on the surface of the wafer; When,
Placing the dummy wafer in a non-contact manner with at least a portion of the upper surface of the support;
Supplying an etching gas into the reaction chamber and cleaning the holder;
Including a cleaning method. A dummy wafer placed on the holder when cleaning a reaction by-product deposited on a holder formed on the upper surface of a plurality of support portions for supporting the wafer from below,
The dummy wafer has a plurality of notches that are not in contact with at least a part of the upper surfaces of the plurality of support portions at positions corresponding to the plurality of support portions when placed on the holder. A dummy wafer.   The dummy wafer according to claim 2, wherein the notch is formed from an outer edge toward a central portion.   The dummy wafer according to claim 2, wherein the notch is formed at least on a lower surface side. A dummy wafer placed on the holder when cleaning a reaction by-product deposited on a holder formed on the upper surface of a plurality of support portions for supporting the wafer from below,
The dummy wafer has a plurality of convex contact areas in contact with a part of each upper surface of the plurality of support portions at positions corresponding to the plurality of support portions when placed on the holder. A dummy wafer characterized by

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