JP5569190B2 - Wafer charge auxiliary stand - Google Patents

Description

  The present invention relates to a wafer charge auxiliary table that is preferably used when a vertical boat on which wafers are set is transported and set in a vertical heat treatment furnace, and more particularly to a wafer position adjustment structure in a vertical boat. is there.

A PBS (Poly Back Seal) process is known as one of silicon wafer processing processes. The PBS process is a process of adding a gettering effect by exposing the back surface of a silicon wafer to a high-temperature monosilane (SiH ₄ ) gas atmosphere and forming a polysilicon film by thermal decomposition of SiH ₄ . In this PBS process, a vertical boat is used to set a large number of wafers in a vertical heat treatment furnace (see, for example, Patent Document 1). A large number of wafers are charged in this vertical boat, and the entire vertical boat is set in a vertical heat treatment furnace.

  In the PBS process, it is necessary to form a polysilicon film only on the back surface of the silicon wafer, so the back-to-back method is used in which the non-film-forming surfaces of the wafer are overlapped to form a film. Patent Document 2). That is, the two wafers are stacked and brought into close contact so that only one surface is exposed, and set in a vertical boat in this state. When a wafer is charged in the vertical boat, the vertical boat is placed in a horizontal position and charged using a wafer jig.

  When a wafer is charged in a horizontally placed vertical boat, the outer peripheral portion on the lower end side of the wafer is brought into contact with the vertical boat column by gravity. The vertical boat charged with wafers is set in the vertical heat treatment furnace, but even if the vertical boat is set upright to be set in the vertical heat treatment furnace, the outer periphery of the wafer is placed on the vertical boat column. It remains in contact. However, if the wafers are unevenly arranged in the vertical boat in an upright state and the outer peripheral portion of the wafer is in contact with the support of the vertical boat, the film formation on that portion becomes incomplete. Therefore, after the vertical boat is set in the vertical boat, the position of the wafer is adjusted after setting so that each wafer is in a non-contact state with the support.

JP 2002-217275 A JP-A-9-199428

  A problem with the polycoated wafer obtained through the PBS process is that it has a higher incidence of dent defects than a normal wafer that is not subjected to the PBS process. The defective dent is caused by foreign matter adhering to the back surface of the wafer when the wafer is mirror-polished. In one example, the size of the foreign matter is about 4 μm in height and about 1 μm in width, and grows to about 5 μm in height and about 4 μm in width after polycoating. If foreign matter is adhered during mirror polishing of the wafer, a protrusion is formed on the opposite surface. When polishing is performed in this state, a dent defect is formed on the polished surface. Since a wafer on which a dent defect is formed is a defective product and cannot be provided as a product, a countermeasure to bring the dent defect occurrence rate to zero as much as possible is required.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a wafer charge auxiliary table that can reduce the occurrence of dent defects in a polycoated wafer.

  As a result of intensive research on the cause of the dent defect in the PBS process, the inventor of the present application is made of polysilicon, which is the coating material of the vertical boat, and the dent defect is caused by the wafer and the vertical boat. It has been found that the occurrence of dent defects can be prevented if such rubbing is prevented, since many occur near the places where they rub against each other.

  The present invention is based on such technical knowledge, and the wafer charge auxiliary table according to the present invention is used for transporting a vertical boat charged with a wafer, and supports the vertical boat. A vertical boat that supports two or more of the outer periphery of the wafer in the vertical boat mounted horizontally on the support table, and supports the wafer in the vertical state, It is characterized by comprising a pair of support rods that ensure a non-contact state with the end face.

  According to the present invention, when a wafer is charged in the vertical boat, contact between the wafer and the support of the vertical boat can be prevented, and after the wafer is charged together with the vertical boat in the vertical heat treatment furnace. Wafer position adjustment work can be eliminated. Therefore, it is possible to prevent dust generation due to contact between the wafer and the support of the vertical boat, and finally, it is possible to reduce the occurrence rate of the dent defect of the polycoat wafer.

  “Supporting two or more points on the outer periphery of the wafer” means that the contact between the support bar and the wafer includes not only exact point contact but also line contact and surface contact. When supporting two points (including line support) on the outer periphery of the wafer using a pair of support rods, the wafer can be reliably supported while minimizing contact with the wafer. The number of support rods is not limited to two, but may be three or more, but at least two support rods are required to support two points on the outer periphery of the wafer.

  In the present invention, it is preferable that at least the surface of the support rod is made of quartz, resin or silicon carbide. According to this configuration, contamination of the wafer due to contact between the wafer and the support rod can be reliably prevented.

  The wafer charge auxiliary base according to the present invention preferably further includes a handle portion provided on the support base, and the handle portion is preferably provided on one end side in the longitudinal direction of the support base. According to this configuration, it is possible to easily carry and start up the wafer charge auxiliary base.

  The wafer charge auxiliary table according to the present invention preferably further includes a wheel provided on the other end side in the longitudinal direction of the support table. According to this configuration, it is possible to easily erect a vertical boat placed in a horizontal state, and it is possible to easily move the vertical boat into the vertical heat treatment furnace. Further, when the vertical boat is erected, the wafer and the vertical boat column do not come into contact with each other, so that dust generation due to friction between them can be prevented.

  According to the present invention, it is possible to charge a vertical boat with a wafer, thereby suppressing adhesion of foreign matters during polycoat film formation, and to prevent the occurrence of a dent defect in the polishing process.

1 is a schematic perspective view showing a configuration of a wafer charge auxiliary table according to a preferred embodiment of the present invention, and shows a state where a vertical boat is mounted. 1 is a schematic perspective view showing a configuration of a wafer charge auxiliary table according to a preferred embodiment of the present invention, in which a vertical boat is not mounted. 1 is a schematic perspective view showing a configuration of a vertical boat 10 and shows a state where no wafer is accommodated. FIG. It is a schematic sectional drawing which shows the state in which the wafer was accommodated in the vertical boat. 2 is a schematic cross-sectional view showing the arrangement of wafers 20 in a vertical boat 10 that is not mounted on the wafer charge auxiliary table 1. FIG. 2 is a schematic cross-sectional view showing a preferred arrangement of wafers 20 in a vertical boat 10. FIG. 2 is a schematic cross-sectional view showing a state of wafers in a vertical boat 10 mounted on a wafer charge auxiliary table 1. FIG. It is a schematic diagram for demonstrating the conveyance method of the vertical boat 10 by the wafer charge auxiliary | assistant stand 1, Comprising: The movable state is shown. It is a schematic diagram for demonstrating the conveyance method of the vertical boat 10 by the wafer charge auxiliary | assistant stand 1, Comprising: The upright state is shown.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 and 2 are schematic perspective views showing the configuration of a wafer charge auxiliary table according to a preferred embodiment of the present invention. FIG. 1 shows a state where a vertical boat is mounted, and FIG. 2 shows a case where a vertical boat is mounted. Each state is not shown.

  As shown in FIGS. 1 and 2, the wafer charge auxiliary table 1 supports a support table 2 that supports the vertical boat 10 and an outer periphery of the wafer 20 in the vertical boat 10 that is mounted on the support table 2. A pair of support rods 3 </ b> A and 3 </ b> B, a handle portion 4 provided on one end side in the longitudinal direction of the support base 2, and a wheel 5 provided on the other end side in the longitudinal direction of the support base 2 are provided.

  The support base 2 includes an elongated rectangular bottom plate portion 2a, first and second side plate portions 2b and 2c provided on two sides parallel to the longitudinal direction of the bottom plate portion 2a, and a short direction of the bottom plate portion 2a. Third and fourth side plate portions 2d and 2e provided on two parallel sides, respectively. These four side plate portions 2b to 2e are provided for positioning the vertical boat 10 on the support base 2, and are flat plate members orthogonal to the bottom plate portion 2a. The bottom plate portion 2a constitutes the bottom surface (mounting surface) of the vertical boat 10 when the vertical boat 10 is mounted on the horizontal support base 2 shown in the drawing, and the fourth side plate portion 2e is a vertical type. When the support table 2 on which the boat 10 is mounted is brought into an upright state, the bottom surface (mounting surface) of the vertical boat 10 is configured.

  The pair of support rods 3A and 3B are in contact with the end surfaces of the respective wafers 20 in the vertical boat 10, thereby ensuring a non-contact state between the end surfaces of the respective wafers 20 and the columns of the vertical boat 10. Yes. The support bars 3A and 3B are fixed to the upper ends of the first and second side plate portions 2b and 2c, respectively. The material of the support rods 3A and 3B is preferably a resin, quartz or silicon carbide as a nonmetallic material capable of preventing contamination of the wafer, and includes a material in which only the surface is coated with quartz or silicon carbide. The resin is inexpensive, and both quartz and silicon carbide are compounds containing silicon, which is the composition of the wafer, and are preferable in terms of high purity and high durability. As described above, when at least the surfaces of the support rods 3A and 3B are made of resin, quartz, or silicon carbide, contamination of the wafer can be prevented at the time of contact with the wafer.

  Next, the structure of the vertical boat 10 mounted on the wafer charge auxiliary table 1 will be described.

  FIG. 3 is a schematic perspective view showing the configuration of the vertical boat 10 and shows a state in which no wafer is accommodated. FIG. 4 is a schematic cross-sectional view showing a state where wafers are accommodated in a vertical boat.

  As shown in FIG. 3, the vertical boat 10 has a structure in which four support columns 13 to 16 are erected between a disk-shaped top plate 11 and a bottom plate 12. The bottom plate 12 has a two-piece structure, and stability is ensured by making the bottom side heavy. Each of the columns 13 to 16 defines a housing space for the wafer, and each of the columns 13 to 16 is provided with a large number of grooves 17 at equal intervals, thereby forming a slot for accommodating the wafer. .

  As shown in FIG. 4, a polysilicon film 19 is formed on the surface of the vertical boat 10. The polysilicon film 19 is formed from the beginning in order to prevent contamination of the wafer, and additionally formed through a PBS process. A convex portion 18 existing between two adjacent groove portions 17 and 17 is in contact with the outer peripheral surface of the wafer 20 to support the wafer. In this embodiment, two wafers 20a and 20b are accommodated in one slot, and a PBS process for forming a polysilicon film only on one main surface which is an exposed surface is realized. When the vertical boat 10 is in an upright state, only the lower wafer 20b of the two wafers overlapping in the slot is stationary with the convex portion 18 of each of the columns 13 to 16 (shown only in FIGS. 13 and 14 in this figure). Therefore, it is considered that a part of the polysilicon film 19 is lost and adheres to the surface of the lower wafer 20a due to the friction between the two, which causes a foreign matter.

  FIG. 5 is a schematic cross-sectional view showing the arrangement of the wafers 20 in the vertical boat 10 not mounted on the wafer charge auxiliary table 1.

As shown in FIG. 5, the four columns 13 to 16 are arranged symmetrically with respect to the axis D ₁ in the Y direction passing through the center P of the disk-shaped top plate 11 and the bottom plate 12. When the lower side in the Y direction from the center P of the bottom plate 12 is set as a reference (0 degree), the first pair of support pillars 13 and 14 are respectively provided at positions θ ₁ = ± 90 °, and the second pair The columns 15 and 16 are provided at a position of θ ₂ = ± 30 °. Therefore, when the vertical boat 10 is placed horizontally so that the second pair of support columns 15 and 16 are on the lower side, the wafer 20 can be charged to the vertical boat 10 from above as indicated by the arrow E. . The wafer 20 charged in this way is restricted in movement in the lateral direction (X direction) by the two upper support pillars 13 and 14 and is controlled in lower movement (Y direction) by the two lower support pillars 15 and 16. Then, the movement of the columns 13 and 14 in the extending direction (Z direction) is restricted by the inner side surfaces of the grooves of the columns 13 to 16. Further, when the wafer 20 is set on a horizontal boat, the outer peripheral portion of the wafer 20 is in contact with the two lower support columns 15 and 16 by gravity.

  FIG. 6 is a schematic cross-sectional view showing a preferred arrangement of the wafers 20 in the vertical boat 10.

  As shown in FIG. 6, the outer peripheral portion of the wafer 20 in the vertical boat 10 is preferably in a non-contact state with each of the columns 13 to 16. This is because if the wafer 20 is in contact with the pillars 13 to 16 as shown in FIG. 5, the polysilicon film is not uniformly formed at the contact portion. Conventionally, in the position adjustment of the wafer in the vertical boat 10, the wafer 20 is adjusted to the position of FIG. 5 to FIG. 6 manually by the operator. 16, the polysilicon film 19 covering the surfaces of the pillars 13 to 16 of the vertical boat 10 is missing and adheres to the lower wafer surface, which causes the occurrence of a dent defect. However, in the present embodiment, the non-contact state with the support columns 15 and 16 is ensured only by placing the vertical boat 10 on the wafer charge auxiliary table 1, and the wafer 20 is adjusted to the position of FIG. No problem arises. Hereinafter, a method of using the wafer charge auxiliary table 1 will be described.

  In the use of the wafer charge auxiliary table 1, first, as shown in FIG. 2, the wafer charge auxiliary table 1 is set in the horizontal state, and thereafter, an empty vertical boat 10 is mounted on the wafer charge auxiliary table 1 as shown in FIG. After that, the wafer 20 is charged in the vertical boat 10. At this time, the wafer 20 is charged using a jig and tool, and two wafers are charged in each slot.

  FIG. 7 is a schematic cross-sectional view showing the state of wafers in the vertical boat 10 mounted on the wafer charge auxiliary table 1.

As shown in FIG. 7, the wafer 20 in the vertical boat 10 set on the wafer charge auxiliary table 1 is supported by a pair of support rods 3A and 3B at two points P ₁ and P _{2 on} the outer periphery thereof. Thus, a non-contact state between the end face of the wafer 20 and the lower support columns 15 and 16 of the vertical boat 10 is secured. That is, the wafer 20 is in a state of floating above the lower support columns 15 and 16. Further, the lower end R ₁ of the top plate 11 and the bottom plate 12 of the vertical boat 10 is in contact with the main surface 2 s of the support base 2, but the lower end of the wafer 20 is not in contact with the main surface 2 s of the support base 2.

  FIGS. 8 and 9 are schematic diagrams for explaining a method of transporting the vertical boat 10 by the wafer charge auxiliary table 1. FIG. 8 shows a movable state and FIG. 9 shows an upright state.

  As shown in FIG. 8, when the vertical boat 10 is transported using the wafer charge auxiliary table 1, first, the handle 5 side of the wafer charge auxiliary table 1 is lifted with the wheel 5 as a starting point to make it movable. The charge auxiliary table 1 is carried to a vertical heat treatment furnace (not shown).

  Thereafter, as shown in FIG. 9, the wafer charge auxiliary table 1 is erected in an upright state in front of a vertical heat treatment furnace (not shown), and then the vertical boat 10 is lowered from the wafer charge auxiliary table 1 to form the vertical type. Install in heat treatment furnace. At this time, the mounting surface of the vertical boat 10 is switched from the bottom plate portion 2a of the support base 2 to the fourth side plate portion 2e, and is mounted on the fourth side plate portion 2e. Further, by slowly raising the wafer charge auxiliary base 1, the wafer 20 is placed flat, and the position of the wafer 20 in the vertical boat 10 (see FIG. 7) is maintained as it is. That is, from the time when the vertical boat is charged until it is installed in the furnace, the outer periphery of the wafer 20 is kept at a substantially constant distance from the support columns 15 and 16, and the outer periphery of the wafer 20 is not connected to the support columns 15 and 16. Maintaining contact. As long as the vertical boat 10 is not subjected to excessive vibration or impact, the position of the wafer 20 in the flat state is stably maintained.

  As described above, the wafer charge auxiliary table 1 according to the present embodiment includes the pair of support rods 3A and 3B, and has two outer peripheral portions of the wafer 20 in the vertical boat 10 mounted horizontally on the support table. Since the point is supported and a non-contact state between the end face of the wafer 20 and the support of the vertical boat is ensured, it is not necessary to adjust the position of the wafer after charging the vertical boat 10 in the vertical heat treatment furnace. Can do. As described above, when the wafer and the vertical boat column are in contact, they rub against each other when adjusting the position of the wafer, so that a minute piece of polysilicon film is lost and adheres to the lower wafer surface. And cause dent defects. However, according to the present embodiment, since the wafer position adjustment work is unnecessary, dust generation due to contact between the wafer and the vertical boat column can be prevented. Therefore, it is possible to reduce the incidence of dent defects in the polycoated wafer obtained through the PBS process.

  Further, since the wafer charge auxiliary base 1 according to the present embodiment includes the handle portion 4 and the wheels 5, the vertical boat 10 can be easily started up by lifting the handle portion 4 side, and is easily transported. be able to.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, the support bars 3A and 3B are fixed to the upper ends of the first and second side plate parts 2b and 2c, respectively, but the fixing method of the support bars 3A and 3B is not particularly limited. Therefore, for example, both ends of the support rods 3A and 3B may be fixed to the third and fourth side plate portions 2d and 2e, respectively.

  Moreover, in the said embodiment, although the wafer charge auxiliary | assistant stand 1 is equipped with the wheel 5, the wheel 5 is not essential, for example, the handle part is provided in the both sides of the longitudinal direction of the wafer charge auxiliary | assistant stand 1, and wafer charge auxiliary | assistance is carried out. The table 1 may be lifted and carried by hand. Alternatively, a transfer carriage having wheels may be prepared separately, and the wafer charge auxiliary table 1 may be carried on the transfer carriage. In the present invention, the handle portion 4 can be provided at an arbitrary position, and the handle portion 4 can be omitted.

  In the above embodiment, two wafers are charged in each slot of the vertical boat. However, the present invention is not limited to such a case, and is applicable to the case where one slot is charged. Can do. Further, the present invention is not limited to the PBS process, but can be applied to all film forming processes such as a silicon film, a silicon oxide film, and a silicon nitride film, and can be used in various wafer processing processes using a vertical boat. .

DESCRIPTION OF SYMBOLS 1 Wafer charge auxiliary | assistant stand 2 Support stand 2a Bottom plate part 2b 1st side plate part 2c 2nd side plate part 2d 3rd side plate part 2e 4th side plate part 2s Main surface 3A, 3B of a support stand Support bar 4 Handle part 5 Wheel 10 Vertical boat 11 Top plate 12 Bottom plates 13 to 16 Post 17 Groove portion 18 Protrusion portion 19 Polysilicon coating 20 Wafer 20a Upper wafer 20b Lower wafer

Claims (2)

A wafer charge auxiliary table used for transporting a vertical boat charged with wafers,
A support for supporting the vertical boat;
Supporting at least two points on the outer periphery of the wafer in the vertical boat mounted horizontally on the support table, and supporting the wafer in the vertical position between the column of the vertical boat and the end surface of the wafer A pair of support bars to ensure a non-contact state;
A handle portion provided on one end side in the longitudinal direction of the support base;
A wheel provided on the other end side in the longitudinal direction of the support base ,
The supporting table includes a bottom plate portion that forms a bottom surface of the vertical boat in a horizontally placed state, and a side plate portion that forms a bottom surface of the vertical boat in a vertically placed state .   The wafer charge auxiliary base according to claim 1, wherein at least a surface of the support bar is made of quartz, resin, or silicon carbide.

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