JP4157812B2 - Wafer holding method and single wafer heat treatment apparatus used in this method - Google Patents

Description

  The present invention relates to a semiconductor manufacturing apparatus, and more particularly to a wafer holding method and a wafer support used when holding a wafer and performing a heat treatment.

  In the manufacture of semiconductor devices, display devices, etc., various heat treatment apparatuses are used as semiconductor wafers (hereinafter referred to as wafers), for example, to perform heat treatments such as oxidation, diffusion, film formation, and annealing on disk-shaped wafers. It is used. As this type of heat treatment apparatus, a batch-type heat treatment apparatus that heat-treats a plurality of wafers at once and a single-wafer-type heat treatment apparatus that heat treats one by one are known. Among these, single wafer type heat treatment equipment can relatively easily perform heat treatment that requires rapid temperature rise and fall and uniform heat treatment within the surface of the wafer, compared with batch-type heat treatment equipment. It has come to be.

By the way, when performing heat treatment, the wafer is generally held in a process chamber (processing chamber) made of a quartz member in order to prevent metal contamination and the like. Therefore, in a conventional single wafer heat treatment apparatus, as a method of holding in a chamber, a wafer of 8 inches or less is point-supported by a plurality of pins in order to minimize contact with the wafer. It was done. However, as the diameter of the wafer increases in recent years (for example, a wafer having a diameter of 300 mm), the weight of the wafer increases. In such point support, stress concentration at the support portion increases. In addition, since the holding of the wafer needs to consider interference with the hand of the robot that transfers the wafer, increasing the diameter of the wafer further imposes restrictions on the arrangement of the support portions.
For this reason, it is difficult to uniformly disperse and maintain the in-plane stress, and the occurrence of slips (crystal defects due to dislocations) is a problem. When the slip occurs, the device manufacturing yield deteriorates.

There are two main causes of the occurrence of the slip, one is the above-mentioned stress non-uniformity in the wafer surface, particularly stress concentration, and the other is the in-plane temperature difference of the wafer.
Accordingly, as a countermeasure against stress concentration at the wafer support portion, a heat treatment boat or the like is known that supports the wafer by bringing the outer peripheral edge of the wafer into surface contact with an arc-shaped or ring-shaped support portion (for example, patents). Reference 1 and Patent Reference 2). In addition, as a measure to alleviate the in-plane temperature difference, the heat given during the heat treatment is stored in the holding body, and then the stored heat is conducted to the peripheral edge of the wafer to uniformly heat the entire wafer. A heat treatment apparatus has been proposed (see, for example, Patent Document 3).

JP-A-6-260438 (FIG. 3 and claim 1) JP 2001-284280 A (FIG. 2) Japanese Patent No. 3067658 (FIG. 1 and claim 1)

  However, in the case of supporting the above conventional wafer in surface contact (Patent Document 1), the support is not arranged point-symmetrically with respect to the center of the wafer at the periphery of the wafer. The stress in the wafer surface is not uniform enough. Even in the case of evenly supporting the entire circumference of the wafer (Patent Document 2), since the support is provided on the entire circumference of the wafer, the robot hand cannot be inserted directly during the transfer. For this reason, a lifter pin for lifting the wafer, an actuator for moving the wafer up and down, and the like are indispensable, and the mechanism of the heat treatment apparatus becomes complicated and the cost increases. In addition, in the case where heat is stored in the holding body (Patent Document 3), since the wafer is point-supported, stress concentration occurs in the wafer surface. Thus, the problem of wafer slippage remains a problem.

  In view of such circumstances, the present invention has a simple configuration, and can be used for a wafer holding method and a method for suppressing slip generation by reducing stress non-uniformity in a wafer surface and a temperature difference in the wafer surface to suppress the occurrence of slip. An object of the present invention is to provide a wafer heat treatment apparatus.

In order to achieve the above object, the present invention takes the following technical means.
That is, the present invention is a method for holding a wafer in a processing chamber of a single wafer heat treatment apparatus that stores and heats the wafers one by one, facing the symmetrical positions with respect to the center of the wafer, and A plurality of pairs that extend in the circumferential direction along the wafer periphery while avoiding interference with the bifurcated hand of the wafer transfer robot at positions corresponding to the periphery of the wafer, each having the same contact area with the wafer periphery. Are provided at equal intervals along the peripheral edge, and at least one of them is arranged in a direction orthogonal to the wafer transfer direction, and the other pair is arranged at an axial target position with respect to the transfer direction. In the state, each wafer support is brought into surface contact with the lower surface of the peripheral edge of the wafer to support the lower part of the wafer in each support area.
As a result, the wafer is supported in contact with the surface almost uniformly in a support area provided at a point-symmetrical position on the peripheral edge of the wafer, and stress deviation and stress concentration in the wafer surface are reduced to reduce the in-wafer surface. Stress unevenness is alleviated. At the same time, the temperature difference in the wafer surface is reduced. As described above, since the stress non-uniformity in the wafer surface and the temperature difference in the wafer surface are alleviated, the occurrence of slip can be suppressed. Further, by configuring the wafer support so as not to interfere with the hand of the transfer robot, a wafer lifting mechanism or the like is not required, and the structure of the single wafer heat treatment apparatus can be simplified.

The present invention also provides a single wafer type comprising a processing chamber in which wafers are stored one by one, a heating means for heating the wafer disposed in the processing chamber, and a wafer support for holding the wafer in the processing chamber. In the heat treatment apparatus, a plurality of pairs of the wafer supports are provided at equal intervals along the peripheral edge at positions corresponding to the peripheral edge of the wafer in a state of facing the symmetrical positions with respect to the center of the wafer. In addition, at least one pair of them is disposed in a direction orthogonal to the wafer transfer direction , extends in the circumferential direction along the peripheral edge of the wafer, and the length in the circumferential direction is divided into two forks of the wafer transfer robot hand. The other pair is arranged at an axial target position with respect to the transfer direction and extends in the circumferential direction along the peripheral edge of the wafer, and the length in the circumferential direction is the distance from the hand. It is a dimension that can afford Cage, the wafer support pairs, characterized in that the mounting portion for supporting a lower wafer lower surface brought into surface contact with the wafer peripheral portion in the contact area equal respectively provided.
In this case, since the wafer is supported by surface contact at the wafer support mounting portion provided at a point-symmetrical position on the peripheral edge of the wafer, stress deviation in the wafer surface and stress concentration are reduced. The stress non-uniformity in the wafer surface is alleviated. At the same time, the wafer supports are arranged at regular intervals on the periphery of the wafer, and the temperature difference in the wafer surface is alleviated. As described above, since the stress non-uniformity in the wafer surface and the temperature difference in the wafer surface are alleviated, the occurrence of slip can be suppressed. Further, by configuring the wafer support so as not to interfere with the hand of the transfer robot, a wafer lifting mechanism or the like is not required, and the structure of the single wafer heat treatment apparatus can be simplified.

Further, in the single wafer heat treatment apparatus, it is preferable that the wafer support is provided on a wafer tray, the wafer tray is detachably attached to the processing chamber, and is positioned by a separately provided centering pin.
In this case, by preparing a wafer tray configured for each wafer size, the wafer tray can be appropriately selected and used according to the wafer size to be heat-treated. Further, since the wafer tray is positioned with respect to the processing chamber by the centering pin, the heat treatment can be performed in a state where the wafer is always placed at a fixed position in the processing chamber.
In the single wafer heat treatment apparatus, the wafer support is formed such that the upper surface of the wafer and the upper end surface of the wafer support are flush with each other in a state where the wafer is mounted on the mounting portion. It is preferable. Thereby, since the heat treatment can be performed without disturbing the flow of the process gas at the peripheral edge of the wafer, the quality of the wafer can be stabilized.

Also, in the single wafer heat treatment apparatus, the wafer is heated by temporarily storing heat by the heating means between the wafer supports adjacent to each other and in parallel with the placement surface of the placement unit. It is preferable that a heat storage member is provided.
In this case, since the heat applied to the wafer is stored almost evenly by the wafer support and the heat storage member, the entire wafer is heat-treated uniformly. In addition, rapid temperature rise and cooling of the wafer can be suppressed. The heat storage member is preferably made of a material that does not overlap the wafer support on the horizontal plane and has a heat capacity that is the same as or close to that of the wafer support.

  According to the present invention, since the wafer is supported by surface contact with the support area arranged at equal intervals on the peripheral edge of the wafer, the stress unevenness in the wafer surface and the temperature difference in the wafer surface can be achieved with a simple configuration. The occurrence of slip can be suppressed by relaxing the above.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a single wafer heat treatment apparatus 1 according to the first embodiment of the present invention. The single wafer heat treatment apparatus 1 performs heat treatment such as oxidation, diffusion, CVD, annealing on a disk-shaped wafer W as an object to be processed, and can heat and cool the wafer W one by one. Is.
As shown in FIG. 1, the single wafer heat treatment apparatus 1 includes a processing chamber 2 in which wafers W are stored one by one, and a heating unit 3 that is spaced apart and provided on the outer wall surface side of the processing chamber 2. A cooling medium flow passage 4 is provided between the outer wall surface of the processing chamber 2 and the inner wall surface of the heating unit 3, and further includes a transfer robot for transferring the wafer W into and out of the processing chamber 2. . The transfer robot is provided with a robot hand 7. A wafer tray 5 is installed in the processing chamber 2, and as shown in FIG. 2, wafer supports 6 are configured at four locations on the wafer tray 5, and wafers W are held by the wafer support 6.

  The processing chamber 2 has a bottomed cylindrical processing chamber main body 2a with one end opened, an opening 2b for loading / unloading a wafer provided on one end side (left side in FIG. 1), and the opening 2b It has a flange portion 2c provided at the periphery and a small-diameter vent 2d for gas introduction and deaeration provided on the other end side (right side in FIG. 1). Although not shown, a thermocouple for measuring the ambient temperature is disposed in the processing chamber 2, and a lid or a valve body for making the processing chamber 2 a sealed space is provided in the opening 2b and the vent 2d. Etc. are provided as appropriate.

The processing chamber main body 2a is made of a transparent heat-resistant material such as quartz glass, and the inside thereof has a capacity for accommodating the wafers W one by one. The vent 2d is an inlet for supplying a film forming gas filled in the processing chamber 2 when a film forming process by, for example, thermal CVD is performed as a heat treatment, and is connected to a gas supply device (not shown). .
The heating means 3 employs, for example, a resistance heating type as a heat source of the heating body, and includes a resistance heating element, a heat insulating material surrounding the outer periphery thereof, and an electric supply unit that supplies electricity (not shown). Thus, electricity is supplied to the heating element, and Joule heat is generated by the resistance. However, the heating means 3 is not limited, and other heating means 3 such as an induction heating method may be employed.

FIG. 2 shows a state where the transfer robot hand 7 is inserted into the processing chamber 2 and the wafer W is held by the two pairs of wafer supports 6. The wafer tray 5 is formed by connecting two frames 5a and 5c on the left and right (up and down in FIG. 2) and two frames 5b and 5d on the front and rear (left and right in FIG. 2) in the transfer direction 20 of the wafer W. It is configured in shape. Further, the wafer tray 5 is placed on the bottom surface of the processing chamber 2 and is detachable. One end side of each of the frames 5a and 5c extends to the near side of the frame 5d.
Six centering pins 8 are erected on the bottom surface of the processing chamber 2, and two of them are disposed outside the frame bodies 5a and 5c, and two are disposed outside the frame body 5b. Yes. The wafer tray 5 is brought into contact with each centering pin 8 and the position of the wafer tray 5 is determined. The centering pin 8 is cylindrical and has a length that can protrude upward from the wafer tray 5.

A wafer support 6 is formed on each frame 5a, 5b, 5c, 5d. Among these wafer supports 6, one pair facing each other is disposed along the transfer direction 20, and the other pair facing each other is disposed along a direction orthogonal to the transfer direction 20.
The wafer support 6 is fixed to the wafer tray 5 by two legs 6b provided at the lower portions of both ends. As shown in the enlarged view of the main part of FIG. 1, a stepped portion is formed along the circumferential direction at the upper corner portion on the radially inner side of the support body portion 6a. In this step portion, a mounting portion 9 having a required width for receiving the periphery of the lower surface of the wafer W and a length extending in the circumferential direction of the step portion is formed. Further, the contact areas of the mounting portions 9 formed on the pair of wafer supports 6 to the lower surface of the peripheral portion of the wafer W are the same. Further, the pair of wafer supports 6 have the same heat capacity.

The height L of the step portion of the wafer support 6 (between the upper end surface of the wafer support 6 and the mounting portion 9) is substantially the same as the thickness of the wafer W, and the wafer W is mounted on the mounting portion 9 Thus, the upper surface of the wafer W and the upper end surface of the wafer support 6 are flush with each other.
As shown in FIG. 2, the length in the circumferential direction of the pair of wafer supports 6 facing the transfer direction 20 is set to fit between both ends of the hand 7 divided into two branches. The length of the other pair of wafer supports 6 in the circumferential direction is such that there is a margin between the wafer support 6 and the hand 7. Thereby, the hand 7 and the wafer support 6 do not interfere with each other.

With the single-wafer heat treatment apparatus 1 having the above-described configuration, two pairs of placement units 9 arranged symmetrically with respect to the point are arranged at equal intervals along the periphery of the wafer. A support area is formed that supports the lower surface in uniform surface contact from below.
The holding of the wafer W by this support area is performed as follows. The wafer W before processing is caused to enter right above the wafer support 6 by the hand 7 of the transfer robot, and then the hand 7 is slightly lowered so that the wafer W is loaded on each of the two pairs of wafer supports 6. Passed to the placement unit 9. As a result, the peripheral edge of the wafer W is uniformly brought into surface contact with each support area formed by the mounting portion 9 to hold the wafer W. Next, the transfer robot is retracted outside the processing chamber 2.

Therefore, when the wafer W is held by this wafer holding method, the weight of the wafer W is evenly distributed at the peripheral edge portion thereof, so that stress bias and stress concentration in the wafer W surface are reduced, and Stress unevenness is alleviated.
For example, when a 300 mm wafer is held by three members excluding the wafer support 6 on the frame 5d, the maximum stress concentrated at two specific locations on the peripheral edge is 4.37 × 10 ⁶ N / m ² . there were. On the other hand, when a 300 mm wafer is held by the four wafer supports 6 as in the present embodiment, the stress is evenly distributed at specific eight locations on the peripheral edge, and the maximum stress is 1.79 × 10. ^It showed a low value of ⁶ N / m ² .
On the other hand, each wafer support 6 forming the support area has the same heat capacity. However, in this embodiment, the wafer support 6 is not arranged in a portion biased on the peripheral edge of the wafer W, and is evenly distributed in a point-symmetrical portion. Since they are arranged, the temperature difference in the wafer W surface during the heat treatment is also reduced.
As described above, since the stress non-uniformity in the wafer surface and the temperature difference in the wafer surface are alleviated, the occurrence of slip can be suppressed. As a result, not only the small-diameter wafer W but also the large-diameter 300 mm wafer W is heat-treated, the effect of improving the quality and suppressing the occurrence of slip and preventing the yield from being lowered is exhibited.

Further, since the wafer support 6 does not interfere with the hand 7 of the transfer robot, it is not necessary to provide the wafer W elevating mechanism or the like in the single-wafer type heat treatment apparatus 1 as in the prior art, the structure can be simplified, and the cost can be reduced. Can be suppressed.
In addition, by separately manufacturing a wafer tray 5 having a wafer support 6 that matches the wafer size, the wafer tray is appropriately selected according to the wafer size to be heat-treated and set in the single wafer heat treatment apparatus 1. be able to. For this reason, since it becomes possible to heat-process the wafer W of a different size with the same single-wafer | sheet-fed heat processing apparatus 1, it is highly convenient. Further, since the wafer tray 5 is positioned with respect to the processing chamber by the centering pins 8, the wafer W can be always placed at a fixed position in the processing chamber. Therefore, since the heat treatment can be performed without disturbing the flow of the process gas at the peripheral edge of the wafer, the quality of the wafer can be stabilized.

  Fig.3 (a) has shown sectional drawing which shows schematic structure of the single-wafer | sheet-fed heat processing apparatus 1 concerning 2nd embodiment of this invention, FIG.3 (b) is a partially missing plane in the same embodiment. The figure is shown. This embodiment is different from the first embodiment in that a heat storage member 10 is provided on the upper portion of the wafer support 6. The heat storage member 10 is made of a material (for example, quartz glass or silicon carbide) having the same heat capacity as that of the wafer support 6. The heat storage member 10 has the same shape as the support body 6a, and is provided in parallel with the placement surface of the placement portion 9 of the wafer support 6 without exceeding the interval between the adjacent wafer supports 6. Yes.

In this case, since the heat applied to the wafer W is once stored in the heat storage member 10 and then conducted to the wafer W, the entire wafer is heat-treated almost uniformly. Further, when the temperature is raised, the peripheral portion of the wafer W can be prevented from being heated more rapidly than the central portion of the wafer W, and the temperature gradient between the central portion and the peripheral portion of the wafer W can be made gentle. As a result, the temperature difference in the wafer W surface is further alleviated, so that the effect of suppressing the occurrence of slip is enhanced and a high-quality wafer W is obtained. The heat storage member 10 may be disposed on the lower side of the wafer support 6, or the thickness of the heat storage member 10 is approximately half the thickness of the wafer support 6, and is provided on both upper and lower sides of the wafer support 6. You may arrange.
In addition, this invention is not limited to the form of each above-mentioned Example.
For example, the wafer support 6 according to the first and second embodiments may have a different shape, or the material of the heat storage member 10 may be changed according to the heat treatment conditions and the like. Further, the shape of the wafer tray 5 and the position of the centering pin 8 can be changed as appropriate.

It is sectional drawing which shows schematic structure of the single wafer type heat processing apparatus which concerns on 1st embodiment of this invention. FIG. 2 is a plan view showing a state in which the hand of the transfer robot is inserted into the processing chamber and the wafer is held on the wafer support. (A) is sectional drawing which shows schematic structure of the single-wafer | sheet-fed heat processing apparatus which concerns on 2nd embodiment of this invention, (b) is the partially notch plane which has not mounted the wafer in the embodiment. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single wafer type heat processing apparatus 2 Processing chamber 3 Heating means 5 Wafer tray 6 Wafer support 7 Hand 8 Centering pin 9 Placement part 10 Heat storage member W Wafer L Height of level difference part

Claims (5)

A method for holding a wafer in a processing chamber of a single wafer heat treatment apparatus that heats by storing wafers one by one,
Opposite positions symmetrical to each other across the center of the wafer and in a circumferential direction along the wafer periphery while avoiding interference with the bifurcated hand of the wafer transfer robot at a position corresponding to the periphery of the wafer A plurality of pairs of supporting areas that extend and have the same contact area with the peripheral edge of the wafer are provided at equal intervals along the peripheral edge, at least one of which is arranged in a direction orthogonal to the wafer transfer direction, and the others Each wafer support is brought into surface contact with the lower surface of the peripheral edge of the wafer to support the lower part of the wafer in each support area in a state where the pair is arranged at an axial target position with respect to the transfer direction. Wafer holding method. A single wafer heat treatment apparatus comprising a processing chamber in which wafers are stored one by one, a heating means for heating the wafer disposed in the processing chamber, and a wafer support for holding the wafer in the processing chamber,
A plurality of pairs of the wafer supports are provided at equal positions along the peripheral edge at positions corresponding to the peripheral edge of the wafer in a state of facing the symmetrical positions with respect to the center of the wafer. Is arranged in a direction orthogonal to the wafer transfer direction and extends in the circumferential direction along the peripheral edge of the wafer, and the length in the circumferential direction fits between the two tips of the wafer transfer robot hand. The other pairs are arranged at axial positions with respect to the transfer direction , extend in the circumferential direction along the peripheral edge of the wafer, and the length in the circumferential direction is set to allow a sufficient space between the hand and the hand. And
A single-wafer heat treatment apparatus, wherein a plurality of pairs of wafer supports are provided with mounting portions that are in surface contact with the lower surface of the peripheral edge of the wafer with equal contact areas and support the lower portion of the wafer. 3. A heat storage member that temporarily stores heat by the heating means and heats the wafer is provided between the wafer supports adjacent to each other and in parallel with the mounting surface of the mounting portion. Single wafer type heat treatment apparatus as described in 1.   The said wafer support body is formed so that the upper surface of the said wafer and the upper end surface of the said wafer support body may become the plane in the state which mounted the wafer in the mounting part. Single wafer heat treatment equipment. The single wafer heat treatment according to any one of claims 2 to 4, wherein the wafer support is provided on a wafer tray, and the wafer tray is detachable from the processing chamber and is positioned by a separately provided centering pin. apparatus.

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