JPH10189688A - Substrate transfer method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a substrate treatment device from increasing in floor space with an increase in the diameter of a substrate by a method wherein a substrate treatment system transfers a substrate keeping a normal line to the surface of a transferred substrate nearly horizontal, and the substrate is held by an electrostatic attraction which takes advantage of an electrostatic force in this substrate transfer process. SOLUTION: Substrates 1 are housed in a cassette, and the cassette is placed in a substrate introducing chamber. The substrates 1 are taken out of the cassette one by one and sent to a substrate treatment chamber, and the substrates 1 are taken out of the substrate treatment chamber after they are subjected to treatment and housed in the cassette placed in a substrate delivery chamber. At this point, the substrates 1 are transferred keeping them vertical in position, and a direct-current high voltage is applied between electrodes 18 and 19 to hold the substrate by electrostatic attraction. When the electrodes 18 and 19 are held by an arm 22, the arm 22 is moved in the direction of a normal line to the substrate 1 so as not to cause damage to the substrate 1 by an natural force induced by the movement of the arm 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transferring a substrate in a substrate processing apparatus for forming or processing a thin film on a silicon substrate or the like, and more particularly, to a method of processing a substrate even when the size of the substrate is increased. The present invention relates to a substrate transfer method suitable for minimizing a footprint of an apparatus and an installation area of a substrate processing apparatus, that is, an occupation area of a clean room. Further, as another application field of the present invention, the present invention relates to a substrate transfer method capable of reducing foreign substances adhering to a substrate surface.

[0002]

2. Description of the Related Art A conventional substrate transfer method of a substrate processing apparatus is as follows.
Starting from the state where the substrate surface is stored in a cassette with the substrate surface in the horizontal direction, the substrate is placed on the substrate transfer arm with the substrate surface kept horizontal, transported to the processing chamber, delivered to the substrate processing holder, and processed. It is common to carry it out.
During this time, the substrate surface is kept horizontal. As an example, as described in Japanese Patent Publication No. 4-1989, a wafer (substrate) is placed in each room (a transfer room, a processing room, etc.) by a transfer arm having a horizontal surface and articulated joints. Is transported between Further, a cassette for accommodating a plurality of wafers to transport or store the wafers to another processing apparatus is placed at a wafer loading / unloading section so that the wafer surface is horizontal. This configuration has an advantage that unnecessary force does not act on the substrate because the gravity can be used for holding the substrate, and the substrate transport mechanism is simplified. However, there is a problem that as the substrate size increases, the installation area of the device increases in proportion to the substrate size.

As an example in which the substrate surface is not in the horizontal direction but in the vertical direction (the normal line of the substrate surface is horizontal), for example, as described in US Pat. No. 4,743,570, In some cases, the pre-processing and processing chambers are installed on substantially the same plane, and the substrate is transported while moving each room up and down while the substrate surface is vertical. In this example,
Certainly, even when the diameter of the substrate is increased, it is almost unnecessary to expand the apparatus in the thickness direction of the substrate. However, the size of the substrate processing chamber in the substrate plane must be increased in accordance with the size of the substrate, so that the size of the entire processing apparatus in the vertical plane increases in proportion to the increase in the substrate size. Especially,
If the ceiling height of the clean room is restricted, there may be a case where the apparatus cannot be stored in the clean room depending on the size of the substrate in the future.

[0004]

The size of the substrate gradually increases in diameter. Along with this, the size of the substrate processing apparatus is steadily increasing. At present, 8-inch substrates are mainly used, but 12-inch and 16-inch substrates will be used in the future. At this time, if the substrate surface is transported in the horizontal direction, the size of the substrate processing apparatus increases in proportion to the increase in the substrate area. For example, if the substrate area ratio is 8:12:16
Since (inch) = 1: 2.25: 4, the footprint of a 16-inch compatible device is four times as large as 8 inches. This value means that it is necessary to completely rebuild the clean room, and not only will the investment amount be huge when constructing the next-generation substrate processing line, but the investment amount itself cannot be recovered depending on the speed of generational change. It can also be unacceptable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for transferring a substrate, which prevents an installation area of the substrate processing apparatus from becoming large due to an increase in the diameter of the substrate, and suppresses an increase in a clean room area and an increase in cost of the substrate processing apparatus. It is in.

[0006]

The area of the substrate processing apparatus (projected area on the floor; footprint) of the substrate processing apparatus increases with the increase in the diameter of the substrate (area). This is for transporting or processing as it is. The reason is that (1) the structure of the transfer system can be simplified by placing and handling the substrate without being specially fixed to the transfer jig or the holding device. Transporting is preferable from the viewpoint of preventing foreign matter from adhering. However, if any contact member is required on the substrate processing surface or if it is mechanically fixed and held, there is a high possibility that foreign matter will be generated from that part. . However, if the substrate surface can be transported vertically, the footprint of the substrate processing apparatus can be made constant and small regardless of the substrate size. When the substrate surface is made vertical, if the substrate can be fixed to a transfer jig or the like without contacting the substrate processing surface or the outer peripheral surface, the number of foreign substances adhering to the substrate surface can be reduced.
In the present invention, electrostatic adsorption is used for the method. That is,
The electrostatic attraction can hold the substrate by suction from the back side of the substrate, so that no scratches or foreign substances are attached to the processed surface of the substrate due to the contact at all, and the object of the present invention is satisfied.

[0007]

The thickness of the substrate is sufficiently smaller than the diameter of the substrate.
For example, even if the substrate is increased in diameter from 8 inches to 16 inches and the thickness of the substrate is increased accordingly, the thickness of the substrate is about 1 mm to 2 mm. Compared to the increase in the system footprint, the transfer system footprint having a vertical substrate surface does not need to consider the increase in diameter. In addition, electrostatic attraction does not require adjusting the attraction surface according to the substrate size,
Since the substrate can be sucked and held only by contacting a part of the back surface of the substrate, the substrate can be used without any special consideration when making the substrate large in diameter.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an application example of the present invention, taking an ion implantation apparatus as an example. It goes without saying that the same applies to the case where the substrate processing chamber is not an ion implantation chamber but another sputtering apparatus, etching apparatus, film forming apparatus or the like.

In FIG. 1, when a substrate 1 is silicon and boron, phosphorus, arsenic, antimony or the like is implanted as a dopant ion, these ions are generated by an ion source 2 and an impurity element is removed by a mass analyzer 3. A predetermined energy is given to the ions by the acceleration tube 4, and the substrate 1 held by the substrate holding device 6 provided in the substrate processing chamber 5 is provided.
Ions are implanted on the surface of. At this time, in order to uniformly implant ions into each part of the substrate 1, the substrate 1
May be rotated or moved. The driving of the substrate 1 is performed by the substrate holding device 6. Now, in order to efficiently perform a large amount of ion implantation into the substrate 1, a substrate transport system that loads the substrate 1 into the substrate processing chamber 6, performs processing, and then unloads the substrate 1 is necessary. FIG. 1 shows an example of a so-called single-wafer processing in which the substrates 1 are introduced one by one into the substrate processing chamber 5 for processing, but a batch-type substrate processing in which a plurality of substrates are simultaneously processed in the substrate processing chamber is described. However, in the substrate processing system capable of coping with the large diameter of the substrate, which is aimed at by the present invention, it is technically more difficult to increase the required floor space of the apparatus, but also to increase the size of the substrate holding and driving system thereof. . Therefore, as a large-diameter substrate processing system, the single-wafer processing as shown in FIG. 1 is an essential technology. Assuming that the substrate 1 is transported while maintaining its surface level at such a diameter, the same system as in FIG. 1 has a configuration as shown in FIG. 1 and 2 show the apparatus viewed from above. That is, the outer shape of the plan view directly corresponds to the floor area of the apparatus. In FIG. 1, the cassette 8 is introduced into the substrate introduction chamber 7. The cassette 8 stores a plurality of, for example, 25 8-inch substrates. The substrates 1 are taken out one by one from the cassette by the transfer arm 10 provided in the buffer chamber 9 and sent into the substrate processing chamber 5 to perform ion implantation. Thereafter, the substrate 1 is taken out by the transfer arm 12 provided with the buffer chamber 11 and stored in the cassette 14 of the substrate unloading chamber 13. After the processing of the substrates stored in the cassette 8 is completed, the substrates together with the cassette 14 are taken out of the substrate unloading chamber 13 and a series of processing is completed. During this time, the pressure in the substrate processing chamber 5 is set to 10-5 to prevent ion implantation or to prevent impurity elements from being implanted.
It is kept in a high vacuum below Pascal. In order to quickly carry the substrate from the atmosphere to the high vacuum, the substrate introduction chamber 7, the buffer chamber 9, the substrate processing chamber 5, the buffer chamber 11, and the substrate unloading chamber 13 are isolated by a valve 15, and if necessary, It is opened and closed. Each room is evacuated to a predetermined pressure by a vacuum pump. In the system shown in FIG. 1, the substrate is transported while the substrate surface is vertical. Therefore, the dimension in the left and right direction (the thickness direction of the substrate) in FIG. 1 only depends on the size of the transport arm and the like. Not affected. However, in the case of the substrate horizontal transfer system shown in FIG. 2, the system of the apparatus is exactly the same as that of FIG. 1, but the horizontal area (floor area of the apparatus) is large due to the influence of the size of the substrate 1. It has become something. Further, when the processing of the substrate 16 requires the processing surface of the substrate 16 to be vertical as in the present system, the substrate 16 transported horizontally must be turned by the substrate holding device 17 and mechanically changed. It becomes complicated.

As described above, it has been found that the system for vertically transporting the substrate has a feature of preventing the floor area of the apparatus from increasing when the diameter of the substrate is increased. In order to achieve this system, a technique for transporting the substrate while keeping it vertical is required. FIG. 3 showing an example of the technique shows a cross section of a substrate transfer arm, and holds a substrate by using an electrostatic attraction force. A high DC voltage is applied between the electrode 18 and the electrode 19 to perform electrostatic attraction. An electrostatic attraction member 20 made of an insulating material such as alumina is attached to a portion of the electrode 18 corresponding to the back surface of the substrate 1. A portion of the electrode 19 corresponding to the back surface of the substrate 1 is made of a good electrical conductor. Although not shown in the drawing, if the back surface of the substrate 1 is covered with silicon oxide or the like and it is difficult to establish electrical conduction, needle-like projections may be provided on the surface of the electrode 19. The electrode 18 and the electrode 19 are connected to a lead wire 21,
High voltage is applied. The electrode 18 and the electrode 19 are held by the arm 22, but the movement of the arm 22 in the normal direction perpendicular to the surface of the substrate 1 as will be described later
The substrate 1 can be moved in the normal direction to prevent the substrate 1 from being damaged by excessive force. In this mechanism, electrodes 18 and 19 inserted in a sleeve 23 made of a sliding material and made of an electrically insulating material are pressed by a spring 24 from front and rear. Thus, the electrodes 18 and 19 can move while feeling the resistance of the spring 24 in the axial direction. The reason for providing the resistance of the spring 24 is as follows.
If the electrodes move too freely, the position of the substrate 1 during the transfer of the substrate may not be determined, or a problem may occur such that the position of the substrate 1 from the transfer arm to the transfer of the substrate 1 to another substrate holding device is required. This is because the positions of the electrodes 18 and 19 are always the same after the substrate 1 is electrostatically attracted. In FIG. 3, the electrode 18 and the electrode 19 are moved independently, but they may be integrally formed and the whole electrode may be moved as one. Specifically, the sleeve 23 and the spring 24 on the electrode 19 side may be removed, and the electrode 18 and the electrode 19 may be fixed via an electrical insulating material. Although not shown in FIG. 3, both the electrodes 18 and 19 are fixed by keys or the like so as not to move in the rotation direction.

FIG. 4 shows the entire substrate transfer arm provided with the electrostatic suction mechanism shown in FIG. In FIG. 4, an electrode 18 and an electrode 19 are provided at the distal end of an arm 22, connected to an arm driving unit 26 via another arm 25, and supported by a column 27. Also, arm 2
2 and 25 are provided with a lead wire 21 and a guide 28 for applying a high DC voltage required for electrostatic attraction.
The arms 22 and 25 can be freely moved in the plane of the drawing by the arm drive unit 26. Also, the arm joint 29
Can also rotate. FIG. 5 shows an example of transferring a substrate between such transfer arms. FIG.
, The substrate 1 is transferred between the transfer arm 30 and the transfer arm 31. The substrate 1 is attracted to the electrostatic attracting portion 32 of the transfer arm 30. Transfer arm 30 to transfer arm 3
The substrate 1 is delivered to the electrostatic suction unit 33 provided in the first substrate 1. As shown in FIG. 6, one of the electrostatic chucking portions has a circular shape and the other has a horseshoe shape, so that the electrostatic chucking portions can be electrostatically sucked at the center of the substrate 1 without crossing each other.
As shown in FIG. 6, after the two electrostatic chucking parts move to the center of the substrate and the substrate 1 is ready for delivery, as shown in FIG. 5, the transfer arm 30 or the transfer arm 31 moves in the direction indicated by the arrow. Is driven. The driving unit in the direction of the arrow is shown in FIG.
Is provided in the arm drive unit 26. Both electrostatic suction parts 3
In a state where the substrates 2 and 33 are in contact with the back surface of the substrate 1, a high DC voltage is applied to the electrostatic attraction unit 33 to which the substrate 1 is to be delivered.
The application of the DC high voltage to the electrostatic attraction unit 32 is stopped. As a result, the substrate 1 was held by the electrostatic attraction unit 33. Next, the transfer arm 30 or 31 is driven in the direction of the arrow in FIG. 5 to transfer the substrate 1 to the transfer arm 31.

By repeating such a method, the substrates can be transported one after another. Further, in transferring the substrate from the transfer arm to the substrate holding device, it is effective to provide an electrostatic attraction portion that can move in the normal direction of the substrate on the substrate holding device side. For example, the transfer arm 31 in FIG. 5 is a substrate holding device. In FIG. 6, the position at which the substrate is electrostatically attracted is the center of the substrate.
The electrostatic attraction has an attraction force capable of fixing and transporting the substrate in the same manner anywhere on the back surface of the substrate. Therefore,
In particular, it is not necessary to provide a horseshoe-shaped electrostatic attraction portion as shown in FIG. 6, and the substrate can be delivered by being attracted at one end and the other end of the back surface of the substrate. In this case, both of the electrostatic suction portions may be circular. It suffices that both electrostatic attraction portions are large enough to fit on the back surface of the substrate at the same time.

Although the above-described electrostatic attraction portion of the present invention is relatively large as compared with the thickness of the substrate, the electrostatic attraction portion is relatively large as compared with the thickness of the substrate, for example, 1 mm. There is no need to be thick. It is sufficient that the layer has a thickness that does not cause dielectric breakdown even when a high DC voltage is applied. In the case of alumina,
A few hundred μm is sufficient. However, it is sufficient that the member forming the electrostatic attraction layer is sufficiently thick in terms of strength, and if it is aluminum, it can be as small as about 1 mm depending on the combination of the transfer arms. A place where such a thin electrostatic attraction part is required is when a substrate is taken out or stored from a cassette. An example is shown in FIG. The thinly formed electrostatic attraction unit 34 is inserted between the substrates housed in the cassette 36 by the transport arm 35 also made thin. The thickness of the electrostatic attraction unit 34 is smaller than the dimension between the substrates housed in the cassette 36. Therefore, the electrostatic attraction unit is inserted up to the center (although it may be at the end) of the substrate 1 without contacting the substrate 1. Then, the cassette driving unit 37 moves the cassette 36 to the substrate 1.
At the same time, it moves in one direction toward the back surface of the substrate to be taken out in the direction of the arrow in the figure. By this movement, the back surface of the substrate 1 comes into contact with the electrostatic attraction unit 34, where a DC high voltage is applied to the electrostatic attraction unit. As a result, the substrate 1 was held by the electrostatic attraction unit 34. Next, the transfer arm 35 is moved,
The substrate 1 is taken out of the cassette 36. Cassette 36
When the substrate 1 is stored in the storage device, the procedure is reversed. In the procedure in which the cassette 37 moves in the direction of the arrow in the figure and the electrostatic attraction unit 34 comes into contact with the back surface of the substrate, the substrate transport arm 35 may move in the direction of the arrow instead of the cassette driving unit. This is a procedure similar to that described with reference to FIG. The role of the cassette driving unit 37 at this time is to move the cassette 36 so that the position of the substrate to be transferred is within the movable range of the transfer arm 35.

If a thin transfer arm 35 as shown in FIG. 7 is used, there is a possibility that the arm may vibrate during the movement of the transfer arm and the substrate may come into contact with other members. The degree of the vibration is detected, and the transfer arm 35 is detected.
The distortion sensor 38 shown in FIG. 8 is provided for the purpose of controlling the motion of the camera. The distortion sensor 38 detects the distortion of the transfer arm 35 and can measure the bending amount of the arm, that is, the vibration amplitude. Further, it is also possible to monitor the state of contact between the back surface of the substrate and the electrostatic attraction portion 34 when the substrate is delivered by the distortion sensor 38. Therefore, it can be used as a signal for controlling the movement of the transfer arm 35 at the time of transferring the substrate or the movement of the cassette driving unit 37.

As described above, when the substrate transfer method using the electrostatic attraction force is used, the apparatus can be configured with a floor area irrespective of the substrate size. Of course, the device area in the direction corresponding to the surface of the substrate (the area in the vertical direction) increases. However, this is a sufficiently acceptable size in consideration of the ratio between the ceiling and the substrate size in a clean room or the like where the apparatus is installed. Further, even if the substrate size is increased, the substrate can be transported by replacing the container in the transfer chamber or modifying the apparatus, and the processing apparatus may be used for many generations.

Since the substrate is firmly fixed to the electrostatic attraction member, the substrate and the attraction member are less likely to slip relatively. Therefore, high-speed conveyance becomes possible.

[0017]

According to the present invention, the footprint of the substrate processing apparatus and the transfer system can be reduced even when the diameter of the substrate is increased, so that the exclusive area of the clean room can be reduced. Also, since the footprint of the substrate processing apparatus hardly changes even when the diameter of the substrate is increased,
The same system can be used for the next generation by changing the size of the conveyance system that can carry the substrate size based on the next generation in advance, or by changing the container of the conveyance system of the substrate processing equipment, so that it is possible to reduce the equipment cost. effective. Further, in the transport system, since the electrostatic attraction method is used for holding the substrate, there is no need to contact the substrate surface, so that there is an effect that foreign substances are hardly attached. Furthermore, even if foreign matter drops from the upper surface of the substrate during transport or substrate processing, the foreign matter does not adhere to the substrate processing surface because the substrate surface is vertical, and the yield of substrate processing is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an ion implantation apparatus showing one embodiment of the present invention.

FIG. 2 is an explanatory view of a conventional ion implantation apparatus.

FIG. 3 is a cross-sectional view of the electrostatic suction unit.

FIG. 4 is a front view of a transfer arm.

FIG. 5 is an explanatory diagram of substrate delivery.

FIG. 6 is an explanatory diagram of substrate transfer.

FIG. 7 is an explanatory diagram when a substrate is taken out of a cassette.

FIG. 8 is an explanatory view in which a distortion sensor is attached to a transfer arm.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Ion source, 3 ... Mass analysis part, 4 ... Accelerator tube, 5 ... Substrate processing chamber, 6 ... Substrate holding device, 7 ... Substrate introduction chamber, 8 ... Cassette, 9 ... Buffer chamber, 10 ... Transport Arm, 11: buffer chamber, 12: transfer arm, 13 ...
Substrate unloading chamber, 14 cassette, 15 valve, 16 substrate, 17 substrate holding device, 18 electrode, 19 electrode, 20
... Electrostatic attraction member, 21 ... Lead wire, 22 ... Arm, 23
... Sleeve, 24 ... Spring, 25 ... Arm, 26 ... Arm drive unit, 27 ... Post, 28 ... Guide, 29 ... Arm joint, 30 ... Transport arm, 31 ... Transport arm, 32 ... Electrostatic attraction unit, 33 ... Electrostatic attraction unit, 34 ... Electrostatic attraction unit, 35 ...
Transfer arm, 36: cassette, 37: cassette drive,
38 ... Strain sensor.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/265 H01L 21/265 603C

Claims (1)

[Claims] 1. A substrate transfer method for a substrate processing system, comprising: a substrate introduction chamber, an unloading chamber, and a substrate processing chamber; The substrates were stored in a cassette capable of storing a plurality of substrates, the cassette was placed in the substrate introduction chamber, and the substrates were taken out one by one from the cassette and transported to the substrate processing chamber to process the substrates. Subsequently, a series of steps of taking out the substrate and storing the substrate in a cassette placed in the substrate unloading chamber is performed with the normal line of the surface of the transferred substrate kept substantially horizontal, and holding the substrate during this step The substrate is transferred by an electrostatic attraction force utilizing an electrostatic force.