Substrate transfer method, substrate processing method, substrate transfer device, and program

Abstract

To suppress an occurrence of a defect when each circular substrate having notches of different shapes formed at a peripheral edge part is transferred.SOLUTION: A substrate processing method comprises: a first detection step of detecting positions of different ends of a substrate by a sensor in a state in which a holding part of a substrate transfer device is located at a first position with respect to a mobile object; a second detection step of detecting positions of different ends of the substrate by the sensor in a state in which the holding part is located at a second position; a first calculation step of calculating a change amount in a lateral direction intersecting an advancing / retracting direction of the holding part with respect to an expected center position of the substrate acquired by the first detection step and the second detection step; a second calculation step of calculating a change amount of a size corresponding to a radius of the substrate acquired in each of the first detection step and the second detection step; and a position determination step of determining the position of the substrate in the holding part based on calculation results in the first calculation step and the second calculation step.SELECTED DRAWING: Figure 20

Description

[Technical Field]

[0001] The present disclosure relates to a substrate transfer method, a substrate processing method, a substrate transfer apparatus, and a program. [Background technology]

[0002] In manufacturing semiconductor devices, semiconductor wafers (hereinafter referred to as wafers) are transported and processed within a substrate processing system by a substrate transport apparatus. This substrate transport apparatus may be equipped with a sensor for detecting the position of the wafer held by the substrate transport apparatus, and Patent Document 1 discloses a substrate transport apparatus equipped with such a sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-64918 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure reduces the occurrence of problems when transporting circular substrates with differently shaped notches formed on their peripheries. [Means for solving the problem]

[0005] The substrate transport method of the present disclosure is a substrate transport method in which a substrate is transported by a substrate transport device including a movable body that moves within a substrate transport area, and a holding part that holds the circular substrate having a notch formed on a peripheral edge and is provided on the movable body so as to be able to move forward and backward, a first detection step of optically detecting positions of different edges of the substrate by a sensor provided on the movable body while the holding unit is positioned at a first position relative to the movable body; a second detection step of detecting positions of different edges of the substrate by the sensor while the holder is positioned at a second position relative to the movable body; a first calculation step of calculating a change amount in a lateral direction intersecting with a direction of movement of the holder with respect to an estimated center position of the substrate, which is respectively acquired in the first detection step and the second detection step; a second calculation step of calculating a change amount of a size corresponding to a radius of the substrate obtained by each of the first detection step and the second detection step; a position determination step of determining a position of the substrate in the holder to be used for transporting the substrate based on calculation results in the first calculation step and the second calculation step; Includes. [Effects of the Invention]

[0006] The present disclosure can reduce the occurrence of problems when transporting circular substrates having differently shaped notches formed on their peripheries. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a plan view of a wafer processing system including a substrate transport apparatus of the present disclosure. [Figure 2] FIG. 2 is a front view of the wafer processing system. [Figure 3] FIG. 2 is a perspective view of a wafer transfer mechanism provided in the system. [Figure 4] FIG. 2 is a side view of the wafer transfer mechanism. [Figure 5] FIG. 2 is a plan view of the wafer transfer mechanism and a wafer on which a notch is formed. [Figure 6] FIG. 2 is a plan view of the wafer transfer mechanism and a wafer on which an orientation flat is formed. [Figure 7] FIG. 2 is a plan view of a light-receiving element included in a sensor provided in the wafer transfer mechanism. [Figure 8] 10 is an explanatory diagram showing the relationship between the four sensor groups and the detected wafer center position and radius. FIG. [Figure 9] FIG. 10 is a plan view showing the position of a holder provided on the wafer transfer mechanism during detection. [Figure 10] FIG. 10 is an explanatory diagram showing a change in the position of the sensor during each detection. [Figure 11] FIG. 10 is an explanatory diagram showing the change in the center position of the wafer in each detection. [Figure 12] 10 is a graph illustrating the amount of change in the center position and radius of a wafer. FIG. [Figure 13] FIG. 2 is a plan view for explaining the horizontal axis of the graph. [Figure 14] FIG. 10 is an explanatory diagram showing the change in the radius of the wafer in each detection. [Figure 15] FIG. 10 is a graph illustrating the amount of change in the radius of the wafer. [Figure 16] FIG. 10 is an explanatory diagram showing a change in the position of the sensor during each detection. [Figure 17] 10 is an explanatory diagram showing the positional relationship between the sensor and the wafer W during the first detection. FIG. [Figure 18] 10 is an explanatory diagram showing the positional relationship between the sensor and the wafer W during the second detection. FIG. [Figure 19] 10 is an explanatory diagram showing the positional relationship between the sensor and the wafer W during the first detection. FIG. [Figure 20] FIG. 10 is a flowchart showing a flow for transporting a wafer. [Figure 21] FIG. 10 is a flowchart showing a flow for transporting a wafer. [Figure 22] FIG. 10 is a flowchart showing a flow for transporting a wafer. [Figure 23] FIG. 10 is a flowchart showing a modified example of the flow for transporting a wafer. [Figure 24] FIG. 10 is a flowchart showing a modified example of the flow for transporting a wafer. [Figure 25] FIG. 2 is a plan view of a peripheral exposure device provided in the system. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a wafer processing system as a substrate processing apparatus according to this embodiment will be described with reference to the drawings. In this specification, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0009] <Wafer processing system> First, the configuration of a wafer processing system according to this embodiment will be described. Figures 1 and 2 are a plan view and a front view, respectively, that schematically show the configuration of a wafer processing system 1. In this embodiment, the wafer processing system 1 will be described as an example of a photolithography processing system that performs a resist film forming process and a development process on wafers W.

[0010] 1, the wafer processing system 1 includes a cassette station 2 into which a cassette C containing a plurality of wafers W is loaded and unloaded, and a processing station 3 equipped with a plurality of various processing devices that perform predetermined processing on the wafers W. The wafer processing system 1 has a configuration in which the cassette station 2 and an interface station 4 that transfers the wafers W between the processing station 3 and an exposure device (not shown) adjacent to the opposite side of the processing station 3 are integrally connected. Note that, as shown in FIG. 1, two processing stations 3 are installed between the cassette station 2 and the interface station 4, but one, or three or more processing stations may be installed.

[0011] The cassette station 2 is provided with multiple cassette placement plates 21 and wafer transfer mechanisms 22 and 23. The cassette station 2 transfers wafers between the cassette C placed on the cassette placement plate 21 and the processing station 3 using the wafer transfer mechanism 22 or 23. To this end, the wafer transfer mechanisms 22 and 23 are each provided with drive mechanisms for the X direction, Y direction, vertical direction, and around the vertical axis (θ direction) as needed, and may also be provided with drive mechanisms for all directions. At least one of the wafer transfer mechanisms 22 and 23 is capable of transferring wafers to and from the cassette C, and is also capable of transferring wafers to and from the processing station 3. Note that transferring wafers to and from the processing station 3 refers to, for example, transferring wafers to and from a third block G3 equipped with a transfer device accessible by the wafer transfer mechanism 33 in the processing station 3 (described later). The third block G3 may be provided with multiple transfer devices (not shown) arranged vertically.

[0012] An inspection device (not shown) for inspecting the wafer W may be provided at a position accessible to either the wafer transfer mechanism 22 or 23.

[0013] The processing station 3 is provided with multiple blocks, e.g., three blocks G1, G2, and G4 (first, second, and fourth blocks). Also, as shown in FIG. 2, multiple layers 31 each including the first and second blocks G1 and G2 are stacked vertically. For example, the first block G1 is provided on the front side of the processing station 3 (the negative X-direction side in FIG. 1), and the second block G2 is provided on the back side of the processing station 3 (the positive X-direction side in FIG. 1). The fourth block G4 is provided on the interface station 4 side of the processing station 3 (the positive Y-direction side in FIG. 1) or at a connection portion with another adjacent processing station 3. The fourth block G4 may be provided with multiple transfer devices arranged vertically. The aforementioned third block G3 may also be provided within the processing station 3.

[0014] The first block G1 includes a plurality of processing devices, such as a patterning film forming device and a development processing device (both not shown). The patterning film forming device may include, for example, a resist film forming device and an anti-reflection film forming device.

[0015] For example, a plurality of processing devices may be arranged in a horizontal line, and the number, arrangement, and type of these processing devices may be selected arbitrarily.

[0016] In these patterning film forming apparatuses and developing treatment apparatuses, for example, a predetermined processing liquid or a predetermined gas is supplied onto the wafer W. In this manner, the patterning film forming apparatus forms a resist film used as a mask when forming a pattern on an underlying film, or forms an anti-reflection film for efficiently performing a light irradiation process, such as an exposure process. Meanwhile, in the developing treatment apparatus, a portion of the exposed resist film is removed to form the uneven shape that serves as the mask.

[0017] For example, in the second block G2, heat treatment devices (not shown) that perform heat treatment such as heating and cooling of the wafer W are arranged in a vertical and horizontal direction. Also, in the second block G2, although neither is shown, a hydrophobization treatment device that performs a hydrophobization treatment to improve the adhesion of the resist liquid to the wafer W, and a peripheral exposure device that exposes the peripheral portion of the wafer W are arranged in a vertical and horizontal direction (Z direction in FIG. 2). The number and arrangement of these heat treatment devices, hydrophobization treatment devices, and peripheral exposure devices can also be selected as desired.

[0018] 1, a wafer transfer area 32 is formed in an area sandwiched between a first block G1 and a second block G2 in a plan view. In the wafer transfer area 32, for example, a wafer transfer mechanism 33 is disposed.

[0019] The wafer transfer mechanism 33 has a transfer arm 33a that is movable in, for example, the Y direction, the front-to-rear direction, the θ direction, and the up-and-down direction. The wafer transfer mechanism 33 moves within the wafer transfer area 32 and can transfer the wafer W to predetermined devices in the surrounding first block G1, second block G2, third block G3, and fourth block G4. When there are multiple processing stations 3 as shown in Figure 1, the wafer transfer mechanism 33 provided in the processing station 3 located on the interface station 4 side can transfer the wafer W to predetermined devices in the first, second, and fourth blocks G1, G2, and G3, as well as the fifth block G5 described below.

[0020] A plurality of wafer transfer mechanisms 33 are arranged vertically, for example, as shown in FIG. 2. One wafer transfer mechanism 33 can transfer wafers W to a predetermined device located at the height of the upper layers 31 among the multiple layers 31 stacked vertically. Another wafer transfer mechanism 33 can transfer wafers W to a predetermined device located at the height of multiple layers 31 located below the above layers 31. A plurality of wafer transfer regions 32 are provided to enable such transfer of wafers W. Note that the number of wafer transfer mechanisms 33 and the number of layers 31 corresponding to one wafer transfer mechanism 33 can be selected arbitrarily, such as by providing a wafer transfer mechanism 33 for each layer 31.

[0021] The wafer transfer area 32, the first block G1, or the second block G2 may also include a shuttle transfer mechanism (not shown). The shuttle transfer mechanism linearly transfers the wafer W between a space adjacent to one side of the processing station 3 and another space adjacent to the opposite side.

[0022] The interface station 4 is provided with a fifth block G5 equipped with multiple transfer devices and wafer transfer mechanisms 41 and 42. The interface station 4 uses the wafer transfer mechanism 41 or 42 to transfer the wafer W between the fifth block G5, where the wafer W is transferred by the wafer transfer mechanism 33, and the exposure device. To this end, the wafer transfer mechanisms 41 and 42 are each provided with drive mechanisms for directions such as the X direction, Y direction, up / down direction, and around the vertical axis (θ direction) as needed, and may also be provided with drive mechanisms for all directions. At least one of the wafer transfer mechanisms 41 and 42 can support the wafer W and transfer the wafer W between the transfer devices in the fifth block G5 and the exposure device.

[0023] A cleaning treatment device for cleaning the surface of the wafer W and the aforementioned peripheral exposure device may be provided in the interface station 4 at a position accessible to either of the wafer transfer mechanisms 41 and 42.

[0024] The inspection device may be provided in cassette station 2 as described above, but it may also be provided in processing station 3 and interface station 4 at a position accessible to any of the wafer transport mechanisms (33, 41, 42 in Figure 1 or Figure 2) provided inside each station.

[0025] The wafer processing system 1 described above is provided with a control unit 100. The control unit 100 is, for example, a computer and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of wafers W in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of drive systems such as the various processing devices and transfer mechanisms described above to realize wafer processing in the wafer processing system 1. Each program is structured as a group of steps that control the operation of each part of the wafer processing system 1 to transfer and process wafers W. The control unit 100 includes one or more control circuits and transmits control signals to each part of the wafer processing system 1 to perform each operation of the above-described group of steps, thereby controlling the operation. The above programs may be recorded on a computer-readable storage medium H and installed in the control unit 100 from the storage medium H.

[0026] <Wafer Processing System Operation> The wafer processing system 1 is configured as described above. Next, an example of wafer processing performed using the wafer processing system 1 configured as described above will be described.

[0027] First, a cassette C containing a plurality of wafers W is carried into the cassette station 2 of the wafer processing system 1 and placed on the cassette mounting plate 21. Next, each wafer W in the cassette C is sequentially removed by the wafer transfer mechanism 22 or 23 and transferred to the delivery device in the third block G3.

[0028] The wafer W transferred to the transfer device in the third block G3 is supported by the wafer transfer mechanism 33 and transferred to the hydrophobization treatment device provided in the second block G2, where hydrophobization treatment is performed. The wafer W is then transferred by the wafer transfer mechanism 33 to the resist film forming device, where a resist film is formed on the wafer W, and then transferred to the heat treatment device, where a pre-bake treatment is performed, before being transferred to the transfer device in the fifth block G5. When there are multiple processing stations 3 as shown in FIGS. 1 and 2, the wafer W is temporarily placed in the transfer device in the fourth block G4 before being transferred to the transfer device in the fifth block G5, and then transferred between multiple wafer transfer mechanisms 33. If necessary, the wafer W may also be transferred by the wafer transfer mechanism 33 to a peripheral exposure device, where the peripheral edge of the wafer is exposed.

[0029] The wafer W transferred to the delivery device in the fifth block G5 is transferred to the exposure device by wafer transfer mechanisms 41 and 42, and is exposed to a predetermined pattern. Note that the wafer W may be cleaned in a cleaning device before the exposure process.

[0030] The exposed wafer W is transferred to a transfer device in the fifth block G5 by wafer transfer mechanisms 41 and 42. Thereafter, the wafer W is transferred to a heat treatment device by wafer transfer mechanism 33, where it is subjected to post-exposure baking.

[0031] The wafer W that has been subjected to post-exposure baking is transferred to a developing treatment device by the wafer transfer mechanism 33 and developed. After development is completed, the wafer W is transferred to a heat treatment device by the wafer transfer mechanism 33 and subjected to post-baking.

[0032] The wafer W is then transferred by wafer transfer mechanism 33 to a transfer device in third block G3, and then transferred by wafer transfer mechanism 22 or 23 in cassette station 2 to a cassette C on a predetermined cassette mounting plate 21. This completes the photolithography process. Any unnecessary processing equipment listed above may not be provided, or processing in that equipment may not be performed.

[0033] <Relationship between wafer transfer mechanism and substrate transfer device> As described above, wafer processing system 1 includes wafer transfer mechanisms, which are substrate transfer mechanisms. As will be described in detail later, the position of wafer W held by each wafer transfer mechanism is detected by control unit 100, and each wafer transfer mechanism and control unit 100 constitute a substrate transfer apparatus. Therefore, the programs included in control unit 100 described above not only control the operation of wafer processing system 1 as described above, but also perform various calculations and judgments for detecting such positions, and can execute the operations shown in the flowcharts described below.

[0034] <Configuration of wafer transport mechanism> Hereinafter, each wafer transfer mechanism provided in the wafer processing system 1 described above transfers a wafer W, which is a circular substrate, for example, 300 mm in diameter, with a notch formed therein. This notch is a notch N or an orientation flat (hereinafter referred to as an orientation flat) F formed according to a predetermined standard and is provided on the peripheral edge of the wafer W. The notch N, which is a first notch, has a V-shaped edge that widens from the center of the wafer W toward the peripheral edge, forming a tiny fan shape. The orientation flat F, which is a second notch, has an edge that follows the diameter of the wafer W. In this way, the wafer W to be transferred has one of two differently shaped notches formed. In a plan view, the area of ​​the orientation flat F is larger than the area of ​​the notch N. Note that when the wafer W is transferred from the transfer container, cassette C, it is unknown whether the wafer W has a notch N or an orientation flat F.

[0035] Of the wafer transfer mechanisms, the following will be described in detail, taking as a representative example the wafer transfer mechanism 33 provided in the processing station 3. Note that the wafer transfer mechanisms other than the wafer transfer mechanism 33 have the same configuration as the wafer transfer mechanism 33, except that a moving part 51 (to be described later) constituting the wafer transfer mechanism moves in the X direction instead of the Y direction, or does not move in the X or Y directions, and therefore detailed description thereof will be omitted.

[0036] The wafer transfer mechanism 33 includes a moving unit 51 consisting of a moving body that moves in the Y direction (left and right direction) and an elevating body that is attached to the moving body and moves in the Z direction, a base 52 attached to the elevating body, two holding units 53 attached to the base 52, and a detection unit 6 attached to the base 52. The detection unit 6 is not shown in Fig. 1. In Fig. 1, the holding unit 53 is shown as a transfer arm 33a.

[0037] 3 and 4, which are perspective and side views of base 52, holder 53, and detector 6, respectively, will be referred to as appropriate for the following description. Also, FIGS. 5 and 6 show plan views of wafer W held by wafer transfer mechanism 33, and show a wafer W with a notch N and a wafer W with an orientation flat F, respectively. As described above, by being mounted on movable unit 51, base 52 is movable in the Y direction (i.e., horizontally) and in the Z direction (i.e., vertically). Base 52, which is a movable body, is mounted on the lifting platform of movable unit 51 so as to be rotatable about a vertical axis (Z axis).

[0038] Two holding portions 53, each having a generally C-shape in plan view, are provided on the base 52. Each holding portion 53 includes an enclosing portion 54 that surrounds the side periphery of the wafer W and is formed into a generally C-shaped plate in plan view. The two holding portions 53 can move horizontally and independently on the base 52, with the open side of the C facing forward. The area surrounded by the enclosing portions 54 forms a circular holding area 56 that is slightly larger than the wafer W in plan view. Four support portions 55 are provided on the lower side of the enclosing portions 54, protruding toward the holding area 56 from four circumferentially spaced locations. The peripheral edge of the wafer W is supported on the upper surface of the support portions 55. Suction holes 57 are formed in the upper surface of the support portions 55. While the peripheral edge of the wafer W is placed on the support portions 55, a suction mechanism (not shown) applies suction through the suction holes 57 to suction-hold the peripheral edge of the wafer W to the support portions 55.

[0039] In a plan view, the center of the holding area 56 is designated as P0, and the center of the wafer W held in the holding area 56 is designated as P. Note that the center P of the wafer W is the center if the wafer W were to have no notches and be a perfect circle. FIG. 5 shows a state in which the centers P0 and P are aligned, while FIG. 6 shows a state in which the center P is shifted from the center P0. To distinguish between the two holding units 53, the upper holding unit is sometimes designated as 53A and the lower holding unit is designated as 53B. The direction in which these holding units 53A and 53B move forward and backward is designated as the X' direction, and the horizontal direction perpendicular to the X' direction is designated as the Y' direction. Therefore, the Y' direction is a horizontal direction that intersects with the direction in which the holding units 53 move forward and backward.

[0040] <Operation of the base and holding unit during transportation> When transferring a wafer W from a source apparatus to a destination apparatus, the base 52 moves through the wafer transfer area 32 from near the source apparatus to near the destination apparatus. During this transfer between the apparatuses, the holders 53A and 53B are positioned in a predetermined retracted position, overlapping each other vertically. This retracted position is a position where the holding area 56 overlaps the base 52 in a plan view. The wafer W is held by only one of the holders 53A and 53B, and this wafer W is the wafer W received from the source apparatus. When the base 52 is positioned near the destination apparatus, the one of the two holders 53 that is not holding the wafer W advances along the base 52, receives the wafer W from the destination apparatus, and then returns to the retracted position.

[0041] Next, the other holder 53 holding the wafer W received from the source apparatus advances, moving to a forward position where the holding area 56 does not overlap with the base 52. In this state, the destination apparatus and the base 52 are raised and lowered relative to each other, thereby transferring the wafer W. This relative raising and lowering is specifically a lowering of the base 52 or a raising of the lift pins provided in the destination apparatus. FIG. 4 illustrates the transfer of the wafer W to the apparatus 50 by the wafer transfer mechanism 33, with the lift pins 50A of the apparatus 50 being raised. As described below, the positions of the base 52 and the forward position of the holder 53 during the transfer of the wafer W are appropriately corrected. Note that FIGS. 3 and 4 show the states where the holder 53B is in the retracted position and the holder 53A is in the advanced position. In FIGS. 5 and 6, the holder 53B is not shown, and the holder 53A is shown in the retracted position.

[0042] <Configuration of the detector in the wafer transport mechanism> A detection unit 6 is provided on the base 52. The detection unit 6 is composed of four sensors 61 for optically detecting the position of the edge of the wafer W, and each sensor 61 includes a light-projecting unit 62 and a light-receiving unit 63 aligned in the Z direction. The four sensors 61 are provided at intervals along the periphery of the wafer W held by the holder 53A or the holder 53B in the retracted position, and the light-projecting unit 62 and the light-receiving unit 63 are disposed to sandwich the wafer W in the Z direction. Either the light-projecting unit 62 or the light-receiving unit 63 may be disposed above the wafer W. However, in this example, the light-receiving unit 63 is disposed above the wafer W, and is mounted on the base 52 via a support 64 provided on the base 62.

[0043] As shown in the plan view of FIG. 7 , the light-receiving unit 63 is composed of a number of light-receiving elements 60 arranged in a straight line. This line of light-receiving elements 60 is formed so as to extend from the center of the wafer W held by the holder 53 in the retracted position toward the outer periphery in a plan view. The light-emitting unit 62 is composed of an elongated light source that overlaps the line of light-receiving elements 60 in a plan view. As described above, the sensors 61 are arranged in the circumferential direction of the wafer W held by the holder 53 in the retracted position, so that the detection unit 6, which is composed of four sensors 61, is arranged radially extending from the center of the wafer W toward the outer periphery. Regarding the arrangement of the four sensors 61, as the holder 53 advances and retreats, the center P0 of the holding area 56 for the wafer W moves along a straight line along the X′ direction. In a plan view, the four sensors 61 are arranged symmetrically with respect to this line. Furthermore, as will be described in detail later, one of the sensors 61 may overlap a notch in the wafer W, but the positions of the four sensors 61 are set so that multiple sensors 61 do not overlap a notch.

[0044] When a wafer W is held by either of the holders 53A and 53B, and the holder 53 holding the wafer W is positioned at a retracted position or at a first or second inspection position (described later) near the retracted position, light is emitted from the light-emitting portion 62 of each sensor 61 toward the light-receiving portion 63. The size of the area received by the light-receiving portion 63 changes depending on the edge position of the wafer W. Therefore, the number of light-receiving elements 60 receiving light changes depending on the edge position of the wafer W, and for each light-receiving element 60 receiving light, a signal corresponding to the received light is output to the control unit 100. Therefore, the light-receiving portion 63 transmits a detection signal corresponding to the size of the area receiving light to the control unit 100. Since the size of the light-receiving area corresponds to the edge position of the wafer W, the detection signal of the sensor 61 corresponds to the edge position of the wafer W. Note that if the edge of the wafer W does not overlap with the row of light-receiving elements 60 in a plan view, the sensor 61 including that light-receiving element 60 cannot detect the edge of the wafer W. Hereinafter, the column direction of the light receiving elements 60 may be referred to as the detection direction of the sensor 61.

[0045] <Calculation of sensor combination pattern and wafer center P position and radius R> Hereinafter, for ease of explanation, the four sensors 61 may be referred to as 61A to 61D to distinguish them from one another. Of the four sensors 61, the one located at the front on the left side when viewed from the rear to the front of the holder 53 is designated as 61A. The sensors are designated as 61B, 61C, and 61D in order from sensor 61A along the circumference of the wafer W in a counterclockwise direction in a plan view.

[0046] Using detection signals obtained from a sensor group consisting of three sensors 61 out of 61A to 61D, the control unit 100 detects the position of the edge of the wafer W held by the holder 53 in a coordinate system set on a horizontal plane. That is, it detects the positions of the edges at three locations on the wafer W. Furthermore, the control unit 100 can calculate the position of the center P of the wafer W and the radius R of the wafer W in that coordinate system from the positions of the three edges.

[0047] In this way, a total of four sensors 61 are provided, and the position of the center P and the radius R of the wafer W need only be calculated using the detection results of three of them, so the position of the center P and the radius R of the wafer W can be calculated from a maximum of four combination patterns of sensors 61. That is, there are four patterns for the detection results: a pattern using sensors 61A, 61B, and 61D (referred to as group 1), a pattern using sensors 61A, 61B, and 61C (referred to as group 2), a pattern using sensors 61B, 61C, and 61D (referred to as group 3), and a pattern using sensors 61A, 61C, and 61D (referred to as group 4). Note that groups 1 to 4 thus correspond to first to fourth groups, each containing a different combination of sensors 61.

[0048] The position of the center P of the wafer W and the radius R of the wafer W can be calculated from the positions of the three edges of the wafer W, for example, according to the method described in Patent Document 1. Briefly describing this method, the detected positions of the three edges of the wafer W can be expressed as point a' (X1', Y1'), point b' (X2', Y2'), and point c' (X3', Y3') in an X'Y' Cartesian coordinate system set on a horizontal plane, and the X coordinate of the center P can be calculated using the following equation (13). The Y coordinate of the center P can also be calculated using an equation similar to equation (13).

[0049]

number

[0050] Then, according to the following equation (15), the distance between the calculated position of the center P and the position obtained from a preset sensor 61 among the three edge positions of the wafer W used to determine the center P (referred to as the position of point a' in the equation) is calculated as the radius R of the wafer W.

[0051]

number

[0052] The positions obtained from the preset sensors 61 are assumed to be positions obtained from different sensors 61 when calculating the radius R for each of groups 1 to 4. Specifically, when obtaining the position of the center P of the wafer W from group 1, the distance between the position of the center P and the position detected by sensor 61A is used; when obtaining the position of the center P of the wafer W from group 2, the distance between the position of the center P and the position detected by sensor 61B is used; when obtaining the position of the center P of the wafer W from group 3, the distance between the position of the center P and the position detected by sensor 61C is used; and when obtaining the position of the center P of the wafer W from group 4, the distance between the position of the center P and the position detected by sensor 61D is used. Hereinafter, with regard to the wafer center P and the radius R of the wafer W whose positions are calculated in this manner, those obtained from group 1 will be referred to as P1 and R1, those obtained from group 2 as P2 and R2, those obtained from group 3 as P3 and R3, and those obtained from group 4 as P4 and R4 (see FIG. 8).

[0053] As described above, the position of the wafer center P may be calculated four ways from each of groups 1 to 4, but as will be described later, there may also be cases where it is calculated from only one of groups 1 to 4, that is, where only one is calculated. When only one way is calculated, the control unit 100 determines that calculated value as the position of the wafer center P. When four ways are calculated, the control unit 100 calculates the average value of the four positions of the wafer center P, and determines that calculated value as the position of the wafer center P. That is, in an X'Y' Cartesian coordinate system, the position of the center P is determined by taking the average of the four positions in the X' direction as the X' coordinate of the center P and the average of the four positions in the Y' direction as the Y' coordinate of the center P.

[0054] The position of the wafer center P determined in this manner is used to transfer the wafer W to the destination apparatus 50 described in FIG. 4. In describing this transfer in detail, the position of the wafer W when the center P of the wafer W coincides with the center P0 of the holding area 56 (the position shown in FIG. 5) is defined as the reference position. As described above, the wafer transfer mechanism 33 is capable of moving the base 52 in the Y direction and changing its orientation (rotating about the Z axis), and of moving the holder 53 back and forth. The position of the base 52 in the Y direction, the orientation of the base 52, and the forward position of the holder 53 on the base 52 when transferring the wafer W to the destination apparatus 50 are each preset, assuming that the wafer W is located at the reference position.

[0055] After determining the position of the center P of the wafer W, the control unit 100 calculates the amount of deviation between the center P and the center P0 in a plan view, and corrects the Y-direction position of the base 52, the orientation of the base 52, and the advanced position of the holder 53 on the base 52 from the predetermined positions. This position correction is performed to compensate for the deviation between the centers P and P0. In other words, even if there is a deviation between the centers P and P0, when the holder 53 is positioned in the advanced position, the control unit 100 controls the positions of the base 52 and the holder 53 so that the center P of the held wafer W is located above a predetermined position in the destination apparatus 50. Therefore, when the wafer W is subsequently transferred to the apparatus 50 by the relative elevation of the base 52 and the apparatus 50, the wafer W is placed at a predetermined position in the apparatus 50.

[0056] <Outline of determining the position of the center P of the wafer W> Before describing in detail the operations performed in the process of determining the position of the center P of the wafer W, an overview will be provided. Note that the control unit 100 performs data processing, such as calculations, comparisons, judgments, and decisions, performed before determining the position. The detection of the edge position of the wafer W by the sensors 61A-61D to determine the position of the center P (first detection of the edge position of the wafer W) is performed while the wafer holder 53 holding the wafer W is in the retracted position. However, as described above, the wafer W has a notch N or an orientation flat F formed thereon. When detecting the edge position of the wafer W, one of the sensors 61A-61D may be caught by this notch. More specifically, this occurs when the light source and the array of light-receiving elements 60 of any of the four sensors 61 overlap the notch in a plan view, causing light to be irradiated onto the notch. In other words, this occurs when the notch forms an optical path between the light-emitting unit 62 and the light-receiving unit 63 of the sensor 61, and light passes through the notch.

[0057] With sensor 61 engaging the notch in this way, there are cases where the position of the edge of wafer W can be detected by sensor 61. Specifically, this is the case where light is projected onto the position of the edge of wafer W where the notch is formed, and the position is detected, which can also be said to be detecting the position of the edge of the notch. Figure 8 shows an example of detecting the position of the edge of wafer W where the notch is formed, and illustrates notch N as the notch and sensor 61D as the sensor engaging the notch.

[0058] As will be described later, it is possible to determine whether or not there is a sensor 61 detecting the edge position of the wafer W that forms a notch, based on the results of the first detection of the edge position of the wafer W. In order to accurately calculate the position of the wafer center P, it is necessary to use the detection results of a group that excludes the sensor 61 that detects the edge position of the wafer W that forms the notch (hereinafter referred to as an inappropriate sensor 61). Therefore, if it is determined that there is an inappropriate sensor 61, second and subsequent detections of the edge position of the wafer W are performed until the position of the center P of the wafer W is determined, and the sensor 61 is identified based on the position detection results of each detection. The detection results of the group from which the identified inappropriate sensor 61 has been excluded are used to determine the position of the center P of the wafer W.

[0059] However, when detecting the position of the edge of the wafer W for the first time, there are cases where the sensor 61 falls on a notch, making it impossible for the sensor 61 to detect the position of the edge of the wafer W. In other words, this is the case when light is not projected onto the edge of the notch, and the edge of the notch is not detected as the edge of the wafer W. While there are cases where detection by one of the sensors 61 is impossible due to the influence of the notch, there are also cases where detection by one of the sensors 61 is impossible due to the position at which the wafer W is held in the holding area 56 of the holder 53 being significantly deviated from the reference position.

[0060] If one of the four sensors 61 is unsuccessful, the second and subsequent edge position detections of the wafer W are performed until the position of the center P of the wafer W is determined. Based on the results of each position detection, a determination is made as to whether the sensor 61 failed to detect the wafer W because it was caught on a notch during the first detection, or whether the sensor failed to detect the wafer W because the wafer W was significantly misaligned from its reference position. If a determination is made that the failure was due to the notch, the detection results of the group excluding the sensor caught on the notch (the three sensors that have been able to detect the wafer W edge position since the first position detection) are used to determine the position of the wafer W's center P. If a determination is made that the failure was due to a significant misalignment from the reference position, a determination is made that an abnormality has occurred (an error determination), and the operation of the wafer transfer mechanism 33 is stopped. That is, the transfer of the wafer W is halted.

[0061] The operations performed up to the determination of the position of the center P of the wafer W outlined above will now be described in detail. <When the edge of the wafer W can be detected by four sensors> 5 and 6, sensors 61A-61D detect the edge position of wafer W (first position detection). Assume that all of sensors 61A-61D detect the edge of wafer W during this first position detection. However, as described above, there is a possibility that one of sensors 61A-61D is an inappropriate sensor 61 for detecting the edge position of wafer W in which a notch is formed. Therefore, the positions of centers P1-P4 of wafer W are calculated from each of groups 1-4, each consisting of three sensors, as described above, and further, radii R1-R4 of wafer W are calculated.

[0062] If none of the sensors 61A to 61D is an unsuitable sensor 61, the variation in the radii R1 to R4 is small, and the maximum and minimum values ​​of the radii R also fall within the allowable range. However, if any of the sensors 61 is an unsuitable sensor 61, the variation in the radii R1 to R4 becomes relatively large, and the maximum and minimum values ​​of the radii R fall outside the allowable range. The allowable range is, for example, 30 μm or less. Note that the determination as to whether the maximum and minimum values ​​of the radii R fall within the allowable range is the determination as to whether or not there is an unsuitable sensor 61, as described above.

[0063] A further explanation of the relationship between the radius R and the notch is provided below. The radii R of the two groups each including an inappropriate sensor 61 are smaller than the radius of the actual wafer W (the radius if the wafer W were a perfect circle). However, due to the notch, the calculated position of the center P of the wafer W is shifted from the actual center of the wafer W, and the radius R obtained from the distance between the center P and the detection position of the inappropriate sensor 61 may be close to the radius of the actual wafer W. FIG. 8 shows an example in which the inappropriate sensor 61 is sensor 61D, and radius R4 calculated from group 4 including sensor 61D is close to the actual radius in this way.

[0064] From the above, the unsuitable sensor 61 is one of the two sensors commonly included in the smallest group and the second smallest group in terms of radius R, and for convenience, these two sensors that are candidates for the unsuitable sensor are referred to as verification sensors. The largest and second largest groups in terms of the calculated radius R include one of the two verification sensors, and the verification sensors included in these groups are different from each other. Hereinafter, for convenience of explanation, two groups each including one unsuitable sensor candidate that is different from each other will be referred to as verification groups.

[0065] The verification sensors and verification groups will be described in detail with reference to FIG. 8. When sensor 61D is placed over the notch (notch N in the example shown in FIG. 8), radius R1 obtained from group 1 (sensors 61A, 61B, 61D) and radius R3 obtained from group 3 (sensors 61B, 61C, 61D) are the smallest or second smallest of the radii R obtained from each group. Radius R2 obtained from group 2 (sensors 61A, 61B, 61C) and radius R4 obtained from group 4 (sensors 61A, 61C, 61D) are the largest or second largest of the radii R obtained from each group, so groups 2 and 4 are verification groups. Sensors 61B and 61D, which are included in both groups 1 and 3, are verification sensors, and sensor 61B is included in group 2, which is a verification group, and sensor 61D is included in group 4, which is also a verification group. Therefore, the verification group includes one of the two verification sensors, and the verification sensors included in the two verification groups are different from each other.

[0066] Once the verification sensor is identified in this way, the holder 53 holding the wafer W is slightly advanced. The distance advanced is, for example, 1 mm, and the position advanced in this way is designated as the first verification position. In FIG. 9, the first verification position is indicated by a solid line, and the retreated position where the holder 53 was previously located is indicated by a two-dot chain line. After this movement of the holder 53, the position of the edge of the wafer W is detected again by the sensors 61A to 61D. In other words, a second detection is performed.

[0067] <Notch N> Assuming that the notch is notch N, the following description will be given with reference to FIG. 10. Also, in FIG. 10, the inappropriate sensor 61 is shown as 61A. Therefore, one of the two verification sensors is 61A. In FIG. 10, examples of the position of sensor 61A relative to wafer W during the first and second position detections are shown by dashed and solid lines, respectively. As mentioned above, notch N is relatively small and has a V-shaped edge. Therefore, when sensor 61A detects the position of the edge of wafer W for the second time, the detection position is either a position on notch N that is different from the detection position in the first detection, or a position other than notch N. In FIG. 10, the detection position is shown as being other than notch N during the second detection (sensor 61 does not overlap notch N).

[0068] Except for exceptional cases described later, such a change in the detection position changes the distance between the actual center of the wafer W and the detection position. As a result, of the centers P of the wafer W calculated from the two verification groups, the position of the center P1 of the wafer W calculated from group 1 including the unsuitable sensor 61A changes significantly in the Y' direction. Figure 11 shows the change in the X'Y' coordinate system of the center P1 calculated from group 1 including the sensor 61A shown in Figure 10. Note that for the other verification group not including the unsuitable sensor 61, such a change in the center position in the Y' direction does not occur or only a slight change occurs due to a detection error.

[0069] The explanation will continue with the amount of change in the position of the center P of the wafer W in the Y' direction being ΔY'. From the above, for each of the two verification groups, the control unit 100 calculates ΔY' between the position of the center P of the wafer W calculated by the first detection of the edge position of the wafer W and the position of the center P of the wafer W calculated by the second detection of the edge position of the wafer W, and determines whether ΔY' for each group is equal to or greater than a preset threshold value (sometimes referred to as the ΔY' threshold value). If any of the two verification groups has ΔY' equal to or greater than the threshold value, it can be assumed that the verification sensor included in that verification group with ΔY' equal to or greater than the threshold value is an unsuitable sensor 61.

[0070] If ΔY′ in only one of the two verification groups is equal to or greater than the threshold, the verification sensor included in that verification group is identified as an unsuitable sensor 61. Depending on the setting of the ΔY′ threshold, it is possible for the ΔY′ in both of the two verification groups to be equal to or greater than the threshold. In such a case, the ΔY′ in these groups is compared, and the verification sensor included in the group with the larger ΔY′ is identified as the unsuitable sensor 61. This identification of the unsuitable sensor 61 also involves identifying which of the two verification groups does not include the unsuitable sensor 61. The position of the center P of the wafer W is then determined from the results of the second edge detection of the wafer W using the verification group identified as not including the unsuitable sensor 61. The ΔY′ threshold can be set to any value, for example, 0.03 mm.

[0071] 8, to specifically explain the identification of the unsuitable sensor 61, of the verification groups, group 2 (sensors 61A, 61B, 61C) and group 4 (sensors 61A, 61C, 61D), ΔY′ of group 4 is equal to or greater than the ΔY′ threshold, and ΔY′ of group 4 is greater than ΔY′ of group 2. As described above, the verification sensor is either 61B or 61D, and because ΔY′ of group 4 fluctuates greatly, the unsuitable sensor 61 is identified as sensor 61D included in group 4. Then, the position of the center P of the wafer W is determined from the results obtained in the second detection of the edge of the wafer W by group 2, which does not include sensor 61D.

[0072] In each case of determining the center P described below, if the position of the center P of the wafer W can be calculated from the detection results of each detection, the position of the center P of the wafer W calculated from the latest detection is determined as the center P of the wafer W to be used for transfer, but the center P obtained from an earlier detection result may also be determined as the center P of the wafer W. In other words, although the second detection result is used to determine the center P of the wafer W in the above example, the first detection result may also be used instead.

[0073] <Notch is Orientation Flat F> Suppose that the notch caught by sensor 61 during the first edge position detection of wafer W with holder 53 in the retracted position is orientation flat F. To explain this case, we will first refer to the graph in FIG. 12, which was obtained by conducting an evaluation test. FIG. 12 shows data obtained from the group containing the unsuitable sensor 61, one of the verification groups mentioned above. First, we will explain the horizontal axes of the graphs shown in the upper and lower sections of FIG. 12. Suppose that one of sensors 61 catches orientation flat F. Compared to the case where wafer W is assumed to be a perfect circle, this orientation flat F causes the detection position of the wafer W edge to shift toward the center of wafer W. The horizontal axis represents the distance of this shift. More specifically, as described above, sensor 61 includes a linear array of light-receiving elements. In the direction of this array (the direction of detection by sensor 61), the value on the horizontal axis represents the distance between the edge of wafer W, assuming that wafer W is a perfect circle, and the position actually detected due to the presence of orientation flat F. This distance will hereafter be referred to as shortened distance L. The plan view of wafer W in Figure 13 shows shortened distance L in the detection direction of sensor 61. A relatively short shortened distance L indicates that sensor 61 is positioned near the edge of orientation flat F in the longitudinal direction, while a relatively long shortened distance L indicates that sensor 61 is positioned near the center of orientation flat F in the longitudinal direction.

[0074] 12 shows the relationship of ΔY' between the position of the center P of the wafer W calculated from the result of the first detection of the edge position of the wafer W and the position of the center P of the wafer W calculated from the result of the second detection of the edge position of the wafer W, to the shortened distance L. The lower graph shows the relationship of the difference between the radius R of the wafer W calculated from the result of the first detection of the edge position of the wafer W and the radius R of the wafer W calculated from the result of the second detection of the edge position of the wafer W, to the shortened distance L. Hereinafter, the difference in radius will be referred to as ΔR.

[0075] As shown in the upper graph, ΔY′ generally increases as the shortened distance L decreases. Note that ΔY′ obtained from verification groups that do not include unsuitable sensors 61 either does not change or changes only slightly due to detection error. Therefore, when the shortened distance L is relatively short, as in the case of a notch N, two verification groups are identified in the first detection, followed by a second detection. The sensor 61 that overlaps the orientation flat F can be identified by determining whether the ΔY′ calculated from each verification group exceeds a threshold value. However, when the shortened distance L is relatively long, ΔY′ is relatively small, approaching zero. To prevent erroneous determination, there is a limit to how much the ΔY′ threshold can be lowered. In other words, ΔY′ may not exceed the ΔY′ threshold, and in such cases, the sensor 61 that overlaps the orientation flat F cannot be identified based on ΔY′.

[0076] However, as shown in the lower graph, ΔR increases as the shortened distance L increases. The change in ΔR will be explained with reference to FIG. 14. FIG. 14 specifically illustrates the state of each detection when sensor 61A is positioned on orientation flat F and shortened distance L is long. As shown in the figure, the detection position of wafer W relative to the detection direction of sensor 61A (the direction of the array of light-receiving elements 60) changes between the first and second detections due to the movement of wafer W. Therefore, radius R1, calculated as the distance between the detection position of sensor 61A and the center P1 of wafer W calculated by each sensor 61 in group 1, changes relatively significantly, and ΔR of this radius R1 is large. Note that when sensor 61 is positioned on orientation flat F and shortened distance L is short, even if sensor 61 is positioned on orientation flat F during the first detection, sensor 61 will no longer be positioned on orientation flat F during the second detection. Since the amount of displacement of the detection position in the detection direction of the sensor 61 is minute, the amount of change in ΔR is also small.

[0077] As described above, ΔY' and ΔR increase or decrease in opposition to changes in the shortened distance L. Therefore, a threshold value is set in advance so that ΔR is equal to or greater than the threshold value within the range of the shortened distance L (shown as L1 in the graph of FIG. 12) in which ΔY' does not exceed the ΔY' threshold value. Hereinafter, this threshold value for ΔR may be referred to as the ΔR threshold value. This ΔR threshold value is, for example, 0.02 mm.

[0078] The ΔR obtained from the verification group that does not include the unsuitable sensor 61 is either zero or a small value due to detection error. Therefore, if ΔR is equal to or greater than the threshold value for only one of the two verification groups, the verification sensor included in that verification group is identified as the sensor that overlaps the notch. Depending on the setting of the ΔR threshold, the ΔR of both verification groups may be equal to or greater than the threshold value. In such a case, the ΔRs of these groups are compared, and the verification sensor included in the group with the larger ΔR is identified as the unsuitable sensor 61. After identifying the unsuitable sensor 61 as described above, i.e., identifying the verification group that does not include the unsuitable sensor 61, the position of the center P of the wafer W is determined from the detection results of the edge position of the wafer W using the verification group that does not include the identified unsuitable sensor 61, as in the case where the notch is a notch N.

[0079] The graph in Figure 15 shows the relationship between ΔR and the shortened distance L obtained by conducting an evaluation test using a wafer W having a notch N formed as a cutout. The shortened distance L on the horizontal axis of the graph was explained in the explanation of the graph in Figure 12 as representing the amount of displacement of the detection position in the detection direction of sensor 61 due to the presence of orientation flat F. Here, however, it will be assumed to represent the amount of displacement of the detection position due to the presence of notch N instead of orientation flat F. As shown in this graph, ΔR is small for wafers W having notch N formed therein, and does not exceed this ΔR threshold when the threshold for ΔR is set to 0.02 μm as described above.

[0080] The reason why ΔR is smaller when a notch N is formed than when an orientation flat F is formed is due to the fact that the notch N is smaller than the orientation flat and the shape of the notch N. Referring back to FIG. 10 , even if the sensor 61 is over the notch N during the first detection, it will detect a position off the notch N during the second detection, resulting in a slight change in the detection position of the sensor 61 in the detection direction. Also, in FIG. 10 , a virtual line connecting the actual center of the wafer W and the apex of the notch N is indicated as L2, and the notch N is symmetrical with respect to this line L2. Because of this symmetry, the detection position is on one side of the line L2 during the first detection and on the other side of the line L2 during the second detection, resulting in a slight change in the detection direction of the sensor 61. These factors result in a small ΔR.

[0081] For convenience, the case where the cutout is a notch N and the case where the cutout is an orientation flat F have been described separately, but as described above, it is unknown whether the cutout formed in the wafer W is a notch N or an orientation flat F. Therefore, as will be shown in the flow chart below, after it is determined that one of the sensors 61 overlaps the cutout and two verification groups are identified, an inappropriate sensor 61 is identified by making both a determination regarding ΔY' and a determination regarding ΔR for each of those verification groups without specifying the type of cutout.

[0082] <Further Advancement of the Holding Part and Third Detection of the Edge Position of the Wafer W> As mentioned above, when the cutout is a notch N, there is an exceptional case in which ΔY′ obtained from the first and second detections of the edge position of the wafer W for the two verification groups does not exceed the ΔY′ threshold value. This case will be explained with reference to FIG. 16. In FIG. 16, as in FIG. 10, the dashed and solid lines indicate the position of the sensor 61A relative to the wafer W during the first and second detections, respectively.

[0083] As described above, notch N has a symmetrical shape with respect to line L2. Due to this symmetrical shape and the relatively short distance between the retracted position where the first detection is performed and the first verification position where the second detection is performed, there are cases where the position detected by sensor 61 in the first detection and the position detected by sensor 61 in the second detection are both notch N and are symmetrical or nearly symmetrical with respect to line L2, as shown in Fig. 16. In this case, ΔY' is small and does not exceed the threshold value.

[0084] Therefore, if neither ΔY′ nor ΔR obtained from the first and second detections for the two verification groups is equal to or greater than the threshold, the holder 53 holding the wafer W is further advanced slightly. The distance advanced is, for example, 0.5 mm, and this advanced position is designated as the second verification position. At this second verification position, the sensors 61A-61D again detect the edge position of the wafer W. That is, a third detection is performed. Note that, since the second verification position is set as described above, it is 1.5 mm forward of the retracted position where the first detection of the edge position of the wafer W is performed. This second verification position and the first verification position are positions where the holding region 56 of the holder 53 overlaps the base 52. When the wafer W is transferred to the destination device 50, the holder 53 is moved further forward.

[0085] For an unsuitable sensor 61 (61A in this case), even if the detection position in the first detection and the detection position in the second detection are symmetrical or nearly symmetrical with respect to the line L2 as shown in FIG. 16 , the detection position in the first detection and the detection position in the third detection are not symmetrical. Therefore, for the two verification groups, ΔY′ between the position of the center P of the wafer W calculated from the results of the first detection of the edge position of the wafer W and the position of the center P of the wafer W calculated from the results of the third detection of the edge position of the wafer W is calculated, and it is determined whether this ΔY′ is equal to or greater than the ΔY′ threshold. If it is determined that the ΔY′ is equal to or greater than the ΔY′ threshold, the sensor 61 that overlaps the notch is identified in the same manner as in the case where ΔY′ calculated from the results of the first and second detections is determined to be equal to or greater than the ΔY′ threshold. Then, the position calculated by the verification group from which the unsuitable sensor 61 is excluded is determined to be the position of the center P of the wafer W.

[0086] If it is determined that ΔY' obtained from the first and third results of detecting the edge position of the wafer W is not equal to or greater than the ΔY' threshold value, it is deemed impossible to identify an inappropriate sensor 61, and the average of the positions of the center P calculated from each of the four groups as described above is determined to be the center P. Hereinafter, the ΔY' obtained from the first and second results of detecting the edge position of the wafer W may be described as 1-2ΔY', and the ΔY' obtained from the first and third results of detecting the edge position of the wafer W may be described as 1-3ΔY' to distinguish them from each other.

[0087] 12 again, when the shortened distance L is extremely small, as shown in these graphs, neither 1-2ΔY′ nor ΔR is greater than or equal to the threshold value. In such a case where neither 1-2ΔY′ nor ΔR is greater than or equal to the threshold value, the third position detection of wafer W is performed, as described above, and 1-3ΔY′ is calculated. However, evaluation tests have revealed that the relationship between 1-3ΔY′ and shortened distance L is similar to the relationship between 1-2ΔY′ and shortened distance L described in the upper part of FIG. 12. In other words, when the notch is an orientation flat F and the shortened distance L is extremely small, 1-2ΔY′ and ΔR obtained by moving holder 53 to the first verification position are not greater than or equal to the threshold value, and 1-3ΔY′ obtained by subsequently moving holder 53 to the second verification position is also not greater than or equal to the threshold value.

[0088] Therefore, in such a case, it is deemed impossible to identify an inappropriate sensor 61, and the average of the positions of center P calculated for each of the four groups is determined as center P, as described above. In other words, the position of center P of wafer W is determined as if no sensor 61 overlapped the notch. However, such an extremely small shortened distance L means that the sensor 61 detected a position very close to the longitudinal end of orientation flat F. Therefore, there is only a slight deviation between the position of center P of wafer W calculated from the verification group including sensor 61 overlapping orientation flat F and the actual position of center P of wafer W. Therefore, treating it as if it does not overlap orientation flat F does not affect the transfer of wafer W.

[0089] <Change in the number of sensors that can detect edges> When the holder 53 holding the wafer W is moved from the retracted position to the first verification position, there may be cases where the edge position of the wafer W can be detected by four sensors 61 at the retracted position, but only three sensors can detect the edge position of the wafer W at the first verification position. That is, as a result of the movement of the holder 53, only one of groups 1 to 4 can detect the edge position of the wafer W. FIGS. 17 and 18 illustrate such a case. FIG. 17 is a plan view showing the wafer W held by the holder 53 at the retracted position, and FIG. 18 is a plan view showing the wafer W held at the first verification position. As shown in the figures, the sensors 61 that become incapable of detection are likely inappropriate sensors 61 at the retracted position, and therefore are likely to become incapable of detection due to the movement of the holder 53. That is, the sensors 61 of the groups that can still detect the edge position of the wafer W even after the holder 53 is moved to the first verification position are likely not engaging with the notches at either the retracted position or the first verification position. After verifying that the wafer W does not overlap the notch, the center position of the wafer W is determined.

[0090] Specifically, in the above-described verification operation, ΔY' and ΔR are calculated from the results of the first detection of the edge position of the wafer W and the results of the second detection of the edge position of the wafer W for a group in which the edge of the wafer W can still be detected at the first verification position. Then, a determination is made as to whether ΔY' is equal to or greater than the ΔY' threshold value, and whether ΔR is equal to or greater than the ΔR threshold value. In other words, a determination is made as to whether the group includes an unsuitable sensor 61. If it is determined that ΔY' is not equal to or greater than the ΔY' threshold value and that ΔR is not equal to or greater than the ΔR threshold value, the sensors 61 in the group are not unsuitable sensors 61, and the position calculated from the results of the second detection is determined as the position of the center P of the wafer W.

[0091] If it is determined that ΔY' is equal to or greater than the ΔY' threshold value or that ΔR is equal to or greater than the ΔR threshold value, it is considered that the position of the wafer W in the holding area 56 is significantly deviated from the reference position, and therefore it is determined that an abnormality has occurred (an error determination) and the operation of the wafer transfer mechanism 33 is stopped. Therefore, the determination of the position of the center P used for transfer and the transfer based on the position of the center P are performed in accordance with a comparison of ΔY' and ΔR with the threshold values. Furthermore, when moving the holder 53 holding the wafer W from the retracted position to the first verification position, it is possible that, while the edge position of the wafer W can be detected by four sensors 61 at the retracted position, the edge position of the wafer W can be detected by two or fewer sensors at the first verification position. In this case, too, it is possible that the position of the wafer W in the holding area 56 is significantly deviated from the reference position, so an error is determined and the operation of the wafer transfer mechanism 33 is stopped.

[0092] <When the edge position of the wafer W can be detected using only three sensors> Up to this point, we have described a case where four sensors 61 detect the edge position of the wafer W during the first edge position detection of the wafer W when the holder 53 is in the retracted position. However, we will now describe a case where only three sensors 61 (i.e., only one group) can detect the edge position of the wafer W. Figure 19 illustrates a state where the sensor 61D is notched, allowing detection to be performed by only three sensors 61. When only three sensors 61 are capable of detection, a verification operation is performed to determine whether or not those three sensors 61 are unsuitable. If it is determined that they are not, the position calculated from those three sensors 61 is determined to be the position of the center P of the wafer W.

[0093] In the above verification operation, first, the holder 53 holding the wafer W is moved to the first verification position, and the second detection of the edge position of the wafer W is performed. If the edge position of the wafer W is detected by the same three sensors 61 as in the first detection during this second detection, it is highly likely that the sensor 61 that was unable to detect the edge of the wafer W during the first detection is the sensor 61 that was caught in the notch. Note that the detection of the edge position of the wafer W by the same three sensors 61 as in the first detection during the second detection also includes the case where the edge position of the wafer W is detected by all four sensors 61 during the second detection. In other words, it also includes the case where the edge position of the wafer W is detected by a sensor 61 that was unable to detect it during the first detection.

[0094] If detection is thus achieved by the same three sensors 61 as in the first detection, a further verification operation is performed to determine whether 1-2ΔY' is equal to or greater than the ΔY' threshold and whether ΔR is equal to or greater than the ΔR threshold for the group made up of the three sensors 61. As explained above, if 1-2ΔY' is equal to or greater than the ΔY' threshold or ΔR is equal to or greater than the ΔR threshold, this means that the sensor 61 is inappropriate for the group, and a transfer error is detected, and the operation of the wafer transfer mechanism 33 is stopped.

[0095] If the determination indicates that 1-2ΔY′ is not equal to or greater than the ΔY′ threshold and that ΔR is not equal to or greater than the ΔR threshold, further verification is performed. As described in FIG. 13 , if the notch is notch N, there may be exceptional cases in which 1-2ΔY′ is not equal to or greater than the threshold even when the sensor 61 is over the notch. Therefore, whether or not such an exceptional case exists is determined. Specifically, the holder 53 is moved to the second verification position, and the position of the wafer W is detected a third time. Then, for the group whose wafer W position was detected in the first detection, 1-3ΔY′ is calculated, and a determination is made as to whether this 1-3ΔY′ is equal to or greater than the ΔY′ threshold. If it is determined that 1-3ΔY′ is equal to or greater than the ΔY′ threshold, this indicates that the group includes an inappropriate sensor 61, and the operation of the wafer transfer mechanism 33 is stopped as a transfer error. If it is determined that 1-3ΔY′ is not equal to or greater than the ΔY′ threshold, the position obtained by those three sensors is determined as the position of the center P of the wafer W. Even if the edge position of the wafer W can be detected by only three sensors during the first detection, the position of the center P to be used for transfer and the transfer based on the position of the center P are determined by comparing ΔY′ and ΔR with the threshold values.

[0096] <When the edge of the wafer W can be detected by only two or fewer sensors> Even if the position of the wafer W is detected by only two or fewer sensors 61 during the first edge position detection of the wafer W when the holding part 53 is in the retracted position, it is considered that the position of the wafer W in the holding area 56 is significantly deviated from the reference position. Therefore, it is determined that an abnormality has occurred and the operation of the wafer transfer mechanism 33 is stopped.

[0097] <Flow description> 20 to 22 are flowcharts summarizing the operations until the center position of the wafer W is determined or the operation of the wafer transfer mechanism 33 is stopped. First, with the wafer holder 53 holding the wafer W in the retracted position, the four sensors 61 (61A to 61D) perform a first detection of the edge position of the wafer W (step S1). If the four sensors 61 are able to detect the position in step S1 (step S2), the positions of the centers P1 to P4 of the wafer W are detected and the radii R1 to R4 of the wafer W are calculated by each of groups 1 to 4. The maximum and minimum values ​​of the radii R1 to R4 of the wafer W are calculated, and it is determined whether the calculated value is equal to or greater than the threshold value of 30 μm (step S3). If it is determined in step S3 that the calculated value is not equal to or greater than 30 μm, the average of the positions of the centers P1 to P4 of the wafer W of groups 1 to 4 is calculated, and this average is determined as the center P of the wafer W (step S4).

[0098] If it is determined in step S3 that the calculated value is 30 μm or more, the detection position of one of the sensors 61 is determined to be a notch, and two verification groups each including the verification sensor are identified. Then, the holder 53 moves forward by 1 mm to the first verification position, and the four sensors 61 perform a second position detection of the edge of the wafer W (step S5), and the number of sensors 61 capable of position detection is determined (step S6). If this determination shows that position detection is possible with the four sensors 61, 1-2ΔY′ and ΔR of the two verification groups are calculated, and it is determined whether or not there is a verification group in which 1-2ΔY′ is equal to or greater than the ΔY′ threshold value or ΔR is equal to or greater than the ΔR threshold value (step S7).

[0099] If it is determined in step S7 that 1-2ΔY′ and ΔR are not equal to or greater than the thresholds for either of the two verification groups, the holder 53 advances 0.5 mm to the second verification position, and the four sensors 61 detect the edge position of the wafer W for the third time (step S8). Then, 1-3ΔY′ is calculated for the two verification groups, and it is determined whether any of these verification groups has 1-3ΔY′ equal to or greater than the ΔY′ threshold (step S9). If it is determined in step S9 that there is no group whose 1-3ΔY′ is equal to or greater than the ΔY′ threshold, the position of the center P of the wafer W is determined by calculating the average of groups 1 to 4 in step S4 described above.

[0100] If it is determined in step S9 that there is a verification group in which 1-3ΔY' is equal to or greater than the ΔY' threshold, or if it is determined in step S7 that there is a verification group in which 1-2ΔY' is equal to or greater than the ΔY' threshold or ΔR is equal to or greater than the ΔR threshold, it is determined which of the verification groups is larger among those that are equal to or greater than the threshold. That is, it is determined which of the two verification groups is larger among those that are equal to or greater than the threshold in the previous step (step S10).

[0101] More specifically, when step S10 is performed after step S9, it is determined which verification group had a larger value for 1-3ΔY'. When step S10 is performed after step S7, if it is determined in step S7 that there is a verification group in which 1-2ΔY' is equal to or greater than ΔY', it is determined which verification group had a larger value for 1-3ΔY'. If it is determined in step S7 that there is a verification group in which ΔR is equal to or greater than ΔR, it is determined which verification group had a larger value for ΔR.

[0102] As described above, since the verification sensor included in the verification group determined in step S10 to have the two ΔY's ​​(1-2ΔY' or 1-3ΔY') or ΔR large is the inadequate sensor 61, the position of the center P of the wafer W is calculated using the detection result of the edge position of the wafer W by the other verification group. In other words, the position of the center P of the wafer W is calculated using the detection result of the verification group that is not determined to have the large ΔY' or ΔR (step S11).

[0103] Furthermore, if the number of sensors 61 capable of detecting the edge position of the wafer W is determined to be three in step S6, 1-2ΔY′ and ΔR for the group consisting of the three sensors 61 are calculated. Then, it is determined whether 1-2ΔY′ is equal to or greater than the ΔY′ threshold value or whether ΔR is equal to or greater than the ΔR threshold value (step S21, see FIG. 21). If it is determined in step S21 that 1-2ΔY′ is not equal to or greater than the ΔY′ threshold value and that ΔR is not equal to or greater than the ΔR threshold value, the position of the center P of the wafer W is calculated using the detection results of that group (step S22). If it is determined in step S21 that 1-2ΔY′ is equal to or greater than the ΔY′ threshold value or that ΔR is equal to or greater than the ΔR threshold value, or if it is determined in step S6 that the number of sensors 61 capable of detecting the edge position of the wafer W is two or less, an error is determined and the transfer of the wafer W is stopped (step S23).

[0104] If the three sensors 61 are able to detect the edge position of the wafer W in step S1 (see FIG. 20) (step S31, see FIG. 22), the holder 53 moves forward by 1 mm to the first verification position, and a second detection of the edge position of the wafer W is performed (step S32). Then, it is determined whether the same sensors 61 were able to detect the edge position of the wafer W in the second detection (step S33). If it is determined in step S33 that the same sensors 61 were able to detect the edge position of the wafer W, 1-2ΔY′ and ΔR are calculated. Then, it is determined whether 1-2ΔY is equal to or greater than the ΔY′ threshold (step S34). If it is determined in step S34 that 1-2ΔY′ is not equal to or greater than the ΔY′ threshold, it is determined whether ΔR is equal to or greater than the ΔR threshold (step S35).

[0105] If it is determined in step S35 that ΔR is not equal to or greater than the ΔR threshold, the holder 53 moves forward by 0.5 mm to the second verification position, and a third detection of the edge position of the wafer W is performed (step S36). Then, 1-3ΔY' is calculated, and it is determined whether or not the calculated 1-3ΔY' is equal to or greater than the ΔY' threshold (step S37). If it is determined in step S37 that 1-3ΔY' is not equal to or greater than the ΔY' threshold, the position of the center P of the wafer W is determined from the detection results of the group of sensors 61 that have been able to detect the edge position of the wafer W since the first detection (step S38).

[0106] If it is determined in step S33 that the edge position of the wafer W cannot be detected by the same sensors 61 as in the first detection, if it is determined in step S34 that 1-2ΔY′ is equal to or greater than the ΔY′ threshold, if it is determined in step S35 that ΔR is equal to or greater than the ΔR threshold, or if it is determined in step S37 that 1-2ΔY′ is equal to or greater than the ΔY′ threshold, an error is determined and the transfer of the wafer W is stopped (step S41). Also, if it is determined in step S1 that only two or fewer sensors 61 are able to detect the edge position of the wafer W (step S42), step S41 is executed and the transfer of the wafer W is stopped.

[0107] The retracted position, first verification position, and second verification position correspond to the first position, second position, and third position, respectively, and detecting the edge position of the wafer W at the retracted position, first verification position, and second verification position corresponds to the first detection step, second detection step, and third detection step, respectively. The calculation of 1-2ΔY′ and ΔR corresponds to the first calculation step and second calculation step, respectively. The positions of centers P1 to P4 of the wafer W calculated from groups 1 to 4 correspond to the predicted center position of the wafer W. Determining the position of center P of the wafer W corresponds to determining the position of the wafer W in the holder 53 that holds the wafer W. The comparison with the threshold value in step S7 corresponds to the first comparison step, the comparison with the threshold value in step S9 corresponds to the second comparison step performed in response to the first comparison step, the comparison with the threshold value in step S21 corresponds to the third comparison step, the comparison with threshold values ​​in steps S34 and S35 corresponds to the fourth comparison step, and the comparison with the threshold value in step S37 corresponds to the fifth comparison step performed in response to the fourth comparison step.

[0108] <Effectiveness of conveyance in this embodiment> By executing the above-described flow, regardless of whether a notch N or an orientation flat F is formed as a notch in the wafer W, the position of the center P of the wafer W can be determined based on the detection results of the group of sensors 61 excluding the sensor 61 that covers the notch. Therefore, the position of the center P of the wafer W can be determined with high accuracy. Therefore, when the operation of each component of the wafer transfer mechanism 33 is controlled based on the deviation between the position of the center P and the center P0 of the holding area 56 of the holder 53 as described with reference to FIG. 4 to transfer the wafer W, the wafer W can be transferred with high accuracy to a predetermined position in the destination apparatus 50. As a result, the occurrence of processing abnormalities due to deviation in the placement position of the wafer W in the apparatus 50 can be prevented, and a decrease in the yield of semiconductor products manufactured from the wafer W can be prevented.

[0109] Furthermore, according to the above flow, even if one of the four sensors 61 fails to detect the edge position of the wafer W during the first position detection of the wafer W, the transfer of the wafer W is not stopped solely because of that fact. A verification operation (operations of steps S32 to S37) is performed to determine whether the failure to detect is due to a notch or a large misalignment of the wafer W. If the failure is due to a notch, the position of the center P of the wafer W is calculated excluding the sensor that overlaps the notch. This reduces the frequency with which the transfer of the wafer W is stopped due to a transfer error, thereby preventing a decrease in the throughput of the wafer processing system 1. Because the orientation flat F has a relatively large area, the sensors 61 are likely to overlap this orientation flat F. Therefore, not stopping the transfer of the wafer W solely because one sensor 61 fails to detect the edge position of the wafer W is particularly effective in preventing a decrease in throughput.

[0110] In the above flow, in step S21, which is performed when the number of detectable sensors 61 changes to three in the second position detection, 1-2ΔY′ and ΔR are compared with the ΔY′ threshold and ΔR threshold, and then the third position detection and comparison of 1-3ΔY′ with the ΔY′ threshold, which are performed in steps S8 and S9 after step S7, are not performed. This is because such a change in the number of detectable sensors 61 occurs because, as described above, it is substantially certain that the sensors 61 that have become undetectable are unsuitable sensors 61, and the operation of step S21 is an operation to obtain further confirmation of this fact. However, after performing step S21, operations similar to steps S8 and S9 may be performed to obtain further confirmation, and the position of the center P of the wafer W may then be determined.

[0111] While the description has been given for the wafer transfer mechanism 33, the position of the center P is determined for other wafer transfer mechanisms in the same manner as for the wafer transfer mechanism 33. In the above example, after the position of the center P of the wafer W is determined, the positions of the base 52 and the holder 53 in the wafer transfer mechanism are corrected based on the position of the center P to place the wafer W in a predetermined position. Instead of performing such position correction, if the deviation between the determined position of the center P and the center P0 of the holding area 56 of the holder is within an allowable range, the wafer W is transferred to the destination device 50, and if the deviation exceeds the allowable range, the transfer is stopped to prevent the occurrence of transfer abnormalities for the wafer W. The position of the center P calculated in this manner may be used for transfer, and therefore, the position of the center P is not limited to being used for correcting the position of each part of the wafer transfer mechanism 33 when transferring the wafer W to the device 50.

[0112] <Modification of flow by setting the movement distance from the retreat position> 20 to 22 (hereinafter referred to as the reference flow), the distance between the retracted position where the first edge position of the wafer W is detected and the first verification position where the second edge position of the wafer W is detected is relatively short. Therefore, as described in FIG. 16, there may be cases where the first detection position and the second detection position of one sensor 61 are symmetrical or nearly symmetrical with respect to the line L2 passing through the top of the notch N. To prevent such cases from occurring, the first verification position may be set further forward than in the example described in the reference flow. Therefore, even if the detection position of the sensor 61 is located on the notch N in the first detection, the detection position of the sensor 61 in the second detection may be reliably deviated from the notch N.

[0113] It has been confirmed that when the first verification position is set 4 mm or more forward of the retracted position, even if the sensor 61 engages with the notch N at the retracted position, the sensor will be disengaged from the notch N at the first verification position. Therefore, the first verification position is set 4 mm or more forward of the retracted position, more specifically, for example, 4 mm forward. When the first verification position is set in this manner, it is not necessary to move the sensor 61 to the second verification position and determine whether the sensor 61 engages with the notch N.

[0114] By changing the first verification position in this way, the portion of the reference flow shown in FIG. 20 is changed as shown in FIG. 23, and the portion of the reference flow shown in FIG. 22 is changed as shown in FIG. 24. The modified flow is referred to as the modified flow, and differences from the reference flow will be described. As shown in FIG. 23, in step S5 of the modified flow, the advance distance of the holder 53 is 4 mm, as described above. Furthermore, in the modified flow, steps S8 and S9 are not provided. If, in step S7, it is determined whether or not there is a group among the verification groups in which 1-2ΔY′ is equal to or greater than the ΔY′ threshold or ΔR is equal to or greater than the ΔR threshold, step S4 is performed. In other words, the position of the center P of the wafer W is determined by calculating the average. Furthermore, as shown in FIG. 24, in step S32, the advance distance of the holder 53 is 4 mm. Then, steps S36 and S37 are not performed, and if it is determined in step S35 that ΔR is not equal to or greater than the ΔR threshold value, the position of the center P of the wafer W is determined in step S38.

[0115] In this manner, the position of the center P of the wafer W and the decision to stop the transfer may be made using the flow of the modified example. However, by moving the holder 53 relatively far from the retracted position in this manner, the edge position of the wafer W may not be detected by the sensor 61 depending on the position of the wafer W in the holder 53, and there is a risk of interference with structures in the transfer area. Therefore, it is preferable to implement the reference flow rather than the modified example. Furthermore, the reference flow requires a shorter movement distance from the retracted position of the holder 53 to determine the position of the center P of the wafer W. Therefore, using the reference flow is preferable from the viewpoint of increasing the throughput of the wafer processing system 1, since it requires less time to determine the position of the center P.

[0116] <Identification of Notch N and Orientation Flat F> As explained with reference to the graphs in FIGS. 12 and 15, the ΔR threshold can be set so that ΔR does not exceed the ΔR threshold for wafers W with notches N, and only ΔR for wafers W with orientation flats F can exceed the ΔR threshold. The ΔR threshold of 0.02 mm described above is set in this way. An event in which ΔR exceeds the ΔR threshold is referred to as an orientation flat determination event. Furthermore, assuming that the reference flow described with reference to FIGS. 20 to 22 is executed, when steps S7 to S9 are performed, 1-2ΔY′ does not exceed the ΔY′ threshold, and 1-3ΔY′ exceeds the ΔY′ threshold, this event occurs only for wafers W with notches N, and will hereinafter be referred to as a notch determination event.

[0117] As described with reference to FIGS. 1 and 2, in the wafer processing system 1, wafers W are transferred sequentially between multiple wafer transfer mechanisms for processing. During this transfer, the wafer holder 53 moves in the X direction of one wafer transfer mechanism, while the wafer holder 53 moves in the Y direction of the other wafer transfer mechanisms. Therefore, when a wafer W is transferred between wafer transfer mechanisms, for example, via a transfer device, different edge positions of the wafer W can be detected between the wafer transfer mechanisms. Furthermore, some processing devices, such as a film formation device that forms a film by spin coating, rotate the wafer W during processing. Therefore, when a single wafer W is transferred to one processing device and then to the next, different edge positions of the wafer W can be detected using the same wafer transfer mechanism.

[0118] Therefore, if an orientation flat determination event occurs during the execution of the reference flow of each wafer W transfer mechanism from the time the wafer W is removed from the cassette C until it is transferred to a predetermined processing device, such as an edge exposure device described below, it is determined that an orientation flat F has been formed. If a notch determination event occurs, it is determined that a notch N has been formed on the wafer W. If neither of these events occurs, it is determined that a notch N has been formed, as it is highly likely that a notch N has been formed based on the difference in area between the orientation flat F and the notch N.

[0119] The edge exposure apparatus described above exposes the peripheral edge of the wafer W so that unnecessary portions of the resist film formed on the wafer W are removed when the resist film is developed in a developing apparatus. As shown in the plan view of FIG. 25, the edge exposure apparatus includes a stage 71 on which the wafer W is horizontally placed and rotated about a vertical axis, an exposure head 72 for exposing the wafer W, and a sensor 73. The exposure head 72 can move horizontally in a straight line as indicated by the arrow in the figure, and emits light downward. The sensor 73, like the sensor 61 provided in the wafer transfer mechanism, comprises a light-emitting unit and a light-receiving unit. These light-emitting unit and light-receiving unit sandwich the peripheral edge of the wafer W rotated by the rotary stage 71 from above and below, and are provided to optically detect the position of the notch in the circumferential direction of the wafer W.

[0120] For wafers W determined to have a notch N, the exposure head 72 is placed at a predetermined position on the peripheral edge of the wafer W, and the wafer W is rotated around the rotary stage 71 while light is irradiated from the exposure head 72 to expose the entire peripheral edge of the wafer W. For wafers W determined to have an orientation flat F, as in the case of processing wafers W with a notch N formed therein, the exposure head 72 is placed on the peripheral edge of the wafer W, and the wafer W is rotated around the rotary stage 71 while light is irradiated from the exposure head 72 to expose an arc-shaped portion on the peripheral edge of the wafer W.

[0121] As the wafer W is rotated once in this manner, the position of the orientation flat F on the circumference of the wafer W is detected by the sensor 73. After the arc-shaped portion is exposed, the orientation flat F is aligned with the movement path of the exposure head 72 so that the exposure head 72 moves along the orientation flat F as the wafer W rotates. Thereafter, the exposure head 72 is moved as shown in Figure 25 to expose the portion of the peripheral edge of the wafer W that is linear due to the orientation flat F. As described above, in the processing apparatus, the wafer W may be subjected to different types of processing depending on whether the notch formed in the wafer W is a notch N or an orientation flat F.

[0122] <Additional information> In the above description, the radii R1 to R4 of the wafer W are calculated from groups 1 to 4, and the amount of change ΔR between the first and second detections is calculated and compared with a threshold value to determine whether the sensor is covering the notch. Instead of comparing the radii themselves to the threshold value, the determination may be made by multiplying or adding a predetermined constant to the radii R1 to R4 and comparing the resulting value with the threshold value. For example, the diameter of the wafer W may be calculated and compared with the threshold value. That is, the determination may be made by comparing the amount of change in the value corresponding to the radius with the threshold value. The value corresponding to this radius is not limited to the radius itself, but may include values ​​obtained by multiplying or adding a predetermined constant to the radius. In step S3 of the flow, the determination of whether the maximum value minus the minimum value related to the radius is equal to or greater than a threshold value to identify whether the sensor 61 is covering the notch may also be made by comparing the maximum value minus the minimum value corresponding to the radius, rather than the radius itself, with the threshold value.

[0123] The sensor 61 need only be capable of optically detecting the position of the edge of the wafer W, and is not limited to being composed of a light-projecting unit 62 and a light-receiving unit 63. For example, a camera may be used as the sensor 61, and the position of the edge of the wafer W may be detected from the image capture results. Furthermore, although an example in which four sensors 61 are provided has been shown, five or more sensors 61 may be provided, and three of the sensors 61 may be grouped together to calculate ΔR and ΔY′, as in the previously described embodiment.

[0124] When a camera is provided as the sensor 61, for example, only one is provided on the base 52, and an image of the wafer W is captured from above so that the entire circumference or approximately the entire circumference of the wafer W is captured within the captured image range. In this case, the row of four light-receiving elements 60 described above is not provided, but the coordinates of the peripheral edge of the wafer W that overlaps with the row of four light-receiving elements 60 are calculated assuming that the row of four light-receiving elements 60 is present in the image. The center position of the wafer W may be determined by executing the above-described flow by acquiring the coordinates at each position as the holder 53 moves. However, since the entire circumference or approximately the entire circumference of the wafer W can be captured in this manner, the center position of the wafer W can be calculated from the image. In other words, since the center position can be calculated without moving the holder 53, this technology is preferably applied to cases where the peripheral position of the wafer W is locally detected using multiple sensors 61.

[0125] As described above, the holder 53 is positioned further forward of the base 52 during the third detection of the edge position of the wafer W than during the second detection, and further forward of the base 52 during the second detection of the edge position of the wafer W than during the first detection. However, the position of the holder 53 during each detection is not limited to this. For example, the position of the holder 53 during the first detection may be set to be further rearward than during the second and third detections, and the sensor 61 may be positioned accordingly. However, as described above, the holder 53 is positioned more forward as the detection cycle progresses, eliminating the need to retract the holder 53 after the final detection of the edge position of the wafer W and shortening the distance from the position where the edge of the wafer W is detected to the forward position where the wafer W is transferred. This is therefore preferable for preventing a decrease in the throughput of the wafer processing system 1.

[0126] The substrates transported and processed in the substrate processing system are not limited to wafers W. For example, they may be circular substrates (dummy wafers) that are not intended for the manufacture of semiconductor products and are used for the purpose of setting processing parameters for each part in the wafer processing system 1. The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, modified, and combined in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0127] F Orientation Flat N notch W wafer 33 Wafer transport mechanism 52 Foundation 53 Holding part 61A~61D Sensors 100 control section

Claims

1. A substrate transport method for transporting a substrate by a substrate transport device including: a movable body that moves within a substrate transport area; and a holding part that holds the circular substrate having a notch formed on a peripheral edge and is provided on the movable body so as to be able to move forward and backward, a first detection step of optically detecting positions of different edges of the substrate by a sensor provided on the movable body while the holding unit is positioned at a first position relative to the movable body; a second detection step of detecting positions of different edges of the substrate by the sensor while the holder is positioned at a second position relative to the movable body; a first calculation step of calculating a change amount in a lateral direction intersecting with a direction of movement of the holder with respect to the predicted center position of the substrate, which is respectively acquired in the first detection step and the second detection step; a second calculation step of calculating a change amount of a size corresponding to a radius of the substrate obtained by each of the first detection step and the second detection step; a position determination step of determining a position of the substrate in the holder to be used for transporting the substrate based on calculation results in the first calculation step and the second calculation step; A substrate transport method comprising:

2. At least four of the sensors are provided; 2. The substrate transfer method according to claim 1, wherein the predicted center position of the substrate and the size corresponding to the radius of the substrate are calculated from the detection results obtained by a group of three of the sensors.

3. a step of determining, when the position of the edge of the substrate is detected by each of the four sensors in the first detection step, whether or not there is an inappropriate sensor among the sensors whose detection position is the edge of the substrate that forms a notch, based on detection results from the first to fourth groups which each include a different combination of the sensors; 3. The substrate transfer method according to claim 2, wherein the position determining step determines the position of the substrate based on the detection result of the group that does not include the unsuitable sensor among the first to fourth groups.

4. Among the first to fourth groups, two groups each including only one of the two candidates for the unsuitable sensor and including different candidates are designated as verification groups. the first calculation step and the second calculation step are steps of calculating, for each of the verification groups, a change in a predicted center position of the substrate and a change in a size corresponding to a radius of the substrate, A substrate transport method as described in claim 3, wherein the position determination process includes a first comparison process of comparing the change in the predicted center position of the substrate of each of the two verification groups and the change in the size corresponding to the radius of the substrate with a predetermined threshold value in order to identify which of the two verification groups does not contain the unsuitable sensor.

5. The position determining step includes: a third detection step, which is performed according to a result of the first comparison step, of detecting positions of different edges of the substrate by the four sensors in a state where the holder is located at a third position relative to the movable body; a third calculation step of calculating, for each verification group, the amount of change in the lateral direction with respect to the predicted center position of the substrate acquired by the first detection step and the third detection step; A substrate transport method as described in claim 4, further comprising a second comparison step of comparing the change in the predicted center position of the substrate obtained in the third calculation step with a predetermined threshold value in order to identify which of the two verification groups does not contain the unsuitable sensor.

6. In the second detection step, when one of the sensors that was able to detect the position of the edge of the substrate in the first detection step becomes an incapable sensor that cannot detect the position of the edge, 4. The substrate transfer method according to claim 3, wherein the first calculation step and the second calculation step are performed using the detection results of the group that does not include the sensor that cannot perform detection.

7. The position determining step includes: a third comparison step of comparing the calculation results in the first calculation step and the second calculation step with a preset threshold value; The substrate transport method according to claim 6 , further comprising: a step of determining the position of the substrate in the holder based on the detection results of the group that does not include the non-detectable sensor, depending on the result of the third comparison step.

8. when the position of the edge of the substrate is detected by only one of the groups in the first detection step, the first calculation step and the second calculation step are performed on the detection result by that group; The position determining step includes: a fourth comparison step of comparing the calculation results in the first calculation step and the second calculation step with a preset threshold value; 3. The substrate transfer method according to claim 2, further comprising: a step of determining the position of the substrate in the holder based on the detection result of the group in accordance with the result of the fourth comparison step.

9. The position determining step includes: a third detection step, which is performed according to a result of the first comparison step, of detecting positions of different edges of the substrate by the plurality of sensors in a state where the holder is located at a third position relative to the movable body; a third calculation step of calculating a lateral change amount with respect to the predicted center position of the substrate acquired by the first detection step and the third detection step; A substrate transport method as described in claim 8, further comprising a fifth comparison step of comparing the amount of change in the predicted center position of the substrate obtained in the third calculation step with a predetermined threshold value to determine whether the group that detected the edge position of the substrate includes the unsuitable sensor.

10. the notch is a first notch whose edge forms a V-shape extending from the center of the substrate toward the periphery, or a second notch whose edge is parallel to the diameter of the substrate; 2. A substrate transport method according to claim 1, further comprising a step of repeatedly performing the first detection step, the second detection step, the first calculation step, the second calculation step, and the position determination step to determine whether the notch formed in the substrate is the first notch or the second notch.

11. a substrate transport method according to claim 10; performing a process on the substrate in a different manner based on whether the notch formed in the substrate is the first notch or the second notch; A substrate processing method comprising:

12. a substrate transport mechanism including a movable body that moves within a substrate transport area, and a holding part that holds the circular substrate having a notch formed on its periphery and is provided on the movable body so as to be able to move forward and backward; sensors provided on the moving body for optically detecting positions of different edges of the substrate; a control unit that outputs control signals to execute the following steps: a first detection step of optically detecting positions of different edges of the substrate using a sensor provided on the movable body when the holder is located at a first position relative to the movable body; a second detection step of detecting positions of different edges of the substrate using the sensor when the holder is located at a second position relative to the movable body; a first calculation step of calculating an amount of change in a lateral direction intersecting with a direction of advancement and retreat of the holder with respect to an estimated center position of the substrate obtained by the first detection step and the second detection step; a second calculation step of calculating an amount of change corresponding to a radius of the substrate obtained by the first detection step and the second detection step; and a position determination step of determining a position of the substrate on the holder to be used for transporting the substrate based on calculation results in the first calculation step and the second calculation step. A substrate transport device comprising:

13. At least four of the sensors are provided; 13. The substrate transport apparatus according to claim 12, wherein the predicted center position of the substrate and the size corresponding to the radius of the substrate are calculated from detection results obtained by a group of three of the sensors.

14. The control unit When the position of the edge of the substrate is detected by each of the four sensors in the first detection step, a determination step is executed to determine whether or not there is an inappropriate sensor among the sensors whose detection position is an edge of the substrate that forms a notch, based on detection results from the first to fourth groups that include different combinations of the sensors; 14. The substrate transfer apparatus according to claim 13, wherein the position determining step determines the position of the substrate based on the detection result of the group that does not include the unsuitable sensor among the first to fourth groups.

15. Among the first to fourth groups, two groups each including only one of the two candidates for the unsuitable sensor and including different candidates are designated as verification groups. the first calculation step and the second calculation step are steps of calculating, for each of the verification groups, a change in a predicted center position of the substrate and a change in a size corresponding to a radius of the substrate, A substrate conveying device as described in claim 14, wherein the position determination step includes a first comparison step of comparing the change in the predicted center position of the substrate and the change in the size corresponding to the radius of the substrate of each of the two verification groups with a predetermined threshold value in order to identify which of the two verification groups does not contain the unsuitable sensor.

16. The position determining step includes: a third detection step, which is performed according to a result of the first comparison step, of detecting positions of different edges of the substrate by the four sensors, respectively, with the holder positioned at a third position relative to the movable body; a third calculation step of calculating, for each verification group, the amount of change in the lateral direction with respect to the predicted center position of the substrate acquired by the first detection step and the third detection step; A substrate transport device as described in claim 15, further comprising a second comparison step of comparing the change in the predicted center position of the substrate obtained in the third calculation step with a predetermined threshold value in order to identify which of the two verification groups does not contain the unsuitable sensor.

17. 10. A computer program for use in a substrate transport apparatus, the program comprising steps for executing the substrate transport method according to claim 1.

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