Method and apparatus for detecting the position of a wafer

Abstract

A method and system for detecting the position of a wafer. The rotating table rotates in one direction at a relatively high speed to drive the wafer under test placed on the rotating table and having alignment features on its outer edge to rotate. At the same time, the detector detects the outer edge of the wafer under test to generate detection results for the controller, and each detection result corresponds to a rotation angle of the rotating table. After the alignment feature passes by the detector, the rotating table rotates in the reverse direction at a relatively low speed to drive the wafer under test to rotate in the reverse direction. At the same time, the detector detects the outer edge of the wafer under test rotating in the reverse direction to generate detection results for the controller. When the alignment feature passes by the detector again, the rotating table stops rotating, and the controller estimates the eccentric position of the wafer under test and the position of the alignment feature based on the accumulated detection results and the corresponding rotation angles. Thereby, the detection time is saved.

Description

Technical Field

[0001] The present invention relates to a wafer alignment device, in particular to a method and device for detecting the position of a wafer. Background Art

[0002] Generally, before a wafer enters a semiconductor manufacturing device, an eccentric correction is first performed using a Wafer Aligner, that is, the wafer is placed on the rotating table of the Wafer Aligner, and a wafer alignment procedure is carried out on the wafer, that is, the center of the wafer is aligned with the rotation center of the rotating table.

[0003] Japanese Patent Publication No. JP2729297 discloses a device for centering a semiconductor wafer. This device includes a rotating table for placing the wafer and a detector composed of a light projector and a light receiver. This device drives the rotating table on which the wafer is placed to rotate one week at a relatively high speed, and controls the detector to roughly detect the change in the outer edge contour of the wafer in a non-contact manner while the wafer is rotating, so as to find the position of the notch on the outer edge of the wafer. Then, the rotating table is driven to rotate so that the notch on the outer edge returns to the edge of the detection area of the detector, and then the rotating table is driven to rotate at a lower speed, allowing the detector to detect the contour change of this notch in detail. Finally, this device calculates the eccentricity, eccentricity direction, and the orientation of the notch center of this wafer based on the accumulated detection results.

[0004] Japanese Patent Publication No. JP3223584 discloses a device and method for centering a semiconductor wafer. First, this device drives the rotating table to rotate one week, and controls the detector to detect the outer edge of the wafer placed on the rotating table. Then, the rotating table is driven to rotate in sequence with 0 degrees, 90 degrees, 180 degrees, and 270 degrees as the rotation angles, and the detector is controlled to detect the outer edge of this wafer. Finally, the eccentricity, eccentricity direction, and the orientation of the notch center of this wafer are calculated based on the accumulated detection results.

[0005] Japanese Patent Publication No. JP4226241 discloses a wafer positioning device and method. Similarly, the wafer positioning device also drives the rotating table to rotate one week, and controls the line sensor to detect the outer edge of the wafer placed on the rotating table. Then, based on the detection result of the line sensor and the rotation angle of the rotating table, the degree to which the center of the wafer deviates from the rotation center of the rotating table and the orientation of the notch are calculated.

[0006] However, these existing methods for detecting the deviation of the wafer position all require detecting the complete outer edge of the wafer to calculate the degree to which the center of the wafer deviates from the rotation center of the rotating table and the orientation of the notch. Therefore, it is quite time-consuming and is not conducive to subsequent processes for a batch of wafers. Summary of the Invention

[0007] The main object of the present invention is to provide a method and apparatus for detecting the position of a wafer, which can determine the eccentricity position of the wafer by detecting a part of the outer edge of the wafer.

[0008] A method for detecting the position of a wafer according to an embodiment of the present invention includes: placing a wafer to be measured on a rotating table, wherein the outer edge of the wafer to be measured includes alignment features; driving the rotating table to rotate in a first direction at a first rotational speed via a controller to drive the wafer to be measured to rotate in the first direction at the first rotational speed; detecting, by a detector, the outer edge of the wafer to be measured rotating in the first direction at the first rotational speed to generate outer edge data corresponding to respective currently detected positions on the outer edge for the controller, the outer edge data corresponding to the rotation angle of the rotating table; when the controller determines, based on the outer edge data, that the alignment feature passes the detector in the first direction, driving the rotating table to rotate in a second direction at a second rotational speed to drive the wafer to be measured to rotate in the second direction at the second rotational speed, and the second direction is opposite to the first direction; detecting, by the detector, the outer edge of the wafer to be measured rotating in the second direction at the second rotational speed to generate additional outer edge data corresponding to respective currently detected positions on the outer edge for the controller; and when the controller determines, based on the outer edge data, that the alignment feature passes the detector in the second direction, controlling, by the controller, the rotating table to stop rotating, and estimating the eccentricity position of the wafer to be measured and the position of the alignment feature according to the accumulated outer edge data and the rotation angle corresponding to each outer edge data.

[0009] An apparatus for detecting the position of a wafer according to an embodiment of the present invention includes: a rotating stage for carrying a wafer to be measured, the outer edge of the wafer to be measured including alignment features; a detector disposed near the rotating stage; and a controller electrically connected to the rotating stage and the detector for performing a method of detecting the position of the wafer. The method of detecting the position of the wafer includes: the controller driving the rotating stage to rotate in a first direction at a first rotational speed to drive the wafer to be measured to rotate in the first direction at the first rotational speed; the detector detecting the outer edge of the wafer to be measured rotating in the first direction at the first rotational speed to generate outer edge data corresponding to the respective currently detected positions on the outer edge for the controller, the outer edge data corresponding to the rotational angle of the rotating stage; when the controller determines based on the outer edge data that the alignment feature passes the detector in the first direction, driving the rotating stage to rotate in a second direction at a second rotational speed to drive the wafer to be measured to rotate in the second direction at the second rotational speed, and the second direction being opposite to the first direction; the detector detecting the outer edge of the wafer to be measured rotating in the second direction at the second rotational speed to generate additional outer edge data corresponding to the respective currently detected positions on the outer edge for the controller; and when the controller determines based on the outer edge data that the alignment feature passes the detector in the second direction, controlling the rotating stage to stop rotating and estimating the eccentricity position of the wafer to be measured and the position of the alignment feature based on the accumulated outer edge data and the rotational angle corresponding to each outer edge data.

[0010] Accordingly, the method for detecting the position of a wafer and the apparatus using this method provided by the present invention can significantly shorten the time required for detection because only a part of the outer edge of the wafer needs to be detected to obtain a detection result within an acceptable error range. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. is a schematic diagram of a system for detecting the position of a wafer drawn according to an embodiment of the present invention;

[0012] Figure 2 is Figure 1 a top view of the system for detecting the position of a wafer in;

[0013] Figure 3 FIG. is a functional block diagram of a system for detecting the position of a wafer drawn according to an embodiment of the present invention;

[0014] Figures 4A to 4B FIG. presents a flowchart of a method for detecting the position of a wafer drawn according to an embodiment of the present invention;

[0015] Figures 5A to 5DA schematic diagram showing the state of detecting the outer edge of a wafer to be measured in the method of detecting the wafer position according to an embodiment of the present invention;

[0016] Figure 6 A flowchart of a method for determining that a registration feature passes through a detector according to an embodiment of the present invention;

[0017] Figure 7A A curve graph showing that one-dimensional outer edge data is converted into two-dimensional information according to an embodiment of the present invention;

[0018] Figure 7B For Figure 7A A curve graph in which the outer edge data is converted into an instantaneous change amount;

[0019] Figure 8 A flowchart of a first compensation scheme according to an embodiment of the present invention;

[0020] Figures 9A to 9E A schematic diagram showing the state of the detector detecting the outer edge of the wafer to be measured when performing the first compensation scheme according to an embodiment of the present invention;

[0021] Figure 10 A flowchart of a second compensation scheme according to an embodiment of the present invention;

[0022] Figures 11A to 11E A schematic diagram showing the state of the detector detecting the outer edge of the wafer to be measured when performing the second compensation scheme according to an embodiment of the present invention;

[0023] Figure 12 A flowchart of a method for estimating the eccentric position of the wafer to be measured and the position of the registration feature according to an embodiment of the present invention;

[0024] Figure 13 A curve graph showing fitting the accumulated outer edge data into a circular curve according to an embodiment of the present invention;

[0025] Figure 14A A curve graph of a circular curve of a first test result according to an embodiment of the present invention;

[0026] Figure 14B A curve graph of a circular curve of a second test result according to an embodiment of the present invention;

[0027] Figure 14C A curve graph of a circular curve of a third test result according to an embodiment of the present invention; and

[0028] Figure 14D A curve graph of a circular curve of a fourth test result according to an embodiment of the present invention.

[0029] Description of the Symbol Markings in the Drawings

[0030] 10: System

[0031] 11: Base

[0032] 12: Rotary Table

[0033] 13: Moving Platform

[0034] 131: First Moving Mechanism

[0035] 132: Second Moving Mechanism

[0036] 14: Detector

[0037] 141: Detection Range

[0038] 15: Controller

[0039] 16: Storage Device

[0040] 20: Wafer to be Measured

[0041] 21: Outer Edge

[0042] 22: Alignment Feature

[0043] 23: Pole

[0044] AT: Total Measurement Angle

[0045] D1: First Direction

[0046] D2: Second Direction

[0047] ET: Measurement Threshold

[0048] P1: Peak

[0049] P2: Peak

[0050] V1: First Rotation Speed

[0051] V2: Second Rotation Speed

[0052] θ: Angle Detailed Implementation Manner

[0053] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art will understand that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and / or components have not been described in detail so as not to obscure the present invention.

[0055] Please refer to Figures 1 to 3 As shown, a system 10 for detecting the position of a wafer according to an embodiment of the present invention is adapted to be disposed in a wafer alignment device. The system 10 for detecting the position of a wafer includes a base 11, a rotating table 12, a moving platform 13, a detector 14, a controller 15, and a storage device 16. The rotating table 12, the moving platform 13, and the detector 14 are disposed on the base 11, and the controller 15 is electrically connected to the rotating table 12, the moving platform 13, the detector 14, and the storage device 16 to execute a method for detecting the position of a wafer.

[0056] The rotating table 12 is used to carry a wafer 20 to be measured. The rotating table 12 is controlled by the controller 15 to rotate at different speeds, and can also rotate in a first direction (such as the clockwise direction) and in a second direction (such as the counterclockwise direction), the first direction being opposite to the second direction. By the rotation of the rotating table 12, the wafer 20 to be measured placed on the rotating table 12 can be driven to rotate at the same speed and in the same direction.

[0057] The moving platform 13 includes a first moving mechanism 131 and a second moving mechanism 132. The first moving mechanism 131 and the second moving mechanism 132 are movably disposed on the base 11. The first moving mechanism 131 can move along a third direction (such as the X-axis direction), and the second moving mechanism 132 can move along a fourth direction (such as the Y-axis direction), the third direction being perpendicular to the fourth direction. Therefore, when the rotating table 12 is disposed on the moving platform 13, the first moving mechanism 131 and the second moving mechanism 132 cooperate to enable the rotating table 12 to move in the plane along the third direction, the fourth direction, or both of the foregoing directions.

[0058] Detector 14 is disposed near the turntable 12. The detector 14 can be, for example, an optical detector, such as detecting the contour of the outer edge 21 of the wafer 20 to be measured by at least one light emitter and at least one light receiver. The detector 14 has a detection range 141. Taking the example of the detector 14 implemented by one light emitter and one light receiver, this detection range 141 can be, for example, the area covered by the light between this light emitter and the light receiver. In order to enable the detection range 141 of the detector 14 to cover a part of the outer edge 21 of the wafer 20 to be measured, so that the detector 14 can detect the contour of the outer edge 21 of the wafer 20 to be measured, the controller 15 can be moved by at least one of the first moving mechanism 131 and the second moving mechanism 132 that control the moving platform 13, so that the turntable 12 disposed on the moving platform 13 can approach the detector 14, so that the outer edge 21 of the wafer 20 to be measured on the turntable 12 can enter the detection range 141 of the detector 14, for example Figure 5A as shown, a part of the detection range 141 of the detector 14 overlaps with the outer edge 21 of the wafer 20 to be measured.

[0059] The storage device 16 is used to store various program instructions, parameters and thresholds required for the operation of the system 10 for detecting the wafer position, for access by the controller 15, and then execute the method for detecting the wafer position.

[0060] The following will illustrate by way of example how the system 10 for detecting the wafer position executes the method for detecting the wafer position. Please further refer to Figure 4A 、 4B and FIGS. 5A to 5D, the method for detecting the wafer position includes the following steps.

[0061] First, place the wafer 20 to be measured on the turntable 12. As shown in steps S1 and Figure 5A as shown, the outer edge 21 of this wafer 20 to be measured includes alignment features 22. The alignment features 22 can be, for example, notches, flanges or cuts. Then, the controller 15 drives the turntable 12 to rotate in the first direction D1 at the first rotation speed V1, as shown in step S2, to drive the wafer 20 to be measured to rotate at the same speed and in the same direction, as Figure 5B shown.

[0062] While the turntable 12 is rotating, the controller 15 controls the detector 14 to detect the contour of the outer edge 21 of the wafer 20 to be measured rotating under the conditions of the first rotation speed V1 and the first direction D1, so as to generate outer edge data providing the respective currently detected positions on the corresponding outer edge 21, and transmit it to the controller 15, as shown in step S3. And, the controller 15 will record the current rotation angle of the turntable 12 when each piece of outer edge data is obtained, as shown in step S4. The outer edge data is associated with the relative distance from the outer edge 21 of the wafer 20 to be measured to the rotation center of the turntable 12.

[0063] Next, as shown in step S5, the controller 15 determines whether the alignment feature 22 has passed through the detection range 141 of the detector 14 according to the obtained outer edge data. An example of the method for determining whether the alignment feature 22 has passed through the detection range 14of the detector 14 based on the obtained outer edge data is described below. Please refer to Figure 6 and 7A as shown in FIGS. 7A and 7B. Each piece of outer edge data generated when a position on the outer edge 21 is detected corresponds to the rotation angle of the turntable 12, that is, the rotation angle of the wafer 20 to be measured. The detection result of the detector 14 is as shown in Figure 7A . The horizontal axis represents the rotation angle of the turntable 12 (i.e., the wafer 20 to be measured), and the vertical axis represents the value of the outer edge data. Whenever a piece of outer edge data is obtained, the controller 15 calculates the instantaneous change amount of this piece of outer edge data, as shown in step S501. For example, the controller 15 calculates the instantaneous change amount of this outer edge data by means of differential processing, as shown in Figure 7B . Figure 7B In it, the horizontal axis represents the rotation angle of the turntable 12 (i.e., the wafer 20 to be measured), and the vertical axis represents the instantaneous change amount of the outer edge data.

[0064] Then, for each obtained instantaneous change amount, the controller 15 further determines whether this instantaneous change amount is greater than or equal to the measurement threshold, as shown in step S502. This measurement threshold is a default value, indicating that the position measured at this time on the edge 21 of the wafer 20 to be measured is the position of the alignment feature 22. When this instantaneous change amount is greater than or equal to the measurement threshold, the controller 15 determines that the alignment feature 22 has passed through the detection range 141 of the detector 14, as shown in steps S503 and Figure 5C . Compared with other areas of the outer edge 21 of the wafer 20 to be measured, when the alignment feature 22 on the edge 21 of the wafer 20 to be measured passes through the detection range 141 of the detector 14, the instantaneous change amount obtained by the controller 15 will change drastically. For example, as shown in Figure 7B , there is a peak P2 on the curve shown, and the value of this peak P2 is greater than the preset measurement threshold ET. On the contrary, when this instantaneous change amount is less than the measurement threshold, the controller 15 determines that the alignment feature 22 has not passed through the detection range 141 of the detector 14, as shown in steps S504 and Figure 5B .

[0065] When the controller 15 determines that the alignment feature 22 of the wafer 20 to be measured has not passed through the detection range 141 of the detector 14, the controller 15 returns to step S2 and repeats steps S2 to S5 until, in step S5, the alignment feature 22 has passed through the detection range 141 of the detector 14.

[0066] In step S5, when the alignment feature 22 passes through the detection range 141 of the detector 14, the controller 15 further drives the rotating table 12 to rotate in the second direction D2 at a second rotation speed V2. As shown in step S6, the wafer 20 to be measured also rotates at the same speed and in the same direction, as Figure 5D shown. The second rotation speed V2 can be, for example, less than the first rotation speed V1, and the second direction D2 is opposite to the first direction D1. While the rotating table 12 is rotating, the controller 15 controls the detector 14 to detect the contour of the outer edge 21 of the wafer 20 to be measured rotating under the conditions of the second rotation speed V2 and the second direction D2, so as to generate outer edge data corresponding to the respective positions currently detected on the outer edge 21, and provide it to the controller 15, as shown in steps S7 and Figure 5D shown, and the controller 15 records the rotation angle of the rotating table 12 corresponding to this outer edge data, as shown in step S8. Specifically, since the second rotation speed V2 is less than the first rotation speed V1, the outer edge 21 of the wafer 20 to be measured rotating at the second rotation speed V2 can be scanned in more detail to obtain more and more complete outer edge data, especially the outer edge data regarding the alignment feature 22. In this embodiment or other embodiments, at this time, the rotating table 12 is rotating in reverse, and the detector 14 will repeatedly detect some positions on the outer edge 21 of the wafer 20 to be measured, so that some of the multiple outer edge data detected under the conditions of the second rotation speed V2 and the second direction D2 may be repeated with some of the outer edge data detected under the conditions of the first rotation speed V1 and the first direction D1. In this case, among the new and old outer edge data corresponding to the same position on the outer edge 21 of the wafer 20 to be measured, the new outer edge data can, for example, replace the old outer edge data, be retained together with the old outer edge data, or be ignored.

[0067] In addition, the controller 15 also determines whether the alignment feature 22 passes through the detection range 141 of the detector 14 again according to the obtained outer edge data, as shown in step S9. The method of determining whether the alignment feature 22 passes through the detection range 141 of the detector 14 again can refer to the above description of step S5 and will not be elaborated here. Alternatively, the method of determining whether the alignment feature 22 passes through the detection range 141 of the detector 14 again can also be determined by determining whether the angle θ of the rotating table 12 rotating under the conditions of the second rotation speed V2 and the second direction D2 is greater than or equal to a second angle threshold.

[0068] When the alignment feature 22 has not passed through the detection range 141 of the detector 14, return to step S6, and repeat steps S6 to S9 until the alignment feature 22 passes through the detection range 141 of the detector 14. When the alignment feature 22 passes through the detection range 141 of the detector 14, the controller 15 estimates the current total measurement angle AT, as in step S10. The total measurement angle AT may, for example, refer to the angle corresponding to the range detected by the detector 14 on the outer edge 21 of the wafer 20 to be measured when the turntable 12 rotates. Therefore, the controller 15 can calculate the total measurement angle AT from the rotation angles corresponding to the accumulated outer edge data.

[0069] Then, the controller 15 further determines whether this total measurement angle AT is greater than or equal to the first angle threshold, as in step S11. The first angle threshold can be a default value, for example, the angle corresponding to the amount of outer edge data sufficient to calculate the deviation amount within an acceptable error range, and this amount of data is based on the specifications of this wafer 20 to be measured, that is, in order to calculate the deviation amount within an acceptable error range, the angle corresponding to the range that the detector 14 should detect on the outer edge 21 of the wafer 20 to be measured. The first angle threshold is less than 360 degrees.

[0070] When the current total measurement angle AT is greater than or equal to the first angle threshold, it means that the amount of outer edge data (or the total number of records) currently accumulated is sufficient to calculate the deviation amount within the error range. At this time, the controller 15 can control the turntable 12 to stop rotating and the detector 14 to stop detecting, as in step S16. On the contrary, when the current total measurement angle AT is less than the first angle threshold, it means that the amount of outer edge data currently accumulated is still not sufficient to calculate the deviation amount within the error range, and at this time, the shortage of the amount of data needs to be made up. For this purpose, in this embodiment or other embodiments, the system 10 for detecting the wafer position can further provide one or more compensation schemes for the controller 15 to select. At this time, the controller 15 can pre-evaluate the time required to execute each compensation scheme according to the current total measurement angle AT and the preset first angle threshold, as shown in step S12. Then, the controller 15 selects a more time-saving compensation scheme according to the estimated result, as shown in step S13; and, executes the selected compensation scheme, as shown in step S14, to make up the data volume difference. The following lists two compensation schemes as examples for illustration.

[0071] Please refer to Figure 8 and 9A to the first compensation scheme shown in 9E. When executing Figure 4A , 4B steps S1 to S11 in (corresponding to Figures 9A to 9DAfter the process of the wafer 20 to be measured, the controller 15 executes the first compensation scheme as follows. First, the controller 15 continues to drive the turntable 12 to rotate in the first direction D1 at the first rotational speed V1, as shown in step S241, so that the wafer 20 to be measured rotates at the same rotational speed and in the same direction, as Figure 9E shown. While the turntable 12 is rotating, the controller 15 controls the detector 14 to detect the outer edge 21 of the wafer 20 to be measured to generate outer edge data corresponding to the currently detected position of the wafer 20 to be measured, as shown in step S242. And, the controller 15 records the rotational angle of the turntable 12 when this outer edge data is generated, as shown in step S243. Finally, a new total measurement angle AT is estimated based on the accumulated outer edge data, as shown in step S244.

[0072] The time required to execute the first compensation scheme can be estimated, for example, by the following formula (1):

[0073]

[0074] where T1 represents the time required to execute the first compensation scheme; C1 represents the target data volume; C1' represents the currently accumulated data volume; V1 represents the first rotational speed used when roughly detecting the outer edge 21; and Δt1 represents the time required for the turntable 12 to change from rotating under the conditions of the second rotational speed V2 and the second direction D2 to rotating under the conditions of the first rotational speed V1 and the first direction D1.

[0075] Please refer to Figure 10 and 11A to the second compensation scheme shown in FIGS. 11E. When executing Figure 4A 、 4B steps S1 to S11 (corresponding to Figures 11A to 11D the process of the wafer 20 to be measured) in, the controller 15 executes the second compensation scheme as follows. First, the controller 15 continues to drive the turntable 12 to rotate in the second direction D2 at the first rotational speed V1, as shown in step S341, so that the wafer 20 to be measured rotates at the same rotational speed and in the same direction, as Figure 11E shown. While the turntable 12 is rotating, the controller 15 controls the detector 14 to detect the outer edge 21 of the wafer 20 to be measured to generate outer edge data corresponding to the currently detected position of the wafer 20 to be measured, as shown in step S342. And, the controller 15 records the rotational angle of the turntable 12 when this outer edge data is generated, as shown in step S343. Finally, a new total measurement angle AT is estimated based on the accumulated outer edge data, as shown in step S344.

[0076] The time required to execute the second compensation scheme can be estimated, for example, by the following formula (2):

[0077]

[0078] Wherein, T2 represents the time required to execute the second compensation scheme; C1 represents the target data volume; C1' represents the currently accumulated data volume; V1 represents the first rotation speed adopted when roughly detecting the outer edge 21; and Δt2 represents the time required for the rotating table 12 to rotate from rotating under the conditions of the second rotation speed V2 and the second direction D2 to rotating under the conditions of the first rotation speed V1 and the second direction D2.

[0079] Therefore, the controller 15 can estimate the time required to execute each compensation scheme according to the current total measured angle AT and the first angle threshold, that is, the currently accumulated data volume and the target data volume, and select a more time-saving compensation scheme according to the estimated result.

[0080] In this embodiment or other embodiments, in the case of only providing one compensation scheme, the above steps S12 to S13 can be omitted. That is, in step S11, when the total measured angle AT is less than the first angle threshold, the controller 15 directly executes this compensation scheme.

[0081] After obtaining the updated total measured angle AT, the controller 15 determines whether the updated total measured angle AT is greater than or equal to the first angle threshold, as shown in step S15. When the updated total measured angle AT is still less than the first angle threshold, it returns to step S14 and repeats steps S14 to S15 until the updated total measured angle AT is greater than or equal to the first angle threshold.

[0082] When the updated total measured angle AT in step S15 is greater than or equal to the first angle threshold, it means that the currently accumulated data volume has reached the target data volume. The controller 15 can control the rotating table 12 to stop rotating and the detector 14 to stop detecting, as shown in step S16. At this time, the controller 15 can estimate the eccentricity position of the wafer 20 to be measured and the position of the alignment feature 22 according to the accumulated outer edge data and the corresponding rotation angle, as shown in step S17.

[0083] The estimation of the eccentricity position of the wafer 20 to be measured and the position of the alignment feature 22 is illustrated as follows. Please refer to Figure 12 As shown, taking the alignment feature 22 as a notch as an example for illustration. First, map each obtained outer edge data and its corresponding rotation angle into two-dimensional information as shown in Figure 7A As shown, in step S1701. Specifically, the controller 15 can map the one-dimensional outer edge data into two-dimensional data information by using the following formula (3):

[0084]

[0085] Wherein Xi represents the X coordinate of the i-th mapping; Yi represents the Y coordinate of the i-th mapping; Si represents the i-th edge data generated by the detector 14 detecting the edge; and θi represents the rotation angle of the rotating stage 12 when obtaining the i-th detection data.

[0086] Then, the controller 15 fits the two-dimensional information into Figures 14A to 14D As shown in step S1702, the controller 15 can fit the two-dimensional information into a circular curve using the following formula (5):

[0087]

[0088] Where n represents the total number of instantaneous changes; Xi represents the X-coordinate of the i-th instantaneous change; Yi represents the Y-coordinate of the i-th instantaneous change; ΔX represents the center deviation on the X-axis; ΔY represents the center deviation on the Y-axis; and R represents the radius of the circular curve. After fitting the circular curve, the controller 15 calculates the center of the circular curve as the eccentric position of the wafer 20 to be tested, as shown in step S1703.

[0089] Next, the controller 15 defines the minimum value of the accumulated edge data as the edge data of the extreme point 23 of the alignment feature 22, as shown in step S1704. Finally, the controller 15 calculates the position of the alignment feature 22 based on the center of the circular curve and the position of the edge data of the extreme point 23 of the alignment feature 22 on the circular curve, as shown in step S1705.

[0090] Therefore, the wafer alignment device can estimate the center deviation of the wafer 20 to be tested and the angular deviation of the alignment feature 22 according to the eccentric position of the wafer 20 to be tested, the position of the alignment feature 22 and the position of the rotation center of the turntable 12, so as to further compensate for these deviations and align the center of the wafer 20 to be tested with the rotation center of the turntable 12.

[0091] Furthermore, in this embodiment, the measurement threshold ET and the first angle threshold can be obtained by, for example, using existing wafer position detection methods, such as those disclosed in Japanese Patent Publication No. JP2729297, Japanese Patent Publication No. JP3223584, Japanese Patent Publication No. JP4226241, or other existing methods, by performing edge detection on the entire outer edge of the wafer template to obtain test results. The wafer template used is the same wafer as the wafer to be tested 20, and therefore has the same outer edge 21 and the same alignment features 22.

[0092] After detecting the complete outer edge 21 of the wafer template, the controller 15 can calculate the instantaneous variation of each outer edge data and select at least one peak value from these instantaneous variation values, such as Figure 7BThe peak values of the medium peaks P1 and P2 are used to define the measurement threshold ET according to the selected peak value. Taking the peak value of the selected peak P2 as an example, the measurement threshold ET can be, for example, less than or equal to the peak value of the peak P2, but greater than other values on the curve except for the two peaks P1 and P2.

[0093] At this time, since the total number of outer edge data generated by detecting the entire outer edge 21 of the detection wafer template is already known, the controller 15 can perform different tests according to the accumulated outer edge data, the acceptable error range (for example, ±0.1 mm), and the specifications of the wafer template (for example, the specifications of a 12-inch wafer) to estimate the data volume ratio required to calculate the eccentricity within the error range. Then, the controller 15 estimates the first angle threshold according to the data volume ratio. For example, as shown in Table 1, based on the detection process of steps S1 to S9 in the same wafer template and Figure 4A tests are carried out, and the following test results are obtained. First, the data volume ratio of the total number of outer edge data generated by detecting the entire outer edge 21 of the detection wafer template is set to 100%, and the angles corresponding to these outer edge data are 360 degrees, as Figure 13 shown, so the first angle threshold for measuring the entire outer edge 21 is defined as 360 degrees. Then, different data volume ratios are taken for testing to find the minimum data volume ratio required for this wafer specification, and the error of the eccentricity calculation result can be maintained within a permitted range. For example, in the first test result with only 35% of the data volume obtained (that is, the detector 14 only detects the area covered by 126 degrees (360 x 35% = 126) on the outer edge of the wafer template), the circular curve fitted according to the collected outer edge data is as Figure 14A shown, and the error of the eccentricity calculation result (that is, the X-axis error and the Y-axis error) is within the permitted error range (for example, ±0.1 mm). In the second test result with 35% of the data volume as the test condition again, the circular curve fitted according to the collected instantaneous change amount is as Figure 14B shown, and the error of the eccentricity calculation result is still within the permitted error range (for example, ±0.1 mm). In the third test result with 23.5% of the data volume as the test condition, the circular curve fitted according to the collected instantaneous change amount is as Figure 14C shown. Although the error of the eccentricity calculation result is slightly larger than that of the first and second test results (that is, the calculation accuracy is lower), it is still within the permitted error range (for example, ±0.1 mm). In the fourth test result with 23.5% of the data volume as the test condition again, the circular curve fitted according to the collected instantaneous change amount is as Figure 14D shown, and the error of the eccentricity calculation result is also still within the permitted error range (for example, ±0.1 mm).

[0094] Table 1

[0095]

[0096]

[0097] As can be seen from the above test results, based on the same wafer template, the lowest data volume ratio within the allowable error range can be repeatedly tested, and different outer edge measurement schemes, that is, different first angle thresholds, can be formulated according to different data volume ratios. For example, the first angle thresholds of 84.96 degrees (360 x 23.5% = 84.96) and 126 degrees (360 x 35% = 126) are respectively formulated for the data volume ratios of 23.5% and 35% for testers to choose. After selecting one of the first angle thresholds, when subsequently detecting each wafer under test 20 with the same specifications as this wafer template, the controller 15 can directly detect the outer edge 21 of the wafer under test 20 according to the setting of the first angle threshold.

[0098] Similarly, since the above second angle threshold is the angle required for the alignment feature 22 of the wafer under test 20 to move from one side of the detection range 141 of the detector 140 to the opposite side, the second angle threshold that allows the error of the eccentricity calculation result to be within the allowable error range can also be summarized through repeated tests using the same wafer template.

[0099] Although the above implementation manner takes the first rotation speed V1 being greater than the second rotation speed V2 as an example for illustration, the present invention is not limited thereto. In other embodiments of the present invention, the first rotation speed V1 can be substantially equal to the second rotation speed V2, and the rotation direction in the compensation scheme for supplementing the data volume can be adjusted according to the design of the rotation speed to provide more compensation schemes or more efficient compensation schemes.

[0100] In summary, the method and system for detecting the position of a wafer provided by the present invention first rotate the wafer at a relatively fast first rotational speed and detect the outer edge of the wafer. Then, when the alignment feature of the wafer passes through the detection range of the detector, the wafer is rotated in reverse at a slower second rotational speed and the outer edge of the wafer is detected. Finally, when the alignment feature passes through the detection range of the detector again, the eccentric position of the wafer and the position of the alignment feature can be estimated based on the accumulated detection results and the rotation angle of the rotating stage. Since it is not necessary to rotate the wafer for a full circle, the range of repeated detection of the outer edge by the detector can be reduced, significantly shortening the detection time and thus improving the overall efficiency of the wafer manufacturing process. Moreover, the present invention further provides one or more compensation schemes to ensure that the amount of data required to calculate the eccentric position of the wafer and the position of the alignment feature remains sufficient. In addition, the present invention provides the data volume ratio of the data to be collected corresponding to different calculation accuracies as an option for the outer edge measurement scheme. And regardless of which option is selected, the center deviation of the wafer and the angular deviation of the alignment feature obtained by calculation can still be maintained within an acceptable error range.

[0101] In summary, the above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting the position of a wafer, characterized in that, Including the following steps: Place a wafer to be measured on a rotating table, the outer edge of the wafer to be measured including alignment features; Drive the rotating table to rotate in a first direction at a first rotational speed via a controller, so as to drive the wafer to be measured to rotate in the first direction at the first rotational speed; Detect the outer edge of the wafer to be measured rotating in the first direction at the first rotational speed by a detector, so as to generate outer edge data corresponding to each current detected position on the outer edge for the controller, the outer edge data corresponding to the rotation angle of the rotating table; When the controller determines according to the outer edge data that the alignment feature passes the detector in the first direction, drive the rotating table to rotate in a second direction at a second rotational speed, so as to drive the wafer to be measured to rotate in the second direction at the second rotational speed, and the second direction is opposite to the first direction; Detect the outer edge of the wafer to be measured rotating in the second direction at the second rotational speed by the detector, so as to generate a new piece of outer edge data corresponding to each current detected position on the outer edge for the controller; When the controller determines according to the outer edge data that the alignment feature passes the detector in the second direction, control the rotating table to stop rotating by the controller, and estimate the eccentricity position of the wafer to be measured and the position of the alignment feature according to each piece of accumulated outer edge data and the rotation angle corresponding to each piece of outer edge data; Estimate the total measurement angle of the wafer to be measured currently by the controller according to each piece of accumulated outer edge data and the rotation angle corresponding to each piece of outer edge data, the total measurement angle being associated with the angle corresponding to the detected range on the outer edge of the wafer to be measured; Judge by the controller whether the total measurement angle is greater than or equal to a first angle threshold; When the controller determines according to the outer edge data that the alignment feature passes the detector in the second direction and the total measurement angle is greater than or equal to the first angle threshold, control the rotating table to stop rotating by the controller, and estimate the center deviation of the wafer to be measured and the angular deviation of the alignment feature according to each piece of outer edge data and the rotation angle corresponding to each piece of outer edge data; And When the total measurement angle is less than the first angle threshold, execute a first compensation scheme by the controller, the first compensation scheme including the following steps: Drive the rotating table to rotate in the first direction at the first rotational speed again by the controller, so as to drive the wafer to be measured to rotate in the first direction at the first rotational speed again; Detect the outer edge of the wafer to be measured rotating in the first direction at the first rotational speed again by the detector, so as to provide new outer edge data corresponding to each current detected position on the outer edge for the controller; And The controller updates the total measured angle according to the accumulated outer edge data of each and the rotation angle corresponding to each outer edge data, so as to re-determine whether the total measured angle is greater than or equal to the first angle threshold.

2. A method for detecting the position of a wafer, characterized in that, Including the following steps: Place a wafer to be measured on a rotating table, and the outer edge of the wafer to be measured includes alignment features; Drive the rotating table to rotate in a first direction at a first rotation speed via the controller, so as to drive the wafer to be measured to rotate in the first direction at the first rotation speed; Detect the outer edge of the wafer to be measured rotating in the first direction at the first rotation speed by a detector, so as to generate outer edge data corresponding to the respective positions currently detected on the outer edge for the controller, and the outer edge data corresponds to the rotation angle of the rotating table; When the controller determines according to the outer edge data that the alignment feature passes the detector in the first direction, drive the rotating table to rotate in a second direction at a second rotation speed, so as to drive the wafer to be measured to rotate in the second direction at the second rotation speed, and the second direction is opposite to the first direction; Detect the outer edge of the wafer to be measured rotating in the second direction at the second rotation speed by the detector, so as to generate a new outer edge data corresponding to the respective positions currently detected on the outer edge for the controller; When the controller determines according to the outer edge data that the alignment feature passes the detector in the second direction, the controller controls the rotating table to stop rotating, and estimates the eccentricity position of the wafer to be measured and the position of the alignment feature according to the accumulated outer edge data of each and the rotation angle corresponding to each outer edge data; The controller estimates the total current measured angle of the wafer to be measured according to the accumulated outer edge data of each and the rotation angle corresponding to each outer edge data, and the total measured angle is associated with the angle corresponding to the detected range on the outer edge of the wafer to be measured; The controller determines whether the total measured angle is greater than or equal to a first angle threshold; When the controller determines according to the outer edge data that the alignment feature passes the detector in the second direction and the total measured angle is greater than or equal to the first angle threshold, the controller controls the rotating table to stop rotating, and estimates the center deviation of the wafer to be measured and the angle deviation of the alignment feature according to each outer edge data and the rotation angle corresponding to each outer edge data; And When the total measured angle is less than the first angle threshold, the controller executes a second compensation scheme, and the second compensation scheme includes the following steps: The controller drives the rotating table to continue rotating in the second direction at the first rotation speed, so as to drive the wafer to be measured to continue rotating in the second direction at the first rotation speed; Detect the outer edge of the wafer to be measured rotating in the second direction at the first rotation speed by the detector, so as to provide new outer edge data corresponding to the respective positions currently detected on the outer edge for the controller; and The controller updates the total measured angle according to each piece of accumulated outer edge data and the corresponding rotation angle of each piece of outer edge data, so as to re-determine whether the total measured angle is greater than or equal to the first angle threshold.

3. A method for detecting the position of a wafer, characterized in that, including the following steps: Place a wafer to be measured on a rotating table, and the outer edge of the wafer to be measured includes alignment features; The controller drives the rotating table to rotate in a first direction at a first rotation speed, so as to drive the wafer to be measured to rotate in the first direction at the first rotation speed; A detector detects the outer edge of the wafer to be measured rotating in the first direction at the first rotation speed, and generates outer edge data corresponding to the respective positions currently detected on the outer edge to the controller, and the outer edge data corresponds to the rotation angle of the rotating table; When the controller determines according to the outer edge data that the alignment feature passes through the detector in the first direction, the controller drives the rotating table to rotate in a second direction at a second rotation speed, so as to drive the wafer to be measured to rotate in the second direction at the second rotation speed, and the second direction is opposite to the first direction; The detector detects the outer edge of the wafer to be measured rotating in the second direction at the second rotation speed, and generates a new piece of outer edge data corresponding to the respective positions currently detected on the outer edge to the controller; When the controller determines according to the outer edge data that the alignment feature passes through the detector in the second direction, the controller controls the rotating table to stop rotating, and estimates the eccentricity position of the wafer to be measured and the position of the alignment feature according to each piece of accumulated outer edge data and the corresponding rotation angle of each piece of outer edge data; The controller estimates the current total measured angle of the wafer to be measured according to each piece of accumulated outer edge data and the corresponding rotation angle of each piece of outer edge data, and the total measured angle is associated with the angle corresponding to the detected range on the outer edge of the wafer to be measured; The controller determines whether the total measured angle is greater than or equal to a first angle threshold; When the controller determines according to the outer edge data that the alignment feature passes through the detector in the second direction and the total measured angle is greater than or equal to the first angle threshold, the controller controls the rotating table to stop rotating, and estimates the center deviation of the wafer to be measured and the angle deviation of the alignment feature according to each piece of outer edge data and the corresponding rotation angle of each piece of outer edge data; When the total measured angle is less than the first angle threshold, the controller estimates the time required for each compensation scheme among multiple compensation schemes according to the total measured angle and the first angle threshold, and the compensation scheme is associated with the rotation direction and rotation speed of the rotating table; and Based on the time required to execute each of the compensation schemes, the controller determines to execute one of the compensation schemes, so as to increase the detected range on the outer edge of the wafer under test, thereby updating the total measurement angle, and re-determining whether the total measurement angle is greater than or equal to the first angle threshold.

4. The method for detecting the position of a wafer according to claim 1, 2 or 3, characterized in that, The step of estimating the eccentricity position of the wafer under test by the controller according to each of the accumulated outer edge data and the rotation angle corresponding to each of the outer edge data includes: The controller fits a circular curve according to each of the outer edge data and the rotation angle corresponding to each of the outer edge data, and the circular curve corresponds to the outer edge of the wafer under test; and The controller estimates the center of the circular curve as the eccentricity position of the wafer under test.

5. The method for detecting the position of a wafer according to claim 4, wherein The step of estimating the position of the alignment feature by the controller according to each of the accumulated outer edge data and the rotation angle corresponding to each of the outer edge data includes: The controller defines the minimum value among the outer edge data as the outer edge data of the pole of the alignment feature; and The controller estimates the position of the alignment feature according to the center position of the circular curve and the position of the pole.

6. The method for detecting the position of a wafer according to claim 1, 2 or 3, characterized in that, The controller calculates the instantaneous change amount of the outer edge data, and when the controller determines that the instantaneous change amount is greater than or equal to a measurement threshold, it determines that the alignment feature passes through the detector.

7. The method for detecting the position of a wafer according to claim 1, 2 or 3, characterized in that The second rotational speed is less than the first rotational speed.

8. An apparatus for detecting the position of a wafer, characterized in that, Comprising: A rotating table for carrying the wafer under test, and the outer edge of the wafer under test includes an alignment feature; A detector disposed near the rotating table; and A controller electrically connected to the rotating table and the detector for executing the method for detecting the position of the wafer according to claim 1, 2 or 3.

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