JP7849044B2 - Polishing system, wafer transport control method, and work hole detection method - Google Patents

Description

The present invention relates to a polishing system for detecting the position of a work hole in a carrier that holds a wafer being polished by a polishing machine, a wafer transport control method, and a work hole detection method .

Conventional work hole detection devices are known for detecting the position of work holes in a wafer carrier when a wafer is polished using a polishing machine (see, for example, Patent Document 1). Conventional work hole detection devices acquire image data using two cameras positioned to form a predetermined central angle. The central position of the work hole is then detected based on the positions of two points on the edge of the work hole obtained from this image data, and the central angle between the cameras.

Patent No. 4492155

However, when using image data to detect the center position of a work hole, variations in image data quality due to the lighting conditions around the carrier may prevent proper detection of the work hole's edge. Furthermore, because image data is used, if the color of the carrier and the polishing surface (polishing pad, etc.) on which the carrier rests are similar, it becomes difficult to detect the work hole's edge.

The present invention aims to provide a polishing system, a wafer transport control method, and a work hole detection method that can prevent polishing of wafers that are not positioned in a predetermined location and orientation.

To achieve the above objective, the present invention provides a polishing system comprising: a polishing machine for polishing a wafer with a polishing pad attached to a surface plate; and a wafer transport machine for transporting the wafer into a work hole of a carrier placed on the polishing pad attached to the surface plate, wherein the polishing system comprises: a distance measuring unit that irradiates an object with laser light and measures the distance to the object non-contact based on the reflected light reflected by the object , and is mounted on the wafer transport machine and is movable along a predetermined trajectory set in advance from a height detection start position set to the position estimated to be the wafer; and a wafer state estimation unit that estimates whether the wafer is properly positioned in the work hole based on the measurement value obtained while the distance measuring unit moves along the trajectory from the height detection start position .

As a result, it is possible to prevent polishing of wafers that are not positioned in the designated location and orientation.

This is a schematic side view showing the overall configuration of the polishing system to which the work hole detection device of Example 1 is applied. This is a schematic plan view showing the overall configuration of the polishing system to which the work hole detection device of Example 1 is applied. This is an explanatory diagram illustrating the measurement principle of a laser displacement sensor. This is an explanatory diagram showing the various detection positions set during work hole detection and the detected edge positions. This diagram illustrates the various detection positions set during wafer transport state estimation and the movement trajectory of the laser displacement sensor. This figure shows the measured values from the laser displacement meter during edge position detection. (a) An explanatory diagram showing the wafer state during normal wafer transport. (b) A diagram showing the measured values of the laser displacement meter during normal wafer transport. (a) An explanatory diagram showing the wafer state when the wafer is mounted. (b) Figure 1 showing the measured values of the laser displacement meter when the wafer is mounted. (c) Figure 2 showing the measured values of the laser displacement meter when the wafer is mounted. (a) An explanatory diagram showing the wafer state when the wafer is floating. (b) A diagram showing the measured values of the laser displacement meter when the wafer is floating. This flowchart shows the wafer transport control process executed by the main controller in Example 1. This is an explanatory diagram showing other examples of setting the edge detection position. (a) This is an explanatory diagram showing a first modified example of the movement trajectory of the laser displacement meter when estimating the wafer transport state. (b) This is a diagram showing the detected value of the laser displacement meter when the wafer rides up, when the wafer top surface height is detected along the movement trajectory of the first modified example. (a) This is an explanatory diagram showing a second modified example of the movement trajectory of the laser displacement meter when estimating the wafer transport state. (b) This is a diagram showing the detected value of the laser displacement meter when the wafer rides up, when the wafer top surface height is detected along the movement trajectory of the second modified example.

Hereinafter, embodiments for implementing the polishing system, wafer transport control method, and work hole detection method of the present invention will be described based on Embodiment 1 shown in the drawings.

(Example 1)
The configuration of the polishing system 1 to which the work hole detection device of Example 1 is applied will be described below with reference to Figures 1 to 9.

The polishing system 1 shown in Figure 1 comprises a polishing machine 10, a wafer transporter 20, and a main controller 30.

The polishing machine 10 is a double-sided polishing device that polishes both the front and back surfaces of a thin wafer 2 using an upper platen 11 and a lower platen 12. Here, the wafer 2 is polished by a polishing pad 11a attached to the upper platen 11 and a polishing pad 12a attached to the lower platen 12. Furthermore, as shown in Figure 2, the wafer 2 is housed in a work hole 14 of a carrier 13 placed on the polishing pad 12a, and is held by the carrier 13 while being polished.

The carrier 13 is a thin, disc-shaped plate member that is thinner than the wafer 2. The work hole 14 is a hole that penetrates the carrier 13 and has an inner diameter slightly larger than the diameter of the wafer 2. In the example shown in Figure 2, one work hole 14 is formed in the carrier 13, but the number of work holes 14 formed in the carrier 13 can be arbitrarily set.

Furthermore, when the carrier 13 is placed on the polishing pad 12a, its circumferential orientation and position are defined, and its movement trajectory is constantly monitored by, for example, the controller (not shown) of the polishing machine 10. This allows the relative positional relationship between the lower platen 12 and the carrier 13 to be constantly monitored, and the center position of the work hole 14 can be determined by calculation based on this positional relationship. The center position of the work hole 14 calculated based on the relative positional relationship between the lower platen 12 and the carrier 13 is hereinafter referred to as the "teaching position α (see Figure 4)." This teaching position α is defined in the X-Y coordinate system of the wafer transporter 20.

The wafer transfer machine 20 is a robotic arm that is driven based on control commands from the main controller 30 and automatically transfers wafers 2 one by one. The wafer transfer machine 20 includes a transfer head 21 that detachably holds the wafers 2, and an arm section 22 that moves the transfer head 21 in the horizontal and vertical directions.

Prior to polishing the wafers 2, the wafer transfer machine 20 holds the wafers 2, which have been removed from a load port (not shown) containing a large number of wafers 2, using a transfer head 21. Next, the arm 22 is moved to transport the transfer head 21 to a position above a predetermined work hole 14. Finally, the wafers 2 are released from the transfer head 21 and placed inside the work hole 14.

Furthermore, after the wafer 2 has been polished, the wafer transfer machine 20 moves the arm 22 to move the transfer head 21 to a position above the predetermined work hole 14. Next, the transfer head 21 holds the wafer 2 within the work hole 14 and removes the wafer 2. Then, the arm 22 moves to transfer the wafer 2 to an unload port (not shown).

Furthermore, the transport head 21 of Example 1 is equipped with a laser displacement meter R (distance measuring unit). As shown in Figure 3, this laser displacement meter R is a distance sensor that measures the distance L to an object T non-contact by irradiating the object T with laser light S1 and using the reflected light S2 reflected by the object T.

The laser displacement meter R moves in conjunction with the transport head 21 when the transport head 21 is moved by driving the arm 22. Furthermore, since the wafer transport machine 20 can move while maintaining a constant height position for the laser displacement meter R, the laser displacement meter R can measure the thickness of the carrier 13. The laser displacement meter R can also measure the distance to the object T while it is being moved by the wafer transport machine 20. During measurement by the laser displacement meter R, air may be sprayed onto the object T to remove any moisture adhering to it.

The main controller 30 outputs control commands to the wafer transporter 20, controlling the transport of the wafer 2 by the wafer transporter 20, and also controlling the movement of the laser displacement meter R due to the movement of the transport head 21. Furthermore, the main controller 30 calculates a teaching position α based on the relative positional relationship between the lower platen 12 and the carrier 13, and uses this teaching position α to detect the position of three or more (four in Example 1) edges of the work hole 14. Here, the "edge" refers to the inner peripheral edge of the work hole 14, which is the boundary between the work hole 14 and the carrier 13. Then, based on the detected edge positions, the center position of the work hole 14 is calculated. Note that both the edge positions and the center position of the work hole 14 are defined in the X-Y coordinate system of the wafer transporter 20. Furthermore, after the wafer 2 has been transported, the main controller 30 estimates the wafer transport state based on the height of the top surface of the transported wafer.

In other words, the main controller 30 comprises a teaching position calculation unit 31, a detection position setting unit 32, an edge detection unit 33, a center calculation unit 34, a transport control unit 35, and a wafer state estimation unit 36.

The teaching position calculation unit 31, upon receiving information regarding the relative positional relationship between the lower platen 12 and the carrier 13, calculates the teaching position α based on this positional relationship information. This positional relationship information is input, for example, from the controller of the polishing machine 10. The teaching position α calculated by the teaching position calculation unit 31 is input to the detection position setting unit 32.

When the detection position setting unit 32 receives information on the teaching position α from the teaching position calculation unit 31, it sets various detection positions for detecting the position of the work hole 14 based on this teaching position information. Furthermore, after the wafer 2 has been transported, the detection position setting unit 32 receives information on the center position of the work hole 14 (hereinafter referred to as "actual center position β (see Figure 5)") calculated by the center calculation unit 34. Based on this actual center position information, it sets various detection positions for estimating the transport state of the wafer 2. Here, "detection position" refers to the target point of the laser displacement meter R. The detection position information set by the detection position setting unit 32 is input to the transport control unit 35.

Here, when detecting the position of the work hole 14, the height of the carrier 13, which serves as a reference value when detecting the edge portion of the work hole 14, and four positions (see Figure 4) of the first edge position P11, the second edge position P13, the third edge position P15, and the fourth edge position P17 are detected. Therefore, the detection position setting unit 32 sets the reference detection position P10, the first edge portion detection position P12, the second edge portion detection position P14, the third edge portion detection position P16, and the fourth edge portion detection position P18 shown in Figure 4. The "reference detection position P10" is the target point for the laser displacement meter R when detecting the height of the carrier 13. The "first edge portion detection position P12" is the target point for the laser displacement meter R when detecting the first edge position P11. The "second edge portion detection position P14" is the target point for the laser displacement meter R when detecting the second edge position P13. "Third edge detection position P16" is the target point for the laser displacement meter R when detecting the third edge position P15. "Fourth edge detection position P18" is the target point for the laser displacement meter R when detecting the fourth edge position P17.

Furthermore, the first edge detection position P12, the second edge detection position P14, the third edge detection position P16, and the fourth edge detection position P18 are set to positions that can enclose the teaching position α with a line segment γ connecting these four positions in sequence, as shown in Figure 4. In other words, when setting the edge detection positions, the detection position setting unit 32 sets three or more detection positions that can enclose the teaching position α.

The reference detection position P10 is set to a position estimated to be the substrate portion of the carrier 13 based on the teaching position α. The "substrate portion of the carrier 13" refers to the area outside the work hole 14, a flat area where no work hole 14 or other void holes are formed. Furthermore, the first edge detection position P12, the second edge detection position P14, the third edge detection position P16, and the fourth edge detection position P18 are all set to positions estimated to be inside the work hole 14 based on the teaching position α.

Furthermore, when estimating the wafer 2 transport state, in Example 1, the height of the carrier 13, which serves as a reference value for determining the wafer transport state, and the height of the top surface of the transported wafer 2 are detected. Therefore, the detection position setting unit 32 sets the reference detection position P20 and the height detection start position P21 shown in Figure 5. The "reference detection position P20" is the target movement point of the laser displacement meter R when detecting the height of the carrier 13. The "height detection start position P21" is the target movement point of the laser displacement meter R when detecting the top surface height of the wafer 2.

Here, the reference detection position P20 is set to the position estimated to be the substrate portion of the carrier 13 based on the actual center position β. The height detection start position P21 is set to the position estimated to be the wafer 2 based on the actual center position β.

When the edge detection unit 33 receives the measurement value from the laser displacement meter R, it detects the positions of three or more edges of the work hole 14 (four locations in Example 1, from the first edge position P11 to the fourth edge position P17) based on this measurement value. The position information of the edges detected by the edge detection unit 33 is input to the center calculation unit 34.

The edge detection unit 33, when detecting an edge, first sets a reference value based on the measurement obtained by moving the laser displacement meter R to the reference detection position P10. Here, the reference value is the value obtained by subtracting a predetermined value from the measurement obtained at the reference detection position P10. Next, it determines whether the measurement obtained while moving the laser displacement meter R from the first edge detection position P12 along a predetermined trajectory exceeds the reference value. Then, based on the amount of movement x of the laser displacement meter R at the point when the measurement exceeds the reference value, and the first edge detection position P12, the first edge position P11 is detected (see Figure 6).

Furthermore, the edge detection unit 33 also detects the second edge position P13, the third edge position P15, and the fourth edge position P17 each time the laser displacement meter R is moved, in the same manner as the first edge position P11. In other words, the edge detection unit 33 detects the edge position (first edge position P11, etc.) while moving the laser displacement meter R from the edge detection position (first edge position P12, etc.) until it detects the edge position (first edge position P11, etc.) at three or more locations.

The central calculation unit 34 receives position information from three or more edge locations (four locations in Embodiment 1, from the first edge position P11 to the fourth edge position P17) from the edge detection unit 33. Based on this edge location information, it calculates the actual center position β. The information of the actual center position β calculated by the central calculation unit 34 is input to the transport control unit 35. The actual center position β can be determined using the position information from three or more edge locations and a general equation for a circle.

The transport control unit 35 receives information on various detection positions (such as the reference detection position P10) from the detection position setting unit 32 and outputs control commands to the wafer transport machine 20 based on these detection positions. The laser displacement meter R is then moved to the various detection positions as target points in a predetermined order and timing. Furthermore, after moving the laser displacement meter R to a predetermined detection position (such as the first edge position P11), the transport control unit 35 outputs control commands to the wafer transport machine 20 to move the laser displacement meter R in a predetermined direction.

The wafer state estimation unit 36 receives the measurement value from the laser displacement meter R after the wafer 2 has been transported, and estimates the transported state of the transported wafer 2 based on this measurement value. The transported state information estimated by the wafer state estimation unit 36 may be input to, for example, the controller of the polishing machine 10, and reported to the operator of the polishing system 1.

The wafer state estimation unit 36, when estimating the wafer transport state, first sets a reference range (upper threshold and lower threshold) based on the measurement value obtained when the laser displacement meter R is moved to the reference detection position P20. Next, it moves the laser displacement meter R to the height detection start position P21, and determines whether the measurement value (wafer top surface height) obtained while moving along a predetermined trajectory (in this case, an annular trajectory 3 along the periphery of the wafer 2) exceeds the reference range.

For example, as shown in Figure 7(a), when the wafer 2 is properly positioned within the work hole 14, the measured values obtained by the laser displacement meter R as it moves along the annular trajectory 3 fall within the reference range (see Figure 7(b)). That is, when the wafer state estimation unit 36 determines that the measured values fall within the reference range, it estimates that the wafer 2 is properly positioned.

In contrast, as shown in Figure 8(a), if the wafer 2 rides up onto the edge of the work hole 14, the measured value exceeds the reference range while the laser displacement meter R is moving along the annular trajectory 3 (see Figure 8(b)). Note that depending on the relationship between the height detection start position P21 and the position where the wafer 2 rides up, the measured value shown in Figure 8(c) may be obtained. Even in this case, the measured value exceeds the reference range while the laser displacement meter R is moving along the annular trajectory 3. Furthermore, as shown in Figure 9(a), even if the wafer 2 is placed within the work hole 14, if it is lifted off the polishing pad 12a due to the influence of slurry or water, the measured value exceeds the reference range while the laser displacement meter R is moving along the annular trajectory 3 (see Figure 9(b)). Therefore, when the wafer state estimation unit 36 determines that it has obtained a measured value exceeding the reference range, it estimates that the wafer 2 is not properly positioned.

The following describes each step of the wafer transport control process performed by the main controller 30 in Example 1, based on the flowchart shown in Figure 10. This wafer transport control process is repeatedly performed until all wafers 2 are placed in the work holes 14 of the carriers 13 on the polishing pad 12a.

In step S1, a decision is made as to whether or not to start transporting wafer 2. If YES (start transport), proceed to step S2. If NO (do not transport), repeat step S1. The decision to start transport is made, for example, by the transport control unit 35.

In step S2 (the first step), following the determination to start transport in step S1, the teaching position calculation unit 31 calculates the teaching position, the detection position setting unit 32 reads the calculated teaching position α, and the process proceeds to step S3.

In step S3 (the first step), following the reading of the teaching position information in step S2, the detection position setting unit 32 sets various detection positions (reference detection position P10, first edge detection position P12, second edge detection position P14, third edge detection position P16, and fourth edge detection position P18) for detecting the position of the work hole 14 based on the teaching position information, and then proceeds to step S4.

In step S4 (the first step), following the setting of the detection position in step S3, the transport control unit 35 outputs a control command to the wafer transport machine 20. The laser displacement meter R is then moved to the reference detection position P10 set in step S3 as the target point, and the process proceeds to step S5.

In step S5 (the first step), following the movement of the laser displacement meter R in step S4, the distance to the reference detection position P10 is measured by the laser displacement meter R, and the process proceeds to step S6. Here, since the reference detection position P10 is set to a position estimated to be the substrate portion of the carrier 13, the carrier height is detected. Based on this carrier height, a reference value is then set for detecting the edge portion of the work hole 14.

In step S6 (the first step), following the detection of the carrier height in step S5, the transport control unit 35 outputs a control command to the wafer transport machine 20. The laser displacement meter R is moved to the first edge detection position P12, which was set in step S3, as the target point, and the process proceeds to step S7.

In step S7 (the first step), following the movement of the laser displacement meter R in step S6, the laser displacement meter R is moved in a predetermined direction while measuring the distance to the carrier 13 or polishing pad 12a located below. Then, based on the measured value obtained at this time and the reference value set from the carrier height detected in step S5, the edge detection unit 33 detects the first edge position P11, and the process proceeds to step S8.

In step S8 (the first step), following the detection of the first edge position P11 in step S7, the transport control unit 35 outputs a control command to the wafer transport machine 20. The laser displacement meter R is then moved to the second edge detection position P14, which was set in step S3, as the target point, and the process proceeds to step S9.

In step S9 (the first step), following the movement of the laser displacement meter R in step S8, the laser displacement meter R is moved in a predetermined direction while measuring the distance to the carrier 13 or polishing pad 12a located below. Based on the measured value obtained at this time and the reference value set in step S5, the edge detection unit 33 detects the second edge position P13, and the process proceeds to step S10.

In step S10 (the first step), following the detection of the second edge position P13 in step S9, the transport control unit 35 outputs a control command to the wafer transport machine 20. The laser displacement meter R is then moved to the third edge detection position P16, which was set in step S3, as the target point, and the process proceeds to step S11.

In step S11 (the first step), following the movement of the laser displacement meter R in step S10, the laser displacement meter R is moved in a predetermined direction while measuring the distance to the carrier 13 or polishing pad 12a located below. Based on the measured value obtained at this time and the reference value set in step S5, the edge detection unit 33 detects the third edge position P15, and the process proceeds to step S12.

In step S12 (the first step), following the detection of the third edge position P15 in step S11, the transport control unit 35 outputs a control command to the wafer transport machine 20. The laser displacement meter R is then moved to the fourth edge detection position P18, which was set in step S3, as the target point, and the process proceeds to step S13.

In step S13 (the first step), following the movement of the laser displacement meter R in step S12, the laser displacement meter R is moved in a predetermined direction while measuring the distance to the carrier 13 or polishing pad 12a located below. Based on the measured value obtained at this time and the reference value set in step S5, the edge detection unit 33 detects the fourth edge position P17, and the process proceeds to step S14.

In step S14 (the second step), following the detection of the fourth edge position P17 in step S13, the center calculation unit 34 calculates the actual center position β based on the first edge position P11, the second edge position P13, the third edge position P15, and the fourth edge position P17, and then proceeds to step S15.

In step S15, following the calculation of the actual center position β in step S14, the transport control unit 35 outputs a control command to the wafer transporter 20, transporting the wafer 2 into the work hole 14, and proceeding to step S16. At this time, the transport control unit 35 calculates the difference (amount of deviation) between the teaching position α calculated by the teaching position calculation unit 31 and the actual center position β calculated by the center calculation unit 34. Next, the calculated difference (amount of deviation) is corrected for the teaching position α to set the target position. Then, a control command is output to align the center position of the wafer 2 held by the transport head 21 with this target position, and the arm unit 22 is controlled so that the wafer 2 is positioned in the center of the work hole 14.

Step S16 (the third step) follows the transfer of wafer 2 in step S15. The transfer control unit 35 outputs a control command to the wafer transfer machine 20, detects the height of the top surface of the transferred wafer 2, and proceeds to step S17.

Here, prior to detecting the top surface height of wafer 2, the detection position setting unit 32 first sets a reference detection position P20 and a height detection start position P21 based on the actual center position β. Next, the transport control unit 35 moves the laser displacement meter R to the reference detection position P20, and the laser displacement meter R measures the distance to the reference detection position P20. The wafer state estimation unit 36 sets a reference range (upper threshold and lower threshold) based on the measured values obtained at this time. After that, the transport control unit 35 moves the laser displacement meter R to the height detection start position P21. Then, the laser displacement meter R detects the top surface height of wafer 2 while moving along a pre-set annular trajectory 3 from this height detection start position P21.

In step S17 (the fourth step), following the detection of the wafer 2's top surface height in step S16, the wafer state estimation unit 36 estimates the wafer 2's transport state based on the top surface height detected in step S16 and the reference range set from the distance to the reference detection position P20, and then proceeds to the end.

The "work hole position detection function" of the work hole detection device and work hole detection method of Example 1 will be described below.

In the polishing system 1 of Example 1, the wafer 2 is automatically transported onto the lower platen 12 of the polishing machine 10 using the wafer transporter 20. Here, a polishing pad 12a is pre-attached to the lower platen 12, and a carrier 13 having a work hole 14 is placed on top of it. That is, the wafer transporter 20 needs to transport the wafer 2 into the designated work hole 14 in a predetermined orientation.

On the other hand, the carrier 13 has a defined circumferential orientation and position when placed on the polishing pad 12a, and its movement trajectory is constantly monitored. Therefore, the relative positional relationship between the lower platen 12 and the carrier 13 is always known, and the center position of the work hole 14 is determined as the teaching position α. However, due to backlash in the sun gear and internal gear of the polishing machine 10, backlash in the carrier, and increased backlash due to wear, the actual center position of the work hole 14 may deviate from the teaching position α. Therefore, if the wafer 2 is transported using the teaching position α as the target position, there may be cases where the wafer 2 cannot be transported properly.

Therefore, in the wafer transfer machine 20 of Example 1, in order to recognize the position of the work hole 14 where the wafer 2 should be placed, the positions of the edges of three or more work holes 14 are detected using a laser displacement meter R before placing the wafer 2, and the actual center position β defined in the X-Y coordinate system of the wafer transfer machine 20 is calculated. Then, the difference between this actual center position β and the previously determined teaching position α is corrected, and the wafer 2 is placed.

Specifically, in the transport control unit 35 of the main controller 30, step S1 of the flowchart shown in Figure 10 is executed. If it determines that the transport of the wafer 2 should begin, step S2 is executed. As a result, the teaching position calculation unit 31 calculates the teaching position α, and the detection position setting unit 32 reads the information of the teaching position α calculated by the teaching position calculation unit 31.

Next, the detection position setting unit 32 executes step S3 and sets various detection positions (reference detection position P10, first edge detection position P12, second edge detection position P14, third edge detection position P16, and fourth edge detection position P18) for detecting the position of the work hole 14, based on the teaching position information.

Here, the first edge detection position P12, the second edge detection position P14, the third edge detection position P16, and the fourth edge detection position P18 are set to positions that can enclose the teaching position α with a line segment γ connecting these four locations. Furthermore, the reference detection position P10 is set to a position estimated to be the substrate portion of the carrier 13, based on the teaching position α.

Once the detection position is set by the detection position setting unit 32, steps S4 and S5 are executed. The transport control unit 35 moves the laser displacement meter R to the reference detection position P10 as the target point, and the distance to the reference detection position P10 is measured by the laser displacement meter R. Here, the reference detection position P10 is a position where there are no work holes 14 on the carrier 13. Therefore, the laser displacement meter R can detect the height of the carrier 13.

Once the carrier height is detected, steps S6 and S7 are executed. Specifically, the transport control unit 35 moves the laser displacement meter R to the first edge detection position P12 as the target point. The laser displacement meter R measures the distance from the first edge detection position P12 to the object (carrier 13 or polishing pad 12a) while moving. The edge detection unit 33 compares the measured value obtained at this time with a reference value determined from the previously detected carrier height to detect the first edge position P11.

Once the first edge position P11 is detected, steps S8 and S9 are executed. Specifically, the transport control unit 35 moves the laser displacement meter R to the second edge detection position P14 as the target point. The laser displacement meter R measures the distance from the second edge detection position P14 to the object (carrier 13 or polishing pad 12a) while moving. The edge detection unit 33 compares the measured value obtained at this time with a reference value determined from the previously detected carrier height to detect the second edge position P13.

Once the second edge position P13 is detected, steps S10 and S11 are executed. Specifically, the transport control unit 35 moves the laser displacement meter R to the third edge detection position P16 as the target point. The laser displacement meter R measures the distance from the third edge detection position P16 to the object (carrier 13 or polishing pad 12a) while moving. The edge detection unit 33 compares the measured value obtained at this time with a reference value determined from the previously detected carrier height to detect the third edge position P15.

Once the third edge position P15 is detected, steps S12 and S13 are executed. Specifically, the transport control unit 35 moves the laser displacement meter R to the fourth edge detection position P18 as the target point. The laser displacement meter R measures the distance from the fourth edge detection position P18 to the object (carrier 13 or polishing pad 12a) while moving. The edge detection unit 33 compares the measured value obtained at this time with a reference value determined from the previously detected carrier height to detect the fourth edge position P17.

Once the four edge positions (first edge position P11, second edge position P13, third edge position P15, fourth edge position P17, and so on) are detected, step S14 is executed, and the center calculation unit 34 calculates the actual center position β using the information of the four edge positions and the equation of a circle.

Then, once the actual center position β is calculated, the transport control unit 35 executes step S15. That is, the transport control unit 35 determines the difference (amount of deviation) between the teaching position α and the actual center position β, corrects the teaching position α based on this difference (amount of deviation), and outputs a control command to align the center position of the wafer 2 with the set target position, thereby positioning the wafer 2 at the center of the work hole 14.

Thus, in Example 1, the actual center position β is detected based on information about the positions of the four edge portions. The positions of these four edge portions are detected based on measurements obtained by moving a laser displacement meter R, which measures the distance to the object T, and measuring the distance to the object T. Therefore, the position of the edge portions of the work hole 14 can be detected without being affected by the lighting conditions around the detection device or the color of the carrier 13.

This allows for stable detection of the position of the work hole 14 on the carrier 13, which is positioned on the lower platen 12 of the polishing machine 10. Because the position of the work hole 14 can be reliably determined, it becomes possible to accurately position the wafer 2 in a predetermined position and orientation.

Furthermore, the distance to the object T is measured by a laser displacement meter R, which measures this distance using reflected laser light. Therefore, since the distance can be measured without contact with the carrier 13 or polishing pad 12a, the distance L to the object T can be measured with high precision while moving. This allows for high-precision detection of the position of the edge portion of the work hole 14.

Furthermore, in Example 1, the laser displacement meter R is mounted on the transport head 21 of the wafer transport machine 20 that transports the wafer 2. Therefore, the laser displacement meter R can be moved using the wafer transport machine 20, which moves to the vicinity of the work hole 14. This allows the laser displacement meter R to be moved to the appropriate position without requiring a separate mechanism for moving the laser displacement meter R, enabling high-precision detection of the edge position of the work hole 14.

Furthermore, in Embodiment 1, the relative positional relationship between the lower platen 12 and the carrier 13 is monitored, and the teaching position calculation unit 31 calculates the teaching position α based on the relative positional relationship between the lower platen 12 and the carrier 13. This allows the detection position setting unit 32 to set various detection positions for detecting the position of the work hole 14 based on the teaching position α. In other words, the position of the edge portion of the work hole 14 can be detected using the teaching position α as a guide. Therefore, there is no need to unnecessarily move the laser displacement meter R, and the position of the edge portion of the work hole 14 can be detected in a short time.

Furthermore, the edge detection positions (first edge detection position P12, second edge detection position P14, third edge detection position P16, fourth edge detection position P18, and so on) set by the detection position setting unit 32 are set to positions where the teaching position α can be enclosed by the line segment γ connecting these four locations.

In other words, when the detection position setting unit 32 detects the position of the edge portion of the work hole 14, it sets three or more edge portion detection positions that can surround the teaching position α. Then, the edge detection unit 33 repeatedly detects the position of the edge portion of the work hole 14 while moving the laser displacement meter R from each edge portion detection position, thereby detecting three or more positions of the edge portion of the work hole 14. Therefore, as shown in Figure 4, the positions of the edge portion of the work hole 14 detected by the edge detection unit 33 surround the teaching position α, improving the calculation accuracy when calculating the actual center position β based on the position of the edge portion of the work hole 14.

Furthermore, in Example 1, the positions of four edge points are detected. Therefore, when calculating the actual center position β, it becomes possible to establish four calculation formulas, thereby improving calculation accuracy compared to, for example, the case where the positions of three edge points of the work hole 14 are detected.

The following describes the "wafer transport state estimation function" of the work hole detection device and work hole detection method of Example 1.

In the polishing system 1 of Example 1, after transporting the wafer 2, step S16 in the flowchart shown in Figure 10 is executed to set the top surface height of the wafer 2. Specifically, first, the detection position setting unit 32 sets the reference detection position P20 and the height detection start position P21 based on the actual center position β. Then, the transport control unit 35 drives the wafer transporter 20 and moves the laser displacement meter R to the reference detection position P20 and measures the distance to this reference detection position P20. Here, the reference detection position P20 is the position estimated to be the substrate portion of the carrier 13. Therefore, the laser displacement meter R can detect the height of the carrier 13. At this time, the wafer state estimation unit 36 sets a reference range for estimating the transport state of the wafer 2 based on the carrier height. Then, the transport control unit 35 drives the wafer transporter 20 and moves the laser displacement meter R from the height detection start position P21 along the annular trajectory 3. As the laser displacement meter R moves, it measures the distance to the wafer 2 and detects the top surface height of the wafer 2.

Once the laser displacement meter R detects the top surface height of wafer 2, step S17 is executed. The wafer state estimation unit 36 compares the detected top surface height of wafer 2 with a preset reference range and estimates the transport state of wafer 2.

Thus, in Example 1, a wafer state estimation unit 36 is provided that estimates the transport state of the wafer 2 based on the upper surface height of the transported wafer 2 measured by the laser displacement meter R.

This allows the system to detect when wafer 2 is not positioned in its designated location and orientation, such as when it rides up onto the edge of the work hole 14 (see Figure 8(a)) or when it is lifted off the polishing pad 12a (see Figure 9(a)). By notifying the operator of the polishing system 1 of this transport information, the system can correct the position and orientation of the transported wafer 2 or stop the polishing process. In other words, it prevents polishing of wafers that are not positioned in their designated location and orientation.

The work hole detection device and work hole detection method of the present invention have been described above based on Example 1. However, the specific configuration is not limited to this example, and changes or additions to the design are permitted as long as they do not deviate from the gist of the invention as described in each claim.

In Example 1, we showed an example where the edge detection positions were set in a location that could enclose the teaching position α with a line segment γ connecting the four edge detection positions in sequence. However, the method is not limited to this. Since it is sufficient to detect the edge positions of three or more work holes 14, as shown in Figure 11, three or more edge detection positions (in the example shown in Figure 11, the first edge detection position P12', the second edge detection position P14', the third edge detection position P16', and the fourth edge detection position P18') may be set in a location that does not enclose the teaching position α. In other words, the edge detection positions can be set arbitrarily.

Furthermore, while Example 1 shows an example where all edge detection positions are set to positions estimated to be inside the work hole 14 based on the teaching position α, the method is not limited to this. Edge detection positions may also be set outside the work hole 14 (at positions estimated to be the substrate portion of the carrier 13). When setting the edge detection positions to positions inside the work hole 14 and measuring while moving the laser displacement meter R from the inside to the outside of the work hole 14, blowing air onto the carrier 13 as the laser displacement meter R moves makes it easier to remove moisture adhering to the edges of the work hole 14, thereby suppressing the occurrence of measurement errors.

Furthermore, the system may not include a teaching position calculation unit 31 or a detection position setting unit 32. Instead, it may detect the position of the edge portion of the work hole 14 using measurements obtained while moving the laser displacement meter R from any position in any direction, without setting an edge portion detection position.

Furthermore, in Example 1, we demonstrated an example in which the transport state of the wafer 2 is estimated based on measurements obtained by moving the laser displacement meter R along an annular trajectory 3 along the peripheral edge of the wafer 2. However, this is not limited to this example, as it is sufficient to detect the height of the transported wafer 2 at multiple locations.

For example, as shown in Figure 12(a), the transport state of the wafer 2 may be estimated based on measurements obtained by moving the laser displacement meter R along two orthogonal linear trajectories (first trajectory 4, second trajectory 5) at the actual center position β. In this case, as shown in Figure 12(b), even if the measurement obtained by moving the laser displacement meter R along the second trajectory 5 is a constant value, if the measurement obtained by moving the laser displacement meter R along the first trajectory 4 exceeds an upper threshold, the wafer state estimation unit 36 determines that it has obtained a measurement value exceeding the reference range and estimates that the wafer 2 is not properly positioned.

Furthermore, as shown in Figure 13(a), the laser displacement meter R may be moved to a position above any six measurement points (6a, 6b, 6c, 6d, 6e, 6f) near the periphery of the wafer 2, and the transport state of the wafer 2 may be estimated based on the height position of the wafer 2 at each measurement point 6a to 6f. In this case, as shown in Figure 13(b), if any of the six measurement points 6a to 6f exceeds the reference range, the wafer state estimation unit 36 estimates that the wafer 2 is not properly positioned.

Furthermore, while Example 1 showed an example where a laser displacement meter R, which measures distance using reflected laser light S2, was used as the distance measuring unit to measure the distance to the object T, the example is not limited to this. For example, a distance measuring device that extends an extendable measuring rod to the object T and measures the distance by the length of the rod may also be used.

Furthermore, while Example 1 showed an example of transporting a wafer 2 into a single work hole 14 formed in the carrier 13, multiple work holes 14 may be formed in the carrier 13. In this case, for example, the actual center positions of the multiple work holes 14 can be detected one by one, and the wafer 2 can be sequentially placed into the work holes 14 whose actual center positions have been detected.

Furthermore, the detection of the actual center position β of the work hole 14 may be performed while the wafer 2 is held by the transport head 21, or while the wafer 2 is not held. When detecting the actual center position β while the wafer 2 is held, it is not necessary to drive the arm 22 to hold the wafer 2 after the detection of the actual center position β. Therefore, the increase in the transport time of the wafer 2 can be suppressed.

1. Polishing System 2. Wafer 10. Polishing Machine 11. Upper Platen 12. Lower Platen 13. Carrier 14. Work Hole 20. Wafer Transfer Machine 21. Transfer Head 22. Arm 30. Main Controller 31. Teaching Position Calculation Unit 32. Detection Position Setting Unit 33. Edge Detection Unit 34. Center Calculation Unit 35. Transfer Control Unit 36. Wafer State Estimation Unit R. Laser Displacement Meter (Distance Measurement Unit)
α Teaching position β Actual center position

Claims (4)

A polishing system comprising a polishing machine that polishes a wafer using a polishing pad attached to a surface plate, and a wafer transport machine that transports the wafer into a work hole of a carrier placed on the polishing pad attached to the surface plate,
A distance measuring unit is mounted on a wafer transporter and is capable of moving along a predetermined trajectory from a height detection start position set at a position estimated to be the wafer .
A wafer state estimation unit estimates whether the wafer is properly positioned in the work hole based on the measurement values obtained while the distance measuring unit moves along the trajectory from the height detection start position ,
A polishing system characterized by comprising the following features. A method for estimating the placement of a wafer using a polishing system comprising a polishing machine that polishes a wafer using a polishing pad attached to a surface plate, and a wafer transport machine that transports the wafer into a work hole of a carrier placed on the polishing pad attached to the surface plate,
After the wafer has been transported by the wafer transporter, a laser beam is irradiated onto the object, and the distance to the object is measured non-contact based on the reflected light reflected by the object , and the height of the top surface of the transported wafer is detected while moving the distance measuring unit mounted on the wafer transporter along a predetermined trajectory set in advance from a height detection start position set at the position estimated to be the wafer .
A step of estimating whether the wafer is properly positioned in the work hole based on the upper surface height of the wafer,
A method for estimating the arrangement of wafers, characterized by comprising the following: A polishing system comprising a polishing machine that polishes a wafer using a polishing pad attached to a surface plate, and a wafer transport machine that transports the wafer into a work hole of a carrier placed on the polishing pad attached to the surface plate,
A distance measuring unit that measures the distance to the object,
An edge detection unit that uses the distance measured by the distance measuring unit to detect the position of three or more edges of the work hole,
A center calculation unit calculates the actual center position, which is the center position of the work hole, based on the positions of three or more edges detected by the edge detection unit,
The system includes a teaching position calculation unit that calculates a teaching position, which is the center position of the work hole calculated based on the relative positional relationship between the base plate and the carrier,
The edge detection unit compares a reference value, which is a value obtained by subtracting a predetermined value from a measured height obtained at a reference detection position, which is a position set in advance as the base portion of the carrier located outside the work hole, with a measured height obtained while moving the distance measuring unit from an edge detection position set as a position set as the inside of the work hole, and detects the edge portion based on whether the measured height exceeds the reference value.
The predetermined value is a value that sets the reference value to a value greater than the measured height obtained at the edge detection position and less than the measured height obtained at the reference detection position.
The polishing system is characterized in that, when transporting the wafer into the work hole, the wafer transporter is controlled to align the center position of the wafer being transported with a target position set by correcting the difference between the teaching position and the actual center position. In a work hole detection method for detecting the position of a work hole in a carrier placed on a polishing pad attached to the surface plate of a polishing machine,
The first step involves comparing a reference value, which is a value obtained by subtracting a predetermined value from a measured height at a reference detection position set in advance as a position estimated to be the base portion of the carrier outside the work hole, with a measured height obtained by measuring the distance to the object while moving the distance measuring unit from an edge detection position set as a position estimated to be inside the work hole, and detecting the position of the edge portion of the work hole at three or more locations based on a determination of whether the measured height exceeds the reference value.
A second step involves calculating the center position of the work hole based on the positions of three or more of the aforementioned edge portions,
A third step involves using the distance measuring unit to detect the height of the top surface of the transported wafer after the wafer has been transported,
A fourth step of estimating whether the wafer is properly positioned within the work hole based on the upper surface height of the wafer,
Equipped with,
The predetermined value is a value that sets the reference value to a value greater than the measured height obtained at the edge detection position and less than the measured height obtained at the reference detection position.
In the first step, when detecting the position of the edge portion, three or more edge portion detection positions are set that can surround the center position of the work hole calculated from the relative positions of the surface plate and the carrier, and the position of the edge portion is detected at three or more locations while moving the distance measuring unit from the edge portion detection positions.