Method for expanding the elastic membrane of a polishing head, and polishing head system

Abstract

To provide a technique capable of swelling an elastic film into a desired shape and preventing generation of stress in a workpiece when the workpiece is released from a polishing head or the workpiece is held on the polishing head.SOLUTION: The method of the present invention swells an elastic film 34 of a polishing head 1 by supplying a gas into pressure chambers 25A and 25B formed by the elastic film 34 at first and second flowrates adjusted by first and second flowrate control valves FC1 and FC2 when a polished workpiece W is released from the polishing head 1 or the workpiece W to be polished is held on the polishing head 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for inflating an elastic membrane of a polishing head for pressing a workpiece such as a wafer, a substrate, or a panel against a polishing pad, and particularly relates to a technique for inflating an elastic membrane when releasing a workpiece from the polishing head or holding a workpiece with the polishing head. [Background Art]

[0002] Chemical mechanical polishing (CMP) is a technique for polishing the surface of a wafer by supplying a polishing liquid onto a polishing surface, pressing the wafer against the polishing surface, and bringing the wafer into sliding contact with the polishing surface in the presence of the polishing liquid. During wafer polishing, the wafer is pressed against the polishing surface by a polishing head. The surface of the wafer is flattened by the chemical action of the polishing liquid and the mechanical action of abrasive grains contained in the polishing liquid and / or the polishing pad.

[0003] Figure 7 is a cross-sectional view schematically showing an example of a polishing head 100. The polishing head 100 has an elastic membrane 110 that contacts the upper surface of a wafer W1. The elastic membrane 110 forms a plurality of pressure chambers 101 to 104, and the pressure in each of the pressure chambers 101 to 104 can be adjusted independently. Therefore, the polishing head 100 can press a plurality of regions of the wafer W1 corresponding to these pressure chambers 101 to 104 with different forces, and can achieve a desired film thickness profile of the wafer W1.

[0004] Once the polishing of wafer W1 is complete, as shown in Figure 8, the polished wafer W1 is moved by the polishing head 100 to an upper position on the wafer transfer device 114. Then, by increasing the pressure in the pressure chambers 101-104, the elastic film 110 is bent downward, creating a gap between the edge of wafer W1 and the elastic film 110. The release nozzle 115 sprays release gas (for example, an inert gas such as nitrogen gas) into the gap between the edge of wafer W1 and the elastic film 110. As a result, as shown in Figure 9, wafer W1 is released from the polishing head 100 and received by the wafer transfer device 114. After that, the polished wafer W1 is transported to the next process, such as cleaning.

[0005] Figure 10 is a schematic diagram showing the state in which the next wafer W2 to be polished is placed on the wafer transfer device 114. As shown in Figure 10, the next wafer W2 is transported to the wafer transfer device 114 below the polishing head 100 by a transport device (not shown), such as a transport robot. At the same time, the polishing head 100 is cleaned with a liquid (e.g., pure water) supplied from the cleaning nozzle 120, and polishing fluid and polishing debris are removed from the polishing head 100.

[0006] The liquid used to clean the polishing head 100 falls onto the upper surface of the wafer W2. If liquid is present between the wafer W2 and the elastic film 110 of the polishing head 100 during polishing, the polishing head 100 cannot apply force to the wafer W2 properly. Therefore, as shown in Figure 11, the pressure in the pressure chambers 101-104 is increased before the polishing head 100 holds the wafer W2, causing the elastic film 110 to bend downward. Then, as shown in Figure 12, the polishing head 100 is lowered, and the liquid is pushed out to the outside of the wafer W2 by the downwardly bent elastic film 110. This removes the liquid from the upper surface of the wafer W2. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-11432 [Overview of the project] [Problems that the invention aims to solve]

[0008] As wafers become smaller and more multilayered, they are becoming more brittle and prone to cracking. As shown in Figures 8 and 12, the downward-curving elastic film 110 contacts the wafer, causing a certain amount of stress on the wafer. In conventional technology, the pressure in pressure chambers 101-104 is controlled when the elastic film 110 is expanded. However, due to individual differences in the elastic film 110, the structure or material of the elastic film 110 itself, and aging degradation of the elastic film 110, the pressure chambers 101-104 may not expand to the desired shape. For example, the elastic film 110 may expand excessively or expand locally. Due to individual differences in the elastic film 110, there is variation in the pressure required to expand the elastic film 110, and the amount of expansion of the elastic film 110 also changes depending on the volume of pressure chambers 101-104 and the pressure loss in the piping, making predictive control difficult using pressure alone. As a result, excessive stress may be placed on the wafer, potentially causing it to break. These problems are expected to become more pronounced as the number of pressure chambers in the polishing head increases. Specifically, as the number of pressure chambers in the polishing head increases, the volume per pressure chamber decreases, and the way the pressure chambers expand is expected to become more susceptible to the influence of pressure and flow rate.

[0009] Therefore, the present invention provides a technology that allows an elastic film to be expanded into a desired shape when a workpiece such as a wafer, substrate, or panel is released from the polishing head, or when the workpiece is held by the polishing head, thereby preventing excessive stress from being generated on the workpiece. [Means for solving the problem]

[0010] In one embodiment, a method is provided for inflating an elastic membrane of a polishing head, wherein when releasing a polished workpiece from the polishing head or when holding a workpiece to be polished with the polishing head, gas is supplied to a first pressure chamber and a second pressure chamber formed by the elastic membrane at first and second flow rates regulated by a first flow control valve and a second flow control valve, respectively.

[0011] In one embodiment, the volume of the first pressure chamber is greater than the volume of the second pressure chamber, and the first flow rate is greater than the second flow rate. In one embodiment, the gas is supplied to the first pressure chamber at the first flow rate until the cumulative value of the first flow rate reaches a first target cumulative flow rate, and the gas is supplied to the second pressure chamber at the second flow rate until the cumulative value of the second flow rate reaches a second target cumulative flow rate. In one embodiment, the method further includes calculating the first flow rate by dividing the first target flow rate integral value for the first pressure chamber by a preset operating time, and calculating the second flow rate by dividing the second target flow rate integral value for the second pressure chamber by a preset operating time. In one embodiment, at least one of the first flow rate and the second flow rate is changed while the gas is being supplied to the first pressure chamber and the second pressure chamber. In one embodiment, the method further includes measuring the flow rate of the gas supplied to the first pressure chamber by the first flow control valve while the workpiece is being polished by the polishing head, calculating the integrated polishing flow rate which is the sum of the measured flow rates, and determining a defect in the elastic film or an abnormality in the polishing of the workpiece based on the change in the integrated polishing flow rate.

[0012] In one embodiment, a polishing head system for polishing a workpiece is provided, comprising: a polishing head having an elastic membrane forming a first pressure chamber and a second pressure chamber; a first gas transfer line and a second gas transfer line communicating with the first pressure chamber and the second pressure chamber, respectively; a first flow control valve and a second flow control valve connected to the first gas transfer line and the second gas transfer line, respectively; and a system control unit that controls the operation of the first flow control valve and the second flow control valve so that gas is supplied to the first pressure chamber and the second pressure chamber at first flow rates and second flow rates, respectively, when releasing a polished workpiece from the polishing head or when holding a workpiece to be polished with the polishing head.

[0013] In one embodiment, the volume of the first pressure chamber is greater than the volume of the second pressure chamber, and the first flow rate is greater than the second flow rate. In one embodiment, the system control unit is configured to calculate the cumulative value of the first flow rate, issue a command to the first flow control valve to supply the gas to the first pressure chamber at the first flow rate until the cumulative value of the first flow rate reaches the first target cumulative flow rate, and calculate the cumulative value of the second flow rate, issue a command to the second flow control valve to supply the gas to the second pressure chamber at the second flow rate until the cumulative value of the second flow rate reaches the second target cumulative flow rate. In one embodiment, the system control unit is configured to calculate the first flow rate by dividing the first target flow rate integral value for the first pressure chamber by a preset operating time, and to calculate the second flow rate by dividing the second target flow rate integral value for the second pressure chamber by a preset operating time. In one embodiment, the system control unit is configured to give a command to at least one of the first flow control valve and the second flow control valve to change at least one of the first flow rate and the second flow rate while the gas is being supplied to the first pressure chamber and the second pressure chamber. In one embodiment, the first flow control valve measures the flow rate of gas supplied to the first pressure chamber while the workpiece is being polished by the polishing head, the system control unit calculates a polishing flow rate integrated value which is the sum of the measured flow rates, and is configured to determine a defect in the elastic film or an abnormality in the polishing of the workpiece based on the change in the polishing flow rate integrated value. [Effects of the Invention]

[0014] The expansion of the multiple pressure chambers in the polishing head is controlled by the gas flow rate, not the gas pressure. The expansion rate and volume after expansion of each pressure chamber can be easily and appropriately adjusted by the corresponding flow control valve. As a result, the elastic film can be stably expanded into the desired shape, preventing excessive stress on workpieces such as wafers. Since it is possible to supply a predetermined flow rate to the pressure chambers, the amount of expansion of the elastic film can be controlled to be constant, preventing excessive stress. If the flow rate of the supplied gas can be clearly defined, the flow velocity can also be controlled by the relationship between pressure and flow rate, allowing the elastic film to be formed quickly and stably into the desired shape. Furthermore, since the workpiece can be released from the polishing head quickly and reliably, the amount of release gas (see Figures 8 and 9) supplied can be reduced. As a result, drying of the polished workpiece due to release gas can be prevented. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing one embodiment of a polishing apparatus. [Figure 2] This is a cross-sectional view showing one embodiment of a polishing head system. [Figure 3] This diagram illustrates an example of supplying compressed air to multiple pressure chambers at different flow rates when releasing a polished wafer from a polishing head. [Figure 4] This diagram illustrates an example of supplying compressed air to multiple pressure chambers at different flow rates before holding the wafer to be polished in the polishing head. [Figure 5]It is a diagram illustrating an example of removing liquid from the top surface of a wafer to be polished by an elastic membrane curved downward. [Figure 6] It is a graph showing an example of the temporal change in the flow rate of compressed gas supplied to a pressure chamber during polishing of a wafer. [Figure 7] It is a cross-sectional view schematically showing an example of a polishing head. [Figure 8] It is a diagram illustrating an example of curving the elastic membrane downward by changing the pressure in a plurality of pressure chambers. [Figure 9] It is a diagram showing a state where a wafer is released from the elastic membrane of a polishing head. [Figure 10] It is a schematic diagram showing a state where a wafer to be polished is placed on a wafer transfer device. [Figure 11] It is a diagram illustrating an example of curving the elastic membrane downward by changing the pressure in a plurality of pressure chambers. [Figure 12] It is a diagram illustrating a state where a curved elastic membrane is pressed against a wafer to push liquid out of the wafer.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a schematic diagram showing an embodiment of a polishing apparatus. As shown in Figure 1, the polishing apparatus includes a polishing table that supports a polishing pad, a polishing head system including a polishing head that presses a wafer W, which is an example of a workpiece, against the polishing pad, a table motor that rotates the polishing table, and a polishing liquid supply nozzle for supplying polishing liquid (for example, slurry containing abrasive grains) onto the polishing pad. The surface of the polishing pad constitutes a polishing surface for polishing the wafer W.

[0017] The polishing table 3 is connected to a table motor 6, which is configured to rotate the polishing table 3 and the polishing pad 2 together. The polishing head 1 is fixed to the end of the polishing head shaft 11, which is rotatably supported by a head arm 15. The head arm 15 is rotatably supported by a pivot shaft 16. The polishing head shaft 11 is connected to a vertical movement mechanism 18 located within the head arm 15. The vertical movement mechanism 18 is configured to move the polishing head shaft 11 up and down in its axial direction. The vertical movement of the polishing head shaft 11 by the vertical movement mechanism 18 allows the wafer W held by the polishing head 1 to move closer to and further away from the polishing pad 2 on the polishing table 3.

[0018] The polishing apparatus further includes an operation control unit 9 that controls the operation of each component of the polishing apparatus. The operation control unit 9 is electrically connected to the polishing head 1, the table motor 6, the polishing fluid supply nozzle 5, and the vertical movement mechanism 18, and controls the operation of the polishing head 1, the table motor 6, the polishing fluid supply nozzle 5, and the vertical movement mechanism 18.

[0019] The operation control unit 9 comprises a storage device 9a in which a program is stored, and an arithmetic unit 9b that performs calculations according to the instructions contained in the program. The operation control unit 9 is composed of at least one computer. The storage device 9a comprises a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid state drive (SSD). Examples of arithmetic units 9b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 9 is not limited to these examples.

[0020] The wafer W is polished as follows: The motion control unit 9 issues commands to the table motor 6, the polishing head 1, and the polishing fluid supply nozzle 5 to rotate the polishing table 3 and the polishing head 1 in the direction indicated by the arrows in Figure 1, while supplying polishing fluid from the polishing fluid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. As the wafer W is rotated by the polishing head 1, the polishing head 1 presses the wafer W against the polishing surface 2a of the polishing pad 2 with polishing fluid present between the polishing pad 2 and the wafer W. The surface of the wafer W is polished by the chemical action of the polishing fluid and the mechanical action of the abrasive particles contained in the polishing fluid and / or the polishing pad 2.

[0021] Next, a polishing head system 4 having a polishing head 1 will be described. Figure 2 is a cross-sectional view showing one embodiment of the polishing head system 4. The polishing head system 4 includes a polishing head 1 having an elastic membrane 34 that forms a plurality of pressure chambers 25A, 25B, 25C, 25D, gas transfer lines F1, F2, F3, F4 that communicate with the plurality of pressure chambers 25A, 25B, 25C, 25D respectively, flow control valves FC1, FC2, FC3, FC4 connected to the gas transfer lines F1, F2, F3, F4 respectively, and a system control unit 50 that controls the operation of the flow control valves FC1, FC2, FC3, FC4.

[0022] The system control unit 50 includes a storage device 50a in which a program is stored, an arithmetic unit 50b that performs calculations according to instructions included in the program, and an input unit 50c having buttons or a keyboard. The system control unit 50 is composed of at least one computer. The storage device 50a includes a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid-state drive (SSD). Examples of the arithmetic unit 50b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the system control unit 50 is not limited to these examples. In one embodiment, the system control unit 50 and the operation control unit 9 may be configured as a single unit.

[0023] The polishing head 1 comprises a carrier 31 fixed to the end of the polishing head shaft 11, an elastic membrane 34 attached to the lower part of the carrier 31, and a retainer ring 32 positioned below the carrier 31. The retainer ring 32 is positioned around the elastic membrane 34. This retainer ring 32 is an annular structure that holds the wafer W to prevent the wafer W from flying out of the polishing head 1 during polishing.

[0024] The elastic film 34 comprises a contact portion 35 having a contact surface 35a that can contact the upper surface of the wafer W, and inner wall portions 36a, 36b, 36c and an outer wall portion 36d connected to the contact portion 35. The contact portion 35 has substantially the same size and shape as the upper surface of the wafer W. The inner wall portions 36a, 36b, 36c and the outer wall portion 36d are endless walls arranged concentrically. The outer wall portion 36d is located outside the inner wall portions 36a, 36b, 36c and is arranged to surround the inner wall portions 36a, 36b, 36c. In this embodiment, three inner wall portions 36a, 36b, 36c are provided, but the configuration of the polishing head 1 is not limited to this embodiment. In one embodiment, two inner wall portions may be provided, or four or more inner wall portions may be provided.

[0025] Multiple (four in this embodiment) pressure chambers 25A, 25B, 25C, and 25D are located between the elastic membrane 34 and the carrier 31. The pressure chambers 25A, 25B, 25C, and 25D are formed by the contact portion 35, inner wall portions 36a, 36b, and 36c, and outer wall portion 36d of the elastic membrane 34. The pressure chamber 25A located in the center of the elastic membrane 34 is circular, while the other pressure chambers 25B, 25C, and 25D are annular. These pressure chambers 25A, 25B, 25C, and 25D are arranged concentrically. In this embodiment, the polishing head 1 has four pressure chambers 25A to 25D, but in one embodiment, the polishing head 1 may have three pressure chambers in the elastic membrane 34, or it may have five or more pressure chambers.

[0026] An annular membrane (rolling diaphragm) 37 is positioned between the carrier 31 and the retainer ring 32, and a pressure chamber 25E is formed inside this membrane 37. Gas transfer lines F1, F2, F3, F4, and F5 are connected to the pressure chambers 25A, 25B, 25C, 25D, and 25E, respectively. The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 40 attached to the polishing head shaft 11.

[0027] Gas transfer lines F1, F2, F3, F4, and F5 are connected to a compressed gas supply source (not shown) which serves as a utility supply source in the factory where the polishing equipment is installed. Compressed gas, such as compressed air, is supplied to pressure chambers 25A, 25B, 25C, 25D, and 25E, respectively, through gas transfer lines F1, F2, F3, F4, and F5.

[0028] The gas transfer lines F1, F2, F3, F4, and F5 are connected to flow control valves FC1, FC2, FC3, FC4, and FC5, and pressure regulators Ra1, Ra2, Ra3, Ra4, and Ra5, respectively. The flow control valves FC1 to FC5 are located downstream of the pressure regulators Ra1 to Ra5 ​​in the direction of compressed gas flow. Compressed gas from the compressed gas supply source is supplied independently into the pressure chambers 25A to 25E through the pressure regulators Ra1 to Ra5 ​​and the flow control valves FC1 to FC5. The pressure regulators Ra1 to Ra5 ​​are configured to regulate the pressure of the compressed gas in the pressure chambers 25A to 25E. The flow control valves FC1 to FC5 are configured to regulate the flow rate of the compressed gas supplied into the pressure chambers 25A to 25E. Flow rate represents the amount of fluid flowing per unit time.

[0029] The pressure regulators Ra1 to Ra5 ​​and the flow control valves FC1 to FC5 are electrically connected to the system control unit 50. The operation of the pressure regulators Ra1 to Ra5 ​​and the flow control valves FC1 to FC5 is controlled by the system control unit 50. The system control unit 50 sends the respective target pressure values ​​for the pressure chambers 25A to 25E to the pressure regulators Ra1 to Ra5, and the pressure regulators Ra1 to Ra5 ​​operate to maintain the pressure in the pressure chambers 25A to 25E at the corresponding target pressure values.

[0030] The pressure regulators Ra1 to Ra5 ​​can independently change the internal pressure of the pressure chambers 25A to 25E. Therefore, the polishing head 1 can independently adjust the polishing pressure on four corresponding regions of the wafer W, namely the central region, the inner middle region, the outer middle region, and the edge region, and the pressing force of the polishing pad 2 of the retainer ring 32 against the polishing surface 2a. For example, the polishing head 1 can press different regions of the wafer W surface against the polishing surface 2a of the polishing pad 2 with different polishing pressures. Therefore, the polishing head 1 can control the film thickness profile of the wafer W to achieve a target film thickness profile.

[0031] Each of the flow control valves FC1 to FC5, although not shown in the diagram, is equipped with a variable valve whose opening degree can be changed, an actuator that drives the variable valve, and a flow meter that measures the flow rate of the fluid that has passed through the variable valve. The system control unit 50 gives commands to the flow control valves FC1 to FC5 to supply compressed gas at a set flow rate to the pressure chambers 25A to 25E through the flow control valves FC1 to FC5. More specifically, the system control unit 50 sends a command signal to each of the flow control valves FC1 to FC5 indicating the set flow rate, and the flow control valves FC1 to FC5 operate so that compressed air is sent to the pressure chambers 25A to 25E at the set flow rate.

[0032] Vacuum lines Lb1, Lb2, Lb3, Lb4, and Lb5 are connected to gas transfer lines F1, F2, F3, F4, and F5, respectively, upstream of the rotary joint 40. Vacuum valves Vb1, Vb2, Vb3, Vb4, and Vb5 are attached to vacuum lines Lb1, Lb2, Lb3, Lb4, and Lb5, respectively.

[0033] When vacuum valves Vb1 to Vb5 are opened while compressed gas is not being supplied, the compressed gas in pressure chambers 25A to 25E is independently discharged to the outside through gas transfer lines F1 to F5 and vacuum lines Lb1 to Lb5, respectively, creating negative pressure within pressure chambers 25A to 25E. Although not shown in the diagram, pressure chambers 25A to 25E may each be connected to an open-to-the-atmosphere line.

[0034] When the wafer W is being polished by pressing the polishing head 1 against the polishing surface 2a of the polishing pad 2, flow rate control is not performed by the flow control valves FC1 to FC5, and pressure control is performed by the pressure regulators Ra1 to Ra5. As described above, each flow control valve has a flow meter, so during the polishing of the wafer W, the flow control valves FC1 to FC5 are used to measure the flow rate of compressed air supplied to the pressure chambers 25A to 25E. The measured flow rate is sent from the flow control valves FC1 to FC5 to the system control unit 50, and the flow rate of compressed air is monitored by the system control unit 50.

[0035] In contrast, when the polished wafer W is released from the polishing head 1, pressure control is not performed by pressure regulators Ra1 to Ra5, but rather flow rate control is performed by flow control valves FC1 to FC5. That is, the system control unit 50 gives commands to flow control valves FC1 to FC4 to adjust the flow rate of compressed air supplied to pressure chambers 25A to 25D. More specifically, as shown in Figure 3, the system control unit 50 controls the operation of flow control valves FC1, FC2, FC3, and FC4 to supply compressed gas to pressure chambers 25A, 25B, 25C, and 25D at flow rates FR1, FR2, FR3, and FR4, respectively.

[0036] In this embodiment, the volumes of pressure chambers 25A to 25D are different. More specifically, the volume of pressure chamber 25A is larger than the volume of pressure chamber 25B, the volume of pressure chamber 25B is larger than the volume of pressure chamber 25C, and the volume of pressure chamber 25C is larger than the volume of pressure chamber 25D. The flow rates of the compressed gas FR1, FR2, FR3, and FR4 differ according to the volumes of pressure chambers 25A to 25D. That is, the larger the volume of the pressure chamber, the greater the flow rate of the compressed air supplied. In this embodiment, flow rate FR1 is greater than flow rate FR2, flow rate FR2 is greater than flow rate FR3, and flow rate FR3 is greater than flow rate FR4. The size of the arrows labeled FR1, FR2, FR3, and FR4 in Figure 3 represents the magnitude of the flow rates.

[0037] Thus, since the flow rates FR1 to FR4 of the compressed gas differ according to the volume of the pressure chambers 25A to 25D, the pressure chambers 25A to 25D can be expanded, causing the contact surface (bottom surface) 35a of the elastic film 34 to bend downward. In particular, by controlling the flow rate of the compressed air, the elastic film 34 can be expanded into the desired shape within a limited time. As shown in Figure 3, the center of the wafer W is in contact with the contact surface (bottom surface) 35a of the elastic film 34, and the edge of the wafer W is away from the elastic film 34. The release nozzle 51 ejects a release gas (for example, an inert gas such as nitrogen gas) into the gap between the edge of the wafer W and the elastic film 34. As a result, the wafer W is released from the polishing head 1 and supported on the workpiece transfer device 52.

[0038] The flow control valves FC1 to FC4 adjust the flow rate of compressed gas supplied to the pressure chambers 25A to 25D, thereby enabling the stable and rapid formation of the downward-curving shape shown in Figure 3. As a result, the wafer W can be released from the polishing head 1 with a small amount of release gas, preventing the wafer W from drying out due to the release gas.

[0039] The system control unit 50 is configured to supply compressed gas to pressure chambers 25A, 25B, 25C, and 25D at flow rates FR1, FR2, FR3, and FR4, while calculating the integrated values ​​CV1, CV2, CV3, and CV4 of the flow rates FR1, FR2, FR3, and FR4, respectively. The system control unit 50 supplies compressed gas to pressure chambers 25A, 25B, 25C, and 25D at flow rates FR1, FR2, FR3, and FR4 until the integrated values ​​CV1, CV2, CV3, and CV4 reach the corresponding four target flow rate integrated values. Since the shape of each pressure chamber after expansion is roughly determined by the integrated flow rate, the elastic membrane 34 can expand to the desired shape.

[0040] In one embodiment, the system control unit 50 may calculate the flow rates FR1, FR2, FR3, and FR4 of compressed gas to be supplied to pressure chambers 25A, 25B, 25C, and 25D by dividing a plurality of target flow rate integral values ​​corresponding to pressure chambers 25A, 25B, 25C, and 25D by a preset operating time. For example, the system control unit 50 calculates the flow rate FR1 of compressed gas to be supplied to pressure chamber 25A by dividing the target flow rate integral for pressure chamber 25A by a preset operating time. Similarly, the system control unit 50 can calculate the flow rates FR2, FR3, and FR4 of compressed gas to be supplied to pressure chambers 25B, 25C, and 25D.

[0041] As shown in Figure 3, the system control unit 50 issues commands to the flow control valves FC1, FC2, FC3, and FC4 to supply compressed gas to the pressure chambers 25A, 25B, 25C, and 25D at the calculated flow rates FR1, FR2, FR3, and FR4. The above-mentioned preset operating times may be the same for the pressure chambers 25A, 25B, 25C, and 25D, or they may be different for the pressure chambers 25A, 25B, 25C, and 25D.

[0042] The user may input the target flow rate integrated value corresponding to pressure chambers 25A, 25B, 25C, and 25D, and the above operating time, to the system control unit 50 via the input unit 50c. Based on the input target flow rate integrated value and operating time, the system control unit 50 can calculate the flow rates FR1, FR2, FR3, and FR4 of compressed gas to be supplied to pressure chambers 25A, 25B, 25C, and 25D.

[0043] In one embodiment, when the system control unit 50 is inflating the elastic film 34 with compressed air to release the wafer W from the polishing head 1, it may issue commands to the flow control valves FC1 to FC4 to change the flow rates FR1, FR2, FR3, and FR4 of the compressed air. For example, the system control unit 50 may issue commands to the flow control valves FC1 to FC4 to increase the flow rates FR1, FR2, FR3, and FR4 of the compressed air. By increasing the flow rates FR1, FR2, FR3, and FR4 of the compressed air, the pressure chambers 25A to 25D can be quickly expanded to the desired shape, thereby improving the throughput of the polishing apparatus. In addition, since the release operation is shortened, drying of the wafer after polishing due to the release gas can be prevented. The flow rates FR1 to FR4 may be increased in steps (for example, in two steps), or they may be increased linearly or curvilinearly.

[0044] In one embodiment, the system control unit 50 may issue commands to the flow control valves FC1 to FC4 to reduce the compressed air flow rates FR1, FR2, FR3, and FR4. For example, the system control unit 50 issues commands to the flow control valves FC1 to FC4 to reduce the compressed air flow rates FR1, FR2, FR3, and FR4 from the set flow rate for rapid expansion to the set flow rate for normal operation. The set flow rates for rapid expansion and normal operation are predetermined flow rates required for rapid expansion and normal operation, respectively. In this example as well, the pressure chambers 25A to 25D can be rapidly expanded to the desired shape.

[0045] Even when the wafer W to be polished is held by the polishing head 1, the system control unit 50 commands the flow control valves FC1 to FC4 to adjust the flow rate of compressed air supplied to the pressure chambers 25A to 25D. More specifically, as shown in Figure 4, before the wafer W to be polished on the workpiece transfer device 52 is held by the polishing head 1, the system control unit 50 commands the flow control valves FC1 to FC4 to inflate the elastic film 34. Then, as shown in Figure 5, the polishing head 1 is lowered by the vertical movement mechanism 18 (see Figure 1) until the elastic film 34 contacts the upper surface of the wafer W on the workpiece transfer device 52, and the liquid can be removed from the upper surface of the wafer W to be polished by the downwardly curved elastic film 34.

[0046] As shown in Figure 4, the system control unit 50 controls the operation of the flow control valves FC1, FC2, FC3, and FC4 to supply compressed gas to the pressure chambers 25A, 25B, 25C, and 25D at flow rates FR5, FR6, FR7, and FR8. The flow rates FR5, FR6, FR7, and FR8 of the compressed gas differ according to the volume of the pressure chambers 25A to 25D. That is, the larger the volume of the pressure chamber, the greater the flow rate of the compressed air supplied. In this embodiment, flow rate FR5 is greater than flow rate FR6, flow rate FR6 is greater than flow rate FR7, and flow rate FR7 is greater than flow rate FR8. The size of the arrows labeled FR5, FR6, FR7, and FR8 in Figure 3 represents the magnitude of the flow rates.

[0047] The system control unit 50 is configured to supply compressed gas to pressure chambers 25A, 25B, 25C, and 25D at flow rates FR5, FR6, FR7, and FR8, while calculating the integrated values ​​CV5, CV6, CV7, and CV8 of the flow rates FR5, FR6, FR7, and FR8, respectively. The system control unit 50 supplies compressed gas to pressure chambers 25A, 25B, 25C, and 25D at flow rates FR5, FR6, FR7, and FR8 until the integrated values ​​CV5, CV6, CV7, and CV8 of the flow rates FR5, FR6, FR7, and FR8 reach the corresponding four target flow rate integrated values. Since the shape of each pressure chamber after expansion is roughly determined by the integrated flow rate, the elastic membrane 34 can expand to the desired shape.

[0048] In one embodiment, the system control unit 50 may calculate the flow rates FR5, FR6, FR7, and FR8 of compressed gas to be supplied to pressure chambers 25A, 25B, 25C, and 25D by dividing a plurality of target flow rate integral values ​​corresponding to pressure chambers 25A, 25B, 25C, and 25D by a preset operating time. For example, the system control unit 50 calculates the flow rate FR5 of compressed gas to be supplied to pressure chamber 25A by dividing the target flow rate integral for pressure chamber 25A by a preset operating time. Similarly, the system control unit 50 can calculate the flow rates FR6, FR7, and FR8 of compressed gas to be supplied to pressure chambers 25B, 25C, and 25D.

[0049] As shown in Figures 4 and 5, the system control unit 50 commands the flow control valves FC1, FC2, FC3, and FC4 to supply compressed gas to pressure chambers 25A, 25B, 25C, and 25D at the calculated flow rates FR5, FR6, FR7, and FR8. The above-mentioned preset operating times may be the same for pressure chambers 25A, 25B, 25C, and 25D, or they may be different for pressure chambers 25A, 25B, 25C, and 25D.

[0050] The user may input the target flow rate integrated value corresponding to pressure chambers 25A, 25B, 25C, and 25D, and the above operating time, to the system control unit 50 via the input unit 50c. Based on the input target flow rate integrated value and operating time, the system control unit 50 can calculate the flow rates FR5, FR6, FR7, and FR8 of compressed gas to be supplied to pressure chambers 25A, 25B, 25C, and 25D.

[0051] In one embodiment, when the system control unit 50 is inflating the elastic membrane 34 with compressed air to remove liquid from the wafer W using the elastic membrane 34, it may issue commands to the flow control valves FC1 to FC4 to change the flow rates FR5, FR6, FR7, and FR8 of the compressed air. For example, the system control unit 50 may issue commands to the flow control valves FC1 to FC4 to increase the flow rates FR5, FR6, FR7, and FR8 of the compressed air. By increasing the flow rates FR5, FR6, FR7, and FR8 of the compressed air, the pressure chambers 25A to 25D can be rapidly expanded to the desired shape, thereby improving the throughput of the polishing apparatus. The flow rates FR5 to FR8 may be increased in steps (for example, in two steps), or they may be increased linearly or curvilinearly.

[0052] In one embodiment, the system control unit 50 may issue commands to the flow control valves FC1 to FC4 to reduce the compressed air flow rates FR5, FR6, FR7, and FR8. For example, the system control unit 50 issues commands to the flow control valves FC1 to FC4 to reduce the compressed air flow rates FR5, FR6, FR7, and FR8 from the set flow rates for rapid expansion to the set flow rates for normal operation. The set flow rates for rapid expansion and normal operation are predetermined flow rates required for rapid expansion and normal operation, respectively. In this example as well, the pressure chambers 25A to 25D can be rapidly expanded to the desired shape.

[0053] In one embodiment, while the wafer W is being polished by pressing it against the polishing pad 2 with the polishing head 1, the flow control valves FC1 to FC4 are configured to measure the flow rate of compressed gas supplied to the pressure chambers 25A to 25D, respectively. While the wafer W is being polished, the flow control valves FC1 to FC4 measure the flow rate of compressed gas supplied to the pressure chambers 25A to 25D, but do not adjust it.

[0054] Figure 6 is a graph showing an example of the time variation of the flow rate of compressed gas supplied to pressure chamber 25A when the wafer W is being polished by pressing the wafer W against the polishing pad 2 with the polishing head 1. The pressure regulators Ra1, Ra2, Ra3, and Ra4 shown in Figure 2 adjust the pressure of the compressed gas in pressure chambers 25A to 25D. As a result of this pressure adjustment operation, the flow rate of compressed gas supplied to pressure chamber 25A changes, as shown in Figure 6. Although not shown, the flow rate of compressed gas supplied to pressure chambers 25B to 25D also changes in a similar manner.

[0055] The system control unit 50 calculates the integrated polishing flow rates PV1, PV2, PV3, and PV4, which are the cumulative values ​​of the flow rates measured during wafer polishing, and is configured to determine a defect in the elastic film 34 or an abnormality in the polishing of the wafer W based on a change in at least one of the integrated polishing flow rates PV1, PV2, PV3, and PV4. The integrated polishing flow rates PV1, PV2, PV3, and PV4 correspond to the pressure chambers 25A, 25B, 25C, and 25D, respectively.

[0056] More specifically, when at least one of the integrated polishing flow rates PV1, PV2, PV3, and PV4 falls outside the acceptable range, the system control unit 50 detects a defect in the elastic film 34 or a polishing abnormality in the wafer W. For example, if the integrated polishing flow rate PV1 falls outside the acceptable range each time a wafer is polished, the system control unit 50 determines that there is a defect in the elastic film 34 or the pressure regulator Ra1. In another example, if the integrated polishing flow rate PV1 obtained when polishing one of several wafers falls outside the acceptable range, the system control unit 50 determines that a polishing abnormality has occurred in that wafer, or that there is a defect in the wafer itself (for example, excessive variation in wafer film thickness, wafer cracking).

[0057] In one embodiment, the above tolerance range is defined as a range that includes the average value of the integrated polishing flow rate obtained when polishing wafers in the past. Multiple tolerance ranges corresponding to the integrated polishing flow rate values ​​PV1, PV2, PV3, and PV4 are provided.

[0058] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of Symbols]

[0059] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 4. Polishing head system 5. Polishing fluid supply nozzle 6 Table motors 9. Operation Control Unit 9a Storage device 9b Arithmetic unit 11 Polished Head Shaft 15 Head Arm 16 Spindle 18 Vertical movement mechanism 25A, 25B, 25C, 25D, 25E ​​Pressure Chambers 31 Careers 32 Retainer Rings 34 Elastic membrane 35 Contact area 35a Contact surface 36a,36b,36c Inner wall part 36d Exterior wall 37 Membrane (Rolling Diaphragm) 40 Rotary Joint 50 System Control Unit 50a storage device 50b Arithmetic unit 51 Release Nozzle 52 Workpiece transfer device F1, F2, F3, F4, F5 Gas Transfer Line Ra1, Ra2, Ra3, Ra4, Ra5 pressure regulator FC1, FC2, FC3, FC4, FC5 Flow Control Valves Lb1, Lb2, Lb3, Lb4, Lb5 Vacuum Line Vb1, Vb2, Vb3, Vb4, Vb5 Vacuum valves

Claims

1. A method for expanding the elastic membrane of a polishing head, The first flow rate is calculated by dividing the first target flow rate integral value for the first pressure chamber formed by the elastic membrane by a predetermined operating time. The second flow rate is calculated by dividing the second target flow rate integral value for the second pressure chamber formed by the elastic membrane by a predetermined operating time. A method for supplying gas to the first pressure chamber and the second pressure chamber, respectively, at first flow rates and second flow rates adjusted by a first flow control valve and a second flow control valve, when releasing a polished workpiece from the polishing head or when holding a workpiece to be polished in the polishing head.

2. The method according to claim 1, wherein the volume of the first pressure chamber is greater than the volume of the second pressure chamber, and the first flow rate is greater than the second flow rate.

3. The gas is supplied to the first pressure chamber at the first flow rate until the cumulative value of the first flow rate reaches the first target flow rate cumulative value. The method according to claim 1, wherein the gas is supplied to the second pressure chamber at the second flow rate until the cumulative value of the second flow rate reaches the cumulative value of the second target flow rate.

4. The method according to claim 1, wherein at least one of the first flow rate and the second flow rate is changed while the gas is being supplied to the first pressure chamber and the second pressure chamber.

5. While the workpiece is being polished by the polishing head, the flow rate of the gas supplied to the first pressure chamber is measured by the first flow control valve. The integrated polishing flow rate, which is the cumulative value of the measured flow rates, is calculated. The method according to claim 1, further comprising determining a defect in the elastic film or an abnormality in the polishing of the workpiece based on the change in the cumulative value of the polishing flow rate.

6. A polishing head system for polishing workpieces, A polishing head having an elastic membrane that forms a first pressure chamber and a second pressure chamber, A first gas transfer line and a second gas transfer line communicating with the first pressure chamber and the second pressure chamber, respectively, A first flow control valve and a second flow control valve are connected to the first gas transfer line and the second gas transfer line, respectively. A polishing head system comprising: a system control unit that calculates a first flow rate by dividing a first target flow rate integral value for the first pressure chamber by a preset operating time; calculates a second flow rate by dividing a second target flow rate integral value for the second pressure chamber by a preset operating time; and controls the operation of a first flow control valve and a second flow control valve so that when a polished workpiece is released from the polishing head or when a workpiece to be polished is held by the polishing head, gas is supplied to the first pressure chamber and the second pressure chamber at the first flow rate and the second flow rate, respectively.

7. The polishing head system according to claim 6, wherein the volume of the first pressure chamber is greater than the volume of the second pressure chamber, and the first flow rate is greater than the second flow rate.

8. The aforementioned system control unit, The cumulative value of the first flow rate is calculated, The first flow control valve is commanded to supply the gas to the first pressure chamber at the first flow rate until the cumulative value of the first flow rate reaches the first target flow rate cumulative value. The cumulative value of the second flow rate is calculated, The polishing head system according to claim 6, wherein the system is configured to supply the gas to the second pressure chamber at the second flow rate by giving a command to the second flow control valve until the cumulative value of the second flow rate reaches the cumulative value of the second target flow rate.

9. The polishing head system according to claim 6, wherein the system control unit is configured to give a command to at least one of the first flow control valve and the second flow control valve to change at least one of the first flow rate and the second flow rate while the gas is supplied to the first pressure chamber and the second pressure chamber.

10. The first flow control valve measures the flow rate of the gas supplied to the first pressure chamber while the workpiece is being polished by the polishing head. The system control unit calculates the integrated polishing flow rate, which is the cumulative value of the measured flow rates. The polishing head system according to claim 6, configured to determine a defect in the elastic film or an abnormality in the polishing of the workpiece based on the change in the cumulative value of the polishing flow rate.

Images