Polishing method, polishing device, and temperature adjustment program

Abstract

To provide a polishing method that can appropriately control the temperature of a polishing surface of a polishing pad according to the state of a film of a workpiece during polishing of the workpiece such as a wafer.SOLUTION: A polishing method detects a surface condition of a sample using a surface condition detector 20 while polishing the sample on a polishing surface 3a of a polishing pad 3, creates time-series data representing the temporal transition of the surface condition of the sample, determines a point in time when the surface condition of the sample characteristically changes on the basis of the time-series data, decides the temperature control time on the basis of the decided point in time, and controls the temperature of the polishing surface 3a of the polishing pad 3 on the basis of the temperature control time by a pad temperature adjustment device 10 while polishing a workpiece W on the polishing surface 3a of the polishing pad 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for polishing a workpiece on a polishing surface while controlling the temperature of the polishing surface of a polishing pad. [Background technology]

[0002] CMP (Chemical Mechanical Polishing) equipment is used in the process of polishing the surface of a wafer in the manufacture of semiconductor devices. In the CMP equipment, a wafer having a film on it is rotated by a polishing head, which then presses the wafer against a polishing pad on a rotating polishing table, thereby polishing the film that constitutes the wafer's surface. During polishing, a polishing liquid (slurry) is supplied to the polishing pad. The film on the wafer is planarized by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad.

[0003] The polishing rate of a wafer depends not only on the polishing load of the wafer on the polishing pad, but also on the surface temperature of the polishing pad. This is because the chemical action of the polishing liquid on the wafer film depends on temperature. Therefore, in the manufacture of semiconductor devices, it is important to optimally control the surface temperature of the polishing pad during wafer polishing in order to achieve an appropriate polishing rate of the film.

[0004] Therefore, a pad temperature adjustment device for adjusting the surface temperature of a polishing pad has been used in the past (for example, see Patent Document 1). The pad temperature adjustment device has a pad contact member to which temperature-adjusted heating liquid and cooling liquid are supplied. By adjusting the flow rates of the heating liquid and cooling liquid supplied to the pad contact member, the surface temperature of the polishing pad during wafer polishing can be maintained at a desired temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-148933 A Summary of the Invention [Problem to be solved by the invention]

[0006] A wafer usually has a laminated structure including a plurality of films. The film of the wafer to be polished is the uppermost film among the plurality of films constituting the laminated structure. As the wafer is polished, the uppermost film is removed, and the underlying film is exposed. Thus, the underlying film comes into contact with the polishing pad and is polished. In addition, between the film forming process and the polishing process on the wafer, an oxide film may be formed on the film to be polished on the wafer. This oxide film is formed by the reaction of the film formed by the film forming process with oxygen in the air, and has different properties from the films constituting the laminated structure of the wafer. Such an oxide film is removed by polishing the wafer, and the film of the laminated structure below it is subsequently polished.

[0007] The temperature of the polishing surface of the polishing pad that is optimal for polishing may vary depending on the state of the film. That is, in order to achieve the optimal polishing rate of the film, it is necessary to control the temperature of the polishing surface of the polishing pad to an optimal temperature during the polishing of the wafer. Furthermore, just before the end point of the polishing of the wafer, the temperature of the polishing surface of the polishing pad may be lowered to intentionally lower the polishing rate of the wafer in order to prevent excessive etching or erosion of the wafer. Thus, it is required to control the temperature of the polishing surface of the polishing pad to an optimal temperature during the polishing of the wafer depending on the state of the film of the wafer.

[0008] Therefore, the present invention provides a technique that can appropriately control the temperature of the polishing surface of a polishing pad depending on the state of the film on a workpiece, such as a wafer, during polishing of the workpiece. [Means for solving the problem]

[0009] In one aspect, a polishing method is provided, which includes detecting a surface condition of a sample using a surface condition detector while polishing the sample on a polishing surface of a polishing pad, creating time series data representing the temporal progression of the surface condition of the sample, determining a time point at which the surface condition of the sample characteristically changes based on the time series data, determining a temperature control time based on the determined time point, and controlling the temperature of the polishing surface of the polishing pad based on the temperature control time by a pad temperature adjustment device while polishing a workpiece on the polishing surface of the polishing pad.

[0010] In one embodiment, the surface condition detector is a torque measuring device that measures the torque for rotating the polishing pad. In one embodiment, the surface condition detector is a film thickness measurement device that measures a film thickness of the sample. In one aspect, the step of determining the time point at which the surface condition of the sample changed characteristically based on the time series data comprises the steps of: generating time series differential data by performing a differential process on the time series data; determining a characteristic change point on the time series differential data; and determining the time point at which the characteristic change point appeared. In one embodiment, the differentiation process is a second-order differentiation process.

[0011] In one aspect, a polishing apparatus is provided that includes a polishing table that supports a polishing pad, a polishing head that presses a sample and a workpiece against the polishing surface of the polishing pad to polish the sample and the workpiece, a surface condition detector that detects a surface condition of the sample while the sample is being polished on the polishing surface of the polishing pad, a pad temperature adjustment device that adjusts the temperature of the polishing surface of the polishing pad, and an operation control unit that controls the operation of the pad temperature adjustment device, wherein the operation control unit is configured to create time-series data representing the temporal progression of the surface condition of the sample detected by the surface condition detector, determine a time point at which the surface condition of the sample characteristically changes based on the time-series data, determine a temperature control time based on the determined time point, and give a command to the pad temperature adjustment device while the workpiece is being polished on the polishing surface of the polishing pad to control the temperature of the polishing surface of the polishing pad based on the temperature control time.

[0012] In one embodiment, the surface condition detector is a torque measuring device that measures the torque for rotating the polishing pad. In one embodiment, the surface condition detector is a film thickness measurement device that measures a film thickness of the sample. In one aspect, the operation control unit is configured to create time-series differential data by performing a differential process on the time-series data, determine a characteristic change point on the time-series differential data, and determine a time point at which the characteristic change point appears. In one embodiment, the differentiation process is a second-order differentiation process.

[0013] In one aspect, a temperature adjustment program is provided that causes a computer to execute the steps of: creating time series data representing the temporal progression of the surface condition of the sample detected by a surface condition detector while the sample is being polished on the polishing surface of a polishing pad; determining a time point at which the surface condition of the sample characteristically changes based on the time series data; determining a temperature control time based on the determined time point; and giving an instruction to a pad temperature adjustment device to control the temperature of the polishing surface of the polishing pad based on the temperature control time while a workpiece is being polished on the polishing surface of the polishing pad.

[0014] In one aspect, the step of determining the time point at which the surface condition of the sample changed characteristically based on the time series data includes the steps of: generating time series differential data by performing a differential process on the time series data; determining a characteristic change point on the time series differential data; and determining the time point at which the characteristic change point appeared. In one embodiment, the differentiation process is a second-order differentiation process. Effect of the Invention

[0015] According to the present invention, the temperature of the polishing surface of the polishing pad can be appropriately controlled depending on the state of the film on the workpiece while the workpiece is being polished. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a polishing apparatus. [Diagram 2] 1 is a flow chart illustrating an embodiment of a polishing method. [Diagram 3] 1 is a graph showing an example of time-series data representing a change over time in the surface state of a sample. [Figure 4] 4 is a graph showing an example of time-series first-order differential data created by performing a first-order differential process on the time-series data shown in FIG. 3. [Diagram 5]4 is a graph showing an example of time-series second-order differential data generated by performing second-order differentiation processing on the time-series data shown in FIG. 3. [Figure 6] FIG. 13 is a diagram showing an example of a layered structure of a sample that changes as the sample is polished. [Figure 7] 1A and 1B are diagrams showing an example of a pad temperature recipe and an example of a graph showing a temperature change of a polishing surface of a polishing pad according to the pad temperature recipe; [Figure 8] 13A and 13B are diagrams showing another example of a pad temperature recipe and another example of a graph showing a temperature change of the polishing surface of the polishing pad according to the pad temperature recipe. [Figure 9] 11 is a graph showing an example of time series data, time series first differential data, and time series second differential data when a film thickness measuring device is used as a surface state detector. [Figure 10] FIG. 13 is a diagram showing an example of a layered structure of a sample that changes as the sample is polished. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a schematic diagram showing one embodiment of a polishing apparatus. The polishing apparatus includes a polishing table 2 that supports a polishing pad 3, a polishing head 1 that presses a wafer W, which is an example of a workpiece, against the polishing pad 3, a table rotation motor 6 that rotates the polishing table 2, a polishing liquid supply nozzle 4 for supplying a polishing liquid (e.g., a slurry containing abrasive grains) onto the polishing pad 3, and a temperature adjustment system 5 that adjusts the temperature of the polishing surface 3a of the polishing pad 3. The surface (upper surface) of the polishing pad 3 constitutes the polishing surface 3a that polishes the wafer W.

[0018] Specific examples of the workpiece include a wafer, a wiring board, a square board, and the like used in the manufacture of semiconductor devices. The workpiece has a layered structure including a plurality of films. The surface of the wafer W in the embodiment described below is an exposed surface of the layered structure including a plurality of films.

[0019] The temperature adjustment system 5 has a pad temperature adjustment device 10 that adjusts the temperature of the polishing surface 3a of the polishing pad 3, a pad temperature measuring device 12 that measures the temperature of the polishing surface 3a of the polishing pad 3, and an operation control unit 15 that controls the operation of the pad temperature adjustment device 10. In this embodiment, the operation control unit 15 is configured to control the operation of the entire polishing apparatus including the temperature adjustment system 5.

[0020] The operation control unit 15 includes a storage device 15a in which a program is stored, and a calculation device 15b that executes calculations according to instructions included in the program. The operation control unit 15 is composed of at least one computer. The storage device 15a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the calculation device 15b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the operation control unit 15 is not limited to these examples.

[0021] The polishing head 1 is movable in the vertical direction and is rotatable around its axis in the direction indicated by the arrow. The polishing head 1 is connected to a polishing head rotation motor (not shown) and is rotatable in the direction indicated by the arrow. As shown in Fig. 1, the polishing head 1 and the polishing table 2 rotate in the same direction. The polishing pad 3 is affixed to the upper surface of the polishing table 2.

[0022] Polishing of the wafer W is performed as follows. The wafer W to be polished is rotated by the polishing head 1, while the polishing pad 3 is rotated together with the polishing table 2 by a table rotation motor 6. In this state, a polishing liquid is supplied to the polishing surface 3a of the polishing pad 3 from a polishing liquid supply nozzle 4, and the surface of the wafer W is pressed against the polishing surface 3a of the polishing pad 3 by the polishing head 1. The surface of the wafer W is planarized by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 3.

[0023] The temperature adjustment system 5 includes a torque measuring device 20 as a surface condition detector that detects the surface condition of the wafer W. The torque measuring device 20 is configured to measure the torque for rotating the polishing pad 3 and the polishing table 2. The torque measuring device 20 is electrically connected to the operation control unit 15. The surface condition of the wafer W detected by the torque measuring device 20 is the state of the surface to be polished of the wafer W. Examples of the surface condition of the wafer W include unevenness of the surface of the wafer W, the type of film constituting the surface of the wafer W and its thickness (or amount), etc. The torque measuring device 20 is configured to output a detection signal that changes depending on the surface condition of the wafer W. The detection signal is sent to the operation control unit 15.

[0024] The torque measuring instrument 20 as a surface condition detector is electrically connected to the table rotation motor 6 and is configured to measure the current supplied to the table rotation motor 6 to rotate the polishing table 2 and send a detection signal indicating the measured current value to the operation control unit 15.

[0025] When the upper layer film constituting the surface of the wafer W is removed by polishing, the lower layer film present below the upper layer film is exposed. Since the upper layer film and the lower layer film are made of different materials, the friction between the wafer W and the polishing pad 3 changes as the upper layer film is removed. This change in friction appears as a change in the current applied to the table rotation motor 6. For example, when the film constituting the surface of the wafer W is removed (i.e., when the surface condition of the wafer W changes), the friction increases. As a result, the current applied to the table rotation motor 6 to generate the torque required to rotate the polishing table 2 at a preset speed increases. Therefore, the torque measuring device 20 as a surface condition detector can detect the surface condition of the wafer W based on the current that changes according to the torque required to rotate the polishing table 2 at a preset speed.

[0026] The torque measuring instrument 20 in this embodiment, which measures the current applied to the table rotation motor 6, indirectly measures the torque for rotating the polishing pad 3 and the polishing table 2, but in one embodiment, the torque measuring instrument 20 may be configured to directly measure the torque for rotating the polishing pad 3 and the polishing table 2.

[0027] In one embodiment, a film thickness measuring device 21 for measuring the film thickness of the wafer W may be used as a surface condition detector for detecting the surface condition of the wafer W. The film thickness measuring device 21 is disposed in the polishing table 2 and configured to measure the film thickness of the wafer W on the polishing surface 3a of the polishing pad 3 while rotating together with the polishing table 2 and the polishing pad 3. Examples of the film thickness measuring device 21 include an optical film thickness measuring device for measuring the film thickness of the wafer W based on the spectrum of reflected light from the wafer W, and an eddy current film thickness measuring device for measuring the film thickness of the wafer W based on an eddy current generated in the film of the wafer W.

[0028] The thickness of the film constituting the surface of the wafer W decreases as the wafer W is polished. Therefore, the film thickness measuring device 21 serving as a surface condition detector can detect the surface condition of the wafer W based on the film thickness of the wafer W. The film thickness measuring device 21 serving as a surface condition detector is configured to send a detection signal indicating the film thickness of the wafer W to the operation control unit 15. The detection signal indicating the film thickness of the wafer W is a signal that directly or indirectly indicates the film thickness of the wafer W, and changes depending on the film thickness of the wafer W.

[0029] The pad temperature adjustment device 10 includes a pad heater 24 for heating the polishing surface 3a of the polishing pad 3, and a pad cooler 25 for cooling the polishing surface 3a of the polishing pad 3. The pad heater 24 and the pad cooler 25 are located above the polishing table 2 and the polishing pad 3, and are disposed facing the polishing surface 3a of the polishing pad 3. The pad heater 24 and the pad cooler 25 are not in contact with the polishing surface 3a of the polishing pad 3. The pad temperature adjustment device 10 further includes a heating fluid supply line 27 for supplying a heating fluid to the pad heater 24, a heating flow rate control valve 31 for controlling the flow rate of the heating fluid flowing through the heating fluid supply line 27, a cooling fluid supply line 28 for supplying a cooling fluid to the pad cooler 25, and a cooling flow rate control valve 32 for controlling the flow rate of the cooling fluid flowing through the cooling fluid supply line 28.

[0030] The heating flow rate control valve 31 and the cooling flow rate control valve 32 are electrically connected to the operation control unit 15, and the operation of the heating flow rate control valve 31 and the cooling flow rate control valve 32 (i.e., the flow rate of the heating fluid flowing through the heating fluid supply line 27 and the flow rate of the cooling fluid flowing through the cooling fluid supply line 28) is controlled by the operation control unit 15.

[0031] The heating fluid is discharged from the nozzle 24a of the pad heater 24 onto the polishing surface 3a of the polishing pad 3, thereby increasing the temperature of the polishing surface 3a of the polishing pad 3. The cooling fluid is discharged from the nozzle (not shown) of the pad cooler 25 onto the polishing surface 3a of the polishing pad 3, thereby decreasing the temperature of the polishing surface 3a of the polishing pad 3. The operation control unit 15 adjusts the flow rates of the heating fluid and the cooling fluid supplied from the pad heater 24 and the pad cooler 25 to the polishing surface 3a of the polishing pad 3 by operating the heating flow rate control valve 31 and the cooling flow rate control valve 32, thereby making it possible to control the temperature of the polishing surface 3a of the polishing pad 3.

[0032] The pad temperature measuring device 12 measures the temperature of the polishing surface 3a of the polishing pad 3 in a non-contact manner and sends the measured value to the operation control device 15. Examples of the pad temperature measuring device 12 include an infrared radiation thermometer and a thermocouple thermometer. The operation control device 15 operates the heating flow rate control valve 31 and the cooling flow rate control valve 32 based on the measured temperature value so that the temperature of the polishing surface 3a of the polishing pad 3 reaches a preset target temperature.

[0033] In one embodiment, the heating fluid is steam. Examples of steam include water vapor produced by evaporating water, or superheated steam produced by further heating saturated steam. In other embodiments, the heating fluid may be a hot gas (e.g., hot air, nitrogen, or argon).

[0034] In one embodiment, the cooling fluid is a gas at room temperature (e.g., an inert gas such as nitrogen or argon). However, the cooling fluid is not limited to this example. The cooling fluid may be a gas cooled to a temperature lower than room temperature, or a gas at a temperature lower than the target temperature of the polishing surface 3a of the polishing pad 3.

[0035] Although not shown, in one embodiment, the pad temperature adjustment device 10 may further include a suction nozzle adjacent to the pad cooler 25. The suction nozzle has a suction port facing the polishing surface 3a of the polishing pad 3. The suction nozzle is connected to a vacuum source such as a vacuum pump. Increasing or decreasing the amount of air sucked through the suction nozzle changes the amount of heat of vaporization removed from the polishing liquid on the polishing surface 3a, and as a result, the temperature of the polishing surface 3a can be adjusted.

[0036] 1 is configured to directly contact the heating fluid and the cooling fluid with the polishing surface 3a of the polishing pad 3, but the configuration of the pad temperature adjustment device 10 is not limited to the above embodiment as long as it can adjust the temperature of the polishing surface 3a of the polishing pad 3. For example, the pad temperature adjustment device 10 may be configured to flow the heating fluid and the cooling fluid through a heat exchanger arranged opposite to the polishing surface 3a of the polishing pad 3, exchange heat between the heating fluid and the polishing pad 3 through the bottom of the heat exchanger, and exchange heat between the cooling fluid and the polishing pad 3 through the bottom of the heat exchanger, thereby adjusting the flow rate of the heating fluid and the cooling fluid.

[0037] Next, an embodiment of a polishing method will be described. FIG. 2 is a flow chart illustrating one embodiment of a polishing method. In step 1, before polishing the wafer W, the polishing apparatus polishes a sample having the same structure as the wafer W to be polished. In step 2, while the sample is being polished on the polishing surface 3a of the polishing pad 3, the surface condition of the sample is detected by a torque measuring device 20 or a film thickness measuring device 21 as a surface condition detector.

[0038] In step 3, the operation control unit 15 creates time-series data that represents the transition over time of the surface condition of the sample while the sample is being polished. In step 4, the operation control unit 15 determines the time point at which the surface state of the sample changes in a characteristic way, based on the time-series data. In step 5, the operation control unit 15 determines a temperature control time for changing the temperature of the polishing surface 3a of the polishing pad 3 during polishing of the wafer W, based on the time point determined in step 4 above. In step 6, the polishing apparatus polishes the wafer W. In step 7, while the polishing apparatus polishes the wafer W on the polishing surface 3a of the polishing pad 3, the operation control unit 15 issues a command to the pad temperature adjustment device 10 to control the temperature of the polishing surface 3a of the polishing pad 3 based on the temperature control time.

[0039] The operation control unit 15 operates according to instructions included in a program electrically stored in the storage device 15a, and executes the above steps 1 to 7. The program for causing the operation control unit 15 to execute these steps is recorded in a computer-readable recording medium, which is a non-transient tangible object, and is provided to the operation control unit 15 via the recording medium. Alternatively, the program may be provided to the operation control unit 15 via a communication network such as the Internet or a local area network. The operation control unit 15 may be composed of one computer. In another example, the operation control unit 15 may be composed of multiple computers.

[0040] Steps 1 to 7 will now be described in detail. Step 1 is a process of polishing a sample having the same structure as the wafer W with a polishing device before polishing the wafer W. The sample is a workpiece having the same layered structure as the wafer W to be polished. More specifically, the sample has a layered structure including the same multiple films as the wafer W to be polished. If the workpiece to be polished is a wafer, the sample is also a wafer. If the workpiece to be polished is an angular substrate, the sample is also an angular substrate. In this embodiment, since the workpiece to be polished is the wafer W, the sample is also a wafer having the same layered structure as the wafer W.

[0041] The sample is polished in the same manner as the wafer W. That is, the sample is rotated by the polishing head 1, while the polishing pad 3 is rotated together with the polishing table 2 by a table rotation motor 6. A polishing liquid is supplied to the polishing surface 3a of the polishing pad 3 from a polishing liquid supply nozzle 4, and the surface of the sample is pressed against the polishing surface 3a of the polishing pad 3 by the polishing head 1.

[0042] The sample is polished under the same polishing conditions as those for the wafer W. The polishing conditions include the type and flow rate of the polishing liquid used, the rotation speed of the polishing table 2 and the polishing pad 3, the rotation speed of the polishing head 1, the pressing force of the polishing head 1 against the polishing pad 3, and the like.

[0043] Step 2 is a process in which the surface condition of the sample is detected by a torque measuring device 20 or a film thickness measuring device 21 serving as a surface condition detector while the sample is polished on the polishing surface 3a of the polishing pad 3. In an embodiment in which the surface condition detector is the torque measuring device 20, the torque measuring device 20 measures the torque current supplied to the table rotation motor 6 while the sample is being polished, and sends a detection signal indicating the measured torque current to the operation control unit 15. In an embodiment in which the surface condition detector is the film thickness measuring device 21, the film thickness measuring device 21 measures the film thickness of the sample while the sample is being polished, and sends a detection signal indicating the film thickness of the sample to the operation control unit 15.

[0044] Step 3 is a process of creating time series data representing the time transition of the surface state of the sample during the polishing of the sample. More specifically, the operation control unit 15 receives a detection signal indicating the surface state of the sample sent from a surface state detector (torque measuring device 20 or film thickness measuring device 21), and creates time series data as shown in FIG. 3 by arranging the detection signals along the polishing time of the sample. The created time series data is stored in, for example, a storage device 15a provided in the polishing device. In the example shown in FIG. 3, the vertical axis represents the detection signal indicating the surface state of the sample detected by the torque measuring device 20 as the surface state detector, and the horizontal axis represents the polishing time of the sample. The time series data shown in FIG. 3 shows the time transition of the detection signal output from the torque measuring device 20. As can be seen from FIG. 3, the time series data represents the surface state of the sample that changes with the polishing time.

[0045] Step 4 is a process of determining the time point at which the surface condition of the sample changes characteristically based on the time series data. The time point at which the surface condition of the sample changes characteristically is the time point at which a characteristic change point appears on the time series data. In the example shown in FIG. 3, the characteristic change point P1 on the time series data is the point at which the detection signal indicating the surface condition of the sample starts to rise, the characteristic change point P2 on the time series data is the inflection point at which the detection signal indicating the surface condition of the sample changes from an increasing trend to a decreasing trend, and the characteristic change point P3 on the time series data is the point at which the detection signal indicating the surface condition of the sample stops rising. The operation control unit 15 is configured to determine the time points at which the surface condition of the sample changes characteristically, i.e., the time points t1, t2, and t3 at which the characteristic change points P1, P2, and P3 appear on the time series data.

[0046] In order to easily detect the characteristic change points P1, P2, and P3 on the time series data, in one embodiment, as shown in FIG. 4, the operation control unit 15 may create time series differential data by performing a differential process on the time series data, determine the characteristic change points P1', P2', and P3' on the time series differential data, and determine the time points t1, t2, and t3 at which the characteristic change points P1', P2', and P3' appeared. In the embodiment shown in FIG. 4, the differential process is a first-order differential process. The operation control unit 15 creates the time series first-order differential data by performing a first-order differential process on the time series data shown in FIG. 3. As shown in FIG. 4, the time series first-order differential data changes linearly, so the operation control unit 15 can easily determine the characteristic change points P1', P2', and P3' on the time series first-order differential data.

[0047] In one embodiment, as shown in FIG. 5, the operation control unit 15 may perform a second-order differential process on the time-series data shown in FIG. 3. Specifically, the operation control unit 15 may create time-series second-order differential data by further performing a differential process on the time-series first-order differential data shown in FIG. 4, determine characteristic change points P1", P2", and P3" on the time-series second-order differential data, and determine the time points t1, t2, and t3 at which the characteristic change points P1", P2", and P3" appear. As shown in FIG. 5, the time-series first-order differential data changes stepwise, so that the operation control unit 15 can easily determine the characteristic change points P1", P2", and P3" on the time-series first-order differential data.

[0048] Furthermore, in one embodiment, the operation control unit 15 may determine the times t1, t2, and t3 at which the surface condition of the sample characteristically changes based on a combination of the time series data, the time series first differential data, and the time series second differential data.

[0049] Step 5 is a process of determining a plurality of temperature control times based on the time points t1, t2, and t3 at which the characteristic change points appear. Each temperature control time may be the time point itself at which the characteristic change points appear, or may be a time obtained by adding a preset delay time to the time point at which the characteristic change points appear. For example, the temperature control time may be a time t3+d obtained by adding a delay time d to the time points t1 and t2 at which the characteristic change points P1 and P2 (or P1', P2', or P1", P2") appear and the time point t3 at which the characteristic change point P3 (or P3', or P3") appears. That is, examples of determining the temperature control time based on the time points at which the characteristic change points appear include determining a temperature control time that is the time point at which the characteristic change points appear, and determining a temperature control time obtained by adding a delay time to the time point at which the characteristic change points appear. The operation control unit 15 stores the determined temperature control times (for example, t1, t2, t3+d) in the storage device 15a.

[0050] Step 6 is a process of polishing the wafer W by the polishing apparatus. The wafer W is rotated by the polishing head 1, while the polishing pad 3 is rotated together with the polishing table 2 by a table rotation motor 6. A polishing liquid is supplied to the polishing surface 3a of the polishing pad 3 from a polishing liquid supply nozzle 4, and further, the front surface of the wafer W is pressed against the polishing surface 3a of the polishing pad 3 by the polishing head 1.

[0051] Step 7 is a process of controlling the temperature of the polishing surface 3a of the polishing pad 3 based on the temperature control time determined in step 5 above while the wafer W is polished on the polishing surface 3a of the polishing pad 3 by the polishing apparatus. More specifically, the operation control unit 15 issues a command to the pad temperature adjustment device 10 in accordance with a pad temperature recipe created in advance while the wafer W is being polished, to control the temperature of the polishing surface 3a of the polishing pad 3 based on the temperature control time. The pad temperature recipe is an operation sequence of the pad temperature adjustment device 10 for controlling the temperature of the polishing surface 3a of the polishing pad 3 based on the temperature control time while the wafer W is being polished.

[0052] 3 to 5, the change in the surface state of the sample depends on the change in the layered structure constituting the surface of the sample that accompanies sample polishing. Hereinafter, a specific example of the relationship between the change in the layered structure of the sample that accompanies sample polishing and the change in the surface state of the sample (i.e., time-series data) will be described.

[0053] 6 is a diagram showing an example of a layered structure of a sample that changes as the sample is polished. In this example, the sample 100 has a layered structure including a first film F1, a second film F2, and an underlayer F3. The first film F1 is on the second film F2, and the second film F2 is on the underlayer F3. Examples of the first film F1 include a film formed by a film forming apparatus (e.g., a plating apparatus, a CVD apparatus, or a PVD apparatus), and an oxide film formed by reacting a film formed by a film forming apparatus with oxygen in the air.

[0054] The times 0, t1, t2, and t3 shown in FIG. 6 correspond to the times 0, t1, t2, and t3 shown in FIGS. 3 to 5, respectively. The period from time 0 to time t1 shown in Fig. 6 is the period during which the first film F1 is polished. The surface of the sample 100 is composed of the first film F1. 6, the thickness of the first film F1 becomes smaller and the second film F2 begins to be exposed. Most of the surface of the sample 100 is made up of the first film F1, and a part of the surface of the sample 100 is made up of the second film F2. 6 is the time point when most of the first film F1 has been removed and the exposed area of ​​the first film F1 is smaller than the exposed area of ​​the second film F2. The surface of the sample 100 is composed of the first film F1 and the second film F2. 6 is the time when the first film F1 is removed. The surface of the sample 100 is composed of the second film F2.

[0055] As described above, the operation control unit 15 determines the temperature control time based on the time points t1, t2, and t3 at which the characteristic change points appear. For example, the temperature control time is t3+d, which is the time points t1 and t2 at which the characteristic change points P1 and P2 appear and the time point t3 at which the characteristic change point P3 appears, plus a delay time d. This delay time d is added to ensure that the first film F1 has been removed.

[0056] Before polishing the wafer W in step 6, the operation control unit 15 creates a pad temperature recipe to be used for polishing the wafer W, using the temperature control time determined based on the time points t1, t2, and t3. The pad temperature recipe is an operation sequence of the pad temperature adjustment device 10 for controlling the temperature of the polishing surface 3a of the polishing pad 3 during polishing of the wafer W, based on the temperature control time.

[0057] 7 is a diagram showing an example of a pad temperature recipe and an example of a graph showing a temperature change of the polishing surface 3a of the polishing pad 3 according to the pad temperature recipe. In the example of Fig. 7, the temperature control time determined based on the time points t1, t2, and t3 obtained by sample polishing is t1, t2, t3 + d.

[0058] The times 0, t1, t2, and t3 shown in FIG. 7 correspond to the times 0, t1, t2, and t3 shown in FIGS. 3 to 6, respectively. Section 1 of the pad temperature recipe is the period from temperature control time 0 to t1 (see 0 to t1 in FIG. 6). The operation of the pad temperature regulator 10 in this section 1 is to cool the polishing surface 3a of the polishing pad 3. Section 2 of the pad temperature recipe is the period from temperature control time t1 to t2 (see t1 to t2 in FIG. 6). The operation of the pad temperature regulator 10 in this section 2 is to not control the temperature of the polishing surface 3a of the polishing pad 3, i.e., to not heat or cool the polishing surface 3a of the polishing pad 3. Therefore, during the period from temperature control time t1 to t2, the temperature of the polishing surface 3a of the polishing pad 3 gradually increases due to frictional heat.

[0059] Section 3 of the pad temperature recipe is the period from temperature control time t2 to (t3+d) (see t2 to t3 in FIG. 6). The operation of the pad temperature adjustment device 10 in this section 3 is to heat the polishing surface 3a of the polishing pad 3 to a first temperature T1 and then control the temperature to be constant. Section 4 of the pad temperature recipe is the period after temperature control time t3+d (see t3 in FIG. 6). The operation of the pad temperature adjustment device 10 in this section 4 is to heat the polishing surface 3a of the polishing pad 3 to a second temperature T2 higher than the first temperature T1, and then to control the temperature to be constant.

[0060] The pad temperature recipe thus created is stored in the storage device 15a of the operation control unit 15. After the pad temperature recipe is created, the polishing apparatus polishes the wafer W that is to be polished.

[0061] During polishing of the wafer W, the operation control unit 15 issues a command to the pad temperature adjustment device 10 in accordance with the pad temperature recipe to control the temperature of the polishing surface 3a of the polishing pad 3 based on the determined temperature control time. In one example, when the polishing time of the wafer W reaches the temperature control time, the operation control unit 15 operates at least one of the heating flow rate control valve 31 and the cooling flow rate control valve 32 of the pad temperature adjustment device 10 to change the temperature of the polishing surface 3a of the polishing pad 3. In another example, as in the above-mentioned section 2, when the polishing time of the wafer W reaches the temperature control time, the operation control unit 15 closes both the heating flow rate control valve 31 and the cooling flow rate control valve 32 of the pad temperature adjustment device 10.

[0062] During polishing of the wafer W, the operation control unit 15 does not monitor the detection signal from the torque measuring device 20 or the film thickness measuring device 21 serving as a surface condition detector, but controls the temperature of the polishing surface 3a of the polishing pad 3 based on the polishing time of the wafer W and the temperature control time. Since the processing time required for detecting the surface condition of the wafer W by the surface condition detector can be omitted, the operation control unit 15 can quickly control the temperature of the polishing surface 3a of the polishing pad 3 based on the temperature control time.

[0063] Fig. 8 is a diagram showing another example of a pad temperature recipe and another example of a graph showing a temperature change of the polishing surface 3a of the polishing pad 3 according to the pad temperature recipe. In the example of Fig. 8, the temperature control times are time points t1, t2, and t3 obtained by sample polishing. The purpose of the pad temperature recipe shown in Fig. 8 is to improve the finish quality of the polished surface of the wafer W by intentionally lowering the polishing rate at the end of the polishing of the wafer W.

[0064] The times 0, t1, t2, and t3 shown in FIG. 8 correspond to the times 0, t1, t2, and t3 shown in FIGS. 3 to 6, respectively. Section 1 of the pad temperature recipe is the period from temperature control time 0 to t1 (see 0 to t1 in FIG. 6). The operation of the pad temperature adjustment device 10 in this section 1 is to heat the polishing surface 3a of the polishing pad 3 to a first temperature T3 and then control the temperature to be constant. Section 2 of the pad temperature recipe is the period from temperature control time t1 to t2 (see t1 to t2 in FIG. 6). The operation of the pad temperature adjustment device 10 in section 2 is to cool the polishing surface 3a of the polishing pad 3 to a second temperature T4 that is lower than the first temperature T3, and then to control the temperature to a constant value. Section 3 of the pad temperature recipe is the period from temperature control time t2 to t3 (see t2 to t3 in FIG. 6). The operation of the pad temperature regulator 10 in this section 3 is to cool the polishing surface 3a of the polishing pad 3. Section 4 of the pad temperature recipe is the period after temperature control time t3. The operation of the pad temperature adjustment device 10 in this section 4 is to not control the temperature of the polishing surface 3a of the polishing pad 3, i.e., to neither heat nor cool the polishing surface 3a of the polishing pad 3.

[0065] According to the pad temperature recipe of Figure 8, the temperature of the polishing pad 3 is lowered during the temperature control time period t2 to t3 (i.e., when the thickness of the first film F1 in Figure 6 becomes smaller), so that the polishing rate of the first film F1 decreases and the surface finish quality of the wafer W after the first film F1 is removed can be improved.

[0066] Fig. 9 is a graph showing an example of time series data, time series first differential data, and time series second differential data when film thickness measuring device 21 is used as a surface condition detector. Operation control unit 15 receives a detection signal indicating the surface condition of the sample sent from film thickness measuring device 21 as a surface condition detector, and creates time series data as shown in Fig. 9 by arranging the detection signals along the polishing time of the sample. Operation control unit 15 may further create time series first differential data and time series second differential data by performing first differential processing and second differential processing on the time series data.

[0067] In the example shown in FIG. 9, characteristic change point P1 on the time series data is the point at which the detection signal indicating the surface condition of the sample reaches threshold value H1, characteristic change point P2 on the time series data is the point at which the rate of decline of the detection signal indicating the surface condition of the sample starts to decline, and characteristic change point P3 on the time series data is the point at which the decline in the rate of decline of the detection signal indicating the surface condition of the sample stops.

[0068] 10 is a diagram showing an example of a layered structure of a sample that changes as the sample is polished. A sample 200 shown in FIG. 10 has the same structure as the sample 100 shown in FIG. 10 correspond to 0, t1, t2, and t3 shown in FIG. 9, respectively. The first film F1 is polished during the period from time 0 to time t1 shown in Fig. 10. The surface of the sample 200 is composed of the first film F1. 10 is the time when the thickness of the first film F1 becomes smaller and the second film F2 begins to be exposed. Most of the surface of the sample 200 is made up of the first film F1, and a part of the surface of the sample 200 is made up of the second film F2. 10 is the time point when most of the first film F1 has been removed and the exposed area of ​​the first film F1 is smaller than the exposed area of ​​the second film F2. The surface of the sample 200 is composed of the first film F1 and the second film F2. 10 is the time when the first film F1 is removed. The surface of the sample 200 is composed of the second film F2.

[0069] The operation control unit 15 determines the time points t1, t2, and t3 at which the surface state of the sample changes characteristically based on any one of the time series data, the time series first-order differential data, and the time series second-order differential data shown in Fig. 9, or a combination thereof, and determines the temperature control time based on the determined time points t1, t2, and t3. Furthermore, the operation control unit 15 uses the temperature control time to create a pad temperature recipe as shown in Fig. 7 or 8. During polishing of the wafer W, the operation control unit 15 issues a command to the pad temperature adjustment device 10 in accordance with the pad temperature recipe to control the temperature of the polishing surface 3a of the polishing pad 3 based on the determined temperature control time.

[0070] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0071] W wafer 1 Polishing head 2 Polishing table 3 Polishing Pads 3a Polished surface 4 Polishing fluid supply nozzle 5. Temperature Control System 6 Table rotation motor 10 Pad temperature control device 12 Pad temperature measuring device 15 Motion control section 20 Torque measuring instrument (surface condition detector) 21 Film thickness measuring device (surface condition detector) 24 Pad Heater 27 Heated fluid supply line 28 Cooling fluid supply line 31 Heating flow control valve 32 Cooling flow control valve

Claims

1. While polishing the sample on the polishing surface of the polishing pad, a surface condition of the sample is detected by a surface condition detector; creating time series data representing a time transition of the surface condition of the sample; determining a time point when a surface condition of the sample characteristically changes based on the time series data; determining a temperature control time based on the determined time point; A polishing method comprising: controlling a temperature of the polishing surface of the polishing pad based on the temperature control time by a pad temperature adjustment device while polishing a workpiece on the polishing surface of the polishing pad.

2. 2. The polishing method according to claim 1, wherein the surface condition detector is a torque measuring device that measures a torque for rotating the polishing pad.

3. 2. The polishing method according to claim 1, wherein the surface condition detector is a film thickness measuring device that measures a film thickness of the sample.

4. determining a time point at which a surface condition of the sample characteristically changes based on the time series data, generating time-series differential data by performing a differentiation process on the time-series data; determining a characteristic change point on the time series differential data; 2. The polishing method according to claim 1, further comprising the step of determining a time point at which the characteristic change point appears.

5. The polishing method according to claim 4 , wherein the differentiation process is a second-order differentiation process.

6. a polishing table supporting a polishing pad; a polishing head for pressing the sample and the workpiece against a polishing surface of the polishing pad to polish the sample and the workpiece; a surface condition detector that detects a surface condition of the sample while the sample is being polished on the polishing surface of the polishing pad; a pad temperature adjustment device for adjusting the temperature of the polishing surface of the polishing pad; An operation control unit that controls the operation of the pad temperature adjustment device, The operation control unit is creating time series data representing a time transition of the surface condition of the sample detected by the surface condition detector; determining a time point when a surface condition of the sample characteristically changes based on the time series data; determining a temperature control time based on the determined time point; A polishing apparatus configured to, when the workpiece is polished on the polishing surface of the polishing pad, give a command to the pad temperature adjustment device to control the temperature of the polishing surface of the polishing pad based on the temperature control time.

7. 7. The polishing apparatus according to claim 6, wherein the surface condition detector is a torque measuring device that measures a torque for rotating the polishing pad.

8. 7. The polishing apparatus according to claim 6, wherein the surface condition detector is a film thickness measuring device that measures a film thickness of the sample.

9. The operation control unit is generating time-series differential data by performing a differentiation process on the time-series data; determining a characteristic change point on the time series differential data; 7. The polishing apparatus of claim 6, configured to determine when the characteristic change-point occurs.

10. 7. The polishing apparatus according to claim 6, wherein the differential processing is a second-order differential processing.

11. creating time series data representing a time transition of a surface condition of the sample detected by a surface condition detector while the sample is being polished on a polishing surface of a polishing pad; determining a time point at which a surface condition of the sample characteristically changes based on the time series data; determining a temperature control time based on the determined time point; A temperature adjustment program for causing a computer to execute a step of giving an instruction to a pad temperature adjustment device to control the temperature of the polishing surface of the polishing pad based on the temperature control time while a workpiece is being polished on the polishing surface of the polishing pad.

12. The step of determining a time point at which a surface condition of the sample characteristically changes based on the time series data includes: generating time-series differential data by performing a differentiation process on the time-series data; determining a characteristic change point on the time-series differential data; The temperature adjustment program according to claim 11, further comprising a step of determining a time point at which the characteristic change point appears.

13. The temperature regulation program according to claim 11 , wherein the differential processing is a second-order differential processing.

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