Film thickness signal processing apparatus, polishing apparatus, and film thickness signal processing method

Abstract

The invention provides a film thickness signal processing device, a polishing device and a film thickness signal processing method, which can improve the precision of film thickness distribution in a measurement range. The film thickness signal processing device has a receiving unit and a correction unit. The receiving unit receives sensor data output from the eddy current sensor and generates first film thickness data (168) and second film thickness data (172). The correction unit corrects the first film thickness data and the second film thickness data generated by the reception unit. The correction unit obtains corrected film thickness data (166) on the basis of the dimensions of measurement ranges (174, 176) on an object to be polished as measurement objects in one measurement by the eddy current sensor, first film thickness data measured at a first measurement point (146) on the object to be polished, and second film thickness data measured at a second measurement point (148) on the object to be polished. The distance between the first measurement point and the second measurement point is equal to or less than the size of the measurement range.

Description

Technical Field

[0001] The present invention relates to a film thickness signal processing device, a grinding device and a film thickness signal processing method. This application claims priority based on Japanese Patent Application No. 2023-140929 filed on August 31, 2023. All disclosures including the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-140929 are incorporated herein by reference in their entirety. Background Art

[0002] In recent years, with the high integration and high density of semiconductor devices, circuit wiring has become increasingly miniaturized, and the number of layers of multilayer wiring has also increased. In order to achieve multilayer wiring while miniaturizing circuits, it is necessary to flatten the surface of semiconductor devices with high precision.

[0003] As a technology for flattening the surface of semiconductor devices, chemical mechanical polishing (CMP) is known. A polishing device for performing CMP includes a polishing table with a polishing pad attached thereto, and a top ring (holding unit) for holding a polishing object (e.g., a substrate such as a semiconductor wafer or various films formed on the surface of the substrate). The polishing device rotates the polishing table using a motor (driving unit) that can drive the polishing table to rotate, while pressing the polishing object held on the top ring against the polishing pad, thereby polishing the polishing object.

[0004] The polishing device is equipped with a film thickness measuring device in order to detect the end point of the polishing process based on the film thickness of the polishing object. The film thickness measuring device is equipped with a film thickness sensor for detecting the film thickness of the polishing object. The film thickness sensor generally includes an eddy current sensor or an optical sensor.

[0005] The eddy current sensor or the optical sensor is set in a hole formed in the grinding table, and detects the film thickness when facing the grinding object while rotating with the rotation of the grinding table. The eddy current sensor induces eddy current in the grinding object such as a conductive film, and detects the change in the thickness of the grinding object based on the change in the magnetic field generated by the eddy current induced by the grinding object. On the other hand, the optical sensor irradiates light to the grinding object and detects the thickness of the grinding object by measuring the interference wave reflected from the grinding object.

[0006] The film thickness distribution based on the film thickness sensor will correspond the measured value of the film thickness (film thickness data) based on the overall detection signal from the measurement point of the sensor (in the case of an eddy current sensor, the measurement range on the chip where the induced eddy current exists in the chip. In the case of an optical sensor, the range of light irradiation on the chip. Hereinafter referred to as the "measurement range") to the position of the measurement point on the chip. For example, the position of the center of the sensor is sometimes used as the position of the measurement point. The measurement range exists in a certain range in the chip, and its measurement value is associated with the position of the measurement point as a specific position on the chip. Therefore, there is room for improvement in the accuracy of the film thickness distribution within the measurement range, that is, the spatial resolution.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 6795337 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] One aspect of the present invention is to solve such a problem, and an object of the present invention is to provide a film thickness signal processing device that improves the accuracy of film thickness distribution within a measurement range.

[0012] Technical solutions to technical problems

[0013] In order to solve the above-mentioned technical problems, in a first method, a structure of a film thickness signal processing device is adopted, wherein the device comprises: a receiving unit, which receives sensor data output from a film thickness sensor for detecting the film thickness of a polishing object to generate first film thickness data and second film thickness data; and a correction unit, which corrects the first film thickness data and the second film thickness data generated by the receiving unit, the correction unit calculates the corrected film thickness data based on the size of a measurement range on the polishing object as a measurement object in a single measurement of the film thickness sensor, the first film thickness data measured at a first measurement point on the polishing object, and the second film thickness data measured at a second measurement point on the polishing object, wherein the distance between the first measurement point and the second measurement point is less than the size of the measurement range.

[0014] In this embodiment, the correction unit obtains the corrected film thickness data based on the size of the measurement range on the polishing object as the measurement object in one measurement of the film thickness sensor, the first film thickness data measured at the first measurement point on the polishing object, and the second film thickness data measured at the second measurement point on the polishing object. In particular, since the size of the measurement range is used for correction, it is possible to provide a film thickness signal processing device that improves the accuracy of film thickness distribution within the measurement range.

[0015] In a second aspect, the structure of the film thickness signal processing device according to the first aspect is adopted, wherein a first distance from the first measurement point to the center of the polishing object and a second distance from the second measurement point to the center of the polishing object are different.

[0016] In a third aspect, the structure of the film thickness signal processing device according to the first aspect or the second aspect is adopted, wherein the second film thickness data is measured in an initial measurement after the first film thickness data is measured.

[0017] In a fourth embodiment, the structure of a film thickness signal processing device described in any one of the first to third embodiments is adopted, wherein the correction unit obtains at least one of third film thickness data and fourth film thickness data corresponding to a third measurement point and a fourth measurement point on the polishing object at a distance from the size as the film thickness data corrected based on the first film thickness data and the second film thickness data.

[0018] In a fifth aspect, the structure of the film thickness signal processing device described in the fifth aspect is adopted, wherein the difference between the third film thickness data and the fourth film thickness data is proportional to the difference between the first film thickness data and the second film thickness data.

[0019] In a sixth aspect, the film thickness signal processing device according to any one of the first to fifth aspects is configured such that the correction is performed when a time-dependent change amount of the first film thickness data or the second film thickness data exceeds a predetermined value.

[0020] In a seventh aspect, the film thickness signal processing device according to any one of the first to sixth aspects is configured such that the correction is performed when a position-dependent change amount of the first film thickness data or the second film thickness data exceeds a predetermined value.

[0021] In an eighth aspect, the film thickness signal processing device according to any one of the first to seventh aspects is configured, wherein the correction is performed based on the first film thickness data and the second film thickness data measured near an end portion of the polishing object.

[0022] In a ninth aspect, the configuration of the film thickness signal processing device according to the eighth aspect is adopted, wherein the correction is performed when the end portion exists within the measurement range of the film thickness sensor.

[0023] In the tenth embodiment, the structure of the film thickness signal processing device described in any one of the first to ninth embodiments is adopted, wherein the dimension when the distance between the polishing object and the film thickness sensor is a first length is set to a first dimension, and the dimension when the distance between the polishing object and the film thickness sensor is a second length is set to a second dimension, when the first length is longer than the second length, the first dimension is larger than the second dimension.

[0024] In the eleventh embodiment, a structure of a grinding device is adopted, wherein the structure comprises: a film thickness signal processing device according to any one of the first to tenth embodiments; a grinding table to which a grinding pad for grinding the grinding object can be attached; a driving unit to drive the grinding table to rotate; a holding unit to hold the grinding object and to press the grinding object against the grinding pad; and the film thickness sensor, which is arranged in a hole formed in the grinding table and can detect the film thickness of the grinding object as the grinding table rotates.

[0025] In the twelfth embodiment, a structure of a film thickness signal processing method is adopted, wherein a polishing device having a film thickness sensor, a receiving unit and a correction unit is used, wherein the receiving unit receives sensor data output from the film thickness sensor for detecting the film thickness of the polishing object to generate first film thickness data and second film thickness data, and the correction unit corrects the first film thickness data and the second film thickness data generated by the receiving unit, and the correction unit calculates the corrected film thickness data based on the size of a measurement range as a measurement object in a single measurement of the film thickness sensor, the first film thickness data measured at a first measurement point on the polishing object, and the second film thickness data measured at a second measurement point on the polishing object, wherein the distance between the first measurement point and the second measurement point is less than the size of the measurement range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram schematically showing the overall structure of a polishing device.

[0027] Figure 2 It is a schematic diagram showing a configuration example of the eddy current sensor according to the present embodiment.

[0028] Figure 3 This is a diagram showing the actual film thickness distribution and the film thickness distribution obtained by the eddy current sensor.

[0029] Figure 4 This is a diagram showing the film thickness distribution obtained by performing correction based on Japanese Patent No. 6795337.

[0030] Figure 5This is a diagram showing the correction based on Japanese Patent No. 6795337.

[0031] Figure 6 This is a diagram showing a state in which an eddy current sensor disposed on a polishing table rotates as the polishing table rotates.

[0032] Figure 7 This is a diagram showing the trajectory of the eddy current sensor on the polishing object when the eddy current sensor passes through the surface of the polishing object.

[0033] Figure 8 It is a diagram for explaining the method of obtaining the fourth film thickness data.

[0034] Fig. 9 This is a diagram showing an example in which a range at a predetermined distance from an end is selected as the vicinity based on past measured values ​​or prior test data.

[0035] Fig.10 is a flow chart illustrating the calibration method.

[0036] Fig.11 This is a diagram for explaining a method for setting the outer dimensions of a measurement range.

[0037] Fig.12 This is a diagram for explaining a method for setting the outer dimensions of a measurement range.

[0038] Fig.13 This is a diagram for explaining a method for setting the outer dimensions of a measurement range.

[0039] Explanation of symbols

[0040] 100…Grinding device

[0041] 102…Polishing object

[0042] 108…Abrasive pad

[0043] 110…Grinding table

[0044] 112…First Motor

[0045] 122, 124, 126...Film thickness distribution

[0046] 128…end

[0047] 130…Dimensions

[0048] 144…Trajectory

[0049] 146…First measurement point

[0050] 148…Second measurement point

[0051] 150…Measurement range

[0052] 152…First Distance

[0053] 154…Second distance

[0054] 158…Third measurement point

[0055] 162…Fourth measurement point

[0056] 164…Third film thickness data

[0057] 166…Fourth film thickness data

[0058] 168…First film thickness data

[0059] 172…Second film thickness data

[0060] 210…Eddy current sensor

[0061] 230...film thickness signal processing device

[0062] 232…Receiving unit

[0063] 238…Correction Department. DETAILED DESCRIPTION

[0064] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in each of the following embodiments, identical or equivalent components are denoted by the same reference numerals, and repeated descriptions are omitted. In addition, the features shown in each embodiment may also be applied to other embodiments as long as they do not contradict each other.

[0065] Figure 1 Schematically shows the overall structure of a grinding device according to one embodiment of the present invention. Figure 1 As shown, the polishing device 100 includes a polishing table 110, a first motor (driving unit) 112, a top ring (holding unit) 116, and a second motor (driving unit) 118. A polishing pad 108 for polishing an object to be polished (for example, a substrate such as a semiconductor wafer or various films formed on the surface of the substrate) 102 can be attached to the upper surface of the polishing table 110. The first motor 112 drives the polishing table 110 to rotate, and the top ring 116 holds the object to be polished 102 and can press the polishing pad. The second motor 118 drives the top ring 116 to rotate.

[0066] The polishing device 100 also includes a slurry line 120 for supplying a polishing liquid containing an abrasive material to the upper surface of the polishing pad 108. The polishing device 100 includes a polishing device control unit 140 for outputting various control signals related to the polishing device 100.

[0067] The polishing device 100 includes an eddy current sensor 210 (film thickness sensor) which is disposed in a hole formed in the polishing table 110 and detects the film thickness of the polishing object 102 along the polishing surface as the polishing table 110 rotates. In addition, the polishing device 100 also includes a trigger sensor 220 which includes a proximity sensor 222 disposed on the polishing table 110 and a detection block 224 disposed outside the polishing table 110.

[0068] The eddy current sensor 210 includes an excitation coil, a detection coil, and a balance coil. The excitation coil is excited by an AC current supplied by an AC power supply, and an eddy current is formed in the grinding object 102 arranged nearby. The magnetic flux generated by the eddy current formed in the grinding object 102 interlinks with the detection coil and the balance coil. Since the detection coil is arranged at a position close to the conductive film, the balance of the induced voltage generated in the two coils is destroyed. Thus, the eddy current sensor 210 detects the interlinked magnetic flux formed by the eddy current of the grinding object, and detects the thickness of the grinding object based on the detected interlinked magnetic flux. In addition, an example of configuring the eddy current sensor 210 is shown here, but it is not limited to this. An optical sensor can also be configured, which detects the thickness of the grinding object by irradiating light to the grinding object and measuring the interference wave reflected from the grinding object.

[0069] Figure 2 2 is a schematic diagram showing a configuration example of the eddy current sensor 210 according to the present embodiment. Figure 2 As shown, the eddy current sensor 210 is composed of a pot core 60 and three coils 72, 73, 74. The pot core 60 as a magnetic body has a bottom portion 61a, a core portion 61b provided at the center of the bottom portion 61a, and a peripheral wall portion 61c provided around the bottom portion 61a.

[0070] Among the three coils 72, 73, and 74, the central coil 72 is an excitation coil connected to an AC signal source (not shown). The excitation coil 72 uses the magnetic field formed by the voltage supplied by the AC signal source to form eddy currents on the metal film (or conductive film) on the polishing object 102 arranged nearby. The detection coil 73 is arranged on the metal film side of the excitation coil 72 to detect the magnetic field generated by the eddy current formed on the metal film. A balance coil 74 is arranged on the side opposite to the detection coil 73 across the excitation coil 72. The balance coil 74 is used to adjust the balance through a resistance bridge circuit (not shown) for detecting the magnetic field generated by the eddy current. Zero point adjustment can be performed by the balance coil 74. Therefore, the eddy current flowing through the metal film can be detected from the zero state, so the detection sensitivity of the eddy current in the metal film can be improved. The excitation coil 72 is arranged on the magnetic core portion 61b to form eddy currents on the metal film. The detection coil 73 is arranged on the magnetic core portion 61b to detect the eddy currents formed on the metal film. Compared to the eddy current sensor using the conventional solenoid coil, the eddy current sensor 210 has the magnetic flux 20 concentrated and the spread of the magnetic flux 20 narrowed.

[0071] When the thickness of the metal film changes, the eddy current changes, and the impedance of the detection coil 73 and the balance coil 74 changes. The eddy current sensor 210 of this embodiment detects the change in the thickness of the metal film based on the impedance change. The receiving unit 232 detects the impedance based on the sensor data output by the eddy current sensor 210. When the impedance changes, the change in the thickness of the metal film can be detected.

[0072] The receiving unit 232 receives sensor data (e.g., voltage signal) output from the film thickness sensor, and detects impedance based on the sensor data. The receiving unit 232 calculates the difference between the detected impedance and the impedance when the film thickness is "0", and outputs the difference as film thickness data. The impedance when the film thickness is "0" is measured in advance. The reason for calculating the difference is to make the film thickness data "0" when the film thickness is "0".

[0073] The film thickness data is not limited to the difference in impedance. For example, the correspondence between the impedance and the actual film thickness can be measured in advance before grinding, and the receiving unit 232 calculates the film thickness based on the detected impedance according to the correspondence during grinding, and uses the calculated film thickness as the film thickness data. In the embodiment of the present invention described later, the film thickness is calculated based on the detected impedance, and the calculated film thickness is used as the film thickness data. In addition, the film thickness data can be generated using a quantity other than the impedance that depends on the film thickness. In addition, the eddy current sensor 210 is not limited to Figure 2 The pot core shown. For example, a solenoid coil, an E-core, or a U-core can be used.

[0074] The proximity sensor 222 is attached to the bottom surface of the polishing table 110 (the surface to which the polishing pad 108 is not attached). The detection block 224 is disposed outside the polishing table 110 and is detected by the proximity sensor 222. The trigger sensor 220 outputs a trigger signal indicating that the polishing table 110 rotates one circle according to the positional relationship between the proximity sensor 222 and the detection block 224. Specifically, the trigger sensor 220 outputs a trigger signal when the proximity sensor 222 and the detection block 224 are in the closest state.

[0075] The eddy current sensor 210 controls the measurement start time and the measurement end time based on the trigger signal output from the trigger sensor 220. For example, the eddy current sensor 210 uses the time when a predetermined time has passed since the trigger sensor 220 outputted the trigger signal as the measurement start time, and uses the time when a predetermined time has passed since the trigger sensor 220 outputted the trigger signal as the measurement end time. Here, the predetermined time is preset as a parameter.

[0076] When the polishing device 100 polishes the polishing object 102, polishing slurry containing polishing abrasive grains is supplied from the slurry line 120 to the upper surface of the polishing pad 108, and the polishing table 110 is driven to rotate by the first motor 112. Then, the polishing device 100 presses the polishing object 102 held by the top ring 116 against the polishing pad 108 while rotating the top ring 116 around a rotation axis eccentric to the rotation axis of the polishing table 110. Thus, the polishing object 102 is polished and flattened by the polishing pad 108 holding the polishing slurry.

[0077] Next, the film thickness signal processing device 230 of this embodiment is described. Figure 1 As shown, the film thickness signal processing device 230 is connected to the eddy current sensor 210 via the rotary joint connectors 160 and 170. The film thickness signal processing device 230 performs predetermined signal processing on the sensor data output from the eddy current sensor 210 and outputs the signal to the end point detector 240.

[0078] The end point detector 240 monitors the change in the film thickness of the polishing object 102 based on the signal output from the film thickness signal processing device 230. The end point detector 240 is connected to the polishing device control unit 140 that performs various controls related to the polishing device 100. When the end point detector 240 detects the polishing end point of the polishing object 102, it outputs a signal indicating this to the polishing device control unit 140. When the polishing device control unit 140 receives the signal indicating the polishing end point from the end point detector 240, it ends the polishing by the polishing device 100. During polishing, the polishing device control unit 140 controls the pressing force of the polishing object 102 based on the corrected film thickness data.

[0079] Here, the technical problems of the prior art are explained. In the grinding process of semiconductor wafers, the film thickness during grinding and the shape control of the film thickness distribution are taken very seriously. Eddy current sensors and optical sensors are usually used for in-situ film thickness measurement (i.e., film thickness measurement during grinding), and the top ring 116 is used for pressure control based on the measurement results. In the past, when the sensor was located near the end of the wafer and the area outside the wafer (i.e., the area outside the end of the wafer) was included in the measurement range of the sensor, there was a problem that the shape of the film thickness distribution could not be estimated with high precision. In addition, it was previously believed that the output of the sensor measured the average film thickness within the measurement range of the sensor. Therefore, when the film thickness is uneven in an area smaller than the outer dimensions of the measurement range of the sensor, the unevenness cannot be detected. As a result, there is a problem that the shape of the film thickness distribution cannot be estimated with high precision.

[0080] pass Figure 3 , Figure 4 This will be further explained. Figure 3 The actual film thickness distribution 122 and the film thickness distribution 124 obtained by the eddy current sensor 210 are shown. The film thickness distribution 124 is not corrected. Figure 4 Also shown is a film thickness distribution 126 obtained by calibration according to Japanese Patent No. 6795337. The horizontal axis of the figure is the distance (in mm) from the center of the circular grinding object 102 (wafer). However, the film thickness is distributed only in the vicinity of the end 128. Therefore, the center of the grinding object 102 is located in the left direction of the left end of the figure. The vertical axis is the film thickness (in angstroms). However, in order to show in detail the change in film thickness near the end 128 where the film thickness of the grinding object 102 becomes the maximum value, the film thickness of the area with a small film thickness (i.e., the end 128) is not shown so that the vertical axis includes the maximum value of the film thickness. That is, Figure 3 , 4 The minimum value of the vertical axis shown is greater than 0 angstroms. Since there is no metal film outside the end portion, the film thickness at the end portion is 0 angstroms.

[0081] exist Figure 3 In the embodiment, within the outer dimensions 130 of the measurement range of the eddy current sensor 210, the difference 132 between the actual film thickness distribution 122 and the film thickness distribution 124 obtained by the eddy current sensor 210 is quite large. The difference 132 outside the end portion decreases toward the center of the polishing object 102. In the past, the measured film thickness (film thickness before correction) represented by the film thickness distribution 124 was the average of the actual film thickness within the outer dimensions 130, and the average had low accuracy. In the past, it was impossible to measure the correct film thickness distribution 122. Figure 4 A film thickness distribution 126 according to a conventional correction method is shown.

[0082] pass Figure 5 A method for obtaining the film thickness distribution 126 will be described. Figure 5 (a) shows the film thickness distribution 124 obtained by the eddy current sensor 210 and the film thickness distribution 126 obtained by performing the correction of Japanese Patent No. 6795337. The horizontal axis in the figure is the distance from the center of the circular grinding object 102 (in mm). However, it is the film thickness distribution only near the end 128. Therefore, the center of the grinding object 102 is located in the left direction of the left end of the figure. The vertical axis is the film thickness (in angstroms). Outside the end 128, the film thickness distribution 124 becomes 0 angstroms. The actual film thickness is 0 angstroms at the end 128.

[0083] Figure 5 (b) is a graph in which the film thickness distribution 124 is differentiated by the distance from the center of the polishing object 102. The horizontal axis in the graph is the distance from the center of the circular polishing object 102 (in mm). The vertical axis of the graph is the differential value (in angstroms / mm). In the correction according to Japanese Patent No. 6795337, the end 128 of the polishing object 102 is first set to be at the peak position of the differential value. Then, for correction, the value of the film thickness distribution 124 located at a distance x from the end 128 to the outside of the polishing object 102 is added to the value of the film thickness distribution 124 located at a distance x from the end 128 to the inside of the polishing object 102. In this way, the film thickness distribution 126 is obtained. In addition, the value of the film thickness distribution 126 decreases sharply at the end 128 and becomes 0 angstroms. Return to Figure 4 Comparing the film thickness distribution 122 and the film thickness distribution 126 , in the conventional correction method, the difference between the corrected film thickness and the actual film thickness near the end portion is large. Figure 4 , 5 The correction shown is only for the case where the measurement range of the eddy current sensor 210 includes the outside of the end of the polishing object 102. Since an averaged signal is used within the measurement range of the eddy current sensor 210, the local film thickness distribution within the measurement range of the eddy current sensor 210 cannot be considered.

[0084] On the other hand, in one embodiment of the present invention, since the size of the measurement range is used for correction, it is possible to provide a film thickness signal processing device that improves the film thickness distribution within the range of the measurement point, that is, the accuracy of the spatial resolution. In addition, the following effects are also provided. That is, the measurement accuracy near the end 128 (bevel) area of ​​the grinding object 102 is improved. When the eddy current sensor 210 being measured approaches the end 128 of the grinding object 102, a part of the magnetic flux generated by the eddy current sensor does not interlink with the grinding object 102, so the outer shape of the measurement range becomes smaller than before approaching the end 128, or the shape of the measurement range changes. Therefore, the output of the eddy current sensor 210 is difficult to stabilize. According to one embodiment of the present invention, the measurement accuracy near the end is improved.

[0085] The film thickness signal processing device 230 according to the embodiment of the present invention includes a receiving unit 232 and a correcting unit 238. The receiving unit 232 receives sensor data output from the eddy current sensor 210 (film thickness sensor) for detecting the film thickness of the polishing object 102 and generates first film thickness data and second film thickness data. The correcting unit 238 corrects the first film thickness data and the second film thickness data generated by the receiving unit 232.

[0086] use Figure 6 , 7 , 8 describes the correction method of the correction unit 238. Figure 6 (a) is a diagram showing a state in which the eddy current sensor 210 disposed on the polishing table 110 rotates along with the rotation of the polishing table 110. An arrow 136 indicates the rotation direction of the polishing table 110. Figure 6 (b) is an enlarged representation Figure 6 (a) shows a range 134 of the graph. Figure 6 , the eddy current sensor 210 moves from the inside to the outside of the polishing object 102, and the eddy current sensor 210 is located near the end 128 of the polishing object 102. The eddy current sensor 210 moves in the direction indicated by the arrow 142 relative to the polishing object 102. The plurality of eddy current sensors 210 are shown to indicate the position of each measurement point of the eddy current sensor 210.

[0087] Figure 7 The figure shows a track 144 on the grinding object 102 when the eddy current sensor 210 passes through the surface of the grinding object 102. In this figure, three tracks 144 are shown as an example. In actual measurement, the number of tracks 144 is more than three and is distributed over the entire grinding object 102. The position and number of tracks can be set arbitrarily. The arrow on the track 144 indicates the moving direction of the eddy current sensor 210. In this figure, the track 144 passes through the center Cw of the grinding object 102. The track 144 may not pass through the center Cw. There are measuring points such as a first measuring point 146 and a second measuring point 148 on the track 144.

[0088] like Figure 8 As shown, the correction unit 238 obtains the corrected third film thickness data 164 or fourth film thickness data 166 based on the size of the measurement range 150 on the polishing object 102 as the measurement object in one measurement of the eddy current sensor 210, the first film thickness data 168 measured at the first measurement point 146 on the polishing object, and the second film thickness data 172 measured at the second measurement point 148 on the polishing object 102. The distance between the first measurement point 146 and the second measurement point 148 is less than or equal to the outer dimension 130 of the measurement range 150. Here, the so-called one measurement refers to Figure 7The measurements at the first measurement point 146, the second measurement point 148, etc. on a trajectory 144 are shown. Figure 8 The details will be described later.

[0089] exist Figure 7 In the embodiment, the next measurement after the measurement at the first measurement point 146 is performed at the second measurement point 148. That is, the second film thickness data is measured in the first measurement after the first film thickness data is measured. For example, the nth measurement is performed at the first measurement point 146, and the n+1th measurement is performed at the second measurement point 148. The first measurement point 146 and the second measurement point 148 may not be consecutive measurement points, and there may be other measurement points between the first measurement point 146 and the second measurement point 148.

[0090] Here, the measurement range 150 of the eddy current sensor 210 refers to the measurement range on the polishing object 102 where the induced eddy current exists in the case of the eddy current sensor, and refers to the irradiation range of light on the polishing object 102 in the case of the optical sensor. In the case of the eddy current sensor, the measurement range depends on the shape of the magnetic core, the shape of the coil (winding method, configuration, number of turns, etc.), etc. Figure 2 The eddy current sensor 210 shown is a pot-type magnetic core 60. Figure 2 In the case of an E-type core, the outer shape of the measuring range 150 is a circle. The outer dimensions of the measuring range 150 (the diameter of the circle in the case of a circle) are approximately the same as the outer shape of the pot-type core 60, but are slightly larger than the outer shape of the pot-type core 60. The dimension 130 of the measuring range 150 may be smaller than the outer shape of the pot-type core 60. In the case where the magnetic core is an E-type core, the measuring range is an ellipse. An example of a method for determining the outer dimensions of the measuring range 150, including the case of an ellipse, is described later. In the case of an optical sensor, the outer dimensions of the measuring range may be larger than the outer diameter of the optical fiber that irradiates the light (the diameter of the circle), or may be smaller than the outer diameter of the optical fiber that irradiates the light.

[0091] like Figure 7 As shown, a first distance 152 from the first measuring point 146 to the center Cw of the object 102 to be polished is different from a second distance 154 from the second measuring point 148 to the center Cw of the object 102 to be polished. The second distance 154 is greater than the first distance 152. In other words, the second measuring point 148 is closer to the end 128 of the object 102 to be polished than the first measuring point 146.

[0092] like Figure 8As shown, the correction unit obtains one of the third film thickness data 164 and the fourth film thickness data 166 corresponding to the third measurement point 158 ​​and the fourth measurement point 162 at a distance of the size 130 from the measurement range 150 on the polishing object 102 based on the first film thickness data 168 and the second film thickness data 172 as described later. In this figure, the fourth film thickness data 166 is obtained as the fourth film thickness data 166 corrected based on the first film thickness data 168 and the second film thickness data 172. The difference between the third film thickness data 164 and the fourth film thickness data 166 is proportional to the difference between the first film thickness data 168 and the second film thickness data 172 as described later.

[0093] Reference Figure 8 A method of obtaining the fourth film thickness data 166 will be described. Figure 8 It is a diagram for explaining a method of obtaining the fourth film thickness data 166 . Figure 8 The horizontal axis is the distance from the center of the circular grinding object 102 (in mm). However, the film thickness distribution is only in the vicinity of the end 128. The center of the grinding object 102 is located to the left of the left end of the figure. The vertical axis is the film thickness (in angstroms). However, in order to show in detail the film thickness change near the maximum value of the film thickness of the grinding object 102, the vertical axis of the area with a small film thickness (i.e., the end) is not shown so that the vertical axis includes the maximum value of the film thickness. That is, Figure 8 The minimum value of the vertical axis is shown to be greater than 0 angstroms.

[0094] like Figure 8 As shown, it is assumed that the first measurement point 146 and the second measurement point 148 are separated by a distance MI. The third measurement point 158 ​​and the fourth measurement point 162 are separated by a distance S (i.e., the outer dimension 130). The measurement range 150 of the eddy current sensor 210 when the eddy current sensor 210 is located at the first measurement point 146 is indicated by an arrow 174. The first measurement point 146 is located at the center of the arrow 174. The measurement range 150 of the eddy current sensor 210 when the eddy current sensor 210 is located at the second measurement point 148 is indicated by an arrow 176. The second measurement point 148 is located at the center of the arrow 176.

[0095] When the middle position between the first measurement point 146 and the second measurement point 148 is set as position R, the third measurement point 158 ​​is a position half the distance S from position R in the direction of the center Cw. The fourth measurement point 162 is a position half the distance S from position R in the direction of the end 128. At this time,

[0096] The first film thickness data 168 is set to Tmoni(R-MI / 2);

[0097] The second film thickness data 172 is set to Tmoni(R+MI / 2);

[0098] The third film thickness data 164 is set to TAct(RS / 2);

[0099] The fourth film thickness data 166 is set to TAct(R+S / 2).

[0100] Furthermore, the average value of the film thickness data in the measurement range 150 based on the eddy current sensor 210 is set to Toverlapped. In addition, it can be considered that the average value Toverlapped of the film thickness data is substantially the same in the range where the range of arrow 174 and the range of arrow 176 overlap. At this time, it is considered that

[0101] First film thickness data 168 = {average value of film thickness data Toverlapped×(outer dimensions−(distance MI between the measuring point 146 and the second measuring point 148))+third film thickness data 164×(distance MI between the first measuring point 146 and the second measuring point 148)} / outer dimensions (1).

[0102] That is, a value obtained by weighting the average value Toverlapped of the film thickness data and the third film thickness data 164 by the length (S-MI) and the length (MI) is regarded as the first film thickness data 168 .

[0103] If we express equation (1) using only the notations we have already mentioned, we get

[0104] Tmoni(R-MI / 2)={Toverlapped×(S-MI)+TAct(RS / 2)×MI} / S (2).

[0105] The same is true for the second film thickness data 172.

[0106] Second film thickness data 172 = {average value of film thickness data Toverlapped×(outer dimensions−(distance MI between first measurement point 146 and second measurement point 148))+fourth film thickness data 166×(distance MI between measurement point 146 and second measurement point 148)} / outer dimensions (3).

[0107] That is, a value obtained by weighting the average value Toverlapped of the film thickness data and the fourth film thickness data 166 by the length (S-MI) and the length (MI) is regarded as the second film thickness data 172 .

[0108] If we express equation (3) using only the notations we have already mentioned, we get

[0109] Tmoni(R+MI / 2)={Toverlapped×(S-MI)+TAct(R+S / 2)×MI} / S (4).

[0110] If we subtract equation (2) from equation (4) and multiply both sides by (S / MI), we get,

[0111] TAct(R+S / 2)-TAct(RS / 2)

[0112] =(Tmoni(R+MI / 2)-Tmoni(R-MI / 2))×(S / MI) (5).

[0113] That is, the fourth film thickness data 166 can be obtained from the first film thickness data 168 and the second film thickness data 172. The obtained fourth film thickness data 166 is a film thickness distribution 178. When the film thickness distribution 178 is compared with Figure 4 Compared with the film thickness distribution 126 corrected by the prior art, it can be seen that a considerable improvement has been achieved, which is close to the actual film thickness distribution 122.

[0114] Formula (5) is a formula representing the difference between the third film thickness data 164 and the fourth film thickness data 166. Therefore, as described later, when starting correction using formula (5), it is necessary to specify the third film thickness data 164 as the initial value. The method for setting the initial value will be described later. According to formula (5), the film thickness difference between two points separated by a distance S is obtained from the difference in the monitoring values ​​between consecutive measurement points. The previous measurement values ​​are the first film thickness data 168 and the second film thickness data 172, which can be considered to be the average value of the film thickness of the entire measurement range 150. That is, the spatial resolution of the previous film thickness measurement is the distance S (the overall size of the measurement range 150). On the other hand, according to formula (5), the film thickness within the interval of the distance MI can be obtained. Therefore, the measurement spatial resolution can be improved from S to MI.

[0115] In addition, in formula (5), the first film thickness data 168 and the second film thickness data 172 are adjacent measured values, but non-adjacent measured values ​​may also be used in formula (5). In addition, although the third measuring point 158 ​​and the fourth measuring point 162 are used, it does not mean that the third measuring point 158 ​​and the fourth measuring point 162 are the positions where the eddy current sensor 210 actually performs the measurement. The third measuring point 158 ​​and the fourth measuring point 162 indicate the positions where the film thickness data is measured by calibration.

[0116] When starting the correction using formula (5), the third film thickness data 164 needs to be designated as the initial value. The method for setting the initial value is described. The first film thickness data 168 at the location where the correction starts can be set as the initial value of the third film thickness data 164. The location where the correction starts is selected in the following various ways. The correction starts when the time-related change in the first film thickness data 168 or the second film thickness data 172 exceeds a specified value, and then the correction is performed during a specified period. The specified period refers to, for example, until the end 128 is reached. Or the correction is performed when the position-related change in the first film thickness data 168 or the second film thickness data 172 exceeds a specified value.

[0117] This increase in the amount of change often occurs near the end 128. Therefore, it is preferred that the calibration is performed only near the end 128 of the polishing object 102, and the calibration is performed based on the first film thickness data 168 and the second film thickness data measured at the end 128. As the vicinity, a range of a predetermined distance from the end can be selected based on past measured values ​​or prior test data. In addition, the calibration can also be performed when the end 128 of the polishing object 102 is located within the measurement range 150 of the eddy current sensor 210.

[0118] Fig. 9 This is an example of selecting a range of a predetermined distance from the end as a vicinity based on past measured values ​​or prior test data. The horizontal axis in the figure is the distance from the center of the circular polishing object 102 (in mm). The vertical axis is the film thickness (in angstroms). In this figure, the actual film thickness distribution 122, the film thickness distribution 124 as the measured value of the eddy current sensor 210, and the film thickness distribution 125 obtained by calibration according to one embodiment of the present application are shown. Figure 8 The film thickness distribution 178 is shown. The actual film thickness distribution 122 is a measurement value obtained by a more accurate film thickness measuring device, which is different from the eddy current sensor 210 . Fig. 9 A position 180 where correction starts is shown. Correction according to one embodiment of the present application is performed in a region from the position 180 to the end 128 indicated by an arrow 182. The correction range is specified in advance, and correction is performed sequentially from the inside of the polishing object 102 toward the end 128.

[0119] according to Fig.10 The flowchart below illustrates the calibration method. Fig.10In the embodiment, the case of measuring and correcting when the object 102 is polished from the center Cw toward the end 128 is described. In addition, the correction can also be applied to the film thickness data obtained when the object 102 is polished from the end 128 toward the center Cw. For example, after the eddy current sensor 210 passes under the object 102 (one scan), before entering the next scan, the correction can be applied sequentially from the inside of the object 102 toward the end 128 in the film thickness data representing the obtained film thickness distribution. In this way, the film thickness data obtained when the object 102 is polished from the end 128 toward the center Cw can also be corrected. In this embodiment, the order of correction on the film thickness data is from the center Cw to the end 128. That is, the film thickness data at the inner measurement point in the object 102 is used to correct the film thickness data at the outer measurement point. In addition, the correction method of the present invention can also correct the film thickness data in the direction from the end 128 toward the center Cw at a location other than the vicinity of the end 128. From the time when the eddy current sensor 210 enters the polishing object 102 at the end 128 to the time when the eddy current sensor 210 leaves the polishing object 102 at the end 128, Figure 7 Each measurement point of the trajectory 144 shown in FIG. 1 is assigned a consecutive number in advance. The number of the center Cw is Ncenter. The calibration starts from the center Cw (S10).

[0120] First, in order to initialize the value of TAct(RS / 2) as data initialization (S12), the measured value (Tmoni) obtained at the center Cw is added to TAct(RS / 2). That is, TAct=Tmoni. The operation of setting TAct=Tmoni is performed in S22 described later until entering the calibration area and reaching the measurement point where TAct(R+S / 2) is calculated according to equation (5). After reaching the measurement point where TAct(R+S / 2) is calculated, since TAct is obtained by calculation, the operation of setting TAct=Tmoni is not necessary. In addition, if Figure 8 As shown, the position where TAct (RS / 2) is set is S / 2-MI / 2 away from the measurement point where Tmoni (R-MI / 2) is measured. Tmoni does not necessarily exist exactly at the position where TAct (RS / 2) is set. If it does not exist, Tmoni at the nearest position can be used.

[0121] Ncenter is added to the counter n indicating the position of the measurement point (S14). Next, the value of the counter n is determined to determine whether the measurement point has been entered. Fig. 9The calibration area is indicated by the arrow 182 (S16). A number ns indicating the position 180 where calibration starts is set in advance. When the value of the counter n is greater than the number ns, it is determined that the calibration area has been entered (the case of "Yes" in S16). When the value of the counter n is less than the number ns, it is determined that the calibration area has not been entered (the case of "No" in S16). In the case of entering the calibration area, TAct(R+S / 2) is calculated according to formula (5) and calibration is performed (S18). Next, the value of the counter n is determined to determine whether it indicates that the calibration area has been entered. Fig. 9 The end 128 of n = Nedge (S20). When it is reached ("Yes"), the calibration is ended (S24). When it is not reached ("No"), the value of the counter n indicating the position of the measuring point is increased by 1, and the film thickness is measured (S22). Then, enter S16. In S16, if it is judged that the value of the counter n is less than the number ns and has not entered the calibration area ("No" in S16), enter S20.

[0122] Next, through Figure 11 to Figure 13 The method of setting the outer dimension 130 (i.e., the distance S) of the measurement range 150 is described below. The measurement range 150 (the range in which the eddy current sensor 210 responds) is determined based on the distance 184 (see FIG. 184 ) between the eddy current sensor 210 and the polishing object 102. Fig.11 (a) Fig.12 When the distance 184 increases, the sensitivity of the eddy current sensor 210 decreases and the measurement range 150 increases. Fig.11 (b) shows the sensitivity and the measurement range 150 of the eddy current sensor 210 when the distance 184 is narrow. Fig.12 (b) shows the sensitivity and measurement range 151 of the eddy current sensor 210 when the distance 184 is wide. Fig.11 (b) and Fig.12 The horizontal axis of (b) represents the position in the radial direction from the center 186 of the eddy current sensor 210 (unit: mm). Fig.11 (b) and Fig.12 The vertical axis of (b) represents the sensitivity (in mV) at each position in the radial direction from the center 186 of the eddy current sensor 210 . The sensitivity refers to the magnitude of the output of the eddy current sensor 210 .

[0123] Compare Fig.11 (b) and Fig.12As can be seen from (b), even if the eddy current sensor 210 is the same, the appropriate outer dimension 130 is different depending on the thickness of the polishing pad 108 used. Therefore, the value of the outer dimension 130 is adjusted in such a way that the corrected film thickness distribution 178 is consistent with the film thickness distribution 122 measured by a film thickness measuring machine that is more accurate than the eddy current sensor 210, thereby determining the value of the outer dimension 130. The determined outer dimension 130 is used in formula (5). Fig.13 The film thickness distribution 178 is shown when the outer dimension 130 is changed.

[0124] Fig.13 The horizontal axis of each figure is the distance from the center of the circular polishing object 102 (in mm). The vertical axis is the film thickness (in angstroms). However, in order to show in detail the film thickness change near the maximum value of the film thickness of the polishing object 102, the film thickness of the region with a small film thickness (i.e., the end portion) is not shown so that the vertical axis includes the maximum value of the film thickness. That is, Fig.13 The minimum value of the vertical axis shown is greater than 0 angstroms. The film thickness at the end is not shown, but since there is no metal film outside the end, it is 0 angstroms. Fig.13 , for comparison, a film thickness distribution 124 before correction and a film thickness distribution 122 measured by a film thickness measuring device are also shown.

[0125] The corrected film thickness distribution 178 when using the appropriate outer dimensions 130 is shown in FIG. Fig.13 In the case of (b), the film thickness distribution 178 and the film thickness distribution 122 are most consistent. Fig.13 (a) The outer dimensions used are 130 Fig.13 The outer dimension used in (b) is smaller than 130. Fig.13 (c) The outer dimensions used are 130 Fig.13 The outer dimensions used in (b) are 130 mm. Figure 11 to Figure 13 The results are as follows. The distance 184 between the polishing object 102 and the eddy current sensor 210 is Fig.12 The outer dimension 130 at the first length shown in (a) is set as the first dimension. The distance between the polishing object 102 and the eddy current sensor 210 is Fig.11 The outer dimension 130 at the second length shown in (a) is set as the second dimension. At this time, when the first length is longer than the second length, the first dimension is larger than the second dimension.

[0126] When the outer shape of the eddy current sensor 210 is a circle, the diameter of the outer shape can be used as the initial value of the dimension 130. Fig.13The method for determining the outer dimensions of the measurement range 150 when the outer shape of the eddy current sensor 210 is not a circle is described below. When the outer shape of the eddy current sensor 210 is a square, a rectangle, etc., the measurement range 150 is different from a circle. When the outer shape of the measurement range 150 is an ellipse, for example, the length of the minor axis and the major axis of the ellipse is included, and the length before and after the length of the minor axis and the major axis is taken as the dimension 130, as shown in FIG. Fig.13 As shown, the consistency with the film thickness distribution measured by the film thickness measuring machine was checked. The length when the consistency was good was set as the dimension 130.

[0127] When the outer shape of the measurement range 150 is different from a circle or an ellipse, for example, the longitudinal direction of the outer shape and the transverse length perpendicular thereto are included, and the length before and after the longitudinal and transverse lengths is taken as the dimension 130, such as Fig.13 As shown, the consistency with the film thickness distribution measured by the film thickness measuring machine is checked. The length when the consistency is good is defined as dimension 130. Dimension 130 can also be determined by estimating the dimension 130 adopted for similar shapes in the past.

[0128] The following is a description of a film thickness signal processing method. The film thickness signal processing method using a polishing device having an eddy current sensor, a receiving unit, and a correction unit generates first film thickness data 168 and second film thickness data 172 by receiving sensor data output from an eddy current sensor 210 for detecting the film thickness of a polishing object 102 through a receiving unit 232. The first film thickness data 168 and second film thickness data 172 generated by the receiving unit 232 are corrected through a correction unit 238. The correction unit 238 obtains corrected third film thickness data 164 or fourth film thickness data 166 based on the size 130 of a measurement range 150 as a measurement object in one measurement of the eddy current sensor 210, the first film thickness data 168 measured at a first measurement point 146 on the polishing object 102, and the second film thickness data 172 measured at a second measurement point 148 on the polishing object 102. The distance between the first measurement point 146 and the second measurement point 148 is less than the outer dimension 130 of the measurement range 150.

[0129] The polishing device 100 includes a polishing device control unit 140 that controls the overall operation of the polishing device 100. The polishing device control unit 140 and the film thickness signal processing device 230 include a CPU, a memory, a storage medium, etc. The polishing device control unit 140 and the film thickness signal processing device 230 can be configured as a microcomputer that uses software (program) such as a polishing scheme and / or information on machine parameters of related equipment input in advance to achieve a desired function (correction function, etc.), or can be configured as a hardware circuit that performs dedicated calculation processing. The polishing device control unit 140 and the film thickness signal processing device 230 can also be configured by a combination of a microcomputer and a hardware circuit that performs dedicated calculation processing.

[0130] Above, the example of the embodiment of the present invention has been described, but the embodiment of the above invention is to facilitate the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from its purport, and the present invention certainly includes its equivalent. In addition, within the scope of at least a part of the scope that can solve the above-mentioned problem or within the scope of at least a part of the effect, it can be any combination or omission of each constituent element recorded in the scope of the present invention and the specification.

Claims

1. A film thickness signal processing device, characterized in that: have: a receiving unit that receives sensor data output from a film thickness sensor for detecting a film thickness of the polishing object to generate first film thickness data and second film thickness data; as well as a correction unit that corrects the first film thickness data and the second film thickness data generated by the receiving unit, the correction unit obtains the corrected film thickness data based on the size of the measurement range on the polishing object as the measurement object in one measurement by the film thickness sensor, the first film thickness data measured at a first measurement point on the polishing object, and the second film thickness data measured at a second measurement point on the polishing object, The distance between the first measurement point and the second measurement point is less than or equal to the size of the measurement range.

2. The film thickness signal processing device according to claim 1, characterized in that: A first distance from the first measurement point to the center of the polishing object and a second distance from the second measurement point to the center of the polishing object are different.

3. The film thickness signal processing device according to claim 1 or 2, characterized in that: The second film-thickness data is measured in the first measurement after the first film-thickness data is measured.

4. The film thickness signal processing device according to claim 1 or 2, characterized in that: The correction unit obtains at least one of third film thickness data and fourth film thickness data corresponding to a third measurement point and a fourth measurement point on the polishing object at a distance of the size as the film thickness data corrected based on the first film thickness data and the second film thickness data.

5. The film thickness signal processing device according to claim 4, characterized in that: The difference between the third film thickness data and the fourth film thickness data is proportional to the difference between the first film thickness data and the second film thickness data.

6. The film thickness signal processing device according to claim 1 or 2, characterized in that: The correction is performed when the amount of change in the first film thickness data or the second film thickness data with respect to time exceeds a predetermined value.

7. The film thickness signal processing device according to claim 1 or 2, characterized in that: The correction is performed when the amount of change in the first film thickness data or the second film thickness data related to the position exceeds a predetermined value.

8. The film thickness signal processing device according to claim 1 or 2, characterized in that: The correction is performed based on the first film thickness data and the second film thickness data measured near the end of the polishing object.

9. The film thickness signal processing device according to claim 8, characterized in that: The correction is performed when the end portion exists within the measurement range of the film thickness sensor.

10. The film thickness signal processing device according to claim 1 or 2, characterized in that: When the dimension when the distance between the polishing object and the film thickness sensor is a first length is set to a first dimension, and the dimension when the distance between the polishing object and the film thickness sensor is a second length is set to a second dimension, when the first length is longer than the second length, the first dimension is larger than the second dimension.

11. A grinding device, characterized in that: have: The film thickness signal processing device according to claim 1 or 2; A grinding table, to which a grinding pad for grinding the object to be ground can be attached; A driving unit capable of driving the grinding table to rotate; a holding portion that holds the polishing object and is capable of pressing the polishing object against the polishing pad; as well as The film thickness sensor is disposed in a hole formed in the polishing table and can detect the film thickness of the polishing object as the polishing table rotates.

12. A film thickness signal processing method using a polishing device having a film thickness sensor, a receiving unit and a correction unit, characterized in that: The receiving unit receives sensor data output from the film thickness sensor for detecting the film thickness of the polishing object to generate first film thickness data and second film thickness data, The correction unit corrects the first film thickness data and the second film thickness data generated by the receiving unit. The correction unit obtains the corrected film thickness data based on the size of the measurement range as the measurement object in one measurement of the film thickness sensor, the first film thickness data measured at the first measurement point on the polishing object, and the second film thickness data measured at the second measurement point on the polishing object. The distance between the first measurement point and the second measurement point is less than or equal to the size of the measurement range.

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