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

Abstract

To provide a film thickness signal processing apparatus that improves accuracy of a film-thickness distribution within a measurement range.SOLUTION: A film thickness signal processing apparatus includes a receiver and a corrector. The receiver receives sensor data output from an eddy current sensor and generates first film thickness data 168 and second film thickness data 172. The corrector corrects the first film thickness data 168 and the second film thickness data 172 generated by the receiver. The corrector obtains corrected film thickness data 166 on the basis of size of measurement ranges 174, 176 on a polishing object being a measurement target in a single measurement by the eddy current sensor, the first film thickness data 168 measured at a first measurement point 146 on the polishing object, and the second film thickness data 172 measured at a second measurement point 148 on the polishing object. A distance between the first measurement point 146 and the second measurement point 148 is equal to or less than the size of the measurement ranges 174, 176.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a film thickness signal processing device, a polishing device, and a film thickness signal processing method. [Background technology]

[0002] In recent years, with the increasing integration and density of semiconductor devices, the wiring of circuits has become finer and the number of layers in multilayer wiring has also increased. In order to achieve multilayer wiring while miniaturizing circuits, it is necessary to precisely planarize the surface of semiconductor devices.

[0003] Chemical mechanical polishing (CMP) is a technique for flattening the surface of semiconductor devices. A polishing apparatus for performing CMP is equipped with a polishing table to which a polishing pad is attached, and a top ring (holding unit) for holding an object to be polished (for example, a substrate such as a semiconductor wafer, or various films formed on the surface of the substrate). The polishing apparatus polishes an object to be polished by pressing the object to be polished held by the top ring against the polishing pad while rotating the polishing table with a motor (driving unit) that can rotate the polishing table.

[0004] The polishing apparatus is provided with a film thickness measuring device for detecting the end point of the polishing process based on the film thickness of the object to be polished. The film thickness measuring device is provided with a film thickness sensor for detecting the film thickness of the object to be polished. Representative examples of the film thickness sensor include an eddy current sensor and an optical sensor.

[0005] The eddy current sensor or optical sensor is placed in a hole formed in the polishing table, and detects the film thickness when it faces the object to be polished while rotating with the rotation of the polishing table. The eddy current sensor induces eddy currents in the object to be polished, such as a conductive film, and detects the change in the thickness of the object to be polished from the change in the magnetic field generated by the eddy currents induced in the object to be polished. On the other hand, the optical sensor detects the thickness of the object to be polished by irradiating light onto the object to be polished and measuring the interference wave reflected from the object to be polished.

[0006] The film thickness distribution measured by a film thickness sensor is a correspondence between the measured film thickness value (film thickness data) based on the detection signal from the entire measurement spot of the sensor (in the case of an eddy current sensor, the measurement range on the wafer where eddy currents induced in the wafer exist; in the case of an optical sensor, the range of light irradiation on the wafer; hereafter referred to as the "measurement range") and the position of the measurement point on the wafer. For example, the position of the center of the sensor is sometimes used as the position of the measurement point. While the measurement range exists on the wafer with a certain extent, the measured value is linked to the position of the measurement point, which is a specific position on the wafer. For this reason, there is room for improvement in the accuracy of the film thickness distribution within the measurement range, i.e., the spatial resolution. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6795337 Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE PRESENT EMBODIMENT One aspect of the present invention has been made to solve such problems, and an object of the present invention is to provide a film thickness signal processing device that improves the accuracy of the film thickness distribution within a measurement range. [Means for solving the problem]

[0009] In order to solve the above problems, in a first embodiment, a film thickness signal processing device is provided, which includes a receiving unit that receives sensor data output from a film thickness sensor for detecting a film thickness of an object to be polished and generates first and second film thickness data, and a correction unit that corrects the first and second film thickness data generated by the receiving unit, wherein the correction unit determines corrected film thickness data based on the size of a measurement range on the object to be polished that is the measurement target in one measurement by the film thickness sensor, the first film thickness data measured at a first measurement point on the object to be polished, and the second film thickness data measured at a second measurement point on the object to be polished, and the distance between the first measurement point and the second measurement point is less than or equal to the size of the measurement range.

[0010] In this embodiment, the correction unit obtains corrected film thickness data based on the size of the measurement range on the object to be polished that is the measurement target in one measurement by the film thickness sensor, the first film thickness data measured at the first measurement point on the object to be polished, and the second film thickness data measured at the second measurement point on the object to be polished. In particular, since the size of the measurement range is used for correction, it is possible to provide a film thickness signal processing device with improved accuracy of the film thickness distribution within the measurement range.

[0011] In a second embodiment, the film thickness signal processing device according to the first embodiment is configured such that a first distance from the first measurement point to the center of the object to be polished and a second distance from the second measurement point to the center of the object to be polished are different.

[0012] In a third embodiment, the film thickness signal processing device according to the first or second embodiment has a configuration in which the second film thickness data is measured in the first measurement after the first film thickness data is measured.

[0013] In a fourth embodiment, the correction unit is configured as a film thickness signal processing device described in any one of the first to third embodiments, characterized in that it determines one of third film thickness data and fourth film thickness data corresponding to a third measurement point and a fourth measurement point that are separated by a distance of the size on the polishing object as the film thickness data corrected based on the first film thickness data and the second film thickness data.

[0014] In a fifth aspect, the film thickness signal processing device according to the fifth aspect is configured such 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.

[0015] In a sixth embodiment, the film thickness signal processing device according to any one of the first to fifth embodiments is configured so that the correction is performed when the amount of change in the first or second film thickness data with respect to time exceeds a predetermined value.

[0016] In a seventh embodiment, the film thickness signal processing device according to any one of the first to sixth embodiments is configured so that the correction is performed when a change amount relating to the position of the first or second film thickness data exceeds a predetermined value.

[0017] In an eighth embodiment, the film thickness signal processing device according to any one of the first to seventh embodiments is configured so that the correction is performed based on the first and second film thickness data measured in the vicinity of an end of the object to be polished.

[0018] A ninth aspect employs a film thickness signal processing device according to the eighth aspect, characterized in that the correction is performed when the end is within the measurement range of the film thickness sensor.

[0019] In a tenth embodiment, a distance between the object to be polished and the film thickness sensor is a first length. The thickness signal processing device according to any one of the first to ninth embodiments is configured such that, when the above size is a first size and the size when the distance between the object to be polished and the thickness sensor is a second length is a second size, when the first length is longer than the second length, the first size is larger than the second size.

[0020] In an eleventh embodiment, the polishing apparatus is characterized by having a polishing table to which a polishing pad for polishing the object to be polished can be attached, a drive unit capable of rotating the polishing table, a holding unit capable of holding the object to be polished and pressing it against the polishing pad, a film thickness sensor disposed in a hole formed in the polishing table and capable of detecting the film thickness of the object to be polished as the polishing table rotates, and a film thickness signal processing device described in any one of the first to tenth embodiments.

[0021] In a twelfth form, in a film thickness signal processing method using a polishing apparatus having a film thickness sensor, a receiving unit, and a correction unit, the receiving unit receives sensor data output from the film thickness sensor for detecting a film thickness of an object to be polished and generates first and second film thickness data, the correction unit corrects the first and second film thickness data generated by the receiving unit, and the correction unit obtains corrected film thickness data based on a size of a measurement range to be measured in one measurement of the film thickness sensor, the first film thickness data measured at a first measurement point on the object to be polished, and the second film thickness data measured at a second measurement point on the object to be polished, and the distance between the first measurement point and the second measurement point is less than or equal to the size of the measurement range. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a schematic overall configuration of a polishing apparatus. [Diagram 2] FIG. 2 is a schematic diagram showing a configuration example of the eddy current sensor of this embodiment. [Diagram 3] FIG. 3 shows the actual film thickness distribution and the film thickness distribution obtained by an eddy current sensor. [Figure 4] FIG. 4 is a diagram showing the film thickness distribution obtained by performing the correction according to Japanese Patent No. 6795337. [Diagram 5] FIG. 5 shows the amendments made by Patent No. 6795337. [Figure 6] FIG. 6 is a diagram showing how an eddy current sensor disposed on the polishing table rotates with the rotation of the polishing table. [Figure 7] FIG. 7 is a diagram showing the trajectory of an eddy current sensor on a workpiece as it passes over the surface of the workpiece. [Figure 8] FIG. 8 is a diagram for explaining a fourth method for determining film thickness data. [Figure 9] FIG. 9 is a diagram showing an example in which a range at a predetermined distance from the end is selected as the vicinity based on past actual measurements or prior test data. [Figure 10] FIG. 10 is a flowchart illustrating the correction method. [Figure 11] FIG. 11 is a diagram for explaining a method for setting the outer size of the measurement range. [Figure 12] FIG. 12 is a diagram for explaining a method for setting the outer size of the measurement range. [Figure 13] FIG. 13 is a diagram for explaining a method for setting the outer size of the measurement range. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, the same or corresponding components are designated by the same reference numerals, and duplicated descriptions may be omitted. Furthermore, the features shown in each embodiment can be applied to other embodiments as long as they are not mutually inconsistent.

[0024] FIG. 1 is a diagram showing a schematic diagram of the overall configuration of a polishing apparatus according to an embodiment of the present invention. As shown, the polishing apparatus 100 includes a polishing table 110 on whose upper surface a polishing pad 108 can be attached for polishing an object to be polished (e.g., a substrate such as a semiconductor wafer, or various films formed on the surface of a substrate) 102, a first electric motor (drive unit) 112 that rotates the polishing table 110, a top ring (holding unit) 116 that can hold the object to be polished 102 and press it against the polishing pad, and a second electric motor (drive unit) 118 that rotates the top ring 116.

[0025] Polishing apparatus 100 also includes a slurry line 120 that supplies a polishing liquid containing an abrasive to the upper surface of polishing pad 108. Polishing apparatus 100 also includes a polishing apparatus control unit 140 that outputs various control signals related to polishing apparatus 100.

[0026] The polishing apparatus 100 includes an eddy current sensor 210 (film thickness sensor) that is disposed in a hole formed in the polishing table 110 and detects the film thickness of the object 102 along the polishing surface as the polishing table 110 rotates. The polishing apparatus 100 also includes a trigger sensor 220 that includes a proximity sensor 222 disposed on the polishing table 110 and a dog 224 disposed outside the polishing table 110.

[0027] 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 from an AC power source, and forms an eddy current in the polishing object 102 disposed nearby. The magnetic flux generated by the eddy current formed in the polishing object 102 interlinks with the detection coil and the balance coil. Since the detection coil is disposed closer to the conductive film, the balance of the induced voltages generated in both coils is lost. As a result, the eddy current sensor 210 detects the interlinkage magnetic flux formed by the eddy current in the polishing object, and detects the thickness of the polishing object based on the detected interlinkage magnetic flux. Note that, although an example of disposing the eddy current sensor 210 is shown here, the present invention is not limited to this, and an optical sensor may be disposed that detects the thickness of the polishing object by irradiating light on the polishing object and measuring the interference wave reflected from the polishing object.

[0028] Fig. 2 is a schematic diagram showing a configuration example of an eddy current sensor 210 of this embodiment. As shown in Fig. 2, the eddy current sensor 210 is composed of a pot core 60 and three coils 72, 73, and 74. The pot core 60, which is a magnetic body, has a bottom surface portion 61a, a magnetic core portion 61b provided in the center of the bottom surface portion 61a, and a peripheral wall portion 61c provided around the bottom surface portion 61a.

[0029] Of 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 generates an eddy current in a metal film (or conductive film) on the polishing object 102 placed nearby by a magnetic field generated by a voltage supplied from the AC signal source. A detection coil 73 is arranged on the metal film side of the excitation coil 72, and detects a magnetic field generated by an eddy current formed in the metal film. A balance coil 74 is arranged on the opposite side of the excitation coil 72 from the detection coil 73. The balance coil 74 is a resistance bridge circuit (not shown) used to detect a magnetic field generated by an eddy current, and is for adjusting the balance. The balance coil 74 can adjust the zero point. Therefore, it is possible to detect an eddy current flowing in the metal film from a zero state, and the detection sensitivity of the eddy current in the metal film is improved. The excitation coil 72 is arranged in the magnetic core 61b, and generates an eddy current in the metal film. The detection coil 73 is arranged in the magnetic core 61b, and detects an eddy current formed in the metal film. It can be seen that in the eddy current sensor 210, the magnetic flux 20 is concentrated and spreads less in comparison with the conventional eddy current sensor using a solenoid coil.

[0030] When the thickness of the metal film changes, a change occurs in the eddy current, and the impedance of the detection coil 73 and the balance coil 74 changes. The receiving unit 232 detects the impedance from the sensor data output by the eddy current sensor 210. When the impedance changes, it is possible to detect the change in the thickness of the metal film.

[0031] The receiving unit 232 receives sensor data (e.g., a voltage signal) output from the film thickness sensor and detects the impedance from 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 so that the film thickness data becomes "0" when the film thickness is "0".

[0032] The film thickness data is not limited to the difference in impedance. For example, the correspondence between the impedance and the actual film thickness may be measured before polishing, and the receiver 232 may obtain the film thickness from the detected impedance based on the correspondence during polishing, and the obtained film thickness may be used as the film thickness data. In an embodiment of the present invention described later, the film thickness is obtained from the detected impedance, and the obtained film thickness is used as the film thickness data. Note that a quantity dependent on the film thickness other than the impedance may be used to generate the film thickness data. The eddy current sensor 210 is not limited to the pot-type core shown in FIG. 2. For example, a solenoid coil, an E-type core, or a U-type core may be used.

[0033] The proximity sensor 222 is attached to the lower surface of the polishing table 110 (the surface on which the polishing pad 108 is not attached). The dog 224 is disposed outside the polishing table 110 so as to be detected by the proximity sensor 222. The trigger sensor 220 outputs a trigger signal indicating that the polishing table 110 has made one rotation based on the positional relationship between the proximity sensor 222 and the dog 224. Specifically, the trigger sensor 220 outputs the trigger signal when the proximity sensor 222 and the dog 224 are closest to each other.

[0034] The eddy current sensor 210 controls the measurement start timing and measurement end timing based on the trigger signal output from the trigger sensor 220. For example, the eddy current sensor 210 sets the measurement start timing to the timing when a predetermined time has elapsed since the trigger signal is output from the trigger sensor 220, and sets the measurement end timing to the timing when a predetermined time has elapsed since the trigger signal is output from the trigger sensor 220. Here, it is assumed that the predetermined time is set in advance as a parameter.

[0035] When polishing the object 102, the polishing apparatus 100 supplies a polishing slurry containing abrasive grains from a slurry line 120 to the upper surface of the polishing pad 108, and rotates the polishing table 110 by a first electric motor 112. Then, the polishing apparatus 100 presses the object 102 held by the top ring 116 against the polishing pad 108 while rotating the top ring 116 about a rotation axis eccentric to the rotation axis of the polishing table 110. As a result, the object 102 is polished and planarized by the polishing pad 108 holding the polishing slurry.

[0036] Next, the film thickness signal processing device 230 of this embodiment will be described. As shown in Fig. 1, the film thickness signal processing device 230 is connected to the eddy current sensor 210 via 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 data to the end point detector 240.

[0037] The end point detector 240 monitors the change in the film thickness of the object 102 to be polished based on the signal output from the film thickness signal processing device 230. The end point detector 240 is connected to a polishing apparatus control unit 140 that performs various controls related to the polishing apparatus 100. When the end point detector 240 detects the end point of polishing of the object 102 to be polished, it outputs a signal indicating that to the polishing apparatus control unit 140. When the polishing apparatus control unit 140 receives the signal indicating the polishing end point from the end point detector 240, it The polishing by the polishing apparatus 100 is then terminated. During polishing, the polishing apparatus control section 140 controls the pressing force of the object 102 to be polished based on the corrected film thickness data.

[0038] Here, the problems of the conventional technology will be described. In the polishing process of semiconductor wafers, it is very important to control the film thickness during polishing and the shape of the film thickness distribution. It is common to use an eddy current sensor or an optical sensor to perform in-situ film thickness measurement (i.e., film thickness measurement during polishing) and to control the pressure by the top ring 116 based on the measurement results. In the past, when the sensor is located near the edge of the wafer and the measurement range of the sensor includes an area outside the wafer (i.e., an area outside the edge of the wafer), there was a problem that the shape of the film thickness distribution could not be estimated with high accuracy. In addition, in the past, the output of the sensor is considered to measure the average film thickness within the measurement range of the sensor. Therefore, if there are irregularities in the film thickness within an area smaller than the external size of the measurement range of the sensor, the irregularities cannot be detected. As a result, there was a problem that the shape of the film thickness distribution could not be estimated with high accuracy.

[0039] This will be further explained with reference to Figs. 3 and 4. Fig. 3 shows an actual film thickness distribution 122 and a film thickness distribution 124 obtained by an eddy current sensor 210. The film thickness distribution 124 has not been corrected. Fig. 4 also shows a film thickness distribution 126 obtained by performing correction according to Japanese Patent No. 6795337. The horizontal axis of the figure is the distance (unit: mm) from the center of the circular polishing object 102 (wafer). However, this is the film thickness distribution only in the vicinity of the end 128. Therefore, the center of the polishing object 102 is to the left of the left end of the figure. The vertical axis is the film thickness (unit: angstroms). However, in order to show in detail the change in film thickness in the vicinity of the end 128 where the film thickness of the polishing object 102 is maximum, the film thickness in the region where the film thickness is small (i.e., the end 128) is not shown so that the vertical axis includes the maximum film thickness. In other words, the minimum value of the vertical axis shown in Figs. 3 and 4 is greater than 0 angstroms. The film thickness at the end is 0 angstroms because there is no metal film outside the end.

[0040] In Fig. 3, within the external size 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 other than at the ends decreases toward the center of the object 102 to be polished. Conventionally, the measured film thickness (film thickness before correction) indicated by the film thickness distribution 124 is the average of the actual film thickness within the external size 130, and the accuracy of the average is low. Conventionally, it has not been possible to measure an accurate film thickness distribution 122. Fig. 4 shows a film thickness distribution 126 obtained by a conventional correction method.

[0041] The method of determining the film thickness distribution 126 will be explained with reference to FIG. 5. FIG. 5(a) shows the film thickness distribution 124 obtained by the eddy current sensor 210 and the film thickness distribution 126 obtained by performing correction according to Patent No. 6795337. The horizontal axis of the figure is the distance (unit: mm) from the center of the circular object to be polished 102. However, this is the film thickness distribution only in the vicinity of the end 128. Therefore, the center of the object to be polished 102 is to the left of the left edge of the figure. The vertical axis is the film thickness (unit: angstroms). Outside the end 128, the film thickness distribution 124 is 0 angstroms. The actual film thickness at the end 128 is 0 angstroms.

[0042] FIG. 5(b) shows the film thickness distribution 124 differentiated by the distance from the center of the object to be polished 102. The horizontal axis of the figure is the distance (unit: mm) from the center of the circular object to be polished 102. The vertical axis of the figure is the differential value (unit: angstroms / mm). In the correction according to Patent No. 6795337, it is first assumed that the edge 128 of the object to be polished 102 is at the position of the peak of the differential value. Then, for correction, the value of the film thickness distribution 124 located at a distance x from the edge 128 to the outside of the object to be polished 102 is added to the value of the film thickness distribution 124 located at a distance x from the edge 128 to the inside of the object to be polished 102. In this way, the film thickness distribution 126 is obtained. Then, the value of the film thickness distribution 126 is suddenly reduced at the edge 128 to 0 angstroms. Returning to FIG. 4, when comparing the film thickness distribution 122 and the film thickness distribution 126, in the conventional correction method, the film thickness distribution 124 near the edge is reduced by 0 angstroms. 4 and 5 is only for the case where the measurement range of the eddy current sensor 210 includes the outside of the edge of the polishing object 102. Since the signal averaged within the measurement range of the eddy current sensor 210 is used, the local film thickness distribution within the measurement range of the eddy current sensor 210 cannot be taken into consideration.

[0043] 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 accuracy of the film thickness distribution within the measurement spot, i.e., the spatial resolution. In addition, the following effects are obtained. That is, the measurement accuracy is improved near the end 128 (bevel) region of the polishing object 102. When the eddy current sensor 210 during measurement approaches the end 128 of the polishing object 102, a part of the magnetic flux from the eddy current sensor is no longer interlinked with the polishing object 102, so that the outer shape of the measurement range becomes smaller or the shape of the measurement range changes compared to before approaching the end 128. Therefore, the output from the eddy current sensor 210 is less likely to be stable. According to one embodiment of the present invention, the measurement accuracy is improved near the end.

[0044] The film thickness signal processing device 230 according to an embodiment of the present invention includes a receiving unit 232 and a correcting unit 238. The receiving unit 232 receives sensor data output from an 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 and second film thickness data generated by the receiving unit 232.

[0045] The correction method of the correction unit 238 will be described with reference to Figs. 6, 7 and 8. Fig. 6(a) is a diagram showing the state in which the eddy current sensor 210 arranged on the polishing table 110 rotates with the rotation of the polishing table 110. An arrow 136 indicates the rotation direction of the polishing table 110. Fig. 6(b) is a diagram showing an enlarged view of the range 134 shown in Fig. 6(a). In Fig. 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 in the vicinity of 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. A plurality of eddy current sensors 210 are displayed in order to indicate the position of each measurement point of the eddy current sensor 210.

[0046] FIG. 7 shows a trajectory 144 on the object to be polished 102 when the eddy current sensor 210 passes over the surface of the object to be polished 102. In this figure, three trajectories 144 are shown as an example. In an actual measurement, the number of trajectories 144 is more than three and is distributed over the entire object to be polished 102. The position and number of trajectories can be set arbitrarily. The arrow on the trajectory 144 indicates the movement direction of the eddy current sensor 210. In this figure, the trajectory 144 passes through the center Cw of the object to be polished 102. The trajectory 144 does not have to pass through the center Cw. There are measurement points such as a first measurement point 146 and a second measurement point 148 on the trajectory 144.

[0047] The correction unit 238 obtains the third film thickness data 164 or the fourth film thickness data 166 corrected based on the size of the measurement range 150 on the object to be polished 102 to be measured in one measurement of the eddy current sensor 210, the first film thickness data 168 measured at the first measurement point 146 on the object to be polished, and the second film thickness data 172 measured at the second measurement point 148 on the object to be polished, as shown in Fig. 8. The distance between the first measurement point 146 and the second measurement point 148 is equal to or less than the outer size 130 of the measurement range 150. Here, one measurement means the measurement at each of the first measurement point 146, the second measurement point 148, etc. on one trajectory 144 shown in Fig. 7. Details of Fig. 8 will be described later.

[0048] In Fig. 7, after a measurement is performed at the first measurement point 146, the next measurement is performed at the second measurement point 148. That is, in the first measurement after the first film thickness data is measured, the second film thickness data is measured. For example, the nth measurement is performed at the first measurement point 146, the n+1th measurement is performed at the second measurement point 148, and so on. A measurement of the eye is taken at the second measurement point 148. The first measurement point 146 and the second measurement point 148 do not have to be consecutive measurement points, and there may be other measurement points between the first measurement point 146 and the second measurement point 148.

[0049] Here, the measurement range 150 of the eddy current sensor 210 is the measurement range on the polishing object 102 where induced eddy currents exist in the case of an eddy current sensor, and is the light irradiation range on the polishing object 102 in the case of an optical sensor. In the case of an eddy current sensor, the measurement range depends on the shape of the core and the shape of the coil (winding method, arrangement, number of turns, etc.). The eddy current sensor 210 shown in FIG. 2 is a pot core 60. In the case of FIG. 2, the outer shape of the measurement range 150 is circular. The outer size of the measurement range 150 (in the case of a circle, the diameter of the circle) is almost the same as the outer shape of the pot core 60, but is slightly larger than the outer shape of the pot core 60. The size 130 of the measurement range 150 may be smaller than the outer shape of the pot core 60. When the core is an E-shaped core, the measurement range is elliptical. An example of how to determine the outer size of the measurement range 150, including the case of an ellipse, will be described later. In the case of an optical sensor, the outer size of the measurement range may be larger or smaller than the outer diameter (diameter of the circle) of the optical fiber that irradiates the light.

[0050] 7, a first distance 152 from the first measurement point 146 to the center Cw of the object to be polished 102 is different from a second distance 154 from the second measurement point 148 to the center Cw of the object to be polished 102. The second distance 154 is greater than the first distance 152. In other words, the second measurement point 148 is closer to the end 128 of the object to be polished 102 than the first measurement point 146.

[0051] The correction unit obtains one of third film thickness data 164 and fourth film thickness data 166 corresponding to a third measurement point 158 ​​and a fourth measurement point 162 that are separated by a distance of the size 130 of the measurement range 150 on the polishing object 102 as shown in Fig. 8, 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.

[0052] A method for obtaining the fourth film thickness data 166 will be described with reference to FIG. 8. FIG. 8 is a diagram for explaining a method for obtaining the fourth film thickness data 166. The horizontal axis in FIG. 8 is the distance (unit: mm) from the center of the circular object to be polished 102. However, this is the film thickness distribution only in the vicinity of the end 128. The center of the object to be polished 102 is to the left of the left end of the figure. The vertical axis is the film thickness (unit: angstroms). However, in order to show in detail the change in film thickness in the vicinity of the maximum film thickness of the object to be polished 102, the vertical axis in the region where the film thickness is small (i.e., the end) is not shown so that the vertical axis includes the maximum film thickness. In other words, the minimum value of the vertical axis shown in FIG. 8 is greater than 0 angstroms.

[0053] As shown in Figure 8, 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 external size 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.

[0054] If the midpoint between the first measurement point 146 and the second measurement point 148 is defined as position R, the third measurement point 158 ​​is a position that is half the distance S away from position R in the direction of the center Cw. The fourth measurement point 162 is a position that is half the distance S away from position R in the direction of the end 128. The thickness data of 168 is Tmoni(R-MI / 2), The second film thickness data 172 is Tmoni(R+MI / 2), The third film thickness data 164 is TAct(RS / 2), The fourth film thickness data 166 is set to TAct(R+S / 2). Furthermore, the average value of the film thickness data in the measurement range 150 by the eddy current sensor 210 is set to Tooverlapped. The average value Tooverlapped of the film thickness data is considered to be substantially the same in the range where the range of the arrow 174 and the range of the arrow 176 overlap. First film thickness data 168 = {Average film thickness data Tooverlapped × (Outer size - (Distance MI between measurement point 146 and second measurement point 148)) + Third film thickness data 164 × (Distance MI between first measurement point 146 and second measurement point 148)} / Outer size (1) That is, the first film thickness data 168 is considered to be the weighted average of the film thickness data average value Tooverlapped and the third film thickness data 164, weighted by the length (S-MI) and the length (MI). If we express formula (1) using only the symbols already mentioned, we get Tmoni (R-MI / 2) = {Toverlapped×(S-MI) + TAct(RS / 2) ×MI} / S (2) It becomes.

[0055] Similarly, the second film thickness data 172 Second film thickness data 172 = {Average film thickness data Tooverlapped × (Outer size - (Distance MI between the first measurement point 146 and the second measurement point 148)) + Fourth film thickness data 166 × (Distance MI between the measurement point 146 and the second measurement point 148)} / Outer size (3) That is, the second film thickness data 172 is considered to be the weighted average of the film thickness data average value Tooverlapped and the fourth film thickness data 166, weighted by the length (S-MI) and the length (MI). If we express equation (3) using only the symbols already mentioned, we get Tmoni(R+MI / 2) = {Toverlapped×(S-MI) + TAct(R+S / 2)×MI} / S (4)

[0056] Subtracting equation (2) from equation (4) and multiplying both sides by (S / MI), we get TAct(R+S / 2) - TAct(RS / 2) = (Tmoni (R+MI / 2) - Tmoni (R-MI / 2))× (S / MI) (5) That is, fourth film thickness data 166 can be obtained from first film thickness data 168 and second film thickness data 172. The obtained fourth film thickness data 166 is film thickness distribution 178. Comparing film thickness distribution 178 with film thickness distribution 126 corrected by the conventional technique shown in FIG. 4, it can be seen that it has been significantly improved and is closer to actual film thickness distribution 122.

[0057] Equation (5) is an equation that expresses the difference between the third film thickness data 164 and the fourth film thickness data 166. Therefore, as described later, when starting correction using equation (5), it is necessary to specify the third film thickness data 164 as an initial value. The method of setting the initial value will be described later. According to equation (5), the film thickness difference between two points separated by a distance S is obtained from the difference in the monitor value between consecutive measurement points. The conventional measurement values ​​are the first film thickness data 168 and the second film thickness data 172, which are considered to be the average film thickness over the entire measurement range 150. In other words, the spatial resolution of the conventional film thickness measurement is the distance S (the size of the entire measurement range 150). On the other hand, according to equation (5), the film thickness in the section of the distance MI can be obtained. Therefore, the measurement spatial resolution can be improved from S to MI.

[0058] In addition, in formula (5), the first film thickness data 168 and the second film thickness data 172 are adjacent measurement values, but in formula (5), measurement values ​​that are not adjacent may be used. In addition, although the expressions "third measurement point 158" and "fourth measurement point 162" are used, the third measurement point 158 ​​and the fourth measurement point 162 do not mean that they are positions where the eddy current sensor 210 actually performs measurements. The third measurement point 158 ​​and the fourth measurement point 162 mean that they are positions where film thickness data is measured by correction.

[0059] When starting correction using equation (5), the third film thickness data 164 is specified as the initial value. It is necessary. A method for setting the initial value will be described. The first film thickness data 168 at the point where the correction starts can be set as the initial value of the third film thickness data 164. The point where the correction starts can be selected by various methods as follows. The correction starts when the amount of change with respect to time of the first film thickness data 168 or the second film thickness data 172 exceeds a predetermined value, and is performed for a predetermined period thereafter. The predetermined period is, for example, until the end 128 is reached. Alternatively, the correction is performed when the amount of change with respect to the position of the first film thickness data 168 or the second film thickness data 172 exceeds a predetermined value.

[0060] Such an increase in the amount of change often occurs near the end 128. Therefore, it is preferable that the correction is performed only near the end 128 of the object to be polished 102, and 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 at a predetermined distance from the end can be selected based on past actual measurements or prior test data. Furthermore, the correction may be performed when the end 128 of the object to be polished 102 is within the measurement range 150 of the eddy current sensor 210.

[0061] FIG. 9 shows an example in which a range at a predetermined distance from the end is selected as the vicinity based on past actual measurements or prior test data. The horizontal axis of the figure is the distance (unit: mm) from the center of the circular polishing object 102. The vertical axis is the film thickness (unit: angstroms). This figure displays an actual film thickness distribution 122, a film thickness distribution 124 measured by the eddy current sensor 210, and a film thickness distribution 178 shown in FIG. 8 obtained by correction according to an embodiment of the present application. The actual film thickness distribution 122 is measured by a more accurate film thickness measuring device different from the eddy current sensor 210. FIG. 9 shows a position 180 where correction is started. The correction according to an embodiment of the present application is performed in the area indicated by the arrow 182 from the position 180 to the end 128. The range to be corrected is specified in advance, and correction is performed from the inside of the polishing object 102 toward the end 128.

[0062] The correction method will be described with reference to the flowchart of FIG. 10. In FIG. 10, a case will be described in which measurement and correction are performed from the center Cw of the object to be polished 102 toward the end 128. The correction may be performed on the film thickness data obtained from the end 128 toward the center Cw. For example, after the eddy current sensor 210 passes under the object to be polished 102 (one scan), before the next scan, the correction may be applied sequentially from the inside of the object to be polished 102 toward the end 128 in the film thickness data showing the obtained film thickness distribution. In this way, the film thickness data obtained from the end 128 toward the center Cw of the object to be polished 102 can also be corrected. In this embodiment, the order of applying the correction on the film thickness data is from the center Cw to the end 128. That is, the film thickness data at the outer measurement point of the object to be polished 102 is corrected using the film thickness data at the inner measurement point. In the correction method of the present invention, the order of applying the correction to the film thickness data may be from the end 128 toward the center Cw in a location other than the vicinity of the end 128. 7. A consecutive number is assigned in advance to each measurement point of the trajectory 144 shown in FIG. 7 from when the eddy current sensor 210 enters the workpiece 102 at the end 128 until when the eddy current sensor 210 exits the workpiece 102 at the end 128. The number of the center Cw is Ncenter. Correction starts from the center Cw (S10).

[0063] First, in data initialization (S12), the measurement value (Tmoni) obtained at the center Cw is entered into TAct(RS / 2) to initialize the value of TAct(RS / 2) described above. In other words, TAct=Tmoni is set. The operation of setting TAct=Tmoni is performed in S22, which will be described later, until the correction area is entered and a measurement point is reached where TAct(R+S / 2) is calculated according to equation (5). After TAct(R+S / 2) has reached the measurement point obtained by calculation, TAct has been obtained by calculation, so there is no need to set TAct=Tmoni. Note that the position where TAct(RS / 2) is set is separated by S / 2-MI / 2 from the measurement point where Tmoni(R-MI / 2) is measured, as shown in FIG. 8. Tmoni does not necessarily exist exactly at the position where TAct(RS / 2) is set. If it does not exist, the closest Tmoni is used. Good.

[0064] Ncenter is entered into the counter n indicating the position of the measurement point (S14). Next, the value of the counter n is judged to determine whether or not the measurement point is within the correction area indicated by the arrow 182 in FIG. 9 (S16). A number ns indicating the position 180 where the correction starts is set in advance, and when the value of the counter n is equal to or greater than the number ns, it is judged to be within the correction area (Y in S16). When the value of the counter n is less than the number ns, it is judged not to be within the correction area (N in S16). When the measurement point is within the correction area, TAct(R+S / 2) is calculated according to the formula (5) and correction is performed (S18). Next, the value of the counter n is judged to determine whether or not n=Nedge indicating the end 128 in FIG. 9 is reached (Y) (S20). When the measurement point is reached (N), the correction is terminated (S24). When the measurement point is not reached (N), the value of the counter n indicating the position of the measurement point is incremented by 1, and the film thickness is measured (S22). Then, proceed to S16. In S16, if it is determined that the value of the counter n is less than the number ns and the area is not within the correction area (N in S16), the process proceeds to S20.

[0065] Next, a method for setting the outer size 130 (i.e., distance S) of the measurement range 150 will be described with reference to Figs. 11 to 13. The measurement range 150 (the range in which the eddy current sensor 210 responds) varies depending on the distance 184 (see Figs. 11(a) and 12(a)) between the eddy current sensor 210 and the object 102 to be polished. As 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 of the eddy current sensor 210 and the measurement range 150 when the distance 184 is narrow. Fig. 12(b) shows the sensitivity of the eddy current sensor 210 and the measurement range 151 when the distance 184 is wide. The horizontal axis in Figs. 11(b) and 12(b) indicates the radial position (unit: mm) from the center 186 of the eddy current sensor 210. 11(b) and 12(b) indicate sensitivity (in mv) at each position in the radial direction from the center 186 of the eddy current sensor 210. The sensitivity is the magnitude of the output of the eddy current sensor 210.

[0066] 11(b) and 12(b), it can be seen that even if the eddy current sensor 210 is the same, the appropriate outer size 130 differs depending on the thickness of the polishing pad 108 used. For this reason, the value of the outer size 130 is determined by adjusting the value of the outer size 130 so that the corrected film thickness distribution 178 matches the film thickness distribution 122 measured by a film thickness measuring device that is more accurate than the eddy current sensor 210. The determined outer size 130 is used in equation (5). Figure 13 shows the film thickness distribution 178 when the outer size 130 is changed.

[0067] The horizontal axis of each diagram in FIG. 13 is the distance (in mm) from the center of the circular object to be polished 102. The vertical axis is the film thickness (in angstroms). However, in order to show in detail the change in film thickness in the vicinity of the maximum film thickness of the object to be polished 102, the film thickness in the region where the film thickness is small (i.e., the end) is not shown so that the vertical axis includes the maximum film thickness. That is, the minimum value of the vertical axis shown in FIG. 13 is greater than 0 angstroms. The film thickness at the end is not shown, but is 0 angstroms because there is no metal film outside the end. For comparison, FIG. 13 also shows a film thickness distribution 124 before correction and a film thickness distribution 122 measured by a film thickness measuring device.

[0068] In the case of FIG. 13(b) showing the film thickness distribution 178 after correction when an appropriate outer size 130 is used, the film thickness distribution 178 and the film thickness distribution 122 are most consistent. The outer size 130 used in FIG. 13(a) is smaller than the outer size 130 used in FIG. 13(b). The outer size 130 used in FIG. 13(c) is larger than the outer size 130 used in FIG. 13(b). The results of FIGS. 11 to 13 can be summarized as follows. The outer size 130 when the distance 184 between the object to be polished 102 and the eddy current sensor 210 is the first length shown in FIG. 12(a) is defined as the first size. The outer size 130 when the distance 184 between the object to be polished 102 and the eddy current sensor 210 is the second length shown in FIG. 11(a) is defined as the second size. At this time, The first size is greater than the second size if the first length is greater than the second length.

[0069] When the outer shape of the eddy current sensor 210 is a circle, the size 130 can be determined by the method shown in FIG. 13 using the diameter of the outer shape as the initial value of the size 130. A method for determining the size of the outer shape of the measurement range 150 when the outer shape of the eddy current sensor 210 is not a circle will be described. When the outer shape of the eddy current sensor 210 is a square or a rectangle, the measurement range 150 is different from a circle. When the outer shape of the measurement range 150 is considered to be an ellipse, for example, the length of the short axis and the long axis of the ellipse are included, and the degree of agreement with the film thickness distribution measured by a film thickness measuring device is examined as shown in FIG. 13. The length when the degree of agreement is good is set as the size 130.

[0070] When the outer shape of the measurement range 150 is different from a circle or an ellipse, for example, the length from front to back of the lengthwise and horizontal lengths, including the lengthwise direction of the outer shape and the length in the horizontal direction perpendicular to the lengthwise direction, is taken as size 130, and the degree of agreement with the film thickness distribution measured by a film thickness measuring instrument is examined as shown in Fig. 13. The length when the degree of agreement is good is taken as size 130. Size 130 can also be determined by estimating from sizes 130 used in the past for similar shapes.

[0071] Next, a method for processing a film thickness signal will be described. In the method for processing a film thickness signal using a polishing apparatus having an eddy current sensor, a receiving unit, and a correcting unit, the receiving unit 232 receives sensor data output from an eddy current sensor 210 for detecting the film thickness of the polishing object 102, and generates first film thickness data 168 and second film thickness data 172. The correcting unit 238 corrects the first film thickness data 168 and second film thickness data 172 generated by the receiving unit 232. The correcting unit 238 obtains the third film thickness data 164 or the fourth film thickness data 166 corrected based on the size 130 of the measurement range 150 to be measured 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 102, 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 equal to or less than the outer size 130 of the measurement range 150 .

[0072] The polishing apparatus 100 includes a polishing apparatus control unit 140 that controls the overall operation of the polishing apparatus 100. The polishing apparatus control unit 140 and the film thickness signal processing device 230 include a CPU, a memory, a storage medium, and the like. The polishing apparatus control unit 140 and the film thickness signal processing device 230 may be configured as a microcomputer that realizes a desired function (such as a correction function) using software (programs) such as a polishing recipe and / or information on machine parameters of related devices that have been input in advance, or may be configured as a hardware circuit that performs dedicated arithmetic processing. The polishing apparatus control unit 140 and the film thickness signal processing device 230 may be configured as a combination of a microcomputer and a hardware circuit that performs dedicated arithmetic processing.

[0073] Although the above describes examples of the embodiments of the present invention, the above-described embodiments of the present invention are intended to facilitate understanding of the present invention and do not limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention naturally includes equivalents thereof. Furthermore, any combination or omission of each component described in the claims and specification is possible within the scope of solving at least a part of the above-mentioned problems or achieving at least a part of the effects. [Explanation of symbols]

[0074] 100...Polishing equipment 102...Polished object 108...Polishing pad 110…Polishing table 112...first electric motor 122, 124, 126...Film thickness distribution 128...End 130…Size 144…Trajectory 146…First measurement point 148…Second measurement point 150…Measuring range 152…First distance 154…Second Distance 158…Third measurement point 162…4th measurement point 164...Third film thickness data 166...Fourth film thickness data 168...First film thickness data 172...Second film thickness data 210...Eddy current sensor 230...Thickness signal processing device 232…Receiver 238…Correction section

Claims

1. a receiving unit that receives sensor data output from a film thickness sensor for detecting a film thickness of an object to be polished and generates first and second film thickness data; a correction unit that corrects the first and second film thickness data generated by the receiving unit, the correction unit determines corrected film thickness data based on a size of a measurement range on the object to be polished that is a measurement target in one measurement by the film thickness sensor, the first film thickness data measured at a first measurement point on the object to be polished, and the second film thickness data measured at a second measurement point on the object to be polished; 4. A film thickness signal processing device, wherein a distance between the first measurement point and the second measurement point is equal to or smaller than a size of the measurement range.

2. 2. The film thickness signal processing device according to claim 1, wherein a first distance from said first measurement point to the center of said object to be polished is different from a second distance from said second measurement point to said center of said object to be polished.

3. 3. The film thickness signal processing apparatus according to claim 1, wherein the second film thickness data is measured in the first measurement after the first film thickness data is measured.

4. 3. The film thickness signal processing device according to claim 1, wherein the correction unit determines at least one of third film thickness data and fourth film thickness data corresponding to a third measurement point and a fourth measurement point that are separated by a distance of the size on the polishing object, as the film thickness data corrected based on the first film thickness data and the second film thickness data.

5. 6. The film thickness signal processing apparatus according to claim 5, wherein the difference between said third film thickness data and said fourth film thickness data is proportional to the difference between said first film thickness data and said second film thickness data.

6. 3. The film thickness signal processing apparatus according to claim 1, wherein the correction is performed when the amount of change with respect to time of the first or second film thickness data exceeds a predetermined value.

7. 3. The film thickness signal processing apparatus according to claim 1, wherein the correction is performed when a change amount with respect to the position of the first or second film thickness data exceeds a predetermined value.

8. 3. The film thickness signal processing apparatus according to claim 1, wherein the correction is performed based on the first and second film thickness data measured in the vicinity of an edge of the object to be polished.

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

10. 3. The film thickness signal processing device according to claim 1, wherein the size when the distance between the object to be polished and the film thickness sensor is a first length is defined as a first size, and the size when the distance between the object to be polished and the film thickness sensor is a second length is defined as a second size, and when the first length is longer than the second length, the first size is larger than the second size.

11. a polishing table to which a polishing pad for polishing the object to be polished can be attached; a drive unit capable of rotating the polishing table; a holding part capable of holding the object to be polished and pressing it against the polishing pad; The polishing table is rotated to rotate the polishing member. The film thickness sensor is capable of detecting a film thickness of an object; 3. A polishing apparatus comprising the film thickness signal processing device according to claim 1.

12. A film thickness signal processing method using a polishing apparatus having a film thickness sensor, a receiving unit, and a correction unit, comprising: receiving, by the receiving unit, sensor data output from the film thickness sensor for detecting a film thickness of the object to be polished, and generating first and second film thickness data; The correction unit corrects the first and second film thickness data generated by the receiving unit; the correction unit determines corrected film thickness data based on a size of a measurement range to be measured 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; 4. The method for processing a film thickness signal, wherein the distance between the first measurement point and the second measurement point is equal to or smaller than the size of the measurement range.

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