Grinding device and grinding method

Abstract

The present application provides a kind of grinding device and grinding method of the determination precision of the grinding process carried out condition is improved.The grinding device (100) is pressed in the grinding pad (108) and carries out the grinding of the grinding object (102).Eddy current sensor (210) determines the impedance that can change according to the film thickness variation of grinding object (102) at multiple positions of grinding object (102), and outputs measurement signal.Difference calculation unit (222) generates data corresponding to film thickness based on measurement signal.Furthermore, difference calculation unit (222) in the center (C W ) of grinding object (102), the difference between data at different time is calculated based on the measurement signal output by eddy current sensor (210) at different time.End point detection unit (221) detects grinding end point indicating grinding end based on the difference calculated by difference calculation unit (222).

Description

Technical Field

[0001] This invention relates to a grinding apparatus and a grinding method, and particularly to the detection of the grinding endpoint. Background Technology

[0002] In recent years, with the increasing integration and density of semiconductor components, circuit wiring has become increasingly finer, and the number of layers in multilayer wiring has also increased. In order to achieve circuit miniaturization and multilayer wiring, precise planarization processing is required on the surface of semiconductor components.

[0003] Chemical mechanical polishing (CMP) is a well-known technique for planarizing the surface of semiconductor components. A polishing apparatus for CMP includes: a polishing table with an polishing pad attached; and a top ring for holding the object to be polished (e.g., a substrate such as a semiconductor wafer, or various films such as metal films or barrier films formed on the substrate surface). The polishing apparatus rotates the polishing table, supplies polishing slurry (paste) to the polishing pad, and polishes the object to be polished by pressing it against the polishing pad while it is held in the top ring.

[0004] In order to grind an object to a desired thickness, a grinding apparatus typically determines the grinding endpoint. For example, conventional technology uses eddy current thickness sensors to detect the thickness of the conductive film. However, it is difficult to immediately end the grinding process at the point when the target thickness is reached. This is because there is a detection delay when detecting the film thickness, and a certain amount of time is required to actually stop grinding the conductive film. Therefore, in the past, during the grinding process, the grinding speed was calculated, and a provisional endpoint film thickness was calculated from the grinding speed, which is the target thickness at which grinding should actually stop, plus a predetermined bias value. After detecting this provisional endpoint film thickness, the conductive film was ground for a predetermined grinding time.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-076449

[0008] The problem the invention aims to solve

[0009] However, conventional techniques suffer from insufficient accuracy in measuring the progress of the grinding process. For example, when aiming only to correctly remove the metal film, the method of calculating the provisional endpoint film thickness from the grinding speed lacks accuracy. That is, conventional techniques introduce detection delays when measuring film thickness, resulting in insufficient accuracy and causing problems when aiming for complete metal film removal. Insufficient metal film removal can lead to electrical short circuits, and excessive grinding to prevent short circuits can over-grind the insulating film beneath the metal film. One aspect of the present invention aims to solve this problem by providing a grinding apparatus and grinding method that improves the accuracy of measuring the progress of the grinding process. Summary of the Invention

[0010] Problem-solving methods

[0011] To solve the above problems, the first approach is to employ a grinding device structure. This grinding device rotates a grinding table supporting a grinding pad for grinding the object while pressing the object onto the grinding pad to grind it. The grinding device includes: a sensor that measures a physical quantity that changes according to the film thickness of the object being ground and outputs a measurement signal; a difference calculation unit that generates data corresponding to the film thickness based on the measurement signal, and calculates the difference between the data at different times based on the measurement signal output by the sensor at a predetermined position on the object being ground; and an endpoint detection unit that detects the grinding endpoint indicating the end of the grinding process based on the difference calculated by the difference calculation unit.

[0012] One reason for detection delays in the past when measuring film thickness was the time-shifting averaging of the sensor output measurement signal. The rationale for time-shifting averaging is to reduce the impact of outliers when they occur in the sensor output measurement signal. In this embodiment, the difference calculation unit does not perform time-shifting averaging of the sensor output measurement signal. Instead, the difference calculation unit calculates the difference between the sensor output measurement signals at different times at a predetermined position on the object being ground. Therefore, detection delays caused by moving averaging do not occur when measuring film thickness. A grinding apparatus that improves the accuracy of measuring the progress of the grinding process can be provided.

[0013] The second method is to use a structure where the specified position is the center of the object being ground. The third method is to use a structure where the specified position is near the center of the object being ground. Because the film thickness variation is smaller at the center and its vicinity compared to the periphery of the object being ground, the film thickness can be accurately measured. The so-called vicinity of the center of the object being ground can be, for example, (1) the range where the grinding profile is stable; or (2) the range of overall averaging within the sensor's spot diameter. The range where the grinding profile is stable is the actual flat range where the grinding surface does not produce unevenness during grinding. This range depends on the grinding conditions (i.e., the material of the object being ground, the grinding time, the pressure distribution during grinding, etc.). The range of overall averaging within the sensor's spot diameter is the range where the unevenness of the grinding surface cannot be detected within a range smaller than a certain size due to the constraint of the sensor's spot diameter, but the average grinding state can be detected.

[0014] The fourth method employs a structure where the different times differ to a degree that the grinding table takes to rotate one or more times. When the time required for one or more rotations of the grinding table differs, the same position on the object being ground can be measured. Because the film thickness does not change due to different positions when measured at the same position on the object being ground, the film thickness can be accurately measured.

[0015] The fifth approach employs a structure with multiple sensors. In this case, multiple measurements can be taken at a predetermined position on the object being ground as the grinding table rotates one revolution. Therefore, the different times can be set to be shorter than the time required for the grinding table to rotate one revolution.

[0016] The sixth method is to use a structure where the specified positions are different from multiple positions. The seventh method is to use a structure where the endpoint detection unit averages the multiple differences calculated by the difference calculation unit to detect the grinding endpoint.

[0017] The eighth method employs a grinding method, characterized in that: while rotating a grinding table supporting a grinding pad for grinding the object, the object is pressed onto the grinding pad for grinding, grinding is performed, a physical quantity that changes according to the film thickness of the object is measured, a measurement signal is output, and data corresponding to the film thickness is generated based on the measurement signal. At a predetermined position on the object, based on the measurement signals output at different times, the difference between the data at the different times is calculated, and based on the calculated difference, a grinding endpoint indicating the end of grinding is detected. Attached Figure Description

[0018] Figure 1It is a diagram that schematically represents the overall structure of the grinding apparatus.

[0019] Figure 2 This is a diagram showing the structure of an eddy current sensor.

[0020] Figure 3 This is a schematic diagram showing an example of the structure of a sensor coil used in an eddy current sensor.

[0021] Figure 4 This is an explanatory diagram of the output of a comparative example used for comparison with one embodiment of the present invention.

[0022] Figure 5 This is an explanatory diagram of the output of one embodiment of the present invention.

[0023] Symbol Explanation

[0024] 100 Grinding device

[0025] 102 Grinding Object

[0026] 108 Grinding Pad

[0027] 110 Grinding Table

[0028] 112 First Electric Motor

[0029] 116 Top Ring

[0030] 118 Second Electric Motor

[0031] 120 Grouting Pipeline

[0032] 140 Grinding Unit Control Section

[0033] 160 Rotary Joint Connector

[0034] 210 Eddy Current Sensor

[0035] 222 Difference Calculation Section

[0036] 224 Endpoint Testing Department Detailed Implementation

[0037] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the various embodiments described below, the same or equivalent components are labeled with the same symbols and repeated descriptions are omitted.

[0038] like Figure 1As shown, the polishing apparatus 100 includes: a polishing table 110 on its upper surface on which a polishing pad 108 for polishing a polishing object (such as a substrate, semiconductor wafer, or various films such as metal films or barrier metals formed on the surface of the substrate) 102 can be mounted; a first electric motor 112 for rotating and driving the polishing table 110; a top ring 116 for holding the polishing object 102; and a second electric motor 118 for rotating and driving the top ring 116.

[0039] Furthermore, the grinding apparatus 100 includes a slurry line 120 that supplies grinding fluid containing abrasive particles (grinding agent) to the upper surface of the grinding pad 108. The grinding apparatus 100 rotates the grinding table 110, which supports the grinding pad 108 for grinding the object 102, and presses the object 102 onto the grinding pad 108 to grind the object 102. The grinding apparatus 100 includes a grinding apparatus control unit 140 that outputs various control signals regarding the grinding apparatus 100.

[0040] When the grinding apparatus 100 grinds the workpiece 102, a grinding slurry containing abrasive particles is supplied from the slurry line 120 to the upper surface of the grinding pad 108, and the grinding table 110 is rotated by the first electric motor 112. Then, while the grinding apparatus 100 rotates the top ring 116 around a rotation axis eccentric to the rotation axis of the grinding table 110, the workpiece 102 held in the top ring 116 is pressed against the grinding pad 108. Thus, the workpiece 102 is flattened by grinding with the grinding pad 108 holding the grinding slurry.

[0041] like Figure 1 As shown, the polishing apparatus 100 includes: an eddy current sensor 210 serving as a sensor; and a difference calculation unit 222 and an endpoint detection unit 224 connected to the eddy current sensor 210 via rotary joint connectors 160 and 170. The eddy current sensor 210 measures physical quantities that vary depending on the film thickness of the polished object at multiple locations and outputs measurement signals. In this embodiment, the physical quantities are the resistance and inductance of the polished object 102. Furthermore, this embodiment illustrates an example using the eddy current sensor 210, but it is not limited to this; an optical sensor utilizing light reflection could also be used.

[0042] The difference calculation unit 222 generates data corresponding to the film thickness based on the measurement signal at the center (predetermined position) of the workpiece 102 being ground. For the measurement signal, the difference calculation unit 222 calculates the difference between data at different times based on the measurement signals output by the eddy current sensor 210 at different times at the predetermined position of the workpiece 102 being ground. In this embodiment, the difference calculation unit 222 does not perform the moving average method described later on the measurement signal. The endpoint detection unit 224 detects the grinding endpoint, indicating the end of grinding, based on the difference calculated by the difference calculation unit 222. In this embodiment, the predetermined position is the center of the workpiece 102 being ground.

[0043] Furthermore, the designated location is not limited to the center of the object being ground 102, but may also be near the center of the object being ground 102. Additionally, the designated location is not limited to one point, but may be multiple points. When there are multiple designated locations, the endpoint detection unit 224 averages the multiple differences calculated by the difference calculation unit 222 to detect the grinding endpoint. Alternatively, the difference calculation unit 222 may calculate the difference between the average values ​​after averaging the measurement signals output by the eddy current sensor 210. The endpoint detection unit 224 detects the grinding endpoint based on the differences calculated by the difference calculation unit 222. In this embodiment, the different times are different to the extent that the grinding table 110 takes one revolution. The different times may also be different to the extent that the grinding table 110 takes multiple revolutions.

[0044] First, the eddy current sensor 210 will be described. A hole is formed in the grinding table 110 so that the eddy current sensor 210 can be inserted from the back side of the grinding table 110. The eddy current sensor 210 is then inserted into the hole formed in the grinding table 110.

[0045] Eddy current sensor 210 is disposed at the center C of the grinding object 102 held in the top ring 116 during grinding. W The position of the symbol C. T It is the rotation center of the grinding table 110.

[0046] Grinding object 102 with center C W It rotates around an axis. Additionally, as the grinding table 110 rotates, the eddy current sensor 210 rotates around its center C. T The grinding table 110 rotates around a center of rotation. As a result, the grinding process of grinding the object 102 includes a first state where the eddy current sensor 210 does not pass under the object 102 and is not opposite to it. Furthermore, the grinding process includes a second state where the eddy current sensor 210 passes under the object 102 and is opposite to it. The first and second states alternate as the grinding table 110 rotates.

[0047] In addition, the polishing slurry is supplied to the polishing pad 108 and moves toward the outside of the polishing pad 108 due to the centrifugal force of the rotation of the polishing table 110, and rotates as the polishing table 110 rotates.

[0048] Figure 2 This is a structural diagram showing the eddy current sensor 210. Figure 2 (a) is a block diagram showing the structure of the eddy current sensor 210, while Figure 2 (b) is the equivalent circuit diagram of the eddy current sensor 210.

[0049] like Figure 2 As shown in (a), the eddy current sensor 210 includes a sensor coil 260 disposed near a polished object 102, such as a metal film, to be detected. The sensor coil 260 is connected to an AC signal source 262. Here, the polished object 102 to be detected is, for example, a thin film of copper (Cu), aluminum (Al), gold (Au), tungsten (W), etc., formed on a semiconductor wafer. The sensor coil 260 is disposed, for example, at a distance of about 0.5 to 5.0 mm relative to the polished object 102 to be detected.

[0050] Eddy current sensor 210 has a frequency-based type that detects the conductive film based on the change in the oscillation frequency of AC signal source 262 caused by eddy currents generated by the abrasive object 102. Furthermore, eddy current sensor 210 also has an impedance-based type that detects the conductive film based on the change in impedance observed from AC signal source 262 caused by eddy currents generated by the abrasive object 102. That is, the frequency-based type... Figure 2 In the equivalent circuit shown in (b), the impedance Z changes due to the change in eddy current I2, resulting in a change in the oscillation frequency of the AC signal source (variable frequency oscillator) 262. The eddy current sensor 210 detects this change in oscillation frequency by the detection circuit 264, thus detecting the change in the conductive film. Impedance type... Figure 2 In the equivalent circuit shown in (b), the impedance Z changes due to the change in eddy current I2, resulting in the impedance Z change observed from the AC signal source (fixed-frequency oscillator) 262. The eddy current sensor 210 detects this impedance Z change by the detection circuit 264, and can detect the change in the conductive film.

[0051] Impedance-type eddy current sensors extract the real and imaginary parts of the impedance Z, i.e., the signal outputs X and Y, the phase of impedance Z, and the absolute value of impedance Z. Measurement information of the conductive film is obtained from the frequency F or the signal outputs X and Y. Eddy current sensor 210, for example... Figure 1 As shown, it can be installed inside the grinding table 110 near the surface. When the eddy current sensor 210 is positioned opposite the grinding object 102 via the grinding pad, it can detect changes in the conductive film from the eddy current flowing into the grinding object 102.

[0052] The impedance-type eddy current sensor will now be described in detail. The AC signal source 262 is a fixed-frequency oscillator in the range of 1 to 50 MHz, such as a crystal oscillator. A current I1 flows into the sensor coil 260 through the AC voltage supplied by the AC signal source 262. As the current flows into the sensor coil 260, which is positioned near the object to be ground 102, the magnetic flux generated from the sensor coil 260 links with the object to be ground 102. As a result, an inductance M is formed between the sensor coil 260 and the object to be ground 102, and an eddy current I2 flows into the object to be ground 102. Here, R1 is the primary resistance of the sensor coil 260, and L1 is also the primary inductance of the sensor coil 260. On the object to be ground 102 side, R2 is the resistance corresponding to the eddy current loss, and L2 is the inductance of the object to be ground 102. Viewed from terminals a and b of the AC signal source 262, the impedance Z on the sensor coil 260 side changes due to the influence of the magnetic lines of force generated by the eddy current I2.

[0053] Figure 3 This is a schematic diagram showing an example of the structure of a sensor coil used in an eddy current sensor. For example... Figure 3 As shown, the sensor coil 260 of the eddy current sensor includes three coils 272, 273, and 274 wound around a winding tube 270. Coil 272 is an excitation coil connected to an AC signal source 262. The excitation coil 272 is energized by an AC current supplied from the AC signal source 262, generating eddy currents in the nearby grinding object 102. A detection coil 273 is disposed on the grinding object 102 side of the winding tube 270 to detect the magnetic field generated by the eddy currents formed in the grinding object 102. A balancing coil 274 is disposed on the opposite side of the detection coil 273, sandwiching the excitation coil 272.

[0054] When the object to be ground 102 is near the detection coil 273, the magnetic flux generated by the eddy currents formed in the object to be ground 102 links with the detection coil 273 and the balancing coil 274. At this time, since the detection coil 273 is positioned close to the conductive film, the balance of the induced voltages generated by the two coils 273 and 274 is disrupted, thereby allowing the detection of the linked magnetic flux formed by the eddy currents passing through the conductive film.

[0055] Secondly, through Figure 4 , 5 Explain the detection of the grinding endpoint. Figure 4 This is a diagram showing a comparative example used for comparison with this embodiment. Figure 4 (a) The horizontal axis is time, and the vertical axis is, for example, the absolute value 20 of the impedance of the film thickness obtained from the measurement signal output from the eddy current sensor 210. Figure 4(b) The horizontal axis represents time, and the vertical axis represents the difference between the absolute values ​​of the impedance corresponding to the measurement signal output from the eddy current sensor 210 and the absolute values ​​of the impedance 20. The comparative example is a moving average of the absolute value 20 of the impedance over the period 22 during which the grinding table 110 rotates twice.

[0056] During one rotation of the grinding table 110, there are the first state and the second state. In the first state, no measurement signal of the object being ground is output from the eddy current sensor 210; only in the second state is a measurement signal from the object being ground output from the eddy current sensor 210. When calculating the moving average, the interpolated data in the first state uses dummy data 24. Dummy data 24 is, for example, the average of the absolute values ​​20 immediately preceding the dummy data 24 in the second state. Therefore, in this comparative example, dummy data 24 is a constant value during one rotation of the grinding table 110, i.e., in the first state during one rotation.

[0057] The second state is that the eddy current sensor 210 outputs multiple measurement signals, for example, 100 measurement signals. During one revolution of the grinding table 110, the length of the first state is several times to about 10 times the length of the second state. Figure 4 In the diagram, for clarity, the multiple absolute values ​​20 in the second state are represented by a single solid circle; however, there are actually 100 absolute values ​​20. Similarly, for clarity, the virtual data 24 in the first state are represented by three dashed circles; however, there are actually hundreds of virtual data 24.

[0058] When calculating the moving average, these absolute values ​​20 are averaged with the dummy data 24 over the entire period 22. Period 22 is the period during which the grinding table 110 rotates twice. Period 22 is... Figure 4 (a) and Figure 4 (b) represents the same length, but the same length is not required. The moving average is calculated from the moment measured by the eddy current sensor 210, using the past absolute value 20 of the length portion of period 22 and virtual data 24. Therefore, within period 22, the diagram shows two solid circles and six dashed circles. Figure 4 As shown in (a), the periods 22 are gradually staggered and averaged. The obtained average value 28 is obtained before reaching the grinding endpoint. Figure 4 In the comparative example, it is on the lower right straight line 30.

[0059] In order to calculate the moving average, a delay time 32 is generated between the time of measurement by the eddy current sensor 210 and the time of obtaining the moving average. The delay time 32 illustrated is the difference between the time 34 when the metal film is completely removed and the time 36 when the process of calculating the moving average using the absolute value 20 measured at time 34 ends.

[0060] Figure 4 (b) represents the difference 38 between the average value 28 obtained from the measurement signal output from the eddy current sensor 210 and the average value 40 obtained by moving the difference 38. The difference 38 is the difference between the average value 28 at a certain time point and the average value 28 during the period when the grinding table 110 rotates one revolution earlier than that time point. The average value 40 is calculated by moving the difference 38 over the entire period 22 of the same length as the period in which the average value 28 was obtained.

[0061] In the comparative example, these processes result in the following detection delay time. Here, the detection delay time is the difference between the actual grinding endpoint time, i.e., time 34, and the time 58 at which the grinding endpoint is detected by obtaining the average value 40 of the difference. The detection delay time includes: the delay time 32 of the moving average processing for calculating the average value 28, the delay time 42 of the difference processing for calculating the difference value 38, the delay time 46 caused by the difference being a portion of the time it takes for the grinding table 110 to rotate one revolution, and the delay time 44 of the moving average processing for calculating the average value 40. The total detection delay time 48, in the comparative example, is equivalent to the period of 3 rotations of the grinding table 110.

[0062] In the comparative example, the reason for using virtual data 24 is that the output data of the eddy current sensor 210 obtained when the grinding table 110 rotates one revolution is small (that is, the length of the first state period is several to about 10 times the length of the second state period), and corrections are made when outliers occur in the output data. When virtual data 24 is added when the grinding table 110 rotates one revolution, as mentioned above, the influence of outliers is reduced by using moving averages when calculating the average value 28 and the average value 40.

[0063] In the comparative example, the amount of film remaining can be detected by the average value 28. Furthermore, whether the average value 40, which is considered a differential value, is "0" can be used to detect whether the metal film has been completely removed, i.e., whether the metal has been removed.

[0064] In cases where the likelihood of outliers in the output data is low due to improved sensor performance and stable processing during the grinding process, or where outliers in the output data have a minor impact, a delay in the moving average is undesirable. In the comparative example, delays occur at two calculation points: a delay of 32 for calculating the moving average of 28 and a delay of 44 for calculating the moving average of 40. Because these delays can lead to over-grinding (disc-like defects, corrosion, etc.), these delays should be minimized. These delays are particularly undesirable in cleaning metals where high precision is required for the remaining film thickness after grinding.

[0065] exist Figure 5In one embodiment of the present invention, the measured value of the eddy current sensor 210 is compared (difference) with the measured value at a certain time point and after the grinding table 110 has rotated one revolution from that time point. If the absolute value of the difference is less than a certain value, it indicates that the metal has been removed. Thus, the endpoint can be detected without performing a moving average.

[0066] Alternatively, instead of performing differential calculations and moving averages, the data obtained from the center of the wafer (or just one point near the center) per revolution of the polishing stage 110 can be averaged, and the polishing endpoint can be detected from the obtained data.

[0067] The following explanation Figure 5 The implementation method shown. Figure 5 (a) The horizontal axis represents time, and the vertical axis represents the absolute value 20 of the impedance corresponding to the film thickness obtained from the measurement signal output from the eddy current sensor 210. Figure 5 (b) The horizontal axis represents time, and the vertical axis represents the difference 54 calculated by subtracting the absolute value of the impedance corresponding to the film thickness obtained from the measurement signal output from the eddy current sensor 210. In this embodiment, no moving average is performed. Only the center data of the object to be ground 102 obtained per revolution of the grinding table 110 is used; that is, only the data obtained at one point on the object to be ground 102 is used, and the removed metal is detected from the obtained data.

[0068] The difference calculation unit 222 generates an absolute value 50 of the impedance corresponding to the film thickness based on the measurement signal output by the eddy current sensor 210. For example... Figure 5 As shown in (a), an absolute value 50 is generated at various different times. These different times differ in the degree to which the time 52 required for the grinding table 110 to rotate one revolution is estimated. The difference calculation unit 222 does not perform a moving average on the absolute value 50, but instead calculates the difference 54 between the data at different times based on the measurement signal output by the eddy current sensor 210. In this embodiment, compared with the comparative example, the delay time 32 and delay time 44 caused by the moving average are not generated. Therefore, the detection accuracy of the grinding endpoint where metal has been removed is improved. This embodiment only generates a delay in the time 52 required for the grinding table 110 to rotate one revolution because the difference is the difference during the rotation of the grinding table 110.

[0069] A further method to shorten the time 52 is to arrange multiple eddy current sensors 210 within the grinding table 110. The multiple eddy current sensors 210 are positioned at the center C of the object being ground 102. W The location. For example, configured in relation to Figure 1 The eddy current sensor 210 shown is about the rotation center C TThe positions are symmetrical. Thus, when two eddy current sensors 210 are arranged inside the grinding table 110, the next measurement signal is obtained when the grinding table 110 rotates half a circle. The difference in this embodiment can be the difference during the half-circle rotation of the grinding table 110. Therefore, the delay time caused by the difference being the difference during the half-circle rotation of the grinding table 110 is... Figure 5 The time 52 shown is halved. Because the delay time is halved, the accuracy of endpoint detection is improved.

[0070] The endpoint detection unit 224 detects the difference 54 calculated by the difference calculation unit 222, corresponding to the grinding endpoint 56 indicating the end of grinding. When the endpoint detection unit 224 detects the grinding endpoint of the grinding object 102, it outputs a signal indicating its endpoint to the grinding apparatus control unit 140. When the grinding apparatus control unit 140 receives the signal indicating the grinding endpoint from the endpoint detection unit 224, it stops the grinding apparatus 100 from grinding.

[0071] The film thickness or equivalent signal of the object to be ground 102 detected by the film thickness sensor can also be transmitted to a higher-level main computer (a computer connected to and managed by multiple semiconductor manufacturing devices) and stored in the main computer. Then, based on the film thickness or equivalent signal of the object to be ground 102 transmitted from the grinding device side, the main computer calculates the difference 54 between data at different times. When the grinding endpoint of the object to be ground 102 is detected based on the difference 54, a signal indicating its significance is transmitted to the grinding device control unit 140.

[0072] The above description illustrates examples of embodiments of the present invention. However, these embodiments are provided for ease of understanding and are not intended to limit the invention. The present invention can be modified and improved without departing from its spirit, and its equivalents are naturally included. Furthermore, the scope of the claims and the components described in the specification may be arbitrarily combined or omitted within the scope of solving at least a portion of the above-mentioned problems or achieving at least a portion of the effects.

Claims

1. An apparatus for polishing, which polishes a polishing object by rotating a polishing table that supports a polishing pad for polishing the polishing object while pressing the polishing object against the polishing pad, characterized by comprising: a sensor that measures a physical quantity that varies in accordance with a film thickness change of the polishing object at a prescribed position of the polishing object and outputs a measurement signal; a difference calculation section that generates data corresponding to the film thickness based on the measurement signal, and calculates a difference between the data at different times based on the measurement signal output at the different times by the sensor while the polishing table is rotating, at the prescribed position of the polishing object; and an end point detection section that detects a polishing end point that indicates an end of the polishing when an absolute value of the difference calculated by the difference calculation section is smaller than a certain value.

2. The apparatus for polishing according to claim 1, characterized in that the prescribed position is a center of the polishing object.

3. The apparatus for polishing according to claim 1, characterized in that the prescribed position is a vicinity of the center of the polishing object.

4. The apparatus for polishing according to claim 1, characterized in that the different times are times that differ by an extent of a time required for one rotation or a plurality of rotations of the polishing table.

5. The apparatus for polishing according to claim 1 or 4, characterized in that the prescribed position is a plurality of different positions.

6. The apparatus for polishing according to claim 5, characterized in that the end point detection section detects the polishing end point by averaging a plurality of differences calculated by the difference calculation section.

7. A polishing method that polishes a polishing object, characterized by comprising: polishing the polishing object by rotating a polishing table that supports a polishing pad for polishing the polishing object while pressing the polishing object against the polishing pad; measuring a physical quantity that varies in accordance with a film thickness change of the polishing object at a prescribed position of the polishing object by a sensor, and outputting a measurement signal; generating data corresponding to the film thickness based on the measurement signal, and calculating a difference between the data at different times based on the measurement signal output at the different times while the polishing table is rotating, at the prescribed position of the polishing object; and detecting a polishing end point that indicates an end of the polishing when an absolute value of the calculated difference is smaller than a certain value.

8. The polishing method according to claim 7, characterized in that the prescribed position is a center of the polishing object.

9. The polishing method according to claim 7, characterized in that the prescribed position is a vicinity of the center of the polishing object.

10. The polishing method according to claim 7, characterized in that the different times are times that differ by an extent of a time required for one rotation or a plurality of rotations of the polishing table.

11. The polishing method according to claim 7 or 10, characterized in that the prescribed position is a plurality of different positions.

12. The polishing method according to claim 11, characterized in that the end point detection section detects the polishing end point by averaging a plurality of differences calculated by the difference calculation section. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The data is generated from the measurement signals outputted by the plurality of sensors at the different time instants, and the difference between the data at the different time instants is calculated at each of the different time instants.

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