Polishing method, polishing device, and program for making computer execute the polishing method

Abstract

To provide a polishing method which allows accurate detection of a polishing end point of a substrate by using an acoustic sensor.SOLUTION: A polishing method includes: detecting environmental sound containing sound caused by a polishing environment of a substrate, by using an acoustic sensor; outputting an environmental sound signal representing the environmental sound from the acoustic sensor; generating an environmental sound spectrum indicating a relationship between a frequency and a sound pressure level from the environmental sound signal; detecting polishing sound of the substrate, by using the acoustic sensor, while pressing and polishing the substrate against a polishing surface of an abrasive pad; outputting a polishing sound signal representing the polishing sound from the acoustic sensor; generating a polishing sound spectrum indicating a relationship between a frequency and a sound pressure level from the polishing sound signal; calculating a difference between the polishing sound spectrum and the environmental sound spectrum; generating a differential spectrum; and monitoring a polishing progress of the substrate, on the basis of the differential spectrum.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a polishing method and a polishing apparatus for polishing a substrate such as a wafer, and also to a program for executing such a polishing method. [Background technology]

[0002] In the manufacturing process of semiconductor devices, chemical mechanical polishing (CMP) equipment is used to polish the surface of a substrate such as a semiconductor substrate. The CMP equipment is equipped with a polishing pad attached to a polishing table and a polishing head for pressing the substrate against the polishing surface of the polishing pad. The CMP equipment supplies a polishing liquid containing abrasive grains onto the polishing pad, while pressing the substrate against the polishing surface of the polishing pad with the polishing head, so that the surface of the substrate and the polishing surface of the polishing pad come into sliding contact with each other. The surface of the substrate is planarized by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad.

[0003] Since substrate polishing is terminated when the substrate has been polished to a target amount (film thickness), it is necessary to accurately monitor the progress of substrate polishing. Various techniques for monitoring the progress of substrate polishing have been proposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5511600 [Patent Document 2] Patent No. 7182653 Summary of the Invention [Problem to be solved by the invention]

[0005] One method for monitoring the progress of polishing a substrate is to detect a change in the polishing sound of the substrate using an acoustic sensor. This method utilizes the fact that the polishing sound changes when an upper layer (e.g., an insulating film, a metal film, a silicon layer, etc.) constituting the surface of the substrate is polished and a lower layer (e.g., a stopper layer) existing below the upper layer is revealed or when the surface condition of the substrate changes. However, the polishing sound detected by the acoustic sensor while the substrate is being polished may include various environmental sounds, such as vibrations and noise caused by the operation of the polishing device. Such environmental sounds may affect accurate monitoring of the progress of polishing the substrate.

[0006] Therefore, the present invention provides a polishing method and a polishing apparatus that can accurately monitor the progress of polishing a substrate by using an acoustic sensor. Furthermore, the present invention provides a program for executing such a polishing method. [Means for solving the problem]

[0007] In one aspect, a polishing method is provided in which an acoustic sensor detects environmental sounds including sounds caused by the polishing environment of a substrate, an environmental sound signal representing the environmental sound is output from the acoustic sensor, an environmental sound spectrum indicating the relationship between frequency and sound pressure level is generated from the environmental sound signal, the substrate is pressed against a polishing surface of a polishing pad while being polished, the acoustic sensor detects polishing sounds of the substrate, a polishing sound signal representing the polishing sounds is output from the acoustic sensor, a polishing sound spectrum indicating the relationship between frequency and sound pressure level is generated from the polishing sound signal, a difference between the polishing sound spectrum and the environmental sound spectrum is calculated to generate a difference spectrum, and the polishing progress of the substrate is monitored based on the difference spectrum. In one aspect, the polishing method further includes a step of generating a difference spectrum map showing a time change of the difference spectrum by arranging the difference spectrum along a time axis, and the step of monitoring the polishing progress is a step of monitoring the polishing progress based on a change in the sound pressure level in the difference spectrum map.

[0008] In one aspect, the step of monitoring the polishing progress includes detecting a polishing endpoint of the substrate, and the polishing method further includes the step of terminating polishing of the substrate based on the polishing endpoint. In one aspect, the environmental sound spectrum is generated by performing a Fourier transform on the environmental sound signal, and the polishing sound spectrum is generated by performing a Fourier transform on the polishing sound signal. In one embodiment, the environmental sound is sound detected after polishing of the substrate begins. In one embodiment, the environmental sound is a sound detected when a polishing apparatus is operated to polish the substrate before the substrate is polished. In one aspect, the process of generating the environmental sound spectrum is a process of generating a plurality of environmental sound spectra from the environmental sound signal output from the acoustic sensor during a predetermined period, calculating a representative value of the sound pressure level for each frequency from the plurality of environmental sound spectra, and generating the environmental sound spectrum showing the relationship between the frequency and the representative value of the sound pressure level. In one aspect, the polishing method further comprises monitoring the polishing environment based on the environmental sound spectrum.

[0009] In one aspect, a polishing apparatus is provided, comprising: a polishing table that supports a polishing pad; a polishing head for pressing a substrate against the polishing surface of the polishing pad; an acoustic sensor attached to the polishing table or the polishing head, that detects sound and outputs a signal representing the sound; and a processing system that generates a frequency spectrum from the signal output from the acoustic sensor, wherein the acoustic sensor is configured to detect environmental sound including sound caused by the polishing environment of the substrate and output an environmental sound signal representing the environmental sound, and to detect polishing sound of the substrate and output a polishing sound signal representing the polishing sound, and the processing system is configured to generate an environmental sound spectrum indicating the relationship between frequency and sound pressure level from the environmental sound signal, generate a polishing sound spectrum indicating the relationship between frequency and sound pressure level from the polishing sound signal, calculate the difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum, and monitor the polishing progress based on the difference spectrum. In one aspect, the processing system is configured to align the difference spectra along a time axis to generate a difference spectrum map showing changes in the difference spectra over time, and to monitor the polishing progress based on changes in the sound pressure level in the difference spectrum map.

[0010] In one aspect, the processing system is configured to monitor the polishing progress to detect a polishing endpoint of the substrate, and to terminate polishing of the substrate based on the polishing endpoint. In one aspect, the processing system is configured to generate the environmental sound spectrum by performing a Fourier transform on the environmental sound signal, and to generate the polishing sound spectrum by performing a Fourier transform on the polishing sound signal. In one aspect, the processing system is configured to instruct the acoustic sensor to detect the environmental sound after polishing of the substrate begins. In one aspect, the processing system is configured to instruct the acoustic sensor to detect the environmental sound when the polishing apparatus is operated prior to polishing the substrate. In one aspect, the processing system is configured to generate a plurality of environmental sound spectra from the environmental sound signal output from the acoustic sensor during a predetermined period, calculate a representative value of the sound pressure level for each frequency from the plurality of environmental sound spectra, and generate the environmental sound spectrum showing the relationship between the frequency and the representative value of the sound pressure level. In one aspect, the processing system is configured to monitor the polishing environment based on the environmental sound spectrum.

[0011] In one aspect, a program is provided that causes a computer to execute the following steps: detecting environmental sounds, including sounds caused by the polishing environment of a substrate, using an acoustic sensor, and outputting an environmental sound signal representing the environmental sound from the acoustic sensor; generating an environmental sound spectrum indicating the relationship between frequency and sound pressure level from the environmental sound signal; detecting polishing sounds of the substrate using the acoustic sensor while pressing the substrate against the polishing surface of a polishing pad and outputting a polishing sound signal representing the polishing sound from the acoustic sensor; generating a polishing sound spectrum indicating the relationship between frequency and sound pressure level from the polishing sound signal; calculating the difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum; and monitoring the polishing progress of the substrate based on the difference spectrum. In one aspect, the program is configured to cause the computer to further execute a step of generating a difference spectrum map showing a time change of the difference spectrum by arranging the difference spectrum along a time axis, and the step of monitoring the polishing progress is a step of monitoring the polishing progress based on a change in the sound pressure level in the difference spectrum map. Effect of the Invention

[0012] According to the present invention, an environmental sound spectrum is generated based on environmental sounds including sounds caused by the polishing environment of the substrate, and a difference between the environmental sound spectrum and a polishing sound spectrum generated based on the polishing sound detected during polishing is calculated to generate a difference spectrum. Since noise caused by the polishing environment is removed from this difference spectrum, the polishing progress of the substrate can be monitored with high accuracy based on the difference spectrum. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a polishing apparatus. [Diagram 2] FIG. 2 is a side view diagrammatically illustrating the polishing apparatus shown in FIG. [Diagram 3] 1 is a graph showing an example of a change over time in a grinding sound signal output by an acoustic sensor. [Figure 4] 1 is a graph illustrating an example of a polishing sound spectrum produced by a processing system. [Diagram 5] 11A and 11B are diagrams for explaining an embodiment in which environmental sound is detected after polishing of a substrate is started. [Figure 6] 1 is a graph showing an example of a polishing sound spectrum, an environmental sound spectrum, and a difference spectrum generated by the processing system. [Figure 7] 1 is a graph illustrating an example of a difference spectrum map generated by the processing system. [Figure 8] 1 is a flow chart illustrating an embodiment of a method for polishing a substrate. [Figure 9] 10 is a flow chart illustrating another embodiment of a method for polishing a substrate. [Figure 10] 13 is a flow chart illustrating yet another embodiment of a method for polishing a substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a polishing apparatus 1, and FIG. 2 is a side view showing the polishing apparatus 1 shown in FIG. 1. The polishing apparatus 1 is an apparatus for chemically and mechanically polishing a substrate W such as a wafer or a panel. As shown in FIG. 1, the polishing apparatus 1 includes a polishing table 3 for supporting a polishing pad 2, a polishing head 5 for pressing the substrate W against a polishing surface 2a of the polishing pad 2, and a polishing liquid supply nozzle 10 for supplying a polishing liquid (e.g., a slurry) to the polishing pad 2. The polishing pad 2 is attached to the upper surface of the polishing table 3. The exposed surface of the polishing pad 2 constitutes the polishing surface 2a for polishing the substrate W.

[0015] The polishing apparatus 1 further includes a support shaft 14, a polishing head arm 16 connected to the upper end of the support shaft 14, a polishing head shaft 18 rotatably supported at the free end of the polishing head arm 16, and a polishing head rotating device 20 that rotates the polishing head 5 together with the polishing head shaft 18. The polishing head 5 is fixed to the lower end of the polishing head shaft 18. The polishing head 5 is configured so that the substrate W can be held on its lower surface by vacuum suction. The substrate W is held by the polishing head 5 so that the surface to be polished faces downward.

[0016] The polishing head rotating device 20 is disposed in the polishing head arm 16. The polishing head rotating device 20 is connected to the polishing head shaft 18 and configured to rotate the polishing head shaft 18 and the polishing head 5 in the direction indicated by the arrow. The polishing head rotating device 20 is configured, for example, by a combination of a motor, a timing pulley, and a belt. In Figs. 1 and 2, the polishing head rotating device 20 is illustrated diagrammatically.

[0017] The polishing apparatus 1 further includes a table motor 6 that rotates the polishing table 3. The table motor 6 is disposed below the polishing table 3, and the polishing table 3 is connected to the table motor 6 via a table shaft 3a. The table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 about the table shaft 3a in the direction indicated by the arrow.

[0018] The polishing apparatus 1 further includes a processing system 40. The polishing head 5, the table motor 6, the polishing liquid supply nozzle 10, and the polishing head rotation device 20 are electrically connected to the processing system 40, and the operations of the polishing head 5, the table motor 6, the polishing liquid supply nozzle 10, and the polishing head rotation device 20 are controlled by the processing system 40.

[0019] The processing system 40 is composed of at least one computer. The processing system 40 includes a storage device 40a in which a program is stored, and an arithmetic device 40b that executes calculations according to instructions included in the program. The storage device 40a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic device 40b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the processing system 40 is not limited to these examples.

[0020] In one embodiment, the processing system 40 may be composed of multiple computers or multiple servers connected by a communication network such as the Internet or a local area network. For example, the processing system 40 may be a combination of an edge server and a cloud server. In one embodiment, the storage device 40a may be located remotely from the computing device 40b.

[0021] The substrate W is polished as follows. The polishing head 5 and the polishing table 3 are rotated in the directions indicated by the arrows, and the polishing liquid is supplied from the polishing liquid supply nozzle 10 onto the polishing surface 2a of the polishing pad 2. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2. The surface of the substrate W is polished by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0022] The polishing apparatus 1 further includes an acoustic sensor 30 attached to the polishing table 3 or the polishing head 5. In this embodiment, the acoustic sensor 30 is installed inside the polishing table 3. The acoustic sensor 30 detects the amount of the polishing force at a predetermined time interval (e.g., 1×10 -6 The acoustic sensor 30 is configured to detect sound at intervals of 100 s and output (generate) a signal representative of the sound. The acoustic sensor 30 is electrically connected to a processing system 40, and the operation of the acoustic sensor 30 is controlled by the processing system 40.

[0023] During polishing of the substrate W, the acoustic sensor 30 detects the polishing sound of the substrate W and outputs (generates) a polishing sound signal representing the polishing sound. Specifically, the processing system 40 issues a command to the acoustic sensor 30 to detect the polishing sound during polishing of the substrate W and output a polishing sound signal representing the polishing sound from the acoustic sensor 30. The arrangement of the acoustic sensor 30 is arbitrary as long as it can detect the polishing sound of the substrate W, and is not limited to this embodiment. For example, the acoustic sensor 30 may be attached to the polishing head 5. In this embodiment, the polishing apparatus 1 includes a single acoustic sensor 30, but in one embodiment, the polishing apparatus 1 may include two or more acoustic sensors.

[0024] The polishing sound of the substrate W changes depending on the surface condition of the substrate W. For example, when the polishing of an upper layer (e.g., an insulating film, a metal film, a silicon layer, etc.) constituting the surface of the substrate W progresses and a lower layer (e.g., a stopper layer) existing under the upper layer is exposed, the polishing sound of the substrate W changes. This is because the materials constituting the upper layer and the lower layer of the substrate W are different, and the friction coefficient of the upper layer and the friction coefficient of the lower layer are different. In another example, when the polishing of the substrate W progresses and the surface roughness of the substrate W changes, the polishing sound of the substrate W changes. This is because the frictional force (friction resistance) of the substrate W changes depending on the surface roughness of the substrate W. The processing system 40 of this embodiment monitors the polishing progress of the substrate W by utilizing the change in the polishing sound detected by the acoustic sensor 30. Monitoring the polishing progress of the substrate W includes detecting the end point of polishing of the substrate W.

[0025] FIG. 3 is a graph showing an example of the change over time of the polishing sound signal output by the acoustic sensor 30. In FIG. 3, the horizontal axis represents the polishing time, and the vertical axis represents the intensity of the polishing sound signal. In this embodiment, the acoustic sensor 30 starts detecting the polishing sound from a predetermined detection start time T1. The detection start time T1 is a time before the end point of polishing of the substrate W, which is determined in advance based on polishing data from the time when a substrate was polished in the past. In one embodiment, the acoustic sensor 30 may start detecting the polishing sound together with the start of polishing of the substrate W. The acoustic sensor 30 detects the polishing sound at a predetermined time interval (e.g., 1×10 -6The acoustic sensor 30 detects the polishing sound at intervals of 100 to 2000 s and outputs (generates) a polishing sound signal representative of the polishing sound. The polishing sound signal output by the acoustic sensor 30 is sent from the acoustic sensor 30 to a processing system 40.

[0026] The processing system 40 is configured to generate a polishing sound spectrum, which indicates a relationship between frequency and sound pressure level, from the polishing sound signal sent from the acoustic sensor 30. More specifically, the processing system 40 performs a Fourier transform on the polishing sound signal sent from the acoustic sensor 30 to analyze frequency components and their intensities, and generates the polishing sound spectrum. In one embodiment, the processing system 40 performs a fast Fourier transform (FFT) on the polishing sound signal to generate the polishing sound spectrum.

[0027] A predetermined number of data pieces of polishing sound signals are used to generate one polishing sound spectrum. In the example shown in Fig. 3, the acoustic sensor 30 outputs a predetermined number of data pieces of polishing sound signals used to generate one polishing sound spectrum during a predetermined time dt (e.g., 10 seconds). Therefore, the processing system 40 generates a polishing sound spectrum every time it acquires a predetermined number of data pieces of polishing sound signals output from the acoustic sensor 30 during the predetermined time dt.

[0028] Fig. 4 is a graph showing an example of a polishing sound spectrum generated by the processing system 40. In Fig. 4, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. As described above, when the polishing sound of the substrate W changes with a change in the surface condition of the substrate W, the peaks (i.e., peak position, peak height, and peak width) appearing in the polishing sound spectrum change. Therefore, during polishing of the substrate W, the processing system 40 can monitor the progress of polishing of the substrate W based on the polishing sound spectrum.

[0029] The polishing sound detected by the acoustic sensor 30 during polishing of the substrate W includes environmental sounds including sounds resulting from the polishing environment of the substrate W, such as vibrations and noise caused by the operation of the polishing apparatus 1. The polishing sound spectrum generated based on the polishing sound including such environmental sounds may not allow accurate monitoring of the polishing progress of the substrate W. Therefore, the processing system 40 generates a difference spectrum by removing the environmental sound components from the polishing sound spectrum, and monitors the polishing progress of the substrate W based on the difference spectrum.

[0030] The acoustic sensor 30 detects environmental sounds, including sounds caused by the polishing environment of the substrate W, at predetermined time intervals (e.g., 1×10 -6 2 seconds) and outputs (generates) an environmental sound signal representing the environmental sound. In this embodiment, the environmental sound is sound detected after polishing of the substrate W begins. Specifically, the processing system 40 issues a command to the acoustic sensor 30 to detect the environmental sound after polishing of the substrate W begins, and to output an environmental sound signal representing the environmental sound from the acoustic sensor 30.

[0031] FIG. 5 is a diagram for explaining an embodiment in which environmental sound is detected after the start of polishing the substrate W. The graph shown in FIG. 5 is the same as the graph showing an example of a change over time in the polishing sound signal output by the acoustic sensor 30 shown in FIG. 3. In the embodiment shown in FIG. 5, the acoustic sensor 30 detects environmental sound in a predetermined period from time T2 to time T3 after the start of polishing the substrate W, and outputs an environmental sound signal representing the environmental sound. The predetermined period for detecting the environmental sound is a predetermined period immediately after the start of polishing the substrate W, or before the surface condition of the substrate W changes in the initial polishing stage. The environmental sound detected after the start of polishing the substrate W may include a polishing sound of the substrate W that does not affect the monitoring of the polishing progress of the substrate W.

[0032] The environmental sound signal output from the acoustic sensor 30 is sent from the acoustic sensor 30 to the processing system 40. The processing system 40 is configured to generate an environmental sound spectrum indicating a relationship between frequency and sound pressure level from the environmental sound signal sent from the acoustic sensor 30. More specifically, the processing system 40 performs a Fourier transform on the environmental sound signal sent from the acoustic sensor 30 to analyze frequency components and their intensities, and generates the environmental sound spectrum. In one embodiment, the processing system 40 may perform a fast Fourier transform (FFT) on the environmental sound signal to generate the environmental sound spectrum. The generated environmental sound spectrum is stored in a storage device 40a of the processing system 40.

[0033] A predetermined number of data items of environmental sound signals are used to generate an environmental sound spectrum. In the embodiment shown in FIG. 5, the acoustic sensor 30 outputs a predetermined number of data items of environmental sound signals used to generate one environmental sound spectrum in a predetermined time dt (e.g., 10 seconds). Therefore, the processing system 40 generates an environmental sound spectrum every time it acquires a predetermined number of data items of environmental sound signals output from the acoustic sensor 30 in the predetermined time dt. In the embodiment shown in FIG. 5, the predetermined period from time T2 to time T3 is three times the predetermined time dt, and the processing system 40 generates three environmental sound spectra. In this way, the processing system 40 may generate multiple environmental sound spectra from the environmental sound signals output from the acoustic sensor 30 in the predetermined period.

[0034] In one embodiment, the processing system 40 may calculate a representative value of the sound pressure level for each frequency from a plurality of environmental sound spectra, and generate an environmental sound spectrum that indicates the relationship between the frequency and the representative value of the sound pressure level. Examples of the representative value include an average value, a median value, a maximum value, and a minimum value.

[0035] In one embodiment, the environmental sound may be a sound detected when the polishing apparatus 1 is operated before the substrate W is polished. Specifically, the processing system 40 issues a command to the acoustic sensor 30 to detect the environmental sound while the polishing apparatus 1 is operated before the substrate W is polished, and causes the acoustic sensor 30 to output an environmental sound signal representing the environmental sound. For example, the environmental sound is detected when the polishing head 5 and the polishing table 3 are rotated and the polishing liquid is supplied from the polishing liquid supply nozzle 10 onto the polishing pad 2 in a state where the substrate W held by the polishing head 5 is separated from the polishing pad 2. In this case, the processing system 40 may also generate a plurality of environmental sound spectrums from the environmental sound signal output from the acoustic sensor 30 during a predetermined period, calculate a representative value of the sound pressure level for each frequency from the plurality of environmental sound spectrums, and generate an environmental sound spectrum indicating the relationship between the frequency and the representative value of the sound pressure level.

[0036] The processing system 40 is configured to calculate the difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum. FIG. 6 is a graph showing an example of the polishing sound spectrum, the environmental sound spectrum, and the difference spectrum generated by the processing system 40. In FIG. 6, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. The graph shown by the dashed line is an example of the polishing sound spectrum generated by the processing system 40, the graph shown by the thin line is an example of the environmental sound spectrum generated by the processing system 40, and the graph shown by the thick line is an example of the difference spectrum generated by the processing system 40. The processing system 40 calculates the difference between the sound pressure level of the polishing sound spectrum and the sound pressure level of the environmental sound spectrum for each frequency, and generates a difference spectrum from the calculated difference in sound pressure level for each frequency.

[0037] As described above, the processing system 40 generates a polishing sound spectrum every time a predetermined number of polishing sound signals are acquired from the acoustic sensor 30. Every time the processing system 40 generates a polishing sound spectrum, it calculates the difference between the polishing sound spectrum and the environmental sound spectrum stored in the storage device 40a to generate a difference spectrum. The processing system 40 is configured to monitor the polishing progress of the substrate W based on the generated difference spectrum. Since the difference spectrum is the polishing sound spectrum with the environmental sound components removed, the processing system 40 can accurately monitor the change in the polishing sound caused by the change in the surface condition of the substrate W.

[0038] In one embodiment, the processing system 40 is configured to detect the polishing end point of the substrate W based on the difference spectrum. As described above, when polishing of an upper layer (e.g., an insulating film, a metal film, a silicon layer, etc.) constituting the surface of the substrate W progresses and a lower layer (e.g., a stopper layer) existing below the upper layer is exposed, the polishing sound of the substrate W changes. By utilizing such a change in the polishing sound, the processing system 40 can detect the polishing end point of the substrate W. For example, the processing system 40 detects the polishing end point of the substrate W when the sound pressure level at a predetermined frequency of the difference spectrum reaches a target value. The target value of the sound pressure level at the predetermined frequency is predetermined based on polishing data when the substrate was polished in the past.

[0039] The processing system 40 is configured to terminate polishing of the substrate W based on the detected polishing end point of the substrate W. Specifically, the processing system 40 issues a command to the polishing head rotation device 20 and the table motor 6 to stop rotation of the polishing head 5 and the polishing table 3 based on the polishing end point of the substrate W, thereby terminating polishing of the substrate W. In one embodiment, the processing system 40 may terminate polishing of the substrate W when a predetermined transition time has elapsed from the polishing end point of the substrate W.

[0040] In one embodiment, the processing system 40 is configured to detect a change in the polishing conditions for the substrate W based on the difference spectrum. When polishing of an upper layer constituting the surface of the substrate W progresses and a lower layer existing below the upper layer is exposed, the polishing conditions for the substrate W (e.g., the rotation speed of the polishing head 5, the pressing force of the polishing head 5 against the substrate W, the rotation speed of the polishing table 3, the type of polishing liquid supplied onto the polishing pad 2, etc.) may be changed. For example, the processing system 40 detects a change in the polishing conditions for the substrate W when the sound pressure level at a predetermined frequency of the difference spectrum reaches a reference value. The reference value is determined in advance based on polishing data obtained when a substrate was polished in the past, etc.

[0041] The processing system 40 is configured to change the polishing conditions of the substrate W based on the detected change in the polishing conditions of the substrate W. Specifically, the processing system 40 issues a command to the table motor 6, the polishing liquid supply nozzle 10, and / or the polishing head rotation device 20 to change their operations in accordance with the polishing conditions to be changed based on the change in the polishing conditions of the substrate W. In one embodiment, the processing system 40 may change the polishing conditions of the substrate W when a predetermined transition time has elapsed since the change in the polishing conditions of the substrate W.

[0042] In one embodiment, the processing system 40 is configured to monitor the surface roughness of the substrate W based on the difference spectrum. As described above, the surface roughness of the substrate W can be monitored by utilizing the fact that the polishing sound of the substrate W changes when the surface roughness of the substrate W changes. For example, the processing system 40 may monitor the surface roughness of the substrate W based on the peak position, peak height, and peak width of the difference spectrum. In another example, the processing system 40 detects that the surface roughness of the substrate W has changed when the sound pressure level at a predetermined frequency of the difference spectrum exceeds a threshold value or falls below the threshold value. The processing system 40 may detect that the surface roughness of the substrate W has changed and detect the end point of polishing of the substrate W. The threshold value is determined in advance based on polishing data of past substrates.

[0043] In one embodiment, the processing system 40 is configured to generate a difference spectrum map indicating a time change of the difference spectrum by arranging the difference spectra along a time axis. Fig. 7 is a graph showing an example of a difference spectrum map generated by the processing system 40. In Fig. 7, the X-axis represents frequency, the Y-axis represents time, and the Z-axis represents sound pressure level. The processing system 40 generates the difference spectrum map every time it generates a difference spectrum. More specifically, the processing system 40 generates (updates) the difference spectrum map by adding a newly generated difference spectrum along the time axis of the difference spectrum map.

[0044] The processing system 40 is configured to monitor the progress of polishing the substrate W based on the change in sound pressure level in the difference spectrum map. For example, the processing system 40 detects the end point of polishing the substrate W, which is the time point at which the amount of change in sound pressure level in a predetermined monitor frequency range of the difference spectrum map exceeds a reference value. The monitor frequency range is determined in advance based on polishing data obtained when a substrate was polished in the past. The monitoring of the progress of polishing the substrate W based on the difference spectrum map can be applied to any of the above-mentioned detection of the end point of polishing the substrate W, detection of changes in the polishing conditions for the substrate W, and monitoring of the surface roughness of the substrate W.

[0045] FIG. 8 is a flow chart showing an embodiment of a method for polishing a substrate W. In step S101, the processing system 40 issues commands to the polishing head 5, the table motor 6, the polishing liquid supply nozzle 10, and the polishing head rotating device 20 to supply a polishing liquid (e.g., slurry) from the polishing liquid supply nozzle 10 onto the polishing pad 2 while rotating the polishing head 5 and the polishing table 3. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2, and polishing of the substrate W is started.

[0046] In step S102, the processing system 40 issues a command to the acoustic sensor 30 to detect the environmental sound after starting polishing of the substrate W and to output an environmental sound signal representing the environmental sound from the acoustic sensor 30. The output environmental sound signal is sent to the processing system 40. The detection of the environmental sound is performed immediately after starting polishing of the substrate W or in the initial polishing stage, before the surface condition of the substrate W changes.

[0047] In step S103, the processing system 40 generates an environmental sound spectrum indicating the relationship between frequency and sound pressure level from the environmental sound signal sent from the acoustic sensor 30. More specifically, the processing system 40 performs a Fourier transform (e.g., a fast Fourier transform) on the environmental sound signal sent from the acoustic sensor 30 to generate the environmental sound spectrum. In one embodiment, a plurality of environmental sound spectra may be generated from the environmental sound signal output from the acoustic sensor 30 during a predetermined period after the start of polishing the substrate W, and a representative value of the sound pressure level may be calculated for each frequency from the plurality of environmental sound spectra to generate an environmental sound spectrum indicating the relationship between frequency and the representative value of the sound pressure level. The generated environmental sound spectrum is stored in the storage device 40a of the processing system 40.

[0048] In step S104, the processing system 40 issues a command to the acoustic sensor 30 to detect the polishing sound during polishing of the substrate W and to output a polishing sound signal representing the polishing sound from the acoustic sensor 30. The output polishing sound signal is sent to the processing system 40. The detection of the polishing sound by the acoustic sensor 30 may be performed from a predetermined detection start time T1 (see FIG. 3) or may be performed simultaneously with the start of polishing of the substrate W. In step S105, the processing system 40 generates a polishing sound spectrum indicating the relationship between frequency and sound pressure level from the polishing sound signal sent from the acoustic sensor 30. More specifically, the processing system 40 performs a Fourier transform (e.g., a fast Fourier transform) on the polishing sound signal sent from the acoustic sensor 30 to generate the polishing sound spectrum.

[0049] In step S106, the processing system 40 calculates the difference between the generated polishing sound spectrum and the environmental sound spectrum stored in the storage device 40a to generate a difference spectrum. More specifically, the processing system 40 calculates the difference between the sound pressure level of the polishing sound spectrum and the sound pressure level of the environmental sound spectrum for each frequency, and generates a difference spectrum from the calculated difference in sound pressure level for each frequency.

[0050] In step S107, the processing system 40 monitors the progress of polishing the substrate W based on the difference spectrum. More specifically, in the embodiment shown in FIG. 8, the processing system 40 determines whether the end point of polishing the substrate W has been reached based on the difference spectrum. For example, the processing system 40 detects the end point of polishing the substrate W, which is the time when the sound pressure level at a predetermined frequency of the difference spectrum reaches a target value. When the processing system 40 does not detect the end point of polishing the substrate W ("NO" in step S107), it continues polishing the substrate W and repeats steps S105 to S107. When the processing system 40 detects the end point of polishing the substrate W ("YES" in step S107), it ends the polishing of the substrate W (step S108). Specifically, the processing system 40 issues a command to the polishing head rotating device 20 and the table motor 6 based on the end point of polishing the substrate W to stop the rotation of the polishing head 5 and the polishing table 3, thereby ending the polishing of the substrate W.

[0051] In this embodiment, in step S107, the processing system 40 detects the polishing end point of the substrate W, but in one embodiment, in step S107, the processing system 40 may detect a change in the polishing conditions of the substrate W or a change in the surface roughness of the substrate W.

[0052] FIG. 9 is a flowchart showing another embodiment of the method for polishing a substrate W. In step S201, the processing system 40 operates the polishing apparatus 1 before polishing the substrate W. For example, the processing system 40 issues commands to the table motor 6, the polishing liquid supply nozzle 10, and the polishing head rotation device 20 to supply a polishing liquid from the polishing liquid supply nozzle 10 onto the polishing pad 2 while rotating the polishing head 5 and the polishing table 3 with the substrate W held by the polishing head 5 separated from the polishing pad 2.

[0053] In step S202, the processing system 40 issues a command to the acoustic sensor 30 to detect the environmental sound while the polishing apparatus 1 is operating before polishing the substrate W, and to output an environmental sound signal representing the environmental sound from the acoustic sensor 30. The output environmental sound signal is sent to the processing system 40. In step S203, the processing system 40 generates an environmental sound spectrum indicating the relationship between frequency and sound pressure level from the environmental sound signal sent from the acoustic sensor 30. More specifically, the processing system 40 performs a Fourier transform (e.g., a fast Fourier transform) on the environmental sound signal sent from the acoustic sensor 30 to generate the environmental sound spectrum. In one embodiment, a plurality of environmental sound spectra may be generated from the environmental sound signal output from the acoustic sensor 30 during a predetermined period, and a representative value of the sound pressure level for each frequency may be calculated from the plurality of environmental sound spectra to generate an environmental sound spectrum indicating the relationship between frequency and the representative value of the sound pressure level. The generated environmental sound spectrum is stored in the storage device 40a of the processing system 40.

[0054] In step S204, the processing system 40 issues commands to the polishing head 5, the table motor 6, the polishing liquid supply nozzle 10, and the polishing head rotating device 20 to supply a polishing liquid (e.g., slurry) from the polishing liquid supply nozzle 10 onto the polishing pad 2 while rotating the polishing head 5 and the polishing table 3. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2, and polishing of the substrate W is started.

[0055] Steps S205 to S209 are similar to steps S104 to S108 in the embodiment described with reference to FIG. 8, and therefore a duplicated description will be omitted.

[0056] FIG. 10 is a flowchart showing still another embodiment of the method for polishing a substrate W. Steps S301 to S306 are similar to steps S101 to S106 in the embodiment described with reference to Fig. 8, and therefore the duplicated description will be omitted. In one embodiment, the process of generating an environmental sound spectrum in steps S201 to S203 in the embodiment described with reference to Fig. 9 may be applied to the process of generating an environmental sound spectrum in the embodiment in Fig. 10.

[0057] In step S307, the processing system 40 generates a difference spectrum map indicating a time change of the difference spectrum by arranging the difference spectra along the time axis. More specifically, the processing system 40 adds the newly generated difference spectrum along the time axis of the difference spectrum map to generate (update) the difference spectrum map.

[0058] In step S308, the processing system 40 monitors the progress of polishing the substrate W based on the change in sound pressure level in the difference spectrum map. More specifically, the processing system 40 determines whether or not the end point of polishing the substrate W has been reached based on the change in sound pressure level in the difference spectrum map. For example, the processing system 40 detects the end point of polishing the substrate W, which is the time when the amount of change in sound pressure level in a predetermined monitor frequency range (see FIG. 7) of the difference spectrum map exceeds a reference value. When the processing system 40 does not detect the end point of polishing the substrate W ("NO" in step S308), it continues polishing the substrate W and repeats steps S305 to S308. When the processing system 40 detects the end point of polishing the substrate W ("YES" in step S308), it ends the polishing of the substrate W (step S309). Specifically, based on the polishing end point of the substrate W, the processing system 40 issues a command to the polishing head rotation device 20 and the table motor 6 to stop the rotation of the polishing head 5 and the polishing table 3, thereby completing polishing of the substrate W.

[0059] The processing system 40 operates according to instructions contained in a program electrically stored in the storage device 40a. The processing system 40 executes each operation step in each of the above-described embodiments according to instructions contained in the program. The program for causing the processing system 40 to execute these steps is recorded in a computer-readable recording medium, which is a non-transitory tangible object, and is provided to the processing system 40 via the recording medium. Alternatively, the program may be input to the processing system 40 via a communication network such as the Internet or a local area network.

[0060] In one embodiment, the processing system 40 may be configured to monitor the polishing environment of the substrate based on the environmental sound spectrum. An environmental sound spectrum generated based on environmental sounds detected under the same conditions basically has the same peak (i.e., peak position, peak height, and peak width). However, if an abnormality occurs in the polishing environment of the substrate, for example, if a malfunction occurs in the polishing apparatus 1, the vibration and sound caused by the operation of the polishing apparatus 1 will change, and the peak of the generated environmental sound spectrum will also change. Therefore, the polishing environment of the substrate can be monitored based on the environmental sound spectrum.

[0061] The processing system 40 generates an environmental sound spectrum by the above-mentioned method every time a substrate is polished, and monitors the polishing environment of the substrate based on the environmental sound spectrum. In one embodiment, the processing system 40 may generate an environmental sound spectrum every time a plurality of substrates are polished, and monitor the polishing environment of the substrate based on the environmental sound spectrum. For example, the processing system 40 detects that an abnormality has occurred in the polishing environment of the substrate when the sound pressure level at a predetermined frequency of the environmental sound spectrum reaches an abnormality threshold. The abnormality threshold of the sound pressure level at the predetermined frequency is determined in advance based on the environmental sound spectrum generated based on the environmental sound detected by the acoustic sensor 30 when an abnormality has occurred in the polishing environment of the substrate. When an abnormality has occurred in the polishing environment of the substrate, the operator performs maintenance as necessary.

[0062] In one embodiment, the processing system 40 may generate an environmental sound spectrum by the above-mentioned method based on the environmental sound detected by the acoustic sensor 30 in a state where no abnormality occurs in the substrate polishing environment (i.e., the substrate polishing environment is normal), and store this environmental sound spectrum in the storage device 40a as a reference environmental sound spectrum. In this case, the processing system 40 monitors the substrate polishing environment based on a comparison between the reference environmental sound spectrum stored in the storage device 40a and the environmental sound spectrum. Specifically, the processing system 40 detects that an abnormality occurs in the substrate polishing environment when the environmental sound spectrum changes with respect to the reference environmental sound spectrum.

[0063] As described above, the environmental sound spectrum may be generated based on environmental sound detected after the start of polishing the substrate, or may be generated based on environmental sound detected before polishing the substrate and while the polishing apparatus 1 is operating. Therefore, monitoring of the substrate polishing environment based on the environmental sound spectrum may be performed when the environmental sound spectrum is generated based on environmental sound detected after the start of polishing the substrate, or may be performed when the environmental sound spectrum is generated based on environmental sound detected before polishing the substrate and while the polishing apparatus 1 is operating.

[0064] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0065] 1 Polishing equipment 2 Polishing Pads 2a Polished surface 3 Polishing table 3a Table axis 5 Polishing Head 6 Table Motor 10 Polishing liquid supply nozzle 14 Spindle 16 Polishing head arm 18 Polished head shaft 20 Polishing head rotation device 30 Acoustic Sensor 40 Processing System 40a storage device 40b Arithmetic unit W substrate

Claims

1. detecting an environmental sound including a sound caused by a polishing environment of the substrate with an acoustic sensor, and outputting an environmental sound signal representing the environmental sound from the acoustic sensor; generating an environmental sound spectrum indicating a relationship between frequency and sound pressure level from the environmental sound signal; While pressing the substrate against the polishing surface of the polishing pad to polish the substrate, the acoustic sensor detects a polishing sound of the substrate, and outputs a polishing sound signal representing the polishing sound from the acoustic sensor; generating a grinding sound spectrum indicating a relationship between frequency and sound pressure level from the grinding sound signal; Calculating a difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum; The polishing method further comprises monitoring a polishing progress of the substrate based on the difference spectrum.

2. The method further includes a step of generating a difference spectrum map showing a time change of the difference spectrum by arranging the difference spectrum along a time axis, The polishing method according to claim 1 , wherein the step of monitoring the polishing progress is a step of monitoring the polishing progress based on a change in the sound pressure level in the difference spectrum map.

3. monitoring the polishing progress includes detecting a polishing endpoint of the substrate; The polishing method according to claim 1 , further comprising the step of terminating polishing of the substrate based on the polishing endpoint.

4. The environmental sound spectrum is generated by performing a Fourier transform on the environmental sound signal; The polishing method of claim 1 , wherein the polishing sound spectrum is generated by performing a Fourier transform on the polishing sound signal.

5. The polishing method according to claim 1 , wherein the environmental sound is a sound detected after polishing of the substrate begins.

6. 2. The polishing method according to claim 1, wherein the environmental sound is a sound detected when a polishing apparatus for polishing the substrate is operated before the substrate is polished.

7. The polishing method according to claim 1, wherein the step of generating the environmental sound spectrum is a step of generating a plurality of environmental sound spectra from the environmental sound signal output from the acoustic sensor during a predetermined period, calculating a representative value of the sound pressure level for each frequency from the plurality of environmental sound spectra, and generating the environmental sound spectrum showing the relationship between the frequency and the representative value of the sound pressure level.

8. The polishing method of claim 1 , further comprising the step of monitoring the polishing environment based on the environmental sound spectrum.

9. a polishing table supporting a polishing pad; a polishing head for pressing a substrate against the polishing surface of the polishing pad; an acoustic sensor attached to the polishing table or the polishing head, detecting an acoustic sound and outputting a signal representing the acoustic sound; a processing system for generating a frequency spectrum from the signal output from the acoustic sensor; The acoustic sensor includes: Detecting an environmental sound including a sound caused by a polishing environment of the substrate, and outputting an environmental sound signal representing the environmental sound; a polishing sound signal representative of the polishing sound is outputted; The processing system includes: generating an environmental sound spectrum indicating a relationship between frequency and sound pressure level from the environmental sound signal; generating a grinding sound spectrum indicating a relationship between frequency and sound pressure level from the grinding sound signal; Calculating a difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum; a polishing apparatus configured to monitor the polishing progress based on the difference spectrum.

10. The processing system includes: arranging the difference spectra along a time axis to generate a difference spectrum map showing a change in the difference spectra over time; The polishing apparatus of claim 9 , configured to monitor the polishing progress based on changes in the sound pressure level in the difference spectrum map.

11. The processing system includes: monitoring the polishing progress to detect a polishing endpoint of the substrate; 11. The polishing apparatus according to claim 9, further comprising: a polishing end point determining unit configured to terminate polishing of the substrate based on the polishing end point.

12. The processing system includes: generating an environmental sound spectrum by performing a Fourier transform on the environmental sound signal; The polishing apparatus of claim 9 , configured to generate the polishing sound spectrum by performing a Fourier transform on the polishing sound signal.

13. 10. The polishing apparatus of claim 9, wherein the processing system is configured to issue a command to the acoustic sensor to detect the environmental sound after polishing of the substrate begins.

14. 10. The polishing apparatus of claim 9, wherein the processing system is configured to instruct the acoustic sensor to detect the environmental sound when the polishing apparatus is operated prior to polishing the substrate.

15. The processing system includes: generating a plurality of environmental sound spectra from the environmental sound signal output from the acoustic sensor during a predetermined period of time; Calculating a representative value of sound pressure level for each frequency from the plurality of environmental sound spectra; The polishing apparatus according to claim 9 , configured to generate the environmental sound spectrum indicating a relationship between the frequency and the representative value of the sound pressure level.

16. The polishing apparatus of claim 9 , wherein the processing system is configured to monitor the polishing environment based on the environmental sound spectrum.

17. detecting an environmental sound including a sound caused by a polishing environment of the substrate by an acoustic sensor, and outputting an environmental sound signal representing the environmental sound from the acoustic sensor; generating an environmental sound spectrum indicating a relationship between frequency and sound pressure level from the environmental sound signal; a step of detecting a polishing sound of the substrate by the acoustic sensor while pressing the substrate against a polishing surface of a polishing pad and polishing the substrate, and outputting a polishing sound signal representing the polishing sound from the acoustic sensor; generating a polishing sound spectrum indicating a relationship between frequency and sound pressure level from the polishing sound signal; Calculating a difference between the polishing sound spectrum and the environmental sound spectrum to generate a difference spectrum; A program that causes a computer to execute a step of monitoring the polishing progress of the substrate based on the difference spectrum.

18. The program is configured to cause the computer to further execute a step of generating a difference spectrum map indicating a time change of the difference spectrum by arranging the difference spectrum along a time axis, The program according to claim 17 , wherein the step of monitoring the polishing progress is a step of monitoring the polishing progress based on a change in the sound pressure level in the difference spectrum map.

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