JP2009059828A - Polishing termination point of time detecting method using torque change, and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing termination point of time detecting device which detects the change in torque waveform purely due to a wafer state, by removing the noise that is not due to the wafer state in real time, and which surely detects a polishing termination point of time, with high accuracy. <P>SOLUTION: The polishing termination point of time detecting device includes a torque measuring means 9 for measuring torque; a periodic component analyzing means 10 for analyzing a periodic component, by applying Fourier transformation to measured data; an average processing time calculating means 11 of calculating a moving average processing time for removing periodic noise components; an averaging processing means 12 of correcting a waveform, by performing averaging processing on the basis of the moving average processing time calculated in real time for the data; a film kind decision means 13 of deciding the kind of a predetermined film by monitoring the change in the waveform with a plurality of algorithms and collating monitoring results with a plurality of restriction conditions; and a termination point of time detecting means 14 of detecting the polishing termination time point of the predetermined film by monitoring the change in the waveform. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing end point detection method using torque change and an apparatus therefor, and in particular, removes periodic noise and the like that fluctuate continuously in real time in CMP (Chemical Mechanical Polishing). In addition, the present invention relates to a polishing end point detection method and a device using a torque change capable of reliably detecting the polishing end point with high accuracy by an algorithm for detecting the polishing end point according to the film type of the film to be polished. .

  It is known to detect the end of polishing of the conductive film when the conductive film on the wafer is mechanically polished by monitoring the change in torque waveform (see, for example, Patent Document 1). ). The torque waveform itself measured when polishing the conductive film on the wafer includes various disturbances. How to process such a torque waveform and detect what kind of change is a key point in reliably detecting the polishing end point.

  On the other hand, as another conventional technique, for example, the following end point detection method is known. This prior art assumes a box of an appropriate size with a torque change amount as a vertical side h and a polishing time width as a horizontal side w with respect to an input waveform showing the relationship between polishing time and torque change. Then, the waveform is input into the box at a point of h / 2 on one vertical side h of the box, and the torque fluctuation is analyzed depending on which side of the box the input waveform intersects and goes out of the box. ing. That is, when the input waveform crosses the upper side, it is classified as up, when it crosses the lower side, down, and when it crosses the other vertical side, it is classified into three types: side. Monitor trends. In this box method, by adjusting the size of the box, the locus of the input waveform is analyzed, and the input waveform that repeats the peak and valley is detected as the polishing end point when the nth peak or valley is detected. (For example, refer to Patent Document 2).

Further, as another conventional technique, for example, the following polishing end point detection device is known. This prior art is a polishing apparatus that polishes and removes an adhering material different from the base material that adheres to the base material, and includes at least a first rotating shaft that drives the platen and a second rotating shaft that rotates the object to be polished. A measuring mechanism that measures one torque, and a determination unit that determines that at least one of the torque measured by the measuring mechanism and the time differential value of the torque has changed to a preset value or more, The next stage of the measurement mechanism includes a low-pass filter having a cut-off frequency lower than the larger one of the rotation speed of the first rotation shaft and the rotation speed of the second rotation shaft or the first rotation shaft. A notch filter having a notch frequency corresponding to at least one of the rotation speed and the rotation speed of the second rotation shaft is inserted to remove noise from the measured torque, and the determination result of the determination means is determined. From and to detect the polishing end point (e.g., see Patent Document 3).
(For example, refer to Patent Document 3).
US Pat. No. 5,069,002. U.S. Pat. No. 5,190,614. JP-A-6-315850.

  In the prior art described in Patent Document 1, the end point of polishing is detected by monitoring the torque waveform measured during polishing. However, the torque waveform itself includes various disturbances. For this reason, it is impossible to detect the polishing end point by simply monitoring such a change in torque waveform. In order to expand to a practical level, the actual torque process must be processed appropriately, and if there is no way to detect what changes in the torque waveform after processing, the actual process Not applicable.

  In the prior art described in Patent Document 2, the input waveform indicating the relationship between polishing time and torque change is a waveform that repeats a peak and a valley, and the time point at which the nth peak or valley is detected is detected as the polishing end point. I have to. However, the torque change at the time of polishing the conductive film on the wafer changes suddenly at the end of polishing. For this reason, when the box is applied, there is a problem that the polishing end point cannot be detected unless the condition of detecting up or down for n times is satisfied, and the polishing torque of the conductive film on the wafer having individual differences is monitored. In this case, the polishing end point is erroneously detected. Then, the analysis of the torque change is performed by digital judgment of “0” and “1” in which the torque waveform is input into the box and then waits for the torque waveform to go out of the box. For this reason, the analysis of the degree of inclination (numerical value) of the waveform is unknown, it is difficult to use the applied algorithm together, and it is difficult to detect the polishing end in real time. Moreover, disturbances of drift components such as the surface state of the polishing pad cannot be removed.

  In the prior art described in Patent Document 3, noise is removed using a low-pass filter and a notch filter, and the polishing end point is detected by a torque from which the noise is removed or a differential value of the torque. Hereinafter, a method for removing a disturbance related to a torque waveform and how to determine information related to the polishing end point in a state where the disturbance element is removed, etc. The difference between the prior art and the case of the present invention will be described.

  In this prior art, the disturbance is removed using a low-pass filter and a notch filter. However, for example, when only a low-pass filter is used, it is impossible to remove low-cycle noise. Therefore, in order to remove such periodic noise, the periodic vibration caused by the rotation of the platen and the head is removed by a notch filter. In addition, the processing materials that are the subject of this prior art are planar magnetic devices, optical components, electrical wiring, optical wiring, and the like. However, in such a series of parts, the noise state entering during polishing is assumed to be constant both at the beginning and before the end of polishing, and it is assumed that the noise state changes only near the end of polishing. For this reason, the periodic vibration to be removed only removes the fixed periodic component of the rotation of the platen and the polishing head.

  On the other hand, the vibration generated in the material to be polished handled in the present invention is clearly different from the vibration state in such a wide polishing process. First, in the planarization process dealt with in the present invention, there are minute irregularities on the surface of the wafer, and a multilayer wiring or the like is to be formed by planarizing the minute irregularities. In addition, these minute irregularities are uniformly formed on the surface of the wafer with waviness, but when polishing, it is possible to flatten the minute irregularities while following the waviness and polishing uniformly. Desired. For this reason, the friction state during polishing is clearly different between the wafer surface state at the initial stage of polishing and the wafer surface state immediately before the end of polishing. Since there are minute irregularities in the initial stage, the frictional force is large, and disturbances resulting from the natural vibrations of various members are mixed.

  However, near the end of polishing, sufficient flattening to ensure the depth of focus of the stepper in forming the multilayer wiring is achieved, so that the wafer surface is relatively smooth and the frictional force is small. For this reason, the ratio with which the disturbance element resulting from the natural vibration of various members mixes with it is also small. From the above, in the polishing process used for planarizing the device wafer handled in the present invention, the vibration state clearly changes between the initial stage and the end of the polishing, and the disturbance state mixed in the torque waveform also changes greatly.

  In this conventional technique, a method for removing fixed noise has been described. However, such a method cannot be used to remove a disturbance component of a torque waveform in device wafer flattening. This is because in flattening CMP, a periodic component that varies continuously in real time is more dominant as a disturbance factor than a fixed periodic component such as a platen or a polishing head. Therefore, a torque waveform disturbance removal method in device wafer flattening requires removal of periodic noise that fluctuates in real time and continuously, instead of fixed periodic noise.

  Further, in CMP required for planarization of a semiconductor device wafer, the cause of torque fluctuation is not only the state of the wafer. The surface condition of the polishing pad that changes due to dressing is also a major factor in torque fluctuation. For example, when dressing with a dresser having a great dressing effect, the surface of the polishing pad is dressed (conspicuous), so that the frictional force between the wafer and the polishing pad increases, and as a result, the monitored torque also increases. On the contrary, when dressing is not performed, the polishing pad is clogged, so that the wafer slides on the polishing pad, and the monitored torque is small.

  In the present invention, there are cases of in-situ dressing and interval dressing, etc., often depending on the polishing process. In-situ dressing is when dressing while polishing. Interval dressing is performed between polishing and does not perform dressing during polishing. In particular, in the case of interval dressing, dressing is performed before polishing, but since dressing is not performed during polishing, clogging gradually develops even though the surface state of the polishing pad is minute during polishing. As a result, the polishing torque gradually decreases even when a normal blanket oxide film wafer is polished regardless of the surface state of the wafer.

  Even in the in-situ dressing, if the dressing according to the degree of clogging in the polishing pad surface is performed in real time in accordance with the clogging of the polishing pad, the torque is theoretically constant. However, actually, dressing is performed by using a small dresser and scanning the dresser in the radial direction of the polishing pad. Therefore, in principle, clogging of the polishing pad cannot be eliminated at a time, and only a part of the polishing pad is dressed in one rotation of the platen, so that the torque monitored as a result is not completely constant. Rather, a torque waveform corresponding to the dresser scan is observed.

  Thus, when actually monitoring the torque, not only the torque fluctuation due to the surface condition of the wafer is necessarily monitored, but the torque fluctuation according to the state of the polishing pad during polishing and the dressing state is also a disturbance factor. Will enter as. The disturbance element due to the surface state of the polishing pad cannot be removed as the periodic noise as described above because the waveform changes gently as a kind of drift. It is obvious that even a low-pass filter cannot be removed. For this reason, even if the fluctuation of the periodic waveform is removed, it is difficult to remove the slowly changing noise accompanying the change in the surface state of the polishing pad. It is predicted that a false detection will occur.

  Furthermore, in this prior art, the torque value or the time derivative of the torque value is detected by one algorithm for detecting the polishing end point stored in the judging means for the torque value from which noise has been removed using a low-pass filter and a notch filter. The polishing end point is detected by determining that the value has changed to a preset value or more. However, the waveform of the torque sampled with the progress of polishing of the adhered material generally differs in shape depending on the film quality, film thickness, etc. of the adhered material. For this reason, if the torque values having different waveforms are processed by only one fixed algorithm, the polishing end point is erroneously detected or cannot be detected.

  Therefore, continuously changing periodic noise and noise not caused by the wafer state such as drift noise caused by the dressing condition and polishing pad state are removed in real time to detect a change in the torque waveform caused purely by the wafer state. At the same time, an appropriate algorithm for detecting the polishing end point according to the film type of the film to be polished causes a technical problem to be solved in order to reliably detect the polishing end point with high accuracy. The purpose is to solve the problem.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is characterized in that a wafer having a predetermined film with minute irregularities on its surface is held on a polishing head, and is placed on the surface of a rotating platen. The predetermined film is pressed against the provided polishing pad while rotating the polishing head for polishing, and data indicating polishing torque that changes as the polishing progresses is monitored to determine the polishing end point of the predetermined film. A polishing end point detection method using a change in torque to be detected, the first step of measuring the torque or an index corresponding to the torque, and a periodic component in the data by performing Fourier transform on the measured data A second step of analyzing the data, a third step of calculating a moving average processing time for removing a periodic noise component based on the periodic component, and a calculation in real time for the data. A fourth step of correcting the waveform by performing an averaging process based on the moving average processing time, a change in the corrected torque waveform is monitored by a plurality of algorithms, and the monitoring result is set to a plurality of preset values. A fifth step of discriminating the film type of the predetermined film in comparison with the limiting condition, and the torque waveform corrected by the polishing end point detection algorithm corresponding to the determined film type of the predetermined film A sixth method of detecting a polishing end point of the predetermined film by monitoring a change and a polishing end point detection method using torque change.

  According to this configuration, since the surface of the predetermined film has minute irregularities, the frictional force is large, and accordingly, disturbance caused by natural vibrations of various members in the polishing machine is mixed into the polishing torque. By applying Fourier transform to the data indicating such polishing torque, dressing such as fixed periodic components generated in synchronization with the rotation of the platen motor and head motor, and interval dressing and in-situ dressing (dressing while polishing) Periodic components in the data, such as periodic components that vary continuously in real time due to conditions and the surface condition of the polishing pad that changes depending on the dressing, are analyzed. By applying the averaging process to the data with the minimum necessary moving average processing time calculated in real time based on the analyzed periodic component, the torque waveform corrected by removing the periodic noise component from the data is efficiently obtained. Desired. Next, differences in the slope of the corrected torque waveform, particularly when rising in the initial stage of polishing, are monitored by a plurality of algorithms, and the monitoring results are compared with a plurality of limiting conditions to determine the film quality of a predetermined film that is a film to be polished. The film type such as the film thickness is discriminated. Then, by monitoring the change in the torque waveform as the polishing progresses with an algorithm for detecting the polishing end point selected according to the film type, the polishing end point of a given film is reliably detected at an appropriate timing. Is done.

  According to a second aspect of the present invention, a wafer having a predetermined film with minute irregularities on its surface is held by a polishing head, and the predetermined film is rotated while rotating the polishing head on a polishing pad provided on the surface of a rotating platen. Polishing end point detection method using torque change to detect the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes as the polishing progresses, A first step of measuring a torque or an index corresponding to the torque, a second step of performing Fourier transform on the measured data to analyze a periodic component in the data, and a periodic noise based on the periodic component A third step of calculating a moving average processing time for removing components, and correcting the waveform by averaging the data based on the moving average processing time calculated in real time. A fourth step of monitoring the change of the corrected torque waveform with a plurality of algorithms, and comparing the monitoring result with a plurality of preset limiting conditions to determine the film type of the predetermined film The first differential value of the corrected torque waveform is calculated by an algorithm for detecting the end point of polishing according to the step 5 and the film type of the determined predetermined film, and polishing with respect to the first differential value at the initial stage of polishing is calculated. A sixth method for detecting the polishing end point of the predetermined film based on a change in at least one of the ratio of the primary differential value near the end or the difference between the primary differential value near the polishing end and the primary differential value in the predetermined initial stage of polishing. And a polishing end point detection method using torque change.

  According to this configuration, the first derivative value of the torque waveform is calculated by the polishing end point detection algorithm selected according to the film type. Next, a change in at least one of the ratio of the primary differential value near the polishing end to the primary differential value at the predetermined polishing initial stage or the difference between the primary differential value near the polishing end and the primary differential value at the predetermined polishing initial stage is monitored. Based on this change, the polishing end point of the predetermined film is appropriately detected without being affected by drift noise in which the polishing torque decreases due to the dressing state of the polishing pad and the like.

  According to a third aspect of the present invention, a wafer having a predetermined film with minute irregularities on its surface is held by a polishing head, and the predetermined film is rotated while rotating the polishing head to a polishing pad provided on the surface of a rotating platen. Polishing end point detection method using torque change to detect the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes as the polishing progresses, A first step of measuring a torque or an index corresponding to the torque, a second step of performing Fourier transform on the measured data to analyze a periodic component in the data, and a periodic noise based on the periodic component A third step of calculating a moving average processing time for removing the component and an average process based on the moving average processing time calculated in real time for the data to correct the waveform. A fourth step of monitoring the change of the corrected torque waveform with a plurality of algorithms, and comparing the monitoring result with a plurality of preset limiting conditions to determine the film type of the predetermined film The second differential of the corrected torque waveform is performed by the step 5 and an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the change of the second derivative waveform near the polishing end is performed. There is provided a polishing end point detection method using torque change including a sixth step of detecting a polishing end point of the predetermined film based on a point.

  According to this configuration, in most cases, the waveform of the first derivative in the vicinity of the polishing end has a shape of convex upward and concave downward and convex downward and convex upward at the change point. When the second derivative is further applied to the first derivative in the region in the vicinity of the polishing end, the second derivative value changes from decreasing to increasing at the change point (minimum point). Therefore, the second derivative is applied to the torque waveform, the change point is obtained from the point where the second derivative value starts to increase, and the polishing is performed based on the dressing state of the polishing pad and the like based on the change point. Thus, the polishing end point of the predetermined film is appropriately detected without being affected by drift noise in which the torque decreases.

  According to a fourth aspect of the present invention, the plurality of limiting conditions in the fifth step include at least an inclination determination condition as to whether or not an inclination at the time of rising of the torque waveform at the initial stage of polishing is a predetermined set value or more, and polishing. In the initial stage, the contents of the rising value determination condition for determining whether the torque waveform rises above a predetermined threshold, the inclination determination condition, and the rising value determination condition are immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. There is provided a polishing end point detection method using a torque change including a temporal division condition indicating whether or not it occurs within a predetermined time period.

  According to this configuration, at least the inclination determination condition, the rising value determination condition, the temporal division condition, and the like are set in the plurality of restriction conditions for film type determination, and each specific content in the plurality of determination conditions overlaps. As a result, the film type of the predetermined film as the film to be polished is determined with a high probability.

  The invention according to claim 5 performs Fourier transform on the measured data in the second step to analyze a plurality of periodic components in the data, and corresponds to each of the plurality of periodic components in the third step. A plurality of moving average processing times are calculated, and in the fourth step, a torque change that corrects a waveform by performing a plurality of average processing based on the plurality of moving average processing times calculated in real time for the data is used. Provided is a polishing end point detection method.

  According to this configuration, the data indicating the polishing torque is caused by the fixed periodic component generated in synchronization with the rotation of the platen motor or the head motor, the dressing condition, the surface condition of the polishing pad changed by the dressing, and the like. Thus, a plurality of periodic components such as a periodic component that continuously changes in real time are generated. Therefore, the plurality of periodic noise components are removed from the data and corrected by performing a plurality of average processes on the data at the minimum required moving average processing time calculated in real time for each of the plurality of periodic components. A torque waveform is obtained.

  According to a sixth aspect of the present invention, a wafer having a predetermined film with minute irregularities on its surface is held on a polishing head, and the predetermined film is rotated while rotating the polishing head on a polishing pad provided on the surface of a rotating platen. A polishing end point detection device using torque change for detecting the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes as the polishing progresses, Torque measuring means for measuring torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and the moving average processing calculated in real time for the data Average processing means for correcting the waveform by averaging processing based on the interval, the change of the corrected torque waveform is monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of preset limiting conditions. The film type discriminating means for discriminating the film type of the predetermined film, and the change in the corrected torque waveform is monitored by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, A polishing end point detecting device using torque change having an end point detecting means for detecting the polishing end point of the film is provided.

  According to this configuration, since the surface of the predetermined film has minute irregularities, the frictional force is large, and accordingly, the polishing torque measured by the torque measuring means comes from the natural vibrations of various members in the polishing machine. Disturbance comes in. By applying Fourier transform to the data indicating the polishing torque by the periodic component analysis means, the fixed periodic component generated in synchronization with the rotation of the platen motor or the head motor, the dressing conditions, and the polishing pad that changes depending on the dressing are used. Periodic components in the data, such as periodic components that vary continuously in real time due to the surface state or the like, are analyzed. Based on the analyzed periodic components by the average processing time calculation means, the minimum required moving average processing time is calculated in real time, and the average processing is performed on the data with the moving average processing time calculated in real time by the average processing means. As a result, a torque waveform corrected by removing the periodic noise component from the data is efficiently obtained. Next, in the film type discriminating means, differences in the corrected torque waveform, such as an inclination at the time of rising in the initial stage of polishing, are monitored by a plurality of algorithms, and the monitoring result is compared with a plurality of limiting conditions to determine the film to be polished. A film type such as a film quality and a film thickness of the predetermined film is discriminated. Then, by monitoring the change of the torque waveform with the progress of polishing by the polishing end point detection algorithm selected according to the film type in the end point detecting means, the polishing end point of the predetermined film is appropriately set. It is reliably detected at the timing.

  According to a seventh aspect of the present invention, a wafer having a predetermined film with minute irregularities on a surface is held on a polishing head, and the predetermined film is rotated while rotating the polishing head on a polishing pad provided on a surface of a rotating platen. A polishing end point detection device using torque change for detecting the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes as the polishing progresses, Torque measuring means for measuring torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and the moving average processing calculated in real time for the data Average processing means for correcting the waveform by averaging processing based on the interval, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions, A first derivative value of the corrected torque waveform is calculated by an algorithm for detecting a polishing end point according to the determined film type of the predetermined film, and a first derivative value near the polishing end with respect to a predetermined first differential value of polishing Torque having an end point detecting means for detecting a polishing end point of the predetermined film based on a change in at least one of a ratio of the first differential value near the polishing end point and a first differential value in the vicinity of the polishing end. Provided is a polishing end point detection device using change.

  According to this configuration, the first derivative value of the torque waveform is calculated by the end point detection means by the polishing end point detection algorithm selected according to the film type. Next, at least one of the ratio of the primary differential value near the polishing end to the primary differential value at the predetermined polishing initial stage or the difference between the primary differential value near the polishing end and the primary differential value at the predetermined polishing initial stage is monitored, and these changes are monitored. Based on the above, the polishing end point of the predetermined film is appropriately detected without being affected by drift noise in which the polishing torque decreases due to the dressing state of the polishing pad or the like.

  According to an eighth aspect of the present invention, a wafer having a predetermined film with minute irregularities on a surface is held by a polishing head, and the predetermined film is rotated while rotating the polishing head on a polishing pad provided on a surface of a rotating platen. A polishing end point detection device using torque change for detecting the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes as the polishing progresses, Torque measuring means for measuring torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and the moving average processing calculated in real time for the data Average processing means for correcting the waveform by averaging processing based on the interval, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions, A second derivative of the corrected torque waveform is performed by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the predetermined difference is determined based on the change point of the second derivative waveform near the polishing end. A polishing end point detection device using torque change, characterized in that it has an end point detection means for detecting the polishing end point of the film.

  According to this configuration, in most cases, the waveform of the first derivative in the vicinity of the polishing end has a shape of convex upward and concave downward and convex downward and convex upward at the change point. When the second derivative is further applied to the first derivative in the region in the vicinity of the polishing end, the second derivative value changes from decreasing to increasing at the change point (minimum point). Therefore, in the end point detection means, the torque waveform is subjected to a second derivative by the polishing end point detection algorithm selected according to the film type, and the change point from the point where the second derivative value is changed from decrease to increase. Is required. Based on this change point, the polishing end point of the predetermined film is appropriately detected without being affected by drift noise in which the polishing torque decreases due to the surface condition of the polishing pad. .

  According to the ninth aspect of the present invention, the plurality of limiting conditions in the film type determining means include at least an inclination determining condition as to whether or not an inclination at the time of rising of the torque waveform at an initial stage of polishing is a predetermined set value or more, and polishing In the initial stage, the contents of the rising value determination condition for determining whether the torque waveform rises above a predetermined threshold, the inclination determination condition, and the rising value determination condition are immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. There is provided a polishing end point detecting device using a torque change including a time division condition indicating whether or not it occurs within a predetermined time period.

  According to this configuration, at least the inclination determination condition, the rising value determination condition, the temporal division condition, and the like are set in the plurality of restriction conditions for film type determination in the film type determination means, and each specification in the plurality of determination conditions The film type of the predetermined film as the film to be polished is discriminated with a high probability on the condition that the above-mentioned contents are duplicated.

  According to a tenth aspect of the present invention, the periodic component analysis means performs Fourier transform on the measured data to analyze a plurality of periodic components in the data, and the average processing time calculation means corresponds to the plurality of periodic components, respectively. A plurality of moving average processing times are calculated, and the average processing means uses a torque change that corrects the waveform by performing a plurality of average processing on the data based on the plurality of moving average processing times calculated in real time. Provided is a polishing end point detection device.

  According to this configuration, in the data indicating the polishing torque measured by the torque measuring unit, the fixed periodic component generated in synchronization with the rotation of the platen motor or the head motor, the dressing condition, and the polishing that changes depending on the dressing. A plurality of periodic components such as a periodic component that varies continuously in real time due to the surface state of the pad and the like are generated. Therefore, in the average processing time calculation means, the moving average processing time that is the shortest necessary for each of the plurality of periodic components is calculated in real time, and the average processing means calculates a plurality of data for each moving average processing time calculated in real time. By performing the averaging process, a plurality of periodic noise components are removed from the data, and a corrected torque waveform is obtained.

  The invention according to claim 1 is a first step of measuring a torque or an index corresponding to the torque, a second step of performing a Fourier transform on the measured data and analyzing a periodic component in the data, A third step of calculating a moving average processing time for removing a periodic noise component based on the periodic component, and a waveform obtained by averaging the data based on the moving average processing time calculated in real time The fourth step of correcting the torque and the change in the corrected torque waveform are monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of preset limiting conditions to determine the film type of the predetermined film. A change in the corrected torque waveform is monitored by a fifth step and an algorithm for detecting the polishing end point according to the determined film type of the predetermined film to detect the polishing end point of the predetermined film. 6th Therefore, we analyze the fixed periodic component and the periodic component that fluctuates in real time due to the dressing conditions and the surface condition of the polishing pad, etc., and real time based on the analyzed periodic component By performing the averaging process on the data indicating the polishing torque with the moving average processing time calculated in (1), it is possible to efficiently obtain the torque waveform from which the periodic noise component has been removed. Subsequently, the change of the torque waveform is monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of limiting conditions, whereby the film type of a predetermined film can be determined. And, by monitoring the change of the torque waveform with the progress of polishing with the algorithm for detecting the polishing end point selected according to the film type, the polishing end point of the predetermined film can be detected with high accuracy and reliability. There is an advantage that can be.

  The invention according to claim 2 is a first step of measuring a torque or an index corresponding to the torque, a second step of analyzing a periodic component in the data by applying a Fourier transform to the measured data, A third step of calculating a moving average processing time for removing a periodic noise component based on the periodic component, and a waveform obtained by averaging the data based on the moving average processing time calculated in real time The fourth step of correcting the torque and the change in the corrected torque waveform are monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of preset limiting conditions to determine the film type of the predetermined film. A first differential value of the corrected torque waveform is calculated by a fifth step and an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the first differential value of the predetermined initial polishing is calculated. Detecting a polishing end point of the predetermined film based on a change in at least one of a ratio of a primary differential value near the polishing end or a difference between the primary differential value near the polishing end and the primary differential value near the predetermined polishing initial stage. Therefore, the first differential value of the torque waveform is calculated by the algorithm for detecting the polishing end point selected according to the film type, and based on this primary differential value, the polishing pad There is an advantage that the polishing end point of a predetermined film can be reliably detected with high accuracy without being affected by drift noise in which polishing torque decreases due to a dressing state or the like.

  The invention according to claim 3 is a first step of measuring a torque or an index corresponding to the torque, a second step of analyzing a periodic component in the data by performing Fourier transform on the measured data, A third step of calculating a moving average processing time for removing a periodic noise component based on the periodic component, and a waveform obtained by averaging the data based on the moving average processing time calculated in real time The fourth step of correcting the torque and the change in the corrected torque waveform are monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of preset limiting conditions to determine the film type of the predetermined film. A second derivative of the corrected torque waveform is performed by a fifth step and an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the second derivative waveform near the polishing end is obtained. Strange And a sixth step of detecting the polishing end point of the predetermined film based on the point, so that the torque waveform is subjected to second-order differentiation by the algorithm for detecting the polishing end point selected according to the film type. The change end point is obtained, and based on this change point, the polishing end point of the predetermined film is increased without being affected by drift noise that decreases the polishing torque due to the dressing state of the polishing pad, etc. There is an advantage that it can be detected reliably with accuracy.

  According to a fourth aspect of the present invention, the plurality of limiting conditions in the fifth step include at least an inclination determination condition as to whether or not an inclination at the time of rising of the torque waveform at the initial stage of polishing is a predetermined set value or more, and polishing. In the initial stage, the contents of the rising value determination condition for determining whether the torque waveform rises above a predetermined threshold, the inclination determination condition, and the rising value determination condition are immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. Since it includes a time division condition whether or not it occurs within a predetermined time zone, there are a plurality of limiting conditions for film type discrimination, such as an inclination discrimination condition, an increase value discrimination condition, a temporal division condition, etc. By setting each of the determination conditions, and on the condition that each specific content in the plurality of determination conditions is duplicated, it is possible to determine the film type of the predetermined film that is the film to be polished with high probability. The benefit of being able to There is.

  The invention according to claim 5 performs Fourier transform on the measured data in the second step to analyze a plurality of periodic components in the data, and corresponds to each of the plurality of periodic components in the third step. Since a plurality of moving average processing times are calculated, and the waveform is corrected by performing a plurality of averaging processes based on the plurality of moving average processing times calculated in real time for the data in the fourth step. In the case where a plurality of periodic components such as a fixed periodic component and a real-time and continuously changing periodic component are included in the data indicating the polishing torque, each moving average calculated in real time for each of the plurality of periodic components. By performing a plurality of averaging processes in the processing time, it is possible to efficiently obtain a torque waveform from which a plurality of periodic noise components are removed from the data. There is.

  The invention according to claim 6 is a torque measurement means for measuring a torque or an index corresponding to the torque, a periodic component analysis means for performing a Fourier transform on the measured data and analyzing a periodic component in the data, and an analysis An average processing time calculating means for calculating a moving average processing time for removing a periodic noise component based on the periodic component, and an average processing based on the moving average processing time calculated in real time for the data The average processing means for correcting the waveform and the change of the corrected torque waveform are monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of preset limiting conditions to determine the film type of a predetermined film. The change in the corrected torque waveform is monitored by the film type discriminating means for discriminating and the polishing end point detection algorithm corresponding to the discriminated film type of the predetermined film. Since there is an end point detection means for detecting the polishing end point of the film, it varies continuously in real time due to the periodic component fixed by the periodic component analysis means, the dressing conditions, the surface condition of the polishing pad, etc. Analyzing the periodic component that goes, and averaging the data showing the polishing torque with the moving average processing time calculated in real time from the periodic component by the average processing means, the torque waveform from which the periodic noise component has been removed is efficiently You can often ask. Next, the change in the torque waveform is monitored by a plurality of algorithms in the film type discriminating means, and the film type of a predetermined film can be discriminated by comparing the monitoring result with a plurality of limiting conditions. Then, by monitoring the change in the torque waveform with the progress of polishing by the polishing end point detection algorithm selected according to the film type in the end point detecting means, the polishing end point of the predetermined film can be determined with high accuracy. There is an advantage that it can be detected reliably.

  The invention according to claim 7 is a torque measuring means for measuring a torque or an index corresponding to the torque, a periodic component analyzing means for performing a Fourier transform on the measured data and analyzing a periodic component in the data, and an analysis An average processing time calculating means for calculating a moving average processing time for removing a periodic noise component based on the periodic component, and an average processing based on the moving average processing time calculated in real time for the data Average processing means for correcting the waveform, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions, and the determined predetermined film The first derivative value of the corrected torque waveform is calculated by an algorithm for detecting the polishing end point according to the film type, and the ratio of the first derivative value near the polishing end to the predetermined first differential value of polishing is determined. Or an end point detecting means for detecting a polishing end point of the predetermined film based on a change in at least one of a difference between a primary differential value in the vicinity of the polishing end and a predetermined initial differential value. Therefore, the first differential value of the torque waveform is calculated by the polishing end point detection algorithm selected according to the film type in the end point detection means, and the dressing state of the polishing pad, etc. is based on this primary differential value. There is an advantage that it is possible to reliably detect the polishing end point of a predetermined film with high accuracy without being affected by drift noise in which polishing torque decreases due to the above.

  The invention according to claim 8 is a torque measuring means for measuring a torque or an index corresponding to the torque, a periodic component analyzing means for performing a Fourier transform on the measured data and analyzing a periodic component in the data, and an analysis An average processing time calculating means for calculating a moving average processing time for removing a periodic noise component based on the periodic component, and an average processing based on the moving average processing time calculated in real time for the data Average processing means for correcting the waveform, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions, and the determined predetermined film A second derivative of the corrected torque waveform is performed by an algorithm for detecting the polishing end point according to the film type, and the predetermined film is polished based on the change point of the second derivative waveform near the polishing end. The end point detection means for detecting the end point is provided, so that the change point is obtained by performing a second derivative on the torque waveform by the polishing end point detection algorithm selected according to the film type by the end point detection means. Based on this change point, the polishing end point of a given film is reliably detected with high accuracy without being affected by drift noise that reduces polishing torque due to the dressing condition of the polishing pad, etc. There is an advantage that you can.

  According to the ninth aspect of the present invention, the plurality of limiting conditions in the film type determining means include at least an inclination determining condition as to whether or not an inclination at the time of rising of the torque waveform at an initial stage of polishing is a predetermined set value or more, and polishing In the initial stage, the contents of the rising value determination condition for determining whether the torque waveform rises above a predetermined threshold, the inclination determination condition, and the rising value determination condition are immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. Including a time division condition for whether or not it occurs within a predetermined time zone, and as a plurality of limiting conditions for film type discrimination in the film type discrimination means, an inclination discrimination condition, an increase value discrimination condition, and By setting each discrimination condition such as temporal segmentation conditions, and on the condition that each specific content in the plurality of discrimination conditions is duplicated, it is highly probable that the film type of the predetermined film that is the film to be polished Discriminate by There is the advantage that it is possible.

  According to a tenth aspect of the present invention, the periodic component analysis means performs Fourier transform on the measured data to analyze a plurality of periodic components in the data, and the average processing time calculation means corresponds to the plurality of periodic components, respectively. Since the plurality of moving average processing times are calculated, the average processing means performs a plurality of average processing on the data based on the plurality of moving average processing times calculated in real time to correct the waveform. When a plurality of periodic components such as a fixed periodic component and a periodic component that continuously changes in real time are included in the data indicating the polishing torque, the average processing time calculation unit moves each of the plurality of periodic components. The average processing time is calculated in real time, and the average processing means performs a plurality of average processing on each moving average processing time for the data, thereby obtaining the data. There is an advantage that a plurality of periodic noise components from the data can be obtained efficiently removed torque waveform.

  Periodic noise that fluctuates continuously and noise that does not originate in the wafer state, such as drift noise due to dressing conditions and polishing pad state, are removed in real time to detect changes in the torque waveform that are purely caused by the wafer state and In order to achieve the purpose of reliably detecting the polishing end point with high accuracy by an algorithm for detecting the end point of polishing suitable for the film type of the polishing film, a wafer having a predetermined film with minute irregularities on the surface is prepared. Data indicating polishing torque that changes with the progress of the polishing by holding the predetermined film against the polishing pad provided on the surface of the rotating platen held by the polishing head and pressing the predetermined film while rotating the polishing head. A polishing end point detection method using a torque change for monitoring and detecting a polishing end point of the predetermined film, A first step of measuring an index corresponding to the torque or the torque, a second step of performing a Fourier transform on the measured data and analyzing a periodic component in the data, and a periodic noise based on the periodic component A third step of calculating a moving average processing time for removing the component, and a fourth step of correcting the waveform by averaging the data based on the moving average processing time calculated in real time. A fifth step of monitoring a change in the corrected torque waveform with a plurality of algorithms, comparing the monitoring result with a plurality of preset limiting conditions, and determining a film type of the predetermined film; A sixth step of detecting a polishing end point of the predetermined film by monitoring a change in the corrected torque waveform by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film. thing More was achieved.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. First, the configuration of the polishing end point detection device using torque change according to the present embodiment will be described. FIG. 1 is a schematic configuration of a chemical mechanical polishing apparatus and a block diagram of a polishing end point detection apparatus.

In FIG. 1, the chemical mechanical polishing apparatus 1 mainly includes a platen 2 and a polishing head 3. The platen 2 is formed in a disk shape, and a polishing pad 4 is attached to the upper surface thereof, and a platen motor M _{1 serving as} a rotational drive source is connected to the center of the lower surface via a platen rotating shaft 5. The polishing head 3 is formed in a disk shape smaller than the platen 2 side, and a head motor M _{2 serving as} a rotation drive source is connected to the center of the upper surface via a head rotation shaft 6.

The chemical mechanical polishing apparatus 1 holds a wafer W with a polishing head 3 and supplies a predetermined conductive film 7 on the wafer W (lower side in FIG. 1) while supplying slurry onto the polishing pad 4 from a nozzle (not shown). In this state, the platen 2 and the polishing head 3 are rotated by the platen motor M ₁ and the head motor M ₂ , respectively, so that a predetermined conductive film 7 on the wafer W is formed on the chemical machine. Polished.

A torque measuring unit 9 as torque measuring means in the polishing end point detecting device 8 is attached to the platen rotating shaft 5. The torque measuring unit 9 measures data indicating the polishing torque of the predetermined conductive film 7 based on the torque of the platen rotating shaft 5. The measurement of the data indicating the polishing torque is performed by measuring the torque of the head rotating shaft 6 or the torque such as the current flowing through the platen motor M ₁ or the head motor M ₂ instead of measuring the torque of the platen rotating shaft 5. It may be performed by measuring a corresponding index.

  In addition to the torque measuring unit 9, the polishing end point detecting device 8 performs a Fourier transform on the measured data at the subsequent stage of the torque measuring unit 9 to analyze a periodic component in the data. A periodic component analysis unit 10 as a means, an average processing time calculation unit 11 as an average processing time calculation means for calculating a moving average processing time for removing a periodic noise component based on the analyzed periodic component, and the data On the other hand, an average processing unit 12 serving as an average processing means for correcting a waveform by averaging processing based on the moving average processing time calculated in real time, and monitoring a change in the corrected torque waveform by a plurality of algorithms. The film type discriminating unit 13 as the film type discriminating means for discriminating the film type of the predetermined conductive film 7 by comparing the result with a plurality of preset limiting conditions and the determined predetermined The end point of time when the change of the torque waveform is monitored by an algorithm for detecting the end point of polishing according to the film type of the conductive film 7 and the polishing end point of the predetermined conductive film 7 is detected based on the change of the torque waveform. Terminal time point detection units 14 as detection means are sequentially connected.

  Next, the polishing end point detection method by the polishing end point detection device 8 configured as described above is performed by “removing the periodic noise component from the data indicating the measured polishing torque” and “the periodic noise component is removed. "Determination of the film type of a predetermined conductive film by monitoring the change of the torque waveform with a plurality of algorithms" and "Change of the torque waveform with the algorithm for detecting the end point of polishing according to the film type of the predetermined conductive film" Will be described in the order of "detection of polishing end point by monitoring".

  “Removal of periodic noise component from data indicating measured polishing torque” will be described with reference to FIGS. 2 and 3A to 3D. FIG. 2 is a diagram for explaining how the minute unevenness on the wafer surface is flattened as the polishing progresses, and FIG. 3 shows an example of data indicating the torque of polishing and a torque waveform obtained by averaging the data. (A) is a waveform diagram of an example of data showing polishing torque, (b) is a waveform diagram showing an example of analysis results of periodic components analyzed from the data of FIG. (A), (c) is FIG. 4A is a waveform diagram showing a torque waveform obtained by averaging the data of FIG. 1A, and FIG. 2D is a waveform diagram showing an example of analysis results of periodic noise components of the torque waveform of FIG.

As shown in FIG. 2, there are minute convex portions 7a, 7a,... On the surface of the predetermined conductive film 7 on the wafer W applied to the present embodiment. The conductive film 7 having the minute projections 7a, 7a,... On the surface is polished and removed to flatten to form a multilayer wiring or the like. Therefore, the frictional force in the process of flattening the minute convex portions 7a, 7a,... Shown in FIG. 2 is large, and the data indicating the polishing torque measured by the torque measuring unit 9 is accompanied by chemical mechanical polishing. Disturbances caused by various devices including the platen motor M ₁ and the head motor M ₂ in the apparatus 1 and the natural vibrations of the members are mixed.

FIG. 3A shows torque data Ta measured by the torque measuring unit 9, and the torque data Ta is generated in synchronization with the rotation of the platen motor M ₁ and the head motor M _{2 in} the chemical mechanical polishing apparatus 1. A plurality of periodic noise components corresponding to periodic components that vary continuously in real time due to fixed periodic components and dressing conditions, the surface state of the polishing pad that changes due to the dressing, and the like are mixed. For this reason, it is difficult to accurately detect the polishing end point of the predetermined conductive film 7 from the change using the torque data Ta directly.

  In this embodiment, first, the periodic component analysis unit 10 performs Fourier transform on the torque data Ta, thereby analyzing the plurality of periodic components generated in the torque data Ta, and calculating an average processing time calculation unit. The moving average processing time corresponding to each periodic component that is the shortest necessary for removing the plurality of periodic noise components from the plurality of periodic components analyzed in 11 is calculated in real time. Then, the average processing unit 12 applies, in real time, a plurality of average processes for the moving average processing time corresponding to each periodic component to the torque data Ta, so that the torque waveform Tb from which the plurality of periodic noise components have been removed is obtained. Looking for.

  FIG. 3B shows a plurality of periodic components analyzed by applying Fourier transform to the torque data Ta by the periodic component analyzing unit 10. In the waveform of the periodic noise component Na including the plurality of periodic components, a periodic noise component having a particularly high intensity includes a periodic noise component having a period of u seconds, a periodic noise component having a period of v seconds, a periodic noise component having a period of w seconds, and the like. Existing. Next, the average processing time calculation unit 11 uses each periodic component that is the shortest necessary for removing a plurality of periodic noise components from these periodic components, that is, the u-second periodic component, the v-second periodic component, the w-second periodic component, and the like. The moving average processing time corresponding to each is calculated in real time. The minimum required moving average processing time is slightly longer than each period of a plurality of periodic noise components.

  FIG. 3C shows a torque waveform Tb obtained by subjecting the torque data Ta to a plurality of average processing for the moving average processing time calculated in real time corresponding to each periodic component. FIG. 3D shows a waveform of the periodic noise component Nb analyzed by applying Fourier transform to the torque waveform Tb. A plurality of periodic noise components including the strong periodic noise component are removed from the waveform of the noise component Nb.

  “Determination of the film type of a predetermined conductive film by monitoring changes in the torque waveform from which the periodic noise component has been removed with a plurality of algorithms” will be described with reference to FIG. FIG. 4 monitors torque waveform changes with a plurality of algorithms (first to third in the present embodiment) and collates the monitoring results with a plurality of preset limit conditions for polishing end detection. It is a figure which shows the method of discriminating the film | membrane type of a predetermined conductive film.

Each torque waveform Tb ₁ , Tb ₂ , Tb ₃ accompanying the progress of polishing shown in FIG. 4 is formed on the semiconductor substrate by the film quality including the material of the predetermined conductive film 7 and the film thickness, and further by the conductive film 7. It generally takes different forms depending on the density of the pattern. In FIG. 4, three types of torque waveforms Tb ₁ to Tb ₃ are shown so as to correspond to the first to third algorithms. Thus, in order to reliably detect the polishing end, an algorithm is selected according to the film type of the predetermined conductive film 7 corresponding to each torque waveform Tb ₁ , Tb ₂ , Tb ₃ , and the selected algorithm is used. It is necessary to process each torque waveform Tb ₁ , Tb ₂ , Tb ₃ . Therefore, the film type discriminating unit 13 discriminates the film type of the predetermined conductive film 7 prior to detection of the polishing end point by the end point detecting unit 14.

The plurality of limiting conditions for determining the film type in the film type determining unit 13 include at least the gradients (dTb ₁ / dt) and (dTb ₂ / d) when the torque waveforms Tb ₁ , Tb ₂ , and Tb ₃ are increased in the initial stage of polishing. dt), (dTb ₃ / dt) are inclination determination conditions as to whether or not each is greater than or equal to a predetermined inclination threshold (the inclination threshold is not shown), and torque waveforms Tb ₁ , Tb ₂ , Tb _{3 at the} initial stage of polishing are The content of each of the rising value determination condition whether to rise above a predetermined level threshold value Sth ₁ , Sth ₂ ,..., The inclination determination condition, and the rising value determination condition is determined immediately after the start of polishing or from the start of polishing. Including the time division condition of whether or not it occurs within a predetermined time zone t _D1 , t _D2 , t _D3 , t _D4 , etc. after the passage of time, each specific content in these discrimination conditions is duplicated Subject to There.

In addition to the inclination determination condition, the increase value determination condition, and the time division condition, the torque waveforms Tb ₁ , Tb ₂ , and Tb ₃ include the predetermined level threshold values Sth ₁ , Sth ₂ , Sth as a plurality of limiting conditions. ₃ After the rise exceeds, the inflection point whether or not the inflection points P ₁ , P ₂ , P ₃ are generated after the increased torque value is maintained within a predetermined fluctuation range and a predetermined time elapses. By setting the point determination condition, the film type of the predetermined conductive film 7 can be determined with a higher probability.

When the torque waveform Tb ₁ is generated as the polishing progresses, the change of the torque waveform Tb ₁ is monitored by the first algorithm, and collation with each of the above limiting conditions is performed. As a result of this collation, the inclination comparison result between the inclination (dTb ₁ / dt) when the torque waveform Tb ₁ rises in the initial stage of polishing and the first inclination threshold value is “inclination (dTb ₁ / dt)”> No. 1 inclination threshold ”, and the increase value comparison result between the increase value of the torque waveform Tb ₁ and the first level threshold value Sth _{1 in the} initial stage of polishing is“ the increase value of the torque waveform Tb ₁ ”>“ the first level threshold value ” Sth ₁ ”and the contents of the inclination comparison result and the increased value comparison result occur within the first time period t _D1 immediately after the start of polishing. Further, after the torque waveform Tb ₁ rises exceeding the first level threshold value Sth ₁ , the increased torque value is maintained within a predetermined fluctuation range, and a third time period t _D3 after a predetermined time has elapsed from the start of polishing. An inflection point P ₁ occurs in the region. On the condition of these collation results, the predetermined conductive film 7 is discriminated as a conductive film of the first film type taking the form of the torque waveform Tb _{1 as} the polishing proceeds.

When the torque waveform Tb ₂ is generated with the progress of polishing, the change of the torque waveform Tb ₂ is monitored by the second algorithm, and collation with each of the limiting conditions is performed. As a result of this collation, the inclination comparison result between the inclination (dTb ₂ / dt) when the torque waveform Tb ₂ is increased in the initial stage of polishing and the first inclination threshold and the second inclination threshold is “the first inclination threshold. ”>“ Tilt (dTb ₂ / dt) ”>“ second tilt threshold value ”, and the increase value of the torque waveform Tb _{2 in} the initial stage of polishing and the first level threshold value Sth ₁ and the second level threshold value Sth ₂ The rise value comparison result is “first level threshold value Sth ₁ ”> “rise value of torque waveform Tb ₂ ”> “second level threshold value Sth ₂ ”, and the slope comparison result and the rise value comparison result Each content occurs within the first time zone t _D1 . Further, after the torque waveform Tb ₂ rises exceeding the second level threshold value Sth ₂ , the increased torque value is maintained within a predetermined fluctuation range, and the inflection point P ₂ is set within the third time zone t _D3 . Has occurred. On the condition of these collation results, the predetermined conductive film 7 is discriminated as a conductive film of the second film type taking the form of the torque waveform Tb _{2 as} the polishing proceeds.

When the torque waveform Tb ₃ is generated with the progress of polishing, the change of the torque waveform Tb ₃ is monitored by the third algorithm, and collation with each of the limiting conditions is performed. As a result of this collation, the inclination comparison result between the inclination (dTb ₃ / dt) when the torque waveform Tb ₃ rises in the initial stage of polishing and the second inclination threshold and the third inclination threshold is “the second inclination threshold. ">" Inclination (dTb ₃ / dt) ">" Third inclination threshold value ", and the increase value of the torque waveform Tb _{3 in} the initial stage of polishing, the second level threshold value Sth ₂ and the third level threshold value Sth ₃ The rise value comparison result is “second level threshold value Sth ₂ ”> “rise value of torque waveform Tb ₃ ”> “third level threshold value Sth ₃ ”, and the inclination comparison result and the rise value comparison result Each content occurs within the second time zone t _D2 . Further, after the torque waveform Tb ₃ rises exceeding the third level threshold value Sth ₃ , the increased torque value is maintained within a predetermined fluctuation range, and the inflection point P ₃ is set within the fourth time zone t _D4 . Has occurred. On the condition of these collation results, the predetermined conductive film 7 is discriminated as a conductive film of the third film type taking the form of the torque waveform Tb _{3 as} the polishing proceeds.

  Next, “detection of the polishing end point by monitoring the change of the torque waveform with an algorithm for detecting the polishing end point according to the film type of the predetermined conductive film” is used with reference to FIGS. I will explain. FIG. 5 is a diagram for explaining a method of detecting the polishing end point based on a change in torque waveform. FIG. 5A is a waveform showing an example of a torque waveform that varies under the influence of drift noise due to a difference in dressing method. FIGS. 4A and 4B are diagrams for explaining a method of detecting a polishing end point by applying a first derivative to the torque waveform of FIG. A, and FIG. 4C applying a second derivative to the torque waveform of FIG. It is a figure for demonstrating the method to detect the polishing end time.

  After the film type discriminating unit 13 discriminates the film type of the predetermined conductive film 7, the change in torque waveform accompanying the progress of polishing in the terminal time point detecting unit 14 depends on the discriminated film type. The predetermined end point of polishing of the conductive film 7 is detected by monitoring the torque waveform by applying a first derivative or a second derivative to the selected torque end point detection algorithm.

A method of detecting the polishing end point by first-order differentiation of the torque waveform Tb using FIGS. 5A and 5B will be described. In FIG. 5A, Tb ₄ is a torque waveform accompanying the progress of polishing of the predetermined conductive film 7 in the case of in-situ dressing where dressing of the polishing pad 4 is performed while polishing, whereas Tb ₅ is polishing. 6 is a torque waveform accompanying the progress of polishing of the predetermined conductive film 7 in the case of interval dressing in which dressing of the polishing pad 4 is performed before. In the case of interval dressing, since dressing is not performed during polishing, clogging gradually progresses during polishing although the surface state of the polishing pad 4 is minute. As a result, the torque waveform Tb _{5 in} the case of interval dressing is gradually reduced as the polishing proceeds as shown in the figure due to the influence of drift noise.

For this reason, when the torque waveform reaches a predetermined slope (first derivative value), for example, when it is set as the polishing end point detection time, in the case of the torque waveform Tb ₄ that is not affected by drift noise, it is predetermined at point E. This point E is detected as the polishing end point. On the other hand, in the case of the torque waveform Tb ₅ that is affected by drift noise, a predetermined slope (first differential value) is reached at point G, and erroneous detection is performed for the correct polishing end point E. Mae.

Therefore, in the present embodiment, as shown in FIG. 5B, first, the first derivative is applied to any torque waveform, and the first derivative (dTb ₄ / dt) waveform with respect to the torque waveform Tb ₄ , and The waveform of the first derivative (dTb ₅ / dt) with respect to the torque waveform Tb ₅ is obtained. And as follows, the ratio of the primary differential value of the for both first-order derivative value, polishing end vicinity t ₂ for a given primary differential value of the polishing initial t ₁ (t ₂ in FIG. 5 (b) equal to point E) That is, (dTb ₄ / dt) _t2 / (dTb ₄ / dt) _t1 (1)
(DTb ₅ / dt) _t2 / (dTb ₅ / dt) _t1 (2)
Is being monitored. The values of the above equations (1) and (2) are almost equal. As a result, it is possible to correctly detect the polishing end point E of the predetermined conductive film 7 without being affected by drift noise in which polishing torque decreases due to the dressing state of the polishing pad 4 and the like.

Further, as follows, the difference between the primary differential value near the polishing end t _{2 and} the primary differential value of the predetermined initial polishing t ₁ , that is, (dTb ₄ / dt) _{t 2} − (dTb ₄ / dt) _t 1 (3)
(DTb ₅ / dt) _t2 − (dTb ₅ / dt) _t1 (4)
To monitor. The values of the above equations (3) and (4) are almost equal. As a result, as in the case of using the relationship of the expressions (1) and (2), the influence of drift noise in which the polishing torque decreases due to the dressing state of the polishing pad 4 and the like is not affected. The polishing end point E of the predetermined conductive film 7 can be detected correctly.

A method of detecting the polishing end point by performing the second derivative on the torque waveform Tb will be described with reference to FIG. Instead of detecting the polishing end point by applying a first derivative to the torque waveform Tb, a change point is obtained by a second derivative with respect to the torque waveforms Tb ₄ and Tb ₅ as follows. However, the polishing end point of the predetermined conductive film 7 can be detected.

That is, both of the waveforms of the first derivative (dTb ₄ / dt) and (dTb ₅ / dt) near the polishing end t ₂ are almost the boundary between the change points Q ₁ and Q ₂ which are substantially equal to the position of the E point. Then, the shape is convex upward and concave downward, and convex downward and concave upward. When the second derivative (d ² Tb ₄ / dt ² ) and (d ² Tb ₅ / dt ² ) are further applied to the respective first derivative waveforms in the region near the polishing end t ₂ , FIG. As shown, the values of the second derivative (d ² Tb ₄ / dt ² ) and (d ² Tb ₅ / dt ² ) decrease from the change points (minimum points) Q ₁ and Q ₂ , respectively. It starts to increase. Therefore, the second derivative (d ² Tb ₄ / dt ² ) and (d ² Tb ₅ / dt ² ) are applied to the torque waveforms Tb ₄ and Tb ₅ , and the value of the second derivative is changed from decreasing to increasing. the calculated change point Q ₁ or Q _2, the change point Q ₁ or Q ₂ in the same manner as the by the base, drift noise torque of polishing due to the dressing state of the polishing pad 4 is decreased The polishing end point E of the predetermined conductive film 7 can be correctly detected without being affected by the above.

  When the polishing end point E is detected by any of the above methods, it is difficult to detect the moment when the predetermined conductive film 7 is completely removed as the polishing end point E. For this reason, a predetermined conductive film 7 is obtained by giving an overpolish time with another parameter from the end point detected by an algorithm selected according to the film type, and ending the polishing process after continuing the polishing for a certain time. Can be guaranteed.

  As described above, in the polishing end point detection method and apparatus using torque change according to the present embodiment, a plurality of average processes are performed on the torque data Ta at each moving average processing time calculated in real time for each of a plurality of periodic components. The torque waveform Tb corrected by removing a plurality of periodic noise components can be obtained efficiently.

  The change of the torque waveform Tb from which the periodic noise component has been removed is monitored by a plurality of algorithms, and the monitoring result is collated with a plurality of limiting conditions including an inclination determination condition, an ascending value determination condition, and a temporal division condition, By setting each specific content in the conditions to be duplicated, the film type of the predetermined conductive film 7 that is the conductive film to be polished can be determined with high probability.

First-order differentiation is performed on the torque waveform Tb accompanying the progress of polishing with an algorithm for detecting the polishing end point selected according to the film type, and the first-order differential value near the polishing end t _{2 with} respect to the first-order differential value of the predetermined polishing initial t ₁ Or at least one of the difference between the first differential value in the vicinity of the polishing end t _{2 and} the first differential value in the predetermined initial polishing t ₁ , which is caused by the dressing state of the polishing pad 4 and the like. Thus, the polishing end point E of the predetermined conductive film 7 can be reliably detected with high accuracy without being affected by drift noise in which the polishing torque decreases.

  By applying a second derivative to the torque waveform Tb accompanying the progress of polishing with an algorithm for detecting the polishing end point selected according to the film type, a change point Q is obtained, and based on this change point Q, Similarly, the polishing end point E of the predetermined conductive film 7 is reliably detected with high accuracy without being affected by drift noise in which polishing torque decreases due to the dressing state of the polishing pad 4 and the like. Can do.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

FIG. 1 shows a polishing end point detection method and apparatus using torque change according to an embodiment of the present invention.
1 is a block diagram showing a schematic configuration of a chemical mechanical polishing apparatus and a polishing end point detection device. FIG. The figure for demonstrating a mode that the micro unevenness | corrugation of a wafer surface is planarized with progress of grinding | polishing. It is a wave form diagram which shows the torque example etc. which performed the data example which shows the torque of grinding | polishing, and this data, (a) is a wave form diagram of the data example which shows the torque of grinding | polishing, (b) is a figure of (a). (C) is a waveform diagram showing a torque waveform obtained by averaging the data of FIG. (A), (d) is a torque waveform of FIG. (C) The wave form diagram which shows the example of an analysis result of the periodic noise component. The wave form diagram for demonstrating the method to monitor the change of a torque waveform with a some algorithm, and to discriminate | determine the film | membrane type of a to-be-polished conductive film. It is a figure for demonstrating the method of detecting the grinding | polishing terminal end time based on the change of a torque waveform, (a) is a wave form diagram which shows the example of a torque waveform which changes under the influence of the drift noise by the difference in a dressing method, ( (b) is a diagram for explaining an example of a method for detecting the end point of polishing by applying a first derivative to the torque waveform of FIG. (a), and (c) is a polishing by applying a second derivative to the torque waveform of FIG. (a). The figure for demonstrating the example of a method of detecting an end time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chemical mechanical polishing apparatus 2 Platen 3 Polishing head 4 Polishing pad 5 Platen rotating shaft 6 Head rotating shaft 7 Conductive film 7a Minute convex part 8 Polishing end time detection apparatus 9 Torque measuring part (torque measuring means)
10 Periodic component analysis unit (periodic component analysis means)
11 Average processing time calculation unit (average processing time calculation means)
12 Average processing section (average processing means)
13 Film type discriminating section (film type discriminating means)
14 Termination point detection unit (Termination point detection means)
M ₁ platen motor M ₂ head motor Na Periodic noise component Nb Noise component Ta Torque data Tb Torque waveform

Claims (10)

A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A method for detecting a polishing end point using a torque change for monitoring a polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of the method,
A first step of measuring the torque or an index corresponding to the torque; a second step of performing Fourier transform on the measured data to analyze a periodic component in the data; and a period based on the periodic component A third step of calculating a moving average processing time for removing a noise component, and a fourth step of correcting the waveform by averaging the data based on the moving average processing time calculated in real time And a change of the corrected torque waveform with a plurality of algorithms, and a fifth step of discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions; A sixth step of detecting a polishing end point of the predetermined film by monitoring a change in the corrected torque waveform by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film; Have Polishing end point detecting method using a torque change characterized by and. A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A method for detecting a polishing end point using a torque change for monitoring a polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of the method,
A first step of measuring the torque or an index corresponding to the torque; a second step of performing Fourier transform on the measured data to analyze a periodic component in the data; and a period based on the periodic component A third step of calculating a moving average processing time for removing a noise component, and a fourth step of correcting the waveform by averaging the data based on the moving average processing time calculated in real time And a change of the corrected torque waveform with a plurality of algorithms, and a fifth step of discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions; A first differential value of the corrected torque waveform is calculated by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the vicinity of the polishing end with respect to the first differential value of the predetermined initial polishing is calculated. A sixth step of detecting a polishing end point of the predetermined film based on a change in at least one of a ratio of a second derivative value or a difference between a first derivative value near the polishing end and a first differential value in a predetermined polishing initial stage; A method for detecting the end point of polishing using a torque change. A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A method for detecting a polishing end point using a torque change for monitoring a polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of the method,
A first step of measuring the torque or an index corresponding to the torque; a second step of performing Fourier transform on the measured data to analyze a periodic component in the data; and a period based on the periodic component A third step of calculating a moving average processing time for removing a noise component, and a fourth step of correcting the waveform by averaging the data based on the moving average processing time calculated in real time And a change of the corrected torque waveform with a plurality of algorithms, and a fifth step of discriminating the film type of the predetermined film by comparing the monitoring result with a plurality of preset limiting conditions; A second derivative of the corrected torque waveform is performed by an algorithm for detecting a polishing end point according to the determined film type of the predetermined film, and the second derivative waveform near the polishing end is changed based on a change point of the second derivative waveform. Polishing end point detecting method using the torque variation and having a sixth step of detecting the polishing end point of the constant of the film.   The plurality of limiting conditions in the fifth step include at least an inclination determination condition as to whether or not an inclination at the time of rising of the torque waveform at the initial stage of polishing is a predetermined set value or more, and the torque waveform is predetermined at the initial stage of polishing. Each condition of the rising value determination condition for whether or not to rise beyond the threshold, the inclination determination condition and the rising value determination condition occurs within a predetermined time zone immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. 4. The polishing end point detection method using torque change according to claim 1, further comprising a time division condition for determining whether or not the polishing is completed.   In the second step, the measured data is subjected to Fourier transform to analyze a plurality of periodic components in the data, and in the third step, a plurality of moving average processing times respectively corresponding to the plurality of periodic components are calculated. In the fourth step, the waveform is corrected by performing a plurality of averaging processes on the basis of the plurality of moving average processing times calculated in real time for the data. Alternatively, a polishing end point detection method using a torque change described in 4. A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A polishing end point detection device using a torque change to detect the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of
Torque measuring means for measuring the torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and an average for correcting the waveform by averaging the data based on the moving average processing time calculated in real time Processing means and film type discriminating means for monitoring a change in the corrected torque waveform with a plurality of algorithms and comparing the monitoring result with a plurality of preset limiting conditions to discriminate the film type of the predetermined film And the change of the corrected torque waveform is monitored by an algorithm for detecting the polishing end point according to the determined film type of the predetermined film, and the polishing end of the predetermined film is monitored. Polishing end point detecting apparatus using a torque variation and having a termination point detection means for detecting a point. A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A polishing end point detection device using a torque change to detect the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of
Torque measuring means for measuring the torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and an average for correcting the waveform by averaging the data based on the moving average processing time calculated in real time Processing means, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring results with a plurality of preset restriction conditions, and polishing according to the determined film type of the predetermined film A first derivative value of the corrected torque waveform is calculated by an algorithm for detecting the end point, and the ratio of the first derivative value near the polishing end to the predetermined first derivative value of polishing or the polishing end value is calculated. A torque having an end point detecting means for detecting a polishing end point of the predetermined film on the basis of a change in at least one of a difference between a primary differential value in the vicinity and a primary differential value in a predetermined initial stage of polishing; Polishing end point detection device using change. A wafer having a predetermined film with minute irregularities on the surface is held by a polishing head, and the predetermined film is pressed against the polishing pad provided on the surface of the rotating platen while rotating the polishing head to polish the polishing film. A polishing end point detection device using a torque change to detect the polishing end point of the predetermined film by monitoring data indicating polishing torque that changes with the progress of
Torque measuring means for measuring the torque or an index corresponding to the torque, periodic component analyzing means for analyzing the periodic component in the data by performing Fourier transform on the measured data, and based on the analyzed periodic component Average processing time calculation means for calculating a moving average processing time for removing periodic noise components, and an average for correcting the waveform by averaging the data based on the moving average processing time calculated in real time Processing means, film type discrimination means for discriminating the film type of the predetermined film by comparing the monitoring results with a plurality of preset restriction conditions, and polishing according to the determined film type of the predetermined film Performs a second derivative of the modified torque waveform by an end point detection algorithm, and detects the polishing end point of the predetermined film based on the change point of the second derivative waveform near the polishing end. Polishing end point detecting apparatus using a torque variation and having a termination point detection means that.   The plurality of limiting conditions in the film type discriminating means include at least an inclination discriminating condition as to whether or not an inclination at the time of rising of the torque waveform at the initial stage of polishing is equal to or greater than a predetermined set value, Each condition of the rising value determination condition for whether or not to rise beyond the threshold, the inclination determination condition and the rising value determination condition occurs within a predetermined time zone immediately after the start of polishing or after a predetermined time has elapsed since the start of polishing. 9. The polishing end point detection device using torque change according to claim 6, 7 or 8, characterized in that it includes a time division condition of whether or not it is a dry one.   The periodic component analysis means performs a Fourier transform on the measured data to analyze a plurality of periodic components in the data, and the average processing time calculation means calculates a plurality of moving average processing times respectively corresponding to the plurality of periodic components. 9. The average processing means corrects the waveform by performing a plurality of average processing on the data based on the plurality of moving average processing times calculated in real time. Or a polishing end point detection device using a torque change described in 9;

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