JP2010067918A - Method and device for predicting and detecting end of polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing end prediction and detection method capable of predicting an ending point precisely and timely just before the ending point, in order to detect the ending point certainly. <P>SOLUTION: At least two sensors which monitor the surface state of a wafer W during polishing, are arranged to predict the polishing end. A surface eddy current sensor 12 which predicts the polishing end point based on a change in magnetic flux by skin effect depending on materials of the conductive film as one factor, is used as one sensor. The polishing end point is predicted by using the characteristic change based on the skin effect, before completion of removing a metal film as a predetermined conductive film. The other sensor is a multiwavelength spectroscopic sensor 13, which irradiates light to the wafer W through a window 11 prepared in a platen 2, and monitors reflection light from the metal film to detect the polishing end point. These two sensors are attached to the window 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing end prediction / detection method and an apparatus therefor, and in particular, uses a plurality of sensors having independent operation principles in chemical mechanical polishing (CMP) and the like. The present invention relates to a polishing end prediction / detection method and apparatus capable of predicting and detecting the polishing end point with high detection sensitivity and high accuracy immediately before the end of polishing.

  Conventionally, for example, the following polishing method is known. This prior art is based on [0031] in the publication in which the prior art is disclosed. By mounting two types of sensors on a polishing apparatus, the Cu layer becomes a predetermined thickness until the Cu layer reaches a predetermined thickness. The film thickness is monitored by processing the signal, and when the film thickness reaches a predetermined thickness and can be detected by the optical sensor, the film thickness of the thin film is processed by processing the optical sensor signal. It is described to be monitored. Regarding the eddy current sensor, [0025], the system principle of the eddy current process monitor is that a high frequency current is passed through the sensor coil to generate an eddy current in the Cu layer of the wafer, and this eddy current varies with the film thickness. The film thickness is monitored by monitoring the combined impedance with the sensor circuit. That is, when a high-frequency current is passed through the sensor coil, an eddy current is generated in the Cu layer. Then, the impedance Z in the circuit is monitored. It is described that the impedance Z in the circuit has a shape in which L and C of the sensor unit and R of the Cu layer are coupled in parallel, and Z changes as R changes. For the optical sensor, [0030], the principle of film thickness measurement applied to the optical sensor utilizes light interference caused by the film and its adjacent media. When light is incident on the thin film on the substrate, a part of the light is first reflected by the surface of the film and the rest is transmitted. A part of the transmitted light is further reflected by the substrate surface and the rest is transmitted, but is absorbed when the substrate is a metal. Interference occurs due to the phase difference between the reflected light on the surface of the film and the reflected light on the substrate surface. That is, the reflection intensity changes according to the wavelength of incident light, the film thickness, and the refractive index of the film. It is described that the thickness of the film is measured from the intensity of the reflected light (see, for example, Patent Document 1).

  Conventionally, for example, the following substrate polishing method is known. In this prior art, [0045] in the publication in which the prior art is disclosed, an eddy current type film thickness measuring device and an optical film thickness measuring device are provided in the polishing table, and are held on the top ring. It is described that the film thickness of the polished surface of the semiconductor substrate being polished is measured. For the eddy current type film thickness measuring instrument, in [0046], a high frequency current is passed through the sensor coil to generate an eddy current in the conductive film (Cu film) of the semiconductor substrate. It is described that the film thickness is monitored by changing the thickness and monitoring the combined impedance with the sensor circuit. For the optical film thickness measuring device, in [0047], the optical film thickness measuring device comprises a light projecting element and a light receiving element, and the surface to be polished of the semiconductor substrate is irradiated with light from the light projecting element, Reflected light from the surface to be polished is received by a light receiving element. When the conductive film of the semiconductor substrate reaches a predetermined thickness, a part of the light irradiated to the polished surface from the light projecting element is transmitted through the conductive film and from the oxide film under the conductive film. There are two types of reflected light: reflected light reflected and reflected light reflected from the surface of the conductive film. It is described that the film thickness is measured by receiving and processing these two types of reflected light with a light receiving element (see, for example, Patent Document 2).

  Furthermore, conventionally, for example, an integrated end point detection system using the following optical and eddy current monitoring is known. In the prior art, [0027] in the publication in which the prior art is disclosed, the first polishing station includes an eddy current monitoring system and an optical monitoring system that function as a polishing process control and end point detection system. It is described. Regarding the eddy current monitoring system, in [0029] and [0031], the eddy current monitoring system detects a eddy current induced in the metal layer and a driving system for inducing eddy current in the metal layer on the substrate. And a sensing system. The drive system includes a drive coil to which an oscillator is connected. During operation, the oscillator drives a drive coil to generate a magnetic field, which generates eddy currents in the metal layer. The eddy current acts on the metal layer as an impedance source in parallel with the sensing coil and the capacitor. When the thickness of the metal layer changes, the impedance changes, and the Q factor of the sensing mechanism changes. By detecting this change in Q factor, the eddy current sensor is described as sensing a change in the strength of the eddy current, and thus a change in the thickness of the metal layer. With regard to the optical monitoring system, [0041] describes that the optical monitoring system includes a light source such as a laser and a detector, and functions as an interferometer. [0047] Then, in [0047], the CMP apparatus uses an eddy current monitoring system and an optical monitoring system to determine when most of the packed bed has been removed and to determine when the underlying stop layer is substantially exposed. It is described that it is determined (see, for example, Patent Document 3).

As described above, Patent Documents 1, 2, and 3 describe each eddy current sensor having substantially the same configuration and action and each optical sensor having substantially the same configuration and action.
Japanese Patent No. 3916375. Japanese Patent No. 3916846. JP-T-2004-525521.

  By the way, the present invention is a method for predicting and detecting the end point of polishing by combining a skin eddy current sensor and a multi-wavelength spectroscopic sensor. Among these, individual skin eddy current sensors are disclosed in the specification and drawings attached to the application of Japanese Patent Application No. 2007-134707 relating to the patent application of the present applicant. Further, as for individual multi-wavelength type spectroscopic sensors, Japanese Patent Application Laid-Open No. 2005-32790 relating to the patent application of the present applicant discloses a sensor having substantially the same configuration and operational effects.

Therefore, first, the operational effects of the configuration in which the eddy current sensor and the optical sensor described in Patent Documents 1, 2, and 3 are combined, and the configuration in which the skin eddy current sensor and the multi-wavelength spectroscopic sensor in the present invention are combined. Differences will be described in comparison with “differences in configuration / effects of individual sensors”.
A. Differences in configuration / effects of individual sensors.
(A) About the difference between the eddy current sensor in a prior art, and the skin eddy current sensor in this invention.

  The eddy current sensor generates an eddy current for the entire film thickness of the conductive film to be polished, and this eddy current changes according to the change in the film thickness, and monitors the combined impedance with the sensor circuit. Thickness is monitored. In addition to the above-mentioned Patent Documents 1, 2, and 3, a method for measuring the change in film thickness by generating an eddy current for the entire film thickness of such a conductive film is disclosed in JP-A-8-285514 (Patent No. 2878178) and JP-A-8-285515 (Japanese Patent No. 3290347) also discloses. As described above, an eddy current sensor in the prior art is one that monitors the film thickness in a relationship in which the film thickness amount of the conductive film and the eddy current amount correspond to each other.

The epidermal eddy current sensor according to the present invention is different from the eddy current sensor in configuration and operational effects. In the skin eddy current sensor according to the present invention, since the magnetic field exists only in the surface layer of the conductive film due to the skin effect at the initial stage of polishing, no eddy current is generated in the conductive film. When the conductive film becomes very thin just before the end of polishing, a magnetic field penetrates the conductive film and partially leaks to the substrate side, thereby generating an eddy current in the conductive film and increasing it. However, since the film thickness that induces eddy current substantially decreases as soon as the conductive film becomes thinner, the eddy current immediately starts to decrease. As a result, an inflection point of eddy current is induced in the conductive film just before the end of polishing. This is a method for predicting the polishing end point using this inflection point as a reference point. This method has the following advantages (operational effects) as compared with the conventional eddy current sensor.
-It is possible to predict the polishing end point with high sensitivity even immediately before the end. That is, the sensitivity is good at the end of polishing.
・ The magnetic field is not shaped and introduced into the film. A distributed magnetic field is used, and no magnetic field is applied to the elements in the substrate due to the skin effect. That is, the element is not damaged.
・ The eddy current sensor estimates the amount of change in film thickness (the amount of film thickness decrease due to polishing) by the amount of change in eddy current, whereas the skin eddy current sensor uses the remaining film thickness (absolute film thickness) corresponding to the skin depth. Accordingly, since the inflection point of the eddy current appears, it is possible to predict the polishing end point from the remaining film thickness regardless of the film thickness variation at the initial stage of polishing.
(B) About the difference between the optical sensor in the prior art and the multi-wavelength spectroscopic sensor in the present invention.

  Optical sensors in the prior art monitor film thickness using light interference. That is, a specific wavelength in light is used, and the film thickness is estimated by interference due to the specific wavelength.

  The multi-wavelength spectroscopic sensor according to the present invention is different from the optical sensor in configuration and operational effects. In the multi-wavelength spectroscopic sensor, the state change of the conductive film is estimated at a ratio of the integrated value of the reflectance intensity in another wavelength region to the integrated value of the reflectance intensity in a certain wavelength region.

  In the case of interference by a prior art optical sensor, film thickness measurement may not be possible if the light intensity changes due to the slurry present between the window and the wafer at a particular wavelength. On the other hand, when looking at the integrated value ratio of the reflectance intensity in the multi-wavelength spectroscopic sensor, the observation wavelength region may be wide, even if the light intensity changes due to the presence of slurry on the wafer, so much There is no significant impact. Further, since the evaluation is made based on the relative ratio of the reflectance intensity, there are few malfunctions.

  Furthermore, light interference by an optical sensor uses only a specific wavelength, and can be applied only to a case of a partially semipermeable membrane. This is because if it is not transparent, interference itself does not occur. On the other hand, when the spectral reflectance is measured by the multi-wavelength spectroscopic sensor, the light color is detected. The degree of color is determined by the sum of the reflectances of the respective wavelengths, but it is not a semi-permeable film but a film that does not cause interference due to the relative change in reflectance according to the wavelength. Even so, it is possible to monitor changes in the material of the film as the polishing progresses.

Such a principle has a Cu / Ta / Oxide film structure particularly in the case of CMP for planarizing a wiring film, but it can be applied even when Ta is exposed after Cu polishing. When both Cu and Ta are sufficiently thick, they are metal films and light is not permeated but reflected from the surface, so it is impossible to monitor the film thickness using light interference. However, with the spectral reflectance, it becomes possible to accurately monitor the switching point of the film by polishing.
B. Differences in the effects of combining the sensors.

  The following description is given as an effect produced by the combination of the eddy current sensor and the optical sensor of the prior art. For example, in Patent Document 1, an eddy current sensor is used for measuring a Cu film thickness, and an optical sensor is used for measuring a thin Cu film and a Ta film. Also, in Patent Document 2, the sensitivity of the eddy current sensor becomes worse when the Cu film becomes thinner in [0049] in the same patent document, but when the sensitivity becomes worse, the film is replaced with an optical sensor instead of the eddy current sensor. The thickness is supposed to be measured. Conversely, when the Cu film thickness is thick, light does not pass through the Cu film, but the eddy current sensor has a high sensitivity for film thickness measurement because a large amount of eddy current flows. Therefore, an eddy current sensor is used for a thick Cu film, and when the Cu film is thinly transmitted, an optical sensor is used. Such a complementary relationship is the same not only in Patent Document 2 but also in other Patent Documents 1 and 3 that use the same principle.

  On the other hand, the complementary relationship between the skin eddy current sensor and the multi-wavelength spectroscopic sensor in the present invention is completely different from the complementary relationship between the eddy current sensor and the optical sensor of the prior art. In the present invention, both the skin eddy current sensor and the multi-wavelength spectroscopic sensor have poor sensitivity at the start of polishing, but both have the highest sensitivity at the end. In the case of a multi-wavelength type spectroscopic sensor, for example, when changing from the spectral reflectance of Cu to the spectral reflectance of Ta, the color of Cu becomes lighter, and the change as the most sensor is the portion where the color of Ta has become visible. Can be grabbed. The skin eddy current sensor also has a film thickness at which the magnetic field corresponding to the skin depth leaks as the polishing progresses, eddy current is generated, and the eddy current is reduced by further subsequent film thickness reduction. appear. In the case of Cu, the maximum point appears at 1000 mm or less and appears almost at the end of polishing, so that the polishing end point can be accurately predicted.

  In other words, the skin eddy current sensor and the multi-wavelength spectroscopic sensor according to the present invention are sensitive to each other at the end of polishing, so that the setting of each other can be checked. If the sensing results do not match each other, it is a sensor failure, and the temporary operation can be stopped and both sensors can be checked. Further, by mounting two sensors and independently monitoring the polishing end point, it is possible to detect the end point with higher accuracy while compensating for the weak points of the sensors.

  Here, the weak points of the mutual sensors in the present invention are as follows. Epidermal eddy current sensors are most sensitive to the distance between the wafer and the sensor. The magnetic field formed by the sensor is formed as a divergent magnetic field, and whether or not the magnetic field penetrates into the Cu film under the same condition also depends on the distance (gap) between the sensor and the wafer. When the sensor and the wafer are close to each other, the magnetic field penetration angle becomes steep and the magnetic field easily enters the wafer. In particular, in the process in which the polishing pad is worn by dressing, the gap between the wafer and the sensor may change, and the change in the gap changes the way the magnetic field enters although it is minute.

  On the other hand, in a multi-wavelength spectroscopic sensor, variations in a minute gap between the sensor and the wafer are hardly related. This is because, in the process of irradiating the wafer with light, the amount of reflected light from the wafer hardly changes even if the wafer is minutely moved back and forth. Therefore, the multi-wavelength spectroscopic sensor can compensate for variations in sensitivity with respect to the gap between the wafer and the sensor, which is a problem in the skin eddy current sensor.

  On the other hand, in the multi-wavelength spectroscopic sensor, the slurry existing between the wafer and the window becomes a problem. That is, when the slurry is placed on the window during polishing, the light transmittance is lowered, and the sensitivity may be lowered as a whole. In an extreme case, when a large number of abrasive grains are densely present in the slurry, a large amount of light may be lost due to scattering by the slurry, resulting in a problem of poor sensitivity (Japanese Patent No. 3431115).

  On the other hand, the skin eddy current sensor does not have the problem of slurry inclusion between the wafer and the window. This is because the state of the polishing end point is monitored by applying the magnetic field formed by the planar inductor to the wafer, but the water or abrasive grains used in the slurry are usually non-magnetic and the permeability is This is because it is almost 1. Therefore, if an appropriate gap is secured between the appropriate sensor and the wafer, the magnetic flux stably enters the Cu film according to the state of the conductive film such as Cu, even if the slurry is interposed on the window. However, a small amount of eddy current is generated in a thin Cu film. As described above, the skin eddy current sensor can compensate for the sensitivity variation with respect to the interposition of the slurry between the wafer and the window, which is a problem in the multi-wavelength spectroscopic sensor.

  As described above, the multi-wavelength spectroscopic sensor and the skin eddy current sensor have the advantage of being highly sensitive and reliable at the end of polishing, while the multi-wavelength spectroscopic sensor is a slurry between the window and the wafer. The skin eddy current sensor is vulnerable to changes in the gap between the wafer and the sensor.

  In the present invention, since the two weaknesses have a complementary configuration, an epidermis eddy current sensor is assembled in the light transmission window of the multi-wavelength spectroscopic sensor, or the multi-wavelength spectroscopic sensor and the epidermis eddy are combined. The sensor configuration is such that the current sensors are integrally arranged. By doing so, the window surface is roughened by polishing or dressing, and the slurry stays on the window surface, so the sensitivity to receive the reflected light from the wafer surface required for the multi-wavelength spectroscopic sensor decreases. However, the eddy current sensor can effectively compensate for this.

  Conversely, when the sensitivity of the skin eddy current sensor changes due to a change in the gap between the sensor and the wafer, when the reflected light from the wafer surface is transmitted through the window composed of the integral part, the window And the gap change between the wafers is almost unrelated. Therefore, the multiwavelength spectroscopic sensor can compensate for the sensitivity change of the skin eddy current sensor.

  From the above, since the two sensors have complementary actions, even if the state of polishing changes, even if either sensor state changes, the action to compensate for it works, and for stable and robust end point detection Can be controlled.

  In addition, as a clear difference between the conventional sensor combined with the eddy current sensor and the optical sensor, in the case of the composite sensor according to the prior art, when the film is thick with a metal film such as Cu, the light sensor does not transmit light. Therefore, only an eddy current sensor can measure it. On the contrary, in the case of a thin metal film thickness, an eddy current is generated only in a negligible amount, and rather, it can be measured only by an optical sensor that begins to transmit light to the extent that interference occurs. In other words, the cases are only classified as the states to be measured. It does not have means for confirming whether or not each other's sensors are malfunctioning by other sensors.

  On the other hand, the skin eddy current sensor and the multi-wavelength spectroscopic sensor in the present invention can check whether each device is normally set or operating. This is because both are most sensitive in the vicinity of the end of polishing and are sufficiently reliable as they are. On top of that, we will confirm each other's reliability. If the results of the two sensors do not match, it is an important step to stop the device there and verify which sensor has a configuration or operational problem.

  If you have been operating with complementary functions for a long time without going through these steps, for example, polishing a lot without noticing the deficiencies of the optical sensor, detecting the wrong end point, ruining many wafers It can happen. In addition, for example, a large number of polishing may be performed without noticing the deficiency of the eddy current sensor, erroneous end point detection may be performed, and a large number of wafers may be ruined.

  Therefore, in order to reliably detect the end point during polishing, it is possible to accurately predict the end point immediately before the end point, and all the sensors having independent operation principles have high sensitivity at the end of polishing. It is possible to detect the polishing end point in a timely and accurate manner just before the end of polishing, and use multiple sensors with independent operating principles to confirm that each sensor is set and operating normally. Multiple sensors with independent operating principles all have good sensitivity near the end, but the other sensor is in principle independent of the weak points when one sensor operates. It is possible to improve the accuracy of end point detection by giving a property, and the other sensor compensates for the weak point of one sensor, so one sensor is the other sensor. A technical problem to be solved in order to stably and surely detect the polishing end point arises by assembling it in a light transmission window or by arranging one sensor and the other sensor integrally. Therefore, an object of the present invention is to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 is directed to a conductive film on the wafer by pressing the wafer against a polishing pad on the platen and rotating the wafer relative to the platen. A polishing completion prediction / detection method for predicting and detecting a polishing end point when a predetermined conductive film is properly removed, and at least two sensors for monitoring the surface state of the wafer during polishing One sensor uses a skin eddy current sensor that predicts the polishing end point based on the change in magnetic flux due to the skin effect determined by the material of the conductive film as a factor, and the predetermined conductive film is used as the predetermined conductive film. Before finishing the removal of the metal film, a characteristic change based on the skin effect is used to predict the polishing end point, and the other sensor passes through the window provided in the platen. A multi-wavelength spectroscopic sensor that irradiates light to a light and monitors reflected light from the metal film to detect a polishing end time, wherein the epidermis eddy current sensor is attached to the window. Provide a prediction / detection method.

  According to this configuration, the skin eddy current sensor installed in the light transmitting window is provided with magnetic field generating means such as a planar inductor. The planar inductor is driven at a high frequency to generate a magnetic field corresponding to the period of the high frequency. At the initial stage of polishing, the magnetic field exists only in the surface layer of the metal film due to the skin effect, so no eddy current is generated in the metal film. When the metal film reaches a very thin film thickness corresponding to the skin depth at the end of polishing, a magnetic field penetrates the metal film and partially leaks to the substrate side, thereby generating an eddy current in the metal film. And then increase. Thereafter, as the film thickness further decreases, the film thickness itself that induces eddy current substantially decreases, so that the eddy current rapidly decreases. As a result, a characteristic change including an inflection point (peak) occurs in the eddy current induced in the metal film just before the end of polishing. Based on this characteristic change, the polishing end point can be predicted with high sensitivity and high accuracy immediately before the end of polishing.

  On the other hand, a multi-wavelength spectroscopic sensor irradiates a wafer with light through a window and takes in reflected light from a metal film. The integrated value of the reflectance intensity in another wavelength region with respect to the integrated value of the reflectance intensity in another wavelength region Ratio, ie R.V. S. By evaluating the value of A (Ratio of Spectral Area), the change in the thickness of the metal film as the polishing progresses is monitored. In the initial stage of polishing, R.I. S. The value A proceeds at a substantially constant value. Near the end of polishing, the metal film becomes thin and the skin effect causes an inflection point to eddy current, so that some light passes through the metal film and is affected by the barrier film under the metal film and polished. The color of the surface changes optically. As a result, the spectral reflectance changes and the R.P. S. The characteristics of the A value change abruptly. And this R.I. S. The occurrence of a sharp change in the A value and the accurate prediction of the polishing end point by the skin eddy current sensor are combined to detect the polishing end point in a timely and accurate manner.

  The skin eddy current sensor is sensitive to the gap between the window (sensor) and the wafer. The magnetic field formed by the skin eddy current sensor is formed as a divergent magnetic field, but whether or not the magnetic field penetrates into the metal film under the same conditions depends on the window or gap between the skin eddy current sensor and the wafer. Dependent. When the skin eddy current sensor is close to the wafer, the magnetic field penetration angle becomes steep, and the magnetic field easily enters the wafer. On the other hand, in the multi-wavelength spectroscopic sensor arranged in the same window portion, the minute gap variation between the window (sensor) and the wafer is hardly related. This is because, in the process of irradiating the wafer with light, the amount of reflected light from the wafer hardly changes even if the wafer is minutely moved back and forth. Therefore, the multiwavelength spectroscopic sensor can compensate for variations in sensitivity with respect to the gap between the window (sensor) and the wafer, which is a problem in the skin eddy current sensor.

  Next, the multiwavelength spectroscopic sensor has a problem of slurry existing between the window and the wafer. That is, when a slurry is interposed between the window and the wafer during polishing, the light transmittance is lowered, and the sensitivity may be lowered as a whole. On the other hand, the skin eddy current sensor installed in the same window does not have the problem of the slurry intervening between the window and the wafer. This is because the state of the polishing end point is monitored by applying the magnetic field formed by the planar inductor to the wafer, but the water or abrasive grains used in the slurry are usually non-magnetic and the permeability is This is because it is almost 1. Therefore, if an appropriate gap is secured between the window (sensor) and the wafer, the magnetic flux stably enters the metal film according to the film state of the metal film even if the slurry is interposed on the window, and is thin. A small amount of eddy current is generated in the metal film. Therefore, the skin eddy current sensor can compensate for the sensitivity variation with respect to the interposition of the slurry between the window and the wafer, which is a problem in the multi-wavelength spectroscopic sensor. In addition, even when the window surface is roughened and roughened during polishing, light is scattered and the sensitivity of the multi-wavelength spectroscopic sensor is low, the skin eddy current sensor installed in the same window can accurately determine the polishing end point. Predict. In the case where there is no disturbance as described above, both the sensors themselves have a very high detection sensitivity when the thickness of the metal film is reduced at the end of polishing in principle. As a result, both sensors provided in the same window portion have complementary actions at the end of polishing.

  As described above, the skin eddy current sensor and the multi-wavelength spectroscopic sensor generate a prediction and detection signal for the polishing end point with high accuracy immediately before the end of polishing. If the sensing results of both sensors do not match, it is possible to stop the temporary operation and check which sensor has a problem in setting or operation.

  The invention according to claim 2 is the invention according to claim 1, wherein the skin eddy current sensor is assembled in the upstream window region with respect to the movement direction of the wafer, and the downstream window region is arranged in the multi-wavelength spectroscopic type. Provided is a polishing end prediction / detection method in which a light transmission region in a sensor is set and a rubbing plate is attached above the skin eddy current sensor so as to be flush with the polishing pad.

  According to this configuration, a constant gap is formed between the skin eddy current sensor and the wafer by the rubbing plate attached above the skin eddy current sensor. When the surface of the rubbing plate is roughened by polishing or dressing, the slurry may stay slightly on the roughened surface. However, there is almost no influence on the gap length between the skin eddy current sensor and the wafer due to the slurry slightly staying on the roughened surface portion, and the gap length is kept substantially constant thereafter, and the gap between the sensor and the wafer is maintained. Variation in the sensitivity of the skin eddy current sensor with respect to. The rubbing plate acts to crush the slurry and prevent the slurry from entering the window region where the light transmission region immediately downstream thereof is set. Thereby, the dispersion | variation in the sensitivity of the multiwavelength type | mold spectral sensor by interposition of the slurry between a window and a wafer is suppressed.

  The invention according to claim 3 is a polishing end prediction / detection method for polishing and predicting a polishing end point when a predetermined conductive film is properly removed by polishing the conductive film, At least two sensors that monitor the surface condition of the wafer are integrated, and one sensor is an epidermis vortex that predicts the end of polishing based on the change in magnetic flux due to the skin effect determined by the material of the conductive film as a factor. A current sensor is used to predict the polishing end time using a characteristic change based on the skin effect before the completion of removing the Cu film as the predetermined conductive film, and the other sensor detects the polishing end time. A function of setting a detection range when performing polishing, and the other sensor is a multi-wavelength spectroscopic sensor, and provides a polishing end prediction / detection method for detecting a polishing end point existing in the detection range Do

  According to this configuration, the skin eddy current sensor and the multi-wavelength spectroscopic sensor, which have a high detection sensitivity and play a complementary role immediately before the end of polishing in principle, are integrally disposed. Of these, in the skin eddy current sensor, when the Cu film is thin enough to correspond to the skin depth just before the end of polishing, the magnetic field penetrates the Cu film and partially leaks to the substrate side. Eddy currents are generated in the film and increase. Thereafter, as the film thickness further decreases, the film thickness itself that induces eddy current substantially decreases, so that the eddy current rapidly decreases. A change in magnetic flux induced in the Cu film by the behavior of the eddy current, that is, a characteristic change appears as a remarkable change having an inflection point (peak) accompanied by a steep rise and a steep fall. The epidermis eddy current sensor accurately predicts the polishing end point from the characteristic change of the magnetic flux, and sets a detection range when the multiwavelength spectroscopic sensor detects the polishing end point. The multi-wavelength spectroscopic sensor arranged integrally with the epidermis eddy current sensor has an R.P. S. The value of A is evaluated and the R.P. S. The polishing end point is detected based on the occurrence of a sudden change in the A value. As a result, the polishing end point can be detected reliably and efficiently with high accuracy.

  The multi-wavelength spectroscopic sensor can compensate for variations in sensitivity to the gap between the wafer and the sensor, which is a problem in the epidermis eddy current sensor. It becomes possible to compensate for the sensitivity variation with respect to the interposition of the slurry between the wafer and the window, which is a problem in the type sensor. In this way, the two sensors arranged in an integrated manner act complementarily at the end of polishing. Furthermore, when the sensing results between the two types of sensors do not match, the epidermis eddy current sensor and the multi-wavelength spectroscopic sensor stop the temporary operation and determine which side of the sensor has a setting or operation problem. It becomes possible to check.

  The invention according to claim 4 includes one sensor constituted by a skin eddy current sensor and the other sensor constituted by a multi-wavelength spectroscopic sensor, wherein the skin eddy current sensor is the multi-wavelength spectroscopic sensor. Polished end prediction, which is assembled to a light transmission window in the sensor, predicts and detects a polishing end point when the metal film as a predetermined conductive film is polished and properly removed A polishing end prediction / detection device for executing the polishing end prediction / detection method according to claim 1 is provided.

  According to this configuration, the polishing end prediction / detection device having the configuration in which the skin eddy current sensor is assembled in the light transmission window in the multi-wavelength type spectroscopic sensor is polished by the skin eddy current sensor assembled in the window. When the metal film reaches a very thin film thickness corresponding to the skin depth, a characteristic change including an inflection point occurs in the eddy current induced in the metal film. Based on the change, the polishing end point is predicted with high sensitivity and high accuracy immediately before the end of polishing. On the other hand, the multi-wavelength spectroscopic sensor irradiates the wafer with light through the same window and takes in reflected light from the metal film. S. By evaluating the A value, the change in the thickness of the metal film accompanying the progress of polishing is monitored. R. S. The polishing end point is detected based on the rapid change in the A value. As a result, the polishing end point is accurately detected in a timely manner.

  In addition, the multi-wavelength spectroscopic sensor can compensate for the variation in sensitivity to the gap between the window and the wafer, which is a problem with the skin eddy current sensor, and conversely, the skin eddy current installed in the same window. The current sensor can compensate for the sensitivity variation with respect to the interposition of the slurry between the window and the wafer, which is a problem in the multi-wavelength spectroscopic sensor. In this way, both sensors provided in the same window portion act complementarily at the end of polishing. Furthermore, if the sensing result between the skin eddy current sensor and the multi-wavelength spectroscopic sensor does not match, stop the temporary operation and check which side of the sensor has a setting or operation problem. It becomes possible to do.

  According to a fifth aspect of the present invention, there is provided a Cu film as a predetermined conductive film in which one sensor constituted by a skin eddy current sensor and the other sensor constituted by a multi-wavelength spectroscopic sensor are integrally disposed. A polishing end prediction / detection device for predicting and detecting a polishing end point when the Cu film is properly removed, and performing the polishing end prediction / detection method according to claim 3 A prediction / detection device is provided.

  According to this configuration, in principle, the prediction of the end of polishing having a configuration in which a skin eddy current sensor and a multi-wavelength type spectroscopic sensor, which have a high detection sensitivity and play a complementary role immediately before the end of polishing, are integrally arranged. The detection device includes an inflection point in the eddy current induced in the Cu film when polishing progresses and the Cu film becomes a very thin film thickness corresponding to the skin depth by the skin eddy current sensor. A characteristic change occurs, and from this characteristic change, the polishing end point is accurately predicted with high sensitivity immediately before the end of polishing, and the detection range when the multiwavelength spectroscopic sensor detects the polishing end point is set. . On the other hand, the multi-wavelength spectroscopic sensor disposed integrally with the epidermis eddy current sensor allows R.P. S. A value is evaluated and R.P. S. The polishing end point is detected based on the rapid change in the A value. As a result, the polishing end point can be detected reliably and efficiently with high accuracy.

  The multi-wavelength spectroscopic sensor can compensate for variations in sensitivity to the gap between the wafer and the sensor, which is a problem in the epidermis eddy current sensor. It becomes possible to compensate for the sensitivity variation with respect to the interposition of the slurry between the wafer and the window, which is a problem in the type sensor. In this way, the two sensors arranged in an integrated manner act complementarily at the end of polishing. Furthermore, when the sensing results between the two types of sensors do not match, the epidermis eddy current sensor and the multi-wavelength spectroscopic sensor stop the temporary operation and determine which side of the sensor has a setting or operation problem. It becomes possible to check.

  According to the invention of the polishing end prediction / detection method according to claim 1, the skin eddy current sensor installed in the window has a characteristic change including an inflection point in the eddy current induced in the metal film immediately before the end of polishing. A multi-wavelength spectroscopic sensor that is generated and arranged in the same window is R.I. S. A sudden change occurs in the A value. Therefore, both sensors having independent operating principles are both highly sensitive immediately before the end of polishing, and by the operation of both sensors, the end point of polishing can be predicted and detected in a timely, reliable and accurate manner just before the end of polishing. . As described above, the skin eddy current sensor and the multi-wavelength spectroscopic sensor provided in the same window portion accurately generate the prediction signal and the detection signal at the end of the polishing immediately before the end of the polishing. By looking at the coincidence of the results, it can be confirmed that each sensor is normally set and operating. The sensitivity of the skin eddy current sensor is sensitively affected by the gap between the window (sensor) and the wafer. On the other hand, the sensitivity of the wavelength-type spectroscopic sensor disposed in the same window portion using light as an operating medium is hardly affected by a small gap variation between the window and the wafer. On the other hand, the sensitivity of the multi-wavelength spectroscopic sensor may decrease due to the influence of the slurry existing between the window and the wafer. On the other hand, the sensitivity of the skin eddy current sensor does not have the problem of the slurry intervening between the window and the wafer. Therefore, both sensors having independent operation principles have a property that, in principle, the other sensor is strong against the weak point, while the other sensor is a weak point when the one sensor operates. The accuracy of detection of the polishing end point can be improved due to the characteristics of both sensors. In addition, the skin eddy current sensor installed in the same window can be polished accurately even when the window surface is roughened by grinding during polishing and light is scattered and the sensitivity of the multi-wavelength spectroscopic sensor is low. Predict. Therefore, both sensors provided in the same window portion can operate in a complementary manner so that the other sensor compensates for the weak point of one sensor and can stably detect the polishing end point. There are advantages.

  In addition to the effect of the invention according to claim 1, the invention of the polishing completion prediction / detection method according to claim 2 is further flush with the polishing pad above the skin eddy current sensor installed in the window. By attaching the rubbing plate, the gap length between the skin eddy current sensor and the wafer can be kept substantially constant, and variations in the sensitivity of the skin eddy current sensor with respect to the gap between the sensor and the wafer can be suppressed. In addition, by installing a skin eddy current sensor in the window area on the upstream side with respect to the moving direction of the wafer, the slurry is squeezed at the rubbing plate and the light transmission area immediately downstream is set. This is advantageous in that the dispersion of the sensitivity of the multi-wavelength spectroscopic sensor due to the interposition of the slurry between the window and the wafer can be suppressed.

  The invention of the polishing end prediction / detection method according to claim 3 is characterized in that, in principle, the epidermal eddy current sensor and the multi-wavelength spectroscopic sensor, which have a high detection sensitivity immediately before the end of polishing and play a complementary role, are integrated. Has been placed. Among these, the skin eddy current sensor accurately predicts the polishing end point from the characteristic change of magnetic flux just before the end of polishing and sets the detection range when the multi-wavelength spectroscopic sensor detects the polishing end point, The multi-wavelength spectroscopic sensor has an R.P. S. By detecting the polishing end point based on the rapid change in the A value, it is possible to detect the polishing end point accurately and reliably with high accuracy. In addition, the multi-wavelength spectroscopic sensor can compensate for the variation in sensitivity to the gap between the wafer and the sensor, which is a problem with the epidermis eddy current sensor. Sensitivity variation with respect to the interposition of slurry between the wafer and the window, which is a problem in the sensor, can be compensated. Therefore, the two sensors arranged integrally have an advantage that they can work complementarily at the end of polishing to improve the accuracy of detecting the end of polishing.

  According to the invention of the polishing completion prediction / detection device according to claim 4, the eddy current induced in the metal film by the skin eddy current sensor assembled in the light transmission window in the multi-wavelength spectroscopic sensor is just before the polishing is finished. A characteristic change including an inflection point occurs, and R.P. S. A sudden change in the A value occurs. Therefore, each sensor having an independent operation principle has high sensitivity immediately before the end of polishing, and the operation of each sensor can predict and detect the end point of polishing in a timely, reliable and accurate manner just before the end of polishing. . Further, by looking at the coincidence of the sensing results between the two sensors provided in the same window portion, it can be confirmed that each sensor is normally set and operating. Furthermore, the multi-wavelength spectroscopic sensor can compensate for the variation in sensitivity to the gap between the window and the wafer, which is a problem with the skin eddy current sensor, and conversely, the skin eddy current installed in the same window. The sensor can compensate for the sensitivity variation with respect to the interposition of the slurry between the window and the wafer, which is a problem in the multi-wavelength spectroscopic sensor. As described above, the two sensors provided in the same window portion act in a complementary manner at the end of polishing, so that there is an advantage that the accuracy of detection of the end of polishing can be improved.

  The invention of the polishing end prediction / detection device according to claim 5 includes an inflection point in the eddy current induced in the Cu film by the epidermis eddy current sensor among the two sensors arranged integrally just before the end of polishing. A characteristic change occurs and the polishing end point is predicted with high sensitivity and high accuracy and the detection range when the multi-wavelength spectroscopic sensor detects the polishing end point is set. On the other hand, the multi-wavelength spectroscopic sensor In the set detection range, R.I. S. The polishing end point is detected based on the rapid change in the A value. Therefore, it is possible to reliably and efficiently detect the polishing end point with high accuracy. In addition, the multi-wavelength spectroscopic sensor can compensate for the variation in sensitivity to the gap between the wafer and the sensor, which is a problem with the epidermis eddy current sensor. Sensitivity variation with respect to the interposition of slurry between the wafer and the window, which is a problem in the sensor, can be compensated. As described above, the two sensors arranged in an integrated manner act complementarily just before the end of polishing, thereby improving the accuracy of detection of the end point of polishing. Furthermore, when the sensing results between the two types of sensors do not match, the epidermis eddy current sensor and the multi-wavelength spectroscopic sensor stop the temporary operation and determine which side of the sensor has a setting or operation problem. There is an advantage that it can be checked.

  In order to reliably detect the end point during polishing, it is possible to accurately predict the end point immediately before the end point, and multiple sensors with independent operating principles are all highly sensitive at the end of polishing. It is possible to detect the polishing end point in timely and accurately, and use multiple sensors with independent operation principles to confirm that each sensor is set correctly and operating. Multiple sensors with independent operating principles all have good sensitivity near the end, but the other sensor has an independent property that in principle, the other sensor is strong against that weak point. This makes it possible to improve the accuracy of end point detection, and because one sensor compensates for the weakness of one sensor, one sensor transmits light from the other sensor. In order to achieve the purpose of stably and surely detecting the end point of the polishing by assembling it in the window of the sensor or by arranging one sensor and the other sensor integrally, the wafer is polished on the platen. A polishing end prediction / detection method that predicts and detects the end point of polishing when a predetermined conductive film is properly removed by polishing the conductive film on the wafer by rotating relative to the platen. At least two sensors for monitoring the surface condition of the wafer during polishing are arranged, and one of the sensors determines the end point of polishing based on the magnetic flux change due to the skin effect determined by the material of the conductive film as one factor. Use the skin eddy current sensor to predict, and use the characteristic change based on the skin effect before finishing the removal of the metal film as the predetermined conductive film Multi-wavelength spectroscopy that predicts the polishing end point, and the other sensor detects the polishing end point by irradiating the wafer with light through a window provided in the platen and monitoring the reflected light from the metal film. The skin eddy current sensor was realized by being assembled to the window.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a wafer polishing apparatus (CMP apparatus) in which a polishing completion prediction / detection apparatus is incorporated, and FIG. 2 is a block diagram of a skin eddy current sensor and a multi-wavelength spectroscopic sensor incorporated in the wafer polishing apparatus. 3 is an enlarged vertical sectional view of the window portion in FIG. First, the configuration of the polishing end prediction / detection method and apparatus according to this embodiment will be described from the configuration of a wafer polishing apparatus applied thereto.

  In FIG. 1, a wafer polishing apparatus 1 is mainly composed of a platen 2 and a polishing head 3. The platen 2 is formed in a disk shape, and a rotary shaft 4 is connected to the center of the lower surface thereof. The platen 2 rotates in the direction of arrow A when the motor 5 is driven. A polishing pad 6 is adhered to the upper surface of the platen 2, and a slurry that is a mixture of an abrasive and a chemical is supplied onto the polishing pad 6 from a nozzle 7 (see FIG. 2).

  The polishing head 3 is formed in a disk shape smaller than the platen 2, and a rotary shaft 8 is connected to the center of the upper surface thereof. The polishing head 3 presses the wafer W (see FIG. 2) against the polishing pad 6 at a position eccentric from the rotation center of the platen 2, and is driven by a motor (not shown) through the rotating shaft 8 to rotate in the arrow B direction. To do. Further, the polishing head 3 is driven by a lifting / lowering means (not shown) and moves up and down vertically with respect to the polishing pad 6.

  The wafer polishing apparatus 1 presses the wafer W held by the polishing head 3 during the polishing process against the polishing pad 6 with a predetermined pressure, and rotates the polishing pad 6 and the wafer W from the nozzle 7 to the polishing pad 6. A slurry is supplied to the upper surface, and a predetermined film on the wafer W is polished. The wafer polishing apparatus 1 includes a control unit 9 (see FIG. 2) that controls the driving of the entire apparatus.

  As shown in FIGS. 2 and 3, an observation hole 10 is formed through the platen 2 and the polishing pad 6 at a predetermined position in the platen 2 through which the polishing head 3 passes. A window 11 made of a transparent material such as a polyurethane piece is fitted in the observation hole 10. Then, the skin eddy current sensor 12 is assembled in the upstream window region 11a located on the upstream side with respect to the movement direction (rotation direction B in FIG. 1) of the wafer W, and the downstream window region 11b is irradiated on the downstream side. A multi-wavelength spectroscopic sensor 13 is incorporated as a light transmission region for light and reflected light. In this way, the skin eddy current sensor 12 and the multi-wavelength spectroscopic sensor 13 are integrally disposed in the window 11 portion.

  The skin eddy current sensor 12 is composed of a planar inductor 14 and a resonance box 15 as will be described later. The planar inductor 14 and the resonance box 15 are connected by a signal cable 16 and the planar inductor 14 is The resonating box 15 is assembled at a position below the upstream window region 11a so as to face a predetermined conductive film on the surface of the wafer W. A rubbing plate (pad) 17 is attached on the planar inductor 14 so as to be flush with the polishing pad 6.

  A constant gap is formed between the skin eddy current sensor 12 and the wafer W by the rubbing plate 17. When the surface of the rubbing plate 17 is roughened by polishing, dressing or the like, the slurry may stay slightly on the roughened surface. However, the slurry slightly staying on the roughened surface portion hardly affects the gap length between the skin eddy current sensor 12 and the wafer W, and the gap length is kept substantially constant thereafter and the sensor and the wafer W Variation in the sensitivity of the skin eddy current sensor 12 with respect to the gap between them is suppressed. The rubbing plate 17 acts to crush the slurry and prevent the slurry from entering the downstream window region 11b immediately downstream. As a result, it is possible to suppress variations in sensitivity of the multi-wavelength spectroscopic sensor 13 due to the presence of slurry between the window 11 and the wafer W.

  A signal indicating a characteristic change or the like from the resonance box 15 in the skin eddy current sensor 12 is output to an external computer 19 via a slip ring 18. The computer 19 performs arithmetic processing according to a predetermined algorithm, and predicts the polishing end point.

  As described above, the skin eddy current sensor 12 and the multi-wavelength spectroscopic sensor 13 are integrally disposed on the window 11 portion, so that the surface of the window 11 is roughened and roughened during polishing, and light is scattered. Even when the sensitivity of the multi-wavelength spectroscopic sensor 13 becomes low, the polishing end point is accurately predicted by the skin eddy current sensor 12 installed in the same window 11. Further, even when the gap between the wafer W and the skin eddy current sensor 12 changes, the reflected light of the multi-wavelength spectroscopic sensor 13 transmitted through the same window 11 can detect the polishing end point almost regardless of the gap change. It becomes possible. Therefore, the skin eddy current sensor 12 and the multi-wavelength spectroscopic sensor 13 act complementarily very effectively.

  FIG. 4 shows a modification of the window 11. In this modification, an upstream slope 11 c and a downstream slope 11 d are formed on the upper surface of the window 11 with the rubbing plate 17 as a top. The upper surface portion of the window 11 on which the downstream slope 11d is formed is the upper surface portion of the downstream window region 11b. By the upstream slope 11c, the crushing action of the slurry by the rubbing plate 17 portion is more reliably generated. Further, although a gap is formed between the upper surface of the downstream window region 11b and the wafer W by the downstream slope 11d, the sensitivity of the multi-wavelength spectral sensor 13 is hardly affected. The formation of the downstream slope 11d prevents the upper surface of the downstream window region 11b from being roughened by polishing or dressing. Even if the slurry enters the upper surface of the downstream window region 11b, the slurry flows down the downstream slope 11d. Therefore, the sensitivity reduction of the multi-wavelength spectroscopic sensor 13 due to the slurry is surely suppressed. In the following description, the window 11 shown in FIG. 3 is applied.

  The skin eddy current sensor 12 will be described with reference to FIGS. FIG. 5 is a block diagram showing a detailed configuration of a skin eddy current sensor (inductor type sensor), FIG. 6 is a diagram showing a basic configuration example of an oscillation circuit in the skin eddy current sensor, (a) is a configuration diagram, b) is the equivalent circuit, and FIGS. 7A to 7D are diagrams showing the results of electromagnetic simulation of the orientation of the magnetic field generated from the coil in the skin eddy current sensor on the conductor film. FIG. 8 is a diagram for explaining the inductance changing action due to the magnetic field generated by the electromagnetic coupling in the skin eddy current sensor, and FIGS. 9A to 9E are accompanied by the removal of the polishing of the conductive film by the wafer polishing apparatus. It is a set figure for demonstrating the example of a change of magnetic flux etc. by a skin effect, and the detection effect | action of a characteristic change.

In FIG. 5, an oscillation circuit 20 constituting the main body of the skin eddy current sensor (inductor type sensor) 12 includes a two-dimensional planar inductor 14 having an inductance L and a lumped capacitor 21 having a capacitance C _{0 in} series. The LC circuit is configured by being connected. The planar inductor 14 is formed in a square spiral using a conductive material such as Cu on a rectangular substrate 14a made of an insulator. The planar inductor 14 is manufactured with a very fine line width by forming a conductive film such as Cu on a substrate 14a made of an insulator such as glass, epoxy, paper, or phenol, and then manufacturing it by etching or the like. The overall shape can also be reduced to a square shape with a side of about 23 mm. A small magnetic field can be efficiently generated by downsizing the planar inductor 14, and the change behavior near the end point where the conductive film is removed can be accurately detected without deeply penetrating the magnetic film into the conductive film. It is possible to detect well.

  An output signal from the LC circuit is input to an amplifier 22, and an output of the amplifier 22 is input to a feedback network 23 composed of a resistor or the like. The output signal of the feedback network 23 is positively fed back to the planar inductor 14, whereby the oscillation circuit 20 including the planar inductor 14 is configured.

As shown in the configuration example of FIG. 6, the oscillation circuit 20 basically has an oscillation frequency band f of the inductance L of the planar inductor 14 and the lumped constant capacitor 21 as shown in the following equation (1). It has an oscillation circuit of the Colpitts like determined by the capacitance C _0.

  A frequency counter 24 is connected to the output terminal of the amplifier 22. A detection signal indicating a film thickness reference point, which will be described later, is digitally output from the frequency counter 24 to the outside. By digitally transmitting the detection signal output, the influence of noise and output attenuation are prevented. In addition, manageability of the film thickness data can be obtained. By arranging the oscillation circuit 20 in the epidermis eddy current sensor (inductor type sensor) 12 and the frequency counter 24 for monitoring the change of the oscillation (resonance) frequency in close proximity, the oscillation circuit 20 and the frequency counter 24 are arranged. A distributed constant circuit is formed in the wiring / connection portion between them to prevent the inductance and capacitance from becoming unnecessarily large, and the change in magnetic flux accompanying the progress of polishing of the conductive film provided to the skin eddy current sensor 12 can be accurately performed. It is possible to detect well.

  In the skin eddy current sensor 12, other components or circuits other than the planar inductor 14 are integrated into an IC (integrated circuit) and are housed in a resonance box 15. The planar inductor 14 is covered with a thin insulating film, and in FIG. 3, the planar inductor 14 and the resonance box 15 are connected by a signal cable 16, but the planar inductor 14 is connected to the resonance box 15. It can also be fixed to the surface portion. The capacitance of the lumped constant capacitor 21 constituting the oscillation circuit 20 is variable, and the skin eddy current sensor 12 can select an oscillation frequency within a required oscillation frequency band. .

In this embodiment, a characteristic change is detected based on a change in magnetic flux when the predetermined conductive film being polished has a film thickness corresponding to the skin depth δ of the predetermined conductive film. The skin depth δ in the predetermined conductive film is determined as shown in Expression (2) depending on the material of the predetermined conductive film and the oscillation frequency f of the oscillation circuit 20.

  ω: 2πf, μ: permeability, σ: conductivity.

  Then, the oscillation of the oscillation circuit 20 is performed such that the skin depth δ is smaller than the initial film thickness of the predetermined conductive film and larger than the film thickness of the predetermined conductive film in the portion excluding the embedded portion at the end of polishing. The frequency f is selected. When the material of the conductive film to be polished and removed is Cu, the oscillation frequency band is selected to be 20 MHz or higher.

  Here, “the film thickness corresponding to the skin depth” and “the magnetic flux change caused by the skin effect” will be described with reference to FIGS. FIG. 7 is an electromagnetic simulation of the orientation of the magnetic field generated from the coil (planar inductor) in the skin effect sensor on the conductor film ((a) to (d) in the lower arrow ←). FIG. 4A is a diagram showing the results. FIG. 4A shows a case where the oscillation frequency from the sensor is 1 MHz and the film thickness of the conductor film is 0.2 μm. FIG. When the film thickness is 1 μm, the figure (c) shows the case where the oscillation frequency from the sensor is 40 MHz and the film thickness of the conductor film is 0.2 μm, and the figure (d) shows the case where the oscillation frequency from the sensor is 40 MHz and the conductor film This is a case where the film thickness is 1 μm.

  In the electromagnetic simulation setting, the inductor that forms the magnetic field is a planar inductor having no directivity. The “film thickness corresponding to the skin depth” means “film thickness at which magnetic flux changes due to the skin effect”. When the oscillation frequency of the sensor is 1 MHz, the magnetic flux on the conductor film existing on the lower side of the coil is directed in the vertical direction. At this frequency, even if the film thickness is 1 μm and 0.2 μm, the magnetic flux penetrates through the conductor film (FIGS. 7A and 7B). When the magnetic flux penetrates through such a conductor film, as shown in the conventional example, the eddy current generated inside the conductor film decreases as the film thickness decreases. Therefore, in the case of 1 MHz, the film thickness is 1 μm or less, which is a monotonous behavior. Therefore, the skin effect does not appear, and the “film thickness corresponding to the skin depth” is also considered to be at least 1 μm thick.

  On the other hand, when the oscillation frequency of the sensor is 40 MHz, the direction of magnetic flux on the conductor surface is clearly horizontal, and when the film thickness is 1 μm, it hardly penetrates into the conductor (FIG. 7 (d)). Obviously, the direction of the magnetic flux entering the conductor film is different from the case where the oscillation frequency is 1 MHz and the film thickness is 1 μm (FIG. 7B).

  However, when the oscillation frequency is 40 MHz and the conductor film is thinned to 0.2 μm (FIG. 7C), only a part of the magnetic flux is directed toward the inside of the conductor film. This indicates that even if the conductor film is Cu, a part of the magnetic flux penetrates the conductor film when the conductor film is thin.

  In the case of the alternating magnetic flux of 40 MHz, the penetration state of the magnetic flux in the conductor film changes corresponding to the skin effect. Due to the effect of gradually increasing the penetrating magnetic flux, the frequency rapidly rises to about 700 mm. When the film thickness is 1 μm or more, the magnetic flux hardly penetrates. Therefore, in this case, the “film thickness corresponding to the skin depth” can be about 1 μm. For this reason, when the oscillation frequency is increased to 40 MHz and a planar inductor is used, almost no magnetic flux enters the 1 μm thick Cu conductor film, which is due to the skin effect.

When the Cu conductor film has an oscillation frequency of 40 MHz and the Cu conductivity is 58 × 10 ⁶ S / m, the skin depth δ is 9.34 μm. In the calculation, if the film thickness is 1 μm, the magnetic flux sufficiently enters the conductor film, but since a planar inductor is used and the magnetic flux has no directivity, the film actually has an oscillation frequency of 40 MHz. Even if the thickness is 1 μm, the magnetic field does not enter the conductor film due to the skin effect. As the conductor film becomes thinner, part of the magnetic flux enters the conductor film and a slight eddy current is generated. From this, instead of actively using eddy currents to measure the film thickness, when a thin film thickness near the end point is reached, a slight leakage / penetration magnetic flux is used due to the skin effect to make the conductor The inflection point (maximum point) of the mutual inductance induced in the film can be used to monitor the film thickness state near the end point of the conductor film.

  Next, a characteristic change detection operation by the epidermis eddy current sensor 12 and a method for predicting the polishing end point will be described with reference to FIGS. 8 and 9A to 9E. FIGS. 9A to 9D are diagrams showing examples of changes in magnetic flux and eddy current accompanying removal of polishing of the conductive film, and FIG. 9E shows examples of changes in resonance frequency with respect to changes in the thickness of the conductive film. FIG. In (a) to (d) of FIG. 9, the planar inductor 14 is displayed in a round spiral for easy viewing of the drawing.

  The planar inductor 14 is driven at a high frequency oscillated from the oscillation circuit 20, and a magnetic flux φ that changes with time corresponding to the period of the high frequency is generated from the planar inductor 14. The magnetic flux φ induced in the predetermined conductive film 25 in the initial stage of polishing passes only the region having the skin depth δ substantially in parallel along the film surface, and exceeds the skin depth δ in the predetermined conductive film 25. Intrusion of the magnetic flux φ into the area is avoided (FIG. 9A). Further, the resonance frequency oscillated from the skin eddy current sensor 12 is also kept constant regardless of the change in the film thickness of the predetermined conductive film 25 (region a in FIG. 9E).

When polishing progresses predetermined conductive film 25 is in the vicinity of the film thickness corresponding to the skin depth [delta], part of the magnetic flux phi leakage flux through the predetermined conductive film 25 phi _L begins to occur. The magnetic flux φ that does not penetrate the predetermined conductive film 25 passes through the film surface as it is in substantially parallel. Then, an eddy current Ie is generated in proportion to the number of leakage magnetic fluxes φ _L penetrating into the predetermined conductive film 25 (FIG. 9B).

Moreover the polishing progresses, generated wide region eddy current Ie is increasing leakage flux phi _L is along the film surface of the conductive film 25 (FIG. 9 (c)). Eddy current Ie generated in this large area, as shown in FIG. 8, further creating a magnetic field M, the magnetic field M acts so as to cancel the magnetic flux phi _L generated from the original planar inductor 14. As a result, due to the magnetic field M formed by the conductive film 25, the mutual inductance Lm increases, and the apparent inductance L of the original planar inductor 14 decreases. As a result, the oscillation frequency f oscillated from the epidermis eddy current sensor 12 increases as shown in Expression (3).

  Therefore, due to the mutual inductance, the inductance of the sensor circuit system is equivalently reduced and the resonance frequency oscillated from the skin eddy current sensor 12 is increased (regions b and c in FIG. 9 (e)).

Furthermore the leakage flux phi _L with the progress of polishing is increased by saturated. However, the eddy current Ie rapidly decreases as the film thickness volume of the predetermined conductive film 25 decreases (FIG. 9D). Due to the rapid decrease of the eddy current Ie, the mutual inductance also decreases rapidly. This rapid decrease in mutual inductance leads to a decrease in the inductance decrease Lm in equation (3). As a result, the inductance of the sensor circuit system increases equivalently, and the resonance frequency oscillated from the skin eddy current sensor 12 is increased. Decreases rapidly (region d in FIG. 9E).

  As described above, after the predetermined conductive film 25 reaches a film thickness corresponding to the skin depth δ due to the progress of polishing, the eddy current Ie is generated, and the inductance of the sensor circuit system once decreases due to the rapid decrease thereafter. And then turn to an increase. Due to this behavior, a characteristic change is generated in the waveform of the resonance frequency oscillated from the skin eddy current sensor 12 including the rising start point, the rising rate, the rising amount, the inflection point (peak) P, and the changing rate from rising to falling. . The prediction of the end point of polishing immediately before the end of polishing from at least one of the rising start point, the rising rate, the rising amount, the inflection point (peak) P or the changing rate from rising to falling, and the multi-wavelength spectroscopic sensor 13 polishes. A detection range for detecting the end point is set. When the predetermined conductive film 25 is Cu, the remaining film amount at the time when the inflection point P occurs is approximately 1000 mm.

Incidentally, the skin eddy current sensor 12, in addition to the mutual inductance of the resonant frequency, the eddy current Ie, the characteristic changes, including an inflection point P based on at least one of a change of the change in leakage flux phi _L It is possible to generate and predict the polishing end point. The change in mutual inductance can be obtained from the change in the oscillation frequency of the epidermis eddy current sensor 12 using the equation (3), and since the eddy current Ie is proportional to the mutual inductance, the change in the eddy current Ie. it is to seek the can be determined using the change in mutual inductance, also the change of the leakage magnetic flux phi _L is the leakage flux phi _L since it is proportional to the eddy current Ie with the change of the eddy current Ie it can.

  The multi-wavelength spectroscopic sensor 13 will be described with reference to FIG. 2 and FIGS. FIG. 10 is a configuration diagram of a spectroscope in the multi-wavelength spectroscopic sensor 13, FIG. 11 is a diagram showing a change in the color of the polished surface of the TEOS / SiN insulating film accompanying polishing of the TEOS portion, and FIG. FIG. 13 is a characteristic diagram showing the change in reflectance with respect to the wavelength of the oxide film. S. FIG. 6 is a characteristic diagram showing a change in A.

  The multi-wavelength spectroscopic sensor 13 mainly includes a light source unit 26 such as a halogen lamp that generates white light, an irradiation / light receiving optical system 27, a light receiving unit 28, a spectroscope 29, and the same computer as the skin eddy current sensor 12. 19 is provided. The irradiating / receiving optical system 27 incorporates a condensing lens (not shown) in the lens barrel, and is supported by a bracket (not shown) and installed at a position below the window 11.

  The white light emitted from the light source unit 26 is guided to the irradiation / light reception optical system 27 by the light guide 30, collected by the irradiation / light reception optical system 27, and then downstream of the window 11 provided on the platen 2. The wafer W on the polishing pad 6 is irradiated through the region 11b. The irradiated white light is reflected by the polished surface of a predetermined conductive film on the wafer W, the reflected light is collected by the irradiation / light receiving optical system 27 and received by the light receiving unit 28 through the light guide 31a, Further, the light is guided to the spectroscope 29 through the light guide 31b. As described above, since the reflected light data is acquired when the white light from the light source unit 26 and the reflected light from the predetermined conductive film pass through the window 11, the control unit 9 rotates and rotates the platen 2. Synchronization with the wavelength-type spectroscopic sensor 13 is established.

  As shown in FIG. 10, the spectroscope 29 is provided with an entrance slit 32, a plane mirror 33, a concave diffraction grating 34, an array light receiving element 35, and a multiplexer 36. The reflected light guided to the spectroscope 29 via the light guide 31 b is guided to the concave diffraction grating 34 by the plane mirror 33 via the entrance slit 32. Then, the light is split into reflected light for each wavelength by the concave diffraction grating 34 and imaged on the array light receiving element 35. The imaged light is converted into an electric signal corresponding to the reflected light intensity for each wavelength, and is output to the computer 19 via the multiplexer 36.

  In the memory of the computer 19, a reference light amount that is a reflected light amount due to reflection from a mirror as a reference sample and a darkness light amount that is a reflected light amount from the window 11 portion in the wafer polishing apparatus 1 are acquired and stored in advance. The computer 19 calculates the ratio of each reflected light when the light amount obtained by subtracting the darkness light amount from the reference light amount at each wavelength is 100%, and the reflected light intensity input to the computer 19 for each wavelength is calculated for each wavelength. Converted to reflectivity intensity. The computer 19 calculates an electrical signal corresponding to the reflectance intensity for each wavelength in accordance with a predetermined end point detection algorithm, and detects a polishing end point of the predetermined conductive film 25.

  At the end of polishing of the conductive film 25, the color of the polished surface changes optically under the influence of the barrier film under the conductive film 25 and the like. The degree of color is determined from the sum of the reflectance of each wavelength. FIGS. 11A and 11B show, as an example, reflection for each wavelength of the polished surface of the TEOS (SiO film formed by CVD of organooxysilane) / SiN (silicon nitride) with polishing of the TEOS portion of the laminated insulating film. FIG. 4A shows a change in rate, that is, a change in hue, (a) is an enlarged view of the TEOS portion with respect to the polishing time, and (b) is a hue of the polished surface when the SiN portion is exposed as polishing progresses. Shows changes. FIG. 11 shows that the polishing state of the material to be polished can be detected by monitoring the change in the reflectance of each wavelength of the polishing surface with the progress of polishing.

  Further, it is known that the Cu film has a higher reflectance intensity in another wavelength region than the reflectance intensity in a certain wavelength region. FIG. 12 shows the change in reflectance with respect to wavelength for the Cu film and the Ta / oxide film, which is a barrier film under the Cu film. As shown by the r curve in FIG. 12, in the case of the Cu film, the reflectance in the 500 to 550 nm region is approximately 0.75%, whereas the reflectance in the 700 to 750 nm region is approximately 1.1%. It ’s getting bigger. The Cu film maintains such a reflectance curve before and during polishing. On the other hand, in the case of the Ta / oxide film, as shown by the s curve, the reflectance slightly decreases in the high wavelength region side in the entire white light range of 400 to 750 nm, but is about 0.6%. The characteristic shows little change in value.

When the Cu film is polished and the Ta / oxide film is exposed on the polished surface, the reflectance from the polished surface is determined from the r curve that is the reflectance curve of the Cu film, and the reflectance curve of the Ta / oxide film. It moves to s curve which is. Therefore, in the 500 to 550 nm region, the reflectivity slightly decreases, but the change is small. On the other hand, in the wavelength region of 700 to 750 nm, the reflectance rapidly decreases from about 1.1% to a value of about 0.6%. Therefore, the multi-wavelength spectroscopic sensor 13 of the present embodiment has a ratio of the integrated value of the reflectance intensity in the 700 to 750 nm region to the integrated value of the reflectance intensity in the 500 to 550 nm region, as shown in Equation (4). R. S. By evaluating the value of A (Ratio of Spectral Area), the change in the thickness of the Cu film as the polishing progresses is monitored, and the polishing end point of the Cu film is accurately detected.

  13 shows the reflectance integrated value R in the 700 to 750 nm region and the reflectance integrated value S and R.R in the 500 to 550 nm region with respect to the polishing time. S. Each change in the A value is shown. From the change characteristics of FIG. 13, during the polishing of the Cu film, the reflectance integrated value S in the 500 to 550 nm region advances at a value of approximately 0.75, and slightly decreases to a value of approximately 0.65 at the polishing end point. On the other hand, the reflectance integrated value R in the 700 to 750 nm region advances at a value of approximately 1.1, and at the polishing end point, it rapidly increases to a value of approximately 0.65, which is substantially the same as the reflectance integrated value in the 500 to 550 nm region. descend.

  Therefore, during polishing of the Cu film, R.D. S. The A value proceeds while maintaining a value of about (0.75 / 1.1 =) 0.68, and rapidly increases to a value of just over 1.0 at the polishing end point. This R.I. S. In this embodiment, R.R. S. A threshold value T of a predetermined value is set for the A value, and the R. S. The time when the A value exceeds the threshold T is detected as the polishing end time.

  R.A. S. A can detect the end point of polishing using a value obtained by reversing the denominator (integral reflectance value in the 700 to 750 nm region) and the numerator (integral reflectance value in the 500 to 550 nm region) in Equation (4). can do. At this time, R.I. S. In contrast to the characteristic curve shown in FIG. 13, the change characteristic of the A value is a characteristic curve that rapidly decreases at the polishing end point.

  Further, since the multi-wavelength spectroscopic sensor 13 of this embodiment includes the spectroscope 29, it can also function as a spectrometer. Then, with this spectrometer, the reflected light from the wafer W is divided into reflectances with respect to wavelengths, and based on changes in reflectance intensity in a specific wavelength band, for example, changes in reflectance intensity in the 700 to 750 nm region in FIG. It is also possible to determine whether or not the reflectance intensity has reached a predetermined value, and to detect the polishing end point from the determination result.

  Next, as described above, the operation of the polishing end prediction / detection device having the skin eddy current sensor 12 and the multi-wavelength spectroscopic sensor 13 having independent operation principles will be described with reference to FIGS. 14 to 16. . 14 is a flowchart for explaining the prediction and detection action at the polishing end time by the polishing end prediction / detection device, FIG. 15 is a flowchart for explaining another detection action at the polishing end time, and FIG. 16 is an epidermis eddy current sensor. FIG. 6 is a waveform diagram showing a waveform example of a polishing end point prediction signal by, and a waveform example of a polishing end point detection signal by a multi-wavelength spectroscopic sensor.

  The prediction and detection action of the polishing end time by the polishing end prediction / detection device will be described with reference to the flowchart of FIG. When polishing of a predetermined film on the wafer W is started by the wafer polishing apparatus 1, a polishing start signal is transmitted from the control unit 9 to the computer 19 (step S1). When the computer 19 receives the polishing start signal (step S2), it starts predicting and detecting the polishing end point (step S3). Then, the sensor signal is received from the epidermis eddy current sensor 12, and arithmetic processing is executed according to a predetermined algorithm (step S4), and the polishing end point is predicted (step S5). In parallel with this, the computer 19 receives an electrical signal corresponding to the reflected light intensity for each wavelength from the spectroscope 29, converts the reflected light intensity into the reflectance intensity for each wavelength, and then detects a predetermined end point. An arithmetic process is executed according to the algorithm (step S6), and the polishing end point after the polishing end point prediction is detected (step S7). When the detected time difference between the detected signal detection time at the end of polishing and the detection signal detection time at the end of polishing is within an assumed margin (Yes in step S8), the wafer polishing apparatus 1 A polishing end point signal is output to the controller 9 (step S9), and the polishing process is terminated (step S10). On the other hand, when the time difference is outside the assumed margin range (No in step S8), an error signal is output to the control unit 9 of the wafer polishing apparatus 1 (step S11), from the control unit 9 to the wafer polishing apparatus 1 Causes an error to be issued (step S12).

  In step S5, the polishing end point is predicted based on the sensor signal from the epidermis eddy current sensor 12, and the detection range for detecting the polishing end point in step S7 is set. It can be detected efficiently. Further, after the polishing end point is predicted by the sensor signal from the skin eddy current sensor 12 in step S5, the high-frequency current supplied to the inductor in the skin eddy current sensor 12 is reduced or turned off. It is possible to reduce or turn off the magnetic flux induced in the conductive film and to prevent an excessive magnetic field from being applied to the elements formed on the device wafer below the conductive film.

  Next, another detection action at the end of polishing will be described using the flowchart of FIG. The processing from step S21 to step S27 in the flowchart of FIG. 15 is substantially the same as the processing from step S1 to step S7 in the flowchart of FIG. In this other detection operation at the end of polishing, the prediction signal at the end of polishing based on the sensor signal from the epidermis eddy current sensor 12 is regarded as equivalent to the detection signal at the end of polishing in step S25. When the polishing end point is detected in both step S25 and step S27, or when the polishing end point is detected in either step S25 or step S27 (step S28), the control unit of the wafer polishing apparatus 1 The polishing end point signal is output to 9 (step S29), and the polishing process is terminated (step S30).

  Next, a specific example of the setting of polishing conditions in the wafer polishing apparatus 1 and the prediction and detection method of the polishing end point will be described.

First, the setting of polishing conditions for the wafer polishing apparatus 1 is as follows.
[Polishing conditions]
(the expendables)
Slurry: PL7105 manufactured by Fujimi Incorporated
Polishing pad: IC1400 K-Grv manufactured by Rohm & Haas Co., Ltd.
Dress: # 100, 4inch Disc Type
Wafer film configuration: Cu 1000 nm / Ta 25 nm / Oxide 800 nm / Si
(Polishing conditions)
Wafer / retainer pressure: 2.5 psi / 1.5 psi
Platen / polishing head rotational speed: 95 rpm / 93 rpm
Slurry flow rate: 300ml / min
(Interval dress condition)
Dress weight: 4kgf
Platen / dress rotation speed: 80/88 rpm
Interval dress time: 30 sec
Here, while showing an example of the waveform of the polishing end point prediction signal by the epidermis eddy current sensor 12 and an example of the waveform of the polishing end point detection signal by the multi-wavelength spectroscopic sensor 13 with reference to FIG. Explain the point. FIG. 16 shows the result of signal measurement by both sensors 12 and 13 at the same time. One of the waveform examples is the waveform of the skin eddy current obtained by the skin eddy current sensor 12, and the other is the R.D. obtained by the multiwavelength spectroscopic sensor 13. S. It is a waveform of A value.

  The epidermis eddy current sensor 12 has a large inflection point P immediately before removing the conductive film. When the inflection point P is passed, the sensor output suddenly decreases and the polishing end point is reached. On the other hand, the multi-wavelength spectroscopic sensor 13 has a sharp R.D. from the Q point where the skin eddy current obtained by the skin eddy current sensor 12 with the conductive film removed reaches the inflection point P. S. The curve of A value changes.

  In these behaviors, first, the skin eddy current sensor 12 is a phenomenon in which a magnetic field that could not penetrate due to the skin effect begins to gradually enter the conductive film, and the eddy current generated on the surface of the conductive film gradually increases. From then on, the magnetic field penetrates into the conductive film, but is caused by a transition to a phenomenon in which the eddy current itself caused by the magnetic field penetrated into the conductive film is substantially reduced due to a decrease in the film thickness of the conductive film itself. . As a result, a peak P appears immediately before the end of polishing due to the change in the state, and this peak P is a point for accurately predicting the polishing end point.

  On the other hand, since the magnetic field that could not enter due to the skin effect gradually enters the conductive film, and the eddy current reaches the inflection point P due to the magnetic field, the surface conductive film is optically colored. It changes a little. That is, although it is a metallic film, a part of light can pass through the metallic film. Here, the peak time is about 55 seconds, and the signal intensity of the skin eddy current sensor 12 reaches a peak P due to the formation of the eddy current. Thereafter, the polishing end time is reached at 59 seconds, which is about 4 seconds later. At this time, the threshold value T of the signal for telling the end point of the multi-wavelength spectroscopic sensor 13 is set in advance as about 59 sec ± 1 sec. In this specific example, the R.V. by the multi-wavelength spectroscopic sensor 13 at 59 sec, which is 4 sec after preset. S. When the A value exceeds a preset threshold value T, the multi-wavelength spectroscopic sensor 13 also detects the polishing end point.

  As a result, the prediction of the polishing end point and the detection of the polishing end point of both sensors 12 and 13 have just been combined, so that the polishing end point can be 59 sec and the polishing can be stopped at 59 sec. If the polishing end point detection of the multi-wavelength spectroscopic sensor 13 deviates significantly from the previously detected prediction of the skin eddy current sensor 12, this means that the sensor is abnormal and the polishing is immediately terminated. It is also possible to stop the polishing. What is necessary is just to investigate after this whether both prediction detection and end point detection shifted | deviated. In this way, it is possible to accurately predict and detect the end point of polishing using both sensors 12 and 13 and detect the end of polishing of the wafer polishing apparatus 1.

  In this embodiment, two sensors, the skin eddy current sensor 12 and the multi-wavelength spectroscopic sensor 13, are mounted on the wafer polishing apparatus 1, but the number of sensors mounted on the wafer polishing apparatus 1 is three or more. It is good. By setting the number of sensors to be three or more, prediction and detection of the polishing end point of the conductive film on the wafer can be performed more timely and accurately.

  Further, 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 prediction / detection method and apparatus according to an embodiment of the present invention.
1 is a perspective view of a wafer polishing apparatus in which a polishing completion prediction / detection device is incorporated. 1 is a block diagram of a skin eddy current sensor and a multiwavelength spectroscopic sensor incorporated in a wafer polishing apparatus. The expanded longitudinal cross-sectional view of the window part in FIG. The longitudinal cross-sectional view which shows the modification of the window in FIG. The block diagram which shows the detailed structure of a skin eddy current sensor. It is a figure which shows the basic structural example of the oscillation circuit in an epidermis eddy current sensor, (a) is a block diagram, (b) is an equivalent circuit of figure (a). It is a figure which shows the result of carrying out the electromagnetic simulation about what direction the magnetic field generated from the coil in a skin eddy current sensor is arranged on a conductor film, (a) is the oscillation frequency of a sensor film with the oscillation frequency from a sensor being 1 MHz. When the film thickness is 0.2 μm, (b) is when the oscillation frequency from the sensor is 1 MHz and the film thickness of the conductor film is 1 μm, and (c) is when the oscillation frequency from the sensor is 40 MHz and the film thickness of the conductor film is 0 In the case of 2 μm, (d) is the case where the oscillation frequency from the sensor is 40 MHz and the film thickness of the conductor film is 1 μm. The block diagram for demonstrating the change effect | action of the inductance by the magnetic field which generate | occur | produces by the electromagnetic coupling in an epidermis eddy current sensor. FIG. 4 is a set of diagrams for explaining an example of a change in magnetic flux and the like due to a skin effect caused by removal of polishing of a conductive film by a wafer polishing apparatus, and a characteristic change detection action; (a) to (d) of FIG. The figure which shows the example of a change of the magnetic flux etc. accompanying grinding | polishing deletion, (e) is a characteristic figure which shows the example of a change of the resonant frequency with respect to the film thickness change of an electroconductive film. The block diagram of the spectrometer in a multiwavelength type | mold spectral sensor. It is a figure which shows the change of the color of the grinding | polishing surface accompanying the grinding | polishing of a TEOS part about a TEOS / SiN insulating film, (a) expands and shows a TEOS part about grinding | polishing time, (b) is SiN accompanying progress of grinding | polishing. The figure which shows the change of the hue of the grinding | polishing surface when a part is exposed. The characteristic view which shows the reflectance change with respect to the wavelength of Cu film | membrane and Ta / oxide film. Change in reflectance integrated value with respect to polishing time and R.I. S. The characteristic view which shows the change of A. FIG. The flowchart for demonstrating the prediction and detection effect | action of the completion | finish time of grinding | polishing by a grinding | polishing completion | finish prediction and detection apparatus. The flowchart for demonstrating the other detection effect | action of the grinding | polishing completion time by the grinding | polishing completion prediction and detection apparatus. The wave form diagram which shows the waveform example of the grinding | polishing end point prediction signal by a skin eddy current sensor, and the waveform example of the grinding | polishing end point detection signal by a multiwavelength type | mold spectral sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer polisher 2 Platen 3 Polishing head 4 Rotating shaft 5 Motor 6 Polishing pad 7 Nozzle 8 Rotating shaft 9 Control part 10 Observation hole 11 Window 11a Upstream window area 11b Downstream window area 12 Skin eddy current sensor 13 Multiwavelength type spectroscopy Type Sensor 14 Planar Inductor 15 Resonant Box 16 Signal Cable 17 Scraping Plate 18 Slip Ring 19 Computer 20 Oscillation Circuit 21 Lumped Capacitor 22 Amplifier 23 Feedback Network 24 Frequency Counter 25 Predetermined Conductive Film 26 Light Source 27 Irradiation / Reception Optical System 28 Light receiving unit 29 Spectroscope 30 Light guide 31 Light guide 32 Incident slit 33 Plane mirror 34 Concave diffraction grating 35 Array light receiving element 36 Multiplexer

Claims (5)

A wafer is pressed against a polishing pad on a platen and rotated relative to the platen to polish the conductive film on the wafer, and a polishing end point when a predetermined conductive film is properly removed is predicted and detected. Polishing end prediction / detection method,
At least two sensors for monitoring the surface condition of the wafer during polishing are arranged, and one sensor predicts the end point of polishing based on the magnetic flux change due to the skin effect determined by the material of the conductive film as one factor. An eddy current sensor is used to predict the polishing end point using a characteristic change based on the skin effect before the end of removing the metal film as the predetermined conductive film, and the other sensor in the platen A multi-wavelength spectroscopic sensor for irradiating light to the wafer through a window provided on the substrate and monitoring reflected light from the metal film to detect a polishing end time, wherein the skin eddy current sensor is applied to the window. A polishing end prediction / detection method characterized by being assembled.   The skin eddy current sensor is assembled in the upstream window region with respect to the movement direction of the wafer, the downstream window region is set as a light transmission region in the multi-wavelength spectroscopic sensor, and the skin eddy current sensor 2. The polishing end prediction / detection method according to claim 1, wherein a rubbing plate is attached above the polishing pad so as to be flush with the polishing pad. A polishing end prediction / detection method for predicting and detecting a polishing end point when a conductive film is polished and a predetermined conductive film is properly removed,
At least two sensors that monitor the surface condition of the wafer during polishing are integrated, and one sensor predicts the end point of polishing based on the magnetic flux change due to the skin effect determined by the material of the conductive film as a factor. The skin eddy current sensor is used to predict the polishing end time using the characteristic change based on the skin effect before the Cu film as the predetermined conductive film is removed and the other sensor finishes polishing. It has a function of setting a detection range when detecting a time point, and the other sensor is a multi-wavelength spectroscopic sensor, and detects a polishing end point existing in the detection range. Polishing end prediction / detection method. One sensor composed of a skin eddy current sensor and the other sensor composed of a multi-wavelength spectroscopic sensor, the skin eddy current sensor serving as a light transmission window in the multi-wavelength spectroscopic sensor A polishing end prediction / detection device that polishes a metal film as a predetermined conductive film and predicts and detects a polishing end time when the metal film is properly removed,
A polishing completion prediction / detection apparatus, wherein the polishing completion prediction / detection method according to claim 1 is executed. One sensor constituted by an epidermis eddy current sensor and the other sensor constituted by a multi-wavelength type spectroscopic sensor are integrally arranged, and a Cu film as a predetermined conductive film is polished, and the Cu film A polishing end prediction / detection device for predicting and detecting the end point of polishing when is properly removed,
4. A polishing completion prediction / detection apparatus, wherein the polishing completion prediction / detection method according to claim 3 is executed.

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