JP2022088758A - Polishing monitoring method and polishing monitoring device for workpiece - Google Patents

Abstract

To provide a method capable of accurately monitoring polishing of a workpiece while excluding an influence of a pattern formed on a top surface of the workpiece, a polishing environment (for example, slurry), etc.SOLUTION: A method comprises: irradiating a workpiece with light during polishing of the workpiece; generating a spectrum of reflected light from the workpiece; calculating a variation quantity of the spectrum in every predetermined time; correcting the variation quantity of the spectrum when the variation quantity of the spectrum satisfies a predetermined exclusion condition; and integrating a variation quantity of the spectrum which does not meet the exclusion condition and the variation quantity of the spectrum having been corrected along the polishing time to calculate a spectrum cumulative variation quantity.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method and an apparatus for polishing a workpiece such as a wafer, a substrate, and a panel, and more particularly to a technique for monitoring the polishing of the workpiece based on optical information contained in the reflected light from the workpiece.

In the process of manufacturing a semiconductor device, various materials are repeatedly formed in a film shape on a silicon wafer to form a laminated structure. In order to form this laminated structure, a technique for flattening the surface of the uppermost layer is important. Chemical mechanical polishing (CMP) is used as one means of such flattening.

Chemical mechanical polishing (CMP) is performed by a polishing device. This type of polishing device generally has a polishing table that supports the polishing pad, a polishing head that holds a workpiece (for example, a wafer having a film), and a polishing liquid that supplies a polishing liquid (for example, a slurry) onto the polishing pad. It is equipped with a supply nozzle. When polishing the work piece, the surface of the work piece is pressed against the polishing pad by the polishing head while supplying the polishing liquid onto the polishing pad from the polishing liquid supply nozzle. By rotating the polishing head and the polishing table, respectively, to move the work piece and the polishing pad relative to each other, the layer to be polished forming the surface of the work piece is polished.

In order to measure the thickness of a layer to be polished such as an insulating film or a silicon layer, the polishing device generally includes an optical film thickness measuring device. This optical film thickness measuring device guides the light emitted from the light source to the surface of the workpiece and analyzes the spectrum of the reflected light from the workpiece to determine the thickness of the polished layer of the workpiece. It is composed of.

Patent Document 1 discloses a technique for determining the film thickness based on the amount of change in the spectrum of reflected light. FIG. 8 is a graph showing the relationship between the amount of change in the spectrum and the polishing time. The amount of change in the spectrum is the amount of change in the shape of the spectrum per unit time. The spectrum of reflected light changes according to the thickness of the layer to be polished. Therefore, the amount of change in the spectrum of the reflected light corresponds to the amount of removal of the layer to be polished per unit time.

FIG. 9 is a graph showing the cumulative amount of change in the spectrum obtained by integrating the amount of change in the spectrum along the polishing time. As can be seen from FIG. 9, the cumulative change in the spectrum increases substantially monotonously with the polishing time. Therefore, the amount of polishing of the layer to be polished (that is, the current thickness or the current amount of removal) can be determined from the cumulative amount of change in the spectrum.

JP-A-2015-156503

However, as shown in FIG. 10, local noise may be applied to the amount of change in the spectrum due to the influence of the pattern formed on the surface of the workpiece, the influence of the polishing environment (for example, slurry), and the like. .. Therefore, as shown in FIG. 11, the cumulative amount of change in the spectrum may not increase monotonically, and as a result, the amount of polishing of the layer to be polished may be erroneously estimated.

Therefore, the present invention provides a method and an apparatus capable of accurately monitoring the polishing of the workpiece by eliminating the influence of the pattern formed on the surface of the workpiece, the polishing environment (for example, slurry), and the like. ..

In one aspect, it is a method of monitoring the polishing of a workpiece by irradiating the workpiece with light during the polishing of the workpiece to generate a spectrum of reflected light from the workpiece, said in a predetermined time. The amount of change in the spectrum is calculated, and when the amount of change in the spectrum satisfies a predetermined exclusion condition, the amount of change in the spectrum is corrected, and the amount of change in the spectrum that does not satisfy the exclusion condition and the corrected spectrum. A method is provided in which the amount of change is integrated along the polishing time to calculate the cumulative amount of change in the spectrum.

In one aspect, the exclusion conditions are that the amount of change in the spectrum is greater than the threshold, the amount of change in the current spectrum, and the average of the amount of change in the spectrum already obtained during polishing of the workpiece. The difference from the value is larger than the threshold value, and the amount of change in the spectrum is out of the range of ± Xσ from the average value of the normal distribution of the amount of change in multiple spectra obtained in the past (X is in advance). (It is a defined coefficient), and the amount of change in the spectrum is determined to be an outlier by the Smirnov-Grabs test.

In one aspect, the step of correcting the amount of change in the spectrum is a step of correcting the amount of change in the spectrum by extrapolation or interpolation.
In one aspect, the extrapolation correction uses a plurality of changes in the spectrum aligned with the polishing time, and the interpolation correction uses the spectra acquired at the plurality of measurement points aligned on the workpiece. Use multiple changes.

In one aspect, it is a work piece polishing monitoring device, in which an optical sensor head that irradiates the work piece with light during polishing of the work piece and receives the reflected light from the work piece, and the intensity of the reflected light are wavelengthed. The data processing unit includes a spectroscope for measuring each, a storage device in which a program is stored, and a data processing unit having a calculation device for executing an operation according to an instruction included in the program, and the data processing unit measures the intensity of the reflected light. A spectrum of the reflected light is generated from the data, the amount of change in the spectrum per predetermined time is calculated, and when the amount of change in the spectrum satisfies a predetermined exclusion condition, the amount of change in the spectrum is corrected. Provided is a polishing monitoring device configured to calculate the cumulative spectral change amount by integrating the change amount of the spectrum and the corrected change amount of the spectrum that do not satisfy the exclusion condition along with the polishing time.

In one aspect, the exclusion conditions are that the amount of change in the spectrum is greater than the threshold, the amount of change in the current spectrum, and the average of the amount of change in the spectrum already obtained during polishing of the workpiece. The difference from the value is larger than the threshold value, and the amount of change in the spectrum is out of the range of ± Xσ from the average value of the normal distribution of the amount of change in multiple spectra obtained in the past (X is in advance). (It is a defined coefficient), and the amount of change in the spectrum is determined to be an outlier by the Smirnov-Grabs test.

In one aspect, the data processing unit is configured to correct the amount of change in the spectrum by extrapolation or interpolation.
In one aspect, the data processing unit performs the extrapolation correction using a plurality of changes in the spectrum aligned along the polishing time, and the interpolation correction on the workpiece. It is configured to be performed using multiple changes in the spectrum obtained at the measurement points of.

According to the present invention, the amount of change in the spectrum satisfying the exclusion condition (that is, including noise) is corrected, and the polishing of the workpiece can be accurately monitored.

It is a schematic diagram which shows one Embodiment of a polishing apparatus. It is a figure which shows an example of the spectrum generated by the data processing part. It is a figure which shows the spectrum which changed in a unit time. It is a graph which shows the change with the polishing time of the spectral change amount while polishing a work piece. It is a graph which shows the spectral cumulative change amount obtained by integrating the spectral change amount along with the polishing time. FIG. 6A is a graph in which the amount of change in the spectrum containing noise is removed, and FIG. 6B is a graph in which the amount of change in the spectrum missing due to the removal is replaced with the amount of change in the spectrum containing no noise. It is a graph. It is a figure which shows the approximate expression generated from a plurality of changes in a spectrum obtained during polishing of a workpiece. It is a graph which shows the relationship between the amount of change of a spectrum and polishing time. It is a graph which shows the spectral cumulative change amount obtained by integrating the spectral change amount along with the polishing time. It is a graph which shows the relationship between the amount of change of a spectrum including local noise, and polishing time. 6 is a graph showing the relationship between the cumulative spectral change amount obtained by integrating the spectral changes shown in FIG. 10 and the polishing time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a polishing device. As shown in FIG. 1, the polishing apparatus includes a polishing table 3 that supports the polishing pad 2, a polishing head 1 that presses a workpiece W such as a wafer, a substrate, or a panel having a layer to be polished against the polishing pad 2, and polishing. A table motor 6 for rotating the table 3 and a polishing liquid supply nozzle 5 for supplying a polishing liquid such as a slurry on the polishing pad 2 are provided. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W.

The polishing head 1 is connected to a head shaft 10, and the head shaft 10 is connected to a polishing head motor (not shown). The polishing head motor rotates the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow. The polishing table 3 is connected to the table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow.

The workpiece W is polished as follows. While rotating the polishing table 3 and the polishing head 1 in the direction indicated by the arrow in FIG. 1, the polishing liquid is supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While the work piece W is rotated by the polishing head 1, the work piece W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 in a state where the polishing liquid is present on the polishing pad 2. The layer to be polished constituting the exposed surface of the workpiece W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains and the polishing pad 2 contained in the polishing liquid. Examples of the layer to be polished of the workpiece W include, but are not limited to, an insulating film and a silicon layer.

The polishing device includes an optical polishing monitoring device 40 that monitors the polishing of the workpiece W. The optical polishing monitoring device 40 includes a light source 44 that emits light, a spectroscope 47, an optical sensor head 7 optically connected to the light source 44 and the spectroscope 47, and a data processing unit 49 connected to the spectroscope 47. It is equipped with. The optical sensor head 7, the light source 44, and the spectroscope 47 are attached to the polishing table 3 and rotate integrally with the polishing table 3 and the polishing pad 2. The position of the optical sensor head 7 is a position that crosses the workpiece W on the polishing pad 2 each time the polishing table 3 and the polishing pad 2 make one rotation.

The data processing unit 49 includes a storage device 49a in which a program for executing a spectrum generation and polishing monitoring of the workpiece W, which will be described later, is stored, and an arithmetic unit 49b for executing an operation according to an instruction included in the program. .. The data processing unit 49 is composed of at least one computer. The storage device 49a includes a main storage device such as a RAM and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the arithmetic unit 49b include a CPU (central processing unit) and a GPU (graphic processing unit). However, the specific configuration of the data processing unit 49 is not limited to these examples.

The light emitted from the light source 44 is transmitted to the optical sensor head 7 and guided from the optical sensor head 7 to the workpiece W. The light is reflected by the workpiece W, and the reflected light from the workpiece W is received by the optical sensor head 7 and sent to the spectroscope 47. The spectroscope 47 decomposes the reflected light according to the wavelength and measures the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is sent to the data processing unit 49.

The data processing unit 49 is configured to generate a spectrum of reflected light from the intensity measurement data of the reflected light. The spectrum of the reflected light is represented as a line graph (that is, a spectral waveform) showing the relationship between the wavelength and the intensity of the reflected light. The intensity of the reflected light can also be expressed as a relative value such as reflectance or relative reflectance.

FIG. 2 is a diagram showing an example of a spectrum generated by the data processing unit 49. The spectrum is represented as a line graph (ie, a spectral waveform) showing the relationship between the wavelength and intensity of light. In FIG. 2, the horizontal axis represents the wavelength of the reflected light from the workpiece W, and the vertical axis represents the relative reflectance derived from the intensity of the reflected light. The relative reflectance is an index showing the intensity of reflected light, and is a ratio of the intensity of light to a predetermined reference intensity. By dividing the light intensity (measured intensity) at each wavelength by a predetermined reference intensity, unnecessary noise such as variation in the intensity peculiar to the optical system of the device or the light source can be removed from the measured intensity.

The reference intensity is the intensity of light measured in advance for each wavelength, and the relative reflectance is calculated for each wavelength. Specifically, the relative reflectance is obtained by dividing the light intensity (measured intensity) at each wavelength by the corresponding reference intensity. The reference intensity is obtained, for example, by directly measuring the intensity of the light emitted from the optical sensor head 7, or by irradiating the mirror with light from the optical sensor head 7 and measuring the intensity of the reflected light from the mirror. .. Alternatively, the reference strength is when the silicon substrate (bare substrate) on which the film is not formed is water-polished on the polishing pad 2 in the presence of water, or the silicon substrate (bare substrate) is on the polishing pad 2. It may be the intensity of the reflected light from the silicon substrate measured by the spectroscope 47 when placed.

ここで、λはワークピースＷからの反射光の波長であり、Ｅ（λ）は波長λでの強度であり、Ｂ（λ）は波長λでの基準強度であり、Ｄ（λ）は光を遮断した条件下で測定された波長λでの背景強度（ダークレベル）である。 In actual polishing, the dark level (background strength obtained under the condition of blocking light) is subtracted from the measured strength to obtain the corrected measured strength, and the dark level is subtracted from the standard strength to obtain the corrected reference strength. Then, the relative reflectivity is obtained by dividing the corrected actual measurement intensity by the correction reference intensity. Specifically, the relative reflectance R (λ) can be obtained by using the following equation (1).

Here, λ is the wavelength of the reflected light from the workpiece W, E (λ) is the intensity at the wavelength λ, B (λ) is the reference intensity at the wavelength λ, and D (λ) is the light. It is the background intensity (dark level) at the wavelength λ measured under the condition of blocking.

Each time the polishing table 3 makes one rotation, the optical sensor head 7 guides light to a plurality of measurement points on the workpiece W while crossing the workpiece W, and receives reflected light from these plurality of measurement points. The reflected light is sent to the spectroscope 47. The spectroscope 47 decomposes the reflected light from each measurement point according to the wavelength, and measures the intensity of the reflected light at each wavelength. The reflected light intensity measurement data is sent to the data processing unit 49, and the data processing unit 49 generates a spectrum as shown in FIG. 2 from the reflected light intensity measurement data. In the example shown in FIG. 2, the spectrum of the reflected light is a spectral waveform showing the relationship between the relative reflectivity and the wavelength of the reflected light, but the spectrum of the reflected light is the intensity of the reflected light itself and the wavelength of the reflected light. It may be a spectral waveform showing the relationship between.

ここで、λは反射光の波長であり、λ１，λ２は監視対象とするスペクトルの波長範囲を指定する最小波長および最大波長であり、ｔは研磨時間であり、Δｔは所定の単位時間であり、Ｒ（λ，ｔ）は、波長λ、時間ｔのときの相対反射率（反射光の強度）である。Δｔとしては、例えば、研磨テーブルがｐ回転（ｐは小さな自然数（例えば１））するのに要する時間とすることができる。 The spectrum of reflected light changes according to the thickness of the layer to be polished of the workpiece W. Therefore, the data processing unit 49 monitors the polishing of the workpiece W from the spectrum of the reflected light as follows. The data processing unit 49 calculates the amount of spectral change ΔS (t) per unit time using the following equation (2).

Here, λ is the wavelength of the reflected light, λ1 and λ2 are the minimum wavelength and the maximum wavelength that specify the wavelength range of the spectrum to be monitored, t is the polishing time, and Δt is a predetermined unit time. , R (λ, t) are relative reflectances (intensity of reflected light) at wavelength λ and time t. As Δt, for example, it can be the time required for the polishing table to rotate p (p is a small natural number (for example, 1)).

FIG. 3 is a diagram showing spectra changed during the unit time Δt. The spectral change amount ΔS (t) calculated by the above equation (2) corresponds to a region (shown by hatching) surrounded by two spectra acquired at two different time points. The area of this region corresponds to the thickness of the layer to be polished changed per unit time Δt. Therefore, it is expected that the change in the thickness of the layer to be polished can be captured by integrating the amount of spectral change ΔS (t) during polishing.

ここで、ｔ０は膜厚変化の監視を開始する時間である。 FIG. 4 is a graph showing changes in the amount of spectral change ΔS (t) along the polishing time while polishing the workpiece W. As shown in FIG. 4, the spectral change amount ΔS (t) fluctuates periodically, but the average level of the spectral change amount ΔS (t) is almost constant. The data processing unit 49 calculates the spectral cumulative change amount, which is the cumulative value of the spectral change amount ΔS (t) along the polishing time, using the following equation (3).

Here, t0 is the time to start monitoring the change in film thickness.

FIG. 5 is a graph showing the cumulative spectral change amount A (t) calculated using the above equation (3). As described above, since the amount of spectral change fluctuates periodically, the error from the average level due to the fluctuation is hardly accumulated. Therefore, as shown in FIG. 5, the cumulative spectral change amount A (t) increases substantially linearly with the polishing time. The cumulative spectral change amount A (t) corresponds to the polishing amount of the workpiece W (that is, the amount of removal of the layer to be polished). The data processing unit 49 described above calculates the cumulative spectral change amount during polishing of the workpiece W, and monitors the progress of polishing of the workpiece W based on the cumulative spectral change amount. Further, the data processing unit 49 may determine the polishing end point of the workpiece W from the cumulative spectral change amount. The polishing end point can be a time point when the cumulative spectral change amount reaches a predetermined target value.

As described with reference to FIG. 10, local noise is applied to the amount of change in the spectrum due to the influence of the pattern formed on the surface of the workpiece W and the influence of the polishing environment (for example, slurry). Sometimes. Such noise interferes with accurate monitoring of the polishing of the workpiece W.

Therefore, the data processing unit 49 is configured to correct the amount of change in the spectrum to which noise is added. That is, as shown in FIG. 6A, the data processing unit 49 removes the amount of change in the spectrum including noise, and as shown in FIG. 6B, the amount of change in the spectrum missing due to the removal is noise. It is configured to replace the amount of change in the spectrum that does not include. More specifically, the data processing unit 49 corrects the amount of change in the spectrum when the amount of change in the spectrum satisfies a predetermined exclusion condition, and the amount of change in the spectrum that does not satisfy the exclusion condition and the corrected spectrum. It is configured to integrate the amount of change along the polishing time to calculate the cumulative amount of change in the spectrum.

The predetermined exclusion condition is a condition for determining that noise is included in the calculated change amount of the spectrum. Specific examples of the predetermined exclusion conditions include the following.
(I) The amount of change in the spectrum is larger than the threshold value (ii) The difference between the amount of change in the current spectrum and the average value of multiple changes in the spectrum already obtained during the polishing of the workpiece W Greater than the threshold (iii) The amount of change in the spectrum is outside the range of ± Xσ from the mean of the normal distribution of multiple changes in the spectrum obtained in the past (X is a predetermined coefficient). Is)
(Iv) The amount of change in the spectrum is determined to be an outlier by the Smirnov-Grabs test.

With respect to the above (i), the threshold value is a preset fixed value and is determined based on the data of the amount of change in the spectrum obtained in the past. For example, the threshold value is a value that can significantly divide the spectrum change data obtained in the past into a noise-free spectrum change group and a noise-containing spectrum change group. To.

With respect to (ii) above, the plurality of spectral changes already obtained during polishing of the workpiece W are, for example, the most recent N spectral changes, not including the current spectral changes. The number N is a preset value. When the difference between the amount of change in the current spectrum and the average value of multiple changes in the already obtained spectrum is larger than the threshold value, the amount of change in the current spectrum is likely to contain noise. This threshold may be a fixed value. Alternatively, the threshold value may be a value that fluctuates according to the above average value. For example, the threshold value may be a value deviating from the above average value by a predetermined ratio (%).

With respect to (iii) above, the plurality of changes in the spectrum obtained in the past are the plurality of changes in the spectrum obtained while polishing at least one workpiece having the same structure as the workpiece W. It may be a plurality of changes in the spectrum already obtained during polishing of the workpiece W.

With respect to (iv) above, the sample data used in the Smirnov-Grabs test is a plurality of changes in the spectrum obtained while polishing at least one workpiece having the same structure as the workpiece W. It may be a plurality of changes in the spectrum already obtained during polishing of the workpiece W.

It is presumed that the amount of change in the spectrum that satisfies any of the above-mentioned exclusion conditions (i) to (iv) includes noise. Therefore, the data processing unit 49 corrects the amount of change in the spectrum when the amount of change in the spectrum calculated during polishing of the workpiece W satisfies any one of the above-mentioned plurality of exclusion conditions. The correction of the amount of change in the spectrum is a process of removing noise. The exclusion condition may be one selected in advance from the above exclusion conditions (i) to (iv).

In one embodiment, the data processing unit 49 corrects the amount of change in the spectrum satisfying the exclusion condition by extrapolation or interpolation. More specifically, the data processing unit 49 excludes the amount of change in the spectrum that satisfies the exclusion condition (that is, includes noise), and does not satisfy the exclusion condition (that is, noise) that corresponds to the amount of change in the excluded spectrum. The amount of change in the spectrum (not included) is determined by extrapolation or interpolation. Extrapolation correction uses multiple changes in the spectrum aligned along the polishing time, and interpolation correction uses multiple changes in the spectrum acquired at multiple measurement points aligned on the workpiece W. do.

The data processing unit 49 is configured to correct the amount of change in the spectrum satisfying the exclusion condition by executing any one of the following operations.
(I) Operation of replacing the amount of change in the spectrum that satisfies the exclusion condition (that is, including noise) with the amount of change in the spectrum that does not satisfy the exclusion condition (that is, does not contain noise) (II) The amount of change in the spectrum that satisfies the exclusion condition , Operation of replacing with the average value of a plurality of changes in the spectrum already obtained during polishing of the workpiece W (III) The amount of change in the spectrum satisfying the exclusion condition is obtained at a plurality of adjacent measurement points on the workpiece W. Operation to replace with the average value of multiple changes in the obtained spectrum (IV) An approximate expression is generated from the multiple changes in the spectrum already obtained during polishing of the workpiece W, and the change in the spectrum satisfying the exclusion condition is calculated. , Operation to replace with the value obtained by the above approximation formula

Regarding (I) above, the amount of change in the spectrum that does not satisfy the exclusion condition (that is, does not include noise) is the amount of change in the spectrum already obtained during polishing of the workpiece W. In one embodiment, the amount of change in the spectrum that does not satisfy the exclusion condition (that is, does not include noise) is the amount of change in the most recent spectrum acquired immediately before the amount of change in the spectrum that satisfies the exclusion condition is acquired.

With respect to (II) above, the plurality of changes in the spectrum already obtained during polishing of the workpiece W are the plurality of changes in the spectrum that do not satisfy the exclusion condition (that is, do not include noise). In one embodiment, the plurality of spectral changes already obtained during polishing of the workpiece W are the most recent M spectral changes, not including the current spectral changes. The number M is a preset value.

Regarding (III) above, the adjacent measurement points on the workpiece W are a plurality of measurement points adjacent to the measurement points on the workpiece W from which the amount of change in the spectrum satisfying the exclusion condition has been acquired. As described above, each time the polishing table 3 makes one rotation, the optical sensor head 7 guides light to a plurality of measurement points on the workpiece W while traversing the workpiece W, and reflects from these plurality of measurement points. Receive light. Adjacent measurement points on the workpiece W may be, for example, a plurality of measurement points located on both sides of the measurement point from which the amount of change in the spectrum satisfying the exclusion condition (that is, including noise) has been acquired. The amount of change in the spectrum acquired at each adjacent measurement point is the amount of change in the spectrum that does not satisfy the exclusion condition (that is, does not include noise).

Regarding (IV) above, the approximate expression is an expression on a coordinate system having coordinate axes representing the amount of change in the spectrum and the polishing time, as shown in FIG. The approximate expression has the polishing time as a variable. The approximation formula is determined from a plurality of data points on the coordinate system specified by the plurality of changes in the spectrum that do not meet the exclusion criteria (ie, noise-free) and the corresponding polishing times. The approximate expression may be expressed by a polynomial. The method of obtaining the approximate expression is not particularly limited. The data processing unit 49 generates an approximate expression during polishing of the workpiece W, and inputs the polishing time obtained by acquiring the amount of change in the spectrum satisfying the exclusion condition (that is, including noise) into the approximate expression. The amount of change can be corrected.

The data processing unit 49 integrates the amount of change in the spectrum that does not satisfy the exclusion condition (that is, does not include noise) and the amount of change in the corrected spectrum along the polishing time to calculate the cumulative amount of change in the spectrum, and accumulates the spectrum. The amount of polishing of the workpiece W is monitored based on the amount of change. Since the spectral cumulative change amount is a cumulative value of the spectral change amount that does not include noise, the data processing unit 49 can accurately monitor the polishing amount of the workpiece W.

The above-described embodiments have been described for the purpose of allowing a person having ordinary knowledge in the technical field to which the present invention belongs to carry out the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the invention is not limited to the described embodiments, but is to be construed in the broadest range according to the technical ideas defined by the claims.

1 Polishing head 2 Polishing pad 2a Polishing surface 3 Polishing table 5 Polishing liquid supply nozzle 6 Table motor 7 Optical sensor head 10 Head shaft 40 Optical polishing monitoring device 44 Light source 47 Spectrometer 49 Data processing unit 49a Storage device 49b Computing device

Claims (8)

A method of monitoring the polishing of workpieces
While polishing the workpiece, the workpiece was irradiated with light to obtain light.
Generate a spectrum of reflected light from the workpiece and generate
The amount of change in the spectrum per predetermined time is calculated,
When the amount of change in the spectrum satisfies a predetermined exclusion condition, the amount of change in the spectrum is corrected.
A method for calculating the cumulative spectral change amount by integrating the change amount of the spectrum that does not satisfy the exclusion condition and the corrected change amount of the spectrum along the polishing time. The exclusion condition is
The amount of change in the spectrum is larger than the threshold value.
The difference between the current spectral change and the average of multiple spectral changes already obtained during polishing of the workpiece is greater than the threshold.
The amount of change in the spectrum is outside the range of ± Xσ from the average value of the normal distribution of the amount of change in the plurality of spectra obtained in the past (X is a predetermined coefficient), and the change in the spectrum. The quantity is judged to be an outlier by the Smirnov-Grabs test,
The method according to claim 1, which is any of the above. The method according to claim 1 or 2, wherein the step of correcting the amount of change in the spectrum is a step of correcting the amount of change in the spectrum by extrapolation or interpolation. The extrapolation correction uses a plurality of changes in the spectrum arranged along the polishing time, and the interpolation correction uses a plurality of changes in the spectrum acquired at a plurality of measurement points arranged on the workpiece. 3. The method of claim 3. A work piece polishing monitoring device
An optical sensor head that irradiates the work piece with light while polishing the work piece and receives the reflected light from the work piece.
A spectroscope that measures the intensity of the reflected light for each wavelength,
A data processing unit having a storage device in which a program is stored and an arithmetic unit that executes an operation according to an instruction included in the program is provided.
The data processing unit
A spectrum of the reflected light is generated from the measurement data of the intensity of the reflected light.
The amount of change in the spectrum per predetermined time is calculated,
When the amount of change in the spectrum satisfies a predetermined exclusion condition, the amount of change in the spectrum is corrected.
A polishing monitoring device configured to integrate the amount of change in the spectrum that does not satisfy the exclusion condition and the amount of change in the corrected spectrum along with the polishing time to calculate the cumulative amount of change in the spectrum. The exclusion condition is
The amount of change in the spectrum is larger than the threshold value.
The difference between the current spectral change and the average of multiple spectral changes already obtained during polishing of the workpiece is greater than the threshold.
The amount of change in the spectrum is outside the range of ± Xσ from the average value of the normal distribution of the amount of change in the plurality of spectra obtained in the past (X is a predetermined coefficient), and the change in the spectrum. The quantity is judged to be an outlier by the Smirnov-Grabs test,
The polishing monitoring device according to claim 5, which is one of the above. The polishing monitoring device according to claim 5 or 6, wherein the data processing unit is configured to correct the amount of change in the spectrum by extrapolation or interpolation. The data processing unit performs the extrapolation correction using a plurality of changes in the spectrum arranged along the polishing time, and the interpolation correction at a plurality of measurement points arranged on the workpiece. The polishing monitoring device according to claim 7, wherein the polishing monitoring device is configured to perform using a plurality of variations of the acquired spectrum.

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