JP2001225262A - Polishing state measuring device and measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device capable of stably measuring a polishing state with high accuracy by solving low accuracy and unstability in measuring the polishing state such as measuring residual film thickness and detecting a polishing end point under the influence of residual film thickness distribution of the polished surface of the wafer, inherent in a CMP device in a conventional measuring device used for a CMP process. SOLUTION: As shown in the figure 1, a first measuring device enlarges a measuring area from conventional C to D by controlling the signal acquisition time of probe light irradiated to a waver face, and a second measuring device enlarges a measuring area by adjusting a light shielding slit to adjust an irradiation area on the wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing process for removing a thin film on an object to be polished, for example, a CMP polishing apparatus for flattening and polishing a semiconductor element which is carried out in a process for manufacturing a semiconductor device such as ULSI. The present invention relates to a measuring device suitable for measuring the measurement.

[0002]

2. Description of the Related Art As the degree of integration and miniaturization of semiconductor integrated circuits increases, the number of steps in a semiconductor manufacturing process increases and becomes more complicated. Along with this, the surface of a semiconductor device is not necessarily flat. The presence of a step on the surface causes disconnection of the wiring, an increase in local resistance, etc., resulting in disconnection and a decrease in electric capacity. In addition, in the case of an insulating film, withstand voltage degradation and leakage may occur.

On the other hand, the light source wavelength of photolithography has been shortened with the increase in the degree of integration and miniaturization of semiconductor integrated circuits, and the numerical aperture (NA) has been increasing.
The depth of focus of a semiconductor exposure apparatus has been substantially reduced. In order to cope with the shallower depth of focus, the surface of the semiconductor element is required to be flatter than ever. As a method of flattening such a semiconductor surface, chemical mechanical polishing (Chemical Mechanical Polishing or Chemica
l Mechanical Planarization (hereinafter referred to as CMP) technology is a promising method.

FIG. 11 is a view showing a conventional CMP apparatus. In FIG. 11, 2 is a polishing pad, 7 is a platen, 3 is an object holding part (holder), 4 is an object to be polished (wafer), 5 is an abrasive supply section, and 6 is an abrasive (slurry). As the polishing pad, a sheet made of foamed polyurethane or a non-foamed resin having a groove structure on its surface is used. The holder 3 is rotated about the axis A in the direction of arrow 100 by means not shown, and the platen 7 is rotated about the axis B in the direction of arrow 101 by means not shown. Further, the axis A swings linearly approaching and leaving the axis B. In these processes, the surface to be polished of the wafer 4 is polished by the chemical action and the mechanical action of the polishing agent 6 and the polishing pad 2.

As a method for detecting whether or not the wafer surface has been polished by a predetermined amount in the above-mentioned polishing process and flattened, that is, a method of detecting a polishing state to know a remaining film thickness, a polishing end point, and the like, an optical measurement method is high. Attention has been paid for measurement accuracy. In this measuring method, the wafer 4 is irradiated with light, and the measurement is performed by the reflected light. In FIG. 11, reference numeral 8 denotes a measuring device, and 10 denotes a light transmitting window. For this measurement, the probe light emitted from the measuring device 8 passes through the light transmitting window 10 and irradiates the surface to be polished of the wafer 4, and the signal light reflected from the surface to be polished transmits through the light transmitting window in the opposite direction. Detected by the measuring device. As can be seen from FIG.
And the rotation 101, the measurement is performed when the light transmitting window 10 is rotated to a position where the probe light and the reflected signal light are transmitted.

[0006]

FIG. 12 shows the CM shown in FIG.
FIG. 3 shows in detail the optical system of the measuring device 8 shown in the schematic diagram of the P device. In FIG. 12, 11 is a light source, 2
0 and 21 are lenses, 12 is a beam splitter, 22 is a lens, 4 is a wafer, 23 is a lens, 13 is a photodetector, 3
0 is a signal processing device. The probe light emitted from the light source 11 is transmitted to lenses 20, 21 and a beam splitter (hereinafter, referred to as beam splitter).
12). The probe light transmitted through the BS 12 transmits through the lens 22 and is incident on the wafer 4 almost perpendicularly. At this time, the size of the beam spot irradiated on the wafer 4 is about 1 mmφ. The reflected signal light reflected by the wafer 4 passes through the lens 22, and a part of the reflected light is reflected by the BS 12. The signal light reflected by the BS 12 is collected by the lens 23 and enters the detector 13. Detector 1
At 3, the reflected signal light is photoelectrically converted, and the change in the intensity is measured by the signal processing device 30 as a reflected light signal. Considering the polishing process of the metal electrode thin film for embedding the metal electrode film as shown in FIG. 9, since the excess metal thin film after the lamination of the metal electrode thin film is removed by polishing, the reflection from the surface of the metal thin film is considered. Light is getting smaller. When the excess metal thin film is removed, the area of the metal electrode thin film does not change, so that the intensity of the reflected signal light does not change. By monitoring such a change in the intensity of the reflected signal light, it is possible to detect the polishing end point of the wafer.

However, in the conventional CMP apparatus, the polishing rate of the film is not completely uniform in the wafer surface, and therefore, the distribution of the remaining film thickness in the wafer sometimes becomes non-uniform. The conventional measuring apparatus shown in FIG. 12 does not take measures against the nonuniformity of the residual film thickness distribution.

Generally, a wafer to be polished includes a plurality of dies (one semiconductor device is manufactured from each die after the wafer is cut). The non-uniformity includes the distribution of the remaining film thickness between the dies in one wafer (that is, the unevenness of the remaining film thickness) and the distribution of the remaining film thickness in each of the dies.

The distribution of the remaining film thickness between the dies includes a flatness error of the wafer, a flatness error of the polishing pad, a polishing pressure distribution between the dies, and a distribution between the dies of a relative speed between the dies and the polishing pad. , Etc. are the causes of the occurrence. Therefore, even if the metal layer is removed by measuring one die, and the barrier layer under the die is exposed and the polishing end point is detected, many other dies still do not have the metal layer completely cut off. Remains
There are various cases where the timing of the polishing end point has not been reached, and conversely, for many other dies, the metal layer is excessively ground.

[0010] The distribution of the remaining film thickness in each die may be different pattern types in each die, that is, different pattern densities, or different definitions, or different pattern densities and different definitions. Is the cause of the occurrence. Where the different degrees of definition are
For example, it corresponds to the size of the line width of various electrode lines. If the pattern density is different, the thin film formed on the pattern is formed according to the pattern, so the ratio of the convex portion and the concave portion corresponding to the pattern position is also different, so the average of the convex portion and the concave portion is averaged. Since the polishing rates are different, a residual film thickness distribution occurs. In addition, if the fineness of the pattern is different, the thin film formed on the pattern is formed according to the pattern, so that the fineness of the pattern formed by the convex portions and the concave portions is different. The residual film thickness distribution occurs because the magnitude of the chemical polishing action and the like differ depending on the area difference and the like. For this reason, even in one die, for example, there are places where the metal layer is cut by polishing and places where the metal layer remains.

As described above, the metal electrode film on the wafer polished by the conventional CMP apparatus has a residual film thickness distribution.
The intensity of the reflected signal light changes depending on the location where the measurement spot hits. This means that the change in the intensity of the reflected signal light due to the difference in the measurement location on the wafer includes a component of a magnitude that cannot be ignored in the change in the intensity of the reflected signal light due to the progress of the polishing of the entire wafer. In addition, it is difficult to accurately measure a polishing state such as a remaining film thickness and a polishing end point due to a change in intensity of the reflected signal light.

According to the present invention, the remaining film thickness distribution in the wafer is C
It is an object of the present invention to provide a measuring apparatus capable of measuring the polishing state with high accuracy by reducing the influence of the MP apparatus on the measurement accuracy of the polishing state.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention firstly provides a method for polishing a polishing object with a polishing agent interposed between a polishing object having a thin film on its surface and a polishing object. And an apparatus for measuring a polishing state by a reflected signal light obtained by irradiating a probe light on the thin film which is a surface to be polished while removing the thin film by polishing by relatively moving the object and the object to be polished. A light source that emits the probe light, a photodetector that receives the reflected signal light, a signal processing unit that processes a reflected light signal output from the photodetector to output a polishing state, and the polished surface. And a means for adjusting the measurement area.

Secondly, there is provided the measuring apparatus according to claim 1, wherein the adjusting means of the measuring area is a control section of the signal processing section for controlling the acquisition time of the reflected light signal.

Third, the means for adjusting the measurement area comprises a light-shielding slit for adjusting the size of the irradiation area of the probe light on the surface to be polished.
A measurement device is provided.

Fourthly, the probe light emitted from the light source has a plurality of wavelength components, and a polishing state is measured from a change in a spectral characteristic of the reflected signal light. 3. A measuring device according to claim 1.

Fifth, the photodetector detects only a regular reflection component of the reflected signal light and does not detect a first-order or higher-order diffracted light component. A measurement device is provided.

Sixth, the measurement according to any one of claims 1 to 5, wherein the measurement of the polishing state is one or both of the measurement of the remaining film thickness of the thin film and the measurement of the polishing end point. Provide equipment.

Seventhly, the thin film is polished by relatively moving the polishing body and the polishing object in a state where an abrasive is interposed between the polishing object and the polishing object having a thin film on the surface. A measuring method of measuring a polishing state by a reflected signal light obtained by irradiating a probe light on the thin film which is a surface to be polished while removing the probe light; Spatially scanning the light irradiation spot on the surface to be polished to reduce the influence of the residual film thickness distribution; receiving the reflected signal light while performing the scanning; Controlling the acquisition time of the reflected light signal obtained.

Eighth, the thin film is polished by relatively moving the polishing body and the polishing object in a state in which an abrasive is interposed between the polishing object and the polishing object having a thin film on the surface. This is a measuring method of measuring a polishing state by a reflected signal light obtained by irradiating a probe light on the thin film which is a surface to be polished while removing, and reducing the influence of the probe light to reduce the influence of the residual film thickness distribution. A measuring method comprising: adjusting a spot diameter; irradiating the surface to be polished with the probe light; and receiving the reflected signal light.

Ninth, the measurement of the polishing state is one or both of the measurement of the remaining film thickness of the thin film and the measurement of the polishing end point. Provide a way.

Tenthly, there is provided the measuring method according to any one of claims 7 to 9, wherein the object to be polished is a semiconductor wafer having a thin film of a semiconductor device formed on a surface thereof.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] FIG. 1 shows a relationship between a probe light irradiation area of a measuring apparatus of the present embodiment and a surface to be polished of an object to be polished (wafer), and FIG. FIG. 3 is a schematic diagram of a measuring device. FIG. 7 shows an outline of a CMP apparatus for which the measuring apparatus of the present invention measures a polishing state. This C
The MP device itself is exactly the same as the device of the prior art shown in FIG. FIG.
Is different from the conventional measuring device shown in FIG. 12 only in that the signal processing device 8 includes a signal acquisition control unit and controls the timing of signal acquisition. Therefore, the operation of the optical system is redundant. It is omitted to avoid the problem. In the measuring device of FIG. 2, the reflected light signal output from the photodetector 13 is input to the signal processing device 50, and the control unit for the acquisition time of the reflected light signal controls the signal acquisition as follows.

In general, a photodetector can obtain a reflected light signal in a few milliseconds. Conventionally, the polishing state has been measured using the signal acquired in this several msec. During this few msec, the wafer rotates 100. However, since the moving distance during this period is generally short, the irradiation area (measurement area) is almost the same as the area of the spot diameter of the probe light, and is shown in FIG. The diameter was about 1 mmφ and had a C-like shape, which was generally smaller than the size of the die. For this reason, even if the measurement position was slightly shifted in the die, the reflected light changed due to unevenness in the remaining film thickness in the die. Further, when the measurement position is largely shifted and another die is measured, the distribution of the remaining film thickness between the dies is added, so that the reflected signal light further changes. These changes in the reflected signal light have caused the measurement results to be inaccurate. The present invention includes a controller for controlling the acquisition time of the reflected light signal, and reduces the influence of the remaining film thickness distribution (remaining film thickness non-uniformity) of polishing by the photodetector 1.
3 to control the acquisition time of the reflected light signal. We have noted that when using the CMP apparatus of FIG. 7, the reflected light signal can be continuously acquired while the rotating translucent window crosses the reflected signal light. Since the wafer 4 polished by the CMP apparatus in FIG. 7 during the acquisition of the reflected light signal is rotating 100, during this time, the probe light spot starts at the position 32, crosses a plurality of dies, and reaches the position 33. Since the scanning is performed on the wafer, the measurement area can be enlarged as indicated by the area D. In FIG. 1, reference numeral 4 denotes an object to be polished (wafer), and a hatched portion (C or D) is an irradiation area. C corresponds to the irradiation area when the conventional acquisition time of the reflection signal is short, and D corresponds to the irradiation area when the acquisition time of the reflection signal of the present invention is long. Each rectangle divided by a dotted line corresponds to the die 31. The maximum value of the measurement area is determined by the effective diameter of the light transmitting window 10, the rotation speed of the platen, and the rotation speed of the wafer. There are two types of measurement modes in the area D. The first mode is a method of individually acquiring a plurality of sets of reflected signals in the area D. Specifically, it is a method of individually acquiring the reflected light signal every several msec from the first position 32 to the last position 33 and processing these plural signals. Position 32
From the last position 33 to the reflected light signal continuously,
In this method, the integrated values of these acquired signals are processed as one signal.

This second mode is equivalent to making the spot shape of the probe light into an elongated shape like D, so that it is necessary to measure average information in an area D wider than C in the wafer 4. This has the effect of averaging the change in the reflected signal light due to the remaining film thickness unevenness. By enlarging the measurement area in this way, even if the measurement position is slightly shifted, the change in the intensity of the reflected signal light due to the unevenness of the remaining film thickness is reduced, and as a result, the measurement result more appropriately indicates the polishing state of the entire wafer. become. When this measuring apparatus is applied to a polishing process for removing an extra metal film of a metal electrode film as shown in FIG. 9, for example,
The change in the intensity of the reflected light signal indicates the progress of polishing of the entire wafer more appropriately, and the average remaining film thickness of the entire wafer can be measured more appropriately and more accurately, and the polishing can be more accurately and stably performed. An end point can be determined.

In the first mode, a plurality of reflected light signals are acquired in the irradiation area D of the probe light. Since each signal generally shows a different reflected signal light intensity due to uneven remaining film thickness, each of the remaining film thicknesses measured for each reflected signal light is also different. The remaining film thickness of the region D can be obtained by statistical processing of the thickness. A preferred method of statistical processing is arithmetic averaging. Whether or not the region D has reached the polishing end point can be determined by a logical operation of the determination result of each measurement point of the polishing end point determined from the remaining film thickness of each measurement point individually measured. . For example, the logical product of the polishing end point signals of two or more measurement points (YES if the polishing end point has been reached, NO if not reached) is YES (the polishing end point has been reached).
It is determined that the polishing is finished when.

The measuring apparatus 8 of the present embodiment for detecting the polishing end point from the intensity measurement of the reflected signal light can be preferably applied particularly to a metal layer polishing process as shown in FIG. 9, but is not limited to this. This is not the only thing
It can also be used for element isolation (Shallow Trench Isolation) as shown in the drawings and detection of the polishing end point in the process of flattening the interlayer insulating film as shown in FIG.

In this embodiment, the measurement of the remaining film thickness and the detection of the polishing end point are performed by measuring the intensity of the reflected signal light.
It is a preferable method to measure the reflected signal light using the spectrally reflected signal light obtained by spectrally separating the reflected signal light, which will be described in a second embodiment below. [Embodiment 2] FIG. 1 shows a relationship between an irradiation area of a probe light of a measuring apparatus of the present embodiment and a surface to be polished of an object to be polished (wafer), and FIG. 3 is a schematic diagram of the measuring apparatus of the present embodiment. is there. FIG. 7 shows an outline of a CMP apparatus for measuring a polishing state for explaining the measuring apparatus of the present embodiment. FIG. 1 differs from the first embodiment only in that the probe light is not monochromatic but contains multiple wavelength components. Further, since the CMP apparatus in FIG. 7 is exactly the same as the apparatus in the first embodiment, the description is omitted to avoid redundancy. In the measuring apparatus shown in FIG. 3, reference numeral 18 denotes a white light source having a multi-wavelength component, preferably a xenon lamp or a halogen lamp. Also, white LE
D can also be used. The probe light emitted from the light source 18 passes through the lenses 20, 21 and BS12,
At 2, the light is converted into substantially parallel light, and is perpendicularly incident on the polishing object (wafer) 4. The reflected signal light from the wafer 4 passes through the lens 22 and a part thereof is reflected by the BS 12. The measurement light reflected by the BS 12 is made substantially parallel by the lens 23, reflected by the mirror 14, and transmitted through the lenses 24 and 25. The light transmitted through the lens 25 is split by the diffraction grating 16, the light of different wavelengths is diffracted at different angles, and is incident on a linear sensor 17 having a plurality of separated minute light detecting elements corresponding to different angles. Thereby measuring the spectral reflection signal light. Here, considering the reflected signal light from the wafer on which the semiconductor device pattern exists, the reflected signal light includes not only specularly reflected light (zero-order light) but also first-order or higher-order diffracted light (diffraction spot) that cannot be ignored in terms of light quantity. Are generally present in large numbers. Since this diffracted light has a different effect on the reflected signal light depending on the change in the pitch of the semiconductor device pattern on the wafer, it is complicated to calculate an accurate remaining film thickness from the reflected light signal obtained from the reflected signal light. Or, it becomes difficult, and as a result, the measurement error of the remaining film thickness and the error in detecting the polishing end point from the remaining film thickness are increased. Therefore, in this embodiment, the diffracted light is removed. The removal of the diffracted light was performed as follows.

In general, the diffraction spot has a pitch (microstructure period) d of the device pattern and a wavelength λ of the probe light.
, An n-th order diffraction spot is generated in the diffraction angle θ direction represented by the following equation (1).

Dsin θ = nλ (1) As shown by the equation (1), among the reflected signal lights reflected from the wafer, the specularly reflected light (0-order light) is reflected in the normal direction of the polished surface of the wafer. However, the nth-order diffracted light is reflected in an angle θ direction different from the specularly reflected light. Therefore, the nth-order diffracted light enters the lens 22 at an angle different from that of the regular reflection light, enters the BS 12 at a different angle, enters the lens 23 at a different angle, enters the mirror 14 at a different angle, and enters the mirror 14 at a different angle. The light enters the lens 24 and is refracted at a position different from the optical axis of the lens 24 at a different angle to form an image. The measuring device of the present embodiment includes a light-shielding slit 19 having an opening having an appropriate diameter at a focal position on the optical axis. The position and diameter of the light-shielding slit 19 are determined so that specularly reflected light passes through the opening but diffracted light of the first or higher order cannot pass through the opening. For this purpose, the first or higher order diffracted light is blocked
9 and is not incident on the linear sensor 17.
The linear sensor 17 measures the reflected light intensity for each wavelength of the incident regular reflected light, and inputs the spectral reflected light signal to the signal processing device 50. Since the contribution of the first-order or higher-order diffracted light is thus removed from the spectral reflected light signal, it is not necessary to consider the influence of the pitch of the device pattern. Become. Now, consider a case where an interlayer insulating film 41 of SiO ₂ is formed on a wafer as shown in FIG. The reflectance of white light reflected on a wafer having an interlayer insulating film is
It has a dispersion characteristic according to the remaining film thickness of the interlayer insulating film, that is, a spectral reflection characteristic. It is generally not easy to analytically calculate the remaining film thickness from the spectral reflection characteristics. Therefore, in order to measure the remaining film thickness, the spectral reflection characteristics for various remaining film thicknesses are obtained in advance as reference values. This reference value may be either a spectral reflection characteristic measured for various remaining film thicknesses measured by other well-known film thickness measurement methods measured in advance, or a spectral reflection characteristic calculated by simulation.
The remaining film thickness is measured by comparing the similarity between the reference values and the spectral reflection characteristics. For comparison of the similarity, fitting of the reference value and the measured spectral reflection characteristic is performed. Although the fitting method is not particularly limited, the cross-correlation coefficient between the reference spectral reflection characteristic and the measured spectral reflection characteristic is calculated, and the film thickness corresponding to the spectral reflection characteristic that maximizes the value is defined as the measured film thickness. The method or the least squares measurement method is a preferred method. The method of measuring the remaining film thickness by comparing the similarity is described in Japanese Patent Application No. 11-1 / 1999.
89388. Since the measured spectral reflection characteristic varies according to the remaining film thickness distribution, the spectral reflection characteristic varies depending on the variation of the irradiation position of the probe light. As a result, the measured remaining film thickness fluctuates, and the timing for determining the detected polishing end point fluctuates. In order to prevent this, as shown in FIG. 1, in the present embodiment, as in the first embodiment, the operation of the reflected light signal acquisition time control unit provided in the signal processing device increases the reflected signal light acquisition time. The reflected signal light is acquired from the irradiated area D. In the case of the present embodiment, the first mode in which a plurality of sets of spectral reflected light signals are acquired in the region D is particularly preferable. As in the case of the first embodiment, spectral reflection light signals are acquired every several msec from the first position 32 to the last position 33 within the measurement area D, and the results (residuals) obtained from the plurality of spectral reflection light signals are obtained. One or both of the determination of the film thickness or the polishing end point) is processed as follows.

That is, when a plurality of reflected signal lights are acquired in the irradiation region D of the probe light, the respective reflected signal lights acquired for each measurement point are generally different from each other, and determined for each reflected signal light ( Since each measured remaining film thickness is also different, the remaining film thickness of the region D can be obtained by statistical processing of these different plurality of remaining film thicknesses. A preferred method of statistical processing is arithmetic averaging. The determination as to whether or not the region D has reached the polishing end point can be made by a logical operation of the determination result at each measurement point at the polishing end point determined from the remaining film thickness at each measurement point. That is, when the remaining film thickness is determined for each measurement point, it is determined for each measurement point whether each measurement point has reached the polishing end point. A logical operation is performed on the determination result for each of these measurement points. For example, when the logical product of the polishing end point signals of two or more measurement points (YES if the polishing end point has been reached, NO if not reached) is YES (the polishing end point has been reached), the polishing is terminated. I do. As described above, the measurement apparatus of the present embodiment uses statistical processing and logical operation from a plurality of remaining film thicknesses obtained by reflected signal light from a plurality of measurement locations and a plurality of polishing end point determination results. Since the measurement of the remaining film thickness and the determination of the polishing end point are performed comprehensively, the influence of the distribution of the remaining film thickness in the wafer can be reduced and the polishing state can be accurately measured.

The measuring apparatus 8 of the present embodiment for detecting the remaining film thickness or the polishing end point from the spectral reflection characteristics of the reflected signal light is preferably applied particularly to flattening and polishing of an interlayer insulating film. Metal electrode film polishing process as shown, FIG.
It can also be applied to element isolation (Shallow Trench Isolation) as shown. [Embodiment 3] FIG. 4 shows the relationship between the irradiation area of the probe light of the measuring apparatus of the present embodiment and the surface to be polished of the object to be polished (wafer), and FIG. 5 is a schematic diagram of the measuring apparatus of the present embodiment. is there. FIG. 7 shows an outline of a CMP apparatus for measuring a polishing state for explaining the measuring apparatus of the present embodiment. Since the CMP apparatus in FIG. 7 is exactly the same as the apparatus in the first embodiment, description thereof will be omitted to avoid redundancy. The measuring device of FIG. 5 differs from that of FIG.
Measurement device. Further, in FIG. 5, in order to clarify the function of the light-shielding slit, the light rays are displayed not in the optical axis as in FIG.

In the measuring apparatus shown in FIG.
21 is a lens, 15 is a light shielding slit, 12 is a beam splitter, 22 is a lens, 4 is a wafer, 23 is a lens, 1
3 is a photodetector, 30 is a signal processing device. The probe light emitted from the light source 11 is converted into parallel light by a lens 20, the size of a light beam is adjusted by a light shielding slit 15, and the lens 21 and a beam splitter (hereinafter, referred to as BS) 12.
Through. The probe light transmitted through the BS 12 is the lens 2
2 and enter the wafer 4 almost perpendicularly. At this time, the size of the beam spot irradiated on the wafer 4 is adjusted by the light shielding slit 15. The reflected signal light reflected by the wafer 4 is stopped down by the lens 22, and a part of the reflected light is reflected by the BS 12. The signal light reflected by the BS 12 is condensed by the lens 23 and enters the detector 13. The reflected signal light is photoelectrically converted by the detector 13 and the reflected light signal is sent to the signal processing device 30. The signal processing device 30 measures the polishing state based on a change in the reflected light signal. Considering the polishing process of the metal electrode film for embedding the metal electrode film as shown in FIG. 9, as the excess metal thin film after the lamination of the metal electrode thin film is removed by polishing, the reflection from the surface of the metal electrode thin film is increased. Light is getting smaller. When the excess metal thin film is removed, the area of the metal electrode film does not change,
The intensity of the reflected signal light also does not change. By monitoring such a change in the intensity of the reflected signal light, it is possible to detect the polishing end point of the wafer.

The light shielding slit 15 of the measuring apparatus according to the present embodiment
Has a function of adjusting the size of the spot diameter as described above. Increasing the slit width of the light-shielding slit 15 increases the spot diameter of the probe light applied to the wafer, and decreases the diameter in the opposite case. When the spot diameter is increased, as shown in FIG.
For example, irradiating a wafer over a plurality of dies, and the enlarged irradiation area means that the measurement area is enlarged. For this reason, the remaining film thickness can be calculated as average information in a wide measurement area in the wafer, and the measured film thickness does not vary greatly even if the measurement position slightly changes. Therefore, the change in the remaining film thickness can be continuously and stably detected, and the polishing end point can be stably determined.

As described above, the measuring apparatus of the present embodiment
Since the influence of the distribution of the remaining film thickness in the wafer on the deterioration of the measurement accuracy of the polishing state is reduced, the polishing state can be accurately measured even if the distribution of the remaining film thickness exists. [Embodiment 4] FIG. 4 shows the relationship between the irradiation area of the probe light of the measuring apparatus of the present embodiment and the surface to be polished of the object to be polished (wafer), and this relationship is the same as in the case of Embodiment 3.
FIG. 6 shows an outline of the measuring apparatus of the present embodiment. FIG. 7 shows an outline of a CMP apparatus for measuring a polishing state for explaining the measuring apparatus of the present embodiment. Since the CMP apparatus in FIG. 7 itself is exactly the same as the apparatus in the first embodiment, description of the operation is omitted to avoid redundancy. The measuring device of FIG.
It differs from the measuring apparatus of Embodiment 2 whose outline is shown in FIG. 3 only in that a light-shielding slit 15 is additionally provided. FIG.
Is a white light source having a multi-wavelength component, preferably a xenon lamp or a halogen lamp. Also, white LEDs can be used. The probe light emitted from the light source 18 passes through the lens 20 and passes through the light-shielding slit 15, whereby the size of the light beam is adjusted,
The light passes through the lens 21 and the BS 12, is converted into substantially parallel light by the lens 22, and vertically enters the polishing target (wafer) 4. The reflected signal light from the wafer 4 passes through the lens 22,
A part thereof is reflected by the BS 12. The measurement light reflected by the BS 12 is made substantially parallel by the lens 23 and
The light is transmitted through the lens 24, the first-order or higher order diffracted light component is removed by the light-shielding slit 19, transmitted through the lens 25, and enters the diffraction grating 16. Light incident on the diffraction grating 16 is split, and light of different wavelengths is diffracted at different angles,
The spectral reflected light signal is measured by being incident on a linear sensor 17 having a plurality of separated minute light detecting elements corresponding to different angles.

The light shielding slit 15 of the measuring apparatus according to the present embodiment
Has a function of adjusting the size of the spot diameter as described above. Increasing the slit width of the light-shielding slit 15 increases the spot diameter of the probe light applied to the wafer, and decreases the diameter in the opposite case. When the spot diameter is increased, as shown in FIG.
For example, the wafer is irradiated over a plurality of dies, and the increased spot diameter means that the measurement area is enlarged. For this reason, the remaining film thickness can be calculated as average information in a wide measurement area in the wafer, and the measured film thickness does not vary greatly even if the measurement position slightly changes. Therefore, the change in the remaining film thickness can be continuously and stably grasped, and the polishing end point can be stably and accurately determined.

As described above, the measuring apparatus of the present embodiment
Since the influence of the distribution of the remaining film thickness in the wafer on the deterioration of the measurement accuracy of the polishing state is reduced, the polishing state can be accurately measured even if the distribution of the remaining film thickness exists.

Since the measurement area can be adjusted by using the measurement method described in the description of the measurement apparatus of the first, second, third, and fourth embodiments, the remaining film thickness can be accurately measured in CMP polishing of a semiconductor device. The polishing end point can be detected accurately and stably.

As described above, as the light source 18 of the multi-wavelength component in the second and fourth embodiments, even if it is a light source having a relatively wide spectral range continuously in the visible region, such as a white light source, a plurality of light sources having a relatively narrow half-value width are used. A light source that emits light having a spectrum of? In the above description, the end point of polishing is detected based on the measurement result of the remaining film thickness. However, the remaining film thickness is not necessarily measured, and may be directly detected by another method. For example, the metal electrode film polishing step as shown in FIG. 9 may be performed based on, for example, detection of an increase or decrease in the number of extreme values in a spectral reflection light signal.

In the first and second embodiments, the control area provided in the signal processing apparatus corresponds to the size of the remaining film thickness distribution of each polishing apparatus and the device pattern of each die. Is adjusted by appropriately controlling the length of signal acquisition time and the number of signal acquisition times of the signal processing device.

Furthermore, the control unit of the acquisition time of the reflected light signal in the first and second embodiments is not only provided inside the signal processing device but also separately provided outside the signal processing device. It goes without saying that it is included in the scope of the invention.

Furthermore, the measurement area in the third and fourth embodiments is measured by adjusting the spot diameter according to the size of the remaining film thickness distribution of each polishing apparatus and the device pattern of each die. It is typically between a few hundred microns in diameter and a few tens of millimeters in diameter.

In addition to the effect of reducing the influence of the remaining film thickness distribution on the measurement accuracy deterioration common to the third and fourth embodiments, the intensity of the probe light is substantially increased and the amount of light incident on the photodetector is increased. It also has the effect of stabilizing the measurement.

In the measuring apparatus described in the first, second, third, and fourth embodiments, the measurement is performed by passing through the light transmitting window of the CMP apparatus shown in FIG. 7, but the present invention is not limited to this method. is not. For example, it is a preferable method to measure at the moment when the wafer is shifted out of the polishing pad and jumps out while the wafer performs relative movement with the polishing pad. In a polishing apparatus in which the polishing pad is smaller than the wafer,
The measurement can also be performed on a portion of the wafer that is exposed outside the polishing pad. As described above, the present invention can be applied to any polishing apparatus including any CMP apparatus, regardless of the polishing method, as long as the surface to be polished of the wafer can be irradiated with probe light and its reflected signal light can be measured.

The invention of the first, second, third and fourth embodiments has been described with reference to the limited schematic diagrams. However, the scope of the present invention is not limited to the scope shown in these drawings, and the present invention is not limited thereto. The whole sphere of spirit. For example, if a light source that emits infrared light is used, measurement can be performed by irradiating the silicon wafer with probe light from the back side. Furthermore, if a light source that emits infrared light is used, measurement can be performed using transmitted signal light. Therefore, a measuring apparatus that measures the polishing state by these methods falls within the scope of the present invention.

[0046]

As described above, Embodiments 1, 2, 3, and 4
According to the invention of the above, since the measurement area is adjusted, it is possible to accurately measure the polishing state even if there is some residual film thickness distribution in the CMP apparatus. Further, since the measurement is performed by one or both of statistical processing of the measurement results at a plurality of measurement points or one or both of the logical operations, it is possible to cope with more various wafers and various polishing conditions.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a comparison between a measurement area (irradiation area) on a wafer in Embodiments 1 and 2 and a conventional measurement apparatus.

FIG. 2 is a schematic diagram showing a measuring device according to the first embodiment.

FIG. 3 is a schematic diagram illustrating a measurement device according to a second embodiment.

FIG. 4 is a conceptual diagram showing a comparison between a measurement area (irradiation area) on a wafer in Embodiments 3 and 4 and a conventional measurement apparatus.

FIG. 5 is a schematic diagram illustrating a measuring device according to a third embodiment.

FIG. 6 is a schematic diagram illustrating a measuring device according to a fourth embodiment.

FIG. 7 is a CM used to describe the measuring apparatus according to the first to fourth embodiments.
It is a schematic diagram of a P device and a measuring device.

FIG. 8 is a schematic view of a cross section of a thin film showing a step of polishing an interlayer insulating film, wherein the upper figure shows a state before polishing and the lower figure shows a state after polishing.

FIG. 9 is a schematic diagram of a cross section of a thin film showing a polishing process of a metal film, wherein an upper diagram shows a state before polishing and a lower diagram shows a state after polishing.

FIG. 10 is a schematic view of a cross section of a thin film on a wafer showing an element isolation step, wherein the upper figure shows a state before polishing and the lower figure shows a state after polishing.

FIG. 11 is a schematic diagram of a CMP apparatus and a measuring apparatus used for describing a conventional measuring apparatus.

FIG. 12 is a schematic diagram of a conventional measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 CMP apparatus 2 Polishing body (polishing pad) 3 Polishing object holding | maintenance part (holder) 4 Polishing target (wafer) 5 Abrasive supply part 6 Abrasive (slurry) 7 Surface plate 8 Measuring apparatus 10 Translucent window 11 Light source 12 Beam splitter (BS) 13 Photodetector 14 Mirror 15 Shielding slit 16 Spectroscope (diffraction grating) 17 Photodetector (linear sensor) 18 Light source 19 Shielding slit 20-25 Lens 30 Signal processing device 31 Die 32 First reflection signal acquisition position 33 end of the reflected signal acquisition position 41 interlayer insulating film 42 a metal electrode film 43 dielectric film 44 Si _x N film 45 Si 46 trenches 50 of acquisition time of the reflected optical signal control unit of the signal processing device 100 holder comprising a Rotation direction 101 Rotation direction of surface plate C Measurement area (irradiation area) with respect to conventional signal acquisition time D Signal acquisition time is long Measurement area (irradiation area) C 'Measurement area (irradiation area) relative to conventional spot diameter E Measurement area (irradiation area) when spot diameter is large

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/66 H01L 21/302 LF term (Reference) 2F065 AA30 BB03 BB16 CC17 CC19 CC31 FF42 FF48 FF61 GG02 GG03 GG07 GG22 GG24 HH04 HH13 JJ02 JJ09 JJ25 LL04 LL12 LL28 LL30 LL42 LL46 LL67 NN12 NN20 PP13 QQ00 QQ14 QQ28 QQ38 QQ41 QQ42 3C058 AA07 AC02 BA01 BA07 CB01 CB03 DA17 4A106 DH01A12DH CB09 CB16 DB08 EB02

Claims (10)

[Claims] 1. A polishing method for removing a thin film by polishing by relatively moving the polishing body and the polishing object in a state where an abrasive is interposed between the polishing object and a polishing object having a thin film on the surface. A light source for emitting the probe light, and a photodetector for receiving the reflected signal light, the device being a device for measuring a polishing state by a reflected signal light obtained by irradiating the thin film as a surface to be polished with a probe light. A signal processing unit for processing a reflected light signal output from the photodetector to output a polishing state, and a means for adjusting a measurement area on the surface to be polished, . 2. A measuring apparatus according to claim 1, wherein said adjusting means for adjusting the measuring area is a control section of the signal processing section for controlling the acquisition time of the reflected light signal. 3. A measuring apparatus according to claim 1, wherein said measuring area adjusting means comprises a light-shielding slit for adjusting the size of the irradiation area of the probe light on the surface to be polished. 4. The probe light emitted from the light source has a plurality of wavelength components, and a polishing state is measured from a change in spectral characteristics of the reflected signal light.
The measuring device according to claim 1. 5. The photodetector according to claim 1, wherein the photodetector detects only a regular reflection component of the reflected signal light and does not detect a first-order or higher-order diffracted light component. measuring device. 6. The measuring apparatus according to claim 1, wherein the measurement of the polishing state is one or both of a measurement of a remaining film thickness of the thin film and a measurement of a polishing end point. 7. A polishing method for removing the thin film by polishing by relatively moving the polishing body and the polishing object in a state in which an abrasive is interposed between the polishing object and the polishing object having a thin film on the surface. A method for measuring a polishing state by reflection signal light obtained by irradiating the thin film which is the surface to be polished with probe light, and irradiating the surface with the probe light with the probe light; Spatially scanning the irradiation spot on the surface to be polished to reduce the influence of the remaining film thickness distribution, receiving the reflected signal light while performing the scanning, and receiving the light. Controlling the acquisition time of the reflected light signal. 8. The thin film is removed by polishing by relatively moving the polishing body and the polishing object in a state where an abrasive is interposed between the polishing object having a thin film on the surface and the polishing body. A method for measuring a polishing state by a reflected signal light obtained by irradiating a probe light on the thin film, which is a surface to be polished, and a spot diameter of the probe light to reduce an influence of a residual film thickness distribution. A measuring method, a step of irradiating the surface to be polished with the probe light, and a step of receiving the reflected signal light. 9. The measuring method according to claim 7, wherein the measurement of the polishing state is one or both of the measurement of the remaining film thickness of the thin film and the measurement of the polishing end point. 10. The measuring method according to claim 7, wherein the object to be polished is a semiconductor wafer having a thin film of a semiconductor device formed on a surface thereof.