JP2001280938A - Method and instrument for measuring opening ratio for thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure an opening ratio for thin films by utilizing a characteristic that spectroscopic reflection spectra shift in response to the opening ratio. SOLUTION: This method comprises a step S1 for measuring the spectroscopic reflection spectra, a step S4 for extracting only a component of the first thin film as an extracted spectroscopic reflection spectrum, a step S5 for preparing a theoretical spectroscopic reflection spectrum of the first thin film as a theoretical spectroscopic reflection spectrum, steps S6-S10 for calculating the opening ratio of the first thin film to the second thin film based on a difference between the extracted spectroscopic reflection spectrum and the theoretical spectroscopic reflection spectrum, which are excecuted respectively. An influence by the second thin film is found based on the difference between the extracted spectroscopic reflection spectrum and the theoretical spectroscopic reflection spectrum to find the opening ratio of the first thin film to the second thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a circular semiconductor wafer or a glass substrate (hereinafter simply referred to as a substrate) with light, and opening a thin film formed on the substrate based on light reflected from the substrate. The present invention relates to a method and an apparatus for measuring the aperture ratio of a thin film for measuring the ratio.

[0002]

2. Description of the Related Art In recent semiconductor manufacturing processes, finer patterns have been developed, and the line width and spacing (Line & S
pace (abbreviated as L & S) is less than 1 μm.
A second thin film (for example, an oxide film) that has been finely patterned by such L & S is buried and covered with a second thin film.
The substrate on which the thin film (for example, a copper film) is applied is polished in a CMP (Chemical Mechanical Polishing) process, and an extra film is removed to perform wiring by the second thin film. I have.

[0003] However, if the polishing condition is poor and the polishing is not performed uniformly, the opening ratio of the first thin film and the second thin film on the substrate surface in plan view changes, and the substrate is designed with a fine pattern. Since the pattern may be broken, use a SEM to inspect the polishing state.
By using a (scanning electron microscope) and observing the cross section, the aperture ratio between the first thin film and the second thin film is measured.

[0004]

However, the prior art having such a structure has the following problems. That is, in order to measure the aperture ratio with the SEM, the substrate must be broken as a matter of course, and there is a problem that the measurement cannot be performed easily.

The present invention has been made in view of such circumstances, and makes it possible to easily measure the aperture ratio of a thin film by utilizing the characteristic that the spectral reflection spectrum is displaced in accordance with the aperture ratio. It is an object of the present invention to provide a method and an apparatus for measuring a thin film aperture ratio.

[0006]

The present invention has the following configuration in order to achieve the above object. That is, the invention according to claim 1 is a method for measuring the aperture ratio of a thin film based on reflected light from a substrate on which the thin film is formed, wherein the first thin film and the first thin film are measured. A photometric process of measuring a spectral reflection spectrum from within a measurement region that is different from the thin film and that includes a second thin film formed between the first thin films in plan view; An extraction step of extracting only the components of the first thin film as an extracted spectral reflection spectrum, and a creating step of creating a theoretical spectral reflection spectrum of the first thin film as a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum And a calculating step of calculating an aperture ratio between the first thin film and the second thin film based on a difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. Than it is.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: covering a surface of a substrate on which a first thin film is formed; removing a second thin film different from the first thin film by a predetermined amount; A method of measuring an aperture ratio of a thin film on a substrate in a process of exposing a layer including a first thin film and a second thin film on the thin film, the method comprising: A photometric process of measuring a spectral reflection spectrum from within a measurement region including the formed second thin film;
A comparison process of comparing the spectral reflection spectrum of the thin film of
In the comparison process, the spectral reflection spectrum from within the measurement area and the second
When the spectral reflection spectrum of the thin film of
An extraction step of extracting only the components of the first thin film as an extracted spectral reflection spectrum from the spectral reflection spectrum from within the measurement region, and a theoretical spectral reflection spectrum of the first thin film based on the extracted spectral reflection spectrum. Performing a creation process of creating a reflection spectrum and a calculation process of calculating an aperture ratio between the first thin film and the second thin film based on a difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. It is a feature.

[0008] The invention described in claim 3 is the first invention.
Or in the method of measuring the aperture ratio of a thin film according to 2, wherein the calculating step adjusts the amplitude of the extracted spectral reflection spectrum by adjusting the amplitude by a coefficient to match the theoretical spectral reflection spectrum, and the first based on the coefficient. The aperture ratio between the thin film and the second thin film is calculated.

[0009] The invention described in claim 4 is the invention according to claim 3.
In the method of measuring the aperture ratio of a thin film according to the above, the calculating step multiplies the amplitude of the extracted spectral reflection spectrum by a coefficient, adds an offset to adjust to match the theoretical spectral reflection spectrum, and adjusts the coefficient and the coefficient. An aperture ratio between the first thin film and the second thin film is calculated based on the offset.

According to a fifth aspect of the present invention, there is provided a thin film aperture ratio measuring apparatus for measuring an aperture ratio of a thin film based on light reflected from a substrate on which the thin film is formed. The first thin film is different from the first thin film and the first thin film is viewed from above.
A photometric means for measuring a spectral reflection spectrum from within a measurement region including a second thin film formed between the thin films of the above, and extracting only the component of the first thin film from the spectral reflection spectrum as an extracted spectral reflection spectrum Extracting means for generating a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum as a theoretical spectral reflection spectrum; and a first means for generating a theoretical spectral reflection spectrum based on a difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. Calculating means for calculating an aperture ratio between the thin film and the second thin film.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: removing a predetermined amount of a second thin film different from the first thin film while covering a surface of the substrate on which the first thin film is formed; A thin film aperture ratio measuring device for measuring an aperture ratio of a thin film on a substrate in a process of exposing a layer including a first thin film and a second thin film on the first thin film. Photometric means for measuring a spectral reflection spectrum from within a measurement region including the formed second thin film;
Comparing means for comparing the spectral reflection spectrum of the thin film of
When the spectral reflection spectrum from within the measurement area does not match the spectral reflection spectrum of the second thin film, only the component of the first thin film is extracted as the extracted spectral reflection spectrum from the spectral reflection spectrum from within the measurement area. Means for generating a theoretical spectral reflection spectrum of the first thin film based on the extracted spectral reflectance spectrum as a theoretical spectral reflectance spectrum; and a creating means for generating a theoretical spectral reflectance spectrum based on the difference between the extracted spectral reflectance spectrum and the theoretical spectral reflectance spectrum. Calculating means for calculating an aperture ratio between the first thin film and the second thin film.

The invention described in claim 7 is the same as the invention described in claim 5.
Or in the thin film aperture ratio measuring apparatus according to 6, wherein the calculating means adjusts the amplitude of the extracted spectral reflection spectrum by a coefficient to adjust the amplitude to the theoretical spectral reflection spectrum, and based on the first coefficient, The aperture ratio between the thin film and the second thin film is calculated.

[0013] The invention described in claim 8 is the invention according to claim 7.
In the thin film aperture ratio measurement apparatus according to the above, the calculating means, while multiplying the amplitude of the extracted spectral reflection spectrum by a coefficient, adjust to add the offset to match the theoretical spectral reflection spectrum, the coefficient and the An aperture ratio between the first thin film and the second thin film is calculated based on the offset.

[0014]

The operation of the method according to the first aspect is as follows. A spectral reflection light spectrum from a measurement area including the first thin film and the second thin film is measured, and an extracted spectral reflection spectrum is extracted from this, in which components of the second thin film are removed and only the components of the first thin film are removed. I do. Although peaks and valleys appear in the extracted spectral reflection spectrum, the number thereof depends on the thickness of the first thin film. Therefore, first, a theoretical spectral reflection spectrum of the first thin film is created as a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum, particularly, the number of peaks and valleys. Naturally, there is a difference between the extracted spectral reflection spectrum extracted from the actually measured spectral reflection spectrum and the theoretical spectral reflection spectrum obtained by calculation. The inventors have found from various experiments and the like that the difference is in accordance with the aperture ratio between the first thin film and the second thin film, and that the aperture ratio can be determined based on the difference.

According to a second aspect of the present invention, a predetermined amount of the second thin film which covers the surface of the substrate on which the first thin film is formed and which is different from the first thin film is removed. In the process of exposing the layer including the first thin film and the second thin film on the substrate, the spectral reflection spectrum was measured. As a result, the profiles of the spectral reflection spectrum and the spectral reflection spectrum of the second thin film were matched. Is in a state where the surface of the substrate is covered with the second thin film,
Even if the spectral reflection spectrum is measured, the extracted spectral reflection spectrum cannot be determined from this. Therefore, whether or not the first thin film is exposed is checked in the process of comparing the spectral reflection spectrum with the spectral reflection spectrum of the second thin film, and the process proceeds to the extraction process only when the two do not match.

The exposing process includes a state in which the second thin film remains and a state in which the second thin film is completely removed to expose the first thin film.

According to the third aspect of the present invention, the amplitude of the extracted spectral reflection spectrum is multiplied by a coefficient so as to eliminate the difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. Adjust to match the reflection spectrum. The coefficient thus obtained has a correlation with the aperture ratio between the first thin film and the second thin film.

According to a fourth aspect of the present invention, the amplitude of the extracted spectral reflection spectrum is multiplied by a coefficient so as to eliminate the difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. Adjustments are made to match the reflection spectrum, and components that cannot be adjusted only by the amplitude are adjusted by offset. The coefficients and offsets obtained in this way depend on the aperture ratio between the first thin film and the second thin film.

Further, according to the apparatus described in claim 5, the spectral reflection light spectrum from the measurement area including the first thin film and the second thin film is measured by the photometry means, and the second reflected light spectrum is measured.
Then, the extracted spectral reflection spectrum is extracted by the extracting means. Although peaks and valleys appear in the extracted spectral reflection spectrum, the number thereof depends on the thickness of the first thin film. Therefore, the creation unit creates a theoretical spectral reflection spectrum of the first thin film as a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum. Naturally, there is a difference between the extracted extracted spectral reflection spectrum and the theoretical spectral reflection spectrum.
And the second thin film. Therefore, the calculation means can calculate the aperture ratio based on this difference.

Further, according to the apparatus of the present invention, a predetermined amount of the second thin film different from the first thin film is removed while covering the surface of the substrate on which the first thin film is formed. Then, in the process of exposing the layer including the first thin film and the second thin film on the substrate, if the profiles of the spectral reflection spectrum and the spectral reflection spectrum of the second thin film match, the surface becomes the second. 2 and is in a state of being covered with the thin film, and the extracted spectral reflection spectrum cannot be extracted based on the measured spectral reflection spectrum. Therefore, whether the first thin film is exposed is determined by comparing the spectral reflection spectrum of the second thin film with the spectral reflection spectrum of the second thin film.

Further, according to the present invention, the amplitude of the extracted spectral reflection spectrum is multiplied by a coefficient so as to eliminate the difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. The calculation means adjusts to match the spectrum, and calculates the aperture ratio based on this coefficient.

Further, according to the apparatus described in claim 8, the calculating means assigns a coefficient to the amplitude of the extracted spectral reflection spectrum so as to eliminate the difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. The multiplication is adjusted so as to match the theoretical spectral reflection spectrum, and components that cannot be adjusted only by the amplitude are adjusted by offset. The aperture ratio is determined based on the coefficient and offset thus obtained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A thin film aperture ratio measuring apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a schematic configuration of a thin film aperture ratio measuring apparatus.

The substrate W to be measured for the aperture ratio of the thin film is:
It is mounted on a stage 1 that is configured to be movable in a horizontal plane by a moving mechanism (not shown). Above the stage 1, a light source unit 3 is provided. Light emitted laterally from the light source unit 3 is reflected downward by the beam splitter 5, passes through the objective lens 7, and irradiates the substrate W. Is done. A predetermined range within a range in which the substrate W is irradiated with light through the objective lens 7 corresponds to a measurement region in the present invention,
Its size depends on the magnification of the objective lens 7 and the plate 1 described later.
The diameter is determined by the size of the pinhole formed in a, and is approximately several tens μm.

The light source unit 3 includes a lamp 3a having a halogen lamp or a halogen lamp and a deuterium lamp, and a plurality of lenses 3b, and emits visible light including visible light or ultraviolet light. Note that, depending on the thickness and the type of the target thin film to be measured, the lamp 3a may be configured only with a deuterium lamp to emit only ultraviolet light.

The reflected light from the surface of the substrate W passes through the objective lens 7 again, passes through the beam splitter 5 provided on the optical axis above the objective lens 7, and is collected by the tube lens 9 provided above the same. Lighted and spectral unit 11
Is incident on.

A prism 13 is provided between the spectroscopic unit 11 and the tube lens 9 so as to extract a part of the reflected light from the substrate W. A part of the extracted reflected light is guided to the imaging unit 15 and collected at a predetermined position via the lens 15a. An image sensor 15b is provided at the light condensing position, and an image signal corresponding to the measurement area is output to the image processing unit 17.

The image processing section 17 performs predetermined processing on the input image signal and outputs the processed signal to the I / O 21. The output image signal is output to the display device 25 under the control of the control unit 23 having a built-in CPU and memory. The measurer operates the operation unit 27 to move the stage 1 while watching the image displayed in this manner, and sets the measurement area at a desired position on the surface of the substrate W to measure the film thickness. Has become.

The spectroscopy unit 11 includes a plate 11a having a pinhole formed at the incident position of the reflected light, a concave diffraction grating 11b provided above the plate 11a to split the reflected light, and a concave diffraction grating 11b. A photodetector 11c for detecting the intensity of the spectral light of the diffracted diffracted light. The photodetector 11c is composed of, for example, a photodiode array, a CCD, or the like, and is arranged in a conjugate relationship with a pinhole formed in the plate 11a. Therefore, the reflected light that has entered the spectroscopic unit 11 is split by the concave diffraction grating 11b, and a signal corresponding to the intensity of the split light is output from the light detection 11c to the data processing unit 19 as a spectral reflection spectrum.

Note that the spectroscopy unit 11 corresponds to the photometric means in the present invention.

The data processing unit 19 will be described in detail later.
The control unit 23 based on a measurer's instruction via the operation unit 27
The processing is performed in accordance with the control signal from.

The specific processing will be briefly described. The first processing applied to the substrate W based on the measured spectral reflection spectrum
Out of the thin film and the second thin film, only the spectral reflection spectrum of the first thin film is extracted, and the theoretical spectral reflection spectrum is calculated based on the profile of the extracted spectral reflection spectrum thus obtained. Processing such as finding the aperture ratio between the first thin film and the second thin film based on the difference between the reflection spectrum and the theoretical spectral reflection spectrum is performed. The aperture ratio thus determined is displayed on the display device 25.

The data processing section 19 stores in advance a spectral reflection spectrum of a second thin film which is different from the first thin film and formed between the first thin films in plan view. Prior to the process of obtaining the aperture ratio, the profile is compared with the profile of the measured spectral reflection spectrum, and if they are substantially the same, it is determined that the polishing process is insufficient. Therefore, it is assumed that the first thin film is still covered with the second thin film and the aperture ratio between the first thin film and the second thin film cannot be measured. Is displayed. Alternatively, the profiles of the spectral reflection spectrum of only the second thin film and the measured spectral reflection spectrum are compared.
It is determined that the thin film does not cover the first thin film, and data processing for aperture ratio measurement is performed. The spectral reflection spectrum of the second thin film to be compared may be actually measured in advance, or may be a spectrum obtained from a theoretical calculation.

Further, the data processing section 19 stores the following "calibration curve data relating to the aperture ratio".

That is, a "substrate in which the first thin film and the second thin film are formed with a known aperture ratio" is used as a sample substrate, and an extracted spectral reflection spectrum based on a spectral reflection spectrum measured on such a sample substrate is obtained. Differences from the theoretical spectral reflection spectrum (coefficients and offsets having a correlation between a correction coefficient k and an offset f, which will be described later) are obtained and stored in association with the aperture ratio. Further, similar processing is performed on substrates having various aperture ratios, and the various aperture ratios and the differences in spectra are stored in association with each other.

The data processing section 19 described above corresponds to the extracting means, the creating means and the calculating means in the present invention, and also corresponds to the comparing means.

Next, a description will be given with reference to the flowchart of FIG. FIG. 2 is a flowchart showing the flow of the method for measuring the aperture ratio of a thin film according to the present invention.

As shown in a plan view and a longitudinal sectional view showing the state of the thin film in the measurement region R of FIG. 3, the substrate W is, for example, an oxide film corresponding to a first thin film on a silicon substrate Wa. F1 is formed, a barrier metal film F2 such as tantalum nitride (TaN) is deposited thereon, and a copper film F3 for copper wiring corresponding to a second thin film is further formed thereon.
Is attached.

Then, as shown in FIG. 3B, the copper film F
3 is polished together with the barrier metal film F2 and finally polished until the oxide film F1 is exposed on the surface, as shown in FIG. Therefore, the present invention is carried out immediately before the completion of polishing as shown in FIG. 3 (c) in order to confirm whether or not the polishing process has been performed normally.

In this embodiment, in the film thickness measurement after the polishing treatment shown in FIG. 3C, the second thin film is used as the copper film F3 and this component is removed from the spectral reflection spectrum. Is not removed. This is because the line width d3 of the barrier metal film F2 is extremely small compared to the line width d1 of the oxide film F1 and the line width (d1−d3 × 2) of the copper film F3 and has little influence.

Step S1 (photometric process) First, the measurer places the substrate W, which has been polished for the moment, on the stage 1, and operates the operation unit 27 while watching the image of the measurement region R displayed on the display device 25. Then, the measurement region R is positioned at a desired position by moving the stage 1.

Then, when it moves to a desired position,
An instruction to start measurement is issued via the operation unit 27. Then, the spectral reflection spectrum from the measurement region R is converted into the spectral unit 11.
To the data processing unit 19. FIG. 4 is a graph showing an example of the spectral reflection spectrum measured in this way.

Step S2 (comparison process) The data processor 19 compares the measured spectral reflection spectrum with
The spectral reflection spectrum of the copper film F3, which is the second thin film, is compared with the spectral reflection spectrum stored in advance, and the process branches depending on the result.

That is, in step S2, FIG.
The polishing process proceeds from the state (b), and it is determined whether the polishing process is completed and the oxide film F1 is exposed to the surface at a predetermined aperture ratio as shown in FIG. 3C. If the polishing process has not been completed, the measured spectral reflection spectrum coincides with the spectral reflection spectrum of the copper film F3 as the second thin film (FIG. 5). Returning to step S2, if the processing is completed, they do not match, so the next step S2
Move to 4.

As shown in FIG. 5, the spectral reflection spectrum of the copper film F3 alone increases gradually toward the longer wavelength side, sharply increases at around 550 nm, and then gradually increases at around 600 nm. It is designed to draw a rising curve. In the present embodiment, in order to simplify the processing, the profile of the spectral reflection spectrum from 400 to 550 nm in wavelength is compared with the profile of the measured spectral reflection spectrum. Further, in the extraction processing described later, the processing is performed only for this wavelength range. However, the comparison processing and the extraction processing may be performed for the entire wavelength range.

When the opening ratio between the oxide film F1 and the copper film F3 is measured after the entire surface of the substrate W is covered with the copper film F3, it is determined whether or not the unnecessary copper film F3 has been removed. ,
The determination can be made by comparing with the profile of the spectral reflection spectrum of the copper film F3. As a result of the comparison, if the profiles do not match, it is determined that the copper film F3 has been removed.
The aperture ratio can be measured appropriately.

Step S4 (extraction process) Here, the component of the copper film F3 as the second thin film is removed from the spectral reflection spectrum measured in step S2, and only the component of the oxide film F1 as the first thin film is removed. Extract.

Specifically, the extracted spectral reflection spectrum F (λ) is calculated by the following equation (1). The symbol λ in the formula is 400 to 550 (or 800) nm,
M (λ) is a spectral reflection spectrum in the measurement region R, and N (λ) is a spectral reflection spectrum of the copper film F3 as the second thin film. Further, k is a correction coefficient according to L & S of the first thin film, and f (offset) represents a reflection ratio offset, which is unknown here.

{F (λ) = {M (λ) −N (λ) · k + f (offset)} (1)

According to the formula (1), the spectral reflection spectrum N (λ) of the copper film F3 as the second thin film is subtracted from the spectral reflection spectrum M (λ) measured in step S1, and the extracted spectral reflection spectrum F ( λ) (for the sake of illustration, FIG. 5 is subtracted from FIG. 4). Note that the spectral reflection spectra M (λ) and N (λ) in the present embodiment are relative reflectances with respect to the silicon substrate Wa.

However, the oxide film F1 as the first thin film and the second
The line width ratio L & S to the copper film F3 which is a thin film of
Is different, the correction coefficient k for compensating for the difference is
And the spectral reflectance spectrum M of the substrate W surface including the copper film F3
The offset f (offset) for compensating for the tendency to shift in the spectral reflection ratio direction (vertical direction) as a whole by removing the component of the copper film F3 from (λ) is unknown. Therefore,
The extracted spectral reflection spectrum F obtained by the above equation (1)
(Λ) includes these correction coefficient k and offset f (offset)
Are included as errors.

FIG. 6 shows an extracted spectral reflection spectrum including an error, which is obtained by removing the components shown in FIGS. 4 and 5 according to the above equation (1). In addition, for the reason mentioned above,
In this case, what is effective is a wavelength of 550 nm indicated by a two-dot chain line.
It is as follows.

Step S5 (Preparation Process) The data processing section 19 analyzes the profile of the extracted spectral reflection spectrum F (λ) obtained as described above, obtains an approximate film thickness, and calculates a theoretical value of the film thickness. A typical spectral reflection spectrum is calculated as a theoretical spectral reflection spectrum.

This conceptually shows that, as shown in FIG. 7, if the film quality is the same, the approximate film thickness can be known from the profile of the spectral reflection spectrum. That is, when the film thickness is small, the number of peaks and valleys is small as shown in FIG. 7A, and as the film thickness is large, interference increases and the number of peaks and valleys increases as shown in FIG. 7B. Therefore, if the number of peaks and valleys and the relationship between their positions and the like are examined in advance, the extracted spectral reflection spectrum F
By analyzing (λ), a theoretical spectral reflection spectrum can be obtained.

FIG. 8 is an example of the theoretical spectral reflection spectrum obtained based on the number of peaks and valleys in the extracted spectral reflection spectrum F (λ) shown in FIG. 6 and their wavelength positions.

Step S6 (Confirmation Step) It is confirmed whether or not the theoretical spectral reflection spectrum created in Step S5 is appropriate.
If not, the process returns to step S6 to calculate a theoretical spectral reflection spectrum at a film thickness obtained by slightly changing the approximate film thickness obtained in step S6.

The determination as to whether or not the theoretical spectral reflection spectrum is appropriate is made, for example, by determining the position information of the peaks and valleys of the extracted spectral reflection spectrum and the theoretical reflection spectrum (peak and valley peaks and bottoms with respect to the horizontal axis wavelengths shown in FIGS. If the positions are the same, or the difference is within the reference value, the theoretical spectral reflection spectrum is determined to be appropriate, and the others are determined to be inappropriate.

Step S7 (Calculation Process) The extracted spectral reflection spectrum F (λ) of FIG. 6 is compared with the theoretical spectral reflection spectrum of FIG. The amplitude is adjusted by multiplying the extracted spectral reflection spectrum F (λ) by a coefficient so as to match the profile. When schematically shown, the adjustment is performed as shown by a dotted line and a dotted arrow in FIG.

Step S8 (calculation process) The extracted spectral reflection spectrum F whose amplitude has been adjusted by multiplying by a coefficient
An error between (λ) and the theoretical spectral reflection spectrum is obtained, and the processing branches accordingly. If the error exceeds the reference value, the process returns to step S6 and the amplitude is readjusted.
If it is within the reference value, the flow branches to the next step S8.

Step S9 (Calculation Process) In the above steps S6 and S7, only the amplitude is adjusted, so that the extracted spectral reflection spectrum F (λ) may not be able to be accurately matched with the theoretical spectral reflection spectrum. Therefore, here, fine adjustment is performed by adding an offset to the extracted spectral reflection spectrum F (λ) whose amplitude has been adjusted. This process is schematically shown by a two-dot chain line and a two-dot chain arrow in FIG. 6, and the amplitude profile is adjusted so as to be shifted in the vertical direction as it is.

Step S10 (calculation process) The error between the extracted spectral reflection spectrum F (λ) adjusted by adding the offset and the theoretical spectral reflection spectrum is obtained, and the process branches according to the relationship with the reference value. That is, if the error is larger than the reference value, step S
8, the offset is readjusted, and if it is within the reference value, the flow branches to the next step S10.

Step S11 (Calculation Process) In steps S6 to S9, the extracted spectral reflection spectrum F (λ) (see FIG. 6) was adjusted to match the theoretical spectral reflection spectrum (see FIG. 8). The oxide film F1 is determined based on the coefficient and the offset, which are the adjustment values at that time.
Of the aperture between the substrate and the copper film F3 is determined.

As described above, this is obtained, for example, from the previously stored calibration curve data relating to the aperture ratio and the correspondence between the above-mentioned coefficients and offsets.

As described above, according to this embodiment, the extracted spectral reflection spectrum F (λ) containing only the component of the oxide film F1
Then, the influence of the copper film F3 can be obtained based on the difference between the calculated value and the calculated theoretical spectral reflection spectrum. Thus, the aperture ratio between the oxide film F1 and the copper film F3 can be obtained. Therefore, the aperture ratio between the oxide film F1 and the copper film F3 can be obtained by a simple method of measuring the spectral reflection spectrum from the substrate W, and can be measured nondestructively. Is required.

The present invention can be modified as follows.

(1) When the aperture ratio measurement is performed on a substrate for which polishing processing is clearly completed, steps S2 and S3 need not be performed.

(2) The process of removing the second thin film such as the copper film F3 is not limited to the polishing process. For example, the present invention may be applied in the process of removing the second thin film by etching. .

(3) The above-described thin film aperture ratio measuring apparatus may be incorporated in a polishing processing apparatus so that the aperture ratio can be measured in-line while performing the polishing processing.

(4) After the polishing process (FIG. 3C), the influence of the barrier metal film is neglected by using only the copper film as the second thin film, but the extraction is performed in consideration of the spectral reflection spectrum. The reflection spectrum may be calculated.

(5) In the above-described embodiment, the aperture ratio of the thin film is obtained based on the spectral reflection spectrum of the substrate after the polishing process. However, the aperture ratio may be obtained based on the spectral reflection spectrum of the substrate during the polishing process. FIG. 9 shows a state between the state shown in FIG. 3B and the state shown in FIG.
A layer composed of barrier metal film F2 / oxide film F1 is polished by a predetermined amount, and copper film F is formed on barrier metal film F2 on oxide film F1.
3 is a state formed with a thickness F4. When the thickness d4 of the copper film F3 becomes, for example, 50 μm or less, light passes through the copper film F3, so that the oxide film F1 and the barrier metal film F2 are formed.
Can be measured. The extracted spectral reflection spectrum may be calculated by removing the components of the copper film F3 and the barrier metal film F2 from the measured spectral reflection spectrum, and the aperture ratio of the thin film may be obtained based on the extracted spectral reflection spectrum.

The polishing process proceeds further from the state of FIG. 9, and even when only the barrier metal film F2 remains in the oxide film F1, the copper film F3 and the barrier metal film F2 are obtained from the spectral reflection spectrum measured in the same manner as described above. By removing the components, only the components of the oxide film F1 can be extracted.

(6) In the above-described embodiment, the first thin film is an oxide film and the second thin film is a copper film. However, it goes without saying that the present invention is not limited to these film types.
For example, the transparent film for the measurement wavelength may be the first thin film, and the opaque film for the measurement wavelength such as a metal film may be the second thin film. When a plurality of types of transparent films exist in the measurement region, one of them can be used as the first thin film and the other transparent film can be used as the second thin film.

[0073]

As is apparent from the above description, according to the method of the present invention, the extracted spectral reflection spectrum containing only the component of the first thin film and the theoretical spectral reflection spectrum obtained by calculation are obtained. The effect of the second thin film can be obtained based on the difference between the first thin film and the second thin film, whereby the aperture ratio between the first thin film and the second thin film can be obtained. Therefore, the aperture ratio of the thin film can be obtained by a simple method of measuring the spectral reflection spectrum from the substrate,
Moreover, it can be measured nondestructively. Therefore, the aperture ratio of the thin film can be easily obtained.

According to the second aspect of the present invention, the extracted spectral reflection spectrum can be accurately obtained by branching the processing depending on whether or not the surface is covered with the second thin film. Can be extracted. Therefore,
The aperture ratio can be determined more accurately.

According to the third aspect of the present invention, the first thin film and the second thin film are adjusted by multiplying the amplitude of the extracted spectral reflection spectrum by the correction coefficient so as to match the theoretical spectral reflection spectrum. A correction coefficient corresponding to the aperture ratio with the thin film can be obtained. Therefore, the aperture ratio can be calculated based on this correction coefficient.

Further, according to the method of the present invention, the amplitude of the spectral reflection spectrum is multiplied by the correction coefficient, and a component which cannot be corrected by itself is added to the theoretical spectral reflection spectrum by adding an offset. Adjust as follows. This makes it possible to accurately adjust the spectral reflection spectrum to the theoretical spectral reflection spectrum. Therefore, the aperture ratio can be calculated more accurately by the correction coefficient and the offset corresponding to the aperture ratio between the first thin film and the second thin film.

According to the apparatus described in claim 5, the method described in claim 1 can be suitably implemented.

According to the apparatus of the sixth aspect, the method of the second aspect can be suitably implemented.

According to the apparatus described in claim 7, the method described in claim 3 can be suitably implemented.

According to the apparatus described in claim 8, the method described in claim 4 can be suitably implemented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a thin film aperture ratio measuring apparatus according to the present invention.

FIG. 2 is a flowchart showing a flow of a method of measuring an aperture ratio of a thin film according to the present invention.

3A and 3B are a plan view and a vertical sectional view showing a state of a thin film in a measurement region on a substrate.

FIG. 4 is a graph showing a spectral reflection spectrum from a measurement area.

FIG. 5 is a graph showing a spectral reflection spectrum from a copper film.

FIG. 6 is a graph showing a spectral reflection spectrum after removing a component of a copper film.

FIG. 7 is a graph showing spectral reflection spectra for various film thicknesses measured using a substrate having a known film thickness.

FIG. 8 is a graph showing a theoretically determined spectral reflection spectrum.

FIG. 9 is a longitudinal sectional view showing a state of a thin film in a measurement region on a substrate.

[Explanation of symbols]

 W: substrate Wa: silicon substrate F1: oxide film (first thin film) F3: copper film (second thin film) M (λ): spectral reflection spectrum of oxide film N (λ): spectral reflection spectrum of copper film F (Λ) Extracted spectral reflection spectrum 1 Stage 3 Light source unit 5 Beam splitter 11 Spectroscopic unit 19 Data processing unit

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[Procedure amendment]

[Submission date] April 4, 2000 (200.4.4)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 9

[Correction method] Change

[Correction contents]

FIG. 9

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Tamada 4-chome Tenjin Kitamachi 1-chome, Horikawa-dori-Terauchi, Kamigyo-ku, Kyoto F-term (reference) in Dainippon Screen Mfg. Co., Ltd. 2F065 AA56 AA58 CC19 CC25 CC31 FF41 FF61 GG02 HH04 HH13 JJ03 JJ26 LL30 LL42 LL46 LL67 PP12 QQ25 QQ31 SS13 2G020 AA03 AA04 AA05 BA02 BA18 CA12 CB26 CB33 CB42 CB43 CC05 CC47 CC63 CD04 CD12 CD16 CD24 CD33 CD37 EE01H03 BB01 GG01 BBH JJ12 JJ22 KK04 MM05 MM10 PP04 4M106 AA01 BA04 CA48 DH03 DH12 DH31 DJ11 DJ18 DJ20 DJ23 5F004 CB02

Claims (8)

[Claims] 1. A method for measuring an aperture ratio of a thin film based on reflected light from a substrate on which the thin film is formed, wherein the first thin film is different from the first thin film. ,And,
A photometric process of measuring a spectral reflection spectrum from within a measurement region including a second thin film formed between the first thin films in a plan view; and only a component of the first thin film from the spectral reflection spectrum. An extracting step of extracting as an extracted spectral reflection spectrum; a creating step of creating a theoretical spectral reflection spectrum of the first thin film as a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum; A method of calculating an aperture ratio between a first thin film and a second thin film based on a difference from a theoretical spectral reflection spectrum. 2. The method according to claim 1, wherein the first thin film is formed on the substrate by covering a surface of the substrate on which the first thin film is formed and removing a second thin film different from the first thin film by a predetermined amount. A method of measuring an aperture ratio of a thin film on a substrate in a process of exposing a layer including a thin film of the first thin film, comprising a second thin film formed between the first thin films in plan view. A photometric process of measuring a spectral reflection spectrum from within the measurement region; a comparing process of comparing the spectral reflection spectrum with the spectral reflection spectrum of the second thin film;
When the spectral reflection spectrum of the thin film of
An extraction process of extracting only the components of the first thin film as an extracted spectral reflection spectrum from the spectral reflection spectrum from within the measurement region; and a theoretical spectral reflection spectrum of the first thin film based on the extracted spectral reflection spectrum. Creating a reflection spectrum, and calculating an aperture ratio between the first thin film and the second thin film based on a difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. Characteristic method of measuring aperture ratio of thin film. 3. The method of measuring an aperture ratio of a thin film according to claim 1, wherein in the calculating step, an amplitude of the extracted spectral reflection spectrum is multiplied by a coefficient to adjust the amplitude to match the theoretical spectral reflection spectrum; An aperture ratio measurement method for a thin film, comprising calculating an aperture ratio between a first thin film and a second thin film based on the coefficient. 4. The method of measuring an aperture ratio of a thin film according to claim 3, wherein in the calculating step, an amplitude of the extracted spectral reflection spectrum is multiplied by a coefficient, and an offset is added to match the theoretical spectral reflection spectrum. And calculating an aperture ratio between the first thin film and the second thin film based on the coefficient and the offset. 5. A thin film aperture ratio measuring apparatus for measuring an aperture ratio of a thin film based on reflected light from a substrate on which the thin film is formed, wherein the first thin film and the first thin film are different types. ,And,
A photometric means for measuring a spectral reflection spectrum from within a measurement region including a second thin film formed between the first thin films in a plan view; and only a component of the first thin film from the spectral reflection spectrum Extracting means for extracting as an extracted spectral reflection spectrum; creating means for creating a theoretical spectral reflection spectrum as a theoretical spectral reflection spectrum based on the extracted spectral reflection spectrum; and Calculating means for calculating an aperture ratio between the first thin film and the second thin film based on the difference; and an aperture ratio measuring device for the thin film. 6. A first thin film and a second thin film, which cover the surface of the substrate on which the first thin film is formed and which are different from the first thin film by a predetermined amount, are removed from the substrate. A thin film aperture ratio measuring device for measuring an aperture ratio of a thin film on a substrate in a process of exposing a layer including the thin film, wherein the second thin film is formed between the first thin films in plan view. Photometric means for measuring the spectral reflection spectrum from within the measurement area; comparison means for comparing the spectral reflection spectrum with the spectral reflection spectrum of the second thin film; Extracting means for extracting only a component of the first thin film as an extracted spectral reflection spectrum from the spectral reflection spectrum from within the measurement area when the spectral reflection spectrum does not match; Thin Creating means for creating a theoretical spectral reflection spectrum as a theoretical spectral reflection spectrum; and calculating an aperture ratio between the first thin film and the second thin film based on a difference between the extracted spectral reflection spectrum and the theoretical spectral reflection spectrum. A thin film aperture ratio measuring device, comprising: 7. The thin film aperture ratio measuring apparatus according to claim 5, wherein the calculating means adjusts the amplitude of the extracted spectral reflection spectrum by multiplying the amplitude by a coefficient to match the theoretical spectral reflection spectrum, An aperture ratio measurement apparatus for a thin film, wherein an aperture ratio between the first thin film and the second thin film is calculated based on the coefficient. 8. The thin film aperture ratio measuring apparatus according to claim 7, wherein the calculating means multiplies the amplitude of the extracted spectral reflection spectrum by a coefficient and adds an offset to match the theoretical spectral reflection spectrum. Wherein the aperture ratio between the first thin film and the second thin film is calculated based on the coefficient and the offset.