JP2002277218A - Apparatus and method for measuring film thickness - Google Patents

Abstract

(57) [Problem] To provide a film thickness measuring apparatus capable of continuously analyzing a thin film of a measurement sample even when calibrating aging of a light source is performed on the way. SOLUTION: A mirror 31 reflects light from a light source 1 so as to irradiate a reference substrate 9 arranged at a position different from the measurement substrate 3. The computer 6 calibrates the aging of the light source 1 based on the intensity of the reflected light of the reference substrate 9 decomposed by the spectroscope 5 when the aging of the light source 1 is calibrated. Therefore, even when the aging of the light source 1 is calibrated, no special operation is required, and the computer 6 can continuously analyze the thin film of the measurement substrate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the thickness of a transparent or translucent thin film formed in the manufacture of a semiconductor device, a liquid crystal display device, a solar cell, and the like. The present invention relates to a film thickness measuring apparatus and method for automatically calibrating and measuring optical constants such as a film thickness, a refractive index and an absorption coefficient of a thin film.

[0002]

2. Description of the Related Art In recent years, thin film forming techniques such as a plasma process method and a sputtering method have been widely used in the manufacture of semiconductor devices, liquid crystal display devices, solar cells and the like. By detecting various characteristics of a thin film formed by these thin film forming techniques, parameters for forming the thin film are derived, and various defects at the time of film formation are detected.

[0003] Among the various properties of such a thin film, the thickness particularly affects not only the properties of the thin film, such as conductivity and insulating property, but also the pattern formation of the thin film. Is an important management item.

As a conventional technique for measuring the thickness of a thin film formed by a thin film forming apparatus, a measuring apparatus using a contact method for directly measuring a step of a thin film or a measuring method using an ellipsometer has been put to practical use. However, these measuring devices are mainly used for off-line measurement because it is difficult to measure the thickness of a thin film on a wiring pattern or the measurement time is long.

In order to solve this problem, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 2000-193424 a film thickness measuring apparatus capable of continuously measuring the film thickness of a thin film on a production line. . FIG.
FIG. 4 is a block diagram illustrating a schematic configuration of a film thickness measurement device disclosed in Japanese Patent Application Publication No. 4 (JP-A) No. 4;

The film thickness measuring apparatus includes a light source 101 for generating white light, and guides light from the light source 101 onto a substrate 103.
Branch type optical fiber 1 for receiving light reflected from substrate 103
02, a light reception limiting shutter 104 for selectively blocking a plurality of reflected lights from the substrate 103, a spectroscope 105 for decomposing the reflected light guided by the branched optical fiber 102 into light intensities for each wavelength, and light for each wavelength A computer 106 for analyzing the strength and analyzing the film thickness of the thin film is included.

FIG. 5 is a view showing an example of a measurement result of a silicon nitride (SiN) film by the film thickness measuring device shown in FIG. The spectroscope 105 decomposes the reflected light from the substrate 103 into light intensity (spectrum) for each wavelength. Computer 106
Calculates the reflectance curve M of the thin film from the spectrum data acquired from the spectroscope 105 and the spectrum data of the reference substrate whose reflectance is known in advance. Then, the computer 106 optimizes the reflectance M so that the theoretical curve R of the reflectance using the thickness d of the thin film, the refractive index n, the absorption coefficient k, and the wavelength λ of the irradiation light as the variables is the closest. By calculating the thickness, the thickness of the thin film is calculated.

Here, a theoretical formula for analyzing the thickness of a thin film will be described. The refractive index of the substrate is n ₀ , the refractive index of the p-th layer thin film is n (p), the refractive index of air is n (p + 1),
The absorption coefficient of the p-th thin film is k (p), and the thickness of the thin film is d.
(P) Assuming that the wavelength of the light source 1 is λ, the intensity R (p + 1,0) of the reflected light from the substrate can be expressed by the equations (3) to (7).

[0009]

(Equation 2)

Specifically, an appropriate initial value is substituted for the film thickness d. N (p) and k as optical constants
(P) includes, for example, SiO ₂ and Al ₂ as transparent materials.
In the case of O ₃ , Si ₃ N ₄ , ITO (stannic oxide of indium) or the like, a value set by the material dispersion formula defined by the Caucy equation is used. In this manner, the logical reflectance R (λ) at a certain section wavelength can be obtained.

The Caucy equation is represented by equations (8) to (9), where A _n , B _n and C _n are the refractive indices n corresponding to each material.
, And A _k , B _k, and C _k are material coefficients that determine the absorption coefficient k corresponding to each material. The unit of the wavelength λ is nm.

[0012]

(Equation 3)

R (λ) calculated using equation (3),
By comparing the actually measured reflectivity M (λ) with the film thickness d and changing the film thickness d, the film thickness d can be obtained by the least square method.
Further, when n ₁ and k is unknown, by substituting an appropriate initial value n ₁ and k, it is changed to d, n ₁ and k,
It is possible to simultaneously obtain the film thickness d, the refractive index n ₁ and the absorption coefficient k by the least square method.

[0014]

Generally, the light intensity of the light source 101 changes over time due to deterioration of the lamp, changes in the ambient temperature, and the like. For this reason, a calibration process of measuring the light intensity for each wavelength of the light source 101 is required about once every several hours, at least once a day. However, the above-described conventional film thickness measuring apparatus does not include a mechanism for easily performing the calibration process, and thus has a problem that the calibration process cannot be easily performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to analyze a thin film of a measurement sample even when calibrating the aging of a light source on the way. An object of the present invention is to provide a film thickness measuring device and a method thereof that can be performed continuously.

A second object of the present invention is to provide a film thickness measuring apparatus and a method thereof which can calibrate aging of a light source and analyze a thin film of a sample with the same optical system.

[0017]

According to one aspect of the present invention, a film thickness measuring device comprises: a light emitting means for generating light so as to irradiate a measurement sample and a first reference sample; And a reflecting unit for reflecting light generated by the light emitting unit so as to irradiate a second reference sample disposed at a position different from the first reference sample;
Light receiving means for receiving reflected light from the first reference sample and the second reference sample, and light emitting means based on the intensities of the reflected light of the first reference sample and the second reference sample received by the light receiving means Analysis means for calibrating the secular change of the sample and analyzing the thin film of the measurement sample.

The light generated by the light emitting means is reflected so that the reflecting means irradiates the second reference sample, and the analyzing means calibrates the aging of the light emitting means based on the intensity of the reflected light. Even when calibrating the aging of the light emitting means, no special operation is required. Therefore, it is possible to continuously analyze the thin film of the measurement sample.

Preferably, the film thickness measuring device further moves the reflecting means forward to reflect the light from the light emitting means when calibrating the aging of the light emitting means, and retracts the reflecting means when measuring the film thickness of the thin film of the measurement sample. Moving means for irradiating the measurement sample with light from the light emitting means.

Therefore, calibration of the aging of the light emitting means and analysis of the thin film of the sample can be performed only by moving the reflecting means by the moving means, and the same optical system can be used.

Preferably, the analysis means acquires the intensity of the reflected light of the first reference sample and the second reference sample at the time of the initial adjustment, and obtains the intensity of the reflected light of the second reference sample at the time of calibrating the aging of the light emitting means. The intensity is acquired, and the aging of the light emitting means is calibrated.

Therefore, the analyzing means can analyze the thin film of the measurement sample in consideration of the aging of the light emitting means.

More preferably, the analyzing means sets the intensity of the reflected light of the first reference sample at the time of the initial adjustment to X (λ),
The intensity of the reflected light of the second reference sample at the time of the initial adjustment is K
(Λ), the intensity of the reflected light of the second reference sample at the time of calibration is K ′ (λ), the intensity of the reflected light of the measurement sample is M (λ), and the reflectance of the first reference sample is c (λ). Then, the reflected light data m (λ) of the measurement sample is obtained by the equations (1) and (2).
Is calculated, the thickness of the thin film of the measurement sample is calculated.

Accordingly, the analyzing means can calibrate the secular change of the light emitting means by calculation, and can accurately measure the thickness of the thin film of the sample.

Preferably, the film thickness measuring apparatus further includes a light condensing means for condensing light reflected from the measurement sample, the first reference sample, and the second reference sample, and the second reference sample comprises: The distance from the light collecting means to the measurement sample or the first reference sample is the same as the distance from the light collecting means to the second reference sample via the reflecting means.

Therefore, the calculation means can easily calibrate the aging of the light emitting means by calculation.

More preferably, the reflecting means is provided at an angle of about 45 ° with respect to the light from the light collecting means.

Therefore, it is possible to measure the intensity of the reflected light of the second reference sample without changing the position of the first reference sample.

According to another aspect of the present invention, a method for measuring a film thickness includes a step of generating light so as to irradiate a measurement sample and a first reference sample, wherein the method differs from the measurement sample and the first reference sample. Reflecting the generated light so as to irradiate the second reference sample disposed at the position; and receiving reflected light from the measurement sample, the first reference sample, and the second reference sample. Calibrating the aging of the light source based on the intensity of the reflected light of the received first reference sample and the second reference sample, and analyzing the thin film of the measurement sample.

Since the generated light is reflected so as to irradiate the second reference sample and the aging of the light source is calibrated based on the intensity of the reflected light, the aging of the light source is calibrated. Even so, no special work is required. Therefore, it is possible to continuously analyze the thin film of the measurement sample.

[0031]

FIG. 1 is a block diagram showing a schematic configuration of a film thickness measuring apparatus according to an embodiment of the present invention.
This film thickness measuring apparatus includes a light source 1 for generating white light, and an optical fiber 2 for guiding light from the light source 1 onto a measurement substrate 3 having a thin film 33 formed on a surface thereof and receiving reflected light from the measurement substrate 3. A spectroscope 5 for decomposing the reflected light guided by the optical fiber 2 into light intensities for each wavelength, a computer 6 for analyzing the light intensity for each wavelength to analyze the thickness of the thin film, and a calibration reference substrate 9 And a substrate processing apparatus 1 for forming a thin film on a measurement substrate 3
2, a process management device 13 connected to a LAN (Local Area Network) to manage the entire process, and a mirror 3 for reflecting light from the light source 1 so as to enter the calibration reference substrate 9
1 and a measurement lens 32 for collecting light reflected from the measurement substrate 3 or the calibration reference substrate 9.

The mirror 31 is located below the measuring lens 32, for example, at 45 ° with respect to the light from the measuring lens 32.
It is provided so that it may become the angle of. Further, the calibration reference substrate 9 includes an optical path length from the measurement lens 32 to the measurement substrate 3,
Calibration reference substrate 9 from measurement lens 32 via mirror 31
The optical path length is set at a position where the optical path length is equal. The mirror 31 is provided so as to be able to move forward or backward in the direction shown by arrow A by electromagnetic force or air pressure. Note that the mechanism for moving the mirror 31 is a general mechanism, and therefore will not be described in detail.

FIG. 2 is a diagram for explaining the position of the mirror 31 when measuring the film thickness of the normal measurement substrate 3 (when measuring the reflected light of the reference substrate 9 ') and the position of the mirror 31 during calibration. is there. As shown in FIG. 2A, when the film thickness of the normal measurement substrate 3 is measured (when the reflected light of the reference substrate 9 'is measured), the mirror 31 stands by at the retracted position. Is directly applied to the measurement substrate 3 (reference substrate 9 ′). The optical path length at this time is L.

As shown in FIG. 2B, at the time of calibration, the mirror 31 moves forward, so that light from the measuring lens 32 is reflected by the mirror 31 and irradiated on the calibration reference substrate 9. become. The optical path length at this time is L as in the case of measuring the film thickness of the normal measurement substrate 3 (when measuring the reflected light of the reference substrate 9 '). The movement of the mirror 31 is controlled by the computer 6
Is controlled by

The light source 1 has at least one lamp. Usually, when measuring a film thickness of 60 nm or more, 40
A halogen lamp having a wavelength range from 0 nm to 850 nm is used. When measuring a film thickness of 60 nm or less, a deuterium lamp having a wavelength range of 220 nm to 400 nm is used together with a halogen lamp. The distance from the measuring lens 32 to the measuring substrate 3 and the distance from the measuring lens 32 via the mirror 31 to the calibration reference substrate 9 are 10 mm.
~ 100mm, spot diameter is 5mm ~ 10m
m, and the positions of the respective parts are adjusted so that the respective distances and spot diameters become equal. The calibration reference substrate 9 (reference substrate 9 ') has a known reflectance, and for example, a silicon wafer is used.

The spectroscope 5 has a CCD (Charge Coupl) inside.
ed Device) 11 is disposed, and reflected light from the measurement substrate 3 (reference substrate 9 ′) or the calibration reference substrate 9 is collected by the measurement lens 32 and received by the CCD 11 via the optical fiber 2. . The spectroscope 5 decomposes an electric signal corresponding to the light intensity output from the CCD 11 into light intensity for each wavelength and outputs the light signal to the computer 6.

The computer 6 analyzes the light intensity for each wavelength output from the spectroscope 5 to calculate and calibrate the thickness and optical constant of the thin film. The computer 6 includes a measurement substrate 3
Is connected to a substrate processing apparatus 12 for forming a thin film. The substrate processing apparatus 12 is connected to a process management device 13 via a LAN, and is controlled by the process management device 13. The substrate processing apparatus 12 is provided with a plasma CVD (Chemical Vapor).
Deposition apparatus, sputtering apparatus, resist coater apparatus, light distribution film printing apparatus, etc., and any apparatus that forms a thin film may be used.

FIG. 3 is a flowchart for explaining a processing procedure of the film thickness measuring apparatus according to the embodiment of the present invention. First, the computer 6 retracts the mirror 31 and measures the reflected light of the reference substrate 9 'as a reference sample (S1). White light emitted from the light source 1 is reflected by the reference substrate 9 ′, and the reflected light is received by the CCD 11 in the spectroscope 5. The computer 6 acquires the spectrum for each wavelength decomposed by the spectroscope 5 as the reference sample data X (λ) in the measurement system.

Next, the computer 6 moves the mirror 31 forward,
The white light emitted from the light source 1 is applied to the reference substrate 9, and the reflected light from the reference substrate 9 is measured (S2). White light from the light source 1 is reflected by the reference substrate 9, and the reflected light is received by the CCD 11 in the spectroscope 5.
The computer 6 acquires the spectrum for each wavelength decomposed by the spectroscope 5 as the reference sample data K (λ) in the calibration system.

The processes in steps S1 and S2 are performed only once at the time of initial adjustment. The reference substrates 9 and 9 ′ for calibration have known reflectances,
The reflectivity does not necessarily have to be the same.

Next, the computer 6 moves the mirror 31 forward to check the aging of the light source 1, and the calibration reference substrate 9
Is measured (S3). The calculator 6 acquires the spectrum for each wavelength decomposed by the spectroscope 5 as the reference sample data K ′ (λ). Then, the computer 6 calculates the data X (λ) measured in steps S1 to S3,
The reflected light data X ′ (λ) of the reference substrate 9 ′ in the measurement system is calculated by substituting K (λ) and K ′ (λ) into Expression (1) (S4).

Next, the computer 6 moves the mirror 31 backward,
The reflected light from the measurement substrate 3 is measured (S5). Calculator 6
The spectrum for each wavelength decomposed by the spectroscope 5 is
Obtained as measurement data M (λ). And computer 6
Are the reflected light data X ′ (λ) of the reference substrate 9 ′ calculated in step S4, the reflectance data c (λ) of the reference substrate 9 ′ obtained in advance, and the measurement data M (λ) measured in step S5. ) Is substituted into equation (2) to perform normalization, and calculate normalized reflected light data m (λ) (S
6).

Finally, the computer 6 calculates the film thickness from the normalized reflected light data m (λ) and the sample model registered in advance by the method described in the background art (S).
7). The processes of steps S5 to S7 are repeatedly executed until the next calibration is performed, and the thickness of the measurement substrate 3 is sequentially measured.

When the computer 6 receives the calibration start command and the measurement start command from the substrate processing apparatus 12, the calibration shown in steps S3 and S4 and the steps S5 to S7 are performed.
Is automatically executed, and a calibration result or a measurement result is returned to the substrate processing apparatus 12. Normally, the calibration may be performed about once an hour. Therefore, when the computer 6 receives the calibration command from the substrate processing apparatus 12 within one hour after the completion of the calibration, the computer 6 returns the calibration command to the substrate processing apparatus 12 without performing the calibration. Only do.

As described above, according to the film thickness measuring apparatus of the present embodiment, when checking the aging of the light source 1, the mirror 31 is moved forward and the reflected light of the reference substrate 9 is measured. Since the calibration is performed by calculating the reflected light of the reference substrate 9 ', the calibration can be performed without stopping the substrate processing apparatus 12, and the measurement of the measurement substrate 3 can be performed continuously and stably. It has become possible.

Further, since the calibration and the measurement can be performed only by moving the mirror 31 forward or backward, it is possible to perform them by the same optical system. Therefore, only one set of the light source 1 for irradiating the sample with light, the spectroscope 5 for receiving the reflected light from the sample and spectrally decomposing, and the light transmission path from the light source 1 to the spectroscope 5 via the sample are provided. Alone, and the configuration of the optical system can be simplified.

Further, the calibration and measurement can be performed with the same optical system only by moving the mirror 31 forward / backward, so that the aging of the light source 1 can be accurately reflected in the calibration result. Was.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0049]

According to one aspect of the present invention, the light generated by the light emitting means is reflected so that the reflecting means irradiates the second reference sample, and the analyzing means determines the intensity based on the intensity of the reflected light. Thus, the aging of the light emitting means is calibrated, so that no special operation is required even when calibrating the aging of the light emitting means. Therefore, it is possible to continuously measure the thickness of the thin film of the measurement sample.

When the moving means calibrates the aging of the light emitting means, the reflecting means advances to reflect the light from the light emitting means, and when the thickness of the thin film of the measurement sample is measured, the reflecting means recedes and the light from the light emitting means is adjusted. Since light is applied to the measurement sample,
Calibration of the aging of the light emitting means and analysis of the thin film of the sample can be performed only by moving the reflecting means by the moving means, and the same optical system can be used.

The analyzing means obtains the intensity of the reflected light of the first reference sample and the second reference sample at the time of the initial adjustment, and calculates the intensity of the reflected light of the second reference sample at the time of calibrating the aging of the light emitting means. Acquisition and calibration of the aging of the light emitting means are performed, so that it is possible to analyze the thin film of the measurement sample in consideration of the aging of the light emitting means.

In addition, the analysis means uses the equations (1) and (2)
After calculating the reflected light data m (λ) of the measurement sample, the thickness of the thin film of the measurement sample is calculated, so that the aging of the light emitting means can be calibrated by calculation, and the thickness of the thin film of the sample can be calculated. The measurement can be performed accurately.

In the second reference sample, the distance from the light collecting means to the measurement sample or the first reference sample is equal to the distance from the light collecting means to the second reference sample via the reflecting means. Thus, the analysis means can easily calibrate the aging of the light emitting means by calculation.

Further, since the reflecting means is provided at an angle of about 45 ° with respect to the light from the condensing means, the reflected light of the second reference sample can be changed without changing the position of the first reference sample. It became possible to measure the strength.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a film thickness measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the position of the mirror 31 when measuring the film thickness of the normal measurement substrate 3 and the position of the mirror 31 during calibration.

FIG. 3 is a flowchart illustrating a processing procedure of a film thickness measuring apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a conventional film thickness measuring device.

5 is a diagram showing an example of a measurement result of a silicon nitride (SiN) film by the film thickness measuring device shown in FIG.

[Explanation of symbols]

1,101 light source, 2,102 optical fiber, 3,10
3 measurement board, 5,105 spectrometer, 6,106 computer, 9, 9 'reference board for calibration, 11 CCD, 12
Substrate processing device, 13 process control device, 31 mirror, 3
2 Measurement lens, 33 thin film, 104 Reception limit shutter.

Continued on front page F term (reference) 2F065 AA30 CC17 CC25 CC31 DD06 EE00 FF51 FF61 GG02 GG03 GG24 HH04 LL02 LL04 LL12 LL67 NN17 QQ17 QQ18 QQ26 QQ28 QQ42 4M106 AA01 AA12 CA48 DH03 DH12 DJ19

Claims (7)

[Claims] 1. A light emitting means for generating light so as to irradiate a measurement sample and a first reference sample, and a second reference arranged at a position different from the measurement sample and the first reference sample A reflecting unit for reflecting light generated by the light emitting unit so as to irradiate the sample; and a unit for receiving reflected light from the measurement sample, the first reference sample, and the second reference sample. Calibrating the aging of the light emitting means based on the intensity of the reflected light of the first reference sample and the second reference sample received by the light receiving means, and analyzing the thin film of the measurement sample A film thickness measuring apparatus including an analyzing means for performing the measurement. 2. The film thickness measuring apparatus further comprises: advancing the reflecting means to reflect light from the light emitting means when calibrating the aging of the light emitting means; and reflecting the light from the light emitting means when measuring a film thickness of the thin film of the measurement sample. 2. The film thickness measuring apparatus according to claim 1, further comprising a moving means for retracting a reflecting means and irradiating the measurement sample with light from the light emitting means. 3. The method according to claim 1, wherein the analyzing unit performs the first adjustment at an initial adjustment.
Acquiring the intensity of the reflected light of the reference sample and the second reference sample, and acquiring the intensity of the reflected light of the second reference sample at the time of calibrating the aging of the light-emitting means, and obtaining the aging of the light-emitting means. The film thickness measuring device according to claim 1, wherein the calibration is performed. 4. The analysis means sets the intensity of the reflected light of the first reference sample at the time of the initial adjustment to X (λ) and the intensity of the reflected light of the second reference sample at the time of the initial adjustment to K (λ).
(Λ), the intensity of the reflected light of the second reference sample at the time of the calibration is K ′ (λ), and the intensity of the reflected light of the measurement sample is M
(Λ), assuming that the reflectance of the first reference sample is c (λ), the reflected light data m (λ) of the measurement sample is given by the following equation.
After calculating, the thickness of the thin film of the measurement sample is calculated,
The film thickness measuring device according to claim 3. (Equation 1) 5. The film thickness measuring apparatus further includes a light condensing unit for condensing light reflected from the measurement sample, the first reference sample, and the second reference sample, and The reference sample is configured such that the distance from the focusing unit to the measurement sample or the first reference sample is the same as the distance from the focusing unit to the second reference sample via the reflecting unit. The film thickness measuring device according to any one of claims 1 to 4, which is provided. 6. The film thickness measuring apparatus according to claim 5, wherein said reflection means is provided at an angle of about 45 ° with respect to light from said light collection means. 7. A step of generating light so as to irradiate the measurement sample and the first reference sample; and irradiating a second reference sample arranged at a position different from the measurement sample and the first reference sample. Reflecting the generated light; receiving the reflected light from the measurement sample, the first reference sample and the second reference sample; and A film thickness measurement method, comprising: calibrating aging of a light source based on the intensities of reflected light of a reference sample and the second reference sample; and analyzing a thin film of the measurement sample.