JPH0694618A - Microscopic raman spectro photometer for measuring stress - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable rapid measurement of stress distribution in a Raman spectrophotometer. [Structure] A two-dimensional detector is used as a detector, the width of an entrance slit is set to be equal to or less than the width of an element of the detector, the sample stage is tilted, and a sample stage moving mechanism perpendicular to the slit is provided. [Effect] Since the resolution of the Raman spectrum can be increased and the measurement in the slit direction can be performed at one time, the stress distribution can be measured quickly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining a stress of a sample by measuring a change in Raman peak wave number of the sample in a micro Raman spectrophotometer, and using a two-dimensional detector and a stage moving mechanism. The stress distribution of is quickly obtained.

[0002]

2. Description of the Related Art As an example of a conventional Raman spectrophotometer, there is an apparatus described in Japanese Utility Model Laid-Open No. 58-1151. This device has a structure as shown in FIG. An incident laser beam 2 generated from a laser light source 1 is applied to a sample 6 placed under a microscope objective lens 5. The Raman light 7 generated from the sample 6 is separated by the diffraction gratings 15a and 15b of the spectroscope and then detected by the detector 24.

By the way, as described in Takashi Kawatoda, "Evaluation of Semiconductors by Laser Raman Spectroscopy" (The University of Tokyo Press), it is known that the amount of change in the wave number of Raman light and the stress of the sample are approximately proportional. ing. In order to measure the stress of the sample by this method, it is generally necessary to measure the wave number of Raman light with a wave number resolution of ¹ cm to ¹ or less. However, in the above-mentioned conventional technique, it is not considered to measure the wave number of the Raman peak with high resolution and simultaneously obtain the Raman spectra of many points of the sample at the same time. In order to obtain it, it was necessary to measure the Raman spectrum at each minute point while moving the sample stage, and to calculate the stress value from the peak wave number of the spectrum each time, so the measurement took time.

[0004]

In the above-mentioned prior art, it is not considered to measure both the Raman peak wave number with high resolution and to simultaneously obtain Raman spectra of many points of the sample. Therefore, in order to measure the two-dimensional distribution of stress, it is necessary to measure the Raman spectrum at each minute point while moving the sample stage and calculate the stress value from the peak wave number of the spectrum each time. It was Therefore, the measurement of the stress distribution over a wide range in two dimensions requires a large number of measurements and takes time.

An object of the present invention is to simultaneously obtain the Raman peak wavenumber with high resolution and simultaneously obtain Raman spectra of many points of the sample at the same time, and quickly obtain a two-dimensional distribution of stress of the sample. To enable.

[0006]

In order to achieve the above object, a two-dimensional detector is used as a detector so that the width of a slit image formed on the two-dimensional detector is 1 pixel or less. By setting the slit width, the Raman spectrum of many points on a straight line parallel to the entrance slit is measured with high wavenumber resolution so that the stress distribution in this direction can be obtained by a single measurement. By obtaining the stress distribution in the vertical direction by moving the sample stage, it is possible to quickly obtain a two-dimensional stress distribution without the need to move the sample stage in the direction parallel to the entrance slit. It was done.

[0007]

The operation of the present invention will be described with reference to FIGS.

FIG. 1 is a side view showing the structure of an example of the apparatus. 1 is a laser light source, 2 is laser light, 3 is a lens system, 4
Is a half mirror, 5 is an objective lens, 6 is a sample, 7 is Raman light, 8 is a mirror, 9 is a slit imaging lens, 10 is an entrance slit, 14a and b are concave mirrors, 15a is a diffraction grating, 20
Is a two-dimensional detector, 21 is a data processing device, 22 is a display device, 30 is a sample stand, 31 is a fixed stand, 32 is a sample stand moving mechanism, w is a slit width, and Y is a Y coordinate. This figure shows a single-stage spectroscope. The upper and lower views of FIG. 2 are a top view of the same device and a cross-sectional view seen from above the diffraction grating 15a. h is the slit height, and X is the X coordinate.
FIG. 3 shows the image produced on the two-dimensional detector 20. V _{1 to} V ₅
Indicates a pixel address in a direction parallel to the entrance slit 10, and W _{1 to} W ₅ indicate pixel addresses in a direction perpendicular to this.

The laser light 2 emitted from the laser light source 1 is irradiated onto a wide range on the sample 6 by the lens 3 and the objective lens 5. As a result, the Raman light 7 is emitted from the sample 6. The Raman light 7 is imaged on the slit 10 by the slit imaging lens 9. This image is further analyzed by the diffraction grating 15
After being separated by a, the image is formed on the two-dimensional detector 20. Here, the width of the slit 10 is set so that the width of the image of the slit 10 formed on the two-dimensional detector is equal to or less than the width of one pixel, and the sample table 30 is tilted to shift the focus of the peripheral portion. Thereby, there is an effect that the wave number resolution of the Raman spectrum detected by the two-dimensional detector 20 can be increased. The element address in the X-axis direction of the two-dimensional detector 20 is V, and the element address in the direction perpendicular to this is W. As shown in FIG. 2, the address V corresponds to the position in the height h direction of the image on the entrance slit 10, and further corresponds to the X coordinate of the measurement position of the sample. Further, the address V corresponds to the wave number of the Raman light 7 as shown in FIG. That is, as shown in FIG. 3, if the image formed on the two-dimensional detector 20 is represented by a matrix I (V, W), spectra {I (V ₁ , W)} to {I (for each V row. V ₅ ,
W)} is possible. From this, the stress distribution in the X-axis direction of the sample can be quickly obtained by obtaining the address W where the signal intensity reaches the peak for each V row. Further, by the program, the sample table 30 is sequentially moved in the Y-axis direction, and the stress value at each point of the sample is displayed as a function of the X coordinate value obtained from the address V and the Y coordinate value of the sample table 30. The stress distribution can be measured quickly.

[0010]

【Example】

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS.

FIG. 1 is a side view showing the structure of the apparatus of the first embodiment. 1 is a laser light source, 2 is laser light, 3 is a lens system, 4 is a half mirror, 5 is an objective lens, 6 is a sample, 7
Is Raman light, 8 is a mirror, 9 is a slit imaging lens, 10 is an entrance slit, 14a and b are concave mirrors, 15a is a diffraction grating, 20 is a two-dimensional detector, 21 is a data processing device, 22
Is a display device, 30 is a sample table, 31 is a fixed table, 32 is a sample table moving mechanism, w is a slit width, and Y is a Y coordinate. This figure shows a single-stage spectroscope. Also, FIG.
The top and bottom views are a top view of the device and a sectional view of the diffraction grating 15a as viewed from above. h is the slit height, and X is the X coordinate.

The laser light 2 emitted from the laser light source 1 illuminates a wide range on the sample 6 by the lens 3 and the objective lens 5. As a result, the Raman light 7 is emitted from the sample 6. The Raman light 7 is imaged on the slit 10 by the slit imaging lens 9. This image is further analyzed by the diffraction grating 15
After being separated by a, the image is formed on the two-dimensional detector 20. Here, by narrowing the width w of the slit 10 and tilting the sample table 30 to shift the focus of the peripheral portion, the wave number resolution of the Raman spectrum detected by the two-dimensional detector 20 can be increased. As a result, the two-dimensional detector 2
The Raman wave number can be measured with high resolution from the peak positions W and W'on 0, and the stress of the sample can be measured. Also, slit 1
By increasing the height h of 0, the Raman image of the sample in the X-axis direction can be detected by the two-dimensional detector 20. From this, the relationship between the position of the sample in the Y direction and the stress can be obtained once. In addition, on the fixed base 31 that tilts the sample base 30,
By sliding in the Y-axis direction perpendicular to the X-axis, the measurement position in the Y-direction can be changed without shifting the focus of the sample. Therefore, it is not necessary to move the sample in the X-axis direction, and the stress distribution can be measured quickly.

In the first embodiment, the spectroscope is a one-stage type and the focal length is 6
40 mm, the number of engraved lines of the diffraction grating was 1800 lines / mm, and the wavelength line dispersion was 0.7 nm / mm. If the wavelength of the laser light is 514.5 nm, the wave number line dispersion is (1/5
14.5 × 10 ~ ⁹ ) ² × 0.7 × 10 ~ ⁹ = 2600m ~
¹ / mm = 26 cm to ¹ / mm. The size of one element of the two-dimensional detector 20 is 22 μm × 22 μm, and the number of elements is 578 in the spectrum direction and 385 in the X-axis direction. Further, as the objective lens 5, an infinite focusing lens with a magnification of 50 times and a focal length f ₃ of 5 mm was used, and as the slit imaging lens 9, a focal length f ₄ of 225 mm was used. Therefore, the magnification of the image on the entrance slit 10 with respect to the sample is 45 times. The width w of the entrance slit 10 is 20
When γμm and the height h are set to 8.5 mm, the wave number resolution is determined by the size of the element of the two-dimensional detector 20.
It is a 6cm ~ ¹ /mm×0.022mm=0.6cm~ ^1. Further, the X-direction positional resolution and width of the sample 6 that can be measured at one time are determined by the size of the elements of the two-dimensional detector 20, the number of elements, and the magnification of the image on the entrance slit 10 with respect to the sample, and each is 0.022 mm / 45. = 0.5 μm and 0.022 mm × 385/45 = 0.19 mm.

(Embodiment 2) Embodiment 2 of the present invention is shown in FIG. In this embodiment, the sample 9 is tilted in the first embodiment, and at the same time, a cylindrical lens having a function of converging or expanding light in the X direction is used as the lens 3. As a result, the laser light that irradiates the sample 6 can be expanded in the X direction and converged in the Y direction. As a result, in addition to narrowing the width w of the entrance slit 10, the wave number resolution can be further improved.

(Embodiment 3) Embodiment 3 of the present invention is shown in FIG. In this embodiment, the spectroscope is a three-stage addition-dispersion type,
A wave number resolution of 0.2 cm to ^{1 which} is three times that of Example 1 can be obtained.

(Embodiment 4) A program of Embodiment 4 of the present invention is shown in FIGS. FIG. 6 shows the main routine. First, the device-specific constants S _X , S _Y (S _X is the width in the X-axis direction, S _Y is the width in the direction perpendicular to this), which are device-specific constants, and the wavenumber line of the spectroscope. The variance D is stored as a constant in the program in advance. Next, the program will be described in the order of execution.

(1) Input parameters. Where K
_MIN and K _MAX are the lower and upper limits of the measured wave number, and are for selecting the peak wave number range used for stress calculation in the spectrum detected by the two-dimensional detector 20. K ₀ is the wave number corresponding to the state where the stress is 0.
Y _MIN , Y _MAX and D _Y are the start point, end point and interval of the Y coordinate of the measurement position. M is the magnification of the image on the entrance slit 10 with respect to the sample 6, and X ₀ is the X coordinate value of the center of the measurement position.
D _T is a proportional constant that connects the change in Raman wave number and the stress. This is according to the above mentioned literature

[0018]

[Equation 1]

Is given by Here, p and q are parameters that connect strain and spring constant, and S ₁₁ and S ₁₂ are elastic parameters that connect stress and strain.

(2) The spectroscope is set to the wave number K0.

(3) K _MIN and K _MAX are pixel addresses W _MIN and W
Convert to _MAX .

(4) Obtain the number of measurement points U _MAX in the Y-axis direction from Y _MIN , Y _MAX , D _Y.

(5) U is increased by 1 from 0 to U _MAX by 1 and the position of the sample stage in the Y direction is sequentially moved from Y _MIN to Y _MAX to read the signal of the two-dimensional detector 20 and process the data. To do.

(6) Data is output.

FIG. 6 shows a subroutine for reading data used in (5) above. This program will be described in the order of execution.

(1) The signal of the two-dimensional detector 20 is converted into the matrix I
Read to (V, W). Here, V and W are pixel addresses in the X-axis direction and in the direction perpendicular thereto, respectively.

(2) Smoothing and peak wave number detection are performed for each V row of the matrix I. The peak wave number is entered in the (U, V) element of the matrix K _P for each V row. However, the peak wave number is detected between the pixel addresses W _MIN and W _MAX determined in (3) of the main routine. Further, the stress is calculated from this peak wave number and is entered in the (U, V) element of the matrix T.

By the above processing, each element of the matrices KP and T contains values corresponding to the X and Y coordinates of the measurement position.

FIG. 7 shows a subroutine for outputting data. This program outputs the X coordinate, Y coordinate, peak wave number, and stress of the measurement position in association with each other. With the above program, the two-dimensional distribution of stress in the sample can be measured quickly.

(Fifth Embodiment) FIG. 9 shows a data reading subroutine of the fifth embodiment. The main routine and the data output subroutine are the same as in the fourth embodiment. In the present embodiment, instead of the smoothing of the fourth embodiment, curve fitting is used to smooth the spectrum. In this curve fitting, the peak of the spectrum is approximated by a least square method using a Gaussian function, a Lorentz function or the like.

Example 6 FIG. 10 shows the result of measurement of the Raman spectrum of the SiN film on the wiring of the liquid crystal display element by the device of the present invention. The stress was measured from the change in the wave number of the Raman spectrum of this SiN film. The constant D _T was obtained by measuring the Raman spectrum of a standard sample with known stress. The top view of the sample is shown in the upper diagram of FIG. 11, and the measurement result of the stress distribution is shown in the lower diagram of FIG. The shaded area indicates wiring. Also, 1
00-400 shows a stress value (GPa). in this way,
According to the present invention, the stress distribution of a sample can be measured quickly.

[0032]

According to the present invention, it is possible to obtain a high wave number resolution necessary for measuring the stress of a sample by Raman spectrum, and it is not necessary to move the sample in the X direction, so that the stress distribution can be measured quickly. it can.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an apparatus according to a first embodiment.

2A and 2B are a side view and a cross-sectional view showing the configuration of the device according to the first embodiment.

FIG. 3 is a diagram showing an image on a two-dimensional detector 20.

FIG. 4 is a side view showing the configuration of the apparatus of Example 2.

FIG. 5 is a side view showing a configuration of an apparatus of Example 3.

FIG. 6 is a diagram showing a main routine of a fourth embodiment.

FIG. 7 is a diagram showing a data reading subroutine of the fourth embodiment.

FIG. 8 is a diagram showing a data output subroutine of the fourth embodiment.

FIG. 9 is a diagram showing a data reading subroutine of the fifth embodiment.

FIG. 10 is a diagram showing a measurement example of a Raman spectrum.

FIG. 11 is a diagram showing an example of measurement of stress distribution.

FIG. 12 is a configuration diagram of a conventional technique.

[Explanation of symbols]

1 ... Laser light source, 2 ... Laser light, 3 ... Lens, 3 '... Cylindrical lens, 4 ... Half mirror, 5 ... Objective lens, 6 ... Sample, 7 ... Raman light, 8 ... Plane mirror, 9 ... Slit imaging lens, 10 ... Entrance slit, 14a-f ... Concave mirror, 15a-c ... Diffraction grating, 16a-e ... Plane mirror, 20 ... Two-dimensional detector, 21 ... Data processing device, 22 ... Display device, 30 ... Sample stand, 31 ... Fixed base, 32 ... sample table moving mechanism, the height of h ... entrance slit 10, the width of w ... entrance slit 10, V, V ', W ... pixel address, X, Y ... coordinate and K ₀ ... stress is zero Wave number at time, K _MIN ... lower limit of measured wave number, K _MAX ... upper limit of measured wave number, Y _MIN ... start point of measurement position in Y-axis direction, Y _MAX ... end point of measurement position in Y-axis direction, _DY ... Y-axis direction Of the measurement position of M, the sample of the image formed on the M ... entrance slit 10 Magnification, X ₀ ... center of measurement position in the X-axis direction, D _T ... proportional constant for connecting wave number change and stress, S _X ... element size in X-axis direction, S _Y ... element size in Y-axis direction Well, D ... Wave number line dispersion.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Wakana 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory

Claims (6)

[Claims] 1. Raman spectroscopy comprising a laser light source, optical means for irradiating a sample with a laser, a single-stage or multi-stage spectroscope, a slit provided at the entrance of the spectroscope, and a two-dimensional detector. A micro Raman spectrophotometer for stress measurement, comprising a sample stage that is parallel to the slit and is inclined with respect to the optical axis of the laser beam, and a mechanism for moving the sample stage. 2. Raman spectroscopy comprising a laser light source, optical means for irradiating a sample with a laser, a single-stage or multi-stage spectroscope, a slit provided at the entrance of the spectroscope, and a two-dimensional detector. In a photometer, for stress measurement, which is provided with an optical element having a light converging or diffusing action only in a direction parallel to the slit on the optical path of the laser beam, and a moving mechanism for the sample stage. Microscopic Raman spectrophotometer. 3. The Raman spectrophotometer according to claim 1 or 2, wherein the slit width formed on the two-dimensional detector is less than the width of one pixel of the two-dimensional detector. Micro Raman spectrophotometer for stress measurement characterized by having. 4. A Raman spectrophotometer according to any one of claims 1 to 3, which is a program for processing a Raman spectrum generated on the two-dimensional detector and controlling the sample stage moving mechanism. (1) A command to sequentially move the position of the sample table in the Y-axis direction perpendicular to the slit based on a value input in advance (2) An image on the two-dimensional detector is arranged in a matrix I (V, W) ( V
Is a pixel parallel to the slit, and W is a pixel address in a direction perpendicular to the slit) (3) A process of obtaining an address W corresponding to the peak of the Raman spectrum for each V row of the matrix I (4) ) Processing for obtaining the X coordinate of the measurement position on the sample and the Raman peak wavenumber and stress from the pixel addresses V and W of the two-dimensional detector, respectively (5) The Raman peak wavenumber and the stress for the sample table Y
A program comprising: displaying as a function of the axial position and the X coordinate of the measurement position on the sample. 5. The program according to claim 4, including smoothing of spectrum or curve fitting, or both of them. 6. A semiconductor stress evaluation apparatus comprising the Raman spectrophotometer according to claim 1, 2 or 3 and the program according to claim 4 or 5.