JPH03220433A - Evaluating method of stress in silicon crystal - Google Patents

Abstract

PURPOSE:To evaluate the stress correctly without the necessity for temperature adjustment by using two bright lines as a standard light. CONSTITUTION:A laser light from a light source 1 is introduced through a filter 2 to a sample within a sample chamber 3. The scattering light is guided to a spectroscope 4 and the Raman spectrum is detected by a detector 5. The Raman spectrum is measured by using two bright lines (natural lights) as a standard light. A Raman shift of a silicon crystal is obtained from this spectrum by performing the following corrections. That is, assuming that the corrected Raman shift of the silicon crystal is Psi<0>, the read Raman shift of the silicon crystal is Psi<1>, the wave number of the incident light is Pin, the wave number of the one standard light is P1<0>, the read Raman shift of the one standard light is P1<1>, the wave number of the other standard light is P2<0>, and the read Raman shift of the other standard light is P2<1>, the corrected value Psi<0> is obtained according to the formula. Therefore, it becomes possible to obtain the Raman shift of the silicon crystal more correctly without being influence by the change of the distance between scales.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for evaluating stress in a silicon crystal using Raman spectroscopy.

[Prior Art] Currently, local stress evaluation in silicon crystals with a spatial resolution of about 1 φ is performed using microlaser Raman spectroscopy.

This method uses Raman shift 52 in Raman spectrometry.
When a silicon crystal with a peak around 0 cm-1 is subjected to external stress, the Raman shift of the silicon crystal deviates from the Raman shift of the silicon crystal when there is no stress depending on the magnitude of the stress. This is the principle. Therefore, it is important to accurately measure the Mann shift of silicon crystals.

Conventionally, when reading the Raman shift in evaluating local stress in a silicon crystal using Raman spectroscopy, an argon ion laser with a wavelength of 488.0 nm is used as the incident light, and an argon ion laser with a wavelength of 500.90 m is used as the standard light. The Raman shift of the silicon crystal was determined by correcting the read wave number by using a laser spontaneous emission line or a neon lamp emission line with a wavelength of 500.5.

This correction method is based on the assumption that the scale interval on the wavenumber axis is always constant. That is, the corrected Raman shift of the silicon crystal is psio, the read Raman shift is psi', the wave number of the incident light is Pin, the wave number of the standard light peak is Pl, and the read Liraman shift is P+1.
Then, the correction value p s of the Raman shift of the silicon crystal is
io can be obtained by correcting the following equation.

・0 ・1 Ps+ =Ps+ 10 Pin-P10-P11...
・(1) [Problem to be solved by the invention] However, with the correction method described above, there is no particular problem when the spectrometer is used in a stable state, but if some changes occur in the spectrometer, Sufficient correction will not be possible. That is, this is a case where a change occurs in the scale interval on the wave number axis.

For example, when the optical path length of a spectrometer becomes longer due to changes in the temperature of the device, the dispersion at the detector becomes wider than usual, and the distance between the peak of the silicon crystal and the peak of the standard light on the Raman spectrum becomes wider, and this correction is required. When the standard light is the spontaneous emission line of an argon ion laser, the value is a smaller Raman shift than originally expected, and when the standard light is the emission line of a neon lamp, it is a large Raman shift. Conversely, when the optical path length of the spectrometer becomes shorter, the opposite occurs. In other words, in any case, the optical path length of the spectrometer changes due to changes in the temperature of the device, etc.
The Raman shift of the silicon crystal could not be sufficiently corrected using one standard light. For this reason, in the past, in order to suppress changes in the spectrometer, it was necessary to adjust the temperature of the entire device or only the spectrometer part to keep the spectrometer as stable as possible, making the device complicated. There was a drawback.

The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to provide a method for accurately evaluating stress in a silicon crystal without the need for temperature adjustment.

[Means for Solving the Problems] The present invention provides a stress evaluation method in a silicon crystal, which comprises using Raman spectroscopy and correcting the reading wavenumber using standard light to measure the Raman shift of the silicon crystal. This is a stress evaluation method in a silicon crystal characterized by using two bright lines as standard light.

[Operation] In the present invention, a Raman spectrum is measured using two emission lines as standard light, and the Raman shift of the silicon crystal is determined from this spectrum by performing the correction described below.

Assuming that the wave number of the incident light is Pin and the read Raman shift of one of the two standard lights is P2', a correction value P sio of the Raman shift of the silicon crystal can be obtained by correcting using the following equation.

PsiO=Pin-pi O+ By this method, it is possible to obtain a more accurate Raman shift of the silicon crystal that is not affected by changes in the scale interval.

[Example] Next, examples of the present invention will be described.

FIG. 2 is a block diagram of an example of an apparatus for carrying out the method of the invention. In FIG. 2, light from a light source 1 is passed through a filter 2 and applied to a sample in a sample chamber 3, and the scattered light is introduced into a spectrometer 4, where a Raman spectrum is detected by a detector 5.

Light source 1 is an argon ion laser, wavelength 48B, On
m single mode oscillation. However, the laser light includes spontaneous emission lines.

The requirements for filter 2 are the transmittance of the laser beam and the two standard beams, so that the peak of the silicon crystal in the Raman spectrum and the peaks of the two standard beams provide sufficient intensity to read the Raman shift. The transmittance of natural luminescent rays can be adjusted.

The wavelengths of the two spontaneous emission lines used as standard light in this example are 500.91 m and 501.7 nm.

In the sample chamber 3, a microscope may be used to narrow down the laser beam to about 1 φ and the laser beam may be focused on the sample, or the laser beam may be focused using a lens with a small magnification and applied to the sample.

The spectrometer 4 is preferably a double monochromator.

The detector 5 may be a multi-channel detector or a normal photomultiplier tube.

FIG. 1 shows a Raman spectrum obtained using the apparatus described above. Raman shift peak around 520cm-' is silicon crystal, peak around 530cm-1 and 560cm''
Nearby peaks are peaks caused by two standard lights.

In this example, peak separation was performed using a Lorentzian curve for the silicon crystal peak in the Raman spectrum shown in Figure 1, a Gaussian curve for the two standard light peaks, and a straight line for the baseline. The Raman shift is read and corrected using equation (2) to determine the Raman shift of the silicon crystal.

As a result of evaluating the stress in the silicon crystal using this method, we were able to obtain a stable Raman shift value for the silicon crystal that is not affected by changes in the spectrometer due to temperature changes.

[Effects of the Invention] As explained above, according to the method of the present invention, there is no need for temperature adjustment, and stress evaluation of a silicon crystal can be performed more easily and more accurately.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a Raman spectrum obtained using the method of the present invention, and FIG. 2 is a block diagram of an example of an apparatus used in the method of the present invention. 1... Light source 2... Filter 3... Sample chamber 4... Spectrometer 5... Detector

Claims (1)

[Claims] (1) Two emission lines are used as standard light in the stress evaluation method in silicon crystal, which uses Raman spectroscopy and measures the Raman shift of the silicon crystal by correcting the reading wavenumber using standard light. A method for evaluating stress in silicon crystals.