JPH11326215A - Correction method in glow discharge emission spectrochemical analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an analysis result where influence due to the fluctuation of a sputtering speed is included, by correcting the fluctuation of sputtering distance caused by the fluctuation of the sputtering speed, and standardizing the fluctuation of an element concentration in a glow discharge emission spectrochemical analysis. SOLUTION: With a correction method, in a glow discharge emission spectrochemical analysis for performing an element analysis by performing the spectral detection of atom emission while sputtering a sample surface by glow discharge, the light intensity 6f each element in an element contained in the sample is converted to concentration, the total concentration value of total elements being converted on each measurement is obtained, and the fluctuation of an analysis result is corrected due to the fluctuation of the sputtering speed using the obtained, total concentration value. On each measurement, the ratio of the total concentration value at each measurement for the total, maximum concentration value during total measurement is multiplied by the sputtering distance that is obtained from the sputtering speed, thus correcting the influence due to the fluctuation of the sputtering speed of the sputtering distance, and obtaining a coefficient where the total concentration value is the same through total measurement, and the coefficient is multiplied by the concentration and hence correcting the fluctuation of the element concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to glow discharge optical emission spectroscopy, and more particularly to a correction method for correcting fluctuations in analysis results due to fluctuations in element concentrations in film composition analysis and the like.

[0002]

2. Description of the Related Art When a high voltage is applied between electrodes in a low-pressure argon atmosphere, a glow discharge occurs. Ar ions generated by the glow discharge are accelerated by a high electric field, collide with the cathode side, and strike a substance from the cathode side.
The particles (atoms, molecules, ions) emitted by the sputtering emit light having a wavelength specific to the element when returning from the excited state to the ground state in the plasma. In glow discharge emission spectroscopy, this light emission is analyzed by a spectroscope to perform elemental analysis or the like.

[0003] In this glow discharge emission spectroscopy, the sample surface is removed by sputtering, and the temporal change in the luminescence intensity of each element can be measured, whereby element analysis in the depth direction can be performed. Can be applied to the evaluation of the film composition. As a method of obtaining the distance in the depth direction, in the evaluation of the film composition of the light-transmitting thin film,
There is known one that uses light interference generated by a phase shift and an optical path difference of reflected light reflected at the boundary between the surface of a thin film sample and a substrate (for example, JP-A-6-43100).

[0004]

Normally, the concentration of an element contained in a sample is not constant but may fluctuate. When the element composition of such a sample is determined by glow discharge emission spectroscopy, the measured light intensity fluctuates due to fluctuations in the sputtering rate. Such a change in the sputtering rate occurs between the measurement data of each sample and the measurement data of one sample.

[0005] In the conventional glow discharge emission spectroscopy, the sputtering rate is assumed to be constant, and the analysis result is not corrected by the fluctuation of the sputtering rate. For example, when obtaining the sputtering distance, the sputtering speed is assumed to be constant, and the standard sample sputtering speed is applied as it is. Therefore, if there is a variation in the sputtering rate, the obtained sputtering distance includes a variation in element concentration as an error,
This means that accurate distribution information in the depth direction cannot be obtained.

Therefore, the conventional glow discharge emission spectroscopy method has a problem that accurate analysis results cannot be obtained due to fluctuations in the concentration of elements contained in the sample.

The method disclosed in Japanese Patent Application Laid-Open No. 6-43100 is an analysis method using a light-transmitting thin film as an object to be measured. Therefore, when the sample is a non-light-transmitting thin film, it can be applied. There is also the problem that it cannot be done.

Accordingly, an object of the present invention is to provide a correction method in glow discharge optical emission spectroscopy which can correct the effect of fluctuations in the sputtering rate on the analysis results of elements contained in a sample. Yes, and in more detail, one object is to correct the variation of the sputtering distance due to the variation of the sputtering speed,
Another object is to obtain a corrected composition ratio by normalizing the fluctuation of the sputtering rate.

[0009]

In order to determine the elemental composition of a sample such as a thin film by glow discharge emission spectroscopy, the light intensity of light directly obtained from glow discharge emission is used. In addition,
In the case of a sample with a light-transmitting thin film, the measurement light contains a direct current related to the elemental composition of the sample due to optical interference caused by the phase shift and optical path difference of the reflected light reflected at the boundary between the surface of the thin film sample and the substrate. In addition to the fluctuation, the fluctuation due to the interference light is included. Here, when the fluctuation due to the interference light is included in the measurement data, the analysis of the elemental composition and the correction of the analysis result due to the fluctuation of the sputtering speed are performed by using the DC component obtained by removing the fluctuation.

In glow discharge emission spectroscopy, in which atomic emission is spectrally detected while sputtering a sample surface by glow discharge and elemental analysis is performed, the correction method of the present invention is as follows.
The light intensity of each element in the elements contained in the sample is converted to the concentration, the total value of the concentrations of all the elements converted at each measurement is obtained, and the fluctuation of the analysis result due to the fluctuation of the sputtering speed is determined using the obtained total value of the concentration. It is to be corrected. This correction is
Analysis results for the influence of the fluctuation of the sputtering rate at each measurement time point are performed using the total concentration value at that time point. This is based on the fact that the total concentration is proportional to the sputtering rate.

In the first embodiment of the present invention, the analysis result for performing the correction is used as the sputtering distance. In the first embodiment, atomic emission is spectrally detected while sputtering the sample surface by glow discharge, and in glow discharge emission spectral analysis for elemental analysis, the light intensity of each element in the elements contained in the sample is converted into a concentration, The total value of the concentrations of all the elements converted at each measurement is obtained. And, at the time of each measurement,
The ratio of the total concentration at each measurement to the maximum total concentration during all measurements is multiplied by the sputtering distance determined from the sputtering rate. By multiplying by the ratio of the total concentration, the influence of the variation of the sputtering speed on the sputtering distance is corrected, and elemental analysis in the depth direction not affected by the variation of the sputtering speed can be performed.

To determine the sputtering distance from the sputtering rate, a standard sample is sputtered,
The sputtering speed at this time is determined, and the sputtering distance can be determined by multiplying the sputtering speed by a predetermined time interval. This sputtering distance is a reference value that does not take into account fluctuations in the sputtering rate. In the first embodiment, the concentration fluctuation is corrected by multiplying this reference sputtering distance by the ratio of the total concentration.

According to a second embodiment of the present invention, an analysis result to be corrected is used as an element concentration. In the second embodiment, atomic emission is spectrally detected while sputtering the sample surface by glow discharge, and in glow discharge emission spectral analysis for elemental analysis, the light intensity of each element in the elements contained in the sample is converted into a concentration, The total value of the concentrations of all the elements converted at each measurement is obtained. Then, at each measurement, a coefficient that makes the total value of the concentration at the time of the measurement the same throughout the measurement is obtained, and this coefficient is multiplied by the coefficient. By multiplying this coefficient, the influence of the fluctuation of the sputtering rate is corrected, and a standardized element concentration that is not affected by the fluctuation of the sputtering rate can be obtained.

Further, the first embodiment corrects the effect of the sputtering distance due to the fluctuation of the sputtering speed, and
By combining with the correction of the influence of the variation of the sputtering rate according to the second embodiment, it is possible to perform the elemental analysis in the depth direction which is not affected by the variation of the sputtering rate.

Further, according to the present invention, the sputtering distance can be obtained even when the sample is a non-light-transmitting thin film.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a glow discharge optical emission spectrometer to which a correction method in glow discharge optical emission spectroscopy of the present invention can be applied. Glow discharge emission spectrometer 1 shown in FIG.
Is a method in which a discharge electrode 3 formed in a hollow shape and a sample S are arranged to face each other, and vacuum evacuation is performed while flowing argon gas to maintain a low vacuum atmosphere.
And a stable discharge glow discharge plasma of argon is formed between the discharge electrodes 3. In addition, when supplying high frequency power, it can be performed by the high frequency power supply 4 and the matching device 5.

The positive ions of the plasma sputter the surface of the sample S uniformly and are cut at a speed on the order of, for example, 10 nm / sec. Sputtered sample S
Are excited in the plasma to emit light peculiar to the element. The high-frequency glow discharge emission spectrometer 1 splits the emitted light with the spectroscope 2 and detects it with the photodetector 23. Reference numeral 21 denotes a slit, and reference numeral 22 denotes a spectroscope such as a diffraction grating. In general, the glow discharge optical emission spectrometer 1 having the above-described configuration measures the distribution of the elements in the sample S in the depth direction by measuring the temporal change of the emission.

In the glow discharge emission spectral analysis according to the present invention, the glow discharge emission spectral analyzer 1 described above
The light intensity is detected for each wavelength, and the composition of the contained element is determined from the magnitude of the measured light intensity.

The procedure of the correction method in the glow discharge optical emission spectroscopy of the present invention will be described below with reference to the flowchart of FIG. 2 and the graphs of FIGS. In addition,
3 to 6 are graphs for explaining the procedure for obtaining the total concentration of all elements, FIG. 7 is a graph for explaining the correction of the sputtering distance, and FIG. 8 is a graph for explaining the correction for normalizing the concentration. FIG. 9 is a graph in which sputtering distance and concentration correction are combined.

In the flowchart of FIG. 2, first, the sample is subjected to glow discharge emission analysis to measure the depth distribution data of the elements contained in the sample. The depth distribution data can be obtained by dispersing light from glow discharge light emission at a wavelength specific to the contained element and detecting the light intensity. The graph of FIG. 3 shows that elements a, b,
FIG. 3 schematically shows depth distribution data obtained by measuring the light intensity I at a wavelength specific to each element together with the time change of sputtering when the element c is included.

For example, the light intensities Ia and Ib of the elements a and b
Shows a peak at times 1 and 2, then gradually decreases with time, and the light intensity Ic of element c gradually increases with time after time 4 and shows peaks at times 8, 9, and 10. .

FIG. 3 shows a case where the measurement is performed at a predetermined time interval (here, a constant time interval).

The light intensities Ia, Ib, and Ic of the respective elements indicate values based on the element composition in the sample. Also,
Assuming that the sputtering rate is constant, a change in the light intensity Ia, Ib, Ic of each element indicates a change in the depth direction (step S1).

From the light intensity I obtained in step S1, the concentration Ca, Cb, Cc of each element a, b, c is converted. This concentration conversion can be performed by performing glow discharge emission spectroscopy on a standard sample of each element in advance, and using the standard sample sensitivity obtained thereby.

The standard sample sensitivity can be obtained by proportionally calculating the light intensity I obtained in step S1 using the relationship between the light intensity and the concentration at one point, or the light intensity I formed from a plurality of data. The density C for the light intensity I obtained in step S1 can also be obtained using the calibration curve of the density C for 4A, 4B and 4C show the light intensity I
An example of a calibration curve of the concentration C with respect to is schematically shown for each of the elements a, b, and c. The concentration C is a weight concentration, and the maximum value is represented by 100.

FIG. 5 shows that each element a, b,
The light intensities Ia, Ib, and Ic of c (the light intensities in FIG. 3) are calculated using a calibration curve (the calibration curves in FIGS. 4A, 4B, and 4C).
The values are obtained by converting into the concentrations Ca, Cb, and Cc, and show the time change of the concentrations Ca, Cb, and Cc for each element (step S2).

The concentration data obtained by the concentration conversion in step S2 is the concentration of each element, and the magnitude of each concentration may fluctuate due to the fluctuation of the sputtering speed at the time of measurement. . Therefore, in order to determine the fluctuation of the sputtering rate at each measurement time (hereinafter, the processing at each measurement time is represented by step i), the total value Ci of the concentrations of all the elements is obtained.

FIG. 6 shows the concentration of each element shown in FIG.
The total density value Ci obtained by adding Cb and Cc for each step i is shown. Therefore, the time variation of the sputtering speed during sputtering can be known from FIG. 6 (step S3).

In the following, the fluctuation of the sputtering distance due to the fluctuation of the sputtering speed is corrected in steps S4 to S6 using the total value Ci of the concentrations of all the elements obtained in step S3, and the concentration is corrected by normalization in step S7. Do.

In order to correct the sputtering distance,
A standard sputtering rate is determined in advance using a standard sample. The first to determine this standard sputtering rate
In the embodiment, a standard sample having a composition similar to the sample is prepared, and this standard sample is sputtered under the same analysis conditions as the analysis conditions of the sample, and the cutting depth is measured after sputtering.
The sputtering rate is determined from the cutting depth and the sputtering time.

In a second mode for obtaining the standard sputtering rate, a standard sample of a thin film having a composition similar to that of the sample and having a known thickness is prepared, and this thin film standard sample is analyzed under the same analysis conditions as those of the sample. Sputtering and elemental analysis are performed, and the time from when the cutting of the thin film portion is completed to when the element of the substrate portion is detected is measured as the sputtering time, and the sputtering speed is determined from the thin film thickness and the sputtering time (step S4). .

Next, a standard value Kstd of the sputtering distance is obtained from the standard sputtering speed obtained in step S4. The standard value Kstd of the sputtering distance is a distance when sputtering is performed at a standard sputtering speed for a predetermined time. Here, a time interval between steps i can be used as the predetermined time.

Therefore, the standard sputtering rate is v
Assuming that the time interval between each step i is T, the standard value Kstd of the sputtering distance can be represented by Kstd = vstd × T (1) (step S5).

Next, the sputtering distance Ki in each step i is determined by using the total concentration value Ci of all the elements determined in step S3. This sputtering distance Ki is
Standard value Kst of the sputtering distance obtained in step S3
It can be obtained by multiplying d by the ratio of the total concentration at each measurement to the maximum total concentration during the measurement.

Here, the maximum concentration total value C during all measurements.
Since i max is represented by 100 when the concentration is weight concentration, the sputtering distance Ki can be represented by the following equation: Ki = Kstd × (Ci / Cimax) = Kstd × (Ci / 100 (2) The value Ki corrected for the variation in the sputtering distance due to the variation in the sputtering speed can be obtained. here,
(Ci / 100) represents a correction coefficient for correcting the fluctuation of the sputtering distance.

FIG. 7 shows that the sputtering distance Ki at each step i measured at equal time intervals is obtained by equation (2).
This is schematically illustrated on an axis representing a distance, and shows a relationship with a time axis.

Accordingly, the elemental analysis in the depth direction which is not affected by the fluctuation of the sputtering speed can be performed by the correction of the sputtering distance (step S).
6).

Next, the density C obtained in step S2 is normalized. Each element concentration Ca, Cb obtained in step S2
, Cc (FIG. 5) may have a total density value that varies from 100% due to a density variation. Therefore, a coefficient is determined such that the total concentration value in each step i is the same throughout all the measurements, and the coefficient is determined for each element concentration Ca,
The element concentration is normalized by multiplying b and Cc.

For example, since the total density value shown in FIG. 6 is represented by a maximum of 100, the value of the total density value is expressed in%, and the reciprocal of this value can be used as a coefficient for normalization. FIG. 8 shows a temporal change of the concentration after the normalization. In each step i, the sum of the element concentrations is 100.
(Step S7).

FIG. 9 shows steps S4 to S
6 shows a case where both the correction of the sputtering distance and the correction of the concentration in step S7 are combined. The horizontal axis shows the corrected sputtering distance, and the vertical axis shows the normalized concentration.

Therefore, according to the method of the present invention, the depth distribution of the elements contained in the sample can be corrected with respect to distance and concentration.

Further, according to the embodiment of the present invention, since the calculation of the sputtering distance can be performed without using light interference, the sputtering distance can be set regardless of whether the sample is light-transmitting or non-light-transmitting. You can ask.

[0043]

As described above, in the glow discharge optical emission spectroscopy, the fluctuation of the sputtering distance due to the fluctuation of the concentration is corrected, the fluctuation of the element concentration is standardized, and the analysis result based on the fluctuation of the concentration of the element contained in the sample is obtained. Can be corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a glow discharge optical emission spectrometer to which a correction method in glow discharge optical emission spectroscopy of the present invention can be applied.

FIG. 2 is a flowchart illustrating a procedure of a correction method in glow discharge emission spectroscopy according to the present invention.

FIG. 3 is a graph showing a temporal change in sputtering of light intensity I of each element in a sample.

FIG. 4 is a graph schematically showing an example of a calibration curve of concentration C with respect to light intensity I;

FIG. 5 is a graph showing a temporal change in concentration for each element obtained by converting light intensity into concentration.

FIG. 6 shows a total concentration value Ci obtained by adding the concentrations of the respective elements.
FIG.

FIG. 7 is a graph illustrating correction of a sputtering distance.

FIG. 8 is a graph illustrating correction for normalizing density.

FIG. 9 is a graph combining sputtering distance and concentration correction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glow discharge optical emission spectrometer, 2 ... Spectroscope, 3 ... Discharge electrode, 4 ... High frequency power supply, 5 ... Matching device, 6 ... High frequency plasma, S ... Sample.

Claims (3)

[Claims] In glow discharge emission spectroscopy for atomically detecting atomic emission while sputtering a sample surface by glow discharge and performing elemental analysis, the light intensity of each element in the elements contained in the sample is converted into a concentration. A correction method in glow discharge optical emission spectroscopy in which a total value of concentrations of all elements converted at the time of measurement is obtained, and a fluctuation in an analysis result due to a fluctuation in a sputtering rate is corrected using the total value of the concentrations. 2. In glow discharge emission spectroscopy, in which atomic emission is spectrally detected while sputtering the sample surface by glow discharge and elemental analysis is performed, the light intensity of each of the elements contained in the sample is converted into a concentration. The total concentration of all elements converted at the time of measurement is determined, and at each measurement, the ratio of the total concentration at the time of measurement to the maximum total concentration during measurement is multiplied by the sputtering distance obtained from the sputtering speed. Correction method in glow discharge emission spectroscopy for correcting fluctuations in sputtering distance due to fluctuations in sputtering speed. 3. Glow discharge emission spectroscopy for performing atomic analysis by sputter-detecting atomic emission while sputtering the sample surface by glow discharge and converting the light intensity of each of the elements contained in the sample into a concentration. The total concentration of all elements converted at the time of measurement is obtained, and at each measurement, a coefficient that makes the total concentration at the measurement the same throughout the measurement is obtained, and the coefficient is multiplied by the concentration to obtain the element concentration. Correction method in glow discharge emission spectroscopy, in which correction is performed by normalizing the fluctuation of the light emission.