JP4176535B2 - Infrared analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an infrared analyzer.
[0002]
[Prior art]
A signal (measurement signal) proportional to the infrared energy of the intrinsic absorption wavelength of the specific component gas obtained at that time by allowing the infrared light from the light source to pass through the cell in which the sample gas containing the specific component gas is introduced, Amplification of the difference from the signal (comparison signal) proportional to the infrared energy of the wavelength where there is no absorption due to the specific component gas or only negligible absorption, and the amount of infrared absorption at the measurement wavelength (specific absorption wavelength) In the infrared analysis apparatus in which the concentration of the specific component gas is obtained from the above, it is necessary to periodically perform zero point adjustment and span calibration.
[0003]
And, in order to perform zero point adjustment and span calibration in the infrared analyzer, conventionally, after zero gas is introduced into the cell and the indication is stabilized, zero point adjustment is performed, and then the span gas supplied by the gas cylinder Span calibration is performed after the indication is stabilized by introducing (a specific component gas having a predetermined known concentration) into the cell.
[0004]
[Problems to be solved by the invention]
However, many of the gas species introduced to the gas supply side of the semiconductor process and used for manufacturing the semiconductor device are not easily supplied by the gas cylinder, and in such a case, the calibration means as described above cannot be taken.
[0005]
The present invention has been made in consideration of the above points, and its purpose is to perform infrared analysis capable of performing calibration as well as measurement when the calibration gas of the specific component gas is a gas species that is not easily supplied by a gas cylinder. Is to provide a device.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the infrared analyzer of the invention according to claim 1 is an infrared analyzer having an infrared analyzer whose measurement target is a specific component gas, and for measuring the specific component gas to be measured. Wavelength and measuring wavelength detecting means for detecting two types of comparative wavelengths which are not absorbed by the specific component gas or have a negligible absorption, respectively, and the specific component gas gas introduction switching unit for switching to each other introduction into the infrared analyzer cell of Comparative gases known concentration of the infrared absorption spectrum has an absorption wavelength in the comparison wavelength do not overlap in the infrared absorption spectrum of the specific component gas及benefactor In addition, when the specific component gas is introduced into the cell of the infrared analyzer, the comparison wavelength output from the comparison wavelength detecting means Calculate the concentration measurement signal of the specific component gas by subtracting the measurement wavelength signal output from the measurement wavelength detector from the product obtained by multiplying the signal gain by the measurement time gain, while introducing the reference gas of known concentration into the cell When this is done, the comparison wavelength signal output from the comparison wavelength detector is subtracted from the product of the calibration wavelength gain multiplied by the measurement wavelength signal output from the measurement wavelength detector, and the concentration comparison signal of the comparison gas is calculated. In addition, the present invention is characterized in that it has a calculation unit that calibrates the infrared analyzer based on the calculated concentration measurement signal of the specific component gas and the concentration comparison signal of the comparison gas.
The infrared analyzer of the invention according to claim 3 is an infrared analyzer having an infrared analyzer whose measurement target is a specific component gas, the measurement wavelength of the specific component gas to be measured, and a specific component two kinds of comparative wavelength only absorption degree absorption by the gas is not or negligible, measurement wavelength detection means for detecting, respectively, and a comparative wavelength detector, the infrared absorption spectrum of the specific component gas及benefactor Is provided with a gas introduction switching unit that mutually switches the introduction of the reference gas having a known concentration having an absorption wavelength at the comparison wavelength into the infrared analyzer cell without overlapping the infrared absorption spectrum of the specific component gas, and When the specific component gas is introduced into the cell of the infrared analyzer, the comparison wavelength signal output from the comparison wavelength detection means and the measurement wave While calculating the concentration measuring signal of the specific component gas from the measured wavelength signal and measuring the time gain obtained from the signal intensity ratio of the comparison gas and the specific component gas is output from the detecting means, a reference gas of the known concentration to the cell When introduced, from the measurement wavelength signal output from the measurement wavelength detection means, the comparison wavelength signal output from the comparison wavelength detection means, and the gain at the time of calibration obtained from the signal intensity ratio of the specific component gas and the comparison gas It has a calculation unit for calculating a concentration comparison signal of the reference gas and calibrating the infrared analyzer based on the calculated concentration measurement signal of the specific component gas and the concentration comparison signal of the comparison gas. To do.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The present invention is not limited thereby.
[0008]
1 to 4 show an embodiment of the present invention.
[0009]
FIG. 1 shows a schematic configuration of an infrared analysis apparatus provided with an infrared analyzer 20 of a so-called one light source and one cell type. FIG. 2 shows a use environment of the infrared analyzer. 3A shows a gas supply state in the semiconductor process, and FIG. 3B shows an enlarged portion thereof.
[0010]
4 can not calibration gas it is easily supplied by a gas cylinder, for example, the specific component gas (measurement target gas) having a measurement wavelength of 1350cm ^-1 ~1400cm ^-1 and the infrared absorption spectrum Q of A ₁ Infrared rays of the comparative gas A ₂ having no absorption due to the specific component gas A ₁ or only negligible absorption and having an absorption wavelength as close as possible to the measurement wavelength (for example, 880 cm ^{−1 to} 920 cm ⁻¹ ). The absorption spectrum P is shown. In this embodiment, Pb (DPM) ₂ as a raw material for film formation used in a semiconductor device is sublimated to generate a specific component gas A ₁ to be measured. In this embodiment, NF ₃ gas is used as the comparison gas A ₂ that satisfies the above conditions.
[0011]
In FIG. 1, reference numeral 1 denotes a cell of the infrared analyzer 20, which includes a gas inlet 2 and a gas outlet 3, and infrared transmissive cell windows 4 and 5 are formed at both ends. 6 is a light source that emits infrared rays provided outside one cell window 4 of the cell 1 so that the infrared rays from the light source 6 pass through the cell 1 and enter a detection unit 8 described later. is there. FIG. 5 shows the light quantity characteristics of the light source 6 to be used. L is a light quantity characteristic curve. A non-dispersive infrared analyzer is used as the infrared analyzer 20.
[0012]
Reference numeral 7 denotes a modulation chopper provided between the cell 1 and the detection unit 8 and is configured to rotate by a driving mechanism (not shown). A modulation chopper 7 may be provided between the cell 1 and the light source 6.
[0013]
Reference numeral 8 denotes a detection unit provided outside the other cell window 5 of the cell 1, and mainly includes a comparison wavelength detector 10 and a measurement wavelength detector 9 arranged in parallel with each other. The measurement wavelength detector 9 includes a bandpass filter 11 that transmits infrared light having a measurement wavelength of 1350 cm ⁻¹ to 1400 cm ⁻¹ absorbed by the specific component gas A ₁ , and a measurement wavelength signal proportional to the transmitted infrared energy. (Hereinafter referred to as S signal) is output. Further, the comparative wavelength detector 10 has no absorption due to the specific component gas A ₁ or has negligible absorption, and an infrared ray having a comparative wavelength of 880 cm ⁻¹ to 920 cm ⁻¹ as close as possible to the measurement wavelength. And a comparative wavelength signal (hereinafter referred to as C signal) proportional to the transmitted infrared energy. The comparison wavelength detector 10 and the bandpass filter 12 constitute comparison wavelength detection means for detecting the comparison wavelength, and the measurement wavelength detector 9 and the bandpass filter 11 measure the measurement wavelength. A wavelength detecting means for use is configured.
[0014]
By the way, in general, various analyzers such as an infrared analyzer are used to correct errors caused by temperature drifts or changes with time in the detection unit, amplification unit, etc. It is necessary to perform point adjustment and span calibration. Among them, span calibration is performed by supplying a calibration gas of a specific component gas (measurement target gas) having a predetermined known concentration from a gas cylinder or the like to a cell.
[0015]
However, as described above, when the calibration gas for the specific component gas to be measured is a gas that is not easily supplied by the gas cylinder, the calibration means as described above cannot be taken. The present invention can be calibrated using a gas cylinder containing a calibration gas (comparison gas) having a known concentration having an approximate wavelength when the calibration gas of the specific component gas A ₁ cannot be easily supplied. is there.
[0016]
That is, the present invention is an infrared analyzer having an infrared analyzer whose measurement object is a gas A ₁ obtained by sublimating Pb (DPM) ₂ , for example, in which calibration gas is not easily supplied by a gas cylinder. analyzer, for example a measuring wavelength of 1350cm ^-1 ~1400cm ^-1, for example, as a means for detecting the two kinds of comparative wavelength of 880cm ^-1 ~920cm ^-1, the measuring wavelength detector, a wavelength detection comparator Have a means.
[0017]
In the present invention, the concentration measurement signal C of the specific component gas A ₁ and the concentration comparison signal D of the comparison gas are calculated using two wavelengths of the measurement wavelength and the comparison wavelength.
[0018]
The calculation unit 15 calculates a concentration measurement signal of a specific component gas [gas obtained by sublimating Pb (DPM) ₂ ] A ₁ and calculates a concentration comparison signal of the comparison gas (NF ₃ ) A _2. A signal switching processing function for switching the introduction of the specific component gas A ₁ and the comparison gas A ₂ into the cell 1 by, for example, a three-way solenoid valve 33, Based on the concentration measurement signal C and the concentration comparison signal D obtained repeatedly, it has a function of creating a concentration calibration curve for the specific component gas A ₁ and the comparison gas A ₂ , and has a known concentration during the measurement operation. A function for determining whether calibration of the infrared analyzer 20 is necessary based on the concentration comparison signal D ′ obtained by introducing the comparison gas A ₂ of D into the cell 1 and the concentration calibration curve.
[0019]
Further, the calculation of the concentration measurement signal C is performed by adding a measurement gain G _X to the C signal output from the comparison wavelength detecting means 10 and 12 in a state where the specific component gas A ₁ is introduced into the cell 1 of the infrared analyzer 20. The S signal output from the measurement wavelength detecting means 9 and 11 is subtracted from the product obtained by multiplying by.
That is, G _x × C signal (880 cm ^{−1 to} 920 cm ⁻¹ )
-S signal (1350cm ^-1 ~1400cm ^-1) = the concentration measuring signal of the specific component gas A ₁ ... _(1).
[0020]
The concentration comparison signal D is calculated by subtracting the C signal from the signal obtained by multiplying the S signal by the calibration gain G _C while the reference gas A ₂ having a known concentration is introduced into the cell 1. Is called.
That is, G _C × S signal (1350 cm ^{−1 to} 1400 cm ⁻¹ )
-C signal (880 cm ^{-1 to} 920 cm ^-1 ) = comparison signal of comparison gas (NF ₃ ) A ₂ (2).
[0021]
In these calculations, it is preferable that the signal intensity ratio between the specific component gas A ₁ and the comparison gas A ₂ is obtained in advance and the measurement gain G _X and the calibration gain G _C are optimized before the calculation.
[0022]
The concentration measurement signal C of the specific component gas A ₁ and the concentration comparison signal D of the comparison gas are calculated using the two wavelengths of the measurement wavelength and the comparison wavelength because the amount of infrared light emitted from the light source 6 is As shown in FIG. 5, the absorption signal amount 50 due to the specific component gas A ₁ and the absorption signal amount 51 due to the comparison gas A ₂ are extremely large, 10 to 100 times, so that the measurement wavelength band is, for example, 1350 cm ⁻¹ . with selecting 1400 cm ^-1, detected by the band-pass filter 11 having a selective light quantity detection wavelength at that time for example, 880cm ^-1 ~920cm ^-1, and wherein (1), shown in equation (2) This is because, by taking the difference as described above, elements that affect the detection sensitivity of the infrared analyzer such as the light amount of the light source can be removed.
[0023]
Thus, prior to the measurement operation of flowing the specific component gas A ₁ into the CVD chamber in the semiconductor process via the infrared analyzer, a concentration calibration curve for the specific component gas A ₁ and the comparative gas A ₂ is created.
[0024]
In this case, the container 52 in which the powder Pb (DPM) ₂ is accommodated is heated by a heater so that the specific component gas A ₁ is generated by sublimating the Pb (DPM) ₂ and the three-way solenoid valve 33 is measured. In the state switched to the line 70 side, a specific component gas A ₁ is introduced into the cell 1 using Ar as a carrier gas, and infrared rays from the light source 6 are projected onto the cell 1 to modulate by the chopper 7.
[0025]
Since the specific component gas A ₁ is flowing, the concentration measurement signal C can be obtained from the equation (1).
[0026]
Thereafter, the cell 1 is purged and the three-way solenoid valve 33 is switched from the measurement line 70 to the comparison gas supply line 80 side. These two switching operations are performed by the calculation unit 15.
[0027]
After the switching, the reference gas A ₂ having a known concentration is introduced into the cell 1, and infrared rays from the light source 6 are projected onto the reference gas A ₂ and modulated by the chopper 7.
[0028]
Since the comparison gas A ₂ is flowing, the concentration comparison signal D can be obtained from the equation (2).
[0029]
A concentration calibration curve of the specific component gas A ₁ and the comparison gas A ₂ can be created from the concentration measurement signal C and the concentration comparison signal D obtained by repeating the signal switching several times.
[0030]
Next, a measurement operation for flowing the specific component gas A ₁ into the CVD chamber through an infrared analyzer is performed.
[0031]
The specific component gas A ₁ is introduced into the cell 1, and the infrared rays from the light source 6 are projected onto the cell 1 and modulated by the chopper 7.
[0032]
Since the specific component gas A ₁ is flowing, the concentration measurement signal C is obtained from the equation (1).
[0033]
Thereafter, the cell 1 is purged and the three-way solenoid valve 33 is switched from the measurement line 70 to the comparison gas supply line 80 side. These two switching operations are performed by the calculation unit 15.
[0034]
After the switching, the reference gas A ₂ having a known concentration is introduced into the cell 1, and infrared rays from the light source 6 are projected onto the reference gas A ₂ and modulated by the chopper 7.
[0035]
Since the comparison gas A ₂ is flowing, the concentration comparison signal D ′ can be obtained from the equation (2).
[0036]
The necessity of calibration of the infrared analyzer is determined based on the concentration comparison signal D ′ and the concentration comparison signal D obtained by introducing them into the cell 1 based on the concentration calibration curve.
[0037]
When calibration is required, the span C of (D ′ / D) × C can be performed to measure the concentration C ′ of the specific component gas A ₁ that has flowed into the CVD chamber.
[0038]
As described above, in many cases, the gas in the semiconductor process is such that the calibration gas (comparison gas) A ₂ is not easily supplied by a gas cylinder or the like, but as described above, the comparison wavelength is as close to the measurement wavelength as possible. The measurement wavelength detection means 9 and 11 and the comparison wavelength detection means 10 and 12 for detecting two wavelengths of the measurement wavelength and the comparison wavelength are provided, and when measuring the concentration of the specific component gas A ₁ By using the equation (1) and using the equation (2) when measuring the concentration of the reference gas A ₂ , an infrared analyzer having a calibration function and a measurement function can be obtained with a simple configuration.
[0039]
Each of the S signal and the C signal represents the total light amount of the optical system. For example, a decrease in the light amount due to contamination of the optical path (indicated by L ′ in FIG. 5) is an output signal of the S signal or C signal. Further, the alarm signal may be generated when the initial light amount is reduced to a predetermined light amount (alarm level) due to contamination of the optical path, for example.
[0040]
【The invention's effect】
As described above, according to the present invention, when the calibration gas for the specific component gas is a gas species that is not easily supplied by the gas cylinder, there is an effect that it is possible to provide an infrared analyzer that can perform calibration as well as measurement.
[Brief description of the drawings]
FIG. 1 is an overall configuration explanatory view showing an embodiment of the present invention.
FIG. 2 is a configuration explanatory diagram showing a use environment in the embodiment.
FIG. 3A is a diagram showing a gas supply state in a semiconductor process.
FIG. 3B is an enlarged view of a part of FIG.
FIG. 4 is a characteristic diagram showing infrared absorption spectra of a specific component gas (measurement target gas) and a comparative gas.
FIG. 5 is a diagram showing an absorption signal amount by a specific component gas and an absorption signal amount by a comparative gas.
[Explanation of symbols]
1 ... cell, 9,11 ... measuring wavelength detection means, 10, 12 ... comparison wavelength detection means, 15 ... operation unit, 20 ... infrared analyzer, 33 ... three-way electromagnetic valve, A ₁ ... specific component gas, A ₂ ... comparative gas.

Claims (3)

An infrared analyzer having an infrared analyzer for measuring a specific component gas, the wavelength for measurement of the specific component gas to be measured and the absorption by the specific component gas is not absorbed or negligible two kinds of comparative wavelength, measuring the wavelength detection means for detecting, respectively, and, the comparison with comparative wavelength detector, the infrared absorption spectrum of the specific component gas及patron is not overlap the infrared absorption spectrum of the specific component gas A gas introduction switching unit for mutually switching the introduction of the reference gas having a known concentration having an absorption wavelength at the wavelength for use into the cell of the infrared analyzer, and when the specific component gas is introduced into the cell of the infrared analyzer The output from the measurement wavelength detection means is obtained by multiplying the comparison wavelength signal output from the comparison wavelength detection means by the gain at the time of measurement. When the reference gas having a known concentration is introduced into the cell, the measurement wavelength signal output from the measurement wavelength detector is calibrated. The comparison wavelength signal output from the comparison wavelength detection means is subtracted from the product multiplied by the gain to calculate the concentration comparison signal of the comparison gas, and the calculated concentration measurement signal of the specific component gas and the comparison gas An infrared analyzer having an arithmetic unit for calibrating an infrared analyzer based on a concentration comparison signal.   Prior to the measurement operation for introducing the specific component gas to the gas supply side of the semiconductor process, the arithmetic unit repeats the switching of the introduction of the specific component gas and the comparison gas several times, and the concentration measurement signal and the concentration comparison signal are obtained. A concentration calibration curve for the specific component gas and the comparison gas based on the above, and the concentration comparison signal and the concentration calibration curve obtained by introducing the reference gas of the known concentration into the cell during the measurement operation. The infrared analyzer according to claim 1, having a function of determining whether calibration of the infrared analyzer is necessary based on the function. An infrared analyzer having an infrared analyzer for measuring a specific component gas, the wavelength for measurement of the specific component gas to be measured and the absorption by the specific component gas is not absorbed or negligible two kinds of comparative wavelength, measuring the wavelength detection means for detecting, respectively, and, the comparison with comparative wavelength detector, the infrared absorption spectrum of the specific component gas及patron is not overlap the infrared absorption spectrum of the specific component gas A gas introduction switching unit for mutually switching the introduction of the reference gas having a known concentration having an absorption wavelength at the wavelength for use into the cell of the infrared analyzer, and when the specific component gas is introduced into the cell of the infrared analyzer , measurement wavelength signals and JP output from comparator wavelength signal and the measuring wavelength detecting means is outputted from the comparison wave detecting means While calculating the concentration measurement signal of the specific component gas from the measurement gain obtained from the signal intensity ratio of the component gas and the comparison gas, when the reference gas of the known concentration is introduced into the cell, the measurement wavelength detection means Calculating a comparison gas concentration comparison signal from the output measurement wavelength signal, the comparison wavelength signal output from the comparison wavelength detection means, and the gain at the time of calibration obtained from the signal intensity ratio between the specific component gas and the comparison gas; and An infrared analysis apparatus comprising a calculation unit for calibrating the infrared analyzer based on the calculated concentration measurement signal of the specific component gas and the concentration comparison signal of the comparison gas.

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