JP2016138798A - Film thickness measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film thickness measurement device with which it is possible to freely move an infrared beam irradiation position on a sample during measurement.SOLUTION: A film thickness measurement device 10 is a film thickness measurement device based on infrared spectroscopy, the device comprising a light emission unit 1 for emitting an infrared beam, a detector 2 for detecting the infrared beam routed via a sample S, and mirrors 3, 4 (light guide means) for guiding the infrared beam from the light emission unit 1 to the detector 2 via the sample S, the mirrors 3, 4 being able to move relatively to the light emission unit 1, the detector 2, and the sample S, making it possible to move an infrared beam irradiation position.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a film thickness measuring apparatus, and more particularly to a film thickness measuring apparatus using infrared spectroscopy.

  A film thickness measuring apparatus using infrared spectroscopy is used for measuring various film thicknesses. For example, Patent Document 1 describes a method of measuring the film thickness of a single crystal thin film on an SOI substrate using a Fourier transform infrared spectrophotometer.

Japanese Patent Laid-Open No. 5-308096

  Since the infrared spectrophotometer described in Patent Document 1 does not have a mechanism for moving the emission position of the infrared light beam, the irradiation position of the infrared light beam on the sample cannot be freely moved during the measurement. Therefore, the infrared spectrophotometer described in Patent Document 1 cannot quickly measure the film thickness at a plurality of positions on the sample, and it has been difficult to perform in-line film thickness measurement.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a film thickness measuring apparatus that can freely move the irradiation position of the infrared light beam on the sample during the measurement. .

The film thickness measuring device of the present invention is
An apparatus for measuring film thickness by infrared spectroscopy,
A light emitting unit for emitting infrared luminous flux;
A detector for detecting the infrared luminous flux passing through the sample;
A light guide means for guiding the infrared light flux from the light emitting unit to the detector via the sample, and
The light guide means can move the position where the infrared light beam is irradiated by moving with respect to the light emitting unit, the detector, and the sample.

  In the film thickness measuring apparatus of the present invention, the position where the infrared light beam is irradiated can be moved by moving the light guiding means relative to the light emitting unit, the detector and the sample. Thereby, the film thickness measuring apparatus of this invention can move the irradiation position of the infrared light beam on a sample freely during a measurement.

  ADVANTAGE OF THE INVENTION According to this invention, the film thickness measuring apparatus which can move freely the irradiation position of the infrared light beam on a sample during a measurement can be provided.

1 is a side view showing a film thickness measuring apparatus according to Embodiment 1. FIG. 1 is a plan view showing a film thickness measuring apparatus according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an internal configuration of a light emitting unit according to Embodiment 1. 3 is a flowchart showing a method for determining a quality of a thin film sample using the film thickness measuring apparatus according to the first embodiment. Wavenumber is a diagram showing the infrared spectrum of the electrolyte layer in the range of 900 cm ^-1 from 1500 cm ^-1. Wavenumber is a diagram showing the infrared spectrum of the reinforcing layer in the range of 450 cm ^-1 from 1250 cm ^-1. It is a figure which shows the calibration curve of the peak near wave number 990cm < ^-1 >. It is a figure which shows the calibration curve of the peak near wave number 1325cm- ¹ . It is the figure which put the calculation result of the peak area of a non-defective part and a defective part on the calibration curve shown in FIG. It is a figure which shows the result of having calculated the thickness of the electrolyte membrane in a non-defective part and a defective part by changing the conveyance speed of an electrolyte membrane. It is a figure which shows an example of the irradiation position of the infrared light beam in the film thickness measurement by traverse measurement. It is a figure which shows an example of the film thickness measurement result of the electrolyte layer by traverse measurement.

[Embodiment 1]
Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the film thickness measuring apparatus 10 according to the present embodiment includes a light emitting unit 1, a detector 2, mirrors 3 and 4, a stage 5, and a control unit (not shown). And having. The film thickness measuring device 10 measures the film thickness of the sample S by infrared spectroscopy. The film thickness measuring device 10 is a film thickness measuring device using a spectrophotometer, and the light emitting unit 1, the detector 2, and the mirrors 3 and 4 constitute a spectrophotometer. The sample S is placed on the stage 5 and the film thickness is measured.

The light emitting unit 1 emits an infrared light beam. Preferably infrared light beam emitted from the light emitting unit 1 is a parallel light beam, the wavelength of the infrared light beam is preferably in the range to be 400 cm ^-1 wave number 4000 cm ^-1. The infrared light beam may be a condensed light beam, but the parallel light beam can increase the spot diameter for irradiating light. The detector 2 detects the intensity of the infrared light beam after passing through the sample S. In the present embodiment, the intensity of the infrared light beam transmitted through the sample S is detected.

  As shown in FIG. 3, when using Fourier Transform Infrared Spectroscopy (FT-IR), the light emission unit 1 includes an infrared light source 11, a beam splitter 12, a fixed mirror 13, and the like. And a movable mirror 14. The infrared light source 11, the beam splitter 12, the fixed mirror 13, and the moving mirror 14 are arranged so as to constitute a Michelson interferometer.

  The infrared light source 11 is a light source that emits infrared light. For example, a high-luminance ceramic light source is preferably used. The beam splitter 12 divides the optical path of the incident light beam into two. The intensity of the light beam split by the beam splitter 12 is about half that at the time of incidence. The fixed mirror 13 is a mirror that reflects the light beam, and the light reflected by the fixed mirror 13 becomes reference light. The movable mirror 14 is a mirror that reflects a light beam, and can move in a direction along the optical axis. Interference light is generated by the light beam R2 reflected by the movable mirror 14 and the light beam R1 of the reference light. The intensity of the interference light detected by the detector 2 varies depending on the amount of movement of the movable mirror 14.

  As shown in FIG. 1, the mirrors 3 and 4 guide the infrared light beam emitted from the light emitting unit 1 to the detector 2 via the sample S. The pair of mirrors 3 and 4 are disposed with the sample S in between, one mirror 3 is disposed on the light emitting unit 1 side, and the other mirror 4 is disposed on the detector 2 side. The pair of mirrors 3 and 4 serve as a light guide means from the light emitting unit 1 to the detector 2.

  The mirrors 3 and 4 can move the position where the infrared light beam is irradiated by moving on the sample S. In the film thickness measuring apparatus 10 according to the present embodiment, the mirrors 3 and 4 can move in the X-axis direction in the figure. For example, it is good also as a structure which the mirrors 3 and 4 move, when the support member which supports the mirrors 3 and 4 slides on a rail.

  The film thickness measuring apparatus 10 can move the sample S on the stage 5 in the Y-axis direction. A configuration in which the stage 5 on which the sample S is placed moves on a rail may be used, or a configuration in which the stage 5 is on a belt conveyor and the sample S moves in the Y-axis direction by the belt conveyor may be used.

  The film thickness measuring device 10 can perform line measurement and traverse measurement by changing the movement pattern of the irradiation position of the infrared light beam on the sample S. In line measurement, the position of the mirrors 3 and 4 in the X-axis direction is fixed, and the sample S is moved in the Y-axis direction. In traverse measurement, the mirrors 3 and 4 are moved in the X-axis direction, and the sample S is moved in the Y-axis direction.

  The control unit controls the movement of the mirrors 3 and 4 and calculates an infrared spectrum from the detection result of the detector 2. In the case of FT-IR, an infrared spectrum is calculated by performing Fourier transform on the detection result of the detector 2. As the control unit, for example, a personal computer (PC) having a CPU (Central Processing Unit) can be used. By executing a specific program on the personal computer, the mirrors 3 and 4 can be controlled and the infrared spectrum can be calculated.

  The quality determination method for a thin film sample using the film thickness measuring apparatus 10 according to the present embodiment will be described with reference to FIG. First, the mirrors 3 and 4 are moved so that the irradiation position of the infrared light beam comes to the background measurement area AB in FIG. 2, and enters the detector 2 in a state where the sample S is not irradiated with the infrared light beam. The intensity of the infrared light beam is measured, and the background is measured (ST401).

  Next, the mirrors 3 and 4 are moved on the sample S so that the desired measurement position on the sample S is irradiated with the infrared light beam, and the irradiation position of the infrared light beam is moved (ST402). Then, a desired measurement position on the sample S is irradiated with an infrared beam, the infrared beam transmitted through the sample S is detected by the detector 2, and an infrared spectrum is measured (ST403).

Next, the peak area of a peak appearing in the vicinity of a predetermined wave number is calculated from the measurement result of the infrared spectrum (ST404). For example, an area surrounded by a peak generated in the vicinity of a wave number of 1500 cm ⁻¹ to 900 cm ⁻¹ is calculated.

  Next, the film thickness of the sample S is calculated by comparing the calculated peak area with the peak area in the calibration curve prepared in advance (ST405). The calibration curve is created by measuring an infrared spectrum of a plurality of samples S with known film thicknesses, calculating their peak areas, and determining an approximate straight line between the film thickness and the peak area.

  Next, it is determined whether the calculated film thickness falls within a predetermined reference range (ST406). If the calculated film thickness is not within the reference range (NO in ST406), the sample S is determined to be defective (ST409), and the measurement is terminated.

  If the calculated film thickness is within the reference range (YES in ST406), it is determined whether infrared spectra have been calculated for all measurement positions (ST407). If it is determined that the infrared spectrum has not been calculated for all positions (NO in ST407), the irradiation position is moved to the next measurement position (ST402), and the infrared spectrum is measured at the next measurement position (ST403). When it is determined that infrared spectra have been calculated for all positions (ST407 YES), the sample S is determined to be non-defective (ST408), and the measurement is terminated.

  As described above, according to the film thickness measuring device 10 according to the present embodiment, the mirrors 3 and 4 (light guiding means) move with respect to the light emitting unit 1, the detector 2, and the sample S. The position where the infrared light beam is irradiated can be moved. Thereby, the film thickness measuring apparatus 10 of the present invention can freely move the irradiation position of the infrared light beam on the sample S during the measurement.

An example in which a polymer electrolyte membrane for a fuel cell is used as the sample S will be described. The electrolyte membrane has a configuration in which an electrolyte layer and a reinforcing layer are bonded to each other. The infrared spectrum which permeate | transmitted the electrolyte layer or the reinforcement layer with the film thickness measuring apparatus 10 was measured. 5 and 6 show examples of infrared spectra measured by the film thickness measuring device 10. FIG. 5 and 6, the horizontal axis is the wave number [cm ⁻¹ ], and the vertical axis is the absorbance. The infrared spectra shown in FIG. 5 and FIG. 6 are average values of the results obtained by measuring three locations for samples having the same film thickness.

FIG. 5 shows an infrared spectrum of the electrolyte layer in the wave number range of 1500 cm ⁻¹ to 900 cm ⁻¹ . Electrolyte layer for a fuel cell is a fluorine-based polymer having a sulfonic acid group (-SO _2), the wave number ^1325cm -1 IR spectrum of the electrolyte layer that corresponds to a sulfonic acid group, having a peak around 900 cm ^-1.

FIG. 6 shows an infrared spectrum of the reinforcing layer in the wave number range of 1250 cm ⁻¹ to 450 cm ⁻¹ . The reinforcing layer for the fuel cell is polytetrafluoroethylene (PTFE), and the infrared spectrum of the reinforcing layer has a peak near a wave number of 556 cm ⁻¹ corresponding to —CF ₂ —.

Next, a calibration curve used for film thickness measurement was created. FIG. 7 is a diagram showing a calibration curve of a peak in the vicinity of a wave number of 990 cm ⁻¹ . FIG. 8 is a diagram showing a calibration curve of a peak in the vicinity of a wave number of 1325 cm ⁻¹ . An infrared spectrum was measured for an electrolyte membrane (sample S) having a plurality of known film thicknesses, and a peak area of the infrared spectrum was measured. The electrolyte membrane having an electrolyte layer thickness of 5.0 μm, 8.0 μm, 9.0 μm, 10.0 μm was used. The calibration curve was created by plotting the relationship between the film thickness and the peak area and obtaining an approximate straight line. 7 and 8, the correlation coefficient of the approximate line is r ² = 0.999.

When the calibration curves shown in FIGS. 7 and 8 were created, the peak areas were measured at five locations in each sample, and the average value thereof was used. 7 and 8 show the maximum value and the minimum value of the peak area in each sample as an error range (error bar). In the measurement of the infrared spectrum, the wave number is in the range of 4000 cm ⁻¹ to 400 cm ⁻¹ , the moving speed of the mirrors 3 and 4 is 20 mm / sec, and the measurement speed is 1.2 sec / 2 data.

Next, for the non-defective part and the defective part of the electrolyte membrane having an electrolyte layer thickness of 10.0 μm, the infrared spectrum was measured in a state where the electrolyte membrane was stationary, and the peak area of the peak near the wave number of 990 cm ⁻¹ was calculated. . Here, the defective portion refers to a portion where the electrolyte layer is not present on the surface of the electrolyte membrane and the reinforcing layer is exposed.

  FIG. 9 is a diagram in which the calculation results of the peak areas of the non-defective part and the defective part are placed on the calibration curve shown in FIG. In FIG. 9, the non-defective part is indicated by a circle and the defective part is indicated by a cross. As shown in FIG. 9, the peak area of the non-defective part is almost on the calibration curve, but the peak area at the defective part is off the calibration curve.

  Next, while fixing the positions of the mirrors 3 and 4 and moving only the electrolyte membrane, infrared spectra were acquired at intervals of 1.2 seconds, and the thickness of the electrolyte layer was calculated. FIG. 10 shows the result of calculating the thickness of the electrolyte layer in the non-defective part and the defective part by changing the transport speed of the electrolyte membrane. In FIG. 10, the non-defective part is indicated by a circle and the defective part is indicated by a cross. In FIG. 10, even when the conveyance speed was 10 m / min, a difference in the thickness of the electrolyte layer calculated by FT-IR was observed between the non-defective part and the defective part. Thereby, even when the conveyance speed is 10 m / min, it can be said that the quality of the electrolyte layer can be judged by FT-IR, and the film thickness measuring apparatus 10 according to the present embodiment is effective for the quality judgment in-line. It has been shown.

  Next, the film thickness was measured by traverse measurement while moving the mirrors 3 and 4 in the X-axis direction and the electrolyte membrane in the Y-axis direction. As shown in FIG. 11, the irradiation position of the infrared luminous flux was moved zigzag on the electrolyte membrane, the infrared spectrum at each point was measured, and the thickness of the electrolyte layer was calculated.

  FIG. 12 shows an example of a film thickness measurement result by traverse measurement. When the film thickness is measured sequentially from the first measurement position in FIG. 11, the film thickness at the 25th measurement position is smaller than the film thickness at the other measurement positions. From this, it can be seen that the measurement position No. 25 is a defective part.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the present invention is not limited to a film thickness measurement apparatus using Fourier transform infrared spectroscopy (FT-IR), but can be applied to a film thickness measurement apparatus using other infrared spectroscopy. it can. Further, the present invention is not limited to the film thickness measuring device that detects the infrared light beam transmitted through the sample S, but is also applied to the film thickness measuring device that detects the infrared light beam reflected by the sample S. Can do.

DESCRIPTION OF SYMBOLS 1 Light emission unit 2 Detector 3, 4 Mirror 5 Stage 10 Film thickness measuring apparatus 11 Infrared light source 12 Beam splitter 13 Fixed mirror 14 Moving mirror AB Background measurement area S Sample

Claims (1)

An apparatus for measuring film thickness by infrared spectroscopy,
A light emitting unit for emitting infrared luminous flux;
A detector for detecting the infrared luminous flux passing through the sample;
A light guide means for guiding the infrared light flux from the light emitting unit to the detector via the sample, and
The said light guide means can move the position which irradiates the said infrared light beam by moving with respect to the said light emission unit, the said detector, and the said sample.

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