JP2011007700A - Surface state inspection apparatus using photoelectric effect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface state inspection apparatus using the photoelectric effect and capable of acquiring temporally stable OSEE signals.SOLUTION: The surface state inspection apparatus includes: an ultraviolet generating source for generating ultraviolet light; a photoelectron collecting part for collecting photoelectrons discharged from the surface of metal by the irradiation of ultraviolet light; an amplification part for amplifying a photocurrent acquired from the photoelectron collecting part; and a band passing means for passing only a spectral component in a region in the vicinity of 185 nm among ultraviolet light generated by the ultraviolet generating source and is constituted in such a way as to irradiate ultraviolet light passed through the band passing means to the surface of metal to be inspected.

Description

  The present invention relates to a surface condition inspection apparatus using a photoelectric effect generated by irradiating a metal surface with ultraviolet rays.

  Ultraviolet (UV) light is applied to metal surfaces such as general metal surfaces and wafer surfaces to detect dirt and oil, and to measure the thickness of lubricant applied to the magnetic disk surface. Irradiation with light, thereby measuring photoelectrons emitted by the photoelectric effect. This technique is known as, for example, Patent Documents 1 and 2 as a surface quality inspection method and lubricant film thickness measurement method using OSEE (Optically Stimulated Electron Emission).

  In addition, a surface condition inspection apparatus for inspecting the state of a metal surface in a non-contact manner using this OSEE is actually on the market and is used as a surface quality monitor.

JP-A-60-257343 JP 2004-095025 A

  Such a surface condition inspection apparatus irradiates UV light having a spectral component in the ultraviolet region from a UV generation source such as a mercury lamp, collects photoelectrons emitted from the metal surface by the photoelectric effect, obtains an OSEE signal, and emits it. It is configured to measure the amount of electrons that are generated.

  However, according to the conventional surface condition inspection apparatus, there is a large difference in the stability of the obtained OSEE signal depending on the position of the metal surface. That is, there is a surface region in which the obtained OSEE signal is stable in time and a surface region in which the OSEE signal is unstable in time, and why a region in which the OSEE signal fluctuates greatly according to the elapsed time is generated. The cause was unknown.

  Accordingly, an object of the present invention is to provide a surface condition inspection apparatus using a photoelectric effect that can obtain a more stable OSEE signal in terms of time.

  According to the present invention, a UV source that generates UV light, a photoelectron collector that collects photoelectrons emitted from the metal surface when irradiated with UV light, and a photocurrent obtained from the photoelectron collector are amplified. And a band pass means for passing only the spectral components in the region near 185 nm of the UV light generated by the UV generation source, and the metal to be inspected by the UV light that has passed through the band pass means A surface condition inspection apparatus using a photoelectric effect configured to be irradiated on a surface is provided.

  Of the UV light generated by the UV source, only the spectral components in the region near 185 nm are passed, and the other spectral components of the UV light are blocked by the band pass means and are not irradiated on the metal surface. That is, only the spectral component near 185 nm that contributes to photoelectron emission and thus contributes to the acquisition of the OSEE signal is irradiated on the metal surface, and the spectral component near 254 nm and other spectral components are not irradiated on the metal surface.

  The inventor of the present application has been diligently researching the conventional surface condition inspection apparatus in order to pursue the cause of the surface area where the obtained OSEE signal is stable and unstable over time. However, this phenomenon is caused when ozone is decomposed with a specific force of spectral components near 254 nm to generate oxygen atoms and oxygen molecules when spectral components near 185 nm and 254 nm are irradiated on the metal surface. I inferred that it was a major cause. The UV generation source used in the present invention, such as a low-pressure mercury lamp, has a spectral component in the vicinity of at least 185 nm and 254 nm. When the spectral component in the vicinity of 254 nm is irradiated on the metal surface, the OSEE signal is output. We found that pulsation occurred. That is, ozone generation and ozonolysis occur due to the irradiation of spectral components near 254 nm, and the generation of oxygen atoms with strong oxidizing power constantly causes decomposition of the oxide film on the measurement surface, which generates pulsation of the OSEE signal. I found out that this is the cause. Therefore, by configuring such that only the spectral component near 185 nm effective for obtaining the photoelectric effect is irradiated and the harmful spectral component near 254 nm is not irradiated, OSEE more stable in time over the entire metal surface. A signal can be obtained.

  It is preferable that the band-pass means is a band-pass optical filter provided in the passage of UV light from the UV generation source.

  The UV source is preferably a low pressure mercury lamp or a semiconductor light source.

  It is also preferable to further include bias means for biasing the photoelectron collecting unit to a positive potential with respect to the metal surface.

  According to the present invention, a more stable OSEE signal can be obtained over time over the entire metal surface.

It is a figure which shows roughly the one part structure in one Embodiment of the surface state inspection apparatus of this invention. It is a characteristic view which shows the transmission characteristic of the band pass optical filter used in embodiment of FIG. It is a characteristic view which shows the OSEE signal characteristic of the aluminum sample measured with the conventional surface state inspection apparatus, and its regression line. It is a characteristic view which shows the OSEE signal characteristic of the aluminum sample measured with the surface state inspection apparatus of this invention, and its regression line. It is a characteristic view which shows the OSEE signal characteristic of the bronze sample measured with the conventional surface state inspection apparatus, and its regression line. It is a characteristic view which shows the OSEE signal characteristic of the bronze sample measured by the surface state inspection apparatus of this invention, and its regression line. It is a characteristic view which shows the OSEE signal characteristic of the white copper sample measured with the conventional surface state inspection apparatus, and its regression line. It is a characteristic view which shows the OSEE signal characteristic of the white copper sample measured with the surface state inspection apparatus of this invention, and its regression line.

  FIG. 1 schematically shows a part of the configuration of an embodiment of the surface condition inspection apparatus according to the present invention, in which (A) is a schematic perspective view of a sensor head portion, and (B) is an axis of a tip portion of the sensor head. Sectional drawing and (C) are top views of the front-end | tip part of a sensor head.

  In these drawings, 10 is a sensor head, 11 is a control and display unit connected to the sensor head 10, 12 is a housing of the sensor head 10, and 13 is a low pressure that is a UV generation source mounted inside the sensor head 10. A mercury lamp, 14 is an anode electrode for collecting photoelectrons provided at the tip of the sensor head 10, 15 is a band-pass optical filter covering the through hole 14 a of the anode electrode 14, and 16 is an amplification provided in the sensor head 10. Reference numeral 17 denotes a bias circuit provided in the sensor head 10.

  The low-pressure mercury lamp 13 includes a lamp main body 13a and a light emitting unit 13b, is driven by a high voltage supplied from the control and display unit 11, and has UV light having spectral components in the vicinity of at least 185 nm, 254 nm, and 365 nm. Radiate.

  The anode electrode 14 has a ring shape having a circular through hole 14a (in this embodiment, a diameter of 6 mm) in the center, and is made of stainless steel. The anode electrode 14 constitutes a photoelectron collector that collects photoelectrons emitted from the metal surface to be inspected by the photoelectric effect, and is biased to a positive potential by the bias circuit 17 from the metal surface. Specifically, when the metal surface is grounded, a positive DC bias voltage is applied from the bias circuit 17.

  The anode electrode 14 is connected to a high gain amplifier circuit 16 via a bias circuit 17, and a photocurrent based on the photoelectrons collected by the anode electrode 14 is amplified by the amplifier circuit 16, and is about 1 to 5V. The OSEE signal is obtained. This OSEE signal is output to the control and display unit 11 and processed as a detection signal for surface quality inspection of the metal surface or for lubricant film thickness measurement.

  The UV light from the low-pressure mercury lamp 13 is radiated to the outside of the housing 12 through the through hole 14a of the anode electrode 14. In this embodiment, the band-pass optical filter 15 passes through the opening of the through hole 14a. It is adhered to the anode electrode 14 so as to cover it. Therefore, the UV light always passes through the band-pass optical filter 15.

  This band-pass optical filter 15 is a band-pass filter that allows only a spectral component in a region near 185 nm to pass. In this embodiment, a UV band-pass filter FN185-N-5D manufactured by Acton Optics & Coating is used. Yes. This band pass filter has a pass band with a peak wavelength of 185 ± 2.5 nm. FIG. 2 shows the transmittance versus frequency characteristic of this band-pass filter.

  However, as the band-pass optical filter 15, other types of filters may be used as long as they pass only the spectral components in the region near 185 nm. Further, in the present embodiment, the band-pass optical filter 15 is fixed to the outside of the anode electrode 14, but the installation position may be anywhere as long as it is provided in the UV light passage. Furthermore, a band-selective reflector other than a filter may be used as long as it allows band-pass.

  Thus, according to this embodiment, the bandpass optical filter 15 irradiates only the spectral component in the region near 185 nm to the metal surface to be inspected. Since the photoelectric effect is caused by the spectral component in the vicinity of 185 nm, the emitted photoelectrons can be collected by the anode electrode 14 to obtain an OSEE signal. At that time, since the spectral component in the vicinity of 254 nm is not irradiated on the metal surface, ozone is decomposed by the unique force of the spectral component in the vicinity of 254 nm by irradiating the metal surface with both of the spectral components in the vicinity of 185 nm and 254 nm. Oxygen atoms and oxygen molecules are generated, and the metal surface can be effectively prevented from being oxidized. That is, ozone generation and ozone decomposition occur due to irradiation of spectral components in the vicinity of 254 nm, and the OSEE signal pulsates due to generation of oxide film decomposition on the measurement surface due to generation of strong oxidizing oxygen atoms. This can be prevented in advance, and a more stable OSEE signal can be obtained in time over the entire metal surface.

  In addition to the low-pressure mercury lamp, a UV light source that generates UV light includes a UV light source, a semiconductor light-emitting source such as a UV light emitting diode (LED) element, a UV laser source that generates UV laser light, or a visible light that has been generated. A visible light laser source having means for converting light into UV laser light may be used.

  Next, the result verified about the effect of the surface state inspection apparatus of this embodiment is demonstrated.

  FIG. 3 and FIG. 4 are characteristic diagrams respectively showing OSEE signal characteristics of an aluminum sample and its regression line measured by the conventional surface condition inspection apparatus and the surface condition inspection apparatus of the present embodiment. In these figures, the horizontal axis represents the time (seconds) from the measurement start time, and the vertical axis represents the OSEE signal (V / 200).

  Actually, as the conventional surface condition inspection apparatus, an apparatus obtained by removing the band-pass optical filter 15 from the surface condition inspection apparatus of this embodiment is used. However, the distance between the sample surface and the anode electrode 14 was kept constant for all samples regardless of the presence or absence of a filter.

  For measurement by the surface condition inspection apparatus of the conventional and this embodiment, 10 aluminum samples (100% aluminum) are prepared, and each sample is thoroughly cleaned with isopropyl alcohol before measurement, and then dried. Measurement was started after a certain period of time. When starting the measurement, it was confirmed that the cleanliness of the sample was within a certain range by irradiating light UV light first. In order to obtain a measurement result, in addition to 60 seconds which is the measurement time of one sample, about 90 seconds are required including data confirmation and sample replacement. By shortening this time as much as possible, consideration was given so as to prevent the natural oxide film from adhering to the sample surface and to attenuate the OSEE signal as much as possible, and to prevent errors in measurement. Moreover, UV light was measured with a UV meter at the measurement start time and measurement end time, and it was confirmed that the amount of change in UV light during the measurement period was within 1%. For this measurement, a UV meter sensitive to a wavelength of 254 nm was used. According to the report of the manufacturer of the low-pressure mercury lamp 13, the attenuation characteristics of the spectral component at 185 nm and the spectral component at 254 nm are linked to each other. Therefore, by observing the slow fluctuation of the spectral component at 254 nm, It is possible to know indirectly whether or not there is a change in spectral components.

  In most cases, the OSEE signal has a tendency to rise rapidly immediately after irradiation with UV light, and then to fall rapidly, regardless of the presence or absence of a filter. After 5 to 6 seconds from the start of irradiation, it became clear that a stable OSEE signal could be obtained with or without a filter, so only data from 5 to 6 seconds after the start of measurement that is meaningful as data was obtained. It is represented. The measurement was completed until 60 seconds had elapsed from the start. From the measurement start to the measurement end, the same position of the same sample was continuously measured, and this measurement was performed on 10 different samples. There are 10 when there is a filter and 10 when there is no filter. There is some variation in the absolute value of the OSEE signal because there are some dirt and inherent aging differences between individual samples.

The linear regression equation in the case of no filter in FIG. 3 is as follows.
(A) y = −0.0225x + 78.539, R ² = 0.1447,
(B) y = 0.068x + 75.592, R ² = 0.0054,
(C) y = −0.0381x + 47.030, R ² = 0.3730,
(D) y = −0.1594x + 68.552, R ² = 0.7484,
(E) y = −0.1889x + 74.179, R ² = 0.8143,
(F) y = −0.1149x + 86.366, R ² = 0.6402,
(G) y = −0.0712x + 62.820, R ² = 0.4757,
(H) y = 0.0613x + 54.311, R ² = 0.5994,
(I) y = 0.2338x + 88.009, R ² = 0.2945,
(J) y = −0.1203x + 83.734, R ² = 0.7738.

The linear regression equation with the filter in FIG. 4 is as follows.
(A) y = −0.1036x + 85.649, R ² = 0.6546,
(B) y = −0.0719x + 65.675, R ² = 0.5290,
(C) y = −0.0082x + 116.02, R ² = 0.0073,
(D) y = −0.0992x + 115.76, R ² = 0.6743,
(E) y = −0.0526x + 126.53, R ² = 0.1454,
(F) y = −0.0125x + 130.34, R ² = 0.0144,
(G) y = −0.0278x + 131.76, R ² = 0.0787,
(H) y = −0.0488x + 125.23, R ² = 0.2424,
(I) y = −0.0473x + 86.329, R ² = 0.2702,
(J) y = −0.0784x + 106.43, R ² = 0.4302.

  The average of the slope (absolute value) of the linear regression equation without filter in FIG. 3 is 0.1017, whereas the average of the slope (absolute value) of the linear regression equation with filter in FIG. Was a much smaller 0.0550.

  5 and 6 are characteristic diagrams respectively showing the OSEE signal characteristic of the bronze sample and its regression line measured by the conventional surface state inspection apparatus and the surface state inspection apparatus of the present embodiment. In these figures, the horizontal axis represents the time (seconds) from the start of measurement, and the vertical axis represents the OSEE signal (V / 200).

  Ten bronze samples (copper 95%, zinc 4%, tin 1%) were prepared for the measurement by the surface condition inspection apparatus of the conventional and this embodiment, and the surface of each sample was carefully cleaned with isopropyl alcohol before measurement. And then, after drying, measurement was started after a certain period of time.

  Other measurement methods are the same as those of the aluminum sample shown in FIGS.

The linear regression equation without filter in FIG. 5 is as follows.
(A) y = −0.4848x + 237.01, R ² = 0.8334,
(B) y = −0.7383x + 318.06, R ² = 0.8264,
(C) y = −0.3643x + 193.85, R ² = 0.8459,
(D) y = −0.4851x + 372.73, R ² = 0.8257,
(E) y = −0.0923x + 107.34, R ² = 0.3665,
(F) y = −0.7143x + 309.07, R ² = 0.9755,
(G) y = −0.5211x + 295.36, R ² = 0.8541,
(H) y = −0.6472x + 284.14, R ² = 0.9757,
(I) y = −0.6073x + 292.59, R ² = 0.9695,
(J) y = −0.5681x + 228.77, R ² = 0.9789.

The linear regression equation with the filter in FIG. 6 is as follows.
(A) y = −0.1840x + 418.57, R ² = 0.7177,
(B) y = −0.0075x + 320.94, R ² = 0.0004,
(C) y = −0.1812x + 421.65, R ² = 0.9060,
(D) y = −0.1313x + 380.22, R ² = 0.8634,
(E) y = −0.2060x + 401.26, R ² = 0.8955,
(F) y = −0.1376x + 359.83, R ² = 0.8583,
(G) y = −0.2181x + 423.66, R ² = 0.8677,
(H) y = −0.1437x + 382.70, R ² = 0.7961,
(I) y = −0.1313x + 380.22, R ² = 0.8634,
(J) y = −0.0994x + 371.46, R ² = 0.6599.

  The average of the slope (absolute value) of the linear regression equation without filter of FIG. 5 is 0.5223, whereas the average of the slope (absolute value) of the linear regression equation with filter of FIG. Was 0.1440, much smaller than this.

  FIGS. 7 and 8 are characteristic diagrams showing OSEE signal characteristics of a bronze sample and a regression line thereof measured by the conventional surface condition inspection apparatus and the surface condition inspection apparatus of the present embodiment, respectively. In these figures, the horizontal axis represents the time (seconds) from the start of measurement, and the vertical axis represents the OSEE signal (V / 200).

  For the measurement by the surface condition inspection apparatus of the prior art and this embodiment, 10 white copper samples (copper 75%, nickel 25%) are prepared, and each sample is carefully cleaned with isopropyl alcohol before measurement, Thereafter, measurement was started after a certain period of time after drying.

  Other measurement methods are the same as those of the aluminum sample shown in FIGS.

The linear regression equation without filter in FIG. 7 is as follows.
(A) y = −0.3069x + 115.67, R ² = 0.8969,
(B) y = −0.3501x + 203.73, R ² = 0.8928,
(C) y = −0.3602x + 193.11, R ² = 0.8278,
(D) y = −0.3065x + 227.52, R ² = 0.9214,
(E) y = −0.4097x + 255.36, R ² = 0.7598,
(F) y = −0.2326x + 220.97, R ² = 0.8365,
(G) y = −0.3518x + 270.76, R ² = 0.9258,
(H) y = −0.2551x + 205.59, R ² = 0.6889,
(I) y = −0.5186x + 256.65, R ² = 0.9267,
(J) y = −0.2466x + 163.19, R ² = 0.8547.

The linear regression equation with the filter in FIG. 8 is as follows.
(A) y = −0.1375x + 337.53, R ² = 0.6298,
(B) y = −0.0970x + 345.17, R ² = 0.6322,
(C) y = −0.1382x + 280.56, R ² = 0.7955,
(D) y = −0.0842x + 337.10, R ² = 0.6930,
(E) y = −0.1720x + 322.99, R ² = 0.9238,
(F) y = −0.1489x + 339.51, R ² = 0.8171,
(G) y = −0.1309x + 349.00, R ² = 0.7487,
(H) y = −0.1355x + 333.93, R ² = 0.8054,
(I) y = −0.1448x + 302.00, R ² = 0.7667,
(J) y = −0.1429x + 323.32, R ² = 0.7732.

  The average of the slope (absolute value) of the linear regression equation without filter of FIG. 7 is 0.3338, whereas the average of the slope (absolute value) of the linear regression equation with filter of FIG. Was 0.1332, much smaller than this.

  Thus, in any sample of aluminum, bronze, and white bronze, the slope of the linear regression equation is considerably smaller than when there is no bandpass optical filter 15. The reason is that ozone, oxygen atoms, and oxygen molecules are generated by a unique environment when there is no filter and spectral components near 254 nm and spectral components near 185 nm are present at the same time. Since the surface of the sample is oxidized, the negative slope coefficient with respect to the passage of time of the OSEE signal increases. On the other hand, if a filter is attached and only the spectral component near 185 nm is irradiated on the sample surface, oxygen atoms are hardly generated and surface oxidation does not occur, so that the OSEE signal greatly decreases with time. The phenomenon does not occur. That is, the slope of the linear regression equation of the OSEE signal is small.

  Therefore, as in this embodiment, if the bandpass optical filter 15 is configured so that only the spectral component in the region near 185 nm is irradiated onto the metal surface to be inspected, the oxidation on the metal surface can be suppressed. Thus, an OSEE signal that is always stable over time can be obtained over the entire surface.

  In addition, although the sample mentioned above is a case of aluminum, bronze, and white bronze, even if it is a metal material other than that, if a photoelectron is emitted by a photoelectric effect from the relation of a work function, the same effect can be expected. it is obvious.

  The above-described embodiments are all illustrative of the present invention and are not limited to the present invention, and the present invention can be implemented in various other variations and modifications. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

DESCRIPTION OF SYMBOLS 10 Sensor head 11 Control and display part 12 Housing 13 Low pressure mercury lamp 13a Lamp main body 13b Light emission part 14 Anode electrode 14a Through-hole 15 Band pass type optical filter 16 Amplifying circuit 17 Bias circuit

Claims (5)

  An ultraviolet light source that generates ultraviolet light; a photoelectron collector that collects photoelectrons emitted from the metal surface when irradiated with ultraviolet light; an amplifier that amplifies the photocurrent obtained from the photoelectron collector; Band pass means for passing only the spectral component in the region near 185 nm of the ultraviolet light generated by the ultraviolet ray generation source, and the ultraviolet light that has passed through the band pass means is irradiated onto the metal surface to be inspected. A surface state inspection apparatus using a photoelectric effect, characterized in that it is configured as described above.   2. The surface condition inspection apparatus according to claim 1, wherein the band-pass means is a band-pass optical filter provided in a passage of ultraviolet light from the ultraviolet light source.   The surface condition inspection apparatus according to claim 1, wherein the ultraviolet ray generation source is a low-pressure mercury lamp.   The surface condition inspection apparatus according to claim 1, wherein the ultraviolet ray generation source is a semiconductor light emission source.   5. The surface state inspection apparatus according to claim 1, further comprising bias means for biasing the photoelectron collecting unit to a positive potential with respect to the metal surface.

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