JPH0645632A - Photodetector - Google Patents

Abstract

PURPOSE:To obtain a photodetector wherein the amount of light of soft X-rays can be measured and, at the same time, an image can be detected by a method wherein the photodetector is provided with an image sensing element whose pixel electrodes for individual pixels have been exposed on its photodetection face and with a mesh-shaped anode electrode which is installed on the front of the pixel electrodes for the image sensing element. CONSTITUTION:A photodetector is composed of an image sensing element 1 whose pixel electrodes 1a connected to capacity structure regions for individual pixels are exposed on its photodetection face and of a wire-mesh-shaped anode electrode 2 installed on the front of the pixel electrodes 1a, and a potential difference is given across the pixel electrodes 1a and the anode electrode 2 by a bias power supply. When soft X-rays are incident, the pixel electrodes 1a emit photoelectrons e<-> and holes are generated inside the electrodes. As the holes are generated, an electric charge whose amount corresponds to the emitted photoelectrons e<->, in other words an electric energy corresponding to the incident energy of the soft X-rays, is accumulated in the capacitor structure regions. As a result, when the amount of the accumulated electric charge is measured, the amount of light of the soft X-rays can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a photodetector for converting radiation energy into electric energy to quantitatively measure radiation, and particularly used in an X-ray telescope, a soft X-ray microscope, a soft X-ray inspection apparatus and the like. The present invention relates to a photodetector for measuring soft X-rays.

[0002]

2. Description of the Related Art Among soft X-ray detectors, an X-ray diode is used for measuring light quantity, and a solid-state image pickup device for soft X-ray such as CCD is used for image detection. Figure 6 is X
The conceptual diagram of a line diode (henceforth "XRD") is shown. In the figure, XRD is a cathode electrode 41, a wire mesh-shaped anode electrode 42, and a bias power source 43.
And a load resistor 44. Bias power source 43
When a potential difference is generated between the cathode electrode 41 and the anode electrode 42 by the above, when a soft X-ray to be measured enters the cathode electrode 41, photoelectrons e ⁻ are generated according to its quantum efficiency. The photoelectrons e ⁻ are captured by the anode electrode 42 and flow as a current to the load resistor 44, and the light amount of the soft X-ray can be obtained by measuring the amount of this current or the amount of charge.

That is, if the charge amount ρ is measured by the incidence of a soft X-ray having a wavelength λ, the quantum efficiency of the cathode electrode 41 is QE (λ), and the spectrum of the incident soft X-ray is S (λ), e.
Is the electron charge amount, the charge amount ρ is given by the following equation (1). ρ = e∫QE (λ) S (λ) Cdλ (1) where C is a correction coefficient. In the above formula (1),
Since e, QE (λ) and S (λ) are known values and ρ is a measured value, the correction coefficient C can be obtained by the following equation (2). C = ρ / [e∫QE (λ) S (λ) dλ] (2) On the other hand, when the photon energy of the wavelength λ is E (λ), the incident energy I is given by the following equation (3). I = C∫S (λ) E (λ) dλ (3) Therefore, by substituting the value of the correction coefficient C obtained by the above equation (2) into the above equation (3), the soft X-rays incident on the XRD can be obtained. The incident energy, that is, the amount of light can be measured. The E (λ) is an energy conversion value, and for example, the value shown in the following equation (4) is used. E (λ) [eV] = 12398 / λ [Å] (4)

The amount of light can also be measured by installing a filter having a known spectral transmittance distribution on the soft X-ray incident side of the anode electrode 42. 7 and 8 are diagrams showing the characteristics of such a filter. In the figure, Y (E)
Is the product of the filter transmittance T (E) and the quantum efficiency QE (E) of the cathode when nickel mesh is used for the anode electrode and aluminum is used for the cathode electrode.
As a material for forming the filter, FIG.
μm thick platinum and 0.1 μm thick N-Parylene
When (commercial product name, chemical name: poly-paraxylylene) is used, the figure (b) shows 0.3 μm thick platinum and 0.1 μm.
When N-Parylene with a thickness of 0.6 μm and beryllium with a thickness of 0.6 μm are used, FIG.
When 1 μm thick N-Parylene is used, FIG. 7B shows 0.1 μm thick gold and 0.1 μm thick N-Par.
The case of using ylene and beryllium having a thickness of 0.6 μm are shown.

When a filter is installed on the XRD, the above equation (1) can be expressed by the following equation (5). ρ = e∫Y (E (λ)) S (λ) C _F dλ (5) where C _F is a correction coefficient. In the above formula (5),
Since e, Y (E (λ)) and S (λ) are known values and ρ is a measured value, the correction coefficient C _F can be obtained by the following equation (6). C _F = ρ / [e∫Y (E (λ)) S (λ) dλ] (6) On the other hand, when the photon energy of the wavelength λ is E (λ), the incident energy I is given by the above formula (3). Therefore, by substituting the value of the correction coefficient C _F obtained by the above equation (6) into the equation (3), the light quantity of the soft X-ray can be measured.

Further, the difference between the light quantity measured using the filter shown in FIG. 8A and the light quantity measured using the filter shown in FIG. 3K
It is possible to measure the amount of light in the wavelength range that cannot be directly measured with a filter in the eV range. In addition to limiting the wavelength range of incident light, the filter is also effective in removing unnecessary particle beams from a light source or the like.

[0007]

The above-mentioned conventional XRD is
The light quantity for the soft X-rays can be measured, but the soft X-ray image could not be detected. On the other hand, the solid-state image sensor for soft X-rays can detect an image but cannot measure the light amount. Therefore, when it is desired to detect the soft X-ray image and obtain the distribution of the light quantity, for example, when measuring the soft X-ray image and the light quantity of the sample for the purpose of material analysis, XRD is performed for all measurement points on the sample. The amount of light must be measured while scanning sequentially, and then the measured data must be listed to form an image.
Not only is handling of the RD troublesome, but there is also a problem that the measurement and the processing of the measurement data take time.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to measure the light quantity of soft X-rays and image detection at the same time, and to handle them. It is to provide an easy photodetector.

[0009]

In order to achieve the above object, a photodetector according to the present invention comprises an image pickup device in which a pixel electrode connected to a capacitive structure region of each pixel is exposed on a light receiving surface, and an image pickup device. And a mesh-shaped anode electrode provided on the front surface of the pixel electrode of the device. Further, the photodetector according to the present invention includes an image pickup device in which a pixel electrode connected to a capacitive structure region of each pixel is exposed on a light receiving surface, and a wavelength selective filter provided in front of the pixel electrode of the image pickup device. And has.

[0010]

1 is a conceptual diagram of the photodetector of the present invention. In the figure, 1 is a pixel electrode 1 connected to the capacitive structure region of each pixel.
An image sensor 2 in which a is exposed on the light receiving surface is a wire mesh-shaped anode electrode provided on the front surface of the pixel electrode 1a. A potential difference is applied between the pixel electrode 1a and the anode electrode 2 by a bias power source (not shown), and the anode electrode 2 is grounded via the bias power source.

When soft X-rays enter, the pixel electrode 1a emits photoelectrons e ^- and holes are formed in the electrodes. Along with the formation of holes, an amount of charges corresponding to the emitted photoelectrons e ⁻ , that is, electric energy corresponding to the incident energy of soft X-rays, is accumulated in the capacitive structure region. That is, if each pixel corresponds to XRD and the quantum efficiency of the pixel electrode 1a is known, the light quantity of the soft X-ray can be measured by measuring the accumulated charge quantity. On the other hand, when the emitted photoelectrons e ⁻ are incident on the pixel electrode 1a, the amount of accumulated charge changes and the amount of light cannot be accurately measured. Therefore, by arranging the anode electrode 2 and capturing the emitted photoelectrons e ⁻ , a correct and accurate amount of charge is accumulated in the capacitive structure region of each pixel, and an accurate light amount can be measured. Since the accumulated charge of each pixel can be detected by a normal read operation of the image sensor, the handling is easy.

Further, since the measuring light only needs to be in a certain wavelength range, if a filter having wavelength selectivity is installed on the front surface of the image pickup device 1, the wavelength range of incident light is limited and unnecessary particle beams are generated. Can be removed. In this case, the light quantity can be measured without applying a grounding treatment to the filter. However, the photoelectrons e ⁻ emitted as described above are not
It is desirable to perform a grounding process in order to prevent the incident on the anode and to improve the measurement accuracy, and the anode electrode may be installed together with the filter.

[0013]

Embodiments will be described with reference to the drawings. FIG. 2 shows a sectional structure of one pixel of the photodetector of the first embodiment.
Reference numeral 11 is an internal amplification type solid-state image sensor (AMI: Amplified MO).
S Imager), 12 are anode electrodes formed of nickel mesh. Reference numeral 11a denotes a pixel electrode made of aluminum exposed on the surface of the element and connected to the photodiode structure region 11b formed in the lower layer thereof. The anode electrode 12 is connected to the ground side of the photodiode structure region 11b via a bias power source (not shown).

FIG. 3 is an equivalent circuit diagram of the image pickup device 11 described above, and the inside of the one-dot chain line frame corresponds to one pixel. Pixel electrode 1
When a soft X-ray is incident on 1a, photoelectrons e ⁻ are emitted from the surface according to the quantum efficiency and are captured by the anode electrode 12. At this time, charges corresponding to the emitted photoelectrons e ⁻ are stored in the capacitance C _PD . It is stored in the photodiode section D. If the photoelectrons e ⁻ captured by the anode electrode 12 are configured to flow to the ground side of the photodiode structure region 11b, the quantitativeness of the accumulated charges can be improved. The potential due to this accumulated charge is applied to the gate of the amplifying transistor Ta, and the amplified current is applied to the vertical scanning switch Ty,
It is read out via the horizontal scanning switch Tx.

Since this embodiment is constructed as described above, each pixel corresponds to an XRD, and the pixel electrode 11a
If the quantum efficiency of is known, the light quantity of the soft X-ray can be measured by measuring the accumulated charge quantity. Further, since the emitted photoelectrons e ⁻ are reliably captured by the anode electrode 12, the light quantity can be measured with high accuracy. Furthermore, since the accumulated charge of each pixel can be detected by a normal read operation of the image sensor, the light quantity of the soft X-ray and the image can be detected by simple handling. By installing a filter having the characteristics shown in FIGS. 7 and 8 instead of or together with the anode electrode 12, it is possible to measure soft X-rays within a desired wavelength range.

FIG. 4 shows the structure of one pixel of the photodetector of the second embodiment. This is the surface electrode 20 of the internal amplification type solid-state image pickup device 21 of the laminated photodiode structure shown in FIG.
c and the photoelectric conversion layer 20d are removed, and the pixel electrode 20a is exposed on the surface of the element, and the solid-state image sensor is composed of the wire mesh-shaped anode electrode 22. In FIG. 4, a photodiode structure region 21b (capacitance structure region which is a constituent of the present invention) of the image pickup device 21 is a diode D formed by providing an n ⁺ type region B on the surface of the p-type substrate A and the surface of the substrate A. A field oxide film C is formed to cover the contact portion D ′ of the diode D, and the pixel electrode 21 including the first aluminum layer E, the second aluminum layer F and the third aluminum layer G exposed on the device surface is formed.
The equivalent circuit is the same as that of FIG.

With this configuration, the soft X-ray is applied to the pixel electrode 21a.
When the line is incident, photoelectrons e ⁻ are emitted from the surface according to the quantum efficiency, and the emitted photoelectrons e ⁻ are reliably captured by the anode electrode 22 and the amount of photoelectrons e ⁻ at the pixel electrode 21 a corresponding to the emitted photoelectrons e ⁻ . Electric charges are accumulated in the photodiode part D of the capacitance C _PD , and the light amount of the soft X-ray can be measured by measuring the accumulated charge amount. Instead of the anode electrode 22 or together with the anode electrode, a filter may be installed.

[0018]

As described above, according to the present invention, it is possible to provide a photodetector capable of simultaneously measuring the light quantity of soft X-rays and detecting an image and being easy to handle.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a photodetector of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of an embodiment of a photodetector of the present invention.

FIG. 3 is an equivalent circuit diagram of the device shown in FIG.

FIG. 4 is a diagram showing a cross-sectional structure of another embodiment of the photodetector of the present invention.

FIG. 5 is a diagram showing a cross-sectional structure of an internal amplification type solid-state imaging device of a conventional photodetector.

FIG. 6 is a conceptual diagram of a conventional X-ray diode.

FIG. 7 is a diagram showing characteristics of a filter.

FIG. 8 is a diagram showing characteristics of another filter.

[Explanation of symbols]

 1, 11 and 21 Image sensor 1a, 11a and 21a Pixel electrode 2, 12 and 22 Anode electrode

[Procedure amendment]

[Submission date] December 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Among soft X-ray detectors, an X-ray diode is used for measuring light quantity, and a solid-state image pickup device for soft X-ray such as CCD is used for image detection. Figure 6 is X
The conceptual diagram of a line diode (henceforth "XRD") is shown. In the figure, XRD is a cathode electrode 41, a wire mesh-shaped anode electrode 42, and a bias power source 43.
And a load resistor 44. Bias power source 43
When a potential difference is generated between the cathode electrode 41 and the anode electrode 42 by the above, when a soft X-ray to be measured enters the cathode electrode 41, photoelectrons e ⁻ are generated by the photoelectric effect. The photoelectrons e ⁻ are captured by the anode electrode 42 and flow as a current to the load resistor 44, and the light amount of the soft X-ray can be obtained by measuring the amount of this current or the amount of charge.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

QE of the quantum efficiency of the cathode electrode 41
(Λ), and letting the spectrum of the incident soft X-ray be S (λ),
The obtained charge amount ρ is given by the following equation (1), where e is the electron charge amount. ρ = e∫QE (λ) S (λ) Cdλ (1) where C is a correction coefficient. In the above formula (1),
Since e, QE (λ) and S (λ) are known values and ρ is a measured value, the correction coefficient C can be obtained by the following equation (2). C = ρ / [e∫QE (λ) S (λ) dλ] (2) On the other hand, when the photon energy of the wavelength λ is E (λ), the incident energy I is given by the following equation (3). I = C∫S (λ) E (λ) dλ (3) Therefore, by substituting the value of the correction coefficient C obtained by the above equation (2) into the above equation (3), the soft X-rays incident on the XRD can be obtained. The incident energy, that is, the amount of light can be measured. The E (λ) is an energy conversion value, and for example, the value shown in the following equation (4) is used. E (λ) [eV] = 12398 / λ [Å] (4)

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

The amount of light can also be measured by installing a filter having a known spectral transmittance distribution on the soft X-ray incident side of the anode electrode 42. 7 and 8 are diagrams showing the characteristics of such a filter. In the figure, Y (E)
Is the product of the filter transmittance T (E) and the quantum efficiency QE (E) of the cathode when nickel mesh is used for the anode electrode and aluminum is used for the cathode electrode.
E is a value based on the energy display of light shown by the above formula (3). As a material for the filter, FIG.
(A) is 0.3 μm thick platinum and 0.1 μm thick N-Pa.
In the case of using rylene (trade name of another company, chemical name: poly-paraxylylene), the same figure (b) used 0.3 μm thick platinum, 0.1 μm thick N-Parylene and 0.6 μm thick beryllium. In the case of FIG. 8 (a), 0.1 μm
In the case of using thick gold and 0.1 μm thick N-Parylene, the same figure (b) shows the case of using 0.1 μm thick gold, 0.1 μm thick N-Parylene and 0.6 μm beryllium. Are shown respectively.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichiro Mochimaru 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (2)

[Claims] 1. An image pickup device having a pixel electrode connected to a capacitive structure region of each pixel exposed on a light receiving surface, and a mesh-shaped anode electrode provided in front of the pixel electrode of the image pickup device. Photo detector. 2. A light having an image pickup device in which a pixel electrode connected to a capacitive structure region of each pixel is exposed on a light receiving surface, and a wavelength selective filter provided in front of the pixel electrode of the image pickup device. Detector.