JP3242449B2 - Soft X-ray imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft X-ray imaging device particularly suitable for detecting soft X-rays.

[0002]

2. Description of the Related Art Conventionally, a microchannel plate (MCP) and a charge-coupled device (CC) have been used as soft X-ray detectors.
D) and the like are used. FIG. 9 and FIG.
In this MCP, a large number of fine microchannels are formed in a bundle as shown in the figure, and a high voltage is applied to both ends of the microchannels. When soft X-rays enter from one end of the MCP, secondary electrons are emitted from the inner wall of the microchannel, and the emitted secondary electrons are accelerated by the electric field and collide with the inner wall one after another, thereby reducing the number of secondary electrons. It will double. Usually M
A fluorescent screen is installed on the other end of the CP, and observation is performed using a CCD or the like. As shown in FIG. 11, a CCD is formed by cascade-connecting a number of MOS capacitors which are electrically coupled to each other, and transfers and processes charges injected from the outside one after another along the semiconductor surface. That is, such C
FIG. 12 shows an example of the drive pulse waveform and output of the CD.

[0003]

SUMMARY OF THE INVENTION However, MCP
In, since the resolution is determined by the thickness of the microchannel, high resolution can hardly be expected. On the other hand, in the case of a CCD, since a relatively thick protective layer for protecting the transfer gate structure and the like exists, most of soft X-rays are absorbed by this protective layer. For this reason, even when visualization is performed using the above-described fluorescent film during observation, there is a problem that the sensitivity itself is rather poor. By the way, in order to obtain an image of light of a desired wavelength from white light such as emitted light, it is necessary to make a single color using a diffraction grating or a zone plate. In this case, however, there is a disadvantage that one optical element is added. According to an imaging element such as an objective lens using a multilayer film, its wavelength selectivity can be used, but it is not only limited to a specific wavelength designed but also the multilayer film itself is expensive. .

The present invention has been made in view of the above circumstances, and has as its object to provide a soft X-ray imaging device having high sensitivity and high resolution and capable of easily approaching monochromatic light.

[0005]

According to the present invention, there is provided a soft X-ray imaging device according to the present invention, wherein a photoelectric conversion layer is provided on a pixel electrode, and a surface electrode layer is provided on the photoelectric conversion layer. The measurement wavelengths for which the surface electrode layer forming materials are different from each other
It is composed of at least two types of pixels having an absorption edge in the region .

[0006]

[0007] Then, a soft X-ray imaging device according to the present invention includes a plurality of pixels having a filter unit, composed of two or more pixels having an absorption edge in the measurement wavelength region material of the filter section are different from each other In addition, a processing system for calculating a signal difference between adjacent different kinds of pixels is provided.

[0008] The soft X-ray imaging device according to the present invention comprises:
A plurality of pixels having a filter section,
With two or more types of pixels whose substances have different absorption edges
Compute and calculate signal differences between adjacent dissimilar pixels
A processing system is provided.

In the above case, the imaging device of the present invention can be configured as a stacked solid-state imaging device having a pixel structure as shown in FIG. 1, for example. That is, in the figure, a photoelectric conversion layer 2 is provided on a photodiode portion 1 having a pixel electrode 8, and a surface electrode layer 3 is provided on the photoelectric conversion layer 2. The surface electrode layer 3 is composed of an electrode portion 9 and a filter portion 10, and the filter portion 10 has a different absorption for each pixel.
It is formed of a material having an edge . The photodiode unit 1 is an amplification type image pickup device (AM) as shown in FIG.
The structure of I) may be used.

[0010]

The light incident on the surface electrode layer 3 immediately reaches the photoelectric conversion layer 2 to generate electron-hole pairs. In this case, the light to be photoelectrically converted is selected for each pixel depending on the forming material of the filter unit 10. If the material of the photoelectric conversion layer 2 is a semiconductor such as Si, for example, the quantum efficiency of soft X-rays is improved, and high sensitivity is obtained. Thus, charges are accumulated in the photodiode section 1, and the accumulated charges are read out by the readout circuit.

On the other hand, in the case of the AMI, a signal is read after being amplified in a pixel. In the operation of the AMI, FIG.
Referring to (a) and (b), first, the photodiode shown in FIG. 2 is set to a reset voltage by the reset FET 4. Each photodiode absorbs electrons in response to the incident light, and lowers the potential. This is further amplified by the amplification FET 5 and taken out of the image sensor by the horizontal selection FET 6 and the vertical selection FET 7.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a soft X-ray imaging device according to the present invention will be described below with reference to FIGS. The soft X-ray imaging device according to the present invention is composed of at least two types of pixels in which the material for forming the surface electrode layer is different from each other. In particular, in this embodiment, as shown in FIG. B is used. In FIG. 4, reference numeral 11 denotes a photodiode portion, 12 denotes a photoelectric conversion layer, and 13 denotes a surface electrode layer.

The pixels A and B are connected to the filter unit 14
The structure is the same except that the thickness of the material is different from that of the material.
Transmittances T ₁ and T ₂ for soft X-rays of _three wavelengths L ₁ , L ₂ and L ₃ in the filter unit 14 having a thickness d (μm)
And shows the T ₃ in Table 1 below.

[0014]

The transmittances T ₁ , T ₂ and T ₃ were calculated by the following equation (1). T = exp (-4πkd / λ) (1) In the equation (1), k is an absorption coefficient. Then, the wavelength L ₁ = 27.4 °, the wavelength L ₂ = 24.3 °, and the wavelength L
_The absorption coefficient k for ₃ = 23.6 ° was used.
Henke's Table (ATOMIC DATA AND NUCLEAR TABLES 27,
1-144 (1982)).

FIG. 5 shows an example of the arrangement of the pixels A and B when the image pickup device of the present invention is viewed from the incident light side. As is clear from FIG. 5, the pixels A and B are uniformly and uniformly distributed on the light receiving surface of the image sensor. Then, as in this arrangement example, the pixels A and the pixels B are alternately arranged along the light receiving surface.

The imaging device for soft X-rays of the present invention is constructed as described above. First, the relationship between the wavelengths L ₁ , L ₂ and L ₃ and the absorption edge of the substance forming the filter section 14 is shown in FIG. It is like. That is, by taking the difference between the signals obtained by the pixels A and B, the signal in the wavelength region m can be left, and the signals in the wavelength regions 1 and n can be made smaller than the signal in the wavelength region m. . Wavelength L ₁ , L ₂ and L
_By simply calculating the difference S in transmittance using ₃ as a representative value of each wavelength region, S ₁ = 1.1E-2; S ₂ = 6.4E-1;
Since S ₃ = 1.0E−2, the wavelength region m is emphasized. By calculating the signal difference in this way, it is not necessary to consider the difference in absorption due to the difference in wavelength between the filter unit 14 and the photoelectric conversion layer 12. However, it is assumed that incident light is previously limited to light only in the soft X-ray region by some method. Note that Al is selected as a material for forming the electrode portion 15 and Si is selected as a material for forming the photoelectric conversion layer 12, and their thicknesses are appropriately set.

Although the pixels A and B are arranged as shown in FIG. 5, a pixel pair is formed by the adjacent pixels A and B, and a process for obtaining a signal difference among them is performed. Will be When the arrangement pitch of the pixels A and B is p1 as in the example shown in FIG. 5, the arrangement pitch of one of the pixels A or B is p2 (= p1 × √2).
Becomes That is, when attention is paid to a specific wavelength band, the pixel pitch is p2, but since p1 is about 10 μm at present, even in such a case, the pitch is finer than the standard MCP pitch. That is, high resolution is guaranteed.

FIG. 7 shows a second embodiment of the soft X-ray imaging device. In the second embodiment, in the pixel C, the surface electrode layer 13 includes only the electrode portion 13a. By taking the other pixel as D and taking the difference between the signals obtained at these pixels C and D, it is possible to remove light having a wavelength longer than the absorption edge of the substance forming the filter portion of the pixel D. Is obtained.

Here, in the soft X-ray imaging device of the present invention, the wavelength to be emphasized can be freely switched by selecting three or more types of pixels and appropriately combining them. For example, as shown in FIG. 8, three types of pixels A, B and E are arranged as shown. Further, by using the AMI (see FIG. 2) described above in each of the above embodiments, detection with even higher sensitivity can be realized.

[0021]

As described above, according to the soft X-ray imaging device of the present invention, a soft X-ray detector having high sensitivity and high resolution can be realized. Moreover, it is possible to image with light close to monochromatic light, and there are advantages such as excellent performance as a soft X-ray detector of this kind.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a laminated solid-state imaging device showing a basic structure of a soft X-ray imaging device of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration example of an amplification type solid-state imaging device according to the present invention.

3A and 3B are diagrams for explaining the operation and configuration of the amplification type solid-state imaging device, and FIG. 3B is a partially enlarged view of FIG.

FIG. 4 is a longitudinal sectional view of a soft X-ray imaging device according to a first embodiment of the present invention.

FIG. 5 is a plan view showing an example of pixel arrangement in the first embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a wavelength and an absorption edge of a substance forming a filter section in the first embodiment of the present invention.

FIG. 7 is a longitudinal sectional view of a soft X-ray imaging device according to a second embodiment.

FIG. 8 is a plan view illustrating another arrangement example of the pixel according to the present invention.

FIG. 9 is a cutaway perspective view of a main part of a microchannel plate as a conventional soft X-ray detector.

FIG. 10 is a side sectional view for explaining the operation of the microchannel plate.

FIG. 11 is a longitudinal sectional view of a charge-coupled device as a conventional soft X-ray detector.

FIG. 12 is a diagram showing a drive pulse waveform of the charge-coupled device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photodiode part 2 Photoelectric conversion layer 3 Surface electrode layer 8 Pixel electrode 9 Electrode part 10 Filter part 11 Photodiode part 12 Photoelectric conversion layer 13 Surface electrode layer 13a Electrode part 14 Filter part 15 Electrode part A pixel B pixel C pixel D pixel E pixel

Continuation of the front page (72) Inventor Hiroaki Nagai 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Industrial Co., Ltd. (56) References JP-A-63-224253 (JP, A) JP-A-3-3 73883 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 27/14 H01L 31/09

Claims (3)

(57) [Claims] 1. A stacked solid-state imaging device in which a photoelectric conversion layer is provided on a pixel electrode and a surface electrode layer is provided thereon, wherein the material of the surface electrode layer absorbs in different measurement wavelength regions. An imaging device for soft X-rays, comprising a processing system configured of two or more types of pixels having a control edge and calculating a signal difference between adjacent different types of pixels. 2. The soft X-ray imaging device according to claim 1, wherein pixels of each type are alternately arranged along a light receiving surface. 3. A pixel having a plurality of pixels having a filter portion, wherein the material of the filter portion is composed of two or more types of pixels having absorption edges in different measurement wavelength regions, and a signal difference between adjacent different kinds of pixels. An imaging device for soft X-rays, comprising a processing system for calculating the following formula.