JPH07170456A - Image pickup device - Google Patents

Abstract

PURPOSE:To stably detect an object image by emitted ray with a simple configuration, high resolution with low noise. CONSTITUTION:The image pickup device scanning an image pickup board subjected to ray emission to pick up a sample image is provided with a semiconductor board, an insulation film formed on the surface of the semiconductor board, very small plural electrodes arranged on the insulation film, the image pickup plate 101, conductive probes 103 arranged opposite to each other on the insulation film or the very small electrode, scanning means 11, 123 allowing the probes 103 to scan relatively with respect to the insulation film and the very small electrode, a voltage application means 131 applying a predetermined voltage between the probe 103 and the semiconductor board, and a current detecting means 132 detecting a current flowing between the probe 103 and the semiconductor board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and in particular, an electron-hole pair generated by irradiation of light rays such as X-rays in a semiconductor in an arrayed MIS structure is measured by a current probe. The present invention relates to a technique that enables high-resolution imaging by detecting by detecting.

[0002]

2. Description of the Related Art Various optical analyzers have been developed so far. Among them, an imaging method using X-rays has attracted attention as an imaging method that can obtain higher resolution than ordinary visible light, and an X-ray microscope and an X-ray telescope are known. Such an optical analyzer is generally an optical system for irradiating a sample with a light beam to magnify an image formed by the light beam and sending it to an imaging device, and a magnified image of the sample light beam sent thereto as an electric signal. It is composed of an imaging device for taking out.

As an image sensor used in an image pickup device, an image pickup tube and a CCD are typical. Both types have been developed for X-ray as well as visible light. These image sensors can extract the intensity of light as an electric signal and can also be used in a vacuum container. The pixel size is about 10 μm. On the other hand, films and resists can also be used in vacuum containers, and the spatial resolution is higher than that of image pickup tubes and CCDs, but development is required, which requires time and labor,
Lack of real time.

In the optical analyzer, the resolution related to sample analysis is determined by the magnification of the optical system and the pixel size of the image pickup device (resolution related to sample analysis = pixel size of the image pickup device / magnification of the optical system). . For example, if the pixel size of the image pickup device is 10 μm and the magnification of the optical system is 10 times, a resolution of 1000 nm can be obtained in the sample. Conversely, when it is desired to obtain a resolution of 10 nm in the sample, if the magnification of the optical system is 10 times, the pixel size of the image pickup device is 0.
Must be 1 μm or less. However, the wavelength of the light beam irradiating the sample needs to be shorter than the obtained resolution.

[0005]

In order to obtain a resolution (10 nm or less) corresponding to X-rays in an optical analyzer such as the X-ray microscope described above, the optical system (imaging system) of this apparatus is used. Alternatively, it is necessary to increase the resolution of at least one of the image pickup devices (light receiving means). When an image pickup tube or CCD is used for the image pickup device, the pixel size is about 10 μm, and in order to observe the sample with a spatial resolution of 10 nm, the magnification of the optical element must be 1000 times. However, the magnification of an X-ray optical element such as a Walter mirror is about 50 times at most due to problems such as processing accuracy.

When observing a sample with a spatial resolution of 10 nm, if the pixel of the image pickup device is 1 μm or 0.1 μm, the magnification of the optical element can be 100 times or 10 times, respectively. However, if the pixel of the image pickup tube or CCD is 1μ
There have been problems with various technical difficulties in making m or 0.1 μm.

Several imaging methods have been proposed to address such problems. Basically, the X-ray absorption film is irradiated with the X-ray image of the sample, the probe facing the surface of the X-ray absorption film is scanned on the surface, and the space between the X-ray absorption film and the probe at each scanning point is scanned. The intensity distribution of the X-ray image of the sample is obtained by detecting the current value and the electric potential. For example, Japanese Patent Laid-Open No.
In the X-ray image visualization device of -123700 publication, a conductive material is used as the probe, an insulating film is used as the X-ray absorption film, a material exhibiting charging or conductivity, or an insulating material is used. When a film is used, electrons emitted when an X-ray image is projected on the film are detected by a probe that simultaneously scans, and in the case of a charging material, the charge generated by irradiating X-rays after charging the X-ray absorbing film The intensity distribution is scanned by a probe and detected as a current. On the other hand, in the case of an insulating material, X is applied to the insulating material.
The intensity distribution of the electric charge formed after the electron beam is emitted by irradiating the line image is scanned by the probe and detected as a current. Japanese Patent Laid-Open No. 5-5
In the X-ray image magnifying apparatus and method of 2780, a photoconductive thin film is used as an X-ray absorbing film, and electrons emitted when the X-ray absorbing film is irradiated with an X-ray image are detected by a probe that simultaneously scans. To do. Moreover, a method of detecting a current caused by electrons generated by the probe during X-ray irradiation is also proposed.

However, in each of the conventional devices described above, the X-ray absorption film is not divided into pixels, so that when the probe absorbs electrons, the distance between the probe and the probe is different. The absorption range varies depending on the applied voltage. This adjustment is difficult, there is a problem that the absorption range is widened, and the ideal high resolution that can be obtained when using X-rays cannot be easily obtained. Further, in the above-described device, the probe scans the surface to be inspected at a close distance, so that an error occurs in the detected current amount due to a change in distance. Therefore, with the conventional structure of the probe and the X-ray absorbing film and the scanning method of the probe, it is difficult to obtain a high resolution characteristic and to obtain it stably.

In view of the problems in the above-mentioned conventional apparatus, an object of the present invention is to provide an object image by irradiation of light rays such as X-rays with an extremely high resolution on the order of nanometers with a relatively simple structure. The object is to provide a practical image pickup device that can detect the above-mentioned signals and stably detect them with low noise.

[0010]

In order to achieve the above object, according to the present invention, an image pickup device which scans an image pickup plate irradiated with a light beam which has passed through a sample or which is reflected from the sample to photograph a sample image is obtained. In the device, the image pickup plate including a semiconductor substrate, an insulating film formed on the surface of the semiconductor substrate, and a plurality of microelectrodes arranged on the insulating film, and facing the insulating film or the microelectrode. A conductive probe disposed, a scanning means for scanning the probe relative to the insulating film and the microelectrode, and a voltage for applying a predetermined voltage between the probe and the semiconductor substrate. Application means and current detection means for detecting a current flowing between the probe and the semiconductor substrate are provided.

At this time, in the image pickup device, it is effective to bring the probe into contact with the insulating film or the microelectrode with a predetermined biasing force by using a biasing means.

Further, when the plurality of microelectrodes are two-dimensionally arranged on the insulating film, it is effective in simplifying scanning and data processing.

It is convenient in manufacturing that the probe is formed of a conductive material or a conductive material is deposited on a non-conductive material.

Furthermore, the scanning means scans the probe with respect to the insulating film and the microelectrodes, and the voltage application means charges the necessary microelectrodes.
Next, after irradiating the imaging plate with a light beam that has passed through or reflected the sample, the probe is sequentially moved to the charged microelectrode, and the current is detected to flow between the probe and the semiconductor substrate. The current is controlled so as to be sequentially detected, and an electric signal corresponding to the position of the probe is generated from the detected value, and the detected value or the electric signal corresponds to the position of the probe, and a numerical value is obtained. Advantageously, it is arranged to be displayed as an image and / or as an image.

[0015]

In the above structure, first, the scanning means scans the probe with respect to the insulating film and the minute electrodes, and at the same time, the necessary minute electrodes are charged by the voltage applying means, and then the sample is transmitted to the imaging plate. After irradiating the light beam reflected from the sample to generate electron-hole pairs corresponding to the sample image, the probe is sequentially moved to the charged microelectrode, and the probe is sequentially moved between the probe and the semiconductor substrate by the current detection means. The control is performed so that the flowing current is sequentially detected.

Further, in the structure of the image pickup apparatus to which the biasing means is further added, the basic operation of the image pickup is similar to the above, but the biasing means causes the probe to move to the image pickup plate during scanning. The action of contacting is added. Specifically, in the above operation, before the probe is scanned on the surface of the image pickup plate by the scanning means to charge each microelectrode, first the biasing means causes the probe to bend the cantilever with respect to the image pickup plate. So that the value becomes a predetermined value. After that, the charging operation, the irradiation of the light beam image to the image pickup plate, and the current detection operation are performed in the order shown above.

As a result of the above operation, the current corresponding to the intensity distribution of the sample image obtained by irradiation of the light beam can be detected, but subsequently, an electric signal corresponding to the position of the probe is generated from the detected value and detected. A value or an electric signal is displayed as a numerical value and / or an image corresponding to the position of the probe.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an image pickup apparatus according to an embodiment of the present invention. The image pickup apparatus includes an image pickup plate 101 to which a light ray image 151 transmitted through a sample or reflected from the sample is irradiated, a conductive probe 103 arranged so as to face the image pickup plate 101, and a probe 103. An actuator 111 and a driving unit 123 that are in contact with 101 to scan in XYZ directions, a voltage applying unit 131 that applies a predetermined voltage between the probe 103 and the imaging plate 101, and the probe 10.
3 and a current detection unit 132 that detects a current flowing between the image pickup plate 101. The probe 103 is attached to the cantilever 102.
Is an actuator 1 controlled by a driving means 123
11 is operated. Further, the image pickup apparatus includes, as an urging means, a laser light source 112 for detecting the bending of the cantilever 102 by an optical lever method, a light receiving element 113 for detecting the laser light, and a light intensity received by the light receiving element 113. A measuring unit 121 for measuring and a power source 122 for supplying power to the laser light source 112 are provided. Further, the present imaging apparatus has a computer 141 that performs centralized management of data obtained from each of the above means, and a C that displays video information.
It is equipped with RT142. The lens 152 is for focusing the light ray image 151 on the imaging plate 101 to form an image.

FIG. 2 shows the structure of the image pickup plate 101 used in this embodiment. In the imaging plate 101, the semiconductor substrate 3
The insulating film 302 is formed on the surface of the insulating film 302.
A plurality of minute metal electrodes 303 are two-dimensionally arranged on the top. That is, a [metal-insulator-semiconductor] MIS structure is formed. As the semiconductor substrate 301, boron-doped p-type [100] Si of 0.1 to 20 Ωcm is used. The insulating film 302 is an oxide film of 20 to 50 nm where there is a metal electrode on the surface, the thickness of the metal electrode 303 is 0.1 μm, and the surface of the oxide film is similar to the metal electrode 303 where there is no metal electrode 303. Designed to be high. The metal electrode 303 is made of Al and is 0.3
The pitch is 0.5 μm in μm angle. As shown in the drawing, the back surface is etched, and the thickness of the area where the metal electrodes are arranged is 1 to 5 μm. Electrode 3 with ohmic contact with Si by Al in the unetched part
05 is attached.

A process of reading the sample image absorbed by the image pickup plate 101 in the image pickup apparatus having the above-mentioned structure will be described with reference to FIG. The basic operation is probe 1
03 is brought into contact with the surface of the image pickup plate 101, then the probe 103 is scanned with respect to the image pickup plate 101 to charge the metal electrode 303 by the voltage applying means 131, and then the sample is attached to the image pickup plate 101. After the irradiation of the light beam image 151, the probe 103 is sequentially moved to the charged metal electrode 303 to sequentially detect the current flowing between the probe 103 and the semiconductor substrate 301 by the current detecting means 132. An electric signal corresponding to the position of the probe 103 is generated from the current value, and the CRT 142 is generated corresponding to the position of the probe 103.
And the step of displaying as an image on. The management of each operation described above is controlled by the computer 141, and the computer 14 also performs calculations and processing required for each operation.
Done by 1. Hereinafter, these operations will be described in detail in order.

First, the probe 103 is brought into contact with the image pickup plate 101 using an urging means with an extremely weak urging force that does not damage the image pickup plate. This contact operation is performed as follows. The movement of the probe 103 is performed by moving the cantilever 102 using the actuator 111. However, the actuator 111 in this embodiment uses the probe cantilever 10.
2 can be moved in three directions of XYZ. Here, the Z direction is a direction that changes the distance between the probe 103 and the image pickup plate 101, and the XY direction is a direction perpendicular to the Z axis. For moving the cantilever 102 in the Z-axis direction, a moving mechanism (coarse moving mechanism, not shown) is provided for coarse movement. The probe 103 is brought close to and brought into contact with the imaging plate 101 by using this coarse movement mechanism. For the contact, the cantilever 102 is irradiated with laser light from the laser light source 112, the reflected light from the cantilever 102 is detected by the two-divided light receiving element 113 by the optical lever method, and the movement of the cantilever 102 by the coarse movement mechanism is stopped. When the predetermined contact pressure can be set, the output of the laser light source 112 is stopped. This is because the laser light is simultaneously detected at the time of image capturing and becomes noise, so the displacement of the cantilever is not detected during measurement, and the displacement is detected as necessary and a predetermined displacement is set. However, if the wavelength of the laser does not affect the measurement of the current, the biasing force may be detected simultaneously with the measurement of the current. The above contact operation may be performed for each measurement, or may be performed for a certain time or for each frame. By using the actuator 111 and controlling by the computer 141, for example, 1 × 10 ⁻⁸
It is possible to adjust to a very weak biasing force such as N (Newton). A biasing force of about 10 ⁻⁷ to 10 ⁻⁸ N is preferable in order to reduce the pixel area without damaging the substrate.

Next, the probe 103 scans the image pickup plate 101 to charge the metal electrode 303 by the voltage applying means 131. This scanning is performed for each two-dimensionally distributed metal electrode by moving in the XY directions of the image pickup plate 101 using the actuator 111 and the driving unit 123. However,
Since one metal electrode 303 acts as a pixel of the image pickup plate and serves as a unit of resolution, its principle and action will be described focusing on one metal electrode.

FIG. 3 is an explanatory view showing the principle of the image pickup method in the embodiment of the present invention. In this explanatory diagram, the imaging plate 10
The structure of the portion where the metal electrode 1 exists is schematically shown, and the principle of detecting the electron-hole pair generated by irradiation of light rays such as X-rays in the semiconductor in the MIS structure with a probe is introduced. it can. The metal electrode 303 and the insulating film 3 in FIG.
02, the semiconductor substrate 301, and the electrode 305 are the metal electrode 203, the insulating film 202, the semiconductor substrate 201, and the electrode 2, respectively.
Indicated by 05. In addition, the probe 103 in FIG.
It is shown as 4. Regarding the semiconductor substrate 201, the case where a p-type semiconductor material is used is described here, but in practice, either p-type or n-type can be used.

First, the probe 204 is brought into contact with the metal electrode 203, and a voltage is applied between the probe 204 and the electrode 205 by the voltage applying means 131 so that the probe 204 side is positive. This applied voltage is about 1V. Metal electrode 203
The semiconductor substrate 201 and the semiconductor substrate 201 form a capacitor separated by an insulating film 202. Since the probe 204 side is positive, the metal electrode 203 is positively charged. At this time, a depletion layer 206 is formed in the vicinity of the metal electrode 203 inside the semiconductor substrate 201 by applying a voltage. After charging the metal electrode 203, the probe 204 is moved to the next metal electrode and similarly charged. In this way, the required number of metal electrodes are charged and the preparation for imaging is completed. Metal electrode 203
It is more convenient to increase the thickness of the insulating film 202 and eliminate the unevenness of the surface in a place where there is no such a point so that scanning can be performed while the probe 204 is in contact.

Next, a light ray image 151 from the sample is applied to the image pickup plate having a plurality of charged metal electrodes. This ray image 1
A part of the light beam 51 is applied as a light beam 207 to one of the plurality of metal electrodes. When the depletion layer formed on the charged metal electrode is irradiated with light 207, electron-hole pairs are generated and the electrons are attracted to the vicinity of the boundary with the insulating film 202. Since the insulating film between the metal electrode 203 and the semiconductor substrate 201 is sufficiently thin, electrons tunnel from the semiconductor substrate 201 to the metal electrode 203. The potential of the positively charged metal electrode is lowered by the tunneled electrons. This decrease in potential increases as the amount of light increases and more electron-hole pairs are generated.

Then, when the probe 204 comes into contact with the metal electrode 203 again after one round of scanning, the potential drops, and a current flows between the probe 204 and the electrode 205 to compensate for this. This current increases as the amount of light increases in the pixel, and the amount of light is detected as current. In addition, a predetermined potential can be set again by the inflow of the current, and the preparation for the imaging of the next frame is made at the same time.

By the way, the light quantity of the light ray 207 applied to the metal electrode 203 varies depending on the metal electrode according to the intensity distribution of the light ray image. Further, the metal electrode constitutes a minute electrode and is surrounded by an insulator so that the metal electrodes do not come into contact with each other and are isolated from other metal electrodes. Therefore, when the current is taken out from the metal electrode with the probe, only the current of the target metal electrode can be taken out, and the current is not taken simultaneously from the surrounding metal electrodes. That is, by arranging the microelectrodes as in the present invention, one metal electrode can be made to act as the minimum unit that can take out an electric signal, that is, a pixel. In a device in which no microelectrode is arranged, the range of the image pickup plate from which the electrical signal is taken out by the probe is widened and high resolution may not be expected in some cases. However, according to the present invention, the resolution is determined by the pixel size and 1 μm. Since the following pixel sizes are sufficiently possible, high resolution can be expected.

At the final step, an electric signal corresponding to the position of the probe 103 is generated from the detected current value, and the probe 1
The image is displayed as an image on the CRT 142 shown in FIG. 1 corresponding to the position 03. Actually, the current data measured by the current detection means 132 is transferred to the computer 141, where it is converted into an electric signal corresponding to the position of the metal electrode and displayed on the CRT 142 as a numerical value and / or an image.

In the above description of the embodiments, the case where the probe 103 or 204 contacts the image pickup plate 101 or the metal electrode 203, respectively, is shown. It is also possible to detect the current by arranging them. However, in the method of arranging the probes close to each other, the variation in the distance between the probe and the imaging plate or the like may affect the detection value. In this case, it can be solved by a method of controlling so that the distance is always kept constant, or a method of controlling the distance so that the current value becomes constant and detecting the control signal. However, the contact scanning method described in the above embodiment has the advantage that the influence of the distance between the probe and the image pickup plate is completely eliminated, and that the current can be reliably detected for each metal electrode.

Further, in the above embodiment, the case where the plurality of metal electrodes on the image pickup plate are arranged two-dimensionally as shown in FIG. 2 has been described, but this is used for scanning the probe and analyzing the data. This is for ease of consideration. Therefore, the metal electrodes need not necessarily be arranged two-dimensionally as shown in FIG. 2, but may be arranged one-dimensionally, or may be arranged spirally or concentrically.

By the way, the probe 1 used in the above embodiment
03 or 204 has conductivity, but it may be formed of a conductive material or may be formed by forming a film of a conductive substance on a non-conductive material. There is also a method of integrally forming with the cantilever 102. FIG. 4 shows an example of a probe integrally formed with the cantilever.

The probe 401 and the cantilever 402 are made of Si.
An N (silicon nitride) core body 403 is integrally formed.
The support 404 is made of glass. On the core body 403 including the probe 401 and the cantilever 402, a NiCr alloy having a thickness of 1 nm is formed on the surface in order to provide electrical conduction, and further a Au film having a thickness of 390 nm is formed on the NiCr alloy film. A metal film 405 is formed. The core body 403 is
Like the cantilever and the probe used in the atomic force microscope (AFM), they can be produced by using the lithography technique. In addition to SiN, SiO ₂ (silicon dioxide) or the like can be used for the core body 403. The NiCr alloy film of the metal film 405 is provided to increase the adhesiveness between the core body 403 and the Au metal film 405, and is not provided when a conductive substance having good adhesiveness to the core body is used. Good. These, Ni
Both the Cr alloy film and the Au film are formed by the vapor deposition method. At this time, the length of the cantilever is, for example, 300μ.
m and the spring constant can be set to 0.1 N / m, for example. The tip radius of the probe can be set to, for example, 0.01 to 0.1 μm.

Further, in this embodiment, the computer can be used for managing the operation of each means and processing the obtained data. The scanning of the probe 103 can be performed by controlling the voltage from the driving means 123 and controlling the actuator 111 according to a command from the computer 141. Similarly, for switching the laser light source 112, the power source 122 is turned on and off by a command from the computer.
It can be performed by FF. The contact pressure between the probe 103 and the imaging plate 101 can be achieved by receiving the signal of the measuring means 121 for measuring the output from the light receiving element 113 by the computer and sending the signal to the driving means 123 of the actuator 111.

In each of the above-described embodiments, the case where X-rays are used as the light beam for irradiating the sample has been described. However, not only X-rays but also visible light can be used. Rays of up to wavelengths are applicable.

[0035]

As described above, according to the present invention, the structure of the pixels on the image pickup plate can be simplified by separating the image pickup plate and the means for reading the electric signal of the image from the image pickup plate. , The pixel size can be reduced to submicron. In particular, in the structure of the present invention, since a plurality of microelectrodes are provided so that they do not interfere with each other, each microelectrode can act as a pixel,
An electrical signal can be read out in pixel units. Unlike the conventional method in which the microelectrodes are not provided, the range in which the electrical signal is read does not change due to the distance from the probe, the applied voltage, or the like. As a result, the resolution can be increased almost 100 times as compared with the conventional one without requiring complicated adjustment such as miniaturizing the reading range. Moreover, with the configuration of the present invention, it is possible to further improve the resolution in accordance with the progress of the pixel miniaturization technology in the fabrication of the image pickup plate (for example, development of nanometer-sized pixels by lithography technology). By achieving such a high resolution, the condensed state of the laser light can be directly observed.

Further, in the present invention, it is possible to add an urging means for bringing the probe into contact with the image pickup plate. In this case, compared with the case where the probe is not in contact, the detection value due to the variation in the distance between the probe and the image pickup plate is added. Instability can be eliminated.

Further, if the present invention is applied to an X-ray microscope, the magnification of the X-ray optical element can be reduced, and there is a margin in processing, which leads to simplification of design and processing steps.
Further, due to the margin of magnification of this optical element, the lens barrel can be shortened and the microscope can be made compact.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a structure of an image pickup plate used in an example of the present invention.

FIG. 3 is an explanatory diagram showing a principle of an imaging method according to an embodiment of the present invention.

FIG. 4 is a schematic view showing a structure of a cantilever used in an example of the present invention.

[Explanation of symbols]

 101 image pickup plate 102 cantilever 103 probe 111 actuator 112 laser light source 113 light receiving element 121 measuring means 122 power supply 123 driving means 131 voltage applying means 132 current detecting means 141 computer 142 CRT 151 ray image 152 lens 201 semiconductor substrate 202 insulating film 203 metal electrode 204 probe 205 electrode 206 depletion layer 207 light ray 301 semiconductor substrate 302 insulating film 303 metal electrode 305 electrode 401 probe 402 cantilever 403 core body 404 support body 405 metal film

Claims (5)

[Claims] 1. An image pickup device for photographing an image of a sample by scanning an image pickup plate irradiated with a light beam transmitted through the sample or reflected by the sample, comprising: a semiconductor substrate; and an insulation formed on the surface of the semiconductor substrate. An image pickup plate including a film and a plurality of microelectrodes arranged on the insulating film; a conductive probe arranged to face the insulating film or the microelectrode; A scanning unit that relatively scans the film and the microelectrode, a voltage applying unit that applies a predetermined voltage between the probe and the semiconductor substrate, and a scanning unit between the probe and the semiconductor substrate. An image pickup device comprising: a current detection unit that detects a flowing current. 2. A biasing means for contacting the probe with the insulating film or the microelectrode by a predetermined biasing force when the probe is arranged in contact with the insulating film or the microelectrode. The image pickup apparatus according to claim 1, further comprising: 3. The image pickup device according to claim 1, wherein the plurality of microelectrodes are two-dimensionally arranged on the insulating film. 4. The probe according to claim 1, wherein the probe is formed of a conductive material or is formed by depositing a conductive substance on a non-conductive material. Two
The imaging device described. 5. The scanning means causes the probe to scan the insulating film and the microelectrode, and at the same time, the voltage application means charges the necessary microelectrode.
Next, after irradiating the imaging plate with a light beam that has passed through or reflected the sample, the probe is sequentially moved to the charged microelectrode, and the current is detected to flow between the probe and the semiconductor substrate. The current is controlled so as to be sequentially detected, and an electric signal corresponding to the position of the probe is generated from the detected value, and the detected value or the electric signal corresponds to the position of the probe, and a numerical value is obtained. And / or it is displayed as an image. The image pickup device according to claim 1.