KR830000682B1 - Radiation receiving surface - Google Patents

Abstract

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Description

Radiation receiving surface

1 is a cross-sectional view of a photoconductive imaging tube that is a representative example of a scaled light receiving device.

2 and 3 are plan and cross-sectional views of the light receiving surface of the present invention, respectively.

4 is a cross-sectional view of the embodiment

5 is an explanatory diagram of an apparatus for forming an amorphous silicon film

6 is a view for explaining an example in which the light receiving surface of the present invention used the light receiving line.

7 is an explanatory diagram of an example in which the light-receiving surface of the present invention is applied to a direct change X-ray saline-mediated tube

8 is a cross-sectional view of an example of a wave impact target.

The present invention relates to a novel radiation receiving surface.

A representative example of the light receiving surface conventionally used for the storage mode is the target of the photoconductive scratch tube as shown in FIG.

This is composed of a transparent substrate 1, a transparent conductive film 2, a photoconductive layer 3, an electron gun 4, and an outer container 5, which are usually called face plates.

The optical image of the incident light 7 formed on the photoconductor layer 3 through the face plate 1 is photoelectrically converted and accumulated on the surface of the photoconductor layer 3 as a charge pattern.

This accumulated charge is read in time series by the scanning electron beam 6.

At this time, an important characteristic required for the photoconductor layer 3 is that the charge pattern does not disappear by diffusion during the time interval (that is, the accumulation time) at which a particular rare is scanned by the scanning electron beam 6.

Therefore, as the material of the photoconductor layer 3, a semiconductor having a specific resistance of 10 ^k10 cm or more, for example, Sb, S ₃ , PbO, Se-based chalcogen glass, or the like is used.

If a material having a resistivity of less than 10 ^kL0 cm is used, such as Si single crystal, it is necessary to divide the surface on the electron beam scanning side into a mosaic shape to prevent the disappearance of the charge pattern.

Among these materials, Si single crystals have a complicated processing process, and other high-resistance semiconductors usually contain a high concentration of trap levels that hinder the running of the optical carrier, and thus have poor response characteristics.

Therefore, as an imaging device, the inconvenience that long afterimages and burnouts occur is likely to occur.

The present invention seeks to address the above drawbacks.

An object of the present invention is to provide a light receiving surface that can be applied to a light receiving element of a high resolution storage mode. In addition, the light receiving surface of the present invention has extremely small baking phenomenon, and the afterimage characteristic is also preferable.

By the way, the manufacturing method is simple.

The basic configuration of the present invention is as follows.

In addition, the light receiving surface of the present invention can be applied to light receiving such as infrared rays, visible rays, and electron beams.

Including these incident rays, electron beams, etc., it is only called radiation hereafter.

A plan view of the light receiving surface is shown in FIG. 2, and A-A cross-sectional view of FIG. 2 is shown in FIG.

The ohmic electrode 21 is installed on a part of the silicon single crystal substrate or polycrystalline substrate 20.

In this specification, both substrates are referred to simply as silicon substrates.

The electrode may be installed on the entire surface of the incident side of the silicon crystal plate as necessary, but in order to avoid absorption of radiation such as light or electron beam by the electrode layer, it is preferable to install the electrode in a ring shape around the silicon crystal substrate. .

On the back side of the radiation incident surface of the silicon crystal substrate 21, an amorphous silicon layer 22 containing hydrogen is formed.

Hydrogen-containing amorphous silicon layers generally have higher electrical resistance than silicon crystal substrates and are suitable as charge storage layers of light-receiving elements of storage modes.

In this light receiving surface, energy of incident radiation is absorbed by the silicon crystal substrate 20 to generate a conductive carrier, which is injected into the amorphous silicon layer 22 and accumulated on the surface thereof to form a charge pattern.

This charge pattern can be taken out as an electric signal, for example, by a charge reading means such as scanning of an electron beam like a scratch tube.

The thickness of the light receiving portion of the silicon crystal substrate 20 varies depending on the use of the light receiving surface, but 5 to 30 µm is suitable for imaging of visible light and high-speed electron beams, or 30 to 100 µm for receiving infrared rays.

If the incident radiation is light, the silicon crystal substrate can be formed on the light-transmissive support plate, but if the incident radiation is an electron beam, the silicon crystal substrate must be self-supporting in order to avoid a decrease in transmittance caused by the support plate. It is necessary to form ring-shaped thick portions to increase the mechanical strength of the substrate.

In general, the thickness of the thick portion is suitably 200 to 300 µm.

The thickness of the amorphous silicon layer 22 film containing hydrogen is preferably set to 1 to 10 m.

In order to reduce capacitive afterimage in an image pickup tube or the like, it is preferable that the layer is thick. However, if the layer is too thick, it is difficult to travel the injection carrier.

Therefore, the required electric field becomes high and the difficulty in using a light receiving surface increases.

The hydrogen content in amorphous silicon is preferably 5 to 40 at%.

If the hydrogen concentration is less than or equal to this, the specific resistance of the amorphous silicon layer is lower than 10 ^k10 cm, which makes it unsuitable as an accumulation type image tube photoconductive surface.

If the hydrogen concentration increases further, the difference in specific resistance with the silicon crystal substrate becomes apparent, and the sensitivity of the conductive carrier generated in the silicon crystal substrate to the amorphous silicon layer deteriorates and the sensitivity decreases.

The characteristics of hydrogen in amorphous silicon, sensitivity, resolution, and peeling of the film are shown in Table I.

TABLE 1

According to the inventor's stone, it has been found that an amorphous material containing silicon and hydrogen at the same time has the following advantages and is extremely preferable for use in a light receiving surface for imaging.

① The hydrogen content can be easily set to a high specific resistance of 10 ^l0 Ω · cm or more easily.

(2) In addition, since there are few traps that hinder the operation of the optical carrier, there is less seizure and good afterimage characteristics (the specific resistance of about 10 ^l4 Ω · cm may be the upper limit in reality).

This property can be found even when some impurities such as carbon, germanium, fluorine and phosphorus are contained in an amorphous material containing silicon and hydrogen simultaneously.

In the case of containing carbon, the specific resistance of the amorphous material is increased, and in the case of containing germanium, the specific resistance of the amorphous material is increased, and in the case of containing germanium, the specific resistance is lowered.

Germanium is particularly useful for controlling spectral sensitivity.

In water-containing Si-Ge amorphous materials, it is used in many cases to contain about 10 to 50 at% of silicon.

In addition, boron, phosphorus, and the like are effective for inclining the conductivity of the amorphous material to P-type or n-type, respectively.

These impurities are used in the range of lx10 <^-3> % to l% of red as needed.

Moreover, some oxygen is easy to contain during manufacture of an amorphous material.

The electron beam scanning surface of the light-receiving surface of this structure is preferably covered with a thin film of a suitable material because secondary electrons are generated due to the impact of the scanning electron beam, or injection of the scanning electron beam is likely to increase the dark current. Do.

As such a beam Ianding Iayer material, Sb ₂ S ₃ , CeO ₂ , AS ₂ Se _3, etc. are suitable, and in particular, a thin film obtained by depositing a Sb ₂ S ₃ porter film with a thickness of l00 mm exhibits good characteristics. Indicates.

Advantages of the present invention are as follows.

(1) Since the amorphous silicon layer 22 is present as a high resolution charge storage layer, there is no need to form a mosaic structure that prevents charge from flowing sideways on the electron beam scanning side as in the conventional silicon target.

Therefore, it is structurally simple.

② At the same time, the resolution is improved.

(3) When a strong incidence force enters, so-called image spreading called "blooming" has occurred due to the short circuit between elements occurring in accordance with the diffusion of charge in the conventional silicon target.

In the target of this structure, such a phenomenon and the quenching phenomenon by strong light do not occur.

(4) The light receiving surface of this structure does not require a supporting substrate like the conventional Sb ₂ S ₃ light receiving surface or PbO light receiving surface, and can be made to be self-supporting. .

⑤ Since the capacity of the light receiving surface is not determined by the capacity of the Pn junction, but by the capacity of the amorphous silicon film as in the conventional silicon target imager, the capacitive afterimage can be reduced by appropriately selecting the thickness of the amorphous silicon film. have.

(6) By forming the same kind of amorphous silicon layer on the crystalline silicon substrate, the adhesion between the two is better than that of forming other photoconductor layers.

(7) This amorphous silicon layer 22 can be formed by decomposition of silane by glue discharge, sputtering of silicon in an atmosphere containing hydrogen, electron beam deposition, or the like.

Therefore, the manufacturing method is extremely simple.

Prior to describing specific examples of the present invention, a method for producing an amorphous material used in the present invention will be described.

The most representative sputtering method is explained first.

5 shows a schematic diagram of a device used in this reactive sputtering method. The device itself is a common sputtering device.

Numeral 101 denotes a container capable of evacuating to vacuum, 102 denotes a sputter target, 103 denotes a sample substrate, 104 denotes a shutter, 105 denotes an input from a sputtered high frequency oscillator, and 106 denotes a Heater for substrate heating, 107 is a water cooling tube for substrate cooling, 108 is a high purity hydrogen inlet, 109 is a gas inlet such as argon, 110 is a pool, 111 is a pressure gauge, and 12 Is a vacuum gauge, and 113 is a connection port to an exhaust system.

The target for sputter | spatter may use what cut | disconnected the melted silicon. In the case of an amorphous material containing silicon, gelatin, or carbon, a target that combines these three Group IV elements is used.

In this case, for example, it is most preferable to use a target obtained by removing flakes such as graphite and gelium on a silicon substrate.

The composition of the amorphous material can be controlled by appropriately selecting the area ratio of silicon, gelium and carbon. Of course, on the contrary, for example, a thin silicon plate may be installed on the carbon substrate.

In addition, both materials may be juxtaposed and a target may be comprised, or the melt of a composition may be used.

As the sputtering target, for example, Si containing phosphorus (P), arsenic (As), boron (B) and the like can be introduced beforehand as these elements as impurity elements.

By this method, n-type, P-type, etc. conductivity type amorphous materials can be obtained.

In addition, by adding such an impurity, the resistance value of the material can be changed, and a high resistance of about 10 ^l3 kPa-cm can be realized.

In addition, the addition of such an impurity can also take the method of mixing diborane and a phosphine in ash gas.

Using the apparatus as described above, in the Ar atmosphere containing hydrogen (H ₂ ) at various mixing ratios, a high frequency discharge is generated, the Si and graphite are sputtered, and this is deposited on a substrate, thereby obtaining a pesticide. have.

In this case, the pressure of the Ar atmosphere containing hydrogen may be any range as long as it can maintain a glow discharge.

Generally, about 10 ^-3 to 1 Torr is used.

It is a good example that the pressure of hydrogen is in the range of 10 ^-4 to 10 ^-1 Torr, and the hydrogen partial pressure is 2 to 50%.

The temperature of the sample substrate is preferably selected between room temperature and 300 ° C.

150-200 degreeC is the most practical.

This is because it is difficult to introduce hydrogen into the amorphous material in a good state at too low a temperature, and hydrogen tends to be released from the amorphous ash at an excessively high temperature.

The amount of hydrogen contained is controlled by controlling the partial pressure of hydrogen in the Ar atmosphere.

When the amount of hydrogen in the atmosphere is set to 5 to 20%, the content of about 10 to 30 atomic% in the amorphous material can be realized.

For other compositions, the hydrogen partial pressure may be set based on this ratio.

The hydrogen component in the material quantifies the hydrogen gas generated by heating by mass spectrometry.

In addition, Ar in the atmosphere can be replaced with another rare gas such as Kr.

In addition, a magnetron type low temperature high speed sputtering device is preferable for obtaining a high resistance film.

The second method of producing the amorphous material of the present invention is a method using glow discharge.

Subjected to glow discharge decomposition of SiH ₄ up by the SiH ₄ is formed standing because the deposition on the substrate.

In the case of an amorphous material containing Si and C, a mixed gas of SiH ₄ and CH ₄ may be used.

In this case, the pressure of the mixed gas of SiH ₄ and CH ₄ is maintained between 0.1 to 5 Torr.

The glow discharge may be a direct current bias method or a high frequency discharge method.

In addition, since the change rate of the mixed gas of SiH ₄ and CH ₄ on, it is possible to control the ratio of the Si and C.

Next, the present invention will be described in detail using specific examples.

Example 1

This will be described using FIG.

A ring-shaped electrode 21 is formed around the glass substrate (thickness 2.5 mm, radius 13 mm) 10.

The electrode material is chrome and is about 500mm thick.

On the other hand, a circular silicon crystal having a thickness of 200 mm and a radius of 11 mm is etched in a portion having an inner diameter of 20 mm to 15 μm in thickness using fluoroacetic acid.

Etch masks are sufficient by using zone waxes on the epidermis.

The silicon crystal 20 thus prepared is bonded onto the electrode 2l with silver paste.

Subsequently, the prepared glass substrate is mounted on the spatter device.

The apparatus is as described using FIG.

Silicon was deposited by spattering at an Ar pressure of 5 × 10 ⁻³ Torr and a hydrogen partial pressure of 1 × 10 ⁻³ T0rr.

The frequency is 13.56 MHz and the pressure is 300 W.

As a result, an amorphous silicon film 22 having a hydrogen content of 25at% can be formed at 3 mu m.

Further, on this, the non-landing layer Sb ₂ S ₃ film 23 is deposited to a thickness of 100 nm in Ar of 5 x 10 ^-2 Torr.

In this way, the light-receiving surface for converting light could be produced.

As shown in FIG. 1, this light receiving surface was attached to the imaging tube as a target, and the characteristic was tested.

As a result, good results were obtained at a target voltage of 30 V, with a white light sensitization of 0.1 μA / 1 lux, a limit resolution of 900 TVs, less than 1 second of baking, 9% of no afterimage, and no blooming.

In addition, the peak of the spectral sensitivity of this imaging tube exists in wavelength 1.1micrometer, and is generally corresponded to the spectral intensity of crystalline silicon.

In addition, even when a polycrystalline plate is used as the silicon substrate, similar effects can be obtained by judging the charge to the amorphous silicon layer.

Needless to say, it is preferable that a single crystal plate is used because there is no adverse effect on image uniformity due to grain boundaries.

Example 2

The example which used the light receiving surface of this invention for light reception of an electron beam is demonstrated.

6 is this explanatory diagram.

Reference numeral 6l denotes an electron gun, and 62, 63, and 64 denote condensing lenses, objective lenses, and projection lenses, respectively, and all of them are constitutions in a conventional electron microscope.

Denoted at 60 is a sample, and 70 at the end of the sample.

The light receiving surface 65 of this invention was provided in this vertical position, and the side charge to which this light receiving surface is measured was taken out as an electrical signal by the scanning means of the electron beam similar to an imaging tube.

The configuration of the light receiving surface is as follows.

A portion of a 20 mm inner diameter of a circular silicon crystal having a thickness of 200 μm and a radius of 11 mm is etched to a thickness of 5 μm, and an amorphous Si-Ge alloy (amount of Ge is atomic%) at a thickness of 2 μm using a magnetron-type spatter device on the back side thereof. Spatter.

The Ar pressure during spattering is 8x10 ^-3 Torr and the hydrogen partial pressure is 3x10 ^-3 Torr. On top of this, a CeO ₂ film was deposited to a thickness of 50 nm in Ar of 7 × 10 ⁻² Torr.

The electron beam scanning means similar to the imaging tube is provided on the hydrogen-containing amorphous Si-Ge film side of the light-receiving surface described above.

The ring-shaped rapid plate may be sealed on the signal electrode 66 by the silicon crystal substrate 67 and the scratch portion by sealing the container in which the electron beam scanning means is built, using the metal plate 66 as the substrate.

Reference numeral 69 denotes an electron gun for scanning.

The inside of the mirror body is exhausted at 5 × 10 ⁻⁶ Torr, and the high-speed electron beam image 70 having an acceleration voltage of 180 KV is imaged on the silicon crystal surface 67.

The CeO ₂ surface side is then scanned with a low speed electron beam using an electron gun.

The current gain obtained at this time amounts to 5 × 10 ⁻³ .

Thus, it has been proved that this light receiving surface is useful as an electron multiplication target.

Example 3

The application example which used the light receiving surface of this invention for the electron shock target of an X-ray fluorescence pipe is shown.

7 is a cross-sectional explanatory diagram of the X-ray fluorescence pipe.

Except for the output part, it is basically the same as the conventional apparatus.

An input surface is provided inside the input side of the outer container 19 mainly made of glass or the like.

The input surface is generally formed on the output side of the substrate 11 made of aluminum or glass, and the photoelectric surface 13 is formed on the input surface.

The input fluorescent surface 12 is a fluorescent surface containing a halogenated alkali such as a oxide as a conductor and generally containing Na, Li, Tl, etc. as an activator.

Usually, it is about 100-500 micrometers thick.

The photoelectric surface 13 generally uses a cesium-antimony-based photoelectric surface and the like and has a thickness of about 1 μm or less.

In addition, an anode 16 and an electron impact target 14 are disposed inside the output side of the outer container 19, and the focusing electrode 17 is provided in connection with the side wall inside the outer container 19 again.

The inside of the outer container 19 is of course maintained in a vacuum.

Further, for example, the electron gun l5 is provided as a means for taking out the accumulated charges, facing the electron shock target 14.

The electron gun may be a normal video cone type one.

In this application, the photoelectrons generated in the same manner as in the normal X-ray fluorescence multiplication tube are bombarded with an electron shock target using a connection electrode, and are converted directly into an electric signal.

8 shows a cross-sectional configuration of the electron shock target 14.

Targets generally use a circle.

The ohmic electrode 21 is installed on a part of the silicon carbon crystal substrate or the polycrystalline substrate 20.

In this specification, both substrates are referred to as simply silicon crystal substrates.

In this country, in order to avoid the electron beam being absorbed by the electrode layer, an amorphous semiconductor layer 22 containing hydrogen is formed on the back side of the incident surface of the silicon crystal substrate 20.

Examples of the amorphous semiconductor layer include amorphous silicon, amorphous silicon containing gelum, and the like.

The electron beam scanning surface of the target of this structure has secondary electrons due to the impact of the scanning electron beam, or injection of the scanning electron beam is likely to increase the dark current, so that the thin film 23 of a suitable material is used. It is preferable to coat.

As such _{material, Sb 2 S 3, CeO 2} , As 2 Se 3 , etc. This would suitable, in particular, indicates that the thin film deposited porous film of Sb ₂ S ₃ to a thickness of about 100mm good properties.

Next, this electron shock target will be described in detail using specific examples.

A circular silicon crystal having a thickness of 200 mu m and a radius of 1 hnm is etched to a thickness of 15 mu m using a fluoroacetic acid in a portion having an inner diameter of 200 mm.

Etch mask is enough to use Effie wax.

The silicon crystal 20 thus prepared is bonded onto the electrode 2l with silver paste.

Then, the prepared glass gas is mounted on the spatter device.

Silicon was deposited by spattering at an Ar pressure of 5 × 10 ⁻³ Torr and a hydrogen partial pressure of 1 × 10 ⁻³ Torr.

The frequency is l3.56MHz and the input is 300W.

As a result, an amorphous silicon film 23 having a hydrogen content of 25at% can be formed to 3 mu m.

Further, a SbS ₃ film 23 is deposited to a thickness of 100 nm in Ar of 5 x 10 ^-2 Torr.

In this way, an electron shock target could be made.

The video cone-type electron gun 15 is provided to face the electron shock target.

The external terminal 10 is connected to the electrode 21.

The target voltage is, for example, about 30V.

In addition, an example of a hydrous amorphous Si-Ge film is described as a target.

A portion of a 20 mm inner diameter of a circular silicon crystal having a thickness of 200 μm and a radius of 1 lmm was etched to a thickness of 5 μm, and a non-crystalline Si-Ge alloy (the amount of Ge was 10at%) at a thickness of 2 μm using a magnetron-type spatter device on the back side. Spatter.

Ar pressure during spattering is 8.5x10 &lt; ^-3 &gt; Torr and hydrogen partial pressure is 3x10 &lt; ^-3 &gt; Torr.

On top of this, a CeO ₂ film was deposited to a thickness of 52 nm in Ar of 7 × 10 ⁻² Torr.

The electron beam scanning means similar to the imaging tube is provided on the water-containing amorphous Si-Ge film side of the light-receiving surface described above.

As described above, a direct change type X-ray image intensifier tube having an input fluorescent film, a photoelectric surface, and an electron shock target is constructed.

When DC25KV and DC100-200V are applied to the photoelectrode (cathode) wave anode and the connection electrode, the X-ray image is taken out as a video signal.

The performance is a conversion factor of ²⁰⁰ cd / m ² / mR / S and a resolution of 5.01p / mm, which is high sensitivity and high resolution compared to the conventional line image enhancement tube.

Claims (1)

A crystalline silicon substrate positioned on the incidence side of the radiation, and an amorphous silicon film containing hydrogen on the opposite side to the incidence side of the radiation, wherein a non-landing layer is formed on top of the amorphous silicon film. Light-receiving surface.

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