JPH0644451B2 - Method for manufacturing image pickup tube target - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a photodiode type image pickup tube target using a photoconductive film mainly composed of Se on a light receiving surface thereof, and particularly to an increase in image sticking and a signal during long-time operation. The present invention relates to a method of manufacturing a good image pickup tube target with suppressed current fluctuation with good reproducibility.

[Background of the Invention]

Amorphous Se exhibits photoconductivity and generally has p-type conductivity and makes rectifying contact with an n-type conductivity material, so that a photodiode-type image pickup tube target having this characteristic can be produced. . In this case, since Se does not have sensitivity to long-wavelength light, a method of adding Te to a part of the Se layer has been adopted to improve this (Japanese Patent Publication No. Sho 5).
2-30091, Japanese Patent Publication No. 56-41145).

FIG. 1 shows an example of the structure of a red-sensitized target according to the prior art, in which 1 is a transparent substrate, 2 is tin oxide,
An n-type translucent conductive film made of indium oxide or a mixture thereof, 3 is a p-type photoconductive layer made of Se-As-Te, 4 is a p-type photoconductive layer made of Se-As, and 5 is porous. Is a scanning electron beam landing layer made of Sb ₂ S ₃ . The rectifying contact is formed between the n-type translucent conductive film 2 and the p-type photoconductive film 4. Of the components contained in the p-type photoconductive films 3 and 4, Se is a material as a base material that makes contact with the n-type transparent conductive film 2 to form a rectifying contact.
Is a component for enhancing the sensitivity to red light as described above, and As is a component for enhancing the viscosity of the amorphous film mainly composed of Se and enhancing the thermal stability. Porous S
The b ₂ S ₃ layer 5 not only assists the landing of the scanning electron beam, but also has a function of preventing the scanning electrons from being injected into the p-type photoconductive film 4.

Since the transparent conductive film is positively biased with respect to the electron beam scanning plane in the image pickup tube, injection of holes and scanning electrons from the transparent conductive film 2 is blocked in the image pickup tube target as shown in FIG. A so-called photodiode type operation is exhibited, and good imaging characteristics such as a small dark current and a fast signal response (afterimage) with respect to a time change of incident light can be obtained.

However, if the above-mentioned image pickup tube target is continuously operated for a long time, there is a possibility that an increase in image sticking or a change in signal current may occur, and that the reproducibility of characteristics is not always sufficient from the viewpoint of mass production. It was

[Object of the Invention]

An object of the present invention is to provide a method of manufacturing an image pickup tube target which is capable of reproducibly producing a good light-receiving surface which suppresses an increase in image sticking and a change in signal current in a long-time operation of the image pickup tube target mainly composed of amorphous Se. Is to provide.

[Outline of Invention]

In order to achieve the above object, the gist of the present invention is to form the photoconductive film mainly composed of Se by heating and holding the substrate at an appropriate temperature when depositing the photoconductive film by the vapor deposition method.

According to the inventors, as a result of detailed investigation of the relationship between the manufacturing conditions of the photodiode type camera tube target mainly composed of Se and the camera tube characteristic, an increase in image sticking when the camera tube target is continuously operated for a long time or It has been found that the fluctuation of the signal current and the reproducibility of the characteristics are extremely dependent on the substrate temperature when the light receiving surface mainly composed of Se is formed.

A detailed description will be given below with reference to the drawings. FIG. 2 shows an example of a specific structure of the light receiving film for the image pickup tube target to which the present invention can be applied. In this example, Te for increasing the red light sensitivity does not exist at the position where the film thickness is zero, which corresponds to the interface with the transparent conductive film (3a part), and the concentration rapidly increases from the film thickness 500 Å part. It is added over a thickness of 1000Å (3b portion). As added to the portions 3a and 3b is for enhancing the thermal stability of Se. In the portion 3c, As has a film thickness of 10 in Se.
It is added so as to decrease with a uniform gradient over 00Å. As in Se has the property of forming a deep localized trap level for electrons and forming a negative space charge, in addition to the action of improving the thermal stability described above. Utilizing this property, the portion 3c is a sensitization auxiliary layer for effectively giving an internal electric field to the portions 3a and 3b which absorb the incident light and generate most of the signal current. The portion 4 is a layer for reducing the electrostatic capacity of the image pickup tube target to reduce the afterimage, and In this example, As is added at a uniform concentration in order to enhance the heat resistance. FIG. 3 shows an example of the applied electric field dependency of the photocurrent when such a target is formed by vacuum deposition without controlling the heating of the substrate. Fs in the figure is an electric field where the photocurrent begins to saturate. The target produced by the above method does not always have sufficient Fs reproducibility.
It varies within a range of × 10 ^{4 to} 6 × 10 ⁴ V / cm. In this case, if Fs is too small, the rectifying contact between the portion of FIG. 2a and the transparent conductive film is impaired and dark current is apt to increase when Fs is used under normal operating electric field strength. If it is too large, the sensitivity at normal operating electric field strength is insufficient. Such variations in Fs are due to poor reproducibility of the substrate temperature during film formation. FIG. 4 (a) shows an example of substrate temperature change during vapor deposition. Even when vapor deposition is started with the substrate at room temperature, the substrate temperature slightly increases due to radiant heat from the vapor deposition source. The manner of this increase largely depends on the initial substrate temperature and the vapor deposition rate. Due to such changes in the substrate temperature, the properties of the Se film are different, and Fs changes.

FIG. 4 (b) is an example of substrate temperature control for explaining the present invention. In this example, the film formation is performed while the substrate temperature is kept constant at 45 ° C. from the start of the deposition to the completion of the deposition. By such substrate heating vapor deposition, the fluctuation of Fs becomes 1/5 or less,
The reproducibility is greatly improved. Generally, when the substrate temperature is low, Fs is large, and when the substrate temperature is high, Fs is small. Therefore, when an image pickup tube target is obtained by substrate heating vapor deposition, it is desirable to reduce the film thickness of the portion 3c in FIG. 2 and the amount of As added so that the Fs is optimized.

Fig. 5 shows the substrate temperature and film pick-up tube target during film deposition.
It is a diagram showing the relationship of image sticking during continuous operation for a time.
With a target having a Te addition concentration of 40% by weight or less, the baking is once decreased as the substrate temperature during film deposition is increased, and is increased when the temperature is further increased. Therefore, the substrate temperature during film deposition must be 60 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower. Also, Te
On the other hand, if a target having an additive concentration of 40% by weight or more is used, vapor deposition of the substrate will cause an increase in baking, which is not effective.

It is clear that by performing the substrate heating vapor deposition as described above, the reproducibility of the characteristics and the baking after operating for a long time can be improved. However, the substrate temperature profile during deposition for obtaining these substrate heating vapor deposition effects is As shown in FIG. 4 (b), it does not have to be constant during the deposition, and may change with time. In this case, if the substrate temperature at the start of deposition is too high, the film at the initial stage of deposition will not be formed normally,
In-plane uniformity of properties at the interface is lost due to island-shaped formation or partial crystallization of the film,
Rectifying junction characteristics may be impaired and dark current may increase. Therefore, it is effective to control the substrate temperature at the initial stage of deposition to the lowest temperature during deposition.

Next, FIG. 6 shows another example of the specific structure of the light receiving film for an image pickup tube target to which the present invention can be applied.

In this example, Te does not exist at the position where the film thickness is zero, which corresponds to the interface with the transparent conductive film (3a ′ portion), and the film thickness is 500.
The concentration increases rapidly from the Å part, and the film thickness is 1 at 30% concentration.
It is added over 000Å (3b 'part).
As is uniformly distributed at a concentration of 6% in the portion 3a 'and 3% in the portion 3b'. The thickness of 3c 'is 50
Å The As concentration in that part is 20% and is evenly distributed. Further, GaF ₃ is uniformly distributed in this portion at a concentration of 1500 ppm. A target with such a structure has less image sticking to strong light and less change in sensitivity immediately after startup. An example of the substrate temperature control applicable to this target is shown in FIG. 6 (b).

In this example, the substrate temperature at the start of deposition is 35 ° C.
This temperature is gradually increased to 40 ° C. during the deposition of the part of FIG. After that, the portion shown in FIG. 3b 'is formed while the substrate temperature is kept at 40 ° C. Next, FIG. 6c '
Is formed while gradually increasing the substrate temperature to 45 ° C. Next, the portion of FIG. 6 is formed while gradually raising the temperature from 45 ° C. to 50 ° C. At this time, the vapor deposition rate is 30 nm / min for all layers.

In the case of this example, not only the effect of improving the reproducibility of the characteristics described above and the reduction of image sticking during long-time operation but also the effect of improving the sensitivity fluctuation during long-time operation can be recognized. FIG. 7 shows the sensitivity variation rate in the case of irradiating 10 × white light and continuously operating for 200 hours under normal operating electric field strength. In the target obtained within the range of the prior art, as shown in FIG. 6A, the sensitivity decreases due to long-term operation. However, in the target obtained by applying the present invention, the sensitivity change is suppressed as shown in FIG.

As a specific method for performing the substrate heating vapor deposition as described above, a method of heating by incorporating a heater in the substrate holder, a method of providing a heater close to the substrate holder and heating by radiant heat, and a halogen There is a method of heating the substrate holder or the substrate itself by using a light source such as a lamp, an infrared lamp, an incandescent bulb, or a laser as a heating source. Further, the heating source does not necessarily have to be provided inside the vapor deposition apparatus and may be provided outside the apparatus. It is also possible to use some of the above methods in combination.
Importantly, the film deposition substrate can be controlled to the desired heating temperature.

Further, the substrate heating vapor deposition can of course be combined with the rotary vapor deposition method as disclosed in JP-B-53-31829. In this case, the substrate temperature may pulsate microscopically depending on the configuration of the heating source, but the substrate temperature described here is a temperature obtained by averaging such pulsations.

Hereinafter, the present invention will be described according to examples.

Example of Invention

Example 1. A transparent conductive film mainly composed of tin oxide is formed on a glass substrate, and GeO ₂ is used as a rectifying contact auxiliary layer.
Å, CeO ₂ at a thickness of 150 Å 3 × 10 ^-6 Torr
Vapor deposition in vacuum. Next, the substrate temperature was raised to 30 ° C., and Se, As ₂ Se ₃ was added from another vapor deposition boat to 1 μm.
Evaporate to a thickness of ˜6 μm in a vacuum of 3 × 10 ⁻⁶ Torr. At this time, the As concentration is set to 3% and is uniformly distributed in the film thickness direction. Further, the substrate temperature is raised with time so that it becomes 45 ° C. at the end of vapor deposition.

Example 2. A transparent conductive film composed mainly of tin oxide is formed on a glass substrate, and the substrate temperature is kept at 30 ° C., and Se is deposited as a first layer to a thickness of 100 to 500 Å. Next, the substrate temperature is raised to 40 ° C., Se, As ₂ Se ₃ , and Te are evaporated from separate vapor deposition boats to form a second layer having a thickness of 500 to 1000 Å. At this time, the Te concentration is 25 to 3
The As concentration is 5% and the As concentration is 2%, and it is uniformly distributed in the film thickness direction.
Next, the substrate temperature is raised to 45 ° C., and as a sensitization auxiliary layer,
The third layer composed of Se, As, and In ₂ O ₃ is 50 to 90 Å
Evaporated to a thickness of. When depositing the third layer, Se, As
₂ Se ₃ and In ₂ O ₃ are simultaneously vaporized from separate vapor deposition boats. At this time, the As concentration is 20% and the In ₂ O ₃ concentration is 500 ppm, which are uniformly distributed in the film thickness direction. Next, while keeping the substrate temperature at 45 ° C., Se and As _{2 are used} as the fourth layer.
Se ₃ is vapor-deposited at the same time so that the total film thickness becomes 6 μm. At this time, the As concentration is set to 2% and is uniformly distributed in the film thickness direction. 2 × 10 ⁻⁶ T from the first layer to the fourth layer
Deposition in a vacuum of orr.

Example 3. A transparent conductive film mainly composed of indium oxide is formed on a glass substrate, and Se, As ₂ Se ₃ as a first layer is formed thereon.
Is vapor-deposited from separate vapor deposition boats to a thickness of 300Å. The As concentration is 6% and is uniformly distributed in the film thickness direction. At this time, the substrate temperature is controlled at 30 ° C. at the start of vapor deposition and at 35 ° C. at the end of vapor deposition.
Se, As ₂ Se ₃ , Te as a second layer on the first layer
Are vapor-deposited from different vapor deposition boats to a thickness of 500 Å. The Te concentration is 35% and the As concentration is 2%, which are uniformly distributed in the film thickness direction. The substrate temperature is 35 during deposition.
Gradually raise the temperature from ℃ to 40 ℃. A third layer is deposited on the second layer. As the third layer, first, Se, As ₂ Se ₃ , and In ₂ O ₃ are vapor-deposited by separate vapor deposition boats to a thickness of 50 Å as the first half. As concentration of this part is 2
5%, In ₂ O ₃ concentration is 300 ppm and is uniformly distributed in the film thickness direction. On top of that, 30 as the second half of the third layer
Se, As ₂ Se ₃ , and In ₂ O ₃ are vapor-deposited by separate vapor deposition boats to a thickness of Å. As concentration is 3%, I
The n ₂ O ₃ concentration is 300 ppm and is uniformly distributed in the film thickness direction. The substrate temperature during the third layer deposition is from 40 ° C to 43 ° C,
Gradually raise the temperature. Next, a fourth layer made of Se and As is vapor-deposited to have a total film thickness of 4 μm. The As concentration of the fourth layer is set to 3% and is uniformly distributed in the film thickness direction. The substrate temperature at the time of vapor deposition of the fourth layer is gradually raised from 43 ° C. to 45 ° C. during the first vapor deposition of 3 μm, and gradually lowered from 45 ° C. to 40 ° C. in the remaining portion. The vapor deposition from the first layer to the fourth layer is performed in a vacuum of 2 × 10 ⁻⁶ Torr.

Example 4. A transparent conductive film containing tin oxide as a main component is formed on a glass substrate, and CeO ₂ is added in an amount of 3 × 1 as a rectifying contact auxiliary layer.
Deposition is performed in a vacuum of 0 ⁻⁶ Torr to a thickness of 300 Å.
Se, As ₂ Se ₃ , and LiF as the first layer are vapor-deposited thereon from separate vapor deposition boats to a thickness of 200 Å. At this time, the As concentration is 10% and the LiF concentration is 800 ppm, which are uniformly added in the film thickness direction. The substrate temperature is kept constant at 30 ° C. Next, as a second layer, Se, As ₂ Se ₃ , Te, Li
Deposit F from separate vapor deposition boats to a thickness of 600Å.
At this time, the As concentration is 2%, the Te concentration is 33%, and the LiF concentration is 4000 ppm in the first half of the second layer, and 0 ppm in the latter half. The substrate temperature is 35 ° C. in the first half of the second layer and 4 in the latter half.
Hold at 0 ° C. Then a third layer is deposited. For the third layer, first, Se, As ₂ Se ₃ , and GaF ₃ are vapor-deposited to a thickness of 50 Å from separate vapor deposition boats. At this time, the As concentration is 20
%, GaF ₃ concentration is 1500 ppm and is uniformly distributed in the film thickness direction. The substrate temperature is kept at 40 ° C. Furthermore, Se and As ₂ Se ₃ were added from above to each other by 3 vapor deposition boats.
Evaporate to a thickness of 00-450Å. At this time, the As concentration is 10% and is uniformly distributed in the film thickness direction. The substrate temperature is maintained at 43 ° C. Next, a fourth layer of Se and As is deposited. For the fourth layer, Se and As ₂ Se ₃ are vapor-deposited from separate vapor deposition boats so that the total film thickness is 6 μm. The As concentration is 2.5%, and the As concentration is uniformly distributed. The substrate temperature is gradually raised from 43 ° C to 45 ° C.

Example 5. A transparent conductive film mainly composed of indium oxide is formed on a glass substrate, and GeO ₂ 15 is used as a rectifying contact auxiliary layer.
0Å and CeO ₂ 150Å are deposited in a vacuum of 4 × 10 ⁻⁶ Torr. Next, the first layer is deposited by the following procedure. First, _Se, depositing a As ₂ Se 3, LiF from separate evaporation boats thickness of 80-250A. At this time, the As concentration is 6% and the LiF concentration is 1000 ppm, and they are uniformly distributed in the film thickness direction. The substrate temperature is kept at 30 ° C.
Next, Se, As ₂ Se ₃ , and LiF are vapor-deposited to a thickness of 60 Å from separate vapor deposition boats. At this time, the As concentration is 10
%, The LiF concentration is 6000 ppm, and is uniformly distributed in the film thickness direction. The substrate temperature is kept at 35 ° C. Next, the second layer is deposited by the following procedure. The second layer is Se, As ₂ S
e ₃ , Te, CaF ₂ 300 Å from separate evaporation boats
Evaporated to a thickness of. As concentration is 2%, Te concentration is 30
%, CaF ₂ concentration is 2000 ppm, and is uniformly distributed in the film thickness direction. The substrate temperature is kept at 40 ° C. Next, Se, As ₂ Se ₃ , and Te were added from separate evaporation boats 30
Evaporate to a thickness of 0Å. As concentration is 2%, Te concentration is 3
Evenly distributed in the film thickness direction at 3%. Substrate temperature is 40 ° C
Hold on. Then a third layer is deposited. The third layer is Se, A
s ₂ Se ₃ is vapor-deposited with a thickness of 300Å from separate vapor deposition boats. At this time, the As concentration is linearly reduced from 30% to 2% according to the film thickness. The substrate temperature is 4
Set to 3 ° C. Next, the substrate temperature is set to 45 ° C. so that the total thickness of the fourth layer is 5 μm. The fourth layer is Se and A
s ₂ Se ₃ is vapor-deposited from separate vapor deposition boats so that the As concentration is 2% and uniform in the film thickness direction.

In Examples 1 to 5, Sb ₂ S ₃ , which is a layer for assisting the landing of the scanning electron beam, was added to the film formed by the method described in each example, 2 × 10 ⁻¹ Torr of Ar or N _2. It is formed to a thickness of 500 to 700Å in the atmosphere to complete the light receiving film for the image pickup tube target.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain an image pickup tube target which is excellent in characteristic reproducibility and has less image sticking or sensitivity fluctuation during long-term operation without deteriorating the conventionally obtained characteristic.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional image pickup tube target, FIG. 2 is a view showing a component distribution of a main part of the target shown in FIG. 1, and FIG. 3 is a view showing a VI characteristic of photocurrent. FIG. 4 is a diagram showing changes in substrate temperature during film deposition, FIG. 5 is a diagram showing relationship between substrate temperature and baking, FIG. 6 is a diagram showing changes in substrate temperature during film deposition, and FIG. It is a figure which shows the sensitivity change during time operation. 1 ... Translucent substrate, 2 ... Transparent conductive film, 3 ... P-type photoconductive film sensitized portion, 4 ... P-type photoconductive film, 5 ... Beam landing auxiliary layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadaaki Hirai 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inori Eisen, 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara Plant, Ltd. (72) Inventor Ikumitsu Nonaka 3300, Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory (72) Inventor Toshio Ogino, 3300, Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory (72) Inventor Shitara Keiichi 1-10-11 Kinuta, Setagaya-ku, Tokyo Within the Japan Broadcasting Corporation Broadcasting Technology Research Laboratory (72) Inventor Takashi Yamashita 1-10-11 Kinuta, Setagaya-ku, Tokyo Within the Japan Broadcasting Corporation Broadcasting Technology Research Institute (72) Inventor Kawamura Tatsuro 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Broadcasting Research Laboratories, Japan Broadcasting Corporation (72) Inventor Kenkichi Tanioka Tokyo 1-10-11 Kinuta, Setagaya-ku, Japan Broadcasting Technology Research Laboratories, Japan Broadcasting Corporation (72) Inventor, Eku Hisa 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Broadcasting Technology Research Laboratories, Japan Broadcasting Corporation

Claims (2)

[Claims] 1. An n-type conductive film and Se as a main component,
In the step of manufacturing an image pickup tube target having a p-type photoconductive film that forms a rectifying contact at an interface with the n-type conductive film, the photoconductive film is vapor-deposited while the substrate is heated and maintained at a temperature of 60 ° C. or less. A method of manufacturing an image pickup tube target, comprising: 2. The manufacturing of an image pickup tube target according to claim 1, wherein the p-type photoconductive film contains Te in an amount of 40% by weight or less in at least a part of the Se layer. Method.