JPS5946738A - Photoelectric conversion target and its manufacturing method - Google Patents

Abstract

PURPOSE:To reduce baking and residual image events under low illumination and obtain a good spectral sensitivity characteristic by joining the Sb2S3 area with different Sb concentrations and gradually varying the Sb concentration of a porous layer. CONSTITUTION:A photoelectric conversion target is comprised with a transparent conductive layer 2 applied and formed on a substrate 1, the first dense layer 3 made of Sb2S3 or Sb2S3 with excessive Sb applied and formed on the transparent conductive layer 2, the second dense layer 4 whose primary component is the Sb2S3 with excessive Sb applied and formed on the first dense layer 3, porous layers 5 and 6 whose primary component is the Sb2S3 formed on the second dense layer 4, and the third dense layer 7 whose primary component is the Sb2S3 with excessive Sb applied and formed on the porous layers 5 and 6. In addition, the Sb concentration of the said porous layers 5 and 6 is gradually or continuously increased as the layers go to the third dense layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photoelectric conversion array for an image pickup tube used in a color television camera, etc., and a method for manufacturing the same.

Conventional Structure and Problems Generally, the photoelectric conversion target of a vidicon type color image pickup tube used in a color television camera includes a photoconductive film made of antimony trisulfide (Sb2Ss). Such a photoconductive film can obtain good characteristics by forming a multilayer structure in which dense layers of sb, s5 and porous layers of Sb2S3 are alternately laminated.
The resulting charge gearing is not particularly satisfactory in terms of printing, image retention, and gamma characteristics. There was no.If strong light enters under low illumination, the black will be strongly burned in, resulting in very poor image quality.
The value tends to be excessive, resulting in insufficient color signal output in dark places.

Purpose of the Invention The present invention has spectral sensitivity characteristics particularly suitable for color image pickup tubes incorporated in single-type image pickup tube type color televisions/yeon cameras, and has less printing phenomenon at low or medium illuminance. The present invention provides a photoelectric conversion target for an image pickup tube that has excellent image retention characteristics and has sufficient color reproducibility under a wide illuminance range, and a method for manufacturing the same. The photoelectric conversion target consists of a transparent conductive layer deposited on a substrate, and a first layer made of Sb2S3 or 5b2s3 with excess sb deposited on the transparent conductive layer.
a dense layer, a 241st open can layer containing Sb-excess Sb2S3 as a main component and formed on this first dense layer, and a 241st open can layer containing 8b2S5 as a main component and formed on this second dense layer. and a third dense layer formed on the porous layer and containing 5b283 with excess sb as a main component, the porous layer has a sb concentration of It is characterized by having a stepwise or continuous height increase as it approaches the layer side, and its details and manufacturing method will be explained in detail below along with illustrated embodiments.

DESCRIPTION OF EMBODIMENTS A first diagram showing a cross section of a photoelectric conversion target in which the present invention is implemented.
In the figure, a glass disk 4 (Oj, 1) has a transparent conductive layer 2 on one surface thereof.

The transparent conductive layer 2 is made of, for example, indium oxide (In20
3) is deposited to a thickness of 500 to 1000 layers by sputtering, and a first dense layer 3 of 5b2Sx containing an excess of sb is deposited on the transparent conductive layer 2. ing. The first dense layer 3 can be formed under a vacuum level of 1 x 10 Torr or less, but in order to obtain a good layer that does not contain impurities or defects, it is recommended to form it under a vacuum level of 5 x 166 Torr or less. I like lever.

A second dense layer 4 made of 5b23° containing an excess of sb is formed on the first dense layer 3, and this second dense layer 4 is also formed under a vacuum degree of 5 x 10-' Torr or less. Preferably, it is formed below.

The first and second dense layers 3 and 4 are sensitivity regions that greatly contribute to photoelectric conversion sensitivity, and by adding excessive Sb, sensitization can be performed in a wide range centered on the optical wavelength of approximately 60011 m. You can do it. As a result of experiments, it was found that by adding an excessive amount of sb, the properties as a P-type semiconductor are strengthened. Therefore, when two Sb2S5 regions having different sb concentrations are joined together, a weak rectifying junction is obtained.

Figure 2 shows the voltage-' current characteristics of this rectifying junction. When a DC voltage is applied, it is difficult for current to flow compared to when a DC voltage is applied with the opposite polarity.
The greater the difference in concentration of b, the greater the tendency of the 11J rectification.

Furthermore, as shown in FIG.
An internal voltage is generated concentrated at the junction surface of the wafer, and this situation is shown in Fig. 3.

As is clear from this, when the Sb concentrations in the two regions are made uniform, the electric field acting inside is uniform, whereas when the Sb concentrations in the two regions are made different, the electric field is concentrated at the junction surface. An electric field is generated.

When such a concentrated electric field forming region is provided in the charge conversion section, charge carriers generated by light incidence are broken at a speed of force 1j in the region. Therefore, positive and negative carriers quickly reach both electrodes without recombining, improving sensitivity. And for that purpose, the 18'il dense layer 3
It is necessary to make the sb concentration of the second dense layer 4 more moderate than that of the second dense layer 4.

The difference in SbG content between the first and second dense layers 3 and 4 is large (
・I'i1% l The electric field becomes stronger, which is advantageous in terms of sensitivity. -However, the spectral sensitivity changes due to the photosensitizing action of sb at a specific wavelength, so there are restrictions on the sb concentration from the perspective of spectral sensitivity.

The first dense layer 3 needs to have -Jl high sensitivity mainly to achromatic light, and for this purpose, it is more advantageous to have a smaller value of sb. However, the transparent conductive layer 2 which is an N-type semiconductor
s of the first dense layer 3 for the purpose of forming an electric field at the boundary with
b is 71.68 to 76% by weight. Furthermore, it is advantageous to include sb in the second dense layer 4 at a higher concentration than in the first dense layer 3 to form a strong electric field, but if the sb concentration becomes too high, the spectral sensitivity will decrease. The peak shifts to the red side, making it unsuitable as a photoelectric conversion target for single-tube color image pickup tubes.

Therefore, the limit for sb of the second dense layer 4 is 76 to 80% by weight. In addition, the first and second dense layers 3 and 4
No matter which layer thickness is larger, the peak of spectral sensitivity shifts toward the red side. When used as a photoelectric conversion target for a single-tube color image pickup tube, it is preferable that the evening color sensitivity is 1.h, so it is advantageous in terms of spectral sensitivity that both layer thicknesses are smaller. (7) However, if the thickness is too thin, the overall sensitivity will decrease, so the thickness of each layer of the first and second dense layers 3 and 4 should be 1
00 to 1000 people is appropriate.

After forming the second dense layer 4, Ar, N2. Sb containing excess sb in an inert gas such as Ne or He
2S3 is evaporated and condensed to form first and second porous layers 6, 6 made of sb, s3. Since the porous layer 5.6 has a low density, its apparent dielectric constant is small, and the capacitance of the entire target becomes small.

Unfortunately, the porous JiQ layer has the property of allowing electrons to pass through but trapping holes, so by forming the porous layers 5 and 6, the overall electrostatic capacity becomes smaller and the afterimage characteristics are significantly improved. Furthermore, out of the large number of holes generated by photoelectric conversion, those holes directed toward the electron scanning side are absorbed. Then, the remaining n holes even after light irradiation are absorbed, and the image retention phenomenon is reduced.

However, the holes captured in the porous layer are transferred to the transparent conductive layer 2.
Since a reverse electric field is generated toward the side and cancels out the electric fields of the first and second dense layers 3 and 4, which are sensitive regions, the sensitivity of the portion where light is incident is lowered and a negative image-printing phenomenon occurs. In addition, the holes captured in the porous layers 5 and 6 combine with electrons gradually injected from the electron scanning side and disappear, so the dark current in this part decreases and is strong under low illuminance. When light is incident, a strong negative burn-in phenomenon occurs.

Therefore, in this invention, the sb concentration of the porous layer mainly composed of 5b2s is not uniformly changed, but is changed stepwise or continuously to generate an internal electric field, and the trapped holes are drawn by the internal electric field. By peeling it off, the above-mentioned seizure phenomenon is reduced. In addition, when forming a porous layer, the degree of vacuum is 1x l
If it is less than o-' Torr, it will not become completely porous and will become close to a dense layer.

However, if the degree of vacuum exceeds I x 10'-"i:orr, the porosity becomes strong and the passage W through the stopper hole decreases too much, reducing the sensitivity. Therefore, when forming a porous layer, The degree of vacuum is 1 × I Q-' Torr ~ I X 1
It should be set within the range of σ' Torr. however,
It should be taken into account that the addition of 02 to the inert gas slightly increases the porosity. Also, the degree of vacuum is 1X1
As the value approaches 0 Torr, not only the hole passage degree decreases, but also the ratio γ value of the signal to the amount of incident light may decrease.

Therefore, the degree of vacuum is set taking these into consideration. Since the thickness of the porous layer affects the γ value, the thickness of each of the first and second porous layers 6, 6 is preferably selected from a range of 100 to 4000 layers. Second dense layer 4 compared to first porous layer 5
When the sb concentration is low, no internal electric field is formed between the first multilayer layer 6 and the second dense layer 4, and no improvement in sensitivity can be expected, resulting in a large dark current. If a large amount of sb is added to the first porous layer 5, Sb2S3 and sb will separate. Since it is necessary to add sb to the second porous layer 6 at a higher concentration than the first porous layer 5, the practical sb@ degree in the first porous layer 5 is sb of 76 to It is 80% by weight.

The second porous layer 6 has a higher concentration of s than the first porous layer 5.
It is necessary to contain Sb, and the Sb concentration is 80 to 9.
It is appropriate to keep the oN amount within the range.

5b2s containing an excess of sb on the second porous through layer 6;

In order to make the third dense layer 7 a complete dense layer like the second dense layer 4, the third dense layer 7 has a temperature of I x 10-' Torr or more, preferably 5 x
It is formed in a vacuum of 1σ' Torr or less. If the Sb concentration is lower than that of the third NjM dense layer 7, the dark current will increase, so the Sb concentration is set to be equal to or higher than that of the second porous layer 6. Also, if the Sb concentration is too high, sb, sb and s
Since sb and b are separated, the sb-added crucible in the third iris layer 7 is 8
0-90 Heavy goods section is appropriate.

If the third dense layer 7 is too thick, the red sensitivity will be slightly increased. However, if it is too thick, the afterimage will increase, and if it is too thin, electrons from the electron scanning side will enter the first and second porous layers 5 and 6, impairing the fatness of the porous layer. 3rd dense layer 70 layer 1+, 4 1000 to 6000 people
The person is appropriate.

After the photoelectric conversion target formed as described above is enclosed in a vacuum device or a vacuum envelope of an image pickup tube,
Heat treatment is performed at a temperature of 50 to 200°C for 30 minutes or more. The required surface distance t''2 for this vacuum heat treatment is shorter if the temperature is high;
Set it longer if the temperature is low. This vacuum heat treatment improves the conformability of the contact surfaces between the layers, changes the grain structure, improves sensitivity, and prevents undesired temporal fluctuations in the signal current.

By changing the thickness distribution of the first porous layer 6 and the second porous layer 6, it is possible to particularly effectively reduce either the seizure under medium illuminance or the seizure under low illuminance. In other words, when the J layer thickness ratio of the first porous layer 5 is reduced, the "burning" phenomenon is reduced, especially under medium illuminance, and when the layer thickness ratio of the second porous layer 6 is reduced, it is reduced, especially under low illuminance. The firing phenomenon is reduced by ΦY. As for the flute body, it can be reduced more than the conventional one, regardless of the size of the layer thickness ratio. The following table shows specific numerical examples.

All measurements show the firing rate after 15 seconds of pattern imaging and light irradiation, and if the layer thickness distribution of the porous layer is appropriately selected, medium illuminance firing, low illumination firing and It can be seen that the problem of 1st problem can be reduced compared to the conventional method. In particular, burn-in under low illumination, which conventionally caused image quality to deteriorate significantly, is effectively improved. However, by appropriately selecting the pressure of the inert gas, the γ characteristic can be arbitrarily selected, and a sufficient color signal can be produced under a wide illuminance range. Therefore, particularly when used as a photoelectric conversion target for a single-tube color image pickup tube, good color reproduction characteristics can be achieved.

In addition, in the above embodiment, the porous layer is placed between the first layer and the second layer.
Although it is formed in layers, it may be formed in three or more layers, and instead of increasing the Sb concentration stepwise toward the third dense layer, it may be increased continuously. Furthermore, Sb2S
A small amount of impurity may be mixed into each layer of 3.

Effects of the invention Photoelectric conversion target i↓ of this invention, front! Since it is constructed with a double-sided structure, it is possible to reduce the image sticking phenomenon and image retention phenomenon under low or medium illuminance, and not only can good spectral sensitivity characteristics be obtained, but also the γ characteristics can be set arbitrarily. Therefore, it can be particularly applied to a color image pickup tube to obtain a satisfactory color signal output under a wide illuminance range.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a photoelectric conversion target in which the present invention is implemented, Figure 2 is a diagram showing the rectification characteristics at the junction surface of two Sb2S5 regions with different sb concentrations, and Figure 3 (a) is a diagram showing the rectification characteristics at the junction surface of two Sb2S5 regions with different sb concentrations. 611, a diagram showing the joint surface, Fig. 3 (1))
is a diagram showing the internal voltage at the junction surface. Name of agent: Patent attorney Satoshi Nakao IJ3 +・1
Figure 1 Figure 2 Figure 3 Figure C B

Claims (2)

[Claims] (1) A transparent conductive layer deposited on a substrate, a first dense layer made of Sb2S5 but still Sb excess Sb2S3 deposited on the transparent conductive layer, and a first dense layer deposited on the first dense layer. A second dense layer containing excess Sb2S3 as a main component, and a 5b2 layer formed on the second dense layer.
A porous layer containing S3 as a main component, and a third dense layer containing S3 as a main component with an excess of Sb adhered to the porous layer, the Sb concentration of the porous layer being is the third
A photoelectric conversion target characterized by increasing its height stepwise or continuously toward the dense layer side. (2) 5b2s with Sb of 71.6.8~76N
3 on the transparent conductive layer in a vacuum of 1 x 10-' Tor, r or less to form a first dense layer with a layer thickness of 100 to 100 people, and sb of 76 to 80 %Sb
2S5 in a vacuum of less than I x 10" Torr
I. Sb is deposited on the first dense layer, and Sb is deposited on the first dense layer.
The step of forming a second dense layer with a high concentration and a layer thickness of 100 to 1000 layers, and the step of forming a second dense layer with a Sb content of 76 to 80% Sb+) in a gas atmosphere of 83 f I X 10' Tor r or more Deposited on the second dense layer, layer 1'
forming a first porous layer with r% of 100 to 4000, and depositing Sb on the first porous layer in the gas atmosphere; (The Sb concentration is higher than that of the stroma layer) Must be I1. ° is 100 to 4ooO people / 152 multilayered 7ji layer formation stage, and sb is 80 to 90 folds jt% tvsb2s. and forming a third dense layer having a layer thickness of 1000 A to 6000 A by vapor-depositing it on the second porous layer in a vacuum of 1×10 Torr or less. Method.