JPS5954146A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain an image pickup device not deteriorating the resolution even if the operating voltage of a photoconductive film is reduced by forming the photoconductive film with a p-i-n structure and varying the thickness or specific resistance of a (p) layer or (n) layer with high specific resistance by location. CONSTITUTION:An n<+> area is formed on a p type semiconductor substrate 10 to make a diode 11. An n<-> well 12 constituting a CCD transfer means constitutes MOSFET together with the diode 11, a gate oxide film 13, and a gate electrode 14. An electrode 15 on one side of a photoconductive film 16 is insulated from a signal scanning circuit except part of the diode 11 by low-melting point glass 17 such as phosphorus silicate glass. An insulation layer 18 made of SiO2 with a grain size from tens A to several hundreds A is formed in the area on the photoconductive film 16, and In2O3(Sn) is formed on the photoconductive film 16 and an insulation film 16 by spattering deposition to make a transparent electrode 19, then light rays 20 enter through the transparent electrode 19 side.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the improvement of a solid-state imaging device having a combination of an image pickup tube or a photoconductive film and a scanning circuit board. The present invention relates to an imaging device that prevents resolution deterioration that occurs when the operating voltage of a photoconductive film is lowered.

Conventional configurations and their problems Conventionally, the target voltage of an image pickup tube target required a target voltage of several tens of volts. ), it is possible to lower the target voltage to about several volts, and since it has a blocking structure, it has good withstand voltage, and it is possible to widen the operating margin as an image pickup tube.

On the other hand, even in solid-state imaging devices that have a structure in which a photoconductive film is laminated on a substrate with a signal scanning function (hereinafter referred to as a stacked solid-state imaging device), in addition to limiting the power supply voltage, there are also restrictions on blooming and afterimage phenomena, and scanning circuits. Due to limitations from the withstand voltage of the photoconductive film, it is essential to lower the operating voltage of the photoconductive film.
From the i-layer, a photoconductive film such as (○goX, /;1.QiY41) is used.

As described above, there is a strong desire to reduce the operating voltage of photoconductive films in image pickup tube targets and stacked solid-state imaging devices. However, in the past, when the photoconductive film was operated with a lower voltage applied to it, there was a noticeable decrease in resolution, although there was no decrease in sensitivity or burn-out phenomenon.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an imaging device in which the resolution does not deteriorate even when the operating voltage of the photoconductive film is lowered.

In other words, the imaging device of the present invention includes a photoconductive film formed on a substrate, an electrode formed on the photoconductive film, and a signal scanning circuit, and includes a photoconductive film immediately after resetting the photoconductive film. The electric field in the thickness direction has different values depending on the in-plane direction of the film.

Explanation of Embodiment 6 Next, an embodiment according to the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a stacked solid-state imaging device in which a CCD is used in the signal scanning circuit, in which a plurality of cells are formed, and FIG. 2 is a plan view of the solid-state imaging device shown in FIG. It is a diagram showing a cross-sectional structure in the -B direction. FIG. 3 shows a driving pulse waveform of the solid-state imaging device (D) shown in FIG.

First, the operation of the solid-state imaging device shown in FIGS. 1 and 2 will be explained. When a signal read pulse is applied at time t1, the signal charge accumulated in the photoconductive film and the diode moves to the COD transfer stages 12a and 12b.
The diodes 11a-11c and the photoconductive film are charged to a certain value.

The pulse applied to the transparent electrode is to prevent the signal charge from moving outward due to the transfer pulse, and serves to keep the diode potential at a high potential except during the reset period due to capacitive coupling. Transfer stage 3 transfer 0I-1 load 0・-
'to, i・°°]''°ゝ1゛'' frequency is transmitted.

In the configuration shown in FIG. 1, the 6-page charge transfer stage is provided with potential blocking regions 30a to 30d and storage regions 31a to 31c, and can be transferred by two-phase driving. The diode and photoconductive film are arranged in one frame (33, 3
m5) After accumulating optical signals, it is charged again. The above is the field person's signal reading operation, and field B is reset in the same way as the field person after one field period (16,67 m5).

The above is an explanation of the operation of the solid-state imaging device shown in FIG. Next, a method for manufacturing the above solid-state imaging device will be described.

A diode 11 is formed by forming an n region on a p-type semiconductor substrate 1o.
shall be. Reference numeral 12 denotes an n-well constituting a COD transfer stage, and the diode 11, gate oxide film 13, and gate electrode 14 constitute a MOSFET. 16 is one electrode of the photoconductive film 16; Except for a part of the diode 11, the signal scanning circuit is insulated with a low melting point glass 17 such as phosphosilicate glass. The photoconductive film 16 is a7
8i: Jiglow discharge or sputtering of H 7 Formed by vapor deposition into an n-i-p structure or one-layer single-layer structure, but in either case, carbon or Nitrogen or llj: Oxygen and S
It may also be a compound with i. An insulating layer 18 made of SiO2 with a thickness of several tens of amperes to several hundred amperes is formed in a partial area on the photoconductive film 16, and In203 (Sn) is formed on the photoconductive film 16 and the insulating film 18 by sputtering deposition. A transparent electrode 19 is formed, and light 20 is incident from the transparent electrode 19 side.

The behavior of carriers generated by light incidence in the photoconductive film of the stacked solid-state imaging device configured as described above will be explained using FIG. 4. In particular, in this embodiment, since the signal charge is an electron, the behavior of the electron will be mainly explained in its entirety. For simplicity, FIG. 4 is a schematic vertical band model diagram of one cell in the case where the photoconductive film 16 is a single i-layer. Figure 4(a)
represents when a bias is applied to the photoconductive film in a dark state, where the part with the insulator layer (hereinafter referred to as large area) is shown by a solid line, and the part without an insulator (hereinafter referred to as area B) is shown by a dotted line. It shows. FIG. 4(b) is a plan view showing the relationship between area A and area B. As is clear from this figure, the potential of region A is set lower than that of region B due to the presence of the insulating layer. If there is light incidence, the electrode 16"
Charges other than those generated in region B reach the i-layer-insulator layer 17 interface due to the electric field. A part of these charges is trapped in the interface level between the photoconductive film 16 and the low melting point glass 17, and increases the potential of this interface.

As a result, as shown in FIG. 4C, two regions A sandwiching region B are separated by a potential barrier formed by region B over the entire thickness direction of the photoconductive film.

FIG. 4(d) shows the case of a conventional solid-state imaging device without an insulator layer, in which a potential barrier exists near the interface between the i layer and the insulator layer 17, but the transparent electrode 190 The potential barrier in the most important region for photoelectric conversion is very small. In order to explain the states of FIGS. 4(C) and (d) more clearly, FIG. 6 shows the lateral potential distribution of the photoconductive film 16, and FIG. In the case of the embodiment, FIG. 5(b) shows a conventional example. From FIG. 6(a), using the present invention, it is possible to effectively confine the signal charge in the area A, and the flow of the charge 40 in the lateral direction is reduced, which has the effect of not deteriorating the resolution. You can see what you can get. Further, the probability that electrons 40 flow in the region B and holes 41 flow in the region B increases. This reduces the probability of recombination of electrons and holes, making it possible to further reduce the operating voltage of the photoconductive film.

In the embodiment described above, the i of a-3t is used as the photoconductive film 16.
Although a single layer is used, the same effect can be obtained by using a-3tf having an n-1-p structure.

In the n-1-p structure, when the p layer is made of a compound of carbon, nitrogen, or oxygen and silicon and is used as a high resistance layer, it is possible to have a structure different from the above embodiment.
This will be explained using FIG.

FIG. 6 is a band model diagram similar to FIG. 4, and the region A indicated by the solid line is the signal charge confinement region. here,
As shown in FIG. 4(b), if a thinner part of the p layer is formed as the B region, the potential on the Boehmi electrode 19 side of the transparent electrode 10 is the same in the A and B regions. As shown by the dotted line in the figure, a potential barrier similar to that obtained when an insulator is formed is formed. The above-mentioned structure (is also possible with a single i-layer photoconductive film, but in this case, the A region and B region
An effective potential barrier cannot be formed unless the film thickness difference between the regions is made sufficiently large.

By the way, the method of forming an insulator or a high resistance layer on a photoconductive film is similar to that of other photoconductive films with low operating voltages, such as Zn.
xCdl-xSe-ZnyCdyTe (In) (
A similar effect can be obtained even when applied to OIX l'1, OI Y l1'). In addition, in the example shown in FIG. 2, one pixel has one A area and a B area existing around it, but there are multiple independent A areas within one pixel area. However, there is no particular need for alignment.

In the embodiments described above, among solid-state imaging devices that combine a photoconductive film and a scanning circuit, a solid-state imaging device that uses a CAN as a scanning circuit is particularly described.
Since the present invention concerns the photoconductive film portion, it goes without saying that similar effects can be obtained even if a scanning circuit having a BBD or 11.times.MOS address function is used. When applied to an image pickup tube, a high resistance layer or an insulating layer is formed in some areas on the side where light enters, and in the case of a photoconductive film with an n-1-p structure, an n A similar effect can be obtained by varying the layer thickness.

Effects of the Invention The imaging device of the present invention can prevent deterioration in resolution that occurs when the operating voltage of the photoconductive film is lowered, and has extremely great industrial significance.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a plurality of units of a solid-state imaging device in which a scanning circuit has a stack of photoconductive films formed by COD, and FIG.
The figure is a cross-sectional view of one pixel of the solid-state imaging device shown in FIG. 1, and FIGS. 3 (-) to (C) are pulse waveform diagrams for driving the solid-state imaging device shown in FIG. 1. , Fig. 4(a) ~(
d), ts (a), (b), and FIG. 6 are detailed illustrations of the present invention. 10...p-type semiconductor substrate, 11...diode, 12...n wenope 13...
・Gate oxide film, 14... Gate electrode, 15.
...Electrode, 16...Photoconductive film, 17...
...phosphosilicate glass, 18... high resistance layer,
19...Transparent electrode, 2o...Incoming light. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 ℃1 Shoten Figure 5-253- Figure 6

Claims (7)

[Claims] (1) It has a photoconductive film formed on a substrate, an electrode formed on the photoconductive film, and a signal scanning circuit, and the electric field in the film thickness direction immediately after resetting the photoconductive film is An imaging device characterized by setting different values depending on in-plane directions. (2) The photoconductive film is formed with a p-1-n structure of an amorphous semiconductor thin film mainly composed of silicon, and the thickness or resistivity of the p-layer or n-layer, which has a high resistivity, is varied locally. An imaging device according to claim (1), characterized in that: (3) At least either the p layer or the n layer,
The imaging device according to claim (2), characterized in that a compound semiconductor thin film made of silicon and at least one element among carbon, nitrogen, or oxygen is used. (4) Amorphous semi-2 whose photoconductive film is mainly composed of silicon
ti-, , :・ The invention is characterized in that it consists of a conductor thin film and an insulator or high-resistance layer formed on a part of one side of the amorphous semiconductor thin film. imaging device. (5) The photoconductive film is ZnxCd, -xSe-ZnyC
d,−,Te(In)(0,ffX,<1,Of
Y,<1) and the above Zn, Cd, -,5e-Zn
yCdyTe(In) (0,?Xf1, OfY,
ff1) The imaging device according to claim 1, further comprising an insulating material or a high-resistance layer formed on a partial region of one side of the ff1). (6) Claims (1), (2), and (4), wherein the signal scanning circuit includes an electron beam. or (the imaging device described in Section 4). (7) Claims 0) and 2), wherein the signal scanning circuit is a charge transfer element or a MOS address element formed in a substrate. The imaging device according to item (4) or item (5).