JPS61154374A - Photoelectric converting device - Google Patents

Abstract

PURPOSE:To obtain a photoelectric converting device of simple construction, high reliability, light weight and economic excellence by providing a means for controlling an electric potential in a control elelctrode area of a capacitor and the like. CONSTITUTION:In a reading operation of a photosensor cell, a positive voltage of Vcc is applied to a wiring 12 and a reading pulse voltage VR with a wiring 25 grounded is applied to a capacitor 13, and then a displacememt of a base voltage is shown by an expression. Since Ck indicates a variable capacity, the base electric potential during a reading operation can be controlled by changing it. Namely, by enlarging Ck, the base electric potential during the reading operation is lowered, thereby an output read from an emitter electrode 8 is made small. On the contrary, by making small Ck, the output relatively becomes large. During a refresh operation, Ck is cut and made as small as possible and the base electric potential is completely heightened relative to an emitter electric potential to perform an effective refreshing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric conversion device, and particularly to a photoelectric conversion device having means for controlling the potential of a control electrode region of a photoelectric conversion transistor.

The present invention is applied to photoelectric conversion devices such as broadcast televisions and general video cameras.

[Prior art].

In recent years, research on photoelectric conversion devices, especially solid-state imaging devices, has been
With the progress of semiconductor technology, this has been actively carried out, and in some cases it has begun to be put into practical use.

One type of solid-state imaging device is a photoelectric conversion device disclosed in Japanese Patent Application No. 120755/1982. The photoelectric conversion device is based on the principle that charges generated by the incidence of light are accumulated in the pace of a bipolar transistor, and the collector current is controlled by the pace current flowing due to the charges.

The basic structure and operation of the optical sensor cell of the photoelectric conversion device will be described below with reference to the drawings.

Figure 5(a) shows a plan view of the optical sensor cell.
) shows a cross-sectional view of the AA' portion of the plan view of FIG. 5(,).

FIG. 6 is an equivalent circuit of the above-mentioned optical sensor cell.

It should be noted that parts common to FIGS. 5 and 6 are numbered the same.

As shown in FIGS. 5(a) and 5(b), this optical sensor cell consists of a silicon substrate 1 doped with impurities such as phosphorous, antimony (Sb), and arsenic (Am) to make it h-type or n+ type. On top of this, a paci-pace usually made of a PSG film or the like,
An insulating film 2 made of silicon oxide film (SiO2) and an insulating film made of SlO□ or 513N4 or a polysilicon film for electrically insulating between the optical sensor cell and the adjacent optical sensor cell. Element isolation region 4 composed of low impurity concentration n formed by epitaxial technology etc.
- region 5; p region 6, which is the base of a bipolar transistor doped with an impurity such as boron 0) using an impurity diffusion technique or an ion implantation technique; a bipolar transistor formed by an impurity diffusion technique, an ion implantation technique, etc. Will it be the emitter of a transistor? Area 7; For example, aluminum clad A (A
j) , Aj, -8t, A4-Cu-8i, or other conductive material 8;
Electrode 9 for applying a pulse; its arrangement [10: N+ region 1 with high impurity concentration formed by impurity diffusion technology etc. to make ohmic contact with the back surface of the substrate 1;
1; An electrode 12 formed of a conductive material such as aluminum for applying a substrate potential, that is, a collector potential of a bipolar transistor;

Note that reference numeral 19 in FIG. 5 (&) is a contact portion for connecting the n+ region 7 and the wiring 8. In addition, the alternating portions of the wiring 8 and the wiring 10 are so-called two-layer wiring,
9. These are insulating regions formed of an insulating material such as SiO2, and are insulated from each other. That is, it has a two-layer metal wiring structure.

The capacitor 13 in the equivalent circuit of FIG. 6 has an electrode 9 and an insulating film 3.
, is composed of MO8 structure of p region 6, and its capacitance is Co
Let it be x. The bipolar transistor 14 is composed of an n1 region 7 as an emitter, a p region 6 as a paste, an n- region 5 with a small impurity concentration, and an n or n+ region 1 as a collector.

The bipolar transistor 14 has a pace emitter junction capacitance Cbe 15, a pace emitter pn junction diode Dbe 16, and a pace collector junction capacitance Cba.
17. Base-collector pn junction diode Dbc
18 is used to express "C".

The shallow water operation of the optical sensor cell will be described below with reference to FIGS. 5 and 6.

The basic operation of this photosensor cell consists of a charge accumulation operation by light incidence, a readout operation, and a readout operation. In charge storage operation, for example, the emitter is grounded through the wiring 8, and the collector is biased to a positive potential through the wiring 12. It is also assumed that the pace has been brought to a negative potential, that is, to a reverse bias state with respect to the emitter 7, by applying a positive /4 pulse voltage to the capacitor 13 through the wiring 10 in advance. This Co
The operation of biasing pace 6 to a negative potential by applying irradiation to

When explaining the operation, explain it in detail.

In this state, when light 20 enters from the front side of the photosensor cell as shown in FIG. 5(b), electron-hole pairs are generated within the semiconductor.

Of these, electrons flow toward the n-region 1 because the n-region 1 is biased to a positive potential, but holes are rapidly accumulated in the p-region 6. Due to the accumulation of holes in the p region, the potential of the p region 6 gradually changes toward a positive potential.

Eventually, the accumulation of holes will cause the cypase potential to change to the emitter potential, in this case to ground potential, where it will be clipped.

More precisely, the space between the pace and the emitter is biased deeply in the forward direction, and the holes accumulated in the pace are clipped at a voltage that begins to flow out to the emitter. That is, the saturation potential of the photosensor cell in this case is approximately given by the potential difference between the bias potential when the Kp region is initially biased to a negative potential and the ground potential. When n4 region 7 is not grounded and accumulates charges generated by optical input in a floating state, p region 6 can accumulate charges to approximately the same potential as n region 1.

The operation of reading out the voltage generated by the charges accumulated in p region 6 as described above to the outside will be described next.

In the read operation state, the emitter and wiring 8 are in a floating state,
The collector is held at a positive potential vcc.

Now, before irradiating light, assume that the potential when PACE 6 is biased to a negative potential is -V, and irradiate 1 cJ of light? ) The generated accumulated voltage is V, then the base potential is -VII+Vp
The potential is as follows. In this state, when a positive voltage for reading (■) is applied to the electrode 9 through the wiring 10, this positive potential v8 is divided into the oxide film capacitance Cox13, the pace-emitter junction capacitance Cbe15, the pace-collector junction capacitance, and the amount C
The capacity is divided by 17.

Voltage is added to the pace. Therefore, the pace potential becomes. Here, if the following conditions are satisfied, the pace potential becomes - itself, the accumulated voltage V generated by light irradiation. When the pace potential is biased in a positive direction with respect to the emitter potential in this way, electrons are injected from the emitter to the pace, and since the collector potential is positive, they are accelerated by the drift electric field. Reach the collector.

When the positive voltage ■8 applied to the electrode 9 is returned to zero gelt, a voltage opposite to that when applied is added to the pace potential, so the pace potential is the state before applying the positive voltage vR, In other words, the current flow stops because the emitter is reverse biased.Next, the operation of refreshing the charges accumulated in the p region 6 will be explained.

In the optical sensor cell having the above configuration, as already mentioned, the charges accumulated in the p region 6 are not eliminated by the read operation. Therefore, in order to input new optical information, a fresh operation is required to eliminate the previously accumulated charge. At the same time, it is necessary to charge the potential of p region 6, which is in a floating state, to a predetermined negative voltage.

In the optical sensor cell having the above configuration, the refresh operation is also performed by applying a positive voltage to the electrode 9 through the wiring 1O, similarly to the read operation. At this time, the ivy is grounded through the wiring 8. The collector is grounded or at a positive potential through the electrode 12.

In this state, when a positive voltage of potential V□ is applied to the electrode 9, the paste 22 has an oxide film capacitance Cox, a paste-emitter junction capacitance Cbs 15, and a paste-collector junction capacitance Cbc 17. During the division, a voltage is applied instantaneously as in the previous read operation. Due to this voltage, the pace-emitter junction diode Dbs1
6 and pace-collector junction diode Dbc 1
8 is forward biased and becomes conductive, current begins to flow, and the pace potential gradually decreases. And Su7
As the pulse of the positive voltage ■□ for recieving falls, the pace potential is set to the initial negative potential -■, and the above operations are repeated in the same manner.

The basic operation of the optical sensor cell has been described above, but in order to control the output of the optical sensor cell, it is necessary to control the potential in the °C pace region in the storage operation described above. Generally, the intensity of the incident light is adjusted using a mechanical shield.
Since the structure is complex, the number of parts is large, resulting in a high failure rate, and automatic exposure requires a motor drive, which increases weight and requires a large power supply.

[Purpose of the invention]

In view of the problems of the prior art described above, an object of the present invention is to provide a photoelectric conversion device that has a simple structure, is highly reliable, and is lightweight and economical by providing an electrical output control means. It's true.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized in that output control is performed by providing means for controlling the potential of the control electrode region.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

In the following figures, corresponding parts are denoted by the same reference numerals and repeated explanation will be omitted.

FIG. 1 is a sectional view of a photosensor cell in a first embodiment of a photoelectric conversion device according to the present invention.

FIG. 2 is an equivalent circuit diagram of the optical sensor cell in the first embodiment.

In FIG. 1, 22 is a p region with high impurity concentration for making ohmic contact with p region 6;
is the wiring to connect the pace and the variable capacitor.

In FIG. 2, 24 is a variable capacitor C which is connected to the pace through the wiring 23. 25 is a wiring connected to the variable capacitor 22.

Now, in the readout operation of the optical sensor cell, with a positive voltage of vcci applied to the wiring 12 and the wiring 25 grounded,
When the read voltage pulse voltage vIL is applied to the capacitor 13, the displacement of the pace potential becomes. Since CI is a variable capacitor, by changing it, the pace potential during the read operation can be controlled. That is, by increasing CK, the pace potential during the read operation is lowered, thereby reducing the output read from the emitter electrode 8. Conversely, if CK is made smaller, the output becomes relatively larger.

Incidentally, during the refresh operation, by cutting off the C or making it as small as possible and making the pace potential sufficiently higher than the emitter potential, the flex can be performed reliably.

The photoelectric conversion device according to the present invention has been described above in terms of a type of photosensor cell that stores charge in the gate of a piezoelectric transistor. Even if the storage type photosensor cell is busy, the SIT f-) or MOS) transistor f-
By connecting a variable capacitor to ), a function to control the output can be provided.

FIG. 3 shows a second embodiment of the photoelectric conversion device according to the present invention. FIG. 3(&) is a plan view of the optical sensor cell, and FIGS. 3-) are cross-sectional views taken along the line B-B' of the plan view.

FIG. 4 is a circuit diagram of a drive circuit for an optical sensor cell in the second embodiment.

In FIG. 3(a), 24s24' and 24# indicate thin portions of the insulating oxide film 3, which are called r-) oxide films.

9. 9', 9' are electrodes for applying pulses to the pace by burning the dirt oxide film.

In FIG. 4, 13, 13'@13' are the p region 6, the f-) oxide film 24*24'e24', and the electrode 9.9'.

It is a MOB capacitor composed of 91 and 91, respectively.

Let the capacities be Cox, C'ox, and d'o, respectively.
Let it be x.

27.27', 27# are MOS capacitors 13.13'
.

13' is a MOS) transistor, 26°26'126' is a MOS) transistor 27.27',
This is the wiring for applying voltage to the 27N dart.

In Figure 4, three MOS transistors 27°2
The capacitance division ratio of the read voltage vIL can be changed depending on the combination of ON and OFF for 7'$27'.

For example, the capacitance of a MOS capacitor t COX : C
When designed so that 'ox:C''ox=4:2:1, the potential applied to the pace region by the read voltage vIL is as follows.m is MOS) transistor 27
．． This is a constant determined by the on/off combination of 27' and 27'.

For example, if MOS) transistor 27.27# is in the ON state and 27' is in the OFF state, the total capacity is (4+1)C
%! Therefore, m = 5.

In this way, by appropriately selecting the value of m, the pace potential during the read operation can be controlled, and therefore the output can be adjusted.

Incidentally, the storage operation and the 7-receipt operation are the same as those in the first embodiment of the photoelectric conversion device according to the present invention, and the explanation thereof will be omitted.

〔Effect of the invention〕

As described in detail above, according to the photoelectric conversion device according to the present invention, the output of the optical sensor cell can be controlled by providing means for controlling the potential of the control electrode region such as a capacitor. This makes it possible to provide a photoelectric conversion device that has a simple structure, high reliability, light weight, and excellent economic efficiency compared to conventional mechanical output control.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a photosensor cell in a first embodiment of a photoelectric conversion device according to the present invention. FIG. 2 is an equivalent circuit diagram of the optical sensor cell in the first embodiment. , FIG. 3(,) is a plan view of a photosensor cell in a second embodiment of the photoelectric conversion device according to the present invention. FIG. 3(a) is a cross-sectional view of the BB' portion of the plan view of FIG. 3(a). FIG. 4 is a circuit diagram of the optical sensor cell in the second embodiment. FIG. 5(,) is a plan view of a photosensor cell of a conventional photoelectric conversion device. FIG. 5(b) is a sectional view of the AA' portion of the plan view of FIG. 5(,). FIG. 6 is an equivalent circuit diagram of a photosensor cell of a conventional photoelectric conversion device. 1... Silicon substrate, 2... and silicone film,
3... Insulating oxide film, 4... Element isolation region, 5...
n- region (collector region), 6...p region (pace region), 7...n+ region (emitter region), 8.23...
·wiring. 9.12...electrode, 22...p region, 24.24
'. 24'...Dart Oxide Film Agent Patent Attorney Yama Shimozumi Figure 1 cc Figure 3 Figure 5

Claims (1)

[Scope of Claims] (1) By controlling the potential of the floating control electrode region of the photoelectric conversion transistor via a capacitor, carriers generated by photoexcitation are accumulated in the control electrode region, and the accumulated amount Read out the voltage generated in response to
Alternatively, a photoelectric conversion device that performs an operation of extinguishing accumulated carriers, further comprising a potential adjustment means for adjusting the potential of the control electrode region during the readout operation or the carrier extinguishment operation. . (2) The photoelectric conversion device according to claim 1, wherein the potential adjustment means is a variable capacitor connected to the control electrode region. (3) The photoelectric conversion device according to claim 1, wherein the potential adjustment means includes selection means for selecting the capacitance of the capacitor to a desired value. (4) The capacitor is comprised of a plurality of capacitors each having a desired capacitance, and the selection means selects one or more of the plurality of capacitors to set the desired capacitance. The photoelectric conversion device according to item 3.