JPH01184954A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To form a high-sensitivity contact type image sensor in low cost by a method wherein a means for amplifying a signal from a photoelectric conversion element is provided in every photoelectric conversion element and all of the photoelectric conversion elements, a scanning circuit and the amplifying means are formed on the same insulating substrate. CONSTITUTION:All of photoelectric conversion elements, a scanning circuit and amplifying means are formed on the same insulating, substrate. When light is emitted to a photodiode 104, a charge stored in this photodiode is discharged according to the amount of incident light. That is, when the amount of incident light is little, a voltage, which is applied to a gate of a thin film transistor TFT 102 for amplification, is high and reversely, when the amount of incident light is much, the gate voltage of the TFT transistor 102 is reduced. The signal output of the diode 104 is amplified through this TFT 102. The amplified signal is outputted to a video line 105 by the scanning circuit 100 through a TFT 101. Hereinafter, the operation similar to the above is conducted in every pixel and a read of the amount of one line is finished by one time of scanning.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to 1. an amplifying solid state 5 & imaging device;

[Conventional technology]

Since the one-dimensional covert image sensor has a sensor length that is the same size as the document, it greatly contributes to miniaturization and cost reduction of facsimiles and image scanners.

For this reason, its development has become active in recent years. Television Society Technical Report V o 1.10, No-22 ED
As shown in 983, a contact image sensor in which a photoelectric conversion element and a scanning circuit for driving the same are integrated on the same quartz substrate has been developed and put into practical use.

On the other hand, with the aim of increasing the sensitivity of solid-state imaging devices, imaging probes in which each pixel is provided with an amplification function have been proposed. For example, a MOS type image sensor as shown in TV Zenten 3-4 (1986), IEEE Trans,
There are SIT type image pickup devices as shown in ED-33, 8 (1986).

[Problem to be solved by the invention]

In the MO3ffi contact image sensor shown in the conventional example, it is relatively easy to increase the length of the sensor and increase the resolution, but it is difficult to increase the reading speed because the output signal of the sensor is small. In addition, in conventional solid-state imaging devices with built-in amplification functions, the elements are formed on single-crystal silicon wafers, so the length of one chip is short. However, there was a problem in that the Senna implementation cost was high.

The present invention solves the above problems, and its purpose is to provide a high-sensitivity dense tU image sensor at low cost.

[Means to solve the problem]

The present invention provides a solid-state imaging device that includes a plurality of photoelectric conversion elements arranged periodically on an insulating substrate and a scanning circuit that drives the photoelectric conversion elements, including means for amplifying signals from the photoelectric conversion elements. Each photoelectric conversion element is provided, and the photoelectric conversion element, the scanning circuit, and the amplifying means are all formed on the same insulating substrate.

[Operation] FIG. 3 shows an equivalent circuit of the solid-state imaging device of the present invention. 10
0 is a scanning circuit, 101 is a thin film transistor (hereinafter TET)
) switch, 102 is an amplification TFT 1103, reset TFT 1104 is a 7-to-1 diode, 105 is a video line, 106 is a delay circuit, 200 is a video output terminal, 201 is a positive voltage application terminal, and 202 is a start pulse input terminal. In the figure, the part surrounded by a dotted line is an equivalent circuit for one pixel.

The operation of the circuit will be explained below. When a start pulse is applied to the terminal 202, the reset TPTIO3 is output and the voltage v0 applied to the terminal 201 is applied to the photodiode 104.
It takes. In this state, the photodiode is reverse biased, and charges are accumulated in the photodiode.

When light is incident on the photodiode, the charges accumulated in the photodiode are discharged according to the amount of incident light. That is, when the amount of incident light is small, the voltage applied to the gate of the amplifying TFT 102 is high, and conversely, when the amount of incident light is large, the gate voltage of the TFT 102 is low (this TFT 10
2, the signal output of the photodiode is amplified. The amplified signal is sent to the TF by the scanning circuit 100.
It is output to the video line 105 through Tlol. Similar operations are thereafter performed for each pixel, and reading for -line is completed in -times of scanning.

〔Example〕

The it diagram shows a cross-sectional view of the solid-state imaging device of the invention, and FIG. 2 shows a manufacturing process diagram of the solid-state imaging device of the invention. 1 is an insulating substrate, 2 is a TPT switch, 3 is an amplification TFT 14 and an interlayer insulating film, 5 is a transparent electrode, 6 is a photoelectric conversion element, 7 is an upper electrode and wiring material, and 8 is a protective film.

Examples will be explained below, following the steps. First, a polycrystalline silicon film (hereinafter referred to as polycrystalline silicon) is deposited on an insulating substrate 1 by low pressure CVD.
-3i) is deposited by 1000 to 2000 people. This insulating substrate may be made of Pyrex 7o59 (trade name) or fused silica glass, but in order to create a high-performance TPT, a quartz substrate that can be used in a high-temperature process is desirable. Next, pol on the board
y-Si is photo-etched into the desired TPT pattern (Fig. 2-(a)). At this time, Po1y-3i is TPT.
This is the channel section 10 of the TFTl shown in FIG.
ol, 102, 103, and TPT that constitutes the scanning circuit
Create at the same time. In FIG. 1.2, only two of these, the TPT switch 2 and the amplifying TFT 3, are depicted. This P
The surface of o1y-3i is thermally oxidized to form a gate oxide film 11, and po Iy-3, which will become the gate electrode 12, is formed on this.
About 5,000 people will form i. Phosphorus is thermally diffused into the upper poly-3i to lower the resistance of the gate electrode. Gate electrode 1
Baking po]y-3i into the form of 2. In this state, B+ ions are implanted into the channel section 10 to form a P channel section, and then P+ ions are implanted into the P channel section 20 with masking to form an N channel (Fig. 2-b). )6, the NSG of the living room insulating film is placed on top of the TPT thus formed.
Approximately 8,000 people will form a film using the CVD method. Next, the process moves on to forming a photoelectric conversion section (pixel section). Approximately 2,000 transparent electrodes, which will become the lower electrodes of the pixel portion, are formed by sputtering and patterned into a desired pattern. In this example, the transparent electrode is made of ITO (In
dium-Tin-Oxide) film was used, but SnO
*A membrane may also be used (*Figure 2-(C)). On this transparent electrode, amorphous silicon that will become a photoelectric conversion element is formed to a thickness of about 1 μm by plasma CVD, and patterned into a pixel pattern. Next, open the TPT contact hole (Fig. 2-(d)
)). Next, AJ2-8i-Cu becomes the upper electrode of the pixel part.
Approximately 7,000 people are sputtering to form a desired pattern.

At this time, TPT wiring is also done at the same time. Finally, a horizontal polyimide film (such as Photonice (trade name)) that will serve as a protective film is spin-coded to a thickness of approximately 1 μm, and cured in 220'C N gas to complete the solid-state imaging device chip. Figure 2-(e)).

In this example, poly-3i was used as the TPT material, but at the stage of poly-3i film formation (before patterning) in Figure 2-(a), means such as laser annealing or in-phase epitaxial growth were used. It is possible to single-crystallize poly-31 and improve the performance of TFTs.

In particular, when high performance is required only for the amplification TFT 102 (Figure 3), laser annealing only needs to irradiate the area where the TPT' 102 is located on the substrate, increasing throughput. You can also do it. In addition, by applying H and plasma to the TPT at a stage before the ITO buffing in FIG. 2-(C), P o 1
It is also possible to improve the performance of TPT by reducing the interface state of y-S i and increasing electron mobility. In some cases, the poly-
Amorphous 5isS by plasma CVO instead of 3t
i-Ge1 etc. may also be used.

Furthermore, in the circuit example shown in Fig. 3, an FET is used as the signal amplification element, but it is of course possible to use a thin-film bipolar transistor, static induction transistor (SIT), etc. as the amplification element, although the circuit configuration is different. . Further, in FIG. 8, signal amplification is performed only by FET-stages, but if it is desired to further increase the gain, the circuit can be configured to have a multi-stage amplification structure. In this case as well, if all the necessary transistors are made into thin films and integrated on the same substrate, the process can be exactly the same as that for conventional contact type image sensors that do not have an amplification function, and both the amplification element and the scanning circuit can be used for photoelectric conversion. Since it is integrated close to the element, it also has the advantage of achieving a high SZN ratio.

The solid-state imaging device shown in this embodiment has a signal output that is 100 times or more greater than that of a solid-state imaging device that does not have an amplification function.

[Effects of the Invention] As described above, according to the present invention, it is possible to realize a close-contact image sensor that can essentially extract a large output current without using an external amplification means. In the future, as contact image sensors become faster and higher in resolution, the storage time will become shorter, the pixel area will become even finer, and the output current that can be extracted directly from the pixels will become smaller. Considering these trends, the effect of the solid-state imaging device of the present invention, which can essentially produce a large output, is extremely large.

In addition, since all processes can be performed using thin film processes, it can be manufactured in the same process as the conventional contact imager/f by simply changing the photomask, and it is easy to lengthen the senna. It is.

Therefore, although it is provided with an amplification function, it can be manufactured at the same low cost as conventional contact imagers.

As described above, the present invention makes it possible to realize a high-performance solid-state imaging device at low cost, and the effects of the invention are tremendous.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the solid-state imaging device of the present invention. FIGS. 2(a) to 2(e) are process diagrams for manufacturing the solid-state imaging device of the present invention. FIG. 3 is an equivalent circuit diagram of the solid-state imaging device of the present invention. 1... Insulating substrate 2... TPT switch 3... TPT for amplification 4... Interlayer insulating film 5... Transparent electrode 6... Photoelectric conversion element 7... Upper electrode and wiring material 8. ...Protective film 10...TPT channel part 11...Gate insulating film 12...Gate insulating film 13...Contact hole 20...Source (drain) part 100...Scanning circuit 101... TPT switch 102... TPT for amplification 103... TPT for reset 104... Photodiode 105... Video line 106... Delay circuit 200... Video output terminal 201... Positive voltage application terminal 202 ...Start pulse input terminal amount Applicant Seiko Even Co., Ltd., Nol:? J Hi 14 Judgment Figure 1

Claims (2)

[Claims] (1) In a solid-state imaging device having a plurality of photoelectric conversion elements arranged periodically on an insulating substrate and a scanning circuit for driving the photoelectric conversion elements, each photoelectric conversion element has a means for amplifying a signal from the photoelectric conversion elements. A solid-state imaging device characterized in that each conversion element is provided, and the photoelectric conversion element, the scanning circuit, and the amplification means are all formed on the same insulating substrate. (2) The solid-state imaging device according to claim 1, wherein the photoelectric conversion element, the scanning circuit, and the amplification means are all formed of a thin film material.