JPH03196675A - Optical sensor and image sensor including the optical sensor - Google Patents

Abstract

PURPOSE:To improve light absorption characteristics and reduce the number of production processes by forming a polycrystalline silicon layer to be used for both photosensor section and TFT section and turning only the surface of the polycrystalline silicon layer of the photosensor section into amorphous one. CONSTITUTION:On an insulating substrate 1, areas of a source 21, a channel 22 and a drain 23 are formed. This active layer 2 is formed and, on this, a gate insulating coat 3 is formed. If the active layer 2 is polycrystalline silicon, a silicon oxide coat 3 is formed for the gate insulation. Then, polycrystalline silicon is formed on the silicon oxide coat 3 and patterned, and a gate section 4 and a base layer 51 of a sensor section are formed and an amorphous silicon layer 51 is formed on the area of the base layer 51 by implanting ions. Then, a silicon oxide layer 52 is formed on the surface of the amorphous silicon layer 51 by implanting ions, and a layer insulating coat 7, contact holes 9 and 10, contacts 11 and 12 for coplanar electrodes and a wiring 13 are formed. This enables improvement of light absorption characteristics and reduction of the number of production processes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical sensor using a polycrystalline material and an amorphous material as a photoelectric conversion element, and an image sensor having this optical sensor.

[Prior art]

Conventionally, amorphous silicon films used as photoelectric conversion elements have a characteristic of high light absorption, and are therefore suitable for use as optical sensors and have been praised. However, after forming the TFT section using polycrystalline silicon as a base material, a processing step is required in which an amorphous silicon film is deposited and this amorphous silicon film functions as a sensor section, resulting in a decrease in yield. , which has an impact on high costs. On the other hand, if polycrystalline silicon is used for both the TFT section and the optical sensor section, the number of steps can be reduced, but polycrystalline silicon has low light absorption and therefore has insufficient characteristics as a photoelectric conversion element.

JP-A-59-126666 is characterized in that a photoreceptor thin film is provided on the drain electrode of T F' T or an extraction electrode from the drain, and a transparent electrode is formed on the photoreceptor thin film, and the photosensitive thin film is as follows: Zn-5e, Cd-Te, 5
It is disclosed that amorphous films such as e-As-Te and Si, and polycrystalline films of Si are preferable.

Furthermore, Japanese Patent Laid-Open No. 60-22881 discloses that the channel portion of the TPT is made of polycrystalline silicon, and the first main conversion element is an amorphous silicon thin film.

〔the purpose〕

An object of the present invention is to provide an optical sensor that fully utilizes the characteristic that an amorphous silicon film has high light absorption.
An object of the present invention is to provide an optical sensor and an image sensor in which the optical sensor section and the TFT section can be formed in the same process.

〔composition〕

One of the present inventions is an optical sensor characterized in that a silicon oxide layer, an amorphous silicon layer, a silicon oxide layer, and a polycrystalline silicon layer are sequentially stacked in contact with a pair of coplanar electrodes. .

Another aspect of the present invention is an optical sensor and a thin film transistor (T
The present invention is an image sensor equipped with a scanning circuit and a switching circuit, each of which is composed of an optical fiber (FT), and is characterized in that the optical sensor is connected to the switching circuit.

The most important point of the present invention is that a polycrystalline silicon layer used in both the optical sensor section and the TFT section is formed, and only the surface layer of the polycrystalline silicon layer in the optical sensor section is made amorphous. It is.

The thickness of the silicon oxide layer in contact with the coplanar electrode is 500 mm.
The thickness of the amorphous silicon layer is 1,000 to 7,500, and the thickness of the silicon oxide layer not in contact with the coplanar electrode is 500 to 1,0.
00 people is preferable.

The coplanar electrode in contact with the silicon oxide layer is made of Cr,
A metal electrode such as AQ, Ti, Mo, etc. is preferable.

The amorphous silicon layer may be formed using one type of amorphous silicon, or may be formed using two types of amorphous silicon.

The amorphous silicon layer contains at least one selected from the group consisting of hydrogen atoms, halogen atoms, and inert gas atoms.
It is preferable to contain a seed atom (hereinafter referred to as A).

The polycrystalline silicon layer may be made of a single component, but may contain the above-mentioned A.

These atom introduction methods will be explained next.

In order to contain hydrogen atoms, there are H2 plasma treatment method, hydrogen ion implantation (method), etc. For example, when performing H2 plasma treatment, the conditions are H, 0,1 to 1 Torr in an atmosphere. (It is preferable to carry out the process using an RF power of 1 to 2.0 kW at a substrate temperature of 200 to 300°C. In addition, when incorporating halogen atoms, there are methods such as CVD (method) and ion implantation (method). The processing conditions are as follows:
For example, in the CVD method, 5iH2F may be mixed as a raw material gas when creating a polycrystalline matrix. Note that the halogen atoms, particularly F, play a role similar to H in compensating for the structural defects of a-5i. In case of ion implantation method, 2~4XIO15/
Perform alf doping. This improves the characteristics of the amorphous portion and TPT.

The present invention will be specifically described with reference to the drawings.

FIG. 1 shows a circuit including a scan circuit and a switching circuit composed of a TPT according to the present invention.

A specific example of an image sensor in which an optical sensor section is connected to the switching circuit is shown.

An active layer 2 is formed on an insulating substrate 1 made of quartz glass or the like with a buffer layer (not shown) interposed therebetween as required.

This active layer 2 is formed by forming a polycrystalline silicon thin film at a temperature of about 1,000 to 5,0
By depositing and patterning source 2
I, channel 22, and drain 23 regions are formed. In this formed portion, a P-type or N-type region is created as the source and drain 21, 23 by ion implantation, coating, glass formation, or the like. The dose is usually 2 to 4×10”/d of B+ or P.

A gate insulating film 3 is then formed on the active layer 2. When the active layer 2 is a polycrystalline silicon layer, a silicon oxide film 3 for gate insulation is formed by thermal oxidation or CVD. 50 at 1020-1070℃ for thermal oxide film
Approximately 0 to 1,000 people will be formed.

Thereafter, polycrystalline silicon is deposited on the oxide film by low-pressure CVD at a temperature of 630 DEG C. for 2,000 to 8,000 layers, and patterned to form the gate section 4 and the matrix 51 of the sensor section. Gate part 4 has Bo or P″″
Dope 2 to 4×10”/aJ.

The base body 51 region of the sensor section is filled with Si0 by ion implantation or the like in an amount of 1×101s to 5×10”/d.
The implanted amorphous portion 51 is formed within the range of . At this time, it is preferable that the thickness of the amorphous portion 51 be 1,000 to 7,000.

Furthermore, ion implantation of 09 (1 to 2
XIO"/cnt) L, SiO, and WI52 are formed. Then, thermal annealing is performed at 900° C. for 30 minutes. After this, H2 plasma treatment is performed.

For H22 plasma processing, H2 is 0.1~IT
1.0 to 3 in an atmosphere of orr. This is carried out at a substrate temperature of 200 to 400°C using OKW RF power. This improves the characteristics of the amorphous silicon layer and TPT (FIGS. 2 and 3).

Furthermore, as the N-open fiber membrane 7, SiO21S1ON, Si
A N film or the like is formed by approximately 3,000 to 7,000 CVD methods to form contact holes 9 for the source portion 21 and drain portion 23. Contacts for IO and coplanar electrodes 11.
After that, a metal thin film such as AQ, AQSi, etc. is formed and patterned, and a pattern a13 is performed.

〔effect〕

In the laminated optical sensor of the present invention, since there is an amorphous silicon film, the light absorption property is large and the product #JllJli
Since this is partially the same as the TFT section, the number of steps can be reduced.

Further, in the image sensor of the present invention, since the optical sensor and the TFT section can be partially manufactured in the same process, the number of processes can be reduced and the yield can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a specific example of the image sensor of the present invention. FIG. 2 shows the illuminance dependence of current characteristics in a single layer of amorphous silicon. FIG. 3 is a characteristic diagram of n-TPT. FIG. 4 shows a current characteristic diagram with respect to the film thickness of the silicon oxide layer 52 of a coplanar sensor according to the present invention, where the solid line is the dark current and the dotted line is the photocurrent at a wavelength of 550 nm and an illuminance of 100 Ru. 1... Insulating substrate 2... Active layer (polycrystalline silicon) 3... Gate insulating film (silicon oxide layer) 4... Gate portion 7... Interlayer insulating film 9.10... Contact hole 11.12...Contact for coplanar electrode 13...
- Metal wiring 21...Source region 22...Channel region 23...Drain region 51...Sensor base (amorphous silicon) 52...
Sin, layer Fig. 1 Fig. 4 5102 Film thickness (8)

Claims (1)

Claims: 1. An optical sensor characterized in that a silicon oxide layer, an amorphous silicon layer, a silicon oxide layer, and a polycrystalline silicon layer are sequentially stacked in contact with a pair of coplanar electrodes. 2. An image sensor equipped with a scanning circuit and a switching circuit composed of an optical sensor and a thin film transistor (TFT), wherein the switching circuit is provided with the above-mentioned claim 1.
An image sensor characterized in that an optical sensor is connected to the image sensor.