JPH01136364A - Image sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an image sensor, a process of which is simplified and which has high yield and stable characteristics, by forming a source-drain electrode for an a-SiTFT for a switch and a lower electrode for an a-Si photodiode of a common wiring conductor film and directly shaping the a-Si photodiode onto the source-drain electrode. CONSTITUTION:A gate electrode 2 is formed onto an insulating substrate 1, and a gate insulating film 3, an undoped a-Si film 4, and an N<+>-a-Si film 5 to which phosphorus is doped are shaped continuously. The undoped a-Si film 4 and the N<+>-a-Si film 5 in a section except a section to which a TFT is formed are removed, source-drain electrodes 6 are shaped onto the whole surface, and the source-drain electrodes 6 for the TFT are formed while a lower electrode section for an a-Si photodiode is shaped simultaneously. N<+>-a-Si in a section corresponding to a channel section for the TFT is gotten rid of through etching, and a protective film 7 and a light-shielding film 8 are formed. An a-Si film 9 as the photodiode is shaped, and a transparent electrode 10 is formed, thus completing a device.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image sensor and a method for manufacturing the same.
In particular, amorphous silicon (hereinafter referred to as a) is placed on the same insulating substrate.
-3l) Photodiode and switching a-
3iFi film transistor (hereinafter referred to as thin film transistor TP)
The present invention relates to an image sensor that is inexpensive and has stable characteristics and is formed by integrating an image sensor (referred to as T), and a method for manufacturing the same.

[Conventional technology]

FIG. 2 is a cross-sectional view of an image sensor (line sensor) that integrates a conventional a-5i photodiode and a switching a-3 ITFT disclosed in, for example, Japanese Patent Application Laid-Open No. 61-89661. In the figure showing only the pixels, 1 is the insulating substrate, 2 is the gate electrode, 3 is the gate insulating film, 4 is the AND-PRO-3i film, and 5 is the insulating substrate.
is an n''-a-3t film doped with phosphorus to make ohmic contact with the source/drain electrode 8i6, 6 is the source/drain electrode, 7a is a channel protective film, and 7b is TP.
10 is a transparent electrode; 11a and 11b are electrode materials for connecting the a-Sl photodiode and the switching a-3iTPT.

The operation of this image sensor is well known; the incident light is photoelectrically converted by the electrode material jib, the a-3i film 9, and the transparent electrode 10, and the converted signal is converted by turning on the TPT gate. Read externally.

[Problem that the invention seeks to solve]

Conventional a-3l photodiode and switching a-
Since the image sensor that integrates the 3LTPT is configured as described above, the a-3l photodiode and the switching a-3i TFT are formed separately, so the a-Sl photodiode and the switching a-3i TFT are formed separately. a-3i TFT must be connected with the electrode material 11a, and the transparent electrode 9 or the source/drain electrode must be connected at the contact area between the electrode material 11b and the transparent electrode 9 or the contact area between the electrode material 11a and the source/drain electrode 6. The oxide film formed on the electrode material 11 may cause a contact failure due to the oxide film formed on the n''-a-3t film 5.
There is a risk that the gap with the AND-PRO-3i film 4 cannot be covered and the wire will be disconnected, causing a poor connection between the a-3i photodiode and the switching a-3i TFT, making the characteristics unstable and reducing the yield. There was a risk of lowering the

This invention was made in order to solve the problems of the conventional ones as described above, and provides an image sensor and its manufacture that can obtain an image sensor with a simple process, high yield, and stable characteristics. The purpose is to find out how.

[Means for solving problems]

An image sensor and a manufacturing method thereof according to the present invention include:
The source/drain electrode 6 of the switching a-3i TFT and the lower electrode of the a-3i photodiode are used as a common wiring conductor film, and the a-3t photodiode is directly formed on the source/drain electrode 6 of the switching a-3i TPT. It was designed to do so.

[Effect]

In this invention, the source/drain electrode 6 of the switching a-31TPT and the lower electrode of the a-3l photodiode are used as a common wiring conductor film, and the a-3t photodiode is formed directly on the source/drain electrode 6. This not only simplifies the process, but also eliminates connection defects between the A-3T photodiode and the switching A-3LTPT, making it possible to obtain an image sensor with stable characteristics at a high yield.

(Example〕 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an image sensor according to an embodiment of the present invention, in which 1 is an insulating substrate such as a glass substrate, 2 is
is a gate electrode made of Cr, for example, and 3 is a gate electrode made of, for example, 513N.
4 is an AND-PRO-8L film which is an active layer; 5 is a phosphorus-doped N-A- film for making ohmic contact with the source/drain electrode 6;
3iM, 6 is a source/drain electrode made of, for example, Cr, 7 is a protective film made of, for example, S l s Na, 8 is a light-shielding film made of, for example, AI and prevents light from entering the channel portion of the TPT, and 9 is a photoconductor. a forming a diode
-3L membrane, for example, an and-pro-3L membrane. Further, 10 is a transparent electrode made of, for example, indium tin oxide (ITO).

Next, a method for manufacturing this example will be explained using the process flow diagram of FIG. First, a switching a-3i TFT is formed on a wA green substrate (see FIG. 3(a)). A gate electrode 2 is formed on an insulating substrate 1, and a gate insulating film 3. AND-PRO-3i membrane 4. phosphorus doped n
"-a-3t film 5 is continuously formed by RF plasma CVD method (see FIG. 3(b)), and then an and-pro-5t film 4.n"-a-3t film is formed in the area other than the part where TPT is formed. 5 is removed by etching, source/drain electrodes 6 are formed on the entire surface by vacuum evaporation (see FIG. 3(C)), forming the TPT source/drain electrodes 6 and forming the lower electrode of the a-3L photodiode. Form parts simultaneously. Furthermore, n''-a-3t of the portion corresponding to the channel portion of the TPT is removed by etching, and a protective film 7 for protecting the channel portion is formed thereon (see FIG. 3(d)). A light-shielding film 8 is formed to prevent light from entering the channel portion (see Fig. 3).
(see e)).

Next, form an a-3l photodiode. The lower electrode of the a-St photodiode is a-3iT for switching.
Since it has already been formed when forming the source/drain electrodes 6 of the FT, no special process is required to form this lower electrode.

The a-3t film 9 that will become a photodiode is exposed to RF plasma P.
After forming by CVD method, a-3t film 9 and Schottky barrier are formed, and a-3iP! When a transparent electrode 10 for guiding light to the first electrode 9 is formed (see FIG. 3(f)), the first
The device shown in the figure is completed.

As described above, according to this embodiment, the source/drain electrodes of the switching amorphous silicon thin film transistor and the lower electrode of the amorphous silicon photodiode are formed from a common silicon substrate film, which simplifies the process. This eliminates the risk of disconnection due to the step between the eyebrows, eliminates the need for an electrode material between the thin film transistor and the photodiode, and eliminates connection defects caused by the formation of an oxide film, resulting in a high yield.

In the above embodiments, an and-pro-St single-layer a-3t photodiode was described, but boron-doped a-3L (p"-a-3t), and-pro-3t, and phosphorus-doped a'- 3i (n” -a-
The three layers of Si) are p + a -3t/undoped a
-3l/n''-a-3i, or in the reverse order.Also, p''-a-
3i/undoped a-3t or and-pro-3t
A photodiode configured with two layers of /n''-a-St or a photodiode stacked in the reverse order may be used.

Furthermore, in the above embodiment, an a-3t film was used as the active layer of the switching a-3t TFT, but polycrystalline Si (
Poly-31) may also be used (it has the same effect as the above embodiment).

〔Effect of the invention〕

As described above, according to the image sensor and the manufacturing method thereof according to the present invention, the source/drain electrodes of the switching a-3 ITFT and the lower electrode of the a-3T photodiode are used as a common wiring conductor film, and the source/drain electrodes Since the a-3i photodiode is formed directly on top, the process can be simplified and connection defects between the a-3i photodiode and the switching a-3 ITFT can be eliminated, resulting in high yield and stable characteristics. This has the effect of making it possible to obtain a high-quality image sensor.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an image sensor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a conventional image sensor, and FIG. 3 is a diagram showing a process flow of an image sensor according to an embodiment of the present invention. . In the figure, 1 is an insulating substrate, 2 is a gate electrode, 3 is a gate insulating film, 4 is an AND-PRO-3L film, and 5 is an n+-a-
3l film, 6 a source/drain film, 7 a protective film, 8 a light shielding film, 9 an a-3t film, and 10 a transparent electrode.

Claims (3)

[Claims] (1) In an image sensor in which pixels consisting of an amorphous silicon photodiode and a switching amorphous silicon thin film transistor are integrated on the same insulating substrate, the source/drain electrodes of the switching amorphous silicon thin film transistor and the amorphous silicon An image sensor characterized in that a lower electrode of a photodiode and a common wiring conductor film are formed. (2) The image sensor according to claim 1, wherein the common wiring conductor film is formed using any one of Cr, Ta, Ti, and Mo. (3) A method for manufacturing an image sensor in which pixels consisting of an amorphous silicon photodiode and a switching amorphous silicon thin film transistor are integrated on the same insulating substrate. A step of forming the gate electrode of the transistor on the insulating substrate. and a step of sequentially forming an amorphous silicon film forming the gate insulating film, active layer, and source/drain region of the transistor on the same insulating substrate, and a common film forming the source/drain electrode and the lower electrode of the photodiode. a step of forming a wiring conductor film; a step of forming a light-shielding film that prevents light from entering the channel portion of the photodiode; and a step of forming an amorphous silicon film constituting the photodiode on the same insulating substrate. and forming a transparent electrode for guiding light to the amorphous silicon film.