JPH05335543A - Contact type image sensor - Google Patents

Abstract

PURPOSE:To protect a photodetector with high moisture resistance without impairing element characteristics by forming a protective film of the photodetector made of amorphous silicon of polyimide resin. CONSTITUTION:An ITO film is adhered about 5000Angstrom as a first electrode 22 on a light transmission insulating board. An amorphous silicon film is so adhered about 7000Angstrom by a glow discharging method as to cover the electrode 22, a photodetector 23 and an SnO2 film by a CVD are adhered about 4000Angstrom on the entire board 20, and then a second electrode 24, an interconnection 26, the electrode 33 and an interconnection 37 for externally connecting, and a first layer interconnection 30 of a matrix interconnection part are formed by reactive ion etching using CF gas containing Cl. Then, the entire board 30 is rotatably coated repeatedly three times with polyimide resin at 1000rpm for 30sec, and cured at 250 deg.C for 30min to form a polyimide film 3, cured at 350 deg.C for 2 hours to simultaneously form a protective film 25 and an insulating film 34 made of polyimide resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact-type image sensor having photodetection elements arranged one-dimensionally on a substrate.

[0002]

2. Description of the Related Art A contact image sensor is, for example, an image sensor for reading image information which is used in a one-dimensional arrangement of photo-detecting elements having the same width as a document and having a desired resolution and used in proximity to the document. Since the image reading device can be downsized, development has been actively made in recent years.

In the contact type image sensor, a high density wiring technique on a large area substrate is required to obtain a sufficient resolution. This is due to the fact that the number of photodetectors used has become extremely large with the demand for higher resolution, and that a large number of ICs are mounted on the substrate in order to reduce the number of wirings to the outside. For example, an A4 size contact image sensor with a resolution of 8 pixels / mm has as many as 1728 photodetector elements in a 216 mm width, and several dozen ICs can be mounted to drive these photodetector elements. The number of wires to the outside is several. In addition, as the wiring density increases, it is the current situation that the mounting portion of the IC has to be multi-layered.

In recent years, it has been proposed to use amorphous silicon as the light detecting element. Amorphous silicon is a relatively stable film, but it has photoconductive C
Since it has a smaller photoconductivity than other thin films such as dS, it is easily affected by humidity and oxygen ions in the air, and it is sensitive to dirt because it handles optical information. Therefore, at present, a light-transmitting thin film is mainly used for protection of the photodetecting element, and is adhered onto the photodetecting element with a transparent adhesive.

FIG. 1 shows an example of a conventional contact type image sensor using amorphous silicon as a light detecting element. 1 (a) is a plan view, and FIG. 1 (b) is a sectional view taken along the line AA 'in FIG. 1 (a) as seen in the direction of the arrow. In FIG. 1, (1) is an insulation Substrate such as an alumina substrate, (2) is an individual electrode formed by using chromium on the insulating substrate (1), and (3) is amorphous silicon formed so as to cover the end of the individual electrode (2). Photo detector,
(4) is an I.D. formed on the photodetector (3). T. O. A common electrode composed of a thin film, (5) is a glass plate adhered with a transparent adhesive (6) silicone resin on the photodetector (3),
(7) is a wiring connecting the driving IC (8) mounted to drive the photodetector (3) and the outside, (9) is a wiring connecting the common electrode (4) and the outside, and (10) is It is a jumper wire that connects the wirings of the drive unit.

In this contact type image sensor, image information from a document enters in the direction of the arrow shown in FIG. 1 (b). A voltage is always applied to the photodetector element (3) by the common electrode (4), and the amount of electric charge stored every time it is selected by the driving IC (8) is sent out as image information to the outside in time series. The glass plate (5) and the transparent adhesive (6) protect the photodetector element (3) from the external environment.

[0007]

In the above contact type image sensor, a glass plate and a silicone resin are used to protect the photodetecting element, but a protective film having better moisture resistance is desired.

The present invention has been made in order to solve the conventional drawbacks described above, and an object thereof is to provide a contact type image sensor capable of safely protecting a photodetection element without deteriorating the element characteristics. I am trying.

[0009]

[Means for Solving the Problems] That is, a contact type image sensor according to a first aspect of the present invention is a light-transmissive insulating substrate and a light formed of amorphous silicon one-dimensionally formed on the translucent insulating substrate. It is characterized in that it is provided with a detection element and a protective film made of a polyimide resin which covers the photo detection element.

The contact image sensor according to claim 2 is the contact image sensor according to claim 1, wherein
A conductor connected to the photodetector via an insulating film made of a polyimide resin formed on the translucent insulating substrate at a position different from that of the photodetector is provided with a wiring part in which the conductor is wired in multiple layers. It has a feature.

[0011]

According to the contact type image sensor of the present invention, since the protective film of the photodetection element made of amorphous silicon is formed of polyimide resin, the photodetection element is protected with good moisture resistance without deteriorating the element characteristics. ..

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a contact type image sensor according to an embodiment of the present invention. 2A is a plan view and FIG.
2B shows a cross-sectional view of the cross section taken along the line BB ′ in FIG.

As shown in FIG. 2, a first electrode (22), for example, a common electrode is provided on the transparent insulating substrate (20) along the one side (21), and the first electrode (22) is provided. And translucent insulating substrate (2
A photodetection element (23) made of amorphous silicon is provided on the surface (0) so as to cover the first electrode (22). The light detecting element (23) is formed to have a length of about 220 mm corresponding to an A4 size document, for example.

A second electrode (24), for example, an individual electrode, is provided on the photodetection element (23) and the translucent insulating substrate (20) so that one end thereof is located on the photodetection element (23). ing. The second electrode (24) is formed with 1728 lines at a density of 8 lines / mm. A protective film (25) is further formed on the photodetector (23) and the second electrode (24).
Is provided. The other end of the second electrode (24) formed on the translucent insulating substrate (20) has the other end of the second electrode (24) mounted on the translucent insulating substrate (20) by a wiring (26) for driving a photodetection element (27). ) Is connected to an input bonding pad (28) provided around the. In the region of the translucent insulating substrate (20) opposite to the part where the photodetector (23) is provided, the first layer wiring (30) whose one end is connected to the output bonding pad (29) is provided. It is provided. In FIG. 2, (31) and (32) are the driving IC (27) and wiring, respectively.
(26) is a bonding wire for connecting the first layer wiring (30), and (33) is a die pad for mounting an IC. First
An insulating film (34) is formed on the substrate provided with the layer wiring (30) so as to cover the first layer wiring (30), and the second layer wiring (34) is formed on the insulating film (34). 35) has been formed. First layer wiring (3
0) and the predetermined wiring of the second layer (35) are connected to each other through a contact hole (36) provided in the insulating film (34).

In this embodiment, the image information from the original is transmitted through the transparent insulating substrate (20) and the first electrode (22) in the direction of the arrow shown in FIG. ).
The first electrode (22) is attached to the lower side of the photodetector element (23),
A voltage is constantly applied to the photodetector element (23), and the photodetector element (23) is selected through the second electrode (24) provided on the photodetector element (23).

Next, an example of a method of manufacturing the contact type image sensor of this embodiment will be described. A transparent insulating substrate (20), for example, a Pyrex glass substrate, is sputtered on the P.I. T. O. Attach the membrane to about 5000 angstroms
Of the electrode (22). Then, a glow discharge method was used to cover the first electrode (22) with an amorphous silicon film for about 7,000
Angular photo detector (23), S by CVD
A second electrode (24), a wiring (26), and a first electrode are formed by applying an nO2 film on the entire surface of the translucent insulating substrate (20) for about 4000 Å and then performing reactive ion etching using CF4 gas containing Cl. A wiring (37) connecting the wiring (22) and the outside and a wiring (30) of the first layer of the matrix wiring portion are formed.

After that, the entire surface of the translucent insulating substrate (20) was spin-coated with a polyimide resin at 1000 rpm for 30 seconds and cured at 250 ° C. for 30 minutes three times to form three layers of polyimide film.
Curing is performed at 350 ° C. for 2 hours to simultaneously form a protective film (25) made of a polyimide resin film and an insulating film (34).

Next, after removing the polyimide resin film corresponding to the IC mounting portion, the contact hole (36) of the multilayer wiring and the input / output terminal portions (28) and (29) by photoetching, Ti
Of 0.1 μm and Au of 1 μm in sequence and then photoetching the second layer wiring (3
5), IC die pad (33) and bonding pad (2
8) and (29) are formed, and IC die bonding and wire bonding are performed.

In the above process, the polyimide resin film is
It is formed by applying polyimide resin by spin coating method and then polymerizing it by applying heat treatment at about 350 ° C. Since it is a dense and homogeneous film, it is a protective film (25) for the photodetector element (23) made of amorphous silicon. ) And excellent element performance is not deteriorated. Further, by coating the polyimide resin film by a spin coating method, a uniform film thickness and a smooth surface state can be obtained and etching processing is possible, and therefore it is also excellent as an insulating film (34) for thin film multilayer wiring. There is. That is, by using a polyimide resin film, the protective film (25) of the photodetector (23) and the insulating film (3
Since the same coating can be used for both 4), the manufacturing process is simplified.

By adjusting the viscosity of the polyimide resin, the polyimide resin film can be applied not only by the spin coating method but also by the screen printing method. In this case, the process can be further simplified and the cost can be reduced as compared with the case of using the spin coating method.

According to this contact type image sensor, since the protective film of the photodetection element made of amorphous silicon is formed of the polyimide resin as described above, the photodetection element is protected with good moisture resistance without impairing the element characteristics. To be done.

[0023]

As described above, according to the contact type image sensor of the present invention, since the protective film of the photodetection element made of amorphous silicon is formed of polyimide resin, the photodetection element is not impaired. Is protected against moisture.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view showing a conventional contact image sensor.

FIG. 2 is a plan view and a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 (20) ... transparent insulating substrate (22) ... first electrode (23) ... photodetector (24) ... second electrode (25) ... protective film (30) ... first layer wiring (34) … Insulating film (35)… Wiring of the second layer (36)… Contact hole

Claims (2)

[Claims] 1. A translucent insulating substrate, a photodetector made of amorphous silicon one-dimensionally formed on the translucent insulating substrate, and a protective film made of a polyimide resin covering the photodetector. A contact-type image sensor characterized by being equipped. 2. The contact image sensor according to claim 1, wherein the photodetector is connected to the photodetector via an insulating film made of a polyimide resin formed on the translucent insulating substrate at a position different from that of the photodetector. Image sensor having a wiring portion in which the formed conductor is wired in multiple layers.