JPH03173473A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To restrain the disconnection of a lead part and the generation of pin holes of a common electrode, stabilize the sensor output, an improve the yield, by forming the lead part of an upper wiring electrode on the lead part of a lower individual electrode, and forming a device by using a plurality of layers. CONSTITUTION:A plurality of lower individual electrodes 16 and a common lower leading-out electrode 18 made of Cr and the like are formed on an insulating substrate 12. A photosensitive layer 26 which is made of a-Si or the like and completely covers the picture element part 20 of a plurality of the electrodes 16 is formed. The layer 26 is formed by depositing an I-P type, an MIS type, a hetero type, etc., in the order from the electrode 16 side. On the layer 26, a common electrode 28 composed of a transparent conducting film is formed in a part from the picture element part 20 to an electrode 18. An upper wiring electrode 30 and an upper leading-out electrode 32 are formed on the electrodes 16, 18. The electrodes 30, 32 are constituted of two layers; a first layer 34 is made of Cr, Ti, Ni, etc.; a second layer 36 is made of Al or Al alloy. The electrode 30 is composed of a lead part 38 and a bonding pad part 40.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a contact type image sensor.

[Conventional technology]

Conventionally, linear image sensors have been used in image scanners, reading units of facsimile machines, and the like. Among these, a contact type image sensor in which the reading width and the pixel row width are the same is preferably used because it is compact and it is easy to design the mechanism of the equipment in which it is used.

The manufacturing method and structure of this contact type image sensor will be explained in detail with reference to FIGS. 5 to 9.

In FIG. 5, a metal layer such as chromium is formed on a substrate 102 made of an insulator such as glass or alumina, and the metal layer is photoetched to form individual electrodes 104 and lower wiring electrodes 10.
6 are formed simultaneously. As shown in FIG. 6, the individual electrode 104 has rectangular parts 108 and 110 at both ends, and
8 and 110, one rectangular portion 108 serves as a pixel portion (108) serving as an electrode portion for reading pixels, and the other rectangular portion 1
Reference numeral 10 denotes a bonding pad portion (110) that serves as an electrode for bonding wires for external connection.

Next, as shown in FIG. 7, the lead portion 1 of the individual electrode 104 is
12 and from the pixel portion 108 to the substrate 102,
Photosensitive layer 11 made of amorphous silicon semiconductor material
4 is formed by plasma CVD method. Further, as shown in FIG. 8, a pixel portion 108 on which a photosensitive layer 114 is formed
A transparent conductor thin film (116) such as ITO is deposited by sputtering or vapor deposition from the lower wiring electrode 106 to the upper common electrode 116 on the light incident side.

Next, as shown in FIG. 9, an aluminum film is formed on the lower wiring electrode 106 portion and the bonding pad portion 110 by vapor deposition or sputtering, and then external electrodes are formed on the aluminum film using a photoetching method. For this purpose, a bonding pad portion 118 and an upper wiring electrode 120 are formed, and a contact type image sensor is manufactured.

In the resulting contact type image sensor, the light beam reflected by the original to be read is irradiated onto the contact type image sensor from the common electrode 116 side, passes through the common electrode 116, and reaches the photosensitive layer 114. The photosensitive layer 114 is provided with a large number of individual electrodes 104 that are in contact with each other, and a large number of pixels arranged one-dimensionally are formed in the photosensitive layer 114, and each pixel receives an amount of photocarriers corresponding to the amount of incident light. Occur. By collecting these photocarriers with each individual electrode 104, one-dimensional image information can be obtained.

(Problems to be Solved by the Invention) In this way, in the contact type image sensor, the lower electrode is the individual type+! 1i 104 and the lower wiring electrode 106, ITO is applied to the common electrode 116, and the upper electrode, that is, the bonding pad portion 118 and the upper wiring electrode 12.
0 is mainly made of aluminum. Chromium has good adhesion to the substrate and the amorphous silicon semiconductor layer, and also has excellent heat resistance to the amorphous silicon semiconductor layer. On the other hand, such materials are used because ITO is easy to form and pattern, and aluminum has good wire bonding properties and is inexpensive.

However, the individual electrodes 104 are made of a chromium layer IN, and as chromium becomes thicker, it peels off.
It was not possible to increase the film thickness.

For this reason, during the photoetching process, especially the lead portion 1
There was a problem in that the probability of occurrence of wire breakage at 12 was high.

In addition, since the chromium layer (110) of the individual electrode 104 and the aluminum layer of the upper electrode (118) come into contact with each other at the bonding pad portion through a photo-etching process, the chromium layer (
110) and the aluminum layer (11B) was weakened, and there was also a problem that wire bonding properties were significantly reduced.

Furthermore, in the wiring electrode section, the ITO of the common electrode 116 and the aluminum of the upper electrode are in direct contact with each other, and the adhesion between the ITO and aluminum is weak.
In processes that are exposed to high temperatures of 100°C or higher, such as the aluminum patterning process or the protective resin coating process on the element surface, aluminum peels off, which not only impairs the appearance but also makes it difficult to maintain stable yields in manufacturing. I couldn't.

Moreover, when etching the aluminum of the upper electrode,
Since ITO exists directly under the aluminum to be removed, pinholes are likely to occur in the ITO on the amorphous silicon-based semiconductor layer in the pixel area or the like due to an oxidation-reduction reaction via the aluminum enchantment or aluminum etchant. This phenomenon is particularly noticeable in protrusions of the amorphous silicon semiconductor, dust, and thin ITO film parts, and there is a problem in that the current output of the image sensor decreases due to pinholes in the ITO.

The present invention has been made in order to solve the above-mentioned conventional problems, and in a contact image sensor, it is possible to suppress the occurrence of disconnection of the lead part and the occurrence of pinholes in the common electrode, and to prevent This was done to improve the adhesion of the electrode, stabilize sensor output, improve yield, and improve wire bonding properties.

[Means to solve the problem]

The gist of the contact image sensor according to the present invention is that it includes an insulating substrate, a lower individual electrode made of a good electrical conductor on the substrate, and a photosensitive layer that generates an amount of photocarriers in accordance with the amount of light received. and a common electrode made of a transparent conductive film are laminated, an upper wiring electrode formed on the lower individual electrode, and an upper wiring electrode formed on the common electrode. wherein the upper wiring electrode covers the lower individual electrode to the extent that it does not come into contact with the common electrode and other adjacent electrodes, and a bonding pad portion for bonding at least a wire for external connection among the upper wiring electrode; Each of the upper wiring electrodes is composed of two layers: a first layer in contact with the lower individual electrode or the common electrode, and a second layer formed on the first layer.

Further, in such a contact type image sensor, the photosensitive layer is made of an amorphous silicon-based semiconductor, and the lower individual electrode and the upper wiring electrode made of the two layers and the first layer of the upper wiring electrode are made of chromium Cr or titanium. Ti1
Nickel Ni, tungsten W, platinum pt, molybdenum Mo, manganese Mn.

The second layer is made of a material selected from the group consisting of zirconium Zr, and the second layer is made of aluminum or an aluminum alloy.

Furthermore, in this contact type image sensor, the film thickness of the upper wiring electrode and the first layer of the upper wiring electrode is 50 to 30 mm.
00 Å, preferably 500 to 2000 people, and the second
The thickness of the layer is 5,000 to 30,000 Å, preferably 100 Å
The reason is that the number of people is between 00 and 20,000.

Furthermore, in such a contact image sensor, the first layer of the lower individual electrode and the upper wiring electrode are formed of the same constituent material, and the bonding pad portion of the upper wiring electrode is The chromium layer of the individual electrode, the first chromium layer of the upper wiring electrode, and the second aluminum layer of the upper wiring electrode are laminated in this order.

[Function] According to the contact type image sensor of the present invention, photocarriers are generated depending on the amount of light incident on the photosensitive layer, and the photocarriers are collected by the lower individual electrode and the common electrode. The photocarriers collected by the pixel part of the lower individual electrode are guided to the bonding pad part through the lead part of the lower individual electrode and the lead part of the upper wiring electrode formed on the lead part, and are led out to the outside via the wire. I am made to do so. On the other hand, photocarriers collected by the common electrode are led out from the upper wiring electrode via a wire.

Here, an upper wiring electrode is formed to cover the lead part and bonding pad part of the lower individual electrode except for the pixel part. Therefore, even if a break occurs in the lead portion of the lower individual electrode during the photo-etching process for forming the lower individual electrode, electrical continuity of the lead portion is ensured by forming the upper wiring electrode thereon.

Furthermore, even if the adhesion of the material mainly composed of aluminum deteriorates due to the photo-etching process for forming the lower individual electrodes, the first layer made of the same or similar material to the material constituting the lower individual electrodes can be removed from the lower individual electrodes. After forming on the individual electrodes to increase adhesion, a second layer mainly made of aluminum is formed, and the upper wiring electrodes are firmly attached to the lower individual electrodes. Therefore, when the wire is bonded to the bonding pad portion of the upper wiring electrode, the wire is firmly connected.

Furthermore, even when an upper wiring electrode mainly made of aluminum, which has excellent wire bonding properties, is provided on a common electrode made of a transparent conductive film such as ITO, it is possible to use a first layer that has excellent adhesion to the transparent conductive film. The second layer (upper wiring electrode) is formed mainly of aluminum and miniram.
The layers are not peeled off. Moreover, in the process of etching the electrodes into a predetermined pattern, the common electrode is covered with the first layer and is protected by the first layer, so even if the common electrode is made of ITO, , no pinholes or the like occur in the ITO.

[Example] Next, an example of the contact type image sensor according to the present invention will be described in detail based on the drawings.

In FIGS. 1 and 2, reference numeral 10 denotes a contact type image sensor according to the present invention, and this contact type image sensor 10 has a number of unit sensors 14 arranged in one row on a substrate 12, each of which can function independently. It was formed. Board 1
2 is a substrate made of an insulator such as alumina or glass with a 5 in 2 film formed on at least one surface, or a substrate whose surface has been treated with a thin film of an insulator. Metal thin films such as these are deposited by methods such as electron beam evaporation and sputtering.

The deposited metal thin film is photoetched to simultaneously form a plurality of lower individual electrodes I6 and a common lower wiring electrode. The lower individual electrode 16 has a shape in which rectangular parts 20 and 22 arranged at both ends are connected by a narrow lead part 24, and one of the rectangular parts 20 is formed in accordance with a pixel by a photosensitive layer formed thereon. The pixel portion (20) serves as an electrode portion that collects photocarriers generated by the process, and the other rectangular portion 22 serves as a bonding pad portion (22) that serves as an electrode portion to which a wire is bonded for external connection. .

The metal thin films formed on the lower individual electrodes 16 and the lower wiring electrodes 18 include, for example, chromium Cr, titanium Ti, nickel N, etc.
i, tungsten W, platinum pt, molybdenum Mo,
A material selected from the group consisting of manganese Mn, zirconium Zr, etc. is used, and the film thickness is preferably 500 to 5000. In this example, a metal thin film was formed to a thickness of approximately 1,500 layers. If the thickness of the metal thin film is as thin as 500 or more, local variations in film thickness are likely to occur, and there is also a high risk of disconnection in the lead portion 24 of the lower individual electrode 16 during a process such as photo etching. Become. on the other hand,
When the film thickness increases to about 5,000, the thin metal film formed tends to peel off and productivity deteriorates.
Moreover, a step coverage problem arises when forming a photosensitive layer and a common electrode on the molded electrodes 16 and 18, which is undesirable.Although it is not necessarily necessary to provide the lower wiring electrode 1B, it is necessary to form the lower wiring electrode 1B on the substrate I2. ITO transparent electrode
It is preferable to provide a lower wiring electrode 18 from the viewpoint of adhesion between the common electrode and the substrate 12.

After forming the lower individual electrode 16 and the lower wiring electrode 18,
Plasma CVD is performed in a band shape using a metal mask so that the photosensitive layer 26 made of an amorphous silicon-based semiconductor at least completely covers the pixel portion 20 of the plurality of lower individual electrodes 16.
Formed by methods such as law. The amorphous silicon semiconductors constituting this photosensitive layer 26 include amorphous silicon a-5i, hydrogenated amorphous silicon a
-5i:tl.

Hydrogenated amorphous silicon carbide a-5iC:t
In addition to silicon Si, carbon C, and germanium Ge.

Amorphous silicon semiconductor a-5iC, aSi made of an alloy with other elements such as tin Sn, nitrogen N, and fluorine F
N, a-5iF, a-3iSn, a-5iGe, etc. can be used, and not only amorphous but also a material μC5i containing microcrystals can be used. These amorphous silicon-based semiconductors are arranged in order from the lower individual electrode 16 side to i
In addition to -p type, n-1-p type, etc., it is used by being deposited in old S type, hetero type, homo type, Shontokey barrier type, etc.

For example, in the case of forming an IP type semiconductor, an i-layer of intrinsic amorphous silicon a-5i is formed to a thickness of about 2 μm using silane gas. Subsequently, p-type doped a-5iC is deposited as a second layer using a mixed gas of silane gas, diborane gas, and methane gas to a thickness of approximately 500 nm.

In addition, when forming an n-1-p type semiconductor, before depositing the i-layer in the i-p type semiconductor, a mixed gas of silane gas and phosphine gas is used as the n-layer, and the n-type semiconductor is formed by approximately 300 layers. be deposited.

The film thicknesses of these n-layer, i-layer, and 2-layer are 50 to 30, respectively.
It can be changed in the range of 00 Å, 5000 to 35000 Å, and 50 to 3000 people.

On the photosensitive layer 26 formed by depositing an amorphous silicon semiconductor in a predetermined shape, a common electrode 28 made of a transparent conductive film is formed by a method such as an electron beam method, a sputtering method, or a thermal CVD method. . The common electrode 28 is deposited at least from the pixel portion 20 of the lower individual electrode 16 to the lower wiring electrode 18, and a metal mask is used to prevent the common electrode 28 from protruding from the photosensitive layer 26 and coming into contact with the lower individual electrode 16. Alternatively, it is formed by photo-etching after forming a transparent conductive film. The transparent conductive film constituting this common electrode 28 is lTO,In
Thin films such as zOl, Snow or ZnO are used. Conditions must be set so that the transparent conductive film has low resistance, sufficient light transmission, and no reflection. For example, when an ITO film is used in combination with an amorphous silicon semiconductor, The thickness of rTO film is 800~
Preferably 1000 people.

After forming the common electrode 28 made of a transparent conductive film, an upper wiring electrode 30 and an upper wiring electrode 32 are formed on the lower individual electrode 16 and the lower wiring electrode 18, respectively. Both the upper wiring electrode 30 and the upper wiring electrode 32 have a two-layer structure, and the first layer 34 formed in contact with the lower individual electrode 16 or the common electrode 28 is made of, for example, chromium Cr, titanium Ti, etc. , nickel Ni, tungsten W,
A material selected from the group consisting of platinum pt, molybdenum MO, manganese Mn, zirconium Zr, etc. is used,
The second layer 36 formed on the first layer 34 is made of aluminum or an aluminum alloy.

The upper wiring electrode 30 and the upper wiring electrode 32 composed of the first layer 34 and the second layer 36 are successively formed by a method such as electron beam evaporation or sputtering.

The upper wiring electrode 30 is composed of a lead part 38 and a bonding pad part 40 corresponding to the lower individual electrode 16, and the width of the lead part 38 is equal to the lead part 2 of the lower individual electrode 16.
Upper wiring electrode 30 having a width approximately equal to or adjacent to No. 4
The lead portion 38 is formed so as not to come into contact with the common electrode 28 made of a transparent conductive film. The ends of the lead portions 38 can be set arbitrarily within a range that does not come into contact with the common electrode 2, but if the first layer 34 of the upper wiring electrode 30 and the lower individual electrodes 16 are made of the same material, the end portions may be set as desired during photoetching. In order to prevent wire breakage, it is necessary to extend the ends of the lead portions 38 above the photosensitive layer 26. On the other hand, the upper wiring electrode 32 is formed on the common electrode 2 at approximately the same location as the lower wiring electrode 1, and the upper wiring electrode 30 and the upper wiring electrode 32 are formed by photo-etching.

The film thicknesses of the first layer 34 and second layer 36 of the upper wiring electrode 30 and the upper wiring electrode 32 are 50 to 3000 Å and 500 Å, respectively.
It can be set arbitrarily within the range of 0 to 30,000 people. However, the thickness of the first layer 34 is 11 mm to compensate for the disconnection of the lead portion 24 of the lower individual electrode 16, and
In order to ensure adhesion between the second layer 36 and the photosensitive layer 26 or the bonding pad portion 22 of the lower individual electrode 16, and in consideration of productivity, the number of people is preferably in the range of 500 to 2000. On the other hand,
The thickness of the second layer 36 is preferably 10,000 to 20,000 from the viewpoint of wire bonding performance and productivity.

In the obtained contact image sensor 10, wires for external connection are bonded to the bonding pad portions 40 of the individual upper wiring electrodes 30 and the upper wiring electrodes 32. Light reflected from the surface of the object to be read by the contact image sensor 10 is made incident from the common electrode 28 side made of a transparent conductive film. Close-contact image sensor 1
0 reaches the photosensitive layer 26 and the lower individual electrode 1
An amount of photocarriers corresponding to the amount of light reaching the photosensitive layer 26 between the pixel portion 20 of No. 6 and the common electrode 28 is generated.

The generated photocarriers are taken out to the outside for each unit sensor 14 via the lower individual type $7i16 and the common electrode 28, and -dimensional information is obtained.

As shown in this embodiment, in the present invention, since the upper wiring electrode 30 is formed on the lead portion 24 of the lower individual electrode 16 which is easily disconnected, the lower individual electrode 16 is formed in the photo-etching process.
Even if the lead part 24 of the lead part 24 is disconnected, the lead part 24
Electrical continuity is ensured by the lead portion 38 of the upper wiring electrode 30 formed above. In addition, the upper wiring electrode 30
is composed of two layers, a first layer 34 and a second layer 36,
Since the aluminum layer or aluminum alloy layer of the second layer 36 is firmly attached to the lower individual electrode 16 via the first layer 34, wire bondability is dramatically improved. Furthermore, the upper wiring electrode 32 is similarly composed of two layers, and the aluminum layer or aluminum alloy layer of the second layer 36 is firmly attached to the common electrode 28, which is a transparent conductive film, via the first layer 34. Therefore, the second layer 36 will not peel off even if exposed to high temperatures in a subsequent process.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments.

For example, as shown in a contact type image sensor 42 in FIG. 3, the lead portion 46 of the upper wiring electrode 44 is formed of only the first layer 48, and the bonding pad portion 50 is configured to have a second layer 52. It's okay.

Conversely, as in the contact type image sensor 54 shown in FIG.
can also be formed by the second layer 62 of the bonding pad portion 58.

In both the embodiments shown in FIGS. 3 and 4, the bonding pad portion 5058 to which the wire of the upper wiring electrode 44.56 is bonded is located in the first layer 48.60.
The aluminum layer or aluminum alloy layer of the second layer 52.62 is attached to the lower individual electrode 16 via the bonding pad portion 50.58 with good wire bondability. On the other hand, the lead portion 24 of the lower individual electrode 16 is connected to the lead portion 46 of the upper wiring type 1M44.56.
．． 64 to ensure electrical continuity. In both of the embodiments, since the resist patterns of the first layer and the second layer are different, there is a possibility that productivity may be reduced.

Further, it is preferable that the first layer of the lower individual electrode and the upper wiring electrode be made of the same material from the viewpoint of adhesion between the two and simplification of manufacturing equipment, but they are not limited to the same material. In particular, it is preferable to use chromium for the first layer of the lower individual electrode and the upper wiring electrode, and to use aluminum for the second layer of the upper wiring electrode, from the viewpoint of ease of film formation and patterning, cost, etc. .

Further, after forming the upper wiring electrode and the upper wiring electrode, it is preferable to remove the silicide layer formed on the photosensitive layer that is not covered by the lead portions of the common electrode and the upper wiring electrode by a method such as plasma etching. This makes it possible to prevent minute leakage current through the oxide.

It goes without saying that it is possible to use a transparent substrate such as glass as the substrate so that the light incident side is on the transparent substrate side, and the shape of the lower individual electrodes etc. can be set arbitrarily. The present invention can be implemented with various improvements, modifications, and variations based on the knowledge of those skilled in the art without departing from the spirit thereof.

〔Effect of the invention〕

According to the present invention, the lead part of the upper wiring electrode is provided in the lead part of the lower individual electrode, and the lead part of the upper wiring electrode is formed by a plurality of layers. Conductivity is ensured by the lead portion.

In addition, in the bonding pad part of the upper wiring electrode,
The second layer of aluminum or its alloy layer is attached to the lower individual electrode via the first layer made of the same or similar material to that of the lower individual electrode, so the upper wiring The adhesion between the electrode and the lower individual electrode is improved, and wire bonding properties are significantly improved.

Furthermore, in the upper wiring electrode as well, since the first layer made of a material such as chromium is provided between the common electrode such as ITO and the upper wiring electrode (second layer) mainly made of aluminum, the common electrode The adhesion between the electrode and the upper wiring electrode is improved,
The occurrence of poor appearance and poor conductivity due to peeling etc. is suppressed,
Yield is improved.

Moreover, even when ITO is used as the common electrode, a first layer made of a material such as chromium is provided between the ITO and the upper wiring electrode (second layer) mainly made of aluminum formed thereon. IT
Since O is covered, ITO is removed by photo-etching.
The present invention has excellent effects such as no pinholes are generated in the image sensor and the output of the contact type image sensor can be made uniform.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the contact type image sensor according to the present invention, and in FIG. -1 sectional view. FIG. 2 is a plan view of essential parts of the contact type image sensor shown in FIG. 1. FIG. 3 and FIG. 4 are sectional views showing other embodiments of the contact type image sensor according to the present invention, respectively. 5 to 9 are diagrams for explaining the manufacturing method and structure of a conventional contact type image sensor, in which FIG. 5 is a front view, FIG. 6 is a plan view showing the lower individual electrode, and FIG. figure,
8 and 9 are cross-sectional views. 10.42, 54; contact image sensor 12; base plate 16; lower individual electrode 20; pixel portion 22; bonding pad portion 24; lead portion 18; lower wiring electrode 26; photosensitive layer 28; common electrode 30.44; 56; Upper wiring electrode 3B, 46, 64; Lead portion 40.50.58; Bonding bunt' portion 32; Upper wiring electrode 34.60i 1st layer 36.52, 62; 2nd layer

Claims (5)

[Claims] (1) An insulating substrate, a lower individual electrode made of a good electrical conductor on the substrate, a photosensitive layer that generates an amount of photocarriers according to the amount of received light, and a common electrode made of a transparent conductive film are laminated. and an upper wiring electrode formed on the lower individual electrode, and an upper lead-out electrode formed on the common electrode, wherein the upper wiring electrode is connected to the common electrode and adjacent to the common electrode. covering the lower individual electrode to the extent that it does not come into contact with other electrodes;
A bonding pad portion for bonding at least a wire for external connection among the upper wiring electrodes and the upper lead-out electrode are each formed on a first layer in contact with the lower individual electrode or the common electrode and on the first layer. A contact image sensor comprising two layers: a second layer. (2) The photosensitive layer is made of an amorphous silicon-based semiconductor, and the first layer of the lower individual electrode and the upper wiring electrode and upper lead-out electrode consisting of the two layers is made of chromium Cr.
, titanium Ti, nickel Ni, tungsten W, platinum Pt, molybdenum Mo, manganese Mn, and zirconium Zr, and the second layer is made of aluminum or an aluminum alloy. 2. The contact type image sensor according to claim 1, wherein the contact type image sensor includes: (3) The thickness of the first layer of the upper wiring electrode and the upper extraction electrode is 50 to 3000 Å, preferably 500 to 2000 Å.
The contact image sensor according to claim 1 or 2, wherein the second layer has a film thickness of 5,000 to 30,000 Å, preferably 10,000 to 20,000 Å. (4) The contact type image according to any one of claims 1 to 3, wherein the first layer of the lower individual electrode and the upper wiring electrode are formed of the same constituent material. sensor. (5) The bonding pad portion of the upper wiring electrode is formed by laminating in order a chromium layer of the lower individual electrode, a first chromium layer of the upper wiring electrode, and a second aluminum layer of the upper wiring electrode. Claim 1 characterized in that
The contact image sensor according to any one of items 1 to 4.