JPH07107929B2 - Image sensor and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image sensor using a photoconductive element array and matrix wiring, and a method for manufacturing the same.

[Technical Background of the Invention and Problems Thereof] As a form of a long image sensor such as a contact type image sensor, a device utilizing a photoconductive effect is known. FIG. 7 is a plan view showing an example of the insulating base.
Photoconductive film such as hydrogenated amorphous silicon film on 21
22 and a photoconductive element array 25 including counter electrodes 23 and 24 are formed. The photoconductive element array 25 is divided into a plurality of groups each having a plurality of continuous elements as one unit, and the counter electrodes 23 on one side are commonly connected by a common electrode 26 for each group, and the counter electrodes 24 on the other side. The groups that face each other are commonly connected by the matrix wiring 27. The matrix wiring 27 includes a first wiring 28 connected to the counter electrode 24, a second wiring 29 formed parallel to the arrangement direction of the photoconductive element array 25 so as to intersect with the first wiring 28, and both wirings. It is composed of an interlayer insulating film 30 for insulating between the wirings 28 and 29. The first wiring 28 and the second wiring 29 are connected to each other through an opening 31 formed at an intersection position of the first and second wirings 28, 29 of the interlayer insulating film 30.

When the light reflected from the document surface is incident on the photoconductive element array 25, the electric resistance of the photoconductive element array 25 changes according to the amount of the light, so that, for example, a voltage is sequentially applied to the common electrode 26 and the second electrode is applied. An image on the original can be read by sequentially scanning the wiring 29 and reading the resistance change as an electric signal.

However, this configuration has the following problems.
The photoconductive film 22 is generally masked in the area of the photoconductive element array 25.
Although it is formed in a band shape by the CVD method or the like, the amount of protrusion in the width direction of the photoconductive film 22 is uneven due to non-uniform contact between the mask and the deposited film. Overhanging photoconductive film
Since the edge portion of 22 has a non-uniform film thickness, if the interlayer insulating film 30 is formed to overlap this portion, the adhesion of the interlayer insulating film 30 becomes unstable. Therefore, in order to prevent the interlayer insulating film 30 from overlapping the end portion of the photoconductive film 22, it is necessary to make the space between them sufficiently long, which leads to an increase in the size of the image sensor.

In order to solve this problem, it is conceivable that the photoconductive film 22 is deposited on the entire surface of the insulating substrate 21 and only the region of the photoconductive element 25 is left as a thin strip by etching. However, in order to etch the photoconductive film 22, it is necessary to go through the steps of resist coating, exposure, development, etching, and resist removal, which causes a high cost. In addition, the yield decreases due to the increase in the number of steps.

Further, in the structure shown in FIG. 7, the photoconductive film 22 is usually formed after forming the second wiring 29 and the interlayer insulating film 30 in the matrix wiring 27. This is because if the photoconductive film 22 is formed first, the photoconductive film 22 is altered by an etchant such as hydrazine used in the etching step for forming the opening of the interlayer insulating film 30. However, when the photoconductive film 22 is formed before the second wiring 29 and the interlayer insulating film 30, the exposed portion (lead-out portion, etc.) of the second wiring 29 is formed.
Also, due to the influence of the material of the interlayer insulating film 30 (for example, polyimide or epoxy), it becomes difficult to uniformly form the photoconductive bear 22. In addition, in cleaning as a pretreatment when forming the photoconductive film 22, there is a problem that the second wiring 29 and the interlayer insulating film 30 are damaged by a cleaning liquid such as a mixed solution of hydrogen peroxide and ammonia. To do.

Further, in the structure shown in FIG. 7, a protective insulating film must be additionally formed on the photoconductive element array 25, which further increases the number of steps.

On the other hand, when a large number of image sensors are formed on the same insulative substrate for the purpose of enhancing mass productivity, and when the sensors are diced to be separated from each other, in the structure of FIG.
Must be formed in large numbers. For this mask CV
There is a problem that a metal mask having a large number of elongated openings for D is required, and the number of steps increases due to cleaning and mounting of the metal mask, resulting in an increase in cost and a decrease in yield. For example, the width of one image sensor is 3mm
Then, if the width of the photoconductive film is 2 mm, the opening with a width of 2 mm is 1 m.
Masks formed at m intervals must be formed, and it is practically impossible to form such a mask, and even if such a mask can be formed, handling is extremely difficult. Therefore, when a large number of image sensors are formed on the same insulating substrate, it is desirable to form the photoconductive film on the entire surface.
In the conventional structure, it is impossible because the first wiring needs to be formed first.

[Object of the Invention] The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an image sensor that is easy to manufacture, has a high yield, and is low in cost, and a manufacturing method thereof. .

SUMMARY OF THE INVENTION An image sensor according to the present invention comprises a photoconductive film and a counter electrode in contact with the photoconductive film. The photoconductive device array is divided into a plurality of groups, and one end of each photoconductive element array is provided. A common electrode commonly connected to each group, a first wiring connected to each other end of the photoconductive element array, and a crossing provided with the first wiring, and via the first wiring A second wiring that connects the other ends of the photoconductive element arrays to corresponding ones of the groups, and is interposed between the first and second wirings,
In an image sensor in which an interlayer insulating film having an opening for connecting both wirings is formed on a base, the first wiring is formed between the base and the interlayer insulating film, and the second wiring is formed. Wiring is formed on the interlayer insulating film, and a protective insulating film having a light-transmitting property made of the same material as the interlayer insulating film is formed continuously on the photoconductive element array, The photoconductive film is formed on the substrate by Ta, C
at least one metal oxide, carbide or nitride selected from the group consisting of r, Al, Ti and V, or an oxide of Si,
It is characterized in that it is formed on the entire surface of the substrate through an adhesive layer made of carbide or nitride.

Further, in manufacturing such an image sensor, the present invention comprises a photoconductive element array which is divided into a plurality of groups and which is composed of a photoconductive film and a counter electrode in contact with the photoconductive film, and a photoconductive device array of the photoconductive device array. A common electrode having one end commonly connected to each group, and a first electrode connected to each other end of the photoconductive element array.
Of the first wiring and the wiring of the first wiring.
Second wiring for connecting the other ends of the photoconductive element arrays to each other through corresponding wirings, and for interposing both wirings between the first wiring and the second wiring. In the method of manufacturing an image sensor, the interlayer insulating film having an opening of 1 is formed on a substrate, and at least one metal oxide selected from the group consisting of Ta, Cr, Al, Ti and V is formed on the entire surface of the substrate. Of the photoconductive film after forming the photoconductive film through an insulating adhesive made of a metal, a carbide or a nitride, or an oxide of Si, a carbide or a nitride, and forming the counter electrode and the first wiring. An element array is formed, and then the interlayer insulating film is formed. At the same time, a light-transmitting protective insulating film made of the same material as the interlayer insulating film is formed on the photoconductive element array by connecting with the interlayer insulating film. Formed and then the layer The second wiring is formed on the insulating film.

EFFECTS OF THE INVENTION According to the present invention, when the photoconductive film is formed in a band shape in the region of the photoconductive element array, even if the amount of protrusion in the width direction of the photoconductive film is uneven, the interlayer insulation is formed on the unevenness. Since the protective insulating film is formed continuously with the film, adhesion between the interlayer insulating film and the protective insulating film can be improved, and reliability is improved. In other words, the photoconductive element array and the matrix wiring can be formed close to each other, and the image sensor can be downsized accordingly. Further, there is no increase in the number of steps as in a method of leaving a photoconductive film on the entire surface of a substrate and then leaving it in a strip shape by etching, which is advantageous in terms of yield manufacturing cost.

Further, in the present invention, since the photoconductive film can be first formed on the substrate, the photoconductive film can be formed in a state where the substrate is cleaned without adversely affecting other elements (wiring, interlayer insulating film, etc.). . Moreover, since there is no metal such as wiring or organic resin that serves as an interlayer insulating film on the substrate when the photoconductive film is formed, the photoconductive film is homogeneous without being affected by those materials. It can be formed in any state.
Conventionally, when the photoconductive film is first formed, there is a problem that the photoconductive film is deteriorated by the etchant in the etching process for forming the opening of the interlayer insulating film. Since the photoconductive film is protected against the etchant by the protective insulating film formed continuously with the interlayer insulating film, such a problem does not occur.

Further, according to the present invention, the protective insulating film can be formed simultaneously with the interlayer insulating film, and the number of steps is reduced as compared with the conventional one in which the protective insulating film is formed in a step different from the step of forming the interlayer insulating film. To do.

Further, in the present invention, when a large number of image sensors are simultaneously formed on the same substrate, it is not necessary to form the photoconductive film in a strip shape, but the photoconductive film can be formed on the entire surface of the substrate. The complicated process is unnecessary, and also from this point, the manufacturing cost can be reduced and the yield can be improved.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings. First
FIG. 1A is a plan view of the image sensor, and FIG. 1B is a sectional view taken along the line AA.

In the figure, an insulating substrate 1 is, for example, a non-alkali glass substrate or a glazed ceramic substrate, and a photoconductive element array 5 composed of a photoconductive film 2 and counter electrodes 3 and 4 is formed on the substrate 1. The photoconductive film 2 is, for example, hydrogenated amorphous silicon (a-Si: H), that is, a film containing 5% or more of H and 20% or more of Si. In this example, a mask CVD method using a metal mask is used. It is formed in a band shape. Further, the photoconductive film 2 has a thickness of 0.5 μm to 2 in this example.
High resistance layer (i layer) 2a with a specific resistance of 10 ¹⁰ Ω · cm or more at μm
And a-Si: H further doped with P to a thickness of 0.005 μm
It is composed of a low resistance layer (n ⁺ layer) 2b of 0.5 μm. The reason why the low resistance layer 2b is provided is to make good ohmic contact with the metal (the counter electrodes 3, 4, etc.) formed on the photoconductive film 2.

The photoconductive element array 5 is divided into a plurality of groups each having a plurality of continuous elements (six elements in the example in the figure) as one unit, and the counter electrode 3 on one side is shared by the common electrode 6 for each group. The other opposing electrodes 4 are commonly connected by matrix wirings 7 that face each other between the groups, that is, those that have the same position in each group.

The matrix wiring 7 is a first electrode connected to the counter electrode 4 respectively.
Wiring 8, a second wiring 9 formed in parallel with the arrangement direction of the photoconductive elements in the photoconductive element array 5 so as to intersect with the first wiring 8, and these first and second wirings 8. , 9
It is composed of an interlayer insulating film 10 for insulating the spaces.
The interlayer insulating film 10 has an opening 1 at the intersection of the first and second wirings 8 and 9.
1 is provided, and the first wiring 8 and the second wiring 9 are connected through these openings 11.

Here, in the present invention, a translucent protective insulating film 12 made of the same material as the interlayer insulating film 10 in the matrix wiring 7 is formed on the photoconductive element array 5 in a form in which the interlayer insulating film 10 is extended. Is forming.

Explaining one example of a method of manufacturing this image sensor, first, the insulating substrate 1 is washed with, for example, a mixed solution of hydrogen peroxide and ammonia, and then the photoconductive film 2 is formed by a mask CVD method. At the time of forming the photoconductive film 2, other elements such as organic substances and metals do not exist on the substrate 1 after cleaning, so that the photoconductive film 2 is not affected by these elements. Next, using the refractory metal such as Ti, Cr, Al, Mo, Mn, Nb, V, W, Ta, Sb, the counter electrodes 3 and 4, the common electrode 6 and the first wiring 8 in the matrix wiring 7 are used. Is formed by a vapor deposition or sputtering method and a PEP process. Next, the interlayer insulating film 10 in the matrix wiring 7 and the photoconductive element array 5
The upper protective insulating film 12 is applied and formed. Examples of the material of the interlayer insulating film 10 and the protective insulating film 12 include polyimide, polyamide, polyethylene organic material, acrylic organic material, epoxy organic material, SiO ₂ , SixNy, Ta ₂ O ₅
Among them, those having a light transmittance of about 10% or more are used. Then, an opening 11 for contacting the first wiring 8 and the second wiring 9 is formed in the interlayer insulating film 10 by etching using an etchant such as hydrazine. In addition,
When photosensitive polyimide is used as the material of the interlayer insulating film 10, a developing solution is used instead of the etchant. At this time, since the photoconductive film 2 is covered with the protective insulating film 12,
It is not attacked by etchants or developers.
Then, Ti, Cr, a single metal such as Al, or Cr-Au, Cr-Al,
The second wiring 9 in the matrix wiring 7 is formed by a vapor deposition or sputtering method and a PEP process using a composite metal such as Ti-Au, Cr-Cu, Ti-Cr.

FIG. 2 is an equivalent circuit diagram of this image sensor, in which a driving voltage is sequentially applied to the common electrode 6 to select each group of the photoconductive element array 5, and each group is passed through the second wiring 9 in the matrix wiring 7. An image signal can be obtained by repeating the operation of sequentially reading out the signal based on the resistance change due to the amount of incident light of the photoconductive element.

An example of the present invention will be described. It is also possible to use comb-shaped electrodes as shown in FIG. 3 as the counter electrodes 3 and 4 in the photoconductive element array 5, and this can improve the sensitivity.

Further, in FIG. 1, the photoconductive film 2 is formed in a band shape only in the region of the photoconductive element array 5, but in the present invention, it is formed on the entire surface of the insulating substrate 1 as shown in FIG. It has a feature. In this case, a region of the photoconductive film 2 other than the photoconductive element array 5 (a region mainly in contact with the first wiring 8)
It is necessary to consider the leak between the photoconductive element arrays 5 through each other (element-to-element leak), but this leak is a practical problem by devising the shapes and dimensions of the counter electrodes 3 and 4 and the first wiring 8. It can be reduced to the extent that it does not exist.
That is, as shown in FIG. 3, the gap of the counter electrodes 3, 4 in each element of the photoconductive element array 5 is set to L ₁ , the counter electrode 3,
When the width of 4 is W ₁ , the resistance of each element of the photoconductive element array 5 is proportional to L ₁ / W ₁ . On the other hand, the inter-element resistance of the photoconductive element array 5 is proportional to L ₂ / W ₂ when the distance between the first wirings 8 is L ₂ and the length is W ₂ . In this case, if the condition L ₁ / W ₁ << L ₂ / W ₂ is satisfied, the interelement leakage can be ignored, and the photoconductive film 2 is formed on the entire surface of the insulating substrate 1 as shown in FIG. But there is no problem. As a specific example, for example, L ₁ =
When L ₂ = 75 μm and W ₂ = 2 mm when 6 μmm, W ₁ = 500 μm, the ratio of the above two types of resistance is 27 times, which is sufficient for practical use.

Further, even when such a condition is not satisfied, a structure in which light does not enter the region other than the photoconductive element array 5 in the photoconductive film 2, for example, a light shielding film is formed on the region or the photoconductive element is formed. By adopting a configuration such as using a lens system for image formation in which light is incident only on the region of the array 5, it is possible to suppress the leak between the elements to a small level. That is, if the specific resistance of the area where light is incident is ρ _P and the specific resistance of the area where light is not incident is ρ _D , the resistance of each element of the photoconductive element array 5 is proportional to ρ _P / L ₁ / W ₁ . However, since the inter-element resistance of the photoconductive element array 5 is proportional to ρ _D · L ₂ / W ₂ , L ₁ / W ₁ << ρ
If the condition _P · L ₂ / W ₂ is satisfied, the inter-element leakage can be ignored.

Further, as another method, a region other than the photoconductive element array 5 of the photoconductive film 2 is previously irradiated with strong light, and the resistance of the region is increased by a so-called photodegradation effect so that leakage between elements can be ignored. Is also possible.

When the photoconductive film 2 is formed on the entire surface of the insulating substrate 1 as described above, the counter electrodes 3 and 4 of the low resistance layer 2b (n ⁺ layer) in the photoconductive film 2 are formed as shown in FIG. By leaving only the lower portions of the common electrode 6 and the first wiring 8 by etching, the insulation resistance between the elements of the photoconductive element array 5 may be increased. That is, the high resistance layer 2a (i layer) in the photoconductive film 2 has a specific resistance of 10 ¹² Ω · when it is an a-Si: H film.
Since it is as high as cm, the insulation resistance can be sufficiently secured by doing so, and the leakage between the elements can be suppressed to a level where there is no practical problem.

The present invention can form a photoconductive film on the entire surface of an insulating substrate as described above, and is therefore effective when a large number of image sensors are simultaneously formed on the same insulating substrate. FIG. 6 shows an embodiment thereof, and a plurality (four in this example) of image sensors 15 to 18 are formed on the insulating substrate 13 via the adhesive layer 14. After the image sensors 15 to 18 are formed in this way, dicing is performed at the position indicated by the broken line and separation is performed, whereby a plurality of image sensors can be manufactured at the same time, and mass productivity is improved. In this case, the tension of the photoconductive film in the direction orthogonal to the array direction of the photoconductive element array (left-right direction in FIG. 6) is divided during dicing, so that the photoconductive film is easily peeled off from the end portion of the base 13. . Therefore, in this embodiment, the adhesive layer 14 is provided between the photoconductive film and the substrate 13.
Intervening to increase the adhesive force of the photoconductive film and prevent peeling during dicing. As the adhesive layer 14, a film containing silicon nitride as a main component (SiNx, SiNxOy, SiNxHy, etc.) is most desirable, and Ta, Si, Cr, Al, Ti, V, Al or other metal oxides, nitrides or carbides are preferable. Suitable, C for metal oxides
After depositing a material such as r, Al, Ti, V having a relatively small free energy for oxidation on the substrate 13, the surface may be oxidized by anodic oxidation or the like, or may be treated by oxygen plasma. Also, it is desirable in terms of cost to form the Si ₃ N ₄ film used as the adhesive layer by a sputtering method or a plasma CVD method, but in addition, thermal CVD method, vapor deposition method, MOCVD method, ion plating method, class ion beam method Any method such as photo CVD method, MBE method and the like may be used. Further, when the adhesive layer is used on the substrate, the substrate is not limited to glass or the like, and a metal such as stainless steel or a semiconductor can be used. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and A of the image sensor.
-A sectional view taken along arrow A, FIG. 2 is an equivalent circuit diagram thereof, FIG. 3 is a diagram showing a more preferable electrode shape in the photoconductive element array, and FIG. 4 is a plan view showing a first embodiment of the present invention. Fifth
FIG. 7 is a sectional view showing a second embodiment of the present invention, FIG. 6 is a sectional view schematically showing a third embodiment of the present invention, and FIG. 7 is a plan view of a conventional image sensor. 1 ... Insulating substrate, 2 ... Photoconductive film, 2a ... High resistance layer,
2b ... Low resistance layer, 3,4 ... Counter electrode, 5 ... Photoconductive element array, 6 ... Common electrode, 7 ... Matrix wiring, 8
...... First wiring, 9 ...... Second wiring, 10 ...... interlayer insulating film, 11 ...... opening, 12 ...... insulating protective film, 13 ...... insulating substrate, 14 ...... adhesive layer, 15 ~ 18 …… Image sensor.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Osamu Shimada 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute, Inc. (72) Inventor Kenichi Mori 1 Komukai-Toshiba, Kawasaki-shi, Kanagawa (56) Reference JP-A-60-167479 (JP, A) JP-A-59-126666 (JP, A) JP-A-59-138371 (JP, A) JP-A-60- 42877 (JP, A)

Claims (11)

[Claims] 1. A photoconductive element array comprising a photoconductive film and a counter electrode in contact with the photoconductive film and divided into a plurality of groups, and one end of each of the photoconductive element arrays is commonly connected to each group. An electrode, a first wiring connected to each of the other ends of the photoconductive element array, and a wiring provided so as to intersect with the first wiring, and each of the other portions of the photoconductive element array provided through the first wiring. On the base body, there are provided a second wiring whose ends are connected to each other corresponding to each other, and an interlayer insulating film which is interposed between the first and second wirings and has an opening for connecting both wirings. In the formed image sensor, the first wiring is formed between the base and the interlayer insulating film, the second wiring is formed on the interlayer insulating film, and further on the photoconductive element array. And a light-transmitting film made of the same material as the interlayer insulating film, which is continuous with the interlayer insulating film. Protective insulating film having is formed,
An adhesive layer made of at least one metal oxide, carbide or nitride selected from the group consisting of Ta, Cr, Al, Ti and V, or an oxide, carbide or nitride of Si, is formed on the substrate by the photoconductive film. An image sensor, which is formed on the entire surface of the base body via. 2. The image sensor according to claim 1, wherein the substrate is an insulator, a semiconductor or a metal. 3. The photoconductive film according to claim 2, further comprising a high resistance layer and a low resistance layer formed between the high resistance layer and the counter electrode. Image sensor. 4. A gap between the opposing electrodes in each photoconductive element is L1, a width between the opposing electrodes is W1, an interval between the first wirings is L2, and a length of the first wirings is W2. And when
The image sensor according to claim 1, wherein L1 / W1 << L2 / W2. 5. The image sensor according to claim 1, wherein a region of the photoconductive film other than a region of the photoconductive element array is not irradiated with light. 6. The image sensor according to claim 1, wherein a region of the photoconductive film other than a region of the photoconductive element array has a high resistance. 7. The photoconductive film has a high resistance layer and a low resistance layer formed between the high resistance layer and the counter electrode, the common electrode and the first wiring. The image sensor according to claim 1. 8. The adhesive layer is SiN _x (1 ≦ x ≦ 4/3), SiN _x O
The image sensor according to claim 1, wherein the image sensor is a thin film or a thick film composed of _y and SiN _x H _z . 9. A photoconductive element array comprising a photoconductive film and a counter electrode in contact with the photoconductive film and divided into a plurality of groups, and one end of this photoconductive element array is commonly connected to each group. An electrode, a first wiring connected to each of the other ends of the photoconductive element array, and a wiring provided so as to intersect with the first wiring, and each of the other portions of the photoconductive element array provided through the first wiring. On the base body, there are provided a second wiring whose ends are connected to each other corresponding to each other, and an interlayer insulating film which is interposed between the first and second wirings and has an opening for connecting both wirings. In the method of manufacturing the image sensor formed, at least one metal oxide, carbide or nitride selected from the group consisting of Ta, Cr, Al, Ti and V is formed on the entire surface of the substrate, or
After forming the photoconductive film via an adhesive layer made of Si oxide, carbide or nitride, the counter electrode and the first wiring are formed to form the photoconductive element array,
Next, the interlayer insulating film is formed, and at the same time, a light-transmitting protective insulating film made of the same material as the interlayer insulating film is formed on the photoconductive element array by connecting to the interlayer insulating film. A method of manufacturing an image sensor, comprising forming the second wiring on an interlayer insulating film. 10. The adhesion layer is a plasma CVD method, a thermal CVD method,
Sputtering method, evaporation method, MOCVD method, ion plating method, class ion beam method, optical CVD method or MBE
The method for manufacturing an image sensor according to claim 9, wherein the film is formed by a method. 11. The adhesive layer is formed by forming at least one metal selected from the group consisting of Cr, Al, Ti and V on the substrate and then oxidizing the surface thereof. A method of manufacturing an image sensor according to claim 9.