JPH0614542B2 - Long document reading element - Google Patents

Description

The present invention relates to a long document reading element, and more particularly to the structure thereof.

[Prior art and its problems]

Recently, an image reading device used for an input unit of a facsimile does not need a reduction optical system, and the device is downsized and the device cost is low. Are being used.

The long original reading element has a basic structure of a sandwich type sensor in which a photoconductor layer is sandwiched by a lower electrode and a translucent upper electrode, and a photoelectric conversion unit formed of the sandwich type sensor on a long insulating substrate. Is a predetermined number (for example, if it is 8 dots / mm, it is 172 for Japanese Industrial Standard A row 4)
8 pieces, 2048 pieces for the same standard B row No. 4) are arranged side by side.

In order to enable accurate reading, these sensors are completely independent of each other and receive light (sensor).
The areas of the parts must also be the same.

For example, in the most basic long thin film reading element, the lower electrode 102 and the photoconductor layer 104 are separately formed for each sensor as shown in FIG.
Also, the main portion is divided and formed, and the region where the photoconductor layer is sandwiched between the lower electrode 102 and the translucent upper electrode 103 is defined as a light receiving area (sensor area), and each sensor is formed separately. .

In this structure, the lower electrode, the photoconductor layer, the upper electrode, and the photolithographic etching process must be used for all of them, and the manufacturing process is complicated.
There is a problem that the light receiving area of each sensor varies due to a pattern shift or the like. Further, in the photolithographic etching process for forming the upper electrode, there is also a problem that the end portion of the photoconductor layer is contaminated and damaged at the portion corresponding to the boundary with the mask, resulting in lower reliability and lower yield. .

Further, in a long thin film reading element using non-doped amorphous silicon as a photoconductor layer, amorphous silicon itself has high resistance (resistivity in darkness: 10 ⁹ Ωcm), so that adjacent bits (adjacent bits) (Between each sensor)
It is also proposed that the lower electrode is divided and formed, and the photoconductor layer and the upper electrode are integrally formed by omitting the isolation.

For example, as shown in FIG. 6 (a) and FIG. 6 (b) as this example, this long thin film reading element includes n photoelectric conversion units LE ₁ , LE ₂ , ..., LEn in one column. Lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn arranged in parallel on the insulating substrate 1 at a predetermined interval, and the electrodes S.
A hydrogenated amorphous silicon layer 2 as a photoconductor layer formed so as to overlap one end of E ₁ , SE ₂ , SE ₃ , ..., SEn, and further formed on the hydrogenated amorphous silicon layer 2. It is composed of a transparent upper electrode 3.

Then, such an operation of the long thin document reading device, for example in advance by applying an appropriate magnitude of the bias voltage to the photoelectric conversion unit LE ₂ shown in FIG. 6, the sensor area L ₂
When light having an appropriate wavelength is irradiated onto the sensor area, electrons and holes are generated in the sensor area L ₂ , and the electrons and holes move toward the lower electrode SE ₂ and the upper transparent electrode 3, respectively. Thus, the photocurrent flowing corresponding to the intensity of the applied light is taken out as a read signal.

The photoelectric conversion unit _{LE 1, LE 2, LE 3} , ..., in LEn, as a sensor, parts performing a function (hereinafter, referred to as sensor _{area) L 1, L 2, L} 3, ..., Ln are lower electrode _SE 1, , SEn where SE ₂ , SE ₃ , ..., SEn intersect with the upper electrode 3.

By the way, such a long thin film reading element is manufactured as follows.

(1) First Step A conductor layer is formed over the entire surface of the insulating substrate 1, and the conductor layer is subjected to photolithography etching to form lower electrodes SE ₁ , SE ₂ , SE having an appropriate shape and size.
_3, ..., to form a SEn (FIG. 7 (a) refer).

(2) Second Step A hydrogenated amorphous silicon layer 2 is deposited to an appropriate thickness (for example, 1 μm) by plasma CVD on one end of the lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn (see FIG. See Fig. 7 (b)).

(3) Third step A metal mask (not shown) having an appropriately shaped opening is attached to the substrate 1 on which the hydrogenated amorphous silicon layer 2 is formed, and a method such as a reactive vacuum deposition method or a reactive sputtering method is used. The translucent upper electrode 3 is formed in a strip shape (see FIG. 7 (c)).

The sensor areas L ₁ , L ₂ , L ₃ , ..., Ln need to have the same size. However, in consideration of the alignment error of the metal mask when forming the upper electrode 3, Even if the position of the sensor area is shifted, the sensor areas L ₁ , L ₂ ,
, Ln other than the optical signal extraction portions LS ₁ , LS ₂ , LS ₃ , ..., LSn of the lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn so that the sizes of L ₃ ,. The width of the part is made as narrow as possible (Fig. 6).
(See (a)). Even in such a configuration, the area of the sensor area is defined by the overlap between the upper electrode and the lower electrode, and the photolithographic etching process is used only when forming the lower electrode, and the film deposition of the upper electrode is performed by sputtering through a metal mask or the like. Although it is selectively performed by a method or the like and the manufacturing process is simplified, the underlying photoconductor layer is damaged at the portion corresponding to the end of the metal mask, which leads to a reduction in manufacturing yield.

By the way, in order to improve the resolution of the long thin-film original reading element, it is conceivable to increase the array density of photoelectric conversion units and reduce the length of each photoelectric conversion unit, that is, the length of the sensor area. . For example, in order to double the resolution when reading a two-dimensional image, the array density of the photoelectric conversion units forming the long thin film original reading element is set to 2
The width of the photoelectric conversion part must also be halved and the size of the light receiving part will be reduced to about 1/4, making it difficult to align the metal mask when forming the upper electrode. Therefore, it becomes necessary to manufacture the upper electrode.

However, the width of the upper electrode must be narrowed with an increase in the array density of the photoelectric conversion units (for example, 50 μm or less at an array density of 16 lines / mm), and the length of the upper electrode becomes relatively long. Therefore, when a bias voltage is applied to each photoelectric conversion unit, there is a problem in that there occurs a photoelectric conversion unit to which a desired bias voltage is not applied due to the resistance of the upper electrode.
In addition, as the arrangement density of the photoelectric conversion units increases, the width of the portion of the lower electrode other than the optical signal extraction portion is made as narrow as possible, so that there is a problem that the possibility of disconnection increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a long thin film reading element having uniform characteristics and high reliability.

[Means for solving problems]

Therefore, in the present invention, a plurality of lower electrodes arranged in a predetermined arrangement, a photoelectric conversion layer, and a translucent upper electrode are sequentially laminated on a substrate, in the long reading element, the lower electrode and the An opening window that defines the sensor area is provided between the photoelectric conversion layer and an insulating layer that covers the peripheral edge of the opening window.

[Action]

According to the above configuration, since the sensor area is defined by the insulating layer formed on the lower electrode, the sensor area area of each sensor is defined with high accuracy and exhibits extremely uniform characteristics.

Further, since the sensor area is not influenced by the pattern of the upper electrode and is determined only by the opening window formed in the insulating layer, the pattern accuracy of the upper electrode is not required. Therefore, since it may be formed in a large size by using a metal mask or the like, photolithography is not necessary, manufacturing is easy, and the photoelectric conversion layer is not contaminated. In addition, when the upper electrode is formed using the metal mask, even when the underlying photoconductor layer is damaged at the end portion of the metamask when the upper electrode is formed using the metal mask, the sensor area Since the peripheral edge of is defined by an insulating film, that portion can be outside the sensor area, so that the yield is improved and the reliability is high.

Further, when the insulating layer covers the periphery of the opening window and is arranged at a high density, the sensor area can be maximized, and as a result, the maximum output can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 (a) and 1 (b) are views showing a long thin film reading element according to an embodiment of the present invention. (Fig. 1 (b) is A- of Fig. 1 (a).
It is a figure which shows an A'section. ) This long thin film reading element includes lower electrodes LS ₁ , LS ₂ , ..., LSn formed of n pieces of chromium film patterns having a width T arranged in a row at a predetermined interval and a sensor area on the lower electrodes. A silicon nitride film 4 as an insulating layer selectively formed on the entire surface of the substrate as specified, and a band-shaped hydrogenated amorphous silicon layer 2 as a photoelectric conversion layer formed so as to cover a portion to be a sensor area. In addition, a light-transmissive upper electrode 3 made of a strip-shaped indium tin oxide (ITO) layer formed so as to cover a portion serving as a sensor area in the upper layer is sequentially laminated, and the sensor area L _{, 1 to} Ln are evenly arranged in one line to form n photoelectric conversion units LE ₁ , ..., LEn.

Next, the manufacturing process of this long thin film reading element will be described.

(1) First step A chromium film is deposited on the surface of the insulating substrate 1 to a thickness of about 3000Å, and photolithography and etching are applied to form the lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn. (See Fig. 2 (a)).

(2) Second step Silicon nitride is deposited on the substrate 1 on which the lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn are formed to a thickness of about 6000 Å by plasma CVD to form a silicon nitride film 4. (See Fig. 2 (b)).

(3) Third Step Photolithography and etching are performed on the silicon nitride film 4 to form the lower electrodes SE ₁ , SE ₂ , S.
, En of E ₃ , ..., SEn, optical signal extraction portions LS ₁ , L
The silicon nitride film 4 on S ₂ , LS ₃ , ..., LSn is removed to form a window serving as a sensor area (see FIG. 2 (c)). As shown in the plan view (see FIG. 3) of the substrate 1 at the end of the third step, each optical signal extraction portion L
The sizes of S ₁ , LS ₂ , LS ₃ , ..., LSn need to be the same, but this can be performed by the photolithography and etching described above.

Although the silicon nitride film 4 is used as the insulating layer in this embodiment, the present invention is not limited to this, and the temperature range is 200 ° C. to 300 ° C. when the hydrogenated amorphous silicon film is formed in the next fourth step.
Any material that does not deteriorate can be used, and materials such as PSG (phosphorus-doped silicon oxide), silicon oxynitride, and polyimide may be used.

(4) Fourth step Hydrogenated amorphous silicon is deposited to a thickness of about 10,000Å so as to cover the window for forming the sensor area, that is, the window for forming the sensor area, that is, the light signal extraction portions LS ₁ , LS ₂ , LS ₃ ,. A hydrogenated amorphous silicon layer 2 is formed (see FIG. 2 (d)).

(5) Fifth step The hydrogenated amorphous silicon layer 2 on the light signal extraction portions LS ₁ , LS ₂ , LS ₃ , ..., LSn, that is, the sensor areas L ₁ , L ₂ , L ₃ ,. Like I
TO is deposited to a thickness of about 2000 Å to form the upper electrode 3 to complete a long thin film original reading element (Fig. 1 (b)).
reference).

Regarding the performance of the long thin-film reading element manufactured as described above, the characteristics of each photoelectric conversion unit are more uniform than those of the case of manufacturing by the conventional method.

Further, since the hydrogenated amorphous silicon layer can be formed without a photolithography step after the formation, the hydrogenated amorphous silicon layer is not deteriorated in the etching step and has high reliability.

Further, even when the density is increased, the width of the upper electrode does not need to be narrowed, and the sensor area is defined by the insulating layer.
The width of the upper electrode can be made large, and the occurrence of variations in the reading characteristics of the sensor due to an increase in the resistance of the upper electrode can be prevented.

In addition, the lower electrode does not need to be narrowed in a width other than the sensor area as in the conventional case, and is formed to have the same width as the sensor area.Therefore, when forming the upper hydrogenated amorphous silicon layer and the upper electrode, a metal mask is used. There is no possibility of breaking the wire due to the contact of.

Since the step portions of the lower electrodes SE ₁ , SE ₂ , SE ₃ , ..., SEn are covered with the silicon nitride film and are not the sensor area, electric field concentration occurs in the photoelectric conversion layer thinned on the step as in the conventional case. The occurrence of dielectric breakdown is eliminated, and the probability that a photoelectric conversion unit having inferior characteristics will occur is smaller.

By forming the passivation film of the element using the same material as the insulating layer such as a silicon nitride film used for the long thin-film original reading element, it is possible to manufacture an element stable against thermal stress.

〔The invention's effect〕

As described above, according to the present invention, since the sensor area (light signal extraction portion) is defined by the insulating layer formed on the lower electrode, the photoelectric conversion layer and the upper electrode have high precision. It is possible to obtain a long thin film reading element in which the characteristics of each sensor are uniform without requiring patterning. In addition, since the photoelectric conversion layer and the upper electrode may be formed so as to cover a region corresponding to the sensor area, deterioration of the amorphous silicon layer as a photoelectric conversion layer which is easily formed without a photolithography process and bonding characteristics Reliability is improved without causing deterioration.

Especially, since it is not necessary to narrow the width of the upper electrode,
The occurrence of variations in sensor reading characteristics due to the resistance of the upper electrode is prevented.

Further, since the lower electrode is covered with the insulating layer except for the portion corresponding to the sensor area, it is not necessary to narrow the width of the lower electrode other than the sensor area, and the mechanical contact and the mechanical contact at the time of forming the upper photoelectric conversion layer, the upper electrode, etc. Breakage due to wear or the like is also prevented.

[Brief description of drawings]

FIG. 1 (a) and FIG. 1 (b) are views showing a long original reading element of an embodiment of the present invention, and FIGS. 2 (a) to 2 (d) and FIG. 3 are the same elements. Manufacturing process drawing, Fig. 4 (a) and 4
FIG. 6 (b) is a view showing another embodiment of the present invention, FIG. 5 and FIG.
(a) and FIG. 6 (b) are diagrams showing a conventional long original reading element, and FIGS. 7 (a) to 7 (c) are FIGS. 6 (a) and 6 (b). FIG. 6 is a manufacturing process diagram of the element shown in FIG. 1 ... Insulating substrate, 2 ... Hydrogenated amorphous silicon film, 3 ... Upper electrode, 4 ... Silicon nitride film, SE ₁ ,
SE ₂ , SE ₃ , ..., SEn ... Lower electrodes.

Claims (1)

[Claims] 1. A long original reading element comprising a plurality of lower electrodes arranged at a predetermined interval on an insulating substrate, a photoelectric conversion layer, and a translucent upper electrode, which are sequentially stacked. Between each lower electrode and the photoelectric conversion layer, an insulating layer that covers the periphery of the lower electrode and has an opening that opens only the upper surface of the lower electrode is interposed, and the photoelectric conversion layer and the upper electrode are: A long original reading element, which is formed so as to cover the opening and an insulating layer around the opening.