JPH04355560A - Multi-color photoelectric conversion element - Google Patents

Abstract

PURPOSE:To provide an image sensor with high resolution in which a light receiving face is minutely divided by adopting a face facing in a direction orthogonal to the direction of deposition of the film of photoconductive layers as the light receiving face. CONSTITUTION:One end face 8 appearing in the lengthwise direction of a photoconductive layer 3a is adopted for a light receiving face on which a light from an original face is made incident and an incident light shown in a void arrow is made incident on the light receiving face 8. Then part of the light made incident on the light receiving face 8 is absorbed when the light passes through the photoconductive layer 3a and the light not absorbed in the photoconductive layer 3a through a transparent insulation layer 5 is led to a photoconductive layer 3b. Then the processing accuracy of the light receiving face 8 in the longitudinal direction almost depends on the deposition method of the film of the photoconductive layer 3, and the accuracy is implemented very high as almost 1/10 of the processing accuracy in the length of the lateral direction as 0.1-0.5mum.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a photoelectric conversion element used in an image input section of a facsimile machine or an image scanner, and in particular, the present invention relates to a photoelectric conversion element used in an image input section of a facsimile machine or an image scanner. The present invention relates to a structure for achieving high resolution in a multicolor photoelectric conversion element that includes elements that are compatible with multicolor light (for example, red, green, and blue) for reading images.

0002

2. Description of the Related Art In order to reduce the size of devices, development of contact type image sensors that do not use a reduction optical system is being actively pursued. This type of contact image sensor is shown in Fig. 1, for example.
6, a rectangular lower electrode 101, a strip-shaped photoconductive layer 102, and a strip-shaped upper electrode 10 are individually arranged for each pixel.
It is constructed by disposing a large number of photoelectric conversion elements having a thin film sandwich structure, each of which has a thin film sandwich structure, in which the photoelectric conversion elements are sequentially laminated on a glass substrate 100. In this photoelectric conversion element array, the upper electrode 103 or the lower electrode 101 is formed of a transparent conductive film, and a common bias voltage is applied to each photoelectric conversion element via the strip-shaped upper electrode 103. Reflected light from a document surface (not shown) is irradiated from the top or bottom surface of the element array, and charges generated in the photoconductive layer 102 by the reflected light according to the density of the document surface are separated into individual lower electrodes 101. The signal is extracted as an electrical signal in time series through the lead wire 104.

In order to read a color image using the above contact type image sensor, as shown in FIG. 17, red, green, and blue filters (R, G, B) are periodically and repeatedly placed along the array direction (main scanning direction). Also,
As shown in Figure 18, photoelectric conversion element arrays are arranged in three rows in parallel, and red, green, and blue band-shaped filters (R, G, B) are arranged in parallel.
are placed on each photoelectric conversion element array. Also,
The photoelectric conversion element array is arranged in one row, and the light that illuminates the document surface is a three-color light source (for example, red, green, and blue), which is selectively turned on to provide color-separated illumination, thereby generating image signals corresponding to each color. can be obtained.

0004

[Problems to be Solved by the Invention] In the contact type image sensor having the above structure, light enters from the top or bottom surface of the photoelectric conversion element, so the light receiving area of the photoelectric conversion element is determined by the area of the individualized lower electrodes 101. . Therefore, when aiming for high resolution, the resolution that can be achieved depends on how small the area of the lower electrode 101 can be. Since this lower electrode 101 is formed by photolithography and etching after depositing a metal thin film, the resolution is determined by the precision of microfabrication by resist patterning and etching.

Currently, the patterning and etching accuracy of these resists is about 5 to 10 μm square, so the resolution is at most 600 to 800 DPI (
42 to 32 μm pitch), and there was a limit to obtaining a photoelectric conversion element having a thin film structure with higher resolution.

The present invention has been made in view of the above-mentioned circumstances, and is intended to increase the sensitivity of a multicolor photoelectric conversion element in which a photoelectric conversion element has a thin film laminated structure in which a photoconductive layer is arranged between opposing electrodes. The purpose is to provide a structure for

[0007]

[Means for Solving the Problems] In order to solve the problems of the conventional example, the multicolor photoelectric conversion element according to the present invention includes a photoconductive layer disposed between opposing electrodes, and a film of the photoconductive layer is deposited in a direction in which the photoconductive layer is deposited. The device is characterized in that a plurality of photoelectric conversion elements are arranged along the direction of light incidence, and each of the photoelectric conversion elements has a light-receiving surface on which light enters, the surface facing in a direction orthogonal to the direction perpendicular to .

[0008]

[Operation] Therefore, the light-receiving surface is perpendicular to the direction in which the photoconductive layer is deposited, and in particular, one of the sides defining this surface is along the direction in which the photoconductive layer is deposited. The precision of microfabrication on that side is determined by the deposition precision of the photoconductive layer, but this precision can be made higher than that of the conventional light-receiving surface, that is, the surface facing the deposition direction of the photoconductive layer. can. Therefore, high resolution can be achieved by finely processing the film thickness in the deposition direction when depositing the photoconductive layer. In addition, photoelectric conversion elements corresponding to each color light are arranged along the light incident direction, and multicolor separation is performed using the difference in the color absorption characteristics of each color light within the photoconductive layer, so that the same light receiving area can be simultaneously Multicolor image information can be read.

[0009]

Embodiment One pixel of the multicolor photoelectric conversion element of the present invention will be explained with reference to FIGS. 1 to 3. FIG. 1 is a plan view of a multicolor photoelectric conversion element according to an example, and FIG.
-A line sectional view is shown, and FIG. 3 shows a BB line sectional view of FIG. 1, respectively. The multicolor photoelectric conversion element of this embodiment includes an insulating substrate 1 made of a member such as glass, and a metal such as chromium formed on the insulating substrate 1 in a rectangular shape with the long side along the direction of light incidence. and three photoconductive layers 3a and 3b separately formed on this lower electrode 2.
, 3c, and photoconductive layers 3a, 3b, made of metal such as aluminum and facing the aforementioned lower electrode 2, respectively.
3c, and an insulating layer 5 made of an insulating material such as polyimide that covers the aforementioned lower electrode 2, upper electrode 4, and photoconductive layer 3. The conversion elements 9, 9, 9 are arranged along the direction of incidence of light. The lower electrode 2 and the like constituting the multicolor photoelectric conversion element of this embodiment are formed by successive film deposition and patterning on the insulating substrate 1 described above. Moreover, each upper electrode 4a, 4b
, 4c are contact holes 6a, 6 formed in the insulating layer 5.
It is connected to lead lines 7a, 7b, and 7c via lines b and 6c.

In this embodiment, one end surface 8 (see FIGS. 1 and 2) appearing in the longitudinal axis direction of the photoconductive layer 3a is used as a light-receiving surface on which light from the document surface is incident. As shown by the white arrow in , incident light is made to enter this light receiving surface 8 . Part of the light incident on the light-receiving surface is absorbed when passing through the photoconductive layer 3a, and the unabsorbed light is absorbed by the photoconductive layer 3a via the transparent insulating layer 5, and the remaining light is absorbed by the photoconductive layer 3b. be guided.

Here, the processing accuracy of the lateral length X of the light-receiving surface 8 in FIG. , which is approximately determined by the photolithography and etching accuracy. On the other hand, the processing accuracy of the vertical length Y (X>Y) of the light-receiving surface 8 is approximately determined by the film deposition method of the photoconductive layer 3 (details will be described later); It is possible to achieve high precision of about 0.1 to 0.5 μm, which is about 1/10 of the processing precision of .

Next, the manufacturing process of the above-mentioned photoelectric conversion element will be explained. First, the insulating substrate 1 of this embodiment is
It is made of a glass member, and a specific example of this member is Corning 7059, for example. Then, chromium (Cr) is deposited on the entire surface of the insulating substrate 1 to a thickness of about 500 to 1000 angstroms by sputtering, and then this chromium film is shaped into a predetermined shape (in the direction of light incidence) by photolithography. The lower electrode 2 is formed by patterning into a rectangle whose long sides are along the sides. Next, the photoconductive film was formed by plasma CVD.
A film is deposited on the entire surface so as to cover the lower electrode 2 by a method. The photoconductive film of this example is made of pin-type hydrogenated amorphous silicon (a-Si:H), and the p layer is made of silane (
1 diborane (B2H6) gas in SiH4) gas
% doping, the i-layer becomes silane (SiH4)
Using only gas, the n-layer is prepared by doping phosphine (PH3) gas into silane (SiH4) gas. The film deposition temperature in the plasma CVD method of this example was 200 to 250°C, and the above p,
The thickness of each of the i and n layers is set, for example, to about 200 to 1000 angstroms for the p layer and n layer, and about 1 to 20 .mu.m for the i layer.

Following the formation of the photoconductive film, aluminum (
500 to 10 by sputtering or vapor deposition
A film of about 0.00 angstroms is deposited to form upper electrodes 4a, 4b, and 4c each having a predetermined shape, that is, in this embodiment, patterned into three island shapes separately arranged on the lower electrode 2. Next, the previously deposited photoconductive film is patterned by dry etching using the same resist pattern used for the upper electrode 4 described above.
Photoconductive layers 3a, 3b, 3c whose planar shapes are slightly larger than upper electrodes 4a, 4b, 4c are formed. In this dry etching, portions protruding like eaves from the upper electrodes 4a, 4b, 4c are generated during side etching, but these portions are removed by wet etching using the same resist pattern used for dry etching. Remove by applying.

Next, polyimide (Hitachi Chemical PIX-1400 or PIX-
8803, Toray Photonice, etc.) to a thickness of about 1 to 5 μm by roll coating or spin coating to form the insulating layer 5, and the above-mentioned upper electrodes 4a, 4b, 4c are arranged. A contact hole 6 is formed at the location by photolithography.

Finally, a film of aluminum (Al) is deposited by sputtering or vapor deposition, and patterned into a predetermined shape by photolithography to form lead lines 7a, 7b, and 7c, thereby forming the multicolor photoelectric conversion element 10. is completed. In addition, in the multicolor photoelectric conversion element 10 of this example, the photoconductive layer 3a,
Although 3b and 3c are pin type, they may be i type. Moreover, as a member forming the upper electrode 4, indium tin oxide (ITO) is used instead of aluminum in this embodiment.
Alternatively, chromium (Cr) or the like can be used as a material for forming the insulating layer 5, and silicon nitride (S) can be used instead of polyimide in this embodiment.
iNx), silicon oxide (SiO2) or SiNx
Oy etc. may be used respectively. Furthermore, the lower electrode 2
, the members forming the upper electrode 4 and the lead wire 7 are as follows:
Tantalum (Ta), molybdenum (Mo), nickel (N
i), metal such as tungsten (W), a-Si compound, CdS, CdS as a member forming the photoconductive layer 3;
E or an organic semiconductor may be used, respectively.

With the above configuration, three photoelectric conversion elements 9
are arranged along the light incident direction so that the end faces of the photoconductive layers 3a, 3b, 3c of each photoelectric conversion element 9 are at different distances from the light receiving surface 8.
can be obtained. That is, when the white light incident from the light receiving surface 8 passes through the photoconductive layer 3a of the first photoelectric conversion element 9, it is absorbed depending on the light absorption coefficient of the photoconductive layer 3a, and the unabsorbed light is sequentially absorbed. Second and third photoelectric conversion elements 9
reaches the photoconductive layers 3a and 3b. The absorption coefficient of light increases as the wavelength becomes shorter, so as shown in Figure 4, light absorption is reduced by short wavelength light (blue light), medium wavelength light (green light), and long wavelength light (red light). The length of the photoconductive layer 3 along the incident direction required for this purpose differs. Therefore, the lengths L1, L2, of each photoconductive layer 3a, 3b, 3c along the light incident direction,
By adjusting L3, the first photoelectric conversion element 9 absorbs all short wavelength light, the second photoelectric conversion element 9 absorbs all middle wavelength light, and the third photoelectric conversion element 9 absorbs long wavelength light. It can absorb all wavelengths of light. According to the multicolor photoelectric conversion element 10 in which the length of each photoconductive layer 3 is set in this way,
The output signals S1, S2, S3 extracted from the extraction electrodes 7a, 7b, 7c of each photoelectric conversion element 9 are divided into short wavelength light (blue light), medium wavelength light (green light), and long wavelength light (red light). The amount of incident light for each color is C1 and C2, respectively.
, C3, it is expressed as the following equation. S1 = C1 + αC2
+ βC3
S2 = (1-α)C2 +
β'C3 S3 =

(1-β-β')C3 That is, each signal of short wavelength light (blue light), medium wavelength light (green light), and long wavelength light (red light) is mixed into the output signal S1, and the output signal S2 for,
The medium wavelength light (green light) and long wavelength light (red light) signals are mixed, and the output signal S3 contains only the long wavelength light (red light) signal. Therefore, the lead lines 7a, 7b
, 7c, the signal processing circuit extracts the signal from C
1, C2, and C3, the amount of incident light corresponding to each color can be calculated, and color-separated image signals can be obtained. Note that α, β, and β' are constants resulting from the amount of absorption calculated from the absorption coefficient of each color in the photoconductive layer.

FIG. 5 shows another embodiment in which the photoconductive layer 3 is continuously formed in each photoelectric conversion element 9. Hydrogenated amorphous silicon constituting the photoconductive layer 3 has a high sheet resistance value, so the multicolor photoelectric conversion element 1 is
Even if the photoelectric conversion elements 9 constituting the photoelectric conversion elements 9 are made common, the signals extracted from the lead lines 7a, 7b, and 7c of the respective photoelectric conversion elements 9 will not be mixed. Other configurations are shown in Figure 2.
Since it is similar to the above, the same reference numerals are given to the same constituent parts and the explanation thereof will be omitted. According to this embodiment, since it is not necessary to finely etch the photoconductive layer 3, it is possible to improve the yield and simplify the manufacturing process.

FIGS. 6 to 8 show an image reading device in which multicolor photoelectric conversion elements are arranged in an array. Components having the same configuration as those in FIGS. 1 to 3 are designated by the same reference numerals. That is, a plurality of multicolor photoelectric conversion elements 10 shown in FIGS. 1 to 3 are arranged in the main scanning direction, and the lead line 7a
, 7b, and 7c are formed into strips for each photoelectric conversion element 9 along the main scanning direction corresponding to each color light. This lead line 7a
, 7b, 7c are connected to amplifiers 11, respectively, and are configured so that signals are extracted via the amplifiers 11. Further, a voltage is applied to the lower electrode 2 of each multicolor photoelectric conversion element 10 via a switching element SW.

As shown in FIG. 9, the equivalent circuit of the image reading device described above is such that the other end of each switching element SW is connected to each terminal of a shift register SR. Further, the anode side (upper electrode 7 side) of the photodiode PD, which equivalently represents each photoelectric conversion element 9, is connected to a common signal line for each photoelectric conversion element 9 along the main scanning direction corresponding to each color light. , and is configured to extract the output signal via the amplifier 11. The shift register SR has a data terminal DA.
TA and a clock terminal CK are provided, and a data terminal DAT is provided.
The data pulse input from A is shifted and sequentially output as a drive pulse from each terminal of the shift register SR.

The reading operation of this image reading device will be explained with reference to the equivalent circuit shown in FIG. That is, the already charged photodiode PD is irradiated with reflected light from the document surface (not shown), and a photocurrent proportional to the amount of the irradiated light flows into the anode side of the photodiode PD, and the photodiode PD The accumulated charge is discharged (accumulation period). Subsequently, the switching element SW is closed, and a drive pulse is applied from the shift register SR to reset the cathode voltage of the photodiode PD to a substantially constant value (signal reading period). Therefore,
The same amount of charge as the positive charge of the cathode electrode flowing out as a photocurrent during the accumulation period is replenished (charged) from the outside by the signal reading operation. The amplifier 11 uses this supplementary charge as a sensor current from a common signal line (upper electrode) for each color.
By detecting the respective colors through the , it is possible to obtain color-separated image signal outputs. The above operation is performed every time a drive pulse is sequentially applied from each terminal of the shift register SR to the multicolor photoelectric conversion elements 10 arranged in the main scanning direction, and each color-separated image signal of one line on the document is can be obtained in chronological order.

FIGS. 10 and 11 show an image reading device according to another embodiment, in which each photoelectric conversion element 9 has a photodiode PD and a blocking diode BD connected in series so that the polarities are opposite to each other. It is composed of Components having the same configuration as those in FIGS. 6 to 8 are designated by the same reference numerals. As shown in FIGS. 11 and 12, the photoconductive layer 3 of each multicolor photoelectric conversion element 10 includes a p layer, an i layer, an n layer,
The i-layer and p-layer are laminated in order, and the upper and lower p-layers, i-layers,
By forming diodes in each of the n layers and using the n layer in common, it is possible to form a series connection with opposite polarities in which the cathodes of the photodiode (upper side) and the blocking diode (lower side) are connected to each other.

As shown in FIG. 13, the equivalent circuit of the image reading device described above is such that the anode side (lower electrode 2 side) of each blocking diode BD constituting each multicolor photoelectric conversion element 10 is connected to each terminal of the shift register SR. has been done. Also,
Anode side of each photodiode PD (upper electrode 4 side)
is a photoelectric conversion element 9 along the main scanning direction corresponding to each color light.
They are connected to a common signal line. The shift register SR is provided with a data terminal DATA and a clock terminal CK, and a data pulse input from the data terminal DATA is shifted and sequentially output as a drive pulse from each terminal of the shift register SR.

The signal reading operation will be explained with reference to FIG. That is, the already charged photodiode PD is irradiated with reflected light from the document surface (not shown), and a photocurrent proportional to the amount of the irradiated light flows into the anode side of the photodiode PD, and the photodiode PD The accumulated charge is discharged (accumulation period). Next, from the shift register SR to the blocking diode BD
A driving pulse is applied to the anode side of the blocking diode BD, and the blocking diode BD is biased in the forward direction to reset the cathode voltage between the diodes to a substantially constant value (signal reading period). Therefore, the same amount of charge as the positive charge of the cathode electrode flowing out as a photocurrent during the accumulation period is replenished (charged) from the outside by the signal reading operation. By detecting this supplementary charge as a sensor current from a common signal line (upper electrode) for each color via an amplifier 11,
Color-separated image signal output can be obtained. The above operation is performed every time a drive pulse is sequentially applied from each terminal of the shift register SR to each multicolor photoelectric conversion element 10 arranged in the main scanning direction, and the color-separated image signal of one line on the document is processed. Each can be obtained in chronological order.

FIGS. 14 and 15 show another example of a multicolor photoelectric conversion element formed by connecting two diodes in series with opposite polarities. It is constructed by adhering it to. The photoelectric conversion elements 9 corresponding to each color are arranged along the light incident direction, as shown in FIG. That is, on the first glass substrate 21, a first electrode 22 common to each photoelectric conversion element 9, a photoconductive layer 23 in which a p layer, an i layer, and an n layer are sequentially laminated.
, a second electrode 24, a light-transmitting insulating layer 25, and a bump-shaped electrode 26 which has been subjected to bump processing. The bump-shaped electrode 26 is connected to the second electrode 24 via a contact hole 27 formed in the insulating layer 25. On the second glass substrate 31, a first electrode 3 separated by each photoelectric conversion element is provided.
2a, 32b, 32c, a photoconductive layer 33 in which a p layer, an i layer, and an n layer are sequentially laminated, a second electrode 34, a transparent insulating layer 35,
A bump-shaped electrode 36 is formed. Bump-shaped electrode 36
is connected to the second electrode 34 through a contact hole 37 formed in the insulating layer 35, similar to the structure described above. By connecting the bump-shaped electrodes 26 and 36 in contact with each other, the multicolor photoelectric conversion element 10 is constructed by connecting diodes in series with opposite polarities. 14 and 15 show the state before bonding. Further, instead of performing bump processing, ordinary electrodes may be formed and bonded with a transparent anisotropic conductive resin. According to this embodiment,
Since the two diodes are manufactured separately, it is possible to improve the yield of the multicolor photoelectric conversion element 10 obtained by joining them together.

According to the embodiment described above, the light-receiving surface 8 on which light from the document surface enters is on the end surface side of the photoconductive layer 3a, so that each photoelectric conversion element 9 constituting the multicolor photoelectric conversion element 10
The light-receiving surfaces are the side surfaces of the photoconductive layers 3a, 3b, and 3c, respectively, and the direction perpendicular to the film deposition direction of the photoconductive layer 3 is the light-receiving surface. Therefore, among the sides defining the light-receiving surface 8, one direction is along the film deposition direction of the photoconductive layer 3, so the microfabrication accuracy of that side is determined by the deposition accuracy of the photoconductive layer. can be made higher than the microfabrication accuracy of the conventional light-receiving surface, that is, the surface facing the deposition direction of the photoconductive layer, and the resolution of the multicolor photoelectric conversion element 10 can be increased. In addition, photoelectric conversion elements 9 corresponding to each color light are arranged along the light incident direction, and multicolor separation is performed using the difference in color absorption characteristics of each color light within the photoconductive layer 3, so that the same light receiving area It is possible to read multicolor image information at the same time, and there is no need for color filters for color separation or light sources for color separation illumination as in conventional systems, simplifying the device when used as an image reading device. can be achieved. Furthermore, multicolor image information can be read simultaneously in the same light-receiving area, it is possible to prevent misalignment of the reading area due to color separation, and signal processing can be simplified.

[0026]

According to the present invention, since the surface of the photoconductive layer facing in the direction perpendicular to the film deposition direction is used as the light-receiving surface on which light enters, when depositing the photoconductive layer, the film in the deposition direction is Since the area of the light-receiving surface can be controlled by adjusting the thickness, the light-receiving surface can be subdivided, and a high-resolution image sensor can be obtained. In addition, photoelectric conversion elements corresponding to each color are arranged along the light incident direction, and multicolor separation is performed using the difference in color absorption characteristics of each color within the photoconductive layer. image information can be read, eliminating the need for color filters and color separation illumination light sources, and preventing shifts in the reading area due to color separation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view of a multicolor photoelectric conversion element showing one embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view taken along line AA in FIG. 1.

FIG. 3 is an explanatory cross-sectional view taken along line B-B in FIG. 1.

FIG. 4 is a graph explaining the light absorption characteristics of each photoelectric conversion layer of a multicolor photoelectric conversion element.

FIG. 5 is a cross-sectional explanatory diagram showing another example of a multicolor photoelectric conversion element.

FIG. 6 is a structural explanatory diagram showing a part of an image reading device formed by arranging a plurality of multicolor photoelectric conversion elements.

7 is an explanatory cross-sectional view taken along line CC in FIG. 6. FIG.

8 is an explanatory cross-sectional view taken along the line DD in FIG. 6. FIG.

9 is an equivalent circuit diagram of the image reading device of FIG. 6. FIG.

FIG. 10 is a structural explanatory diagram showing another example of an image reading device.

FIG. 11 is an explanatory cross-sectional view taken along line EE in FIG. 10.

12 is an explanatory cross-sectional view taken along line FF in FIG. 10.

13 is an equivalent circuit diagram of the image reading device of FIG. 10. FIG.

14 is a cross-sectional explanatory diagram showing another example of the multicolor photoelectric conversion element used in the image reading device of FIG. 10. FIG.

FIG. 15 is an explanatory cross-sectional view of the multicolor photoelectric conversion element same as above.

FIG. 16 is an explanatory plan view showing a conventional photoelectric conversion element array.

FIG. 17 is a schematic plan view showing a filter arrangement of a color image sensor using one row of photoelectric conversion element arrays.

FIG. 18 is a schematic plan view illustrating a filter arrangement of a color image sensor including a multi-row photoelectric conversion element array.

[Explanation of symbols]

1... Insulating substrate, 2... Lower electrode, 3... Photoconductive layer,
4... Upper electrode, 5... Insulating layer, 7... Outgoing wire, 8... Light receiving surface, 9... Photoelectric conversion element, 10
...Multicolor photoelectric conversion element

Claims (1)

[Claims] Claim 1: A photoelectric conversion element comprising a photoconductive layer disposed between opposing electrodes, and a surface of the photoconductive layer facing perpendicular to the film deposition direction as a light-receiving surface on which light enters, in the direction of light incidence. A multicolor photoelectric conversion element characterized in that a plurality of multicolor photoelectric conversion elements are arranged along the line.