JP2501199B2 - Photoelectric conversion device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device, and more particularly, to a photoelectric conversion unit, a charge storage unit provided corresponding to the photoelectric conversion unit, and a switch on a substrate. And a photoelectric conversion device having a section.

[Prior Art] Conventionally, a reading system using a reduction optical system and a CCD type sensor has been used as a reading system for a facsimile, an image scanner, or the like, but in recent years, hydrogenated amorphous silicon (hereinafter a-Si: H) has been used. By developing a photoconductive semiconductor material represented by (1), it is remarkable to develop a so-called contact type line sensor in which the photoelectric conversion part and the signal processing part are formed on a long substrate and read with an optical system of the same size as the original. .

In particular, the a-Si: H is not only used as a photoelectric conversion material,
Since it can be used also as a semiconductor material of a field effect transistor, it has an advantage that the photoconductive semiconductor layer of the photoelectric conversion section and the semiconductor layer of the signal processing section can be simultaneously formed.

FIG. 10 is a vertical cross-sectional view of a configuration example of a conventional line sensor.

As shown in the figure, the wiring part 2 and the photoelectric conversion part are provided on the substrate 1.
3, a charge storage unit 4, and a switch unit 5 are provided. Board 1
Lower layer electrode wiring 6 of the wiring section 2, lower layer electrode wiring 7 of the charge storage section 4, and lower layer electrode wiring 8 forming the gate electrode of the switch section 5 are formed on the upper side, and further these lower layer electrode wirings 6, 7,
An insulating layer 9 is formed on the surface 8. A semiconductor layer (here, a-Si: H) 11 is formed on the insulating layer 9 of the switch section 5, and a photoconductive semiconductor layer made of a photoconductive material (here, a-Si: H) 11 is formed on the substrate 1 of the photoelectric conversion section 3. , A-Si: H) 10 is formed. Here, the semiconductor layer 11 and the photoconductive semiconductor layer 10 are simultaneously formed.

The lower layer electrode wiring 6 and the upper layer electrode wiring 12 form a matrix wiring portion with an insulating layer 9 interposed therebetween. The photoconductive semiconductor layer 10 and the semiconductor layer 11 are connected by the upper layer electrode wiring 13. The upper layer electrode wiring 13 is connected through the insulating layer 9 of the charge storage section 4, and the upper layer electrode wiring 13, the insulating layer 9 and the lower layer electrode wiring 7 form a storage capacitor. A portion of the upper layer electrode wiring 13 connected to one end of the semiconductor layer 11 becomes a drain electrode, and an upper layer electrode wiring 14 connected to the other end of the semiconductor layer 11 becomes a source electrode.

The above is the configuration in the case where the photoelectric conversion unit and the signal processing unit are formed on the same substrate, but as shown in the figure, the semiconductor layer is formed only in the photoelectric conversion unit 3 and the switch unit 5, and the insulation The layer 9 and the photoconductive semiconductor layer 10 and the semiconductor layer 11 formed on the insulating layer 9 are both formed by a manufacturing method such as a glow discharge method. Patterned by lithography.

[Problems to be Solved by the Invention] However, in the above conventional line sensor,
In the photoetching process of the semiconductor layer and the insulating layer, the etching selectivity between the semiconductor layer and the insulating layer is very poor, and when the semiconductor layer is etched, the insulating layer is also etched, resulting in poor insulation, pinholes, etc. Occurred, and the yield was remarkably reduced.

In order to solve the above problems, the photoelectric conversion part, the charge storage part, the switch part, the wiring part, etc. are formed by completely different films,
Although it may be formed in the elementization process step, the manufacturing process of the line sensor becomes complicated, the number of steps increases, the advantage of integrally forming on the same substrate cannot be utilized, and the cost increases. It was

An object of the present invention is to provide a photoelectric conversion device having a simple manufacturing process, a high yield, and a low cost.

[Means for Solving the Problems] The above problems are caused by a photoelectric conversion device having a photoelectric conversion unit, a charge storage unit provided corresponding to the photoelectric conversion unit, and a switch unit on a substrate. In the photoelectric conversion unit, at least a pair of electrodes, an insulating layer, a semiconductor layer provided on the insulating layer and an ohmic contact layer provided between the electrode and the semiconductor layer, the charge storage unit is An electrode, an insulating layer, a semiconductor layer provided on the insulating layer, a counter electrode provided on both sides of the electrode and the semiconductor layer and the insulating layer on a substrate, and between the semiconductor layer and the counter electrode. The switch portion is provided with an ohmic contact layer provided, a gate electrode, an insulating layer provided on the gate electrode, a semiconductor layer provided on the insulating layer, and an ohmic contact layer provided on the semiconductor layer. Source / drain electrodes are respectively provided, and the insulating layer of the photoelectric conversion unit, the semiconductor layer, and the ohmic contact layer are respectively the insulating layer of the charge storage unit, the semiconductor layer, and the ohmic contact layer. And the insulating layer of the switch part, the semiconductor layer, and the ohmic contact layer are formed at the same time by using the layers formed at the same time, which is solved by the photoelectric conversion device of the present invention. It

[Operation] In the photoelectric conversion device of the present invention, at least the photoelectric conversion portion, the charge storage portion, and the switch portion have the insulating layer, the semiconductor layer provided on the insulating layer, and the ohmic contact layer. It is possible to prevent the deterioration of the insulating layer in the manufacturing process and improve the reliability.
Further, since the insulating layer and the semiconductor layer can be simultaneously formed in each component of the photoelectric conversion device, the manufacturing process can be simplified and a small-sized photoelectric conversion device can be provided. Further, since the semiconductor layer and the ohmic contact layer can be provided in the photoelectric conversion part, the charge storage part, and the switch part in the same step, the number of steps does not increase, and the photoelectric conversion is excellent with a high yield. A conversion device can be provided.

In addition, by having the semiconductor layer and the ohmic contact layer in the charge storage portion, it is possible to maintain an excellent insulating layer,
It is possible to suppress variations in charge storage capacity, and by providing an ohmic contact layer,
It is possible to eliminate unnecessary electric charges accumulated in the charge accumulating unit and prevent unnecessary electric charges from being accumulated in the amount of signal charges accumulated in the electric charge accumulating unit. It can be made more stable.

In the photoelectric conversion device of the present invention, when a matrix wiring portion is further provided, the photoelectric conversion portion, the charge storage portion, the switch portion, and the matrix wiring portion are made the same by using the insulating layer and the semiconductor layer as an interlayer insulating layer. An interlayer insulating layer can be formed in the process.

EXAMPLES Examples of the present invention will be described below in detail with reference to the drawings. A line sensor will be described as an example of the photoelectric conversion device of the present invention. In the following explanation,
The same members as those of the line sensor shown in FIG. 10 are designated by the same reference numerals.

FIG. 1 is a sectional view of an embodiment of a line sensor according to the present invention.

In FIG. 1, a lower layer electrode wiring 6 of a wiring portion 2, a lower layer electrode wiring 7 of a charge storage portion 4, and a lower layer electrode wiring 8 which is a gate electrode of a switch portion 5 are formed on a substrate 1. An insulating layer 9 is formed on the wirings 6, 7, 8 and on the substrate 1 between them. A photoconductive semiconductor layer 10 is formed on the insulating layer 9, and a part of the insulating layer 9 and the photoconductive semiconductor layer 10 on the wiring portion 2 is opened for connection. Upper layer electrode wirings 12, 13 and 14 are formed on the photoconductive semiconductor layer 10, and an opening between the upper layer electrode wiring 12 ′ and the upper layer electrode wiring 13 serves as a photoelectric conversion region of the photoelectric conversion unit 3. Become. The upper layer electrode wiring 13, the photoconductive semiconductor layer 10, the insulating layer 9, and the lower layer electrode wiring 7 form a storage capacitor, and one end of the upper layer electrode wiring 13 on the switch section 5 side serves as a drain electrode. Upper layer electrode wiring
One end of 14 on the switch section 5 side becomes a source electrode. Although not shown, the photoconductive semiconductor layer 10 and the upper electrode wiring 12, 1
A doping layer is provided between the electrodes 3 and 14 to make ohmic contact. In this embodiment, the insulating layer 9 and the photoconductive semiconductor layer 10 are provided in each of the wiring section 2, the photoelectric conversion section 3, the charge storage section 4, and the switch section 5, and they are formed in the same step. In the wiring section 2, a photoconductive semiconductor layer is provided between the lower layer electrode wiring 6 and the upper layer electrode wiring 12 in addition to the insulating layer 9.
Although 10 is provided, the insulation between the lower layer electrode wiring 6 and the upper layer electrode wiring 12 may be maintained, and the presence of the photoconductive semiconductor layer 10 does not affect.

In the photoelectric conversion part 3, the photoconductive semiconductor layer 10 is provided on the substrate 1 via the insulating layer 9, which appears as a change in energy level at the interface between the photoconductive semiconductor 10 and the insulating layer 9. There is no change in the basic properties of photoconductive properties. In this case, the substrate 1 of the photoelectric conversion unit 3
An electrode between the insulating layer 9 and the photoconductive semiconductor layer 10
It is possible to optimize by controlling the energy level of the interface.

In the charge storage section 4, the photoconductive semiconductor layer 10 provided on the insulating layer 9 affects the charge storage capacity. This effect is the bias dependence of the capacitance, and the capacitance changes due to band bending of the semiconductor layer at the insulating layer interface. However, in the charge / discharge operation of electric charges used in this embodiment, this bias dependence can be almost ignored by negatively biasing the electrode on the insulating layer 9 side.

The film thickness of the photoconductive semiconductor layer 10 is set to a value at which good photoelectric conversion characteristics of the photoelectric conversion section 3 and switching characteristics of the switch section 5 can be obtained.

Next, a case where the switch part of the line sensor is formed by a matrix switch array will be described.

FIG. 2 shows an equivalent circuit of a line sensor having a matrix switch array.

In the figure, S1, S2, ..., SN (hereinafter referred to as SY1)
Is an optical sensor showing the photoelectric conversion unit 3. C1, C2, ..., C
N (hereinafter, referred to as CY1) is a storage capacitor indicating the charge storage unit 4, and stores the photocurrent of the photosensor SY1. ST1, ST
2, ..., STN (hereinafter referred to as STY1) is a storage capacitor CY
Transfer switches SR1, SR2, ..., SRN (hereinafter referred to as SRY1) for transferring the charge of 1 to the load capacitor CX1 are discharge switches for resetting the charge of the storage capacitor CY1. In this example, the switch unit 5 is a transfer switch.
It consists of STY1 and discharge switch SRY1.

The optical sensor SY1, the storage capacitor CY1, the transfer switch STY1 and the discharge switch SRY1 are arranged in a single row array and are divided into N × M blocks. Transfer switch STY1, discharge switch SRY provided in an array
The gate electrode of 1 is connected to the matrix wiring portion 15. The gate electrode of the transfer switch STY1 is commonly connected to the gate electrodes of the transfer switches of the same rank in other blocks, and the gate electrode of the discharge switch SRY1 is the gate electrode of the transfer switch of the next rank in each block. It is circulated and connected to.

Common lines of the matrix wiring section 15 (gate drive lines G1, G2 ,.
.., GN) is driven by the gate drive unit 16. On the other hand, the signal output is the lead wire 18 (signal output wires D1, D2, ..., D
M) to the signal processing unit 17.

FIG. 3 is a timing chart showing the operation of the line sensor.

Gate drive unit 1 for the gate drive lines (G1, G2, ..., GN)
Selection pulses (VG1, VG2, VG3, ..., VGN) are applied sequentially from 6. First, when the gate drive line G1 is selected, the transfer switch ST1 is turned on, and the charge stored in the storage capacitor C1 is transferred to the load capacitor CX1. Next, when the gate drive line G2 is selected, the transfer switch ST2 turns off.
The N state is entered, and the charge accumulated in the storage capacitor C2 is transferred to the load capacitor CX1 and at the same time the discharge switch SR1
This resets the charge on the storage capacitor C1. Similarly, G3, G4, ..., GN are also selected and the reading operation is performed. In the figure, VC1, VC2, ..., VCN
Indicates the change in the potential of the storage capacitor CY1. These operations are performed for each block, and the signal output of each block VX
1, VX2, ..., VXM are inputs D1, D2, ..., D of the signal processing unit 17.
It is sent to M, converted into a serial signal and output.

 FIG. 4 shows a perspective view of the line sensor.

In FIG. 4, reference numeral 1 is a substrate, and on the substrate 1, a matrix wiring portion 15, a photoelectric conversion portion 3, a charge storage portion 4 for storing output charges of the photoelectric conversion portion 3, and a charge of the charge storage portion 4 are signaled. An array-shaped transfer switch 19 for transferring to the processing IC 21 and an array-shaped discharge switch 20 for resetting the charge storage section 4 are formed. The transfer switch 19 and the discharge switch 20 are divided into N × M blocks. The drain electrode of the transfer switch 19 is connected to the corresponding charge storage section 4, and the source electrode is one for each block. They are put together and connected to a load capacitor (not shown) and the signal processing IC 21. On the other hand, the gate electrodes of each block are connected to the matrix wiring portion 15 so that the gate electrode lines of the same rank in each block are commonly connected.
The common electrode of the matrix wiring section 15 is a gate drive IC
Connected to 22. The signal processing IC 21 is composed of a switch array, shift register, buffer amplifier, etc.
The signal transferred to is read out and reset. The signal processing IC 21 is arranged near the center of the substrate 1 so as to minimize the wiring length of the lead wire 18. In addition, a shield pattern (not shown) having a ground potential is arranged between the lead lines 18.

 FIG. 5 is a partial structural plan view of the line sensor.

In the figure, reference numeral 15 is a matrix wiring section, 3 is a photoelectric conversion section, 4 is a charge storage section, 19 is a transfer switch, 20 is a discharge switch for resetting the charge of the charge storage section 4, and 18 is a transfer switch signal. A lead wire 23 for connecting the output to the signal processing IC, and a load capacitor 23 for accumulating and reading the charges transferred by the transfer switch 19.

In this embodiment, a-S is used as the photoconductive semiconductor layer constituting the photoelectric conversion unit 3, the transfer switch 19 and the discharge switch 20.
An i: H film is used, and a silicon nitride film (SiNH) by glow discharge is used as an insulating layer.

In addition, in FIG. 5, in order to avoid complexity, only upper and lower electrode wirings are shown, and the photoconductive semiconductor layer and the insulating layer are not shown. The photoconductive semiconductor layer and the insulating layer are the photoelectric conversion unit 3, the charge storage unit 4, the transfer switch 19
In addition to being formed on the discharge switch 20, it is also formed between the upper layer electrode wiring and the substrate. Further, an n ⁺ -doped a-SiH layer is formed at the interface between the upper electrode wiring and the photoconductive semiconductor layer, and ohmic contact is established.

Further, in the wiring pattern of the line sensor of the present embodiment, all signal paths output from each photoelectric conversion unit are wired so as not to intersect with other wirings, and crosstalk between each signal component and gate electrode wiring It prevents the generation of induction noise from the.

FIG. 6 is a partial vertical sectional view of FIG. 5, and FIG.
Is a sectional view taken along the line AA ', FIG. 6 (b) is a sectional view taken along the line BB', and FIG. 6 (c) is a sectional view taken along the line CC '.

FIG. 6 (a) is a vertical cross-sectional view of the photoelectric conversion unit 3, where 24 is a lower electrode wiring connected to the gate electrode of the transfer switch 19, 9 is an insulating layer, 10 is a photoconductive semiconductor layer, 12, Reference numeral 13 is an upper layer electrode wiring. The incident light changes the conductivity of the a-Si: H photoconductive semiconductor layer 10 and changes the current flowing between the upper layer electrode wirings 12 and 13 facing each other in a comb shape.

FIG. 6B is a vertical cross-sectional view of the charge storage portion 4, which includes the lower electrode wiring 7, the insulating layer 9 and the photoconductive semiconductor layer 10 formed on the lower electrode wiring 7. And the upper electrode wiring 13 formed on the photoconductive semiconductor layer 10
It is composed of The structure of this charge storage unit 4 is so-called
It has the same structure as an MIS capacitor (Metal-Insulator-Semiconductor). Both positive and negative bias conditions can be used, but stable capacitance and frequency characteristics can be obtained by using the lower electrode wiring 7 in a state of always being negatively biased.

FIG. 6 (c) shows a transfer switch 19 and a discharge switch.
20 is a vertical cross-sectional view showing a transfer switch 19 including a lower electrode wiring 24 that is a gate electrode and an insulating layer 9 that forms a gate insulating layer.
A photoconductive semiconductor layer 10, an upper electrode wiring 14 as a source electrode, and an upper electrode wiring 13 as a drain electrode. The gate insulating layer and the photoconductive semiconductor layer of the discharge switch 20 are the same layers as the insulating layer 9 and the photoconductive semiconductor layer 10, the source electrode is the upper layer electrode wiring 13, the gate electrode is the lower layer electrode wiring 27, and the drain. The electrode is the upper layer electrode wiring 26. The transfer switch 19 and the discharge switch 20 form a thin film field effect transistor (TFT).

As described above, the n ⁺ layer of a-Si: H is interposed at the interface between the upper electrode wiring 13, 14, 26 and the photoconductive semiconductor layer 10 to form ohmic contact.

The upper part of the TFT is usually a passivation film (SiNH, S
Although iO ₂ , silicon-based, organic-based resin, etc. are formed, they are not shown in FIG. 6 (c).

As described above, in the line sensor according to the present invention, all the constituent parts of the photoelectric conversion part, the accumulated charge part, the transfer switch, the discharge switch, and the matrix wiring part have a laminated structure of a photoconductive semiconductor layer and an insulating layer. Therefore, each part can be simultaneously formed by the same process.

FIG. 7 is a partial plan view showing another embodiment of the line sensor according to the present invention.

The line sensor of the present embodiment is a so-called lensless type photoelectric conversion device in which light is emitted from the substrate 1 side and the photoelectric conversion unit 3 directly reads the reflected light of the original brought into contact with the photoelectric conversion unit 3.

The photoelectric conversion unit 3 is provided with a light blocking layer 25 that blocks the illumination light incident from the substrate side. Further, an illumination window 28 for illuminating the original is provided.

8 is a partial vertical sectional view of FIG. 7, and FIG. 8 (a)
Is a DD 'sectional view, and FIG. 8 (b) is an EE' sectional view.

As shown in FIG. 8A, the illumination window 28 is an upper layer electrode wiring.
A part of 12 is opened and formed. This lighting window
28 may be formed by lower layer electrode wiring.

As shown in FIG. 8B, the light shielding layer 25 is formed by the lower layer electrode wiring. A negative bias voltage is usually applied to the light-shielding layer 25, and the dark current is controlled to be sufficiently small.

FIG. 9 shows a partial plan view of the lead wire 18 shown in FIG.

In the figure, a ground pattern 29 is arranged between the lead lines 18 of adjacent blocks. By the ground pattern 29, crosstalk due to capacitive coupling between adjacent lead lines can be avoided. The line capacitance generated between the lead wire 18 and the ground pattern 29 operates as a part of the load capacitor. The difference in capacitance due to the difference in the length of the lead wire of each block is
By adjusting the area of 23, the effective capacitance of the load capacitor of each block is kept constant. Reference numeral 30 is a lead terminal connected to the lead wire 18.

In the circuit configuration of the present embodiment, the matrix wiring is performed on the gate electrode side of the switch section, and the source electrodes of the transfer switches in each block are integrated into one, but the embodiment of the present invention has this circuit configuration. The present invention is not limited to this, and can be applied to various circuit configurations such as a configuration in which matrix wiring is provided on the source electrode side.

[Effects of the Invention] As described in detail above, according to the photoelectric conversion device of the present invention, at least the photoelectric conversion portion, the accumulated charge portion, and the switch portion have an insulating layer, a semiconductor layer provided on the insulating layer, and an ohmic layer. By having the contact layer, each component of the photoelectric conversion device can be formed at the same time, so that the manufacturing process such as film formation and element formation process can be simplified, and the basic configuration of each component is the same. Therefore, it is possible to provide a compact photoelectric conversion device suitable for integration. In particular, since the semiconductor layer and the ohmic contact layer can be provided in the photoelectric conversion part, the charge storage part, and the switch part in the same step, the number of steps does not increase, and the photoelectric conversion of the excellent characteristics with a high yield is achieved. A conversion device can be provided. Furthermore, since the deterioration of the insulating layer in the manufacturing process such as the etching process can be eliminated, the short circuit of the capacitor part in the charge storage part and the matrix wiring part, the variation of the capacity, the insulation deterioration of the electrode wiring crossing, etc. can be significantly reduced. be able to.

As a result, the cost can be reduced, the degree of freedom in setting is high, and a highly reliable photoelectric conversion device can be provided. Further, by having the semiconductor layer and the ohmic contact layer in the charge storage portion, it is possible to maintain an excellent insulating layer, and it is possible to suppress the variation in the charge storage capacity. It is possible to eliminate unnecessary electric charges accumulated in the accumulating unit and prevent unnecessary electric charges from being accumulated in the signal charge amount accumulated in the electric charge accumulating unit. Can be stabilized.

In the photoelectric conversion device of the present invention, when a matrix wiring portion is further provided, by using the insulating layer and the semiconductor layer as an interlayer insulating layer, the photoelectric conversion portion, the charge storage portion, and the switch portion can be interlayer insulated in the same step. Layers can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a line sensor according to the present invention. FIG. 2 shows an equivalent circuit of a line sensor having a matrix switch array. FIG. 3 is a timing chart showing the operation of the line sensor. FIG. 4 shows a perspective view of the line sensor. FIG. 5 is a partial structural plan view of the line sensor. FIG. 6 is a partial vertical sectional view of FIG. FIG. 7 is a partial plan view showing another embodiment of the line sensor according to the present invention. FIG. 8 is a partial vertical sectional view of FIG. FIG. 9 shows a partial plan view of the lead wire 18 shown in FIG. FIG. 10 is a vertical sectional view of a conventional line sensor. 1 ... Substrate 2 ... Wiring part 3 ... Photoelectric conversion part 4 ... Charge storage part 5 ... Switch part 6,7,8 ... Lower electrode wiring 9 ... Insulating layer 10 ... Photoconductive semiconductor layer 12 , 13,14 …… Upper layer electrode wiring

 ─────────────────────────────────────────────────── (72) Inventor Nobuko Kitahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hideyuki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Incorporated (56) Reference JP 56-138968 (JP, A) JP 60-5557 (JP, A) JP 59-177964 (JP, A) JP 59-138371 (JP, A) A)

Claims (3)

(57) [Claims] 1. A photoelectric conversion device having a photoelectric conversion section, a charge storage section provided corresponding to the photoelectric conversion section, and a switch section on a substrate, wherein the photoelectric conversion section has at least a pair of electrodes. An insulating layer, a semiconductor layer provided on the insulating layer, and an ohmic contact layer provided between the electrode and the semiconductor layer, the charge storage section on the substrate, the electrode, the insulating layer, the insulating layer. A semiconductor layer provided on a layer, a counter electrode provided by sandwiching the electrode and the semiconductor layer and the insulating layer, an ohmic contact layer provided between the semiconductor layer and the counter electrode, the switch unit Has a gate electrode, an insulating layer provided on the gate electrode, a semiconductor layer provided on the insulating layer, and source / drain electrodes provided on the semiconductor layer via an ohmic contact layer, respectively. Each of the insulating layer of the photoelectric conversion unit, the semiconductor layer, and the ohmic contact layer, each of the insulating layer of the charge storage unit, the semiconductor layer, and the ohmic contact layer, and the insulating layer of the switch unit. A photoelectric conversion device, wherein the photoelectric conversion device is formed by using a layer formed simultaneously with each of the semiconductor layer and the ohmic contact layer. 2. The photoelectric conversion device according to claim 1, wherein the semiconductor layer is an amorphous silicon layer. 3. The photoelectric conversion device according to claim 1, wherein the ohmic contact layer is an amorphous silicon n ⁺ layer.