JPH0746720B2 - 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 that converts an optical signal into an electric signal and a transistor unit that amplifies the electric signal. The present invention relates to a photoelectric conversion device.

[Prior Art] With the recent widespread use of so-called electronic office machines such as facsimiles and image readers, the demand for compact, low-cost image input devices has increased, the reading resolution is high, high-speed reading is possible, and gradation characteristics are high. A good contact image sensor has been demanded.

Conventionally, the contact image sensor has been made of amorphous silicon (a-
The one using a photoelectric conversion element consisting of a semiconductor layer such as Si) has been used, but with the increase in density, the photocurrent decreases,
Problems have been raised such that the gradation characteristics are deteriorated and the light response cannot be remarkably improved. As a means for solving these problems, there is a photoelectric conversion device as shown in FIG. In this photoelectric conversion device, a source electrode 2 and a drain electrode 3 are provided on an insulating substrate 1, and a semiconductor layer 4, an insulating layer 5, and a gate electrode 6 are stacked on the source electrode 2 and the drain electrode 3, and a thin film transistor portion is formed thereon. The semiconductor layer 7,
The photoelectric conversion unit includes a transparent electrode 8 and an electrode 9 connected to a series resistor. The gate potential of the thin film transistor unit is changed according to the optical signal input to the photoelectric conversion unit, and an electrical signal obtained by amplifying the optical signal is output between the source electrode and the drain electrode.

[Problems to be Solved by the Invention] However, since the photoelectric conversion device has a laminated structure, the manufacturing process is complicated, resulting in poor yield and high manufacturing cost.

[Means for Solving Problems] The above-mentioned problems include a photoelectric conversion element, a series resistance connected in series to one terminal of the photoelectric conversion element, the one terminal of the photoelectric conversion element, and the terminal. A thin film transistor having a gate electrode electrically connected to one terminal of the series resistor electrically connected, wherein the photoelectric conversion element, the series resistor and the thin film transistor are formed by the same film forming process. The photoelectric conversion device of the present invention is characterized by having a crystalline thin film semiconductor layer.

[Operation] In the photoelectric conversion device of the present invention, an amorphous thin film semiconductor layer formed in the same film forming process is used as a semiconductor layer of a photoelectric conversion element and a thin film transistor, and the amorphous thin film semiconductor layer is further used as a constituent layer of series resistance. By using, the number of laminated layers is reduced and the manufacturing process is simplified.

EXAMPLES Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural view of a first embodiment of a photoelectric conversion device of the present invention, (a) is a plan view, (b) is a plan view (A) of FIG.
It is an A'longitudinal sectional view.

In FIG. 1, a gate electrode 19, an insulating film 11 of silicon nitride (Si Nx: H), silicon oxide (SiO ₂ ) or the like is formed on a glass substrate 10, and amorphous silicon (a-Si) is formed thereon. And the semiconductor layer 12 and the n ⁺ layer 13 of the ohmic contact layer are sequentially formed. On top of that, the electrodes 14, 1 of the photoelectric conversion unit 20
5, source electrode 17 and drain electrode of the thin film transistor section 21
18, the ground electrode 16 of the series resistance portion 22 is formed. The electrode 15 of the photoelectric conversion section 20 is connected to the gate electrode 19 of the thin film transistor section 21, and the gate electrode 19 is connected to the series resistance section 22. In the present embodiment, the insulating film 11 of the photoelectric conversion portion 20 and the thin film transistor section 21, the semiconductor layer 12, n ⁺ layer 13 and the like are formed simultaneously and the semiconductor layer 12, n ⁺ layer 13 of the series resistor 22 is also the photoelectric conversion Since the part 20 and the semiconductor layer 12, n ⁺ 13 of the thin film transistor part 21 are formed at the same time, the number of steps in the manufacturing process can be reduced.

FIG. 2 is an equivalent circuit diagram of the photoelectric conversion device.

In FIG. 2, the photoelectric conversion device 28 is a broken line portion in the figure,
The photoelectric conversion element 23 indicates the photoelectric conversion section 20, the thin film transistor 24 indicates the thin film transistor section 21, and the series resistance 25 indicates the series resistance section 22. One end of the photoelectric conversion element 23 is connected to the gate electrode of the thin film transistor 24 and one end of the series resistor 25. The other end of the series resistor 25 is grounded, and voltages V _G and V _D are applied to the other end of the photoelectric conversion element 23 and the source electrode of the thin film transistor 24, respectively. The drain electrode of the thin film transistor 24 is connected to a capacitor 26 and an amplifier 27 for accumulating charges.

Next, the operation of the photoelectric conversion device of the present invention will be described using this equivalent circuit.

When the conductance of the photoelectric conversion element 23 is G ₁ and the conductance of the series resistance 25 is G ₂ , the potential V _{g of the} gate electrode is Is expressed as

Now, when light is incident on the photoelectric conversion element 23, the conductance G ₁ is larger than before the incidence, and therefore the potential V _g of the gate electrode of the thin film transistor 24 is also larger. That is, the optical signal incident on the photoelectric conversion element 23 is converted into an electric signal and further amplified by the thin film transistor 24. The amplified electric signal is stored in the capacitor 26 and further amplified by the amplifier 27.

FIG. 3 shows an example in which the first embodiment is used as a line sensor. Note that the same parts as those in the equivalent circuit diagram shown in FIG.

In FIG. 3, the charge transfer unit 31 includes photoelectric conversion devices 28 _l- 2
Capacitors 26 _{l to} 26 _n connected to the drain electrodes of the 8 _n thin film transistors 24 _{l to} 24 _n , transistors 29 _{l to} 29 _n and transistors 29 _{l to} 29 for transferring the charges accumulated in the capacitors 26 _{l to} 26 _n. Shift register 30 for sequentially operating _n
1 to 30 _n , and an amplifier 27 for amplification. Normally, charge transfer unit
31 is integrated as a driving IC.

Next, a method of manufacturing the photoelectric conversion device of the first embodiment will be described.

Glass substrate (both Corning # 7059) 10 polished on both sides
Was subjected to normal washing with a neutral detergent. Next, Cr was deposited to a thickness of 0.05 μm by a sputtering method, and a photoresist pattern was formed into a desired shape using a positive photoresist (OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.), and then ceric ammonium nitrate and perchlorine were used. The gate electrode 19 of the thin film transistor was formed using an aqueous mixed solution of acids. Then, after removing the photoresist, the glass substrate 10 was set in a capacitively coupled glow discharge decomposition apparatus, and the glass substrate 10 was placed under an exhaust vacuum of 1 × 10 ⁻⁶ Torr for 20 minutes.
Maintained at 0 ° C. Next, 100 sccm of hydrogen-diluted 10% SiH ₄ gas (manufactured by Komatsu Electronics) and 50 sc of 99.999% NH ₃ gas were placed in the device.
The gas flow rate was set to 0.4 Torr, and a high-frequency power supply of 13.56 MHz was used to control the RF (Radio-Frequenc
y) Glow discharge for 1 hour at discharge power of 50W
An insulating film 11 of SiNx: H layer was formed. A desired pattern is formed using a positive photoresist, and the RIE (reactive ion etching) method is used to perform C by using the photoresist as a mask.
F ₄ gas 20 sccm, gas pressure 0.1 Torr, dry etching is performed with RF power 100W, 10% after stripping of the photoresist SiH ₄ 40sc
cm, gas pressure 0.1 Torr, RF discharge power 50W, glow discharge for 3 hours to form semiconductor layer 12 (film thickness 5000Å) such as a-Si, 10% SiH ₄ 40sccm, hydrogen diluted 100ppmPH ₃ gas 200scc
Glow discharge was performed for 1 hour with RF discharge power of 200 W at m, gas pressure of 0.2 Torr, and n ⁺ layer of n ⁺ layer (film thickness)
1000Å) 13 formed. Next, a photoresist pattern is formed in a desired shape using a positive photoresist, and CF ₄ gas 20 sccm, gas pressure 0.1 Torr, RF discharge power 100 W by RIE (reactive ion etching) method using the photoresist as a mask. Then, dry etching was performed to remove the unnecessary n ⁺ layer, semiconductor layer, and insulating film on the gate electrode 19. Then,
Al was deposited to a thickness of 0.5 μm by the sputtering method, and a photoresist pattern was formed into a desired shape using a positive photoresist, then phosphoric acid (85% aqueous solution), nitric acid (60%)
Aqueous solution), acetic acid and water were mixed in a volume ratio of 16: 1: 2: 1 to etch a pattern.

Next, after removing the photoresist, the RIE is performed by the same method as above.
By the method, the unnecessary n ⁺ layer is removed by dry etching,
A photoelectric conversion device as shown in FIG. 1 was obtained.

FIG. 4 is a structural view of a second embodiment of the photoelectric conversion device of the present invention, (a) is a plan view, (b) is a plan view (A).
It is an A'longitudinal sectional view. The same parts as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the duplicated description will be omitted.

In FIG. 4, a gate electrode 19 made of a transparent electrode such as ITO or SnO ₂ is formed on a glass substrate 10.
An n ⁺ layer 13 and an insulating film 11 are formed on the semiconductor layer, and a semiconductor layer is formed thereon.
12 and n ⁺ layer 13 are sequentially formed. In this embodiment, one of the electrodes of the photoelectric conversion unit 20 is shared with the source electrode 18, so that the area occupied by the photoelectric conversion unit 20 can be reduced.

FIG. 5 is an equivalent circuit diagram of the photoelectric conversion device. In addition,
The same parts as those of the equivalent circuit diagram shown in FIG.

As shown in FIG. 5, in the present embodiment, one electrode of the photoelectric conversion element 23 of the photoelectric conversion device 32 and the thin film transistor.
A common voltage V _D is applied to the 24 source electrodes.

The operation of the second embodiment of the photoelectric conversion device of the present invention is the first
This is similar to the embodiment and is represented by the following equation.

The detailed description is omitted.

Next, a method of manufacturing the photoelectric conversion device of the second embodiment will be described.

Glass substrate (both Corning # 7059) 10 polished on both sides
Was subjected to normal washing with a neutral detergent. Next, ITO was deposited to a thickness of 0.1 μm by a sputtering method, a photoresist pattern was formed into a desired shape using a positive photoresist (manufactured by Shipley), and then a mixed aqueous solution of hydrochloric acid and ferric chloride was used. The gate electrode 19 of the thin film transistor was formed.
Next, after forming the n ⁺ layer 13 of the ohmic contact layer, a photoresist pattern for the photoelectric conversion part was formed using a positive photoresist, and then a pattern was formed by dry etching. After removing the photoresist, an insulating film 11 of SiNx: H was formed, and a pattern was formed similarly to the n ⁺ layer 13. Then a
-Si semiconductor layer 12, n ⁺ layer 13 is laminated in the same manner as in Example 1,
After forming a photoresist pattern using a positive photoresist (OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.), dry etching was performed in the same manner as in Example 1 using the photoresist pattern as a mask, and unnecessary gate electrode 19 was removed. Insulation film,
The semiconductor layer and n ⁺ layer were removed. After removing the photoresist, Al was deposited to 0.5 μm by an electron beam evaporation method, and then a desired electrode pattern was formed in the same manner as in the first embodiment, and an unnecessary n ⁺ layer was removed by dry etching, Fourth
A photoelectric conversion device as shown in the figure was obtained.

[Effects of the Invention] As described in detail above, according to the photoelectric conversion device of the present invention, an amorphous thin film semiconductor layer formed in the same film forming step is used as a semiconductor layer of a photoelectric conversion element and a thin film transistor, and By using the amorphous thin film semiconductor layer as the constituent layer of the series resistance, the number of manufacturing steps can be reduced,
The yield can be improved and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a structural view of a first embodiment of a photoelectric conversion device of the present invention, (a) is a plan view, (b) is a plan view (A) of FIG.
It is an A'longitudinal sectional view. FIG. 2 is an equivalent circuit diagram of the photoelectric conversion device. FIG. 3 shows an example in which the first embodiment is used as a line sensor. FIG. 4 is a structural view of a second embodiment of the photoelectric conversion device of the present invention, (a) is a plan view, (b) is a plan view (A).
It is an A'longitudinal sectional view. FIG. 5 is an equivalent circuit diagram of the photoelectric conversion device. FIG. 6 is a vertical sectional view of a conventional photoelectric conversion device. 10 …… Glass substrate 11 …… Insulating film 12 …… Semiconductor layer 13 …… n ⁺ layer 14,15 …… Electrode 16 …… Grounding electrode 17 …… Source electrode 18 …… Drain electrode 19 …… Gate electrode 20 …… Photoelectric conversion part 21 …… Thin film transistor part 22 …… Series resistance part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsunori Hatanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masaki Fukaya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Incorporated (56) Reference JP-A-58-67075 (JP, A) JP-A-61-187363 (JP, A) JP-A-62-159477 (JP, A)

Claims (2)

[Claims] 1. A photoelectric conversion element, a series resistor connected in series to one terminal of the photoelectric conversion element, the one terminal of the photoelectric conversion element and one of the series resistors electrically connected to the terminal. A thin film transistor having a gate electrode electrically connected to two terminals, wherein the photoelectric conversion element, the series resistor, and the thin film transistor have an amorphous thin film semiconductor layer formed in the same film forming process, Photoelectric conversion device. 2. The photoelectric conversion device according to claim 1, wherein the amorphous thin film semiconductor layer is amorphous silicon.