JP2001320040A - Photoelectric conversion device and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: In a photoelectric conversion device in which a photoelectric conversion element and a TFT are simultaneously formed, a light receiving sensitivity of the photoelectric conversion element is not reduced and a transfer speed of an electric signal by the TFT is not reduced. . SOLUTION: In a photoelectric conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed by the same process, the thickness of a semiconductor layer provided in the switch element is reduced. The thickness is smaller than the thickness of the semiconductor layer provided in the photoelectric conversion element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed in the same layer structure, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art In recent years, hydrogenated amorphous silicon (a
-Reading elements such as scanners, digital copiers and X-ray imaging devices using semiconductor materials represented by -Si)
In addition, a semiconductor device in which a switch TFT of the semiconductor device is formed one-dimensionally or two-dimensionally on a large-area substrate has been put to practical use.

In particular, a-Si can be formed uniformly on a large-area substrate at a low temperature, and therefore has the advantage that an inexpensive glass substrate can be used.
T) can be used not only as a semiconductor material of T) but also as a photoelectric conversion material.
Also has the advantage that they can be formed simultaneously.

Conventionally, a photoelectric conversion device represented by this type of semiconductor device generally includes a PIN photodiode as a photoelectric conversion element and a TFT as a switch element, but uses a-Si. As a result, a photoelectric conversion element and a TFT can be formed at the same time. Therefore, a photoelectric conversion element using an MIS photodiode has been put to practical use.

FIG. 5 is a basic equivalent circuit diagram of a photoelectric conversion device including a plurality of pixels each having a TFT 7 and a photoelectric conversion element 8. In FIG. 5, the gate electrode of each TFT 7 is connected to a common gate line 1, and the gate line 1
The FT 7 is connected to a gate driver 2 for controlling ON and OFF. Further, the source or drain electrode of each TFT 7 is connected to the common signal wiring 3, and the signal wiring 3 is connected to the amplifier IC 4.

The signal line 3 forms a signal line capacitance (C 2) 9 by a cross portion of the TFT 7 and the gate line 1. Further, a drive wiring 5 for driving each photoelectric conversion element 8 is connected to a common electrode driver 6.

FIG. 6 is a sectional view of a pixel having the TFT 7 and the photoelectric conversion element 8 shown in FIG. In FIG. 6, 1
01 is an insulating substrate, 102 is a gate electrode and a gate wiring 1
And 103, 104, and 10
Reference numeral 5 denotes an interlayer insulating layer, an intrinsic semiconductor layer, and an ohmic contact layer. Reference numeral 106 denotes a second conductive layer forming the source electrode and the drain electrode of the TFT 7, the signal wiring 3, and the driving wiring 5.

The signal wiring 3 is composed of the TFT 7 and the gate wiring 1
And the signal line capacitance C2 is formed by the cross portion of the photoelectric conversion device.
1 and the capacitance C2 of the signal wiring 3. That is, the charge generated and accumulated in the photoelectric conversion element 8 from the incident light is distributed to the capacitors C1 and C2 by the TFT 7, and the potential of the signal wiring 3 is read out by the amplifier IC 4 to be image information.

Here, the manufacturing process of the photoelectric conversion device shown in FIG. 6 will be described. First, Cr is placed on the insulating substrate 101.
A film is formed by sputtering to a thickness of, for example, 1000 °. Subsequently, the gate electrode 102 and the gate wiring are formed by, for example, wet etching. Thereafter, a SiN / a-Si / a-Si (n ⁺ ) film is continuously formed by a CVD method so as to have a thickness of, for example, 3000 °, 6000 °, and 750 °, respectively, to form an interlayer insulating layer 103 and an intrinsic semiconductor layer. (I layer) 104 and an ohmic contact layer 105 are formed.

Next, a contact hole is formed by, for example, dry etching. Then, an Al film is formed to a thickness of, for example, 1 μm by sputtering to form a source electrode, a drain electrode, the signal wiring 3, and the Vs wiring 106. Subsequently, the n ⁺ layer in the TFT channel portion is removed by, for example, dry etching. Thereafter, a protective layer (not shown) is laminated.

[0011]

In recent years, there has been a demand for miniaturization of pixels. However, in a photoelectric conversion device as shown in FIG.
There is a problem that the ability of T is reduced. This problem can be solved by optimizing the thicknesses of the intrinsic semiconductor layer of the photoelectric conversion element and the intrinsic semiconductor layer of the TFT.

However, when a conventional TFT and a photoelectric conversion element are formed on the same layer to form a photoelectric conversion device, the thickness of the intrinsic semiconductor layer 104 forming the TFT shown in FIG. Since the thickness of the semiconductor layer 104 is the same, it is difficult to optimize the thickness of the intrinsic semiconductor layer 104 between the TFT and the photoelectric conversion element.

Here, the thickness of the intrinsic semiconductor layer 104 is determined to be optimal for the photoelectric conversion element in order to improve the light receiving sensitivity. There has been a problem that the signal transfer speed is reduced.

Therefore, the present invention provides a photoelectric conversion element and a TFT.
It is an object of the present invention to prevent a light-receiving sensitivity of a photoelectric conversion element from being lowered and a transfer speed of an electric signal by a TFT from being slowed down in a photoelectric conversion device in which both are formed at the same time.

[0015]

According to the present invention, a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed by the same process. In the photoelectric conversion device described above, the thickness of the semiconductor layer included in the switch element is smaller than the thickness of the semiconductor layer included in the photoelectric conversion element.

Further, according to the present invention, in a method for manufacturing a photoelectric conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed by the same process, Forming, and thinning the semiconductor layer of the switch element among the formed semiconductor layers.

That is, in the present invention, the semiconductor layer of the TFT is made thinner than the semiconductor layer of the photoelectric conversion element.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a manufacturing process diagram of a photoelectric conversion device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a photomask for forming each layer shown in FIG. In the present embodiment, a case will be described in which an intrinsic semiconductor layer of a TFT is thinned, surface treatment is performed by H2 plasma or the like, and then an ohmic contact layer is formed by a CVD method, taking a photoelectric conversion device of a MIS type + TFT as an example. I do.

First, a Cr film is formed on the insulating substrate 101 using a photomask as shown in FIG.
A film is formed by sputtering with a thickness of 00 °. Thus,
A gate electrode 102 is formed on an insulating substrate 101 (FIG. 1)
(A)).

Subsequently, an SiN / a-Si film is formed by a CVD method so as to have a thickness of, for example, 3000/6000 ° using a photomask as shown in FIG. 103 and the intrinsic semiconductor layer (i
Layer) 104 is formed. Then, the surface of the intrinsic semiconductor layer (i-layer) 104 is removed by, for example, dry etching to reduce the thickness to, for example, 3000 ° or less (FIG. 1B).

Next, using a photomask as shown in FIG. 2C, the interlayer insulating layer 103 and the intrinsic semiconductor layer (i-layer) 104 are separated between elements by, for example, dry etching (FIG. 1C). . Then, an H2 plasma treatment or the like is performed.
The protective film 107 is formed by the method D. Subsequently, using a photomask as shown in FIG.
Patterning is performed so as to leave the channel portion of the portion to be the FT 7 and the light receiving surface portion of the portion to be the photoelectric conversion element 8 (FIG. 1D).

Next, an ohmic contact layer 105 is formed by depositing an a-Si (n ⁺ ) film to a thickness of, for example, 750 ° by a CVD method. Then, FIG.
A contact hole is formed by, for example, dry etching using a photomask as shown in FIG.
(E)). Then, an Al film is formed to a thickness of, for example, 1 μm by sputtering using a photomask as shown in FIG.
An ig wiring and a Vs wiring 106 are formed (FIG. 1F).

Subsequently, using a photomask as shown in FIG.
For the purpose of forming the FT channel portion, the n ⁺ layer (the ohmic contact layer 105) other than the photoelectric conversion portion is removed. Thereafter, a protection layer (not shown) is formed. In this way, the thickness of each intrinsic semiconductor layer 104 of the TFT 7, the photoelectric conversion element 8, and the signal line capacitance section 9 is optimized.

[Embodiment 2] FIG. 3 is a manufacturing process diagram of a photoelectric conversion device according to Embodiment 2 of the present invention. FIG. 4 is a diagram showing a photomask for forming each layer shown in FIG. In this embodiment, carried out as an example the photoelectric conversion device of the MIS + TFT 7, after thinning the intrinsic semiconductor layer 104 of the TFT 7, perform doping due PH ₃ plasma, and the formation treatment process and the ohmic contact layer on the surface simultaneously The case will be described.

First, a Cr film is formed on the insulating substrate 101 using a photomask as shown in FIG.
A film is formed by sputtering with a thickness of 00 °. Thus,
A gate electrode 102 is formed on an insulating substrate 101 (FIG. 3)
(A)).

Subsequently, a SiN / a-Si film is formed by a CVD method using a photomask as shown in FIG. 103 and an intrinsic semiconductor layer (i-layer) 104 are formed. Then, the surface of the intrinsic semiconductor layer (i-layer) 104 is removed by, for example, dry etching to reduce the thickness to, for example, 3000 ° or less (FIG. 3B).

Next, using a photomask as shown in FIG. 4C, the interlayer insulating layer 103 and the intrinsic semiconductor layer (i-layer) 104 are separated from each other by, for example, dry etching (FIG. 3C). . Then, for example, SiN is set to 200
A protective film 107 is formed by a CVD method with a thickness of 0 °. Subsequently, using a photomask as shown in FIG. 4D, patterning is performed so as to remove the TFT channel portion and the light receiving surface portion of the photoelectric conversion element (FIG. 3).
(D)).

Next, treatment of the surface of the intrinsic semiconductor layer (i-layer) 104 by PH ₃ plasma doping or the like and the ohmic contact layer 105
It is formed with a thickness of 50 °. Then, using a photomask as shown in FIG. 4E, a contact hole is formed by, for example, dry etching (FIG. 3E). Then, using a photomask as shown in FIG.
An Al film is formed to a thickness of, for example, 1 μm by sputtering, and a source electrode, a drain electrode, a Sig wiring,
The s wiring 106 is formed (FIG. 3F).

[0030]

As described above, the present invention is formed in a conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading out the converted electric signal are formed by the same process. Of the semiconductor layers, the thickness of the semiconductor layer of the switch element is reduced so that the light receiving sensitivity of the photoelectric conversion element is not reduced, the transfer noise of the TFT is not increased, and the transfer speed of an electric signal in the TFT is not slowed down. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a photoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is a photomask diagram for forming the photoelectric conversion device of FIG. 1;

FIG. 3 is a schematic sectional view of a photoelectric conversion device according to a second embodiment of the present invention.

FIG. 4 is a photomask diagram for forming the photoelectric conversion device of FIG. 3;

FIG. 5 is an equivalent circuit diagram of a conventional photoelectric conversion device.

FIG. 6 is a schematic cross-sectional view of a conventional photoelectric conversion device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vg line 2 Gate driver 3 Sig line 4 Amplifier IC 5 Drive wiring 6 Common electrode driver 7 TFT 8 Photoelectric conversion element 9 Signal line capacitance part 101 Insulating substrate 102 Gate electrode and gate wiring 103 Interlayer insulating layer 104 Intrinsic semiconductor layer 105 Ohmic contact Layer 106 source or drain electrode of switch TFT and Sig line 107 protective film

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4M118 AA01 AB01 AB10 CA40 CB06 5C024 CX41 CY47 GX03 GY31 5F049 MA15 MB05 MB12 NA03 NA08 NB03 NB05 PA04 PA07 PA14 RA04 RA08 SS01 SZ12 WA07 5F110 AA01 BB10 CC07 DD01 FF03 GG03 EE04 GG02 GG24 GG35 GG44 HK09 HK34 HL03 HL23 NN02 NN12 NN24 NN35 QQ04

Claims (9)

[Claims] 1. A photoelectric conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed by the same process, wherein the thickness of a semiconductor layer provided in the switch element is Is smaller than the thickness of a semiconductor layer provided in the photoelectric conversion element. 2. The photoelectric conversion device according to claim 1, wherein said semiconductor layer is formed of amorphous silicon. 3. The photoelectric conversion device according to claim 1, wherein the thickness of the semiconductor layer provided in the switch element is 1,000 Å or more and 3000 Å or less. 4. A method for manufacturing a photoelectric conversion device in which a photoelectric conversion element for converting an optical signal into an electric signal and a switch element for reading the converted electric signal are formed by the same process. And a step of thinning a semiconductor layer of the switch element among the formed semiconductor layers. 5. The method according to claim 4, wherein the semiconductor layer is formed of amorphous silicon. 6. The method according to claim 4, wherein the semiconductor layer in the switch element portion is thinned by etching. 7. The method according to claim 6, wherein a treatment process is performed on the surface of the thinned semiconductor layer after the etching. 8. The method according to claim 7, wherein the treatment is a plasma treatment or a hydrofluoric acid treatment. 9. A semiconductor layer is formed between a first signal line for transferring the electric signal read by the switch element and a second signal line for transferring a signal for turning on / off the switch element. 4. The photoelectric conversion device according to claim 1, wherein a thickness of the semiconductor layer is the same as a thickness of the semiconductor layer provided in the photoelectric conversion element. 5.