JPH0397271A - Image sensor - Google Patents

Abstract

PURPOSE:To reduce the number of processes and to decrease the number of sheets of masks to be used by a method wherein the same material consisting of polycrystalline silicon or single crystal silicon is used for both of a transistor and a sensor. CONSTITUTION:A polycrystalline silicon layer or a single crystal silicon layer for forming a TEF active layer (a TFT part) 2 and a sensor part photosensitive layer (a sensor part) 2' is formed on an insulating substrate 1 consisting of quartz, glass or the like. Whereby the active layers of the TFT and sensor parts are formed in the same process. Then, gate insulating films 3 and 3' and gate electrodes 4 and 4' are simultaneously formed at the TFT and sensor parts. Moreover, an activation using an ion-implantation for forming source and drain regions is performed. Then, the formation of interlayer insulating layers 5 and the formation of contact holes 6 are performed. Lastly, wiring electrodes 7 are formed. Thereby, the number of sheets of masks to be used can be limited to 4 sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image sensor used in an optical reading device or the like.

[Prior art]

In the typical conventional image sensor manufacturing process, the photosensitive layer for the sensor section was formed after the transistor section was formed, so the number of steps for forming the sensor section was increased in addition to the number of steps for forming the transistor section. It required a very large number of steps. This will be explained with reference to FIG.

1 shows the process of forming a thin film transistor (TPT) active layer, in which a polycrystalline silicon (Poly-Si) layer 2 as a TFT active layer is formed on an IIAs substrate 1. (2) is a step of forming a gate electrode, in which a gate oxide film (Sin2 film) 3 and a gate electrode 4 made of Poly-Si are formed on the Poly-Si layer 2. ■ is an activation process by ion implantation into the source and drain regions. 3 shows the process of forming the interlayer insulating film 5 and the contact hole 6. ■ is the formation process of the wiring electrode (corresponding to the lower electrode of the sensor) 7;
■ is a-Si layer (sensor photosensitive layer) 8 with photoelectric conversion function
(2) is the process of forming the sensor part by etching. (2) is the shape or process of the contact hole 9 in the sensor section, and (2) is the formation process of the electrode 10 in the sensor section. As described above, in the conventional method, the thin film transistor section and the sensor section must be formed separately, which not only increases the number of steps but also increases the number of resists, masks used for etching, etc. ■、■、■、■、■、■
A total of 7 sheets are required in this process.

This not only increases costs, but also reduces reliability due to increased constraints in each process.

〔the purpose〕

An object of the present invention is to reduce the number of steps and the number of masks used, thereby reducing costs and maintaining high product reliability.

[structure precepts]

The present invention includes a thin film transistor section provided on an insulating substrate;
An image sensor consisting of a sensor section formed on the same substrate is characterized in that both the transistor and the sensor use the same material made of polycrystalline or single crystal silicon. Further, it is preferable that a transparent conductive layer is provided on the gate insulating film of the thin film transistor section.

The invention will be explained with reference to FIG.

(2) is a step of forming a polycrystalline silicon layer or a single crystalline silicon layer on an insulating substrate 1 made of quartz, glass, etc. in order to form a TFT active layer 2 and a sensor part photosensitive layer N2'. As a result, the active layers of the TFT section and the sensor section are formed in the same process. ■ is the gate insulating film 3, 3 on the TFT part and the sensor part at the same time.
This is the step of forming the gate electrodes 4 and 4'. ■
is an activation step using ion implantation to form source/drain regions. (2) is the step of forming the glabella insulating layer 5 and the contact hole 6. (2) is a process for forming the wiring electrode 7. This allows the number of masks to be used to be reduced to four.

When using a transparent electrode as the gate electrode of the sensor section, or when implanting H0 ions into the sensor section to improve photosensitivity, a maximum of 6 masks are required.
Compared to the conventional method described above, both the number of steps and the number of masks used are reduced.

〔Example〕

First, a Poly-SL layer with a thickness of 3000λ is formed on a quartz substrate by the LP-CVD method. The forming conditions are SiH. 100%
, 600° C., and 0.1 torr, thereby forming a Poly-Si film with a grain size of approximately 500 Å. After that, by keeping it at 1000℃ for 2 hours under the leaves
00 gate oxide is formed. Next, LP-C
By VD method, n''-Poly-Sil is formed to a thickness of about 3000 mm.The conditions for forming are Si containing 33% PH.
The temperature was 600° C. and 0.1 torr using H 4 . Gate @ pole buttering is SF630SCCM, 0,
This was done by ltorr dry etching. after that,
Phosphorus was implanted through the Sin2 film by 1XIO "am-" dose ion implantation, and activated at 900°C for 30 minutes to form the source/drain regions of the TFT section and sensor section. After that, using the self-line of the gate,
It is immersed in HF:H20=1:6 for 60 seconds to etch away the Sin layer that covered the source/drain regions during ion implantation, and then forms a contact hole interlayer 1# layer. Sunawachi, S by LP-CVD method
A Si02 layer with a thickness of about 5000 A is formed under the condition of iH4/o2=80/200 (SCCM).

Next, contact holes are formed by wet etching. The etching conditions are the same as those for normal thermal Sin2 removal.

After that, AQ was applied to about 1 μm by magnetron sputtering.
The image sensor of the present invention was obtained by forming a thick film and dry etching with a Cx F t + SIC Q 4 system. [Effects] By adopting the layered structure of the present invention, the number of manufacturing steps can be greatly reduced compared to conventional products, and the number of masks used can also be greatly reduced. As a result, we were able to reduce the cost of image sensors and obtain highly reliable products.

[Brief explanation of drawings]

1: Insulating substrate 6: Contact hole 2: TFT
Active layer 7: Wiring electrode 2': Sensor part photosensitive layer 8: Sensor photosensitive layer 3: Gate oxide film 9: Contact hole 4: Gate electrode 1
0: Electrode 5: Insulating layer between eyebrows

Claims (1)

[Claims] 1. In an image sensor consisting of a thin film transistor section provided on an insulating substrate and a sensor section formed on the same substrate, both the transistor and the sensor are made of the same material made of polycrystalline or single crystal silicon. An image sensor characterized by its use. 2. The image sensor according to claim 1, further comprising a transparent conductive layer provided on the gate insulating film of the thin film transistor section.