JPH02211665A - Solid-state image sensing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a step structure between a light receiving section of a solid-state imaging device and wiring.

[Summary of the Invention] The present invention provides a solid-state imaging device fabricated on an insulating substrate by providing a stepped portion between a light receiving element and a conductor wired from the light receiving element in at least two directions. , it is possible to reduce the resistance component of the stepped portion caused by the film quality of the light-receiving element and the sputtering direction of the conductor, and it is possible to custom manufacture a high-quality solid-state imaging device that does not depend on the film quality of the light-receiving element and the sputtering direction of the conductor. This is what I did.

[Prior Art] In a conventional solid-state imaging device, a stepped portion formed between a light receiving element and a conductor wired from the light receiving element is only in one direction. FIG. 2(a) shows a plan view of a conventional light receiving element. Second
FIG. 2(b) is a cross-sectional view taken along line A-a in the plan view of FIG. 2(a), and shows a thin film transistor. Same figure (
In a), l is a-5i: H12 is a transparent electrode (IT
3 is an aluminum electrode. Broken line B in figure (a)
The figure (C) is a diagram cut along the line -b. Same figure (
From c), the stepped portion formed between the a-3i:H layer 1 and the aluminum electrode layer 3 is only in one direction.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, in order to cover the step portion with the conductor with good step coverage, the thickness of the step portion must be twice or less than the thickness of the conductor. For example, when the photodetector is formed of a-5i:H with a Pin structure, when etching a-3iH, the uppermost n layer protrudes because the etching rate of the n layer is slower than that of the p and i layers. It remains. When sputtering a conductor onto the n-layer that remains in the protruding shape, if the stepped portion is in one direction, depending on the sputtering direction, the thickness of the protruding conductor will be 1/1/2 of the thickness of the flat conductor layer. It will be about 10. In the case of devices that convert light into minute amounts of electricity, such as solid-state imaging devices, the large resistance of the conductor in the eaves prevents the flow of sufficient current, resulting in a distorted bright output waveform. It ends up. (Hereafter, this waveform will be referred to as the N waveform.) Furthermore, if the deposition is performed under conditions that suppress the N waveform, the dark current will increase. The present invention is intended to solve these problems, and its purpose is to provide a highly reliable solid-state imaging device that can provide a process margin in design.

[Means for Solving the Problems] A solid-state imaging device of the present invention is a solid-state imaging device in which a light receiving element and a thin film transistor for driving the light receiving element are formed on an insulating substrate. The step portion formed between the conductor and the light receiving element is characterized in that the step portion is covered with a conductor in at least two directions.

[Function 1] According to the above-described structure of the present invention, the conductor layer can cover the step portion with extremely good step coverage in a certain direction, regardless of the sputtering direction of the conductor layer or the film quality of the light receiving element. can be formed with. Thereby, the N waveform can be suppressed and does not depend on film quality. In other words, a-5i:H
If we focus only on the conditions for suppressing dark current under layer deposition conditions, N
The waveform can be suppressed, and a large margin can be obtained regarding the deposition conditions of the a-3i:H layer.

[Embodiment 1] FIG. 1(a) shows a plan view of a light receiving element in an embodiment of the present invention. Figure (b) shows a cross-sectional view of the structure along A-8 in Figure (a) and the thin film transistor, and Figure (c) shows Figure (c).
A structural sectional view taken along line B-b in a) is shown. Here, an example will be described in which a polycrystalline silicon thin film transistor and an a-3i:H (hydrogenated amorphous Si) light receiving element are used. In the same figure (a), l is a-5i: H12 is a transparent electrode (such as ITO), and 3 is an aluminum electrode. ITO
and a-5i:H, as shown in the same figure (a), there is a part that overlaps on the same line, and about 4 μm = 10 on the inside of the same line.
It has a structure in which an aluminum electrode exists at LLm.

In the figure (b), 4 is an insulating substrate, 5 is polycrystalline silicon, 6 is a gate oxide film, 7 is a gate electrode, 8 is an interlayer insulating film, and 9 is a P-type semiconductor layer doped with boron.
t-+t Cx:H, 10 is a ■-type semiconductor layer a-5i:
Hll is an N-type semiconductor layer doped with non-containing a-3it.
-xc:H. Note that the value of X is 0<x≦1. 1
a-3j:H is the 3rd layer of 9.10.11, that is P-i-
It consists of n structure.

Figure (c) shows a cross-sectional view of the structure between B-b in Figure (a). The stepped portion formed from 3 is in 3 directions.

In this example, the thickness of each layer forming the light receiving element is 500 for the P-type semiconductor layer 9, 8000 for the 1-type semiconductor layer 10, and 500 for the N-type semiconductor layer 11 as shown in FIG. 1(b). Made into a person. The step portion covered by the aluminum electrode layer of No. 3 is 900
0 people, and the film thickness required for the aluminum electrode layer is generally 4
Although a thickness of 500 Å or more is required, in this example, the thickness of the aluminum electrode layer was set to 4500 lum.

When forming the n-type semiconductor layer of No. 11, methane (CH4) is introduced to suppress dark current, but as the amount of methane increases, the etching of the n-type semiconductor layer when etching a-3i/H increases. The rate becomes slower and the protrusion of the n-type semiconductor layer becomes larger. Conversely, if the amount of methane is suppressed in order to reduce the protrusion of the n-type semiconductor layer, the dark current will increase, and the dark current will increase by 1×
This results in a deterioration of the S/N ratio by exceeding J O-"A. Tables 1 and 2 show the results of evaluating the bright output waveform rounding or dark current by varying the amount of methane and the debo time. Shown below.

Table 1 N waveform occurrence rate Table 2 Dark current occurrence rate (> I is 170
sec is a desirable condition, but a dark current of 1 to 2% occurs even under this condition. Therefore, when the light-receiving element part is structured as shown in Figure 1 (a), (b), and (c), although the dark current generation rate is unchanged from Table 2, N
Regarding the waveform generation rate, the generation of N waveforms could be suppressed under any of the conditions shown in Table 1.

In other words, although there are no conditions for suppressing all dark current due to the relationship between the amount of CH4 and the debo time, it was possible to suppress the N waveform under all conditions in which dark current does not occur. As a result, it was possible to increase the process margin from a design standpoint, and it was possible to provide a highly reliable solid-state imaging device.

〔Effect of the invention〕

As described above, according to the present invention, the following effects of the invention can be obtained.

(2) The N waveform output can be suppressed without depending on the film formation conditions of the light receiving element.

■Independent of the spuck direction of the AJ2 conductive layer, even if the thickness of the stepped portion is 2.5 times the thickness of the conductor, the stepped portion can be covered with good step coverage in a certain direction. N waveform output can be suppressed.

■Process margin can be increased in design, and not only N waveform but also dark current can be suppressed.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view of a light receiving element of a solid-state imaging device of the present invention. FIG. 1(b) is a sectional view taken along line A-a in FIG. 1(a), and a sectional view of a thin film transistor connected to the light receiving element. FIG. 1(c) is a sectional view taken along line B-b in FIG. 1(a). FIG. 2(a) is a plan view of a conventional solid-state imaging device. FIG. 2(b) is a cross-sectional view of the light-receiving element of FIG. 2(a) taken along line A-a, and a cross-sectional view of a thin film transistor connected to the light-receiving element. FIG. 2(c) is a sectional view taken along line B-b in FIG. 2(a). a-5i:H ・Transparent electrode...Aluminum electrode Insulating substrate Polycrystalline silicon gate oxide film Gate electrode interlayer insulating film P-type semiconductor layer processing type semiconductor layer N-type semiconductor layer and above

Claims (1)

[Claims] In a solid-state imaging device comprising a light-receiving element and a thin film transistor for driving the light-receiving element formed on an insulating substrate, at least two steps are formed between the conductor wired from the light-receiving element and the light-receiving element. A solid-state imaging device characterized in that a stepped portion is covered with a conductor in a direction or more.