JPS61124172A - Manufacturing method of amorphous silicon image sensor - Google Patents

Abstract

PURPOSE:To solve a problem of positioning an amorphous silicon film and a lower electrode by continuously removing by etching the amorphous silicon film and the lower electrode with a lower wiring pattern as a mask. CONSTITUTION:Before a lower electrode 12 coated on a substrate 11 is patterned, a a-Si film 13 is formed by a plasma CVD method, and a lower electrode pattern is formed with a photoresist 14. Then, parallel flat plate dry etching unit is used the film 13 is etched by CF4+O2 gas plasma, the gas is then replaced with chlorine gas to etch the electrode 12, the resist 14 is removed, and a diode forming portion of the film 13 is coated by a resist 15. The film 13 is selectively etched by the plasma to remove the resist 15. An interlayer film 16 is formed, the interlayer film contacting hole is opened, and upper wirings 18 are formed. Then, a diode array is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an amorphous silicon image sensor, and more particularly to a method of forming a photodiode and a blocking diode of such an image sensor.

[Conventional technology]

For example, to read 4-size paper with an image sensor,
Requires 1728 photodiodes.

If these photodiodes are arranged horizontally at a ratio of, for example, 8 photodiodes per photodiode, even if one electrode is shared, the same number of switch elements must be installed, and the lead wiring for them must be arranged in one layer.
728 must be provided.

Therefore, in order to simplify these lead wiring, for example, three photodiodes each are made common.
In such an arrangement, the current of the image sensor flows into the photodiode, so in order to prevent this, blocking diodes are connected in series with the photodiodes so that their polarities are opposite, and these blocking diodes are also shared. Now, taking 44 size as an example, the photodiode and blocking diode are shared, respectively, and 54 and 32 lead lines are provided, and 86 lines lead to 17
Wiring for 28 light receiving elements is provided.

[Problem that the invention seeks to solve]

In the conventional method for forming photodiodes and blocking diodes described above, a lower electrode pattern is first formed, and then an amorphous silicon pattern is formed on the pattern. However, in this case, it is necessary to align the patterns, and therefore, it is necessary to allow for an alignment margin of about 5 to 20 μm at the time of design. Therefore, there are drawbacks such as a decrease in the effective area of the diode and a decrease in yield due to poor alignment.

Referring to FIG. 2, numeral 81 shows a conventional method of forming a diode. First, a lower electrode 21 transparent to light is formed.
(SnO2, indium tin oxide (ITO), etc.) is patterned using an etching method to form an amorphous silicon (a-3t) film on the entire surface, and a
-3t pattern 22 is formed using photoresist. At this time, the alignment margin (1) is 5 to 2 around the pattern.
This requires a thickness of approximately 0 μm, which poses a problem of reducing the effective area of the electrode.

Further, FIG. 2 (bl) shows the case where the pattern is shifted during alignment, and if the a-5i pattern 22 is shifted as shown, there is a problem that it will short-circuit with the adjacent element.

[Means for solving problems]

The present invention provides a method for forming a diode that solves the above-mentioned problems, and the means thereof is to form a photodiode for an image sensor using amorphous silicon by forming a transparent lower electrode and an amorphous silicon film on the entire surface of the substrate. A step of continuously etching away the amorphous silicon film and the lower electrode using a lower wiring pattern mask, and a step of covering only the diode portion with photoresist and selectively etching away the amorphous silicon in unnecessary parts. The invention is made by a method of manufacturing an image sensor characterized in that the method can also be implemented in the formation of blocking diodes.

[Effect]

An object of the present invention is to provide a method of forming a lower electrode using amorphous silicon as a mask in order to solve the above-mentioned problems. Continuous etching removal solves the problem of alignment between the amorphous silicon film and the lower electrode in the prior art.

〔Example〕

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

The embodiment of the present invention, that is, the process of forming an amorphous silicon photodiode is shown in FIGS.
(A), (C), (D), (E)
fa), (e), (d), and (e) corresponding to the above are shown in plan views.

See Figure 1 (A): Before patterning the lower electrode 12 (made of SnO2 + ITO, etc., which is transparent to light and conductive) deposited on the substrate 1), an a-5i film 13 is formed by plasma CVD. Then, the photoresist 14 is patterned with a lower electrode pattern. In FIG. 1 fal, which is a corresponding plan view, a, -
5i film and resist are indicated by diagonal lines similar to the cross-sectional view.

See Figure 1 (B): Next, using a parallel plate dry etching device, CFq
The a-5i film 13 is etched with +02 gas plasma, and then the gas is etched with chlorine-based gas (e.g. CCJI!2F2).
), the lower electrode 12 is etched, and the resist 14 is etched.
remove.

Refer to FIG. 1(C): The diode formation portion of the a-5t film 13 is covered with a resist 15.

Refer to FIG. 1(D): The a-3t film 13 is selectively etched using Ch + 02 plasma, and the resist 15 is removed. The corresponding figure 1 (d
+ indicates the state before resist removal. In the process up to this point,
The basis of an a-S+ film diode of the same size as the bottom electrode 12 is formed.

Refer to FIG. 1(E): An interlayer film 16 (organic or inorganic) is formed, this glabellar film contact hole is opened, and an upper wiring 18 is formed to complete the diode array. In addition, in the same figure, 1
Reference numeral 9 indicates a contact hole for the lower electrode 12, 20 indicates an extraction wiring, and arrows indicate incident light beams.

In the second embodiment of the present invention, that is, a method for manufacturing an amorphous silicon blocking diode for preventing image sensor current from running around, the lower electrode is made of a conductive material that does not transmit light, such as platinum (Pt), and its etching is carried out by etching.
This method does not differ from the method described above, except for the sputtering using gas.

Also, the diagram explaining the process is the same as Figure 1, so
Description and drawings of the second embodiment will be omitted.

As explained above, according to the present invention, since the lower electrode is formed using the A-3T layer as a mask, no alignment margin is required, and the diode area can be used effectively to the maximum, and a decrease in yield due to poor alignment can be avoided. It has a preventive effect.

[Brief explanation of drawings]

FIGS. 1(A) to E) are cross-sectional views showing the steps of carrying out the method of the present invention, FIGS. 1(a), (C1, [d), +e)
2 is a plan view corresponding to (A), (C), (D), and (E), and FIG. 2 (al and (bl) are plan views showing the conventional process. , 12 is the lower electrode, 13 is the a-5t film, 14 and 15 are the resist films, 16 is the glabellar membrane, 17 and 19
2 indicates a contact hole, and 20 indicates a wiring layer.

Claims (2)

[Claims] (1) In a method of forming a photodiode for an image sensor using amorphous silicon, a step of forming a transparent lower electrode and an amorphous silicon film on the entire surface of the substrate, and successively etching and removing the amorphous silicon film and the lower electrode using a lower wiring pattern mask. a step of covering only the diode portion with photoresist and selectively etching away unnecessary portions of amorphous silicon;
A method of manufacturing an image sensor, comprising: (2) The method according to claim 1, wherein the lower electrode is made of a conductive material that is non-transparent to light.