JPS61278173A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To stabilize the characteristics by forming an electrode immediately after forming an amorphous silicon layer, thereby making the Schottky junction or ohmic contact between the amorphous silicon layer and the electrode good. CONSTITUTION:An amorphous silicon layer 3 is formed by means of the plasma CVD method on the surface of an insulating substrate 1 having a lower electrode 2 formed thereon, and immediately thereafter an ITO is formed as a first upper electrode 6a by means of the vapor deposition method. Then, photographic plate making is performed, with a photoresist 7 as a mask the upper electrode 6a is etched away first, subsequently with the same photoresist 7 as a mask the amorphous silicon layer 3 is also etched away, and thereafter the photoresist 7 is removed. Next, after an insulating film 4 such as SiO2 is formed to protect the end face of the diode, a contact hole 5 is formed by means of the photoetching method. Finally, an ITO is formed as a second upper electrode 6b again by means of the vapor deposition method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device using an amorphous semiconductor.

[Conventional technology]

As an application of semiconductor devices using amorphous semiconductors,
Close-contact image sensors are being considered.

A photodiode or a booting diode constituting this image sensor is generally made of amorphous silicon.

A conventional method of manufacturing a photodiode using amorphous silicon will be explained with reference to FIGS. 2(&) to (d). First, as shown in FIG. 2(a)K, a metal such as nichrome or the like is deposited on the surface of an insulating substrate 1 made of K, glass, etc. through a photolithographic process.

Subsequently, an amorphous silicon layer 3Y is formed on the surface by a method such as plasma CVD. In this case, when forming a Schottky diode, a single layer of intrinsic amorphous layer is used.

Also, when formed as a PIN diode, P, I
, N deaf amorphous layers.

Next, the amorphous layer is patterned and etched by photolithography to form separate and independent elements as shown in FIG. 2(b). Although only one element is shown in FIG. 2(b), a large number of elements are actually arranged.

Subsequently, as shown in FIG. 2(C), an insulating film such as a silicon oxide film or a silicon nitride film is coated with a 4YCVD method, and a contact hole 5 is formed by photolithography, etching, etc. to form amorphous silicon. Layer 3 is partially exposed to K11.

Finally, as shown in FIG. 2(d'), the upper electrode 6 is formed through processes such as vapor deposition, photolithography, and etching.

In order to use it as a photodiode, the upper electrode 6
is made of a transparent conductive film such as ITO, and has a structure that allows light to be received from the top surface.

[Problem that the invention seeks to solve]

In the conventional manufacturing method as described above, between the patterning step of the 7 mol 7 as silicon layer 3 and the vapor deposition step of the upper electrode 6, the surface of the 7 mol 7 as silicon layer 30,
In other words, the surface in contact with the upper electrode 6 is exposed to the V cysts and their removal liquids, the insulating film 4 and the etching liquid used when buttering the same, and the V cyst removal liquid. Therefore, careful pretreatment is required before the deposition of the upper electrode 6 in order to obtain good electrical contact.

However, due to the presence of the lower electrode 2 that has already been formed, it is impossible to perform a highly reactive and strong pretreatment such as aqueous treatment with hot sulfuric acid, etc., and the surface of the clean amorphous silicon layer 3 is It is difficult to make W* appear. Therefore, when creating a Schottky diode, the characteristics may vary, resulting in poor reproducibility or PIN
When creating a diode, there was a problem that good ohmic contact could not be made.

This invention was made to solve these problems without adding a photolithography process.

It provides good electrical contact between the amorphous silicon layer and the upper electrode.

[Means for solving problems]

In the method for manufacturing a semiconductor device according to the present invention, electrodes are formed immediately after forming an amorphous silicon layer.

[Effect]

In this invention, the surface of the amorphous silicon layer is not contaminated or aluminized after film formation, and the upper electrode is immediately attached to it. A layer is formed.

〔Example〕

1(a) to 1(d) show the steps of the method for manufacturing a semiconductor device of the present invention, and in these figures, the same reference numerals as in FIGS. 2(a) to 2(d) indicate the same parts. ing. Note that 6m is the first upper IKff1.6b is the second upper side L7 is 7o) L/cyst.

First, as shown in FIG. 1(a), an amorphous silicon layer 3 is formed by plasma CVD on the surface of an insulating substrate 10 on which a lower electrode 2Y has been formed, and then immediately formed as a first upper electrode 6& in accordance with the present invention. ITO is formed by a vapor deposition method. The method of forming the lower electrode 2 and the structure of the amorphous silicon layer 3 are the same as in the conventional example.

Next, photolithography is performed, and as shown in FIG. 1(b)K, first, the first upper electrode 6aY is etched and removed using the photoresist 7' as a mask, and then the same 7-hole/disdoor is used as a mask. , 7 mol 7 as silicon layer 3 is also removed by etching, and then 7 mol 7 assilicon layer 3 is removed.

Subsequently, as shown in FIG. 1(c), an insulating film 4'Y of 5iO1 or the like is formed to protect the diode end face tI, and then a contact hole 5 is formed by photolithography.

Finally, as shown in FIG. 1(d)K, a second upper electrode 6b is formed using the vapor deposition method. Although ITO was used for both cases, different materials 5 such as ITO and tin oxide (5n01) may be used as long as they are transparent conductive films.

According to this embodiment, the first upper electrode 61 is immediately formed on the surface of the amorphous silicon layer 30 simply by exposing it to the atmosphere, so that good electrical contact with good reproducibility is achieved.

Amorphous silicon layer 3 created by plasma CVD method
The 0 surface is terminated with hydrogen atoms, and therefore the surface is relatively stable compared to single crystal silicon or polysilicon formed by thermal CVD.

For example, the surface remains water repellent even after being exposed to the atmosphere for several days.
Natural oxidation reactions hardly proceed. Sara K, Blaz'''
The fCVD device and the sputter deposition device are almost similar in structure and can perform continuous film formation, and in this case, the Alfsilicon layer 3 is not exposed to the atmosphere.

Further, since the same photonist is used for patterning the first upper side Ia and the 7 mol silicon layer 3, the number of photolithography steps is not increased compared to the conventional process.

The cross section of the PIN diode made according to this invention is:
As shown in FIG. 1(d) Ic, the electrode extends to the active layer surface. Therefore, there was a concern that the reverse leakage current would increase compared to the conventional type with the structure shown in Figure 2 (dl).However, as a result of actually comparing the two, it was found that -8V
When biased, both showed a leakage current of about -1X 10'''''A/(-1, and no particular problem was found. Also, regarding the forward bias, it was clearly a good voltage with less fluctuation, probably due to this invention. The current relationship was shown.

In the above embodiment, the 77 rufus silicon layer 3 was formed by the plasma CVD method, and each electrode 2. Although eat6b was formed by a vapor deposition method, other methods may be used. Further, although the insulating film 4KSi02 is used, 5i3H, etc. may also be used.

〔Effect of the invention〕

As explained above, in this invention, since the electrode is formed immediately after forming the 77R7A silicon layer, the Schottky junction or ohmic connection between the amorphous silicon layer and the electrode is good, and the characteristics are stable and high. Reproducibility is obtained. Furthermore, the same photonodist is used for electrodes and 77 Ruf7.
Since it can be formed with a silicon layer, there are advantages such as no increase in the number of photolithography steps.

[Brief explanation of drawings]

Figures 1 (&) to (d) are the results of this invention.
The cross-sectional views shown in FIGS. 2(a) to 2(d) are diagrams for explaining the conventional manufacturing method. In the figure, 1 is an insulating substrate, 2 is a lower electrode, 3 is an amorphous silicon layer, 4 is an insulating film, 5 is a contact hole, 6h is a first upper electrode, 6b is an upper S electrode of part 2, and 7 is a photo/ It is raster. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A step of forming an amorphous silicon layer on the surface of an insulating substrate, a step of vapor depositing an electrode material on the surface of the amorphous silicon layer, forming a photoresist thereon and forming an electrode by photolithography, and a step of forming the electrode by photolithography. A method for manufacturing a semiconductor device, comprising the step of etching the amorphous silicon layer using the used photoresist.