JPH02249272A - Semiconductor device - Google Patents

Abstract

PURPOSE:To achieve junction between a semiconductor and an electrode provided with good reproducibility and stability by constituting a semiconductor including a semiconductor material which contain silicon as a constituent and an electrode material consisting of a mixture of a metal oxide and a tin oxide and by allowing the amount contained within the electrode material to exceed a specific value. CONSTITUTION:The title item is a semiconductor device which includes a semiconductor material containing silicon as a constituent and an electrode material consisting of a mixture of a metal oxide and a tin oxide as constituting units, where the amount of contained thin oxide of the above electrode material exceeds 10%. For example, a gate electrode 31 is formed on a light-transmissive substrate 30. Then, after forming a gate insulating layer 32, a-Si 33, and a passivation layer 34, the passivation layer 34 is eliminated excluding one part on the gate electrode 31. Then, after the n<+> a-Si 35 is formed and the n<+> a-Si 35 and a-Si 33 are etching-eliminated, a transparent electrode 36 consisting of a tin oxide and indium oxide exceeding 10% as the source/drain electrode is formed, n<+> a-Si 35 on the gate electrode 31 is etched and eliminated for completing a LCD device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to thin film transistors, diode elements, or photoelectric conversion elements used in liquid crystal display devices or image sensors.

Conventional technology In recent years, thin film transistors (hereinafter abbreviated as TPT) have been developed on substrates with the aim of applying them to liquid crystal display devices and image sensors.
There is active development of semiconductor devices that form semiconductors, diodes, etc. An example of the structure of such a semiconductor device will be described with reference to FIG. 4 in the case of a liquid crystal display device. 1 is a TFT formed on a transparent substrate (not shown) whose constituent elements are polycrystalline silicon or amorphous silicon; 2 is a TFT;
This is a liquid crystal display in which liquid crystal is injected between a transparent electrode electrically connected to the drain of 1 and a transparent counter electrode on a transparent substrate forming a color filter.
are arranged at positions corresponding to each pixel in the video display area 3, and in addition to the capacitance caused by the liquid crystal, a capacitance formed on the active matrix substrate may be added as an auxiliary capacitance.

4 is the gate wiring connected to the gate electrode of TFTI, 5
is a source wiring connected to the source electrode of TFTl.

The structure of TPT, which is one component of the liquid crystal display device as described above, will be explained below with reference to FIG.

FIG. 5a is a plan view of a TPT having an inverted staggered structure, and FIG. 5a is a sectional view taken along line A-8 of the TPT.

6 is a glass substrate which is a transparent substrate, and 7 is a gate electrode. 8.9 and 10 are a gate insulator layer, a semiconductor layer, and a badge Basilon layer, respectively. 11 and 12 are a drain electrode and a source electrode, respectively.

Reference numeral 13 denotes an n-semiconductor layer for making ohmic contact with the semiconductor layer 9 and the source/drain electrodes 12 and 11.

Reference numeral 14 denotes a transparent electrode commonly connected to the drain electrode and the source electrode 11, and serves as a picture element electrode for applying voltage to the liquid crystal layer.

Problems to be Solved by the Invention In order to manufacture the thin film transistor of the liquid crystal display device as described above, a photolithography process is required at least eight times. Manufacturing thin film transistors for liquid crystal display devices requires microfabrication, so exposure machines and ancillary equipment that have the same level of performance as those used in semiconductor processes are used. Therefore, the more times the photolithography process is performed, the higher the cost of the display device will be. Furthermore, the greater the number of photolithography steps, the lower the yield.

As one means to solve the above-mentioned cost increases and yield decreases, it has been proposed to simultaneously form source/drain electrodes and picture element electrodes using the same material (Japanese Patent Application No. 83-97008). reference).

However, there were problems with the reproducibility and thermal stability of the device.

Means for Solving the Problems A semiconductor device is constructed which includes, as its constituent units, a semiconductor material containing silicon as a component and an electrode material composed of a mixture of a metal oxide and tin oxide, and the tin oxide content of the electrode material is 10% or more.

Effect By using the above configuration and changing the mixing ratio of metal oxides depending on the Fermi level of the semiconductor, it is possible to obtain a reproducible and stable bond between the semiconductor and the electrode, which reduces the cost of the semiconductor device. This greatly contributes to increased production and higher yields.

Example The present invention will be described in detail below with reference to the drawings.

Embodiment 1 FIG. 1 is a step-by-step diagram showing a liquid crystal display device which is one embodiment of a semiconductor device according to the present invention.

Cr+ Ta+ TL Mo on the transparent substrate 30
A thin film of +N L N i Cr or silicide of these metals is formed by sputtering, and a desired pattern is applied to form the gate electrode 31 (FIG. 1a).

A gate insulating layer 32, an amorphous silicon layer (a-8i) 33, and a badge Basilon layer 34 are formed by plasma CVD or the like.
After forming, the badge Basilon layer 34 is removed except for a portion on the gate electrode 31 (FIG. 1b). Next, P-doped amorphous silicon (n+a-8
1) Form 35, except for a part n+a-8i35 and a
-8i33 is etched away (Figure 1C). Transparent electrodes 36 made of a mixture of tin oxide and metal oxide are formed as source and drain electrodes, and the P-doped amorphous silicon layer 35 on the gate electrode 31 is etched and removed (FIG. 1d). , a liquid crystal display device is completed. here,
The transparent electrode 36 is a mixture of metal oxides, n+a-
Its composition is changed depending on the Fermi level Ef of 8i35.

To give a concrete numerical value, when the amount of P doping is small and the activation energy value is about 0.8 eV, 10
% of tin oxide and indium oxide, the work function of the transparent electrode is 4.8 eV and good ohmic contact can be achieved (Fig. 2a). On the other hand, the amount of P doped is very large, and the activation energy value is When is around 0.3 eV, tin oxide with no intentionally added impurities is used. In this way, the work function of the transparent electrode becomes 4.2 eV, and good ohmic contact can be achieved in this case as well (Fig. 2b).
). Even if the P doping amount is arbitrary, the activation energy value will vary from around 0.3 eV to 0.3 eV. Since it is an intermediate value of around 8eV, the amount of metal oxide mixed with tin oxide is controlled,
Good ohmic contact can be obtained by changing the work function of the transparent electrode. In this embodiment, amorphous silicon doped with P and a transparent electrode are described, but the same effect can be obtained even if single crystal or polycrystalline silicon and a transparent electrode are used. Alternatively, the transparent electrode may be formed in two layers. For example, the junction with the semiconductor layer may be made of a metal oxide containing 10% or more of tin oxide, and a metal oxide of a different composition may be laminated thereon.

Embodiment 2 FIG. 3 shows an image sensor which is another embodiment of the semiconductor device according to the present invention.

On the transparent substrate 41, Crl Ta, T i+
M 01NL A thin film of NiCr or silicide of these metals is formed by sputtering and subjected to desired patterning to form the gate electrode 42a of the thin film transistor and one electrode 42b of the photoelectric conversion element (Fig. 3a).
). Silicon nitride 43, amorphous silicon 44, and amorphous silicon 45 doped with P by plasma CVD method
After forming a part of the silicon nitride 43 on the transparent substrate 41
, the amorphous silicon 44 and the P-doped amorphous silicon 45 are removed by etching to form a light introduction port 4B (third
Figure b). A mixture of metal oxides is formed by sputtering and buttered to form the other electrode 47 of the photoelectric conversion element (FIG. 3C). Here, as for the mixture of metal oxides, the mixture ratio of tin oxide and other metal oxides may be determined to match the Fermi level of P-doped amorphous silicon, as in Example 1. Next, by sputtering method, A L Mos Crl T
After forming 11 Tas N + and silicides of these metals and performing desired patterning to form the source electrode 48a and drain electrode 48b of the thin film transistor,
The P-doped amorphous silicon 45 and a portion of the amorphous silicon in the portions not covered by the source/drain electrodes are removed (FIG. 3d). In this way, one unit of an image sensor is formed, so if they are arranged one-dimensionally, they become a -dimensional image sensor, and if they are formed two-dimensionally, they become a two-dimensional image sensor.

In this embodiment, the photoelectric conversion material and the material for forming the thin film transistor are the same and are formed at the same time, but they may be formed using different materials. For example, a silicon oxide film or an aluminum oxide film 1 is used as a gate insulating film in a thin film transistor.
．． Tantalum oxide film, polycrystalline silicon film as semiconductor layer,
A recrystallized silicon film, cadmium selenide, or the like may also be used. In addition, photoelectric conversion materials include films mainly composed of amorphous selenium, films mainly composed of cadmium sulfide, films mainly composed of lead oxide or lead sulfide, and solid solutions of cadmium telluride and zinc telluride. A film or the like may also be used.

In addition, although a thin film transistor is used in the optical signal reading circuit in this embodiment, other signal charge reading means,
For example, a charge transfer element such as a COD may be used in part.

Effects of the Invention According to the present invention, ohmic contact between a semiconductor and an electrode in a liquid crystal display device or an image sensor can be stably produced with good reproducibility, and yields can be improved and costs reduced. Therefore, its industrial significance is extremely high.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing one embodiment of the method for manufacturing a semiconductor device of the present invention, FIG. 2 is an energy band diagram of a semiconductor and a transparent electrode for explaining the present invention, and FIG. 4 is a circuit diagram of a liquid crystal display device, which is one of the semiconductor devices, and FIGS. 5a and 5b are a plan view and a cross-sectional view, respectively, of a thin film transistor constituting the liquid crystal display device. . 30... Transparent substrate, 31... Gate metal, 3
2... Gate insulating film, 33... Amorphous silicon layer, 35... P-doped amorphous silicon layer, 3
B...Transparent electrode. Name of agent: Patent attorney Shigetaka Awano and one other person? t”(2
Ji

Claims (7)

[Claims] (1) A semiconductor device comprising, as its constituent units, a semiconductor material comprising silicon as a component and an electrode material comprising a mixture of a metal oxide and tin oxide, wherein the tin oxide content of the electrode material is 10% or more. A semiconductor device characterized by: (2) In a semiconductor device in which a plurality of thin film transistors are formed on a light-transmitting substrate, each consisting of a gate electrode, a dielectric layer, a semiconductor layer, and a source/drain electrode, the source/drain electrodes are made of metal oxide and tin oxide. A semiconductor device, wherein the electrode material has a tin oxide content of 10% or more. (3) The semiconductor device according to claim 1 or 2, characterized in that the metal oxide includes indium oxide. (4) In a semiconductor device having a first electrode on a substrate, a semiconductor layer, and a second electrode as constituent elements, the second electrode is made of an electrode material made of a mixture of metal oxide and tin oxide, and the A semiconductor device characterized in that a material has a tin oxide content of 10% or more. (5) The semiconductor device according to claim 4, wherein a scanning circuit element is formed on the substrate. (6) The semiconductor device according to claim 4 or 5, wherein the semiconductor layer is composed of a plurality of thin film layers including an n-type semiconductor layer, and the n-type semiconductor layer has electrical contact with the second electrode. (7) The semiconductor device according to claim 1, wherein the electrode is composed of two or more layers of materials having different compositions.