JPS5814575A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To obtain an insulating film at low temperatures not inferior to a thermally oxidized film by a method wherein source and drain electrodes patterns on a substrate are covered with a non-insulting thin film and the electrodes work as anodes in a process of anodizing the non-insulating film. CONSTITUTION:Patternd narrow line shaped electrodes 2 are formed on a substrate 1 by lift off and etching, which work as anode oxide electrodes as well as source and drain electrodes. Next, the entire surface including them is coated with a non-insulating thin film 3, and the electrodes function as anodes and opposite electrodes 4 provided on the rear side of the substrate as cathodes in an anodizing process. In this way, an oxide film 5 is created overlying a thin film 3, and the two films are subjected to patterning which the parts of the two films overlapping the electrodes survive. After this, a gate electrode 6 is attached to the remaining film 5 surviving as an gate insulating film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a gate insulating film at a low temperature, which influences the switching characteristics of a thin film transistor (TPT).

The structure of an insulated gate thin film transistor is a substrate, a semiconductor thin film, an insulating layer, and a conductive layer. In order to take advantage of the large area and low cost that characterize thin film transistors, it is conceivable to use glass or ceramics as the substrate, but in that case, processing at high temperatures becomes difficult.

Gate insulating films currently used in semiconductor technology include 5102 and A/03;
Thermal oxidation method is mainly used. Generally used thermal oxidation is difficult when temperature is restricted by the oxidizer or substrate. Other insulating film formation methods include PVD and CVD, but compared to thermal oxide films, these methods have disadvantages such as film uniformity, insulating properties, defects in the film, impurity density, interface state density, etc. Are you inferior? The present invention creates an insulating film comparable to a thermal oxide film at low temperatures.
The present invention provides a method of forming the film using anodic oxidation.

Conventionally, anodic oxidation was mainly applied to metals, and in semiconductor technology, it was used for good conductor films. However, in the present invention, by using a battened electrode, it can be applied to high resistance films. This method is also suitable as a method for manufacturing thin film transistors in terms of process and area because a uniform film can be formed and these electrodes are used as source and drain electrodes.

Possible methods for forming a semiconductor film on an insulating substrate include CVD using plasma and low pressure at low temperatures, PVD, etc.; However, in the present invention, as source and drain electrodes, battened electrodes, e.g., thin wire electrodes, are formed in advance on a substrate, and then a non-insulating thin film, e.g. A semiconductor film is formed, the above electrode is used as an anode, the semiconductor film is anodized in layers, the layered anodic oxide film is used as an insulating film, for example, a gate film, and the thin wire electrodes are used as source and drain electrodes. In addition, when using glass or ceramics as a substrate, an impurity trapping film is formed on the substrate in advance using silicon nitride or the like in order to prevent vibrations, and For example, the present invention also provides a method of manufacturing an anodized transistor by attaching a semiconductor film and forming source and drain electrodes in a switch/deutsch shape.

In this case, the impurity trap film is important for preventing adverse effects on the semiconductor film during anodic oxidation, improving the batting accuracy of the electrode to be battened, and improving the switching characteristics of the transistor. Furthermore, by forming the trap film described above, it is possible to use substrates and electrodes that have been difficult to use in the past, which is effective in improving the adaptability of anodic oxidation. In addition, in the manufacture of thin film transistors, which includes the process of anodizing non-insulating thin films, the i-patterned sources, drains, and electrodes are formed on the substrate.
□ After forming the electrode in advance, form a non-insulating thin film 5 and anodize the non-insulating thin film using the source and drain electrodes without forming a new anode.
It becomes possible to form a uniform and highly insulating film. Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a process diagram illustrating the manufacture of a thin film transistor according to an embodiment of the present invention.

FIG. 1(A) shows the process of forming thin wire electrodes on a substrate. The thin wire-like electrodes are formed by using lift-off, etching, etc., and 1 is a substrate, and 2 is a battened electrode, for example, a thin wire-like electrode. This thin wire electrode 2 is used as an anodic oxidation electrode, and also as a source and drain electrode.

In FIG. 1(B), a non-insulating thin film, for example, a semiconductor thin film 3 is formed on the thin wire electrode formed in FIG. 1(A), and sufficient contact between the semiconductor thin film 3 and the thin wire electrode 2 is made. By taking this and shortening the distance 20 between the electrodes, even if the semiconductor thin film 3 has a high resistance, the surface potential can be made uniform, and as shown in FIG. An oxide film 5 is formed.

Anodic oxidation can be performed in either liquid phase or gas phase, and in particular, the gas phase method using oxygen plasma has a low conductance in the gas phase, so it is possible to obtain a uniform and high-quality oxide film even on high-resistance materials. . 4 is a counter electrode during anodic oxidation, and 5 is an oxide film formed by anodic oxidation. Figure 1<
D > +i, the semiconductor thin film 3 formed in FIG. 1(B) and the oxide film 5 formed in FIG. 1(C) are buttered, and the thin wire-shaped electrode 2 in FIG. 1(A) is The oxide film 5 is used as a drain electrode, and a gate electrode 6 is attached on the oxide film 5 to form an insulated gate thin film transistor.

FIG. 2 shows a case where a step including forming an impurity trap film 11 of silicon nitride or the like is added between the substrate and the thin wire electrode 21 in order to prevent impurity diffusion into the substrate 10. FIG. 2 (A-1) shows a step of forming the impurity trap layer 11 in advance. The other steps are the same as in the case of FIG. 1, and in this case, as shown in FIG. 2(C), the thin wire electrode 21 has a sandwich structure of the impurity trap film 11 and the semiconductor film 31. ing. Although the process shown here does not involve doping, it is possible to include a doping process, and the impurity trap of the sandwich structure shown in FIG. It also includes membranes. Note that 41 is a counter electrode for anodic oxidation, 51 is an oxide film, and 61 is a gate electrode.

FIG. 3 is an explanatory diagram showing an outline of the anodic oxidation device in question. 30 is an insulating material used to reduce fluctuations in voltage due to the rise and fall of the electrolytic solution 35 and form a uniform film; 34 is a non-insulating film to be anodized; 66
is a battened electrode that doubles as a source and drain, and is used as an anode. 32 is a substrate, 66 is
It is a cathode. 37 is a power source.

As is clear from the above process examples, the present invention does not involve forming a new electrode for use in anodic oxidation. The use of this method simplifies the process and allows the formation of a uniform insulating film, as well as the formation of source and drain electrodes at the same time.

In addition, semi-insulating films can also be anodized, making it possible to form uniform and high-quality films at low temperatures, which is effective in taking advantage of the advantages of TPT.

The present invention particularly focuses on TP on display panel substrates using liquid crystal etc.
This technology is effective for T, and is particularly suitable as a display device for small portable devices such as wristwatches.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for manufacturing a thin film transistor according to the present invention. FIG. 2 is a process diagram showing another manufacturing process for a thin film transistor according to the present invention. FIG. 3 is an explanatory diagram showing an outline of the anodizing device. 1.10.62... Substrate, 2.21... Parallelized source, drain electrode, 6.31... 4# semiconductor Film, 4.36.41... Counter electrode during anodic oxidation, 5.51... Oxide film (gate isolation RM),
6.61... Gate electrode, 11... Impurity trap film, 65... Electrolyte, 36... Cathode. Figure 1 [ (B)

-7\C( (D)

-\-1~10 4-2-2 □ Figure 3 35'

Claims (1)

[Claims] (+) A step of forming a patterned source/drain/electrode on a substrate, a step of forming a non-insulating thin film on the electrode, and a step of forming a patterned source/drain electrode. A step of anodic oxidizing the non-insulating thin film using as an anode.
A method for manufacturing a thin film transistor, characterized in that: (2) forming and forming an impurity trap film on the substrate;
forming a patterned source/drain/electrode on the impurity layer; forming a non-insulating thin film on the electrode; using the patterned source/drain electrode as an anode; 1. A method for manufacturing a thin film transistor, comprising the step of anodizing a thin film.