JPH03227068A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a thin film transistor improved for not only manufacturing yield but also operating characteristics by a method wherein a gate electrode composed of a low resistive first gate metal and an anodized second gate metal is formed on an insulating substrate, and a gate insulating film, an I-type semiconductor layer, an N-type semiconductor layer, and a source and a drain electrode are formed thereon. CONSTITUTION:A low resistive conductive metal film is formed on an insulating substrate 11, the unused part is removed through etching to form a first gate metal 121, and a negative resist 18 is applied onto the whole surface, the rear of the substrate 11 is exposed to light to form a gap between the first gate metal 121 and the resist 18. Then, a tantalum film serving as a second gate metal 122 is formed on the whole face, the resist 18 and the tantalum film formed on the resist 18 are removed together, the surface of the second gate metal 122 is anodized to form an insulating layer 123. Then, a gate insulating film 13, an I-type semiconductor layer 14, and an N-type semiconductor layer 15 are formed in multilayer, and a source electrode 16 and a drain electrode 17 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film transistor and a method for manufacturing the same.

[Prior Art] Conventionally, there is an inverted stagger type thin film transistor as shown in FIG. This inverted stagger type thin film transistor has a gate electrode 2 formed on an insulating substrate 1 such as glass, and a silicon nitride (silicon nitride) (
A gate insulating film 3 made of SI N) is formed, and an n-type semiconductor layer 4 made of i-type amorphous silicon (ia-8i) is formed on this gate insulating film 3 to face the gate electrode 2. Furthermore, source/drain electrodes 6.7 are formed on this n-type semiconductor layer 4 via an n-type semiconductor layer 5 made of n-type amorphous silicon (n''-a-3t).

Incidentally, in such a thin film transistor, a conductive metal such as copper (Cu) or aluminum (A, #2) is used as the gate electrode 2 formed on the insulating substrate 1. For this reason, if a defect (binpole or cumic) occurs in the gate insulating film 3 covering the gate electrode, a short circuit will occur between the gate electrode 2 and the drain electrode b6 or between the gate electrode 2 and the source electrode 7, leading to the production of thin film transistors. This had the disadvantage of lowering the yield of the upper layer.

In order to solve this problem, a thin film transistor having the structure shown in FIG. 4 has been proposed. In other words, as the gate electrode 2, the surface of the gate metal 2a made of tantalum (Ta) is anodized to form tantalum oxide (Ta).
By using the insulating layer 2b of O),
This prevents a short circuit between the gate electrode 2 and the drain electrode 6 or between the gate electrode 2 and the source electrode 7, thereby preventing a decrease in yield in manufacturing thin film transistors.

[Problem to be solved by the invention] However, as the gate electrode 2, tantalum (Ta)
When using a gate metal 2a made of tantalum (Ta) whose surface is anodized to form an insulating layer 2b of tantalum oxide (TaO), the gate metal 2a made of tantalum (Ta2) is
This has the drawback of significantly deteriorating the operating characteristics of the thin film transistor because the electrical resistance at the thin film transistor increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thin film transistor that can improve the manufacturing yield and has excellent operating characteristics, and also to provide a method for manufacturing the same.

[Means for Solving the Problems] The thin film transistor of the present invention includes a first gate metal having low resistance on an insulating substrate, and a second gate metal formed on the first gate metal and at least anodized. A gate electrode made of a gate metal is formed, and a gate insulating film, an n-type semiconductor layer, an n-type semiconductor layer, and source/drain electrodes are formed on the gate electrode.

Further, the method for manufacturing a thin film transistor of the present invention includes forming a first gate metal made of a low-resistance conductive metal film on an insulating substrate, and forming a second gate metal on the first gate metal. a step of forming a gate electrode by anodizing at least the surface of the second gate metal to form an insulating layer, and then a gate insulating film, an n-type semiconductor layer,
This step consists of forming an n-type semiconductor layer and source/drain electrodes.

[Function] The thin film transistor of the present invention includes a gate electrode formed on a substrate, a first gate metal having low resistance, and a second gate formed on the first gate metal and having at least the surface anodized. Since it is made of metal, it is possible to prevent short circuits occurring between the gate electrode and the drain electrode or between the gate electrode and the source electrode by the insulating layer formed on the second gate metal by anodization. Furthermore, the electrical resistance of the gate electrode can be reduced by using the low-resistance first gate metal, resulting in excellent electrical characteristics.

Further, according to the method for manufacturing a thin film transistor of the present invention,
After forming a first gate metal with low resistance on an insulating substrate, a second gate metal is formed on the entire surface of the first gate metal, and at least the surface of the second gate metal is anodized to insulate it. Since the gate electrode is obtained by forming layers, short circuits occurring between the gate electrode and the drain electrode or between the gate electrode and the source electrode can be prevented, and the manufacturing yield can be improved.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of an inverted staggered thin film transistor of the same embodiment. In the figure, 11 is an insulating substrate made of glass or the like, and a gate electrode 12 is formed on this insulating substrate 11.

In this case, the gate electrode 12 is made of tantalum (Ta) on a first gate metal 121 made of a low resistance metal such as chromium (Cr), aluminum (CAD), or gold (Au).
) is formed, and this second gate metal 122 is formed of
The surface of the gate metal 122 is anodized to form an insulating layer 123 of tantalum oxide (Ta 2 O).

A gate insulating film 13 made of silicon nitride (StN) is formed to cover this gate electrode 12. Further, on this gate insulating film 13, i-type amorphous silicon (ia-
3i), and on top of this i-type semiconductor layer 14, an n-type amorphous silicon (n''-a
Source/drain electrodes 16 and 17 are formed via an n-type semiconductor layer 15 made of -3t).

FIG. 2 shows the method for manufacturing the thin film transistor in the order of steps.

First, as shown in FIG. 2(a), a low-resistance conductive metal film such as chromium (Cr) is formed on an insulating substrate 11 such as glass, and unnecessary parts are etched to form the first gate metal. 121 is formed.

Next, a negative resist 18 is applied to the entire surface of the substrate 11 and the first gate metal 121, and by exposure from the back surface of the substrate 11, the first gate metal 121 is coated as shown in FIG.
Remove part of the resist. In this case, a gap of about several hundreds is formed between the first gate metal 121 and the resist 18 by adjusting the exposure amount.

Next, as shown in FIG. 3(c), the first gate metal 121
Then, a film of tantalum (Ta), which will become the second gate metal 122, is formed on the entire surface of the resist 18.

Then, the resist 18 is removed as shown in FIG. 2(d). At this time, tantalum (Ta) on the resist 18 is also removed. Then, the surface of tantalum (Ta 2 ) forming the second gate metal 122 is anodized to form an insulating layer 123 of tantalum oxide (Ta 2 O).

After this, as shown in FIG. 2(e), silicon nitride (SIN) is deposited over the entire surface of the substrate 11 by plasma CVD or the like to form a gate insulating film 13, and then i-type amorphous silicon (i- a-3t), n
The i-type semiconductor layer 1 is formed by continuously depositing type amorphous silicon (n''-a-31) by plasma CVD or the like.
4 and an n-type semiconductor layer 15 are laminated, and metal films of source/drain electrodes 16 and 17 are formed on the n-type semiconductor layer 15. Then, the source/drain region, device area, etc. are etched to complete the thin film transistor.

Therefore, in the thin film transistor configured in this way, the gate electrode 12 formed on the insulating substrate 11 is made of chromium (Cr), aluminum (1), etc.
, a second gate metal 122 made of tantalum (Ta) is formed on a first gate metal 121 made of a low resistance metal such as gold (Au), and the second gate metal 122 is made of tantalum (Ta).
The surface of 2 is anodized to form tantalum oxide (TaO
), the insulating layer 123 obtained by anodizing the second gate metal 122 serves to connect the gate electrode 12 and the drain electrode 16 or the gate electrode 12 and the source electrode 17. It is possible to reliably prevent short circuits occurring between the two. Furthermore, since the electrical resistance of the gate electrode 12 can be reduced by the first gate metal 121 made of a low-resistance metal, a thin film transistor with excellent operating characteristics can be obtained.

Further, according to the method for manufacturing a thin film transistor described above, after forming the first gate metal 121 made of a low-resistance conductive metal film on the insulating substrate 11, the entire surface of the substrate 11 and the first gate metal 121 is coated. A negative resist 18 is applied and exposed from the back side of the substrate 11 to form the first gate metal 1.
21 portion of the resist is removed and a gap is formed between the first gate metal 121 and the resist 18, and then a second gate metal 122 is formed on the entire surface of the first gate metal 121 and the resist 18. And the above resist 1
8 and anodizing the surface of the second gate metal 122 to form an insulating layer 123. Short circuits occurring between the electrode 12 and the source electrode 17 can be prevented, and the manufacturing yield of thin film transistors can be improved. moreover,
A thin film transistor can be manufactured in which the electrical resistance of the gate electrode 12 can be reduced. Note that the thickness of the insulating layer 123 formed by anodic oxidation of the second gate electrode 122 is the same as that of the first gate electrode 121. The thickness may be sufficient as long as it can reliably prevent short-circuiting with the drain/source electrodes 16 and 17, and the entire thickness of the second gate electrode may be anodized. Further, the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist. For example, in the embodiments described above, an inverted stagger type thin film transistor was described, but the present invention can also be applied to an inverted cobraner type thin film transistor.

[Effects of the Invention] The thin film transistor of the present invention includes a first gate metal having low resistance on an insulating substrate and a second gate metal formed on the first gate metal and having at least the surface anodized. A gate electrode is formed, and a gate insulating film, an n-type semiconductor layer, an n-type semiconductor layer, and a source/drain electrode are formed on the gate electrode. Since the resistor is composed of a first gate metal and an anodized second gate metal formed on the first gate metal, insulation due to anodization formed on the second gate metal is The layer can reliably prevent short circuits occurring between the gate electrode and the drain electrode or between the gate electrode and the source electrode, and the low-resistance first gate metal can also reduce the electrical resistance at the gate electrode. A thin film transistor with excellent operating characteristics can be obtained.

Further, in the method for manufacturing a thin film transistor of the present invention, a first gate metal made of a low-resistance conductive metal film is formed on an insulating substrate, and a second gate metal is formed on the first gate metal. and forming a gate electrode by anodizing at least the surface of the second gate metal to form an insulating layer, and then forming a gate insulating film, an n-type semiconductor layer, an n-type semiconductor layer and a source layer. Since the drain electrode is formed, there is a gap between the gate electrode and the drain electrode.
Alternatively, it is possible to prevent leaks occurring between the gate electrode and the source electrode, and to improve the manufacturing yield.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the thin film transistor of the present invention, FIG. 2 is a view showing the manufacturing method of the same thin film transistor in order of steps, and FIGS. 3 and 4 are cross-sectional views showing a conventional thin film transistor, respectively. It is a diagram. 11... Substrate, 12... Gate electrode, 121...
First gate metal, 122...Second gate metal, 1
23... Insulating layer, 13... Gate insulating layer, 14...
・N-type semiconductor layer, 15...n-type semiconductor layer, 16...
source drain electrode.

Claims (2)

[Claims] (1) Consisting of an insulating substrate, a low-resistance first gate metal formed on this substrate, and a second gate metal whose at least the surface is anodized and formed on the first gate metal. A thin film transistor comprising a gate electrode, a gate insulating film, an i-type semiconductor layer, an n-type semiconductor layer, and source/drain electrodes formed on the gate electrode. (2) forming a first gate metal made of a low-resistance conductive metal film on an insulating substrate; forming a second gate metal on the first gate metal; A step of forming a gate electrode by anodizing at least the surface to form an insulating layer, and then forming a gate insulating film;
A method for manufacturing a thin film transistor, comprising the steps of forming an i-type semiconductor layer, an n-type semiconductor layer, and source/drain electrodes.