JPS6194366A - Thin-film transistor - Google Patents

Abstract

PURPOSE:To equalize the quality of a semiconductor thin-film formed onto a source electrode and a drain electrode by burying these electrodes into recessed sections shaped to an insulating substrate. CONSTITUTION:A source electrode 12 and a drain electrode 13 are buried in recessed sections 11 formed to an insulating substrate 10. Impurity-doped amorphous Si films 14 are each shaped onto the electrodes 12, 13, and there is not stepped section between the surfaces of the films 14 and the surface of the substrate 10 and both surfaces are smoothed. A semiconductor thin-film 15 is formed extending over the electrode 12 and the electrode 13 on the substrate 10. An insulating film 16 is shaped so as to coat the film 15, and a gate electrode 17 is formed onto the film 16. Accordingly, the film 15 is deposited under the state in which a stepped section is hardly formed in the surface of the substrate 10, thus generating no unevenness due to the positions in the film 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thin film transistor using a semiconductor thin film such as amorphous silicon.

[Technical background of the invention]

In recent years, advances in thin film formation technology have made it possible to obtain high quality amorphous semiconductor thin films, and thin film transistors have been attracting attention. For example, a large number of thin film transistors are formed in a matrix on a transparent substrate and used in an active matrix type liquid crystal display device.

FIG. 4 is a diagram showing an example of a conventional thin film transistor, in which a source electrode (2) and a drain electrode (3) are formed on a glass substrate (1), and these two electrodes (2), (3)
An impurity-doped amorphous silicon film (4) is further formed thereon. An undoped amorphous silicon film (5) is formed to cover the two electrodes (2) and (3).

Here, the impurity-doped amorphous silicon film (4) is connected to this undoped amorphous silicon film (5) and the two electrodes (2).

(3) It has the function of improving contact with.

Then, an insulating film (6) such as silicon oxide or silicon nitride is formed to cover the undoped amorphous silicon (5), and a gate-1 pole (7) is further formed on the insulating film (6). There is.

[Problems in the Background Art] However, in this thin film transistor, the film quality of the formed undoped amorphous silicon film (5) is different between the step portions of the source electrode (2) and the drain electrode (3) and the other portions. It may be different. This may result in poor characteristics of thin film transistors or undoped amorphous silicon films (
During selective etching (5), non-uniform etching may occur, making it difficult to obtain a predetermined shape.

[Purpose of the invention]

The present invention has been made to solve these conventional drawbacks, and an object of the present invention is to provide a thin film transistor in which the quality of the formed semiconductor thin film can be made uniform.

[Summary of the invention]

That is, the present invention provides an insulating substrate having a plurality of recesses, a source electrode and a drain electrode buried in the recesses, a semiconductor thin film formed over the source electrode and the drain electrode, and an insulating film formed on the semiconductor thin film. This is a thin film transistor characterized by comprising a gate electrode formed on an insulating film and a gate electrode formed on an insulating film, and the level difference on the surface underlying the semiconductor thin film is reduced compared to the conventional one.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, in which an insulating substrate a1
For example, in a plurality of recesses (11) provided in a glass substrate, source electrodes (12 and drain electrodes αy, for example, ITO
is buried. Furthermore, these two electrodes (1 shi.

(A phosphorus-doped impurity-doped amorphous silicon film (14) is formed on each of the 13, and the surface of the impurity-doped amorphous silicon film I and the surface of the insulating substrate part are smooth without any step. A semiconductor thin film α9, for example, an undoped amorphous silicon film, is formed on the insulating substrate αQ over the source electrode f13 and the drain electrode 03. Here, an impurity-doped amorphous silicon film N(14) is formed.
is this semiconductor thin film (one and two electrodes ([2, (13
It has the function of improving contact with people. Then, an insulating film [9, for example, silicon oxide or silicon nitride] is formed to cover the semiconductor thin film a9, and an insulating film C10 is formed to cover the semiconductor thin film a9.
A gate TX pole αη, for example aluminum, is formed thereon.

Next, the manufacturing method of this example will be described. FIG. 2 is a diagram showing an example of this. First, as shown in FIG. 2 (al), after forming a resist pattern (IQ) on an insulating substrate (1G), using this as a mask, the surface of the insulating substrate (10) is etched by 200 OA to form a recess (1Dt-).

Next, as shown in FIG. 2 (bl), a film (11 and an impurity-doped amorphous film) which is the material of the source electrode and drain electrode (13) is coated on the entire surface of the insulating substrate part with the resist notch remaining. silicon film α4 and 150 μm each in this order.
It is formed to a thickness of 0λ and 500λ. And Figure 2 (cl.
As shown in FIG. 1, two films on the insulating substrate part are removed by removing the resist pattern.

(Remove 1'l and fill in the recess (11) with the source electrode, drain electrode 03, and impurity-doped amorphous silicon film.Next, as shown in FIG. 2(d), , a semiconductor thin film (Is is deposited to a thickness of 3000λ and then etched in a predetermined number of turns).
) As shown in the diagram, after depositing the insulating film and the film that will become the material for the gate electrode αη in this order to a thickness of 4000λ and 1 μm, the upper film is etched into a predetermined pattern to form the gate electrode ( 1'l) is formed. In this way, a desired thin film transistor is obtained.

FIG. 3 is a diagram showing another example of the manufacturing method of this embodiment. First, as shown in FIG. 3(a), the surface of the insulating substrate Q is etched by 4'000λ to form a recess αυ. Next, as shown in FIG. 3 (bl-), the film layer 9 and the impurity-doped amorphous silicon film I, which are the materials of the source electrode U and the drain electrode α3, are each coated in this order with a thickness of 1500χ.
After forming it to a thickness of 3500λ, smoothing it by applying a smoothing material (a) such as polyimide or photoresist,
The thickness of the smooth material on the recess (Ll) is about 1.5 μm. Then, as shown in Fig. 3 (C), all of them were etched by the ILIB method under conditions set so that the etching rates of the smoothing plate, the film (14, α1, and the insulating substrate α■) were all the same. Next, as shown in Fig. 3(d), the semiconductor thin film (L5 is etched by 3
After the film is deposited to a thickness of 000λ, it is etched into a predetermined pattern. Then, as shown in FIG. 3(e), the insulating film and the film that is the material of the gate electrode
After being deposited to a thickness of 0001.1 μm, the upper film is etched into a predetermined pattern to form a gate electrode (I7). In this way, a desired thin film transistor is obtained.

As mentioned above, in this embodiment, the source 'tN pole (
121 and the drain electrode α3 are buried in the recess αυ of the insulating substrate (II), and the semiconductor thin film α9 is deposited on the surface of the insulating substrate (II) with almost no steps. Because non-uniformity in film quality does not occur during selective etching of the semiconductor thin film (lE9), a predetermined shape can be easily obtained.Also, there is non-uniform film quality in the conductive part of the thin film transistor. Therefore, a thin film transistor with good characteristics can be obtained.

〔Effect of the invention〕

As explained above, in the thin film transistor of the present invention, the source electrode and the drain electrode are embedded in a recess provided in an insulating substrate, so there are fewer steps on the insulating substrate when forming a semiconductor thin film than in the past.

Therefore, semiconductor thin films can be formed with uniform film quality,
Its characteristics are good.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, FIGS. 2 and 3 show an example of the manufacturing method of the invention, and FIG. 4 shows an example of a conventional thin film transistor. ■・Insulating substrate (11)・Concave part・Source electrode (13 Drain・Semiconductor thin film
Housing e... Insulating film housing η... Gate electrode agent Patent attorney Nori Chika Kensuke (and 1 other person) Figure 2 (a>
tt Jino (C)
<d) (entti rl Fig. 3 (rL) Lδ] tc) td) (e) Fig. 4

Claims (1)

[Claims] an insulating substrate provided with a plurality of recesses, a source electrode and a drain electrode buried in the recesses, a semiconductor thin film formed across the source electrode and the drain electrode, and an insulating film formed on the semiconductor thin film. , and a gate electrode formed on the insulating film.