JPS61131481A - Thin film transistor - Google Patents

Abstract

PURPOSE:To dispose electrodes in a high density by disposing gate electrodes opposed to source/drain electrodes through a semiconductor layer, and disposing to surround one of source and drain electrodes with the other, thereby reducing the length of an element. CONSTITUTION:A gate electrode 12 is disposed to oppose to a source electrode 15 and a drain electrode 16 through a semiconductor layer 14, and an arcuately formed source electrode 15 is disposed to surround the drain electrode 16 formed in an arcuated shape smaller in radius than that of the electrode 15 on the same flat surface. Since such a construction is formed, a thin film transistor having 10mum channel length and 5mm channel width capable of obtaining 100muA of source and drain current is contained in a diameter of approx. 1.9mm, and can be reduced in length to approx. 1/3 of the thin film transistor necessary for the length of approx. 5.1mm in the direction of channel width in the channel length to heretofore obtain the same source and drain current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film transistor (TPT).

[Conventional technology]

Conventional thin film transistors of this type each have substantially rectangular gate electrodes, source electrodes, and drain electrodes arranged in parallel. In such conventional thin film transistors, a method is adopted to increase or decrease the source-drain current by increasing or decreasing the channel width, that is, the lengths of the gate electrode, source electrode, and drain electrode. Channel width 500t
The source-drain current of a typical thin film transistor with m is about 10 μA. Therefore, if a large source-drain current of 100 μA is required, the channel width should be approximately 5.5 μA. It ends up being as long as lWn.

On the other hand, in a field effect transistor using a crystalline material as a substrate, in order to increase the soustrain current, devises have been made such as making the electrodes comb-shaped or vertically wave-shaped. (Reference unknown) [Problem to be solved by the invention] As mentioned above, in order to obtain a source-drain current of 100 μA, the channel length must be set to 10. Toshimata case.

The channel width is approximately 5. IN becomes very long.

When the channel width or channel length increases in one direction as described above, there arises a problem that the margin for element design becomes narrower and the applications are also narrowly limited.

In addition, in field effect transistors using crystalline materials as substrates, in which the electrodes are designed to have a comb shape or a straight wave shape, the three electrodes are on the same plane (coplanar type). (i) Electrodes cannot be arranged in high density.

(...) Current microfabrication techniques have the problem that the distance between the electrodes cannot be made sufficiently small, and the distance between the electrodes becomes large, making it impossible to use a semiconductor thin film with low carrier mobility.

[Means for solving problems]

In order to solve the problems of the prior art described above, the thin film transistor of the present invention has a gate electrode arranged to face a source electrode and a drain electrode with a semiconductor layer interposed therebetween, and one of the source electrode and the drain electrode. One electrode surrounds the other on almost the same plane.
It is arranged so that Alternatively, the source electrode and the drain electrode may have multiple branches. With such a configuration, the present invention can be used without increasing the channel width or channel length (that is, the length of the electrode) in one direction.
This effectively utilizes the substrate area and achieves high density.

〔Example〕

Example 1 FIG. 1(5k) is a plan view of a thin film transistor according to an example of the present invention, and FIG. 1(b) is a sectional view taken along line CD in FIG. 1(a). The thin film transistors shown in these figures were fabricated.

That is, first, a Cr electrode (gate electrode) 12 was formed on a glass substrate 11 in vacuum by electron beam evaporation.

Next, a silicon nitride layer (gate insulating layer) 13 having a film thickness of 0.3 mm was formed thereon by plasma CVD. The reaction gas used at this time was a mixed gas of SiH, NH, and N2 (pressure 0.5 to I Torr).

Furthermore, an amorphous hydrogenated silicon layer (semiconductor layer) 14 having a film thickness of 0.3#II was formed thereon by plasma CVD. The reaction gas used at this time was SiH.

and H2 (pressure 0.5 to I Torr).

In this embodiment, amorphous hydrogenated silicon containing silicon and hydrogen as the main component was used as the semiconductor layer 14. A film containing carbon, nitrogen, oxygen, etc. can be used. Of course, it is not limited to this.

On the final song, Cr electrodes (source electrode 15 and drain electrode 16) were formed by electron beam evaporation. Note that the channel length is 10. , the channel width was 5 mm.

The thin film transistor of this example is as shown in Figure 1.

The gate electrode 12 connects to the source electrode 15 via the semiconductor layer 14.
and are arranged facing the drain electrode 16,
A source electrode 15 formed in an arc shape is arranged so as to surround a drain electrode 16, which is also formed in an arc shape with a smaller radius, on the same plane.

With this configuration, a thin film transistor with a channel length of 10 mm and a channel width of 5 mm, which can obtain a source-drain current of 100 μA, can be housed within a diameter of approximately 1.9 mm, which is different from conventional Compared to a thin film transistor which requires a length of about 5.1 mm in the channel width direction for the same channel length to obtain the same source-drain current, the length can be reduced to about 173 mm. Furthermore, a gate electrode 12, a source electrode 15. Since the drain electrodes 16 are all formed in a linear shape as shown, current leakage and short circuit can be prevented.

Embodiment 2' FIG. 2(a) is a plan view of a thin film transistor according to another embodiment of the present invention, and 21m(b) is a sectional view taken along line EF in FIG. 2(a). A *mh transistor as shown in the figure was produced in the same manner as in Example 1.

In the thin film transistor of this embodiment, the gate electrode (Cr electrode) 22 is arranged to face the source electrode 25 and the drain electrode 26 (C: rfft pole) via the semiconductor layer 24, and the source electrode 25 is on the same plane. It is arranged so as to surround the drain electrode 26 on the top. Furthermore, in this embodiment, the source electrode 25 and the drain electrode 26 each have a plurality of branches.

Note that the film thicknesses of the gate insulating layer (silicon nitride layer) 23 and the semiconductor layer (amorphous hydrogenated silicon layer) 24 are both 0.
3. and the channel length is 110l1. Channel width is 5■
And so. With this configuration, 100μ
A thin film transistor with a channel length of 10 and a channel width of 5, which can obtain a source-drain current of A, can be housed within a square of 1.2+n in length and width. Compared to the required length of 5.1 m, the length could be reduced to approximately 174 m.

In this way, in this example, by dividing the electrode into a plurality of branches, the effective area relative to the substrate can be made larger than in Example 1, and a larger source-drain current can be obtained. moreover.

Gate electrode 22, source electrode 25. The drain electrodes 26 are all formed in a linear shape as shown in the figure.

Current leakage and short circuits can be prevented.

As described above, in the thin film transistor of Example 1.2, a large source-drain current could be extracted without increasing the channel width or channel length in one direction as in the conventional case.

Further, since the gate electrode is arranged to face the source electrode and the drain electrode with the semiconductor layer in between, the distance between the electrodes can be reduced, and the electrodes can be arranged at high density.

Note that the present invention is not limited to the above embodiments,
It goes without saying that there may be various modifications such as the shape of the electrode within the scope of the claims. stomach,.

Further, although the above embodiment shows a thin film transistor having a gate insulating layer, it may also be applied to a Schottky type thin film transistor having no gate insulating layer. The structure shown above has a gate insulating layer on top, a semiconductor layer on top of that, and a source-drain electrode on top of that in order, but the source-drain electrodes are on top of the substrate! The present invention may be applied to a thin film transistor in which a pole, a semiconductor layer thereon, a gate insulating film thereon, and a gate electrode thereon are sequentially stacked;
The gate electrode and the source-drain electrode may be overlapped with each other with a semiconductor layer interposed therebetween, and in this case, the electrodes can be arranged with even higher density.

C. Effects of the Invention] As explained above, the present invention provides a structure in which the gate electrode is arranged so as to face the source-drain electrode through the semiconductor layer, and one of the source electrode and the drain electrode surrounds the other. By arranging the electrodes, the length of the element can be reduced and the electrodes can be arranged with high density. therefore,
This has the effect of increasing the margin of element design and expanding the range of applications.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a thin film transistor according to an embodiment of the present invention, FIG. 1(b) is a sectional view of 07, D in FIG. 1(a),
FIG. 2(a) shows another embodiment of the present invention. Thin film transistor flat fa11. Figure 2(b) shows the second
It is EF sectional drawing of figure (a).

Claims (3)

[Claims] (1) In a thin film transistor including at least a substrate, a source electrode, a gate electrode, a drain electrode, and a semiconductor layer, the gate electrode is arranged to face the source electrode and the drain electrode with the semiconductor layer interposed therebetween, and the source electrode and a drain electrode, one of which is arranged so as to surround the other electrode on substantially the same plane. (2) The thin film transistor according to claim 1, wherein at least one of the source electrode and the drain electrode is divided into a plurality of branches. (3) The semiconductor layer according to claim 1, wherein the semiconductor layer has at least one of silicon or germanium as a main component and contains at least one of hydrogen, fluorine, chlorine, carbon, nitrogen, and oxygen. Thin film transistor.