JPS62216372A - A-si thin film transistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] In a top-gate staggered a-3i thin film transistor, the concave portion between the source electrode and the drain electrode is filled with an inorganic thin film, and the gap between the source electrode and the drain electrode and the substrate is By eliminating the step difference and planarizing the a-Si active layer formed thereon, breakage of the a-3i active layer is prevented.

[Industrial application field]

Field-effect transistors using an a-Si (amorphous silicon) active layer include a top-gate staggered type that has a source electrode and a drain electrode on the insulating substrate side, and a top-gate staggered type that has a data electrode on the insulating substrate side. , there is an inverted staggered type that has a source electrode and a drain electrode at the top. The present invention relates to the former top gate staggered A-3IL film transistor.

[Conventional technology]

FIG. 3 is a diagram showing a cross-sectional structure of a conventional top-gate staggered a-Si thin film transistor.

Reference numeral 1 denotes an insulating substrate, on which a source electrode S and a drain electrode are formed with a thickness of about 1,000 at intervals, and ohmic contact layers 2s and 2d are formed on both electrodes.
There are about 300 to 500 people stacked up. Then, a zero-thickness insulating film 4 of about 1,000 to 1,500 people was formed to form an active N3 layer made of a-Si by about 1,000 people, and finally a gate electrode G was formed.

[Problem that the invention seeks to solve]

However, in such a cross-sectional structure, the total thickness of the source/drain electrode and the ohmic contact layer is 1300~1.
500, and the difference in level between the insulating substrate 1 and the insulating substrate 1 becomes large, so that the a-3t active layer 2 and the gate insulating film 3 formed thereon also have a step part.

As a result, the a-3i active layer 3 has cracks in the stepped portion and plenum formation, resulting in poor stability of properties.

The technical problem of the present invention is to solve such problems in the conventional a-3i FI film transistor.
The purpose is to create a structure in which no step occurs in the i-active layer 3.

[Means for solving problems]

FIG. 1 is a sectional view illustrating the basic principle of an A-3IL film transistor according to the present invention. A source electrode S and a drain electrode are formed on the insulating substrate 1.
, D has a structure in which an inorganic thin film 5 is buried in the recess. Then, an a-3i active layer 3 and a gate insulating film 4 are laminated in this order on these, and a gate G is formed thereon. Note that when an ohmic contact layer is provided on the source electrode S and the drain electrode, the surfaces of the ohmic contact layer and the inorganic thin film 5 are made to be at the same height.

[Effect]

In this way, the recess between the source electrode S and the drain electrode is filled with the inorganic thin film 5, and the lower surface of the a-3i active layer 3 is planarized, so that there is no step difference in the a-3i active layer 3 and the gate insulating film 4. does not occur. Therefore, a-3i active layer 3
There is no risk of cracks or plenums occurring, resulting in stable characteristics and improved reliability.

〔Example〕

Next, how the a-3i FI film transistor according to the present invention is actually implemented will be explained using examples.

FIG. 2 is a cross-sectional view showing an embodiment of an A-3IL film transistor according to the present invention and a method of manufacturing the device of the embodiment in the order of steps. In this embodiment, as shown in (f), an inorganic thin film 5 is provided between a source electrode S and a drain electrode on an insulating substrate 1, and an ohmink contact layer is formed on the source and drain electrodes S and D. 2s.

The surface 2d and the surface of the inorganic thin film 5 are arranged on the same plane. On the thus planarized surface, an a-3i active layer 3 and a gate insulating film 4 are formed in this order, and a gate G is formed at the top.

In this device, with the drain voltage constant,
When the gate voltage is changed, the drain current exhibits a characteristic in which the drain current increases rapidly at a certain point as the gate voltage increases, providing a switching function. Note that the drain current flows through the path of source electrode S-ohmic contact layer 2s-a-3i active layer 3-ohmic contact layer 2d-drain electrode.

Next, the manufacturing method of this example device will be explained step by step. First, like fat, an inorganic thin film 5a is formed on the entire surface of the insulating substrate 1 using a glow discharge decomposition method or the like. This nothingness 8! As the thin film 5a, a-3ts S+0□, SiN
, SiC, a-C, etc. are suitable. Next, as shown in (bl), a resist mask 6 with an inverted shape of the source/drain electrodes S and D is formed, and the inorganic thin film on the source electrode S and drain electrode portion is removed by etching.
form. Then (as in C1, resist mask 6
From above, sources such as TI% old Cr, Cr, AI, etc.
A drain electrode material is vacuum deposited, and then an ohmic contact layer 2 is formed by a glow discharge decomposition method such as n+a-3i. And by removing the resist mask 6,
The excess portion is lifted off and planarized as shown in (dl). Then, the a-Si active layer 3, SiN, SiO□
A gate insulating film 4 consisting of the above is continuously formed, patterned and etched, and the excess region is removed to form a +el structure. Finally, a gate G is formed by depositing and patterning NiCr, AI, Mo, Cr, etc., thereby completing a top-gate staggered thin film transistor such as (fl).

〔Effect of the invention〕

As described above, according to the present invention, since the lower surface of the a-Si active layer is flat, unevenness does not occur in the a-3i active layer and the gate insulating film, and film cracks and linings do not occur. As a result, a highly reliable a-3i thin film transistor with stable characteristics can be realized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view explaining the basic principle of an a-Sifi film transistor according to the present invention, FIG. FIG. 3 is a cross-sectional view showing a 3i thin film transistor. In the figure, S is the source electrode, D is the drain electrode, 2s
, 2d is an ohmic contact layer, 3 is an a-Si active layer, 4 is a gate insulating film, and G is a gate. Patent Applicant: Fujitsu Limited Agent, Patent Attorney Minoru Aoyagi (Figure 1) 41-s i Book #) Lasijimata Figure 3 Inorganic conductive film 5δ (C) Examples and manufacturing process Figure 2 (fn)

Claims (1)

[Claims] In a top-gate staggered a-Si thin film transistor in which the source electrode and drain electrode are arranged on the insulating substrate side, an inorganic thin film is formed in the recess between the source electrode (S) and the drain electrode (D). By providing (5), the a-Si active layer (3)
1. An a-Si thin film transistor characterized by having a flat surface.