JPS62221159A - Formation of thin film transistor matrix - Google Patents

Abstract

PURPOSE:To reduce the short-circuit defects of a transistor and to obtain a highly reliable thin film transistor matrix by a method wherein, before formation of a gate insulating film and an operating semiconductor layer, the substrate provided with a gate and a gate bus line is flattened. CONSTITUTION:A pattern corresponding to the pattern, which will be turned to a gate electrode, is formed on a conductive film 2 using a resist 3, and besides, a resist mask pattern 5 corresponding to a matrix driving bus line is formed. The conductive film 2, excluding the part where the resist 3 is coated, is directly exposed to an electrolyte, and an Al2O3 oxide film 8 is grown. After a selective oxidation has been performed, the resist 3 mask pattern on a flat glass substrate 1 is exfoliated, silicon nitride is formed as an insulating film 6 and hydrogenated, silicon nitride is formed as an insulating film 6 and hydrogenated amorphous silicon is formed as an operating semiconductor layer 7 (active layer) on a gate electrode 4 successively by performing a plasma CVD (chemical vapor deposition) method, and the source electrode 9 and the drain electrode 10, consisting of N-type hydrogenated amorphous silicon, titanium Ti and aluminum A1, are formed.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a thin film transistor formed on a planar panel substrate, so-called an active matrix panel. The purpose of the present invention is to reduce short-circuit defects in transistors by planarizing a substrate on which gates and gate bus lines are formed, thereby providing a highly reliable thin film transistor matrix.

[Industrial application field]

The present invention relates to a method of forming a thin film transistor matrix that is integrally incorporated into a flat display panel.

For example, large-area display devices such as liquid crystal display panels generally form pixel cells in an m x n lattice arrangement, and each pixel cell is driven by providing m and one pass lines orthogonal to each other. A matrix drive method is used.

Generally, each pixel cell driven in a matrix manner is provided with a thin film transistor directly connected to the cell electrode, the active layer of which is a semiconductor film made of, for example, hydrogenated amorphous silicon.

The present invention relates to a method of forming the thin film transistor, and in particular, to forming a stable display panel by eliminating steps in the gate insulating film portion of the transistor and improving voltage resistance performance.

[Conventional technology]

FIG. 3 is a cross-sectional view of a main part of a thin film transistor having an inverted staggered configuration, illustrating the structure and formation process of the thin film transistor.

FIG. 2A shows a diagram in which a conductive film is formed on the surface of an insulating substrate 20 such as glass, and a gate electrode 21 is formed on the conductive film using a normal etching method or lift-off method.

The same figure (bl is chemical vapor deposition method in plasma gas space (
2 is a diagram in which a gate insulating film 22 and a semiconductor active layer 23 of, for example, hydrogenated amorphous silicon are successively formed on the gate electrode 21 by a CVD method or a thermal CVD method.

The figure (C1 is a diagram in which a source electrode 24 and a drain electrode 25 of a transistor are each patterned on the semiconductor active layer 23).

However, since the gate insulating film 22 of the thin film transistor formed by the method described above has a step at the electrode end 26 corresponding to the thickness of the underlying gate electrode 21, the insulating film 27 at the step has a film quality of electrical This poses a problem because the physical withstand voltage decreases.

[Problem that the invention seeks to solve]

The stepped portion 27 of the gate insulating film 22 of the thin film transistor is more likely to have pinholes in the film than a flat portion, which causes short circuit defects and a reduction in electrical breakdown voltage. Particularly in large-area display panels, if thin film transistors arranged in a two-matrix arrangement have the aforementioned drop in breakdown voltage or short-circuit defects, the yield of panel formation will drop significantly.

[Means for solving problems]

FIGS. 1 and 2 are cross-sectional views illustrating an embodiment of the method for forming a thin film transistor of the present invention, which solves the above-mentioned problems.

After forming a conductive film 2 on the entire surface of a flat substrate 1, the conductive film 2 is selectively oxidized using a resist mask 3 on the conductive film 2 to form a gate electrode 4. and a step of simultaneously forming a pass line 5 as one matrix drive line provided at the same level as the electrode 4, followed by a step of forming a gate insulating film 6 and a semiconductor active layer 7.
In this method, a thin film transistor in a matrix arrangement is formed by sequentially forming the following steps.

[For production]

The method of selectively oxidizing the conductive film before forming the gate insulating film of the thin film transistor may be an anodic oxidation method as shown in the examples below or a thermal oxidation method, which maintains the conductive film thickness and insulating film quality. Since the gate insulating film and the semiconductor active layer are stacked in a down state while the flatness of the substrate is maintained, a high thin film transistor matrix without short circuit defects is formed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the structure and method of forming a transistor of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1(a) is a cross-sectional view (false) to (e) is also a cross-sectional view of a flat substrate, for example, a glass substrate 1, and a conductive film 2 of aluminum is deposited over the entire surface of the substrate by, for example, vapor deposition means.

In FIG. 0), first, a pattern corresponding to a pattern to be a gate electrode is formed on a conductive film 2 using a resist 3. However, although not shown in the drawings, at the time of forming the resist pattern, a resist mask pattern 5 for the matrix drive pass line is also formed. This substrate is then immersed in an oxalic acid electrolyte and anodized using a carbon cathode at an appropriate current density, so that the conductive film 2 except for the portion where the resist 3 is adhered is directly exposed to the electrolyte, resulting in the oxidation of A1) O, A film is produced.

In the same figure (C1 is a diagram in which the resist 3 mask pattern on the substrate is peeled off after the selective oxidation. In the figure, 8 is the At20.electrolytically oxidized portion of the conductive film 2.

In the same figure (d+ is the same figure) silicon nitride as the insulating film 6 and hydrogenated amorphous silicon as the active semiconductor layer 7 (active layer) are sequentially formed on the gate electrode 4 of C1 by plasma CVD method. This is what I did.

Furthermore, the same figure (e) shows a source electrode 9 made of n-hydrogenated amorphous silicon/titanium Ti/aluminum AI.
FIG. 3 is a diagram in which a thin film transistor is completed by forming a drain electrode 10 and a drain electrode 10. FIG.

Next, another embodiment of the present invention in which a conductive film is thermally oxidized instead of the selective oxidation of the conductive film by electrolytic chemical formation will be described according to the process shown in FIG.

The difference from FIG. 1 is that a quartz substrate is used as the flat substrate 1 in FIG. 1A, and n-type polysilicon is used as the conductive film 1) deposited on the entire surface of the substrate 1. The quartz substrate can withstand high temperature oxidation processes.

Furthermore, Tb) silicon nitride is used as a mask 12 for selective oxidation of the n-type polysilicon conductive film 1) shown in the figure.

(C) - (The basic process shown in Figure 81 is almost the same as in Figure 1. That is, the mask 12 made of silicon nitride is peeled off and removed. A gate insulating film 6 of silicon nitride and an active semiconductor N7 of hydrogenated amorphous silicon are successively formed thereon by plasma CVD.

13 in the figures (C) to (e) is a thermally oxidized film of the conductive film 1).

Next, by forming the source electrode 9 and the drain electrode 10, a thin film transistor matrix with few short circuit defects and high device breakdown voltage will be formed.

〔Effect of the invention〕

Before forming the gate insulating film described in detail above.

According to the thin film transistor matrix of the present invention in which a gate insulating film and a pass line are patterned using selective oxidation of a conductive film, a thin film transistor array with fewer short circuit defects and high element withstand voltage can be formed, and the yield of panel assembly can be improved. Therefore, an inexpensive display panel can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the method for forming a thin film transistor of the present invention. FIG. 2 is a cross-sectional view of an embodiment of the method for forming a thin film transistor of the present invention. FIG. 3 is a diagram showing the structure and formation process of a conventional thin film transistor. In the figure, l is a flat substrate, and 2 and 1) are conductive films. 3 and 12 are resist masks. 4 is a gate electrode, 5 is a pass line. 6 is a gate insulating film, and 7 is a semiconductor active layer. 8 is an anodic oxide film, and 13 is a thermal oxide film. 9 is a source electrode, and lO is a drain electrode. Agent Patent Attorney Sada Igata - Ne ``Block Sun Moon Thin Piece'' Transistor Punishment Bun Manj Naofumi If Line Farm 1 Mouth! #How to get to the F-run star form on the first flight of Kai J Getsuki Z
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Claims (1)

[Claims] (1) After forming a conductive film (2) on the entire surface of a flat substrate (1), the conductive film (2) is selectively oxidized using a resist mask (3) on the conductive film (2). A thin film transistor comprising the steps of simultaneously forming a gate electrode (4) and a gate bus line (5), and then sequentially forming a gate insulating film (6) and a semiconductor active layer (7). How to form a matrix. (2) The conductive film (2) described in the previous section is formed of polysilicon and the selective oxidation resist mask (3)
2. The method for forming a thin film transistor matrix according to claim 1, wherein said material is silicon nitride. (3) The method for forming a thin film transistor matrix according to claim (1), wherein the step of selectively oxidizing the conductive film (2) is either anodic oxidation or thermal oxidation.