JPS63258071A - Manufacture of thin-film transistor - Google Patents

Abstract

PURPOSE:To improve the characteristics of a thin-film transistor and thereby enhance the yield and reliability of products incorporating thin-film transistors by a method wherein a gate material layer is formed on a substrate, reverse spattering is accomplished for the conversion of the surface into a damaged layer, and then etching is accomplished for the construction of a gate electrode. CONSTITUTION:A gate material layer 8 is formed on a substrate 2, the gate material layer 8 is exposed to reverse spattering for the formation of a damaged layer 9, and the gate material layer 8 is subjected to etching for the construction of a gate electrode 3. For example, on a glass substrate 2, a gate material layer 8 is formed of molybdenum or the like by spattering. A process follows wherein the upper layer of the gate material layer 8 is subjected to reverse spattering for the formation of a damaged layer 9. Next, the gate material layer 8 is subjected to etching for the construction of a gate electrode 3 of a prescribed geometry, when the resultant gate electrode 3 is provided with a roundish surface. An insulating film 4, semiconductor film 5, source electrode 6, and drain electrode 7 are formed for the completion of a thin-film transistor 1.

Description

Detailed Description of the Invention "Field of Industrial Application" This invention is directed to thin film transistors used in switching elements of active matrix liquid crystal display devices.
TPT).

"Prior Art" Conventionally, a thin film transistor having a structure as shown in FIG. 5, for example, has been known as a thin film transistor used as a switching element of an active matrix liquid crystal display element. In this figure, reference numeral 1 indicates a thin film transistor. This thin film transistor l includes a gate electrode 3 formed on a glass substrate 2, an insulating film 4 formed on the glass substrate 2 to cover the gate electrode 3, and a semiconductor film 5 formed on the insulating film 4. and a source electrode 6 and a drain electrode 7 formed on the semiconductor film 5.

By the way, in order to fabricate a thin film transistor l having such a structure, first a gate material layer made of molybdenum or the like is formed on the glass substrate 2 by sputtering, and then the gate material layer is subjected to etching such as photolithography or etching. A gate electrode 3 having a predetermined shape is formed together with a gate bus (not shown), and then an insulating film 4 is formed on the glass substrate 2 to cover the gate electrode 3, and then a semiconductor film is formed on the insulating film 4. A source electrode 6 and a drain electrode 6 are further formed on this semiconductor film S. ! i
T&7 are formed respectively to obtain the thin film transistor 1.

``Problems to be Solved by the Invention'' However, in the thin film transistor 1 described above, since the gate electrode 4 is formed by etching such as photography etching, its cross-sectional shape is angular as shown in FIG. corner 3a of the gate electrode 3.

The thickness of the insulating films 4a, 4a on the corners 3a becomes thinner, and the electric field concentrates on the corners 3a, 3a.
There was a problem in that current leakage in the insulating films 4a, 4a on the insulating films 3a increased. Furthermore, if thin film transistors with large current leakage are used in liquid crystal display devices, etc., the liquid crystal display devices will not operate properly, and this will reduce the yield of products using the thin film transistors, such as liquid crystal display devices. There was a problem with the decline.

The present invention has been made in view of the above circumstances, and its purpose is to improve the characteristics of thin film transistors and further improve the yield and reliability of products using these thin film transistors.

"Means for Solving the Problems" In order to solve the above problems, the present invention forms a gate material layer on a substrate, then performs reverse sputtering on this gate material layer to form a damaged layer on the surface, and then A thin film transistor is formed by performing etching such as photolithography and etching on the limb gate material layer to form a gate electrode.

Therefore, in the method for manufacturing a thin film transistor of the present invention, a mechanically weak damaged layer can be formed in the upper layer of the gate material layer by performing reverse sputtering on the gate material layer, and then etching is performed to form the gate electrode. When formed, the upper layer of this gate electrode consists of a fragile damaged layer, so its corners are naturally shaved off, thereby forming a gate electrode with no rounded corners. Can be done.

"Example" Hereinafter, an example of the method for manufacturing a thin film transistor of the present invention will be described in detail using FIGS. 1 to 4. In addition,
In these figures, the same elements as those shown in FIG. 5 are given the same reference numerals.

First, as shown in FIG. 1, molybdenum, tantalum, aluminum, etc. are sputtered onto a glass substrate 2.
A gate material layer 8 made of chromium, titanium, etc. is formed.

Next, as shown in FIG. 2, reverse sputtering is performed on this gate material layer 8 to form a damaged layer 9 on the upper layer of the gate material layer 8. Here, reverse sputtering refers to using the gate material layer 8 itself as a target material and colliding accelerated ions with it as shown by the arrows in FIG. 2 to form the gate material layer 8 from the upper layer of the gate material layer 8. It refers to releasing atoms or molecules to the outside. Furthermore, the damaged layer 9 is a layer in which the reverse sputtering has been performed as described above, and atoms or molecules are emitted from the upper layer of the gate material layer 8 and its crystal structure has been damaged, resulting in weak mechanical strength. means.

And when reverse sputtering is not performed on the gate material layer 8,
For example, the ion pressure (sputtering pressure) of argon, etc.
The upper layer of the gate material layer 8 is sputtered at approximately Ps.

Next, the gate material layer 8 on which the damaged layer 9 has been formed is etched to form a gate electrode 3 having a predetermined shape as shown in FIG. For etching, a photoresist is applied, a mask pattern is transferred thereto, and the underlying film (gate material layer 8 in the example of the present invention) is processed (etched) using the resist pattern. This is done by well-known photolithography, etching, etc. Also, Gut formed in this case? Since the upper layer of the 1f pole 3 is a mechanically fragile damaged layer 9, the corners of the corners 3a, 3a are naturally shaved off when etching is performed, and the upper layer becomes rounded. It has a tinged shape.

Next, as shown in FIG. 4, an insulating film 4 such as silicon nitride (SiNx) is formed on the glass substrate 2 to cover the gate electrode 3, and then a semiconductor such as hydrogenated amorphous silicon is formed on the insulating film 4. A film 5 is formed to cover the semiconductor film 5, and a source electrode 6 and a drain electrode 7 made of aluminum or the like are respectively formed on the semiconductor film 5 to obtain the thin film transistor 1.

"Effects of the Invention" As explained above, the method for manufacturing a thin film transistor of the present invention includes forming a gate material layer on a substrate, then performing reverse sputtering on this gate material layer to form a damaged layer, and then forming a damaged layer on the gate material layer. Since the gate electrode is formed by etching the gate material layer, by not performing reverse sputtering on the gate material layer, it is possible to form a fragile damaged layer on the upper layer of the gate material layer. When a gate/electrode is formed by etching such as lithography/etching, the upper layer of the gate electrode is made up of a fragile damaged layer, so the corners of the gate electrode are naturally shaved off. A gate electrode without rounded corners can be formed, and the so-called step coverage of the insulating film can be improved. Therefore, it is possible to prevent inconveniences such as thinning of the insulating film on the corners of the gate electrode or concentration of electric fields at the corners, and to suppress current leakage in the insulating film on these corners. Therefore, the characteristics of the thin film transistor can be improved, and the yield and reliability of products using this thin film transistor can be improved.

[Brief explanation of drawings]

1 to 4 are diagrams showing an example of the method for manufacturing a thin film transistor of the present invention in the order of steps, in which FIG. 1 is an explanatory diagram showing a state in which a gate material layer is formed, and FIG. 3 is an explanatory diagram showing a state in which a damaged layer has been formed by etching, FIG. 4 is a schematic diagram of the structure of the obtained thin film transistor, and FIG. 5 is a schematic diagram of a conventional thin film transistor. FIG. l...Thin film transistor, 2...Glass substrate 3...Gate 7I\pole, 3a...
corner, 8... gate material layer, 9... damaged layer;

Claims (1)

[Claims] A method for manufacturing a thin film transistor, comprising forming a gate material layer on a substrate, then performing reverse sputtering on the gate material layer to form a damaged layer, and then etching the gate material layer to form a gate electrode. .