JP2854025B2 - Method for manufacturing thin film transistor - Google Patents

Description

The present invention relates to a method for manufacturing a thin film transistor (hereinafter abbreviated as TFT), and particularly relates to a TF having a small number of steps utilizing back exposure.
It relates to a method for manufacturing T.

(B) Conventional technology FIG. 5 shows a cross-sectional view of a general TFT. In manufacturing the TFT, the gate electrode (A), the gate insulating film (B), the semiconductor film (C), the display electrode (D), and the source / drain electrodes (E) are respectively patterned.

Among them, the gate insulating film can be processed with a metal mask, etc.
A photomask is not necessarily required.

Therefore, at least four mask steps are required for TFT manufacturing.

On the other hand, a TFT is manufactured by repeating three steps of a film forming step, a photolithographic step, and an etching step.

(C) Problems to be Solved by the Invention It is the exposure process using a mask aligner that requires high-precision alignment that determines the throughput in manufacturing a TFT.

Therefore, reducing the number of photomasks used in the TFT manufacturing process increases manufacturing throughput (yield), thereby reducing manufacturing costs.

It is no exaggeration to say that with current equipment capabilities, for example, if a TFT manufactured with four photomasks is manufactured with three photomasks, the throughput will be 4/3 times as large.

(D) Means for Solving the Problems According to the method of manufacturing a thin film transistor of the present invention, an opaque first metal is deposited on a transparent insulating substrate, and a gate electrode and a gate wiring are formed using a first photomask. A second step of depositing a transparent gate insulating film and a semiconductor film, a third step of forming a resist having substantially the same shape as the first metal by back exposure, and a third step of etching the semiconductor film, and depositing a transparent conductive film over the entire surface A fourth step of forming a resist having a shape substantially inverted from that of the first metal by back exposure, etching the transparent conductive film, and continuously etching the transparent conductive film and the semiconductor film using a second photomask. , Transparent conductive film
A fifth step of forming a drain electrode and a display electrode, forming an active layer of a transistor with a semiconductor film, and a sixth step of depositing a second metal and forming a drain wiring with a third photomask are described. Make a summary.

Further, the gist of the method for manufacturing a thin film transistor of the present invention is that the drain wiring made of the second metal formed in the sixth step is in contact with the semiconductor film.

(E) Function In the method of manufacturing a thin film transistor according to the present invention, the number of photomask steps can be reduced as compared with the conventional process.

Further, since a self-alignment process is employed, an inexpensive exposure apparatus that does not require a high-precision positioning mechanism can be used, and a high-precision pattern can be formed.

(F) Embodiment FIG. 3 is a plan view of a TFT formed by the manufacturing method of the present invention, and FIG. 4 is a cross-sectional view taken along line AA 'in FIG.

FIG. 1 and FIG. 2 are a plan view and a sectional view, respectively, in the order of steps of the manufacturing method of the present invention.

Hereinafter, the manufacturing method of the present invention will be described in detail with reference to FIG. 1 and FIG.

(Example 1) 1) A gate wiring and a gate electrode made of a first metal (1) are formed on a glass substrate using a first photomask. (See FIGS. 1A and 2A.) 2) A gate insulating film and a semiconductor film are deposited, and a resist (2) having substantially the same shape as the gate electrode is formed by back exposure. In the formation of the resist, it is more preferable to form the resist in a pattern larger than the gate electrode by adjusting the conditions of exposure dose-development time and adjusting the resist baking conditions.
(See FIG. 2 (b)) 3) Etch the semiconductor film (3). (See FIGS. 1B and 2C) 4) A transparent conductive film is deposited on the entire surface, and a gate electrode and a resist (2) having an inverted pattern are formed by back exposure. In the formation of the resist, it is more preferable that the resist partially overlaps with the gate electrode by adjusting the conditions of the exposure amount and the developing time, adjusting the conditions of the resist baking, and the like. (See FIG. 2 (d)) 5) Etch the transparent conductive film (5). (See FIGS. 1C and 2E.) 6) A resist (2) is formed using a second photomask (see FIG. 1D), and a transparent conductive film is formed using the resist as a mask. The semiconductor film is continuously etched, source / drain electrodes and display electrodes are formed using a transparent conductive film, and an active layer of a transistor is formed using the semiconductor film. (See FIGS. 1E and 2G.) 7) A second metal is deposited, and a drain wiring (9) is formed using a third photomask. (See FIG. 1 (f) and FIG. 2 (h)) In the above steps 1) to 7), the number of photomasks to be used is defined as I) gate electrode (first metal), II) semiconductor film, A TFT can be formed with three sheets of a display electrode made of a transparent conductive film, a drain / source electrode, and III) a drain wiring (second metal).

In this process, the overlapping region of the gate electrode (1), the drain electrode (6), and the source electrode (7) (transparent electrode film) is formed by self-alignment (self-alignment).
TFT with very small overlapping area and small parasitic capacitance
Can be made.

(Example 2) After forming a drain electrode (6) and a source electrode (7) with a transparent conductive film in the same process as in Example 1, as shown in FIG. 1 (g) and FIG. 2 (i). The drain electrode (6) and the source electrode (7) are made into two layers with the metal 2. Also,
An auxiliary capacitance electrode (10) is formed of the second metal.

The distance between the drain electrode (6) and the source electrode (7) made of the second metal is smaller than the distance between the drain electrode (6) and the source electrode (7) made of the transparent conductive film, and the second metal is also similar to the transparent conductive film. Since the semiconductor film is in contact with the semiconductor film, the parasitic capacitance is larger than in the first embodiment, but the contact resistance between the semiconductor film (3) and the drain electrode (6) and the source electrode (7) is smaller.

Further, it is possible to manufacture a TFT even under a process condition in which a semiconductor film and a transparent conductive film are difficult to overlap with each other.
Process margin is larger than that.

In the second embodiment, since the contact with the semiconductor film is made of the second metal, it is not always necessary to leave the transparent conductive film on the drain electrode (6).

Further, according to the above-described first and second embodiments, when performing fine processing of the semiconductor film and the transparent conductive film, the conventional photomask process requires two steps.
Since the number of photomask processes is reduced by one in comparison with the number of processes required, TFTs can be manufactured with three photomask processes, one fewer than in the conventional process, thereby improving throughput and reducing manufacturing costs. it can.

That is, according to the first and second embodiments, the semiconductor film is formed in a self-aligned pattern in the same shape as the gate electrode by back exposure, and the transparent conductive film is removed from the gate electrode in a self-aligned manner by back exposure. (A gate electrode and a transparent conductive film having an inverted pattern are formed.) Then, the transparent conductive film and the semiconductor film are successively etched again using a photomask to form a predetermined pattern. In the case of fine processing of a conductive film, a conventional photomask process requires two steps.
Since the number of photomask processes is reduced by one in comparison with the number of processes required, TFTs can be manufactured with three photomask processes, one fewer than in the conventional process, thereby improving throughput and reducing manufacturing costs. it can.

(G) Effects of the Invention According to the method for manufacturing a thin film transistor of the present invention, a TFT can be manufactured with a smaller number of photomasks than in the conventional process, thereby improving throughput and reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a plan view of a TFT according to a manufacturing method of the present invention in the order of manufacturing steps, FIG. 2 is a sectional view of a TFT according to a manufacturing method of the present invention in the order of manufacturing steps, and FIG. FIG. 4 is a cross-sectional view taken along line AA 'of FIG. 3, and FIG. 5 is a cross-sectional view of a TFT manufactured by a conventional manufacturing method. (1) ... first metal, (2) ... resist, (3) ...
... Semiconductor film, (4) ... Gate insulating film, (5) ... Transparent conductive film, (6) ... Drain electrode, (7) ... Source electrode, (8) ... Display electrode, (9) ... ... second metal, (1
0) Auxiliary capacitance electrode, (A) Gate electrode, (B)
... Gate insulating film, (C) semiconductor film, (D) display electrode, (E) source / drain electrode.

Claims (2)

(57) [Claims] A first step of depositing an opaque first metal on a transparent insulating substrate and forming a gate electrode and a gate wiring with a first photomask; and depositing a transparent gate insulating film and a semiconductor film. Two steps, a resist having substantially the same shape as the first metal is formed by back exposure, a third step of etching the semiconductor film, a transparent conductive film is deposited on the entire surface, and a substantially reverse shape of the first metal is formed by back exposure. A fourth step of forming a resist and etching the transparent conductive film. The transparent conductive film and the semiconductor film are continuously etched using the second photomask, and the source / drain electrode and the display electrode are formed by the transparent conductive film. A fifth step of forming an active layer of the transistor by using a semiconductor film; and a sixth step of depositing a second metal and forming a drain wiring with a third photomask. Manufacturing method. 2. The method according to claim 1, wherein the drain wiring made of the second metal formed in the sixth step is in contact with the semiconductor film.