JPH0240962A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To prevent discharge breakdown of insulation between electrodes caused by electrostatic charge, by forming a guard conductor and linking wires in the stage before a capacitor between electrodes of a thin film transistor is formed. CONSTITUTION:A guard conductor 5 and linking wires 6 are formed simultaneously with a layer which is formed on a substrate 1 in the first place. As a result, when electrodes of gate G, source S and drain D of a thin film transistor are formed and wirings 8 between said electrodes and pads 3 are formed, each electrode is kept at an identical electric potential at the same time. Hence the potential difference from another electrodes never increases, even if electrostatic charge generates in the later manufacturing process. In the final stage of manufacturing process, the substrate is cut along a substrate cutting line 4, and a part of the linking lines 6 and the guard conductor 5 are cut off. Thereby, discharge between electrodes of the thin film transistor 2 can be prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a thin film transistor device comprising a plurality of thin film transistors on a substrate such as glass.

[Conventional technology]

When manufacturing a large-area device containing many thin film transistors, many thin film transistors are formed on a substrate such as glass, and the substrate is finally cut into a predetermined size to produce a product. FIG. 5 shows a conventional manufacturing method of a thin film transistor.
In FIG. 5, 1 is a substrate such as glass, 2 is a thin film transistor, 3 is a pad, 4 is a substrate cutting line, 8 is a wiring, G is a gate, S is a source, and D is a drain. A thin film transistor 2 is formed on a substrate 1 by lamination, and wirings 8 and pads 3 connected to these electrodes are formed. Thereafter, the substrate 1 is cut along the substrate cutting line 4 and the thin film transistor device is taken out.

[Problems to be solved by the invention]

(Problem) However, the conventional manufacturing method for thin film transistor devices described above has a problem in that the insulation between the gate and the drain or between the gate and the source may be destroyed by discharge due to static electricity generated during the manufacturing process. Ta. (Explanation of the problem) FIG. 6 shows a cross-sectional view of the stacked layers of a conventional thin film transistor. In FIG. 6, 2 is a thin film transistor, 8 is a wiring,
9 is a gate, 10 is an insulating layer, 11 is a semiconductor active layer, 12
13 is a source, 14 is a drain, and 15 is a conductor layer. The gate 9 is formed to extend long in the direction perpendicular to the plane of the paper and to be connected to the gates of other thin film transistors (see G in FIG. 5). The source, drain, and gate electrodes are made of a conductor, and an insulating layer 10 is interposed between them. Therefore, between the gate and source, and between the gate and drain,
Capacitance exists. FIG. 7 is a diagram showing that there is capacitance between the electrodes of a thin film transistor. C1 indicates the capacitance between the gate G and the source S, and C2 indicates the capacitance between the gate G and the drain D. By the way, in the manufacturing process, the substrate 1 on which the thin film transistor 2 is formed is transported by a transport line, but at that time, undesired static electricity may be applied. Static electricity is applied, for example, when transferring from one conveyance line to the next, or when there is a speed difference between the conveyance lines. If there is a speed difference, one of the transport lines will slip with respect to the substrate 1. That means,
The substrate 1 is simply rubbed by the transport line, and this friction imparts static electricity. The "+" mark in FIG. 6 indicates the generated static electricity. If static electricity is evenly distributed, there is relatively no problem, but if it is concentrated locally, problems arise. Since various layers are formed in various shapes on the substrate, they tend to be concentrated in some areas. As a result of local concentration, when the potential difference between the gate and drain becomes large, the insulation between them is broken down by discharge. The same thing can be said between the gate and the source. When such discharge breakdown occurs, the thin film transistor no longer operates as a thin film transistor. An object of the present invention is to solve the above-mentioned problems.

[Means to solve the problem]

In order to solve the above problems, in the method for manufacturing a thin film transistor of the present invention, a thin film transistor, a guard conductor, and a connecting line connecting the thin film transistor and the guard conductor are formed on a substrate, and the guard conductor is is formed before the interelectrode capacitance of the thin film transistor is formed, and then the connecting line is cut together with the substrate to separate the guard conductor from the thin film transistor. Since it is formed before the capacitance between the electrodes is formed, when the electrodes are formed, it has the effect of shorting all the electrodes through the pads (however, they are used without being connected to other things. (excluding output electrodes that have pads). As a result, even if the insulation between the short-circuited electrodes is charged with static electricity during the manufacturing process, it will not be destroyed by discharge. Further, the guard conductor surrounding the thin film transistor has the function of preventing static electricity generated around the guard conductor from penetrating into the guard conductor. As a result, even if there is an output electrode that is not short-circuited by the guard conductor because it has a pad that is used unconnected to other electrodes, the potential difference between that output electrode and the other electrodes is It is not large enough to cause electrical discharge damage to the insulation between the two.

[For production]

The guard conductor and connection line are between the gate and source of a thin film transistor, or between the gate and drain.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. [First Embodiment] FIG. 1 shows a first embodiment of the present invention.
It corresponds to the one shown in the figure. And 5 is a guard conductor,
6 is a connecting line. The guard conductor 5 is a conductor layer applied around the board cutting line 4, and the connection line 6 is a conductor layer that connects the pad 3 and the guard conductor 5. With these, all pads 3
are short-circuited and have the same potential. FIG. 4 shows a cross-sectional view of the stacked layers of a thin film transistor according to the present invention, and the reference numerals correspond to those in FIG. 6. 6th
The only difference from the figure is that a guard conductor 5 and a connecting wire 6 are further provided. The guard conductor 5 and the connecting wire 6 are formed at the same time as the first layer formed on the substrate l. Therefore, the electrodes (gate, source, drain) are formed, the wiring 8 between them and the pad 3 is formed, and at the same time each electrode is kept at the same potential. As a result, even if static electricity is generated in the subsequent manufacturing process, the static electricity will be concentrated on the electrode (e.g., drain) of the thin film transistor 2, and the potential difference with other electrodes (e.g., gate) will become large. It disappears. This prevents discharge damage between the electrodes of the thin film transistor 2. At the final stage of the manufacturing process, a portion of the connecting wire 6 and the guard conductor 5 are separated by cutting along the board cutting line 4. FIG. 3 shows an enlarged view of the area around the pad of the thin film transistor. The connection line 6 is cut along the substrate cutting line 4, and a portion remains connected to the pad 3. However, since the pad 3 is connected to other circuit elements by bonded wires, even if a portion of the connecting wire 6 remains, it does not pose any problem in circuit operation. [Second Embodiment] Depending on the intended use of the thin film transistor, if a portion of the connecting line 6 remains connected to the pad, it may not be possible to perform the intended operation. For example, in printers, corotron (charger)
This generates charges floating in the air, and it is necessary to control the flow. In that case, control of the charge flow is controlled by the output electrode (e.g. source) of the thin film transistor.
There is a method that performs this by controlling the potential of pads connected to the . That is, by changing the potential of the pad, the electric field above the pad changes, thereby controlling the flow of charges floating in the air. In the case of thin film transistors used for such purposes, the width and shape of the pad connected to the output electrode have a large influence on the control of the charge flowing above it.The shape of the pad is important for achieving the desired control. , the width must be of a predetermined value. If such a pad is also connected to the guard conductor via a connecting line, the part of the connecting line 6 that remains when the board is cut at the cutting line (see Figure 3) will be removed during the above control. works similarly to a pad, i.e. the shape of the pad,
This corresponds to the width being substantially changed. However, the shape and width of the part of the connection line 6 that remains when the board is cut along the board cutting line varies depending on the way the board is cut, that is, the position of the board cutting line, and is not constant. The flow will not be controlled accurately. When manufacturing a thin film transistor for use in such applications, the process is as shown in FIG. FIG. 2 shows a second embodiment of the invention. The sign is the first
Corresponds to the figure. Reference numeral 7 denotes a pad that is connected only to the output electrode of the thin film transistor and is not connected to anything else. In such a pad 7, the potential appearing on the pad 7 is used as a control signal. Pad 7 is not connected to guard conductor 5. On the other hand, the pads 3 connected to other electrodes are connected to other circuit elements by bonded wires, so even if a part of the connecting wire 6 remains as shown in FIG. 3, it does not affect the operation. , are short-circuited to each other at the guard conductor 5 via the connecting wire 6, as in the case of FIG. If this treatment is done at the beginning of the manufacturing process, the connection line 6. between the gate and drain will be connected. Since they are short-circuited via the guard conductor 5 and kept at the same potential, even if static electricity is generated, the insulating layer interposed between the gate and drain will not be destroyed by discharge. Since the gate and the output electrode (source) are not short-circuited, if static electricity is generated, a potential difference may occur. However, since the guard conductor 5 is placed around the group of FII membrane transistors 2, it is prevented from penetrating into the guard conductor, and the potential difference is large enough to cause discharge breakdown of the insulation between the gate and output electrode. It is not. As mentioned above, the pad 7 to which the connection line 6 cannot be connected
Even when manufacturing the thin film transistor 2 having the above structure, discharge breakdown of the insulation between the electrodes can be prevented.

【Effect of the invention】

As described above, according to the present invention, in the manufacturing process of a thin film transistor, between the gate and the source or between the gate and the
The possibility that the insulation between the drains will be destroyed by discharge due to static electricity can be reduced.

[Brief explanation of the drawing]

Fig. 1... A diagram showing the first embodiment of the present invention Fig. 2...
- Whistling figure 3 showing the second embodiment of the present invention... Enlarged view of the area around the pad of a thin film transistor Fig. 4... Lamination cross-sectional view of the thin film transistor according to the present invention Fig. 5... Conventional manufacturing method of a thin film transistor Figure 6 shows a conventional single-film transistor stacked cross-sectional view Figure 7
Figure...A diagram showing that there is capacitance between the electrodes of a thin film transistor, l is the substrate, 2 is the thin film transistor, 3 is the pad, 4 is the substrate cutting line, 5 is the guard conductor, 6 is the connecting line, 7 is a pad, 8 is a wiring, 9 is a gate, 10 is an insulating layer,
11 is a semiconductor active layer, 12 is an ohmic contact layer,
13 is a source, 14 is a drain, and 15 is a conductor layer.

Claims (1)

[Claims] A thin film transistor, a guard conductor, and a connecting line connecting the thin film transistor and the guard conductor are formed on a substrate, and the guard conductor is formed at a stage before an interelectrode capacitance of the thin film transistor is formed. 1. A method for manufacturing a thin film transistor device, comprising: cutting the connecting line together with the substrate to separate the guard conductor from the thin film transistor.