Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Patent
1991-04-15
1994-10-25
Mintel, William
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
257 72, 257350, 257761, 257765, 359 87, 359 95, 345 87, 348792, H01L 2904, H01L 31036, H01L 2701, H01L 2348
Patent
active
053592069
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention concerns an active-matrix addressed TFT substrate using a thin film transistor (hereinafter referred to as TFT), a manufacturing method and an anodic oxidation method thereof, a liquid crystal display panel using the TFT substrate and a liquid crystal display equipment using the liquid crystal display panel.
2. Background Art
FIG. 2 shows an example of a TFT substrate for a liquid crystal display panel, using an amorphous silicon (hereinafter simply referred to as a-Si) TFT, using Al as a gate electrode and constituting a portion of a gate insulation it film with Al.sub.2 O.sub.3 obtained by anodic oxidation thereof. FIGS. 2(a), (b) and (c) show, respectively, an equivalent circuit diagram, a plan view and a cross sectional view of the TFT substrate. There are depicted for gate terminals by G.sub.1, G.sub.2, gate bus-lines by G.sub.1 ', G.sub.2 ', drain terminals by D.sub.1, D.sub.2, TFT by T.sub.11, T.sub.12, T.sub.21, T.sub.22, liquid crystal by LC, common terminal disposed on the side of the color filter substrate by V.sub.com. Further, there are also depicted substrate 10, Al 12', Al.sub.2 O.sub.3 13, SiN 14, transparent electrode (pixel electrode) 17, non-doped a-Si(i) 15, phosphorus-doped hydrogenated amorphous silicon (hereinafter simply referred to as a-Si(n.sup.+)) 16, signal bus-line 18, source electrode 18' connecting the a-Si(n.sup.+) TFT and the pixel electrode. In FIG. 2, boundary line 11 indicates the boundary between the regions undergoing and not undergoing the anodic oxidation. With reference to the boundary line 1.sub.1, the right area is a region undergoing anodic oxidation, while the left area is a region not undergoing the same.
Further, a structure as shown in FIG. 32(a), (b) has been used near the gate electrode of a conventional TFT substrate. FIG. 32(a) is a plan view near the gate electrode and FIG. 32(b) is a cross sectional view taken along line AA' thereof. In the figure, are shown substrate 10, Cr 11, Al 12', SiN 14 a-Si 15', source electrode 55, signal bus-line also serving as the drain electrode 18 and transparent electrode 17 as a pixel electrode.
As shown in the figure, Cr has been used for the gate electrode and SiN has been used for the gate insulator film. On the other hand, two layers of metals of Cr and Al are used for the gate bus-line. The reason why the gate electrode and the gate bus-line are constituted with different materials will now be described below.
At first, the conditions for the metal of the gate electrode are that it has good adhesion with the substrate, has no unevenness at the surface and does not suffer from deterioration in the course of forming SiN as the gate insulation film. Cr is suitable for the conditions. On the other hand, it is demanded for the gate bus-line that the resistance is low. Since Cr has a intrinsic resistivity higher by one or more of orders as compared with Al it is not suitable to the gate bus-line. On the other hand, A is liable to cause hillocks, tending to cause acicularly protruded defects at the surface. Further, since there is a problem that the hillocks generate in the step of forming SiN as the gate insulation film (usually deposited by means of a plasma CVD method at a substrate temperature of 200.degree. to 350.degree. C.), it can not be used for the gate electrode. Accordingly, Cr has been used for the gate electrode and metals of two layer structure comprising Cr and Al have been used for the gate bus-line.
On the other hand, there is Ta or Al anodic oxidation technology in the prior art (refer, for example, to Manual of Electrochemistry (Maruzen), p 874-892, published December, 1964). This is a technique of electrochemically oxidizing the surface of metal which has been used for the capacitor or surface coating.
The merit of the oxide film (insulator film) formed by this technique is that it less causes defects due to foreign particles. Accordingly, there has been a prior art of utilizing the above-mentioned technology to TFT (Japanese Patent Laid-Open Sho 58
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Matsukawa Yuka
Matsumaru Haruo
Sasano Akira
Shirahashi Kazuo
Tanaka Yasuo
Hitachi , Ltd.
Loke Steven
Mintel William
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