JPS61256375A - Thin film diode for display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film diode for a display device that improves the display quality of a liquid crystal display device and expands the field of application of liquid crystals.

[Conventional technology]

Various display devices such as liquid crystal, EL, EC, PDP, and fluorescent displays have all reached the stage of practical use, and the current goal is high-density matrix type displays.

For display systems that have problems with matrix driving, a so-called "active matrix" method using active additive elements is effective.

By using thin-film nonlinear resistance elements such as MIM and diodes in display devices, high-density and high-quality displays are possible, and thin-film nonlinear resistance elements (thin-film rectifiers) are superior as active additive elements for display devices. This is well known.

A diode element as an active element for a display device has a structure as shown in FIG. In Fig. 4, 5 is the substrate, 6
7 is a first electrode, 7 is an interlayer insulating film, 8 is a second electrode, and 9 is a semiconductor layer, which has a three-layer structure of P, I, and N. 10 is an active element section, and 10' is a contact section.

[Problems that the invention attempts to solve]

However, the conventional diode element shown in FIG. 4 requires patterning four times during its manufacture: patterning of the first electrode B, patterning of the semiconductor layer 9, patterning of the interlayer insulating film 7, and patterning of the second electrode 8. In particular, mask alignment accuracy is important when patterning an interlayer insulating film, and this patterning accuracy is strictly required.

Therefore, there is a drawback that it causes a decrease in yield and an increase in cost.

An object of the present invention is to provide a diode with improved yield and low cost.

[Means for solving the problem] In order to solve the above-mentioned problems, the present invention eliminates the interlayer insulating film of the diode and adopts a structure in which the resistance of the semiconductor layer on the first electrode side is increased instead of the interlayer insulating film.

[Example] FIG. 1 is a sectional view showing the structure of a diode of the present invention. In FIG. 1, 40 is the substrate, 41 is the first electrode, and 42 is
) type semiconductor layer, 43 is a ■ type semiconductor layer, 44 is an N type semiconductor layer, and 45 is a second electrode.

Generally, the characteristics of a diode used as a display element are as shown in Figure 2, and the display writing voltage and current Von
, I on, voltage and current during non-writing ■ off, I
off , I on / , 1 The thicker the value of off, the better. I on is only 1! 'Y is constant depending on the conductor layer, but Ioff varies greatly depending on the presence or absence of an interlayer insulating film.In general, if there is no interlayer insulating film, [off is large (and cannot be used).

That is, as shown in FIG. 4, since the J electrode 6 and the second electrode 8 are completely separated by the interlayer insulating film 7, the 7-node current Ioff between them is small.

On the other hand, the diode of the present invention has a structure as shown in FIG. For this reason, I off becomes large (becomes thick) in the current state. In order to prevent this, in the diode of the present invention, the resistance of the P-type semiconductor layer 42 in contact with the first electrode 41 is increased.

That is, by reducing the impurity concentration of the P-type semiconductor layer 42, the resistance of the -type semiconductor layer 42 is increased, and the leakage current Ioff between the first electrode 41 and the second electrode 42 is decreased. This resistance value must be approximately r10Ω.

FIG. 3 shows the sheet resistance R3 of the P-type semiconductor layer 42 and the contrast T when the diode of the present invention is used for driving a liquid crystal.
It is a graph of on/Toff ratio.

If the contrast ratio Ton/Toff is 2 or more, the sheet resistance needs to be 10Ω or more.

FIG. 5 is a circuit diagram when the diodes of the present invention are connected in a ring to drive a liquid crystal. In the example, a diode with P, ■, and N layers from the first electrode was used as an example;
The same holds true for diodes stacked in this order.

〔Effect of the invention〕

As is clear from the above description, the present invention provides a thin film diode that does not have an interlayer insulating film and has a structure in which a first electrode and a second electrode are separated by a semiconductor. By increasing the resistance value, a thin film diode having good characteristics with less leakage can be realized.

Further, in particular, by setting the sheet resistance of the lowest layer of the semiconductor film forming the semiconductor layer to 10Ω or more, a stable and good thin film diode with little leakage can be obtained. Furthermore, by utilizing the present thin film diode in a liquid crystal display device, high-density display or large-sized display becomes possible, and it is believed that the present invention will contribute to the development of liquid crystal display devices. Furthermore, by utilizing the present invention, the manufacturing process for thin film diodes can be shortened.

A sheet resistor of a semiconductor layer on the first electrode of a membrane diode? A circuit diagram that connects the odes in a ring to drive the liquid crystal.

40......Substrate, 41...First electrode, 42...P-type semiconductor layer, 46...
......■-type semiconductor device 44...
- N-type semiconductor layer, 45...second electrode.

Claims (2)

[Claims] (1) A first electrode formed on a substrate and a P, I, N junction formed on the first electrode in the order of P, I, N or N, I, P from the substrate side. One sheet of the P-type or N-type semiconductor layer of the thin film diode has a semiconductor layer with a resistance of 10^1^0Ω and a second electrode formed on the semiconductor layer.
A thin film diode for a display device characterized by the above. (2) The thin film diode for a display device according to claim 1, wherein the thin film diode is ring-connected.