JPS61278883A - 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 use of liquid crystals.

[Conventional technology]

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

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

By using a thin-film nonlinear resistance element in a display device, high-density, high-quality display becomes possible. There are already several examples of using thin film nonlinear resistance elements in liquid crystal display devices. For example, there is a thin film diode that uses a semiconductor layer with rectifying properties as an active layer.

Amorphous silicon (a-8i) is attracting attention as a material that can form a semiconductor layer uniformly and stably at low temperatures and that can be controlled by impurity ions.

FIG. 12 shows the structure of a conventional thin film diode using an amorphous silicon PIN junction in the active layer. Second
In the figure, 11 is a glass substrate, 12 is a transparent electrode (IT
O), 16 is amorphous, 71): I7 (a −
S i ), 14 is an interlayer insulating film S I 02.15 is an interconnection electrode Cr. When using a conventional thin film diode as an active element for a liquid crystal display, there is a method of connecting a plurality of diodes in series for the purpose of improving the appearance, an example of which is shown in FIG. FIG. 3 is a structural diagram and an equivalent circuit when thin film diodes are connected in series. The third country is an element with a structure in which conventional thin film diodes are connected in series with interconnection electrodes Cr.
) in Figure 3 utilizes a conventional device structure and uses P in the semiconductor layer.
This element has a structure in which INPIN and PIN junctions are vertically stacked in two stages. In FIG. 3, 21 is a glass substrate;
2 is a transparent electrode (ITO), 26, 23 and 27, 28 are PIN semiconductor layers, 24 is 5IO2, and 25 is an interconnection electrode Cr.

[Problem to be solved]

However, since the third country and (Bl) elements have an interlayer insulating film, the film quality and thickness uniformity of the interlayer insulating film, etc.
There were strict requirements for interlayer insulation films.

Furthermore, etching control of the interlayer insulating film is strictly controlled, and there are strict requirements for mutual mask alignment accuracy, making it difficult to form a large number of thin film diodes with a good yield. In the case of the element with the structure shown in Figure 3, the structure shown in the 3rd National Conference is different from the structure shown in Figure 3 (B), in that the desired number of thin film diodes (two) are connected using mutual wiring electrodes. , the number of elements doubles, the area occupied by the elements increases, the aperture ratio decreases, and the display quality deteriorates (see Figure 3). Since it is thick, step coverage of the glabellar insulating film becomes a problem.

[Means for solving problems]

Therefore, the present invention provides a semiconductor layer having a multi-sided PIN junction structure, for example, a P-type semiconductor film and an N-type semiconductor film in a semiconductor layer with a two-stage structure of a PIN junction formed in the order of PINPIN. By increasing the sheet resistance, leakage between the first electrode and the second electrode is reduced, making it possible to remove the glabellar insulating film.

〔Example〕

Embodiments of the present invention will be described based on the drawings. Figure 1 shows
FIG. 1 is a cross-sectional view of a thin film diode showing the present invention. In FIG. 1, 1 is a glass substrate, 2 is a first electrode (ITO), and 3 is a glass substrate.
and 6 are P-type semiconductor films, 4, and 6 and 6 are PIN
It is a semiconductor layer (a-8i), and 7 is a '2nd electrode (interconnection electrode: Cr). Figure 1 shows that the interlayer insulating film is
, the first electrode and the second electrode are separated by a semiconductor layer.

102% compared to P-type or N-type semiconductor films.
Since the resistance is ~108 times as large, leakage between the first and second electrodes is caused by the P-type semiconductor films 6 and 6 and the N-type semiconductor film 5.
This can be prevented by increasing the sheet resistance. FIG. 4 is a graph showing the sheet resistance of P-type and N-type semiconductor films and display quality (contrast: Ton/Toff) when the thin film diode of this example is used for display. Since the displayable area requires a contrast of about 2, the sheet resistance of the P-type and N-type semiconductor films needs to be 1010 or more. FIG. 5 is an equivalent circuit diagram showing a state in which thin film diodes of the present invention are connected in a ring to form a liquid crystal display element. In FIG. 5, 51 is a timing electrode for inputting a timing signal, 52 and 53 are thin film diodes, and 52 and 53 are stacked vertically in two stages (
This embodiment is a two-stage stacked diode having a structure shown in FIG. 54 is a two-stage diode. 55 is a liquid crystal,
56 is a data electrode for inputting a data signal.

In the above embodiments, a-8i was used as the semiconductor film.
Amorphous silicon oxide (a-si:c) or amorphous silicon nitride (a-8i:N
) or amorphous silicon oxide (a-si:
Semiconductor films such as O) can be used, and although an example was used in which the semiconductor films were formed from the substrate in the order of P→process→N, good characteristics can also be obtained by forming in the order of N→■→P.

〔Effect of the invention〕

゛ As is clear from the above description, the present invention provides a thin film diode in which a semiconductor layer has a structure in which a plurality of PIN junctions are vertically formed, in which a first electrode and a second electrode are separated by a semiconductor layer, And P in the semiconductor layer
By increasing the sheet resistance of the type and N-type semiconductor films, it is possible to eliminate the glabellar insulating film.The present invention simplifies the manufacturing process of thin film diodes and improves the yield of devices.

Furthermore, by ring-connecting the present thin film diode and using it 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.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the thin film diode of the present invention. FIG. 2 is a sectional view showing the structure of a conventional thin film diode. FIG. 3 is a cross-sectional view showing a case where two stages of thin film diodes are connected in series, and the third arrangement is a case where they are connected using mutual wiring electrodes. , PIN PIN and PIN junction are formed in two stages. Figure 4 is a graph showing the sheet resistance and contrast ratio of P and N type semiconductor films, and Figure 5 is a graph showing the thin film diode of the present invention in a ring connection. 1.11.21...Glass substrate, 2.12.2
2-----First electrode (ITO), conductor layer (a-3i
), 7.15.25 ...---Second electrode (Cr). 542-stage diode 54. 2-stage diode

Claims (3)

[Claims] (1) A first electrode, a semiconductor layer, and a second electrode formed on a substrate.
In a thin film diode for a display device comprising an electrode, the semiconductor layer partially protrudes onto the glass substrate from the first electrode, and the second electrode extends over the semiconductor layer on the first electrode and the glass substrate. It has a structure in which PIN junctions formed with PINs or NIPs are stacked in at least two stages from the substrate side, and P type and N type in the semiconductor layer. The sheet resistance of the type semiconductor film is 10
A thin film diode for display devices characterized by having a resistance of ^1^0Ω or more. (2) The sheet resistance of the P-type and N-type semiconductor films excluding the topmost P-type or N-type semiconductor layer among the semiconductor layers is 10^1^
The thin film diode for a display device according to claim 1, characterized in that the resistance is 0Ω or more. (3) The thin film diode for a display device according to claim 1, wherein the thin film diode for a display device is ring-connected.