JPS5890770A - Semiconductor device - Google Patents

Abstract

PURPOSE:To contrive the improvement of picture quality of the display picture image, by using a material with high specific dielectric constant as the dielectric material for an accumulation condenser connected to a thin film transistor in a semiconductor device which switches the picture element. CONSTITUTION:On a transparent insulator substrate 1 of glass, etc., a thin film transistor TFT constituted of a semiconductor layer 2, a gate insulation layer 3, an insulation layer 4, a semiconductor layer 5, a gate electrode 6, a source electrode 7 and a drain electrode 8 is formed. The accumulation condenser connected to the electrode 8 constituted of a liquid crystal display electrode 9, the dielectric material 10 and the lower electrode 11 is formed. In this constitution, as the material 10, one with high specific dielectric constant e.g. Ti oxide is used. Thereby, as compared with the case of using an Si nitride film with the same thickness as the material 10, the area of 1/25 thereof is enough. Therefore, the area space factor approx. 3% of the picture element area is sufficient enough. Accordingly, an accumulation condenser with small area can be realized resulting in the reduction of faulty conduction thereof and high integration of the picture element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor devices, particularly thin film transistors (hereinafter referred to as FFTs) formed on the surface of a transparent insulating substrate such as glass.
This relates to a semiconductor device that switches pixels such as a liquid crystal display element using TPT (abbreviated as T), and uses grouped titanium as the dielectric material of a storage capacitor connected to TPT.
This design aims to reduce the area of the storage capacitor, reduce conduction defects in the capacitor, and reduce the pixel size to improve the quality of displayed images.

Figure 1 shows an example of one pixel for image display of a liquid crystal display element using conventional TPT, Figure 2 shows an equivalent circuit of one pixel, and Figure 8 shows an example of driving waveforms for liquid crystal image display. It is something.

In FIG. 1, (1) is a transparent insulating substrate made of glass or the like.

(2) is a semiconductor layer made of polycrystalline silicon or amorphous silicon or other semiconductor, (3) is a gate insulating layer, (
4) is an insulating layer such as silicon oxide, (6) is a semiconductor layer doped with impurities at a high concentration, (6) is a gate electrode made of aluminum or the like, (7) is a source electrode, (8) is a drain electrode, (9) is a liquid crystal display electrode made of indium oxide, tin oxide, etc., and Q□ is a dielectric material of a storage capacitor.

a is the lower electrode of the capacitor.

Figure 2 shows an equivalent circuit when pixels of a liquid crystal image display are constructed using such a TPT.
F T , Q3 indicates a liquid crystal. When displaying images on a television or the like, the drive input No. 100 has a waveform with a pulse width of 685 μ8% and a repetition period of 16.7 ms, as shown in FIG. It is necessary to hold this input voltage for 68.5 μs at a certain voltage value or more until the next input. For this purpose, a few pF of 1
It is necessary to install a rectifier capacitor. Q2 in Figure 2 is the horizontal storage capacitor.

In the conventional semiconductor device indicated by No. 114, materials such as silicon oxide and silicon nitride are used as the dielectric material indicated by DI. For example, when using silicon nitride here,
A sputtering method or a plasma CVD method is used, but it is necessary to form a film with a thickness of 1 μm fJ to avoid conduction defects due to pinholes and the like. For example, the required capacity of a capacitor is 29F.
Then, the dielectric constant of silicon nitride εs = 6.8, and the capacitor area is s = a, axlo-(//j', ).For example, if one pixel is 200μ x 200μ, the pixel area s' = 4. Since it is oxto-(*), it occupies more than 80% of the area in the 1-element.

Furthermore, as the area increases, the probability of normal defects due to pinholes and defects 41 increases. On the other hand, by making the pixels even smaller, 1
Even when increasing the degree of pixel integration, there are drawbacks such as being limited by the area of the capacitor.

An object of the present invention is to provide a semiconductor device that eliminates the above-mentioned drawbacks.

A feature of this invention is the use of titanium oxide, which has a high dielectric constant, as the dielectric material of the storage capacitor.

According to this invention, it is possible to realize a small-area storage capacitor that is stable against large temperature changes with a large dielectric constant, and to realize a semiconductor device that can reduce common failures of storage capacitors and enable high integration of pixels. can.

A semiconductor device according to the present invention will be explained below.

FIG. 4 shows one embodiment of the structure of the present invention, and a case will be described in which titanium oxide is used as the dielectric material of the storage capacitor.

The conductivity of the capacitor is 29F, and the relative permittivity of titanium oxide is ε.
5 = 170, and if the titanium oxide film thickness is 1 μm, the capacitor area S = 0.18 (1' (m)), which is 1
/25 area is sufficient. Therefore, for example, one pixel is 200
If μX200μ, pixel area S'=4. OX101(
m) An area occupancy rate of about 8% is sufficient.

The titanium oxide film can be formed by sputtering or electron beam evaporation, and a stable small-area storage capacitor can be realized with little temperature change in the dielectric constant εS. Furthermore, by reducing the area, the probability of normal defects can be drastically reduced, and furthermore, there is no restriction due to the capacitor area when integrating 14 pixels.

The dielectric material is not limited to titanium oxide, but also tantalum oxide (Ta20).
s), aluminum oxide (A1203), and other paraelectric materials having a higher dielectric constant than the silicon nitride film.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional TPT for display switching, FIG. 2 is its equivalent circuit, and FIG. 3 is an example of input signal waveforms and drive waveforms when displaying an image.
FIG. 4 is a sectional view showing one embodiment of the present invention. In the figure, (() is an insulating substrate such as glass, (2) is a semiconductor layer, (3) is a gate insulating layer, (4) is an insulating substrate, (
5> is the high impurity concentration layer, (6) is the gate electrode, (7) is the source single pole, (8) is the drain electrode, (9) is the liquid crystal display electrode, αq is the storage capacitor (body layer, 0υ is the storage The lower electrode of the capacitor, a4 is the storage capacitor, (to) is the liquid crystal no, and α is the TPT. In addition, the same symbols in the figure indicate the same or corresponding parts, respectively. Agent Shin Kuzuno - (1 other person) 1st Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) In a display switching TPT consisting of a thin film transistor (hereinafter referred to as TPT) provided on an insulating substrate such as glass and a thin film capacitor connected to its drain electrode, the capacitor's a'tit
Materials include titanium oxide, tantalum oxide, (Tag, Os
) % Aluminum oxide (Ah Oa) and other materials having a dielectric constant greater than that of silicon nitride film (gs=6J3) are dielectric materials. Device.