JPH04338731A - active device - Google Patents

Abstract

PURPOSE:To improve the adhesive strength between a 1st wiring layer and a ferroelectric layer and to prevent the layers from peeling off at a device active part by forming an insulating layer, the 1st wiring part, the ferroelectric conductor layer, and a 2nd wiring layer on a glass substrate in order. CONSTITUTION:An insulating layer 2 is formed on a glass substrate 1, and an ITO film is formed thereupon and patterned to form a 1st wiring layer 3. Then a ferroelectric layer 4 is formed thereupon and an Al layer is formed thereupon and patterned to form a 2nd wiring layer 5. A dielectric film 4 is formed not directly on the glass substrate 1, but on the insulating layer 2, so the adhesive strength is increased. Therefore, even when vibration is caused by stress generated between the 1st wiring layer 3 and 2nd wiring layer 5 by the application of an AC voltage, sufficient adhesive strength is obtained at the peripheral part of the device active part 6, not to mention the device active part 6, thereby eliminating the possibility that the dielectric layer 4 is peeled off.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The active device of the present invention is
The present invention relates to a thin film laminated structure for applying a voltage to a capacitive layer, for example, for use in liquid crystal displays.

0002

2. Description of the Related Art Conventionally, an active device as shown in FIG. 2 has been known. The structure of FIG. 2 is as follows. Only a first wiring layer 3 made of ITO is provided on a glass substrate 1, and a ferroelectric layer 4 made of a VDF/TrFE (vinylidene fluoride/trifluoroethylene) copolymer is provided thereon. A second wiring layer 5 made of Al is provided thereon.

0003

However, the above-mentioned prior art active devices have the following problems. That is, in order to operate as an active device, it is necessary to generate polarization in the ferroelectric layer 4 and to reverse the polarization. For this purpose, an alternating current voltage is applied between the first wiring layer 3 and the second wiring layer 5. However, since the ferroelectric layer 4 has piezoelectricity, applying a voltage generates a stress T expressed by the following equation. Therefore, reversing the voltage will correspondingly cause oscillations in the device active part 6 in FIG. 2-(b).

0004

[Formula 1] T=eV T: stress e: piezoelectric constant V: applied voltage This vibration causes the ferroelectric layer 4 to peel off from the first wiring layer 3 in the device active portion 6. However, the vibration is not limited to only the device active part 6, but also extends to the peripheral parts of the device active part 6, and also causes vibrations between ITO and V.
The adhesive strength between glass and VD is higher than that of DF/TrFE copolymer.
Since the adhesive strength of F/TrFE copolymer is lower,
The peeling extends over a fairly wide area centering on the device active part 6, and as a result, the distance between the first wiring layer 3 and the second wiring layer 5 increases, and a voltage sufficient to cause polarization in the ferroelectric layer 4 is applied. It becomes impossible to apply voltage.

Furthermore, since this delamination increases over time, the characteristics of the device also deteriorate over time.

[0006] The present invention is intended to overcome these problems, and its purpose is to improve the adhesive strength between the first wiring layer 3 and the ferroelectric layer 4 compared to conventional devices. It is an object of the present invention to provide a device in which peeling is prevented in the active part 6 of the device, and its life and reliability are improved.

[0007]

[Means for Solving the Problems] The active device of the present invention includes an insulating layer formed on a glass substrate, a first wiring layer formed on the insulating layer, and a strong conductive layer formed on the first wiring layer. It is characterized by having a dielectric layer and a second wiring layer formed on the ferroelectric layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. 1-(a) and (b) are diagrams showing an active device according to the present invention, in which FIG. 1-(a) is a top view, and FIG. 1-(b) is a top view, and FIG. FIG.

The structure of the embodiment shown in FIG. 1 is as follows. That is, an insulating layer 2 made of silicon nitride is provided on a glass substrate 1, a first wiring layer 3 made of ITO is provided on it, and a VDF/TrFE (vinylidene fluoride/trifluoroethylene) layer is provided thereon. A ferroelectric layer 4 made of a copolymer is provided, and a second wiring layer 5 made of Al is provided thereon.

Next, a method for manufacturing an active device will be briefly explained with reference to FIG. First, the glass substrate 1 is cleaned,
On top of that, 2
An insulating layer 2 having a thickness of 00 to 20,000 Å is formed. On top of that, 20
An ITO layer with a thickness of 0 to 9000 Å is formed. The formed ITO layer is patterned to form a first wiring layer 3 made of ITO. On top of that, a mixture of the VDF/TrFE copolymer and an organic solvent (ethers containing dioxane, ketones, or highly polar solvents such as amines) is applied using a spin coater method, and a ferroelectric layer of several thousand Å is applied. A body layer 4 is formed. Next, after drying and baking it, an Al layer with a thickness of several thousand angstroms is formed thereon by vapor deposition or sputtering. The formed Al layer is patterned to form a second wiring layer 5 made of Al.

According to the device structure according to the prior art, a ferroelectric layer 4 made of a VDF/TrFE copolymer is formed on the glass substrate 1 except on the first wiring layer 3 made of ITO.
is formed directly. However, glass and VDF/TrF
The adhesive strength of the E copolymer is very low compared to the adhesive strength of ITO and VDF/TrFE copolymers. Therefore, when vibration occurs in the device active portion 6 due to the stress T described above, the vibration first causes separation between the glass substrate 1 and the ferroelectric layer 4 in the peripheral portion of the device active portion 6. Since this peeling increases with the passage of time, it eventually affects the device active portion 6, causing the ITO and VDF/TrFE copolymer of the device active portion 6 to peel off. However, according to the structure of the device according to the present invention, the ferroelectric layer 4 is not in direct contact with the glass substrate 1, but is formed on the insulating layer 2 made of silicon nitride. The adhesive strength between silicon nitride and the VDF/TrFE copolymer is much greater than the adhesive strength between the glass substrate 1 and the VDF/TrFE copolymer. Therefore, even when vibration occurs in the device active portion 6 due to the stress T described above, sufficient adhesive strength is obtained not only in the device active portion 6 but also in the peripheral portion of the device active portion 6, and there is no fear that the ferroelectric layer 4 will peel off. disappears.

By forming the insulating layer 2 on the glass substrate 1 as described above, the adhesion strength is greatly improved by several hundred to several thousand times, so the risk of peeling is drastically reduced, and the first wiring layer 3 and second
It is possible to prevent the distance between the wiring layers 5 from increasing. therefore,
Since a voltage sufficient to polarize the ferroelectric layer 4 can be applied for a long period of time, it has become possible to manufacture devices with extremely long life and high reliability.

According to the experimental results, the adhesive strength between silicon nitride and VDF/TrFE copolymer is the same as that between glass and VDF/TrFE copolymer.
The adhesive strength is tens to hundreds of times higher than that of the /TrFE copolymer. However, according to the structure of the device according to the present invention, the adhesive strength between the silicon nitride and the VDF/TrFE copolymer in the peripheral area of the device active part 6 is extremely high and the effect is tremendous, so that peeling in the device active part 6 is not possible. It has become clear that this can be suppressed as much as possible, and the lifespan of the device can be improved by several hundred to several thousand times.

Furthermore, the ferroelectric layer 4 must be prevented from being contaminated with impurities as much as possible, and the insulating layer 2 protects the impurities from the glass substrate 1 from diffusing into the ferroelectric layer 3. It has the effect of

Furthermore, in order to actually use this device as a liquid crystal display, an alignment film (for example, polyimide) is formed on the second wiring layer 5 and rubbed, but the insulating layer 2 remains strong even during rubbing. This has the effect of preventing peeling of the dielectric layer 4 and greatly contributing to improving the alignment state of the liquid crystal.

Note that the insulating layer 2 does not necessarily need to be formed over the entire surface, and the insulating layer 2 below the first wiring layer 3 may be omitted. The method for forming the insulating layer 2 is not limited to the sputtering method or the vapor deposition method, and another method such as the CVD method may be used. The insulating layer 2 is not limited to silicon nitride, and T
Other transparent insulating materials such as aOx or VDF/TrF
A ferroelectric material such as E copolymer may also be used. The first wiring layer 3 is not limited to ITO, and may be other transparent electrodes. The second wiring layer 5 is not limited to Al, and may be made of other metals. The ferroelectric layer 4 does not need to be limited to VDF/TrFE copolymer, and may be PVDF (polyvinylidene fluoride).
, organic ferroelectric materials such as VDF/TeFE (vinylidene fluoride/tetrafluoroethylene) copolymer, vinylidene cyanide/vinyl acetate copolymer, or BaTiO
An inorganic ferroelectric material such as No. 3 may also be used. Ferroelectric layer 4
does not necessarily have to be formed on the entire surface, and may be formed only on the device active portion 6. The first wiring layer 3 may be made of Al, and the second wiring layer 5 may be made of ITO.

Next, an embodiment of a liquid crystal display using the present invention will be explained based on the drawings. 3-(a) and (b) are diagrams showing a liquid crystal display using the present invention, and FIG. 3-(a)
) is a top view, and figure-(b) is a sectional view taken along line XX in figure-(a).

The structure of the embodiment shown in FIG. 3 is as follows. That is, a substrate on which a third wiring layer 7 made of ITO is provided on a counter glass substrate 8 is provided to face the active device shown in FIG. 1 with an interval of 1 to 100 μm. Both substrates hold the liquid crystal.

[0019]

Effects of the Invention As described above, the device structure of the present invention greatly reduces the risk of peeling between thin films compared to conventional devices, resulting in a device with significantly improved lifespan and reliability. can be provided.

[Brief explanation of drawings]

FIG. 1 (a) is a top view showing an active device according to the present invention. (b) is a sectional view taken along the line XX in FIG. 1-(a).

FIG. 2(a) is a top view showing a conventional active device. (b) is a sectional view taken along the line XX in FIG. 2-(a).

FIG. 3(a) is a top view showing a liquid crystal display using an active device according to the present invention. (b) is a sectional view taken along the line XX in FIG. 3-(a).

[Explanation of symbols]

1 Glass substrate 2 Insulating layer 3 First wiring layer 4 Ferroelectric layer 5 Second wiring layer 6 Device active part 7 Third wiring layer 8 Opposing glass substrate

Claims (1)

[Claims] 1. An insulating layer formed on a glass substrate, a first wiring layer formed on the insulating layer, a ferroelectric layer formed on the first wiring layer, and an insulating layer formed on the ferroelectric layer. An active device comprising a second wiring layer formed thereon.