Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Patent
1996-11-29
1999-02-02
Gorgos, Kathryn
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
205188, 205189, 205224, 205229, 427377, 427404, 4274192, 349 49, C23C 2800, C25D 550, B05D 302, G02F 1135
Patent
active
058672346
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/JP96/00903 filed Apr. 1, 1996.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a manufacturing method of a MIM (Metal-Insulator-Metal) nonlinear device, and to an MIM nonlinear device and a liquid crystal display device.
2. Related Art
Generally, active matrix liquid crystal display devices comprise two substrates, between which liquid crystal is filled. On one substrate, a switching device is provided for each pixel region to form a matrix array, and on the other substrate, a color filter is formed. The orientation of the liquid crystal is controlled in each pixel region, thereby displaying prescribed information. As the switching device, a three-terminal device, such as a TFT (Thin Film Transistor), or a two-terminal device, such as MIM nonlinear device, are typically used. A MIM nonlinear device is advantageous in responding to the demand for a large-sized screen and reduced manufacturing cost. Moreover, a MIM nonlinear device has another advantage of eliminating crossover short-circuit between the scan line and the data line because scan lines and data lines are separately provided on different substrates. That is, scan lines are provided on the substrate having a matrix array formed thereon while data lines are provided on the other substrate.
FIG. 14 shows an example of the conventional active matrix liquid crystal display device 100 using an MIM nonlinear device, in which a matrix is formed by a plurality of scan lines 74 connected to the scan line driving circuit 72, and a plurality of data lines 78 connected to the data line driving circuit 76. Pixel region 80 is formed in each element of the matrix. Pixel region 80 includes a MIM nonlinear device 50 connected to the data line 78 at one end, and a liquid crystal display element 60 connected between the MIM nonlinear device 50 and the scan line 74. Liquid crystal display element 60 is driven based on the differential voltage between the signal applied to the scan line 74 and the signal applied to the data line 78. If the threshold voltage of liquid crystal element 60 is represented as (Vb), and the threshold voltage of MIM nonlinear device 50 is represented as (Vth), and if the voltage at both terminals of the liquid crystal display element 60, which turns on the liquid crystal display element 60, is represented as (Vb+.DELTA.V), then the liquid crystal display element 60 is in the ON state when the differential voltage is (Vb+Vth+.DELTA.V) during a selected period, while the liquid crystal display element 60 is in the OFF state when the differential voltage is (Vb+Vth). During a non-selected period, the differential voltage is set to less than (Vth) to maintain the state decided during the selected period.
FIG. 15 is a cross-sectional view of the active matrix liquid crystal display device 100 using an MIM nonlinear device. Liquid crystal layer 40 is positioned between the electrode substrates 10 and 30. Electrode substrate 10 comprises a transparent board 12, MIM nonlinear devices 50 formed on the transparent board 12, and pixel electrodes 22 connected to the corresponding MIM nonlinear device 50. MIM nonlinear device 50 is composed of a Ta electrode layer 16 formed on the transparent electrode 12, a Ta.sub.2 O.sub.5 film 18 formed on the Ta electrode 16, and a Cr electrode layer 20 formed on the Ta.sub.2 O.sub.5 film 18. Ta.sub.2 O.sub.5 film 18 is formed on the surface of the Ta electrode layer 16 through anodic oxidation of the Ta electrode layer 16 so that the film thickness becomes uniform without generating pin holes. (See Japanese Patent Application Laid-Opens 5-297389 and 5-313207.)
With the conventional method, MIM nonlinear device 50 having such a structure is manufactured as follows: forming a tantalum oxide layer 14 with a thickness of about 1000 .ANG. by depositing a tantalum layer on the transparent substrate 12 by sputtering, followed by heat oxidation; depositing a tantalum layer up to about 3000 .ANG. by sputtering, and patterning the tantalum layer to
Inoue Takashi
Seki Takumi
Takano Yasushi
Yoshimizu Yasuhiro
Gorgos Kathryn
Seiko Epson Corporation
Wong Edna
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