JPS62164025A - Production of electrooptic device - Google Patents

Abstract

PURPOSE:To form an MIM element which has a god nonlinear characteristic and has no variance without requiring fine alignment by forming the 1st electrode to a tapered shape and dry etching the insulating film on said electrode so as to have a reverse tapered shape. CONSTITUTION:The 1st electrode 2 of the MIM element is formed to the tapered shape on a substrate 1 and the thick insulating film 3 is formed thereto to the reverse tapered shape by dry etching; further the thin insulating film 4 is formed by anodic oxidation method on the wall surface of the 1st electrode 2. The 2nd electrodes 5', 5 of the MIM element are formed on the thick insulating film 3 and the thin insulating film 4 in succession thereto and transparent picture element electrodes 6', 6 are formed thereon. The 2nd electrodes 5', 5 and the transparent picture element electrodes 6', 6 are so formed that these electrodes are cut at the step parts with the thin insulating film 4 by the poor step covering as the thick insulating film 3 is formed to the reverse taper shape. The capacity component and resistance component contributing to the deterioration of the nonlinear characteristic are thereby separated and the MIM element having the excellent nonlinear characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an electro-optical device in which a lateral MIM element is coupled to each pixel.

[Conventional technology]

As a conventional manufacturing method of an electro-optical device combining MIM elements, S. MOrOzumi, etal Japan
Display 83. P.

404-407.1983, and the 1-stroke cross section is shown in No. 67. A first electrode 2 and an insulator 3 of an MIM element are formed on a substrate 1 and processed into a predetermined shape. Next, after forming a transparent pixel electrode 6 and processing it into a predetermined shape, an insulator 4 is formed on the side of the first electrode by an anodic oxidation method. Next, in order to make electrical contact between the second electrode 5 of the MIM element and the transparent pixel electrode 6, and to improve the nonlinear characteristics of the MIM element, the overlapping portion 15 with the first electrode 2 of the MIM element is made as small as possible. It was formed in a similar manner.

[Problem that the invention seeks to solve]

However, in the conventional manufacturing method, in order to obtain nonlinear characteristics of the M process 1'J element without deteriorating the display quality of the electro-optical device, fine photolithography technology is used especially when forming the second electrode 5 of the MIM element. This requires fine alignment, which causes variations in nonlinear characteristics, and lowers yield, resulting in lower display quality and higher costs.

The present invention is intended to solve these problems, and its purpose is to provide a method for manufacturing an electro-optical device with high display quality by forming an MIM element with good nonlinear characteristics and no variation without requiring 7-line alignment. Our goal is to provide the following.

[Means for solving problems]

The method for manufacturing an electro-optical device according to the present invention is characterized in that the first electrode constituting the MIM element is made into a tapered shape, and the insulating film formed on the first electrode is dry etched so as to have an inverted tapered shape. shall be.

Furthermore, after forming the MIM element, is it possible to irradiate the element surface with ultraviolet light? Features.

[Effect]

A schematic diagram 2 of an MIM device according to the invention is shown in FIG. 1st
1-(a) is a sectional view, and FIG. 1-(b) is a plan view 2.

The first electrode 2 of the MIM element is tapered on the substrate 1,
A thick insulating film 3 is formed in an inverted tapered shape, and a thin insulating film 4 is further formed on the wall surface of the first electrode 2 by anodic oxidation. Next, M is deposited on the thick insulating film 3 and the thin insulating film 4.
second electrode 5' of the mm element; 5. Transparent pixel electrodes 6', 6 are formed thereon. Here, the second electrode 5
', 5 and transparent pixel electrodes 6', 6 are formed by thick insulating film 3.
Since it has an inverted tapered shape, the step force balayage is poor, so it is cut at the step between it and the thin insulating film 4.

The operation of the above MIM element will be explained using FIG. FIG. 2 shows an equivalent circuit (solid line) of one pixel of an electro-optical device combined with the MIM element of the present invention in comparison with a conventional equivalent circuit (solid line and broken line combined). 7 is the capacitance of the insulator 3, and 8 is the resistance of the insulator 5. 9 is the capacitance of the MIM element, and 10 is M
This is the nonlinear resistance of the IM resistor. Further, 11 is the capacitance of the liquid crystal layer, and 12 is the resistance of the liquid crystal layer. When driving the liquid crystal layer with the MUM resistor, the nonlinear resistance of the MIM resistor is 10
It is necessary that the non-linearity of the liquid crystal layer is good, and that the capacitance 9 of the MIM resistor is sufficiently small compared to the capacitance ff111 of the liquid crystal layer. However, the conventional MIM
The capacitance 7 of the insulator 3 is connected in parallel with the capacitance 9 of the M-string. In other words, the equivalent capacity of the MIM capacitance becomes large, and cannot be made sufficiently smaller than the capacitance 9 of the liquid crystal layer, thereby deteriorating the display quality of the electro-optical device. Further, a resistor 8 of an insulator 3 is connected in parallel with the nonlinear resistor 10 of the MIM element. The nonlinear resistor 10 of the MIM system has a characteristic that it has a high resistance when a low voltage is applied, and a low resistance when a high voltage is applied. For this reason, when the resistors 8 of the insulator 3 are connected in parallel, the resistance value of the MIM element becomes small when a low voltage is applied, which deteriorates the display quality of the electro-optical device. However, according to the present invention, M
There is no capacitance connected in parallel to the IM element. Therefore, the capacitance connected in series with the capacitance 11 of the liquid crystal layer is only the capacitance fjkg of the MIM element, which makes the capacitance 9 of the MIM element sufficiently smaller than the capacitance 11 of the liquid crystal layer. This makes it possible to improve the display quality of the electro-optical device. Also, there is no resistor connected in parallel to the MIM element. Therefore, the feature that the nonlinear resistor 10 of the MIM element exhibits high resistance when a low voltage is applied and low resistance when a high voltage is applied can be fully utilized. Moreover, the second electrode 5 and transparent electrode 6 of the MIM element are
Since there is only the side surface of the first electrode 2 of the MIM element on which the insulator 4 of the MIM element is formed, there is no need for stacking and otolithography techniques, and an MIM element with excellent nonlinear characteristics can be obtained.

However, even in the MIM element formed in this way, if there are variations in the interface state between the electrode 2 and the insulating film 4 of the broom 1 and between the insulating film 4 and the second ILE electrode 5, variations will occur in the nonlinear characteristics of the MIM 2 elements. Put it away. This will be explained using FIG. 4. Figure 4 shows the voltage-current characteristics when using Ta for the first electrode, anodized Ta, 05 for the insulating film, and Or for the second electrode, with positive polarity on the Ta side and negative polarity on the Cr side. This is a Poole-Frenkel plot when a positive electric field is applied. As shown in Figure 4-(α), if there are variations in the interface state as described above, the MIM chord Ae B*
Variations occur in the voltage-current characteristics of c. This is thought to be because the state of electrons contributing to conduction changes depending on the interface state. In order to suppress the above-mentioned variations, it is sufficient to eliminate the variations in the interface state, but at present,
Since it is very difficult to control the interface shape and nodding, MIM
It is conceivable to correct it after forming the element. Generally, a method of annealing at a cavity temperature (200°C to 500°C) in a specific atmosphere is used, but this method has the disadvantage that the effect is small and that the overall characteristics will shift significantly if annealing is performed too much. Ta. Therefore, as a result of intensive research, the present inventor found that MI
It was found that the variation could be improved by irradiating ultraviolet light after forming the M element.

Figure 4-(l) is the pressure-current characteristic after irradiating the MIM element in Figure 4-(α) with ultraviolet light.As is clear from the figure, there is almost no variation. In this case, it is possible to deal with variations ranging from local variations to overall variations, and it is also excellent in workability because it is not affected by the irradiation time as long as the intensity is kept constant.

The two inventions described above? By using them together, MIM elements with excellent nonlinear characteristics can be stably obtained without variation.

〔Example〕

FIG. 3 shows an embodiment of the process according to the invention. First, the first electrode 2 (Ta) of the MIM element is formed on the substrate 1,
Then, a thick insulating film 3 (Ta, O,) is formed by anodic oxidation.
form. Next, the photoresist 14 is processed into a predetermined pattern by the G-near oxidation method (α). By using a zero-order dry etching device (0DE manufactured by Tokuyo Seisakusho) and using a mixed gas of OF and 0□ as an etchant, the MIM element is The first electrode 2 (Ta) is made into a tapered shape, and the insulating film 3 (Ta, O,) thereon is etched into a reverse tapered shape (b). By changing the composition of the etchant, the Taber shape can be controlled.
a20. ) both become forward taper and 0. If there is little, both tend to become reverse taper. Therefore, in order to obtain the shape of the present invention, it is necessary to optimize and precisely control the flow rate of 0□. Next, after peeling off the photoresist 14, the insulating film 4 is again formed on the wall surface of the first electrode 2 (Ta) of the MIM element by anodic oxidation (c).

Next, the second electrode 5 (C!r) of the MIM element and the transparent image
The E electrode 6 (TO) 3 is formed on the entire surface of the substrate by vacuum evaporation or sputtering, and the photoresist 14 is processed into a predetermined pattern again by the 7-otolithography method (d). At this time, the shape of the thick insulating film 3 deteriorates step force coverage, and the electrode is formed by being cut at the step between the thick insulating film 3 and the wide insulating film 4.

Next, the second electrode 5 (Or) and transparent pixel electrode 6 (To) of the MIM element are etched into a predetermined pattern, and the photoresist 14 is peeled off.Finally, ultraviolet light 15 is applied to eliminate variations in the MIM element. irradiate (i.

A cross section 3 of a TN type reflective liquid crystal display device manufactured using the MIM element according to the present invention is shown in FIG. Traditional MIM
The display quality has been significantly improved compared to liquid crystal display devices using elements.

〔Effect of the invention〕

As described above, in the present invention, the first electrode constituting the MIM element is made into a tapered shape, and the insulating film formed on the first electrode is made into an inverted tapered shape. M with excellent nonlinear characteristics because it can separate
An IM element is obtained. Further, after forming the MIM element, by irradiating it with ultraviolet light, variations in nonlinear characteristics can be eliminated. Thereby, the display quality of the electro-optical device combined with the MIM element can be significantly improved.

[Brief explanation of drawings]

FIG. 1-(α)*Cb) shows a cross-sectional view and a plan view of one pixel of an electro-optical device according to the present invention. 3 shows the process of the second device. A pool 7 Lenkel plot of the voltage-current characteristics of a 4 mW MIM device is shown. FIG. 5 shows a cross-sectional view of one pixel of a liquid crystal display device using an MIM element according to the present invention. FIG. 6 shows a sectional view of one pixel of a conventional 'JL optical device. 1.1'...Substrate 2...First electrode 3 of MIM resistor...
Insulator 4...Insulator 5.5' of MIM element...Second electrode 6.6' of MIM element
...Transparent electrode 7...Capacitance of insulator 38...Resistance of insulator 39...Capacitance of MIM element 10...・Nonlinear resistance 11 of the MIM element...Capacitance 12 of the liquid crystal layer...Resistance 13 of the liquid crystal layer...The first electrode 2 and the second electrode of the MIM element Overlapping portion 14 of electrode 5...visitype photoresist 15...
...Ultraviolet light 17...MIM element length 18...MIM element section 19...Liquid crystal 20...Polarizing plate 21...・Reflector or above Applicant Seiko Epson Co., Ltd. 2, MIX plaster V4 Lee 3, insulator (G) (b) 1st prisoner 2nd figure r π (Il) Tori 4th figure 2, Shida-Mine Give Me 11 Den O-

Claims (2)

[Claims] (1) Row electrodes are formed on one substrate and column electrodes are formed on the other substrate, which face each other with a liquid crystal interposed therebetween.
In an electro-optical device formed by combining R-Metal) elements, a first electrode constituting the MIM element is formed into a tapered shape, and an insulating film formed on the first electrode is formed into an inverted tapered shape. A method for manufacturing a featured electro-optical device. (2) The method for manufacturing an electro-optical device according to claim 1, characterized in that after forming the MIM element, ultraviolet light is irradiated onto the element surface.