JPH03114268A - Thin film diode - Google Patents

Abstract

PURPOSE:To enable the title thin film diode to be easily manufactured in a compact manufacturing facility by a method wherein a cuprous oxide layer to be electrolytically separated forming a Schottky junction with the first electrode layer as well as the second electrode layer forming ohmic junction are formed. CONSTITUTION:A substrate 10 with an electroless plated layer formed thereon is immersed in an electrolyte using the electroless plated layer as a cathode as well as a coper electrode as an anode and then the substrate 10 is supplied with direct current for one minute to produce a cuprous oxide on the electroless plated layer. Next, a resist layer is formed while any needless part of the cuprous oxide layer 12 is etched away to form the pattern of the cuprous oxide layer 12. Furthermore, another resist layer is formed on the specified part of the non-electrolytic plated layer while the copper of the electroless plated layer of the needless part and a nickel are simultaneously etched away to form another pattern of a scanning electrode 11 (copper).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to liquid crystals, electroluminescence (EL),
The present invention relates to a thin film diode that is suitably used in an active matrix display device that includes display elements such as electrochromism (EC).

[Conventional technology 1] In matrix display devices using display elements such as liquid crystal, electroluminescence (EL), and electrochromism (EC), the number of pixels is increased without reducing the contrast ratio of the display panel, and it is possible to As a method for realizing a display panel, an active matrix method, in which each pixel is provided with a switching element such as a thin film transistor element or diode element, is attracting attention.

In particular, since the manufacturing process of diode elements is simpler than that of transistor elements, it is thought that high yields can be expected.

Conventionally, diode elements have been made using hydrogenated amorphous silicon (Japanese Unexamined Patent Publication No. 138515/1983) as a semiconductor layer.
, hydrogenated amorphous silicon carbide (JP-A-60)
-50962), polysilicon (Japanese Unexamined Patent Publication No. 58-7
9280) and the like are known.

[Problems to be Solved by the Invention] However, diode elements using semiconductor layers such as hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, or polysilicon require sputtering or CVD methods to manufacture these semiconductor layers. It is necessary to use a vacuum film forming apparatus.

Therefore, there is a problem in that large-scale manufacturing equipment is required to mass-produce active matrix substrates on which a large number of thin film diodes are formed, and there is also the disadvantage of increased manufacturing costs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thin film diode that does not require the use of special equipment such as a vacuum film forming apparatus and can be easily manufactured using small manufacturing equipment.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the present invention provides a first electrode made of a copper layer formed on a substrate by electroless plating, and an electrode on the first electrode. A cuprous oxide layer that is analyzed and forms a Schottky junction with the first electrode layer, and a second electrode layer that is formed on the cuprous oxide layer and forms an ohmic contact with the cuprous oxide layer. The present invention provides a thin film diode having the following.

Examples of materials for the substrate forming the thin film diode of the present invention include insulating materials such as glass, epoxy resin, polyester, polyurethane, and polyimide, and nickel, silver, chromium, indium tin oxide, indium oxide, etc. Examples include substrates on which conductive layers such as tin oxide and tin oxide-antimony are formed.

The thickness of the first copper electrode layer formed on the substrate by electroless plating of the present invention is usually 0.1 to 5 μm; if this electrode layer is too thin, defects are likely to occur; if it is too thick, the Peeling of layers is likely to occur. Note that the first electrode layer can also be formed in a pattern after forming the semiconductor layer.

The thickness of the cuprous oxide layer formed as a semiconductor layer by electrolytic deposition on the first copper electrode layer is usually 0.01 to 10 μm,
The thickness is preferably 0.1 to 5 μm; if this semiconductor layer is too thin, defects are likely to occur, and if it is too thick, the resistance of the diode becomes too thick.

The electrolytic solution used when forming cuprous oxide by electrolytic deposition includes, for example, ■ anhydrous cupric sulfate or cupric sulfate pentate 0.1 to 1 mol/2, ■ calcium hydroxide, hydroxide. Sodium, ammonia.

An aqueous metal complex solution in which 0.1 to 10 mol/2 of a basic compound such as triethylamine and 0.1 to 5 mol/β of a ligand compound capable of forming a complex with copper in a basic solution are dissolved in water. can be mentioned.

Examples of the ligand compounds used in this electrolytic solution include aspartic acid, lactic acid, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, iminoniacetic acid, malonic acid, nitrilotriacetic acid, or sodium of these ligand compounds. The ligand compound is not particularly limited as long as a salt or the like can be used and a metal complex soluble in a basic aqueous solution can be formed.

The voltage applied between the cathode and the anode is usually 0.01 to 1
Ov(DC), preferably 0.05-IV(DC)
The current density of the current flowing through the electrode bath for depositing cuprous oxide is usually 0.01 to 50 mA/c, preferably 1 to 20 mA/cm. If the current density is too low, oxidation Cupric (Cub) tends to precipitate (on the other hand, if the temperature is too high, copper tends to precipitate).

Further, the temperature of the electrolytic solution may be any temperature as long as the electrolytic solution does not solidify or boil, but is preferably in the range of 30 to 90°C. If the electrolyte temperature is too low,
Cupric oxide tends to precipitate.

By the electrolytic deposition method under the conditions described above, a resistivity of 1
A semiconductor layer made of cuprous oxide having a thickness of 01 to 10 6 Ω·cm is formed.

The second electrode layer formed on the semiconductor layer is a film made of a conductive material, such as chromium, nickel, silver, gold,
A conductive film made of carbon or the like can be mentioned.

The thickness of these second electrode layers is usually 0.1 to 5 μm.
If this electrode layer is too thin, defects are likely to occur (and if it is too thick, the electrode layer is likely to peel off).

The second electrode layer is made of, for example, chromium or nickel.

It can be obtained by forming a conductive film of silver, gold, carbon, etc. by a method such as sputtering, vapor deposition, or electroless plating, and then patterning it by etching.
It can also be formed by applying a paste in which metal particles such as silver or gold are dispersed in a binder in a pattern by printing or the like, and then baking the paste. When the electrode layer is formed of a carbon film, it can be obtained by applying a paste in which carbon particles are dispersed in a binder in a pattern by printing or the like, and drying it.

In order for the diode element to have rectifying properties and function as a switch element, it is necessary to form a Schottky junction with the copper layer that is the first electrode and the cuprous oxide layer that is the semiconductor layer. When forming a cuprous oxide layer by electrolytic deposition, a good Schottky junction can be formed by forming the first electrode layer by electroless plating.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

An active matrix substrate for a liquid crystal display on which the thin film diode of the present invention shown in FIG. 1 was formed was manufactured in the following manner.

1(A) is a plan view, and FIG. 1(B) is a sectional view taken along line B-8' in FIG. 1(A).

(1) A nickel layer 11A was formed on a silicon oxide coated glass substrate 10 having dimensions of 1 mm x 50 mm x 60 mm by electroless nickel plating. The electroless plating method is a known method. That is, after cleaning the glass (2) substrate 1O and immersing it in an aqueous palladium chloride solution to activate it, a plating bath consisting of nickel sulfate 2 log #2, sodium citrate 5 g/2 and lactic acid 3 g #/β was applied. After plating, it was washed with water. In this way, a 0.2 μm thick nickel plating layer was obtained. Furthermore, a copper layer was formed on this nickel layer by a conventional electroless plating method. Copper sulfate 5g/ρ.

A plating bath consisting of 25 g/l of Rochelle salt, formalin log/I2 and 7 g of sodium hydroxide #2 was used. After cleaning the glass substrate with electroless nickel plating,
After being immersed in an aqueous pararam chloride solution for activation, it was immersed in the above plating bath for plating, and then washed with water. In this way, a copper plating layer with a thickness of 0.15 μm was obtained.

On the other hand, using a glass container, cupric sulfate pentahydrate 99.8
g, sodium hydroxide 158.2g and lactic acid 270g
．． Electrolyte solution containing copper complex 100 g dissolved in pure water
0 ml was prepared.

(3) (4) The substrate on which the electroless plating layer was formed in (1) above is immersed in the electrolyte solution prepared in this way, and the electroless plating layer is used as a cathode, and a separate copper electrode is placed as an anode in the electrolyte solution. When a direct current was applied for 1 minute at an electrolyte temperature of 60°C and a current density of 10 mA/cm on the cathode side, cuprous oxide with a thickness of about 1 μm was generated on the electroless plating layer. .

Next, a resist layer is formed by lithography on the portion of the formed cuprous oxide layer that will become the diode, and unnecessary portions of the cuprous oxide layer are removed by etching using an aqueous solution of 17 g/9 ammonia as an etching agent. A pattern of the cuprous oxide layer 12 was formed.

Furthermore, a resist layer was formed on a predetermined portion of the electroless plating layer by lithography, and 50 g/β of ferric chloride was formed.
Then, the substrate was immersed in an aqueous solution containing 50 g of hydrochloric acid/I2, and unnecessary portions of the copper and nickel of the electroless plating layer were simultaneously etched away to form a pattern for the scanning electrodes 11.

(5) Next, as the insulating layer 13, a pattern of cyclized polyisoprene (trade name: ClR702, manufactured by Japan Synthetic Rubber ■) was formed by photolithography.

(6) Next, screen print the ITO coating liquid,
A pattern of transparent electrodes 14 was formed.

(7) Finally, screen print the silver paste and
A matrix substrate having diode elements shown in FIG. 1 was obtained.

When the IV characteristics of the diode elements of the obtained matrix substrate were measured, the rectification characteristics shown by the solid line in FIG. 2 were confirmed.

[Comparative Example] An active matrix substrate was manufactured under the same conditions as in the example except that the copper layer in the example was formed by vapor deposition instead of electroless plating. When the ■-■ characteristics of the diode element of the obtained matrix substrate were measured, the rectification characteristics shown by the dotted line in FIG. 2 were observed. It was clearly confirmed that the diode element of the present invention has a small reverse current and has excellent characteristics as a switch element.

[Effects of the Invention] As explained above, the thin film diode of the present invention does not require the use of a vacuum film forming apparatus for forming the semiconductor layer, and can be easily manufactured using small-sized manufacturing equipment. Furthermore, since manufacturing costs can be reduced, there is also the advantage that an inexpensive active matrix type display device can be provided.

[Brief explanation of drawings]

FIG. 1(A) is a plan view of an active matrix substrate for a liquid crystal display device using a thin film diode according to the present invention, FIG. 1(B) is a cross-sectional view thereof, and FIG. It is an IV characteristic curve which shows the rectification characteristic of the thin film diode element of a comparative example. 11... Scanning electrode, 12... Cuprous oxide, 13... Insulating layer, 14... Transparent electrode, 15... Electrode. Figure 1

Claims (1)

[Claims] (1) A first electrode made of a copper layer formed on a substrate by electroless plating, and an oxidized first electrode electrolytically deposited on the first electrode to form a Schottky junction with the first electrode layer. A thin film diode comprising: a copper layer; and a second electrode layer formed on the cuprous oxide layer and forming an ohmic contact with the cuprous oxide layer.