DD253512A1 - METHOD FOR STRUCTURING TRANSPARENT CONDUCTIVE METAL OXIDE LAYERS - Google Patents

Abstract

The invention relates to a process for producing transparent, conductive metal oxide structures on glass, ceramic, semiconductor and organic polymer substrates, in particular of doped indium oxide, tin dioxide and cadmium oxide structures and of structures of mixed compounds of these oxides and is used in the optical system. and microelectronics. In the method according to the invention, the transparent conductive oxide layer on cold substrate, preferably at temperatures below 100C, preferably by reactive Zerstaeuben applied by means of a magnetron / Plasmatronanlage, then covered in a known manner and the uncovered areas of the layer with a verduennten acid, preferably at Concentrations below 1% or a saline solution dissolved.

Description

Field of application of the invention

The invention relates to a process for producing transparent, conductive metal oxide structures on glass, ceramic, semiconductor and organic polymer substrates, in particular doped indium oxide-tin dioxide and cadmium oxide structures and structures of mixed compounds of these oxides and is used in the opto and Microelectronics, for example the production of liquid crystal and electroluminescent displays, of components of the optical fiber communication, radiation emitters and detectors and radiation sensors.

Characteristic of the known technical solutions

One known method of forming transparent, conductive metal oxide structures on foreign substrates is to apply the oxide material to the substrate by vacuum evaporation or other deposition techniques using masks in which the structure to be formed is recessed. However, the structures obtained by such methods do not meet the requirements of the electronics industry with regard to the quality of the structure boundaries, in particular with small web widths of the structure and also with regard to the economy.

The presently preferred technologies for producing transparent, conductive oxide structures, which are predominantly used for the production of liquid crystal displays, electroluminescent displays and other liquid crystal component variants, consists in the fact that the substrate is first coated over the entire surface with the oxide, using mainly tin-doped indium oxide, ITO and the coating is usually carried out by electron beam vacuum evaporation of the oxide or reactive cathode jet sputtering, starting from an indium / tin alloy in the presence of oxygen. Thereafter, the structure to be produced is covered by means of a photoresist or screen printing technique and the uncovered areas of the oxide are dissolved by wet processes using suitable etching media.

After the subsequent removal of the paint protective layer, the desired structure of the oxide layer then remains on the substrate surface.

The relatively low reactivity of the oxide layers thus produced requires the use of concentrated etching media. Thus, as suitable etchant for the transparent metal oxide layers, in particular for ITO, hydrochloric acid (US Pat. No. 4,336,295), hydrogen iodide (DE-OS 3,447,702) and also other acid solutions (DE-OS 3,047,218) have been proposed. From the aspect of a long service life of the etchant, the use of mixtures of concentrated hydrochloric acid and concentrated iron chloride solution in particular has proven successful (DE-OS 2635245) and enforced in the production of small-area liquid crystal displays.

For the structuring of tin dioxide-containing layers of greater thickness, etchants with suitable, reducing additives or with the addition of complexing agents have been proposed to avoid edge beads and pittings in the edge regions

or else the entire surface application of a thin metal layer which is readily soluble in acids, which accelerates the etching process and avoids the edge precipitation during etching.

A disadvantage of these processes is the necessity to use highly concentrated acids (over 20%) or concentrated ferric chloride solutions and as a result a high chemical consumption, a corrosive effect on the plants, environmental pollution and also an impairment of the quality of the structures due to underetching phenomena. By using electrochemical structuring variants, it becomes possible to work at low acid concentrations

(WP 234038), but these methods are primarily suitable for large-area displays and in particular for the production of matrix displays, their use is difficult and makes high demands on the technology in connection with the contacting.

Object of the invention

The aim of the invention is to reduce the environmental impact in the production of transparent conductive metal oxide structures and to increase the quality of the layers, in particular with regard to underestimation phenomena.

Explanation of the essence of the invention

It is an object of the invention to provide a method for producing transparent, conductive metal oxide structures, in particular ITD structures for displays, which makes it possible to use etching media of low acid concentrations or iron chloride concentrations and to carry out the etching without additional heating at room temperature. According to the invention, this object is achieved in that the layer of transparent, conductive oxide on cold substrate, at temperatures below 100 ⁰ C, is applied, preferably by means of a magnetron Plasmatron system by reactive sputtering, the desired structure is then covered, for example with suitable paints by photolithography or screen printing without the layer is brought to temperatures above 100 ⁰ C and the uncovered portions of the layer then with a dilute acid, preferably at acid concentrations below 1% or an acidic salt are dissolved. After the subsequent removal of the lacquer, the desired layer structure is present and its quality in terms of conductivity and transparency is further improved by a subsequent annealing step or annealing in connection with further technological stages of display production. The deposited on cold substrate layers of transparent, conductive oxides have more than 10OOmal higher reactivity to acidic media than those on hot substrate over 200 ⁰ C, deposited layers or as annealed layers. According to the invention technologically convenient etch rates of about 20nm / min without additional heat supply to the etching medium, achieved at temperatures between 25-40 ⁰ C with the following etchants:

- 0.01 to 0.1 mol / l of aqueous solutions of strong inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, wherein the use of a 5 · 10 ^-2 mol / l hydrochloric acid - is preferably - corresponding to about 0.2% hydrochloric acid

- oxalic acid in the concentration range of 2 x 10 ^-3 to 10 ^-2 mol / l, wherein a 0.05 to 0.1% strength solution of oxalic acid is preferred.

Salts of cations which are strong Lewis acids, the use of FeCl3 solutions in the concentration range of 0.5 to 2% and / or AICI ₃ solutions in the concentration range of 1 to 10% being preferred.

Mixtures of FeCl ₃ solutions and / or AlCl ₃ solutions with mineral acids or organic acids in the above-mentioned concentration range.

According to the invention it is to improve the service life, multiple use over a long period of time, strong mineral acids iog concentration range, oxalic acid or FeC ^ or AICI _{3 of} the above concentrations with concentrated neutral salt or weakly acidic salt solutions, preferably NH ₄ Cl, NaCl or To mix MgCl2 solutions. The method according to the invention is preferably used for transparent, conductive tin- or fluorine-doped indium oxide films on glass, quartz or semiconductor substrates, preferably Si or AmB _v semiconductors. However, this method is also suitable for the structuring of cadmium stannate and tin dioxide layers.

embodiments

The invention will be explained in more detail below with reference to examples:

example 1

By means of a magnetron / plasmatron system was prepared using an alloy target In / Sn (10% Sn) by reactive sputtering with an Ar / O ₂ mixture (p _Ar = 1,2Pa, p _to t = 1,4Pa) and an energy of generates 0.5 kW at a substrate temperature of 4O ⁰ C ITO layers having a thickness of 40 nm on glass and silicon substrates. The structures were covered by the screen printing process. The resolution of the non-covered regions of the structure was carried out with a 0.2% hydrochloric acid at 3O ⁰ C and a trigger rate of 20 nm / min.

With sulfuric, nitric and perchloric acid of the same concentration, the etching rate was only slightly lower.

After about 1.5 to 2 minutes, the ITO layers were dissolved. The screen printing ink was removed from the structure and after washing and annealing at 300 ⁰ C for 15 minutes is the structure with transparency values of the ITO to 95%, and surface resistances of 200 ohms before.

Further examples:

The transparent, conductive layers were produced analogously to example 1. The covering of the desired structures is carried out not only by the screen printing technology but also by the photolithographic process. Etch rates to 20 nm / min at 30 ⁰ C are achieved with the following etchants:

0.03% oxalic acid

0.5% aqueous FeCl ₃ solution

- 5% AICl3 solution

- 1 mol / l ammonium chloride with 0.1 mol / l acetic acid

- 1 mol / l ammonium chloride with 0.5% FeCl ₃ solution

- 1 mol / l ammonium chloride with 0.5% FeCl ₃

- 1 mol / l ammonium chloride with 2% AICI ₃

The etching process of the layers produced according to Example 1 is complete after only 2 s with the etching solution previously used in technology, 45% strength FeCl ₃ solution and concentrated hydrochloric acid mixed with 2: 1, and speeds of about 20 nm / min become 500 times greater Dilution of this solution received.

Claims (4)

claims: A process for structuring transparent, conductive metal oxide layers, for example indium oxide, tin dioxide or cadmium oxide layers or mixtures of these layers, preferably In / Sn mixed oxides, on foreign substrates, for example glass, quartz or semiconductors, preferably Si or Am B _v semiconductors characterized in that the transparent conductive oxide layer on cold substrate, preferably at temperatures below 100 ° C, preferably by reactive sputtering by means of a magnetron / Plasmatronanlage is applied, then the desired structure is covered in a known manner, without the temperature of 100 ⁰ C exceeded and the uncovered areas of the layer are dissolved with a dilute acid, preferably at concentrations below 1%, or a saline solution whose cation component is a strong Lewis acid. 2. The method according to claim 1, characterized in that as dilute acids 0.01 to 0.1 mol / i aqueous solutions of strong inorganic acids, for example hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, preferably 0.2% hydrochloric acid solution, or 2 10 ~ ³ to 10 ~ ² mol / l aqueous oxalic acid solutions, preferably 0.05 to 0.1% oxalic acid solution at temperatures between 20 and 40 ° C and a dissolution rate of 20nm / min are used. 3. The method according to claim 1, characterized in that as salt solutions whose cation component is a strong Lewis acid, preferably 0.5 to 2% FeCl ₃ and / or 1 to 10% AICI ₃ solutions at temperatures between 20 and 40 ⁰ C and a dissolution rate of 20 nm / min are used. 4. The method according to claim 1, 2 and 3, characterized in that acids or Lewis acids are used in low concentration in the presence of neutral or weakly acidic salts, for example NH ₄ Cl or MgCl ₂ in the concentration range of 0.1 to 2mol / l.