Amorphous ITO Film Calcium Doping Low-Temperature Crystallization
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Solution Overview
Problem
In the production of ITO films for flat panel displays, existing methods face challenges in maintaining amorphous films without crystallization during sputtering, leading to etching residue and high resistivity issues, and existing solutions like adding zinc to indium oxide result in high resistivity and inferior light transmission.
Innovation Solution
A sputtering target with a composition of indium, tin, and calcium or magnesium is used, with specific atomic ratios, to produce amorphous films that can be crystallized at low temperatures, preventing etching residue and achieving low resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If water is added during sputtering to prevent crystallization, then the film remains amorphous, but particles are generated on the film surface
Solution Approach 1:
The invention extracts and removes water from the sputtering atmosphere, replacing it with a dry atmosphere (nitrogen or oxygen). This eliminates the source of particle generation while maintaining the amorphous state of the film through controlled deposition conditions and subsequent low-temperature annealing
Solution Approach 2:
The invention introduces a mediator substance (nitrogen or oxygen gas) to replace water in the sputtering atmosphere. This intermediary maintains the desired film properties without causing particle generation, serving as a benign alternative to water vapor
2Stability of the object's composition
If water concentration is increased to ensure complete amorphization, then crystallization is prevented, but crystallization temperature becomes extremely high
Solution Approach 1:
The invention changes the compositional parameters of the sputtering atmosphere from water-containing to dry (nitrogen/oxygen), and adjusts the calcium content in the target material. These parameter changes enable amorphous film formation without requiring high water concentrations, and subsequently allow crystallization at low temperatures (100-250°C) rather than extremely high temperatures
3Object-generated harmful factors
If conventional ITO sputtering is performed without water addition, then particles are not generated, but partial crystallization occurs during deposition
Solution Approach 1:
The invention performs preliminary action by adding calcium to the ITO target material before sputtering. This compositional modification prevents crystallization during deposition without requiring water addition, thereby avoiding particle generation while maintaining film amorphousness
Solution Approach 2:
The invention creates a composite material system by incorporating calcium into the ITO target (forming ITO-Ca composite). This composite material exhibits modified deposition characteristics that prevent crystallization during sputtering, allowing particle-free amorphous film formation without water addition
4Stability of the object's composition
If zinc is added to indium oxide to maintain amorphous structure, then crystallization is suppressed, but resistivity increases and light transmission deteriorates
Solution Approach 1:
The invention replaces zinc (which causes long-term performance degradation) with calcium, which achieves the same amorphous structure maintenance function without the harmful side effects. The calcium-based solution acts as a superior alternative that maintains both structural stability and electrical/optical performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for the production of amorphous ITO films that can be efficiently crystallized at lower temperatures, reducing etching residue and achieving low resistivity, thus improving the productivity and performance of ITO films in flat panel displays.
Implementation Method 1
the deposition method of the ITO film in today's industrial production process is mostly based on the so-called sputter deposition method of performing sputtering using an ITO sintered compact as the target
Implementation Method 2
thermal annealing is subsequently performed to crystallize the ITO film
Implementation Method 3
some particles that adhere to the substrate due to sputtering have a high energy level, the temperature of the film becomes so high as to exceed the crystallization temperature due to the transfer of energy after the particles adhere to the substrate
Data Source
AI summary
An amorphous film comprising indium, tin, calcium and oxygen, wherein tin is contained at a ratio of 5 to 15% based on an atomicity ratio of Sn/(In+Sn+Ca) and calcium is contained at a ratio of 0.1 to 2.0% based on an atomicity ratio of Ca/(In+Sn+Ca), and remnant is indium and oxygen, is provided. The film can be crystallized by annealing at 260° C. or lower in which resistivity of the film will be 0.4 mΩcm or less. In this manner, an ITO thin film for use as a display electrode or the like in a flat panel display can be made into an amorphous ITO film by way of sputter deposition without heating the substrate or adding water during deposition. This ITO film can be crystallized by annealing at a low temperature and will have low resistivity. Methods of producing such films and sintered compacts are provided.