Amorphous ITO Sputtering Using AC Bias to Prevent Grain Boundaries
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Solution Overview
Problem
Existing PVD methods for depositing indium tin oxide (ITO) films on substrates result in columnar crystal structures with grain boundaries, which can lead to etchant penetration and undesirable compounds, and low-temperature deposition to avoid grain boundaries increases resistivity, necessitating additional processes that increase manufacturing time and cost.
Innovation Solution
A method and apparatus using AC bias during PVD to sputter indium tin oxide onto substrates, disrupting crystal formation by bombarding the film with argon atoms, thereby forming an amorphous ITO film without the need for additional processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PVD processes are used to deposit ITO films, then the films can be formed on substrates, but the films develop columnar crystal structure with grain boundaries that allow etchant penetration
Solution Approach 1:
The patent applies AC bias to the substrate during PVD deposition, changing the electrical parameter of the deposition process. This AC bias creates ion bombardment that disrupts crystal formation, transforming the film structure from columnar with grain boundaries to amorphous without grain boundaries, thereby preventing etchant penetration while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses periodic AC bias applied to the substrate during deposition. The alternating current creates periodic ion bombardment that continuously disrupts crystal nucleation and growth, preventing the formation of columnar structures with grain boundaries and producing an amorphous film structure instead
2Shape
If low substrate temperature is used during PVD deposition, then amorphous ITO films without grain boundaries can be formed, but the films exhibit higher resistivity
Solution Approach 1:
The patent changes the electrical parameter by applying AC bias to the substrate, which creates ion bombardment heating and enhanced adatom mobility. This allows the formation of amorphous ITO films with suitable electrical resistivity even at low substrate temperatures, eliminating the need for high-temperature annealing processes
Solution Approach 2:
The patent replaces the thermal mechanism (high substrate temperature) with an electrical mechanism (AC bias applied field). Instead of using thermal energy to control film structure and properties, the AC bias uses electrical energy to create ion bombardment that achieves amorphous structure formation with appropriate resistivity at lower temperatures
3Reliability
If additional processes are performed to recover resistivity of low-temperature deposited ITO films, then electrical performance improves, but manufacturing time and cost increase
Solution Approach 1:
The patent performs preliminary action by applying AC bias during the deposition process itself to ensure the ITO film is formed with suitable electrical resistivity from the start. This preliminary control of resistivity during deposition eliminates the need for subsequent annealing or resistivity-recovery processes, reducing manufacturing steps and improving productivity
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 produces amorphous ITO films with suitable resistivity for transparent electrodes, reducing manufacturing time and cost by eliminating the need for post-deposition treatments.
Implementation Method 1
flowing a plasma-forming gas into the process volume
Implementation Method 2
sputtering the indium tin oxide onto the substrate
Implementation Method 3
sputtering the indium tin oxide onto the substrate while applying AC bias to the substrate
Data Source
AI summary
Methods and apparatus for processing a substrate in a process chamber include: positioning a substrate on a substrate support in a process volume so that the substrate is opposite a sputter target comprising indium tin oxide; flowing a plasma-forming gas into the process volume; and sputtering the indium tin oxide onto the substrate while applying AC bias to the substrate.