IGZO Sputtering Target with Bixbyite Structure
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Solution Overview
Problem
Current sputtering targets for oxide semiconductor thin films face issues with high resistance, low sintering density, and abnormal discharge, leading to unstable film formation and reduced mobility in thin film transistors, which are inadequate for high-resolution displays and fast-switching applications.
Innovation Solution
A sputtering target with a sintered body comprising Ga- or Al-doped indium oxide and a positive tetravalent metal, having a bixbyite crystal structure, with specific atomic ratios and bulk resistance, is used, along with a method involving controlled heating and sintering to achieve high relative density and low resistance, preventing abnormal discharge during film deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If sintering is conducted in an oxidizing atmosphere to increase sintering density, then relative density is improved, but target resistance increases and requires additional reduction treatment
Solution Approach 1:
The patent changes the sintering atmosphere parameter from oxidizing to reducing atmosphere, and adjusts the sintering temperature to 900-1100°C. This parameter change allows simultaneous achievement of high sintering density (97% or more) and low target resistance without requiring additional reduction treatment steps.
Solution Approach 2:
The patent uses a composite target material comprising InGaZnO4 (IGZO) as the base material with controlled doping of Ga and Zn. This composite composition enables the material to achieve both high density and low resistance when sintered in a reducing atmosphere, resolving the contradiction between density improvement and resistance increase.
2Productivity
If sputtering target is used for long period of time, then productivity is improved, but abnormal discharge occurs and film properties change
Solution Approach 1:
The patent optimizes the sintering parameters (temperature: 900-1100°C, atmosphere: reducing, time: 10-50 hours) to create a target with uniform microstructure and controlled crystal grain size. This parameter optimization ensures stable plasma discharge and consistent film properties even during prolonged sputtering operations, preventing abnormal discharge.
Solution Approach 2:
The patent performs preliminary sintering treatment under carefully controlled reducing atmosphere conditions before the sputtering process begins. This preliminary action creates a target with optimal microstructure and uniform composition, which prevents abnormal discharge and maintains discharge stability throughout extended film formation periods.
3Reliability
If crystalline silicon-based thin film is used to achieve high mobility, then field effect mobility is improved, but production cost and complexity increase
Solution Approach 1:
The patent changes the material composition parameter by using InGaZnO4 (IGZO) oxide semiconductor instead of crystalline silicon. Combined with sintering in a reducing atmosphere at 900-1100°C, this parameter change achieves high field effect mobility (2 cm²/Vs or more) while avoiding the complex laser annealing processes and high-temperature treatments required for crystalline silicon, thereby reducing production complexity and cost.
Solution Approach 2:
The patent applies local quality control by precisely controlling the Ga and Zn doping ratios in the IGZO target (Ga: 1-10 at%, Zn: 3-20 at%). This local compositional control enables the material to exhibit high mobility characteristics while maintaining ease of manufacture through conventional sintering processes, avoiding the need for complex crystallization equipment.
4Ease of manufacture
If amorphous silicon is used to enable large-area display production, then ease of manufacture is improved, but field effect mobility is insufficient for high-resolution displays
Solution Approach 1:
The patent uses a composite InGaZnO4 (IGZO) oxide semiconductor material that combines the advantages of both amorphous and crystalline materials. The target can be sintered to achieve high density while maintaining a microstructure that enables high field effect mobility (2 cm²/Vs or more). This composite material approach allows large-area film formation similar to amorphous silicon while achieving the high mobility required for high-resolution displays.
Solution Approach 2:
The patent changes the material phase parameter by controlling the sintering process to achieve a fine-grained microstructure with high density (97% or more) in the IGZO target. This parameter control enables the material to exhibit high mobility characteristics while maintaining ease of large-area manufacture through conventional sintering processes, avoiding the need for complex crystallization equipment.
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 solution provides a high-density, low-resistant sputtering target that enables the formation of high-quality oxide semiconductor thin films with improved field effect mobility, suitable for high-resolution displays and efficient, cost-effective production.
Implementation Method 1
a thin film transistor using an oxide semiconductor film formed of indium oxide, zinc oxide and gallium oxide has been studied. In general, an oxide semiconductor thin film is formed by sputtering using a target (sputtering target) composed of an oxide sintered body.
Implementation Method 2
If the target is used for a long period of time, problems arise that the properties of the resulting thin film or the film-forming speed largely change; abnormal discharge due to abnormal growth of InGaZnO4 or In2Ga2ZnO7 occurs; particles are frequently generated during film formation or the like.
Implementation Method 3
In order to reduce the resistance of the target, a reduction treatment at a high temperature is required to be conducted after sintering.
Data Source
AI summary
A sputtering target including a sintered body:the sintered body including:indium oxide doped with Ga or indium oxide doped with Al, anda positive tetravalent metal in an amount of exceeding 100 at. ppm and 1100 at. ppm or less relative to the total of Ga and indium, or Al and indium,the crystal structure of the sintered body substantially including a bixbyite structure of indium oxide.