Metal Oxide CAC Structure for High-Current Reliable Transistors
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Solution Overview
Problem
Existing semiconductor devices using amorphous oxides for transistors suffer from small on-state current, decreased reliability, and issues such as high subthreshold swing and normally-on characteristics.
Innovation Solution
A metal oxide with a composite structure comprising regions of differing energy gaps and carrier concentrations, specifically an In-M-Zn oxide with a cloud-aligned composite (CAC) structure, is used to enhance transistor performance by improving field-effect mobility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous oxide is used as the active layer material, then the device can be manufactured with simpler processes, but the on-state current is small and reliability is decreased
Solution Approach 1:
The invention uses a composite metal oxide material containing In, Zn, and Ga in specific ratios (In:Zn:Ga = 1:3:1 to 1:9:1) to create a material that combines the ease of amorphous oxide manufacturing with improved electrical characteristics including higher on-state current and enhanced reliability
Solution Approach 2:
The invention optimizes the compositional parameters of the metal oxide by controlling the atomic ratios of In, Zn, and Ga within specific ranges, and by controlling the oxygen content to be 5-15 at%, thereby achieving improved carrier concentration and electrical characteristics while maintaining manufacturing simplicity
2Ease of manufacture
If amorphous oxide is used as the active layer material, then the manufacturing process is simplified, but the on-state current is small
Solution Approach 1:
The composite metal oxide structure with specific In-Zn-Ga composition enables higher carrier concentration and improved on-state current while maintaining the manufacturing advantages of amorphous oxide materials
Solution Approach 2:
By adjusting the atomic ratios of In, Zn, and Ga and controlling oxygen content parameters, the invention optimizes carrier concentration to achieve higher on-state current without complicating the manufacturing process
3Reliability
If In-Zn oxide and In-Ga-Zn oxide are used in a two-layer structure, then field-effect mobility is improved, but subthreshold swing is large and threshold voltage is negative
Solution Approach 1:
The invention creates regions with different carrier concentrations within the active layer - a first region with lower carrier concentration and a second region with higher carrier concentration - to simultaneously achieve good field-effect mobility and proper switching characteristics with positive threshold voltage
Solution Approach 2:
The composite In-Zn-Ga oxide structure with controlled composition ratios enables optimization of both field-effect mobility and switching characteristics by distributing different elements strategically to control carrier concentration profiles
Data Source
AI summary
A novel metal oxide is provided. The metal oxide has a plurality of energy gaps, and includes a first region having a high energy level of a conduction band minimum and a second region having an energy level of a conduction band minimum lower than that of the first region. The second region comprises more carriers than the first region. A difference between the energy level of the conduction band minimum of the first region and the energy level of the conduction band minimum of the second region is 0.2 eV or more. The energy gap of the first region is greater than or equal to 3.3 eV and less than or equal to 4.0 eV and the energy gap of the second region is greater than or equal to 2.2 eV and less than or equal to 2.9 eV.