Self-Aligned III-V HEMT Terminals for Tighter Gate Spacing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
III-V semiconductor transistors, such as HEMTs and MISHEMTs, face misalignment issues during lithographic patterning, leading to device failures and limited performance enhancement due to separation distance constraints between device terminals.
Innovation Solution
The development of a transistor structure with self-aligned gates and source terminals, featuring a T-shaped gate configuration and asymmetric gate sidewall spacers, which allows for reduced separation distances between the gate and source/drain terminals, improving alignment and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic patterning is used to form transistor terminals, then manufacturing process simplicity is maintained, but misalignment between gate and source/drain terminals occurs leading to device failures
Solution Approach 1:
Gate sidewall spacers are formed on the gate structure before source/drain terminal formation. These spacers pre-establish the precise lateral position and separation distance for the source/drain terminals, ensuring accurate alignment without requiring additional lithographic steps. The spacers are deposited conformally and then etched back to create the desired geometry, which automatically defines the terminal positions relative to the gate.
Solution Approach 2:
Gate sidewall spacers serve as intermediary structures between the gate and source/drain terminals. These spacers mediate the alignment relationship by providing a physical reference that determines the exact position and separation distance of the source/drain terminals from the gate, eliminating direct alignment requirements between the gate and terminals.
2Productivity
If separation distance between gate and source/drain terminals is reduced to improve performance, then on-resistance decreases and switching speed increases, but misalignment and image size variation during lithography become more critical
Solution Approach 1:
The gate sidewall spacers are formed in advance to precisely define the separation distance between the gate and source/drain terminals. By establishing this critical dimension through spacer thickness control rather than lithographic alignment, the process achieves sub-50nm separation distances with high precision, enabling fast switching performance without suffering from lithographic alignment limitations.
3Length of moving object
If device size is scaled down to improve performance, then speed and efficiency increase, but misalignment of terminals during lithographic patterning increases
Solution Approach 1:
Gate sidewall spacers act as intermediary structures that decouple the alignment requirements between the gate and source/drain terminals. The spacers are formed conformally on the gate, ensuring that the source/drain terminal positions are determined by the spacer geometry rather than by lithographic alignment, thereby enabling reliable sub-50nm device scaling.
Solution Approach 2:
The patent replaces the mechanical/lithographic alignment system with a self-aligned system based on conformal spacer deposition. Instead of relying on lithographic pattern alignment between different layers, the critical dimensions are defined by the thickness and geometry of the deposited spacer material, which can be controlled with atomic-layer precision.
Data Source
AI summary
Disclosed are embodiments of a transistor (e.g., a III-V high electron mobility transistor (HEMT), a III-V metal-insulator-semiconductor HEMT (MISHEMT), or the like) that has multiple self-aligned terminals. The self-aligned terminals include a self-aligned gate, a self-aligned source terminal and, optionally, a self-aligned drain terminal. By forming self-aligned terminals during processing, the separation distances between the terminals (e.g., between the gate and source terminal and, optionally, between the gate and drain terminal) can be reduced in order to reduce device size and to improve performance (e.g., to reduce on resistance and increase switching speeds). Also disclosed herein are method embodiments for forming such a transistor.