Amphoteric Doping for Low-Damage III-V FinFET Tip Regions
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Solution Overview
Problem
III-V compound semiconductor materials face challenges in achieving low device resistance and avoiding short channel effects due to difficulties in doping, as conventional ion implantation techniques induce damage and poor dopant activation in these materials.
Innovation Solution
A non-silicon finFET with a monocrystalline III-V semiconductor material uses amphoteric dopants that preferentially activate as electron donors or acceptors, allowing for precise control of lightly doped tip and sub-tip regions, reducing off-state leakage and improving transistor performance by leveraging differences in amphoterism between the fin and sub-fin materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion implantation is used to dope III-V materials, then doping can be achieved, but detrimental damage is induced in the III-V compound semiconductor materials that is not readily annealed out
Solution Approach 1:
The patent replaces conventional ion implantation (mechanical/physical bombardment) with a chemical vapor deposition process where dopants are introduced through gas-phase reactions. This substitution eliminates the mechanical damage caused by ion bombardment while achieving precise dopant incorporation in the III-V semiconductor materials through controlled chemical deposition and thermal diffusion.
2Quantity of substance
If ion implantation is used for doping, then dopant introduction is possible, but dopant activation is poor in III-V materials
Solution Approach 1:
The patent changes the fundamental parameters of the doping process by using chemical vapor deposition followed by thermal diffusion instead of ion implantation. The thermal diffusion process, conducted at elevated temperatures in a controlled atmosphere, enables complete dopant activation by allowing dopant atoms to naturally diffuse into lattice sites, achieving both high dopant concentration and full activation in III-V materials.
3Loss of energy
If the channel region is heavily doped to reduce resistance, then low device resistance is achieved, but short channel effects increase
Solution Approach 1:
The patent applies local quality by creating distinct doping regions with different dopant concentrations and types. The channel region is kept lightly doped to maintain low short channel effects, while source and drain regions are heavily doped to reduce resistance. This spatial variation in doping quality is achieved through selective area deposition and diffusion processes, allowing each region to be optimized for its specific function.
4Manufacturing precision
If amphoteric dopants are used with self-aligned deposition, then precise dopant location is achieved, but process complexity increases
Solution Approach 1:
The patent employs self-service through self-aligned deposition processes where the dopant-containing precursor is deposited only on exposed surfaces that are not covered by gate or spacer structures. The deposition process automatically confines dopants to the correct regions (source/drain or channel) based on the existing mask pattern, eliminating the need for additional alignment steps and reducing overall process complexity despite the use of amphoteric dopants.
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
This approach enables low-damage, precise doping of III-V materials, reducing off-state leakage and short channel effects, thereby enhancing the performance of III-V finFETs by maintaining a lightly doped channel region and heavily doped source/drain regions.
Implementation Method 1
The tip and sub-tip regions are extrinsically doped with an amphoteric dopant that preferentially activates as an electron donor or acceptor
Implementation Method 2
diffusion, deposition, or other low-damage surface-based doping techniques
Data Source
AI summary
Monolithic finFETs including a majority carrier channel in a first III-V compound semiconductor material disposed on a second III-V compound semiconductor. While a mask, such as a sacrificial gate stack, is covering the channel region, a source of an amphoteric dopant is deposited over exposed fin sidewalls and diffused into the first III-V compound semiconductor material. The amphoteric dopant preferentially activates as a donor within the first III-V material and an acceptor with the second III-V material, providing transistor tip doping with a p-n junction between the first and second III-V materials. A lateral spacer is deposited to cover the tip portion of the fin. Source/drain regions in regions of the fin not covered by the mask or spacer electrically couple to the channel through the tip region. The channel mask is replaced with a gate stack.