Germanium Source/Drain Doping for Lower FinFET Contact Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As the semiconductor industry advances to nanometer technology process nodes, FinFET devices face challenges in reducing contact resistance due to scaling issues, particularly in achieving high surface dopant concentration and strain in source/drain regions for improved device performance.
Innovation Solution
The implementation of a nanosecond-scale implantation process and melting anneal process to achieve high surface dopant concentration and retrograde dopant profiles in epitaxial source/drain structures, utilizing germanium concentration and amorphousness to preferentially melt the source/drain structures, thereby bringing dopants and germanium to the surface, reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional doping processes are used in scaled FinFET devices, then manufacturing simplicity is maintained, but contact resistance remains high due to insufficient surface dopant concentration
Solution Approach 1:
The patent changes the doping parameters by implementing a two-stage process: first forming a high concentration dopant region at the surface through selective implantation, then forming a lower concentration bulk region. This parameter differentiation resolves the contradiction by achieving both high surface dopant concentration for low contact resistance and controlled bulk concentration for proper device operation.
Solution Approach 2:
The patent applies local quality by creating spatially varying dopant concentrations within the source/drain region. The surface region receives high dopant concentration to reduce contact resistance, while the bulk region maintains lower concentration. This local differentiation allows each region to optimize its function, resolving the contradiction between contact resistance and manufacturing precision.
2Reliability
If higher temperature processes are applied to increase dopant activation, then dopant activation is improved, but thermal budget increases causing damage to other device structures
Solution Approach 1:
The patent performs preliminary doping actions at lower temperatures during the epitaxial growth process, incorporating dopants into the source/drain regions before subsequent high-temperature gate formation. This preliminary doping achieves sufficient dopant activation without exposing the entire device to high temperatures that would damage gate dielectrics or cause dopant diffusion, thus resolving the contradiction between dopant activation and thermal budget.
Solution Approach 2:
The patent skips the conventional high-temperature dopant activation step by incorporating dopants during low-temperature epitaxial growth. This rushing through of the doping process at lower temperatures achieves the necessary dopant concentration without incurring the thermal budget costs of traditional high-temperature activation, resolving the contradiction between dopant activation and temperature control.
3Reliability
If source/drain structures are melted to bring dopants to surface, then contact resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent employs self-service by utilizing the eutectic melting phenomenon where the dopant-germanium combination naturally creates a low-melting-point region that melts selectively during standard thermal processing. This self-directed melting brings dopants to the surface without requiring external melting equipment or complex process control, reducing fabrication complexity while achieving low contact resistance.
Solution Approach 2:
The patent replaces mechanical or external thermal melting systems with a chemically-driven eutectic melting mechanism. The dopant-germanium interaction creates spontaneous localized melting at the intended locations during standard annealing, eliminating the need for complex external melting apparatus or precise thermal field control, thus reducing manufacturing complexity while achieving the desired dopant surface redistribution.
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 effectively reduces contact resistance and enhances device performance by achieving high surface dopant and germanium concentrations, minimizing dopant diffusion, and allowing for higher temperature processes without increasing the thermal budget.
Implementation Method 1
heating the source/drain structure to liquidize and convert at least the amorphous region into a crystalline region
Implementation Method 2
heating the source/drain structure to liquidize and convert at least the amorphous region into a crystalline region
Implementation Method 3
implanting a first dopant into the first region of the source/drain structure to form an amorphous region
Data Source
AI summary
Embodiments disclosed herein relate to using an implantation process and a melting anneal process performed on a nanosecond scale to achieve a high surface concentration (surface pile up) dopant profile and a retrograde dopant profile simultaneously. In an embodiment, a method includes forming a source/drain structure in an active area on a substrate, the source/drain structure including a first region comprising germanium, implanting a first dopant into the first region of the source/drain structure to form an amorphous region in at least the first region of the source/drain structure, implanting a second dopant into the amorphous region containing the first dopant, and heating the source/drain structure to liquidize and convert at least the amorphous region into a crystalline region, the crystalline region containing the first dopant and the second dopant.