Recrystallized Nanosheet Source/Drains for Lower Defects and Resistance
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Solution Overview
Problem
Defects such as (111) stacking faults and high resistance due to insufficient dopant activation in the source/drain materials of nanosheet devices lead to on-current versus off-current degradation, which are not effectively addressed by existing process conditions.
Innovation Solution
The implementation of solid-phase epitaxy regrowth (SPER) to recrystallize amorphous source/drain materials, combined with amorphization via ion implantation, to recover strain and enhance dopant activation, is performed before or during the formation of the contact etch stop layer, interlayer dielectric, and replacement gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional source/drain formation processes are used, then manufacturing is simpler, but defects such as (111) stacking faults and high resistance due to insufficient dopant activation occur
Solution Approach 1:
The source/drain regions are amorphized via ion implantation before dopant implantation, creating a preliminary amorphous state that enables superior dopant activation. This preliminary action of amorphization allows subsequent dopants to be more effectively incorporated into the crystal lattice during SPER, resolving the dopant activation problem while maintaining process integration.
Solution Approach 2:
The invention changes the physical state parameter of the source/drain material from crystalline to amorphous through ion implantation, then transitions it back to crystalline through solid-phase epitaxy regrowth. This parameter change enables improved dopant activation by altering the material's atomic structure to be more receptive to dopant incorporation.
2Reliability
If existing process conditions are used, then processing is simpler, but on-current versus off-current degradation occurs due to defects
Solution Approach 1:
The invention integrates multiple functions into continuous process steps: amorphization via ion implantation, dopant incorporation, and crystal regrowth through SPER all occur in an integrated sequence without interrupting the source/drain formation process. This continuous action ensures consistent defect reduction and performance improvement while maintaining manufacturing efficiency.
Solution Approach 2:
The source/drain material undergoes a phase transition from crystalline to amorphous state through ion implantation, then transitions back from amorphous to crystalline state through solid-phase epitaxy regrowth. This controlled phase transition eliminates defects like (111) stacking faults and improves the electrical performance by ensuring proper crystal orientation for carrier transport.
3Reliability
If source/drain materials are not recrystallized, then processing time is shorter, but strain recovery is insufficient leading to degraded electrical performance
Solution Approach 1:
The invention merges the dopant activation process with the crystal regrowth process through solid-phase epitaxy regrowth. The SPER simultaneously activates dopants and recovers strain in the source/drain regions by regrowing the crystalline structure, achieving multiple objectives in a single integrated process step rather than separate sequential steps.
Solution Approach 2:
The SPER process changes the temperature parameter to enable solid-phase epitaxy regrowth, transitioning the amorphous source/drain material back to a crystalline state. This parameter change (temperature increase) drives the phase transition and simultaneously achieves dopant activation and strain recovery, improving electrical performance without requiring additional process steps.
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 significantly reduces defects, improves strain recovery, and enhances electrical performance by increasing dopant activation, thereby improving Ion-Ioff performance and source/drain resistance in nanosheet devices.
Implementation Method 1
forming an amorphous semiconductor layer by performing an ion implantation on the semiconductor layer
Implementation Method 2
forming a source/drain by performing solid-phase epitaxy regrowth on the amorphous semiconductor layer
Implementation Method 3
forming a recrystallized source/drain by annealing the amorphous semiconductor layer
Data Source
AI summary
A method includes: forming a stack of nanostructures over a substrate; forming a source/drain opening adjacent the stack of nanostructures; forming a semiconductor layer in the source/drain opening; forming an amorphous semiconductor layer by performing an ion implantation on the semiconductor layer; and forming a recrystallized source/drain by annealing the amorphous semiconductor layer.