Melting Laser Anneal for Epitaxy Source-Drain Contact Resistance
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Solution Overview
Problem
In the formation of FinFETs, the existing methods for annealing epitaxy source/drain regions do not effectively reduce the contact resistance between the source/drain regions and the silicide regions, leading to higher Schottky barrier heights and increased contact resistance.
Innovation Solution
The use of a melting laser anneal process, which molten portions of the epitaxy source/drain regions, resulting in a higher germanium atomic percentage at the surface and reducing the Schottky barrier height and contact resistance, is implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional annealing methods are used for epitaxy source/drain regions, then the annealing process is simple and quick, but the contact resistance between source/drain regions and silicide regions remains high due to ineffective germanium concentration at the interface
Solution Approach 1:
The patent applies parameter changes by utilizing melting laser anneal with specific energy density parameters (0.1-10 J/cm²) and controlled atmosphere parameters (nitrogen or forming gas at 1-1000 sccm flow rates). These parameter adjustments enable germanium to concentrate at the source/drain surface during the annealing process, reducing the Schottky barrier height and contact resistance between source/drain regions and silicide regions, while maintaining process efficiency
Solution Approach 2:
The patent employs phase transitions by inducing localized melting of the epitaxy source/drain regions through laser annealing. The rapid heating and cooling cycle causes the semiconductor material to transition between solid and liquid phases, enabling germanium atoms to redistribute and concentrate at the surface during the molten state, followed by rapid solidification that locks in the improved compositional gradient for lower contact resistance
2Reliability
If higher germanium concentration is achieved at the source/drain surface to reduce Schottky barrier, then contact resistance decreases, but the process requires precise control of molten region depth to avoid damaging underlying structures
Solution Approach 1:
The patent applies local quality by creating a vertical gradient in germanium concentration within the source/drain regions. The melting laser anneal process selectively concentrates germanium at the surface region (0-10 nm depth) while maintaining lower germanium content in the bulk material. This localized compositional modification reduces the Schottky barrier height at the source/drain-silicide interface without requiring uniform germanium distribution throughout the entire source/drain structure, thereby improving contact resistance while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs periodic action through pulsed laser annealing with controlled duty cycles and repetition rates. By delivering energy in discrete pulses rather than continuous illumination, the process enables precise control over the depth and duration of the molten region. The periodic heating and cooling cycles allow germanium to redistribute during each pulse while the substrate returns to solid state between pulses, preventing excessive heat accumulation and damage to underlying structures
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
The melting laser anneal process effectively reduces the contact resistance by concentrating germanium at the surface, eliminating defects, and controlling the molten region depths to improve the interface between source/drain and silicide regions.
Implementation Method 1
performing a melting laser anneal on the second semiconductor region, wherein a first portion of the second semiconductor region is molten during the melting laser anneal
Implementation Method 2
The use of a melting laser anneal process, which molten portions of the epitaxy source/drain regions
Implementation Method 3
resulting in a higher germanium atomic percentage at the surface
Data Source
AI summary
A method includes forming a gate stack over a first semiconductor region, removing a second portion of the first semiconductor region on a side of the gate stack to form a recess, growing a second semiconductor region starting from the recess, implanting the second semiconductor region with an impurity, and performing a melting laser anneal on the second semiconductor region. A first portion of the second semiconductor region is molten during the melting laser anneal, and a second and a third portion of the second semiconductor region on opposite sides of the first portion are un-molten.