Laser Melt Processing Metal Interconnects Resistivity
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Solution Overview
Problem
Increasing integration demands in semiconductor manufacturing require improved electrical performance of metal interconnects, which existing technologies have not adequately addressed despite the shift from aluminum to copper.
Innovation Solution
A method and system using a P-polarized continuous-wave or quasi-continuous wave laser to selectively melt and recrystallize metal features on semiconductor wafers, with controlled irradiance and dwell time, to reduce resistivity, while avoiding melting of non-metal features with higher melting temperatures, utilizing an F-θ scanning system and acousto-optical modulator for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional processing methods are used for metal interconnects, then the manufacturing process is simple, but the electrical performance (resistivity) cannot be sufficiently improved
Solution Approach 1:
The patent replaces conventional thermal processing (heating) with laser irradiation to achieve metal interconnect processing. The laser provides localized energy delivery that melts and recrystallizes the metal to reduce resistivity, substituting mechanical/thermal systems with an optical field-based system for more precise control of electrical performance
Solution Approach 2:
The patent changes the physical state of the metal interconnect through controlled laser heating, transitioning the metal through melting and rapid recrystallization phases. By controlling parameters such as laser power, scan speed, and focus depth, the process achieves optimal grain structure formation that reduces resistivity while maintaining interconnect integrity
2Reliability
If higher laser power is used to reduce resistivity, then electrical performance improves, but non-metal features may be damaged
Solution Approach 1:
The patent applies laser energy locally to specific regions of the metal interconnect while avoiding adjacent non-metal features. By controlling the laser spot size, scan path, and focus depth, the process delivers energy only where needed to reduce metal resistivity without exposing dielectric or semiconductor structures to damaging temperatures
Solution Approach 2:
The patent uses pulsed or modulated laser delivery rather than continuous irradiation. The periodic application of laser energy allows brief intervals for heat dissipation, preventing cumulative thermal damage to non-metal features while still achieving the necessary melting and recrystallization of the metal interconnect to improve electrical performance
3Manufacturing precision
If the laser spot dwell time is increased to ensure complete melting, then metal recrystallization is improved, but the processing speed decreases
Solution Approach 1:
The patent employs dynamic control of the laser scanning system, adjusting scan speed, spot size, and power in real-time based on the specific features being processed. This dynamic approach allows optimized dwell time for complete melting and recrystallization in critical areas while maintaining higher speeds in less critical regions, balancing quality and throughput
Solution Approach 2:
The patent uses preliminary heating or pre-processing steps before the main laser treatment. By pre-heating the metal interconnect or preparing the surrounding structure, the process reduces the required dwell time for complete melting and recrystallization, thereby increasing processing speed while maintaining recrystallization quality
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 method effectively reduces the resistivity of metal interconnects by enlarging crystal grain structures, enhancing electrical performance without damaging non-metal features, thereby improving the performance of metal interconnects in semiconductor manufacturing.
Implementation Method 1
directing a P-polarized laser beam at the metal feature at an incident angle that is within 2 degrees of a Brewster angle for the metal feature
Implementation Method 2
scanning the focused laser spot over the IC structures to irradiate both the at least one metal feature and the at least one non-metal feature such that the at least one metal feature melts and recrystallizes
Implementation Method 3
the at least one metal feature melts and recrystallizes while the at least one non-metal feature does not melt
Implementation Method 4
the metal layer locally melts and recrystallizes so that the metal layer has a second resistivity that is less than the first resistivity
Implementation Method 5
forming a focus spot from a laser beam emitted by a continuous-wave or quasi-continuous wave laser
Implementation Method 6
directing a P-polarized laser beam at the metal feature at an incident angle that is within 2 degrees of a Brewster angle for the metal feature
Data Source
AI summary
Methods disclosed herein include scanning a focus spot formed by a laser beam over either a metal layer or IC structures that include a metal and a non-metal. The focus spot is scanned over a scan path that includes scan path segments that partially overlap. The focus spot has an irradiance and a dwell time selected to locally melt the metal layer or locally melt the metal of the IC structures without melting the non-metal. This results in rapid melting and recrystallization of the metal, which decreases the resistivity of the metal and results in improved performance of the IC chips being fabricated. Also disclosed is an example laser melt system for carrying out methods disclosed herein is also disclosed.