Location-Specific Laser Annealing for Interconnect Grain Control
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Solution Overview
Problem
Fine grains with varied orientations on interconnects lead to lower electromigration lifetimes and higher resistance due to electron scattering, which existing techniques have failed to effectively address, especially in advanced metallization schemes using high melting point metals like cobalt and tungsten.
Innovation Solution
The method involves using electron backscatter diffraction (EBSD) to detect and selectively treat grain orientations in overburden layers through localized laser annealing, promoting or discouraging specific grain growth to improve microstructural recrystallization and reduce resistance in interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional annealing techniques are used on interconnects, then the overall grain structure is uniformly treated, but fine grains with varied orientations persist leading to lower electromigration lifetimes and higher resistance
Solution Approach 1:
The patent applies localized laser annealing to specific regions of the interconnect based on grain orientation maps obtained from EBSD. By selectively heating only those areas with undesirable grain orientations, the method promotes grain growth and reorientation in targeted zones while leaving other areas unchanged, thereby achieving local microstructure optimization that improves electromigration lifetime and reduces resistance.
Solution Approach 2:
The patent performs EBSD mapping and grain orientation analysis before the annealing process to identify which specific regions require treatment. This preliminary characterization allows the subsequent laser annealing to be precisely targeted at areas with fine grains and unfavorable orientations, ensuring that the annealing action is applied only where needed to improve electromigration properties.
2Strength
If advanced metallization schemes with high melting point metals like cobalt and tungsten are used, then interconnect durability is improved, but large grain microstructures become difficult to achieve leading to increased resistance
Solution Approach 1:
The patent utilizes the unique properties of high melting point metals (cobalt, tungsten) by applying localized laser heating that temporarily raises the temperature in treated regions above the metal's melting point. This localized parameter change enables grain growth and reorientation in treated areas without requiring bulk heating, thereby achieving large grain microstructures in advanced metallization schemes that would otherwise be difficult to form.
Solution Approach 2:
The patent divides the interconnect into multiple regions based on grain orientation characteristics, treating only those segments with undesirable properties through localized laser annealing. This segmentation approach allows the high melting point metals to maintain their durability benefits while achieving improved grain structures in specific critical regions, thereby reducing resistance without compromising overall interconnect strength.
3Manufacturing precision
If selective laser annealing is applied to specific grain orientations, then grain growth control is improved, but process complexity increases due to the need for EBSD mapping and location-specific treatment
Solution Approach 1:
The patent integrates EBSD mapping and laser annealing into a unified process flow that can be applied to any interconnect metallization scheme (copper, cobalt, tungsten, etc.). The same methodology and equipment platform serve multiple functions: characterizing grain orientations, identifying treatment regions, and executing selective annealing, thereby reducing overall process complexity despite the advanced capabilities employed.
Solution Approach 2:
The EBSD mapping process automatically generates the grain orientation data needed to guide the subsequent laser annealing treatment. The system uses its own characterization capability to inform its processing actions, eliminating the need for separate manual analysis and treatment planning steps. This self-service approach simplifies the overall process despite the sophisticated techniques employed.
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 enhances grain control, increasing electromigration lifetimes and reducing resistance by promoting desired grain orientations and discouraging undesired ones, thereby improving the reliability and performance of interconnects in semiconductor devices.
Implementation Method 1
selectively providing location-specific treatment so as to either promote or discourage specific grain orientations from growing at specific locations
Implementation Method 2
localized laser annealing, promoting or discouraging specific grain growth to improve microstructural recrystallization
Implementation Method 3
electron backscatter diffraction (EBSD), as used to map orientation of early-growth grains on the top surface of the device
Data Source
AI summary
A method (and structure) includes performing an initial partial anneal of a metal interconnect overburden layer for semiconductor devices being fabricated on a chip on a semiconductor wafer. Orientation of an early recrystallizing grain at a specific location on a top surface of the metal overburden layer is determined, as implemented and controlled by a processor on a computer. A determination is made whether the orientation of the early recrystallizing grain is desirable or undesirable.