Fin Isolation via Pre-Amorphizing Implant and Laser Melt Anneal
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Solution Overview
Problem
Three-dimensional transistor devices face leakage current issues due to dopant diffusion beneath the fin structure, which compromises the isolation between the source and drain regions, leading to inefficiencies in current passage and device performance.
Innovation Solution
A method involving a pre-amorphizing implant to create an amorphized region, followed by selective dopant implantation and a laser melt anneal to confine the dopant profile within the amorphized region, thereby reducing dopant diffusion and enhancing isolation through the creation of doped fin structures with improved box-like dopant distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant is implanted into the fin structure, then the fin structure is doped to enable current conduction, but dopant diffuses to a depth beneath the intended region, creating leakage paths
Solution Approach 1:
An amorphizing implant is performed first to transform the crystalline silicon into an amorphous layer before dopant implantation. This preliminary action creates a confined region that prevents dopant diffusion during subsequent processing, ensuring dopant remains within the intended depth range and eliminating leakage paths beneath the fin structure.
Solution Approach 2:
The patent utilizes a two-step thermal process: a first anneal to repair damage from amorphizing implant, then a second anneal to recrystallize the amorphous layer. These controlled parameter changes (temperature, time sequence) enable precise dopant confinement while maintaining electrical activation, resolving the contradiction between doping effectiveness and depth control.
2Manufacturing precision
If a pre-amorphizing implant is performed to confine dopant, then dopant diffusion is controlled, but additional process steps are required
Solution Approach 1:
The patent combines multiple functions into the amorphizing implant step: it creates the dopant confinement barrier, defines the fin structure depth, and establishes the crystalline-amorphous interface that guides subsequent recrystallization. This merging of functions achieves precise dopant profiling without requiring separate barrier layer deposition or etching steps.
Solution Approach 2:
The patent exploits the phase transition between crystalline and amorphous silicon states. The amorphizing implant creates an amorphous layer that acts as a diffusion barrier, and controlled thermal annealing recrystallizes this layer in a predictable manner. This phase transition mechanism provides inherent dopant confinement while maintaining process integration efficiency.
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 minimizes leakage current by restricting dopant diffusion, improving the isolation between fin structures and surrounding regions, thereby enhancing the reliability and consistency of three-dimensional transistor devices.
Implementation Method 1
A portion of the workpiece is subjected to a pre-amorphizing implant to create an amorphized region
Implementation Method 2
The doped amorphized region is then subjected to a laser melt anneal which crystallizes the amorphized region
Implementation Method 3
performing a laser melt anneal after the dopant species are implanted into the amorphized region to form a doped crystalline region
Implementation Method 4
This amorphized region is then implanted with dopant species, at an implant energy and dose so that the dopant species are contained within the amorphized region
Data Source
AI summary
A method of processing a workpiece to create a doped fin structure is disclosed. A portion of the workpiece is subjected to a pre-amorphizing implant to create an amorphized region. This amorphized region is then implanted with dopant species, at an implant energy and dose so that the dopant species are contained within the amorphized region. The doped amorphized region is then subjected to a laser melt anneal which crystallizes the amorphized region. The dopant profile is box-like, and the dopant is confined to the previously amorphized region.