FinFET Oxide Isolation via Blocking Layer and Annealing
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Solution Overview
Problem
Existing methods for forming fin isolation regions in FinFET semiconductor devices, such as the BOTS process, result in uneven surfaces and complex processing sequences, making them difficult to integrate in mass production and leading to varying insulation thicknesses between fins.
Innovation Solution
The use of an oxidation-blocking layer and a thermal anneal process to convert portions of the fin into an oxide fin isolation region, with specific trench formation and spacer placement techniques to achieve uniform and thin oxide fin isolation regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BOTS process is used to form fin isolation regions, then isolation is achieved, but the surface becomes uneven and processing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the oxidation-blocking layer (silicon nitride) on the fin surfaces before the thermal oxidation step. This pre-positioned barrier prevents oxidation in specific regions, allowing the isolation oxide to form uniformly only where needed, thereby simplifying subsequent processing while maintaining effective isolation.
Solution Approach 2:
The oxidation-blocking layer acts as an intermediary material between the fin structure and the oxidation environment. This intermediate layer selectively prevents oxygen diffusion to specific fin surfaces, enabling controlled and uniform oxide formation without requiring complex multi-step isolation processes.
2Reliability
If the BOTS process is used to form fin isolation regions, then isolation is achieved, but insulation thickness varies between fins
Solution Approach 1:
The patent applies local quality by creating spatially varying oxidation characteristics through the oxidation-blocking layer. The blocking layer is positioned to prevent oxidation on specific fin surfaces (e.g., bottom and sidewalls) while allowing oxidation on others, resulting in uniform isolation thickness across all fins rather than the variable thickness produced by conventional BOTS.
Solution Approach 2:
By pre-forming the oxidation-blocking layer with controlled thickness and position before oxidation, the patent establishes predetermined oxidation barriers that ensure uniform oxide growth. This preliminary structuring of the fin surfaces with blocking material guarantees consistent isolation thickness across the wafer.
3Reliability
If conventional isolation methods are used, then fin isolation is achieved, but the process is difficult to integrate in mass production
Solution Approach 1:
The patent merges the isolation oxide formation with the existing thermal oxidation steps already present in FinFET manufacturing flows. By utilizing the same oxidation equipment and conditions for both device oxide growth and isolation oxide formation, the process integrates seamlessly into mass production without requiring additional specialized equipment or process steps.
Solution Approach 2:
The patent changes the oxidation parameters (temperature, time, atmosphere) to simultaneously achieve both device oxide and isolation oxide formation in a single thermal oxidation step. This parameter optimization allows the isolation process to be consolidated with device processing, improving productivity and mass production integrability.
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 results in relatively thin oxide fin isolation regions with a planar bottom surface, improving surface uniformity and simplifying the manufacturing process, reducing complexity and variability in insulation thickness.
Implementation Method 1
performing a thermal anneal process to convert a part, but not all, of the lower portion of fin positioned above the first oxidation-blocking layer of insulating material into an oxide fin isolation region positioned under the fin
Data Source
AI summary
A method includes forming a plurality of trenches to define a fin, forming a first layer of insulating material in the trenches, forming a sidewall spacer on opposite sides of the fin above an upper surface of the first layer, removing the first layer and performing a fin-trimming etching process to define a plurality of increased-size trenches. The method also includes forming a first oxidation-blocking layer of insulating material in the increased-size trenches, forming a second layer of insulating material above the oxidation-blocking layer, and performing a thermal anneal process to convert at least a part of the portion of the fin that is in contact with the second layer of insulating material into an oxide fin isolation region.