SiN Liner for Stable High-Ge SiGe FinFET Fabrication
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Solution Overview
Problem
High germanium content SiGe fins in FinFET devices are vulnerable to oxygen ingression during processing, leading to structural instability and reduced carrier mobility due to fin collapse, especially when germanium content exceeds 25%, limiting fin height to less than 35 nm.
Innovation Solution
A silicon nitride (SiN) liner is used to prevent oxygen penetration at the base of the SiGe fin, providing a stable barrier even with a thickness less than 5 nm, allowing for the fabrication of stable SiGe-on-insulator FinFET devices with higher germanium content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high germanium content (>25%) is used in SiGe fins to maintain compressive strain and prevent relaxation, then carrier mobility is improved and fin height can be increased, but the fins become vulnerable to oxygen ingression during processing, leading to structural instability and fin collapse
Solution Approach 1:
A silicon nitride (SiN) liner is introduced as an intermediary barrier layer between the oxygen-containing environment and the SiGe fin base. This thin liner (less than 5 nm) effectively blocks oxygen diffusion into the fin structure during processing, preventing oxidation-induced instability while allowing the fin to maintain its high germanium content and associated benefits
Solution Approach 2:
The silicon nitride liner creates an inert protective environment around the SiGe fin base, isolating it from oxygen exposure during subsequent processing steps. This inert barrier prevents harmful oxidation reactions without requiring changes to the fin's compositional properties
2Reliability
If oxygen penetration is prevented using conventional thicker barrier layers, then fin stability is improved, but the fabrication process complexity and manufacturing steps increase
Solution Approach 1:
The thickness parameter of the silicon nitride liner is optimized to be less than 5 nm, which is surprisingly sufficient to block oxygen diffusion. This thin-film approach achieves the same protective function as much thicker conventional barriers, reducing process complexity and fabrication steps while maintaining fin stability
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 SiN liner effectively blocks oxygen access, maintaining fin stability and carrier mobility, enabling the fabrication of SiGe fins with higher germanium content without collapse, thus supporting taller fins and improved device performance.
Implementation Method 1
A silicon nitride (SiN) liner is used to prevent oxygen penetration at the base of the SiGe fin
Data Source
AI summary
A method of making a structurally stable SiGe-on-insulator FinFET employs a silicon nitride liner to prevent de-stabilizing oxidation at the base of a SiGe fin. The silicon nitride liner blocks access of oxygen to the lower corners of the fin to facilitate fabrication of a high-concentration SiGe fin. The silicon nitride liner is effective as an oxide barrier even if its thickness is less than about 5 nm. Use of the SiN liner provides structural stability for fins that have higher germanium content, in the range of 25-55% germanium concentration.