FinFET SiOC Isolation Structure for Fin Bending Reduction
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Solution Overview
Problem
The existing methods for forming isolation structures in FinFET devices often result in undesirable fin bending and height variations due to the annealing process and planarization steps, which introduce thermal stress and height inconsistencies across the substrate.
Innovation Solution
The use of a silicon oxycarbon (SiOC) isolation structure, where a first insulating material layer comprising silicon, oxygen, and carbon is formed between the fins, eliminating the need for annealing and ensuring self-aligning etch processes to reduce thermal budget and height variations, with a second insulating material layer being planarized to expose the SiOC layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annealing process is performed to densify the first oxide layer, then the isolation structure is formed, but thermal stress is introduced causing fin bending
Solution Approach 1:
The patent removes the annealing step from the isolation structure formation process. By forming the SiOC layer through CVD deposition without subsequent annealing, the thermal stress that causes fin bending is eliminated while still achieving a dense, reliable isolation structure.
Solution Approach 2:
The patent changes the material composition parameter by using silicon oxycarbon (SiOC) instead of traditional silicon oxide. This material substitution allows the isolation layer to be formed densely through CVD deposition at lower temperatures, eliminating the need for high-temperature annealing that causes fin bending.
2Ease of operation
If a planarization process is performed to expose the cap layer, then the second oxide layer is recessed, but height variations are introduced across the substrate
Solution Approach 1:
The patent removes the mechanical planarization step from the process flow. By using a self-aligned etch approach where the SiOC layer protects the fin regions, the cap layer is exposed uniformly across the substrate without introducing pitch-dependent height variations.
Solution Approach 2:
The SiOC isolation layer serves a dual function: it acts as the isolation material and simultaneously as a protective layer during etching. The self-aligned etch process uses the SiOC layer itself to define the exposure regions, eliminating the need for separate planarization and mask alignment steps that cause height variations.
3Reliability
If multiple process steps including annealing and planarization are performed, then the isolation structure is formed, but the process complexity increases
Solution Approach 1:
The patent combines multiple functions into the SiOC layer formation step. The CVD deposition of SiOC simultaneously creates the isolation structure and provides the protective mask for subsequent etching, eliminating the need for separate annealing and planarization steps.
Solution Approach 2:
The SiOC layer performs multiple functions: it serves as the isolation material between fins, acts as a protective layer during etching, and defines the exposure regions through self-aligned etching. This multi-functionality reduces the total number of process steps required.
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 reduces fin bending and height variations, simplifying the process flow and enhancing the uniformity of the isolation structure, thereby improving the reliability and performance of FinFET devices.
Implementation Method 1
forming a first insulating material layer comprising silicon, oxygen and carbon in the trenches between the plurality of fins
Data Source
AI summary
A method includes forming a plurality of fins on a semiconductor substrate by defining a plurality of trenches in the substrate. A first insulating material layer comprising silicon, oxygen and carbon is formed in the trenches between the plurality of fins. The first insulating material layer has an upper surface that is at a level that is below an upper surface of the fins. A second insulating material layer is formed above the first insulating material layer. The second insulating material layer is planarized to expose a top surface of the plurality of fins. The second insulating material layer is removed to expose the first insulating material layer.