Composite Isolation Structures for FinFET Void Prevention
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Solution Overview
Problem
As fin pitch in FinFETs shrinks, deposition of gap fill materials becomes problematic due to void formation, and high temperature seam anneal can cause fin oxidation, leading to defects.
Innovation Solution
A method involving forming a first dielectric layer around fins, recessing a second dielectric layer, conformally depositing a liner, and exposing the first dielectric layer to reduce voids and prevent oxidation, including a densified local isolation layer and a global isolation layer to protect the fins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flowable oxide is used to fill gaps, then void formation is reduced, but high temperature seam anneal causes fin oxidation
Solution Approach 1:
A liner layer is introduced as an intermediary between the flowable oxide gap fill material and the fin structure. This liner prevents direct oxidation of the fin during high temperature seam anneal while allowing the flowable oxide to successfully fill gaps without void formation.
Solution Approach 2:
The isolation structure uses a composite approach combining multiple materials: liner layer (first material), flowable oxide (second material), and cap layer (third material). Each layer serves a specific function - the liner prevents oxidation, the flowable oxide fills gaps, and the cap provides mechanical protection.
2Ease of manufacture
If HARP SiO2 is used for gap fill, then deposition is straightforward, but voids form as fin pitch shrinks
Solution Approach 1:
The patent changes the deposition parameters by using flowable oxide instead of HARP SiO2. Flowable oxide is deposited in a liquid state and then densified through anneal, allowing it to flow into and fill narrow gaps completely without forming voids, even as fin pitch shrinks.
Solution Approach 2:
The flowable oxide undergoes a phase transition from liquid to solid during the densification anneal process. This phase change allows the material to flow into gaps in liquid form, then solidify into a dense, void-free structure after deposition.
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 reduces or eliminates voids in gap fill material, preventing oxidation defects in the bottom inactive regions of the fins, ensuring high-quality FinFET fabrication.
Implementation Method 1
preventing oxidation defects in the bottom inactive regions of the fins
Implementation Method 2
reduces or eliminates voids in gap fill material, preventing oxidation defects
Data Source
AI summary
Structures for the isolation of a fin-type field-effect transistor and methods of forming isolation for a fin-type field-effect transistor. A first dielectric layer is formed that encapsulates a plurality of fins. A second dielectric layer is formed that surrounds the first dielectric layer and the plurality of fins. A surface of the second dielectric layer relative to a surface of the first dielectric layer. A liner is conformally deposited on the surface of the first dielectric layer and on the recessed surface of the second dielectric layer. A section of the liner is removed to expose the surface of the first dielectric layer. The exposed surface of the first dielectric layer is recessed to reveal a portion of each of the plurality of fins.