FinFET Electrical Isolation via Selective Oxidation of Sacrificial Layer
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Solution Overview
Problem
FinFET devices on bulk semiconductor substrates face punch-through leakage due to current leakage through the ungated portion of the fin, leading to increased static power consumption, and existing solutions like punch-through-stopper dopant implantation introduce variability and lower carrier mobility.
Innovation Solution
The method involves creating a semiconductor stack with a bulk semiconductor substrate, an oxidizable layer, and an active layer, where the oxidizable layer is selectively oxidized to form a dielectric layer, electrically isolating the active region of the fin and providing direct physical support, thereby preventing punch-through leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If punch-through-stopper dopant implantation is used to control leakage, then leakage is reduced, but carrier mobility decreases and variability increases
Solution Approach 1:
The patent removes the dopant implantation step entirely and replaces it with a sacrificial layer oxidation approach. The sacrificial layer is selectively oxidized to form a dielectric barrier that prevents punch-through leakage without introducing dopants into the channel, thus eliminating the harmful side effects of RDF and mobility degradation.
Solution Approach 2:
The patent changes the material state of the sacrificial layer from conductive/semiconductive to dielectric through oxidation. This parameter change (from electrically active to electrically insulating) creates an effective barrier against punch-through leakage while maintaining mechanical support and avoiding dopant-related variability.
2Object-generated harmful factors
If the oxidizable layer is selectively oxidized to electrically isolate the active region, then punch-through leakage is reduced, but the structural integrity may be compromised
Solution Approach 1:
The oxidizable sacrificial layer serves as an intermediary element between the active fin region and the substrate. It is selectively oxidized to form a dielectric mediator that provides electrical isolation while the surrounding structures (mandrel, spacers, and epitaxial layers) provide mechanical support, thus resolving the contradiction between electrical isolation and structural integrity.
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 punch-through leakage by converting the oxidizable layer into a dielectric, enhancing electrical isolation and maintaining mechanical stability, thus minimizing static power consumption and variability in FinFET devices.
Implementation Method 1
electrically isolating the active layer of the at least one fin by converting the oxidizable layer to a dielectric layer, resulting in a semiconductor structure, the converting of the oxidizable layer resulting in a converted layer, the converting including selectively oxidizing the oxidizable layer of the at least one fin
Data Source
AI summary
A semiconductor stack of a FinFET in fabrication includes a bulk silicon substrate, a selectively oxidizable sacrificial layer over the bulk substrate and an active silicon layer over the sacrificial layer. Fins are etched out of the stack of active layer, sacrificial layer and bulk silicon. A conformal oxide deposition is made to encapsulate the fins, for example, using a HARP deposition. Relying on the sacrificial layer having a comparatively much higher oxidation rate than the active layer or substrate, selective oxidization of the sacrificial layer is performed, for example, by annealing. The presence of the conformal oxide provides structural stability to the fins, and prevents fin tilting, during oxidation. Selective oxidation of the sacrificial layer provides electrical isolation of the top active silicon layer from the bulk silicon portion of the fin, resulting in an SOI-like structure. Further fabrication may then proceed to convert the active layer to the source, drain and channel of the FinFET. The oxidized sacrificial layer under the active channel prevents punch-through leakage in the final FinFET structure.