Semiconductor Fin Oxidation for Junction Leakage Reduction
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Solution Overview
Problem
Bulk semiconductor substrates face challenges in device isolation as junction doping increases with scaling, leading to junction leakage, and typical finFETs require costly semiconductor-on-insulator (SOI) substrates for electrically isolated semiconductor fins.
Innovation Solution
A semiconductor structure is formed with epitaxial layers of different semiconductor materials, where the first epitaxial layer acts as an etch stop and is oxidized to create a localized oxide layer, allowing for the formation of semiconductor fins without an SOI substrate, using anisotropic etches and oxygen-impermeable spacers to maintain electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If junction doping is increased to maintain junction isolation in bulk semiconductor substrates, then junction isolation is improved, but junction leakage increases
Solution Approach 1:
The invention divides the isolation function into two parts: physical separation of devices through fin structure, and electrical isolation through localized oxide layers formed at specific regions. This segmentation allows isolation without heavy junction doping, reducing leakage while maintaining isolation effectiveness.
Solution Approach 2:
The localized oxide layer acts as an intermediary element that provides electrical isolation between semiconductor fins without requiring increased junction doping. The oxide layer mediates the isolation function, preventing direct electrical interaction between adjacent doped regions.
2Reliability
If SOI substrates are used to provide electrically isolated semiconductor fins, then electrical isolation is improved, but manufacturing cost increases
Solution Approach 1:
Instead of using SOI substrates that provide global electrical isolation across the entire wafer, the invention applies oxide layers locally only where isolation is needed between specific fins. This local quality approach achieves necessary electrical isolation while avoiding the high cost of complete SOI substrates.
Solution Approach 2:
The invention replaces expensive SOI substrates with a more economical approach using localized oxide layers formed through selective oxidation processes. This substitute provides equivalent electrical isolation functionality at lower manufacturing cost, making finFET production more economically viable.
3Reliability
If fin height varies after oxide layer formation, then manufacturing uniformity deteriorates, but short channel performance is improved
Solution Approach 1:
The invention controls the oxidation parameters (temperature, time, atmosphere) to precisely regulate oxide layer thickness and growth rate. By optimizing these parameters, uniform fin height is maintained across the wafer while still achieving the necessary oxide thickness for electrical isolation and short channel performance enhancement.
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 method enables the formation of finFETs with enhanced short channel performance and uniform fin height without the need for expensive SOI substrates, reducing manufacturing costs and junction leakage.
Implementation Method 1
At least an upper portion of the first epitaxial semiconductor layer is oxidized to provide a localized oxide layer that electrically isolates the semiconductor fins
Implementation Method 2
An anisotropic etch is performed through the second epitaxial semiconductor layer employing the patterned etch mask layer as an etch mask
Implementation Method 3
A remaining portion of the semiconductor fin is vertically spaced from an unoxidized semiconductor material portion of the semiconductor substrate by the semiconductor oxide portion
Data Source
AI summary
A semiconductor substrate including a first epitaxial semiconductor layer is provided. The first epitaxial semiconductor layer includes a first semiconductor material, and can be formed on an underlying epitaxial substrate layer, or can be the entirety of the semiconductor substrate. A second epitaxial semiconductor layer including a second semiconductor material is epitaxially formed upon the first epitaxial semiconductor layer. Semiconductor fins including portions of the second single crystalline semiconductor material are formed by patterning the second epitaxial semiconductor layer employing the first epitaxial semiconductor layer as an etch stop layer. At least an upper portion of the first epitaxial semiconductor layer is oxidized to provide a localized oxide layer that electrically isolates the semiconductor fins. The first semiconductor material can be selected from materials more easily oxidized relative to the second semiconductor material to provide a uniform height for the semiconductor fins after formation of the localized oxide layer.