Device Isolation Structure for Multi-Voltage FET Integration
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Solution Overview
Problem
Semiconductor devices face challenges in integrating field effect transistors (FETs) operating at different threshold voltages due to the lack of effective device isolation layers with sufficient corrosion resistance and durability, which affects the yield and reliability of metal oxide semiconductor (MOS) devices.
Innovation Solution
A device isolation layer structure is implemented, featuring outer insulating layers in trenches and a guard ring region with etching selectivity, electrically separating regions with different operational voltages and allowing for the formation of gate insulating layers of varying thicknesses, enhancing the integration of FETs with different threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a device isolation layer is formed to separate FETs operating at different threshold voltages, then electrical separation and integration capability are improved, but corrosion resistance and durability during gate insulation layer formation deteriorate
Solution Approach 1:
The device isolation layer is segmented into a first device isolation layer and a second device isolation layer with different materials. The first layer (closer to gate electrodes) uses material with high corrosion resistance, while the second layer (deeper in substrate) uses material with good electrical isolation properties. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between corrosion resistance and electrical separation.
Solution Approach 2:
Different regions of the device isolation layer are assigned different material qualities based on their functional requirements. The region adjacent to gate electrodes receives material with superior corrosion resistance, while other regions use material optimized for electrical isolation. This local differentiation enables simultaneous achievement of both corrosion resistance and electrical separation capabilities.
2Adaptability or versatility
If gate insulating layers of different thicknesses are formed for FETs with different threshold voltages, then functionality and integration are improved, but manufacturing precision and yield deteriorate due to alignment errors
Solution Approach 1:
The device isolation layer is formed preliminarily before forming gate insulating layers of different thicknesses. This preliminary structure serves as a reference baseline that remains constant throughout subsequent processing steps. By establishing this stable reference first, alignment errors during subsequent gate insulating layer formation are minimized, enabling precise manufacturing of multi-thickness structures.
Solution Approach 2:
The device isolation layer acts as an intermediary structure between the substrate and the gate insulating layers. It provides a stable intermediate platform that facilitates precise formation of different thickness gate insulating layers. This intermediary structure absorbs and compensates for alignment variations, enabling high-precision manufacturing of integrated FETs with different threshold voltages.
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 solution improves the corrosion resistance and durability of the device isolation layer, increasing the yield and reliability of semiconductor devices by effectively separating regions with different operational voltages and allowing for the formation of gate insulating layers of varying thicknesses, thus enabling the integration of FETs with different threshold voltages in a single semiconductor chip.
Implementation Method 1
a device isolation structure in the substrate between the first and second regions... the device isolation structure may electrically separate the transistors of the first region from the transistors of the second region
Implementation Method 2
The outer portions of the device isolation structure may be formed of a material having an etching selectivity with respect to that of the inner portion
Data Source
AI summary
An integrated circuit device includes a substrate having adjacent first and second regions, and a device isolation structure in the substrate between the first and second regions. The first and second regions of the substrate may respectively include transistors configured to be driven at different operational voltages, and the device isolation structure may electrically separates the transistors of the first region from the transistors of the second region. The device isolation structure includes outer portions immediately adjacent to the first and second regions and an inner portion therebetween. The outer portions of the device isolation structure comprise a material having an etching selectivity with respect to that of the inner portion. Related devices and fabrication methods are also discussed.