Source/Drain Dielectric Isolation for Latch-Up Prevention
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Solution Overview
Problem
Conventional semiconductor integrated circuit (IC) designs face challenges with latch-up failure mechanisms, particularly in bulk substrates, where parasitic bipolar transistors can lead to device destruction, and existing latch-up prevention structures like tap cells occupy valuable space and reduce functional density.
Innovation Solution
The formation of a pseudo silicon-on-insulator (SOI) structure using a semiconductor oxide feature below the source/drain feature to prevent latch-up without the need for tap cells or guard rings, which also addresses anti-punch-through implantation region leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tap cells and isolation structures are used to prevent latch-up, then device reliability is improved, but the overall size of the integrated circuit increases
Solution Approach 1:
The patent extracts the latch-up prevention function from separate tap cells and isolation structures and integrates it into the source/drain region itself by forming a semiconductor oxide feature directly in the source/drain region, eliminating the need for additional prevention structures
Solution Approach 2:
The patent merges the latch-up prevention function with the source/drain region by forming a semiconductor oxide feature within it, combining two previously separate functions (source/drain operation and latch-up prevention) into a single integrated structure
2Reliability
If tap cells are placed among standard cells, then latch-up prevention is achieved, but functional device area is reduced
Solution Approach 1:
The patent removes the need for separate tap cells by extracting the latch-up prevention function and embedding it directly in the source/drain region through the semiconductor oxide feature
Solution Approach 2:
The source/drain region is given multiple functions: it serves as both the electrical connection region for the transistor and as the latch-up prevention structure through the integrated semiconductor oxide feature
3Ease of manufacture
If conventional bulk substrate structures are used, then manufacturing simplicity is maintained, but parasitic bipolar transistors cause latch-up failure
Solution Approach 1:
The patent introduces a semiconductor oxide feature as an intermediary element within the source/drain region that blocks the formation of parasitic bipolar transistors while maintaining compatibility with bulk substrate manufacturing processes
Solution Approach 2:
The patent applies a localized modification (semiconductor oxide feature) only in specific regions where source/drain regions are formed, rather than changing the entire substrate structure, thus maintaining manufacturing simplicity while providing localized latch-up prevention
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 prevents latch-up and leakage while maintaining the benefits of both bulk and SOI devices, potentially increasing functional density by eliminating the need for space-consuming latch-up prevention structures.
Implementation Method 1
a bottom dielectric feature over the source/drain region... The bottom dielectric feature insulates the source/drain region from the substrate, thereby preventing latch-up
Data Source
AI summary
A semiconductor device according to the present disclosure includes an active region including a channel region and a source/drain region adjacent the channel region, a vertical stack of channel members over the channel region, a gate structure over and around the vertical stack of channel members, a bottom dielectric feature over the source/drain region, a source/drain feature over the bottom dielectric feature, and a germanium layer disposed between the bottom dielectric feature and the source/drain region.