Semiconductor Fin Etching for Self-Aligned T-Channel Stacking
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is to increase integration density and mobility while maintaining device performance, as existing methods struggle to optimize channel width and mobility in FinFETs without increasing space requirements or manufacturing costs.
Innovation Solution
The formation of vertically stacked, self-aligned 'T' shaped channel regions is achieved through a repetitive self-limited etching process, which includes specific etching and deposition cycles to enhance channel width and align with CMOS fabrication processes, using materials like silicon-germanium and III-V compound semiconductors for fins and epitaxial source/drain regions to improve mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional FinFET manufacturing methods are used, then device performance is maintained, but integration density and mobility cannot be optimized
Solution Approach 1:
The patent transitions from planar FinFET structures to vertically stacked T-shaped channel regions, utilizing the vertical dimension to increase effective channel width. Multiple channel regions are stacked vertically above the substrate, allowing increased integration density without proportionally increasing the footprint area, thus resolving the contradiction between integration density and channel width optimization.
Solution Approach 2:
The channel region is segmented into multiple discrete T-shaped segments stacked vertically. Each segment contributes to the total effective channel width while maintaining precise alignment through self-aligned formation processes. This segmentation enables independent optimization of each segment's dimensions while achieving cumulative performance benefits.
2Reliability
If channel width is increased to improve mobility, then device performance improves, but space requirements increase
Solution Approach 1:
Instead of increasing channel width in the planar direction, the patent stacks multiple channel regions vertically. The effective channel width is accumulated through vertical stacking while the footprint area remains compact. This dimensional transition allows mobility improvement without proportionally increasing the device area.
Solution Approach 2:
Multiple T-shaped channel regions are nested vertically within a compact footprint. The stacked structure allows one channel region to be positioned above another, creating a nested arrangement that maximizes effective channel width within a limited planar space, thus improving mobility without increasing space requirements.
3Manufacturing precision
If complex etching processes are used to form T-shaped channels, then channel width and alignment improve, but manufacturing complexity increases
Solution Approach 1:
The etching process is designed to be self-aligned, where the T-shaped channel regions automatically align with the gate stack and each other through the self-limited etching mechanism. The etchant selectively removes material based on anisotropic etching rates, creating vertically aligned channels without requiring additional alignment steps or complex masking sequences, thus reducing manufacturing complexity while achieving precise alignment.
Solution Approach 2:
The self-limited etching process incorporates feedback mechanisms where the etching rate is controlled by the exposure of specific crystal planes (such as {110} planes in silicon). When the etchant reaches these planes, the etching rate decreases or stops, providing automatic feedback that ensures precise channel depth and alignment. This feedback mechanism simplifies the overall process control while achieving high manufacturing precision.
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 increases effective channel width and mobility, optimizing device performance while maintaining low manufacturing costs and compatibility with CMOS processes, thereby enhancing integration density.
Implementation Method 1
The formation of vertically stacked, self-aligned 'T' shaped channel regions is achieved through a repetitive self-limited etching process
Implementation Method 2
forming a gate stack on a top surface and sidewalls of the semiconductor fin
Implementation Method 3
depositing a first dielectric layer on sidewalls of the gate stack and the first portion of the first recess
Implementation Method 4
using materials like silicon-germanium and III-V compound semiconductors for fins and epitaxial source/drain regions to improve mobility
Data Source
AI summary
A method includes etching a substrate to form a semiconductor fin, forming a gate stack on a top surface and sidewalls of the semiconductor fin, and forming a first recess in the semiconductor fin on a side of the gate stack, wherein forming the first recess comprises, performing a first etching process to form a first portion of the first recess, depositing a first dielectric layer on sidewalls of the gate stack and the first portion of the first recess, performing a second etching process to form a second portion of the first recess using the first dielectric layer as a mask, wherein the second portion of the first recess extends under the gate stack, and performing a third etching process to remove the first dielectric layer.