Dual Depth Trench Isolation via Self-Limiting Polymer Etch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current shallow trench isolation (STI) techniques in semiconductor fabrication require additional mask steps and etch processes, increasing production costs and potentially limiting the electrical properties of CMOS devices due to limited control over trench depth differences between array and periphery sections.
Innovation Solution
A dry etch process using specific RF plasma etcher settings and etch chemistries, such as HBr/Cl2/CH2F2, is employed to create desired trench depths in both array and periphery sections with controlled side wall slopes, allowing for self-limiting etches and selective etching to achieve controllable trench depth differences without additional mask steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional mask steps and etch processes are used to increase trench depth difference, then trench depth control is improved, but production cost increases and device complexity increases
Solution Approach 1:
The etch process is designed to be self-limiting through controlled side wall slope formation. The polymer deposition during etching automatically limits the etch depth in array sections while allowing deeper etching in periphery sections, eliminating the need for additional mask steps to control trench depth differences
Solution Approach 2:
The invention changes etch process parameters (RF power, pressure, gas flow ratios) to control side wall slope angles differently in array versus periphery sections. By adjusting these parameters, the etch process automatically achieves the desired trench depth difference without additional process steps
2Manufacturing precision
If additional mask steps and etch processes are used to increase trench depth difference, then trench depth control is improved, but production cost increases
Solution Approach 1:
The self-limiting etch process automatically controls trench depths through polymer deposition and side wall slope formation, eliminating the need for additional mask and etch steps that would increase production costs
Solution Approach 2:
The invention combines the trench depth control function with the standard STI etch process itself. The same etch process that creates the trenches also automatically controls their relative depths through side wall slope formation, merging multiple functions into a single process step
3Device complexity
If conventional STI etch process is used, then process simplicity is maintained, but trench depth difference control is insufficient
Solution Approach 1:
The invention modifies conventional etch parameters (increasing CH2F2 flow ratio, adjusting RF power and pressure) to enable side wall slope formation. These parameter changes transform the standard etch process into one that automatically controls trench depth differences while maintaining process simplicity
Solution Approach 2:
Polymer deposition acts as an intermediary mechanism during the etch process. The polymer builds up on trench walls and limits further etching in array sections, automatically controlling trench depth differences without requiring additional process steps
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 improves electrical properties by achieving precise trench depth control, reducing production costs, and enabling better isolation between neighboring active devices in semiconductor flash memory devices.
Implementation Method 1
A first dry etch is performed to form array trenches and periphery trenches
Implementation Method 2
A second dry etch is performed to increase the depth of the periphery trenches and deposit a polymer on the array trenches
Data Source
AI summary
Trench isolation structures and methods to form same for use in the manufacture of semiconductor devices are described. The trench isolation structures are formed using several processing schemes that utilize disclosed dry etching processes to form a significant depth Δ between an array trench depth and a periphery trench depth. One etching method creates a trench delta depth utilizing a single dry etch step, while two other etching methods create a trench Δ depth by utilizing three dry etch steps.