STI Structure Etching for Uniform Fin Step Heights
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Solution Overview
Problem
As semiconductor devices are scaled down, the heights of shallow trench isolation (STI) material can vary across the wafer, leading to fin height non-uniformity due to loading effects, which affects the performance and scalability of silicon-based transistors.
Innovation Solution
The method involves depositing STI material around multiple fins and using a combination of etching processes, including thermal and plasma-activated etching, along with a radical treatment process, to achieve substantially uniform STI step heights across the fins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If STI material is deposited around multiple fins, then isolation structures are formed, but loading effects cause non-uniform STI step heights across the wafer
Solution Approach 1:
The patent applies multiple etching processes with different parameters (thermal etching followed by plasma-activated etching) to remove STI material at different rates from inner and outer portions, thereby compensating for the non-uniform deposition and achieving uniform step heights
Solution Approach 2:
The etching process is segmented into multiple stages: a first thermal etching process that removes STI material at a first rate, and a second plasma-activated etching process that removes STI material at a second rate, allowing differential removal to correct loading effects
2Manufacturing precision
If multiple etching processes are used to achieve uniform STI step heights, then fin height uniformity is improved, but process complexity increases
Solution Approach 1:
The patent changes physical and chemical parameters between etching steps (thermal vs. plasma-activated conditions) to achieve different removal rates, enabling precise control of STI step heights while maintaining a systematic approach to process management
3Reliability
If STI step heights are made uniform, then device performance is improved, but manufacturing time increases due to multiple etching steps
Solution Approach 1:
The patent employs continuous sequential etching processes where the first thermal etching and second plasma-activated etching are performed in succession without interruption, maintaining productive action throughout the STI planarization process
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 ensures that the STI step heights are uniform, which helps in maintaining consistent fin heights and improving the performance and scalability of semiconductor devices by reducing device footprint and enhancing electrostatic control.
Implementation Method 1
performing a first etching process on the STI material to etch the first portion of the STI material at a first etching rate
Implementation Method 2
performing a second etching process on the STI material to etch the second portion of the STI material at a second etching rate greater than the first etching rate
Data Source
AI summary
The present disclosure describes a method that includes forming a fin protruding from a substrate, the fin including a first sidewall and a second sidewall formed opposite to the first sidewall. The method also includes depositing a shallow-trench isolation (STI) material on the substrate. Depositing the STI material includes depositing a first portion of the STI material in contact with the first sidewall and depositing a second portion of the STI material in contact with the second sidewall. The method also includes performing a first etching process on the STI material to etch the first portion of the STI material at a first etching rate and the second portion of the STI material at a second etching rate greater than the first etching rate. The method also includes performing a second etching process on the STI material to etch the first portion of the STI material at a third etching rate and the second portion of the STI material at a fourth etching rate less than the third etching rate.