Radical Dummy Gate Etching for Straight Gate Spacer Sidewalls
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the damage to gate spacer sidewalls during the removal of polysilicon gates, leading to non-straight profiles which affect the uniformity of metal gate performance, particularly in advanced process nodes.
Innovation Solution
A radical etching process is employed to remove dummy gate stacks, utilizing radicals as etchants and avoiding ion bombardment to maintain a straight sidewall profile of the gate spacer, thereby ensuring uniformity and integration with existing fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to remove polysilicon gates, then the gate removal is achieved, but the gate spacer sidewalls are damaged resulting in non-straight profiles
Solution Approach 1:
The patent changes the etching mechanism from ion-based to radical-based etching. This parameter change in the etching process chemistry and physics enables selective removal of polysilicon without the ion bombardment that causes sidewall damage, thereby preserving straight sidewall profiles during gate removal
Solution Approach 2:
The patent replaces the mechanical ion bombardment mechanism with a chemical radical etching mechanism. By substituting the physical sputtering action of ions with the chemical reaction of radicals, the process achieves gate removal without the mechanical damage that creates non-straight sidewalls
2Reliability
If replacement gate process is used to improve device performance, then high-temperature processing steps are reduced, but gate spacer sidewall damage still occurs during polysilicon removal
Solution Approach 1:
The patent modifies the etching process parameters by using radical chemistry instead of ion physics. This fundamental parameter change enables the replacement gate process to proceed without sidewall damage, maintaining both device performance improvements and sidewall profile uniformity
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
The radical etching method preserves a substantially straight sidewall profile, enhancing the uniformity of gate structure performance and facilitating easy integration into existing semiconductor fabrication processes.
Implementation Method 1
A radical etching process is employed to remove dummy gate stacks, utilizing radicals as etchants and avoiding ion bombardment
Implementation Method 2
generating plasma with a precursor gas in a plasma region of the process chamber, the plasma including radicals and charged ions
Data Source
AI summary
A semiconductor device includes a substrate, an isolation structure on the substrate, a fin protruding from the substrate and through the isolation structure, a gate stack engaging the fin, and a gate spacer on sidewalls of the gate stack. The gate spacer includes an inner sidewall facing the gate stack and an outer sidewall opposing the inner sidewall. The inner sidewall has a first height measured from a top surface of the fin and a bowed structure in a top portion of the inner sidewall. The bowed structure extends towards the gate stack for a first lateral distance measured from a middle point of the inner sidewall. The first lateral distance is less than about 8% of the first height.