Partial Directional Dummy Gate Etch to Protect Source/Drain Regions
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Solution Overview
Problem
The existing gate last process in semiconductor manufacturing often damages surrounding structures like source/drain regions during the removal of dummy gate structures, leading to issues such as partial removal, pitting, and potential total removal of these critical regions.
Innovation Solution
A two-step etch process is employed, where an initial isotropic etch removes a portion of the dummy gate stack, followed by a directional anisotropic etch that minimizes damage to adjacent structures by leaving remnant portions of the dummy gate material to protect them, and subsequently, a metal gate is formed in the remaining trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etch process is used to remove the dummy gate stack, then the dummy gate structure is completely removed, but damage occurs to surrounding structures such as source/drain regions
Solution Approach 1:
The patent applies partial action by performing an etch process that removes only a portion of the dummy gate stack rather than completely removing it. The etch process is controlled to remove the upper portion of the dummy gate while intentionally leaving a remnant portion at the bottom to protect adjacent source/drain regions from etchant damage
Solution Approach 2:
The remnant portion of the dummy gate material serves as an intermediary protective element. This remaining material acts as a physical barrier or mask that shields the vulnerable source/drain regions from direct exposure to the etchant, thereby preventing damage while still allowing the upper dummy gate structure to be removed
2Object-affected harmful factors
If the dummy gate stack is completely removed, then no remnant material is left to protect adjacent structures, but complete removal is difficult to achieve without damaging surrounding areas
Solution Approach 1:
The etch process is deliberately designed to be incomplete, removing only the necessary upper portion of the dummy gate while intentionally preserving a remnant portion. This partial removal strategy achieves the dual goal of clearing the upper structure while maintaining protective material at the critical interface with source/drain regions
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 reduces damage to source/drain regions and fin structures during dummy gate stack removal, enhancing device performance and reliability by protecting these areas from etchant attack.
Implementation Method 1
a directional anisotropic etch that minimizes damage to adjacent structures by leaving remnant portions of the dummy gate material to protect them
Implementation Method 2
an initial isotropic etch removes a portion of the dummy gate stack
Data Source
AI summary
In a gate replacement process, a dummy gate and adjacent structure, such as a source/drain region, are formed. The dummy gate is removed, at least in part, using a directional etch to remove some but not all of the dummy gate to form a trench. A portion of the dummy gate remains and protects the adjacent structure. A gate electrode can then be formed in the trench. A two step process can be employed, using an initial isotropic etch followed by the directional etch.