Dummy Gate Partial Etch for Source/Drain Protection
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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 isotropic etch is used to remove the top portion of the dummy gate stack, followed by an anisotropic etch to partially remove the bottom portion, leaving remnant material that protects adjacent structures and allows for the subsequent formation of a metal gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etch process is used to remove the dummy gate structure, then the dummy gate is completely removed, but surrounding structures such as source/drain regions are damaged
Solution Approach 1:
The patent applies partial action by performing an etch process that removes only a portion of the dummy gate structure rather than completely removing it. The etch process is controlled to remove the top portion of the dummy gate while leaving a remnant portion that protects adjacent source/drain regions from damage, thus achieving partial removal to prevent harmful effects
Solution Approach 2:
The remnant portion of the dummy gate structure serves as an intermediary protective element. This remaining material acts as a sacrificial barrier that absorbs etch damage and prevents the etchant from reaching and damaging the critical source/drain regions, while still allowing the top portion of the dummy gate to be removed
2Ease of manufacture
If the dummy gate is completely removed, then the structure is cleared for metal gate formation, but adjacent structures suffer from partial removal, pitting, and potential total removal
Solution Approach 1:
The etch process is intentionally stopped before complete removal of the dummy gate, leaving a controlled remnant portion. This partial removal strategy prevents the harmful effects of complete removal (damage to source/drain regions) while still providing sufficient clearance for subsequent metal gate formation processes
Solution Approach 2:
The remnant portion of the dummy gate is intentionally left in place as a protective cushion before metal gate formation. This remaining material serves as a sacrificial layer that protects adjacent structures during subsequent processing steps, ensuring their integrity before the metal gate is formed
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 minimizes damage to source/drain regions and fin structures, enhancing device performance and reliability by protecting these areas during the dummy gate removal process.
Implementation Method 1
an isotropic etch is used to remove a top portion of the dummy gate stack
Implementation Method 2
an anisotropic etch is used to partially remove the bottom portion of the dummy gate stack
Data Source
AI summary
In a gate replacement process, forming a dummy gate and an adjacent structure; 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.