Dummy Gate Partial 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, necessitating improved etch processes and resulting structures.
Innovation Solution
A two-step etch process is employed, first using an isotropic etch to partially remove the dummy gate stack, followed by an anisotropic etch to further remove the dummy gate stack while leaving remnant portions that protect adjacent structures, ultimately forming 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 stack, then the dummy gate structure is completely removed, but damage occurs to surrounding structures such as source/drain regions and fins
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 leave remnant portions of the dummy gate that continue to protect adjacent structures from damage while still achieving the necessary exposure for subsequent processing steps.
Solution Approach 2:
The patent applies preliminary anti-action by leaving remnant portions of the dummy gate stack in place before subsequent processing. These remnants act as a protective barrier that prevents damage to source/drain regions and fins during later etching or processing steps, counteracting the harmful effects that would otherwise occur.
2Productivity
If the dummy gate stack is completely removed, then subsequent processing can proceed, but adjacent structures become vulnerable to damage
Solution Approach 1:
The patent removes only a partial portion of the dummy gate stack, leaving sufficient remnants to maintain protection of adjacent structures. This partial removal approach balances the need for process continuity with the need to maintain structural integrity during subsequent processing steps.
Solution Approach 2:
The remnant dummy gate portions serve as an intermediary protective element between the processing equipment and the vulnerable adjacent structures. These remnants mediate the interaction by absorbing or deflecting potential damage while allowing the processing to continue.
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 adjacent structures during dummy gate stack removal, enhancing device performance and reliability by protecting source/drain regions and fins.
Implementation Method 1
first using an isotropic etch to partially remove the dummy gate stack
Implementation Method 2
followed by an anisotropic etch to further remove 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.