Self-Aligned Hard Mask for FinFET Metal Gate Height Precision
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Solution Overview
Problem
The recessing of hard masks in metal gate formation for FinFETs leads to metal gate loss and pattern-loading effects, causing uneven heights and difficulties in gap-filling, as the metal gates need to be formed higher to compensate for lost height and suffer from pattern-loading issues during etching.
Innovation Solution
A self-aligned hard mask is formed by selectively depositing it on the metal gates and gate spacers, eliminating the need for recessing and allowing the metal gates to be formed at their final height, with the hard mask being grown upwardly from the gate electrodes and horizontally from the sidewalls, thus avoiding pattern-loading effects and improving gap-filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hard masks are recessed to form metal gates, then metal gate loss is compensated by forming gates higher than final height, but this causes difficulty in gap-filling and increases process complexity
Solution Approach 1:
The hard mask is formed at the final metal gate height from the beginning, rather than recessing it and compensating by forming higher gates. This preliminary positioning eliminates the need for subsequent gap-filling operations to compensate for height differences, directly resolving the technical contradiction by preventing the problem at its source.
2Ease of operation
If hard masks are recessed, then contact openings can be formed, but pattern-loading effect causes uneven metal gate heights across different regions
Solution Approach 1:
The hard mask structure serves multiple functions simultaneously: it defines the metal gate pattern, provides the final height reference, and enables contact opening formation without suffering from pattern-loading effects. By making the hard mask self-aligned and forming it at the correct height from the start, the system eliminates the uneven height problem while maintaining ease of contact opening formation.
3Loss of substance
If metal gates are formed higher than final height to compensate for hard mask loss, then metal gate loss is addressed, but the increased height causes difficulty in gap-filling operations
Solution Approach 1:
The hard mask is formed with the correct final height from the beginning, eliminating the need to form metal gates higher than their final height. This preliminary correct positioning prevents metal gate material loss and eliminates the associated gap-filling difficulties, directly resolving the contradiction between preventing material loss and maintaining manufacturing ease.
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 eliminates the need for metal gates to be formed higher than necessary, simplifies gap-filling, and reduces the pattern-loading effect, resulting in more uniform metal gate heights and improved process efficiency.
Implementation Method 1
selectively depositing it on the metal gates and gate spacers, eliminating the need for recessing and allowing the metal gates to be formed at their final height, with the hard mask being grown upwardly from the gate electrodes and horizontally from the sidewalls
Data Source
AI summary
A method includes forming a metal gate in a first inter-layer dielectric, performing a treatment on the metal gate and the first inter-layer dielectric, selectively growing a hard mask on the metal gate without growing the hard mask from the first inter-layer dielectric, depositing a second inter-layer dielectric over the hard mask and the first inter-layer dielectric, planarizing the second inter-layer dielectric and the hard mask, and forming a gate contact plug penetrating through the hard mask to electrically couple to the metal gate.