Metal Gate Etch-Back Using Dielectric Fill Regions in FinFET Trenches
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Solution Overview
Problem
The formation of metal gates in FinFETs is hindered by the pattern-loading effect during the etch-back process, leading to inconsistent recessing of metal gates across different channel lengths, which complicates gap-filling and results in uneven metal gate heights.
Innovation Solution
The introduction of filling regions made of dielectric materials, which are deposited before the etch-back of metal gates, helps to uniformize the gate widths and reduce the pattern-loading effect by occupying spaces that would otherwise be filled by metal gates, allowing for more consistent etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal gates are etched simultaneously across different channel lengths, then the etching process is efficient and fast, but the pattern-loading effect causes inconsistent metal gate recessing and height uniformity
Solution Approach 1:
The patent applies local quality by introducing filling regions with different materials (e.g., dielectric materials with different etch selectivity) into specific areas of the trench based on channel length. Short-channel transistor regions receive filling regions with etch selectivity that compensates for their faster etching rate, while long-channel transistor regions receive filling regions with etch selectivity that compensates for their slower etching rate. This localized material differentiation ensures uniform metal gate recessing across different channel lengths while maintaining simultaneous etching efficiency.
2Ease of manufacture
If hard masks are recessed to form contact openings, then contact openings can be formed, but metal gate loss occurs requiring increased metal gate height which complicates gap-filling
Solution Approach 1:
The patent applies preliminary action by forming the filling regions into the trenches before depositing the metal gates. These filling regions are positioned to occupy the spaces where metal gates will later be recessed during the etch-back process. By preparing these compensatory filling regions in advance, the metal gates can be deposited at their final desired height without needing to be over-formed, thereby simplifying the subsequent gap-filling process while still enabling contact opening formation through hard mask recessing.
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 ensures more uniform gate widths across different channel lengths, reducing the pattern-loading effect and achieving consistent metal gate heights, thereby improving the etch-back process and overall metal gate formation.
Implementation Method 1
The introduction of filling regions made of dielectric materials, which are deposited before the etch-back of metal gates
Data Source
AI summary
A method includes removing a dummy gate to leave a trench between gate spacers, forming a gate dielectric extending into the trench, depositing a metal layer over the gate dielectric, with the metal layer including a portion extending into the trench, depositing a filling region into the trench, with the metal layer have a first and a second vertical portion on opposite sides of the filling region, etching back the metal layer, with the filling region at least recessed less than the metal layer, and remaining parts of the portion of the metal layer forming a gate electrode, depositing a dielectric material into the trench, and performing a planarization to remove excess portions of the dielectric material. A portion of the dielectric material in the trench forms at least a portion of a dielectric hard mask over the gate electrode.