Protective Cap for ILD in FinFET Gate Removal
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Solution Overview
Problem
Conventional remove metal gate (RMG) processes face challenges in critical dimension (CD) reduction, particularly with conformal atomic layer deposition and physical vapor deposition techniques, which struggle with feature pinching and high aspect ratios, impacting the protection of interlayer dielectric (ILD) during sacrificial gate material removal in FinFET manufacturing.
Innovation Solution
Employing a protective cap made from transition metal oxides and nitrides that are resilient to aggressive dry etches, allowing independent thickness selection and scalability across various aspect ratios, including <1:1, to effectively shield ILD during etching without requiring high aspect ratios, thus preventing feature pinching and ensuring effective downstream processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal atomic layer deposition or physical vapor deposition techniques are used to protect ILD during sacrificial gate material removal, then the ILD protection is achieved, but feature pinching occurs and high aspect ratios are required
Solution Approach 1:
The patent applies preliminary action by forming the protective cap layer over the ILD surface before the sacrificial gate material removal process. This pre-formed cap provides protection during subsequent aggressive etching operations, eliminating the need for conformal deposition techniques that cause feature pinching. The cap is deposited only where needed on the ILD surface, avoiding the sidewall coverage issues of conformal methods.
Solution Approach 2:
The protective cap is applied locally only to the ILD surface areas that require protection during etching, rather than conformally coating all surfaces. This localized application allows the cap thickness to be independently optimized for protection without being constrained by aspect ratio requirements, enabling aggressive etching while preventing feature pinching.
2Productivity
If aggressive dry etching is used to remove sacrificial gate material, then etching efficiency is improved, but ILD damage occurs without adequate protection
Solution Approach 1:
The protective cap is formed on the ILD surface before the aggressive etching process begins. This preliminary protection layer withstands the aggressive dry etching conditions, allowing high etching efficiency to be achieved without damaging the underlying ILD. The cap serves as a sacrificial barrier that protects the ILD during the high-speed removal of sacrificial gate material.
Solution Approach 2:
The protective cap acts as an intermediary layer between the aggressive etching plasma and the ILD. It absorbs the harmful effects of the aggressive etch chemistry, allowing the etching process to proceed efficiently while the cap gradually consumes itself rather than allowing direct attack on the ILD.
3Reliability
If conventional helmet processes are used, then ILD protection is provided, but they require high aspect ratios and are vulnerable to feature pinching
Solution Approach 1:
The protective cap is deposited only on the exposed ILD surface areas, not conformally on all surfaces. This localized deposition approach allows the cap thickness to be independently controlled and optimized for protection purposes without being constrained by the aspect ratio of the underlying structures. The process works effectively across a wide range of aspect ratios, including low aspect ratio structures.
Solution Approach 2:
The patent changes the deposition parameters and geometry of the protective layer from conformal sidewall coverage to localized surface coverage. This parameter change enables the process to work with various aspect ratios without requiring high aspect ratios, making the process versatile for different device geometries and technology nodes.
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
The solution enables precise protection of ILD, minimizing topography and allowing for aggressive etching, thereby maintaining the integrity of ILD for subsequent processing steps, even at smaller technology nodes like 10 nm and beyond, enhancing the scalability and effectiveness of FinFET production.
Implementation Method 1
Employing a protective cap made from transition metal oxides and nitrides that are resilient to aggressive dry etches
Implementation Method 2
conformal atomic layer deposition and physical vapor deposition techniques
Data Source
AI summary
An embodiment includes a system comprising: a first gate and a first contact that correspond to a transistor and are on a first fin; a second gate and a second contact that correspond to a transistor and are on a second fin; an interlayer dielectric (ILD) collinear with and between the first and second contacts; wherein (a) the first and second gates are collinear and the first and second contacts are collinear; (b) the ILD includes a recess that comprises a cap layer including at least one of an oxide and a nitride. Other embodiments are described herein.