Gate Spacer Air Gap Formation to Protect FinFET Epitaxy
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to efficiently form transistors with precise control over the formation of fins and gate stacks, while minimizing damage to epitaxy structures during the etching process.
Innovation Solution
The method involves forming Fin Field-Effect Transistors (FinFETs) using a process that includes the formation of protruding fins, the deposition of dummy gate stacks, and the use of sacrificial spacer films with varying Si/N ratios and densities to control etching rates and reduce damage to epitaxy structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching processes are used to form fins and gate stacks, then transistor fabrication can proceed, but damage is inflicted on epitaxy structures
Solution Approach 1:
A sacrificial spacer film is introduced as an intermediary layer between the gate stack and the epitaxy structure. This spacer film absorbs etching damage and prevents direct contact between the etching process and the epitaxy structure, thereby protecting the epitaxy structure from damage while enabling the etching process to proceed
Solution Approach 2:
The sacrificial spacer film is designed to be a temporary, disposable component that is intentionally damaged or removed during the etching process. It serves its protective function during etching and is then discarded, allowing the epitaxy structure to remain intact
2Ease of manufacture
If gate spacers are formed in direct contact with epitaxy structures, then manufacturing is simplified, but stress control and device performance are compromised
Solution Approach 1:
The space between the gate stack and epitaxy structure is segmented into two distinct regions: an air gap that provides stress isolation and a dielectric residue region that maintains proper spacing. This segmentation allows the gate spacer to be formed without direct contact with the epitaxy structure, preserving device performance while simplifying manufacturing
3Reliability
If air gaps are formed between gate spacers and epitaxy structures, then stress isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The sacrificial spacer film is formed in advance before the etching process, pre-establishing the framework for air gap formation. This preliminary action simplifies the overall process by preparing the structure beforehand, reducing the complexity of forming air gaps during subsequent steps
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 enables the formation of transistors with improved precision and reduced damage to epitaxy structures, enhancing the overall performance and reliability of semiconductor devices.
Implementation Method 1
the use of sacrificial spacer films with varying Si/N ratios and densities to control etching rates and reduce damage to epitaxy structures
Data Source
AI summary
A semiconductor device includes source/drain regions, a gate structure, a first gate spacer, and a dielectric material. The source/drain regions are over a substrate. The gate structure is laterally between the source/drain regions. The first gate spacer is on a first sidewall of the gate structure, and spaced apart from a first one of the source/drain regions at least in part by a void region. The dielectric material is between the first one of the source/drain regions and the void region. The dielectric material has a gradient ratio of a first chemical element to a second chemical element.