Cryogenic Dielectric Etching for High-Aspect-Ratio Profiles
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Solution Overview
Problem
High aspect ratio etching of dielectrics in semiconductor devices faces challenges in achieving high etch selectivity, low sidewall etching, and straight profiles, particularly due to spontaneous chemical etching which compromises directionality, and existing methods require strong sidewall protection and trade-offs between etch rate and selectivity.
Innovation Solution
The method involves cooling the stack to cryogenic temperatures, using a leaner etch chemistry with reduced polymerizing components, and generating a plasma with specific etch gases like CF4, CHF3, and BCl3 to suppress chemical etching and enhance ion-induced etching, allowing for selective etching of dielectric layers with reduced lateral etching and increased etch rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used, then etching can proceed, but spontaneous chemical etching occurs which compromises directionality and results in poor sidewall profiles
Solution Approach 1:
The patent changes the temperature parameter to cryogenic conditions (below -20°C) to suppress spontaneous chemical etching reactions while maintaining ion-induced etching, thereby improving etch directionality and sidewall profile quality
Solution Approach 2:
The patent uses a fluorocarbon-based plasma environment that creates a protective polymer coating on sidewalls, effectively creating an inert protective layer that prevents unwanted chemical reactions and maintains straight sidewall profiles
2Object-generated harmful factors
If strong sidewall protection is used, then sidewall etching is reduced, but etch selectivity and etch rate must be compromised
Solution Approach 1:
The patent changes the temperature parameter to cryogenic conditions, which allows the use of leaner etch chemistries with reduced polymerizing components, thereby achieving sidewall protection without sacrificing etch rate or selectivity
Solution Approach 2:
The patent employs a composite approach combining cryogenic temperature control with specific fluorocarbon-based plasma chemistry to achieve both sidewall protection and high etch performance simultaneously
3Productivity
If high etch rate is achieved, then productivity improves, but selectivity to the mask decreases
Solution Approach 1:
The patent changes the temperature parameter to cryogenic conditions, which enables the use of leaner etch chemistries that maintain high etch rates while improving mask selectivity through reduced polymer deposition on the mask surface
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 high aspect ratio etching of dielectrics with improved selectivity and reduced bowing, striation, and tapering, while eliminating the need for strong sidewall protection, thus enhancing etch rate and contact shape quality.
Implementation Method 1
A plasma is generated from the etch gas. Features are selectively etched into the stack with respect to the patterned mask
Implementation Method 2
enhance ion-induced etching
Implementation Method 3
The stack is cooled with a coolant with a coolant temperature below −20°0 C.
Implementation Method 4
suppress chemical etching
Data Source
AI summary
A method for etching features in a stack below a patterned mask in an etch chamber is provided. The stack is cooled with a coolant with a coolant temperature below −20° C. An etch gas is flowed into the etch chamber. A plasma is generated from the etch gas. Features are selectively etched into the stack with respect to the patterned mask.