Non-conformal liner for 3D NAND etch critical dimension control
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Solution Overview
Problem
The increasing aspect ratios in 3D NAND structures during etch processes lead to challenges in maintaining critical dimension control, with current deposition methods failing to adequately protect sidewalls and resulting in bow critical dimension issues.
Innovation Solution
A non-conformal liner is deposited on the sidewalls and bottom of the etch opening using chemical vapor deposition, comprising boron, nitrogen, or carbon, which is selectively etched from the bottom to allow precise control of the etch process and reduce bow critical dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal deposition processes (ALD/MLD/furnace) are used to deposit protective liners, then sidewall protection is improved, but the bottom of the opening accumulates excessive liner material that prevents breakthrough etching
Solution Approach 1:
The patent applies non-conformal deposition to create a liner with spatially varying thickness: thicker on sidewalls for protection, thinner at the bottom for breakthrough control. This local quality variation resolves the contradiction by providing targeted protection where needed while preventing excessive accumulation at the bottom.
Solution Approach 2:
Instead of using conformal deposition that deposits uniformly in all directions, the patent inverts the approach by using non-conformal deposition that deliberately deposits preferentially on sidewalls while minimizing bottom accumulation. This inversion of the deposition pattern solves the breakthrough etching problem.
2Quantity of substance
If higher aspect ratio structures are etched to increase storage density, then storage capacity is improved, but critical dimension control deteriorates due to bow CD issues
Solution Approach 1:
The non-conformal liner provides localized protection on sidewalls during high aspect ratio etching, maintaining critical dimension control in the most challenging regions. The varying thickness profile ensures adequate protection where the etch front encounters the most resistance.
Solution Approach 2:
The non-conformal liner acts as an intermediary protective layer between the etch plasma and the underlying structure. It mediates the etching process by providing selective protection that maintains CD control while allowing the etch to proceed through high aspect ratio structures.
3Reliability
If thicker liners are deposited to enhance sidewall protection, then etch selectivity is improved, but the liner removal process becomes more difficult and time-consuming
Solution Approach 1:
The non-conformal liner has thicker regions on sidewalls for protection and thinner regions at the bottom for easy removal. This local quality differentiation allows the liner to provide adequate selectivity during etching while enabling rapid removal afterward without requiring excessive time or aggressive removal processes.
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 non-conformal liner effectively reduces bow critical dimension and facilitates breakthrough etching by providing selective protection to the sidewalls, ensuring precise profile control and easier breakthrough during high aspect ratio etching.
Implementation Method 1
depositing a non-conformal liner by chemical vapor deposition on the at least one sidewall and the bottom surface of the opening
Data Source
AI summary
A non-conformal, highly selective liner for etch methods in semiconductor devices is described. A method comprises forming a film stack on a substrate; etching the film stack to form an opening; depositing a non-conformal liner in the opening; etching the non-conformal liner from the bottom of the opening; and selectively etching the film stack relative to the non-conformal liner to form a logic or memory hole. The non-conformal liner comprises one or more of boron, carbon, or nitrogen.