Multi-Level Contact Etch with WF6 for Uniform 3D NAND Recesses
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Solution Overview
Problem
Existing methods for multi-level contact etching in 3D NAND memory fabrication face challenges such as slower etch rate, bowing, clogging, striation, under etch, and CD non-uniformity, particularly due to the use of fluorocarbons, which affect the precision and selectivity of the process.
Innovation Solution
Incorporating a small amount of tungsten hexafluoride (WF6) into the plasma etch process gas composition, along with fluorocarbons, to improve etch selectivity and rate, while minimizing contact deformation and maintaining precise control over recess depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorocarbons are used in the plasma etch process, then etch rate is improved, but manufacturing precision deteriorates due to contact deformation and CD non-uniformity
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma etch process by introducing WF6 (tungsten hexafluoride) at a specific flow rate ratio (0.01%-2% of total gas flow rate) to fluorocarbon-based process gases. This parameter modification enables simultaneous achievement of high etch rate and uniform bottom critical dimension by optimizing the chemical reactions in the plasma phase, reducing contact deformation, and improving etch selectivity without sacrificing productivity.
2Productivity
If conventional plasma etching is used to form deep holes in high aspect ratio openings, then productivity is improved, but manufacturing precision deteriorates due to profile control and uniformity issues
Solution Approach 1:
The patent modifies the plasma etch process parameters by incorporating WF6 into fluorocarbon-based process gases at controlled flow rates. This chemical composition change improves etch selectivity to nitride etch stop layers, maintains vertical profile control in high aspect ratio openings, and ensures uniform etching across the substrate surface, thereby achieving both high productivity and manufacturing precision simultaneously.
3Manufacturing precision
If etch selectivity to nitride etch stop layers is enhanced, then manufacturing precision is improved, but productivity deteriorates due to slower etch rate
Solution Approach 1:
The patent optimizes the chemical composition of the plasma etch process by adding WF6 (0.01%-2% of total gas flow rate) to fluorocarbon-based process gases. This parameter change creates a synergistic effect where WF6 enhances etch selectivity to nitride etch stop layers through specific chemical reactions, while the fluorocarbon component maintains high etch rate, thereby resolving the trade-off between selectivity and productivity.
4Manufacturing precision
If contact deformation is minimized, then manufacturing precision is improved, but productivity deteriorates due to extended process time
Solution Approach 1:
The patent modifies the plasma etch process by introducing WF6 into fluorocarbon-based process gases at optimized flow rates. This chemical composition change reduces contact deformation by controlling the etch front propagation and minimizing lateral etching, while maintaining sufficiently high etch rate to complete the process in acceptable time, thus achieving both precision and productivity.
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 method enhances etch selectivity to nitride etch stop layers, reduces contact deformation, and improves bottom critical dimension uniformity, achieving high aspect ratio features with efficient process times.
Implementation Method 1
exposing the substrate to a plasma generated from a process gas including a fluorocarbon, dioxygen (O2), and tungsten hexafluoride (WF6)
Data Source
AI summary
A method of processing a substrate that includes: forming a conformal etch stop layer (ESL) over a staircase pattern of the substrate, the staircase pattern including staircases, each of the staircases including a conductive surface; forming a dielectric layer over the ESL; planarizing a top surface of the dielectric layer; forming a patterned hardmask over the dielectric layer; and etching the dielectric layer selectively to the ESL using the patterned hardmask as an etch mask to form a plurality of recesses, each of the plurality of recesses landing on each of the staircases, the ESL protecting the conductive surface from the etching, the etching including exposing the substrate to a plasma generated from a process gas including a fluorocarbon, O2, and WF6, a flow rate of WF6 being between 0.01% and 1% of a total gas flow rate of the process gas.