UNCD Hard Mask Deposition for Low-Roughness Plasma Etching
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving uniform etch and maintaining yield and performance in 3D NAND storage as the number of oxide-nitride layers increases, due to the degradation of traditional amorphous carbon hard masks during aggressive plasma etching.
Innovation Solution
The method involves forming an ultrananocrystalline diamond (UNCD) hard mask by exposing a substrate to a deposition gas containing a dopant gas, carbon gas, and argon, and igniting a pulsed microwave plasma at a temperature less than or equal to 550°C to achieve a film with an average roughness less than 10 nm and a modulus greater than or equal to 250 GPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick amorphous carbon films are used as hard masks, then the hard mask can withstand plasma etching, but the film roughness increases and etch uniformity deteriorates
Solution Approach 1:
The patent changes the material parameters by transitioning from amorphous carbon to ultrananocrystalline diamond (UNCD) films, and controls deposition parameters (temperature ≤550°C, specific gas compositions with dopants) to achieve films with simultaneously low roughness (<10 nm) and high plasma resistance
Solution Approach 2:
The patent creates a composite material structure by incorporating dopant atoms (boron, nitrogen, sulfur, phosphorous) into the UNCD film matrix, resulting in a composite material that combines the hardness and plasma resistance of diamond with enhanced structural properties from the dopants
2Quantity of substance
If the number of oxide-nitride layers is increased to increase storage capacity, then memory density increases, but the aspect ratio increases making uniform etch more difficult
Solution Approach 1:
The patent changes the hard mask material properties by using UNCD films with specific mechanical properties (modulus ≥250 GPa) and surface characteristics (roughness <10 nm), enabling uniform plasma etching across high aspect ratio structures with 128+ layers
Solution Approach 2:
The patent achieves vertical profile maintenance during etching by using UNCD hard masks that resist plasma attack, preserving the curved/vertical sidewall geometry of high aspect ratio structures throughout the etching process
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 results in a hard mask that effectively withstands aggressive plasma etching, maintaining pattern integrity and vertical profile, thus enhancing device yield and performance in 3D NAND storage.
Implementation Method 1
A plasma is ignited from the deposition gas to form an ultrananocrystalline diamond film
Implementation Method 2
igniting a pulsed microwave plasma at a temperature less than or equal to 550°C
Implementation Method 3
The deposition gas comprises a dopant gas comprising one or more of a boron dopant species, a nitrogen dopant species, a sulfur dopant species or a phosphorous dopant species
Data Source
AI summary
Hard masks and methods of forming hard masks are described. The hard mask has an average roughness less than 10 nm and a modulus greater than or equal to 400 GPa. The method comprises exposing a substrate to a deposition gas comprising a dopant gas or a precursor (solid (e.g. Alkylborane compounds) or liquid (e.g. Borazine)), a carbon gas and argon at a temperature less than or equal to 550 C, and igniting a plasma from the deposition gas to form an ultrananocrystalline diamond film having an average roughness less than 10 nm and a modulus greater than or equal to 400 GPa.