Organic Pillar CD Trimming With Selective Isotropic Plasma Etching
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Solution Overview
Problem
Existing semiconductor fabrication techniques face limitations in reducing pillar critical dimension (CD) and achieving highly parallel sidewalls, particularly in structures like MRAM and PCM, due to lithography constraints and material selectivity issues during etching.
Innovation Solution
Employing isotropic plasma etching with high selectivity to silicon-containing antireflective coating (SiARC) and silicon nitride (SiN) to trim the critical dimension of sacrificial organic layer pillars, using gases like Ar/N2/CO2, maintaining parallel sidewalls and preserving the integrity of the SiARC and SiN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography and etching techniques are used, then existing fabrication processes can be maintained, but pillar critical dimension reduction and highly parallel sidewall achievement are limited
Solution Approach 1:
The etching process is divided into multiple selective etching steps, each targeting specific layers (sacrificial organic layer, SiARC, SiN) with different etch selectivities. This segmentation allows precise control over pillar CD reduction while maintaining ease of manufacture by using standard plasma etching equipment with optimized gas chemistry and process parameters.
Solution Approach 2:
The patent employs parameter changes in the form of different gas compositions (CHF3, CF4, Ar/N2/CO2) and etching conditions to achieve high selectivity for trimming sacrificial organic layer pillars. By adjusting etch selectivity parameters, the process achieves superior CD control and parallel sidewalls without requiring fundamentally new fabrication equipment.
2Manufacturing precision
If isotropic plasma etching with high selectivity is used to trim pillar CD, then highly parallel sidewalls and reduced critical dimension are achieved, but process selectivity control becomes more critical
Solution Approach 1:
The patent implements feedback control through selective etching monitoring, where the etching process is carefully controlled to stop at predetermined layers (SiARC and SiN) based on their distinct etch selectivities. This feedback mechanism ensures highly parallel sidewalls are achieved while maintaining manageable process control through real-time monitoring of etch depth and rate.
Solution Approach 2:
Different regions of the structure receive different etching treatments through the selective removal of sacrificial organic material while preserving SiARC and SiN layers. This local quality approach creates highly parallel sidewalls in the pillar regions while maintaining material integrity elsewhere, with process control achieved through spatially selective etching chemistry.
3Manufacturing precision
If conventional etching is used, then existing materials can be processed, but material selectivity between SiARC, SiN, and sacrificial organic layer is insufficient
Solution Approach 1:
The patent uses composite material properties of the sacrificial organic layer, SiARC, and SiN layers to achieve high material selectivity. By exploiting the distinct chemical compositions and etch responses of these materials, the process achieves superior selectivity in a single integrated etching step rather than requiring multiple separate process steps.
Solution Approach 2:
The sacrificial organic layer acts as an intermediary material that facilitates selective removal during etching. This intermediary layer allows the etch process to selectively trim pillars while protecting underlying SiN and overlying SiARC layers, achieving high material selectivity without increasing overall device complexity.
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
Enables the fabrication of MRAM and PCM cells with highly parallel sidewalls and reduced CD, allowing for denser memory arrays and overcoming lithography limitations, while maintaining material integrity and etch selectivity.
Implementation Method 1
etching the initial structure to remove portions of the sacrificial organic layer and the anti-reflective coating not protected by the patterned photoresist down to the hard mask
Implementation Method 2
trimming a critical dimension (CD) of the sacrificial organic layer pillars by etching with a gas that is selective to the anti-reflective coating and the hard mask
Data Source
AI summary
Provide an initial structure comprising a substrate, a hard mask outward of the substrate, a sacrificial organic layer outward of the hard mask, an anti-reflective coating outward of the sacrificial organic layer, and a patterned photoresist outward of the anti-reflective coating. Etch the initial structure to remove portions of the sacrificial organic layer and the anti-reflective coating not protected by the patterned photoresist down to the hard mask, to form sacrificial organic layer pillars under the patterned photoresist. Trim a critical dimension (CD) of the sacrificial organic layer pillars by etching with a gas that is selective to the anti-reflective coating and the hard mask, to trim sidewalls of the sacrificial organic layer pillars.