Ion Beam Etching Sidewall Cleaning MRAM Tunnel Barrier
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Solution Overview
Problem
The challenge in etching magnetic random access memory (MRAM) stacks lies in the sensitivity of tunnel barrier layers to reactive chemistries, which can damage these layers and impact the electrical and magnetic properties of MRAM.
Innovation Solution
A method of ion beam etching (IBE) is employed to etch through MRAM layers, including the tunnel barrier layer, without using reactive chemistries. This method involves forming patterned MRAM stacks and then performing an IBE trim etch to remove dielectric and conductive materials from the sidewalls, using a gapfill dielectric material to prevent exposure of the tunnel barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reactive chemistries are used to etch MRAM layers, then etching efficiency is improved, but the tunnel barrier layer is damaged
Solution Approach 1:
A gapfill dielectric material is deposited as an intermediary layer between the etch front and the tunnel barrier layer. This dielectric material absorbs the ion beam impact and prevents direct damage to the tunnel barrier layer during IBE trim etch, while still allowing effective etching of the MRAM layers above it.
Solution Approach 2:
The patent replaces reactive chemistry-based etching with ion beam etching (IBE) for the trim etch step. IBE uses physical ion bombardment instead of chemical reactions, eliminating the harmful chemical effects on the tunnel barrier layer while maintaining etching capability through controlled ion energy and angle.
2Manufacturing precision
If IBE trim etch is performed to clean sidewalls, then sidewall contamination is removed, but recess into the underlayer occurs
Solution Approach 1:
The gapfill dielectric material is deposited in advance before the IBE trim etch step. This preliminary action creates a protective cushion that prevents the ion beam from reaching and etching the underlayer, allowing aggressive sidewall cleaning without compromising underlayer integrity.
Solution Approach 2:
The gapfill dielectric material serves as a beforehand cushioning layer that absorbs excess ion beam energy and prevents it from penetrating into the underlayer. This cushioning effect enables the IBE trim etch to aggressively remove sidewall contamination while maintaining a safety margin that prevents underlayer damage.
3Productivity
If ion beam energy is increased to improve etching rate, then productivity increases, but sidewall damage increases
Solution Approach 1:
The patent applies different ion beam energies at different stages of the etching process. High ion beam energy is used for the main etching step to achieve high productivity, while low ion beam energy is used for the trim etch step to minimize sidewall damage. The gapfill dielectric material enables this local quality differentiation by protecting the sidewalls during the low-energy trim etch.
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 IBE method effectively patterns MRAM stacks while protecting the tunnel barrier layer from damage, maintaining the integrity of the MRAM's electrical and magnetic properties.
Implementation Method 1
etching through the plurality of MRAM layers includes ion beam etching (IBE) through at least the tunnel barrier layer
Implementation Method 2
performing an IBE trim etch to remove at least some of the gapfill dielectric material and electrically conductive materials deposited on sidewalls
Data Source
AI summary
Patterned magnetoresistive random access memory (MRAM) stacks are formed by performing a main etch through a plurality of MRAM layers disposed on a substrate, where the main etch includes using ion beam etching (IBE). After the main etch, gapfill dielectric material is deposited in spaces between the patterned MRAM stacks, and the gapfill dielectric material is selectively etched or otherwise formed to an etch depth that is above a depth of an underlayer. After the gapfill dielectric material is formed, at least some of the gapfill dielectric material and any electrically conductive materials deposited on sidewalls of the patterned MRAM stacks are removed by performing an IBE trim etch.