Multilayer MTJ Etching in Vacuum to Reduce Contamination Damage
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Solution Overview
Problem
Conventional etching methods for multilayer magnetic tunnel junctions (MTJs) face challenges in achieving precise patterning and reducing metal contamination and sidewall damage, especially as device sizes decrease, leading to performance bottlenecks and limited yield due to the limitations of ion beam etching (IBE) and the inability to effectively use chemical etching components.
Innovation Solution
A multilayer MTJ etching method utilizing a combination of reactive ion plasma etching and ion beam etching chambers within a vacuum environment, with specific steps for etching, cleaning, and dielectric coating to maintain steepness and prevent metal contamination, allowing for precise control and protection of the MTJ structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ion beam etching (IBE) is used to protect MTJ sidewall from chemical erosion, then sidewall cleanliness is improved, but physical bombardment disrupts atomic layer ordering and degrades magnetic characteristics
Solution Approach 1:
The etching process is segmented into multiple steps using different etching methods. Reactive ion plasma etching is used for initial patterning, followed by IBE for sidewall cleaning, and then alternating steps for subsequent layer etching. This segmentation allows each method to be used for its optimal function without causing harm.
Solution Approach 2:
The patent implements periodic alternation between reactive ion plasma etching and IBE steps. After each etching step, a cleaning step is periodically performed to remove metal contamination and sidewall damage layers. This periodic action maintains sidewall quality while preserving magnetic characteristics.
2Object-affected harmful factors
If IBE is performed at a certain angle to achieve sidewall protection, then sidewall damage is reduced, but etching cannot reach the bottom of high aspect ratio MTJ structures
Solution Approach 1:
The patent dynamically adjusts the ion beam angle during different etching steps. For initial etching, a larger angle is used to protect sidewalls, while for bottom etching of high aspect ratio structures, the angle is adjusted to allow etchant access to the bottom while still maintaining sidewall protection through subsequent cleaning steps.
Solution Approach 2:
A mask layer is applied beforehand to protect sidewalls during etching. This preliminary protective action allows the use of more aggressive etching angles to reach the bottom of high aspect ratio structures, with the mask layer preventing sidewall damage that would otherwise occur.
3Manufacturing precision
If multiple etching steps are performed to etch through multiple isolation layers, then complete patterning is achieved, but process time increases and productivity decreases
Solution Approach 1:
The patent implements continuous processing by loading multiple wafers into the etching chamber simultaneously. While one wafer is being etched, another is being prepared or is undergoing cleaning, maintaining continuous useful action and reducing idle time between steps.
Solution Approach 2:
Dielectric layers are deposited beforehand to form protective sidewall spacers before etching. This preliminary action enables self-aligned etching processes that reduce the number of alignment steps and improve throughput while maintaining complete patterning of multiple isolation layers.
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 method significantly improves the performance and reliability of MTJ devices by maintaining good steepness and reducing metal contamination and damage, enhancing production efficiency and etching process precision, and enabling the creation of MRAM devices with step-like structures.
Implementation Method 1
a reactive ion plasma etching chamber
Implementation Method 2
reactive ion plasma etching
Implementation Method 3
an IBE chamber
Implementation Method 4
ion beam etching (IBE)
Data Source
AI summary
A multilayer magnetic tunnel junction etching method and an MRAM device. A wafer is processed according to particular steps without interrupting vacuum. A reactive ion plasma etching chamber (10) and an ion beam etching chamber (11) are used separately at least one time. The processing of a multilayer magnetic tunnel junction is always in a vacuum environment, thereby avoiding the impact of an external environment on etching. By means of the process of combining etching and cleaning, a device structure maintains good steepness, and the metal contamination and damage of a magnetic tunnel junction film structure are significantly decreased, thereby greatly increasing the performance and reliability of a device. In addition, use of both the ion beam etching chamber (11) and the reactive ion plasma etching chamber (10) solves the technical problem of an existing single etching method, and increases production efficiency and etching process precision.