MTJ Etching via Reactive Ion and Ion Beam Segmentation
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Solution Overview
Problem
Conventional etching methods for magnetic tunnel junctions (MTJs) in semiconductor devices face challenges such as physical bombardment damage, limited angle constraints, and low yield due to the use of ion beam etching, which affects the magnetic characteristics and integration of MTJ devices as they shrink in size.
Innovation Solution
A semiconductor device manufacturing method combining reactive ion plasma etching and ion beam etching, with additional steps for surface cleaning and dielectric thin film coating, to minimize sidewall contamination and structural damage, allowing for precise control and improved etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion beam etching is used for MTJ patterning, then sidewall cleanliness is improved, but physical bombardment damage occurs and etching efficiency decreases
Solution Approach 1:
The etching process is divided into multiple stages: first using reactive ion etching to remove the majority of the MTJ structure, then switching to ion beam etching for precise sidewall cleaning and final patterning. This segmentation allows each method to be used for its optimal function, combining high removal rate with clean sidewalls.
Solution Approach 2:
The patent employs periodic alternation between reactive ion etching and ion beam etching modes during the patterning process. The process cycles through reactive ion etching for bulk material removal, followed by ion beam etching for sidewall refinement, repeating this sequence to achieve both efficiency and precision.
2Manufacturing precision
If ion beam etching is used at conventional angles, then sidewall protection is improved, but etching cannot reach the bottom of small-size MTJ structures
Solution Approach 1:
The patent dynamically adjusts the etching angle during the process. Initially, etching is performed at a shallower angle to protect sidewalls, then the angle is increased or the sample is repositioned to allow ions to reach the bottom of high-aspect-ratio structures. This dynamic angle adjustment enables both sidewall protection and complete etching through challenging geometries.
Solution Approach 2:
The patent introduces angular dimensionality to the etching process by using multi-angle incidence. Instead of fixed-angle etching, the sample or ion beam is rotated to approach the structure from different angles, allowing ions to access bottom regions that would be shadowed at a single angle while maintaining sidewall protection during other phases.
3Productivity
If reactive ion etching is used for MTJ patterning, then etching speed is improved, but chemical erosion of the sidewall occurs
Solution Approach 1:
The etching process is segmented into reactive ion etching phases for high-speed material removal and ion beam etching phases for sidewall protection and refinement. By separating these functions into distinct process steps, the patent achieves both high etching speed and maintained sidewall integrity.
Solution Approach 2:
The patent uses ion beam etching as an intermediary step between reactive ion etching stages. This intermediary process removes the chemically damaged layer created by reactive ion etching and provides a clean surface, effectively mediating between the high-speed but damaging reactive ion etching and the final patterning requirements.
4Length of moving object
If ion beam etching is used with high physical bombardment force, then etching penetration is improved, but atomic layer ordering is disrupted and magnetic characteristics are degraded
Solution Approach 1:
The patent applies ion beam etching with controlled, moderate bombardment energy rather than maximum force. The etching is performed in multiple passes with adjusted parameters, using just enough physical bombardment to achieve the required penetration depth without excessive energy that would disrupt atomic layer ordering. This partial action approach maintains magnetic characteristics while achieving sufficient etching depth.
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 reduces sidewall metal contamination and structural damage, enhances etching efficiency, and improves device performance and yield by leveraging the strengths of both etching techniques while mitigating their limitations.
Implementation Method 1
a first reactive ion etching step: the sample entering the reactive ion plasma etching chamber, etching the sample by means of reactive ion etching
Implementation Method 2
an IBE step: transferring the sample from the vacuum transport chamber to the IBE chamber, etching the sample into the fixed layer by means of IBE
Implementation Method 3
a first ion beam cleaning step: the sample entering the IBE chamber, and removing metal residues and treating a sample surface
Implementation Method 4
a protection step: the sample entering the film coating chamber, forming a dielectric thin film on the upper surface of and around the sample
Data Source
AI summary
A semiconductor device manufacturing method, wherein the etching apparatus used includes a sample loading chamber (15), a vacuum transition chamber (14), a reactive ion plasma etching chamber (10), an ion beam etching chamber (11), a film coating chamber (12), and a vacuum transport chamber (13). Without interrupting the vacuum, reactive ion etching is first adopted to etch to an isolation layer (102); then, ion beam etching is performed to etch into a fixed layer (101) and stopped near a bottom electrode metal layer (100), leaving only a small amount of the fixed layer (101); subsequently, reactive ion etching is adopted to etch to the bottom electrode metal layer (100); and finally, ion beam cleaning is performed to remove metal residues and sample surface treatment, and coating protection is performed.