Atomic Layer and Ion Beam Etching for Vertical MRAM Profiles
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Solution Overview
Problem
Current patterning technologies for magnetic random access memory (MRAM) face challenges such as sidewall re-deposition, tapered profiles, and corrosion during the etching process, especially for small critical dimension and tight pitch features, due to limitations in ion incidence shadowing and chemical damage.
Innovation Solution
A method combining atomic layer etch (ALE) and ion beam etch (IBE) processes, where ALE forms volatile etch byproducts to minimize sidewall re-deposition and IBE removes residues, ensuring vertical profiles and reducing halogen species damage, thereby enabling effective patterning of high-density MRAM arrays without re-deposition or corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion beam etching is used to pattern MRAM stack, then etching capability is improved, but sidewall re-deposition occurs causing tapered profile
Solution Approach 1:
The patent divides the etching process into multiple sequential steps with different purposes: a first IBE step for initial etching, followed by a second IBE step for sidewall cleaning, and integrated with ALE steps. This segmentation allows each step to be optimized for its specific function, preventing sidewall re-deposition while maintaining etching capability.
Solution Approach 2:
The patent employs periodic alternation between IBE and ALE processes in a cyclic manner. The IBE process etches the material while ALE removes residues and prevents re-deposition. This periodic action ensures continuous prevention of sidewall damage while maintaining effective etching.
2Productivity
If chlorine-containing chemistry is used to etch metal, then etching rate is improved, but non-volatile byproducts re-deposit onto sidewalls causing defects
Solution Approach 1:
The patent changes the chemical parameters by using fluorine-based chemistry instead of chlorine-containing chemistry. This parameter change results in volatile etch byproducts that can be easily removed, preventing re-deposition onto sidewalls while maintaining high etching rates.
Solution Approach 2:
The patent converts the potential harm of byproduct accumulation into a benefit by using fluorine-based chemistry that produces volatile byproducts. These byproducts are easily evacuated, and the fluorine species actually help prevent metal migration and provide protective effects during etching.
3Device complexity
If single-step IBE recipe is used for large CD structures, then process simplicity is improved, but patterning of small CD features becomes difficult due to ion incidence shadowing
Solution Approach 1:
The patent employs dynamic adjustment of ion beam incidence angles during different etching steps. By varying the angle of ion incidence, the process overcomes shadowing effects that prevent effective etching of small CD features, while maintaining process control and simplicity through automated angle adjustment.
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 integrated ALE and IBE process effectively removes residues and minimizes damage, allowing for precise etching of high aspect ratio and tight pitch features, overcoming the limitations of traditional IBE and RIE techniques, and enhancing the scalability and reliability of MRAM devices.
Implementation Method 1
An atomic layer etch is provided to at least partially etch the stack, wherein the atomic layer etch forms at least some residue
Implementation Method 2
An ion beam etch is provided to etch the stack, wherein the ion beam etch removes at least some of the residue from the atomic layer etch
Data Source
AI summary
A method for selectively etching a stack with respect to a mask is provided. An atomic layer etch is provided to at least partially etch the stack, wherein the atomic layer etch forms at least some residue. An ion beam is provided to etch the stack, wherein the ion beam etch removes at least some of the residue from the atomic layer etch.