Magnetic Tunnel Junction Patterning via HDPCVD Sidewall Passivation
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Solution Overview
Problem
The patterning of magnetic tunnel junction (MTJ) stacks in magnetic memory devices faces challenges due to non-volatile by-products condensing on sidewalls, leading to leakage and shorting issues, which degrades performance and increases error rates, and existing methods require multiple machines and are complex and costly.
Innovation Solution
A method using high-density plasma chemical vapor deposition (HDPCVD) to pattern the MTJ stack, where a non-conformal sidewall protection layer is deposited in-situ during etching, preventing accumulation of conducting residues and allowing for single-tool processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional plasma etch chemistries are used to pattern the MTJ stack, then the etching process can be performed, but non-volatile by-products condense on sidewalls causing leakage and shorting issues
Solution Approach 1:
A sacrificial layer is introduced as an intermediary component between the MTJ stack and the patterning process. This sacrificial layer protects the sidewalls during etching, preventing by-product condensation and subsequent leakage/shorting issues, while being removable afterward to restore the original structure.
Solution Approach 2:
The method applies preliminary protective action by depositing a sidewall protection layer before the etching process. This pre-protection prevents the harmful condensation of non-volatile by-products on the sidewalls during etching, thereby avoiding leakage and shorting issues before they can occur.
2Ease of manufacture
If non-reactive Ion Beam Etch (IBE) methods are used to sputter off materials, then materials can be removed in unwanted areas, but sputtered materials re-deposit on MTJ sidewalls causing leakage or short issues
Solution Approach 1:
The sacrificial layer serves as a mediator that intercepts sputtered materials during IBE processing. By placing this layer on the sidewalls, it captures re-depositing materials that would otherwise cause leakage or shorting, allowing the IBE process to proceed effectively while protecting the MTJ structure.
Solution Approach 2:
The method converts the harmful re-deposition of sputtered materials into a beneficial process by directing these materials onto the sacrificial layer instead of the MTJ sidewalls. The sacrificial layer absorbs the harmful by-products, transforming what would be damage into a protective mechanism.
3Loss of substance
If organic chemicals are added to argon plasma to increase by-product volatility, then etched by-products can be pumped out more easily, but etch rate slows down and residual organometallic complexes impact MTJ long term reliability
Solution Approach 1:
The harmful organometallic complexes are extracted from the etching process by using the sacrificial layer to capture them physically. Instead of relying on chemical modification to remove by-products, the sacrificial layer physically traps the complexes, preventing them from remaining as residues that would degrade MTJ reliability.
4Reliability
If multiple machines and processes are used for partial etching, insulator deposition, and further etching, then sidewall protection can be formed, but the process becomes complex and time-consuming
Solution Approach 1:
The method merges multiple separate processes (etching, sidewall protection formation, and material removal) into a single integrated process using one machine. The sacrificial layer approach allows all these steps to be combined in one tool, significantly reducing process complexity and time while maintaining effective sidewall protection.
Solution Approach 2:
The sacrificial layer serves multiple functions simultaneously: it protects sidewalls during etching, captures re-deposited materials, and can be selectively removed afterward. This multi-functionality eliminates the need for separate processes for each protective action, simplifying the overall manufacturing process.
5Reliability
If multiple machines and processes are used including ALD and ALE with sidewall protection, then protection can be achieved, but it requires new machine development which is expensive and time-consuming
Solution Approach 1:
The sacrificial layer is a temporary, disposable component that performs its protective function during the process and is then removed. This approach uses a simple, inexpensive material rather than requiring complex, expensive new machine development, achieving sidewall protection through a cost-effective temporary structure.
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 approach improves yield and throughput, reduces costs, and enhances MTJ performance by preventing sidewall shorts and leakage, enabling more efficient and reliable manufacturing of magnetic memory devices.
Implementation Method 1
high-density plasma chemical vapor deposition (HDPCVD) to pattern the MTJ stack, where a non-conformal sidewall protection layer is deposited in-situ during etching
Implementation Method 2
high-density plasma chemical vapor deposition (HDPCVD)
Implementation Method 3
The MTJ stack is then subjected to a MTJ patterning process in a high-density plasma chemical vapor deposition (HDPCVD) chamber, thereby sputtering off the MTJ stack not covered by the patterned sacrificial layer
Data Source
AI summary
A method for forming a magnetic memory device is disclosed. At least one magnetic tunneling junction (MTJ) stack is formed on the substrate. The MTJ stack comprises a reference layer, a tunnel barrier layer and a free layer. A top electrode layer is formed on the MTJ stack. A patterned sacrificial layer is formed on the top electrode layer. The MTJ stack is then subjected to a MTJ patterning process in a high-density plasma chemical vapor deposition (HDPCVD) chamber, thereby sputtering off the MTJ stack not covered by the patterned sacrificial layer. During the MTJ patterning process, sidewalls of layers or sub-layers of the MTJ stack are simultaneously passivated in the HDPCVD chamber by depositing a sidewall protection layer.