MRAM MTJ Etching Using Top Electrode Barriers
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Solution Overview
Problem
Current magnetoresistive random access memory (MRAM) manufacturing methods face challenges in maintaining the integrity and characteristics of magnetic tunnel junctions (MTJs) due to issues like etching residue removal, electrode selectivity, and redeposition of materials, which can lead to degraded device performance and magnetization reversal characteristics.
Innovation Solution
A method for manufacturing a semiconductor memory device involving sequential deposition of layers, including a magnetic tunnel junction (MTJ) layer, and using specific etch barriers such as the second top electrode layer to control etching processes, thereby minimizing losses and preventing collapse or redeposition of materials, ensuring accurate formation of MTJs and electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional etching methods are used to remove etching residue, then the etching residue can be removed, but the MTJ layer and electrodes are damaged or collapsed
Solution Approach 1:
A sacrificial layer is introduced as an intermediary between the MTJ layer and the etching process. This sacrificial layer absorbs the etching damage that would otherwise affect the MTJ layer and electrodes. The sacrificial layer is specifically designed to be etched away after serving its protective function, thereby resolving the contradiction between removing etching residue and preserving the integrity of critical structures.
Solution Approach 2:
The sacrificial layer is deposited beforehand to cushion and protect the MTJ layer and electrodes from etching damage. This pre-positioned protective layer ensures that when etching is performed to remove residue, the underlying critical structures are shielded from direct etching exposure, thus maintaining their integrity while still allowing effective residue removal.
2Productivity
If high-density current is applied to change magnetization direction, then data can be written, but the spin direction alignment becomes difficult when magnetization directions are anti-parallel
Solution Approach 1:
The patent introduces a magnetization reversal characteristic improvement layer with specific local magnetic properties between the pinned layer and free layer. This layer has tailored magnetization characteristics that differ from the adjacent layers, creating favorable local conditions for spin direction alignment. The improvement layer's specific magnetic properties facilitate easier spin alignment during the writing process, resolving the contradiction between writing speed and alignment precision.
3Manufacturing precision
If multiple etching processes are performed to form patterns, then accurate patterning is achieved, but material redeposition and aspect ratio degradation occur
Solution Approach 1:
The sacrificial layer serves as a mediator during the etching process. It allows the etching to proceed effectively for accurate patterning while preventing material redeposition on the MTJ layer and electrodes. The sacrificial layer is positioned to intercept and contain etched materials, preventing them from redepositing on critical structures, thus maintaining the aspect ratio while achieving accurate patterning.
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 enhances the magnetization reversal characteristics and prevents the collapse of electrodes, reducing losses and maintaining the intended aspect ratio of the memory device, thereby improving the overall performance and reliability of the MRAM.
Implementation Method 1
a magnetoresistive random access memory (MRAM) using tunneling magneto-resistance
Implementation Method 2
An MRAM uses a spin transfer torque (STT) phenomenon to write data to a memory cell. The STT phenomenon refers to a phenomenon that a spin-polarized current is transferred as an angular momentum of a ferromagnetic material by a change of an angular momentum instantly generated when the spin-polarized current passes through the ferromagnetic material.
Implementation Method 3
sequentially depositing a bottom electrode layer, an MTJ layer, a first top electrode layer, a second top electrode layer and a mask layer
Data Source
AI summary
A method for manufacturing a semiconductor memory device includes sequentially depositing a bottom electrode layer, a magnetic tunnel junction (MTJ) layer, a first top electrode layer, a second top electrode layer and a mask layer, etching the mask layer and forming a mask pattern, etching the second top electrode layer and the first top electrode layer by using the mask pattern as an etch barrier, etching the MTJ layer by using the mask layer and the second top electrode layer as an etch barrier, and etching the bottom electrode layer by using the first top electrode layer as an etch barrier.