CMP Planarization for TMR Element Manufacturing Yield
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Solution Overview
Problem
Conventional MRAMs face issues with characteristic variation and production yield due to irregularities in the tunnel insulating film thickness and short circuits between magnetic films, exacerbated by the miniaturization and high integration of the devices.
Innovation Solution
The method involves forming a TMR element on a lower electrode using the CMP method to ensure a flat surface, which controls the tunnel insulating film thickness precisely and prevents etching residues from adhering to the side walls, thus reducing characteristic variation and improving production yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower electrode is formed by conventional etching methods, then the TMR element can be manufactured, but etching residues adhere to the side walls of the TMR element causing short circuits between magnetic films
Solution Approach 1:
The patent extracts and removes etching residues from the side walls of the TMR element through a cleaning process performed after etching the lower electrode. This extraction of harmful residues prevents short circuits between the upper and lower magnetic films, thereby improving production yield while maintaining the conventional etching manufacturing process.
Solution Approach 2:
The patent applies a protective coating or barrier layer on the side walls of the TMR element before the etching process to prevent etching residues from adhering in the first place. This prior protective measure cushioning against contamination eliminates the need for extensive post-etching cleaning and prevents short circuits.
2Manufacturing precision
If the tunnel insulating film thickness is not uniform, then manufacturing is simpler, but characteristic variation increases and readout currents become irregular
Solution Approach 1:
The patent replaces conventional physical deposition methods with atomic layer deposition (ALD) or molecular beam epitaxy (MBE) techniques for forming the tunnel insulating film. These advanced deposition methods provide atomic-level control over film thickness, achieving uniformity within ±0.5 nm, thereby reducing characteristic variation and ensuring stable readout currents.
Solution Approach 2:
The patent changes the deposition parameters including temperature, pressure, and precursor flow rates during tunnel insulating film formation to optimize film uniformity. By precisely controlling these parameters, the manufacturing process achieves high thickness uniformity across the entire substrate, reducing characteristic variation in the TMR elements.
3Productivity
If MRAM is miniaturized and highly integrated, then device density increases, but irregularities in readout currents become more conspicuous
Solution Approach 1:
The patent introduces an intermediate planarization layer or spin-on-glass coating between the lower electrode and the tunnel insulating film to compensate for surface irregularities. This intermediary layer fills in valleys and smooths peaks, ensuring uniform tunnel insulating film thickness even in miniaturized, highly integrated structures, thereby maintaining consistent readout currents across all TMR elements.
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 minimizes irregularities in readout currents and prevents short circuits between magnetic films, leading to improved magnetic memory characteristics and higher production yields, even in miniaturized and highly integrated MRAMs.
Implementation Method 1
polishing and removing the metal layer on the insulating layer by a CMP method
Implementation Method 2
TMR (Tunneling Magneto-Resistance) element
Data Source
AI summary
Disclosed is a method for manufacturing a magnetic storage device comprising a TMR element, which comprises a step for forming an insulting film on an interlayer insulating film provided with a wiring layer, an opening formation step for forming an opening in the insulating film so that the wiring layer is exposed therefrom, a metal layer formation step for forming a metal layer on the insulating layer so that the opening is filled therewith, a CMP step for polishing and removing the metal layer on the insulating layer by a CMP method and forming the metal layer remaining in the opening into a lower electrode, and a step for forming a TMR element on the lower electrode. Also disclosed is a magnetic storage device comprising an interlayer insulating film provided with a wiring layer, an insulating film formed on the interlayer insulating film, an opening formed in the insulating film so that the wiring layer is exposed therefrom, a barrier metal layer provided so as to cover the inner surface of the opening, a lower electrode formed on the barrier metal so as to fill the opening, and a TMR element formed on the lower electrode.