Charge Diffusion Prevention Mask for Nonvolatile Memory Etching
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Solution Overview
Problem
Resistance variable nonvolatile memory devices exhibit variations in initial resistance values due to oxygen concentration disorders caused by etching plasma charge diffusion during the manufacturing process, particularly when using oxygen-deficient transition metal oxide layers.
Innovation Solution
A manufacturing method involving a charge diffusion prevention mask film, which is insulative and has a lower etching rate than the electrode films, is used to prevent etching plasma charge from diffusing to the resistance variable layer, ensuring a stable oxygen concentration profile by stacking layers with different oxygen contents and using materials like Ta2O5 or SiN for the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hard mask is used for dry etching the electrode layer, then etching selectivity is improved, but etching plasma charge diffuses to the resistance variable layer causing oxygen concentration disorder
Solution Approach 1:
An insulative charge diffusion prevention mask film is introduced as an intermediary layer between the hard mask and the resistance variable layer. This mask film serves as a mediator that allows the hard mask to perform its etching function while simultaneously preventing etching plasma charge from reaching and disordering the oxygen concentration profile in the resistance variable layer.
Solution Approach 2:
The mask structure is segmented into multiple functional layers: a hard mask layer for providing etching selectivity and an insulative charge diffusion prevention mask film for preventing charge diffusion. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between achieving good etching selectivity and maintaining oxygen concentration profile precision.
2Manufacturing precision
If the mask film is made insulative to prevent charge diffusion, then oxygen concentration stability is improved, but etching rate decreases
Solution Approach 1:
The mask system is divided into two segments with different properties: an insulative charge diffusion prevention mask film that contacts the resistance variable layer to prevent charge diffusion and maintain oxygen concentration stability, and a conductive hard mask layer that provides high etching rate and selectivity. This segmentation allows the insulative property to be localized where needed without compromising overall etching productivity.
Solution Approach 2:
The insulative property is applied locally only to the mask film portion that directly interfaces with the resistance variable layer, while the hard mask layer maintains its conductive properties for efficient etching. This local application of insulative quality ensures oxygen concentration stability at the critical interface without reducing the overall etching rate of the mask system.
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 effectively reduces variations in initial resistance values, leading to a more stable and reliable nonvolatile memory device with improved performance and reduced manufacturing costs.
Implementation Method 1
depositing a charge diffusion prevention mask film on the upper electrode film... dry etching the upper electrode film, the resistance variable film, and the lower electrode film, using the charge diffusion prevention mask as a mask
Implementation Method 2
the charge diffusion prevention mask film is insulative, and is lower in etching rate of dry etching than the upper electrode film and the lower electrode film
Data Source
AI summary
A nonvolatile memory device (10A) comprises an upper electrode layer (2); a lower electrode layer (4); a resistance variable layer (3) sandwiched between the upper electrode layer (2) and the lower electrode layer (4); and a charge diffusion prevention mask (1A) formed on a portion of the upper electrode layer (2); wherein the resistance variable layer (3) includes a first film comprising oxygen-deficient transition metal oxide and a second film comprising oxygen-deficient transition metal oxide which is higher in oxygen content than the first film; at least one of the upper electrode layer (2) and the lower electrode layer (4) comprises a simple substance or alloy of a platinum group element; and the charge diffusion prevention mask (1A) is insulative, and is lower in etching rate of dry etching than the upper electrode layer (2) and the lower electrode layer (4).