Nonvolatile Storage Electrode Shape Control
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Solution Overview
Problem
Conventional nonvolatile storage elements using difficult-to-etch materials like platinum for electrodes face challenges in maintaining stable characteristics due to dimensional differences and shape variations during etching, leading to unstable connections and variations in resistance values.
Innovation Solution
A manufacturing method involving a conductive connecting electrode layer, a lower electrode layer made of non-noble metal nitride, and an upper electrode layer made of noble metal, with a variable resistance layer between them, using a mask layer to control etching and minimize shape shifts, allowing for precise formation of electrode shapes and stable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum is used as electrode material, then variable resistance is facilitated and characteristics become stable, but dimensional difference between upper and lower electrodes increases due to tapered shape after etching
Solution Approach 1:
The patent segments the electrode structure into multiple layers: a lower electrode layer (easy-to-etch material like tungsten), an intermediate layer, and an upper electrode layer (platinum). This segmentation allows each layer to serve different functions - the lower layer provides etching reference for dimensional accuracy while the upper layer provides stable electrical characteristics.
Solution Approach 2:
The patent introduces an intermediate layer between the lower electrode layer and upper electrode layer. This intermediate layer acts as a mediator that connects the easy-to-etch lower layer with the difficult-to-etch upper layer, enabling both dimensional precision and characteristic stability to be achieved simultaneously.
2Ease of manufacture
If conventional photoresist is used as mask, then etching of Pt is facilitated, but mask dimensions are reduced and shape variation increases
Solution Approach 1:
The patent uses a sacrificial oxide layer that is intentionally deposited and then completely removed during the etching process. This disposable layer protects the underlying electrode structures during etching and is then discarded, eliminating the need for mask removal and preventing inter-layer insulating film damage.
Solution Approach 2:
The patent performs preliminary oxidation of the electrode layers to form protective oxide masks before the actual etching process. This preliminary action creates a temporary protective layer that maintains shape accuracy during etching, and is subsequently removed along with the photoresist mask.
3Ease of manufacture
If mask removal etching is performed, then mask is removed, but inter-layer insulating film is etched and shape variation increases
Solution Approach 1:
The patent uses a sacrificial oxide layer that is intentionally deposited and then completely removed during the etching process. This disposable layer protects the underlying electrode structures during etching and is then discarded, eliminating the need for mask removal and preventing inter-layer insulating film damage.
Solution Approach 2:
The patent extracts the mask removal step from the conventional process by using an oxide layer that is removed together with the photoresist in the same etching step. This extraction eliminates the separate mask removal step that would otherwise damage the inter-layer insulating film.
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 ensures minimal dimensional difference and shape shift between electrodes, resulting in stable and reliable nonvolatile storage device characteristics with controlled etching of inter-layer insulating films, enabling stable operation and reliable data storage.
Implementation Method 1
a variable resistance layer disposed between the lower electrode layer and the upper electrode layer and whose resistance value varies reversibly based on an electrical signal applied between the lower electrode layer and the upper electrode layer
Implementation Method 2
performing continuous three-layer etching on the upper electrode layer, the variable resistance layer, and the lower electrode layer, using the mask layer that has been formed into the predetermined shape as a mask
Implementation Method 3
forming the mask layer into a predetermined shape, using a photoresist film as a mask
Data Source
AI summary
A method for manufacturing a nonvolatile storage element that minimizes shape shift between an upper electrode and a lower electrode, and which includes: depositing, in sequence, a connecting electrode layer which is conductive, a lower electrode layer and a variable resistance layer which are made of a non-noble metal nitride and are conductive, an upper electrode layer made of noble metal, and a mask layer; forming the mask layer into a predetermined shape; forming the upper electrode layer, the variable resistance layer, and the lower electrode layer into the predetermined shape by etching using the mask layer as a mask; and removing, simultaneously, the mask and a region of the connecting electrode layer that has been exposed by the etching.