Confined Resistance Variable Memory Cell via Conformal Deposition
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Solution Overview
Problem
Conventional sputtering processes for depositing GST films in high aspect ratio structures, such as contact vias, lack conformality, leading to high reset currents required for switching GST materials between crystalline and amorphous states in PCRAM cells.
Innovation Solution
A method involving the use of germanium amidinate and antimony ethoxide precursors, with subsequent di-t-butyl telluride deposition, is employed to form a conformal phase change material within confined via structures, reducing reset currents and improving adhesion to conductive contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sputtering processes are used for GST film deposition in high aspect ratio structures, then the deposition process is simple and fast, but the conformality is poor leading to high reset currents
Solution Approach 1:
The patent replaces the physical sputtering process with a chemical deposition process (MOCVD or ALD). This substitution allows for superior conformality in high aspect ratio structures through chemical reactions that uniformly coat all surfaces, while maintaining manufacturing efficiency through established semiconductor fabrication processes.
Solution Approach 2:
The patent changes the deposition parameters by using different precursor materials (germanium amidinate, antimony ethoxide, di-t-butyl telluride) and controlling deposition temperature and pressure. These parameter changes enable conformal film formation in confined via structures, reducing reset currents while maintaining processability.
2Use of energy by moving object
If GST material is confined into vias to reduce heat dissipation, then reset current is reduced, but conventional sputtering cannot achieve conformality in high aspect ratio structures
Solution Approach 1:
The patent replaces physical sputtering with chemical deposition methods (MOCVD or ALD) that can achieve uniform conformal coverage in high aspect ratio vias. This enables GST material confinement for reduced heat dissipation and lower reset currents while maintaining manufacturing feasibility through chemical processes that naturally conform to complex geometries.
3Quantity of substance
If multi-level storage is implemented in PCRAM cells, then storage capacity is increased, but the complexity of resistance state control increases
Solution Approach 1:
The patent applies local quality by creating distinct GST regions with different compositions or structures within the same memory cell. This enables different regions to represent different resistance states, achieving multi-level storage without requiring complex external control mechanisms, as the local material properties encode the additional storage states.
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 achieves reduced reset currents, increased throughput, and improved conformality and composition uniformity of the phase change material, enhancing the performance of confined resistance variable memory cell structures.
Implementation Method 1
forming a resistance variable material in the via by performing a process that includes providing a germanium amidinate precursor and a first reactant to a process chamber having the memory cell structure therein and providing an antimony ethoxide precursor and a second reactant to the process chamber
Implementation Method 2
providing a di-t-butyl telluride precursor in the absence of additional reactant to the chamber subsequent to removing excess first and second reactant from the chamber
Implementation Method 3
The solid phases of GST can rapidly change from crystalline state to amorphous state or vise versa upon heating and cooling cycles. The amorphous GST has relatively higher electrical resistance while the crystalline GST has relatively lower electrical resistance.
Implementation Method 4
The resistance state of the PCRAM cell may be altered by heating the cell with a programming current
Data Source
AI summary
Confined resistance variable memory cell structures and methods are described herein. One or more methods of forming a confined resistance variable memory cell structure includes forming a via in a memory cell structure and forming a resistance variable material in the via by performing a process that includes providing a germanium amidinate precursor and a first reactant to a process chamber having the memory cell structure therein and providing an antimony ethoxide precursor and a second reactant to the process chamber subsequent to removing excess germanium.