Composite Top Electrode for Memory Cell via Contact
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Solution Overview
Problem
The integration of memory devices with complementary metal-oxide-semiconductor (CMOS) logic fabrication processes faces challenges due to contact issues between the top electrode and the top electrode via (TEVA) in memory cells, resulting in high contact resistance and increased resistance-capacitance delay, primarily caused by the formation of a native interfacial oxide layer during exposure.
Innovation Solution
A composite top electrode comprising a tantalum nitride (TaN) layer and a titanium nitride (TiN) film is used, with TiN as the uppermost portion, which eliminates or reduces the interfacial oxide layer, thereby improving the contact resistance and capacitance properties between the top electrode and the TEVA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the top electrode is exposed to form TEVA, then the TEVA can be formed to connect the top electrode to interconnect layers, but a native interfacial oxide layer forms causing high contact resistance
Solution Approach 1:
The top electrode uses a composite structure with a TaN layer and a TiN layer. The TiN layer serves as an outer protective layer that prevents oxide formation at the exposed surface, while the TaN layer provides the primary conductive function. This composite material approach resolves the contradiction by combining materials with complementary properties to simultaneously achieve good electrical contact and oxide resistance.
Solution Approach 2:
The TiN layer acts as an intermediary between the TaN electrode layer and the external environment (TEVA). It provides a protective interface that prevents direct oxidation of the TaN layer while maintaining electrical conductivity, thus mediating between the need for exposed contact and the harm of oxide formation.
2Ease of operation
If the top electrode is exposed to form TEVA, then connectivity to interconnect layers is achieved, but resistance-capacitance delay increases
Solution Approach 1:
The dual-layer composite electrode structure reduces contact resistance by preventing oxide formation at the exposed surface. The TiN outer layer maintains a clean, conductive interface with TEVA, while the TaN inner layer provides bulk conductivity. This reduces the RC time constant by minimizing the resistance component at the interface.
Solution Approach 2:
By changing the material composition and structure of the top electrode from a single layer to a composite of TaN and TiN layers, the electrical parameters (contact resistance, capacitance) are optimized. The TiN layer specifically modifies the interface properties to reduce resistance and improve overall RC performance.
Data Source
AI summary
A memory cell with a composite top electrode is provided. A bottom electrode is disposed over a substrate. A switching dielectric having a variable resistance is disposed over the bottom electrode. A capping layer is disposed over the switching dielectric. A composite top electrode is disposed over and abutting the capping layer. The composite top electrode comprises a tantalum nitride (TaN) layer and a titanium nitride (TiN) film disposed directly on the tantalum nitride layer. By having the disclosed composite top electrode, an interfacial oxidized layer is eliminated or less formed when exposing the composite top electrode for top electrode via formation, thereby improving RC properties between the top electrode and the top electrode via. A method for manufacturing the memory cell is also provided.