Reflow Soldering Capability Improvement by Utilizing TaN Interfacial Layer in 1Mbit RRAM Chip

Area of Science:

• Semiconductor Device Physics
• Materials Science
• Electrical Engineering

Background:

• Oxide Resistive Random-Access Memory (OxRRAM) offers high density and low power consumption.
• Embedded RRAM in advanced CMOS technology faces challenges with thermal stability during assembly.
• Current fabrication methods struggle to maintain RRAM integrity under high-temperature processing.

Purpose of the Study:

• To investigate the thermal stability of a 1 Mbit OxRRAM array in 28 nm CMOS technology.
• To propose and validate a back-end-of-line (BEOL) solution to enhance RRAM reliability.
• To address the failure rate of embedded RRAM after reflow soldering assembly.

Main Methods:

• Fabrication of a 1 Mbit OxRRAM array using 28 nm CMOS technology.
• Implementation of a TaN-Ta interfacial layer (IL) within the BEOL stack.
• Thermal stress testing, including reflow soldering at 260 °C.
• Analysis of oxygen defect redistribution and electromigration in Cu interconnects.

Main Results:

• The proposed TaN-Ta interfacial layer effectively eliminated the failure rate of the OxRRAM array after 260 °C reflow soldering.
• Oxygen defects within the conductive filament were successfully redistributed by the TaN-Ta IL.
• Electromigration lifetimes of Cu-based damascene interconnects were significantly improved.
• The optimized BEOL structure demonstrated enhanced overall device reliability.

Conclusions:

• The TaN-Ta interfacial layer is a viable solution for improving the thermal stability and reliability of embedded OxRRAM.
• This approach enables the practical application of embedded RRAM beyond the 28 nm technology node.
• The findings contribute to the advancement of high-performance, integrated memory solutions.