Enhancing Charge Trapping Performance of Hafnia Thin Films Using Sequential Plasma Atomic Layer Deposition

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Device Physics

Background:

• Hafnium oxide (HfO2) is a promising material for charge-trapping layers in advanced NAND flash memory.
• Optimizing deposition processes is key to improving the performance and reliability of HfO2-based memory devices.

Purpose of the Study:

• To develop a reliable atomic layer deposition (ALD) process for HfO2 charge-trapping layers.
• To investigate the impact of sequential remote plasma (RP) and direct plasma (DP) deposition on memory device characteristics.
• To optimize the thickness ratio of RP and DP deposited films for enhanced device performance.

Main Methods:

• Fabrication of charge-trapping memory devices using a novel sequential RP and DP ALD process.
• Analysis of device operational characteristics, including memory window, retention, leakage current, and interface defect density.
• Systematic variation of the thickness of the initially RP-deposited thin film.

Main Results:

• Increased thickness of the RP-deposited film improved memory window and retention.
• Higher RP film thickness led to decreased interface defect density and leakage current.
• A 7 nm RP-deposited film achieved a maximum memory window of 10.1 V at ±10 V and a minimum interface trap density (Dit) of 1.0 × 10^12 eV^-1cm^-2.

Conclusions:

• The sequential RP and DP ALD process effectively improves HfO2 charge-trapping memory device performance.
• Optimizing film thickness in the sequential deposition mitigates ion bombardment effects, enhancing the Si/SiO2/HfO2 interface.
• This method offers a pathway to resolve interface instability issues and boost device reliability and process throughput.