Trench Gate Barrier Layer Formation for Leakage Reduction
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Solution Overview
Problem
Conventional semiconductor memory devices face challenges in increasing integration density while maintaining reliability, as SiO2-based barrier layers can act as insulating layers, leading to deteriorated electric characteristics and metal contamination issues during deposition and removal processes.
Innovation Solution
A semiconductor memory device is fabricated with a trench structure containing a first gate electrode, a barrier layer formed by oxidizing and nitrifying the top surface of the first gate electrode, and a second gate electrode with a lower work-function, using a barrier layer of metal oxynitride to prevent diffusion and improve electric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TiN-based metal layer is deposited and sidewall portion is removed, then barrier layer formation is achieved, but dispersion errors cannot be controlled and metal contamination occurs
Solution Approach 1:
The problematic sidewall removal step is completely eliminated from the process. The barrier layer is formed directly on the gate electrode without requiring subsequent sidewall portion removal, thus avoiding dispersion errors and metal contamination while maintaining effective barrier layer formation.
Solution Approach 2:
The metal oxynitride material serves as an intermediary that achieves barrier layer formation without the need for aggressive sidewall removal processes, preventing both dispersion errors and metal contamination in the gate oxide sidewall portion.
2Productivity
If integration density is increased, then productivity is improved, but reliability decreases due to thermal treatment intermixing
Solution Approach 1:
The barrier layer is designed as a thin, sacrificial-like structure that prevents intermixing during thermal treatment. The metal oxynitride barrier layer is sufficiently thin to maintain electrical properties but effective enough to prevent diffusion, enabling high integration density while maintaining reliability.
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
The solution reduces gate-induced-drain-leakage current and enhances the reliability of semiconductor memory devices by preventing silicon and n-type impurity diffusion, while maintaining optimal electric characteristics and controlling dispersion errors in the barrier layer formation.
Implementation Method 1
oxidizing a top surface of the first gate electrode to form a preliminary barrier layer
Implementation Method 2
nitrifying the preliminary barrier layer to form a barrier layer
Data Source
AI summary
A method of fabricating a semiconductor memory device includes etching a substrate that forms a trench that crosses active regions of the substrate, forming a gate insulating layer on bottom and side surfaces of the trench, forming a first gate electrode on the gate insulating layer that fills a lower portion of the trench, oxidizing a top surface of the first gate electrode where a preliminary barrier layer is formed, nitrifying the preliminary barrier layer where a barrier layer is formed, and forming a second gate electrode on the barrier layer that fills an upper portion of the trench.