Amorphous Nitride Barrier for Boron Diffusion in Semiconductor Memory
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Solution Overview
Problem
In three-dimensional semiconductor memory devices, the diffusion of boron from tungsten or molybdenum electrode layers into insulating layers during heat treatment can deteriorate the characteristics of the insulating layers, leading to increased electron leakage and difficulties in achieving desired threshold changes during erasing operations.
Innovation Solution
A semiconductor device structure is implemented with a metal layer containing boron, a semiconductor film, a charge storage film, and a nitride film stack, where the nitride film includes amorphous and titanium nitride layers to inhibit boron diffusion and enhance adhesion, thereby preventing boron from reaching the insulating layers and maintaining the integrity of the block dielectric film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten or molybdenum electrode layers containing boron are used in three-dimensional memory devices, then the electrode material properties are improved, but boron diffuses into the insulating layer during heat treatment causing deterioration of insulating layer characteristics
Solution Approach 1:
A nitride film is introduced as an intermediary barrier layer between the metal electrode layer containing boron and the insulating layer. This nitride film prevents boron from diffusing into the insulating layer during heat treatment, while still allowing the electrode to function properly. The intermediary layer thus resolves the contradiction by blocking the harmful boron diffusion path without compromising electrode performance.
Solution Approach 2:
The interface structure between the metal electrode layer and insulating layer is segmented into multiple distinct layers: the metal layer, an intermediate nitride film layer, and the insulating layer. This segmentation creates a controlled transition zone that prevents direct contact and boron diffusion between the metal and insulating layers, while maintaining the functional integrity of each layer.
2Reliability
If heat treatment is applied to the metal layer containing boron, then the electrode characteristics are enhanced, but boron diffusion to the insulating layer increases causing deterioration
Solution Approach 1:
The nitride film serves as a thermal barrier and boron diffusion barrier during heat treatment processes. It allows the metal electrode layer to undergo heat treatment for characteristic enhancement while preventing boron from migrating into the insulating layer, thus maintaining insulating layer quality even under thermal processing conditions.
Solution Approach 2:
The nitride film is formed in advance before heat treatment of the metal layer. This preliminary action creates a protective barrier that remains in place during subsequent heat treatment processes, preventing boron diffusion issues that would otherwise occur during the necessary thermal processing for electrode characterization.
3Device complexity
If a simple interface structure between metal layer and insulating layer is used, then device complexity is reduced, but boron diffusion cannot be effectively prevented
Solution Approach 1:
The interface structure is segmented into three distinct layers (metal layer, nitride film, insulating layer) rather than a simple two-layer structure. This segmentation, while adding one additional layer, creates a highly effective boron diffusion barrier with minimal impact on overall device complexity, as the nitride film can be formed using standard semiconductor fabrication processes.
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 use of an amorphous nitride film between the metal layer and the block dielectric film effectively suppresses boron diffusion, maintaining the quality of the insulating layers and ensuring a desired threshold variation in memory cells, thus improving the memory device's performance and reliability.
Implementation Method 1
a nitride film which includes a first titanium nitride film which is in contact with the first dielectric film, a second titanium nitride film which is in contact with the metal layer, and an amorphous nitride film which is provided between the first titanium nitride film and the second titanium nitride film
Data Source
AI summary
According to one embodiment, a semiconductor device includes a metal layer containing boron, a semiconductor film extending in a direction intersecting with a direction in which the metal layer extends, a charge storage film provided between the semiconductor film and the metal layer, a first dielectric film provided between the charge storage film and the metal layer, and a nitride film provided between the first dielectric film and the metal layer. The nitride film includes a first titanium nitride film provided in contact with the first dielectric film, a second titanium nitride film provided in contact with the metal layer, and an amorphous nitride film provided between the first titanium nitride film and the second titanium nitride film.