3D NAND Hardmask Layer for Accurate Staircase Profile Control
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Solution Overview
Problem
The challenge in manufacturing next-generation semiconductor devices lies in achieving accurate pattern transfer and dimensional control for sub-half micron features, particularly in three-dimensional stacking, where conventional hardmask layers fail to provide sufficient etching resistance and selectivity, leading to inaccurate profile and dimension control.
Innovation Solution
A hardmask layer comprising a seed layer, a transition layer, and a bulk layer formed using a boron-based and tungsten-based gas mixture, with tungsten nitride (WN) providing high etching selectivity and resistance, is deposited on a substrate to facilitate precise pattern transfer and dimension control in three-dimensional semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hardmask layers (silicon oxynitride, silicon carbine, or carbon films) are used, then the manufacturing process is simple, but the etching resistance is insufficient leading to inaccurate pattern transfer
Solution Approach 1:
The hardmask layer is divided into three distinct sub-layers: a first sub-layer (5 nm-20 nm thick) with high etching selectivity to adjacent layers, a second sub-layer (20 nm-50 nm thick) providing transition and additional protection, and a third sub-layer (50 nm-100 nm thick) serving as the bulk hardmask. This segmentation allows each sub-layer to be optimized for specific functions, achieving superior overall etching resistance and pattern transfer accuracy.
Solution Approach 2:
The patent employs a composite hardmask structure where each sub-layer is formed from different material compositions. The first sub-layer uses materials with highest etching selectivity, the second sub-layer uses transition materials, and the third sub-layer uses bulk hardmask materials. This composite approach combines the advantages of different materials to achieve both high etching resistance and accurate pattern transfer.
2Productivity
If the hardmask layer is exposed to aggressive etchants for a long period, then the pattern transfer is complete, but the hardmask layer undergoes dimensional changes resulting in loss of dimensional control
Solution Approach 1:
The first sub-layer is designed with exceptionally high etching selectivity to adjacent layers, creating a protective barrier before the bulk hardmask is exposed to aggressive etchants. This preliminary protective layer prevents dimensional changes in the underlying hardmask structure during the etching process, maintaining dimensional control throughout the complete pattern transfer.
Solution Approach 2:
The multi-layer structure provides beforehand cushioning against etchant attack. The first and second sub-layers act as sacrificial protective layers that absorb the majority of etchant exposure, cushioning the third sub-layer and underlying structures from dimensional changes. This ensures that even after prolonged exposure to aggressive etchants, the final pattern maintains accurate dimensional control.
3Stability of the object's composition
If the hardmask layer material is similar to adjacent layers, then the material compatibility is good, but the etch selectivity is poor resulting in non-uniform and deformed profile
Solution Approach 1:
Different sub-layers of the hardmask are assigned different material qualities and compositions. The first sub-layer uses materials with highest etching selectivity to adjacent layers, the second sub-layer uses transition materials with intermediate properties, and the third sub-layer uses bulk hardmask materials. This local differentiation of material quality ensures both compatibility with adjacent layers and sufficient etch selectivity for uniform profile formation.
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 proposed hardmask layer ensures accurate profile and dimension control, superior electrical performance, and robust film properties, enhancing the manufacturing process for three-dimensional semiconductor devices by maintaining high etching selectivity and low surface roughness.
Implementation Method 1
forming a seed layer comprising boron on a film stack disposed on a substrate by supplying a seed layer gas mixture in a processing chamber, forming a transition layer comprising boron and tungsten on the seed layer by supplying a transition layer gas mixture in the processing chamber, and forming a bulk hardmask layer on the transition layer by supplying a main deposition gas mixture in the processing chamber
Data Source
AI summary
Embodiments of the present disclosure provide an apparatus and methods for forming a hardmask layer that may be utilized to transfer patterns or features to a film stack with accurate profiles and dimension control for manufacturing three dimensional (3D) stacked semiconductor devices. In one embodiment, a method of forming a hardmask layer on a substrate includes forming a seed layer comprising boron on a film stack disposed on a substrate by supplying a seed layer gas mixture in a processing chamber, forming a transition layer comprising born and tungsten on the seed layer by supplying a transition layer gas mixture in the processing chamber, and forming a bulk hardmask layer on the transition layer by supplying a main deposition gas mixture in the processing chamber.