Single-Layer Semiconductor Channel in 3D NAND Memory
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Solution Overview
Problem
The two-step semiconductor material deposition process in prior art creates a substantially contiguous interface with grain boundaries, leading to defects, reduced grain size, and deteriorated electrical characteristics in three-dimensional NAND string memory devices, such as increased grain boundary area and lattice defects, which affect memory cell performance.
Innovation Solution
A method involving the formation of a memory film layer within a memory opening, followed by a sacrificial material layer deposition and selective removal, allowing for a single semiconductor material layer to be deposited without interfacial layers, thereby avoiding contiguous grain boundaries and improving semiconductor channel quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-step semiconductor material deposition process is used, then the semiconductor channel can be formed with protective layers, but contiguous grain boundaries are created leading to defects and deteriorated electrical characteristics
Solution Approach 1:
The patent removes the intermediate protective layer (first semiconductor material layer) that causes grain boundary formation. By extracting this harmful intermediate layer, the process deposits a single continuous semiconductor material layer directly on the substrate, eliminating the contiguous grain boundaries that deteriorate electrical characteristics.
Solution Approach 2:
The patent merges the protective function and the channel formation function into a single deposition step. Instead of separately depositing protective layers and channel layers in two steps, the process combines these functions by depositing a single semiconductor material layer that serves both purposes, thereby avoiding grain boundary formation.
2Manufacturing precision
If a single semiconductor material layer is deposited, then grain size is improved and defects are reduced, but the process requires precise control to avoid exposing substrate prematurely
Solution Approach 1:
The patent applies a sacrificial material layer to the substrate before depositing the semiconductor material layer. This preliminary action protects the substrate during the deposition process and enables precise control of the semiconductor layer formation without requiring complex real-time monitoring, thus improving manufacturing precision while maintaining ease of manufacture.
Solution Approach 2:
The sacrificial material layer acts as an intermediary between the substrate and the semiconductor material layer. It facilitates precise control of the deposition process by providing a temporary protective interface, allowing the semiconductor layer to be formed with controlled grain size and minimal defects, while the intermediary can be removed afterward without affecting the semiconductor channel quality.
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
This approach reduces defects and enhances the electrical characteristics of memory cells by eliminating contiguous grain boundaries, improving grain size, and minimizing program noise and variability.
Implementation Method 1
The sacrificial material layer is removed selective to a remaining portion of the memory film layer
Data Source
AI summary
A memory film layer is formed in a memory opening through an alternating stack of first material layers and second material layers. A sacrificial material layer is deposited on the memory film layer. Horizontal portions of the sacrificial material layer and the memory film layer at the bottom of the memory opening is removed by an anisotropic etch to expose a substrate underlying the memory opening, while vertical portions of the sacrificial material layer protect vertical portions of the memory film layer. After removal of the sacrificial material layer selective to the memory film, a doped semiconductor material layer can be formed directly on the exposed material in the memory opening and on the memory film as a single material layer to form a semiconductor channel of a memory device.