Self-Aligned Damascene Memory Pillar Fabrication
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Solution Overview
Problem
The fabrication of high-density three-dimensional memory arrays faces challenges such as misalignment of features during fabrication, leading to reduced yield and increased difficulties as feature size decreases, particularly due to improper placement of photomasks causing short circuits in memory elements.
Innovation Solution
A method involving the formation of pillar-shaped elements using self-aligned openings and deposition of semiconductor materials to create a monolithic three-dimensional memory array, where a first pillar-shaped element is formed, followed by the creation of a second pillar-shaped element above it, and the use of sacrificial materials and dielectric layers to reduce alignment errors and enhance density and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask alignment methods are used, then fabrication process is simpler, but manufacturing precision deteriorates due to misalignment of features
Solution Approach 1:
The patent applies preliminary action by pre-forming sacrificial pillars and openings before depositing the final semiconductor material. The sacrificial pillars are positioned in advance to define the exact locations where openings will be created, ensuring self-alignment without requiring high-precision photomask alignment. This preliminary structuring eliminates alignment errors that would otherwise occur during subsequent fabrication steps.
Solution Approach 2:
The patent uses sacrificial pillars as intermediary structures that facilitate the self-aligned formation of openings. These temporary sacrificial structures act as mediators between the substrate and the final memory structure, defining precise locations for openings without requiring direct photomask alignment. After the openings are formed and filled with semiconductor material, the sacrificial pillars are removed, leaving the precisely aligned final structure.
2Productivity
If feature size is reduced to increase density, then productivity improves, but manufacturing precision deteriorates due to increased sensitivity to misalignment
Solution Approach 1:
The patent implements self-service through self-aligned fabrication processes where structures automatically align themselves without requiring external alignment tools. The sacrificial pillars and openings are positioned relative to each other through self-alignment mechanisms inherent in the fabrication process, eliminating the need for high-precision photomask alignment. This allows feature sizes to be reduced for increased density while maintaining manufacturing precision, as the self-aligned process is not sensitive to misalignment errors.
3Ease of manufacture
If misalignment occurs during fabrication, then ease of manufacture is maintained, but reliability deteriorates due to short circuits
Solution Approach 1:
The patent applies preliminary anti-action by pre-preventing misalignment errors through self-aligned fabrication processes. The sacrificial pillars are positioned in advance to define exact locations for openings, and the subsequent steps are designed to automatically align with these pre-defined positions. This preliminary structuring prevents misalignment from occurring in the first place, thereby preventing short circuits and maintaining high reliability and yield, while still using relatively simple fabrication processes.
Data Source
AI summary
A method of forming a memory cell is provided. The method includes forming a first pillar-shaped element that includes a first semiconductor material, forming a first opening self-aligned with the first pillar-shaped element, and depositing a second semiconductor material in the first opening to form a second pillar-shaped element above the first pillar-shaped element. Other aspects are also provided.