3D AND Flash Memory Channel Pillar Cap for Leakage Isolation
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Solution Overview
Problem
3D AND flash memory devices face issues with shorting or leakage paths between conductive pillars and the top-most word line layer due to improper control of the channel pillar height during the etching process.
Innovation Solution
A protective cap is formed on the channel pillar to prevent damage during etching and ensure the top surface is flush with the charge storage structure, preventing shorting or leakage by isolating the conductive pillars from the top gate layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the channel pillar height is not properly controlled during etching, then the device structure becomes simpler, but shorting or leakage paths occur between conductive pillars and the top-most word line layer
Solution Approach 1:
The patent applies preliminary action by forming a protective cap on the channel pillar before the etching process. This protective cap prevents the channel pillar from being etched too deeply, thereby preventing shorting or leakage paths between conductive pillars and the top-most word line layer while maintaining device reliability
Solution Approach 2:
The protective cap serves as an intermediary element between the channel pillar and the etching process. It mediates the etching action to ensure the channel pillar is not over-etched, thus preventing harmful electrical connections while allowing the etching process to proceed
2Reliability
If the channel pillar is exposed during etching without protection, then the manufacturing process is simpler, but the channel pillar gets damaged
Solution Approach 1:
The protective cap is formed on the channel pillar before the etching process begins. This preliminary protective measure ensures the channel pillar integrity is maintained during etching, preventing damage while adding a step to the manufacturing process
Solution Approach 2:
The protective cap provides beforehand cushioning by shielding the channel pillar from excessive etching action. This protective layer absorbs or redirects the etching process, preventing direct damage to the channel pillar while allowing controlled material removal
3Reliability
If the top surface of channel pillar is not flush with charge storage structure, then fabrication is easier, but shorting or leakage paths occur
Solution Approach 1:
The protective cap is formed in advance to establish a predetermined height reference. This ensures the top surface of the channel pillar will be flush with the charge storage structure after etching, maintaining proper electrical isolation without requiring post-processing alignment adjustments
Solution Approach 2:
The patent replaces mechanical alignment control with a chemical/physical solution. Instead of mechanically controlling the channel pillar height during etching, the protective cap's material properties and formation process are used to automatically establish the correct surface alignment, ensuring electrical isolation
Data Source
AI summary
A 3D AND flash memory device includes a gate stack structure, a channel pillar, a first and a second conductive pillars, a charge storage structure, and a protective cap. The gate stack structure is disposed on a dielectric substrate and includes gate layers and insulating layers alternately stacked with each other. The channel pillar penetrates through the gate stack structure. The first and the second conductive pillars are disposed in the channel pillar and penetrate through the gate stack structure, and the first and the second conductive pillars are separated from each other and each connected to the channel pillar. The charge storage structure is disposed between the gate layers and a sidewall of the channel pillar. The protective cap covers at least a top surface of the channel pillar and isolates the first conductive pillar and the second conductive pillar from a top gate layer of the gate layers.