Memory Die Isolation Cavities With Selective Merging to Reduce Taper
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Solution Overview
Problem
The formation of deep trenches with high taper during memory die manufacturing leads to misalignment, structural defects, poor process margins, and increased costs, affecting the structural stability and manufacturing tolerances of memory devices.
Innovation Solution
Form isolation regions by merging patterns of cavities using selective material removal and filling the cavities with a dielectric material, reducing the taper and improving structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deep trenches are formed using conventional material removal operations, then isolation regions can be created, but high taper is generated leading to misalignment, structural defects, and poor process margins
Solution Approach 1:
The patent divides the isolation region formation into multiple discrete cavity structures rather than forming a single continuous deep trench. By segmenting the isolation regions into multiple cavities with smaller depths, the taper effect is reduced in each individual cavity, improving alignment precision and structural stability while maintaining the overall isolation function
Solution Approach 2:
The patent transitions from conventional planar trench isolation to three-dimensional cavity structures within the substrate. By utilizing vertical cavity structures with controlled depths and spacing, the solution addresses the taper problem by distributing the isolation function across multiple dimensional parameters (depth, spacing, width) rather than relying on a single deep trench
2Reliability
If deep trenches are formed, then isolation can be achieved, but structural stability and manufacturing tolerances deteriorate
Solution Approach 1:
By segmenting the isolation structure into multiple shallow cavities rather than one deep trench, each cavity can be formed with better process control and smaller taper, improving both structural stability and manufacturing tolerances. The distributed cavity structure reduces the risk of defects compared to deep trench formation
Solution Approach 2:
The patent changes the geometric parameters of the isolation structures from deep and narrow trenches to multiple shallower cavities with optimized depth, width, and spacing. This parameter transformation reduces the aspect ratio of each structure, improving process margins and structural stability while achieving the same electrical isolation effect
3Ease of manufacture
If conventional trench formation is used, then isolation regions are created, but manufacturing costs increase
Solution Approach 1:
The segmented cavity approach enables the use of standard fabrication processes with better process margins, reducing the need for expensive corrective operations. The smaller, distributed cavity structures can be formed using conventional lithography and etching processes with higher precision, lowering overall manufacturing costs compared to deep trench formation which requires specialized high-precision equipment
Data Source
AI summary
Methods, systems, and devices for selective cavity merging for isolation regions in a memory die are described. For example, formation of material structures of a memory die may include depositing a stack of alternating layers of a first material and a second material over a substrate of the memory die, forming a pattern of cavities through the stack of alternating material layers, and forming voids between layers of the first material based on removing portions of the second material. An electrical isolation region may be formed between portions of the memory die based on depositing a dielectric material in at least some of the cavities and in at least a portion of the voids between the layers of the first material.