Floating Gate Contact Hole Width Design for Etch Residue Removal
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Solution Overview
Problem
As semiconductor devices are downsized, gaps between memory cells decrease, leading to short defects due to fluctuations in base structures and manufacturing conditions, causing operational faults and data retention issues.
Innovation Solution
A method of manufacturing a semiconductor device with a stacked gate structure, where the width of the contact hole in the X direction is larger than the width of the floating gate, allowing for the removal of etch residue and preventing shorting between adjacent floating gates, and the formation of sidewall spacers to isolate etch residue and prevent operational faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gaps between memory cells are decreased to increase device density, then the device integration is improved, but short defects between adjacent memory cells occur due to fluctuations in base structures and manufacturing conditions
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure before the floating gate to define and maintain precise spacing between adjacent memory cells. This mandrel serves as a pre-established reference that guides subsequent material deposition and patterning steps, ensuring consistent cell spacing even as device dimensions are reduced to increase density.
Solution Approach 2:
The patent introduces a mandrel as an intermediary structure that mediates between the base structure and the floating gate. This intermediary element provides a stable reference framework that compensates for fluctuations in manufacturing conditions, preventing short defects while allowing continued scaling for higher device density.
2Ease of manufacture
If conventional etching processes are used without mandrel structures, then the manufacturing process is simpler, but etch residue remains between adjacent floating gates causing operational faults
Solution Approach 1:
The patent extracts the problematic etch residue by designing the mandrel structure to protrude beyond the floating gate edges. This geometric configuration ensures that when materials are deposited and patterned, the mandrel physically defines boundaries that prevent residue accumulation in the critical gaps between adjacent floating gates, eliminating operational faults while maintaining manufacturing feasibility.
Solution Approach 2:
The mandrel structure is formed in advance to establish precise geometric boundaries before floating gate fabrication. This preliminary structuring creates built-in spacing references that guide subsequent etching and deposition processes, ensuring clean separation between cells without requiring complex multi-step patterning procedures.
3Reliability
If mandrel structures are introduced to prevent short defects, then reliability is improved, but device structure complexity increases
Solution Approach 1:
The mandrel structure serves multiple functions simultaneously: it defines cell spacing, guides floating gate patterning, prevents etch residue accumulation, and establishes alignment references for subsequent interconnect formation. By consolidating these multiple functions into a single structural element, the patent achieves improved reliability without proportionally increasing overall device complexity.
Solution Approach 2:
The mandrel structure creates a uniform reference framework across the device that establishes consistent spacing and alignment conditions throughout the array. This equipotential approach to structural referencing ensures that all memory cells experience equivalent geometric conditions, simplifying the overall design by providing a universal template rather than requiring individualized structuring for each cell.
Data Source
AI summary
A conductive film having a first width in a first direction, an ONO film, and a control gate are formed above a tunnel gate insulating film. With the control gate as a mask, the conductive film is etched to form a floating gate. Then, an inter-layer insulating film is formed. A contact hole whose width in the first direction is larger than the first width is formed in the inter-layer insulating film. Then, sidewall spacer is formed on an inside wall of the contact hole.