Notched Conductive Pattern for Flash Memory Charge Retention
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Solution Overview
Problem
Flash memory devices experience charge loss due to conductive residues formed during the patterning of floating gates, leading to data retrieval failures and reduced yield and reliability, as existing methods to prevent this increase costs and complexity.
Innovation Solution
A semiconductor device design featuring a conductive pattern with a notch on its side face, formed through a two-step reactive ion etching process, which minimizes the formation of conductive residues and prevents electrical short-circuits between adjacent floating gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive spacer is additionally formed beside the conductive film to prevent conductive residue, then charge loss is reduced, but the number of steps increases and cost increases
Solution Approach 1:
The conductive pattern is formed with a preliminary notch structure before the intermediate insulating film is deposited. This pre-formed notch prevents the intermediate insulating film from acting as an etching mask during patterning, thereby preventing conductive residue formation without requiring additional conductive spacer formation steps.
Solution Approach 2:
The conductive pattern is segmented with a notch that divides the side face into distinct regions. This segmentation prevents the continuous conductive path that would otherwise allow charge leakage, while avoiding the need for separate conductive spacer structures.
2Manufacturing precision
If the intermediate insulating film is formed on an inclined surface of a spacer, then conductive residue is minimized, but manufacturing complexity increases
Solution Approach 1:
The notch is formed in the conductive pattern before depositing the intermediate insulating film. This preliminary action ensures that when the intermediate insulating film is deposited, it cannot bridge across the notch to create a conductive residue, achieving precise control without complex spacer formation.
Solution Approach 2:
The problematic inclined surface and conductive spacer structure are removed entirely. Instead, a simple notch is formed directly in the conductive pattern, extracting the unnecessary intermediate structures while maintaining the function of preventing conductive residue.
3Ease of manufacture
If conventional patterning is used without notch formation, then manufacturing is simpler, but conductive residues form causing charge loss
Solution Approach 1:
The notch is formed as a preliminary feature in the conductive pattern before subsequent processing steps. This simple preliminary action prevents conductive residue formation during intermediate insulating film deposition, maintaining manufacturing simplicity while improving reliability.
Solution Approach 2:
The notch creates a local discontinuity in the conductive pattern at the critical location where the intermediate insulating film is deposited. This localized modification prevents charge leakage paths without requiring changes to the overall patterning process or additional structures.
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
The notch formation in the conductive pattern reduces charge loss and enhances the yield of semiconductor devices by eliminating conductive residues, thereby improving the reliability and efficiency of data storage in flash memory cells.
Implementation Method 1
a two-step reactive ion etching process
Implementation Method 2
a two-step reactive ion etching process
Data Source
AI summary
A semiconductor device which has a semiconductor substrate, an isolation insulating film formed in the semiconductor substrate, a conductive pattern formed over the semiconductor substrate and the isolation insulating film, so that a side face of the conductive pattern is formed over the isolation insulating film, and an insulating film is formed over the isolation insulating film, the conductive pattern and the side face of the conductive pattern, and the side face of the conductive pattern comprises a notch.