Semiconductor Floating Gate Sidewall Asymmetry
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Solution Overview
Problem
The steep slope on the side surface of the floating gate in semiconductor memory devices leads to uneven resistance values of the control gate due to incomplete formation of the metal silicide film, resulting in deteriorated semiconductor memory characteristics.
Innovation Solution
The method involves forming a floating gate with a gentler side surface inclination angle on the outermost floating gate, using etching techniques to create a sparse pattern and devising conditions for the control gate etching, which reduces the steep slope of the control gate and prevents incomplete metal silicide film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal silicide film is formed over the control gate to reduce resistance, then the resistance value of the control gate is reduced, but the steep slope on the side surface of the floating gate causes the metal silicide film to be incomplete at the steep slope part, resulting in uneven resistance values
Solution Approach 1:
The patent applies asymmetry by forming a sidewall insulation film only on the outer side surface of the floating gate, creating an asymmetric structure. This asymmetric sidewall film modifies the top surface profile of the control gate, making the slope gentler on the outer side where the steep slope problem occurs, thereby enabling complete metal silicide film formation and uniform resistance values across the control gate
Solution Approach 2:
The sidewall insulation film acts as an intermediary element between the floating gate and the control gate. By introducing this intermediate layer on the outer side surface of the floating gate, the patent modifies the geometric relationship between structures, preventing the steep slope from directly affecting the control gate top surface and enabling uniform metal silicide deposition
2Manufacturing precision
If a sidewall insulation film is formed over both side surfaces of the floating gate to alleviate the steep slope, then the steep slope of the control gate is reduced, but this increases the complexity of the manufacturing process
Solution Approach 1:
The patent applies local quality by forming the sidewall insulation film selectively only on the outer side surface of the floating gate rather than on both side surfaces. This localized approach addresses the specific steep slope problem on the outer side while avoiding unnecessary process complexity, achieving the desired slope modification with minimal additional manufacturing steps
Data Source
AI summary
A method of manufacturing a semiconductor device has forming a first conductive film over a semiconductor substrate, etching the first conductive film, forming a plurality of first conductive patterns arranged in a first direction, and forming a side surface on an outside of a conductive pattern positioned at an end among the plurality of first conductive patterns such that the side surface has a first inclination angle smaller than a second inclination angle of a side surface on an inside of the conductive pattern positioned at the end, forming a first insulation film over the plurality of first conductive patterns, and forming a second conductive pattern over the first insulation film.