Correcting Trench Profiles for Reliable Flash Memory Manufacturing
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Summary
Problems
The production of NAND flash memory is hindered by the flawed profile of trenches formed by dry etching, leading to trapezoidal shapes that affect floating gate isolation and data storage efficiency, causing confusion and data access errors.
Innovation solutions
A method involving the formation of a spacer on the sidewall of the STI oxide spacer to amend the trench profile from inverted trapezoidal to trapezoidal, using a sacrificial oxide and poly-Si layers, and conformal oxide deposition to correct the shape and enhance floating gate poly-Si layer placement.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If dry etching is used to form STI, then the trench can be formed efficiently, but the profile becomes inverted trapezoid causing poly-Si remnants and data storage issues
Why choose this principle:
A spacer layer is introduced as an intermediary element between the etched trench walls and the final STI structure. This spacer is deposited conformally and then selectively removed to correct the inverted trapezoid profile, enabling precise control of the final STI geometry without compromising the efficiency of the initial dry etching process
Principle concept:
If dry etching is used to form STI, then the trench can be formed efficiently, but the profile becomes inverted trapezoid causing poly-Si remnants and data storage issues
Why choose this principle:
The spacer deposition and removal process is performed as a preliminary correction step before final STI formation. This preliminary action pre-adjusts the trench profile from inverted trapezoid to desired shape, preventing poly-Si remnants and ensuring accurate floating gate placement in subsequent processing steps
Application Domain
Data Source
AI summary:
A method involving the formation of a spacer on the sidewall of the STI oxide spacer to amend the trench profile from inverted trapezoidal to trapezoidal, using a sacrificial oxide and poly-Si layers, and conformal oxide deposition to correct the shape and enhance floating gate poly-Si layer placement.
Abstract
A method for manufacturing a flash memory includes providing a substrate with a sacrificial oxide layer, a sacrificial poly-Si layer, a hard mask layer and a trench exposing part of the substrate and filled with an oxide layer, later depositing a oxide layer conformally on the sacrificial oxide layer and the oxide layer, and afterwards removing the oxide layer on the sacrificial oxide layer and on the top of the oxide layer and the sacrificial oxide layer to form a spacer as a STI oxide spacer.