Nonvolatile Memory Charge Accumulating Layer with Si-N Insulation
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Solution Overview
Problem
The miniaturization of nonvolatile semiconductor memory elements leads to increased reliability issues due to the formation of 'bird's beak' in tunnel insulating films, causing variations in capacitance and device performance, which existing methods struggle to control effectively.
Innovation Solution
A nonvolatile semiconductor memory structure featuring a charge accumulating layer with a third insulating film containing an Si—N bond on its bottom surface and side surfaces, along with a manufacturing method that includes oxynitriding the inner walls of trenches and forming buried insulating films to suppress the formation of 'bird's beak' and reduce gate size variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If miniaturization of memory elements is pursued, then storage density is improved, but bird's beak formation increases causing reliability deterioration
Solution Approach 1:
A nitride film is formed on the surface of the floating gate electrode before the tunnel insulating film formation. This preliminary nitridation creates a protective layer that prevents oxidizer penetration during subsequent oxidation steps, thereby preventing bird's beak formation even as element size is reduced for higher storage density.
Solution Approach 2:
The nitride film acts as an intermediary protective layer between the floating gate electrode and the oxidizer. This intermediate layer blocks the harmful oxidation effect that would otherwise occur at the interface, allowing miniaturization to proceed without compromising insulating film reliability.
2Manufacturing precision
If post-oxidation is performed to form tunnel insulating film, then film quality is improved, but bird's beak formation occurs causing capacitance variations
Solution Approach 1:
The nitride film is formed in advance to counteract the harmful oxidation effect that would occur during the necessary post-oxidation process. This preliminary protective action allows the oxidation to proceed for film quality improvement while the nitride film prevents bird's beak formation, thus maintaining capacitance uniformity.
3Reliability
If floating gate electrode oxidation is suppressed, then bird's beak formation is reduced, but manufacturing complexity increases
Solution Approach 1:
The surface properties of the floating gate electrode are modified by nitridation, changing the chemical composition and oxidation resistance parameters. This parameter change enables suppression of bird's beak formation through a simple material modification rather than complex process control.
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
This approach enhances device performance and reliability by preventing oxidizer penetration and minimizing gate size variations, thereby stabilizing tunnel current distribution and capacitance.
Implementation Method 1
a third insulating film including an Si—N bond that is formed on a bottom surface and side surfaces of the charge accumulating layer
Implementation Method 2
a manufacturing method that includes oxynitriding the inner walls of trenches
Data Source
AI summary
A nonvolatile semiconductor memory has a semiconductor substrate, a first insulating film formed on a channel region on a surface portion of the semiconductor substrate, a charge accumulating layer formed on the first insulating film, a second insulating film formed on the charge accumulating layer, a control gate electrode formed on the second insulating film, and a third insulating film including an Si—N bond that is formed on a bottom surface and side surfaces of the charge accumulating layer.