Flash Memory Nitride Layer Selective Nitrogen Removal
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Solution Overview
Problem
Flash memory devices face challenges in achieving improved electrical reliability and reduced charge loss due to leakage currents, which are exacerbated by the presence of nitrogen atoms in the nitride layer, particularly in the second nitride layer portion on the isolation layer.
Innovation Solution
The method involves forming a nitride layer with a first portion on the floating gate and a second portion on the isolation layer, where nitrogen atoms are selectively removed from the second nitride layer portion using processes such as wet or dry treatments, leaving the first nitride layer portion intact to enhance the inter-gate dielectric layer and suppress leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride layer is formed on both the floating gate and isolation layer to improve electrical characteristics, then the breakdown voltage and cell distribution characteristic are enhanced, but nitrogen atoms in the second nitride layer portion cause stress-induced leakage current and charge loss
Solution Approach 1:
The nitride layer is divided into two distinct portions: a first nitride layer portion on the floating gate that is retained to provide electrical reliability, and a second nitride layer portion on the isolation layer that is selectively removed to eliminate leakage current sources. This segmentation allows differential treatment of nitrogen atoms in different locations.
Solution Approach 2:
Nitrogen atoms are selectively extracted from the second nitride layer portion on the isolation layer through thermal treatment and wet etching processes, while preserving the first nitride layer portion on the floating gate. This extraction removes the harmful nitrogen atoms that cause leakage current while maintaining the beneficial nitride layer for electrical reliability.
2Loss of energy
If nitrogen atoms are removed from the second nitride layer portion to reduce charge loss, then stress-induced leakage current is suppressed, but the electrical reliability and breakdown voltage may be compromised
Solution Approach 1:
Different quality treatments are applied to different portions of the nitride layer: the first nitride layer portion on the floating gate is preserved with its nitrogen atoms to maintain electrical reliability and breakdown voltage, while the second nitride layer portion on the isolation layer is treated to remove nitrogen atoms to reduce charge loss and leakage current.
3Object-affected harmful factors
If a nitride layer is formed on the isolation layer to improve isolation characteristics, then the electrical insulation is enhanced, but the nitrogen atoms create charge trap characteristics and stress-induced leakage
Solution Approach 1:
The nitride layer on the isolation layer initially provides good electrical insulation but creates charge trap characteristics. By selectively removing nitrogen atoms from this second nitride layer portion, the harmful charge trap characteristics are eliminated while the beneficial isolation characteristics are maintained through the remaining oxide-based isolation layer.
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 improves the electrical reliability and data capabilities of flash memory devices by reducing charge loss and leakage currents, as the remaining nitride layer on the floating gate enhances the cell distribution characteristic and breakdown voltage, while removing the unstable nitrogen atoms from the isolation layer reduces stress-induced leakage current and charge trap characteristics.
Implementation Method 1
forming a nitride layer including a first nitride layer portion that is formed on an exposed surface of the floating gate and a second nitride layer portion that is formed on an exposed surface of the isolation layer
Implementation Method 2
performing a thermal treatment process on the nitride layer before performing the wet process on the nitride layer. The thermal treatment process is performed at a temperature of from about 150° C. to about 600° C.
Implementation Method 3
selectively removing nitrogen atoms from the second nitride layer portion of the nitride layer may include performing a wet process on the nitride layer in order to selectively remove the nitrogen atoms from the second nitride layer portion of the nitride layer. The wet process may include exposing the nitride layer to deionized water maintained at a temperature of from about 40° C. to about 100° C.
Implementation Method 4
selectively removing nitrogen atoms from the second nitride layer portion of the nitride layer may comprise performing a dry process on the nitride layer in order to selectively remove the nitrogen atoms from the second nitride layer portion of the nitride layer. The dry process may be performed using an oxygen radical.
Data Source
AI summary
A method of manufacturing a flash memory device includes: forming a dielectric layer on an active region of a substrate having an isolation region and the active region; forming a floating gate on the dielectric layer; forming an isolation layer in the isolation region; forming a nitride layer including a first nitride layer portion formed on an exposed surface of the floating gate and a second nitride layer portion formed on an exposed surface of the isolation layer; selectively removing nitrogen atoms from the second nitride layer portion of the nitride layer; forming an inter-gate dielectric layer on both the first nitride layer portion and the isolation layer; and forming a control gate on the inter-gate dielectric layer.