Remote Plasma Radical Nitridation of Tunnel Oxide
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Solution Overview
Problem
The existing methods for manufacturing NAND flash memory devices face challenges in incorporating nitrogen into the tunnel oxide and floating gate interfaces to enhance reliability and prevent dopant diffusion, while also minimizing nitrogen incorporation into shallow trench isolation regions to avoid charge leakage paths.
Innovation Solution
A radical nitridation process using a remote plasma applicator generates nitrogen-containing radicals that selectively react with the tunnel oxide and floating gate surfaces, reducing ion presence to minimize unwanted nitrogen incorporation into shallow trench isolation regions, thereby improving nitrogen concentration and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high thermal budget nitridation process is used to increase nitrogen concentration at the floating gate and tunnel oxide interface, then the program window and reliability are improved, but dopant diffusion out of the floating gate increases and manufacturing time exceeds 30 seconds
Solution Approach 1:
The patent changes the fundamental parameter of the nitridation process from thermal diffusion to radical-based chemical reaction. By using a plasma source to generate nitrogen radicals (N, NH, NH2) and introducing them into the processing chamber, the process achieves high nitrogen concentration at the floating gate interface in seconds rather than requiring prolonged high-temperature thermal treatment. This parameter change from thermal to radical-based mechanism directly resolves the time-budget contradiction.
2Reliability
If high thermal budget nitridation process is used to increase nitrogen concentration at the floating gate and tunnel oxide interface, then the program window is improved, but dopant diffusion out of the floating gate increases
Solution Approach 1:
The patent employs a radical-based nitridation process instead of thermal nitridation, fundamentally changing the mechanism from heat-driven diffusion to radical-driven surface reaction. The nitrogen radicals react directly with the floating gate surface at low temperatures, achieving the desired nitrogen concentration for improved program window without the thermal energy that would cause dopant diffusion. This mechanism change preserves dopant stability while achieving the reliability improvement.
3Quantity of substance
If conventional plasma nitridation is used to incorporate nitrogen into the tunnel oxide, then nitrogen concentration is increased, but nitrogen is also incorporated into shallow trench isolation regions forming charge leakage paths
Solution Approach 1:
The patent applies local quality by making the nitrogen radical incorporation selective to specific regions. The floating gate structure, being conductive and positioned at a specific potential, attracts and concentrates nitrogen radicals preferentially at the floating gate and tunnel oxide interface. The shallow trench isolation regions, having different electrical properties and geometry, receive significantly fewer nitrogen radicals. This spatial and electrical field-based selectivity achieves high nitrogen concentration where needed while preventing harmful nitrogen incorporation in STI regions.
Solution Approach 2:
The patent introduces an intermediary mechanism - the plasma-generated nitrogen radicals - that mediate the nitridation process. These radicals serve as the active species that can be selectively delivered to different regions based on electrical field distribution and surface properties. By controlling the plasma parameters and processing conditions, the intermediary radicals preferentially react with the floating gate structure rather than the STI regions, achieving selective nitridation that improves tunnel oxide quality without creating charge leakage paths in isolation regions.
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 allows for higher nitrogen incorporation at the tunnel oxide and floating gate interfaces without compromising the shallow trench isolation, enhancing the memory device's reliability and reducing charge leakage, thus improving the program window and preventing dopant diffusion.
Implementation Method 1
generating a plasma comprising nitrogen-containing radicals in a remote plasma applicator
Implementation Method 2
exciting the gas mixture to produce a plasma comprising nitrogen-containing radicals
Implementation Method 3
incorporating nitrogen in the exposed surface of the oxide layer of the substrate
Implementation Method 4
radical nitridation process to incorporate nitrogen into exposed surfaces of a tunnel oxide or SiO2 gate dielectric
Data Source
AI summary
Embodiments described herein generally relate to methods for manufacturing flash memory devices. In one embodiment, the method includes generating a plasma comprising nitrogen-containing radicals in a remote plasma applicator, flowing the plasma comprising nitrogen-containing radicals into a processing region of the processing chamber where a semiconductor device is disposed, wherein the semiconductor device has a substrate comprising an oxide layer formed thereon, exposing an exposed surface of the oxide layer to the nitrogen-containing radicals, and incorporating nitrogen in the exposed surface of the oxide layer of the substrate.