Nitrided Capping Layer for Dopant Diffusion Control
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Solution Overview
Problem
Current methods for fabricating NAND flash memory devices face challenges with dopant out-diffusion during anneal and activation, leading to instability in doped materials, particularly due to nitrogen incorporation in shallow trench isolation regions, which affects device performance and reliability.
Innovation Solution
A method involving a remote plasma source is used to generate and de-ionize nitrogen plasma, forming a nitrided capping layer with a low ion-to-neutral species ratio, which is then applied to the doped layer to minimize dopant diffusion during thermal annealing, thereby stabilizing the doped materials and enhancing dopant retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitridation process is used to incorporate nitrogen into the floating gate surface to improve reliability and suppress dopant diffusion, then tunnel oxide reliability is improved, but nitrogen is also incorporated into shallow trench isolation regions forming charge leakage paths
Solution Approach 1:
The patent applies different processing conditions to different regions: the floating gate receives nitrogen incorporation at lower temperatures (600-800°C) to form a stabilized surface layer, while the shallow trench isolation regions are protected from nitrogen incorporation by controlling plasma exposure and timing, thus achieving local differentiation in nitrogen content and preventing charge leakage paths
Solution Approach 2:
The floating gate surface is nitrided before subsequent high-temperature annealing processes. By incorporating nitrogen into the floating gate surface in advance, the surface is stabilized against dopant diffusion during later thermal processing steps, preventing the formation of harmful nitrogen-rich regions in the STI areas
2Reliability
If thermal annealing is used to promote dopant substitutional bonding and repair damaged semiconductor, then dopant activation is improved, but dopant out-diffusion increases
Solution Approach 1:
The floating gate surface is nitrided before subsequent high-temperature annealing processes. By incorporating nitrogen into the floating gate surface in advance, the surface is stabilized against dopant diffusion during later thermal processing steps, allowing dopant activation without excessive out-diffusion
Solution Approach 2:
The patent changes the physical-chemical state of the floating gate surface by incorporating nitrogen, which alters the surface properties and creates a barrier that reduces dopant out-diffusion during thermal annealing, while still allowing sufficient dopant activation
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
The approach significantly reduces dopant out-diffusion and improves dopant retention, resulting in improved device performance and reliability by selectively incorporating nitrogen radicals into the doped layers without affecting shallow trench isolation regions.
Implementation Method 1
generating an ionized nitrogen plasma in a remote plasma source, de-ionizing the ionized nitrogen plasma while forming non-ionized nitrogen plasma
Implementation Method 2
forming a nitrided capping layer from an upper portion of the doped layer by exposing the doped layer within the processing region to the non-ionized nitrogen plasma
Implementation Method 3
heating the substrate containing the nitrided capping layer disposed on the doped layer during a thermal annealing process
Data Source
AI summary
A method for incorporating radicals of a plasma into a substrate or a material on a semiconductor substrate using a remote plasma source. In one embodiment, a method for processing doped materials on a substrate surface is provided and includes forming a doped layer on a substrate and optionally cleaning the doped layer, such as by a wet clean process. The method also includes generating an ionized nitrogen plasma in a remote plasma source, wherein the ionized nitrogen plasma has an ion concentration within a range from about 0.001% to about 0.1%, de-ionizing the ionized nitrogen plasma while forming non-ionized nitrogen plasma. The method further includes flowing the non-ionized nitrogen plasma into a processing region within a processing chamber, forming a nitrided capping layer from an upper portion of the doped layer by exposing the doped layer within the processing region to the non-ionized nitrogen plasma during a stabilization process.