MOSFET Gate Insulating Layers Using Nitrogen-Injected Oxynitride
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Solution Overview
Problem
The challenge lies in fabricating metal oxide semiconductor field effect transistors (MOSFETs) with gate insulating layers of different thicknesses, which is difficult to achieve while ensuring compatibility between low and high voltage devices and preventing harmful effects between PMOS and NMOS devices.
Innovation Solution
The method involves forming a nitrogen injection layer on a semiconductor substrate by converting an oxide layer to an oxynitride layer and then forming insulating layers with different thicknesses on these oxynitride layers, using techniques like nitrogen plasma treatment or thermal treatment, to create gate insulating layers with varying thicknesses and materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate insulating layers with different thicknesses are formed for low and high voltage MOSFET devices, then device performance is improved, but manufacturing complexity increases
Solution Approach 1:
The gate insulating layer is segmented into multiple regions with different thicknesses within the same layer structure. By forming the gate insulating layer in a first region for low voltage devices and a second region for high voltage devices with different thicknesses, the patent enables differentiated device performance while maintaining a unified layer structure, thus reducing manufacturing complexity.
Solution Approach 2:
The gate insulating layer exhibits local quality variations where the thickness is optimized for specific regions. The first region has a thickness suitable for low voltage MOSFET devices while the second region has a different thickness for high voltage devices, allowing each region to have the precise local characteristics needed for its intended function.
2Productivity
If gate insulating layers with different thicknesses are formed simultaneously, then production efficiency is improved, but precision control becomes more difficult
Solution Approach 1:
The patent applies preliminary action by forming a thickness difference between the first and second regions before completing the gate insulating layer formation. This preliminary thickness differentiation is established during the formation process itself, allowing subsequent processing steps to proceed uniformly while maintaining the desired thickness variation, thus preserving both production efficiency and precision control.
3Reliability
If nitrogen injection is used to modify oxide layers, then dielectric properties are improved, but process complexity increases
Solution Approach 1:
The patent merges the oxide layer formation and nitrogen injection processes into a single integrated step. By forming the gate insulating layer including the oxide layer and injecting nitrogen into it simultaneously or in close sequence, the patent achieves improved dielectric properties while minimizing process complexity through process consolidation.
Solution Approach 2:
The oxide layer serves multiple functions: it provides the base insulating structure and simultaneously acts as the target for nitrogen injection to enhance dielectric properties. This multi-functionality reduces the need for separate layers or processes, thereby improving dielectric performance without proportionally increasing process complexity.
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 the simultaneous realization of low and high voltage MOSFET devices with gate insulating layers of distinct thicknesses, enhancing device parameters like threshold voltage without harming each other, and improving on-current and off-current characteristics.
Implementation Method 1
injecting nitrogen into the oxide layer to form a nitrogen injection layer and to change the oxide layer to an oxynitride layer
Implementation Method 2
The methods may further include forming an oxide layer on a semiconductor substrate and injecting nitrogen into the oxide layer
Implementation Method 3
The insulating layer may have a higher dielectric constant than the oxide layer
Data Source
AI summary
In some embodiments of the inventive subject matter, methods include forming an oxide layer on a semiconductor substrate, injecting nitrogen into the oxide layer to form a nitrogen injection layer and to change the oxide layer to an oxynitride layer, removing a part of the oxynitride layer to leave a portion of the oxynitride layer in a first area and expose the nitrogen injection layer in a second area and forming an insulating layer comprising a portion on the portion of the oxynitride layer in the first area and a portion on the nitrogen injection layer in the second area. The insulating layer may have a higher dielectric constant than the oxide layer.