HfSiON Gate Insulator Nitrogen Diffusion Control
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to enhance the performance and reliability of MISFETs by controlling nitrogen diffusion at the IL/High-k interface, particularly when using Hf-based gate insulating films, as existing techniques struggle to maintain the integrity of the gate insulating film thickness and reduce gate leakage currents.
Innovation Solution
A semiconductor device with a Hf-based gate insulating film containing hafnium, oxygen, nitrogen, and silicon, where the silicon concentration is higher in the upper part of the film, and a manufacturing method using a laminate film of HfON and HfSiON to form a high-dielectric-constant gate insulating film, which helps in reducing gate leakage currents and improving transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin silicon oxide film is used as the gate insulating film to scale down the MISFET element, then the capacitance is improved, but the gate leakage current increases due to electron and hole tunneling
Solution Approach 1:
The patent changes the dielectric constant parameter of the gate insulating film from silicon oxide (k=3.9) to high-k material such as hafnium oxide (k=20-30). This allows achieving the same capacitance with a thicker physical film, thereby reducing tunneling current while maintaining the required capacitive coupling between gate and channel.
Solution Approach 2:
The patent employs a composite gate insulating film structure combining high-k material (hafnium oxide) with silicon oxide or silicon oxynitride layers. This composite structure optimizes both the capacitance characteristics and the barrier properties against tunneling current, while ensuring good interface quality with the semiconductor substrate.
2Object-generated harmful factors
If a Hf-based gate insulating film is used to reduce gate leakage current, then the gate leakage current is reduced, but nitrogen diffusion into the IL/High-k interface occurs which degrades device reliability
Solution Approach 1:
The patent introduces an interfacial layer (IL) composed of silicon oxide or silicon oxynitride between the semiconductor substrate and the high-k hafnium oxide layer. This intermediary layer acts as a diffusion barrier that prevents nitrogen from the high-k material from migrating into the substrate interface, thereby maintaining device reliability while preserving the low leakage current benefits of the high-k material.
Solution Approach 2:
The patent creates a gate insulating film with non-uniform composition and properties at different locations. The interfacial region contains silicon oxide or silicon oxynitride with specific properties optimized for interface quality and nitrogen barrier, while the upper region contains high-k hafnium oxide optimized for capacitance and leakage current reduction. This local quality differentiation resolves the contradiction between reliability and leakage current.
3Object-generated harmful factors
If the physical film thickness of the gate insulating film is increased to reduce leakage current, then the gate leakage current is reduced, but the capacitance decreases
Solution Approach 1:
The patent changes the dielectric constant parameter from k=3.9 (silicon oxide) to k=20-30 (high-k materials). This parameter change allows the capacitance C=kε0A/d to be maintained at higher values while increasing the physical thickness d, thereby simultaneously achieving both reduced leakage current and preserved capacitance.
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 effectively reduces gate leakage currents and enhances the reliability and performance of semiconductor devices by maintaining the integrity of the gate insulating film thickness and controlling nitrogen diffusion, thereby improving the overall performance of MISFETs.
Implementation Method 1
it is important to control the diffusion of nitrogen into an IL (Inter Layer)/High-k interface
Implementation Method 2
electrons and holes tunnel through a barrier formed by the silicon oxide film
Data Source
AI summary
Over a semiconductor substrate, a gate insulating film including an interfacial layer, a HfON film, and a HfSiON film is formed. Then, over the HfSiON film, an Al-containing film and a mask layer are formed. Subsequently, the mask layer and the Al-containing film are selectively removed from an n-channel MISFET formation region. Then, a rare-earth-element-containing film is formed over the HfSiON film in the n-channel MISFET formation region and over the mask layer in a p-channel MISFET formation region. Heat treatment is performed to cause a reaction between each of the HfON film and the HfSiON film and the rare-earth-element-containing film in the n-channel MISFET formation region and cause a reaction between each of the HfON film and the HfSiON film and the Al-containing film in the p-channel MISFET formation region. Thereafter, the unreacted rare-earth-element-containing film and the mask layer are removed, and then metal gate electrodes are formed.