MIS Transistor Gate Insulation Protrusion for Threshold Stability
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Solution Overview
Problem
In semiconductor devices, the threshold voltage of n-type MIS transistors with high-k gate insulating films containing adjustment metals like lanthanum increases with reduced gate width, hindering further miniaturization due to oxygen-induced dipole neutralization during thermal treatments.
Innovation Solution
The semiconductor device design includes a configuration where the first gate insulating film with a high-k film containing lanthanum has a reduced protrusion amount relative to the separation region, minimizing oxygen exposure and dipole neutralization, while the second gate insulating film with aluminum maintains low threshold voltage increase even with reduced gate width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate width of n-type MIS transistors is reduced to enable miniaturization, then device density and integration are improved, but the threshold voltage increases due to oxygen-induced dipole neutralization in the high-k film
Solution Approach 1:
The patent applies local quality by creating different protrusion amounts for gate insulating films of different transistor types. Specifically, the n-type MIS transistor's gate insulating film has a reduced protrusion amount over the separation region compared to conventional designs, while the p-type MIS transistor's gate insulating film maintains a conventional protrusion amount. This localized differentiation protects the n-type transistor's high-k film from oxygen exposure during thermal treatments, preventing dipole neutralization and threshold voltage increase, while allowing the p-type transistor to maintain normal operation.
Solution Approach 2:
The patent implements preliminary anti-action by pre-configuring the gate insulating film structure to counteract the harmful effect of oxygen exposure. The reduced protrusion amount of the gate insulating film over the separation region is designed in advance to minimize oxygen diffusion into the high-k film during subsequent thermal processing steps. This preliminary structural adjustment prevents the neutralization of dipoles in the high-k film, thereby maintaining stable threshold voltage throughout the device lifecycle.
2Reliability
If the protrusion amount of the gate insulating film over the separation region is reduced to minimize oxygen exposure, then dipole neutralization is prevented, but the gate insulating film coverage is reduced
Solution Approach 1:
The patent applies local quality by creating different protrusion amounts for gate insulating films of different transistor types. Specifically, the n-type MIS transistor's gate insulating film has a reduced protrusion amount over the separation region compared to conventional designs, while the p-type MIS transistor's gate insulating film maintains a conventional protrusion amount. This localized differentiation protects the n-type transistor's high-k film from oxygen exposure during thermal treatments, preventing dipole neutralization and threshold voltage increase, while allowing the p-type transistor to maintain normal operation.
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 effectively reduces or prevents the increase in threshold voltage of n-type MIS transistors during miniaturization, ensuring stable performance and low power consumption.
Implementation Method 1
If the Hf-based film contains La, dipoles are generated in the Hf-based film. As a result, the flat-band voltage is shifted toward the negative region, so that the effective work function of the n-type MIS transistor is shifted toward the band edge, whereby the threshold voltage of the n-type MIS transistor can be reduced.
Implementation Method 2
it has been found that, in a thermal treatment, oxygen (O) is supplied from the separation region to the high-k film, so that dipoles are neutralized
Data Source
AI summary
A semiconductor device includes a first-conductivity-type first MIS transistor and a second-conductivity-type second MIS transistor. The first and second MIS transistors include a first and a second gate insulating film formed on a first and a second active region surrounded by a separation region of a semiconductor substrate, and a first and a second gate electrode formed on the first and second gate insulating films. The first and second gate insulating films are separated from each other on a first separation region of the separation region. A distance s between first ends of the first and second active regions facing each other with the first separation region being interposed therebetween, and a protrusion amount d1 from the first end of the first active region to a first end of the first gate insulating film located on the first separation region establish a relationship d1<0.5s.