At the forefront of chip research
At the 27th IEEE IPCF Conference, IMEC announced the joint research results with famous European universities KU Leuven and TU Wien. The team expanded the research model of HCD (hot carrier degradation) effect, and comprehensively considered the correlation and interaction between HCD effect and self-heating effect, which was verified in the actual measurement of nanowire transistors.
In advanced integrated circuit devices, the reduction of device size is greater than the reduction of working voltage and bias stress voltage, resulting in high electric field; In addition, the channel length of the transistor is equal to or shorter than the average free path of carriers, and the energy dissipated by carriers due to scattering is greatly reduced. To sum up, the factors will lead to significant acceleration of carriers, and then lead to significant hot carrier degradation * (HCD). In nanowire transistor devices and integrated circuit devices with dimensions of 10nm and sub-10nm, such as FinFET, the HCD effect is further aggravated due to the self-heating effect, which is considered to be the most damaging problem to the device reliability.
However, bias temperature instability (BTI), which is closely related to HCD, is not as destructive as HCD in transistors. In recent years, technical measures to control and mitigate BTI have been proposed and verified. Most of these works are based on two points: one is to transfer the defect band to the energy region that carriers can't reach by adjusting the work function, and the other is to introduce a dipole between the SiO layer and the high K layer. However, so far, there is no effective way to slow down the HCD effect, and a better understanding of the physical mechanism leading to HCD will help to explore ways to slow down the HCD effect.
Self-heating enhances the HCD effect, and the accurate HCD prediction model should consider the influence of self-heating effect. However, the current models to simulate the influence of self-heating on HCD are all based on experimental experience and isolated guesses and assumptions, which are one-sided. In order to deepen the understanding of HCD induction mechanism and establish a research model closer to the actual working conditions of the circuit, IMEC, Ku Leuven and Tu Wien jointly proposed and verified a new physical model. The related results were published in the 27th IEEE International Conference on Integrated Circuit Physics and Failure Analysis (IPFA). Stanislav Tyaginov, alexander makarov and other 10 researchers from IMEC and two famous European universities were co-authors of this paper, and the project was funded by Marie Curie scholar project under the "EU Horizon 2020" scientific research plan.
* Hot carrier degradation: Hot carrier degradation, also known as hot carrier degradation, means that some carriers inside the device are influenced by the outside world and become high-energy hot carriers. These hot carriers will break the Si-H bond and produce the interface state, which will eventually lead to the decrease of the average free time of carriers and the electron mobility, thus reducing the source and drain current of the device. With the increase of working time, the degradation of key electrical characteristics of the device is more and more obvious. When the degradation is greater than a certain degree, it will cause the failure of the device and even the whole chip, which will bring serious reliability problems.
PNWFETS nanowire field effect transistor, a GAA ring gate transistor device structure.
Based on the basic principles of physics, the research team proposed and verified the modeling framework of self-heating and hot carrier degradation (HCD). The research shows that the influence factors of self-heating on HCD are superimposed in many aspects: one is the carrier transport characteristics at the distribution temperature, the other is the dependence of temperature on the vibration life of chemical bonds, and the third is the thermal contribution of bond dissociation. In order to solve the lattice temperature change caused by self-heating effect, the team comprehensively solved the drift-diffusion equation and heat flow formula; The influence of non-uniform temperature distribution on carrier transport shows that the carrier energy distribution function tends to high energy region. The extended framework of our research team can accurately reproduce the hot carrier degradation process of pNWFETs in the experimental environment. At the same time, it is found that if the self-heating effect is ignored, the severity of HCD effect calculated by the model will be much lower than the actual observation value.
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IMEC and KU Leuven and TU Wien of famous universities have established innovative physical models to deeply study the relationship between the self-heating effect of nanowire transistors and the physical mechanism of hot carrier degradation. The nanowire transistor is about to enter the mass production stage. It is expected that this achievement will be of great significance to improve the yield and device reliability of nanowire transistors in the future, and the expanded research and development based on this achievement will also be beneficial to the process research and development of nanosheets and fork devices in the future.
Dr Stanislav Tyaginov, the team leader, was born in St Petersburg, Russia. He received his Ph.D. in physics in 2006 and is a member of IIRW and IRPS technical planning committees. He led the development team of HCD model in Duveen Microelectronics Research Institute, and published more than 100 papers in scientific journals and conference proceedings. At present, Dr. Tyaginov's research fields include: transistor physical model simulation, research on HCD effect in transistors based on Si and SiC, modeling of BTI and delayed breakdown, and tunneling in MOS devices.
IMEC, full name: International University Microelectronics Center, Belgian Microelectronics Research Center, is a company founded in? 1984? Where is the technology research and development center? Headquartered in Leuven, Belgium. IMEC？ In the field of nano-electronics and digital technology, IMEC is strategically positioned as a leading forward-looking major innovation center in the world. From where? 2004? Participated in the research and development of chip cutting-edge technology from 45nm to 7nm.
TU Wien, formerly known as Imperial College London, Vienna, is a comprehensive university established as the Academy of Science and Technology of the Royal Academy of Sciences of Austria-Hungary and the first university of science and technology in German-speaking countries. It is recognized internationally and domestically in the fields of teaching and research, and is one of the top universities in Europe.
KU Leuven is the highest university in Belgium, one of the top 100 universities in the world and one of the top ten universities in Europe. Its integrated circuit related disciplines are among the best in Europe, and it has in-depth and comprehensive cooperation with Belgium IMEC in the research and development of integrated circuit technology.
Original link:
https://ieeexplore.ieee.org/document/9260648