No abstract

Moment expansion approach to calculate impact ionization rate in submicron silicon devices A model of impact ionization due to the primary hole in silicon for a full band Monte Carlo simulation High electric fields, that are characteristic of sub-micron devices, produce highly energetic electrons, lack of equilibrium between electrons, optical phonons, and acoustic phonons, and high rates of heat generation. A simple coupled thermal and electrical model is developed for sub-micron silicon semiconductor devices consisting of the hydrodynamic equations for electron transport and energy conservation equations for different phonon modes. An electron Reynolds number is proposed and used to simplify the electron momentum equation. On a case study of the metal-oxide-semiconductor field-effect transistor with 0.24 m gate length, the calculated transconductance of 0.175 1/⍀ m agreed well with measured value of 0.180 1/⍀ m at 2 V drain voltage. The maximum electron temperature is found to occur under the drain side of the gate where the electric field is the highest. Comparison with experimental data shows the predictions of optical and acoustic phonon temperature distributions to have the correct trend and the observed asymmetric behavior. Increase in substrate boundary temperature by 100°C reduces the drain current by 17% and decreases the maximum electron temperature by 8%. The first effect increases device delay and the second effect decreases the possibility of device degradation by charge trapping in the gate oxide.

We have developed a new and simple technique for thermal imaging with submicrometer spatial resolution using the atomic force microscope. The method is particularly unique for simultaneously obtaining thermal and topographical images of biased electronic devices and interconnects where there could be different materials and potential variations on a scan surface. Application to a biased metal-semiconductor field-effect transistor showed the heating under the gate and a hot spot between the gate and drain where the electric field is known to be the highest. Thermal images of a biased polycrystalline Al-Cu via structure showed the grain boundaries to be hotter than within the grain. With the development of electronic devices and structures in the submicrometer range, this technique can become very useful as a tool for thermal characterization and property measurement.

A multi-mode analysis of micro-cantilever dynamics is presented. We derive the power spectral density of the cantilever displacement due to a thermal noise source and predict the cantilevers's fundamental resonant frequency and higher harmonics. The first mode in the multi-mode model is equivalent to the traditional single-mode model. Experimental results obtained with a silicon nitride cantilever at 300 K are in excellent qualitative agreement with the multi-mode model. The multi-mode model may be used to obtain accurate values of the cantilever properties such as the elastic modulus, effective mass, thickness and moment of inertia.

No abstract