Research Of Heat Generation And Transfer In High Power Electronic Devices

Transistors are the key element in the integrated circuit.It is wildly applied in wireless devices, such as radar, communications satellites. The transistor is scaled to smaller dimensions and higher power to improve speed and functionality. The gate length of the transistor is currently in the range of 200 run to 500 nm. This generates very high local heat dissipation flux up to 200W/cm2 and results in the high local temperature inside the transistor. It is well known that the thermal characteristic of the transistor is very important for optimum device designs of the reduction of the heat dissipation rate itself and for the cooling designs with effective heat removal from the transistor device. Therefore, it is very necessary to investigate the characteristics of heat generation and transport in high-power devices. The main work of this paper completed as follows:1 Establishment of micro/nano-scale high-power electronic devicesTraditional macroscopic method is incapable of describing the heat generation and transfer mechanism in high-power electronic devices, when either characteristic dimensions become comparable or less than the mean free path of phonons,or characteristic timescale of devices equals to or smaller than the relaxation time of phonons. In order to reveal the heat generation and transfer mechanism in micro/nano-scale devices, the collisions between electrons and phonons should be considered in the model.Fristly, a multiscale lattice Boltzmann modeling of FET with different conditions is proposed. In this model, a source term is introduced to describe the scattering of phonons and electrons. Under different working conditions and thermal managements (such as the location of hot spot, peak value of temperature, average temperature),the temperature distribution of a FET is investigated. By analyzing heat generation and transfer mechanism of FET in micro/nano-scale, It provides theoretical reference to engineers.Then, A coupled thermal and electrical model comprising of electron transport equations and phonon energy conservation equations is established. The differences between acoustic phonons and optical phonons have been ignored. According to the difference of frequency, phonons can be divided into optical phonons and acoustic phonons. The group velocity of optical phonons is close to zero, which leads to quite small conductivity. Whereas the group velocity of acoustic phonon is around 6000ms-1, so that acoustic phonons are main heat carriers in semiconductor materials.Therefore, in order to improve calculation accuracy, the new model is established. Electric field, temperature and Joule hear are calculated.2. Simulation of electric and thermal feature in Double-finger transistorFor the electric device, the structure of the electric device is periodically. In previous researches, the single-finger unit is considered as a computational element in the whole semiconductor device, which is unsuitable. In actual situation, the electrodes are arranged with source gate, drain gate, and source gate. Therefore, double-finger unit should be the minimum unit of the whole device. The temperatue distribution is impacted on the location of the gate, source and drain.Thus, a fouble finger transistor is studied in this paper.3 Analysis of the temperature distribution in the deviceHeat generation and transfer process in nanoscale semiconductor device is described as follows. The driven voltage leads to a lateral electric field, then the electrons gain energy from this field, generating energetic electrons. The energetic electrons can collide with each other, with phonons, with material interface, with imperfections or impurity atoms. However, only the collisions between electrons and phonons have influence on the energy transport. By obtaining the energetic electrons energy, the lattice temperature increases. The effects of different drain voltage, substrate temperature, and doping concentration on the location of hot spot, maximum temperature and average temperature are discussed. It provides theoretical reference to engineers...