The New Structure And Process Research Of Silicon And Gallium Nitride Based Semiconductor Functional Device

With the continuous development of science and technology, Wide bandgap semiconductor devices have become one of the most important researchs in the current semiconductor industry. Because of the advantages of GaN materials, such as excellent piezoelectric and thermoelectric properties, stable physical and chemical properties and so on, it has become the most popular wide band gap semiconductor material, and especially AlGaN/GaN HFET has shown the outstanding performance in high frequency, high temperature and other application fields.In the aspect of biosensor, because of the special biocompatibility and stable chemical characteristics of GaN materials, GaN HEMT has been used as the biosensors. At the same time due to the particularity of biological detection and biological response, how to improve the sensitivity of biological detection has always been the focus of this research. For this problem, this paper carried out a kind of processing technology on the gate surface, by comparing the device parameters such as saturation current, transconductance before and after the processing, to find a kind of effective method to improve the device sensitivity. Experiment processing is shown as following, M4L Dry stripping machine treatment90s under200w power, then using HC1(1:1O) aqueous solution to remove the oxide layer by washing90s; after that, O2plasma treatment gate surface under200W power for5min to form a gate dielectric layer, then followed by the deposition of gate metal Au. After the experiment it is found that the saturation current of sample B device with5min O2plasma treatment was about72.45mA/mm with Vgs=2V and Vds=10V, while the saturation current of the sample A device without O2plasma treatment was about68mA/mm with Vgs=2V and Vds=10V. The device saturation current is shown to be increased significantly after O2plasma treatment. But the transconductance of the device has been decreased from10.25mS/mm (device without O2plasma treatment) to9.485mS/mm (device with5min O2plasma treatment). Thus, although this processing method could improve the saturation current, at the expense of the maximum transconductance, further work still is needed to improve the process in the later.In the aspect of GaN based integrated circuit, because the AlGaN/GaN materials has a high concentration of2DEG even without external applied gate voltage, almost AlGaN/GaN devices with normal heterostructure are depletion-type devices, which has hindered the integrated circuit application of GaN HFET, so the research of enhanced A1GaN/GaN devices has attracted more interests. Nowadays, the fabrication methods of enhanced AlGaN/GaN HFET devices include: groove gate structure, F ion implantation, thin AlGaN barrier layer structure, p-type gate structure, and non-polar a-plane channel structure and so on, of which groove gate structure was the most popular structure. Because of the stable chemical and physical properties of GaN materials, traditional grooves grating etching process are almost based on the dry etching, which are believed to result in significant defects on devices. According to this situation, a new wet etching process for GaN heterostructure was adopted:first thermal annealing the device for45min under650(?), then treatment by70(?)KOH liquor. Adopting this wet etching process, about19nm gate grooves was fabricated. After the groove process, Al2O3Gate dielectric was deposited, and then MOSHEMT was fabricated. The threshold voltage were found to transfer from-3.28V (normal AlGaN/GaN HEMT) to+0.42V (GaN MOSHEMT), positive voltage shift of3.70V, meet the requirement of the enhanced device. The measurement results of the enhancement GaN MOSHEMT show that the maximum transconductance is15.6mS/mm, output drain current is51.6mA/mm when Vgs=5V and Vds=10V. The simulation work was performed by ADS software, where all devices parameters are determined according to the experimental data. The simulation of a simple ring oscillator based on GaN HEMT E/D inverter was completed to shown an excellent performance. Our simulation results shown that9cycles of ring circuits were required to obtain100MHz ring oscillator. The simulation work provides a theory basis for the future development of GaN based integrated circuit.