Study On The Electrical Properties Of Trench Barrier Schottky Diode

After the emerging of planar schottky diode, it has received widespread attention. Planar schottky diode has excellent characteristics like higher frequency and lower forward voltage compared with PN junction diode. All these unique properties make it has enormous potentials to be used in the applications of solar cell, switching power supply, automotive and mobile phone. But under the influence of barrier lowering effect caused by the image force, the leakage current of planar schottky diode under reverse bias is increased by some orders of magnitude, so planar schottky diode has the weakness of poor reverse blocking capability. In order to resolve this problem, people invented a variety of new devices with novel structures step by step. Among them, three structures have got widespread attentions after invented. The first one is the merged PN schottky diode which contains the PN structure in Schottky diode. The second one is schottky diode with double barrier metals. The third one is trench mos barrier diode (TMBS) which uses the metal-oxide-semiconductor structure (mos structure). Among them, we think TMBS is the best one because of its high frequency characteristic and its structure which is easy to be adjusted.In this paper, we devoted to study the influence of trench shape and the constitution of the oxide in the trench to the electrical properties of trench mos barrier schottky diode and tried to develop the TMBS process with Ti as metal of schottky diode in IC foundry.Firstly, we carefully studied the working mechanism of the traditional TMBS device with right angle trench (traditional TMBS) and delved into the influence of the trench depth, trench spacing and the thickness of the oxide in the trench on the electrical properties of TMBS, containing the breakdown voltage, leakage current density and forward turn-on voltage of the device. During this process, we found that the shape of trench has important influence on the properties of the traditional TMBS. So we proposed two novel trench structures. One is the filleted corner trench TMBS (filleted TMBS), and the other is the ladder trench TMBS (ladder TMBS). By simulating with Medici, we found that compared with traditional TMBS, filleted TMBS could have a15.8%higher breakdown voltage, while maintain the same leakage current density and forward turn-on voltage. And, ladder TMBS diodes can reduce the leakage current density by35%, while have a breakdown voltage not smaller than that of traditional TMBS and a forward turn-on voltage only a little bit higher than that of traditional TMBS.Although by changing the shape of trench in TMBS, we can get ladder TMBS which has a35%lower leakage current density compared with traditional TMBS. But this improvement is at the cost of sacrificing a little of the forward turn-on voltage. After analyzing, we found using the ladder trench is not the only way to enhance the reverse blocking capability of the TMBS device. If we change the oxide in the trench from one material to two (with a kind of high dielectric material used to construct the upper oxide in the trench and SiO2as the material used to construct the lower oxide in the trench)(in the following text we named this device TMBS with high dielectric constant material to construct the oxide in trench), we can not only reduce the value of reverse leakage current density, and the more important point is that at the same time of improving the problem of large leakage current, the breakdown voltage and the forward turn-on voltage of the device keep almost the same as traditional TMBS. The simulation result in this paper showed that, with the configuration parameters described in our paper, this TMBS can reduce the leakage current density by19.8%, while the breakdown and forward voltage almost keep the same as traditional TMBS. Moreover, in order to reduce the cost of the TMBS device by achieving all the TMBS process in fab, where has the traditional CMOS process only. We tried to produce the45V TMBS device with forward current capacity of10A in fab. The metal we used to construct schottky diode is Ti. Although we have not got succeed, we got some periodical results which we have showed in our article for your reference.Then, I list some good results I got before studying of TMBS device. The main work of this part is that we synthesized a kind of composite material with polyaniline and pt nanoparticles, and constructed glucose sensor with this material. The results showed that our glucose sensor exhibited unprecedented sensitivity, as high as96.1μA·mM-1·cm-2, with an average response time of3s, a linear range from0.01to8mM, and a low detection limit of0.7μM.At last, we presented our prospects of subsequent research of trench barrier schottky diode. Firstly, for filleted TMBS, we want to optimize the simulation condition, and study the influence of the radius of the round corner on the electrical properties of the device. This is necessary for guiding the fabrication of the device. Secondly, we hope to study the reliability of TMBS devices. Finally, although the process of the silicon based device is mature, but accompanied by the gradually clearly understanding the limiting of device performance by the material property of silicon, we known that the device performance should be improved by changing the semiconductor material to get large improvement, so the next step we want to simulate TMBS device using SiC as the semiconductor material and also we will pay more attention to develop the process of SiC based devices.