The Study Of Semiconductor Crystal's Surface Contact Electrical Characteristics And Electrical Discharge Machining Milling

Semiconductors, such as silicon, germanium,are sensitive to light, heat, electricity and magnetism. Because of this unique electrical properties, they have become the most active advanced materials in the fields of science and technology. However, their high hardness and brittleness make them difficult to process. The current processing methods have many shortcomings: high processing cost, high loss, low efficiency. therefore, new processing methods are urgent. Our team had tried to process Si and Ge by wire electrical discharge machining(WEDM). Because of the special nature of semiconductor, contact resistance and passivation exist during processing. This paper studied contact resistance and passivation based on theoretical study and experiment.Then a practical processing technology was proposed. At last Si was processed by EDM milling based on the study.Following are main research work:1. For silicon, first, this paper analysed the causes of contact resistance theoretically and then established conductivity theory model of cutting conductive loop. Then, it analyzed several factors's effect on the contact resistance. The factors include: cantact way, conact material, contact pressure. The following conclusions can be drawn from the experiment: conact material's work function must be close to semiconductor material's; more contact area, smaller contact resistance; While the contact pressure should be maximized to reduce the contact gap within the extent permitted, a smaller contact resistance would be gained.2. experiment simulated germanium crystal's process processed by WEDM. a new concept, "passive film", was proposed. Through theoretical analysis and the observation of experimental phenomenon, using XRD techniques, we could determine that this passive film is the semiconductor oxides. Then another "passive" experiment also was carried out with silicon. It found that silicon's passivation was very weak, almost negligible. For Passivation of germanium, this paper proposed two methods to prevent and eliminate this phenomenon. experiments showed that "smear method" was an more effective measure to prevent passivation. experimental verification and the actual processing were carried out using this method. Compared with the original method, results demonstrated that cutting efficiency and stability had been greatly improved with this method.3. A three-dimensional milling work platform and its power supply were designed. Silicon was milled with this equipment. Moreover, this paper researched several factors (unload voltage, pulse width, duty cycle) related with the milling. Deep grooves, "U" and "L"-shaped slot were processed. That demonstrated the feasibility of electrical discharge milling technology for processing silicon. Electrical discharge milling machining technology was extended to the field of semiconductor processing. So it is necessary to further study this technology.