为改善高电阻率硅的电火花线切割可加工性,提出了一种在半导体电镀金属薄膜表面放电的方法(简称进电端放电法)。首先在硅(电阻率为2.1Ω.cm)表面电镀一层铜膜,然后利用铜刷作电极,在铜膜表面进行放电,利用放电形成的高温在硅表面形成重掺杂层,以降低接触势垒。分析了表面重掺杂层的形成机理,制备了硅试件并得到了伏安曲线,结果表明,试件的进电端接触电阻明显减小。最后采用进电端放电法对电阻率为2.1Ω.cm、直径为100mm的硅锭进行电火花线切割试验,加工效率可由12mm2/min提高至30mm2/min。
In order to improve EDM machinability of high resistivity silicon, a new method aimed at reducing the contact barrier was raised by EDM sweeping on the surface of metal film on the electric feeder termination, named electric-- feeder-- termination-- discharge (EFTD). First, a copper film was deposited on the surface of silicon (2.1Ω·cm). Then, electrical discharge happened between a copper brush and the copper film. Finally, a heavily doped layer between the silicon and copper film was formed by the action of high temperature. The formation mechanism of heavy doped layer was analyzed. The test specimen (silicon) was prepared, and the I--U characteristic curve was measured. The results show the reduction of contact resistance. In the end, an EDM experiment on silicon ingot with the resistivity of 2.1Ω· cm and the diameter of 100mm was conducted. The EDM efficiency is as 30mm2/min.