Aiming at improving accuracy of photoetching technology in conventional double-mesa process,this article introduced buried-metal layers and developed silicon based buried-metal self-aligned process in order to increase the mesa area utilization efficiency.

With the novel modulated doping QW base and buried metal self-align process, the base lateral resistance and contact resistance of ultra-thin-base small-size SiGe HBTs are decreased by 42% and 55% respectively, which provides an effective method of resolution on base serial resistance.

In this work, on the one hand, the contact-shadow-mask method and technique were used to micro-fabricate the magnetic tunnel junction (MTJ) and optimize the experimental conditions.