The early days of MOS technology

In the past couple of decades, the increasing influence of electronics on human life has promoted MOS technology to a role of similar significance for cultural change as, for example, electric power transmission and combustion engine transport. The basic device for this development, the metal–oxide–semiconductor field-effect transistor (MOSFET), was patented in 1928 by Lilienfeld. The invention had to wait for realization until 1961 when Khang at Bell Telephone Labs first demonstrated a working device. Until then, one of the main hurdles for implementing Lilienfeld’s idea was finding a material combination such that a surface channel for charge carriers could be brought about by an external electric field. A charge-free surface or interface was needed, which required a structure free of charge carrier traps. Here, silicon technology opened new possibilities. By thermally oxidizing the surface of silicon crystals into SiO2, an insulator was obtained with eminent properties and with a low concentration of traps at the SiO2/Si interface and in its volume. At the beginning of the 1960s, a considerable amount of work was performed to optimize the properties of SiO2 prepared this way and to understand the metal–oxide–semiconductor system. Important contributions to the understanding of the MOS system came from a group of William Shockley’s former disciples at Fairchild Semiconductor in Palo Alto. In the same period, activities were also initiated at the IBM Thomas Watson Research Center, at the Bell labs and at some universities in the USA.