Foreword
Semiconductor electronic properties are extremely sensitive to the presence of trace amounts of foreign substances. This fundamental property of doped semiconductors is the basis for the fabrication of electronic devices. From the dawn of semiconductor based electronic devices, it has been clear that undesired impurities must be kept at very low levels and material purification methods were essential to the successful operation of such devices.
In the 1950’s and 1960’s, the solid state device of choice was the bipolar junction transistor (BJT), which required a sufficiently long free-carrier recombination lifetime and thus, a low metallic impurity concentration. To achieve this, semiconductor surfaces were cleaned at critical steps in the manufacturing process. In the early 1970’s, the first systematic cleaning studies were carried out and resulted in the “RCA cleaning” process. The aqueous oxidizing mixtures (SC-1 and SC-2) were found to be very efficient at removing a broad range of contaminants such as organics and metals. SC-1, in particular, very effectively removes particles. These mixtures were highly selective towards silicon because of the stability of the passivating SiOx on the silicon surface.
Although the metal-insulator-semiconductor lateral-field effect transistor had been invented in the 1920’s, it was not until the late 1970’s that the metal-oxide-semiconductor field-effect transistor (MOSFET) became a useful electronic device. It was only at that point ...
