Photo-Induced Organometallic Processes in Semiconductor Surface Technology

Abstract

Semiconductor workers have been among those who have most eagerly taken up the investigation of photo-assisted deposition, for the following reasons. Firstly, they are faced with stringent requirements over the deceptively simple parameters of thickness and compositional uniformity of the wafer. The thermal or plasma-generating electric fields needed to give this uniformity are difficult to achieve on scales of several centimetres, and require large-scale equipment; whereas progress in developing uniform excimer laser profiles of these dimensions has been encouraging. Secondly they have requirements to deposit what are often very refractory materials, on delicate substrates where conventional methods allow little leeway between uneconomically slow deposition and thermal destruction of the sample. Thirdly they have to cope with multistage photolithography to produce the patterned surfaces of integrated devices, and photo-deposition has long promised to relieve them of part or all of this burden. Fourthly, the recent development of organometallic epitaxial deposition (MOVPE), which already produces very precisely controlled structures in III–V materials, offers the exciting prospect of a considerable extension in scope if photolytic decomposition of the precursors can be substituted, in whole or in part, for the pyrolytic (thermal) mechanism.