Gas phase preparation and analysis of semiconductor surfaces in a clustered reactor apparatus

Abstract

An integrated reactor system was built for studying gas phase surface preparation chemistries. The system integrates HF/vapor and UV photochemistry modules with an ultrahigh vacuum deposition reactor and a surface analysis chamber (x-ray photoelectron spectroscopy and Auger) for in situ surface preparation, deposition, and analysis. Each vacuum chamber is mounted on a separate, isolated branch from a main sample transfer tube. The system was designed for samples with variable shapes and thickness, but less than 64mm (212in.) in diameter. This design allows for rapid transfer times between chambers (<5min) and for the simultaneous processing and storage of up to four samples. Use of standard sample transfer and vacuum hardware components minimized initial equipment costs and system maintenance. The capabilities of the clustered reactor apparatus and the importance of surface termination were demonstrated by (1) the removal of a mixed oxide and fluorocarbon residue on silicon, leaving the surface completely terminated with Cl atoms, (2) the removal of copper oxide and copper metal from silicon, (3) the deposition of Ti preferentially on a nonannealed, aqueous-cleaned SiO2 surface relative to an annealed surface, and (4) the use of complementary surface analysis techniques to chemically identify hydrogen-bonded silanol groups on a silicon surface after HF/vapor etching. Gas phase cleaning and surface termination utilized a combination of HF/vapor (100Torr, 27°C for 200s) and UV∕Cl2 (10SCCM Cl2, 90°C for 15min) steps. The results demonstrate that integrated processing provides a means to clean thin layers of organic, oxide, and metal contaminants from semiconductor surfaces and to control the terminating atom or chemical group.