A MASS-SPECTROMETRY STUDY OF THE GAS PYROLYSIS OF PH3 AND A PH3 SI2H6MIXTURE/

The thermal dissociation of phosphine and of a phosphine-disilane gas mixture as a function of temperature has been studied in an impinging jet type LPCVD reactor. In order to measure the influence of homogeneo us gas phase reactions, two configurations (cold and hot wall) were us ed. A quadrupole mass spectrometer (QMS) coupled with the reactor usin g a sampling system near the substrate surface was used to follow the gas phase composition. PH3 begins to decompose at 550-degrees-C. Forma tion of the phosphorus dimer (P2) and tetramer (P4) is demonstrated; P 4 is the main product. When Si2H6 is added to this gaseous mixture, fo rmation of monosiiylphosphine SiPH5 is observed.