Production of Si + and Cl + ion beams from a Freeman type ion source using low toxicity and non-corrosive vapours as source gas

Abstract

A method is proposed for production of Si + and Cl + ions in Freeman type ion sources using low toxicity and non-corrosive vapours of hexamethyldisilane ((CH 3) 3SiSi(CH 3) 3) and carbon tetrachloride (CCl 4), respectively. These source materials can be used without expensive and complicated safety systems required for silane and chlorine source gases. Experimental X-ray photoelectron spectroscopy results show that in the case of (CH 3) 3SiSi(CH 3) 3 vapour used as the ion source gas, the ion beam, after using standard magnetic field ion mass analysis for mass 28, contains about 62% of 28Si + ions. It is assumed that the molecular ions C 2H 4 + with the same mass 28 are the main component of the remaining 38% of this ion beam. In the case of the use of CCl 4 vapour as ion source gas and magnetic field mass analysis set for mass 35, a pure Cl + beam is observed; there are no other ions of mass 35 that can be formed from the source gas. The same system when used with water vapour as a source gas can produce pure ion beams of O + and/or H + ions without adverse effects produced in the ion source by oxygen gas (oxidation) or typical safety problems with a hydrogen gas supply (explosive).