System for combined SIMS-AES-XPS studies of solids

Abstract

We have have assembled a system for combined surface and thin film studies by SIMS, AES and XPS. The SIMS and AES investigations are performed in the same UHV chamber, while for XPS measurements the sample is transfered into the XPS system via an isolation valve. The SIMS-AES and XPS units can be operated independently, thus increasing the versatility of the entire instrumentation. The primary ion gun, used for sample erosion, supplies velocity-analyzed ions of either nonreactive or reactive gases at an acceleratiang potential of up to 15 kV. The ion source is differentially pumped. The base pressure in the target chamber after bakeout is in the mid 10-8 Pa. The unique feature of the primary ion column is a movable Einzel lens, which allows the width of the square shaped rastered area to be increased to about 5 mm at 12 keV. The large area scanning capability is required for XPS measurements. The SIMS instrumentation comprises a quadrupole mass spectrometer, a secondary ion energy filter and electronic gating in conjunction with rastering. By use of a capillary the sample can be exposed to a directed flow of oxygen gas (oxygen jet). AES studies are performed by use of a cylindrical mirror analyzer with a coaxial electron gun which is also employed for primary ion charge compensation in SIMS studies of insulators. Both the SIMS systems and the XPS unit can be operated under computer control. The performance characteristics of the complete SIMS-AES-XPS system are described in detail and are illustrated by several examples.