CRYSTALS WAFERS AND EPITAXIAL LAYERS

RECENT IMPROVEMENTS IN LEC-GROWN GAAS CRYSTALS AND MBE-GROWN EPITAXIAL LAYERS HAVE LED TO MATERIAL PURITIES EXCEEDING THE DETECTION LIMITS OF CONTEMPORARY TRACE-ELEMENT ANALYSIS, E.G. SPARK SOURCE MASS SPECTROMETRY (SSMS) AND HIGH PERFORMANCE SECONDARY ION MASS SPECTROMETRY (SIMS). THIS IS NOT TO SAY, HOWEVER, THAT DOPANTS/ IMPURITIES ARE NO LONGER OF CONCERN IN ADVANCED DEVICES GIVEN SUCH PHENOMENA AS ELECTROMIGRATION OR DEFECT GETTERING AND THE DESIRE TO FABRICATE MORE COMPLEX, HIGHER POWER GAAS CIRCUITS WITH LONG TERM RELIABILITY. EVEN WHEN EXISTING ANALYTICAL TECHNIQUES ARE ABLE TO DETECT IMPURITIES, QUANTITATION HAS BEEN, AT BEST, DIFFICULT AND TIME CONSUMING. A NEW TECHNIQUE, VIZ. GLOW DISCHARGE MASS SPECTROMETRY (GDMS), HAS NOW BECOME COMMERCIALLY AVAILABLE AND OFFERS THE POTENTIAL FOR DRAMATICALLY IMPROVED DETECTION LIMITS AND MORE ACCURATE ROUTINE QUANTITATION COMPARED TO EITHER SIMS OR SSMS. RESEARCH IS NEEDED TO REALIZE THESE CAPABILITIES IN THE CONTEXT OF GAAS. THE PHASE I PROGRAM PROPOSED HEREIN IS DESIGNED TO EVALUATE THE INSTRUMENT AND THE TECHNIQUE SPECIFICALLY FOR GAAS ANALYSIS (INCLUDING DEPTH PROFILING, IF POSSIBLE) AND ASSESS ANY HARDWARE/ PROCEDURES OPTIMIZATION NEEDED TO ACHIEVE SUB-PART-PER-BILLION DETECTION LIMITS AND QUANTITATIVE ACCURACIES OF 1-3% OF THE IMPURITY CONCENTRATION DETECTED.