DEVELOPMENT OF A DEPTH PROFILING METHOD FOR USE WITH A TOTAL REFLECTANCE X-RAY FLOURESCENCE SYSTEM

SIMOX MATERIAL IS RAPIDLY BECOMING THE SOI MATERIAL OF CHOICE FOR MANY IC APPLICATIONS, INCLUDING RADIATION HARDENED. A CONSTANT THEME OF CONCERN THROUGHOUT THE DEVELOPMENT OF THIS TECHNOLOGY HAS BEEN THE METALLIC IMPURITY CONTENT IN THE MATERIAL. MAJOR EFFORTS HAVE ADDRESSED THE ELIMINATION OF THE METALLIC CONTAMINATION BY MODIFICATION OF THE IMPLANTATION EQUIPMENT USED TO FABRICATE SIMOX MATERIAL, WITH RECENT MATERIAL HAVING CONTAMINATION LEVELS AT THE DETECTION LIMITS OF SIMS. HOWEVER, A NEW CONTAMINATION MEASUREMENT TECHNOLOGY HAS BECOME AVAILABLE; TOTAL REFLECTANCE X-RAY FLORESCENCE (TXRF). THIS MEASUREMENT SYSTEM IS MUCH MORE SENSITIVE THAN SIMS AT DETECTING CONTAMINATION ON THE SURFACE OF A SILCON WAFER. HOWEVER, TO BE MOST USEFUL FOR SIMOX, THE TECHNOLOGY MUST BE DEVELOPED TO ALLOW FOR CONTAMINATION PROFILING IN-DEPTH INTO A SIMOX WAFER. TWO METHODS ARE PROPOSED FOR OBTAINING THIS DEPTH INFORMATION: A MODIFICATION OF THE MEASUREMENT TECHNOLOGY (INCREASE ANGLE OF INCIDENCE) AND ETCHING OR OXIDIZING THE SIMOX WAFER TO EXPOSE THE LOWER SILICON LAYERS AT THE SURFACE.