HOLOGRAPHIC AND REFLECTION X-RAY LASER MICROSCOPE FOR INTEGRATED CIRCUIT INSPECTION

WE PROPOSE TO DEVELOP A SYSTEM FOR HIGH RESOLUTION ( 0.05 MU) INSPECTION OF DEFECTS ON RELATIVELY LARGE AREA INTEGRATED CIRCUITS (IC). THE SYSTEM WOULD COMBINE A HIGH RESOLUTION HOLOGRAM (INTERFEROGRAM) OF AN IC WITH A REFLECTION X-RAY MICROSCOPE(1). THE X-RAY HOLOGRAM WOULD ENABLE THE FAST LOCALIZATION OF DEFECTS, AND THE X-RAYMICROSCOPE WOULD PROVIDE A HIGH RESOLUTION IMAGE OF ANY DEFECTS. INITIALLY A SOFT X-RAY LASER, WHICH WAS DEVELOPED AT PRINCETON UNIVERSITY, WILL BE USED AS A COHERENT SOURCE OF RADIATION. HOWEVER PXL IS PLANNING TO BUILD A SMALL (PORTABLE) SOFT X-RAY LASER WITH A MULTILAYER MIRROR CAVITY AND THIS WILL BE USED FOR THE CONSTRUCTION BY PXL OF AN ENGINEERING (COMMERCIAL) DEVICE. THE INSPECTION SYSTEM WILLBE BASED ON THE FACT THAT SURFACES OF DIFFERENT MATERIALS HAVE SIGNIFICANT REFLECTION COEFFICIENTS (UP TO SEVERAL PERCENT) FOR SOFT X-RAY RADIATION IN THE REGION 10-20 NM. THE REFLECTION COEFFICIENT STRONGLY DEPENDS ON THE MATERIAL OF THE SURFACE AND THE ANGLE OF INCIDENCE OF THE RADIATION, THEREFORE GOOD CONTRAST CAN BE OBTAINED FOR LITHOGRAPHIC MATERIALS. THE INSPECTION OF IC WILL CONSIST OF TWO STEPS. IN THE FIRST STEP A HIGH RESOLUTION HOLOGRAM (INTERFEROGRAM)OF A RELATIVELY LARGE AREA OF AN IC WILL BE REGISTERED USINGA CCD DEVICE. THE HOLOGRAM OF THE IC UNDER INVESTIGATION WILL BE COMPARED BY COMPUTER WITH A HOLOGRAM (INTERFEROGRAM)OF A NON-DEFECTIVE IC STORED IN THE COMPUTER MEMORY IN ORDERTO RAPIDLY IDENTIFY AREAS WITH DEFECTS. IN THE NEXT STEP, THESE SPECIFIC AREAS WILL BE IMAGED AT 0.05 MUM RESOLUTION BY THE REFLECTION X-RAY MICROSCOPE. PHASE I WOULD BE DEDICATED TO: THE COMPUTER RAY TRACING, DETAILED ANALYSIS OF NOISE, CONTRAST AND SPECKLE PROBLEMS, AND THE METHODS OF ELIMINATING OR MINIMIZING THESE PROBLEMS,REDUCTION OF DATA TRANSMITTED TO THE COMPUTERS MEMORY AND THE DESIGN OF THE SYSTEM.