Non-Destructive, Remote Testing of Silicon Wafers by Observation of Photo-Luminescence Characteristics at Room Temperature

Non-Destructive, Remote Testing of Silicon Wafers by Observation of Photo-Luminescence Characteristics at Room Temperature

A non-destructive, remote testing of silicon wafers by the observation of photo-luminescence (PL) characteristics from a silicon wafer in an imaging mode at room temperature exposes various types of wafer defects that are detrimental to the ultimate performance of the inscribed circuitry. Flashlamps 11 (with reflectors 10) pulsed at 10 - 50 Hz, with a pulse duration of 50 - 300 mms and with a filtered (12) spectral emission of 400 - 800 nm, can be used to illuminate the wafer 13 with a power density of 50 - 100 W/cm2 (Fig.
1). Electrons and holes (EH) generated by the flashlamp 11 excitation recombine in defect-free silicon by emitting radiation in a band near 1.1 eV. Certain crystal defects will act as regions for non-radiative EH recombination, resulting in very weak local PL. Other defects associated with strain fields may act as funnels where EH pairs can read much higher than ambient concentrations, with the main recombination channel remaining radiative. These defects will appear as regions of strong PL. When PL is viewed on a Vidicon 14, good parts of a wafer 13 will appear as a bright field. An IR pass filter 18 and a lens 19 reject lamp light and pass photo-luminescence band from wafer 13 for viewing by detector 14. Non-radiative recombination sights will appear as dark areas, while EH funnels will appear as brighter-than-average are...