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Free carrier concentration profiles were determined by Fourier Transform Infrared (FTIR) variable angle spectroscopic ellipsometry. The technique exploits carrier absorption in the mid-infrared spectral range and combines the sensitivity of ellipsometry with a simple Drude free carrier absorption model to determine the carrier profile. In this study, the carrier profiles were modeled as graded multilayers that were constrained to a specific functional form (e.g. Gaussian, complementary error function) when appropriate. Carrier profiles from boron and arsenic ion-implanted that had been subjected to furnace or Rapid Thermal Annealing (RTA) annealed silicon wafers were compared to Spreading Resistance Probe and Secondary Ion Mass Spectrometry profiles. p−p+doped epitaxial silicon samples (before and after annealing) were also measured and the results were compared to theory.

The effects on Si wafers of (1) Ge or Si amorphization implants, (2) B or BF2 dopant implants at low energies (15 keV through 16 nm of screen oxide) and (3) rapid thermal processing (RTP) at 800–1050° have been systematically studied. Sheet resistance (Rs), spreading resistance probe (SRP), Rutherford backscattering (RBS) and ultrahigh vacuum secondary ion mass spectrometry (SIMS) have been used to study the resulting electrical and materials properties of these wafers. Values for Rs versus junction depth are below any results reported in the literature. The Rs maps show lower Rs and better uniformity in the wafers that were amorphized with Ge or Si and received a B rather than a BF2 implant. The effects of channeling, molecular breakup of BF2, B solid solubility, and annealer uniformity are discussed.

The corrosion performance of both unencapsulated and plastic encapsulated parts has been studied under temperature-humidity-bias (THB) stresses using a patterned test chip with aluminum metallization. The effect of encapsulation materials and ionic contaminants purposely introduced on the chip surface has been determined for both accelerated THB and severe, real life conditions. Unencapsulated test chips exhibited very different THB performance characteristics from encapsulated parts including a near-zero induction time and a shallow post-induction slope on the % failures vs time curve. The induction time and mean-time-to-failure (MTF) for encapsulated devices were strong functions of both the polymeric class of encapsulant and the particular compound employed. At least part of the difference in performance between molding compounds has been attributed to impurities inherent in the compounds. Impurities contributed from conductive epoxies used for die attach also adversely affect the device's MTF, as do normal contaminants present on as-plated leadframes. The environmental factors of temperature, relative humidity and bias greatly affect the performance of encapsulated devices. In this study, the MTF decreased dramatically with bias between 5 and 30 volts, the range over which most devices operate. The acceleration factors relating device performance in an 85°C/85%RH environment to severe, real life conditions were surprisingly small and somewhat dependent on the encapsulant.