Laser-induced morphological and electrical changes to silicon CCD devices have been studied. The devices were poly -silicon gate Time Delay Integrating (TDI) CCD arrays of 2048x96 elements. The laser source for these experiments was a Q-switched Nd:YAG laser at 1.06 µm with 10 ns pulses at a 10 Hz repetition rate focused to an approximately 400 gm spot radius. Single pulse and multiple pulse damage behavior was studied. Both CCD arrays and diagnostic structures from the wafer periphery were tested. The additional diagnostic structures included poly -Si resistors and MOS -FET gates. Of the measurements made, it was found that drain -to-substrate and drain -to-source leakage currents and transconductance in FETs were the most sensitive parameters to laser-induced change. The onset of electrical parameter changes was observed as low as 0.2 J /cm2. Severe electrical parameter changes began at 0.5 J /cm2 and continued up to the onset of severe morphological damage at 1.0 J /cm2. Above this fluence, both poly -Si and aluminum interconnect lines were melted and broken.

Laser-induced damage in two types of silicon photosensor array has been studied. The samples were MOS CCD time delay integration (TDI) sensors with a 2048×96 element array of pixels and CID photodiode arrays of 512×1 pixels. The laser source was a Q-switched 1064 nm Nd:YAG laser (10 Hz rep rate, 10 ns pulses with a 250 μm spot radius). Tests for morphological and electrical damage to the CCD arrays have been reported previously. In new experiments, the micro-damage morphology is examined and correlated with both the observed electrical degradation and newly observed stress effects. We report the observation of surface deformation and lattice defects due to laser-induced stresses in the SiO2 and poly-silicon thin films on the silicon substrate. Measurements of damage for the CID arrays show them to be more resistant to laser damage than MOS structures such as CCD arrays. In addition, electrical degradation of these arrays was observed which affected the video output signal from the devices.

The characteristics of laser-induced electrical failure in biased silicon avalanche photodiodes have been observed. The samples were RCA reach-through avalanche photodiodes with antireflection coatings. They were biased at typical operating voltages during irradiation. The laser source was a Q-switched 1064 nm Nd:YAG pulsed laser operating at 10 Hz with a 10 ns pulse length and with a 300 μm spot radius. The current-voltage characteristics were monitored for permanent change as a function of laser fluence and the degradation thresholds were found. Two types of change were observed. The first type was a large increase in bulk leakage current. It may be modeled by the introduction of defects into the depletion region by deep melting transients. The second type was catastrophic failure in which the devices were electrically shorted after irradiation. It may be modeled by excessive current density in the photodiode junction. The type of failure was determined by the parameters of the biasing circuit.