Kaoru Motonami

Direct Observation of Crystal-Originated Particles on Czochralski-Grown Silicon Wafer Surface and Effect on Gate Oxide Reliability

We found that crystal-originated particles (COP) on a Czochralski-grown Si wafer surface consist of single pits and pair pits, using a pattern-defect inspection machine and SEM. The influence of these pits on the gate oxide reliability was studied by means of a time dependent dielectric breakdown (TDDB) test under constant voltage stress (8 MV/cm). It was clearly demonstrated that when the gate oxide thickness was around 10 nm, in the active region pair pits caused gate oxide failure, while single pits did not. It was also found that broad pair pits, formed by preferential oxidation/etching treatment, did not degrade the gate oxide reliability even when situated in the active region.

Generation Current Reduction at Local Oxidation of Silicon Isolation Edge by Low-Temperature Hydrogen Annealing

The effect of low temperature hydrogen annealing (LTHA) in reducing the generation current at the local oxidation of silicon (LOCOS) isolation edge can be successfully investigated by C-t measurement of metal-oxide-semiconductor (MOS) capacitors with varying periphery-to-area ratio. The generation current, at the LOCOS isolation edge, can then be measured by the separation of the generated peripheral current and the surface and bulk current generated under the gate electrode. As a result, it becomes clear that the generation current is strongly reduced by annealing at a temperature below 400°C, but at 450°C the reduction is rather small.

Crystallization of amorphous‐Si films by pulsed YAG2ω green laser for polycrystalline Si TFT fabrication

— A pulsed YAG2ω green laser with a line-shaped beam was applied in the crystallization process to fabricate polycrystalline-Si TFTs, and this procedure was compared with excimer-laser annealing (ELA). YAG2ω lasers are superior to excimer lasers in that they have fewer items to maintain and a longer working time ratio. The crystallization mechanism for YAG2ω laser annealing (YLA) based on the lateral growth of grain is different from that of ELA. Its fluence margin was obtained from the n-channel mobility measured from fabricated TFTs and was found to be twice as large as that for ELA. We also found that overlapping irradiation does not change the mobility of TFTs. This is because the distribution of grain size is almost the same as in non-overlapping regions. This suggests the possibility of overlapping irradiation in YLA.

Generation Current Reduction at LOCOS Isolation Edge by Low Temperature Hydrogen Annealing

The generation crurent at the LOCOS isolation edge can be measured by the separation of the peripheral current generation and the surface and bulk current generation under the gate electrode. This method is accomplished by a C+ measurement of MOS capacitors with varying a gate area, and the effects of the generation curent reduction at the LOCOS isolation edge by low temperature hydrogen annealing (LTI{A) can be successfully investigated. As a result, it becomes clear that the generation curent is strongly reduced by annealing at a temperature below 400C, but at 450C the reduction is rather small.