Lateral-Transistor Test Structures for Evaluating the Effectiveness of Surface Doping Techniques

This paper presents a lateral-transistor test structure for evaluating the effectiveness of surface doping techniques used to fabricate ultrashallow diodes and ohmic contacts. The test structure requires very limited processing, and simple $I$ – $V$ measurements provide a separation of the hole and electron currents across the junction under investigation. The theoretical behavior is verified by Sentaurus simulations. The ability to discern between Schottky-like and pn-junction diodes is demonstrated by the measurement of a series of junctions fabricated by arsenic dopant deposition plus laser annealing. The activation and drive-in of the deposited arsenic is tuned by the laser energy. The anomalous behavior theoretically predicted for very thin, lightly-doped junctions is observed experimentally. Considerations for an optimal design of the test structures are given.