Non-Contact Implant Dose and Energy Metrology for Advanced CMOS Low Energy Implants

摘要

Ultra Shallow Junctions are required to successfully improve device performance with scaling to have a better threshold voltage control, improve transistor performance, reduce CHC (Channel Hot Carrier) degradation and reduce parasitic capacitance. All these play an increasingly critical role as we move on to the 45 nm node and beyond to provide the required ac and dc device performance for CMOS devices. In the low energy implant regime, four point probe based sheet resistivity measurement becomes highly unreliable as does silicon damage based metrology systems used currently for advanced process control and monitoring. A non-contact metrology method is investigated based on leakage and tunneling currents in a non-conductive film that contains the implanted dose. These shallow implants damage the non-conductive film causing leakage paths to the silicon substrate. The implant damage is proportional to the dose and energy of the implanted species. Furthermore implanting the non-conductive film causes the top layers of the film to become conductive thus changing the electrical oxide thickness of this film. Excellent correlation was found among the implanted dose, energy to the equivalent oxide thickness. Results from controlled experiments indicate that this method has potential for use in low energy implanter qualification and ultra large scale integration process control and monitoring.