Implant dose monitoring by MOS C–V measurement

The most critical parameter for deep sub-micron MOS field effect transistors is the threshold voltage, which is highly dependent on processing specifically, the ion implanted channel dose. Monitoring the channel doping on product wafers is highly desirable and is a major issue for process engineers. MOS C–V methods are widely used for process ramp up and monitoring and MOS C–V doping profiling is an introduced method for monitoring of low dose implants. However, the failure of the depletion approximation in the near surface region implies that conventional MOS C–V measurements yield erroneous doping profiles in that region. Integrating MOS C–V doping profiles yields only a partial implant dose excluding the important near surface dose portion. Here, we report a new approach, which enables the determination of the entire implant dose, taking into account the crucial surface region. Moreover, the MOS threshold voltage can be obtained self-consistently. The method is also applicable to MOS structures with ultra thin gate oxides.