Constant resistance deep level transient spectroscopy (CR-DLTS) system and method, averging methods for DLTS, and apparatus for carrying out the methods

摘要

A system, methods and apparatus for determining the properties of electrically active imperfections in semiconductor materials by Deep Level Transient Spectroscopy (DLTS) are disclosed. Source-drain resistance of a field-effect transistor (FET) is compared with a reference resistor and the difference is applied through a feedback circuit to the gate. The obtained voltage transient compensates for the threshold voltage changes resulting from the emission of charges trapped by the imperfections during pulses applied to the gate and alternating with the action of the feedback circuit. Knowledge of the free charge carrier mobility is not necessary, and the intensity of the DLTS signal and the sensitivity of the measurement are area independent. Thereof, the method is advantageous for measurement of deep submicron FETs. In the disclosed system, the DLTS signal is digitized and numerically processed by a combination of two averaging and data reduction methods that offers advantageous signal to noise ratio and convenience for use comparable to these usually found in analog DLTS systems, whereas the transient analysis can be executed by advantageous numerical analytical techniques. By utilizing the disclosed combination of numerical processing methods, a DLTS signal substantially free from noise can be displayed and the expected exponential behavior of the transient decay can be verified immediately. This combination of numerical processing methods is not limited to the disclosed system and can be employed in many other DLTS methods or in other experiments requiring analyses of transient data.