LPT and SLPT Measurement Methods of Flat-Band Voltage (VFB) in MOS Devices

Abstract

The photoelectric techniques are often used for the measurements of metal oxide semiconductor (MOS) structure parameters. These methods, which consist in illuminating the MOS structure with a semitransparent metal gate by a UV light beam, are often competitive for typical electric measurements. The results obtained by different photoelectric methods are, in many cases, more accurate and reproducible than the results of other measurements. The flat-band voltage VFB is an important parameter of any MOS structure since its value influences the threshold voltage VT , which decides for example about power consumption of MOS transistors. One of the methods to measure the VFB value is the electric method of C(V) characteristic. This method involves certain calculations and requires the knowledge about parameters of the investigated sample. The accuracy of this method is rarely better than ±100 mV (for higher doping of the substrates the accuracy is worse). The other method of VFB value determination, outlined in this article, is the photoelectric light pulse technique (LPT) method. This method based on the idea proposed by Yun is currently being optimized and verified experimentally.

Keywords

• flat-band voltage
• light pulse technique
• MOS system
• photoelectric methods
• scanned light pulse technique