New measurement structure for TAV testing of semiconductor: an experimental analysis

A measurement structure has been introduced in transverse acoustoelectric voltage (TAV) nondestructive testing of semiconductors, which makes it possible to reduce the effect of the parasitic rear resistance on acoustoelectric measurements. The structure uses a tungsten point contact on the back surface of the semiconductor to improve TAV detection. Decrease of TAV rise time and differentiation of rise and fall time were observed as a consequence of the reduced contact resistance. The effect of compression on the electronic state of the sample under test was studied. A pressure threshold was observed above which TAV decreases and a relevant number of stress-induced traps appears at the Si/SiO₂ interface. It is concluded that care must be taken to keep the applied pressure below the threshold to perform true nondestructive measurements