ULTRASENSITIVE GAS PHASE DETECTION OF AIRBORNE MOLECULAR CONTAMINATION IN METROLOGY APPLICATIONS

Contamination of airborne molecular contamination (AMC) is responsible for numerous defects in integrated circuit manufacturing ^[1],[3]. The ability to sense these contaminations "in-situ" within the fabrication line vacuum chambers will allow yield increase and cost reduction. Effective detection of those AMC with selective properties are vital to insure that contaminators are not damaging the processes and machinery within the very large scale integration (VLSI) production line ^[3]. In our research the detection was done by exploiting the electric characteristics of Si nanowire field-effect transistors sensors (Si NWFET). The use of SiNW FET are showing promising capabilities in the recognition of the contaminating species, even at low concentrations as low as 400ppt (parts-per-trillion) in their gaseous phase. SiNW FETs provide advantages when compared to other sensing methods such as: low power consumption, gate voltage controllability, simple multiple device signals analysis, and their small dimensions ^[2]. We will present a novel use of SiNW FETs to detect AMCs, with detection times of a few seconds. By heating permeation tubes in an oven, with a constant flow of N₂ carrying gas, we were able to control the concentration of the AMCs. In order to detect the AMCs we have modified the SiNWs surface with different silane-derivative molecular layers, and tested the change of electrical current through the NWs devices in response to their interaction with the AMCs molecular species. The AMC molecules, physisorbed to the modified SiNWs surface, induced a change in the surface potential of the NW-based sensing devices, which resulted in change of current through the NWs. In this work we have successfully tested the presence of Acetone and NMP molecules, while using different modifications.