Influence of nitrogen microwave radicals on sequential plasma activated bonding

The role of nitrogen microwave (MW) radicals in sequential plasma activated bonding of silicon/silicon has been investigated through contact angle and electron energy loss spectroscopy (EELS) observations. The contact angle for the sequentially activated (using oxygen RIE time for 60 s followed by variable times of nitrogen MW) silicon surfaces was higher than that of the oxygen RIE activated surfaces below 300 s but it was lower than that of the surfaces treated with oxygen RIE for a prolonged activation of 1200 s. The amorphous layer of the sequentially activated interface became thicker compared to the oxygen RIE treated interface and became thinner after prolonged activation using Nitrogen radicals. The EELS measurements showed no nitrogen in the silicon and interfacial amorphous silicon oxide, but showed oxygen deficiency in the amorphous layer.