Plasma-activated direct bonding of diamond-on-insulator wafers to thermal oxide grown silicon wafers

Diamond-on-insulator (DOI) wafers featuring ultrananocrystalline diamond are studied via atomic force microscopy, profilometer and wafer bow measurements. Plasma-activated direct bonding of DOI wafers to thermal oxide grown silicon wafers is investigated under vacuum. DOI wafer with chemical mechanical polishing (CMP) on the diamond surface makes a poor bonding to silicon wafers with thermal oxide. Our results show that plasma enhanced chemical vapor deposition of silicon dioxide on top of the DOI wafer, CMP of the oxide layer and annealing are essential to achieve very high quality direct bonding to thermal oxide grown on silicon wafers. Plasma activation results in the formation of high quality bonds without exceeding 550 °C in the direct wafer bonding process.

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► Plasma activated direct bonding is used with a maximum temperature of 550 °C.
► Diamond-on-insulator wafers featuring UNCD with minimum residual stress are used.
► UNCD makes a poor direct bonding to oxidized silicon wafer.
► Using a thin PECVD-grown SiO2 interlayer on UNCD makes a good bonding.
► Annealed SiO2 interlayer improves the direct bonding quality.