Experimental Investigation of Ultrathin Al₂O₃ Ex-Situ Interfacial Doping Strategy on Laminated HKMG Stacks via ALD

In this work, a p-type high-
${k}$
metal gate (HKMG) with 3-nm interfacial Al
₂
O
₃
doping HfO
₂
laminated dielectric is presented to achieve the required gate electrode effective work function (EWF). Through the ex-situ interfacial doping strategy with various Al
₂
O
₃
thickness, the electrical and interface characteristics of p-type HKMG MOSCAP are investigated. The results show that these parameters are strongly dependent on the thickness of the Al
₂
O
₃
. By increasing the Al
₂
O
₃
thickness, the flat-band voltage (
${V}_{\text {FB}}$
) positive shift is elevated by 360 mV, and the trap/detrap electrons density (
${N}_{\text {ot}}$
) is significantly suppressed by an order of magnitude. In addition, the interface charge density (
${N}_{\text {SS}}$
) is significantly reduced, and interface trap density (
${D}_{\text {it}}$
), time-dependent dielectric breakdown (TDDB), and positive bias stress (PBS) is obviously improved. Finally, EWF modulation was increased from 4.976 to 5.206 eV (over the valence band edge of 5.17 eV). The results reveal that it is possible to tailor dielectric and electrical properties of high-
${k}$
layers by adding a proper amount of interfacial Al
₂
O
₃
doping into HfO
₂
, meeting the criteria required for gate electrode p-type EWF. These results and discussion provide an effective method for the integration of the HKMG stack in the MOSFETs and also useful for design of CMOS integration.