Comparative Investigation of Flat-Band Voltage Modulation by Nitrogen Plasma Treatment for Advanced HKMG Technology

Abstract

This paper presents a comparative investigation of flatband voltage (V FB ) adjustment scheme with the nitrogen plasma treatment (NPT) in the high-k/metal-gate (HKMG) Metal-Oxide-Semiconductor Capacitor (MOSCAP) for scaling of the further CMOS fabrication technology. The NPT process on the first ALD-TiN capping layer demonstrates significant V FB modulation capability and causes a controllable effective gate work function in metal-gate: 1) shifting to band center with the increasing of RF powers both for P-/N-MOSCAPs; 2) shifting to opposite directions (P-to band edge, N-to band center) with reduced nitrogen flow ratio for P-/N-MOSCAPs; 3) shifting from −220mV to +60mV and from +130mV to +420mV for P-/N-MOSCAPs, respectively. One unique theoretical model including N-vacancy/Al-trap effect is successfully proposed to illustrate the complicated shift behaviors both for HKMG P-/N-MOSCAPs. The demonstrated process results and the physical model indicate that the advanced NPT technology is a simple, effective and CMOS-compatible method for both P-/N-logic devices scaling beyond 7nm technology node.

Mechanisms of TiN Effective Workfunction Tuning at Interfaces with HfO2 and SiO2

“…8−11 Another option is provided by exposure of TiN to nitrogen plasma, which points toward significant impact of the metal stoichiometry. 12,13 However, there is an additional factor affecting stoichiometry of TiN at interfaces with oxide insulators: the oxygen "scavenging" from the underlying oxide leads to oxidation of the PVD-grown TiN films on SiO 2 and Al 2 O 3 . 14,15 In this work we explore the mechanisms, which make possible the change of EWF of metallic TiN electrodes at interfaces with SiO 2 and HfO 2 insulators by varying TiN deposition technique or by introducing additional interlayers.…”

“…While the EWF of atomic layer deposition (ALD)-grown stoichiometric TiN ranges from 4.7 to 4.9 eV, relevant for low V th in p-channel MIS transistor, doping of TiN with low WF metal, e.g., Al, results in lower EWF values in the range 4.1–4.4 eV. − Another option is provided by exposure of TiN to nitrogen plasma, which points toward significant impact of the metal stoichiometry. , However, there is an additional factor affecting stoichiometry of TiN at interfaces with oxide insulators: the oxygen “scavenging” from the underlying oxide leads to oxidation of the PVD-grown TiN films on SiO 2 and Al 2 O 3 . , …”

Novel Band-Edge Work Function Performance Modulation via NPT with PMOS1st/NMOS1st Laminated Stack for PMOS Low Power Target

“…5 Moreover, with the physical gate length shrinking less than 18 nm for 5 nm technology node and beyond, the serious issues of the sufficient space for complex gate stacks are eager to be addressed out. Therefore, novel techniques are proposed to enable a simplified process flow and effective modulation capability, including high-k metal gate doping, [6][7][8][9] and dipole formation. 10 The general strategy to realize multi-V T is focusing on gate laminated stacks, which is generally utilized as dual-work function metal stacks.…”

“…Our previous work demonstrates the effective work function modulation for CMOS with in-house nitrogen plasma treatment (NPT) process. 8,9 However, high band-edge work function via NPT need further improvement and investigation with the advanced PMOS 1st and NMOS 1st laminated stacks. Besides, to our knowledge, very rare studies can focus on the combination of novel technique and PMOS 1st /NMOS 1st integration scheme.…”

Multi-Vt Performance Dependence on Capping Layer Position by NPT for PMOS Device Applications

“…1,2 Although the gate stack design and channel doping strategy have attracted many efforts and attentions, 3 the strong quantum confinement effect and random dopant fluctuation can ruin the actual Vt and performance target in the nanoscale channel. 4,5 Therefore, novel modulation techniques based on HKMG technology are proposed and investigated, including NPT for gate stack, 6 high-k dipole formation, 7 and novel workfunction material. 8 All the novel methods typically prefer the capping layer in the metal gate stack, with the purpose of significantly reducing void formation in high-k layer 9 and metal atom inter-diffusion.…”