Tailoring of dopant profiles in advanced nMOS transistors


Tailoring of dopant profiles in advanced nMOS transistors

Lebedev, A.; Posselt, M.; Feudel, T.; Variam, N.

The properties of advanced CMOS transistors are strongly influenced by the dopant distribution in the transition region between the source (drain) and the channel. The tailoring of this distribution is achieved by appropriate halo and extension implants and subsequent annealing. Process and device simulations are performed to investigate the influence of the corresponding process parameters. The boundary condition used throughout the simulations is to keep the threshold voltage VTsat for the nominal nMOS transistor (sub-70 nm gate length) at 0.2 V. The following process conditions are studied:

(i) B+ halo implant: energy below 10 keV, tilt 45 degree, rotation 4x90 degree, dose varied to achieve VTsat = 0.2 V
(ii) As+ extension implant: 0.5, 1.0, 2.0 keV, tilt 0 degree, 1015 cm-2, and 2 keV, 1015 cm-2, tilt 20 degree, rotation 4x90 degree
(iii)RTA after both implants with special emphasis on soak and spike anneals (950...1100 degree C)
The model parameters employed in the simulation of the formation of the ultra-shallow extension profiles are calibrated using SIMS profiles of as-implanted and annealed samples, and sheet resistance data. The VTsat vs. LGate curve of the nMOS transistor is calculated. The dependence of the roll-off and roll-on behaviour on the process conditions considered is discussed.

Keywords: ion implantation; annealing; process and device simulation; TCAD; Si technology

  • Lecture (Conference)
    EMRS 2001 Spring Meeting, June 5-8, 2001, Strasbourg, France, Symposium B: Defect Engineering of Advanced Semiconductor Devices

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Publ.-Id: 4031