Latent Noise in Schottky Barrier MOSFET UPoN 2008 Latent Noise in Schottky Barrier MOSFET Sheng-Pin Yeh, Chun-Hsing Shih*, Jeng Gong, and Chenhsin Lien Institute of Electronics Engineering, National Tsing Hua University, Taiwan *Department of Electrical Engineering, Yuan Ze University, Taiwan *Email: chshih@saturn.yzu.edu.tw Latent Noise in Schottky Barrier MOSFET UPoN 2008

Latent Noise in Schottky Barrier MOSFET Necessity of Metallic Source/Drain I-V Curves of SBMOS Noise in SBMOS and MOSFET Latent Noise Mechanisms in SBMOS Summary Latent Noise in Schottky Barrier MOSFET UPoN 2008

Necessity of Metallic Source/Drain Xj Rsd Gate S/D Gate Length SDE Resistance SDE Depth Source: ITRS Unacceptable SDE resistance will limit the use of impurity doped S/D Latent Noise in Schottky Barrier MOSFET UPoN 2008

Recent Research of SBMOS Eliminating the limits on the dopant source/drain junctions makes metallic S/D SBMOS as one of the most attracting candidates for use in future CMOS devices. Latent Noise in Schottky Barrier MOSFET UPoN 2008

Latent Noise in Schottky Barrier MOSFET Necessity of Metallic Source/Drain I-V Curves of SBMOS Noise in SBMOS and MOSFET Latent Noise Mechanisms in SBMOS Summary Latent Noise in Schottky Barrier MOSFET UPoN 2008

SBMOS vs. MOSFET (Drain Current) Lg = 90 nm, Tox = 2.5 nm, SBH = 0.4 eV SBMOS suffers from potential constraints on the drain currents because of its unique Schottky barrier source/drain junctions. Latent Noise in Schottky Barrier MOSFET UPoN 2008

SBMOS vs. MOSFET (Energy Band Diagrams) Thermal Emission Vg= 0V Vg= 0V e- e- φBn SB Tunneling Vg= 1V Vg= 1V Vd= 1V Vd= 1V In SBMOS, carriers can thermonicly emit over or laterally tunnel through Schottky barrier to contribute drain current. Unique Impact Ionization is observed in SBMOS. Latent Noise in Schottky Barrier MOSFET UPoN 2008

Ambipolar Conduction SBMOS presents the ambipolar conduction as a function of gate voltage. At a negative bias, holes can also pass through the drain Schottky barrier, forming a hole channel, yielding an undesirable drain current. And, SBH must be minimized. Latent Noise in Schottky Barrier MOSFET UPoN 2008

Dopant Segregated Schottky Barrier MOSFET (DS-SBMOS) Inserting a heavily doped segregation layer effectively modifies the Schottky barriers to increase the driving current and suppress the ambipolar behavior. Latent Noise in Schottky Barrier MOSFET UPoN 2008

Interface States Generated during Metal Silicidation Formation of the metallic source/drain using silicidation brings about interface states and noise sources. Importantly, trap and detrap depend on Vg and SBH. Drain Hole Latent Noise in Schottky Barrier MOSFET UPoN 2008

Latent Noise in Schottky Barrier MOSFET Necessity of Metallic Source/Drain I-V Curves of SBMOS Noise in SBMOS and MOSFET Latent Noise Mechanisms in SBMOS Summary Latent Noise in Schottky Barrier MOSFET UPoN 2008

Noise in Conventional MOSFETs For MOSFETs Drain current fluctuates due to variations of Number of inversion charge density ∆Qi <traps in gate oxide> (and number of inversion carriers in channel ∆N=WL∆ Qi) Effective channel mobility ∆μeff <phonon scattering> Latent Noise in Schottky Barrier MOSFET UPoN 2008

Unique Noise in Schottky Barrier MOSFET NMOS, p-Si T. Asano, Jpn. J. Appl. Phys., 2002, p. 2306. Observations: 1. More Noisy in SBMOS than MOSFET 2. Unique noise observed in different metals silicidation SBMOS (SBH: PtSi = 0.85 eV, NiSi = 0.65 eV for electron) Latent Noise in Schottky Barrier MOSFET UPoN 2008

Unique Noise in Schottky Barrier MOSFET (Cont.) PMOS M. V. Haartman, ICNF 2005, p. 307. Observations: 1. More Noisy in SBMOS (PMOS), SBH: NiSi = 0.45 eV for hole 2. Strong dependence of noise on gate bias Latent Noise in Schottky Barrier MOSFET UPoN 2008

Latent Noise in Schottky Barrier MOSFET Necessity of Metallic Source/Drain I-V Curves of SBMOS Noise in SBMOS and MOSFET Latent Noise Mechanisms in SBMOS Summary Latent Noise in Schottky Barrier MOSFET UPoN 2008

Noise Mechanisms in SBMOS: at Silicon Surface φBn Vg= 0V Vg= 1V Vd= 1V e- Mechanisms: 1. Number Fluctuation <traps in gate oxide> 2. Mobility Fluctuation <phonon scattering> 3. But with unique impact ionization in Source Latent Noise in Schottky Barrier MOSFET UPoN 2008

Noise Mechanisms in SBMOS: at Source φBn Interface States EC EF EV EFi Schottky Source Si Vg Mechanisms: 1. Trap levels in Schottky barrier contact (SBH and Gate bias dependent) 2. Trap levels in substrate metallic Source contact (SBH and substrate bias dependent) 3. Different in DS-SBMOS and SBMOS Latent Noise in Schottky Barrier MOSFET UPoN 2008

Noise Mechanisms in SBMOS: at Drain 1. Trap levels in channel and substrate metallic (Schottky barrier) contact (SBH and bias dependent) 2. Noise generations in Drain is different to those in Source due to ambipolar conduction. Latent Noise in Schottky Barrier MOSFET UPoN 2008

Noise Problems in SBMOS Latent Noise in Schottky Barrier MOSFET UPoN 2008

Summary Eliminating the limits on the dopant junctions makes SBMOS as one of the most attracting candidates for future CMOS devices, while SBMOS suffers from potential problems on its unique Schottky barrier junctions. Schottky barrier MOSFETs present particular ambipolar conduction as a function of gate voltage. Formation of the metallic source/drain using metals silicidation brings about interface states and noise sources. Unique noises in SBMOS were observed. Proposed noise mechanisms in SBMOS are presented. Proper noise behavior and mechanisms in SBMOS require further thorough investigations. Latent Noise in Schottky Barrier MOSFET UPoN 2008