Chih-Hao Dai

Hot carrier effect on gate-induced drain leakage current in high-k/metal gate n-channel metal-oxide-semiconductor field-effect transistors

This paper investigates the channel hot carrier stress (CHCS) effects on gate-induced drain leakage (GIDL) current in high-k/metal-gate n-type metal-oxide-semiconductor field effect transistors. It was found that the behavior of GIDL current during CHCS is dependent upon the interfacial layer (IL) oxide thickness of high-k/metal-gate stacks. For a thinner IL, the GIDL current gradually decreases during CHCS, a result contrary to that found in a device with thicker IL. Based on the variation of GIDL current at different stress conditions, the trap-assisted band-to-band hole injection model is proposed to explain the different behavior of GIDL current for different IL thicknesses.

On the Origin of Hole Valence Band Injection on GIFBE in PD SOI n-MOSFETs

This letter systematically investigates the mechanism of gate-induced floating-body effect (GIFBE) in advanced partially depleted silicon-on-insulator metal-oxide-semiconductor field-effect transistors. Based on different operation conditions, we found that the hole current collected by the body terminal is strongly dependent on electrons in the inversion layer under a source/drain ground. This implies that GIFBE can be attributed to anode hole injection (AHI) rather than the widely accepted mechanism of electron valence band tunneling. Moreover, GIFBE was also analyzed as a function of temperature. The results provide further evidence that the accumulation of holes in the body results from the AHI-induced direct tunneling current from the gate.

On the Origin of Gate-Induced Floating-Body Effect in PD SOI p-MOSFETs

This letter systematically investigates the origin of gate-induced floating-body effect (GIFBE) in partially depleted silicon-on-insulator p-type MOSFETs. The experimental results indicate that GIFBE causes a reduction in the electrical oxide field, leading to an underestimate of negative-bias temperature instability degradation. This can be partially attributed to the electrons tunneling from the process-induced partial n+ polygate. However, based on different operation conditions, we found that the dominant origin of electrons was strongly dependent on holes in the inversion layer under source/drain grounding. This suggests that the mechanism of GIFBE at higher voltages is dominated by the proposed anode electron injection model, rather than the electron valence band tunneling widely accepted as the mechanism for n-MOSFETs.

Impact of Mechanical Strain on GIFBE in PD SOI p-MOSFETs as Indicated From NBTI Degradation

This letter investigates the impact of mechanical strain on gate-induced floating-body effect in partially depleted silicon-on-insulator p-channel metal-oxide-semiconductor field-effect transistors. The strained FB device has less NBTI degradation than unstrained devices. This behavior can be attributed to the fact that more electron accumulation induced by strain effect reduces the electric oxide field significantly during NBTI stress. Analysis of the body current under source/drain grounded and floating operation indicates an increase in the anode electron injection and electron tunneling from conduction band which occur at the partial poly-Si gate and Si substrate, respectively. This phenomenon can be attributed to the bandgap narrowing which has been induced by the strain effect.

NBTI Degradation in LTPS TFTs Under Mechanical Tensile Strain

This letter investigates the negative-bias temperature instability (NBTI) degradation of p-channel low-temperature polycrystalline-silicon thin-film transistors (LTPS TFTs) under mechanical tensile stress. Experimental results reveal that the interface state density Nit and grain boundary trap density Ntrap of tensile-strained LTPS TFTs are more pronounced than those of unstrained LTPS TFTs. Extracted density of states and conduction activation energy Ea both show increases due to the strained Si-Si bonds, which implies that strained Si-Si bonds are able to react with dissociated H during NBTI stress. Therefore, NBTI degradation is more significant after tensile strain than in an unstrained condition.

Charge trapping induced drain-induced-barrier-lowering in HfO2/TiN p-channel metal-oxide-semiconductor-field-effect-transistors under hot carrier stress

This letter studies the channel hot carrier stress (CHCS) behaviors on high dielectric constant insulator and metal gate HfO2/TiN p-channel metal-oxide-semiconductor field effect transistors. It can be found that the degradation is associated with electron trapping, resulting in Gm decrease and positive Vth shift. However, Vth under saturation region shows an insignificant degradation during stress. To compare that, the CHC-induced electron trapping induced DIBL is proposed to demonstrate the different behavior of Vth between linear and saturation region. The devices with different channel length are used to evidence the trapping-induced DIBL behavior.

Abnormal interface state generation under positive bias stress in TiN/HfO2 p-channel metal-oxide-semiconductor field effect transistors

This Letter studies positive bias stress-induced abnormal interface state on TiN/HfO2 p-channel metal-oxide-semiconductor field effect transistors. It can be found that the degradation is associated with electron trapping, resulting in Vth shift but without subthreshold slope degradation. However, charge pumping current (ICP) shows a significant degradation after stress. Accordingly, the impact ionization-induced Nit located HfO2/SiO2 is proposed to demonstrate the ICP degradation. The AC stress with several frequencies is used to evidence the occurrence of impact ionization. Further, the device with additional pre-existing Nit located SiO2/Si has insignificant degradation due to reduction in stress electric field.