Search

This paper examines the edge direct tunneling (EDT) of holes from p/sup +/ polysilicon to underlying p-type drain extensions in off-state p-channel MOSFETs having ultrathin gate oxides that are 1.2 nm-2.2 nm thick. It is for the first time found that for thinner oxides, hole EDT is more pronounced than both conventional gate-induced drain leakage (GIDL) and gate-to-channel tunneling. As a result, the induced gate and drain leakage is more accurately measured per unit gate width. Terminal currents versus input voltage are measured from a CMOS inverter with gate oxide thickness T/sub OX/=1.23 nm, exhibiting the impact of EDT in two standby modes. For the first time, a physical model is derived for the oxide field E/sub OX/ at the gate edge by accounting for the heavy and light holes' subbands in the quantized accumulation polysilicon surface. This model relates E/sub OX/ to the gate-to-drain voltage, oxide thickness, and doping concentration of the drain extension. Once E/sub OX/ is known, an existing direct tunneling (DT) model consistently reproduces EDT current-voltage (I-V), and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to hole EDT is projected.

This paper examines the edge direct tunneling (EDT) of electron from n/sup +/ polysilicon to underlying n-type drain extension in off-state n-channel MOSFETs having ultrathin gate oxide thicknesses (1.4-2.4 nm). It is found that for thinner oxide thicknesses, electron EDT is more pronounced over the conventional gate-induced-drain-leakage (GIDL), bulk band-to-band tunneling (BTBT) and gate-to-substrate tunneling, and as a result, the induced gate and drain leakage is better measured per unit gate width. A physical model is for the first time derived for the oxide field E/sub OX/ at the gate edge by accounting for electron subband in the quantized accumulation polysilicon surface. This model relates E/sub OX/ to the gate-to-drain voltage, oxide thickness, and doping concentration of drain extension. Once fox is known, an existing DT model readily reproduces EDT I-V consistently and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to EDT is projected as well.

A model of the hole direct tunneling gate current accounting for heavy and light hole's subbands in the quantized inversion layer is built explicitly. This model comprises four key physical parameters: inversion layer charge density, hole impact frequency on SiO/sub 2/-Si interface, WKB transmission probability, and reflection correction factor. With the effective hole mass m/sub oxh/=0.51 M/sub o/ for the parabolic dispersion relationship in the oxide, experimental reproduction without any parameter adjustment is consistently achieved in p/sup +/ poly-gate pMOSFETs with 1.23, 1.85, and 2.16 nm gate oxide thicknesses. The proposed model can thereby serve as a promising characterization means of direct tunnel oxides. In particular, it is calculated that the secondary subbands and beyond, although occupying few holes, indeed contribute substantially to the direct tunneling conduction due to effective lower barrier heights, and are prevailing over the first subbands for reducing the oxide field down below 1 MV/cm.

To achieve ultra small form factor package solution, an ultra-thin (50µm) Si interposer utilizing through-silicon-via (TSV) technology has been developed. Challenges associated with handling thin wafer and maintaining package co-planarity have been overcome to stack thin dies (200 µm) on ultra-thin interposer. Improved electrical performance and the advantages of this innovative thin interposer are highlighted in this paper. Warpage behavior is investigated with simulation and experiments to ensure reliability and robustness of the Si stack. Reduction in package thickness is realized to achieve high functionality, small form factor, better electrical performance and robust reliability by stacking thin dies on ultra-thin interposer.

An orthotropic stress field was observed in the vicinity of the Cu-filled TSV on nominal (100) silicon substrate from both μRaman measured data and validated FEM result. The orthotropic elastic behavior of silicon in the (100) plane is believed to be the reason. The FEM model was further validated by the comparison with the measured electrical data, and used to predict the device performance shift under the influence of the TSV-induced stress. The performance shift pattern also showed an orthotropic pattern. This finding has profound implication on 3D silicon stacking design rule and system integration.

Technology challenges and solutions in the development and fabrication of high-density three dimensional (3D) chip integration structures have been investigated. Critical 3D integrated circuit (IC) enabling technologies, such as through silicon via (TSV), wiring and redistribution layer (RDL), wafer thinning and handling, micro-bump (µ-bump) processes and joining, that form the building blocks for 3D IC technology were developed based on established Si foundry technologies. Test vehicles (TV's) have been designed to develop and optimize the processes, structures, as well as to evaluate the performance, yield and reliability of the 3D integration scheme.

High density through-silicon-via (TSV) and cost-effective 3D die-to-wafer integration scheme are proposed as best-in-class foundry solutions for high-end CMOS chips at 28 nm node and beyond. Key processes include: TSV formation, extreme thinning of the TSV wafer and die-to-wafer assembly. The impact of extreme thinning on device threshold voltage, leakage currents, and I on -I off characteristics of bulk CMOS devices with and without e-SiGe/CESL stressors has been minimized. The presence of TSV caused no significant changes in Cu/ELK reliability. These excellent characteristics suggest the 300mm 3D-IC processes are promising and suitable for adoption in next generation integrated circuits and interconnects.

A three dimensional integrated circuit (3DIC) integration flow, process and electrical results are reported. Well-controlled high aspect ratio (AR=8:1 and AR=15:1) through silicon vias (TSVs) were successfully filled with both copper (Cu) and tungsten (W). Metal to metal diffusion bonding was demonstrated with good uniformity and resulted in good electrical performance. For the first time, a cost effective wafer thinning without decreasing effective area by a proprietary process is described. By wafer level electrical testing, yielding 20K through silicon vias with aspect ratio of 15:1 and resistance of through silicon via chain are demonstrated.

The drain leakage current in MOSFET's in the present standard process is separated into three distinct components: the subthreshold conduction, the surface band-to-band tunneling (BTBT), and the bulk BTBT. Each of the three shows different dependencies on back-gate bias. As a result, the bulk BTBT, increasing exponentially with increasing the magnitude of back-gate reverse bias, promptly dominates the drain leakage. Additional experiment highlights the effect of the increased bulk dopant concentrations as in next-generation scaled MOSFET's on the bulk BTBT. This sets the bulk BTBT a significant constraint to the low-voltage, low-power, high-density CMOS integrated circuits employing the back-gate reverse bias. In this work, the measured drain leakage of interest is successfully reproduced by two-dimensional (2-D) device simulation.

We demonstrate for the first time high performance 35 nm CMOS FinFETs. Symmetrical NFET and PFET off-state leakage is realized with a simple technology. For 1 volt operation at a conservative 24 /spl Aring/ gate oxide thickness, the transistors give drive currents of 1240 /spl mu/A//spl mu/m for NFET and 500 /spl mu/A//spl mu/m for PFET at an off current of 200 nA//spl mu/m. Excellent hot carrier immunity is achieved. Device performance parameters exceed ITRS projections.

Proposes a new structure of partially-depleted SOI MOSFETs tunneling-biased MOSFETs (TBMOS). In this structure, the floating body potential is pulled up by the carriers which tunnel from specially doped polysilicon gate to the floating body. Compared with bulk MOSFET (represented by body grounded device), TBMOS produces excellent swing (/spl sim/66 mV/dec), and >15% increase in I/sub D,SAT/. TBMOS also has better hot carrier immunity than body grounded device.

This paper examines the edge direct tunneling (EDT) of hole from p+ polysilicon to underlying p-type drain extension in off-state p-channel MOSFETs having ultrathin gate oxide thicknesses (1.2-2.2 nm). It is found that for thinner oxide thicknesses, hole EDT is more pronounced over the conventional GIDL and gate-to-channel tunneling, and as a result, the induced gate and drain leakage is better measured per unit gate width. A physical model accounting for heavy and light hole's subbands in the quantized accumulation polysilicon surface is built explicitly. This model consistently reproduces EDT I-V and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to EDT is projected as well.