K. Papathanasiou

Compact Model of Drain Current in Short-Channel Triple-Gate FinFETs

An analytical compact drain current model for undoped (or lightly doped) short-channel triple-gate fin-shaped field-effect transistors (finFETs) is presented, taking into account quantum-mechanical and short-channel effects such as threshold-voltage shifts, drain-induced barrier lowering, and subthreshold slope degradation. In the saturation region, the effects of series resistance, surface roughness scattering, channel length modulation, and saturation velocity were also considered. The proposed model has been validated by comparing the transfer and output characteristics with device simulations and with experimental results. The good accuracy and the symmetry of the model make it suitable for implementation in circuit simulation tools.

A Lambert-Function Charge-Based Methodology for Extracting Electrical Parameters of Nanoscale FinFETs

We developed a new Y-based methodology for extracting the electrical parameters in modern nanoscale double-gate and triple-gate FinFET devices. Using the drain-current equation in the linear region, which involves the Lambert W -function of the charge at the source, the nonlinear Y-function in these devices is reduced to the linear one of a traditional long-channel MOSFET. The derived new Y-function can be readily applied and evaluate all electrical parameters in a traditional fashion, since all related curves are now linear and easily extrapolated. The present methodology for extracting the electrical parameters was verified in both simulated and experimental nanoscale FinFETs, demonstrating its simplicity and good accuracy.

Compact Modeling of Nanoscale Trapezoidal FinFETs

An analytical compact model for the drain current of undoped or lightly doped nanoscale FinFETs with trapezoidal cross section is proposed. The compact model of rectangular FinFETs is extended to trapezoidal FinFETs using equivalent nonplanar device parameters and corner effects. The model has been validated by comparing the results with those of 3-D numerical device simulations. The very good accuracy of the drain current and transcapacitances makes the proposed model suitable for implementation in circuit simulation tools.

Compact Capacitance Model of Undoped or Lightly Doped Ultra-Scaled Triple-Gate FinFETs

A charge-based compact capacitance model has been developed describing the capacitance-voltage characteristics of undoped or lightly doped ultra-scaled triple-gate fin field-effect transistors. Based on a unified expression for the drain current and the inversion sheet charge density, i.e., the Ward-Dutton linear-charge-partition method and the drain current continuity principle, all trans-capacitances are analytically derived. The developed capacitance model is valid in all regions of operation, from the subthreshold region to the strong inversion region and from the linear region to the saturation region. The gate and source trans-capacitances have been validated by 3-D numerical simulations over a large range of device dimensions. The parameters of the capacitance model can be used to accurately predict the transfer and output characteristics of the transistors, making this compact model very useful for circuit designers.

The sperm deformity and the sperm multiple anomalies indexes in patients who underwent unilateral orchectomy and preventive radiotherapy

Two new indices, the sperm deformity and the sperm multiple anomalies index, were assessed in 16 male patients who underwent unilateral orchectomy owing to seminoma and in preventive radiotherapy of paraortic and of the iliac lymph glands homolateral to the testis excised. The aim was to assess the value of these two morphological sperm parameters in distinguishing the semen between the above mentioned group of men from the semen of men with other causes of infertility. It was found that: (1) the values of the sperm deformity index and those of the sperm multiple anomalies index were not significantly different between men who underwent unilateral orchectomy and preventive radiotherapy and the men with other causes of subfertility and (2) the values of the above indices were significantly higher in the semen specimens of men who underwent unilateral orchectomy and preventive radiotherapy and in the semen specimens of men with other causes of subfertility than in the semen specimens of fertile men. It is concluded that testicular response, as far as sperm morphology is concerned, is the same irrespective of the cause exerting a negative effect on spermatogenesis.

The effect of testicular seminoma in semen quality

Although male subfertility has been reported in a variety of malignancies, most notably testicular carcinoma, the literature that refers to semen quality in males with testicular seminoma is very limited. This study was designed to evaluate the effect of testicular seminoma in semen quality and especially in its three main parameters. Semen specimens from 12 men, aged 24-38 years, with testicular seminoma before they underwent orchidectomy and adjuvant radiotherapy to the ipsilateral para-aortic and pelvic lymph nodes, and from 60 fertile men, aged 24-44 years, were studied. The results support the view that testicular seminoma exerts a deleterious effect on spermatogenesis and consequently to the three main parameters of the semen. The mechanism though of the deleterious effect of seminoma on spermatogenesis remains unclear.

Anterior vaginal wall reconstruction: anterior colporrhaphy reinforced with tension free vaginal tape underneath bladder base

Objective. To assess the effectiveness of the polypropylene tape in preventing cystocele recurrence. Methods. Fifty Caucasian women aged 50‐77 years (mean age 66.6 years), with stage II–IV pelvic organ prolapse, enrolled into the study. Vaginal reconstructive surgery included an anterior colporrhaphy on all patients, posterior colpoperineorrhaphy on 28 patients and hysterectomy on 36 patients. Patients were divided into a study group of 28 women and a control group of 22 women. As reinforcement to the anterior colporrhaphy procedure, in the study group a polypropylene tape (TVT‐O) was placed underneath the bladder base and fixed with polyglactin sutures. Postoperative follow‐up was carried out every 4 months (total 48 months). The assessment of the anatomic result included both clinical evaluation of the operated sites and perineal sonography. Results. The mean postoperative distance of the bladder base to the inferior edge of the symphysis pubis was 1.5 cm (range: 1.0–2.2 cm) in the study group and 2.8 cm (range: 2.0–3.8) in the control group. Postoperatively, there were two cases of stress incontinence and two cases of urge incontinence, one in each group. No case of tape erosion was noted, no dyspareunia and no recurrent cystocele in the study group. Four cases of recurrent cystocele (20%) were reported in the control group. Conclusion. While the preliminary results of our study are encouraging, larger series of patients and longer follow‐up are required to verify the effectiveness of the aforementioned modification.

Analytical low-frequency noise model in the linear region of lightly doped nanoscale double-gate metal-oxide-semiconductor field-effect transistors

An analytical model for the transconductance to drain current ratio (gm/Id) of lightly doped nanoscale double-gate metal-oxide-semiconductor field-effect transistors (DG MOSFETs) has been developed in the weak inversion and from linear to saturation region, using the conductive path potential approach. The obtained analytical model for gm/Id in the weak inversion has been extended in the strong inversion and in the linear region including the short-channel effects, as well as the surface roughness scattering, series resistance, and saturation velocity effects. The obtained gm/Id model from weak to strong inversion has been verified by comparing simulation and experimental results of DG MOSFET with gate length 50 nm and it has been implemented in modeling the 1/f low-frequency noise. The introduced noise model has been validated by developing a Verilog-A transistor noise model, which is in good agreement with the experimental noise results of DG MOSFET with gate length 50 nm in the linear region from weak ...

Analysis and Design of Charge Pumps for Telecommunication Applications

This chapter addresses modern telecommunication integrated circuits from the synthesizer focal point; in particular it concentrates at the analysis and the design of integrated charge pump circuit blocks. It presents an overview of charge pump topologies in addition to a coherent analysis of the associated benefits and shortcomings of all circuit alternatives. Moreover a novel favorable charge pump combining current steering techniques with well utilized unity gain buffers in a novel, noiseless feedback scheme, is introduced to improve on switching speed, inherent charge pump ac noise, dead-zone interval, therefore overall steady state aliased loop noise; while on the other hand this charge pump exhibits superb DC matching characteristics in a wide output voltage range. Furthermore a well documented estimation of the active devices that contributes mostly to the overall charge pump noise performance is presented. Also an associated mathematical analysis concerning the frequency content of the charge pump noise current is given. This proposed topology manifests its applicability to charge pump alternatives, as it is demonstrated by the associated simulation results from a 0.18μm design. Because of the low-noise and accurate properties of this improved charge pump, it is ideally suited to modern telecommunication standards synthesizer realizations.

Compact modeling of nano-scale trapezoidal cross-sectional FinFETs

Analytical compact model for the drain current and trans-capacitances of undoped or lightly doped nanoscale FinFETs with trapezoidal cross section is presented. The compact model of rectangular FinFETs is applied in trapezoidal FinFETs using the concept of the equivalent device parameters. The model is compared with the results of three-dimensional numerical device simulations. The overall results reveal the very good accuracy of the proposed compact model, making it suitable for circuit design simulation tools.