Συντάχθηκε 10-05-2016 10:11
από Esthir Gelasaki
Email συντάκτη: egelasaki<στο>tuc.gr
Ενημερώθηκε:
10-05-2016 12:24
Ιδιότητα: υπάλληλος.
ΠΟΛΥΤΕΧΝΕΙΟ ΚΡΗΤΗΣ
Σχολή Ηλεκτρονικών Μηχανικών και Μηχανικών Υπολογιστών
Πρόγραμμα Μεταπτυχιακών Σπουδών
ΠΑΡΟΥΣΙΑΣΗ ΔΙΔΑΚΤΟΡΙΚΗΣ ΔΙΑΤΡΙΒΗΣ
ΝΙΚΟΛΑΟΥ ΜΑΥΡΕΔΑΚΗ
με θέμα
Statistical charge-based modeling of 1/f noise in standard and high-voltage MOS transistors
Εξεταστική Επιτροπή
Αναπληρωτής Καθηγητής Ματτίας Μπούχερ (επιβλέπων), Σχολή ΗΜΜΥ, Πολυτεχνείο Κρήτης
Καθηγητής Κωνσταντίνος Μπάλας (μέλος τριμελούς επιτροπής), Σχολή ΗΜΜΥ, Πολυτεχνείο Κρήτης
Καθηγητής Χαράλαμπος Δημητριάδης (μέλος τριμελούς επιτροπής), Τμήμα Φυσικής, ΑΠΘ
Καθηγητής Κωνσταντίνος Καλαϊτζάκης, Σχολή ΗΜΜΥ, Πολυτεχνείο Κρήτης
Καθηγητής Αλέξιος Μπίρμπας, Τμήμα ΗΜΤΥ, Πανεπιστήμιο Πατρών
Καθηγητής Christian Enz, School of Engineering, EPFL, Ελβετία
Καθηγητής Gérard Ghibaudo, INPG, Γαλλία
Abstract
Nowadays, analog and RFIC (Radio Frequency Integrated Circuit) applications are almost exclusively designed in CMOS technology because of many advantages such as the high level of integration, the low power consumption and low cost that it offers. Apart from conventional CMOS, high-voltage (HV)-MOS process is also widely used in specific applications such as automotive industry, scientific and medical applications and consumer electronics. The latter kind of power applications created the need of the usage of power devices such as HV-MOSFETs and nowadays in circuit design, high-voltage parts are integrated together with low-voltage modules. Nevertheless, the performance of both CMOS and HV-MOS design can be limited by low frequency noise (LFN) which becomes really significant in state-of-the-art technologies because it is inversely proportional to channel area. While LFN is dominant at lower frequencies below the corner frequency, it can prove to be a significant hurdle even in high-frequency (RF) applications such as mixers or due to its up-conversion in phase noise in VCOs for example. As far as HV-MOSFETs are concerned, circuits such as oscillators, analog baseband and bandgap reference can be limited by LFN.
LFN is distinguished into two kinds; random telegraph signal (RTS) noise and flicker or 1/f noise. RTS noise is created by trapping/detrapping mechanism at the silicon oxide interface. Each such trap can create an RTS in time domain or a Lorentzian-like spectrum in frequency domain. RTS noise prevails in smaller area transistors where the traps are only few. In larger devices, on the other hand, the number of traps is quite large and the superposition of Lorentzian spectra can lead to 1/f behavior and thus it creates 1/f noise. This connection of RTS with 1/f noise is fully described by carrier number fluctuation effect which constitutes one of the main 1/f noise generators in MOS devices. Two other phenomena create 1/f noise and these are mobility fluctuation and series resistance effects, giving rise to a complicated bias- and geometrical behavior.
Mean value and variability of LFN are both area- and bias-dependent. Variability increases as device dimensions shrink bearing similarity with the behavior of mean value noise. The same trend can be observed in the bias-dependence of 1/f noise variability. Carrier number fluctuation effect has been proved to increase normalized flicker noise WL* SID/ID2 at 1Hz , in moderate and strong inversion and the same is confirmed for its variability while mobility fluctuation effect is considered responsible for the increase of normalized 1/f noise in weak inversion and its variability also increases there. This bias-dependence of flicker noise variability is of great concern especially since the downscaling of advanced nanotechnologies has led to circuit operation in moderate or even in weak inversion.
Flicker noise in HV-MOSFETs is expected to be generated by the same causes as in conventional MOSFETs since the same operating principles rule both kinds of these MOS devices due to the existence of the oxide interface in the channel part. The main question was if any similar effect is observed in drift region. Our analysis showed that the extension of gate oxide in the surface of drift region, causes a similar carrier number fluctuation effect which can give rise to 1/f noise.
Because of the significant impact of LFN in advanced analog and RF circuit design, the usage of correct, physics-based, compact models both for mean value and statistical behavior of LFN has become essential for variation-aware IC design. Within the context of this Thesis, a charge-based compact model both for the mean-value and the variability of 1/f noise was developed, implemented, and validated for a 180nm CMOS process with measurements performed at our lab and appended in the charge-based EKV3 compact MOSFET model. The mean value model was also validated for a 90nm CMOS process provided by the industry. The analytical, charge-based approach for 1/f noise statistics is directly related to the physical effects that generate 1/f noise in MOS devices and this is something proposed for the first time. A similar charge-based 1/f noise compact model is proposed for the first time for HV-MOSFETs. This mean value model was validated with data from an 350nm HV-MOS process. Measurements were performed using a new 1/f noise measurement set-up specialized for HV-MOSFETs.
In summary, the compact models developed within this work enable, for the first time, noise variation-aware design of IC solutions in standard and HV-CMOS technologies.
Τόπος: Λ - Κτίριο Επιστημών/ΗΜΜΥ, ΑΙΘΟΥΣΑ ΣΥΝΕΔΡΙΑΣΕΩΝ
Έναρξη: 12/05/2016 10:00
Λήξη: 12/05/2016 11:00
