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1/f noise in Si and Si0.7Ge0.3 pMOSFETs
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0001-6705-1660
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0001-6459-749X
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2003 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 50, 2513-2519 p.Article in journal (Refereed) Published
Abstract [en]

Strained layer Si0.7Ge0.3 pMOSFETs were fabricated and shown to exhibit enhanced hole mobility, up to 35% higher for a SiGe device with 3-nm-thick Si-cap, and lower 1/f noise compared to Si surface channel pMOSFETs. The 1/f noise in the investigated devices was dominated by mobility fluctuation noise and found to be lower in the SiGe devices. The source of the mobility fluctuations was determined by investigating the electric field dependence of the 1/f noise. It was found that the SiO2/Si interface roughness scattering plays an important role for the mobility fluctuation noise, although not dominating the effective mobility. The physical separation of the carriers from the SiO2/Si interface in the buried SiGe channel pMOSFETs resulted in lower SiO2/Si interface roughness scattering, which explains the reduction of 1/f noise in these devices. The 1/f noise mechanism was experimentally verified by studying 1/f noise in SiGe devices with various thicknesses of the Si-cap. A too large Si-cap thickness led to a deteriorated carrier confinement in the SiGe channel resulting in that considerable 1/f noise was generated in the parasitic current in the Si-cap. In our experiments, the SiGe devices with a Si-cap thickness in the middle of the interval 3-7 nm exhibited the lowest 1/f noise.

Place, publisher, year, edition, pages
2003. Vol. 50, 2513-2519 p.
Keyword [en]
1/f noise in MOSFETs, low-frequency (LF) noise, mobility fluctuations, SiGe MOSFETs, surface roughness scattering
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5495DOI: 10.1109/TED.2003.819258ISI: 000188004300025OAI: oai:DiVA.org:kth-5495DiVA: diva2:9880
Note
QC 20100928Available from: 2006-03-21 Created: 2006-03-21 Last updated: 2017-11-21Bibliographically approved
In thesis
1. Low-frequency noise characterization, evaluation and modeling of advanced Si- and SiGe-based CMOS transistors
Open this publication in new window or tab >>Low-frequency noise characterization, evaluation and modeling of advanced Si- and SiGe-based CMOS transistors
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A wide variety of novel complementary-metal-oxide-semiconductor (CMOS) devices that are strong contenders for future high-speed and low-noise RF circuits have been evaluated by means of static electrical measurements and low-frequency noise characterizations in this thesis. These novel field-effect transistors (FETs) include (i) compressively strained SiGe channel pMOSFETs, (ii) tensile strained Si nMOSFETs, (iii) MOSFETs with high-k gate dielectrics, (iv) metal gate and (v) silicon-on-insulator (SOI) devices. The low-frequency noise was comprehensively characterized for different types of operating conditions where the gate and bulk terminal voltages were varied. Detailed studies were made of the relationship between the 1/f noise and the device architecture, strain, device geometry, location of the conduction path, surface cleaning, gate oxide charges and traps, water vapour annealing, carrier mobility and other technological factors. The locations of the dominant noise sources as well as their physical mechanisms were investigated. Model parameters and physical properties were extracted and compared. Several important new insights and refinements of the existing 1/f noise theories and models were also suggested and analyzed. The continuing trend of miniaturizing device sizes and building devices with more advanced architectures and complex materials can lead to escalating 1/f noise levels, which degrades the signal-to-noise (SNR) ratio in electronic circuits. For example, the 1/f noise of some critical transistors in a radio receiver may ultimately limit the information capacity of the communication system. Therefore, analyzing electronic devices in order to control and find ways to diminish the 1/f noise is a very important and challenging research subject.

We present compelling evidence that the 1/f noise is affected by the distance of the conduction channel from the gate oxide/semiconductor substrate interface, or alternatively the vertical electric field pushing the carriers towards the gate oxide. The location of the conduction channel can be varied by the voltage on the bulk and gate terminals as well by device engineering. Devices with a buried channel architecture such as buried SiGe channel pMOSFETs and accumulation mode MOSFETs on SOI show significantly reduced 1/f noise. The same observation is made when the substrate/source junction is forward biased which decreases the vertical electric field in the channel and increases the inversion layer separation from the gate oxide interface. A 1/f noise model based on mobility fluctuations originating from the scattering of electrons with phonons or surface roughness was proposed.

Materials with a high dielectric constant (high-k) is necessary to replace the conventional SiO2 as gate dielectrics in the future in order to maintain a low leakage current at the same time as the capacitance of the gate dielectrics is scaled up. In this work, we have made some of the very first examinations of 1/f noise in MOSFETs with high-k structures composed by layers of HfO2, HfAlOx and Al2O3. The 1/f noise level was found to be elevated (up to 3 orders of magnitude) in the MOSFETs with high-k gate dielectrics compared to the reference devices with SiO2. The reason behind the higher 1/f noise is a high density of traps in the high-k stacks and increased mobility fluctuation noise, the latter possibly due to noise generation in the electron-phonon scattering that originates from remote phonon modes in the high-k. The combination of a TiN metal gate, HfAlOx and a compressively strained surface SiGe channel was found to be superior in terms of both high mobility and low 1/f noise.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xx, 124 p.
Series
Trita-EKT, ISSN 1650-8599 ; 2006:2
Keyword
MOSFET, SOI, SiGe, strain, high-k, metal gate, 1/f noise, low-frequency noise, mobility fluctuations, phonons, number fluctuations, traps, buried channel, mobility, substrate bias
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-3888 (URN)
Public defence
2006-04-06, Aulan, KTH-Forum, Isafjordsgatan 39, Kista, 10:15
Opponent
Supervisors
Note
QC 20100928Available from: 2006-03-21 Created: 2006-03-21 Last updated: 2010-09-28Bibliographically approved

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Publisher's full texthttp://ieeexplore.ieee.org/xpls/abs_all.jsp?isnumber=28087&arnumber=1255616&count=41&index=26

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Hellström, Per-ErikMalm, Gunnar

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