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| 2. |
- von Haartman, Martin, et al.
(författare)
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Random telegraph signal noise in SiGe heterojunction bipolar transistors
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:8, s. 4414-4421
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Tidskriftsartikel (refereegranskat)abstract
- In this work, random telegraph signal (RTS) noise in SiGe heterojunction bipolar transistors (HBTs) was characterized both as a function of bias voltage and temperature. The RTS amplitudes were found to scale with the total base current, and the characteristic times in the higher and lower RTS state were found to decrease rapidly with bias voltage, approximately as 1/exp(qV(BE)/kT) or stronger. The RTS amplitudes were explained by a model based on voltage barrier height fluctuations across the base-emitter junction induced by trapped carriers in the space charge region. It was shown that the relative RTS amplitudes DeltaI(B)/I-B decrease exponentially with temperature in this model, which also was verified by measurements. The trapping/detrapping mechanism was suggested to be electron and hole capture, where the hole capture process occurs by tunneling. The characteristic times in both the lower and higher RTS state were in some cases found to decrease exponentially with temperature, characteristic for a thermally activated process, and in some cases found to be only weakly temperature dependent. The former behavior was explained by a multiphonon process with thermally activated capture cross sections, and an activation energy of 0.39 eV was extracted. RTS amplitudes proportional to the nonideal base current component or weaker were also found, originating from traps at the Si/SiO2 interface at the emitter periphery. The trapped carriers affect the recombination rate in the base-emitter space charge region, probably by changing the number of carriers. In this case, DeltaI(B)/I-B only showed a weak temperature dependence, which correlates well with this model. Characteristic times that decreased exponentially with temperature were observed, originating from a multiphonon process in the SiO2 with an activation energy for the capture cross section of 0.29 eV.
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| 3. |
- Hållstedt, Julius, et al.
(författare)
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Hole mobility in ultrathin body SOI pMOSFETs with SiGe or SiGeC channels
- 2006
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 27:6, s. 466-468
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Tidskriftsartikel (refereegranskat)abstract
- The hole mobilities of SiGe and SiGeC channel pMOSFETs fabricated on ultrathin silicon-on-insulator substrates are investigated and compared with reference Si channel devices. The total thickness of the fully depleted Si/SiGe(C)/Si body structure is similar to 25 nm. All devices demonstrated a near ideal subthreshold behavior, and the drive current and mobility were increased with more than 60% for SiGe and SiGeC channels. When comparing SIMOX and UNIBOND substrates, no significant difference could be detected.
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| 4. |
- Hållstedt, Julius, et al.
(författare)
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Noise and mobility characteristics of bulk and fully depleted SOI pMOSFETs using Si or SiGe channels
- 2006
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 3:7, s. 67-72
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Tidskriftsartikel (refereegranskat)abstract
- State of the art bulk and fully depleted SOI Si and SiGe channel pMOSFET devices with gate lengths ranging from 0.1 to 200 μm were fabricated and analyzed in terms of drain current drivability, mobility and noise performance. In general the SOI devices demonstrated superior mobility and significantly reduced I/f noise compared to bulk devices maintaining a well controlled short channel effects due to the ultra thin body.
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| 5. |
- Isheden, Christian, et al.
(författare)
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pMOSFETs with recessed and selectively regrown Si1-xGex source/drain junctions
- 2005
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 8:1-3, s. 359-362
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Tidskriftsartikel (refereegranskat)abstract
- A new source/drain formation concept based on selective Si etching followed by selective regrowth of in situ B-doped Si(1-x)Ge(x)is presented. Both process steps are performed in the same reactor to preserve the gate oxide. Well-behaved transistors are demonstrated with a negligibly low gate-to-substrate leakage current.
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| 6. |
- Malm, Bengt Gunnar, et al.
(författare)
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Influence of dislocations on low frequency noise in nMOSFETs fabricated on tensile strained virtual substrates
- 2007
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Ingår i: Noise and Fluctuations. - : AIP. - 9780735404328 ; , s. 133-136
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Konferensbidrag (refereegranskat)abstract
- In this work sSi nMOSFETs with 13 run sSi thickness on 27% Ge virtual substrates (VS) are investigated and an increased LF noise level with a characteristic gate bias dependence is found. High off-state leakage of the MOSFETs indicates the presence of misfit dislocations in the channel region. A channel conductance based model is proposed to analyse the noise originating from a highly localized defect in the channel.
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| 7. |
- Seger, Johan, et al.
(författare)
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Lateral encroachment of Ni-silicides in the source/drain regions on ultrathin silicon-on-insulator
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:25
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Tidskriftsartikel (refereegranskat)abstract
- Lateral growth of Ni silicide towards the channel region of metal-oxide-semiconductor transistors (MOSFETs) fabricated on ultrathin silicon-on-insulator (SOI) is characterized using SOI wafers with a 20-nm-thick surface Si layer. With a 10-nm-thick Ni film for silicide formation, p-channel MOSFETs displaying ordinary device characteristics with silicided p(+) source/drain regions were demonstrated. No lateral growth of NiSix under gate isolation spacers was found according to electron microscopy. When the Ni film was 20 nm thick, Schottky contact source/drain MOSFETs showing typical ambipolar characteristics were obtained. A severe lateral encroachment of NiSix into the channel region leading to an increased gate leakage was revealed, while no detectable voiding at the silicide front towards the Si channel was observed.
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| 8. |
- von Haartman, Martin, et al.
(författare)
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1/f noise in Si and Si0.7Ge0.3 pMOSFETs
- 2003
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 50, s. 2513-2519
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- von Haartman, Martin, et al.
(författare)
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Comprehensive study on low-frequency noise and mobility in Si and SiGe pMOSFETs with high-κ gate dielectrics and TiN gate
- 2006
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 53:4, s. 836-846
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency noise and hole mobility are studied in Si and SiGe surface channel pMOSFETs with various types of high-kappa dielectric stacks (Al2O3, Al2O3/HfAlOx/Al2O3 and Al2O3/HfO2/Al2O3) and TiN as gate electrode material. Comparisons are made with poly-SiGe-gated pMOSFETs as well as P0lY-Si/SiO2/Si references. The choice of channel material (strained SiGe or Si), gate material (TiN or poly-SiGe), and high-kappa material (Al2O3, HfO2, HfAlOx) is discussed in terms of mobility and low-frequency noise. A TiN gate in combination with a surface SiGe channel is advantageous both for enhanced mobility and low 1/f noise. The dominant sources of carrier scattering are identified by analyzing the mobility measured at elevated temperatures. The 1/f noise is studied from subthreshold to strong inversion conditions and at different substrate biases. The mobility fluctuation noise model and the number fluctuation noise model are both used to investigate the 1/f-noise origin.
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| 10. |
- von Haartman, Martin, et al.
(författare)
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Effect of channel positioning on the 1/f noise in silicon-on-insulator metal-oxide-semiconductor field-effect transistors
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:3
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Tidskriftsartikel (refereegranskat)abstract
- p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on silicon-on-insulator (SOI) substrates with an ultrathin (similar to 20 nm) lightly p-doped Si body were found to show about an order of magnitude lower 1/f noise than that in conventional bulk Si pMOSFETs when biased in strong inversion. In order to investigate the origin of the 1/f noise and find an explanation for the 1/f noise reduction, the 1/f noise in the SOI devices was studied as a function of the back gate voltage. The 1/f noise was found to increase with increasing back gate voltage, which acts to push the carriers closer towards the front gate oxide interface. The average distance of the inversion carriers from the gate oxide interface was obtained from simulations and used to interpret the 1/f noise behavior. The Hooge parameter, extracted for several different 1/f noise experiments where one or two terminal voltages were varied, exhibited a general behavior similar for both the SOI and bulk Si pMOSFETs. The Hooge parameter was shown to increase markedly when the average carrier-oxide separation is around 2 nm. Possible explanations of the results were discussed in terms of the mobility fluctuation noise model.
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