J. Semicond. > 2017, Volume 38 > Issue 10 > 104001
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SEMICONDUCTOR DEVICES

Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis

Piyas Samanta

+ Author Affiliations

 Corresponding author: Piyas Samanta, Email: piyas@vcfw.org

DOI: 10.1088/1674-4926/38/10/104001

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Abstract: The conduction mechanism of gate leakage current through thermally grown silicon dioxide (SiO2) films on (100) p-type silicon has been investigated in detail under negative bias on the degenerately doped n-type polysilicon (n+-polySi) gate. The analysis utilizes the measured gate current density JG at high oxide fields Eox in 5.4 to 12 nm thick SiO2 films between 25 and 300 °C. The leakage current measured up to 300 °C was due to Fowler–Nordheim (FN) tunneling of electrons from the accumulated n +-polySi gate in conjunction with Poole Frenkel (PF) emission of trapped-electrons from the electron traps located at energy levels ranging from 0.6 to 1.12 eV (depending on the oxide thickness) below the SiO2 conduction band (CB). It was observed that PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm and throughout the temperature range studied here. Understanding of the mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown (TDDB) of metaloxide–semiconductor (MOS) devices and to precisely predict the normal operating field or applied gate voltage for lifetime projection of the MOS integrated circuits.

Key words: FN tunneling, PF emission, image force lowering, trap depth



[1]
Yang B L, Lai P T, Wong H. Conduction mechanisms in MOS gate dielectric films. Microelectron Reliab, 2004, 44: 709 doi: 10.1016/j.microrel.2004.01.013
[2]
Lenzlinger M, Snow E H. Fowler—Nordheim tunneling into thermally grown SiO2. J Appl Phys, 1969, 40: 278 doi: 10.1063/1.1657043
[3]
Weinberg Z A. Tunneling of electrons from Si into thermally grown SiO2. Solid-State Electron, 1977, 20: 11
[4]
Weinberg Z A. On tunneling in metal–oxide–silicon structures. J Appl Phys, 1982, 53: 5052 doi: 10.1063/1.331336
[5]
Krieger G, Swanson R M. Fowler—Nordheim electron tunneling in thin Si-SiO2-Al structures. J Appl Phys, 1981, 52: 5710 doi: 10.1063/1.329510
[6]
Depas M, Vermeire B, Mertens P W, et al. Determination of tunneling parameters in ultra-thin oxide layer poly-Si/SiO2/Si structures. Solid-State Electron, 1995, 38: 1465 doi: 10.1016/0038-1101(94)00269-L
[7]
Pananakakis G, Ghibaudo G, Kies R, et al. Temperature dependence of the Fowler—Nordheim current in metal—oxidedegenerate semiconductor structures. J Appl Phys, 1995, 78: 2635 doi: 10.1063/1.360124
[8]
Hadjadj A, Salace G, Petit C. Fowler-Nordheim conduction in polysilicon (n+)-oxide-silicon (p) structures: Limit of the classical treatment in the barrier height determination. J Appl Phys, 2001, 89: 7994 doi: 10.1063/1.1374479
[9]
Roca M, Laffont R, Micolau G, et al. A Modelisation of the temperature dependence of the Fowler—Nordheim current in EEPROM memories. Microelectron Reliab, 2009, 49: 1070 doi: 10.1016/j.microrel.2009.06.036
[10]
Aygun G, Roeder G, Erlbacher T, et al. Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO2 layer on a large wafer area. J Appl Phys, 2010, 108: 073304 doi: 10.1063/1.3481348
[11]
Waters R, Zeghbroeck B V. On field emission from a semiconducting substrate. Appl Phys Lett, 1999, 75: 2410 doi: 10.1063/1.125030
[12]
Samanta P, Mandal K C. Leakage current conduction and reliability assessment of passivating thin silicon dioxide films on n-4H-SiC. Proceedings of SPIE (SPIE, Bellingham, WA, 2016), 2016, 9968: 99680E
[13]
Samanta P, Mandal K C. Leakage current conduction, hole injection, and time-dependent dielectric breakdown of n-4H-SiC MOS capacitors during positive bias temperature stress. J Appl Phys, 2017, 121: 034501 doi: 10.1063/1.4973674
[14]
Sze S M, Ng K K. Physics of semiconductor devices. New Jersey: John Wiley & Sons, Inc., 2007
[15]
Alay J L, Hirose M. The valence band alignment at ultrathin SiO2/Si interfaces. J Appl Phys, 1997, 81: 1606 doi: 10.1063/1.363895
[16]
Afanasev V V, Bassler M, Pensl G, et al. Band offsets and electronic structure of SiC/SiO2 interfaces. J Appl Phys, 1996, 79: 3108 doi: 10.1063/1.361254
[17]
Rossinelli M, Bosch M A. Reflectance spectrum of crystalline and vitreous SiO2 at low temperature. Phys Rev B, 1982, 25: 6482 doi: 10.1103/PhysRevB.25.6482
[18]
Persson C, Lindefelt U, Sernelius B E. Band gap narrowing in n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si. J Appl Phys, 1999, 86: 4419 doi: 10.1063/1.371380
[19]
Murphy E L, Good R H. Thermionic emission, field emission, and the transition region. Phys Rev, 1956, 102: 1464 doi: 10.1103/PhysRev.102.1464
[20]
Samanta P. Mechanistic analysis of temperature dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures. J Appl Phys, 2017, 122: 094502
[21]
Wolfram Research, Inc., Mathematica, Version 11.0, 2016 (Champaign, IL)
[22]
Banerjee S, Shen B, Chen I, et al. Conduction mechanisms in sputtered Ta2O5 on Si with an interfacial SiO2 layer. J Appl Phys, 1989, 65: 1140 doi: 10.1063/1.343052
[23]
Harrell W R, Gopalakrishnan C. Implications of advanced modeling on the observation of Poole–Frenkel effect saturation. Thin Solid Films, 2002, 405: 205 doi: 10.1016/S0040-6090(01)01752-7
[24]
Lu Z Y, Nicklaw J, Fleetwood D M, et al. Structure, properties, and dynamics of oxygen vacancies in amorphous SiO2. Phys Rev Lett, 2002, 89: 285505 doi: 10.1103/PhysRevLett.89.285505
Fig. 1.  (a) Fowler–Nordheim (FN) plot of the measured[8] leakage current density JG during electron injection from n+-polySi gate into thermally grown thin SiO2 films in as-grown MOS capacitors on p-Si with oxide thickness and temperature as parameters. Curves are fits to LS Eq. (1) and symbols are from experiment[8]. Inset shows the schematic band diagram of FN tunneling of electrons through the effective triangular barrier energy ΦB (measured from the Fermi level in accumulated n+-polySi) at the interface. (b) Temperature variation of the effective electron barrier height ΦB at the n+-polySi/SiO2 interface determined from the FN slope BFN of the measured[8] JG versus Eox data for different oxide thicknesses (filled symbols). Also shown are the theoretically estimated (open circles) results considering temperature dependent Fermi level incomplete ionization of the dopant atoms in n+-polySi using FD statistics.

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Fig. 2.  Schematic band diagram illustrating (a) thermal narrowing of bandgaps of n+-polySi and SiO2 due to downward shifts of the CBs towards midgap, while the valence bands are aligned[15] and (b) FN tunneling of electrons below the CB edge of accumulated n+-polySi through the triangular energy barrier at the n+-polySi/SiO2 interface incorporating image force barrier lowering.

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Fig. 3.  Applied oxide field dependence of FN current density JFN (curves) calculated using Eq. (5) and (a) measured[8] (symbols) leakage current density JG during electron injection from n+-polySi in as-grown MOS devices with oxide thickness and temperature as parameters. (b) Measured[3] (symbols) leakage current density JG during electron injection at room temperature from n-Si in as-grown MOS devices with oxide thickness as a parameter.

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Fig. 4.  Difference (symbols) between the absolute magnitudes of the measured JG and the calculated JFN at a given applied uniform oxide field with tox and temperature as parameters. Curves are fit to PF Eq. (9). Inset: schematic of the PF emission of electrons from oxide electron traps.

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Fig. 5.  (a) Arrhenius plot of the intercepts of the PF plots of the JG–JFN data for varying oxide thicknesses. (b) Temperature variation of the acceptor compensation factor ξ.

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Fig. 6.  Variation of the saturation field for PF emission with temperature during negative bias on n+-polySi gate. Curve is guide to eye only.

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Table 1.   Temperature dependent bandgap Eg and electron barrier height at the cathode (n+-polySi) having ND = 1020 cm−3.

Temperature (°C) Eg (n+-polySi)(eV) Eg (SiO2)(eV) Φec(eV)
25 1.004 8.900 3.334
100 1.015 8.883 3.339
200 0.980 8.859 3.348
300 0.944 8.847 3.359
DownLoad: CSV
[1]
Yang B L, Lai P T, Wong H. Conduction mechanisms in MOS gate dielectric films. Microelectron Reliab, 2004, 44: 709 doi: 10.1016/j.microrel.2004.01.013
[2]
Lenzlinger M, Snow E H. Fowler—Nordheim tunneling into thermally grown SiO2. J Appl Phys, 1969, 40: 278 doi: 10.1063/1.1657043
[3]
Weinberg Z A. Tunneling of electrons from Si into thermally grown SiO2. Solid-State Electron, 1977, 20: 11
[4]
Weinberg Z A. On tunneling in metal–oxide–silicon structures. J Appl Phys, 1982, 53: 5052 doi: 10.1063/1.331336
[5]
Krieger G, Swanson R M. Fowler—Nordheim electron tunneling in thin Si-SiO2-Al structures. J Appl Phys, 1981, 52: 5710 doi: 10.1063/1.329510
[6]
Depas M, Vermeire B, Mertens P W, et al. Determination of tunneling parameters in ultra-thin oxide layer poly-Si/SiO2/Si structures. Solid-State Electron, 1995, 38: 1465 doi: 10.1016/0038-1101(94)00269-L
[7]
Pananakakis G, Ghibaudo G, Kies R, et al. Temperature dependence of the Fowler—Nordheim current in metal—oxidedegenerate semiconductor structures. J Appl Phys, 1995, 78: 2635 doi: 10.1063/1.360124
[8]
Hadjadj A, Salace G, Petit C. Fowler-Nordheim conduction in polysilicon (n+)-oxide-silicon (p) structures: Limit of the classical treatment in the barrier height determination. J Appl Phys, 2001, 89: 7994 doi: 10.1063/1.1374479
[9]
Roca M, Laffont R, Micolau G, et al. A Modelisation of the temperature dependence of the Fowler—Nordheim current in EEPROM memories. Microelectron Reliab, 2009, 49: 1070 doi: 10.1016/j.microrel.2009.06.036
[10]
Aygun G, Roeder G, Erlbacher T, et al. Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO2 layer on a large wafer area. J Appl Phys, 2010, 108: 073304 doi: 10.1063/1.3481348
[11]
Waters R, Zeghbroeck B V. On field emission from a semiconducting substrate. Appl Phys Lett, 1999, 75: 2410 doi: 10.1063/1.125030
[12]
Samanta P, Mandal K C. Leakage current conduction and reliability assessment of passivating thin silicon dioxide films on n-4H-SiC. Proceedings of SPIE (SPIE, Bellingham, WA, 2016), 2016, 9968: 99680E
[13]
Samanta P, Mandal K C. Leakage current conduction, hole injection, and time-dependent dielectric breakdown of n-4H-SiC MOS capacitors during positive bias temperature stress. J Appl Phys, 2017, 121: 034501 doi: 10.1063/1.4973674
[14]
Sze S M, Ng K K. Physics of semiconductor devices. New Jersey: John Wiley & Sons, Inc., 2007
[15]
Alay J L, Hirose M. The valence band alignment at ultrathin SiO2/Si interfaces. J Appl Phys, 1997, 81: 1606 doi: 10.1063/1.363895
[16]
Afanasev V V, Bassler M, Pensl G, et al. Band offsets and electronic structure of SiC/SiO2 interfaces. J Appl Phys, 1996, 79: 3108 doi: 10.1063/1.361254
[17]
Rossinelli M, Bosch M A. Reflectance spectrum of crystalline and vitreous SiO2 at low temperature. Phys Rev B, 1982, 25: 6482 doi: 10.1103/PhysRevB.25.6482
[18]
Persson C, Lindefelt U, Sernelius B E. Band gap narrowing in n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si. J Appl Phys, 1999, 86: 4419 doi: 10.1063/1.371380
[19]
Murphy E L, Good R H. Thermionic emission, field emission, and the transition region. Phys Rev, 1956, 102: 1464 doi: 10.1103/PhysRev.102.1464
[20]
Samanta P. Mechanistic analysis of temperature dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures. J Appl Phys, 2017, 122: 094502
[21]
Wolfram Research, Inc., Mathematica, Version 11.0, 2016 (Champaign, IL)
[22]
Banerjee S, Shen B, Chen I, et al. Conduction mechanisms in sputtered Ta2O5 on Si with an interfacial SiO2 layer. J Appl Phys, 1989, 65: 1140 doi: 10.1063/1.343052
[23]
Harrell W R, Gopalakrishnan C. Implications of advanced modeling on the observation of Poole–Frenkel effect saturation. Thin Solid Films, 2002, 405: 205 doi: 10.1016/S0040-6090(01)01752-7
[24]
Lu Z Y, Nicklaw J, Fleetwood D M, et al. Structure, properties, and dynamics of oxygen vacancies in amorphous SiO2. Phys Rev Lett, 2002, 89: 285505 doi: 10.1103/PhysRevLett.89.285505

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    Received: 23 November 2016 Revised: 30 April 2017 Online: Accepted Manuscript: 13 November 2017Published: 01 October 2017

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      Article Navigation >  Journal of Semiconductors  > 2017  >  38(10): 104001
      Piyas Samanta. Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis[J]. Journal of Semiconductors, 2017, 38(10): 104001. doi: 10.1088/1674-4926/38/10/104001 ****P Samanta. Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis[J]. J. Semicond., 2017, 38(10): 104001. doi: 10.1088/1674-4926/38/10/104001.
      Citation:
      Piyas Samanta. Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis[J]. Journal of Semiconductors, 2017, 38(10): 104001. doi: 10.1088/1674-4926/38/10/104001 ****
      P Samanta. Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis[J]. J. Semicond., 2017, 38(10): 104001. doi: 10.1088/1674-4926/38/10/104001.
      shu

      Mechanism of oxide thickness and temperature dependent current conduction in n+-polySi/SiO2/p-Si structures — a new analysis

      DOI: 10.1088/1674-4926/38/10/104001

      • Department of Physics, Vidyasagar College for Women, 39 Sankar Ghosh Lane, Kolkata 700006, India

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      • Corresponding author: Email: piyas@vcfw.org
      • Received Date: 2016-11-23
      • Revised Date: 2017-04-30
      • Published Date: 2017-10-01

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