Limitations of Poole–Frenkel Conduction in Bilayer $\hbox{HfO}_{2}/\hbox{SiO}_{2}$ MOS Devices

Atomic layer deposited (ALD) high-dielectric-constant (high-k) materials have found extensive applications in a variety of electronic, optical, optoelectronic, and photovoltaic devices. While electrical, optical, and interfacial properties have been the primary consideration for such devices, thermal and mechanical properties are becoming an additional key consideration for many new and emerging applications of ALD high-k materials in electromechanical, energy storage, and organic light emitting diode devices. Unfortunately, a clear correspondence between thermal/mechanical and electrical/optical properties in ALD high-k materials has yet to be established, and a detailed comparison to conventional silicon-based dielectrics to facilitate optimal material selection is also lacking. In this regard, we have conducted a comprehensive investigation and review of the thermal, mechanical, electrical, optical, and structural properties for a series of prevalent and emerging ALD high-k materials including aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), hafnium oxide (HfO 2 ), and beryllium oxide (BeO). For comparison, more established silicon-based dielectrics were also examined, including thermally grown silicon dioxide (SiO 2 ) and plasma-enhanced chemically vapor deposited hydrogenated silicon nitride (SiN:H). We find that in addition to exhibiting high values of dielectric permittivity and electrical resistance that exceed those of SiO 2 and SiN:H, the ALD high-k materials exhibit equally exceptional thermal and mechanical properties with coefficients of thermal expansion ≤ 6 × 10 -6 / • C, thermal conductivites (κ) of 3-15 W/m K, and Young's modulus and hardness values exceeding 200 and 25 GPa, respectively. In many cases, the observed extreme thermal/mechanical properties correlate with the presence of crystallinity in the ALD high-k films. In contrast, some of the electrical and optical properties correlate more strongly with the percentage of ionic vs. covalent bonds present in the high-k film. Overall, the ALD high-k dielectrics investigated concurrently exhibit compelling thermal/mechanical and electrical/optical properties. The drive to reduce gate leakage currents in highly scaled complementary metal-oxide-semiconductor (CMOS) transistors has led to the exploration and development of a wide variety of high-dielectricconstant (high-k) materials to replace silicon dioxide (SiO 2 ) as the insulating gate dielectric material.1-8 Many of these same high-k materials have found additional applications in future non-CMOS logic and memory storage products such as solid-state electrolytes in resistive switching devices, 9,10 tunnel barriers in spin-transport devices, 11 and as a ferroelectric in magnetoelectric devices. While electrical, physical, and thermodynamic properties have clearly been a key consideration in all of the above applications, thermal properties have become an additional important consideration for higk-k dielectrics as aggressive dimensional scaling of devices has created the need to dissipate ...

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“…[221][222][223][224] This is consistent with the general appearance of the HfO 2 IV trace in Fig. 4 differing from that for Al 2 O 3 and SiO 2 .…”

supporting

confidence: 84%

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Gaskins

Hopkins

Merrill

et al. 2017

ECS J. Solid State Sci. Technol.

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“…In case of chemical IL devices, the estimated trap level energy (u t ) of 0.19 eV is very close to the reported value of 0.21 eV (Ref. 18) since in both cases the measurement was taken on exactly the similar gate stacks, HfO 2 (3 nm)/SiO 2 (1.1 nm), and also u t value was extracted from the temperature dependent I-V data. Thus, doubly negatively charged oxygen vacancies are the active defects in HfO 2 dielectric for the PF conduction mechanism in our devices for both ILs.…”

supporting

confidence: 83%

“…16 The trap level energy of 0.16 eV for ISSG IL devices is a good match with the reported value of 0.3 eV obtained from the temperature dependent I-V measurements on similar gate stacks. 17 Since the u t value is thickness dependent for bulk high-k dielectric, 18 we expect a smaller value of u t in our gate stacks with ISSG IL having a 3 nm high-k layer whereas Chowdhury and Misra 17 have used a thicker high-k layer of 3.5 nm. In case of chemical IL devices, the estimated trap level energy (u t ) of 0.19 eV is very close to the reported value of 0.21 eV (Ref.…”

mentioning

confidence: 98%

Interfacial layer growth condition dependent carrier transport mechanisms in HfO2/SiO2 gate stacks

Sahoo¹,

Misra²

2012

Applied Physics Letters

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The temperature and field dependent leakage current in HfO2/SiO2 gate stack for in situ steam grown and chemical interfacial layers (ILs) are studied in the temperature range of 20 °C to 105 °C. Poole-Frenkel mechanism in high field whereas Ohmic conduction in low field region are dominant for both devices. Leakage current decreases whereas both trap energy level (ϕt) and activation energy (Ea) increase for chemically grown IL devices. The trap level energy, (ϕt) ∼ 0.2 eV, indicates that doubly charged oxygen vacancies (V2−) are the active electron traps which contribute to the leakage current in these gate stacks.

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“…For the past few decades, dimension of silicon (Si)-based metal-oxide-semiconductor (MOS) devices has been continuously downscaled to comply with the demand of a better electronic performance [1][2][3]. Ultimately, native oxide of the Si (SiO 2 ) has been pushed to its theoretical limits when its physical thickness is reduced to 1 nm range.…”

Section: Introductionmentioning

confidence: 99%

Effects of post-deposition annealing ambient on Y2O3 gate deposited on silicon by RF magnetron sputtering

Quah

Cheong

2012

Journal of Alloys and Compounds

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Limitations of Poole–Frenkel Conduction in Bilayer $\hbox{HfO}_{2}/\hbox{SiO}_{2}$ MOS Devices

Cited by 50 publications

References 22 publications

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Interfacial layer growth condition dependent carrier transport mechanisms in HfO2/SiO2 gate stacks

Effects of post-deposition annealing ambient on Y2O3 gate deposited on silicon by RF magnetron sputtering

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