Gaurang Pant

Stabilization of higher-κ tetragonal HfO2 by SiO2 admixture enabling thermally stable metal-insulator-metal capacitors

The authors report the relationship between HfO2 crystalline phase and the resulting electrical properties. Crystallization of amorphous HfO2 into the monoclinic phase led to a significant increase in leakage current and formation of local defects. Admixture of 10% SiO2 avoided formation of these defects by stabilization of the tetragonal phase, and concurrently increased the permittivity to 35. This understanding enabled fabrication of crystalline HfO2 based metal-insulator-metal capacitors able to withstand a thermal budget of 1000°C while optimizing capacitance equivalent thickness (<1.3nm) at low leakage [J(1V)<10−7A∕cm2].

Effect of poly (3-hexylthiophene) film thickness on organic thin film transistor properties

We present the effect of poly (3-hexylthiophene) (P3HT) thickness on the performance of organic thin film transistors (OTFTs). The P3HT film thickness varies from 11to186nm. The devices have channel lengths of 5, 10, 20, 40, and 80μm and a channel width of 500μm. The mobility and on/off ratio are up to 0.08cm2∕Vs and 7×103, respectively. The drain current and the mobility increase with thickness. At the same P3HT thickness, the drain current and mobility become higher when the channel length is reduced. The on/off ratio decreases quickly and then saturates for thickness >64nm. Short channel devices have higher on/off ratio than long channel devices. For short channel devices (5μm), the on/off ratio does not change significantly with thickness. The devices with shorter channel length and thicker P3HT films tend to have smaller threshold voltages. The threshold voltage saturates for long channel (20–80μm) devices, for films thicker than 110nm. The gate leakage (ID offset) is higher for thicker film devices....

Comparison of electrical and chemical characteristics of ultrathin HfON versus HfSiON dielectrics

The electrical and chemical properties of ultrathin HfON and HfSiON gate dielectrics are investigated as a function of physical thickness. Grazing incidence x-ray diffraction was used to detect phase separation and crystallization of 1.5, 2.0, 2.5, and 4.0nm films of HfON and HfSiON after a 1000°C-10s activation annealing. X-ray photoelectron spectroscopy was used to determine the chemical composition of the dielectrics. No evidence of crystallization was detected in 1.5nm HfON or HfSiON films after the activation annealing. The HfON film showed crystallization at a 2.0nm thickness whereas the 2.0nm HfSiON film remained amorphous.

Ultrascaled hafnium silicon oxynitride gate dielectrics with excellent carrier mobility and reliability

A hafnium silicon oxynitride gate dielectric with a universal channel mobility of ∼90% at 1MV∕cm, equivalent oxide thickness of approximately 1nm, and leakage current 200× less than SiO2 is reported. X-ray photoelectron spectroscopy results suggest that the small peak mobility loss observed in scaled HfSiON may be attributed to increased Si–N bonding near the silicon interface. In accordance with these mobility results, the Si–N:Hf–N bond ratio decreases with increasing HfSiON physical thickness. Threshold voltage instability at 1nm equivalent oxide thickness is less than 10mV after a 1000s stress at 22MVcm. ΔVTH monotonically increases with HfSiON physical thickness. This is associated with greater crystallization in thicker HfSiON films.

Effect of thickness on the crystallization of ultrathin HfSiON gate dielectrics

The crystallization of ultrathin hafnium silicon oxynitride (HfSiON) gate dielectric is studied as a function of physical thickness. Grazing incidence x-ray diffraction (GI-XRD) was used to detect phase separation and crystallization of 1.5, 2.0, 2.5, and 4.0 nm HfSiON films after 1000°C10s dopant activation anneal. Crystallization peaks corresponding to monoclinic and tetragonal HfO2 were detected in 2.5 and 4.0 nm HfSiON films. These GI-XRD results were supported by plan-view transmission electron microscopy images of the HfSiON films. Film crystallinity seems to impact voltage instability in thicker HfSiON films.

High performance gate first HfSiON dielectric satisfying 45nm node requirements

We show an ALD based HfSiON gate dielectric scaled to 1 nm EOT with excellent performance and reliability. Furthermore, the HfSiON dielectric films are integrated in a gate first approach that includes a 1000degC-5s anneal. It is also demonstrated that this 1 nm EOT HfSiON can achieve electron and hole mobilities comparable to that of SiON. This progress is enabled due to better understanding of the relationship between charge trapping, HfSiON thickness and crystallinity. Performance and reliability improvement is attributed to reduced charge trapping due to suppressed crystallization of the optimized HfSiON films

Mobility and charge trapping comparison for crystalline and amorphous HfON and HfSiON gate dielectrics

Mobility and charge trapping results for n-channel transistors gated with HfON and HfSiON are reported as a function of physical thickness (Tphys). HfSiON peak mobility improves with Tphys over the range of 1.8–2.7nm, achieving 260cm2∕Vs at 2.7nm. However, HfSiON mobility degrades at a critical thickness, Tphys⩾3.5nm. HfON mobility response is different. It is a maximum (230cm2∕Vs) at Tphys=1.2nm but degrades with increasing thickness, particularly for the critical thickness ⩾2.5nm. Mobility loss and trapping occur concurrently for both dielectrics when these critical thicknesses are exceeded. These critical thicknesses are the minimum required to achieve dielectric crystallization. Interfacial defects along crystalline grain boundaries may negatively impact electrical performance of both dielectrics.

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in H1- and H2-containing atmospheres was investigated. H1 profiling was accessed by means of nuclear resonant reaction profiling, whereas H2 incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of H1 and H2 from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated H1, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

Tetragonal Phase Stabilization by Doping as an Enabler of Thermally Stable HfO2 based MIM and MIS Capacitors for sub 50nm Deep Trench DRAM

We show for the first time that control of the crystalline phases of HfO2 by tetravalent (Si) and trivalent (Y,Gd) dopants enables significant improvements in the capacitance equivalent thickness (CET) and leakage current in capacitors targeting deep trench (DT) DRAM applications. By applying these findings, we present a MIM capacitor meeting the requirements of the 40 nm node. A CET < 1.3 nm was achieved at the deep trench DRAM thermal budget of 1000 degC

Low-temperature deposition of hafnium silicate gate dielectrics

The physical and electrical properties of hafnium silicate (HfSi/sub x/O/sub y/) films produced by low-temperature processing conditions (/spl les/150/spl deg/C) suitable for flexible display applications were studied using sputter deposition and ultra-violet generated ozone treatments. Films with no detectable low-/spl kappa/ interfacial layer were produced. Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy were used to determine the composition, chemical bonding environment, thickness, and film interface. The electrical behavior of the as-deposited and annealed hafnium silicate films were determined by current-voltage (I--V) and capacitance-voltage (C--V) measurements.