Multideposition Multiroom-Temperature Annealing via Ultraviolet Ozone for HfZrO High- $\kappa$ and Integration With a TiN Metal Gate in a Gate-Last Process

Tran

ECS Solid State Letters

et al. 2012

Self Cite

The performance of a single-layer graphene field effect transistor treated with UV/ozone at various temperatures is studied. It is observed that the number of the defects in graphene sheet increases with the UV/ozone treatment time, evidenced by Raman spectra. Moreover, the UV/ozone treatment dopes graphene into p-type as the time increases, which is consistent with the electric transfer measurements. With the increase in the UV/ozone treatment time, the mobility of graphene transistor degrades, and the degradation accelerates with the increase in temperature. We further verified by XPS measurement that the oxygen related carbon group O=C-O formation is the main cause for the mobility degradation.Graphene, a two-dimension single-layer of carbon atoms with honeycomb structure, where carbon-carbon bonds in plane are sp 2 hybridized, has been widely investigated owing to its unique and attractive electrical, physical and chemical properties. 1-9 Graphene is an energy gapless material, in which the conduction and valence bands meet at Dirac point. 1 It exhibits ballistic transport on a submicron meter scale, very high mobility for both hole and electron, 1,2 and high current carrying capability, 5 leading to a promising material for potential applications for high frequency device, 7 gas sensor, 10,11 flexible electronics, 12,13 and photonics, 14,15 etc.Previously, the Ultraviolet/ozone (UVO) treatment is applied to reduce the concentration of oxygen vacancies in high-k gate stack, suppress the gate leakage current and improve the properties of conventional silicon based MOSFETs. 16,17 For graphene, the oxygen molecule is known to adsorb on graphene surface and induce chemical hole doping. 18,19 It has also been recently reported that the oxygen content in graphite oxides affects the electronic structure. The transmittance and energy bandgap of graphite oxide film can be tuned by the oxidation time. For example, the energy bandgap can be tuned from 1.7 to 2.4 eV by varying the oxidation time. 20 The ab initio density functional theory method has been performed to study the adsorption of ozone molecules on graphene basal plane. 21 It is reported that the orbital rehybridization induced by epoxide groups trigger a strong intervalley scattering and changes dramatically the conduction properties of graphene. 21 Very recently, the large chemical enhancement in surface-enhanced Raman scattering (SERS) has been reported, where the UVO treated graphene grown by chemical vapor deposition (CVD) method significantly improves the reproducible SERS signals over a centimeter-scale graphene surface. 22 However, the UVO impact on a single-layer graphene (SLG) field effect transistor at various temperatures has not been addressed so far.Raman spectroscopy has been widely applied in the study of graphite by providing useful information on the disorder or defects induced D band, in-plane vibration of sp 2 carbon atoms and the stacking orders related G and 2D bands. 23 The full width at half maximum (FWHM) of 30 cm −1 at 2D band can be ...

mentioning

confidence: 99%

Characteristics of a Single-Layer Graphene Field Effect Transistor with UV/Ozone Treatment

Tran

ECS Solid State Letters

et al. 2012

Self Cite

“…Similar, to what has been found previously, crystallinity is found for the HfO 2 films undergoing anneal. (12,13,16,17) In addition, we find that the thicknesses of the HfO 2 as well as the SiO 2 as measured by HRTEM do not vary significantly based on the deposition process In order to better understand the changes in HfO 2 and interface layer thickness we developed an in-line, non-destructive measurement method based on a combination of spectroscopic ellipsometry (SE) and X-ray reflectivity (XRR), that has been reported by others previously. (22) In our case, we use center point measurements of the entire dielectric stack, including HfO 2 and SiO 2 , by SE, and of the HfO 2 only by XRR.…”

Section: Methodsmentioning

confidence: 94%

“…(12,13) We have termed this process DUDU or Dep.-UVO-Dep.-UVO. In addition we have attempted to optimize the electrical performance of the resulting films both by reducing the oxygen concentration in the RTUVO process and by introducing thermal anneals during and after the DUDU process.…”

Section: Introductionmentioning

confidence: 99%

Optimizing ALD HfO₂ for Advanced Gate Stacks with Interspersed UV and Thermal Treatments- DADA and MDMA Variations, Combinations, and Optimization

et al. 2011

We have recently reported electrical performance improvements of atomic layer deposited (ALD) HfO 2 films grown by use of a cyclical deposition and annealing scheme (termed DADA) compared to a single deposition with or without a post-deposition anneal (PDA). Likewise, a process for improving leakage and reliability characteristics of ALD HfZrO by use of an interspersed room temperature ultraviolet ozone (RTUVO) treatments, referred to as multi-deposition multi-room temperature annealing (MDMA), has recently been reported. We have developed a version of this MDMA process on our 300 mm clustered tool with in situ RTUVO treatments interspersed between ALD HfO 2 depositions. In this report we compare these two processes (DADA vs. MDMA) for HfO 2 dielectric formation in a low temperature MOSCAP flow with in-line measurements of the HfO 2 and interface layer thicknesses.

IEEE Trans. Plasma Sci.

“…The barrier metal not only provides the adjustment of the work function in device operation, such as p-channel MOSFET work function metal and n-channel MOSFET work function metal, but promotes the thermal stability to protect the metal gate from the gate dielectric to form some unpredictable reaction and deteriorate the device performance. Considering the possibility of forming polycrystallization for high-k dielectric, the GL process [16] was used in this 28-nm process. Some strained technologies [17] were also applied to enhance the channel mobility such as stress memorization technology and contact-etch-stop-layer process, producing a tensile strain to the n-channel location.…”

Section: Processes For Device Preparationmentioning

confidence: 99%

Modification of Early Effect for 28-nm nMOSFETs Deposited With HfZrO<sub><italic>x</italic></sub> Dielectric After DPN Process Accompanying Nitrogen Concentrations

Lee

Wang

et al. 2014

The model of the Early effect at nanonode devices should be modified owing to the unignored contribution of vertical gate field. This effect is more obvious when the channel length is decreased more. Using higher decoupled plasma nitridation nitrogen treatment after high-k dielectric deposition, besides enhancing the drive current due to promoting the microscopic homogeneity of the Hf-based film, seems also to little suppress the Early effect. This phenomenon at L = 0.03 μm device is proved and due to the lower β-slope of influencing the high-vertical field.Index Terms-Decoupled plasma nitridation (DPN), Early effect, high-k (HK) dielectric, model, MOSFET.