Ultimate Scaling of High-κ Gate Dielectrics: Higher-κ or Interfacial Layer Scavenging?

Current status and challenges of aggressive equivalent-oxide-thickness (EOT) scaling of high-κ gate dielectrics via higher-κ (>20) materials and interfacial layer (IL) scavenging techniques are reviewed. La-based higher-κ materials show aggressive EOT scaling (0.5–0.8 nm), but with effective workfunction (EWF) values suitable only for n-type field-effect-transistor (FET). Further exploration for p-type FET-compatible higher-κ materials is needed. Meanwhile, IL scavenging is a promising approach to extend Hf-based high-κ dielectrics to future nodes. Remote IL scavenging techniques enable EOT scaling below 0.5 nm. Mobility-EOT trends in the literature suggest that short-channel performance improvement is attainable with aggressive EOT scaling via IL scavenging or La-silicate formation. However, extreme IL scaling (e.g., zero-IL) is accompanied by loss of EWF control and with severe penalty in reliability. Therefore, highly precise IL thickness control in an ultra-thin IL regime (<0.5 nm) will be the key technology to satisfy both performance and reliability requirements for future CMOS devices.     

MOSFET探测器在全身放疗质量控制中的应用

目的探讨MOSFET探测器在全身放疗质量控制中的价值。方法在源轴距360cm处使用电离室对MOSFET探测器进行标定,同时根据体模入射面、出射面与中间层面的剂量换算关系,利用标定后的MOSFET探测器检测行全身放疗患者的辐射剂量,控制并减少相应误差。结果10＋MOSFET探测器中,有7个最大偏差均〈3％,另3个经再次重新标定后,最大偏差亦〈3％,均可用于临床测量。结论在全身放疗中应用MOSFET探测器能够起到监测治疗剂量、控制误差的作用。     

Comprehensive Study of Lanthanum Aluminate High-Dielectric-Constant Gate Oxides for AdvancedCMOS Devices

A comprehensive study of the electrical and physical characteristics of Lanthanum Aluminate (LaAlO₃) high-dielectric-constant gate oxides for advanced CMOS devices was performed. The most distinctive feature of LaAlO₃ as compared with Hf-based high-k materials is the thermal stability at the interface with Si, which suppresses the formation of a low-permittivity Si oxide interfacial layer. Careful selection of the film deposition conditions has enabled successful deposition of an LaAlO₃ gate dielectric film with an equivalent oxide thickness (EOT) of 0.31 nm. Direct contact with Si has been revealed to cause significant tensile strain to the Si in the interface region. The high stability of the effective work function with respect to the annealing conditions has been demonstrated through comparison with Hf-based dielectrics. It has also been shown that the effective work function can be tuned over a wide range by controlling the La/(La + Al) atomic ratio. In addition, gate-first n-MOSFETs with ultrathin EOT that use sulfur-implanted Schottky source/drain technology have been fabricated using a low-temperature process.     

Characterization of responses and comparison of calibration factor for commercial MOSFET detectors

A commercial metal oxide silicon field effect transistor (MOSFET) dosimeter of model TN502-RD has been characterized for its linearity, reproducibility, field size dependency, dose rate dependency, and angular dependency for Cobalt-60 (⁶⁰Co), 6-MV, and 15-MV beam energies. The performance of the MOSFET clearly shows that it is highly reproducible, independent of field size and dose rate. Furthermore, MOSFET has a very high degree of linearity, with r-value > 0.9 for all 3 energies. The calibration factor for 2 similar MOSFET detectors of model TN502-RD were also estimated and compared for all 3 energies. The calibration factor between the 2 similar MOSFET detectors shows a variation of about 1.8% for ⁶⁰Co and 15 MV, and for 6 MV it shows variation of about 2.5%, indicating that calibration should be done whenever a new MOSFET is used. However, the detector shows considerable angular dependency of about 8.8% variation. This may be due to the variation in radiation sensitivity between flat and bubble sides of the MOSFET, and indicates that positional care must be taken while using MOSFET for stereotactic radiosurgery and stereotactic radiotherapy dosimetric applications.     

金属氧化物半导体场效应晶体管测量组织补偿胶对乳腺癌胸壁照射皮肤X线表面剂量的影响

目的使用金属氧化物半导体场效应晶体管（metal oxide semiconductor field effect transistor,MOSFET）探测器测量不同厚度组织补偿胶对乳腺癌胸壁照射X线皮肤表面剂量的影响。方法选用6MV、15MV X线进行照射,分为有补偿胶组和无补偿胶组,补偿胶按厚度分为3mm、5mm、10mm、15mm、20mm5组,用MOSFET分别测量,每组测10次。结果使用组织补偿胶后表面剂量明显增加,不同厚度补偿胶对表面剂量的影响程度不同。结论使用补偿胶后射线的剂量建成区出现变化,表面剂量明显提高。临床治疗中需要根据肿瘤类型及深度选用合适的补偿胶。     

Microstructures of HfOx Films Prepared via Atomic Layer Deposition Using La(NO3)3·6H2O Oxidants

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfO_x films deposited using a conventional oxidant (H₂O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H₂O. HfO_x films deposited using the LNS oxidant had smaller crystallites than those deposited using H₂O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfO_x films deposited using LNS and H₂O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends.     

Entrance skin dose measured with MOSFETs in children undergoing interventional radiology procedures

Background  Interventional procedures frequently employ fluoroscopy or digital subtraction angiography (DSA). Few studies have documented radiation doses received by children during these procedures. Objective  To measure skin entrance dose received during common pediatric interventional procedures. Materials and methods  MOSFET dosimeters were placed to record skin doses in 143 children undergoing any of five procedures: 30 PICC insertions, 34 CVL/port insertions, 30 G/GJ tube insertions, 25 sclerotherapy/vascular anomaly procedures, 24 cerebral angiography procedures. The highest recorded dose (HRD) from the five MOSFET probes was assumed to be the peak skin dose per child. HRD values were averaged for children within each group and correlated with patient weight, fluoroscopy time and number of DSA frames. Results  Average HRD was 1.8 mGy for PICC insertions, 1.4 mGy for CVL/port insertions, 3.9 mGy for G/GJ tube insertions, 39.1 mGy for sclerotherapy/vascular anomaly procedures, and 149.9 and 101.6 mGy for frontal and lateral portions of cerebral angiography procedures. These entrance doses corresponded to effective dose estimates in the range 0.4–3 mSv. There were only modest correlations between peak skin dose and fluoroscopy time, patient weight and DSA frames (r ²<0.4, P < 0.01). Conclusion  Pediatric interventional procedures are associated with a wide range of doses; those at the higher end require careful monitoring.     

Online in vivo dosimetry in high dose rate prostate brchytherapy with MOSkin detectors: In phantom feasibility study

MOSkin detectors were studied to perform real-time in vivo dose measurements in high dose rate prostate brachytherapy. Measurements were performed inside an urethral catheter in a gel phantom simulating a real prostate implant. Measured and expected doses were compared and the discrepancy was found to be within 8.9% and 3.8% for single MOSkin and dual-MOSkin configurations, respectively. Results show that dual-MOSkin detectors can be profitably adopted in prostate brachytherapy treatments to perform real-time in vivo dosimetry inside the urethra.