EVALUATION OF THE RadFET RADIATION SENSOR PERFORMANCE IN 18 MV-EXTERNAL BEAM

Objective & Hypothesis:The radiation response of RadFET irradiated with 18 MV X-rays emitted from a linear accelerator was examined on threshold voltage shifts and trap densities.

📊

Key Findings & Data:The ΔVth – D graph showed excellent linearity of up to just about 2 Gy.

💡

Conclusion & Impact:From the threshold voltages measured under zero gate voltage in a certain time interval, the percentage fading range was calculated as 0.004-1.235%.

🔬Design:Research Article

📍Scope:Comprehensive Sample

⚙️Variables:RadFET · Radyasyon Cevabı · Radyoterapi

Abstract

The radiation response of RadFET irradiated with 18 MV X-rays emitted from a linear accelerator was examined on threshold voltage shifts and trap densities. The measured threshold voltages were compared before and after irradiation. Trap densities calculated using various techniques in the gate oxide and oxide/silicon interface were interpreted. The ΔVth – D graph showed excellent linearity of up to just about 2 Gy. The RadFETs response to radiation started to deviate from linearity after 2 Gy due to increasing oxide trapped charges induced by electric field screening. The experimental outcomes are in good accordance with the fitting function given for RadFETs. Fixed and switching traps formed by irradiation were investigated. The density of the fixed traps was significantly higher than the density of the switching traps. From the threshold voltages measured under zero gate voltage in a certain time interval, the percentage fading range was calculated as 0.004-1.235%.

Özet

Lineer hızlandırıcıdan yayılan 18 MV’luk X-ışınları ile ışınlanan RadFET’lerin radyasyon cevapları, eşik voltaj kaymaları ve tuzak yoğunlukları üzerinden incelenmiştir. Işınlamadan önce ve sonra eşik voltajları ölçülerek karşılaştırılmıştır. Çeşitli teknikler kullanılarak kapı oksitinde ve oksit/silikon arayüzeyinde hesaplanan tuzak yoğunlukları değerlendirilmiştir. ΔVth – D grafiği, yaklaşık 2 Gy’e kadar mükemmel doğrusallık göstermiştir. RadFET’in radyasyon cevabı, elektrik alan perdelemesi tarafından uyarılan oksit tuzak yüklerinin artmasıyla 2 Gy sonrasında doğrusallıktan sapmaya başlamıştır. Deneysel sonuçlar, RadFET’ler için verilen fit fonksiyonuyla iyi bir uyum içindedir. Işınlama sonucunda oluşan sabit ve anahtarlama tuzakları incelenmiştir. Sabit tuzakların yoğunluğu, anahtarlama tuzaklarının yoğunluğundan önemli bir miktar daha yüksek olarak bulunmuştur. Sıfır kapı voltajı altında ölçülen eşik voltajlarından yüzde zayıflama aralığı %0.004 – %1.235 olarak hesaplanmıştır.

Keywords

RadFET Radyasyon Cevabı Radyoterapi Radiation Response Radiotherapy

🔖

Cite This Article

MORKOÇ, B., KAHRAMAN, A., YEĞEN, D., YILMAZ, E. (2019). EVALUATION OF THE RadFET RADIATION SENSOR PERFORMANCE IN 18 MV-EXTERNAL BEAM. Uludağ Üniversitesi Mühendislik Fakültesi Dergisi, Cilt: 24 - Sayı: 3, 309–317. https://ajindex.com/articles/329825

📄 Full Text PDF Viewer

Open in New Tab ↗

↗New Tab

📄

PDF görüntüleyici hazırlanıyor...

References (3)

Andjelkovic, M.S., Ristic, G.S. and Jaksic, A.B. (2015) Using RADFET for the real-time measurement of gamma radiation dose rate, Measurement Science and Technology, 26, 025004. doi: 10.1088/0957-0233/26/2/025004 Brugler, J.S. and Jespers, P.G.A. (1969)
Charge pumping in MOS devices, IEEE Transactions on Electron Devices, 16, 297-302. doi: 10.1109/T-ED.1969.16744 Fröhlich, L., Casarin, K., Quai, E., Holmes-Siedle, A., Severgnini, M. and Vidimari, R. (2013) Online monitoring of absorbed dose in undulator magnets with RADFET dosimeters at FERMI@Elettra, Nuclear Instruments and Methods in Physics Research A, 703, 70-79. doi: 10.1016/j.nima.2012.11.021 Groeseneken, G., Maes, H.E., Beltran, N. and De Keersmaecker, R.F. (1984) A reliable approach to charge-pumping measurements in MOS transistors, IEEE Transactions on Electron Devices, 31, 42-53. doi: 10.1109/T-ED.1984.21472 Holmes-Siedle, A. and Adams, L. (1986) RADFETs: a review of use of metal/oxide/silicon devices as integrating dosimeters, Radiation Physics and Chemistry, 28, 235-244. doi: 10.1016/1359-0197(86)90134-7
Holmes-Siedle, A., Ravotti, F. and Glaser, M. (2007) The dosimetric performance of RadFETs in radiation test beams, IEEE Radiation Effects Data Workshop, 42-57. doi: 10.1109/REDW.2007.4342539 Jaksic, A., Ristic, G., Pejovic, M., Mohammadzadeh, A. and Lane, W. (2002) Characterization of radiation response of 400 nm implanted gate oxide RADFETs, 23rd International conference on microelectronics, 727-730. doi: 10.1109/MIEL.2002.1003360 Kahraman, A., Kaya, S., Jaksic, A. and Yilmaz, E. (2015) A comprehensive study on the photon energy response of RadFET dosimeters using the PENELOPE Monte Carlo code, Radiation Effects and Defects in Solids, 170:5, 367-376. doi: 10.1080/10420150.2015.1010167 Lu, L., Wang, M. and Wong, M. (2011) A new observation of the Elliot curve waveform in charge pumping of poly-Si TFTs, IEEE Electron Device Letter, 32, 506-508. doi: 10.1109/LED.2010.2104311 Martinez-Garcia, M.S., Torres del Rio, J., Palma, A.J., Lallena, A.M., Jaksic, A. and Carvajal, M.A. (2015) Comparative study of MOSFET response to photon and electron beams in reference conditions, Sensors and Actuators A, 225, 95-102. doi: 10.1016/j.sna.2015.02.006 McWhorter, P.J. and Winokur, P.S. (1986) Simple technique for separating the effects of interface traps trapped-oxide charge in metal-oxide-semiconductor transistors, Applied Physics Letters, 48, 133-135. doi: 10.1063/1.96974 O’Connell, B., Kelleher, A., Lane, W.