Proton-Induced Mobility Degradation in FinFETs With Stressor Layers and Strained SOI Substrates

• Published in: IEEE transactions on nuclear science Vol. 58; no. 3; pp. 800 - 807
• Main Authors: Kobayashi, D, Simoen, E, Put, S, Griffoni, A, Poizat, M, Hirose, K, Claeys, C
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2011; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Degradation; FinFETs; Logic gates; Proton irradiation; Radiation effects; Samples; semiconductor device radiation effects; SOI; Statistical analysis; Statistical methods; Strain; strain engineering; Stress; Stresses; Tuning
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2011.2109967

Proton irradiation effects on fin-type field effect transistors (FinFETs) are examined from the viewpoint of their electrical-performance parameter of mobility. They are fabricated with various types of combination of strain/stress techniques to control their mobilities. The base stress level is globally modified by means of nonstrained or strained silicon-on-insulator wafers. Some process splits, additionally, receive a local strain tuning with a contact-etch-stop layer (CESL). Both n - and p -type FinFETs are evaluated. A 60-MeV proton irradiation with a fluence of 10 12 p/cm 2 leads to mobility changes for wide-fin samples: degradation for n -type and enhancement for p -type. These mobility variations can be explained with a change in the number of charged interface traps at the Si and buried-oxide interface. Narrow-fin devices exhibit mobility changes unnoticeable statistically. A comparison with previous studies indicates an elevated source/drain structure plays a role in this mobility preservation. Although the mobility is kept intact in the narrow-fin samples, a close investigation based on a two channel-component model can reveal noticeable mobility variations at a component level. In this study, observed mobility changes are complex depending on the adopted stress techniques as well as process parameters and cannot be explained by the stress levels simply.