Ti/Au/Al/Ni/Au Low Contact Resistance and Sharp Edge Acuity for Highly Scalable AlGaN/GaN HEMTs

• Published in: IEEE electron device letters Vol. 40; no. 1; pp. 67 - 70
• Main Authors: Yadav, Yogendra K., Upadhyay, Bhanu B., Meer, Mudassar, Bhardwaj, Navneet, Ganguly, Swaroop, Saha, Dipankar
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acuity; Aluminum gallium nitride; Aluminum gallium nitrides; Annealing; Contact resistance; current gain cut-off frequency; Edge acuity; GaN; Gold; HEMT; HEMTs; High electron mobility transistors; High temperature; MODFETs; Nickel; ohmic contact resistance; Ohmic contacts; Scaling formulae; Semiconductor devices; smooth surface; Titanium; Transconductance; Wide band gap semiconductors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2018.2884155

In this letter, we have reported a novel metal scheme Ti/Au/Al/Ni/Au for ohmic contact on AlGaN/GaN high-electron-mobility transistors. The reported metal scheme is observed to show minimum metal out-diffusion and sharp edge acuity at high-temperature annealing, which facilitates aggressive scaling of source-drain separation (<inline-formula> <tex-math notation="LaTeX">{L} _{\textsf {SD}} </tex-math></inline-formula>). We have demonstrated <inline-formula> <tex-math notation="LaTeX">{L} _{\textsf {SD}} </tex-math></inline-formula> as low as 300 nm with gate length (<inline-formula> <tex-math notation="LaTeX">{L} _{\textsf {g}} </tex-math></inline-formula>) of 100 nm for this metal stack. We observed improvement in ON-resistance (<inline-formula> <tex-math notation="LaTeX">{R} _{\mathrm{\scriptscriptstyle ON}} </tex-math></inline-formula>) from 3 to <inline-formula> <tex-math notation="LaTeX">1.25~\Omega \cdot </tex-math></inline-formula>mm, transconductance (<inline-formula> <tex-math notation="LaTeX">{g} _{\textsf {m}} </tex-math></inline-formula>) from 276 to 365 mS/mm, saturation drain current (<inline-formula> <tex-math notation="LaTeX">{I} _{\textsf {DS,sat}} </tex-math></inline-formula>) from 906 to 1230 mA/mm, and unity current gain frequency (<inline-formula> <tex-math notation="LaTeX">{f} _{\textsf {T}} </tex-math></inline-formula>) from 70 to 93 GHz by scaling <inline-formula> <tex-math notation="LaTeX">{L} _{\textsf {SD}} </tex-math></inline-formula> from <inline-formula> <tex-math notation="LaTeX">3~\mu \text{m} </tex-math></inline-formula> to 300 nm. The gate lengths for all devices were 100 nm.