Performance stability of AlGaN/GaN HFET: effect of plasma processing

Abstract

Effect of fluoride‐based plasma treatment on performance stability of AlGaN/GaN HFET was systematically investigated. The plasma‐based processes can introduce different type of damage that can be permanent or temporary, depending on electrical field in the device, plasma density, and energy of radicals and total process thermal budget. In order to understand more clearly the mechanism of fluorine based plasma treatment on device performance, we compare the effects of Ar, O2 and CF4 based plasma treatments applied before gate definition. Ar plasma was chosen for comparison with CF4 because of high ionization rate of Ar and chemically neutral behavior of Ar ions. Under the same medium range of 40 V DC bias in RIE system for these two gases, the shift of drain current and threshold voltage was similar that indicate the common mechanism of plasma damage. We supposed that the major effect for this phenomenon is a negative electron charge inserted in semiconductor during plasma treatment, because at the same accelerated field the penetration depth for electrons is higher than the penetration depth for fluoride ions. Devices stressed under impact ionization conditions show an improvement of breakdown voltage (for O2 plasma treatment) and some recovery of threshold voltage similar to “walkout effect”. This performance non‐stability raise the serious concern about application of fluorine based technology for power applications, where large voltage/current swing may push device to the impact ionization region. The experimental results show that the implementation of fluoride based plasma treatment for power device manufacturing can affect the performance stability of AlGaN/GaN power HFET. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of Low-Pressure Plasma Treatment Parameters on Wrinkle Features

“…It is known that the argon molecules are heavier than the oxygen and nitrogen molecules that have similar weights. Because argon molecules have a larger mass and, thus, a higher floating potential under the same electron temperature, the energy of argon ions bombarding the polymer surface is higher, leading to deeper penetration into the polymer surface and resulting in a thicker rigid layer [ 22 , 23 , 24 ]. The wavelength of the wrinkles ( λ w ) is proportional to the height of the rigid layer, as shown by the following equation [ 4 ]: where h and are the thickness and elastic modulus of the rigid layer, respectively.…”

Electrical and EDX‐analysis of CF4 and Ar plasma treated AlGaN/GaN HEMTs

“…Also, a negative threshold voltage shift was observed by Ref. [7] when devices were stressed under impact ionization conditions. Any significant difference between CF 4 -and Ar-treated samples was not observed (Fig.…”

Polarization‐Engineered n+GaN/InGaN/AlGaN/GaN Normally‐Off MOS HEMTs

“…In contrary, in more matured concept of the p‐GaN capping, only limited activation of Mg could be expected . Similarly, the established concept of fluoride implantation may face problems of low thermal and electrical stability . The reasons for less studied polarization engineering might be different.…”