Dry Surface Cleaning of Plasma-Etched Hemts

1992 ◽  
Vol 282 ◽  
Author(s):  
S. J. Pearton ◽  
F. Ren ◽  
A. Katz ◽  
U. K. Chakrabarti ◽  
E. Lane ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
High Electron Mobility Transistors ◽  
Surface Cleaning ◽  
High Electron ◽  
Chemical Cleaning ◽  
Electron Mobility Transistors ◽  
Short Period ◽  
Wet Chemical ◽  
Dry Etch

ABSTRACTFabrication of sub-micron high electron mobility transistors (HEMTs) involves dry etch removal of GaAs from an underlying AlGaAs or InGaAs stop layer. The etch selectivity is achieved by formation of AlF3 on AlGaAs, or InCl3 and InF3 on InGaAs, which must be removed before processing can proceed. Wet chemical cleaning has difficulty in such a situation because of surface tension effects. We have investigated use of Electron Cyclotron Resonance (ECR) H2 or Ar discharges, or hexafluoroacetylacetone (HFAC) vapor, for in-situ dry etch cleaning of HEMTs exposed to low bias BCl3/SF6 discharges. The HFAC vapor can remove most of the remnant fluorine, but is effective only when the sample is heated above ∼250°C. This relatively high temperature is not compatible with in-situ cleaning of the etched device. Low-bias(−75V) sputter cleaning with an Ar discharge removes all remnant Cl and ∼40% of the F, but dc biases above -125V are required for complete cleaning, and this ion bombardment can lead to damage in the HEMT. ECR H2 discharge exposure is effective in removing all Cl- and F-related residues in a short period (∼5 mins) with low dc biases (−25 V) on the sample.

Improved device performance of recessed-gate AlGaN/GaN HEMTs using by in-situ N2O radical treatment

2022 ◽  
Author(s):  
Xinchuang Zhang ◽  
Mei Wu ◽  
Bin Hou ◽  
Xuerui Niu ◽  
Hao Lu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Electron Mobility Transistors ◽  
Device Performance ◽  
High Electron ◽  
Electron Mobility Transistors ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Recessed Gate ◽  
Gate Recess

Abstract In this work, the N2O radicals in-situ treatment on gate region has been employed to improve device performance of recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The samples after gate recess etching were treated by N2O radicals without physical bombardment. After in-situ treatment (IST) processing, the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST. The fabricated HEMTs with the IST process show a low reverse gate current of 10-9 A/mm, high on/off current ratio of 108, and high fT×Lg of 13.44 GHz·μm. A transmission electron microscope (TEM) imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface. X-ray photoelectron spectroscopy (XPS) measurement shows that the content of the Al-O and Ga-O bonds elevated after IST, indicating that the Al-N and Ga-N bonds on the AlGaN surface were broken and meanwhile the Al-O and Ga-O bonds formed. The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.

Donor passivation in pseudomorphic-high electron mobility transistors due to plasma-incorporated fluorine impurities observed using x-ray photoemission spectroscopy

2006 ◽  
Vol 21 (5) ◽  
pp. 1331-1335 ◽  
Author(s):  
Hiroyuki Uchiyama ◽  
Takeshi Kikawa ◽  
Takafumi Taniguchi ◽  
Takashi Shiota
Keyword(s):  
Electron Mobility ◽  
High Electron Mobility Transistors ◽  
Photoemission Spectroscopy ◽  
High Electron ◽  
Plasma Exposure ◽  
High Electron Mobility ◽  
X Ray ◽  
Electron Mobility Transistors ◽  
Wet Chemical ◽  
Wet Chemical Etching

To investigate the effect of plasma-incorporated fluorine on Si donors in pseudomorphic-high electron mobility transistors (P-HEMTs), we used x-ray photoemission spectroscopy to analyze three layers near the Si δ-doped layer and the Si δ-doped layer itself, in which we previously found fluorine accumulation after post-thermal annealing following fluorocarbon-based plasma exposure. For this evaluation, we developed controllable and low-speed AlGaAs wet-chemical etching using citric-acid-based wet etchant. We used it to expose one of the layers to be analyzed: one 7.5 nm above the Si δ-doped layer, one 1.5 nm above it, the δ-doped layer itself, and one 1.5 nm below it. We found that the accumulated fluorine localized in the δ-doped layer and reacted with Si donors. This is apparently the main reason for the carrier passivation in the fluorocarbon-based plasma-exposed P-HEMTs.

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