Characterization of reactive ion etched surface of GaN using methane gas with chlorine plasma

Abstract

Effect of dry etching conditions on surface morphology and optical properties of GaN films in chlorine-based inductively coupled plasmasReactive ion etching of GaN has been carried out in two different plasma chemistries using 10Cl 2 /10Ar and 1CH 4 /9Cl 2 /10Ar at various applied radio frequency ͑rf͒ power. We have addressed the postetch surface characteristics of GaN, and the effect of CH 4 addition to chlorine plasma and the variation of rf power are discussed. Surface contamination, roughness, and stoichiometry have been determined from the results of secondary ion mass spectrometry. It is observed that in the case of plasma with 5% CH 4 , above 125 W, contamination of carbon is minimal and roughness is similar to that of the as-grown sample. At rf power less than 125 W, the Ga/N ratio of the etched surface is almost unity, whereas at rf power more than 125 W, it is more than unity. When the GaN surface is etched with only chlorine plasma, the surface is Ga excess at all rf power applied. The intensity of the main band-to-band photoluminescence peak is found to decrease when 10Cl 2 /10Ar is used, and the intensity was a minimum at 200 W. When 5% CH 4 is added to the plasma, the intensity at 200 W became almost the same as that of the as-grown sample, indicating minimal damage induced in the surface.

Recovery of Dry-Etch Damage in Gallium-Nitride Schottky Barrier Diodes

“…300 Å turn out to be slightly Ga deficient ͑Ga/N ratio of ca. 0.87͒ when the rf power increases up to 200 W. This is quite the opposite of the result of Cl 2 /Ar-based etching reported by Basak et al 5 As they observed, with an increase in rf power from 50 to 200 W, the Ga/N ratio increased up to ca. 3 under Cl 2 /Ar plasma in their conventional RIE system.…”

“…Several research groups 5,12 have carried out stoichiometric studies of the Ga/N ratio at different plasma etch chemistries. The Ga/N ratio at the surface is dependent on the combination of gases, and each gas composition in the plasma as well as plasma-source type, rf power, source power, substrate temperature, and process pressure.…”

“…Much effort has been made on dry etching the GaN using various plasma sources including Cl 2 /Ar, CH 4 /Cl 2 /Ar, BCl 3 , Cl 2 /H 2 /Ar/CH 4 , and SiCl 4 gases to enhance etch rate and etching performance. [5][6][7][8] These etching methods with chlorine-radial plasma chemistry normally produce etch damage on the surface. This, therefore, degrades Schottky barrier characteristics at electrode-metal/semiconductor interfaces when fabricating field effect transistor ͑FET͒ devices.…”

Method for modulating the wafer bow of free-standing GaN substrates via inductively coupled plasma etching

“…With the further increase in the ICP etching time from 21 to 77 min, the intensity of the NBE became stronger, but that of the YL disappeared. The intensity of the NBE was found to increase with the increase in the surface roughness, and change in the surface reflectivity and decrease in the defects were observed to act as nonradiative recombination centers [19]. Reshchikov and Morkoc -reported that V Ga -O N complex defects increase the YL emission and decrease the density of V Ga -O N complex defects with increasing GaN thickness [20].…”

Cl2/Ar based inductively coupled plasma etching of GaN/AlGaN structure

“…D. Basak et. al, have also reported similar trend in etched surface roughness during GaN etching using RIE with 1CH 4 /9Cl 2 /10Ar gas chemistry at 10Pa of process pressure [18]. They have reported the highest roughness ~ 10nm at RF power of 75W, which decreased as RF power is increased due to reduction in carbon contamination.…”