Improvement of the photo-bias stability of the Zn–Sn–O field effect transistors by an ozone treatment

Abstract

Highly improved negative bias illumination stress stability was achieved in a Zn-Sn-O field effect transistor after an ozone (O 3 ) treatment. The untreated ZTO FET exhibited a huge negative threshold voltage shift of 4.2 V but the O 3 treated device exhibited superior stability under NBIS conditions: the V th value of the O 3 treated ZTO FET for 600 s showed almost no change (DV th ¼ À0.07 V) under the same NBIS. The improvement in NBIS stability of the O 3 treated ZTO FETs was attributed to the lower oxygen vacancy concentration and retarded desorption of adsorbed oxygen under photon irradiation by the O 3 treatment.

Atomic layer deposited zinc tin oxide channel for amorphous oxide thin film transistors

“…The SS value was as low as 0.27 V/decade for 2.5Z1T channel as shown in inset of Fig. 3b and this value is comparable or better than other reports for ZTO transistors 8,9,11 The minimum off-current was generally in the range of 10 -13 -10 -14 A, which is below the maximum level of 10 -12 A for flat-panel displays. 1 The Zn/Sn ratio clearly influenced the mobility of the transistors.…”

“…The I ON /I OFF ratio was as high as ~10 9 -10 10 , which is comparable to or better than other reports for well-6 behaved transistors. 9,11 The I ON /I OFF ratio derived from the transfer curve for V DS of 20 V showed clear decreasing trend with decreasing Zn/Sn ratio; it was ~10 9 -10 10 for 3Z1T, 2.5Z1T, and 2Z1T and it decreased to ~10 7 -10 8 and further to ~10 6 for 1Z1T and 1Z2T, respectively. Turn-on voltage, 5 the gate voltage at the onset of the initial sharp increase in a transfer curve, was mainly at 0 -3 V except 1Z2T transistor, which was largely negative-shifted (-9 V).…”

“…[5][6][7][8][9] Other growth methods, such as pulsed laser deposition 10 , solution deposition 11 , inkjet printing 12 , and combustion 13 , have been reported. However, growth of ZTO by atomic layer deposition (ALD) and detailed study of its performance in devices have remained largely unexplored up to now.…”

Photo-bias instability of metal oxide thin film transistors for advanced active matrix displays

“…As a similar approach, the ozone treatment was also shown to reduce the oxygen deficiency concentration in the ZTO film. 76 Similar to oxygen HPA and the oxygen plasma treatment, an ozone treatment can annihilate the oxygen deficiencies of the ZTO film and prevent the NBIS-induced instability of the resulting ZTO TFTs. On the other hand, the surface of the evaluated ZTO film were not encapsulated, the retarded desorption of adsorbed oxygen species was partially responsible for the improvement in NBIS stability.…”

“…72 To improve the NBIS stability of metal oxide TFTs, the control of oxygen nonstoichiometry in the metal oxide semiconductor was also attempted based on the mechanism of photoionization of oxygen vacancy defects. Because the photoionization of V O to V 2þ O responsible for NBIS degradation is proportional to the concentration of preexisting V O defects in the channel layer, the intentional supply of oxygen species, such as high pressure annealing (HPA), 34,73,74 oxygen-containing plasma treatment, 75 and ozone radical treatment, 76 into the oxygen deficient channel region would result in a decrease in [V O ], leading to the suppression of NBIS-induced V th instability. This group reported that the removal of the V O defect centers using intentional oxygen diffusion results in the strong suppression of NBIS instability in IGZO TFTs, as shown in Fig.…”