Change of electrical and chemical properties in amorphous SiZnSnO thin-film transistor with tunable threshold voltage by CF4 plasma treatment

초록

To control the threshold voltage (Vth), we investigated the effect of varying plasma treatment power using an Ar + CF4 gas mixture on the a-SiZnSnO (a-SZTO) active channel layer. As a result, the Vth shifted significantly from 2.37 V to-10.25 V, indicating that Ar + CF4 plasma treatment can effectively modulate the carrier concentration within the a-SZTO layer. In contrast, despite the increase in carrier concentration, the field-effect mobility exhibited only a modest change from 20.30 cm2/Vs to 23.21 cm2/Vs suggesting a limited improvement compared to the large shift in Vth. XPS analysis of the Zn 2p and O 1s spectra revealed prominent peaks associated with hydrogen, and the influence of hydrogen became more pronounced with increasing plasma power. These results imply that the changes in electrical properties of a-SZTO are driven by a combination of effects, including F-ion incorporation, Ar ion bombardment, and hydrogen-related interactions induced by the plasma treatment. Also applied localized Ar + CF4 plasma treatment to a single active channel layer, successfully inducing regions with different carrier concentrations within the same channel. Ultimately, demonstrated the ability to achieve two distinct Vth characteristics in a single active layer, suggesting that this approach holds potential for application in multi-valued logic.

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