Incorporation of High-k HfO2 Thin Films in a-IGZO Thin Film Transistor Devices

In this study, HfO2 [hafnium oxide] thin films are investigated extensively as part of indium gallium zinc oxide (IGZO) thin film transistor (TFT) devices. They are incorporated into the TFTs, both as a gate insulator and a passivation layer. First, the HfO2 [hafnium oxide] films themselves are investigated through an annealing study and through I-V and C-V measurements. Then, HfO2 [hafnium oxide] is suggested as a replacement for commonly used SiO2 [silicon dioxide] gate insulator, as it has a dielectric constant that is 4 – 6 times higher. This higher dielectric constant allows for comparable TFT performance at a lower operation voltage (5 V vs. 20 V). Finally, HfO2 [hafnium oxide] is applied as a passivation layer in IGZO TFTs, and an annealing study is conducted to determine which processing steps will allow for optimal TFT performance. The HfO2 [hafnium oxide] passivation layer proves to show a good level of uniformity. Therefore, taking all results into consideration, both HfO2 [hafnium oxide] gate insulators and passivation layers can be used in conjunction with IGZO TFTs to produce a full electrowetting array, which should prove to be useful in “lab on a chip” studies.