Effects of composition on optical and electrical properties of amorphous In-Ga-Zn-O films deposited using radio-frequency sputtering with varying O2 gas flows

This study used powders containing various In₂O₃-Ga₂O₃-ZnO (IGZO) chemical compositions to manufacture targets by using a metallurgical process. The resulting targets were used to deposit amorphous In-Ga-Zn-O (a-IGZO) channel films using a radio frequency (r.f.) magnetron sputtering process. The average transmittance increased and achieved saturation; the resistivity increased in conjunction with the O₂ flow ratio of less than 6%; and subsequently, the resistivity decreased with increasing the O₂ flow ratio larger than 6%. This study examined the effects of compositions on electrical characteristics and optical properties of a-IGZO films at varied O₂ flow rates. The effects of composition on optical and electrical characteristics of a-IGZO films indicate that the average transmittance of a-IGZO films with more zinc atoms (approximately 50%) had more than 80% at various O₂ flow ratios because of the higher oxygen absorption of the zinc atoms. However, the average transmittance of a-IGZO film with a lower zinc atomic ratio (approximately 20%) without an O₂ flow ratio decreased to below 10% because of the indium and indium oxide crystalline precipitation in the indium-rich a-IGZO films. The results revealed that the resistivity increased when the gallium atomic ratio increased and the indium atomic ratio decreased.