Paper TF1-FrM8
Sputtered In₂O₃ and ITO Thin Films Containing Zirconium

Friday, October 19, 2007, 10:20 am, Room 602/603

The deposition of high-quality tin-doped In₂O₃ (ITO) films by vacuum sputtering is well established. Nevertheless, coating specialists are keenly aware that maintaining high electrical and optical quality in a production environment represents significant challenges. ITO films with high carrier concentration and mobility generally are produced using high substrate temperature (250-350°C) in an ambient where the oxygen partial pressure is controlled to yield a slight oxygen deficiency in the film. Unfortunately, if the sputter ambient becomes too oxygen deficient, the optical transparency of the film decreases. The challenge during ITO deposition is to incorporate enough oxygen to produce films with high transparency while retaining slight oxygen deficiency to yield optimum electrical properties. In a large-area production coating system, this critical oxygen partial pressure must be achieved not only across a large deposition area, but also take into account variations such as target use, seasonal changes, and maintenance activities. Our recent investigations have identified a method to produce ITO-like films that are less sensitive to variations in the oxygen-containing deposition ambient. We are studying the effect of adding small amounts of Zr to both In₂O₃ and ITO ceramic sputtering targets. These targets are then used to produce thin films on glass substrates by r.f. magnetron sputtering. Electrical (Hall) and optical (UV-Vis-NIR spectrophotometry) analysis of these films shows that high-quality Zr-doped In₂O₃ (IZrO target = 9 wt.% ZrO₂+ 91 wt.% In₂O₃) films can be produced at high substrate temperatures (250-350°C) without adding oxygen to the sputter ambient. This result is in contrast to films produced from typical ITO targets (ITO target = 9 wt.% SnO₂+ 91 wt.% In₂O₃), where deposition in pure Ar yields films with very poor optical transparency. Films produced using a target where a small amount of Zr is added to a standard ITO target (ITO:Zr target = 1 wt.% ZrO₂+ 9 wt.% SnO₂+ 90 wt.% In₂O₃) show that the Zr addition allows for a broader range of oxygen partial pressure during deposition. We believe these results may embody significant advantages for large-area ITO film production, and could point the way toward similar benefits in other TCOs such as those based on ZnO or SnO₂ This abstract is subject to government rights.