Characteristics of the ZnO thin film transistor by atomic layer deposition at various temperatures

Abstract

ZnO thin films were deposited by atomic layer deposition (ALD) at various temperatures and the resulting electrical and chemical properties were examined. The fraction of O-H bonds in ZnO films decreased from 0.39 to 0.24 with increasing processing temperatures. The O/Zn ratio decreased from 0.90 at 70 • C to 0.78 at 130 • C. The carrier concentration and resistivity changed sharply with decreasing temperature. The ZnO thin film transistors (TFTs) were fabricated at processing temperatures of 70 to 130 • C and the electrical properties of the TFT were as follows: the field-effect mobility ranged from 8.82 × 10 −3 to 6.11 × 10 −3 cm 2 V −1 s −1 , the on/off current ratio ranged from 1.28 × 10 6 to 2.43 × 10 6 , the threshold voltage ranged from −12.5 to 14.7 V and the subthreshold swing ranged from 1.21 to 24.1 V/decade. The electrical characteristics of the ZnO TFT were enhanced as the processing temperature decreased.

Electrical Characteristics of Top-Down ZnO Nanowire Transistors Using Remote Plasma ALD

“…The advantage of using remote plasma ZnO ALD compared to water-based oxidation [3]- [5] is the reduction of OH impurities which can increase film resistivity. ZnO nanowires were fabricated using an anisotropic reactive ion CHF 3 etch in an OIPT 80+ system to form nanowires at the sides of the SiO 2 pillars, as shown in Fig.…”

“…Even though there have been numerous reports on ZnO deposition techniques, recent attention has been focused on conventional atomic layer deposition (ALD) as the preferred growth method due to the low growth temperature and good control of thickness, composition, and uniformity [3]. ZnO thin-film transistors (TFTs) fabricated with thermal and plasma-enhanced ALD have shown excellent electrical characteristics [3], [4].…”

Remote plasma enhanced atomic layer deposition of ZnO for thin film electronic applications

“…3(b). However, it is still high compared with other ALD ZnO films [6,8]. The carbon content can be further reduced by optimizing the DEZ dose time.…”

“…However, these depositions require high temperatures and it is difficult to perform large area deposition on low cost substrates. Recent attention has been focused on conventional ALD as the preferred growth method due to the low growth temperature, good crystallinity and good control of thickness, composition and uniformity [6][7][8][9][10]. ZnO thin film transistors fabricated with ALD ZnO have shown excellent electrical characteristics [6][7][8].…”

“…This is called thermal ALD and has been extensively studied and can be considered as a model system for ALD [6][7][8][9][10]. Recently, plasma assisted ALD method has been explored [11][12][13][14][15][16][17][18][19][20] and it is found that the use of plasma species as reactants allows more freedom in processing conditions and wider range of material properties compared with the conventional thermal ALD.…”