Effects of impurity hydrogen in amorphous In-Ga-Zn-O: ultralow optimum oxygen supply for ultrahigh vacuum sputtering and bandgap widening by impurity hydrogen
Effects of impurity hydrogen in amorphous In-Ga-Zn-O: ultralow optimum oxygen supply for ultrahigh vacuum sputtering and bandgap widening by impurity hydrogen
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非晶In-Ga-Zn-O中杂质氢的影响：超高真空溅射的超低最佳供氧量和杂质氢的禁带宽度
DOI：
10.1002/pssa.201700832
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
and Toshio Kamiya
中科院分区：
文献类型：
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作者：
Keisuke Ide;Kyohei Ishikawa;Haochun Tang;Takayoshi Katase;Hidenori Hiramatsu;Hideya Kumomi;Hideo Hosono;and Toshio Kamiya
通常认为，为了减少氧缺乏并抑制自由电子的产生，器件品质氧化物半导体的沉积需要稍微高的氧供应。本文报道了这样的高氧供应对于代表性的非晶氧化物半导体，非晶In-Ga-Zn-O（a-IGZO）不是必要的要求。也就是说，最佳氧流量比（RO 2）对于基准压力为10 - 10 - 4Pa的标准（STD）溅射是10 - 3%，而对于基准压力为10 - 10 - 7 Pa的超高真空（UHV）溅射则急剧降低到10 - 3-10 - 5%。我们认为超低最佳氧供应来源于残余氢，因为STD和UHV薄膜的氢含量不同，分别为1020和1019 cm −3。该比较还表明，杂质氢的包含使光学带隙加宽了100.1eV，这通过在10500 °C下对STD a-IGZO膜进行后退火而导致带隙最小值，伴随着以H2O的形式去除并入的氢。此外，晶化起始温度显着降低了约100 K的UHV a-IGZO薄膜。
It is generally thought that deposition of device‐quality oxide semiconductors requires somewhat high oxygen supply in order to reduce oxygen deficiency and to suppress generation of free electrons. This paper reports that such high oxygen supply is not an essential requirement for a representative amorphous oxide semiconductor, amorphous In‐Ga‐Zn‐O (a‐IGZO). That is, the optimum oxygen flow rate ratio (RO2) is ≈3% for standard (STD) sputtering with the base pressure of ≈10−4Pa, while it is reduced dramatically to 10−3–10−5% for ultrahigh vacuum (UHV) sputtering with the base pressure of ≈10−7Pa. We consider that the ultralow optimum oxygen supply originates from residual hydrogen, because the STD and the UHV films have different hydrogen contents at the orders of 1020and 1019cm−3, respectively. This comparison also suggests that the inclusion of impurity hydrogen widens the optical bandgap by ≈0.1 eV, which causes a bandgap minimum by post annealing at ≈500 °C for the STD a‐IGZO films accompanying the removal of incorporated hydrogen as H2O. Furthermore, crystallization onset temperature is reduced remarkably by ≈100 K for the UHV a‐IGZO films.