氧化鋅鎂鉿熱退火及雷射表面處理之薄膜特性

Abstract

本論文利用射頻磁控濺鍍(Radio frequency magnetron sputtering)法在室溫下成長HfxMg0.05Zn0.95-xO (x = 0、0.025、0.05、0.075、0.1)薄膜於康寧玻璃基板及矽晶圓基板上，再經由爐管空氣下200、300、400、500、600 oC的後熱退火處理及不同能量40、60、80、100、120 mJ/cm2雷射表面處理後，對材料性質進行研究與探討。 從電子微探儀分析比較HfxMg0.05Zn0.95-xO薄膜與原靶材成分發現，相較於靶材，薄膜中鉿原子比例較靶材高出約一倍，經過爐管空氣下後熱退火處理，薄膜中各原子比例則沒有明顯改變。透過X光繞射光譜觀察到2θ= 34o 左右時有(002)氧化鋅繞射峰訊號，隨鉿原子比例摻雜增加其繞射峰半高寬增加且往小角度偏移，顯示鉿摻雜取代具非晶化效果。穿透光譜可知道在可見光波長下薄膜平均穿透率超過80%，且吸收邊界介於紫外光波長間，且吸收邊界隨鉿原子摻雜比例增加往短波長偏移。由Tauc bandgap fitting將薄膜光學能隙計算得知，薄膜光學能隙隨鉿原子摻雜比例增加10 at%，會由3.35 eV增加至3.95 eV。而熱退火也會影響光學能隙。薄膜電阻率由電流-電壓量測計算可知，在鉿原子摻雜至2.5 at% 其電阻率約為2x107 ohm cm，經爐管後熱退火處理有顯著的改善。 雷射表面處理在濺鍍氣氛為純氬氣之HfxMg0.05Zn0.95-xO薄膜，在發數為1發下，能量提升至80 mJ/cm2，表面出現裂痕且薄膜顏色發生變化，而能量超過100 mJ/cm2，薄膜有剝落現象。發數為1000發下，能量提升至60 mJ/cm2，則薄膜即出現剝落現象。

The films were deposited onto glass substrates (Eagle 2000, Corning Inc.) and/or silicon(100) wafer substrates by rf sputtering from HfxMg0.05Zn0.95-xO (x = 0、0.025、0.05、0.075、0.1) targets at room temperature. We analyze the film properties before and after annealing at 200、300、400、500、600 oC. Other set of samples were treated by KrF excimer laser with various laser power density of 40、60、80、100、120 mJ/cm2.The material properties of thin films were characterized by EPMA、XRD、transmission spectra、SEM and current-voltage measurement, etc. From the results of EPMA, Hf concentrations of sputtered films were twice those of original targets. The sputtered Mg0.05Zn0.95O thin films exhibited strong (002) preferred orientation with XRD peak located at 2θ= 34o. With the increase of Hf doping concentration, the XRD peak shifted slightly to lower angle due to the replacement of Mg or Zn atoms with Hf atoms in the crystals. The full-width-at-half-maximum (FWHM) of XRD peak were also greatly increased, indicating that the material amorphorization proceeds with the addition of Hf. All HfxMg0.05Zn0.95-xO thin films were highly transparent (> 80 %) in the visible region and had sharp absorption edges in the UV region. The absorption edge shifts to the shorter wavelength as the Hf content increases, inferring the increase of tauc bandgap. Optical bandgap calculated by Tauc plot increased from 3.35eV to 3.95eV as the concentration of Hf increased from 0 to 10 at.%. Thermal annealing also influenced the optical bandgaps of sputtered HfMgZnO thin films. Electrical resistivity of Hf0.025Mg0.05Zn0.925O thin films were 2×107 ohm-cm and remarkably improved after post thermal annealing. For HfxMg0.05Zn0.95-xO thin films treated by KrF excimer laser. With one irradiation pulse, the surface of the films were cracked and colored as the irradiation laser power density was below 80 mJ/cm2 . Beyond this power density, the films started to peel off. With 1000 pulses of laser irradiation, the films immediately peeled over 60 mJ/cm2.