砷化鎵半導體是無線通訊及光纖通訊的關鍵元件，全球砷化鎵的IC約有60%是用在手機上，因此砷化鎵在手機的功率放大器元件上扮演著非常重要的角色。本研究以負型光阻作為pHEMT閘極微影製程的開發，探討閘極製程的異常種類、進行實驗分析與製程改善，使pHEMT閘極製程穩定與良率得以提昇。
從微影製程的原理，當負型光阻曝光能量越小，顯影後光阻厚度越小(即顯影後光阻損失厚度越大)，閘極線寬亦越大。此外變更曝光晶片圖像可增加晶片曝光速率，減少晶片邊緣圖形焦距失焦的異常缺陷、增加晶片邊緣曝光shot的完整性。另外改變晶片製程順序發現曝光後烘烤的順序影響閘極線寬甚鉅。本研究所發現之負型光阻特性與製程順序的差異，可作為下次閘極製程開發的借鏡，縮短閘極製程開發時程、與製程穩定的改善方針。

GaAs semiconductor is an important component in wireless and optical fiber communications. Over 60% of GaAs’s IC chips are used in mobile power amplifiers worldwide. Hence GaAs plays an important role in mobile power amplifier components. This research uses negative PR resists for the pHEMT gate photolithography process development to make the process stable and to increase the yield.
From the photolithography process principle, as negative PR resist exposure energy gets smaller, the thickness of PR becomes smaller after developing (i.e. larger PR resist thickness loss);gate ADM CD also gets larger. Besides, by changing the exposure map,the exposure throughput is increased and the locally defocusing issue of the wafer edge ugly dies is reduced. In addition, by changing the process step after exposure bake, the Gate ADM CD is greatly influenced. This study found the characteristics difference of negative PR resists affected by the process steps. By following the rules obtained for the development of new gate process, the process development speed can be reduced and the process stability can be improved.

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