熱敏阻型紅外線焦面陣列感測元的技術發展

Abstract

本論文之研究旨在探討免凍式紅外線焦面陣列輻射感測元件的元件製作，感測材料特性，功能量測，以及感測元與ＩＣ之匹配製程設計。元件製作之關鍵在細微加工技術形成一熱隔離良好之懸浮薄膜結構，並在此結構上以不同的電阻性材料形成感測元件。功能之測量含感測材之電阻率與其溫度係數、雜訊以及電壓反應率等等。由測量結果可計算出歸化偵測度與等效溫差做為紅外線焦面陣列之功能評估。焦面陣列的製程設計原則是探討與目前積體電路代工廠之標準互補式金－氧－半元件製程（ＣＭＯＳ）相匹配，以期達到低成本量產之目的。研究之感測材薄膜有白金、鍺與多晶矽等三種。在電阻溫度係數方面，由測試結果得知：不同厚度之白金薄膜值在0.27%/oC 到0.31%/ oC 之間；各種退火溫度下之鍺薄膜是值在-0.1%/ oC 至-4.5%/ oC 範圍；多晶矽則依雜值濃度的差異其電阻溫度係數可從-0.01%/ oC 到-5.9%/ oC。可瞭解半導體薄膜材料之電阻溫度係數較大，故亦擁有較高之電壓反應率。在雜訊量度方面，白金薄膜主要的雜訊源是電阻本身之強生雜訊；鍺及多晶矽薄膜主要的雜訊源則是1/f雜訊，遠大於元件本身之強生雜訊，而使此種半導體元件的信號雜訊比表現較白金型為差。以鍺薄膜製作之單感測元電壓反應率之量測，在大氣及真空的狀態下，分別得到 7000以及400000 V/W 的靈敏度。綜合量測結果，並以1.2 □m ＣＭＯＳ製程為設計基準下，我們可估算此三種材料之歸化偵測度D*及等效溫差NETD。如何將微加工技術完成之感測元件與標準互補式金－氧－半元件之製程相互整合來製作，亦是本文之重點討論項目，此舉可使現有的積體電路代工廠完成大部份的製程。因此，其產率及製作成本都可得特殊應用積體電路（ＡＳＩＣ）製作般的經濟效益。

In this thesis, fabrication and characterization of CMOS-process-compatible microbolometer IRFPAs detectors are explored. These monolithic IRFPAs made of metal and semiconductor films and having thermally isolated structures are fabricated by combining IC process with bulk micromachining technique. The resistivity, TCR, noise and responsivity of single microbolometers of various material films have been fabricated and measured, which performances were characterized by calculating the D* and NETD for proposed IRFPA detectors. In the studies, platinum, germanium and polysilicon thin films are used as the sensing materials. The platinum films shows TCR values of 0.27, 0.28 and 0.31 %/oC with 200, 500 and 1000 A thickness, respectively. For germanium, TCR is ranged from -0.1 to -4.5 %/ oC with various annealing conditions. While for polysilicon thin films, TCR values extended from -0.01 to -5.9 %/ oC with different impurity dosage. Our noise measurement found that single Pt bolometer exhibits only Johnson noise, but germanium and polysilicon sensors show significant 1/f noise over their Johnson noise. Our experiment shows that one of the fabricated germanium bolometers has voltage responsivity of 7000 and 400000 V/W in air and vacuum, respectively, with proper annealing around 370 oC. The values of D* and NEDT of various proposed IRFPA detectors, based on our measured results and the design rule of a 1.2 □m CMOS-process, are also calculated theoretically. It shows that the Pt IRFPA detector has the best performance in the three materials. The processes are designed to be compatible with the standard CMOS process in current IC foundries make it possible to commercialize the IRFPA devices with low cost and high reliability in the future.