利用混合式微影技術製作THz輻射場之光混頻器

Abstract

利用兩連續雷射光混頻(photomixing)產生THz輻射場，這方法至少需要兩個基本元件：一是穩定之兩單頻可調連續的雷射光源，與一有效率可將近紅外雷射光轉換成次毫米波之光混頻器(photomixer)。本論文就是希望能製作一個具備高轉換效率、高頻寬、高受光強度、以及低雜訊等效能的光混頻器。 本論文是研究混合式微影（Mix-Match Lithography）製程技術，已完成光混頻器（photomixer），也就是結合光學微影（OL）和電子束微影（EBL）兩道程序，如此兼具有電子束微影高解析度和高密集度，以及光學微影高產能的優點。關鍵性製程，如密集的MSM結構、閘極、接觸窗等，可由電子束直寫微影製作，而其他大尺寸的圖案層則交由光學微影製作。 為了使製程保持一定的穩定性，分別對光學微影和電子束微影二部分進行製程條件測試，以找出最佳製程條件，並且研究混合製程的對準問題。最後在尺寸為7000μm二臂螺旋形天線的中心，大小為20μm×20μm的主動區域，成功直寫線寬為0.7μm、間距為1.3μm的交錯式指尖電極（interdigitated electrode）結構。

The photomixer is a compact solid-state source that uses two single-frequency tunable diode lasers to generate a THz difference frequency by photoconductive mixing in low-temperature-grown GaAs (LTG-GaAs). We choose the self-complementary spiral antenna to be the photomixer because its high convertible efficiency, wide bandwidth, and frequency-independent. In this thesis, the mix-match lithography process technology is proposed to accomplish the photomixer. This technology is to mix optical lithography (OL) and electron beam lithography (EBL). It have the advantage of high resolution of EBL and high throughput of OL. Using OL to accomplish the big size patterns, like spiral antennas. Then, using EBL to directly writing the critical structure, like interdigitated electrode structures in the active region of antenna. The key of this process technology is to match and align the two layers. It is important to keep the process stable. We test OL and EBL process to find out the best process conditions or the process window. We successfully made 2-arm spiral antennas with interdigitated electrode structures of 0.7µm line-width and 1.3µm line-space in the 20μm×20μm active region of 7000µm antenna.