以SU-8為TSV結構的低電阻銀之低溫噴墨列印和填充製程

Abstract

目前預測摩耳定律可能於2020年之前失效，因為晶片微縮到5奈米以下時，半導體製程將達到物裡極限。在三維半導體製程和封裝技術之下，垂直矽穿孔(TSV) Through-Silicon Via金屬連結技術，為微系統製造的重要技術之一；是一種能讓延續摩耳定律演進的互連技術。然而傳統TSV製程包含晶圓薄化、鑽孔、導電材料填孔所需之電鍍、濺鍍和化學或物理沉積製程運用等，製程複雜且具汙染性。此外根據(IOT)Internet Of Things物聯網的成熟發展，市場對感測微系統的需求不斷增加，TSV應用於軟性基板的需求也增加。因此本論文沿用先前實驗室所開發之噴墨式低電阻導線製程技術，以SU-8製作TSV結構應用於軟性基板中。透過噴墨列印填充技術的低汙染、低耗能與低成本等具有綠能製造之特性，研發出低溫噴墨列印填充技術，於相對濕度80%、溫度低於600C的控制條件下，藉由層與層間之銀鏡反應，不僅可以消除噴墨列印結構因為咖啡環效應所造成材料填充困難，或孔洞內部填充不完整所產生之製程可靠度問題外，更提高了噴印填充材料的導電性並實現具高深寬比的TSV結構填充。該技術已成功實現口徑50μm、高度80μm、300μΩ•cm電阻率之垂直銀導線結構與軟性基板之上。

TSV is a critical interconnect structure for signal transmission with high density, speed, and flexibility in microsystems. Instead of electroplating, recent studies also explored the feasibility of inkjet printing and filling process for (TSV) Through-Silicon Via fabrication due to the superior characteristics of less chemical waste, processing time, and process temperature applicable for different TSV substrates. Nevertheless, the approach still needs to resolve the process difficulties such as process instability, high via resistance and aspect ratio restriction, etc. In the thesis, a low temperature (with 60°C) inkjet printing and filling process is developed to realize low resistive Ag TSV with the aspect ratio of via depth vs. diameter from 2 to 5 in a SU-8 substrate potential for flexible microsystem applications. Combining humidity control and layer-by-layer Ag mirror reaction, the proposed process technology can accomplish fully filled TSV with the lowest electrical resistivity of 300-cm in comparison with the prior printing and filling technologies. The newly developed inkjet printing and filling technology for TSV fabrication in a flexible substrate has shown a great potential not only for flexible microsystem but also 3D-IC and MEMS applications.