整合噴墨技術與 CMOS 系統晶片

Integration of Inkjet Printing Technology with CMOS System-on-Chip

李長鴻(Chang-Hung Lee)

指導教授 ： 林致廷

國立臺灣大學/電機資訊學院/電子工程學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.00904

摘要

有機電子材料的發展，將賦予有機電子元件更多樣化的功能，例如具有生物相容性或氣體/化學感測特性的材料，能使有機元件應用在更多領域。然而有機電子電路受限於材料與製程的瓶頸，其運算效能仍難與矽晶片匹敵。若將有機電子與矽半導體元件，在晶片層面整合製作，即能兼取兩者之優點製作更多功能、高度整合且具有良好速度的新型晶片。本論文主要發展非接觸式噴墨印刷製程，噴印多種有機電子元件，並進一步將有機電子元件噴印於矽晶片表面，製作垂直堆疊結構，有效節省晶片面積的同時，亦提供整合度更高、更低功率的電子元件應用。以下為所研發之噴墨電子元件摘要介紹：
1. 雙絕緣層可調變臨界電壓電晶體
由可整合CMOS製程的電子電路著眼，利用噴墨製程製作全噴墨全有機的電晶體元件，展現可在任意表面製作簡易電子電路的製程能力。並以局部噴印high-k / low-k雙絕緣層製程，利用氟系聚合物的壓電特性，使絕緣層中產生內建電場，調變電晶體的臨界電壓，實驗結果可由-13 V平移至10 V。以此特性在同一基板上製作空乏型與增強型電晶體，實現更有彈性的電路架構。
2. 噴墨式濕度感測器
為了展現以噴墨製程實現感測器整合晶片的潛力。以有機導電聚合物材料PEDOT:PSS與噴墨製程，製作低成本低功耗的濕度感測器元件，並驗證感測材料偵測其他氣體的可能性。感測材料添加二氧化矽以及鋁氧化鋅奈米顆粒，使其對水汽的感測靈敏度提昇一倍以上，且元件的穩定性亦有顯著提昇。最後進一步以材料分析光譜探討感測機制成因。發現奈米顆粒對於水汽的物理吸附特性，使得混合感測材料的靈敏度有進一步提昇。
3. 金屬、有機導電材料傳導介面
於研究過程中亦發現，因材料的功函數差異，導電高分子材料與鋁金屬接面，會產生接觸電阻的問題。造成有機電子元件與矽晶片無法形成良好的歐姆接觸。初步研究使用奈米金溶液在鋁電極表面噴印一層奈米金薄膜，可以有效改善接觸問題。實驗將鋁金屬電極上噴印奈米金粒子薄膜作為中介層，再噴印一層PEDOT:PSS薄膜於兩電極中央通道，測量其導電性有明顯改善。
4. 實做噴墨印刷濕度感測器整合電路晶片
使用台積電0.35 μm製程技術以及BioMEMS後製程，將濕度感測材料噴印於CMOS晶片上層金屬電極表面，製作整合感測晶片。由於有機導電材料可在室溫下感測的特性，使感測元件不需額外加溫器，因此可與CMOS晶片做垂直堆疊整合，相較於現有3D IC製程技術，噴墨印刷更適合於晶片表面直接製作氣體感測器陣列。感測器晶片操作在3V，平均功耗僅154 μW，為適於應用在室內空氣品質監測、物聯網、醫療照護的低功率感測晶片。

關鍵字

噴墨印刷 ； 有機電晶體 ； 導電聚合物 ； 氣體感測器 ； 奈米粒子 ； 生物微機電 ； 立體晶片 ； 異質整合

並列摘要

The organic electronic devices provide promising features with the development of organic materials. For example, the organic materials with bio-compatible or gas/chemical sensing function could be utilized in the applications for bio or sensor networks. However, compare to silicon IC, the operation speed of organic circuits is still limited by the materials and fabrication processes. If the organic devices could be integrated with silicon devices on the chip level, we could take both strengths from organic and silicon electronic devices, and build a highly-integrated, multi-functional novel IC. In this dissertation, a heterogeneous integration technique which vertically connects organic electronic devices and CMOS IC is demonstrated by non-contact inkjet printing process. By inkjet printing technique, more integrated devices could be realized with lower power consumption, higher integration, and save more chip area.
First, an all-inkjet-printed organic thin-film transistor (OTFT) with double insulator layer is proposed. By using the double-layer structure with different dielectric materials, the threshold-voltage of OTFT can be adjusted. The threshold-voltage shift can be controlled by changing the composition of dielectric layers. That is, an enhancement-mode OTFT can be converted to a depletion-mode OTFT by selectively printing additional dielectric layers to form a high-k/low-k double-layer structure. The threshold-voltages of the OTFTs shift between -13 V and 10 V. This study demonstrates an additional design parameter for organic electronics manufactured using inkjet printing technology.
Than an inkjet printable humidity sensing material, PEDOT:PSS, is developed to improve the fabrication capability. Besides, different kinds of nanoparticles, SiO2 and aluminum zinc oxide (AZO), are also employed to enhance the stability and sensitivity to humidity sensing. Based on experimental results, the sensitivity can be improved by 100%; the stability can also be noticeably enhanced. To understand the sensing mechanism, a series of material analysis method is executed. Based on the material investigations, the sensing enhancement is due to physical adsorption of the blending nanoparticles. This work proposes a high sensitivity and low cost humidity sensing material for different applications
Because of the energy barrier between conductive polymer and metal, most of the metal/organic interfaces are difficult to form an ohmic contact, which could impede the integration of conductive polymer devices and CMOS chip. An inkjet-printed gold nanoparticle film as a buffer layer could modify the aluminum electrode and conquered the contact barrier. The improvement of contact resistance between nano-gold-modified aluminum electrodes and PEDOT:PSS film is experimentally tested.
Finally, a low-power, wide-dynamic-range integrated humidity sensing chip is implemented using a printable polymer sensing material with an on-chip pulse-width-modulation interface circuit. By using the inkjet printing technique, PEDOT:PSS that has humidity sensing features can be printed onto the top metal layer of a 0.35 μm CMOS IC. The developed printing-on-chip humidity sensor achieves a heterogeneous three dimensional sensor system-on-chip architecture. The humidity sensing of the implemented printing-on-chip sensor system is experimentally tested. The power consumption keeps only 154 μW. This printing-on-chip sensor provides a practical solution to fulfill an miniaturized sensing system for the applications in healthcare, indoor-air-quality monitoring, and machine-to-machine networks.

並列關鍵字

inkjet printing ； organic thin-film transistor ； conductive polymer ； gas sensor ； nanoparticle ； Bio-MEMS ； 3D IC ； heterogeneous integration

參考文獻

[15] 林世惠, "噴墨式有機濕度感測元件之開發," 碩士論文, 國立台灣大學工學院工程科學及海洋工程研究所, 2012.

[18] 許峻豪, "軟性電子元件與噴墨技術之開發與應用," 碩士論文, 國立臺灣大學工程科學及海洋工程研究所, 2008.

[19] 莊孟哲, "軟性電子元件及電路噴墨製程平台研製," 碩士論文, 國立臺灣大學工程科學及海洋工程學研究所, 2007.

[16] 劉淑白, "全噴墨有機半導體摻雜石墨烯之薄膜電晶體效能提升研究," 碩士論文, 國立臺灣大學工程科學及海洋工程研究所, 2011.

[17] 李長鴻, "全噴墨鐵電材料有機記憶體元件之製作," 碩士論文, 國立臺灣大學電子工程學研究所, 2009.