Development Of 3D Microstructures By Using Grayscale Photolithographic Technique
Perkembangan pesat teknologi seperti bio-chip, peranti pendalir mikro, peranti mikro-optik dan sistem mikro elektro-mekanikal (MEMS) memerlukan keupayaan membina struktur tiga dimensi (3D) yang kompleks di skala mikro. Bagi membina struktur 3D di skala mikro, kebiasaannya beberapa topeng cahaya digu...
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Online Access: | http://eprints.usm.my/41609/1/Development_Of_3D_Microstructures_By_Using_Grayscale_Photolithographic_Technique.pdf |
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| Summary: | Perkembangan pesat teknologi seperti bio-chip, peranti pendalir mikro, peranti mikro-optik dan sistem mikro elektro-mekanikal (MEMS) memerlukan keupayaan membina struktur tiga dimensi (3D) yang kompleks di skala mikro. Bagi membina struktur 3D di skala mikro, kebiasaannya beberapa topeng cahaya digunakan bagi menghasilkan corak 3D diatas beberapa lapisan photoresist yang ditindan. Namun begitu teknik ini memakan masa, tidak efisien dan rumit untuk diadaptasi dalam industri pembuatan. Teknik lithografi terbaru seperti litografi mengunakan pancaran elektron (EBL), pancaran ion terfokus (FIB) dan sinar ultraviolet ekstrem (EUV) memerlukan kos terlalu tinggi dan kepakaran yang mahir dalam bidang tersebut. Tujuan utama kajian ini adalah untuk menghasilkan teknik mudah bagi menghasilkan struktur 3D pada skala mikro mengunakan topeng emulsi dengan teknik litografi skala kelabu. Kajian dimulakan dengan mencari prosedur dan parameter yang sesuai bagi menghasilkan hasilan microfabrikasi yang optimum. Dalam eksperimen ini, kepekatan skala kelabu ditentukan dengan mengawal peratusan titik hitam di sesuatu kawasan. Peratusan skala kelabu yang tinggi akan menghasilkan struktur mikro yang lebih tebal. Corak yang telah direka akan dicetak di atas kertas plastik lutsinar. Corak ini yang akan dipindahkan ke atas topeng kaca emulsi (Plat Cahaya Berprestasi Tinggi). Plat ini dihasilkan oleh Konica Minolta Inc. Selepas itu, corak dari topeng kaca emulsi akan dipindahkan ke atas photoresist MicroChem SU-8 2010 yang telah didepositkan di atas substrak kaca. Dengan mengunakan teknik mikrofabrikasi ini, struktur mikro antara 17 μm sehingga 750 μm dapat dihasilkan dengan hanya mengunakan sekali pendedahan cahaya sahaja. Kajian seterusnya adalah untuk menghasilkan saluran mikrofluidik mengunakan teknik litografi skala kelabu. Saluran mikrofludik ini dinilai mengunakan sistem mengukur Infinite Fokus daripada ALICONA dan mikroskop imbasan elektron (SEM). Dengan mengunakan teknik mikcofabrikasi ini, liang yang berdiameter 35 μm telah berjaya dihasilkan dalam saluran mikrofluidik. Kesimpulannya, ketebalan struktur mikro adalah ditentukan oleh peratusan skala kelabu di peringkat mereka bentuk.
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Recently, the rapid development of technology, such as biochips, microfluidic device, micro-optical devices, and micro-electromechanical-systems (MEMS), demands the capability to create complex designs of three-dimensional (3D) microstructures. Nevertheless, in order to create 3D microstructures, the traditional photolithography process often requires multiple photomasks to generate a 3D pattern from several stacked photoresist layers. This fabrication method is extremely time consuming, has low throughput, and is complicated for high volume manufacturing scale. On the other hand, the next generation lithography, such as electron beam lithography (EBL), focused ion beam lithography (FIB), and extreme ultraviolet lithography (EUV) is however too costly and requires experts to setup the machines. Therefore, the purpose of this study had been to develop a microfabrication method in producing 3D curvature microstructures by employing the single-step grayscale emulsion mask photolithography technique. In the first part of this study, suitable procedure and parameters were determined to produce optimum microfabrication results. In the experiment, the concentration of grayscale was determined by the percentages of halftone dots filling in a particular area. Therefore, the lower the concentration of halftone dots on the emulsion mask, the thicker the developed microstructure will be. First, the designed patterns were printed out on a transparent sheet. Then, the patterns were transferred onto an emulsion glass mask (High Precision Photo Plate) from Konica Minolta, Inc. After that, SU-8 2010 negative photoresist (MicroChem) was deposited on a glass substrate, while the patterns from the emulsion glass were transferred onto a photoresist coated glass substrate. From this microfabrication method, a microstructure with maximum and minimum thickness of 750 μm and 17 μm respectively had been obtained in a single-step lithography exposure. On the other hand, as for the second part of this study, this grayscale fabrication method was demonstrated on the fabrication of microfluidic channel. The microfluidic channel was then evaluated under InfiniteFocus measurement systems from ALICONA and also under scanning electron microscope (SEM). By using this microfabrication method, microfluidic channel with 35 μm pores was successfully fabricated. Therefore, it is concluded that different thickness of developed photoresist can be obtained by manipulating the percentage of grayscale concentration during the mask designing stage.
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