Hard-Baked Photoresist as a Sacrificial Layer for Sub-180 °C Surface Micromachining Processes

• Published in: Micromachines (Basel) Vol. 9; no. 5; p. 231
• Main Authors: Tawfik, Hani H, Elsayed, Mohannad Y, Nabki, Frederic, El-Gamal, Mourad N
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 11.05.2018; MDPI
• Subjects: Aluminum; CMOS; Critical point; Etching; Letter; low thermal budget; Materials selection; Metal oxide semiconductors; Micromachining; photoresist; sacrificial layer; Selectivity; Silicon carbide; Silicon carbide (SiC); Substrates; surface micromachining; Titanium; low thermal budget; surface micromachining; sacrificial layer; photoresist; Silicon carbide (SiC)
• ISSN: 2072-666X; 2072-666X
• DOI: 10.3390/mi9050231

This letter proposes a method for utilizing a positive photoresist, Shipley 1805, as a sacrificial layer for sub-180 °C fabrication process flows. In the proposed process, the sacrificial layer is etched at the end to release the structures using a relatively fast wet-etching technique employing resist remover and a critical point dryer (CPD). This technique allows high etching selectivity over a large number of materials, including silicon-based structural materials such as silicon-carbide, metals such as titanium and aluminum, and cured polymers. This selectivity, as well as the low processing thermal budget, introduces more flexibility in material selection for monolithic integration above complementary metal oxide semiconductor (CMOS) as well as flexible substrates.