Fabrication of poly-silicon microwire using conventional photolithography technique: Positive resist mask vs aluminium hard mask

Abstract

We have demonstrated a simple and low-cost method to fabricate poly-silicon microwire by conventional photolithography technique. There are two different steps process flow were involved in the conventional photolithography technique which are employed the positive resist as a mask and aluminium (Al) as hard mask. Low pressure chemical vapour deposition (LPCVD) was used to deposit 50 nm poly-silicon layer on the Si-SiO 2 -Si 3 N 4 layer. Wire mask must be first designed using AutoCAD before patterning onto chrome mask. Initially the 300 nm thick layer of positive resist is coated on the sample. Subsequently, the coated sample were exposed to UV light for 10 seconds and followed by development process. The critical part in this development process is to control the development time and resist profile. There are three types of resist profile problems such as underdevelopment, incomplete development and overdevelopment resist profile. These resist profiles problems can negatively affect in the subsequent etch process. Next process is an etching process. For positive resist as a mask process flow, the developed sample was loaded into SAMCO Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) 10iP to anisotropic etching of poly-silicon for 7 seconds. Meanwhile, for Al as a hard mask, the developed sample was dipped into Aluminium (Al) etchant for 3 minutes then followed by resist stripping and anisotropic etching of poly-silicon as similar to the resist mask process flow. Finally, the dimensions and etch profiles of < 1um poly-silicon microwire were morphologically characterized using optical microscopy.

An In-House Approach for Fabrication of Poly-Silicon Nanobiosensor Using Conventional Photolithography and Etching Method

“…1 2 are corresponding SEM and AFM images after trimming process of wire. It is seen from all figures that highly uniform, high resolution structure [1] and perfectly aligned polysilicon nanowires are produced. Based on the result, a poly-silicon nanowires with a diameter of 100 nm and height of approximately 50 nm is achieved.…”

“…Recently, fabrication of poly-silicon nanowires was developed using conventional photolithography and etching method [1][2][3]. As poly-silicon nanowires can be easily formed on flat and any surface, one of the potential applications is biosensor devices because it have widths similar to the dimensions of biomolecular [4][5].…”

Fabrication and characterization of undoped polysilicon nanowire for pH sensor

“…Developing process must be controlled due to the very small size of the wire. This factor makes the wire more prone to be over-developed over the area which will bring about resist profile problems [6]. The develop-bake process was repeated until unwanted photoresist was removed and the wire was clearly seen under the High Power Microscopy (HPM).…”

“…Besides normal developed, there were several resist problem occur if development process not properly controlled [6]. Visual inspection was taken once the device was completely fabricated.…”

“…The top-down method starts with a large structure followed by patterning and etching the smaller features, hence producing a nanostructure [5]. Top-down approach usually uses RIE etching, which are costly to avoid any unsuspected etching profile [3], [5], [6]. However, in bottom-up approach, atoms assemble one at a time in predetermined order or metal catalytic growth [3].…”