Abstract

Wet etching is a critical fabrication step for the mass production of micro and nanoelectronic devices. However, when an extremely corrosive acid such as hydrofluoric (HF) acid are used during etching, an undesirable damage might occur if the device includes a material that is not compatible with the acid. Polyimide thin films can serve as sacrificial/structural layers to fabricate freestanding or flexible devices. The importance of polyimide in microelectronics is due to its relatively low stress and compatibility with standard micromachining processes. In this work, a fast delamination process of a 4-μm-thin film of polyimide from a silicon substrate has been demonstrated. The films’ detachment has been performed using a wet-based etchant of HF acid. Specifically, the effect of HF concentration on the delamination time required to detach the polyimide film from the substrate has been investigated. This study is intended to provide the information on the compatibility of using polyimide films with HF, which can help in the design and fabrication of polyimide-based devices.

Highlights

  • The fabrication of microelectronic devices and their subsets involves the use of a range of acids, organic/inorganic polymers, metals, and semiconductor materials

  • We have demonstrated the delamination of thin polyimide films in a wet-based etchant

  • Polyimide films of a thickness of around 4 μm attached to a silicon substrate have been immersed in HF-based etchant solutions to investigate how the etchants can affect the detachment of the polymeric films from the substrate

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Summary

Introduction

The fabrication of microelectronic devices and their subsets involves the use of a range of acids, organic/inorganic polymers, metals, and semiconductor materials. The fabrication process includes several steps, such as deposition, photolithography, and etching. It is common in the fabrication of microelectromechanical systems (MEMS) that a sacrificial layer of a material of interest is deposited on a substrate before it is subsequently removed by a specific type of etchants. There might be a considerable reliability concern when the materials/processes used in the fabrication are not compatible with each other [1]. The incompatibility could result from fabrication processes that require the use of chemicals and materials with different properties [2]. We focus on determining whether the application of a layer of polyimide is fully compatible with the etching process when a wet-based etchant of hydrofluoric (HF) acid is used during the fabrication process

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