Aluminum Patterned Electroplating from AlCl₃⁻[EMIm]Cl Ionic Liquid towards Microsystems Application.

Muhammad Al Farisi,Silvia Hertel,Maik Wiemer,Thomas Otto

doi:10.3390/mi9110589

Abstract

Electroplating process is being used to deposit a relatively thick film of metallic materials for various microsystems applications, such as for the wafer-level bonding sealing frame and as a thermal actuator. Recently, the Al electroplating process from ionic liquid has been an attractive deposition method for anti-corrosion coatings. To extend the utilization of the film, in particular for microsystems application, a microstructure formation by patterned electroplating of Al from AlCl–1-ethyl-3-methylimidazolium chloride ((EMIm)Cl) ionic liquid is investigated in this study. The influences of each deposition parameters to the electroplating process as well as the resulting surface morphology are evaluated. Electroplated Al deposits on both Au and Al seed layers are both studied. It is also found that a recurrent galvanic pulse plating process yields in a higher current efficiency. Finally, Al electroplating on a 2 µm-trenched 100 mm-wafer is also demonstrated.

Highlights

Electroplating is an essential process to deposit metallic materials for a microsystems application
This study provides an investigation of Al patterned electroplating from AlCl3–[EMIm]Cl ionic liquid to form microstructures
Recurrent galvanic pulse (RGP) electroplating is an electroplating process in which the forward and reverse currents are alternately applied in a relatively longer period compared to the standard pulse plating

Summary

Introduction

Electroplating is an essential process to deposit metallic materials for a microsystems application. Various methods for integrating micro-electro mechanical systems (MEMS) and complimentary metal-oxide semiconductor (CMOS) large scale integration (LSI) utilizing metallic materials have been studied. Surface activated bonding (SAB) was used for integration as well as hermetic packaging for different devices [1]. The bonding mechanism of SAB relies on the atomic interdiffusion between different layers that have a small surface roughness and was activated using an Ar ion-beam prior to the bonding step. Electroplated Au is smoothed using either lift-off or imprint method before bonded at room temperature by SAB method [2]. Electroplated Cu is used for hermetic sealing using SAB at room temperature after chemical-mechanical polishing for surface planarization [3]

Methods

Results

Conclusion