Browse Prior Art Database

Controll of copper surface roughness

IP.com Disclosure Number: IPCOM000016138D
Original Publication Date: 2002-Oct-11
Included in the Prior Art Database: 2003-Jun-21
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Abstract

Disclosed is a method for controlling copper surface roughness during processing of microelectromechanical systems (MEMS) resonators. MEMS devices are micro-miniature devices formed on a substrate using fabrication steps common to the manufacture of integrated circuits. These MEMS devices generally combine electrical and mechanical functionality to form devices such as sensors, motors, switches, resonators, etc. The fabrication of these devices is generally based on the deposition and photolithographic patterning of alternate layers of conductors, dielectric layers, and a sacrificial layer. Once the MEMS device structure is completed, the sacrificial material is removed, which process provides free space in the device allowing for mechanical movement of the structures built [1, 2]. The method described herein is directed to providing a thin Nickel-phosphide (Ni-P) coating that helps protect the exposed Cu surfaces during device fabrication. The Ni-P layer is formed by selective electroless plating resulting in typical film thickness of 10-100nm and surface roughness defined by root mean square (RMS) value of <15nm and/or a Rmax value of <150nm. Figure 1 shows a schematic of a MEMS resonator.

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Controll of copper surface roughness

  Disclosed is a method for controlling copper surface roughness during processing of microelectromechanical systems (MEMS) resonators. MEMS devices are micro-miniature devices formed on a substrate using fabrication steps common to the manufacture of integrated circuits. These MEMS devices generally combine electrical and mechanical functionality to form devices such as sensors, motors, switches, resonators, etc. The fabrication of these devices is generally based on the deposition and photolithographic patterning of alternate layers of conductors, dielectric layers, and a sacrificial layer. Once the MEMS device structure is completed, the sacrificial material is removed, which process provides free space in the device allowing for mechanical movement of the structures built [1, 2]. The method described herein is directed to providing a thin Nickel-phosphide (Ni-P) coating that helps protect the exposed Cu surfaces during device fabrication. The Ni-P layer is formed by selective electroless plating resulting in typical film thickness of 10-100nm and surface roughness defined by root mean square (RMS) value of <15nm and/or a Rmax value of <150nm. Figure 1 shows a schematic of a MEMS resonator.

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Figure 1. A Schematic of a MEMS resonator, where layers 37 are Ni-P thin films coated on Cu (20, 35).

During the processing of the MEMS device the metal films are exposed to high temperature anneal in inert ambient. The effect of thin Ni-P coating on Cu surface to the surface roughness stability during high temperature anneal is shown in Figure 2.

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