3D integration technologies for MEMS
This paper describes selected technologies for the 3D integration of MEMS devices. This comprises a Via Last approach for the formation of MEMS TSVs and a Cu based thermo-compression bonding method for the realization of small 3D-WLP devices. Moreover, the Aerosol Jet technique is discussed as method for the final assembly by means of printing conducting lines over 3D topography.
Low-Temperature Cu-Cu Wafer Bonding
Metal thermo-compression bonding is a process suitable for 3D interconnects applications at wafer level. The process requires typically bonding temperatures of ~400{degree sign}C and high contact pressure applied during bonding. Temperature reduction below such values is required in order to solve some issues regarding wafer-to-wafer misalignment after bonding and to minimize thermo-mechanical stresses. Low-temperature (LT) Cu-Cu wafer bonding was successfully demonstrated at 175{degree sign}C. The bond quality, bond strength, metal interface layers microstructure and chemical composition of Cu-Cu wafer pairs bonded under different process conditions were investigated. Experimental results on various Cu native oxide methods evaluation as well as results obtained for various bonding and annealing temperatures are presented.
Inkjet printing of conductive materials: a review
Purpose – The purpose of this paper is to present an exhaustive review of research studies and activities in the inkjet printing of conductive materials.Design/methodology/approach – This paper gives a detailed literature survey of research carried out in inkjet printing of conductive materials.Findings – This article explains the inkjet printing process and the various types of conductive inks. It then examines the various factors that affect the quality of inkjet printed interconnects such as printing parameters, materials and substrate treatments. Methods of characterising both the inkjet printing process and the electrical properties of printed conductive materials are also presented. Finally relevant applications of this technology are described.Originality/value – Inkjet printing is currently one of the cheapest direct write techniques for manufacturing. The use of this technique in electronic manufacturing, where interconnects and other conductive features are required is an area of increasing rele...