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Micromachines
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MEMS Packaging Technologies and 3D Integration, 2nd Edition
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MEMS Packaging Technologies and 3D Integration, 2nd Edition

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D：Materials and Processing".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 10385

Special Issue Editor

Dr. Seonho Seok

E-Mail Website
Guest Editor
Center for Nanoscience and Nanotechnology (C2N), University-Paris-Saclay, F-91405 Orsay, France
Interests: packaging; MEMS; integration; bonding; polymer; adhesion
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

MEMS packaging is an essential technique for successful commercialization of MEMS products, as MEMS has moving parts and an application-specific nature. The classic approach of MEMS packaging is to bond silicon or glass cap wafer to MEMS wafers. Therefore, it is typically implemented under high-pressure and high-temperature conditions. Advanced approaches use the thin-film deposition technique, and then the cavity for MEMS is realized by sacrificial etch through access holes at the thin-film cap. The packaging cap transfer technique is a compromise between the two approaches since it makes it possible to bond and transfer the thin packaging cap to the released MEMS device. MEMS devices and IC are being integrated in 3D fashion to achieve better performance, and the implantable device needs special packaging techniques. Thus, this Special Issue seeks research papers, communications, and review articles that focus on MEMS packaging technologies and related integration methods.

Dr. Seonho Seok
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • MEMS
  • packaging
  • bonding
  • integration
  • vacuum
  • implantable
  • biocompatibility
  • reliability

Related Special Issues

Published Papers (7 papers)

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Research

Jump to: Review

19 pages, 5797 KiB  
Article
Cu-Cu Thermocompression Bonding with a Self-Assembled Monolayer as Oxidation Protection for 3D/2.5D System Integration
by Maria Lykova, Iuliana Panchenko, Martin Schneider-Ramelow, Tadatomo Suga, Fengwen Mu and Roy Buschbeck
Micromachines 2023, 14(7), 1365; https://doi.org/10.3390/mi14071365 - 30 Jun 2023
Cited by 1 | Viewed by 1271
Abstract
Cu-Cu direct interconnects are highly desirable for the microelectronic industry as they allow for significant reductions in the size and spacing of microcontacts. The main challenge associated with using Cu is its tendency to rapidly oxidize in air. This research paper describes a [...] Read more.
Cu-Cu direct interconnects are highly desirable for the microelectronic industry as they allow for significant reductions in the size and spacing of microcontacts. The main challenge associated with using Cu is its tendency to rapidly oxidize in air. This research paper describes a method of Cu passivation using a self-assembled monolayer (SAM) to protect the surface against oxidation. However, this approach faces two main challenges: the degradation of the SAM at room temperature in the ambient atmosphere and the monolayer desorption technique prior to Cu-Cu bonding. In this paper, the systematic investigation of these challenges and their possible solutions are presented. The methods used in this study include thermocompression (TC) bonding, X-ray photoelectron spectroscopy (XPS), shear strength testing, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results indicate nearly no Cu oxidation (4 at.%) for samples with SAM passivation in contrast to the bare Cu surface (27 at.%) after the storage at −18 °C in a conventional freezer for three weeks. Significant improvement was observed in the TC bonding with SAM after storage. The mean shear strength of the passivated samples reached 65.5 MPa without storage. The average shear strength values before and after the storage tests were 43% greater for samples with SAM than for the bare Cu surface. In conclusion, this study shows that Cu-Cu bonding technology can be improved by using SAM as an oxidation inhibitor, leading to a higher interconnect quality. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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12 pages, 4769 KiB  
Article
FEM Analysis of Buckled Dielectric Thin-Film Packaging Based on 3D Direct Numerical Simulation
by Seonho Seok
Micromachines 2023, 14(7), 1312; https://doi.org/10.3390/mi14071312 - 26 Jun 2023
Viewed by 986
Abstract
This paper presents a 3D direct numerical simulation of buckled thin-film packaging based on transferred elastic thin-film wrinkling bonded on a compliant polymer ring. The mode change of the fabricated thin-film cap is found by measuring the thin-film cap shape at different times [...] Read more.
This paper presents a 3D direct numerical simulation of buckled thin-film packaging based on transferred elastic thin-film wrinkling bonded on a compliant polymer ring. The mode change of the fabricated thin-film cap is found by measuring the thin-film cap shape at different times after Si substrate debonding. The conventional linear and nonlinear buckling simulations are not adequate to understand the behavior of the thin-film buckling mechanism creating such packaging cap mode change. Direct buckling simulation is recently reported as an easy and useful numerical wrinkling simulation method. A novel 3D FEM model of a thin-film package suitable for direct 3D buckling simulation is built to reduce the mode mixture between different buckling modes. Buckling modes of the packaging cap are investigated in terms of elastic moduli of package materials and applied strain due to thermal expansion coefficient difference. Based on the simulation results, it is found that there are two main modes in the fabricated thin-film buckling package determining the shape of the transferred thin-film packaging cover depending on the elasticity ratio between the cap and sealing ring materials. The mode shift from wrinkling cap mode to out-of-plane cap mode due to applied strain along a polymeric sealing ring is found. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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12 pages, 4867 KiB  
Article
Direct Numerical Simulation of Surface Wrinkling for Extraction of Thin Metal Film Material Properties
by Seonho Seok, HyungDal Park, Philippe Coste and Jinseok Kim
Micromachines 2023, 14(4), 747; https://doi.org/10.3390/mi14040747 - 28 Mar 2023
Cited by 1 | Viewed by 1159
Abstract
This paper presents a direct numerical simulation for the extraction of material properties based on thin-film wrinkling on scotch tape. Conventional FEM-based buckling simulation sometimes requires complex modeling techniques concerning mesh element manipulation or boundary conditions. The direct numerical simulation differs from FEM [...] Read more.
This paper presents a direct numerical simulation for the extraction of material properties based on thin-film wrinkling on scotch tape. Conventional FEM-based buckling simulation sometimes requires complex modeling techniques concerning mesh element manipulation or boundary conditions. The direct numerical simulation differs from FEM (finite element method)-based conventional two-step linear–nonlinear buckling simulation in that mechanical imperfections are directly applied into the elements of the simulation model. Hence, it can be performed in one step to find the wrinkling wavelength and amplitude, which are key parameters to extract the material mechanical properties. Moreover, the direct simulation can reduce simulation time and modeling complexity. Using the direct model, the effect of the number of imperfections on wrinkling characteristics was first studied, and then wrinkling wavelengths depending on the elastic moduli of the associated materials were prepared for the extraction of material properties. Thin-film wrinkling test patterns on scotch tape were fabricated using the transfer technique with low adhesion between metal films and the polyimide substrate. The material properties of the thin metal films were determined by comparing the measured wrinkling wavelengths and the proposed direct simulation results. By consequence, the elastic moduli of 300 nm thick gold film and 300 nm thick aluminum were determined as 250 GPa and 300 GPa, respectively. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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13 pages, 4949 KiB  
Article
A Design Approach to Reducing Stress and Distortion Caused by Adhesive Assembly in Micromachined Deformable Mirrors
by Wenkuan Man and Thomas G. Bifano
Micromachines 2023, 14(4), 740; https://doi.org/10.3390/mi14040740 - 27 Mar 2023
Viewed by 1537
Abstract
A common problem in deformable mirror assembly is that the adhesion of actuators to an optical mirror face sheet introduces unwanted topography due to large local stresses generated at the adhesive joint. A new approach to minimizing that effect is described, with inspiration [...] Read more.
A common problem in deformable mirror assembly is that the adhesion of actuators to an optical mirror face sheet introduces unwanted topography due to large local stresses generated at the adhesive joint. A new approach to minimizing that effect is described, with inspiration taken from St. Venant’s principle, a fundamental precept in solid mechanics. It is demonstrated that moving the adhesive joint to the end of a slender post extending from the face sheet largely eliminates deformation due to adhesive stresses. A practical implementation of this design innovation is described, using silicon-on-insulator wafers and deep reactive ion etching. Simulation and experiments validate the effectiveness of the approach, reducing stress-induced topography on a test structure by a factor of 50. A prototype electromagnetic DM using this design approach is described, and its actuation is demonstrated. This new design can benefit a wide range of DMs that rely on actuator arrays that are adhesively bonded to a mirror face sheet. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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24 pages, 11344 KiB  
Article
Localized Induction Heating of Cu-Sn Layers for Rapid Solid-Liquid Interdiffusion Bonding Based on Miniaturized Coils
by Christian Hofmann, Maulik Satwara, Martin Kroll, Sushant Panhale, Patrick Rochala, Maik Wiemer, Karla Hiller and Harald Kuhn
Micromachines 2022, 13(8), 1307; https://doi.org/10.3390/mi13081307 - 12 Aug 2022
Cited by 2 | Viewed by 1770
Abstract
Considering the demand for low temperature bonding in 3D integration and packaging of microelectronic or micromechanical components, this paper presents the development and application of an innovative inductive heating system using micro coils for rapid Cu-Sn solid-liquid interdiffusion (SLID) bonding at chip-level. The [...] Read more.
Considering the demand for low temperature bonding in 3D integration and packaging of microelectronic or micromechanical components, this paper presents the development and application of an innovative inductive heating system using micro coils for rapid Cu-Sn solid-liquid interdiffusion (SLID) bonding at chip-level. The design and optimization of the micro coil as well as the analysis of the heating process were carried out by means of finite element method (FEM). The micro coil is a composite material of an aluminum nitride (AlN) carrier substrate and embedded metallic coil conductors. The conductive coil geometry is generated by electroplating of 500 µm thick copper into the AlN carrier. By using the aforementioned micro coil for inductive Cu-Sn SLID bonding, a complete transformation into the thermodynamic stable ε-phase Cu3Sn with an average shear strength of 45.1 N/mm2 could be achieved in 130 s by applying a bond pressure of 3 MPa. In comparison to conventional bonding methods using conduction-based global heating, the presented inductive bonding approach is characterized by combining very high heating rates of about 180 K/s as well as localized heating and efficient cooling of the bond structures. In future, the technology will open new opportunities in the field of wafer-level bonding. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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15 pages, 12927 KiB  
Article
Mechanical Characterization and Analysis of Different-Type Polyimide Feedthroughs Based on Tensile Test and FEM Simulation for an Implantable Package
by Seonho Seok, HyungDal Park, Yong-Jun Kim and Jinseok Kim
Micromachines 2022, 13(8), 1295; https://doi.org/10.3390/mi13081295 - 11 Aug 2022
Cited by 1 | Viewed by 1574
Abstract
This paper presents the mechanical behaviors of different types of polyimide feedthroughs that are frequently used for implantable polymer encapsulation. Implantable packages of electronic devices often comprise circuits mounted on printed circuit boards (PCBs) encapsulated in a biocompatible polymer material, with input/output feedthroughs [...] Read more.
This paper presents the mechanical behaviors of different types of polyimide feedthroughs that are frequently used for implantable polymer encapsulation. Implantable packages of electronic devices often comprise circuits mounted on printed circuit boards (PCBs) encapsulated in a biocompatible polymer material, with input/output feedthroughs for electrical interconnections. The feedthroughs are regarded as essential elements of the reliability of the package since they create inevitable interfaces with the encapsulation materials. Flexible materials are frequently used for feedthroughs owing to their ease of manufacturing; thus, their mechanical properties are crucial as they directly interact with parts of the human body, such as the brain and neurons. For this purpose, tensile tests were performed to characterize the mechanical properties of flexible PCBs (FPCBs) and photosensitive polyimides (PSPIs). Commercial FPCBs and homemade PSPIs of two different thicknesses were subjected to tensile tests for mechanical characterization. The FPCBs showed typical stress–strain curves, while the PSPIs showed brittleness or strain hardening depending on the thickness. The material properties extracted from the tensile tests were used for explicit modeling using the finite element method (FEM) and simulations to assess mechanical behaviors, such as necking and strain hardening. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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Review

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21 pages, 6380 KiB  
Review
A Review of Silver Wire Bonding Techniques
by Bin An, Hongliang Zhou, Jun Cao, Pingmei Ming, John Persic, Jingguang Yao and Andong Chang
Micromachines 2023, 14(11), 2129; https://doi.org/10.3390/mi14112129 - 20 Nov 2023
Viewed by 1103
Abstract
The replacement of gold bonding wire with silver bonding wire can significantly reduce the cost of wire bonding. This paper provides a comprehensive overview of silver wire bonding technology. Firstly, it introduces various types of silver-based bonding wire currently being studied by researchers, [...] Read more.
The replacement of gold bonding wire with silver bonding wire can significantly reduce the cost of wire bonding. This paper provides a comprehensive overview of silver wire bonding technology. Firstly, it introduces various types of silver-based bonding wire currently being studied by researchers, including pure silver wire, alloy silver wire, and coated silver wire, and describes their respective characteristics and development statuses. Secondly, the development of silver-based bonding wire in manufacturing and bonding processes is analyzed, including common silver wire manufacturing processes and their impact on silver wire performance, as well as the impact of bonding parameters on silver wire bonding quality and reliability. Subsequently, the reliability of silver wire bonding is discussed, with a focus on analyzing the effects of corrosion, electromigration, and intermetallic compounds on bonding reliability, including the causes and forms of chlorination and sulfurization, the mechanism and path of electromigration, the formation and evolution of intermetallic compounds, and evaluating their impact on bonding strength and reliability. Finally, the development status of silver wire bonding technology is summarized and future research directions for silver wire are proposed. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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