Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror

Henri Ailas; Jaakko Saarilahti; Tuomas Pensala; Jyrki Kiihamäki

doi:10.23919/NORDPAC.2019.8760353

Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror

Henri Ailas, Jaakko Saarilahti, Tuomas Pensala, Jyrki Kiihamäki

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

2 Citations (Scopus)

Abstract

In this study, a low temperature wafer-level packaging process aimed for encapsulating MEMS mirrors was developed. The glass cap wafer used in the package has an antireflective (AR) coating that limits the maximum temperature of the bonding process to 250°C. Copper thermocompression was used as copper has a high self-diffusivity and the native oxidation on copper surfaces can be completely removed with combination of ex situ acetic acid wet-etch and in situ forming gas anneal. Making it suitable for a development of a low temperature bonding process. In this work, bonding on of sputtered and electrodeposited copper films was studied on temperatures ranging from 200°C to 300°C as well as the effect of pretreatment on bond strength. The study presents a successful thermocompression bonding process for sputtered Cu films at a low temperature of 200°C with high yield of 97 % after dicing. The bond strength was recorded to be 75 MPa, well above the MIL-STD-883E standard (METHOD 2019.5) rejection limit of 6.08 MPa. The high dicing yield and bond strength suggest that the thermocompression bonding could be possible even at temperatures below 200°C. However, the minimum bonding temperature was not yet determined in this study.

Original language	English
Title of host publication	2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019
Publisher	IEEE Institute of Electrical and Electronic Engineers
Pages	12-16
ISBN (Electronic)	978-91-519-2090-0
ISBN (Print)	978-1-7281-2884-9
DOIs	https://doi.org/10.23919/NORDPAC.2019.8760353
Publication status	Published - 11 Jun 2019
MoE publication type	A4 Article in a conference publication
Event	IMAPS Nordic Annual Conference, NordPac 2019 - Technical University of Denmark, Lyngby, Denmark Duration: 11 Jun 2019 → 13 Jun 2019 https://nordic.imapseurope.org/event/nordpac-2019/

Conference

Conference	IMAPS Nordic Annual Conference, NordPac 2019
Country/Territory	Denmark
City	Lyngby
Period	11/06/19 → 13/06/19
Internet address	https://nordic.imapseurope.org/event/nordpac-2019/

Funding

This work was possible by the financial support of the Horizon 2020 programme of the European union under ’Programmable Systems for Intelligence in Automobiles’ (PRYSTINE-783190). The project was partially funded by Business Finland in the framework of ECSEL.

Keywords

bonding
Cu
MEMS
Thermocompression
wafer-level packaging
OtaNano

Access to Document

10.23919/NORDPAC.2019.8760353

Cite this

@inproceedings{eab9f7a1ee49489fb93561f8a17ccb93,

title = "Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror",

abstract = "In this study, a low temperature wafer-level packaging process aimed for encapsulating MEMS mirrors was developed. The glass cap wafer used in the package has an antireflective (AR) coating that limits the maximum temperature of the bonding process to 250°C. Copper thermocompression was used as copper has a high self-diffusivity and the native oxidation on copper surfaces can be completely removed with combination of ex situ acetic acid wet-etch and in situ forming gas anneal. Making it suitable for a development of a low temperature bonding process. In this work, bonding on of sputtered and electrodeposited copper films was studied on temperatures ranging from 200°C to 300°C as well as the effect of pretreatment on bond strength. The study presents a successful thermocompression bonding process for sputtered Cu films at a low temperature of 200°C with high yield of 97 % after dicing. The bond strength was recorded to be 75 MPa, well above the MIL-STD-883E standard (METHOD 2019.5) rejection limit of 6.08 MPa. The high dicing yield and bond strength suggest that the thermocompression bonding could be possible even at temperatures below 200°C. However, the minimum bonding temperature was not yet determined in this study.",

keywords = "bonding, Cu, MEMS, Thermocompression, wafer-level packaging, OtaNano",

author = "Henri Ailas and Jaakko Saarilahti and Tuomas Pensala and Jyrki Kiiham{\"a}ki",

year = "2019",

month = jun,

day = "11",

doi = "10.23919/NORDPAC.2019.8760353",

language = "English",

isbn = "978-1-7281-2884-9",

pages = "12--16",

booktitle = "2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019",

publisher = "IEEE Institute of Electrical and Electronic Engineers",

address = "United States",

note = "IMAPS Nordic Annual Conference, NordPac 2019 ; Conference date: 11-06-2019 Through 13-06-2019",

url = "https://nordic.imapseurope.org/event/nordpac-2019/",

}

Ailas, H , Saarilahti, J , Pensala, T & Kiihamäki, J 2019, Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror. in 2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019., 8760353, IEEE Institute of Electrical and Electronic Engineers, pp. 12-16, IMAPS Nordic Annual Conference, NordPac 2019, Lyngby, Denmark, 11/06/19. https://doi.org/10.23919/NORDPAC.2019.8760353

Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror. / Ailas, Henri ; Saarilahti, Jaakko ; Pensala, Tuomas et al.
2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019. IEEE Institute of Electrical and Electronic Engineers, 2019. p. 12-16 8760353.

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

TY - GEN

T1 - Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror

AU - Ailas, Henri

AU - Saarilahti, Jaakko

AU - Pensala, Tuomas

AU - Kiihamäki, Jyrki

PY - 2019/6/11

Y1 - 2019/6/11

N2 - In this study, a low temperature wafer-level packaging process aimed for encapsulating MEMS mirrors was developed. The glass cap wafer used in the package has an antireflective (AR) coating that limits the maximum temperature of the bonding process to 250°C. Copper thermocompression was used as copper has a high self-diffusivity and the native oxidation on copper surfaces can be completely removed with combination of ex situ acetic acid wet-etch and in situ forming gas anneal. Making it suitable for a development of a low temperature bonding process. In this work, bonding on of sputtered and electrodeposited copper films was studied on temperatures ranging from 200°C to 300°C as well as the effect of pretreatment on bond strength. The study presents a successful thermocompression bonding process for sputtered Cu films at a low temperature of 200°C with high yield of 97 % after dicing. The bond strength was recorded to be 75 MPa, well above the MIL-STD-883E standard (METHOD 2019.5) rejection limit of 6.08 MPa. The high dicing yield and bond strength suggest that the thermocompression bonding could be possible even at temperatures below 200°C. However, the minimum bonding temperature was not yet determined in this study.

AB - In this study, a low temperature wafer-level packaging process aimed for encapsulating MEMS mirrors was developed. The glass cap wafer used in the package has an antireflective (AR) coating that limits the maximum temperature of the bonding process to 250°C. Copper thermocompression was used as copper has a high self-diffusivity and the native oxidation on copper surfaces can be completely removed with combination of ex situ acetic acid wet-etch and in situ forming gas anneal. Making it suitable for a development of a low temperature bonding process. In this work, bonding on of sputtered and electrodeposited copper films was studied on temperatures ranging from 200°C to 300°C as well as the effect of pretreatment on bond strength. The study presents a successful thermocompression bonding process for sputtered Cu films at a low temperature of 200°C with high yield of 97 % after dicing. The bond strength was recorded to be 75 MPa, well above the MIL-STD-883E standard (METHOD 2019.5) rejection limit of 6.08 MPa. The high dicing yield and bond strength suggest that the thermocompression bonding could be possible even at temperatures below 200°C. However, the minimum bonding temperature was not yet determined in this study.

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M3 - Conference article in proceedings

SN - 978-1-7281-2884-9

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EP - 16

BT - 2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019

PB - IEEE Institute of Electrical and Electronic Engineers

T2 - IMAPS Nordic Annual Conference, NordPac 2019

Y2 - 11 June 2019 through 13 June 2019

ER -

Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror

Abstract

Conference

Funding

Keywords

Access to Document

Other files and links

Fingerprint

PRYSTINE: Programmable Systems for Intelligence in Automobiles

OtaNano

Cite this

Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS Mirror

Abstract

Conference

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Projects

PRYSTINE: Programmable Systems for Intelligence in Automobiles

Equipment

OtaNano

Cite this