Recycled low-temperature direct bonding of Si/glass and glass/glass chips for detachable micro/nanofluidic devices

doi:10.1016/j.jmst.2019.11.034

Abstract

Abstract:

Silicon and glass are two of the most ideal materials for micro/nanofluidic devices, which have been widely used for research in multidisciplinary fields. However, many micro/nanofluidic devices enable only single use due to the irreversible bonding between Si/glass or glass/glass chips. If the silicon- and glass-based devices are fabricated to be detachable, the substrates can be reused and bonded again without repeating expensive micro/nanofabrication processes. Herein, we present a recycled direct bonding method for Si/glass and glass/glass chips based on oxygen plasma activation and low-temperature annealing processes. Strong bonding strength and void-free bonding interface are obtained after annealing at 150 °C. The surfaces and the bonding interfaces are characterized to elucidate the bonding mechanisms. Moreover, immersion tests are carried out to investigate the interfacial corrosion resistance in various chemical and biological solutions as well as explore a detachable method. The bonding strengths are controlled to meet the demand for micro/nanofluidic devices and the bonding interfaces can be separated in ethanol. As a result, we succeed in the experiment of bonding and detaching of glass substrates without fracturing, which is repeated for three times.

Key words: Low-temperature bonding, Plasma activation, Interface, Corrosion, Detachable

Chenxi Wang, Hui Fang, Shicheng Zhou, Xiaoyun Qi, Fanfan Niu, Wei Zhang, Yanhong Tian, Tadatomo Suga. Recycled low-temperature direct bonding of Si/glass and glass/glass chips for detachable micro/nanofluidic devices[J]. J. Mater. Sci. Technol., 2020, 46: 156-167.

Figures/Tables 15

Fig. 1. (a) Experimental procedure of low-temperature direct bonding process via oxygen plasma activation; (b) Detachment of the bonded pair and surface energy calculation.

Table 1 Chemical and biological solutions used for immersion tests.

Solution	Composition	pH	Application
NaOH (0.1 mol/L)	Na⁺, OH^-	13	Washing microfluidic channels
NaCl (0.9%)	Na⁺, Cl^-	6.7	Maintaining the electrolytes in human body
SBF	Na⁺, Cl^-, etc.	7.4	Bioactivity monitoring
DI water	H₂O	7	Control
Ethanol	CH₃-CH₂-OH	7	Washing microfluidic channels
C₆H₅Na₃O₇ (0.01 mol/L)	Na⁺,	8	Correcting acidity of blood and human body fluid

Fig. 2. (a) Surface roughness and (b) water contact angle of silicon; (c) surface roughness and (d) water contact angle of glass as a function of plasma activation time.

Fig. 3. Raman spectra of the surfaces for (a) silicon and (b) glass before and after plasma activation for 90 s.

Fig. 4. XPS O 1s spectra of (a)-(c) silicon and (d)-(f) glass before and after plasma activation.

Fig. 5. Annealing curves of (a) Si/glass and (b) glass/glass bonded pairs; Bonding area ratio and bonding strength of (c) Si/glass and (d) glass/glass bonded pairs.

Fig. 6. Cross-sectional SEM images, line scan of elemental analysis across the bonding interface, O map in green and Si map in red of (a-d) Si/glass bonded pairs and (e-h) glass/glass bonded pairs.

Fig. 7. (a) Cross-sectional TEM image and (b) HRTEM image of bonding interface in Si/glass bonded pairs, (c-g) EDS mapping analysis (C map in green, O map in blue and Si map in red) of Si/glass bonded pairs and (h) line scan of elemental analysis across the bonding interface.

Fig. 8. Schematic drawing of the plasma activated low-temperature bonding mechanism for Si/glass and glass/glass pairs: (a) surface cleaning and (b) activation, (c) pre-bonding, (d) storage at room temperature, (e) annealing process, and (f) the final bonded pair.

Fig. 9. Bonding area ratio for (a) Si/glass and (b) glass/glass pairs in various chemical and biological solutions as a function of immersion time; (c) and (d) show bonding strength for Si/glass and glass/glass pairs as a function of immersion time, respectively.

Fig. 10. SEM images of bonding interface for (a) Si/glass and (b) glass/glass bonded pairs after the immersion for 16 days in various chemical and biological solutions.

Fig. 11. (a) Bonding strength of Si/glass and glass/glass bonded pairs under the temperature and humidity of 85 °C and 85%; (b) Schematic drawing of corrosion mechanisms for Si/glass or glass/glass bonded pairs.

Fig. 12. Optical images of detaching processes for (a) Si/glass and (b) glass/glass bonded pairs (2-in. wafers) in ethanol using crack propagation.

Table 2 Calculated surface energy (mJ/m2) of bonded samples using crack propagation in various environments.

Samples	Ethanol	DI water	Air
Si/glass	92.99	118.51	272.95
Glass/glass	33.02	118.02	528.26

Fig. 13. (a) Optical images of detaching glass/glass bonded pairs (a standard microfluidic chip size of 75 mm × 25 mm × 500 μm) in ethanol using crack propagation; (b) Surface energy and (c) number of covalent bonds of glass/glass bonded pairs during detachment for 3 times.

References 41

[1]	Y. Xu, K. Jang, T. Yamashita, Y. Tanaka, K. Mawatari, T. Kitamori, Anal. Bioanal. Chem. 402(2012) 99-107.
[2]	C.A. Aguilar, H.G. Craighead, Nat. Nanotechnol. 8(2013) 709-718. DOI URL
[3]	W. Sparreboom, A. van den Berg, J.C.T. Eijkel, Nat. Nanotechnol. 4(2009) 713-720.
[4]	K. Shirai, K. Mawatari, R. Ohta, H. Shimizu, T. Kitamori, Analyst 143 (2018) 943-948. DOI URL
[5]	I. Vlassiouk, Z.S. Siwy, Nano Lett. 7(2007) 552-556. DOI URL
[6]	R. Karnik, C. Duan, K. Castelino, H. Daiguji, A. Majumdar, Nano Lett. 7(2007) 547-551.
[7]	L. Lin, K. Mawatari, K. Morikawa, Y. Pihosh, A. Yoshizaki, T. Kitamori, Analyst 142 (2017) 1689-1696. DOI URL
[8]	Y. Xu, Adv. Mater. 30(2018), 1702419.
[9]	R. Ohta, K. Mawatari, T. Takeuchi, K. Morikawa, T. Kitamori, Biomicrofluidics 13 (2019), 024104. DOI URL
[10]	K. Shirai, K. Mawatari, T. Kitamori, Small 10 (2014) 1514-1522. DOI URL
[11]	Y. Xu, Q. Wu, Y. Shimataniab, K. Yamaguchi, Lab Chip 4 (2015) 3856-3861.
[12]	J. Xu, C. Wang, T. Wang, Y. Liu, Y. Tian, Appl. Surf. Sci. 453(2018) 416-422. DOI URL
[13]	K. Ren, J. Zhou, H. Wu, Acc. Chem. Res. 46(2013) 2396-2406. DOI URL
[14]	K. Mawatari, Y. Kazoe, H. Shimizu, Y. Pihosh, T. Kitamori, Anal. Chem. 86(2014) 4068-4077.
[15]	C. Mai, M. Li, S. Yang, RSC Adv. 5(2015) 42721-42727.
[16]	T. Tsukahara, K. Mawatari, A. Hibara, T. Kitamori, Anal. Bioanal. Chem. 391(2008) 2745-2752. DOI URL
[17]	J.S. Mellors, V. Gorbounov, R.S. Ramsey, J.M. Ramsey, Anal. Chem. 80(2008) 6881-6887. DOI URL
[18]	C. Wang, Y. Wang, Y. Tian, C. Wang, T. Suga, Appl. Phys. Lett. 110(2017), 221602. DOI URL
[19]	B.R. Fonslow, M.T. Bowser, Anal. Chem. 77(2005) 5706-5710.
[20]	S. Queste, R. Salut, S. Clatot, J.-Y. Rauch, C.G. Khan Malek, Microsyst. Technol. 16(2010) 1485-1493. DOI URL
[21]	W. Reisner, J.P. Beech, N.B. Larsen, H. Flyvbjerg, A. Kristensen, J.O. Tegenfeldt, Phys. Rev. Lett. 99(2007), 058302. DOI URL
[22]	Y. Xu, C.X. Wang, Y.Y. Dong, L.X. Li, K. Jang, K. Mawatari, T. Suga, T. Kitamori, Anal. Bioanal. Chem. 402(2012) 1011-1018. DOI URL
[23]	L.D. Menard, J.M. Ramsey, Nano Lett. 11(2011) 512-517.
[24]	Y. Xu, N. Matsumoto, RSC Adv. 5(2015) 50638-50643.
[25]	C. Wang, Y. Liu, Y. Li, Y. Tian, C. Wang, T. Suga, ECS J. Solid State Sci. Technol. 6(2017) 373-P378.
[26]	W.P. Maszara, G. Goetz, A. Caviglia, J.B. McKitterick, J. Appl. Phys. 64(1988) 4943-4950. DOI URL
[27]	C. Tan, W. Yu, J. Wei, Appl. Phys. Lett. 88(2006), 114102. DOI URL
[28]	S. Agnello, D. Di Francesca, A. Alessi, G. Iovino, M. Cannas, S. Girard, A. Boukenter, Y. Ouerdane, J. Appl. Phys. 114(2013), 104305. DOI URL
[29]	F. Rubio, J. Rubio, J.L. Oteo, Spectrosc. Lett. 31(1998) 199-219. DOI URL
[30]	J.A. Theil, D.V. Tsu, M.W. Watkins, S.S. Kim, G. Lucovsky, J. Vac, Sci. Technol., A 8 (1990) 1374-1381.
[31]	G.E. Walrafen, P.N. Krishnan, J. Chem. Phys. 74(1981) 5328-5330.
[32]	A. Pasquarello, R. Car, Ateneo Veneto 80 (1998) 5145-5147.
[33]	D. Winterstein-Beckmann, D. Möncke, E.I. Palles, L. Kamitsos, J. Wondraczek, Non-Cryst. Solids 401 (2014) 110-114. DOI URL
[34]	Q. Zhang, J. Gu, G. Chen, T. Xing, Appl. Surf. Sci. 387(2016) 446-453. DOI URL
[35]	S.-M. Shang, Z. Li, Y. Xing, J.H. Xin, X.-M. Tao, Appl. Surf. Sci. 257(2010) 1495-1499. DOI URL
[36]	T. Plach, K. Hingerl, S. Tollabimazraehno, G. Hesser, V. Dragoi, M. Wimplinger, J. Appl. Phys. 113(2013), 094905. DOI URL
[37]	V. Masteika, J. Kowal, N. S.J.Braithwaite, T. Rogers, ECS J. Solid State Sci.Technol. 3(2014) Q42-Q54.
[38]	T.A. Michalske, S.W. Freiman, J. Am. Ceram. Soc. 66(1983) 284-288.
[39]	T.A. Michalske, B.C. Bunker, J. Am. Ceram. Soc. 76(1993) 2613-2618.
[40]	R. He, M. Fujino, A. Yamauchi, T. Suga, J. Appl. Phys. 54(2015), 030218. DOI URL
[41]	R. He, M. Fujino, A. Yamauchi, T. Suga, J. Appl. Phys. 55 (2016), 04EC02. DOI URL