Wafer Bonding

Cunningham, Shawn; Kupnik, Mario

doi:10.1007/978-0-387-47318-5_11

Cited by 10 publications

(8 citation statements)

References 70 publications

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“…Unlike traditional hermetic bonding methods requiring high temperatures (>300 °C) for long periods (>1 h), cold welding allows for a low-temperature (150 °C) bonding process in a short time (10 min) to prevent VUV window cracking caused by the large thermal expansion coefficient (CTE) mismatch (CTE Si = 2.6; CTE MgF2 = 13.7; CTE LiF = 37; unit: 10 –6 /K). On the other hand, compared to other low-temperature bonding techniques − ( e.g.…”

Section: Resultsmentioning

confidence: 99%

“…Unfortunately, most established hermetic bonding techniques ( e.g. , eutectic, anodic, and fusion) ,, are not applicable for bonding MgF 2 or LiF with silicon, since fluoride glass is easy to crack at the high temperatures required for processing (>300 °C) due to the large thermal mismatch.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is desirable to integrate a VUV window on top of the microfluidic chip glue-free. 8 Unfortunately, most established hermetic bonding techniques (e.g., eutectic, anodic, and fusion) 7,13,36 are not applicable for bonding MgF 2 or LiF with silicon, since fluoride glass is easy to crack at the high temperatures required for processing (>300 °C) due to the large thermal mismatch. The present work is aimed at achieving (1) glue-free bonding between a VUV lamp and a silicon chip for future high-yield mass production and (2) increased lifetime of a VUV lamp and hence PID, especially an Ar-based lamp with a LiF window.…”

Section: ■ Introductionmentioning

confidence: 99%

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Ultrathin Silica Integration for Enhancing Reliability of Microfluidic Photoionization Detectors

et al. 2023

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Microfluidic photoionization detectors (μPIDs) based on silicon chips can rapidly and sensitively detect volatile compounds. However, the applications of μPID are limited by the manual assembly process using glue, which may outgas and clog the fluidic channel, and by the short lifetime of the vacuum ultraviolet (VUV) lamps (especially, argon lamps). Here, we developed a gold−gold cold welding-based microfabrication process to integrate ultrathin (10 nm) silica into μPID. The silica coating enables direct bonding of the VUV window to silicon under amicable conditions and works as a moisture and plasma exposure barrier for VUV windows that are susceptible to hygroscopicity and solarization. Detailed characterization of the silica coating was conducted, showing that the 10 nm silica coating allows 40−80% VUV transmission from 8.5 to 11.5 eV. It is further shown that the silica-protected μPID maintained 90% of its original sensitivity after 2200 h of exposure to ambient (dew point = 8.0 ± 1.8 °C), compared to 39% without silica. Furthermore, argon plasma inside an argon VUV lamp was identified as the dominant degradation source for the LiF window with color centers formation in UV−vis and VUV transmission spectra. Ultrathin silica was then also demonstrated effective in protecting the LiF from argon plasma exposure. Lastly, thermal annealing was found to bleach the color centers and restore VUV transmission of degraded LiF windows effectively, which will lead to future development of a new type of VUV lamp and the corresponding μPID (and PID in general) that can be mass produced with a high yield, a longer lifetime, and better regenerability.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Ultrathin Silica Integration for Enhancing Reliability of Microfluidic Photoionization Detectors

et al. 2023

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“…Interestingly, in case HF vapor etching is used, the BOX layer can not contain an oxide-to-oxide bonding interface, because the horizontal etch rate at such an interface is by far too high. For more details on this see [13]. …”

Section: Resultsmentioning

confidence: 99%

CMUT fabrication based on a thick buried oxide layer

Kupnik

Vaithilingam

Torashima

et al. 2010

2010 IEEE International Ultrasonics Symposium

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We introduce a versatile fabrication process for direct wafer-bonded CMUTs. The objective is a flexible fabrication platform for single element transducers, 1D and 2D arrays, and reconfigurable arrays. The main process features are: A low number of litho masks (five for a fully populated 2D array); a simple fabrication sequence on standard MEMS tools without complicated wafer handling (carrier wafers); an improved device reliability; a wide design space in terms of operation frequency and geometric parameters (cell diameter, gap height, effective insulation layer thickness); and a continuous front face of the transducer (CMUT plate) that is connected to ground (shielding for good SNR and human safety in medical applications). All of this is achieved by connecting the hot electrodes individually through a thick buried oxide layer, i.e. from the handle layer of an SOI substrate to silicon electrodes located in each CMUT cell built in the device layer. Vertical insulation trenches are used to isolate these silicon electrodes from the rest of the substrate. Thus, the high electric field is only present where required -in the evacuated gap region of the device and not in the insulation layer of the post region. Array elements (1D and 2D) are simply defined be etching insulation trenches into the handle wafer of the SOI substrate.

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“…rthowe@stanford.edu (roughness <2 Å rms 10 ) on both wafers to obtain a high fabrication yield. As polishing SiC is extremely difficult, the SiC wafer can be thermally oxidized prior to the hydrogen implantation, and the oxide layer can then be polished after implantation to get a smooth surface.…”

Section: Introductionmentioning

confidence: 99%

Smart-cut layer transfer of single-crystal SiC using spin-on-glass

Lee

Bargatin

Park

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The authors demonstrate "smart-cut"-type layer transfer of single-crystal silicon carbide (SiC) by using spinon-glass (SoG) as an adhesion layer. Using SoG as an adhesion layer is desirable because it can planarize the surface, facilitate an initial low temperature bond, and withstand the thermal stresses at high temperature where layer splitting occurs (800-900 °C). With SoG, the bonding of wafers with a relatively large surface roughness of 7.5-12.5 Å rms can be achieved. This compares favorably to direct (fusion) wafer bonding, which usually requires extremely low roughness (<2 >Å rms), typically achieved using chemical mechanical polishing (CMP) after implantation. The higher roughness tolerance of the SoG layer transfer removes the need for the CMP step, making the process more reliable and affordable for expensive materials like SiC. To demonstrate the reliability of the smart-cut layer transfer using SoG, we successfully fabricated a number of suspended MEMS structures using this technology. Smart-cut layer transfer of single-crystal SiC using spin-on-glass The authors demonstrate "smart-cut"-type layer transfer of single-crystal silicon carbide (SiC) by using spin-on-glass (SoG) as an adhesion layer. Using SoG as an adhesion layer is desirable because it can planarize the surface, facilitate an initial low temperature bond, and withstand the thermal stresses at high temperature where layer splitting occurs (800-900 C). With SoG, the bonding of wafers with a relatively large surface roughness of 7.5-12.5 Å rms can be achieved. This compares favorably to direct (fusion) wafer bonding, which usually requires extremely low roughness (<2 Å rms), typically achieved using chemical mechanical polishing (CMP) after implantation. The higher roughness tolerance of the SoG layer transfer removes the need for the CMP step, making the process more reliable and affordable for expensive materials like SiC. To demonstrate the reliability of the smart-cut layer transfer using SoG, we successfully fabricated a number of suspended MEMS structures using this technology. Disciplines Mechanical Engineering

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Wafer Bonding

Cited by 10 publications

References 70 publications

Ultrathin Silica Integration for Enhancing Reliability of Microfluidic Photoionization Detectors

Ultrathin Silica Integration for Enhancing Reliability of Microfluidic Photoionization Detectors

CMUT fabrication based on a thick buried oxide layer

Smart-cut layer transfer of single-crystal SiC using spin-on-glass

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