Combined Surface-Activated Bonding (SAB) Technologies for New Approach to Low Temperature Wafer Bonding
Bibliographic record
Abstract
Surface activating/cleaning is of great importance for low temperature wafer bonding and various surface activating methods have been studied. Fast atom bombardment activation removes oxides and contaminations on bonding surface and it is efficient for room temperature wafer bonding for semiconductors and metals, etc. Plasma activated bonding has been developed for low temperature hydrophilic bonding for silicon and silicon oxide wafers[1] and Au bonding. Formic acid gas treatment reduces Cu oxide to Cu and then the Cu can be bonded at temperature below 200°C [2]. Water vapor-assisted SAB method introduces water vapor onto the FAB activated surfaces at atmospheric pressure, and then homogeneous and heterogeneous bonding of Cu, SiO2, and polyimide can be achieved at 150°C and atmospheric pressure [3]. SAB with a modification using nano-adhesion layer at the interface realized room temperature bonding of polymer films and glass[4]. However, every activating method has its advantages and limitations depending the bonding materials and applications. Thus, there is a need to combine various surface activating methods for novel low temperature wafer bonding approaches development. The objectives of this study are to develop new approach for low temperature wafer bonding by using combined surface-activated bonding (SAB) technologies and to explore the mechanisms of the bonding processes. We used Ar plasma and Ar fast atom bombardment (FAB) to activate the Cu/polymer hybrid surface for removal of Cu native oxide and organic contaminations on Cu surface. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical composition and state of the activated surfaces. The results show that Ar FAB is more effective for Cu oxides and organic contaminations removal than Ar plasma. The XPS spectra (Figure 1) show that Cu hydroxide, Cu oxides and organic contaminations on Cu surface could be removed by FAB activating for 9 minutes. However, Cu contamination on polymer surface is observed after both Ar plasma and Ar FAB activation. To develop new low temperature bonding approaches, we designed a combined surface-activated bonding system, which consists of two main subsystems: a surface activating subsystem and a wafer bonding subsystem. The surface activating subsystem could employ combined surface activating processes, including oxygen, nitrogen, and fluorine containing plasma, formic acid gas, water vapor and FAB surface treatments. The wafer bonding subsystem could perform wafer alignment and bonding process in ultra high vacuum. In this paper, we report the design and results of a combined surface-activated bonding system that we have constructed to explore the effects of combined surface activating processes on bonding surfaces, and conclude with prospects for the future. References [1] C. Wang and T. Suga, “Room-Temperature Direct Bonding Using Fluorine Containing Plasma Activation,” J. Electrochem. Soc., vol. 158, no. 5, pp. H525–H529, May 2011. [2] W. Yang, M. Akaike, M. Fujino, and T. Suga, “A New Combined Process of Formic Acid Pretreatment for Low-temperature Bonding of Copper Electrodes,” ECS Trans., vol. 50, no. 7, pp. 133–138, Mar. 2013. [3] A. Shigetou and T. Suga, “Vapor-Assisted Surface Activation Method for Homo- and Heterogeneous Bonding of Cu, SiO2, and Polyimide at 150°C and Atmospheric Pressure,” J. Electron. Mater., vol. 41, no. 8, pp. 2274–2280, Aug. 2012. [4] T. Matsumae, M. Nakano, Y. Matsumoto, and T. Suga, “Room Temperature Bonding of Polymer to Glass Wafers Using Surface Activated Bonding (SAB) Method,” ECS Trans., vol. 50, no. 7, pp. 297–302, Mar. 2013.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".