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Surface Preparation of AlN for Metallization: Effect of Temperature on Surface Reactivity

Introduction: Background. Advances in Microelectronics PackagingComponent sizes decreasing, power density increasingHigher thermal conductivity requiredBeO Replacing Al2O3Higher thermal conductivityHowever, toxicity issues lead search for green materialAdvantages of AlN Competitive thermal co

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Surface Preparation of AlN for Metallization: Effect of Temperature on Surface Reactivity

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    1. Surface Preparation of AlN for Metallization: Effect of Temperature on Surface Reactivity Andrew Crawford+*, Christina Deitch*, Alan Meier* and Robert Fagan** +CEER 2003 Summer UG Fellowship Recipient *School of Engineering, Alfred University, Alfred, NY **St. Gobain Advanced Ceramics, Sanborn, NY CEER 2004 Annual Meeting at Alfred University 3 May 2004 (Based on Work Presented at the 106th Annual Meeting of The American Ceramic Society) (Indianapolis, IN, 20 April 2004)

    2. Introduction: Background Advances in Microelectronics Packaging Component sizes decreasing, power density increasing Higher thermal conductivity required BeO Replacing Al2O3 Higher thermal conductivity However, toxicity issues lead search for green material Advantages of AlN Competitive thermal conductivity Environmentally friendly Disadvantages of AlN High reactivity with water leads to reliability performance issues Existing cleaning process for AlN (typically aqueous) developed for oxide substrates

    3. Introduction: Previous Work Campman et al. [2003]: AlN Submerged in Solutions for Extended Times at 20oC 3 Types of Behavior Observed Corrosion with spalling Corrosion without spalling No corrosion Goal of this Study: Extend Work to Other Temperatures Limited data available (typically for powders) Gain control of process Understand kinetics of the surface reactions

    4. Experimental Procedure: Approach Perform Extended Duration Exposure Tests at Various Temperatures 5oC, 50oC, 90oC 86.4ks (1 day) to 2419.2ks (28 days) Expand on Matrix of Previous Work (Campman et al. [2003]) Solutions showing significant results used in this study Acidic and Basic (varied pH), organic, and water solutions Extrapolate Back to Cleaning Times of Commercial Interest

    5. Experimental Procedure: Test Matrix

    6. Experimental Procedure: Specifics Sample Exposure Tests 1 sample for each condition (temperature, solution, and exposure time) Acidic and basic solution pH’s adjusted every 21.4ks (6 hrs) for elevated temperature tests and 42.8ks (12 hrs) for 5oC tests Analysis of Surface Roughening Behavior As-received roughness measured to determine if measurable roughening occurred Average surface roughness (Ra) measured with white light interferometer SEM analysis of exposed surface

    7. Results: General 5 Types of Roughening Behavior Complicated Kinetics – No Single Mechanism Minor Changes – Minor Microstructural Changes Linear Surface Roughening – Pitted Grains Exponential Surface Roughening – Formation of Single Product on Surface Logarithmic Surface Roughening – Formation of Single Product on Surface Miscellaneous Surface Roughening – Formation of Multiple Products on Surface

    8. Results: Type I Behavior Minor Changes Type I Systems 5oC: HCl pH=3, H2SO4 pH=3, NaOH pH=8, NaOH pH=10, NaOH pH=12, Deionized Water, Alfred Tap Water 50oC: HCl pH=3, Oleic Acid 90oC: Citric Acid, Oleic Acid Observations AlN surface microstructure exhibited minor changes Exception: Citric Acid at 90oC exhibited citric acid product growth on AlN surface

    9. Results: Type II Behavior Linear Surface Roughening

    10. Results: Type III Behavior Exponential Surface Roughening

    11. Results: Type IV Behavior Logarithmic Surface Roughening

    12. Results: Type V Behavior Miscellaneous Surface Roughening

    13. Summary and Conclusions AlN samples exposed to possible cleaning solutions at varied temperatures for extended times: Low temperature slowed reaction kinetics Elevated temperatures lead to more rapid surface roughening and changes in reaction mechanisms Typically non-linear roughening behavior Results confirm surface cleaning procedure effects reliability However, cleaning potential not included in study and should be evaluated

    14. Future Work Evaluate Cleaning Efficiency of Promising Systems All low temperature solutions Solutions that exhibited minor changes and linear changes at elevated temperatures Solutions that exhibited non-linear changes at elevated temperature possibly promising Determine if a Physical Basis Exists for Empirically Fit Curves Evaluate the Effect of Sample Decomposition and Product Growth on Surface High temperature and high pH systems caused sample decomposition Current commercial cleaning solutions including Micro-90 and Citric Acid exhibited product growth on surface

    15. Acknowledgements Center for Environmental and Energy Research (CEER) at Alfred University 2003 Summer Fellowship Alfred University Equipment and Funding St. Gobain Advanced Ceramics, Sanborn, NY AlN Substrates Rob Campman and Dawn Mandich Previous Work Brett Schulz and Ward Votava at Alfred University Equipment Training and Assistance

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