Direct bonding of heterogeneous wafers using surface activated bonding method at room temperature

Tsukasa Watanabe, Teak Ryong Chung, Tadatomo Suga
Research Center for Advanced Science and technology (RCAST), University of Tokyo,
4-6-1 Komaba, Meguroku, Tokyo 153, Japan

We successfully bonded the GaAs (p-type) wafer and Si (n-type) wafer at room temperature using the surface activated bonding method (SAB).  The SAB is the unique bonding method utilizing the strong adhesive force that the surface essentially has.  It is enough in order to make a strong interface that the surfaces of two wafers are made atomically clean by argon fast atom beam (Ar-FEB) in ultra high vacuum (UHV) and brought into contact.  The bonded interface was as strong as that made by the conventional annealing process and no void was found in the interface when no particle remains on the surface.  It is a unique advantage of SAB that residual thermal stresses caused by thermal expansion mismatch are not generated since no heating process is required.  No layer of high electrical resistance in the interface was expected since the electrical characteristic (I-V characteristic) showed sharp rectification.  Also the 1.3mm InGaAsP strained layer quantum-well laser diode (LD) fabricated in InP substrate was bonded on GaAs substrate by SAB method.  It shows no degradation of photoluminescence (PL) intensity after it is bonded.




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