Interfacial synergy between back‐grinding‐induced surface roughness and silane chemistry for high‐thermal‐performance <scp>DAF</scp> ‐less <scp>3D</scp> stacking

Abstract A die attach film (DAF)‐less multi‐die stacking strategy is demonstrated for advanced three‐dimensional (3D) semiconductor packaging. Conventional DAF‐based stacking introduces a thick, low‐thermal‐conductivity polymeric interlayer that increases inter‐die spacing and impedes heat transfer. To overcome these limitations, back‐grinding‐induced surface roughness control is combined with silane chemistry. Si chips with rough‐ground (Z1), fine‐ground (Z2), and polished (Z3) surfaces are systematically evaluated. The 3‐aminopropyltriethoxysilane/3‐glycidyloxypropyltrimethoxysilane molar ratio of 1:2 (APG12) provides balanced amine–epoxy coupling. The APG12‐treated Z2–Z2 configuration exhibits a narrow interfacial gap of ca. 0.31 μm and a shear strength of 4.2 MPa, comparable to the Z3–Z3 (4.3 MPa) without an additional step. Infrared thermography shows that the temperature rise of the DAF‐less package after 15 s is ca. 1.3‐fold greater than that of the DAF‐based package, indicating improved heat‐transfer efficiency. This strategy provides a process‐compatible route toward mechanically reliable and thermally efficient high‐density 3D integration.