| Abstrakt: |
Pure Cu substrate has been previously electroplated on p-GaN side of vertical structure GaN-based light emitting diode (LED) to mechanically hold thin GaN-based multilayer after removal of a sapphire substrate by laser lift-off process. The ductile Cu substrate needs to be mechanically strengthened to prevent the GaN-based multilayer from being damaged during vertical LED chip fabrication. In this study, the formation of Cu substrate with W addition on Au-seeded LED wafer by electroplating is introduced. W presents as W03 in the Cu substrate. W content of W-added Cu deposits was dependent on constant reduction potential in an acidic citrate bath. The reduction potential also influenced directly the electrical resistivity, hardness, and residual stress of W-added Cu substrates. Applying moderate reduction potentials like -1.1 V resulted in 1.5 times larger hardness than that of pure Cu substrate by adding around 1.0 at % W to Cu. Nevertheless, the electrical resistivity of W-added Cu substrate was maintained as low as that of pure Cu substrate. At more positive reduction potentials than -1.1 V, very low residual Stress between 4 and 42 MPa was measured. Wafer bowing induced by large residual stress of W-added Cu substrate can cause serious mechanical damage to LED structure. [ABSTRACT FROM AUTHOR] |
