Layer Transfer Using Plasma Processing for SMART-Wafer SFR Workshop November 8, 1999 Changhan Yun, Yonah Cho, and Nathan Cheung Berkeley, CA New applications of plasma processing for system integration of photonics, MEMS, and electronics. 11/8/99

Motivation: Layer Transfer for System Integration Membrane by Ion-cut GaN LED array by Laser Liftoff Si GaN 1mm 100mm Integration of Optics, MEMS, and Electronics Oxide Electronic LED/LASER Devices Membrane 11/8/99

Ion-Cut Layer Transfer Process H+ 1. H+ Plasma Implantation SiO2 Hydrogen peak Si donor Handle wafer Si donor 2 Plasma activated Wafer Bonding Bonding interface Handle wafer Si donor 3. Donor wafer cleavage with heat treatment Hydrogen induced Si layer cleavage Transferred Si overlayer Handle wafer 11/8/99

Wafer Bonding with Plasma Surface Treatment Wafer direct bonding 1) Chemical (piranha, HF, RCA) cleaning 2) Plasma surface treatment to increase bond strength XPS Result before and after Plasma Treatment Bond Strength Measurement Wafer t 2y 5000 before Razor after L Counts (a.u.) Bond strength = 1000 3 Et3y2 SiO2 Si 8 L4 112 108 104 100 96 92 Binding Energy (eV) 11/8/99

Results: SOI fabrication by Plasma Implantation V bias= -20kV, Dose = 1017 H/cm2, T cut = 550C Transferred silicon layer, 120nm Buried oxide, 200nm 1mm 29nm 0nm 2mm 0mm AFM scan over 2mm2mm area of transferred silicon layer surface RMS roughness ~ 4.1nm (as-cut) 11/8/99

Results: Oxide Membrane Fabrication 1. H+ Implantation & Etching Cavity 2. Wafer Bonding at room temp. 3. Si Cleavage at ~500OC 4. XeF2 Etching of Si overlayer Si donor Oxide Membrane Silicon on Oxide H+ Etched Cavity Handle wafer 20 mm 100mm SEM Cross-section 1mm Optical micrographic top view 11/8/99

Excellent resonator Q-factor expected from uniform , smooth membranes Discussion * Membrane thickness uniformity across 100mm wafer is less than 0.3%. *AFM scan over membrane surface. The as-cut surface micro-roughness is 6nm. Excellent resonator Q-factor expected from uniform , smooth membranes 11/8/99

Progress vs Milestones Year 1 Single-crystal Si membrane on buried cavities with thickness good uniformity (<0.3%) and surface micro-roughness (<10nm) Plasma surface-activated Si-Si direct bonding and anodic Si-Glass bonding demonstrated. Year 2 Demonstrate GaN Blue-LED layer transfer Integration of GaN LED array and c-Si resonator array in progress 11/8/99

Future Work (2000-2002) Prototyping of integrated optical, micro-mechanical resonator and active IC devices on a SMART wafer for real-time processing diagnostics LED resonator Thermal Sensor 11/8/99