Process optimization of AlGaInP red micro-LED arrays with a 3.75 μm pitch

This study reports the fabrication of a 0.12-inch red micro-LED display on a silicon substrate utilizing wafer bonding technology. The passive emission array features a resolution of 496 × 660 and a pixel pitch of 3.75 μm, resulting in a pixel density of 6773 pixels per inch (PPI). The technical challenges and optimization strategies involved in fabrication process are systematically elucidated. In particular, a SiO 2 layer is employed as the etching mask to address the enlargement of the mesa base when photoresist serves as the mask. Furthermore, Ti is selected to replace Cr as the adhesive metal layer to prevent substantial mesa detachment after metal etching process. Additionally, the hard mask thinning and benzocyclobutene (BCB) thinning procedures are conducted individually to minimize breakage of the indium tin oxide (ITO) layer between adjacent pixels. Under the optimized process conditions, the red micro-LED arrays are successfully switched on in full screen. Finally, the optoelectric properties of the micro-LED arrays are investigated.