High brightness and bonding yield of integrated Si-CMOS and GaN LED wafers

To improve the bonding yield and the brightness of the final integrated Si-CMOS + GaN LED wafers, two issues have to be addressed. The first problem is the surface protrusions such as melt-back etching and hillocks which are the common surface imperfections on the surface of GaN/Si substrates. This prevents the direct contact of the two wafers and results in unbonded area. To address this, a CMP process that using conventional SiO ₂ slurry with the addition of diamond nanoparticles is carried out on the GaN (LED)-on-Si wafer prior to the bonding to the Si-CMOS wafer. The second issue is that the Si substrate of the GaN LED wafer absorbs photons which lowers the light emitting efficiency of the LEDs. We address this issue by transferring the Si-CMOS + GaN LED films from the Si (111) wafer onto a transparent quartz substrate. By addressing these issues, a high bonding yield and high brightness of Si-CMOS + GaN LED on quartz substrate can be realized.