Sapphire-removed induced the deformation of high power InGaN light emitting diodes

Thick copper films on vertically structures InGaN LEDs play a critical role after sapphire removed. The most commonly used GaN thin film growth technique is metal-organic chemical vapor deposition (MOCVD), which provides a high growth temperature, as a result, high intrinsic stress takes place between sapphire and InGaN surface. If the aforementioned metal supporter experiences a large warpage induced from intrinsic stress after sapphire removed, the subsequent processes would be very difficult to carried out. To solve the above issue, a finite element (FE) numerical simulation was employed for stress-strain behavior analysis of the LED device, the results reveal that, increasing the thickness of metal layer or implementing a pre-metal deposition buffer layer can apparently reduce the device warpage after sapphire removal. Based on the above design concepts, the experimental result depicts that, the warpage of LED wafer can be effectively reduced by 25% when metal layer increased from 62.5 um to 82.5 um, which shows good agreements with FE result, hence validates the established research methodology. And more importantly, based on the process modelling and sapphire-removal simulation-technique developed in this study, an optimal novel LED structure is designed for the reduction of process induced warpage. To conclude, a LED chip structural design-process modeling-fabrication methodology was successfully developed, and can be further contributed to the LED industry.