We want to remove the metal cap on top to examine the inside. Datasheet says it's a sealed IC for protection from environment. How can we remove of metal cap to see it under the microscope? It is in size about 2mm
If you want to be sure, order a replacement identical part and take the lid off it using a milling machine. Then you can modify your approach to the real device based on the successes or failures in milling the replacement. If necessary, step and repeat on more replacements until you are sure your technique is correct.