R620 does not have BIOS recovery feature. If BIOS is corrupted then motherboard need to be replaced. Can you AC Power Cycle the server and check the behavior. You can also try to boot the server with Minimum to POST components. Minimum to POST configuration is the configuration that has the minimum components required to complete POST. Typically, the minimum to POST configuration is PSU1, CPU1, memory module in A1 slot, and the default riser without expansion cards. You can also try resetting BIOS to default with NVRAM_CLR option (Refer below link for details) and check the behavior. [URL] 
I had a power issue while I was upgrading the BIOS from LifeCycle.  Now the machine will not POST.  I can get into the iDrac and watch the post cycle I see it copy BIOS from ROM to RAM, then it does the CPU Initialization just fine.  It then hangs on the BIOS Startup which makes sense being it is most likely corrupt. Any idea how to fix the BIOS.  I have a rollback job schedules in the iDrac for the BIOS.  However, it appears the iDrac will not execute this job until the machine POSTs correctly. This is iDrac7 so I don't have the niffy recover feature that is on the iDrac9 Does this system have any type of backup BIOS feature.      
Recover R620 BIOS