Backup Iphone SE11 with Locked Screen

If you're talking about enabling automatic iCloud backup overnight, your iPhone MUST meet ALL the requirements listed at the section "Automatically back up with iCloud Backup" in the support article that led you here, that is to say: backup enabled, iPhone plugged into power, connected to a wifi network with internet access, screen locked (it goes to lock status automatically, according to the time you adjusted with Autolock in Settings>Display & Brightness).

If you mean something different, please better spcify your needs.

Regards

Giulio

No, if you're trying to backup your device manually (using "backup now"), you don't need to lock the screen, but if you lock it, the backup process should proceed anyway.