Not possible.
Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support - "Note: You can’t delete or turn off a primary iCloud Mail address. You can’t use an alias to create a separate Apple ID, and an email alias can’t be converted to a primary iCloud Mail address."
You could only use the main iCloud address as an Apple ID, and only after a 30 day wait if you have just created it.
From:
Change your Apple ID - Apple Support
- There's special instructions if you want to change your Apple ID to an @icloud.com address.
"If you try to change your Apple ID to an @icloud.com email address that was created within the last 30 days, you will be asked to try again later."
Personally I would not use the same iCloud mail address for your Apple ID. If you have problems with your account you also could not get access to the emails Apple sends you helping you with recovering your account.