Did Serverssl profile require certificate?

It is not a requirement. The default server-ssl profile works without certifcate checking.

Checking the backend certificate enhances the security. Import is done like any other certificates System -> Certificate Management -> Traffic Certificate Management

Hi kridsana , 
you don't need a certificate or key in server side , it will be fine with you. 
Let me explain some points. 

Imagine you you are browsing a website such as { F5.com } , will you need to setup a specified F5 digital certificate to visit their site ? Actually no , you do not need that , and this common in all public websites. 

So in the case of { SSL bridging } or adding server ssl , it's only you make Bigip to act as a client with the web application server/ pool member which locates behind your Bigip. 

The Bigip in this Case do what you do when visiting any website. 

even if the Server/pool member Certificates don't signed by Public CA , your Bigip will ignore this "trust" Challenge and proceed in ssl negotiations and establishing the needed secure connections between Bigip and the selected pool member. 

This make sense because as a client you don't have to offer a digital certificate to any website , but you as a client waits to receive the "Web site digital Certificate " signed by a well known CA , after that you as a client verifies this Certificate and it's valid duration and signature , then you as a client starts to the Key exchange phase with web site servers ( maybe it is a Bigip or any firewall has the server certificate /public key ..... ). 

Without going in-depth in ssl negotiations and connections , but your connections as a client similar to server side connections in case of ssl bridging , and you can achieve your requirements without adding extra certificates , I mean use the default ssl-server profile , it will not make issues with you.

I hope this helps you.