What scope to use to get id_token in response in OAuth

What scope to use to get id_token in response in OAuth

I have generated client id and secret using  https://accounts.zoho.com/developerconsole. While making a oauth request without passing a scope in the query params, therefore after making the access token request, i am able to get id_token along with access_token in the response, but when using the scope parameter, id_token is not received. Please specify which scope value to be use to get the id_token in the response.