There are few CPM ad networks that are not pop-up / pop-under ads. Propeller Ads is a CPM ad network that offers multiple types of ads including banner ads. However, in order to use CPM banner ads, you need a website with huge traffic. If you do not have a lot of traffic, you end up using pop-under ads from Propeller Ads. I have used this ad network and stopped using it after the first payment of $5.