Method of forming ultra thin coreless substrates are described. In an embodiment, the method utilizes a debond layer including high and low adhesion surface areas to the carrier substrate, and cutting through the low adhesion surface areas to remove a build-up structure from the carrier substrate. An electrical short layer may be formed as a part of or on the debond layer to facilitate electrical testing of the build-up structure prior to debonding, and aid in the formation a “known good” substrate on a support substrate.