Protection of M1 Cu Surface Prior to M2 Evaporation
Original Publication Date: 1981-Nov-01
Included in the Prior Art Database: 2005-Feb-12
In MCP (metallized ceramic polyimide) substrate technology, interconnects between the two layers of circuitry is achieved by etching vias in the polyimide layer and exposing the Cu surface of M1 and then evaporating the M2 layer on top of it. Oxidation of the M1-Cu surface has been seen to cause high resistance in the vias and degrade via reliability. Although there are oxide-removing steps in the process, such as immersion in 10% sulphuric acid, reoxidation takes place during the rinse and drying steps and upon exposure to the air during loading into the evaporator dome. The reoxidation of Cu during and after the 10% sulphuric acid dip process is at present inevitable and creates an uncontrolled situation.