Planarization of Copper Circuits for Multilevel Ceramic Package
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Background: In order to reduce transmission line delay times due to capacitive coupling, copper circuit lines are embedded in a low dielectric constant material. Method: This invention describes a process for the planarization of copper transmission lines in a low dielectric constant material, such as polyimide. The process is as follows: a. Spin polyimide on a ceramic substrate. b. Semicure the polyimide by heating to a temperature from 100 to 200 C. c. Deposit copper; either (1) make a blanket coating and etch or (2) deposit through a lift-off photoresist d. Heat and press copper in the form of a circuit into the polymer under conditions where the polymer flows. e. Final cure. Alternatively, before the final cure the polymer can be textured followed by the application of a polymer layer. Then proceed to the final cure.