| abstract |
The present invention provides a method for modifying a C4 device, the device including a circuit, a polyimide layer, and a plurality of solder bumps in the active region of the C4 device. The method includes removing the polyimide layer using a plasma etch, the plasma etch comprising a mixture of oxygen and an inert gas; modifying the circuit; and cleaning the modified C4 device with a reactive flux. By mixing the oxygen with an inert gas, the oxidation of the solder bumps due to the plasma etch are reduced. Because the top layer features are now readily visible, circuit structures are more easily located, and modification can be more easily performed and with more accuracy. In the preferred embodiment, the device is then cleaned with a reactive flux, which removes any oxidation layer which has formed on the solder bumps. In this manner, circuit modification may be performed more quickly while also minimizing the oxidation of the solder bumps. The reduced oxidation of the solder bumps will help the C4 packaging process to be successful for electrical testing after focused beam ion (FIB) modification. Also, since the costly FIB process is not required to locally remove the polyimide layer for locating circuit structures, the cost of device fabrication is reduced. |