C4 Pb/Sn evaporation process

Claim 2

A process of Pb/Sn evaporation to form solder bump interconnects and reduce critical molybdenum mask sensitivity comprising the steps of: sensing in situ process temperature at a wafer surface and a mask surface; and in response to the sensed process temperature, maintaining parallel temperature gradients between the molybdenum mask and the wafer during vacuum evaporation through which Pb/Sn pads are deposited, thus resulting in elimination of connecting haloes and yield losses.

Claim 3

The process of Pb/Sn evaporation to form solder bump interconnects recited in claim 1 wherein the step of sensing is performed with a thermocouple located in a path of an evaporant.

Claim 4

A process of Pb/Sn evaporation to form solder bump interconnects and reduce critical molybdenum mask sensitivity comprising the steps of: sensing in situ process temperature at a wafer surface and a mask surface; and in response to the sensed process temperature, maintaining parallel temperature gradients between the molybdenum mask and the wafer during vacuum evaporation through which Pb/Sn pads are deposited, thus resulting in elimination of connecting haloes and yield losses, wherein the step of sensing is performed with a thermocouple located in a path of an evaporant, and wherein the step of maintaining parallel temperature gradients between the molybdenum mask and the wafer during vacuum evaporation is performed according to the following profile: ______________________________________ Set Segment Time Description Point Actual ______________________________________ 50 2.0 Min PbSn phase change sol-liq 50 39 1 2.0 Min PbSn phase change sol-liq 60 45 2 5.0 Min Initial Pb evaporation 70 64 3 5.0 Min Initial Pb evaporation 80 79 4 10.0 Min Rate controlled evaporation 120 118 5 5.0 Min Rate controlled evaporation 150 149 6 40.0 Min Final Pb evaporation 170 168 7 10 Sec Pb evaporation end point 170 150' 8 30 Sec Pre Sn power 170 131 9 4.0 Min Sn evaporation 210 210 10 7.0 Min Sn evaporafion 215 212 11 Vent 49 Off ______________________________________ wherein segments 4 and 5 are rate controlled to minimize the wafer ΔT and segments 6 and 7 are rate controlled to maximize cycle time efficiency.

Claim 5

A process of Pb/Sn evaporation to form solder bump interconnects and reduce critical molybdenum mask sensitivity comprising the steps of: sensing in situ process temperature at a wafer surface and a mask surface; and in response to the sensed process temperature, maintaining parallel temperature gradients between the molybdenum mask and the wafer during vacuum evaporation through which Pb/Sn pads are deposited, thus resulting in elimination of connecting haloes and yield losses, wherein the step of sensing is performed with a thermocouple located in a path of an evaporant, and wherein the step of maintaining parallel temperature gradients between the molybdenum mask and the wafer during vacuum evaporation is performed according to the following profile: ______________________________________ Set Segment Time Description Point Actual ______________________________________ 50 2.0 Min PbSn phase change sol-liq 50 39 1 2.0 Min PbSn phase change sol-liq 60 45 2 5.0 Min Initial Pb evaporation 70 64 3 5.0 Min Initial Pb evaporation 80 79 4 10.0 Min Rate controlled evaporation 120 118 5 5.0 Min Rate controlled evaporation 150 149 6 40.0 Min Final Pb evaporation 170 168 7 10 Sec Pb evaporation end point 170 150' 8 30 Sec Pre Sn power 170 131 9 4.0 Min Sn evaporation 210 210 10 7.0 Min Sn evaporafion 215 212 11 Vent 49 Off ______________________________________ wherein segments 4 and 5 are rate controlled to minimize the wafer ΔT and segments 6 and 7 are rate controlled to maximize cycle time efficiency.