Tin Deposition Rate Control
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
In the fabrication of contact pads for semiconductor integrated circuit devices, it is desirable to accurately control the deposition of tin used in the contact pad metallurgy. The described monitoring apparatus uses sensor crystals to permit the precise control of tin content or the thickness of a tin layer on the contact pads. Prior deposition processes used lead-tin pellets evaporated from a single source cup to produce a contact pad of the desired height and having a specified tin content. A predetermined amount of tin was completely evaporated from the source cup during the deposition step. If the process were interrupted, for example, by a failure of the source cup, it was difficult to determine the exact amount of tin required to complete the evaporation.