Tom Jarman, Process Engineer, Texas Instruments
Chemical mechanical planarization (CMP) is a process used in the semiconductor industry in which a layer of the chip is planarized or flattened in preparation for putting another layer on top of it. The chemical part consists of chemical reactions occuring between the liquid polishing slurry and the top layer of the substance being polished, which is often softened in the process. The mechanical part occurs after the chemical softening, removing the top layer and exposing the next atomic layer for chemical reaction. The polishing is crucial to ensure that the subsequent layer doesn't have electrical opens or shorts due to its topography on the preceding layer. Many CMP processes consist of bulk polish on one table and then a final polish on a second table. This two-table process helps achieve the maximum possible output from a CMP tool if the two tables are properly balanced for bulk and final polish times.
I gathered and analyzed data in JMP to show the polish time vs. polish pad life relationship for Tables I and II for a CMP process at one of Texas Instruments' fabrication facilities. I then used JSL built-in integration function to calculate area under the polish time vs. pad life curve for Tables I and II. Finally, I used a system of equations to solve for a Table I polish time starting point that created equal polish time vs. polish pad life integrated areas for Tables I and II, ensuring a maximized tool output for this CMP process.