Existing methods to control CMP-processes are either based on simple timing, on frictional change, on optical measurement of thickness or on measurement control in-line or off-line. All these methods need a relatively large process window. CMP processes depend on quite a large number of parameters such as downward pressure, rotational speed of the platen and the carrier, relative rotational directions, kind and condition of the pad, slurry, temperature and much more.

For STI all above parameters are changing. STI has also a very small process window, so the methods mentioned above are poorly suited or very time consuming.

The big challenge has been for many years:

M17 is based on a process-state technology measuring the whole wafer and therefore delivers a representative signal for active structures at the chip. This non-intrusive system measures polishing progress in-situ and in real-time, independent of any kind of removal rate variations. M17 stops the CMP process precisely on layers containing a nitride change. It is designed to run round the clock with minimum maintenance (a few hours a year). It drastically reduces and, in many cases completely eliminates, the measurement of incoming and post CMP wafer thickness. This results in drastic increase of throughput and almost eliminates any over- or underpolish, enhancing process yield. Both features give tremendous savings.

The system is basically so reliable because it measures the light emitted as a result of chemical reactions occurring during the polishing process and in the M17 itself.