satisfactory spectra. However, these electroplate formed copper grids are not noted for their purity, so a much more pure grid must be employed to render meaningful results. Grids formed by e-beam evaporation of high purity Al or Au should be excellent. This discussion only applies to oxide films greater than 1500 angstroms thick. Thinner oxides behave the same as bare silicon. Therefore, when searching for the source of contaminants, such as furnace tubes, the oxide thickness should be kept below about 1200°C which just happens to be the gate oxide thickness of most MOS devices.

No presentation concerning oxide analysis would be complete without illustrating the mobile ion problem shown by Ron Baxter1 in Figure 18. These profiles were taken on the same sample using both a positive and negative beam. The conclusion is that using a positive beam, the Na all moves to the interface and with a negative beam, it is all drawn to the surface. The grid technique may help this problem as well, but to date the grid itself has been the dominant source of sodium.

To summarize this presentation, a look at secondary ion mass spectroscopy with respect to five criteria for surface analysis is in order.

1. Accuracy of Chemical Analysis

The qualitative analysis was shown to be very good and the Ag experiment showed quantitative potential is fair.