| abstract |
A multistep aluminum sputtering process is disclosed wherein aluminum is sputtered onto the surface of a semiconductor wafer and low areas between closely spaced apart raised portions on the wafer, such as closely spaced apart steps, narrow trenches, or small diameter vias, are completely fulled in by the sputtered aluminum. This results in the formation of an aluminum layer which is not thinned out in such low areas, and which has a surface which ranges from substantially planar to a positive slope, such as shown at 24' and 26' in FIG. 2. The first step is carried out by sputtering from about 200 to about 2000 Angstroms of aluminum while the wafer temperature is within a range of from about 50° C. to about 250° C. and the sputtering plasma is at a power of from about 1 to about 16 kilowatts. The power level range is then changed to from about 14 to about 20 kilowatts, a DC or AC bias is applied to the wafer, and aluminum is then sputtered either for an additional time period of about 20 to about 40 seconds or until the wafer temperature reaches 500° C., whichever occurs first, in a second step. Then the back side of the wafer is contacted by a thermally conductive gas to control the wafer temperature while further aluminum is optionally sputtered onto the wafer for an additional 0 to 45 seconds in a third step. |