| US 7,476,849 B2 | ||
| Technique for monitoring and controlling a plasma process | ||
| Bon-Woong Koo, Andover, Mass. (US); Ludovic Godet, Beverly, Mass. (US); Vassilis Panayotis Vourloumis, Peabody, Mass. (US); Vikram Singh, North Andover, Mass. (US); and Ziwei Fang, Beverly, Mass. (US) | ||
| Assigned to Varian Semiconductor Equipment Associates, Inc., Gloucester, Mass. (US) | ||
| Filed on Mar. 10, 2006, as Appl. No. 11/371,907. | ||
| Prior Publication US 2007/0210248 A1, Sep. 13, 2007 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. H01J 49/40 (2006.01); G01N 27/26 (2006.01); G01N 33/00 (2006.01) | ||
| U.S. Cl. 250—287 [250/288; 250/299; 250/281; 250/282; 315/111.21; 315/111.31] | 21 Claims |
| 1. A time-of-flight ion sensor for monitoring ion species in a plasma chamber, comprising:
a drift tube;
an extractor electrode and a plurality of electrostatic lenses disposed at a first end of the drift tube, wherein the extractor
electrode is biased to attract ions from a plasma in the plasma chamber, and wherein the plurality of electrostatic lenses
cause at least one portion of the attracted ions to enter the drift tube and drift towards a second end of the drift tube
within a limited divergence angle;
an ion detector disposed at the second end of the drift tube, wherein the ion detector detects arrival times associated with
the at least one portion of the attracted ions; and
a housing for the extractor, the plurality of electrostatic lenses, the drift tube, and the ion detector, wherein the housing
accommodates differential pumping between the ion sensor and the plasma chamber,
wherein the plasma chamber holds a wafer for processing in the plasma, wherein the ion sensor as positioned along a side of
the wafer so that the ion sensor and the wafer share substantially the same vantage point with respect to the plasma, and
the wherein the housing is biased at approximately the same potential as the wafer.
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