| US 7,405,099 B2 | ||
| Wide and narrow trench formation in high aspect ratio MEMS | ||
| Bishnu P. Gogoi, Scottsdale, Ariz. (US) | ||
| Assigned to Freescale Semiconductor, Inc., Austin, Tex. (US) | ||
| Filed on Jul. 27, 2005, as Appl. No. 11/192,198. | ||
| Prior Publication US 2007/0026636 A1, Feb. 01, 2007 | ||
| Int. Cl. H01L 21/00 (2006.01) | ||
| U.S. Cl. 438—50 [438/51; 438/52; 438/53; 257/414; 257/415; 257/417] | 19 Claims |
| 1. A method of forming a high-aspect ratio microelectromechanical (MEM) device on a substrate including a substrate layer,
an active layer, and a first sacrificial layer disposed at least partially therebetween, the method comprising the steps of:
forming a first trench, a second trench, and a third trench in the active layer, each trench having an opening and sidewalls
defining substantially equal first trench widths;
forming a second sacrificial layer over a surface of the active layer and the sidewalls of each of the trenches;
forming a third sacrificial layer over the second sacrificial layer and sealing the openings of each of the trenches with
the third sacrificial layer;
forming an etch hole in the second sacrificial layer and the third sacrificial layer between the first trench and the second
trench to expose a portion of the active layer;
removing material from the active layer between the first trench and the second trench to form a cavity having sidewalls and
an opening;
forming a fourth sacrificial layer over the third sacrificial layer and the sidewalls of the cavity and sealing the cavity
and its opening with the fourth sacrificial layer; and
removing the second sacrificial layer, the third sacrificial layer, and the fourth sacrificial layer to expose the third trench
and form a fourth trench in the active layer from the first and the second trench, the fourth trench having sidewalls defining
a second trench width that is greater than the first trench width.
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