Method and apparatus for making a MEMS scanner
Devices are formed on a semiconductor wafer in an interdigitated relationship and are released by deep reactive ion etching. MEMS scanners are formed without a surrounding frame. Mounting pads extend outward from torsion arms. Neighboring MEMS scanners are formed with their mounting pads interdigitated such that a regular polygon cannot be formed around a device without also intersecting a portion of one or more neighboring devices. MEMS scanners may be held in their outlines by a metal layer, by small semiconductor bridges, or a combination.
1. A method for manufacturing semiconductor devices; comprising:
deep etching outlines of a plurality of interdigitated shapes in a semiconductor wafer, the interdigitated shapes comprising a MEMS device having a first resonant frequency during operation;
doping the semiconductor wafer with phosphorus to allow a conduit for joule heating of the semiconductor wafer to cause the MEMS device to have a second resonant frequency in response to the joule heating; and
removing the plurality of interdigitated shapes from the semiconductor wafer to produce a plurality of semiconductor devices having irregular outlines.
2. The method for manufacturing semiconductor devices of claim 1 ; wherein the pattern of outlines of the plurality of interdigitated shapes corresponds to the pattern of a photo-mask.
3. The method for manufacturing semiconductor devices of claim 2 ; further comprising:
applying a photo-resist to the semiconductor wafer;
selectively exposing the photo-resist using the photo-mask, the photo-mask having a plurality of interdigitated shapes formed thereon; and
selectively removing photo-mask material from the semiconductor wafer.
4. The method for manufacturing semiconductor devices of claim 1 ; wherein the semiconductor devices are MEMS scanners.
5. The method for manufacturing semiconductor devices of claim 4 ; wherein each MEMS scanner is formed with a substantially constant thickness, substantially equal to the thickness of the semiconductor wafer.
6. The method for manufacturing semiconductor devices of claim 1 ; wherein the semiconductor devices are removed from the wafer without dicing the wafer.
7. The method for manufacturing semiconductor devices of claim 1 ; wherein the etched outlines of the plurality of interdigitated shapes each includes a plurality of semiconductor bridges thereacross.
8. The method for manufacturing semiconductor devices of claim 7 ; wherein removing the plurality of interdigitated shapes from the semiconductor wafer to produce a plurality of semiconductor devices having irregular outlines includes cracking the bridges.
9. The method for manufacturing semiconductor devices of claim 1 ; wherein deep etching outlines of a plurality of interdigitated shapes in a semiconductor wafer includes deep reactive ion etching.
10. The method for manufacturing semiconductor devices of claim 1 ; wherein deep etching outlines of a plurality of interdigitated shapes in a semiconductor wafer includes etching completely through the semiconductor wafer.
11. A method for fabricating a MEMS semiconductor, comprising:
etching outlines of a plurality of interdigitated shapes in a semiconductor wafer to form a MEMS device having a first resonant frequency during operation;
doping the semiconductor wafer with phosphorus to allow a conduit for joule heating of the semiconductor wafer to cause the MEMS device to have a second resonant frequency in response to the joule heating; and
removing the plurality of interdigitated shapes from the semiconductor wafer to produce a plurality of semiconductor devices having irregular outlines.
12. A method as claimed in claim 11 , wherein said doping is performed to a depth of about 0.5 microns.
13. A method as claimed in claim 11 , said doping comprising doping to a concentration of about 1×10 20 phosphorus 31 atoms/cm 3 .