Method of forming plastically deformable microstructures

Details Method of forming plastically deformable microstructures Method of forming plastically deformable microstructures

1998-10-22

2001-07-17

Dixon, Merrick (Department: 1774)

Plastic and nonmetallic article shaping or treating: processes

Forming electrical articles by shaping electroconductive...

C205S050000, C205S070000, C205S122000, C257S522000, C257S735000, C257S773000

Reexamination Certificate

active

06261494

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
Surface micromachining has become a popular method for fabricating micromechanical sensors and actuators. In the most commonly used method of forming micromechanical devices, polysilicon is used as the mechanical material. The process involves starting with a substrate. A layer of sacrificial material is deposited on the substrate. A via or other void is provided in the sacrificial layer. The mechanical material, typically polysilicon, is deposited and patterned to form the micromechanical structure. The sacrificial layer is then removed, leaving the micromechanical structure attached to the substrate and having a portion suspended over the substrate. All the structures formed in this manner tend to be generally parallel with the substrate. The distance the suspended part of the structure is disposed above the substrate is typically 2 microns, which limits the degree of movement of the suspended microstructure before it contacts the substrate.
A drawback associated with typical micromechanical devices is that suspended structures are limited to a gap of only a few microns between the suspended portion of the structure and the substrate. As such, the movement of the suspended structure relative to the substrate is severely limited.
Referring now to
FIG. 1
, a typical micromechanical device formation process is shown. Initially, a layer of sacrificial material
20
is deposited on a substrate
10
. At the next step a via
30
is produced in the sacrificial layer. At the next step a layer of material, typically polysilicon, is deposited, forming the micromechanical structure
40
. At the next step the micromechanical structure
40
is released by removal of the sacrificial layer
20
. As can be seen, the micromechanical structure
40
is only movable a small distance (typically 2 microns) before it contacts the substrate.
A technique has been developed which attempts to overcome the problem of limited movement of the suspended micromechanical structure by utilizing hinges which rotate the structure further away from the substrate after the micromechanical structure is formed. Additionally, mechanical latching has been used to support the micromechanical structures once formed. These devices have proven to be very difficult to manufacture, especially in large quantities. It would be desirable to be able to manufacture a micromechanical structure having a more pronounced three dimensional aspect and a concomitant larger degree of movement with respect to the substrate.
BRIEF SUMMARY OF THE INVENTION
A method of creating plastically deformed devices which have a three dimensional aspect. Micromechanical structures are created from a material which is plastically deformable and then a section of the micromechanical structure is bent to an out-of-plane position and can be maintained there without being supported by other mechanical devices such as latches or hinges. The bending of the structures may be done mechanically, by electrostatic forces or by magnetic forces. The bending can also be done in a batch mode where a plurality of devices are bent at the same time as part of the same process. Fuses can be utilized to allow only a predetermined number of devices to be bent in batch mode. The fuses are later blown or otherwise removed, thereby providing a plurality of devices which include suspended portions that are generally parallel to the substrate as well as a plurality of devices having suspended portions which are generally out-of-plane with respect to the substrate.


REFERENCES:
patent: 5439535 (1995-08-01), Snagovski et al.
patent: 5529681 (1996-06-01), Reinecke et al.
patent: 5716741 (1998-02-01), Reinecke et al.
patent: 5726480 (1998-03-01), Pister

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