Abstract:
The invention provides a general fabrication method for producing MicroElectroMechanical Systems (MEMS) and related devices using Silicon-On-Insulator (SOI). One first obtains an SOI wafer that has (i) a handle layer, (ii) a dielectric layer, and (iii) a device layer. A mesa etch has been made on the device layer of the SOI wafer and a structural etch has been made on the dielectric layer of the SOI wafer. One then obtains a substrate (such as glass or silicon), where a pattern has been etched onto the substrate. The SOI wafer and the substrate are bonded together. Then the handle layer of the SOI wafer is removed, followed by the dielectric layer of the SOI wafer.
Abstract:
The present invention relates to a fabrication process for manufacture of micro electromechanical (MEM) devices such as cantilever support beams. This fabrication process requires only two lithographic masking steps and offers moveable electromechanical devices with high electrical isolation. A preferred embodiment of the process uses electrically insulating glass substrate (102) as the carrier substrate and single crystal silicon (108) as the MEM component material. The process further includes deposition of an optional layer of insulating material (110) such as silicon dioxide on top of a layer of doped silicon (108) grown on a silicon substrate. The silicon dioxide (110) is epoxy bonded to the glass substrate (102) to create a silicon-silicon dioxide-epoxy-glass structure (200). The silicon is patterned using anisotropic plasma dry etching techniques. A second patterning then follows to pattern the silicon dioxide layer (110) and an oxygen plasma etch is performed to undercut the epoxy film (120) and to release the silicon MEM component. This two-mask process provides single crystal silicon MEMs with electrically isolated MEM component. Retaining silicon dioxide insulating material (110) in selected areas mechanically supports the MEM component.
Abstract:
A method of forming a membrane with nanometer scale pores includes forming a sacrificial etch stop layer on a substrate. A base layer is constructed on the sacrificial etch stop layer. Micrometer scale pores are formed within the base layer. A sacrificial base layer is built on the base layer. The sacrificial base layer is removed from selected regions of the base layer to define nanometer scale pores within the base layer. The resultant membrane has sub-fifty nanometer pores formed within it.
Abstract:
To increase the sensitivity of the sensor the suspended structure (40) forming the seismic mass has a tungsten core (26) which has high density. To manufacture it, a sacrificial layer (21) of silicon oxide, a polycrystal silicon layer (24), a tungsten layer (26) and a silicon carbide layer (28) are deposited in succession over a single crystal silicon body (1); the suspended structure (40) is defined by selectively removing the silicon carbide (28), tungsten (26) and polycrystal silicon (24) layers; spacers (30') of silicon carbide are formed which cover the uncovered ends of the tungsten layer (26); and the sacrificial layer (21) is then removed.
Abstract:
A dissolved wafer micromachining process is modified by providing an etch control seal around the perimeter of a heavily doped micromechanical structure formed on a substrate. The micromechanical structure is fabricated on a wafer using conventional methods including the formation of a trench that surrounds and defines the shape of the micromechanical structure in the substrate. The etch control seal comprises a portion of the substrate in the form of a raised ring extending around the perimeter of the micromechanical structure and its defining trench. Selected raised areas of the heavily doped micromechanical structure and the top of the raised etch control seal are bonded to a second substrate. A selective etch is then used to dissolve the first substrate so that the heavily doped micromechanical structure remains attached to the second substrate only at the bonded areas. The etch control seal reduces exposure of the micromechanical structure and bonded areas to the etch by preventing the etch from contacting the heavily doped structure until the etch leaks through the dissolving floor of the trench. This occurs only during the final stages of the substrate dissolution step, thus minimizing exposure of the micromechanical structure and bonded areas to the damaging effects of the etch. Use of an etch control seal increases design flexibility and improves micromechanical device yield and quality in a dissolved wafer fabrication process.