Wisconsin Alumni Research Foundation

Todd R Christenson

Henry Guckel

Kenneth J Skrobis

In the formation of microstructures, a preformed sheet of photoresist, such as polymethylmethacrylate (PMMA), which is strain free, may be milled down before or after adherence to a substrate to a desired thickness. The photoresist is patterned by exposure through a mask to radiation, such as X-rays, and developed using a developer to remove the photoresist material which has been rendered susceptible to the developer. Micrometal structures may be formed by electroplating metal into the areas from which the photoresist has been removed. The photoresist itself may form useful microstructures, and can be removed from the substrate by utilizing a release layer between the substrate and the preformed sheet which can be removed by a remover which does not affect the photoresist. Multiple layers of patterned photoresist can be built up to allow complex three dimensional microstructures to be formed.

Formation of microstructures using a preformed photoresist sheet

Micromechanical devices are formed on a substrate using a sacrificial layer deep X-ray lithography process to produce a rotating microrotor which is driven magnetically. The rotor typically has a diameter of a few hundred microns or less and is formed as a free structure which is assembled onto a hub formed on a substrate. Stator pole pieces are formed on the substrate of a ferromagnetic material surrounding the rotor, and are also preferably formed by a deep X-ray lithography process followed by electroplating of a ferromagnetic material such as nickel. The stator pole pieces are supplied with magnetic flux, such as from a current flowing through a conductor surrounding the magnetic pole pieces which is integrated with the pole pieces on the substrate. Separate electromagnets can also be utilized to provide the magnetic flux to the pole pieces to provide a rotating magnetic field in the region of the rotor to drive the rotor.

Micromechanical magnetic devices

Micromechanical devices are formed on a substrate using a sacrificial layer deep X-ray lithography process to produce a rotating microrotor which is driven magnetically. The rotor typically has a diameter of a few hundred microns or less and is formed as a free structure which is assembled onto a hub formed on a substrate. Stator pole pieces are formed on the substrate of a ferromagnetic material surrounding the rotor, and are al

Method of manufacturing micromechanical devices

Microminiature pressure transducers are formed on semiconductor substrates such as silicon and include a membrane which spans a cavity over the substrate, with the membrane being mounted to and sealed to the substrate at the peripheral edges of the membrane. The bottom of the cavity forms an overpressure stop to prevent over deflections of the membrane toward the substrate. An overpressure stop formed as a bridge of a material such as nickel extends above the membrane and is spaced therefrom to allow the membrane to deflect freely under normal pressure situations but prevent over deflections. The thickness of the polysilicon membrane and the spacing between the membrane and the overpressure stops is preferably in the range of 10 micrometers or less, and typically in the range of one micrometer. The overpressure stop bridge is formed utilizing deep X-ray lithography to form a well-defined bridge structure. The gap between the membrane and the bottom surface of the bridge is established with a sacrificial layer, such as a polyimide film, which dissolves in a solvent. The transducer is formed utilizing processing techniques which do not affect the performance of the membrane as a pressure sensor and which allow the substrate to have further micromechanical or microelectronic devices formed thereon.

Growing community of inventors

Madison, WI, United States of America

Todd R Christenson