Low resistance microfabricated filter

A method of using a microfabricated filtration device, the method comprising:

• delivering a fluid to a filtration device, the filtration device including:
• a planar membrane section comprising a plurality of pores, each pore having a width of less than about 100 nm, and
• a support section comprising a substrate coupled with the membrane section, the substrate comprising a plurality of thick portions and a plurality of recesses between the thick portions in a second thin portion that is between adjacent thick portions, wherein the recesses are in communication with the pores in the plurality of pores;
• flowing the fluid over the planar membrane section to produce a filtered fluid;
• and
• delivering the filtered fluid from the filtration device.

A microfabricated filtration device comprising:

• a membrane section having a thickness of less than about 1 μm in height and defining a plurality of pores having a width of less than about 10 nm;
• and
• a support section comprising a substrate coupled with the membrane section, the substrate at least partially defining a cavity and a plurality of recesses, wherein:
• the cavity is located in the backside of the substrate and is in communication with the plurality of recesses, wherein the recesses are in communication with the defined pores, and
• the plurality of recesses are defined by portions of the substrate such that each portion of the substrate located between any two recesses comprises a height of about 50 μm or less.

A method of making a microfabricated filtration device, the method comprising:

• depositing a dielectric layer over a semiconductor substrate;
• forming a first layer of a membrane material on the dielectric layer and etching a pattern in the first membrane material layer;
• forming a sacrificial dielectric layer over the patterned first membrane material layer and forming a second membrane material layer over the sacrificial dielectric layer;
• forming a protective layer over the second membrane material layer;
• etching the substrate with a first etchant process that produces a cavity that does not extend to the layers of membrane material;
• etching the substrate with a second etchant process that forms a plurality of recesses through the remaining portion of the substrate;
• and
• etching the filtration device with a third etchant process that removes the sacrificial dielectric layer forming pores through the membrane material layers, which provides access to the recesses such that the combination of the pores, recesses, and the cavity produce apertures through the filtration device.

A method of filtering a fluid, comprising

• delivering a first fluid into a filtration device;
• flowing the first fluid across a front side of a filtration member located in the filtration device that includes a membrane section having a thickness of less than about 1 μm in height and defining a plurality of pores with each pore having a width of less than about 50 nm;
• flowing a second fluid across a backside of the filtration member located in the filtration device that includes a support section comprising a substrate coupled with the membrane section, the substrate at least partially defining a cavity and a plurality of recesses, wherein:
• the cavity is located in the backside of the substrate and is in communication with the plurality of recesses, wherein the recesses are in communication with the defined pores,
• the plurality of recesses are defined by portions of the substrate such that each portion of the substrate located between any two recesses comprises a height of about 50 μm or less, and
• the second fluid flows through the cavity to provide the second fluid to the recesses so that diffusive transport occurs across the membrane section between the first and second fluids to produce filtered first fluid;
• and
• transferring the filtered first fluid from the filtration device.