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Method of forming small features using stacked laminated dry resist films on a substrate containing cavities

IP.com Disclosure Number: IPCOM000016478D
Original Publication Date: 2003-Jun-24
Included in the Prior Art Database: 2003-Jun-24
Document File: 2 page(s) / 49K

Publishing Venue

IBM

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  Method of forming small features using stacked laminated dry resist films on a substrate containing cavities

   Method of Forming Small Features on a Substrate Containing Cavities using Stacked Laminated Dry Resist Films

Disclosed is a novel method for forming small features on a substrate containing cavities by first patterning a thick dry film resist layer and then processing a second thinner dry film resist layer on top. In the fabrication of MEMs (microelectromechanical) devices or SiOBs (silicon optical benches) it is frequently necessary to pattern further layers on a substrate wafer after large cavities, up to a mm in size and hundred's of microns deep, have been formed. The presence of the cavities make it impossible to spin-coat a uniform layer of photoresist on the wafer as a large puddle of resist is formed in the cavities. Alternative means of patterning on a wafer which contains large cavities include spray coated resists, electrophoretic resists, or laminated dry film resists. The spray coated resists have the disadvantage that the surface area around the cavity edges are depleted of resist. Electrophoretic resists require a conducting coating and special equipment to process. Complexed combinations have also been proposed where spin coating is used over a dry film resist [1]. The dry film resists are the lowest cost to process but the resolution is limited to approximately the thickness of the material. When processing wafers with large cavities, the minimum dimension of the cavity determines what thickness of dry film resist is needed to span the cavity during processing. For example, a 15 micron thick dry film resist was able to span a 150 micron trench during processing, but it tore when spanning a 1 mm wide cavity. A 40 micron thick dry film resist was able to span the 1 mm wide cavity successfully.

Our novel method is to first pattern a dry film resist layer which is thick enough to survive processing while spanning the cavities which are present in the substrate and to then process a secon...