Process for fabricating silicon channel structures with variable cross-sectional areas
First Claim
1. A method of fabricating a three dimensional structure from a silicon wafer having at least one recess with a variable cross-sectional area, the wafer having a thickness and two opposing, substantially parallel surfaces, the fabricating method comprising the steps of:
- forming a first layer of etch resistant material on both surfaces of the wafer;
patterning the first layer of etch resistant material on one of the wafer surfaces to delineate a plurality of vias, said vias exposing the surface of the wafer, at least one of the vias having opposing ends and sides with opposing via extensions extending in opposite directions from each via side at a location therealong;
depositing a second layer of etch resistant material on both sides of the wafer and over the first layer of etch resistant material and vias therein;
patterning the second layer of etch resistant material on the same wafer surface as that patterned in the first layer of etch resistant material to produce at least one via within a boundary of one of the vias in said first layer of etch resistant material to expose the silicon wafer surface;
placing the wafer into a first anisotropic etchant to etch coarsely the wafer to produce at least one recess in the wafer through the vias in the second layer of etch resistant material;
removing the second layer of etch resistant material from the wafer to expose the first layer of etch resistant material and the vias in said one surface thereof which expose the wafer surface through said vias;
placing the wafer into a second anisotropic etchant for a time period to produce relatively fine recesses in the exposed wafer surface through the vias in the first layer of etch resistant material, the extensions on opposing sides of said at least one recess causing the second etchant to etch along the {111} crystal planes, so that the second etchant etches under the via extensions of said at least one via in the etch resistant material in opposing directions towards the recess ends, thereby enlarging the recess cross-sectional area intermediate the via ends while the wafer is in the second etchant; and
removing the wafer from the second anisotropic etchant within a time period sufficient to stop the etching under the first layer of etch resistant material to delineate a recess shape having a different cross-sectional area at each end than at a location intermediate the etched recess ends.
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Accused Products
Abstract
Three dimensional silicon structures having variable depths such as ink flow channels and reservoirs are fabricated from silicon wafers by a two-step anisotropic etching process from a single side of the wafer. Two different etching masks are formed one on top of the other prior to the initiation of etching with the coarsest mask formed last and used first. Once the coarse anisotropic etching is completed, the coarse etch mask is removed and the finer anisotropic etching is accomplished through the remaining mask. The shape of the mask for the finer anisotropic etching in combination with a predetermined etch time produces a channel having varying depths and widths by controlled undercutting of the mask by the finer anisotropic etching. The preferred embodiment is described using an ink flow directing part of a thermal ink jet printhead where the coarse etching step provides the reservoir and the timed fine etching step provides the ink channels having varying cross-sectional flow areas.
127 Citations
8 Claims
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1. A method of fabricating a three dimensional structure from a silicon wafer having at least one recess with a variable cross-sectional area, the wafer having a thickness and two opposing, substantially parallel surfaces, the fabricating method comprising the steps of:
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forming a first layer of etch resistant material on both surfaces of the wafer; patterning the first layer of etch resistant material on one of the wafer surfaces to delineate a plurality of vias, said vias exposing the surface of the wafer, at least one of the vias having opposing ends and sides with opposing via extensions extending in opposite directions from each via side at a location therealong; depositing a second layer of etch resistant material on both sides of the wafer and over the first layer of etch resistant material and vias therein; patterning the second layer of etch resistant material on the same wafer surface as that patterned in the first layer of etch resistant material to produce at least one via within a boundary of one of the vias in said first layer of etch resistant material to expose the silicon wafer surface; placing the wafer into a first anisotropic etchant to etch coarsely the wafer to produce at least one recess in the wafer through the vias in the second layer of etch resistant material; removing the second layer of etch resistant material from the wafer to expose the first layer of etch resistant material and the vias in said one surface thereof which expose the wafer surface through said vias; placing the wafer into a second anisotropic etchant for a time period to produce relatively fine recesses in the exposed wafer surface through the vias in the first layer of etch resistant material, the extensions on opposing sides of said at least one recess causing the second etchant to etch along the {111} crystal planes, so that the second etchant etches under the via extensions of said at least one via in the etch resistant material in opposing directions towards the recess ends, thereby enlarging the recess cross-sectional area intermediate the via ends while the wafer is in the second etchant; and removing the wafer from the second anisotropic etchant within a time period sufficient to stop the etching under the first layer of etch resistant material to delineate a recess shape having a different cross-sectional area at each end than at a location intermediate the etched recess ends. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification