US5034091A — Method of forming an electrical via structure

Claim 1

Independent Claim 220 words

A method of forming a via through a first layer of material which overlies a second layer of material, comprising: forming a laterally erodible mask over said first layer with a window in said mask over the desired via location, eroding mask material laterally around said window to expand said window, and simultaneously therewith eroding material from said first layer which is exposed through said window, the eroded portion of said first layer having a taper in the area underlying the laterally eroded portion of said mask, the degree of taper angle being determined by the materials selected for said mask and first layer, the erosion conditions, and the initial window taper; said first layer comprising a dielectric, and said second layer comprising a conductor; forming a non-erodible mask between said dielectric layer and said erodible mask in an area lateral to said via, forming said via with said non-erodible mask in place, removing said non-erodible mask and any remaining portion of the erodible mask after said via has been formed, and forming a second conductive layer over said dielectric layer over at least a portion of the area from which said non-erodible mask was removed, said non-erodible mask resisting the replication of defects from the erodible mask through the non-erodible mask into the dielectric layer during said erosion step.

Claim 2

Independent Claim 220 words

A method of forming a via through a first layer of material which overlies a second layer of material, comprising: forming a laterally erodible mask over said first layer with a window in said mask over the desired via location, eroding mask material laterally around said window to expand said window, and simultaneously therewith eroding material from said first layer which is exposed through said window, the eroded portion of said first layer having a taper in the area underlying the laterally eroded portion of said mask, the degree of taper angle being determined by the materials selected for said mask and first layer, the erosion conditions, and the initial window taper; said first layer comprising a dielectric, and said second layer comprising a conductor; forming a non-erodible mask between said dielectric layer and said erodible mask in an area lateral to said via, forming said via with said non-erodible mask in place, removing said non-erodible mask and any remaining portion of the erodible mask after said via has been formed, and forming a second conductive layer over said dielectric layer over at least a portion of the area from which said non-erodible mask was removed, said non-erodible mask resisting the replication of defects from the erodible mask through the non-erodible mask into the dielectric layer during said erosion step.

Claim 3

Dependent Claim 30 words

The method of claim 1, wherein said dielectric is eroded through said conductor in the area underlying the portion of the dielectric that was exposed by the original mask window.

Claim 4

Dependent Claim 50 words

The method of claim 2, further comprising the step of depositing a layer of conductor material over the tapered walls of said via into contact with said conductor layer, the degree of taper of said walls being selected to support a deposit of conductor material with a generally uniform width.

Claim 5

Dependent Claim 40 words

The method of claim 3, further comprising the steps of forming a similar via in at least one similarly layered structure by a substantially similar process, said layered structures being stacked with their respective vias vertically aligned and electrically connected.

Claim 6

Dependent Claim 39 words

The method of claim 2, the thicknesses of said erodible mask and dielectric layer being selected so that said dielectric is eroded through to said conductor layer while a portion of said erodible mask remains on said dielectric layer.

Claim 7

Dependent Claim 25 words

The method of claim 1, said non-erodible mask having a window surrounding the via which is larger than the final eroded area of the via.

Claim 8

Dependent Claim 63 words

The method of claim 6, wherein said second conductive layer extends into said via and coats the walls thereof, further comprising the step of patterning said second conductive layer by projection lithography to electrically isolate said via from at least a portion of the second conductive layer which overlies at least a portion of said area from which said non-erodible mask was removed.

Claim 9

Dependent Claim 13 words

The method of claim 1, said non-erodible mask being formed from a metal.

Claim 10

Dependent Claim 18 words

The method of claim 1, said mask material and first layer material being eroded by reactive ion etching.

Claim 11

Dependent Claim 27 words

The method of claim 1, the taper angle of said via being in the approximate range of 15°-45° to the plane of said second layer of material.

Claim 12

Dependent Claim 14 words

The method of claim 1, said via being formed with a generally bowl-like profile.

Claim 13

Independent Claim 202 words

A method of forming a via through a dielectric layer which overlies a conductive layer, comprising: forming a layer of photoresist over said dielectric layer, opening a tapered window in the photoresist over the desired via location. simultaneously etching said photoresist and the portion of the dielectric layer exposed by said window, the etching parameters, the materials for said dielectric and photoresist, and the degree of taper for said window being selected so that said window expands and progressively exposes additional portions of said dielectric as said etching proceeds, whereby a via having walls with a desired degree of taper is etched through said dielectric, forming an etch-resistant mask between said dielectric layer and said photoresist layer in an area lateral to said via, forming said via with said etch-resistant mask in place, removing said etch-resistant mask and any remaining portion of the photoresist after said via has been formed, and forming a second conductive layer over said dielectric layer over at least a portion of the area from which said etch-resistant mask was removed, said etch-resistant mask being selected from a material which resists the replication of defects from the photoresist through the etch-resistant mask into the dielectric layer during etching.

Claim 14

Independent Claim 202 words

A method of forming a via through a dielectric layer which overlies a conductive layer, comprising: forming a layer of photoresist over said dielectric layer, opening a tapered window in the photoresist over the desired via location. simultaneously etching said photoresist and the portion of the dielectric layer exposed by said window, the etching parameters, the materials for said dielectric and photoresist, and the degree of taper for said window being selected so that said window expands and progressively exposes additional portions of said dielectric as said etching proceeds, whereby a via having walls with a desired degree of taper is etched through said dielectric, forming an etch-resistant mask between said dielectric layer and said photoresist layer in an area lateral to said via, forming said via with said etch-resistant mask in place, removing said etch-resistant mask and any remaining portion of the photoresist after said via has been formed, and forming a second conductive layer over said dielectric layer over at least a portion of the area from which said etch-resistant mask was removed, said etch-resistant mask being selected from a material which resists the replication of defects from the photoresist through the etch-resistant mask into the dielectric layer during etching.

Claim 15

Dependent Claim 25 words

The method of claim 12, said etch-resistant mask having a window surrounding the via which is larger than the final etched area of the via.

Claim 16

Dependent Claim 62 words

The method of claim 13, wherein said second conductive layer extends into said via and coats the walls thereof, further comprising the step of patterning said second conductive layer by projection lithography to electrically isolate said via from at least a portion of the second conductive layer which overlies at least a portion of said area which said etch-resistant mask was removed.

Claim 17

Dependent Claim 50 words

The method of claim 12, further comprising the step of depositing a layer of conductor material over the tapered walls of said via into contact with said conductor layer, the degree of taper of said walls being selected to support a deposit of conductor material with a generally uniform width.

Claim 18

Dependent Claim 13 words

The method of claim 12, wherein said etching comprises a reactive ion etching.

Claim 19

Dependent Claim 25 words

The method of claim 12, the taper angle of said via being in the approximate range of 15°-45° to the plane of said conductive layer.

Claim 20

Dependent Claim 14 words

The method of claim 12, said via being formed with a generally bowl-like profile.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-07-22	1995-01-21	1995-07-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-07-22	1999-01-21	1999-07-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-07-22	2003-01-21	2003-07-23	$7700.00	Window Closed / Lapsed

Method of forming an electrical via structure

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