US4707218A — Lithographic image size reduction

Claim 1

Independent Claim 88 words

Process for forming a mask having an opening of a size smaller than obtainable by lithography, comprising: providing a substrate coated with a photosensitive material; patterning the photosensitive material to form an opening therein, said opening having substantially vertical walls and minimum size dictated by resolution limit of lithography; forming a conformal layer of a material on the resulting structure including said vertical walls; and anisotropically etching said conformal layer to provide said conformal layer material on said vertical walls whereby said size of said opening is reduced.

Claim 2

Dependent Claim 88 words

Process for forming a mask having an opening of a size smaller than obtainable by lithography, comprising: providing a substrate coated with a photosensitive material; patterning the photosensitive material to form an opening therein, said opening having substantially vertical walls and minimum size dictated by resolution limit of lithography; forming a conformal layer of a material on the resulting structure including said vertical walls; and anisotropically etching said conformal layer to provide said conformal layer material on said vertical walls whereby said size of said opening is reduced.

Claim 3

Dependent Claim 20 words

The process as in claim 1 wherein said substrate is selected from a group consisting of semiconductor, insulator and conductor.

Claim 4

Dependent Claim 20 words

The process as in claim 1 wherein said substrate is composed of either silicon, glass, metal or a combination thereof.

Claim 5

Dependent Claim 25 words

The process as in claim 1 wherein said conformal layer material is silicon dioxide, Si x O y , silicon nitride, silicon oxynitride or polysilicon.

Claim 6

Dependent Claim 20 words

The process as in claim 1 wherein said material is Si x O y obtained by plasma deposition of hexamethyldisilazane.

Claim 7

Dependent Claim 12 words

The process as in claim 1 wherein said photosensitive material is photoresist.

Claim 8

Dependent Claim 23 words

The process as in claim 1 further comprising forming on said substrate a readily removable layer prior to coating with said photosensitive layer.

Claim 9

Dependent Claim 18 words

The process as in claim 1 further comprising hardening said photosensitive material prior to forming said conformal layer.

Claim 10

Dependent Claim 23 words

The process as in claim 1 wherein the size of said opening is reduced by approximately twice the thickness of said conformal layer.

Claim 11

Dependent Claim 20 words

The process as in claim 7 wherein said photosensitive layer is thick compared to the thickness of said removable layer.

Claim 12

Dependent Claim 73 words

A process for reducing the size of a lithographic image in a mask material comprising: forming on a substrate a mask material having at least one opening of minimum size A determined by the resolution limit of lithographic exposure tooling, said opening having substantially vertical interior walls; and establishing sidewalls of a material of a thickness B on said walls, whereby the new size C of said opening is at least approximately A-2B.

Claim 13

Dependent Claim 73 words

A process for reducing the size of a lithographic image in a mask material comprising: forming on a substrate a mask material having at least one opening of minimum size A determined by the resolution limit of lithographic exposure tooling, said opening having substantially vertical interior walls; and establishing sidewalls of a material of a thickness B on said walls, whereby the new size C of said opening is at least approximately A-2B.

Claim 14

Dependent Claim 21 words

The process as recited in claim 11 wherein the percentage reduction in the size A of said opening is about 2B/A.

Claim 15

Dependent Claim 40 words

The process as recited in claim 11 wherein said sidewall material has a lower etch rate than that of said substrate enabling said mask material in combination with said sidewalls to function as an etch mask for etching said substrate.

Claim 16

Dependent Claim 38 words

The process as recited in claim 11 wherein the step of establishing sidewalls comprises: forming a conformal layer of said sidewall material; and anisotropically etching to remove said sidewall material from everywhere except the walls of said opening.

Claim 17

Dependent Claim 144 words

Process for forming a mask on a substrate surface for integrated circuit manufacture comprising: providing a substrate covered with a relatively thick layer of a first material; coating said first material with a photosensitive layer having an opening of a minimum size dictated by the resolution limit of lithography, said opening having substantially vertical surfaces; depositing a conformal layer of an insulator material on said first material including said vertical surfaces and on the substrate exposed by said opening; anisotropically etching to remove said conformal layer from everywhere except said walls of said opening, thereby reducing the size of said opening by approximately twice the thickness of said conformal layer; and anisotropically etching said first material layer to transfer thereto an image of said opening of reduced size in said photosensitive layer and transform said first material layer into a mask for said substrate.

Claim 18

Dependent Claim 144 words

Process for forming a mask on a substrate surface for integrated circuit manufacture comprising: providing a substrate covered with a relatively thick layer of a first material; coating said first material with a photosensitive layer having an opening of a minimum size dictated by the resolution limit of lithography, said opening having substantially vertical surfaces; depositing a conformal layer of an insulator material on said first material including said vertical surfaces and on the substrate exposed by said opening; anisotropically etching to remove said conformal layer from everywhere except said walls of said opening, thereby reducing the size of said opening by approximately twice the thickness of said conformal layer; and anisotropically etching said first material layer to transfer thereto an image of said opening of reduced size in said photosensitive layer and transform said first material layer into a mask for said substrate.

Claim 19

Dependent Claim 32 words

The process as recited in claim 15 further comprising removing said photosensitive layer and the sidewalls of said conformal layer associated with the opening therein following said etching of said first material.

Claim 20

Dependent Claim 34 words

The process as recited in claim 16 further comprising forming a release layer on said first material prior to coating said photosensitive layer to facilitate removal of said photosensitive layer and said associated sidewalls.

Claim 21

Dependent Claim 19 words

The process as recited in claim 17 further comprising hardening said photosensitive layer prior to depositing said conformal layer.

Claim 22

Dependent Claim 13 words

The process as in claim 18 wherein said conformal layer is plasma-deposited hexamethyldisilazane.

Claim 23

Dependent Claim 31 words

The process as in claim 19 further comprising using said mask anisotropically etching said substrate to form an extremely narrow and deep trench of a width equivalent to said reduced size.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-11-16	1991-05-18	1991-11-17	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-11-16	1995-05-18	1995-11-17	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-11-16	1999-05-18	1999-11-17	$7700.00	Window Closed / Lapsed

Lithographic image size reduction

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