US 10,520,818 B1Granted

Critical dimension (CD) uniformity of photoresist island patterns using alternating phase shifting mask

AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.

InventorsJesmin Haq, Tom Zhong, Zhongjian Teng

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Abstract

A photoresist film is patterned into an array of island shapes with improved critical dimension uniformity and no phase edges by using two alternating phase shifting masks (AltPSMs) and one post expose bake (PEB). The photoresist layer is exposed with a first AltPSM having a line/space (L/S) pattern where light through alternating clear regions on each side of an opaque line is 180° phase shifted. Thereafter, there is a second exposure with a second AltPSM having a L/S pattern where opaque lines are aligned orthogonal to the lengthwise dimension of opaque lines in the first exposure, and with alternating 0° and 180° clear regions. Then, a PEB and subsequent development process are used to form an array of island shapes. The double exposure method enables smaller island shapes than conventional photolithography and uses relatively simple AltPSM designs that are easier to implement in production than other optical enhancement techniques.

Claims21

Dependent claims

A method of forming an array of island shapes in a photoresist layer, comprising:

(a) providing a positive tone photoresist layer on a substrate;
(b) performing a first patternwise exposure of the photoresist layer through a first alternating phase shifting mask (AltPSM) comprised of a first set of parallel opaque lines each having a width w3 and aligned in a first direction on a first transparent substrate relative to the photoresist layer, wherein each of the first set of parallel opaque lines has a first clear region having a width w1 on one side and a second clear region having a width w2 on a second side thereof such that light during the first patternwise exposure that passes through the first and second clear regions is phase shifted by 180°, and the first and second clear regions alternate across the first transparent substrate;
(c) performing a second patternwise exposure of the photoresist layer through a second AltPSM without moving the substrate after the first patternwise exposure, wherein the second AltPSM is comprised of a second set of parallel opaque lines aligned in a second direction orthogonal to the first direction, and are formed on a second transparent substrate, and wherein each of the second set of parallel opaque lines has a width w6, and has a third clear region having a width w4 on one side and a fourth clear region having a width w5 on a second side thereof such that light passing through the third and fourth clear regions is phase shifted by 180°, and the third and fourth clear regions alternate across the second transparent substrate;
(d) performing a post-expose bake (PEB) of the photoresist layer on the substrate after the second patternwise exposure;
and
(e) applying a developer solution to photoresist layer on the substrate to remove first and second patternwise exposed regions and thereby form an array of island shapes that are unexposed regions of the photoresist layer.

3 more elements

A method of fabricating an array of magnetic tunnel junction (MTJ) cells on a substrate, comprising:

(a) providing a MTJ stack of layers on the substrate, and a bottom antireflective coating (BARC) or a dielectric antireflective coating (DARC) on a top surface of the MTJ stack;
(b) coating a positive tone photoresist layer on the BARC or DARC;
(c) performing a first patternwise exposure of the photoresist layer through a first alternating phase shifting mask (AltPSM) comprised of a first set of parallel opaque lines each having a width w3 and aligned in a first direction on a first transparent substrate relative to the photoresist layer, wherein each of the first set of parallel opaque lines has a first clear region having a width w1 on one side and a second clear region having a width w2 on a second side such that light passing through the first and second clear regions during the first patternwise exposure is phase shifted by 180°, and the first and second clear regions alternate across the first transparent substrate;
(d) performing a second patternwise exposure of the photoresist layer through a second AltPSM without moving the substrate after the first patternwise exposure, wherein the second AltPSM is comprised of a second set of parallel opaque lines aligned in a second direction orthogonal to the first direction, and are formed on a second transparent substrate, and wherein each of the second set of parallel opaque lines has a width w6, and has a third clear region having a width w4 on one side and a fourth clear region having a width w5 on a second side such that light passing through the third and fourth clear regions is phase shifted by 180°, and the third and fourth clear regions alternate across the second transparent substrate;
(e) performing a post-expose bake (PEB) of the photoresist layer on the substrate after the second patternwise exposure;
(f) applying a developer solution to photoresist layer on the substrate to remove first and second patternwise exposed regions and thereby form an array of island shapes in unexposed regions of the photoresist layer;
and
(g) transferring the island shapes through the BARC or DARC, and then through the MTJ stack of layers with a plurality of etch steps.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/133,869Filed 18 Sep 2018
Granted: 31 Dec 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification16 codes

G03F 7/203
Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal;…:…
G03F 1/30
Phase shift masks [PSM]; PSM blanks; Preparation thereof: alternating PSM, e.g. Levenson-Shibuya PSM; Preparation thereof
G03F 1/70
Preparation processes not covered by groups G03F1/20 - G03F1/50: adapting basic layout or design of masks to lithographic process requirements,…
G03F 7/039
Photosensitive materials: macromolecular compounds which are photodegradable, e.g. positive electron resists