US-12625432-B2 - Methods of forming patterns

US12625432B2US 12625432 B2US12625432 B2US 12625432B2US-12625432-B2

Abstract

A method of forming sub-resolution features that includes: exposing a photoresist layer formed over a substrate to a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer through a mask configured to form features at a first critical dimension, the photoresist layer including first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation after exposing with the first UV radiation; exposing the first portions and the second portions to a second UV radiation; and developing the photoresist layer after exposing the photoresist layer to the second UV radiation to form the sub-resolution features having a second critical dimension less than the first critical dimension.

Inventors

Daniel Fulford
Jodi Grzeskowiak
H. Jim Fulford
Sean Smith
Partha Mukhopadhyay
Michael Murphy
Anton deVilliers

Assignees

TOKYO ELECTRON LIMITED

Dates

Publication Date: 20260512
Application Date: 20211104

Claims (19)

1 . A method of forming sub-resolution features, the method comprising: exposing a photoresist layer formed over a substrate to a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer through a mask, the photoresist layer comprising first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation after exposing with the first UV radiation, the second portions having a first height and a first critical dimension; exposing the first portions and the second portions to a second UV radiation, the second UV radiation being a blanket radiation with no pattern; forming a plurality of features, the forming comprising developing the photoresist layer after exposing the photoresist layer to the second UV radiation, the plurality of features having a second height and a second critical dimension less than the first critical dimension, the second height being less than the first height; and spacer patterning, the spacer patterning comprising: depositing a layer of a spacer material over the plurality of features; performing a spacer etch back to remove a lateral portion of the spacer material; performing a pull etch to remove the plurality of features and form a spacer pattern; and performing a pattern transfer etch using the spacer pattern as an etch mask.
2 . The method of claim 1 , further comprising, before developing, performing a post-exposure bake by thermally treating the substrate.
3 . The method of claim 1 , further comprising selecting conditions for exposing the first portions and the second portions to the second UV radiation to form the sub-resolution wherein the plurality of features have a width between 200 nm and 360 nm, a height between 20 nm and 900 nm, or a ratio of height to width between 3 and 100.
4 . The method of claim 1 , wherein exposing the first portions and the second portions to the second UV radiation is performed using a pixel-based projection system having an array of independently addressable projection points.
5 . The method of claim 1 , wherein the first wavelength is 365 nm and the second UV radiation has a wavelength of 266 nm.
6 . The method of claim 1 , further comprising generating the first UV radiation and the second UV radiation in a common lithography tool.
7 . A method of forming sub-resolution features, the method comprising: exposing a photoresist layer formed over a substrate to a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer through a first mask, the photoresist layer comprising first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation after exposing with the first UV radiation, the second portions having a first critical dimension; developing the photoresist layer after exposing the photoresist layer to the first UV radiation to remove the first portions; depositing a resin over the photoresist layer; exposing the second portions to a second UV radiation having a second wavelength; and developing the photoresist layer after exposing the photoresist layer to the second UV radiation to form the sub-resolution features having a second critical dimension less than the first critical dimension, the sub-resolution features comprising a trench between the photoresist layer and the resin.
8 . The method of claim 7 , wherein depositing the resin before exposing the second portions to the second UV radiation, the second UV radiation inducing a photochemical reaction generating an acid within the second portions, the acid laterally diffusing into the resin to form acid-reacted layers on side walls of the resin.
9 . The method of claim 8 , wherein developing the photoresist layer after exposing the photoresist layer to the second UV radiation removes the acid-reacted layers, and wherein widths of the acid-reacted layers determine the second critical dimension.
10 . The method of claim 8 , further comprising, before exposing the second portions to the second UV radiation, inserting a second mask into an optical path of the second UV radiation.
11 . The method of claim 7 , wherein the resin is deposited over the photoresist layer after exposing the second portions to the second UV radiation, wherein exposing the second portions comprises forming third portions exposed to the second UV radiation by converting a portion of the second portions, the remaining second portions forming fourth portions not being exposed to the second UV radiation.
12 . The method of claim 11 , wherein the third portions cover sidewalls of the fourth portions.
13 . The method of claim 11 , wherein developing the photoresist layer comprises removing top portions of the resin to expose the third portions, and removing the third portions.
14 . The method of claim 7 , further comprising performing a pattern transfer etch using the sub-resolution features as an anti-spacer.
15 . A method of forming sub-resolution features, the method comprising: loading a substrate in a lithography tool, the substrate comprising a photoresist layer formed thereon; generating, in the lithography tool, a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer; exposing the photoresist layer to the first UV radiation through a single mask, the photoresist layer comprising first reacted portions exposed to the first UV radiation and first unreacted portions unexposed to the first UV radiation after exposing with the first UV radiation, the first unreacted portions having a first height and a first critical dimension; generating, in the lithography tool, a second UV radiation having a second wavelength; exposing the photoresist layer to the second UV radiation, the second UV radiation being a blanket radiation with no pattern, the exposing forming, from the first unreacted portions, second reacted portions exposed to the second UV radiation and second unreacted portions unexposed to the second UV radiation after exposing with the second UV radiation, the second unreacted portions having a second height and a second critical dimension less than the first critical dimension, the second height being less than the first height, wherein exposing to the second UV radiation is performed using a pixel-based projection system having an array of independently addressable projection points; and forming a plurality of features, the forming comprising developing the photoresist layer after exposing the photoresist layer to the second UV radiation, the developing removing the first reacted portions and the second reacted portions while retaining the second unreacted portions to form the plurality of features.
16 . The method of claim 15 , further comprising spacer patterning, the spacer patterning comprising: depositing a layer of a spacer material over the plurality of features; performing a spacer etch back to remove a lateral portion of the spacer material; performing a pull etch to remove the plurality of features and form a spacer pattern; and performing a pattern transfer etch using the spacer pattern as an etch mask.
17 . The method of claim 15 , further comprising, before developing, performing a post-exposure bake by thermally treating the substrate.
18 . The method of claim 15 , wherein the plurality of have a width between 200 nm and 360 nm, a height between 20 nm and 900 nm, or a ratio of height to width between 3 and 100.
19 . The method of claim 15 , wherein the first wavelength is 365 nm and the second wavelength is 266 nm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to of U.S. Provisional Application No. 63/233,559, filed on Aug. 16, 2021, which application is hereby incorporated herein by reference. TECHNICAL FIELD The present invention relates generally to a method of processing a substrate, and, in particular embodiments, to a method of forming patterns. BACKGROUND Generally, a semiconductor device, such as an integrated circuit (IC) is fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials over a semiconductor substrate to form a network of electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias) integrated in a monolithic structure. At each successive technology node, the minimum feature sizes are shrunk to reduce cost by roughly doubling the component packing density. Photolithography is a common patterning method in semiconductor fabrication. A photolithography process may start by exposing a coating of photoresist comprising a radiation-sensitive material to a pattern of actinic radiation to define a relief pattern. For example, in the case of positive photoresist, irradiated portions of the photoresist may be dissolved and removed by a developing step using a developing solvent, forming the relief pattern of the photoresist. The relief pattern then may be transferred to a target layer below the photoresist or an underlying hard mask layer formed over the target layer. Innovations on photolithographic techniques may be needed to satisfy the cost and quality requirements for patterning at nanoscale features. SUMMARY In accordance with an embodiment of the present invention, a method of forming sub-resolution features that includes: exposing a photoresist layer formed over a substrate to a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer through a mask configured to form features at a first critical dimension, the photoresist layer including first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation after exposing with the first UV radiation; exposing the first portions and the second portions to a second UV radiation; and developing the photoresist layer after exposing the photoresist layer to the second UV radiation to form the sub-resolution features having a second critical dimension less than the first critical dimension. In accordance with an embodiment of the present invention, a method of forming sub-resolution features that includes: exposing a photoresist layer formed over a substrate to a first ultraviolet light (UV) radiation having a first wavelength of 365 nm or longer through a first mask configured to form features at a first critical dimension, the photoresist layer including first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation after exposing with the first UV radiation; developing the photoresist layer after exposing the photoresist layer to the first UV radiation to remove the first portions; depositing a resin over the photoresist layer; and exposing the second portions to a second UV radiation having a second wavelength; developing the photoresist layer after exposing the photoresist layer to the second UV radiation to form the sub-resolution features having a second critical dimension less than the first critical dimension, the sub-resolution features including a trench between the photoresist layer and the resin. In accordance with an embodiment of the present invention, a lithography tool that includes: a chamber sized and configured to receive a wafer for processing; a wafer holder to hold a 200 mm wafer; a first ultraviolet light (UV) radiation source configured to emit a first UV radiation having a first wavelength of 365 nm, the first UV radiation source configured to form first features having a first critical dimension larger than a first optical resolution limit based on the first UV radiation; a second UV radiation source configured to emit a second UV radiation having a second wavelength, the second UV radiation source configured to form second features having a second critical dimension larger than a second optical resolution limit based on the second UV radiation; where the lithography tool includes instructions to expose a photoresist layer formed over the wafer with the first UV radiation through a first mask configured to form the first features at the first critical dimension, the photoresist layer including first portions exposed to the first UV radiation and second portions unexposed to the first UV radiation; and expose the second portions to the second UV radiation to define sub-resolution features having a critical dimension less than the first optical resolution limit. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, and the advantages thereof, re