US-12619160-B2 - Systems and methods for reducing pattern shift in a lithographic apparatus

US12619160B2US 12619160 B2US12619160 B2US 12619160B2US-12619160-B2

Abstract

A method for improving imaging of a feature on a mask to a substrate during scanning operation of a lithographic apparatus. The method includes obtaining a dynamic pupil representing evolution of an angular distribution of radiation exposing a mask during a scanning operation of a lithographic apparatus and determining a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask. The method includes configuring a mask parameter and/or or a control parameter of the lithographic apparatus to reduce the variation of shift of the feature.

Inventors

Joost Cyrillus Lambert Hageman
Marie-Claire VAN LARE
Hans Van Der Laan

Assignees

ASML NETHERLANDS B.V.

Dates

Publication Date: 20260505
Application Date: 20221109
Priority Date: 20211208

Claims (20)

1 . A non-transitory computer-readable medium having instructions that, when executed by a computer system, are configured to cause the computer system to at least: obtain a dynamic pupil representing evolution of an angular distribution of an intensity of radiation to expose a mask during a scanning operation of a lithographic apparatus; determine a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask; and configure a mask parameter and/or a control parameter of the lithographic apparatus, to reduce the variation of shift of the feature.
2 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to determine the variation of shift of the feature are further configured to cause the computer system to: obtain an intensity map of the dynamic pupil, wherein the intensity map is representative of an angular distribution of an intensity of the radiation of an illumination within the lithographic apparatus at multiple moments during the scanning operation; obtain multiple pupils forming the dynamic pupil, wherein each pupil of the multiple pupils (a) corresponds to an angular distribution of an intensity of the radiation at the mask, and (b) is obtained at a different moment of the multiple moments; obtain multiple aerial images of the feature for the multiple pupils, wherein each aerial image of the multiple aerial images is (a) obtained for a different pupil of the multiple pupils, and (b) associated with an angular distribution of the intensity of the radiation at the mask at the moment the corresponding pupil is obtained; and determine the variation of shift of the feature based on determined individual shifts of each of the aerial images relative to their respective nominal positions.
3 . The computer-readable medium of claim 2 , wherein the intensity map is determined in a scanning direction of the lithographic apparatus.
4 . The computer-readable medium of claim 2 , wherein the instructions configured to cause the computer system to determine the variation of the shift of the feature are further configured to cause the computer system to: obtain a first pupil, a second pupil and a third pupil at different moments of the scanning operation, wherein the first pupil corresponds to an angular distribution of the intensity of the radiation at the mask from a first pole of the illumination, wherein the second pupil corresponds to an angular distribution of the intensity of the radiation at the mask from a second pole of the illumination, and wherein the third pupil corresponds to an angular distribution of the intensity of the radiation at the mask from the first pole and the second pole of the illumination; obtain a first aerial image, a second aerial image, and a third aerial image for the first pupil, the second pupil and the third pupil, respectively, wherein the first aerial image is associated with an angular distribution of the intensity of the radiation at the mask at a time the first pupil is obtained, wherein the second aerial image is associated with an angular distribution of the intensity of the radiation at the mask at the time the second pupil is obtained, and wherein the third aerial image is associated with an angular distribution of the intensity of the radiation at the mask at the time the third pupil is obtained; and determine the variation of shift of the feature based on a shift in a center of gravity of each of the aerial images relative to a nominal center of gravity in the intensity map.
5 . The computer-readable medium of claim 1 , wherein the variation of shift of the feature is indicative of a displacement variation of the feature at the substrate around an intended position of the feature according to a design layout.
6 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to configure the control parameter are further configured to cause the computer system to configure a tilt of a reticle stage of the lithographic apparatus holding the mask to reduce the variation of shift of the feature.
7 . The computer-readable medium of claim 6 , wherein the instructions are further configured to cause the computer system to: determine an overlay error introduced due to the tilt of the reticle stage; and configure a design of the mask to compensate for the overlay error.
8 . The computer-readable medium of claim 6 , wherein the instructions are further configured to cause the computer system to: determine a focus error introduced due to the tilt of the reticle stage; and configure a wafer stage of the lithographic apparatus to compensate for the focus error.
9 . The computer-readable medium of claim 6 , wherein the instructions are further configured to cause the computer system to: determine, from an aerial image associated with the feature, an image parameter that is representative of blurring, fading, or loss of contrast; and configure the tilt of the reticle stage to reduce or minimize the image parameter.
10 . The computer-readable medium of claim 9 , wherein the image parameter includes moving standard deviation.
11 . The computer-readable medium of claim 10 , wherein the moving standard deviation is determined as a function of the shift of the feature and a pole intensity of multiple poles of an illumination within the lithographic apparatus.
12 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to configure the control parameter are further configured to cause the computer system to configure an illumination within the lithographic apparatus.
13 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to configure the control parameter are further configured to cause the computer system to configure a projection lens of the lithographic apparatus.
14 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to configure the mask parameter are further configured to cause the computer system to configure a bias of the mask.
15 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to configure the control parameter or the mask parameter are further configured to cause the computer system to configure at least one selected from: a design of the mask, a reticle stage of the lithographic apparatus holding the mask, a wafer stage of the lithographic apparatus holding the substrate, an illumination within the lithographic apparatus, or a projection lens of the lithographic apparatus.
16 . A computer-implemented method for improving imaging of a feature on a mask to a substrate during a scanning operation of a lithographic apparatus, the method comprising: obtain a dynamic pupil representing evolution of an angular distribution of an intensity of radiation to expose a mask during a scanning operation of a lithographic apparatus; determine a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask; and configure a mask parameter and/or a control parameter of the lithographic apparatus, to reduce the variation of shift of the feature.
17 . The method of claim 16 , wherein configuring the control parameter or the mask parameter includes configuring at least one selected from: a design of the mask, a reticle stage of the lithographic apparatus holding the mask, a wafer stage of the lithographic apparatus holding the substrate, an illumination within the lithographic apparatus, or a projection lens of the lithographic apparatus.
18 . The method of claim 16 , wherein determining the variation of shift of the feature includes: obtaining an intensity map of the dynamic pupil, wherein the intensity map is representative of an angular distribution of an intensity of the radiation of an illumination within the lithographic apparatus at multiple moments during the scanning operation; obtaining multiple pupils forming the dynamic pupil, wherein each pupil of the multiple pupils (a) corresponds to an angular distribution of an intensity of the radiation at the mask, and (b) is obtained at a different moment of the multiple moments; obtaining multiple aerial images of the feature for the multiple pupils, wherein each aerial image of the multiple aerial images is (a) obtained for a different pupil of the multiple pupils, and (b) associated with an angular distribution of the intensity of the radiation at the mask at the moment the corresponding pupil is obtained; and determining the variation of shift of the feature based on determined individual shifts of each of the aerial images relative to their respective nominal positions.
19 . A method for improving imaging of a feature on a mask to a substrate during scanning operation of a lithographic apparatus, the method comprising: obtaining a dynamic pupil representing evolution of an angular distribution of radiation to expose the mask during scanning operation of the lithographic apparatus; determining, by a hardware computer system, a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask; and configuring a lithographic process related parameter to reduce the variation of shift of the feature, wherein the lithographic process related parameter includes at least one selected from: a design of the mask, a reticle stage of the lithographic apparatus holding the mask, a wafer stage of the lithographic apparatus holding the substrate, an illumination within the lithographic apparatus, or a projection lens of the lithographic apparatus.
20 . A non-transitory computer-readable medium having instructions that, when executed by a computer system, are configured to cause the computer system to at least perform the method of claim 19 .

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is the U.S. national phase entry of PCT Patent Application No. PCT/EP2022/081291, which was filed on Nov. 9, 2022, which claims the benefit of priority of European Patent Application No. 21213192.4 which was filed on Dec. 8, 2021 and which is incorporated herein in its entirety by reference. TECHNICAL FIELD The description herein relates to lithographic apparatuses and processes, and more particularly to a tool to determine and minimize mask 3D effects. BACKGROUND A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). For example, an IC chip in a smart phone, can be as small as a person's thumbnail, and may include over 2 billion transistors. Making an IC is a complex and time-consuming process, with circuit components in different layers and including hundreds of individual steps. A patterning process can include a patterning step to transfer a pattern from a patterning device (such as a mask) to the substrate. The mask is a master template for a given IC design. It is placed in a lithography apparatus, which projects light through the mask. That, in turn, is used to pattern images on the substrate (often referred to as a “wafer”). Various variations (e.g., variations in a patterning process or the lithographic apparatus) can potentially limit lithography implementation for semiconductor high volume manufacturing (HVM). The patterning device (mask) is typically a multi-layer structure having three dimensional (3D)-like features jutting out on top of the mask. In operation, when the radiation from an illumination source of the lithographic apparatus (e.g., EUV light) hits the mask at an angle (e.g., 6-degrees), the oblique incident radiation field and the 3D features, alone or in combination, may cause various effects in the lithographic projection process such as a shadowing effect or photomask-induced imaging aberrations on the wafer. These effects are commonly referred to as “Mask 3D effects” (M3D effects) and may result in unwanted feature-size dependent focus and pattern placement shifts depending on the incident illumination setting (e.g., pupil filling). Current techniques to mitigate the impact of M3D effects (pattern shifts for example) are based on the assumption that for a given illumination setting the illumination source is stationary during exposure of the features on the mask. It was found that this assumption may in some cases not be valid, the pupil filling may change dynamically during the exposure (the pupil is “dynamic”), and consequently current techniques of mitigating the impact of M3D effects may be sub-optimal. BRIEF SUMMARY It is an object of the invention to mitigate the impact of M3D effects for cases wherein the illumination source varies during exposure of one or more features on the mask. In particular the inventors have observed that in these cases so-called fading effects may occur leading to degradation of the quality of the features applied to the substrate. Current methods of configuring or setting up a lithographic apparatus may not account for the interaction between a dynamic pupil and the M3D effects. Current methods of M3D effect correction may consider an average pupil but not a dynamic pupil, and therefore, any potential interaction between the dynamic pupil and the M3D effects may be disregarded, thereby causing patterns to be printed on the substrate in an erroneous manner. In an embodiment, there is provided a non-transitory computer-readable media comprising instructions that, when executed by a computer, cause the computer to execute a method for improving imaging of a feature on a mask to a substrate during a scanning operation of a lithographic apparatus. The method includes: obtaining a dynamic pupil representing evolution of an angular distribution of an intensity of radiation exposing a mask during a scanning operation of a lithographic apparatus; determining a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask; and configuring at least one of a mask parameter or a control parameter of the lithographic apparatus to reduce the variation of shift of the feature. In an embodiment, there is provided a non-transitory computer-readable media comprising instructions that, when executed by a computer, cause the computer to execute a method for improving imaging of a feature on a mask to a substrate during scanning operation of a lithographic apparatus. The method includes: obtaining a dynamic pupil representing evolution of an angular distribution of radiation exposing a mask during a scanning operation of a lithographic apparatus; determining a variation of shift of a feature at a substrate during the scanning operation due to interaction of the dynamic pupil with the mask; and