KR-20260064737-A - Optical filter, a heterodyne interferometer system including the filter, and a method for filtering an input beam for a heterodyne interferometer

KR20260064737AKR 20260064737 AKR20260064737 AKR 20260064737AKR-20260064737-A

Abstract

A heterodyne interferometer system comprises: a first light source providing a first laser beam having a first frequency (f1); a second light source providing a second laser beam having a second frequency (f2) different from the first frequency; a combiner for polarizing the first and second laser beams and for providing an input beam in which the polarized first and second laser beams are combined; an optical resonator cavity—the cavity comprising an odd number of at least partially reflective mirrors disposed within the cavity to reflect and circulate the input beam within the cavity, and the optical resonator cavity is adjusted to receive the input beam and provide an output beam comprising a first spatial mode having a first frequency (f1) and a first polarization and a second spatial mode having a second frequency (f2) and a second polarization different from the first polarization—; and a heterodyne interferometer for receiving the output beam.

Inventors

크위 패트릭

Assignees

에이에스엠엘 네델란즈 비.브이.

Dates

Publication Date: 20260507
Application Date: 20240801
Priority Date: 20230912

Claims (15)

As an optical filter for a heterodyne interferometer, An optical resonator cavity adjusted to receive an input beam comprising radiation having at least a first frequency (f1) and a second frequency (f2) different from the first frequency - an odd number of at least partially reflective mirrors disposed within the cavity to reflect and circulate the input beam within the cavity - Includes, The optical resonator cavity is an optical filter configured to provide an output beam comprising a first spatial mode having a first frequency (f1) and a first polarization and a second spatial mode having a second frequency (f2) and a second polarization different from the first polarization.
In Article 1, An optical filter, wherein the optical resonator cavity includes a length adjustment means capable of adjusting the length of the cavity.
In Article 2, The above length adjustment means is an optical filter comprising one or more of a piezoelectric actuator and a heater.
In Article 1, The optical filter described above is an optical filter comprising a frequency adjustment means for adjusting a first frequency and/or a second frequency.
In Article 1, An optical filter in which the first polarization is s-polarized and the second polarization is p-polarized.
In Article 1 An odd number of mirrors, - A first mirror having partial transmittance and reflectance - The first mirror is adjusted to receive the input beam -; - A second mirror having substantially the same partial transmittance and reflectance as the first mirror - the second mirror is adjusted to provide the output beam -; and - At least one third mirror having substantially perfect reflectivity An optical filter including
In Article 6, The first mirror and the second mirror are optical filters having the same composition.
As a heterodyne interferometer system, A first light source for providing a first laser beam having a first frequency (f1); A second light source for providing a second laser beam having a second frequency (f2) different from the first frequency; A combiner for polarizing the first laser beam and the second laser beam, and providing an input beam in which the polarized first laser beam and the polarized second laser beam are combined; Optical resonator cavity - the optical resonator cavity comprises an odd number of at least partially reflective mirrors disposed within the cavity to reflect and circulate the input beam within the cavity, and the optical resonator cavity is adjusted to receive the input beam and provide an output beam comprising a first spatial mode having a first frequency (f1) and a first polarization and a second spatial mode having a second frequency (f2) and a second polarization different from the first polarization -; and Heterodyne interferometer for receiving the above output beam A heterodyne interferometer system including
A projection system for a photolithography system comprising an optical filter according to any one of claims 1 to 7.
A projection system for an optical lithography system comprising a heterodyne interferometer system according to claim 8.
As a method for filtering an input beam for a heterodyne interferometer, Step of providing an optical resonator cavity tuned to receive an input beam comprising at least a first frequency (f1) and a second frequency (f2) different from the first frequency - wherein an odd number of at least partially reflective mirrors are disposed within the cavity to reflect and circulate the input beam within the cavity -; and Using the optical resonator cavity above, a step of providing an output beam comprising a first spatial mode having a first frequency (f1) and a first polarization and a second spatial mode having a second frequency (f2) and a second polarization different from the first polarization. A method for filtering an input beam, comprising
In Article 11, The above method is, A method for filtering an input beam, comprising the step of providing the output beam to the heterodyne interferometer.
In Article 11, The above method is, A method for filtering an input beam, comprising the step of adjusting the length of the optical resonator cavity so that at least one mode resonates with respect to at least a first frequency and a second frequency.
In Article 13, The step of adjusting the above length is, A method for filtering an input beam, comprising at least one of activating a piezoelectric actuator to move at least one of the mirrors and heating the cavity.
In any one of Articles 11 to 14, The above method is, A method for filtering an input beam, comprising the step of adjusting at least one of a first frequency and a second frequency so that at least one mode resonates within the cavity.

Description

Optical filter, a heterodyne interferometer system including the filter, and a method for filtering an input beam for a heterodyne interferometer Cross-reference regarding related applications This application claims priority to EP application No. 23196954.4 filed on September 12, 2023, the entire contents of which are incorporated by reference of this application. The present invention relates to a system and method for mode cleaning a heterodyne interferometer input. The present invention also relates to a lithography apparatus comprising the system, and a projection system for an optical lithography system comprising the system. A lithography device is a machine configured to apply a desired pattern to a substrate. A lithography device can be used, for example, in the manufacture of an integrated circuit (IC). A lithography device can project a pattern (also called a "design layout" or "design") of, for example, a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer). As semiconductor manufacturing processes continue to advance, the number of functional elements, such as transistors, per device has steadily increased over decades, following a trend generally known as 'Moore's Law,' while the dimensions of circuit elements have continued to decrease. To keep Moore's Law going, the semiconductor industry is seeking technologies that enable the creation of increasingly smaller features. To project patterns onto a substrate, lithography devices can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features patterned on the substrate. Commonly used wavelengths currently are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Lithography devices using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 nm to 20 nm, for example, 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than lithography devices using electromagnetic radiation with a wavelength of, for example, 193 nm. Interferometers are used for various measurements in other equipment related to the semiconductor manufacturing process, including lithography devices and metrology. Interferometers are also used in projection systems for optical lithography systems and other exposure devices. For example, wavelength tracers can be used to control the stability of laser beam inputs, and the position of movable equipment, such as wafer stages, can be controlled down to the nm level using one or more phase-tracking interferometers. The performance of a planar mirror interferometer typically depends on the quality of the input laser beam. Various factors can negatively affect the quality of the input laser beam, leading to residual errors in the interferometer output due to input beam quality issues. Conventional technology has several problems. In the case of a heterodyne interferometer using two laser beams of different frequencies, the problems may include, for example, one or more of the following: - Collinearity and cobore errors of the two combined laser beams output from the remote optical coupler result in a decrease in the ac/dc ratio. Ultimately, this leads to an overall decrease in the signal-to-noise ratio and an increase in noise. - Polarization clocking error results in a larger cyclic error with a larger residual value after SW correction. - Wavefront error causes interferometer error. Laser intensity noise at heterodyne frequencies—that is, the frequency difference between two laser beams—causes phase errors. Shot noise is dominant when the typical power of the interferometer is relatively low. However, for higher-power lasers, intensity noise becomes a significant factor. - High-frequency phase noise can cause interferometer errors. - Drift of components within the remote optical coupler results in suboptimal alignment of the interferometer. - Since all interferometers must be realigned, replacing the remote optical coupler results in additional downtime. Wavelength fluctuations cause interferometric errors due to the highly asymmetric arm length of the interferometer. The document "High-extinction-ratio resonant cavity polarizer for quantum-optics measurements" by Saraf et al., APPLIED OPTICS Vol. 46, No. 18, June 20, 2007, pp. 3850–3855 describes a quantum noise measurement system for an Nd:YAG free-space saturation amplifier (see Fig. 4). The high-power beam saturates the gain of a 100 W class slab amplifier and is separated from the probe beam, which is precisely superimposed after the amplifier. Three Fabry-Perot cavities within this setup function as spatial and spectral filters and resonant polarizers. This enables the generation of a single-space mode and single-polarization shot-noise-limited probe beam, the precise superposition of the high-power beam and the probe beam, and finally, the precise separation of the beams after amplification. The doctoral dissertation "Signal Extrac