阅读说明：本技术 一种深紫外平板偏振分光镜及其设计方法 (Deep ultraviolet flat plate polarization spectroscope and design method thereof ) 是由 张伟丽 冯操 朱瑞 王建国 朱美萍 孙建 刘晓凤 沈雪峰 易葵 邵建达 于 2021-01-08 设计创作，主要内容包括：一种深紫外平板偏振分光镜及其设计方法,该偏振分光镜由基板及基板两面的偏振膜和增透膜三部分构成,其中偏振膜的膜系结构包括膜层应力调节层和偏振分光膜层；初始结构为：Air/(aHbL)～nM/Sub/HL/Air。本发明在非布儒斯特角度下实现深紫外波段高透过率和高消光比的同时,解决了氟化物多层薄膜张应力大导致的膜层龟裂难题,适用于ArF 0F级熔石英或紫外CaF-2基板,可实现入射角为65±1°,波长为180nm-220nm范围内的某一波长处p光透过率大于91％,消光比大于60:1,对于深紫外光学系统中的偏振控制以及系统轻量化设计有重要的意义。(A deep ultraviolet flat polarizing beam splitter and its design method, this polarizing beam splitter is formed by three parts of polarizing film and antireflection coating of base plate and base plate two sides, wherein the film system structure of the polarizing film includes membranous layer stress control layer and polarizing beam splitting membranous layer; the initial structure is as follows: Air/(aHbL) n M/Sub/HL/Air. The invention realizes high transmittance and high extinction ratio of deep ultraviolet waveband at non-Brewster angle, solves the problem of film cracking caused by large tensile stress of fluoride multilayer film, and is suitable for ArF 0F-grade fused quartz or ultraviolet CaF 2 The substrate can realize that the p-light transmittance at a certain wavelength within the range of the wavelength of 180nm-220nm is more than 91% and the extinction ratio is more than 60:1 when the incident angle is 65 +/-1 DEG, and has important significance for polarization control in a deep ultraviolet optical system and light weight design of the system.)

1. A deep ultraviolet flat polarizing beam splitter is characterized by comprising a substrate, a polarizing film and an antireflection film on two sides of the substrate, wherein the film system structure of the polarizing film comprises a film stress adjusting layer and a polarizing beam splitting film layer; the initial structure is as follows: Air/(aHbL)ⁿM/Sub/HL/Air, Sub denotes a substrate, H and L respectively denote an optical thickness of lambda₀4, a and b are coefficients of H and L layers respectively, M is a film stress adjusting layer, and n is the period number of the polarization splitting film layer (aHbL).

2. The deep ultraviolet flat-panel polarizing beamsplitter of claim 1, wherein the substrate comprises fused ArF0F grade quartz or ultraviolet CaF₂(ii) a The material of the high-refractive-index film layer comprises LaF₃，GdF₃Or NdF₃(ii) a The material of the low-refractive-index film layer comprises AlF₃Or MgF₂(ii) a The material of the stress adjusting film layerIs SiO₂。

3. The deep ultraviolet plate pbs according to claim 1 or 2, wherein the incident angle of the incident light of the ultraviolet plate pbs is 65 ± 1 °, the transmittance at a certain wavelength in the range of 180nm to 220nm is greater than 91%, and the extinction ratio is greater than 60: 1.

4. A design method of a deep ultraviolet flat plate polarizing beam splitter is characterized by comprising the following steps:

(1) the polarizing film in the deep ultraviolet flat polarizing beam splitter is designed according to the following steps:

initial structure of selected polarizing film Air/(aHbL)ⁿM/Sub, wherein n is the number of cycles of the polarization beam splitting film layer (aHbL) and the value is between 12 and 18; a and b are coefficients of the H and L layers respectively, and are related to the refractive index of the material, and the value is between 0.8 and 2; m is a stress adjusting layer with a thickness of (aHbL)ⁿ1/3-1/2 of film stack thickness;

reference wave λ of selected polarization film₀Selecting a substrate material, a high refractive index material H, a low refractive index material L and a stress adjusting layer material M for the film system structure;

setting an optimized target value according to the technical index requirements of the polarizing film, wherein the optimized target value comprises the use wavelength, the use angle and the transmittance of p light and s light, and performing the optimized design of the polarizing film according to the target value;

(2) the antireflection film in the deep ultraviolet flat polarizing spectroscope is designed according to the following steps:

selecting an antireflection film initial structure Sub/HLH/Air;

reference wave λ of selected polarization film₀Selecting a substrate material, a high refractive index material H and a low refractive index material L for the film structure;

setting an optimized target value according to the technical index requirements of the antireflection film, wherein the optimized target value comprises a use wavelength, a use angle and a p light transmittance, and performing optimized design on the antireflection film according to the target value;

(3) and (3) respectively superposing the optimized polarizing film and the optimized antireflection film on the substrate, fitting and calculating the transmittance and the extinction ratio of the deep ultraviolet flat polarizing spectroscope, finishing the design if the transmittance and the extinction ratio meet the target value, and returning to the step (1) if the transmittance and the extinction ratio do not meet the target value.

5. The method of claim 4, wherein the design method comprises: the reference wavelength λ₀Is any wavelength between 180nm and 220 nm.

6. The method of claim 4, wherein the design method comprises: the optimization design is completed by using TFCalc, Macleod or Optilayer membrane system design software.

7. The method of claim 4, wherein the design method comprises: the spectral wavelength and the spectral effect of the polarizing beam splitter can be adjusted by selecting different reference wavelengths, high and low refractive index materials and film stack period numbers.

Technical Field

The invention belongs to the technical field of optical films, and particularly relates to a deep ultraviolet flat plate polarizing beam splitter and a design method thereof. In particular to a flat-plate polarizing spectroscope with any ultraviolet wavelength in the range of 180nm-220 nm.

Background

Very Large Scale Integration (VLSI) is the basis for the development of all high technology areas in the modern world. Integrated circuits have evolved from only a few tens of devices per chip in the 60's to now containing about 10 hundred million devices per chip, and so have been able to evolve at a rapid pace, with support from photolithographic techniques playing a crucial role. The emergence of each new generation of integrated circuits has always been marked by the line widths obtained by photolithography. The method for reducing the line width comprises the steps of reducing the wavelength of a light source, adopting high-resolution photoresist, increasing the radius of a lens, adopting a medium with high refractive index, optimizing an optical prism system and the like. The reduction of the wavelength of the light source can greatly improve the resolution ratio and is also a mark for the generation division of the photoetching machine. The development of exposure wavelength has gone through g-line (436nm) and i-line (365nm) of high-pressure mercury lamps, KrF excimer laser (248nm), ArF excimer laser (193nm), and is progressing toward Extreme Ultraviolet (EUV) (13.5 nm). At present, 193nm immersion lithography is not only the mainstream technology of 28nm node, but also is expected to be applied to 7nm node lithography production in large scale.

193nm lithography machines use a large number of thin film elements, wherein a polarizing beam splitter, which is an optical element that splits incident light into transmitted and reflected light having mutually orthogonal polarization planes, is often used as an optical switch or optical isolation element in laser systems. In laser systems, especially in uv laser systems, the performance of the polarizing beam splitter has a crucial impact on the overall laser system. Currently, a lot of laser systems are used, including an α -BBO glan laser prism, a glass polarization beam splitter prism using optical cement, or a flat plate polarization beam splitter.

The existing glass polarization beam splitter prism mainly comprises a pair of 45-degree right-angle prisms, the inclined planes of the two prisms are in butt joint gluing or are formed by adopting optical cement, in an ultraviolet laser system, the glued polarization beam splitter prism can not be used almost in ultraviolet, the common glue is almost light-proof, and the optical cement process is complex and is not good in optical cement.

The deep ultraviolet flat polarizing spectroscope can realize high transmittance and high extinction ratio in a deep ultraviolet band by plating a deep ultraviolet flat polarizing film and an antireflection film on the back surface on the substrate, and meanwhile, the deep ultraviolet flat polarizing spectroscope has the advantages of small volume and light weight.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a deep ultraviolet flat plate polarization beam splitter and a design method thereof, which are used for solving the technical problem of polarization beam splitting of a deep ultraviolet waveband, reducing the volume and the weight of an ultraviolet laser optical system and improving the flexibility of the design of the optical system.

In order to solve the technical problems, the technical solution of the invention is as follows:

on one hand, the invention provides a deep ultraviolet flat polarizing beam splitter, which is characterized by comprising a substrate, a polarizing film and an antireflection film on two sides of the substrate, wherein the film system structure of the polarizing film comprises a film stress adjusting layer and a polarizing beam splitting film layer; the initial structure is as follows: Air/(aHbL)ⁿM/Sub/HL/Air, Sub denotes a substrate, H and L respectively denote an optical thickness of lambda₀4, a and b are coefficients of H and L layers respectively, M is a film stress adjusting layer, and n is the period number of the polarization splitting film layer (aHbL).

The material of the substrate comprises fused ArF0F grade quartz or ultraviolet CaF₂(ii) a The material of the high-refractive-index film layer comprises LaF₃，GdF₃Or NdF₃(ii) a The material of the low-refractive-index film layer comprises AlF₃Or MgF₂(ii) a The stress adjusting film layer is made of SiO₂。

The incident angle of the incident light of the ultraviolet flat plate polarizing spectroscope is 65 +/-1 degrees, the transmittance of the ultraviolet flat plate polarizing spectroscope at a certain wavelength within the wavelength range of 180nm-220nm is more than 91 percent, and the extinction ratio is more than 60: 1.

On the other hand, the invention also provides a design method of the deep ultraviolet flat plate polarizing beam splitter, which is characterized by comprising the following steps:

(1) the polarizing film in the deep ultraviolet flat polarizing beam splitter is designed according to the following steps:

initial structure of selected polarizing film Air/(aHbL)ⁿM/Sub, wherein n is the number of cycles of the polarization beam splitting film layer (aHbL) and the value is between 12 and 18; a and b are coefficients of the H and L layers respectively, and are related to the refractive index of the material, and the value is between 0.8 and 2; m is a stress adjusting layer with a thickness of (aHbL)ⁿ1/3-1/2 of film stack thickness;

reference wave λ of selected polarization film₀Selecting a substrate material, a high refractive index material H, a low refractive index material L and a stress adjusting layer material M for the film system structure;

setting an optimized target value according to the technical index requirements of the polarizing film, wherein the optimized target value comprises the use wavelength, the use angle and the transmittance of p light and s light, and performing the optimized design of the polarizing film according to the target value;

(2) the antireflection film in the deep ultraviolet flat polarizing spectroscope is designed according to the following steps:

selecting an antireflection film initial structure Sub/HLH/Air;

reference wave λ of selected polarization film₀Selecting a substrate material, a high refractive index material H and a low refractive index material L for the film structure;

setting an optimized target value according to the technical index requirements of the antireflection film, wherein the optimized target value comprises a use wavelength, a use angle and a p light transmittance, and performing optimized design on the antireflection film according to the target value;

(3) and (3) respectively superposing the optimized polarizing film and the optimized antireflection film on the substrate, fitting and calculating the transmittance and the extinction ratio of the deep ultraviolet flat plate polarizing spectroscope, finishing the design if the target value is met, and returning to the step (1) if the target value is not met.

The reference wavelength λ₀Is any wavelength between 180nm and 220 nm.

The optimization design is completed by using TFCalc, Macleod or Optilayer membrane system design software.

The spectral wavelength and the spectral effect of the polarizing beam splitter can be adjusted by selecting different reference wavelengths, high and low refractive index materials and film stack period numbers.

Compared with the prior art, the invention has the beneficial effects that:

the deep ultraviolet flat polarizing spectroscope prepared by the invention can realize high transmittance and high extinction ratio in a deep ultraviolet band, the film layer has no cracking problem, and meanwhile, the deep ultraviolet flat polarizing spectroscope has the advantages of small volume and light weight.

Drawings

The invention will now be further described with reference to the accompanying drawings by way of example.

FIG. 1 is a schematic structural diagram of a deep ultraviolet plate polarizing beam splitter according to the present invention.

FIG. 2 is a designed transmission curve for a deep ultraviolet plate polarizing beamsplitter in accordance with the present invention.

FIG. 3 is a measured transmission curve of a deep ultraviolet plate polarizing beamsplitter according to an embodiment of the present invention.

Detailed Description

In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.

The embodiment provides a design method of a deep ultraviolet flat plate polarizing beam splitter, which comprises the following steps:

the basic structure of the polarizing beam splitter is determined as shown in fig. 1: plating a film stress adjusting layer on the substrate, and plating a polarization beam splitting film on the layer; plating an anti-reflection film on the back of the substrate;

selecting the use wavelength to be 193.4nm and the use angle to be 65 +/-1 degrees;

the substrate is ArF 0F-grade fused quartz, and the high-refractive-index film layer is made of LaF₃The low refractive index film layer is made of AlF₃And using SiO₂As a stress adjusting layer;

selection of Air/(aHbL)ⁿThe M/Sub is used as an initial structure of a polarizing film system, the selected substrate, the high-refractive-index film layer material and the low-refractive-index film layer material are used for correspondingly designing and optimizing the film system, and the optimally designed film system structure is as follows:

Sub/12.5M1.17L1.00H1.14L0.97H1.11L0.95H1.09L0.93H1.08L0.92H1.07L0.92H1.07L0.92H1.07L0.92H1.08L0.93H1.09L0.95H1.11L0.97H1.13L0.99H1.16L1.02H1.19L1.24H/Air；

selecting Sub/HLH/Air as an initial structure of the antireflection film, and correspondingly designing and optimizing a film system by using the same use wavelength, use angle, substrate material and high-low refractive index material as those of the polarizing film, wherein the optimized antireflection film system has the following structure: Air/6.18H/6.18 L6.18H/Sub;

and adding a polarizing film and an antireflection film on two surfaces of the substrate at the same time, and simulating and calculating the transmittance and the extinction ratio of the polarizing beam splitter.

The design curve of the flat polarizing film of the present invention is shown in fig. 2, and the design result is: under an incident angle of 65 +/-1 DEG and at 193.4nm, the transmittance of a P polarization component is more than 91%, the transmittance of an S polarization component is less than 1.5%, and the extinction ratio is more than 60: 1.

The optimized film system is plated on an ArF 0F-grade fused quartz substrate, and electron beam evaporation and resistance thermal evaporation coating processes are adopted.

Detecting by using a deep ultraviolet spectrometer after plating, wherein the testing environment is high-purity N₂The transmission curve is shown in FIG. 3. From FIG. 3, it can be obtained that at an incident angle of 65 + -1 deg., at 193.4nm, the transmittance of the P-polarized component is greater than 91%, the transmittance of the S-polarized component is less than 1.5%, and the extinction ratio is greater than 60:1, i.e. the plated deep ultraviolet plate polarizing beam splitter is in accordance with the theoretical design.

The deep purple provided by the inventionThe design method of the outer flat plate polarizing beam splitter comprises the steps of respectively designing a polarizing film and an antireflection film on two sides of a film coating flat plate, and optimally designing the refractive index and the film thickness of a multilayer polarizing beam splitting film and a film stress adjusting layer to realize high transmittance and high extinction ratio of a deep ultraviolet band at a non-Brewster angle and solve the problem of film cracking caused by large tensile stress of a fluoride multilayer film. The flat plate polarizing spectroscope provided by the design method is suitable for ArF 0F-level fused quartz and ultraviolet CaF₂The substrate can realize that the p-light transmittance at a certain wavelength within the range of the wavelength of 180nm-220nm is more than 91% and the extinction ratio is more than 60:1 when the incident angle is 65 +/-1 DEG, and has important significance for polarization control in a deep ultraviolet optical system and light weight design of the system.

It should be noted that, for those skilled in the art, the adjustment of the film system may be made or other coating processes such as magnetron sputtering, ion beam sputtering, atomic layer deposition, etc. may be adopted without departing from the technical principle of the present invention, and such adjustment and modification should also be considered as the protection scope of the present invention.