JP2005049827A - Ultraviolet polarizing beam splitter with minimum apodization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a beam splitter having a comparatively flat apodization function over a wide angle range, which can be used in ultraviolet photolithography. <P>SOLUTION: The beam splitter includes a first fluoride prism and a second fluoride prism. A coating interface is provided between the first and second fluoride prisms, wherein an overall R(s)*T(p) function of the beam splitter varies no more than ±2.74% in the range of 40-50 degrees of incidence. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical system, and more particularly to a beam splitter used in microlithography.

Related Art Photolithography (also referred to as microlithography) is a semiconductor manufacturing technology. Photolithography uses ultraviolet light or visible light to generate fine patterns in semiconductor device design. Many types of semiconductor devices such as diodes, transistors and integrated circuits can be manufactured using photolithography techniques. In semiconductor manufacturing, exposure systems or exposure tools are used to perform photolithography techniques such as etching. The exposure system can include a light source, a reticle, a reduction optical system, and a wafer alignment stage. The image of the semiconductor pattern is printed or manufactured on a reticle (also called a mask). The reticle is irradiated by the light source, and an image of each reticle pattern is generated. Reduction optics are used to provide a high quality image of the reticle pattern to the wafer. See Nonogaki et al., Microlithography Fundamentals in Semiconductor Devices and Fabrication Technology, Marcel Dekker, Inc., New York, NY (1998). This is a reference for the present invention.

  Integrated circuits are becoming more and more complex. The number of components present in the layout and the integration density are increasing. In addition, there is a high demand for always reducing the minimum feature size. The minimum feature size (also referred to as line width) is the smallest dimension of a semiconductor feature that can be manufactured within an acceptable range. For this reason, it is becoming increasingly important to provide higher resolutions with photolithography systems and photolithography techniques.

  One attempt to improve resolution is to shorten the wavelength of light used during manufacturing. The resolution can also be improved by increasing the numerical aperture (NA) of the reduction optical system. Indeed, commercial exposure systems have been developed by shortening the wavelength of light and increasing the NA.

  The mirror provided in the catadioptric reduction optical system reflects the imaging light after reaching the wafer through the reticle. A beam splitter cube is used in the optical path of the system. However, conventional beam splitter cubes transmit about 50% of incident light and reflect about 50% of incident light. Thus, depending on the particular configuration of the optical path, significant light loss can occur at the beam splitter.

  However, what is important in ultraviolet photolithography is to maintain a high degree of light transmission through a reduction optical system with little or no loss. In this case, the exposure time and the entire semiconductor manufacturing time depend on the intensity or magnitude of the light emitted to the wafer. In order to reduce the loss of light in the beam splitter, a polarizing beam splitter and a quarter wave plate are used. In general, polarizing beam splitters are designed for maximum optical throughput, in which case they are placed on the pupil of the projection optics without special consideration for apodization. In the case of an optical system with a small numerical aperture (ie for a numerical aperture corresponding to a relatively small operating angle range in the beam splitter coating) this is not a significant problem. This is because the natural bandwidth of the coating is generally large enough to meet the requirements. However, higher numerical apertures add to the complexity of the coating design, resulting in an increase in undesirable performance variations over the operating angle range.

  Therefore, there is a need for a beam splitter that has a relatively flat apodization function over a wide range of angles that can be used in ultraviolet photolithography.

SUMMARY OF THE INVENTION According to the present invention, a technique for providing a beam splitter having a relatively flat apodization function is realized.

  According to one embodiment of the present invention, a beam splitter is provided in which the product of P transmittance and S transmittance is relatively flat.

  According to another embodiment of the present invention, there is provided a beam splitter having the above-described properties that can be used for ultraviolet and deep ultraviolet photolithography applications.

  According to one aspect of the present invention, a beam splitter having a first fluoride prism and a second fluoride prism is provided. A coating interface is provided between the first fluoride prism and the second fluoride prism. In this case, the entire R (s) * T (p) function of the beam splitter is 40 to 50 degrees incident. It does not vary more than ± 2.74% within the angular range.

  Other features and advantages of the present invention are described in the following description. They will be apparent in part from the description which follows, or can be learned in the practice of the invention. The goals and other advantages of the invention will be realized, for example, by the structure described in the description and claims hereof and the accompanying drawings.

  In order to achieve these and other advantages in accordance with the objectives of the present invention, the accompanying drawings will be used. The accompanying drawings, together with the following description, illustrate the invention, which is useful for explaining the principles of the invention and which enable those skilled in the art to practice and use the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings. In the figures, the same or functionally similar elements are given the same reference numerals. Further, in the reference numerals, the leftmost numeral indicates the drawing in which the reference numerals first appear.

  Although the present invention will now be described based on embodiments relating to specific applications, the present invention is not limited thereto. Those skilled in the art can find additional variations and applications as well as embodiments within the scope of the present invention, as well as additional fields in which the present invention is extremely useful, from what has been described herein.

Terminology The term “beam splitter” or “cube” as used in connection with the present invention has a broad meaning and includes, but is not limited to, general cube shapes, cube shapes or chamfered cube shapes or similar shapes. It refers to the beam splitter that has it.

  The term “conjugate far end” refers to a plane at the end of an object or reticle in a reduction optical system.

  The term “conjugate near end” refers to the image at the reduction optics or a plane at the edge of the wafer.

  The term “wafer” refers to a base material in semiconductor manufacturing that has undergone a series of photomask steps, etching steps and / or mounting steps.

  The term “wave plate” refers to a retardation plate or phase shifter made of a material having birefringence.

1A and 1B illustrate a conventional polarizing beam splitter cube 100 used in a conventional catadioptric conventional reduction optical system. The polarizing beam splitter cube 100 has two prisms 110 and 150 and a coating interface 120. The prisms 120 and 150 are made of quartz glass or molten glass, which is transparent at wavelengths of 248 nm and 193 nm. The coating interface 120 is a multilayer laminate. A multilayer stack is thin film layers arranged alternately. This alternating thin film layer is composed of a plurality of films having a relatively high refractive index and a relatively low refractive index (n ₁ and n ₂ ). The alternating thin film layers and their individual refractive indices are selected such that the MacNeille condition (also referred to as the Brewster condition) is met. In one example, the high refractive index material is aluminum oxide and the low refractive index material is aluminum fluoride. A protective layer can be added during stack manufacture. Cement or glue is included to attach one of the alternating layers to the prism 150 at the interface 152 or to attach a protective layer to the prism 110 at the interface 112. As shown in FIG. 2A (as described in US Pat. No. 2,403,731), the MacNeille condition means that the light incident on the multilayer stack is split into two beams 260, 280 in different polarization states. It is a condition when it is divided. For example, the outgoing beam 260 is an S-polarized beam and the outgoing beam 280 is a P-polarized beam (or beams that are 90 degrees polarized with respect to each other). FIG. 2B illustrates the advantage of using a polarizing beam splitter in a catadioptric reduction optical system to minimize light loss. Incident light 200 (usually having S-polarized light and P-polarized light) passes through quarter-wave plate 210. The quarter-wave plate 210 converts all incident light 200 into a linearly polarized beam in the S polarization state. Beam splitter cube 100 reflects all or a portion of the S-polarized light to quarter wave plate 220 and mirror 225. The quarter-wave plate 220 operates like a half-wave plate if it is passed twice. The quarter-wave plate 220 converts S-polarized light into circularly-polarized light, reflects the light from the mirror 225, and then converts it into P-polarized light. The P-polarized light passes through the beam splitter cube 100 and is emitted toward the wafer as a P-polarized beam 290. In this way, light loss in the catadioptric reduction optical system including the mirror 225 is avoided by the polarizing beam splitter 100 and the quarter wavelength plates 210 and 220. As an alternative, the mirror 225 and the quarter-wave plate 220 can be arranged not at the interface A of the cube 100 but at the interface B, which also provides the same complete light transmission through a compact optical path length. Or almost complete light transmission is achieved.

  The invention described below can be used in a catadioptric photolithography system. It can be used in any polarizing beam splitter system where a beam splitter is used over a range of angles and light passes through the beam splitter twice in the form of orthogonal polarization.

  Although the exemplary polarizing beam splitters described so far with reference to FIGS. 1A-2B are designed to maximize optical throughput, they do not require special consideration for apodization. Put on your eyes. In systems with a small numerical aperture (ie systems with a relatively small range of operating angles in the beam splitter coating) this is not a significant problem. In such a system, the original bandwidth of the coating is large enough to meet the requirements. Larger numerical apertures add to the complexity of the coating design, resulting in increased undesirable performance variation over the operating angle range.

  In the case of the beam splitter of the present invention, the light passes through the beam splitter twice, the first time becomes S-polarized light and the second time becomes P-polarized light again. The two performance curves (S and P as a function of angle) are multiplied together to determine the overall apodization that the coating causes on the pupil of the system. Previous efforts to design coatings with low pupil apodization have focused on flattening the S and P performance curves individually. For beam splitter coating designs, it is easier to change the performance of S-polarized light and it is more difficult to change the performance of P-polarized light. Passing the beam splitter twice in the system can compensate for variations in P-polarization performance by coatings with “traces” that have opposite S-polarization performance. Multiplying the two functions R (s) and T (p) together produces a relatively flat apodization function R (s) * T (p).

  In order to achieve a relatively flat R (s) * T (p) function, an ultraviolet (UV) polarizing beam splitter is provided according to the present invention. The UV polarizing beam splitter is transparent to light having a wavelength of 200 nm or less, and is transparent to light having a wavelength of 193 nm or 157 nm, for example. UV polarizing beam splitters can image with high quality incident light over a wide range of reflectance and transmittance. Furthermore, the UV polarization beam splitter can be adapted to diverging light in a reduction optical system whose numerical aperture in the wafer plane is larger than 0.6, for example 0.75. In various embodiments, the UV polarizing beam splitter can have a cube shape, a cube shape, a chamfered cube shape, or a shape close thereto.

According to one embodiment, the UV polarizing beam splitter cube has a pair of prisms and a coating interface. The prism is made of at least one fluoride material, for example, calcium fluoride (CaF ₂ ) or barium fluoride (BaF ₂ ). The coating interface has multiple layers of thin film fluoride material. According to one embodiment, the coating interface is a multilayer stack consisting of alternating layers of thin film fluoride material. The layer in which the thin film fluoride materials are alternately arranged is composed of the first fluoride material and the second fluoride material. The first fluoride material and the second fluoride material have a first refractive index and a second refractive index, respectively. In this case, the first refractive index is higher than the second refractive index. According to one feature of the invention, the first and second refractive indices form a laminate made of a fluoride material having a relatively high refractive index and a relatively low refractive index, according to the coating interface. Depending on the two polarized states, UV light is separated (this UV light includes light with a wavelength shorter than 200 nm, eg 193 nm or 157 nm).

In order to achieve a relatively flat R (s) * T (p) function according to one embodiment, the coating interface has a multilayer design in the form of (H L) ⁿ H or (H L) ^n. Yes. Here, H represents a layer of the first fluoride material having a relatively high refractive index. The first fluoride material can include the following materials. However, it is not limited to this: gadolinium trifluoride (GdF ₃ ), lanthanum trifluoride (LaF ₃ ), samarium fluoride (SmF ₃ ), europium fluoride (EuF ₃ ), terbium fluoride (TbF ₃₎ ), fluoride Jisupuroshimu _(DyF 3), fluoride holmium _(HoF 3), erbium fluoride _(ErF 3), fluoride thulium _(TmF 3), ytterbium fluoride _(YbF 3), fluoride lutetium _(LuF 3), Zirconium fluoride (ZrF ₄ ), hafnium fluoride (HfF ₄ ), yttrium fluoride (YF ₃ ), neodymium fluoride (NdF ₃ ), other lanthanide series trifluorides, metal fluorides, or high refractive index One of the UV transparent materials. L represents the second layer of fluoride material having a relatively low refractive index. The second fluoride material can include the following materials. However, it is not limited to this: magnesium fluoride (MgF ₂ ), aluminum trifluoride (AlF ₃ ), barium fluoride (BaF ₂ ), strontium fluoride (SrF ₂ ), calcium fluoride (CaF ₂ ) , Lithium fluoride (LiF), sodium fluoride (NaF), or other low refractive index UV transmissive materials. Furthermore, the value n represents that the base (H L) group is repeated n times in the multilayer stack, where n is an integer of 1 or greater.

  According to yet another feature, the prism and coating interface are joined by an optical contact. Although it does not prevent the use of cement, it is not necessary here.

  In addition, multi-layer designs can be formed by iterative design with a computer. Also, each layer in the multilayer stack can be stepped over the slope of the prism to adjust the layer thickness at any point for the purpose of compensating for changes in the incident angle of light.

  According to the present invention, a method for splitting an incident light beam based on a polarization state is provided. The method includes orienting a coating interface having a plurality of fluoride material layers at an angle relative to incident light, whereby the coating interface directs incident light in a first polarization state. Transmit and reflect incident light in the second polarization state. According to one embodiment, the method further comprises the step of selecting the thickness of the alternating thin film layers as well as their respective refractive index, according to which the coating interface has a wavelength below 200 nm. Is transmitted in the first polarization state, and incident light having a wavelength of 200 nm or less is reflected in the second polarization state.

UV Polarizing Beam Splitter FIG. 3A shows a perspective view of a UV polarizing beam splitter cube 300 according to one embodiment of the present invention. The UV polarizing beam splitter cube 300 has a set of prisms 310 and 350 and a coating interface 320. Advantageously, the prisms 310, 350 are made of a fluoride material. The coating interface 320 has a plurality of thin film fluoride material layers.

In the embodiment shown in FIG. 3A, prism 310 is a right-angle prism having five surfaces, and these five surfaces consist of two side surfaces, two end surfaces, and one inclined surface. The two sides form a right angle (or nearly a right angle) at their boundary and share a right corner 314,316. FIG. 3A shows one side B, and the other side is not shown. Both end faces are right triangles. One end face A shown in FIG. 3A has its 90 ° (or about 90 °) angle at the corner 314 and two 45 ° (or about 45 °) angles opposite the corner 314. It forms a right triangle around it. The other end face (not shown) is perpendicular at its periphery by an angle of 90 ° (or about 90 °) at the corner 316 and two 45 ° (or about 45 °) angles opposite the corner 316. It is a triangle. The bevel is a flat surface 312 which is on the hypotenuse of the right-angle prism 310 opposite the right-angle corners 314, 316. The prism 350 is a right angle prism having five surfaces, and these five surfaces are composed of two side surfaces, two end surfaces, and one inclined surface. The two sides form a right angle (or nearly a right angle) at their boundaries and share the right corners 354 and 356. In FIG. 3A, one side D is shown and the other side is not shown. Both end faces are right triangles. One end face C shown in FIG. 3A has its 90 ° (or about 90 °) angle at the corner 354 and two 45 ° (or about 45 °) angles opposite the corner 354. It forms a right triangle around it. The other end face (not shown) forms a right triangle by an angle of 90 ° (or about 90 °) at the corner 356 and two 45 ° (or about 45 °) angles opposite the corner 356. is doing. The slope is a flat surface 352 that is on the hypotenuse of the right-angle prism 310 opposite the right-angle corners 354,356. The coating interface 320 is between the slopes 312 and 352. The width, depth, and height dimensions of the UV polarizing beam splitter cube 300 have values of d1, d2, and d3, respectively, as shown in FIG. 3A. According to one embodiment, d1, d2, and d3 are equal (or nearly equal) and when prisms 310 and 350 are joined along their faces 312 and 352, the overall shape is a cube or cube. I will have. According to one embodiment, the prisms 310, 350 are made of a calcium fluoride (CaF ₂ ) material, a barium fluoride (BaF ₂ ) material, or a combination thereof.

Coating Interface FIG. 3B details a cross-sectional view of an example of a coating interface 320 used to achieve a relatively flat R (s) * T (p) function. The coating interface 320 includes a laminate composed of layers in which thin film fluorinated materials (331 to 337 and 341 to 346) are alternately arranged and a protective layer 351. An anti-reflective (AR) coating (not shown) can also be included at the coating interface 320. The protective layer 351 and the AR coating are optional. Further, the present invention is not limited to 13 layers in which thin film fluorinated materials are alternately arranged. As will be understood by those skilled in the art from the description of the present specification, the number of alternately arranged layers of the thin film fluorinated material can be generally increased or decreased. Further, FIG. 3B shows that the coating interface 320 is attached to the surface 352 of the prism 350. A stack of alternating layers of thin film fluorinated materials (331-337, 341-346) and / or protective layers can be grown and etched or finished on surface 352 using conventional thin film techniques. it can. A prism 310 is then placed in optical contact with the coating interface 320. In this way, prisms 310 and 350 are strongly coupled via coating interface 320, resulting in a very robust polarizing beam splitter cube. According to yet another feature of the invention, the optical contact (where the optical elements are tightly joined so that the elements are coupled together by van der Waals forces), such as the slope of the prism 310, A complex geometric shape including an angled surface is provided. The alternating layers of thin film fluoride material include two groups of layers. The first layer group 331 to 337 has a first refractive index _{n 1.} The second layer group 341 to 346 has a second refractive index _{n 2.} According to one feature of the invention, the first and second refractive indices n ₁ and n ₂ are different. For example, the second refractive index n ₂ is lower than the _first refractive index n ₁ . Coating interface 320 in this way, it will contain a relatively high refractive index _{n 1} and a relatively low refractive index _{n 2} made of fluoride materials 331～337,341～346 having alternately stacked body, thereby The coating interface 320 separates incident UV light based on two different polarization states, such as an S polarization state and a P polarization state. In accordance with the present invention, the polarizing beam splitter cube 300 can be used with light having a wavelength of 200 nm or less, such as 193 nm or 157.6 nm.

As mentioned above, the coating interface 320 has a multilayer design in the form of (H L) ⁿ H or (H L) ⁿ in order to achieve a relatively flat R (s) * T (p) function. Where H represents a layer of a first fluoride material having a relatively high refractive index. The first fluoride material can include the following materials. However, it is not limited to this: gadolinium trifluoride (GdF ₃ ), lanthanum trifluoride (LaF ₃ ), samarium fluoride (SmF ₃ ), europium fluoride (EuF ₃ ), terbium fluoride (TbF ₃₎ ), fluoride Jisupuroshimu _(DyF 3), fluoride holmium _(HoF 3), erbium fluoride _(ErF 3), fluoride thulium _(TmF 3), ytterbium fluoride _(YbF 3), fluoride lutetium _(LuF 3), Zirconium fluoride (ZrF ₄ ), hafnium fluoride (HfF ₄ ), yttrium fluoride (YF ₃ ), neodymium fluoride (NdF ₃ ), other lanthanide series trifluorides, metal fluorides, or high refractive index One of the UV transparent materials. L represents a layer made of a second fluoride material having a relatively low refractive index. The second fluoride material can include the following materials. However, it is not limited to this: magnesium fluoride (MgF ₂ ), aluminum trifluoride (AlF ₃ ), barium fluoride (BaF ₂ ), strontium fluoride (SrF ₂ ), calcium fluoride (CaF ₂ ) , Lithium fluoride (LiF), sodium fluoride (NaF), or other low refractive index UV transmissive materials. Furthermore, the value n represents that the base (H L) group is repeated n times in the multilayer stack, where n is an integer of 1 or greater.

  Also, as will be appreciated by those skilled in the art from the description herein, other designs for the multilayer coating interfaces 320, 520 can be generated by iterative techniques with a computer.

  Next, it will be shown how a flat overall function R (s) * T (p) can be realized using a plurality of alternating layers.

Beam splitter example 1
The table below shows an example of a coating interface 320 for 156.7 nm, which uses a total of 27 layers (n = 13) with alternating MgF ₂ and LaF _3. Thus, the requirement for a flat R (s) * T (p) apodization function is satisfied. According to this example, a relatively flat R (s) * T (p) is obtained at an incident angle between 35 ° and 55 °. In this range, the R (s) * T (p) function takes from a maximum value of 70.85 to a minimum value of 65.37, or a delta of 5.48% (± 2.74%).

  In FIG. 4, the R (s), T (p) and overall R (s) * T (p) functions are shown graphically, and in Table 2 below, these are shown in tabular form. :

Beam splitter example 2
Table 3 below shows another example of the coating interface 320 for 157.6 nm, according to which a total of 29 layers (n = 14) with alternating MgF ₂ and LaF ₃ Is used to satisfy the requirement of a flat R (s) * T (p) apodization function. According to this example, a relatively flat R (s) * T (p) function is obtained at an incident angle between 35 ° and 55 °. In this range, the R (s) * T (p) function ranges from a maximum value of 67.9% to a minimum value of 66.15%, or a delta of 1.74% (± 0.87%).

  FIG. 5 graphically illustrates the R (s), T (p) and overall R (s) * T (p) functions, and Table 4 below illustrates them in tabular form. :

Beam splitter example 3
Table 5 below shows another example of the coating interface 320, which uses a total of 26 layers (n = 13) with alternating MgF ₂ and LaF ₃ , The requirement for a flat R (s) * T (p) apodization function is met. According to this example, a relatively flat R (s) * T (p) function is obtained with an incidence between 40 ° and 60 °. In this range, the R (s) * T (p) function takes from a maximum value of 72.69% to a minimum value of 71.80%, or a delta of 0.89% (± 0.445%).

  FIG. 6 graphically illustrates the R (s) * T (p) and overall R (s) * T (p) functions, and Table 6 below illustrates them in tabular form. :

Beam splitter example 4
Table 7 shows another example of the coating interface 320, which uses a total of 32 layers (n = 16) with alternating AlF ₃ and NdF _{3 and} is flat. The requirement of R (s) T * (p) apodization function is satisfied. According to this example, a relatively flat R (s) * T (p) function is obtained at an incident angle between 35 ° and 55 °. In this range, the R (s) * T (p) function takes from a maximum value of 72.55% to a minimum value of 71.24%, or a delta of 1.31% (± 0.655%).

  In FIG. 7, R (s), T (p) and overall R (s) * T (p) are shown graphically, and in Table 8 below they are shown in tabular form:

Beam splitter example 5
Table 9 below shows another example of a coating interface 320 for 193 nm, which uses a total of 30 layers (n = 15) with alternating AlF ₃ and NdF ₃ Thus, the requirement for a flat R (s) * T (p) apodization function is satisfied. According to this example, a relatively flat R (s) * T (p) function is obtained at an incident angle between 35 ° and 55 °. In this range, the R (s) * T (p) function ranges from a maximum value of 74.60% to a minimum value of 70.38%, or a delta of 4.33% (± 2.11%). .

  FIG. 8 shows the R (s), T (p) and overall R (s) * T (p) functions, which are shown in tabular form in Table 10 below:

Beam splitter example 6
Table 11 below shows another example of a coating interface 320 for 157.6 nm, which uses a total of 21 layers with alternating LaF ₃ and MgF ₂ to create a flat R (s) * T (p) apodization function requirements are satisfied. According to this example, a relatively flat R (s) * T (p) function is obtained with an incidence between 44 ° and 60 °. In this range, the R (s) * T (p) function ranges from a maximum value of 68.08% to a minimum value of 67.95%, or a delta of 0.128% (± 0.064%).

  In FIG. 9, the R (s), T (p) and R (s) * T (p) functions are shown graphically, and in Table 12 below they are shown in tabular form:

Beam splitter example 7
Table 13 below shows another example of a coating interface 320 for 157.6 nm, which uses a total of 11 layers of alternating LaF ₃ and MgF ₂ to create a flat R (s) * T (p) apodization function requirements are satisfied. According to this example, a relatively flat R (s) * T (p) function is obtained at an incident angle between 44 ° and 60 °. In this range, R (s) * T (p) ranges from a maximum value of 63.11% to a minimum value of 62.897%, or a delta of 0.21% (± 0.1%).

  In FIG. 10, the R (s), T (p) and R (s) * T (p) functions are shown graphically, and in Table 14 below they are shown in tabular form:

  While specific embodiments of the present invention have been described above, these are only examples and are not intended to be limiting. It will be apparent to those skilled in the art that various modifications can be made in form and detail without departing from the spirit and scope of the invention as set forth in the claims. Therefore, the scope of the present invention is not limited to the above-described embodiments, but is defined only by the description of the claims and equivalents thereof.

It is a perspective view of a conventional polarization beam splitter cube. 1B is a cross-sectional view of a conventional coating interface of the polarizing beam splitter cube of FIG. 1A. FIG. FIG. 1B shows how the polarizing beam splitter cube of FIG. 1A separates light into distinct polarization states. Polarizing beam splitter cube of FIG. 1A is a diagram showing how it can be used as any part of a catadioptric reduction optical system in the order of transmission efficiency. 1 is a perspective view of a UV polarizing beam splitter cube according to one embodiment of the present invention. FIG. FIG. 3B is a cross-sectional view of the coating interface for the UV polarizing beam splitter cube of FIG. 3A. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention. It is a figure which shows the permeation | transmission performance of the beam splitter by this invention.

Claims (42)

In the beam splitter,
A first fluoride prism, a second fluoride prism, and a coating interface provided between the first fluoride prism and the second fluoride prism;
A beam splitter characterized in that the overall R (s) * T (p) function of the beam splitter varies within ± 2.74% within an incidence range of 40 ° to 50 °. The beam splitter according to claim 1, wherein the coating interface includes layers in which MgF ₂ and LaF ₃ are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 27 layers in which a high refractive index material and a low refractive index material are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 27 layers in which a high refractive index material and a low refractive index material are alternately arranged. The beam splitter according to claim 1, wherein the coating interface has layers in which NdF ₃ and AlF ₃ are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 30 layers in which a high refractive index material and a low refractive index material are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 32 layers in which a high refractive index material and a low refractive index material are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 11 layers in which a high refractive index material and a low refractive index material are alternately arranged.   The beam splitter according to claim 1, wherein the coating interface has at least 21 layers in which a high refractive index material and a low refractive index material are alternately arranged. The beam splitter according to claim 1, wherein the first and second prisms include CaF ₂ .   The beam splitter according to claim 1, wherein the first and second prisms include quartz glass.   The beam splitter according to claim 1, wherein the overall R (s) * T (p) function of the beam splitter varies within ± 0.87% over an incident range of 35 ° to 55 °.   The beam splitter according to claim 1, wherein the overall R (s) * T (p) function of the beam splitter varies within ± 2.74% in the incident range of 35 ° to 55 °.   The beam splitter according to claim 1, wherein the beam splitter operates near 157.6 nm. The beam splitter according to claim 1, wherein the beam splitter operates near 193 nm. In the beam splitter,
A first fluoride prism, a second fluoride prism, and a coating interface provided between the first fluoride prism and the second fluoride prism;
A beam splitter characterized in that the overall R (s) * T (p) function of the beam splitter varies within ± 0.445% in the 40 ° -50 ° incidence range. The beam splitter according to claim 16, wherein the coating interface has layers in which MgF ₂ and LaF ₃ are alternately arranged.   The beam splitter according to claim 16, wherein the coating interface has at least 27 layers of alternating high and low refractive index materials.   The beam splitter according to claim 16, wherein the coating interface has at least 29 layers of alternating high and low refractive index materials. The beam splitter according to claim 16, wherein the coating interface includes layers in which NdF ₃ and AlF ₃ are alternately arranged.   The beam splitter according to claim 16, wherein the coating interface has at least 30 layers of alternating high and low refractive index materials.   The beam splitter according to claim 16, wherein the coating interface has at least 32 layers of alternating high and low refractive index materials.   The beam splitter according to claim 16, wherein the coating interface has at least 11 layers in which a high refractive index material and a low refractive index material are alternately arranged.   The beam splitter according to claim 16, wherein the coating interface has at least 21 layers of alternating high and low refractive index materials. The beam splitter according to claim 16, wherein the first and second prisms include CaF ₂ .   The beam splitter according to claim 16, wherein the first and second prisms include quartz glass. 17. A beam splitter according to claim 16, wherein the overall R (s) * T (p) function of the beam splitter changes by only 87% within the incidence range of 35 [deg.] To 55 [deg.] In the ultraviolet region. In the beam splitter,
A first fluoride prism, a second fluoride prism, and a coating interface provided between the first fluoride prism and the second fluoride prism;
A beam splitter characterized in that the apodization function of the beam splitter is relatively flat within an incident range of 40 ° to 50 °. In the beam splitter,
A first fluoride prism, a second fluoride prism, and a coating interface provided between the first fluoride prism and the second fluoride prism;
A beam splitter characterized in that the overall R (s) * T (p) function of the beam splitter varies within ± 0.1% in the 44 ° -60 ° incidence range.   30. The beam splitter according to claim 29, wherein the overall R (s) * T (p) function of the beam splitter varies within ± 0.064% within an incident range of 44 [deg.]-60 [deg.].   30. The beam splitter of claim 29, wherein the coating interface has at least 21 layers of alternating high and low refractive index materials. Said first and second prisms are included CaF _2, the beam splitter of claim 29, wherein. In a method of forming a beam splitter,
A step of forming a coating on the first fluoride prism is provided, wherein the apodization function of the beam splitter is relatively flat within an incident range of 40 ° to 50 °;
The step of combining the first fluoride prism with the second fluoride prism to form a beam splitter is provided,
A method of forming a beam splitter. Wherein the coating-forming step, MgF ₂ and LaF ₃ is included the step of forming a layer are arranged alternately, the method of claim 33. By the step of forming a layer MgF ₂ and LaF ₃ are alternately arranged to form a layer disposed on at least 27 alternating The method of claim 33. Wherein the coating-forming step, NdF ₃ and AlF ₃ are included the steps of forming a layer are arranged alternately, the method of claim 33. And said first and second prism CaF ₂ prism 34. The method of claim 33, wherein.   34. The method of claim 33, wherein the first and second prisms are quartz glass prisms.   34. The method of claim 33, wherein the coating is such that the overall R (s) * T (p) function of the beam splitter varies within ± 0.87% over an incident range of 35-55 [deg.].   34. The method of claim 33, wherein the overall R (s) * T (p) function of the beam splitter is coated to vary within ± 2.74% over an incident range of 35-55 [deg.].   34. The method of claim 33, wherein the beam splitter is coated to operate near 157.6 nm.   34. The method of claim 33, wherein the beam splitter is coated to operate near 193 nm.   34. The method of claim 33, wherein the coating is performed such that the apodization function of the beam splitter varies within ± 0.87% over an incident range of 35-55 [deg.].   The method of claim 33, wherein the beam apodization function of the beam splitter is coated to vary within ± 2.74% in an incident range of 35 ° to 55 °.

Images