CN102629082B - Design method of extreme ultra-violet lithography compound eye lighting system - Google Patents

Abstract

The invention provides a design method of a compound eye lighting system for extreme ultraviolet lithography. The specific steps are: determine the exit pupil distance of the illumination system according to the parameters of the specified projection objective lens; determine the coordinate system and obtain the coordinates of each device; according to the exit pupil distance and the coordinates of the center of the mask surface to determine the coordinates of the center of the exit pupil; make the center of the exit pupil coincide with the non-adjacent focus of the grazing-incidence mirror, and calculate the radius of curvature of the grazing-incidence mirror; make the non-adjacent focus of the first relay mirror The adjacent focus of the second relay mirror is coincident, and the radius of curvature of the first relay mirror is calculated; the adjacent focus of the second relay mirror is overlapped with the adjacent focus of the first relay mirror, and the radius of curvature of the second relay mirror is calculated; The non-adjacent focal point is the converging point of the outgoing rays of the uniform light system, and the arrangement of the compound eye elements on the compound eye plate of the diaphragm and the compound eye plate of the field of view in the uniform light system is determined according to the convergent point. The design method of the present invention can be applied to different projection objective lenses.

Description

A Design Method of Compound Eye Illumination System for Extreme Ultraviolet Lithography

technical field

The invention provides a design method of a compound eye lighting system for extreme ultraviolet lithography, and belongs to the technical field of lithography lighting.

Background technique

The current large-scale integrated circuits are generally manufactured using photolithography systems. The lithography system is mainly divided into four parts: illumination system, mask, projection system and wafer. The light emitted by the light source is focused by the condenser and then incident on the mask; after passing through the mask, the light is incident on the wafer coated with photoresist through the projection system, so that the mask pattern is copied on the wafer.

Extreme ultraviolet lithography (EUVL) is a microelectronic lithography technology that uses extreme ultraviolet EUV rays with a wavelength of 11-14nm as the exposure light source. It is suitable for mass production of integrated circuits with a feature size of 32nm and a thinner line width. The core component of the projection lithography machine is the projection exposure optical system, and the most important components of the system are the illumination system and the projection objective lens system. The main function of the illumination system is to provide uniform illumination for the mask surface, control the exposure dose and realize the off-axis illumination mode. As an important part of the lithography machine, the lighting system is very important to improve the performance of the whole lithography machine, so designing the lighting system is an important part of completing the entire projection exposure system.

At present, the design ideas of the extreme ultraviolet lithography lighting system mainly include: double-row compound eye lighting, corrugated plate lighting and free-form surface lighting design, etc. Among them, the double-row compound eye lighting has good light uniformity effect, relatively mature processing technology, and is easy to control. The advantages of easy realization of off-axis illumination have become the mainstream design structure of extreme ultraviolet lithography illumination system.

At present, some EUV lithography compound eye lighting systems have been disclosed abroad. According to the direction of beam propagation, they include: light source, condenser lens, uniform light system (including diaphragm compound eye plate and field of view compound eye plate), relay mirror group (including the first The first relay mirror and the second relay mirror) and the grazing incidence mirror; the uniform light system is a double row of compound eyes, while the condenser, relay mirror group and grazing incidence mirror are all quadric surfaces, and the relay mirror group is an ellipsoid , the grazing mirror is a hyperboloid. The parameters of each compound-eye illumination system are determined according to the illumination requirements of the matching lithography projection objective lens. Once the illumination requirements of the projection objective lens change, the parameters of each optical element in the illumination system may change. Therefore, it is necessary to develop a method that can obtain a compound eye illumination system that meets the illumination requirements of a specific projection objective lens based on an existing initial structure faster and more accurately, and there is no report on a complete related design method so far.

The relevant literature (US7456408) proposed a set of compound eye illumination design results for extreme ultraviolet lithography. In the design method part, it only mentioned that the mask surface was used as the aperture diaphragm of the system to develop the design, and no detailed design was given. process.

The relevant literature (US20070295919) proposed a set of compound eye lighting design results for extreme ultraviolet lithography. This design is only effective for the arc area with an illumination area of 100mm×8mm. It does not propose how to design a suitable A method for compound-eye illumination systems for arbitrary EUV lithography projection objectives.

Contents of the invention

The invention provides a design method of a compound eye illumination system for extreme ultraviolet lithography. The method is based on the structure of the existing compound eye illumination system, and can quickly obtain the design parameters of each device that meets the illumination requirements of the specified extreme ultraviolet lithography projection objective lens.

Realize the technical scheme of the present invention as follows:

A design method for a compound eye lighting system for extreme ultraviolet lithography, the lighting system includes a light source, a condenser lens, a uniform light system composed of a diaphragm compound eye plate and a field of view compound eye plate, and a first relay mirror and a second relay mirror The relay mirror group and grazing incidence mirror, the specific steps are:

Step 101, determine the exit pupil distance L of the lighting system according to the parameters of the specified projection objective lens;

Step 102, determine the symmetry axis of the grazing incidence mirror as the main optical axis of the illumination system, select the vertex of the grazing incidence mirror as the origin, take the main optical axis as the z axis, and establish a coordinate system (x, y, z) according to the principle of the right-handed coordinate system ), obtain the vertex coordinates (Z _G21 , Y _G21 ) of the first relay mirror, the vertex coordinates (Z _G22 , Y _G22 ) of the second relay mirror, and the center coordinates of the mask surface (Z _MASK , Y _MASK );

Step 103. Determine the coordinates (Z _EP , Y _EP ) of the exit pupil center of the lighting system according to the exit pupil distance L and the mask surface center coordinates (Z _MASK , Y _MASK );

Step 104, make the exit pupil center coincide with the non-adjacent focus F _collector1 of the grazing incidence mirror, and calculate the curvature radius R _G1 of the grazing incidence mirror according to (Z _EP , Y _EP );

Step 105, make the non-adjacent focal point F _relay11 of the first relay mirror coincide with the adjacent focal point F _collector2 of the grazing incidence mirror, and calculate the curvature radius R _G21 of the first relay mirror according to (Z _G21 , Y _G21 );

Step 106, make the adjacent focal point F _relay21 of the second relay mirror coincide with the adjacent focal point F _relay12 of the first relay mirror, and calculate the radius of curvature R _G22 of the second relay mirror according to (Z _G22 , Y _G22 );

Step 107: Make the non-adjacent focal points of the condenser mirrors the converging points of the outgoing rays of the uniform light system, and determine the arrangement of the compound eye elements on the compound eye plate of the diaphragm and the compound eye plate of the field of view in the uniform light system according to the convergent points.

Further, the present invention determines the size of the arc-shaped field of view incident on the mask surface by the illumination system, and sets an aperture stop on the mask surface. The size of the aperture stop is the same as the size of the arc-shaped field of view. A light source is arranged on the exit pupil surface, and the angles of the first relay mirror and the second relay mirror are adjusted according to the chief ray emitted by the light source on the exit pupil surface.

Beneficial effect

The present invention determines the relative positional relationship between the focal points of each component, so when providing a lighting system that meets the requirements for a specified projection objective lens, it only needs to calculate the parameters of each component based on the determined relative positional relationship, thus making the present invention The design method can be adapted to different projection objectives.

Secondly, the present invention proposes a design idea of reverse ray tracing, which regards the actual object (i.e. light source) as the image of the system, the actual image (exit pupil of the lighting system) as the object, and the image on the mask surface The arc-shaped field of view is set as the aperture stop of the system. This design idea transforms the technical requirements of the original system image space into the technical requirements of the object space, and the latter is easier to realize in design than the former.

Description of drawings

FIG. 1 is a schematic diagram of a typical structure of an existing EUV lithography system on which the present invention is based.

Figure 2 is a schematic diagram of the structure of the grazing incidence mirror.

Figure 3 is a schematic diagram of the structure of the relay mirror.

Figure 4 is a schematic diagram of the structure of the condenser.

FIG. 5 is a schematic diagram of a typical EUV lithography arc-shaped field of view structure.

Fig. 6 is a schematic diagram of the position of the exit pupil surface of the lighting system.

Fig. 7 is a schematic diagram of ray tracing of a grazing incidence mirror in the implementation of the present invention.

FIG. 8 is a schematic diagram of ray tracing of the grazing incidence mirror and the relay mirror 1 in the implementation of the present invention.

FIG. 9 is a schematic diagram of ray tracing of the grazing incidence mirror and system G1 in the implementation of the present invention. Figure 10 is a schematic diagram of a typical field of view compound eye arrangement.

Figure 11 is a schematic diagram of a typical diaphragm compound eye arrangement.

Fig. 12 is a schematic diagram of a compound eye lighting system without a condenser and a light source.

Fig. 13 is a schematic diagram of determining the position of a single imaging channel.

Fig. 14 is a schematic diagram of compound eye grouping in field of view.

Fig. 15 is a schematic diagram of grouping compound eyes with apertures.

Fig. 16 is a schematic diagram of the exit pupil light intensity distribution of the illumination system.

FIG. 17 is a schematic diagram of the light intensity distribution of the illumination system on the mask surface.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a schematic diagram of a typical structure of an EUV lithography system. The compound eye lighting system for extreme ultraviolet lithography is a total reflection off-axis optical system, and the structure of the condenser needs to be determined according to the characteristics of the light source. Therefore, the design method of the compound eye lighting system for extreme ultraviolet lithography in the present invention is only for the uniform light system and the relay lens group. And the parameters of the grazing incidence mirror are solved. For the convenience of explanation, the structure of the above components is defined in advance as follows:

Set the label of the grazing incidence mirror as G1, the label of the relay lens group as G2, and the label of the uniform light system as G3.

As shown in Figure 2, the solid line on the right side of the coordinate system represents the grazing incidence mirror, and the dotted line on the left side of the coordinate system represents the _hyperboloid symmetrical to the grazing incidence mirror. The focus of F _collector1 is the non-adjacent focus of the grazing incidence mirror.

As shown in Figure 3, the solid line on the right side of the coordinate system represents the relay mirror, and the focus on the right is defined as the adjacent focus of the relay mirror, and the focus on the left is the non-adjacent focus of the relay mirror.

As shown in Figure 4, the solid line on the right side of the coordinate system represents the condenser, and the focus on the right is defined as the adjacent focus of the condenser, and the focus on the left is the non-adjacent focus of the condenser.

Concrete process of the present invention is as follows:

Step 101, determine the exit pupil diameter D, exit pupil distance L of the illumination system and the size of the arc-shaped field of view incident on the mask surface by the illumination system according to the parameters of the specified projection objective lens, wherein the size of the arc-shaped field of view includes arc The outer diameter R, inner diameter r and chord length d of the field of view are shown in Figure 5. The exit pupil diameter D of the illumination system is equal to the entrance pupil diameter of the projection objective, and the exit pupil distance L of the illumination system (that is, the distance between the mask surface and the exit pupil surface) is equal to the entrance pupil distance of the projection objective.

Step 102. In the present invention, since the structure of the selected compound eye lighting system is determined, the relative positional relationship between each component is determined, and the aspheric quadratic coefficients on each component are also determined.

In this step, the symmetry axis of the grazing incidence mirror is determined as the main optical axis of the illumination system, the vertex of the grazing incidence mirror is selected as the origin, the main optical axis is the z axis, and the coordinate system (x, y, z) is established according to the principle of the right-handed coordinate system ; Since the vertices of each optical element in this system are all in the YZ plane, according to the relatively determined positional relationship of each component, the vertex coordinates (Z _G21 , Y _G21 ) and the aspheric quadratic coefficient K _G21 of the first relay mirror are obtained , the vertex coordinates (Z _G22 , Y _G22 ) of the second relay mirror and the aspherical quadratic coefficient K _G22 , the center coordinates (Z _MASK , Y _MASK ) of the mask surface and the aspheric quadratic coefficient of the grazing incidence mirror are K _G1 .

Step 103: Determine the coordinates (Z _EP , Y _EP ) of the center of the exit pupil of the lighting system according to the exit pupil distance L and the coordinates (Z _MASK , Y _MASK ) of the center of the mask surface.

According to the working principle of the lithography machine, the center of the exit pupil surface of the illumination system and the center of the arc-shaped field of view on the mask surface are located on the main optical axis of the projection objective lens, and the mask surface is perpendicular to the main optical axis, as shown in Figure 6 shown. According to the exit pupil distance L and the mask surface center coordinates (Z _MASK , Y _MASK ), the coordinates (Z _EP , Y _EP ) of the exit pupil center can be determined.

Step 104, make the center of the exit pupil coincide with the non-adjacent focus F _collector1 of the grazing incidence mirror, and calculate the radius of curvature of the grazing incidence mirror; the specific calculation process is:

The distance l between the exit pupil center and the vertex of the grazing incidence mirror is:

$\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; EP</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; EP</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Since the grazing incidence mirror is a hyperboloid, if the length of the real axis is a _G1 and the length of the imaginary axis is b _G1 , then:

$\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">G</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\sqrt{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">G</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">b</figure-callout></span><figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}^{\mathrm{<span\; class="notranslate">G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="K\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">K</figure-callout></span><figure-callout\; id="1"\; label="K\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">G</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">b</figure-callout></span><figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}^{\mathrm{<span\; class="notranslate">G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">G</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

According to a _G1 and b _G1 calculated by formulas (2) and (3), the radius of curvature R _G1 of the grazing incidence mirror is calculated, as shown in formula (4):

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">R</figure-callout></span><figure-callout\; id="1"\; label="R\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">b</figure-callout></span><figure-callout\; id="1"\; label="b\; G"\; filenames="HDA0000158542040000011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}^{\mathrm{<span\; class="notranslate">G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Since the surface shape of the grazing incidence mirror is determined, the grazing incidence mirror can be designed using the calculated curvature radius R _G1 .

Since the process of light transmission is reversible, the center point on the pupil plane is taken as the object of the system, and the structural diagram of the grazing incidence mirror is obtained by ray tracing, as shown in Figure 7.

From steps 105 to 107 in the following process, the adjustment of the angle of each device is based on the design idea of reverse ray tracing. The actual object plane (that is, the plane where the light source is located) is regarded as the image plane of the system, and the actual The image plane of the illumination system (i.e., the exit pupil plane of the illumination system) is regarded as the object plane of the system, and an aperture stop is set at the mask surface, and the size of the aperture stop is the same as that of the arc-shaped field of view described in step 101, A light source is arranged on the exit pupil surface of the lighting system, and the chief ray emitted by the light source on the exit pupil surface adjusts the angles of the first relay mirror and the second relay mirror. This design idea transforms the technical requirements of the original system image space into the technical requirements of object space, and the latter is easier to realize in design than the former.

Step 105 , according to the real axis length a _G1 and imaginary axis length b _G1 obtained in step 104 , calculate the coordinates (Z _G1F , Y _G1F ) of the adjacent focal point F _collector2 of the grazing incidence mirror. Make the non-adjacent focal point F _relay11 of the first relay mirror coincide with the adjacent focal point F _collector2 of the grazing incidence mirror, and calculate the curvature radius of the first relay mirror; the specific calculation process is:

Since the first relay mirror is an ellipsoid, if its long semi-axis is a _G21 , its short semi-axis is b _G21 , and its focal length is F _G21 , then

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

According to a _G21 and b _G21 calculated by formulas (5) and (6), the radius of curvature R _G21 of the grazing incidence mirror is calculated, as shown in formula (7):

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Since the surface shape of the first relay mirror is determined, the calculated curvature radius R _G21 can be used to design the first relay mirror.

Determine the angle of the first relay mirror: rotate the first relay mirror to ensure that the incident angle of the chief ray incident from the exit pupil surface is between 6° and 8°, thus obtaining the inclination angle θ of the first relay mirror ₁ , as shown in Figure 8.

Step 106, according to the first relay mirror obtained in step 105, calculate the coordinates (Z _G21F , Y _G21F ) of the first relay mirror adjacent to the focal point F _relay12 ; make the adjacent focal point F _relay21 of the second relay mirror The adjacent focal points F _relay12 of the relay mirror coincide, and the radius of curvature of the second relay mirror is calculated; the specific calculation process is:

Since the second relay mirror is an ellipsoid, if its major semi-axis field is a _G22 , its minor semi-axis length is b _G22 , and its focal length is F _G22 , then

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

According to a _G22 and b _G22 calculated by formulas (8) and (9), the radius of curvature R _G22 of the grazing incidence mirror is calculated, as shown in formula (10):

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Since the surface shape of the second relay mirror is determined, the calculated curvature radius R _G22 can be used to design the second relay mirror.

Determine the angle of the second relay mirror: fine-tune the second relay mirror so that the light emitted from it converges on one point, and the distance from this point to the second relay mirror 2 is not greater than 1500mm and not less than 1000mm; at the same time, rotate the second relay mirror to ensure that the angle at which the chief ray reflected from the first relay mirror is incident on the second relay mirror is between 9° and 12°, thereby obtaining the inclination angle θ ₂ of the second relay mirror, as shown in Figure 9 .

Step 107: Let the non-adjacent focus of the condenser be the converging point of the light emitted by the uniform light system (that is, the image point of the uniform light system), and determine the compound eye elements on the compound eye plate of the diaphragm and the compound eye plate of the field of view in the uniform light system according to the convergence point arrangement.

The specific process of step 107 will be further described in detail below.

Step 201, set the center point of the exit pupil plane as the object point, and place a diaphragm compound eye plate near the image point obtained after the object point passes through the grazing incidence mirror and the relay lens group, and the centers of all the diaphragm compound eye elements are located on the plate Top: Rotate the compound eye plate of the diaphragm to ensure that the incident angle of the chief ray of the light emitted from the object point incident on the compound eye plate of the diaphragm is between 6° and 8°, thus obtaining the inclination angle θ _PF of the compound eye plate of the diaphragm.

Step 202, place the field of view compound eye plate on the light path of the light beam reflected by the diaphragm compound eye, and at the same time ensure that the field of view compound eye plate does not block the light reflected by the second relay mirror, and the centers of all the field of view compound eye elements are located on the plate; rotate the view field The field compound eye plate ensures that the incident angle of the chief ray of the light emitted from the object point incident on the field of view compound eye plate is between 9° and 12°, and thus the inclination angle θ _FF of the field of view compound eye plate is obtained.

Step 203: Since the double row of compound eyes does not have a magnifying effect, the magnification of the lighting system can be determined after the size of the relay lens group and the grazing incidence mirror are determined; therefore, this step is based on the magnification Γ of the lighting system and the arc field of view Dimensions, determine the length and width of the rectangular compound eye element on the compound eye in the field of view, let the length of the compound eye element be l _a , and the width be l _b ; then:

$l_a=\frac{d}{\mathrm{\&Gamma;}}$ $l_b=\frac{R-r}{\mathrm{\&Gamma;}}$

Wherein, d is the chord length of the arc-shaped field of view, R is the outer diameter of the arc-shaped field of view, and r is the inner diameter of the arc-shaped field of view;

Step 204, let the light source fill the entire exit pupil, obtain the size of the light spot incident on the compound eye plate of the field of view after passing through the grazing incidence mirror, the relay lens group and the compound eye of the diaphragm, and determine the size of the above light spot as the size of the compound eye plate of the field of view, Combined with the size of the compound eye elements of the field of view calculated in step 203, the arrangement of the compound eye elements of the field of view is determined; usually, the compound eye elements of the field of view are arranged in an approximately circular area, and the reflection surface of the compound eye elements of the field of view is rectangular, as shown in Figure 10 .

Step 205, determine the size and arrangement of the compound eye elements of the diaphragm. Since the grazing incidence mirror will distort the exit pupil, the diaphragm compound eyes should be arranged in a pre-corrected distortion, that is, the diaphragm compound eyes are arranged in an approximately circular area, and the reflective surface of each compound eye element is circular. The diameter is usually 8-11mm, as shown in Figure 11; this is the prior art, so only a brief description will be given.

Step 206: Determine the alignment relationship between the compound eyes of the field of view and the compound eyes of the diaphragm. There is a one-to-one correspondence between the compound eyes of the field of view and the compound eyes of the diaphragm, that is, each compound eye of the field of view corresponds to a compound eye of the diaphragm. The determination process is as follows: divide the two rows of compound eyes into several parts, and in a large area, according to the principle of proximity, that is, the compound eyes of the central field of view roughly correspond to the compound eyes of the central diaphragm, and the compound eyes of the peripheral field of view roughly correspond to the compound eyes of the peripheral field of view. To determine the compound eye alignment relationship: in a small area, the same principle of proximity can be used to ensure that the inclination angle of each compound eye element is as small as possible, and the principle of cross correspondence can also be used to ensure maximum illumination uniformity on the exit pupil surface.

Step 207: Let the non-adjacent focus of the condenser be the converging point of the outgoing rays of the uniform light system, according to the alignment relationship between the compound eye element of the field of view and the compound eye element of the diaphragm determined in step 206, determine the corresponding position of the selected object point through ray tracing The coordinates and inclination angles of the compound eye elements of the diaphragm and the coordinates and inclination angles of the compound eye elements of the field of view corresponding to the compound eye elements of the diaphragm make the outgoing light converge on the non-adjacent focus of the condenser.

The concrete process of step 207 is:

Select a certain point on the exit pupil plane as the object of the lighting system, the light rays pass through the system’s grazing incidence mirror and relay lens group, and then enter the compound eye plate of the diaphragm, and the intersection point of the chief ray on the compound eye plate of the diaphragm is the object point The coordinates of the corresponding compound eye element of the diaphragm; according to the compound eye alignment relationship determined in step 206, rotate the compound eye element of the diaphragm to an appropriate inclination angle, so that the chief ray emitted by the compound eye element of the diaphragm accurately enters the compound eye of the corresponding field of view yuan on. According to the working principle of the compound eye lighting imaging system, the compound eye of the field of view will converge all incident light rays to the image point F, and the point F is the non-adjacent focus of the condenser, as shown in Figure 12 (Figure 12 does not include the light source system and the condenser Schematic diagram of the lighting system structure, the focus F is the non-adjacent focus of the condenser, and the surface EP is the exit pupil surface. In the design method of the present invention, a light-transmitting aperture stop is placed on the mask surface). Therefore, in order to make all the light emitted by the compound eye in this field of view converge to point F, it must be given an appropriate inclination angle. Thus, the coordinates and inclination angles of a pair of diaphragm compound eye elements and field of view compound eye elements corresponding to the imaging channel are determined. A schematic diagram of the position determination of a single imaging channel is shown in FIG. 12 . Take a new point on the exit pupil plane, and follow the method of determining the coordinates and angles of the single imaging channel above, until the coordinates and inclination angles of all compound eyes on the compound eye of the diaphragm and the compound eye of the field of view are determined.

Implementation example of the present invention:

As shown in Table 1, firstly, according to the parameters of the extreme ultraviolet lithography projection objective lens designed in the laboratory, the exit pupil diameter, exit pupil distance and the size of the arc-shaped field of view on the mask surface of the illumination system were determined.

Table 1

Exit pupil diameter D 162.32mm Exit pupil distance L 1246.5mm Arc field of view outer diameter 124mm Inner diameter of arc field of view 116mm Chord length of arc field of view 104mm

As shown in Table 2, on the basis of the existing extreme ultraviolet lithography compound-eye illumination system, taking the symmetry axis of the G1 system as the main optical axis of the entire illumination system, the center of the mask surface, each component of the G1 and G2 systems are respectively obtained The vertex coordinates and surface quadratic coefficients and the center coordinates of the exit pupil.

Table 2

Z coordinate Y coordinate quadratic coefficient mask center 167.6228mm -237.3910mm - Grazing incidence mirror G1 0 0 61.4278 Relay Mirror 1 470.6719mm -1087.2000 -943.7142 Relay Mirror 2 300.000mm -654.9322mm -730 Exit pupil center -1065.7365mm 0 -

As shown in Table 3, the surface parameters and inclination angles of systems G1 and G2 can be calculated based on the data in Table 2.

table 3

Radius R quadratic coefficient Tilt angle mask center 167.6228mm - 4.4° Grazing incidence mirror G1 0 61.4278 0 Relay Mirror 1 470.6719mm -943.7142 -68.1055° Relay Mirror 2 300.000mm -730 -51.6698° Exit pupil center -1065.7365mm - 4.4°

The image point of the light source can be obtained by ray tracing of the system obtained according to Table 1 to Table 3, and the compound eye plate with diaphragm is placed near this point; the compound eye plate with field of view is placed at an appropriate position behind the compound eye with the diaphragm to ensure that the light path is not blocked. The data of the double-row compound eyes thus obtained are shown in Table 4.

Table 4

Z coordinate Y coordinate Tilt angle PF plate 1519.6180 -1411.4138 -35.24° FF tablet 539.0418 -895.7333 -38.24°

The coordinates of the focal point F can be determined as (-1600, 1542.4900) by ray tracing the system obtained according to Table 1 to Table 4. At this time, the light distribution area on the field of view compound eye plate is a circle with a radius of 160mm, combined with the magnification of the lighting system, the size of a single field of view compound eye element can be determined: length 80mm, width 5.1mm, a total of 216 field of view compound eye elements , and its arrangement is shown in Figure 14.

According to the arrangement of the compound eyes in the field of view and the total number of compound eyes, the arrangement of the compound eyes in the diaphragm can be determined as shown in Figure 15. The reflective surface of a single compound eye in the field of view is circular with a diameter of 10mm.

As shown in Figure 14 and Figure 15, the alignment relationship between the compound eye of the field of view and the compound eye of the diaphragm can be obtained according to the principle of proximity. In this example, the compound eye elements on each compound eye plate are divided into 13 areas, and the alignment is performed according to the principle of proximity.

As shown in Table 5 and Table 6, according to the alignment relationship shown in Figure 15, 216 points are evenly selected on the exit pupil surface as object points, and the field of view compound eye elements and light elements corresponding to 216 imaging channels can be determined by ray tracing. The coordinates and inclination angles of the compound eye elements of the appendix.

Place a point light source at the focal point F obtained in the above steps, and perform ray tracing and simulation on the systems G3, G2, and G1 in sequence, and an arc-shaped field of view can be obtained on the specified mask surface, as shown in Figure 16; Through ray tracing and simulation, a circle with a diameter of about 160mm can be obtained on the exit pupil surface of the system, as shown in Figure 17. The results in Fig. 16 and Fig. 17 prove that the present invention is simple and feasible, and for any specified extreme ultraviolet lithography projection objective lens, an illumination system that meets the requirements can be quickly obtained on the basis of the existing compound eye illumination system.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (3)

1. the method for designing of an extreme ultraviolet photolithographic fly-eye illumination system, this illuminator comprises light source, condenser, the relay lens group and the glancing incidence mirror that form by diaphragm compound eye flat board and the dull and stereotyped even photosystem that forms of visual field compound eye, by the first relay lens and the second relay lens, determine illuminator distance of exit pupil L according to the parameter of the projection objective of appointment, it is characterized in that, concrete steps are:

Step 101, determine that the axis of symmetry of glancing incidence mirror is the primary optical axis of illuminator, coordinate system (x, y, z) take primary optical axis as the z axle, set up according to the right-handed coordinate system principle as initial point in the summit of selected glancing incidence mirror, obtains the apex coordinate (Z of the first relay lens _G21, Y _G21), the apex coordinate (Z of the second relay lens _G22, Y _G22), the centre coordinate (Z of mask face _MASK, Y _MASK);

Step 102, according to described distance of exit pupil L and mask face centre coordinate (Z _MASK, Y _MASK), determine the coordinate (Z at illuminator emergent pupil center _EP, Y _EP);

Step 103, make emergent pupil center and the non-adjacent focal point F of glancing incidence mirror _Collector1Overlap, according to (Z _EP, Y _EP) calculate the radius of curvature R of glancing incidence mirror _G1

Step 104, make the non-adjacent focal point F of the first relay lens _Relay11Contiguous focal point F with the glancing incidence mirror _Collector2Overlap, according to (Z _G21, Y _G21) calculate the radius of curvature R of the first relay lens _G21

Step 105, make the contiguous focal point F of the second relay lens _Relay21Contiguous focal point F with the first relay lens _Relay12Overlap, according to (Z _G22, Y _G22) calculate the radius of curvature R of the second relay lens _G22

Step 106, to make the non-adjacent focus of condenser be the convergent point of even photosystem emergent ray, determines arranging of compound eye unit on the dull and stereotyped and visual field compound eye flat board of diaphragm compound eye in even photosystem according to described convergent point.

2. the method for designing of extreme ultraviolet photolithographic fly-eye illumination system according to claim 1, it is characterized in that, determine that described illuminator incides the size of the arc visual field on the mask face, the place arranges aperture diaphragm at the mask face, the described shape of the size of this aperture diaphragm visual field measure-alike, on illuminator emergent pupil face, a light source is set, sends the chief ray of light according to light source on the emergent pupil face, regulate the angle of the first relay lens and the second relay lens.

3. the method for designing of extreme ultraviolet photolithographic fly-eye illumination system according to claim 1, is characterized in that, the detailed process of described step 106 is:

Step 201, the central point that sets out the pupil face are object point, place the diaphragm compound eye near the picture point that obtains dull and stereotyped after object point is through glancing incidence mirror and relay lens group, and the center of all diaphragm compound eyes unit all is positioned on this flat board; The rotary diaphragm compound eye is dull and stereotyped, guarantees to incide chief ray incident angle on diaphragm compound eye flat board between 6 °～8 ° from the light of object point outgoing;

Step 202, to place the visual field compound eye on the light path of diaphragm compound eye folded light beam dull and stereotyped, guarantees that simultaneously visual field compound eye flat board does not block the light of the second relay lens reflection, and the center of all visual field compound eye units all is positioned on this flat board; Rotation visual field compound eye is dull and stereotyped, guarantees to be incident to chief ray incident angle on the compound eye flat board of visual field between 9 °～12 ° from the light of object point outgoing;

Step 203, according to the size of the enlargement ratio Γ of illuminator and arc visual field, determine the length of rectangle compound eye on the compound eye of visual field unit and wide, the length of establishing compound eye unit is l _a, wide is l _b:

$l_a=\frac{d}{\mathrm{\&Gamma;}}$ $l_b=\frac{R-r}{\mathrm{\&Gamma;}}$

Wherein, d is the chord length of arc visual field, and R is the external diameter of arc visual field, and r is the internal diameter of arc visual field;

Step 204, allow light source be full of the emergent pupil of whole illuminator, obtain the size that is incident to hot spot on the compound eye flat board of visual field after glancing incidence mirror, relay lens group and diaphragm compound eye flat board, and above-mentioned spot size is defined as the size of visual field compound eye flat board, and the size of the visual field compound eye unit of integrating step 203 calculating, determine arranging of visual field compound eye unit;

Step 205, determine the size of diaphragm compound eye unit and arrange; Be that the diaphragm compound eye should be taked arranging of precorrection distortion, the reflecting surface of its each compound eye unit is rounded, and the span of diameter is 8～11mm;

Step 206, determine the contraposition relation of visual field compound eye unit and diaphragm compound eye unit, i.e. a corresponding diaphragm compound eye unit of each visual field compound eye unit;

Step 207, to make the non-adjacent focus of condenser be the convergent point of even photosystem emergent ray, according to the visual field compound eye unit that determines in step 206 and the first contraposition relation that gets of diaphragm compound eye, determine the coordinate of the diaphragm compound eye unit that selected object point is corresponding and coordinate and the pitch angle of pitch angle and diaphragm compound eye unit corresponding visual field compound eye unit by ray tracing, make the light of outgoing converge on the non-adjacent focus of condenser.

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