CN102681357B - Design method for extreme ultraviolet photoetching projection lens - Google Patents

Abstract

The invention provides a design method for an extreme ultraviolet photoetching projection lens. The design method comprises the following steps: confirming a projection lens in a photoetching system as a six-reflector structure and setting parameters of an optical system of the projection lens; selecting six reflectors and diaphragms and arranging between a mask and a silicon wafer in the photoetching system, and confirming proportion parameters between the reflectors; calculating a space which does not shield the light emitted from a second reflector (M2) and a first reflector (M1) and/or a main light incident angle of the first reflector according to a given object space numerical aperture and an object space main light incident angle; and judging if the set parameters of the optical system are reasonable according to the calculated parameters, thereby lastly finishing the design for the photoetching projection lens. According to the design method provided by the invention, the extreme ultraviolet photoetching projection lens can be designed and searched according to different user requirements, and the blindness in performing modification and trial and error on the present structure according to the traditional optical design method is avoided.

Description

A kind of method for designing extreme ultraviolet lithography projection objective

Technical field

The present invention relates to a kind of method for designing extreme ultraviolet lithography projection objective, belong to optical design technical field.

Background technology

In the manufacturing process of VLSI (very large scale integrated circuit), need to use high precision projection objective that the figure on mask is accurately doubly reduced on the silicon chip that is coated with photoresist.The LASER Light Source that current deep-UV lithography utilization wavelength is 193nm, auxiliary with resolution enhance technology such as off-axis illumination, phase-shift mask, optical edge effect calibration, can realize the industrialized requirement of 45nm technology node, but for 32nm or the industrialization demand of hi-tech node more, semicon industry is generally placed hope on extreme ultraviolet lithography.Extreme ultraviolet source wavelength is about 11 ~ 15nm, identical with deep UV (ultraviolet light) lithography, and extreme ultraviolet photolithographic also adopts stepping-scan pattern.

Extreme ultraviolet etching system is by plasma light source, reflective illuminator, and reflective masks, reflection type projection object lens, are coated with the silicon chip of extreme ultraviolet photolithographic glue and synchronizes workpiece platform etc. and partly form.Light beam by light source outgoing after, through illuminator shaping and even light, be irradiated in reflective masks.After mask reflection, light is incident to projection objective system, finally exposure image on the silicon chip that is coated with extreme ultraviolet photolithographic glue.

Typical EUV projection objective is centered optical system, and object plane, image planes and all catoptrons are all about optical axis Rotational Symmetry, and this is designed with to be beneficial to debugs and avoided as far as possible possible aberration.Owing to there being light path folding and blocking in reflecting system, projection objective should adopt and annularly from axle visual field, design.In general, except given design objective, the design of EUV projection objective also needs to meet following requirement: 1. attainable diaphragm face arranges, and is generally positioned in certain one side of 2nd～5 reflectings surface; 2. enough large object space, image space working distances, guarantees the axial installing space of mask and silicon chip; 3. without blocking design, between the reflector space of each reflecting surface and territory, transparent zone, to leave certain flat plate margin; 4. can coordinate reflective masks to use, light incides on mask with low-angle; 5. high resolving power; 6. minimum distortion; 7. the image space heart far away.

Prior art (M.F.Bal, Next-Generation Extreme Ultraviolet Lithographic Projection Systems[D], Delft:Technique University Delft, 2003) method for designing extreme ultraviolet lithography projection objective is disclosed, the method is by paraxial structural parameters (the catoptron radius to EUVL projection objective, each optical surface spacing etc.) carry out exhaustive-search, by the enlargement ratio of system, the conditions such as diaphragm conjugate relation are as constraint, and program and its light path of light is carried out to light path block judgement, unscreened light path is analyzed to selection, thereby select suitable initial configuration, basis as further optimization and calculating.The shortcoming of this method is: calculated amount is excessive, with existing computing machine, calculates speed, and an average week just can be found an available design.

Summary of the invention

The invention provides a kind of method for designing extreme ultraviolet lithography projection objective, the method can be designed extreme ultraviolet lithography projection objective according to different parameter requests, and its calculated amount is little, realizes speed fast.

Realize technical scheme of the present invention as follows:

A method for designing for extreme ultraviolet lithography projection objective, concrete steps are:

Step 101, determine that in etching system, projection objective is six mirror structures, and set the optical system parameter of this projection objective; Choosing six pieces of catoptrons and diaphragm is arranged in etching system between mask and silicon chip, the setting position of six pieces of catoptrons and diaphragm: start to be followed successively by the first mirror M 1, diaphragm, the second mirror M 2, the 3rd mirror M 3, the 4th mirror M 4, the 5th mirror M 5 and the 6th mirror M 6 along optical path direction from mask, and diaphragm is positioned in the second mirror M 2; Determine the scale parameter between each catoptron;

Step 102, calculating mask to the distance of the first mirror M 1 are-l ₁with the distance of the second mirror M 2 to first mirror M 1 be-d ₁, and the current radius that obtains the first mirror M 1 is r ₁;

Step 103, given object space numerical aperture NAO and object space chief ray incident angle CA, according to described-d ₁and r ₁, whether rationally judge optical system parameter given in step 101, concrete deterministic process is:

Step 201, calculate in described scale parameter the second mirror M 2 to first mirror M 1 distances with mask to the first mirror M 1 ratio of distances constant radio ₂higher limit Uradio ₂;

Uradio ₂＝1-FWDI·radio ₁/YOB

Wherein, FWDI is the minimum working distance of projection objective, and YOB is true field height, radio ₁for true field height and the mask scale parameter to the first mirror M 1 distance;

Step 202, given object space numerical aperture NAO and object space chief ray incident angle CA, set radio ₂step-size in search be ξ _r2, set cycle index k=1, radio ₂(1)=0, radio ₂lower limit Dradio ₂=0;

Step 203, judgement radio ₂(k) whether be less than Uradio ₂, if so, enter step 204, otherwise enter step 209;

Step 204, according to described-d ₁and r ₁, according to ray tracing principle, calculate and utilize radio ₂(k) CLEAPE2 of designed optical projection system (k) and/or CA ₁(k), wherein CLEAPE2 (k) represents the space that the light of the second mirror M 2 and the first mirror M 1 outgoing does not block, CA ₁(k) represent the first mirror M 1 chief ray incident angle;

Step 205, the type that step 204 is calculated to parameter judge, when only calculating CLEAPE2 (k), enter step 206, when only calculating CA ₁(k) time, enter step 207, when simultaneously, calculate CLEAPE2 (k) and CA ₁(k), time, enter step 208;

Step 206, judge whether CLEAPE2 (k) > 0 sets up, if so, radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203;

Step 207, judgement CA ₁(k) whether < MAXCA1 sets up, and if so, incites somebody to action now radio ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, wherein MAXCA1 is the in advance given maximum chief ray incident angle of the first catoptron, otherwise makes k=k+1, order

return to step 203;

Step 208, judgement CA ₁(k) whether < MAXCA1 and CLEAPE2 (k) > 0 all sets up, if so, by radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203;

Step 209, judgement Dradio ₂whether=0 set up, and if so, judges that the optical system parameter of given projection objective is unreasonable, do not have the second mirror M 2 to first mirror M 1 distances and the scale parameter radio of mask to the first mirror M 1 distance ₂, and finish, if not, output Dradio ₂and enter step 104;

Step 104, according to the distance-d of described the second mirror M 2 to first mirror M 1 ₁, the radius that calculates the second mirror M 2 is r ₂;

Step 105, to calculate the 5th mirror M 5 be d to the spacing between the 6th mirror M 6 ₅, and according to described d ₅obtain the radius r of the 5th mirror M 5 ₅radius r with the 6th mirror M 6 ₆;

Step 106, choose the radius r of the 3rd mirror M 3 ₃according to image conjugate relation, enlargement ratio relation, hereby ten thousand and condition and pupil conjugate relation, and utilize above-mentioned definite the first mirror M 1, the second mirror M 2, the 5th mirror M 5 and the radius of the 6th mirror M 6 and distance each other, utilize paraxial iterative algorithm to obtain the radius r of the 4th mirror M 4 ₄, the 3rd mirror M 3 and the 4th mirror M 4 spacing d ₃, the distance d between the 3rd mirror M 3 and the second catoptron ₂, and the image distance l ' of the 4th mirror M 4 ₄;

Radius and the corresponding position relationship of step 107,6 pieces of catoptrons calculating according to above-mentioned steps, obtain extreme ultraviolet lithography projection objective.

Further, when judging Dradio ₂=0 when be false, and the present invention is at radio ₁in desirable scope, it is upgraded, utilize the radio after upgrading ₁repeating step 201-209, obtains Dradio ₂, and then whether judge the given optical system parameter of step 101 reasonable.The detailed process of this judgement is:

Step 301, setting radio ₁step-size in search be ξ _r1, set cycle index k '=1, radio ₁(1)=YOB/TTL, sets N for being greater than (YOB/FWDI-YOB/TTL)/ξ _r1smallest positive integral, make radio ₁upper limit Uradio ₁=YOB/TTL+ (N-1) * ξ _r1, make radio ₁lower limit Dradio ₁=YOB/TTL+ (N-1) * ξ _r1, the true field height that wherein YOB is light projection photoetching objective lens, TTL is light projection photoetching objective lens total length, working distance before the minimum that FWDI is light projection photoetching objective lens;

Step 302, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 303;

Parameter radio in step 303, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if return to step 302, otherwise makes Dradio ₁=radio ₁(k '), and enter step 304;

Step 304, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 305;

Parameter radio in step 305, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if enter step 306, otherwise makes Uradio ₁=radio ₁(k '), and return to step 304;

Step 306, judgement Dradio ₁=Uradio ₁whether set up, if so, given systematic parameter is unreasonable in determination step 101, and finish, if not, and output Uradio ₁and Dradio ₁and enter step 104.

Further, the present invention is when calculating r ₂after, the space the CLEAPE1 further light of the first mirror M 1 of setting and the second mirror M 2 outgoing not being blocked judges, when CLEAPE1 > 0 and CLEAPE1 < UCLEAPE1 set up, enter step 105, otherwise judge unreasonablely according to given systematic parameter, and finish; Wherein

$\mathrm{<figure-callout\; id="1"\; label="UCLEAPE"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">UCLEAPE</figure-callout>}1=h_{b1}-\frac{-{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">l</figure-callout>}}_1^{\&prime;}\&CenterDot;{\mathrm{radio}}_1}{l_2}$

H wherein _b1for the height of glazed thread and the first mirror M 1 intersection point, l ' ₁for the image distance of mask pattern through the first mirror M 1, l ₂=l ₁'-d ₁.

Beneficial effect

The present invention proposes a set of complete initial configuration design proposal, can according to different customer requirements, design and search for, avoided traditional optical method for designing on existing structure, to modify and the blindness of trial and error.To divide into groups light path search of whole system, greatly saved search time.Simultaneously based on real-ray trace, avoided the light path circumstance of occlusion that the difference of paraxial light path and actual light path causes to judge by accident.

Secondly, " mask shadow effect ", the chief ray incident angle of each reflecting surface, largest beam bore have been taken into full account, and the factor such as visual field width, by providing the methods such as approximate funtcional relationship, iterative computation and traversal screening, obtained the usable range of each parameter, for meticulous search provides reliable foundation, be convenient to improve the precision of search, evade irrational parameter request.

Accompanying drawing explanation

Fig. 1 is EUVL six reflective projection object lens packet design schematic diagram;

Fig. 2 is first mirror group G1 light path schematic diagram;

Fig. 3 is the Calculation of Optical Path schematic diagram of the first mirror M 1;

Fig. 4 is radio ₂lower limit Dradio ₂calculation flow chart;

Fig. 5 is radio ₁upper limit Uradio ₁with lower limit Dradio ₁calculation flow chart;

Fig. 6 is the Calculation of Optical Path schematic diagram of the second mirror M 2;

Fig. 7 is the reverse light path schematic diagram of the 3rd mirror group G3;

Fig. 8 is the Calculation of Optical Path schematic diagram of the 6th mirror M 6;

Fig. 9 is the Calculation of Optical Path schematic diagram of the 5th mirror M 5;

Figure 10 is the second mirror group G2 light path schematic diagram;

Figure 11 (a) is the second mirror group parameter d ₃radius r with M3 ₃the situation that changes and change;

Figure 11 (b) is second mirror group parameter-l ₃-ENP ₂radius r with M3 ₃the situation that changes and change;

Figure 11 (c) be the second mirror group parameter l ' ₄radius r with M3 ₃the situation that changes and change;

Figure 11 (d) is the second mirror group parameter r ₄radius r with M3 ₃the situation that changes and change;

Figure 12 (a) is the second mirror group parameter d ₃screening situation;

Figure 12 (b) is second mirror group parameter-l ₃-ENP ₂screening situation;

Figure 13 is the convergence situation that the actual enlargement ratio M of the second mirror group increases with iterations;

Figure 14 (a) is one of the present invention and implements the selected G1 mirror of example group index path;

Figure 14 (b) is one of the present invention and implements the selected G3 mirror of example group index path;

Figure 14 (c) is three kinds of G2 mirror group index paths that enforcement example obtains of the present invention;

Figure 14 (d) is three kinds of EUVL, the six reflecting objective index paths that enforcement example obtains of the present invention;

The 4th kind of EUVL six reflecting objective index paths that Figure 15 (a) obtains for application method for designing of the present invention;

The 5th kind of EUVL six reflecting objective index paths that Figure 15 (b) obtains for application method for designing of the present invention;

The 6th kind of EUVL six reflecting objective index paths that Figure 15 (c) obtains for application method for designing of the present invention;

Figure 16 is EUVL projection lithography system schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, further the present invention is described in detail.

First the parameter-definition of the present invention being used describes.

Actual object point/picture point is defined as the intersection point of two marginal rays, and actual image height/object height is defined as the height of actual image point/object point; Actual image planes/object plane was defined as the face that actual image point/object point is vertical with optical axis; It is actual that to enter interpupillary distance be the distance of actual object plane and actual entrance pupil face; Actual emergent pupil distance is the distance of actual image planes and actual emergent pupil face; The actual entrance pupil face here and actual emergent pupil face are determined by the intersection point of the chief ray from axle visual field and optical axis.For convenience's sake, in later discussion, above-mentioned parameter just, referred to as object point/picture point, object height/image height, object plane/image planes, emergent pupil/entrance pupil etc., if when this parameter is paraxial parameter, can particularly point out.For the purpose of directly perceived, light angle related in the present invention is all considered as positive-angle, for the light angle of different directions (counterclockwise or clockwise) not symbolization rule distinguished, and only in computing formula, use sign of operation to represent.

Step 101, determine that in this etching system, projection objective is six mirror structures, and set the optical system parameter of this projection objective; Described parameter comprises the enlargement ratio M of projection objective, true field height YOB, true field width FWOB, image space height YIM, image space width FWIM, image space exposure visual field chord length CL, the maximum chief ray incident angle of each catoptron MAXCA1～MAXCA6, the total length TTL of projection objective, minimum front working distance FWDI, and minimum back work distance BWDI(is the distance between silicon chip to the five mirror M 5).

Due to the designing requirement of etching system, the system enlargement ratio M of extreme ultra-violet lithography object lens is generally 1/4 or 1/5.

From geometric optical theory:

YOB＝YIM/|M|

FWOB＝FWIM/|M|

If object space numerical aperture is NAO, image space numerical aperture is NAI, has

NAO＝NAI·|M|

Choosing six pieces of catoptrons and diaphragm is arranged in etching system between mask and silicon chip, the setting position of six pieces of catoptrons and diaphragm: start to be followed successively by the first mirror M 1, diaphragm, the second mirror M 2, the 3rd mirror M 3, the 4th mirror M 4, the 5th mirror M 5 and the 6th mirror M 6 along optical path direction from mask, and diaphragm is placed in the second mirror M 2, can guarantee that like this diaphragm can realize adding man-hour.

For follow-up being convenient to, describe, EUVL six reflective projection objective system PO can be divided into three mirror groups, the first catoptron group G1 comprises the first mirror M 1 and the second mirror M 2; The second catoptron group G2 comprises the 3rd mirror M 3 and the 4th mirror M 4; The 3rd catoptron group G3 comprises the 5th mirror M 5 and the 6th mirror M 6, as shown in Figure 1.

Further determine the scale parameter between each catoptron, described scale parameter comprises that true field height and mask are to the scale parameter radio of the first mirror M 1 distance ₁, the second mirror M 2 to first mirror M 1 distances and the scale parameter radio of mask to the first mirror M 1 distance ₂, the space CLEAPE1 that the light of the first mirror M 1 and the second mirror M 2 outgoing does not block, the 5th mirror M 5 is the scale parameter radio apart from BWDI to the 6th mirror M 6 spacing and silicon chip to the five mirror M 5 ₃, the space CLEAPE6 that the incident ray of the 6th mirror M 6 and the 5th mirror M 5 does not block, the space CLEAPE5 that the light of the 6th mirror M 6 outgoing and the 5th mirror M 5 are not blocked.

Step 102, to obtain mask be-l to the distance of the first mirror M 1 ₁,

radio ₁＝YOB/|-l ₁|

|-l ₁|＝YOB/radio ₁

If the distance of the second mirror M 2 to first mirror M 1 is-d ₁,

radio ₂＝|-d ₁|/|-l ₁|＝|-d ₁|·radio ₁/YOB

|-d ₁|＝YOB/radio ₁·radio ₂

The radius that further obtains the first mirror M 1 is r ₁;

R ₁obtain principle and process is as follows:

As shown in Figure 2, chief ray 104 is incident to the first mirror M 1 from mask, then reflexes to the situation in the second mirror M 2 by M1.Can physics realization in order to ensure the diaphragm of system, assurance system is without veiling glare, and the diaphragm of EUVL reflection lithographic objective is all positioned in the second mirror M 2 conventionally, and chief ray is by M2 center.The condition that is positioned at the second mirror M 2 according to object space chief ray incident angle CA and diaphragm STOP, can calculate different radio ₁and radio ₂the radius r of corresponding M1 ₁.

As shown in Figure 3, according to real-ray trace formula, have

${\mathrm{<figure-callout\; id="1"\; label="h\; z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">h</figure-callout>}}_z/{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">r</figure-callout>}}_1=\tan {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">z</figure-callout>}1}$

$=\tan (I_{z2}-{\mathrm{<figure-callout\; id="1"\; label="I\; z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">I</figure-callout>}}_z^1)$

$=\tan (I_{z2}-\frac{(\mathrm{CA}+I_{z2})}{2})$

$=\tan (\frac{I_{z2}}{2}-\frac{\mathrm{CA}}{2})$

$=\tan (\frac{\arctan ({\mathrm{<figure-callout\; id="1"\; label="h\; z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">h</figure-callout>}}_z/(-{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1+z_{z1}))}{2}-\frac{\mathrm{CA}}{2})$

So have

${\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">r</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="h\; z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">h</figure-callout>}}_z/\tan (\frac{\arctan ({\mathrm{<figure-callout\; id="1"\; label="h\; z"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">h</figure-callout>}}_z/({-\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1+z_{z1}))}{2}-\frac{\mathrm{CA}}{2})$

Wherein, θ _z1for the incidence point normal of the chief ray on M1 and the angle of optical axis; h _z1height for chief ray and M1 intersection point; I _z1for being incident to the incident angle of the chief ray on M1; I ' _z1for being incident to the reflection angle of the chief ray on M1; I _z2for the upper chief ray of outgoing of M1 and the angle of optical axis; z _z1axial distance for the upper chief ray incidence point of M1 and M1 summit.

Work as r ₁after determining, can utilize optical design software CODEV to calculate near the unobstructed space CLEAPE2 of light path of M2 catoptron.

Step 103, given object space numerical aperture NAO and object space chief ray incident angle CA, according to described-d ₁and r ₁, utilize radio ₂whether rationally judge optical system parameter given in step 101.

Below first choosing of CA analyzed, more specifically provided the process of judgement;

According to the result of lithography simulation analysis in the past, show, when the main angle of incident light on mask is not 0 °, will produce " shadow effect " of mask, thereby cause the skew of the lines position of exposing on silicon chip, when simulation result shows that the chief ray incident angle on mask is less than 6 °, " shadow effect " can be compensated and proofread and correct.So have object space chief ray incident angle on be limited to 6 °.

Because the mask of extreme ultraviolet photolithographic is reflective masks, illuminator is incident to the light path of mask and can not mutually blocks with the light path that is incident to projection objective from mask.So, the chief ray 104 of light beam, glazed thread 105, lower light 106 should be simultaneously higher than true field height YOB, or simultaneously lower than true field height YOB, and as shown in Figure 1, to guarantee that light path do not block, now the scope of object space chief ray incident angle is

|CA|＞arcsin(NAO)

Be object space chief ray incident angle under be limited to arcsin (NAO).Table 1-1 is the object space chief ray incident angle scope of several typical object space numerical apertures.

The chief ray incident angle scope of several typical object space numerical apertures of table 1-1

NAO	Minimum CA	Maximum CA
			0.04	2.292443	6.000000
0.05	2.865984	6.000000
			0.06	3.439813	6.000000
0.07	4.013987	6.000000
			0.08	4.588566	6.000000
0.09	5.163607	6.000000
			0.10	5.739170	6.000000
0.1045	6.000000	6.000000

As shown in Table 1, for six reflection EUVL projection objectives, when diaphragm is in second mirror M 2 time, object space numerical aperture is larger, and its available object space chief ray incident angle scope is just less, and the maximum object space numerical aperture that can reach is 0.1045.

As shown in Figure 4, the deterministic process to step 103 below is specifically described:

Step 201, calculate in described scale parameter the second mirror M 2 to first mirror M 1 distances with mask to the first mirror M 1 ratio of distances constant radio ₂higher limit Uradio ₂;

Uradio ₂＝1-FWDI·radio ₁/YOB

Wherein, FWDI is working distance before projection objective minimum, and YOB is true field height, radio ₁for true field height and the mask scale parameter to the first mirror M 1 distance.

Owing to can not blocking between the second mirror M 2 and object space incident ray, so step 101 need guarantee CLEAPE2 > 0 when given scale parameter, on the first catoptron, the incident angle of chief ray must be less than MAXCA1 simultaneously, according at least one in this two condition, can determine roughly at certain object space numerical aperture NAO and object space chief ray incident angle CA, determine radio ₂lower limit Dradio ₂, concrete steps are:

Step 202, given object space numerical aperture NAO and object space chief ray incident angle CA, set radio ₂step-size in search be ξ _r2, set cycle index k=1, radio ₂(k)=0, radio ₂lower limit Dradio ₂=0.

Step 203, judgement radio ₂(k) whether be less than Uradio ₂, if so, enter step 204, otherwise enter step 209.

Step 204, according to described-d ₁and r ₁, according to ray tracing principle, calculate and utilize radio ₂(k) CLEAPE2 of designed projection objective (k) and/or CA ₁(k), wherein CLEAPE2 (k) represents the space that the incident ray in the second mirror M 2 and the first mirror M 1 does not block, CA ₁(k) represent chief ray incident angle in the first mirror M 1.

Step 205, the type that step 204 is calculated to parameter judge, when only calculating CLEAPE2 (k), enter step 206, when only calculating CA ₁(k) time, enter step 207, when simultaneously, calculate CLEAPE2 (k) and CA ₁(k), time, enter step 208.

Step 206, judge whether CLEAPE2 (k) > 0 sets up, if so, radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203.

Step 207, judgement CA ₁(k) whether < MAXCA1 sets up, and if so, incites somebody to action now radio ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203.

Step 208, judgement CA ₁(k) whether < MAXCA1 and CLEAPE2 (k) > 0 all sets up, if so, by radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203.

Step 209, judgement Dradio ₂whether=0 set up, and if so, judges that the optical system parameter of given projection objective is unreasonable, do not have the second mirror M 2 to first mirror M 1 distances and the scale parameter radio of mask to the first mirror M 1 distance ₂, and finish, if not, output Dradio ₂and enter step 104.

The operational flowchart of above-mentioned steps as shown in Figure 4.

Table 2 is that object space numerical aperture NAO is 0.06, several typical object space chief ray incident angle CA and corresponding given comparatively typical radio ₁time; In this table, provide in step 204 and only calculate in CLEAPE2 (k) and step 204 and only calculate CA ₁(k) both of these case, when calculating CLEAPE2 (k), the bound limit assignment of obtaining is: Dradio ₂₁=Dradio ₂; When calculating CA ₁(k), time, the bound limit assignment of obtaining is: Dradio ₂₂=Dradio ₂, given step value ξ in table 2-1 _r2be 0.005.

Table 2-1

When judging Dradio ₂=0 when be false, and the present invention can be further at radio ₁in desirable scope, it is upgraded, utilize the radio after upgrading ₁repeating step 201-209, obtains Dradio ₂, and then whether judge the given optical system parameter of step 101 reasonable.The detailed process of this judgement is:

Step 301, setting radio ₁step-size in search be ξ _r1, set cycle index k '=1, radio ₁(k ')=YOB/TTL, sets N for being greater than (YOB/FWDI-YOB/TTL)/ξ _r1smallest positive integral, make radio ₁upper limit Uradio ₁=YOB/TTL+ (N-1) * ξ _r1, make radio ₁lower limit Dradio ₁=YOB/TTL+ (N-1) * ξ _r1.

Step 302, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 303;

Parameter radio in step 303, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if return to step 302, otherwise makes Dradio ₁=radio ₁(k '), and enter step 304;

Step 304, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 305;

Parameter radio in step 305, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if enter step 306, otherwise makes Dradio ₁=radio ₁(k '), and return to step 304;

Step 306, judgement Dradio ₁=Uradio ₁whether set up, if so, given systematic parameter is unreasonable in determination step 101, and finish, if not, and output Uradio ₁and Dradio ₁and enter step 104.

When table 3-1 is several typical object space numerical apertures and corresponding typical object space chief ray incident angle CA value, radio ₁upper limit Uradio ₁lower limit Dradio ₁value.At Dradio ₁, Uradio ₁calculating in, step value ξ _r1be 0.0225.

Table 3-1

Step 104, according to the distance-d of described the second mirror M 2 to first mirror M 1 ₁, the radius that calculates the second mirror M 2 is r ₂;

Detailed process is as follows:

As shown in Figure 6, completely unobstructed in space from axial light path due to extreme ultraviolet photolithographic object lens, and to, according to element processing technology and level to reserving certain surplus (being CLEAPE1) between the retroreflective regions of catoptron and territory, transparent zone, according to real-ray trace formula and geometric relationship, have

$\frac{h_{a2}}{r_2}=\tan {\mathrm{\&theta;}}_{a2}$

$=\tan (U_{a2}-I_{a2})$

$=\tan (U_{a2}-\frac{(I_{a2}+I_{a2}^{\&prime;})}{2})$

$=\tan (\frac{U_{a2}}{2}-\frac{U_{a2}^{\&prime;}}{2})$

$=\tan (\frac{U_{a2}}{2}-\frac{\arctan \left(\frac{h_{b1}-\mathrm{CLEAPE}1-h_{a2}}{{-d}_1}\right)}{2})$

So have

$r_2=h_{a2}/\tan (\frac{U_{a2}}{2}-\frac{\arctan \left(\frac{h_{b1}-\mathrm{CLEAPE}1-h_{a2}}{{-d}_1}\right)}{2})$

Wherein, θ _a2be the incidence point normal of the glazed thread in the second mirror M 2 and the angle of optical axis; h _a2height for glazed thread and the second mirror M 2 intersection points; h _b1height for lower light and the first mirror M 1 intersection point; I _a2it is the glazed thread incident angle in the second mirror M 2; I ' _a2it is the glazed thread reflection angle in the second mirror M 2; U _a2for being incident to glazed thread in the first mirror M 1 and the angle of optical axis; U ' _a2be the glazed thread of the first mirror M 1 outgoing and the angle of optical axis.

As determine-l ₁,-d ₁, r ₁and r ₂after, can calculate the actual image height YIM1 of first mirror group G1, actual emergent pupil is apart from EXP1, actual exit pupil diameter EXD1, wherein computation process is prior art, therefore at this, does not tire out and states.

Ought calculate r in the present embodiment ₂after, further the CLEAPE1 setting being judged, concrete deterministic process is:

Step 401, from the unscreened condition of light path, generally, the lower limit DCLEAPE1 of CLEAPE1 is 0.

Step 402, to establish mask pattern be l ' through the image distance of the first mirror M 1 ₁, according to paraxial optics principle, have

$\frac{1}{(\mathrm{YOB}/{\mathrm{radio}}_1)}+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">l</figure-callout>}}_1^{\&prime;}}=\frac{2}{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">r</figure-callout>}}_1}$

${\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">l</figure-callout>}}_1^{\&prime;}=\frac{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">r</figure-callout>}}_1\&CenterDot;(\mathrm{YOB}/{\mathrm{radio}}_1)}{2(\mathrm{YOB}/{\mathrm{radio}}_1)-{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">r</figure-callout>}}_1}$

The object distance of the first catoptron imaging to the second mirror M 2 is l ₂, according to paraxial optics principle, have

l ₂＝l ₁′-d ₁

When CLEAPE1 obtains maximal value, the image distance of mask pattern after the second mirror M 2 imagings is-d ₁.Now the upper limit UCLEAPE1 of CLEAPE1 is:

$\mathrm{<figure-callout\; id="1"\; label="UCLEAPE"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">UCLEAPE</figure-callout>}1=h_{b1}-\frac{{-\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSA00000696538700021.png,HSA00000696538700031.png"\; state="\{\{state\}\}">l</figure-callout>}}_1^{\&prime;}\&CenterDot;{\mathrm{radio}}_1}{l_2}$

H wherein _b1height for lower light and the first mirror M 1 intersection point;

So the usable range upper limit UCLEAPE1 of CLEAPE1 is

lower limit DCLEAPE1 is 0.

Step 403, judge whether CLEAPE1 > 0 and CLEAPE1 < UCLEAPE1 set up, if set up, enter step 105, otherwise the given systematic parameter of determination step 101 is unreasonable, method ends.

Step 105, to calculate the 5th mirror M 5 be d to the spacing between the 6th mirror M 6 ₅, and according to described d ₅obtain the radius r of the 5th mirror M 5 ₅radius r with the 6th mirror M 6 ₆.

Concrete process is:

If the 5th mirror M 5 is d to the spacing between the 6th mirror M 6 ₅, | d ₅|=BWDIradio ₃.

The 3rd mirror group is positioned at image planes (being a silicon chip) side of six anti-lithographic objectives.In actual design, the light path of G3 mirror group is taked reverse design method.As shown in Figure 7, G3 mirror group light path is contrary with the forward optical path direction of EUVL projection objective.For fear of causing, obscure, in G3 mirror group, each parameter still adopts the method for expressing in forward light path.

Determine image space numerical aperture NAI, known when determining systematic parameter

NAO＝NAI·|M|

Determine image space height YIM, known when determining systematic parameter

YOB＝YIM/|M|

Determine the spacing d between the 5th mirror M 5 the 6th mirror M 5 ₅for:

|d ₅|＝BWDI·radio ₃

Virtual D1 is set in light path, and the locus of virtual D1 is identical with the locus of the 5th mirror M 5, and the chief ray of establishing the upper outgoing of M6 is parallel with optical axis OA, and the radius of further establishing the 6th mirror M 6 is r ₆;

In reverse light path, it is between silicon chip and the 6th mirror M 6, in the 6th mirror M 6 the place aheads.According to unscreened condition between the condition of the image space heart far away and silicon chip incident ray and the 5th piece of catoptron, and by radio ₃definite r ₆, can calculate the radius r of M6 when diverse location ₆, as shown in Figure 8.

${\mathrm{<figure-callout\; id="6"\; label="h\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">h</figure-callout>}}_b/{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">r</figure-callout>}}_6=\tan {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="6"\; label="b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">b</figure-callout>}6}$

$=\tan (U_{b6}-I_{b6})$

$=\tan (U_{b6}-\frac{({\mathrm{<figure-callout\; id="6"\; label="I\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">I</figure-callout>}}_b+{\mathrm{<figure-callout\; id="6"\; label="I\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">I</figure-callout>}}_b^6)}{2})$

$=\tan (\frac{{\mathrm{<figure-callout\; id="6"\; label="U\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">U</figure-callout>}}_b}{2}+\frac{{\mathrm{<figure-callout\; id="6"\; label="U\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">U</figure-callout>}}_b^6}{2})$

$=\tan (\frac{\arctan ((h_{b6}-(h_{\mathrm{bD}1}-\mathrm{CLEAPE}5))/({-d}_5-z_{b6}))}{2}+\frac{{\mathrm{<figure-callout\; id="6"\; label="U\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">U</figure-callout>}}_b^6}{2})$

So have

${\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">r</figure-callout>}}_6={\mathrm{<figure-callout\; id="6"\; label="h\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">h</figure-callout>}}_b/\tan (\frac{\arctan ((h_{b6}-(h_{\mathrm{bD}1}-\mathrm{CLEAPE}5))/(-d_5-z_{b6}))}{2}+\frac{{\mathrm{<figure-callout\; id="6"\; label="U\; b"\; filenames="HSA00000696538700021.png"\; state="\{\{state\}\}">U</figure-callout>}}_b^6}{2})$

Wherein

θ _b6for being incident to lower light incidence point normal in the 6th mirror M 6 and the angle of optical axis; h _b6for being incident to lower light in the 6th mirror M 6 and the height of the 6th mirror M 6 intersection points; h _bD1height for lower light and virtual D1 intersection point; I _b6it is the lower angle of incidence of light in the 6th mirror M 6; I ' _b6it is the lower light reflection angle in the 6th mirror M 6; U _b6it is the angle of light and optical axis under the 6th mirror M 6 incidents; U ' _b6it is the angle of light and optical axis under the 6th mirror M 6 outgoing; z _b6it is the axial distance on chief ray incidence point and the 6th mirror M 6 summits in the 6th mirror M 6.

If the radius r of the 5th catoptron ₅.

As shown in Figure 9, virtual D2 is set in light path, the locus of virtual D2 is identical with the locus of the 6th mirror M 6, but in reverse light path, between the 5th mirror M 5 and the second mirror group G2, at the 5th mirror M 5 rears.In the radius r that calculates the 6th mirror M 6 ₆basis on, according to the unobstructed space CLEAPE6 between the 5th catoptron incident ray and the 6th catoptron, radius r that can calculating place M6 M5 when diverse location ₅.

$h_{b5}/r_5=\tan {\mathrm{\&theta;}}_{b5}$

$=\tan (U_{b5}-I_5^{\&prime;})$

$=\tan (U_{b5}-\frac{(I_{b5}^{\&prime;}+I_{b5})}{2})$

$=\tan (\frac{U_{b5}}{2}+\frac{U_{b5}^{\&prime;}}{2})$

$=\tan (\frac{\arctan ((h_{b5}-(h_{a6}-\mathrm{CLEAPE}6))/({-d}_5-z_{a6}))}{2}+\frac{U_{b5}^{\&prime;}}{2})$

So have

$r_5=h_{b5}/\tan (\frac{\arctan ((h_{b5}-(h_{a6}-\mathrm{CLEAPE}6))/({-d}_5-z_{a6}))}{2}+\frac{U_{b5}^{\&prime;}}{2})$

Wherein, θ _b5for being incident to the incidence point normal of the lower light in the 5th mirror M 5 and the angle of optical axis; h _b5for being incident to lower light in the 5th mirror M 5 and the height of the 5th mirror M 5 intersection points; h _a6for the glazed thread through the 5th mirror M 5 reflections and the height of the 6th mirror M 6 intersection points; I _b5it is the incident angle of the lower light in the 5th mirror M 5; I ' _b5it is the reflection angle of the lower light in the 5th mirror M 5; U _b5it is the angle of light and optical axis under the 5th mirror M 5 incidents; U ' _b5it is the angle of light and optical axis under the 5th mirror M 5 outgoing; z _a6it is the axial distance on the 6th mirror M 6 place's glazed thread incidence points and the 6th mirror M 6 summits;

As definite d ₅, r ₆, r ₅, after BWDI, can calculate the actual object height YOB3 of the 3rd mirror group G3, actually enter interpupillary distance ENP3, wherein computation process is prior art, therefore at this, does not tire out and states.

Step 106, choose the radius r of the 3rd mirror M 3 ₃according to image conjugate relation, enlargement ratio relation, hereby ten thousand and condition and pupil conjugate relation, and utilize above-mentioned definite the first mirror M 1, the second mirror M 2, the 5th mirror M 5 and the radius of the 6th mirror M 6 and distance each other, utilize paraxial iterative algorithm to obtain the radius r of the 4th mirror M 4 ₄, the 3rd mirror M 3 and the 4th mirror M 4 spacing d ₃, the distance d between the 3rd mirror M 3 and the second mirror M 2 ₂the i.e. object distance l of the 3rd mirror M 3 ₃, and the image distance l ' of the 4th mirror M 4 ₄.

The detailed process of this step is:

As shown in figure 10, using the second mirror group as optical system independently, its parameter to be determined mainly comprises optical system parameter and Optic structure parameter.Optical system parameter has the second mirror group entrance pupil diameter END2, the second mirror group to enter the i.e. distance of actual object plane 1001 to the second mirror group entrance pupils 1002 of the second mirror group of interpupillary distance ENP2() and the second mirror group object height YOB2; Distance (the l that Optic structure parameter comprises the second mirror group object plane 1001 to the 3rd mirror M 3 ₃), the 3rd mirror M 3 is to the distance (d of the 4th mirror M 4 ₃), the distance of the 4th mirror M 4 to second mirror group image planes IM2 (l ' ₄), the radius (r of M3 ₃), the radius (r of M4 ₄) five parameters.

Because the structural parameters of first mirror group G1 are selected, the exit pupil diameter EXD1 of G1 is the entrance pupil diameter END2 of G2, i.e. END2=EXD1;

The actual image height YIM1 of first mirror group G1 is the actual object height YOB2 of the second mirror group G2, i.e. YOB2=YIM1;

The entrance pupil that the emergent pupil of first mirror group G1 is the second mirror group G2 apart from EXP1 is apart from ENP2, i.e. ENP2=EXP1;

Because the structural parameters of the 3rd mirror group G3 are selected, the distance of exit pupil EXP2(that the entrance pupil of G3 is the second mirror group G2 apart from ENP3 i.e. the distance of actual image planes 1403 to the second mirror group emergent pupils 1404 of the second mirror group), i.e. EXP2=ENP3;

The actual object height YOB3 of G3 is the actual image height YIM2 of the second mirror group G2, i.e. YIM2=YOB3;

Use the mode of paraxial calculating and iterative computation combination, by above-mentioned parameter, can be calculated the structural parameters of G2.

The structural parameters of considering G2 mirror group solve, and structure to be asked need to meet four known conditions, i.e. image conjugate relation, enlargement ratio, ten thousand Hes hereby, four known conditions of pupil conjugate relation.If provide the radius r of M3 ₃, can try to achieve the paraxial solution that meets corresponding conditions.

By image conjugate relation, had

$\frac{1}{l_3}+\frac{1}{l_3^{\&prime;}}=\frac{2}{r_3}$

l ₄-l′ ₃＝-d ₃

$\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4}+\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4^{\&prime;}}=\frac{2}{{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">r</figure-callout>}}_{\text{4}}}$

Wherein, l ₃it is the object distance of the 3rd mirror M 3; L ' ₃it is the image distance of the 3rd mirror M 3; d ₃it is the spacing of the 3rd mirror M 3 and the 4th mirror M 4; l ₄it is the object distance of the 4th mirror M 4; L ' ₄it is the image distance of the 4th mirror M 4;

By enlargement ratio relation, there is (the multiplying power here),

$\frac{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4^{\&prime;}}{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4}\&CenterDot;\frac{l_3^{\&prime;}}{l_3}=\mathrm{\&beta;}$

β is the paraxial enlargement ratio of G2 system;

By hereby ten thousand and condition have

${\mathrm{pizsum}}_2=-(\frac{1}{r_1}-\frac{1}{r_2}+\frac{1}{r_5}-\frac{1}{r_6})$

Can obtain

$\frac{1}{r_3}-\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">r</figure-callout>}}_4}={\mathrm{pizsum}}_2$

By diaphragm conjugate relation, had

$\frac{1}{(l_3-{\mathrm{enp}}_2)}+\frac{1}{l_{p3}^{\&prime;}}=\frac{2}{r_3}$

l _p4-l′ _p3＝-d

$\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="l\; p"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_p}+\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4^{\&prime;}+{\exp }_2}=\frac{2}{{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">r</figure-callout>}}_4}$

Wherein, enp ₂be that the second mirror group G2 paraxial enters interpupillary distance, even enp ₂distance of exit pupil for G1; L ' p ₃be that the entrance pupil of the second mirror group G2 is through the paraxial image distance of M3 imaging; l _p4it is the paraxial object distance of the emergent pupil mirror M4 imaging of the second mirror group G2; exp ₂be the emergent pupil distance of the second mirror group G2, even exp ₂entrance pupil distance for G3;

By image conjugate relation, enlargement ratio relation, hereby ten thousand and condition and pupil conjugate relation can solve

$d_3=\frac{1}{4}\&CenterDot;\frac{{r_3}^2\&CenterDot;(2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2-{\exp }_2+{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2)}{\mathrm{\&beta;}\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\exp }_2\&CenterDot;(1+{\mathrm{pizsum}}_2\&CenterDot;r_3)}$

$l_3=\frac{1}{2}\&CenterDot;\frac{2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3-r_3\&CenterDot;{\exp }_2+r_3\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;\exp +2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2}{-{\exp }_2+{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2}$

$l_3^{\&prime;}=\frac{1}{4}\&CenterDot;\frac{(2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3-r_3\&CenterDot;{\exp }_2+r_3\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\exp }_2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2)\&CenterDot;r_3}{(\mathrm{\&beta;}\&CenterDot;r_3{\&CenterDot;\mathrm{pizsum}}_2+1+\mathrm{\&beta;}){\&CenterDot;\mathrm{enp}}_2\&CenterDot;{\exp }_2}$

${\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4=\frac{1}{4}\&CenterDot;\frac{(r_3\&CenterDot;{\exp }_2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2-{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">r</figure-callout>}}_4\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2+{2\mathrm{\&beta;}}^2\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{enp}}_2+{2\mathrm{\&beta;}}^2\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{pizsum}}_2)\&CenterDot;r_3}{{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2\&CenterDot;(1+\mathrm{\&beta;}+2\mathrm{\&beta;}\&CenterDot;r_3\&CenterDot;{\mathrm{pizsum}}_2+{\mathrm{pizsum}}_2\&CenterDot;r_3+{{\mathrm{pizsum}}_2}^2\&CenterDot;{r_3}^2\&CenterDot;\mathrm{\&beta;})}$

${\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_4^{\&prime;}=-\frac{1}{2}\&CenterDot;\frac{r_3\&CenterDot;{\exp }_2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2-r_3\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2+{2\mathrm{\&beta;}}^2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\exp }_2+2\&CenterDot;{\mathrm{\&beta;}}^2\&CenterDot;r_3\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2}{{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2-{\exp }_2-{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3+r_3\&CenterDot;{\mathrm{\&beta;}}^2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;{\mathrm{enp}}_2}$

$l_{p3}^{\&prime;}=\frac{1}{4}\&CenterDot;\frac{(2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3-r_3\&CenterDot;{\exp }_2+r_3\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{\&beta;}}^2+2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2+{{2\mathrm{enp}}_2}^2\&CenterDot;{\mathrm{\&beta;}}^2)}{({\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3+{\exp }_2+{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;})\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}}$

${\mathrm{<figure-callout\; id="4"\; label="l\; p"\; filenames="HSA00000696538700012.png,HSA00000696538700081.png"\; state="\{\{state\}\}">l</figure-callout>}}_p=-\frac{1}{4}\&CenterDot;\frac{(-2\&CenterDot;{{\exp }_2}^2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3-r_3\&CenterDot;{\exp }_2-2\&CenterDot;{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\exp }_2-2\&CenterDot;{{\exp }_2}^2+r_3\&CenterDot;{\mathrm{enp}}_2\&CenterDot;{\mathrm{\&beta;}}^2)}{(2\&CenterDot;{\exp }_2\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;{\mathrm{enp}}_2+{{\mathrm{pizsum}}_2}^2\&CenterDot;{r_3}^2\&CenterDot;{\exp }_2+{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}+{\mathrm{enp}}_2\&CenterDot;\mathrm{\&beta;}\&CenterDot;{\mathrm{pizsum}}_2\&CenterDot;r_3+{\exp }_2)}$

r ₄＝r ₃/(1+pizsum ₂·r ₃)

Can calculate the radius r of the 4th mirror M 4 ₄, the 3rd mirror M 3 and the 4th mirror M 4 spacing d ₃, the 3rd mirror M 3 object distance l ₃and the image distance l ' of the 4th mirror M 4 ₄.

Radius and the corresponding position relationship of step 107,6 pieces of catoptrons calculating according to above-mentioned steps, obtain extreme ultraviolet lithography projection objective.

Above-mentioned r ₃artificially rule of thumb to choose at random, but because the conditional parameter of input is non-paraxial parameter, the parameter that above formula calculates does not generally meet the requirement of non-paraxial parameter, but can be by the variation tendency of this paraxial parameter, under the combination condition of judgement G1 and G3, whether exist rational G2 to match, and determine r according to this variation tendency ₃scope.

The present invention is using the second mirror group G2 as optical system independently, by the paraxial enlargement ratio β=M of G2 system ₂, M here ₂=YOB3/YIM1, the second mirror group G2 paraxial enters interpupillary distance enp ₂the distance of exit pupil that equals G1 is enp ₂the emergent pupil of=ENP2, the second mirror group G2 is apart from exp ₂the entrance pupil distance that equals G3 is exp ₂=EXP2,1500mm > (l ₃-enp ₂) > 0 and 0 > d ₃> 1500mm is as constraint condition, according to image conjugate relation, enlargement ratio, hereby ten thousand and and pupil conjugate relation, determine r ₃scope, from the scope of obtaining, choose a value as the radius of the 3rd mirror M 3.

The paraxial solution that illustrates G2 lens group is below selected r ₃scope.The value of input parameter is as shown in table 1.

Table 1

1/r 3	-0.002~0.002
		Entrance pupil is apart from ENP2	-1883.508480
Distance of exit pupil EXP2	352.613104
		Hereby ten thousand and pizsum 2	-0.000811
Enlargement ratio M 2	-0.496181

Entrance pupil diameter END2	143.574801
		Object height YOB2	-174.424131

Order

enp ₂＝ENP2

exp ₂＝EXP2

β＝M ₂

Obtain each parameter with 1/r ₃variation and the chart that changes as shown in Figure 11 (a) ~ Figure 11 (d).For available EUVL lithographic projection system, require system length to control within the specific limits.Here system physics overall length is controlled in 2000mm, and M3 should be positioned at M2 rear, M4 is positioned at M3 the place ahead, and spacing should be slightly shorter than system overall length, so 1500mm > (l ₃-enp ₂) > 0 and 0 > d ₃> 1500mm.

For convenience's sake, we are made as zero by the object distance beyond between available area and spacing, and Figure 11 (a) and Figure 11 (b) become Figure 12 (a) and Figure 12 (b), and the chart obtaining can comparatively clearly be seen r ₃usable range, relatively Figure 12 (a) and Figure 12 (b), known under this group physical condition, whether has available G2 solution.

From chart above, 1/r ₃usable range be about 0.0005 ~ 0.002.Be r ₃scope be 500mm ~ 2000mm.

Paraxial enlargement ratio β and actual enlargement ratio M due to given G2 system ₂difference, the paraxial distance of exit pupil exp of G2 system ₂with actual distance of exit pupil EXP ₂difference, the above-mentioned optical system parameter calculating can not be directly as the result of second group of calculation of parameter.

In fact, the visual field off-axis optical system forming for any two spherical reflectors, paraxial value and the actual value of above-mentioned two parameters are all not the same.

But, when its actual parameter meets the requirements, must there is one group of corresponding paraxial parameter value in the visual field off-axis optical system forming for any one two spherical reflector.We can try to achieve by the method for relatively approaching.Concrete grammar is as follows:

Further G2 optical parametric is optimized below, concrete steps are:

Step 501, choose the radius r of the 3rd mirror M 3 ₃, specification error factor ξ _bwith

, and make β (1)=M ₂, make exp ₂(1)=EXP2, sets cycle index k=1;

Step 502, utilize β (k), exp ₂and selected r (k) ₃, according to image conjugate relation, enlargement ratio relation, hereby ten thousand and condition and pupil conjugate relation, obtain the structural parameters d of G2 system ₃(k), l ₃(k), l ₄' (k) and r ₄(k);

Step 503, r ₃, d ₃(k), l ₃(k), l ₄' (k) and r ₄(k) be input in optical design software CODEV, obtain the actual enlargement ratio M of the second catoptron group G2 ₂and actual distance of exit pupil EXP2 (k) (k);

Step 204, judgement and | M ₂(k)-M ₂|≤ξ _bwhether set up, if finish to optimize, by r now ₃, d ₃(k), l ₃(k), l ₄' (k) and r ₄(k) as the structural parameters of the second catoptron group G2, if not, enter step 505;

Step 505, make β (k+1)=β (k) [M ₂/ M ₂(k)] ^σ, exp ₂(k+1)=exp ₂(k) [EXP2/EXP2 (k)] ^σ, wherein σ≤1, makes k add 1, returns to step 502.

The present invention

here we claim [M ₂/ M ₂(k)] ^σ[EXP2/EXP2 (k)] ^σfor approaching the factor; If G2 solution space is now less, when σ=1, [M ₂/ M ₂(k)] ¹[EXP2/EXP2 (k)] ¹with this pair of paraxial enlargement ratio of factor pair and paraxial emergent pupil of approaching, apart from processing, may cause result to jump out rational structural parameters scope, or Approaching Results is not restrained.So can choose approach the factor for [M ₂/ M ₂(k)] ^1/2[EXP2/EXP2 (k)] ^1/2, or

approach the factor for [M ₂/ M ₂(k)] ^1/4[EXP2/EXP2 (k)] ^1/4, the 3rd group to approach factor search procedure more stable, but its iterations is more, and the second factor is between the first group factor and the 3rd group factor, and range of application is wider, generally can meet the requirement of calculating.

Figure 13 is σ=1 o'clock, the convergence situation that the actual enlargement ratio M2 of the second mirror group increases with iterations.

Embodiment of the present invention:

For to have selected the structure of one group of G1 arbitrarily, the diaphragm of this structure is positioned on dihedral reflector Figure 14 (a).Object space chief ray incident angle is decided to be 5 °.The arrangement of elements of this structure is reasonable, and difficulty of processing is lower, and optical system parameter and the Optic structure parameter of G1 are as shown in table 2, wherein

Table 2

NAO	0.05
		CA	5.00000
radio 1	0.153
		radio 2	0.352
YOB	132.5000
		-l 1	304.7500
-d 1	-304.749986
		r 1	-1160.173602
r 2	-9301.878824
		l 2′	1970.7450
YIM1	-368.998492
		EXP1	1970.744988
pizsum 1	-0.000754435

, for to have selected the structure of one group of G3 arbitrarily, optical system parameter and the Optic structure parameter of G3 are as shown in table 3 for Figure 14 (b), wherein

Table 3

NAI	0.25
		CA	telecentricity
radio 3	9.000000
		YIM	26.5000
l 6′	320.0000
		d 5	-288.0000
r 6	-358.854572
		r 5	-411.048060
-l 5	273.972300

YOB3	-76.985423
		ENP3	354.566741
pizsum 3	-0.000354

According to the structural parameters of above-mentioned G1 and G2, obtaining G2, to calculate required parameter as shown in table 4.

Table 4

1/r 3	-0.002~0.002
		Entrance pupil is apart from ENP2	-1970.744988
Distance of exit pupil EXP2	354.566741
		Hereby ten thousand and pizsum 2	-0.001108
Enlargement ratio M 2	-0.208633
		Entrance pupil radius END2	72.144399
Object height YOB2	-368.998492

Calculate r ₃radius is 500mm, 450mm, and three kinds, the G2 structure of-500mm, its index path is as shown in Figure 14 (c).

Be connected above-mentioned three mirror groups, for different G2 mirror groups, the six reflective projection objective lens arrangement that obtain are as shown in Figure 14 (d).Comparison diagram 14(d) several structures in, table 7 is the system overall length of three structures and the comparison of maximum reflection aperture of mirror, the wherein c that parameter is determined in table 5, table 6 and table 7 below ₁=1/r ₁, c ₂=1/r ₂, c ₃=1/r ₃, c ₄=1/r ₄, c ₅=1/r ₅, c ₆=1//r ₆, d ₁.D ₁for the spacing of mask and the first mirror M 1, d ₂～d ₆be the spacing of first to the 5th mirror M 1 ~ M5 and a corresponding rear catoptron, d ₇it is the spacing of the 6th mirror M 6 and silicon chip.M3 is positioned at the place ahead of object plane (mask 101), is unfavorable for the work of stepping work stage.The system overall length of structure one (embodiment1) is shorter, but maximum element bore is larger.The maximum element relative aperture of structure three (embodiment3) is less, but system overall length is relatively long.Can select suitable M3 radius according to the needs of engineering reality.

Table 5

Table 6

Table 7

Table 8

System#

Total length

Max diameter

System1	1737.1874	888.3862
			System2	1779.8679	771.7360
System3	1769.1643	407.6502

Other several systems of selecting choosing by grouping are as shown in Figure 15 (a), Figure 15 (b), Figure 15 (c).Its structural parameters are as shown in table 9, table 10, table 11.Wherein some structure may and be unfavorable for Project Realization, only as grouping, selects the exemplifying embodiment that selects search procedure herein.

Table 9

Table 10

Table 11

Figure 16 is typical extreme ultraviolet photolithographic system schematic, light beam by light source 1601 outgoing after, through illuminator 1602 shapings and even light, be irradiated in reflective masks 101.After mask 101 reflections, light is incident to projection objective system 1603, is finally being coated with exposure image on the silicon chip 102 of extreme ultraviolet photolithographic glue.The EUVL light projection photoetching objective lens that the present invention's design obtains can be applied in the middle of this system.Wavelength is the extreme ultraviolet light source Emission Lasers of 13.5nm, after illuminator, be irradiated on mask, after mask reflection, along optical path direction, through the first mirror M 1, the second mirror M 2, the 3rd mirror M 3, the 4th mirror M 4, form successively, become intermediary image, intermediary image images on silicon chip through the 5th mirror M 5, the 6th mirror M 6.

Although described by reference to the accompanying drawings the specific embodiment of the present invention, for those skilled in the art, under the premise of not departing from the present invention, can also do some distortion, replacement and improvement, these are also considered as belonging to protection scope of the present invention.

Claims (3)

1. a method for designing for extreme ultraviolet lithography projection objective, is characterized in that, concrete steps are:

Step 101, determine that in etching system, projection objective is six mirror structures, and set the optical system parameter of this projection objective; Choosing six pieces of catoptrons and diaphragm is arranged in etching system between mask and silicon chip, the setting position of six pieces of catoptrons and diaphragm: start to be followed successively by the first catoptron (M1), diaphragm, the second catoptron (M2), the 3rd catoptron (M3), the 4th catoptron (M4), the 5th catoptron (M5) and the 6th catoptron (M6) along optical path direction from mask, and diaphragm is positioned on the second catoptron (M2); Determine the scale parameter between each catoptron; Wherein

Described optical system parameter comprises the enlargement ratio M of projection objective, true field height YOB, true field width FWOB, image space height YIM, image space width FWIM, image space exposure visual field chord length CL, the maximum chief ray incident angle of each catoptron MAXCA1～MAXCA6, the total length TTL of projection objective, minimum front working distance FWDI, and minimum back work distance BWDI;

Scale parameter between described each catoptron comprises that true field height and mask are to the scale parameter radio of the first mirror M 1 distance ₁, the second mirror M 2 to first mirror M 1 distances and the scale parameter radio of mask to the first mirror M 1 distance ₂, the space CLEAPE1 that the light of the first mirror M 1 and the second mirror M 2 outgoing does not block, the 5th mirror M 5 is the scale parameter radio apart from BWDI to the 6th mirror M 6 spacing and silicon chip to the five mirror M 5 ₃, the space CLEAPE6 that the incident ray of the 6th mirror M 6 and the 5th mirror M 5 does not block, the space CLEAPE5 that the light of the 6th mirror M 6 outgoing and the 5th mirror M 5 are not blocked;

Step 102, calculating mask to the distance of the first catoptron (M1) are-l ₁with the second catoptron (M2) to the distance of the first catoptron (M1), be-d ₁, and the current radius that obtains the first catoptron (M1) is r ₁;

Step 103, given object space numerical aperture NAO and object space chief ray incident angle CA, according to described-d ₁and r ₁, whether rationally judge optical system parameter given in step 101, concrete deterministic process is:

Step 201, calculate in described scale parameter the second catoptron (M2) to the first catoptron (M1) distance with mask to the first catoptron (M1) ratio of distances constant radio ₂higher limit Uradio ₂;

Uradio ₂＝l-FWDI·radio ₁/YOB

Wherein, FWDI is the minimum object space working distance of projection objective, the true field height that YOB is projection objective, radio ₁for true field height and the mask scale parameter to the first catoptron (M1) distance;

Step 202, given object space numerical aperture NAO and object space chief ray incident angle CA, set radio ₂step-size in search be ξ _r2, set cycle index k=1, radio ₂(1)=0, radio ₂lower limit Dradio ₂=0;

Step 203, judgement radio ₂(k) whether be less than Uradio ₂, if so, enter step 204, otherwise enter step 209;

Step 204, according to described-d ₁and r ₁, according to ray tracing principle, calculate and utilize radio ₂(k) CLEAPE2 of designed optical projection system (k) and/or CA ₁(k), wherein CLEAPE2 (k) represents the space that the light of the second catoptron (M2) and the first catoptron (M1) outgoing does not block, CA ₁(k) represent the first catoptron (M1 master) angle of incidence of light degree;

Step 205, the type that step 204 is calculated to parameter judge, when only calculating CLEAPE2 (k), enter step 206, when only calculating CA ₁(k) time, enter step 207, when simultaneously, calculate CLEAPE2 (k) and CA ₁(k), time, enter step 208;

Step 206, judge whether CLEAPE2 (k) > 0 sets up, if so, radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203;

Step 207, judgement CA ₁(k) whether < MAXCA1 sets up, and if so, incites somebody to action now radio ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, wherein MAXCA1 is the in advance given maximum chief ray incident angle of the first catoptron, otherwise makes k=k+1, makes radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203;

Step 208, judgement CA ₁(k) whether < MAXCA and CLEAPE2 (k) > 0 all sets up, if so, by radio now ₂(k) be defined as radio ₂lower limit Dradio ₂even, Dradio ₂=radio ₂(k), enter step 209, otherwise make k=k+1, make radio ₂(k)=radio ₂(k-1)+ξ _r2, return to step 203;

Step 209, judgement Dradio ₂whether=0 set up, and if so, judges that the optical system parameter of given projection objective is unreasonable, do not exist the second catoptron (M2) to the first catoptron (M1) distance and the scale parameter radio of mask to the first catoptron (M1) distance ₂, and finish, if not, output Dradio ₂and enter step 104;

Step 104, the distance-d according to described the second catoptron (M2) to the first catoptron (M1) ₁, the radius that calculates the second catoptron (M2) is r ₂;

Step 105, to calculate the 5th catoptron (M5) be d to the spacing between the 6th catoptron (M6) ₅, and according to described d ₅obtain the radius r of the 5th catoptron (M5) ₅radius r with the 6th catoptron (M6) ₆;

Step 106, choose the radius r of the 3rd catoptron (M3) ₃according to image conjugate relation, enlargement ratio relation, hereby ten thousand and condition and pupil conjugate relation, and utilize above-mentioned definite the first catoptron (M1), the second catoptron (M2), the 5th catoptron (M5) and the radius of the 6th catoptron (M6) and distance each other, utilize paraxial iterative algorithm to obtain the radius r of the 4th catoptron (M4) ₄, the spacing d of the 3rd catoptron (M3) and the 4th catoptron (M4) ₃, the distance d between the 3rd catoptron (M3) and the second catoptron ₂, and the image distance l ' of the 4th catoptron (M4) ₄;

Radius and the corresponding position relationship of step 107,6 pieces of catoptrons calculating according to above-mentioned steps, obtain extreme ultraviolet lithography projection objective.

2. extreme ultra-violet lithography objective designing method according to claim 1, is characterized in that, when judging Dradio ₂=0 when be false, and before entering step 104, utilizes radio ₁whether rationally further judge the given optical system parameter of step 101; Detailed process is:

Step 301, setting radio ₁step-size in search be ξ _r1, set cycle index k '=1, radio ₁(1)=YOB/TTL, sets N for being greater than (YOB/FWDI-YDB/TTL)/ξ _r1smallest positive integral, make radio ₁upper limit Uradio ₁=YOB/TTL+ (N-1) * ξ ₁, make radio ₁lower limit Dradio ₁=YOB/TTL+ (N-1) * ξ _r1, the true field height that wherein YOB is light projection photoetching objective lens, TTL is light projection photoetching objective lens total length, working distance before the minimum that FWDI is light projection photoetching objective lens;

Step 302, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 303;

Parameter radio in step 303, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if return to step 302, otherwise makes Dradio ₁=radio ₁(k '), and enter step 304;

Step 304, judge whether cycle index k ' > N sets up, and if so, enters step 306, otherwise makes k '=k '+1, makes radio ₁(k ')=radio ₁(k '-1)+ξ _r1, and enter step 305;

Parameter radio in step 305, renewal optical projection system ₁for radio ₁(k '), repeating step 201 to 209, judgement Dradio ₂whether=0 set up, if enter step 306, otherwise makes Uradio ₁=radio ₁(k '), and return to step 304;

Step 306, judgement Dradio ₁=Uradio ₁whether set up, if so, given systematic parameter is unreasonable in determination step 101, and finish, if not, and output Uradio ₁and Dradio ₁and enter step 104.

3. extreme ultra-violet lithography objective designing method according to claim 1, is characterized in that, when calculating r ₂after, the space the CLEAPE1 further light of the first catoptron (M1) of setting and the second catoptron (M2) outgoing not being blocked judges, when CLEAPE1 > 0 and CLEAPE1 < UCLEAPE1 set up, enter step 105, otherwise judge unreasonablely according to given systematic parameter, and finish; Wherein

$\mathrm{UCLEAPEl}=h_{b1}-\frac{-d_1\&CenterDot;{l_1}^{\&prime;}\&CenterDot;{\mathrm{radio}}_1}{l_2}$

H wherein _b1for the height of glazed thread and the first catoptron (M1) intersection point, l ' ₁for the image distance of mask pattern through the first catoptron (M1), l ₂=l ₁'-d ₁.

Images