CN104483816B - A kind of class critical illumination system for extreme ultraviolet photolithographic - Google Patents
A kind of class critical illumination system for extreme ultraviolet photolithographic Download PDFInfo
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- CN104483816B CN104483816B CN201410797135.5A CN201410797135A CN104483816B CN 104483816 B CN104483816 B CN 104483816B CN 201410797135 A CN201410797135 A CN 201410797135A CN 104483816 B CN104483816 B CN 104483816B
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Abstract
Class critical illumination system for extreme ultraviolet photolithographic belongs to the critical illumination system field in extreme ultraviolet etching system, this system includes condenser system, relay system, etching system vacuum chamber and corrugated tube, condenser system includes light source, optically focused primary mirror, condenser system secondary mirror, anti-dandruff system and condenser system vacuum chamber, anti-dandruff system along light path arrangement on the axis of symmetry of light source outgoing covering of the fan；Described condenser system secondary mirror and optically focused primary mirror are sequentially positioned at anti-dandruff system rear, and light source, condenser system secondary mirror and optically focused primary mirror collectively form the German system of Schwarz Qi Er；Condenser system secondary mirror and optically focused primary mirror are respectively positioned in condenser system vacuum chamber；Described anti-dandruff system front end is connected with the rear end of condenser system secondary mirror near light source, its rear end.The present invention reaches 0.48Sr to the solid angle of source-collector, and center area blocks less than 25%, drastically increases light energy collection efficiency；Anti-dandruff system is made to increase EFFECTIVE RANGE such that it is able to preferably to play anti-dandruff effect.
Description
Technical field
The invention belongs to the critical illumination system field in extreme ultraviolet etching system, be specifically related to a kind of for pole
The class critical illumination system of ultraviolet photolithographic.
Background technology
The optical bodies structure of etching system generally includes illuminator and objective system two parts, such as Fig. 2 institute
Showing, existing objective system 3 includes primary mirror 31 (namely the objective system 3 of mask plane 30, objective system 3
Entrance pupil), the secondary mirror 32 of objective system 3 and wafer face 33, the illuminating ray of illuminator outgoing sequentially warp
After the reflection of mask plane 30, objective system 3 primary mirror 31 and objective system 3 secondary mirror 32, mask plane the most at last
Graphic pattern projection on 30 produces corrasion on wafer face 33 and to it.
Illuminator can be divided into critical illumination and Kohler illumination because of different lighting theories, is disclosed in 1998
Patent US5737137 on April 7 describes a kind of illuminator using critical illumination mode, this system
Including three pieces of reflecting mirrors: the optical frames groups collection luminous energy of front two pieces of employing German systems of Schwarz Qi Er, the 3rd
Mirror mates with entrance pupil with mask, emergent pupil for realizing light source, and realizes specifically illuminating coherence factor.Should
Critical illumination system realizes the scanning in arc visual field also by the mode of mobile light source or deviation primary mirror
Exposure.
The lithographic pitch of 22nm is typically the bottleneck that existing lithography fabrication techniques is difficult to break through, and extreme ultraviolet photolithographic
(EUVL:Extreme Ultraviolet Lithography) is considered as then may to break through this technical bottleneck
The Next Generation Lithography of tool potentiality.See theoretically, compared with the etching system using Kohler illumination system,
If extreme ultraviolet etching system can use critical illumination system, higher capacity usage ratio permissible can be obtained
Reduce the layout difficulty of intraware.
As the most accurate a kind of etching system, extreme ultraviolet etching system to be researched and developed is to core component
Manufacture, layout and use environment are proposed the most harsh many requirement.
Such as, extreme ultraviolet etching system need to use extreme ultraviolet optical filtering transmission film filter to exposure system be harmful to
Veiling glare spectrum, and only transmission and retain extreme ultraviolet spectrum.But, owing to all substances are equal to extreme ultraviolet
Opaque, so even be extreme ultraviolet optical filtering transmission film, its thickness to be also strict controlled in tens of to be received to hundred
The magnitude of rice is to reduce it to the Absorption of operating spectral in extreme ultraviolet spectrum.Thus, thickness is the most tens of
Inevitable the least to its bore of extreme ultraviolet filter coating element of hundred nanometer scale, its overall dimensions cannot be made
Too big, this not only makes exposure projections system become a kind of small field of view exposure projections system, also limit whole simultaneously
The full-size of other optical element and spacing in individual extreme ultraviolet etching system.
The most such as, in extreme ultraviolet etching system, light source used is gas discharge plasma light source, its gas electricity
Pole can produce a large amount of high-temperature particle chip in luminescence process, when these chips are adsorbed onto the reflection of illuminator
Will pollute during mirror surface and corrode minute surface on optical reflection plated film, and then reduce minute surface reflectance.
In order to remove described particle chip, can use a kind of anti-dandruff system 13, this anti-dandruff system is adopted 13 and is used forceful electric power
Magnetic field is from being perpendicular to the direction of light path by the particle chip sucking-off with electric charge, and uses simultaneously and inversely purge wind
The neutral particle blowout light path will advanced along light path.
For another example, in order to reduce air to the Absorption of operating spectral, extreme ultraviolet photolithographic in extreme ultraviolet spectrum
The objective system of system should be placed in theory in the vacuum environment of isolation air and use, but, extreme ultraviolet
But the electro-plasma gas electrode light source of etching system necessarily be under an air pressure environment being unlikely to the lowest
Could effectively be excited, therefore, objective system and illuminator in a whole set of extreme ultraviolet etching system should be located
In two environment being isolated from each other, so that the environment of the two is all close to vacuum, the environment of the latter is then in
One air pressure lower limit being both higher than light source activation, has again under the air pressure level of certain vacuum degree, in order to the greatest extent
Amount reduces the air therein Absorption to extreme ultraviolet spectrum.And above-mentioned two vacuum rings being isolated from each other
Border needs again not cause light path to block and affect, and spacing both it again can be according to the focusing requirement of illuminator
Do certain adjustment.
But, the classical critical illumination system of the patented technology quoted from above is also provided without any optical filtering transmission film
Filtering the veiling glare spectrum harmful to etching system, therefore it is only applicable to the laser plasma that spectrum is purer
Light source；Meanwhile, the theoretical boundary of the light source distance secondary mirror designed by the patented technology quoted from above is relatively
Little, and cannot do more, this causes the two not have enough gaps, anti-dandruff system to will be unable to be attached to face
In boundary's illuminator, or make anti-dandruff system cannot play due effect because operating distance is the shortest.And,
This patented technology, in addition to lacking the design of the vacuum insulation between objective system and illuminator, is used
Illuminator is too high and irregular with objective system compact in design degree, and this will make a whole set of extreme ultraviolet photolithographic system
The difficulty of processing of system and later stage debug the difficulty of calibration and all increased.
On the other hand, by increase fixing shielding device with improve illumination uniformity be a kind of relatively conventional and
Effective method, but the shielding device that the method is used at present is typically maintained fixed, once
After having been debug in the optical path, its position, angle and effective shielded area in the optical path are the most no longer
Change, do not possess and illumination uniformity in light path is continuously adjusted function.
Summary of the invention
Being only applicable to pure spectrum light source to solve existing classical critical illumination system, it lacks permission light path and passes through
Secondary vacuum shielding system, extreme ultraviolet optical filtering transmission film and effective anti-dandruff system placement space, therefore
Cannot be used directly for building extreme ultraviolet etching system, meanwhile, its illuminator used and objective system cloth
Office's compactness is too high and irregular, adds each component processing difficulty and the later stage debugs the difficulty of calibration.Separately
On the one hand, existing conventional shielding device cannot be by changing position, angle and effective screening in the optical path
Block face amasss, and does not possess the technical problem that illumination uniformity in light path continuously adjusts function, and the present invention provides
A kind of class critical illumination system for extreme ultraviolet photolithographic.
It is as follows that the present invention solves the technical scheme that technical problem taked:
A kind of class critical illumination system for extreme ultraviolet photolithographic, it includes condenser system, relay system, exposure
Photosystem vacuum chamber, corrugated tube and conically shaped, condenser system includes light source, optically focused primary mirror, condenser system
Secondary mirror, anti-dandruff system and condenser system vacuum chamber, anti-dandruff system along light path arrangement at light source outgoing light cone
On rotation axes of symmetry；Described condenser system secondary mirror and optically focused primary mirror are sequentially positioned at anti-dandruff system rear, optically focused system
System secondary mirror and optically focused primary mirror collectively form the German system of Schwarz Qi Er；Condenser system secondary mirror and the equal position of optically focused primary mirror
In condenser system vacuum chamber；Described anti-dandruff system front end is near light source, its rear end and condenser system secondary mirror
Front end be connected, the rear end of condenser system secondary mirror be receive light reflecting surface；Described relay system includes along light
Optical filter, optics shielding device, spherical reflector, field lens and the reflective toroid that road is sequentially connected with；Its
In, optics shielding device includes the round-meshed baffle plate of center band and central obscuration, and described central obscuration is positioned at gear
In the circular hole of plate, the rotary shaft of central obscuration overlaps with the Y-axis of baffle plate coordinate system, and described rotary shaft can be along X
Axle or Z axis microspur displacement；Described optical filter is that the extreme ultraviolet of the zirconium film being added with anti-oxidation cap layers filters
Transmission film.
Above-mentioned relay system can make the mask plane conjugation of light source and objective system, and, relay system also simultaneously
Optically focused primary mirror is made to be conjugated with objective system primary mirror.
Above-mentioned relay system and objective system are all enclosed within inside exposure system vacuum chamber, condenser system vacuum
The entrance of the outlet of casing and exposure system vacuum chamber is positioned on same optical axis, condenser system vacuum chamber with
Exposure system vacuum chamber is connected by corrugated tube；One end that conically shaped bore is bigger is connected with bellows end,
The other end of conically shaped stretches into inside etching system vacuum chamber, and optical filter is arranged at conically shaped pyramid tip
Opening part.
Beneficial effects of the present invention is as follows:
1) present invention by carrying out the improvement of necessity to old classical critical illumination system, has innovated a kind of suitable
Class critical illumination system for small field of view wide spectrum light source extreme ultraviolet photolithographic.
2) condenser system based on the German system of Schwarz Qi Er has been significantly increased light energy collection efficiency, relaying system
System is simultaneously achieved mask plane conjugation, the aperture diaphragm of illuminator and the objective system of light source and objective system
Two conjugate relations of entrance pupil conjugation.
3) in relay system, the introducing of field lens has efficiently controlled system bore, reduces optical element dimension,
It is achieved thereby that relay system and the compatibility of small field of view objective system；Light communication space expanded by field lens, increases
Optical path length, makes to be more easy to realize object plane, the upset of pupil face in extremely limited space, is accomplished and real
The pupil coupling of existing illuminator and objective system, on those bases, by adjusting the radius of curvature of field lens
Realize the approximation conjugate imaging of mask plane and light source, form class critical illumination system.
4) condenser system vacuum chamber and exposure system vacuum chamber all can be greatly reduced air to extreme ultraviolet spectrum
The Absorption of middle operating spectral, both it, corrugated tube and conically shaped by having focusing effect connect, filter
Mating plate is arranged in the top of conically shaped, namely at the intermediate image plane of illuminator, the light beam of illuminator converges
For the thinnest, optical filter on the manufacture difficulty of zirconium film therefore can be greatly reduced, meanwhile, optical filter can filter light
The veiling glare spectrum that etching system is harmful, can also play the effect of vacuum insulation simultaneously.Critical illumination system is again with more
Big rear cut-off distance, each provides enough layouts for etching system vacuum chamber and condenser system vacuum chamber
Space, too increases the EFFECTIVE RANGE of anti-dandruff system simultaneously, improves its using effect.
5) the toroid energy correction system astigmatism introduced in relay system, it is achieved X-axis and Y-axis two direction
The coupling of enlargement ratio, by changing position or the angle of optics shielding device, to regulate it in the optical path
Effective shielded area, equivalence realizes, to blocking the regulation of size and aspect ratio, it to be made to possess in light path
Illumination uniformity continuously adjust function.
Accompanying drawing explanation
Fig. 1 is present invention stereoscopic arrangement figure of optical element in the class critical illumination system of extreme ultraviolet photolithographic；
Fig. 2 is the present invention light path principle figure for the class critical illumination system of extreme ultraviolet photolithographic；
Fig. 3 is the light path principle figure of relay system of the present invention；
Fig. 4 is the structural representation of optics shielding device of the present invention；
Fig. 5 is the schematic perspective view of central obscuration of the present invention.
Detailed description of the invention
Below in conjunction with the accompanying drawings the present invention is described in further details.
As shown in Figures 1 to 5, a kind of class critical illumination system for extreme ultraviolet photolithographic, this illuminator
Including condenser system 1, relay system 2, exposure system vacuum chamber 4, corrugated tube 5 and conically shaped 6, poly-
Photosystem 1 includes light source 10, optically focused primary mirror 11, condenser system secondary mirror 12, anti-dandruff system 13 and optically focused system
System vacuum chamber 14, anti-dandruff system 13 along light path arrangement on the rotation axes of symmetry of light source 10 outgoing light cone；
Described condenser system secondary mirror 12 and optically focused primary mirror 11 are sequentially positioned at anti-dandruff system 13 rear, and light source 10 is wide
Spectrum DPP light source, condenser system secondary mirror 12 and optically focused primary mirror 11 collectively form the German system of Schwarz Qi Er,
The center area the ratio of obstruction of the German system of this Schwarz Qi Er is less than 25%, and linear the ratio of obstruction is less than 50%.Optically focused
System secondary mirror 12 and optically focused primary mirror 11 are respectively positioned in condenser system vacuum chamber 14；Described anti-dandruff system 13
Front end is connected with the front end of condenser system secondary mirror 12 near light source 10, its rear end, condenser system secondary mirror 12
Rear end is the reflecting surface receiving light.
Optical filter 20 that described relay system 2 includes being sequentially connected with along light path, optics shielding device 21, sphere
Reflecting mirror 22, field lens 23 and reflective toroid 24；Wherein, optics shielding device 21 include center with
The baffle plate 21-1 and central obscuration 21-2 of circular hole, described central obscuration 21-2 is positioned at the circular hole of baffle plate 21-1,
The rotary shaft of central obscuration 21-2 overlaps with the Y-axis of baffle plate 21-1 coordinate system, and described rotary shaft can also be along X
Axle or Z axis microspur displacement.Described optical filter 20 is the pole of zirconium (Zr) film of the cap layers being added with anti-oxidation
Ultraviolet light optical filtering transmission film.Position or angle by change optics shielding device 21 are to regulate it in the optical path
Effective shielded area, it can be made to possess illumination uniformity in light path is continuously adjusted function.
Described optical filter 20 is that extreme ultraviolet optical filtering transmission film is to filter the veiling glare spectrum harmful to etching system.
Described relay system 2 can make light source 10 be conjugated with the mask plane 30 of objective system 3, and, relaying
System 2 the most also makes optically focused primary mirror 11 be conjugated with the primary mirror 31 of objective system 3.
It is internal that described relay system 2 and objective system 3 are all enclosed within exposure system vacuum chamber 4, optically focused system
The outlet of system vacuum chamber 14 is positioned on same optical axis with the entrance of exposure system vacuum chamber 4, condenser system
Vacuum chamber 14 and exposure system vacuum chamber 4 all can be greatly reduced air to operating spectral in extreme ultraviolet spectrum
Absorption, connected by corrugated tube 5 both it, light path can not caused the premise blocked and affect
Under adjust position by corrugated tube 5, it is achieved the adjustment that aligns and focus of light path.
For definition according to classical critical illumination, it needs to meet strict conjugate relation, i.e. light source through facing
Boundary's illuminator images on the object plane of objective system 3, namely mask plane 30, meanwhile, and going out of critical illumination
Pupil coincides with the entrance pupil of objective system 3.In the class critical illumination system of the present invention, due to optically focused primary mirror
11 is also the aperture diaphragm of illuminator simultaneously, and the primary mirror 31 of objective system 3 also entering for objective system 3
Pupil, therefore, relay system 2 is simultaneously achieved the mask plane 30 of light source 10 and objective system 3 and is conjugated, shines
Two conjugate relations that the aperture diaphragm of bright system is conjugated with objective system 3 entrance pupil, this meets classical critical photograph
Bright definition.
But then, if meeting strict critical illumination relation, then the inhomogeneities that light source 10 is intrinsic will
It is directly reflected on the object plane of objective system 3, namely mask plane 30, causes the illumination of objective system 3 object plane
Uneven.Therefore, the present invention makes the object plane of objective system 3, namely mask plane 30, is in illuminator
Certain out of focus face, this placement scheme with certain out of focus has differentiation with the definition of strict critical illumination, is
The one of critical illumination derives, and therefore can be called class critical illumination system.
Optically focused primary mirror 11 is also the aperture diaphragm of illuminator, this aperture diaphragm sequentially through condenser system secondary mirror 12,
After relay system 2 and mask plane 30, image in the entrance pupil face of objective system 3, be also the master of objective system 3
Mirror 31, its primary mirror 31 the linear dimension of illumination region and the entrance pupil of objective system 3 planar than i.e.
For the partial coherence illumination factor of illuminator, this parameter will affect aerial image quality and Jiao of etching system
Deeply.
Owing to thing side's mask guiding mechanism and the alignment auxiliary device such as mechanism for monitoring of mask plane 30 the most strictly limit
Make object space so that optical element dimension and arrangement are greatly retrained, and the most also need to consider that it adjusts
The realizability of machinery, therefore, introduces one piece of field lens 23 in relay system 2, to expand light propagation sky
Between, add optical path length, it is simple to optical element layout.Meanwhile, the introducing of field lens 23 greatly simplifies
Illuminator and the matching relationship of objective system pupil so that in what space a limited number of, realize relay system 2
Demand picture to easy imaging relations, and each optical element in relay system 2 also shared by field lens 23
Corner burden.
Owing to needing to overlap after the condenser system 1 repeated system 2 of optical axis orthogonal with objective system 3,
Therefore relay system 2 there will be relatively large deviation at the enlargement ratio in X and Y two direction, thus causes X and Y
The pupil in direction is asymmetric, and makes the resolution of X and Y-direction inconsistent.For making up this deficiency, in
The system that continues 2 introduces one piece and has the toroid 23 correcting astigmatism function.
The optics shielding device 21 of the present invention is a set of homogeneity correction dress matched with critical illumination system
Put, owing to requiring that mask plane 30 is conjugated with optical filter 20 at critical illumination system, therefore filtered by adjustment
The Illumination Distribution of sheet 20 can be with the illumination uniformity in modulation mask face 30.By in the filter practised physiognomy as centre
Adding optics shielding device 21 near mating plate 20, the central obscuration 20-2 that can translate and rotate is right to realize
Blocking of different piece luminous energy, equivalence realizes the regulation blocking size and aspect ratio, and then compares continuously
Bright uniformity is optimized.After using this optics shielding device 21, mask plane 30 illuminate heterogeneity by ±
9% is reduced to ± 4%, and its uniformity is doubled, and edge illumination does not declines.
Class critical illumination system is divided into condenser system 1 and relay system 2 two parts to set respectively by the present invention
Meter, completes different function allocations, reduces design difficulty, is also class critical illumination system structure cloth simultaneously
Office provides convenience.The useful bigger rear cut-off distance of such critical illumination system, for etching system vacuum chamber 4
Enough arrangement space are each provided with condenser system vacuum chamber 14.
Optical filter 20 is arranged, owing to being light source 10 at optical filter 20 at the intermediate image plane of condenser system 1
Conjugate point position, therefore at this, beam size is minimum, thus arranges optical filter 20 herein, can make its bore
Minimize, thus ensure that optical filtering light 20 also to have enough intensity when thickness is the least and be unlikely to damaged；
Optical filter 20 also acts as slow down air motion thus plays the effect of vacuum insulation at this simultaneously.Owing to filtering
Sheet 20 bore is only in several millimeters magnitude, it is therefore desirable to introduce a conically shaped 6, conically shaped 6 bore bigger one
End is connected with corrugated tube 5 end, and it is internal that the other end of conically shaped 6 stretches into etching system vacuum chamber 4, filters
Sheet 20 is arranged at the opening part of conically shaped 6 pyramid tip.Optical filter 20 be extreme ultraviolet optical filtering transmission film with
Filter the veiling glare spectrum harmful to etching system.
In relay system 2, the introducing of field lens 23 mainly has three advantages: first, efficiently controlled system
Bore, reduces optical element dimension, it is achieved thereby that relay system 2 and the compatibility of objective system 3；Its
Secondary, the introducing of field lens 23 adds light path, is more easy to realize object plane, the upset of pupil face in extremely limited space；
Furthermore, due to the introducing of field lens 23, can preferentially realize the pupil coupling of illuminator and objective system 3,
On the basis of Xie, realize mask plane 30 by the radius of curvature adjusting field lens 23 and be conjugated into the approximation of light source 10
Picture.
Additionally, the condenser system 1 of the present invention can realize emergent light whole to light source 10 under existing processing conditions
Collection, its collect solid angle reach 0.48Sr, center area blocks less than 25%, drastically increases luminous energy
Collection efficiency；The condenser system 1 matched with rear cut-off distance bigger in class critical illumination system is also anti-dandruff system
System provides longer arrangement space, makes the EFFECTIVE RANGE that anti-dandruff system increases such that it is able to preferably
Play anti-dandruff effect.
Being limited and cost consideration by processing and manufacturing level, the bore of optically focused primary mirror 11 is strictly limited at 300mm
In, need to collect luminous energy as much as possible in addition, therefore the light source 10 distance away from optically focused primary mirror 11 cannot be greater than
400mm；In order to reduce the light source 10 pollution to anti-dandruff system 13, extend the working cycle, anti-dandruff system 13
Need away from light source 10 at least 25mm；And in order to ensure anti-dandruff quality, reduce chip to subsequent optical element
Polluting, anti-dandruff system 13 length at least needs 220mm；Consider further that the thickness of condenser system secondary mirror 12 with
And system debugs surplus, and reduce light as much as possible on optically focused primary mirror 11 and condenser system secondary mirror 12
Angle of incidence, the distance between condenser system secondary mirror 12 and optically focused primary mirror 11 is set to 150mm；Due to air pair
Extreme ultraviolet has strong absorption, and therefore exposure system need to be placed in vacuum chamber, and needs and another device
Compatibility, therefore condenser system 1 need sufficiently long after work intercept, finally determine table after optically focused primary mirror 11
Face and intermediate image plane, the i.e. distance of optical filter 20 place plane are at least 1450mm, and optically focused primary mirror 11
Thickness is taken as 45mm.At optical filter 20, namely at intermediate image plane 20, it is that the light beam of illuminator converges
Carefully, optical filter 20 is arranged the most in this place, to reduce the manufacture difficulty of zirconium film on optical filter 20.
Light source 10 is broad spectrum light source DPP, and its light sent is through condenser system 1 and above-mentioned optical filter 20
Rear spectrum narrows, and enters relay system 2.Owing to relay system 2 entirety has stretched in objective system 3, because of
This its optical element dimension and space layout need strict restriction.First, the bore of spherical reflector 22 is by thing
The restriction of mirror system 3 associated support, it is impossible to higher than 25mm, thus determine spherical reflector 22 with middle
The distance upper limit of image planes 20, needs to dispose optical filter 20 and for the spy debug at intermediate image plane 20 simultaneously
Survey device and vacuum chamber 4 size compatibility with objective system 3, intermediate image plane 20 and spherical reflector 22
Distance have to be larger than again a lower limit, through analyzing spherical reflector 22 and intermediate image plane 20 in initiating structure
Distance be taken as 200mm, and optimize in design as optimized variable follow-up.Reflective toroid 24 needs
Secondary mirror 32 back side of objective system 3 to be supported on, it is contemplated that supporting construction is arranged and debugs surplus, reflective
The toroid 24 distance away from mask plane 30 cannot be greater than 80mm；Meanwhile, chief ray is in mask plane 30
Angle of incidence is 4 ° of degree, and the position of the most reflective toroid 24 is certain in the entire system.
According to critical illumination principle, needing to meet two conjugate relations, i.e. illuminator aperture diaphragm, the most poly-
Light primary mirror 11 images in objective system 3 after condenser system secondary mirror 12, relay system 2 and mask plane 30
On the primary mirror 31 of entrance pupil, i.e. objective system, and light source 10 images in through condenser system 1 and relay system 2
At mask plane 30.Known luminaire 10 images at intermediate image plane 20 after condenser system 1, optically focused primary mirror 11
After condenser system secondary mirror 12, the one-tenth virtual image is near condenser system secondary mirror 12, i.e. light source 10 and condenser system master
Mirror 1 achieves the imaging relations of AB ' BA ' through condenser system 1 tailing edge positive z direction, then relay system 2 needs
The imaging relations meeting B ' A ' → A " B " could realize the conjugate imaging relation of critical illumination, and A ", B "
Be real image, therefore at A ' A " between must add the middle real image of a B, i.e. B ' A ' B " ' A " B " could be real
Existing illuminator and the pupil matching relationship of objective system.Secondary mirror 32 in view of mask plane 30 with objective system 3
Between the confined space, a pupil real image B will be formed in relay system 2 " ', then need to add a field lens 23,
To increase light path.For the ease of initial structural configuration, it is assumed that illuminator aperture diaphragm, i.e. optically focused primary mirror 11
Intermediary image be i.e. positioned on field lens 23, according to pupil matching relationship try to achieve respectively spherical reflector 22 and reflection
The radius of curvature of formula toroid 24, the conjugate relation further according to intermediate image plane 20 with mask plane 30 tries to achieve field lens
The radius of curvature of 23.Owing to the intermediary image of the primary mirror 11 of illuminator aperture diaphragm, i.e. condenser system 1 is on the scene
On mirror 23, therefore the radius of curvature change of field lens 23 will not destroy pupil matching relationship.
The inclined biography of the inclination light to be realized of three pieces of reflecting mirrors about 90 °, light is unsuitable at the average angle of incidence of each mirror
More than 20 °, the most also need to take into full account light in communication process can not with the supporting construction of mask plane 30,
Aligning guides etc. interfere, and need spherical reflector 22, the deflection angle of field lens 23, spacing from machinery
Angle is preferentially laid out, and then it is finely adjusted optimization system.
The deflection of above-mentioned relay system 2 light path to be realized 90 °, and be both needed to use the reflecting mirror with radius of curvature,
Therefore can bring bigger astigmatism, make relay system 2 inconsistent at the enlargement ratio of X and Y-direction, then can make
Become an oval picture after obtaining illuminator aperture diaphragm, the i.e. repeated system of optically focused primary mirror 11 2, i.e. cause photograph
Bright system is inconsistent at the partial coherence factor of X and Y-direction so that the exposure resolution ratio in both direction goes out
Existing deviation, this is totally unfavorable for etching system.Therefore reflective toroid 24 is set to toroid with
Compensate spherical reflector 22 and the astigmatism of field lens 23 generation.
In sum, following table enumerate a kind of illuminator of the present invention parameter arrange:
As previously described, because system use critical illumination mode, the characteristics of luminescence of light source 10 by reflection to mask
In the axial direction in face 30, light source 10 is gas discharge plasma light source, is one light source, therefore light source 10
Having certain length, and then not all light all can focus at intermediate image plane 20, a part of light will be from
Jiao becomes the veiling glare of system, it is therefore desirable to add one at intermediate image plane 20 or near it with circular port 21-1
Baffle plate 21, with stop veiling glare enter objective system 3；Radially, the light intensity of light source is Gauss distribution, by
In using critical illumination mode, only cannot realize meeting the uniform of requirement by condenser system 1 and relay system 2
Property, need to use homogeneity correction means.One the most direct homogeneity correction means as shown in Figure 4,
Circular port 21-1 adds and blocks 21-2 and stop the luminous energy entering mask plane 30 central area, and inconspicuous weakening
Enter the luminous energy of marginal area, thus it is poor to reduce the illumination in whole exposure area, improve uniformity.Due to
System, about YOZ plane symmetry, therefore only need to carry out translation and around OY to blocking 21-2 in YOZ plane
Axle carries out rotating and realizes modulating the optimization of uniformity, and both operations mainly realizes three kinds of functions:
The first, block the 21-2 translation adjustment in OY direction and block the 21-2 relative position with optical axis, modulation
The uniformity of Y-direction on mask face 30；
The second, block the 21-2 translation in OZ direction and be equivalent to block the change of 21-2 size；
3rd, block 21-2 to adjust around the rotation of OY axle and block 21-2 in X and the size of Y-direction
Ratio.After using this correcting unit, mask plane illumination heterogeneity is reduced to ± 4% by ± 9%, and it is uniform
Property is doubled, and edge illumination does not declines.
Claims (3)
1. the class critical illumination system for extreme ultraviolet photolithographic, it is characterised in that: this illuminator includes
Condenser system (1), relay system (2), exposure system vacuum chamber (4), corrugated tube (5) and conically shaped
(6), condenser system (1) include light source (10), optically focused primary mirror (11), condenser system secondary mirror (12),
Anti-dandruff system (13) and condenser system vacuum chamber (14), anti-dandruff system (13) along light path arrangement at light source
(10) on the rotation axes of symmetry of outgoing light cone；Described condenser system secondary mirror (12) and optically focused primary mirror (11)
Sequentially it is positioned at the common structure of anti-dandruff system (13) rear, condenser system secondary mirror (12) and optically focused primary mirror (11)
Become the German system of Schwarz Qi Er；Condenser system secondary mirror (12) and optically focused primary mirror (11) are respectively positioned on condenser system
In vacuum chamber (14)；Described anti-dandruff system (13) front end is near light source (10), its rear end and optically focused system
The front end of system secondary mirror (12) is connected, and the rear end of condenser system secondary mirror (12) is the reflecting surface receiving light；Institute
State optical filter (20) that relay system (2) includes being sequentially connected with along light path, optics shielding device (21), ball
Face reflecting mirror (22), field lens (23) and reflective toroid (24)；Wherein, optics shielding device (21)
Including the round-meshed baffle plate of center band (21-1) and central obscuration (21-2), described central obscuration (21-2)
It is positioned at the circular hole of baffle plate (21-1), the rotary shaft of central obscuration (21-2) and baffle plate (21-1) coordinate system
Y-axis overlap, described rotary shaft can be along X-axis or Z axis microspur displacement；Described optical filter (20) is to add
There is the extreme ultraviolet optical filtering transmission film of the zirconium film of anti-oxidation cap layers.
2. the class critical illumination system for extreme ultraviolet photolithographic as claimed in claim 1, it is characterised in that:
Described relay system (2) can make mask plane (30) conjugation of light source (10) and objective system (3), and
And, relay system (2) the most also makes optically focused primary mirror (11) be conjugated with objective system primary mirror (31).
3. the class critical illumination system for extreme ultraviolet photolithographic as claimed in claim 1, it is characterised in that:
It is internal that described relay system (2) and objective system (3) are all enclosed within exposure system vacuum chamber (4), poly-
The outlet of photosystem vacuum chamber (14) is positioned on same optical axis with the entrance of exposure system vacuum chamber (4),
Condenser system vacuum chamber (14) is connected by corrugated tube (5) with exposure system vacuum chamber (4)；Cone
One end that shape cylinder (6) bore is bigger is connected with corrugated tube (5) end, and the other end of conically shaped (6) stretches into light
Etching system vacuum chamber (4) is internal, and optical filter (20) is arranged at the opening of conically shaped (6) pyramid tip
Place.
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| CN201410797135.5A CN104483816B (en) | 2014-12-19 | 2014-12-19 | A kind of class critical illumination system for extreme ultraviolet photolithographic |
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| CN104483816B true CN104483816B (en) | 2016-10-26 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104914681B (en) * | 2015-05-29 | 2017-06-23 | 中国科学院长春光学精密机械与物理研究所 | With the chip suppression system for reducing optical element thermal deformation and high-transmission efficiency |
| CN105446086A (en) * | 2015-12-21 | 2016-03-30 | 中国科学院长春光学精密机械与物理研究所 | Illumination uniformity measuring method in photolithography system |
| CN110673316A (en) * | 2019-09-25 | 2020-01-10 | 中国电子科技集团公司第十一研究所 | Compact catadioptric optical system |
| CN111257232A (en) * | 2020-03-19 | 2020-06-09 | 中国科学院长春光学精密机械与物理研究所 | Carbon pollution experimental device for multilayer film optical element for efficiently collecting EUV light |
| CN113970534B (en) * | 2021-12-27 | 2022-03-11 | 中国工程物理研究院流体物理研究所 | Application method of vacuum cavity for carrying out toxic material in-situ diagnosis based on laser device |
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