CN106067652A - A kind of dual wavelength anti-reflection film for excimer laser and optical film thickness monitoring system - Google Patents
A kind of dual wavelength anti-reflection film for excimer laser and optical film thickness monitoring system Download PDFInfo
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- CN106067652A CN106067652A CN201610622067.8A CN201610622067A CN106067652A CN 106067652 A CN106067652 A CN 106067652A CN 201610622067 A CN201610622067 A CN 201610622067A CN 106067652 A CN106067652 A CN 106067652A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/034—Optical devices within, or forming part of, the tube, e.g. windows, mirrors
Abstract
The invention discloses a kind of dual wavelength anti-reflection film for excimer laser and for preparing the optical film thickness monitoring system of this anti-reflection film, the excimer laser instrument compatible to be applied to deep ultraviolet 193nm, 248nm.A kind of dual wavelength anti-reflection film for excimer laser, including substrate and set gradually the multilayer film being alternately made up of on the substrate high refractive index film and low refractive index film；High refractive index film is lanthanum fluoride, and described low refractive index film is Afluon (Asta)；The number of plies of multilayer film is 4～10 layers.A kind of optical film thickness monitoring system, including electron beam evaporation source, thermal resistance evaporation source, plated substrate, is provided with baffle plate between described electron beam evaporation source and thermal resistance evaporation source and plated substrate.The dual wavelength anti-reflection film for deep knowledge base of the present invention, not only wavelength 193nm and 248nm has the residual reflectivity of low-down substrate surface, and has minimum absorption scattering loss.
Description
Technical field
The present invention relates to deep knowledge base instrument field, be specifically related to a kind of dual wavelength for excimer laser
Anti-reflection film and optical film thickness monitoring system.
Background technology
Excimer laser is a kind of gas laser, and its working gas is mainly by highly stable lazy of chemical property under normality
The more active halogen atom fluorine (F) of property gas atom argon (Ar), krypton (Kr), xenon (Xe) and chemical property, chlorine (Cl), bromine (Br),
Iodine (I) forms.Intert-gas atoms will not form molecule with other atoms in the ordinary course of things, if but mix with halogen atom,
And encourage with discharge type, just can produce excited state molecule.Atom it is reduced to the most again when excited state molecule transition returns to ground state,
And release photon, photon launches laser after resonator cavity amplifies.Owing to the molecule of this excited state is fleeting, its life-span
Being only few tens of nano-seconds, therefore claim its " quasi-molecule ", its laser launched claims its excimer laser.
Excimer laser has more than ten kinds so far, and most important wavelength is 157nm (F2), 193nm (ArF), 248nm
(KrF), 308nm (XeCl) and 351nm (XeF) etc., that the most most widely used is 193nm and 248nm in deep ultraviolet wave band, institute
Meaning deep ultraviolet (DUV), often refers to wave band 190nm～280nm, and wavelength then claims VUV (VUV) less than 190nm, and wavelength is more than
280nm then claims near ultraviolet (NUV).
Deep knowledge base has obvious feature: first, and deep ultraviolet laser belongs to cold laser, makees with biological tissue
What the used time occurred is not heat effect, but photochemical reaction, so-called photochemical reaction, when referring to tissue by deep ultraviolet laser effect,
Molecule associative key will be interrupted and Direct Resolution volatilization, and do not affect surrounding tissue, thus at laser medicine, particularly at ophthalmology
With cardiovascular treatment has important application.Secondly, deep ultraviolet laser output wave length, particularly wavelength 193nm is in
Deep ultraviolet and VUV edge, it is still can be in atmosphere with the minimal wave length of relatively low-loss propagation, it is known that wavelength is more
Short, resolution is the highest, so being highly suitable in semiconductor lithography process etching accurate pattern, this is IC chip system
Make one of technology of middle most critical.Finally, the photon energy of deep ultraviolet laser is the highest, and the photon energy at wavelength 193nm is
6.42eV, the photon energy at 248nm is 5eV, and the power of Sing plus can reach hectowatt grade to MW class, the energy of Sing plus
Amount up to several joules to tens joules, so be highly suitable for Laser focus, material process and as laser weapon etc..
It is contemplated that propose a kind of dual wavelength anti-reflection film for deep knowledge base, with adapt to 193nm,
Deep knowledge base instrument compatible for 248nm uses.But, on this wave band, not only the base material of high transparency is very
Limited, and the thin-film material being suitable for is the most very limited, particularly high-index material.The most notably, though only seldom
Number several can material selection, due to the Electronic bandgap band gap of photon energy the most closely material, thus all can produce high absorption,
The shortest plus wavelength, surface scattering is the highest, so optical loss is very big, this does not only result in absorbance and is substantially reduced,
And cause the superlaser destruction to thin film, Just because of this, the optical loss reducing thin film has become deep ultraviolet quasi-molecule to swash
The difficult point of optical thin film device design, here it is the present invention waits the key problem explored and solve.
Summary of the invention
It is an object of the invention to provide a kind of dual wavelength anti-reflection film for excimer laser and anti-reflection for preparing this
The optical film thickness monitoring system of film, the excimer laser instrument compatible to be applied to deep ultraviolet 193nm, 248nm.
The dual wavelength anti-reflection film for deep knowledge base of the present invention, does not require nothing more than wavelength 193nm and 248nm tool
There is the residual reflectivity of low-down substrate surface, and require that anti-reflection film has minimum absorption scattering loss, thus, not only
Make anti-reflection film obtain the highest absorbance, and improve the excimer laser threshold value to film destruction.Design for this present invention
As follows:
First, find the thin-film material that extinction coefficient are the least.For wavelength 193nm and 248nm, it is necessary to multiple folding
Rate of penetrating is to describe the optical characteristics of thin-film material, and complex refractivity index N is the function of wavelength X, is represented by: N (λ)=n (λ)-ik
(λ), in formula, n (λ) is refractive index, and k (λ) claims extinction coefficient, and it can characterize the size absorbing scattering loss.To wavelength 193nm and
248nm, it is necessary first to be determined by experiment the various thin-film material that may be applied to this wave band and complex refractivity index thereof.Secondly,
By the complex refractivity index obtained, select high refractive index film and low-refraction membrane material according to principle chosen below: 1). high and low refraction
The refractivity of rate bi-material is bigger；2). the refractive index of low-index material is the least；3). the more important thing is high and low
The extinction coefficient of refractive index bi-material will be sufficiently small；4). the machinery of material, chemical property disclosure satisfy that actually used wanting
Ask.
Owing to thin-film material applies simultaneously to wavelength 193nm and 248nm, and the loss of wavelength 193nm is always than 248nm
Greatly, so the photon energy of wavelength available 193nm and Electronic bandgap band gap the foundation of Preliminary screening spillage of material might as well be used as.
Make simple process: because when photon energy h ν is equal to Electronic bandgap band gap EgTime, it is just the short-wave absorption belt edge of material,
Then the wavelength X at material short-wave absorption edge can be obtained wherebyc, i.e. due to Eg=h ν=hc/ λc, in formula, h, ν, c are the most general
Bright gram of constant, light frequency and the light velocity, the then wavelength X at short-wave absorption edgec=hc/Eg, to long wave further away from λc, light loss is more
Little.Lacking data if calculated, the most also can more simply utilize the relation of Refractive Index of Material n: n4/λc≈ constant, to the present invention's
Material, the constant of high-index material is about 42, and the constant of low-index material is about 35.Accordingly, the present invention obtains
The high-index material being likely to be suited for wavelength 193nm has LaF3And Al2O3, obtain being likely to be suited for the low refraction of wavelength 193nm
Rate material mainly has MgF2And SiO2.Then these four material tested and test inverting, obtain wavelength 193nm and
The complex refractivity index of 248nm is as shown in table 1.
Table 1
As known from Table 1, in two kinds of high-index materials, although Al2O3The refractive index of film is higher, thus can reach high and low
The refractivity of refractive index bi-material is relatively big, but regrettably Al2O3Extinction coefficient k too big, it is advantageous to LaF3；Two kinds
In low-index material, MgF2Refractive index less, Bees Wax k is the least, preferably MgF2.Thus determine LaF3With
MgF2Respectively as currently preferred high-index material and low-index material.
Second, according to the material determined and complex refractivity index, the anti-reflection film of design high-transmission rate.According to preservation of energy: T+R+L
=1, in formula, T represents the absorbance of anti-reflection film, and R represents the residual reflectivity of anti-reflection film, and L is the absorption scattering loss of anti-reflection film.
In longer wavelengths of visible region, owing to L is sufficiently small and usually it is left in the basket, as long as so final design can make reflectance enough
Little, absorbance just can be close to 1；But to wavelength 193nm and 248nm, absorb scattering loss relatively big, so substrate table should be realized
The low residual reflectivity in face, realizes the low-loss of thin film the most simultaneously, and absorbance just can be made to reach very big.In other words, at long wave
The design in low-loss district is only substrate surface " antireflective ", therefore often claims antireflective coating；And at deep ultraviolet 193nm and 248nm, if
Meter emphasis includes " antireflective " of substrate surface and " low-loss " of film layer, to obtain high-transmission rate, therefore claims anti-reflection film, and unsuitable
Claim antireflective coating again.Conceive according to this, residual reflectivity and absorption scattering loss are both included as commenting during design anti-reflection film
The composition part of valency function, and be sufficient to unlike long wave low-loss district only evaluates residual reflectivity.
According to above-mentioned conception, select high-index material LaF3With low-index material MgF2, increasing in four kinds of quartz substrate
The design result of permeable membrane is listed in table 2.By design result it appeared that: 1). the high refractive index film of anti-reflection film and low refractive index film
Total film number of plies is even number, and wherein, odd-level is the LaF of high index of refraction3, even level is the MgF of low-refraction2；2). along with anti-reflection
Film total film number of plies increase, total thicknesses of layers thickens accordingly, residual reflectivity tend to reduce (can with two wavelength and evaluate),
So only in terms of antireflecting effect, increasing total film number of plies and be highly profitable, but, owing to total film number of plies increases, total film layer
Thickness tends to thicken, and the loss of thin film can steeply rise, and the most final absorbance declines on the contrary, here it is the present invention's is anti-reflection
Film and the essential distinction of conventional antireflective coating, in other words, at wavelength 193nm and 248nm, it is impossible to only consider residual reflectivity,
Prior being intended to considers minimum thin film loss and the absorbance of maximum, and this not only can increase transmission potential, it is often more important that
Improve the threshold for resisting laser damage of anti-reflection film；3). at wavelength 193nm and 248nm, owing to thin film loss is far longer than residual reflectivity
Rate, so, on the premise of ensureing sufficiently small residual reflectivity, it is lost with minimum thin film or maximum transmission rate is reasonable for criterion
, by this criterion, preferred version should select 4 Rotating fields of film layer gross thickness minimum rather than residual reflectivity less undoubtedly
6,8,10 Rotating fields.So, the anti-reflection film of 2 Rotating fields whether result can more preferably？Answer is negative, though because 2 Rotating fields
So thin film loss is less than 4 layers, but due to design parameter very little, is not enough to obtain the anti-reflection film of dual wavelength, namely to ripple
Long 193nm and 248nm, 2 Rotating fields are without solving.
Table 2
3rd, how to manufacture and meet the dual wavelength anti-reflection film that design requires.At deep ultraviolet, the problem of most critical is thickness prison
Control.Prior art commonly uses two kinds of methods when solving deep ultraviolet film thickness monitoring: one is to use quartz crystal to control film quality
Obtain thickness, but the control error of this method is relatively big, the most suitable；Two is independently to set up a set of photovoltaic films apparatus for controlling thickness, but
Owing to deep ultraviolet light source-optical system-receptor is completely different with visible region, so not only expenses is very big, and
Time-consuming the longest.Proposition plate washer method of the present invention solves this problem, if the centre wavelength taking 193nm and 248nm is 220nm, then
Selecting visible ray to control wavelength 440nm, plate washer used is precisely gear and removes the vapor molecule stream of half, and plate washer designs and make both letters
Single the most accurate.So there is no need to change coater original blooming control system, as long as increasing below by plated film substrate
Add one piece of plate washer, it is possible to realize the film thickness monitoring of DUV district anti-reflection film with the photo-electric control of existing visible region.
For achieving the above object, the concrete technical scheme that the present invention is taked is:
A kind of dual wavelength anti-reflection film for excimer laser, including substrate and set gradually on the substrate by height
The multilayer film that refractive index film and low refractive index film are alternately constituted；
Described high refractive index film is lanthanum fluoride (LaF3), described low refractive index film is Afluon (Asta) (MgF2)；
The number of plies of described multilayer film is 4～10 layers.
In the present invention, the dual wavelength anti-reflection film for excimer laser of said structure, have concurrently less thin film loss and relatively
High absorbance, is highly suitable for the compatible excimer laser instrument of deep ultraviolet 193nm, 248nm.
Following as the preferred technical solution of the present invention:
Described substrate is for melting quartz or calcium fluoride (CaF2)。
Described double wave a length of argon fluoride lasers wavelength 193nm and KrF laser wavelength 248nm.
Described high refractive index film LaF3Complex refractivity index at wavelength 193nm is 1.72-i7 × 10-4, at wavelength 248nm
Complex refractivity index be 1.68-i3 × 10-4；
Described low refractive index film MgF2Complex refractivity index at wavelength 193nm is 1.44-i4.7 × 10-4, at wavelength
The complex refractivity index of 248nm is 1.41-i1 × 10-4；
Total film number of plies (i.e. high refractive index film and total film number of plies of low refractive index film) of described multilayer film is even number, its
In, outside by substrate, odd-level is lanthanum fluoride (LaF3), even level is Afluon (Asta) (MgF2)。
Total film number of plies of described multilayer film is 10 layers, and film layer gross thickness is 255.2nm, and outside by substrate, odd-level is
Lanthanum fluoride (LaF3), even level is Afluon (Asta) (MgF2), the thickness of the 1st to 10 layer is followed successively by: 15.34, and 23.17,10.06,
34.50,30.93,21.16,10.46,40.17,31.61,37.80, unit is nm.
Total film number of plies of described multilayer film is 8 layers, and film layer gross thickness is 194.6nm, and outside by substrate, odd-level is fluorine
Change lanthanum (LaF3), even level is Afluon (Asta) (MgF2), the thickness of the 1st to 8 layer is followed successively by: 5.03, and 8.66,40.64,22.67,
3.92,44.04,31.94,37.70, unit is nm.
Total film number of plies of described multilayer film is 6 layers, and film layer gross thickness is 181.4nm, and outside by substrate, odd-level is fluorine
Change lanthanum (LaF3), even level is Afluon (Asta) (MgF2), the thickness of the 1st to 6 layer is followed successively by: 44.51, and 24.15,3.41,40.89,
31.16,37.23, unit is nm.
Total film number of plies of described multilayer film is 4 layers, and film layer gross thickness is 169.2nm, and outside by substrate, odd-level is fluorine
Change lanthanum (LaF3), even level is Afluon (Asta) (MgF2), the thickness of the 1st to 4 layer is followed successively by: 16.47, and 83.38,30.31,38.99,
Unit is nm.
The preferred version of excimer laser dual wavelength anti-reflection film is 4 film structure, and the gross thickness of its multilayer film is
169.2nm；Being followed successively by from the thickness of the outside each film layer of substrate: 16.47,83.38,30.31,38.99, unit is nm.This is preferred
Technical scheme can obtain: to wavelength 193nm (ArF), and one side absorbance is 99.40%；To wavelength 248nm (KrF), one side transmission
Rate is 99.82%.
The manufacturing technology scheme of this excimer laser dual wavelength anti-reflection film is preferably used plate washer method, in order to use original visible ray
The film thickness monitoring of the photoelectricity extreme value control realization DUV district anti-reflection film in district.If the centre wavelength taking 193nm and 248nm is
220nm, then select visible ray to control wavelength 440nm and control film thickness, and now, plate washer keeps off half vapor molecule stream just,
Plate washer is made to design and produce the simplest but also accurate.Further, use 8 stepper plate to replace 2 stepper plate, thin films growing microstructure can be made to obtain
To improving.
A kind of optical film thickness monitoring system, including light source, condenser lens, film thickness monitoring sheet, optical filter, receptor, electronics
Beam evaporation source, thermal resistance evaporation source, work piece holder dish and plated substrate, described electron beam evaporation source and thermal resistance evaporation source and quilt
It is provided with baffle plate, to block electron beam evaporation source and a part of thin-film material time thermal resistance evaporation source evaporates respectively divides between plating substrate
Son, obtains the deep ultraviolet thickness of requirement in substrate.
Described baffle plate is circular, and centre is provided with plate washer central circular hole.
Described baffle plate uses bisection method segmentation, clips half at the baffle plate being provided with plate washer central circular hole.
Described baffle plate uses octave device segmentation, and the circumference at the baffle plate being provided with plate washer central circular hole is divided into the eight of equal portions
Block, clip interval in eight pieces four pieces.
Compared with prior art, the invention has the beneficial effects as follows:
1). the excimer laser anti-reflection film of prior art is only applicable to the situation of Single wavelength, such as the quasi-molecule of wavelength 193nm
Laser anti-reflection film, the excimer laser anti-reflection film etc. of wavelength 248nm, it is clear that these anti-reflection films are not applied for up-to-date proposition
In the excimer laser instrument of 193nm and 248nm dual wavelength dual-purpose.But the excimer laser manufacturing and designing dual wavelength dual-purpose increases
Permeable membrane, not only difficulty is greatly increased, and, the most notably, from Fig. 2 and Fig. 4 it can be seen that the excimer laser of dual wavelength dual-purpose
The thin film loss of anti-reflection film can be bigger many than Single wavelength anti-reflection film, and this is a challenge the biggest to the damage from laser of thin film.Study carefully
Its reason, be primarily due to Single wavelength anti-reflection film gross thickness can ratio relatively thin, as to wavelength 193nm, the gross thickness of anti-reflection film
It is only 110nm, decreases about 1/3 than gross thickness 169.2nm the thinnest in the dual wavelength anti-reflection film of the present invention.Obviously, design and
Prepare low-loss dual wavelength anti-reflection film of crucial importance to deep knowledge base application.
2). the antireflecting coating design of prior art the most only evaluates residual reflectivity, but divides in the deep ultraviolet standard of the present invention
In sub-laser film, only evaluate residual reflectivity and can not obtain minimum optical loss, protecting to this end, the present invention proposes
On the premise of demonstrate,proving sufficiently small residual reflectivity, using minimum thin film loss or maximum transmission rate as the criterion of design evaluatio.With this
Criterion, is possible not only to increase the transmission potential of deep knowledge base instrument, reduces veiling glare, improve contrast and resolution
Rate, it is often more important that owing to minimum thin film loss can be obtained in dual wavelength anti-reflection film, thus dual wavelength can be improved and increase
The threshold for resisting laser damage of permeable membrane.
3). quartz crystal film-thickness monitoring is commonly used in the preparation of the deep ultraviolet thin film of prior art, but due to this kind of instrument
Control principle obtain film thickness based on film quality, so closely related with the density of film layer, in other words, thin
Film thickness is closely related with preparation parameter, thus easily causes bigger film thickness error.To this end, to high accuracy film thickness monitoring, must
The photo-electric control of optically-based interference must be used to obtain optical thickness.Regrettably, at deep ultraviolet wave band, Light Electronic Control System
It is entirely different with near ultraviolet and visible region, so developing new DUV electrolemma thickness control system is not only a cost but also expense
Time thing.Propose for this present invention and solve this difficult problem by plate washer method, if the centre wavelength taking 193nm and 248nm is
220nm, then select visible ray to control wavelength 440nm, and plate washer used is precisely gear and removes the vapor molecule stream of half, and this makes plate washer
Design and making are the simplest but also accurate.So on the premise of not changing coater original visible ray film thickness monitoring system, as long as
One piece of plate washer is increased, so that it may realize the film of DUV district anti-reflection film with the photo-electric control of visible region below by plated film substrate
Thick control.
Accompanying drawing explanation
Fig. 1 is bent for test refractive index (a) and the extinction coefficient (b) of deep knowledge base anti-reflection film thin-film material
Line, wherein, in Fig. 1, (a) is the test refractive index curve for deep knowledge base anti-reflection film thin-film material, in Fig. 1 (b)
For the extinction coefficient curve for deep knowledge base anti-reflection film thin-film material；
Fig. 2 is reflectance (solid line) and the loss (dotted line) of the deep knowledge base Single wavelength anti-reflection film of prior art
Curve, wherein, the reflectance of the deep knowledge base Single wavelength anti-reflection film of prior art under (a) is wavelength 193nm in Fig. 2
(solid line) and loss (dotted line) curve, the deep knowledge base Single wavelength of prior art under (b) is wavelength 248nm in Fig. 2
The reflectance (solid line) of anti-reflection film and loss (dotted line) curve；
Fig. 3 is thickness and the corresponding relation figure of refractive index of the deep knowledge base dual wavelength anti-reflection film of the present invention,
Wherein, in Fig. 3 (a) be the present invention total film number of plies be thickness and the refraction of the deep knowledge base dual wavelength anti-reflection film of 10 layers
The corresponding relation figure of rate；In Fig. 3 (b) be the present invention total film number of plies be the deep knowledge base dual wavelength anti-reflection film of 8 layers
The corresponding relation figure of thickness and refractive index；In Fig. 3 (c) be the present invention total film number of plies be the deep knowledge base double wave of 6 layers
The thickness of long anti-reflection film and the corresponding relation figure of refractive index；In Fig. 3 (d) be the present invention total film number of plies be that the deep ultraviolet standard of 4 layers is divided
The thickness of sub-laser dual wavelength anti-reflection film and the corresponding relation figure of refractive index；
Fig. 4 is reflectance (solid line) and loss (dotted line) song of the deep knowledge base dual wavelength anti-reflection film of the present invention
Line comparison diagram；Wherein, in Fig. 4 (a) be the present invention total film number of plies be the deep knowledge base dual wavelength anti-reflection film of 10 layers
Reflectance (solid line) and loss (dotted line) curve comparison diagram；In Fig. 4 (b) be the present invention total film number of plies be that the deep ultraviolet standard of 8 layers is divided
The reflectance (solid line) of sub-laser dual wavelength anti-reflection film and loss (dotted line) curve comparison diagram；In Fig. 4, (c) is the present invention total film layer
Number is reflectance (solid line) and loss (dotted line) curve comparison diagram of the deep knowledge base dual wavelength anti-reflection film of 6 layers；Fig. 4
In (d) be the present invention total film number of plies be the deep knowledge base dual wavelength anti-reflection film of 4 layers reflectance (solid line) and loss
(dotted line) curve comparison diagram；
The transmittance graph comparison diagram of the deep knowledge base dual wavelength anti-reflection film of Fig. 5 present invention；Wherein, in Fig. 5
(a) be the present invention total film number of plies be the transmittance graph comparison diagram of the deep knowledge base dual wavelength anti-reflection film of 10 layers；Fig. 5
In (b) be the present invention total film number of plies be the transmittance graph comparison diagram of the deep knowledge base dual wavelength anti-reflection film of 8 layers；Figure
In 5 (c) be the present invention total film number of plies be the transmittance graph comparison diagram of the deep knowledge base dual wavelength anti-reflection film of 6 layers；
In Fig. 5 (d) be the present invention total film number of plies be that the transmittance graph of the deep knowledge base dual wavelength anti-reflection film of 4 layers compares
Figure；
Fig. 6 be baffle plate used by the present invention with by the relative position of plated film substrate and the structure of blooming control system
Schematic diagram；
Fig. 7 is the schematic shapes of baffle plate used by the present invention, and wherein, in Fig. 7, (a) is the baffle plate using bisection method segmentation
Structural representation, in Fig. 7, (b) is the structural representation of the baffle plate using octave device segmentation.
Detailed description of the invention
The present invention to be implemented it may first have to find and be expected the high refractive index, thin film materials for deep ultraviolet wave band and low folding
Penetrate the thin-film material of rate.Owing to the loss of wavelength 193nm is always big than 248nm, it is possible to be applicable to the material of wavelength 193nm
Material, must also can be suitably used for wavelength 248nm.As such, it is possible to photon energy and Electronic bandgap band gap by means of wavelength 193nm are made
For the foundation of Preliminary screening spillage of material, through screening, show that high-index material has LaF3And Al2O3, and low-index material
The most, such as MgF2、AlF3、CaF2And SiO2Deng, but comprehensive according to character such as machinery, chemistry and optics, select MgF2And SiO2
The most rationally.Then these two kinds of high-index materials and two kinds of low-index materials are carried out monolayer and multilayer film evaporation experiment with
And optical constant test inverting, Fig. 1 represents that the refractive index (a) and delustring system obtained tested by deep ultraviolet wave band these four thin-film material
Number (b) curve, wherein, two kinds of high refractive index films are as follows in the optical constant of wavelength 193nm: to LaF3, refractive index is 1.72, disappears
Backscatter extinction logarithmic ratio is 7 × 10-4；To Al2O3, refractive index is 1.83, and extinction coefficient are 6 × 10-3.And two kinds of low refractive index films are at wavelength
The optical constant of 193nm is: to MgF2, refractive index is 1.44, and extinction coefficient are 4.7 × 10-4；To SiO2, refractive index is 1.57,
Extinction coefficient are 5.6 × 10-4.Similarly, two kinds of high refractive index films are as follows in the optical constant of wavelength 248nm: to LaF3, refraction
Rate is 1.68, and extinction coefficient are 3 × 10-4；To Al2O3, refractive index is 1.78, and extinction coefficient are 1 × 10-3.And two kinds of low refractions
Rate film in the optical constant of wavelength 248nm is: to MgF2, refractive index is 1.41, and extinction coefficient are 1 × 10-4；To SiO2, refraction
Rate is 1.53, and extinction coefficient are 1.1 × 10-4.To high refractive index film, high refractive index means to obtain little residual reflectivity.
From the optical constant of test it is recognized that while Al2O3Refractive index more than LaF3, but want owing to obtaining low extinction coefficient (low-loss)
Than obtaining high index of refraction much more significant, therefore undoubtedly should LaF that preferably extinction coefficient are much smaller3.To low refractive index film, the lowest folding
The rate of penetrating means the least residual reflectivity, it is clear that at MgF2And SiO2Extinction coefficient much the same in the case of, should preferably reflect
The MgF that rate is lower2.In the following embodiments, the present invention all takes high-index material LaF3With low-index material MgF2Carry out
Implement.
Fig. 2 is reflectance (solid line) and the loss (dotted line) of the deep knowledge base Single wavelength anti-reflection film of prior art
Curve, wherein, (a) is wavelength 193nm, and (b) is wavelength 248nm.Although Single wavelength anti-reflection film 2 Rotating fields of prior art also has
Solve, but can not be accepted because its residual reflectivity is the highest, and 3-tier architecture can obtain satisfied result, this and total film
The number of plies is that the dual wavelength anti-reflection film of even number has essential difference.To wavelength 193nm, total thicknesses of layers of 3-tier architecture is
110nm, residual reflectivity is zero, and loss is 0.379%；And to wavelength 248nm, total thicknesses of layers of 3-tier architecture is 145nm, residual
Coreflection is zero, and loss is 0.129%.Regrettably, the Single wavelength anti-reflection film of prior art can not meet the double wave of the present invention
The use condition of long anti-reflection film.
Similar to Fig. 2, Fig. 4 is the reflectance (solid line) of the deep knowledge base dual wavelength anti-reflection film of the present invention and damages
Relatively, wherein, (a) film number of plies is 10 layers to consumption (dotted line) curve ratio, and (b) is 8 layers, and (c) is 6 layers, and (d) is 4 layers.It should be mentioned that
It is that Fig. 4 illustrate only 4 solutions, it is clear that also have more solution, but owing to the inevitable film number of plies of these solutions is more, gross thickness is more
Thickness, so its result will not be better than these 4 solutions illustrated, thus the most just there is no need to give again.
Embodiments of the invention 1: the film number of plies is 10 layers, wherein odd-level is high-index material LaF3, even level is low
Refraction materials MgF2.Film layer gross thickness is 255.2nm, from the beginning of quartz is melted in substrate, each layer high and low refractive index alternate membrane
Thickness is followed successively by: 15.34, and 23.17,10.06,34.50,30.93,21.16,10.46,40.17,31.61,37.80, unit is
Nm, Fig. 3 (a) represent the corresponding relation of its thicknesses of layers and refractive index.Residual reflectivity and the loss of the present embodiment 1 are shown in Fig. 4
(a), and its absorbance is shown in Fig. 5 (a), the residual reflectivity of its medium wavelength 193nm is 0.001%, and loss is 0.947%, in
Being that one side absorbance reaches 99.052%, and the residual reflectivity of wavelength 248nm is 0.000%, loss is 0.266%, then
One side absorbance can reach 99.734%.Obviously, the reason causing the present embodiment 1 transmission loss is exactly thin film loss, and surface
Residual reflectivity is negligible.
Embodiments of the invention 2: the film number of plies is 8 layers, wherein odd-level is high-index material LaF3, even level is low folding
Penetrate rate material MgF2.Film layer gross thickness is 194.6nm, from the beginning of quartz is melted in substrate, and the thickness of each layer high and low refractive index alternate membrane
Degree is followed successively by: 5.03, and 8.66,40.64,22.67,3.92,44.04,31.94,37.70, unit is that nm, Fig. 3 (b) represent its film
Layer thickness and the corresponding relation of refractive index.The residual reflectivity of the present embodiment 2 and loss are shown in Fig. 4 (b), and its absorbance is shown in
Fig. 5 (b), the residual reflectivity of its medium wavelength 193nm is 0.006%, and loss is 0.749%, and then one side absorbance can reach
99.245%, and the residual reflectivity of wavelength 248nm is 0.011%, loss is 0.206%, and then one side absorbance can reach
99.783%.Obviously, the reason causing the present embodiment 2 transmission loss is mainly thin film loss.
Embodiments of the invention 3: the film number of plies is 6 layers, wherein odd-level is high-index material LaF3, even level is low folding
Penetrate rate material MgF2.Film layer gross thickness is 181.4nm, from the beginning of quartz is melted in substrate, and the thickness of each layer high and low refractive index alternate membrane
Degree is followed successively by: 44.51, and 24.15,3.41,40.89,31.16,37.23, unit is that nm, Fig. 3 (c) represent its thicknesses of layers and folding
Penetrate the corresponding relation of rate.The residual reflectivity of the present embodiment 3 and loss are shown in Fig. 4 (c), and its absorbance is shown in Fig. 5 (c), its
The residual reflectivity of medium wavelength 193nm is 0.008%, and loss is 0.678%, and then one side absorbance can reach 99.314%,
And the residual reflectivity of wavelength 248nm is 0.010%, loss is 0.196%, and then one side absorbance can reach 99.794%.
Embodiments of the invention 4: the film number of plies is 4 layers, wherein odd-level is high-index material LaF3, even level is low folding
Penetrate rate material MgF2.Film layer gross thickness is 169.2nm, from the beginning of quartz is melted in substrate, and the thickness of each layer high and low refractive index alternate membrane
Degree is followed successively by: 16.47, and 83.38,30.31,38.99, unit is the correspondence that nm, Fig. 3 (d) represent its thicknesses of layers and refractive index
Relation.The residual reflectivity of the present embodiment 4 and loss are shown in Fig. 4 (d), and its absorbance is shown in Fig. 5 (d), its medium wavelength 193nm
Residual reflectivity be 0.002%, loss is 0.601%, and then one side absorbance can reach 99.397%, and wavelength 248nm
Residual reflectivity be 0.028%, loss is 0.156%, and then one side absorbance can reach 99.816%.Obviously, this enforcement
Example 4 has the thin film loss of minimum and maximum absorbance.
From above four embodiments it can be seen that 1). along with dual wavelength anti-reflection film total film number of plies gradually decreases, total film thickness
Spend the most thinning, residual reflectivity tend to be gradually increased (with two wavelength of 193nm and 248nm and evaluate)；2). total film layer
Number reduces, and total thicknesses of layers is thinning, and the loss of thin film strongly reduces, and absorbance increases.In other words, at deep ultraviolet wavelength, no
Can only consider to obtain minimum residual reflectivity, it is often more important that will consider that the thin film loss of minimum is to obtain maximum transmission
Rate, this not only can increase the transmission potential of thin film, it is often more important that can improve the anti-excimer laser damage threshold of thin film；3).
At deep ultraviolet wave band, particularly wavelength 193nm, owing to thin film loss is far longer than residual reflectivity, it is advantageous to scheme is undoubtedly
4 Rotating fields of film layer gross thickness minimum rather than 6,8,10 Rotating fields that residual reflectivity is less should be selected；4). the film number of plies is more than 10
During layer, the contribution to reducing residual reflectivity is the most atomic, but considerably increases the loss of film layer, therefore the film number of plies can not be more than 10 layers；
5). when the film number of plies is less than 4 layers, to the dual wavelength anti-reflection film of 193nm and 248nm without solution.
Manufacturing above-mentioned deep ultraviolet dual wavelength anti-reflection film, the problem of most critical is how to implement film thickness monitoring, and that is afraid of the simplest
4 single film structure are the most such.As it was previously stated, the quartz crystal that prior art solves deep ultraviolet film thickness monitoring controls, film
Thick control error is bigger；And independently set up a set of DUV electrolemma apparatus for controlling thickness, not only cost but also time-consuming.To this end, the present invention carries
Go out and solve this problem by plate washer method, so there is no need to change coater original blooming control system, as long as at quilt
Increase by one piece of plate washer below plated film substrate and can implement the film thickness monitoring of deep ultraviolet wave band.Fig. 6 be baffle plate used by the present invention with
By relative position and the configuration schematic diagram of original blooming control system of plated film substrate.As shown in Figure 6, blooming prison
Ore-controlling Role is mainly made up of light source 6, condenser lens 7, film thickness monitoring sheet 8, optical filter 9 and receptor 10 etc..The thickness of every layer film
Degree is all measured with monitoring piece 8.In Fig. 6,1 is electron beam evaporation source, and 2 is thermal resistance evaporation source, the most successively evaporation high index of refraction material
Material LaF3With low-index material MgF2.Plated substrate 3 is placed on work piece holder dish 4 (actual to be piled at work piece holder dish 4 periphery
Plated substrate 3, the most only plated substrate 3 shown in figure), due to work piece holder dish 4 quick rotation during plated film, so institute
It is the same for having plated suprabasil characteristic.Thickness baffle plate 5 just nestles up the lower section being placed in plated substrate 3, to block electron beam
A part of thin-film material molecule when evaporation source 1 and thermal resistance evaporation source 2 evaporate respectively, obtains the dark purple adventitia of requirement in substrate
Thick.
Fig. 7 shows shape and the manufacture method of baffle plate used by the present invention, and wherein, (a) is bisection method, and (b) is octave device.
If the centre wavelength taking 193nm and 248nm is 220nm, then selecting visible ray to control wavelength 440nm, plate washer need to keep off one just
Half thin-film material vapor molecule stream, the design of such plate washer and making are very simple again can be the most accurate.As shown in Fig. 7 (a), plate washer
The diameter of 5 is equal with work piece holder dish 4, in order to be installed to below work piece holder dish 4；The diameter of plate washer central circular hole 11 and thickness
Monitoring piece 8 is equal, in order to the control light of wavelength 440nm all passes through；Keep off half vapor molecule stream, only need to be plate washer pair
Point, clip half, retain second half shadow region.If the thickness 440nm so on film thickness monitoring sheet 8, then plated
Thickness in substrate 3 is just 220nm.The shortcoming of this bisection method is, it is raw that thin film growth affects thin film because interval time is longer
Long structure, for avoiding or alleviate this impact, proposes to use eight stepper plate, based on eight stepper plate utilize 45 ° of fan shape baffles, as
Shown in the shadow region of Fig. 7 (b), this makes to manufacture and design and remains to keep simple and accurate feature, but alleviates and lack stepper plate
Point.
Claims (10)
1. the dual wavelength anti-reflection film for excimer laser, it is characterised in that include substrate and be successively set on described
The multilayer film being alternately made up of high refractive index film and low refractive index film in substrate；
Described high refractive index film is lanthanum fluoride, and described low refractive index film is Afluon (Asta)；
The number of plies of described multilayer film is 4～10 layers.
Dual wavelength anti-reflection film for excimer laser the most according to claim 1, it is characterised in that described substrate is
Melt quartz or calcium fluoride.
Dual wavelength anti-reflection film for excimer laser the most according to claim 1, it is characterised in that described dual wavelength
For argon fluoride lasers wavelength 193nm and KrF laser wavelength 248nm.
Dual wavelength anti-reflection film for excimer laser the most according to claim 1, it is characterised in that described multilayer film
Total film number of plies be even number, wherein, outside by substrate, odd-level is lanthanum fluoride, and even level is Afluon (Asta).
Dual wavelength anti-reflection film for excimer laser the most according to claim 4, it is characterised in that described multilayer film
Total film number of plies be 10 layers, film layer gross thickness is 255.2nm, and outside by substrate, odd-level is lanthanum fluoride, and even level is fluorination
Magnesium, the thickness of the 1st to 10 layer is followed successively by: 15.34, and 23.17,10.06,34.50,30.93,21.16,10.46,40.17,
31.61,37.80, unit is nm.
Dual wavelength anti-reflection film for excimer laser the most according to claim 4, it is characterised in that described multilayer film
Total film number of plies be 8 layers, film layer gross thickness is 194.6nm, and outside by substrate, odd-level is lanthanum fluoride, and even level is Afluon (Asta),
The thickness of the 1st to 8 layer is followed successively by: 5.03, and 8.66,40.64,22.67,3.92,44.04,31.94,37.70, unit is nm.
Dual wavelength anti-reflection film for excimer laser the most according to claim 4, it is characterised in that described multilayer film
Total film number of plies be 6 layers, film layer gross thickness is 181.4nm, and outside by substrate, odd-level is lanthanum fluoride, and even level is Afluon (Asta),
The thickness of the 1st to 6 layer is followed successively by: 44.51, and 24.15,3.41,40.89,31.16,37.23, unit is nm.
Dual wavelength anti-reflection film for excimer laser the most according to claim 4, it is characterised in that described multilayer film
Total film number of plies be 4 layers, film layer gross thickness is 169.2nm, and outside by substrate, odd-level is lanthanum fluoride, and even level is Afluon (Asta),
The thickness of the 1st to 4 layer is followed successively by: 16.47, and 83.38,30.31,38.99, unit is nm.
9. an optical film thickness monitoring system, including electron beam evaporation source, thermal resistance evaporation source, plated substrate, it is characterised in that institute
It is provided with baffle plate between electron beam evaporation source and thermal resistance evaporation source and the plated substrate stated.
Optical film thickness monitoring system the most according to claim 9, it is characterised in that described baffle plate is circular, this baffle plate
Centre is provided with plate washer central circular hole, and baffle plate uses bisection method segmentation or octave device segmentation.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112904461A (en) * | 2021-02-02 | 2021-06-04 | 南京波长光电科技股份有限公司 | Ultraviolet band ultra-low absorption double-sided antireflection film and preparation method thereof |
| CN114853355A (en) * | 2022-04-08 | 2022-08-05 | 常州市万华激光科技有限公司 | Preparation method of ultraviolet 193nm antireflection film |
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| CN105163939A (en) * | 2013-03-01 | 2015-12-16 | V·莱普特新 | Anti-reflective coating |
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| CN112904461A (en) * | 2021-02-02 | 2021-06-04 | 南京波长光电科技股份有限公司 | Ultraviolet band ultra-low absorption double-sided antireflection film and preparation method thereof |
| CN112904461B (en) * | 2021-02-02 | 2022-05-24 | 南京波长光电科技股份有限公司 | Ultraviolet band ultra-low absorption double-sided antireflection film and preparation method thereof |
| CN114853355A (en) * | 2022-04-08 | 2022-08-05 | 常州市万华激光科技有限公司 | Preparation method of ultraviolet 193nm antireflection film |
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