CN101676750A - Full-ring photon sieve and method of producing same - Google Patents

Abstract

The invention discloses a full-ring photon sieve comprising a photon sieve and etching round holes. The photo sieve is produced on transparent medium, and the diffraction aperture of the photo sieve is equal to the width of a corresponding Fresnel annular zone; the etching round holes are arranged on the left Fresnel annular zones; the decision rules on the number and the position of the etching round holes are the same as those of the rings of the photon sieve; the number of the rings of the photo sieve increases from the original even number to the odd number or increases from the original odd number to the even number; both the odd-number annular zones and the even-number annular zones of a zone plate are provided with light-transmission parts which are the light-transmission holes of the odd-number annular zones and the etching-phase light-transmission holes of the even-number annular zones; the diameter of each light-transmission hole is equal to the width of a corresponding annular zone; and the etching round holes and the original diffraction holes form phase plates. The invention also discloses a method for producing the full-ring photon sieve. The focusing diffraction light intensity of the photo sieve produced with the method is improved, and the energy of the main laser-beam far-field diffraction spots is improved.

Description

Full-ring photon sieve and preparation method thereof

Technical field

The present invention relates to shaping technique field, laser beam corrugated, particularly a kind ofly be used to realize that laser beam is at full-ring photon sieve of far field construction hot spot master spot energy lift and preparation method thereof.This kind photon screen can be used for beam shaping, microelectronics non-mask etching, light laser concentration of energy and other needs energy focusing in the various instruments of center spot.

Background technology

Carry out energy lift for laser diffraction spot master spot by all means, and the energy of the other spot of inhibition is practical problem.Need energy focusing in the various instruments of center spot at beam shaping, microelectronics non-mask etching, light laser concentration of energy and other, all need minimum main spot width and high main spot energy.

Position phase modulation technique is to propagate the position distribution mutually in cross section by changing diffracted ray, thereby realizes the technology that the expection diffraction intensity distributes.The method that is used to modulate has multiple, the phase board that has fixed bit to distribute mutually, also the modulation sheet that can be distributed mutually by the Control of Voltage position made of using light electric crystal.Because the utilization ratio of diffraction phase board luminous energy is the highest, so the most frequently used.

So-called photon screen is a kind of novel focal imaging diffraction optical device, utilizes it to focus on and imaging X-ray, and this is that the image optics device of general prism and glass material can't be realized.Photon screen is compared with traditional optical element Fresnel zone plate, has advantages such as high resolving power and inhibition second-order diffraction principal maximum, can improve the contrast of imaging.And, as novel diffraction element, advantages such as volume is little, in light weight, transreplication that it has.

Photon screen can be applied to high resolution microscope, astronomical telescope, photoetching of future generation, the controlled nuclear fusion of laser (ICF) research etc.

In calendar year 2001, Kipper et al. has proposed a kind of novel diffraction optical device first: photon screen, come grenz ray and EUV radiating light source are focused on and imaging [Kipp with it, L., Skibowski, M., Johnson, R.L., Berndt, R., Adelung, R., Harm, S., and Seemann, R.Sharperimages by focusing soft X-ray with photon sieves.Nature[J], 2001.414,184-188.].

Gil and Menon in 2003 is reported in " beam flying photoetching " and (ZPAL) substitutes zone plate [Menon with photon screen in the system, R., Gil, D.Barbastathis, G., and Smith, H.I.Photon-sieve lithography[J] .Opt.Soc.Am.A, 2005.22 (2), 342-345.].

After this, because the superior performance that photon screen itself has, people are more and more interested in it, and it is applied to various new research fields, as EUV telescope around solar satellite, [S.Wang and X.Zhang.Terahertz tomographic imaging with aFresnel lens[J] .Opt.Photon.2002.News 13,59 such as THZ ripple holography].

Photon screen (Photon Sieve, PS) be the diffraction optical elements of on the Fresnel zone ring, making a large amount of transparent micropores that suitably distribute with different radii (Diffraction Optical Element, DOE).

Photon screen has good application in the focusing of grenz ray, extreme ultraviolet line and imaging, can be applicable to fields such as high resolving power microscopy, spectroscopy, photoetching of future generation.Replace fresnel's zone plate Fresnel zone plate (FZP) that grenz ray is focused on and imaging with photon screen (PS), can obtain higher resolution, reduce requirement the photoetching technique manufacture craft.But the hot spot mainboard energy that photon screen focuses on can be done further lifting.

The phase-type fresnel's zone plate is the fresnel's zone plate with relief surface structure.The thickness of embossment is in wavelength magnitude, and figure should can be realized the high diffraction efficiency of expecting as far as possible near design load.[referring to binary optical, Jin nation Pan, Yan Yingbai, Wu Minxian, chapter 4]

The present invention defines central energy than being the energy of the energy of diffractional field central authorities main lobe divided by whole diffractional fields.It can characterize central main lobe energy concentration degree.The definition first zero is the position at the energy-minimum place between the main lobe and first secondary lobe.Its position can characterize the size of central main lobe.

Summary of the invention

(1) technical matters that will solve

In view of this, fundamental purpose of the present invention is to provide a kind of full-ring photon sieve and preparation method thereof, with the lifting again of the main spot energy of realizing laser beam far field construction spot.

(2) technical scheme

For reaching an above-mentioned purpose, the invention provides a kind of full-ring photon sieve, this full-ring photon sieve comprises:

Photon screen, this photon screen is produced on the transparent medium, and its diffraction aperture equates with corresponding Fresnel endless belt width; Etching circular hole, this etching circular hole are positioned at remaining Fresnel endless belt place; The decision rule of this etching circular hole quantity and position is identical with the photon screen annulus, be increased to odd loop from original even loop, perhaps be increased to even loop from original odd loop, odd number endless belt and even number endless belt at zone plate all have the light transmission part, it is respectively the etching position light hole mutually of the light hole of odd number endless belt and even number endless belt, the diameter of each light hole is identical with corresponding endless belt width, and this etching circular hole and original opening diffracting formation phase board.

In the such scheme, the position of described etching position phase light hole is π mutually.

In the such scheme, the size of described phase board is suitable with corresponding common photon screen, and the size of opening diffracting is reduced to 1 times by 1.5 times of corresponding endless belt, and the transmittance of this opening diffracting is 1.

In the such scheme, the odd loop of described corresponding fresnel's zone plate annulus or even loop constitute etching concentric ring circular hole position phase diffraction element, and the position of circular hole value mutually is π, and the odd number even number is decided by the position odd even of photon screen circular hole.

In the such scheme, described each etching concentric ring circular hole position phase diffraction element and photon screen opening diffracting constitute the light transmission part jointly, and remainder is light tight.

For reaching above-mentioned another purpose, a kind of method of making full-ring photon sieve of the present invention, this method utilize lsi technology technology and plane photoetching process technology to realize that this method comprises:

Utilize the electron-beam direct writing legal system to make mother matrix;

Master pattern is transferred on the optical glass that scribbles photoresist by the contact photolithography method;

Utilize the inductive couple plasma lithographic technique, will move on to pattern etch on the optical glass photoresist in optical glass.

In the such scheme, describedly master pattern is transferred in the step on the optical glass that scribbles photoresist by the contact photolithography method, the error of repelication of described contact exposure is less than 0.5 μ m, and the photoresist that is adopted is Shipley s1818, and thickness is 1.8 μ m.

In the such scheme, in the described step of pattern etch in the optical glass that will move on on the optical glass photoresist, the etching gas that is adopted is fluoroform CHF ₃, flow is 30SCCM, and RF power is 500W, and bias power is 200W, is 0.077 μ m/min to the etch rate of quartz substrate.

(3) beneficial effect

Full-ring photon sieve provided by the invention, it is the phase circular hole diffraction unit, position that adds etching by the circular aperture of the common photon screen diffraction of control break for the annulus hole, make collimation parallel laser form of the center master spot energy raising of center master's spot in the far field than photon screen diffraction by it, but the optical field distribution that the main lobe size does not significantly increase.

The present invention combines the high-diffraction efficiency of phase-type fresnel's zone plate and emerging photon screen, realized that photon screen focuses on the light distribution that the main spot energy of diffraction improves again, promptly realized the raising again of the main spot energy of laser beam far field construction spot, this be traditional photon screen can't realize.This also is traditional irrealizable content of phase-type fresnel's zone plate.

Description of drawings

Fig. 1 is 50 common ring photon screen synoptic diagram, and diffraction element is circular diffraction aperture;

Fig. 2 is the synoptic diagram of the 50 ring full-ring photon sieve structures of one of girdle photon sieve embodiment of the present invention, and diffraction element is the circular hole of opening diffracting and etching;

Fig. 3 is based on the full-ring photon sieve of 10 ring fresnel's zone plates; Among the figure black be etching the position be the diffraction circular hole of π mutually, white is light hole, grey is lighttight part;

Fig. 4 is diffraction intensity and the diffraction intensity of the common photon screen of 50 rings and the comparison diagram of radial distance of 50 ring full-ring photon sieves; Can see the central energy ratio among the figure, common photon screen is 0.9137, and first zero position is 17, and the central energy of full-ring photon sieve ratio is 0.9713, and first zero position is 17.And under identical incident light situation, the diffraction intensity peak value of replacement photon screen is 4 times of common photon screen approximately, has greatly increased the luminous energy of diffractional field;

Fig. 5 is the experiment pick-up unit of full-ring photon sieve.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

Full-ring photon sieve is a kind of novel diffraction optics phase part, i.e. phase board.This phase board is positioned over before or after the diffraction limit lens, and laser beam far field construction hot spot spectrum light intensities at different levels are revised, and realizes the diffraction center diffraction spot more concentrated than the diffraction center spot energy of common photon screen.The less diffraction circular hole that phase board of the present invention (full-ring photon sieve) adopts and replace the Dan Yuan diffraction aperture of common photon screen mutually for the etching diffraction borehole structure of π.The present invention has provided the project organization of circular hole diffraction position facies unit, and has carried out relevant simulated experiment.Experimental verification adopt full-ring photon sieve can realize the further lifting of laser beam far field main spot energy.The technology of the present invention can be used for beam shaping, microelectronics non-mask etching, light laser concentration of energy and other needs energy focusing in the various instruments of center spot.

This full-ring photon sieve provided by the invention, be a kind of on transparent medium, make common photon screen earlier, but the diffraction aperture of photon screen is reduced into one times (common photon screen opening diffracting diameter is 1.5 times of corresponding Fresnel endless belt width) of corresponding Fresnel annulus, then at remaining Fresnel endless belt place still etching circular hole, the decision rule of the quantity of circular hole and position is identical with the photon screen annulus, just be increased to odd loop, perhaps be increased to even loop from original odd loop from original even loop.Odd and even number endless belt at zone plate all has the light transmission part like this, is respectively the etching position light hole mutually of the light hole of odd loop and even loop, and the position of etching position phase light hole is π mutually.The size of each light hole is identical with corresponding endless belt width.This etching circular hole and original opening diffracting constitute phase board.The size of described phase board is suitable with corresponding common photon screen, the position of etching circular hole be distributed in mutually in the same circular hole the position mutually value be identical, all be π.Originally the position of circular hole is 0 mutually.

Fig. 2 is the synoptic diagram of the 50 ring full-ring photon sieve structures of one of full-ring photon sieve embodiment of the present invention, and etching circular hole position is π mutually, the black among the figure, and the circular hole position is 0 mutually, the white among the figure.All the other grey color parts are light tight.If the position of diffraction element has only two values mutually on all phase boards, 0 and π, just be called two-value position phase full-ring photon sieve.

Two-value phase board (binary phase-only mask).The full-ring photon sieve characterising parameter has

1) central energy of full-ring photon sieve ratio: the coherent light of collimation passes through girdle photon sieve, in the diffractional field that is produced, and the energy ratio of main spot and total diffractional field.Ratio is high more, illustrates that the energy of main spot gathering is many more.

2) first zero of full-ring photon sieve: the first zero is minimizing position between the main spot and first diffraction maximum.Be worth greatly more, illustrate that main spot chassis is big more.Be worth more for a short time, illustrate that main spot chassis is more little.

By the conclusion of diffraction optics angular spectrum as can be known:

Be located at and introduce an infinitely-great opaque screen that includes the photon screen structure on the z=0 plane, desirable plane wave impinges upon on the photon screen.The transmittance function of photon screen is:

$E(x,y,0)=\left\{\begin{array}{cc}1& {(x-x_{\mathrm{ij}})}^2+{(y-y_{\mathrm{ij}})}^2\≤r_i^2\\ 0& \mathrm{other}\end{array}\right.---\left(1\right)$

In (1), xij, yij represent micropore central coordinate of circle on the wavestrip, i=1, and 2......n, (n is the zone plate number of rings) j=1,2 ... m (m is the number cells on the respective rings).Discrete Fourier transformation obtains the angular spectrum F0 (fx, fy, 0) of incident light on diffraction screen to E (x, y, 0) through two-dimensional space.

$E(f_x,f_Y,0)=\underset{-\∞}{\overset{\∞}{\∫}}\underset{-\∞}{\overset{\∞}{\∫}}E(x,y,0)\exp [-j2\mathrm{\π}(f_{X}x+f_{Y}y)]\mathrm{dxdy}---\left(2\right)$

In (2), f _X, f _YBe spatial frequency,

(α, β are wave vectors

With X-axis, the angle between the Y-axis).Incident light is propagated along the Z direction through behind the photon screen.At the Z=z place, the frequency spectrum E. of spatial frequency (fx, fy z) are:

$E(f_X,f_Y,z)=E(f_X,f_Y,0)\exp (j2\mathrm{\π}\sqrt{\frac{1}{{\mathrm{\λ}}^2}-f_X^2-f_Y^2}.z)---\left(3\right)$

In (3), f _xf _YMust satisfy condition

This formula shows that the effect of propagating the z of a segment distance has just changed the relative phase of each angular spectrum component.But work as

The time, (fx, fy z) are the frequency spectrum E. of spatial frequency

E(f _X，f _Y，z)＝E(f _X，f _Y，0)exp(-μz)????(4)

In (4), $\mathrm{\μ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\sqrt{{\left(\frac{x}{z}\right)}^2+{\left(\frac{y}{z}\right)}^2-1}.$

Because μ is an arithmetic number, these wave components increase decay rapidly because of propagation distance.(4) formula is done inverse Fourier transform, obtain light wave amplitude E (x, y, z)

$E(x,y,z)={\∫}_{-\∞}^{\∞}{\∫}_{-\∞}^{\∞}E(f_X,f_Y,0)\exp (j2\mathrm{\π}\sqrt{\frac{1}{{\mathrm{\λ}}^2}-f_X^2-f_Y^2}.z)\exp \left[j2\mathrm{\π}(f_{X}x+f_{Y}y)\right]d{f}_{X}d{f}_Y---\left(5\right)$

It more than is the diffraction theory of common photon screen.At full-ring photon sieve, what need modification is exactly each transmittance function.Become circular hole by the circular aperture of complete printing opacity and add etching circular hole phase-type diffraction element.

The present invention has provided the design parameter of full-ring photon sieve.The present invention has provided the comparison curves of the central energy ratio and the first zero in Fig. 4.The present invention has selected the common photon screen of 50 rings and the girdle photon sieve of 50 rings.The reason of Xuan Zeing is the fresnel's zone plate of this two device based on identical number of rings like this.

Two kinds of phase board diffraction relatively are shown in the table 1.The central energy ratio of common photon screen is 0.9592.As shown in Figure 4, full-ring photon sieve lifting by a relatively large margin main spot diffraction intensity peak value, and make encircled energy increase.

	Based on fresnel's zone plate number of rings (F)	The central energy ratio	The first zero (unit diffractional field point)
				Full-ring photon sieve	??50	??0.9713	17
Common photon screen	??50	??0.9137	17

Table 1

Full-ring photon sieve of the present invention in the application of reality as shown in Figure 5.The 1st, collimation laser device, the 2nd, condenser lens, the 3rd, full-ring photon sieve of the present invention, the 4th, CCD photodetector.Light process condenser lens 2 and full-ring photon sieve 3 from collimation laser 1 sends produce main spot diffractogram on the focal plane of condenser lens 2.Such diffraction master spot intensity distributions can be detected and confirmed it by the ccd detector on the focal plane that is placed on condenser lens 24.

After experimental results show that the designed full-ring photon sieve of adding, realized of the further lifting of far field construction hot spot main lobe energy really than the main spot energy of common photon screen.This explanation the present invention can be used for beam shaping, microelectronics non-mask etching, light laser concentration of energy and other needs energy focusing in the various instruments of center spot.

The method of this making full-ring photon sieve provided by the invention utilizes lsi technology technology and plane photoetching process technology to realize, specifically may further comprise the steps:

Step 1, utilize the electron-beam direct writing legal system to make mother matrix;

Step 2, master pattern is transferred on the optical glass that scribbles photoresist by the contact photolithography method;

Step 3, utilize the inductive couple plasma lithographic technique, will move on to pattern etch on the optical glass photoresist in optical glass.

Above-mentioned manufacturing full-ring photon sieve utilizes lsi technology technology and plane photoetching process technology to realize.At first, utilize the electron-beam direct writing legal system to make mother matrix, by the contact photolithography method, master pattern has been transferred on the optical glass that scribbles photoresist.The photoresist that is adopted is Shipley s1818, and thickness is 1.8 μ m.The error of repelication of contact exposure is less than 0.5 μ m.Each parameter of annular photon screen provides in preamble.At last, utilize the inductive couple plasma lithographic technique, with pattern etch in optical glass.The etching gas that is adopted is fluoroform (CHF ₃), flow is 30SCCM, and RF power is 500W, and bias power is 200W, is 0.077 μ m/min to the etch rate of quartz substrate.Corresponding to 0.6328 mum wavelength, the refractive index of optical glass is 1.521, thereby the corresponding degree of depth in π position is 0.607 μ m.The degree of depth of utilizing Taylor's contourgraph to measure full-ring photon sieve is 0.607 μ m.Light path synoptic diagram according to Fig. 5 arranges the measurement light path. and the laser works wavelength is 632.8nm.Expand bundle, collimation then.In experiment, the photon screen focal length is 100 millimeters and places circular ring type photon screen, places ccd detector, the considerable thus size of measuring diffraction pattern then at the focal beam spot place.Measured data has proved the correctness of Theoretical Calculation.

Full-ring photon sieve with one 50 ring is an example below, describes its method for making:

1, determines optical maser wavelength and photon screen focal length, number of rings;

2, according to the definite common photon screen that will make of need of work; But the radius of all circular holes is identical with corresponding fresnel's zone plate endless belt width, no longer is 1.5 times of circle hole radius of common photon screen.

3, according to the position phase circular hole of all the other endless belt of method etching as herein described.

4, make full-ring photon sieve.

Suppose that optical maser wavelength is 6328 nanometers, focal length is 100 millimeters, and number of rings is 50 rings.Always have 2673 original micropores and 2688 etching diffraction positions that increase newly hole mutually.5361 altogether.The position is 0 micropore and mutually for the etching micropore of π distributes alternately at fresnel's zone plate odd number even number endless belt mutually, and the radius of micropore is from big to small:

52.0988??39.9768??33.7020??29.6921??26.8437??24.6853??22.9765

21.5800??20.4109??19.4134??18.5493??17.7912??17.1191??16.5179

15.9758??15.4839??15.0348??14.6227??14.2427??13.8908??13.5639

13.2589??12.9737??12.7061??12.4544??12.2171??11.9929??11.7806

11.5792??11.3877??11.2055??11.0318??10.8658??10.7072??10.5553

10.4097??10.2699??10.1357??10.0065??9.8822???9.7624???9.6469

9.5353 9.4276 9.3234 9.2226 9.1250 9.0304 8.9387 microns.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, a kind of full-ring photon sieve is characterized in that, this full-ring photon sieve comprises:

Photon screen, this photon screen is produced on the transparent medium, and its diffraction aperture equates with corresponding Fresnel endless belt width;

Etching circular hole, this etching circular hole are positioned at remaining Fresnel endless belt place;

The decision rule of this etching circular hole quantity and position is identical with the photon screen annulus, be increased to odd loop from original even loop, perhaps be increased to even loop from original odd loop, odd number endless belt and even number endless belt at zone plate all have the light transmission part, it is respectively the etching position light hole mutually of the light hole of odd number endless belt and even number endless belt, the diameter of each light hole is identical with corresponding endless belt width, and this etching circular hole and original opening diffracting formation phase board.

2, full-ring photon sieve according to claim 1 is characterized in that, the position of described etching position phase light hole is π mutually.

3, full-ring photon sieve according to claim 1 is characterized in that, the size of described phase board is suitable with corresponding common photon screen, and the size of opening diffracting is reduced to 1 times by 1.5 times of corresponding endless belt, and the transmittance of this opening diffracting is 1.

4, girdle photon sieve according to claim 1, it is characterized in that, the odd loop of described corresponding fresnel's zone plate annulus or even loop constitute etching concentric ring circular hole position phase diffraction element, and the position of circular hole value mutually is π, and the odd number even number is decided by the position odd even of photon screen circular hole.

5, girdle photon sieve according to claim 4 is characterized in that, described each etching concentric ring circular hole position phase diffraction element and photon screen opening diffracting constitute the light transmission part jointly, and remainder is light tight.

6, a kind of method of making full-ring photon sieve, this method utilize lsi technology technology and plane photoetching process technology to realize, it is characterized in that this method comprises:

Utilize the electron-beam direct writing legal system to make mother matrix;

Master pattern is transferred on the optical glass that scribbles photoresist by the contact photolithography method;

Utilize the inductive couple plasma lithographic technique, will move on to pattern etch on the optical glass photoresist in optical glass.

7, the method for making full-ring photon sieve according to claim 6, it is characterized in that, describedly master pattern is transferred in the step on the optical glass that scribbles photoresist by the contact photolithography method, the error of repelication of described contact exposure is less than 0.5 μ m, the photoresist that is adopted is Shipleys1818, and thickness is 1.8 μ m.

8, the method for making full-ring photon sieve according to claim 6 is characterized in that, in the described step of pattern etch in the optical glass that will move on on the optical glass photoresist, the etching gas that is adopted is fluoroform CHF ₃, flow is 30SCCM, and RF power is 500W, and bias power is 200W, is 0.077 μ m/min to the etch rate of quartz substrate.

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