CN1195794A - Nano pinhole probe in soft X-ray non-redundant holography and preparation method thereof - Google Patents

Abstract

A nano pinhole probe in soft X-ray non-redundant holography and a preparation method thereof. Nano-pinholes have important applications in X-ray non-redundant holography, X-ray scanning microscopy and X-ray imaging microscopy, and in optical disc storage of information. The invention adopts two methods to manufacture the nanometer pinhole, one method is to plate a gold film on the surface of the substrate with manufactured small round glue spots, form small holes by using the round glue spots and then shrink the holes by an electroplating method, and the other method is to directly plate the gold film on the surface by using the unevenness of the surface of the substrate. The two methods can prepare nanometer pinholes with the aperture a less than 200 nanometers, the hole depth H more than 200 nanometers and the hole edge thickness H more than 50 nanometers.

Description

Nanometer pin hole probe and preparation method thereof in the grenz ray nonredundancy holography

The present invention is nanometer pin hole probe and preparation method thereof in the relevant grenz ray nonredundancy holography

The present invention mainly is in grenz ray nonredundancy holography, utilizes nanometer pin hole pointolite for referencial use, to obtain the sample message of nanometer scale.In addition, the present invention can also be widely used in and utilize nanometer pin hole probe technologies to obtain the every field of nanometer information.As in X-ray scanning microscopy and x-ray imaging microscopy, utilize the nanometer pin hole to limit the size of scanning light spot and imaging facula, can obtain the resolution characteristic of nanometer scale.And for example the optical disc storage information density is not only relevant with material, but also depends on the size of read/write head focal length hot spot, if can utilize nanometer pin hole probe to make read/write head, will become the storage density of the raising CD of the order of magnitude.

Prior art

(1) tunnel flying-spot microscope (Scanning Tunneling Microscope STM) is generally paid attention to as a kind of strong nanoprocessing instrument and is used, many external research departments have reported the result of their miniature carving nanoscale successively, have affirmed fully the feasibility of utilizing the tunnel flying-spot microscope to carry out nanoprocessing.Tunnel flying-spot microscope processing characteristic is as follows: 1) high lateral resolution.2) form high field easily.3) has the low-energy electron of enough energy.4) process time and state are controlled easily.5) have processing and measurement dual-use function concurrently.Therefore can utilize the tunnel flying-spot microscope to process the nanometer pin hole, still, hole depth can only be accomplished about 5 nanometers.In soft X holography, because the synchrotron radiation luminous energy height of incident, energy flux density is big, if the peritreme thickness of nanometer pin hole will be breakdown less than 30 nanometers and cause the reaming phenomenon.(see also E.J.Van Loenen, people such as D.DijKamp are published in AppliedPhysics Letter, 55,1312,1989 article; People such as Y.Z.Li are published in Applied Physics Letter, 54,1424,1989 article; L. people such as Stockman is published in Phantoms Newsletter, N.2, and September-October, 1993 article; And J.Tersff and D.R.Hamanm are published in PhysicsReview, B31,805,1985 article.)

(2) laser boring, beam direction is good and output power is high.By optical shaping and focusing system, can obtain 10 at the focus place ⁹The power density of W/cm can make the work piece surface temperature up to 10 ⁴℃, machined material is in instant melting and vaporization.But the Laser Processing pin hole is subjected to the influence of the limited focal spot yardstick of laser, and its focal spot yardstick has been subjected to the restriction of diffraction limit yardstick just as we all know.Also can only be reduced to 1/2 of former Airy disk to focal beam spot even use confocal technology at present, can not obtain the following pin hole of 200 nanometers.(works of Jiang Xinrong " trickle process technology ", Beijing, Electronic Industry Press, 1990; And the article of C.J.R.Sheppard " Scanning OpticalMicroscopy ", In Advances In Optical and Electron Microscopy, Vol.10, R.Barer and V.E.Cosslett edit, 1-98, Academic Press, London, 1987.)

(3) photoetching technique.We know that general photoetching technique all is subjected to the restriction of optical diffraction limit, can't make the pin hole of nanoscale.Though it is short-wavelength light lithography such as X smooth lithography are practical ways, bad owing to beam quality, cost dearly and limited its application.Especially strong inadequately when synchrotron radiation source brightness, when monochromaticity was also good inadequately, it was very difficult to make the nanometer pin hole with X smooth lithography.

(4) electron beam exposure and ion beam sputtering.Electron-optical system can provide micron and even nano level pin hole.The mechanism of its processing is a kind of thermal process basically, is evaporated by the material production spot heating that high energy electron bombards.In process, for thick sample, along with the lengthening of process time, the breadth wise dimension in hole also can strengthen.So on the processing thickness with on the breadth wise dimension certain restricting relation is being arranged.Reaching on the thickness more than 50 nanometers still is difficult.And the kinetic energy of ion is big, and the processing mechanism complexity utilizes this method only can process micron-sized pin hole at present, can not be littler, and this is because the quality of bundle is limit.(see also K.Kanaya, people such as K.Shimizu are published in Bull.Electrotech.Lab., and 32,280-292,1968.)

(5) electroplate shrinkage cavity.Utilize electron beam exposure or additive method to obtain the aperture of micron order or submicron order earlier, utilize the electric plating method thickening again, fill up aperture, make the aperture dwindle gradually.Suitably the time of control plating, can obtain nano level pin hole.But simple the use electroplated the shrinkage cavity method, and the edge of the aperture that micron-sized macropore shrinkage cavity is obtained is thinner, will produce the reaming phenomenon under the impact of high energy grenz ray.And, because electroplating time is longer, the impurity in the electroplate liquid and the scrambling of former hole shape, make that the space distribution of electric current is very complicated, even anisotropy occurs, cause the shape in the hole after the shrinkage cavity very irregular, the branch reticulate texture also appears in peritreme easily, influences the diffraction characteristic of nano-pore.

Since the roentgen found X ray in 1895, people constantly recognize the peculiar advantage of X-ray: penetrability and wavelength consumingly suitably, just in time filled up the vacancy between optical microscope and the electron microscope, particularly the soft X-ray (2.3-4.4 nanometer) of " water window " wave band has natural contrast mechanism and enhancement mechanism to biological sample.If can obtain nanometer resolution, will make people might see the three-dimensional structure of biomolecule and the change procedure of chemical reaction clearly on cellular level at this wave band, this will give related disciplines such as modern biology and science of heredity with powerful expulsive force.At present, the research of X-ray microscopy launches in the world, but owing to be difficult to make high-precision optical imaging system, so far the multiple microscopy that the X-ray wave band was once advised none can reach nanometer resolution.Therefore we propose nanometer pin hole probe technologies is applied to the X-ray wave band, attempt to break through the level of X-ray microtechnic in the past.(see also the article in the king Zhijiang River, Science Bulletin, 38,2205,1993.)

The objective of the invention is in order to finish the record of soft X-ray nonredundancy hologram.Wherein most critical is that to obtain to can be used as the aperture of nm probe little, and hole depth is dark, the nanometer pin hole that peritreme is thick.For this reason, propose the method for making of practicable acquisition nanometer pin hole, overcome the problem that various method for makings exist in the above-mentioned prior art.

(1) nm probe and X-ray holography

The recording mode of the X-ray holography of generally adopting has two kinds at present: a kind of is in-line holographic, and another kind is the nonredundancy holography.For nonredundancy holographic recording mode, to differentiate the ability of details and the resolution of recording medium and have nothing to do, the lateral resolution of this moment depends on the size with reference to point source.(see also J.C.Solem, LA-9508-MS, UC-48,1982.) about this point, we can analyze like this:

Under rectangular coordinate, the reference sphere ground roll sends from a R (0,0,0), any 2 A on the sample face, and B is without loss of generality, and supposes that its coordinate is respectively S1 (0, c, 0), S2 (0, d, 0).

Then above-mentioned 3 points on the holographic recording plane (amplitude of b) locating is respectively for x, y: $E_r=A/{(x^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="A9710636600092.png"\; state="\{\{state\}\}">y</figure-callout>}}^2+b^2)}^{1/2}\exp \{-\mathrm{ik}{(x^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="A9710636600092.png"\; state="\{\{state\}\}">y</figure-callout>}}^2+b^2)}^{1/2}\}$ $E_{\mathrm{nl}}=a/[x^2+{(y-c)}^2+b^2{]}^{1/2}\exp \{-\mathrm{ik}{(x^2+{(y-c)}^2+b^2)}^{1/2}\}$ ${\mathrm{<figure-callout\; id="2"\; label="E\; n"\; filenames="A9710636600092.png"\; state="\{\{state\}\}">E</figure-callout>}}_n=a/[x^2+{(y-d)}^2+b^2{]}^{1/2}\exp \{-\mathrm{ik}{(x^2+{(y-d)}^2+b^2)}^{1/2}\}---\left(1\right)$

I is a complex factor in the following formula, , k is a wave number,

, 1 is the incident light wavelength.If c, d satisfies relational expression: c between the b, d＜＜b, then phase factor is reduced to: $[x^2+{(y-c)}^2+b^2{]}^{1/2}\&ap;r{(1-2\mathrm{cy}/r^2)}^{1/2}\&ap;r(1-\mathrm{cy}/r^2)$ $[x^2+{(y-d)}^2+b^2{]}^{1/2}\&ap;r(1-\mathrm{dy}/r^2)---\left(2\right)$ Amplitude factor is reduced to: $[x^2+{(y-c)}^2+b^2{]}^{1/2}\&ap;{(x^2+{(y-d)}^2+b^2)}^{1/2}\&ap;{(x^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="A9710636600092.png"\; state="\{\{state\}\}">y</figure-callout>}}^2+b^2)}^{1/2}=r---\left(3\right)$ By (1), (b) high light on is distributed as for x, y: I=(E on the plane as can be known for (2), (3) _r+ E _S1+ E _S2) (E _r+ E _S1+ E _S2)=1/r ²{ A ²+ 2a ²+ 2Aacos (kcy/r)+2Aacos (kdy/r)+2a ²Cos[k (c-d) y/r] }=1/r ²{ A ²+ 2a ²+ 4Aacos (k (c+d) y/2r) cos[k (c-d) y/2r]+2a ²Cos[k (c-d) y/r] }=I ₁+ I ₂+ I ₃(4) light distribution of (4) formula can be divided into three: I ₁=1/r ²{ A ²+ 2a ²(5) I ₂=(4Aa/r ²) cos[k (c+d) y/2r] cos[k (c-d) y/2r] (6) I ₃=(2a ²/ r ²) cos[k (c-d) y/r] (7) first I ₁Representative is at (x, y, the direct current component of record light intensity b), second I ₂Include object information, the 3rd I ₃Be the interference between the sample itself, belong to distracter.

For linear process situation: t (x, y)=(x y), as long as meet some requirements during reproduction, can separate for second, so we only considers second to alpha+beta I.Second I ₂Be a quick oscillation function of being modulated, oscillation frequency is proportional to the distance of sample barycenter to reference point, is inversely proportional to the distance of object plane to hologram plane, and modulating frequency is proportional to sample and arrives the distance of reference point and the ratio that sample plane arrives the record plan range.Lowest modulation frequency must satisfy following formula:

k(c-d)y/2r| _y＝δ＝π(c-d)δ/(λr)≥π (8)

Above-mentioned (8) formula is illustrated on the hologram and will writes down at least a modulation period.δ be with reference to point source on the plane (x, y, b) diffraction spot radius on:

δ～λr/a (9)

Here a, because b＞＞a, so can think Fu Lang and fraunhofer-diffraction with reference to the diffraction of point source on holographic facet.

By (8), (9) formula obtains:

c-d≥a (10)

Though, at above-mentioned distribution mid point R, S ₁, S ₂On same straight line, putting us and also can obtain similar conclusion for any distribution.The above results has only been considered 2 points on the sample face in addition, but we it be easy to show that many arbitrarily points also stand good by linear theory.

From above analysis as can be known: the lateral resolution that has determined holographic recording with reference to the size of point source.If adopt the nanometer pin hole as the reference point, just can use nonredundancy X-ray holography record, make to reproduce to reach nanoscale, and be spatial structure as the details resolution characteristic, avoided scanning electron microscope to obtain the reconstructed error that steric information comprises.Using nm probe in the X-ray holography is a kind of new way of obtaining nanometer information.

On the other hand, be applied to the nanometer pin hole of X-ray wave band, it not only has the requirement of breadth wise dimension, also has the requirement of vertical scale.

At the X-ray wave band, medium has the optical constant of plural number, and its expression formula is:

n＝1-(N _ar _sλ ²/2π)(f ₁+if ₂)＝1-δ-ic (11)

(11) N in the formula _aBe atomic density in the material, r _sBe the classical radius of electronics, λ is the X-ray wavelength, f ₁+ if ₂Plural dispersion factor for atom.In soft X-ray zone, δ is generally 10 ^-2, c is the coefficient relevant with absorbed, also less than 10 ^-2(see also J.H.Underwood and D.T.Attwood, Physics Today, 4,44,1984.)

The light intensity attenuation coefficient is:

β＝exp(-4πct/λ) (12)

(12) t is a penetration thickness in the formula.

According to the definition of penetration depth, then penetration depth can be expressed as:

H＝λ/(4πc) (13)

For gold (Au): n=0.99310-10.00954, (λ=4.47nm), then H～37nm.

We can know based on above-mentioned analysis, and desired pin hole is not only a little pin hole to the nanometer lateral yardstick in X-ray nonredundancy holography, and is the dark pin hole of one at least 40 nanometer thickness, so there is certain degree of difficulty in its making.

Nanometer pin hole probe of the present invention comprises substrate 1, and golden film 2 is arranged on the surface of substrate 1, and a macropore 4 is arranged on the substrate 1, in the golden film 2 on the macropore 4 pin hole 3 is arranged, the aperture a of pin hole 3＜200 nanometers, the hole depth H of pin hole 3＞200 nanometers, the peritreme thickness h of pin hole 3＞50 nanometers.As shown in Figure 1.

Pin hole of the present invention is the requirement that meets this holography, and method for making has two kinds.

First method: utilization gold-plated film on the substrate that has dot glue is made aperture, uses the electrochemical plating shrinkage cavity again, and specific embodiment is as follows:

1) preparation substrate: if substrate 1 elects gallium arsenide film as, the gallium arsenide film that cuts through correct grinding, mechanical buffing, is made the substrate that thickness is about 120 microns, cleaning again, the water flushing, and use phenixin, and acetone, the alcohol heated wash is clean, dry for standby;

2) make grid: on substrate 1 surface, make the grid of similar rectangular coordinate style, so that seek and location nanometer aperture with the used method of custom integrated circuit.And on the existing surface mesh of substrate, be coated with the last layer glue-line equably;

3) making circle glue selects: use the method for photoetching to make 1 micron round glue point on the substrate glue-line, and utilized the principle of developing to obtain the roundlet glue point of about 300 nanometers of diameter;

4) gold evaporation film: utilize the method for evaporation to have at substrate 1 on the surface of roundlet glue point and plate the golden film 2 of a layer thickness greater than 200 nanometers.

5) the above-mentioned substrate that has golden film is placed in the solution that can dissolve above-mentioned glue-line,, just can obtains the circular hole of about 300 nanometers of diameter as the molten roundlet glue point that goes of acetone soln.

6) electroplate shrinkage cavity: the substrate that has the nanometer circular hole on the golden film 2 is placed in the electroplate liquid electroplates, when increasing thickness, little bore edges is inwardly expanded, form the pin hole 3 about 30 nanometers.

7) another side that has plated golden film 2 relatively at substrate with the selective etching method is opened a macropore 4 with substrate, exposes golden film 2 parts of band nanometer pin hole 3.As shown in Figure 1.

Second method: utilize substrate surface out-of-flatness making aperture:

1) at first, prepare substrate, the material of substrate can be selected gallium arsenide or select silicon nitride, and makes grid on substrate.Specific practice is identical with above-mentioned first method.

2) have directly long-time gold evaporation film 2 on the substrate of grid, can select the thickness of gold evaporation film as required.

3) another side that is coated with golden film surface at substrate with the selective etching method is opened a macropore 4 with substrate, exposes golden film.Because the out-of-flatness of substrate surface makes golden film form pin hole 3.

First method utilizes photoetching circle glue to put the position of controlling the nanometer pin hole of producing at last, the diameter of controlling the nanometer pin hole with method of cross developing and electric plating method, can make the single pin hole of different-diameter, also can be manufactured with the pin hole group that the mutual alignment relation requires.But, the prescription of developer solution and electroplate liquid, concentration, and cross the time length of developing and electroplating, all need strict the grasp.Second method is simply direct, but the randomness of the aperture of the pin hole of making and position is bigger, can only be used to make single nanometer pin hole.

The pin hole that utilizes above-mentioned two kinds of methods to make need carry out careful check, to determine the aperture and the position of pin hole.(application number is: 93112518.9) to utilize a kind of optical inspection means of submicron resolution of inventions such as inventor Wang Gui English and method, can find the nanometer pin hole easily, and utilize the scale of microscope adjusting knob and in advance on substrate the coordinate of etching determine the position of pin hole.

The topmost advantage of the present invention is that pin hole has reached nanometer scale on breadth wise dimension, and has hole depth H＞200 nanometers on vertical scale, peritreme thickness h＞50 nanometers.Being circular in shape basically, meet the requirement that soft X-ray is learned holography.Manufacture craft is simple in addition.Do not relate to tunnel flying-spot microscope and short wavelength and even X smooth lithography technology.

Description of drawings

Fig. 1 is the synoptic diagram of nanometer pin hole sonde configuration of the present invention.

Fig. 2 is the enlarged photograph that the embodiment of the invention 2 adopts substrate 1 surface irregularity making pin hole 3.

Embodiment 1

The structure of nanometer pin hole probe as shown in Figure 1.Substrate 1 is got gallium arsenide film, and substrate 1 is of a size of 6 millimeters * 6 millimeters, and macropore 4 is of a size of 4 millimeters * 4 millimeters, and golden film 2 is thick in 200 nanometers, hole depth H＞200 nanometers, peritreme thickness h＞50 nanometers.Pin hole 3 aperture a ₁≈ 120 nanometers, a ₂≈ 95 nanometers, a ₃≈ 146 nanometers, a ₄≈ 60 nanometers, a ₅≈ 72 nanometers.

Embodiment 2

Fig. 2 is the enlarged drawing that utilizes the pin hole 3 that above-mentioned second method makes.(application number is: 93112518.9) measure aperture a to utilize a kind of optical inspection means of submicron resolution of inventions such as inventor Wang Gui English and method ₁≈ 100 nanometers, a ₂≈ 60 nanometers.Hole depth H＞200 nanometers, peritreme thickness h＞50 nanometers.Detect error 10%.

Claims (3)

1. nanometer pin hole probe in the grenz ray nonredundancy holography, comprise substrate (1), substrate has golden film (2) on (1) one surface, macropore (4) is arranged on the substrate (1), on the gold film (2) pin hole (3) is arranged, the horizontal aperture a of pin hole (3)＜200 nanometers is characterized in that hole depth H＞200 nanometers of pin hole (3), the peritreme thickness h of pin hole (3)＞50 nanometers.

2. the preparation method of nanometer pin hole probe in the grenz ray nonredundancy holography, adopt the electrochemical plating shrinkage cavity, it is characterized in that going up making roundlet glue point and gold-plated film (2) at substrate (1), dissolve away roundlet glue point again and on golden film, form aperture, constitute pin hole (3) with the electrochemical plating shrinkage cavity then, concrete technological process is:

＜1〉preparation substrate (1): size section on request, correct grinding, polishing, and carry out cleaning,

＜2〉make grid: on a surface of above-mentioned substrate (1), make grid, and have at substrate (1) on the surface of grid and be coated with the last layer glue-line,

＜3〉making circle glue selects: on the substrate glue-line, make the round glue point of 1 micron of diameter, with the method for development make the roundlet glue point of about 300 nanometers of diameter,

＜4〉gold evaporation film: have evaporation last layer gold film on the surface of roundlet glue point at substrate (1),

＜5〉substrate (1) that above-mentioned surface is had golden film (2) places the solution that can dissolve above-mentioned glue-line, and the molten roundlet glue point that goes obtains the circular hole of about 300 nanometers,

＜6〉electroplate shrinkage cavity: electroplate for a long time for the golden film (2) on the substrate (1),

＜7〉at another side substrate (1) is opened a macropore (4) with the selective etching method, expose golden film (2) part of band pin hole (3) with respect to gold-plated film (2).

3. the preparation method of nanometer pin hole probe in the grenz ray nonredundancy holography is characterized in that utilizing the substrate surface out-of-flatness to form pin hole on golden film, and concrete manufacture craft flow process is:

＜1〉preparation substrate (1), section, correct grinding, polishing, cleaning, and on the surface of substrate, make grid,

＜2〉have long-time gold evaporation film (2) on the surface of grid at substrate (1),

＜3〉another side that is coated with golden film (2) at substrate (1) with the selective etching method is opened a macropore (4) with substrate (1), exposes the golden film (2) that has pin hole (3).

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