CN101029949A - Optical element and method of manufacturing optical element - Google Patents
Optical element and method of manufacturing optical element Download PDFInfo
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- CN101029949A CN101029949A CN 200710085082 CN200710085082A CN101029949A CN 101029949 A CN101029949 A CN 101029949A CN 200710085082 CN200710085082 CN 200710085082 CN 200710085082 A CN200710085082 A CN 200710085082A CN 101029949 A CN101029949 A CN 101029949A
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Abstract
The present invention provides an optical element having a three-dimensional structure which can function in a visible range and can improve adherence at a structural interface of the element, and a method of manufacturing the optical element. The optical element including a substrate and at least a first layer and a second layer on the substrate is manufactured such that each of the first layer and the second layer has a repetition structure of spaces and structural parts at a pitch equal to or less than a wavelength of visible light, and at an interface between the first layer and the second layer, overlapped structures are provided in which the repetition structure of the first layer and the repetition structure of the second layer overlap in a stack direction of the layers.
Description
Technical field
The present invention relates to a kind of optical element and make the method for this optical element.Particularly, the present invention relates to a kind of optical element with three-dimensional hollow structure, for example polarization beam apparatus, polarizer or bandpass filter have the face intercycle structure shorter than wavelength of visible light in its surface, also relate to the method for making this optical element.
Background technology
In recent years, proposed to have the optical module of three-dimensional hollow structure energetically.In the future, obtaining so three-dimensional hollow structure will be that to improve the function of optical module necessary.Yet the structure of this optical module is in nanometer scale, does not formulate its manufacture method as yet, also has much the practical problems about the intensity of this element etc.In order to obtain so three-dimensional hollow structure, there is a kind of method of using sacrifice layer on micron dimension, to make hollow structure, promptly so-called MEMS (microelectromechanical-systems) (seeing U.S. Patent No. 4,662,746).
Such MEMS structure provides digital mirror device.This digital mirror device has the hinge that is used to hold the work catoptron, be used to be received in the yoke of the external force that forms on the hinge and the catoptron of the ambient light that is used for forming on the deflection yoke.This structure is of a size of several microns to the hundreds of micron, and the adhesion between the upper and lower is enough strong, does not cause practical problems.
In addition, Japanese Patent Application Publication No.2001-074955 discloses a kind of structure and manufacture method thereof of photon crystal wave-guide.The expectation photon crystal wave-guide is by forming fault of construction in having a plurality of layer of line and space (line-and-space) structure, and along the direction that is perpendicular to one another they piled up, to obtain three-dimensional waveguide.According to manufacture method disclosed herein, use semiconductor material at high temperature to carry out the agglomerate transmission of semiconductor element, to form knot.Material knot place such has metallic bond or covalent bond, and the upper and lower can be together adhering to each other very doughtily.
Semiconductor material is transparent in infra-red range, and is opaque in visible range, therefore, and the optical element that such semiconductor material can not be used for working in visible range.So, need to use dielectric material.Yet, when dielectric material is heated to high temperature, be difficult to carry out the agglomerate transmission of element between dielectric material sometimes to form knot.In this way, according to material, be difficult to sometimes by adding the thermosetting knot.In addition, when bottom-up structure that attempt to use sacrifice layer process to obtain to pile up, be less than or equal at wavelength under the situation of nanostructured of visible wavelength, the contact area between the upper and lower becomes extremely little.So, cause the adhesion at the interface between each layer minimum, and this element is very fragile.
In view of the above problems, the present invention has been proposed.The purpose of this invention is to provide a kind of method with optical element and this manufacturing optical element of three-dimensional structure, this optical element can be worked in visible range, and can improve the adhesion at the structural interface place of this element.
Summary of the invention
In order to address the above problem,, a kind of optical element of the three-dimensional structure with formation as described below and the method for making this optical element are provided according to the present invention.
According to a first aspect of the invention, provide a kind of optical element, having comprised: substrate; And the ground floor that forms on this substrate and the second layer, wherein each in ground floor and the second layer all comprises space and the repetitive structure of structure member on the direction vertical with the stacking direction of described layer, the pitch of described repetitive structure is less than or equal to wavelength of visible light, and overlapping on the stacking direction of described layer at the interface between the ground floor and the second layer of the repetitive structure of the repetitive structure of ground floor and the second layer wherein.
Optical element according to a first aspect of the invention can also be included in a plurality of layers between substrate and the ground floor, and in this optical element, from the substrate number, ground floor can be formed by the i layer, and the second layer can be formed by (i+1) layer.
In optical element according to a first aspect of the invention, in overlay structure, the repetitive structure of ground floor and the repetitive structure of the second layer can be more than or equal to 3nm and be less than or equal in the scope of 20nm overlapping.
In optical element according to a first aspect of the invention, the repetitive structure of each can comprise line and space structure, has the structure in hole and have any in a little the structure in the ground floor and the second layer.
In optical element according to a first aspect of the invention, the pitch that is less than or equal to wavelength of visible light described in the ground floor and the second layer can and be less than or equal to 200nm more than or equal to 10nm.
In optical element according to a first aspect of the invention, the repetitive structure of ground floor and the repetitive structure of the second layer can be formed by identical materials.
In optical element according to a first aspect of the invention, the repetitive structure of ground floor and the repetitive structure of the second layer can be formed by dielectric material.
According to a second aspect of the invention, provide a kind of method of making optical element, this optical element comprises the ground floor and the second layer that forms on substrate and this substrate, and this method may further comprise the steps: form ground floor on this substrate; Processing comprises the repetitive structure of space and structure member in ground floor, and the pitch of this repetitive structure is less than or equal to wavelength of visible light; Fill space in this repetitive structure with the material of sacrifice layer; This sacrifice layer of etching is to expose the top of this repetitive structure from this sacrifice layer; On this repetitive structure and this sacrifice layer, form the second layer; Processing comprises the repetitive structure of space and structure member in the second layer, and the pitch of this repetitive structure is less than or equal to wavelength of visible light; And remove described sacrifice layer.
In the method for according to a second aspect of the invention manufacturing optical element, the step on the top that exposes repetitive structure from sacrifice layer, the side surface of described repetitive structure can expose from the upper surface of described repetitive structure more than or equal to 3nm and be less than or equal to the scope of 20nm.
According to the present invention, can improve the adhesion between the upper and lower on the substrate, can prevent poor adhesion.In addition, in manufacture process etc., for example when external force works, can avoid peculiar problem of micromechanism such as pattern to collapse.
According to the description of carrying out below in conjunction with accompanying drawing, it is obvious that other features and advantages of the present invention will become.
Description of drawings
Figure 1A, 1B and 1C are used for the synoptic diagram of diagram according to the structure of the optical element with three-dimensional structure of the embodiment of the invention.
Fig. 2 is the substrate of diagram example 1 according to the present invention and the figure of patterned arrangement.
Fig. 3 A and 3B are the figure of the pattern form of the ground floor of diagram three-dimensional structure of the optical element of example 1 according to the present invention and the second layer.
Fig. 4 A, 4B, 4C, 4D, 4E, 4F, 4G, 4H and 4I are the schematic cross-sectional view of manufacture process that is used for the optical element with three-dimensional structure of diagram example 1 according to the present invention.
Fig. 5 A, 5B, 5C, 5D, 5E, 5F, 5G, 5H and 5I are the schematic cross-sectional view of manufacture process that is used for the optical element with three-dimensional structure of diagram example 3 according to the present invention.
Fig. 6 be used for example 3 more of the present invention polarizer phase difference characteristics and with the figure of the phase difference characteristics of the quartzy polarizer of making.
Fig. 7 is the average transmittance of diagram polarizer of example 3 according to the present invention and according to the figure of the average transmittance of the polarizer of comparative example 2.
Fig. 8 A, 8B, 8C and 8D are the synoptic diagram that diagram example 4 according to the present invention is used for the process on the prism that substrate is adhered to.
Fig. 9 is the figure of the spectral-transmission favtor of the S polarized light of polarization beam apparatus of diagram example 4 according to the present invention and P polarized light.
Figure 10 is the figure of diagram another example of the optical element of example 4 according to the present invention.
Figure 11 is the figure of the exemplary patterns of diagram line and space structure.
Embodiment
Various details embodiment.Figure 1A to 1C is used for the synoptic diagram of diagram according to the structure of the optical element with three-dimensional structure of present embodiment.Figure 1A is a skeleton view, and Figure 1B is the viewgraph of cross-section of seeing from the indicated direction of arrow i, and Fig. 1 C is the viewgraph of cross-section of seeing from the indicated direction of arrow ii.In the present embodiment, shown in Figure 1A to 1C, optical element is included in the stacked structure of the repetitive structure of space (air gap) 301 and structure member 302 in the repetitive structure that piled up space (air gap) 201 and structure member 202 in the ground floor (first structure) 2 on the substrate 1 and the second layer (second structure) 3.In this case, a plurality of layer can be set between the substrate 1 and first structure 2, and can be used as from the several i layers of substrate structure 2 is set.In addition, a plurality of layers can be set as the upper strata on second structure 3.
Here, when by when the several i layers of substrate form substrate 2, each layer in i layer and (i+1) layer is treated to space and structure member perpendicular to the repetitive structure on the direction of this stacking direction of a plurality of layers, and its pitch is less than or equal to wavelength of visible light.On the interface between these layers, this patterning is overlapping on its stacking direction.More particularly, on the interface between i layer (first structure 2) and (i+1) layer (second structure 3), it is overlapping on its stacking direction that the pitch that the pitch of i layer is less than or equal to the repetitive structure of wavelength of visible light and (i+1) layer is less than or equal to the repetitive structure of wavelength of visible light.In other words, repetitive structure be engaged with each other (engage).Hereinafter the state that repetitive structure is engaged with each other is called " overlap condition ", and hereinafter the structure that is engaged with each other is called " overlay structure ".In addition, the part 4 that hereinafter these structures is engaged with each other is called " lap ".
According to present embodiment, overlay structure can make the contact area between i layer and (i+1) layer bigger, this feasible adhesion that can improve interlayer.In addition, the existence of such lap can prevent such as the collapse microtexture defective of (pattern collapse) of pattern.Here, on the interface between above-mentioned i layer (first structure 2) and (i+1) layer (second structure 3), the highest lap 4 of overlap condition degree is preferably more than or equal to 3nm and be less than or equal in the scope of 20nm.Under the situation of maximum lap, in making, in the face during skewness, might cause bad adhesion in the part less than 3nm.In addition, under the situation of maximum lap less than 3nm, the contact area between the levels is little, can not obtain enough adhesion strengths.On the other hand, when maximum lap during greater than 20nm, the planarity of (i+1) layer is not enough, can produce the optics harmful effect such as light scattering.In addition, because the value of the refractive index of lap is between the refractive index of i layer and (i+1) layer, so can not obtain desired characteristics at the thick lap of optics.
In addition, in this embodiment, can be used as line and space structure, have the hole structure, have in the structure a little any, form above-mentioned i layer and (i+1) layer repetitive structure, its pitch is less than or equal to wavelength of visible light.Under the situation of online and space structure, pattern is anisotropic with respect to the polarisation of light component, therefore, is effective structure when the structure that obtains such as polarizing beam splitter or low-pass filter.In addition, the line of line and space structure can be separated (referring to Figure 11) by the pitch that is less than or equal to wavelength of visible light.By such separation, can prevent to peel off owing to ply stress causes pattern.In addition, pattern be column have a little structure or pattern be poroid structure with hole situation under, pattern is isotropic with respect to the polarisation of light component, so its antireflection film as multi-coated interference film or bandpass filter is effective.
Here, be less than or equal to wavelength of visible light, can prevent the diffraction phenomena under the used wavelength of optical element, therefore can obtain the characteristic of optical stabilization by the pitch that makes repetitive structure.Here, the pitch of repetitive structure is more than or equal to 10nm and to be less than or equal to 200nm be desirable.Particularly, when pitch is less than or equal to 150nm, use 45 ° incident angle not produce diffraction light in the optical element of in the visible region of wavelength, working, so this optical element is worked effectively more than or equal to 400nm.If pitch less than 10nm, then is difficult to structure is maintained like this.In addition, the effectiveness of the layer that is formed by space (hereinafter becoming " air gap ") and structure member specifically is the refractive index that can obtain to expect.In general, every kind of material has its oneself refractive index, is difficult to obtain optional refractive index.Yet, when by air gap and structure member cambium layer, can obtain optional refractive index by the ratio of control air gap and structure member.
More particularly, in theory, refractive index can be controlled at from the refractive index of the material of this structure to greater than the refractive index of air promptly in the scope greater than 1 value.Particularly, can be stably be 1.38 as the refractive index of the magnesium fluoride of layer with low-refraction.Yet (refractive index: 1.46) as structure, the ratio of air gap is 90%, and forms when having the structure in hole, and refractive index is 1.146, therefore, can obtain to have the layer with the inaccessiable low-down refractive index of dielectric when using monox.In addition, when same air gap ratio with 90% formed line and space structure, it is littler that refractive index becomes, and the refractive index anisotropy occurs.Refractive index with respect to electric field (the light vibration component that is parallel to the direction of line) is 1.055, and is 1.028 with respect to the refractive index of magnetic field (perpendicular to the light vibration component of the direction of line).
In addition, in the present embodiment, the structured material of i layer and (i+1) layer can be identical.When by this way, when the structured material of i layer and (i+1) layer is identical, because the influence of the refractive index between above-mentioned each layer can ignore, so easier acquisition desired characteristics.In addition, in the present embodiment, can make structured material with dielectric.The material of the optical element of working in visible-range does not absorb only desirable in the visible-range.Many dielectrics are transparent in visible-range, and are effective as the structured material according to optical element of the present invention.Particularly, monox, titanium dioxide, tantalum pentoxide, zirconia etc. are effective materials, because it is etched in etch process easily.
Next, the method for making according to the optical element with three-dimensional structure of present embodiment is described.At first, be less than or equal in the process of repetitive structure of wavelength of visible light, using photoetching technique to carry out etching after carrying out patterning in the pitch that forms the i layer.In photoetching technique, can carry out exposure by any method, described method is had no particular limits, as long as its pitch that can obtain to expect, for example ledex (stepper), electron beam drawing equipment, X ray exposure sources or interference exposure sources.In addition, because etched structure is superfine little, be desirable so use dry etching.Can carry out this dry etching by any method, this method is had no particular limits, as long as its pitch that can obtain to expect, and this dry etching can be for example active-ion-etch (RIE), inductively coupled plasma (ICP) or neutral loop discharge (NLD, NeutralLoop Discharge).Also can carry out wet etching, as long as the pitch that can obtain to expect.When using resist as the mask etching dielectric, selectivity is a problem sometimes.In this case, the mask that is used for this structure of etching is that the multilayer mask is desirable so that can obtain selectivity.
Next, can carry out the process of filling the material of sacrifice layer to this space by using coating technology commonly used.For example, can use spin coating, spraying or slit coating.In addition, the material of sacrifice layer can be any can be by the material of oxygen ashing, as photo anti-corrosion agent material, bottom anti-reflective coating (BARC, Bottom Anti-Reflection Coating) material, acryl resin or polystyrene resin.In addition, in order to improve the planarity of sacrificial layer surface, be more greatly desirable from the thickness of the upper surface of this structure.On the other hand, in order to make the required time of planarization process shorter, thickness is less to be desirable.So, from the sacrificial layer thickness of the upper surface of this structure more than or equal to 50nm and to be less than or equal to 200nm be desirable.In order to improve the planarity of sacrifice layer, repeatedly to use sacrifice layer is effective.
Next, it is desirable adopting dry etching commonly used the process with the top that exposes i repetitive structure from sacrifice layer of the whole surface of etching (eat-backing (etch back)) sacrifice layer.For example, can use parallel-plate-type RIE equipment.From sacrifice layer expose repetitive structure from the upper surface 3nm of this repetitive structure or the side surface in as many as 20nm or the scope still less more.Can control etch quantity by etching period.Here, use oxygen as etching gas.When oxygen is pure oxygen, because the etch-rate height, so the controllability of etch quantity is bad.By with CF
4Or CHF
3Cl gas and oxygen mix can reduce etch-rate to improve the controllability of etch quantity.
Next, can be by using film formation technology commonly used to carry out on the i layer, to form the process of (i+1) layer.For example, can use vapour deposition, sputter or CVD.Be noted that in order not make sacrifice layer distortion or quality deterioration, must the control processing temperature.Next, to carry out the process that the pitch that forms (i+1) layer is less than or equal to the repetitive structure of wavelength of visible light with the similar mode of the situation of i layer.Because carry out etching up to exposing sacrifice layer, so the top of i layer pattern is etched to the degree of depth (referring to the Reference numeral among Fig. 1 C 4) of the scope of the height that equals lap.Perhaps, as long as optical characteristics allows, can be in the height of lap or bigger scope the top of etching i layer pattern.This has formed the difference in height between i layer pattern and (i+1) layer pattern, therefore easier removal sacrifice layer.Finally, can carry out the process of removing the sacrifice layer of filling the space in the i layer by dry etching.For example, can use the etching of carrying out with pure oxygen by RIE equipment commonly used.Perhaps, can use the incineration equipment that only is used for resist.This process also can be controlled by the time.By said method, can obtain to have the optical element of three-dimensional structure.
As mentioned above,, the adhesion between the upper and lower on the substrate can be improved, poor adhesion can be prevented according to this embodiment.In addition, in manufacture process etc., for example when external force works, can avoid peculiar problem of micromechanism such as pattern to collapse.In addition, when to process diameter simultaneously be 6 inches, 8 inches etc. big zone, because can use whole surface effectively, so the element number that can obtain from this zone becomes big, this had allowed to produce efficiently.In addition, although thick and heavy folded some effects optical characteristics,,, can easily obtain desired optical by making lap in 20nm or littler scope.
Example of the present invention is described below.
(example 1)
The substrate and the patterned arrangement of three-dimensional structure of the optical element of this example at first, described referring to figs. 2 and 3 A, 3B.Go up nine patterns 6 of composition at substrate 5 (6 inches quartz wafers), the size of each pattern 6 all is 25mm * 25mm.Here, as shown in Figure 3A, the pitch of the pattern of ground floor is 0.26 μ m, and the diameter of sectional hole patterns 7 is 0.13 μ m, and sectional hole patterns 7 is arranged on the summit of equilateral triangle.Shown in Fig. 3 B, the pitch of the pattern of the second layer is 0.26 μ m, and the diameter of sectional hole patterns 8 is 0.2 μ m, and sectional hole patterns 8 is arranged on the summit of equilateral triangle.Although in this example, use identical mask to form the hole, and come the control punch diameter by exposure, also can change mask.
Next, the manufacture process of the optical element with three-dimensional structure is described.Fig. 4 A to 4I illustrates the manufacture process according to the optical element of this example.At first, description is to the composition of ground floor.After 6 inches quartz wafer substrates 9 being cleaned and made its exsiccation, form the thick silicon oxide film of 100nm by sputter, to form silicon oxide layer 10.As a result, acquisition is used to form the layer (Fig. 4 A) of the structure of ground floor.Then, carry out the lithography step that is used for silicon oxide layer 10 compositions.Here, as the photoresist that is used for composition, use Clariant AX6850P.Apply this resist by spin coating, and the execution coating makes that film thickness is 300nm.After coating, carried out prebake two minutes down at 110 ℃.Then, the ledex FPA-5000-ES4b that makes with Canon Inc. carries out exposure.With regard to exposing patterns, using pitch in 25mm * 25mm zone is the sectional hole patterns of 0.26 μ m.The diameter in hole is 0.13 μ m, and sectional hole patterns is arranged on the summit of equilateral triangle.Exposure is 32mJ/cm in this case
2Nine some places carry out exposure on these 6 inches substrates.After exposure, carried out PEB (post exposure bake) two minutes down at 120 ℃.
Then, the substrate that will have the structure of ground floor in containing the developer of 2.38% TMAH (Tetramethylammonium hydroxide) soaked one minute, and by the pure water thrower developer was rinsed well, to obtain the sectional hole patterns 11 (Fig. 4 B) of resist.Etching silicon oxide layer then.By parallel-plate-type RIE equipment CHF
3As etching gas under the air pressure of 2.7Pa with 100W (0.3W/cm
2) RF power carry out 4.3 minutes etching.In addition, in order to remove remaining resist, use oxygen as etching gas ashing of one minute of RF power execution with 100W under the air pressure of 2.7Pa.By this way, obtaining hole depth is the monox sectional hole patterns 12 (Fig. 4 C) of 100nm.
Next, filling and planarization steps are described.As packing material, the AZ Exp.KrF-17C8 that uses Clariant company to make.Carry out filling by spin coating.After 2500rpm spin coating 30 seconds, carried out prebake one minute down at 180 ℃.Repeat aforesaid operations twice, to finish filling (Fig. 4 D).As a result, the complanation interface 13 of the position of 50nm acquisition packed layer on the upper surface 14 of monox sectional hole patterns.By carrying out complanation with the equipment that is used for etched unit affinity.With oxygen (17vol%) and CHF
3Mixing (83vol%) as etching gas under the air pressure of 3Pa with 20W (0.06W/cm
2) RF power carry out 5.5 minutes ashing.Measurement by AFM shows, with the exposure of the 3nm of the structure of monox (upper surface 14 from the upper surface of sacrifice layer to silicon oxide pattern, the height that the side surface 141 of silicon oxide pattern is exposed, indicated as the Reference numeral A among Fig. 4 E) acquisition complanation substrate (Fig. 4 E).
Next, description is to the composition of the second layer.To the second layer composition time, form the thick silicon oxide film of 10nm by sputter, as the second layer that is used for this substrate.As a result, can obtain to have the continuous and uniform silicon oxide layer 15 (Fig. 4 F) of enough planarityes.Then, carry out the lithography step that is used for second silicon oxide layer is carried out composition.This is to carry out similarly with the situation of first silicon oxide layer, and just exposure is 50mJ/cm
2The pitch of the pattern after the development is 0.26 μ m, and the diameter in hole is 0.2 μ m.Then, with the situation of first silicon oxide layer etching second silicon oxide layer similarly, just etching period is 0.5 minute.In addition, in order to remove remaining resist, use oxygen as etching gas ashing of one minute of RF power execution with 100W under the air pressure of 2.7Pa.By this way, obtaining hole depth is the monox sectional hole patterns 16 (Fig. 4 G) of 10nm.Fig. 4 G shows along the cross sectional representation of the a-a ' of the line among Fig. 4 I intercepting.
Next, the ashing of sacrifice layer is described.Use RIE equipment utilization oxygen under the air pressure of 3Pa, to carry out the ashing of sacrifice layer three minutes with the power of 100W.Remove the sacrifice layer of filling the hole in the ground floor, to obtain hollow structure 17 (Fig. 4 H).Sacrifice layer is vaporized by plasma, and removes (Fig. 4 I) from very small slit 18.Require the material of sacrifice layer to have following material behavior.That is, this material require is solid-state at normal temperatures, and in the time of in being dissolved in organic solvent, this material require is the material that can make film by spin coating or spraying.Basically, any can use by the material that uses oxygen plasma to be decomposed into gas with high-vapor-pressure.By this way, obtain the two-layer three-dimensional structure of monox.About all nine patterns in 6 inches surfaces, the 25mm * 25mm zone that forms pattern looks it is uniformly, and even after the nitrogen blowing of carrying out 0.5MPa, outward appearance does not change yet, and is gratifying structure.In addition, with FE-SEM the observation along the cross section of the center of this pattern intercepting is confirmed: on the interface between the ground floor and the second layer, this is two-layer to adhere to each other each other very doughtily.
(example 2)
In example 2, planarization steps was carried out six minutes.After complanation, the upper exposed 20nm of monox structure.The thickness of second silicon oxide layer is 70nm, and etched 3.5 minutes of second silicon oxide layer.Except that above-mentioned with example 1 under the identical condition, obtain the two-layer three-dimensional structure of monox.After the process that forms second silicon oxide layer, observing cross sections.The result is, although concavo-convex height that should the surface is about 5nm, forms continuous film, and can carry out the process of back similarly.About all nine patterns in 6 inches surfaces, the 25mm * 25mm zone that forms pattern looks it is uniformly, and even after the nitrogen blowing of carrying out 0.5MPa, outward appearance does not change yet, and is gratifying structure.In addition, with FE-SEM the observation along the cross section of the center of this pattern intercepting is confirmed: on the interface between the ground floor and the second layer, this is two-layer to adhere to each other each other very doughtily.
(example 3)
In example 3, similar with the situation of example 1, come to carry out exposure with optics glass substrate (6 inches wafers) at nine some places.Fig. 5 A to 5I is used for the view of diagram according to the manufacture process of the three-dimensional structure of the optical element of this example.At first, the S-TIH53 optical glass substrate 19 that Ohara company makes is cleaned, then, carried out the vapour deposition of tantalum pentoxide layer 20, make that film thickness is 960nm (Fig. 5 A).Then, as the mask material that is used for the etching tantalum pentoxide, form WSi layer 21 by sputter.Then, as the mask material that is used for etching WSi layer 21, form silicon oxide layer 22.When in the etching step that is described below at photoresist with when wanting can not to guarantee suitable selectivity between the etched layer, such multilayer mask layer is effective.The thickness of WSi layer and the thickness of silicon oxide layer are respectively 200nm and 120nm.
Then, as the mask that is used for etching silicon oxide layer, form the photoresist pattern.Use and interfere the step of exposure of exposure method execution the photoresist pattern.Here because in the multilayer mask, used WSi, so when exposure the light grow that returns by the rear surface.Therefore, back light and incident light interfere with each other, and are not the problems of rectangle thereby generation exposure and post-develop cause the cross sectional shape of resist.So, BARC layer 23 being set absorbing the light that the rear surface is returned, the cross sectional shape that makes exposure and post-develop cause resist becomes rectangle.Photoresist used herein is the UV-170 that is made by Shipley company.BARC used herein is the AZ Exp.KrF-17C8 that Clariant company makes.Each material spin coating has been formed thereon on the substrate of multilayer mask material.180 ℃ of following prebake BARC one minute, film thickness was 115nm here.100 ℃ of following prebake photoresists two minutes, film thickness was 140nm here.
Then, by using the two-beam interference exposure method with this substrate exposure.Use wavelength to be 266nm (Nd-YAG (Nedymium: light source the 4th harmonic wave yttrium aluminum garnet)).Incident angle on the substrate is 56 °.By optical beam expander laser beam is expanded 100 times.Exposure is 30mJ/cm
2Under the situation of three beam interference exposure, can form the sectional hole patterns in the example 1.After exposure, carried out PEB (post exposure bake) 1.5 minutes down at 120 ℃.Then, soaked 30 seconds substrate being contained in the solution of 2.38% TMAH (Tetramethylammonium hydroxide), with the pure water thrower this solution is rinsed well, with acquisition photoresist pattern 24 (Fig. 5 B).Here, can guarantee the pattern effective coverage of 35mm * 35mm.
Then, etching BARC, monox, WSi and tantalum pentoxide layer.Use ICP equipment to carry out etching.Use and example 1 similar etching gas etching BARC and silicon oxide layer under similar etching condition.Use SF
6The gas that mixes in 1: 2 ratio with chlorine under the air pressure of 2.7Pa with 1.5W/cm
2RF power with WSi layer etching 40 seconds.After this, use SF
6As etching gas, under the air pressure under the situation of the bias voltage that substrate side is applied 20W, at 6Pa, with 1.2W/cm
2Power with tantalum pentoxide layer etching 50 seconds, to obtain the line and the space structure 25 (Fig. 5 C) of tantalum pentoxide.Here, the pitch of line, space and line and space structure is respectively 130nm, 30nm and 160nm.Then, carry out filling and planarization steps.Carry out filling step similarly with the situation of example 1.As a result, the position of the above 50nm of upper surface that obtains at the tantalum pentoxide pattern has obtained the substrate of filling (Fig. 5 D) at the complanation interface 26 of packed layer.Then, to carry out planarization process 5.6 minutes with example 1 similar mode.As a result, obtain the substrate of complanation, upper surface 27 wherein from the upper surface of sacrifice layer to the tantalum pentoxide structure, the side surface 271 of tantalum pentoxide structure exposes 5nm on short transverse.Then, form the second layer and the 3rd layer (Fig. 5 E).After thereby execution vacuum vapor deposition has the thickness of 24nm with evaporation tantalum pentoxide layer 28, the thickness (Fig. 5 F) of evaporation silicon oxide layer 29 to have 10nm.
After this, form the multilayer mask, and interfere exposure method, to form the photoresist pattern with the similar mode of the situation of ground floor by using.Here, exposure is 25mJ/cm
2After this, with the similar mode of the situation of ground floor, etching multilayer mask, silicon oxide layer, tantalum pentoxide layer.To the etching of silicon oxide layer and tantalum pentoxide layer be with the similar condition of condition of the tantalum pentoxide of etching ground floor under carry out simultaneously.Etching period is 1.5 minutes.Fig. 5 G shows the cross sectional representation of this moment.This cross sectional representation is the viewgraph of cross-section of seeing from the indicated direction of the arrow i of Fig. 5 F.This illustrates pattern in the ground floor and the pattern in the second layer is perpendicular to one another.Here, the pitch of line, space and line and space structure 30 is respectively 96nm, 64nm and 160nm.
Then, similar with the situation of example 1, the ashing sacrifice layer is to obtain to have the three dimensional optical components (Fig. 5 H) of hollow structure 31.The cross sectional representation of Fig. 5 H is the view of seeing from the indicated direction of the arrow ii of Fig. 5 G.With regard to all nine patterns in 6 inches surfaces, the 35mm * 35mm zone that forms pattern looks it is uniformly, and even after the nitrogen blowing of carrying out 0.5MPa, outward appearance does not change yet, and is gratifying structure.In addition, with FE-SEM (field-emission scanning electron microscope) observation along the cross section of the center of this pattern intercepting is confirmed: on the interface between the ground floor and the second layer, this is two-layer to adhere to each other each other very doughtily.
Optical element according to this example is used as polarizer.Fig. 6 is used for comparison according to the phase difference characteristics of the polarizer of this example with the figure of the phase difference characteristics of the quartzy polarizer of making commonly used.The phase difference characteristics of the solid black square diagram conventional quartz polarizer among Fig. 6, and the solid dark circle loop graph is separated the phase difference characteristics with polarizer of structure shown in Fig. 5 I.The result shows, therefore the change of phase differential in visible range of the polarizer of making less than quartz according to the change of phase differential in visible range of the polarizer of this example, be remarkable according to the optical characteristics of the polarizer of this example.Fig. 7 shows the measurement result of average transmittance in visible range.Fig. 7 illustrates the interior average transmittance of visible range near 100%, therefore can obtain anti-reflection effect simultaneously.The structure that anti-reflection effect is considered to the monox that is provided with in one deck in the end shows during as layer with low-refraction effectively.
(example 4)
In example 4, use and the top similar optical glass substrate of in example 3, describing of optical glass substrate, and to form thickness by sputter be the titanium oxide layer of 360nm.Then, similar with the situation of example 3, form the multilayer mask thereon by sputter.This multilayer mask is made of 50nm thick chromium and the thick monox of 80nm.Then, similar with the situation of example 3, after coating BARC and photoresist, carry out composition and etching, to obtain the structure of ground floor, the incident angle when wherein interfering exposure on the substrate is 72 °, exposure is 35mJ/cm
2, the gas that mixes in 1: 3 ratio with chlorine and oxygen applies as etching gas, in substrate side under the situation of bias voltage of 120W, under the air pressure of 6Pa, with the RF power of 50W with chromium etching one minute and 40 seconds.With titanium oxide layer etching 25 minutes.By this way, obtain the structure of ground floor.Here, the pitch of the line of ground floor, space and line and space structure is respectively 30nm, 110nm and 140nm.
Then, carry out filling and planarization steps similarly with the situation of example 3.In filling step, use materials similar, carry out spin coating after 30 seconds with 1000rpm, carried out prebake one minute down at 180 ℃.Above-mentioned processing is repeated twice to finish filling.As a result, obtain the complanation interface of packed layer in the position of the above 200nm of upper surface of titanium dioxide pattern.Carrying out complanation, and carry out ashing 22 minutes with the similar mode of the situation of example 3.By AFM to nine patterns on 6 inches optical glass substrates shown in Figure 2 separately the measurement result of the exposure of the titanium dioxide at center be: for pattern 6-1,6-3,6-7 and 6-9 is 20nm; For pattern 6-2,6-4,6-6,6-8 is 15nm; And be 10nm for pattern 6-5.
Then, form the second layer.Similar with the situation of ground floor, use sputtering method by forming the thick oxidation titanium film of 70nm, and forming the multilayer mask that constitutes by thick chromium layer of 50nm and the thick silicon oxide layer of 80nm, form the second layer.Then, form the resist pattern.Exposure is 18mJ/cm
2The structure of the second layer be with the similar condition of the formation condition of ground floor under form, just the etching period to titanium dioxide is five minutes.The pitch of the line of the second layer, space and line and space structure is respectively 120nm, 20nm and 140nm.
Then, similar with the situation of example 3, with the hollow structure of sacrifice layer ashing with the formation ground floor.In addition, carry out similarly filling and planarization with the situation of ground floor.Form the thick titanium oxide layer of 360nm on the substrate by sputtering at.Similarly the titanium oxide layer is carried out composition with the situation of ground floor.Similar with the situation of ground floor, the pitch of line, space and line and space structure is respectively 30nm, 110nm and 140nm.At last, similar with the situation of ground floor, with the hollow structure of sacrifice layer ashing with the formation second layer.Even when directly forming the 3rd film,, form the 3rd layer process so can carry out, to form continuous film thereon because the space of the second layer is little not using the process that forms sacrifice layer.
With regard to all nine patterns in 6 inches surfaces, the 35mm * 35mm zone that forms pattern looks it is uniformly, even and after the nitrogen blowing of carrying out 0.5MPa, outward appearance does not change yet, and is gratifying structure.In addition, with FE-SEM the observation along the cross section of the center of this pattern intercepting is confirmed: on the interface between the ground floor and the second layer, this is two-layer to adhere to each other each other very doughtily; And on the interface between the second layer and the 3rd layer, this is two-layer to adhere to each other each other very doughtily.Then, the substrate scribing of the three-decker that obtained marking the rectangle of 28.3 * 20mm, and is formed nine substrates with three-dimensional structure.In these nine substrates each is bonded on the S-TIH53 substrate.
Fig. 8 A to 8D is the synoptic diagram that is used for the process of diagram bonded substrate.At first, S-TIH53 substrate 32 is cleaned (Fig. 8 A).Then, spin coating adhesion layer and execution are interim solidifies.As bonding agent, use PLENACT KR-55, it is the titanate coupling agent of being made by Ajinomoto-Fine-Techno company, and with isopropanol 60 times.Carry out spin coating 30 seconds with 5000rpm, and execution is solidified two minutes to obtain to have the substrate (Fig. 8 B) of adhesion layer 33 temporarily under 180 ℃.Then, the substrate with three-dimensional structure 34 of above-mentioned scribing is covered on the adhesion layer, make part contact with adhesion layer with structure division.Then, under the load of 2kg, 200 ℃, the substrate that is covered is stayed heating plate last five minute (Fig. 8 C).After the substrate cooling, this substrate is adhered to 45 ° of prisms 35 being made by S-TIH53, so that it is clipped in therebetween, obtain prism (Fig. 8 D).
Optical element according to this example is used as polarizing beam splitter.Fig. 9 diagram is with regard to the spectral-transmission favtor of S polarized light and P polarized light with regard to the incident angle of 45 ° ± 10 ° on the prism of this example.As shown in Figure 9, except the transmissivity of S polarized light when 35 ° of the incident angles increases and the transmissivity of P polarized light reduces when incident angle is 55 °, no problem.Particularly, when incident angle is 45 ° ± 5 °, characteristic changes hardly, and can see, according to the optical characteristics brilliance of the optical element of this example (because 40 ° with 50 ° incident angle under characteristic identical with characteristic under 45 ° the incident angle, so in Fig. 9, omitted the graphic presentation of the characteristic under the incident angle of 40 ° and 50 °).Although this three-dimensional structure is formed into the substrate end among Fig. 8, between substrate end and structure, can have living space, as shown in figure 10.Because such structure can be guaranteed the space of element opening part, thus the fire damage that causes owing to the temperature flip-flop can be alleviated, and can suppress gas and discharge from the junction surface.This makes it possible to obtain projected image more stable with regard to surrounding environment.
(comparative example 1)
In comparative example 1, in the process of the packed layer of complanation ground floor, carry out ashing 20 minutes.Here, by AFM to nine patterns on 6 inches optical glass substrates shown in Figure 2 separately the measurement result of the exposure of the titanium dioxide at center be: for pattern 6-1,6-3,6-7 and 6-9 is 1nm; For pattern 6-2,6-4,6-6,6-8 be-4nm; And for pattern 6-5 be-9nm.Here, negative value represents that titanium dioxide is not exposed, and sacrifice layer keeps in its surface.After this, carry out and example 4 similar processes.In pattern 6-2,6-4,6-6,6-8 and 6-5, after the ashing sacrifice layer, cause light scattering.As the result who measures the defect part cross section with FE-SEM, the titanium oxide layer of the second layer has defective on the whole surface of tiny area.In addition, because with regard to outward appearance, there is not any inconvenience, so pattern 6-1,6-3,6-7 and 6-9 are clipped between the prism.After cure remain in the step of bonding agent 200 ℃ during, observe peeling off from the interface.
(comparative example 2)
In comparative example 2, carry out 6.1 minutes complanation.In this case, the exposure of tantalum pentoxide is 25nm.Except that above-mentioned with under the example 3 similar conditions, obtaining polarizer.As a result, this polarizer obviously is in unintelligible state.In addition, confirm when the measure spectrum transmissivity: shown in the solid black triangle among Fig. 7, transmissivity reduces.
Although reference example embodiment has described the present invention, should be understood that to the invention is not restricted to disclosed example embodiment.The scope of claims should be endowed the wideest explanation, so that contain all such modification and equivalent structure and function.
Claims (9)
1. optical element comprises:
Substrate; And
The ground floor that forms on this substrate and the second layer,
Wherein each in ground floor and the second layer all comprises space and the repetitive structure of structure member on the direction vertical with the stacking direction of described layer, and the pitch of described repetitive structure is less than or equal to wavelength of visible light, and
Wherein the repetitive structure of the repetitive structure of ground floor and the second layer is overlapping on the stacking direction at described layer at the interface between the ground floor and the second layer.
2. according to the optical element of claim 1, also be included in a plurality of layers between substrate and the ground floor, wherein, from the substrate number, ground floor is formed by the i layer, and the second layer is formed by (i+1) layer.
3. according to the optical element of claim 1, wherein, the repetitive structure of ground floor and the repetitive structure of the second layer are more than or equal to 3nm and be less than or equal in the scope of 20nm overlapping.
4. according to the optical element of claim 1, wherein, each repetitive structure in the ground floor and the second layer all comprises line and space structure, have the structure in hole and have any in a little the structure.
5. according to the optical element of claim 1, wherein, the pitch that is less than or equal to wavelength of visible light described in the ground floor and the second layer is more than or equal to 10nm and be less than or equal to 200nm.
6. according to the optical element of claim 1, wherein, the repetitive structure of ground floor and the repetitive structure of the second layer are formed by identical materials.
7. according to the optical element of claim 1, wherein, the repetitive structure of ground floor and the repetitive structure of the second layer are formed by dielectric material.
8. method of making optical element, this optical element comprises the ground floor and the second layer that forms on substrate and this substrate, this method may further comprise the steps:
On this substrate, form ground floor;
Processing comprises the repetitive structure of space and structure member in ground floor, and the pitch of this repetitive structure is less than or equal to wavelength of visible light;
Fill space in this repetitive structure with the material of sacrifice layer;
This sacrifice layer of etching is to expose the top of this repetitive structure from this sacrifice layer;
On this repetitive structure and this sacrifice layer, form the second layer;
Processing comprises the repetitive structure of space and structure member in the second layer, and the pitch of this repetitive structure is less than or equal to wavelength of visible light; And
Remove described sacrifice layer.
9. the method for manufacturing optical element according to claim 8, wherein, the step on the top that exposes described repetitive structure from sacrifice layer, the side surface of described repetitive structure exposes from the upper surface of described repetitive structure more than or equal to 3nm and be less than or equal to the scope of 20nm.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102765240A (en) * | 2010-12-29 | 2012-11-07 | 友达光电股份有限公司 | Vacuum imprinting device, vacuum laminating device and method for manufacturing laminated optical element |
| CN108680978A (en) * | 2018-03-19 | 2018-10-19 | 中国科学院上海光学精密机械研究所 | 5 × 5 lattice diffracting rasters based on two single ridge gratings |
| CN113589407A (en) * | 2018-06-07 | 2021-11-02 | 华东师范大学 | Control device for lattice period and arrangement rule of three-dimensional triangular photonic crystal, tetragonal photonic crystal and pentagonal photonic quasicrystal |
| CN113675722A (en) * | 2021-07-14 | 2021-11-19 | 威科赛乐微电子股份有限公司 | Cap layer etching optimization method |
| CN114008540A (en) * | 2019-07-15 | 2022-02-01 | Asml荷兰有限公司 | Alignment, overlay, alignment mark, method of manufacturing pattern forming apparatus, and method of manufacturing pattern mark |
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| JP2000284136A (en) * | 1999-01-28 | 2000-10-13 | Nippon Telegr & Teleph Corp <Ntt> | Production of two-dimensional and three-dimensional photonic crystals |
| JP2001074955A (en) * | 1999-08-31 | 2001-03-23 | Susumu Noda | Photonic crystal waveguide |
| JP2001257425A (en) * | 2000-03-13 | 2001-09-21 | Matsushita Electric Ind Co Ltd | Semiconductor laser element and its manufacturing method |
| US6611085B1 (en) * | 2001-08-27 | 2003-08-26 | Sandia Corporation | Photonically engineered incandescent emitter |
| DE10222609B4 (en) * | 2002-04-15 | 2008-07-10 | Schott Ag | Process for producing structured layers on substrates and methodically coated substrate |
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| CN102765240A (en) * | 2010-12-29 | 2012-11-07 | 友达光电股份有限公司 | Vacuum imprinting device, vacuum laminating device and method for manufacturing laminated optical element |
| CN102765240B (en) * | 2010-12-29 | 2015-06-10 | 友达光电股份有限公司 | Vacuum imprinting device, vacuum laminating device and method for manufacturing laminated optical element |
| CN108680978A (en) * | 2018-03-19 | 2018-10-19 | 中国科学院上海光学精密机械研究所 | 5 × 5 lattice diffracting rasters based on two single ridge gratings |
| CN113589407A (en) * | 2018-06-07 | 2021-11-02 | 华东师范大学 | Control device for lattice period and arrangement rule of three-dimensional triangular photonic crystal, tetragonal photonic crystal and pentagonal photonic quasicrystal |
| CN113589407B (en) * | 2018-06-07 | 2022-10-25 | 华东师范大学 | Control method for lattice period and arrangement rule of three-dimensional triangular photonic crystal, tetragonal photonic crystal and pentagonal photonic quasicrystal |
| CN114008540A (en) * | 2019-07-15 | 2022-02-01 | Asml荷兰有限公司 | Alignment, overlay, alignment mark, method of manufacturing pattern forming apparatus, and method of manufacturing pattern mark |
| CN113675722A (en) * | 2021-07-14 | 2021-11-19 | 威科赛乐微电子股份有限公司 | Cap layer etching optimization method |
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