CN102053491B - Ultra-deep subwavelength tunable nano photoetching structure and method based on surface plasma resonant cavity - Google Patents

Ultra-deep subwavelength tunable nano photoetching structure and method based on surface plasma resonant cavity Download PDF

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CN102053491B
CN102053491B CN 201010585229 CN201010585229A CN102053491B CN 102053491 B CN102053491 B CN 102053491B CN 201010585229 CN201010585229 CN 201010585229 CN 201010585229 A CN201010585229 A CN 201010585229A CN 102053491 B CN102053491 B CN 102053491B
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surface plasma
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photoresist
thickness
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王钦华
葛伟豪
曹冰
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Suzhou University
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Abstract

The invention discloses an ultra-deep subwavelength tunable nano photoetching structure and method based on a surface plasma resonant cavity. The photoetching structure successively comprises an upper transparent substrate layer, a metal grating layer, a photoresist layer and a lower substrate layer, and is characterized in that a metal film layer is arranged between the photoresist layer and the lower substrate layer; and the metal grating layer, the photoresist layer and the metal film layer form the surface plasma resonant cavity structure. By utilizing the photoetching structure, the resolution ratio of a stripe can be changed by adjusting the thickness of the photoresist, the boundedness in the aspects of the resolution ratio, tenability and exposure depth of the traditional surface plasma photoetching technology can be broken through, and a new path is opened for tunable two-dimensional photoetching with ultra-deep exposure depth, large area and any shape.

Description

Based on the tunable nano-photoetching structure and method of the super dark sub-wavelength in surface plasma body resonant vibration chamber
Technical field
The present invention relates to a kind of photoetching making method of nanometer scale device, be specifically related to a kind of nano-photoetching method based on the surface plasma bulk effect.
Background technology
Along with the fast development of nanosecond science and technology, it is unusually important that the making of nanometer scale device seems.The photolithography method is owing to it is easy to copy, cost of manufacture is low and the advantages such as making in suitable large zone are widely used.But the processing dimension of this photoetching technique is subject to the restriction of optical diffraction limit, is difficult to break through the resolution of half-wavelength magnitude.A kind of main method that improves at present resolution is to use more short wavelength's light source, such as EUV light source (EUV), soft X-ray, atomic beam, but short wavelength's optical exposure light source is difficult to make, serviceable life is short, supporting lens material and mask are difficult to select, and the exploitation of the photoresist (photoresist) of corresponding coupling difficulty causes the cost of these methods high simultaneously, process is complicated, and the ability that further improves resolution is restricted.
Document Luo, X.; Ishihara, T. Opt. Exp. 2004,12,3058. in a kind of novel photoetching method based on metal and electrolyte meter surface plasma (SPPs) effect is disclosed, the layer of metal thin layer is set, be provided with slit much smaller than lambda1-wavelength at metal film layer, form the metal grating layer, between metal grating layer and photoresist, produced thus based on metal and electrolytical surface plasma (SPPs) effect, because under the same light frequency, the wave vector of SPP is more much larger than ordinary light source, this " visible frequency; the wavelength of X-ray magnitude " just occurred, utilizes the resulting resolution of photoetching process of this surface plasma more much larger than traditional diffraction limit.Be 436nm such as lambda1-wavelength, adopt one dimension silver grating, the grating cycle is 300nm, can obtain the striped that the cycle is 100nm; Incident wavelength is 365nm, and the two-dimentional Ag grating cycle is 200nm, can obtain the dot matrix that the cycle is 100nm.Similar method is also disclosed in the document.
Adopt said method can realize the photoetching of high-resolution, but, after lambda1-wavelength is determined, change photoresist thickness to the not impact of etched diffraction grating cycle, the thickness that changes metal grating is also very little on the impact in grating cycle, therefore, and when carrying out etching with the method, the cycle adjustable extent of the grating of institute's etching is little, and namely the resolution of etching striped is adjustable hardly.A metal grating template can only produce the optical grating construction of a fixed cycle.
Therefore, how overcoming the limitation of prior art aspect resolution, tunability and exposure depth, is to need a problem solving during nano-device is made.
Summary of the invention
The object of the invention provides a kind of super dark sub-wavelength nano-photoetching method based on the surface plasma bulk effect, and the nanometer grating resolution that produces is higher than existing conventional surface plasma technology, and simultaneously, the resolution of etching nanometer grating can be regulated easily; The present invention provides a kind of structure that realizes said method simultaneously.
For achieving the above object, the technical solution used in the present invention is: a kind of super dark sub-wavelength nano-photoetching structure based on the surface plasma bulk effect, described photolithographic structures comprises transparent upper basalis, metal grating layer, photoresist layer and lower basalis successively, be provided with metal film layer between described photoresist layer and lower basalis, described metal grating layer, photoresist layer and metal film layer consist of the structure of resonant cavity of surface plasma together.
In the technique scheme, the cycle of described metal grating layer is no more than 3000nm, and thickness is for being no more than 500nm.The metal grating cycle is larger, more easily makes; If but the grating cycle is excessive, then the fringe intensity of adjacent two seam centre is lower than the fringe intensity near two seam places, is unfavorable for forming in photoresist the striped of even intensity.
The thickness of described photoresist layer is no more than 80nm.The thickness of photoresist layer has determined that the surface plasma bulk effect that upper metal grating layer/photoresist layer interface occurs carries out the thickness of efficient coupling with the surface plasma bulk effect of lower metal layer/photoresist layer interface generation, if photoresist is too thick, both just can not efficient coupling.
The thickness of described metal film layer is not less than 5nm.Too thin such as thickness of metal film, the surface plasma bulk effect that lower metal layer/photoresist layer interface occurs too a little less than, to such an extent as to the surface plasma bulk effect of the surface plasma bulk effect that upper metal grating layer/the photoresist layer interface occurs and lower metal layer/photoresist layer interface generation does not have resonance coupling.
A kind of super dark sub-wavelength nano-photoetching method based on the surface plasma bulk effect adopts above-mentioned photolithographic structures to carry out photoetching, and incident light exposes at photoresist layer after passing through upper basalis and metal grating layer, obtains lithographic images.
Because technique scheme is used, the present invention compared with prior art has following advantages:
1. resonant cavity of the present invention is comprised of metal grating, photoresist layer, metal film layer, the nanometer striped resolution that produces is higher than existing conventional surface plasma technique, can change by the thickness of regulating photoresist simultaneously the resolution of striped, break through tradition and utilized the limitation of surface plasma photoetching technology aspect resolution, tuning performance and exposure depth.
2. structure devices of the present invention is comprised of five-layer structure, the resolution of the photoetching striped that produces has improved much based on surface plasma bulk effect photoetching process than tradition, in simulation process, utilize the laser of 436nm wavelength, cycle is the metal grating of 600nm, can obtain the striped that the minimum fringes width is 16.5nm, and need to utilize the sandwich construction of 193nm incident light irradiation tens layers metal-nonmetal medium to obtain at the striped of this size in the past; This structure devices can be regulated resolution by the thickness that changes photoresist, also namely utilizes a metal grating template can make the nanostructured grating of different cycles, and existing traditional technology can only change striped resolution by changing the metal grating template; And this structure can obtain more even, the interference fringe of better visibility and darker exposure depth, than fixing metal grating, the super dark sub-wavelength nanoimprinting technology based on the surface plasma body resonant vibration chamber of this novelty has been opened up new road to the two-dimentional photoetching of tunable, super dark exposure depth, large zone and arbitrary shape.
Description of drawings
Fig. 1 is the structural representation of the embodiment of the invention one.
Fig. 2 is the distribution map of the electric field of embodiment one.
Fig. 3 is the extremely distribution map of the electric field of unit's (SPP) photoetching process (namely without the SPP resonant cavity) of traditional surface plasma.
Fig. 4 is that surface plasma body resonant vibration chamber (SPReC) structure of the present embodiment is for the Electric Field Distribution contrast schematic diagram of different photoresist thickness.
Fig. 5 is the dispersion relation comparison diagram between SPP wave vector and the incident wave wavelength when having or not the SPP resonant cavity.
Fig. 6 is the dispersion relation comparison diagram of SPP wave vector and incident light when different photoresist thickness.
Fig. 7 is notional result and the analog result comparison diagram of fringe period and photoresist thickness relationship.
Fig. 8 is the metal grating SPP wave vector of different-thickness and the dispersion relation comparison diagram of incident light.
Embodiment
The invention will be further described below in conjunction with drawings and Examples:
Embodiment one: referring to shown in Figure 1, be the super dark sub-wavelength nano-photoetching structural representation of the present embodiment, the SPP resonant cavity is comprised of three parts.From top to bottom be: SiO 2The upper basalis, metal grating layer, photoresist layer, metal film layer, the SiO that consist of 2The lower basalis that consists of, top metal grating layer and following metal film layer all adopt material silver (Ag) preparation, and incident P polarized light is from top to bottom vertically injected, and wavelength is 436nm, SiO 2With the refractive index of photoresist be respectively 1.5 and the specific inductive capacity of 1.7, Ag be ε Ag=-6.489+0.064i carries out simulated experiment to said structure, and Y-direction is considered to endless in simulation process, and the software that simulation is adopted is FDTD Solutions.
The distribution map of the electric field of Fig. 2 and the SPReC that is respectively the present embodiment design shown in Figure 3 and traditional SPP photoetching process (namely without the SPP resonant cavity).In Fig. 2, the cycle of metal grating and thickness are respectively 600nm and 50nm, and grating seam width is 60nm, and the thickness of photoresist is 50nm, and the thickness of following metal film layer is 50nm; Do not have metal film layer among Fig. 3, other structure is identical.Incident wavelength is 436nm.From Fig. 2 and Fig. 3, can find out, the nanometer striped of two kinds of methods gained in photoresist is all different in resolution and exposure depth, 8 interference fringes are arranged in the SPReC structure photoresist in Fig. 2, and in Fig. 3, only have 6 interference fringes in the traditional SPP photoetching, and can see that the exposure depth in the photoresist is also deeply a lot of than traditional photoetching among the SPReC.
What Fig. 4 represented is that the SPReC structure of the present embodiment is for the Electric Field Distribution contrast schematic diagram of different photoresist thickness, the cycle of Ag grating and thickness are respectively 600nm and 50nm, the width of grating seam is 60nm, the Ag layer thickness is 50nm, and the thickness that (a) among Fig. 3, (b), (c), (d) zone correspond respectively to photoresist is 50nm, 30nm, 20nm, 10nm.Along with reducing of photoresist thickness, fringe number in the photoresist between two adjacent seams increases gradually, 8 10 of being increased to successively in (b) from (a), (c) in 12 and (d) in 16, can find out that this simple structure has great benefit for the raising that produces striped exposure depth and resolution.Utilize SPReC, incident light is 436nm, when the thickness of photoresist is 10nm, the resolution of striped can be brought up to 16.5nm, be equivalent to 3 times of traditional SPP resolution of optical lithography, and this resolution need utilize 193nm light just can reach by 30 pairs of metals-electrolytical sandwich construction in the past in photoetching side.So, the resolution of the striped that this structure produces can directly be regulated by the thickness that changes photoresist, and do not need to change cycle of metal grating, thickness etc., this has just overcome the limitation that traditional SPP photoetching process can only change by changing the metal grating template resolution of striped, and much wider than the scope that the change metal grating brings by changing photoresist thickness adjusting striped resolving range.
The SPReC of the present embodiment can make an explanation by the dispersion relation of sandwich construction than the much bigger reason of traditional SPP resolution of optical lithography.As shown in Figure 1, SPPeC is comprised of five parts, from top to bottom is respectively: electrolyte 1(specific inductive capacity is ε 1), (specific inductive capacity is ε to metal grating 2, thickness is d 2), (specific inductive capacity is ε to photoresist 3, thickness is d 3), (specific inductive capacity is ε to metal film layer 4, thickness is d 4), electrolyte 2(specific inductive capacity is ε 5), metal grating layer and metallic film layer material are metal A g herein, and electrolyte 1,2 is SiO 2, be under the P polarized light condition at incident light, use field boundary condition (electric field is continuous to component, and the magnetic field normal component is continuous) at each dielectric interface, the dispersion relation of SPReC structure is as follows:
Figure DEST_PATH_IMAGE001
(1)
i=1, 2, 3, 4 (2)
Wherein, k SpAnd k 0The wave vector that represents respectively light in the wave vector of SPP and the vacuum, k iBe illustrated on the i bed interface wave vector perpendicular to the interface evanescent wave, in computation process, for simplicity and since the lower metal thin layer only play with the photoresist layer interface on form the effect of SPP, so the thickness of thin layer is for being made as infinite thickness.Can obtain k under different parameters by equation (1) SpAnd the dispersion relation of λ (incident light wavelength in a vacuum).
Figure 5 shows that the dispersion relation that has or not between SPP resonant cavity (being SPReC and traditional SPP photoetching process) SPP wave vector and the incident wave wavelength, metal grating layer and metal film layer all adopt Ag, other parameters all adopt the parameter among Fig. 2 and Fig. 3, as can see from Figure 5, the SPP wave vector of SPReC structure is all the time than the photolithographic wave vector of traditional SPP large (being that the former striped resolution will be higher than the latter) under the incident light of any wavelength, under the irradiation of 436nm light, both wave vectors are respectively 0.0434nm -1And 0.0335nm -1, utilize the definition of fringe period: fringe period Λ=λ Sp/ 2=π/k Sp, the fringe period that can draw both is respectively: the former 73nm, latter 94nm, this and utilize software to simulate resulting 75nm and 100nm is substantially identical.
Figure 6 shows that the dispersion relation at different cavity length (being the thickness of different photoresists) SPP wave vector and incident light, structural parameters adopt the parameter among Fig. 4.As can be seen from Figure 6, the SPP wave vector changes very obvious along with the variation of PR thickness, be 436nm at lambda1-wavelength, and the length in chamber (thickness of photoresist) is got respectively 50nm, 30nm, and 20nm, the resulting SPP wave vector of 10nm is respectively 0.0434nm -1, 0.0533nm -1, 0.0663nm -1And 0.108nm -1, convert striped resolution to and be respectively 73nm, 59nm, 48nm and 30nm, this and be respectively 75nm from the cycle that software simulation obtains striped, 60nm, 50nm, 33nm are substantially identical.Fig. 7 has specifically compared notional result and the analog result of fringe period and photoresist thickness relationship.
Figure 8 shows that the metal grating SPP wave vector of different-thickness in this structure and the dispersion relation of incident light.Adopt the parameter among Fig. 4, the thickness setting of photoresist is 50nm, and as can be seen from Figure 8 the wave vector of SPP also can change along with the change of the thickness of metal grating, sensitivity just when particularly metal thickness is less than 30nm, and this is the same with traditional SPP photoetching process.But can find out that from Fig. 7 and Fig. 8 the variation that changes photoresist resolution that thickness brings is than changing much bigger that metal grating (metal thickness) brings.

Claims (3)

1. super dark sub-wavelength nano-photoetching structure based on the surface plasma bulk effect, described photolithographic structures comprises transparent upper basalis, metal grating layer, photoresist layer and lower basalis successively, it is characterized in that: be provided with metal film layer between described photoresist layer and lower basalis, described metal grating layer, photoresist layer and metal film layer consist of the structure of resonant cavity of surface plasma together; The thickness of described photoresist layer is no more than 80nm; The thickness of described metal film layer is not less than 5nm.
2. the super dark sub-wavelength nano-photoetching structure based on the surface plasma bulk effect according to claim 1, it is characterized in that: the cycle of described metal grating layer is no more than 3000nm, and thickness is no more than 500nm.
3. super dark sub-wavelength nano-photoetching method based on the surface plasma bulk effect, it is characterized in that: adopt photolithographic structures claimed in claim 1 to carry out photoetching, incident light exposes at photoresist layer after passing through upper basalis and metal grating layer, obtains lithographic images.
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