CN102798902A - Novel multilayer film for improving extreme ultraviolet (EUV) spectral purity - Google Patents

Abstract

The invention discloses a novel multilayer film for improving extreme ultraviolet (EUV) spectral purity, belonging to the field of EUV lithography. The multilayer film can enable the reflectivity of an out-off-band waveband to be effectively inhibited on the premise that the reflectivity loss of a position of 13.5 nm is guaranteed to be little. The novel multilayer film comprises a substrate and a Mo/Si multilayer film as well as an SPE (spectral purity enhancing) layer, wherein the Mo/Si multilayer film is formed on the substrate, and the SPE layer is formed on the Mo/Si multilayer film. According to the novel multilayer film for improving the EUV spectral purity, the SPE layer is formed on the basis of not changing the shape of a film system, not additionally arranging optical elements and not increasing additional processing steps, and the imaging quality and lithographing quality of a lithography system are improved through inhibiting the out-off-band waveband under the condition that the reflectivity loss can be neglected.

Description

A kind of novel multi-layer film that improves the extreme ultraviolet spectral purity

Technical field

The invention belongs to the extreme ultraviolet photolithographic field, be specifically related to a kind of novel multi-layer film that improves the extreme ultraviolet spectral purity.

Background technology

Extreme ultraviolet photolithographic is the photoetching technique of future generation that most possibly realizes the 22nm technology node.The extreme ultraviolet etching system uses wavelength to be 13.5nm, and at this wave band, the absorption coefficient of most of materials is all very high, so can only adopt the total-reflection type system.In order further to shorten the time shutter, improve output, need on optical element, be coated with the high precision multilayer film to improve reflectivity.The multilayer film that extreme ultraviolet waveband preferably is coated with is that periodicity is that 40-60, periodic thickness are the Mo/Si multilayer film of 6.9-7.2nm.Though the reflectivity of this periodicity Mo/Si multilayer film at the 13.5nm place very high (can reach more than 68%), its cut off band width is very narrow: increase gradually at the ultraviolet band reflectivity, reach as high as 60%; At visible light wave range, reflectivity is 38%-47%; Also can reach 30% at the minimum reflectivity of infrared band.

Laser plasma light source is the light source commonly used of extreme ultraviolet etching system, and this light source not only has higher radiation intensity at extreme ultraviolet waveband, and in the radiation intensity of ultraviolet band, visible waveband and infrared band also than higher.The resolution R of etching system and depth of focus formula DOF are respectively:

$R=\frac{k_1\mathrm{\λ}}{\mathrm{NA}}---\left(1\right)$

$\mathrm{DOF}=\frac{k_2\mathrm{\λ}}{{\left(\mathrm{NA}\right)}^2}---\left(2\right)$

Wherein, k ₁And k ₂The expression coefficient, λ representes wavelength, NA representes numerical aperture, knows that by formula (1) and (2) the resolution R of etching system is all relevant with wavelength X with depth of focus DOF, if cut off band width is narrow, can influence the image quality of etching system.

The photoresist material that uses in the extreme ultraviolet photolithographic is mainly polystyrene and acrylates mixing macromolecular material or acrylates macromolecular material.The photoresist that uses in the extreme ultraviolet photolithographic is not only to the photaesthesia of 13.5nm, and also very sensitive to the light with outer wave band.Wavelength photoresist in the 160nm-240nm wavelength band is comparatively responsive, its susceptibility even be higher than the EUV wave band, and also also bigger at the light source output power of this wave band.

To sum up, wavelength is the maximum magnitude of 160nm-240nm wave band for the responsive value of the outer wave band photoresist of band, and photoresist can influence photoetching quality in the exposure of this wave band.

Summary of the invention

In order to solve the problem that exists in the prior art; The invention provides a kind of novel multi-layer film that improves the extreme ultraviolet spectral purity; This novel multi-layer film is effectively suppressed the reflectivity of the outer wave band of band under the little prerequisite of the reflectivity loss that guarantees the 13.5nm place.

The technical scheme that technical solution problem of the present invention is adopted is following:

A kind of novel multi-layer film that improves the extreme ultraviolet spectral purity, this novel multi-layer film comprises: substrate and periodicity Mo/Si multilayer film also comprise SPE (spectral purity enhancing improves spectral purity) layer; Periodically the Mo/Si multilayer film formation is in substrate, and the SPE layer is produced on the periodicity Mo/Si multilayer film.

The invention has the beneficial effects as follows: the present invention is in the profile that does not change film system; Do not increase optical element; Do not increase on the basis of extra procedure of processing yet; Make the SPE layer, under the negligible situation of reflectivity loss, improve the image quality of etching system and the quality of photoetching through suppressing the outer wave band of band.

Description of drawings

A kind of novel multi-layer membrane structure synoptic diagram that improves the extreme ultraviolet spectral purity of Fig. 1 the present invention.

Fig. 2 wavelength of the present invention is five kinds of different novel multi-layer films and Mo/Si multilayer film periodically in 12.8nm-14.2nm, the contrast synoptic diagram of reflectivity.

Fig. 3 wavelength of the present invention is five kinds of different novel multi-layer films and Mo/Si multilayer film periodically in 13.1nm-13.8nm, the contrast synoptic diagram of reflectivity.

Fig. 4 wavelength of the present invention is five kinds of different novel multi-layer films and Mo/Si multilayer film periodically in 160nm-240nm, the contrast synoptic diagram of reflectivity.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is explained further details.

A kind of novel multi-layer film that improves the extreme ultraviolet spectral purity, this multilayer film comprises: substrate and periodicity Mo/Si multilayer film also comprise the SPE layer; Periodically the Mo/Si multilayer film formation is in substrate, and the SPE layer is produced on the periodicity Mo/Si multilayer film.

The material of SPE layer mainly contains C, SiC and Si ₃N ₄, because most of materials are all very high at the absorption coefficient of extreme ultraviolet waveband, so the thickness of SPE layer should not be too thick, generally about 9-12nm, 10nm is a most preferred thickness.The outer sensitive band of the band of different extreme ultraviolet photolithographic glue is different, satisfies different photoresists to the requirement with outer wave band inhibition degree through the material, thickness and the combination that change the SPE layer.

Novel multi-layer film of the present invention is particularly suitable for being applied in in the exigent extreme ultraviolet etching system of spectral purity.Under the radiation of laser plasma light source, after the reflection of the novel multi-layer film through being coated with the SPE layer among the present invention, the minimum reflectivity of the outer wave band of band can reach below 3%.The thickness of SPE layer is about 10nm, and the SPE layer with this thickness is suitable for being with outer wave band to carry out effective destructive interference, and because the thickness of SPE layer is thinner, its absorption to the 13.5nm place is relatively little.

Periodically the preferred layer cycle of Mo/Si multilayer film is 40-60, corresponding Si layer of layer and the adjacent Mo layer of this Si layer, and wherein periodically the thickness of the inner Si layer of multilayer film and Mo layer is constant at this, and 7nm is preferred thickness.Because the limited depth of interaction of the radiation in this SPECTRAL REGION; Under layer the further raising of quantity is only had slight effect to the reflection of this multilayer film, can be implemented in the height reflection in the narrow SPECTRAL REGION of a given wavelength X through this periodicity Mo/Si multilayer film.

In the present invention; A SPE layer is set on periodicity Mo/Si multilayer film; The SPE layer is different with the layer of periodicity Mo/Si multilayer film so that under the little prerequisite of the reflectivity loss that guarantees 13.5nm place, make and be with the reflectivity of outer wave band effectively to be suppressed on material and thickness.Replace single SPE layer, two or more SPE layers can be set based on the different needs of photoresist.

The inhibition of the outer wave band reflectivity of the band of novel multi-layer film can realize in the following manner: after being coated with periodicity Mo/Si multilayer film in the substrate of surfaceness less than 0.2nm; On periodicity Mo/Si multilayer film, be coated with the SPE layer, with albedometer its reflectivity characterized then.

As shown in Figure 1, the novel multi-layer film 1 that the structure of this multilayer film is made up of the Si layer that replaces 3 and Mo layer 4 and design SPE layer 5 above that is set in the substrate 2 wherein corresponding Si layer 3 and corresponding Mo layer 4 formation one-period.8 cycles only are shown among Fig. 1, and optimal period quantity is 40.The preferred thickness of SPE layer 5 is about 10nm, because the existence of SPE layer can make this novel multi-layer film 1 reduce under the little prerequisite at 13.5nm place reflectivity, to its band outer wave band, especially 160nm-240nm, reflectivity has an effective inhibiting effect.Various piece connection in the novel multi-layer film 1 realizes through magnetron sputtering that all what wherein Si layer 3 and Mo layer 4 were selected for use is magnetically controlled DC sputtering, SPE layer 5 preferred rf magnetron sputtering, and the working gas that uses is argon gas.

Fig. 2 representes wavelength five kinds of different novel multi-layer films and Mo/Si multilayer film in 12.8nm-14.2nm, the synoptic diagram that concerns between wavelength and the reflectivity.In instance of the present invention, be provided with different SPE layers respectively on the MO/Si multilayer film that be 40 at periodicity, periodic thickness is about 7nm, the material of these SPE layers and thickness thereof are respectively the Si of 9.6nm ₃N ₄Layer, the SiC layer of 9nm, the C layer of 11.6nm, the SiC of 4.6nm add the Si of 4.5nm ₃N ₄The C of layer and 6.6nm adds the SiC layer of 3nm.As shown in Figure 3, the Mo/Si multilayer film is about 73% at the reflectivity at 13.5nm place, add the SPE layer after because the absorption of SPE layer, reflectivity can decrease: the SPE layer is the Si of 9.6nm ₃N ₄Or reflectivity is about 62% during the C of 11.6nm; Reflectivity was about 68% when the SPE layer was the SiC of 9nm; The reflectivity at 13.5nm place loses little for the reflectivity that makes the outer wave band of band is suppressed simultaneously as much as possible; And make the outer wave band largest inhibition degree of band be in the different wave length place and adapt to different photoresists, among the present invention above-mentioned three kinds of SPE layer materials and thickness thereof are made up.The SiC that two example combinations among the present invention are respectively 4.6nm adds the Si of 4.5nm ₃N ₄Add the SiC of 3nm with the C of 6.6nm, the reflectivity at its 13.5nm place all is about 66%, and the reflectivity than individual layer improves.Learnt, on the Mo/Si multilayer film, be coated with in the novel multi-layer film of SPE layer do not have because being coated with the SPE layer plays very big influence to reflectivity by Fig. 2 and Fig. 3, the loss of reflectivity is within the acceptable scope.

Fig. 4 wavelength is five kinds of different novel multi-layer films and Mo/Si multilayer film in 160nm-240nm, the partial schematic diagram that concerns between wavelength and the reflectivity.The reflectivity of Mo/Si multilayer film can reach 60% at the reflectivity of deep ultraviolet wave band.In novel multi-layer film of the present invention, the deep ultraviolet reflectivity all is no more than 40%, and the largest inhibition degree of different its deep ultraviolet wave bands of SPE layer and inhibition zone are different.The SPE layer is the Si of 9.6nm ₃N ₄The time, the reflectivity at the 194nm place is merely 3%; When the SPE layer was the SiC of 9nm, the reflectivity at the 215nm place was merely 5%; When the SPE layer was the C of 11.6nm, the reflectivity at the 160nm place was merely 4%; The SPE layer is the Si that the SiC of 4.6nm adds 4.5nm ₃N ₄The time, the reflectivity at the 220nm place approaches 0%; The SPE layer is the C of 6.6nm when adding the SiC of 3nm, and the reflectivity at the 208nm place is merely 2%.Above-mentioned five instances can effectively suppress to the exposure of the different photoresist of sensitive band to its wave band outside band.

Claims (7)

1. A novel multilayer film that improves the purity of the extreme ultraviolet spectrum, the multilayer film comprising: a substrate and a Mo/Si multilayer film, characterized in that it also includes an SPE layer; the Mo/Si multilayer film is made on the substrate , The SPE layer is made on the Mo/Si multilayer film. 2. A novel multi-layer film for improving extreme ultraviolet spectral purity according to claim 1, characterized in that the material of the SPE layer is selected from one or both of C, SiC and Si ₃ N ₄ . 3. A novel multilayer film for improving extreme ultraviolet spectral purity as claimed in claim 1, wherein the thickness of the SPE layer is 9-12nm. 4. A novel multilayer film for improving extreme ultraviolet spectral purity as claimed in claim 3, wherein the most preferred thickness of the SPE layer is 10 nm. 5. A new type of multilayer film for improving extreme ultraviolet spectral purity according to claim 1, characterized in that the Mo/Si multilayer film has a period number of 40-60 and a period thickness of 6.9-7.2nm. 6 . A novel multilayer film for improving extreme ultraviolet spectral purity according to claim 5 , characterized in that the most preferred thickness of the Mo/Si multilayer film is 7 nm. 7. A novel multilayer film for improving extreme ultraviolet spectral purity according to claim 1, characterized in that the surface roughness of the substrate is less than 0.2nm.

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