Process for producing a three-dimensional patterned coating and coating obtained by the process

Abstract

The present disclosure concerns a process for producing a three- dimensional patterned coating (20), comprising forming a multilayer coating (20) comprising a plurality of layer systems (21-24) successively deposited on the substrate (10), each layer system (21-24) having an ablation threshold (Th); and performing at least a patterning step using laser irradiation generated by a pulsed laser device (50) to etch at least a cavity (30) in the coating (30). Said at least a patterning step comprises adjusting laser parameters of the pulsed laser device (50) as a function of the ablation threshold of a selected layer system (21-24) corresponding to one of the layer systems (21-24), such that said at least a cavity (30) is etched with a cavity depth (D) extending between an upper surface (201) of the uppermost layer system to the upper surface (210) of the layer system (21-24) underneath the selected layer system.

Description

Process for producing a three-dimensional patterned coating and coating obtained by the processField

[0001] The present invention concerns a process for producing a three- dimensional patterned coating on a substrate. The present invention further concerns a patterned coating obtained by the process.Background

[0002] Depositions of coatings are commonly used in industry in general and in the watchmaking and jewelry, optics and molds fabrication for lithography fields in particular, to produce coatings having aesthetic and / or technical applications.

[0003] Some of the thin layer deposition methods commonly used are the Physical Vapor Deposition (PVD) methods particularly comprising the sputtering method and the thermal or e-beam evaporation methods; the Chemical Vapor Deposition (CVD) methods; the galvanic growth metal deposition methods; and the Atomic Layer Deposition (ALD) methods.Summary

[0004] The present disclosure concerns a process for producing a three- dimensional patterned coating, comprising: providing a substrate; forming a multilayer coating comprising a plurality of layer systems successively deposited on the substrate, each layer system having an ablation threshold; and performing at least a patterning step using laser irradiation generated by a pulsed laser device to etch at least a cavity in the coating;wherein said at least a patterning step comprises adjusting laser parameters of the pulsed laser device as a function of the ablation threshold of a selected layer system corresponding to one of the layer systems, such that said at least a cavity is etched with a cavity depth extending between an upper surface of the uppermost layer system to the upper surface of the layer system underneath the selected layer system.

[0005] The present disclosure further concerns a patterned coating obtained by the process.

[0006] With respect to what is known in the art, the invention provides the advantage that none of wet chemistry, vacuum, or plasma processes using reactive gases need to be used, and very precise ablation steps can be made with unprecedented lateral resolution corresponding to the spot size of a pulsed laser and a nanometer depth resolution that can be designed by the materials properties forming the multilayer.Brief description

[0007] Exemplar embodiments of the invention are disclosed in the description and illustrated by the drawings in which:Fig. 1 illustrates a multilayer coating formed on a substrate and a pulsed laser device, according to an embodiment;Fig. 2 illustrates the coating of Fig. 1 after a patterning step, according to an embodiment;Fig. 3 illustrates the coating comprising a first layer system having a first ablation threshold, a second layer system having a second ablation threshold, according to an embodiment;Fig. 4 illustrates the patterned coating of Fig. 3 after the patterning steps;Fig. 5 shows a layer systems comprising a first sublayer and a second sublayer, according to an embodiment;Fig. 6 shows a layer systems comprising a first sublayer and a second sublayer, according to another embodiment;Fig. 7 represents the pulsed laser device configured to be moved in the plane of the coating surface, according to an embodiment;Fig. 8 shows a graph of the laser power as a function of the thickness of the coating configured as in the Figs. 1 to 5; andFig. 9 shows a graph of the laser power as a function of the thickness of the coating configured as in Fig. 6.Detailed description

[0008] In an embodiment shown in Figs. 1 and 2, a process for producing a three-dimensional patterned coating 20 comprises the steps of: providing the substrate 10; forming a multilayer coating 20 comprising a plurality of layer systems 21, 22 successively deposited on the substrate 10 (on the top surface 11 of the substrate); and performing at least a patterning step using laser irradiation generated by a pulsed laser device 50 to etch at least a cavity 30 in the coating 20.

[0009] Each layer system 21, 22 has an ablation threshold Th. The ablation threshold Th increases from the uppermost layer system (layer system 22 in Figs. 1 and 2) to the lowest layer system (layer system 21 in Figs. 1 and 2).

[0010] The patterning step comprises adjusting laser parameters of the pulsed laser device 50 as a function of the ablation threshold of a selected layer system 21, 22 corresponding to one of the layer systems 21, 22, such that said at least a cavity 30 is etched with a cavity depth D extending between an upper surface 201 of the uppermost layer system to the uppersurface 201 of the layer system 21, 22 underneath the selected layer system 21, 22.

[0011] In Fig. 1, the coating 20 is shown with two deposited layer systems, namely a first layer system 21 and a second layer system 22 deposited on top of the first layer system 21. The pulsed laser device 50 is represented generating a laser beam 51 irradiating the coating 20. The first layer system 21 has a first ablation threshold thi and the second layer system 22 has a second ablation threshold th2 that is smaller than the first ablation threshold thi.

[0012] In the illustrated example, the pulsed laser parameters are adjusted such that the laser beam 51 is mostly absorbed in the second layer system 22 (selected layer system) and removes the material only in the second layer system 22. A cavity 30 is thus formed in the second layer system 22 while the first layer system 21 remains unaffected. The cavity 30 has a cavity depth D that extends between upper surface 201 of the second layer system 22 (corresponding to the uppermost layer system, and the top surface 40 of the coating 20) to the upper surface 201 of the first layer system 21 underneath the selected layer system (second layer system 22).

[0013] Fig. 2 illustrates the patterned coating 20 after the patterning step, showing a cavity 30 that has been formed in the second layer system 22. The cavity 30 has a cavity depth D that corresponds to the thickness of the second layer system 22.

[0014] Fig. 3 illustrates the coating 20 comprising four layer systems successively deposited on the substrate 10 (on the upper surface 11 of the substrate), namely a first layer system 21 having a first ablation threshold thi, a second layer system 22 having a second ablation threshold th2, a third layer system 23 having a third ablation threshold ths, and a fourth layer system 24 having a fourth ablation threshold tFu. The ablation threshold increases from the fourth ablation threshold TFu to the first ablation threshold thi. In Fig. 3, the pulsed laser device 50 is represented generatinga laser beam 51 irradiating the coating 20 in the case of three possible patterning steps, whereby the laser beam 51 is mostly absorbed in the fourth layer system 24 (a), the third layer system 23 (b), or the second layer system 22 (c).

[0015] Fig. 4 illustrates the patterned coating 20 comprising the four layer systems 21-14 successively deposited between the substrate 10 and the top surface 40 of the coating 20, after the patterning steps.

[0016] As illustrated in Figs. 3 and 4, performing at least a patterning step can comprise a first patterning step (a), wherein the pulsed laser parameters are adjusted such that the laser beam 51 is mostly absorbed in the fourth layer system 24 (selected layer system). The laser beam 51 removes material only in the fourth layer system 24 such as to etch a first cavity 30a having a first cavity depth Di extending between upper surface 201 of the fourth layer system 24 (corresponding to the top surface 40 of the coating 20) to the upper surface 201 of the third layer system 23. The other layer systems 21-23 remain unaffected.

[0017] Performing at least a patterning step can further comprise a second patterning step (b), wherein the pulsed laser parameters are adjusted such that the laser beam 51 is mostly absorbed in the third layer system 23 (selected layer system). The laser beam 51 removes material in the third and fourth layer systems 23, 24 such as to etch a second cavity 30b having a second cavity depth D2 extending between upper surface 201 of the fourth layer system 24 to the upper surface 201 of the second layer system 22. The first and second layer systems 21-22 remain unaffected.

[0018] Performing at least a patterning step can further comprise a third patterning step (c), wherein the pulsed laser parameters are adjusted such that the laser beam 51 is mostly absorbed in the second layer system 22 (selected layer system). The laser beam 51 removes material in the second, third and fourth layer systems 22, 23, 24 such as to etch a third cavity 30c having a third cavity depth D3 extending between upper surface 201 of thefourth layer system 24 to the upper surface 201 of the first layer system 21.The first layer system 21 remains unaffected.

[0019] It should be noted that the coating 20 may comprise less or more than four layer systems 21-24. For example, the coating 20 can comprise up to ten layer systems 21-24, or more. The ablation threshold Thi-TFu should increase from the uppermost layer system to the lowest layer system.

[0020] The multilayer arrangement of the coating 20 enables the controlled absorption of the laser beam 51 energy in the selected layer system by appropriately adjusting the layer parameters, such as to ablate the material in the selected layer system and the layer systems on top of the selected layer (if any), while the layer systems underneath the selected layer system remain unaffected.

[0021] As illustrated in Fig. 4, the coating 20 comprising a plurality of layer systems 21-24 can be patterned with adjusting the laser parameters of the pulsed laser device 50 at each patterning step such as to etch a plurality of cavities 30 having different cavity depths D.

[0022] Relevant pulsed laser parameters can include its wavelength, power and energy, pulse duration, repetition rate, number of laser pulses, and beam diameter.

[0023] In an embodiment shown in Fig. 5, the layer system 21-24 can comprise a first sublayer arranged underneath the second sublayer. The first sublayer comprises a material having a first absorption coefficient. The second sublayer comprises a material having a second absorption coefficient that is larger than the first absorption coefficient.

[0024] In one aspect, the first sublayer 210 comprises, or is made of, a metal or a metal alloy layer. The first sublayer 210 can comprise, or can bemade of, any one or an alloy of: Al, Ag, Au, Cr, Cu, Ni, Ti, Si, Sn, Zn, Zr, Rh Pd, or a combination of these elements or alloys.

[0025] In one aspect, the second sublayer 211 comprises, or is made of, an oxide, a nitride, a carbide, a carbonitride, a metal oxide, or a metal oxynitride, or a combination of these materials. For example, the second sublayer 211 can comprise, alone or in combination: SiCh or TiCh.

[0026] The first sublayer 210 can be adapted to reflect at least partially the laser beam 51 to help concentrating the absorption of the laser beam energy within the targeted layer system. In other words, the first sublayer 210 can be considered as such a (at least partially) reflecting layer.

[0027] In an embodiment, the layer system 21-24 can have a thickness between 1 nm and 1 |im, or between 2 nm and 500 nm, or between 5 nm and 200 nm. Such thicknesses allow for the targeted layer system to absorb an amount of laser pulse energy to avoid damaging the layer systems 21-24 underneath the selected layer system. Such thicknesses further enable controlled partial ablation by the selected layer system and layer systems 21-24 on top of the selected layer system (if any) by the laser beam 51. The total thickness Ts of the coating 20 can be up to a few micrometers, for example up to 1 .m or up to 3 |im.

[0028] Each of the first and second sublayers 210, 211 can have a thickness between 2 nm and 500 nm, or between 5 nm and 200 nm.

[0029] In an embodiment, the layer system 21-24 can be configured such that its upper surface 201 provides a color effect. When a cavity 30 is formed, the color of the exposed upper surface of the layer system 21-24 at the bottom of the cavity 30 becomes visible. The patterned coating 20 can thus exhibit at least two colors. For example, referring again to Fig. 2, the patterned coating 20 can exhibit two colors in the case the upper surface of the second layer system 22 has a different color than the color of the upper surface of the first layer system 21. The color of the upper surface of thefirst layer system 21 is visible in the bottom of the cavity 30. Referring again to Fig. 4, the patterned coating 20 can exhibit up to four colors in the case the upper surfaces of each of the first to fourth layer systems 21-24 have a different color and if the coating 20 comprises cavities 30 having different cavity depths D such that at least a portion of each layer system is exposed. The number of colors that can be obtained for the patterned coating 20 depends on the number of layer systems 21-24 and the color of the exposed surface of each layer system 21 -24.

[0030] The color effect on the layer system 21-24 can be obtained by a texturing of its surface (e.g., nanotexturing). Alternatively, the layer system 21-24 can comprise the first sublayer 210 comprising, or being made of, a metal or a metal alloy layer, and the second sublayer 211 comprising, or being made of, an oxide, a nitride, a carbide, a carbonitride, a metal oxide, or a metal oxynitride, or a combination of these materials. In the latter case, the color can be obtained by interference of thin oxide layers on a metal, for example, Cr-SiCh or Cr-TiCh.

[0031] In Table 1, the ablation threshold has been calculated for bulk materials in air, for the first sublayer 210 made of Cr (material 1) and the second sublayer 211 made of SiChThe first line (<|)th,Air) corresponds to the ablation threshold has been calculated for Cr in air (without the oxide). The calculations can be advantageously used for selecting the appropriate laser parameters for a given configuration of the layer systems 21-24 in the coating 20. In table 1, materials 2 and 3 can correspond to another metal or alloy, such as Ag, Au. Alternatively, the ablation threshold can be measured for the different material combinations.Table 1

[0032] Referring again to the example of Figs. 1 and 2, the first layer system 21 can comprise a bilayer with the first sublayer 210 comprising, or being made of, Cr and the second sublayer 211 comprising, or being made of, SiO2. The second layer system 22 can comprise a bilayer with the first sublayer 210 comprising, or being made of, Cr and the second sublayer 211 comprising, or being made of, TiCh.

[0033] Referring to Table 1, the second ablation threshold TF12 of the Cr- TiCh bilayer of the second layer system 22 is estimated at 0.20 J / cm2. The first ablation threshold Thi of the Cr-SiCh bilayer of the first layer system 21 is estimated at 0.25 J / cm2, greater than second ablation threshold TF12. In this configuration, the second layer system 22 can be ablated without affecting the first layer system 21.

[0034] It should be noted that the ablation threshold Th of the layer system 21-24 can be tailored by the choice of material, the thickness and / or reflectivity of the layer system 21-24.

[0035] In yet another embodiment represented in Fig. 6, the layer system 21-24 comprises an absorber layer 211 having a first ablation threshold Thi and a functional layer 210 having a second ablation threshold TF12 that is lower that the first ablation threshold Thi. The first ablation threshold Thi can have the same value as the absorber layer 211 in all the layer systems 21-24. The absorber layer 211 acts as an absorber for the laser beam energy and allows for precisely ablate the functional layer 210 upper the corresponding absorber layer 211. Each of the first and second sublayers 210, 211 can have a thickness between 2 nm and 500 nm, or between 5 nm and 200 nm.

[0036] In the configuration of Fig. 6, the ablation of cavities of different thicknesses, or the ablation of one or several the layer systems 21-24, can be achieved by varying the number of laser pulses that are emitted at a given point (location) on the top surface 40 of the coating 20 or, in other words, the irradiation time by the laser beam 51 at the given point.Indeed, for a given number of laser pulses (or irradiation time) the energy transmitted in the coating 20 by the laser beam 51 may be sufficient to ablate the topmost layer system 21-24, while the residual energy (the energy not absorbed in the topmost layer system 21-24 and transmitted to the lower layer systems 21-24) may not suffice to ablate the lower layer systems 21-24. Increasing the number of laser pulses (or irradiation time) allows for ablating the underneath layer systems 21-24. The number of laser pulses (or irradiation time) can be selected to ablate one or several underneath layer systems 21-24 such as to obtain cavities having different depths D1-D3).

[0037] In a possible configuration illustrated in Fig. 7, the pulsed laser device 50 can be configured to be moved in the plane of the coating surface 40, allowing to pattern cavities 30 having complex two-dimensional shapes.

[0038] The spot zize of the laser beam 51 can be between 1 and 20 pm, corresponding to the lateral resolution of the patterned cavities 30. The depth resolution depends on the multilayer design and layer thickness.

[0039] Fig. 8 shows a graph of the laser power as a function of the thickness of the coating 20 configured as in the examples of Figs. 1 to 5. The graph shows that cavities 30 having increased cavity depths D1-D3 can be patterned in the coating 20 by increasing the laser power (energy) of the pulsed laser device 50 depending on the ablation thresholds Thi-TFu of the different layer systems 21-24.

[0040] The speed of the moving pulsed laser device 50 in the plane of the coating surface 40 can be selected such that one aur several laser pulses are emitted at a given coordinate point in the plane. The energy of the laser beam 51 can be varied during the movement of the pulsed laser device 50 such as to ablate cavities 30 having different depths across the top surface 40 of the coating 20. Alternatively, or in combination, the pulsed laser device 50 may comprise a plurality of beam emitting devices,each beam emitting device emitting a laser beam 51 having a different laser powers.

[0041] Fig. 9 shows a graph of the laser power as a function of the thickness of the coating 20 configured as in the examples of Fig. 6. In the case the first ablation threshold Thi has the same value for the absorber layer 211 in all the layer systems 21-24, cavities 30 having increased depths D1-D3 (corresponding to increasing thicknesses) can be patterned in the coating 20 by using the same laser power of the pulsed laser device 50.

[0042] In the case of the configuration of Fig. 6, increasing the number of laser pulses can be achieved by increasing the number of passages of the laser beam 51 over the same location on the top surface 40 by the moving pulsed laser device 50.

[0043] The layer systems 21-24 can be formed by using physical vapor deposition (PVD) or atomic layer deposition (ALD).

[0044] The pulsed laser parameters can comprise pulses smaller than 1 ps or 1 ns or 1 ps, or 50 fs. The pulse energy is typically a few microjoules (it depends on the ablation threshold of the layer to be ablated. The spot size of the laser beam 51 can be between 1 and 20 pm. The laser penetration depth in metals is typically 5-50nm, and larger in absorbing nitrides, oxides, or carbides. The laser pulse energy is typically of a few microjoules. The laser wavelength can be in the UV, VIS or NIR.

[0045] The process disclosed herein allows for producing a patterned coating presenting a multi-color pattern, presenting complex three- dimensional micro or nano structures, and / or presenting micro or nano optical properties.

[0046] The process and pattern coating obtained by the process can find applications in horology, jewelry, semiconductors, and optical devices.Reference numbers and10 substrate11 upper surface of the substrate20 coating201 upper surface20221 first layer system210 first sublayer211 second sublayer22 second layer system23 third layer system24 fourth layer system30 cavity 30a first cavity30b second cavity 30c third cavity 40 top surface50 pulsed laser device51 laser beamD cavity depthDi first cavity depthD2 second cavity depthD3 third cavity depthTh ablation thresholdThi first ablation thresholdTh2 second ablation thresholdThs third ablation thresholdTh4 fourth ablation thresholdTs coating thickness

Claims

Claims1. Process for producing a three-dimensional patterned coating (20), comprising: providing a substrate (10); forming a multilayer coating (20) comprising a plurality of layer systems (21-24) successively deposited on the substrate (10), each layer system (21-24) having an ablation threshold (Th); and performing at least a patterning step using laser irradiation generated by a pulsed laser device (50) to etch at least a cavity (30) in the coating (30); wherein said at least a patterning step comprises adjusting laser parameters of the pulsed laser device (50) as a function of the ablation threshold of a selected layer system (21-24) corresponding to one of the layer systems (21-24), such that said at least a cavity (30) is etched with a cavity depth (D) extending between an upper surface (201) of the uppermost layer system to the upper surface (210) of the layer system (21- 24) underneath the selected layer system (21-24).

2. The process according to claim 1, wherein said at least a patterning step comprises a plurality of patterning steps, such as to etch a plurality of cavities (30).

3. The process according to claim 2, wherein the plurality of patterning steps comprises sequentially adjusting laser parameters of the pulsed laser device (50) as a function of the ablation threshold of a plurality of selected layer systems (21-24), such as to etch a plurality of cavities (30) with different cavity depths (D).

4. The process according to any one of claims 1 to 3, wherein the ablation threshold (Th) increases from the uppermost layer system () to the lowest layer system ().

5. The process according to any one of claims 4, wherein each layer system (21-24) comprises a first sublayer (210) comprising a material having a first absorption coefficient and a second sublayer (211) comprising a material having a second absorption coefficient that is larger than the first absorption coefficient; and wherein the first sublayer (210) is underneath the second sublayer (211).

6. The process according to claim 5, wherein the first sublayer (210) comprises, or is made of, a metal or a metal alloy layer.

7. The process according to claim 6, wherein the first sublayer (210) comprises, or is made of, any one or an alloy of: Al, Ag, Au, Cr, Cu, Ni, Ti, Si, Sn, Zn, Zr, Rh, or Pd.

8. The process according to any one of claims 5 to 7, wherein the second sublayer (211) comprises, or is made of, an oxide, a nitride, a carbide, a carbonitride, a metal oxide, or a metal oxynitride.

9. The process according to claim 8, wherein the second sublayer (211) comprises, or is made of, any one or a combination of: SiCh or TiCh.

10. The process according to any one of claims 1 to 9, wherein said laser parameters comprise the laser power and energy.

11. The process according to any one of claims 1 to 3, wherein each layer system (21-24) comprises a first sublayer (210) having a first ablation threshold (Th 1) and a second sublayer (211) having the second ablation threshold (Th2) that is larger than the first ablation threshold (Thi): and wherein the first sublayer (210) is underneath the second sublayer (211).

12. The process according to claim 11, wherein the first and second ablation threshold (Thi, Th2) are constant from one layer system (21-24) to another.

13. The process according to claim 11 or 12, wherein said laser parameters comprise the number of laser pulses.

14. The process according to any one of claims 1 to 13, wherein the pulsed laser device (50) is configured to be moved in the plane of the coating surface (40); and wherein said at least a patterning step comprises moving the laser device (50) along the plane of the coating surface (40) in at least one direction.

15. The process according to claim 14, wherein said at least a patterning step comprises selecting the speed of the moving pulsed laser device (50) such as to adjust power and energy of the laser beam (51) at a given position on the coating surface (40) to control the depth (D) of the cavity (30).

16. The process according to claim 15, wherein said at least a patterning step comprises selecting the time the pulsed laser device (50) remains at a given position on the coating surface (40), and / or selecting the number of passages made by the moving pulsed laser device (50) at a given position on the coating surface (40) to control the depth (D) of the cavity (30).

17. The process according to any one of claims 1 to 16, wherein each layer system (21-24) is configured such that its upper surface (201) provides a color effect, such that the patterned coating (20) exhibits at least two colors.

18. Patterned coating (20), obtained by the process of any one of claims 1 to 17.

Images