Patent ID: 12195383

DETAILED DESCRIPTION OF EMBODIMENTS

FIG.2schematically shows a deposition device to controllably deposit a functional material2onto a target surface51of a target5using monochromatic radiation R3having a wavelength λR3. The deposition device ofFIG.2comprises a carrier plate1, a holder7to hold the target5, a monochromatic photon radiation source3and a controller8to control the monochromatic radiation source3.

As schematically shown inFIG.2, the carrier plate1has a substrate10with a first surface11to be directed towards the target surface51and a second surface12to receive the monochromatic photon radiation R3. The first surface11is patterned with one or more recessed areas111. In the example ofFIG.2only one recessed area111is shown, but in practice, the carrier plate1may have a plurality of recessed areas. Recessed areas may be of any type, e.g. circular wells, curved or straight trenches and the like. The recessed areas may for example have a width of 10 micron and smaller, but also larger sized recessed areas may be contemplated depending on the application. In the example shown inFIG.2, the entire first surface11provided with a dielectric coating4. Alternatively, the dielectric coating4may be exclusively provided in the portions of the first surface11defined by the recessed area(s)111, and be absent outside these areas. The recessed areas111are filled with the functional material2to be deposited on the target. As schematically shown further inFIG.2, the dielectric coating4comprises a sequence of dielectric coating layers41,42,43that alternate in refractive index. The dielectric coating layers41,42,43are applied with a uniform thickness so that the dielectric coating4has a relatively high reflectivity for monochromatic radiation R3B incident thereto in a perpendicular direction and has a relatively low reflectivity for monochromatic radiation R3S incident thereto in a direction deviating from said perpendicular direction, i.e. at an angle of 45 degrees.

In operation of the deposition device the controller8causes the monochromatic radiation source3to render monochromatic photon radiation R3with an intensity and a duration that causes a transfer of functional material2from the one or more recessed areas111to the target surface51. The monochromatic radiation source3directs the monochromatic radiation R3towards the second surface12of the carrier plate1. To that end the monochromatic radiation source3may include a laser, e.g. an excimer laser or a scanning laser and optional further optical components, such as a telecentric lens.

As shown schematically inFIG.2, for monochromatic radiation R3B directed towards the bottom111B of the recessed area111is incident to the dielectric coating4in a perpendicular direction so that a relatively large portion is reflected. Contrary thereto monochromatic radiation R3S directed towards the side wall111S of the recessed areas111is incident to the dielectric coating4in a direction deviating from the perpendicular direction, so that only a relatively small portion thereof is reflected. Therewith the radiation intensity at the bottom111B of the recessed area(s)111is reduced as compared to the case wherein a dielectric coating4is absent. As a consequence a difference between the heat flux developed near the sidewall111S and the bottom111B is reduced.

A first example is shown in more detail inFIG.3A,3B. ThereinFIG.3Ashows a portion of the bottom111B of a recessed area111, andFIG.3Bshows a portion of the side wall1115of a recessed area111. In the example shown the substrate10of the plate is of silicon dioxide, and a dielectric coating4is provided with a first high refractive index (n=2.4) layer41of TiO2 with a thickness of 40 nm, a first low refractive index (n=1.45) layer42of SiO2 with a thickness of 40 nm, and a second high refractive index layer43of TiO2 with a thickness of 40 nm. Also a protective coating layer45of Al2O3 with a thickness of 40 nm is provided. The latter has a refractive index n=1.75.

It is noted that in dielectric mirrors the thickness of the layers multiplied with their refractive index is typically a quarter of the wavelength of the radiation to be reflected, so that the high refractive index layers are thinner than the layers with a lower refractive index. In the present application it is not necessary that the dielectric coating reflects all radiation, but it is sufficient that the radiation directed towards the bottom of the recessed portions is attenuated to a sufficient extent to achieve a substantially homogeneous distribution of the transmitted heat flux over the inner surface of the recessed areas. Suitable coatings that meet this requirement can selected without undue effort using a simulation. For example starting from the following input, a wavelength XR3of the monochromatic radiation used, a slanting angle of the walls of the recessed elements a number of dielectric layers in the dielectric coating and a selection of the mutually different dielectric materials for these layers, the thickness can be varied in the simulation to determine for which thickness the required attenuation is achieved. It can be presumed in the simulation that the thickness of the layers is equal, or that the layer thicknesses for high- and low refractive index layers mutually have a fixed thickness ratio. Therewith only one parameter needs to be varied in the simulation. https://www.filmetrics.com/reflectance-calculator provides a simulator suitable for this purpose.

At each interface10-41,41-42,42-43and43-45and45, a reflection occurs and these reflections reinforce or cancel each other depending on the path length difference. The path length through each layer is the product of the layer thickness (d) and its refractive index (n).

The strength of the reflection at the interface of mutually subsequent layers depends on their refractive indices (no, ns) according to the following relationship.

R=(n0-nSn0+nS)2

The extent to which reflections mutually cancel each other depends on their phase difference.

In an example, the wavelength λR3of the monochromatic radiation source used is 532 nm. Therewith for the layers41,42,43,45the bidirectional optic path length (*λR3) for radiation incident in the direction of the surface normal expressed as a fraction of the wavelength is as follows:

LayerMaterialn.d*λR341, 43TiO2 (n = 2.4)960.3642SiO2 (n = 1.45)580.2245Al2O3 (n = 1.75)700.26

In the center of the recessed area, the incident angle of the light is transverse to the plane of the layers. The various partial reflections are out of phase but are not fully in counter phase, so that part of the radiation R3B is reflected, and does not arrive at the bottom111B of the recessed area111.

In the case ofFIG.3B, showing the radiation R3S directed to the side wall111S of the recessed areas111, the path length is increased, as the radiation R3S has a direction deviating from the normal direction of the coating4. Therewith the partial reflections occurring at the layer interfaces are to a larger extent out of phase, so that a relatively small part of the radiation R3S is reflected. Therewith a larger part can reach the side wall111S of the recessed area111.

FIG.4shows the relationship between the normalized heatflux (normalized power density) and the angle of incidence of the beam. In this example, the normalized heatflux gradually increases from about 1 to 1.8 when increasing the angle from 0 to 45 degrees, and decreases to 0 when the angle is further decreased to 90 degrees. For an angle of 70 degrees, corresponding to the angle of the sidewall the111S, the normalized heatflux is approximately equal to 1, so that a substantially uniform heatflux is achieved within the recessed area111. It is noted that the heat flux transmitted through a surface is defined as the power density (W/m2) in the normal direction of the surface. The normalized heat flux is a dimensionless value obtained by dividing the heat flux for a particular angle by the heat flux at an angle of 0. In some cases, it may be desired that the heat flux through the side walls of the recessed area is slightly higher (e.g. about 5 or 10%) than the heat flux through the bottom, so that the side releases just before the bottom releases. Therewith a risk of occurrence of a shear force can be further mitigated.

In another example, the wavelength λR3of the monochromatic radiation source used is 308 nm and the dielectric coating4is provided with a first high refractive index (n=2.1) layer41of HfO2 with a thickness of 38 nm, a first low refractive index (n=1.45) layer42of SiO2 with a thickness of 38 nm, and a second high refractive index layer43of HfO2 with a thickness of 38 nm. Also a protective coating layer45of Al2O3 with a thickness of 25 nm is provided. The latter has a refractive index n=1.75.

LayerMaterialn.d*λR341, 43HfO2 (n = 2.1)550.3642SiO2 (n = 1.45)800.5145Al2O3 (n = 1.75)440.28

FIG.5shows for this example the normalized heat flux as a function of the angle of incidence. The dependency of the normalized heat flux on the angle of incidence is qualitatively the same as in preceding example, but quantitatively there is a difference. With an angle in a range of 0 to about 65 degrees, the normalized heat flux does not differ more than about 10% from the reference value 1. Therewith recessed areas111with a variety of side wall angles within this range of angles can be provided in the carrier plate, all having a substantially uniform distribution of heat flux over their bottom wall and side wall.

FIG.6shows an alternative embodiment of the claimed deposition device. Parts therein corresponding to those inFIG.2have the same reference. As an additional feature the non-recessed portions of the first surface11of the carrier plate are provided with a reflective coating6, e.g. a reflecting metal coating or a further dielectric coating6that substantially reflects (R3R) the monochromatic radiation R3. The dielectric coating4extending over the further dielectric coating6can therewith cooperates with the latter. This is because the dielectric coating4is already designed to partially reflect incident radiation perpendicular to the surface. The further dielectric coating6below the dielectric coating4provides additional dielectric coating layers that further enhance the reflectivity outside the recessed areas.

Therewith it is avoided that any functional material2″ present in these areas is transferred to the target surface51, even if the monochromatic radiation R3is directed thereto. It is not necessary that a reflective coating6fully reflects the radiation R3. It is sufficient if the monochromatic radiation R3is sufficiently reduced in strength to avoid the transfer.

In the embodiment shown inFIG.6the recessed area111is further provided with a photon radiation absorbing layer9between the dielectric coating4and the functional material2. Therewith the photon radiation is very efficiently converted into heat, regardless the type of functional material2used.

FIG.7schematically shows a method for controlled deposition of a functional material onto a target surface using monochromatic radiation having a wavelength. The method comprises a step S1, wherein a transparent carrier plate is provided having a substrate with a first and a second mutually opposite surfaces, therewith providing the first surface with one or more recessed areas. In an embodiment step S1comprises a first sub-step S1A, wherein the transparent carrier plate is provided, e.g. made of glass or silicon oxide, and a second sub-step S1B, wherein the first surface is provided with one or more recessed areas.

In the embodiment ofFIG.7, an additional sub-step S1C is performed. In this sub-step S1C, a reflective coating is deposited at the first surface that substantially reflects the monochromatic radiation incident perpendicular to the reflective coating. Sub-step S1C comprises for example depositing a reflecting metal coating, e.g. a silver layer. Preferably however a dielectric coating is applied using a sequence of sub-sub-steps wherein dielectric coating layers are subsequently deposited to form a dielectric mirror that (optionally in combination with a dielectric coating4) substantially reflects perpendicularly incident monochromatic radiation of said wavelength. With a dielectric mirror an amount of heat absorption van be relatively modest as compared to when using a metal coating, therewith reducing the risk of damage. In the example ofFIG.7, sub-step S1C is performed before providing in step S1B the first surface with one or more recessed areas. As a result, a plate is obtained as used in the deposition device ofFIG.6, wherein non-recessed portions of the first surface11of the plate1are provided with a reflective coating6that substantially reflects the monochromatic radiation R3. As discussed with reference toFIG.6, therewith the risk that materials are unintendedly transferred outside the recessed portions is reduced. Because in this embodiment of the method sub-step S1B is performed subsequent to sub-step S1C, it is not necessary to accurately align the deposition process in sub-step S1C. In sub-step S1C, the dielectric coating6or other reflective coating can simply be deposited over the entire first surface of the plate, and in sub-step S1B this coating is locally removed in the portions of the first surface occupied by the recessed portions. Nevertheless, it may be contemplated to perform sub-step S1C subsequent to sub-step S1B provided that care is taken that the first surface occupied by the recessed portions remains free from the material used for the reflective coating.

In step S2of the method, a dielectric coating is deposited Step S2comprises a sequence of sub-steps wherein in each subsequent sub-step a dielectric coating layer is deposited having a refractive index different from that of the dielectric coating layer deposited in the preceding sub-step. It is sufficient that the dielectric coating obtained therewith extends within the portions of the first surface defined by the one or more recessed areas, but alternatively the dielectric coating may also extend beyond the one or more recessed areas. Typically the dielectric coating is deposited over the entire surface of the plate, therewith obviating masking and aligning issues.

The dielectric coating has a reflectivity for the monochromatic radiation incident perpendicular thereto that is relatively high in comparison to a reflectivity for said monochromatic radiation incident at an angle of 45 degrees to the dielectric coating.

In a subsequent step S3the one or more recessed areas are filled with the functional material, e.g. copper, aluminum, tungsten, chromium, polysilicon to be deposited. Other materials than metal are also suitable for use as a functional material. The functional material may for example be provided as an ink wherein conductive particles are suspended. Rheological properties of the functional material may be modified by additives or solvent, for example to obtain a shear-thickening, a shear-thinning, a thixotropic, a rheopectic or a Bingham plastic behavior. In particular donor materials with a shear-thinning behavior are favorable. Donor materials with this behavior have a viscosity that decreases with the rate of shear strain. Shear-thinning donor materials remain as a stable layer on the donor substrate, but are relatively easily morphed at the time of deposition. By way of example, the functional material is a viscous silver nanoparticle ink with a high metal load.

It is noted further process steps may take place before the one or more recessed areas are filled with the functional material. For example a photon radiation absorbing layer may be deposited subsequent to the step of depositing the dielectric coating, and preceding the step of filling the one or more recessed areas with said functional material. As noted above this improves the conversion of the monochromatic radiation into heat. Alternatively or additionally a vaporizable material may be deposited the one or more recessed areas before filling with the functional material.

After the one or more recessed areas are filled in step S3with the functional material, the transparent carrier plate is ready for use in a deposition device, for example as shown inFIG.2orFIG.6.

Therewith the transparent carrier plate1is positioned between the monochromatic radiation source3and the target surface51of a target, with the first surface11facing the target surface51, as shown inFIGS.2and6for example.

In operation the monochromatic radiation R3of the monochromatic radiation source3is directed in step S4towards the second surface12of the plate1. Therewith the monochromatic radiation R3has an intensity and a duration that causes a transfer S5of functional material2from the one or more recessed areas111to the target surface51. Optimal values for intensity and duration can be determined by routine tests for a selected functional material and the transmissivity of the coating layers. The duration of the heat irradiation is typically short, e.g. in terms of microseconds, usually even shorter, nano-seconds. In practice good results with modest technical requirements may be obtained with a pulse duration in the order of a few to a few tens of ns. Nevertheless, in some cases an even shorter pulse duration may be applied, e.g. in the range of 10-500 ps. In a test phase the intensity can be varied from a relatively low value (e.g. corresponding to an exposure (fluence) of about 0.1 J/cm2) to a relatively high value (e.g. corresponding to an exposure (fluence) of about 1 J/cm2) to determine for which value or value range the transfer of the functional material2is optimal in terms of deposition accuracy.

According to one approach, the entire second surface12of the plate1is irradiated with a beam of homogeneous power density. In that case a homogeneous exposure is achieved having an exposure value equal to the product of the power density and the exposure time.

According to another approach, as illustrated inFIG.8, a scanning beam is used that is scanned with a speed v in a scanning direction Sy, parallel to axis y, along the second surface12opposite the recessed area111(here a trench shown in dotted lines) at the first surface.

In this case, the exposure E(x,y) can be determined as:
E(x,y)=∫t=−∞+∞P(x,v,t)Q(t)dt
Wherein P(. , . ) specifies the spatial distribution of the beam R3and Q( ) specifies how the total beam power varies in time t.

FIG.8shows the footprint31of the scanning beam when it is pulsed during scanning. Previous pulses are indicated as dotted circles, e.g.31″. As a result of said scanning, uniformity of the energy density at the second surface is obtained in the scanning direction provided that the distance between subsequently pulsed areas31″,31is subsequently small, e.g. the distance should be smaller than one third times the size of the footprint in the scanning direction. Also in the direction x, perpendicular to the scanning direction, exposure variations may be limited. For example, it may be required that the maximum exposure Emax and the minimum exposure Emin in the range x1<x<x2 are bounded with the following relationship:

(E⁢max-E⁢minE⁢max+E⁢min)<0.05

This may be achieved with a highly uniform beam. Alternatively, as shown inFIG.8, a beam may be applied having a footprint extending beyond the boundaries of the recessed area111, which is sufficiently uniform within these boundaries. When using a pulsed laser, the pulse frequency should be sufficiently high to uniformly heat the functional material, for example a frequency of 100 kHz or higher. A continuous wave laser can also be used where the timed release is controlled by the scan speed.

As noted with reference toFIG.6, precautions can be taken to reduce the risk that functional material accidently is transferred as result of exposure of the plate by the beam in areas outside the recessed areas.

Returning toFIG.7, it is further shown therein that upon completion of the deposition process in step S4, S5, recessed areas of the carrier plate can be refilled with functional material in step S3, so that the carrier plate is ready for reuse. Optionally, the carrier plate, in particular its first surface may be cleaned in an additional step S6before refilling in step S3.

FIG.9A-9Cshow further embodiments of a transparent carrier plate1. Parts therein corresponding to those inFIG.2andFIG.6have the same reference number. For clarity, the dielectric coating4is shown without further detail. The dielectric coating4at the first surface11may for example have a stack of dielectric coating layers41,42,43as shown in more detail inFIG.3A,3Band described above with reference toFIGS.3A,3B,4and5. Also other layers may be provided such as a protective coating. In the embodiments shown inFIG.9A-9C, the transparent carrier plate1is additionally provided with a gray-scale mask122to control a heat flux of the monochromatic photon radiation R3.

In the example shown inFIG.9A, gray-scale mask122has a transparent first zone122BS which corresponds to an area defined by the recessed areas111. The gray-scale mask122has second opaque zones1220complimentary thereto. Upon exposure of the plate1to radiation R3, the portion of the radiation incident at the transparent first zone122BS is transmitted towards the dielectric coating4in the recessed area111, with which it is achieved that a transmitted heat-flux in the surface of the side wall1115and a transmitted heat-flux in the surface of the bottom wall111B have substantially the same magnitude.

In the example shown inFIG.9B, gray-scale mask122has a central zone122B corresponding to the surface area of the bottom wall111B of the recessed area111, a boundary zone122S corresponding to the surface area of the side wall111S of the recessed area111and a complementary zone122O. In this example the gray-scale mask122is provided to control a heat flux of the monochromatic photon radiation R3to cooperate with the dielectric coating4to provide for an at least substantially homogeneous transmitted heat flux at the inner surface of the one or more recessed areas111. Therewith an additional degree of freedom is available. For example if recesses with side walls with mutually different slanting angles are provided therein, the gray-scale mask122can be designed to achieve the at least substantially homogeneous transmitted heat flux, even if the dielectric coating would not be capable to provide the proper compensation for the full range of side wall angles. For example in case the plate provided with the coating described with reference toFIG.4comprises in addition to recesses with a wall angle of 70 degrees also recesses with a wall angle of 45 degrees or 80 degrees. In the example shown inFIG.9B, the central zone122B for example has a transmissivity of 60% and the boundary zone1225has a transmissivity of approximately 100%. In that case for a recession with a side wall at an angle of 80 degrees, using the coating described with reference toFIG.4, a substantially homogeneous transmitted heat flux would be available over the inner surface of the recession. In the example ofFIG.9B, the transmissivity of the complementary zone1220is also approximately 100%.

In the example shown inFIG.9C, the gray-scale mask122combines the functionalities provided in the examples ofFIGS.9A and9B.