LIFT DEPOSITION APPARATUS AND METHOD

Abstract

A deposition method is provided wherein a donor substrate (10) is arranged opposite a target substrate (20), the donor substrate having a surface (12) facing the target substrate that is provided with a viscous donor material (14). An optical beam (30) is directed via the donor substrate to the donor material so as to release the donor material and to therewith transfer the donor material as a jet towards the target substrate. In the method provided herein an input signal (D.sub.S) is received that specifies a shape to be assumed by the jet with which the donor material is to be transferred and an energy profile of the optical beam is accordingly controlled. Additionally or alternatively the energy profile of the optical beam may be controlled in accordance with a pattern according to which the donor material is to be deposited on the target substrate. Likewise a corresponding deposition apparatus is provided.

Claims

1. A deposition apparatus to deposit a donor material having viscous properties, from a donor surface, onto a target surface of a target substrate, wherein the apparatus comprises: a target substrate carrier to carry the target substrate; a donor substrate carrier to carry a donor substrate having the donor surface such that the donor surface of the donor material and the target surface of the target substrate face each other; an optical beam generator positioned to generate an optical beam directed through the donor substrate to the donor material, the optical beam having an optical axis with a point of intersection in the target surface; a positioning device to control a position of the point of intersection; and a controller to control operation of the optical beam generator, and to control the positioning device, wherein, in an operational state of the deposition apparatus, the controller is configured to: receive specification data specifying a desired spatial distribution of donor material on the target surface; and generate, in accordance with said desired spatial distribution: a position control signal to control the positioning device, and a beam generator control signal to control operation of the optical beam generator; wherein the optical beam generator generates the optical beam in accordance with the beam generator control signal to cause donor material to be transferred from the donor surface towards a position on the target surface in accordance with the position control signal; wherein the optical beam generator is further configured to generate the optical beam to eject a portion of donor material with a controllable spatial energy distribution, wherein the controller is configured to generate the beam generator control signal in accordance with the received specification data to control the spatial energy distribution, and characterized in that wherein the optical beam generator is configured to generate an optical beam that results in a transfer of the donor material as a jet, the controller being configured to control the optical beam generator to generate the optical beam with a substantially asymmetric spatial distribution on the basis of a shape to be assumed by the jet according to said specification data.

2. The deposition apparatus according to claim 1, wherein the controller is configured to issue a beam generator control signal that causes the optical beam generator to generate the optical beam with a spatial energy distribution that has a higher average energy density in a ring shaped zone around its optical axis than an average energy density within an inner boundary of the ring shaped zone.

3. The deposition apparatus according to claim 1, wherein the optical beam generator comprises a source of optical radiation and a beam shaper.

4. The deposition apparatus according to claim 3, wherein the beam shaper includes a pair of a first axicon and a second axicon.

5. The apparatus according to claim 1, further comprising a feed back control unit to adapt a response of the controller to received specification data in accordance with observation data.

6. The apparatus according to claim 5, further comprising a jet monitoring apparatus that provides jet observation data indicative for an observed development of the jet of transferred donor material as observation data.

7. The apparatus according to claim 5, further comprising a target monitoring apparatus that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

8. A deposition method comprising: arranging a donor substrate opposite a target substrate, the donor substrate having a surface facing the target substrate that is provided with a viscous donor material, the donor material having viscoelastic properties at an elevated temperature, generating an optical beam, and directing the optical beam via the donor substrate to the donor material so as to release the donor material and transfer the donor material towards the target substrate, receiving an input signal, controlling an energy profile of the optical beam based on said input signal; and generating the optical beam to transfer the donor material as a jet, the optical beam being controllably generated with a substantially asymmetric spatial distribution based on a shape to assumed by the jet according to a specification in the input signal.

9. The deposition method according to claim 8, wherein the donor material is a shear-thinning substance.

10. The deposition method according to claim 8, further comprising: obtaining jet observation data indicative for an observed development of the jet of transferred donor material, and c controlling an intensity profile of the optical beam based on a difference between a shape of the jet as specified by the input signal and a shape of the jet as indicated by the jet observation data.

11. The deposition method according to claim 8, further comprising: obtaining target observation data indicative for observed properties of deposited donor material on the target surface, and controlling an intensity profile of the optical beam based on a difference between a pattern of deposited material specified by the input signal and a pattern of deposited material as indicated by the target observation data.

12. The deposition apparatus according to claim 2, wherein the optical beam generator comprises a source of optical radiation and a beam shaper.

13. The apparatus according to claim 12, further comprising a feed back control unit to adapt a response of the controller to received specification data in accordance with observation data.

14. The apparatus according to claim 13, further comprising a target monitoring apparatus that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

15. The apparatus according to claim 2, further comprising a feed back control unit to adapt a response of the controller to received specification data in accordance with observation data.

16. The apparatus according to claim 15, further comprising a target monitoring apparatus that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

17. The apparatus according to claim 3, further comprising a feed back control unit to adapt a response of the controller to received specification data in accordance with observation data.

18. The apparatus according to claim 17, further comprising a target monitoring apparatus that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

19. The apparatus according to claim 4, further comprising a feed back control unit to adapt a response of the controller to received specification data in accordance with observation data.

20. The apparatus according to claim 19, further comprising a target monitoring apparatus that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and other aspects are described in more detail with reference to the drawing. Therein:

[0018] FIG. 1 schematically shows a deposition apparatus according to a first embodiment,

[0019] FIG. 1A schematically shows a part of a second embodiment of the deposition apparatus,

[0020] FIG. 2 schematically shows a deposition apparatus according to a third embodiment,

[0021] FIG. 2A shows a part of this embodiment in more detail,

[0022] FIG. 3A and FIG. 3AA show an example of an applied intensity profile in more detail, therein FIG. 3AA shows an intensity distribution of the radiation beam in the x-y plane coinciding with the donor substrate and the main drawing of FIG. 3A shows the intensity distribution along the dashed line parallel to the y-axis,

[0023] FIG. 3B shows a picture of a jet of donor material, taken shortly after impingement of the radiation beam,

[0024] FIG. 4A-4G schematically show a development of a jet of ejected donor material in time, when an intensity distribution as shown in FIG. 4 is used,

[0025] FIG. 5B shows a shape of a jet of ejected donor material at a fixed point in time in a series of experiments using the intensity distribution of FIG. 5A, 5AA,

[0026] FIG. 6B shows a shape of a jet of ejected donor material at a fixed point in time in a series of experiments using the intensity distribution of FIG. 6A, 6AA.

DETAILED DESCRIPTION OF EMBODIMENTS

[0027] Like reference symbols in the various drawings indicate like elements unless otherwise indicated.

[0028] FIG. 1 schematically shows an embodiment of a deposition apparatus 100 to deposit donor material 14 having viscoelastic properties from a donor surface 12 of a donor substrate 10 on a target surface 22 of a target substrate 20. Dependent on the application, the donor material 14 may for example be provided as a layer of a few micron to few hundred micron on the donor surface 12. For example the layer may have a thickness of a few tens of micron, e.g. 40 micron.

[0029] The apparatus 100 as shown in FIG. 1 comprises a target substrate carrier 120 to carry the target substrate 20 and a donor substrate carrier 110 to carry the donor substrate 10 opposite the target substrate 20. The target substrate 20 and the donor substrate 10 are carried with the donor surface 12 and the target surface 22 facing each other. The target substrate 20 may be held at a distance from the donor substrate 10, which may be in a range of a few tenths of microns up to few millimeters and in extreme cases the donor substrate and the target substrate may even be placed a few centimeter apart.

[0030] The donor material is a visco-elastic material, typically paste like materials. These materials do not easily break into separate droplets. For example viscous inks and pastes, containing a high metal load of Cu or Ag nano- or micronparticles, or a conductive adhesive may be used.

[0031] The apparatus further comprises an optical beam generator 130 to generate an optical beam 30 to be directed through the donor substrate 10 towards the donor material 14. The optical beam has an optical axis 32 with a point of intersection 34 in the target surface 22. The apparatus includes a positioning device 140 to control a position of the point of intersection 34. As shown in FIG. 1 the apparatus can control the position of the point of intersection in this embodiment by controlling a position where the optical beam generator 130 projects the beam. Alternatively, the apparatus may include a positioning device to control a position of the target substrate. In again another embodiment the apparatus may include a positioning device 150 and a target substrate positioning device for the target substrate. For example, it may comprise the target substrate positioning device for a course positioning of the position of the point of intersection 34 and the positioning device 150 for the purpose of fine positioning. The position device 150 may for example be a fast beam modulator such as a galvano mirror, a polygon mirror, an acousto-optic or electro-optic modulator.

[0032] In the embodiment shown, the apparatus further includes a positioning device 140 to position the donor substrate carrier 110.

[0033] As shown in FIG. 1, the apparatus further comprises a controller 160 to control operation of the optical beam generator 130, and the positioning devices 140, 150 respectively.

[0034] In an operational state of the deposition apparatus 100, the controller 160 is configured to receive specification data D.sub.S specifying a desired spatial distribution of donor material on the target surface 22. The specification data D.sub.S may for example be retrieved from a memory unit or via a communication channel from a host processor. The specification data may specify a desired distribution of donor material on the target substrate 20, for example in the form of electrically conductive tracks on the target substrate, as electrical connections functional elements as a filling to form through silicon via's (TSVs).

[0035] In the operational state, the controller 160 generates position control signals S.sub.140, S.sub.150 to control the positioning devices 140, 150, and a beam generator control signal S.sub.130 to control operation of the optical beam generator 130 in accordance with the spatial distribution specified by the specification data D.sub.S. In response to the beam generator control signal S130 the optical beam generator 130 generates the optical beam 30. When the optical beam 30 impinges on the donor substrate it causes donor material to be transferred as a jet 14j from the donor surface 12 towards a position on the target surface 22 dependent on the position control signal S.sub.150.

[0036] The optical beam generator 130 is further configured to generate the optical beam 30 to eject a portion of donor material with a controllable spatial energy distribution. Furthermore, the controller 160 is configured to generate the beam generator control signal S.sub.130 in accordance with the received specification data D.sub.S to control the spatial energy distribution.

[0037] In an embodiment the controller 160 is configured to issue a beam generator control signal S.sub.130 that causes the optical beam generator 130 to generate the optical beam with a spatial energy distribution that has a higher average energy density in a ring shaped zone 30r around its optical axis than an average energy density within an inner boundary 30ri of the ring shaped zone. In this manner is achieved that the ejected material better stays together than is the case with operation with a gaussian or uniform shaped beam. For example the ring shaped pattern may have a width/diameter ratio in the range of 1/10 to and the diameter may be in the order of 50 to 500 micron. For example the radiation beam ring has a diameter of approximately 150 micron and a width of a approximately 20 micron. Accordingly the radiation energy density is relatively low in an inner area with a diameter of 110 micron in that example.

[0038] A setting of the laser fluence/energy leading to a stable nice jet depends on layer thickness. A thicker layer typically requires more energy, but allows longer and more stable jets. If a very high resolution is required a smaller thickness of the donor layer is recommended and consequently a lower laser energy should be applied. The laser energy is defined here as the total energy used to release a portion of the donor material from the donor surface.

[0039] Alternatively or additionally, the controller 160 may be configured to issue a beam generator control signal S130 that causes the optical beam generator 130 to generate the optical beam 30 with a substantially asymmetric spatial distribution. Therewith an improved coverage of the donor material at edges on the target substrate can be achieved. In a ring-shaped energy distribution the ringshaped beam for example has an increased intensity in an angular portion of for example 10 to 90 degrees, for example within a region of about 50 degrees.

[0040] FIG. 1A shows a portion of an alternative embodiment, wherein the donor substrate 10 is maintained at a fixed position with respect to the target substrate 20 by means of shims or spacers 105.

[0041] FIG. 2 schematically shows an assembly comprising an embodiment of the deposition apparatus and a monitoring apparatus for monitoring the deposition process in an operational state of the deposition apparatus. FIG. 2A shows a portion of the deposition apparats in more detail.

[0042] In the embodiment shown, the optical beam generator of the deposition apparatus comprises a main optical source 131 to generate a beam of coherent optical radiation and a beam shaper. In the embodiment shown, the main optical source 131 is a laser of type AVIA-335-4500. In this example, as shown in more detail in FIG. 2A, the beam shaper includes a first and a second axicon 134, 135. The beam shaper 134, 135 is controlled by signal S.sub.130 from controller 300. The controller controls the apparatus on the basis of specification data D.sub.S retrieved from a memory unit 320. In response to the control signals 130, a distance along the optical path between the first and the second axicon is set to scale the size of the ring-shaped beam. Furthermore an asymmetric intensity profile may be obtained by shifting one of the axicons for example the second axicon in a direction away from the optical axis. Additional optical elements may be provided, such as a beam-director 138 and one or more other optical elements to focus the beam on the donor substrate 10.

Alternatively another type of beam shaper may be provided such as a digital micromirror device (DMD). In a still further embodiment a beam shaper may be integrated in the optical source, for example inside a cavity of a laser serving as the optical source.

[0043] In the embodiment shown, the monitoring apparatus is provided as a shadowgraphy arrangement that comprises a further optical source 200 of radiation, an a microscopy camera arrangement with a microscope 230 and a camera 240. The further optical source 210 generates an auxiliary beam that is directed according to an optical path via the environment including the trajectory of the jet towards the microscopy camera arrangement. Therewith the optical path extends in a direction transverse to the trajectory of the jet to be ejected. An alternative monitoring apparatus may be considered wherein the jet is observed with reflection imagery.

[0044] A controller 300 is provided that activates the further optical source 200 with a trigger signal St1, before activating the main optical source 131 with a trigger signal St2. The further optical source 210 may cooperate with a delay element 210 in the optical path to monitor the jet at different points in time. Alternatively or additionally a controllable delay may be achieved by selection of the time interval between the points in time at which the trigger signals St1, St2 are issues. Also a video camera may be employed that upon triggering by the signal St1 records the complete development of the jet in a single cycle. In the embodiment shown, the monitoring apparatus includes additional components 220 to condition the auxiliary beam. In this case a fluorescent element converts the UV-radiation issued by the further auxiliary source 200 into visible radiation. Alternatively, an alternative auxiliary radiation source may be used that renders radiation in the visible spectrum, or a microscopy camera arrangement may be employed that is suitable for UV-imaging. The additional components 220 may further include elements like lenses.

[0045] In the embodiment shown in FIG. 2, the apparatus comprises a feed back control unit 310 to adapt a response of the controller 300 to received specification data D.sub.S in accordance with observation data S.sub.fb. In the embodiment shown the observation data S.sub.fb is jet observation data that is obtained from the camera 240 with which the development of the jet of transferred donor material is observed.

[0046] Alternatively or additionally a target monitoring apparatus may be included that provides target observation data indicative for observed properties of deposited donor material on the target surface as observation data.

[0047] Experiments were performed using a viscous silver nanoparticle ink with a high metal load. Specifically the ink used has a surface tension of about 35 dyn/cm, a metal load of about 70% ww, and a static viscosity of about 6 Pas.

[0048] FIG. 3A and FIG. 3AA show an example of an applied intensity profile in more detail. In particular, FIG. 3AA shows an intensity distribution of the radiation beam in the x-y plane coinciding with the donor substrate and the main drawing of FIG. 3A shows the intensity distribution along the dashed line parallel to the y-axis. The intensity is expressed W/cm.sup.2 and the y-position is indicated in mm. FIG. 3B shows in more detail the jet 14j short after impingement of the beam 30 on the donor material. It is noted that in this case, as will typically be the case, the spatial intensity distribution does not change in the time-interval in which the radiation pulse is applied. Accordingly the energy distribution is simply the product of the intensity distribution and the duration of the time-interval.

[0049] In FIG. 3AA it can be seen that the intensity distribution of the optical beam is substantially ring-shaped. In the example shown, the radiation beam ring has a diameter of approximately 150 micron and a width of a approximately 20 micron. As further shown in the main part of FIG. 3A, an asymmetry is present in that the ring beam has an increased intensity in an angular portion delimited between about 25 to about 25 degrees from the y-axis. In the example shown in FIG. 3A, 3AA, the maximum intensity in this region of increased intensity is about 150 W/cm.sup.2. In the remainder the maximum in the ring is in the ranged of 50 to 60 W/cm.sup.2.

[0050] Upon ejection, the jet 14j of ejected material has a momentum pattern corresponding to the force pattern induced by the optical beam, and as can be seen in FIG. 3B, the jet of ejected material is morphed according to this momentum pattern. Hence, as further illustrated in the examples below, the jet can be controllably directed in a particular direction by generating an optical beam which has an asymmetrical energy distribution in that the energy of the beam is relatively high at a side corresponding to that particular direction. This is surprising, it was found very complicated to control direction in inkjet deposition methods. Therein the effect of the surface tension of the material is of the same order of magnitude as the effect of the momentum pattern (inertia) with which the material is originally ejected. Because the effect of the surface tension of the material is a tendency to direct the ejected material in a direction away from the side of the highest intensity, and these effects are of a comparable strength, a direction control therein is complicated. It could be expected, that due to the small dimensions prevailing in LIFT-processing, in the present application the effect of inertia is even smaller, therewith rendering a direction control impossible. However, as observed above, a clear relationship was found between the asymmetry of the energy distribution of the optical beam and the direction of the jet, whereas the surface tension of the ejected material is only of minor importance in this process.

[0051] FIG. 4A-4G schematically shows subsequent stages of development of a jet of ejected viscous donor material resulting from exposure to a radiation beam having an intensity profile as shown in FIG. 4. FIG. 4A-4G are micrograph pictures taken respectively at 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s after the point in time the exposure took place. The micrograph pictures are obtained with the arrangement presented in FIG. 2. As can be seen in this sequence of figures FIG. 4A-4G, the donor material can ejected from a relatively surface area of the donor surface and controllably directed to a relatively small surface are on the target. Therewith it is also rendered possible to transfer the donor material as long jets bridging a distance up to a few cm between the donor substrate and the target substrate. This enables a broad range of applications, ranging from face-up integration of thin and relatively thick components to conformal printing.

[0052] A shown in FIG. 5A, 5AA, 5B and FIGS. 6A, 6AA, and 6B, the shape of the jet, and therewith the pattern with which the donor material is deposited can be reproducibly controlled by the energy distribution.

[0053] As a first example FIG. 5A, FIG. 5AA show again the energy distribution like that in FIG. 3A, 3AA which is repeatedly applied in a series of experiments (a)-(f). FIG. 5B shows for each of these experiments the jet of donor material that is observed a point in time 35 s after exposure to the optical beam. As can be seen in these series of micrographs hardly any variance of the shape of the jet is visible.

[0054] As a second example FIG. 6A, FIG. 6AA show another energy distribution using the same representation and scale as the one in FIG. 3A, 3AA which is also repeatedly applied in a series of experiments (a)-(f). FIG. 6B shows for each of these experiments the jet of donor material that is observed a point in time 35 s after exposure to the optical beam. As can be seen in these series of micrographs the very rugged shape of the jet is accurately reproduced.

[0055] In summary, in operation of a device as claimed a deposition method is executed. Therein a donor substrate 10 is arranged opposite a target substrate 20. The donor substrate 10 has a surface 12 facing the target substrate 20 that is provided with a viscous donor material 14. The donor material 14 has viscoelastic properties, in particular at an elevated temperature. Having the donor substrate 10 and the target substrate 20 so arranged, an optical beam 30 is generated, and directed via the donor substrate 10 to the donor material 14 so as to release the donor material and transfer the donor material as a jet 14j towards the target substrate. In the claimed method, an input signal is received that specifies a shape to be assumed by the jet in which the donor material is to be transferred and an energy profile of the optical beam is controlled based on the specified shape. Alternatively or in addition an energy profile of the optical beam may be controlled based on specifications for a pattern in which donor material is to be deposited on the target substrate.

[0056] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. In particular, unless clear from context, aspects of various embodiments that are treated in various embodiments separately discussed are deemed disclosed in any combination variation of relevance and physically possible and the scope of the invention extends to such combinations. Other variations to the disclosed embodiments can be understood and by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. A single unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.