Replication and related methods and devices, in particular for minimizing asymmetric form errors

Abstract

The method regards manufacturing devices by replication, wherein each of the devices comprises a device surface. The method comprises producing the devices from a replication material by replication using a replication tool (1), wherein the replication tool (1) comprises a tool material comprising replication sites (4) comprising a replication surface (5) each. Each of the replication surfaces (5) corresponds to a negative of the device surface of a respective one of the devices. The tool material comprises, in addition to the replication sites, one or more mitigating features (7) for reducing asymmetric form errors of the device surfaces. Replication tools (1) and methods for manufacturing these are also described.

Claims

1. A method for manufacturing devices by replication, each of the devices comprising a device surface, the method comprising: producing the devices from a replication material by replication using a replication tool; wherein the replication tool comprises a tool material comprising replication sites comprising a replication surface each, wherein each of the replication surfaces corresponds to a negative of the device surface of a respective one of the devices, and wherein the tool material comprises, in addition to the replication sites, one or more mitigating features, wherein the mitigating features comprise recesses, grooves, cuts or protrusions, and wherein the replication sites and the mitigating features are separated by the tool material so that the replication material does not flow between the replication sites and the mitigating features during manufacturing and the devices are solely shaped by the replication sites, wherein the mitigating features are features for at least one of: reducing a directionality of shape deviations of the replication surfaces; reducing a directionality of shape deviations of the replication surfaces from a negative of respective desired device surface shapes; avoiding or at least reducing asymmetric form errors of the device surfaces; reducing a directionality of a distribution of tool material in a respective region around each of the replication sites; increasing a uniformity of a distribution of the tool material in respective regions around each of the replication sites; and relieving stress in the tool material.

2. The method according to claim 1, further comprising producing the mitigating features after producing the replication surfaces, and wherein the mitigating features are features for at least one of: for provoking at least partial reversal of an undesired deformation of the replication surfaces; for provoking a desired deformation of the replication surfaces, wherein said desired deformation at least partially reverses a pre-existing undesired deformation of the replication surfaces.

3. The method according to claim 1, further comprising producing the mitigating features at the time of producing the replication surfaces, and wherein the mitigating features are features for avoiding or at least reducing a deformation of the replication surfaces, wherein the method comprises producing the replication surfaces by means of shaping surfaces of a master during manufacture of the replication tool, and wherein said deformation is a deformation relative to a negative of respective shaping surfaces of the master.

4. The method according to claim 1, wherein the replication surfaces comprise recesses in the tool material.

5. The method according to claim 1, wherein the devices are rotationally symmetric optical devices.

6. The method according to claim 1, wherein a lateral distribution of the replication sites has a symmetry lower than a rotational symmetry of order two, wherein the rotational symmetry is a two-fold mirror symmetry.

7. The method according to claim 1, wherein the producing the devices by replication comprises a carrying out an embossing process.

8. The method according to claim 1, wherein the replication tool comprises a rigid carrier to which the tool material is attached, and wherein the tool material is resilient and/or has an open-porous structure, and wherein the tool material is a silicone.

9. The method according to claim 1, wherein the mitigating features are interspersed with the replication sites.

10. A replication tool for manufacturing devices by means of replication, the replication tool comprising a multitude of replication sites established in a tool material of the replication tool, each of the replication sites having a replication surface having a shape corresponding to a negative of a device surface of one of the devices; and, in addition, one or more mitigating features, wherein the mitigating features are features for avoiding or at least reducing asymmetric form errors of the devices wherein the mitigating features comprise recesses, grooves, cuts or protrusions, and wherein the replication sites and the mitigating features are separated by the tool material so that the replication material does not flow between the replication sites and the mitigating features during manufacturing and the devices are solely shaped by the replication sites.

11. The replication tool according to claim 10, wherein the replication sites are arranged on a non-square rectangular grid, and the mitigating features are interlacing the grid.

12. The replication tool according to claim 10, wherein the replication sites are arranged in mutually parallel rows, and at least a portion of the mitigating features are arranged between neighboring ones of the rows, wherein at least a portion of the mitigating features are arranged between each pair of neighboring ones of the rows.

13. The replication tool according to claim 10, wherein the mitigating features are located in the vicinity of each of the replication sites and are distinct from the replication surfaces and the replication sites.

14. The replication tool according to claim 10, wherein the replication surfaces comprise recesses in the tool material, wherein the replication surfaces are concave.

15. The replication tool according to claim 10, comprising a carrier to which the tool material is attached, wherein the carrier is stiffer than the tool material, wherein the tool material is a resilient material, wherein the tool material is a silicone.

16. The replication tool according to claim 10, wherein the mitigating features are features for reducing asymmetric form errors of the replication surfaces.

17. The replication tool according to claim 10, wherein the tool material has an open porous structure, wherein the tool material is a silicone.

18. The replication tool according to claim 17, wherein the tool material is a polydimethylsiloxane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is described in more detail by means of examples and the included drawings. In the drawings, same reference numerals refer to same or analogous elements. The figures show schematically:

(2) FIG. 1 a schematic illustration of a replication tool with locally applied replication material, in a cross-sectional view;

(3) FIG. 2 a schematic illustration of shaping of replication material during an embossing process using the replication tool of FIG. 1, in a cross-sectional view;

(4) FIG. 3 a schematic illustration of a removal of the replication tool of FIGS. 1 and 2 from produced devices, in a cross-sectional view;

(5) FIG. 4 a schematic illustration for explaining an asymmetric form error;

(6) FIG. 5 a schematic illustration of a replication tool having mitigating features, in a top view onto the tool material;

(7) FIGS. 6a, 6b a schematic illustration of a replication tool having mitigating features, in a vertical view and in a cross-sectional view, respectively;

(8) FIGS. 7a, 7b a schematic illustration of a replication tool having mitigating features, in a vertical view and in a cross-sectional view, respectively;

(9) FIG. 8 a replication tool and a master for producing the replication tool, in a cross-sectional view;

(10) FIG. 9 the replication tool of FIG. 8 and devices produced using the replication tool, in a cross-sectional view.

(11) The described embodiments are meant as examples or for clarifying the invention and shall not limit the invention.

DETAILED DESCRIPTION OF THE INVENTION

(12) FIG. 1 schematically illustrates a replication tool 1 in a cross-sectional view which is a wafer-level replication tool for embossing. It includes a tool material 2 which adheres to a rigid carrier 3 such as a glass plate. The tool material 2 establishes a number of replication sites 4, four of which are illustrated in FIG. 1. In each replication site, a replication surface 5 is provided which exhibits the negative of the shape of a surface of a device to be produced by replication using the replication tool 1.

(13) Replication tool 1 includes mutually distanced replication sites 4, for the manufacture of separate devices by replication, such as a multitude of microlenses.

(14) The tool material 2 can be a resilient material, and it can be a material which is interspersed pores and/or channels.

(15) The tool material can be a spongy material.

(16) The tool material can be, e.g., a polydimethylsiloxane (PDMS).

(17) In FIGS. 1 to 3, a replication process is illustrated. The replication process in the illustrated embodiment is an embossing process. A replication material 9 is applied between tool material 2 and a substrate 11 which can be a rigid plate such as a glass plate. Replication material 9 can be applied locally, in a plurality of separate portions. In FIG. 3, this is the case, and replication material 9 is applied to tool material 2, but, e.g., application to substrate 11 (in addition or alternatively) would be possible, too.

(18) The replication material 9 can be, e.g., a curable material, e.g., a curable epoxy resin.

(19) With replication material 9 between substrate 11 and replication tool 1, these two are moved towards each other, e.g., until they abut each other, cf. FIG. 2. In this position, replication material 9 is shaped at the replication sites 4 of replication tool 1, and more particularly, each portion of the applied replication material 9 is shaped by one of the replication surfaces 5. At the same time, replication material 9 is in contact with substrate 11, too.

(20) While maintaining the relative position of substrate 11 and replication tool 1, replication material 9 is hardened, e.g., cured, e.g., by UV irradiation and/or by application of heat.

(21) After the hardening process, a plurality of separate devices 10 is produced on substrate 11 each of which has a device surface 15 having a shape corresponding to the negative of the shape of one of the replication surfaces 5, and replication tool 1 is removed, cf. FIG. 3.

(22) As an option, it is possible to subject the replication tool 1, in particular the tool material 2, to a conditioning step before carrying out the replication process, e.g., by exposing the tool material 2 to a conditioning material. Such a conditioning material can be, e.g., the same material as the replication material used in the replication processes, e.g., they both can be the same epoxy resin. The conditioning material can be applied locally (such as illustrated in FIG. 1 for the replication material) or, e.g., by applying a continuous film of conditioning material which covers all replication sites 4.

(23) In reaction to the exposure to the conditioning material, tool material 2 can slightly change dimensionally, e.g., it undergoes a slight swelling process. For example, a portion of conditioning material can afterwards be present in pores and channels of an open porous structure of tool material 2, wherein it can have replaced a portion of material, e.g., of PDMS precursors and uncured PDMS, respectively, present in the pores and channels prior to the exposure to conditioning material.

(24) Subsequently, the conditioning material is removed from tool material 2. A possible way of removing the conditioning material from replication tool 1 is to harden the initially liquid conditioning material, e.g., by exposing it to energy, such as by irradiating it with UV radiation and/or by heating it, and then to remove the hardened conditioning material.

(25) The conditioning can effect that a size of produced devices 10 can be more precisely predicted and that the size of produced devices 10 can be kept very constant during several replication processes which are successively carried out using one and the same replication tool 1. Further details regarding the conditioning are described in the U.S. provisional application Ser. No. 62/503,464 mentioned above.

(26) However, an effect observed by the inventors relates not so much to the (overall) size of the produced devices 10, but rather to their shape, and more particularly to asymmetric form errors the devices 10 can exhibit.

(27) FIG. 4 is a schematic illustration for explaining an asymmetric form error, as it may occur in a replication process such as in the embossing process illustrated in FIGS. 1 to 3. The elliptical shape illustrates a produced device 10 in a top view, i.e. in a vertical view onto the lateral plane (x-y-plane). The dotted circle illustrates a desired shape 15a of the device. Obviously, there is a discrepancy between the desired (rotationally symmetric) shape 15a and the actual shape 15 which merely as an elliptical symmetry, i.e. there are shape deviations between the desired shape 15a and the actually produced shape which have a directionality. (If the discrepancies were identical along all directions, there would be no directionality of the the shape deviations, and a simple overall scaling could convert the produced shape 15 into the desired shape 15a.)

(28) In the illustrated simple case, the size of device 10 along the x-axis corresponds to the desired size, but the size along the y-axis is smaller than desired.

(29) Of course, shape deviations can be much more complicated, exhibiting a more complicated directional dependencies. And generally, also the third dimension (along the z-axis) could be considered. However, how to handle these more complicated approaches and cases will become clear from the explanations regarding the instant relatively simple case.

(30) Concentrating on merely a dimension along the x-axis and a dimension along the y-axis, one can simply quantify the shape deviations by two scaling factors, Fx and Fy, for the respective two directions. E.g., Fx=(device size along x)/(desired size along x) and Fy=(device size along y)/(desired size along y). In the illustrated case, Fx equals 1, and Fy is lower than one, e.g., is approximately 0.8.

(31) A numerical value for the directionality can be defined, e.g., by forming the quotient of the (absolute values of the) scaling factors (Fx, Fy) for the considered directions and subtracting 1 therefrom, i.e. in the instant case a value for the directionality would be 1.0/0.8−1=1.25−1=0.25. Other ways of defining a numerical value for the directionality are readily at hand, such as involving integration over directions and/or other ways of normalizing.

(32) Reducing this value, optimally to zero, is a goal to be achieved for improved shape fidelity in replication. This can be achieved by the provision of mitigating features, e.g., in the way as herein described.

(33) Whereas FIG. 4 has been explained above in terms of illustrating the produced device 10, it is also possible to regard FIG. 4 as illustrating a replication surface 5 of a replication tool 1 (in a vertical view)—at the time of shaping the replication material (such as in FIG. 2). And the dashed circle would illustrate a desired device shape The explanations are analogous.

(34) FIG. 5 illustrates in a top view a replication tool 1 having mitigating features 7. The replication sites 4 and replication surfaces 4 are arranged on points of a non-square rectangular grid. The next-neighbor distances in x- and y-direction are dx and dy, respectively, with dx>dy. Similarly as in FIG. 4, the dotted circles labelled 5a indicate the desired shape of the replication surfaces 5—in this view in the lateral plane; and the ellipses symbolize the actual shapes labelled 5 in absence of mitigating features 7 exhibiting an asymmetric form error (a directionality of shape deviations). The replication surfaces 5 can be, e.g., concave surfaces, resulting in convex produced device surfaces. The mitigating features 7 are in this embodiment cuts in the tool material. The mitigating features 7 can run, as illustrated in the instant embodiment, along mutually parallel lines, e.g., parallel to the direction along which the next neighbor distance is lower (i.e. along the y-direction), and the mitigating features 7 can be located in the middle between neighboring rows of replication sites 5.

(35) With the mitigating features 7 provided in the replication tool 1 and more particularly in the tool material 2, the asymmetry of the form errors (and the directionality of the shape deviations) is much reduced, such that the replication surfaces 5 assume at least approximately the shape illustrated by the dashed circles labelled 5a.

(36) The cuts can be applied to the tool material after producing the replication sites 5, such as after hardening the tool material 2 (provided that the tool material is shaped in a replication process).

(37) Assumed reasons why the provision of the mitigating features 7 makes possible to overcome asymmetric form errors (at least in part) have been explained above.

(38) Mitigating features 7 can also be different from cuts. E.g., they can be recesses in the tool material.

(39) FIGS. 6a, 6b are schematic illustrations of a replication tool 1 having mitigating features 7 which are recesses in the tool material 2. FIG. 6a illustrates the replication tool 1 in a vertical view; FIG. 6b in a cross-sectional view.

(40) The mitigating features 7 in FIGS. 6a, 6b are single recesses which are aligned in mutually parallel rows centering between neighboring rows of the replication sites 5. They may exhibit the same shape as the replication sites or (slightly) different shapes, such as illustrated in FIG. 6b. A difference between the replication sites 4 and the mitigating features 7 is established, e.g., in that the mitigating features 7 are not brought in contact with replication material from which the devices 10 are formed. E.g., the mitigating features 7 are not brought in contact with any replication material (optionally except for an exposure thereto in an optional conditioning process carried out prior to the actual replication process); and/or the mitigating features 7 are not exposed to a replication material during the replication process in which the devices 10 are produced; and/or the mitigating features 7 are exposed to a replication material during the replication process in which the devices 10 are produced, but whatever may be produced this way is not one of said devices 10.

(41) Mitigating features 7 of such a kind can be produced, e.g., by shaping the tool material 2 accordingly, in particular already at the time of shaping the replication sites 5. This can be accomplished, e.g., using a suitably structured master in a replication process for shaping the tool material 2.

(42) Here and in the other illustrated embodiments, the mitigating features 7 are not features which are merely peripherically located at the replication tool 1. But the arrangement of the mitigating features 7 overlaps the arrangement of the replication sites 5. And more particularly, the mitigating features 7 can interlace a grid defined by the replication sites 5.

(43) FIGS. 7a, 7b are schematic illustrations of a replication tool 1 having mitigating features 7 which are grooves in the tool material 2. FIG. 7a illustrates the replication tool 1 in a vertical view; FIG. 7b in a cross-sectional view.

(44) The mitigating features 7 in FIGS. 7a, 7b are grooves. A portion of the grooves runs parallel to rows defined by next-neighbor replication sites 5 (i.e. aligned along the y-axis), and another portion perpendicularly thereto (i.e. aligned along the x-axis). The widths and/or the depths of the grooves can be different for the two portions. The grooves can be considered to establish a single mitigating feature, namely a mitigating feature constituting a groove lattice. The grooves can have cross-sections as illustrated in FIG. 7b. But they may also have different cross-sections, e.g., rectangular cross-section.

(45) As described for FIGS. 6a, 6b, the mitigating features of FIGS. 7a, 7b can be produced, e.g., already at the time of shaping the replication sites 5, but they may, alternatively, be produced later, for example, by machining the tool material 2 (not illustrated).

(46) FIG. 8 illustrates an example for such a way of producing mitigating features 7 at the time of shaping the replication sites 5.

(47) FIG. 8 illustrates, in a cross-sectional view, a replication tool 1 and a master 20 used in producing the replication tool 1, more particularly for shaping the tool material 2 in a replication process.

(48) Master 20 has shaping sites 24 for shaping the replication sites 4 of replication tool 1. Each shaping site 24 includes a shaping surface 25 for shaping a respective replication surface 5. Accordingly, the shaping sites 24 correspond (with respect to their shapes) to device surfaces of devices 10 to be produced and to negatives of the replication surfaces 5.

(49) Furthermore, master 20 is shaped to exhibit further structures adjoining the shaping surfaces 25 for shaping additional surfaces portions 8 of the replication tool 1. These are useful in case the devices shall be produced by embossing with flow control, as will be explained below (cf. FIG. 9).

(50) Still furthermore, master 20 includes in addition to the shaping sites 24 additional shaping sites 27 which are provided for shaping the mitigating feature(s) 7. Since the mitigating features 7 establish a recess, e.g., a groove, in the illustrated case, the additional shaping sites 27 establish a protrusion of master 20.

(51) For example, tool material 2 in its initial, e.g., uncured, state can be applied to carrier 3 and shaped by master 20 in a vacuum injection molding process. During the shaping, it is hardened, e.g., cured. Then, the master is removed.

(52) FIG. 9 illustrates, in a cross-sectional view, replication tool 1 of FIG. 8 and devices 10 produced on a substrate 11 using replication tool 1. Each of the devices 10 constitutes a main portion of a structure produced from replication material using replication tool 1. Each device 10 exhibits a device surface 15. In addition, the produced structure includes a surrounding portion 18 at least partially surrounding (laterally) the respective device 10. The shape of the surrounding portions 18 is partially determined, more particularly shaped, by the additional surface portions 8 of replication tool 1 and partially shaped by flow of the replication material and the involved forces, predominantly by capillary forces.

(53) The devices 10 can be, e.g., optical devices, such as lenses, more particularly microlenses. Asymmetric form errors of the described kind can lead, e.g., to an undesired optical aberrations such as an astigmatism of the (ideally rotationally symmetric) lenses. I.e. the lenses would exhibit different focal lengths for light impinging on the lens along different directions. The mitigating features 7 can reduce or remove such undesired astigmatism or other undesired (optical) effects arising from asymmetric form errors.

(54) Depending on the circumstances, there are various reasons for which the mitigating features 7 can be applied and various effects the mitigating features 7 can have. For example:

(55) The mitigating features can be provided for avoiding or at least reducing asymmetric form errors of the device surfaces produced.

(56) The mitigating features can be provided for reducing a directionality of shape deviations (or: for reducing direction-dependent shape deviations) of the replication surface; more particularly for reducing a directionality of shape deviations of the replication surfaces from respective initial shapes of the replication surfaces. The initial shapes can correspond to a negative of the shape of a shaping surface of a master and/or to a negative of a shaping surface of a master and/or to a negative of a desired device surface. And/or the initial shapes correspond to shapes exhibited by the replication surface at the time of shaping the replication surfaces.

(57) The mitigating features can be provided for reducing a directionality of shape deviations of the devices, more particularly of shape deviations of the device surfaces. The deviations can be deviations from a desired shape.

(58) The mitigating features can be provided for reducing a directionality of shape deviations of the replication surfaces from respective shaping surfaces of a master used for shaping the tool material (and in particular the replication sites) in a replication process

(59) The mitigating features can be provided for reducing a directionality of shape deviations of the replication surfaces from a negative of respective desired device surfaces.

(60) The mitigating features can be provided for increasing a homogeneity (or, vice versa, decreasing a directionality) of a distribution of tool material in a respective region around each the replication sites.

(61) The mitigating features can be provided for provoking a (desired) deformation of the replication surfaces, in particular wherein said (desired) deformation at least partially reverses a pre-existing (undesired) deformation of the replication surfaces. This can in particular be the case if the mitigating features are produced after the replication sites have been produced. Reasons for the occurrence of such undesired deformations have been herein described.

(62) The mitigating features can be provided for provoking an at least partial reversal of an (undesired) deformation of the replication surfaces; wherein said (undesired) deformations can have taken place after shaping the replication surfaces (e.g., using a suitable master). And said deformations can have occurred before shaping replication material by means of the replication surface to produce the devices. This can in particular apply if the mitigating features are produced after the replication sites have been produced.

(63) The mitigating features can be provided for avoiding or reducing a deformation of the replication surfaces, in particular a deformation relative to a negative of a shaping surface of a master by means of which the replication surfaces are shaped during manufacturing the replication tool. This can in particular be the case if the mitigating features are produced simultaneously with the replication sites.

(64) The mitigating features can establish one or more stress-relieving structures at which the tool material can relieve stress, in particular thermo-mechanical stress.

(65) The mitigating features can contribute to making a distribution of the tool material in respective a region around each of the replication sites more uniform.

(66) The mitigating features can effect that asymmetric form errors (and/or a directionality of shape deviations; from a respective master and/or from a (desired) device, as herein described) of the produced devices (and/or of the replication surfaces at the time of producing the devices by replication using the replication tool) which would occur with another replication tool, which is identical with the replication tool but merely does not include the mitigating features, are reduced (or even completely avoided). The identity of the replication tool and the other replication tool (without the mitigating features) can also include that both are manufactured identically—of course except for the provision of the mitigating features.

(67) The mitigating features can be provided for reducing asymmetric form errors (as described) with respect to asymmetric form errors occurring when using another replication tool which is an identical replication tool, but which differs from the replication tool merely in that it is void of the mitigating features.

(68) As will have become clear, the provision of the mitigating features can improve shaping fidelity and can result in the production of better quality devices.