Wafer-level manufacture of devices, in particular of optical devices

Abstract

The wafer-level method for applying N2 first elements to a first side of a substrate, wherein the substrate has at the first side a first surface including the steps of providing the substrate, wherein at least N barrier members are present at the first side, and wherein each barrier member is associated with one of the first elements. For each of the first elements, the method includes bringing a first amount of a hardenable material in a flowable state in contact with the first surface, the first amount of hardenable material being associated with the first element; controlling a flow of the first amount of hardenable material on the first surface with the associated barrier member; and hardening the first amount of hardenable material to interconnect the first surface and the respective element.

Claims

1. A wafer-level method for applying N2 first elements to a first side of a substrate, the substrate providing at the first side a first surface, the method comprising: a) replicating at least N barrier members and an initial first element on the first surface of the substrate by an embossing-type or molding-type process, wherein the initial element and at least one of the at least N barrier members are simultaneously and integrally formed, and wherein each of the N barrier members is associated with one of the N first elements; b) bringing a respective first amount of a hardenable material in a flowable state in contact with the first surface, the respective first amount of hardenable material being subsequently used to form a respective one of the N first elements; c) performing an embossing-type replication technique that includes pressing a replication tool into the first amount of the hardenable material; d) controlling a flow of the respective associated first amount of hardenable material on the first surface, during the embossing-type replication technique, by means of a respective barrier member integrally formed with the initial first element; e) hardening the respective associated first amount of hardenable material to form the respective one of the N first elements.

2. The method according to claim 1, wherein a contact angle for the hardenable material on the barrier member amounts to at most 90.

3. The method according to claim 1, wherein the hardenable material is hardenable via the introduction of energy.

4. The method according to claim 1, wherein each of the N first elements is or comprises one or more of a replicated structure replicated at the first surface comprising steps b), c) and d); an item to be bonded to the first surface; a micro-optical component; a passive optical component; an active optical component; an electronic component; a light emitting element; a light-detecting element; a micro-mechanical component; a micro-fluidic component; a portion of a wafer.

5. The method according to claim 1, wherein each of the N barrier members comprises a protrusion protruding beyond an average level described by the first surface, the respective protrusion comprising a first partial surface, said first partial surface is at least one of: facing towards the respective first element in its position at the end of step d) and being horizontally aligned within 35, and a second partial surface facing away from the respective first element in its position at the end of step d), wherein the first partial surface is, at the end of step d), at least partially covered by hardenable material of the respective associated first amount of hardenable material, and wherein the second partial surface is, at the end of step d), free from hardenable material of the respective associated first amount of hardenable material.

6. The method according to claim 1, wherein each of the N barrier members forms a protrusion protruding beyond an average level described by the first surface by at least 2 m or by at most 150 m or by both, at least 2 m and at most 150 m.

7. The method according to claim 1, wherein a contact angle for the hardenable material on the barrier member amounts to at most 45.

8. The method according to claim 1, wherein the hardenable material is hardenable by one or both of heating it and irradiating it with electromagnetic radiation.

9. The method according to claim 1, wherein each of the N first elements is an optical element.

10. The method according to claim 5, wherein the first and second partial surface are adjoining at an edge and the first partial surface is, at the end of step e), covered by hardenable material of the respective associated first amount of hardenable material up to the edge.

11. The method of claim 1 including hardening the respective associated first amount of hardenable material to form the respective one of the first elements surrounded laterally by the associated one of the barrier members.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is described in more detail by means of examples and the included drawings. The figures show in a strongly schematized way:

(2) FIG. 1 a substrate with barrier members, in a cross-sectional view;

(3) FIG. 2 the substrate of FIG. 1 during the process of applying an element to the substrate, in a cross-sectional view;

(4) FIG. 3 the substrate of FIGS. 1 and 2 with the element attached in its target position, in a cross-sectional view;

(5) FIG. 4 the substrate of FIG. 1 during the process of applying an element which is a wafer, in a cross-sectional view;

(6) FIG. 5 the substrate of FIGS. 1 and 4 with the wafer attached in its target position, in a cross-sectional view;

(7) FIG. 6 the substrate of FIG. 1 during the process of applying an element which is a replicated optical element, in a cross-sectional view;

(8) FIG. 7 the substrate of FIG. 6 with the optical element present on the substrate in its target position, in a cross-sectional view;

(9) FIG. 8 an illustration of an application of an element onto a substrate by replicating the element on the substrate, wherein a barrier member is provided by another element replicated on the substrate, in a cross-sectional view;

(10) FIG. 9 an illustration of wafer-level manufactured devices which are opto-electronic modules, in a cross-sectional view;

(11) FIG. 10 an illustration of a flow of material onto a barrier member integrated in a substrate, in a cross-sectional view;

(12) FIG. 11 an illustration of a flow of material onto a barrier member dispensed onto a substrate, in a cross-sectional view;

(13) FIG. 12 an illustration of a flow of material towards a barrier member which is a depression in a substrate, in a cross-sectional view;

(14) FIG. 13 an element and an associated barrier member as as well as further items on a substrate, in a top view;

(15) FIG. 14 an element and an associated barrier member as as well as a further item on a substrate, in a top view;

(16) FIG. 15 an element and an associated discontinuous barrier member as as well as a further item on a substrate, in a top view;

(17) FIG. 16 an illustration of a flow of material onto a barrier member such as a barrier member formed by photo resist material, in a cross-sectional view.

(18) The described embodiments are meant as examples and shall not limit the invention.

(19) The presented figures are all strongly schematized.

DETAILED DESCRIPTION OF THE INVENTION

(20) FIG. 1 shows, in a cross-sectional view, a substrate 1 having at a first side a first surface 1a and at a second side a second surface 1b. Substrate 1 is a wafer, and only a small portion of the wafer is visible in FIG. 1.

(21) At surface 1a, a barrier member 40 is present, which may describe a closed-loop shape such as a circle or a rectangle. In FIG. 13, a barrier member 40 describing a circular closed loop is illustrated in a top view.

(22) Substrate 1 defines lateral directions, which are directions parallel to the first and second sides of substrate 1 and, accordingly, also vertical directions, which are perpendicular to the lateral directions. An average level of first surface 1a is referred to as 1m.

(23) Barrier member 40 has a first partial surface 41 and a second partial surface 42 which are at an angle amounting, in the example of FIG. 1 to about 320. Partial surfaces 41, 42 may, as illustrated in FIG. 1 adjoin at an edge 45.

(24) In particular, second partial surface 42 may, in general for protruding barrier members 40, be vertically aligned, at least within 35 or rather within 15.

(25) Furthermore, barrier member 40 may, in general for protruding barrier members 40, protrude beyond an average level described by the first surface by at least 2 m or by at least 8 m, and/or by at most 150 m or by at most 80 m.

(26) FIG. 2 illustrates substrate 1 of FIG. 1 in the same cross-sectional view, but during the process of applying an element 10 to substrate 1. A hardenable material 5 in a flowable state (typically a liquid hardenable material 5) has been brought into contact with surface 1a, such that on surface 1a, an amount of the material 5 is present. Hardenable material 5 may be, e.g., a heat-curable and/or a UV-curable adhesive, e.g., a heat-curable and/or a UV-curable epoxy resin. With barrier member 40 present on substrate 1, element 10 is brought into contact with material 5, as illustrated by the open arrow in FIG. 2.

(27) In FIG. 3, the substrate of FIGS. 1 and 2 is illustrated with element 10 attached to substrate 1 in its target position. Material 5 is hardened, such that element 10 is permanently fixed to substrate 1. The presence of barrier member 40 effects that a flow of material 5 (prior to the hardening) is controlled. In particular, material 5 shall not flow across barrier member 40. This way, features or elements or any kind of items present beyond barrier member 40 are not exposed to and/or (partially) covered by some of the material 5. Accordingly, using barrier members can make possible to achieve a particularly high density of elements on a substrate.

(28) It is noted that partial surface 41 of barrier member 40 is at least partially covered by material 5. In contrast to other concepts such as, e.g., solder masks, this is a desired effect, and, accordingly, a contact angle between the material of barrier member 40 and hardenable material 5 is rather low, e.g., =14 as illustrated in the example of FIG. 3.

(29) Furthermore, it is usually not intended to encapsulate the element, as can also be seen from the fact that a top surface 18 of element 10 is completely free from material 5.

(30) It is noted that the region of surface 1a where element 10 is present at surface 1a (with some of material 5 in between, of course) is smooth, free of edges, and in addition, it is also planar, essentially flat.

(31) Element 10 may be virtually any kind of item to be attached to substrate 1, in particular a pre-fabricated item, e.g., an active optical component or a passive optical component, or an electronics component.

(32) FIGS. 4 and 5 illustrate, similarly to FIGS. 2 and 3, respectively, the case that element 10 is a part of an extended substrate such as of a waferscale substrate, wherein on the waferscale substrate, elements may possibly be provided (pre-assembled elements). Element 10 may be a wafer or a portion of a wafer. Again, element 10 is in its target position (cf. FIG. 5) not before material 5 is applied to surface 1a.

(33) However, the application of an element 10 to substrate 1 may also be accomplished in such a way that the element 10 is simultaneously (in one and the same process) created and applied (or attached) to surface 1a, e.g., as shown in FIG. 6.

(34) FIG. 6 shows again the substrate of FIG. 1 during the process of applying an element 10, but element 10 includes a replicated optical element to be created on surface 1a in an embossing-type process. A replication tool 50 is provided that determines at least in part the shape of element 10. Hardenable material 5 is more specifically a replication material, e.g., a curable epoxy resin. Material 5 is applied between replication tool 50 and substrate 1, e.g., as illustrated in FIG. 6, applied to replication tool 50. Then, replication tool 50 is brought close to or even in contact with surface 1a, as illustrated by the open arrow.

(35) With replication tool 50 in place, hardening of material 5 is started or even completed. In particular, when optical element 10 is a transparent optical element such as a lens, material 5 is an optically transparent material, and, as illustrated in FIG. 6, substrate 1 may also be transparent, at least in part. Transparency may of course possibly refer to only a portion of the electromagnetic spectrum such as to infrared light only.

(36) Whereas hardenable material 5 is a replication material constituting element 10 in the example of FIG. 6, it is merely an adhesive or bonding material in the examples of FIGS. 2, 3 and 4, 5.

(37) FIG. 7 shows substrate 1 of FIG. 6 with replication tool 50 removed and material 5 completely hardened. The element 10 is now created and present on (and solidly interconnected to) substrate 1 in its target position.

(38) In an embossing-type replication process, elements may be produced which include, as illustrated in FIG. 7, a main portion 11 constituting a functional element such as a lens element and, in addition, a surrounding portion 12, which completely (or at least in part) laterally surrounds the main portion 11. Main portion 11 and surrounding portion 12 are produced in one and the same process and of the same material. They constitute an integrally formed part (namely element 10). Usually, the surrounding portion 12 does not have a specific function, e.g., no optical function, but merely is a result of the way of manufacturing the main portion 11.

(39) However, such a surrounding portion may be used as a barrier member, as will be described referring to FIG. 8.

(40) FIG. 8 is a cross-sectional illustration of an application of an element 10 onto a substrate 1 by replicating the element 10 on substrate 1, wherein a barrier member 40 is provided by another element 20 previously replicated on the substrate 1.

(41) Accordingly, initially, an element 20 has been produced on substrate 1 using an embossing-type process using a replication tool (not shown) and a flowable and/or liquid hardenable (replication) material 6. That element 20 includes a main portion 21 and a surrounding portion 22. Surrounding portion 22 provides two partial surfaces 41, 42, which are at a large angle with each other and form an edge 45. The particular shape of surrounding portion 22 basically originates from a suitable design of the replication tool, which may, e.g., correspond to the design of the replication tool 50 of FIG. 6. Partial surface 42 is a replication of a surface of the replication tool, whereas partial surface 42 has a meniscus shape, which is determined by the amount of material 6 used in the replication process and by material properties, more particularly by the contact angle between material 6 and the material of the replication tool and also by the contact angle between material 6 and the material at surface 1a.

(42) Element 20, more particularly surrounding portion 22 and still more particularly partial surfaces 41, 42 (and edge 45) may, for a subsequent process, function as a barrier member 40.

(43) That subsequent process may be, e.g., again a replication process and more particularly an embossing process, as illustrated in FIG. 8. FIG. 8 illustrates the situation at the beginning of a hardening process for a (replication) material 5 applied to surface 1a that is formed by a replication tool 50. Material 5 (cf. the dotted lines in FIG. 8) is forced to flow as indicated by the black arrows. Its flow is controlled and stopped by barrier member 40 provided by surrounding portion 22 of the structure present on substrate 1 already in advance (cf. above). Material 5 constitutes a main portion 11 and a surrounding portion 12.

(44) After hardening (in particular curing) material 5, two elements 10, 20 are present on substrate 1 that include, e.g., a lens element each and that are very close to each other. Their respective surrounding portions 12, 22 are (laterally) overlaping.

(45) FIG. 9 is an illustration of wafer-level manufactured devices, which are opto-electronic modules 100, in a cross-sectional view before dicing. In the illustrated case, various elements have been applied to different substrates using barrier members for flow control. More particularly, on a substrate 1, a hardenable material 5 (bonding material) has been used for connecting elements 10 such as image sensors to a substrate 1, and for connecting elements 30 such as replicated lens elements to a substrate 2, and for interconnecting substrates 1 and 2 via a spacer wafer representing an element 60.

(46) The application of the respective elements may be accomplished, e.g., in one of the above-described ways. Substrate 2 includes a non-transparent portion 2b through which light cannot pass and transparent portions 2t through which light can pass.

(47) After separation of the wafer stack illustrated in FIG. 9 into a plurality of individual opto-electronic modules 100, the latter can be incoporated in a device such as a smart phone or a photographic device or another light sensing device or illumination device or still other optical device. Separation lines (dicing tracks) are referenced 9 in FIG. 9.

(48) FIG. 10 is a cross-sectional illustration of a flow of material onto a barrier member 40 integrated in a substrate 1. Barrier member 40 has a shape similar to the one illustrated in FIG. 8 for the barrier member constituted by a surrounding portion of a replicated structure, having a concavely curved first partial surface 41. However, as illustrated in FIG. 10, it is also possible to provide a pre-shaped substrate 1 that incorporates barrier members. In particular, it is possible to produce such pre-shaped substrates by means of replication techniques, e.g., by molding or embossing.

(49) The dotted line in FIG. 10 symbolizes the surface of the hardenable material 5. The dark arrow indicates the direction of flow of material 5. As can be seen in FIG. 10, partial surface 41 is covered by material 5. And edge 45 (particularly in combination with a steep, e.g., as illustrated, vertical surface 42) is a particularly strong barrier to the flow of material 5. Considerable amounts of material 5 may be present, while material 5 is still precluded from wetting partial surface 42 and from flowing across and beyond barrier member 40. Thus, the flow of material 5 is controlled by barrier member 40, and material can be hardened, in particular in the state illustrated in FIG. 10.

(50) FIG. 11 is an illustration of a flow of a hardenable material 5 onto a barrier member 40 dispensed onto a substrate 1. The illustration is similar to the one of FIG. 10, however in this case, the substrate 1 is not pre-shaped (but is simply planar), and barrier member 40 has been added after manufacture of the (planar) substrate 1. A dispenser can be used for depositing material 5 on substrate 1, e.g., a dispenser like used for underfilling processes in electronics packaging.

(51) In the illustrated case of FIG. 11, there is no edge or at least no pronounced edge present between the partial surfaces 41, 42 of barrier member 40. However, their mutual angle makes is difficult for material 5 to flow across the highest point.

(52) FIG. 16 is another cross-sectional illustration of a flow of material onto a barrier member 40, wherein the barrier member 40 is a structure protruding from substrate 1, more particularly the barrier member is provided by structured photoresist material. Otherwise, the illustration is similar to the one of FIG. 10. Barrier member 40 has a first partial surface 41, a second partial surface 42, and a third partial surface 43. Partial surface 41 is interconnecting partial surfaces 42 and 43.

(53) In one way to obtain such barrier members, a photoresist material is applied (on the first side of substrate 1), e.g., by spinning. This way, a photoresist film may be created. The film may cover one continuous region. Then, the photoresist material is structured, in particularly photolithographically structured, by locally illuminating it, e.g., with UV light, and subsequently removing the illuminated or the not illuminated part of the photoresist material. At least part of the remaining photoresist material then provides barrier members 40. Photoresist barrier members 40 may show an undercut, as illustrated in FIG. 16. This way, a more efficient flow stopping at the edge between first partial surface 41 and second partial surface 42 is achieved. However, it is also possible that other flanks (not undercut flanks), e.g., straight flanks, are provided.

(54) In case of photoresist barrier members, the first partial surface 41 is usually horizontally aligned. Even though the flow of hardenable material 5 may stop already at the edge between third partial surface 43 and first partial surface 41, flow stopping is more effectively accomplished at the edge between intermediate partial surface 41 and second partial surface 42. Thus, usually, finally, third partial surface 43 and first partial surface 41 are both covered by hardenable material 5, while second partial surface 42 is free from hardenable material 5.

(55) FIG. 12 is yet another illustration similar to the ones of FIGS. 10, 11 and 16, but it is an illustration of a flow of material 5 towards a barrier member 40 which is a depression in a substrate 1. This substrate 1 may be either a pre-fabricated one in the sense that its shape (including the barrier members) is determined by its manufacture (e.g., by replication), in particular without additional steps for producing barrier members 40, or may be a substrate 1 obtained by manufacturing an initial substrate such as a planar substrate (cf. also FIG. 11), and then, material of the substrate is selectively removed in order to form barrier members 40. The subsequent removal of material may be accomplished, e.g., by using laser ablation, using selective etching (e.g., in lithographic methods), or by using a dicing saw.

(56) It can be advantageous for the flow control to provide an edge 14 at that end of barrier 40, which is closest to the target position of the element to be applied to the substrate 1, i.e. at that end of barrier 40 that is closest the origin of flow of material 5. The edge 14 may, in general for depressions, be present where the first partial surface adjoins the first surface of substrate 1. However, also there, it is possible have a rounded transition instead of an edge 14, similar to the case of FIG. 11 versus FIG. 10.

(57) Having a particularly large angle between partial surface 41 and surface 1a (where it adjoins partial surface 41) can improve the flow control or flow-stop properties of barrier member 40. In the example of FIG. 12, the angle is 270.

(58) In case of a depression, such as illustrated in FIG. 12, it applies that in general, the first partial surface 41 may be vertically aligned, at least within 35 or rather within 15.

(59) Furthermore, a barrier member may, in general for recessed barrier members (depressions), extend below an average level described by the first surface by at least 2 m or by at least 8 m, and/or by at most 150 m or by at most 80 m;

(60) FIG. 13 illustrates a top view of an element 10 and an associated barrier 40 member on a substrate 1. As already mentioned in conjunction with FIG. 1, barrier member 40 may describe a loop completely laterally circumscribing element 10. This way, it can be prevented that any of the items 80 present on substrate 1 would be wetted or covered by material 5. And/or it can be prevented that place intended to be taken by items 80 would be covered or wetted by material 5. This might be useful, e.g., in case items 80 cannot be properly connected to substrate 1 if some of material is present in the intended location on substrate 1. The outer lateral boundary of material 5 is illustrated by the dotted line in FIG. 13.

(61) FIG. 14 is a similar illustration as FIG. 13. However, the barrier member 40 does not describe a closed-loop shape. An item 80 is located at substrate 1 in such a way that barrier member 40 is arranged laterally between it and the element 10 when applied to substrate 1. A thick solid straight line section illustrates points at the surface of substrate 1 that are prevented from being covered by material 5 by barrier member 40. An extension of the line passes through two points P1, P2, wherein P1 is a central point of element 10 in the surface, more particularly a center of mass of the footprint of element 10 at the surface. And point P2 designates a central point of barrier member 40 at the surface, more particularly a center of mass of the footprint of barrier member 40 at the surface.

(62) FIG. 15 is a similar illustration as FIGS. 13 and 14. In FIG. 15, it is illustrated that a barrier member can also be discontinuous. Alternatively, FIG. 15 can also be interpreted to show several barrier members associated with element 10, and these barrier members protect item 80 from material 5.

(63) As has been described above, it is usually provided that an element 10 is in its target position not before the material 5 gets into contact with the surface 1a of the substrate 1. Accordingly, the element is mounted on the surface 1a not before the material 5 gets into contact with the surface 1a. A process of mounting the element 10 on the substrate 1 is usually finished only after the hardenable material 5 is hardened (solidified).

(64) In a lateral area where a barrier member is present at the substrate 1, the substrate 1 usually is thicker or thinner than its avergage thickness of substrate.

(65) As will have become clear from the above, it is usually provided that a boundary of a footprint of an element 10 in the target position on surface 1a is (laterally) at a distance from the associated barrier member 40. And in particular, after the hardening of the material 5, the surface 1a is (typically completely) covered by the hardenable material 5 along said distance.

(66) It is noted that various possibilities are described in the present patent application as to how elements and items present at the substrate may be embodied.

(67) A high density of (functional) elements on a substrate in wafer level manufacture can be achieved by means of the described methods. And specific ones of the elements can be positioned very close to each other, in particular without undesired overlap of material.

(68) It is noted that contact angles described in the present patent application are, more precisely, advancing contact angles rather than receding contact angles, as is also clear from the described process.