Method for forming redistribution structure and redistribution structure

Abstract

A method includes forming a first metal line; forming a first dielectric layer, wherein the first metal wire is located in the first dielectric layer; the first metal line is etched back to form a trench in the first dielectric layer. A lower portion of the first metal line remains below the trench. The method further includes filling the trench with a photosensitive material, and performing a lithographic process to pattern the photosensitive material. A via opening is formed in the first dielectric layer and the photosensitive material. A second metal line and a via are formed, where the via is formed in the via opening, and the second metal line is over and connected to the via. The embodiment of the invention also relates to a method for forming the redistribution structure and the redistribution structure.

Description

Technical Field

[0001] This application relates to a method for forming a redistributed structure and the redistributed structure itself. Background Technology

[0002] In integrated circuit fabrication, redistribution structures are commonly used to interconnect device dies and reroute electrical signals. Redistribution structures typically consist of multiple layers of redistribution lines. These multilayer redistribution lines are interconnected vias, forming the lower portion of the redistribution line. For example, the lower redistribution line may include metal pads. A dielectric layer is formed above the metal pads. The upper redistribution line includes vias in the dielectric layer and line portions above the dielectric layer. The vias have a smaller length and width compared to the metal pads to allow them to rest on the metal pads. Summary of the Invention

[0003] One aspect of this application provides a method for forming a redistributed structure, comprising: forming a first metal line; forming a first dielectric layer, wherein the first metal line is located in the first dielectric layer; etching back the first metal line to form a trench in the first dielectric layer, wherein a lower portion of the first metal line remains below the trench; filling the trench with a photosensitive material; performing a photolithography process to pattern the photosensitive material, wherein a via opening is formed in the first dielectric layer and the photosensitive material; and forming a second metal line and a via, wherein the via is formed in the via opening, and the second metal line is located above the via and connected to the via.

[0004] Another aspect of this application provides a redistribution structure, comprising: a first metal line having a first sidewall and a second sidewall parallel to the first sidewall; a via located above and in contact with the first metal line, wherein the via includes a third sidewall perpendicularly aligned to the first sidewall and a fourth sidewall perpendicularly aligned to the second sidewall; a first dielectric layer, wherein the first metal line and the via are located in the first dielectric layer; a second metal line located above and connected to the via, wherein the bottom surface of the second metal line contacts the top surface of the first dielectric layer; and a second dielectric layer, wherein the top surfaces of the second metal line and the second dielectric layer are coplanar.

[0005] Another aspect of this application provides a redistribution structure, comprising: a first metal wire having a first sidewall and a second sidewall parallel to the first sidewall; a through hole located above and in contact with the first metal wire, wherein the through hole includes: a third sidewall, wherein, in a cross-section of the redistribution structure, the third sidewall and the first sidewall are aligned to the same first straight line; and a fourth sidewall, wherein, in the cross-section of the redistribution structure, the fourth sidewall and the second sidewall are aligned to the same second straight line; and a second metal wire located above and connected to the through hole. Attached Figure Description

[0006] The various aspects of the invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industrial practice, the components are not drawn to scale. In fact, for clarity of discussion, the dimensions of the components may be arbitrarily increased or decreased.

[0007] Figure 1 and Figure 2 The formation of a redistribution structure according to some embodiments is illustrated;

[0008] Figure 3A , Figure 3B ,and Figure 3C to Figure 8A , Figure 8B ,and Figure 8C The formation of a lower redistribution line and a through-hole opening offset from the end of the underlying metal line is shown according to some embodiments;

[0009] Figure 9A , Figure 9B ,and Figure 9C to Figure 14A , Figure 14B ,and Figure 14C The formation of a lower redistribution line and a through-hole opening aligned with the end of the underlying metal wire is shown according to some embodiments;

[0010] Figure 15A , Figure 15B ,and Figure 15C to Figure 18A , Figure 18B ,and Figure 18C The formation of an upper redistribution line, which has a length direction different from that of the lower redistribution line, is shown according to some embodiments;

[0011] Figure 19A , Figure 19B ,and Figure 19C to Figure 22A , Figure 22B ,and Figure 22C The formation of an upper redistribution line, which has a length direction parallel to the length direction of the lower redistribution line, is shown according to some embodiments;

[0012] Figure 23 to Figure 26 The formation of a package based on a redistributed structure according to some embodiments is illustrated;

[0013] Figure 27A , Figure 27B ,and Figure 27C Cross-sectional views of several metal wires and through holes according to some embodiments are shown;

[0014] Figure 28 A process flow for forming a redistribution line according to some embodiments is shown. Detailed Implementation

[0015] The following disclosure provides numerous different embodiments or examples for implementing various features of the invention. Specific examples of components and arrangements are described below to simplify the invention. Of course, these are merely examples and are not intended to limit the invention. For example, in the following description, forming a first component above or on a second component can include embodiments where the first and second components are in direct contact, and can also include embodiments where an additional component can be formed between the first and second components, thereby allowing the first and second components to not be in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0016] Furthermore, for ease of description, spatial relative terms such as "below," "under," "lower part," "above," and "upper part" may be used herein to readily describe the relationship between one element or component and another (or other elements or components) as shown in the figure. In addition to the orientations shown in the figure, spatial relative terms are intended to encompass different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein can be interpreted accordingly.

[0017] A redistribution structure and a method for forming the same are provided. According to some embodiments of the invention, a metal line is formed and positioned within a first dielectric layer. The metal line is recessed to form a trench in the first dielectric layer. A dielectric material is filled into the trench and patterned to form via openings. The dielectric material may be formed from a photosensitive material. Redistribution lines are then formed, with vias formed in the via openings. Thus, the edges of the vias defined by the trench are perpendicularly aligned to the corresponding edges of the underlying recessed metal line. Therefore, the vias are self-aligned to the metal line, and the metal line does not need to have large pads for the vias to rest upon. Therefore, the minimum spacing of the redistribution lines can be reduced, and the density of the redistribution lines can be increased.

[0018] The embodiments discussed herein are intended to provide examples to enable the making or use of the subject matter of this disclosure, and modifications that can be made while remaining within the intended scope of the different embodiments will be readily understood by those skilled in the art. Throughout the various views and illustrative embodiments, the same reference numerals are used to denote the same elements. Although method embodiments may be discussed as being implemented in a particular order, other method embodiments may be implemented in any logical order.

[0019] Figure 1 and Figure 2 A cross-sectional view of an intermediate stage in the formation of a redistribution structure according to some embodiments of the present invention is shown. Details of the formation of redistribution lines and dielectric layers in the redistribution structure are shown in... Figure 3A , Figure 3B , Figure 3C to Figure 22A , Figure 22B ,and Figure 22C The corresponding processes of some embodiments are also schematically reflected in process flow 200, such as... Figure 28 As shown in the image.

[0020] Figure 1 A carrier 20 and a release film 22 formed on the carrier 20 are shown. The carrier 20 may be a glass carrier, a silicon wafer, an organic carrier, etc. The release film 22 may be formed of a polymer-based material and / or an epoxy-based thermally release material (e.g., a photothermal conversion (LTHC) material) that can be decomposed under radiation such as a laser beam, thereby allowing the carrier 20 to be peeled off from the structure formed in subsequent processes. According to some embodiments, the release film 22 is applied to the carrier 20 by spin coating or adhesive bonding.

[0021] Further reference Figure 1 A portion of a redistribution structure 28 is formed over the release film 22, comprising a plurality of dielectric layers 24 and a plurality of redistribution lines (RDLs) 26. The redistribution structure 28 may alternatively be referred to as a plug-in 28. The plug-in 28 may be an organic plug-in comprising an organic dielectric layer and redistribution lines.

[0022] According to some embodiments, the redistribution structure 28 is formed layer by layer starting from the release film 22. Figure 3A , Figure 3B , Figure 3C to Figure 22A , Figure 22B ,and Figure 22C The formation process of the lower and upper RDLs is shown in detail in the figure, and will be discussed in subsequent paragraphs.

[0023] Figure 2 The formation of the additional dielectric layer 24 and the additional RDL 26 used to extend the redistribution structure is shown. Throughout the specification, the dielectric layers 24A, 24B, 24C, and 24D (as shown) are subsequently formed. Figure 18B and 18Cor Figure 22B and 22C The layers shown in the figure are individually and uniformly referred to as dielectric layer 24, while RDL 26A and 26B are individually and uniformly referred to as RDL 26.

[0024] After forming the top dielectric layer in the redistribution structure 28, the electrical connector 32 can be formed. The electrical connector 32 can be formed from, or include, microbumps, metal pads, metal pillars, under-bump metallization (UBM), solder areas, and / or the like. The formation of the electrical connector 32 can also be similar to the formation of the RDL, and the formation process may include: patterning the top dielectric layer 24 to expose the underlying RDL 26, depositing a metal seed layer, forming a patterned plating mask, performing one or more plating processes to form the metal pillars 32, removing the plating mask, and etching the metal seed layer. The electrical connector 32 may include copper, aluminum, cobalt, nickel, gold, silver, tungsten, solder, alloys thereof, and / or multiple layers thereof.

[0025] Figure 3A , Figure 3B ,and Figure 3C to Figure 8A , Figure 8B ,and Figure 8C The formation of a lower redistribution line and a through-hole opening in a redistribution structure 28 according to some embodiments is shown. The through-hole opening is vertically aligned to the middle portion of the lower redistribution line (and offset from the end of the line).

[0026] Figure 9A , Figure 9B ,and Figure 9C to Figure 14A , Figure 14B ,and Figure 14C The formation of a lower redistribution line and a through-hole opening in a redistribution structure according to an alternative embodiment is shown. The through-hole opening is vertically aligned to the end of the lower redistribution line.

[0027] It should be understood that, such as Figure 3A , Figure 3B ,and Figure 3C to Figure 8A , Figure 8B ,and Figure 8C The embodiments shown can be compared with those shown in the figure. Figure 9A , Figure 9B ,and Figure 9C to Figure 14A , Figure 14B ,and Figure 14C The embodiments shown are implemented simultaneously. Accordingly, in the same device die, some via openings are aligned to the middle portion of the corresponding lower redistribution line, while some other via openings are aligned to the end portion of the corresponding lower redistribution line.

[0028] Figure 15A , Figure 15B ,and Figure 15C to Figure 18A , Figure 18B ,andFigure 18C The formation of an upper redistribution line according to some embodiments is illustrated. The upper redistribution line has a length direction different from that of the lower redistribution line. The upper redistribution line includes, for example... Figure 8B and Figure 8C The through-hole opening shown in the image or as... Figure 14B and Figure 14C The through hole shown in the figure.

[0029] Figure 19A , Figure 19B ,and Figure 19C to 22A , Figure 22B ,and Figure 22C The formation of an upper redistribution line according to an alternative embodiment is illustrated. The upper redistribution line has a length direction parallel to the length direction of the lower redistribution line. The upper redistribution line may also include, for example... Figure 8B and Figure 8C The through-hole opening shown in the image or as... Figure 14B and Figure 14C The through hole shown in the figure.

[0030] in other words, Figure 3A , Figure 3B ,and Figure 3C to Figure 8A , Figure 8B ,and Figure 8C The embodiments shown herein and Figure 9A , Figure 9B ,and Figure 9C to Figure 14A , Figure 14B ,and Figure 14C Each of the embodiments shown can be associated with Figure 15A , Figure 15B ,and Figure 15C to Figure 18A , Figure 18B ,and Figure 18C The embodiments shown in the document or Figure 19A , Figure 19B ,and Figure 19C to Figure 22A , Figure 22B ,and Figure 22C Any combination of the embodiments shown herein.

[0031] It should be understood that Figure 15A , Figure 15B ,and Figure 15C to Figure 18A , Figure 18B ,and Figure 18C The embodiments shown can be compared with Figure 19A , Figure 19B ,and Figure 19C to Figure 22A , Figure 22B ,and Figure 22CThe embodiments shown are implemented simultaneously. Accordingly, in the same device die, some vias are aligned to the middle portion of the corresponding lower redistribution line, while other vias are aligned to the end portion of the corresponding lower redistribution line.

[0032] Subsequent figures can be represented by numbers followed by the letters A, B, or C. Figures including the letter A show a top view of the structure. Figures including the letter B show cross-sectional views of the structure, with these cross-sections showing sections A-A' of the corresponding top view. Figures including the letter C show cross-sectional views of the structure, with these cross-sections showing sections B-B' of the corresponding top view.

[0033] Figure 3A , Figure 3B ,and Figure 3C A top view and a cross-sectional view are shown during the formation of an initial structure according to some embodiments. A dielectric layer 24A is formed, and RDLs 26A1 and 26A2 (also referred to as metal lines) are formed over the dielectric layer 24A. Figure 3A , Figure 3B ,and Figure 3C The dielectric layer 24A can be any dielectric layer 24 on which redistribution lines are formed (i.e., any dielectric layer 24 on which redistribution lines are formed). Figure 2 ).

[0034] According to some embodiments, dielectric layer 24A may be formed of or include a photosensitive material, such as polyimide, polybenzoxazole (PBO), benzocyclobutene (BCB), etc. When RDLs 26A1 and 26A2 are formed, dielectric layer 24A has already cured and is therefore no longer photosensitive. This means that exposure processes and subsequent development processes performed on dielectric layer 24A will not be able to pattern dielectric layer 24A.

[0035] According to some embodiments, RDLs 26A1 and 26A2, individually and collectively referred to as RDL 26A, are formed above dielectric layer 24A. The corresponding processes are as follows: Figure 28 The process flow shown in the diagram is designated as process 202. The length directions of RDLs 26A1 and 26A2 are parallel to each other. Although Figure 3B and Figure 3C Not shown, but RDL 26A1 and 26A2 may (or may not) include vias in dielectric layer 24A. The height (thickness) of RDL 26A1 and 26A2 is intentionally formed to be greater than the expected thickness of RDL 26 in the final structure. Figure 2 For example, the thickness of RDL 26A1 and 26A2 can be equal to or greater than the sum of the thickness of RDL 26A1 and 26A2 in the final structure plus the height (thickness) of the via above.

[0036] RDLs 26A1 and 26A2 can be formed of, or comprise, copper, nickel, titanium, tungsten, or other materials. For example, RDLs 26A1 and 26A2 may comprise a titanium seed layer and a copper layer above the titanium seed layer. The formation process of RDLs 26A1 and 26A2 may include forming a metal seed layer (not shown) that comprises a portion above dielectric layer 24A. Dielectric layer 24A may (or may not) include openings. When via openings are formed in dielectric layer 24A, the metal seed layer may extend into dielectric layer 24A. The metal seed layer may be formed using, for example, physical vapor deposition (PVD) or a similar process.

[0037] A patterned plating mask, such as a photoresist (not shown), can then be formed over the metal seed layer. Metal material is then deposited on the exposed metal seed layer using a metal plating process. The patterned plating mask and the portion of the metal seed layer covered by the patterned plating mask are then removed, leaving RDL 26A, as shown. Figure 3A , Figure 3B ,and Figure 3C As shown in the diagram. Plating materials may include copper, aluminum, cobalt, nickel, gold, silver, tungsten, or alloys thereof. The plating process may be carried out using, for example, an electrochemical plating process.

[0038] refer to Figure 4A , Figure 4B ,and Figure 4C This forms a dielectric layer 24B. The corresponding process is as follows: Figure 28 The process flow 200 shown is illustrated as process 204. According to some embodiments, dielectric layer 24B may be formed of the same material as dielectric layer 24A. In the resulting structure, dielectric layers 24A and 24B may be distinguishable from each other (e.g., there is a distinct interface between them) or indistinguishable from each other. Alternatively, dielectric layer 24B may be formed of a different material than dielectric layer 24A. Accordingly, in the resulting structure, dielectric layers 24A and 24B are distinguishable from each other.

[0039] According to some embodiments, dielectric 24B is formed of or comprises organic materials, which may be photosensitive polymers such as polyimide, PBO, BCB, etc. The formation of dielectric 24B may include dispensing dielectric 24B in a flowable form and curing dielectric 24B into a solid. A planarization process, such as chemical mechanical polishing (CMP) or mechanical polishing, is then performed to make dielectric layer 24B flush with the top surfaces of RDL 26A1 and RDL 26A2. The corresponding processes are as follows: Figure 28 The process flow shown in the diagram is illustrated as process 206. Curing is performed, and dielectric 24B is no longer photosensitive.

[0040] According to alternative embodiments, the dielectric 24B can be formed from non-photosensitive materials, such as non-photosensitive organic materials (e.g., polymers) or inorganic dielectric materials. For example, the dielectric 24B can be formed from silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or combinations thereof, or include these materials.

[0041] Figure 5A , Figure 5B ,and Figure 5C Top and cross-sectional views of RDL 26A1 and 26A2 recessed according to some embodiments are shown. Figure 5B and Figure 5C As shown, RDL 26A1 and 26A2 are etched back (recessed) using an etching process to form trenches 36A and 36B. The corresponding process is as follows: Figure 28 The process flow 200 shown is illustrated as process 208. According to some embodiments, the recess depth is in the range of approximately 30% to approximately 70% of the height of RDLs 26A1 and 26A2.

[0042] The recess is implemented using an etchant that etches RDLs 26A1 and 26A2 but not the dielectric layer 24B. Accordingly, the trenches are formed self-aligned to RDLs 26A1 and 26A2, wherein the edges of the sidewalls of the dielectric layer 24B exposed to the trenches 36A and 36B are vertically aligned to the edges of the corresponding underlying RDLs 26A1 and 26A2. When as... Figure 4B When the edges of RDL 26A1 and 26A2 shown in the figure are slanted and straight (e.g., having the same as), Figure 27A and Figure 27C (The same outline shown in the figure), the sidewalls of dielectric layer 24B exposed to trenches 36A and 36B as Figure 5B The image shown is both tilted and straight.

[0043] Figure 6A , Figure 6B ,and Figure 6C Top and cross-sectional views are shown in the filling of trenches 36A and 36B according to some embodiments. According to some embodiments, a photosensitive material (which may include polymers), such as polyimide, PBO, etc., is dispensed into trenches 36A and 36B in a flowable form. The corresponding process is as follows: Figure 28 The process flow 200 shown is illustrated as process 210. The photosensitive material is baked to a solid state. However, the baked photosensitive material is not cured, so it remains photosensitive.

[0044] Then, a planarization process, such as CMP or mechanical polishing, is performed to make the top surface of the photosensitive material flush with the top surface of the dielectric layer 24B. The remaining portion of the photosensitive material consists of photosensitive strips 24C1 and 24C2.

[0045] In the above process, dielectric layer 24B acts as a mold to define the shape and size of photosensitive strips 24C1 and 24C2. The top of RDL 26A1 and 26A2 etched in the previous process defines the shape and size of photosensitive strips 24C1 and 24C2.

[0046] Next, as before Figure 6B and Figure 6C As shown, a photomask 42 is placed over a previously formed structure comprising a dielectric layer 24B and photosensitive strips 24C1 and 24C2. The photomask 42 includes opaque portions for blocking light and transparent portions for allowing light to pass through. In the following discussion, it is assumed that photosensitive strips 24C1 and 24C2 comprise positive photoresist, therefore portion 42B is transparent and portion 42A is opaque. It should be understood that photosensitive strips 24C1 and 24C2 may also comprise negative photoresist, and the patterns of the opaque and transparent portions of the photomask 42 will be reversed.

[0047] According to some embodiments, such as Figure 6B and Figure 6C As shown, the opaque portion 42A is directly above and overlaps with some portions of the photosensitive strip 24C2 and the photosensitive strip 24C1. A portion of the photosensitive strip 24C2 is directly below and overlaps with the transparent portion 42B.

[0048] Then, an exposure process is performed to expose the portion of photosensitive strip 24C2 directly below the transparent portion 42B. In such a way... Figure 6B In the cross-sectional view shown, the transparent portion 42B is enlarged, wider than the edge of the underlying photosensitive strip 24C2, and extends laterally beyond the edge of the photosensitive strip 24C2 to ensure that even if photolithographic misalignment occurs, portions of the underlying photosensitive strip 24C2 can still be exposed from edge to edge. Since the dielectric layer 24B has already been cured (if initially formed from a photosensitive material), although some portions of the dielectric layer 24B are exposed to light, these exposed portions will not be removed in subsequent development processes.

[0049] exist Figure 6C In the cross-sectional view shown, the transparent portion 42B overlaps with the middle portion of RDL 26A2, and RDL 26A2 extends laterally beyond the opposite edge of the transparent portion 42B.

[0050] Figure 7A , Figure 7B ,and Figure 7C The diagram shows a top view and a cross-sectional view of photosensitive strips 24C1 and 24C2 after development. The exposed portion of photosensitive strip 24C2 is removed, forming a through-hole 44. The corresponding process is as follows:Figure 28 The process flow shown in the diagram is illustrated as process 212 in section 200. For example... Figure 7B As shown, the through-hole opening 44 is self-aligned to the underlying RDL 26A2. (See figure.) Figure 7C As shown, the through-hole opening 44 is aligned with the middle portion of RDL 26A2 and is offset perpendicularly to the line end of RDL 26A2.

[0051] In subsequent processes, such as Figure 8A , Figure 8B ,and Figure 8C As shown, a curing process is performed on photosensitive strips 24C1 and 24C2, rendering them non-photosensitive and converting them into the dielectric layer of the resulting structure. The corresponding process is described in... Figure 28 The process flow 200 shown is illustrated as process 214. Throughout the specification, photosensitive strips 24C1 and 24C2 are alternatively referred to as dielectric strips 24C1 and 24C2. The resulting dielectric strips 24C1 and 24C2 may comprise the same dielectric material as or a different dielectric material than the dielectric layer 24B. The resulting dielectric strips 24C1 and 24C2 may (or may not) be distinguishable from the dielectric layer 24B. Accordingly, the interface between the dielectric layer 24B and the dielectric strips 24C1 and 24C2 is shown as a dashed line.

[0052] In such Figure 3A , Figure 3B , Figure 3C to Figure 8A , Figure 8B ,and Figure 8C In the embodiments discussed above shown, a through-hole opening 44 is formed (which is vertically aligned to the middle portion of the underlying RDL 26A2 (instead of being aligned to the end portion)). Figure 9A , Figure 9B , Figure 9C to Figure 14A , Figure 14B ,and Figure 14C Some alternative embodiments are shown for forming through-hole openings 44 for the line end portions vertically aligned to the underlying RDL 26A2. Unless otherwise stated, the materials, construction, and forming processes of the components in these embodiments are substantially the same as those of the same components indicated by the same reference numerals in the previous embodiments. Throughout the specification, the details regarding the materials, construction, and forming processes provided in each embodiment can be applied to any other applicable embodiments.

[0053] Figure 9A , Figure 9B ,and Figure 9CA top view and a cross-sectional view of the initial structure are shown, in which dielectric layer 24A has been formed, and RDLs 26A1 and 26A2 (referred to individually and collectively as RDL 26A) are formed on top of dielectric layer 24A. Details of the materials, structures, and formation methods of dielectric layers 24A and RDLs 26A1 and 26A2 can be found in the discussion of the previous embodiments and will not be repeated here.

[0054] Figure 10A , Figure 10B ,and Figure 10C A top view and a cross-sectional view are shown during the formation of dielectric layer 24B. The materials and formation methods of dielectric layer 24B have been discussed in the previous embodiments and will not be repeated here. For example, dielectric layer 24B may include a photosensitive material that is dispensed, cured, and polished. Therefore, dielectric layer 24B is no longer photosensitive. Alternatively, dielectric layer 24B may be formed from an inorganic dielectric material.

[0055] Figure 11A , Figure 11B ,and Figure 11C Top and cross-sectional views are shown respectively of the recesses in RDL 26A1 and 26A2 to form grooves 36A and 36B.

[0056] Figure 12A , Figure 12B ,and Figure 12C Top and cross-sectional views are shown respectively of the formation of photosensitive strips 24C1 and 24C2 in trenches 36A and 36B. The top surfaces of photosensitive strips 24C1 and 24C2 can be coplanar with the top surface of dielectric layer 24B, for example, through a planarization process. Photosensitive strips 24C1 and 24C2 in... Figure 12A , Figure 12B ,and Figure 12C The structure shown is still photosensitive.

[0057] Figure 12B and Figure 12C Further illustration shows an exposure process 40 implemented on photosensitive strips 24C1 and 24C2 according to some embodiments. A photomask 42 is used to define the pattern, and the exposure process 40 is implemented. The exposure process 40 and the photomask 42 are... Figure 6B and Figure 6C The two are essentially the same, except that the transparent portion 42B of the photomask is aligned to the line end of RDL 26A2, rather than to the middle portion of RDL 26A2.

[0058] According to some embodiments, in such Figure 12B In the cross-section shown, the transparent portion 42B is enlarged and extends laterally beyond the opposite edge of the photosensitive strip 24C2. In... Figure 12CIn the cross-section shown, the transparent portion 42B is also enlarged and extends laterally beyond one end of the photosensitive strip 24C2. Since the dielectric layer 24B has been cured (if it was originally formed from a photosensitive material), although some portions of the dielectric layer 24B are exposed to light, the exposed portions of the dielectric layer 24B will not be removed in the subsequent development process.

[0059] Figure 13A , Figure 13B ,and Figure 13C A top view and a cross-sectional view are shown during the development of photosensitive strips 24C1 and 24C2 according to some embodiments. This forms a through-hole 44. The exposed portion of photosensitive strip 24C2 is removed, exposing the underlying RDL 26A2. Since the exposed portion of photosensitive strip 24C2 is self-aligned to the end sidewall of RDL 26A2 (the left sidewall shown), the left end of the corresponding through-hole opening 44 is vertically aligned to the left end sidewall of RDL 26A2.

[0060] In subsequent processes, such as Figure 14A , Figure 14B ,and Figure 14C As shown, a curing process is performed on photosensitive strips 24C1 and 24C2, thereby desensitizing them and allowing them to be referred to as dielectric strips 24C1 and 24C2. The resulting dielectric strips 24C1 and 24C2 may comprise the same dielectric material as or a different dielectric material than the dielectric layer 24B. The resulting dielectric strips 24C1 and 24C2 may (or may not) be distinguishable from dielectric layer 24B.

[0061] Figure 15A , Figure 15B ,and Figure 15C to Figure 18A , Figure 18B ,and Figure 18C The formation of an upper redistribution line according to some embodiments is shown. The length direction of the upper redistribution line differs from the length direction of the lower redistribution lines 26A1 and 26A2. Figure 15A , Figure 15B ,and Figure 15C The process shown can be based on the embodiments illustrated. Figure 8A , Figure 8B ,and Figure 8C The structure shown herein, however, according to alternative embodiments, the process can also be based on... Figure 14A , Figure 14B ,and Figure 14C The structure shown in the image.

[0062] Figure 15A , Figure 15B ,and Figure 15C The formation of the metal seed layer 50 is shown, which is formed in...Figure 8A , Figure 8B ,and Figure 8C The structure shown is as described. According to some embodiments, the metal seed layer 50 may include a titanium layer and a copper layer located above the titanium layer. The metal seed layer 50 is formed by a conformal deposition process such as physical vapor deposition (PVD).

[0063] Figure 15C Further illustration shows the formation of a mask 52, which may include patterned photoresist, according to some embodiments. The mask 12 includes trenches 54A and 54B. When a plating process is to be performed, the mask 52 is also referred to as a plating mask. The corresponding process is as follows: Figure 28 The process flow shown in the diagram is illustrated as process 216. Trench 54A is used to form a metal wire therein. Trench 54B is used to form a metal wire therein and an underlying through-hole.

[0064] Next, as Figure 16A , Figure 16B ,and Figure 16C As shown, metal material 57 is deposited into trenches 54A and 54B. The deposition of metal material 57 can be carried out by electrochemical deposition (ECD), and according to some embodiments, ECD may include an electrochemical plating (ECP) process. The corresponding process is described in... Figure 28 The process flow shown in the diagram is referred to as process 218 in process 200.

[0065] Figure 17A , Figure 17B ,and Figure 17C The diagram shows a portion of the underlying metal seed layer 50 exposed by removing the plating mask 52. The corresponding process is as follows: Figure 28 The process flow 200 shown is illustrated as process 220. Next, the exposed portion of the metal seed layer 50 that is not directly beneath the metal lines 58A and 58B is removed by etching. The plating material 57 and the underlying metal seed layer 50 together form the metal lines 58A and 58B and the via 54. The metal lines 58A and 58B are above the dielectric layer 24B. The via 54 is formed beneath the metal line 58B and is connected to the metal line 58B; there is no distinguishable interface between the via 54 and the metal line 58B.

[0066] As from Figure 16C and Figure 17C As can be seen, some portions of the metal seed layer 50 lie directly above RDL 26A2. Since the characteristics of RDL 26A2 are closer to those of the metal seed layer 50 than those of the dielectric layer 24B, over-etching of the metal seed layer 50 may create recesses in RDL 26A2. Dashed line 60 schematically shows the top surface of the recessed RDL 26A2.

[0067] Figure 18A , Figure 18B ,and Figure 18C The formation of dielectric layer 24D is shown. The corresponding process is as follows: Figure 28 The process flow 200 shown is illustrated as process 222. According to some embodiments, dielectric layer 24D may be formed of a material selected from the same group of candidate materials for forming dielectric layers 24A, 24B, and / or 24C. The material of dielectric layer 24D may be the same as or different from the material of dielectric layers 24A, 24B, and / or 24C.

[0068] Dielectric layer 24D can be formed of organic dielectric materials (e.g., photosensitive polymers) or inorganic dielectric materials. Dielectric layers 24A, 24B, and 24D, as well as dielectric layers 24C1 and 24C2 (individually and collectively referred to as dielectric layer 24C), are collectively referred to as dielectric layer 24. Figure 2 As shown in the diagram, some lower portions of the dielectric layer 24D may be located within the dielectric strip 24C2 to contact the via 54.

[0069] According to embodiments of this application, height alignment can be achieved to align the sidewall of the through-hole 54 with the corresponding sidewall of the underlying metal wire. For example, in... Figure 18B In the cross-section shown, the sidewall 54SW of the through hole 54 is vertically aligned with the sidewall 26A2SW of the metal wire 26A2. This is because the metal wire 26A2 ( Figure 10B and Figure 10C Etching back ( Figure 11B and Figure 11C The process defines the size of the via 54. Therefore, the dielectric layer 24B maintains the top dimension of the metal line 26A2. This process allows the via formed in subsequent processes to have the same width as the underlying metal line 26A2 without the risk of misalignment.

[0070] Figure 19A , Figure 19B ,and Figure 19C to Figure 22A , Figure 22B ,and Figure 22C The formation of the upper redistribution line according to an alternative embodiment is shown. According to these embodiments, the length direction of the upper redistribution line is parallel (rather than perpendicular) to the length direction of the lower redistribution lines 26A1 and 26A2.

[0071] refer to Figure 19A , Figure 19B ,and Figure 19C ,exist Figure 8A , Figure 8B ,and Figure 8CA metal seed layer 50 is formed on the structure shown. According to some embodiments, the metal seed layer 50 may include a titanium layer and a copper layer located above the titanium layer. The metal seed layer 50 is formed by a conformal deposition process such as physical vapor deposition (PVD). A mask 52 is then formed, in which trenches 54A and 54B are formed. When a plating process is to be performed, the mask 52 is also referred to as a plating mask.

[0072] like Figure 19A and Figure 19B As shown, in section A-A', the groove 54B is wider than the through-hole opening 44 below. This allows for increased process margins to accommodate misalignment with the through-hole opening 44 when forming the groove 54B.

[0073] Next, as Figure 20A , Figure 20B ,and Figure 20C As shown, metallic material 57 is deposited into trenches 54A and 54B. Therefore, metallic lines 58A and 58B are formed above the dielectric layer 24B.

[0074] Figure 21A , Figure 21B ,and Figure 21C The removal of mask 52 and subsequent etching remove the exposed portion of the metal seed layer 50 are shown. The remaining portion of the metal seed layer 50 can be considered as part of metal lines 58A and 58B and via 54. Via 54 is formed beneath and connected to metal line 58B, with no distinguishable interface between them.

[0075] Figure 22A , Figure 22B ,and Figure 22C The formation of dielectric layer 24D is illustrated. According to some embodiments, dielectric layer 24D may be formed from a material selected from the same group of candidate materials used to form dielectric layers 24A, 24B, and / or 24C. The material of dielectric layer 24D may also be the same as or different from the materials of dielectric layers 24A, 24B, and / or 24C. Dielectric layers 24A, 24B, 24C (including 24C1 and 24C2), and 24D are individually and collectively referred to as dielectric layer 24, as well as... Figure 2 As shown in the image.

[0076] According to embodiments of this application, height alignment can be achieved to align the sidewall of the through-hole with the corresponding sidewall of the underlying metal wire. For example, in Figure 22B In the cross-section shown, the sidewall 54SW of the through hole 54 is vertically aligned with the sidewall 26A2SW of the metal wire 26A2. Additionally, as... Figure 18C As shown, sidewall 54SW and the corresponding lower sidewall 26A2SW are aligned to the same straight line in the section (see also reference). Figure 27Aand Figure 27C ).

[0077] Figure 15A , Figure 15B ,and Figures 15C to 22A , Figure 22B ,and Figure 22C The process shown in the diagram illustrates the middle portion of the metal line 26A2 below (as shown in the diagram). Figure 8A , Figure 8B ,and Figure 8C (As shown in the diagram) forming a through-hole 54 and an upper metal wire 58B. According to an alternative embodiment, the same process can also be performed to form a through-hole 54 and an upper metal wire 58B from the wire end portion of the lower metal wire 26A2 (as shown in the diagram). Figure 14A , Figure 14B ,and Figure 14C As shown in the diagram, a through-hole 54 and an upper metal line 58B are formed. In the corresponding final structure, the through-hole opening 44 (and thus the through-hole 54 that fills the through-hole opening 44) will have three sidewalls (where the first and second sidewalls are as shown in the diagram). Figure 14B As shown in the image, the third one is... Figure 14C As shown in the diagram, align vertically with the sidewall of the corresponding lower metal line 26A2 without worrying about misalignment. The corresponding structure can be recognized.

[0078] Figures 23 to 26 The remaining processes for forming the package, according to some embodiments, are illustrated. This process begins with... Figure 2 The structure shown in the image continues. For example... Figure 23 As shown, package assembly 70 is bonded to interconnect structure 28. Package assembly 70 may include device die, package, die stack, etc. A sealant 72 is formed to seal package assembly 70 therein. Sealant 72 may include molding compound, underfill, molded underfill, etc. Package 76 is thus formed.

[0079] Next, as Figure 24 As shown, carrier 74 is attached to package 76 via release film 75, and then carrier 20 is removed. An electrical connector 78, which may include a solder area, can then be formed as a surface feature of package 76. Figure 25 and Figure 26 The connection of package 76 to package assembly 80 is shown to form package 82.

[0080] Figure 27A , Figure 27B ,and Figure 27C The sidewall profile of the through hole and the underlying metal wire is shown according to some embodiments. Figure 27A As shown, the through hole 54 and the metal wire 26A2 are inverted trapezoidal in cross-section. Figure 27B As shown, the through hole 54 and the metal wire 26A2 are rectangular in cross-section. Figure 27C As shown, the through-hole 54 and the metal wire 26A2 are trapezoidal in cross-section. The sidewall 54SW of the through-hole 54 is aligned with the corresponding lower sidewall 26A2SW of the metal wire 26A2, and has the same inclination angle θ. Additionally, sidewall 54SW is connected to sidewall 26A2SW. Sidewall 54SW and the corresponding lower sidewall 26A2SW are also aligned with a straight line in the cross-sectional view, where the line is either vertical or inclined.

[0081] in addition, Figure 27A , Figure 27B ,and Figure 27C The structure shown may exist within the same device die. Although Figure 27A , Figure 27B ,and Figure 27C The structures shown are formed in the same dielectric layers 24A, 24B, 24C, and 24D, and the sidewalls of the vias and the corresponding underlying metal lines can be aligned to the same straight line. However, the tilt angles θ of the different redistribution lines may differ from one another, such as... Figure 27A , Figure 27B ,and Figure 27C As shown in the image.

[0082] Additionally, due to the etch-back process, such as Figure 18C As shown, the left end sidewall of metal wire 26A2 and the left end sidewall of left dielectric strip 24C2 are aligned to the same straight line, which can be vertical or inclined, similar to... Figure 27A or Figure 27C Additionally, when the through-hole 54 is formed to align with the end of the metal wire 26A2 (not shown), the end sidewall of the metal wire 26A2 and the end sidewall of the through-hole 54 will align to the same straight line, which can be vertical or inclined, similar to... Figure 27A or Figure 27C .

[0083] In the embodiments shown above, some processes and features according to some embodiments of the present invention are discussed to form a three-dimensional (3D) package. Other features and processes may also be included. For example, test structures may be included to assist in verification testing of the 3D package or 3D IC device. Test structures may include, for example, test pads formed in a redistribution layer or on a substrate, which allow testing of the 3D package or 3D IC device using probes and / or probe cards. Verification testing can be performed on intermediate and final structures. Furthermore, the structures and methods disclosed herein can be combined with test methods incorporating intermediate verification of known good dies to increase yield and reduce costs.

[0084] Embodiments of the present invention have several advantageous features. By employing a recessed process on the metal line to leave recesses / grooves in the dielectric layer, vias defined by trenches are formed, with the vias self-aligned to the metal line. This eliminates misalignment of the vias to the underlying metal line. It can also increase the pattern density of the redistribution lines.

[0085] According to some embodiments of the present invention, a method includes: forming a first metal line; forming a first dielectric layer, wherein the first metal line is located in the first dielectric layer; etching back the first metal line to form a trench in the first dielectric layer, wherein a lower portion of the first metal line remains below the trench; filling the trench with a photosensitive material; performing a photolithography process to pattern the photosensitive material, wherein a via opening is formed in the first dielectric layer and the photosensitive material; and forming a second metal line and a via, wherein the via is formed in the via opening, and the second metal line is located above the via and connected to the via.

[0086] In one embodiment, the method further includes: performing a planarization process prior to the photolithography process to make the first top surface of the photosensitive material flush with the second top surface of the first dielectric layer. In another embodiment, the method further includes: performing a planarization process prior to etching back the first metal line to make the first dielectric layer flush with the top surface of the first metal line. In another embodiment, the trench and the lower portion of the first metal line have the same length and the same width.

[0087] In one embodiment, the via opening has an end portion perpendicularly aligned to the end of the first metal wire. In another embodiment, the via opening overlaps with a middle portion of the lower part of the first metal wire. In yet another embodiment, the method further includes curing a photosensitive material prior to forming the second metal wire and the via. In yet another embodiment, the method further includes forming a plating mask on the cured photosensitive material, wherein the second metal wire and the via are plated from the plating mask.

[0088] In one embodiment, the method further includes: removing the plating mask; and forming a second dielectric layer over and in contact with the photosensitive material, wherein the second metal line is located in the second dielectric layer. In another embodiment, etching back the first metal line causes the opposite sidewalls of the first dielectric layer to be exposed to the trench, and wherein the opposite sidewalls of the first dielectric layer are exposed to the via opening after the via opening is formed.

[0089] According to some embodiments of the present invention, a structure includes: a first metal line having a first sidewall and a second sidewall parallel to the first sidewall; a through-hole located above and contacting the first metal line, wherein the through-hole includes a third sidewall perpendicularly aligned to the first sidewall and a fourth sidewall perpendicularly aligned to the second sidewall; a first dielectric layer, wherein the first metal line and the through-hole are located in the first dielectric layer; a second metal line located above and connected to the through-hole, wherein the bottom surface of the second metal line contacts the top surface of the first dielectric layer; and a second dielectric layer, wherein the top surfaces of the second dielectric layer and the second metal line are coplanar.

[0090] In one embodiment, the via overlaps with the middle portion of the first metal wire. In another embodiment, the via overlaps with the end portion of the first metal wire, and the via further includes a first end sidewall aligned with a second end sidewall of the first metal wire. In yet another embodiment, the structure further includes a third dielectric layer overlapping the first metal wire, wherein the third dielectric layer includes a fifth sidewall perpendicularly aligned with the first sidewall and a sixth sidewall perpendicularly aligned with the second sidewall.

[0091] In one embodiment, the third dielectric layer comprises a photosensitive material. In another embodiment, the second dielectric layer comprises a first lower portion located within the first dielectric layer and contacting a third sidewall of the via. In yet another embodiment, the second dielectric layer further comprises a second lower portion located within the first dielectric layer and contacting a fourth sidewall of the via. In both embodiments, the first and second dielectric layers comprise organic materials.

[0092] According to some embodiments of the present invention, a structure includes: a first metal wire having a first sidewall and a second sidewall parallel to the first sidewall; a through hole located above and in contact with the first metal wire, wherein the through hole includes a third sidewall, wherein, in a cross-section of the structure, the third sidewall and the first sidewall are aligned to the same first straight line; and a fourth sidewall, wherein, in a cross-section of the structure, the fourth sidewall and the second sidewall are aligned to the same second straight line; and a second metal wire located above the through hole and connected to the through hole.

[0093] In one embodiment, the first metal wire further includes a first end sidewall, the through hole further includes a second end sidewall, and wherein, in a cross-section of the structure, the first end sidewall and the second end sidewall are aligned to the same third straight line.

[0094] The foregoing has outlined features of several embodiments to enable those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures for performing the same or similar purposes and / or achieving the same or similar advantages as this disclosure. Those skilled in the art should also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure.

Claims

1. A method for forming a redistributed structure, comprising: Form the first metal wire; A first dielectric layer is formed, wherein the first metal line is located in the first dielectric layer; The first metal line is etched back to form a trench in the first dielectric layer, wherein the lower portion of the first metal line remains below the trench; The groove is filled with a photosensitive material; A photolithography process is performed to pattern the photosensitive material, wherein via openings are formed in the first dielectric layer and the photosensitive material; and A second metal wire and a through hole are formed, wherein the through hole is formed in the opening of the through hole, and the second metal wire is located above the through hole and connected to the through hole.

2. The method for forming a redistributed structure according to claim 1, further comprising: Prior to the photolithography process, a planarization process is performed to make the first top surface of the photosensitive material flush with the second top surface of the first dielectric layer.

3. The method for forming a redistributed structure according to claim 1, further comprising: Before etching back the first metal line, a planarization process is performed to make the first metal line flush with the top surface of the first dielectric layer.

4. The method for forming a redistributed structure according to claim 1, wherein, The trench and the lower portion of the first metal wire have the same length and the same width.

5. The method for forming a redistributed structure according to claim 1, wherein, The through-hole opening has an end that is vertically aligned with the end of the first metal wire.

6. The method for forming a redistributed structure according to claim 1, wherein, The opening of the through hole overlaps with the middle portion of the lower part of the first metal wire.

7. The method for forming a redistributed structure according to claim 1, further comprising: The photosensitive material is cured before the second metal wire and the through hole are formed.

8. The method for forming a redistributed structure according to claim 7, further comprising: A plating mask is formed on the already cured photosensitive material, wherein the second metal line and the through hole are plated from the plating mask.

9. A redistribution structure, comprising: The first metal wire has a first sidewall and a second sidewall parallel to the first sidewall; A through hole is located above and in contact with the first metal wire, wherein the through hole includes a third sidewall perpendicularly aligned to the first sidewall and a fourth sidewall perpendicularly aligned to the second sidewall; A first dielectric layer, wherein the first metal line and the via are located in the first dielectric layer; A second metal wire is located above and connected to the through-hole, wherein the bottom surface of the second metal wire contacts the top surface of the first dielectric layer; and The second dielectric layer, wherein the top surface of the second metal line and the second dielectric layer are coplanar.

10. A redistribution structure, comprising: The first metal wire has a first sidewall and a second sidewall parallel to the first sidewall; A through-hole, located above and in contact with the first metal wire, wherein the through-hole includes: The third sidewall, wherein, in the cross-section of the redistributed structure, the third sidewall and the first sidewall are aligned to the same first straight line; and A fourth sidewall, wherein, in the cross-section of the redistributed structure, the fourth sidewall and the second sidewall are aligned to the same second straight line; and A second metal wire is located above the through hole and connected to the through hole.

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