Semiconductor device interconnection structure and method thereof

Abstract

The invention relates to a semiconductor device interconnect structure and a method thereof. A method of fabricating a semiconductor device interconnect structure is provided. The method includes forming a copper pillar over a semiconductor die by means of a plating process. A proximal portion of the copper pillar has a first width dimension and a distal portion of the copper pillar has a second width dimension. The second width dimension of the distal portion of the copper pillar is configured to be less than the first width dimension of the proximal portion of the copper pillar. A sidewall of the distal portion of the copper pillar is selectively roughened. A roughened sidewall of the distal portion of the copper pillar is configured to promote solder wetting.

Description

Technical Field

[0001] This disclosure generally relates to semiconductor device packaging, and more specifically to a semiconductor device interconnect structure and a method of forming the same. Background Technology

[0002] Today, there is an increasing trend to include sophisticated semiconductor devices in everyday products and systems. These sophisticated semiconductor devices may include features specific to a particular application that can influence the configuration of the semiconductor device package. For some features and applications, the configuration of the semiconductor device package may be susceptible to lower reliability, lower performance, and higher product or system costs. Therefore, there is a significant challenge in accommodating these features and applications while minimizing the impact on the reliability, performance, and cost of the semiconductor device. Summary of the Invention

[0003] Generally, a method is provided, comprising: forming a first copper pillar on a semiconductor die by means of a plating process, the first copper pillar having a proximal portion having a first width dimension and a distal portion having a second width dimension, the second width dimension being smaller than the first width dimension; and selectively roughening the sidewalls of the distal portion of the first copper pillar, the roughened sidewalls of the distal portion of the first copper pillar being configured to promote solder wetting. The first copper pillar may be formed on an under-bump metallization (UBM) structure of the semiconductor die. The method may further include plating the distal surface of the distal portion of the first copper pillar with a solder material. The proximal portion of the first copper pillar has a first length dimension, and the distal portion of the first copper pillar has a second length dimension, the second length dimension being longer than the first length dimension. The second length dimension of the method may be in the range of 60% to 80% of the total length dimension of the first copper pillar, the total length dimension being substantially equal to the first length dimension plus the second length dimension. The second width dimension may be a width substantially consistent with the second length dimension through the distal portion of the first copper pillar. The distal portion of the first copper pillar may be formed in a tapered configuration having a first tapered width dimension adjacent to the proximal portion of the first copper pillar and a second tapered width dimension at the distal end of the distal portion of the first copper pillar, the first tapered width dimension being approximately equal to the first width dimension of the proximal portion, and the second tapered width dimension being approximately equal to the second width dimension of the distal portion of the first copper pillar. The method may further include forming a second copper pillar on the semiconductor die by means of a plating process, the second copper pillar being arranged with a fine pitch near the first copper pillar. The method may further include interconnecting the semiconductor die to a printed circuit board (PCB) via the first copper pillar during a reflow process, the reflow process causing solder to wet the roughened sidewalls of the distal portion of the first copper pillar.

[0004] In another embodiment, a method is provided comprising: forming a first copper pillar and a second copper pillar on a semiconductor die by means of a plating process, each copper pillar including a proximal portion having a first width dimension and a distal portion having a second width dimension smaller than the first width dimension; and selectively roughening the sidewalls of the distal portion of each copper pillar, the roughened sidewalls of the distal portion of the copper pillar being configured to promote solder wetting. The second copper pillars may be arranged in a fine-pitch configuration near the first copper pillars, the fine-pitch configuration having a centerline-to-centerline spacing substantially less than or equal to 150 micrometers. The method may further include plating the distal surface of the distal portion of each copper pillar with a solder material. The proximal portion of each copper pillar has a first length dimension, and the distal portion of each copper pillar has a second length dimension, the second length dimension being longer than the first length dimension. The second width dimension may be a width substantially consistent with the second length dimension throughout the distal portion of each copper pillar. Selectively roughening the sidewalls of the distal portion of each copper pillar may include forming nanostructures on the sidewalls of the distal portion of each copper pillar.

[0005] In another embodiment, a semiconductor device is provided, the semiconductor device comprising: a semiconductor die; a first copper pillar formed on the semiconductor die, the first copper pillar having a proximal portion having a first width dimension and a distal portion having a second width dimension, the second width dimension being smaller than the first width dimension; and a roughened surface formed on a sidewall of the distal portion of the first copper pillar, the roughened surface formed by the sidewall of the distal portion of the first copper pillar being configured to promote solder wetting. The semiconductor device may further include a solder cap formed at a distal end of the distal portion of the first copper pillar. The proximal portion of the first copper pillar has a first length dimension, and the distal portion of the first copper pillar has a second length dimension, the second length dimension being longer than the first length dimension. The roughened surface may include nanostructures in the form of dendrites, particles, needles, wires, bands, or tubes. The semiconductor device may further include a second copper pillar formed on the semiconductor die, the second copper pillar being arranged in a fine pitch near the first copper pillar, the fine pitch arrangement having a centerline-to-centerline spacing of substantially less than or equal to 150 micrometers. Attached Figure Description

[0006] This invention is illustrated by way of example and is not limited to the accompanying drawings, in which similar reference numerals indicate similar elements. For simplicity and clarity, the elements in the drawings are shown, and these elements are not necessarily drawn to scale.

[0007] Figure 1An example semiconductor device with an interconnect structure in the manufacturing stage is shown in a simplified cross-sectional view according to one embodiment.

[0008] Figure 2 An example semiconductor device with interconnect structure in a subsequent manufacturing stage according to an embodiment is shown in a simplified cross-sectional view.

[0009] Figure 3 An alternative example semiconductor device with an interconnect structure at the manufacturing stage is shown in a simplified cross-sectional view according to one embodiment.

[0010] Figure 4 An alternative example semiconductor device with interconnect structure in a subsequent manufacturing stage according to an embodiment is shown in a simplified cross-sectional view.

[0011] Figure 5 A simplified flowchart view illustrates an example method for manufacturing a semiconductor device having an interconnect structure according to one embodiment. Detailed Implementation

[0012] Generally, a semiconductor device with an interconnect structure is provided. The semiconductor device includes an under-bump metallization (UBM) structure connected to die pads formed on a semiconductor die. Copper pillars are formed on a seed layer portion above each UBM structure. Each pillar is formed having a proximal portion and a distal portion. The distal portion of each copper pillar undergoes a surface treatment configured to roughen the sidewall surface of the distal portion. The roughened sidewall surface is configured to promote solder wetting. By forming copper pillars with roughened sidewall surfaces of the distal portion in this manner, when the semiconductor die interconnects with a substrate, reflow solder forms a thin profile around the distal portion of each copper pillar. The thin solder profile allows the copper pillars to be configured with a fine pitch arrangement while virtually eliminating the risk of solder bridging. Thus, each conductive connection is formed with excellent structural integrity and reliability, where stress is minimal and voids are absent.

[0013] Figure 1 A simplified cross-sectional view shows a portion of an example semiconductor device 100 with an interconnect structure in the manufacturing stage according to one embodiment. At this stage, the device 100 includes a semiconductor die 102, a UBM structure 104 connected to die pads (not shown) of the semiconductor die, and copper pillars 106 formed over portions of the UBM structure 104. The copper pillars 106 are typically formed on each semiconductor die 102, in wafer form. In this embodiment, the copper pillars 106 are formed on exposed portions of a seed layer (not shown) covering the UBM structure 104 by means of an electrodeposition plating process. For example, the copper pillars 106 may be characterized as an interconnect structure configured to interconnect the semiconductor die with a packaging substrate or printed circuit board (PCB).

[0014] In this embodiment, the copper pillar 106 is configured to have a "stepped" or "T" shaped configuration. The proximal portion 110 of the copper pillar 106 is formed to have a first width dimension 116 and a first length dimension 120, and subsequently, the distal portion 112 of the copper pillar is formed to have a second width dimension 118 and a second length dimension 122. In this embodiment, the width dimension 118 (e.g., diameter) of the distal portion 112 of the copper pillar 106 is smaller than the width dimension 116 (e.g., diameter) of the proximal portion 110. That is, the distal portion 112 of each copper pillar 106 is narrower than the proximal portion 110. For example, the width dimension 118 of the distal portion 112 of the copper pillar 106 can be in the range of 60% to 80% of the width dimension 116 of the proximal portion 110, thereby forming a stepped shape.

[0015] The length dimension 120 of the proximal portion 110 of each copper pillar 106 is depicted as the vertical distance between the UBM structure 104 and the step at the beginning of the distal portion 112. In this embodiment, the width dimension 116 is a substantially consistent width over the entire length dimension 120 of the proximal portion 110 of each copper pillar. The length dimension 122 of the distal portion 112 of each copper pillar 106 is depicted as the vertical distance between the step at the end of the proximal portion 110 of each copper pillar 106 and the end or tip of the distal portion 112. Therefore, the total length dimension of each copper pillar 106 is substantially equal to the length dimension 120 of the proximal portion 110 plus the length dimension 122 of the distal portion 112. In this embodiment, the width dimension 118 is a substantially consistent width over the entire length dimension 122 of the distal portion 112 of each copper pillar. In this embodiment, the length dimension 122 of the distal portion 112 of each copper pillar 106 is longer than the length dimension 120 of the proximal portion 110. For example, the length dimension 122 of the distal portion 112 is approximately in the range of 60% to 80% of the total length dimension of each copper pillar 106. In this embodiment, the distal surface 111 of the distal portion 112 of each copper pillar is plated with solder material to form a solder cap 108.

[0016] In this embodiment, a roughened surface 114 is selectively formed on the sidewalls and stepped portions 113 of the distal portion 112 of each copper pillar 106. In some embodiments, the roughened surface 114 may be selectively formed on the sidewalls, stepped portions 113, and distal surface 111 of the distal portion 112 of each copper pillar 106 (e.g., before forming the solder cap 108). In this embodiment, the roughened surface 114 is configured to promote solder wetting. The roughened surface 114 may be formed by means of an additive (e.g., electrodeposition, sputtering) or subtractive (e.g., etching) surface treatment process. For example, the roughened surface 114 may include microstructures or nanostructures in the form of dendrites, particles, needles, lines, bands, tubes, etc. In this embodiment, the roughened surface 114 may be characterized as a hydrophilic surface formed by means of a surface treatment process.

[0017] Semiconductor die 102 has an active side (e.g., a main side having circuitry and bonding pads) and a back side (e.g., a main side opposite the active side). Figure 1 As depicted in a cross-sectional view, for example, the semiconductor die 102 is positioned downwards on the active side. The semiconductor die 102 can be formed of any suitable semiconductor material, such as silicon, germanium, gallium arsenide, gallium nitride, etc. The semiconductor die 102 may further include digital circuitry, analog circuitry, RF circuitry, power supply circuitry, memory, processor, sensors, etc., and combinations thereof, located on the active side.

[0018] like Figure 1 As depicted, a semiconductor die 102 having copper pillars 106 is positioned above a substrate structure 132 (e.g., a package substrate, a PCB). The substrate structure includes a non-conductive substrate 124, a solder mask layer 126 formed above the substrate 124, conductive substrate pads 128 exposed through the solder mask, and interconnect traces (not shown) embedded in the substrate. Solder balls 130 are attached to the substrate pads 128 and are configured to interconnect with the copper pillars 106 during reflow processes in subsequent manufacturing stages. Unless otherwise described, the term "conductive" as used herein generally refers to electrical conductivity.

[0019] Figure 2 A simplified cross-sectional view shows a portion of an example semiconductor device 100 with an interconnect structure in a subsequent manufacturing stage according to one embodiment. In this state, the device 100 includes a semiconductor die 102 having copper pillars 106 bonded to a substrate structure 132. In this embodiment, the copper pillars 106 are interconnected with substrate pads 128 of the substrate structure 132 by means of reflow solder 202. For example, during the reflow process, the copper pillars 106 are connected to solder balls 130 (… Figure 1The contact allows molten solder (of the solder balls 130) to wet along the roughened surface 114, thereby forming a conductive connection between the semiconductor die 102 and the substrate structure 132. By forming the conductive connection in this way, the reflow solder 202 forms a thin profile (e.g., minimal solder bumps) around the distal portion 112 of each copper pillar 106. Thus, each formed conductive connection has excellent structural integrity while minimizing stress and eliminating voids. In this embodiment, the reflow solder 202 does not wet along the sidewalls of the proximal portion 110 of each copper pillar 106. That is, after the reflow process, the sidewalls of the proximal portion 110 of each copper pillar 106 remain substantially solder-free.

[0020] In this embodiment, the copper pillars 106 are arranged in a fine-pitch configuration, the fine-pitch configuration having a center-to-center dimension 204 of less than or equal to 150 micrometers. By using... Figure 2 The finely shaped reflow solder 202 depicted forms a conductive connection between the semiconductor die 102 and the substrate structure 132, and can form copper pillars 106 with a fine pitch arrangement, thereby virtually eliminating the risk of solder bridging.

[0021] Figure 3 A simplified cross-sectional view illustrates a portion of an alternative example semiconductor device 300 with an interconnect structure during the manufacturing stage according to one embodiment. At this stage, device 300 includes a semiconductor die 302, a UBM structure 304 connected to die pads (not shown) of the semiconductor die, and copper pillars 306 formed over portions of the UBM structure 304. In this embodiment, the copper pillars 306 are formed on exposed portions of a seed layer (not shown) covering the UBM structure 304 by means of an electrodeposition plating process. For example, the copper pillars 306 may be characterized as an interconnect structure configured to interconnect the semiconductor die with a package substrate or PCB.

[0022] In this embodiment, the copper pillar 306 is configured with a tapered (e.g., conical) shape. The proximal portion 310 of the copper pillar 306 is formed with a first width dimension 316 and a first length dimension 320, and subsequently, the distal portion 312 of the copper pillar is formed with a second (tapered) width dimension 318 and a second length dimension 322. In this embodiment, the width dimension 318 (e.g., diameter) of the distal portion 312 of the copper pillar 306 is smaller than the width dimension 316 (e.g., diameter) of the proximal portion 310. Figure 3As depicted, the width of the distal portion 312 of the copper pillar 306 begins slightly smaller than the width dimension 316 of the proximal portion 310 (adjacent to the proximal portion 310) and gradually decreases towards the end or tip of the distal portion 112 of each copper pillar 106, thus forming a tapered shape. For illustrative purposes, the width dimension 318 can be generally characterized as the width of the distal portion 112 of each copper pillar 106 at the distal end of the distal portion 312. In this embodiment, the width dimension 318 (at the distal end of the distal portion 312) can be in the range of 60% to 80% of the width dimension 316 of the proximal portion 310. In this embodiment, the tapering of the distal portion 112 of each copper pillar 106 is generally linear. In other embodiments, for example, the tapering of the distal portion can be non-linear or microstepped.

[0023] The length dimension 320 of the proximal portion 310 of each copper pillar 306 is depicted as the vertical distance between the UBM structure 304 and the beginning of the distal portion 312. In this embodiment, the width dimension 316 is a substantially uniform width over the entire length dimension 320 of the proximal portion 310 of each copper pillar. The length dimension 322 of the distal portion 312 of each copper pillar 306 is depicted as the vertical distance between the end of the proximal portion 310 and the end or tip of the distal portion 312 of each copper pillar 306. Therefore, the total length dimension of each copper pillar 306 is substantially equal to the length dimension 320 of the proximal portion 310 plus the length dimension 322 of the distal portion 312. In this embodiment, the width dimension 318 is a substantially tapering width (e.g., decreasing) over the entire length dimension 322 of the distal portion 312 of each copper pillar. In this embodiment, the length dimension 322 of the distal portion 312 of each copper pillar 306 is longer than the length dimension 320 of the proximal portion 310. For example, the length dimension 322 of the distal portion 312 is approximately in the range of 60% to 80% of the total length dimension of each copper pillar 306. In this embodiment, the distal surface 311 of the distal portion 312 of each copper pillar is plated with solder material to form a solder cap 308.

[0024] In this embodiment, a roughened surface 314 is selectively formed on the sidewall of the distal portion 312 of each copper pillar 306. In some embodiments, the roughened surface 314 may be selectively formed on the sidewall of the distal portion 312 of each copper pillar 306 and on the distal surface 311 of the distal portion 312 (e.g., before forming the solder cap 308). In this embodiment, the roughened surface 314 is configured to promote solder wetting. The roughened surface 314 may be formed by means of an additive (e.g., electrodeposition, sputtering) or subtractive (e.g., etching) surface treatment process. For example, the roughened surface 314 may include microstructures or nanostructures in the form of dendrites, particles, needles, lines, bands, tubes, etc. In this embodiment, the roughened surface 314 may be characterized as a hydrophilic surface formed by means of a surface treatment process. That is, after the reflow process, the sidewall of the proximal portion 310 of each copper pillar 306 remains substantially free of solder.

[0025] Semiconductor die 302 has an active side (e.g., a main side having circuitry and bonding pads) and a back side (e.g., a main side opposite the active side). Figure 3 As depicted in a cross-sectional view, for example, the semiconductor die 302 is positioned downwards on the active side. The semiconductor die 302 can be formed of any suitable semiconductor material, such as silicon, germanium, gallium arsenide, gallium nitride, etc. The semiconductor die 302 may further include digital circuitry, analog circuitry, RF circuitry, power supply circuitry, memory, processor, sensors, etc., and combinations thereof, located on the active side.

[0026] like Figure 3 As depicted, a semiconductor die 302 with copper pillars 306 is positioned above a substrate structure 332 (e.g., a package substrate, a PCB). The substrate structure includes a non-conductive substrate 324, a solder mask layer 326 formed above the substrate 324, conductive substrate pads 328 exposed through the solder mask, and interconnect traces (not shown) embedded in the substrate. Solder balls 330 are attached to the substrate pads 328 and configured to interconnect with the copper pillars 306 during reflow processes in subsequent manufacturing stages.

[0027] Figure 4 A simplified cross-sectional view shows a portion of an example semiconductor device 300 with an interconnect structure in a subsequent manufacturing stage according to one embodiment. In this state, the device 300 includes a semiconductor die 302 having copper pillars 306 bonded to a substrate structure 332. In this embodiment, the copper pillars 306 are interconnected with substrate pads 328 of the substrate structure 332 by means of reflow solder 402. For example, during the reflow process, the copper pillars 306 are connected to solder balls 330 (… Figure 3The solder ball 330 makes contact with the substrate structure 332, allowing the molten solder to wet along the roughened surface 314, thereby forming a conductive connection between the semiconductor die 302 and the substrate structure 332. By forming the conductive connection in this way, the reflow solder 402 forms a thin profile (e.g., minimal solder bumps) around the distal portion 312 of each copper pillar 306. Thus, each formed conductive connection has excellent structural integrity while minimizing stress and eliminating voids. In this embodiment, the reflow solder 402 does not wet along the sidewalls of the proximal portion 310 of each copper pillar 306.

[0028] In this embodiment, the copper pillars 306 are arranged in a fine-pitch configuration, the fine-pitch configuration having a center-to-center dimension 404 of less than or equal to 150 micrometers. By using... Figure 4 The finely shaped reflow solder 402 depicted forms a conductive connection between the semiconductor die 302 and the substrate structure 332, which can form copper pillars 106 with fine spacing, thereby virtually eliminating the risk of solder bridging.

[0029] Figure 5 A simplified flowchart view illustrates an example method 500 for manufacturing an example interconnect structure according to one embodiment. Method 500 in this embodiment is for... Figure 1 and 2 Example interconnect structure 106 and as depicted in Figure 3 and 4 The alternative example interconnect structure 306 depicted is consistent.

[0030] In step 502, the seed layer on the UBM structure is patterned. In this embodiment, the semiconductor die includes die pads interconnected to the corresponding UBM structure. A seed layer is formed over the semiconductor die (at the wafer level) and the seed layer is patterned such that a portion of the seed layer is exposed over the UBM structure. For example, the seed layer may be formed as a single sputtered seed layer (e.g., copper) or a combined layer comprising a sputtered barrier layer (e.g., tantalum, tantalum nitride, titanium) followed by a sputtered seed layer (e.g., copper). The seed layer can be patterned using known photolithography and etching processes.

[0031] In step 504, copper is electroplated onto the seed layer to form pillars. In this embodiment, copper pillars are formed above the UBM structure by means of an electroplating process. After patterning the seed layer formed above the semiconductor die, copper pillars are electroplated onto the exposed portion of the seed layer above the UBM structure. Each of the copper pillars is configured to have a proximal portion and a distal portion. In this embodiment, the proximal portion is wider than the distal portion. For example, a stepped copper pillar shape may include a width dimension of the distal portion formed having a uniform diameter smaller than that of the proximal portion. In another example, a tapered copper pillar shape may include a width dimension of the distal portion formed having a tapered diameter smaller than that of the proximal portion. The electrodeposition of the stepped or tapered shape used to form the copper pillars can utilize known single-step or multi-step photolithography processes.

[0032] In step 506, solder is electroplated onto the copper pillars. In this embodiment, solder material is plated onto the ends or tips of the copper pillars. After the copper pillars are formed, solder material is plated onto the distal surface of the distal portion of each copper pillar to form a solder cap. The solder material may include, for example, a solder alloy such as tin-silver.

[0033] In step 508, portions of the copper pillars are selectively processed. In this embodiment, a roughened surface is selectively formed on the sidewalls of the distal portion of each copper pillar. For example, after the copper pillars are formed, the distal portions are subjected to a surface treatment process to roughen the sidewalls of the distal portions. The roughened surface can be formed by means of additive (e.g., electrodeposition, sputtering) or subtractive (e.g., etching) surface treatment processes. For example, the roughened surface may include microstructures or nanostructures in the form of dendrites, particles, needles, lines, bands, tubes, etc. In this embodiment, the roughened surface is configured to promote solder wetting.

[0034] To date, it should be understood that a semiconductor device with an interconnect structure has been provided. The semiconductor device includes a UBM structure connected to die pads formed on a semiconductor die. Copper pillars are formed on a seed layer portion above each UBM structure. Each pillar is formed having a proximal portion and a distal portion. The distal portion of each copper pillar undergoes a surface treatment configured to roughen the sidewall surface of the distal portion. The roughened sidewall surface is configured to promote solder wetting. By forming copper pillars with roughened sidewall surfaces of the distal portion in this manner, when the semiconductor die interconnects with a substrate, reflow solder forms a fine profile around the distal portion of each copper pillar. The fine solder profile allows the copper pillars to be configured with a fine pitch arrangement while virtually eliminating the risk of solder bridging. Thus, each conductive connection is formed with excellent structural integrity and reliability, where stress is minimal and voids are absent.

[0035] The terms “front,” “back,” “top,” “bottom,” “above,” “under,” and similar terms (if applicable) used in the specification and claims are for descriptive purposes and are not necessarily used to describe permanent relative positions. It should be understood that such terms are interchangeable where appropriate, so that embodiments of the invention described herein (e.g.) can operate in orientations other than those described or otherwise.

[0036] While the invention has been described herein with reference to specific embodiments, various modifications and changes may be made without departing from the scope of the invention as set forth in the appended claims. Therefore, the specification and drawings should be viewed in an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of the invention. It is not intended that any benefit, advantage, or solution to a problem described herein with reference to specific embodiments be construed as a key, necessary, or essential feature or element of any or all claims.

[0037] Furthermore, the term "a" is defined as one or more. And the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed as implying that the introduction of another claim element by the indefinite article "a" or "one" would limit any particular claim containing this introduced claim element to an invention containing only one such element, even when the same claim includes the introductory phrase "one or more" or "at least one" and indefinite articles such as "a" or "one". The same applies to the use of definite articles.

[0038] Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish the elements described by such terms. Therefore, these terms are not necessarily intended to indicate the temporal or other priorities of these elements.

Claims

1. A method, characterized in that, include: A first copper pillar is formed on a semiconductor die by means of a plating process. The proximal portion of the first copper pillar has a first width dimension, and the distal portion of the first copper pillar has a second width dimension, the second width dimension being smaller than the first width dimension. as well as The sidewalls of the distal portion of the first copper pillar are selectively roughened, and the roughened sidewalls of the distal portion of the first copper pillar are configured to promote solder wetting.

2. The method according to claim 1, characterized in that, The proximal portion of the first copper pillar has a first length dimension, and the distal portion of the first copper pillar has a second length dimension, the second length dimension being longer than the first length dimension.

3. The method according to claim 1, characterized in that, The distal portion of the first copper pillar is formed in a tapered configuration having a first tapered width dimension adjacent to the proximal portion of the first copper pillar and a second tapered width dimension at the distal end of the distal portion of the first copper pillar, the first tapered width dimension being approximately equal to the first width dimension of the proximal portion and the second tapered width dimension being approximately equal to the second width dimension of the distal portion of the first copper pillar.

4. The method according to claim 1, characterized in that, Additionally, the process includes forming a second copper pillar on the semiconductor die using the plating process, the second copper pillar being arranged with a fine pitch near the first copper pillar.

5. A method, characterized in that, include: A first copper pillar and a second copper pillar are formed on a semiconductor die by means of a plating process. Each copper pillar includes a proximal portion having a first width dimension and a distal portion having a second width dimension, wherein the second width dimension is smaller than the first width dimension. as well as The sidewalls of the distal portion of each copper pillar are selectively roughened, and the roughened sidewalls of the distal portion of the copper pillar are configured to promote solder wetting.

6. The method according to claim 5, characterized in that, The proximal portion of each copper pillar has a first length dimension, and the distal portion of each copper pillar has a second length dimension, the second length dimension being longer than the first length dimension.

7. The method according to claim 5, characterized in that, Selectively roughening the sidewalls of the distal portion of each copper pillar includes forming nanostructures on the sidewalls of the distal portion of each copper pillar.

8. A semiconductor device, characterized in that, include: Semiconductor die; A first copper pillar is formed on the semiconductor die, the proximal portion of the first copper pillar has a first width dimension, and the distal portion of the first copper pillar has a second width dimension, the second width dimension being smaller than the first width dimension; as well as A roughened surface is formed on the sidewall of the distal portion of the first copper pillar, and the roughened surface formed by the sidewall of the distal portion of the first copper pillar is configured to promote solder wetting.

9. The semiconductor device according to claim 8, characterized in that, The proximal portion of the first copper pillar has a first length dimension, and the distal portion of the first copper pillar has a second length dimension, the second length dimension being longer than the first length dimension.

10. The semiconductor device according to claim 8, characterized in that, Additionally, a second copper pillar is formed on the semiconductor die, the second copper pillar being arranged with a fine pitch near the first copper pillar, the fine pitch arrangement having a center-to-center spacing of approximately less than or equal to 150 micrometers.

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