Background

[0001] The vias that form electrical interconnections between metal layers in an integrated circuit (IC) substrate are generally initially formed using a laser. The vias that are formed by using a laser are typically tapered (i.e., wider at the top than the bottom). This tapering often results in a narrow via bottom that causes concerns relative to the reliability of the via and its ability to conduct electrical current.

[0002] The concerns that are associated with narrow via bottoms are often addressed with additional laser shots. However, additional laser shots may have a dramatic impact on throughput and add significant manufacturing cost. Additionally, even with these extra laser shots the via will still have a taper.

[0003] Using a laser to form a tapered opening for a via also usually leaves behind organic residue in the opening. The organic residue is commonly known as smear.

[0004] Smear is typically addressed through a chemistry based removal process known as desmear. The conventional desmear process suffers from a variety of drawbacks.

[0005] As an example, desmear etches the opening of the via drilled in the dielectric. This etching of the dielectric widens the via thereby making it more difficult to scale the size of the via.

[0006] As another example, conventional desmear roughens the outer surface of the dielectric. Since this outer surface is used as the base for the next Cu layer the dielectric roughness is translated to the next layer's Cu trace. This roughening of the conductive surface may negatively impact electrical performance of the IC that includes the via.

[0007] Both the presence of smear and a narrow via bottom potentially contribute to poor via reliability, especially as the size of a via becomes smaller. Therefore, a need exists for a process to remove organic residue from the bottom of a via opening while also improving the electrical reliability of the via. Brief Description of the Drawings

[0008] FIG. 1 is a flow diagram illustrating an example method of forming a via opening in an electric component.

[0009] FIG. 2 is a flow diagram illustrating another example method of forming a via opening in an electric component.

[0010] FIG. 3 is a flow diagram illustrating yet another example method of forming a via opening in an electric component.

[0011] FIG. 4 illustrates an example via opening in an electronic component before a desmearing agent has been inserted into the via opening.

[0012] FIG. 5 shows the via opening of FIG. 4 after a desmearing agent has been inserted in to the via opening.

[0013] FIG. 6 shows the via opening of FIG. 5 being rinsed with a solution to remove the desmearing agent and solubilized reaction products.

[0014] FIG. 7 shows the via opening after the rinsing operation of FIG.

6.

[0015] FIG. 8 shows an example via opening before a desmearing agent that includes an active third species has been inserted into the via opening 10.

[0016] FIG. 9 shows the via opening of FIG. 8 after a desmearing agent that includes an active third species has been inserted in to the via opening to roughen the via opening.

[0017] FIG. 10 shows the via opening of FIG. 9 after removing the desmearing agent that includes an active third species from the via opening.

[0018] FIG. 11 is block diagram of an electronic apparatus that includes the methods described herein.

Description of Embodiments

[0019] The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims. [0020] Orientation terminology, such as "horizontal," as used in this application is defined with respect to a plane parallel to the conventional plane or surface of a wafer or substrate, regardless of the orientation of the wafer or substrate. The term "vertical" refers to a direction perpendicular to the horizontal as defined above. Prepositions, such as "on," "side" (as in

"sidewall"), "higher," "lower," "over," and "under" are defined with respect to the conventional plane or surface being on the top surface of the wafer or substrate, regardless of the orientation of the electrical interconnect or electronic package.

[0021] The methods described herein may utilize a geometry of a via in combination with fact that radicals decay approximately with distance squared to (i) widen the via bottom; and/or (iii) clean smear from the via. In addition, the method may clean smear from an exposed conductor (e.g., copper) without roughening the outer surface of the conductor.

[0022] As an example, the method may be accomplished in a single solution that includes an inactive desmear agent, an initiator that forms radicals upon contact with Cu(0) and a deactivator. One example method may be summarized as follows:

1. The initiator contacts the Cu(0) pad and generates radicals.

2. The radicals activate the desmear agent. In some forms, more radicals are activated near the Cu surface due to short lifetime of the radicals.

3. The desmear agent removes organic material until it meets the deactivator. Controlling the amount of deactivator within the solution may allow for some control over the final via shape. This control over the final via shape may be accomplished by balancing the ratio of radicals to deactivator.

[0023] Fig. 1 is a flow diagram illustrating an example method [100] of forming a via opening 10 in an electronic component 11. FIG. 4 shows an example via opening 10 before the method [100] is applied to the via opening 10.

[0024] The method [100] includes [110] inserting a desmearing agent 12

(see FIG. 5) into a via opening 10 to remove smear 13 (shown in FIG. 4) from the via opening 10 in a dielectric layer 17. The desmearing agent 12 includes a first species R which forms radicals R° when coming into contact with a conductor 14 within the via opening 10. The radical R° activates an inactive second species to form an active second species 15 that is part of the desmearing agent 12. The active second species 15 converts smear 13 within the via opening 10 to solubilized reaction products.

[0025] The method [100] further includes [120] rinsing the via opening

10 to remove the desmearing agent 12 and the solubilized reaction products from the via opening 10. As an example, FIG. 6 shows the via opening 10 being rinsed with a solution 18 (e.g., an acidic solution such as sulfuric acid, hydrochloric acid or oxalic acid) to remove the desmearing agent 12 and the solubilized reaction products. FIG. 7 shows the via opening of FIGS. 4-6 after the [120] rinsing operation.

[0026] In some forms, [110] inserting a desmearing agent 12 into a via opening 10 to remove smear 13 from the via opening 10 includes inserting the electrical component 11 into a chemical bath. It should be noted other forms of inserting the desmearing agent 12 into the via opening 10 are contemplated (e.g., spray, immersion or flood type).

[0027] As an example, the inactive second species may have an electrochemical potential such that the inactive second species does not oxidize the smear 13. In addition, the active second species may have an

electrochemical potential such that the active second species 15 oxidizes the smear 13.

[0028] The method [100] described herein may remove smear 13 from the bottom of the via opening 10 that has been drilled (e.g., laser drilled) while still permitting control of the via opening 10 shape and surface roughness. An example radical activated desmearing process is shown in equations 2 through 5 and illustrated in FIG. 5.

R + Cu _{ s)→R* + Cu(I) _{aq) (2)

R* + D(inactive)→R + D(active) (3)

D(active) + Smear(s)— > D( _ac tive) + Soluble Byproduct^) (4)

D(active) + I— » D(active) + / (5) [0029] Radicals are generated at the Cu surface and activate the desmearing agent 12. There may be more radical activation at the bottom of the via opening 10 than the top of the via opening 10 (see FIG. 5). This distribution of the radical activation in the via opening 10 may promote a wider bottom at the via opening 10 and some amount of Cu removal depending on the components used (see FIG. 7).

[0030] It should be noted that the conductor 14 may be copper and that some copper may be etched. This copper etching may actually be desirable for via integrity because an undercut 16 may be created. Creating an undercut 16 may be especially useful for fine pitch via openings 10 because the undercut serves as anchor to provide the fine pitch via with additional strength.

[0031] In addition, the method [100] may allow for some control over the surface morphology of the dielectric layer 17. There may be a balance between adhesion (which favors high surface roughness of the dielectric material) and electrical performance (which favors low surface roughness on the conductor 14). In some forms, if greater surface roughness is desired for adhesion, then an active oxidizer may be added to the desmearing agent 12 in order permit some control of the surface morphologies for the dielectric layer 17 and the conductor 14.

[0032] In some forms, the desmearing agent 12 includes a deactivator that makes some of the radicals in the first species inactive in order to control a width of the via opening 10. As examples, adding more deactivator into the desmearing agent 12 may reduce the effect of the radicals on the via opening 10, and adding less deactivator into the desmearing agent 12 may increase the effect of the radicals on the via opening 10.

[0033] In addition, adding less deactivator into the desmearing agent 12 may change the aspect ratio of the via opening 10. As an example, adding less deactivator into the desmearing agent 12 may make the via opening 10 wider at the bottom of the opening 10 without widening the top of the via opening 10 (see FIG. 7). As an example, fine pitch via openings 10 may benefit from having via openings 10 with larger bottoms in order promote electrical reliability in the electrical component 11. [0034] The deactivator may include an antioxidant. As an example, the antioxidant may include a substituted phenol or polyethylene glycol. A variety of deactivators are contemplated.

[0035] Fig. 2 is a flow diagram illustrating an example method [200] of forming a via opening 10 in an electronic component 11. FIG. 4 shows an example via opening 10 before the method [200] is applied to the via opening 10.

[0036] The method [200] includes [210] inserting a desmearing agent 12 into a via opening 10 in a dielectric layer 16 to remove smear 13 from the via opening 10. The desmearing agent includes a first species which forms radicals when coming into contact with a conductor 14 (e.g., copper) within the via opening 10. The radical activates an inactive second species to form an active second species 15 that is part of the desmearing agent 12 (see FIG. 5). The active second species 15 converts smear to solubilized reaction products within the via opening 10.

[0037] The method [200] includes [220] inserting an active third species into the via opening 10 together with the desmearing agent 12 which may allow the active third species to roughen the via opening 10 and an outer surface 19 of the dielectric layer 17. It should be noted that roughening the outer surface 19 may promote adhesion with another conductor 14 that forms the next layer.

[0038] This process of roughening the via opening 10 and the outer surface 19 is illustrated in FIGS. 8-10. FIG. 8 shows the example via opening 10 and outer surface 19 before a desmearing agent 12 that includes an active third species has been inserted into the via opening 10. FIG. 9 shows the via opening 10 and outer surface 19 of FIG. 8 after the desmearing agent 12 that includes an active third species has been inserted into the via opening 10 to roughen the via opening 10 and the outer surface 19. FIG. 10 shows the via opening 10 of FIG.

9 after removing the desmearing agent 12 that includes an active third species from the via opening 10 and the outer surface 19.

[0039] The method [200] further includes [230] rinsing the via opening

10 (e.g. with an acidic solution) to remove the desmearing agent 12 from the via opening 10. As an example, the via opening 10 may be rinsed with an acidic solution 18 (see FIG. 6). [0040] In some forms, the active third species may include a metal with a chemical potential that is sufficient to oxidize the dielectric layer. In addition, the active third species may be similar to the active second species.

[0041] Fig. 3 is a flow diagram illustrating an example method [300] of forming a via opening 10 in an electronic component 11. FIG. 4 shows an example via opening 10 before the method [300] is applied to the via opening 10.

[0042] The method [300] includes [310] inserting a desmearing agent 12 into a via opening 10 to remove smear 13 from the via opening 10. The desmearing agent 12 includes an alkyl halide which forms radicals R° when coming into contact with copper within the via opening 10. The radicals R° activate an inactive manganate to form an active manganate 15 that is part of the desmearing agent 12. The active manganate 15 converts the smear 13 to carbonate within the via opening 10.

[0043] The method [300] further includes [330] rinsing the via opening

10 to remove the desmearing agent 12 and the carbonate from the via opening 10 (see FIG. 6). As an example, the via opening 10 may be rinsed with an acidic solution 18.

[0044] It should be noted that [310] inserting a desmearing agent 12 into a via opening 10 to remove smear 13 from the via opening 10 includes inserting the electrical component 11 into a chemical bath. It should be noted other forms of inserting the desmearing agent 12 into the via opening 10 are contemplated.

[0045] In some forms, radicals are initially generated using an alkyl halide (RX) which reacts with the exposed Cu surface to form a radical (R°) and Cu halide (CuX) (see equation 6 below). The radical R° then extracts an electron from Mn0 ₄ ^2~ forming the active permanganate Mn0 ₄ ^" (see equation 7 below). The active permanganate would then oxidize the smear using the mechanism shown in equation 8. Formation of radicals R° from alkyl halides over Cu(0) requires that the R group must be chosen to have the appropriate electrochemical potential to oxidize Mn0 ₄ ^2~ .

RX + Cu(s)→ R° + Cu(I)X (6)

Mn0 ₄ ² - + R°→ Mn0 ₄ ^" + R (7)

Smear + xMn0 ₄ ^" → xC0 ₃ ^2" + xMn0 ₄ ^2" + xH ₂ 0 (8) [0046] The methods [100], [200], [300] described herein may widen via bottoms to improve via reliability with electronic components. The methods [100], [200], [300] may also allow for a reduction in the laser shot count that is typically used to create vias. Reducing laser shot count may increase manufacturing throughput and reduce capital costs associated with purchasing lasers.

[0047] FIG. 11 is a block diagram of an electronic apparatus 1100 incorporating at least one method [100], [200], [300] described herein.

Electronic apparatus 1100 is merely one example of an electronic apparatus in which the method [100], [200], [300] may be used.

[0048] Examples of an electronic apparatus 1100 include, but are not limited to, personal computers, tablet computers, mobile telephones, game devices, MP3 or other digital music players, etc. In this example, electronic apparatus 1100 comprises a data processing system that includes a system bus

1102 to couple the various components of the electronic apparatus 1100. System bus 1102 provides communications links among the various components of the electronic apparatus 1100 and may be implemented as a single bus, as a combination of busses, or in any other suitable manner.

[0049] An electronic assembly 1110 that uses any of the methods [100],

[200], [300] as describe herein may be coupled to system bus 1102. The electronic assembly 1110 may include any circuit or combination of circuits. In one embodiment, the electronic assembly 1110 includes a processor 1112 which can be of any type. As used herein, "processor" means any type of

computational circuit, such as but not limited to a microprocessor, a

microcontroller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a graphics processor, a digital signal processor (DSP), multiple core processor, or any other type of processor or processing circuit.

[0050] Other types of circuits that may be included in electronic assembly 1110 are a custom circuit, an application-specific integrated circuit (ASIC), or the like, such as, for example, one or more circuits (such as a communications circuit 1114) for use in wireless devices like mobile telephones, tablet computers, laptop computers, two-way radios, and similar electronic systems. The IC can perform any other type of function.

[0051] The electronic apparatus 1100 may also include an external memory 1120, which in turn may include one or more memory elements suitable to the particular application, such as a main memory 1122 in the form of random access memory (RAM), one or more hard drives 1124, and/or one or more drives that handle removable media 1126 such as compact disks (CD), flash memory cards, digital video disk (DVD), and the like.

[0052] The electronic apparatus 1100 may also include a display device

1116, one or more speakers 1118, and a keyboard and/or controller 1130, which can include a mouse, trackball, touch screen, voice-recognition device, or any other device that permits a system user to input information into and receive information from the electronic apparatus 1100.

[0053] To better illustrate the method and apparatuses disclosed herein, a non-limiting list of embodiments is provided herein:

[0054] Example 1 includes a method of forming a via opening in an electric component. The method includes inserting a desmearing agent into a via opening to remove smear from the via opening. The desmearing agent includes a first species which forms radicals when coming into contact with a conductor within the via opening. The radical activates an inactive second species to form an active second species that is part of the desmearing agent. The active second species converts smear to solubilized reaction products within the via opening. The method further includes rinsing the via opening to remove the desmearing agent and the solubilized reaction products from the via opening.

[0055] Example 2 includes the method of example 1, wherein inserting a desmearing agent into a via opening to remove smear from the via opening includes inserting the electrical component into a chemical bath.

[0056] Example 3 includes the method of any one of examples 1-2, wherein the conductor is copper.

[0057] Example 4 includes the method of any one of examples 1-3, wherein the inactive second species may have an electrochemical potential such that the inactive second species does not oxidize the smear. [0058] Example 5 includes the method of any one of examples 1-4, wherein the active second species may have an electrochemical potential such that the active second species oxidizes the smear.

[0059] Example 6 includes the method of any one of examples 1-5, wherein rinsing the via opening to remove the desmearing agent and solubilized reaction products from the electrical component includes rinsing the via opening with an acidic solution.

[0060] Example 7 includes the method of any one of examples 1-6, wherein the desmearing agent includes a deactivator that makes some of the radicals in the first species inactive in order to control a width of the via opening.

[0061] Example 8 includes the method of any one of examples 1-7, wherein adding more deactivator into the desmearing agent reduces the effect of the radicals on the via opening.

[0062] Example 9 includes the method of any one of examples 7-8, wherein adding less deactivator into the desmearing agent increases the effect of the radicals on the via opening.

[0063] Example 10 includes the method of example 9, wherein adding less deactivator into the desmearing agent changes the aspect ratio of the via opening.

[0064] Example 11 includes the method of any one of examples 9-10, wherein adding less deactivator into the desmearing agent makes the via opening wider, wherein the desmearing agent makes the via opening wider at the bottom without making the via opening wider at the top.

[0065] Example 12 includes the method of any one of examples 1-11, wherein the deactivator includes an antioxidant.

[0066] Example 13 includes the method of examples 12, wherein the antioxidant includes a substituted phenol or polyethylene glycol.

[0067] Example 14 includes a method of forming a via opening in an electric component. The method includes inserting a desmearing agent into a via opening in a dielectric layer to remove smear from the via opening, wherein the desmearing agent includes a first species which forms radicals when coming into contact with a conductor within the via opening. The radical activates an inactive second species to form an active second species that is part of the desmearing agent. The active second species converts smear to solubilized reaction products within the via opening. The method further includes inserting an active third species into the desmearing agent before the desmearing agent is inserted into the via opening such that the active third species roughens the via opening and an outer surface of the dielectric layer when the desmearing agent is inserted into the via opening and on the outer surface of the dielectric layer. The method further includes rinsing the via opening to remove the desmearing agent and the solubilized reaction products from the via opening.

[0068] Example 15 includes the method of example 14, wherein roughening the via opening promotes adhesion with another conductor that fills the via opening.

[0069] Example 16 includes the method of any one of examples 14-15, wherein the active third species includes a metal with a chemical potential that is sufficient to oxidize the dielectric layer.

[0070] Example 17 includes the method of any one of examples 14-16, wherein the active third species is similar to the active second species.

[0071] Example 18 includes a method of forming a via opening in an electric component. The method includes inserting a desmearing agent into a via opening to remove smear from the via opening. The desmearing agent includes an alkyl halide which forms radicals when coming into contact with copper within the via opening. The radical activates an inactive manganate to form an active manganate that is part of the desmearing agent. The active manganate converts the smear to carbonate within the via opening. The method further includes rinsing the via opening to remove the desmearing agent and the carbonate from the via opening.

[0072] Example 19 includes the method of example 18, wherein rinsing the via opening to remove the desmearing agent and carbonate from the electrical component includes rinsing the via opening with an acidic solution.

[0073] Example 20 includes the method of any one of examples 18-19, wherein inserting a desmearing agent into a via opening to remove smear from the via opening includes inserting the electrical component into a chemical bath.

[0074] This overview is intended to provide non-limiting examples of the present subject matter. It is not intended to provide an exclusive or exhaustive explanation. The detailed description is included to provide further information about the methods.

[0075] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as "examples." Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0076] In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of "at least one" or "one or more." In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indicated. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0077] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. In addition, the order of the methods described herein may be in any order that permits fabrication of an electrical interconnect and/or package that includes an electrical interconnect. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. [0078] The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0079] Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.