1. Field
The present disclosure generally relates to semiconductor device assembly. More specifically, the present disclosure relates to a conductive interconnect including an inorganic collar for protecting the conductive interconnect during a seed layer etch and preventing a solder bridge during chip attach.
2. Background
In flip-chip packaging, an active device region of an integrated circuit (IC) (e.g., a die) is on a surface facing a package substrate (e.g., downward). In this arrangement, interconnects (such as pillars) from the IC may electrically couple with contact pads on the package substrate. The pillar can be copper, tin solder or silver solder. A copper pillar may be fabricated according to a plating method, for example, as shown in
As shown in
The electroplating method 100 includes a seed layer etch to remove portions of the conductive seed layer 104 between the pillars 120 to form an under bump conductive layer 130. This etch may be a non-isotropic etch that removes the conductive seed layer 104 in all directions. Removal of the conductive seed layer 104 between the pillars 120 prevents shorting of the copper pillars 120 causing faulty interconnect operation. Unfortunately, the etch process also over-etches the copper layer 122 to form an undercut 126. The undercut 126 reduces the contact area of the copper pillars 120 on the semiconductor substrate 102. The reduced contact area may degrade the connectivity as well as the integrity of the copper pillars 120.
In this example, the undercut 126 may be in the range of three (3) microns on each side of the copper pillars 120. The current control limit for the manufacturing site (e.g., the foundry) is less than six microns of undercut on each side of a bump interconnect of the copper pillars 120. The undercut amount is significant when the bump diameter is, for example, less than sixty microns. At this size, six microns of over etch may result in a 10% to 20% loss in the copper pillars 120. As a result, fabricating copper pillars 120 for fine pitch/size designs is challenging due to copper over etching. After the etching, a thermal process reflows the solder layer 124 of the copper pillars 120. Consequently, surface tension causes a round shape of the solder layer 124.
Conventional solutions for preventing the undercut 126 to the copper layer 122 of the copper pillars 120 include changing the etch process to reduce an amount of the undercut 126. Changing the etch process, however, involves a fundamental process change to develop a new etch mechanism. Another conventional solution is increasing a bump diameter of the copper pillars 120, for example, as shown in
According to one aspect of the present disclosure, conductive interconnect including an inorganic collar is described. The conductive interconnect includes a conductive support layer. The conductive interconnect also includes a conductive material on the conductive support layer. The conductive interconnect further includes an inorganic collar partially surrounding the conductive material. The inorganic collar is also disposed on sidewalk of the conductive support layer.
According another aspect of the present disclosure, a method for fabricating a conductive interconnect including an inorganic collar is described. The method includes fabricating a conductive material on a conductive seed layer. The method also includes forming an organic collar to partially surround the conductive material. The method further includes heating the conductive interconnect to transition the organic collar into an inorganic collar that partially surrounds the conductive material. The inorganic collar is also disposed on sidewalls of a conductive support layer from the heating of the conductive interconnect.
According to a farther aspect of the disclosure, a conductive interconnect including an inorganic collar is described. The conductive interconnect includes a conductive material on a conductive support layer. The conductive interconnect also includes means for protecting the conductive material and the conductive support layer of the conductive interconnect.
This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout.
The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts. As described herein, the use of the term “and/or” is intended to represent an “inclusive OR”, and the use of the term “or” is intended to represent an “exclusive OR”.
Aspects of the present application provide solutions for improved assembly of integrated circuit (IC) devices (e.g., flip chip devices or micro-electromechanical systems (MEMS) devices). For example, as shown in
Conventional solutions for preventing the undercut 126 to the copper layer 122 include changing the etch process to reduce an amount of the undercut 126. Changing the etch process, however, involves a fundamental process change to develop a new etch mechanism. Another conventional solution is increasing a bump diameter of the copper pillars, for example, as shown in
One aspect of the disclosure provides an inorganic collar for protecting a conductive interconnect during a seed layer etch. The inorganic collar also prevents a solder bridge from forming during chip attach.
As shown in
In another aspect of the disclosure, a barrier layer (not shown) may be deposited between the first conductive layer 322 and the second conductive layer 324. A thickness of the first conductive layer 322 may be in the range of a few to hundreds of microns. A thickness of the second conductive layer 324 may be in the range of a few to hundreds of microns. Next, an organic spin on dielectric material 306 may be applied on the conductive seed layer 304 and the conductive material stacks 320. In one configuration, the organic spin on dielectric material 306 is a photosensitive spin on dielectric material that transitions from an organic material to an inorganic material following a thermal process. An example material is a photosensitive spin on dielectric (NOD) from AZ Electronic Materials.
As further shown in
In one configuration, the thermal process causes a transition of the spin on dielectric material 306 of the organic collar 310 from an organic material to an inorganic material that may be similar in composition to, for example, silicon dioxide (SiO2). In this configuration, the inorganic material forms an inorganic collar 350 that partially surrounds the conductive interconnects 340. In one aspect of the disclosure, the inorganic collar 350 is composed of a curable inorganic material, including silicon, that exhibits a thermal cross link reaction during the thermal process. As a result, the thermal process for forming the inorganic collar 350 causes the spin on dielectric material 306 to flow onto the sidewalls of the conductive support layer 330 prior to curing into the inorganic collar 350.
In one aspect of the disclosure, a thermal crosslink reaction during the thermal treatment causes the spin on dielectric material 306 of the organic collar 310 to flow onto the conductive seed layer 304. In this aspect of the disclosure, a thermal cross link reaction is a chemical reaction that joins the smaller molecules of the spin on dielectric material 306 into a large network that forms a cured, solid matter of the inorganic collar 350. That is, the thermal treatment may cause the spin on dielectric material 306 to flow onto the sidewalls of the conductive support layer 330
Moreover, the inorganic collar 350 has good thermal conductivity. The semiconductor substrate 302, including the conductive interconnects 340, may be assembled into an integrated circuit (IC) device package. In this configuration, the inorganic collar 350 provides an improved heat dissipation path when compared to the other organic materials around the conductive interconnects 340, such as underfill and/or molding compound of the assembled package. Thus, heat is easily dissipated through the inorganic collar 350 of the conductive interconnects 340. In addition, the inorganic collar 350 can withstand high temperatures.
In this aspect of the disclosure, the use of the inorganic collar 450 protects the composition of the first conductive layer 422 of the conductive interconnects 440 during the seed layer etch to eliminate or reduce any undercutting to the first conductive layer 422. Protecting the composition of the first conductive layer 422 may increase an extremely low-K (ELK) robustness and improve a interconnect fatigue life of the conductive interconnects 440. In addition, the inorganic collar 450 prevents the solder bridge problem shown in
As shown in
In block 712, an organic collar is formed to partially surround the conductive material. For example, as shown in
Referring again to
Accordingly, the method 700 of
As noted, etch loss to a conductive material during a seed layer etch process is a concern for the conductive material(s) during the conductive interconnect formation process, for example, as shown in
In this aspect of the disclosure, a thermal process causes a transition of the spin on dielectric material 306/506 from an organic material to an inorganic material, such as silicon dioxide (SiO2). In addition, the thermal process causes the spin on dielectric material 306/506 to flow onto the sidewalls of the conductive support layer 330/530 to form the inorganic collar 350/550. The inorganic collar 350 around the conductive material stacks 320 also prevents the solder bridge problem during semiconductor chip assembly. Eliminating the solder bridge problem enables a further reduction of the interconnect pitch to support fine pitch/size, designs for semiconductor devices. Furthermore, eliminating undercutting maintains a diameter of the first conductive layer 422 or the single conductive material 520 of the conductive interconnects 440/540. This configuration provides an increased contact area of the conductive interconnects 440/540 to the semiconductor substrate 402/502. The increased contact areas also improve the connectivity as well as the integrity of the conductive interconnects 440/540.
In one configuration, a conductive interconnect includes a conductive material on a conductive support layer. The conductive interconnect also includes means for protecting the conductive material and the conductive support layer of the conductive interconnect. The protecting means may partially surround the conductive material and is disposed on sidewalls of the conductive support layer. In one aspect, the protecting means may be the inorganic collar 350/450/550/650 configured to perform the functions recited by the protecting means. In another aspect, the aforementioned means may be any component or any structure configured to perform the functions recited by the aforementioned means.
In
Although specific circuitry has been set forth, it will be appreciated by those skilled in the art that not all of the disclosed circuitry is required to practice the disclosed configurations. Moreover, certain well known circuits have not been described, to maintain focus on the disclosure. Similarly, although the relative terms “upper” and “lower” are used, these terms are non-limiting. For example if a device is rotated by 90 degrees the terms “upper” and “lower” would refer to “left most” and “right most” portions.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.
The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two.
The methodologies described herein may be implemented by various components depending upon the application. For example, these methodologies may be implemented in hardware, firmware, software, or any combination thereof For a hardware implementation, the processing units may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or a combination thereof.
For a firmware and/or software implementation, the methodologies may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. Any machine-readable medium tangibly embodying instructions may be used in implementing the methodologies described herein. For example, software codes may be stored in a memory and executed by a processor unit. Memory may be implemented within the processor unit or external to the processor unit. As used herein the term “memory” refers to any type of long term, short term, volatile, nonvolatile, or other memory and is not to be limited to any particular type of memory or number of memories, or type of media upon which memory is stored.
If implemented in firmware and/or software, the functions may be stored as one or more instructions or code on a computer-readable medium. Examples include computer-readable media encoded with a data structure and computer-readable media encoded with a computer program. Computer-readable media includes physical computer storage media. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer; disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
In addition to storage on computer readable medium, instructions and/or data may be provided as signals on transmission media included in a communication apparatus. For example, a communication apparatus may include a transceiver having signals indicative of instructions and data. The instructions and data are configured to cause one or more processors to implement the functions outlined in the claims.
Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the technology of the disclosure as defined by the appended claims. For example, relational terms, such as “above” and “below” are used with respect to a substrate or electronic device. Of course, if the substrate or electronic device is inverted, above becomes below, and vice versa. Additionally, if oriented sideways, above and below may refer to sides of a substrate or electronic device. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
The present application claims the benefit, under 35 U.S.C. §119(e), of U.S. provisional patent application No. 61/721,889, filed on Nov. 2, 2012, in the names of Sun et al., the disclosure of which is expressly incorporated by reference herein in its entire.
Number | Date | Country | |
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61721889 | Nov 2012 | US |