Abstract:
Transferring electronic probe assemblies to space transformers. In accordance with a first method embodiment, a plurality of probes is formed in a sacrificial material on a sacrificial substrate via microelectromechanical systems (MEMS) processes. The tips of the plurality of probes are formed adjacent to the sacrificial substrate and the remaining structure of the plurality of probes extends outward from the sacrificial substrate. The sacrificial material comprising the plurality of probes is attached to a space transformer. The space transformer includes a plurality of contacts on one surface for contacting the plurality of probes at a probe pitch and a corresponding second plurality of contacts on another surface at a second pitch, larger than the probe pitch, wherein each of the second plurality of contacts is electrically coupled to a corresponding one of the plurality of probes. The sacrificial substrate is removed, and the sacrificial material is removed, leaving the plurality of probes intact.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application 61/607,889, entitled, “Methods to Transfer Logic Probe Assemblies on to Space Transformers,” filed 7 Mar. 2012, to Namburi and Cros, which is hereby incorporated herein by reference in its entirety. 
         [0002]    Co-pending, commonly-owned U.S. patent application ______, attorney docket ATST-U0075.US, entitled, “Fine Pitch Probe Array from Bulk Material,” filed 7 Mar. 2013, to Namburi, is hereby incorporated herein in its entirety by reference. 
         [0003]    U.S. Pat. No. 7,271,022, entitled “Process for Forming Microstructures,” to Tang et al. is hereby incorporated herein in its entirety by reference. 
     
    
     FIELD OF INVENTION 
       [0004]    Embodiments of the present invention relate to the field of integrated circuit design, manufacture and test. More specifically, embodiments of the present invention relate to systems and methods for transferring electronic probe assemblies to space transformers. 
       BACKGROUND 
       [0005]    Integrated circuit testing generally utilizes fine probes to make contact with test points of an integrated circuit in order to inject electrical signals and/or measure electrical parameters of the integrated circuit. Conventional circuit probes are produced singly, and manually assembled into an array, sometimes known as or referred to as a “probe card,” corresponding to some or all of the test points on an integrated circuit. 
         [0006]    With increasing numbers of test points, and decreasing pad/bump spacing required of modern integrated circuits, it is challenging to assemble probes one at a time. Probe assemblies formed using surface micromachining techniques such as MEMS (microelectromechanical systems) or wire-EDM (electric discharge machining) are becoming attractive for probe cards. However, it is very difficult to build probe assemblies on top of a fine pitch space transformer such as a silicon space transformer, as the space transformers are quite complex and are very fragile. The stresses involved in building MEMS probes far exceed the strength of the fine pitch space transformers. 
         [0007]    Most probe cards require repeated repair because probes are often damaged due to mishandling or are burned due to faulty die under test. Probes are generally replaced using a probe repair tool, a manual process that involves heating and un-mounting a damaged individual probe and reattaching a new probe. This is essential to restore the probe card to full functionality. However in the case of fine pitch probing with a pitch, e.g., probe to probe spacing, of less than about 50 μm, it is extremely difficult to replace individual probes. This is because of the small geometries and also due to insufficient clearance to handle the probe. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore, what is needed are systems and methods for transferring electronic probe assemblies to space transformers. What is additionally needed are systems and methods transferring electronic probe assemblies to space transformers that eliminate manual assembly and reduce lead times. A further need exists for systems and methods for transferring electronic probe assemblies to space transformers that are compatible and complementary with existing systems and methods of integrated circuit design, manufacturing and test. Embodiments of the present invention provide these advantages. 
         [0009]    In accordance with a first method embodiment, a plurality of probes is formed in a sacrificial material on a sacrificial substrate via microelectromechanical systems (MEMS) processes. The tips of the plurality of probes are formed adjacent to the sacrificial substrate and the remaining structure of the plurality of probes extends outward from the sacrificial substrate. The sacrificial material comprising the plurality of probes is attached to a space transformer. The space transformer includes a plurality of contacts on one surface for contacting the plurality of probes at a probe pitch and a corresponding second plurality of contacts on another surface at a second pitch, larger than the probe pitch, wherein each of the second plurality of contacts is electrically coupled to a corresponding one of the plurality of probes. The sacrificial substrate is removed, and the sacrificial material is removed, leaving the plurality of probes intact. 
         [0010]    In accordance with a another embodiment, an article of manufacture includes a space transformer having first contacts at a first pitch on a first face, and second contacts at a second pitch on a second face and a fine pitch space transformer having third contacts at the second pitch on a first face and fourth contacts at a probe pitch on a second face. The first face of the fine pitch space transformer functionally coupled to the second contacts of the second face of the space transformer. The article also includes a plurality of fine pitch electronic probes, suitable for contacting test points of an integrated circuit, at a probe pitch functionally coupled to the fourth contacts of the second face of the fine pitch space transformer. The plurality of fine pitch electronic probes is configured to be removed as a whole from an assembly of the space transformer and the fine space transformer. 
         [0011]    In accordance with another method embodiment of the present invention, a plurality of probes is formed in a primary sacrificial material on a sacrificial substrate via microelectromechanical systems (MEMS) processes. The tips of the plurality of probes are formed away from the sacrificial substrate and the remaining structure of the plurality of probes extends outward from the sacrificial substrate. The primary sacrificial material is removed. The plurality of probes is encapsulated in a secondary sacrificial material. The encapsulated plurality of probes is bonded to a space transformer, and the secondary sacrificial material is removed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. Unless otherwise noted, the drawings are not drawn to scale. 
           [0013]      FIG. 1  illustrates an electronic probe assembly with space transformers  100 , in accordance with embodiments of the present invention. 
           [0014]      FIGS. 2 ,  3 ,  4 ,  5 ,  6 ,  7  and  8  illustrate a method of forming an electronic probe assembly, e.g., an electronic probe assembly, in accordance with embodiments of the present invention. 
           [0015]      FIGS. 9 and 10  illustrate a method of forming an electronic probe assembly, e.g., an electronic probe assembly, in accordance with embodiments of the present invention. 
           [0016]      FIGS. 11 ,  12  and  13  illustrate a method of forming an electronic probe assembly, e.g., an electronic probe assembly, in accordance with embodiments of the present invention. 
           [0017]      FIGS. 14 ,  15 ,  16 ,  17  and  18  illustrate a method of forming an electronic probe assembly, e.g., an electronic probe assembly, in accordance with embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with these embodiments, it is understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be recognized by one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the invention. 
       NOTATION AND NOMENCLATURE 
       [0019]    Some portions of the detailed descriptions which follow (e.g., processes  200 ,  900 ,  1100  and  1400 ) are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that may be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
         [0020]    It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “accessing” or “forming” or “mounting” or “removing” or “encapsulating” or “bonding” or “releasing” or “coating” or “attaching” or “processing” or “singulating” or “roughening” or “filling” or “performing” or “generating” or “adjusting” or “creating” or “executing” or “continuing” or “indexing” or “computing” or “translating” or “calculating” or “determining” or “measuring” or “gathering” or “running” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
       Transferring Electronic Probe Assemblies to Space Transformers 
       [0021]      FIG. 1  illustrates an electronic probe assembly with space transformers  100 , in accordance with embodiments of the present invention. Electronic probe assembly  100  comprises a plurality, generally in an array, of fine pitch probes  135 . The pitch, or probe to probe spacing, of the probes may be 50 μm or less. The fine pitch probes  135  may be mounted to, or formed on a through-via probe carrier  130 . 
         [0022]    Co-pending, commonly-owned U.S. patent application ______, attorney docket ATST-U0075.US, filed 7 Mar. 2013, entitled, “Fine Pitch Probe Array from Bulk Material,” to Namburi, illustrates systems and methods of such fine pitch probe arrays, and is incorporated herein in its entirety by reference. The disclosures of the referenced US patent application are compatible and complementary with the disclosures of the present application. It is appreciated that embodiments in accordance with the present application are also well suited to other formations of fine pitch probe arrays, e.g., microelectromechanical systems (MEMS). 
         [0023]    The disclosures of U.S. Pat. No. 7,271,022, entitled “Process for Forming Microstructures,” to Tang et al. incorporated herein in its entirety by reference, discloses forming microstructures on a substrate, e.g., via microelectromechanical systems (MEMS), that are compatible and complementary with the disclosures of the present application. For example, an exemplary MEMS process may comprise a repetitive process of plating a substrate, e.g., with a layer of copper (Cu) and, using photolithographic processes, etching a pattern in the copper and filling with patterned metal, e.g., a nickel-manganese (NiMn) alloy. In this manner a complex shape comprising a probe of nickel-manganese may be constructed. 
         [0024]    The through-via probe carrier  130  is mounted to a fine pitch space transformer  120  by any suitable process utilizing any suitable materials, e.g., solder ball attachment. Fine pitch space transformer  120  changes, or transforms, the pitch of the fine pitch probes, e.g., a pitch of about 50 μm or less, to a larger pitch, e.g., in a range of about 50 μm to about 200 μm or larger. 
         [0025]    The fine pitch space transformer  120  is mounted to a space transformer  110  by any suitable process utilizing any suitable materials, e.g., solder ball attachment. Space transformer  110  may comprise a low temperature co-fired ceramic (LTCC) or organic laminate, for example. Space transformer  110  changes, or transforms, the pitch of the fine pitch space transformer  120 , e.g., from less (or equal) to about 50 μm to about 200 μm, to a larger pitch, e.g., about 400 μm or larger, suitable for a higher level electronic assembly. 
         [0026]    The stack of space transformer  110 , fine pitch space transformer  120  and the fine pitch probe array comprising through-via probe carrier  130  and fine pitch probes  135 , are mounted on a higher level electronic assembly  101  by any suitable process comprising any suitable materials, e.g., solder balls. Higher level electronic assembly  101  may comprise, for example, a printed circuit board (PCB) and/or a high density interconnect (HDI) PCB 
         [0027]    Under the conventional art, when a probe is damaged or otherwise in need of replacement, a probe array and a space transformer generally must be replaced. In contrast, in accordance with embodiments of the present invention, only the probe array, comprising through-via probe carrier  130  and fine pitch probes  135 , may be replaced. This beneficially reduces the rework required, resulting in advantageously reduced down time and decreased costs. 
         [0028]      FIGS. 2 through 8  illustrate a method  200  of forming an electronic probe assembly, e.g., electronic probe assembly  100 , in accordance with embodiments of the present invention. In  FIG. 2 , a plurality of fine pitch probes  235  are formed by microelectromechanical systems (MEMS) methods on a primary sacrificial substrate  230 , e.g., a ceramic substrate. The fine pitch probes  235  are formed within a primary sacrificial material  240 , e.g., copper (Cu). The fine pitch probes  235  are formed such that the probe tips, e.g., a portion of the probe designed to contact a test point of an integrated circuit, are formed away from the primary sacrificial substrate  230 . 
         [0029]    In general, the materials comprising primary sacrificial material  240 , as used in the formation of the fine pitch probes  235 , are not compatible with subsequent process operations. Accordingly,  FIG. 3  illustrates release of the primary sacrificial material  240 , in accordance with embodiments of the present invention. If the primary sacrificial material  240  is compatible with subsequent operations, the processes of  FIGS. 3 and 4  (below) may not be necessary. 
         [0030]      FIG. 4  illustrates encapsulating the fine pitch probes  235  with a secondary sacrificial material  440 , in accordance with embodiments of the present invention.  FIG. 5  illustrates bonding of the fine pitch probes  235  within secondary sacrificial material  440  to a space transformer  520 , in accordance with embodiments of the present invention. 
         [0031]      FIG. 6  illustrates removal of secondary sacrificial material  440 , leaving a probe array comprising fine pitch probes  235  mounted to space transformer  520 , in accordance with embodiments of the present invention. 
         [0032]    In an alternative embodiment, the fine pitch probes  235  within secondary sacrificial material  440  may be bonded to a through via probe carrier, e.g., through-via probe carrier  130 , as illustrated in  FIG. 1 .  FIG. 7  illustrates the fine pitch probes  235  within secondary sacrificial material  440  bonded to a through via probe carrier  130 , in accordance with embodiments of the present invention.  FIG. 8  illustrates removal of secondary sacrificial material  440 , leaving a probe array comprising fine pitch probes  235  and through-via probe carrier  130 , in accordance with embodiments of the present invention. The probe array may be coupled to other assemblies, e.g., as illustrated in  FIG. 1 . 
         [0033]      FIGS. 9 through 10  illustrate a method  900  for forming an electronic probe assembly, e.g., electronic probe assembly  100  ( FIG. 1 ), in accordance with embodiments of the present invention.  FIG. 9  illustrates fine pitch MEMS probes  935  in a primary sacrificial material  940  fabricated on top of a through via probe carrier substrate  930  attached to a support substrate  910  using a temporary adhesive, in accordance with embodiments of the present invention. The support substrate  910  provides the mechanical strength to run it through a microelectromechanical systems (MEMS) fabrication process. 
         [0034]    After the completion of microelectromechanical systems (MEMS) fabrication process, the support substrate  910  is debonded and the primary sacrificial material  940  is released, in accordance with embodiments of the present invention, and as illustrated in  FIG. 10 . The probe array, comprising fine pitch probes  935  and through-via probe carrier  930  may be coupled to other assemblies, e.g., as illustrated in  FIG. 1 . 
         [0035]    Method  1100 , illustrated in  FIGS. 11 through 13 , comprises attaching a secondary sacrificial substrate on top of fine pitch probes while covered in primary sacrificial material. The secondary sacrificial substrate serves as a handle to hold the fine pitch probes. The primary sacrificial substrate is released where by the probe feet are freed for attachment to a space transformer either directly or using a through-via probe carrier substrate in between. The secondary sacrificial substrate and primary sacrificial material are subsequently released. 
         [0036]    In accordance with embodiments of the present invention,  FIG. 11  illustrates fine pitch probes  1135 , formed within primary sacrificial material  1140 , attached to a primary sacrificial substrate  1120 , and bonded to a secondary sacrificial substrate  1150  on the top, or “probe tip” end of the fine pitch probes  1135 . 
         [0037]    In  FIG. 12 , the primary sacrificial substrate  1120  is released, and the remaining assembly, comprising fine pitch probes  1135  and secondary sacrificial substrate  1150 , is aligned and bonded to a through via probe carrier  1130  using any suitable materials and processes, e.g., soldering, in accordance with embodiments of the present invention. 
         [0038]      FIG. 13  illustrates the release of secondary sacrificial substrate  1150  and removal of the primary sacrificial material  1140 , in accordance with embodiments of the present invention. The probe array, comprising fine pitch probes  1135  and through-via probe carrier  1130 , may be coupled to other assemblies, e.g., as illustrated in  FIG. 1 . 
         [0039]      FIGS. 14 through 18  illustrate a method  1400  for forming an electronic probe assembly, e.g., electronic probe assembly  100  ( FIG. 1 ), in accordance with embodiments of the present invention. In  FIG. 14 , a plurality of fine pitch probes  1435  are formed in a primary sacrificial material  1440  on a primary sacrificial substrate  1420 , in accordance with embodiments of the present invention. It is to be appreciated that the fine pitch probes  1435  are formed “upside down” relative to previous Figures, for example, fine pitch probes  235  of  FIG. 2 . For example, the tips of fine pitch probes  1435 , e.g., the portion of the probe designed to contact a test point of an integrated circuit, are formed next to the primary sacrificial substrate  1420 . 
         [0040]      FIG. 15  illustrates mounting the assembly comprising fine pitch probes  1435 , primary sacrificial material  1440  and primary sacrificial substrate  1420  onto a through-via probe carrier  1430 , in accordance with embodiments of the present invention. It is to be appreciated that the base of the fine pitch probes  1435  are attached to the through-via probe carrier  1430 . 
         [0041]      FIG. 16  illustrates removal of the primary sacrificial substrate  1420 , in accordance with embodiments of the present invention. The primary sacrificial material  1440  may be removed by any suitable process, including chemical etching, for example. Primary sacrificial material  1440  may be removed proximate to the removal of sacrificial substrate  1420 . However, in accordance with embodiments of the present invention, it may be beneficial to remove primary sacrificial substrate  1420  after additional processing, e.g., after attachment to a higher level assembly. The probe array, comprising fine pitch probes  1440  and through-via probe carrier  1430 , may be coupled to other assemblies, e.g., as illustrated in  FIG. 1 . 
         [0042]    In an alternative embodiment, the fine pitch probes  1435 , primary sacrificial material  1440  and primary sacrificial substrate  1420  may be mounted onto a space transformer  1450 , in accordance with embodiments of the present invention.  FIG. 17 , proceeding from  FIG. 14 , illustrates mounting the assembly comprising fine pitch probes  1435 , primary sacrificial material  1440  and primary sacrificial substrate  1420  onto a space transformer  1450 , in accordance with embodiments of the present invention. It is to be appreciated that the bases of the fine pitch probes  1435  are attached to the space transformer  1450 . 
         [0043]      FIG. 18  illustrates removal of the primary sacrificial substrate  1420 , in accordance with embodiments of the present invention. The primary sacrificial material  1440  may be removed by any suitable process, including chemical etching, for example. Primary sacrificial material  1440  may be removed proximate to the removal of sacrificial substrate  1420 . However, in accordance with embodiments of the present invention, it may be beneficial to remove primary sacrificial substrate  1420  after additional processing, e.g., after attachment to a higher level assembly. The probe array, comprising fine pitch probes  1440  and space transformer  1450 , may be coupled to other assemblies, e.g., as illustrated in  FIG. 1 . 
         [0044]    Embodiments in accordance with the present invention provide systems and methods for transferring electronic probe assemblies to space transformers. In addition, embodiments in accordance with the present invention provide systems and methods for transferring electronic probe assemblies to space transformers that eliminate manual assembly and reduce lead times. Further, embodiments in accordance with the present invention provide systems and methods for transferring electronic probe assemblies to space transformers that are compatible and complementary with existing systems and methods of integrated circuit design, manufacturing and test. 
         [0045]    Various embodiments of the invention are thus described. While the present invention has been described in particular embodiments, it should be appreciated that the invention should not be construed as limited by such embodiments, but rather construed according to the below claims.