US20010007427A1 - Method and apparatus for capacitively testing a semiconductor die - Google Patents
Method and apparatus for capacitively testing a semiconductor die Download PDFInfo
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- US20010007427A1 US20010007427A1 US09/797,795 US79779501A US2001007427A1 US 20010007427 A1 US20010007427 A1 US 20010007427A1 US 79779501 A US79779501 A US 79779501A US 2001007427 A1 US2001007427 A1 US 2001007427A1
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- G—PHYSICS
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/302—Contactless testing
- G01R31/312—Contactless testing by capacitive methods
Definitions
- the present invention is directed toward a method and apparatus for capacitively applying a test signal to a semiconductor die.
- Semiconductor dies form the core of semiconductor modules and other devices which are used extensively throughout the computer industry, telecommunication industry, and myriad related industries.
- the dies are typically tested during the manufacturing process to ensure that the dies conform to operational specifications.
- the resulting dies are then installed in the semiconductor module or device.
- test leads are typically tested by placing conductive test leads in contact with respective bond pads of the die, applying a test signal to the bond pads via the test leads, and determining whether the die responds with the proper output signals.
- the test leads may be placed in physical contact with the bond pads of the die using a variety of methods.
- One method is to solder the leads to the bond pads.
- Another method is to couple the leads to terminals and then force the terminals into engagement with the bond pad, deforming both the terminals and the bond pad.
- One drawback of the foregoing methods is that they include at least temporarily connecting the leads or terminals to the bond pads prior to testing and then disconnecting the leads or terminals subsequent to testing. Connecting and disconnecting the leads is time consuming and may damage the bond pads, making it difficult to permanently install the die in a semiconductor module when testing has been completed.
- test leads which are capacitively coupled to corresponding bond pads of the die.
- the capacitive coupling is formed by a dielectric layer positioned between an electrically conductive portion of the test pad and the corresponding conductive portion of the bond pad. No direct physical contact is required between the conductive portions of the test pads and the corresponding bond pads. As a result, the likelihood that the bond pads will become damaged by the test pads is reduced.
- This method may also be less expensive than conductive testing methods because capacitively coupling and decoupling the bond pads and test pads may require less time and effort than conductively connecting and disconnecting the bond pads and test leads.
- Another drawback with a conventional method and device used to capacitively test semiconductor dies is that the device has a thermal expansion coefficient which is different than the thermal expansion coefficient of the die material. As a result, when the die is tested at high temperatures, the die and the test device expand at different rates and capacitive coupling may not be maintained between the die and the test apparatus.
- the present invention is a method and apparatus for capacitively testing a semiconductor die or wafer having first and second die terminals.
- the apparatus comprises a substrate positionable proximate the die and having a coefficient of thermal expansion approximately equal to a thermal expansion coefficient of the die.
- the apparatus further comprises first and second test terminals positioned on a surface of the substrate.
- the first test terminal has a conductive portion aligned with and spaced apart from a conductive portion of the first die terminal.
- the first test terminal may accordingly be capacitively coupled to the first test terminal when the substrate is positioned proximate to the die.
- the second test terminal is aligned with the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal.
- the apparatus further comprises a dielectric material positioned intermediate the conductive portion of the first test terminal and the conductive portion of the first die terminal.
- the dielectric material is attached to the conductive portion of the first test terminal in one embodiment and is attached to the first die terminal in another embodiment.
- the die is one of a plurality of dies comprising a silicon wafer and the substrate is sized and shaped to be positioned adjacent the silicon wafer.
- the invention is also directed toward a method for manufacturing an apparatus for capacitively testing a semiconductor die having first and second die terminals, each connector having a conductive surface.
- the method comprises forming a first test terminal on a substrate such that the first test terminal has a conductive surface aligned with and spaced apart from the conductive surface of the first die terminal.
- the method further comprises forming a second test terminal on the substrate having a conductive portion aligned with the second die terminal while the first test terminal is aligned with the first die terminal.
- the method further comprises positioning a dielectric material intermediate at least the conductive portion of the first test terminal and the conductive surface of the first die terminal when the first test terminal is aligned with the first die terminal.
- a method for manufacturing an apparatus in accordance with the invention further comprises applying a layer of photoresist material to a surface of the substrate, exposing a first region of the photoresist material to a selected radiation to form an exposed region of photoresist material, and shielding a second region of the photoresist material from exposure to the selected radiation to form a shielded region of photoresist material.
- the method further comprises removing one of the exposed and shielded regions, and removing substrate material previously covered by the other of the exposed and shielded regions to form a projection which is aligned with the first die terminal when the substrate is positioned proximate the die.
- the first test terminal is formed by applying an insulating layer to a surface of the substrate and forming a first portion of conductive material on the insulating layer, the first portion of conductive material being aligned with the first die terminal when the substrate is positioned proximate to the die.
- the method further comprises forming a second portion of conductive material on the insulating layer aligned with the second die terminal when the first portion of conductive material is aligned with the first die terminal.
- FIG. 1 is a cross-sectional side view of a test apparatus and die in accordance with a first embodiment of the invention.
- FIG. 2 is an exploded isometric view of a die and a substrate of a test apparatus in accordance with the first embodiment of the invention.
- FIG. 3 is an exploded, enlarged cross-sectional view of a portion of the substrate and die shown in FIG. 2.
- FIGS. 4 A- 4 G are schematic cross-sectional views illustrating a method of forming a test apparatus in accordance with an embodiment of the invention.
- FIG. 5 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a second embodiment of the invention and a die having a dielectric layer overlaying the bond pads thereof.
- FIG. 6 is an exploded isometric view of a substrate of a test apparatus in accordance with a third embodiment of the invention and a semiconductor wafer.
- FIG. 7 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a fourth embodiment of the invention and a flip chip.
- FIG. 8 is a top plan view of a portion of a test apparatus and die in accordance with a fifth embodiment of the invention.
- FIG. 9 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a sixth embodiment of the invention and a flip chip.
- FIG. 10A is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a seventh embodiment of the invention having compressible test terminals in a noncompressed state.
- FIG. 10B is an exploded cross-sectional view of the portion of the test apparatus shown in FIG. 10A having compressible test terminals in a compressed state.
- the present invention is directed toward a method and apparatus for capacitively coupling bond pads or terminals of a semiconductor die directly to the corresponding test terminals of a test apparatus.
- An aspect of one embodiment of the invention is that the test terminals of the apparatus are aligned with the corresponding die terminals of the die. Accordingly, the die need not be modified in any way to align the terminals thereof with the test terminals of the test apparatus.
- a substrate of the apparatus may comprise material having the same coefficient of thermal expansion as that of the die. Accordingly, when the die is tested with the test apparatus at elevated temperatures, the die terminals remain aligned with the test terminals.
- FIGS. 1 - 10 B illustrate various embodiments of the apparatus and methods in accordance with the invention, and like reference numbers refer to like parts throughout the various figures.
- FIG. 1 is a cross-sectional view of a test apparatus 10 in accordance with an embodiment of the present invention engaging a bare semiconductor die 40 .
- the test apparatus 10 comprises a substrate 20 having test terminals 60 projecting upwardly therefrom.
- the test terminals 60 are coupled to die terminals 70 of the die 40 to transmit test signals to the die and receive response signals from the die.
- the response signals are compared with desired response signals to determine whether or not the die conforms with operational specifications.
- the test apparatus 10 includes a bridge clamp 50 which urges the die 40 toward the substrate 20 .
- the bridge clamp 50 is removably attached to the substrate 20 by passing mounting tabs 55 of the bridge clamp through slots 21 of the substrate and engaging the mounting tabs with a lower surface 26 of the substrate.
- the bridge clamp 50 includes internal tabs 53 which engage a spring 51 .
- the spring 51 is bowed downwardly toward the substrate 20 and engages a pressure plate 54 which in turn engages the die 40 .
- the pressure plate uniformly distributes the force supplied by the spring 51 over the surface of the die 40 .
- the bridge clamp 50 When the bridge clamp 50 is attached to the substrate 20 , the spring 51 urges the pressure plate 54 and die 40 toward the substrate so that the bond pads 70 of the die firmly engage the test terminals 60 projecting upwardly from the substrate.
- the bridge clamp 50 further includes flanges 52 , preferably formed by bending edges of the bridge clamp downwardly. The flanges 52 substantially prevent the bridge clamp 50 from bowing upwardly under the force of the spring 51 .
- FIG. 2 is an exploded isometric view of the die 40 and the substrate 20 shown in FIG. 1.
- the die terminals 70 are positioned on a lower surface 46 of the die and may comprise bond pads as shown in FIG. 1, or other structures as discussed below with reference to FIG. 7.
- the die terminals 70 include constant signal die terminals 72 and variable signal die terminals 71 . Both the constant signal die terminals 72 and variable signal die terminals 71 comprise conductive materials.
- the terms constant signal die terminal and variable signal die terminal are used herein to distinguish die terminals which transmit or receive a constant signal, such as V cc terminals and certain enable terminals, among others, from die terminals which may transmit or receive a variable signal.
- the test terminals 60 of the substrate 20 comprise constant signal test terminals 62 and variable signal test terminals 61 .
- the constant signal test terminals 62 are aligned with constant signal die terminals 72 of the die 40 and the variable signal test terminals 61 are aligned with corresponding variable signal die terminals 71 .
- the constant signal test terminals 62 of the test apparatus 10 may be coupled to a source of constant power (not shown) and may engage the constant signal die terminals 72 to form a conductive electrical connection therebetween and transmit a constant signal to the constant signal die terminals.
- the variable signal test terminals 61 may be coupled to a source of variable power (not shown) and may be capacitively coupled to the variable signal die terminals 71 to transmit a variable signal to the variable signal die terminals.
- test terminals 60 are preferably positioned in a recessed well 27 of the substrate 20 to provide for proper alignment between the test terminals on the substrate and the die terminals 70 on the die 40 .
- the substrate 20 and/or the die 40 may further include visual alignment markings or indentations to further ensure proper alignment between the test terminals 60 and the die terminals 70 .
- FIG. 3 is an enlarged cross-sectional view of the substrate 20 and die 40 .
- the substrate 20 includes projections 30 which extend upwardly toward the die 40 and form the cores of the test terminals 60 .
- the projections 30 have a pyramidal shape in a preferred embodiment and may have other shapes in other embodiments.
- the projections 30 have a center-to-center spacing D which is approximately 0.005 inch to 0.006 inch, corresponding to the spacing between the die terminals 70 of the die 40 . In other embodiments, the spacing D may be less than or greater than 0.005 inch to align the projections 30 with bond pads 70 having a correspondingly smaller or larger spacing, respectively.
- the substrate 20 and the projections 30 comprise silicon and the substrate and projections are formed integrally, as will be discussed in greater detail below with respect to FIGS. 4 A- 4 G.
- Silicon is a preferred material for the substrate 20 because it has the same coefficient of thermal expansion as the silicon comprising the die 40 . Accordingly, when the die 40 is tested at varying temperatures, the die and the substrate 20 expand and contract at substantially identical rates so that the die terminals 70 of the die remain aligned with the test terminals 60 of the substrate.
- the substrate 20 may comprise other materials having coefficients of thermal expansion similar to or identical with the thermal expansion coefficient of silicon.
- Other materials include ceramics, such as Mullite, which is available from Coors Technical Ceramics Co., Oak Ridge, Tenn.
- the substrate 20 may have a thermal expansion coefficient different than that of the die 40 .
- An apparatus 10 in accordance with this embodiment may still be effective when used to test the die 40 at varying temperatures if the die is relatively small, and/or if the die terminals 70 are relatively large so that the test terminals 60 maintain alignment with the die terminals despite the fact that the die 40 and substrate 20 may expand and contract at different rates at the varying temperatures.
- the substrate 20 including the projections 30 , is covered with an insulating layer 22 comprising an electrically insulative material.
- Conductive layers 23 are selectively positioned over the insulating layer 22 to cover each projection 30 .
- the conductive layers 23 are separated from each other as shown in FIG. 3 so that electrical signals may be separately transmitted to or received from each test terminal 60 .
- Bond wires 25 are accordingly connected to each conductive layer 23 to transmit test signals to or from the corresponding test terminals 60 .
- the conductive layers 23 completely cover each projection 30 , including an upper surface 31 and side surfaces 32 thereof.
- the conductive layers 23 cover the upper surfaces 31 and only one side surface 32 of each projection 30 . Accordingly, electromagnetic coupling or “cross talk” between adjacent conductive layers 23 is reduced, reducing the likelihood that electrical signals transmitted to one test terminal 60 will affect signals transmitted to a neighboring test terminal.
- the variable signal test terminals 61 each include a dielectric layer 24 covering the conductive layers 23 which prevents direct contact between the conductive layer 23 and the corresponding variable signal die terminals 71 when the die 40 is engaged with the test apparatus 10 .
- the dielectric layer 24 may comprise any number of dielectric materials which include but are not limited to nitrides, barium strontium titanate, or oxides, such as tantalum pentoxide. The composition and thickness of the dielectric layer 24 is selected to provide a desired capacitance between the variable signal test terminals 61 and the variable signal die terminals 71 .
- the dielectric layer 24 defines a contact surface 65 at an upper end of the variable signal test terminal 61 which is sized to engage a contact surface 75 of the corresponding variable signal die terminal 71 .
- the contact surface 65 of each variable signal test terminal 61 is preferably sized to engage the contact surface 75 of the corresponding variable signal die terminal 71 without resting on the passivation layer, substantially eliminating any gap between the contact surfaces 65 and 75 . Accordingly, the dielectric constant between each variable signal test terminal 61 and corresponding variable signal die terminal 71 is determined by the composition and thickness of the dielectric layer 24 and not by a gap which might otherwise be formed between the variable signal test terminal and the variable signal die terminal.
- the contact surface 65 is elevated above the substrate 20 by a distance that is greater than the thickness of the passivation layer 44 to ensure that the contact surface 65 of the test terminal engages the contact surface 75 of the variable signal die terminal 71 .
- the contact surface 65 is elevated a sufficient distance above the substrate 20 that small particles 90 , which may comprise dust or other contaminates and which may be present between the test terminals 60 , do not engage and potentially damage the die 40 .
- each constant signal test terminal 62 includes an insulating layer 22 and conductive layer 23 but does not include a dielectric layer. Accordingly, the conductive layers 23 of the constant signal test terminals 62 firmly engage with the corresponding constant signal die terminals 72 to provide electrical connections therebetween. To further ensure proper engagement between the constant signal test terminals 62 and the constant signal die terminals 72 , the constant signal test terminals are provided with serrations 63 positioned to engage the constant signal die terminals. The serrations 63 releasably penetrate the contact surface 75 of the constant signal die terminals 72 and are separated by stop surfaces 64 to prevent the serrations from penetrating too deeply into the constant signal die terminals.
- the stop surfaces 64 are positioned such that the serrations 63 penetrate one-half the thickness of the constant signal die terminals 72 .
- the stop surfaces 64 are aligned with the contact surfaces 65 of the variable signal test terminals 61 . Accordingly, when the stop surfaces 64 prevent further penetration by the serrations 63 into the constant signal die terminals 72 , the contact surfaces 65 of the variable signal test terminals 61 engage the contact surfaces 75 of the corresponding variable signal die terminals 71 . By aligning the contact surfaces 65 with the stop surfaces 64 , the die 40 will rest solidly on the test terminals 60 to more reliably transmit electrical signals between the die and the test apparatus 10 .
- the test apparatus 10 is used to test the die 40 by placing the die in the recessed well 27 of the substrate 20 as shown in FIG. 2.
- the user then aligns the variable signal test terminals 61 of the test apparatus 10 with the corresponding variable signal die terminals 71 of the die 40 , and aligns the constant signal test terminals 62 with the corresponding constant signal die terminals 72 as shown in FIGS. 2 and 3.
- the die 40 is firmly engaged with the test apparatus 10 by first placing the pressure plate 54 on the die and then clamping the pressure plate and the die against the substrate 20 by inserting the mounting tabs 55 of the bridge clamp 50 through the slots 21 of the substrate, as shown in FIG. 1.
- Constant signals are then applied to the bond lines 25 connected to the constant signal test terminals 62 and variable signals are applied to the bond lines connected to the variable signal test terminals 61 .
- a varying signal is applied to the variable signal test terminals 61 , the signal is capacitively coupled to the corresponding variable signal die terminal 71 .
- the varying current may take the form of a single pulse, an alternating current signal, or any other variable current signal.
- the response signals received from the die 40 may then be used to determine whether or not the die complies with operational specifications and accordingly qualifies as a good die. It will be understood that any one variable signal test terminal 61 may transmit or receive test signals, depending on the characteristics of the particular die terminal 71 with which it is engaged, and upon the particular phase of the test process.
- test apparatus 10 may be used to test the die 40 by capacitively coupling test terminals 61 of the apparatus to variable signal die terminals 71 of the die 40 , and by supplying a variable current signal to the capacitive bond pads to test the performance of the die.
- Conductive connections between the test apparatus 10 and die 40 are used only where the die requires a constant signal. Accordingly, the number of conductive connections between the test apparatus and die, which may physically damage the die terminals, is reduced.
- a further advantage of the test apparatus and method shown in FIGS. 1 - 3 is that the variable signal test terminals 61 of the test apparatus 10 are aligned with the corresponding variable signal die terminals of 71 of the bare die 40 when the die is engaged with the test apparatus. The alignment is maintained even where the center-to-center spacing between the die terminals is on the order of 0.005 inch to 0.006 inch, or less. Accordingly, a user need not manipulate the die 40 in any way to align the variable signal die terminals 71 of the die with the variable signal test terminals 61 of the test apparatus 10 .
- the user need not add to the die 40 a layer which includes intermediate terminals which are electrically connected to the die terminals 70 , but spaced to correspond to the locations of the variable signal test pads of a test device. As a result, testing of the bare die 40 is considerably simplified.
- the substrate 20 shown in FIGS. 1 - 3 may comprise a material having a coefficient of thermal expansion similar to or identical with the thermal expansion coefficient of the die 40 . Accordingly, the test apparatus 10 may be used to test the die 40 at varying temperatures while maintaining alignment between the die terminals 70 of the die 40 and the test terminals 60 of the test apparatus.
- Still a further advantage of an embodiment of a test apparatus 10 is that the nature of the capacitive coupling between the test apparatus 10 and the die 40 may be controlled by controlling the thickness and/or composition of the dielectric layer 24 . The user accordingly has greater control over the capacitance between the test apparatus 10 and the die 40 by manipulating two variables. Furthermore, unlike conventional methods, controlling the dielectric constant between the die 40 and the test apparatus 10 requires only manipulating the test apparatus and not the die itself. Unlike conventional methods, which may require that a dielectric liquid or gel be placed on the variable signal die terminals, the test apparatus 10 requires no contamination of the variable signal die terminals, which may be difficult to remove after testing has been completed.
- FIGS. 4 A- 4 G A method for fabricating an apparatus 10 having variable signal test terminals 61 in accordance with an embodiment of the invention is shown in FIGS. 4 A- 4 G.
- the method includes providing a substrate 20 having a substantially flat upper surface 28 .
- the substrate 20 may comprise silicon, and may comprise other materials in other embodiments, as discussed below.
- the upper surface 28 of the substrate 20 is coated with a layer of positive or negative photoresist material 82 .
- a mask 80 is then placed upon the photoresist material 82 .
- the mask 80 may preferably be an exact or nearly exact mirror image of a mask used to form the die terminals 70 on the die 40 . Accordingly, the test terminals 60 formed by the mask 80 will have locations corresponding exactly or nearly exactly with the locations of the die terminals 70 when the die 40 is placed face down on the substrate 20 .
- the mask 80 has apertures 81 which correspond to the locations of the die terminals 70 of the die 40 .
- the apertures 81 correspond to the regions between the die terminals 70 .
- the photoresist material 82 is shown as being positive in FIGS. 4 A- 4 G.
- the substrate 20 with photoresist material 82 and mask 80 in place is exposed to a selected radiation 83 which hardens the photoresist material 82 a located beneath the apertures 81 while leaving the photoresist material 82 b beneath the mask 80 in a nonhardened state. It will be understood that where a negative photoresist material is used, the photo resist material 82 b is hardened while the photoresist material 82 a remains in a non-hardened state.
- the mask 80 is removed and the photoresist material 82 rinsed in a chemical bath, which washes away the unhardened photoresist material 82 b while leaving the hardened photoresist material 82 a in place, as shown in FIG. 4C.
- the substrate 20 with the hardened photoresist material 82 a in place, is then exposed to an etching solution which anisotropically etches away portions of the substrate not covered by the photoresist material 82 a and creates the projections 30 as shown in FIG. 4D.
- the hardened photoresist material 82 a is then removed.
- the substrate 20 may be exposed to an oxidizing agent which oxidizes the surface of the substrate not covered by the photoresist material 82 a. The oxidized portion may then be stripped leaving the projections 30 in place.
- the projections 30 may be formed by depositing material on the upper surface 28 of the substrate 20 .
- the photoresist layer 82 is eliminated and the mask 80 is placed directly on the substrate 20 .
- Material comprising the projections 30 is then deposited using an overhead ion deposition apparatus or similar device to build the projections up from the upper surface 28 of the substrate 20 .
- Such an alternate method may be used where the substrate 20 comprises a ceramic or other material which may not be as conducive as silicon to etching.
- the resulting projections 30 may be planarized using chemical-mechanical planarization to flatten the upper surfaces 31 of the projections 30 .
- the flattened upper surfaces 31 accordingly provide the foundation for test terminals 61 having flat contact surfaces 65 which mate well with the corresponding flat contact surfaces 75 of the variable signal die terminals 71 (FIGS. 3).
- Ridges 33 may be formed on the projects 30 which will form constant signal test terminals 62 .
- the ridges may be formed using photoresist and etching techniques similar to those discussed above and described in greater detail in U.S. Pat. No. 5,483,741 to Akram et al. and U.S. Pat. No. 5,326,428 to Farnworth et al., both of which are incorporated herein by reference.
- the insulating layer 22 is formed on the projections 30 , as shown in FIG. 4E.
- the substrate 20 comprises silicon
- the substrate is exposed to an oxidizing atmosphere to form a layer of silicon dioxide (SiO) 2 , an electrically insulative compound.
- SiO 2 or Si 3 N 4 may be deposited on the surface of the substrate 20 by chemical vapor deposition.
- tetraethylorthosilane (TEOS) is injected at high temperature into a chamber surrounding the substrate 20 to grow an insulating layer 22 of SiO 2 on the substrate 20 .
- the insulating layer 22 is deposited on the substrate 20 by chemical vapor deposition or similar deposition techniques. Such an alternate embodiment may be used where the substrate 20 comprises a ceramic material which does not oxidize as readily as does silicon.
- the conductive layers 23 comprising a conductive material are formed atop the insulating layer 22 , as shown in FIG. 4F.
- an initially continuous conductive layer 23 may be deposited on the insulating layer 22 using chemical vapor deposition.
- a photoresist and masking process similar to that discussed above with reference to FIGS. 4 A- 4 D, may then be used to etch away portions of the conductive layer 23 located between the projections 30 to form individual conductive paths to each projection.
- the conductive layers 23 may be etched to cover the entirety of each projection 30 , or may be etched to cover the upper surface 31 of each projection and enough of a side surface 32 to form a conductive path to the projection.
- the conductive layer 23 and insulating layer 22 conform to the ridges 33 of the constant signal test terminal 62 , forming the serrations 63 .
- the serrations 63 may be further roughened by using an electroplating process and controlling the composition of the electrolyte solution used in the process to form a textured or roughened surface which amplifies the serrated surface created by the etching process.
- the formation of roughened electroplated surfaces is further discussed in U.S. Pat. No. 5,487,999 to Farnworth, incorporated herein by reference.
- the dielectric layers 24 are formed on the conductive layers 23 of the variable signal test terminals 61 , as shown in FIG. 4G.
- an initially continuous dielectric layer 24 is deposited on the conductive layer 23 by chemical vapor deposition.
- the initially continuous dielectric layer 24 may be deposited using an electrophoretic process to form an even layer of dielectric over the projections 30 .
- An electrophoretic process is described in U.S. Pat. No. 5,607,818 to Akram et al., which is incorporated herein by reference.
- the electrophoretic process includes charging the conductive layer 23 , either positively or negatively, and imparting the opposite charge to the dielectric material. The dielectric material is accordingly attracted to the conductive layer 23 and gradually builds up the dielectric layer 24 thereon.
- An advantage of the electrophoretic process is that it results in an even coating of dielectric material over the conductive layer 23 notwithstanding the non-uniform topography created by the projections 30 .
- Another advantage is that the electrophoretic process is self-limiting because as the conductive layer 23 becomes coated with dielectric material, it tends to have less affinity for additional dielectric material. Accordingly, the amount of dielectric material electrophoretically deposited on the conductive layer 23 may be controlled by controlling the charge applied to the conductive layer. Furthermore, the dielectric layer tends to be thicker at higher temperatures than at lower temperatures. Accordingly, the temperature at which the electrophoretic process is carried out may be used to further control the dielectric characteristics of the dielectric layer 24 .
- portions of the dielectric layer may then be etched away using a photoresist and masking process similar to the process discussed above with reference to FIG. 4A- 4 D.
- Dielectric material located between the projections 30 may be removed as shown in FIG. 4G to isolate the variable signal test terminals 61 from each other.
- any dielectric material covering the constant signal test terminals 62 may be removed to ensure proper electrical contact between the constant signal test terminals and the corresponding constant signal die terminals 72 .
- An advantage of the process discussed above with reference to FIGS. 4 A- 4 G is that the process uses a mask layer 80 which is a mirror image of the mask layer used to create the die terminals 70 on the bare die 40 . Accordingly, the projections 30 which form the test terminals 60 of the test apparatus 10 may be precisely aligned with the corresponding die terminals 70 of the bare die 40 . As a result, the need to form an interlayer between the die 40 and the test apparatus 10 is eliminated, as discussed above with reference to FIGS. 1 - 3 .
- a further advantage of the process shown in FIGS. 4 A- 4 G is that the dielectric layer 24 is formed on the test apparatus 10 , eliminating the need to removably apply liquid or gel dielectric substances to the die 40 , as was also discussed above with reference to FIGS. 1 - 3 .
- FIG. 5 is an exploded, cross-sectional view of a test apparatus 10 in accordance with a second embodiment of the invention, and a die 40 having dielectric layers 24 a attached to the variable signal die terminals 71 thereof.
- the dielectric layers 24 a may comprise oxide coatings which form naturally on the metallic die terminals 70 .
- the dielectric layers 24 a may comprise other organic dielectric materials which may be deliberately formed on the variable signal die terminals 71 .
- the dielectric layers 24 are eliminated from the variable signal test terminals 61 of the test apparatus 10 because their function is performed by the dielectric layers 24 a on the variable signal die terminals 71 . Accordingly, the contact surfaces 65 a of the variable signal test terminals 61 comprise a portion of the conductive layer 23 as shown in FIG. 5, rather than a portion of the dielectric layer 24 as shown in FIG. 3.
- the serrations 63 of the constant signal test terminals are capable of penetrating the dielectric layer 24 a formed on the constant signal die terminal 72 .
- the serrations accordingly form a conductive connection with the constant signal die terminal 72 notwithstanding the presence of the dielectric material.
- the dielectric layers 24 a may be prevented from forming on the constant signal die terminals 72 so that the constant signal test terminals 62 form solid conductive contacts with the constant signal die terminals.
- the dielectric layers 24 a may be removed from the constant signal die terminals 72 by using masking and etching process, as discussed previously with reference to FIGS. 4 A- 4 D.
- An advantage of an embodiment of the test apparatus shown in FIG. 5 is that the test apparatus requires no dielectric layer 24 . Accordingly, at least one process step required to form the test apparatus 10 may be eliminated. Conversely, an advantage of an embodiment of the test apparatus shown in FIGS. 1 - 3 is that the die 40 need not be manipulated to either form or remove the dielectric layer.
- the dielectric oxide layers may form naturally on the dies 40 .
- the oxide layers may form after the dies have been electrically partitioned from each other on a silicon wafer but remain in a wafer form.
- a test apparatus 10 in accordance with a third embodiment of the invention is sized to accommodate and test an entire wafer 100 comprising a plurality of partitioned dies 40 , as shown in FIG. 6.
- the test apparatus 10 comprises a substrate 20 having slots 21 to accommodate a bridge clamp (not shown).
- the bridge clamp is used to releasably couple the wafer 100 to the substrate 20 , as discussed previously with reference to FIG. 1.
- the substrate 20 comprises test terminals 60 , which are aligned with corresponding die terminals 70 at the wafer 100 . Accordingly, variable signal test terminals 61 are aligned with variable signal die terminals 71 and constant signal test terminals 62 are aligned with constant signal die terminals 72 , as discussed previously with reference to FIGS. 1 - 3 .
- test apparatus 10 shown in FIG. 6 permits a user to engage the test apparatus with an entire wafer 100 of dies 40 in one operation. Accordingly, the user need not individually engage each die 40 with the test apparatus 10 before testing and then remove each die after testing.
- the test apparatus 10 shown in FIG. 6 may use the oxide layer naturally forming on the dies 40 of the wafer 100 to act as dielectric layers between the die terminals 70 of the dies and the test terminals 60 of the test apparatus, reducing the number of processing steps required to produce the test apparatus 10 , as discussed above with reference to FIG. 5.
- FIG. 7 is an exploded, cross-sectional view of a test apparatus 10 in accordance with a fourth embodiment of the invention positioned adjacent a flip chip 40 a in FIG. 7.
- the die terminals 70 a of the flip chip 40 a include variable signal die terminals 71 a and constant signal die terminals 72 a.
- the die terminals 72 a may comprise solder balls formed from lead or a similar soft, conductive material.
- Each die terminal 70 a has an end surface 76 spaced apart from the lower surface 46 of the flip chip 40 a and side surfaces 77 intermediate the end surface and the lower surface of the flip chip.
- the die terminals 70 a may have an oxide coating 78 which covers the bond pads and deforms when the flip chip 40 a is engaged with the substrate 20 .
- the oxide coating 78 generally deforms sufficiently to create a conductive electrical connection between the die terminals 70 a and the test terminals 60 against which they press. Accordingly, the oxide coating 78 is not relied upon to form a dielectric layer between the variable signal die terminals 71 a and the variable signal test terminals 61 as was discussed above with reference to FIG. 5. Instead, the dielectric layer 24 , positioned on the variable signal test terminals 61 , provides the capacitive coupling between the test apparatus 10 and the flip chip 40 a, substantially as discussed above with reference to FIGS. 1 - 3 .
- the oxide layer 78 deforms when the flip chip 40 a is pressed into engagement with the substrate 20 , the contact between the constant signal test terminal 62 and the constant signal die terminal 72 a is sufficient to create a constant signal connection therebetween, as discussed above. The need for serrations on the conductive test terminal 62 is accordingly eliminated.
- FIG. 8 is a top plan view of a portion of a test apparatus 10 in accordance with a fifth embodiment of the invention shown engaging a portion of a flip chip 40 a.
- the test apparatus 10 shown in FIG. 8 is similar to the apparatus shown in FIG. 7 except that the contact surfaces 65 b of the test terminals 60 are positioned parallel to the side surfaces 32 rather than the upper surfaces 31 of the projections 30 (FIG. 7). Accordingly, the side surfaces 77 of the die terminals 70 slide along the contact surfaces 65 b of the test terminals 60 as the flip chip 40 a is pressed into engagement with the substrate 20 .
- pairs of test terminals 60 having diagonally opposed contact surfaces 65 b may be oriented in an alternating pattern to substantially prevent lateral motion of the flip chip 40 a relative to the substrate 20 once the die terminals 70 a have been engaged with the test terminals 60 .
- the test terminals 60 accordingly aid the user in orienting the flip chip 40 a relative to the substrate 20 and maintain the orientation until the die is deliberately disengaged from the test apparatus 10 .
- FIG. 9 is an exploded, cross-sectional view of a portion of a test apparatus 10 in accordance with a sixth embodiment of the invention.
- the test apparatus 10 comprises a substrate 20 without large projections 30 . Instead, the insulating layer 22 , conductive layers 23 , and dielectric layers 24 are consecutively formed directly on the upper surface 28 of the substrate to form variable signal test terminals 61 a and constant signal test terminals 62 a.
- the projections 30 are not necessary to provide an offset between the substrate 20 and the flip chip 40 a. Instead, the solder balls of the flip chip 40 a provide a sufficient offset between the substrate 20 and the flip chip 40 a to prevent dust particles or other contaminants 90 from becoming clamped therebetween.
- An advantage of an embodiment of the test apparatus 10 shown in FIG. 9 is that the process steps required to form raised projections may be eliminated, simplifying the manufacture of the test apparatus 10 .
- FIG. 10A is an exploded, cross-sectional view of a portion of a test apparatus 10 in accordance with a seventh embodiment of the invention having compressible test terminals 60 b.
- the substrate 20 includes an insulating layer 22 and conductive layers 23 formed directly thereon.
- the projections 30 a are formed atop the conductive layers 23 in a subsequent step.
- the projections 30 a comprise a conductive material which may be sputtered or spun on the conductive layers 23 or may be deposited on the conductive layers using chemical vapor deposition.
- the resulting continuous layer may then be etched using the photoresist and masking techniques discussed previously with reference to FIGS. 4 A- 4 G to form individual projections 30 a.
- the projection 30 a may be formed from an incompressible conduction material.
- the projections 30 a may be formed from a compressible, conductive material such as a z-axis elastomer.
- a compressible, conductive material such as a z-axis elastomer.
- elastomers are available from Zymet of East Hannover, N.J.
- the elastomer contains conductive particles 34 which are dispersed therethrough and are shown schematically in FIG. 10A. When the elastomer is compressed in a direction normal to the upper surface 28 of the substrate 20 , the particles 34 come into contact with each other and create a conductive path through the elastomer.
- Dielectric layers 24 are then applied atop the conductive layers 23 of the variable signal test terminals 61 b.
- the dielectric layers 24 preferably comprise a flexible material, such as a polyamide, which will flex as the projections 30 a compress.
- the polyamide may be applied using a spray process or an electrophoretic process, such as was discussed previously with reference to FIG. 4G.
- no dielectric layer is applied to the constant signal test terminals 62 b, so as to provide conductive connections between the constant signal test terminals and the constant signal die terminals 72 .
- the die 40 is compressed against the substrate 20 so as to compress the projections 30 a, creating conductive paths from the conductive layers 23 through the projections, as shown in FIGS. 10 b.
- the variable signal test terminals 61 form capacitive connections with the variable signal die terminals 71 and the constant signal test terminals form conductive connections with the constant signal die terminals 72 , as discussed previously with respect to FIGS. 1 - 3 .
- An advantage of the test apparatus 10 shown in FIGS. 10A and 10B is that the compressible test terminals 60 b flex in a vertical direction when the die 40 is engaged with the substrate 20 .
- the test terminals 60 b accordingly maintain an electrical coupling with the die terminals 70 of the die 40 even if the lower surface 26 of the die is not parallel with the upper surface 28 of the substrate.
- a further advantage is that the compressible constant signal test terminals 62 b are biased toward the corresponding constant signal die terminals 72 , increasing the likelihood of a good conductive connection therebetween and eliminating the need for serrations on the constant signal test terminals.
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Abstract
An apparatus, process for forming an apparatus, and method for testing a semiconductor die having first and second die terminals. The apparatus includes a substrate having a coefficient of thermal expansion approximately equal to a thermal expansion coefficient of the die. The substrate includes first and second test terminals positioned on a surface of the substrate and positionable proximate to the die. The first test terminal is a conductive portion aligned with and spaced apart from a conductive portion of the first die terminal when the substrate is positioned proximate to the die. The first test terminal is coupleable to a variable power source current to generate a variable signal at the first test terminal and capacitively generate a corresponding signal at the first die terminal. The second test terminal is aligned with the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal.
Description
- The present invention is directed toward a method and apparatus for capacitively applying a test signal to a semiconductor die.
- Semiconductor dies form the core of semiconductor modules and other devices which are used extensively throughout the computer industry, telecommunication industry, and myriad related industries. The dies are typically tested during the manufacturing process to ensure that the dies conform to operational specifications. The resulting dies are then installed in the semiconductor module or device.
- Semiconductor dies are typically tested by placing conductive test leads in contact with respective bond pads of the die, applying a test signal to the bond pads via the test leads, and determining whether the die responds with the proper output signals. To ensure proper transmission of the test signals to the die, the test leads may be placed in physical contact with the bond pads of the die using a variety of methods. One method is to solder the leads to the bond pads. Another method is to couple the leads to terminals and then force the terminals into engagement with the bond pad, deforming both the terminals and the bond pad. One drawback of the foregoing methods is that they include at least temporarily connecting the leads or terminals to the bond pads prior to testing and then disconnecting the leads or terminals subsequent to testing. Connecting and disconnecting the leads is time consuming and may damage the bond pads, making it difficult to permanently install the die in a semiconductor module when testing has been completed.
- One approach to solving the foregoing problem has been to replace the test leads with test pads, which are capacitively coupled to corresponding bond pads of the die. The capacitive coupling is formed by a dielectric layer positioned between an electrically conductive portion of the test pad and the corresponding conductive portion of the bond pad. No direct physical contact is required between the conductive portions of the test pads and the corresponding bond pads. As a result, the likelihood that the bond pads will become damaged by the test pads is reduced. This method may also be less expensive than conductive testing methods because capacitively coupling and decoupling the bond pads and test pads may require less time and effort than conductively connecting and disconnecting the bond pads and test leads.
- Conventional methods for capacitively testing a semiconductor die suffer from several drawbacks. The capacitive test pads of a device used to test the die may be large compared to bond pads and may not be aligned with the bond pads. As a result, an interlayer must be placed between the bond pads of the die and the capacitive test pads. Contacts on the surface of the interlayer are aligned with the capacitive test pads of the test device and are connected through the interlayer to the bond pads of the die. Forming the interlayer requires an additional manufacturing step and it may be necessary to remove the interlayer before the die may be permanently installed, requiring yet another manufacturing step.
- Another drawback with a conventional method and device used to capacitively test semiconductor dies is that the device has a thermal expansion coefficient which is different than the thermal expansion coefficient of the die material. As a result, when the die is tested at high temperatures, the die and the test device expand at different rates and capacitive coupling may not be maintained between the die and the test apparatus.
- Yet another draw back with conventional testing devices is that the capacitive test pads may be flush with the surface of the test device. When the test device is placed adjacent the die for testing, dust particles or other contaminants may become trapped between the test device and the die, damaging the die. Still another drawback of conventional testing methods is that they may require that a liquid or gel dielectric material be placed on the bond pads of the die prior to testing. The liquid or gel dielectric material may be difficult to remove after testing, contaminating the die and inhibiting good connections between the bond pads of the die and lead wires which are connected to the bond pads when the die is permanently installed.
- The present invention is a method and apparatus for capacitively testing a semiconductor die or wafer having first and second die terminals. In one embodiment, the apparatus comprises a substrate positionable proximate the die and having a coefficient of thermal expansion approximately equal to a thermal expansion coefficient of the die. The apparatus further comprises first and second test terminals positioned on a surface of the substrate. The first test terminal has a conductive portion aligned with and spaced apart from a conductive portion of the first die terminal. The first test terminal may accordingly be capacitively coupled to the first test terminal when the substrate is positioned proximate to the die. The second test terminal is aligned with the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal.
- In one embodiment of the invention, the apparatus further comprises a dielectric material positioned intermediate the conductive portion of the first test terminal and the conductive portion of the first die terminal. The dielectric material is attached to the conductive portion of the first test terminal in one embodiment and is attached to the first die terminal in another embodiment. In yet another embodiment, the die is one of a plurality of dies comprising a silicon wafer and the substrate is sized and shaped to be positioned adjacent the silicon wafer.
- The invention is also directed toward a method for manufacturing an apparatus for capacitively testing a semiconductor die having first and second die terminals, each connector having a conductive surface. The method comprises forming a first test terminal on a substrate such that the first test terminal has a conductive surface aligned with and spaced apart from the conductive surface of the first die terminal. The method further comprises forming a second test terminal on the substrate having a conductive portion aligned with the second die terminal while the first test terminal is aligned with the first die terminal. The method further comprises positioning a dielectric material intermediate at least the conductive portion of the first test terminal and the conductive surface of the first die terminal when the first test terminal is aligned with the first die terminal.
- In one embodiment, a method for manufacturing an apparatus in accordance with the invention further comprises applying a layer of photoresist material to a surface of the substrate, exposing a first region of the photoresist material to a selected radiation to form an exposed region of photoresist material, and shielding a second region of the photoresist material from exposure to the selected radiation to form a shielded region of photoresist material. The method further comprises removing one of the exposed and shielded regions, and removing substrate material previously covered by the other of the exposed and shielded regions to form a projection which is aligned with the first die terminal when the substrate is positioned proximate the die.
- In yet another embodiment of a method in accordance with the invention, the first test terminal is formed by applying an insulating layer to a surface of the substrate and forming a first portion of conductive material on the insulating layer, the first portion of conductive material being aligned with the first die terminal when the substrate is positioned proximate to the die. The method further comprises forming a second portion of conductive material on the insulating layer aligned with the second die terminal when the first portion of conductive material is aligned with the first die terminal.
- FIG. 1 is a cross-sectional side view of a test apparatus and die in accordance with a first embodiment of the invention.
- FIG. 2 is an exploded isometric view of a die and a substrate of a test apparatus in accordance with the first embodiment of the invention.
- FIG. 3 is an exploded, enlarged cross-sectional view of a portion of the substrate and die shown in FIG. 2.
- FIGS.4A-4G are schematic cross-sectional views illustrating a method of forming a test apparatus in accordance with an embodiment of the invention.
- FIG. 5 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a second embodiment of the invention and a die having a dielectric layer overlaying the bond pads thereof.
- FIG. 6 is an exploded isometric view of a substrate of a test apparatus in accordance with a third embodiment of the invention and a semiconductor wafer.
- FIG. 7 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a fourth embodiment of the invention and a flip chip.
- FIG. 8 is a top plan view of a portion of a test apparatus and die in accordance with a fifth embodiment of the invention.
- FIG. 9 is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a sixth embodiment of the invention and a flip chip.
- FIG. 10A is an exploded, cross-sectional view of a portion of a test apparatus in accordance with a seventh embodiment of the invention having compressible test terminals in a noncompressed state.
- FIG. 10B is an exploded cross-sectional view of the portion of the test apparatus shown in FIG. 10A having compressible test terminals in a compressed state.
- The present invention is directed toward a method and apparatus for capacitively coupling bond pads or terminals of a semiconductor die directly to the corresponding test terminals of a test apparatus. An aspect of one embodiment of the invention is that the test terminals of the apparatus are aligned with the corresponding die terminals of the die. Accordingly, the die need not be modified in any way to align the terminals thereof with the test terminals of the test apparatus. Another aspect of an embodiment of the invention is that a substrate of the apparatus may comprise material having the same coefficient of thermal expansion as that of the die. Accordingly, when the die is tested with the test apparatus at elevated temperatures, the die terminals remain aligned with the test terminals. FIGS.1-10B illustrate various embodiments of the apparatus and methods in accordance with the invention, and like reference numbers refer to like parts throughout the various figures.
- FIG. 1 is a cross-sectional view of a
test apparatus 10 in accordance with an embodiment of the present invention engaging a bare semiconductor die 40. Thetest apparatus 10 comprises asubstrate 20 havingtest terminals 60 projecting upwardly therefrom. Thetest terminals 60 are coupled to dieterminals 70 of the die 40 to transmit test signals to the die and receive response signals from the die. The response signals are compared with desired response signals to determine whether or not the die conforms with operational specifications. - The
test apparatus 10 includes abridge clamp 50 which urges the die 40 toward thesubstrate 20. Thebridge clamp 50 is removably attached to thesubstrate 20 by passing mountingtabs 55 of the bridge clamp throughslots 21 of the substrate and engaging the mounting tabs with alower surface 26 of the substrate. Thebridge clamp 50 includesinternal tabs 53 which engage aspring 51. Thespring 51 is bowed downwardly toward thesubstrate 20 and engages apressure plate 54 which in turn engages thedie 40. The pressure plate uniformly distributes the force supplied by thespring 51 over the surface of thedie 40. When thebridge clamp 50 is attached to thesubstrate 20, thespring 51 urges thepressure plate 54 and die 40 toward the substrate so that thebond pads 70 of the die firmly engage thetest terminals 60 projecting upwardly from the substrate. Thebridge clamp 50 further includesflanges 52, preferably formed by bending edges of the bridge clamp downwardly. Theflanges 52 substantially prevent thebridge clamp 50 from bowing upwardly under the force of thespring 51. - FIG. 2 is an exploded isometric view of the
die 40 and thesubstrate 20 shown in FIG. 1. Thedie terminals 70 are positioned on alower surface 46 of the die and may comprise bond pads as shown in FIG. 1, or other structures as discussed below with reference to FIG. 7. Thedie terminals 70 include constant signal dieterminals 72 and variable signal dieterminals 71. Both the constant signal dieterminals 72 and variable signal dieterminals 71 comprise conductive materials. The terms constant signal die terminal and variable signal die terminal are used herein to distinguish die terminals which transmit or receive a constant signal, such as Vcc terminals and certain enable terminals, among others, from die terminals which may transmit or receive a variable signal. - The
test terminals 60 of thesubstrate 20 comprise constantsignal test terminals 62 and variablesignal test terminals 61. The constantsignal test terminals 62 are aligned with constant signal dieterminals 72 of thedie 40 and the variablesignal test terminals 61 are aligned with corresponding variable signal dieterminals 71. Accordingly, the constantsignal test terminals 62 of thetest apparatus 10 may be coupled to a source of constant power (not shown) and may engage the constant signal dieterminals 72 to form a conductive electrical connection therebetween and transmit a constant signal to the constant signal die terminals. The variablesignal test terminals 61 may be coupled to a source of variable power (not shown) and may be capacitively coupled to the variable signal dieterminals 71 to transmit a variable signal to the variable signal die terminals. - The
test terminals 60 are preferably positioned in a recessed well 27 of thesubstrate 20 to provide for proper alignment between the test terminals on the substrate and thedie terminals 70 on thedie 40. Thesubstrate 20 and/or the die 40 may further include visual alignment markings or indentations to further ensure proper alignment between thetest terminals 60 and thedie terminals 70. - FIG. 3 is an enlarged cross-sectional view of the
substrate 20 and die 40. Thesubstrate 20 includesprojections 30 which extend upwardly toward thedie 40 and form the cores of thetest terminals 60. Theprojections 30 have a pyramidal shape in a preferred embodiment and may have other shapes in other embodiments. Theprojections 30 have a center-to-center spacing D which is approximately 0.005 inch to 0.006 inch, corresponding to the spacing between thedie terminals 70 of thedie 40. In other embodiments, the spacing D may be less than or greater than 0.005 inch to align theprojections 30 withbond pads 70 having a correspondingly smaller or larger spacing, respectively. - In a preferred embodiment, the
substrate 20 and theprojections 30 comprise silicon and the substrate and projections are formed integrally, as will be discussed in greater detail below with respect to FIGS. 4A-4G. Silicon is a preferred material for thesubstrate 20 because it has the same coefficient of thermal expansion as the silicon comprising thedie 40. Accordingly, when thedie 40 is tested at varying temperatures, the die and thesubstrate 20 expand and contract at substantially identical rates so that thedie terminals 70 of the die remain aligned with thetest terminals 60 of the substrate. - In other embodiments, the
substrate 20 may comprise other materials having coefficients of thermal expansion similar to or identical with the thermal expansion coefficient of silicon. Other materials include ceramics, such as Mullite, which is available from Coors Technical Ceramics Co., Oak Ridge, Tenn. In still another embodiment, thesubstrate 20 may have a thermal expansion coefficient different than that of thedie 40. Anapparatus 10 in accordance with this embodiment may still be effective when used to test the die 40 at varying temperatures if the die is relatively small, and/or if thedie terminals 70 are relatively large so that thetest terminals 60 maintain alignment with the die terminals despite the fact that thedie 40 andsubstrate 20 may expand and contract at different rates at the varying temperatures. - In a preferred embodiment, the
substrate 20, including theprojections 30, is covered with an insulatinglayer 22 comprising an electrically insulative material.Conductive layers 23 are selectively positioned over the insulatinglayer 22 to cover eachprojection 30. Theconductive layers 23 are separated from each other as shown in FIG. 3 so that electrical signals may be separately transmitted to or received from eachtest terminal 60.Bond wires 25, some of which are omitted from FIG. 3 for purposes of clarity, are accordingly connected to eachconductive layer 23 to transmit test signals to or from thecorresponding test terminals 60. - As shown in FIG. 3, the
conductive layers 23 completely cover eachprojection 30, including anupper surface 31 and side surfaces 32 thereof. In an alternate embodiment, theconductive layers 23 cover theupper surfaces 31 and only oneside surface 32 of eachprojection 30. Accordingly, electromagnetic coupling or “cross talk” between adjacentconductive layers 23 is reduced, reducing the likelihood that electrical signals transmitted to onetest terminal 60 will affect signals transmitted to a neighboring test terminal. - The variable
signal test terminals 61 each include adielectric layer 24 covering theconductive layers 23 which prevents direct contact between theconductive layer 23 and the corresponding variable signal dieterminals 71 when thedie 40 is engaged with thetest apparatus 10. Thedielectric layer 24 may comprise any number of dielectric materials which include but are not limited to nitrides, barium strontium titanate, or oxides, such as tantalum pentoxide. The composition and thickness of thedielectric layer 24 is selected to provide a desired capacitance between the variablesignal test terminals 61 and the variable signal dieterminals 71. Thedielectric layer 24 defines acontact surface 65 at an upper end of the variablesignal test terminal 61 which is sized to engage acontact surface 75 of the corresponding variable signal dieterminal 71. Where thedie 40 includes apassivation layer 44, which may extend partially over thedie terminals 70, thecontact surface 65 of each variablesignal test terminal 61 is preferably sized to engage thecontact surface 75 of the corresponding variable signal die terminal 71 without resting on the passivation layer, substantially eliminating any gap between the contact surfaces 65 and 75. Accordingly, the dielectric constant between each variablesignal test terminal 61 and corresponding variable signal die terminal 71 is determined by the composition and thickness of thedielectric layer 24 and not by a gap which might otherwise be formed between the variable signal test terminal and the variable signal die terminal. - In a preferred embodiment, the
contact surface 65 is elevated above thesubstrate 20 by a distance that is greater than the thickness of thepassivation layer 44 to ensure that thecontact surface 65 of the test terminal engages thecontact surface 75 of the variable signal dieterminal 71. In a further preferred embodiment, thecontact surface 65 is elevated a sufficient distance above thesubstrate 20 thatsmall particles 90, which may comprise dust or other contaminates and which may be present between thetest terminals 60, do not engage and potentially damage thedie 40. - As shown in FIG. 3, each constant
signal test terminal 62 includes an insulatinglayer 22 andconductive layer 23 but does not include a dielectric layer. Accordingly, theconductive layers 23 of the constantsignal test terminals 62 firmly engage with the corresponding constant signal dieterminals 72 to provide electrical connections therebetween. To further ensure proper engagement between the constantsignal test terminals 62 and the constant signal dieterminals 72, the constant signal test terminals are provided withserrations 63 positioned to engage the constant signal die terminals. Theserrations 63 releasably penetrate thecontact surface 75 of the constant signal dieterminals 72 and are separated bystop surfaces 64 to prevent the serrations from penetrating too deeply into the constant signal die terminals. - In a preferred embodiment, the stop surfaces64 are positioned such that the
serrations 63 penetrate one-half the thickness of the constant signal dieterminals 72. In a further preferred aspect of this embodiment, the stop surfaces 64 are aligned with the contact surfaces 65 of the variablesignal test terminals 61. Accordingly, when the stop surfaces 64 prevent further penetration by theserrations 63 into the constant signal dieterminals 72, the contact surfaces 65 of the variablesignal test terminals 61 engage the contact surfaces 75 of the corresponding variable signal dieterminals 71. By aligning the contact surfaces 65 with the stop surfaces 64, thedie 40 will rest solidly on thetest terminals 60 to more reliably transmit electrical signals between the die and thetest apparatus 10. - In operation, the
test apparatus 10 is used to test the die 40 by placing the die in the recessed well 27 of thesubstrate 20 as shown in FIG. 2. The user then aligns the variablesignal test terminals 61 of thetest apparatus 10 with the corresponding variable signal dieterminals 71 of the die 40, and aligns the constantsignal test terminals 62 with the corresponding constant signal dieterminals 72 as shown in FIGS. 2 and 3. Thedie 40 is firmly engaged with thetest apparatus 10 by first placing thepressure plate 54 on the die and then clamping the pressure plate and the die against thesubstrate 20 by inserting the mountingtabs 55 of thebridge clamp 50 through theslots 21 of the substrate, as shown in FIG. 1. - Constant signals are then applied to the
bond lines 25 connected to the constantsignal test terminals 62 and variable signals are applied to the bond lines connected to the variablesignal test terminals 61. When a varying signal is applied to the variablesignal test terminals 61, the signal is capacitively coupled to the corresponding variable signal dieterminal 71. The varying current may take the form of a single pulse, an alternating current signal, or any other variable current signal. The response signals received from the die 40 may then be used to determine whether or not the die complies with operational specifications and accordingly qualifies as a good die. It will be understood that any one variablesignal test terminal 61 may transmit or receive test signals, depending on the characteristics of theparticular die terminal 71 with which it is engaged, and upon the particular phase of the test process. - One advantage of the method and apparatus shown in FIGS.1-3 is that the
test apparatus 10 may be used to test the die 40 by capacitivelycoupling test terminals 61 of the apparatus to variable signal dieterminals 71 of the die 40, and by supplying a variable current signal to the capacitive bond pads to test the performance of the die. Conductive connections between thetest apparatus 10 and die 40 are used only where the die requires a constant signal. Accordingly, the number of conductive connections between the test apparatus and die, which may physically damage the die terminals, is reduced. - A further advantage of the test apparatus and method shown in FIGS.1-3 is that the variable
signal test terminals 61 of thetest apparatus 10 are aligned with the corresponding variable signal die terminals of 71 of thebare die 40 when the die is engaged with the test apparatus. The alignment is maintained even where the center-to-center spacing between the die terminals is on the order of 0.005 inch to 0.006 inch, or less. Accordingly, a user need not manipulate the die 40 in any way to align the variable signal dieterminals 71 of the die with the variablesignal test terminals 61 of thetest apparatus 10. Unlike conventional methods, the user need not add to the die 40 a layer which includes intermediate terminals which are electrically connected to thedie terminals 70, but spaced to correspond to the locations of the variable signal test pads of a test device. As a result, testing of thebare die 40 is considerably simplified. - Yet a further advantage is that the
substrate 20 shown in FIGS. 1-3 may comprise a material having a coefficient of thermal expansion similar to or identical with the thermal expansion coefficient of thedie 40. Accordingly, thetest apparatus 10 may be used to test the die 40 at varying temperatures while maintaining alignment between thedie terminals 70 of thedie 40 and thetest terminals 60 of the test apparatus. - Still a further advantage of an embodiment of a
test apparatus 10 is that the nature of the capacitive coupling between thetest apparatus 10 and the die 40 may be controlled by controlling the thickness and/or composition of thedielectric layer 24. The user accordingly has greater control over the capacitance between thetest apparatus 10 and the die 40 by manipulating two variables. Furthermore, unlike conventional methods, controlling the dielectric constant between the die 40 and thetest apparatus 10 requires only manipulating the test apparatus and not the die itself. Unlike conventional methods, which may require that a dielectric liquid or gel be placed on the variable signal die terminals, thetest apparatus 10 requires no contamination of the variable signal die terminals, which may be difficult to remove after testing has been completed. - A method for fabricating an
apparatus 10 having variablesignal test terminals 61 in accordance with an embodiment of the invention is shown in FIGS. 4A-4G. As shown in FIG. 4A, the method includes providing asubstrate 20 having a substantially flatupper surface 28. In a preferred embodiment, thesubstrate 20 may comprise silicon, and may comprise other materials in other embodiments, as discussed below. Theupper surface 28 of thesubstrate 20 is coated with a layer of positive ornegative photoresist material 82. As shown in FIG. 4B, amask 80 is then placed upon thephotoresist material 82. Themask 80 may preferably be an exact or nearly exact mirror image of a mask used to form thedie terminals 70 on thedie 40. Accordingly, thetest terminals 60 formed by themask 80 will have locations corresponding exactly or nearly exactly with the locations of thedie terminals 70 when thedie 40 is placed face down on thesubstrate 20. - Where the
photoresist material 82 is a positive photoresist material, themask 80 hasapertures 81 which correspond to the locations of thedie terminals 70 of thedie 40. Where thephotoresist material 82 is a negative photoresist material, theapertures 81 correspond to the regions between thedie terminals 70. For purposes of illustration, thephotoresist material 82 is shown as being positive in FIGS. 4A-4G. - The
substrate 20 withphotoresist material 82 andmask 80 in place, is exposed to a selectedradiation 83 which hardens thephotoresist material 82 a located beneath theapertures 81 while leaving thephotoresist material 82 b beneath themask 80 in a nonhardened state. It will be understood that where a negative photoresist material is used, the photo resistmaterial 82 b is hardened while thephotoresist material 82 a remains in a non-hardened state. After exposure to the selectedradiation 83, themask 80 is removed and thephotoresist material 82 rinsed in a chemical bath, which washes away theunhardened photoresist material 82 b while leaving thehardened photoresist material 82 a in place, as shown in FIG. 4C. - The
substrate 20, with thehardened photoresist material 82 a in place, is then exposed to an etching solution which anisotropically etches away portions of the substrate not covered by thephotoresist material 82 a and creates theprojections 30 as shown in FIG. 4D. Thehardened photoresist material 82 a is then removed. Alternatively, thesubstrate 20 may be exposed to an oxidizing agent which oxidizes the surface of the substrate not covered by thephotoresist material 82 a. The oxidized portion may then be stripped leaving theprojections 30 in place. - In an alternate method of manufacture, the
projections 30 may be formed by depositing material on theupper surface 28 of thesubstrate 20. In one such embodiment, thephotoresist layer 82 is eliminated and themask 80 is placed directly on thesubstrate 20. Material comprising theprojections 30 is then deposited using an overhead ion deposition apparatus or similar device to build the projections up from theupper surface 28 of thesubstrate 20. Such an alternate method may be used where thesubstrate 20 comprises a ceramic or other material which may not be as conducive as silicon to etching. The resultingprojections 30 may be planarized using chemical-mechanical planarization to flatten theupper surfaces 31 of theprojections 30. The flattenedupper surfaces 31 accordingly provide the foundation fortest terminals 61 having flat contact surfaces 65 which mate well with the corresponding flat contact surfaces 75 of the variable signal die terminals 71 (FIGS. 3). -
Ridges 33 may be formed on theprojects 30 which will form constantsignal test terminals 62. The ridges may be formed using photoresist and etching techniques similar to those discussed above and described in greater detail in U.S. Pat. No. 5,483,741 to Akram et al. and U.S. Pat. No. 5,326,428 to Farnworth et al., both of which are incorporated herein by reference. - The insulating
layer 22 is formed on theprojections 30, as shown in FIG. 4E. In one method of manufacture, in which thesubstrate 20 comprises silicon, the substrate is exposed to an oxidizing atmosphere to form a layer of silicon dioxide (SiO)2, an electrically insulative compound. In alternate embodiments, SiO2 or Si3N4 may be deposited on the surface of thesubstrate 20 by chemical vapor deposition. In yet another alternate embodiment, tetraethylorthosilane (TEOS) is injected at high temperature into a chamber surrounding thesubstrate 20 to grow an insulatinglayer 22 of SiO2 on thesubstrate 20. In still another alternate embodiment, the insulatinglayer 22 is deposited on thesubstrate 20 by chemical vapor deposition or similar deposition techniques. Such an alternate embodiment may be used where thesubstrate 20 comprises a ceramic material which does not oxidize as readily as does silicon. - The
conductive layers 23 comprising a conductive material are formed atop the insulatinglayer 22, as shown in FIG. 4F. In one embodiment, an initially continuousconductive layer 23 may be deposited on the insulatinglayer 22 using chemical vapor deposition. A photoresist and masking process, similar to that discussed above with reference to FIGS. 4A-4D, may then be used to etch away portions of theconductive layer 23 located between theprojections 30 to form individual conductive paths to each projection. As discussed previously with reference to FIG. 3, theconductive layers 23 may be etched to cover the entirety of eachprojection 30, or may be etched to cover theupper surface 31 of each projection and enough of aside surface 32 to form a conductive path to the projection. - The
conductive layer 23 and insulatinglayer 22 conform to theridges 33 of the constantsignal test terminal 62, forming theserrations 63. Theserrations 63 may be further roughened by using an electroplating process and controlling the composition of the electrolyte solution used in the process to form a textured or roughened surface which amplifies the serrated surface created by the etching process. The formation of roughened electroplated surfaces is further discussed in U.S. Pat. No. 5,487,999 to Farnworth, incorporated herein by reference. - The dielectric layers24 are formed on the
conductive layers 23 of the variablesignal test terminals 61, as shown in FIG. 4G. In one embodiment, an initiallycontinuous dielectric layer 24 is deposited on theconductive layer 23 by chemical vapor deposition. In another embodiment, the initiallycontinuous dielectric layer 24 may be deposited using an electrophoretic process to form an even layer of dielectric over theprojections 30. An electrophoretic process is described in U.S. Pat. No. 5,607,818 to Akram et al., which is incorporated herein by reference. The electrophoretic process includes charging theconductive layer 23, either positively or negatively, and imparting the opposite charge to the dielectric material. The dielectric material is accordingly attracted to theconductive layer 23 and gradually builds up thedielectric layer 24 thereon. - An advantage of the electrophoretic process is that it results in an even coating of dielectric material over the
conductive layer 23 notwithstanding the non-uniform topography created by theprojections 30. Another advantage is that the electrophoretic process is self-limiting because as theconductive layer 23 becomes coated with dielectric material, it tends to have less affinity for additional dielectric material. Accordingly, the amount of dielectric material electrophoretically deposited on theconductive layer 23 may be controlled by controlling the charge applied to the conductive layer. Furthermore, the dielectric layer tends to be thicker at higher temperatures than at lower temperatures. Accordingly, the temperature at which the electrophoretic process is carried out may be used to further control the dielectric characteristics of thedielectric layer 24. - Once a
continuous dielectric layer 24 has been formed, portions of the dielectric layer may then be etched away using a photoresist and masking process similar to the process discussed above with reference to FIG. 4A-4D. Dielectric material located between theprojections 30 may be removed as shown in FIG. 4G to isolate the variablesignal test terminals 61 from each other. In addition, any dielectric material covering the constantsignal test terminals 62 may be removed to ensure proper electrical contact between the constant signal test terminals and the corresponding constant signal dieterminals 72. - An advantage of the process discussed above with reference to FIGS.4A-4G is that the process uses a
mask layer 80 which is a mirror image of the mask layer used to create thedie terminals 70 on thebare die 40. Accordingly, theprojections 30 which form thetest terminals 60 of thetest apparatus 10 may be precisely aligned with thecorresponding die terminals 70 of thebare die 40. As a result, the need to form an interlayer between the die 40 and thetest apparatus 10 is eliminated, as discussed above with reference to FIGS. 1-3. A further advantage of the process shown in FIGS. 4A-4G is that thedielectric layer 24 is formed on thetest apparatus 10, eliminating the need to removably apply liquid or gel dielectric substances to thedie 40, as was also discussed above with reference to FIGS. 1-3. - FIG. 5 is an exploded, cross-sectional view of a
test apparatus 10 in accordance with a second embodiment of the invention, and a die 40 havingdielectric layers 24 a attached to the variable signal dieterminals 71 thereof. In one embodiment, thedielectric layers 24 a may comprise oxide coatings which form naturally on themetallic die terminals 70. In other embodiments, thedielectric layers 24 a may comprise other organic dielectric materials which may be deliberately formed on the variable signal dieterminals 71. - In the embodiment shown in FIG. 5, the
dielectric layers 24 are eliminated from the variablesignal test terminals 61 of thetest apparatus 10 because their function is performed by thedielectric layers 24 a on the variable signal dieterminals 71. Accordingly, the contact surfaces 65 a of the variablesignal test terminals 61 comprise a portion of theconductive layer 23 as shown in FIG. 5, rather than a portion of thedielectric layer 24 as shown in FIG. 3. - In one embodiment, the
serrations 63 of the constant signal test terminals are capable of penetrating thedielectric layer 24 a formed on the constant signal dieterminal 72. The serrations accordingly form a conductive connection with the constant signal die terminal 72 notwithstanding the presence of the dielectric material. In another embodiment, thedielectric layers 24 a may be prevented from forming on the constant signal dieterminals 72 so that the constantsignal test terminals 62 form solid conductive contacts with the constant signal die terminals. In still another embodiment, thedielectric layers 24 a may be removed from the constant signal dieterminals 72 by using masking and etching process, as discussed previously with reference to FIGS. 4A-4D. - An advantage of an embodiment of the test apparatus shown in FIG. 5 is that the test apparatus requires no
dielectric layer 24. Accordingly, at least one process step required to form thetest apparatus 10 may be eliminated. Conversely, an advantage of an embodiment of the test apparatus shown in FIGS. 1-3 is that the die 40 need not be manipulated to either form or remove the dielectric layer. - As discussed above, the dielectric oxide layers may form naturally on the dies40. The oxide layers may form after the dies have been electrically partitioned from each other on a silicon wafer but remain in a wafer form. To take advantage of the naturally occurring dielectric layers, a
test apparatus 10 in accordance with a third embodiment of the invention is sized to accommodate and test anentire wafer 100 comprising a plurality of partitioned dies 40, as shown in FIG. 6. Thetest apparatus 10 comprises asubstrate 20 havingslots 21 to accommodate a bridge clamp (not shown). The bridge clamp is used to releasably couple thewafer 100 to thesubstrate 20, as discussed previously with reference to FIG. 1. Thesubstrate 20 comprisestest terminals 60, which are aligned withcorresponding die terminals 70 at thewafer 100. Accordingly, variablesignal test terminals 61 are aligned with variable signal dieterminals 71 and constantsignal test terminals 62 are aligned with constant signal dieterminals 72, as discussed previously with reference to FIGS. 1-3. - An advantage of the
test apparatus 10 shown in FIG. 6 is that it permits a user to engage the test apparatus with anentire wafer 100 of dies 40 in one operation. Accordingly, the user need not individually engage each die 40 with thetest apparatus 10 before testing and then remove each die after testing. A further advantage is that thetest apparatus 10 shown in FIG. 6 may use the oxide layer naturally forming on the dies 40 of thewafer 100 to act as dielectric layers between thedie terminals 70 of the dies and thetest terminals 60 of the test apparatus, reducing the number of processing steps required to produce thetest apparatus 10, as discussed above with reference to FIG. 5. - FIG. 7 is an exploded, cross-sectional view of a
test apparatus 10 in accordance with a fourth embodiment of the invention positioned adjacent aflip chip 40 a in FIG. 7. As shown in FIG. 7, thedie terminals 70 a of theflip chip 40 a include variable signal dieterminals 71 a and constant signal dieterminals 72 a. Thedie terminals 72 a may comprise solder balls formed from lead or a similar soft, conductive material. Each die terminal 70 a has anend surface 76 spaced apart from thelower surface 46 of theflip chip 40 a and side surfaces 77 intermediate the end surface and the lower surface of the flip chip. Thedie terminals 70 a may have anoxide coating 78 which covers the bond pads and deforms when theflip chip 40 a is engaged with thesubstrate 20. Theoxide coating 78 generally deforms sufficiently to create a conductive electrical connection between thedie terminals 70 a and thetest terminals 60 against which they press. Accordingly, theoxide coating 78 is not relied upon to form a dielectric layer between the variable signal dieterminals 71 a and the variablesignal test terminals 61 as was discussed above with reference to FIG. 5. Instead, thedielectric layer 24, positioned on the variablesignal test terminals 61, provides the capacitive coupling between thetest apparatus 10 and theflip chip 40 a, substantially as discussed above with reference to FIGS. 1-3. Furthermore, because theoxide layer 78 deforms when theflip chip 40 a is pressed into engagement with thesubstrate 20, the contact between the constantsignal test terminal 62 and the constant signal die terminal 72 a is sufficient to create a constant signal connection therebetween, as discussed above. The need for serrations on theconductive test terminal 62 is accordingly eliminated. - FIG. 8 is a top plan view of a portion of a
test apparatus 10 in accordance with a fifth embodiment of the invention shown engaging a portion of aflip chip 40 a. Thetest apparatus 10 shown in FIG. 8 is similar to the apparatus shown in FIG. 7 except that the contact surfaces 65 b of thetest terminals 60 are positioned parallel to the side surfaces 32 rather than theupper surfaces 31 of the projections 30 (FIG. 7). Accordingly, the side surfaces 77 of thedie terminals 70 slide along the contact surfaces 65 b of thetest terminals 60 as theflip chip 40 a is pressed into engagement with thesubstrate 20. - As shown in FIG. 8, pairs of
test terminals 60 having diagonally opposed contact surfaces 65 b may be oriented in an alternating pattern to substantially prevent lateral motion of theflip chip 40 a relative to thesubstrate 20 once thedie terminals 70 a have been engaged with thetest terminals 60. Thetest terminals 60 accordingly aid the user in orienting theflip chip 40 a relative to thesubstrate 20 and maintain the orientation until the die is deliberately disengaged from thetest apparatus 10. - FIG. 9 is an exploded, cross-sectional view of a portion of a
test apparatus 10 in accordance with a sixth embodiment of the invention. Thetest apparatus 10 comprises asubstrate 20 withoutlarge projections 30. Instead, the insulatinglayer 22,conductive layers 23, anddielectric layers 24 are consecutively formed directly on theupper surface 28 of the substrate to form variablesignal test terminals 61 a and constantsignal test terminals 62 a. In the embodiment shown in FIG. 9, theprojections 30 are not necessary to provide an offset between thesubstrate 20 and theflip chip 40 a. Instead, the solder balls of theflip chip 40 a provide a sufficient offset between thesubstrate 20 and theflip chip 40 a to prevent dust particles orother contaminants 90 from becoming clamped therebetween. An advantage of an embodiment of thetest apparatus 10 shown in FIG. 9 is that the process steps required to form raised projections may be eliminated, simplifying the manufacture of thetest apparatus 10. - FIG. 10A is an exploded, cross-sectional view of a portion of a
test apparatus 10 in accordance with a seventh embodiment of the invention havingcompressible test terminals 60 b. Thesubstrate 20 includes an insulatinglayer 22 andconductive layers 23 formed directly thereon. Theprojections 30 a are formed atop theconductive layers 23 in a subsequent step. Theprojections 30 a comprise a conductive material which may be sputtered or spun on theconductive layers 23 or may be deposited on the conductive layers using chemical vapor deposition. The resulting continuous layer may then be etched using the photoresist and masking techniques discussed previously with reference to FIGS. 4A-4G to formindividual projections 30 a. - In one embodiment, the
projection 30 a may be formed from an incompressible conduction material. In another embodiment, theprojections 30 a may be formed from a compressible, conductive material such as a z-axis elastomer. Such elastomers are available from Zymet of East Hannover, N.J. The elastomer containsconductive particles 34 which are dispersed therethrough and are shown schematically in FIG. 10A. When the elastomer is compressed in a direction normal to theupper surface 28 of thesubstrate 20, theparticles 34 come into contact with each other and create a conductive path through the elastomer. - Dielectric layers24 are then applied atop the
conductive layers 23 of the variablesignal test terminals 61 b. The dielectric layers 24 preferably comprise a flexible material, such as a polyamide, which will flex as theprojections 30 a compress. The polyamide may be applied using a spray process or an electrophoretic process, such as was discussed previously with reference to FIG. 4G. As discussed previously with reference to FIG. 3, no dielectric layer is applied to the constantsignal test terminals 62 b, so as to provide conductive connections between the constant signal test terminals and the constant signal dieterminals 72. - In operation, the
die 40 is compressed against thesubstrate 20 so as to compress theprojections 30 a, creating conductive paths from theconductive layers 23 through the projections, as shown in FIGS. 10b. The variablesignal test terminals 61 form capacitive connections with the variable signal dieterminals 71 and the constant signal test terminals form conductive connections with the constant signal dieterminals 72, as discussed previously with respect to FIGS. 1-3. - An advantage of the
test apparatus 10 shown in FIGS. 10A and 10B is that thecompressible test terminals 60 b flex in a vertical direction when thedie 40 is engaged with thesubstrate 20. Thetest terminals 60 b accordingly maintain an electrical coupling with thedie terminals 70 of the die 40 even if thelower surface 26 of the die is not parallel with theupper surface 28 of the substrate. A further advantage is that the compressible constantsignal test terminals 62 b are biased toward the corresponding constant signal dieterminals 72, increasing the likelihood of a good conductive connection therebetween and eliminating the need for serrations on the constant signal test terminals. - From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
Claims (74)
1. An apparatus for testing a semiconductor die having first and second die terminals, the apparatus comprising:
a substrate having a coefficient of thermal expansion approximately equal to a thermal expansion coefficient of the die, the substrate positionable proximate to the die; and
first and second test terminals positioned on a surface of the substrate, the first test terminal having a conductive portion aligned with and spaced apart from a conductive portion of the first die terminals to capacitively couple the first test terminal with the first die terminal when the substrate is positioned proximate the die, the second test terminal being aligned with the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal.
2. The apparatus of wherein the first test terminal is coupleable to a variable power source to generate a variable signal at the first test terminal and capacitively generate a corresponding signal at the first die terminal.
claim 1
3. The apparatus of wherein the die is coupleable to a source of power to produce a variable signal at the first die terminal thereof, the first test terminal being positioned to capacitively receive the variable signal.
claim 1
4. The apparatus of wherein at least part of the conductive portion of the first test terminal is spaced apart from the surface of the substrate.
claim 1
5. The apparatus of , further comprising a dielectric material positioned intermediate the conductive portion of the first test terminal and the conductive portion of the first die terminal.
claim 1
6. The apparatus of , further comprising a dielectric material attached to the conductive portion of the first test terminal intermediate the conductive portion of the first test terminal and the conductive portion of the first die terminal.
claim 1
7. The apparatus of wherein the die has a passivation layer adjacent the first die terminal and the first test terminal projects beyond the surface of the substrate by a distance greater than a thickness of the passivation layer.
claim 1
8. The apparatus of wherein at least the first test terminal is least partially compressible in a direction substantially normal to the surface of the substrate, the first test terminal being positioned to compress in the normal direction when engaged with the first die terminal.
claim 1
9. The apparatus of wherein the first die terminal is positioned on a surface of the die and comprises an end surface spaced apart from the die surface and a side surface intermediate the end surface and the surface of the die, the first test terminal engaging the side surface of the first die terminal to align the first test terminal with the first die terminal, the first test terminal having a dielectric material positioned between the conductive portion thereof and the side surface of the first die terminal when the first test terminal engages the side surface.
claim 1
10. The apparatus of wherein a center of the first test terminal is spaced apart from a center of the second test terminal by a distance in the range of approximately 0.005 inch to approximately 0.006 inch.
claim 1
11. The apparatus of wherein the second test terminal has a conductive portion aligned with and spaced apart from a conductive portion of the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal to capacitively couple the second test terminal with the second die terminal.
claim 1
12. The apparatus of wherein the conductive portion of the second test terminal engages a conductive portion of the second die terminal when the conductive portion of the first test terminal is aligned with the first die terminal, the second test terminal being coupleable to a constant power source to generate a constant signal at the second test terminal and a constant signal at the second die terminal.
claim 1
13. The apparatus of , further comprising a biasing device releasably coupled to the substrate and positioned to bias the die toward the substrate when the first test terminal is aligned with the first die terminal and the second test terminal is aligned with the second die terminal.
claim 1
14. The apparatus of wherein the die is one of a plurality of dies comprising a silicon wafer and the substrate is sized and shaped to be positioned adjacent the silicon wafer.
claim 1
15. The apparatus of wherein the substrate comprises silicon.
claim 1
16. The apparatus of wherein the substrate comprises a ceramic material.
claim 1
17. An apparatus for testing a semiconductor die having first and second die terminals, the apparatus comprising:
a silicon substrate;
a first conductive projection connected to and extending away from a surface of the substrate, the first projection being aligned with the first die terminal when the substrate is positioned proximate the die;
a portion of dielectric material attached to the first projection and positioned intermediate the first projection and the first die terminal when the first projection is aligned with the first die terminal;
a second conductive projection connected to an extending away from the surface of the substrate, the second projection being aligned with the second die terminal when the first projection is aligned with the first die terminal.
18. The apparatus of wherein the die is one of a plurality of dies comprising a silicon wafer and the substrate is sized and shaped to be positioned adjacent the silicon wafer.
claim 17
19. The apparatus of wherein the first and second projections comprise silicon.
claim 17
20. The apparatus of wherein the first and second projections are electrically insulated from each other.
claim 17
21. The apparatus of wherein the die has a passivation layer adjacent the first die terminal and at least part of the portion of dielectric material projects beyond the surface of the substrate by a distance greater than a thickness of the passivation layer.
claim 17
22. The apparatus of , further comprising a biasing device releasably coupled to the substrate and positioned to bias the die toward the substrate when the first projection is aligned with the first die terminal and the second projection is aligned with the second die terminal.
claim 17
23. The apparatus of wherein a center of the first projection is spaced apart from a center of the second projection by a distance in the range of approximately 0.005 inch to approximately 0.006 inch.
claim 17
24. The apparatus of wherein the first projection is coupleable to a variable power source to generate a variable signal at the first projection and capacitively generate a corresponding signal at the first die terminal.
claim 17
25. The apparatus of wherein the die is coupleable to a source of electrical power to produce a variable signal at the first die terminal thereof, the first projection being positioned to capacitively receive the variable signal.
claim 17
26. An apparatus for testing a semiconductor die having first and second die terminals, the apparatus comprising:
a silicon substrate having first and second silicon projections extending away from a surface thereof, the first projection being aligned with the first die terminal and the second projection being aligned with the second die terminal when the substrate is positioned adjacent the die;
a first portion of insulating material at least partially covering the first projection;
a second portion of insulating material at least partially covering the second projection;
a first portion of conductive material at least partially covering the first portion of insulating material;
a second portion of conductive material at least partially covering the second portion of insulating material;
a portion of dielectric material attached to the first portion of conductive material and positioned intermediate the first portion of conductive material and the first die terminal when the first projection is aligned with the first die terminal.
27. The apparatus of wherein the first projection is coupleable to a variable power source to generate a variable signal at the first projection and capacitively generate a corresponding signal at the first die terminal.
claim 26
28. The apparatus of wherein the die is coupleable to a source of electrical power to produce a variable signal at the first die terminal thereof, the first projection being positioned to capacitively receive the variable signal.
claim 26
29. The apparatus of wherein the die is one of a plurality of dies comprising a silicon wafer and the substrate is sized and shaped to be positioned adjacent the silicon wafer.
claim 26
30. The apparatus of wherein the first portion of conductive material has a surface proximate the first die terminal when the first projection is aligned with the first die terminal, the surface of the first portion of conductive material being smaller than a surface of the first die terminal with which the surface of the first portion of conductive material is aligned.
claim 26
31. The apparatus of wherein the die has a passivation layer adjacent the first die terminal and at least part of the portion of dielectric material projects beyond the surface of the substrate by a distance greater than a thickness of the passivation layer.
claim 26
32. The apparatus of , further comprising a biasing device releasably coupled to the substrate and positioned to bias the die toward the substrate when the first projection is aligned with the first die terminal and the second projection is aligned with the second die terminal.
claim 26
33. The apparatus of wherein a center of the first projection is spaced apart from a center of the second projection by a distance in the range of approximately 0.005 inch to approximately 0.006 inch.
claim 26
34. The apparatus of wherein the first die terminal has an end surface spaced apart from a surface of the die and an intermediate portion intermediate the end surface and the surface of the die, the dielectric material engaging the intermediate portion of the first die terminal to align the first projection with the first die terminal.
claim 26
35. The apparatus of wherein the first projection has an end surface spaced apart from the surface of the substrate and an intermediate portion intermediate the end surface and the surface of the substrate and a first part of the dielectric material covers the intermediate portion, the first part of the dielectric material engaging the first die terminal to align the first projection with the first die terminal.
claim 26
36. A test apparatus for capacitively testing a semiconductor die having a first and second die terminals, produced by a process comprising:
forming a first test terminal on a substrate, the first test terminal having a conductive portion aligned with and spaced apart from the conductive surface of the first die terminal when the substrate is positioned proximate the die;
forming a second test terminal on the substrate, the second test terminal having a conductive portion aligned with the second die terminal while the first test terminal is aligned with the first die terminal and the substrate is positioned proximate to the die; and
positioning a dielectric material intermediate at least the conductive portion of the first test terminal and the conductive surface of the first die terminal.
37. The test apparatus produced by the process of wherein the process further comprises attaching the dielectric material to the conductive portion of the first test terminal.
claim 36
38. The test apparatus produced by the process of wherein the act of forming the first test terminal comprises:
claim 36
selecting a first region of a surface of the substrate; and
removing a second region of the surface of the substrate adjacent the first region to form a projection on the substrate aligned with the first die terminal when the substrate is positioned proximate the die.
39. The test apparatus produced by the process of wherein the process further comprises:
claim 38
at least partially coating the projection with an insulating material;
at least partially coating the insulating material with a conductive material to form the conductive portion; and
at least partially coating the conductive material with a dielectric material.
40. A test apparatus for capacitively testing a semiconductor die having first and second die terminals, produced by a process comprising:
forming first and second projections on a silicon substrate;
applying a first portion of insulating material to the first projection and a second portion of insulating material to the second projection;
applying a first portion of conductive material to the first portion of insulating material and a second portion of conductive material to the second portion of insulating material; and
providing a dielectric material intermediate at least the first portion of conductive material and the first die terminal.
41. The test apparatus produced by the process of wherein the act of providing a dielectric material comprises:
claim 40
applying a first charge to the first portion of conductive material;
applying a second charge opposite the first charge to the dielectric material; and
depositing the dielectric material on the first portion of conductive material.
42. The test apparatus produced by the process of wherein the act of applying the first and second conductive portions includes depositing conductive material in a vapor form on the first and second portions of insulating material.
claim 40
43. The test apparatus produced by the process of wherein the act of applying the first and second portions of insulating material includes oxidizing at least a portion of the silicon substrate.
claim 40
44. The test apparatus produced by the process of wherein the act of forming the first projection comprises:
claim 40
applying a layer of photoresist material to a surface of the substrate;
exposing a first region of the layer of photoresist material to a selected radiation to form an exposed region of photoresist material;
shielding a second region of the layer of photoresist material adjacent the first region from exposure to the selected radiation to form a shielded region of photoresist material;
removing one of the exposed and shielded regions; and
removing substrate material previously covered by the other of the exposed and shielded regions to form a projection aligned with the first die terminal when the substrate is positioned proximate the die.
45. A test apparatus for capacitively testing a semiconductor wafer comprising at least first and second semiconductor dies each having first and second die terminals, the test apparatus produced by a process comprising:
forming first and second test terminals on a substrate, the first test terminal having a conductive portion aligned with and spaced apart from a conductive surface of the first die terminal of the first die and the second test terminal having a conductive portion aligned with a conductive portion of the second die terminal of the first die while the first test terminal is aligned with the first die terminal of the first die and the substrate is positioned proximate to the wafer;
forming third and fourth test terminals on the substrate, the third test terminal having a conductive portion aligned with and spaced apart from a conductive surface of the first die terminal of the second die and the fourth test terminal having a conductive portion aligned with a conductive portion of the second die terminal of the second die while the third test terminal is aligned with the first die terminal of the second die and the substrate is positioned proximate the wafer; and
positioning a dielectric material intermediate at least the conductive portion of the first test terminal and the conductive surface of the first die terminal of the first die.
46. The test apparatus produced by the process of wherein the process further comprises attaching the dielectric material to the conductive portion of the first test terminal.
claim 45
47. The test apparatus produced by the process of wherein the act of forming the first test terminal comprises:
claim 45
selecting a first region of a surface of the substrate; and
removing a second region of the surface of the substrate adjacent the first region to form a projection on the substrate aligned with the first die terminal of the first die when the substrate is positioned proximate the wafer.
48. The test apparatus produced by the process of wherein the process further comprises:
claim 47
at least partially coating the projection with an insulating material;
at least partially coating the insulating material with a conductive material to form the conductive portion; and
at least partially coating the conductive material with a dielectric material.
49. A test apparatus for capacitively testing a semiconductor wafer comprising a plurality of semiconductor dies each having first and second die terminals, the test apparatus produced by a process comprising:
forming first and second projections on a silicon substrate, the first and second projections being aligned with the first and second die terminals of one of the plurality of dies when the substrate is proximate the wafer;
applying a first portion of insulating material to the first projection and a second portion of insulating material to the second projection;
applying a first portion of conductive material to the first portion of insulating material and a second portion of conductive material to the second portion of insulating material; and
providing a dielectric material intermediate at least the first portion of conductive material and the first die terminal of the one of the plurality of dies.
50. The test apparatus produced by the process of wherein the act of providing dielectric material comprises:
claim 49
applying a first charge to the first portion of conductive material;
applying a second charge opposite the first charge to the dielectric material; and
depositing the dielectric material on the first portion of conductive material.
51. The test apparatus produced by the process of wherein the act of applying the first and second conductive portions includes depositing conductive material in a vapor form on the first and second portions of insulting material.
claim 49
52. The test apparatus produced by the process of wherein the act of forming the first projection comprises:
claim 49
applying a layer of photoresist material to a surface of the substrate;
exposing a first region of the layer of photoresist material to a selected radiation to form an exposed region of photoresist material;
shielding a second region of the layer of photoresist material adjacent the first region from exposure to the selected radiation to form a shielded region of photoresist material;
removing one of the exposed and shielded regions; and
removing substrate material previously covered by the other of the exposed and shielded regions to form a projection aligned with the first terminal when the substrate is positioned proximate the die.
53. A method for testing a semiconductor die with a test apparatus having first and second test terminals, the die having first and second die terminals, the method comprising:
aligning the first test terminal with the first die terminal and the second test terminal with the second die terminal;
capacitively coupling a variable signal from the first test terminal to the first die terminal; and
varying a temperature of the die and test apparatus to vary a size of the die and a size of the test apparatus at approximately equal rates and maintain alignment between the first test terminal and the first die terminal and between the second test terminal and the second die terminal.
54. The method of , further comprising placing a dielectric material intermediate the first die terminal and the first test terminal.
claim 53
55. The method of wherein the act of placing a dielectric material includes attaching the dielectric material to the first test terminal.
claim 54
56. The method of wherein the act of placing a dielectric material includes attaching the dielectric material to the first die terminal.
claim 54
57. A method for manufacturing an apparatus for capacitively testing a semiconductor die having first and second die terminals, the first and second die terminals each having a conductive surface, the method comprising:
forming a first test terminal on a substrate, the first test terminal having a conductive portion aligned with and spaced apart from the conductive surface of the first die terminal when the substrate is positioned proximate the die;
forming a second test terminal on the substrate, the second test terminal having a conductive portion aligned with the second die terminal while the first test terminal is aligned with the first die terminal and the substrate is positioned proximate the die; and
positioning a dielectric material intermediate at least the conductive portion of the first test terminal and the conductive surface of the first die terminal when the first test terminal is aligned with the first die terminal.
58. The method of , further comprising attaching the dielectric material to the conductive portion of the first test terminal.
claim 57
59. The method of wherein the act of forming the first test terminal comprises:
claim 57
selecting a first region of a surface of the substrate; and
removing a second region of the surface of the substrate adjacent the first region to form a projection on the substrate aligned with the first die terminal when the substrate is positioned proximate the die.
60. The method of , further comprising:
claim 59
at least partially coating the projection with an insulating material;
at least partially coating the insulating material with a conductive material to form the conductive portion; and
at least partially coating the conductive material with a dielectric material.
61. The method of wherein the act of forming the first test terminal comprises:
claim 57
applying a layer of photoresist material to a surface of the substrate;
exposing a first region of the layer of photoresist material to a selected radiation to form an exposed region of photoresist material;
shielding a second region of the layer of photoresist material adjacent the first region from exposure to the selected radiation to form a shielded region of photoresist material;
removing one of the exposed and shielded regions; and
removing substrate material previously covered by the other of the exposed and shielded regions to form a projection aligned with the first die terminal when the substrate is positioned proximate the die.
62. The method of wherein the act of shielding a second region of the photoresist layer includes masking the second region with a mask layer having apertures therethrough aligned with a mask layer used to form the first and second die terminals of the die.
claim 61
63. The method of wherein the act of shielding a second region of the photoresist layer includes masking the second region with a mask layer having apertures therethrough which mirror apertures of a mask layer used to form the first and second die terminals of the die.
claim 61
64. The method of wherein the act of forming the first test terminal comprises:
claim 57
forming an insulating layer on a surface of the substrate; and
forming a first portion of conductive material on the insulating layer, the first portion of conductive material being aligned with the first die terminal when the substrate is positioned proximate to the die.
65. The method of wherein the act of forming the second test terminal comprises:
claim 64
depositing a second portion of conductive material on the insulating layer, the second portion of conductive material being aligned with the second die terminal when the first portion of conductive material is aligned with the first die terminal.
66. The method of , further comprising:
claim 65
applying a first portion of dielectric material to the first portion of conductive material; and
applying a second portion of dielectric material to the second portion of conductive material.
67. A method for manufacturing an apparatus for testing a semiconductor die having first and second die terminals, the method comprising:
forming first and second projections on a silicon substrate;
applying a first portion of insulating material to the first projection and a second portion of insulating material to the second projection;
applying a first portion of conductive material to the first portion of insulating material and a second portion of conductive material to the second portion of insulating material; and
providing a dielectric material intermediate at least the first portion of conductive material and the first die terminal.
68. The method of wherein the act of providing a dielectric layer comprises forming a layer of dielectric material on the layer of conductive material.
claim 67
69. The method of wherein the act of providing a dielectric material comprises:
claim 67
applying a first charge to the first portion of conductive material;
applying a second charge opposite the first charge to the dielectric material; and
depositing the dielectric material on the first portion of conductive material.
70. The method of wherein the act of applying the first and second conductive portions includes depositing conductive material in a vapor form on the first and second portions of insulating material.
claim 67
71. The method of wherein the act of applying the first and second portions of insulating material includes oxidizing at least a portion of the silicon substrate.
claim 67
72. The method of wherein the act of forming the first projection comprises:
claim 67
applying a layer of photoresist material to a surface of the substrate;
exposing a first region of the layer of photoresist material to a selected radiation to form an exposed region of photoresist material;
shielding a second region of the layer of photoresist material adjacent the first region from exposure to the selected radiation to form a shielded region of photoresist material;
removing one of the exposed and shielded regions; and
removing substrate material previously covered by the other of the exposed and shielded regions to form a projection aligned with the first terminal when the substrate is positioned proximate the die.
73. The method of wherein the act of removing substrate material includes etching the substrate.
claim 72
74. The method of wherein the act of removing substrate material includes oxidizing substrate material to form oxide layer and removing the oxide layer.
claim 72
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/797,795 US6369597B2 (en) | 1997-10-06 | 2001-03-02 | Method and apparatus for capacitively testing a semiconductor die |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/944,598 US6285201B1 (en) | 1997-10-06 | 1997-10-06 | Method and apparatus for capacitively testing a semiconductor die |
US09/387,649 US6329828B1 (en) | 1997-10-06 | 1999-09-01 | Method and apparatus for capacitively testing a semiconductor die |
US09/797,795 US6369597B2 (en) | 1997-10-06 | 2001-03-02 | Method and apparatus for capacitively testing a semiconductor die |
Related Parent Applications (1)
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US09/387,649 Division US6329828B1 (en) | 1997-10-06 | 1999-09-01 | Method and apparatus for capacitively testing a semiconductor die |
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US20010007427A1 true US20010007427A1 (en) | 2001-07-12 |
US6369597B2 US6369597B2 (en) | 2002-04-09 |
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US08/944,598 Expired - Lifetime US6285201B1 (en) | 1997-10-06 | 1997-10-06 | Method and apparatus for capacitively testing a semiconductor die |
US09/387,649 Expired - Fee Related US6329828B1 (en) | 1997-10-06 | 1999-09-01 | Method and apparatus for capacitively testing a semiconductor die |
US09/797,795 Expired - Fee Related US6369597B2 (en) | 1997-10-06 | 2001-03-02 | Method and apparatus for capacitively testing a semiconductor die |
US09/797,743 Expired - Fee Related US6356092B2 (en) | 1997-10-06 | 2001-03-02 | Method and apparatus for capacitively testing a semiconductor die |
US09/885,325 Expired - Fee Related US6426639B2 (en) | 1997-10-06 | 2001-06-19 | Method and apparatus for capacitively testing a semiconductor die |
US09/932,067 Expired - Lifetime US6420890B2 (en) | 1997-10-06 | 2001-08-17 | Method and apparatus for capacitively testing a semiconductor die |
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US08/944,598 Expired - Lifetime US6285201B1 (en) | 1997-10-06 | 1997-10-06 | Method and apparatus for capacitively testing a semiconductor die |
US09/387,649 Expired - Fee Related US6329828B1 (en) | 1997-10-06 | 1999-09-01 | Method and apparatus for capacitively testing a semiconductor die |
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US09/797,743 Expired - Fee Related US6356092B2 (en) | 1997-10-06 | 2001-03-02 | Method and apparatus for capacitively testing a semiconductor die |
US09/885,325 Expired - Fee Related US6426639B2 (en) | 1997-10-06 | 2001-06-19 | Method and apparatus for capacitively testing a semiconductor die |
US09/932,067 Expired - Lifetime US6420890B2 (en) | 1997-10-06 | 2001-08-17 | Method and apparatus for capacitively testing a semiconductor die |
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Cited By (1)
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US20110235284A1 (en) * | 2010-03-29 | 2011-09-29 | Hon Hai Precision Industry Co., Ltd. | Circuit board |
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US6285201B1 (en) * | 1997-10-06 | 2001-09-04 | Micron Technology, Inc. | Method and apparatus for capacitively testing a semiconductor die |
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-
1999
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2001
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- 2001-03-02 US US09/797,743 patent/US6356092B2/en not_active Expired - Fee Related
- 2001-06-19 US US09/885,325 patent/US6426639B2/en not_active Expired - Fee Related
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US20110235284A1 (en) * | 2010-03-29 | 2011-09-29 | Hon Hai Precision Industry Co., Ltd. | Circuit board |
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US6329828B1 (en) | 2001-12-11 |
US6369597B2 (en) | 2002-04-09 |
US6285201B1 (en) | 2001-09-04 |
US6420890B2 (en) | 2002-07-16 |
US20010017550A1 (en) | 2001-08-30 |
US6426639B2 (en) | 2002-07-30 |
US6356092B2 (en) | 2002-03-12 |
US20010054908A1 (en) | 2001-12-27 |
US20010030548A1 (en) | 2001-10-18 |
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