Patent Application
20170292992
The present technology is directed generally to semiconductor wafer tests. In particular, test signals are transmitted through interposers that have contact pads with a relatively small scale facing a wafer, and contact pads with a relatively large scale facing associated test equipment.
Integrated circuits are used in a wide variety of products. Integrated circuits have continuously decreased in price and increased in performance, becoming ubiquitous in modern electronic devices. These improvements in the performance/cost ratio are based, at least in part, on miniaturization, which enables more semiconductor dies to be produced from a wafer with each new generation of the integrated circuit manufacturing technology. Furthermore, the total number of the signal and power/ground contacts on a semiconductor die generally increases with new, more complex die designs.
Prior to shipping a semiconductor die to a customer, the performance of the integrated circuits is tested, either on a statistical sample basis or by testing each die. An electrical test of the semiconductor die typically includes powering the die through the power/ground contacts, transmitting signals to the input contacts of the die, and measuring the resulting signals at the output contacts of the die. Therefore, during the electrical test at least some contacts on the die must be electrically contacted to connect the die to sources of power and test signals.
Conventional test contactors include an array of contact pins attached to a substrate, e.g., a relatively stiff printed circuit board (PCB). In operation, the test contactor is pressed against a wafer such that the array of contact pins makes electrical contact with the corresponding array of die contacts (e.g., pads or solderballs) on the dies of the wafer. Next, a wafer tester sends electrical test sequences (e.g., test vectors) through the test contactor to the input contacts of the dies of the wafer. In response to the test sequences, the integrated circuits of the tested die produce output signals that are routed through the test contactor back to the wafer tester for analysis and to determine whether a particular die passes the test.
In general, an increasing number of die contacts that are distributed over a decreasing area of the die results in smaller contacts spaced apart by smaller distances (e.g., a smaller pitch). Furthermore, a characteristic diameter of the contact pins of the test contactor generally scales with a characteristic dimension of the contact structures on the semiconductor die or the package. Therefore, as the contact structures on the die become smaller and/or have a smaller pitch, the contact pins of the test contactors become smaller, too. However, it is difficult to significantly reduce the diameter and pitch of the contact pins, e.g., because of the difficulties in machining and assembling such small parts, resulting in low yield and inconsistent performance from one test contactor to another. Furthermore, precise alignment between the test contactor and the wafer is difficult because of the relatively small size/pitch of the contact structures on the wafer. Accordingly, there remains a need for cost effective test contactors that can scale down in size with the size and pitch of the contact structure on the die.
Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on clearly illustrating the principles of the present disclosure. Furthermore, in the drawings, like reference numerals generally designate corresponding parts throughout the several views.
Specific details of several embodiments of representative wafer translators and associated methods for use and manufacture are described below. The wafer translators can be used for testing semiconductor dies on a wafer. The semiconductor dies may include, for example, memory devices, logic devices, light emitting diodes, micro-electro-mechanical-systems, and/or combinations of these devices. A person skilled in the relevant art will also understand that the technology may have additional embodiments, and that the technology may be practiced without several of the details of the embodiments described below with reference to
Briefly described, methods and devices for testing dies on the semiconductor wafers are disclosed. The disclosed methods and systems enable operators to test devices having pads, solderballs and/or other contact structures having small sizes and/or pitches. Solderballs, pads and/or other suitable conductive elements on the dies are collectively referred to herein as “contact structures” or “contacts.” In many embodiments, the technology described in the context of one or more types of contact structures can also be applied to other contact structures.
In some embodiments, a wafer-side of the wafer translator carries the wafer-side contact structures having relatively small sizes and/or pitches (collectively, “scale”). The wafer-side contact structures of the wafer translator are electrically connected to corresponding inquiry-side contact structures having relatively larger sizes and/or pitches at the opposite, inquiry-side of the wafer translator. Therefore, once the wafer-side contact structures are properly aligned to contact the semiconductor wafers, the larger size/pitch of the opposing inquiry-side contact structures enable more robust contact (e.g., requiring less precision). The larger size/pitch of the inquiry-side contact structures may provide more reliable contact and be easier to align against the pins of the test contactor.
In at least some embodiments, undesirable gas bubbles can be trapped between the wafer translator and the wafer. In some embodiments, e.g., when the wafer translator is not rigid, an elastomer, which can be controlled so as to be curved, can be inserted between a wafer translator chuck and the wafer translator to bend the central areas of the wafer translator, thus promoting a desired sequence of contacting the wafer by specific areas of the wafer translator. For example, if the wafer translator is deliberately curved (e.g., bowed), a central portion of the wafer translator may contact the wafer first, with the radially peripheral portions of the wafer translator contacting the wafer subsequently. Such a sequence of contacting the wafer (e.g., from the center in an outward direction) can minimize or at least reduce trapping gas bubbles between the wafer translator and the wafer. In some embodiments, a segmented wafer translator chuck capable of independently moving segments of the translator (e.g., a central segment and radial ring segments) can be used to control the sequence of contact between the wafer translator and the wafer.
Many embodiments of the technology described below may take the form of computer- or controller-executable instructions, including routines executed by a programmable computer or controller. Those skilled in the relevant art will appreciate that the technology can be practiced on computer/controller systems other than those shown and described below. The technology can be embodied in a special-purpose computer, controller or data processor that is specifically programmed, configured or constructed to perform one or more of the computer-executable instructions described below. Accordingly, the terms “computer” and “controller” as generally used herein refer to any data processor and can include Internet appliances and hand-held devices (including palm-top computers, wearable computers, cellular or mobile phones, multi-processor systems, processor-based or programmable consumer electronics, network computers, mini computers and the like). Information handled by these computers can be presented at any suitable display medium, including a CRT display or LCD.
The technology can also be practiced in distributed environments, where tasks or modules are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules or subroutines may be located in local and remote memory storage devices. Aspects of the technology described below may be stored or distributed on computer-readable media, including magnetic or optically readable or removable computer disks, as well as distributed electronically over networks. Data structures and transmissions of data particular to aspects of the technology are also encompassed within the scope of the embodiments of the technology.
In some embodiments, the signals and power can be routed from the tester to the test contactor 30 using cables 39. Conductive traces 38 carried by a test contactor substrate 32 can electrically connect the cables 39 to contacts 36 on the opposite side of the test contactor substrate 32. In operation, the test contactor 30 can contact an inquiry-side 13 of a wafer translator 10 as indicated by arrows A. In at least some embodiments, relatively large inquiry-side contact structures 14 can improve aligning with the corresponding contacts 36 of the test contactor 30. The contact structures 14 are electrically connected with relatively small wafer-side contact structures 16 on a wafer-side 15 of the translator 10 through conductive traces 18 of a wafer translator substrate 18. The size and/or pitch of the wafer-side contact structures 16 are suitable for contacting corresponding die contacts 26 of the wafer 20. In some embodiments, arrows B indicate a movement of the wafer translator 10 to make contact with an active side 25 of the wafer 20. As explained above, the signals and power from the tester can test the DUTs of the wafer 20, and the output signals from the tested DUTs can be routed back to the tester for analysis and a determination as to whether the DUTs are suitable for packaging and shipment to the customer.
The wafer 20 can be supported by a wafer chuck 40. Arrows C indicate the direction of the wafer 20 mating with the wafer chuck 40. In operation, the wafer 20 can be held against the wafer chuck 40 using, e.g., vacuum or mechanical clamping.
In some embodiments, the vacuum source 150 is connected to the wafer translator 110 through evacuation paths 144 in the wafer translator chuck 140 and evacuation paths 124 in the insert 120. In some embodiments, the evacuation paths 144/124 can be drilled, and in other embodiments, other suitable manufacturing methods (e.g., molding) are used. The evacuation paths 144 may be connected to one or more corresponding chuck grooves 142 and corresponding insert grooves 122 for a uniform distribution of the vacuum over the surface of the wafer translator 110. For example, the grooves 142/122 can be circular, resulting in concentric rings of vacuum at the interfaces between the wafer translator chuck 140 and the interface 120, and between the wafer translator 110 and the interface 120. In some embodiments, the vacuum rings can improve the holding force of the vacuum because the rings increase the applied area of the vacuum. Three evacuation paths 144/124 are shown for purposes of illustration, and other suitable numbers and configurations of the evacuation paths are used in other embodiments. A controller 160 can control the operation of the system shown in
In at least some embodiments, the wafer translator 110 is sufficiently deformable (e.g., flexible) in a direction L1 to approximate the convex shape of the insert 120 (e.g., the wafer translator bows or curves away from the translator chuck). In some embodiment, the insert 120 can be curved about 0.1-6 mm or 1-5 mm away from the translator chuck when testing 300 mm wafers. In at least some embodiments, the curvature of the insert 120 exceeds a size of manufacturing imperfections of the translator chuck (e.g., manufacturing-induced roughness, out of planarity tolerance, etc.). In some embodiments, the insert 120 can be made of an elastomer with enough porosity to compress the material under pressure. In some embodiments, the insert 120 and the wafer translator chuck 140 can be combined into one unit by, for example, permanently attaching the insert 120 to the wafer translator chuck 140, or by manufacturing the wafer translator chuck 140 and the insert 120 as an integral unit from the same elastomer stock. In some embodiment, the wafer translator chuck 140 may have a curved outer surface facing the insert 120. In some embodiments, the gasket 130 can prevent vacuum losses (e.g., for a sponge-like insert 120) and/or can keep the insert 120 centered. In operation, the assembly 1010 can be moved in the direction L1 toward the assembly 1020 to bring the wafer translator 110 in contact with the wafer 220.
As the first assembly 1010 contacts the wafer 220, the controller 160 may start reducing vacuum in the evacuation paths 144/124. For example, when the wafer translator 110 generally conforms to the active surface of the wafer 220 beyond the radial position of the innermost groove 122, the vacuum in the innermost evacuation paths 144/122 can be reduced or eliminated, and the process can be repeated for the outwardly located grooves 122 until the vacuum is released for all the evacuation paths 144/122. In at least some embodiments, this controlled release of vacuum may improve the alignment and reduce the incidence of gas bubbles between the wafer translator 110 and the wafer 220.
From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, in some embodiments, the gasket 130 can have a slightly undersized diameter to deform the wafer translator into a convex shape (e.g., an inner diameter of the gasket can be slightly smaller than an outer diameter of the wafer translator). Furthermore, the gasket 130 can be adhesive or tacky (e.g., releasably adhesive) to improve the retention of the gasket against the wafer translator chuck and/or the translator. In various embodiments, pairs of components can be moved toward each other by moving one or both components (e.g., the wafer translator chuck 140 can be moved toward the wafer chuck 240, or the the wafer chuck 240 can be moved toward the wafer translator chuck 140, or both components can be moved into a contact). Moreover, while various advantages and features associated with certain embodiments have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the technology. Accordingly, the disclosure can encompass other embodiments not expressly shown or described herein.
