WHICH SIDE ARE YOU ON? DOUBLE SIDED PROBING

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1 WHICH SIDE ARE YOU ON? DOUBLE SIDED PROBING Traditionally, devices with active regions on both sides of a wafer were limited to discrete devices. With advances in materials, functionality and packaging, particularly in MEMs, Optoelectronics and 3D IC stacking, the need for double sided probing (DSP) has become mainstream. With the modularity of the Probe System for Life, several different test scenarios can be incorporated on a single PS4L system. DOUBLE SIDED PROBING OVERVIEW Simply put, double sided probing enables semiconductor designers, developers and manufacturers to test or stimulate wafers, substrates and die on both sides. Where traditional probing systems provide access and testing to one side of a wafer mounted on a chuck, double sided probers provide full top and bottom side positioning, testing and observation for devices ranging from whole wafers to singulated die. There are a number of configurations available depending on the technology and testing required. The most prevalent technologies driving the need for DSP include: MEMs Optoelectronics Emission / Failure Analysis 3D IC Stacks including Through Silicon Vias (TSV) Double sided testing with the Probe System for Life (PS4L) can be performed on a single die to a full wafer employing a manual, semiautomatic or fully automatic test system. The PS4L can probe in a variety of combinations including top side only, bottom side only, or both side simultaneously and supports both manual or programmable manipulators and probe cards in combination. Manipulators and probe cards can be positioned separately or together on either side of the device under test (DUT). Custom wafer carriers are available for single die, partial wafers, or wafers with hold-down clamps to insure ease of use and stability. Stimulus and output measurements can be applied to the top and/or bottom sides. Virtually any test instrument including solar simulators, integrating spheres, vibrometers, pressure probes and motion analyzers can be integrated with the PS4L test system. When designed with an emission microscope, the PS4L becomes an integrated emission microscopy system for both front side and back side emission analysis. Typically, selection of the test system s capabilities is dependent upon the speed and volume of the testing required versus the costs associated with desired features and functionality.

2 DSP APPLICATIONS Traditionally, double sided probe systems have been predominantly in the domain of failure analysis for both emission and thermal microscopy. Before semiconductor devices were designed with multiple metal layers, the process to identify possible die problems was much simpler. It was accomplished through the use of a dark box and a light amplification camera. One would electrically excite the device on a probe station and identify the point of failure by the faint emission of photons given of at the offending site. With the advent of multiple metal layer technology, locating a buried failure point became much more difficult. It required thinning the wafer or the area of interest, polishing it, and then looking through the silicon on the device under test (DUT) while contacting the front of the wafer. This process had its limitations most notably, its inability to detect dead shorts, which did not emit photons and in turn, dissipated the energy through heat. Modern systems today utilize very sensitive IR cameras and optics. They can locate a host of problems including open lines, ohmic shorts, impedance issues, leakage currents, leaky capacitors, timing errors, oxide defects, resistive vias and dynamic failures. Depending upon the functionality of the test equipment used, these systems are capable of locating dead shorts within a device as well as mapping out temperatures within the device in both active and passive modes. Understanding temperature characteristics become critical in characterizing reliability and performance and the impact of various packaging alternatives in more complex integrated circuits (IC s), multi-chip modules (MCM s) and monolithic microwave integrated circuits (MMIC s). BOTTOM SIDE TESTING - the bottom or the back side of the wafer is facing upwards toward the emission camera or detector. Probes contact the inverted top or front side of the wafer using the back side camera for alignment and contact. Emission Source Device Under Test Probe Tips Wafer moves in X, Y & Z Back Side Camera

3 TOP SIDE TESTING Probes contact the front side of the wafer using normal top side optics, usually a high magnification compound microscope. The emission system is mounted on the underside of the double sided probe system looking up at the back side or bottom of the wafer. Wafer moves in X, Y & Z Device Under Test Probe Tips Retaining Clips Emission Source DOUBLE SIDE TESTING - More recent advances in semiconductor design and materials has led to an expanded need for double sided probing beyond emission microscopy / failure analysis, particularly in the areas of Optoelectronics and MEMs. The common test attribute for these devices is the need for stimulation on one side of the wafer while testing on the other side. There is a variety of stimulation equipment including solar simulators, motion analyzers and magnets. Accurate measurements require close proximity of the stimulus or detector to the top or back side of the wafer and directly beneath the DUT. Detector is stationary Can be mounted on the top or bottom PS4L shown with a fixed position detector and integrated probe card holder Semiconductor packaging advances have also contributed to the expansion of double sided probing. Multichip Modules (MCM), Monolithic Microwave Integrated Circuits (MMIC), and 3D-IC s, which can include Through Silicon Vias (TSV), have active regions on both sides of the wafers, which requires simultaneous double sided probing for testing. Wafer moves in X and Y Probes simultaneously move into contact and separate to move stage to next DUT No Z movement Wafer 2 point aligned after loading

4 CHUCKS AND CARRIERS Given the need for simultaneous testing on both sides, double sided probing requires specialized chucks and carriers with retaining clamps in order to insure stability and accuracy in testing. SemiProbe has developed an extensive line of products to provide this capability, accommodating an assortment of configurations from individual die to complete wafers. The wafer carriers are interchangeable, easy to slide in and out and lock into place. Many of our customers order multiple sets in order to load and prepare test samples while performing tests. We are happy to work with you to design carriers that meet your specific requirements. SOFTWARE Configuration and management of the system can be controlled through the SemiProbe PILOT control software suite. Our software is designed similar to our hardware. Several different types of modules are available and customers only purchase what they require. New modules and capabilities are easily added in the field as required. With its intuitive graphical user interface, PILOT is easy to set up, learn and use. All probing operations may be programmed and controlled through PILOT. The wafer map module quickly creates a specific wafer map for a wafer type and then saves and stores all test data and configuration data to the test wafer file. The data is easily transferred to other downstream equipment or available offline for complete life cycle device monitoring. PILOT software suite main screen display with Navigator and Wafer Map Modules, microscope and manipulator controls and integrated video display PILOT supports a number of common interfaces including TCP/IP, LabView, and GPIB, as well as drivers to interface to test equipment including Agilent and Keithley, for ease of integration and testing.

5 TURNKEY SOLUTIONS SemiProbe also offers full turnkey double sided probing solutions with custom test software and instrumentation to meet your specific test requirements. Our modular Probe System for Life enables you to create complex and customized test configurations requiring multiple sources of stimulation to meet your most challenging test and measurement configurations at cost effective prices. Copyright 2013 SemiProbe, Inc. All rights reserved. Probe System for Life and SemiProbe are registered trademarks. Lab Assistant, WIS Wafer Inspection and Pilot control software are trademarks of SemiProbe, Inc. All other trademarks are the property of their own respective owners. 276 E. Allen Street, Winooski, VT P: F: