WAFER PROBER MODEL. IR-OBIRCH analysis system Infra Red - Optical Beam Induced Resistance CHange AMOS -200

Transcription

1 WAFER PROBER MODEL IR-OBIRCH analysis system Infra Red - Optical Beam Induced Resistance CHange AMOS -200

2 IR-OBIRCH Analysis System The μamos is a semiconductor failure analysis system which uses IR-OBIRCH method for localization of leakage current path and observe the abnormal resistance part of contacts (via contact) in LSI devices. Artificial Shortage Artificial Shortage Artificial Shortage Current Line Current Path Refractive image (Backside observation) Objective lens: NIR 100 Voltage: 4.8 V Current: 1 ma OBIRCH image or PRINCIPLE OF OBIRCH ANALYSIS Laser : = 1.3 μm I A1 Laser (backside) A1 Laser (front side) Heated Si-sub. or V V= R I Leakage Current Path I ( R/V)I 2 I T, TCR *Depends on defects and materials When the interconnect line through which the current is flowing is irradiated by an IR laser beam, the heat generated causes the resistance to increase, which in turn reduces the current. In an OBIRCH image, this is displayed as a dark area. (See the above left photo.) If a void or defect exists in the line, heat conduction in the affected areas is changed in comparison to the normal areas, so that the temperature is different. These areas can be displayed in the contrast along the OBIRCH image. Areas displayed as bright on the OBIRCH image have a negative temperature coefficient of resistance (TCR) for the material configuring the areas, indicating that the heat generated by the IR laser beam has caused the current to increase. I : Current before laser irradiation Defects in Metal Line V : Applied voltage I : Current change due to laser irradiation (when constant voltage is applied) OBIRCH signal V : Voltage change due to laser irradiation (when constant current is applied) R : Resistance increase with the temperature increase due to laser irradiation T : Temperature increase due to laser irradiation TCR : Temperature coefficient of resistance MAIN APPLICATIONS Localization of leakage current path IDDQ failure analysis Detection of metal defect Inspection of defect in the metal line (void, Si nodule) Inspection of abnormal resistance part at contact hole (via contact) Metallization process monitoring * IDDQ (Quiescent power supply current): IDDQ is the quiescent power supply current that flows after the MOS transistor switching is complete. 2 FEATURES High spatial resolution image Backside observation (λ=1.3 μm) Observation of high doped substrate (Epi-sub.) Using an infrared laser (wavelength: 1.3 μm) means that no OBIC signal is produced in the semiconductor field, which enables the OBIRCH signal caused by the defect to be detected. Under macro lens, failure locations in a DUT (Device Under Test) with a chip size of up to 15 mm 15 mm.

3 MEASUREMENT EXAMPLES DRAM, Vdd-GND leakage current failure analysis OBIRCH image The leakage current path is displayed in dark contrast and the defect location is displayed in bright contrast. Observation result under high magnification (OBIRCH superimposed image) The bright contrast was detected between the AI lines. Cross-sectional TEM image of defect location Short circuit exists due to remaining barrier metal. Data supplied by Dr. Kiyoshi Nikawa (NEC Electronics Corporation) IDDQ failure analysis OBIRCH image (Superimposed) Interconnect where current is flowing (sections where the OBIRCH signal has decreased) are displayed in green, and shorted locations (sections where the OBIRCH signal has increased) are displayed in red. Data supplied by Dr. Kiyoshi Nikawa (NEC Electronics Corporation) Objective lens: NIR 5 Voltage: 4.8 V Current:1 ma 3

4 IR-OBIRCH Analysis System MEASUREMENT EXAMPLES Contact failure: Via contact areas have high resistance Detection of a faulty contact among a number of contacts Data supplied by Dr.P.Jacob (EMPA in Switzerland) OBIRCH image (Superimposed) Cross-sectional SEM image of defect location Short circuit between lines: Short circuit due to remaining polymer Example of short circuit due to remaining polymer between the first and second layers Data supplied by Dr.P.Jacob (EMPA in Switzerland) OBIRCH image (Superimposed) Cross-sectional SEM image of defect location Function failure: Void in lines Identification example of defect location causing function failure in an LSI chip The location where a void exists in the lines has been detected. Data supplied by Dr.P.Jacob (EMPA in Switzerland) OBIRCH image (Superimposed) Cross-sectional SEM image of defect location 4

5 SPECIFICATIONS Applicable device Wafer* Packaged IC Obtaining laser scan images Reflected images and OBIRCH images are obtained, and then both images are superimposed Surface Diced chip to 300 mm wafer Backside 200/300 mm wafer (other sizes can be handled with the available options) * According to the specifications of the prober used Surface IC that opened the chip surface Backside IC that mirror polished the Si substrate Confocal laser microscope Laser* Laser diode High power laser (option) Lens magnification 1 2 Scan speed (s/image) The macro lens ( 0.8) can be switched with an objective lens (up to 5 types) Lens 0.8 : A : A : A8009 M-PLAN-NIR-5 M-PLAN-NIR-20 M-PLAN-NIR-50 NIR 50 : A High NA50 : A8018 M-PLAN-NIR-100 NIR 100 : A M-PLAN-NIR-100 HR G-PLAN-APO-NIR-100 HR Standard * 2 lenses can be selected among marked lenses * ** With glass thickness compensation function. ** * ** * * ** Optional Wavelength: 1.3 μm, output: 100 mw 8 16 Wavelength: 1.3 μm, output: 400 mw or more Laser diode (option) Wavelength: 1.1 μm, output: 200 mw (CW), 800mW (pulse) * Cannot use 2 lasers of the same wavelength. Numerical aperture Working distance (mm) μamos-200 Obtaining OBIRCH images Selectable among 3 modes: fixed voltage mode, fixed current mode, and micro current amplifier (fixed current type) mode, which are controlled by the software. Applied voltage Max. current Detectability Fixed voltage type 10 mv to 10 V 100 ma 10 na *1 Fixed current type 10 mv to 10 V 100 ma 5 μa *2 Micro current amplifier 10 mv to 25 V 100 μa 10 pa *1 *1 Minimum detectable pulse signal input into the amplifier *2 Calculated value This lens was specifically designed for infrared observations of wavelengths 1 μm or greater. Laser light-gathering efficiency is increased and pattern image resolution is improved with OBIRCH detection sensitivity and high magnification. Si substrate thickness correction function : 0 μm to 700 μm Glass thickness correction function : 0 mm/2 mm switching Evaluations results of high NA 50 objective lens (comparison of high NA 50 objective lens with M plan NIR 100 lens) NIR100 (NA0.5) High NA, 50 (NA: 0.75) Correction ring 0.4 Backside observations High resolution is achieved using the correction function for the glass thickness and Si substrate thickness. NIR100, 20 mv (1.74 ma) OPTION / SPECIFICATIONS A8018 High NA 50 objective lens High NA50, 20 mv (1.74 ma) Optical stage movement range* X Y Z ±20 mm ±20 mm +75 mm * These values may become smaller due to interference with the prober used and the sample stage. OBIRCH observations High sensitivity is achieved with a high numerical aperture (NA). 5

6 IR-OBIRCH Analysis System OPTIONAL Digital lock-in kit M10383 The M10383 Digital lock-in kit is a new function added to the OBIRCH analysis, in order to boost detection sensitivity by sampling one pixel into multiple data using lock-in processing. The M10383 allows acquiring a sharp and clear image in a short acquisition time compared to the A lock-in kit which uses analog processing method. Analog lock-in Digital lock-in Dynamic analysis by laser stimulation kit Due to the recent high LSI integration and increased performance, analysis of functional fail connected to an LSI tester has become necessary. Dynamic analysis by laser stimulation (DALS) is a new method to analyse device operation conditions by means of laser radiation. When a 1.3 μm laser beam in wavelength is radiated during device operation with a test pattern inputted from an LSI tester, the operating conditions change and the Pass/Fail condition of the device changes due to the heat generated by the laser at wiring faults such as voids or characteristic failed transistors. These changes are imported as signals and expressed as images, which shows the points causing timing delay and marginal defect, etc. Comparing analog lock-in with digital lock-in (short scan period) Analysis done by driving an LSI under conditions at the boundary * The Pass/Fail status changes as a reaction to the laser stimulation Time domain analysis In digital lock-in, the modulation cycle is divided by the number of samplings. Changes in an image over time can be shown (motion image display is possible) by constructing sliced images using this same subdivided timing data. This helps easily identify defect points based on the delay in the OBIRCH signal. This technique is shown in Figure 3, using TEG (test element group) metal as an example. Here the time domain analysis by digital lock-in shows that high-resistance points in the metal react more slowly to laser heat emission than other sections of metal. Number of samplings per cycle (32 data) Creating sliced images Creating sliced images Creating sliced images Creating sliced images from the same subdivided timing data Failure location Status changes due to laser heat LSI tester Image formation Pass/Fail status Pass/Fail map corresponding to laser scan Change in status in reaction to the laser = failure location Concept of the analysis of a failed device by utilizing the "drive voltage operating frequency" characteristics Analysis of an SRAM having insufficient voltage margin For an SRAM that becomes defective over 4 V at VDD, DALS analysis was carried out. The Pass/Fail changes were detected due to laser heat at three locations. Failure mechanism was further investigated with one signal. A change from Fail to Pass was indicated in a transistor of the timing circuit. A delay generated in the transistor switching turns the device into normal operation (Pass). Including the results of the investigations done on the other two locations, the cause was defined as insufficient timing margin between the sense amplifier signal and the word line signal. The problem was fixed by adjusting the timing of the sense amplifier signal slower and the word line Digital lock-in sliced images Fail ( ( Pass ) ) Current detection probe head This head indirectly detects current fluctuations of the power line connected to DUT from an external power source. The capability of using an external power supply enables observation of the devices requiring current of 100 ma or more and voltage of 25 V or more, which previous OBIRCH amplifiers could not perform. The lock-in unit shall be used as a set. 6 Change from Fail to Pass Change from Fail to Pass due to a delay caused by laser. Data supplied by Mr. Seigo Ito (Fujitsu Corporation) Fail ( ( Pass ) )

7 OPTIONAL Sequence software This function enables automatic measurement of OBIRCH observation with following the recipe to be set by a user. OBIRCH images can be sequentially measured and saved in the connection of a semi-automatic prober. Measurements under the condition with a LSI tester or an external power source are possible as well. Laser marker Failure location information can be easily transferred to another analytical instrument by marking the area of an identified failure location, or by marking around it. The laser marker uses a pulse laser and markings with a size down to Φ5 μm is possible when under a 100 lens. EXTERNAL CONNECTION Tester connection/obirch analysis Because the OBIRCH amplifier is equipped with a function to automatically switch between internal and external power sources, OBIRCH analysis can be performed when connected to an LSI tester by inserting the OBIRCH amplifier in the connection cables between the LSI tester head and the device (adapter board) as shown in the figure. * Analysis cannot be performed during dynamic action. The signal will be fixed in a poor state and analyzed. CAD navigation When performing problem analysis of complicated LSI chips on a large scale, it is possible to connect through a navigation software (FEI Knights, Schlumberger Limited, and Adovantest Corporation). This helps the study of the causes of problem locations by superimposing areas where detected or images over the layout diagram. In addition, the optical system of μamos-200 can be controlled externally using the CAD-navigation software. Example of connecting to a μamos tester Connector panel Tester/OBIRCH switching Coaxial cable Signal Connector board Vdd GND Adapter board Internal power source OBIRCH image (superimposed) With CAD navigation LSI tester OBIRCH amplifier 7

8 IR-OBIRCH Analysis System DIMENSIONS / WEIGHT Dimensions / Weight (including option) External dimensions and weight μamos main unit μamos control rack PC desk Width (mm) depth (mm) height (mm), weight (kg) , approx , approx , approx. 80 Utility Line voltage Power consumption Vacuum Compressed air AC 220 V (50/60 Hz) 3000 V A Approx. 80 kpa 0.5 Mpa to 0.7 Mpa LASER SAFETY Hamamatsu Photonics classifies laser diodes, and provides appropriate safety measures and labels according to the classification as required for manufacturers according to IEC When using this product, follow all safety measures according to the IEC. CLASS Ι LASER PRODUCT Description Label (Sample) Caution Label μαmos are registered trademarks of Hamamatsu Photonics K.K. Product and software package names noted in this documentation are trademarks or registered trademarks of their respective manufacturers. Information furnished by HAMAMATSU is believed to be reliable. However, no responsibility is assumed for possible inaccuracies or omissions. Specifications and external appearance are subject to change without notice Hamamatsu Photonics K.K. Web site HAMAMATSU PHOTONICS K.K., Systems Division 812 Joko-cho, Higashi-ku, Hamamatsu City, , Japan, Telephone: (81) , Fax: (81) , export@sys.hpk.co.jp U.S.A. and Canada: Hamamatsu Corporation: 360 Foothill Road, Bridgewater, N.J , U.S.A., Telephone: (1) , Fax: (1) , usa@hamamatsu.com Germany: Hamamatsu Photonics Deutschland GmbH: Arzbergerstr. 10, D Herrsching am Ammersee, Germany, Telephone: (49) , Fax: (49) , info@hamamatsu.de France: Hamamatsu Photonics France S.A.R.L.: 19, Rue du Saule Trapu, Parc du Moulin de Massy, Massy Cedex, France, Telephone: (33) , Fax: (33) , infos@hamamatsu.fr United Kingdom: Hamamatsu Photonics UK Limited: 2 Howard Court, 10 Tewin Road, Welwyn Garden City, Hertfordshire, AL7 1BW, U.K., Telephone: (44) , Fax: (44) , info@hamamatsu.co.uk North Europe: Hamamatsu Photonics Norden AB: Smidesvägen 12, SE Solna, Sweden, Telephone: (46) , Fax: (46) , - info@hamamatsu.se Italy: Hamamatsu Photonics Italia S.R.L.: Strada della Moia, 1/E Arese (Milano), Italy, Telephone: (39) , Fax: (39) , info@hamamatsu.it Cat. No. SSMS0004E05 OCT/2009 Created in Japan