Dynamic Analysis by Laser Stimulation (DALS)

Dynamic Analysis by Laser Stimulation (DALS)
With the recent miniaturization and high performance in LSIs, the failure mode itself has become more
complex. Not only the analysis of current leakage failures in static mode, but also the one of functional
failures in combination with LSI testers has become necessary.
Dynamic Analysis by laser stimulation is a newly introduced method to localize functional failures in a LSI
by observing its operating status (Pass/Fail) change. This document describes the optional function
"Dynamic Analysis function kit (DA function kit)" to carry out such innovative analysis with uAMOS and
■ Overview of Dynamic Analysis by Laser Stimulation
Each device has a characteristic of the "drive voltage-operating frequency (Shmoo Plot)" which expresses the operating status (Pass/Fail).
In case of a device having functional failures, it shows different characteristic compared to a good one (see the figure below). When
driving a device under the conditions around the Pass/Fail boundary and irradiating it by 1.3 μm laser, the characteristics of the Shmoo
Plot changes at a failure points (defective transistors, voids, etc.) due to the thermal effect by laser irradiation. That leads the change of
Pass/Fail status of the device. By reading the status change as a signal and expressing it as an image, the location related to the
functional status change can be identified.
With the "DA function kit", localization of the root cause of functional failure can be done much quickly and easily.
Concept of the analysis of a failed device by utilizing the "drive voltage – operating frequency" characteristics
Analysis done by driving
an LSI under conditions
at the boundary
* The Pass/Fail status
changes as a reaction to
the laser stimulation
LSI tester
Pass/Fail map
corresponding to laser scan
Pass/Fail status
Failure location
Status changes due to
laser heat
Change in status in reaction to
the laser = failure location
Analysis examples
Analysis of an SRAM having insufficient
voltage margin
For a SRAM that becomes defective over 4 V at VDD,
DALS analysis was carried out. The Pass/Fail changes
was 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).
Change from
Fail to 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 signal
Data furnished by: Mr. Seigo Ito, Fujitsu Corporation
Change from Fail to
Pass due to a delay
caused by laser.
Dynamic Analysis function kit (A9771 series)
In order to carry out Dynamic Analysis by Laser Stimulation, Dynamic Analysis
function kit (A9771) shall be added on μAMOS or PHEMOS series.
* In case of retrofitting this kit, modification of the system may be required.
• Tester signal (Pass/Fail) input and imaging
• External control of the scanner by tester signals (loop trigger)
* Refer to the right figure for tester connections.
Full flexible scanning function
• Multi Area Scan
Laser scan area can be set up to 30 areas with necessary size,
scan speed and direction, which makes measurement time much
shorten compared to whole area scan.
• Laser mask
Laser mask area can be set up to 30 areas to skip scanning.
Scan specification
Tester I/F specification
Three ports are prepared as tester signal inputs
(Port shall be selected depending on analysis mode)
Tester signal
Pass/Fail signal
Tester trigger
Timing trigger for data latch
Scan direction*2
Loop trigger
External control of the scanner with test loop trigger
Pixel rate*2
* Inputting Pass/Fail signal into the tester signal connector is the minimum set-up
to carry out dynamic analysis.
Input conditions and trigger signal conditions
Input voltage range
± 5 V (in analog mode)
Trigger level
1.5 V (voltage level during trigger detection)
Input impedance
50 Ω
Scan area
Laser mask
Max. 30
Max. 30
16 to 512 (same in X and Y axis)
Any position within the field of view.
0 ,90 ,180 ,270
Not available
128 to 128 000 μs/pixel
Not available
*1: In multiple of 16.
*2: Each area can be set independently.
Analysis examples
Set up 3 scan areas and execute
scanning only in these areas.
Minimum trigger width Trigger width min. 100ns to max. 10ns
*Trigger level can be set in 0.1V step within the range of +/- 4V.
Input impedance can be changed to 4Ω.
For more details, please contact your local sales written below.
Detects DALS signal
in each set area.
Set up 3 scan areas
and 1 laser masked area.
Reference document
[1] E.I. Cole Jr. et al., Resistive Interconnection Localization,
ISTFA 2001, p.43-50
[2] M.R. Bruce et al., Soft Defect Localization (SDL) on ICs,
ISTFA 2002, p.21-27
[3] F. Beaudoin et al., Laser Stimulation Applied to Dynamic IC Diagnostics,
ISTFA2003, p.371-377
Laser scan skips the
masked area.
★ PHEMOS is registered trademark 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.
© 2009 Hamamatsu Photonics K.K.
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