esd11 · 2011. 8. 3. · title: microsoft powerpoint - esd11.ppt created date: 10/26/2001 2:44:50...
TRANSCRIPT
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• ESD damage often occurs in manufacturing
• Proper monitoring of ESD exposure can:– isolate ESD occurrences– identify exposed parts– alert personnel of ESD problems– provide valuable statistics
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• The most expensive place for ESD damage
• Discharges happen at many steps in IC handling
• If an IC was exposed to significant level of ESD, it shouldn’t be shipped
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• IC is picked up from the input tray• IC is placed in the input shuttle• IC is placed in the test socket• IC is lifted from the test socket• IC is placed in the exit shuttle• IC is placed in the output tray
After IC has been tested.No means of detecting failures at this point
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• There are numerous discharges in any tool –when two metal parts come in contact, there is a discharge
• Difficulties in associating specific discharge with specific action of the tool and specific IC
• Tools move – variations in distance from antenna produces variations in readings
• Tools work fast – detection must be real-time
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• Bring antenna as close to the “action” as possible to improve signal-to-noise ratio
• Keep antenna at constant distance from the “action” for consistency of results
• Synchronize ESD occurrences with specific action of the tool to ignore extraneous events
• Provide supporting circumstantial evidence when possible to further identify relevant events
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Specially-designed antenna contains all RF sensitive circuit inside and can communicate to EM Aware via regular wires already present in the handler. In case of Epson 6000/6400 handler, remote antenna uses spare flex cables connecting robotic arm to the controller.
Antenna is placed directly on the robotic arm as close to the point of contact between the IC to the handler as possible
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Antenna placed directly on the moving robotic arm keeps constant distance between the ICs and the antenna
Near the test socket it is impossible to mount antenna on the moving arm. However the following placement assures reasonably constant distance between sockets and the antenna
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• Relevant discharges to the IC happen only when IC is being picked up or put down
• Enabling EM Aware monitoring only during these “windows” eliminates extraneous ESD occurrences
• Signal is taken from vacuum relay that controls release or pick up of the IC
• Such signals are generally available in almost any tool
• EM Aware has a built-in data buffer that allows looking at the data before and after the release/pick-up event
Trigger
Measurement Window
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• Evaluation has been done whether presence of static field near the placement of the IC is indicative of the discharge at that location
• There wasn’t sufficient correlation found between static field measurements and ESD Event occurrence in real-life situations
• One of the probable reasons is that the IC is extremely small in comparison to normally-grounded metal parts of a handler and it is difficult to detect any noticeable charge on the IC in situ.
• More research is needed to assure validity of data
• Can be very valuable for wafer and photolithography handling due to high voltages and large size of objects
Both ESD Events and static field measurements are done with the same
instrument
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• Integration is highly beneficial to the user. • It involves the following:
– Tool provides signal to ESD monitor in regards to the window of measurements
– ESD monitor provides magnitudes of ESD Events to the tool via chosen protocol (i.e. RS232, etc.)
– Modification to the tool’s software are made to respond to data from ESD monitors.
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• When IC handler is programmed for a specific IC, two ESD levels are entered: damage level and latent damage level.Example: Damage level: 200V CDM Latent damage level: 120V CDM
• If the strength of the ESD Event exceeds damage level, IC is placed in different tray and is not shipped.
• If the strength of the ESD Event is less than the damage level, but above latent damage level, the IC is automatically re-tested.
• If too many high-energy discharges occurred within short period of time, an alarm can sound, indicating problem in the handler.
• Statistics on ESD environment can be collected.
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• Three ESD monitors are installed: input arm, test sockets, output arm
• Each ESD monitor communicates to the handler individually
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• IC handler is just one of the tools that can benefit from ESD control.
• Examples:– Photolithography– Wafer handling
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Vladimir KrazCredence Technologies
[email protected]. 831-459-7488
www.credencetech.com