ATE Thermal Protection Library/SemiTest/-40_Carl...– Sets hard/soft bins • Handler / Prober •...
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ATE Thermal Protection DIB based detection of thermal runaway
Transcript of ATE Thermal Protection Library/SemiTest/-40_Carl...– Sets hard/soft bins • Handler / Prober •...
ATE Thermal Protection
DIB based detection of thermal runaway
Agenda
• Problem Statement• Test Setup• Alternatives Tested• Solutions and Conclusions
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• DIB based mechanism to shut down a site to prevent damage to DIB– What is Thermal Runaway– What already exists– What needs to shut down– How Fast
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Problem Statement
Presenter
Presentation Notes
Customers have found a requirement not satisfied by our tester. The intent of this paper is to provide a DIB circuit that can be used in addition to the built in safeguards in order to create a second level of protection for DIB front end hardware
• As device heats, – internal resistances go down – Causing current to go up– Causing heat to go up
• So?– Probes can melt / weld to wafer -> $$$– Sockets can catch fire -> $$$$
• Internal safeguards already exist– Fold and Overload current limits
• Sometimes disabled by engineers
• Desire for another layer of protection– Generically stated as anything that can provide a logic 1 to indicate a fault
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Thermal Runaway
Presenter
Presentation Notes
Thermal runaway is a cycle where increasing heat reduces internal resistances, which increases current flow, which increases heat Chart shows dual-level alarms already built into DCVS. This can be used to explain the existing internal safeguards already in place. * Green shows a normal device, powering up DIB-caps first, then running device * Animation – on mouse click – red line shows steady state device that starts to run away. When it crosses T0, timer starts. Clamps engage, limiting power. At T2, the fold gate is set to gate off so the current goes to zero. Alternaltely, the gate off can be disabled so that the current would remain in the clamped state. Intent of presentation is to show that instrument has safeguards, but an extra layer of protection can be implemented.
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Test Setup
Used training DIB-strip for HSD signals, PPMU, DCVI
Proto-board used for FETs, switches, etc.
Created dib-strip for VSM signal access
Presenter
Presentation Notes
VSM was used for checkout, but concept applies to any DCVS instrument
• Pin IN used to simulate DUT triggered event
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Pattern used for synchronization
Alternatives• Interlock• DUT_Force• DIB_Force• Merge_Alarm
Criteria• Resets itself so next device can run• Doesn’t affect other sites• Independent of chip design• Shuts down bulk of current• Shuts down fast (<10ms)• Asserts alarm
– Shuts down other site resources– Sets hard/soft bins
• Handler / Prober• Datalog
• Doesn’t affect yield
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VSM Alternatives Tested
Presenter
Presentation Notes
HexVS also has the interlock, dut-force, and dib-force alarms. Merging is done internally on the HexVS, but since this was rejected anyway that really doesn’t matter here. Interlock rejected early because it affects all sites. In testing it was also found that it needed an IG-XL reset to bring the board back. In typical production testing this doesn’t happen. Using the signal in this way (that is, breaking the signal mid-job) caused IGXL to require a reset.
• Analog switch to break connection
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DUT_Sense
Presenter
Presentation Notes
Instead of resistor to ground, a pullup could be used which would force the voltage down. Pullup needs to go to a rail > 250mV over the force signal.
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DIB_Sense
Presenter
Presentation Notes
DIB sense is functionally similar – that it, if it senses that the voltage is more than 300mV away from the forcing voltage it triggers an alarm. The key difference here is that the DIB sense is *not* part of the feedback loop to the driving voltage. Because of this, breaking this line doesn’t affect the force voltage prior to shutdown.
• Kelvins connected to force
• FET used to tie bus to GND on event
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Alarm Bus
Presenter
Presentation Notes
Top pic shows VSM instrument. Bottom pic shows DIB circuitry used to test this bus. On VSM, Alarm bus is a logic signal that’s used to tell all instruments in the group that an alarm occurred.
• The Merge Alarm, sometimes called the alarm bus, causes supplies in merge group to shut down
• But – doesn’t call IG-XL alarm system– Other site resources
not shut down– Site not binned
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Merge_Alarm
• Interlock doesn’t reset without restarting IG-XL, shuts down all sites• Alarm bus doesn’t set alarm• DUT kelvin works, but presents voltage until alarm shuts off supply• DIB Kelvin best solution:
– Integrates with alarm system– Voltage stable until shutdown
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Conclusions
