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GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 5D: ASIC Procurement

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Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 5D: ASIC Procurement. Overview. LAT-PS-1279: General Overview of Tracker ASIC Procurement Design specifications: LAT-SS-00169, LAT-SS-00170 (released) Wafer procurement from MOSIS/Agilent

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Gamma-ray Large Area Space Telescope

GLAST Large Area Telescope:

Tracker Subsystem

WBS 4.1.4

5D: ASIC Procurement

  • LAT-PS-1279: General Overview of Tracker ASIC Procurement
  • Design specifications: LAT-SS-00169, LAT-SS-00170 (released)
  • Wafer procurement from MOSIS/Agilent
    • LAT-PS-1201 (released): Front-end readout chip (GTFE)
    • LAT-PS-1222 (released): Readout controller chip (GTRC)
    • Fabrication completed this month (submitted December 2002)
  • Wafer probing and ASIC screening at UCSC
    • LAT-PS-1250 (release in progress)
  • Wafer lapping, dicing, and inspection
    • LAT-PS-1321 (draft spec in progress)
  • Wafer lot acceptance testing (MIL-STD-883E, Method 5007.6)
  • Radiation testing (See Presentation 2B)
    • LAT-TD-1325 (draft)
  • Destructive physical analysis
  • Electronics qualification and acceptance testing
wafer procurement
Wafer Procurement
  • Vendor: The MOSIS Service of the USC ISI.
    • Checking of design files, including DRC on the layout
    • Subcontracting for fabrication of the masks (Dupont)
    • Subcontracting the wafer fabrication
      • HP/Agilent 0.5 m, 3-metal, epitaxial process (AMOS14TB)
    • Thorough electrical testing of process monitors on each wafer
      • MOSIS guarantees that the wafers meet the Agilent process specifications
      • MOSIS provides the test results in the form of e.g. physical transistor parameter, sheet resistance, etc.
    • Extraction of Spice model parameters for each wafer lot
      • BSIM3 V3.1 models for design verification, especially in case problems arise
    • Shipment of wafers to SLAC
  • LAT specifications: LAT-PS-1201 and LAT-PS-1222 (released)
wafer procurement status
Wafer Procurement Status
  • The flight wafers are locked in a dry-nitrogen cabinet in the wafer-probing clean-room at UCSC.
  • One wafer of each chip type was sacrificed to yield chips for testing.
asic screening
ASIC Screening
  • Procedures, QA provisions, and travelers: LAT-PS-1250
  • Detailed descriptions of the test vectors:
    • LAT-TD-247 for the GTFE
    • LAT-TD-248 for the GTRC
  • Carried out in a cleanroom at UCSC
    • Conforms with the LAT contamination control plan (LAT-MD-404)
    • Conforms with ESD controls in LAT-MD-228 and NASA-STD-8739.7
    • Cascade automated probe station
    • Custom probe cards interface to the VME readout
    • Bad dice are automatically ink marked
    • 100% testing of all functionality
    • GTFE performance testing (to extent possible without SSDs)
    • Data archived in an MS Access database
em asic screening
EM ASIC Screening
  • Only limited wafer probing was achieved with the Engineering Model ASICs:
    • The GTRC probe card had fatal problems (such as the probes being put on backwards by the vendor) and did not work. A new card has since been built and is functional at the full clock rate.
    • The GTFE probe card could only operate at 2 MHz, due to excessive capacitive loading on the IC output drivers. The chip-to-chip outputs could not be tested at all. The probe card design has been updated and new cards built to correct these problems. It now operates at 20 MHz+ and tests all functionality.
    • The probe station operation was not integrated with the test program. We have since updated out software to enable fully automated processing of an entire wafer plus automatic marking of bad dice.
  • Incomplete IC testing caused problems during the EM MCM assembly. The wafer test system is now much improved and is ready for flight production.
flight asic screening
The Cascade automated probe station at the Santa Cruz Institute for Particle Physics.

Located in a small clean room that is dedicated solely to wafer probing.

In addition, it is under a downflow hood with extra HEPA filters.

The work area has recently been upgraded to conform to LAT contamination control and ESD control requirements.

Workers have been formally trained in ESD and cleanroom procedures.

Wafers are stored in a locked dry-nitrogen cabinet in this room.

Flight ASIC Screening
flight asic screening1

Final versions of both probe cards are in hand and tested.

Software details are being finalized and tested and the software put under configuration control.

The procedure (LAT-PS-1250) is in the review/release process.

The clean room has been updated for procedures, ESD, etc. and was inspected.

A date is set to train personnel in clean-room and ESD procedures.

Flight ASIC Screening

New GTRC probe card under test in a manual probe station.

wafer lapping dicing
Wafer Lapping & Dicing
  • Specification, LAT-PS-01321, in progress.
  • A single vendor will do the following:
    • Lap the wafers from 610 microns to about 270 microns. This improves the wire bonding on the MCM
    • Dice the wafers to our specified die size
    • Pick the dice, separate the chip types, and separate bad dice from good dice (according to ink markings) into waffle packs.
    • Visually inspect the dice to reject
      • Scratches or chipped edges
      • Inked dice
      • Dice of the wrong chip type
    • Ship the completed waffle packs to Teledyne
    • Perform wafer lot acceptance testing on each lot according to MIL-STD-883E, Method 5007.6
asic qualification acceptance
ASIC Qualification & Acceptance
  • Qualification and acceptance testing of the ICs cannot be done on the bare dice in any practical way.
  • Therefore, the qualification and acceptance tests are those pertaining to the completed MCMs (Presentation 7C).
  • Qualification:
    • 38 MCMs from the initial production, including 2 for DPA.
    • DPA of some bare dice.
  • Acceptance: all MCMs
    • Complete functional tests of finished MCMs
    • Noise, threshold, and gain performance (without the SSD load)
    • Thermal cycles to acceptance levels
    • Burn-in
  • MCMs failing acceptance testing or not 100% functional after burn-in (except for possibly <<1% bad individual amplifier channels) must be discarded.
  • Radiation testing (Presentation 2B): ICs mounted on mini MCMs.