Difference: Connectivity (5 vs. 6)

Revision 62014-09-25 - KateDoonan

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META TOPICPARENT	name="Tasks"

The connective task has two main areas of work, TSV and flip-chip bonding development.

Flip-chip bonding at STFC-RAL

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STFC/RAL are developing a fine pitched Indium flip-chip process. The samples first have aunder bump metal (UBM) layer deposited upon them where the bump is to be grown. The UBM used to date is Ti/W, Ni, Au. The Ti/W is an adhesion layer to the Aluminium pad of the device. The nickel is the solderable metal layer and the Au is an oxidation barrier. The indium is deposited in a theraml reactor at RAL. The Indium is heated under vacuum and condenses on the sample that is held at a lower temperature. The samples can then be flip-chipped bonded. The flip-chip process is to work at room temperature or slightly elevated temperatures.

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STFC/RAL are developing a fine pitched Indium flip-chip process. The samples first have an under bump metal (UBM) layer deposited upon them where the bump is to be grown. The UBM used to date is Ti/W, Ni, Au. The Ti/W is an adhesion layer to the Aluminium pad of the device. The nickel is the solderable metal layer and the Au is an oxidation barrier. The indium is deposited in a thermal reactor at RAL. The Indium is heated under vacuum and condenses on the sample that is held at a lower temperature. The samples can then be flip-chipped bonded. The flip-chip process is to work at room temperature or slightly elevated temperatures.

There is some worry that the Indium bumps require more pressure to form a bump than should be the case. One suggestion for this high pressure is that the gold used in the UBM is moving into the Indium and forming an Indium/Gold alloy which requires more force to deform. A SEM/FIB/EDX study of an Indium bump formed on a silicon substrate was performed in Glasgow to try and test the hypothesis that the gold had moved into the Indium. The report is found here:

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The report's conclusion is that the gold does indeed appear to have migrated into the Indium bump.

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Frist Indium Flip-chip bonded FE-I4

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First Indium Flip-chip bonded FE-I4

The first indium assembly wafer ID : VMB6NJH die 3

Sensor : CPII Live FE-I4 MPI Guard IBL

Indium_BumpYield_28032014.pptx: Bump Yield Studies March 2013

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Indium Flip-Chipped Modules September 2014

Indium bumps require pressure only to make connections so no high temperatures are required to melt alloy, which reduces bowing effects.

Modules under test:

ID	Bond Force	Comment
14-07-24-S2	20kg	biased to 40V
14-07-25-S2	10kg	short on VDDA line
14-07-25-S4	5kg	biased to 40V (operated at 20V)

IV Scans

IV Scans on wafer and after processing

Screen_Shot_2014-09-25_at_14.50.52.png

Characterisation

USBPix

Bump yield studies performed in August 2014 by Dan Smaranda and Richard Bates

21082014_Indium-DanSmaranda.pdf

RCE System

Bump yield studies performed in September 2014 by Kate Sexton

All modules tuned to and operated at 3000e threshold, 10ToT @ 16ke reference charge.

Bump Yield assessed by performing Threshold Scans with and without sensor bias and performing source scans with Strontium-90 beta source and Americium-241 60keV gamma ray source.

Indium-Characterisation_0914.pptx

Bump yield results

Module	Bond Force	Bump Yield (Sigma plot)	Bump Yield (Source Scans)
Indium1	?	99.48%	99.38%
14-07-24-S2	20kg	82.85%	82.35%
14-07-25-S4	5kg	23.37%	22.54%

Comments

TSV

Details of the TSV activity are given on the next page.

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META FILEATTACHMENT

attachment="Report_on_SEM_Secondary_electron_images_and_EDX_measurements_on_In_bumps_from_RAL.docx" attr="" comment="Report on SEM for Indium bump from RAL" date="1339684065" name="Report_on_SEM_Secondary_electron_images_and_EDX_measurements_on_In_bumps_from_RAL.docx" path="Report on SEM Secondary electron images and EDX measurements on In bumps from RAL.docx" size="10127772" stream="Report on SEM Secondary electron images and EDX measurements on In bumps from RAL.docx" tmpFilename="/usr/tmp/CGItemp39532" user="RichardBates" version="2"

META FILEATTACHMENT

attachment="Indium_BumpYield_28032014.pptx" attr="" comment="Bump Yield Studies March 2013" date="1396510064" name="Indium_BumpYield_28032014.pptx" path="Indium_BumpYield_28032014.pptx" size="651796" user="RichardBates" version="1"

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META FILEATTACHMENT	attachment="21082014_Indium-DanSmaranda.pdf" attr="" comment="Bump Yield Studies by Richard Bates and Dan Smaranda 08/2014" date="1411652282" name="21082014_Indium-DanSmaranda.pdf" path="21082014_Indium-DanSmaranda.pdf" size="613055" user="KateDoonan" version="1"
META FILEATTACHMENT	attachment="Indium-Characterisation_0914.pptx" attr="" comment="Bump yield studies by Kate Sexton" date="1411652373" name="Indium-Characterisation_0914.pptx" path="Indium-Characterisation_0914.pptx" size="593882" user="KateDoonan" version="1"
META FILEATTACHMENT	attachment="Screen_Shot_2014-09-25_at_14.50.52.png" attr="" comment="IV Characteristics of Modules before and after processing" date="1411653108" name="Screen_Shot_2014-09-25_at_14.50.52.png" path="Screen Shot 2014-09-25 at 14.50.52.png" size="159806" user="KateDoonan" version="1"

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