Bergische Universität WuppertalPeter Gerlach

Building Pixel Detector Modules in Multi Chip Module Deposited Technology

IEEE Nuclear Science SymposiumRoma Oct.2004

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Originally…

Christian GrahNow at Desy Zeuthen(Berlin, Germany)

…this talk should havebeen given by my colleagueChristian Grah.

Here you can see, how he looks like, at least.

But if you would have met him during the last years, he probably looked as shown on the right picture!

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Subject of this talk

Application of a ‘thin’ film technology on a high energy physics detector.

Hybrid pixel detector (ATLAS, LHC, CERN)DefinitionGeometrical constrains

Thin film technologyExplanation of the processTypical dimensions

Introduce some prototypes build,gaining from a strong support of

The ATLAS pixel detector projectFraunhofer Institute IZM (Berlin, Germany)

Structures realisedResults optained

Laboratory and test-beam environment

Summary (How to…)

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Hybrid Pixel Detector

Three parts:Sensor

High quality silicon waferPiN structureSegmentation into ‘pixels’

Readout ElectronicsInterconnection

Sizes for e.g. ATLAS Pixel:Module 2x6cm²16 readout chips~50.000 pixels à 50x400µm

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Interconnect via Kapton-foil

3D designnote control chip and components on top

>500 wire-bonds per moduleSensor has to cover gaps in electronics

FE FE

SensorInterconnect„ATLAS Flex“

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Interconnect integrated

FE FE

SensorInterconnect

„ATLAS MCM-D“

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MultiChipModule-Deposited Technology

Spin-On BCB (Benzocyclobuthen)

Photolithographic structuring/exposure

Developing and stripping of unexposed BCB (soft-cure)

Sputtering of Cu – plating base layer

Spin-On and structuring of Photo-Resist

Electroplating of Cu – layer

Stripping of Photo-Resist and etching of plating base

Spin-On next BCB layer ( h) = a) )

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MCM-D wafer after processing

10cm

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MCM-D structures

contact to signal bus system

contact for Probecard(process monitoring)

contact to power distribution system

pixel matrix - feedthroughs

Different scales!

75µm75µm

50µm

500µm

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MCM-D Module Prototype

MCC

readout chips

VBias (backside)

NTC, capacitors and LVDS

termination

Kapton flex circuit

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MCM-D, geometry

Up to 5 copper layers:magnetron sputtered up to 300 nm Ti:W/Cuadditive electroplatingup to 3 m Cu

Minimal width 15µm spacing 15µmFinal metallisation:

5m Cu/200nm Au5m Cu/Ni/200nm Au

“Spin-on” polymer: BCB (Benzocyclobutene / DOW:CYCLOTENE™)

PhotosensitiveSpecific dielectric constantr= 2.7Process temperatures :

1h 220C per layerlast layer 1h 250 C

Thickness / layer 2 - 6 mVia >22 m, Pad >25µm

conductor layers dielectric layers

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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MCM-D Module Prototype

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Geometrically Optimized Pixel Sensor

conventional sensor layout:(inter-chip region)

optimized sensor layout (Equal-sized Bricked):

drawn: sensor layout, top metal layer special thx to Tilman Rohe

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Routing structures

200µm20µm

50µm BCB is etched for visualisation(except of some pillars)

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Equal - Sized - Bricked single chip assembly: distribution of threshold

0 320 640 960 1280 1600 1920 2240 2560 28800

500

1000

1500

2000

2500

3000

3500

Equal Sized Bricked Design

Schw

elle

[e- ]

Kanal (Spalte*160+Reihe)

0 500 1000 1500 2000 2500 3000 3500 40000

200

400

600

800

1000

1200

1400

Chi^2/DoF = 146.42943R^2 = 0.99766 xc 2085.66048 ±0.88028w 159.01999 ±1.66184

Ein

träg

e/B

inSchwelle [e-]

Equal Sized Bricked Design

threshold / e-

thre

shold

/ e

-

Counts

per

bin

Pixel number

No influence of the thin film structures, nor the bricked sensor structure visible

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Equal - Sized - Bricked single chip assembly: distribution of noise

0 320 640 960 1280 1600 1920 2240 2560 28800

100

200

300

400

Equal Sized Bricked Design Standard Sensor Design

Rau

sche

n [e

- ]

Kanal (Spalte*160+Reihe)

0 100 200 300 4000

200

400

600

800

1000

1200

EQB:

1= 184.68 ±0.51

1= 36.01 ±1.06

Standard:

2= 180.85 ±0.76

2= 36.69 ±1.63

Equal Sized Bricked Design Standard Sensor Design

Ein

träg

e/bi

n

Rauschen [e-]ENC / e-

EN

C /

e-

Counts

per

bin

Pixel number

No influence of the thin film structures, nor the bricked sensor structure visible

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Testbeam data

H8 Testbeam at SPS (CERN)

primary: 450 GeV protons

Data was mainly taken with:180 GeV pionsTelescope with 4 x 2 layers of strip-detectors (Strip pitch: 50 µm)

H8 Telescope system

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Charge collection of equal sized bricked base-cell

Charge collectionvery uniformwith expected behaviour of bias grid contacts

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Charge collection forsingle, double and triple hits

Slight charge deficitof double hits is dueto high threshold(chosen by mistake).

This fits to the expected/seen numberof triple hits.

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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Summary

nicehigher manageability and better handling of a modulebump bonds only (no wire-bonding)sensor cell geometry can be optimizedreduced assembly stepsrework of full assembled module possible (detach and reattach of chips)options of final metallization (Cu/CuNi/CuAu/CuNiAu/PbSn) allow different technologieshigher degree of automation during production

not so niceincreased size (but reduced height)lower testability (reduced access to inter-chip signals)high complexity of the process (find vendor)

Experience with MCMD

successfully operated a radhard pixel detector MCMD moduleperformance compatible with Flex modulesCooling ok (chip up design)successfully increased thin film yield

defect tolerant design with reduced "critical" area

high demand on cleanliness (includes new machinery and optimization of process flow)

20.Oct. 2004 NSS Roma 2004; P.Gerlach (Ch.Grah);Multi Chip Module Deposited

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How to build MCMD Modules:

Sensor:1 module per 4” wafersensor dedicated for MCMD (including dicing streets and 1cm rim)Make use of geometrical optimizations!

Electronics:Known good die problem of Multi-Chip Moduleis relaxed by the reworking optionprototyping restrictions: changes in pin-out are expensive (money and time)!thinning: depending on the interconnection technique (reflow)thin chips get bowed during heating up

Thin Film Design:defect tolerant design recommendedset of design rules has been developed

Metal-lines: 15/15um; Via 22umLayer number vs. effort is not linear!

Thin Film Processing:automation <=> cleanlinessindustry keeps increasing wafer size

NO PROBLEM for MCM-D, but4 inch wafer (Sensors) processing might become a problem