13 th IPRD Siena

7. October 201313th IPRD Siena

W. Treberspurg, U. Bartl, T. Bergauer, M. Dragicevic, E. Frühwirth, S. Gamerith, J. Hacker, A. König, F. Kröner, E. Kucher, J. Moser, T. Neidhart, H.-J. Schulze, W. Schustereder, T. Wübben

A new vendor for high volume production of silicon particle detectors

Outline

Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 1

1. Overview of the Project

2. The different Sensor Structures

3. Summary of the Electrical

Characterization

4. Summary of Beam Tests

5. Outlook and Summary


1. Project Overview: Silicon Sensors

History: Silicon is used for detectors since

the 50ies Silicon strip detectors have been

first used in the CERN experiment NA11 in the 80ies

Today up to 200 m2 (CMS) of silicon sensors are used

The same amount can be expected for the upgrades of CMS and ATLAS

Wafer Size: NA11 started with 2” and 3” Today 6” (150 mm) is standard Introduced in the Industry in the

80ies


1. Project Overview: Different Vendors

Small scale R&D production: Many institutes and companies are able to

produce a few 10-100 wafers per year 6 inch is usually available at many sites The sensors differ in a broad spectra of

quality and price Large scale commercial production:

Currently only one company is able to produce a few 1.000 – 10.000 high quality wafers per year

Possible new producer: Infineon Production on thinned 8 inch wafers could

be possible

Dual or multi-source strategy would be preferable


1. Project Overview: Infineon Austria

General: Infineon holds 26700 employers at different sites around the world

Villach (Austria): The Austrian site in Villach holds 2400 and produces 50.000 wafer per week

Villach is aimed for Frontend Production and R&D The Clean room facilities just extended to over 10.000m2

Pilot production lines are developed at Villach, E.g.: worlds first power devices on 12 inch wafer (Oct. 2011)


1. Project Overview: The Collaboration 1

End of 2009: Start of project (intense discussion on technical details) Begin of 2011: Decision of baseline and milestones

Baseline: Wafer Material: 6” n-type, 300 µm

thickness, Approx. 1.2 kΩcm resistivity Process Specifications: Standard p-on-

n technology, AC coupled strips, SiO2/Si3N4 sandwich dielectric, poly silicon resistor biasing

8 photo masks (one for patterning of Si3N4)


1. Project Overview: The Collaboration 2 August 2011: HEPHY finished the final mask

design for the first produced batch October 2011: Production of the first batch

started April 2012: The wafer have been characterized

in Vienna October 2012: Beam tests and irradiation

studies Beam tests at the SPS accelerator at CERN Gamma irradiation at SCK-CEN Mol, Belgium

December 2012: Second batch with the same masks and other split groups is produced and delivered in February 2013

July 2013: Start of irradiation studies with protons (in Karlsruhe at KIT) and neutrons (in Vienna at ATI)

September 2013: Production of third batch with new (modified) masks CMS Track Trigger Prototype Module

with 2 Infineon Baby Sensors


1. Project Overview: Comments

The production in the clean room was accompanied by our diploma students The first batch was accompanied by Edwin Frühwirth The third batch was accompanied by Axel König We were discussing all technical details directly with the engineers and are involved

in the process as far as possible Since the beginning of 2010 we held weekly telephone conferences We finally received every wafer from the production batch (except for one wafer,

damage due mishandling)

no hidden losses

In the cleanroom

Outline





Characterization




2. Wafer Structures: The STL Sensor

The large standard sensor (STL): Size: 64 x 102 mm Active size 61.5 x 99.6 mm 512 strips (4xAPV) 120 µm pitch 20 µm strip implant width

Motivation: The large sensor has the same dimension

as the current CMS sensors

Wolfgang Treberspurg (HEPHY Vienna)7. October 2013

2. Wafer Structures: The STS Sensor

10

The small standard sensor (STS): Size: 23 x 50 mm Active size 20.6 x 48.3 mm 256 strips (2xAPV) 80 µm pitch 20 µm strip implant width

Motivation: The STS sensor is mainly dedicated for

building modules This sensors have been used at tests with

a high energy beam

Wolfgang Treberspurg (HEPHY Vienna)7. October 2013

2. Wafer Structures: The STI Sensor

11

The standard irradiation sensor Size: 7 x 42.5 mm Active size 5.3 x 40.7 mm 64 strips (0.5xAPV) 80 micron pitch 20 strip implant width

Motivation: This sensors have been designed for irradiations in the TRIGA Mark II reactor in Vienna with a narrow irradiation tube The STI sensors have been used for R&D investigations


2. Wafer Structures: Split Groups

Wafer No.

Split1-Split2

Wafer No.

Split1-Split2

01 A-A 14 C-A02 A-A 15 C-A03 A-B 16 C-B04 A-B 17 C-B05 A-C 18 C-C06 A-C 19 C-C07 B-A 20 D-A08 B-A 21 D-A09 B-B 22 D-B10 B-B 23 D-B11 B-C 24 D-C12 B-C 25 D-C

First Batch: 25 wafers produced with photo masks

designed by HEPHY Wafer 13 not delivered because of mechanical

damage Wafer 04 not diced and used for presentation

Split Groups first Batch: 23 wafers split into 12 groups to test different

process parameters First split: Gate Oxide (4 groups A to D) Second split: backside n+ implant diffusion

(3 groups A to C)

Outline





Characterization




3. Electrical Characterization: Measurement Parameter

Global parameters: IV-Curve: Dark Current, Breakdown

Voltage CV-Curve: Depletion Voltage, Total

Capacitance

Strip Parameters: Strip leakage current Istrip

Poly-silicon resistor Rpoly

Coupling capacitance Cac

Dielectric current Idiel


3. Electrical Characterization: Global Values CV: The depletion voltage of structures

on all wafer is around 240 V IV: In general most sensors feature a low

dark current (7 - 30 nA/cm2) Many Sensors are stable up to 1000 V Sensors of the X-C split group feature

low current but early breakdown

STL: ~65 cm2 STS: ~11 cm2

1/C2 for all large sensors


3. Electrical Characterization: The STL Sensor

Istrip/Istripmedian

Cac/Cacmedian

Rpoly/Rpolymedian

The plotted values are normalized the median strip value of each sensor

Homogenous values Accumulation of anomalous

strips around strip no. 500 (and 416 for Istrip)

All split groups are affected


3. Electrical Characterization: The STS Sensor

Istrip/Istripmedian

Cac/Cacmedian

Rpoly/Rpolymedian

Homogenous values Accumulation of anomalous

strips around strip no. 222-248

Same behavior of anomalous strips as on other sensors

All split groups are affected


3. Electrical Characterization: The STI Sensor

Absolute values of measurement plotted

Accumulation of anomalous strips around strip no. 35-55

Same behavior. Increasing Istrip

Decreasing Rpoly

Decreasing Cac

STL: Istrip STS: Istrip


3. Electrical Characterization: Summary

• Criteria:• Istrip > 50 nA (for

STL) and Istrip > 25 nA (for STS)

• Idiel > 1 nA : short between dielectric and metal strip (Pinhole)

• Cac < 1.2 pF: Pinhole• Rpoly: deviation is

less than 20% from the median

• Results STL: • 65 strips of 11776

faulty 5.5‰• 68% of the faulty

strips from area around 500

• Results STS: • 418 strips of 5632

faulty 7% but• 95.3% of the faulty

strips from area around 235

• only 22 (3.9‰) outside bad area remain


3. Electrical Characterization: Affected Strips 1

Inter strip measurements on STI sensors: The inter strip resistance vanishes at

affected strips The inter strip capacitance decreases

A poor strip isolation at this area results in: Increased Istrip, as the leakage current of

more than one strip is measured The sum of all Istrip currents exceeds the

global dark current Decreased Rpoly , as the bias resistors

are some kind of shunted

STI

STI


3. Electrical Characterization: Affected Strips 2 The accumulation of affected strips is always

placed in the same distance to the sensor edge and hence dicing line

STI Sensors of the seconded batch with the same behaviour have been measured On the undiced wafer in Vienna The wafer has been sent to Villach (Infineon)

for dicing And has been measured again

The bad area is generated during the dicing process

STI STI


3. Electrical Characterization: An Explanation

All results indicate an accumulation of charge inside the silicon oxide

Based on that assumption tests with humidity could cure the affected strips

To simulate aging the STI sensor has been exposed 24 h to 180 degree

The sensor still stays cured

The different layer (Implant or Poly Silicon) show no problems

SiO2

Al Al

Al

Implant p+

Implant p+

Si n-type

Implant n+

STI

STI


3. Electrical Characterization: A possible Reason

Bare silicon exposed during later steps of the fabrication At contact holes in the DC pads Metal over etch was larger than

expected Bare silicon prone to

contamination Could be the reason for the

appearance of charge accumulation

Redesign with corrected overlap of contact holes. The new batch is in production

Remark: All layers have been remove by

etching for this picture, only bare silicon is left

Outline





Characterization

4. Summary of Beam Test



4. Results of Beam Test: The Setup

2 detector modules built with STS

sensors 2 detector modules built with strixel

sensors Readout chips (APV25) same as in

the CMS tracker Readout system is a prototype for

the Belle II experiment Detector modules were

Tested at CERN Gamma irradiated at CNK-CEN

Mol Tested again at CERN

Setup atCERN North AreaH6 beam line


4. Results of Beam Test: Sensor Sections

The bad strip area does not stand out clearly in beam profile and seems to be fully efficient

For a more detailed analysis the sensor has been divided into two sections: One good section (green) One bad section (red, strip no. 222 –

238)


4. Results of Beam Test: Different Sections The results indicate problems with the strip isolation at the “bad area”

Clusters are wider in “bad section” The eta distribution indicates an anomalous

charge sharing between the strips


4. Results of Beam Test: Gamma Irradiation

The modules have been gamma irradiation and tested again The gamma irradiation mainly effects the silicon oxide layer on the sensor surface Gamma irradiation seems to cure the problem, which fits well to the assumption of

accumulated charge inside the silicon oxide

Gamma Irradiation

Results just from “bad area”

Outline





Characterization




5. Summary: Beam Test and Characterization

A very first prototype batch of planar p-on-n sensors was produced at Infineon-Villach

The STS sensors show reasonable performance. They have very uniform noise and a standard cluster width- and eta distribution.

Electrical characterisation show promising quality We found areas of strips which behave

abnormal A possible explanation for this effect has been

suggested The explanation will be tested with a new

batch of sensors

Noise of STS

Cluster width of STS (including the “bad area”)


5. Summary: Outlook Irradiation tests:

The reactor in Vienna (neutrons) became operational again The irradiation at Karlsruhe (protons) is in progress

Producing a new batch: Three masks have been redesigned with small corrections to prevent the “bad strip

area” The production is in progress and the sensors will be delivered in the next months

New run planned with CMS in 2014: According to the CMS baseline n-on-p process on 200 µm FZ material Production on 8 inch wafers is considered

Infineon could be a future supplier of high quality silicon sensors for large scale applications

ATLAS and CMS already show an interest in the possibilities offered by Infineon

THANKS FOR YOUR ATTENTION!

317. October 2013 Wolfgang Treberspurg (HEPHY Vienna)


Backup Slides: Electrical Strip Parameter 1

Detector at a reverse bias of 300V• Strip Leakage Current Istrip

- Electrometer connected to DC pad measures strip current for each strip

• Poly-silicon Resistor Rpoly - Resistance measurement between bias-ring and DC pad

• Coupling Capacitance Cac

- Capacitance of dielectric between Al strip and strip implant

• Dielectric Current Idiel

- Current through dielectric at 10V between Al strip and implant


Backup Slides: Electrical Strip Parameter 2

STL Idiel/Idielmedian

STS Idiel/Idielmedian

STLSTS

Pinholes


Backup Slides: Strip ClassificationCriteria STL:• Pinhole: short between dielectric and

metal strip (Idiel > 1nA)

• Coupling capacitance: Cac < 1.2pF• Single strip current: Istrip > 50nA• Polysilicon resistor: more than 20%

deviation from the median

Criteria STS:• Pinhole: short between

dielectric and metal strip (Idiel > 1nA)

• Coupling capacitance: Cac < 1.2pF

• Single strip current: Istrip > 25nA

• Polysilicon resistor: more than 20% deviation from the median

With “bad Area”

Without “bad Area”


Backup Slides: Long term Stability

• Vbias=300V, temperature ~19 °C, rel. humidity 6-50%

• Leakage Current stable for all sensors tested


Backup Slides: Additional Beam Test Results

Clu

ster

Sig

nal

Sig

nal-t

o-N

oise CW1: SNR 32

CW2: SNR 22CW3: SNR 19

CW1CW2CW3

CW1CW2CW3

CW1: SNR 32CW2: SNR 24CW3: SNR 21

Results from „good“ strip area Results from „bad“ strip area

Documents

13 th IPRD Siena