7. october 2013 13 th iprd siena w. treberspurg, u. bartl, t. bergauer, m. dragicevic, e....
TRANSCRIPT
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 2
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 3
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 4
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)
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 5
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)
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 6
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 7
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 8
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 9
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 12
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
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 13
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 14
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 15
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 16
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 17
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 18
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 19
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 20
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 21
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 22
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 23
1. Overview of the Project
2. The different Sensor Structures
3. Summary of the Electrical
Characterization
4. Summary of Beam Test
5. Outlook and Summary
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 24
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 25
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)
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 26
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 27
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 28
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 29
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”)
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 30
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 32
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
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 33
Backup Slides: Electrical Strip Parameter 2
STL Idiel/Idielmedian
STS Idiel/Idielmedian
STLSTS
Pinholes
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 34
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”
Wolfgang Treberspurg (HEPHY Vienna)7. October 2013 35
Backup Slides: Long term Stability
• Vbias=300V, temperature ~19 °C, rel. humidity 6-50%
• Leakage Current stable for all sensors tested