8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

1

Sensor R&D at Syracuse University

Marina Artuso

Chaouki Boulahouache

Brian Gantz

Paul Gelling

JC Wang

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

2

Outline

• Review of the Syracuse R&D activities and facilities– Simulation work

– Sensor characterization – wafer measurements

– Sensor characterization – measurements on sensors bump bonded to readout electronics

• Planned upgrades• Some thoughts on sensor R&D strategy

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

3

Simulation activities

• Standalone program to model charge collection properties of generic pixel sensor & front end electronics definition of cell size & useful input for the front end electronics requirement document

(JC Wang)• Optimization of the geometry of the individual pixel cell

and fine tuning of the sensor technology requires a more complex simulation tool (ISE-TCAD)

(Chaouki Boulahouache)• P-spice simulation of fpix2 (starting) to

understand the details of the sensor formation and capacitive coupling between channels. (Brian Gantz)

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

4

Why undertake the sensor simulation effort?

• Lot of progress has been made to identify silicon pixel detector technologies suitable for high radiation environments

• The preferred technology is quite complex and involves several processing steps. Understanding the implication of the various process parameters will enable us to perform a choice that will optimize yields and radiation resistance

• We are using a professional CAD program (ISE-TCAD) to develop a deeper understanding of the various steps in this process

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

5

ISE-TCAD fundamentals

• What can be studied:– Electric field profile on the sensor (before and after

irradiation) identification of the high field regions that may lead to break-down.

– Equivalent capacitance of the chosen geometry potential effects on intrinsic noise of the pixel cell

– Time development of the signal in the electrodes in the cluster refined modeling of the charge sharing including time dependent effects

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

6

Simulation tools overview

Algorithms explored

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

7

Steps in the electrostatic single cell simulation

Sensor description (Detailed description of the fabrication steps)

Mesh generation (define a grid Of space-points to do the calculation)

Diffusion and recombination + Solution of Poisson equation

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

8

Lateral Field distribution for P-stop and P-spray before Irradiation…

P-stop P-spray

Lateral Field Distribution from the edge of the n+ strips to the middle of the p+ implant region.Distance(m) Distance(m)

Pixel Boundary

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

9

A typical example of p-stop and p-spray sensors for ATLAS DESIGN

Max-Lateral Field in(kV/cm)

Our Result Atlas’s paper result

P-stop P-spray P-stop P-spray

Unirradiated 134 340 120 380

Low Fluence

Nox=1.5*1012

295 225 140 172

High Fluence

(Irradiated case)

349 54 480 192

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

10

Experimental activities at SU

• The pixel sensor lab (clean room) is now equipped to perform wafer-level measurements of:– I-V response

– C-V response

• Planned upgrade:– Laser test-stand to measure

signal properties of instrumented sensors

– Thermally controlled chuck to test radiation damage devices at desired temperature (?? If funds become available)

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

11

First data from c-v measurement station

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

12

Experimental activities at SU - the electronics lab

• VME based test stand to perform FPIX0 and FPIX1 instrumented sensor characterization

• PCI test stand compatible with new PIXEL test stand under development

• Will be adapted to RICH test stand for HPD characterization and future test beam

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

13

The SU pixel test program

• We want to be a full partner with Fermilab in the initial sensor design and characterization

• Now: – Define measurements on a set of chosen sensors and

test structure to cross-calibrate test benches and optimize characterization techniques

– Interplay between measurement and simulation to achieve full understanding of sensor properties

• 2nd step: define quality control criteria & measurements that can be performed at SU

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

14

SENSOR DEVELOPMENT STAGES

• 1st test beam has proven that the needed resolution can be achieved with a variety of sensors

• A variety of p-stop and p-spray sensors are now in our hand to refine the choice on the basis of performance in the beam, reliability and expected yields, radiation resilience.

• Next important submission should include one or two more promising solutions (determined with the measurements and studies proposed before) and a variety of test structures to diagnose possible failure modes:– Vulnerability to breakdown– Depletion voltage – Factors affecting inter-pixel capacitance and resistance

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

15

Additional goals

• Identify 2 or 3 vendors capable to produce our sensors with good yields

• Develop a good understanding of their process and the parameters that can be optimized for our needs

• Define the quality control

production stage

8/22/01 Marina Artuso - Pixel Sensor Meeting - Aug 2001

16

Conclusions

• We have taken several steps to contribute to the sensor design and testing for the BTeV pixel detector

• We have gained good experience with the various front end devices of the FPIXn family

• We consider the next submission to foundry a key milestone in our project and we would like to be active participants in this effort.