Sensor R&D at Syracuse University

1. Sensor R&D at Syracuse University Marina Artuso Chaouki Boulahouache Brian Gantz Paul Gelling JC Wang 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 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) 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 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 Marina Artuso - Pixel Sensor Meeting - Aug 2001

6. Simulation tools overview Algorithms explored 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 Marina Artuso - Pixel Sensor Meeting - Aug 2001

8. Lateral Field distribution for P-stop and P-spray before Irradiation… Pixel Boundary P-stop P-spray Lateral Field Distribution from the edge of the n+ strips to the middle of the p+ implant region. Distance(mm) Marina Artuso - Pixel Sensor Meeting - Aug 2001 Distance(mm)

9. A typical example of p-stop and p-spray sensors for ATLAS DESIGN 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) Marina Artuso - Pixel Sensor Meeting - Aug 2001

11. First data from c-v measurement station 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 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 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 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 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. Marina Artuso - Pixel Sensor Meeting - Aug 2001