1. Analysis of 3D Stacked Fully Functional CMOS Active Pixel Sensor Detectors (1) Istituto Nazionale di Fisica Nucleare Sezione di Perugia – Italy Sezione di Perugia – Italy (2) Dipartimento di Ingegneria Elettronica e dell’Informazione Università degli Studi di Perugia - Italy D. Passeri (1, 2), L. Servoli (1), S. Meroli (1)

2. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 2/24 Outline Introduction: Introduction: - CMOS Active Pixel Sensor (RAPS02/03); -design options (pixel architecture). Motivation and Aim: Motivation and Aim: - suitability of “stacked” all-in-one CMOS APS sensors (3D) for particle tracking purposes. TCAD Device/Circuit simulations: TCAD Device/Circuit simulations: - hit position and incidence angle calculation; - noise analyses; -sensitivity. Geometrical optimization: pitch analyses. Geometrical optimization: pitch analyses. Conclusions. Conclusions.

3. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 3/24 Background CMOS Active Pixel Sensor for Ionizing Particle detection. CMOS Active Pixel Sensor for Ionizing Particle detection. Technology analysis. Technology analysis. Standard CMOS (twin-tub, no-epi) technology –> 0.18  m Standard CMOS (twin-tub, no-epi) technology –> 0.18  m - performance <- device level analyses; - access; - maintenance (since 2001/2002 – Pixel 2002, Carmel); - costs (EUROPRACTICE).

4. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 4/24 Background: the RAPS 02/03 chips UMC 0.18  m 1P6M MM CMOS 3T architecture (nMOS & pMOS); 4x4  m 2, 10x10  m 2 pixel size; sparse read-out prone; high-gain, in-pixel amplification; self-reset mode (event-triggered). RAPS02RAPS03 APS WIPS SHARPS 256x256 pixels, 10x10  m 2 pixel size. ~5mm

5. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 5/24 Motivations and Aim The IC technology trend is to move from 3D flexible configurations (package on package, stacked dies) to 3D ICs:The IC technology trend is to move from 3D flexible configurations (package on package, stacked dies) to 3D ICs: - increased electrical performances; - cost of 3D integration may be cheaper than to keep shrinking 2D. Perspective advantages for particle tracking / vertex detectors:Perspective advantages for particle tracking / vertex detectors: - separation of sensor, analog read-out electronics, A/D conversion layers (increased fill-factor, performance). All-in-one chip featuring multiple, stacked, fully functional CMOS APS detector layers:All-in-one chip featuring multiple, stacked, fully functional CMOS APS detector layers: - momentum measurement (impact point and trajectory) with a single detector; - low material detector (reduced multiple scattering issues).

6. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 6/24 The RAPS03 “stacked” system This is what we have… ~15mm CERN PS Irradiation Facilities, Sept. 08 … and this what we would like to have! ~ 15  m Each layer would be a complete sensor (APS diodes + MOSFETs, read-out and control electronics)! Outputs Global signals

7. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 7/24 FTD … … 10  m ±45° ±15  m … x y The simulated structures Device/Circuit simulation of a 2D cross-section of a CMOS Active Pixel Sensor sub-array (7 pixels). n-well p-sub

8. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 8/24 The simulated structures (2) Up to four (isolated) sub-arrays.Up to four (isolated) sub-arrays. Voltage response as a function of a particle hit (e/h pairs generation corresponding to a Minimum Ionizing Particle).Voltage response as a function of a particle hit (e/h pairs generation corresponding to a Minimum Ionizing Particle). 10  m

9. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 9/24 Overall voltage drop Hit Position (  m) Incidence Angle (°) Voltage Drop (mV)

10. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 10/24 Central pixel responses (voltage drop) Hit Position (  m) Incidence Angle (°) Voltage Drop (mV) Hit Position (  m) Incidence Angle (°) Voltage Drop (mV) Layer #1 Layer #2 Layer #3 Layer #4

11. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 11/24 Signal and Noise analyses We considered a cluster signal, featuring three pixels (the seed pixel and the two neighboring ones).We considered a cluster signal, featuring three pixels (the seed pixel and the two neighboring ones). We considered the (dominant) kTC equivalent noise contribution as measured from our APS sensors (below 1.0mV).We considered the (dominant) kTC equivalent noise contribution as measured from our APS sensors (below 1.0mV). The equivalent noise voltage was added to the voltage response of each pixel (using a Gaussian distribution).The equivalent noise voltage was added to the voltage response of each pixel (using a Gaussian distribution). The hit position and angle were therefore reconstructed, by a weighted average of the voltage signals and linear fitting.The hit position and angle were therefore reconstructed, by a weighted average of the voltage signals and linear fitting. All the results were obtained by considering both charge drift and diffusion components, for a typical CMOS substrate doping concentration and under biasing conditions, and the load effect of reset and source-follower MOSFETs.All the results were obtained by considering both charge drift and diffusion components, for a typical CMOS substrate doping concentration and under biasing conditions, and the load effect of reset and source-follower MOSFETs.

12. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 12/24 Hit position reconstruction error If we have a single layer...If we have a single layer... V0V0V0V0  V -1  V +2  V +1  V -2  Hit a X Ha = -10  m  Ha = 0° X B1 = -10  m } Hit b X Hb = -6  m  Hb = 30° X B2 = -10  m } y x x y x XBXBXBXB BBBB

13. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 13/24 Hit position reconstruction error (2) If we have two (or more) layers... … we can get a “spreading” of tracks… …and better hit and angle reconstruction.

14. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 14/24 Hit position reconstruction error (2) E.g., given an impact point X H =0  m and incidence angle of 20°… y x Hit position (  m) Mean = -1.08  m Sigma = 0.56  m Two Layers Hit position (  m) Mean = -0.76  m Sigma = 0.53  m Three Layers Hit position (  m) Mean = -0.96  m Sigma = 0.49  m Four Layers

15. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 15/24 Incidence angle reconstruction error (2) E.g., given an impact point X H =0  m and incidence angle of 20°… x Incidence angle (°) Mean = 15.83° Sigma = 4.54° Two Layers Incidence angle (°) Mean = 20.90° Sigma = 2.03° Three Layers Incidence angle (°) Mean = 19.40° Sigma = 1.31° Four Layers

16. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 16/24 Impact point reconstruction error Standard deviation of the impact point calculation as a function of the incidence angle and hit position.Standard deviation of the impact point calculation as a function of the incidence angle and hit position.

17. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 17/24 Incidence angle reconstruction error Standard deviation of the incidence angle calculation as a function of the incidence angle and hit position.Standard deviation of the incidence angle calculation as a function of the incidence angle and hit position.

18. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 18/24 Angular Sensitivity Angular sensitivity: How separated have to be two different tracks to be appreciated (as different ones)? 1111 } It depends on the noise (and layer numbers…)

19. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 19/24 Angular Sensitivity (2) Angular sensitivity as a function of the noise. Angular Separation ( ° ) Noise  (mV) 3layers 4 ° ) Noise  (mV) 3layers 4 2 2

20. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 20/24 Pitch analyses Central pixel response (layer I) for different incidence hit positions and angles at different pitches (5, 10, 20  m) Hit Position (  m) Incidence Angle (°) Voltage Drop (mV)

21. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 21/24 Pitch analyses (2) Standard deviation of the impact point calculation as a function of the incidence angle and hit position at different pitch values (4 layers). Hit Position (a.u. – pitch) Incidence Angle (°)  impact point (  m)

22. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 22/24 Pitch analyses (3) Standard deviation of the incidence angle calculation as a function of the incidence angle and hit position at different pitch values (4 layers). Incidence Angle (°)  impact point (  m) Hit Position (a.u. - pitch)

23. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 23/24 On going works… GEANT4 simulations in order to account for magnetic fields effects (multiple scattering).GEANT4 simulations in order to account for magnetic fields effects (multiple scattering). Effects of two separate (Si / Air) multiple-layers sensors on the particle momentum reconstruction.Effects of two separate (Si / Air) multiple-layers sensors on the particle momentum reconstruction. Optimization of pixel architecture/pitch with respect to candidate vertical integration technology.Optimization of pixel architecture/pitch with respect to candidate vertical integration technology.

24. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 24/24 Conclusions Vertically Integrated Circuits (3D) diffusions.Vertically Integrated Circuits (3D) diffusions. Is it worthwhile to have an all-in-one detector featuring multiple stacked APS CMOS layers for particle tracking applications?Is it worthwhile to have an all-in-one detector featuring multiple stacked APS CMOS layers for particle tracking applications? Comprehensive device/circuit simulations demonstrate the advantaged of having two/three stacked (closed, very precisely aligned) fully-functional pixel layers.Comprehensive device/circuit simulations demonstrate the advantaged of having two/three stacked (closed, very precisely aligned) fully-functional pixel layers. Momentum measurement with a single detector.Momentum measurement with a single detector. Low material detector.Low material detector. Is this affordable in terms of design & fabrication costs?Is this affordable in terms of design & fabrication costs? -Tezzaron/Chartered technology; -VIPIX (INFN Italian collaboration, prof. Valerio RE). YES (*) (*) in our opinion…

25. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 25/24 Backup

26. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 26/24 Hit position reconstruction error (3) X B = f (X H,  ) -> X H = f (H B,  )X B = f (X H,  ) -> X H = f (H B,  ) Hit position (a.u. – pitch) Incidence Angle (°) Calculated H B (a.u. – pitch)

27. PIXEL 2008 International Workshop, 23-26 September, 2008 – Fermilab, Batavia, IL 27/24 Overall sensitivity (3) Frequency of ambiguously matching pixel value patterns (reference hit position X H = 0  m and  H = 0°).