# Presentation: 932112

## Progress Towards Active Pixel Sensor Detectors for Solar Orbiter
Dr Nick Waltham 
Head of Imaging Systems Division,
Space Science & Technology Department, Rutherford Appleton Laboratory

**Dr Nick Waltham **
**Head of Imaging Systems Division,**
**Space Science & Technology Department, Rutherford Appleton Laboratory**

##    CCDs for Solar Physics  .  .  .

**CCDs for Solar Physics**
**e.g. SOHO, SMEI, SOLAR-B, STEREO .  .  .**
**Future missions e.g. SDO**
**But inherent limitations  .  .  .**
**External drive electronics needed.**
**Solar physics community always want more pixels, more channels, faster readout.**
**But with smaller/lower size, mass, and power !**
**And for Solar Orbiter  .  .  .**
**Radiation damage !**
**Protons, neutrons, etc**
**Loss of charge transfer efficiency !**
**Pixel Size ?**
**Smaller pixels yield a smaller instrument.**

##    RAL - Current programme  .  .  . 

**SMEI (Solar Mass Ejection Imager) CCD camera**
**Birmingham University, UCSD, AFRL,**
**Primary requirement - high dynamic range.**
**Await launch**
**STEREO/SECCHI solar science mission**
**CCD camera design for 4 instruments with NRL and Birmingham.**
**Key requirements - high speed readout, high dynamic range, yet reduced size, mass, and power.**
**Now feeds into camera designs for SDO AO proposals.**
**R&D Activities**
**ASIC based CCD camera readout electronics.**
**CMOS Active Pixel Sensors.**** **

***Solar Mass Ejection Imager (SMEI)***

##    What are we doing about it  ?

**An alternative sensor technology to CCDs   .   .   .**

***Development of ***
***Science-grade ***
***CMOS Active Pixel Sensors  !***

##    What is an Active Pixel Sensor (APS) ?

##    RAL APS Development Programme 

**1999**
**Design / modelling of pixel test structures (0.5 and 0.7 ********m CMOS).**
**2000**
**Fabrication and testing of pixel test structures.**
**Established formal collaboration with Marconi (EEV) **
**Exchange of designs / ideas, packaging, testing, **
**Back-thinning****	****Unique capability !**
**Design of 512 x 512 pixel sensor (0.5 ********m CMOS)**
**2001**
**Fabrication of 512 x 512 pixel prototype sensors.**
**Birmingham join collaboration (Helen Mapson-Menard, Chris Eyles).**
**EEV thinning test structures and 512 x 512 prototypes.**
**First tests of 512 x 512 prototypes.**
**Planning for Solar Orbiter (move to 0.25 ********m CMOS).**
**2002**
**Design / fabrication of 0.25 ********m CMOS 4kx3k 5********m pixel APS.**
**Full testing of front and back-illuminated 512 x 512 prototypes.**

##    RAL APS test structure development

##  512 x 512 Pixel Prototype Pixel Active Pixel Sensor 

**6 inch wafer of 512 x 512 sensors**

**Wire-bonded to an evaluation PCB**

**Individual**
**512 x 512 pixel **
**APS chip**

##  512 x 512 Pixel Prototype Pixel Active Pixel Sensor 

**Two test Images**

##  512 x 512 Pixel Prototype Pixel Active Pixel Sensor 

**Note Dynamic range and Anti-blooming Performance !**

***   ******So where next  ?***

##    ESA’s Solar Orbiter 

***	******Driven by the proposal of a Spectrometer on Solar Orbiter***

***Detector Requirements***
**EUV sensitive**
**Large format (4k x 4k pixels)**
**Small (5 ********m pixels)**
**Science-grade linearity, **
**      ****low-noise, good uniformity**
**Radiation hard**
**Low power**

##    Solar Orbiter Detector

***Detector Goals***
**4k x 4k pixel sensor**
**5********m pixel size**
**14 bit dynamic range **
**EUV Sensitive **
**4-transistor CDS pixel **
**0.25 ********m rad-hard CMOS process***** ***

***Development Programme***
**Refine requirement specification**
**Develop CAD models and simulations **
**Define architectural design**
**Design, fabricate, and test 5********m pixel test structures**
**Transfer 14-15 bit ADC to 0.25 ********m CMOS**
**Investigate back-thinning with Marconi**
**	****	**** ****Demonstrate feasibility in time for the AO !**

***It can be done !***

##    Solar Orbiter Detector  -  Photodiode pixels.

##    Solar Orbiter Detector  -  Photodiode pixels.

-   **4-MOS transistor pixel.**
**  ****PMOS transfer gate for kTC / FPN noise reduction and increased dynamic range.**

**Schematic**

**Layout**

##    Solar Orbiter Detector  -  Chip Architecture

##    Solar Orbiter Detector  -  Progress

**Area sensor**: ESA’s Solar Orbiter for EUV imaging of Sun  4Kx3K, noise ~ 10 e- rms, DR ~ 12+ bits
**Linear sensor**: TOPSAT-2
- 	BNSC Earth Observation  1 m ground resolution, colour, on-chip 10-bit ADCs, ~ 1500 fps
**3.**	**Electron sensor**: HEP Vertex (Linear Collider, RHIC upgrade, biomed)  intelligence in the pixel, fast readout (50MHz/row), low noise (~ 10 e- rms), data sparsification, radiation resistance

**0.25 ********m CMOS manufactured by TSMC**

**IC design / manufacturing sharing ******** reduction of costs**

##    Solar Orbiter Detector  -  Progress

**4k x 3k Sensor – Predictions from CAD simulation work**
**Full Well Capacity ****	****~ 46k electrons (5 ********m pixel)**
**Readout Noise****	****	****~ 10 electrons rms**
**Dynamic Range****	****	****~ 12+ bits**
**Fill Factor****	****	****~ 30% (but be careful !)**
**Readout rate****	****	****~ 1 MHz (through one port only)**
**Readout time****	****	****~ 12 seconds (full-frame, no windowing)**

##    Solar Orbiter Detector  -  Future

**Future Possibilities**
**Chips of any format up to 4k x 4k (5 ********m) pixels. e.g.**
**4k x 512 (5 ********m) pixel strips on selected ******** bands.**
**2k x 2k (10 ********m) pixels.**
**or you could have odd-shaped pixels (10 x 20 ********m).**
**CMOS allows you to design what **_**you**_** want !**
**Multi-port readout for higher frame rate.**
**Windowed readout.**
**Anything else wanted – besides EUV sensitivity ?**

##  EUV sensitivity – Backthinning, or FIB, or ?

##    Front vs Rear illumination

##    Solar Orbiter Detector  -  Future

***Development Programme***** **
**4k x 3k pixel Array Manufacture   (Delivery Dec 02).**
**Array Packaging   (Jan 03).**
**First light   (Feb 03).**
**Testing of 512 x 512 pixel prototypes (front and rear illuminated).    E2V are delivering thinned sensors this week.**
**Transfer of 14-15 bit ADC to 0.25 ********m CMOS in second phase.**
**Thinning of 4k x 3k pixel array and EUV testing.**

##    Summary

**Requirement**
**EUV Sensitivity**
**4k x 4k pixels**
**5 ********m pixel size**
**Readout < 1 second**
**Low power**
**Cooling**
**Radiation hardness**
**Availability**

**Science-grade CCD**
**Yes**
**Yes (for SDO ?) **
**No**
**Not easily**
**No**
**-80 ****°C**
**Poor (CTE degradation)**
**Soon (12 ********m pixels)**
**?     (5 ********m pixels)**

**APS**
**Probably**
**Yes**
**Yes**
**Yes / Windowed readout**
**Yes**
**-80 ****°C**
**Good (no CTE involved)**
**(2003 – 2006) ?**

##    Solar Orbiter Detector  -  Alternatives

***Have considered naked CMOS APS so far.***
***	******	******Are there alternatives ?***** **
**Diamond / Bold ?****	****    ****	****Progress towards a large format array ?**
**	****	****	****	****	****Smallest pixel ? / Bump bonding ?**
**CID       ****	****Radiation hard but limited availability, small range of**
**	****	****	****formats, large pixels, very high read noise.**
**Intensified APS – like in CDS ?**