Download - RIDL visit-1 BEB 6/24/2015 MIT Lincoln Laboratory Orthogonal-Transfer Charge-Coupled Devices and Low-Noise Charge-Coupled Devices Readout Circuits* Barry.

RIDL visit-1BEB 04/18/23

MIT Lincoln Laboratory

Orthogonal-Transfer Charge-Coupled Devices and Low-Noise Charge-Coupled Devices Readout Circuits*

Barry E. Burke

*The MIT Lincoln Laboratory portion of this work was performed under a Collaboration Agreement between MIT Lincoln Laboratory and The University of Hawaii, Institute for Astronomy (IfA). Opinions, interpretations, conclusions, and recommendations are those of the authors, and do not necessarily represent the view of the United States Government.

MIT Lincoln LaboratoryRIDL visit-2

BEB 04/18/23

Outline

• Review of Orthogonal-Transfer Charge-Coupled Devices (OTCCD)

• Development of the orthogonal transfer array (OTA)

• Low-noise CCD readout circuits

• Summary


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Conventional vs. Orthogonal-Transfer CCDs


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Application Areas

• Compensation of platform motion– Imaging from unstable

and/or moving platforms– TDI (time delay and integrate)

with variable scan direction

• Compensation of scene motion– Ground-based astronomy

Outputregister

Videoout

Framestore

Imagingarea

OTCCD can noiselessly compensatefor scene motion across sensorduring image integration


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Application of OTCCDs in Astronomy

Star-cluster imagery (M71)

With motion compensation, =0.50”SNR increase: 1.7

• Use OTCCD to remove blurring due random motion of star images (electronic tip-tilt)

No motion compensation, =0.73"


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Outline



• Low-noise CCD readout circuits• Summary


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Pan-STARRS(Panoramic Survey Telescope and Rapid Response System)

Proposed Pan-STARRStelescope configuration

Gigapixel focal-planearray (64 CCDs)

• Four 1.8-m telescopes viewing same sky sector– 3˚ FOV, 24 mv sensitivity– High-cadence, wide-field surveys– Detect variable or moving objects

• 1.4-Gpixel CCD focal-plane array on each telescope

First Pan-STARRStelescope on Haleakala

(PS1)


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Orthogonal-Transfer Array

• Wide field-of-view (FOV) imaging– Wavefront tilt decorrelates over

FOV > few arc minutes– Need 2D array of OTCCDs, each

independently clocked to track local wavefront tilt (“rubber focal plane”)

• OTA is a new CCD architecture– Requires on-chip switching logic– More complex layout and

processing than conventional CCDs

2.38 arc min


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Orthogonal Transfer Array

• New device paradigm– 2D array of independent OTCCDs– Independent clocking and readout of OTCCDs

• Advantages– Enables spatially varying tip-tilt correction– Isolated defective cells tolerable (higher yield)

OTA: 88 array ofOTCCD cells

OTA cellwith I/O control

Four-phaseOTCCD pixels

MIT Lincoln LaboratoryRIDL visit-10BEB 04/18/23

OTA Operation

• Subset (4 – 5) of cells chosen to image guide stars

• Map of wavefront tilt constructed from guide-star data and applied to science cells

• Four redundant views of every patch of sky used to fill gaps due to– Guide-star cells– Dead cells– Cosmic rays– Dead areas between cells and

devices


Device Fabrication

• Four OTAs on 150-mm wafer (die size 49.550.1 mm)

• Four-poly, n-buried-channel process

• Fabricated on 5 000 Ω·cm float-zone silicon wafers

• Back-illuminated devices thinned to 75 µm

150-mm wafer withfour OTAs

Photo of pixel array


Sample Imagery

• First devices were fully functional but with some issues (noise, logic “glow”)

• Device redesign resolved issues with prototype devices

• Redesigned devices have been fabricated and most of them packaged

Image from back-illuminated OTA10-µm pixel, 22.6 Mpixels

Image from OTA cell with fixedlight spot and CCD gates clocked


Substrate Bias

• Substrate bias enables thick, fully depleted devices:– High quantum efficiency, 800-1000 nm– Small charge point-spread function


Quantum Efficiency

• Back-surface p+ using ion-implant/laser anneal• Two-layer anti-reflection coating with reflection null at

850 nm for reduced fringing• Thicker device clearly superior beyond 800 nm


OTA Focal Planes

• TC3 focal plane assembled from 16 prototype devices; on-sky tests in February

• GPC1 assembled from lots 2 and 3 (summer 2007)


Outline



• Low-noise CCD readout circuits• Summary


CCD Output Circuits


Output Circuit Comparison

Sense-node capacitance is lower (higher responsivity) for JFET

than MOSFET

Noise spectral voltage is lower for JFET than MOSFET


Noise Comparison

Best MOSFET noise vs. preliminary JFET noise

2000-fps, 160160-pixel imager, 20 ports with JFET output circuits


Summary

• OTCCD developed for astronomical applications but has a potentially much broader range of uses

• OTA development for Pan-STARRS is new OTCCD concept, also with other applications

• Recent work with JFETs shows noise levels better than BCMOSFETs and nearing 1 e-