Amorphous selenium direct detection CMOS digital x-ray imager with 25 micron pixel pitch
Bibliographic record
Abstract
ABSTRACT We have developed a high resolution amorphous selenium (a-Se) direct detection imager using a large-areacompatible back-end fabrication process on top of a CMOS active pixel sensor having 25 micron pixel pitch.Integration of a-Se with CMOS technology requires overcoming CMOS/a-Se interfacial strain, which initiatesnucleation of crystalline selenium and results in high detector dark currents. A CMOS-compatible polyimidebu er layer was used to planarize the backplane and provide a low stress and thermally stable surface for a-Se.The bu er layer inhibits crystallization and provides detector stability that is not only a performance factor butalso critical for favorable long term cost-bene t considerations in the application of CMOS digital x-ray imagersin medical practice. The detector structure is comprised of a polyimide (PI) bu er layer, the a-Se layer, and agold (Au) top electrode. The PI layer is applied by spin-coating and is patterned using dry etching to open thebackplane bond pads for wire bonding. Thermal evaporation is used to deposit the a-Se and Au layers, and thedetector is operated in hole collection mode (i.e. a positive bias on the Au top electrode).High resolution a-Se diagnostic systems typically use 70 to 100 m pixel pitch and have a pre-samplingmodulation transfer function (MTF) that is signi cantly limited by the pixel aperture. Our results con rm that,for a densely integrated 25 m pixel pitch CMOS array, the MTF approaches the fundamental material limit,i.e. where the MTF begins to be limited by the a-Se material properties and not the pixel aperture. Preliminaryimages demonstrating high spatial resolution have been obtained from a rst prototype imager.Keywords: x-ray imaging, high spatial resolution, amorphous selenium, CMOS, CMOS-selenium, array pro-cessing, direct conversion, at panel imaging
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".