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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 6 — Mar. 15, 2010
  • pp: 5861–5872

Microlens performance limits in sub-2μm pixel CMOS image sensors

Yijie Huo, Christian C. Fesenmaier, and Peter B. Catrysse  »View Author Affiliations

Optics Express, Vol. 18, Issue 6, pp. 5861-5872 (2010)

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CMOS image sensors with smaller pixels are expected to enable digital imaging systems with better resolution. When pixel size scales below 2 μm, however, diffraction affects the optical performance of the pixel and its microlens, in particular. We present a first-principles electromagnetic analysis of microlens behavior during the lateral scaling of CMOS image sensor pixels. We establish for a three-metal-layer pixel that diffraction prevents the microlens from acting as a focusing element when pixels become smaller than 1.4 μm. This severely degrades performance for on and off-axis pixels in red, green and blue color channels. We predict that one-metal-layer or backside-illuminated pixels are required to extend the functionality of microlenses beyond the 1.4 μm pixel node.

© 2010 OSA

OCIS Codes
(040.1490) Detectors : Cameras
(050.1940) Diffraction and gratings : Diffraction
(080.3630) Geometric optics : Lenses
(050.1755) Diffraction and gratings : Computational electromagnetic methods
(130.3990) Integrated optics : Micro-optical devices

ToC Category:
Imaging Systems

Original Manuscript: January 25, 2010
Revised Manuscript: March 1, 2010
Manuscript Accepted: March 2, 2010
Published: March 9, 2010

Yijie Huo, Christian C. Fesenmaier, and Peter B. Catrysse, "Microlens performance limits in sub-2μm pixel CMOS image sensors," Opt. Express 18, 5861-5872 (2010)

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