6 August 2009 2048 pixel front illuminated linear CCD for spectroscopy
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Abstract
The charge couple device(CCD) used in spectroscopy requests good response to the wave bands between 190-1000 nm. The common measure to carry out UV response is phosphor coatings or back illuminated. Among them, phosphors are wavelength converters that convert short-wavelength light into the visible spectral region. This technology needs adding special process which not only raises cost, reduces yield, but also reduces the resolution of the image. Back illuminated is reducing CCD thickness to 15um which is thinner than the normal paper by mechanical polishing and chemical corrosion after completing the front processes of CCD. This technology needs special instrument, complex process , and the yield is also low. Both phosphor coatings and back illuminated have some disadvantages such as low space resolution, complex process, low yield, high cost etc. The CCD of traditional structure has no response to the wavelength less than 350nm, the reason is that the length of UV penetrating through Si is shallow, the penetrating length is only 6.5nm of 300nm UV, the shorter wavelength UV, the shallower penetrating length. The junction depth of normal CCD process is above 200nm, some realize shallow junction through molecular beam epitaxy, but the instrument is expensive and the cost is high. The photosensitive area of normal structure CCD adopting portrait P-N junction, light incidences from N area, N area can't be completely depleted because of the restrict of physics, photon can't arrive depletion area directly. On the basis of thorough analysis traditional UV CCD, horizontal P-N junction structure of Photosensitive area is put forward, whose depletion can reach the surface, the photon falls depletion area directly, which can effectively carry out the absorption of the UV light and the collection of photoelectron. As the latent absorption of Si3N4 to UV with less than 248nm wavelength, the Si3N4 passivation on the photosensitive area is take out. The improved 2048 elements linear CCD achieves excellent wide spectral response, the maximum quantum efficiency comes to 65% in the ultraviolet band and the average quantum efficiency comes to 40% between 190nm and 1000nm wave band.
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Chao-min Wang, Chao-min Wang, Chang-ju Liu, Chang-ju Liu, Yu Zheng, Yu Zheng, Ping Li, Ping Li, } "2048 pixel front illuminated linear CCD for spectroscopy", Proc. SPIE 7384, International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Imaging Detectors and Applications, 73842A (6 August 2009); doi: 10.1117/12.835985; https://doi.org/10.1117/12.835985
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