Conference Paper

High performance silicon-based extreme ultraviolet (EUV) radiation detector for industrial application

Delft Univ. of Technol., Delft, Netherlands
DOI: 10.1109/IECON.2009.5414855 Conference: Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE
Source: IEEE Xplore

ABSTRACT Silicon-based p+n junction photodiodes have been successfully fabricated for radiation detection in the extreme ultraviolet (EUV) spectral range. The diode technology relies on the formation of a front p+ active surface region by using pure boron chemical vapor deposition (CVD), which grows delta-like B-doped layers on Si substrates. Therefore, the technique can ensure defect-free, highly-doped, and extremely ultra shallow junctions that significantly enhance the sensitivity to UV radiation with respect to commercial state-of-the-art detectors, as confirmed by near theoretical responsivity (0.266 A/W, at 13.5 nm radiation wavelength). Outstanding performance has also been achieved in terms of extremely low dark current (< 50 pA, at a reverse bias of 10 V) and pulsed response time (< 100 ns) for 0.1 cm2 large area devices. In addition, the fabricated photodiodes exhibit negligible degradation to high-dose radiation exposure. Owing to these features, the presented photodiode technology, which profits from low cost, reduced complexity, and full compatibility with standard Si processing, offers a reliable solution for the implementation of detectors in industrial applications based on EUV radiation, such as next-generation 13.5 nm wavelength lithography.

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    • "The diode anode, is made by selectively depositing a pure boron layer in an opening in a SiO 2 isolation layer by atmospheric/low-pressure chemical vapor deposition (AP/LPCVD) at 700 ºC from a diborane (B 2 H 6 ) gas source [5]. Figure 3(b) shows a highresolution TEM image and SIMS of the B-layer formed after a 10 min B 2 H 6 exposure. The boron coverage is uniform and from the electrical characterization of the p + n diodes it has been determined that there is a well-controlled, ultrashallow p + doping of the Si surface with a depth of a few nanometers [6][7]. Additional coating layers can be deposited on the Blayer diode surface for protection, anti-reflection, or to facilitate the integration of thin film filters with radiation passbands optimized for the specific application. "
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    ABSTRACT: Recently, silicon ultrashallow p + n photodiodes, fabricated by a pure boron deposition technology (B-layer diodes), were evaluated for detection in the Vacuum Ultra-Violet (VUV) spectral range from 115 nm to 215 nm wavelengths, where the attenuation length in silicon is only a few nanometers. Superior sensitivity in the order of 0.1 A/W in the whole VUV spectral range was reported (1). Next to the sensitivity, another important parameter of any photodetector is the response time, which is directly related to its series resistance. In this work a study of the relation between the sensitivity and the series resistance of the B-diodes is presented, supported by simulation results and optical/electrical experimental results. Moreover, practical methods for designing a high sensitivity VUV photodiodes while keeping a relatively low series resistance, are proposed. The experimental results demonstrate that by modifying the diode structure, the series resistance can be effectively reduced. At the same time, the B-layer diodes still maintain a high VUV sensitivity.
    Conference Record - IEEE Instrumentation and Measurement Technology Conference 05/2011; DOI:10.1109/IMTC.2011.5944073
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    • "The depletion region of the analyzed photodiode structure reaches the silicon/oxide interface at the perimeter, as seen in Fig. 1, resulting in dark current degradation due to radiation exposure. It is shown in [6] that the very low dark current of these ultrashallow photodiode structures is degraded by damage at the silicon/oxide interface after EUV radiation exposure. Examples of dark current degradation in a CCD image sensor exposed to high intensity DUV radiation is reported in [7]. "
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    ABSTRACT: Ultrashallow p + -n - -n + silicon photodiodes, fabricated by a pure boron deposition technology, show excellent performance for detection of Deep Ultra Violet (DUV) radiation due to the nanometer deep pn-junctions. The dark current of photodiode is degraded by the damage of the silicon/oxide interface at the diode perimeter region caused by DUV radiation. Reducing the depletion region width across the p + n - junction at the silicon/oxide interface will also invariably increase the electric field, reducing the breakdown voltage and increasing the perimeter component of the junction capacitance. In this paper, the trade-off between the depletion region width, breakdown voltage and junction capacitance is examined for ultrashallow p + -n - -n + photodiodes where an additional ultrashallow doped p- region is introduced as an extension to the p-type guard rings. An optimal doping profile is proposed for the added p-region to obtain minimal degradation of electric characteristics for peak doping of 10 18 cm -3 , 5 � 10 18 cm -3 and 5 � 10 19 cm -3 at junction depths of 50 nm, 10 nm and 2 nm, respectively, and a distance of 0.5 μm between the added p- region and the surrounding n + channel stop.
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