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
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.
Available from: Lis Nanver
- "At the same time, the diodes still maintain a good VUV/EUV sensitivity. Based on the already reported superior electrical and optical performance , , , , the B-layer photodiodes exhibit a great potential for radiation detection in VUV/EUV-based applications, such as DUV/EUV (193 and 13.5 nm) lithography systems, for which high sensitivity, high operational speed, and high stability are desired. "
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ABSTRACT: Recently, a silicon-based ultrashallow-junction p(+)-n photodiode (B-layer diode) has been reported, with very high and very stable sensitivity in the vacuum-ultraviolet and extreme-ultraviolet spectral ranges. However, the ultrashallow nature of the junction leads to a high series resistance of the photodiode if no conductive capping layers are used. In a recent paper by Shi et al., a study on the relation between the sensitivity and the series resistance of the B-layer diodes, which can be large due to the shallow-junction depth, was presented. In this paper, an extensive analysis of the photodiode electrical and optical performance parameters and their interrelation is given. The influence of the series resistance on the response time of the photodiode for different illumination patterns is studied theoretically and also experimentally verified. It has been proven by modeling, simulations, and experiments that the time constant of the photodiode does not change significantly with the illumination spot area. This effect is due to temporary variations, going in opposite directions, of the equivalent series resistance, and the junction capacitance values found at the first instant a photogenerated charge are locally stored in the photodiode p-n junction. Also, the dependence of the degradation of the sensitivity on the incident wavelength and the diode vertical stack is examined through analysis and experimentation.
Available from: Lis Nanver
- "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 . 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 . 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.
Available from: Tihomir Knezevic
- "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  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 . "
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