In extreme-ultraviolet (EUV)-based applications, such as next-generation EUV lithography, the detector surface has to be periodically exposed to aggressive gasses as a cleaning step to prevent the build-up of contaminating layers. In this paper, we report excellent EUV radiation hardness and robustness to harsh working conditions of a Si-based boron-doped ultrashallow junction photodiode (B-layer diode) fabricated by a pure boron chemical vapor deposition (CVD) technology. Experimental results show unchanged responsivity of the photodiode (within the measurement uncertainty) with radiation dose up to 0.22 MJcm2. The surface cleaning tests with hydrogen radicals (H*) confirm that the electrical/optical performance of the detector is stable with only minor change of the characteristics. In addition, the detectors must be operated in vacuum without an air-cooling system, as air is not transparent for EUV photons. An on-chip sensor system, which contains B-layer diodes and bipolar-transistor-based temperature sensors, is developed for compensating the thermal drift of the photodiode output signal when the diode is heated up by the EUV radiation. Furthermore, this on-chip sensor system also demonstrates the full compatibility of this novel pure boron CVD technology with standard Si-based integrated circuit processing.
- Dark current
- extreme-ultraviolet (EUV) radiation
- H cleaning
- radiation hardness
- ultrashallow junctions