Arsenic-Doped High-Resistivity-Silicon Epitaxial Layers for Integrating Low-Capacitance Diodes

Abstract

An arsenic doping technique for depositing up to 40-μm-thick high-resistivity layers is presented for fabricating diodes with low RC constants that can be integrated in closely-packed configurations. The doping of the as-grown epi-layers is controlled down to 5 × 1011 cm−3, a value that is solely limited by the cleanness of the epitaxial reactor chamber. To ensure such a low doping concentration, first an As-doped Si seed layer is grown with a concentration of 1016 to 1017 cm−3, after which the dopant gas arsine is turned off and a thick lightly-doped epi-layer is deposited. The final doping in the thick epi-layer relies on the segregation and incorporation of As from the seed layer, and it also depends on the final thickness of the layer, and the exact growth cycles. The obtained epi-layers exhibit a low density of stacking faults, an over-the-wafer doping uniformity of 3.6%, and a lifetime of generated carriers of more than 2.5 ms. Furthermore, the implementation of a segmented photodiode electron detector is demonstrated, featuring a 30 pF capacitance and a 90 Ω series resistance for a 7.6 mm2 anode area.

PureB low-energy electron detectors with closely-packed photodiodes integrated on locally-thinned high-resistivity silicon

“…3. The LRS version has a very lightly n-doped 40-μm-thick epitaxial layer grown on low resistivity substrates by the technique described in [8]. The doping of the as-grown epi-layers is controlled down to 5×10 11 cm -3 , and an example of the doping profile extracted from CV-measurements for several epi-layer growth conditions is shown in Fig.…”

“…The detectors presently being built into the latest generation of SEM systems are fabricated in a Pure Boron (PureB) technology that is tailored for high sensitivity to beams with shallow-penetration depths such as low-energy electrons, and vacuum-, extreme-and deep-ultraviolet radiation (VUV, EUV, DUV) [5,6,7]. In the electron detector process, p-i-n diodes were fabricated on a 30-μm-thick lightlydoped n-epitaxial Si grown on low-resistivity Si (LRS) to achieve both low capacitance and series resistance [8].…”

“…The layers are grown out of either 10 16 cm -3 , or 10 17 cm -3 seed layers. The doping is profiled up to 5 V reverse bias (W = 25 μm)[8].…”

Low temperature pure boron layer deposition for Si diode and micromachining applications

“…The starting substrates were n-type (100) 1-10 Ωcm Si wafers having a doping range of about 6×10 14 cm -3 to 5×10 15 cm -3 . In some cases, a thick (10 µm or more), n --Si epitaxial layer was grown on the n-type starting wafer to lower the diode capacitance [69]. During photodiode operation, the epi-layer was designed to be fully depleted to avoid the series resistance being determined by the high-ohmic epi-layer.…”

Monolayer Doping of Si with Improved Oxidation Resistance

“…Light As doping may be of use for applications in devices where low defect densities are required to minimise dark currents such as high operating temperature detectors and low-capacitance photodiodes for electron detection 56,57 Similarly to the DPPAdoped substrates, there was no discernible difference in carrier concentrations for samples with the shortest carbon chain lengths and the longest carbon chain lengths. …”