This paper presents a novel method of detecting secondary electrons generated in the scanning electron microscope (SEM). The method suggests that the photomultiplier tube (PMT), traditionally used in the Everhart-Thornley (ET) detector, is to be replaced with a configurable multipixel solid-state photon detector offering the advantages of smaller dimension, lower supply voltage and power requirements, and potentially cheaper product cost. The design of the proposed detector has been implemented using a standard 0.35？μm CMOS technology with optical enhancement. This microchip comprises main circuit constituents of an array of photodiodes connecting to respective noise-optimised transimpedance amplifiers (TIAs), a selector-combiner (SC) circuit, and a postamplifier (PA). The design possesses the capability of detecting photons with low input optical power in the range of 1？nW with 100？μm × 100？μm？sized photodiodes and achieves a total amplification of 180？dBΩ at the output. 1. Introduction The Everhart-Thornley (ET) detector has been widely used as the secondary electron detector for the scanning electron microscope (SEM) for the past half a century [1]. The detector consists mainly of collector, scintillator, light pipe, photomultiplier tube (PMT), and preamplifier. Being a vital component of the ET detector, PMT is responsible for sensing the arrival of photons, converting them to electrons, and multiplying the number of electrons which essentially produce an amplified output current. Its dominance of use is due chiefly to its ability to provide an excellent sensitivity solution. The rapid advancement of semiconductor technologies in recent years has manifested in many applications in various fields. Solid-state method essentially allows the integration of large operating components into a small microchip. Complementary metal-oxide-semiconductor (CMOS) processes, which are silicon based, have become the most popular among all technologies thanks to its ability to provide low-cost solutions and highly integrated design. Certain CMOS processes do attract special attention owing to their ability to include both optical devices and electrical circuits into a monolithic microchip. This form of integration is very popular in the optical communications world, both wired and wireless, in the past decade [2–5]. Apart from communications, it also finds a number of implementations in optical storage systems [6]. In the optical sensory sectors, numerous applications such as camera sensory devices, optical microsensors particularly used in medical monitoring, and
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