A Review of Ion Implantation Technology for Image Sensors †

Abstract

Ion implantation technology is reviewed mainly from the viewpoint of image sensors, which play a significant role in implantation technology development. Image sensors are so sensitive to metal contamination that they can detect even one metal atom per pixel. To reduce the metal contamination, the plasma shower using RF (radio frequency) plasma generation is a representative example. The electrostatic angular energy filter after the mass analyzing magnet is a highly effective method to remove energetic metal contamination. The protection layer on the silicon is needed to protect the silicon wafer against the physisorbed metals. The thickness of the protection layer should be determined by considering the knock-on depth. The damage by ion implantation also causes blemishes. It becomes larger in the following conditions if the other conditions are the same; a. higher energy; b. larger dose; c. smaller beam size (higher beam current density); d. longer ion beam irradiation time; e. larger ion mass. To reduce channeling, the most effective method is to choose proper tilt and twist angles. For P+ pinning layer formation, the low-energy B+ implantation method might have less metal contamination and damage, compared with the BF2+ method.

Opportunities from Doping of Non‐Critical Metal Oxides in Last Generation Light‐Conversion Devices

“…[347] Furthermore, the complex chemical nature of MOSs implies that, after implantation, the diffusion coefficients of ions are altered by the induced vacancies and interstitials, thus affecting in unpredictable way the performances of devices. [348] Third, assuming that both homovalent and aliovalent chemical ion doping produce impurities, [349] features like strain (and in general mechanical ones [350] ), interfacial areas/interface energetics and defects distributions, both in bulk and at interfaces, become extremely relevant and need to be properly investigated when planning the construction of a fully functioning device architectures. It is generally recognized that these features have major effects on physical properties like exciton, charge or ion transport and related studies are attracting increasing interest from the scientific community.…”

Reduction of Fluorine Diffusion and Improvement of Dark Current Using Carbon Implantation in CMOS Image Sensor

“…However, since metal contamination such as tungsten (W) created a trap state, it became the root cause of the dark current. To solve this problem, a plasma shower technology that uses an RF plasma generation method was typically used instead of W [8,9]. To reduce the density of the trap state, a fluorine implantation technology was commonly used in silicon wafer.…”

Fully Depleted, Trench-Pinned Photo Gate for CMOS Image Sensor Applications

“…With rapid CIS developments, the photodiode structure evolved from the early planar pinned photodiode (PPD) [1,2] to the current deep PPD [3], proposed to address the backside illuminated (BSI), high-resolution image sensor market. Even so, this technology is limited by the need to employ ion implantation that can cause crystal damage and metal contamination [4,5]. Indeed, to meet high-resolution imaging requirements, shrinking the pixel size led to space search in silicon depth for the storage of photo-generated charges.…”