Novell Plating Processes for Silicon Based Pixel Detectors

Abstract

New generation silicon detectors produced in Thuringia (Germany) will play an important role in the future, during the upgrade phase of the Large Hadron Collider (LHC) at the CERN nuclear research center. Such detectors are used for monitoring radioactive reactions during the collision of highly accelerated positron radiations produced in large scale experiments like ATLAS (A Toroidal LHC ApparatuS) or CMS (Compact-Muon-Solenoid). The development of the new detectors aims at a functional improvement that will bring an enhanced resistance against radiation damage. At the same time, the surface reengineering for an increased active surface should address also important cost related aspects. This paper will discuss recent results from the authors' labs on the development of such novel sensors. The aim is a full understanding and coverage of the complete production process for the sensor modules. An important challenge to be addressed is the development of low cost metallisation procedures for the silicon detectors that do not require lithographic steps. Especially promising are extreme small and round surfaces of about 10 µm diameter distributed over the entire detector surface with a contact pitch of 50 µm that would add up to several thousand contacts and a high contact density. Given the special structure of the detector surface, electric current can be generated by incoming electromagnetic radiation, e.g. light. This current can be used in a light-induced metallization process of the front side contacts. We will present results from a light-induced plating process involving nickel and tin. The suitability of this layer system for subsequent bonding processes will also be discussed.