Optimizing the quality of silicon strip sensors produced by Infineon Technologies Austria AG

Abstract

The tracking systems of most modern particle physics experiments are realized by silicon based sensors. The size of such systems has continuously increased and nowadays a sensitive area of several 100 m 2 has to be covered. This large amount of sensors might exceed the production capabilities of existing companies and institutes. Therefore the Institute of High Energy Physics of the Austrian Academy of Sciences (HEPHY) and the European semiconductor manufacturer Infineon Technologies Austria AG developed together a production process for p-on-n strip sensors. Although the first prototype run has shown a promising quality, it has been observed that weak strips exist, which are mainly located at distinctive areas on each wafer. At these areas the affected parameters are correlated to each other. A similar behaviour could be reproduced with a smaller second batch, whose sensors have been used for further analysis and advanced measurements. This paper sums up the characteristic behaviour of the specific effect and presents different possibilities how to cure the sensors. The systematic accumulation of weak strips can be traced back to a specific operation during the fabrication process. All data strongly indicate that the effect is caused by local charging effects on an isolating layer.

Results of an electron beam test with prototype silicon sensors manufactured by Infineon Technologies Austria AG

“…Later on both modules have been exposed to a 4 GeV electron beam at DESY, together with another two modules, equipped with sensors of the second batch (APV-Mod-3, -4). Since a distinctive region of affected strips has been observed on all sensors during the electrical characterization (section 1.2), the influence of different treatments had been investigated in [2]. It turned out that the sensors can be cured with water to remove the affected regions.…”

“…The generation of static charge could be lead back to the dicing process and will be avoided in future batches by modifying this process and the surface layer. More details can be found in [2]. Since APV-Mod-1 appeared to be cured after γ irradiation, the impact of the slightly degenerated strip isolation on the recorded data has only been investigated on module APV-Mod-2.…”