ALD-based 3D-capacitors for harsh environments

Passive components like capacitors for harsh environments become more and more important, e. g. in the field of deep drilling, aerospace or in the automotive industry. They have to withstand temperatures up to 300 °C with a good performance concerning leakage current, breakdown voltage and capacitance density. The whole process flow has to be CMOS-compatible in order to offer the possibility for CMOS-integration. A highly n-doped Si-substrate (doping concentration about 10²⁰ cm^-3, phosphorus) acts as bottom electrode to keep the process flow as simple as possible. The capacitors are 3D-integrated to achieve a high capacitance density. For the dielectric layer and the upper electrode, atomic layer deposited (ALD) materials are used. The combination of the medium- and high-k dielectrics and the electrode materials are optimized, as well as some of the ALD-processes, to reach an optimum in leakage current and breakdown voltage. At a bias voltage of 3 V at room temperature, the leakage current amounts about 5 pA/mm², at 300 °C about 40 pA/mm². Up to ± 15 V for room temperature, respectively up to ± 10 V for 300 °C, no soft-breakdown is observed, indicating the absence of significant Fowler-Nordheim tunneling.

I. Introduction

Passive components like capacitors have to operate at harsh environments in many areas, for example in the field of deep drilling (e. g. for oil exploration) aerospace or automotive industry. In this work, operating temperatures up to 300°C are aimed. Thereby, they have to work as reliable as at lower temperatures, referred to leakage current and breakdown voltage. Moreover, capacitors should exhibit a preferably high capacitance density.