Strategic use of SEE mitigation techniques for the development of the ESA microprocessors: past, present, and future

For the past 15 years the European Space Agency (ESA) has developed four generations of microprocessors for their reliable use in space applications. The main design constraint was the space radiation environment with its two main components: the total ionizing dose (TID) and single event effects (SEE). The sensitivity of the CMOS technology to these two radiation components has evolved with the geometry shrinking. The higher SEE sensitivity of the narrow geometry that is used today has become the main design constraint. This paper describes the design approaches that have been used for the successive generations of ESA space microprocessors to cope with the increasing SEE sensitivity of modern CMOS technology and briefly addresses what are the concerns for the future.