This paper reports on the downscaling of solid propellant pyrotechnical microsystems. Sub-millimeter scale micro-thrusters were fabricated in silicon to investigate the limit of integration of this technology. The dimensions of the micro-thrusters chamber and of the igniter were reduced and a highly energetic solid-state propellant was used, the ZPP. Deep reactive ion etching (DRIE) of silicon was used to fabricate the chamber surrounded by thermal insulating grooves. The diverging part of the nozzle was also etched by DRIE, with a maximum angle of 3/spl deg/, and integrated to the igniter part. The igniter was made up of surface micromachined polysilicon micro-heaters, consisting in 2 to 16 parallel heating bridges. An electrical power of 200 mW per beam could be delivered for a few seconds. A minimum temperature of 450/spl deg/C has been reached with 130 mW per beam. Successful ignition of the propellant shows the capability of this promising technology to integrate arrays of devices within a limited area of silicon.