The efficient design of electrically small antennas (ESA) has recently evolved to an outstandingly active area of research. This paper aims to present an improved performance electrically small on-chip antenna design, for the 920 MHz UHF-RFID frequency. Performance improvement is based on creating a slow-wave structure with three-dimensional spiral meandering and dielectric loading of the complete antenna structure. A single layer spiral on-chip antenna simulation is presented first, based on a commercially available product, then an improved single layer spiral antenna and finally an alternative 3D multi-layer spiral on-chip antenna is investigated. The proposed alternative on-chip antenna structure fills a 2.5 x 2.5 x 1.3 mm3 volume and has significantly improved radiation performance compared to the single layer solution.