The paper presents AATMA: a technology mapping algorithm for antifuse based FPGAs. The algorithm is independent of the logic module structure. It can handle large libraries with complex functions and uses a signature-matching based approach to achieve high mapping quality and shorter execution times. This makes it a powerful tool not only for mapping designs onto a logic module but also for the design and evaluation of antifuse-based FPGA logic module architectures. The details of the overall algorithm along with the signature matching technique are presented. The experimental results show that AATMA needs upto 15-20% fewer logic modules than MISII and is upto 15 to 20 times faster.