We fabricated MIM (Metal-Insulator-Metal) antifuses with Al/a-Si/Mo structure and then examined the I-V characteristics and on-state resistance distribution of antifuses. The leakage current of antifuses is below $1Pa/{mu}m^2$, and programming voltage lies within 10 to 11 V. After programming, on-resistance of antifuses is mostly 10-20$Omega$ and 20% of these have above 100$Omega$. In order to reduce on-resistance and the deviation of this distribution, we tried to inject current again into already programed antifuses (we call this re-programming method). From this method, the resistance of antifuses with above 100Ω can be reduced to below 50$Omega$. When antifuses are programmed by re-programming method, these antifuses have more uniform and lower on-resistance than programmed with one-pulse.