A phase-based alignment technique for scanning electron-beam lithography is proposed and evaluated. The approach uses a grid alignment mark rotated with respect to the beam deflection axes and requires only a single, one-dimensional (1D) line scan to perform subpixel registration in both the x and gamma directions. This 1D, phase-based method promises subpixel alignment without interpolation, faster mark signal acquisition, and more computationally efficient detection. Theoretical limits for alignment accuracy and a simple phase-estimation algorithm that approaches these limits are described. Monte Carlo simulations indicate that nanometer-level registration precision can be achieved with modest grid periods and signal to noise ratios (SNRs). Experimental measurements of registration variance as a function of SNR agree well with both theory and simulation. Registration errors of 3 nm (1-standard deviation) are observed using a 1 mu m grid period, 49 nm pixel size, and the highest observed SNR of 5.9. (c) 2005 American Vacuum Society.