In order to better understand the mechanics of metallization structures having very fine features, we performed in-situ, temperature-dependent X-ray strain measurements on Al-Cu films patterned into gratings with linewidths of 0.2-0.8μm, with and without a dielectric covering In comparison with earlier work on coarser structures, we find larger strains and less hysteresis, indicating an increased yield stress. The stress in unpassivated lines is almost independent of the linewidth. The slope of the stress/temperature curves for passivated lines increases with decreasing linewidth, so that the compressive stress at 500°C reaches 900MPa for the narrowest lines. The tensile stress at RT is smaller for the narrower lines, suggesting that these lines may not stress-void as much as wider ones. The significance of these results for stress voiding and electromigration will be discussed.