在镜像投影曝光机上使用相移掩膜提高解像力的初步研究

Preliminary study on improving resolution on mirror projection mask aligner with phase shift mask

实现高PPI(单位面积像素个数),需要更细的线宽和更窄的间距,这往往受到光刻设备解像力的限制,本文对基于不改造镜像投影曝光设备而提高光刻解像力进行研究。用半导体工艺模拟以及器件模拟软件模拟分析了离焦量为0时,相位移掩膜和传统掩膜下2.5μm等间隔线的光强分布。根据设备参数模拟分析离焦量为15、30μm时通过掩膜得到的光刻间距情况,最后,实际比较测量了相同条件下各自曝光剂量范围和切面坡度角。实验结果表明:相位移掩膜能使镜像投影曝光机分辨力以下间距(线宽)的工艺容限增大1倍,并使相应曝光量下间距(线宽)的分布更集中,从而增加细线化的稳定性。使用相位移掩膜能提高镜像投影曝光机的解像力。

Realizing high PPI （Pixel Per Inch） requires finer line width and spacing,but it is difficult because of the restrictions of resolution of MPA （Mirror Projection mask Aligner） exposure equipment,so improvement of photolithographic resolution based on no modification of MPA exposure equipment is investigated.First,we compared the intensity distributions results of equidistant lines （2.5 μm） of the conventional binary mask and PSM （phase shift mask） when defocus is zero by software simulation,then defocus dependency is obtained by simulation analysis according to the MPA equipment parameter.Finally,exposure latitude and SEM profile of the conventional binary mask and PSM in the same condition was compared.Experimental results indicate that PSM can double the process margin of the space or line beyond MPA resolution,and make the CD（critical dimension）distribution more concentrated and increase the stability of the fine line.Thus it concluded that lithog raphy resolution of MPA can be improved by PSM.