七级衍射光栅结构及其制备方法、晶圆光刻对准方法
【技术领域】
[0001] 本发明涉及集成电路制造技术领域，尤其涉及一种提高晶圆光刻对准的七级衍射 光栅结构及其制备方法，此外本发明还涉及一种晶圆光刻对准方法。
【背景技术】
[0002] 高精度光刻对准是微纳器件制作所持续面临的重要问题，目前常用的精确对准结 构是光栅图形结构，基于相位光栅原理，当单色探测光垂直入射到该光栅图形结构时，反射 光在不同角度存在各级衍射光，通过特定光学结构将不同衍射级次光强分离，可以实现远 小于对准结构尺寸的精确的光栅定位目的。
[0003] 目前集成电路芯片制造公司在193nm光刻过程中比较常用的光栅图形结构为同时 包含较强第1级衍射光和第7级衍射光的AH74结构。组成该光栅图形结构的光栅精细结构单 元的俯视图和侧视图如图1所示，其中，〇〇指俯视图，该俯视图中〇和π表示探测光垂直照射 到该光栅图形结构时的反射光在同一近邻高度位置的相位，所谓近邻高度位置，指光从衍 射结构出射时的近场光学有效高度，通常与光波长量级相当；为便于计算和理解，本发明将 光栅图形结构的顶层高度位置作为相位监测的近邻高度位置。01和02是同一光学衍射结构 对应的相位相反的两种侧视图。由于光学相位0和π是相对值，因此01和02结构所对应的衍 射级次和衍射光强完全相同。
[0004] 图1所示的ΑΗ74结构的第0、1、2、3、4、5、6、7级衍射光强的晶圆质量WQ分别为： 45.5、25、1.5、2.8、2.4、1、13.3、32.7。可见，其第1级衍射光10为25，第7级衍射光10为32.7。 同时，其最大的衍射光WQ为0级衍射光，由于0级衍射光会干扰其它衍射级次的光强，因此， ΑΗ74结构中较强的0级衍射光会导致其它衍射级次的对比度较低，降低了 ΑΗ74结构的对准 精度。在某些特定光刻工艺过程中，例如刻蚀或化学机械抛光等造成ΑΗ74对准标记发生部 分损坏而导致第7级衍射光强很弱，此时有可能采用第3级和第5级衍射光进行精对准，但是 ΑΗ74的第3和第5级衍射光WQ分别只有2.8和1，不利于在此情形下的光刻对准。在某些应用 条件下，例如在光栅图形结构上层涂覆高吸光材料涂层时，反射到探测器中的衍射光强将 非常低，甚至无法在探测器中收集到足够强的衍射光强，在这种情况下，为了实现晶圆对 准，需要在光刻工艺中对覆盖光栅图形结构的晶圆顶层高吸收涂层进行部分去除等开孔操 作，从而造成了额外使用一块掩模版，或必须更换顶层涂层材料等不利影响。
【发明内容】
[0005] 有鉴于此，本发明提供了一种提高光栅衍射光强的七级衍射光栅结构及其制备方 法，以提高光刻对准精度，同时增大光刻时在光栅图形结构上涂覆材料及其厚度的可选择 范围，从而为集成电路向更小技术节点研发和量产提供精确对准保证。
[0006] 此外，本发明还提供了一种晶圆光刻对准方法。
[0007] 为了达到上述发明目的，本发明采用了如下技术方案：
[0008] -种七级衍射光栅结构，包括：
[0009] 晶圆；
[0010] 形成于所述晶圆上的光栅图形结构；
[0011] 其中，所述光栅图形结构由一个光栅精细结构单元组成或者由多个光栅精细结构 单元循环排列组成，所述光栅精细结构单元的宽度为一个光栅周期，所述光栅精细结构单 元在宽度方向上等分为28个区域，所述28个区域的每个区域上设置有第一图形结构1st或 第二图形结构2nd;
[0012] 所述第一图形结构1st和第二图形结构2nd在光栅图形结构的宽度方向上按照不 同顺序排列形成不同的光栅精细结构单元，所述光栅精细结构单元为第一光栅精细结构单 元、第二光栅精细结构单元、第三光栅精细结构单元、第四光栅精细结构单元、第五光栅精 细结构单元、第六光栅精细结构单元或第七光栅精细结构单元；
[0013] 所述第一光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0014] 所述第二光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 1st}；
[0015] 所述第三光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0016] 所述第四光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 1st 1st}；
[0017] 所述第五光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0018] 所述第六光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0019] 所述第七光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0020] 其中，第一图形结构1st和第二图形结构2nd在同一近邻高度位置下的光学相位相 差:π〇
[0021] 可选地，所述晶圆为空白晶圆或者已经制作好前层图形的晶圆。
[0022] 可选地，所述光栅周期为16微米或者17.6微米。
[0023] 可选地，所述结构还包括：
[0024] 覆盖在所述光栅图形结构上的至少一层材料层。
[0025] -种七级衍射光栅结构的制备方法，包括：
[0026]提供晶圆；
[0027] 对所述晶圆进行光刻和刻蚀，以在所述晶圆上形成光栅图形结构；
[0028] 其中，所述光栅图形结构由一个光栅精细结构单元组成或者由多个光栅精细结构 单元循环排列组成，所述光栅精细结构单元的宽度为一个光栅周期，所述光栅精细结构单 元在宽度方向上等分为28个区域，所述28个区域的每个区域上分别设置有第一图形结构 1st或第二图形结构2nd;
[0029] 所述第一图形结构1st和第二图形结构2nd在光栅图形结构的宽度方向上按照不 同顺序排列形成不同的光栅精细结构单元，所述光栅精细结构单元为第一光栅精细结构单 元、第二光栅精细结构单元、第三光栅精细结构单元、第四光栅精细结构单元、第五光栅精 细结构单元、第六光栅精细结构单元或第七光栅精细结构单元；
[0030] 所述第一光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0031] 所述第二光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 1st}；
[0032] 所述第三光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0033] 所述第四光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 1st 1st}；
[0034] 所述第五光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0035] 所述第六光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0036] 所述第七光栅精细结构单元的结构为：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0037] 其中，第一图形结构1st和第二图形结构2nd在同一近邻高度位置下的光学相位