Inspection method, lithographic apparatus, mask and substrate

The embodiment of the invention relates to an inspection method, a lithographic apparatus, a mask and a substrate. The invention provides a method and an apparatus for obtaining focus information relating to a lithographic process. The method includes illuminating a target, the target having alternating first and second structures, wherein the form of the second structures is focus dependent, while the form of the first structures does not have the same focus dependence as that of the second structures, and detecting radiation redirected by the target to obtain for that target an asymmetry measurement representing an overall asymmetry of the target, wherein the asymmetry measurement is indicative of focus of the beam forming the target. The invention further relates to an associated mask for forming such a target, and a substrate having such a target. 本公开的实施例涉及检查方法、光刻设备、掩模以及衬底。种用于获得与光刻过程有关的焦距信息的方法和设备。该方法包括：照射目标，该目标具有交替的第和第二结构，其中第二结构的形式是依赖于焦距的，而第结构的形式不具有与第二结构的形式相同的焦距依赖性；以及检测由目标重定向的辐射，以对于该目标获得表示目标的整体非对称性的非对称性测量