BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 illustrates a schematic drawing of step and repeat projective exposure;
FIG. 2A illustrates a BiB overlay mark designed on a photomask as in prior technique;
FIG. 2B illustrates a BiB aligned mark pattern formed on a substrate;
FIG. 2C illustrates an aligned structure of overlaying patterns formed by BiB overlay mark;
FIG. 3A illustrates a AIM overlay mark designed on a photomask as in prior technique;
FIG. 3B illustrates an AIM aligned mark pattern formed on a substrate;
FIG. 3C illustrates an aligned structure of overlaying patterns formed by AIM overlay mark;
FIG. 4 illustrates an overlaying structure of AIM overlay mark patterns of the present invention;
FIG. 5A illustrates a cross-section view of an overlaying structure of the present invention in x orientation;
FIG. 5B illustrates a cross-section view of an overlaying structure of the present invention in y orientation;
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and more particular to FIGS. 4-5B, there are shown exemplary embodiments of the overlay mark configuration according to the present invention.
As indicated in FIG. 4, the embodiment discloses an AIM configuration with improved overlay mark. Similar to that disclosed in and described for FIG. 3C, this overlay configuration includes four aligned rectangular regions 81a, 82a, 83a and 84a, and four rectangular regions 81b, 82b, 83b and 84b. Each rectangular region has plurality of first pattern element 85 distributed evenly in each rectangular region. In addition, as indicated in FIG. 4, both the second aligned rectangular region 82a and the fourth aligned rectangular region 84a on x-orientation have plurality of second pattern element 86 distributed evenly therein; both the first aligned rectangular region 81a and the third aligned rectangular region 83a on y-orientation have plurality of third pattern element 87 distributed evenly therein. When transferred on the wafer, these pattern elements may form trenches or voids on corresponding layers of the wafer. Wherein, the second and the third pattern elements are different from each other.
In IC manufacturing process, to transfer the device patterns more precisely and to avoid the inaccuracy on orientations when transferring, using the predetermined measured distance on both horizontal and vertical orientations for alignment is required. In an embodiment of the present invention, an overlay mark includes different pattern elements on x-orientation and y-orientation respectively for the more accurate alignment on both orientations. It is noted that even the AIM overlay mark on the layer of wafer may be eroded after processes including etching, CMP or ion implant such that alignment procedure can not be performed accurately. However, in the overlay mark of the present invention, when the second pattern element 86 on x-orientation was damaged, the third pattern element 87 on y-orientation may be used to align. Likewise, when the third pattern element 87 on y-orientation was damaged, the second pattern element 86 on x-orientation may be used to align.
FIG. 5A is the cross-section view of an overlay configuration 90 on x-orientation when implemented on the wafer. In the figure, the first trench 95 is formed on the substrate 93 corresponding to the pattern elements 86 of the overlay mark in FIG. 4. In succession, a priming step on the substrate 93 is performed for enhancing adhesive capability between the photo-resist and the substrate 93. This priming step involves usage of Hexamethyldisilazane (HMDS) layer 92. Afterwards, the photo-resist 91 is coated and the overlay mark on the succeeding photomask is transferred to the photo-resist 91 as the second mark pattern 94. The measured distance d1 provided by the first trench 95 and the mark pattern 94 can be used to perform the alignment procedure on x-orientation.
In another aspect, FIG. 5B is the cross-section view of an overlay configuration 90 on y-orientation when implemented on the wafer. In the figure, the second trench 95 is formed on the substrate 93 corresponding to the pattern elements 87 of the overlay mark in FIG. 4. In succession, a priming step on the substrate 93 is performed for enhancing adhesive capability between the photo-resist and the substrate 93. This priming step involves usage of Hexamethyldisilazane (HMDS) layer 92. Afterwards, the photo-resist 91 is coated and the overlay mark on the succeeding photomask is transferred to the photo-resist 91 as the third mark pattern 101. The measured distance d2 provided by the second trench 102 and the mark pattern 101 can be used to perform the alignment procedure on y-orientation.
However, if the first trench 95 on x-orientation is damaged for whatever reasons disallowing role of alignment, the measured distance d2 provided by the second trench 102 on y-orientation and the third mark pattern 101 then can be used as a backup for alignment procedure.
By means of the detailed descriptions of what is presently considered to be the most practical and preferred embodiments of the subject invention, it is expected that the features and the gist thereof be clearly described. Nevertheless, these embodiments are not intended to be construed in a limiting sense. Instead, it will be well understood that any analogous variations and equivalent arrangements will fall within the spirit and scope of the invention.
Patent Application
20080034344
