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; and
FIG. 5 illustrates a cross-section view of an overlaying structure of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and more particular to FIGS. 4-5, 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. As the fourth rectangular region 84b and the fourth aligned rectangular region 84a are enlarged, it is noted that the fourth aligned rectangular region 84a has plurality of first pattern elements 85 distributed evenly in the fourth aligned rectangular region 84a. Further, the fourth rectangular region 84b has plurality of second pattern elements 86 and third pattern elements 87 distributed according to a predetermined way. When transferred on the wafer, these pattern elements may form trenches or voids on corresponding layers of the wafer. Alternatively, the fourth rectangular region 84b includes more than three types of pattern elements.
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, the provision of at least two pattern elements by the embodiment allows other pattern elements be chosen to align when any one of the pattern elements above the substrate is damaged during process.
FIG. 5 is the cross-section view of an overlay configuration 90 when implemented on the wafer. In the figure, the first trench 95 and the second trench 96 are formed on the substrate 93 corresponding to different pattern elements 86 and 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 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. However, if the first trench 95 is damaged for whatever reasons disallowing role of alignment, the measured distance d2 provided by the second trench 96 and the mark pattern 94 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
20080032205
