Patent Application
20070298329
To solve the problems of the exposure image shifting, exposure image rotating and exposure image abnormally magnification due to the exposure image region non-overlap with the mask center, the present invention provides a photomask design in which more than one alignment mark is disposed aside each of the image regions. Therefore, the relative position between the photomask and the wafer can be adjusted by aligning the alignment marks around the selected image region onto the wafer alignment marks on the wafer respectively.
As shown in
In this embodiment, the photomask having one image region and the image center non-overlap with the substrate center are used to describe the present invention. However, the shape and the size of the image region on the photomask of the present invention are not limited to this embodiment. Moreover, the shapes of the alignment marks 120 are not limited to the rectangle shape. That is, the shapes of the alignment marks 120 can be selected from a group consisting of cruciform shape, triangle shape and polygon. Furthermore, the number and the positions of alignment marks 120 are not limited to this embodiment. On the other words, at least one alignment mark 120 is disposed aside one side of the image region 110 or at least one alignment mark 120 is disposed near each of the corners of the image region 110.
As shown in
In this embodiment, the photomask having two image regions with identical shapes and identical sizes and none of the image centers of the image regions non-overlap with the substrate center are used to describe the present invention. The aforementioned photomask having two image regions with identical shapes and identical sizes is the alleged symmetric photomask. However, the number, the shapes and the sizes of the image regions on the photomask of the present invention are not limited to this embodiment. Moreover, the shapes of the alignment marks 220 are not limited to the rectangle shape. That is, the shapes of the alignment marks 220 can be selected from a group consisting of cruciform shape, triangle shape and polygon. Furthermore, the number and the positions of alignment marks 220 are not limited to this embodiment. On the other words, at least one alignment mark 220 is disposed aside one side of each of the image regions 210 or at least one alignment mark 220 is disposed near each of the corners of each of the image regions 210.
As shown in
In this embodiment, the photomask having at least one image region with the shape or the size different from those of other image regions and none of the image centers of the image regions non-overlap with the substrate center are used to describe the present invention. The aforementioned photomask having at least one image region with the shape or the size different from those of other image regions is the alleged asymmetric photomask. Nevertheless, the number, the shapes and the sizes of the image regions on the photomask of the present invention are not limited to this embodiment. Moreover, the shapes of the alignment marks 320 are not limited to the rectangle shape. That is, the shapes of the alignment marks 320 can be selected from a group consisting of cruciform shape, triangle shape and polygon. Furthermore, the number and the positions of alignment marks 320 are not limited to this embodiment. On the other words, at least one alignment mark 320 is disposed aside one side of each of the image regions 310 or at least one alignment mark 320 is disposed near each of the corners of each of the image regions 310.
In the step 400, a photomask is provided. The photomask comprises a substrate having at least one image region and several alignment marks formed thereon. The image regions are located on the substrate and at least one of the image centers of the image regions is non-overlap with the substrate center of the substrate. The alignment marks are located on the substrate and surrounding each of the image regions respectively. Furthermore, at least four alignment marks surround one image region. The arrangements of all elements on the photomask and the method for forming the elements on the photomask can be accomplished according to one of the embodiments stated from
In the step 410, at least one image region selected from the image regions on the photomask is used as an exposure image region to be transferred in this exposure procedure. That is, for one exposure process, more than one image region can be combined to be an exposure region as the exposure image region stated above. Further, the image region can be disposed on any position on the photomask.
Then, in the step 420, the alignment marks around the exposure image region on the photomask are correspondingly aligned onto several wafer alignment marks on the edge of a wafer respectively.
Moreover, in the step 430, the pattern in the exposure image region is transferred onto a photo sensitive material layer on the wafer by using a optical projecting system. The optical projecting system comprises members such as the light source, the condenser lens and the objective lens. In addition, the photo sensitive material layer can be, for example, made of the positive photoresist, the negative photoresist or other proper photo sensitive material.
Altogether, in the present invention, more than one alignment mark is disposed aside each side of each image region or aside each corner of each image region. Moreover, the aforementioned design of the alignment mark around each of the image regions can be applied to various photomask with image center non-overlap with the substrate center no matter the photomask possesses only one image region or several image regions and no matter the photomask is a symmetric photomask or an asymmetric photomask. Therefore, before the photolithography process is performed, the relative position between the photomask and the wafer can be adjusted by aligning the alignment marks around the selected exposure image region onto the wafer alignment marks on the wafer respectively. Accordingly, during the continuously performed exposure process, the exposure image shifting, rotating and abnormal image magnification due to high temperature can be improved. Hence, the image transferring qualities of the dies on the same wafer is uniform and the overlay between the current process layer and the previous process layer is improved. Accordingly, the wafer can be prevented from being discarded and the yield of the photolithography process is improved.
The present invention has been disclosed above in the preferred embodiments, but is not limited to those. It is known to persons skilled in the art that some modifications and innovations may be made without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be defined by the following claims.
