The present invention relates to an overlay mark and a method for fabricating the same, and, more particularly, to an overlay mark and a method for fabricating the same for a spacer double patterning process.
As circuit widths become smaller with the development of the integrated circuit (IC) manufacturing process, the control of critical dimension (CD) of components becomes more important. When two different patterns are formed in two different areas of a wafer, photoresist layers in the two different areas should be formed by different exposures, so that the respective patterns can have predetermined critical dimensions. When the pitch of a pattern is less than the resolution of a single exposure, a double patterning process can be performed to meet the requirements of the pitch of the pattern.
For a well-manufactured integrated circuit product, the pattern transfer process is performed several times to transfer the circuit patterns to each non-processing layer to form the circuit device. Therefore, it is important to align the successive patterned layers to reduce the misalignment as the critical dimension of the semiconductor device becomes smaller.
An overlay mark can be used to insure the alignment precision between the successive patterned layers. That is, after the successive patterned layers are formed, a process for determining the precision of the overlay alignment can be performed by referring to the overlay marks of the successive patterned layers.
However, the traditional mark patterns are too thin and have very low image contrast relative to a background material layer. That is, it is difficult to recognize the overlay mark by referring to the fine pattern. Therefore, for the spacer double patterning process, it is difficult to use a traditional overlay mark to monitor overlay performance. Additionally, a traditional overlay mark cannot be used for overlay measurement.
In view of the above issues, the conventional overlay mark has many problems. Therefore, there is a need for a new overlay mark and a method for fabricating the same.
To solve the problems of the above-mentioned prior art, one aspect of the present invention discloses an overlay mark which is disposed on a substrate comprising a plurality of mark elements, wherein each mark element includes two column elements and a plurality of row elements, and the row elements connect the two column elements to form a plurality of holes exposing a substrate between the two column elements.
To solve the problems of the above-mentioned prior art, another aspect of the present invention discloses a method for fabricating an overlay mark, comprising the steps of: forming a patterned layer on a substrate, wherein the patterned layer comprises at least one mark element forming region, wherein each mark element forming region comprises two column recesses and a plurality of row recesses, and the row recesses connect the two column recesses; growing a mark material from the sidewalls of the column recesses and the row recesses so that the mark material merges in the column recesses and the row recesses; and removing the patterned layer.
The foregoing has outlined rather broadly the features of the present invention in order that the detailed description of the invention to follow may be better understood. Additional features of the invention will be described hereinafter and form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the concept and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
The objectives of the present invention will become apparent upon reading the following description and upon reference to the accompanying drawings in which:
As shown in
Each column recess 16 has a width X′ less than twice the width Si of a first spacer 561 or 562 (predetermined by the user) (see
In this embodiment, each mark element forming region 12 further comprises a plurality of segments 20 arranged between the column recesses 16 and the row recesses 18 and spaced from each other. The segments 20 may be, but are not limited to, polygonal or circular shapes, or a combination thereof.
Referring to
Each column element 56 has a width X less than twice the width 51 of a first spacer 561 or 562 (see
Since each mark element 54 of the overlay mark 5 of the present invention has a width greater than that of the conventional overlay mark, the overlay mark 5 of the present invention can have high image contrast. That is, for spacer double patterning processes, it is effective to use the overlay mark 5 of the present invention to monitor overlay performance, and for overlay measurement.
Although the present invention and its objectives have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the processes discussed above can be implemented using different methodologies, replaced by other processes, or a combination thereof.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.