Measurement of Wafer Focus by Grating Shearing Interferometry
Round 1
Reviewer 1 Report
See uploaded file.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer:
Thank you for your advise! I have update my manuscript correspond your comments:
1, some of the figures in section.2 is updated to correspond the expression; the equation and exprecission is also checked for understanding.
2, the key technique of this method is phase difference calculation between focus and defocus position, a phase parsing technique based on spatial-domain phase shift in introduced in Section.3 and the calculated process is also showed.
3, the English language and grammar is checked and updated.
Reviewer 2 Report
This is a very good paper for section 1 Introduction and 2 Methodology. However, the paper needs improvement in 3 Experiment. Let's start with Table 1.
Table 1 shows an independent variable, Shearing, but has no details about any dependent variables. Please complete this Table. For example, two Shearing settings are used to generate Fig 7; which settings? What are the measured parameters from Fig 7; these measurements should be in Table 1. There should be enough detail to repeat the calculations.
Table 2. Please check the uncertainties. Delta might be too large. Lc is negative?
The Conclusion Section. It is not clear what is measured in this work. The measurement goal is variously stated at "defocus", then "h", then "s1, s2", and finally ending up with "high measurement accuracy (30nm)". What did the authors wish to accomplish, and what did the authors achieve?
Other issues:
Page 2 last sentence: Incomplete sentence
Page 3 eq 3: Equations show alpha, but figure shows theta. Is this correct?
Page 3 Fig 4. Labels are too small. Look at "s1".
Page 5 Fig 6. Labels are blurry in PDF sent for review.
Page 5 Fig 7. Add labels and explain what you are measuring from the images.
Author Response
Dear Reviewer:
Thank you for your advise!
I have check my manuscript and update the paper correspond your advise:
1, in the experiment, the calculated process is explained; the phase difference between focus and defocus position in fig.7 is calculated by spatial-domain phase shift technique and the calcalted result is showed in Table.2
2, in this paper, the defocus of wafer is h, which prodece axis-defocus s1 and vertical axis-defocus s2, the mesurement precision of wafer defocus h is analyzed in Table.1 and calibrated by interferometry.
3, other mistakes in figure/equation is checked
Reviewer 3 Report
Reviewer’s report about the manuscript titled: Measurement of wafer focus by grating shearing interferometry
The manuscript proposed the idea for improving the measurement precision and efficiency of wafer focusing in optical lithography instrument (OLI) . Eben the method si not completely new it can be of some interest for the community.
However, there are some critical points that should be addressed and the manuscript needs to be revised in order to reach the level of acceptance (MAJOR REVISIONS).
The manuscript is quite well written. The experiments and results appear to be consistent.
Major issues:
Nevertheless, there are some critical points that authors should address in revising their manuscript to clarify and/or improve their work before it is suitable for publication.
First of all, in the introduction is missing completely other previus method for “opticsl testing” and some additional refs. Should be added were two beams of grating interferometry/fringe projection is adopted such as for example:
- ""Twin-beams digital holography for 3D tracking and quantitative phase-contrast microscopy in microfluidics." Optics express25 (2011): 25833-25842.
- "Fringe projection based on Moiré method for measuring aberration of axially symmetric optics." Optics communications4-6 (2000): 285-293.
For this reason, the authors should complete the introduction and report on this new tecniques by citing the following papers and eventually more on the same topics.
- Conclusions shoud be enriched by adding some comments on the results of the measurments.
- Limitations about the proposed approach are not discussed; authors shoud indicate and discuss about them;
- It is not clear how the fringe are nalyzed: please make an effort to describe and esxplain this issue;
In summary, the presented work has the above weak issues that required to be addressed. A revised manuscript can be considered for publication provided that it gives consistent answer to the comments.
Re-revision is necessary.
Author Response
Dear Reviewer:
Thank you for your comment!
I have update my manuscipt correspond your advise:
1, research tradional grating interferometry and contrast the advantadge of this method introduced in this paper in Section.1
2, the key technique of this method is phase difference calculation between focus and defocus position, a phase parsing technique based on spatial-domain phase shift in introduced in Section.3 and the calculated process is also showed.
Round 2
Reviewer 3 Report
The manuscript has been revised appropriately and now it s ready for publication.
