Optical 3-D Profilometry for Measuring Semiconductor Wafer Surfaces with Extremely Variant Reflectivities

Round 1

Reviewer 1 Report

This paper reported a dual-sensing measuring methodology for 3-D surface profilometry with extreme surface reflectance variance, mainly focus on industrial IC chip inspection. In order to measure both the diffuse and specular surface at the same time, the authors suggested using two cameras from different view angles. This is a reasonable approach. Overall, this paper is written well, and it will be useful for a practical inspection. However, there is some part in technical term should be clear.

 

(1)   In this paper, the authors used the five-step phase-shifting method (PSM) to determine the phase of the projected fringe pattern. Why the authors used five-step PSM instead of four-step PSM? If a five-step PSM is used, the phase-shifting amount should be 2PI/5. If the phase-shifting amount is 2PI/4, the four-step PSM is enough. 

 

(2)   As a special mapping target, an artifact target was used for the camera calibration procedure. However, there is no detailed information about the special artifact target with size or photograph. 

 

(3)   In Figure 6, both the FOV of camera 1 and camera 2 are shown in a perfect square area. I think the FOV of camera 1 is a rectangular area, and the FOV of the other camera 2 will be a trapezoid area strictly. In such a case, the dual camera mapping should be carried out based on an additional coordinate transform even use of a telecentric lens system. Did the authors use any 3D coordinate transform or skew transform procedure? 

 

(4)   In Sec. 2.2.3, the authors mentioned to achieve precise mapping, they used a unique speckle pattern. Such a speckle pattern was naturally observed from the special target or projected a speckle pattern onto the surface of the target? 

 

(5)   In Sec. 3, The measuring FOV can reach 1.0 mm by 1.0 mm and maximum measuring depth of the system can reach 1.0mm. In this case, did the authors used phase unwrapping or not? If not, why the measuring depth can reach to 1.0 mm without phase unwrapping?

 

(6)   For a shiny reflective surface with arbitrary curvature of the target, how did the authors determine the optimum angle for the second camera? If the measured target, such as a semiconductor wafer or other industrial IC chip, the system setting will be changed?

 

 

There are also some points should be revised. 

 

(1) For the title, generally, the word of "Novel" is not suitable to be used. The authors can be considered as "Optical 3-D Profilometry for Measuring Semiconductor Wafer Surfaces with Extremely Variant Reflectivities based on Dual Camera Sensing". 

 

(2) Both Figure 8 and Figure 9 can be omitted, since these results are a common knowledge. If we use N-step PSM, both the background and amplitude and phase of the grating can be automatically obtained. 

 

(3) For Figure 5 and Figure 7, some text contents (for the second line) are missing. 

 

(4) In Figure 12, the caption of (b) should be by capturing "diffuse light", not "specular light". 

Author Response

Please refer to the attached response letter.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper presents a method to evaluate semiconductor wafer surfaces with extremely variant reflectivities. An optical setup having two cameras for the detection of diffuse and specular components has been developed, and the feasibility of the proposed method has successfully been verified through experiments. The achievement described in this paper is meaningful especially in the field of measurement and instrumentation.

Meanwhile, the authors are expected to revise their manuscript regarding the following comments from the reviewer:

1) The authors are expected to check their manuscript carefully. They can easily find the comments: "Error!: Reference source not found" in several portions in the submitted manuscript.

2) The authors are also expected to check the quality of the figures in the manuscript: See Fig. 7, for example.

3) Scales and the axes are required to be indicated in each of the figures.

4) No citation can be found in the first and second paragraphs.

5) The reviewer believes the authors need to mention the white-light scanning interferometers that are also employed to evaluate 3D profiles of such structures.

6) Similar optical configurations (dual sensing strategy) have also been employed in the laser scattering method for the detection of surface defects on a wafer surface. The authors are expected to clearly explain what is new or the difference compared with the conventional methods. 

7) The authors are also expected to explain that the light source in Fig. 3 is not a laser source but an incoherent light source such as a LED.

Author Response

Please refer to the attached response letter.

Author Response File: Author Response.pdf

Reviewer 3 Report

Details of Fig. 5 and 7 were not correctly edited and should be improved.

Author Response

Please refer to the attached response letter.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

All the comments and suggestions from the reviewer have successfully been addressed. 

Meanwhile, the authors are expected to carefully check the manuscript style again.