Fabrication of 30 µm Sn Microbumps by Electroplating and Investigation of IMC Characteristics on Shear Strength

Round 1

Reviewer 1 Report (Previous Reviewer 2)

I am satisfied with the corrections, except that in Figure 8 the abscissa must have the name "time (s)".

Author Response

I finished saving it to the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 3)

"Fabrication of 30 µm Sn microbumps by electroplating and effects of IMC characteristics on shear strength" manuscript is about forming a pure Sn microbump having a diameter of 30 µm with uniformity height using an electroplating method for solder cap on Cu post/Ni barrier. The authors tried to improve the height flatness (with in die, WID) of pure Sn microbumps with a diameter of 30 µm by optimizing process conditions, plating materials, and plating equipment construction.

In order to form bumps of 30 μm in diameter and 50 μm in spacing on a wafer, within wafer (WIW) evaluation of the plating thickness was performed by determining its correlations with shear strength and Inter Metallic Compound (IMC) characteristics.

The authors must revise their whole paper since are numerous format errors and images moving out of the page.

References are incomplete and are not according to the journal style.

There are very few journal papers and no Electronics published papers archive has not been consulted. I may rhetorically ask why the authors did not considered to submit their work in one of the conferences/journals listed in their reference list. 

Why the paper type has not been posted in the manuscript?

I am very unhappy to say that I see no significant improvement in the quality of the paper since its previous submission.

Since its a Technical Note (or at least it was selected as a technical note in the submission system) I would like to see clearly provided the novelty of the communicated procedure as well as a clear separation between the method and the results.

If it is possible I would like to see the plots depicted with the same font size on their axes.

The same for font face (and size) in all tables.

Poor quality images are not welcomed in general in journals, especially when provides experimental data, such as SEM images and chromatograms. By the way, what is a SEM image, because nowhere in the paper is explicitly given the abbreviation. "E" comes perhaps from electronics?

Since Electronics is an electronic journal I see no problem in accommodating a bigger number of pages, so I would ask the authors to provide the images at their relevant size in order to make visible all measured experimental data (for instance I need an eyeglass to see the bump height measurement by the profiler).

The manuscript requires revisions, in their great majority of style.

Author Response

I finished saving it to the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Title of the paper: Fabrication of 30 μm Sn microbumps by electroplating and effects of IMC characteristics on shear strength

General observations: The research provides preparation of a pure Sn microbump with a diameter of 30 μm using an electroplating method for solder cap on Cu post/Ni barrier subsequently finding its intermetallic compound (IMC)  characteristics and shear strength according to reflow recovery. WID and WIW evaluation methods were employed to obtain bump height uniformity. Bump sizes with a diameter of 30 μm, a height of 40 μm, and a space of 50 μm were formed on a 4-inch wafer. Shear strength was measured according to the number of reflows. IMC was evaluated through cross-sectional and plane analysis of bumps. Its correlation with shear strength according to the number of reflows was derived. Sn plating system optimized each process condition according to Sn concentration, current density, and temperature. The shape, surface condition, and height uniformity of the bump were quantified by the 3D profiler and focused ion beam (FIB) analysis.

Some general observations are as follows:

1)       The manuscript title “Fabrication of 30 μm Sn microbumps by electroplating and effects of IMC characteristics on shear strength” may be modified to “Fabrication of 30 μm Sn microbumps by electroplating and investigating IMC characteristics on shear strength”.

2)       There  is an issue in the citation method, the citation should be included in the sentences to avoid misunderstanding for instance:

“To date, semiconductor industries have been developing technologies to reduce chip sizes.[1-3].” should be

“To date, semiconductor industries have been developing technologies to reduce chip sizes [1-3].’

3)       Please refer to Table 1. Evaluation method for each process of the pure Sn bump needs attention towards the use of  * in *Observation of the surface of the plated bump. The * is may

4)       Figure 1 needs repositioning and needs attention to the description as they are hardly readable.

5)       Figure 1 (b) Bump design needs attention for the description, dimensions are hardly visible.

6)       Figure 1 (c) Bump height measurement by 3D Profiler is hardly visible/readable

7)       The symbol used for µm looks odd and may be modified to match the font types used in the text.

8)       Please refer to Table 4. Condition and measurement of Sn microbumps by temperature change which shows various Bump heights for P1 to P16 in µm, it would be better if this is presented in graphical form to show the changes due to temperature.

9)       Figure 6. Cross-section images of Sn bump with one reflow.  The figure needs a short description/caption to understand the effect of reflow times i.e. 1, 5, and 10 times.

10)   Please refer to Table 6. Process conditions and image of micro bump, the “Evaluation items” may be replaced as “Sr.No.” and “Parameters evaluated”, by changing it to two columns.

11)   Please refer to figures i.e. Figure 4. Height deviation of bump according to temperature variation, and Figure 5. Height deviation of bump by current density, Authors may make clear inferences from these two figures for obtained height deviation for comparison purposes.

12)   Please refer to Figure 11. Correlation between IMC Formation Mechanism and Shear Strength. Some standard values of IMC Area and IMC surface roughness may be included in Figure 11 to draw the comparison.

13)   Some of the abbreviations need to be expanded for better understanding.

 

14)   Some clear limitations and practical difficulties may be included along with future research directions.

Author Response

I finished saving it to the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (Previous Reviewer 3)

In my opinion the manuscript meet now the requirements for publication.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

In general, the article is well written, and sufficient. However, the content and novelty of this research are not suitable with the scope of 'Electronics'. I would recommend the authors targeting on a journal in Technology or Material.

Reviewer 2 Report

The work can be accepted, but corrections are required:

The abstract should be corrected (less details, SI system of measures, etc.);

Figures 1 to 6 need technical improvement;

For the diagrams in Figures 3 to 6, the accuracy should be checked and the number of measurements should be increased;

Figures 9 to 12 need technical improvement.

Reviewer 3 Report

The literature coverage on the selected subject is very poor. The novelty of the technical note was supposed to be supported on the current literature.

There are typo errors (example: "temterpature" in the figure/table 2a).

"For example, High Bandwidth Memory (HBM) is a high-performance RAM interface for 3D-stacked DRAM using advanced packaging technologies from Samsung Electronics, AMD, and SK Hynix." it is an copy/paste altered from Wikipedia (https://en.wikipedia.org/wiki/High_Bandwidth_Memory) but the alteration let out important characteristics while on others is misleading. There are many which adopted the HBM (and HBM2) standard today.

Figure 1 is a Gross copy-paste from same source ("Cut through a graphics card that uses High Bandwidth Memory. See through-silicon vias (TSV)." in https://en.wikipedia.org/wiki/High_Bandwidth_Memory). The authors didn't even bothered to alter the image, even if they actually are referring to a part of it; only the quality of the image were lowered. The source of the image was intentionally omitted.

The rest of the images are of very poor quality as well.

#1 hit on google on "Height deviation of bump" (https://doi.org/10.1016/j.jmatprotec.2016.12.031) is conveninetly left out from the referred literature, even if "Height deviation of bump" it is a hot subject in the paper (with 4 occurrences).

Some images are repeated - Table 2 and Figure 9.

"Conclusion" section do not contain conclusions, only a summary.

References are not according with the journal style. Journal archive has not been consulted. In fact, very few articles published in journals pertinent on the subject has been consulted. 

Novelty is not supported. 

Excepting figure 11 all other X-Y plots are in blur.

Representations and values given in text are not in standard units (ex. gram-force and um in Figure 11).

The manuscript do not seem ready for publication. I recommend its revision and resubmission.