Reply To Reviewer's Comments Final

         James Kolodzey Dept. of Electrical and Computer Engineering 140 Evans Hall University of Delaware Newark, DE 19716 June 7, 2007 Editor JMM

Dear Editor: Please find enclosed an original and a revised manuscript number JMM/241949/PAP/31118,

“Cyclic deep reactive ion etching with mask replenishment””

by T.N.Adam, S.C Kim, P.Lv, S.K. Ray, R.T. Troeger, D. Prather, and J. Kolodzey, along with an attached reply to the referees’ report. We have addressed and incorporated all the reviewer’s comments and believe that they have helped strengthen this paper. We hope that this revised manuscript is now suitable for publication in Journal Micromechanics and Microengineering.

Included is a point-by-point response to the

reviewer’s numbered comments. Thank you for your consideration.

Sincerely yours,

James Kolodzey Enclosures

of

Reply to the first reviewer; 1) In Fig. 1 bottom right the authors show that the cyclic etching yields or could yield a scalloped etch flank, which is not suitable for most applications of such an etch procedure. Very much later in the text in connection to modifications of the process they mention the "sidewall, which then appeared microscopically smooth" or "smooth and nearly straight". Is the "scallopiness" gone or not? An SEM picture would help to convince the reader. Otherwise the success of the whole technological process and thus the manuscript are in question. Please note that Fig. 1 in the original paper has been renamed to Fig.2 in the revised paper due to the insertion of Fig 1. In principle, it is possible that some small amount of scalloping may always exist, but we have demonstrated that the amount of scalloping can be reduced to a level that is negligible depending on the desired smoothness by adjusting the relative timings of the three process steps. The adjustable degree of smoothness was made clear on revised page 4, 23 and in the micrograph of Figure 8. 2) Literature citations should be "[#]" (not with the number as a superscript). All the references’ citations were corrected in the format of [#] (not with the number as a superscript) as the reviewer’s comment. 3) Microns should not be abbreviated "um". The micron units were corrected as µm rather than um in the original paper. 4) Pressures should not be given in "T", rather in "Torr" or recalculated and even better given in "hPa". Pressures are now designated in Torr. We agree with the reviewer that Pascal units are more quantitative, but Torr is still widely used in practice, and we intended for this to be an experimental oriented paper 5) Fig. 1 should be of better quality (maybe colored) to make the points clear. The polymer layer is hardly distinguished from the substrate. Note that Fig. 1 is now Fig. 2 in the revised paper. We have provided original figures in larger scale with careful attention to the image contrast in the revised paper. While color may provide advantages, it is still the case that many printings of journal articles are still done in black & white, as are prevalent photocopies. We sincerely hope that the revised higher contrast figures are acceptable, and note that many published figures have a similar degree of contrast and general appearance.

6) Fig. 7 should be of much better quality. Note that Fig. 7 is now Fig. 8 in the revised paper. We agree with the reviewer and so have organized Fig. 8 with boxes and sizing to make it more clear to the fullest extent possible and added a scale bar. We feel that the micrographs provide important information and are reluctant to change the fundamental impact.

Reply to the second reviewer; Overview 1. The paper does not have remarkable novelty and usefulness. This is because the process described here is quite similar to the Bosch process. It could be novel that the process was developed by using the conventional CC-RIE but it is not enough. The paper should clearly show the general effect that was obtained by the experimental results. As one of many dry etching techniques, even the Bosch process itself is also not novel in a sense. We believe, however, that a method that achieves deep etching in conventional RIE systems (rather than ICP) and that does not require commercial licensing would be valuable to the technical community. There are many groups in possession of standard RIE tools, but who cannot use the official Bosh process, and may have need for deep etching that is compatible with standard mask materials. We have made the advantages of this aspect more clearly in the abstract, in the introduction, and in the conclusions. 2. The author needs to sufficiently think about the structure of the paper again. It is easier to understand the contents of the paper when the paper has “Introduction”, “Experimental method”, “Results and Discussion”, and “Conclusion”. We agree and have reformatted the paper organization to include the suggested categories as following; 1. Introduction 2. Experimental method 3. Results and Discussion 4. Conclusion. 3. The summary (i.e., conclusion) must not have a new description like the microdisk shown in Fig. 8. Before the summary, the author must explain the device in Fig. 8. The current description in the summary is not suitable for the conclusion.

Fig.8. in the original paper is now Fig. 9. In the original paper, a new description of the microdisk was introduced which is not suitable as the reviewer aptly pointed out, so we moved the description of the microdisk, as an example of a device structure made with the technique, into the section on Results & Discussion 4. The microdisk does not have a clear relationship with the process described in the paper. If the microdisk is very important, the paper needs to change the story. For example, to fabricate the microdisk, the specific process using the conventional RIE etcher was developed. Examples are important for any new techniques, and the microdisk is intended as a sample of the kind of structure that can be made with the described process. 5. Why did the author need to experiment using CC-RIE? The paper might need the reason. Compared with an ICP etcher, there are a lot of negative effects for using the CC-RIE. The main reason for our pursuit was the utility of this technique. The formal Bosch process requires a specialized type of etching tool, an ICP tool, that has magnetic based confinement of the plasma, and its official use must be licensed. The process described in this manuscript does not require the specialized ICP tool but can be used on conventional RIE systems that are prevalent. As a process described in the public domain, released to the technical community, it does not required licensing. Most of all, the manuscript describes a new type of process that offers alternatives to conventional approaches, and is therefore novel, and provides utility beyond the state of the art. Therefore, it may be of broad interest to the technical community. The reason that this technique was developed is because the authors had a strong need for deep reactive etching and were not able to obtain the results on the newly installed ICP that was accessible at the time. So the technique was developed to support a real need, and it was considered to be of possible interest to other researchers as well. Details P 1, L 23: There are no descriptions of “high aspect ratios, 100um, and 1um” in the text. If the author wants to mention them in the abstract, it is necessary to describe them in the text. We described the aspect ratios in the “Results and Discussion” section in the revised manuscript in page 23,line 19 as following “Aspect ratio of etched depths over 100 µm was obtained with this technique.” P2, L 2: “Introduction” “1. Introduction” Page 2, line 2 is now page 2, line in the revised paper. We numbered this section as “1. Introduction”

P 2, L 4: The word of “sacrificial” is proper? The word “sacrificial” was removed because this section is beyond the scope of the paper P 2, L 8: Please remove “1.1 Multi-Step Reactive-Ion Etching”. Since we reformatted the paper organization, we removed “1.1 Multi-Step Reactive-Ion Etching” accordingly P 2, L16: A {110}-oriented plane is generally etched faster. The author thinks about KOH etching with IPA? It was not the intent to describe exhaustively the variety of wet etches that are useful, and we erased this section because we think the wet etch characteristics depending on the plane orientation is beyond the scope of this paper. P 4, L14: Please remove the sentence of “Such an alternative….below”, and connect “We describe… applications” in P2 to the end of the sentence of “ Therefore it….plasma excitation” in P4. These were removed and rewritten as suggested in page 4. P 4, L16: “Experimental” “2. Experimental Method” Note that page4, line16 is now page4, line9. This was changed to “ 2. Experimental Method” as suggested. P5, L 7: “amount” “thickness”? Note that page5, line7 is now page4, line27 in the revised paper. This was changed to “thickness” as suggested P5, L13: “though” “through” Note that page5, line13 is now page 5,line8. This typo has been corrected to “through” P5: About the etcher, drawing will help understand what you are mentioning. Figure 1 was added in page 6 to help readers understand the etcher system as suggested. P5, L23: In the text, both step “a)” and step “A” can be seen. Please select one. Note that page5, line23 is now page7, line1. We picked up “A” instead of “a)” P6: Please insert “3. Experimental Results and Discussion” between L1 and L2. Please change from “1.1.1.” to “3.1”. “1.1.1 Isotropic Etch (STEP A)” was changed to “ 2.1 Isotropic Etch (STEP A)” In page 7,line 1. And “3. Experimental and Discussion” was inserted in page19, line13. P 8, L2: What is “microdisk prototype”? The author needs to explain.

Note that page8, line2 is now page9, line1. “microdisk prototype” was renamed to “Structure(microdisk)” for clarity. P 8, L19 and L22: About surface roughness, the data should be shown in the paper. The value is important. Note that page8, line19 is now page9, line22. We added the surface roughness of each case, 500nm for the rough surfaces and 100nm for the smooth surfaces at page 9, line22 as following; “produced rough surfaces (rms surface roughness ≈ 500nm). Mixing SF6 with O2 reduced the etch rate (see Figure 4), but produced smooth surfaces (rms surface roughness ≈ 100nm).” P 9, L4: Not understand “[18]”. What? Note that page9, line4 is now page10, line4. Citation “[18]” was meant to refer to the vendor of a photoresist (NR5) used in the experiment. P11, L16: What does the author want to mention with the comparison between the ICP and the author’s etcher? Just does the author want to mention low etching rate and stable process temperature? Page 11, line 16 moved to Page 12,line 17 in the revised paper. Our intent was to compare our process with alternatives, and to mention its characteristics and limitations. P13, L2: “1.1.2.” “3.2” Note that page13, line 2 is now page 14,line 1 in the revised paper. “1.1.2” was renumbered to “2.2 Isotropic Polymer Deposition (STEP B)” as we reformatted the organization of the paper. P14, L2: “CF4” “CF4” “CF4” has been changed to “CF4” in the revised paper. P14: What is the relationship between the polymer removal process described here and the deposition process? What does the author want to mention here? Note that page14 in the original paper is now described from page 14, line 26 to page 15,line 3. To provide the most information to the reader, we give the conditions for net deposition of protective polymer versus H2 flow. The intention is to have the polymer remain on the sidewalls for protection. To etch the underlying silicon, the polymer must be removed from horizontal surfaces. Therefore both the deposition and the removal of polymer are necessary. P16, L15: “1.1.3.” “3.3” Note that line 15 is now line 14. The section was renumbered to “2.3 Anisotropic Polymer Removal (STEP C)” in the revised paper. P19, L13: “5.3.1. Cyclic Process Adjustments and Discussion” “3.4 Cyclic Process Adjustments”

“5.3.2 Cyclic Process Adjustments and Discussion” has been replaced with “3. Results and Discussion” P 22, Figure 7: What is the meaning of “1:10m, 0:40m, and 3:40m”? What is the meaning of “C too long”? The figure needs scale. Note that Figure 7 is now Figure 8 in the revised paper. The times were changed to seconds for clarity as following; 1:10m1 minute 10 seconds, 0:40m40 seconds1 and 3:40m3 minutes 40 seconds. And a length scale was added. The section of “C too long” in the original paper was a typo, so we removed it. P23, L16: “5.3.2. SUMMARY” “4. Conclusion” We replaced this “5.3.2. SUMMARY” section with “4. Conclusion” at line 20 in the revised paper as suggested P23, L17: Please remove “These results show that”. Page 23,line 17 is now page 23, line 21. This section has been changed as following; “We have described a novel multistep etching process, which operates on conventional RIE tools” P 23, L21: The text of the paper does not mention “a new doping-selective wet etching”. Please explain it in the text first. The section of “ a new doping-selection wet etching” was removed because it ‘s beyond of the scope of this paper. P23: In the text of the paper, there is no description of silicon microdisks. Please describe it in the text first In the original paper, a new description of the microdisk was introduced which is not suitable as the reviewer aptly pointed out, so we moved the description of the microdisk, as an example of a device structure made with the technique, into the section on Results & Discussion P24, L7: Please remove “5.3.3.” As we restructured the paper, we removed 5.3.3 in the revised paper as suggested P24, L8: What is “[33]”? That was a typo, so we removed it.