Review Reports - Boron Impurity Deposition on a Si(100) Surface in a SiHCl3-BCl3-H2 System for Electronic-Grade Polysilicon Production

Round 1

Reviewer 1 Report

In this study, BCl3 and SiHCl3 are mainly adsorbed on the surface of the Si(100) unit cell in the positive position and the hydrogen bottom-two-front position of the molecule, respectively. A study of boron impurities deposited on a Si(100) surface in a SiHCl3- 21 BCl3-H2 system is here reported, using periodic density functional theory with the generalized gradient approximation. The discrete distances of sample are obtained–35.2549 kcal/mol 340 and –10.64 kcal/mol. The results show that BCl3 and SiHCl3 are mainly adsorbed on the surface of the Si(100) unit cell in particular molecular orientations with high performance. I recommend its acceptance for publication after the following issues are well addressed.

1- Abstract: should display the results of the analysis, not the technique.

Fig. 1, 2, 3, 4, 5,6 and 7 Must be elaborated carefully. Edit scales and bring described phased marked on the graphs. The axes are hardly visible.

3-The quality of Figure 8 should be improved for a clear reading.

4-The gas adsorption energy was presented in Table 2, but the correlation between the amount of adsorbed vs. experimental parameters is visible. Did any desorption runs were performer to confirm the amount of adsorber? How the effectiveness was calculated?

5-Section 2 should be corrected. Calculation details? Which parameter?

6-It is better to compare the mechanism procedure developed in this study with previous studies including, A: doi: 10.1016/j.oregeorev.2021.104205, B: doi: 10.1007/s12598-020-01385-6, C: doi: 10.1002/anie.200800172, D: doi: 10.1016/j.coco.2021.101043 and E: doi: 10.1016/j.jallcom.2021.162550

7-The English writing needs to be improved substantially.

Author Response

Response to Reviewer #1

Title: Impurity boron deposition on Si(100) surface in a SiHCl₃-BCl₃-H₂ system for electronic-grade polysilicon production

Dear Prof. ,

Thanks you for your comments concerning our manuscript entitled “Impurity boron deposition on Si(100) surface in a SiHCl₃-BCl₃-H₂ system for electronic-grade polysilicon production” (ID: minerals-1702005). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our further researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised potions are marked in red in the paper. The main corrections in the paper and responds to your comments are as flowing:

Responds to the reviewer’s comments:

In this study, BCl₃ and SiHCl₃ are mainly adsorbed on the surface of the Si(100) unit cell in the positive position and the hydrogen bottom-two-front position of the molecule, respectively. A study of boron impurities deposited on a Si(100) surface in a SiHCl₃- 21 BCl₃-H₂ system is here reported, using periodic density functional theory with the generalized gradient approximation. The discrete distances of sample are obtained–35.2549 kcal/mol 340 and –10.64 kcal/mol. The results show that BCl₃ and SiHCl₃ are mainly adsorbed on the surface of the Si(100) unit cell in particular molecular orientations with high performance. I recommend its acceptance for publication after the following issues are well addressed.

Comment 1: Abstract: should display the results of the analysis, not the technique.

Response: We have revised the abstract by adding results and deleted technique as following:

A study of boron impurities deposited on a Si(100) surface in a SiHCl₃-BCl₃-H₂ system is here reported, using periodic density functional theory with the generalized gradient approximation (GGA). The results show that the discrete distances of BCl₃ and SiHCl₃ from the surface of the Si(100) unit cell are 1.873 Å and 2.340 Å, respectively, and the separation energies are –35.2549 kcal/mol and –10.64 kcal/mol, respectively. BCl₃ and SiHCl₃ are mainly adsorbed on the surface of the Si(100) unit cell in particular molecular orientations, the positive position and the hydrogen bottom-two-front position from the analysis of bond length change and adsorption energy. Adsorption of SiHCl₃ and BCl₃ is accompanied by a charge transfer from the molecule to the surface of the unit cell of 0.24 and 0.29 eV, respectively. BCl₃ reacts more readily than SiHCl₃ with the Si(100) surface, resulting in deposition of impurity boron on the polysilicon surface.

Comment 2: Fig. 1, 2, 3, 4, 5,6 and 7 Must be elaborated carefully. Edit scales and bring described phased marked on the graphs. The axes are hardly visible.

Response: The specific elaboration of these several figures has been modified accordingly in the manuscript.

Comment 3: The quality of Figure 8 should be improved for a clear reading.

Response: We have made changes in the manuscript as following:

Figure 8 State density changes of BCl₃ and SiHCl₃ molecules after adsorption on the Si(100) cell Surface

Comment 4: The gas adsorption energy was presented in Table 2, but the correlation between the amount of adsorbed vs. experimental parameters is visible. Did any desorption runs were performer to confirm the amount of adsorber? How the effectiveness was calculated?

Response: The adsorption of BCl₃ on silicon surface has not reported in the open literature. We have also not calculated the desorption presently. As your comments, we have perform the desorption runs in the present. Thanks for your comment to provide important guiding significance to our further researches.

Comment 5: Section 2 should be corrected. Calculation details? Which parameter?

Response: We have revised Section 2 as Calculational Methods. The parameters have been added in the paper as following:

The convergence criteria for energy, force and maximum displacement are selected at the same time, the values chosen as energy (2×10^–⁵ eV/atom), force (0.05 eV/Å), maximum displacement (2×10^–³Å).

Comment 6: It is better to compare the mechanism procedure developed in this study with previous studies including, A: doi: 10.1016/j.oregeorev.2021.104205, B: doi: 10.1007/s12598-020-01385-6, C: doi: 10.1002/anie.200800172, D: doi: 10.1016/j.coco.2021.101043 and E: doi: 10.1016/j.jallcom.2021.162550

Response: We have compared the mechanism procedure with advised studies in the manuscript.

Comment 7: The English writing needs to be improved substantially.

Response: According to the comment, we have asked a professional company to modify the grammar, and we have revised the manuscript thoroughly to improve the paper and its understanding.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this study of boron impurities deposited on a Si(100) surface in a SiHCl3- BCl3-H2 system. The result, BCl3 reacts more readily than SiHCl3 with the Si(100) surface, resulting in deposition of impurity boron on the polysilicon surface.

Figure image quality can be improve (Fig 2, Fig 3, Fig 4), such as inside the molecular structures and number should be clear.

Author Response

Response to Reviewer #2

Title: Impurity boron deposition on Si(100) surface in a SiHCl₃-BCl₃-H₂ system for electronic-grade polysilicon production

Dear Prof. ,

Responds to the reviewer’s comments:

In this study of boron impurities deposited on a Si(100) surface in a SiHCl₃- BCl₃-H₂ system. The result, BCl₃ reacts more readily than SiHCl₃ with the Si(100) surface, resulting in deposition of impurity boron on the polysilicon surface.

Comment 1: Figure image quality can be improve (Fig 2, Fig 3, Fig 4), such as inside the molecular structures and number should be clear.

Response: Improvements have been made to the clarity of the pictures in the manuscript.

Reviewer 3 Report

Is there a reference stating that poly-si needs to be controlled below 0.33 ppb?
Is poly-Si the same as Si in DFT?
Why were two H atoms added to each Si atom to saturate the covalent bond instead of O atoms? Is SiH cells more general than SiO at the Si surface?
According to Fig. 2, it seems that BCl₃ is bonded with H atoms above Si atoms. Is this right? Using your atomic configuration (SiH), is this explainable that positive position of the molecule is the most favorable in Si (100) surface? What happens if other atoms (such as O atoms) are formed above Si atoms?
It is informative how boron impurity is doped inside poly-Si using DFT. But is there any suggestion or solution to reduce boron impurity inside poly-Si based on your result?

Author Response

Response to Reviewer #3

Title: Impurity boron deposition on Si(100) surface in a SiHCl₃-BCl₃-H₂ system for electronic-grade polysilicon production

Dear Prof. ,

Responds to the reviewer’s comments:

Comment 1: Is there a reference stating that poly-si needs to be controlled below 0.33 ppb?

Response: We have added the reference in the manuscript.

Comment 2: Is poly-Si the same as Si in DFT?

Response: Yes, they are the same and we have added the descript in the manuscript：

The mechanism of SiHCl₃ decomposition on low index plane of polycrystal silicon is performed the same as silicon [30].

Comment 3: Why were two H atoms added to each Si atom to saturate the covalent bond instead of O atoms? Is SiH cells more general than SiO at the Si surface?

Response: Hydrogenation is to maintain the stability of the model, making the model more stable and easier to converge. Thanks for your comments for adding oxygen. We have made changes in the manuscript.

Comment 4: According to Fig. 2, it seems that BCl₃ is bonded with H atoms above Si atoms. Is this right? Using your atomic configuration (SiH), is this explainable that positive position of the molecule is the most favorable in Si (100) surface? What happens if other atoms (such as O atoms) are formed above Si atoms?

Response: We have revised the manufacture as following:

Figure 2 shows the adsorption of BCl₃ on the surface of Si(100). The main bond is the bond between B and Si. From the change of bond length and energy, it can be analyzed that BCl₃ is adsorbed in the positive position of the molecule. Its adsorption energy is negative and the adsorption structure is the most stable.

Comment 5: It is informative how boron impurity is doped inside poly-Si using DFT. But is there any suggestion or solution to reduce boron impurity inside poly-Si based on your result?

Response: We have revised the manufacture as following:

The impurity B may deposit on the surface of the silicon rod competing with polysilicon and the trace impurity B-compound may enrich by the influence of transport phenomena. The above two phenomena are the main reasons causing the high impurity B in the silicon production. It is obvious that the adsorption of BCl₃ on silicon to cause the deposition of B on silicon surface. Therefore, transport phenomenon investigation may be effective method to reduce boron impurity inside poly-silicon, such as increasing mole fraction of H₂ and temperature.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors performed the required modifications. Also, I am grateful for the authors effort in the revised version of the manuscript and after this improvement, I can say that it can be accepted to be published in this journal.

Reviewer 3 Report

No comments