Details
| Original language | English |
|---|---|
| Article number | 9279311 |
| Pages (from-to) | 50-57 |
| Number of pages | 8 |
| Journal | IEEE journal of photovoltaics |
| Volume | 11 |
| Issue number | 1 |
| Early online date | 3 Dec 2020 |
| Publication status | Published - Jan 2021 |
| Externally published | Yes |
Abstract
The POCl3 diffusion is the main technology to form the p-n junction of industrial silicon solar cells. However, the diffusion mechanism of phosphorus (P) into the silicon wafer is not fully understood. In this article, we study the P diffusion mechanism during drive-in by systematically varying the drive-in time in the oxygen (O2) atmosphere and subsequently in nitrogen (N2). When increasing the drive-in time in O2 from 0 to 120 min, the sheet resistance Rsheet stays constant at 485±30sq. Hence, we demonstrate for the first time that the phosphorus diffusion can be completely suppressed in the O2 atmosphere. When adding a drive-in in the N2 atmosphere directly after the drive-in in O2, we find that the SiO2 thickness dSiO2,O2 changes from initially 2 to 10 nm after O2 drive-in to an equilibrium SiO2 thickness dSiO2,eq of 4.7 nm after N2 drive-in. We prove for the first time that if dSiO2,O2 > dSiO2,eq, no P diffuses into the silicon wafer even in the N2 atmosphere. Only if dSiO2,O2 < dSiO2,eq, phosphorus diffuses into the silicon wafer in the N2 atmosphere. We propose a detailed chemical model to explain our experimental results, which assumes that the diffusion of Si from the wafer through the SiO2 interface toward the PSG plays a key role. In this model, P can only diffuse into the Si wafer if P2O5 in the PSG is reduced by the Si from the wafer to P and SiO2.
Keywords
- Diffusion profile, emitter saturation current density, in situ oxidation, phosphorus diffusion, phosphosilicate glass, SiOgrowth
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Electrical and Electronic Engineering
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In: IEEE journal of photovoltaics, Vol. 11, No. 1, 9279311, 01.2021, p. 50-57.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - A Detailed Chemical Model for the Diffusion of Phosphorus into the Silicon Wafer during POCl3Diffusion
AU - Jager, Philip
AU - Mertens, Verena
AU - Baumann, Ulrike
AU - Dullweber, Thorsten
N1 - Funding information: Manuscript received September 11, 2020; revised November 4, 2020; accepted November 4, 2020. Date of publication December 3, 2020; date of current version December 21, 2020. This work was supported by the German State of Lower Saxony and the German Federal Ministry for Economic Affairs and Energy (BMWi) within the research project “GENESIS” under Contract 0324274B. (Corresponding author: Philip Jäger.) The authors are with the Institute for Solar Energy Research GmbH, 31860 Emmerthal, Germany (e-mail: jaeger@isfh.de; mertens@isfh.de; bau-mann@isfh.de; dullweber@isfh.de).
PY - 2021/1
Y1 - 2021/1
N2 - The POCl3 diffusion is the main technology to form the p-n junction of industrial silicon solar cells. However, the diffusion mechanism of phosphorus (P) into the silicon wafer is not fully understood. In this article, we study the P diffusion mechanism during drive-in by systematically varying the drive-in time in the oxygen (O2) atmosphere and subsequently in nitrogen (N2). When increasing the drive-in time in O2 from 0 to 120 min, the sheet resistance Rsheet stays constant at 485±30sq. Hence, we demonstrate for the first time that the phosphorus diffusion can be completely suppressed in the O2 atmosphere. When adding a drive-in in the N2 atmosphere directly after the drive-in in O2, we find that the SiO2 thickness dSiO2,O2 changes from initially 2 to 10 nm after O2 drive-in to an equilibrium SiO2 thickness dSiO2,eq of 4.7 nm after N2 drive-in. We prove for the first time that if dSiO2,O2 > dSiO2,eq, no P diffuses into the silicon wafer even in the N2 atmosphere. Only if dSiO2,O2 < dSiO2,eq, phosphorus diffuses into the silicon wafer in the N2 atmosphere. We propose a detailed chemical model to explain our experimental results, which assumes that the diffusion of Si from the wafer through the SiO2 interface toward the PSG plays a key role. In this model, P can only diffuse into the Si wafer if P2O5 in the PSG is reduced by the Si from the wafer to P and SiO2.
AB - The POCl3 diffusion is the main technology to form the p-n junction of industrial silicon solar cells. However, the diffusion mechanism of phosphorus (P) into the silicon wafer is not fully understood. In this article, we study the P diffusion mechanism during drive-in by systematically varying the drive-in time in the oxygen (O2) atmosphere and subsequently in nitrogen (N2). When increasing the drive-in time in O2 from 0 to 120 min, the sheet resistance Rsheet stays constant at 485±30sq. Hence, we demonstrate for the first time that the phosphorus diffusion can be completely suppressed in the O2 atmosphere. When adding a drive-in in the N2 atmosphere directly after the drive-in in O2, we find that the SiO2 thickness dSiO2,O2 changes from initially 2 to 10 nm after O2 drive-in to an equilibrium SiO2 thickness dSiO2,eq of 4.7 nm after N2 drive-in. We prove for the first time that if dSiO2,O2 > dSiO2,eq, no P diffuses into the silicon wafer even in the N2 atmosphere. Only if dSiO2,O2 < dSiO2,eq, phosphorus diffuses into the silicon wafer in the N2 atmosphere. We propose a detailed chemical model to explain our experimental results, which assumes that the diffusion of Si from the wafer through the SiO2 interface toward the PSG plays a key role. In this model, P can only diffuse into the Si wafer if P2O5 in the PSG is reduced by the Si from the wafer to P and SiO2.
KW - Diffusion profile
KW - emitter saturation current density
KW - in situ oxidation
KW - phosphorus diffusion
KW - phosphosilicate glass
KW - SiOgrowth
UR - http://www.scopus.com/inward/record.url?scp=85097964665&partnerID=8YFLogxK
U2 - 10.1109/JPHOTOV.2020.3038331
DO - 10.1109/JPHOTOV.2020.3038331
M3 - Article
AN - SCOPUS:85097964665
VL - 11
SP - 50
EP - 57
JO - IEEE journal of photovoltaics
JF - IEEE journal of photovoltaics
SN - 2156-3381
IS - 1
M1 - 9279311
ER -