Abstract
One of the leading issues leading to decreased mirror lifetime is that debris contamination and buildup of debris on the surface of the primary mirror optics that comes from the use of both Sn and Li in GDPP or LPP. This debris generation leads to a decreased reflectivity from the added material thickness and increased surface roughness that contributes to scattering. In order to overcome this issue, it is important to understand the implantation of debris material into the optic material matrix and the subsequent diffusion of this debris within the mirror matrix. This change in composition and surface morphology can dramatically affect reflectivity and mirror lifetime. A multifunction test stand was built to investigate this mirror lifetime issues that arise from the use of both Li and Sn. Through the use of both a Li+ ion beam, electron beam evaporator for Li and Sn deposition, and a quartz crystal microbalance to study both lithium implantation and sputtering at various incident ion energies, angles, quantity of debris, and mirror temperatures, the problem of Li generated debris was investigated. Subsequent surface analysis via SEM, XPS, AFM, and TOF-SIMS, were used to study the resultant mirror material properties of composition, diffusion, and surface roughness leading to a better overall understanding of the mirror contamination issue. Preferential Li diffusion through a ruthenium capping layer was seen depthwise into the mirror matrix with minimal radial diffusion while the mirror sample was at room temperature. However, at an elevated temperature, enhanced surface radial diffusion of lithium and segregation in the capping layer was seen with minimal diffusion into the underlying mirror matrix. In conjunction with study of the contamination mechanism, the use of a secondary plasma was investigated as a way to prevent degradation and clean the mirror optics so as to extend the lifetime with no interference to the source or other components. Through the use of a helium helicon plasma, it was possible to induce lithium evaporation and break up of clusters that form on the surface. The plasma parameters were measured using a RF-compensated Langmuir probe to yield electron temperature and density while the sample mirror material was at various temperatures and voltage bias. It was shown that in situ plasma cleaning of optics is a valid method towards achieving improved mirror lifetime. For Sn optics cleaning, the use of halide etching to readily transport Sn off the surface was successfully demonstrated. Ar and Cl plasma and other gas mixtures demonstrated selective etch rate for Sn versus mirror materials of SiO 2, Mo, Si, and Si 3N 4 and it is possible to set a scheme such that Sn debris is preferentially sputtered while leaving the mirror material undisturbed and yielding a long lifetime for the optics.
| Original language | English (US) |
|---|---|
| Article number | 138 |
| Pages (from-to) | 1125-1136 |
| Number of pages | 12 |
| Journal | Progress in Biomedical Optics and Imaging - Proceedings of SPIE |
| Volume | 5751 |
| Issue number | II |
| DOIs | |
| State | Published - Sep 19 2005 |
| Event | Emerging Lithographic Technologies IX - San Jose, CA, United States Duration: Mar 1 2005 → Mar 3 2005 |
Fingerprint
ASJC Scopus subject areas
- Engineering(all)
Cite this
Evaluating advanced fuel candidates in surface cleaning of optics by plasma exposure (scope). / Neumann, M. J.; Shin, H.; Qiu, H.; Ritz, E.; DeFrees, R. A.; Hendricks, M. R.; Alman, D. A.; Jurczyk, B. E.; Ruzic, David N; Bristol, R.
In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE, Vol. 5751, No. II, 138, 19.09.2005, p. 1125-1136.Research output: Contribution to journal › Conference article
}
TY - JOUR
T1 - Evaluating advanced fuel candidates in surface cleaning of optics by plasma exposure (scope)
AU - Neumann, M. J.
AU - Shin, H.
AU - Qiu, H.
AU - Ritz, E.
AU - DeFrees, R. A.
AU - Hendricks, M. R.
AU - Alman, D. A.
AU - Jurczyk, B. E.
AU - Ruzic, David N
AU - Bristol, R.
PY - 2005/9/19
Y1 - 2005/9/19
N2 - One of the leading issues leading to decreased mirror lifetime is that debris contamination and buildup of debris on the surface of the primary mirror optics that comes from the use of both Sn and Li in GDPP or LPP. This debris generation leads to a decreased reflectivity from the added material thickness and increased surface roughness that contributes to scattering. In order to overcome this issue, it is important to understand the implantation of debris material into the optic material matrix and the subsequent diffusion of this debris within the mirror matrix. This change in composition and surface morphology can dramatically affect reflectivity and mirror lifetime. A multifunction test stand was built to investigate this mirror lifetime issues that arise from the use of both Li and Sn. Through the use of both a Li+ ion beam, electron beam evaporator for Li and Sn deposition, and a quartz crystal microbalance to study both lithium implantation and sputtering at various incident ion energies, angles, quantity of debris, and mirror temperatures, the problem of Li generated debris was investigated. Subsequent surface analysis via SEM, XPS, AFM, and TOF-SIMS, were used to study the resultant mirror material properties of composition, diffusion, and surface roughness leading to a better overall understanding of the mirror contamination issue. Preferential Li diffusion through a ruthenium capping layer was seen depthwise into the mirror matrix with minimal radial diffusion while the mirror sample was at room temperature. However, at an elevated temperature, enhanced surface radial diffusion of lithium and segregation in the capping layer was seen with minimal diffusion into the underlying mirror matrix. In conjunction with study of the contamination mechanism, the use of a secondary plasma was investigated as a way to prevent degradation and clean the mirror optics so as to extend the lifetime with no interference to the source or other components. Through the use of a helium helicon plasma, it was possible to induce lithium evaporation and break up of clusters that form on the surface. The plasma parameters were measured using a RF-compensated Langmuir probe to yield electron temperature and density while the sample mirror material was at various temperatures and voltage bias. It was shown that in situ plasma cleaning of optics is a valid method towards achieving improved mirror lifetime. For Sn optics cleaning, the use of halide etching to readily transport Sn off the surface was successfully demonstrated. Ar and Cl plasma and other gas mixtures demonstrated selective etch rate for Sn versus mirror materials of SiO 2, Mo, Si, and Si 3N 4 and it is possible to set a scheme such that Sn debris is preferentially sputtered while leaving the mirror material undisturbed and yielding a long lifetime for the optics.
AB - One of the leading issues leading to decreased mirror lifetime is that debris contamination and buildup of debris on the surface of the primary mirror optics that comes from the use of both Sn and Li in GDPP or LPP. This debris generation leads to a decreased reflectivity from the added material thickness and increased surface roughness that contributes to scattering. In order to overcome this issue, it is important to understand the implantation of debris material into the optic material matrix and the subsequent diffusion of this debris within the mirror matrix. This change in composition and surface morphology can dramatically affect reflectivity and mirror lifetime. A multifunction test stand was built to investigate this mirror lifetime issues that arise from the use of both Li and Sn. Through the use of both a Li+ ion beam, electron beam evaporator for Li and Sn deposition, and a quartz crystal microbalance to study both lithium implantation and sputtering at various incident ion energies, angles, quantity of debris, and mirror temperatures, the problem of Li generated debris was investigated. Subsequent surface analysis via SEM, XPS, AFM, and TOF-SIMS, were used to study the resultant mirror material properties of composition, diffusion, and surface roughness leading to a better overall understanding of the mirror contamination issue. Preferential Li diffusion through a ruthenium capping layer was seen depthwise into the mirror matrix with minimal radial diffusion while the mirror sample was at room temperature. However, at an elevated temperature, enhanced surface radial diffusion of lithium and segregation in the capping layer was seen with minimal diffusion into the underlying mirror matrix. In conjunction with study of the contamination mechanism, the use of a secondary plasma was investigated as a way to prevent degradation and clean the mirror optics so as to extend the lifetime with no interference to the source or other components. Through the use of a helium helicon plasma, it was possible to induce lithium evaporation and break up of clusters that form on the surface. The plasma parameters were measured using a RF-compensated Langmuir probe to yield electron temperature and density while the sample mirror material was at various temperatures and voltage bias. It was shown that in situ plasma cleaning of optics is a valid method towards achieving improved mirror lifetime. For Sn optics cleaning, the use of halide etching to readily transport Sn off the surface was successfully demonstrated. Ar and Cl plasma and other gas mixtures demonstrated selective etch rate for Sn versus mirror materials of SiO 2, Mo, Si, and Si 3N 4 and it is possible to set a scheme such that Sn debris is preferentially sputtered while leaving the mirror material undisturbed and yielding a long lifetime for the optics.
UR - http://www.scopus.com/inward/record.url?scp=24644436331&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=24644436331&partnerID=8YFLogxK
U2 - 10.1117/12.600117
DO - 10.1117/12.600117
M3 - Conference article
AN - SCOPUS:24644436331
VL - 5751
SP - 1125
EP - 1136
JO - Progress in Biomedical Optics and Imaging - Proceedings of SPIE
JF - Progress in Biomedical Optics and Imaging - Proceedings of SPIE
SN - 1605-7422
IS - II
M1 - 138
ER -