For further enhancement of solar energy conversion efficiency the passivation of silicon (Si) sub... more For further enhancement of solar energy conversion efficiency the passivation of silicon (Si) substrate surfaces and interfaces of Si-based solar cell devices is a decisive precondition to reduce recombination losses of photogenerated charge carriers. These losses are mainly controlled by surface charges, the density and the character of rechargeable interface states (Dit) [], which are induced by defects localised in a small interlayer extending over only few Å. Therefore, the application of fast non-destructive methods for characterization of the electronic interface properties directly during the technological process has received an increasing interest in recent years.
ABSTRACT The ratio of cross sections for the E1 and E2 capture amplitudes in the reaction 12C(α, ... more ABSTRACT The ratio of cross sections for the E1 and E2 capture amplitudes in the reaction 12C(α, γ)16O has been determined from γ-ray angular distributions obtained at Ec.m.=1.7-2.8 MeV. The results favor a nonnegligible contribution of the E2 amplitude to the reaction rate at stellar energies.
1997 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat. No.97CH36023), 1997
ABSTRACT In order to optimize HF last processing in situ rinsing is frequently discussed to avoid... more ABSTRACT In order to optimize HF last processing in situ rinsing is frequently discussed to avoid the transition through the air liquid interface. In this work a special tank design for high efficient rinsing post HF wafer treatment was designed, characterized by laser interferometric flow measurements and verified by studies on the etch characteristics of thermal oxide wafers in diluted hydrofluoric acid. An in situ rinse process featuring only 45 seconds of process time and less than 15 gal/batch Di water consumption at uniformities comparable to sequential processing is presented and discussed
Emitter formation of crystalline silicon solar cells by inline diffusion can be affected by non-u... more Emitter formation of crystalline silicon solar cells by inline diffusion can be affected by non-uniformities in dopant deposition prior to the furnace due to insufficient wetting of hydrophobic surfaces. The impact of dissolved ozone treatment after texturing has been investigated with respect to the possibility of improving the emitter formation with a low cost process enhancement. The chemically grown thin oxide improves wetting capability without modification of other surface characteristics that can impact cell efficiency. It could be shown that already low concentrations of ozone in UPW prior to phosphorus doping improve the sheet resistance uniformity on Cz-Si and multi-crystalline Si solar cells between 30 and 100 % compared to HF last treated ones.
1999 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat No.99CH36314), 1999
We present data measured using the wet bench in the prototyping line of IMEC. This wet bench has ... more We present data measured using the wet bench in the prototyping line of IMEC. This wet bench has been running for 3 years an IMEC Clean for prediffusion cleans including the most critical one: the pre-gate oxidation clean. The clean was introduced at IMEC for the 0.35 μm CMOS process and its use has been succesfully extended to the 180
For more than 20 years, the application of ozone dissolved in pure deionised water (DIW-O3) has b... more For more than 20 years, the application of ozone dissolved in pure deionised water (DIW-O3) has been investigated for wafer-cleaning and resist stripping applications in the semiconductor industry [, , ]. To reduce chemical consumption and disposal costs as well as to improve cleaning efficiency, DIW-O3 is used in semiconductor wet cleaning processes as an alternative to traditional sulphuric acid peroxide (H2SO4/H2O2) [] and RCA [] cleans. Silicon solar cell fabrication includes multiple wet cleaning steps involving large amounts of chemicals. In Si substrate manufacturing the wet-chemical oxidation of substrate surface is used mainly for three purposes: (i) the removal of surface contamination and surface micro-roughness by different cleaning and smoothing procedures in H2O2 containing solutions (RCA I and RCA II) [5], in H2SO4/H2O2 [4], (ii) the preparation of hydrophilic surfaces for subsequent layer deposition [,] and (iii) the fabrication of thin oxide layers []. Chemical cons...
For further enhancement of solar energy conversion efficiency the passivation of silicon (Si) sub... more For further enhancement of solar energy conversion efficiency the passivation of silicon (Si) substrate surfaces and interfaces of Si-based solar cell devices is a decisive precondition to reduce recombination losses of photogenerated charge carriers. These losses are mainly controlled by surface charges, the density and the character of rechargeable interface states (Dit) [], which are induced by defects localised in a small interlayer extending over only few Å. Therefore, the application of fast non-destructive methods for characterization of the electronic interface properties directly during the technological process has received an increasing interest in recent years.
ABSTRACT The ratio of cross sections for the E1 and E2 capture amplitudes in the reaction 12C(α, ... more ABSTRACT The ratio of cross sections for the E1 and E2 capture amplitudes in the reaction 12C(α, γ)16O has been determined from γ-ray angular distributions obtained at Ec.m.=1.7-2.8 MeV. The results favor a nonnegligible contribution of the E2 amplitude to the reaction rate at stellar energies.
1997 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat. No.97CH36023), 1997
ABSTRACT In order to optimize HF last processing in situ rinsing is frequently discussed to avoid... more ABSTRACT In order to optimize HF last processing in situ rinsing is frequently discussed to avoid the transition through the air liquid interface. In this work a special tank design for high efficient rinsing post HF wafer treatment was designed, characterized by laser interferometric flow measurements and verified by studies on the etch characteristics of thermal oxide wafers in diluted hydrofluoric acid. An in situ rinse process featuring only 45 seconds of process time and less than 15 gal/batch Di water consumption at uniformities comparable to sequential processing is presented and discussed
Emitter formation of crystalline silicon solar cells by inline diffusion can be affected by non-u... more Emitter formation of crystalline silicon solar cells by inline diffusion can be affected by non-uniformities in dopant deposition prior to the furnace due to insufficient wetting of hydrophobic surfaces. The impact of dissolved ozone treatment after texturing has been investigated with respect to the possibility of improving the emitter formation with a low cost process enhancement. The chemically grown thin oxide improves wetting capability without modification of other surface characteristics that can impact cell efficiency. It could be shown that already low concentrations of ozone in UPW prior to phosphorus doping improve the sheet resistance uniformity on Cz-Si and multi-crystalline Si solar cells between 30 and 100 % compared to HF last treated ones.
1999 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat No.99CH36314), 1999
We present data measured using the wet bench in the prototyping line of IMEC. This wet bench has ... more We present data measured using the wet bench in the prototyping line of IMEC. This wet bench has been running for 3 years an IMEC Clean for prediffusion cleans including the most critical one: the pre-gate oxidation clean. The clean was introduced at IMEC for the 0.35 μm CMOS process and its use has been succesfully extended to the 180
For more than 20 years, the application of ozone dissolved in pure deionised water (DIW-O3) has b... more For more than 20 years, the application of ozone dissolved in pure deionised water (DIW-O3) has been investigated for wafer-cleaning and resist stripping applications in the semiconductor industry [, , ]. To reduce chemical consumption and disposal costs as well as to improve cleaning efficiency, DIW-O3 is used in semiconductor wet cleaning processes as an alternative to traditional sulphuric acid peroxide (H2SO4/H2O2) [] and RCA [] cleans. Silicon solar cell fabrication includes multiple wet cleaning steps involving large amounts of chemicals. In Si substrate manufacturing the wet-chemical oxidation of substrate surface is used mainly for three purposes: (i) the removal of surface contamination and surface micro-roughness by different cleaning and smoothing procedures in H2O2 containing solutions (RCA I and RCA II) [5], in H2SO4/H2O2 [4], (ii) the preparation of hydrophilic surfaces for subsequent layer deposition [,] and (iii) the fabrication of thin oxide layers []. Chemical cons...
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Papers by Klaus Wolke