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The space sector is facing significant upheavals, in particular, in terms of cost reduction challenges, driven by the emergence of low Earth orbit constellations. Concerning solar power generation, it opens up perspectives for alternative solar photovoltaics technologies, instead of the highly performant and expensive III-V multijunction devices. Crystalline silicon solar cells, which have fueled initial space developments, spark a renewed interest, thanks to their industrial maturity, high efficiencies on p-type substrates, and costs of two to three orders of magnitude lower than those of III-V. In this context, we present here the results of electrons radiation hardness studies on p-type (Ga-doped) silicon heterojunction solar cells. Devices with thicknesses down to 60 μm are manufactured and then characterized before and after 1MeV electrons irradiations. The best ultra-thin heterojunction cell shows an end-of-life (1.5 × 1014 e/cm2) externally certified efficiency of 15.9% under AM1.5G at room temperature; this translates into ∼ 14.3% with AM0 spectrum. The benefits of thickness reduction with respect to radiation hardness are presented, and the cells’ improvement pathways discussed.

Volatile hydrocarbons from cleanrooms readily deposit on silicon wafers and interfere with accurate ellipsometry measurement. The resulting error on thin layer measurement can be >10% after only one hour. The […]

The HCl absorption and release by FOUP polymers was characterized through the determination of its solubility and diffusion coefficients in PC and PEEK in clean room conditions (21{degree sign}C and 40% humidity). For the first time, HCl diffusion coefficients were determined (D = 2.9 +/- 1.7 x 10-9 cm2.s-1 in PC and D = 1.4 +/- 0.8 x 10-9 cm2.s-1 in PEEK). These experimental data were then applied. First, the HCl concentration profiles in a FOUP's PC wall depending on the contamination time were calculated showing that HCl migrates until 0.5 mm thickness in less than 16h, but also that the full crossing is likely unreachable in an industrial context. Second, the efficiency of usual cleanings were evaluated depending on the temperature or time. For FOUP materials saturated in HCl, relatively low HCl rate (<35%) were determined even for high process temperature.

The dissemination of metallic contamination occurring during wafer handling is of primary importance for the management of cross contamination issues. This work describes a protocol used to estimate the percentage of contamination transferred from a contaminated wafer to another one via contact on solid surfaces involved during handling. Results suggest that particles size is the most important parameter on the global cross contamination coefficient named K. For sub um particles, the transfer is low, K ranging from 0 to 10%. Above a few um, particles are very easily transferred from contaminated wafers to handling surfaces, with a coefficient K1 which can reach 100%. The decontamination of handling surfaces cycling clean wafers or using wet wipes has also been investigated. For situations leading to high K percentages, efficient and fast cleaning protocols can be applied. This work also discusses the interaction forces between particles and substrates to explain the observed tendencies.

Advanced Integrated Circuit (IC) manufacturing faces both the development of many products and the introduction of a large number of new materials, which represent possible risk of contamination. Therefore, the estimation of the dangerousness of metallic elements must be estimated by relevant short loops. The process steps used in the short loop should represent the production reality or should be performed in the most detrimental conditions. This study shows the impact of different short loop parameters on the dangerousness of metallic elements and their behaviour toward Si and SiO2: type of contamination (depending on the deposition method), thermal budget, oxidizing and non oxidizing atmosphere of the intra-diffusion step, metrology technics. This paper shows that the usual short loops fulfil the conditions of a relevant test. Accordingly, estimation of the dangerousness of the metallic elements can be used to determine detrimental thresholds in manufacturing areas.

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