Role of SiCl4_4 addition in CH3_3F/O2_2 based chemistry for Si3_3N4_4 etching selectively to SiO2_2, SiCO and Si

International audienceDry etching of amorphous silicon nitride (Si3N4) selectively toward silicon dioxide (SiO2), silicon oxicarbide (SiCO) and crystalline silicon (c-Si) in an Inductive Coupled Plasma (ICP) reactor using CHF3/O2/He chemistry with SiCl4 addition is studied. Plasma exposure of c-Si, SiO2 and SiCO leads to an oxide deposition. The deposition rate is the same for all these materials and increases linearly with the amount of SiCl4 added. On the other side, Si3N4 etching is observed at very small amount of SiCl4 added (2sccm) while oxide deposition takes place at higher SiCl4 flow (10sccm). Quasi-in situ Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS) investigation shows oxifluoride SiOxFy deposition on c-Si and SiCO while a thin F-rich reactive layer is observed on Si3N4. The oxidation of Si3N4 surface followed by CHF3/O2/He chemistry with small SiCl4 addition showed that oxidation state plays a significant role on the etching / deposition equilibrium. In addition, it is found that oxifluoride deposition on Si3N4 is driven by ion energy, with deposition observed at 0 V substrate bias voltage while etching is observed for values superior to 150 V. All these results show that a competition takes place between silicon oxifluoride deposition and etching, depending on substrate material, surface oxidation and ion energy. Based on some additional Optical Emission Spectroscopy (OES) data, we proposed some insights to explain the different etching and deposition behaviors observed. It is focused on the crucial role of ion energy and the nitrogen presence in Si3N4 leading to formation of CN and HCN, helping to get a thinner reactive layer and to evacuate etch by-products on Si3N4 while an oxifluoride build-up on the other materials

Gate spacers etching of Si3_3N4_4 using cyclic approach for 3D CMOS devices

International audienceIn this work, we optimize a CH$_3$F/O$_2$/He/SiCl$_4$ chemistry to etch silicon nitride gate spacers for 3D CMOS devices in a 300mm inductivelycoupled plasma reactor. The chemistry has high directivity and high selectivity to Si and SiO$_2$. A cyclic approach, which alternates thischemistry with a CH$_2$F$_2$/O$_2$/CH$_4$/He plasma, is investigated. Using $quasi\ in\ situ$ x-ray photoelectron spectroscopy and ellipsometry measurements,etching mechanisms are proposed to explain the results obtained. As a result of process optimization, silicon nitride spacers with verticalprofile and a small critical dimension loss of 3 nm as well as complete spacers removal on sidewalls of the active area are obtained on3D patterns, confirming the advantages of this approach

Deciphering the molecular mechanisms underpinning the transcriptional control of gene expression by L-AFL proteins in Arabidopsis seed.

International audienceIn Arabidopsis (Arabidopsis thaliana), transcriptional control of seed maturation involves three related regulators with a B3domain, namely LEAFY COTYLEDON2 (LEC2), ABSCISIC ACID INSENSITIVE3 (ABI3), and FUSCA3 (ABI3/FUS3/LEC2[AFLs]). Although genetic analyses have demonstrated partially overlapping functions of these regulators, the underlyingmolecular mechanisms remained elusive. The results presented here confirmed that the three proteins bind RY DNA elements(with a 59-CATG-39 core sequence) but with different specificities for flanking nucleotides. In planta as in the moss Physcomitrellapatens protoplasts, the presence of RY-like (RYL) elements is necessary but not sufficient for the regulation of the OLEOSIN1 (OLE1)promoter by the B3AFLs. G box-like domains, located in the vicinity of the RYL elements, also are required for proper activation ofthe promoter, suggesting that several proteins are involved. Consistentwith this idea, LEC2 andABI3 showed synergistic effects onthe activation of the OLE1 promoter. What is more, LEC1 (a homolog of the NF-YB subunit of the CCAAT-binding complex)further enhanced the activation of this target promoter in the presence of LEC2 and ABI3. Finally, recombinant LEC1 and LEC2proteins produced in Arabidopsis protoplasts could form a ternary complex with NF-YC2 in vitro, providing a molecular explanationfor their functional interactions. Taken together, these results allow us to propose a molecularmodel for the transcriptional regulationof seed genes by the L-AFL proteins, based on the formation of regulatory multiprotein complexes between NF-YBs, which carry aspecific aspartate-55 residue, and B3 transcription factors

Dolutegravir-based dual maintenance regimens combined with lamivudine/emtricitabine or rilpivirine: risk of virological failure in a real-life setting

International audienceBackground Maintenance ART with dolutegravir-based dual regimens have proved their efficacy among HIV-1-infected subjects in randomized trials. However, real-life data are scarce, with limited populations and follow-up. Objectives We assessed virological failure (VF) and resistance-associated mutations (RAMs) on dolutegravir maintenance regimens in combination with rilpivirine or with lamivudine or emtricitabine (xTC) and analysed the factors associated with VF. Methods Between 2014 and 2018, all HIV-1-infected adults included in the Dat’AIDS cohort and starting dolutegravir/rilpivirine or dolutegravir/xTC as a maintenance dolutegravir-based dual regimen were selected. VF was defined as two consecutive HIV RNA values >50 copies/mL or a single value >400 copies/mL. We compared cumulative genotypes before initiation of a maintenance dolutegravir-based dual regimen with genotype at VF. Results We analysed 1374 subjects (799 on dolutegravir/rilpivirine and 575 on dolutegravir/xTC) with a median follow-up of 20 months (IQR = 11–31) and 19 months (IQR = 11–31), respectively. VF occurred in 3.8% (n = 30) of dolutegravir/rilpivirine subjects and 2.6% (n = 15) of dolutegravir/xTC subjects. Among subjects receiving dolutegravir/rilpivirine, two genotypes harboured emerging RAMs at VF: E138K on NNRTI (n = 1); and E138K+K101E on NNRTI and N155H on INSTI (n = 1). Among subjects receiving dolutegravir/xTC, no new RAM was detected. The only predictive factor of VF on dolutegravir/rilpivirine was the history of failure on an NNRTI-based regimen (adjusted HR = 2.97, 95% CI = 1.28–6.93). No factor was associated with VF on dolutegravir/xTC. Conclusions In this large real-life cohort, dolutegravir/rilpivirine and dolutegravir/xTC sustained virological suppression and were associated with a low rate of VF and RAM emergence. Careful virological screening is essential before switching to dolutegravir/rilpivirine in virologically suppressed patients with a history of NNRTI therapy