Application of temporary adherence to improve the manufacturing of 3D thin silicon wafers

International audienceThe presented work concerns the manufacturing of very thin silicon wafers for a 3D Integrated Circuit industrial purpose. One of the key parameters of the 3D integration is the adherence of the bonded structure which involves silicon wafers and a polymer adhesive as an intermediate layer. The scope of the paper is to determine the suitable adherence of the stack for a successful manufacturing onto industrial tools. For this purpose the dismounting capacity of the fully automated equipment EVG (R) 850DB depending on the adherence energy is studied. Direct and polymer bonded silicon pairs are prepared. Their energies of adherence cover a large range of energy from 0.3 to 14 J/m(2). The automatic mechanical dismounting process is successful when the stack adherence is 1.2 J/m(2) or lower. This value does not depend on the bonded structure type direct bonded pairs or thinned polymer bonded pairs exhibit the same behavior regarding the dismounting capacity. And we demonstrate that the industrial manufacturing of 70 pm thin silicon wafers is possible if the adherence is 0.4 J/m(2) to 1.2 J/m(2)

Study of calixarenes thin films as chemical sensors for the detection of explosives

International audienceCalix(n)arenes (n = 4, 6, 8) are used as sensitive coatings for Quartz Crystal Microbalance (QCM)-based chemical sensors, and specially for the detection of dinitrotoluene as a model explosive molecule. Calix(n)arenes complex organic architectures were deposited by spray on gold-coated wafer surfaces, and DNT detection tests were performed by measuring both frequency changes and IR spectra during exposure to DNT vapours. The adsorption of DNT on calixarenes surface is proved by Polarisation Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) experiments, which brings a chemical characterisation of the sensing surfaces. Kinetics of interaction of DNT with the surface was measured by QCM. When deposited onto QCM, calixarenes showed an excellent sensitivity to DNT vapours; no significant effect of the size of the cage was observed.The main drawback is the poor reversibility of these sensors, possibly due to a too strong interaction of dinitrotoluene inside the cage of the calixarenes, or to a loss of the ternary structure of these molecules, which in turn induces a loss of interaction strength with host molecules

Polymer bonding temperature impact on bonded stack morphology and adherence energy

International audienceThis paper deals with the effect of the silicon bonding temperature with thermoplastic adhesive. The bonding temperature exhibits a significant effect on the morphology and on the adherence energy of the bonded stack. A suitable temperature control leads to an excellent homogeneity of the bonded structure and an optimal total thickness variation (TTV) value. Using Brewer Bsi5150 adhesive material, 275 A degrees C appears as the optimal bonding temperature in order to optimize the TTV from 55 A mu m down to 5 A mu m. The adherence of the structure is also increased with high bonding temperatures. Indeed, the adherence energy is above 10 J/m(2) when the temperature is above 250 A degrees C. On the contrary, when the temperature is less than 150 A degrees C, the adherence is only around 1 J/m(2). Noteworthy, this value is suitable for back side processing and a mechanical debonding of the structure without any need of other specific layer which could lead to a very simple temporary bonding process

Development and adhesion characterization of a silicon wafer for temporary bonding

International audienceThe development of a silicon temporary carrier for thin wafer handling for 3D applications was investigated. Process selection and optimization ended up with a silicon carrier entirely covered with an antistick layer based on a fluorinated polymer. The carrier preparation was quite easy because only one coating was used and no sticking edge zone was needed onto the carrier. The fluorinated coating led to a very hydrophobic behavior. When bonded with a thermoplastic glue, it also exhibited very antiadhesive properties because the adherence was as low as 0.4 J/m(2) and lower than the adherence of a stack without any antiadhesive layer (above 4 J/m(2)). The carrier was nevertheless suitable for different back side processes in 300 mm grinding, chemical cleaning, chemical mechanical polishing and silicon oxide deposition. Compared with a commercial carrier, it exhibited the same level of performance for the integration. The proposed carrier was compatible with a mechanical debonding of a thinned bonded structure with a silicon device wafer of 80 pm. The carrier recycling was possible without any new preparation

Numerical prediction of sensitivity and selectivity for gas phase trace detection with coated chemical sensors

AbstractA numerical model has been developed to predict the sensitivity of QCM (Quartz Crystal Microbalance) sensors. Such device is coated with a spray-deposited polymer, which has a specific affinity for a given family of molecules: here, nitro aromatic compounds are the target as they are key compounds for explosives trace detection in gas phase. The model is tested by a set of initial measurements performed on several target and interfering molecules. Physico- chemical characterizations are used to validate the model assumptions. The main goal of our approach is twofold: (i) to improve the choice of sensing material for chemical sensor development with a small number of experimental detection tests and (ii) to predict the response of a given material to other analytes