Search

This study numerically simulates the temperature fields of metal/4H-SiC ohmic contacts during back-side laser annealing, especially once the 4H-SiC substrate has been thinned. The results show that the front-side temperature can be easily controlled by adjusting laser parameters with the formation of ohmic contact when Ni was used as the contact metal before and after thinning. However, the front-side temperature posed a problem in the case of Ti/SiC contact because of the lower capability of thermal conduction of Ti compared with that of Ni. The pulse width of the laser had no obvious effect on front-side temperature because the heat-affected depth in the substrate due to pulse width was limited at the same energy density. In addition, reducing the thickness of the Ti film to below 100 nm helped avoid melting of the Ti surface. Lastly, the thermal budget maps of Ti (30 nm)/SiC (30 μm) and Ni (100 nm)/SiC (30 μm) contacts were protracted, in which the energy density and pulse width of the laser could be obtained for a lower front-side temperature. This method can be used to control the whole temperature fields induced by laser annealing after thinning the SiC substrate. This study also discusses the size effect of the physical properties of the metallic contact films. [ABSTRACT FROM AUTHOR]

Laser annealing has attracted significant attention for ohmic contacts of the 4H-SiC substrate, especially Ni-based ohmic contact. In this study, a metallic capping layer (Ti, Nb, Mo, W, or Ag) was placed on the top of Ni as the absorption layer for a 355 nm laser, and the effect of the absorption layer on the laser annealing thermal budget was investigated. The temperature fields of the layer (30 nm)/Ni (70 nm)/4H-SiC (100 μm) contacts were simulated numerically using the finite element method. The results demonstrated that the thermal budget can be affected by the main properties of the layer, including the laser absorptivity, thermal conduction coefficient, specific heat capacity, and density. In thermal budget recipes, the energy density required for ohmic contact at each pulse width can be reduced when the product of the latter three parameters is low. However, the optical absorptivity of the layer is critical to reducing the thermal budget. Ti, which has high absorptivity, a small product, and a high melting point, is an excellent absorption layer for Ni-based ohmic contacts that connect to the 4H-SiC substrate. [ABSTRACT FROM AUTHOR]

The bonding energy is an important parameter to evaluate the quality of bonded wafers in the semiconductor industry. The most important currently used method to measure the bonding energy is the so-called crack opening method. Unfortunately, the infrared cameras used for the wafer inspection with this method have limiting resolutions, and the derived direct crack length reading error is relatively large. To solve the reading error and adaptability problems, in this study, we improve upon the conventional image processing method and propose a crack length identification method that uses function fitting. The effectiveness and feasibility of the method are verified through experiments. [ABSTRACT FROM AUTHOR]