Accuracy and repeatability of laser micromachined passive alignment features on ceramic optoelectronic substrates

An increase in demand for miniature electronic devices with higher transmission rates and reduced power consumption has led to advances in science and technology. Optoelectronics can be defined as a coalition of optics and electronics. The communication, health care, and the defence sector all vastly benefit from the use of optoelectronics components in various devices such as lasers, optical fibres and imaging sensors. Components in the optoelectronics industry can be surface mounted on to the substrate materials. In this study aluminium oxide (Al₂O₃) and aluminium nitride (AlN) have been laser micro machined in order to study the effects of laser machining on accuracy and repeatability. It was desirable to achieve features of sufficient quality as to be used as passive alignment features in the assembly process. A previous study carried out by Williams et al. (1) concentrated on limiting the epoxy adhesive flow, and demonstrated ways in which epoxy bleed could be successfully controlled. It highlighted excimer laser machining as a repeatable and capable process for producing precise geometries. However, it was concluded that further development was required before the features could be used in an optoelectronic assembly. In this study Al₂O₃ and AlN ceramic substrates were surface micro-machined with KrF excimer laser. The objective of this work was to investigate the feasibility of producing accurate and repeatable micron scale feature designs (<;150μm in size) with laser ablation for use in the manufacture of optoelectronics components. Furthermore, the objectives of the research were to machine features with 90° side wall angles and to achieve surface average roughness (Ra) of less than 0.3μm within machined areas.