Dicing of gallium–arsenide high performance laser diodes for industrial applications: Part I. Scratching operation

Mechanical separation of III–V based high power laser diodes is generally performed in two steps. First, the devices are scratched with a sharp diamond tip followed by a cleavage operation. Micro-scratching and cleavage are key operations for maximizing the yield production and so this contribution is divided into two papers according to these fundamental operations. In this paper, the micromechanics of micro-scratching and particle generation were examined for three material conditions based on gallium–arsenide (GaAs) as well as three geometries of diamond tips (cube corner, conical and Berkovich). This goes from the plastic deformation through in situ observations of micro-scratches to examination of subsurface cracks. The main conclusion is that the depth of the initial defect, also called median crack (a), is well described by the power-law PS ∝ a3/2, where PS is the scratching load. Additionally, when the scratching load became too important, the surface was damaged due to the sharp angles of the indenter tip resulting in a median crack having an uneven depth and where stress concentration appeared due to the plugging of the tip. Moreover, it was found that the initial defect is sensitive to the material conditions. The data analysis of the cleavage operation obtained from scratches performed in this work is presented in Part II [Wasmer, K., Ballif, C., Pouvreau, C., Schulz, D., Michler, J., 2008. Dicing of gallium–arsenide high performance laser diodes for industrial applications. Part II. Cleavage operation, J. Mater. Process. Technol. 198, 105–113]. Based on this complete study, three technological requirements can be set for obtaining cleaved surface atomically flat: (1) crack initiation and propagation must be controlled, even in brittle semiconductors such as GaAs, (2) the scratch load range and tip geometry must be optimized to avoid particles generation and (3) finally, crack opening in Mode I (tension) must be maximized compared to Mode III (shearing).