Plasma Dicing Integration Schemes for Scribe Lane Layout and the Impact on Die Strength

For all applications where a semiconductor device is used, there is a demand for improved performance under all environmental conditions. One such application, which is in regular use, is the smartcard chip that is found predominantly in bank or travel cards and passports. These may endure harsh physical treatment in normal usage and the demands for severe robustness criteria for these card-based applications are continually increasing to ensure that the packaged chips are able to continue functioning without breaking. Key to achieving these exacting standards is the singulation of the chips in a way that does not generate any inherent mechanical weakness. The standard blade sawing process has so far met existing requirements but the technology roadmap for such devices has presented new challenges with the deployment of fragile ultra-low k BEOL dielectrics. This has prompted the introduction of laser grooving before dicing to minimize damage to these materials caused by the sawing blade but this, in combination with mechanical dicing, can itself result in weakening of the die and a higher risk of failure. Plasma dicing has the potential to improve die breakage strength significantly, essentially as there is no mechanical element to the dicing action. However, this technique requires that the silicon be exposed in the dicing street, which must be free of metals and dielectrics before etching. Under some circumstances this can be achieved by mask design and dedicated processing but in practice laser grooving is again a prime candidate for meeting these conditions. To be compatible with the plasma etching process the laser recipe needs to be optimized according to both the presence and layout of test structures in the dicing street. An influential factor is that the options for the street layout are themselves dependent upon the front-end technology and its complexity level. This paper will examine how laser grooving process adjustments devised to promote successful plasma dicing integration can affect the die strength whilst adapting to different structures and materials contained in the dicing street. We will compare results between alternative plasma dicing integration schemes to show how design layout for the scribe lane influences their choice, especially where die strength is a priority. We will also investigate the impact of varying some of the etch process output parameters to seek an understanding of whether the etching step itself has a role to play in die robustness improvement for the practical, future application of plasma singulation to real cases on an industrial scale.