Defect Printability for 2/2 RDL and The Impact of Advanced Reticle Processes

Abstract

In the next few years, advanced process technologies in advanced packaging fabs will migrate rapidly to reduction lithography to achieve 2/2 RDL and beyond. Reticle enhancement techniques, such as Optical Proximity Correction (OPC) may be required in multiple reticle layers to provide sufficient process latitude for high volume manufacturing. However, a challenge in the manufacturing of OPC reticles is the lack of a precise specifications for defect inspection with respect to the printability on wafers [1]. In this paper, the printability of reticle defects for 2/2 micrometers Redistribution Layer (RDL) design rule are studied via i-line resist process. The reticle defect printability is determined by considering the wafer process critical dimension (CD) variability. In the experiment, an i-line 2x reduction stepper with 0.1 NA imaging lens was used to expose the programmed defect reticle. The resist CD response to the reticle defect area is measured under a variety of process conditions, i.e., different exposure dose or focusThe programmed defect reticles consisted of both Clear and Dark Field polarities comprising of 2/2 design rules will be used for the printability study. Defects such as intrusions and protrusions at various sizes on RDL patterns, have been characterized. Defect disposition comparing reticle to designed programmed defects to those without will be shown as well as the impact of the defect on patterning performance. Finally, the allowable reticle defect requirement is assessed where the printable reticle defect size is tied to the wafer process specifications and the actual wafer process CD controllability. The influence of the reticle manufacturing processes on wafer patterning performance is examined. Through this comparison, insights into target specifications (MTT, CDU, defects) for advanced RDL reticles can be derived while balancing cost tradeoffs.