Technology R&D, Semiconductor Manufacturing International Corp.Pudong New Area, Shanghai, P. R. China 201203As the industry enters 45/40 nm technology node and beyond, the effective control of polysilicon gate's critical dimension uniformity (CDU) becomes more important to device performance. However, to achieve good uniformity is very challenging since the CDU has shown high sensitivities to the variations from resist track recipe, scanner variation, and etcher. It is well known, the DoseMapper (DoMa) is a highly effective tool for the improvement of CDU. In this paper, we will focus on the set up of a DoMa application and monitor system for 40 nm poly gate CDU improvement. Through the use of a state of the art immersion exposure tool (ASML 1900Gi), a DoMa application can successfully improve a gate across wafer CDU by 49% in 40 nm node. In addition, DoMa is more effective when it is applied at post-etch stage than at post-litho stage because it can cover the systematic etch CD variation. However, when a DoMa recipe is applied at post-etch stage, at post-litho, the CDU is no longer meaningful. Before the wafer is etched, we need a new metric to monitor the DoMa performance. A new DoMa monitoring system by RSQ function at post-litho has been introduced and the result will be presented in this paper, which can monitor CD map change by SPC (Statistics Process Control) alarm function.
Since the device integration and relating lithography process progressively increasing in complexity, more integrated approach to process control has been very necessary. There is more function in scanners that can be used to improve process window, CDU and OVL etc. When semiconductor technology node achieves to 28 nm, some function of scanner comes out contribution on process window increase. Focus drilling is the scanner implementation to increase the depth of focus (DoF) for contact-hole or via fabrication processes [1][2][3][4][5][6][7]. The basic principle is to smear out the maximum image contrast at best focus (BF) over a specific defocus range. This function applies a wafer stage R x -tilt (X-axis tilt) when scanning along the Y-direction (scanning direction). This allows the wafer stage to scan along a plane parallel to its tilt. This paper relies on Focus drilling to improve DoF of 28nm Via process, meanwhile also to analyze its negative impact on EL and CDU etc. And then try to find a balance focus range (Rx tilt) for 28 nm product. But the experiment result showed focus marginal gain is about 15nm, meanwhile it is hard to increase DoF through Rx tilt expanded.
Critical dimension uniformity (CDU) of hole layer is becoming more and more crucial alongside with the technology node being driven into 28 nm and beyond, since the critical dimension (CD) variation of 2-dimensional (2D) hole pattern is inherently larger than that of 1D pattern (line/space). As the process window becomes more marginal with the more advanced technology node, EFESE tilt (focus drilling method) is a simple but useful way to enhance depth of focus (DOF) (1-4). Despite the compromises in image contrast and exposure latitude (EL), it's still worth the trade-off; especially in BEOL photo process where incoming wafer topography eats significantly into focus control window. We report an abnormal up to 6 nm ADI CD trend-down in Y-direction (exposure scan direction) in the strictly repeated via-hole patterns within an about 9 mm x 6 mm chip in base line (BL) photo condition wafer (short as BL wafer). No CD trend-down or trend up in X-direction. This hole layer BL photo condition uses EFESE tilt to improve DOF. This CD trend-down phenomenon is investigated and a model of "effective EFESE tilt" is proposed and verified. Based on the model, we made a further step into the impact of applying EFESE tilt on not only intra-but also inter-field CDU. Through all this analysis, we give an insight of the safety zone for applying EFESE tilt for future reference.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.