Optimizing integrated optical CD monitoring by floating pre-process variations in a complex multi-layer structure

Historically, in a volume production environment, process induced variation in optical property (n&k) of film stack was not significant for the most of applications using scatterometry. Many papers presented before addressed the CD variation in the production by adopting the fixed optical property approach [1-8]. However, with shrinkage of device size, and introduction of new material and process, n&k variation of some critical layers can not be ignored. In this paper, it presents impacts on measured optical CD due to n&k variation of one critical film in a 70nm DRAM ArF lithography process at a patterned area (A-layer). A solution to minimize the impacts using floating n&k in the scatterometry model is discussed, developed and verified.

[1]  Merritt Funk,et al.  Integrated scatterometry in high-volume manufacturing for polysilicon gate etch control , 2006, SPIE Advanced Lithography.

[2]  G. Jellison,et al.  Parameterization of the optical functions of amorphous materials in the interband region , 1996 .

[3]  Matthias Voigt,et al.  Qualification of an integrated scatterometer for CD measurements of sub-100nm resist structures in a high-volume 300mm DRAM production environment , 2005, SPIE Advanced Lithography.

[4]  Wenge Yang,et al.  90-nm lithography process characterization using ODP scatterometry technology , 2004, SPIE Advanced Lithography.

[5]  Wenge Yang,et al.  ArF scanner performance improvement by using track integrated CD optimization , 2006, SPIE Advanced Lithography.

[6]  David A. Dixon,et al.  Application of integrated scatterometry (iODP) to detect and quantify resist profile changes due to resist batch changes in a production environment , 2007, SPIE Advanced Lithography.

[7]  Kevin R. Lensing,et al.  Scatterometry feasibility studies for 0.13-micron flash memory lithography applications: enabling integrated metrology , 2004, SPIE Advanced Lithography.

[8]  Thomas Marschner,et al.  Application of integrated scatterometry measurements for a wafer-level litho feedback loop in a high-volume 300 mm DRAM production environment , 2006, SPIE Advanced Lithography.

[9]  Merritt Funk,et al.  Advanced profile control and the impact of sidewall angle at gate etch for critical nodes , 2008, SPIE Advanced Lithography.