Sia Kim Tan

Circular apertures for contact hole patterning in 193-nm immersion lithography

A novel concept of contact holes patterning for 193 nm immersion lithography is demonstrated in this study. Conventional contact holes patterning involve targeting a square printed feature on the wafer and applying optical proximity correction (OPC) such as corner serifs addition and dimensional biasing. As dimension of contact holes reduces, the resolution enhancement provided by conventional OPC methods has become limited. This is because at smaller dimension, more light is diffracted towards higher order and is not captured in the pupil plane. As a result, the corners of the printed features are rounded and features appear circular as dimension reduces. Hence, the efforts made to generate OPC assist features using a square target are inefficient. In this paper, the patterning of contact hole using circular target is demonstrated. The imaging performance of isolated and regular contact holes array is reported. Comparison with conventional approach is made. The effects of the proposed method on critical dimension (CD), depth of focus (DOF), and image contrast is investigated.

Progressive growth and hard defect disposition integrated system For 65nm and 45nm ArF immersion lithography

In this paper, a defect disposition integrated system for progressive growth and hard defects has been proposed and discussed for 65 nm and 45 nm immersion lithography. Pre-programmed hard defects on mask with minimum defect size of 60 nm are studied. These mask defects are scanned by STARlight inspection with pixel size P90 for mask defect capturing. Aerial Image Measurement System (AIMS) and printed photoresist features are used for modeling. Line, space and hole in both bright and dark field are used for model setup. Printability for these programmed mask defects is determined from process critical dimension (CD) variability. Experimental wafer results on the programmed defect mask are obtained using 193 nm immersion tool with effective NA of 1.2 imaging lens. The resist CDs response to the mask defect area are measured under the different exposure dose or focus. The correlation of AIMS CD, simulated CD and wafer CD for different defect types and sizes to printability is performed. Scan result of progressive growth defects are captured and verification of its printability using AIMS and Automated Mask Defect Disposition (AMDD) from KLATencor is obtained.