High throughput with high resolution imaging has been key to the development of leading-edge microlithography. However, management of thermal aberrations due to lens heating during exposure has become critical for simultaneous achievement of high throughput and high resolution. Thermal aberrations cause CD drift and overlay error, and these errors lead directly to edge placement errors (EPE). Management and control of high order thermal aberrations is a critical requirement. In this paper, we will show practical performance of the lens heating with dipole and other typical illumination conditions for finer patterning. We confirm that our new control system can reduce the high-order aberrations and enable critical-dimension uniformity CDU during the exposure.
Current technology nodes, as well as subsequent generations necessitate ongoing improvements to the mix-and-match overlay (MMO) capabilities of lithography scanners. This work will introduce newly developed scanner solutions to address this requirement, and performance data from the latest generation immersion scanner, the NSR-S622D, will be introduced. Enhanced MMO accuracy is imperative for the 22 nm half-pitch and future technology nodes. In order for the matched overlay accuracy to approach single machine overlay (SMO) capabilities, MMO errors must be reduced further. The dominant MMO error sources can be divided into three main areas: SMO, lens distortion matching and wafer grid matching. Nikon continues to decrease these matching error contributors over time, and the latest generation NSRS622D immersion scanner provides a number of innovative solutions to satisfy the most demanding overlay matching requirements ; as a result MMO performance within 3nm is achieved on S622D. Moreover, overlay master system is developed for further product overlay accuracy and stability improvement.
Double patterning (DP) is widely regarded as the lithography solution for 32 nm half pitch semiconductor manufacturing,
and DP will be the most likely litho technology for the 22 nm node . When using the DP technique, overlay accuracy
and CD control are of critical importance . We previously introduced the NSR-S620D immersion scanner, which
provides 2 nm overlay capabilities. In the case of the latest generation NSR-S621D system, improvements have been
developed for further overlay accuracy enhancement.
In this paper, we will show the overlay accuracy and Mix-and-Match performance of the NSR-S621D. Further, the
marked improvement in product overlay and the overlay result in Spacer DP as a result of enhanced alignment accuracy
will also be shown.
To achieve the 2 nm overlay accuracy required for double patterning, we have introduced the NSR-S620D immersion
scanner that employs an encoder metrology system. The key challenges for an encoder metrology system include its
stability as well as the methods of calibration. The S620D has a hybrid metrology system consisting of encoders and
interferometers, in XY and Z. The advantage of a hybrid metrology system is that we can continuously monitor the
position of the stage using both encoders and interferometers for optimal positioning control, without any additional
metrology requirements or throughput loss. To support this technology, the S620D has various encoder calibration
functions that make and maintain the ideal grid, and control focus. In this paper we will introduce some of the encoder
calibration functions based on the interferometer. We also provide the latest performance of the tool, with an emphasis
on overlay and focus control, validating that the NSR-S620D delivers the necessary levels of accuracy and stability for
the production phase of double patterning.
Double patterning (DP) has become the most likely candidate to extend immersion lithography to the 32 nm node and
beyond. This paper focuses on experimental results of 32nm half pitch patterning using NSR-S620D, the latest Nikon
ArF immersion scanner. A litho-freeze-litho (LFL) process was employed for this experiment. Experimental results of
line CDU, space CDU, and overlay accuracy are presented. Finally, a budget for pitch splitting DP at the 22 nm half
pitch is presented.
This paper discusses two new techniques that have been developed to improve overlay matching accuracy over multiple wafer scanners: Super Distortion Matching system (SDM) and Grid Compensation for Matching (GCM), and actual data from experiments performed using the techniques. Overlay matching errors can be divided into the two basic categories, intra-shot error and inter-shot error, which can be improved by SDM and GCM, respectively.