Immersion based 20nm technology node and below becoming very challenging to chip designers, process and integration due to multiple patterning to integrate one design layer . Negative tone development (NTD) processes have been well accepted by industry experts for enabling technologies 20 nm and below. 193i double patterning is the technology solution for pitch down to 80 nm. This imposes tight control in critical dimension(CD) variation in double patterning where design patterns are decomposed in two different masks such as in litho-etch-litho etch (LELE). CD bimodality has been widely studied in LELE double patterning. A portion of CD tolerance budget is significantly consumed by variations in CD in double patterning.
The objective of this work is to study the process variation challenges and resolution in the Negative Tone Develop Process for 20 nm and Below Technology Node. This paper describes the effect of dose slope on CD variation in negative tone develop LELE process. This effect becomes even more challenging with standalone NTD developer process due to q-time driven CD variation. We studied impact of different stacks with combination of binary and attenuated phase shift mask and estimated dose slope contribution individually from stack and mask type. Mask 3D simulation was carried out to understand theoretical aspect. In order to meet the minimum insulator requirement for the worst case on wafer the overlay and critical dimension uniformity (CDU) budget margins have slimmed. Besides the litho process and tool control using enhanced metrology feedback, the variation control has other dependencies too. Color balancing between the two masks in LELE is helpful in countering effects such as iso-dense bias, and pattern shifting. Dummy insertion and the improved decomposition techniques  using multiple lower priority constraints can help to a great extent. Innovative color aware routing techniques  can also help with achieving more uniform density and color balanced layouts.
Requalifying semiconductor photomasks remains critically important and is increasingly challenging
for 20nm and 14nm node logic reticles. Patterns are becoming more complex on the photomask,
and defect sensitivity requirements are more stringent than ever before. Reticle inspection tools
are equally important for effective process development and the successful ramp and sustained
yield for high volume manufacturing. The inspection stages considered were: incoming inspection
to match with Mask Shop Outgoing result and to detect defects generated during transport;
requalification by routine cycle inspection to detect Haze and any other defects; and inspection by
in-house or Mask shop at the post cleaning. There are many critical capability and capacity factors
for the decision for best inspection tool and strategy for high volume manufacturing, especially
objective Lens NA, wavelength, power, pixel size, throughput, full-automation inspection linked
with Overhead Transport, algorithm application, engineering application function, and inspection
of PSM and OMOG . These tools are expensive but deliver differentiated value in terms of
performance and throughput as well as extendibility. Performing a thorough evaluation and
making a technically sound choice which explores these many factors is critical for success of a
fab. This paper examines the methodology for evaluating two different photomask inspection
tools. The focus is on ensuring production worthiness on real and advanced product photomasks
requiring accurate evaluation of sensitivity, throughput, data analysis function and engineering
work function on those product photomasks. Photomasks used for data collection are production
reticles, PDM(Program defect Mask), SiN spray defect Reticle which is described that evaluates
how the tools would perform on a contaminated plate.
As the process nodes continue to shrink, overlay budgets are approaching theoretical performance of the tools. It becomes even more imperative to improve overlay performance in order to maintain the roadmap for advance integrated circuit manufacturing. One of the critical factors in 20nm manufacturing is the overlay performance between the Middle of Line (MOL) and the Poly layer. The margin between these two layers was a process limiter, it was essential that we maintain a very tight overlay control between these layers. Due to various process and metrology related effects, maintaining good overlay control became a challenge. In this paper we describe the various factors affecting overlay performance and the measures taken to mitigate or eliminate said factors to improve overlay performance.
The NTD (Negative Tone Developer) process has been embraced as a viable alternative to traditionally, more conventional, positive tone develop processes. Advanced technology nodes have necessitated the adopting of NTD processes to achieve such tight design specifications in critical dimensions. Dark field contact layers are prime candidates for NTD processing due to its high imaging contrast. However, reticles used in NTD processes are highly transparent. The transmission rate of those masks can be over 85%. Consequently, lens heating effects result in a non-trivial impact that can limit NTD usability in a high volume mass production environment. At the same time, Source Mask Optimized (SMO) freeform pupils have become popular. This can also result in untoward lens heating effects which are localized in the lens. This can result in a unique drift behavior with each Zernike throughout the exposing of wafers. In this paper, we present our experience and lessons learned from lens heating with NTD processes. The results of this study indicate that lens heating makes impact on drift behavior of each Zernike during exposure while source pupil shape make an impact on the amplitude of Zernike drift. Existing lens models should be finely tuned to establish the correct compensation for drift. Computational modeling for lens heating can be considered as one of these opportunities. Pattern shapes, such as dense and iso pattern, can have different drift behavior during lens heating.
The objective of this work was to study the trench and contact hole shrink mechanism in negative tone develop resist processes and its manufacturability challenges associated for 20nm technology nodes and beyond. Process delay from post-exposure to develop, or “queue time”, is studied in detail. The impact of time link delay on resolved critical dimension (CD) is fully characterized for patterned resist and etched geometries as a function of various process changes. In this study, we assembled a detailed, theoretical model and performed experimental work to correlated time link delay to acid diffusion within the resist polymer matrix. Acid diffusion is determined using both a modulation transfer function for diffusion and simple approximation based on Fick’s law of diffusion.