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 [2] using multiple lower priority constraints can help to a great extent. Innovative color aware routing techniques [3] can also help with achieving more uniform density and color balanced layouts.
Monte Carlo simulations are used in the semiconductor industry to evaluate variability limits in design rule generation, commonly for interaction between different layers. The variability of the geometry analyzed is determined mainly by the lithography, process and OPC used. Monte Carlo methods for design rule evaluation can provide the requisite level of accuracy, and are suitable for two or more layer interactions because the variations on one can be assumed to be independent of variations on the other(s). The variability parameters and budget utilized in optical Monte Carlo simulations is well-established. With the upcoming implementation of EUV lithography the variability budget will be impacted. EUV has an off-axis illumination angle that complicates the lithography process by causing telecentricity and shadowing errors. Telecentricity errors manifest as a printed feature being shifted relative to the design. The amount the feature is shifted is a function of the pattern density and design. Shadowing is caused by the 3D nature of the mask combined with EUV reflective mask technology. A shadow occurs at feature edges, where the source does not fully illuminate. Telecentricity and shadowing errors, although small at the 10 nm node, will increase in relative size compared to the features printed beyond the 7 nm node. Telecentricity and shadowing errors are complex in nature and can’t be compensated for with a flat bias. These errors unique to EUV are incorporated into Monte Carlo simulations and evaluated against the standard cell design layers. The effect of these variability parameters is evaluated on critical 7 nm node layout clips.
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.
The objective of this work is to describe the advances in 193nm photoresists using negative tone
developer and key challenges associated with 20nm and beyond technology nodes.
Unlike positive tone resists which use protected polymer as the etch block, negative tone
developer resists must adhere to a substrate with a deprotected polymer matrix; this poses
adhesion and bonding challenges for this new patterning technology. This problem can be
addressed when these photo resists are coated on anti-reflective coatings with plentiful silicon in
them (SiARC), which are specifically tailored for compatibility with the solvent developing
resist. We characterized these modified SiARC materials and found improvement in pattern
collapse thru-pitches down to 100nm.
Fundamental studies were carried out to understand the interactions between the resist materials
and the developers. Different types of developers were evaluated and the best candidate was
down selected for contact holes and line space applications. The negative tone developer
proximity behavior has been investigated through optical proximity correction (OPC)
verification. The defectivity through wafer has been driven down from over 1000 adders/wafer to
less than 100 adders/wafer by optimizing the develop process. Electric yield test has been
conducted and compared between positive tone and negative tone developer strategies. In
addition, we have done extensive experimental work to reduce negative tone developer volume
per wafer to bring cost of ownership (CoO) to a value that is equal or even lower than that of
positive tone CoO.
We demonstrate a simple device for measuring two independent ultrashort pulses, each of which can potentially be
complex and can also have very different center wavelength, simultaneously in a single-shot. We call our device
"double-blind" FROG and it is implemented using a polarization-gate geometry. In polarization-gate "double-blind"
FROG, each pulse acts as a reference pulse for the measurement of the other and yields the intensity and phase of both
pulses.
We demonstrate an extremely simple frequency-resolved-optical-gating (GRENOUILLE) device for measuring the
intensity and phase of relatively long-ps-pulses. In order to achieve the required high spectral resolution and large
temporal range, it uses a few-cm-thick second-harmonic-generation crystal in the shape of a pentagon. This has the
additional advantage of reducing the device's total number of components to as few as three simple easily aligned optics,
making it the simplest device ever developed for complete pulse measurement. We report complete intensity-and-phase
measurements of pulses up to 15ps long with a time-bandwidth product of 21.
We measure the complete electric field of extremely complex ultrafast waveforms using the simple linear-optical,
interferometric pulse-measurement technique, MUD TADPOLE. In its scanning variation, we measured waveforms with
time-bandwidth products exceeding 65,000 with ~40 fs temporal resolution over a temporal range of ~3.5ns. In the
single-shot variation we measured complex waveforms time-bandwidth products exceeding 65,000. The approach is
general and could allow the measurement of arbitrary optical waveforms.
We introduce a simple, compact, and automatically distortion-free single-grism pulse compressor that can compensate
for large amounts of material dispersion in ultrashort pulses, which increases the pulse duration and decreases the peak
intensity. Diffraction-grating pulse compressors can compensate for high dispersion, but they do not compensate for
higher-order dispersion (important when GDD is large). Worse, all previous general-purpose grating designs have
involved multiple gratings and so are also difficult to align and prone to distortions: small misalignments cause
unwanted spatio-temporal pulse distortions. A compressor based on grisms solves the higher-order-dispersion problem
because grisms allow the ratio of third-order to second-order dispersion to be tuned to match that of the material that
introduced the GDD. A grism can also compensate for large amounts of dispersion. Unfortunately, previous grism
compressors used multiple grisms and so are difficult to align and prone to spatio-temporal distortions. To overcome this
problem, we introduce a single-grism compressor. It comprises only three elements: a reflection grism, a corner cube,
and a roof mirror. SEA TADPOLE measured the compressor GDD and third-order dispersion, verifying its operation.
This convenient device should be a valuable general tool.
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