To enhance the performance of the Insulated Gate Bipolar Transistor (IGBT), sub-microsecond laser annealing (LA) is propitious to achieve maximal dopant activation with minimal diffusion. In this work, two different lasers are used as annealing resource: a continuous 808 nm laser with larger spot is applied to preheat the wafer and another sub-microsecond pulsed 527 nm laser is responsible to activate the dopant. To optimize the system’s performance, a physical model is presented to predict the thermal effect of two laser fields interacting on wafer. Using the Finite-Element method (FEM), we numerically investigate the temperature field induced by lasers in detail. The process window corresponding to the lasers is also acquired which can satisfy the requirements of the IGBT’s annealing.
Scatterometry is one of the most promising CD profile metrology technologies for future technology nodes. As critical dimension (CD) continues to decrease, sensitivity of scatterometry needs to be improved to measure even more subtle structures. Sensitivity of a scatterometer highly depends on film stack structure and optical properties of the sample and wavelength, incident angle and polarization implemented by the scatterometer. When measuring different types of sample, scatterometer should be capable of optimizing measuring configurations to get best sensitivity. In this work, we attempt to optimize the measuring sensitivity by introducing a hybrid scatterometer, which is able to measure reflected light from a sample through either an angle-resolved method or a spectroscopic method using two complementary measuring arms. In this setup, improvement of sensitivity can be achieved by choosing better measuring method and adjusting light wavelength, incident angle and polarization.
Diffraction Based Overlay (DBO) is widely evaluated by numerous authors, results show DBO can provide better
performance than Imaging Based Overlay (IBO). However, DBO has its own problems. As well known, Modeling based
DBO (mDBO) faces challenges of low measurement sensitivity and crosstalk between various structure parameters,
which may result in poor accuracy and precision. Meanwhile, main obstacle encountered by empirical DBO (eDBO) is
that a few pads must be employed to gain sufficient information on overlay-induced diffraction signature variations,
which consumes more wafer space and costs more measuring time. Also, eDBO may suffer from mark profile
asymmetry caused by processes.
In this paper, we propose an alternative DBO technology that employs a dedicated overlay mark and takes a rigorous
modeling approach. This technology needs only two or three pads for each direction, which is economic and time saving.
While overlay measurement error induced by mark profile asymmetry being reduced, this technology is expected to be as
accurate and precise as scatterometry technologies.
As feature sizes decrease, requirements on critical dimension uniformity have become very strict. To monitor variations
in lithography process and perform advanced process control it is important to establish a fast and accurate measurement
technique for characterizing critical dimension, sidewall angle and height of the resist profile. Various techniques for
feature measurement such as CD-SEM, AFM, FE-SEM, and scatterometry have been developed. Among these
techniques, scatterometry has both high accuracy and a non-deconstructive measurement modality. It thus provides
advantages of low-cost, high throughput, and robustness. Angle-resolved scatterometry has already been shown to
provide in-line feedback information necessary for tight process control.
In present paper, we introduce a novel angle-resolved scatterometer with pupil optimization. The intensity distribution of
the incident light in the pupil plane is optimized considering the feature and the image sensor response properties, which
improve the measurement performance of the scatterometer. A first order analysis of measurement sensitivity at different
polarization conditions is carried out on resist-coated wafers with 45nm and 22nm features using Rigorous Coupled-
Wave analysis (RCWA). Based on the criteria defined as the sum of the absolute difference of the relative intensity
values between the nominal and varied conditions in the pupil, the sensitivity of the new technique and traditional
scatterometer is compared. Simulation results show that, for 45nm feature, the sensitivity in s and p-polarization is
increased by 400% and 300% respectively. While for 22nm feature, the sensitivity is increased by 200% and 130%.
Reproducibility of measurement is also analyzed on 45nm and 22nm features using a Monte Carlo method and models
for detector noise. Comparison of reproducibility for CD, sidewall angle, and resist height measurement is demonstrated.
With reduction of design rules, a number of corresponding new technologies, such as i-HOPC, HOWA and DBO
have been proposed and applied to eliminate overlay error. When these technologies are in use, any high-order error
distribution needs to be clearly distinguished in order to remove the underlying causes. Lens aberrations are normally
thought to mainly impact the Matching Machine Overlay (MMO). However, when using Image-Based overlay (IBO)
measurement tools, aberrations become the dominant influence on single machine overlay (SMO) and even on stage
repeatability performance. In this paper, several measurements of the error distributions of the lens of SMEE SSB600/10
prototype exposure tool are presented. Models that characterize the primary influence from lens magnification, high
order distortion, coma aberration and telecentricity are shown. The contribution to stage repeatability (as measured with
IBO tools) from the above errors was predicted with simulator and compared to experiments. Finally, the drift of every
lens distortion that impact to SMO over several days was monitored and matched with the result of measurements.
Lithographic tool performance is the main contributor to CDU. The tool designers and users require an accurate method
to measure the tool's error factors on the wafer side in order to improve CDU. Engineers typically use the FEM method
to estimate DOF and EL, and then predict the CDU. However, based on the exposure data, it is often difficult to separate
systematic level physical errors, such as DOSE repeatability, focus repeatability, dynamic errors and all the other tool's
In this paper, we introduce a wafer data based method to diagnose tool's performance for CDU improvement. As the
systematic errors have a specific signature, they generate a fingerprint in the exposure data. Based on the knowledge of
the exposure process and process flow, multiple dimensions exposure matrix is designed to analyze and diagnose the
tool's systematic error from wafer data fingerprint.
For SMEE's scanner tool (SSA600/10), we use this method to diagnose tool's systematic error and improve the CDU.
Some typical result is represented in this paper.
In this paper, we present a streamlined aerial image model that is linear with respect to projection optic's aberrations. The
model includes the impact of the NA, partial coherence, as well as the aberrations on the full aerial image as measured on
an x-z grid. The model allows for automatic identification of image's primary degrees of freedom, such as bananicity and
Y-icity among others. The model is based on physical simulation and statistical analysis. Through several stages of
multivariate analysis a reduced dimensionality description of image formation is obtained, using principal components
on the image side and lumped factors on the parameter side. The modeling process is applied to the aerial images
produced by the alignment sensor in a 0.75NA ArF scanner while the tool is integration mode and aberration levels are
high. Approximately 20 principal components are found to have a high signal-to-noise ratio in the image set produced
by varying illumination conditions and considering aberrations represented by 33 Zernike polynomials. The combined
coefficients are extracted and the measurement repeatability is presented. The analysis portion of the model is then
applied to the measured coefficients and a subset of projection lens' aberrations are solved for.
In this paper, we present an image quality model and a process window model that is linear or quadratic with respect to
common pupil space errors. Similar to other CDU models in its simplicity, our model expands linear representation to
comprehensive image quality specs in a large focus-dose grid. With this model we identify corrections to the full
Bossung curve or process window shapes that are proportional to aberration levels.
As critical dimension shrinks, overlay error induced by wavefront aberration of projection lens in lithographic tools has become a serious problem. In the present paper, we introduce a novel algorithm for modeling aberration-induced overlay in the lithographic process. The calculation results of the algorithm show good correlation with that of PROLITH, the widely used simulation program employing the vector model. And the calculating time is reduced to less than 10% with the algorithm.
As the critical dimension shrinks, degradation of lithographic quality because of axial aberrations in the projection optics
has become more obvious. To minimize the adverse effect of axial aberrations on imaging, accurate in-situ measurement
of axial aberrations is necessary.
In this paper, a novel in-situ method to measure axial aberrations is proposed. In this novel method, a new type of
measurement mark for measuring the axial aberrations is designed. By using new marks, the axial aberrations can be
obtained by the linewidth variation of two bars in the marks. The linewidth variation is proportional to the focus shift in
which the measurement mark is exposed. The proportional factor can be obtained by the simulation software Prolith.
From the linewidth variation and proportional factor, the focus shift of the measurement mark in different positions can
be calculated. The axial aberrations can be obtained by the calculated focus shift. In this novel measurement method,
both the measurement procedure and data-processing are simple. As the measurement accuracy of the focus shift in z
direction is increased, the measurement accuracy of axial image quality increases by more than 25%.