Recently, stressed silicon wafers have begun being used and it is necessary to measure the strain in the surface film for
process control. We developed a stress measurement system with a built in film thickness measurement tool. In pursuing
this development we concentrated on the high-throughput and stable results required for semiconductor process control
tools. We achieved the desired results by using a collimator in the microscope.
Our system can measure the stress in 1 dimension line on a 300 mm wafer in less than 30 seconds. Then we proceed to
measure wafer patterns with the same system. We describe this system and the measurement data it provides.
As semiconductor technology has advanced, the films have become thinner and changed to multi-layer films, such as gate
dielectric construction.
To deal with these trends, we are continuing development of our spectroscopic ellipsometer with elliptical polarization.
We chose a Rotating-Analyzer Ellipsometer (RAE) configuration. The incident light in this type of device is usually
polarized linearly, because polarizers do not disperse the light. But the incident light in the ellipsometer described in this
paper is elliptical, which has a nearly circular polarization.
In this paper, we introduce a technique for solving the dispersion problem.
The demands on optical metrology of etched structures continue to increase as microelectronics become more complex and
use higher aspect ratios. We will show the ability of the Dainippon Screen trench measurement tool to measure linear
trench device dimensions, such as trench depth, width monitoring, and mesa oxide thickness, with high precision and
accuracy. The advantages of our tool are high throughput, cost effectiveness and ease of use, because of its optimization
using an optical interference calculation. This tool used has demonstrated repeatability on the order of 3σ < 1 nm in Trench
Depth and SiO2 thickness measurements.
A shrinking design rule has decreased film thickness specifications and is creating challenges as multi-layer structures
and new materials are introduced. We have developed a spectroscopic ellipsometer, the RE-5200, which can measure
several parameters with spot sizes down to 30 um. The advantages of the RE-5200 include high long-term stability, high
accuracy, short measurement time, and low COO. The high precision aspheric mirrors were developed specifically for
this system and allow the measurement of very small areas on the device. In addition, the stress measurement function
meets some of the latest demands, which are high throughput, high accuracy and pattern independent. This paper
presents the optical design and performance of the RE-5200, including measurement results.
Spectroscopic ellipsometry (SE) with microscopic measurement spot is applied to extract geometrical parameters of a bi-periodic array of holes patterned on the top of an Si wafer, namely the holes' diameter and depth, while the period of the patterning is assumed same as the value intended by the manufacturer. The SE response of the structure is simulated by the rigorous coupled-wave analysis implemented as the Airy-like internal reflection series, whose detailed description for the case of 2D gratings is provided with a brief demonstration of its convergence properties. The result of the extraction by SE is compared with results obtained by scanning electron microscopy (SEM) with reasonable agreement. The difference between some of the SE, SEM, and nominal parameters are discussed and the possibility to increase the accuracy of SE-based metrology is suggested.
The rigorous coupled wave analysis (RCWA) implemented as the Airy-like internal reflection series (AIRS) is applied in a theoretical analysis of the optical response of diffraction gratings. Detailed theoretical description of the RCWA with respect to the AIRS implementation is provided, including the application of Li's Fourier factorization rules and the recursive algorithm for sliced relief gratings. Numerical analysis of convergence properties including computation time is demonstrated for structures made of transparent, semiconductor, or metallic materials.
Roman Antos, Martin Veis, Eva Liskova, Mitsuru Aoyama, Jaroslav Hamrle, Takashi Kimura, Pavol Gustafik, Masahiro Horie, Jan Mistrik, Tomuo Yamaguchi, Stefan Visnovsky, Naomichi Okamoto
Spectroscopic ellipsometry (SE) and magneto-optical (MO) spectroscopy are applied to analyze three sets of shallow magnetic gratings. The experimental data of SE are used to extract geometrical parameters of several samples. A half-micrometer thick transparent interlayer present between the periodic magnetic wires and the substrate in one of the sets of the samples is used to increase the sensitivity of SE and MO measurements. Thanks to this sensitivity the geometrical parameters can be extracted together with the material composition of the magnetic film. In order to interpret the magneto-optical Kerr effect (MOKE) measurement, three theoretical approaches are used in the simulations, the rigorous coupled-wave method (CWM), the local mode method (LMM), and a new approach based on comparing CWM with LMM with defining a 'quality factor' of the grating with respect to the wire edges. Using the MOKE spectra in the 0th and -1st diffraction orders, one set of the samples made with a protection capping is analyzed with respect to the native-oxidation process. The quality factor of these samples is extracted from MOKE in the -1st diffraction order for p-polarized incidence. The monitoring system based on both SE and MOKE is rated as highly sensitive and precise, and with accurate determination of the optical and magneto-optical constants it could by applied in multi-parameter fitting.
Shrinking design rules have decreased film thickness specifications and are creating challenges as multi-layer structures and new materials are introduced. Film thickness measurement is one of these challenges that must be addressed. Not only are the structures and materials challenging to measure but in the 300mm wafer process it is required to implement these measurements on small test pads to eliminate dummy wafers and save costs. To meet these requirements, Dainippon Screen Mfg. Co., Ltd. has developed a spectroscopic ellipsometer, RE-3200, which can measure several parameters with a spot size down to 30um. This state-of-the-art film thickness measurement tool has a unique design to support spectroscopic ellipsometry and also optical interferometry and monochromic ellipsometry(optional). The advantages include high long-term repeatability, high accuracy, short measurement time, and low COO. The simple optics does not require any components between polarizers and ensure high optical efficiency and stability. The high-precision aspheric mirrors are developed specifically for this system and allow the measurement of the small areas on the device. In addition, the use of high-contrast polarizers minimizes measurement errors. The RE-3200 system is also strongly recommended for scatterometry applications.
In this paper, the optical design and performance of RE-3200 including measurement results will be presented.
The coupled wave method (CWM) has been applied to the description of electromagnetic wave propagation in binary optic gratings. The electromagnetic field and the permittivity profile are expanded into two-fold Fourier series. The reflection coefficients of 2D periodical structures have been specified and the ellipsometric angles of discussed shapes have been computed. The theoretical results computed for SiO2 and Si3N4 dots are compared with experimental data obtained for the square silicon nitride dots on the Si substrate. The measurements were performed using computer controlled four zone null ellipsometer in spectral range from 240 nm to 700 nm. The influences of Si02 ultrathin oxidation layer and dot thickness on spectral ellipsometric angles are also discussed.
The dielectric function spectra of low dielectric constants (low-k) materials have been determined using spectroscopic ellipsometry, normal incidence spectroscopic reflectometry, and Fourier transform infrared transmission spectrometry over a wide spectral range from 0.03 to 5.4 eV (230nm to 40.5um wavelength region). The electric and ionic contributions to the overall static dielectric constants were determined for representative materials used in the semiconductor industry for interlayer dielectrics: (1) FLARE - organic spin-on polymer, (2) HOSP - spin-on hybrid organic-siloxane polymer from the Honeywell Electric Materials Company, and (3) SiLK- organic dielectric resin from the Dow Chemical Company. The main contributions to the static dielectric constant of the low-k materials studied were found to be the electric and ionic absorption.
CMP is now the planarization method of choice in semiconductor manufacturing. However, CMP is still an immature process. Problems still exist with the uniformity and the stability of the CMP rate. These process variations stem from an incomplete understanding of the mechanism of CMP and the variation of CMP consumable s like slurry, pad and backing film. To compensate for these variations, send- ahead processing and too many measurements are usually required. Obviously, these affect CMP productivity. For better CMP productivity and accurate film thickness control, in-process monitoring is a promising solution. In this paper, a CMP tool with built-in thickness measurement is presented. Such a built-in CMP film thickness monitor must satisfy several requirements: 1) the measurements need to be made at specified chips in the wafer and at specified sites in the chip, 2) the measurements should be accurate, 3) multiple film stack measurements must be possible and 4) high-speed measurements must be possible. These four issues of the built-in film thickness monitor are discussed.
Accurate film thickness controls are indispensable for manufacturing defect-free semiconductor devices. Moreover, recent high integration requires simultaneous measurement of each film thickness and optical constants in multi-layers. This paper explains a microspectroscopic film thickness measurement system that measures film thickness at a very small spot (several micrometers in diameter) in several angstrom increments. This system also enables the user to measure film thickness on bulk wafers and SOI wafers, and determine optical constants of unknown films.
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