In-line Metrology Research Articles

New developments in X-ray fluorescence metrology

A new micro-spot XRF metrology tool has been developed that enables on-product production control of films and stacks used in the semiconductor and data storage industry. The tool has been evaluated using several thin films and stacks and the initial results verify the suitability of this micro-spot XRF method as an in-line metrology technique. Both the classical XRF analysis method as well as the fundamental parameter approach proved to be applicable. The successful combination of micro-spot excitation and fundamental parameter analysis makes the technique a powerful method for on-product characterization of single films and multi-layers.

Scanning Near-Field Microwave Probe for In-line Metrology of Low-K Dielectrics

AbstractWe have developed a novel microwave near-field scanning probe technique for non-contact measurement of the dielectric constant of low-k films. The technique is non-destructive, noninvasive and can be used on both porous and non-porous dielectrics without any sample preparation. The probe has a few-micron spot size, which makes the technique well suited for real time low-k metrology on production wafers. For dielectrics with k<4 the precision and accuracy are better than 2% and 5%, respectively. Results for both SOD and CVD low-k films are presented and show excellent correlation with Hg-probe measurements. Results for k-value mapping on blanket 200mm wafers are presented as well.

In-Line Electrical Metrology for High-K Gate Dielectrics Deposited by Atomic Layer CVD

The use of an in-line electrical metrology tool for evaluation and characterization of high-k dielectrics has been investigated. The equivalent oxide thickness obtained from the KLA-Tencor Quantox agrees well with high-frequency capacitance-voltage (C-V) results. The ACTIV Jg index parameter shows good correlation with the gate current obtained from C-V measurements. Therefore, this tool can be used as a fast and much less expensive evaluation tool for optimization of high-k process conditions and process stability monitoring. © 2003 The Electrochemical Society. All rights reserved.

Modeling of surface acoustic waves in thin film stacks with an arbitrary number of layers (abstract)

An efficient mathematical algorithm for the analysis of surface acoustic waves (SAW) measurements in multilayered thin film stacks has been developed. It allows for a fast and accurate calculation of SAW velocities in stacks composed of an arbitrary number of layers with varying material properties and thicknesses. The inversion algorithm also enables fast determination of multiple stack parameters from SAW dispersion curves. The model is used in a semiconductor metrology tool designed for quality control in the manufacturing of integrated circuits. Surface acoustic waves are described by a special class of solutions of the wave equation satisfying specific boundary conditions at the surface of the media in which they propagate. In the case of a stack composed of thin films, the boundary conditions at the surface of the top layer correspond to a free surface (no stress), at the interface of the individual layers a continuity of both stress and displacement is imposed. In the case of isotropic media, or in certain cases when the wave propagates along planes of symmetry [e.g., (1,0,0) plane of a cubic crystal], the set of boundary conditions results in a system of 4N coupled linear equations for the stress and displacements, where N is the number of layers in the stack. For stacks with a large number of layers, the problem quickly becomes numerically challenging. Requirements imposed by the manufacturing process on the time for data analysis and for processing of the information require fast algorithms. Such an algorithm has been developed and is being implemented in the software to be used in in-line optoacoustic metrology systems. The algorithm is based on the concept of a response function. This function describes the response of an elastic medium to a periodic excitation on its surface. By using the response function the problem of solving a system of 4N linear algebraic equations is reduced to (N−1) matrix multiplications of 4×4 matrices and solving a 2×2 equation. In the application for which this algorithm was developed a laser beam split by a diffraction grating and projected on the surface of the stack produces the excitation of the SAW. The algorithm allows a user to analyze SAW data for a system of an arbitrary large number of layers that can be either elastically isotropic or anisotropic. It significantly accelerates the computation of SAWs, which is of prime importance for industrial applications.

Spectroscopic Ellipsometry as a Potential In-Line Optical Metrology Tool For Relative Porosity Measurements of Low- K Dielectric Films

AbstractThe optical properties of organosilicate glass (OSG) samples were investigated with spectroscopic ellipsometry. We found that samples with dramatically higher hardness had higher indices of refraction (RI) and thus higher electron densities and lower relative porosities than films with lower hardnesses. The reverse was true for films with low hardnesses. As well, these films did not have the same optical properties as porous SiO2 across the spectral range measured, which we show has significant implications for the in-line optical metrology of these materials.

Determination and Critical Assessment of the Optical Properties of Common Substrate Materials Used in III-V Nitride Heterostructures with Vacuum Ultraviolet Spectroscopic Ellipsometry

AbstractAs a first step toward enabling the in-line metrology of III-V nitride heterostructure and materials, we present the optical constants of the two common substrate materials over an unprecendented spectral range. Vacuum Ultraviolet spectroscopic ellipsometry (VUVSE) was used to obtain the optical constants for Al2O3 and the ordinary and extra-ordinary component of the dielectric function for both 4H- and 6H-SiC. The results are discussed in the context of anisotropy, polytypism, bandstructure, optical transitions, and preparation/characterization of abrupt surfaces, where appropriate.

Process integration issues for doping of ultrashallow junctions

Process integration and in-line metrology are now the key agenda items for formation of ultrashallow junctions for ultralarge scale integration devices. Integration of the complete process sequence from selection of the device layer material through introduction and activation of dopants involves dozens of interacting decisions. This article highlights some issues associated with the control of channeling, damage annealing of preamorphized and molecular ion implants, outgassing of oxygen from product wafers during rapid thermal processing cycles and conditions for control of beam divergence and doping microuniformity near gate stack structures.

Consideration of in-line qualification for ultrashallow junction implantation

The electrical characteristics of shallow junction devices are often dependent on tightly controlled ion implants for their performance and yield. However, concerns exist over the ability of existing in-line metrology tools to accurately verify low energy implants, and therefore, determine whether the ion implanter is in control before committing product to it. This article will explore the capabilities of the Therma-Probe TP500, the Tencor OmniMap RS75, and secondary-ion-mass spectroscopy to measure low energy ion implants done on an Applied Materials xR-LEAP with energies 10 keV and below, doses of 1.0E15–3.0E15 cm−2, and both boron and arsenic species.