Process Control in IC Manufacturing with Thermal Waves

In today’s semiconductor market, manufacturers face a daunting challenge. Product concepts evolve rapidly in response to rapidly changing markets while design rules, i.e., device geometries, become increasingly smaller and wafers become larger. Devices must run faster, reliability must improve and the resultant increasing complexity in IC design and fabrication technology intensifies the need for tighter controls of process variables. To compete effectively in this market, manufacturers must improve both product development and product manufacturing processes

Contrast Mechanisms in the Thermoacoustic Microscope

The thermoacoustic microscope [1–9] uses a modulated particle beam (electrons, photons or ions) as a heat source on (or near) the surface of the sample, and a piezoelectric transducer attached elsewhere on the sample as a detector of acoustic waves generated by the beam. The modulation frequency is typically 103 to 107 Hz, so the acoustic signal is in the sonic to ultrasonic range. These acoustic signals are used to produce images of surface and near surface features of the solid by scanning the source over the face of the sample. In order to make full use of this type of microscope as a quantitative NDE tool, one must be able to interpret the images in terms of the physical properties of the features being imaged. The interpretation of an image resulting from variations in, say, the elastic constants as if it were caused by variations in, say, thermal expansion coefficient, could lead to totally incorrect conclusions about the nature of a defect. This paper summarizes a theoretical analysis which can form a basis for assessing the relative importance of different contrast mechanisms

High-Resolution Thermal Wave Imaging of Surface and Subsurface Defects in IC Metal Lines

Using a thermal wave imaging system we have been able to detect and identify a variety of microscopic defects commonly found in fine metal Al connector lines used in the IC industry. The defects of interest are hillocks, surface and subsurface Si and Cu precipitates and subsurface voids and notches. Defects as small as 0.1 μm have been detected. This thermal wave imaging system has also been used to detect subsurface defects in Al and W metal contact plugs

Controlling Restricted Random Testing: An Examination of the Exclusion Ratio Parameter

In Restricted Random Testing (RRT), the main control parameter is the Target Exclusion Ratio (R), the proportion of the input domain to be excluded from test case generation at each iteration. Empirical investigations have consistently indicated that best failure-finding performance is achieved when the value for the Target Exclusion Ratio is maximised, i.e. close to 100%. This paper explains an algorithm to calculate the Actual Exclusion Ratio for RRT, and applies the algorithm to several simulations, confirming that previous empirically determined values for the Maximum Target Exclusion Ratio do give Actual Exclusion Ratios close to 100%. Previously observed trends of improvement in failure-finding efficiency of RRT corresponding to increases in Target Exclusion Ratios are also identified for Actual Exclusion Ratios.published_or_final_versio

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

Human rights, non-refoulement and the protection of refugees in Hong Kong

Although the 1951 Convention relating to the Status of Refugees and its 1967 Protocol do not apply to Hong Kong, asylum seekers have challenged Hong Kong's lack of an adequate refugee policy in a series of judicial review actions grounded in human rights and common law principles. This article focuses on two cases in particular in which the applicants have attempted to rely, in part, on a right to non-refoulement, derived from international and domestic law, to compel the Government to establish procedures to determine the status of refugees and other similar categories of claimants. The first, Secretary for Security v. Sakthevel Prabakar, led to the creation of a 'torture screening' mechanism based on article 3 of the Convention against Torture and other Cruel, Inhuman, or Degrading Treatment or Punishment. In the second, C v. Director of Immigration, the court considered whether a rule of non-refoulement has emerged in customary international law and, if so, whether it applies to Hong Kong and requires government-administered refugee status determination. Although the applicants failed at first instance,1 an analysis of the judgment with reference to Hong Kong's human rights obligations reveals gaps in the court's reasoning and demonstrates the potential for greater reliance on these standards as the basis for developing a more comprehensive protection framework. This examination of the Hong Kong experience may have broader comparative value, especially in the Asian region and in jurisdictions not bound by the Refugee Convention or its Protocol. © The Author (2010). Published by Oxford University Press. All rights reserved.postprin

Prediction of Interlaminar Shear Strength of a Thermally Aged Carbon/Epoxy Composite Material by Fourier Transform Infrared Photoacoustic Spectroscopy

Photoacoustic spectroscopy was used to predict the interlaminar shear strength of a carbon/epoxy composite. Samples were artificially aged by exposing the samples to elevated temperatures in an air environment. Short-beam shear tests were performed to determine mechanically the interlaminar shear strength of the samples. Photoacoustic spectra of the samples were also collected and compared to mechanical data. Chemometrics were performed on the spectral and mechanical data, and a good correlation was found between the near surface chemistry of the composite and overall mechanical integrity.This paper was published in Applied Spectroscopy 58 (2004): 1420 and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: doi:10.1366/0003702042641407.</p