Tim Z. Hossain

Effect of rapid thermal annealing temperature on the formation of CoSi studied by x-ray photoelectron spectroscopy and micro-Raman spectroscopy

The effect of rapid thermal annealing (RTA) temperature on the formation of the cobalt silicide (CoSi) was investigated using x-ray photoelectron spectroscopy (XPS) and micro Raman spectroscopy. With 125 A of Co deposited on single-crystalline Si wafers and capped by a Ti thin film, the wafers were rapid thermal annealed at 450, 460, 470, 480, and 490 °C. These wafers were then stripped with a sulfuric acid peroxide mixture treatment. XPS was used to determine the chemical composition of the CoSi thin films, and the Co Auger parameter was continuously monitored along with ion sputtering to provide a chemical-state depth profile. Micro-Raman spectroscopy was used as a nondestructive method to characterize the film thickness and uniformity of the CoSi thin films on Si wafers. The Raman shifts at 204 and 220 cm−1 due to CoSi and the Raman shift at 150 cm−1 due to Co2Si are reported. The product αd (α is the absorption coefficient, d is the film thickness), which indicates the CoSi film thickness, was calcula...

Raman spectroscopy: a multifunctional analysis tool for microelectronics manufacturing

We have established several applications for the use of Raman spectroscopy in the microelectronics-manufacturing environment. The two primary applications are 1) monitoring thin films and 2) analyzing contaminants. Thin film applications include monitoring cobalt silicide phase transformation and thickness, and crystallinity changes in polysilicon. The same instrument has been used to collect fingerprint Raman spectra of contaminants that can be identified by matching to library or bulk materials spectra.

Future in-fab applications of total reflection X-ray fluorescence spectrometry for the semiconductor industry

Abstract In-fab analytical methods are of increasing interest for wafer monitoring in advanced semiconductor device manufacturing. In particular, an analytical method which allows non-destructive measurements of implant dose and surface roughness would be very beneficial. We investigated the capabilities of total reflection X-ray fluorescence spectrometry (TXRF) to determine implant dose and surface roughness. These advanced applications of TXRF can be used to monitor processes like implantation, rapid thermal annealing, and chemical mechanical polish. As implants in Si at implant energies of 2 keV, 10 keV and 50 keV were studied. Angle resolved TXRF measurements were performed with a commercial Rigaku 3750 system. The TXRF results were compared to secondary ion mass spectrometry (SIMS) measurements.

Ultra-shallow junction depth profile analysis using TOF-SIMS and TXRF

The drive to fabricate ever shallower source/drain and channel junctions in DRAM and microprocessor production constitutes a great challenge for their analytical characterization. Ultra-shallow SIMS profiling requires high depth resolution and a small surface transient region. It also has to account for the interface between the native oxide and the Si bulk. We have investigated the shallow depth profiling capabilities of TOF-SIMS and TXRF. TOF-SIMS is well established for high sensitivity microarea surface analysis. The technique features high mass resolution, high transmission and a parallel mass registration. Depth profiles are performed in the dual beam mode allowing an independent optimization of the analyzing and sputtering ion beam. The application of a low energy SF5+ sputtering ion beam provides depth resolution in the 0.5 nm range and minimizes the width of the near surface transient region. When depth profiling silicon, the oxidation state of the receding surface can be derived from the intensi...

Use and function of TXRF (total reflection x-ray fluorescence) for routine in fab metallic monitoring

As the geometries of semiconductors shrink the sensitivity to metal contamination becomes more apparent. This makes the ability to detect a broad range of metals at levels form 108 to 109 at/cm2 very important. The advent of Copper processing in many cleanrooms also raises the concern of cross-contamination and highlights the need for a fast, sensitive, and easy to use detection tool. The use of a TXRF machine in the silicon wafer fabrication area provides the ability to measure metals at levels ranging from 5E11 to 1E9 at/cm2 without multiple processing steps.

Contaminant sources causing non-stick-on-pad during die bonding

A common problem in die bonding is the non-stick-on-pad (NSOP) when the bond does not pass the pull test. Contaminants are a possible cause of NSOP, particularly if an undesired thick film is developed on the bond pads. Such films effectively diminish the bondability of the pads resulting in a NSOP problem. In one such case Fourier Transform Infra-Red (FTIR) spectroscopy was used to fingerprint the contaminant formed on the bond pads. The contaminant was an aluminum-oxygen-fluorine compound that was very resistant. FTIR showed Al-F bonds and water of hydration. The distinctive chemical signature was critical in solving the NSOP problem quickly. This was accomplished by growing the resistant film under accelerated conditions, thus recreating the compound in the laboratory. Although the chemical compound was not fully identified, the FTIR signature provided confirmation of the compound for various conditions under which it was formed on bond pads. The source of the fluorine was identified and eliminated.

An Optical Approach to Evaluating the Effects of Chlorine on the Quality Of Si/SiO 2 Interfaces

In CMOS, the addition of chlorine particularly in TCA form to the growth of thermal oxides in logic technologies is well-known and pervasive. In addition to the increasing environmental concerns of chlorine use, one of the important parameters is the amount of metallic contamination due to transition metals such as Fe in the Si, and alkali metals like Na in the oxide since these phenomena effect both device performance and quality. However, the ability to measure this parameter on product material is not generally available due to inherent problems with most known methods. In this paper we report on the application of high-injection, frequency based optical surface photovoltage (SPV) and a more recent technique known as a contact potential difference (CPD) to both quantify and qualify as-grown oxides on CZ P-type silicon.

Neutron intercepting silicon chip (NISC) - a sensitive neutron detector

Flash memory chip has been modified to serve as a sensitive solid state neutron detector. A dielectric layer used in the manufacture of the memory chip known as BPSG (borophosphosilicate glass) contains boron and when boron used in this layer is enriched born.

Technique to analyze large-area surface roughness of a wafer using TXRF

Determining the roughness of a wafer surface inside a wafer fabrication plant would be advantageous in solving process problems in semiconductor device manufacturing. Currently, there is not a technique in the fab that will measure the large area surface roughness accurately and non-destructively. Traditionally Atomic Force Microscopy (AFM)1 has been the method of choice for surface roughness analysis. However, AFM typically measures roughness in a micro-area (e.g. 5 μm x 5μm). We have developed a new technique with Total Reflection X-ray Fluorescence (TXRF)2 for the determination of surface roughness using a large area scan. TXRF is used primarily to find trace metal contamination on the surface of a wafer. 3 In the TXRF measurement a secondary fluorescence signal is obtained following irradiation with a primary x-ray beam. We have found that plotting the primary scatter beam (e.g. Au L13 counts per second) versus the secondary fluorescent x-rays (e.g. Si counts per second), a trend is obtained that is linear and specific for a particular wafer. The slope of this linear trend is strongly dependent on the roughness of the wafer surface as determined by AFM. By comparing the slopes of these lines we have found that an increase in slope relates to an increase in roughness. The data has shown that this relationship is independent of the surface type. Polysilicon, oxide and metal stack wafers with varying surface roughness (e.g. AFM) have been studied with the TXRF.

Rapid in-fab monitoring of ion implant doses using total x-ray fluorescence

Total reflection X-ray fluorescence (TXRF) is a useful tool for rapid, nondestructive monitoring of implant doses in semiconductor manufacturing. For As-doped (10 keV and 80 keV) Si wafers with an implant dose of 3 X 1015 at/cm2, As fluorescence yield and accumulated As+ dose measured by Secondary Ion Mass Spectroscopy (SIMS) have been compared. This comparison between TXRF and SIMS demonstrates the power of TXRF as a new nondestructive technique for in-line shallow implant dose and profile monitoring.