Papers

AVS1997 Session MS+AS+VT-TuM: Process and Defect Characterization for Semiconductors

Tuesday, October 21, 1997 8:20 AM in Room N

Tuesday Morning

Start	Invited?	Item
8:20 AM		MS+AS+VT-TuM-1 Quantitative Measurement of Nodule Formation in W-Ti Sputtering C.-F. Lo, D. Draper (Materials Research Corporation) Titanium-Tungsten alloys have been used as a diffusion barrier between Si substrate and Al-based interconnect metallization for more than two decades. Due to the increasing complexity of integrated circuits, the primary concern has been focused on the reduction of particles during sputtering. Flaking of the redeposited nodules on the target surface was suspected to be one of the particulate sources. To control the nodule formation, a fundamental knowledge of the nodule formation mechanism is required. In this study, the influence of target properties and sputtering parameters on nodule formation in sputtering targets of Tungsten with 10wt% and 15wt% Titanium was investigated. The amount and life of the nodules as a function of target life were determined. The distribution and morphology of the redeposited nodules indicate that the nodule formation on the sputter targets is a diffusion-controlled mechanism. The design of experiment with regression analysis has quantitatively correlated the redeposited nodule formation with the target composition, microstructure, geometry and sputtering parameters. A parabolic relation showed a saturated nodule size with increased sputtering life. The existence of fractured nodules confirms the nodules to be the particulate source.
8:40 AM		MS+AS+VT-TuM-2 Spectroscopic Ellipsometry Investigation of Nickel Silicide Formation by Rapid Thermal Process Y.Z. Hu, S.P. Tay (AG Associates Inc.) Titanium and cobalt silicides are used widely in microelectronics fabrication. There are limitations for both silicides. With TiSi₂, a linewidth dependence of sheet resistance for lines narrower than 0.35 µ m has become dramatic. The transformation from the high-resistivity C49 phase to the low-resistivity C54 TiSi₂ is nucleation limited. With CoSi₂ there is much less linewidth dependence of the sheet resistance, but more Si is concumed to form the silicide. With the use of NiSi, these problems can be avoided as reported so far in literature. In this paper we shall report an investigation of rapid thermal silicidation of nickel on single crystalline siliccon wafers in the annealing range of 150 to 1150 °C. It has been found that there are five zones in the dependence of sheet resistance on silicidation temperature as follows: 175, 175-350, 350-650, 650-900 and above 900 °C. In order to extensively study the phase sequence for Ni/Si reactions and the kinetics of nickel silicide formation corresponding to the sheet resistance zones, the spectroscopic ellipsometry (SE) was used to characterize the thin silicide films. The sensitivity and usefulness of SE characterization for studying the intermetallic growth processes and the application of an appropriate algorithm for extracting the information from experimental data is demonstrated. The results obtained by this non-destructive SE techniques, Rutherford backscattering, X-ray diffraction and scanning electron microscopy.
9:00 AM		MS+AS+VT-TuM-3 Particle and Defect Detection and Characterization A.C. Diebold (Sematech) Future generations of IC technology present a very strong challenge for particle and defect detection and characterization. In the 1997 Metrology Roadmap, several near term options for particle and defect characterization are suggested, and long term needs include analysis for sub design rule particles and defects for manufacture of 70 nm IC technology by 2009. Defect detection needs are covered in the Defect Reduction Roadmap. In this talk, the challenges facing defect detection and characterization will be covered. We will show a comparison of Auger, ToF-SIMS, and SEM/EDS analysis of sized 300 nm and 100 nm Al, Al2O3, and TiO2 particles on silicon and 1000 nm thermal oxide films. Initial data for analysis on patterned wafers will be shown. We will also show results of particle analysis using the new microcalorimeter x-ray detector technology done at NIST. Other challenges such as contact and via characterization will be reviewed along with small spot characterization being done in the synchrotron x-ray facilities.
9:40 AM		MS+AS+VT-TuM-5 Ultra-Shallow Junction Measurements: A Review of SIMS Capabilities for Implanted and Processed Wafers V.K. Chia, M.J. Edgell (Charles Evans & Associates) The continued trend to increase device operating speed and lower power consumption is to reduce the channel length and gate dimensions together with gate oxide thickness and the source/drain junction depth. For very large scale integrated/ultralarge scale integrated (VLSI/ULSI) fabrication processes, low energy implants with peak depths of less than 5 nm and rapid thermal annealing (RTA) are required for 0.18 mm technology. SIMS is presently the most commonly used analytical technique for characterizing shallow implants (1-50 keV) due to its high sensitivity and good depth resolution. Advanced protocols for SIMS are required to provide accurate information near the surface and to determine ultra-shallow junction depths. Various analytical protocols have been developed to provide this information. For example, oxygen leak used during the SIMS analysis minimizes the transient region where ion mixing occurs, enabling accurate quantification near the surface. The oxygen leak protocol may be used with magnetic or quadrupole mass spectrometers. The depth resolution may be improved by varying the angle of incidence (normal and oblique angles) and net energy of the primary bombarding ions. We have investigated many analytical protocols using magnetic and quadrupole instruments. This paper presents ultra-shallow implant depth profiles of boron, arsenic, and phosphorus in as implanted and processed (annealed) wafers. Our study suggests that several analytical protocols may be required to extract parameters, such as surface concentration, peak concentration, implant dose, or junction depth.
10:00 AM		MS+AS+VT-TuM-6 In Situ Analysis of Airborne Molecular Contamination Using TOF-SIMS with a Liquid Nitrogen-Cooled Sample Stage: Advantages for Semiconductor Processing G. Strossman, P. Lindley (Charles Evans & Associates); W. Bowers (Femtometrics, Inc.) Airborne molecular contamination (AMC) adsorbed onto wafer surfaces has been implicated in decreased device yields through a variety of mechanisms. For example, organic surface contamination is responsible for causing problems in epitaxial growth, oxidation kinetics, deterioration of gate oxide breakdown voltage, adhesion failure and unintended hydrophobization of wafer surfaces. Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is an ideal analytical tool for detecting and characterizing these types of organic contaminants directly on wafer surfaces. In the past, concerns have been raised about the sensitivity of TOF-SIMS analysis for detecting semivolatile species due to the UHV requirement for analysis. The use of a liquid nitrogen-cooled sample stage makes it possible to detect low levels of nonvolatile and semivolatile molecular contamination. An advantage of TOF-SIMS for characterizing surface contamination is the direct detection and identification of molecular species with excellent mass accuracy. Furthermore, the technique can compliment the more traditional TD/GC/MS by detecting high mass contaminants or highly polar species which may not be detectable by TD/GC/MS. This paper will present several examples of the utility of the cold stage coupled with TOF-SIMS for characterizing surface contamination which is relevant to semiconductor processing.
10:40 AM		MS+AS+VT-TuM-8 The Application of X-ray Photoelectron Spectroscopy for the Routine Monitoring of Surface Composition. D.J. Surman (Kratos Analytical Inc.); C.J. Blomfield, B.J. Tielsch (Kratos Analytical Ltd., United Kingdom) The application of X-ray Photoelectron Spectroscopy as a method of monitoring surface cleanliness and composition in routine production or quality control environments is steadily gaining momentum. The ability of the technique to provide elemental, chemical and quantitative data makes it very attractive in following variations in process conditions. There are several key factors that have enabled this situation to occur. These range from the development of lower cost fully automated instruments to easy to use software packages that require the minimum of operator interaction. This paper discusses the changes in instrumentation and software that have been required to accomplish the routine capability. The effectiveness of the instrument to provide meaningful data in a production capability requires a fully automated sample handling system for high throughput. A software package that will run routine methods, and a basic data reporting facility that allows for a pass/fail detection mode. A series of examples from different applications are used to illustrate the effectivness of the technique to detect changes in the process environment.
11:00 AM		MS+AS+VT-TuM-9 Effect of Post-Al Etch Treatment on Corrosion Control : Determination of Residual Chlorine by Small Area Ion Chromatography C.H. Lee, D. Yang, Y.Y. Yang (Lam Research Corporation); E. Kaiser, S. Heberling (Dionex Corporation) Post-etch aluminum corrosion has well been known as one of the most serious problem for chlorine-based plasma etching process. As the copper added aluminum alloys are commonly used in VLSI technology, corrosion control becomes more difficult and remains critical issue. Several research works have been reported to understand and control of such a corrosion behavior. Commonality of these articles shows that corrosion occurrences are a strong function of residual chlorine levels after wafer processing. In this article, detailed study of various post-etch treatments and metal etch chemistry on corrosion control are carried out for a Lam TCP 9600 metal etcher integrated with a downstream microwave stripper. Post-etch treatments of our interest include thermal treatment, process chemistry, and process time. Analysis method was developed to quantify the levels of residual chlorine on the wafer using ion chromatography of extraction areas as small as 1 cm². Due to the small volume and area extraction, we could successfully trace residual chlorine levels as low as[20 ng/L (ppt)]. In addition, small area extraction enabled us to determine efficiency of residual chlorine removal process by tracing the samples at a few different wafer sites. Experiments were also conducted with different metal etch chemistry, such as BCl₃/Cl₂, BCl₃/Cl₂/N₂, Cl₂/N₂, etc. for further understanding of corrosion characteristics. Theses results show that the minimum chlorine concentration for initiation of corrosion is [5.9 ~ 6.9 ng/cm²] and show dependency on main etch chemistry. Better understanding of corrosion characteristics through this work has enabled us to achieve post-etch process for robust corrosion control as well as to propose the mechanism for corrosion suppression.
11:20 AM		MS+AS+VT-TuM-10 In Situ Particle Monitoring for Vacuum Processes; Today and Tomorrow R.W. Burghard, B.S. Shade (High Yield Technology) In situ particle monitoring has been shown to be a successful method for process monitoring in the semiconductor industry. Several types of vacuum processing equipment have been ideal platforms for the use of these laser-based particle counting systems. These include a variety of etch, chemical vapor deposition (CVD), ion implant, and low pressure CVD systems. Over the past few years semiconductor manufacturers have been able to show significant cost savings after implementing in situ particle monitoring schemes¹. Process equipment environments are becoming more challenging for in situ monitors, as process pressures drop reducing particle flow, and as plasma fields become more dense generating unwanted optical and electrical interference. In situ particle monitoring technology must mature by becoming more sensitive to smaller and fewer particles, and by being more robust to environmental noise. This talk will discuss the present state of in situ particle monitoring including, the process tools which can be monitored, the correlation to other particle measuring techniques, and the benefits realized through their implementation. A roadmap will be developed to show how in situ monitoring must change to meet the needs of next generation process equipment. It will include a discussion of new technologies for improving sensitivity, the use of modeling efforts to determine ideal locations within the vacuum system to detect particulate, and the development of technical partnerships with process equipment manufacturers to provide turn-key integrated process monitoring solutions for the end-users. ¹D. Hoang, M. Grobelny, D. Armor, H. Nguyen, "Productivity Improvement for a Plasma Etch Tool with In Situ Particle Monitoring", Institute of Environmental Sciences Proceedings, 1996.