Oxidation and nitridation of niobium films by rapid thermal processing

Formation of niobium oxynitrides by rapid thermal processing (RTP)

The rapid thermal processing (RTP) system requires critical control of temperature uniformity. For most RTP system, the structure and heating modes of heating component determined the control strategy. Major types of the heating system of nowadays RTP systems were reviewed and compared. Then a heating system for RTP was proposed to improve the uniformity of heaving emission, which includes optimally designed light path and high efficient light reflecting system. The simulating results of that were also given.

Issues of rapid thermal processing (RTP) system design and process applications are reviewed. Temperature measurement is the most important and limiting factor in current RTP systems. Problems related to the temperature measurement and control and potential solutions are discussed. Process uniformity control is another important issue in RTP system design. Reactor chamber design, selection and arrangement of heat source, as well as issues related to dislocation generation, patterned and doped wafer, and ramp-up (down) thennal cycle are considered. Experimental results (RTO, RTCVD silicon nitride and polysilicon) based on an in-house RTP system developed in our laboratory are taken as examples to demonstrate the process applications and system requirements for single wafer processing.

A first-principles approach to the modeling of a rapid thermal processing (RTP) system to obtain temperature uniformity is described. RTP systems are single wafer and typically have a bank of heating lamps which can be individually controlled. Temperature uniformity across a wafer is difficult to obtain in RTP systems. A temperature gradient exists outward from the center of the wafer due to cooling for a uniform heat flux density on the surface of the wafer from the lamps. Experiments have shown that the nonuniform temperature of a wafer in an RTP system can be counteracted by adjusting the relative power of the individual lamps, which alters the heat flux density at the wafer. The model is composed of two components. The first predicts a wafer's temperature profile given the individual lamp powers. The second determines the relative lamp power necessary to achieve uniform temperature everywhere but at the outermost edge of the wafer (cooling at the edge is always present). The model has been verified experimentally by rapid thermal chemical vapor deposition of polycrystalline silicon with a prototype LEISK RTP system. The wafer temperature profile is inferred from the poly-Si thickness. Results showed a temperature uniformity of +or-1%, an average absolute temperature variation of 5.5 degrees C, and a worst-case absolute temperature variation of 6.5 degrees C for several wafers processed at different temperatures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper highlights the basic principles of rapid thermal processing (RTP) systems and the important areas of concern. The basic system characteristics, the fundamental physics involved, and the techniques for temperature measurement and control are extensively reviewed. We summarize the options currently available for 15 RTP equipment manufacturers and point out the latest developments in RTP system design and temperature measurement. Some novel options for temperature control (optical, fiber optical, and photoacoustic) are included.

A new proprietary rapid thermal processing (RTP) method has been developed and implemented for the fast switching of a gas ambient surrounding a wafer inside a RTP furnace operated in the low pressure or atmospheric pressure regime. By controlling the gas flow pattern around a semi-conductor wafer, the effective volume of process gas interacting with the wafer has been reduced by a factor of 33. Thus, real-time gas sequencing can be realized so that multiple rapid thermal processing steps, involving dry and wet rapid thermal oxidation (RTO), rapid thermal nitridation (RTN), rapid thermal annealing (RTA) and chemical vapor deposition (CVD), can be carried out sequentially in a single RTP cycle. Experimental data from ion implant anneal and thermal oxide thin film growth will be presented to illustrate the major technical challenges and solutions associated with the integration of the new method into the Summit/spl trade/ RTP systems. Using this approach, the benefits of rapid thermal processing with high productivity and quick ambient switching is realized.

The complementary metal-oxide-semiconductor (CMOS) industry continues to push the boundaries of what is possible. Along with this, secondary ion mass spectrometry (SIMS) depth profiling continues to support CMOS R&amp;D and high volume manufacturing (due to its unparalleled sensitivity and detection limits over predefined volumes and within acceptable time periods). New developments in SIMS are also being realized to support the move of the CMOS industry from planar structures to three-dimensional (3D) structures. This article presents a perspective of existing SIMS research areas for beyond one-dimensional structural analysis along with potential future SIMS implementation and data processing scenarios. The topics covered include: (1) existing SIMS depth profiling approaches for 3D structures, (2) in-fab SIMS deployment, (3) data analysis of in-fab SIMS derived depth profiles from 3D structures via pattern recognition, and (4) hybrid characterization approaches. With SIMS depth profiling of optimized (for SIMS) 3D structures already demonstrated, the remaining topics may serve to extend these and other capabilities and open new application areas for SIMS.

A novel method for the estimation of the temperature distribution in a rapid thermal processing (RTP) system is developed in this paper. The proposed method uses a proper orthogonal decomposition algorithm to extract the dominant modes of the temperature distribution and a reduced-order model is obtained. Then, a reduced-order sliding-mode observer is developed to capture the dynamics of the dominant modes. The estimated dynamics of the dominant modes can be used to reconstruct the temperature distribution. It is proved that the estimation error would be drawn into a small boundary rapidly. Test results confirm the effectiveness of the proposed observer for the RTP system.

Rapid thermal processing (RTP) is becoming increasingly more important in semiconductor wafer fabrication. A nonlinear physical model for a generic RTP system is described. This generic RTP system is representative of the state-of-the-art RTP systems. A low-order nonlinear model is developed. A model-based LQG controller is designed for the low-order model which successfully controls the full-order nonlinear simulation model.

The use of chemical imaging of secondary ion mass spectrometry (SIMS) data for self‐modeling image analysis (SIA) has special challenges because of the following reasons: (a) At higher counting rates, the data are non‐linear. (b) The heteroscedastic nature of the noise causes structure in the data which gives rise to extra components. (c) There is a high amount of noise in SIMS data and outliers often cause problems. This paper will discuss an adaptation of a pre‐processing method to correct for heteroscedastic noise and a method to minimize the effect of outlying pixels. Examples will be given of the following: (a) Different mixtures of palmitic and stearic acid on aluminum foil. (b) A film coating of polyvinyl acetate (PVA) and polystyrene (PS). (c) A sample of copper and nickel and a fused layer. Copyright © 2008 John Wiley &amp; Sons, Ltd.

In this paper, a model-based control method for RTP (Rapid Thermal Processing) system is proposed. RTP system is a device used to heat semiconductor wafers uniformly. It can heat wafers rapidly and reduce the processing time. However, it is very difficult for a RTP system to achieve the extremely stringent requirement on temperature uniformity (±1[K] or less) without suitably controlling and coordinating the radiative heat flux from the halogen lamps. In this research, the location of lamps is optimized first. Then, a feedback control system is designed which provides optimal temperature control during the thermal processing. The design is carried out based on a linearized model and H2 optimal control. The effect of sensor location is also investigated. Numerous simulations show that satisfactory performances are obtained in both the tracking and the uniformity of wafer temperature.

The design of a decentralized controller has been studied as an integral part of the development of a commercial rapid thermal processing (RTP) system for manufacturing display glass. The glass RTP system uses bulb-type tungsten-halogen lamps for heating. A highly uniform temperature distribution with a maximum temperature difference of less than 6 °C between any two points is required during glass processing, regardless of the size of the glass. In designing a decentralized controller that satisfies this requirement, the problems of optimal sensor location, lamp grouping, optimization-based controller tuning, and time-varying bias input signals were identified and solved. The performance of the controller was investigated experimentally and numerically.

We consider the recursive identification and feedback control of the rapid thermal processing (RTP) system where the asymmetry of the convective heat transfer coefficient, caused by gas flow in the chamber, is taken into consideration. The success of RTP depends on the precise control of water temperature by adjusting the strength of the heating lamps to minimize dopant redistribution as well as wafer warpage. An efficient method of recursive identification and optimal feedback control is developed by separating the radiation field from the temperature field of the wafer and converting the heat conduction equation for the wafer temperature to a reduced-order model by means of the Karhunen-Loève Galerkin procedure.

Nb/B bilayers (thickness: 210 nm) and multilayers (thickness: 306 nm) have been deposited on Si‐(100) wafers with 100 nm thermally grown oxide. The niobium layers were deposited by magnetron sputtering, whereas the boron layers were deposited by electron‐beam‐evaporation. Both types of samples were heated separately via Rapid Thermal Processing (RTP) at varying temperatures, under Ar gas flow to investigate the interdiffusion of niobium and boron, and under NH3 in order to observe the influence of this reactive gas on interdiffusion, as well as to form nitrides. The formation of phases was investigated by X‐Ray Diffraction (XRD). The surface morphology and roughness was studied via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), resp.. Elemental depth profiles of selected samples were recorded by Secondary Ion Mass Spectrometry (SIMS) to track the position of the phases formed in the film. Under the applied experimental setups the formation of NbB2 was observed only. Although NH3 is a reactive gas no nitride phases were found. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

High detection sensitivity in bulk analysis or depth profiling by secondary ion mass spectrometry (SIMS) can only be achieved, for positively charged ions, if the nearsurface regions of the sputter eroded sample are fully oxidized. Using oxygen primary ions, a stationary oxidation state is established after some time of bombardment during which period the sputtering yield decreases and the ionization probability increases. The physical and chemical processes occurring during the transient period are reviewed with emphasis on the results for impurity analysis in silicon, i.e. the matrix material that has been studied most thoroughly in the past. The transient decrease in sputtering yield gives rise to a depth scale offset and an associated apparent shift of impurity profiles towards the surface. The effect is largest at normal beam incidence, ca. 1 nm /keV (O + 2 ), in which case silicon is fully oxidized. The transition depth, i.e. the depth sputtered before achieving a stable ion yield is about twice as large and increases as the impact angle is turned away from normal. The shift and the depth scale offset can be measured safely using thin (delta) layers of isotopically pure tracers, for example 30 Si in 28 Si. Boron delta layers can serve as secondary standards because this impurity behaves almost the same as the host silicon atoms. The profile shift observed with other common dopants may contain contributions due to unidirectional relocation, often driven by segregation away from the surface. At O + 2 energies below about 0.7 keV the transition depths fall below the thickness of typical native oxides, so that the transient changes in sputtering yield and ionization probability can disappear. The transient phenomena may be described by a simple sputtering-oxidation model that connects the depth scale offset to other observable parameters like the initial and final sputtering yield, the transition fluence and the oxide thickness.