Bruce E. Adams

Improved Subthreshold and Output Characteristics of Source-Pocket Si Tunnel FET by the Application of Laser Annealing

To reduce the power consumption and improve the device performance in scaled CMOS integrated circuits, transistors with steep subthreshold swing (SS) is highly desirable. The tunnel field-effect transistor (TFET) based on the band-to-band tunneling has been suggested as a replacement to conventional MOSFETs. In order to improve the device performance of TFET, enhanced carrier transport across the tunneling junction is crucial. In this paper, source-pocket Si TFET is presented and successfully fabricated by laser annealing. This TFET has enhanced lateral electric field across the source tunneling junction, resulting in a reduction of tunneling distance. The experimental data of the proposed paper, for the first time, shows steep SS (46 mV/dec at 1 pA/μm), excellent ION/IOFF ratio ( <; 107), and improved output characteristics at T = 300 K due to the dramatic reduction of the tunneling resistance. Compared with other TFET works, the proposed method is efficient to improve the device performance on TFET.

Pyrometry for laser annealing

Laser annealing is one of the process solutions to enable ultra shallow junction (USJ) formation for the 45 nm technology node. However, variations in the front-side optical properties of device wafers cause large temperature variations on the wafer surface which, in turn, cause large variations in activation of the dopants that form the junction. As a result, pyrometry and closed loop temperature control are critical to establish process uniformity and repeatability for laser annealing. Pyrometry results are presented along with the correlation between the process results (dopant activation) and the pyrometer signal. Closed loop control and future technical challenges are discussed

In‐Situ Optical Wafer Temperature Measurement

The need for increasingly tighter process control is eminently apparent as semiconductor device dimensions become smaller and wafers larger. Today “Thermal Budgets” are shrinking and ramp rates are increasing throughout wafer processing. Wafer temperature is perhaps the most universally critical process variable in front‐end integrated circuits (IC) manufacturing. The use of pyrometry and optical lightpipes continues to gain widespread acceptance as the standard temperature control method in many processes. Lightpipes are used for controlling temperature in chemical vapor deposition (CVD), rapid thermal processing (RTP), epitaxial film growth (EPI) and physical vapor deposition (PVD). Optical thermometry offers numerous advantages over other forms of wafer temperature measurement. This paper presents the current strengths and limitations in optical wafer temperature measurement. Many factors continue to drive the measurement technology. As IC junctions become shallower, thermal budget concerns drive proce...

Characterization of Nickel Silicides Produced by Millisecond Anneals

Nickel silicides serve as the source, drain, and gate contact material in many advanced complementary metal oxide semiconductor (CMOS) logic applications. Nickel has demonstrated numerous advantages over Cobalt and Titanium silicides of earlier technology nodes. Traditionally, these silicides have been formed by Rapid Thermal Processing (RTP) techniques. Two separate RTP anneals are typically used to form the silicides. In this paper, we explore the formation and film characteristics of nickel silicides produced by millisecond anneals. An overview is first provided of the nickel silicide resistivities as a function of RTP anneal temperature. When plotted, this data provides the transformation curves for the RTP Soak and Spike anneals of thin nickel films. A method is described for estimating the nickel silicide activation energy using these transformation curves and, subsequently, a calculation of the requisite laser power to produce a nickel silicide of comparable resistivity. Film characteristics and morphology of the resultant nickel silicides are evaluated by Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD) analysis techniques.

Reliability improvement methods for sapphire fiber temperature sensors

Novel and practical methods of improving reliability of high temperature measurements in harsh environments are discussed. These improvement methods include: mechanical, optical, electrical and software designs. Discussed are mechanical designs for combustion chambers, gas turbines, and especially corrosive environments. Systems are described which use multi-wavelength algorithms for determining the trustworthiness of measurements. These systems use average and difference calculations of the two wavelengths. Also, hybrid optical and thermocouple sensors are presented.

Temperature measurement in RTP: Past and future

RTP emerged as a mainstream technology during the last two decades in part by solving a difficult technical challenge, that of reliable temperature measurement using optical thermometry. Current thermal processing chambers are capable of controlling temperatures which change at hundreds of degrees celsius per second with repeatability of less than one degree with uniformity on the order of a degree. This is accomplished in a radiatively heated environment where the optical properties of the substrate may vary arbitrarily and contact with it is not acceptable or even feasible. This high degree of thermal stability has enabled the production of the current generation of integrated circuits. Processing requirements are pushing the limits of traditional lamp based technology, and new techniques for sub-second anneals are starting to emerge. With the development of the sub-second anneal, temperature heating and cooling rates may exceed millions of degrees per second, and temperature control may become the limiting factor as it was in the early days of the evolution of the industry.

Traceable emissivity measurements in RTP using room temperature reflectometry

The design of an integrating reflectometer specific to the optical and spectral requirements of rapid thermal processing (RTP) is discussed. We report reflectance measurements of various materials. These measurements are correlated to in-situ emittance measurements recorded during rapid thermal processing. We also present the design of an optimized emissometer for an RTP chamber. We propose a means for correlating room temperature reflectance measurements to emittance standards for RTP.

A novel in-situ lightpipe pyrometer calibration technique

We present a novel method for calibrating lightpipe pyrometers in-situ, using an RTP chamber modified for that specific purpose. The chamber uses a wafer of high emissivity, which is further enhanced by a highly reflective, cool surface placed beneath it. We present data comparing consistency of traditional blackbody calibration of lightpipe pyrometers versus the same pyrometers undergoing the new method. We discuss the advantages of this calibration method over traditional blackbody calibration methods. We discuss practical methods for maintaining calibration consistency and repeatability. Finally, we discuss methods for consistent, accurate calibration of multiple pyrometers simultaneously.

Evolution of dopants and defects in silicon under various annealing sequences

Several decades of research into understanding the mechanisms responsible for diffusion and activation of group-III acceptor and group-V donor impurities in silicon has been driven by the technological need for creating electrical junctions in the S/D and extensions of transistors in semiconductor integrated circuits. It is now conclusively known that anomalous diffusion of implanted impurities during annealing results from their interaction with the non-conservative evolution of excess point-defect damage created by the original implantation, and the effect annealing ambients, co-impurities, interfaces and surfaces have on that evolution [1–8]. Early experiments shown in Ref. [2] conclusively proved this by etching away the surface region containing implant damage before annealing, and demonstrating that the anomalous behavior disappeared. Starting from the as-implanted damage, the nucleation, growth and dissolution of a sequence of larger defects at the expense of smaller ones during the anneal, sets the point defect flux and super-saturation levels (the ratio of point defect concentration to its temperature equilibrium value), which then determine the magnitude and durations of the various phases of anomalous diffusion [9].