Aaron Muir Hunter

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

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.

Use of Virtual Metrology for in-situ Visualization of Thermal Uniformity and Handoff Adjustment in RTP Critical Anneals

Applied materials rapid thermal processing (RTP) systems are unique in providing high resolution process data particularly wafer rotation angle and wafer rotation speed as a function of time. This work explores how this information can be used to predict on-wafer process results using an advanced analysis package known as WISR (wafer interdiction and scrap reduction). WISR is an advanced process control platform for the collection, storage, visualization, and analysis of process parameters from production tools. One of the main analysis features of WISR is the ability to create virtual sensors. Virtual sensors are calculated parameters derived from physical sensors that can provide real-time and statistical representation of process health. The focus of this paper is the ability of WISR to transform time series chamber parameters from the pyrometers and the magnetic levitation controller into thermal wafer images at any time during the recipe execution and provide wafer-to-wafer handoff correction. These abilities constitute a virtual sensor module in WISR known as Virtual metrology (VM). We describe the implementation of the VM-analysis and show how temperature maps and handoff corrections correlate with offline metrology in RTP critical anneals. This is an innovative new method to significantly reduce wafer processing errors, enhance yield, and minimize production cost.

Virtual Metrology in RTP with WISR

The Applied Materials RTP systems are unique in providing high resolution process data particularly lamp power and temperature as a function of radial position and time. This work explores how these data can be exploited to predict on-wafer process results using an SPC analysis package named WISR. WISR is an advanced process control platform for collection, storage, visualization, and analysis of data from process tools. The product is collecting data at rates up to 100Hz. It has the ability of notification and interdiction if data goes outside of specification. One of its main features is the ability to create virtual sensors. These are parameters that are derived from physical sensors and provide a statistical representation of the process health. The focus of this paper is the ability of WISR to transform the time series chamber data from the pyrometers into thermal wafer images at any time window during the recipe execution. We describe the data analysis that was deployed, and show how temperature maps generated correlate with metrology data from RTP processes. This is a disruptive new method to significantly save monitor wafer cost, enhance yield and prevent wafer processing errors.

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.

Photon Influence on P and B Diffusion

We investigate photon effects for two thermal processes: implanted dopant activation and diffusion; and silicon oxidation. Because the Applied Materials Radiance Plus RTP system heats only one side of the wafer with lamps, the thermal and photon effects are separable by changing the side of the wafer that is irradiated. The difference in process results can then be interpreted in respect to the spectral difference of the lamp radiation and the grey body radiation emitted by the hot wafer. No significant effect due to the presence of high energy photons in either process was observed.

Applied Materials' Product Portfolio and Roadmap

Applied materials played a pivotal role in the commercial acceptance of rapid thermal processing (RTP) within the semiconductor industry, largely by solving the problem of precisely measuring and controlling the temperature of silicon. Today, our RTP-based products are used for processes as varied as radical oxidation, gate oxide engineering, metal silicide annealing, and ultra shallow junction annealing spanning the temperature range from 240degC to over 1200degC. The next generation RTP - millisecond annealing - is following the same trends by providing the most production worthy yet technically capable tool in the world.

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].

Si spontaneous emission during RTP and its impact on low-temperature pyrometry

Si fluorescence or spontaneous emission was discovered during the development of lower-temperature pyrometer. To reveal unambiguously the Si spontaneous emission, a high-power 980nm laser is used together with a high sensitivity IR spectrometer. Clear Si fluorescence spectra with peaks at ∼1140nm were obtained at different Si temperatures. The Si fluorescence peaks shift to longer wavelength, in agreement with Si bandgap narrowing with increasing temperatures. Wafers of different doping levels and types were studied for Si spontaneous emission. It is found that lightly doped (resisitivity ≪20 ohms-cm) Si has the highest level of Si spontaneous emission. On the other hand, heavily doped Si does not generate any Si spontaneous emission, mainly due to the higher recombination. Since the Si spontaneous emission has a broad spectrum, it spills into the RTP pyrometer spectral bandwidth and acts as s spurious pyrometer signal. Even though Si has very low efficiency for light emission due to its indirect bandgap, the fluorescence emitted light is still on the level of pyrometer signal equivalent to ∼200 to 250C.

Ultra Low Temperature NiSi Processing

Manuscript not released forpublication due to legal issues.