We compare single wafer systems, conventional batch systems and fast ramp batch systems in terms of throughput, cycle time and cost per wafer for four different processes. Comparison is based on dynamic fab simulations done with proprietary software package. The results show that vertical furnaces are the best choice in terms of throughput and cost per wafer for those processes for which both a single wafer and a batch process exist. Fast ramp furnaces are an attractive option to conventional batch furnaces in case a shorter cycle time is needed. Single Wafer systems show a substantially lower cycle time, but a higher cost per wafer. These additional costs might be justified by short cycle times in e.g. ASIC's manufacturing and in product development.

The radiative properties of a silicon wafer undergoing Rapid Thermal Processing (RTP) are contingent upon the doping level of the silicon substrate and film structure on the wafer, and fluctuate drastically with temperature and wavelength. For a lightly doped substrate, partial transparency effects must be considered that significantly affect absorption characteristics. Band gap, free carrier, and lattice absorption are the dominant absorption mechanisms and either individually or in concert have considerable effect on the overall absorption coefficient of the silicon wafer. At high doping levels, partial transparency effects dissipate, and the substrate may be considered optically thick. A numerical model has been developed to examine partial transparency effects, and to compare lightly doped (partially transparent) and heavily doped (opaque) silicon wafers with a multilayer film structure during RTP.

In recent years, simulation techniques have emerged as useful tools for the design of semiconductor equipment. However, the need for rapid assessment of potential designs stretches the capability of even the most advanced tools currently available to the limit. In this paper, a simplified model of a rapid thermal processing (RTP) system that significantly reduces the execution time is presented. The model is based on a coupling of semi-analytical expressions for radiation fluxes with a one-dimensional finite element heat transfer model for wafer and slip-free ring temperatures. Results showing the effects of plate reflectivity and slip-free ring emissivity on wafer temperature are presented. It is shown that the simplified model yields results that are in agreement with detailed two-dimensional simulations of the same geometry.

Isothermal electron beam heating has been combined with in situ optical measurements in order to measure the emissivity of coated silicon samples at elevated temperatures. The coatings include a number of oxide, nitride, and silicon films. Infrared emission spectra were recorded from I to 9 μm for temperatures between 750 and 1200°C. The experimental results were compared with calculated theoretical values, which were predicted from the theory of thin film coatings, using a matrix model incorporating the optical constants for the materials. A good match between experimental and theoretical values validates the use of the infrared optical constants for theoretical modelling related to control and temperature measurements in rapid thermal processing systems.

Flow and heat transfer effects play a critical role in chemical vapour deposition (CVD) reactors. Holographic interferometry offers the possibility to study the flow dynamics of an entire region in real time under process conditions with negligible disturbances of the investigated process. The advantage of the method is the possibility of accurate measurements of flow patterns and temperature profiles in a fast dynamic process under actual experimental conditions. Mixed and forced flow conditions were studied for two gases with distinct different thermophysical properties. The influence of the gas inlet system and buoyancy forces on the resulting fluid flow are highlighted. A special attention was drawn on the visualization of edge effects.

The residual impurity gases in the atmospheric rapid thermal processing (RTP) equipment are becoming an important factor in sub-micron ULSI industry. For example, 1% nitrogen in oxygen decreases the RT oxide thickness, and a small amount of moisture or oxygen in nitrogen may strongly affect the RT titanium silicidation. The effective method to reduce the residual gases is to use process gas to purge the chamber. In the present paper the gas purging mechanisms were in-situ investigated in the flow rate range of 10 to 60 slpm using a Quadrapole Residual Gas Analyser (RGA) and gas sensors. The gases for purging studies are N2, O2, He and Ar. It has been found that there are two regimes in the dependence of the residual gas concentration on purging time. Based on the results of systematic experiments, a purging equation, called Pseudo-PST (“perfectly stirred tank) model, has been developed and was used to give the interpretation of the purging process in the atmospheric RTP system. The limitation of the RGA and the oxygen analyzer used to atmospheric RTP system was also discussed.

Gaseous impurities in the chamber of a SHS2800ε rapid thermal processor were quantitatively measured by using atmospheric pressure ionisation mass spectrometry (APIMS). APIMS is a very sensitive technique to detect trace impurities in a bulk (1 atm) gas. A wide dynamic range (0.1 ppb - 10 ppm) measurement was successfully performed, which allowed in-situ monitoring of impurities during RTP. This work reports the fundamental behaviour of ambient impurities originating from different sources. The sources discussed in this paper are threefold: system background, wafer loading, and the wafer itself. Ambient management requires a better understanding of the independent contribution of each source on processing.

Rapid thermal processing (RTP) has found continually increasing use for oxidation, silicidation, CVD, and other steps in microelectronic fabrication. Kinetic effects in rapid thermal processing (RTP) are often assessed using the concept of thermal budget, with the idea that low thermal budgets should minimize dopant diffusion and interface degradation. Some definitions of budget employ the product of temperature and time (T-t). In previous work, we have shown that this definition for budget often leads to qualitatively incorrect conclusions regarding heating program design. However, other definitions of budget employ the product of diffusivity and time (D-t), where the diffusivity describes unwanted diffusion or interface degradation. Here we show that minimization of D-t by itself is insufficient to kinetically optimize a heating program; account must be taken of the relative rates of the desired and undesired phenomena. We present a straightforward but rigorous method for doing so.

With the development of crystalline-silicon thin-film solar cells (c-SiTFC) CVD has gained importance in a new field of application. In recent years research resulted in a large variety of different concepts of c-SiTFCs. Many of these concepts require the deposition of a silicon film of good quality. i.e., at high temperature. However, little effort has been made up to this point to develop a suitable apparatus for that purpose, especially for the case of mass production of such cells. In this paper we present a self-constructed CVD system that we believe has the potential to meet the goals of an economical production of c-SiTFCs. An extension of the existing apparatus into a system in which the substrates enter the reactor at one side and leave it at the other side in a continuous way is feasable.

The present system is characterized according to its behavior when typical CVD parameters are changed, the silicon conversion yield was investigated, and solar cells with a maximum efficiency of 15.3% were fabricated from epitaxial layers deposited on various substrates

This paper reviews work to develop and improve the temperature measurement and control technology of a commercial rapid thermal processing (RTP) system. A description of the main features of this system is given, which includes a concentric multi-zone lamp heating source, multi-point temperature measurement system and real time wafer temperature control. Innovations in RTP optical thermometry are described which resulted in improved low temperature performance, a real time spectral emissivity measurement tool which enables emissivity independent temperature measurement and an improved temperature calibration capability. The multi-input multi-output (MIMO) optimal wafer temperature control methodology is discussed. Process results demonstrating an equivalent process temperature performance of 4°C, 3-sigma, all-points-all-wafers will be presented.

Rapid thermal processing (RTP) is a key technology for the cluster tool, single wafer manufacturing approach that is used to produce integrated circuits at lower cost with reduced line widths and thermal budgets. However, various problems associated with wafer temperature measurements and dynamic temperature uniformity have hindered the widespread use of RTP in semiconductor device manufacturing. The current technology for calibrating the radiometers employs a thermocouple instrumented wafer. We have accomplished improvements in the accuracy of these measurements through the use of thin-film thermocouples and the new Pt/Pd thermocouple system. These new calibration wafers can reduce the uncertainty in wafer temperature measurement technology by (1) reducing the perturbation due to heat transfer at the thermocouple junctions and (2) replacing conventional thermocouples with the superior Pt/Pd system. The thin-film thermocouples were calibrated using proof specimens fabricated with the Si 200 mm wafers and evaluated in the NIST RTP sensor test bed.

The commercial type K thermocouples yielded temperature measurements within 4 °C of the thin-film Rh/Pt and Pt/Pd thermocouples on the 200 mm calibration wafer between 725°C and 875 °C. The Pt/Pd thin-film thermocouples proved less durable than the Rh/Pt thin films and the limitations of these systems are discussed. We also present a comparison of the radiometric measurements with the thermocouple measurements using a model estimating the wafer temperature from its spectral radiance temperature.

The first qualitative results of the effects of backside surface roughness on the radiative properties of silicon as a function of temperature in the wavelength range of 1–20μm are presented in this study. These measurements have been made utilizing a spectral emissometer operating at near- and mid-IR spectral range. Surface roughness of the silicon wafer has been observed to lead to increased emissivities.

Thermocouples are often used as a calibration standard for rapid thermal processing. Although it has been recognized that the thermocouple temperature can be different from the wafer temperature, the magnitude of the temperature difference is difficult to quantify. In this work, we present a simple analytical model to demonstrate the difference between the thermocouple temperature and the true wafer temperature. The results show that a large difference can exist between the thermocouple and the wafer temperature. This is because the optical and thermophysical properties of the thermocouple and the glue material are different from those of the wafer. The model results show that temperature measurement becomes more accurate if fine diameter thermocouple wires with very low emissivity are used.

A Model Based Control method is presented for accurate control of RTP systems. The model uses 4 states: lamp filament temperature, wafer temperature, quartz temperature and TC temperature. A set of 4 first order, nonlinear differential equations describes the model. Feedback is achieved by updating the model, based on a comparison between actual (measured) system response and modeled system response.

The offset between Si temperature and indicated TC temperature when a thermocouple instrumented wafer is placed in a double side heated RTP system was measured by means of an isothermal cavity, formed by 2 parallel Si wafers mounted in the system. The lamp powers were controlled to get an equal wafer temperature, making the cavity isothermal. Inside the cavity, an R-type TC with a NIST traceable calibration was mounted. Outside the cavity, a standard type K 1530 SensArray thermocouple [1] was exposed to the typical conditions in an RTP system. The offset was measured as the difference between the indicated temperature of the standard 1530 TC and the temperature of the NIST traceable type R TC. The 3 sources of the offset are discussed and a typical correction factor is proposed.

Although a resolution of 1 °C of the grating temperature measurements has been demonstrated in RTP process[l], the conventional etching process to fabricate gratings on large diameter wafers makes it impractical for the production purpose. We, therefore, used the laser ablation technique to fabricate such Si gratings without any lithography and etching process. To increase the sensitivity of measurements, a large-angle diffracted beam was used by optimizing the incident angle and the grating period. As a result, an improvement of sensitivity could be obtained. The Si gratings were fabricated by the interference of two high power laser beams with the wavelength of 266 nm. The grating period was determined by interference condition, and could be varied from 180 to 550 nm, which would be beneficial to increase the measurement sensitivity. HeNe laser was used as the light source to measure the thermal expansion of grating periods for the temperature measurements. The temperature measurement of Si wafer from room temperature to 800 °C was demonstrated.

Although radiometric temperature measurement in rapid thermal processing (RTP) tools has substantially improved in terms of repeatability and uniformity, it still remains a technical challenge. The 1999 requirements of 180 nm line width technology in the 1997 National Technology Roadmap for Semiconductors (NTRS) imply an uncertainty of ± 2 °C in temperature measurement, which will continue the challenge in temperature measurement. In this paper we will discuss the NIST absolute radiometric temperature calibration, measurements, and uncertainty analysis.

Results are presented that demonstrate the use of laser ultrasonic methods to determine the temperature of silicon wafers under conditions consistent with applications in the RTP industry. The results show that it is possible to measure the temperature of Si(100) wafers to an accuracy approaching ± 1°C (1σ) even with wafer thickness variation over a range of 2 to 3 percent.

The growth of high quality thin (<10 nm) oxides is one of the most critical steps in the fabrication of the entire spectrum of silicon based devices. Rapid thermal wet oxidation is emerging as a promising technique for this application due to features such as higher throughput, superior oxide quality, faster response and precise thickness control. In this paper, an integrated pyrogenic steam generator -RTP system is described. Theoretical and experimental growth curves along with thickness contour maps and preliminary reliability results are presented.

We have used low energy cathodolumrdinescence spectroscopy (CLS) to characterize defects at ultrathin (50 Å) silicon dioxide films, prepared on Si substrates by low-temperature plasma deposition. Variable-depth excitation with different electron injection energies provided a clear distinction between deep levels localized within the films versus at their interfaces. Defect bands are evident at 0.8 eV and 1.9 eV, characteristic of an amorphous, silicon-rich local bonding environment. Closer to the film surface, CLS reveals a defect at 2.7 eV indicative of oxygen vacancies in stoichiometric SiO2. The effect of hydrogenation at 400°C, rapid thermal annealing at 900°C, and especially the combination of both processing steps is shown to reduce the density of these defects dramatically.