James S. Nakos

Comparison of transformation to low-resistivity phase and agglomeration of TiSi/sub 2/ and CoSi/sub 2/

The phase transformation and stability of TiSi/sub 2/ on n/sup +/ diffusions are investigated. Narrower n/sup +/ diffusions require higher anneal temperatures, or longer anneal times, than wider diffusions for complete transitions from the high-resistivity C49 phase to the low-resistivity C54 phase. A model is presented which explains this in terms of the probability of forming C54 nuclei on narrow diffusions and the influence of diffusion width on C54 grain size. The results are that more C49 and C54 nucleation events are required to completely transform narrow lines. For thin TiSi/sub 2/ (40 nm), there is a narrow process window for achieving complete transformation without causing agglomeration of the TiSi/sub 2/. The process window decreases with decreasing silicide thickness. A significantly larger process window is achieved with short-time rapid annealing. Similar studies are performed for CoSi/sub 2/ on n/sup +/ and p/sup +/ diffusions. No linewidth dependence is observed for the transformation from CoSi/sub x/ to CoSi/sub 2/. There is a broad process window from 575 degrees C to 850 degrees C using furnace annealing, for which the low-resistivity phase is obtained without causing agglomeration. >

Semiconductor process and structural optimization of shallow trench isolation-defined and polysilicon-bound source/drain diodes for ESD networks

The impact of MOSFET source/drain junction scaling on the ESD robustness of shallow trench isolation (STI)-defined diode structures is shown for the first time. ESD robustness improvements to STI-bound p/sup +/ diodes using germanium preamorphization and deep B11 implants, and polysilicon-bordered ESD networks are also discussed.

Seamless application of rapid thermal processing in manufacturing

Although rapid thermal processing (RTP) has existed for a number of years, difficulties associated with pyrometric temperature measurement and control have prevented RTPs widespread acceptance in manufacturing. We show that nominal process-associated film thickness variations drastically reduce the wafer-to-wafer process repeatability using pyrometry. These thickness variations lead to large changes in wafer emissivity producing temperature errors of as much as +/- 100 K. The result is reduced process capability which limits the utility of RTP in manufacturing. This paper contrasts pyrometric temperature feedback with power control (PC). The data indicate that PC results in significant reduction of wafer-to-wafer temperature fluctuations, to better than +/- 5 K. The improvement is due to minimal sensitivity of PC to dielectric-film-induced wafer emissivity fluctuations. Therefore, PC can be used without the need for back-side strip, allowing seamless integration into semiconductor processing. We also present a theoretical basis for power control and discuss the limitations and boundary conditions governing the technique.

Influence of pyrometer signal absorption due to process gas on temperature control in rapid thermal processing

Influence of Pyrometer Signal Absorption due toProcess Gas on Temperature Control in Rapid Thermal ProcessingJulius C. Chang, Tue Nguyen, James S. Nakos, and JosefW. KorejwaIBM General Technology DivisionEssex Junction, Vermont, USAABSTRACTFuture DRAM devices require higher performance dielectrics for which novel process chemistries must bestudied. Nitrous oxide (N20) has shown promising results as a process gas for rapid thermal oxidation.However, current practice in rapid thermal processing (RTP) has neglected the effect of process gas ontemperature control. For N20, this results in a large temperature offset and oscillation, and poor thicknessuniformity. Evidence is presented indicating that gas-phase absorption of the pyrometer signal produces thedifficulties observed when using N20. These difficulties do not occur if the pyrometer is operated at awavelength not absorbed by the N20. This behavior also does not occur when using 02 as the process gassince it is transparent at the pyrometer wavelengths used. The data shows that one must examine theabsorption spectra of the process gas for compatibility with the pyrometer wavelength used for temperaturemeasurements.2. INTRODUCTIONAccurate temperature control during rapid thermal processing (RTP) is critical for many steps in state-of-the-art semiconductor manufacturing, from oxidation to annealing to forming silicide junctions. Typically,pyrometry is used for remote high-temperature (above 600 °C) measurement and control of a feedback loop.The pyrometer measures the intensity of a specific wavelength of radiation emitted from the backside of awafer. Temperature is computed through a second-order polynomial function of intensity.The accuracy of pyrometry control can be strongly influenced by absorption of the desired wavelength ofradiation by the process gas used for RTP. This absorption can have a negative effect on process control,impacting product development.Consider the example ofa pyrometer that uses a wavelength of4.5 im for temperature measurement.Several commerically available RTP systems use pyrometers that measure temperature using a wavelengthnear this value. Absorption of a 4.5 tm signal by the process gas is not a problem in the present technology.Oxygen, ammonia, and dilute HCI are some ofthe process gases commonly used for formation ofthin gatedielectrics in RTP and their absorption spectra show that these gases are transparent at 4.5 jim.For certain other ambients, however, 4.5 jim may be a poor choice. Current industry practice has notaccounted for the influence of different process gases and the associated problem of signal absorption inpyrometer temperature measurements. For future DRAM technology, it is clear that new process gaschemistries must be explored to develop higher performance dielectrics; therefore, absorption effects must be

Manufacturability comparison of thin oxynitride films

Thin film nitridation has many applications in sub-0.13-micron line width semiconductor processing. We evaluated several single-wafer processing options capable of creating oxynitride films. Analytical results were obtained using ellipsometry, X-ray photoelectron spectroscopy (XPS), and TOFSIMS. These control methods are also compared to electrical performance data. Data are also reviewed with respect to manufacturing requirements such as tool-to-tool matching and process capability; including chamber to chamber, wafer to wafer and within wafer variability

Process influences on the microstructural and electrical properties of rapid thermal chemical vapor deposited polysilicon

Single wafer CVD techniques have been gaining popularity in ULSI manufacturing of advanced technologies. Primarily driven by thermal budget reduction considerations, optimization of the electrical parameters of poly-silicon films is critical to maximizing their successful incorporation into the main stream production. In this work we look at the influences of deposition parameters such as temperature, and pressure, on grain structure, crystallographic texture, electrical resistivity, and electrical Tox depletion. We examine the influence of subsequent heat cycles on these fundamental film parameters