1 / 26

Deal-Grove Model Predictions

Deal-Grove Model Predictions. Once B and B/A are determined, we can predict the thickness of the oxide versus time. Deal-Grove Model of Oxidation. B. P. 1200 C. Mask thickness ( m m). 1200 C. 1100 C. 1100 C. 1000 C. 900 C. 1000 C. 900 C. Diffusion time (hr).

cole
Download Presentation

Deal-Grove Model Predictions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Deal-Grove Model Predictions • Once B and B/A are determined, we can predict the thickness of the oxide versus time

  2. Deal-Grove Model of Oxidation

  3. B P 1200 C Mask thickness (mm) 1200 C 1100 C 1100 C 1000 C 900 C 1000 C 900 C Diffusion time (hr) Oxide as a Diffusion Barrier • Diffusion of As, B, P, and Sb are orders of magnitude less in oxide than in silicon • Oxide is excellent mask for high-temperature diffusion of impurities 10 10 Boron Phosphorus 1 1 0.1 0.1 0.01 0.01 0.1 0.1 1.0 10 100 1.0 10 100

  4. Other Models • A variety of other models have been suggested, primarily to correct the deficiencies of the Deal-Grove model for thin oxides • These include • The Reisman power law model • The Han and Helms model with parallel oxidation paths • The Ghez and van Meulen model to account for the effect of oxygen pressure • Some of these models do a much better job for thin oxides • None are widely accepted

  5. Other Topics • Several topics other than the simple planar growth of wet and dry oxide are important • These include • Thin oxide growth kinetics • Dependence on oxygen pressure • Dependence on crystal orientation • Mixed ambient growth kinetics • 2D growth kinetics

  6. Example: 2D Growth

  7. Example: 2D Growth

  8. Example: 2D Growth • There are several interesting observations • There is significant retardation of the oxide growth in sharp corners • The retardation is more pronounced for low temperature oxidation than for high temperature oxidation • Interior (concave) corners show a more pronounces retardation that exterior (convex) corners

  9. Example: 2D Growth

  10. Example: 2D Growth • Several physical mechanisms are needed to understand these results • Crystal orientation • Oxidant diffusion • Stress due to volume expansion • Kao et al suggested changes to the linear-parabolic (Deal-Grove) model to correct for these effects • Most of these effects are built into the modeling software such as SUPREM IV and ATHENA

  11. Measurement Methods • The parameters of interest include • Thickness • Dielectric constant and strength • Index of refraction • Defect density • There are three classes of measurement • Physical (usually destructive) • Optical (usually nondestructive) • Electrical (usually nondestructive)

  12. Physical Measurements • Simple step height technique (DekTak) • Etch away oxide with HF • Use a small stylus to measure the resulting step height • The resolution is <10 nm • More complex technique uses one or more of the SFM concepts (AFM, MFM, etc) • Technique has atomic resolution • SEM or TEM (electron microscopy) • All require sample preparation that makes the tests destructive and not easy to use in production

  13. Optical Measurements • Most optical techniques use the concept of measuring reflected monochromatic light • If monochromatic light of wavelength  shines on a transparent film of thickness x0, some light is reflected directly and some is reflected from the wafer-film interface • For some wavelengths, the light will be in phase and for others it will be out of phase • constructive and destructive interference • Minima and maxima of intensity are observed as  is varied

  14. Optical Techniques

  15. Color Chart http://www.htelabs.com/appnotes/sio2_color_chart_thermal_silicon_dioxide.htm

  16. Optical Measurements • Instrument from Filmetrics(http://www.filmetrics.com)

  17. Optical Measurements • The positions of the minima and maxima are given bym=1,2,3… for maxima and ½,3/2,5/2,… for minima • This is called reflectometry and works well for thicknesses over a few 10’s of nm

  18. Optical Measurements • If one does not know n, or if the film is very thin, then ellipsometry is better • When multiple wavelengths of light are used, the instrument is known as a spectroscopic ellipsometer

  19. Optical Measurements • Here, one uses polarized light. • The measurement may be performed at multiple angles of incidence to obtain a higher degree of accuracy • One can get the index of refraction as a function of wavelength as well as the extinction coefficient • Can be used to measure thickness to <1 nm • Fitting routines are necessary to take into account rough interfaces between Si and SiO2 layers.

  20. Cauchy Equation Sellmeier Equation

  21. http://en.wikipedia.org/wiki/Cauchy%27s_equation

  22. Electrical Measurements • These measure properties that correlate directly to the performance of the devices fabricated using the oxides • The dominant techniques is the C—V measurement • The basic structure for the measurement is the MOS capacitor • The usual combination is Si-SiO2-(Al or pSi) • Any conductor-dielectric-semiconductorcan be used

  23. MOS Capacitor + Al tox V Si wafer Al -

  24. http://www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/mos_capacitors.htmhttp://www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/mos_capacitors.htm

  25. C-V Plot http://ece-www.colorado.edu/~bart/book/book/chapter6/ch6_3.htm#fig6_3_5

  26. C-V Plot • Differences between high frequency and low frequency C-V data • Doping concentration in Si near Si-oxide interface • Voltage shift proportional to charged defects within oxide

More Related