1 / 28

Lecture 8.0

Lecture 8.0. Silicon Crystal Growth. Silicon Mfg. - old. Produce Silicon metal bar Zone Refining – n times To get purity Cut off impure end Use pieces to fill crystallization apparatus Grow Mono-Crystal of large size. Zone Refining. 0=x-Ut, k=C S /C L.

nicholascarter
Download Presentation

Lecture 8.0

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. Lecture 8.0 Silicon Crystal Growth

  2. Silicon Mfg. - old • Produce Silicon metal bar • Zone Refining – n times • To get purity • Cut off impure end • Use pieces to fill crystallization apparatus • Grow Mono-Crystal of large size

  3. Zone Refining 0=x-Ut, k=CS/CL Co=solute concentration in melt or of solid on first pass Co=0x+L Cs(x)dx - ox-L kCL(x)dx

  4. Si-Fe Phase Diagram

  5. Si-O Phase Diagram

  6. Crystal Growth

  7. Silicon Mfg. - new • Produce ultra pure Silicon cylinder • Use pieces to fill crystallization apparatus • Grow Mono-Crystal of large size

  8. Melt is maintained with a given impurity concentration Melting Point is decreased Solid produced has a given impurity concentation Add Dopants to Silicon Grown

  9. Ultra-pure Silicon Production • Si + 3HClSiHCl3 +H2 • fluidized bed reactor at 500 to 700K • Condense chlorosilane, SiHCl3 • Distillation of liquid SiHCl3 • SiHCl3+H2Si + 3HCl at 1400K • Si vapor Deposits on Si mandrel in a purged fed batch reactor heated to 700K • Results Large diameter Si with impurities at 10 ppt or 14-9’s pure

  10. 12” (30 cm) Boule

  11. Crystal Growth

  12. Czochralski Crystal Growth Apparatus • Figure 4. Today's Czochralski growth furnace, or crystal puller, is a far more sophisticated apparatus than that built by Gordon Teal nearly 50 years ago. It is however fundamentally identical. A crystal is pulled from a feedstock of molten material by slowly withdrawing it from the melt. Czochralski pullers often possess provisions for adding to the melt during a single pull so that crystals larger than what can be obtained in a single charge of the crucible may be produced. Today crystals of a 12-inch diameter are possible, and the industry will spend billions to adopt this new size in the coming years. This figure was taken directly from the Mitsubishi Semiconductor • website: http://www.egg.orjp/MSIL/ english/index-e.html!

  13. Czochralski Growing System

  14. 12” (30 cm) Boule

  15. Crystal Growth Steps • Induce Supersaturation • Sub cooled melt • S=exp[THf/(RT2)dT] • Nucleation • Growth at different rates on each Crystal Face • Results in crystal with a particular Crystal Habit or shape

  16. Nucleation • Free Energy • GTOT=GvV + A • Critical Size • R*=2AVm/(3vRgT lnS) • Nucleation Rate • J=(2D/d5)exp[-G(R*)/(RgT)] • D=diffusion coefficient • d= molecular diameter

  17. Surface Nucleation • Surface energy, , is replaced by  cos , where  is the contact angle between phases • Geometric factors changed • Units #/(cm2sec) • Surface Nucleation • Limits growth of flat crystal surfaces

  18. Crystal Growth • Boundary Layer Diffusion • Surface Diffusion • Edge Diffusion • Kink Site Adsorption • Loss of Coordination shell at each step

  19. Crystal Growth Rate Limiting Steps • Boundary Layer Diffusion • Surface Diffusion • Surface Nucleation • Mono • Poly • Screw Disslocation • Edge Diffusion • Kink Site Adsorption • Loss of Coordination shell

  20. Screw Surface Growth

  21. Fluxes • Boundary Layer • Surface • Edge

  22. Mass Transfer to Rotating Crystal • Local BL-MT Flux • J[mole/(cm2s)] = 0.62 D2/3(Co-Ceq) n-1/6w1/2 • J[mole/(cm2s)] = 0.62 D2/3 Ceq(S-1) n-1/6w1/2 • Franklin, T.C. Nodimele, R., Adenniyi, W.K. and Hunt, D., J. Electrochemical Soc. 135,1944-47(1988). • Uniform, not a function of radius!! • Crystal Growth Rate due to BL-MT as Rate Determining Step

  23. Heat Transfer to Rotating Crystal • Local BL-HT Flux • J[mole/(cm2s)] = h(Teq-T)/Hf • J[mole/(cm2s)] • = 0.62 k -1/3 n-1/6w1/2 (Teq-T)/Hf • Franklin, T.C. Nodimele, R., Adenniyi, W.K. and Hunt, D., J. Electrochemical Soc. 135,1944-47(1988). • Uniform, not a function of radius!! • Crystal Growth Rate due to BL-HT as Rate Determining Step

  24. Crystal Habit • Equilibrium Shape • h1/1=h2/2=h3/3 • Kinetic Shape • h1=G1(S)*t • h2=G2 (S)* t • h3=G3 (S)* t

  25. Crystal Faces • Flat Face • Stepped Face • Kinked Face • Diffusion Distances to Kink sites are shorter on K &S Faces

  26. Crystal Habit

  27. Wafers Cut from Boule & Polished

More Related