1. Background material science ideas that may be of use. This presentation is partially animated. Only use the control panel at the bottom of screen to review what you have seen. When using your mouse, make sure you click only when it is within the light blue frame that surrounds each slide.

3. SiO 2 (Quartzite) Coke Furnace gas SiHCl 3 Finish with EGS Poly-crystalline A) Starting Materials SiC Solid Si liquid Heat Exchanger Si Solid Pulverizer MGS Micron sized particles Fluidized Bed HCl Metallugical grade silicon Start with Sand Distillation Column pure Trichorosilane Hydrogen gas Fuel gas hot Chemical Vapor Deposition Reactor Electronic Grade solid silicon

4. B) Unit Process Models for Proper Control (Process control is best achieved when the equipment follows the model) Crystal growth is an excellent example of how equipment and model cooperate to accomplish the task Crystal Growth Model Growth Approach Adjustments to Model Constraints (Three adjustments to equipment to make growth process match simplify model) 1)Uniformly Heat and insulate the Melt. ( This makes the liquid (dT/dx) Liquid = 0 2)Slow Pull Rates. (This makes (dx) small value and allows use of calculus) 3)Crucible Surface Area Approximates A s and Crystal Rotates Slowly. (This makes heat of fusion the only new heat source and (dT/dx) S predictable) This Gradient has Known Shape and Values Thermal Conductivity for Crystal Near Liquid Interface The small change in solid crystal mass because of a small change in time Temperature gradient in solid crystal near the solid crystal interface Temperature gradient in liquid at a location near the liquid interface (dm/dt) solid (dT/dx) Solid - (dT/dx) liquid " ' s ( dmdt ) s ( k s ) H s ) + ( A ) ( dTdx ) s,

5. Pulled single crystal rod is checked by X-ray camera for crystal alignment Aligned rod carefully polished and then sliced to near wafer dimensions. Wafer Finish Linear Pull Rate Density of Crystal Near Melt Interface (dvdt) ( k s ) H s ) + (1 D s )( dTdx ) s, Single Crystal of Wafer Material with know Amount of Dopent Added. Single Crystal crystal attached to chuck to obtain a specific crystal orientation with plane of melt Seed single crystal is slowly rotated while being pulled out of the melt treated in an arc furnace followed by HCl rinses and Melt comes from Sand ( Quartzite ) that has been factional distillation to become EGS Chuck that Holds Single Crystal Fused Silica Crucible Adds oxygen to Melt Crucible Holder Uniformly Heated Degenerately Doped Electronic Grade Si Czechralski Method (CZ Growth) =

6. Impurity Sources ( PPM) MGS EGSCrucible Metal GradeElectronic Grade Silica B 50 0.001 0.23 Fe 2,100 5. 6 P 30 0.002 - As - 0.01 0.005 C 80 0.6 - 0 - 0.02 0.05 “VLSI Technology”, 2 nd Edition, S.M. Sze, McGraw Hill, 1988 Note: CZ Growth used over 99% of time. Other option is Float Zone Crystal Growth Process. Good reference for CZ growth, “Characterization & Engineering of the Antimony Hero-Antisite Defect in LEC Gallium Arsenide, Ph.D. Dissertation, Marshall Wilson, U. South Fl. 1997

7. BrSe Gallium Arsenic Lewis diagrams show the atom as its symbol plus its electrons in the outer orbit Every atom in a Group has the same number electrons in outer orbit. GeAs Impurities the Crystal Structure Although unwanted impurities exist within a crystal structure, in most micro and nano applications, a “special” impurity, the dopant, is added to the crystal structure. C)Wafer Material Performance Adjustments ArAlPSClSi Ga BNOFC He IIIVVIVIIVIII (with Some Lewis Electron Structures) Group Number I H IV

8. Two views of a cubic crystal structure 3 D Perspective About 6 A Lattice Point About 6 A O Interstitial Location -10 o 1 A = 10 Meters About 6 A

9. Si

10. Doping During Crystal Growth Equilibrium Segregation Coefficient A dopant will be driven by equilibrium considerations to a specific concentration ratio between two possible phases if given enough time and stable conditions to do so. Equilibrium Segregation Coefficient With C ss = Concentration of Dopant in the Crystal Being Pulled C ll = Concentration of Dopant in the Melt below the Crystal k equilibrium ' C s / C Effective Segregation Coefficient Often the driving equilibrium considerations are to complicated to understand because of the arrangement of the equipment and any additional components within the melting system. In this situation an effective segregation coefficient, k seq, is used. Segregation Coefficient With: v = Pull Rate; B = Boundary Layer; D = Diffusion Coefficient Note: k seq takes on values from k eq to 1.0 k seq k eq ( 1 / [ k eq +( 1 - k eq ) ( e - (B/D) (vv ) ] =

11. Summary Two Views of a Doped Cubic Crystal Structure Phosphorus atom on a substitutional lattice location n-type Doped Arrangement p-type Doped Arrangement Boron atom on a substitutional lattice location (Phosphorus's non-bonded outer electron can move about the slab of material and generate local areas of negative charge) (Boron’s unoccupied outer orbit hole can move about the slab of material and generate local areas of positive charge) P B SiB P

12. Local and Universal Charge Characteristics The local charge around the boron adds up to zero. Substrate with Acceptor atom the phosphorus in the n doped slab also adds up to zero. The local charge around the No localized charge inequality in either of these slabs of doped silicon. 1) At Low Temperatures p-type Doped Arrangement Both of these Slabs (n-type and p-type) Remain Overall Neutral n-type Donor Arrangement N = A Substrate with Donor atom Number Density of AcceptorsN = D Number Density of Donors

13. Local and Universal Charge Characteristics 3) Add ion to slab so it finally exchanges with a lattice location An Ion electron left this location so region is now more positive than it was before it left. electron has entered this location so region is now more negative than it was before it got there. N = Density of Charged Acceptors A p = Number Density of Holes Density of Charged Donors n = Number Density "Free" Electrons “Ionized” acceptor Concentration of ions = Concentration of carrier 2) Raise the temperature of the lattice Si B “ionized” donor atom Si P D N = Lattice with new ion becomes charged

14. Orientation (001) (110) (111) a a Surface planes and directions based on Miller Indices -10 o 1 A = 10 Meters About 6 A O D) Wafer Issues (100) (010) (001) (100) (The 111 perspective)

15. Concentration of Constituents Typical Intrinsic Densities Slab Density N total = 5 x 10 22 atoms/cm 3 Face Density N (100) = 6.8 x 10 14 atoms/cm 2 Face Density N (110) = 9.6 x 10 14 atoms/cm 2 Highly Doped Wafer Cross-Section ( p + ) Number Density of Constituents N Boron = 1 x 10 18 atoms/ cm 33 N Silicon = 5 x 10 22 atoms/ cm 33

16. Resistivity (Sometimes before the first process step the wafer may have an excess amount of dopant that defines the wafer’s resistivity.) 10 -3 10 14 10 15 10 17 10 18 10 19 10 20 Dopant Density #/cm 3 Conductivity = (Charge/Carrier)(Mobility of Carrier)(Density of Carrier) Conductivity = (1/ Resistivity) When Dopant is an n-type Material When Dopant is a p-type Material Graph for Educational Value Only. Do not use Values for Accurate Work. 16 Important Parameters Resistively Ohm-Cm 5 x 10 atoms/cm 15-3 10 ohm-cm 5 x 10 atoms/ cm 16 -3 1 ohm-cm;

17. How many Boron (dopant) atoms should be put into an epi layer with a resistivity of; B) 10 ohm-cm Primary reason to build an epi layer coated substrate is to adjust the resistance between the circuit to be built on the top of the epi layer and the back side of the wafer below the epi layer. Resistance of a Material Resistance = (resistivity) ((length material)/ (cross-section area)) R =() A) 1 ohm-cm; from Resistivity plot, 5 x 10 atoms/ cm are needed. 16 -3 (i.e. about 1 PPM) Epitaxial Film 665 micrometers Less than 20 micrometers epi layer Common p-epi layer resistivities values are from 1 0hm-cm through 10 ohm-cm. Example- Epitaxial Film Concentration 5 x 10 atoms/cm are needed. 15-3 (i.e. about 0.1 PPM)from Resistivity plot, ((L)/ ( A ))

18. Energy Levels (levels further away from the nucleus) Energy of Orbit closest to nucleus E 5 E 4 ( E - E ) = 54 Conductance Band The Band Gap (Alone and Lonely) Single Atom Many Atoms Close Together (In a Solid Crystal Lattice) E E 9 6 E 5 Energy Values Higher Negative Values With n being integer energy levels and 13.6 electron volts being Bohr’s energy value for the first orbit of a hydrogen atom Energy Levels from Bohr’s Model E n (1/n)(13.6 ev) 2 = Not to Scale 12345678910 -13.6 ev -0.136 ev -3.40 ev -1.51 ev -0.85 ev -0.21 ev-0.55 ev Related Position of Silicon Energy Levels More Positive Energy Values E 4 E E 3 2 E 1 Valance Band E 1 E 2 E 3 E 5 E 9 Energy Level Approximate Values for Isolated Atom in Space E) Electronic Influence of Contaminates ( -0.55 - [ -0.85] ) = + 0.30 ev

19. Phosphorous in Interstital Spaces Phosphorous in Substitutional Spaces p-type Dopent at Substitutional Sites Metallurgical Junction (Equal Density of Positive and Negative Entities) (the letterSigma indicates that all of the items in the region of interested are added together.) Note: Charge neutrality occurs when; & ' % (N A % n) j (If both n-type and p-type materials are present, the device is said to be compensated) Compensated Device Mask Protecting a Piece of Boron Doped Silicon ( % D p ) j N Number of ionized acceptors Number of holes

20. Image Triggering Vocabulary Metallurgical Grade Silicon (MSG) Electronic Grade Silicon (ESG) CZ Growth Lattice Interstitial Locations Substitutional Locations Lewis Diagrams Miller Indicies Resistivity Epitaxial Film Compensated Device Donors Acceptors Equal Charge Density Metallurigical Junction

21. Image Triggering Vocabulary Metallurgical Grade Silicon (MSG) Electronic Grade Silicon (ESG) CZ Growth Lattice Interstitial Locations Substitutional Locations Lewis Diagrams Miller Indicies Resistivity Epitaxial Film Compensated Device Donors Acceptors Equal Charge Density Metallurigical Junction