Ion Implantation and Synthesis of Materials - Studium

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232 15 Ion Implantation in CMOS Technology: Machine Challengesalthough of significant technological interest for niche applications, has not yetachieved market adoption.15.5 Angle ControlOne of the enabling advantages ion implantation offers is precise spatialplacement of the dopant within the device. There are however a number ofsituations that might lead to an error in placement, either in depth or in the lateraldirection. Energy contamination, discussed in an earlier section, can result in anerror in depth. Similarly, an error in the angular alignment of the beam can resultin an error in ion placement in the lateral direction. Control over the angularalignment of the beam is critical in modern implanters. Angular alignment of thebeam can be influenced by a number of factors including beam steering, beamdivergence, as well as the method of beam scan or endstation design. In thesubsections below we describe a number of endstation and scan configurationswhich can impact angle control. It is worthwhile to note that the need forimproved angle control for smaller devices on larger wafers has been a significantdriving force behind implanter development, particularly during the transitionfrom 125/150 to 200 and 300 mm wafers.15.5.1 Impact of Beam Steering Errors on Device PerformanceThe most general case of angular misalignment is the tilting of an otherwiseperfect (collimated and nondivergent) ion beam relative to the wafer normal. If thetilt of an extension implant is in the plane of the length dimension of a transistor, itwill result in an undercut of the gate stack on one side and shadowing of theextension by the gate stack on the other. It is apparent that any deleterious effectsdue to the shadowing and undercut would only worsen as the transistordimensions and thermal budgets shrink further. Device simulations show that atthe 65 nm node angle tilt errors on the order of 1° can lead to large deviations inthe transistor on current (I on ) from the nominal value, see Fig. 15.13.One technique for reducing the impact of beam steering errors is to employ aquad-mode implant, i.e., an implant whereby a quarter of the dose is implanted atazimuthal rotations of 0°, 90°, 180°, and 270°. For a beam steering angle of −1°, aquad implant restores I on to nearly the maximum value, provided that the tilt-angleis sufficiently large (see Fig. 15.14). A quad-mode implant can be executedefficiently on any endstation with in situ wafer repositioning. In this case verylittle time is wasted between the segments.
15.5 Angle Control 233Fig. 15.13. On current of a 65 nm node NMOS transistor versus beam steering angle.A positive angle corresponds to shadowing of the extension region on the drain side, whilea negative angle corresponds to shadowing on the source side. The curve is not symmetricsince the resistivity of the source side is far more important than the resistivity of the drainside (Ghani et al. 2001)Fig. 15.14. On current of the same NMOS transistor as in Fig. 15.13 as a function of tiltangle for a beam steering angle of −1°, for a single implant (triangles) and for a quadimplant (squares). The line indicates I on for perfect alignment
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M. Nastasi J.W. MayerIon Implantati
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To our loved ones
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xContents4 Cross-Section ..........
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Contentsxiii14.3.2 Punch-Through St
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2 1 General Features and Fundamenta
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10 1 General Features and Fundament
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12 2 Particle InteractionsThe restr
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142 Particle Interactions(a)V(r)r 0
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162 Particle InteractionsHowever, a
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182 Particle Interactionswhere the
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202 Particle Interactionsa0.8853a0L
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3 Dynamics of Binary Elastic Collis
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3.3 Kinematics of Elastic Collision
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3.4 Center-of-Mass Coordinates 27Fi
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3.4 Center-of-Mass Coordinates 29an
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3.5 Motion under a Central Force 31
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3.5 Motion under a Central Force 33
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Problems 35The reduced energy for 1
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4 Cross-Section4.1 IntroductionIn C
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4.2 Scattering Cross-Section 39unit
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4.2 Scattering Cross-Section 41Rdθ
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4.3 Energy-Transfer Cross-Section 4
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4.4 Approximation to the Energy-Tra
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Problems 47ReferencesNastasi, M., M
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5 Ion Stopping5.1 IntroductionWhen
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5.3 Nuclear Stopping 51MeV mg −1
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5.3 Nuclear Stopping 531−m1−2mC
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5.4 ZBL Nuclear Stopping Cross-Sect
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5.5 Electronic Stopping 575.5.1 Hig
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5.5 Electronic Stopping 59Table 5.1
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Problems 61Problems5.1 Calculate th
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64 6 Ion Range and Range Distributi
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78 7 Displacements and Radiation Da
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94 8 Channeling1.00.8Non-aligned Im
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96 8 ChannelingMeV ION BEAMSUBSTITU
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98 8 ChannelingThe channeling effec
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100 8 Channeling4.0Silicon2.0P (mic
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102 8 ChannelingdσσD( ψc) = ∫
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104 8 ChannelingDechanneled fractio
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106 8 ChannelingProblems8.1 Calcula
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108 9 Doping, Diffusion and Defects
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128 10 Crystallization and Regrowth
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144 11 Si Slicing and Layer Transfe
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160 12 Surface Erosion During Impla
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180 13 Ion-Induced Atomic Intermixi
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Page 247 and 248: References 237No. of implants504540
Page 249 and 250: Appendix ATable of the Elementselem
Page 251 and 252: Appendix A 241elementatomicnumber(Z
Page 253 and 254: Appendix A 243element atomicnumber(
Page 265 and 266: Appendix BPhysical constants, conve
Page 267 and 268: IndexAlpha particle 8amorphization
Page 269 and 270: Index 259differential cross-section
Page 271 and 272: Index 261layer transfer 143Lennard-
Page 273: Index 263thermodynamiceffect ion be
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Ion Implantation and Synthesis of Materials - Studium

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