Ion Implantation and Synthesis of Materials - Studium

More documents

Recommendations

Info

224 15 Ion Implantation in CMOS Technology: Machine ChallengesThe challenges of overcoming space charge neutralization to increase lowenergybeam transport are described in the following section. Novel approaches,such as molecular ion implantation, are also discussed.15.3.1 Space Charge NeutralizationA major component of beam degradation at low energies is Coulombic repulsionbetween the charged ions. These repulsive effects, known as space charge, can beminimized by neutralizing the beam with an electron plasma. Figure 15.6 showsthe effects of space charge neutralization on a low energy beam. We modeled azero emittance, zero divergence B + beam of 10 mA at 2 keV in a beamline driftregion 500 mm long. Each individual curve in the figure represents a differentpercentage of the total beam current (in the range 0–4%) that is not neutralized.The effects of space charge forces in producing beam divergence are clearly seen.With 4% non-neutralized current, the beam has expanded in size in one dimensionby a factor of almost six after traveling 500 mm. Even if only 1% of the beamcurrent is non-neutralized, the beam still expands more than a factor of two in thisdistance. The challenge over the past 5–10 years has been to reduce the beamblow up effects. This has been achieved by effective production and trapping oflow-energy electrons in the beam liner and by reducing all transit lengths.15.3.2 Decel ImplantationOne way to contend with the physics limitations on extraction and transport oflow-energy beams is to extract the ions from the ion source at a multiple of thedesired beam energy (the decel-ratio) and decelerate them immediately beforethey reach the wafer. This way, most of the beam transport is accomplished atrelatively high energies, yielding a higher beam current. Unfortunately, a certainfraction of ions always neutralize due to collisions with residual gas atoms; thoseneutrals will not be slowed by the deceleration optics and will therefore beimplanted at the extraction voltage, far higher than the intended implant energy.This phenomenon is referred to as energy contamination, and it degrades theenergy purity of the beam.Energy contamination is inherently difficult to control since it depends on theresidual gas pressure in the beam line. Typical values for the amount of energycontamination (defined here as fraction of ions implanted at a higher energy thanthe desired final energy) are 1–2%. However, energy contamination of as little as1% can pose a problem. Figure 15.7 shows that the as-implanted junction depthfor a 0.5 keV implant increases from 13 to 20 nm when decel from extraction at2 keV is used. Such increases in the implanted dose and the depth of the extensionjunction can shift the transistor’s threshold voltage (Gossmann and Agarwal2004). Figure 15.7 also illustrates that the impact of a finite percent of energycontamination on the junction profile diminishes with the extraction energy at thesource. This brings us back to requiring larger beam currents at low energy.
15.3 Low Energy Productivity: Beam Transport 225Fig. 15.6. Beam size expansion due to space charge at low energies for various amounts ofnon-neutralized beam currentFig. 15.7. Dependence of as-implanted dopant profiles for 0.5 keV boron “decel” implantson the source extraction energy
Page 2 and 3:
M. Nastasi J.W. MayerIon Implantati
Page 4 and 5:
To our loved ones
Page 7 and 8:
xContents4 Cross-Section ..........
Page 10 and 11:
Contentsxiii14.3.2 Punch-Through St
Page 12 and 13:
2 1 General Features and Fundamenta
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
10 1 General Features and Fundament
Page 22 and 23:
12 2 Particle InteractionsThe restr
Page 24 and 25:
142 Particle Interactions(a)V(r)r 0
Page 26 and 27:
162 Particle InteractionsHowever, a
Page 28 and 29:
182 Particle Interactionswhere the
Page 30 and 31:
202 Particle Interactionsa0.8853a0L
Page 33 and 34:
3 Dynamics of Binary Elastic Collis
Page 35 and 36:
3.3 Kinematics of Elastic Collision
Page 37 and 38:
3.4 Center-of-Mass Coordinates 27Fi
Page 39 and 40:
3.4 Center-of-Mass Coordinates 29an
Page 41 and 42:
3.5 Motion under a Central Force 31
Page 43 and 44:
3.5 Motion under a Central Force 33
Page 45 and 46:
Problems 35The reduced energy for 1
Page 47 and 48:
4 Cross-Section4.1 IntroductionIn C
Page 49 and 50:
4.2 Scattering Cross-Section 39unit
Page 51 and 52:
4.2 Scattering Cross-Section 41Rdθ
Page 53 and 54:
4.3 Energy-Transfer Cross-Section 4
Page 55 and 56:
4.4 Approximation to the Energy-Tra
Page 57 and 58:
Problems 47ReferencesNastasi, M., M
Page 59 and 60:
5 Ion Stopping5.1 IntroductionWhen
Page 61 and 62:
5.3 Nuclear Stopping 51MeV mg −1
Page 63 and 64:
5.3 Nuclear Stopping 531−m1−2mC
Page 65 and 66:
5.4 ZBL Nuclear Stopping Cross-Sect
Page 67 and 68:
5.5 Electronic Stopping 575.5.1 Hig
Page 69 and 70:
5.5 Electronic Stopping 59Table 5.1
Page 71:
Problems 61Problems5.1 Calculate th
Page 74 and 75:
64 6 Ion Range and Range Distributi
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
78 7 Displacements and Radiation Da
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
94 8 Channeling1.00.8Non-aligned Im
Page 106 and 107:
96 8 ChannelingMeV ION BEAMSUBSTITU
Page 108 and 109:
98 8 ChannelingThe channeling effec
Page 110 and 111:
100 8 Channeling4.0Silicon2.0P (mic
Page 112 and 113:
102 8 ChannelingdσσD( ψc) = ∫
Page 114 and 115:
104 8 ChannelingDechanneled fractio
Page 116 and 117:
106 8 ChannelingProblems8.1 Calcula
Page 118 and 119:
108 9 Doping, Diffusion and Defects
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
128 10 Crystallization and Regrowth
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
144 11 Si Slicing and Layer Transfe
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
160 12 Surface Erosion During Impla
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185: 174 12 Surface Erosion During Impla
Page 190 and 191: 180 13 Ion-Induced Atomic Intermixi
Page 204 and 205: 194 14 Application of Ion Implantat
Page 223 and 224: 15 Ion Implantation in CMOS Technol
Page 225 and 226: 15.2 Implanters Used in CMOS Proces
Page 233: 15.3 Low Energy Productivity: Beam
Page 237 and 238: 15.4 Low Energy Productivity: Beam
Page 243 and 244: 15.5 Angle Control 233Fig. 15.13. O
Page 245 and 246: 15.5 Angle Control 235Fig. 15.15. I
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
show all

Ion Implantation and Synthesis of Materials - Studium

Create successful ePaper yourself

Delete template?

Save as template?