《Microelectronics Process》lecture2

3155/6.,152] Lecture2 IC Lab overview Prof martin a schmidt Massachusetts Institute of Technology 9/8/2003

3.155J/6.152J Lecture 2: IC Lab Overview Prof. Martin A. Schmidt Massachusetts Institute of Technology 9/8/2003

Outline The mosfet structure Semiconductor Doping The mosfet as a switch A MOSFET Process The Mos capacitor Process Recommended reading Plummer, Chapter 1 Fall 2003-MA schmidt 3. 155J 6.152]-Lecture 2-Slide 2

Outline „ The MOSFET Structure „ Semiconductor Doping „ The MOSFET as a Switch „ A MOSFET Process „ The MOS Capacitor Process „ Recommended reading „ Plummer, Chapter 1 Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 2

MOSFET D Gate G Oxide Source Drain Bulk Fall 2003-MA schmidt 3. 155J 6.152]-Lecture 2-Slide 3

MOSFET G Source Drain Oxide Gate Bulk S D D G S Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 3

N-Channel mosfet OV D Gate Oxide n-type n-type p-type Fall 2003-MA schmidt 3. 155J 6.152]-Lecture 2-Slide 4

N-Channel MOSFET +VG n-type n-type Oxide Gate p-type 0 V +V D Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 4

A Word about Doping Silicon has four valence electrons It covalently bonds with 4 adjacent atoms in the crystal lattice si):(Si)°(Si):(si)。(Si):(Si):(Si)°(si):(Si s):③:(::(:③:(:(s:③° 9:(:○::③⑨:(:③: ③::③:(::(:(:(:( s):():):(s):(s):(s):(S):(S):(i Fall 2003-MA schmidt 3. 155J 6. 152]-Lecture 2-Slide 5

A Word About Doping…. Silicon has four valence electrons It covalently bonds with 4 adjacent atoms in the crystal lattice Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 5

Intrinsic semiconductor Increasing temperature causes creation of free carriers 1010 cm free carriers at 23C(out of 2x cm-3) Intrinsic Conductivity s):(s):(s):(s):(s):(s):(s):(s):(S (:(:(:(:④:(:③S si)。(si)(si)。(si ⑤(::⑤:⑤ ③::③:(::(:(:(:( s):():):(s):(s):(s):(S):(S):(i Fall 2003-MA Schmidt 3. 155J 6.152]-Lecture 2-Slide 6

Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 6 Intrinsic Semiconductor Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Increasing Temperature Causes Creation of Free Carriers 1010 cm-3 free carriers at 23C (out of 2x1023 cm-3) Intrinsic Conductivity

N-type Doping Phosphorus has 5 valence electrons Donates one conduction electron n-type Our substrate has 1055 cm phosphorus(1 in 108) s):(s):(s):(s):(s):(s):(s):(s si):(S):(si):(S):(s):(s):S:(S5):(S)° si)。(si)(si)。(si :⑨:(:⑨:③ ③::③:(::(:(:(:( s):():):(s):(s):(s):(S):(S):(i Fall 2003-MA schmidt 3. 155J 6.152]-Lecture 2-Slide 7

N-type Doping Phosphorus has 5 valence electrons ‘Donates’ one conduction electron – n-type Our substrate has 1015 cm-3 phosphorus (1 in 10 8) Si Si Si Si Si Si Si Si Si SiSiSiSi SiSiSiSi Si SiSiSiSi Si Si Si Si Si SiSiSiSi Si Si Si Si P Si Si Si Si Si Si Si Si Si Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 7

P-type Doping Boron has 3 valence electrons Accepts' one electron from lattice Creates a hole-p-type s):(s):(s):(s):(s):(s):(s):(s):(S s):③:(::(:③:(:(s:③° (③::○:○: ③::③:(:③:(:(:(:( s):():):(s):(s):(s):(S):(S):(i Fall 2003-MA Schmidt 3. 155J 6.152]-Lecture 2-Slide 8

Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 8 P-type Doping B Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Boron has 3 valence electrons ‘Accepts’ one electron from lattice Creates a ‘hole’ – p-type

Counter Doping The addition of one more b than p causes the doping type to change from n-type to p-type si):(Si)°(Si):(si)。(Si):(Si):(Si)°(si):(Si s):③:(::(:③:(:(s:③° si)。(si)(si)。(si :(:(:(: ③::③:(:③:(:(:(:( s):():):(s):(s):(s):(S):(S):(i Fall 2003-MA Schmidt 3. 155J 6.152]-Lecture 2-Slide 9

Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 9 Counter Doping Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si P B The addition of one more B than P causes the doping type to change from n-type to p-type

Counter doping process n-type(1015 cm3) Implant boron and anneal 1015 Concentration p-type(1015 cm3 n-type(1015 cm3) Depth Fall 2003-MA schmidt 3.155/6.152]- Lecture2-side10

Counter Doping Process n-type (1015 cm-3) 1015 Concentration n-type (1015 cm-3) p-type (>1015 cm-3) Implant Boron and Anneal Depth Fall 2003 – M.A. Schmidt 3.155J/6.152J – Lecture 2 – Slide 10