Lecture_2-silicon_wafer_&_Si_epitaxy

Lecture_2-silicon_wafer_&_Si_epitaxy - Lecture 2...

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Wafer fabrication and Silicon epitaxy Lecture 2
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IH2655 SPRING 2009 Mikael Östling KTH Silicon wafer fabrication
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IH2655 SPRING 2009 Mikael Östling KTH
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IH2655 SPRING 2009 Mikael Östling KTH
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IH2655 SPRING 2009 Mikael Östling KTH
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IH2655 SPRING 2009 Mikael Östling KTH
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IH2655 SPRING 2009 Mikael Östling KTH Wafer fabrication Starting material: Electronically-grade Si (EGS) with contamination below ppb level Czochralski method
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IH2655 SPRING 2009 Mikael Östling KTH (Plummer Fig. 3.18 p 128) Standard for CMOS. Dash method for moving dislocations out from the surface at the pulling seed. 300 mm wafers : Multi-wire slicing. Single-wafer lapping. Notch marking replaces major/minor flats. Dopant incorporation: Segregation coefficient k 0 = C Solid /C liquid
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IH2655 SPRING 2009 Mikael Östling KTH Float-zone method No crucible, crystal formed in Ar atmosphere Low oxygen content High-resistivity possible Neutron Transmutation Doping for extremely high-uniform resistivity Difficult to scale up in wafer diameter
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IH2655 SPRING 2009 Mikael Östling KTH Defects in Si (Plummer Fig. 3-4 p 98) Point defects : V vacancy (neutral, single- or double-charged) (see further Plummer p133-138) I interstitial or interstitialcy 1-D defect: dislocation 2-D defect: Stacking fault 3-D defect: Precipitates (oxygen precipitation)
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IH2655 SPRING 2009 Mikael Östling KTH Oxygen in CZ- Si Oxygen dissolves from quartz crucible during CZ growth ~10 18 cm -3 ! Three effects during circuit processing : + Si-O-Si bindings resulting in higher mechanical strength - Oxygen donors (SiO 4 ). 10 16 cm -3 form at 400-500 ° C - Bulk precipitation (SiO 2 ) (but can be controlled by gettering)
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IH2655 SPRING 2009 Mikael Östling KTH Buried oxide layer ~10 3 Åth ick SIMOX: Separation by implanted oxygen BESOI: Bonded and etch-back technology Smart-cut: H implant before BESOI process SOS wafers: Silicon-on-sapphire (SIMOX) (BESOI)
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IH2655 SPRING 2009 Mikael Östling KTH Gettering (Plummer Fig 4-7 p 162) Capture defects at locations far away from the device region. Damaged region will act as "sink" for unwanted elements.
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IH2655 SPRING 2009 Mikael Östling KTH Extrinsic gettering: Treatment on backside of wafer, e.g. n + doping Intrinsic gettering: Intentional SiO 2 precipitation inside bulk. Requires dedicated thermal cycling: (Plummer Fig 4-12)
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IH2655 SPRING 2009 Mikael Östling KTH Silicon epitaxy Outline: Definition and terminology Chemical vapor deposition CVD process and source gases Grove model: • Mass-transfer or surface-reaction controlled growth rate Gas flow and pressure in CVD Chlorine in Si CVD Doping • Autodoping Defects and characterization Reactor types •Batch • Single-wafer •MBE Applications of Si epitaxy • HT epitaxy: Si • LT epitaxy: SiGe • Selective epitaxy: Si and SiGe
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Mikael Östling KTH Book references cited : S.M. Sze: Semiconductor Devices 1985 S-M.Sze ed: VLSI Technology 1988 Chang and S.M. Sze: ULSI Technology 1996
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This note was uploaded on 03/09/2009 for the course EE 300 taught by Professor Y during the Spring '09 term at CUNY City.

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Lecture_2-silicon_wafer_&_Si_epitaxy - Lecture 2...

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