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Silicon Wafer 125-200cm (5’’- 8’’) 0.5-0.8mm
Initial doping ~ 1015 cm-3
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Silicon Oxidation Si
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Silicon Oxidation O2 SiO2 0.44tox Si
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Silicon Epitaxial Growth
p-type Si Epi Layer SiCl4 or SiH4 Gas with Impurities n-type Si
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Silicon Etching Layer to be etched Mask Layer Apply Etch
a,c: Etch selectivities b: Anisotropy
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Ion Implantation Fixed Ions Dopant Ion from an accelerator
Final Implanted Ion Location
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Ion Diffusion High Concentration Low
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Photolithography
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Start with a Silicon Wafer
Photolithography Start with a Silicon Wafer
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Deposit a Layer of Silicon Dioxide
Photolithography Deposit a Layer of Silicon Dioxide
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We want to create this pattern
Photolithography A “Mask” Layer We want to create this pattern on the silicon wafer
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Spin a Photoresist Layer
Photolithography Spin a Photoresist Layer
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Uniform UV Light Illumination
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Uniform UV Light Illumination
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Uniform UV Light Illumination
Negative Photoresist
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Photolithography
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Next we develop the photoresist
Photolithography Next we develop the photoresist
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Then we remove the photoresist
Photolithography Then we remove the photoresist
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Next, we want to implant the dopant ions
Photolithography Next, we want to implant the dopant ions
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Uniform Implantation of dopant ions
Photolithography Uniform Implantation of dopant ions
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Uniform Implantation of dopant ions
Photolithography Uniform Implantation of dopant ions
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Diffusion at High Temperatures
Photolithography Diffusion at High Temperatures
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Remove Silicon Dioxide
Photolithography Remove Silicon Dioxide
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Positive Photoresist Process
Typically for depositing Polysilicon, but also for diffusions is small processes
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Positive Photoresist Process
Start with a Silicon Wafer
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Positive Photoresist Process
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Positive Photoresist Process
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Positive Photoresist Process
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Photolithography
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Photolithography
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Photolithography Develop the pattern
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Photolithography After Etching
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Photolithography Remove the Photoresist We have a polysilicon region
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