5-Thermal Oxidation - Part 5 Thermal Oxidation Reference...

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Ch5-1 Part 5 Thermal Oxidation Reference Hong Xiao: Chap 5.3 Plummer: Chap 6
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Ch5-2 Application of Thermal Oxides
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Ch5-3 1. Masking Oxide Much lower B diffusion rates in SiO 2 than that in Si Much lower P diffusion rates in Si than that in SiO 2 SiO 2 can be used as diffusion mask Si Dopant SiO 2 SiO 2
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Ch5-4 2. Screen Oxide Photoresist Photoresist Si Substrate Dopant Ions Screen Oxide
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Ch5-5 3. Pad Oxide Silicon nitride Silicon Substrate Pad Oxide Relieve strong tensile stress of the nitride Prevent stress induced silicon defects
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Ch5-6 Bare Wafer After Thin Film Deposition Compressive Stress Negative curvature Tensile Stress Positive curvature Substrate Film Stress Substrate Substrate SiO 2 Si At Room Temperature compressive stress 熱膨脹係數: (SiO 2 ) =0.5x10 -6 o C -1 (Si) =2.5x10 -6 o C -1 (Si 3 N 4 )=2.8x10 -6 o C -1
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Ch5-7 USG 4. Barrier Oxides Silicon Pad Oxide Nitride Silicon Pad Oxide Nitride Silicon USG Barrier Oxide 1. Trench Etch 2. Trench Fill 3. USG CMP; USG Anneal; Nitride and Pad Oxide Strip STI Process
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Ch5-8 Silicon Silicon Silicon Silicon Dioxide Field Oxide Wafer Clean Field Oxidation Oxide Etch Activation Area Device Isolation 5. (a) Blanket field oxide Electronic isolation of neighboring devices
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Ch5-9 Silicon nitride P-type substrate P-type substrate Silicon nitride p + p + p + Isolation Doping P-type substrate p + p + p + Isolation Doping SiO 2 Pad Oxide Pad oxidation, nitride deposition and patterning LOCOS oxidation Nitride and pad oxide strip Bird’s Beak SiO 2 Device Isolation 5. (b) Local oxidation of silicon (LOCOS)
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Ch5-10 LOCOS Compare with blanket field oxide Lower step height Disadvantage rough surface topography Bird’s beak Replacing by shallow trench isolation (STI)
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Ch5-11 6. Sacrificial Oxide N-Well P-Well STI USG N-Well P-Well STI USG N-Well P-Well STI USG Sacrificial Oxidation Strip Sacrificial Oxide Gate Oxidation Sacrificial Oxide Gate Oxide Defects removal from silicon surface
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Ch5-12 Device Dielectric 7. Gate oxide Gate oxide: thinnest and most critical layer Capacitor dielectric Poly Si Si Substrate n + Gate Thin oxide Source Drain p-Si n + V D > 0 Electrons V G
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Ch5-13 Native Oxide 正在成長增厚的SiO 2 層會使O 2 的擴散受到阻礙 而變的緩慢。 當裸露的矽晶圓接觸到大氣時,幾乎是立刻就 和空氣中的氧或濕氣產生化學反應,而形成一 層很薄的SiO 2 (約10~20Å) => 原生氧化層。 在室溫時,這層很薄的氧化層就可阻止矽的繼 續氧化。
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Ch5-14 Oxide and Applications Name of the Oxide Thickness Application Time in application Native 15 - 20 Å undesirable - Screen ~ 200 Å Implantation Mid-70s to present Masking ~ 5000 Å Diffusion 1960s to mid-1970s Field and LOCOS 3000 - 5000 Å Isolation 1960s to 1990s Pad 100 - 200 Å Nitride stress buffer 1960s to present Sacrificial <1000 Å Defect removal 1970s to present Gate 30 - 120 Å Gate dielectric 1960s to present Barrier 100 - 200 Å STI 1980s to present
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Ch5-15 Thermal Oxidation Si substrate Si substrate Silicon Dioxide Silicon H 2 O or O 2
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5-Thermal Oxidation - Part 5 Thermal Oxidation Reference...

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