Section 9: CMPMultilevel InterconnectsSurface PlanarizationSpin-On Glass (SOG)Chemical Mechanical Polishing (CMP)CMP RateProblems encountered in CMPEE143 – Ali Javey Slide 9-1Section 9: CMPEE143 – Ali Javey Slide 9-2Nonplanar MetallizationPlanarMetallizationMultilevel InterconnectsEE143 – Ali Javey Slide 9-3Benefits for Lithography Processes: • Lower Depth-of-Focus requirement• Reduced optical reflection effects on resist profiles • Reduced resist thickness variation over steps=>Benefit for Etching Processes:• Reduced over-etch time required due to stepsBenefit for Deposition Processes:• Improved step coverage for subsequent layer depositiontopviewSurface PlanarizationEE143 – Ali Javey Slide 9-4Spin-On Glass (SOG)EE143 – Ali Javey Slide 9-5Wafer is polished using a slurry containing• silica abrasives (10-90 nm particle size)• etching agents (e.g. dilute HF)• Backing film provides elasticity between carrier and wafer• Polishing pad made of polyure-thane, with 1 mm perforations– rough surface to hold slurryChemical Mechanical Polishing (CMP)EE143 – Ali Javey Slide 9-6Preston Model:Local Removal rate R = Kp P vwhere P = local applied pressure v = relative pad-wafer velocityKp = Preston coefficient [unit in pressure-1]function of film hardness, Young’s modulus,slurry, pad composition and structureCMP RateEE143 – Ali Javey Slide 9-7Problems encountered in
View Full Document
Unlocking...