Silicon wafers

What is the main reason silicon wafers must be very flat?

  1. ATo make wafer weights uniform
  2. BBecause during exposure the entire pattern must fall within the depth of focus
  3. CTo make wafer colors uniform
Show answer and explanation

Answer: B. Because during exposure the entire pattern must fall within the depth of focus

The finer the pattern being exposed, the shallower the depth of focus, so even slight unevenness of the wafer surface throws the image out of focus. Flatness is therefore strictly controlled, for example per exposure field (shot).

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More Silicon wafers questions

  1. Which equipment is commonly used to slice a silicon ingot into many wafers at once?
  2. What is the main purpose of chamfering (beveling) the edge of a wafer?
  3. Which impurity is typically added to the melt to make p-type silicon crystals by the CZ method?
  4. When a doped crystal is pulled by the CZ method, the dopant concentration tends to be higher toward the bottom of the crystal (later in the pull). Why?
  5. Which correctly describes 450 mm wafers, developed as the next diameter after 300 mm?