Method and apparatus for measuring stress in semiconductor wafers

Integrated measurement apparatus for measuring layer thickness and bow in a wafer, the apparatus comprising:

• a monochromatic light source,
• a white light source,
• a first switch for switching between said white light source and said monochromatic light source,
• a plurality of beam directors for directing light from said switched light source onto a semiconductor wafer,
• a first optical processor for spectral processing of reflected light from said wafer,
• a second optical processor for processing of reflected light to determine an extent of bow in said wafer, and
• a second optical switch to switch reflected light from said wafer between said first optical processor and said second optical processor.

A method of measuring stress in a silicon wafer, using an integrated measurement apparatus, the method comprising:

• switching in a monochromatic light source to produce at least two monochromatic light beams,
• reflecting said at least two beams of light from a surface of a wafer, a first beam from a central region of said wafer and a second beam from a peripheral region of said wafer,
• determining properties of said reflected beams,
• comparing said determined properties of said reflected light beams to thereby determine an extent of bowing in said wafer, and
• calculating a stress level in said wafer from said extent of bowing.

An method of integrated measurement of stress and thickness in a semiconductor wafer, the method comprising:

• selecting between a white light source and a monochromatic light source,
• with the white light source:
• irradiating a semiconductor at a single point,
• receiving reflected light from said single point,
• spectrally analyzing said reflected light using a transform,
• deriving layer thickness from said analysis,
• with the monochromatic source:
• reflecting at least two beams of light from a surface of a wafer, a first beam from a central region of said wafer and a second beam from a peripheral region of said wafer,
• determining properties of said reflected beams,
• comparing said determined properties of said reflected light beams to thereby determine an extent of bowing in said wafer, and
• calculating a stress level in said wafer from said extent of bowing.