Sensors for In-Situ and In-Process Measurements in Microelectronics Manufacturing.
Abstract
This final report summarizes the progress we have made in developing ultrasonic sensors for in-situ monitoring of IC manufacturing processes. The work was done in collaboration with SRC funding. We report a temperature measurement technique based on the temperature dependence of acoustic wave velocity in silicon wafers. The zeroth order antisymmetric Lamb wave is excited in the wafer using the quartz pins which support the wafer during processing. Extensional waves are generated in the quartz pin by a PZT-5H transducer and the acoustic energy is coupled to the Lamb wave at the contact between the sharpened end of the pin and the wafer surface. The detection is done by a similarly modified quartz pin or pins. By measuring the time of flight of the Lamb wave in the wafer between the two pins, we have monitored the wafer temperature in-situ in the 20 - 1000 deg C range with + or - 1 accuracy. Theoretical models considering wave propagation and thin film effects on the technique are developed for direct comparison with experimental results. With 8 spring loaded pins placed on a circular array around the wafer, 28 different measurements are made giving information about different regions. Using tomographic reconstruction techniques, spatial temperature distribution with 2 cm pixel size is then calculated. Excellent agreement is observed between the readings of thermocouples attached to the wafer, and calculated values for ultrasonic tomography. A method for temperature tomography with a smaller number of sensors is also proposed based on theoretical calculations. jg p.1
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1995
- Accession Number
- ADA299219
Entities
People
- B. T. Khuri-yakub
Organizations
- Stanford University