4/17/2002 1 Micro-thermo-mechanical Actuator for in situ Wafer Temperature Mapping SFR Workshop April 17, 2002 Ranju Arya, Mark Rashid, Dwight Howard, Scott Collins and Rosemary Smith MicroInstruments and Systems Laboratory Electrical & Computer Engineering Mechanical & Aeronautical Engineering UC Davis
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4/17/2002
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Micro-thermo-mechanical Actuator for in situ Wafer Temperature Mapping
SFR WorkshopApril 17, 2002
Ranju Arya, Mark Rashid, Dwight Howard, Scott Collins and Rosemary Smith
MicroInstruments and Systems LaboratoryElectrical & Computer Engineering
Mechanical & Aeronautical EngineeringUC Davis
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Problem Statement
• Small feature reproducibility requires film thickness uniformity
• Uniformity of PECVD films depends on spatial control of process parameters, including:– plasma composition (gas flow rates and pressure) – plasma energy (power)– substrate surface temperature
• Substrate surface temperature relies on – thermal conductivity of substrate and coatings– contact of substrate to platen– surface chemical reactions
Monitoring and control of surface temperature --> improved film uniformity
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State of the Art• Wafer temperature is generally not measured during deposition
(assumed to be same as platen temperature)• During process development, wafer surface temperature may
be spot tested, using either a spring bimorph temperature indicator or thermo-chromic polymer, to calibrate platen temperature to wafer surface temperature.
Our Approach• Design and test a simple, tool independent, low cost, in situ
wafer temperature mapping method for PECVD process development using an array of micro-thermo-mechanical actuators.
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Justification
• Structures are relatively simple to fabricate, are non-intrusive, and non-contaminating to process.
• Readout can be real time, in situ, or post-process, by optical imaging of wafer surface.
• Structures can be configured for electrical readout• Structural design, fabrication, density, sensitivity and range
of operation can all be tailored for a particular process, independent of wafer diameter.