Wednesday, April 23, 2014
Request Quote

Image Reversal

 

image reversal

This process reverses the action of positive resist so negative images can be formed with the same resolution and processing ease that a positive resist allows. What’s more, image reversal allows variations of the slope of the photoresist sidewall for higher resolution and/or lift off profiles.

For example, if the normal slope of approximately 68 degrees is altered to 90 degrees vertical, resolution is increased 20%. And, if an angle of 112 degrees is achieved, there is a strong overhang that makes metal deposition followed by liftoff controllable.

image reversal process

Image reversal advantages:

  • Allows variations of the slope of the photoresist sidewall for higher resolution and improved lift off.
  • Replaces use of harsh chemicals or plasma "metal etch” processes.
  • Using image reversal on two or more layer resist levels can eliminate residual photoresist along the sidewalls, preventing "shorts" from level to level without reducing line width.
  • Image reversal done with dark or light fields eliminates standing waves; this allows steep and straight profiles, repeatable results, and excellent chemical deposition uniformity.
  • Image reversal achieves excellent results for rework problems; underlying substrate is protected (for a double metal process), so unwanted metal can be stripped away without pitting or eroding the underlying level.

Why not just use a negative resist?

Positive resist offers far better resolution, and it doesn’t require solvents for development. In contrast, the resolution limit of negative resist is approximately 1 micron, and it requires solvents known to be carcinogens.

YES image reversal systems deliver anhydrous ammonia (NH3) into a vacuum oven. There are two advantages of an ammonia system: 1) easier control of vapor pressure, and 2) an absence of residual water vapor, which will react with the NH3 to produce NH3OH, a corrosive to the system that also creates contaminating particles.

For more information on achieving repeatable and usable reversals, visit the YES-58TA & 310TA product pages.

Home   |   About Us   |   Products   |   Applications   |   WLP   |   MEMS   |   News   |   Contact Us
©2014 Copyright Yield Engineering Systems, Inc. | All Rights Reserved