Canyon Materials, Inc. - Calibration Plates

Using a HEBS Glass Calibration Plate

Since each user of HEBS-glass masks employs a particular combination of a optical lithographic exposure tool, photoresist, and resist processing, an experimental relationship of photoresist thickness vs. mask density must be established by the user using a HEBS-glass calibration plate. Gray level masks of your designed pattern having predetermined gray levels can be then ordered from Canyon Materials, Inc.

Most binary photoresists (eg. positive and non-chemically amplified Novalac based photoresist) maybe used to produce analog resist profile using an analog processing scheme. An analog resist process makes the contrast curve more linear and reduces the threshold effect. An analog resist process can be derived from the standard binary process with the following modification in the resist processing steps: 

  • A lower temperature and/or shorter duration in the pre-bake of photoresist. 
  • The concentration of the developer is another variable that can be used to achieve a desirable analog resist property. 
Since the dynamic range of photoresists in an analog resist process is in general limited to about unity in log scale, an optical density range of 1.2 or less is in general sufficient for a gray scale mask.

It may be necessary to establish a new calibration of resist thickness vs. mask density, whenever the parameters of the optical exposure tool or photoresist or of photoresist development process are altered. The calibration plate should be kept for future uses. A standard HEBS-glass e-beam mask is a clear field mask. The background areas of the plate are clear and transparent. Nevertheless, a dark field HEBS-glass gray scale mask that is black outside the patterned mask area is also available from Canyon Materials, Inc.. HEBS-glass mask having a dark background outside the pattern area is fabricated by darkening the area surrounding the mask pattern with a flood electron gun.


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