The PHOTOPLOT STORE
the online presence for the International Phototool Company, LLC
Photomask Defect Criteria
A defect is defined as having a size greater than the limit specified. Anything smaller is not considered to be a defect.
A defect can either be a void or a pinhole in what should be the opaque region of the mask, or it can be an opaque spot in what should be a clear region of the mask.
The smallest Defect Size that can be consistently detected by Visual Inspection is 3.0 to 5.0 Ám.
Our Laser PG photomasks are currently limited to Visual Inspection only.
Defect density is typically specified in terms of DPSI, or Defects per Square Inch.
Shorts or Breaks
"Shorts" are defects that consist of extra chrome that connect between two regions of chrome across an area that should otherwise be clear. "Breaks" are the opposite of Shorts, in that they split two regions of what should otherwise be solid chrome with a clear gap.
Banding or Stitching
These terms refer to what can show up on masks that have large, visible arrays of several small features. It is typically an optical phenomenon, visible with the unaided eye or under low magnification. The actual tolerances may be within specification, but the problem shows up nonetheless. It is of critical importance for display applications, but does not often affect many other photomask uses.
For our photomasks, repair of pinholes or breaks is usually be accomplished by applying a spot of epoxy, if epoxy repair is allowed by the customer. Epoxy repair is not recommended if the mask is to be used in a "hard contact" application, because it causes a very slight bump on the mask surface that can distort the surrounding images. For "proximity printing", epoxy repair works well. Repair of opaque spots or shorts can usually be eliminated by using touch-up techniques such as laser ablation.
For other detailed defect specifications, such as concerning those which may be close to or touching the edges of any digitized geometry, or to specify areas of the mask which are more critical than others, please use the comments box at the bottom of our "request for quotation" form.