A Method To Correct For Image Imbalance In Alternating Phase Shift Mask Lithography
Publication Date: 2003-Feb-06
The IP.com Prior Art Database
Insertion of a feature into a 0 degree phase area in a phase shift mask helps compensate for image imbalance due to phase shifting. The feature can be a subresolution feature and can vary in size to compensate for image imbalance. The feature can be combined with other image imbalance techniques such as undercutting phase shift areas and/or biasing lines.
A Method to Correct for Image Imbalance in Alternating Phase Shift Mask lithography.
If you consider an ideal trench for the 180 degree phase , the inside edges diffract the lights causing destructive interference of the 180 degree phase as a result reducing the intensity of light emanating from the 180 degree phase in comparison to the 0 degree phase. This results in an altered feature CD and positioning. Solution
The solution that is described is based on an interference method that allows the manipulation of image intensity by placing sub resolution features within the 0 degree phase regions. This results in an equivalent but easier solution to the image imbalance problem. As simulation results shown with a method to provide such image intensity manipulation, the imbalance is corrected by reducing the intensity of the 0 degree phase to match the 180 degree phase intensity. It has the following advantages:
Please see next page for problem and solution to resolve it effectively.
1. No undercutting problems that will become more serious for the sub 100 nm mask manufacturing.
2. More control (similar to OPC type of control) on the balance of the intensities.
3. Expect to be easier to manufacture compared to under cutting small features since mask manufactures have developed and will continue to develop the capability to manufacture smaller binary features.
4. Due to PSM illumination conditions the risk of printing of these sub- resolution feat...