Assist feature for random, isolated, semi-dense, and other non-dense contacts
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorShinn-Sheng Yu
Life of this patent
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Abstract
An assist feature for isolated, and semi-dense random contacts, as may be present on a photomask used in photolithographic processes for semiconductor device fabrication, is disclosed. The assist feature can be used in conjunction with off-axis illumination (OAI) for such non-dense contacts, for improving the depth of focus (DOF), resolution, or both of photolithography for such contacts, such that the non-dense contact preferably substantially mimics a dense contact during OAI. A photomask of the invention includes a number of assist features situated near and around the non-dense contact. A method for creating a photomask according to the invention, as well as a method for fabricating a semiconductor device using such a mask, are also disclosed.
Claims20
A photo mask for semiconductor photolithography processing comprising:
- a non-dense contact;
- and
- a plurality of assist features situated near and around the non-dense contact, each assist feature having a size smaller than a size of the non-dense contact,
- the plurality of assist features improving at least one of depth of focus (DOF) and resolution of the semiconductor photolithography processing.
A method for producing a photomask comprising:
- creating a non-dense contact on the photomask;
- and
- creating a plurality of substantially identical assist features situated in at least a substantially regular pattern around the non-dense contact, each assist feature having a size smaller than a size of the non-dense contact,
- such that the plurality of assist features allow the non-dense contact to at least more closely mimic a dense contact during off-axis illumination (OAI).
A semiconductor device formed at least in part by a method comprising:
- positioning a photomask over a semiconductor wafer having a top layer of photoresist, the photomask having a plurality of substantially identical assist features situated in at least a substantially regular pattern around a non-dense contact, each assist feature having a size smaller than a size of the non-dense contact;
- exposing the semiconductor wafer through the photomask positioned thereover, such that the top layer of photoresist includes exposed parts under clear parts of the photomask and unexposed parts under opaque parts of the photomask;
- developing the semiconductor wafer to remove the exposed parts of the top layer of photoresist;
- etching the semiconductor wafer where the wafer is revealed through the exposed parts of the top layer of photoresist that has been removed;
- and
- removing the unexposed parts of the top layer of photoresist.
Dependencies are inferred from the claim text.