The critical layer masks for 14 nm and 10 nm logic nodes are typically bright field, and the key features are opaque
structures on the mask. In order to meet the tight critical dimension (CD) requirements on these opaque features the use
of a high quality negative tone chemically amplified e-beam resist (NCAR) is required. Until very recently the only
negative tone e-beam resists available for use by the mask industry were the traditional cross linking type in which ebeam
exposure cross links the material and makes it insoluble in developer. In this paper we will describe the
performance of a new polarity switching type of NCAR resist that works by changing the solubility of the exposed resist
without cross linking. This has the advantage of significantly reduced swelling and scumming and resulted in major
improvements in the resolution of heavily nested features and small clear features on the mask. Additional detailed
characterization results will be described.
Electron beam resists develop a surface potential during exposure that can lead to image placement errors of up to several nanometers [1] and cause poor CD uniformity and image quality. To address this problem, we have formulated a conductive polymer that can be coated onto the resist. Our conductive discharge layer (CDL) is water soluble and it is easily removed during subsequent processing steps. We have established that our material has low enough resistance for full charge dissipation during e-beam exposure and have carried out extensive tests to evaluate the impact of the layer on lithographic performance. We will report these findings, which include measurements of the effect of the CDL application on resist resolution, contrast, speed, and roughness on both wafer and on mask.
Electron beam resists develop a surface potential during exposure, which can lead to image placement
errors of up to several nanometers [1] and result in poor CD uniformity and image quality. To address this
problem, we have synthesized a conductive polymer that can be coated onto a resist. Our conductive
discharge layer (CDL) is water-soluble and is easily removed during subsequent processing steps.
Having established that our material has a low enough resistance for full charge dissipation, we have carried
out extensive tests to evaluate the impact of the layer on lithographic performance. We will report these
findings, which include measurements of the effect of the CDL on the resolution, roughness, and speed of
the resist.
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