Evaluation of overlay accuracy of phase-shift image for 65-nm node masks

Tadashi Komagata; Norio Kimura; Kaoru Funaki; Yasutoshi Nakagawa; Nobuo Gotoh

doi:10.1117/12.568784

6 December 2004 Evaluation of overlay accuracy of phase-shift image for 65-nm node masks

Tadashi Komagata, Norio Kimura, Kaoru Funaki, Yasutoshi Nakagawa, Nobuo Gotoh

Proceedings Volume 5567, 24th Annual BACUS Symposium on Photomask Technology; (2004) https://doi.org/10.1117/12.568784
Event: Photomask Technology, 2004, Monterey, California, United States

Abstract

A 65 nm node mask is required to have total alignment accuracy of 20 nm (3σ) or less for 1st and 2nd layers, including the positional accuracy of each layer. We have developed a new electron beam mask lithography process using “alignment-and-height” marks to minimize the displacement between two layers resulting from additional bowing and contraction on the blank surface after the 1st layer exposure. The new process consists of the following steps: 1. Write “alignment-and-height” marks on the edge of a mask simultaneously with the pattern of the 1st layer. 2. Measure the position and height of “alignment-and-height” marks before writing the 2nd layer. 3. Create a position/height correction map to write the 2nd layer. 4. Write the 2nd layer with reference to the correction map. Basic system attributes, such as beam origin and positional drift of mask blank, are monitored and adjusted throughout the process. We tested the process and achieved an alignment accuracy of 20 nm (3σ) between 1st and 2nd layers regardless of the density of the pattern area ratio, confirming that the process is effective for 65 nm node phase shift mask exposure.

Citation Download Citation

Tadashi Komagata, Norio Kimura, Kaoru Funaki, Yasutoshi Nakagawa, and Nobuo Gotoh "Evaluation of overlay accuracy of phase-shift image for 65-nm node masks", Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004); https://doi.org/10.1117/12.568784

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KEYWORDS

Photomasks

Phase shifts

Lithography

Electron beams

Electron beam lithography

Error analysis

Distortion

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