Irradiation resistance of intravolume shading elements embedded in photomasks used for CD uniformity control by local intra-field transmission attenuation

Eitan Zait; Guy Ben-Zvi; Vladimir Dmitriev; Sergey Oshemkov; Rainer Pforr; Mario Hennig

doi:10.1117/12.681741

20 May 2006 Irradiation resistance of intravolume shading elements embedded in photomasks used for CD uniformity control by local intra-field transmission attenuation

Eitan Zait, Guy Ben-Zvi, Vladimir Dmitriev, Sergey Oshemkov, Rainer Pforr, Mario Hennig

Author Affiliations +

Proceedings Volume 6283, Photomask and Next-Generation Lithography Mask Technology XIII; 62830E (2006) https://doi.org/10.1117/12.681741
Event: Photomask and Next Generation Lithography Mask Technology XIII, 2006, Yokohama, Japan

Abstract

Intra-field CD variation is, besides OPC errors, a main contributor to the total CD variation budget in IC manufacturing. It is caused mainly by mask CD errors. In advanced memory device manufacturing the minimum features are close to the resolution limit resulting in large mask error enhancement factors hence large intra-field CD variations. Consequently tight CD Control (CDC) of the mask features is required, which results in increasing significantly the cost of mask and hence the litho process costs. Alternatively there is a search for such techniques (1) which will allow improving the intrafield CD control for a given moderate mask and scanner imaging performance. Currently a new technique (2) has been proposed which is based on correcting the printed CD by applying shading elements generated in the substrate bulk of the mask by ultrashort pulsed laser exposure. The blank transmittance across a feature is controlled by changing the density of light scattering pixels. The technique has been demonstrated to be very successful in correcting intra-field CD variations caused by the mask and the projection system (2). A key application criterion of this technique in device manufacturing is the stability of the absorbing pixels against DUV light irradiation being applied during mask projection in scanners. This paper describes the procedures and results of such an investigation. To do it with acceptable effort a special experimental setup has been chosen allowing an evaluation within reasonable time. A 193nm excimer laser with pulse duration of 25 ns has been used for blank irradiation. Accumulated dose equivalent to 100,000 300 mm wafer exposures has been applied to Half Tone PSM mask areas with and without CDC shadowing elements. This allows the discrimination of effects appearing in treated and untreated glass regions. Several intensities have been investigated to define an acceptable threshold intensity to avoid glass compaction or generation of color centers in the glass. The impact of the irradiation on the mask transmittance of both areas has been studied by measurements of the printed CD on wafer using a wafer scanner before and after DUV irradiation.

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Eitan Zait, Guy Ben-Zvi, Vladimir Dmitriev, Sergey Oshemkov, Rainer Pforr, and Mario Hennig "Irradiation resistance of intravolume shading elements embedded in photomasks used for CD uniformity control by local intra-field transmission attenuation", Proc. SPIE 6283, Photomask and Next-Generation Lithography Mask Technology XIII, 62830E (20 May 2006); https://doi.org/10.1117/12.681741

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