WLCD: a new system for wafer level CD metrology on photomasks

Martin, Sven; Seitz, H.; Degel, Wolfgang; Buttgereit, Ute; Scherübl, Thomas

doi:10.1117/12.814728

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…To overcome the limitations of 2D feature measurements which are highly loaded with OPC structures the WLCD from ZEISS was utilized. [1] WLCD benefits from the advantage of reduced feature complexity by measuring the CD in aerial image. By doing that it captures OPC and MEEF effects automatically.…”

Section: Process Flow and Methods Descriptionmentioning

confidence: 99%

Automated hotspot analysis with aerial image CD metrology for advanced logic devices

et al. 2014

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Continuously shrinking designs by further extension of 193nm technology lead to a much higher probability of hotspots especially for the manufacturing of advanced logic devices. The CD of these potential hotspots needs to be precisely controlled and measured on the mask. On top of that, the feature complexity increases due to high OPC load in the logic mask design which is an additional challenge for CD metrology. Therefore the hotspot measurements have been performed on WLCD from ZEISS, which provides the benefit of reduced complexity by measuring the CD in the aerial image and qualifying the printing relevant CD. This is especially of advantage for complex 2D feature measurements.Additionally, the data preparation for CD measurement becomes more critical due to the larger amount of CD measurements and the increasing feature diversity. For the data preparation this means to identify these hotspots and mark them automatically with the correct marker required to make the feature specific CD measurement successful. Currently available methods can address generic pattern but cannot deal with the pattern diversity of the hotspots. The paper will explore a method how to overcome those limitations and to enhance the time-to-result in the marking process dramatically. For the marking process the Synopsys WLCD Output Module was utilized, which is an interface between the CATS mask data prep software and the WLCD metrology tool. It translates the CATS marking directly into an executable WLCD measurement job including CD analysis.The paper will describe the utilized method and flow for the hotspot measurement. Additionally, the achieved results on hotspot measurements utilizing this method will be presented.

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Section: Process Flow and Methods Descriptionmentioning

confidence: 99%

Automated hotspot analysis with aerial image CD metrology for advanced logic devices

et al. 2014

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“…It measures the CD on the reticle in the wafer level plane as it is relevant to printing and captures optical proximity effects and optical MEEF effects induced by the scanner illumination [4]. The use of the WLCD significantly simplifies the CD measurement especially for complex mask designs and complex 2D features (see Figure 2).…”

Section: Mask Metrology: Wlcdmentioning

confidence: 99%

Mask CD uniformity metrology for logic patterning and its correlation to wafer data

et al. 2012

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With the next technology nodes 193nm lithography is pushed to its utmost limits. The industry is forced to print at low k1 factor which goes along with a high MEEF. Additionally, new blank materials are being introduced for smaller nodes. From 4x node and beyond, global CD uniformity on wafer is getting more critical and becomes key factor to ensure a high yield in chip production. Advanced process control is required and correction strategies are applied to maintain tight wafer CD uniformity. Beside other parameters, like scanner and etch process, mask CD uniformity is one main contributor to the intra-field CD on wafer. To enable effective CDU correction strategies it is necessary to establish a mask CD uniformity metrology which shows a good correlation to wafer prints. Especially for logic pattern mask uniformity measurements to control intra-field CD uniformity becomes challenging.In this paper we will focus on mask CD uniformity measurement for logic application utilizing WLCD, which is based on aerial image technology. We will investigate 40nm node and 28nm node gate masks using 6% MoSi phase shifting mask and MoSi binary mask respectively. Furthermore, we will correlate the mask CD uniformity data to wafer data to evaluate the capability of WLCD to predict the intra-field wafer CD uniformity correctly in order to support feedforward correction strategies. We will show that WLCD shows an excellent correlation to wafer data. Additionally, we will provide an outlook on logic contact-hole masks showing first CD uniformity data and wafer correlation data.

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“…It measures the CD on the reticle in the wafer level plane as it is relevant to printing (see Figure 2) [1,2]. By doing that it captures optical proximity effects and optical MEEF effects induced by the scanner illumination.…”

Section: Wlcd32 Aerial Image CD Measurement On Maskmentioning

confidence: 99%

CD uniformity correction on 45-nm technology non-volatile memory

et al. 2010

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One of the key parameters necessary to assure a good and reliable functionality of any integrated circuit is the Critical Dimension Uniformity (CDU). There are different contributors which impact the total CDU: mask CD uniformity, scanner and lens fingerprint, resist process, wafer topography, mask error enhancement factor (MEEF) etc.In this work we focus on improvement of intra-field CDU at wafer level by improving the mask CD signature using a CDC200™ tool from Carl Zeiss SMS. The mask layout used is a line and space dark level of a 45nm node Non Volatile Memory (NVM). A prerequisite to improve intra-field CDU at wafer level is to characterize the mask CD signature precisely. For CD measurement on mask the newly developed wafer level CD metrology tool WLCD32 of Carl Zeiss SMS was used. The WLCD32 measures CD based on aerial imaging technology. The WLCD32 measurement data show an excellent correlation to wafer CD data. For CDU correction the CDC200™ tool is used. By utilizing an ultrafast femto-second laser the CDC200™ writes intra-volume shading elements (Shade-In Elements™) inside the bulk of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a manner that improves wafer CDU when the corrected mask is printed.In the present work we will demonstrate a closed loop process of WLCD32 and CDC200™ to improve mask CD signature as one of the main contributors to intra-field wafer CDU.

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WLCD: a new system for wafer level CD metrology on photomasks

Cited by 10 publications

References 7 publications

Automated hotspot analysis with aerial image CD metrology for advanced logic devices

Automated hotspot analysis with aerial image CD metrology for advanced logic devices

Mask CD uniformity metrology for logic patterning and its correlation to wafer data

CD uniformity correction on 45-nm technology non-volatile memory

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