Characterization of binary and attenuated phase shift mask blanks for 32nm mask fabrication

Faure, Thomas; Gallagher, Emily; Hibbs, M.; Kindt, Louis; Racette, Ken; Wistrom, Richard; Zweber, Amy E.; Wagner, Alfred; Kikuchi, Yasutaka; Komizo, Toru; Nemoto, Satoru

doi:10.1117/12.801950

Cited by 16 publications

(8 citation statements)

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“…Another possible benefit of using thin and/or fast etch rate hard mask materials is the capability to reduce dry etch induced CD errors such as etch bias, etch bias uniformity, etch bias linearity, and etch global loading effect. With regard to the thinner chrome effect, Faure et al reported a CD performance advantage by using thin chrome hard mask and thin resist application for the 32-nm mask process [3]. In this report, opaque MoSi on glass (OMOG) that has 10-nm thick chrome showed the best CD performance compared with the conventional phase shift mask (PSM) and chrome binary mask which both use a much thicker chrome layer.…”

Section: Introductionmentioning

confidence: 78%

Etch characterization of binary mask dependence on mask material and resist thickness for 22nm mask fabrication

et al. 2009

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Use of optical photomasks will extend to the 22-nm node and beyond. Mask minimum resolution and critical dimension (CD) requirements for this node are very challenging to the mask industry. Optimization of resist materials and resist thickness are key factors for improving CD performance. In general, thinner resists result in better minimum resolution performance. The minimum useable resist thickness is often linked to the chrome hard mask dry etching performance. More specifically, improvement of chrome etch rate selectivity to resist while simultaneously maintaining good CD performance is difficult. In order to use a very thin e-beam resist, the underlying chrome hard mask material thickness needs to be thin or it needs to be comprised of a material that has a fast etch rate and good dry etch selectivity to resist. Use of thin and/or fast etch rate hard mask materials that are capable of reducing dry etch induced CD error such as etch bias, etch bias uniformity, etch bias linearity, and etch global loading effect is required for meeting 22-nm mask requirements. In this paper, the dry etching effect dependence on hard mask thickness, hard mask material composition and resist thickness for building advanced binary masks for 22-nm node is studied. The results from this work will show that dry etch induced CD error such as etch bias, etch bias uniformity, etch bias linearity, and etch global loading effect are significantly improved by use of an ultra thin or high etch rate hard mask material.

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Section: Introductionmentioning

confidence: 78%

Etch characterization of binary mask dependence on mask material and resist thickness for 22nm mask fabrication

et al. 2009

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“…The ability to pattern both 60 nm (4x) clear and opaque features on the mask is crucial. Previous papers have shown that improved resolution can be achieved with OMOG binary mask blank materials compared to PSM blank materials because the OMOG blank allows for low process bias and the use of thinner e-beam resist films [4]. The resolution performance of the new thin OMOG mask blank for simple space and line features for positive tone and negative tone resist processing is shown in figure 14.…”

Section: Minimum Feature Sizementioning

confidence: 95%

Development and characterization of a thinner binary mask absorber for 22-nm node and beyond

et al. 2010

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The lithography challenges posed by the 22 nm node continue to place stringent requirements on photomasks. The dimensions of the mask features continue to shrink more deeply into the sub-wavelength scale. In this regime residual mask electromagnetic field (EMF) effects due to mask topography can degrade the imaging performance of critical mask patterns by degrading the common lithography process window and by magnifying the impact of mask errors or MEEF. Based on this, an effort to reduce the mask topography effect by decreasing the thickness of the mask absorber was conducted. In this paper, we will describe the results of our effort to develop and characterize a binary mask substrate with an absorber that is approximately 20-25% thinner than the absorber on the current Opaque MoSi on Glass (OMOG) binary mask substrate.For expediency, the thin absorber development effort focused on using existing absorber materials and deposition methods. It was found that significant changes in film composition and structure were needed to obtain a substantially thinner blank while maintaining an optical density of 3.0 at 193 nm.Consequently, numerous studies to assess the mask making performance of the thinner absorber material were required and will be described. During these studies several significant mask making advantages of the thin absorber were discovered. The lower film stress and thickness of the new absorber resulted in improved mask flatness and up to a 60% reduction in process-induced mask pattern placement change. Improved cleaning durability was another benefit. Furthermore, the improved EMF performance of the thinner absorber [1] was found to have the potential to relieve mask manufacturing constraints on minimum opaque assist feature size and opaque corner to corner gap.Based on the results of evaluations performed to date, the thinner absorber has been found to be suitable for use for fabricating masks for the 22 nm node and beyond.

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“…This means that wafer fabs have to live with this phenomenon and with workarounds. One study [7] suggests that keeping the photomasks in an extremely dry air environment would hold the photochemical reaction. However, controlling the humidity rate in the full lithography toolset is complex and costly.…”

Section: Introductionmentioning

confidence: 99%

Inline detection of Chrome degradation on binary 193nm photomasks

et al. 2013

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193nm binary photomasks are still used in the semiconductor industry for the lithography of some critical layers for the nodes 90nm and 65nm, with high volumes and over long periods. However, these 193nm binary photomasks can be impacted by a phenomenon of chrome oxidation [1], [2], [3],[4] , leading to critical dimensions uniformity (CDU) degradation with a pronounced radial signature. If not detected early enough, this CDU degradation may cause defectivity issues and lower yield on wafers. Fortunately, a standard cleaning and repellicle service at the mask shop has been demonstrated as efficient to remove the grown materials and get the photomask CD back on target [2], [4] .Some detection methods have been already described in literature, such as wafer CD intrafield monitoring (ACLV) [2] , giving reliable results but also consuming additional SEM time with less precision than direct photomask measurement. In this paper, we propose another approach, by monitoring the CDU directly on the photomask, concurrently with defect inspection for regular requalification to production for wafer fabs. For this study, we focused on a Metal layer in a 90nm technology node. Wafers have been exposed with production conditions and then measured by SEM-CD. Afterwards, this photomask has been measured with a SEM-CD in mask shop and also inspected on a KLA-Tencor X5.2 inspection system, with pixels 125 and 90nm, to evaluate the Intensity based Critical Dimension Uniformity (iCDU) option [5], [6] . iCDU was firstly developed to provide feed-forward CDU maps for scanner intrafield corrections, from arrayed dense structures on memory photomasks. Due to layout complexity and differing feature types, CDU monitoring on logic photomasks used to pose unique challenges. The selection of suitable feature types for CDU monitoring on logic photomasks is no longer an issue, since the transmitted intensity map gives all the needed information, as shown in this paper. In this study, the photomask was heavily degraded after more than 18,000 300mm wafers exposed and the cleaning brought it back almost to its original state after manufacture. Wafer CD, photomask CD and iCDU results can be compared, before and after a standard mask shop cleaning. Measurement points have be chosen in logic areas and SRAM areas, so that their respective behaviours can be studied separately. Transmitted maps before and after cleaning were analysed in terms of CD shift and CDU degradation. The delta map shows a nice correlation with photomask CD shift. iCDU demonstrated the capability to detect a reliable CD range degradation of 5nm on photomask by a comparison between a reference inspection and the current inspection. Die to die inspection mode provides also valuable data, highlighting the degraded chrome sidewalls, more in the photomask centre than on the edges. Ultimately, these results would enable to trigger the preventive cleanings rather than on predefined thresholds. The expected gains for wafer fabs are cost savings (adapted cleanings frequency), increased phot...

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Characterization of binary and attenuated phase shift mask blanks for 32nm mask fabrication

Cited by 16 publications

References 0 publications

Etch characterization of binary mask dependence on mask material and resist thickness for 22nm mask fabrication

Etch characterization of binary mask dependence on mask material and resist thickness for 22nm mask fabrication

Development and characterization of a thinner binary mask absorber for 22-nm node and beyond

Inline detection of Chrome degradation on binary 193nm photomasks

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