ACLV degradation: root cause analysis and effective monitoring strategy

Tchikoulaeva, Anna; Holfeld, Andre; Arend, Markus; Foca, E.

doi:10.1117/12.793047

Cited by 14 publications

(10 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They also report that there is a form of transmission loss that develops most strongly around the periphery of the image area, which coincidentally is the region of the reticle where field induction is strongest. 2 This would cause ACLV in a similar way to the Sun Effect, 13 but with the opposite radial characteristic.…”

Section: How Electric Field Damages a Reticlementioning

confidence: 97%

See 1 more Smart Citation

Current understanding of the electrostatic risk to reticles used in microelectronics and similar manufacturing processes

Rider

2018

J. Micro/Nanolith. MEMS MOEMS

View full text Add to dashboard Cite

Abstract. This paper explains how an electric field and a reticle interact and describes the different kinds of damage that can be caused to a reticle through its exposure to electric field. It is shown why electrostatic reticle damage has changed from ESD damage (which causes yield to suddenly drop precipitously) into a gradual and cumulative form of degradation that is very difficult to diagnose. It is explained why some of the approaches that have been taken to reduce ESD damage in the semiconductor factory, such as equipotential bonding and the use of static dissipative plastics for making reticle pods, actually increase the risk of this cumulative type of electrostatic degradation in reticles. When assessing the risk to reticles and designing an effective protective strategy for reticle handling, it is shown why one must take into account the temporal characteristics of a reticle's interaction with electric field-including the effect that the reticle's immediate surroundings will have on that interaction-as well as considering the strength of any electric field in the reticle handling environment. Solutions are presented that would allow the electrostatic risk to reticles to be reduced significantly, without requiring major changes to operating procedures in semiconductor manufacturing facilities.

show abstract

Section: How Electric Field Damages a Reticlementioning

confidence: 97%

“…13,14 In EFM type 1, the thermal diffusion is enhanced by the presence of an electric field, while in the Sun Effect it is enhanced by the absorption of 193 nm UV photons.…”

Section: How Electric Field Damages a Reticlementioning

confidence: 99%

Current understanding of the electrostatic risk to reticles used in microelectronics and similar manufacturing processes

Rider

2018

J. Micro/Nanolith. MEMS MOEMS

View full text Add to dashboard Cite

show abstract

“…After many wafer exposures over a long period, some 193nm binary photomasks started to cause dramatic defectivity issues on production lots, such as bridging or pattern collapses, as shown in figures 1 and 2 below. It seems that all 193nm binary photomasks may be impacted in the industry, as described in literature [1], [2], [3], [4] . This phenomenon is commonly named as chrome oxidation, or chrome migration.…”

Section: Introductionmentioning

confidence: 97%

“…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.…”

mentioning

confidence: 98%

See 1 more Smart Citation

Inline detection of Chrome degradation on binary 193nm photomasks

et al. 2013

View full text Add to dashboard Cite

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...

show abstract