Comparison of I-line and DUV high-energy implant litho processes

Grandpierre, A.G.; Berger, Cody M.; Schroeder, Uwe; Schiwon, R.; Kubis, Michael

doi:10.1117/12.655163

Cited by 4 publications

(2 citation statements)

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“…For this paper, emphasis will be placed on "high-aspect ratio" features, defined in this case as lines or trenches in photoresist where the photoresist thickness-to-feature ratio is greater than four, that are common to SRAM applications. a deschner@us.ibm.com; phone 1 …”

Section: Introductionmentioning

confidence: 99%

Optimization of DUV lithography for high-energy well implantation

Deschner¹,

Kim²,

Mann³

et al. 2007

SPIE Proceedings

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Presented here is an analysis of photoresist profile and feature control performance for high-energy well implant lithography as it is implemented in microelectronic devices, specifically SRAMs, at the 45 and 65nm nodes. As device designs become increasingly smaller to the tune of Moore's Law, deep well implant lithography specifications become more and more stringent, and issues related to lateral implant scattering that were more trivial for more relaxed designs begin to make significant contributions to photoresist feature uniformity and implant profile control. Simplified process assumptions that overlook such non-ideal implant phenomena can result in an overestimation of process latitude. Undesirable variability derived from the implantation, lithography, and substrate associated with a deep well formation process can degrade implantation profiles and have adverse effects on device electrical performance. Mechanisms for these adverse effects such as implant scattering and implant straggle will be explored followed by their relationships to process tolerance and electrical performance. Emphasis will be placed on evaluating the optimum photoresist feature profile for a given process and determining its true process latitude as opposed to "centering" a feature in a device layout during design. Finally, challenges confronting process control methods for high-aspect ratio implant mask features will be discussed followed by some proposed process improvement suggestions.

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Section: Introductionmentioning

confidence: 99%

Optimization of DUV lithography for high-energy well implantation

Deschner¹,

Kim²,

Mann³

et al. 2007

SPIE Proceedings

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“…The sub-layer effect (containing significant bottom substrate reflectivity) causes large LWR and unwanted ADI (after develop inspection step) CD variation. Traditionally, the CD variation is dramatically improved by adding BARC or developable BARC to reduce substrate reflection [2], nevertheless a prevalent LDD loop will not introduce BARC for the concern of cost and process complication reduction [2,3].…”

Section: Introductionmentioning

confidence: 99%

Studies of Photo Resist Profile Improvement in 28 nm Implanting Layer’s Lithography Process without BARC

Liu

et al. 2014

ECS Trans.

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For 28 nm node and below, implant layer patterning is becoming challenging with node shrinkage, due to decreasing critical dimension and usage of non-uniform reflective substrates without bottom anti-reflection coating (BARC). The ADI CD uniformity of a test feature is dramatically improved by adding BARC to reduce substrate reflection, nevertheless a prevalent LDD loop will not introduce BARC for the concern of cost and process complication reduction. The considerable bottom substrate reflectivity not only causes standing wave in photo resist but also introduces slight footing between the photo resist line and the substrate poly head if the substrate topography is rough (especially in the SRAM region). It is necessary to optimize the photo resist profile even under a very high bottom reflectivity. In this paper, several factors of the implant litho process that could impact the photo resist profile and line width roughness (LWR) are studied, and a comprehensive optimization based on these factors' splits test are defined and adopted in the 28 nm LDD loop litho process. Firstly we changed the mask CD to wafer CD bias and simultaneously modified the exposure dosage to meet the ADI target, which is based on our previous study that larger mask bias and over-dosage exposure will result in better photo resist profile. Secondly we studied the PR profile dependence on temperature of post exposure baking (PEB), we tried out the best temperature setting to improve photoresist footing. Thirdly we slightly shifted the focus offset during exposure away from the best focus defined by process FEM results, so that the photoresist profile is improved and meanwhile maintaining a large enough depth of focus for the process.

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