Photo Material Readiness at the Eve of EUVL HVM

Abstract

In the last years, the continuous efforts on the development of extreme ultraviolet (EUV) lithography has allowed to push the lithographic performance of the EUV photoresists on the ASML NXE:3300 full field exposure tool and today both chemically amplified (CAR) and metal-oxide (MOR) EUV photoresists have been introduced for patterning imec's 7nm node critical layers. However, the HVM requirement to have a cost-effective high sensitivity photoresist (< 20 mJ/cm 2 ) still remains a big challenge and further efforts are needed to improve the photoresist sensitivity without affecting resolution and patterning quality. In this work, we present the results of the best performing photoresists (both CAR and MOR) at low exposure dose for dense line-space patterns at 32nm pitch, dense contact holes at 36nm pitch and dense pillars at 38nm pitch, reporting the most critical patterning challenges for the investigated structures. Furthermore, we discuss the role of the substrate underneath the EUV photoresist and its impact on the lithographic EUV process setup from both patterning and light-matter interaction standpoint. Finally, we introduce the tone reversal process (TRP) as alternative capability for pillar patterning.

Stability studies on a sensitive EUV photoresist based on zinc metal oxoclusters

“…The latter point thus demands that the photoresists have high sensitivity and can yield nanopatterns at doses as low as 20 mJ∕cm 2 or below. 2,[10][11][12] Although the standard platform for resist materials has been polymer-based chemically amplified resists, EUV lithography technology requires the development of entirely new resist platforms. 2,[13][14][15] As future nodes are continuously decreasing, the size of polymers traditionally used in photoresists has become a critical point especially with regard to linewidth roughness.…”

Zinc-based metal oxoclusters: towards enhanced EUV absorptivity

“…For adequate lithography performance, resists should simultaneously satisfy resolution (< 10 nm), line-width roughness (LWR < 15%) and sensitivity (dose < 20 mJ/cm 2 ) at sustainable production costs. [3][4][5][6] Though the standard platform for resist materials have been polymer-based chemically amplified resists (CAR's), EUV lithography application demands an entirely new platform for resist development. 3,7,8 As the future process nodes are continuously decreasing, the size of traditionally used polymers in photoresists cannot be ignored.…”

The Path to Better Understanding Stochastics in EUV Photoresist

“…However, the high-volume-manufacturing (HVM) requirement to have a cost-effective low exposure dose photoresist (20-30 mJ/cm 2 exposure dose range) remains a big challenge and pattern defectivity at nano-scale is the major limiting factor of the lithographic process window of EUV resist when looking at tight pitches below 40nm. Recent studies on pitch 32nm dense line space patterning and pitch 36nm dense orthogonal contact hole patterning have shown pattern defectivity as nanobridges and broken-lines, and merging or closing, respectively [2,3]. Therefore, it is extremely important to be effective at the early characterization stage of the EUV resist to quantify the nano-failures induced by a stochastic EUV patterning regime, the random nature of the lightmatter interaction and consequent chemical reactions.…”