CD changes of 193-nm resists during SEM measurement

Kudo, Takanori; Bae, Jun-Bom; Dammel, Ralph R.; Kim, Woo-Kyu; McKenzie, Douglas; Rahman, M. Dalil; Padmanaban, Munirathna; Ng, W.

doi:10.1117/12.436847

Cited by 28 publications

(18 citation statements)

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“…It is these reactions that are of most importance to the metrologist since this is the timeframe during which inline metrology will take place. Kudo, et al 4 discuss these reactions for the well-studied case of poly methyl methacrylate (PMMA) resist. For PMMA, continuous e-beam exposure results in chemical changes to the polymer that make it impervious to further mass loss.…”

Section: Discussionmentioning

confidence: 98%

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Electron beam metrology of 193-nm resists at ultralow voltage

Sullivan

Dixson

Bunday³

et al. 2003

SPIE Proceedings

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Resist slimming under electron beam exposure introduces significant measurement uncertainty in the metrology of 193 nm resists. Total critical dimension (CD) uncertainty of up to 10 nm can arise from line slimming through a combination of the line slimming during the initial measurement pass and the variation of line slimming across the wafer. For a 100 nm process, the entire CD error budget, can be consumed by line slimming. This research examines the uncertainty that results from the use of offset techniques to account for resist slimming in the process control of 193 nm resist CDs. The uncertainty associated with such offset techniques can be as great as 10 nm, depending upon the 193 nm resist and landing energy evaluated. Data are presented to demonstrate that 193 nm resist CD features experience line slimming greater than 5 nm at 500 eV landing energy during the initial measurement pass. Further, subsequent measurements demonstrate greatly reduced slimming and as a result are not indicative of the true magnitude of line slimming. Experiments conducted using CD-AFM pre-and post-analysis, demonstrate that ultra low landing energies significantly decrease the line slimming, reducing it to 1 nm or less.

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Section: Discussionmentioning

confidence: 98%

“…The 248 nm resist line slimming behavior has become the benchmark by which the 193 nm resist systems are gauged. 3,4 State-of-the-art 193 nm resists exhibit significant line slimming relative to this benchmark. Several factors further exacerbate the impact of resist line slimming in the sub-100 nm regime.…”

Section: Introductionmentioning

confidence: 98%

Electron beam metrology of 193-nm resists at ultralow voltage

Sullivan

Dixson

Bunday³

et al. 2003

SPIE Proceedings

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“…The slimming process can be fitted well with a triple exponential rate law, indicating three different processes contributing to the CD slimming [10].…”

Section: Influence Of A-beam Curing On the CD Slimming Of 193nm Resistsmentioning

confidence: 99%

Etch Properties of 193nm Resists: Issues and Approaches.

Padmanaban

Alemy

Dammel

et al. 2002

J. Photopol. Sci. Technol.

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Polymer chemistries for 193nm resists are more or less defined and their lithographic performance is quite good to implement 100nm design rules. In spite of the use of high carbon containing adamantane or norbomene moieties in the polymer design, there exists etch selectivity as well as surface roughness issues after treatment with etch plasma. It is very much necessary to modify the etch plasma used for 193 nm resists to improve the surface roughness. Etch rates of several acrylate, methacrylate and hybrid type polymers are measured and compared. While the problem still exists, acrylates in general seem to offer better surface properties than methacrylates. On the process side, a-beam curing of 193nm resists offers improvement in both etch selectivity as well as surface roughness. It was found from the IR spectra of before and after a-beam cured films that ebeam curing reduces the carbonyl groups and compacts the resist film leading to etch improvements. Effects of three different a-beam curing processes (Standard, LT and ESC) on the methacrylate & hybrid type 193nm resists were studied with respect to resin chemistry changes, resist film shrinkage, pattern profiles, etch rates, and CD SEM stability. Etch rate, selectivity and resist surface roughness after etch of both methacrylate and hybrid resists were improved using the a-beam curing process. E-beam curing drastically reduces (from ca. 15% to 2 -5 %) the CD SEM shrinkage; however, considerable shrinkage occurs during the curing process itself.

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“…We previously reported that the methacrylate resists exhibited faster line width reduction than the cycloolefin-maleic anhydride (COMA) systems, and proposed several possible slimming mechanisms of the 193 nm resists [5,6]. However, more detailed studies revealed that the polymer structure was not the only decisive factor for LWS, and the resist components as well as CD SEM settings were found to play an important role.…”

Section: Introductionmentioning

confidence: 99%

“…Su et al [3] proposed a shrinkage model assuming LWS could be caused by crosslinking or other chemical reactions; however, in this study the causes for resist shrinkage were still considered to be uncertain. It was also reported that LWS was moderated by reducing acceleration voltage or flux density of e-beam during the CD SEM measurement [1][2][3][4][5]. So far, the improvement of CD degradation has been mainly studied by equipment or process changes but little research has been reported for resist materials.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Studies on the CD Degradation of 193nm Resists during SEM Inspection.

Kudo

Dammel

Bae

et al. 2001

J. Photopol. Sci. Technol.

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Pattern deformation during SEM inspection has been investigated for different types of 193 nm positive resists. The mechanism of the CD changes is discussed based on the slimming rate analyses as well as on the a-beam penetration depth. As a general tendency, the methacrylate resists exhibit faster line width reduction than the cycloolefin-maleic anhydride (COMA) systems; however, other resist components as well as CD SEM settings play an important role. Based on the exposure time vs. CD loss, the line width slimming (LWS) is found to proceed in three steps, which are assigned as: (1) chemical change of outer resist layer, (2) evaporation of volatiles and (3) bulk chain scission or deprotection. Countermeasures for CD degradation are proposed from both the formulation and process sides. A calculation of a-beam penetration depth suggests that deprotection, chain scission and other reactions occur in the first 20-40 nm, and these reaction rates combined with thermal effects determine LWS. The CD SEM measurement method has been improved to minimize a-beam exposure and to spread out the thermal load over a larger period of time. An optimized formulation exhibits less than 0.2% LWS per measurement with the improved CD measurement program.

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CD changes of 193-nm resists during SEM measurement

Cited by 28 publications

References 0 publications

Electron beam metrology of 193-nm resists at ultralow voltage

Electron beam metrology of 193-nm resists at ultralow voltage

Etch Properties of 193nm Resists: Issues and Approaches.

Mechanistic Studies on the CD Degradation of 193nm Resists during SEM Inspection.

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