Laser bandwidth and other sources of focus blur in lithography

Brunner, Timothy A.; Corliss, Daniel; Butt, S.; Wiltshire, Timothy J.; Ausschnitt, Christopher P.; Smith, Mark D.

doi:10.1117/1.2396926

Cited by 25 publications

(15 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From our experience, and reported elsewhere in literature, [3,5] the typical range of LCA, values for modern lithography scanners is 200nm/pm to 500nm/pm.…”

Section: Modeling Laser Spectral Bandwidthmentioning

confidence: 96%

“…[2][3][4][5] The variation of laser bandwidth modulates the imaging contrast, in turn affecting proximity effects and the validity of OPC models. It has been observed empirically that structures with a more limited depth of focus (DOF) are typically more sensitive to bandwidth variation, but more recently the CD sensitivity to bandwidth has been directly linked to the CD-defocus behavior.…”

Section: Laser Bandwidth Stability and Metrologymentioning

confidence: 99%

See 1 more Smart Citation

Fast and accurate laser bandwidth modeling of optical proximity effects

Lalovic¹,

Kritsun

Bendik³

et al. 2007

SPIE Proceedings

View full text Add to dashboard Cite

In this work, we model the effects of excimer laser bandwidth on optical proximity effects in high-NA ArF dry and immersion lithography. We quantify the errors introduced by using common approximation methods for the laser spectrum, such as the modified Lorentzian and Gaussian forms. Although these approximations are simple to use, and their symmetry properties can lead to reduced simulation run-times, they typically induce significant CD error when compared to the use of measured spectral profiles, which are obtained from high-resolution spectrophotometry. In this paper we establish some accuracy benchmarks and demonstrate the need for inclusion of information about the spectral profile-for the laser type of interest-in order to achieve sub-nanometer image calculation accuracy required for optical proximity correction. We further assess the speed-accuracy tradeoffs in terms of data truncation and sampling, and propose some practical limits for sampling the illumination spectrum.Additionally, in this work, we propose a new physically-based spectrum approximation method, which significantly reduces computation time at a cost of less than 0.25nm residual image-CD error from the fully-sampled image calculation. In addition to aerial image, we compare 45nm-node calibrated resist models and latent image results for 0.92NA dry and 1.2NA immersion processes using measured illumination profiles and lens aberrations. Finally, we consider the laser bandwidth sensitivity of 2D lineend patterns and typical post-OPC designs for a logic gate-process.

show abstract

“…From our experience, and reported elsewhere in literature, [3,5] the typical range of LCA, values for modern lithography scanners is 200nm/pm to 500nm/pm.…”

Section: Modeling Laser Spectral Bandwidthmentioning

confidence: 96%

Section: Laser Bandwidth Stability and Metrologymentioning

confidence: 99%

Fast and accurate laser bandwidth modeling of optical proximity effects

Lalovic¹,

Kritsun

Bendik³

et al. 2007

SPIE Proceedings

View full text Add to dashboard Cite

show abstract

“…Figure 3 plotted the through-pitch CD differences for three L/S features (mask CD 50nm, 60nm and 80nm) between the lithography models with and without the chromatic aberration focus blur effect included. It was observed that, in the smallest pitch region around 100nm pitch, there is almost no impact on CD due to focus blur, and the CD change increases as pitch increases, and in large pitch region the CDs are significantly i Here we adopted some typical value of chromatic aberration reported in existing literature [1], and it represents the baseline chromatic aberration performance of the advanced scanners used in production environment. reduced by an amount up to 14nm.…”

Section: Impact Of Focus Blur (Ca Msdz)mentioning

confidence: 98%

Modeling of focus blur in the context of optical proximity correction

Zhang

Song

Lucas

et al. 2008

Optical Microlithography XXI

View full text Add to dashboard Cite

The concept of focus blur encompasses the effect of laser bandwidth longitudinal chromatic aberration and scanner stage vertical vibration. The finite bandwidth of excimer laser source causes a corresponding finite distribution of focal planes in a range of 100nm or larger for the optical lithography system. Similarly, scanner vertical stage vibration puts the wafer in a finite distribution of focal planes. Both chromatic aberration and vertical stage vibration could introduce significant CD errors, hence can no longer be ignored in current lithography processes development and OPC development that require CD control within a few nanometers. We developed several methodologies to model the laser chromatic aberration and vertical stage vibration in OPC (Optical Proximity Correction) modeling tool. Extensive simulations were done to calculate chromatic aberration and vertical stage vibration focus blur's impact on lithography patterning for a variety of test structures. Chromatic aberration and vertical stage vibration focus blur effect was further included as an regression term in experimental OPC model calibration to capture its impact on litho patterning, and significant benefit to OPC model calibration was observed.

show abstract

“…Isolated lines expose the resist with higher light intensity, resulting in shorter channel lengths, as illustrated in Figure 1. Dense lines also have higher depth of focus, and are more immune to defocusing of the optical system [12].…”

Section: Lithography-induced Variationsmentioning

confidence: 99%