Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Wu, Qiang; Halle, Scott; Zhao, Zengqin

doi:10.1117/12.544255

Cited by 8 publications

(6 citation statements)

References 10 publications

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“…The equation for the MEF can be analytically solved for narrow pitches (When the pitch p is narrower than wavelength/NA). And, especially, when the mask line width and the mask space width are equal, the MEF for dense features can be put into the following simple form [1], as described by Eqs. (2) and (3).…”

Section: Simulation Methodologymentioning

confidence: 99%

“…In this paper, we will obtain the diffusion length through the measurement of the mask error factor (MEF). The mask error factor (MEF) or the mask error enhancement factor (MEEF) [1][2][3][4][5][6][7][8] quantifies the impact of reticle CD errors on the CD of the corresponding printed feature:…”

Section: Simulation Methodologymentioning

confidence: 99%

“…We will also show the data obtained from two scanners with one of them having some residue spherical aberration. In the analysis, we use mask error factor (MEF) [1][2][3][4][5][6][7][8] to define the overall quality of the imaging capability of the exposure system.…”

Section: Introductionmentioning

confidence: 99%

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A systematic study of the dip in the CD through-pitch curve for low-k1 processes

Zhu

Wu²,

Jiang³

et al. 2006

SPIE Proceedings

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Optical proximity correction has been widely used to correct line width variation in various different environments. The most important correction will be the CD through-pitch variation. For deep-UV (DUV) photo processes, it is observed that the CD will have a reduced trend at certain intermediate pitch range around 1.1 to 1.4 wavelength / NA (numerical aperture), also called "forbidden pitch". The process windows within this pitch range are small. In this case, even though we can use OPC to print the CD correctly, the process window can still be limited, which can generate a bottleneck for the entire process. In order to make OPC more effective, we find it necessary to be able to design an optimized process with enough process windows for all pitches. Although this may mean that we need to map out the entire parameter space spanned by relatively unknown parameters in resist, exposure tool quality, mask tolerance, etc, recent developments in the understanding of the effect of illumination selection, scanner lens aberration, and resist blur have provided us with new hints in realizing it. Such new developments include the optimization of off-axis illumination (OAI) condition, the characterization of the effect of lens aberration, and the selection of resists with appropriate effective acid diffusion length. We have studied the effect of illumination, lens aberration, and resist diffusion to the CD and process window at the above described intermediate pitch range both in theory and experiment. We have found that the effective resist diffusion, whose range is from 10nm to 50nm, can affect the process window at the intermediate pitch range, to as much as a few tens of nanometers. We will show that, in general, longer diffusion correlates to a deeper "dip". However, according to the experience in the use of photo resists, short diffusion length can also affect process window through the reduction of depth of focus. Therefore it is important to find an optimized resist diffusion length under various ground-rule and illumination conditions. But there has been no studies reported so far as to how much diffusion that can be tolerated for a given process at the intermediate pitch range. We have also performed experiments on the effect of the scanner lens aberration, we found that the lens aberration, which may be largely ignored in the past, may affect the process performance, causing mask error factor to rise significantly. In this paper, we will present the result of our experiments and theoretical investigations in how much resist diffusion and lens wave front error that can be tolerated for a given photolithographic process with certain CD tolerance. Insight will be provided for the choice of illumination conditions, resolution enhancement techniques, and the resist in realizing the best CD through-pitch performance under any given ground-rule condition.

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Section: Simulation Methodologymentioning

confidence: 99%

Section: Simulation Methodologymentioning

confidence: 99%

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A systematic study of the dip in the CD through-pitch curve for low-k1 processes

Zhu

Wu²,

Jiang³

et al. 2006

SPIE Proceedings

Self Cite

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show abstract

“…To understand how fast line ends will approach each other, one will need the equations for the MEF with effective resist diffusion. Although the diffusion length has been studied earlier [3][4], it has not been used to explain line end shortening under double exposure condition. Recently, in another publication [5], it has been demonstrated that the isolated opposing line ends under single exposure can be explained satisfactorily with three simple equations.…”

Section: Line End Shortening and Process Window Under Single Exposurementioning

confidence: 98%

The improvement of photolithographic fidelity of two-dimensional structures through double exposure method

Wenren¹,

Ding²,

Li³

et al. 2007

SPIE Proceedings

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With the semiconductor fabrication groundrule approaching the 32 nm node, double exposure or patterning method with 1.35 NA immersion seems to be the primary candidate due to its relative easiness to implement when compared to the other two competitors, the high refractive index immersion and the 13.4 nm extremely ultraviolet (EUV) lithography. However, the splitting of one mask into two is not a trivial task. In this paper, we would like to discuss about the best splitting method for several typical 2D structures, such as the isolated opposing line (or space) end shortening, T-like structures with narrow gaps, etc. From our recent experimental studies, we have found that, for line and space photolithography, the optimized illumination condition has a sigma value very close to 0.5. When compared to the single exposure processes, which will typically use more annular condition, a sigma of 0.5 can generate worse process windows for isolated features. This will put more pressure on the precision of the already challenging optical proximity correction (OPC) because the doubly exposed patterns and singly exposed patterns follow two different models. In our study, we find that the extra degrees of freedom in the double exposure method can be utilized to repair some intrinsic printing deficiency, such as, line end shortening. In this paper, we will analyze each typical 2D structure and, for each splitting method of the typical 2D features we study, we will discuss its capabilities in realizing good process windows, the MEF, and OPC correction easiness.

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“…a is the photoacid effective diffusion length, which has been explored in detail in previous studies [4][5], and a I is the blurring caused by diffraction., M(x', y') is the mask function. Notice that the integration in the Y direction is independent of x both where the x is in the gap and non-gap areas.…”

Section: Mef Of the Line End Shorteningmentioning

confidence: 99%

Limit of Line End Shortening Correction under Single Exposure in 193 nm Immersion Lithography

Hao

et al. 2011

ECS Trans.

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As the lithography starts to approach the limit of 193 nm immersion imaging capability under single exposure, successful development of a lithographic process rely on the good balance of the process parameters, such as the exposure latitude and depth of focus for the dense, semi-dense, isolated structures, MEF, LWR, proximity bias, etc. Such balance requires very good understanding of the inter-relationship among them and ways to give reasonable specification to the important materials such as photoresist and photomasks. Although, relatively speaking, 1-dimensional structures, such as, line and space or even square contacts are relatively easy to understand and model with accurate simulations, which is close to perfect, 2-dimensional structures are not easy to understand physically and the simulation for them are up to larger errors. Since previous study on this subject was either done at larger ground-rules or lack of good physical understanding in the simulation, this paper will use both experimental wafer measurement data and physical modeling to probe the limits for the OPC correction of line (or space) end shortening structures at around 50 nm dimensions. Several structures will be studied in theory and wafer data.

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Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Cited by 8 publications

References 10 publications

A systematic study of the dip in the CD through-pitch curve for low-k1 processes

A systematic study of the dip in the CD through-pitch curve for low-k1 processes

The improvement of photolithographic fidelity of two-dimensional structures through double exposure method

Limit of Line End Shortening Correction under Single Exposure in 193 nm Immersion Lithography

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