Advances in process overlay: ATHENA alignment system performance on critical process layers

Laidler, David; Megens, Henry; Lalbahadoersing, S.; Haren, Richard J. F. van; Bornebroek, Frank

doi:10.1117/12.473478

Cited by 9 publications

(8 citation statements)

References 4 publications

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“…For example, when fifth order enhanced mark is under evaluation, fifth order detector will be used. This practice has also been applied in the previous reported work in evaluation of alignment mark using ATHENA system [2][3][4][5] . We only focused in the evaluation of 5 th order SPM, 5 th order NSPM and 7 th order NSPM.…”

Section: Methodsmentioning

confidence: 92%

Evaluation of alignment marks using ASML ATHENA alignment system in 90-nm BEOL process

Tan

Yeo

Koh³

et al. 2003

SPIE Proceedings

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As the critical dimension (CD) in integrated circuit (IC) device reduces, the total overlay budget needs to be more stringent. Typically, the allowable overlay error is 1/3 of the CD in the IC device. In this case, robustness of alignment mark is critical, as accurate signal is required by the scanner's alignment system to precisely align a layer of pattern to the previous layer. Alignment issue is more severe in back-end process partly due to the influenced of Chemical Mechanical Polishing (CMP), which contribute to the asymmetric or total destruction of the alignment marks. Alignment marks on the wafer can be placed along the scribe-line of the IC pattern. ASML scanner allows such type of wafer alignment using phase grating mark, known as Scribe-line Primary Mark (SPM) which can be fit into a standard 80um scribe-line. In this paper, we have studied the feasibility of introducing Narrow SPM (NSPM) to enable a smaller scribe-line. The width of NSPM has been shrunk down to 70% of the SPM and the length remains the same. It is a challenge to the alignment system to collect the NSPM signal and provide comparable alignment capability. The evaluations were completed using short loop wafers, which focus on back-end-of-line (BEOL) via and metal layers in a 90nm Cu dual damascene low k process. The results also look into the overlay performance using different alignment strategies. Offline overlay measurements were performed to verify the results.

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Section: Methodsmentioning

confidence: 92%

Evaluation of alignment marks using ASML ATHENA alignment system in 90-nm BEOL process

Tan

Yeo

Koh³

et al. 2003

SPIE Proceedings

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“…Several other W-CMP / Al-PVD flows [6] have been investigated as well. The results for three alternative process flows (thick Al, thick W, thin oxide layer) of 2 wafers each are shown in Fig.…”

Section: Predictive Recipes On Vspmsmentioning

confidence: 99%

“…We investigated a W-CMP / Al-PVD process flow for which all three gratings of the VSPM are underfilled [6]. The Alignment Advisor is used to measure the W-CMP / Al-PVD processed marks in a grid determined by a set of ideal non-processed marks [4].…”

Section: Predictive Recipes On Vspmsmentioning

confidence: 99%

Overlay performance with advanced ATHENA alignment strategies

et al. 2003

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After the introduction of the ATHENA TM alignment sensor, advanced applications of the sensor data are becoming increasingly important to meet the tightening overlay specifications for future technology nodes. As part of the total overlay budget, the effects of different alignment strategies on overlay performance need to be investigated. Keeping in mind that such strategies are simple and easy to use, two developments are addressed in this paper: advanced alignment recipes and advanced mark designs.An alignment recipe defines which signals from the sensor are used to calculate the aligned position. By making advanced use of the available data, wafer alignment can be made more accurate and more robust to processing effects. It is shown that the new Smooth Color Dynamic alignment recipes exhibit good overlay performance on STI, Cu dual damascene and W-CMP / Al-PVD layers. Since Smooth Color Dynamic also takes away the choice of a particular color in the alignment recipe, it is the preferred alignment recipe for all product layers.The optimum design of an alignment mark depends on the process characteristics. As the process characteristics may vary over time, the optimum mark design can change accordingly. To cover a larger process range, multiple alignment mark designs are combined in a new multi-grating mark: the Versatile Scribeline Primary Mark (VSPM). By measuring all gratings during regular production, the optimum grating of a VSPM can be selected and aligned with a Smooth Color Dynamic alignment recipe. For CMP layers a further overlay improvement can be achieved if all gratings have comparable phase depths. By combining alignment signals from different gratings in a predictive alignment recipe, wafer-to-wafer variations due to CMP effects can be reduced.

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“…It is noted here that these CMP effects to signal strength variation are only attributed to the difference in planarity of the Si wafer, and the polished layer(s) on top of this wafer. Control of alignment signal strength, and thus of alignment mark phase depth, is considered a main improvement possibility for overlay control [5,6,7]. A means to stabilize signal strength is to minimize the number of CMP steps involved for the copper floating marks.…”

Section: Figure 2 Cmp Transfer Function (Left) and Calculated A Substmentioning

confidence: 99%

Alignment robustness for 90 nm and 65 nm node through copper alignment mark integration optimization

Warrick¹,

Hinnen

Morton

et al. 2005

Optical Microlithography XVIII

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In this paper, methods for stacking ASML scribe lane alignment marks (SPM) and improving the mark performance at initial copper metal levels are discussed. The new mark designs and the theoretical reasons for mark design and/or integration change are presented. In previous joint publications between ASML and Freescale Semiconductor [1], improved overlay performance and alignment robustness for Back End Of Line (BEOL) layers by the application of stacked scribe lane marks (SPM) was presented.In this paper, further improvements are demonstrated through the use of optimized Versatile Scribe Lane Mark design (VSPM). With the application of stacked optimized VSPM-marks, the alignment signal strength of marks in the copper metal layer is increased compared to stacked SPM marks. The gains in signal strength stability, which is typical for stacked marks, as well as significantly reduced scribe lane usage, are also maintained. Through the placement of specially designed orthogonal scatter-bars in selected layers under the VSPM-marks, the alignment performance of initial inlaid metal layers is improved as well. The integration of these marks has been evaluated for the 90 nm and 65 nm technology nodes as part of a joint development program between the Crolles2 Alliance and ASML. A measured overlay improvement of ~10-15% was obtained by a strategy change from floating copper marks to stacked optimized VSPM marks.

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Advances in process overlay: ATHENA alignment system performance on critical process layers

Cited by 9 publications

References 4 publications

Evaluation of alignment marks using ASML ATHENA alignment system in 90-nm BEOL process

Evaluation of alignment marks using ASML ATHENA alignment system in 90-nm BEOL process

Overlay performance with advanced ATHENA alignment strategies

Alignment robustness for 90 nm and 65 nm node through copper alignment mark integration optimization

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