Use of diffracted light from latent images to improve lithography control

Hickman, K. C.; Gaspar, S. M.; Bishop, Kenneth P.; Naqvi, S. Sohail H.; McNeil, J. R.; Tipton, Gary D.; Stallard, Brian R.; Draper, B.L.

doi:10.1117/12.44439

Cited by 7 publications

(3 citation statements)

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“…'nor =( 'mes'flofl R0 I R )/(1 R0 I R) ( 1) As the development proceeded, the 'mes decreased. When the 'mes was less than the previous determined 'stop' the control signal was sent from the computer to development unit.…”

Section: Methodsmentioning

confidence: 98%

High-accuracy development monitoring technology

et al. 1999

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ABSRACT A development monitor system capable of highly accurate control of pattern width has been established. This system is composed of a unique monitor pattern on the process wafer, the 0th order diffraction light measuring unit, and the image analysis and process control unit. In the conventional development process in which no monitor system is employed, the CD variation in 200nm line width was about l5nm when +1-5 % dose error exists. However, using the new system, mm of CD variation was obtained. In this article, a high-sensitivity monitor pattern is proposed and its performance in controlling 200nm line and space patterns in the development process is reported.

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Section: Methodsmentioning

confidence: 98%

High-accuracy development monitoring technology

et al. 1999

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“…In addition, the exposure dose should account for wafer-to-wafer variation in photoresist thickness and stability of the intensity of the incident beams. Fortunately, the so-called latent image is produced in exposed, undeveloped photoresist, and a relationship exists between the intensity of light diffracted from a latent image and the amount of energy which is absorbed by the photoresist [5][6]. Thus, the latent image monitoring (LIM) are utilized to improve the control of the exposure process instead of conventional methods that the optimal conditions is attained by exposing large numbers of wafers ahead of product wafers.…”

Section: Exposure End Point Detectionmentioning

confidence: 98%

Methods of controlling grooves profile and the duty cycle of gold transmission phase gratings

Qiu

Liu

et al. 2007

SPIE Proceedings

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It is known that rectangular grooves profile and various duty cycles (line to pitch) are required to attain maximum efficiency. The gold transmission phase gratings have been fabricated using holography and ion-beam etching techniques. The latent image monitoring technique and real time end-point detection technique were utilized to improve control of the shape of grooves and duty cycle during exposure and development, respectively. It is difficult to produce gratings with larger duty cycle in photoresist on gold for standing wave, nevertheless it is revealed in our work that the duty cycle can be more than 0.4 for the case for photoresist on gold substrates if development is stopped where the slope of the monitoring curve begins to drop off, not at the peak of the diffracted signal. In ion-beam milling, the influence of redeposition on the shape of grooves and duty cycle has been overcome by using a thin mask of Chromium with a comparatively low ion-etch rate and tilting and rotating substrates beneath the ion beam. Finally, some gold phase gratings with the duty cycles in the range of 0.25-0.45 have been obtained, whose duty cycle value is about 0.45, and their grooves profile is trapezoidal profile whose left and right facets are both more than 83 degrees approximately.

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“…Several researchers have proposed diffraction intensity measurements to characterize and optimize the latent image formed in photoresist during exposure as a result of the refractive-index modulation experienced by the resist due to illumination (e.g., Refs. 2, [6][7][8]. However, as pointed out by Li et al,9 monitoring and control during the development process is more effective, since the development step occurs later and control of that step can correct for process variations in exposure and other prior steps.…”

Section: Introductionmentioning

confidence: 93%