Ultratech Stepper, Inc.

Ultratech, Inc.

Weijian Wang

Andrew M Hawryluk

David G Stites

Yu Chue Fong

A method and apparatus () for determining a best focus position of an object () relative to a reference position (e.g., axis A) of a dark-field optical imaging system (), with an effective focusing range up to 10 times of the depth of field of the system. The method includes the steps of first forming a dark-field image of the object at different focus positions (z). Each dark-field image has a corresponding image intensity distribution with an average intensity and a variance of intensity. The next step is forming a set of contrast values by calculating a contrast value (C) for each dark-field image based on the variance and the average intensity. The last step is determining the best focus position by fitting a Lorentzian function to the set of contrast values plotted as a function of the different focus positions and identifying the focus position associated with the maximum contract value (C). The second step includes digitizing each dark-field image such that the image intensity distribution for each the dark-field image is a digitized image intensity distribution comprising discrete gray-scale intensity levels (I) corresponding to a discrete plurality of n pixels, and then arranging each the digitized image intensity distribution into a histogram (H(I)) of an amount of the pixels having a given the gray-scale intensity level (I).

Method and apparatus for determining best focus using dark-field imaging

A light tunnel ( ) comprising a hollow light tunnel body ( ) or a solid light tunnel body ( ) having a central axis (A1 or A2), a reflective surface ( or ) facing the axis, and an output end ( or ) having an edge ( or ) with a chamfered surface ( or ) formed on the edge. The chamfered surface is designed to alter the reflective properties of the reflective surfaces of the light tunnel body near the output end so as to reduce or eliminate edge ringing from the light tunnel body edge. In the case of a knife-edge ( ) placed at the output end of the light tunnel body, knife-edge ringing is eliminated by providing a light source ( ) in the form of a laser with a large number of spatial modes (M ). The present invention is expected to be most useful in cases where time-averaging or other interference-eliminating means prove impossible or impractical, such as with applications requiring only one or a few high-irradiance light pulses that need to uniformly irradiate a workpiece.

Apparatus for and method of reducing or eliminating interference effects in a light tunnel illuminator

An method of and apparatus ( ) for performing laser thermal processing (LTP) of a workpiece ( ) having one or more workpiece fields ( ). The apparatus includes a pulsed, solid state laser light source ( ) having more than 1000 spatial modes (M) and capable of emitting one or more pulses of radiation with a temporal pulse length between 1 nanosecond and 1 microsecond, a workpiece stage ( ) for supporting the workpiece, and an illumination optical system having an exposure field ( ). The system is arranged between the laser light source and the workpiece stage so as to illuminate within the exposure field at least one of the one or more workpiece fields with the one or more pulses of radiation, with an irradiance uniformity of less than &plusmn;5%. The method and apparatus is particularly well-suited for LTP processing of workpieces which require a single pulse or only a few pulses of high-irradiance radiation. Other applications of the present invention include rapid thermal annealing of semiconductor devices in semiconductor device manufacturing and processing, recording information in storage media, and, in general, conditioning surfaces.

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San Jose, CA, United States of America

Weijian Wang