Radiant energy – Inspection of solids or liquids by charged particles – Methods
Reexamination Certificate
1999-07-02
2001-12-04
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Methods
Reexamination Certificate
active
06326618
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of semiconductor line width metrology, and more particularly, this invention relates to determining the scale and shape of a patterned feature based on line width metrology.
BACKGROUND OF THE INVENTION
Critical Dimension (CD) line width metrology relates an intensity signal produced from a line width metrology device, such as a scanning electron microscope, to the actual size or scale of a patterned feature, such as a photoresist feature produced on a semiconductor layer. The intensity signal is visualized and manipulated as a signal, profile or, e.g., an amplitude modulated waveform signal. A measurement of the size (scale) of a patterned feature involves the extraction of edge positions from the waveform signal. Traditional line width metrology known to those skilled in the art ignores much of the effect caused by the variation of the shape of the patterned feature. However, the shape must often be determined because the shape has adverse effects on further processing of a semiconductor wafer.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of analyzing a semiconductor surface having a patterned feature using line width metrology such that not only the scale, but also the shape of a patterned feature can be determined.
In accordance with the present invention, the method of analyzing a semiconductor surface having a patterned feature formed on a semiconductor layer comprises the steps of scanning across the patterned feature for generating an amplitude modulated waveform signal of the line width of the patterned feature. This waveform signal is processed for calculating the scale and shape of the patterned feature based on the profile of the amplitude modulated waveform signal, including the intensity profile and the derived curve. The calculated scale and shape of the patterned feature is compared to a template of a normal patterned feature having a desired shape and scale. The template can be formed by scanning across a normal patterned feature having a desired shape and scale for generating an amplitude modulated waveform signal of the line width of the normal patterned feature. The generated amplitude modulated waveform signal is then processed for calculating the scale and shape based on the profile of the generated amplitude modulated waveform signal to obtain the template.
The step also comprises the step of forming the template by deriving a curve of outer line width and inner line spacing. The method also comprises the step of deriving a curve of the line width and inner line spacing for the patterned feature and comparing the derived curve of the patterned feature to the derived curve of the template.
The method also comprises the step of rejecting the patterned feature if the derived curve for the patterned feature deviates a predetermined amount from the derived curve of the template. The amplitude modulated waveform signal can be generated with a scanning electron microscope or a semiconductor stylus measurement tool or similar tool known to those skilled in the art. The method also comprises the step of forming the patterned feature within, for example, a photoresist or any etched feature and topography.
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Kane Brittin C.
McIntosh John M.
Agere Systems Guardian Corp.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Nguyen Kiet T.
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