Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1999-06-17
2001-06-26
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S030000, C382S145000
Reexamination Certificate
active
06251544
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an effective exposure dose measuring technique in an exposure using a mask, and relates, more particularly, to an exposure dose measuring method for measuring an effective exposure dose in an optical lithography using a projection exposure apparatus, and an effective exposure dose measuring mask to be used therefor.
In recent years, a minimum size of an LSI has come closer to a resolution limit in an optical exposure apparatus and it has become impossible to obtain a sufficient process margin (depth of focus and dose latitude) for volume production in an optical lithography. In order to increase the process margin, various techniques have been employed such as a phase shift mask and a modified illumination.
In the mean time, in order to carry out an optical lithography with small process margin, a precise analysis of an error which consumes the process margin and an error budget have come to be attached with importance. For example, even if a large number of chip regions are exposed on a wafer with the same nominal exposure dose, an effective exposure dose varies because of non-uniformity of post exposure baking (PEB), development, resist thickness, and so on, in a wafer.
For measuring variations in the effective exposure dose onto a wafer plane, it has been a conventional practice that a pattern is printed onto a wafer plane by a nominal focus and a nominal exposure dose in an exposure apparatus at constant values, a size of the pattern is measured, and the pattern size is converted into an exposure dose, thereby to obtain an uniformity of the exposure dose inside the wafer plane. According to this method, however, it has been impossible to remove an effect of a subtle focus variation on a feature size. Further, an enormous time has been consumed for the measurement of the size.
As explained above, according to the conventional method of measuring an effective exposure dose inside a wafer plane, it is impossible to avoid an influence of focus variation since a pattern size is measured first and this pattern size is converted into an exposure dose, so that it has been difficult to accurately measure the exposure dose. There has also been a problem that it takes a long time for the measurement.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and it is an object of the present invention to provide an effective exposure dose measuring method for accurately measuring an effective exposure dose in a short time without an influence of focus variation, and an effective exposure dose measuring mask to be used therefor.
In order to solve the above-described problem, according to a first aspect of the present invention, there is provided an exposure dose measuring method for measuring an effective exposure dose on a wafer, comprising the steps of setting a mask formed with mask patterns each having light transmitting sections and light shielding sections repeated in a period p, a ratio of areas of the light transmitting sections to areas of the light shielding sections of each of the mask patterns being different from ratios of those of the others of the mask patterns, to a projection exposure apparatus ha light wavelength &lgr;, a numerical aperture NA at a wafer side, an illumination coherence factor &dgr; and a mask pattern magnification M for patterns to be formed on the wafer; exposing light through the mask patterns of the mask onto a resist coated on the wafer; and observing a state of exposed portions of the resist on the wafer corresponding to the mask patterns, wherein the period p is set so as to satisfy a relationship of
p
/M≦&lgr;/(1+&dgr;)NA.
In a light exposure measuring method according to the first aspect of the present invention, an area of a light transmitting section of a mask pattern which corresponds to a portion of the wafer where a corresponding portion of the resist has been removed, may be measured, and the measured area may be converted into an effective exposure dose.
In a light exposure measuring method according to the first aspect of the present invention, an area of a light transmitting section of a mask pattern which corresponds to a portion of the wafer where a corresponding portion of the resist has become a predetermined film thickness, may be measured, and the measured area may be converted into an exposure dose.
In a light exposure measuring method according to the first aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of lines-and-spaces.
In a light exposure measuring method according to the first aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of repeated holes.
In a light exposure measuring method according to the first aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of repeated rhombuses.
In a light exposure measuring method according to the first aspect of the present invention, the mask patterns may be set so as to have a constant change quantity in the area of a light transmitting section.
In a light exposure measuring method according to the first aspect of the present invention, the mask patterns may be set so as to have a constant change rate in the area of a light transmitting section.
In order to solve the above-described problem, according to a second aspect of the present invention, an exposure dose measuring method for measuring an effective exposure dose on a wafer, comprising the steps of setting a mask formed with mask patterns each having light transmitting sections and light shielding sections repeated in a period p, a ratio of areas of the light transmitting sections to areas of the light shielding sections of each of the mask patterns being different from ratios of those of the others of the mask patterns, to a projection exposure apparatus having an exposure light wavelength &lgr;, a numerical aperture NA at a wafer side, an illumination coherence factor &dgr; and a mask pattern magnification M for patterns to be formed on the wafer; exposing light through the mask patterns of the mask onto a resist coated on the wafer; and observing a pattern on the wafer corresponding to the mask patterns, with an optical microscope having a wavelength &lgr;
m
, a numerical aperture NA
m
at a wafer side, and an illumination coherence factor &dgr;
m
, wherein the period p is set so as to satisfy relationships of
p
/M>&lgr;/(1+&dgr;)NA
and
p
/M≦&lgr;
m
/(1+&dgr;
m
)NA
m
.
In a light exposure measuring method according to the second aspect of the present invention, an area of a light transmitting section of a mask pattern which corresponds to a portion of an imaging plane of the optical microscope where the intensity of the exposure has become a predetermined value, may be measured, and the measured area may be converted into an effective exposure dose.
In a light exposure measuring method according to the second aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of lines-and-spaces.
In a light exposure measuring method according to the second aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of repeated holes.
In a light exposure measuring method according to the second aspect of the present invention, the mask patterns may be a plurality of kinds of patterns of repeated rhombuses.
In a light exposure measuring method according to the second aspect of the present invention, the mask patterns may be set so as to have a constant change quantity in the area of a light transmitting section.
In a light exposure measuring method according to the second aspect of the present invention, the mask patterns may be set so as to have a constant change rate in the area of a light transmitting section.
In order to solve the above-described problem, according to a third aspect of the present invention, there is provided an exposure dose measuring mask to be used for a measurement of an exposure dose, th
Hayasaki Kei
Inoue Soichi
Ito Shin'ichi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Young Christopher G.
LandOfFree
Exposure dose measuring method and exposure dose measuring mask does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Exposure dose measuring method and exposure dose measuring mask, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exposure dose measuring method and exposure dose measuring mask will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486655