Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1998-12-15
2001-04-03
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000, C355S069000, C355S070000, C355S077000, C348S745000, C348S746000, C348S747000
Reexamination Certificate
active
06211947
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an illuminance distribution measuring method and exposing method, which are applicable to an exposure apparatus for performing the exposure of pattern of semiconductor element or liquid crystal display element in the step of photolithography.
In view of the increasing demand for semiconductor element as well as for the reduction of manufacturing cost of semiconductor element in recent years, it is now desired to enhance the throughput of an exposure apparatus to be employed in the manufacture of semiconductor element, etc. According to an exposure apparatus of this kind, a circuit pattern formed on a projection original (hereinafter generically referred to as reticle) such as a reticle and mask is illuminated by a luminous flux from an optical illumination system, and the pattern thus illuminated is then transferred as an image, by making use of a projection type optical system, onto a photosensitive substrate (hereinafter referred to simply as a substrate) such as a glass plate or wafer having thereon a coated layer of photosensitive material such as resist. Under the circumstances, there has been developed a technique to shorten the exposure time by increasing the illuminance at the surface of the substrate, thereby enhancing the throughput of the exposure apparatus.
Meanwhile, the adjustment in quantity of exposure to the surface of substrate in the exposure apparatus of this kind is performed as follows. Namely, a photoelectric sensor provided with a pin-hole plate to be positioned at the same level as that of the surface of substrate is placed on a substrate stage for mounting the substrate in the vicinity of the location where the substrate is to be positioned. Then, the photoelectric sensor is moved to the irradiation region or exposure region of illuminating light. More specifically, as shown in
FIG. 8
, the photoelectric sensor is moved step by step from the measurement starting position P
1
to the measurement finishing position Pm within the exposure region
50
. The measurement of illuminance is performed once at each position starting from the starting position P
1
to the finishing position Pm, thereby obtaining the illuminance distribution of the exposure light. Based on the results of measurement, the magnitude of illuminance and irradiation time (in the case of pulse beam, the number of pulse) of the exposure light are controlled, thereby adjusting the quantity of exposure to the surface of substrate.
However, when the illuminance of the exposure light onto the surface of the substrate is increased, the light irradiation energy onto the substrate is increased, thereby inviting a rise in temperature of the photoelectric sensor per se that has been placed within the exposure region. As a result, the output to be obtained by the photoelectric sensor is influenced by a drift due to this temperature increase. In particular, in the case of a reduction projection type exposure apparatus, since the photoelectric sensor which is designed to measure the uniformity of illuminance (or illuminance irregularity) at the surface of substrate is inevitably exposed to an intense exposure light, the photoelectric sensor is suffered from a large quantity of heat. Therefore, in the conventional method where the photoelectric sensor is moved while stopping at every measurement position within the exposure region thereby to intermittently measure the illuminance of measurement positions, the illumination heat is gradually accumulated in the photoelectric sensor with time, thereby inviting a tendency that the later the time of measurement is, the larger the degree of increase in output (measured value) over the actual illuminance due to a drift. As a result, there is a problem that the measured value is caused to include an illuminance irregularity which is not inherently originated from an optical illumination system and a projection type optical system.
BRIEF SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an illuminance distribution measuring method which is capable of minimizing an influence of drift in temperature to a photoelectric sensor.
Namely, this invention provides a method of measuring an illuminance distribution on a surface of a substrate to be exposed while being mounted on a substrate stage;
which is characterized in that said method comprises a step of reciprocatively moving said substrate stage in such a manner that a detecting sensor positioned on said substrate stage is moved forward along a route during which said detecting sensor is intermittently stopped at a plurality of locations within an exposure region of the surface of said substrate, and, after reaching a turning location among said plurality of locations, moved to return along said route during which said detecting sensor is intermittently stopped again at said plurality of locations within said exposure region;
in that measurement of illuminance is performed an even number of times at each of said plurality of locations except said turning location; and
in that said illuminance distribution in said exposure region of the surface of said substrate is determined based not only on a measured value of illuminance obtained at each of said plurality of locations during the forward movement of said detecting sensor but also on a measured value of illuminance obtained at each of said plurality of locations during the returning movement of said detecting sensor.
The aforementioned step of reciprocatively moving said substrate stage may be performed at least twice. Further, the measurement of illuminance should preferably be performed after preheating the detecting sensor.
This invention further provides an exposing method for forming a pattern on a substrate by irradiating a luminous flux from an optical illumination system onto said substrate through a pattern of mask, while said substrate is being positioned on a substrate stage;
which is characterized in that said method comprises a step of reciprocatively moving said substrate stage in such a manner that a detecting sensor positioned on said substrate stage is moved forward along a route during which said detecting sensor is intermittently stopped at a plurality of locations within an exposure region of the surface of said substrate, and, after reaching a turning location among said plurality of locations, moved to return along said route during which said detecting sensor is intermittently stopped again at said plurality of locations within said exposure region;
in that measurement of illuminance is performed an even number of times at each of said plurality of locations except said turning location;
in that said illuminance distribution in said exposure region of the surface of said substrate is determined based not only on a measured value of illuminance obtained at each of said plurality of locations during the forward movement of said detecting sensor but also on a measured value of illuminance obtained at each of said plurality of locations during the returning movement of said detecting sensor; and
in that a light volume of said luminous flux from said optical illumination system is determined based on said illuminance distribution thus determined.
This invention further provides a method for performing an exposure of a substrate by irradiating a illumination beam onto said substrate through a mask, said method comprising;
a first step of detecting an intensity of illumination beam at a plurality of locations within an irradiation region of said illumination beam in a predetermined order; and
a second step of detecting an intensity of illumination beam at said plurality of locations in an order which is reverse to said predetermined order.
In this case, the location wherein the intensity of illumination beam is detected at last in said first step may be different from the location wherein the intensity of illumination beam is detected at first in said second step, and the number of repeating the detection at each of said plurality of locations except the tur
Adams Russell
Baker & Botts L.L.P.
Brown Khaled
Nikon Corporation
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