1. Field of the Invention
The present invention relates to an exposure apparatus, a method of making the apparatus, an exposure method, and a device and a manufacturing method of the device. More particularly, the invention relates to an exposure apparatus used in a lithographic process, a method of making the apparatus, an exposure method used in a lithographic process, and a device manufactured by the use of the exposure method, and a manufacturing method of the device.
2. Description of the Related Art
Various exposure apparatus are conventionally used in a lithographic process for the manufacture of micro-devices such as integrated circuits. As this exposure apparatus, an optical exposure apparatus such as a step-and-repeat type reducing projection exposure apparatus (known as a stepper) is mainly used. Though within a limited range of fields, there is also utilized a charged particle beam exposure apparatus performing exposure by the use of a charged particle beam such as an electron beam or an ion beam for forming an extra-fine circuit pattern on a substrate such as a wafer. An electron beam exposure apparatus (known also as an EB exposure apparatus) is a typical example of the charged particle beam exposure apparatus.
FIG. 9 schematically illustrates an example of the conventional electron beam exposure apparatus. The electron beam exposure apparatus 110 shown in FIG. 9 comprises a base plate 103 horizontally supported on a plurality of vibration isolators 102, a vacuum chamber 104 of a high degree of vacuum provided adjacent to the base plate 103, a pre-stage chamber of a slightly lower degree of vacuum than in the vacuum chamber 104, an electron beam barrel 108 fixed to an upper portion of the vacuum chamber 104 and having the lower end thereof inserted into the vacuum chamber 104, and a stage 106 housed in the vacuum chamber 104 and moving two-dimensionally while holding a wafer W on the base plate 103.
In this apparatus, it is possible to change the irradiation point on the wafer W by a slight amount by deflecting the electron beam EB emitted from an electron gun 109 and to the right by means of a deflection electrode (not shown in Figs.). A large change of the irradiation point of the electron beam EB relative to the wafer W has however been accomplished through two-dimensional movement of the stage 106.
In the conventional electron beam exposure apparatus, a medium-acceleration type electron beam barrel accelerating an electron beam by a voltage within a range of 30 to 50 kV has mainly been used, taking into account the thickness and the sensitivity of the resist layer used. When carrying out exposure with such a medium-acceleration type electron gun barrel, however, it is necessary to conduct ghost exposure (double exposure) to avoid an adverse effect of back scattered electron, and a Coulomb blur has caused a decrease in resolution.
For the purpose of solving these problems, an electron beam exposure apparatus was recently developed, which eliminated the necessity of the above-mentioned ghost exposure, and particularly, adopted an electron beam barrel performing high-voltage (for example, 50 to 100 kV) acceleration to prevent a decrease in resolution caused by the Coulomb blur and improve the throughput. With such an apparatus, however, the exposing efficiency of the resist relative to the energy necessary for acceleration of the electron beam is reduced to a lower level than in the use of medium-acceleration electron beam. The electron beam barrel is required to be larger, to such a level that the height reaches a value within a range of 150 to 200 cm.
In the conventional electron beam exposure apparatus, as described above, a structure in which a wafer stage making a two-dimensional movement was adopted because of the necessity to adopt a large-scale electron beam barrel including the case of the medium acceleration. With this apparatus, however, the footprint (floor area occupied by the apparatus) of the main body of the apparatus becomes larger along with the tendency toward a large diameter of wafers. More specifically, in order to achieve exposure of the entire surface of a wafer in an apparatus of this type, the stage must provide a movement stroke twice as large as the wafer diameter. In order to expose the entire surface of a 12-inch wafer(a wafer having a diameter of 300 mm), which is likely to become available in the near future, the stage must have a stroke of at least .+-.300 mm around the barrel, as a result the footprint requires over 600 mm square. Actually, it is necessary to provide a vacuum chamber and a wafer introduce/removal mechanism, resulting in a scale twice as large.
In the electron beam exposure apparatus, the exposing speed is lower compared with the optical exposure apparatus. That is, the number of wafers capable of being fabricated in a unit time is small. As a result, when carrying out exposure in the mix-and-match manner with an optical exposure apparatus, i.e., when exposing a layer by optical means and exposing another layer with an electron beam, it becomes necessary to use electron beam exposure apparatus in a number several times as large as that of optical exposure apparatus. For example, while an optical exposure apparatus can expose 80 12-inch wafers per hour, a high-acceleration electron beam exposure apparatus has a throughput of only about five to ten wafers per hour. In order to achieve the same throughput, electron beam exposure apparatus in a number even eight times as large as that of an optical exposure apparatus are necessary. If, in the case, an optical exposure apparatus and an electron beam exposure apparatus are designed with a same concept, and the footprint is designed to be equal between the two, the electron beam exposure apparatus may require a larger footprint due to the area occupied by a vacuum chamber. This result in the necessity of a very large clean room, leading to a very high cost.
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