POSITIONING APPARATUS, LITHOGRAPHY APPARATUS, AND ARTICLE MANUFACTURING METHOD

Provided is a positioning apparatus including a holder configured to hold an original or a substrate and to be movable, and an interferometer for measuring a position of the holder, and positioning the holder based on an output from the interferometer. The positioning apparatus comprises a reference member provided with the holder and including a reference plane; and a plurality of measuring devices respectively configured to face the reference plane, and to respectively measure positions of a plurality of measurement points on the reference plane in a measurement direction intersecting the reference plane.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

Firstly, a description will be given of a positioning apparatus according to a first embodiment of the present invention and a lithography apparatus including the positioning apparatus. The lithography apparatus is an apparatus that is used in a lithography step included in manufacturing steps for a semiconductor device, a liquid crystal display device, and the like. In the present embodiment, the lithography apparatus is a drawing apparatus as an example. The drawing apparatus deflects a single or a plurality of electron beams (charged particle beams) and controls the blanking (OFF irradiation) of electron beams to thereby draw a predetermined pattern at a predetermined position on a wafer (substrate). Here, a charged particle beam is not limited to an electron beam but may also be an ion beam.FIG. 1andFIG. 2are schematic views illustrating a configuration of a drawing apparatus1according to the present embodiment. In particular,FIG. 1is a side view (front view) of the drawing apparatus1andFIG. 2is a plan view of the drawing apparatus1as viewed from the A-A′ plane shown inFIG. 1. InFIG. 1andFIG. 2, a description will be given in which the Z-axis is in a nominal irradiation direction (in the present embodiment, the vertical direction) of an electron beam to a wafer2, and the X-axis and the Y-axis are mutually oriented in directions orthogonal to a plane perpendicular to the Z-axis. The drawing apparatus1has an electron beam barrel (also referred to as “electron optical barrel” or “charged particle optical barrel”)3, a substrate stage4for holding the wafer2, an interferometer5for measuring the position of the substrate stage4, measuring devices6, measuring targets7, and a controller8. Here, the wafer2is an object to be treated consisting, for example, of single crystal silicon. A photosensitive resist (photosensitizer) is coated on the surface of the wafer2.

The electron beam barrel3includes therein an optical system (not shown) that deflects, emits, and focuses the electron beam that has been emitted from an electron gun or a crossover. The electron gun emits an electron (electron beam) by applying heat or an electric field. The optical system includes an electrostatic lens, a blanking deflector that can shield an electron beam, a stopping aperture, a deflector that deflects an image in a specific direction on the surface of the wafer2, and the like. The electron beam barrel3is supported by a support9, and the support9is fixed via a column or the like to the floor surface plate (not shown) laid on the floor. In order to prevent or reduce the attenuation of an electron beam and high voltage discharge between elements constituting the charged particle optical system, the internal pressure of the electron beam barrel3is adjusted to a predetermined high vacuum by a vacuum exhaust system (not shown).

The substrate stage (holder)4is movable in all six directions (in other words, six degrees of freedom) of X-, Y-, Z-axis directions and θx-, θy-, θz-rotational directions about the respective axes by a drive mechanism (not shown) while holding the wafer2by, for example, an electrostatic force. The substrate stage4is also installed in a chamber (not shown) and the internal pressure of the chamber is also adjusted by the vacuum exhaust system.

In order to measure the position of the substrate stage4in six directions, in particular, in the present embodiment, the interferometer5firstly includes a first interferometer5afor X-axis direction and a second interferometer5bfor Y-axis direction each of which has three measurement axes and is installed on the support9via a column10. Furthermore, the interferometer5includes a third interferometer for Z-axis direction (not shown). Among them, the first interferometer5ameasures the position of the substrate stage4in the X-axis direction, the θy rotation amount, and the θz rotation amount. On the other hand, the second interferometer5bmeasures the position of the substrate stage4in the Y-axis direction, the θx rotation amount, and the θz rotation amount. The third interferometer measures the position of the substrate stage4in the Z-axis direction.

The measuring devices6stand facing the reference plane of the measuring targets7to be described below so as to measure the positions of measurement points on the reference plane in a measurement direction intersecting the reference plane. In particular, the measuring devices6in the present embodiment include three measuring devices, i.e., a first measuring device6a,a second measuring device6b,and a third measuring device6cwhich are installed on the support9. In the present embodiment, the measuring devices6ato6care absolute-type capacitance sensors that measure absolute position (distance) and have an advantage in terms of low cost and space-saving.

The measuring targets7are reference members having the reference plane. In particular, in the present embodiment, the measuring targets7consist of three measuring targets7a,7b,and7cthat are installed on the substrate stage4, where the three measuring targets7a,7b,and7ccorrespond to the measuring devices6a,6b,and6c,respectively. If the measuring devices6are capacitance sensors, it is preferable that the measuring targets7consist of a material having conductivity and are grounded in order to stabilize the measured values obtained by the measuring devices6. Three groups of the measuring devices6ato6cand the measuring targets7ato7ccan measure the absolute position of the substrate stage4in the Z-axis direction at three points on the basis of the support9on which the first interferometer5aand the second interferometer5bare installed. Note that specific installation positions of the measuring devices6and the measuring targets7will be described below.

The controller8is constituted, for example, by a computer or the like and is connected to the components of the drawing apparatus1via a line to thereby execute control of the components in accordance with a program or the like. In particular, the controller8of the present embodiment may perform at least positioning of the substrate stage4to a desired position based on the output from the interferometer5and initialization of the interferometer5based on the outputs from the measuring devices6, which will be described below. Here, a control circuit regarding control of the positioning apparatus may be integrated with the controller8that integrally controls the entire drawing apparatus1or may also be separated from the other controller as a controller for controlling only the positioning apparatus. Also, the controller8may be integrated with the rest of the drawing apparatus1(may be provided in a shared housing) or may be installed at a location separate from the location where the rest of the drawing apparatus1is installed (may be provided in a separate housing).

In view of the aforementioned configuration, in the present embodiment, it can be mentioned that the interferometer5, the measuring devices6, the support9for supporting these components, the measuring targets7that are arranged on the substrate stage4, and the controller8are integrally configured as a positioning apparatus that positions the substrate stage4to a desired position.

Next, a description will be given of calibration and initialization of the interferometer5in the positioning apparatus. The controller8determines the attitude (position) of the substrate stage4based on the output from the interferometer5to thereby position (drive) the substrate stage4to a desired position. Here, the interferometer5may produce a measurement error due to change in inclination between the interferometer optical axis and the target (e.g., reflecting mirror) in association with the attitude of the substrate stage4. Hence, the positioning apparatus performs calibration for the output value of the interferometer5relative to the attitude of the substrate stage4prior to performing normal drawing processing. The positioning apparatus stores and refers to interferometer correction information (hereinafter simply referred to as “correction information”) such as a correction formula, a correction table, and the like obtained by the calibration, so that the positioning accuracy of the substrate stage4can be improved, resulting in an improvement in transfer accuracy of the drawing apparatus1. It should be noted that correction information is typically information on the basis of the origin of the attitude of the substrate stage4, and thus, the interferometer5for correctly reproducing the origin needs to be initialized in order to efficiently utilize the correction information. The interferometer5is typically an incremental-type length-measuring device. Thus, for example, when the electric source of the drawing apparatus1(or positioning apparatus) is reactivated after it is turned off, the origin of the attitude of the substrate stage4cannot be reproduced by the interferometer5only. Accordingly, the positioning apparatus of the present embodiment is based on the configuration as described above and further performs initialization of the interferometer5so as to satisfy the following conditions.

Firstly, the controller8can determine the θy attitude of the substrate stage4based on the measured values of the first measuring device6aand the second measuring device6b,which are spaced apart from each other in the X-axis direction, in the Z-axis direction and the installation spacing therebetween. Likewise, the controller8can determine the θx attitude of the substrate stage4based on the measured values of the first measuring device6aand the third measuring device6c,which are spaced apart from each other in the Y-axis direction, in the Z-axis direction and the installation spacing therebetween. In the present embodiment, the measuring devices6, the first interferometer5a,and the second interferometer5bare supported by the same member (the support9) as described above. In other words, the controller8reproduces the attitude of the substrate stage4based on the measured values of the measuring devices6. Consequently, the controller8can also reproduce the attitude of the substrate stage4with respect to the first interferometer5aand the second interferometer5b.Thus, when the controller8initializes the interferometer5using the attitude of the substrate stage4in this state as the origin, correction information obtained by precalibration is suitably applicable, so that the positioning apparatus can position the substrate stage4with high accuracy.

Here, from the viewpoint of measuring the rotation attitude of the substrate stage4with high accuracy, it is preferable that the installation spacing between the measuring devices6is as large as possible. However, if the installation spacing is unnecessarily large, the size, particularly the XY plane size of the substrate stage4becomes large, resulting in an undesirable increase in the size of the entire drawing apparatus1. Also, when the measuring targets7are provided on the outside of the wafer2on the substrate stage4in the configuration of capacitance sensors disclosed in WO 2011/080311 between which the installation spacing is small, the size of the substrate stage4also increases in this case. Thus, in the present embodiment, the measuring devices6are arranged as shown inFIG. 2such that the center position of a virtual circle11passing through the three measurement points of three measuring targets7a,7b,and7cis in the surface (within the area) of the wafer2. Furthermore, the measuring devices6are arranged such that the diameter of the virtual circle11is greater than that of the wafer2. Here, a virtual circle intersecting three measuring targets7a,7b,and7crefers to a circle passing through three measurement points of the measuring targets7measured by the measuring devices6. Note that the measurement point refers to a point within the upper surface of the measuring target7, where the absolute position (the distance from the measuring device6) of the measurement point is measured by the measuring device6. The three groups of three measuring devices6a,6b,and6cand three measuring targets7a,7b,and7cwhich stand facing three measuring devices6a,6b,and6c,respectively, may be located on the respective different quadrants on the substrate stage4. Here, the quadrant refers to one of four quadrants (areas) which are defined by two straight lines orthogonally intersecting at the center of the circle11(may coincide with the center of the wafer2) on the upper surface of the substrate stage4(holder). InFIG. 2, three measuring targets7are arranged at the stage corners of three quadrants, i.e., upper right, lower right, and upper left as an example. By utilizing the space defined by four corners of the substrate stage4, the installation spacing between the measuring devices6can be increased without unnecessary increasing the size of the substrate stage4.

Next, a description will be given of the procedure relating to calibration and initialization of the interferometer5. Firstly, the controller8determines the origin attitude of the substrate stage4on the basis of the measured values of the measuring devices6a,6b,and6c.Note that the origin should lie within the range which can be measured by the measuring devices6a,6b,and6cand the interferometers5aand5b.In order to minimize the correction range, it is preferable that the origin is set near the center of the actual rotational stroke of the substrate stage4. Next, the controller8performs calibration for an interferometer error with respect to the stage attitude on the basis of the origin of the substrate stage4and then creates correction information to thereby store it in a storage device (not shown). Then, the controller8reproduces the origin attitudes θx and θy of the substrate stage4using three measuring devices6a,6b,and6ceach time measurement by the interferometer5is interrupted upon turn-off of the electric source of the positioning apparatus, reactivation or the like to thereby initialize the measured values (Rx and Ry values) of the interferometer5in the attitude state of the substrate stage4.

In this manner, the positioning apparatus of the present embodiment can reproduce the measured values of the interferometer5with high accuracy as in the case of calibration, so that correction information stored in the storage device can be used as it is. The positioning apparatus provides high measurement accuracy for the attitude of the substrate stage4and can reproduce the attitude of the substrate stage4as well as initialize the interferometer5in a short period of time as compared with the case where the attitude of the substrate stage is measured by capacitance sensors disclosed in WO 2011/080311 between which the installation spacing is small. Furthermore, when the wafer surface is measured by capacitance sensors as disclosed in WO 2011/080311, the reproducibility of the attitude of the stage for holding a wafer may be impaired by the influence of wafer surface accuracy, wafer placement error, or the like. In contrast, in the positioning apparatus of the present embodiment, the measuring devices6measure the measuring targets7installed on the substrate stage4, resulting in an advantage of no reduction in reproducibility.

As described above, according to the present embodiment, a positioning apparatus that is advantageous for initializing an interferometer may be provided. According to the drawing apparatus (lithography apparatus) using the positioning apparatus, the stage attitude (stage position) can be measured with high accuracy, resulting in an advantage of improvement in, for example, drawing accuracy (transfer accuracy).

Second Embodiment

Next, a description will be given of a positioning apparatus according to a second embodiment of the present invention. A feature of the positioning apparatus of the present embodiment lies in the fact that the arrangement of the measuring devices6and the measuring targets7corresponding thereto on the substrate stage4is changed from the arrangement illustrated in the first embodiment.FIG. 3is a plan view illustrating a configuration of a drawing apparatus serving as the lithography apparatus according to the present embodiment corresponding to that in the first embodiment shown inFIG. 2. For example, four corners of the substrate stage4may be used for other applications such as arrangement of sensors required for the lithography apparatus or the like, so that the measuring devices6or the measuring targets7may not be arranged at these positions. In this case, for example, as shown inFIG. 3, three measuring targets7a,7b,and7cmay be arranged on the substrate stage4at the stage corners of three quadrants, i.e., lower right, upper left, and lower left, respectively, so as to avoid an area (areas)20for arranging another kind of a sensor (sensors) at four corners of the substrate stage4. As in the first embodiment, in the present embodiment, the measuring devices6are arranged such that the center position of the virtual circle11passing through three measuring targets7a,7b,and7clies within the upper surface of the wafer2and the diameter of the virtual circle11is greater than that of the wafer2. According to the configuration, the installation spacing between the measuring devices6can be increased without unnecessary increasing the size of the substrate stage4as in the first embodiment. Although it is preferable that the installation spacing between two measuring devices6is as large as possible, in contrast to the first embodiment, in the present embodiment, it is also contemplated that it is difficult to adjust the installation spacing not to be smaller than the diameter of the wafer2. However, the required installation spacing depends on the specification of various lithography apparatuses such as positioning accuracy or the like and the configuration of the various lithography apparatuses. Hence, the diameter condition of the virtual circle11may not be smaller than the radius of the wafer2as long as the installation spacing is satisfied with such specification and configuration.

While, in the above embodiment, capacitance sensors are employed as the measuring devices6which can measure the absolute position of the substrate stage4on the basis of the support9, the present invention is not limited thereto. For example, the positioning apparatus may also be configured such that marks are provided on the measuring targets7and the images of these marks are focused on an imaging element (e.g., CCD sensor) arranged on the support9via an optical system. In this case, the controller8determines the positions of the measuring targets7in the Z-axis direction from a contrast of mark images obtained when the substrate stage4is displaced in the Z-axis direction. Also, the measuring targets7may be targets which can be measured by three measuring devices6a,6b,and6c.Although three independent targets may be provided as shown inFIG. 2, three targets may also be constituted by a single object.

In the above embodiment, a description has been given by taking an example in which the present invention is applied to measure the position of the holder in the lithography apparatus having the holder (the substrate stage4) movable by holding the wafer2. In contrast, the present invention may also be applied to measure the position of the holder in the lithography apparatus having the holder movable by holding an original (mask, reticle, or mold) or the like.

Furthermore, while, in the above embodiment, a description has been given by taking an example of a drawing apparatus serving as a lithography apparatus, the lithography apparatus is not limited thereto. For example, the lithography apparatus may also be an exposure apparatus that projects a pattern of an original (reticle or mask) onto a substrate via a projection optical system using ultraviolet light or EUV light. The lithography apparatus may also be an imprint apparatus that molds an imprint material on a substrate using a mold to thereby form a pattern on the substrate. Since each of these exposure apparatus and imprint apparatus is also provided with a barrel or a mold holder instead of an electron beam barrel, the same effects may be provided if the configuration of the present embodiment is applied thereto.

Article Manufacturing Method

An article manufacturing method according to an embodiment of the present invention is preferred in manufacturing an article such as a micro device such as a semiconductor device or the like, an element or the like having a microstructure, or the like. The article manufacturing method may include a step of forming a pattern (e.g., latent image pattern) on an object (e.g., substrate on which a photosensitive material is coated) using the aforementioned lithography apparatus; and a step of processing (e.g., step of developing) the object on which the latent image pattern has been formed in the previous step. Furthermore, the article manufacturing method may include other known steps (oxidizing, film forming, vapor depositing, doping, flattening, etching, resist peeling, dicing, bonding, packaging, and the like). The device manufacturing method of this embodiment has an advantage, as compared with a conventional device manufacturing method, in at least one of performance, quality, productivity and production cost of a device.

This application claims the benefit of Japanese Patent Application No. 2012-275637 filed on Dec. 18, 2012, which is hereby incorporated by reference herein in its entirety.