Exposure apparatus and device manufacturing method

An exposure apparatus comprises a component configured to project a pattern of an original onto a substrate, a structure configured to support the component, a support configured to support the structure, a gas spring which is located between the structure and the support and configured to support the structure, and a stopper accommodated in an internal space of the gas spring so as to prevent the structure from moving relative to the support in excess of an allowable level.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus which projects the pattern of an original onto a substrate, thereby exposing the substrate to light, and a device manufacturing method.

2. Description of the Related Art

In manufacturing micropatterned devices such as a semiconductor device, liquid-crystal device, and micromachine, an exposure apparatus is used to project the pattern of an original (reticle) onto a substrate (for example, a wafer or glass plate), thereby exposing the substrate to light. Examples of the exposure light are visible light, ultraviolet light, EUV light, X-rays, an electron beam, and a charged-particle beam. Examples of a projection system for projecting the pattern of an original onto a substrate are a dioptric system, catoptric system, catadioptric system, and charged-particle lens.

The exposure apparatus is required to accurately align an original stage which holds an original and a substrate stage which holds a substrate. The exposure apparatus is also required to accurately support structures such as an optical system support which supports the projection system, an original stage surface plate which supports the original stage, and a substrate stage surface plate which supports the substrate stage.

Also, the exposure apparatus requires a vibration control device for suppressing any external vibration such as vibration transmitted from bases such as the floor on which the exposure apparatus is installed from being transmitted to, for example, the stages.

To meet this need, the structures such as the surface plates in the exposure apparatus are generally supported by foundation structures such as the floor through a vibration control mount. In this specification, “vibration control” means reducing vibration.

An active vibration control device which detects vibration by a sensor and operates an actuator based on the signal output from the sensor has already been put to practical use. It is a common practice to use, as the actuator for the active vibration control device, an air pressure actuator which regulates the pressure of the internal space of a gas spring, thereby actively controlling a thrust produced by this internal pressure.

To improve a function of reducing the vibration of the structure supported by the vibration control mount, it is effective to decrease the spring constant of the vibration control mount. Then, it is effective to use a gas spring as the vibration control mount. Because a gas spring can easily produce a large thrust by setting its pressure receiving area to be sufficiently large, it can also suitably be used as a support mechanism which supports a heavy structure. Hence, using an air pressure actuator as the actuator for the vibration control mount has a merit that it can also be exploited as the support mechanism, thus attaining a vibration control device having a relatively simple structure (see Japanese Patent Laid-Open No. 11-294520).

Conventionally, when the exposure apparatus is in a normal operative state (including various regulation processes for exposure), a vibration control mount including an air pressure actuator using a gas spring supports a structure in the exposure apparatus with respect to a foundation structure while reducing the vibration of the structure in the exposure apparatus. However, in assembly and regulation of the exposure apparatus, the structure in the exposure apparatus must be supported with respect to the foundation structure with a high rigidity to ensure safety. In this case, not the vibration control mount including a gas spring but a stopper or the like provided separately from the vibration control mount supports the structure in the exposure apparatus. If the exposure apparatus suffers an abnormality and therefore a sufficient amount of driving gas cannot be supplied to the air pressure actuator built in the vibration control mount, the vibration control mount including a gas spring can hardly support the structure in the exposure apparatus. Also in this case, a stopper or the like supports the structure in the exposure apparatus as in the above-described case. The same applies to a case in which signal transmission to the air pressure actuator is disabled or to be stopped.

The support position (the point of action) of the structure in the exposure apparatus changes between when the gas spring supports the structure and when the stopper supports the structure, so its gravitational deformation characteristic changes between the two cases. In one example, the support position changes between when the vibration control mount supports an optical system support which mounts an interferometer and a projection system for the exposure apparatus and when the stopper or the like supports the optical system support, so the deformation characteristic of the optical system support may change on the order of several micrometers.

When a structure in the exposure apparatus mounts two components while being supported by a stopper, and is then supported by a gas spring, the positional relationship between these two components may change. More specifically, when the optical system support mounts a projection system and interferometer while being supported by a stopper, and is then supported by a vibration control mount, the distance between the projection system and the interferometer may change on the order of several micrometers.

Along with the recent increase in the size of the exposure apparatus, the sizes of the structures in the exposure apparatus are also increasing. To decrease the weight of the exposure apparatus, it is necessary to minimize the weights of the structures. To meet this need, the structures in the exposure apparatus are desirably imparted with minimum necessary rigidities while the exposure apparatus is in a normal state, that is, they are supported by vibration control mounts. From this viewpoint, the amount of change in the positional relationship between components due to change in the support position as described above may increase. However, in recent years, considering a demand for a higher accuracy of the exposure apparatus, a change in the positional relationship between components due to change in the support position is non-negligible.

When two components mounted on a structure must be aligned precisely, a process of re-adjusting the positions of the components after mounting them on the structure is necessary. This increases the number of assembly processes and the cost.

The deformation characteristic of a structure in the exposure apparatus changes between when a gas spring supports the structure and when the stopper supports it, so a strain remains in the structure itself or the components mounted on the structure. For example, even when the support position is returned to the original support position, the components may not return to the initial states (for example, the initial position and deformation state) owing to an irreversible effect such as friction. More specifically, when an optical system support mounts a projection optical system while being supported by a stopper, is then temporarily supported by a gas spring, and is supported by the stopper again, the position and deformation state of the projection system may change from the initial state upon mounting.

Along with the recent increase in the accuracy of the exposure apparatus, the number of components in the exposure apparatus is increasing. Considering the limiting condition of the installation space of the exposure apparatus, it is necessary to save the spaces to accommodate the components. This makes it difficult to ensure sufficient spaces to accommodate the stoppers.

Also along with the recent increase in the accuracy of the exposure apparatus, it is demanded to clean the environment in the exposure apparatus and precisely control the temperature in the exposure apparatus. To meet this demand, when a drivable stopper is used, dust, waste heat, and the like released from a stopper driving mechanism to the environment in the exposure apparatus are becoming non-negligible.

SUMMARY OF THE INVENTION

The present invention contributes to, for example, reducing a difference in support position between when a gas spring supports a structure and when a stopper supports it.

According to the first aspect of the present invention, there is provided an exposure apparatus including a component configured to project a pattern of an original onto a substrate, thereby exposing the substrate to light, and a structure configured to support the component, the apparatus comprising a support configured to support the structure, a gas spring which is located between the structure and the support and configured to support the structure, and a stopper accommodated in an internal space of the gas spring so as to prevent the structure from moving relative to the support in excess of an allowable level.

According to the second aspect of the present invention, there is provided a device manufacturing method comprising the steps of exposing a substrate to light by using the above-mentioned exposure apparatus, and developing the substrate.

DESCRIPTION OF THE EMBODIMENTS

An exposure apparatus according to a preferred embodiment of the present invention includes components to project the pattern of an original onto a substrate, thereby exposing the substrate to light, and structures to support the components. The components include, for example, a projection system (optical system barrel), original stage, and substrate stage. The structures include, for example, an optical system support, original stage surface plate, and substrate stage surface plate.

FIG. 2is a view showing the schematic arrangement of an exposure apparatus according to a preferred embodiment of the present invention. An exposure apparatus EX scans an original (reticle)107and a substrate (for example, a wafer or glass plate)104with respect to a projection system105while projecting the pattern of the original107onto the substrate104by the projection system105. With this operation, the substrate104is exposed to light, and the pattern of the original107is transferred onto the substrate104. However, the exposure apparatus EX may expose the substrate104to light while the original107and substrate104stand still.

The exposure apparatus EX includes a base frame116serving as a support which supports an optical system support112, an original stage (reticle stage)106which can move while holding the original107, and a substrate stage (wafer stage)103which can move while holding the substrate104. The exposure apparatus EX also includes an illumination system108which illuminates the original107with illumination light, the projection system105which projects the pattern of the original107onto the substrate104at a predetermined magnification (for example, 4:1), and the optical system support112which holds the projection system105. The exposure apparatus EX also includes an air-conditioning room109which supplies temperature-controlled clean air to spaces such as the optical paths (for example, the interiors of the illumination system108and projection system105).

The illumination system108introduces illumination light by building a light source (for example, an electric-discharge lamp such as a superhigh pressure mercury lamp) in itself or by guiding light from a light source (for example, an excimer laser; not shown) set to be spaced apart from the main body (in this case, a portion other than the light source) of the exposure apparatus EX via a beam line. The illumination system108generates, for example, slit light and illuminates the original107held by the original stage106.

The base frame116is installed on a floor (base)101of a clean room in a semiconductor manufacturing facility. The base frame116is fixed on the floor101with a high rigidity, so it is practically integrated with the floor101or is practically an extension of the floor101. The base frame116typically includes three or four high-rigidity columns and supports the optical system support (an example of the structures)112on the upper portion of each column through a vibration control mount113. The vibration control mount113includes, for example, a gas spring, damper, and actuator. The vibration control mount113prevents high-frequency vibration (vibration having a frequency equal to or higher than the natural frequency of the floor101) from the floor101from being transmitted to the optical system support112, and actively compensates the tilt and shaking of the optical system support112.

The optical system support112which supports the projection system105supports an original stage surface plate110through a support frame111. To detect the position of the substrate stage103with reference to the optical system support112, laser interferometers are fixed on the optical system support112. The laser interferometers include a Z interferometer118which measures the position of the substrate stage103in the Z direction (vertical direction), and an X-Y interferometer114which measures the position of the substrate stage103in the X and Y directions (horizontal direction). As reference mirrors for the laser interferometers, a Z interferometer mirror117and X-Y interferometer mirror102are arranged on the substrate stage103.

The original stage106is installed on the original stage surface plate110and driven in the Y direction in scanning exposure by a driving mechanism (not shown) including a driving source (linear motor) and hydrostatic bearing. The driving profile at this time can include an acceleration interval, constant-velocity movement interval, and deceleration interval in the order named.

The substrate stage103and its periphery will be explained next. The substrate stage103holds the substrate104mounted on it, and can be aligned in a total of six axial directions, that is, the two directions (X and Y directions) on the horizontal plane, the vertical direction (Z direction), and the rotation (ωx, ωy, and ωz) directions about axes parallel to the respective directions. An electromagnetic actuator such as a linear motor can be adopted as an alignment driving source. An alignment mechanism which aligns the substrate stage103includes a two-dimensional stage mechanism including an X stage which rectilinearly moves in the X direction, an X linear motor which drives it, a Y stage which rectilinearly moves in the Y direction, and a Y linear motor which drives it. The alignment mechanism has a structure in which stages which can move in the Z direction, the tilt (ωx and ωy) directions, and the rotation directions are mounted on the two-dimensional stage mechanism. A hydrostatic bearing is used as a guide in each direction. The detailed arrangement of the substrate stage103is described in, for example, Japanese Patent Laid-Open Nos. 1-188241, 3-245932, and 6-267823.

The substrate stage103is supported by a substrate stage surface plate115and moves on the X-Y guide surface of the substrate stage surface plate115. The substrate stage surface plate115can be supported by a base such as the floor through support legs (not shown) or by the base frame (support)116.

FIG. 3is a view showing a partial structure including the vibration control mount113, of the structure shown inFIG. 2. The optical system support112which supports the projection system105is supported by the base frame116through the vibration control mount113and by the floor (base)101as well.

FIG. 1is a view schematically showing the structure of a vibration control mount113in an exposure apparatus according to the first embodiment of the present invention. The vibration control mount113includes a movable portion11and a fixed portion14fixed on a base frame (support)116which supports an optical system support112. The movable portion11has an opening at its bottom portion and can be a box-shaped member which surrounds at least a part of the fixed portion14.

Referring toFIG. 1, as an arrangement which supports the movable portion11in the Z direction, a gas spring15which can expand and contract in the Z direction is located between the outer surface of the fixed portion14and the inner surface of the box-shaped movable portion (box-shaped member)11. The gas spring15supports the optical system support112in the Z direction in cooperation with a space19aformed in the fixed portion14. The gas spring15can typically be an air spring.

Also referring toFIG. 1, as an arrangement which supports the movable portion11in the Y direction, gas springs12and16which can expand and contract in the Y direction are located between the movable portion11and the fixed portion14. The gas springs12and16are arranged to sandwich the movable portion11between themselves. The gas springs12and16support the optical system support112in the Y direction in cooperation with spaces19cand19b, respectively, formed in the fixed portion14. The gas springs15,12, and16can be formed from, for example, rubber.

The spaces19a,19b, and19care connected to a pressure regulating mechanism (not shown) through pipe lines. The pressure regulating mechanism individually controls the internal pressures of the spaces19a,19b, and19cin order to reduce the vibration of the optical system support112.

A Z-direction stopper10which restricts the position of the movable portion11in the Z direction is accommodated in the gas spring15which supports the movable portion11in the Z direction. Y-direction stoppers13and17which restrict the position of the movable portion11in the Y direction are accommodated in the gas springs12and16, respectively, which support the movable portion11in the Y direction. The stoppers10,13, and17prevent the movable portion11or the optical system support112(structure) from moving relative to the fixed portion14or a floor (base)101in excess of an allowable level. The stoppers10,13, and17are also used to support the optical system support112in assembly and regulation of the exposure apparatus.

If the gas spring15cannot support the optical system support112as the internal pressure of the gas spring15is controlled to a prescribed value or less, the optical system support112is supported by the Z-direction stopper10accommodated in the internal space of the gas spring15. For this reason, the support position of the optical system support112does not change largely between when the gas spring15supports the optical system support112and when the stopper10supports the optical system support112. The deformation state of the optical system support112, in turn, does not change largely. The positional relationship among a plurality of components (for example, a projection system105and interferometers114and118) mounted on the optical system support112also does not change largely between when the gas spring15supports the optical system support112and when the Z-direction stopper10supports the optical system support112. In addition, residual strain in the individual components mounted on the optical system support112is reduced.

FIG. 4is a view schematically showing the structure of a vibration control mount113in an exposure apparatus according to the second embodiment of the present invention. The exposure apparatus according to the second embodiment has an arrangement in which the vibration control mount113shown inFIG. 1in the exposure apparatus according to the first embodiment is substituted by the vibration control mount113shown inFIG. 4.

The vibration control mount113includes a box-shaped movable portion (box-shaped member)45having an opening at its bottom portion, and a fixed portion492fixed on a base frame116which supports an optical system support112. The movable portion45is fixed on the optical system support112.

The movable portion45has, at the center of its inner surface, a piston rod42of a gimbal piston serving as a mechanism which tolerates a relative misalignment between the movable portion45and the fixed portion492in a direction parallel to the X-Y plane. The piston rod42extends in the Z direction. The piston rod42is supported on the bottom surface of a cylinder44of the gimbal piston through a metal ball43arranged at the distal end of the piston rod42. With this arrangement, the gimbal piston has a structure flexible in a direction parallel to the X-Y plane.

Also referring toFIG. 4, as an arrangement which supports a movable portion11in the Z direction, a gas spring40which can expand and contract in the Z direction is located between the fixed portion492and a gimbal piston P1to form an enclosed space. The gas spring40supports the optical system support112in the Z direction in cooperation with a space493aformed in the fixed portion492. The gas spring40can typically be an air spring. The gas spring40has a higher rigidity in a direction parallel to the X-Y plane perpendicular to the Z direction than that in the Z direction. For this reason, although the gas spring40prohibits relative movement between the movable portion45and the fixed portion492in a direction parallel to the X-Y plane, the gimbal piston P1enables their relative movement in a direction parallel to the X-Z plane.

The movable portion45has, at the centers of its inner side surfaces, piston rods49and149of gimbal pistons P2and P3each serving as a mechanism which tolerates a relative misalignment between the movable portion45and the fixed portion492in a direction parallel to the X-Z plane. The piston rods49and149extend in the Y direction. The piston rods49and149are supported on the bottom surfaces of cylinders47and147of the gimbal pistons P2and P3though metal balls491and495arranged at the distal ends of the piston rods49and149. With this arrangement, the gimbal pistons P2and P3have a structure flexible in a direction parallel to the X-Z plane.

Also referring toFIG. 4, as an arrangement which supports the movable portion11in the Y direction, gas springs46and146which can expand and contract in the Y direction are located between the fixed portion492and the gimbal pistons P2and P3to form enclosed spaces. The gas springs46and146support the optical system support112in the Y direction in cooperation with spaces493band493c, respectively, formed in the fixed portion492. The gas springs46and146can typically be, for example, air springs. The gas springs46and146have a higher rigidity in a direction parallel to the X-Z plane perpendicular to the Y direction than that in the Y direction. For this reason, although the gas springs46and146prohibit relative movement between the movable portion45and the fixed portion492in a direction parallel to the X-Z plane, the gimbal pistons P2and P3enable their relative movement in a direction parallel to the X-Z plane.

Note that a gimbal piston may be located between the fixed portion492and the movable portion45in the X direction, and, as an arrangement which supports the movable portion11in the X direction, a gas spring which can expand and contract in the X direction may be located between the movable portion45and the gimbal piston to form an enclosed space.

The spaces493a,493b, and493care connected to a pressure regulating mechanism (not shown) through pipe lines. The pressure regulating mechanism individually controls the internal pressures of the spaces493a,493b, and493cin order to reduce the vibration of the optical system support112.

A Z-direction stopper41which restricts the position of the movable portion45in the Z direction is accommodated in the gas spring40which supports the movable portion45in the Z direction. Y-direction stoppers48and148which restrict the position of the movable portion45in the Y direction are accommodated in the gas springs46and146, respectively, which support the movable portion45in the Y direction. The stoppers41,48, and148prevent the movable portion11or the optical system support112(structure) from moving relative to a fixed portion14or a floor (base)101in excess of an allowable level.

If the gas spring40cannot support the optical system support112as the amount of gas (or the pressure) in the gas spring40becomes equal to or less than a prescribed amount, the optical system support112is supported by the Z-direction stopper41. For this reason, the deformation state of the optical system support112does not change largely between when the gas spring40supports the optical system support112and when the Z-direction stopper41supports the optical system support112.

FIG. 5is a view schematically showing the structure of a vibration control mount113in an exposure apparatus according to the third embodiment of the present invention. The exposure apparatus according to the third embodiment has an arrangement in which the vibration control mount113shown inFIG. 1in the first embodiment is substituted by the vibration control mount113shown inFIG. 5.

In the third embodiment, a stopper50accommodated in the internal space of a gas spring15is driven by an actuator51. Likewise, a stopper56accommodated in the internal space of a gas spring12is driven by an actuator57. A stopper66accommodated in the internal space of a gas spring16is driven by an actuator67. The actuators51,57, and67which drive the stoppers50,56, and66can be typically accommodated in the internal spaces of the gas springs15,12, and16, respectively. This arrangement can reduce the adverse influence that dust and heat that may be generated by the actuators51,57, and67inflict on the environment inside the chamber of the exposure apparatus. The actuator51in the Z direction may drive the stopper50to prevent the level of the optical system support112from changing between when the gas spring15supports an optical system support112and when the stopper50supports the optical system support112.

The actuators51,57, and67can include, for example, piezoelectric elements or magnetostrictive elements. The allowable level of movement of a movable portion11or the optical system support112(structure) relative to a fixed portion14or a floor (base)101can be changed in accordance with the amounts of driving of the stoppers50,56, and66by the actuators51,57, and67. In the example shown inFIG. 5, the allowable value is determined in accordance with the distances between the distal ends of the stoppers50,56, and66and stopper receptacles71,72, and73which receive them. Also in the example shown inFIG. 5, the actuators51,57, and67which drive the stoppers50,56, and66, respectively, are fixed on the movable portion11, and the stopper receptacles71,72, and73are formed in the fixed portion14. However, the actuators51,57, and67which drive the stoppers50,56, and66, respectively, may be fixed on the fixed portion14, and the stopper receptacles71,72, and73may be formed in the movable portion11.

In the third embodiment, the vibration control mount113includes, in the internal spaces of the gas springs15,12, and16, displacement sensors52,58, and68, respectively, which detect the sizes of the gaps between the distal ends of the stoppers and portions opposing them. The displacement sensors52,58, and68can be interpreted as relative position sensors which detect the relative position between the fixed portion14and the optical system support112serving as the structure. The displacement sensor52can be supported by a support member53and accommodated in the internal space of the gas spring15. The displacement sensor58can be supported by a support member59and accommodated in the internal space of the gas spring12. The displacement sensor68can be supported by a support member69and accommodated in the internal space of the gas spring16.

The actuators51,57, and67can be controlled based on the outputs from the displacement sensors52,58, and68so that the distances between the distal ends of the stoppers50,56, and66and the stopper receptacles71,72, and73correspond to the allowable level.

The exposure apparatus preferably further includes a vibration sensor which detects the vibration of the floor (base)101which supports the exposure apparatus. The actuators51,57, and67can be controlled so as to decrease the allowable level if the vibration sensor has detected vibration in excess of a prescribed value. Alternatively, the actuators51,57, and67may be controlled so that the fixed portion14supports the optical system support112through the stoppers50,56, and66(especially, the Z-direction stopper50) if the vibration sensor has detected vibration in excess of a prescribed value.

FIG. 6is a view schematically showing a vibration control mount113in an exposure apparatus according to the fourth embodiment of the present invention. The exposure apparatus according to the fourth embodiment has an arrangement in which a kinematic holding mechanism61is added to the vibration control mount113in the exposure apparatus according to any one of the first to third embodiments.FIG. 6illustrates an arrangement in which a kinematic holding mechanism61is added to the vibration control mount113according to the first embodiment as one example. In this case, a support frame includes three columns.

The kinematic holding mechanism61is typically formed in a stopper receptacle which receives a Z-direction stopper10, and restricts the position of an optical system support112serving as the structure in the X and Y directions (horizontal direction) in supporting the optical system support112by the stopper10. A combination of a V-shaped groove, a flat surface, and a conical groove, for example, is used as the kinematic holding mechanism61. However, the present invention is not particularly limited to this, and a known kinematic holding mechanism can be adopted.

FIG. 7is a view schematically showing the structure of a vibration control mount113in an exposure apparatus according to the fifth embodiment of the present invention. The exposure apparatus according to the fifth embodiment has an arrangement in which shock-absorbing members81,82, and83are added to the vibration control mount113in the exposure apparatus according to any one of the first to fourth embodiments.FIG. 7illustrates an arrangement in which shock-absorbing members81,82, and83are added to the vibration control mount113according to the third embodiment as one example.

The shock-absorbing members81,82, and83reduce the shock of collision between stoppers50,56, and66and stopper receptacles71,72, and73which receive them as the stoppers restrict the position of an optical system support112. The shock-absorbing members81,82, and83may be arranged at the distal ends of the stoppers50,56, and66(portions opposing the stopper receptacles71,72, and73) or located in the stopper receptacles71,72, and73. Although rubber, for example, is preferably used as the materials of the shock-absorbing members, the present invention is not particularly limited to this, and ceramics or a metal may be used.

A device manufacturing method according to the preferred embodiments of the present invention is suitable for the manufacture of devices (e.g., a semiconductor device and liquid crystal device). This method can include a step of exposing a substrate coated with a photoresist to light by using the above exposure apparatus, and a step of developing the substrate exposed in the exposing step. In addition to the above steps, the device manufacturing method can include other known steps (e.g., oxidation, film forming, evaporation, doping, planarization, etching, resist removing, dicing, bonding, and packaging steps).

This application claims the benefit of Japanese Patent Application No. 2008-024258, filed Feb. 4, 2008, which is hereby incorporated by reference herein in its entirety.