Exposure apparatus and method for operating the same

AN EXPOSURE APPARATUS AND A METHOD OF OPERATING AN EXPOSURE APPARATUS

1 is a plan view of a stage guided by a window frame;

2 is a side view of a guide, stage and associated structures;

Figures 3a and 3b are enlarged views of a portion of the structure of Figure 2;

Fig. 4 is a plan view of a photolithographic apparatus requiring a stage by means of a guide;

Fig. 5 is a side view of the photolithographic apparatus of Fig. 4;

Figures 6a and 6b is a connecting portion for connecting the window frame member.

*Explanation of symbols for main parts of the drawing*

10 : Stage 14 : Interference mirror

24 : Reticle 26 : Reticle vacuum groove

28 : chuck plate 32: base structure

36 : Air bearing 40 : Window frame member

44 : connecting member 46 : guide

50 : air bearing 52 : air bearing

60 : motor coil 64 : guide

68 : motor coil 70 : magnetic track

80 : outer structure 90: fixture

92 : projection lens

<background-art><p>BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision motion stage, and more particularly, to a stage for use in photolithography, and in particular to a stage suitable for use for supporting a reticle.</p><p>Photolithography is a well-known field, particularly used in semiconductor manufacturing. In a photolithographic apparatus, a stage (XY motion apparatus) supports a reticle (ie, a mask), and another stage supports a semiconductor wafer, that is, a workpiece to be processed. Sometimes a single stage is installed on the wafer or mask.</p><p>Such a stage is indispensable for precise movement in the X-axis and Y-axis directions, and a minute movement is performed for adjustment in the vertical direction (Z-axis). A reticle stage on which a reticle is scanned in a scanning exposure apparatus is generally used, and a smooth and precise scanning motion is executed there, and a small displacement motion perpendicular to the scanning direction and a small yaw (rotation) on the XY plane are controlled. This ensures accurate alignment with respect to the reticle wafer.</p></background-art><tech><p>Conventionally, it has been desirable for such an XY stage to be relatively simple to reduce cost, to be manufactured from commercially available components, and to maintain the desired precision. Also, many prior art stages have guide structures disposed directly below the stage itself. However, this is undesirable for the reticle stage as it is essential that the light beam be directed through the reticle and the stage itself, to a projection lens installed underneath the reticle. Therefore, since the stage itself must form a very large central passage due to the light beam, a stage not provided with a guide directly under the stage itself is required.</p><p>Also, many prior art stages do not drive the stage past the center, which is undesirable, causing torsional motion in the stage, which degrades the frequency response of the stage motion. An object of the present invention is to provide an improved stage in order to solve the above problems. The present invention is particularly suitable for a reticle stage.</p></tech>

<p>In order to achieve the above object, the present invention provides a stage mechanism capable of precision movement, a base forming a main surface, a movable stage disposed on the main surface of the base, and first, second, third and fourth The stage is surrounded from the side by a sash member, and first and second sash members facing each other are in slidable contact with the stage, and the third facing each other. and first and second guides for slidably supporting the fourth window frame member, respectively.</p><p>According to another aspect of the present invention, the window frame is configured such that the first and second window frame members are connected to the third and fourth window frame members from the connecting member, respectively.</p><p>According to another aspect of the present invention, the connecting member has a plurality of metal strips, and the plurality of metal strips is configured to be installed in an X shape.</p><p>According to another aspect of the present invention, in the stage mechanism, a plurality of fluid bearings are provided, and the fluid bearings are provided below the stage to face the base.</p><p>According to another aspect of the present invention, in the stage mechanism, the third and fourth window frame members are respectively provided and have at least two or more fluid bearings facing each of the first and second guides.</p><p>According to another aspect of the present invention, in a stage mechanism, a first driving means is provided on each of the third and fourth window frame members, the first driving means driving the window frame with respect to the first and second guides. made up of</p><p>According to another aspect of the present invention, in the stage mechanism, the structure is provided with the second driving means provided on the base and acting together with each of the first driving means.</p><p>According to another aspect of the present invention, in a stage mechanism, first and second Each of the window frame members has a configuration having a third driving means on a side facing the stage.</p><p>According to still another aspect of the present invention, a stage mechanism includes a support base for supporting the first and second guides and the third and fourth window frame members, the support base being configured to be supported independently from the base. lost.</p><p>According to another aspect of the present invention, in an operation method for operating a stage capable of precise motion in two orthogonal directions, the stage is disposed on the base, and the stage is slidably contacted with the stage by using a frame. and driving the stage in a first direction of two orthogonal directions to the base and driving the stage in a second direction of two orthogonal directions to the frame, surrounding from the side. It was done in a way that</p><p>According to another aspect of the present invention, in a frame structure having a deformable hinge attached thereto, with four rigid frame members arranged in a quadrilateral shape, each frame member is adjacent to each end of the frame member. The four rigid frame members forming an acute-angle structure adjacent to the same acute-angle structure of the member, and a plurality of connecting members connecting each of the two adjacent acute-angle structures, including a connecting member installed in an X shape, consisted of a</p><p>In accordance with another aspect of the present invention, the connection is constructed of stainless steel thinner than 0.05 inches.</p><p>That is, the precision motion stage mechanism of the present invention has a stage itself that moves on the XY plane on a flat base. The side of the stage is surrounded by four frames (hereinafter referred to as sash members) formed in a window shape. The window frame member forms a quadrangular structure (hereinafter referred to as a window frame) assembled at or near the corner. That is, the window frame is formed by connecting four window frame members. The connecting member that performs the connection is the connecting portion, which is a special type of hinge (hinge) in which the quadrilateral moves slightly deforming. That is, a square or a rectangle can be transformed into a parallelogram by this connecting member. In one form, these connections are thin strips of stainless steel attached in an 'X' shape, with the desired amount of hinge movement between two adjacently connected sash members. (Details will be described later with reference to FIG. 6 )</p><p>The sash is driven by motor coils attached to two opposing members of the sash member acting together with magnetic tracks fixed on the substrate, and against two spaced apart, parallel fixed guides, for example, Move the base phase in the X-axis direction.</p><p>The sash actually tracks the stage motion and sends the magnetic track needed for the stage motion in the Y direction (here we are citing the X and Y axes, but this is merely for the purpose of explaining the orientation with respect to this drawing and is constrained to be limited. It will be understood that it does not).</p><p>The stage movement in the direction perpendicular to the movement direction of the window frame (Y axis direction) is It is performed by a stage that moves along a member other than the frame. The stage is driven relative to the sash by a motor coil attached to the stage and cooperating with magnetic tracks attached to the two connected members of the sash.</p><p>To minimize friction, the stage is supported on the base by air bearings or other fluid bearings attached to the underside of the stage. Likewise, the fluid bearing supports the sash member to its fixed guides. In addition, the fluid bearing is loading the sash member against the fixed guide and loading the stage against the sash. To enable slight yaw motion (rotation in the XY plane of the Z-axis rotation), these rod bearings are attached with a spring. The stage itself forms a central passage. The reticle is placed on a chuck attached to the stage. In general, a light source from an illumination source disposed above the reticle proceeds to a projection lens disposed through a central passage passing through the reticle.</p><p>The stage of the present invention is not constrained to support a reticle by appropriate modifications, can also be used as a wafer stage, and is not actually limited to photolithography applications and is generally suitable for precision stages.</p><p>Another feature of the present invention is that the reaction force between the stage and the drive motor driving the window frame is not sent to the support frame of the photolithographic apparatus, but is independently transmitted to the ground surface by an independent support structure. Therefore, the reaction force generated by the stage motion is Does not cause undesirable motion in the element.</p><p>By thus isolating the reaction forces of the stage from the projection lens or associated structure, these reaction forces are prevented from oscillating the projection lens or associated structure. These structures are equipped with an interferometric device for determining the exact position of the XY plane stage and the wafer stage. A reticle stage instrument support is supported independently, spaced apart from elements other than the photolithography machine, and extends to the ground surface.</p><p>This advantage is that the reaction force generated by the operation of the four motor coils moving the stage and the window frame guide is transmitted through the center of the stage, thereby reducing the moment of force (ie, torque). The controller that controls the power to the four drive motor coils takes into account the relative position of the stage and the window frame, and balances the drive force according to the differential drive method.</p><p>Fig. 1 shows a plan view of a stage mechanism according to the present invention. Reference is also made to the co-continuous U.S. patent application filed on April 1, 1994, filed April 1, 1994, entitled 'Guided Stage with Insulated Reaction Stage', filed April 1, 1994, entitled 'Guided Stage with Insulated Reaction Stage'. The present patent application is hereby incorporated by reference and shows a related method of supporting the elements of the stage mechanism, isolating reaction forces from the projection lens and other parts of the lithographic apparatus.</p><p>The stage 10 (plan view) is a rectangular structure made of a rigid material (eg, steel, aluminum, or ceramic). Two interferences placed on stage 10 The system mirrors 14A, 14B interact as usual with the respective laser beams 16A, 16B. In general, laser beam 16A is two sets of laser beams, laser beam 16B is a set of laser beams, and these laser beams relate to three distance measurements. At the lower side of the stage 10, a raised portion 22 is formed (indicated by a dotted line, but not visible in the drawing). That is, the stage 10 is formed so as to cover the upper part of the projection lens 92 . (See Fig. 1).</p><p>The reticle 24 is disposed on the stage 10 and held by a conventional reticle vacuum groove 26 formed on the upper surface of the chuck plate 28 . The stage 10 also forms a central opening 30 (passage) under the reticle 24 . By means of the central opening 30 , a ray (another ray) that has passed through the reticle 24 can be incident on the projection lens 29 underneath the reticle, as will be explained in detail hereinafter. (It will be understood that the reticle 24 itself is not part of the stage mechanism.) Otherwise, if the stage mechanism of the present invention is used for anything other than a reticle stage, i.e., a wafer support, the opening 30 is unnecessary.</p><p>The stage 10 is supported on a common quadrangular base structure 32 having a smooth and flat top surface, for example, rigid, steel, or aluminum. The left and right edges of the base structure 32 (FIG. 1) are indicated by dotted lines and are overlyed by structures other than the above drawings (as described later). In the operating state, the stage 10 is not in direct physical contact with the base structure. Instead, the stage 10 is, in this embodiment, a gas bare It is supported by conventional bearings, such as a ring. In one embodiment, three air bearings 36A, 36B, 36C of the commercially available type are used.</p><p>In other air bearing/vacuum structures, the vacuum portion is adjacent and physically separated from the air bearing portion. Vacuum and compressed air are sent through the tubules between the normal tube bundle and the piping system of the inner tubules (not shown in the drawings for the sake of brevity). Accordingly, in the operating state, the stage 10 is floating on the air bearings 36A, 36B and 36C, about 1 to 3 micrometers above the flat upper surface of the base structure 32. It will be appreciated that other types of bearings (eg, air bearing/magnetic combination types) may be used instead.</p><p>The stage 10 is surrounded on the sides by a window frame, which is a quadrangular structure composed of four window frame members. The four sash members shown in Fig. 1 are, in the figure, an upper sash member 40A, a bottom sash member 40B, a left sash member 40C, and a right sash member 40D. These four window frame members 40A to 40D are made of a material having a high intrinsic rigidity (rigidity/density ratio), such as aluminum or a synthetic material. The four window frame members 40A to 40D are attached together by a hinge structure (connection member). That is, they are integrally connected through the connection member. Thereby, the non-fixing movement of the four window frame members with each other in the XY plane and the Z-axis rotation, also referred to as a yaw motion shown in the drawing, is performed. The hinge is described in detail later. Each hinge 44A, 44B, 44C, 44D is, for example, one or more metallic connections that allow for slight bending of the window frame.</p><p>The window frame is supported on the horizontal surfaces of the fixed guides 46A, 46B and moves along the X axis (left and right in Fig. 1) supported on the vertical surfaces of the fixed guides 64A, 64B. (It will be appreciated that each set of fixed guides 46A, 64A and 46B, 64B is, for example, a single L-shaped fixed guide, or other shaped fixed guides may also be used.) Two air Bearings 50A and 50B are attached to the sash member 40A, and by this air bearing, the sash member 40A is supported on the supporting fixed guide member 46A and moves. Similarly, the air bearings 52A, 52B are attached to the sash member 40B, whereby the sash member 40B is supported on the fixed guide member 46B on which it is supported and moves. The air bearings 50A, 50B, 52A, 52B are similar to the air bearing 36A and the like.</p><p>The window frame is driven along the X axis of the fixed guides 46A, 46B and 64A, 64B by a conventional linear motor. The linear motor has a motor coil 60A attached to a window frame member 40A. The motor coil 60A moves a magnetic track 62A disposed on (or along with) the fixed guide 64A. Similarly, the motor coil 60B attached to the window frame member 40B moves the magnetic track 62B disposed on the fixed guide 64B. The motor coil and track assembly was manufactured by Trilogy, Webstano, Texas, Part No. It is an LM-310. The tracks 62A and 62B are, respectively, a plurality of permanent magnets fixed integrally. The electric wire connected to the motor coil is not shown, but is an ordinary electric wire. Other types of linear motors may be used instead. Since the position of the motor coil and magnetic track of each motor can be changed, for example In other words, the magnetic track has the handicap of lowering its performance, but it is also possible to arrange the magnetic track on the stage 10 and the corresponding motor coil on the window frame member.</p><p>Similarly, the stage 10 moves along the Y axis of FIG. 1 by motor coils 68A and 68B respectively attached to the left and right edges of the stage 10 . The motor coil 68A moves the magnetic track 70A attached to the window frame member 40C. The motor coil 68B moves the magnetic track 70B attached to the window frame member 40D. </p><p>Air bearings 72A, 72B and 72C are shown in FIG. 1 . An air bearing 72A is disposed on the sash member 40A, and the friction between the sash member 40A and the guide 64A to which the sash member is fixed is minimized. By using a single air bearing (72A) at one end and two opposing air bearings (72B, 72C) at the other end, a certain amount of yaw motion (rotation in the XY plane of the Z axis rotation) and movement along the Z axis are possible. becomes In this case, in general, the air bearing 72A is mounted by a gimbal (cruciform suspension device), in order to limit the amount of misalignment between the window frame member 40A and the fixed guide 64A, Alternatively, it is movably mounted to a gimbal disposed on the connection part.</p><p>By using the air bearings 72A opposite the bearings 72B and 72C to each other, it is possible to provide a rod effect for maintaining the window frame guides in proper relation with the fixed guides 64A and 64B. Likewise, the air bearing 76A weights the opposing air bearings 76B, 76C, both attached to the side of the stage 10, the stage 10 relative to the opposing sash members 40B, 40D. properly positioned all. In other words, in this case, one air bearing, such as 76A, is mounted by a gimbal or cross-suspended by a connecting part gimbal (spring) to give a limited amount of misalignment. The air bearings 72A, 72B, 72C and 76A, 76B, 76C are conventional air bearings.</p><p>The outer structure 80 of FIG. 1 is a base support structure for the guides 46A, 46B, 64A, 64B to which the stage mechanism is fixed and the window frame members 40A, 40B, 40C, and 40D. In this way, since the resting support is divided, the reaction force to the base support structure is not transmitted to the stage base structure 32 . The base support structure 80 is supported on the foundation, ie the ground or the building floor, by its own support posts or other common support elements (not shown in this figure). Examples of suitable support structures can be found in the cited U.S. Patent Application No. 1, 1B, 1C of 08/221,375. The independent support structure of this part of the stage mechanism separates the reaction force of the drive motor of the reticle stage mechanism from the frame supporting other elements of the photolithographic apparatus, in particular from the optical element with the projection lens 92 and the wafer stage. It has the above advantages of being separated and transmitted, thereby minimizing the vibration force to the projection lens due to the motion of the reticle stage. This will be explained later in detail.</p><p>The driving force of the stage mechanism is applied past as close as possible to the center of the stage mechanism. As will be understood, the center of the stage mechanism is moved by the stage 10 . Therefore, the stage 10 and the window frame guide are combined to forming a center of gravity. The motor coils 60A, 60B control the force applied by each motor coil 60A, 60B in consideration of the position of the sash guide, so as to maintain an effective force applied to the center. Another conventional type differential drive controller of the motor coils 68A and 68B is put in consideration of the position of the stage 10, and controls the force applied by each motor coil 68A, 68B so that the effective force is applied to the center. keep it going Since the stage 10 performs a large range of motion, it will be understood that the differential driving of the motor coils 60A and 60B includes a wide differential fluctuation. In contrast to this, the sash guide does not change at all, so the differential drive of the motor coils 68A, 68B contains much smaller differential fluctuations, giving a balancing effect. Advantageously by using a window guide, the reaction forces generated by the motion of the reticle stage mechanism are kept in a single plane, thus facilitating isolating these forces from parts other than the photolithographic apparatus.</p><p>FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 . Structures shown in FIG. 2 that are also present in FIG. 1 have the same reference numerals and are not described herein. An illuminator 90 is shown in FIG. 2 , which is a common element and is not shown in detail here and is omitted from FIG. 1 for the sake of brevity. The projection lens upper part (cylindrical) 92 is not shown in detail either in FIG. 2 . Elements other than the lower portion of the projection lens 92 and the photolithographic apparatus are not shown in FIG. 2, but are illustrated and described later.</p><p>The support structure 94 of the projection lens 92 is also shown in FIG. As shown, the structure 94 is separated in all parts from the base support structure 80 of the reticle stage mechanism by a slight void 96 . The air gap 96 insulates vibrations generated by the motion of the reticle stage mechanism from the projection lens 92 and its support 94 . As shown in FIG. 2 , the stage 10 is not a flat structure in the present embodiment, but accommodates the upper part of the lens 92 and forms a raised portion 22 at the lower side. A magnetic track 70A is attached to the top of the window frame guide 40B, and similarly, a magnetic track 70B is attached to the top of the window frame member 40D facing each other.</p><p>3A and 3B are enlarged views of a portion of FIG. 2 having the same reference numerals. FIG. 3A is the left side of FIG. 2 , and FIG. 3B is the right side of FIG. 2 . The spring attachment tool 78 of the air bearing 76A is shown in FIG. 3B. The air bearing 78A is mounted on the side surface of the stage 10 by a spring, whereby a certain amount of yaw (rotation in the XY plane of the Z-axis rotation) and limited movement along the Z-axis are possible. A gimbal mount may be used in place of or in addition to the spring 78 . A limited amount of misalignment between stage 10 and window frame members 40C, 40D (not shown in Fig. 3A) is possible by spring or gimbal mounting.</p><p>4 is a plan view of the photolithographic apparatus having the stage mechanism of FIGS. 1 and 2 , but this is a support base structure 100 supporting the photolithographic apparatus having a frame 94 excluding the reticle stage mechanism in addition to the elements shown in FIG. ) has (The structures shown in Fig. 1 are all marked in Fig. 4 for the sake of brevity. The base structure 100 supports four vertical support posts 102A, 102B, 102C, 102D connected to the structure 94 by bracket structures 106A, 106B, 106C, and 106D, respectively. The size of the base structure 100 is quite large, in one embodiment about 3 meters from top to bottom. Each of 102A, 102B, 102C, 102D has a common servo mechanism (not shown) inside for leveling. The supports 108 and 110 of each laser interferometer (beam splitter, etc.) 112A, 112B, 112C are also shown in FIG. 4 . FIG. 4 will be understood with reference to the cross-sectional view of FIG. 5 taken along section line 5-5 of FIG. 4 .</p><p>4 and 5 , the size of the support structure 94 is shown with the support posts 102A, 102C lying on the base structure, all in contact with the ground via a common foundation (not shown). The reticlestage base support structure 80 is only shown in FIG. 4 (for brevity) and likewise has a set of four posts 114A, 114B, 114C, 114D with connected bracket structures 116A, 116B, 116C, 116D. ), whereby the column extends from the height of the base support structure 80 to the base structure 100 .</p><p>At the bottom of FIG. 5 , support structures 122 , 124 connected to the wafer 120 are shown. The elements of the wafer stage 120 usually consist of a base, the stage itself, a fixed stage guide disposed on the base, a magnetic track disposed on the fixed stage guide, and a motor coil mounted on the magnetic track and connected to the stage itself (as shown in the drawing). not shown), the laser beam from the laser 124 attached to the support 126 is The lens 92 and the stage itself are positioned by an interferometer.</p><p>FIG. 6a is a plan view (corresponding to FIG. 1 ), showing one, eg 44C detail, of a joint structure hinged with a sash guide. Each of the hinges 44A, 44B, 44C, 44D is identical. These joint hinges are more than mechanical type hinges that do not require smoothness, exhibit hysteresis (unless the joint is more curved than its mechanical tolerances), have no mechanical 'slope' and, moreover, are inexpensive to manufacture. have an advantage</p><p>Each individual joint is, for example, 1/4 hardness 302 stainless steel, approximately 20 m (0.02 in) thick, and can withstand up to 0.5 degrees of flex. The width of each joint is not strict, the typical width is 0.5 inches. Two, three or four connections are used for each hinge 44A, 44B, 44C, 44D of FIG. 1 . The number of connections used for each hinge is essentially determined by the amount of voids available, i.e., the height of the sash member. Each of the four connections 130A, 130B, 130C, 130D shown in FIG. 6A (or in the 90 degree rotation diagram of FIG. 6B ) is connected to the clamps 136A, 136B, 136C, 136D with a common screw 134 . window frame members adjacent by (Figs. 6a, 6b) fixed to the frame members 40B and 40D in ) by the The screw is fixed to the corresponding threaded hole of the window frame member 40B, 40D through the hole and clamp of each of the connecting portions 130A, 130B, 130C, 130D.</p><p>The window frame members 40B, 40D of Figs. 6A and 6B are slightly different from Fig. 1 with respect to the acute angle (triangular) structure at the ends of the window frame members 40B, 40D, and there It is worth noting that the connections 130A, 130B, 130C, 130D are mounted. In the embodiment of Fig. 1, this acute-angled structure is omitted, but the existence of these makes it easy to screw the connection part.</p><p>In another embodiment, the frame guide is not hinged, but is a rigid structure. To maintain this rigidity and prevent mating, one of the bearings (72C or 72B) has been disassembled, and the other bearing is moved to the center and mounted as a gimbal without a spring. Other bearings (except for the bearings attached to the stage 10) are also mounted as gimbals.</p><p>The present invention has been illustrated, but not limited, and other modifications will be apparent to those skilled in the art in light of the present invention and do not depart from the scope of the appended claims.</p>

<p>As described above, according to the stage mechanism and operation method of the present invention, a guide that does not block light (exposure light that projects the reticle) is provided on the stage to drive the stage, and there is no need to provide a large opening to the stage. can drive</p><p>In addition, according to the present invention, it is possible to prevent the torsional motion of the stage from occurring, and it is possible to improve the frequency response of the stage motion.</p>