JPH0134746B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a stage control device that performs precise position control and posture control, and includes parallel movement in three-dimensionally set three-axis directions, and The present invention relates to a control device having rotation around and six degrees of freedom. The present invention is particularly suitable as a wafer mounting positioning mechanism for a floodlight type wafer exposure apparatus, but can also be widely applied to precision processing, precision measurement, etc.

[Prior art]

The above-mentioned control device having six degrees of freedom is also used in a projection exposure device that prints a mask pattern on a wafer surface. In the operating procedure of the apparatus, first, it is necessary to project and image a mask pattern onto the surface of a wafer, which is a workpiece, using a projection optical system. The range in which the projection optical system images a high-resolution mask pattern required for the projection optical system is the range near the focal plane of the projection optical system, and the imaging condition deteriorates rapidly as the distance from the focal plane increases. In practice, the tolerance for deviation of the wafer surface from the focal plane of the projection optical system is ±6 μm, and in order to obtain stable resolution, it is necessary to position the wafer surface with high precision on the focal plane of the projection optical system. required. After the above positioning (focusing), the mask pattern and the pattern formed on the wafer surface are moved with high precision (±
0.25 μm) is required. Therefore, the wafer loading device requires a position control function that provides six degrees of freedom in total.

The above six degrees of freedom control is usually performed by setting two horizontal orthogonal axes X, Y and a vertical axis Z, and performing parallel movements in these three axes directions and rotations around the three axes. As a result, the position and orientation of the rigid body in the three-dimensional space are determined. However, the above 3
The axes are not limited to three orthogonal axes, horizontal and vertical, but it is also possible to set three oblique axes to perform six degrees of freedom control.

FIG. 1 shows a schematic front view of a conventional 1:1 reflection projection exposure apparatus.

The stone surface plate 1 is finished with high precision, and the thread 2 moves left and right on the stone surface plate 1 with high precision (±0.08μm).
perform a linear motion. A wafer loading device 3 and a mask loading device 5 are provided on the sled 2, and are capable of loading a wafer 4 and a mask 6, respectively. Further, a reflection projection optical system 7 and an alignment scope 8 are fixed on the stone surface plate 1, and a height reference plate 9 is fixed below the reflection projection optical system 7. The mask pattern of the mask 6, which is illuminated in the shape of an arcuate slit by an illumination optical system (not shown) located below the stone surface plate 1, is projected onto the surface of the wafer 4 by the reflection projection optical system 7. By moving the mask pattern 2 left and right, it is possible to scan and expose the entire surface of the wafer 4 with a mask pattern. The alignment scope 8 has a function of detecting the overlapping state of the alignment mark on the wafer 4 and the alignment mark in the mask pattern.

FIG. 2 shows an enlarged sectional view of the wafer loading device 3 described above. A base 11 of the wafer mounting device is fixed to the aforementioned sled 2, and an XY stage 12 is placed on the wafer mounting device base 11 via a steel ball 16. XY stage 1 above
2 can move freely within a horizontal plane along the upper surface of the base 11 and has two degrees of freedom. The position of this XY stage 12 is controlled within a range of ±3 mm by a feeding mechanism (not shown) in the thread running direction (Y direction) and in the direction perpendicular to this in the horizontal plane (X direction). There is. this
A θ stage 13 is rotatably provided on the XY stage 12 via a ball bearing 17, and a vertical shaft 14 is further provided on this θ stage B. This vertical shaft 14 has a structure in which it is driven vertically by a nut 19, a feed screw 18, and a pulse motor 20.
This is a member that acts as a Z stage. The vertical shaft 14, which is the Z stage, is fixed to the θ stage 13 so as not to rotate, and is supported so as to be vertically slidable.

At the top of this vertical shaft 14, a wafer mounting table 15 is provided.
is placed, and a conical recess at the upper end of the vertical shaft 14,
and the lower spherical seat of the wafer mounting table 15,
The wafer mounting table 15 can be tilted freely.

In this way, the conventional wafer loading device has a wafer loading device base 11 fixed on the sled.
An XY stage 12 is provided, and this XY stage 12
The θ stage 13 is supported by the θ stage 13, which supports the vertical axis 14 and the wafer mounting table 15.
In addition, the wafer 4 was supported in a triple structure.

Next, the operation of this conventional wafer loading apparatus will be explained. First, in the state shown in Figure 2,
The wafer 4 is vacuum suctioned onto the wafer mounting table 15 using the suction hole 22 . Subsequently, the vertical shaft 14 is raised, and the surface of the wafer 4 is pressed against the pad 10 of the height reference plate 9. Then, the inclination of the wafer mounting table 15 is corrected by the reaction force from the pad 10, and it assumes a horizontal position. The above-mentioned pad 10 is placed at the vertex of an equilateral triangle whose center of gravity is the center of the wafer 4, and is placed at a position exactly a specified height (0.5 mm) higher than the focal plane of the catoptric projection optical system 7. Therefore, the surface of the wafer 4 is positioned in height and inclination at a position higher than the focal plane of the reflection projection optical system 7 by the above specified height. In this state, the vacuum chamber 21 is evacuated and the wafer mounting table 15 is suctioned and fixed to the vertical shaft 14, and then the vertical shaft 14 is lowered together with the wafer 4 and the wafer mounting table 15 by the above specified height, so that the wafer surface is reflected. It was moved in parallel to within the depth of focus of the projection optical system 7.

After the above-described operation, the XY stage 12 is moved and the θ stage 13 is rotated to align the alignment mark provided on the wafer 4 with the alignment mark of the mask pattern. In this state, the sled 2 was once moved to the forward side, and then the entire surface of the wafer 4 was exposed with a mask pattern while returning at a constant speed on the return path, and the mask pattern was printed onto the surface of the wafer 4. This resulted in the following drawbacks.

1. After pressing the surface of the wafer 4 against the pad 10 to make it parallel to the focal plane of the reflection projection optical system 7, move it at three locations: the vertical axis 14 (Z stage), the θ stage 13, and the XY stage 12. Or, since the stage is rotated, the vertical movement and inclination due to mechanical errors in these three stages are superimposed, impairing the positioning accuracy of the parallelism and height of the wafer 4 surface with respect to the focal plane of the catoptric projection optical system 7. Cheap.

2 An XY stage 12, a θ stage 13, and a Z stage 14 are mounted on the wafer mounting device base 11.
Since the wafer mounting table 15 is placed on the wafer mounting table 15, the overall positioning rigidity from the wafer mounting device base 11 to the wafer mounting table 15 is low, and the positional stability of the wafer mounting table 15 is poor.

3. Since the XY stage 12 includes the θ stage 13, the vertical shaft 14, and driving means for these, the overall weight of the XY stage 12 is large. Therefore, the XY stage feeding mechanism must drive and control the XY stage 12 that carries the entire weight of the XY stage, reducing the controllability of fine movement feeding.

Furthermore, regarding a stage for positioning a wafer, a technique described in Japanese Patent Application Laid-Open No. 144636/1983 is known. This known technology aims to reduce the weight of moving parts.
This is a mechanism that consolidates three degrees of freedom (x, y, θ) in a plane into one table.

In such a configuration, in order to perform the above-mentioned focusing of the wafer, it is clearly necessary to add a total of three degrees of freedom: translation in the z direction and rotation around the x and y axes. For this reason, if a feeding mechanism is provided above or below the mechanism that has a degree of freedom for translation in the z direction and rotation around the x and y axes,
Although the wafer can be focused, tables with different degrees of freedom are still stacked, and the desired reduction in the weight of the moving parts cannot be achieved. In addition, if you try to directly move the table of this mechanism in three directions: parallel translation in the z direction and rotation around the x and y axes, the simple feeding mechanism of the table of the mechanism cannot move in these three directions. Since these three degrees of freedom are not provided, it is difficult to add a feeding mechanism with these three degrees of freedom, and the wafer cannot be focused.

[Purpose of the invention]

An object of the present invention is to provide a stage control device that can control each of the six degrees of freedom of the stage with high precision, has high positioning rigidity, and has good controllability.

[Summary of the invention]

In the present invention, based on the above-mentioned problems with the conventional device and analysis of their causes, six sets of feeders are provided to drive and control the stage, and these six sets of feeders directly drive the stage without interfering with each other. This is a creation of a configuration that can be controlled.

In order to achieve the above object based on the above principle, the present invention includes a set of feeding mechanisms provided in the X direction;
It has two sets of feed mechanisms provided in the Y direction and three sets of feed mechanisms provided in the Z direction, and a displacement of the feed mechanism is provided between each of the six sets of feed mechanisms and the stage. A transmission mechanism that allows displacement in two directions perpendicular to the feed direction, rotation around the feed direction, and rotation around the two directions perpendicular to the feed direction is installed at the point where the transfer occurs and comes into contact with the stage. The present invention is characterized in that each of the six sets of feeding mechanisms is configured to be able to directly drive the stage independently.

[Embodiments of the invention]

Next, an outline of an embodiment of the present invention will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a vertical sectional view of the stage control device of the present invention, and FIG. 4 is a plan view thereof.

In this embodiment, the stage 42 holding the wafer 4 by suction is configured to perform position control in two horizontal orthogonal axes X, Y and vertical axis Z directions, as well as rotational posture control around the above three axes. but,
When implementing the present invention, it is also possible to control not only three orthogonal axes but also three axes in arbitrary directions.

41 is the base of the wafer mounting device. This base 41 is equipped with one pulse motor 46 for configuring one set of X-direction feeding mechanisms, two pulse motors 60 (Fig. 4) for configuring two sets of Y-direction feeding mechanisms, and three sets. Three pulse motors 52 (FIG. 3) for configuring the Z direction feeding mechanism are fixed. Feed screws 45, 59, 51 are fixed to the shafts of these pulse motors 46, 60, 52, respectively. Nut members 44, 58, and 50, which are screwed onto the feed screws 45, 59, and 51, respectively, are fitted so as to be slidable in the axial direction while locking their rotation relative to the wafer mounting device base 41.

In this embodiment, the 1
Two sets of sending mechanisms are provided in the Y direction, and three sets of sending mechanisms are provided in the Z direction.

A cavity 55 for vacuum suction is provided on the upper surface of the stage 42.
is installed to provide a wafer loading function. The weight of the stage 42 is supported by three nut members 50 via a floating pad 49 and a steel ball 48, which will be described later with reference to FIG. 53 is a spring that biases the above-mentioned own weight.

The above-mentioned stage 42 is installed in the spring 4 in the X direction.
7, press against the nut member 44 via the floating pad 43, which will be described in detail later with reference to FIG.
A directional positioning is made. Similarly, a spring 61 provided in the Y direction presses against the nut member 58 via a floating pad 57, which will be described later, to position the nut member 58 in the Y direction.

Nine capacitive proximity sensors 54 are fixed to the bottom surface of the reflective projection optical system 7 to detect the surface position of the wafer 4 and increase the deviation between the top surface of the wafer 4 and the focal plane of the optical system 7. It is configured to enable non-contact detection with accuracy (±0.2 μm). The nine X marks 56 shown on the surface of the wafer 4 in FIG.
4 detection points are shown.

Details of the aforementioned floating pads 49, 43 will be explained with reference to FIG. Although the floating pad 57 provided in the Y-direction feeding device is not shown in this cross section, it is a component similar to the floating pad 43 of the X-direction feeding device shown in this figure. This floating pad 43 is
The spherical surface at the left end is held by the spherical seat of the nut 44, and the flat surface at the right end is brought into contact with the side surface of the sludge 42 to transmit the feed amount of the feed mechanism to the stage 42. Furthermore, since the spherical and flat surfaces at both ends of the floating pad 43 act as air bearings, they do not create resistance to the vertical movement, forward/backward movement, or inclination of the stage 42 around the X, Y, and Z axes. Therefore, the floating pad 43 has a degree of freedom that does not resist movement of the stage by other feed mechanisms, and at the same time can transmit a corresponding feed amount in the x-axis direction.

The upper surface of the nut member 50 of the Z direction feeding mechanism is made to be precisely parallel to the focal plane of the reflection projection optical system 7. The lower surface of the floating pad 49 that comes into contact with the upper surface of the nut member 50 is an air bearing, and the floating pad 49 can horizontally move on the upper surface of the nut 50 with almost no resistance.
has a sufficiently small diameter, and the frictional force between the steel ball 48 and the conical surface of the stage 42 or the floating pad 49 can be almost ignored. Therefore, the steel ball 48 and the floating pad 49 transmit the feed amount in the Z direction to the stage 42, and at the same time do not act as resistance to the movement and tilting of the stage 42 in the horizontal plane by other feeding mechanisms. A tube 62 supplies air to the floating pads 43 and 49.

In this embodiment, as described above, only the force in the feeding direction of each feeding mechanism is transmitted between each of the nut members of the six sets of feeding mechanisms and the stage 42, and movement in directions other than the feeding direction is permitted. A transmission mechanism is interposed so that each of the six sets of feeding mechanisms can drive the stage 42 independently.

Next, a method of using the stage control device configured as described above will be explained. In this embodiment, an automatic control device (not shown) is provided to electrically and automatically operate the sensors and actuating devices as follows.

First, the wafer 4 is vacuum-adsorbed onto the upper surface of the stage 42. Next, the capacitive proximity sensor 54
The amount of deviation of the surface of the wafer 4 from the focal plane of the reflection projection optical system 7 is detected without contacting the surface of the wafer 4 at nine detection points 56 arranged in a grid pattern. Thereafter, the deviation and inclination between the approximate plane of the surface of the wafer 4 and the focal plane of the reflection projection optical system 7 are determined from the deviation amounts of these nine points. Subsequently, the three pulse motors 52 are rotated to move the nut member 50 up and down as appropriate, and the stage 42 is moved up and down and tilted to correct the above-mentioned deviation and inclination. At this time, since the floating pads 43 and 57 have the spherical and flat surfaces at both ends as air bearing surfaces, as described above, they do not provide resistance to the vertical movement and tilting of the stage 42, and
Since the steel ball 48 also has a sufficiently small diameter, it does not act as resistance to the tilting of the stage 42. Thereafter, the sensor 54 again detects the amount of deviation of the surface of the wafer 4 from the focal plane, and an operation is performed to confirm that the approximate plane of the surface of the wafer 4 coincides with the focal plane with sufficiently high accuracy. Here, if the approximate plane of the surface of the wafer 4 does not match the focal plane, the correction of the height and inclination of the stage 42 and the detection of the amount of deviation are repeated again. As mentioned above, the wafer 4 is
The height and inclination are positioned so that the approximate plane coincides with the focal plane of the reflective projection optical system 7.
That is, the three degrees of freedom of the position of parallel movement in the Z-axis direction and the rotational posture around the X and Y axes are determined. At this time, the plane determined by the center points of the three steel balls 48 becomes a correction plane for correcting the inclination of the surface of the wafer 4.

Next, the pulse motor 4 moves the alignment mark provided on the wafer 4 and the alignment mark in the mask pattern.
6 and 60, the nut members 44 and 58 are appropriately fed and brought into alignment. At this time, the floating pad 49 has its lower surface as an air bearing surface, so it does not act as a resistance to the movement of the stage 42, and the floating pads 43 and 57 also have spherical and flat surfaces on both ends as air bearing surfaces, so the movement and rotation of the stage 42 It is not a resistance. Further, the steel ball 48 supporting the stage 42 does not swing or rotate with the floating pad 49 or the conical surface of the stage 42.
Floating pad 49 with stage 42 in fixed state
The nut member 50 moves on the upper surface of the nut member 50, which is precisely parallel to the focal plane of the reflection projection optical system 7. In this case, strictly speaking, the vertical deviation occurs due to the deviation in parallelism between the top surface of the nut member 50 and the focal plane, but as in this embodiment, the top surface of the nut member 50 can be aligned with the focal plane with high precision. If they are finished in parallel, the above-mentioned deviation in the vertical direction is so small that it can be ignored even in submicron order positioning.

In this way, the stage 42 is positioned in the X direction by the pulse motor 46 that constitutes one set of feed mechanisms, and the
The stage 42 is positioned in the Y direction by the synchronous rotation of the two pulse motors 60. and,
In parallel with this operation, the two pulse motors 60
The stage 42 is rotated about the Z axis by the differential movement.

As explained above, the six sets of feed mechanisms independently and directly push the stage 42 to control the six degrees of freedom, so positioning rigidity is high. Furthermore, since the stage 42 does not carry a feeding mechanism, it is lightweight and therefore does not hinder controllability.

Furthermore, since this embodiment performs position detection on the wafer surface in a non-contact manner, there is no risk of damaging or staining the wafer surface.

In the embodiment shown in FIG. 5, using a transmission mechanism consisting of steel balls 48 and floating pads 49 for positioning in the horizontal direction, and using a transmission mechanism consisting of floating pads 43 in the vertical direction, the same effect as described above can be obtained. It will be done.

FIG. 6 is a vertical cross-sectional view showing a different embodiment from the above, in which a ball bush 64 is able to roll in the direction of the shaft 63 fixed to the stage 42 as a guide. Furthermore, a follower 65 with a spherical outer periphery is combined with the ball bush 64, which transmits the amount of feed from the nut member 66, and also moves the five stages 42: vertical movement, forward/backward movement, rotation, and tilting (in two directions). This constitutes a transmission mechanism that has a degree of freedom that does not create resistance.

Further, instead of using the combination of the ball bush 64 and the follower 65, the same effect can be obtained by using a follower having a bearing structure that allows direct movement in the axial direction and rotational movement around the axis.

The pad 67, the annular ball row 68, and the inclined pad 69 are constructed by replacing the floating pad 49 with an air bearing in the previous embodiment with an annular ball row means 68, and have the same freedom as the air bearing floating pad described above. It is obvious that the transmission mechanism has the same function and effect as the front row.

〔Effect of the invention〕

As detailed above, the stage control device of the present invention includes one set of feeding mechanisms provided in the X direction, two sets of feeding mechanisms provided in the Y direction, and three sets of feeding mechanisms provided in the Z direction. The displacement of the feed mechanism is transmitted between each of the six sets of feed mechanisms and the stage, and the displacement in two directions perpendicular to the feed direction and the axis of the feed direction are transmitted at the point where the feed mechanism contacts the stage. A transmission mechanism is interposed that allows rotation around the axis and rotation about two directions perpendicular to the feeding direction, and each of the six sets of feeding mechanisms is configured to be able to directly drive the stage independently. By doing so, each of the six degrees of freedom of the stage can be controlled with high precision, and excellent practical effects such as high positioning rigidity and good controllability are achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic front view of a reflection projection type wafer exposure apparatus, FIG. 2 is a vertical sectional view of a conventional wafer mounting apparatus, and FIGS. 3 to 5 are an embodiment of the stage control apparatus of the present invention. 3 is a vertical sectional view, FIG. 4 is a plan view, and FIG. 5 is a partially enlarged sectional view.
FIG. 6 is a partially enlarged sectional view of an embodiment different from the above. 4...Wafer, 7...Reflection projection optical system, 41
...Wafer mounting equipment base, 42...Stage,
43...Floating pad, 44...Nut member, 45
...Feed screw, 46...Pulse motor, 47...
Spring, 48...Steel ball, 49...Floating pad, 50
... Nut member, 51 ... Feed screw, 52 ... Pulse motor, 53 ... Spring, 54 ... Capacitive proximity sensor, 55 ... Cavity, 56 ... Detection point, 57 ... Floating pad, 58... Nut member,
59...Feed screw, 60 pulse motor, 61...
Spring, 62...Tube, 63...Shaft, 64...
Ball bushing, 65... Follower, 66...
Nut, 67... Pad, 68... Ball row means, 69... Inclined pad, 70... Steel ball, 71...
...Natsuto.

Claims (1)

[Scope of Claims] 1. A stage that is one movable element on which a workpiece such as a circuit board is loaded, one fixed element, and a stage arranged on the fixed element side in a certain direction along the surface of the workpiece. It has one set of feeding mechanisms, two sets of feeding mechanisms that send along the surface of the workpiece in a direction substantially orthogonal to the feeding mechanism, and three sets of feeding mechanisms that send in the thickness direction of the workpiece, The displacement of the feeding mechanism is transmitted between each feeding mechanism and the stage, and at the point where the feeding mechanism contacts the stage, displacement in two directions perpendicular to the feeding direction, rotation about the feeding direction, and feeding are performed. 6 degrees of freedom, characterized in that a transmission mechanism that allows rotation about two directions orthogonal to the direction is interposed, and the six sets of feeding mechanisms are configured to independently control the position of the stage. A stage control device having a. 2. The control device for a stage having six degrees of freedom as described in item 1, wherein at least one transmission mechanism is comprised of a ball pair mechanism and a plane sliding mechanism. 3. In the control device for a stage having six degrees of freedom as described in paragraph 1, at least one transmission mechanism is constituted by a planar rolling mechanism having a structure in which a plurality of spherical rolling elements are inserted in a plane. Features 6
A stage control device with degrees of freedom. 4. In the stage control device having six degrees of freedom as described in item 1, at least one transmission mechanism is composed of a rotation mechanism 65 having a spherical outer periphery and a mechanism 64 movable in the direction of the rotation axis of the rotation mechanism. A stage control device having six degrees of freedom, characterized in that: