JP2001044109A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the influence of the deformation of the main body structure of an aligner on the exposure accuracy. SOLUTION: An exposure device is provided with stages 2 and 5, which move while the stages 2 and 5 hold an original plate R or a substrate W to which the pattern of the plate R is transferred, a control means 14 which performs exposure treatment with respect to the original plate R or substrate W held on the stages 2 and 5, and active vibration-absorbing devices 9-11 which support a main body structure provided with the stages 2 and 5. The control means 14 performs exposure treatment by taking the drive forces 13a and 13b of the actuators of the vibration-absorbing devices 9-11 into consideration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure apparatus which eliminates or reduces the influence on exposure accuracy due to deformation of a main body structure supported by an active vibration isolator.

[0002]

2. Description of the Related Art Semiconductor exposure apparatuses (steppers, scanners)
It has recently been found that there is an adverse effect on the exposure accuracy caused by the deformation of the main body structure. Looking at the nanometer scale, no matter how rigid the body structure is,
When a force is applied there, it deforms. The main body structure is equipped with a projection optical system which can be regarded as the heart of the semiconductor exposure apparatus, a measurement meter for feedback to various positioning devices, and the like. This causes a poor exposure accuracy. In such a case, the deformation of the main body structure acts to deviate the measured values of these measuring instruments, thereby deteriorating the exposure accuracy.

More specifically, an example of a chain of adverse effects on exposure accuracy will be described below. A laser interferometer for positioning a wafer stage, which is a precision instrument, is mounted on the main body structure. In order to improve productivity, the wafer stage is driven at high acceleration and high speed. Therefore, a large driving reaction force is applied to the main body structure. Failure to properly manage this force will result in deformation of the body structure. When deformation occurs,
It also deforms the members of the laser interferometer that are rigidly connected to the body structure, which ultimately upsets the measurements. Then, the positioning of the wafer stage is performed based on the erroneous measurement value, and the exposure is performed on the wafer stage, so that the exposure accuracy is deteriorated.

[0004] That is, the active vibration isolator functions to suppress the swing of the wafer stage base supporting the wafer stage. However, if the driving reaction force to be suppressed is large and the repetition cycle is short, the vibration damping operation by the active vibration isolator cannot be performed in time, and in particular, an air spring is used as an actuator in the active support leg of the active vibration isolator. When used, it lacks the ability to quickly suppress the swinging of the wafer stage base, and thus easily generates a driving force that flexibly deforms the wafer stage base. The deformation of the wafer stage base plate is transmitted to the main body structure, thereby disturbing the positional relationship of the attached measuring instrument. For example, a wafer laser interferometer that controls the positioning of a wafer stage can be cited as one of the measurement meters. If this measured value is disturbed, the positioning accuracy of the wafer stage will be disturbed, thereby deteriorating the exposure accuracy for the wafer. Similarly, if the mounting position of the reticle laser interferometer that controls the positioning of the reticle stage fluctuates due to the deformation of the structure, it acts to degrade the positioning accuracy of the reticle stage.

[0005]

With the demand for miniaturization of semiconductor devices, the influence of the deformation of the main body structure in the above-described semiconductor exposure apparatus on the exposure accuracy cannot be ignored. Since various measuring instruments are mounted on the main body structure, the deformation of the structure naturally affects the measured values of the measuring instrument having the accuracy of the order of nanometers. Therefore, feedback based on this measurement,
Alternatively, there is a problem that when various corrections are applied, the exposure accuracy is adversely affected as a matter of course.

[0006]

In order to solve this problem, a first exposure apparatus of the present invention controls a stage that holds and moves an original plate or a substrate on which a pattern thereof is exposed, and controls the position of the stage. A control unit for performing an exposure process on an original plate or a substrate held by the stage, and an active anti-vibration device for supporting a main body structure provided with the stage, wherein the control unit includes The exposure process is performed in consideration of the driving force of the actuator of the active vibration isolation device.

A second exposure apparatus according to the first exposure apparatus, wherein the control means calculates a driving force in a deformation mode for flexibly deforming the stage based on a driving force of the actuator. Wherein the exposure processing is performed in consideration of the output of the deformation driving force calculation means.

A third exposure apparatus is the second exposure apparatus, wherein the deformation mode includes a mode in which a portion supported by the active vibration isolator is deformed into a rhombus in the horizontal direction, or a deformation in torsion in the vertical direction. Is included.

A fourth exposure apparatus according to the second or third exposure apparatus, wherein the control means corrects the position of the stage in the exposure processing while performing correction in consideration of the output of the deformation driving force calculation means. It is characterized by performing control.

A fifth exposure apparatus is the exposure apparatus according to any one of the second to fourth exposure apparatuses, wherein the control means controls the exposure in the exposure processing after the output of the deformation driving force calculation means falls within a predetermined tolerance. Is performed.

A sixth exposure apparatus is the exposure apparatus according to any one of the second to fifth exposure apparatuses, wherein the control means controls an output of the deformation driving force calculation means when controlling the position of the stage in the exposure processing. Within the tolerance of
An acceleration / deceleration profile for driving the stage or a running distance prior to scanning at a constant speed is optimized.

In a seventh exposure apparatus, in any one of the second to sixth exposure apparatuses, the parameters of the active vibration isolator are optimally selected so that the output of the deformation driving force calculating means is minimized. It is characterized by the following.

An eighth exposure apparatus is the exposure apparatus according to any one of the first to seventh exposure apparatuses, wherein the actuator of the active vibration isolator is any one of an air spring, an electromagnetic motor, and a displacement generating actuator, or any one of these. , And the driving force to be considered is a driving force by any one of the actuators or a driving force by a resultant force generated by the plurality of actuators. .

A ninth exposure apparatus is the exposure apparatus according to any one of the first to eighth aspects, wherein the active vibration isolator controls the driving force of the actuator by feeding back the driving force of the actuator. It is characterized by having a feedback loop.

In the structure of the present invention, there is a strong correlation between the deformation of the main body structure and the deterioration of exposure accuracy, and the present invention utilizes this. In other words, the driving force in the flexible motion mode for deforming the main body structure is monitored, and the meter for exposure is corrected in accordance with this amount, and as a result, the exposure accuracy due to the deformation of the main body structure is reduced. The influence of the deformation of the main body structure on the exposure accuracy is eliminated by eliminating the influence apparently.

[0016]

FIG. 1 shows a semiconductor exposure apparatus according to one embodiment of the present invention. This apparatus is a scanner in a semiconductor exposure apparatus. As shown in the drawing, the exposure light IL emitted from a light source (not shown) illuminates the reticle R in an illumination area set with uniform illuminance. The reticle stage 1 is supported on a reticle stage base 2, and a movable mirror 3 is provided on the reticle stage 1. Further, a reticle laser interferometer 4 is provided for detecting the position of the reticle stage 1 by irradiating the movable mirror 3 with a laser beam and receiving the reflected light. The reticle stage 1 is in the horizontal direction (y
Scan drive in the axial direction).

A projection optical system P is provided below the reticle stage 1.
O is arranged, and the projection optical system PO reduces and projects the circuit pattern on the reticle R onto the wafer W as a photosensitive substrate at a predetermined reduction ratio. The wafer W is placed on a fine movement stage 5a at the top of the wafer stage 5 that moves on a horizontal two-dimensional plane. The position of the wafer stage 5 can be detected by the wafer laser interferometer 7 capturing reflected light obtained by irradiating the movable mirror 6 with a laser beam. The wafer stage 5 is mounted on a wafer stage base 8. The wafer stage base 8 is supported by active support legs 9. Although not shown, since several structures are connected to the wafer stage base 8, the wafer stage base 8 plays a role of supporting part or all of the main body structure after all.

During the exposure operation, the wafer stage 5 and the reticle stage 1 are driven to scan in directions opposite to each other. In that case, to improve throughput (productivity)
Both stages perform repetitive scan driving with large acceleration and deceleration. Therefore, a repeated driving reaction force is applied to the main body structure.

Therefore, in this embodiment, the exposure accuracy is improved by utilizing the fact that a strong correlation is recognized between the amount by which the main body structure is flexibly deformed and the reading value of the wafer laser interferometer 7 or the reticle laser interferometer 4. Eliminate the negative effects of More specifically, a pressure measuring means 10 for measuring the internal pressure of the air spring actuator of the active support leg constituting the active vibration isolator.
Is provided. Here, a pressure sensor can be suitably used as the pressure measuring means 10. In FIG. 1, the pressure measuring means 10
Although it is illustrated to measure the internal pressure of the air spring actuator 11 in the vertical direction of the two active support legs 9 arranged in front, in practice, all the active support legs supporting the main body structure are provided. The internal pressure of the provided air spring actuator is measured. That is, not only the vertical direction but also the internal pressure of the horizontal air spring actuator (not shown) is measured. These measurement results are led to the deformation driving force calculation means 12 shown in FIG. Here, the mode is a mode for flexibly deforming the main body structure. For example, in the horizontal direction, a driving force mode 13a for deforming the wafer stage base 8 into a rhombus shape as shown at the right end of FIG. Calculates a driving force mode 13b for deforming the wafer stage base 8 in a twisted manner as shown at the right end of FIG.
The calculation result is led to main controller 14.

Here, 13a and 13b as amounts for flexibly deforming the wafer stage base 8 and readings from the wafer laser interferometer 7 as position measuring means for positioning and driving the wafer stage 5, or the reticle stage 1 There is a strong correlation between the reading of the reticle laser interferometer 4 as a position measuring means for positioning and driving the position of the reticle, and the magnitude of the driving force causing a flexible deformation is monitored. , The amount of positioning of the wafer stage 5 or the amount of positioning of the reticle stage 1 is corrected. Then, even if the main body structure is deformed and the reading value of the wafer laser interferometer 7 or the reticle laser interferometer 4 is deviated, the amount is corrected, and as a result, the operation is performed so as not to adversely affect the exposure accuracy. .

Although FIG. 1 shows the application of the present technical concept to a so-called scanner, the application of the present invention is not impeded to a so-called stepper in which the wafer stage 5 is operated in a step-and-repeat manner.

In the actual measurement results of FIGS. 2 and 3 described later, among the modes for deforming the main body structure, the rhombic deformation mode related to the horizontal driving force at the right end in FIG. There is a strong correlation between the relationships. Therefore, referring to FIG. 1, only mode 13a of the driving force for deforming into a rhombus is guided to main controller 14, and main controller 14 corrects the measurement result of wafer laser interferometer 7 or reticle laser interferometer 4 with respect to the measurement result. It should be applied.
However, this is due to the special situation that the main body structure in the semiconductor exposure apparatus of the present embodiment has a correlation between the magnitude of the driving force for deforming into a rhombus and the exposure accuracy. In general, the deformation affecting the exposure accuracy is not limited to a rhombus. That is, depending on the characteristics of the main body structure, there may be a correlation between the exposure accuracy and the torsion mode deformation 13b generated by mainly involving the vertical actuator. Here, the torsion is a mode in which the vibration isolation table is deformed as shown in the right side of FIG.
In this case, it is only necessary to make a correction to make the exposure accuracy good according to the size of only the torsion mode, which also belongs to the present invention. Of course, when both rhombic and torsional deformations affect the exposure accuracy, as shown in FIG.
3b, a correction for improving exposure accuracy is performed.
Note that up to the third from the right side of FIGS. 4 and 5,
The horizontal direction and the vertical direction respectively indicate the azimuths of the rigid mode mainly controlled by the actuators.

Further, in the embodiment of FIG. 1, the actuator of the active vibration isolator is an air spring, and the pressure of the air spring is equivalently measured by the pressure measuring means 10, and then the geometry of the air spring is measured. Using the information of the geometric arrangement, the driving force for flexibly deforming the main body structure was obtained. However, the driving force is not limited to the air spring. There is also an active anti-vibration device including an electromagnetic motor having excellent responsiveness as an actuator. In this case, a driving force for deforming the main body structure is calculated based on the driving force generated by the electromagnetic motor and information on the geometrical arrangement of the motor. Of course, a hybrid active vibration isolator having an electromagnetic motor as an actuator together with the air spring is actually operating in the semiconductor exposure apparatus. In this case, the driving force generated by the electromagnetic motor together with the pressure generated by the air spring is used. Then, the driving force of the resultant force for deforming the main body structure is calculated in consideration of the information on the geometric arrangement of the air spring and the electromagnetic motor.

FIG. 6 is a block diagram showing a configuration of one axis of an active vibration isolator supporting a main body structure of an exposure apparatus according to another embodiment of the present invention. This exposure apparatus has the same configuration as the exposure apparatus of FIG. 1 except for the active anti-vibration apparatus. The active anti-vibration apparatus corresponds to the active support leg 9 in the apparatus of FIG. This active vibration isolator is disclosed by the present applicant in order to prevent exposure errors due to deformation of the main body structure (see Japanese Patent Application Laid-Open No. H10-256141). In this active vibration isolator, a pressure feedback loop is newly added in addition to the position feedback loop and the acceleration feedback so that the main body structure is not deformed by application of a force to the vibration isolation table. Here, the pressure feedback loop is a feedback loop based on the detection output of the pressure measuring means or the load measuring means.

6, reference numeral 61 denotes position measuring means for measuring the position of the wafer stage base 8, reference numeral 62 denotes a deviation amplifier for amplifying and outputting the deviation between the output of the position measuring means 61 and the position target voltage r, and 63. Is a PI compensator for reducing the steady-state error to zero, and these constitute a position feedback loop. 64 is a vibration measuring means for measuring the vibration of the wafer stage base 8, and 65 is a gain compensator having an appropriate amplification factor and time constant, and these constitute an acceleration feedback loop. Reference numeral 66 denotes a portion constituting a pressure feedback loop. Here, the internal pressure of the air spring actuator 67 is measured by the pressure measuring means 68, and the measurement result is appropriately compensated by the pressure compensator 69. This is fed back to the previous stage of the voltage-current converter 70. Reference numeral 71 denotes a PI compensator for allowing the operation amount subjected to the acceleration feedback to function as damping. Here,
Although the configuration for one axis is shown, actually, as described in JP-A-10-256141, for example, translational motion in the x-axis direction, translational motion in the y-axis direction, and rotational motion about the z-axis are described. Is configured such that the steady-state deviation becomes zero for each motion mode and damping is applied.

Now, the pressure feedback 1 is realized.
Let us consider feedback based on the detection output of the pressure measuring means 68, which is one of the means. When the pressure receiving area of the air spring actuator 67 is multiplied by the pressure, the driving force acts on the wafer stage base 8 which is the main body structure. Therefore, applying feedback based on the detection output of the pressure measuring means 68 can be said to be feedback of driving force, and corresponds to managing the force acting on the main body structure. If this pressure feedback loop is not added, the driving force of the air spring actuator 67 that suppresses the driving reaction force due to the step-and-repeat or step-and-scan of the wafer stage 5 gradually shifts. This causes deformation of the main body structure.

On the other hand, in the case of the active vibration isolator of this embodiment to which the pressure feedback loop based on the pressure measuring means 68 is added, control for keeping the driving force of the air spring actuator applied to the main body structure constant is performed. This does not cause deformation of the main body structure.

More specifically, the air spring actuator 1
The state of the driving force applied to the main body structure by the driving force generated by No. 1 will be compared between the case with the pressing force feedback loop as in the present embodiment and the case without the pressing force feedback loop. In particular,
Using the measured results, a comparison is made based on the presence or absence of a pressure feedback loop, which is a type of pressure feedback.

First, FIG. 2 shows a driving force acting on the main body structure when the wafer stage 5 is operated without pressure feedback, in a motion mode in the horizontal direction as shown in FIG. That is, the driving force Fx in the translation x direction (FIG. 2A), the driving force Fy in the translation y direction (FIG. 2B), the moment driving force Mz about the z axis (FIG. 2C), and the removal. Four types of driving force Flex (FIG. 3D) for deforming the shaking table (wafer stage base 8) into a diamond shape are shown. On the other hand, FIG. 3 shows the motion mode of the driving force acting on the main body structure when the pressure feedback is provided. Exercise modes corresponding to (a) to (d) in the figure are the same as those in FIG. The coordinate system is shown in FIG.
As defined at the left end of.

A difference immediately found by comparing FIGS. 2 and 3 is the presence or absence of the generation of the driving force Flex for deforming the vibration isolation table into a rhombus. In the case without the pressure feedback loop in FIG. 2D, Flex is significantly generated, and thus the vibration isolation table is deformed into a rhombus. -, Figure 3 (d)
In the case where the pressure feedback loop is provided, the occurrence of Flex is zero, and it can be seen that the vibration isolation table is not deformed. Actually, when a circuit pattern is printed on a wafer, the present embodiment in which the pressure feedback loop of FIG. 3D is inserted is superior in terms of accuracy.

From the actual measurement results of FIGS. 2 and 3 shown above,
It has been found that when a driving force that causes deformation of the main body structure is generated, poor exposure accuracy is caused. Therefore, the effectiveness in terms of performance of the active vibration isolator provided with the pressure feedback loop has been clarified.

However, in consideration of the pressure feedback in the pressure feedback, a pressure sensor as pressure measuring means must be mounted for each air spring actuator. It is necessary to more strictly manage the characteristics of the spring actuator. Above all, close attention must be paid to the adjustment of the pressure feedback loop, which is responsible for the force management function. It should be noted that the addition of the pressure feedback loop affects the adjustment of other loops.

According to the present embodiment, the deformation of the main body structure can be surely suppressed by the pressure feedback, and the function is performed so as not to cause the exposure accuracy defect. A driving force calculating unit 12;
The main controller 14 corrects the measurement results of the wafer laser interferometer 7 and the reticle laser interferometer 4 based on the driving forces 13a and 13b in the mode for deforming into a rhombus and the mode for causing torsional deformation. It is possible to reliably prevent deformation of the main body structure and eliminate defective exposure accuracy.

It should be noted that the present invention is not limited to these embodiments, but can be implemented with appropriate modifications. For example,
In the above embodiment, the measurement result of the wafer laser interferometer 7 or the reticle laser interferometer 4 is corrected based on the output of the deformation driving force calculation means 12, but instead or in addition to this, Exposure in the exposure processing is performed after the output of the driving force calculation means 12 falls within a predetermined tolerance, or when the position of the stage is controlled in the exposure processing, the deformation driving force calculation means 1
The acceleration / deceleration profile at the time of driving the reticle stage 1 or the wafer stage 5 or the approach distance prior to scanning at a constant speed may be optimized so that the output of No. 2 falls within a predetermined tolerance. This also eliminates the effect of the deformation of the main body structure due to the driving force of the actuator on the exposure accuracy.

The parameters of the active vibration isolator may be optimally selected so that the output of the deformation driving force calculating means 12 is minimized.

[0036]

The effects of the present invention are as follows. (1) Since the exposure process is performed while considering the driving force of the actuator of the active vibration isolation device, it is possible to eliminate the influence of the deformation of the main body structure due to the driving force of the actuator on the exposure accuracy. (2) Since the deformation driving force calculation means is provided, it is possible to calculate the driving force in the deformation mode for flexibly deforming the stage based on the driving force of the actuator. (3) By using the fact that a high correlation is recognized between the driving force in the motion mode and the exposure accuracy, the relationship between the driving force in the same mode and the exposure accuracy can be quantified in advance. (4) Exposure accuracy can be corrected by correcting the position of the original plate and / or the substrate stage according to the relationship and the result of monitoring the driving force in the flexible motion mode.
This has the effect. (5) There is an effect that it greatly contributes to the productivity of the exposure apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a semiconductor exposure apparatus according to one embodiment of the present invention.

FIG. 2 is a graph showing a driving force acting on a main body structure of the semiconductor exposure apparatus when no pressure feedback is provided.

FIG. 3 is a graph showing a driving force acting on a main body structure of a semiconductor exposure apparatus when pressure feedback is provided according to another embodiment of the present invention.

FIG. 4 is a diagram showing a rigid motion mode and a flexible motion mode in the horizontal direction.

FIG. 5 is a diagram showing a rigid motion mode and a flexible motion mode in the vertical direction.

FIG. 6 is a block diagram showing a configuration for one axis in an active vibration isolator supporting a main body structure of an exposure apparatus according to another embodiment of the present invention.

[Explanation of symbols]

1: reticle stage, 2: reticle stage surface plate,
3: Moving mirror, 4: Reticle laser interferometer, 5: Wafer stage, 6: Moving mirror, 7: Wafer laser interferometer, 8: Wafer stage base, 9: Active support leg, 10: Pressure measuring means, 11: Vertical air spring actuator, 1
2: deformation driving force calculating means, 13a: driving force mode for deforming into a rhombus, 13b: driving force mode causing torsion deformation, 14: main control device, 61: position measuring means, 6
2: Deviation amplifier, 63: PI compensator, 64: Vibration measuring means, 65: Gain compensator, 66: Portion constituting a pressure feedback loop, 67: Air spring actuator, 68: Pressure measuring means, 69: Pressure compensator, 70:
Voltage-current converter, 71: PI compensator.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 515G 516B

Claims (9)

[Claims] A stage for holding and moving an original or a substrate on which a pattern thereof is exposed; a control unit for performing an exposure process on the original or substrate held on the stage while controlling a position of the stage; An active vibration isolator that supports a main body structure provided with a stage, wherein the control unit performs the exposure processing while taking into account the driving force of an actuator of the active vibration isolator. An exposure apparatus, comprising: 2. The control means includes a deformation driving force calculation means for calculating a driving force in a deformation mode for flexibly deforming the stage based on a driving force of the actuator,
2. The exposure apparatus according to claim 1, wherein the exposure processing is performed while considering an output of the deformation driving force calculation unit. 3. The deformation mode includes a mode in which a portion supported by the active vibration isolation device is deformed into a rhombus in the horizontal direction, or a mode in which torsional deformation is generated in the vertical direction. The exposure apparatus according to claim 2. 4. The apparatus according to claim 2, wherein the control unit controls the position of the stage in the exposure processing while performing correction in consideration of an output of the deformation driving force calculation unit. 4. The exposure apparatus according to 3. 5. The exposure device according to claim 2, wherein the control unit performs the exposure in the exposure process after an output of the deformation driving force calculation unit falls within a predetermined tolerance. 2. The exposure apparatus according to claim 1. 6. The acceleration / deceleration profile for driving the stage so that the output of the deformation driving force calculation unit falls within a predetermined tolerance when controlling the position of the stage in the exposure processing. The exposure apparatus according to any one of claims 2 to 5, wherein an approach distance prior to scanning at a constant speed is optimized. 7. The active vibration isolator according to claim 2, wherein each parameter of the active vibration isolator is optimally selected such that the output of the deformation driving force calculating means is minimized. Exposure equipment. 8. The actuator of the active vibration isolator uses one or more of an air spring, an electromagnetic motor, and a displacement generating actuator, or a plurality of combinations thereof. 8. The exposure apparatus according to claim 1, wherein the driving force is a driving force generated by any one of the actuators or a driving force generated by the plurality of types of actuators. 9. The active vibration isolator according to claim 1, further comprising a feedback loop for controlling the driving force of the actuator by feeding back the driving force of the actuator. Exposure apparatus according to Item.