JP3547003B2 - Gap adjusting device and adjusting method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gap adjusting device and an adjusting method, and more particularly to a gap adjusting device and an adjusting method suitable for adjusting a gap between a wafer and a mask used in X-ray lithography.
[0002]
[Prior art]
In X-ray lithography, usually, a mask is arranged on a wafer surface to be exposed with a small gap, and the wafer surface is exposed through the mask. In order to increase resolution and alignment accuracy, the gap between the wafer and the mask must be precisely controlled. In particular, if the gap is too wide, the resolution is reduced due to penumbra, and the alignment accuracy is also reduced.
[0003]
As a method of measuring the gap between the wafer and the mask, a method using an electrostatic capacity sensor, a method using image processing using a high-resolution camera, and the like are known.
[0004]
[Problems to be solved by the invention]
Since the capacitance sensor and the high-resolution camera are expensive, the adoption of the gap measurement method using them makes the entire apparatus expensive. In particular, a capacitance sensor capable of measuring a gap of 50 μm or less is very expensive. In addition, an expensive lens is required to image a gap of 20 μm or less.
[0005]
An object of the present invention is to provide a gap adjusting device capable of reducing costs.
[0006]
Another object of the present invention is to provide a method for measuring a gap using the gap measuring device.
[0007]
[Means for Solving the Problems]
According to one aspect of the invention, a first stage defining a first reference plane and a second reference plane are defined such that the second reference plane is parallel to the first reference plane. A second stage opposed to the first stage and a first object having a main surface are oriented such that the main surface faces the second stage side and is parallel to the first reference plane. A first fixing means for fixing to the first stage, and a first displacement sensor attached to the first stage, wherein the first displacement sensor includes The first displacement sensor for measuring a distance to a plane parallel to the second reference plane and the second target having a main surface are arranged such that the main surface faces the first stage and the second displacement sensor measures the distance. Second fixing means for fixing to the second stage so as to be parallel to the reference plane of A second displacement sensor attached to the second stage, wherein a distance from the second displacement sensor to a plane parallel to the first reference plane disposed in front of the second displacement sensor is measured. An eddy current sensor attached to the second displacement sensor and the first stage and having a sensor reference plane parallel to the first reference plane; and an eddy current sensor attached to the second stage and provided with the second reference An eddy current sensor target having a target reference plane parallel to a plane, one of the first stage and the second stage, and a direction parallel to and perpendicular to the first reference plane with respect to the other. And moving the moving mechanism so that the target is located in front of the first displacement sensor, and measuring a distance from the first displacement sensor to a target reference plane of the target. Driving the moving mechanism so that the main surface of the second object is located in front of the first displacement sensor, and moving the moving mechanism from the first displacement sensor to the main surface of the second object. The distance is measured, and the moving mechanism is driven so that the eddy current sensor is located in front of the second displacement sensor. The distance from the second displacement sensor to the sensor reference plane of the eddy current sensor is measured. Measuring, driving the moving mechanism so that the main surface of the first object is located in front of the second displacement sensor, and moving the main surface of the first object from the second displacement sensor. Control means for measuring the distance between the sensor reference plane and the target reference plane by driving the moving mechanism so that the target is positioned in front of the eddy current sensor. An apparatus is provided.
[0008]
From the difference between the distance from the first displacement sensor to the target reference plane and the distance from the first displacement sensor to the main surface of the second target, the difference between the target reference plane and the main surface of the second target is determined. , The height difference from the second reference plane can be known. Similarly, a difference in height between the sensor reference plane and the main surface of the first target object from the first reference plane can be known. From the information of these differences and the distance between the sensor reference plane and the target reference plane, the distance between the main surface of the first target and the main surface of the second target can be obtained.
[0009]
According to another aspect of the invention, the first object is positioned on a first stage defining a first reference plane, such that a main surface of the first object is parallel to the first reference plane. A first step of fixing the object, and a second stage defining a second reference plane parallel to the first reference plane, wherein a main surface of the second object is placed on the second reference plane; A second step of fixing the second object so as to be parallel, and a height of the sensor reference plane of the eddy current sensor mounted on the first stage from the first reference plane; A third step of obtaining or adjusting a relationship between the first reference plane and a height from the main surface of the first object, and a step of detecting an eddy current sensor target mounted on the second stage. A height of the target reference plane from the second reference plane, and a height of the second target object from the second reference plane. A fourth step of obtaining or adjusting the relationship with the height to the surface, and measuring the distance from the sensor reference surface of the eddy current sensor to the target reference surface, and measuring the distance so that the measurement result approaches a target value. There is provided a gap adjusting method including a fifth step of adjusting an interval between a first stage and the second stage.
[0010]
In the third step, the relationship between the height from the first reference plane to the sensor reference plane and the height from the first reference plane to the main surface of the first target object is found. In the fourth step, the relationship between the height from the second reference plane to the target reference plane and the height from the second reference plane to the main surface of the second object can be determined. If the distance from the sensor reference plane to the target reference plane is known, the distance between the main surface of the first target and the main surface of the second target can be obtained.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows an X-ray exposure apparatus according to an embodiment of the present invention. The wafer stage 1 defines a virtual wafer reference plane 3. The mask stage 2 defines a virtual mask reference plane 4. Wafer stage 1 and mask stage 2 are arranged so as to face each other. The wafer reference plane 3 and the mask reference plane 4 are parallel to each other.
[0012]
The wafer chuck 5 is attached to the wafer stage 1 via a moving mechanism 16. The moving mechanism 16 can move the wafer chuck 5 in a direction normal to the wafer reference surface 3. The wafer chuck 5 sucks and fixes the wafer 10 to be exposed. The surface (main surface) of the wafer 10 to be exposed which is attracted to the wafer chuck 5 faces the mask stage 2 and is parallel to the wafer reference surface 3.
[0013]
The wafer-side laser displacement sensor 6 is attached to the wafer stage 1. When the reflecting surface that reflects the laser is placed parallel to the mask reference surface 4 and in front of the wafer-side laser displacement sensor 6, the wafer-side laser displacement sensor 6 measures the distance to this reflecting surface. The measurement error of the laser displacement sensor 6 is 1 μm or less.
[0014]
A mask chuck 7 is attached to the mask stage 2. The mask chuck 7 sucks and fixes the mask 11 for X-ray exposure. The mask surface of the mask 11 attracted to the mask chuck 7 faces the wafer stage 1 side and is parallel to the mask reference plane 4.
[0015]
A mask-side laser displacement sensor 8 is attached to the mask stage 2. When the reflection surface that reflects the laser is placed parallel to the wafer reference surface 3 and in front of the mask-side laser displacement sensor 8, the mask-side laser displacement sensor 8 measures the distance to this reflection surface. The measurement error of the laser displacement sensor 8 is 1 μm or less.
[0016]
An eddy current sensor 20 is attached to the wafer stage 1 via an actuator 21. A target 25 for an eddy current sensor is attached to the mask stage 2 via an actuator 26. The eddy current sensor 20 has a sensor reference plane 22 parallel to the wafer reference plane 3. The target 25 has a target reference plane 27 parallel to the mask reference plane 4. When the target 25 is placed in front of the eddy current sensor 20, the eddy current sensor 20 can measure the distance from the sensor reference plane 22 to the target reference plane 27. The actuator 21 adjusts the height of the eddy current sensor 20 from the wafer reference plane 3. The actuator 26 adjusts the height of the target 25 from the mask reference plane 4.
[0017]
As the eddy current sensor 20, for example, an EX-500 series sensor manufactured by Keyence Corporation can be used. The resolution of the EX-500 series sensor is 0.3 μm to 3.0 μm. Further, as the target 25, a metal plate having a thickness of 0.5 mm or more can be used.
[0018]
The moving mechanism 15 moves the wafer stage 1 in a two-dimensional direction parallel to the wafer reference plane 3. Another moving mechanism 31 moves the mask stage 2 in a direction perpendicular to the mask reference plane 2. The controller 40 controls the wafer-side laser displacement sensors 6 and 8, the eddy current sensor 20, the actuators 21 and 26, and the moving mechanisms 15, 16 and 31.
[0019]
An X-ray light source 45 emits X-rays 46. The X-ray light source 45 is, for example, a synchrotron, and the X-rays 46 are synchrotron radiation (SR light). The X-rays 46 irradiate the surface of the wafer 10 to be exposed through the mask 11.
[0020]
Next, an X-ray exposure method will be described with reference to FIG. In step S <b> 1, the wafer stage 1 is moved to position a predetermined portion of the main surface of the wafer 10 in front of the mask-side laser displacement sensor 8. The distance from the mask-side laser displacement sensor 8 to the main surface of the wafer 10 is measured using the mask-side laser displacement sensor 8.
[0021]
In step S2, the wafer stage 1 is moved to position the eddy current sensor 20 in front of the mask-side laser displacement sensor 8. The distance from the mask-side laser displacement sensor 8 to the sensor reference plane 22 of the eddy current sensor 20 is measured. The measurement result is compared with the measurement result in step S1, and the height of the eddy current sensor 20 from the wafer reference plane 3 is adjusted so that the sensor reference plane 22 is located on the same plane as the main surface of the wafer 10. I do. This adjustment is performed by driving the actuator 21.
[0022]
Proceeding to step S3, the wafer stage 1 is moved to position a predetermined portion of the mask surface of the mask 11 in front of the wafer-side laser displacement sensor 6. The distance from the wafer-side laser displacement sensor 6 to the mask surface of the mask 11 is measured.
[0023]
Proceeding to step S4, the wafer stage 1 is moved to position the target 25 in front of the wafer-side laser displacement sensor 6. The distance from the wafer-side laser displacement sensor 6 to the target reference plane 27 of the target 25 is measured. The measurement result is compared with the measurement result in step S3, and the height of the target 25 from the mask reference plane 3 is adjusted so that the target reference plane 27 is located on the same plane as the mask plane of the mask 11. This adjustment is performed by driving the actuator 26.
[0024]
Proceeding to step S5, the wafer stage 1 is moved so that the target 25 is located in front of the eddy current sensor 20. The distance between the sensor reference plane 22 and the target reference plane 27 is measured by the eddy current sensor 20. The mask stage 2 is moved in a direction perpendicular to the mask reference plane 4 so that this interval approaches the target value. The distance between the sensor reference plane 22 and the target reference plane 27 is equal to the distance between the main surface of the wafer 10 and the mask surface of the mask 11 (the distance between wafer masks). Therefore, the interval between the wafer masks can be made closer to the target value.
[0025]
When the distance between the wafer masks falls within the allowable range, the process proceeds to step S6, where X-ray exposure is performed.
[0026]
In the above embodiment, the distance between the main surface of the wafer 10 and the mask surface of the mask 11 can be adjusted with high accuracy without using an expensive capacitance sensor or high-resolution camera. Further, the interval between wafer masks can be constantly monitored by the eddy current sensor 20. Therefore, when the interval deviates from the target value, the interval can be quickly restored.
[0027]
Further, the laser displacement sensor and the eddy current sensor used in the above embodiment are small and lightweight. For this reason, the sensor can be installed even when there is no large extra space around the stage. Further, the mechanical load applied to the stage can be reduced.
[0028]
Next, a modification of the above embodiment will be described. In the above embodiment, in step S2 shown in FIG. 2, the height of the sensor reference surface 22 is made to match the height of the main surface of the wafer 10, and in step S4, the height of the target reference surface 27 is changed The height of the mask surface. In a modified example, the control device stores the difference between the height of the sensor reference surface 22 and the height of the main surface of the wafer 10 in a process corresponding to step S2 of the above embodiment. In a step corresponding to step S4, the difference between the height of the target reference surface 27 and the height of the mask surface of the mask 11 is stored. It is not necessary to adjust the height of the eddy current sensor 20 and the target 25.
[0029]
In a step corresponding to step S5 in the above embodiment, the distance between the sensor reference plane 22 and the target reference plane 27 is measured. Based on the measured value of this interval, the difference between the height of the sensor reference plane 22 and the height of the main surface of the wafer 10, and the difference between the height of the target reference plane 27 and the height of the mask surface of the mask 11, The interval can be calculated. In this variant, the actuators 21 and 26 shown in FIG. 1 are not required.
[0030]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0031]
【The invention's effect】
As described above, according to the present invention, the distance between two objects can be measured using the eddy current sensor. Since the eddy current sensor is small, the eddy current sensor can be installed at a predetermined position even when the device has insufficient space. Further, since the eddy current sensor is relatively inexpensive, the cost of the device can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view of an X-ray exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a gap adjusting method according to an embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 wafer stage 2 mask stage 3 wafer reference plane 4 mask reference plane 5 wafer chuck 6 wafer side laser displacement sensor 7 mask chuck 8 mask side laser displacement sensor 10 wafer 11 masks 15, 16, 31 moving mechanism 20 eddy current sensors 21, 26 Actuator 22 Sensor reference plane 25 Target 27 Target reference plane 40 Controller 45 X-ray light source 46 X-ray

Claims (4)

A first stage defining a first reference plane;
A second stage that defines a second reference plane and faces the first stage such that the second reference plane is parallel to the first reference plane;
First fixing means for fixing a first object having a main surface to the first stage such that the main surface faces the second stage and is parallel to the first reference plane. When,
A first displacement sensor attached to the first stage, wherein the first displacement sensor measures a distance from the first displacement sensor to a plane parallel to the second reference plane disposed in front of the first displacement sensor. A first displacement sensor;
Second fixing means for fixing a second object having a main surface to the second stage such that the main surface faces the first stage side and is parallel to the second reference plane. When,
A second displacement sensor attached to the second stage, wherein the second displacement sensor measures a distance from the second displacement sensor to a plane parallel to the first reference plane disposed in front of the second displacement sensor. A second displacement sensor;
An eddy current sensor attached to the first stage and having a sensor reference plane parallel to the first reference plane;
An eddy current sensor target attached to the second stage and having a target reference plane parallel to the second reference plane;
A moving mechanism for moving one of the first stage and the second stage relative to the other in a direction parallel to and perpendicular to the first reference plane;
Driving the moving mechanism so that the target is located in front of the first displacement sensor, measuring a distance from the first displacement sensor to a target reference plane of the target, The driving mechanism is driven so that the main surface of the first displacement sensor is located in front of the first displacement sensor, and the distance from the first displacement sensor to the main surface of the second object is measured. Driving the moving mechanism so that a current sensor is located in front of the second displacement sensor, measuring a distance from the second displacement sensor to a sensor reference plane of the eddy current sensor, Driving the moving mechanism so that the main surface of the object is located in front of the second displacement sensor, measuring a distance from the second displacement sensor to the main surface of the first object, The target is in front of the eddy current sensor The moving mechanism is driven so as to location, the gap adjustment device and a control means for measuring the distance between the sensor reference plane and the target reference surface. Further, a first height adjustment mechanism that can adjust a height from the first reference plane to a sensor reference plane of the eddy current sensor;
A second height adjustment mechanism that can adjust the height from the second reference plane to the target reference plane of the target,
The control means may determine that a height from the second reference plane to the target reference plane is higher than a height of the second target object from the second reference plane based on a measurement result by the first displacement sensor. The second height adjustment mechanism is driven so as to be equal to the height to the surface, and the height from the first reference plane to the sensor reference plane is determined based on the measurement result by the second displacement sensor. The gap adjusting device according to claim 1, wherein the first height adjusting mechanism is driven such that the height of the first height adjusting mechanism is equal to the height from the first reference plane to the main surface of the first object. A first step of fixing the first object on a first stage defining a first reference surface such that a main surface of the first object is parallel to the first reference surface; ,
On a second stage that defines a second reference plane parallel to the first reference plane, the second object is placed on the second stage such that the main surface of the second object is parallel to the second reference plane. A second step of fixing the object;
A height of the sensor reference plane of the eddy current sensor mounted on the first stage from the first reference plane, and a height from the first reference plane to a main surface of the first object; A third step of determining or adjusting the relationship of
The height of the target reference plane of the target for the eddy current sensor mounted on the second stage from the second reference plane, and from the second reference plane to the main surface of the second target object A fourth step of determining or adjusting the relationship with the height of the
A fifth step of measuring a distance from a sensor reference plane of the eddy current sensor to the target reference plane, and adjusting an interval between the first stage and the second stage so that a measurement result approaches a target value. And a gap adjusting method comprising: In the third step, the sensor reference plane and the main surface of the first object are adjusted so as to be located on the same plane, and in the fourth step, the target reference plane and the second 4. The gap adjusting method according to claim 3, wherein the adjustment is performed such that the main surface of the target object is located on the same plane.

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