JP2000040651A - Optical apparatus, exposure apparatus and device manufacturing method - Google Patents

Abstract

(57) [PROBLEMS] To measure the movement of an optical element with extremely high accuracy in an optical device such as a projection optical system of an exposure device that requires high-precision optical adjustment. The exposure apparatus includes a movable lens that constitutes a projection optical system of an exposure apparatus, and a capacitance sensor for detecting the movement of the lens, and the capacitance sensor is annularly formed around the optical element. To distribute. The capacitance sensor has an annular electrode and an annular target, and the target is movable together with the optical element, and the electrode is provided on a fixed portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical device which requires an optical element to be moved with high precision, such as a projection optical system of an exposure apparatus.

[0002]

2. Description of the Related Art A semiconductor exposure apparatus is an apparatus for transferring a reticle as an original onto a semiconductor wafer as a substrate to be exposed. In order to create a highly integrated circuit, it is essential to improve the resolution performance and the overlay accuracy. For this purpose, it is necessary to improve the performance of the projection optical system of the semiconductor exposure apparatus. The characteristics of the projection optical system are affected by the environment, temperature, etc. of the optical system. In order to reduce this effect, an optical element of the projection optical system, for example, a lens is adjusted.

It is also known that the overlay error is reduced by actively adjusting the characteristics of the projection optical system such as the projection magnification in response to the distortion generated by the wafer process.

In order to make such an adjustment, a mechanism for moving a part of the lens constituting the projection optical system in the optical axis direction is required. One example is disclosed in Japanese Patent Application Laid-Open No. 9-106944.
There is an apparatus disclosed in Japanese Unexamined Patent Publication (Kokai) Publication. This has a mechanism for minutely moving a lens constituting a projection optical system of a semiconductor exposure apparatus in the optical axis direction. In this mechanism, the lens is movably held in the optical axis direction by a leaf spring guide, and the lens is moved using fluid pressure or the like. The lens position is measured by one displacement sensor in a non-contact manner. ing.

[0005]

In order to further increase the accuracy of lens adjustment in the future, it is necessary to improve the measurement accuracy and stability of a displacement sensor for measuring a lens position. As a promising candidate for this displacement sensor, there is a capacitance type sensor.

However, the capacitance type sensor has a limitation in improving the measurement accuracy due to the limitation of the size of the electrode arranged on the sensor top. When it is used as a displacement meter, some contrivance is required to improve measurement accuracy and stability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to move an optical element extremely in an optical device such as a projection optical system of an exposure apparatus which requires high-precision optical adjustment. It is an object of the present invention to provide an optical device capable of measuring with high accuracy. It is another object of the present invention to provide a more accurate exposure apparatus using the optical apparatus than before, and to provide a more excellent device manufacturing method than before.

[0008]

A preferred embodiment of the optical apparatus according to the present invention for solving the above-mentioned problems comprises a movable optical element and a capacitance sensor for detecting the movement of the optical element, The capacitance sensor is arranged in a ring along the periphery of the optical element.

Here, for example, the capacitance sensor has an annular electrode. Further, the capacitance sensor has a target having a shape corresponding to the annular electrode, the target is movable together with the optical element, and the electrode is provided on a fixed portion.

[0010] For example, the optical element is a lens, and is characterized in that it has a guide for moving the lens in the optical axis direction and a drive mechanism for moving the lens. The guide is a parallel leaf spring provided radially.

An exposure apparatus according to the present invention includes the above optical device as a projection optical system, and projects a reticle pattern onto a wafer by the projection optical system. Further, the device manufacturing method of the present invention is characterized in that a device is manufactured by a manufacturing process including a step of preparing the above-described exposure apparatus and a step of performing exposure using the exposure apparatus.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment of Semiconductor Exposure Apparatus> FIGS. 1 and 2 are views for explaining a part of a projection optical system of a semiconductor exposure apparatus by cutting out. The projection optical system has a magnification adjusting mechanism, and the magnification is adjusted by moving the lens in the optical axis direction. FIG. 1 is a top view, and FIG. 2 is a cross-sectional view as viewed from the side.

In the drawing, 1 is a movable base, 2 is an electrode, 3 is a leaf spring guide, 4 is a drive mechanism (bellows), 5 is a fixed part, 6 is a leaf spring holder, 7 is a lens, 8 is a cell, and 9 is a cell. The target 10 is the optical axis of the optical system.

A lens 7, which is an optical element for adjusting the magnification of the projection optical system, is held by a cell 8, and furthermore, a cell 8
Is fixed to the movable base 1. The movable base 1, the lens 7, and the cell 8 are substantially integrated, and form a movable part.

The leaf spring guide 3 is a parallel leaf spring mechanism using two elastic leaf springs, and a plurality of leaf spring guides 3 are provided radially around the lens 7. The movable table 1 is held by the plurality of leaf spring guides 3 with respect to the fixed portion 5 and guided so as to be movable in the direction of the optical axis 10.

The metal bellows 4 is a lens driving mechanism, and moves the lens in the optical axis direction by adjusting the driving force by changing the pressure of air inside the bellows. Although not shown, the pressure of the bellows 4 is adjusted by a servo valve having a built-in pressure sensor for measuring the pressure of air and control means of the servo valve. Thus, the lens 7 moves to a position where the pressing force of the bellows 4 and the restoring force of the parallel leaf spring 3 are balanced.

Next, the capacitance sensor will be described.
An annular metal electrode 2 is fixedly provided around the fixing portion 5 so as to surround the lens 7 when viewed from the optical axis direction of the lens. An annular target 9 is fixed to the movable base 1 in accordance with the shape of the annular electrode 2. The material of the target 9 is metal, and also serves as a member for fixing the leaf spring guide 3 to the movable base 1. The material of the target 9 may be any material other than metal, such as a dielectric material such as ceramic, which changes the capacitance. The above-mentioned member constitutes an annular capacitance sensor, and the capacitance changes according to the distance between the electrode 2 and the target 9. 1, that is, the displacement of the lens 7 with respect to the fixed part 5 can be measured.

By arranging the electrodes 2 in an annular shape around the lens as described above, the size (area) of the electrode 2 can be increased without providing a large protrusion around the lens. As the size of the electrode increases, the change in capacitance due to the movement of the lens becomes larger, so that the detection accuracy of the capacitance sensor is improved and the detection range of the capacitance sensor can be increased. . Further, since the electrodes are arranged all around the lens, the influence of a change in the posture of the movable portion during movement is reduced, and the position of the center of the lens can be measured.

FIG. 3 is an overall configuration diagram of a semiconductor exposure apparatus having the above-mentioned projection optical system. In the figure, reference numeral 101 denotes a semiconductor wafer coated with a photosensitive agent, which is held on a wafer stage 102 having precise positioning performance. The position of the wafer stage with respect to the reference of the exposure apparatus is measured by a laser interferometer. Reference numeral 103 denotes a reticle on which a pattern serving as an original is drawn. The projection optical system 104 includes the projection magnification adjusting means 110 as described above, and forms a pattern on the reticle on the wafer. An illumination optical system 105 illuminates the reticle. Reference numeral 106 denotes an alignment optical system that detects a positional shift between the pattern on the wafer and the pattern on the reticle created in the previous process. A control device 107 manages the operation of the exposure apparatus. The dimension of the pattern on the wafer can be measured by cooperation of the alignment optical system 106, the wafer stage 102, and the laser interferometer for measuring the position of the wafer stage. The control device 107 sets an optimum exposure magnification based on the dimensions.

On the other hand, as a factor of fluctuation of the projection magnification of the projection optical system, there is a change in atmosphere such as atmospheric pressure. Reference numeral 108 denotes an atmospheric pressure sensor. The control unit 107 determines the optimal position of the lens of the projection magnification adjusting unit 110 from the information on the atmospheric pressure obtained by the atmospheric pressure sensor and the value of the optimal exposure magnification, and sends the position command to the control unit of the projection magnification adjusting unit. Give to 111.

The above-described lens moving mechanism can be applied to other optical elements used in an exposure apparatus, for example, to adjust distortion of a projection lens, coma aberration, spherical aberration, curvature of field, and the like. The present invention can also be applied to the lens driving device.

<Embodiment of Device Manufacturing Method> Next, an example of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 4 shows a flow of manufacturing micro devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, micromachines, etc.). In step 1 (circuit design), a device pattern is designed. Step 2
In (reticle production), a reticle having a designed pattern is produced. On the other hand, in step 3 (substrate manufacture), a substrate is manufactured using a material such as silicon or glass. Step 4 (substrate process) is called a pre-process, and an actual circuit is formed on the substrate by lithography using the prepared reticle and substrate. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the substrate manufactured in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 5 shows a detailed flow of the above substrate process. Step 11 (oxidation) oxidizes the surface of the substrate. In step 12 (CVD), holes are formed on the substrate surface to form an insulating film. In step 13 (electrode formation), electrodes are formed on the substrate by vapor deposition. In step 14 (ion implantation), ions are implanted into the substrate. In step 15 (resist processing), a resist is applied to the substrate. Step 16 (exposure) uses the above-described exposure apparatus to align and print the circuit pattern of the reticle on a plurality of shot areas of the substrate. Step 17 (development) develops the exposed substrate. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the substrate. By using the production method of this embodiment, a high-precision device, which was conventionally difficult to produce, can be produced with high productivity, that is, at low cost.

[0024]

According to the optical apparatus of the present invention, it is possible to effectively utilize the space of the lens driving unit, increase the area of the sensor electrode, and improve the position measurement accuracy and stability. Further, by disposing the sensors in a ring shape, the displacement in the optical axis direction can be measured more accurately.

Further, by using this optical apparatus, it is possible to provide an exposure apparatus with higher precision than before, and to provide a more excellent device manufacturing method than before.

[Brief description of the drawings]

FIG. 1 is a top view of a certain lens portion in a projection optical system.

FIG. 2 is a side view of FIG. 1 viewed from the side.

FIG. 3 is an overall configuration diagram of a semiconductor exposure apparatus.

FIG. 4 is a diagram showing a manufacturing flow of a semiconductor device.

FIG. 5 is a diagram showing a detailed flow of a wafer process.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 movable table 2 annular electrode 3 leaf spring guide 4 bellows 5 fixing part 6 leaf spring retainer 7 magnification adjusting lens 8 cell 9 target 10 optical axis 101 wafer (substrate to be exposed) 102 wafer stage 103 reticle (original) 104 projection optics System 105 Illumination optical system 106 Alignment optical system 107 Controller 108 Barometric pressure sensor 111 Control unit

Claims (7)

[Claims] 1. An optical device comprising: a movable optical element; and a capacitance sensor for detecting the movement of the optical element, wherein the capacitance sensor is annularly arranged along the periphery of the optical element. Optical device. 2. The optical device according to claim 1, wherein the capacitance sensor has an annular electrode. 3. The capacitance sensor has a target having a shape corresponding to the annular electrode, the target is movable together with an optical element, and the electrode is provided on a fixed part. The optical device according to claim 1. 4. The optical element is a lens, having a guide for moving the lens in the optical axis direction, and a drive mechanism for moving the lens, wherein the capacitance sensor is located on the lens when viewed from the optical axis direction. The optical device according to any one of claims 1 to 3, wherein the optical device is arranged in an annular shape along the periphery of the optical device. 5. The optical device according to claim 4, wherein the guide has a parallel leaf spring provided radially. 6. An exposure apparatus comprising the optical device according to claim 1 as a projection optical system, and projecting a reticle pattern onto a wafer by the projection optical system. 7. A device manufacturing method, wherein a device is manufactured by a manufacturing process including a step of preparing the exposure apparatus according to claim 6 and a step of exposing using the exposure apparatus.