JP5118407B2 - Optical system, exposure apparatus, and device manufacturing method - Google Patents

Description

  The present invention relates to an exposure apparatus and a device manufacturing method for exposing an original pattern to a substrate via an optical system.

  The exposure apparatus is used to manufacture various devices such as semiconductor chips such as IC and LSI, display elements such as liquid crystal panels, detection elements such as magnetic heads, imaging elements such as CCDs, and fine patterns used in micromechanics. These elements are manufactured by projecting a reticle pattern onto a substrate coated with a photoresist via a projection optical system.

  Known conventional projection optical systems include, for example, a reflective optical system using concentric or non-concentric concave mirrors and convex mirrors, and a substantially concentric reflective optical system including a negative meniscus lens and a chromatic aberration correction mechanism in addition to concave and convex mirrors. It has been.

  In these reflection optical systems, a good image area is formed in an off-axis semi-arc state area. Then, a reticle pattern image corresponding to the good image area is formed on the substrate, and the entire reticle pattern image is formed on the substrate by scanning the reticle and the substrate as a whole with respect to the reflection optical system. An aligner to do is known.

  However, all of the conventional reflection optical systems have large astigmatism and curvature of field, so that the width of the good image area is extremely narrow, and when applied to an aligner, a lot of scanning time, that is, exposure time is required. There was a problem that the amount of substrate baking processing per hit was relatively small.

A conventional projection optical system includes a convex unit including a convex mirror and a meniscus lens, and a refractive optical member, as in Patent Documents 1 and 2. In particular, in Patent Document 1, enlargement of the good image area is achieved by using a spherical mirror and disposing an aspheric optical element between the concave mirror and the convex mirror. In Patent Document 2, enlargement of a good image area and correction of chromatic aberration are achieved by disposing an aspherical optical element between a concave mirror and a convex mirror in a catadioptric optical system having an enlarged projection magnification.
JP 60-093410 A Japanese Patent Application No. 2006-269022

  According to the above-described conventional technology, it is possible to design an exposure apparatus that does not reduce the amount of substrate baking processing even for a large substrate. However, as the apparatus becomes larger, aberrations that depend on the angle of view, that is, astigmatism (distortion) and distortion (distortion) are likely to occur due to assembly errors and manufacturing errors of the optical members. Become.

  Conventionally, the astigmatic difference and distortion are adjusted by adjusting the position of the convex mirror or the convex unit, or the distortion is adjusted by bending a flat glass disposed near the image plane or the object plane.

  However, there have been cases where satisfactory adjustment accuracy cannot be obtained, for example, aberrations of components other than the component to be adjusted are generated in a non-negligible amount as the apparatus becomes larger.

  The present invention has been made in view of the above problems, and its object is to move a refractive optical member disposed in the vicinity of the object surface and the image plane in a plane perpendicular to the optical axis in order to enlarge the good image area. It is to realize a technique capable of adjusting distortion and / or astigmatism with high accuracy.

In order to solve the above problems and achieve the object, an optical system of the present invention is an optical system for projecting an image of an object plane onto an image plane, and at least one first refraction disposed on the object plane side. It includes an optical member, and includes at least one second refractive optical member disposed on the image plane side, toward perpendicular to the first refractive optical element and the second refractive optical member with respect to the optical axis By adjusting the astigmatic difference and distortion of the optical system independently by moving in the direction of the optical system, and the adjusting means is arranged in the optical axis direction of the first refractive optical member at a certain image height. The amount of distortion generated due to the movement in the direction perpendicular to the amount of distortion and the amount of distortion generated due to the movement of the second refractive optical member in the direction perpendicular to the optical axis direction have different signs , and the total amount of distortion generated But As square smaller than the amount of generation of the first refractive optical element and by moving the second refractive optical element, and adjust the astigmatism of the optical system, or the first refractive optical in certain image height Generation amount of astigmatism due to movement of the member in a direction perpendicular to the optical axis direction and generation amount of astigmatism due to movement of the second refractive optical member in a direction perpendicular to the optical axis direction And the first refractive optical member and the second refractive optical member are moved to adjust the distortion of the optical system so that the generation of the total astigmatism becomes smaller than one of the generations. .

  An exposure apparatus of the present invention has the above optical system, and exposes a pattern of an original on a substrate through the optical system.

  The device manufacturing method of the present invention includes a step of exposing a substrate using the exposure apparatus, and a step of developing the exposed substrate.

  According to the present invention, in order to enlarge the good image area, the refracting optical member arranged in the vicinity of the object surface and the image surface is moved in a plane orthogonal to the optical axis, thereby reducing distortion and / or astigmatism. It can be adjusted with high accuracy.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  The embodiment described below is an example for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment.

[First embodiment]
The first embodiment is a configuration example of an optical system in which the refractive optical element is a spherical lens, and the light ray effective portion of the refractive optical element exists outside the axis not including the optical axis.

  FIG. 1 shows the configuration of the optical system of the first embodiment.

  In FIG. 1, the optical system forms an image via a first refractive optical member 1, a first concave reflecting surface (mirror) 3, a convex reflecting surface (mirror) 5, and a second refractive optical member 6. The first and second refractive optical members 1 and 6 are held so as to be movable in the Y and Z planes orthogonal to the optical axis direction, and at least one of astigmatism and distortion of the optical system can be adjusted.

  In the optical system of FIG. 1, the X axis is the left-right direction in the drawing, the Y axis is the up-down direction in the drawing, and the Z axis is the direction perpendicular to the drawing.

Table 1 below shows optical data of a catadioptric projection system using an off-axis good image area. No represents an optical surface number, and ASP attached to No represents an aspheric lens. In the r column, each term represents the radius of curvature of the surface, and ∞ represents the plane. d column represents a distance on the optical axis of the next optical surface, sign-is inverted each time reflecting the direction of travel of light is positive once. Column n represents the refractive index between the next optical surface.

  The wavelength used can be selected from i-line, h-line, or g-line without selecting or selecting one, and the refractive index of quartz for the wavelength is 1.4745, 1.4696, 1.4668. In this embodiment, the height of the good image area from the optical axis is 240 mm.

  The ASP aspherical shape can be expressed by Equation 1, and the respective aspherical coefficients are as shown in Table 2.

X: optical axis direction distance from tangential plane to aspherical surface k: conical coefficient h: height from optical axis r: radius of curvature A, B, C, D, E, F, G: aspherical coefficient

  In the configuration of FIG. 1, for example, when the first refractive optical member 1 moves 300 μm in the Z plus direction, the distortion changes as shown in FIG. 2, and the astigmatic difference changes as shown in FIG. Similarly, when the second refractive optical member 6 moves 300 μm in the Z plus direction, the distortion changes as shown in FIG. 4 and the astigmatic difference changes as shown in FIG.

  Distortion is the amount of deviation from the ideal imaging point into the Y and Z planes, and astigmatic difference is the deviation in the light direction between the imaging points of the vertical (Y direction) pattern and the horizontal (Z direction) pattern. It is defined as

  The horizontal axis of the graph indicates the Z-axis coordinate of the exposure area, and the vertical axis of the graph indicates the amount of astigmatic difference or distortion. The same applies to the following graphs.

  As shown in FIGS. 6 and 7, when the movement of the first refractive optical member 1 and the movement of the second refractive optical member 6 are simultaneously performed in the Z plus direction by 300 μm, the astigmatic difference substantially changes as shown in FIG. Instead, the distortion changes mainly as shown in FIG. 6 by the addition of FIG. 2 and FIG.

  As shown in FIGS. 8 and 9, for example, when the first refractive optical member 1 moves 300 μm in the Z plus direction and the second refractive optical member 6 moves 300 μm in the Z minus direction, the distortion is as shown in FIG. There is no substantial change, and the astigmatic difference mainly changes as shown in FIG.

That is, the first and second refractive optical element 1,6, the change in distortion or astigmatism is simultaneously moved in a direction in which a different sign-and the absolute value of the amount of distortion or astigmatism is substantially the same Move to become. As a result, the astigmatism or distortion can be adjusted without changing the distortion astigmatism.

Here, the distortion or astigmatic difference when the first and second refractive optical members 1 and 6 are moved simultaneously is the same as when either the first or second refractive optical member 1 or 6 is moved. It becomes 1/2 or less of the generated distortion or astigmatic difference .

  Although the Z direction has been described above, astigmatism and / or distortion can be changed by moving the first and second refractive optical members 1 and 6 in the X and Y directions.

[Second Embodiment]
The second embodiment is an example of the configuration of an optical system in which the refractive optical element is an aspherical lens having no power, and the light beam effective portion of the refractive optical element exists outside the axis that does not include the optical axis.

  FIG. 10 shows the configuration of the optical system of the second embodiment.

  The optical system shown in FIG. 10 is the same as that shown in FIG. 1 except that the meniscus lens 4 is provided and the first and second refractive optical members 1 and 6 are aspherical lenses, and X, Y, Z The direction is the same as defined in the first embodiment.

  Table 3 below shows optical data of a catadioptric projection system using an off-axis good image area. The description of the table is the same as in the first embodiment. In the present embodiment, the height of the good image area from the optical axis is 460 mm.

  Further, the aspheric shape of the ASP can be expressed by Equation 1, and the respective aspheric coefficients are as shown in Table 4.

  In the above configuration, when the optical member is arranged as shown in FIG. 10, for example, when the first refractive optical member 1 is moved by 300 μm in the Z plus direction, the distortion changes as shown in FIG. It changes as follows.

  Even in the movement of the second refractive optical member 6 and the movement of the first and second refractive optical members combined, the astigmatic difference and the amount of distortion are different from those of the first embodiment, but the selective adjustment is performed. The same effects as those of the first embodiment can be obtained.

  Although the above movement has been described with respect to the Z direction, astigmatism and / or distortion can also be generated by moving the first and second refractive optical members 1 and 6 in the X and Y directions. Further, by moving the first and second refractive optical members 1 and 6 in combination, it is possible to change substantially only distortion or substantially only astigmatism.

  Here, an aspheric lens in which the refractive optical element does not have power is illustrated, but a similar effect can be obtained even with an aspheric lens having power due to a synergistic effect with the first embodiment.

[Third embodiment]
The third embodiment is a configuration example of a catadioptric optical system having an enlarged projection magnification.

  FIG. 13 shows the configuration of the optical system of the third embodiment.

  The optical system shown in FIG. 13 is the same as FIG. 1 except that the second concave reflecting surface (mirror) 3 ′ is provided and the first and second refractive optical members 1 and 6 are catadioptric optical members. The X, Y, and Z directions are the same as those defined in the first embodiment.

  Table 5 below shows optical data of the catadioptric projection system using the off-axis good image area. The description of the table is the same as in the first embodiment.

  Although the enlargement magnification β = 1.5 is illustrated here, the same effect can be obtained even when β = 2.5. If it is 2.5 times or more, the distance between the object surface and the first concave mirror 3 becomes short and practical design is difficult. For example, design in mask patterning is also difficult, so 0.4 ≦ | β | ≦ 2.5 is an appropriate imaging magnification. In this embodiment, the height of the good image area from the optical axis is 250 mm.

  Also, the ASP aspherical shape can be expressed by Equation 1, and the respective aspherical coefficients are as shown in Table 6.

  In the above configuration, when the optical member is arranged as shown in FIG. 13, for example, when the first refractive optical member 1 is moved by 300 μm in the Z plus direction, the distortion changes as shown in FIG. It changes like 15. Similarly, when the second refractive optical member 6 moves 300 μm in the Z plus direction, the distortion changes as shown in FIG. 16, and the astigmatic difference changes as shown in FIG.

  Here, the amount of movement of the first refractive optical member 1 and that of the second refractive optical member 6 are the same, but the amount of distortion and astigmatic difference are different because of the enlargement system. By appropriately selecting the movement ratio between the two, it is possible to substantially adjust only the distortion or only the astigmatic difference.

[Fourth Embodiment]
The fourth embodiment is an example in which the present invention is applied to an optical system constituting a lens barrel as shown in FIG.

  Displacement and / or astigmatic difference can be adjusted by moving the first refractive optical member 1 and the second refractive optical member 6.

  Similarly to the above embodiment, only the distortion or only the astigmatic difference can be substantially adjusted by moving the first and second refractive optical members in combination.

  Here, the lens is exemplified, but the same effect can be obtained also in a catadio system using a mirror system and a lens system.

[Exposure equipment]
FIG. 19 shows an exposure apparatus equipped with the optical system of the present invention.

  The exposure apparatus EX of the present embodiment has a trapezoidal mirror 2 added to the configuration in which the distortion and astigmatic difference described in the above embodiments can be adjusted to bend the optical path at a right angle.

  The first refractive optical member 1 is arranged in parallel with the reticle R and the substrate P in the optical path between the reticle R and the trapezoidal mirror 2. The second refractive optical member 6 is disposed in parallel with the reticle R and the substrate P in the optical path between the trapezoidal mirror 2 and the substrate P.

  The illumination optical system IL includes, for example, a light source including a high-pressure mercury lamp and an elliptical mirror that collects a light beam emitted from the light source, and expands the light beam collected by the elliptical mirror. The illumination optical system IL includes a condenser lens that collimates a light beam, and a reticle R that blocks a portion of the parallel light beam from the condenser lens that is not used as irradiation light to the reticle R and defines an illumination area having a predetermined area. A limiting slit plate disposed at a conjugate position. Further, the illumination optical system IL includes a mirror that reflects the light beam from the limiting slit plate and irradiates the reticle R as an original with the slit-shaped illumination light beam.

  The exposure light EL generated by the illumination optical system IL is, for example, a far-field such as KrF excimer laser light (wavelength 248 nm) in addition to the ultraviolet emission lines (g-line, h-line, i-line) emitted from the mercury lamp. Ultraviolet light (DUV light) is used. Further, vacuum ultraviolet light (VUV light) such as ArF excimer laser light (wavelength 193 nm) and F2 laser light (wavelength 157 nm) can be used. The illumination optical system IL can be configured as a so-called Koehler illumination system.

  A projection optical system PL is arranged in the optical path from the reticle R to the substrate P, and the exposure light EL transmitted through the reticle R is incident on the projection optical system PL, and an image of the pattern existing in the illumination area of the reticle R is displayed on the substrate P. To form. As shown in FIG. 10, the projection optical system PL includes, for example, a first refractive optical member 1, a trapezoidal mirror 2, a concave mirror 3, a meniscus lens 4, a convex mirror 5, and a second refractive optical member 6. An image of the pattern is formed on the substrate P. The projection area of the projection optical system onto the substrate P is set to a predetermined shape (for example, an arc shape).

  In the alignment scope AS, for example, the measurement pattern 10a on the reticle stage MST, the measurement pattern 10b on the substrate stage PST, or the substrate P using the e-line and d-line that are part of the emission spectrum of the mercury lamp. Measure the pre-formed pattern.

  The alignment scope AS measures, for example, the focus, magnification, distortion, and astigmatism of the exposure apparatus EX using the measurement pattern 10a on the reticle stage MST and the measurement pattern 10b on the substrate stage PST. The CPU 9 that controls the entire exposure apparatus EX calculates the adjustment amounts of the first and second refractive optical members 1 and 6 from the astigmatism difference and the distortion amount as the measurement results by the alignment scope AS.

  The CPU 9 outputs the movement amount of the optical member corresponding to the adjustment amount of the first and second refractive optical members 1 and 6 to the controllers 8a and 8b that control the actuator of the drive mechanism. The controllers 8a and 8b drive the actuators 7a and 7b to move the first and second refractive optical members 1 and 6 by a predetermined amount.

  Further, the distortion and astigmatism difference can be adjusted by simultaneously driving the convex mirror 5 and the first and second refractive optical members 1 and 6.

  When the exposure is performed with the pattern superimposed on the already patterned substrate, for example, the measurement pattern 10b on the patterned substrate P is measured by the alignment scope AS. Then, the CPU 9 calculates the optimum positions and movement amounts of the first and second refractive optical members 1 and 6 for reducing the deviation between the already formed pattern and the newly formed pattern.

  The CPU 9 outputs the movement amount of the optical member corresponding to the adjustment amount of the first and second refractive optical members 1 and 6 to the controllers 8a and 8b that control the actuator of the drive mechanism. The controllers 8a and 8b drive the actuators 7a and 7b to move the first and second refractive optical members 1 and 6 by a predetermined amount.

  Also, the pattern deviation can be adjusted by simultaneously driving the convex mirror 5 and the first and second refractive optical members 1 and 6.

  The first and second refractive optical members 1 and 6 have drive shafts in the X direction, Y direction, Z direction, tilt X direction, tilt Y direction, and tilt Z direction, respectively. For example, the movement of the second refractive optical member 6 in the Y direction is performed by driving a member that holds the second refractive optical member 6 by the actuator 7b. A drive mechanism such as an actuator is also mounted in the other directions of X, Z, tilt X, tilt Y, and tilt Z (not shown).

  For example, in the exposure apparatus of FIG. 19, the first and second refractive optical members 1 and 6 and the convex unit are moved in combination, during non-exposure, pre-exposure job preparation, pre-exposure substrate measurement, and exposure. A function of adjusting the astigmatic difference and / or distortion at an arbitrary timing may be installed.

  As described above, according to each of the above-described embodiments, distortion and astigmatism difference can be made with high accuracy by moving the object member and the optical member disposed in the vicinity of the image surface in order to enlarge the good image area. Can be adjusted.

  In general, when the distortion or astigmatism is adjusted by moving the optical member, spherical aberration and coma occur as residual aberrations. According to this embodiment, in order to suppress these residual aberrations, Adjustment can be performed by moving the optical member in the vicinity of the surface.

[Device manufacturing method]
Next, a semiconductor device manufacturing process using the exposure apparatus of this embodiment will be described.

  FIG. 20 is a diagram showing a flow of an entire manufacturing process of a semiconductor device. In step S1 (circuit design), a semiconductor device circuit is designed. In step 2 (reticle fabrication), a reticle is fabricated based on the designed circuit pattern. On the other hand, in step S3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step S4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by using the above-described reticle and wafer by the above-described exposure apparatus using the lithography technique. The next step S5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step S4. The assembly process (dicing, bonding), packaging process (chip encapsulation), etc. Process. In step S6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step S5 are performed. A semiconductor device is completed through these steps, and is shipped in step S7.

  The wafer process in step S4 includes the following steps. That is, an oxidation step for oxidizing the wafer surface, a CVD step for forming an insulating film on the wafer surface, an electrode formation step for forming electrodes on the wafer by vapor deposition, and an ion implantation step for implanting ions into the wafer. The image forming apparatus further includes a resist processing step for applying a photosensitive agent to the wafer, an exposure step for forming a latent image pattern on the wafer after the resist processing step by the exposure apparatus, and a development step for developing the wafer exposed in the exposure step. Furthermore, an etching step for removing portions other than the latent image pattern developed in the development step, and a resist stripping step for removing a resist that has become unnecessary after the etching is performed. By repeating these steps, multiple circuit patterns are formed on the wafer.

It is a figure which shows the structure of the optical system of 1st Embodiment which concerns on this invention. It is a figure which shows the distortion change when the 1st refractive optical member of 1st Embodiment is shifted. It is a figure which shows the astigmatic difference change when the 1st refractive optical member of 1st Embodiment is shifted. It is a figure which shows the distortion change when the 2nd refractive optical member of 1st Embodiment is shifted. It is a figure which shows the astigmatic difference change when the 2nd refractive optical member of 1st Embodiment is shifted. It is a figure which shows the distortion change when the 1st, 2nd refractive optical member of 1st Embodiment is shifted simultaneously. It is a figure which shows the astigmatic difference change when the 1st, 2nd refractive optical member of 1st Embodiment is shifted simultaneously. It is a figure which shows the distortion change when the 1st, 2nd refractive optical member of 1st Embodiment is shifted simultaneously. It is a figure which shows the astigmatic difference change when the 1st, 2nd refractive optical member of 1st Embodiment is shifted simultaneously. It is a figure which shows the structure of the optical system of 2nd Embodiment. It is a figure which shows the distortion change when the 1st refractive optical member of 2nd Embodiment is shifted. It is a figure which shows the astigmatic difference change when the 1st refractive optical member of 2nd Embodiment is shifted. It is a figure which shows the structure of the optical system of 3rd Embodiment. It is a figure which shows the distortion change when the 1st refractive optical member of 3rd Embodiment is shifted. It is a figure which shows the astigmatic difference change when the 1st refractive optical member of 3rd Embodiment is shifted. It is a figure which shows the distortion change when the 2nd refractive optical member of 3rd Embodiment is shifted. It is a figure which shows the astigmatic difference change when the 2nd refractive optical member of 3rd Embodiment is shifted. It is a figure which shows the structure of the optical system of 4th Embodiment. It is a figure which shows the structure of the exposure apparatus of this embodiment. It is a figure which shows the flow of the whole manufacturing process of a semiconductor device.

Explanation of symbols

R reticle P substrate MST reticle stage PST substrate stage IL illumination optical system PL projection optical system AS alignment scope EX exposure machine EL exposure light 1 first refractive optical member 2 trapezoidal mirror 3 first concave mirror 3 ′ second concave mirror 4 meniscus lens 5 Convex mirror 6 Second refractive optical member 7a Actuator 7b Actuator 8a Controller 8b Controller 9 CPU
10 Sensor

Claims (9)

An optical system that projects an image of an object surface onto an image surface,
Including at least one first refractive optical member disposed on the object plane side , and including at least one second refractive optical member disposed on the image plane side ,
By moving in the direction perpendicular to the first refractive optical element and the optical axis the second refractive optical member, the adjustment means for adjusting independently the astigmatism and distortion of the optical system Have
The adjusting means includes
The amount of distortion generated by the movement of the first refractive optical member in the direction perpendicular to the optical axis direction at a certain image height and the movement of the second refractive optical member in the direction perpendicular to the optical axis direction. The first refracting optical member and the second refracting optical member are moved so that the amount of distortion generated by the lens is different from the amount of distortion generated and the total amount of distortion generated is smaller than one of the generated amounts. Adjust the point difference,
Or
The amount of astigmatism caused by the movement of the first refractive optical member in the direction perpendicular to the optical axis direction at a certain image height and the direction perpendicular to the optical axis direction of the second refractive optical member . The first refractive optical member and the second refractive optical member are moved so that the generated amount of astigmatism due to the movement of the first and second astigmatism is different and the total generated amount of astigmatic difference is smaller than one generated amount. An optical system characterized by adjusting distortion of the optical system. The adjusting means is a measuring means for measuring at least one of astigmatism and distortion of the optical system, and the optical axis direction of the first refractive optical member and the second refractive optical member from the measurement result of the measuring means. driving means for driving the first refractive optical element and the second refractive optical member based on the movement amount calculated by the calculation means and the calculation means for calculating the amount of movement in a direction perpendicular to, The optical system according to claim 1, comprising: In the optical system, at least a first concave reflection surface, a convex reflection surface, and a second concave reflection surface are arranged in an optical path from the object plane to the image plane,
The first refractive optical member is disposed between the object surface and the first concave reflecting surface;
The optical system according to claim 1, wherein the second refractive optical member is disposed between the second concave reflecting surface and the image plane. Said first refractive optical element and the second refractive optical element is any one of claims 1 to 3, characterized in that it is composed of a spherical lens optically effective part is outside the shaft without the optical axis 1 The optical system according to item. Said first refractive optical element and the second refractive optical element is any one of claims 1 to 3, characterized in that it is composed of aspheric lens optically effective part is outside the axis not including the optical axis 2. The optical system according to item 1. The distortion of the optical system of the first refractive optical element and when moving the second refractive optical element at the same time, the distortion that occurs when moving the first refractive optical element and the second refractive optical member The optical system according to claim 1, wherein the optical system is less than or equal to ½ of the optical system. Astigmatism of the optical system when moving the first refractive optical element and the second refractive optical element at the same time, occurs when moving the first refractive optical element and the second refractive optical member The optical system according to claim 1, wherein the optical system is equal to or less than ½ of an astigmatic difference. It has an optical system given in any 1 paragraph of Claims 1 thru / or 7,
An exposure apparatus for exposing a pattern of an original on a substrate through the optical system. Exposing the substrate using the exposure apparatus according to claim 8;
And developing the exposed substrate. A device manufacturing method comprising:

Images