Patent Application
20060158504
The present invention relates to an exposure apparatus and device manufacturing method and, more particularly, to an exposure apparatus which forms a light source image on an object and moves the object using a stage to form a pattern on the object, and a device manufacturing method using the exposure apparatus.
Along with recent developments in IT (Information Technology) and the expansion of the market, demands for a manufacturing apparatus which manufactures semiconductor devices, liquid-crystal display devices, and the like increase more and more. A particularly important equipment in manufacturing such devices is an exposure apparatus which is used to form a pattern. Regarding the exposure apparatus, emphasis is put not only on the exposure performance but also on the COO (Cost Of Ownership) which supports the price competition of the finished products, i.e., the total operation cost of the manufacturing apparatus.
As an exposure apparatus, a one-to-one imaging exposure apparatus is generally used to illuminate a mask to form a pattern within a predetermined region of the mask on a substrate within a good-image area in a projection imaging system. However, in the above one-to-one imaging exposure apparatus, the cost of a mask having a circuit pattern tends to greatly increase when the substrate size becomes larger. This is because one-to-one imaging basically requires a mask having the same size as a substrate. Accordingly, a reduction in cost of a mask is a serious problem in developing a large-sized display such as a liquid crystal display.
Even in developing leading-edge VLSI submicron lithography, it is troublesome to reduce the cost of a mask, although its technical field is different from the liquid crystal display in a line width, exposure area, and device specification. In the VLSI, the problem is not an increase in size of a mask when the substrate size becomes larger, but an increase in cost due to micropatterning. In particular, since the VLSI requires a large number of, e.g., 20 or more masks to be included in a mask set, mask costs present a serious problem.
To solve the above problems about the mask cost, a technique has been proposed which uses a mask lithography exposure apparatus (see U.S. Pat. No. 6,133,986).
U.S. Pat. No. 6,133,986 discloses a maskless lithography exposure apparatus which selectively reflects part of light using a DMD (Digital Micromirror Device) to expose the substrate surface.
When a glass substrate is used as an exposure target substrate, the working distance often varies due to undulations typically having a size of about 20 μm, which are present on the surface of the glass substrate. If the working distance varies, a light source image is formed at a position which falls outside the surface of the exposure target substrate, resulting in a decrease in accuracy of the light source image formed on the surface of the exposure target substrate.
In U.S. Pat. No. 6,133,986, the working distance is detected using a light sensor. However, since image data obtained using the light sensor needs to be processed, the response speed becomes naturally low. Accordingly, a separate image data processing device is necessary. In addition, the optical path length needs to be assured. These requirements complicate the apparatus arrangement.
The present invention has been made in consideration of the above problems, and has as its object to provide an exposure apparatus capable of performing high-speed response and an exposure process with a simple arrangement.
According to the first aspect of the present invention, there is provided an exposure apparatus which forms a pattern on an object, comprising an exposure head structure in which a plurality of elemental exposure units each including at least one light source and an optical element which forms an image of the light source on the object are arrayed, a sensor which detects a surface position of the object, and a controller which controls exposure by the exposure head structure based on a detection result by the sensor, wherein the controller forms a pattern on the object while selectively operating one of the plurality of elemental exposure units, which satisfies a predetermined condition.
According to the second aspect of the present invention, there is provided an exposure apparatus which forms a pattern on an object, comprising a light source array having a plurality of light sources, an optical element which forms an image of the light source on the object, a sensor which measures a surface position of the object using electromagnetic energy or dynamic energy, and a controller which controls a position of the image to be formed on the object via the optical element, based on a detection result by the sensor.
According to the third aspect of the present invention, there is provided a device manufacturing method comprising steps of forming a pattern on a substrate using the above-described exposure apparatus, and developing the substrate having the pattern.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
An exposure apparatus according to a preferred embodiment of the present invention will be explained below with reference to
For example, the exposure apparatus according to this embodiment can be used to manufacture a TFT array for a large-sized liquid crystal display panel. In this case, a plurality of arrays of the LED light sources 106 and optical systems 105 are arranged in liquid crystal display pixels 107 (which schematically indicate three, R, G, and B pixels) so as to form by exposure a TFT circuit pattern which controls each pixel 107. Since the TFT circuit for a liquid crystal display repeatedly transfers data for each pixel, there is no need to transfer individual pattern data, i.e., ON/OFF control signals of LED light sources to all pixels in a large-sized substrate. The same data can be transmitted to each pixel to control ON/OFF of the LED light sources. In this embodiment, for example, the size of the exposure target substrate as the large-sized substrate is about 700 mm×900 mm (so-called a 46-inch-panel size), the pixel size of the liquid crystal display is 200 μm×600 μm, and the minimum line width of the TFT circuit pattern is 3 μm. However, the present invention is not limited to these sizes.
Regarding the resolution of the light source image, different light-emitting portions within the light-emitting area of the LED light source 106 do not interfere with each other, as indicated by the beam 202, so incoherent images are formed. The points of the light-emitting portions form extended point images, respectively, depending on the performance of the reduction optical system 105. The resultant point images are shifted and adjusted to positions which are determined depending on the size of the LED light source 106 and the magnification of the reduction optical system 105. The sum of the intensities of the point images forms an entire light source image 203 (see
In the preferred embodiment of the present invention, as a sensor for adjusting the interval between the exposure target substrate 102 and exposure head structure 101, a sensor using electromagnetic energy (e.g., magnetic field, electric field, or radio wave), or a sensor using dynamic energy (e.g., liquid, sound, or position) can be adopted. Such a sensor includes a capacitance sensor for detecting a change in capacitance between a detection target and sensor, a magnetic proximity sensor using a magnet, an eddy current displacement sensor using electromagnetic induction, an ultrasound displacement sensor using ultrasound, and a differential transformer contact type displacement sensor using a differential transformer.
The capacitance sensor is a proximity sensor having a sensitivity which changes depending on a detection target. Assuming that the permittivity of air is 1, a permittivity detectable by the capacitance sensor is considered to be 1.5 or more. Since the permittivity of a glass substrate is about 5 to 10, and that of a metal layer formed on the glass substrate is about 50, the capacitance sensor is suitable for a liquid crystal display exposure apparatus using a glass substrate.
The magnetic proximity sensor is a proximity switch for detecting a change in magnetic flux when a detection target approaches the sensor by combining a magnetic detection element with a magnet.
The eddy current displacement sensor is a proximity sensor using a high-frequency magnetic field. The eddy current displacement sensor supplies a high-frequency current to a coil in a sensor head to generate a high-frequency magnetic field. When a TFT circuit or color filter matrix is formed on a glass substrate as an exposure target substrate, a metal film layer is formed on the surface of the glass substrate. In this case, it is possible to employ the eddy current displacement sensor because of the following reason. In the TFT circuit, a gate electrode and wiring portions of the gate and source are made of a metal. In the color filter, a light-shielding body for a black matrix is made of a metal such as chromium. When an exposure process is executed after the metal is patterned, the metal shape (pattern) has an influence on the sensor in detecting a gap. Accordingly, if almost the same patterns are formed side by side, the sensors may be arranged at positions corresponding to integer multiples of the pattern pitch, thereby arranging a plurality of sensors at almost the same positions on the respective patterns. In a liquid crystal display, a plurality of dots (pixels) serving as minimum units for displaying a character or image are two-dimensionally arranged side by side. Hence, when the plurality of sensors are arranged at positions corresponding to integer multiples of the pixel pitch while tracing a gate wiring line to cause each sensor to measure a gap, the gaps can be compared and corrected under almost the same condition.
The ultrasound displacement sensor is a proximity sensor which transmits ultrasound from a sensor head, and receives ultrasound reflected by an object using the sensor head, thereby measuring a gap.
The differential transformer contact type displacement sensor is a contact sensor which differentially couples an induced current generated in a secondary coil when a primary coil is excited by an alternating current, and extracts the resultant current as a voltage difference to obtain a displacement output. As the sensor according to this embodiment, a noncontact sensor such as a proximity sensor is desirable. However, when the surface of an exposure target substrate coated with a resist is brought into contact with a measurement probe, the depth and width of its trace may be about 10 to 100 nm. Hence, a contact sensor can be used in forming a TFT pattern having a line width of 3 μm.
As shown in
An optical system 105a1 is arranged for the liquid crystal display pixel 107a1 in an oblique direction with respect to the x direction. Similarly, an optical system 105a2 is arranged for the liquid crystal display pixel 107a2 in an oblique direction with respect to the x direction. An optical system 105a3 is arranged for the liquid crystal display pixel 107a3 in an oblique direction with respect to the x direction. An optical system 105a4 is arranged for the liquid crystal display pixel 107a4 in an oblique direction with respect to the x direction. LED light sources 106a1 to 106a4 are arranged at positions corresponding to the respective optical systems 105a1 to 105a4, in correspondence with the above arrangement. The LED light sources 106a1 to 106a4 are combined with the corresponding optical systems 105a1 to 105a4 to form elemental exposure units. Each elemental exposure unit forms an image of the corresponding LED light source on the exposure target substrate 102.
The sensors 108a, 108b, and 108c can time-serially measure intervals between themselves and the surface of the exposure target substrate 102 in the x direction when the exposure target substrate 102 moves in the x direction. A controller 307 can adjust positions where light source images in the z direction of the optical systems 105a1 to 105a4 are to be formed, based on the detection results by the sensors 108a, 108b, and 108c. As a method of adjusting the positions where the light source images in the z direction of the imaging optical systems 105a1 to 105a4 are to be formed, it is possible to use a method of adjusting the lens powers of the optical elements (305 and 306 in
Alternatively, the positions where the light source images in the z direction of the optical elements are to be formed may be adjusted in advance differently from each other based on the detection results by the sensors 108a, 108b, and 108c, thereby selectively ON/OFF-controlling the LED light sources. For example, referring to
According to this embodiment, the response speed can be increased and the apparatus arrangement can be simplified using the sensors described above. In addition, when a position where a light source image of an optical element is to be formed is adjusted in advance differently from the remaining imaging positions, and an LED light source of an elemental exposure unit which satisfies desired exposure conditions is selectively operated, the gap adjustment process can be simplified.
The second preferred embodiment according to the present invention will be explained below with reference to FIGS. 8 to 11.
Although four light sources are included in one block in
This embodiment is convenient in that the total number of imaging optical systems can be decreased without decreasing the number of light source images. This amounts to downsizing the exposure heads 104a to 104d in the exposure head array 104 shown in
In the arrangement shown in
The third embodiment will be explained below with reference to FIGS. 12 to 14.
In FIGS. 12 to 13B, the light sources 106 in a row of the scanning direction are continuously arranged in an array without forming a space. However, as shown in
The present invention is not limited to the above-described embodiments, and a sequence and the like can be variously changed. In addition, as the device arrangements of an LED light source and light source array, the following device arrangements can be appropriately selected and used.
For example, a light source 106 includes a solid-state element which emits light by spontaneous emission. As the solid-state element, a light-emitting diode element (to be referred to as “LED element” hereinafter) or EL element can be used. As the LED elements, LED elements having various types of light emission wavelengths, e.g., GaAs, GaAlAs, GaP/GaP, GaAlAs/GaAs, InGaAlP, InGaAlP/GaP, InGaAlP/GaAs, AlInGaN, AlGaN, InGaN, GaN, AlN, ZnO, ZnSe, or diamond can be used. It is more preferable to use LED elements having light emission wavelengths suitable to expose a resist, e.g., AlInGaN, AlGaN, or InGaN, although the present invention is not particularly limited to this. As the EL element, organic EL and inorganic EL can be used.
The light emission wavelength of a LED element is desirably set in accordance with the sensitivity of a resist as the exposure target. An LED element having an emission wavelength with a central wavelength of 365 nm and a spectral half width Δλ of about 10 nm to about 20 nm can be used. When selecting the emission wavelength of the LED element, a LED element which has an optimal emission wavelength and wavelength width may be selected in accordance with the sensitivity curve of the resist regardless of the type of the resist. Furthermore, in the arrangement using the overlay exposure process described above, a plurality of LED elements having different light emission wavelengths may be mixed to exhibit a desired exposure wavelength distribution on the irradiated surface.
In the above-described embodiments, light from an LED is directly used for exposure. That is, no wavelength filter is necessary to select a specific wavelength range. Actually, a wavelength filter may be used when necessary. The wavelength filter may be monolithically formed with each LED element. Resonator LEDs as disclosed in (non-patent reference 1: Science Vol. 265, pp. 943, 1994) may be used.
Since an LED light source can typically take a modulation frequency up to the GHz order at maximum by removing/transporting a substrate in a 10-MHz GaN system, it can be turned on/off at a very high speed. Using this feature, a high output can be obtained by performing an exposure operation, which may be originally ON operation performed once, by finer-pulse driving to perform pulse emission. This is because the LED element radiates heat efficiently using the pulse driving process, so that a larger average current and average power can be supplied to the LED light source. When the repeating frequency is sufficiently high as compared to the exposure time of the exposure apparatus, the resist can be exposed in the same manner as with continuous light. The exposure amount can be adjusted depending on the pulse number.
To improve the use efficiency of light emitted by an LED, an LED element having a light convergence distribution can be used. As the LED element having the light convergence distribution, for example, an LED element which controls the space mode of light emitted from the LED element by spontaneous emission may be used to change the distribution of the spontaneous emission light. More specifically, the space mode of the emitted light may be directly controlled by an LED integral with a resonator in accordance with spontaneous emission control or the like which uses a resonator QED effect described in non-patent reference 1 described above, to change the distribution of the spontaneous emission light.
As the LED array light source, an LED array light source which is formed as a light source with a wafer scale may be used. An optimal number of LED arrays included in one chip for an LED light source can be selected in consideration of the device yield and mounting cost.
As shown in
To fill the gaps between the substrate 1604 and lenses 1602, spacers 1606 may be arranged between them. To reflect wide-angle exit light 1608 from the LED elements 1601 in the direction of the optical axis, the substrate 1604 side portions of the lenses 1602 may be cut out in quadrangular prisms and ridge structures 1607 may be arranged along the resultant space. Aluminum films may be formed on the interfaces between the lenses 1602 and ridge structures 1607 so that the interfaces have high reflectance. The ridge structures 1607 may be hollow. In this case, the inclined interfaces serve as reflection surfaces of total reflection or Fresnel reflection in accordance with a difference in refractive index between the lenses 1602 and air. High-reflectance metal films of aluminum, rhodium, silver, or the like may be formed in advance on the inclined surfaces of the lenses 1602.
A semiconductor device manufacturing process using an exposure apparatus according to a preferred embodiment of the present invention will be explained below.
The semiconductor device process in step 4 includes: an oxidation step of oxidizing the surface of the semiconductor layer; a CVD step of forming an insulating film on the surface; an electrode formation step of forming an electrode on the surface by vapor deposition; an ion implantation step of implanting ions in the semiconductor layer; a resist processing step of applying a photosensitive agent to the substrate; an exposure step of causing the above-mentioned exposure apparatus to form a circuit pattern on the substrate having undergone the resist processing step; a development step of developing the substrate exposed in exposure step; an etching step of etching the resist except the resist image developed in the development step; and a resist removal step of removing an unnecessary etched resist. These steps are repeated to form multiple circuit patterns on the substrate.
As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.
This application claims the benefit of Japanese Application No. 2005-013033, filed on Jan. 20, 2005, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-013033 | Jan 2005 | JP | national |
