Patent Application
20120127445
Exposure apparatuses for semiconductor processing are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage assembly that positions a reticle, an optical assembly, a wafer stage assembly that positions a semiconductor wafer, a measurement system, and a control system. With this design, images from the reticle are transferred to the semiconductor wafer. The size of the images and features within the images transferred onto the wafer from the reticle are extremely small.
As is known, some of the components of the exposure apparatus generate vibration that can reduce the quality of the images that are transferred onto the wafer. For example, vibration transferred to the optical assembly can adversely influence the quality of the features that are transferred to the semiconductor wafer.
The present invention is directed to an optical isolation assembly for reducing the transmission of vibration from an optical barrel to an optical element assembly. In one embodiment, the optical isolation assembly includes an optical mover assembly, a first measurement system, a second measurement system, and a control system. The optical mover assembly moves and positions the optical element assembly relative to the optical barrel along a first axis. The first measurement system generates one or more first measurement signals that relate to the relative position between the optical element assembly and the optical barrel along the first axis. The second measurement system generates one or more second measurement signals that relate to the absolute movement of the optical element assembly along the first axis. The control system controls the optical mover assembly utilizing the first measurement signals and the second measurement signals.
As an overview, in certain embodiments, because the control system utilizes both the first measurement signals and the second measurement signals, the control system can control the optical mover assembly with improved accuracy, and thus, the position of the optical element assembly can be maintained with improved accuracy.
In certain embodiments, the optical mover assembly also moves the optical element assembly along a second axis that is orthogonal to the first axis, along a third axis that is orthogonal to the first axis and the second axis, and about the first, second, and third axes. In one embodiment, the optical mover assembly can include three spaced apart movers, and each mover can be a voice coil type mover that moves the optical element assembly with two degrees of freedom. With this design, the three movers can cooperate to move the optical element assembly with six degrees of freedom.
Further, each mover can include a first mover component that is coupled to the optical barrel, and a second mover component that is coupled the optical element assembly. Moreover, the second mover component can be spaced apart from the first mover component so that vibration from the optical barrel is not transferred via the movers to the optical element assembly.
In certain embodiments, the first measurement system is designed so that the first measurement signals also relate to the position of the optical element assembly relative to the optical barrel along the second and third axes, and about the first, second, and third axes. Further, in certain embodiments, the second measurement system is designed so that the second measurement signals also relate to the absolute movement of the optical element assembly along the second and third axes, and about the first, second, and third axes.
Additionally, the optical isolation assembly can include a support that supports the weight of the optical element assembly relative to the optical barrel along the first axis, while allowing the optical mover assembly to move the optical element assembly relative to the optical barrel. With this design, less power is required by the optical mover assembly to support the weight of the optical element assembly.
In one embodiment, the support includes a first magnetic component that is coupled to the optical barrel and a second magnetic component that is coupled to the optical element assembly. In this design, the second magnetic component is spaced apart from the first magnetic component, and the second magnetic component is repulsed by the first magnetic component. In another embodiment, the support defines a fluid chamber that supports the optical element assembly.
The present invention is also directed to an optical assembly comprising an optical element assembly, an optical barrel, and the optical isolation assembly described above. Moreover, the present invention is directed to an exposure apparatus for transferring an image to a substrate. Further, the present invention is directed to a method for manufacturing a wafer that includes the steps of providing a substrate and transferring an image to the substrate with the exposure apparatus described herein.
In yet another embodiment, the present invention is directed to a method for reducing the transmission of vibration from an optical barrel to an optical element assembly. In this embodiment, the method includes the steps of (i) supporting the optical element assembly relative to the optical barrel along the first axis with an optical mover assembly; (ii) generating a first measurement signal that relates to the position of the optical element assembly relative to the optical barrel along the first axis with a first measurement system; (iii) generating a second measurement signal that relates to the absolute movement of the optical element assembly along the first axis with a second measurement system; and (iv) controlling the optical mover assembly utilizing the first measurement signal and the second measurement signal with a control system.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
As an overview, in
A number of Figures include an orientation system that illustrates an X axis, a Y axis that is orthogonal to the X axis and a Z axis that is orthogonal to the X and Y axes. It should be noted that these axes can also be referred to as the first, second and third axes.
The exposure apparatus 10 is particularly useful as a lithographic device that transfers a pattern (not shown) of an integrated circuit from a reticle 32 onto a semiconductor wafer 34. The exposure apparatus 10 mounts to a mounting base 36, e.g., the ground, a base, or floor or some other supporting structure.
There are a number of different types of lithographic devices. For example, the exposure apparatus 10 can be used as a scanning type photolithography system that exposes the pattern from the reticle 32 onto the wafer 34 with the reticle 32 and the wafer 34 moving synchronously. Alternatively, the exposure apparatus 10 can be a step-and-repeat type photolithography system that exposes the reticle 32 while the reticle 32 and the wafer 34 are stationary.
In one embodiment, the exposure apparatus 10 is an extreme ultra-violet (“EUV”) type exposure apparatus.
However, the use of the exposure apparatus 10 provided herein is not limited to a photolithography system for semiconductor manufacturing. The exposure apparatus 10, for example, can be used as an LCD photolithography system that exposes a liquid crystal display device pattern onto a rectangular glass plate or a photolithography system for manufacturing a thin film magnetic head.
The apparatus frame 12 is rigid and supports the components of the exposure apparatus 10. The apparatus frame 12 illustrated in
In one embodiment, the illumination system 14 includes an illumination source 38 and an illumination optical assembly 40. The illumination source 38 emits an energy beam 41 (irradiation) of light energy. The illumination optical assembly 40 guides the beam 41 of light energy from the illumination source 38 to the reticle 32. The beam 41 illuminates selectively different portions of the reticle 32 and exposes the wafer 34. In
The illumination source 38 can be a g-line source (436 nm), an i-line source (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm) or a F2 laser (157 nm). Alternatively, the illumination source 38 can generate charged particle beams such as an x-ray or an electron beam. For instance, in the case where an electron beam is used, thermionic emission type lanthanum hexaboride (LaB6) or tantalum (Ta) can be used as a cathode for an electron gun and the electron beam 41 is in the extreme ultra-violet wavelength. Furthermore, in the case where an electron beam is used, the structure could be such that either a mask is used or a pattern can be directly formed on a substrate without the use of a mask.
The projection optical assembly 16 guides the light energy 41 to the wafer 34. Depending upon the design of the exposure apparatus 10, the optical assembly 16 can magnify or reduce the image illuminated on the reticle 32. The optical assembly 16 need not be limited to a reduction system. It could also be a 1× or magnification system.
When far ultra-violet rays such as the excimer laser is used, glass materials such as quartz and fluorite that transmit far ultra-violet rays can be used in the optical assembly 16. When the F2 type laser or x-ray is used, the optical assembly 16 can be either catadioptric or refractive. Alternatively, for an EUV energy beam 41, the optical elements 28 are reflective (e.g. mirrors) and the optical path for the EUV beam 41 should be in a vacuum.
The reticle stage assembly 18 holds and positions the reticle 32 relative to the optical assembly 16 and the wafer 34. Somewhat similarly, the wafer stage assembly 20 holds and positions the wafer 34 with respect to the projected image of the illuminated portions of the reticle 32. The design of each stage assembly 18, 20 can be varied to suit the movement requirements of the exposure apparatus 10. In
The sensor system 22 monitors the position of (i) the reticle stage 42 and the reticle 32 relative to the optical assembly 16 or some other reference, and (ii) the wafer stage 46 and the wafer 34 relative to the optical assembly 16 or some other reference. With this information, the control system 24 can control the reticle stage assembly 18 to precisely position the reticle 32 and the wafer stage assembly 20 to precisely position the wafer 34. For example, the sensor system 22 can utilize multiple laser interferometers, encoders, and/or other measuring devices.
The control system 24 is electrically connected to the optical isolation assembly 30, the reticle stage assembly 18, the wafer stage assembly 20, and the sensor system 22. The control system 24 receives information from the sensor system 22 and controls the stage assemblies 18, 20 to precisely position the reticle 32 and the wafer 34. Further, the control system 24 controls the operation of the optical isolation assembly 30 to precisely position and isolate the optical element assembly 28. The control system 24 can include one or more processors and circuits.
Additionally, the exposure apparatus 10 can include one or more additional isolation systems (not shown) that isolate the projection optical assembly 16 from the other components of the exposure apparatus 10.
A photolithography system (an exposure apparatus) according to the embodiments described herein can be built by assembling various subsystems, including each element listed in the appended claims, in such a manner that prescribed mechanical accuracy, electrical accuracy, and optical accuracy are maintained. In order to maintain the various accuracies, prior to and following assembly, every optical system is adjusted to achieve its optical accuracy. Similarly, every mechanical system and every electrical system are adjusted to achieve their respective mechanical and electrical accuracies. The process of assembling each subsystem into a photolithography system includes mechanical interfaces, electrical circuit wiring connections and air pressure plumbing connections between each subsystem. There is also a process where each subsystem is assembled prior to assembling a photolithography system from the various subsystems. Once a photolithography system is assembled using the various subsystems, a total adjustment is performed to make sure that accuracy is maintained in the complete photolithography system. Additionally, it is desirable to manufacture an exposure system in a clean room where the temperature and cleanliness are controlled.
This invention can be utilized in an immersion type exposure apparatus with taking suitable measures for a liquid. For example, PCT Patent Application WO 99/49504 discloses an exposure apparatus in which a liquid is supplied to the space between a substrate (wafer) and a projection lens system in exposure process. As far as is permitted, the disclosures in WO 99/49504 are incorporated herein by reference.
Further, this invention can be utilized in an exposure apparatus that comprises two or more substrate and/or reticle stages. In such apparatus, the additional stage may be used in parallel or preparatory steps while the other stage is being used for exposing. Such a multiple stage exposure apparatus are described, for example, in Japan Patent Application Disclosure No. 10-163099 as well as Japan Patent Application Disclosure No. 10-214783 and its counterparts U.S. Pat. No. 6,341,007, No. 6,400,441, No. 6,549,269, and No. 6,590,634. Also it is described in Japan Patent Application Disclosure No. 2000-505958 and its counterparts U.S. Pat. No. 5,969,411 as well as U.S. Pat. No. 6,208,407. As far as is permitted, the disclosures in the above-mentioned U.S. patents, as well as the Japan Patent Applications, are incorporated herein by reference.
The optical base 26 is rigid and can be secured to the optical barrel 25 (illustrated in
The optical element assembly 28 directs the energy beam 41 (illustrated in
In one embodiment, the optical element 250 is circular disk shaped and includes a reflective coating 254 (illustrated with cross-hatching) that is designed to reflect an EUV energy beam 41. Alternatively, the reflective coating 254 can reflect light at a wavelength other than EUV or the optical element 250 can be designed to transmit the energy beam 41.
Further, in
The element connector assembly 253 secures the optical element 250 to the element mount 252. In one embodiment, the element connector assembly 253 includes three, equally spaced apart connectors 253A (only two are illustrated in
The optical isolation assembly 30 isolates and precisely positions the optical element assembly 28. For EUV lithography systems 10, the reflective optical elements 250 are very position sensitive. In one embodiment, the optical isolation assembly 308 isolates the optical element 250 from vibration.
Further, during operation of the EUV lithography systems 10, a portion of the extreme ultraviolet radiation is absorbed by the optical elements 250. The absorbed ultraviolet radiation heats the illuminated regions of the optical elements 250 and causes the temperature in the illuminated regions to rise to a greater extent than the temperature in non-illuminated regions of the optical elements 250. The increase in temperature in the illuminated regions causes the optical element 250 to distort. This can blur the image that is transferred onto the wafer 34 (illustrated in
In one embodiment, the optical isolation assembly 30 includes an optical mover assembly 256, a first measurement system 258, a second measurement system 260, and a support assembly 262 that cooperate to isolate and accurately position the optical element assembly 28. Alternatively, the optical isolation assembly 30 can have fewer or more components than illustrated in
The optical mover assembly 256 moves the optical element assembly 28 relative to the optical base 26. In one embodiment, the optical mover assembly 256 includes three, equally spaced apart movers 264 that each move with two degrees of freedom so that the three movers 264 cooperate to move the optical element assembly 28 with six degrees of freedom, namely along the X, Y and Z axes, and about the X, Y, and Z axes. Alternatively, for example, the optical mover assembly 256 can be designed to move the optical element assembly 28 with fewer than three degrees of freedom.
The design of each mover 264 can be varied to suit the movement and isolation requirements of the optical element assembly 28. In the embodiment illustrated in
With this design, electrical current (not shown) is supplied to the conductor(s) in each conductor array by the control system 24. For each mover 264, the electrical current in the conductor(s) interact with the magnetic field(s) from the magnets in the magnet array. For each mover 264, this causes a force (Lorentz force) between the conductors and the magnets that can be used to selectively move the optical element assembly 28 with two degrees of freedom.
It should be noted that with the mover 264 illustrated in
The first measurement system 258 generates one or more first measurement signals that relate to the relative movement between the optical element assembly 28 and the optical base 26. In the embodiment illustrated in
In one non-exclusive example, each position sensor 266 can be a linear encoder, such as a laserscale that monitors movement along two axes. With this design, the three position sensors 266 can be used to monitor six degrees of freedom. Alternatively, each position sensor 266 can be a laser interferometer or another type of measuring device.
The second measurement system 260 provides one or more second measurement signals that relate to the absolute movement of the optical element assembly 28. In one non-exclusive embodiment, the second measurement system 260 includes three spaced apart absolute sensors 268 that monitor the absolute movement of the optical element assembly 28 along the X, Y, and Z axes, and about the X, Y, and Z axes. Additionally or alternatively, the second measurement system 260 can be designed to monitor absolute movement of the optical element assembly 28 with less than six degrees of freedom.
In one non-exclusive example, each absolute sensor 268 can be a two axis accelerometer. With this design, the three absolute sensors 268 can be used to monitor six degrees of freedom. Alternatively, for example, each absolute sensor 268 can be a three axis accelerometer. With this design, the two absolute sensors 268 can be used to monitor six degrees of freedom. As another non-exclusive example, three, two-axis short-distance position encoders can be utilized.
The control system 24 directs voltage to and individually controls each of the movers 264 based on both the first measurement signals and the second measurement signals. Because the control system 24 utilizes both measurement signals, the optical isolation assembly 30 is better able to isolate and accurately position the optical element assembly 28.
For example, in the situation in which vibration is being transferred to the optical base 26 via the optical barrel 25 (illustrated in
For example, in one embodiment, the six degree of freedom control system will utilize signals from three, two degree of freedom sensors and convert the signals to six degree of freedom measurement (e.g. along the X, Y, and Z axes, and about the X, Y, and Z axes).
The support assembly 262 supports the weight of the optical element assembly 28 along the Z axis so that the optical mover assembly 256 does not have to be driven to support the weight of the optical element assembly 28 while still allowing the optical mover assembly 256 to move and position the optical element assembly 28. This reduces the amount of heat generated by the optical mover assembly 256. The design of the support assembly 262 can be varied. In
In certain embodiments, the optical mover assembly 256 and the support assembly 262 are coupled to the optical element assembly 28 in a kinematic fashion to inhibit deformation of the optical element 250.
Further, in
In this embodiment, one of the magnetic components 570A, 570B is coupled to the optical base 26 (illustrated in
It should be noted that dashed arrows in
In
Further, in this embodiment, a seal 688 (illustrated as arrows) seals the interface between the support piston 682A and the lower frame 680B and allows the support piston 682A to move within the lower frame 680B. For example, a fluid source 690 can be connected via tubes 692 (two are illustrated in
Moreover, in one embodiment, the support chamber 686 is in fluid communication with the atmosphere via one or more conduits 694 (only one is illustrated in
It should be noted that a somewhat similar support 670 is described in Japanese Publication Number JP2006/140366, entitled “Projection Optical System and Exposure Apparatus”. As far a permitted, the contents of Japanese Publication Number JP2006/140366 are incorporated herein by reference. Semiconductor devices can be fabricated using the above described systems, by the process shown generally in
At each stage of wafer processing, when the above-mentioned preprocessing steps have been completed, the following post-processing steps are implemented. During post-processing, first, in step 715 (photoresist formation step), photoresist is applied to a wafer. Next, in step 716 (exposure step), the above-mentioned exposure device is used to transfer the circuit pattern of a mask (reticle) to a wafer. Then in step 717 (developing step), the exposed wafer is developed, and in step 718 (etching step), parts other than residual photoresist (exposed material surface) are removed by etching. In step 719 (photoresist removal step), unnecessary photoresist remaining after etching is removed.
Multiple circuit patterns are formed by repetition of these preprocessing and post-processing steps.
While the current invention is disclosed in detail herein, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
