1. Field of the Invention
The present invention relates to a pellicle inspection device, an exposure apparatus using the same, and a device manufacturing method.
2. Description of the Related Art
An exposure apparatus is an apparatus that transfers a pattern of an original (reticle or mask) onto a photosensitive substrate (e.g., wafer, glass plate, and the like, where the surface thereof is coated with a resist layer) via a projection optical system in a lithography process in a manufacturing process of a semiconductor device, a liquid crystal display device, and the like. When foreign matter such as fine particles is present on the patterned surface of the original during transfer, foreign matter is also transferred simultaneously, resulting in an decrease in product yield. As a countermeasure to prevent this, for example, a protective film called a “pellicle” is affixed to the surface of a reticle in the semiconductor device manufacturing process in order to prevent foreign matter from adhering to the patterned surface of the reticle or to prevent foreign matter from adhering within the depth of field of a projection lens. With this arrangement, foreign matter of a certain size, which is adhering to the pellicle, is outside the depth of field, whereby the foreign matter is not imaged on a wafer.
However, if foreign matter, which adheres to a pellicle, has a comparatively large size (e.g., 60 μm or more), it may cause degradation of a reticle upon illumination, which may cause the production of defective products. Also, in the event of the breakage of a pellicle, foreign matter may be mixed in from the damaged point to thereby adhere to a patterned surface. Furthermore, a scratch made on a pellicle may cause the degradation of a reticle upon illumination as in the case of the foreign matter adhesion described above.
Accordingly, there have conventionally been proposed various devices that inspect whether or not foreign matter is adhering to a pellicle in advance. Japanese Patent Laid-Open No. 10-221270 discloses a foreign matter inspection device that emits a linearly polarized laser beam from one side to impinge obliquely on the pellicle film mounted on a stage, and causes a light receiving lens disposed in a vertical direction to receive scattered light from foreign matter adhering to the pellicle film for the determination of the presence of foreign matter. In addition, Japanese Patent Laid-Open No. 2003-315982 discloses a degradation identification method in which a pattern for identification is formed on a pellicle film to identify the degradation of the pellicle film from the results of measuring the pattern.
However, in the pellicle inspection devices disclosed in Japanese Patent Laid-Open No. 10-221270 and Japanese Patent Laid-Open No. 2003-315982, damage may not be detected depending on the degradation degree of a pellicle film. In this case, examples of damage to a pellicle film include scratches or breaks such as a hole, a recess, and the like. In particular, in the degradation identification method disclosed in Japanese Patent Laid-Open No. 2003-315982, a scratch or break cannot be detected without printing the pattern for identification on a pellicle film, therefore a special device needs to be introduced.
In view of the foregoing, the present invention provides a pellicle inspection device that can readily detect scratches or breaks in a pellicle film regardless of the degradation degree of the pellicle film.
According to an aspect of the present invention, a pellicle inspection device that detects damage to a pellicle film disposed on an original is provided that includes a measuring unit configured to measure a natural vibration frequency of the pellicle film, wherein the pellicle inspection device detects damage to the pellicle film based on the value of the natural vibration frequency measured by the measuring unit.
According to the present invention, since damage on the pellicle film is detected based on the value of the natural vibration frequency of the pellicle film, damage such as scratches, breaks, or the like of the pellicle film can be readily detected regardless of the degradation degree of the pellicle film.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, preferred embodiments of the present invention will now be described with reference to the attached drawings.
First, the configuration of a pellicle inspection device (hereinafter referred to as “inspection device”) according to a first embodiment of the present invention will now be described.
The pellicle film 2 is a protective film that protects a pattern 8 formed on the surface of the reticle 3 and is affixed to a pellicle frame 7 made of aluminum alloy, which is fixed to the reticle 3, via an adhesive while maintaining a constant tension so as to prevent the looseness of the pellicle film 2. Also, the material of the pellicle film 2 is an organic material such as nitrocellulose or the like having elasticity.
The sound source 5 is a non-contact type vibration inducing unit configured to induce vibration in the pellicle film 2. In the present embodiment, the sound source 5 is capable of changing the vibration frequency of a sound wave radiated to the pellicle film 2. A sound wave is radiated to the pellicle film 2 while changing its vibration frequency as appropriate. At this time, the pellicle film 2 gradually starts vibration when the sound wave impinges it. When the vibration frequency of the sound source 5 is matched with the natural vibration frequency of the pellicle film 2, the amplitude gradually increases, and resonance is thereby started. The microphone 6 is a sound wave type sensor that detects vibration generated at the surface of the pellicle film 2. The microphone 6 detects the amplitude of the vibration of the pellicle film 2 and the vibration period and calculates the vibration frequency at which the maximum amplitude occurs as the natural vibration frequency of the pellicle film 2. The configuration in combination with the sound source 5 and the microphone 6 becomes a unit for measuring a vibration frequency of the pellicle film 2 according to the present embodiment.
Furthermore, the inspection device 1 includes a control section 9 that controls the operation of the sound source 5 and the microphone 6. The control section 9 further includes a storage unit 10 that stores the natural vibration frequency measured by the microphone 6, and an information processing unit 11 that processes vibration frequency measured data. The control section 9 controls the vibration frequency of the sound source 5 as well as manages the natural vibration frequency of the pellicle film 2 obtained for each measurement. The storage unit 10 is a storage unit configured by a magnetic storage medium, a memory, or the like, and stores the parameter (reticle parameter) of management information of the reticle 3 while the parameter corresponds one-to-one with the reticle 3.
Next, the operation of the inspection device 1 of the present embodiment will now be described. In general, when the pellicle film 2 is ruptured, tension decreases, which causes a decrease in the natural vibration frequency. In addition, change in the natural vibration frequency occurs even when the pellicle film 2 is scratched or when the pellicle film 2 is distorted. Hence, the inspection device 1 of the present embodiment detects the change in the natural vibration frequency to thereby determine whether or not the pellicle film 2 has been damaged. Hereinafter, a pellicle film inspection (hereinafter referred to as “damage inspection”) processing step performed by the inspection device 1 will be described with reference to a flowchart of
Next, the aforementioned damage inspection processing step will be described with reference to the specific example.
As described above, according to the present embodiment, since determination of the presence of damage on the pellicle film 2 is implemented based on the change of the natural vibration frequency of the pellicle film 2, damage such as scratches, breaks, or the like of the pellicle film 2 can be readily detected regardless of the degradation degree of the pellicle film 2.
Next, the configuration of an inspection device according to a second embodiment of the present invention will now be described.
As shown in
In the inspection device 20, the pellicle film 2 and the pellicle frame 7 are oscillated by pressure applied by the air cylinder 21. As in the first embodiment, the generated vibration propagates through air, and is detected by the microphone 6 disposed below the pellicle film 2. At this time, although the microphone 6 detects vibration in which the vibration components of the pellicle film 2 and the pellicle frame 7 are combined, the combined vibration frequency may be calculated by using an arithmetic unit such as an FFT analyzer (not shown) or the like separately disposed in the control section 9. Because the processing step for pellicle film inspection, the effect obtained by the inspection device 20, and the like are the same as those described in the first embodiment, no further description will be given here.
Next, the configuration of an inspection device according to the third embodiment of the present invention will now be described. Each of
First, the configuration of a foreign matter inspection section 31 will now be described. The foreign matter inspection section 31 includes a first optical system unit 32 that moves along the upper portion (blank surface) of the reticle 3 mounted on the stage 4, and a second optical system unit 33 that moves along the lower portion (pellicle surface) of the reticle 3. The foreign matter inspection section 31 further includes a drive section consisting of a ball screw or a belt pulley which simultaneously and horizontally moves on the blank surface and the pellicle surface, both of which are the surfaces to be inspected, so as to sandwich the reticle 3, whereby foreign matter can be inspected by a single scanning operation. The configuration of the first optical system unit 32 is the same as that of the second optical system unit 33. Hereinafter, a description of the first optical system unit 32 will be given, the same elements as those of the second optical system unit 33 shown in
The first optical system unit 32 includes illumination system units 34 as illumination units that project light, and a reception system unit 35, which serves as a detection unit. The illumination system unit 34 includes a semiconductor laser 36, a collimator lens 37, and a wave plate 38. The semiconductor laser 36 causes an irradiating light 39, i.e., a linearly polarized light, to impinge obliquely on the surface of the reticle 3 mounted on the stage 4 via the collimator lens 37 and the wave plate 38. By disposing an optical element such as a beam splitter or the like, one of the illumination system units 34 may be shared with the second optical system unit 33 so that irradiating light is split between the blank surface and the pellicle surface. The reception system unit 35 includes an array lens 40, a line sensor 41, and a lens barrel (not shown) that holds the array lens 40 and the line sensor 41. The array lens 40 is an optical element that focuses scattered light emitted from foreign matter, when the foreign matter is present and the irradiating light 39 is irradiated on the foreign matter. Also, the line sensor 41 is a CMOS sensor that converts the scattered light output into a voltage for detection. It should be noted that a plurality of the reception system units 35 may be separately disposed on the blank surface and the pellicle surface. Here, the positional relationship between the illumination system unit 34 and the reception system unit 35 provides a significant contribution to the accuracy of the foreign matter detection. In particular, since the distance (height direction) between the pellicle surface and the second optical system unit 33 may change depending on the relationship between the pellicle film 2 and the pellicle frame 7, the second optical system unit 33 is appropriately adjusted in advance.
Next, the operation of the inspection device 30 according to the present embodiment will now be described. In the present embodiment, first, damage inspection of a pellicle film described in the first embodiment is performed, and then foreign matter inspection is performed by the foreign matter inspection section 31.
As described above, according to the present embodiment, in addition to the same effects as those obtained by the first embodiment which detects damage such as scratches, breaks, or the like of the pellicle film 2, a foreign matter inspection, which detects the presence of foreign matter on the surface of the reticle 3, can also be performed by the inspection device.
Next, an exposure apparatus to which the inspection device of the aforementioned embodiments is applied will now be described. Each of
In addition, the exposure apparatus 50 includes the inspection device described in the aforementioned embodiments in the interior thereof. In the exposure apparatus 50, the inspection device 1 described in the first embodiment is included as an example. Furthermore, the exposure apparatus 50 includes a reticle storing shelf 57, an alignment station 58, an ID reading device 59, and a plurality of conveying robots 60 that carries in and out the reticle 3 between these constituent elements and the inspection device 1 in the interior thereof. The alignment station 58 is a stage that performs the positioning of the reticle 3, when the reticle 3 is mounted on the reticle stage 51. The ID reading device 59 is a device that reads a pattern such as a barcode printed on the reticle 3 for registration or confirmation of the reticle ID.
When an exposure process is performed, first, the reticle 3 is placed on a plurality of load ports 62 located in a planar direction with a single or a plurality of the reticle 3 being accommodated in a reticle carrier 61. Next, an elevator mechanism 63 disposed within the exposure apparatus 50 lowers the reticle carrier 61 on the load port 62, and carries it into the exposure apparatus 50. At this time, the reticle 3 is in its bare state, so that the conveying robots 60 can access the reticle 3. The conveying robots 60 appropriately convey the reticle 3 to the reticle stage 51, the reticle storing shelf 57, the alignment station 58, the ID reading device 59, or the inspection device 1. Here, a user may confirm through a monitor 64 disposed on the wall surface of the exposure apparatus 50 to provide an instruction about the place to which the conveying robots 60 conveys the reticle 3 from an operation panel 65, or the control unit 55 may automatically control such operation in a programmed way.
Next, the operation of the exposure apparatus 50 of the present embodiment will now be described. In the present embodiment, when the reticle 3 is conveyed into the exposure apparatus 50, the exposure apparatus 50, first, performs damage inspection of a pellicle film as described in the first embodiment, and then performs a normal exposure process.
In step S313, the exposure apparatus 50 performs a normal exposure process. First, illumination light for exposure is irradiated from an illumination optical system to the reticle 3 mounted on the reticle stage 51. For example, an illumination light source is an excimer laser light having a wavelength of 193 nm. The irradiation area is a slit-like irradiation area which partially covers the pattern area of the reticle 3. The pattern corresponding to the slit section is reduced, for example, in size to ¼ of the original and is projected on the wafer 53 by the projection optical system 52. The reticle 3 and the wafer 53 are scanned relative to the projection optical system 52 to thereby transfer the pattern area of the reticle 3 onto a photoresist coated on the wafer 53. The scanning exposure is repeatedly performed relative to a plurality of transfer areas (shot) on the wafer 53. When the exposure process in step S313 is completed, the control unit 55 carries out the reticle 3 from the reticle stage 51, and then causes the conveying robots 60 to convey the reticle 3 to the reticle storing shelf 57 (step S314) to terminate processing.
On the other hand, when the control section 9 of the inspection device 1 outputs an error in step S309, the control unit 55 causes the conveying robot 25 to convey the reticle 3, in which damage is present on the pellicle film 2 thereof, to the reticle carrier 61, whereby the reticle 3 is carried out of the exposure apparatus 50 (step S315). Then, the exposure apparatus 50 terminates processing without performing a normal exposure process.
As described above, according to the exposure apparatus of the present embodiment, a damage inspection of a pellicle film (or a foreign matter inspection) can be performed within the exposure apparatus 50. With this arrangement, carrying the reticle 3 out of the exposure apparatus 50 for each pellicle film inspection becomes unnecessary, whereby damage such as scratches, breaks, or the like of the pellicle film 2 can be efficiently detected.
In setting a threshold value, while in the first embodiment, the control section 9 sets a certain vibration frequency value as a threshold value with reference to initial value data, the present invention is not limited thereto. For example, a user may calculate a threshold value by simulations in advance or may determine a threshold value by experiments in advance for setting with respect to the change in the natural vibration frequency of the pellicle film 2, based on the material of the pellicle film 2, the material of the pellicle frame 7, or a bonding method. In this case, when the information processing unit 11 has calculated that the difference between the measurement result of the natural vibration frequency at a certain time (Nth time) and the measurement result of the natural vibration frequency at the previous time ((N-1)th time) is equal to or more than the preset threshold value, the control section 9 determines that the pellicle film 2 has been damaged.
Furthermore, an external vibration caused by the inspection device 1 may be measured with the reticle 3 not being installed on the inspection device 1 in advance. By creating in advance and then removing disturbance eliminating compensation data from the vibration result, which is the result of calculating vibration frequency of the pellicle film 2 or the vibration frequency of the pellicle film 2 and the pellicle frame 7, measurement errors are prevented, and thus the natural vibration frequency can be calculated with higher accuracy.
Next, a method of manufacturing a device (semiconductor device, liquid crystal display device, etc.) as an embodiment of the present invention is described. The semiconductor device is manufactured through a front-end process in which an integrated circuit is formed on a wafer, and a back-end process in which an integrated circuit chip is completed as a product from the integrated circuit on the wafer formed in the front-end process. The front-end process includes a step of exposing a wafer coated with a photoresist to light using the above-described exposure apparatus of the present invention, and a step of developing the exposed wafer. The back-end process includes an assembly step (dicing and bonding), and a packaging step (sealing). The liquid crystal display device is manufactured through a process in which a transparent electrode is formed. The process of forming a plurality of transparent electrodes includes a step of coating a glass substrate with a transparent conductive film deposited thereon with a photoresist, a step of exposing the glass substrate coated with the photoresist to light using the above-described exposure apparatus, and a step of developing the exposed glass substrate. The device manufacturing method of this embodiment has an advantage, as compared with a conventional device manufacturing method, in at least one of performance, quality, productivity and production cost of a device.
While the embodiments of the present invention have been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2009-166495 filed Jul. 15, 2009 which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2009-166495 | Jul 2009 | JP | national |