JP4480392B2 - Foreign matter prevention method - Google Patents

Description

The present invention, foreign materials generated in the pattern surface of the reticle, but about the foreign matter prevention how to prevent by irradiating ultraviolet light on the pattern surface.

Currently, a light reduction projection exposure apparatus (hereinafter simply referred to as an exposure apparatus) is used when manufacturing a semiconductor device. This exposure apparatus uses a reticle in which a predetermined pattern of a chromium film or the like is provided on a glass substrate (reticle substrate). The reticle pattern is projected onto the wafer having a resist film formed on the surface by the optical system of the exposure apparatus, and exposure (baking) is performed.
In order to increase the resistance of foreign matter on the reticle, a method of mounting a pellicle film on a sufficiently cleaned reticle substrate has become common. This is because the size of the foreign matter allowed on the reticle has been reduced with the miniaturization of the line width and the like in the semiconductor element, but on the pellicle film in the non-imaging region sufficiently separated from the reticle substrate surface. This is because the size of the foreign matter is acceptable up to a considerably large size.

As shown in FIGS. 10A to 10C, the reticle 100 includes a glass substrate 102 and a chromium film 106 formed in a predetermined pattern shape on the back surface 104b of the glass substrate 102.
Here, FIG. 10A is a plan view showing the reticle, FIG. 10B is a cross-sectional view taken along line AA of FIG. 10A, and FIG. 10C is a back view of FIG. .

  On the back surface (pattern surface) 104b of the glass substrate 102, a pattern 108 is formed by patterning a chromium film 106 formed on the entire surface into a predetermined shape. This pattern 108 is formed in an effective area 109 to which exposure light is irradiated during pattern exposure by the exposure apparatus. In other regions, the chromium film 106 is left unpatterned and functions as a light shielding film.

Also, as shown in FIG. 10A, a pellicle 110a is provided on the surface 104a of the glass substrate 102. In this pellicle 110a, a pellicle film 114a is adhered to a pellicle frame 112a provided outside the effective area 109 so as to surround the entire effective area 109.
Further, as shown in FIGS. 10B and 10C, a pellicle 110b is also provided on the back surface 104b of the glass substrate. The pellicle 110b has the same configuration as the pellicle 110a on the surface 104a side. That is, the pellicle film 114b is attached to the pellicle frame 112b provided outside the effective area 109, and covers the entire effective area 109.

  If pattern exposure is performed in a state where foreign matter is placed on the surface of the glass substrate 102 of the reticle 100, a predetermined pattern cannot be accurately imaged on the wafer surface. For this reason, a defect occurs in the semiconductor device to be manufactured, and the yield decreases. In order to prevent this, the pellicles 110a and 110b are provided.

The pellicle films 114a and 114b are made of, for example, a nitrocellulose-based material. Examples of the manufacturing method include spin coating. The pellicle films 114a and 114b are formed of cellulose as a raw material, for example, by spin coating, and thus become a porous body. For this reason, the pellicle films 114a and 114b have a large number of fine holes and allow gas to pass therethrough. However, particulate foreign matters such as dust or dust do not pass through. Therefore, by providing the pellicles 110a and 110b, it is possible to prevent particulate foreign matter from adhering to the front surface 104a and the back surface 104b of the glass substrate 102.
Even if foreign matter is placed on the front surfaces of the pellicle films 114a and 114b, the position of the foreign matter is separated from the back surface (pattern surface) 104b of the glass substrate 102, so that an image of the foreign matter is formed on the wafer surface. Therefore, the occurrence of defects can be prevented.
Further, it has been proposed to use, for example, a quartz glass plate having a thickness of 0.5 mm or less as the pellicle film by shortening the exposure wavelength. Even in this case, the same defect generation preventing effect can be obtained.
However, when the thickness of the glass substrate is large, only the pellicle 110b on the back surface 104b side may be provided, and the pellicle may not be provided on the front surface 104a side.
Note that the pellicle film and the glass substrate are transparent and a pattern is actually visible, but the pattern is not shown in FIG.

  In the reticle 100 shown in FIGS. 10A to 10C, when it is recognized that there is a foreign substance on the front surface 104a or the back surface 104b of the glass substrate 102, the pellicles 110a and 110b are removed, and the front surface 104a of the glass substrate 102 is removed. In addition, the back surface 104b is cleaned and the pellicles 110a and 110b are pasted again.

On the other hand, in the reticle 100, when it is recognized that there are foreign objects on the front surface 104a and the back surface 104b of the glass substrate 102, a method of removing the foreign objects without removing the pellicle film has been proposed (see Patent Document 1).
This Patent Document 1 includes a reticle with a pellicle film that is provided with a vent opening that can be opened and closed by an on-off valve at a position opposite to the pellicle frame, and that allows gas to flow from there to remove foreign substances attached to the mask pattern. A method for removing the foreign matter is disclosed. In this reticle, a filter is provided at the vent on the gas inlet side to avoid contamination by foreign matter from the outside. When the gas introduced from the gas inlet side is discharged from the other gas vent, the foreign substance moves by the air flow and is removed from the mask pattern and released from the vent or moved outside the pattern area. It is to do.

  Patent Document 2 discloses a cleaning apparatus that removes foreign matter from a reticle or wafer by irradiation with a KrF excimer laser (ultraviolet light having a wavelength of 248 nm). In Patent Document 2, the reticle or wafer is cooled, and water is condensed on these surfaces. Then, the surface of the reticle or wafer is irradiated with a KrF excimer laser. As a result, the reticle or wafer is heated rapidly, and water condensed on the surface is also instantly evaporated. Due to this instantaneous evaporation, fine particles adhering to the surface of the reticle or wafer are also peeled off from the surface of the reticle or wafer.

  Further, in Patent Document 3, before exposure, exposure light from an ArF excimer laser (ultraviolet light having a wavelength of 193 nm) light source is incident on the projection optical system (lens) of the exposure apparatus from the reticle side (upper side), and An optical element light cleaning method is disclosed in which contaminants adhering to both surfaces of a projection optical system are removed by making reverse emission light branched from light from the same light source incident from the wafer stage side (lower side).

JP-A-5-297572 JP 2003-57258 A JP-A-11-233402

Conventionally, once a state in which no foreign matter exists on the reticle substrate surface covered with the pellicle can be realized, no foreign matter that would otherwise interfere with exposure in the image forming area of the reticle is attached or generated. It was thought that reticle use could be continued permanently until the membrane deteriorates. However, the present inventor has actually found that the occurrence of foreign matter that hinders image formation is recognized by repeated use in an exposure apparatus.
In such a case, even if an attempt is made to remove the foreign matter by the method disclosed in Patent Document 1, the pellicle film has a very low strength, and thus there is a possibility that an air flow sufficient to remove the foreign matter cannot be generated.

Further, in Patent Document 2, once the condensation is formed, the moisture is rapidly heated, and the fine particles adhering to the surface of the reticle or wafer are also peeled off from the surface of the reticle or wafer by instantaneous evaporation. Is. For this reason, the pellicle film is also condensed. As described above, since the strength of the pellicle film is extremely low, the pellicle film may be damaged.
As described above, although proposals such as Patent Documents 1 and 2 have been made, in reality, once a foreign substance adheres to the reticle substrate, it is difficult to remove the foreign substance without removing the pellicle.

  Further, Patent Document 3 aims at cleaning the projection optical system of the exposure apparatus before exposure, and does not describe the cleaning of the reticle.

An object of the present invention, the to solve the prior art based on the problem to provide a foreign matter prevention how it is possible to prevent the occurrence of foreign matter causing manufacturing defects.

In order to achieve the above object, the present inventor first analyzed a mechanism in which foreign matter adheres to the pattern surface. As a result, it was found that the generation of foreign matter can be prevented by irradiating ultraviolet light from the pattern surface side before foreign matter that hinders exposure is recognized.
That is, according to the present invention, a pattern for projecting onto a wafer by irradiating exposure light as ultraviolet light from the glass surface side opposite to the pattern surface is formed in an effective area of the pattern surface of the reticle substrate. And a pattern of a substance adsorbed on a portion outside the chromium film of the pattern surface in the effective area of the pattern surface of the reticle on which the pellicle covering the effective area is mounted on at least the pattern surface side. The sublimation by the energy of exposure light, which is ultraviolet light irradiated from the glass surface side opposite the surface, and the adsorption of the sublimated substance on the surface of the chromium film are repeated for each exposure, whereby the chromium film A method of preventing the occurrence of foreign matter that grows in a branch shape from the edge of the pattern and becomes an obstacle to the projection of the pattern,
After the projection of the pattern onto the wafer, and before the foreign matter is generated by irradiating the exposure light is ultraviolet light exposure apparatus that performs projection of the pattern from the pattern surface side to said reticle, said The present invention provides a foreign matter generation preventing method characterized by preventing the generation of foreign matter.

  Further, in the present invention, the exposure apparatus projects the pattern by irradiating the reticle held on a reticle stage with the exposure light from a surface opposite to the pattern surface, It is preferable that the irradiation of ultraviolet light from the pattern surface side is performed by mounting the reticle on the reticle stage in a direction opposite to that when projecting the pattern.

  Furthermore, in the present invention, the exposure apparatus projects the pattern by irradiating the reticle held on a reticle stage with the exposure light from a surface opposite to the pattern surface, It is preferable that the irradiation of ultraviolet light from the pattern surface side is performed by reversing the exposure light transmitted through the reticle while holding the reticle on the reticle stage in a direction in which the pattern is projected. .

  Furthermore, in the present invention, the reticle is mounted on a reticle stage of an exposure apparatus when performing the pattern projection, and then removed from the reticle stage and stored until the next projection. It is preferable to irradiate the ultraviolet light from the pattern surface side after performing pattern projection after mounting on the reticle stage and before storing.

  Further, in the present invention, the pellicle is obtained by mounting a pellicle film on a pellicle frame provided outside at least the effective area of the pattern surface of the reticle substrate. Irradiation is selectively performed on the effective area, and an uneven portion that is neither a measurement mark nor an identification mark is formed outside the effective area of the pattern surface and inside the pellicle frame. Preferably, it is formed, or an uneven portion is formed on the inner surface of the pellicle frame on the pattern surface side.

  In the foreign matter generation preventing method of the present invention, before the foreign matter is generated, the adsorbate that becomes the core of the foreign matter generation is removed by irradiating ultraviolet light from the pattern surface side of the reticle substrate, thereby preventing the generation of the foreign matter. it can.

In the reticle according to the present invention , an uneven portion that is neither a measurement mark nor a recognition mark is provided outside the effective area of the pattern surface and inside the pellicle frame, or the pellicle on the pattern surface side An uneven portion is provided on the inner surface of the frame. Thereby, since the substance which becomes a nucleus of foreign material generation can be preferentially adsorbed to this uneven part, generation | occurrence | production of the foreign material in an effective pattern area can be prevented.

Further, in the exposure apparatus according to the present invention , a pattern surface irradiating means for irradiating the reticle held on the reticle stage with exposure light from the pattern surface side is provided. As a result, before the generation of foreign matter, ultraviolet light can be irradiated from the pattern surface side of the reticle substrate to prevent the generation of foreign matter.

Hereinafter, with reference to preferred embodiments shown in the accompanying drawings, illustrating a foreign matter prevention how the present invention in detail.

  As described above, by attaching a pellicle film to the reticle, there is almost no possibility of foreign matter adhering to the image formation area of the reticle, and there is almost no possibility of generation, and the reticle is used permanently until the pellicle film deteriorates. It was thought to be possible. However, the present inventors have actually found that foreign substances are likely to be generated due to the remaining amount of cleaning liquid on the reticle or the influence of gas from the usage environment as the exposure light becomes shorter in wavelength. It was.

1 and 2 are schematic perspective views for explaining the principle of foreign matter generation prevention according to the present invention in the order of steps.
As shown in FIG. 1, the reticle 10 is provided with chromium films 14a and 14b having a predetermined pattern shape in an effective area S of one surface (pattern surface) 12b of a glass substrate 12. The effective area S is irradiated with the exposure light EL from the illumination optical system of the exposure apparatus, and an image of a predetermined pattern made of the chromium films 14a and 14b is formed on the surface of the wafer (not shown). Further, in the conventional reticle 10, the portion outside the effective area b of the pattern surface 12b is often formed with a chrome film on the entire surface for light shielding. Assume that chromium films 16a and 16b having a predetermined pattern shape are formed. In FIG. 1, the pellicle is not shown.

As a result of earnest experimental research, the inventors of the present application have found that, by repeating exposure, a foreign substance D growing in a branch shape from the edge of the chromium films 14a and 14b is generated, which hinders exposure. Generation | occurrence | production of such a branch-like foreign material D can be demonstrated by assuming the following mechanisms.
(1) Residual cleaning liquid and gas components contained in the surrounding environment are adsorbed on the surface 12b of the glass substrate 12 of the reticle 10. (2) At the time of wafer exposure, exposure light EL that is ultraviolet light having high energy is applied to the effective area S of the glass substrate 12 from the side opposite to the pattern surface 12b (the lower surface in FIG. 1). Is irradiated to the portions of the pattern surface 12b outside the chromium films 14a and 14b with exposure light transmitted through the glass substrate 12. For this reason, the substance adsorbed on the portion of the pattern surface outside the chromium films 14a and 14b is sublimated by the energy of the exposure light EL. On the other hand, since the chromium films 14a and 14b absorb the exposure light EL and are not irradiated with the exposure light EL on the surfaces of the chromium films 14a and 14b, the adsorbed cleaning liquid and gas components are not sublimated. (3) After the exposure, the sublimated substance is again adsorbed on the pattern surface 12b of the glass substrate 12. At this time, preferential adsorption occurs with the substance that has already been adsorbed on the surfaces of the chromium films 14a and 14b and the rims of the chromium films 14a and 14b as the nucleus. (4) Such sublimation and re-adsorption of the adsorbing material is repeated for each exposure. As a result, island-shaped foreign matter p is generated on the chromium films 14a and 14b, and foreign matter D is generated by growing in a branch shape from the edges of the chromium films 14a and 14b. (5) When it grows in this way, it becomes difficult to sublimate even by irradiation with ultraviolet light. Therefore, during the subsequent exposure, even if the exposure light EL is irradiated from the opposite surface side of the pattern surface 12b to the portion of the branch-like foreign material D that protrudes outward from the edge of the chromium films 14a and 14b, It will not sublimate and will continue to grow.

When the foreign matter D grown in a branch shape extends to the region of the glass substrate 12 that originally transmits light, a defect occurs in a predetermined pattern formed on the wafer.
As countermeasures against the generation of foreign substances, a contrivance to reduce the remaining amount of cleaning liquid, a contrivance to reduce the influence of gas from the surrounding environment, and a contrivance not to emit gas have been made. For this reason, it is necessary to remove the pellicle, clean the reticle, and remount the pellicle every few years, and there are currently only measures that require labor and cost.
However, the present inventors have found that the formation of foreign matter on the chromium film can be suppressed as shown in FIG. 2 by irradiating exposure light from the pattern surface side of the reticle 10 after exposure. That is, before the foreign matter D grows from the edges of the chromium films 14a and 14b shown in FIG. 1, the exposure light EL is irradiated from the pattern surface 12b side to sublimate the adsorbate that becomes the nucleus of the foreign matter growth. The formation of the foreign matter D that hinders pattern exposure can be prevented.
However, the substance sublimated by the irradiation with the exposure light EL does not disappear, and a part of the substance is adsorbed again on the chromium films 14a and 14b after the irradiation. In particular, since the edges of the chromium films 14a and 14b have irregularities, they are preferentially adsorbed. Therefore, even if the exposure light EL is once irradiated from the pattern surface 12b side, thereafter, the exposure light EL is repeatedly irradiated from the surface side opposite to the pattern surface 12b for wafer exposure. Eventually, the foreign matter D is formed. However, during repeated use for wafer exposure, exposure light EL irradiation from the pattern surface 12b side is performed at an appropriate interval, and the substance adsorbed on the chromium films 14a and 14b is sublimated. It is possible to maintain a state in which no foreign matter D exists.

  The exposure light EL is not irradiated outside the effective area b even by irradiation from the pattern surface side. For this reason, when the chromium films 16a and 16b having the pattern shape are formed outside the effective area b, as shown in FIG. 2, island-shaped foreign matter p and branch-like foreign matter D are formed. However, the formation of foreign matter outside the effective area b has no problem because it does not affect the pattern shape formed on the wafer. On the contrary, by providing the chromium films 16a and 16b having the pattern shape outside the effective area b, the substance sublimated by the irradiation of the exposure light EL from the pattern surface 12b side is preferentially adsorbed on the edge, and the effective area It has also been found that the generation of foreign matter in S can be more effectively suppressed. As described above, the present invention has been made based on the knowledge that it is possible to prevent the generation of foreign matters in the effective area S by irradiating the reticle with exposure light from the pattern surface side.

Next, an exposure apparatus according to an embodiment of the present invention will be described.
FIG. 3 is a schematic view showing an exposure apparatus according to an embodiment of the present invention. Here, an example of an exposure apparatus using the step-and-repeat method is shown.
The exposure apparatus 20 includes a light source 22, an illumination optical system 24, a projection optical system 28, a reversing unit (reticle loader) 30, a reticle changer 32, a reticle cassette library 34, a control unit 40, and a reticle stage RS. And wafer stage WS.

The light source 22 can output ultraviolet light having a predetermined wavelength, such as a mercury lamp (wavelength is 365 nm), a KrF excimer laser (wavelength is 248 nm), or an ArF excimer laser (wavelength is 185 nm).
The illumination optical system 24 shapes the light emitted from the light source 22 to a size that allows the entire surface of the effective area S of the reticle 10 to be irradiated. Further, the intensity of the light in the effective area S is within a predetermined range. To make it uniform. The illumination optical system 24 is provided on the emission side of the light source 22.

The reticle stage RS holds the reticle R.
The projection optical system 28 reduces the pattern image formed on the reticle R to a predetermined reduction magnification and forms it on the surface of the wafer W.

  The wafer stage (substrate stage) WS is a substrate on which a wafer W (substrate to be exposed) is placed and holds the wafer W. The wafer stage WS is movable in two orthogonal directions in a horizontal plane while holding the wafer W. Thereby, exposure by step and repeat becomes possible.

The reversing unit 30 reverses the reticle R with respect to the horizontal plane.
The reticle changer 32 conveys and unloads the reticle R to the reticle stage RS from a reticle cassette library 34 in which a plurality of reticles having a predetermined pattern are stored.
The reversing unit 30, reticle changer 32, and reticle cassette library 34 will be described in detail later.

  The control unit 40 is connected to the light source 22, the illumination optical system 24, the reticle stage RS, the reversing unit 30, the reticle changer 32, the reticle cassette library 34, and the wafer stage WS, and controls these operations.

Next, the foreign matter generation preventing method of the present embodiment will be described.
FIG. 4 is a schematic diagram for explaining a foreign matter generation preventing method using the exposure apparatus according to the embodiment of the present invention.
The exposure apparatus 20 shown in FIG. 4 is the same as the exposure apparatus 20 shown in FIG. In FIG. 4, illustration of reticle stage RS and wafer stage WS is omitted, and illustration of illumination optical system 24 and projection optical system 28 is simplified. Further, the reticle blind 27 is illustrated, and the reticle 102 also illustrates the substrate 102 and the pellicles 110a and 110b (the pellicle films 114a and 114b and the pellicle frames 112a and 112b).
Further, since the reticle R has the same configuration as that shown in FIGS. 10A to 10C, detailed description thereof is omitted.

The reticle blind 27 allows the exposure light EL formed by the illumination optical system 24 to enter only the effective area S of the reticle R.
The dimension of the effective area S of the reticle is determined in accordance with the chip size of the semiconductor device to be manufactured within the dimension of the exposure possible area of the exposure apparatus. The illumination optical system 24 forms exposure light EL having an irradiation area that can uniformly irradiate the entire effective area S even when the dimension of the effective area S is maximum. A reticle blind 27 is used to limit the irradiation area according to the size of the effective area S of each reticle.

  Hereinafter, in the present embodiment, for example, an example in which the reticle R is reversed after exposing a lot of wafers and irradiated with exposure light from the pattern surface side to prevent the generation of foreign matters will be described.

First, for example, using a light source having a wavelength of 365 nm (i-line) and an exposure amount of 100 mJ / cm ² , exposure processing is performed with 25 wafers processed as one lot. There are 60 shots per wafer. In this embodiment, the total irradiation amount per lot is 100 × 60 × 25 mJ / cm ² (= 1.5 GJ / m ² ).
When the wafer is exposed, the reticle R is placed on the reticle stage so that the pattern surface 104b of the substrate 102 on which the pattern made of a chromium film is formed is on the lower side of the drawing. Therefore, the exposure light irradiated from the illumination optical system 24 sublimes the substance adsorbed on the portion where the chromium film pattern is not formed in the effective area of the pattern surface 104b by the energy of the exposure light. A part of the sublimated substance is adsorbed on the chrome film and on the edge after the exposure process.

  Next, after the exposure processing for one lot is completed, the reticle R is once removed from the reticle stage, reversed by the reversing unit 30 (see FIG. 4), and placed on the reticle stage again. That is, the reticle R is placed on the reticle stage in the opposite direction to the case of pattern projection.

  Next, an exposure process (cleaning process) is performed under the same exposure conditions as the wafer exposure process. That is, the exposure light is irradiated from the pattern surface 104b side onto the reticle R placed in the reverse direction on the reticle stage. For example, the cleaning process is performed with the same total irradiation amount by the light having the same intensity as the exposure light in the pattern exposure. By this exposure light irradiation from the pattern surface 104b side, the substance adsorbed on the chromium film and the edge after the exposure processing is sublimated. At this time, 25 dummy wafers are used as in exposure.

Next, the reticle is reversed again by the reversing unit, the reticle is stored in the reticle cassette library, and the reticle R is stored.
As described above, in this embodiment, after the pattern exposure (projection) for one lot is completed, the cleaning process is performed, so that the effective area S can be kept free from foreign matter. If the reticle is used for pattern exposure and then stored after cleaning, it is not necessary to perform cleaning again when it is used for the next pattern exposure. In order to prevent the generation of foreign matters due to atmospheric changes during long-term storage, it is preferable to perform a cleaning process before storage.
As described above, in this embodiment, since the generation of foreign matters in the effective area can be prevented, it is possible to prevent a decrease in product yield due to a pattern defect. As a result, the frequency of remounting the pellicle can be reduced, and the reticle can be easily managed.

  In this embodiment, the cleaning process is performed under the same conditions as the exposure process, but the present invention is not limited to this. For example, it is not always essential that the exposure dose of the exposure light irradiated from the pattern surface 104b side of the reticle R for cleaning be the same as the total dose for pattern exposure processing per lot. It is possible to set appropriately according to the foreign matter occurrence situation depending on the cleaning conditions before the pellicles 101a and 101b are mounted, the use environment, and the like.

Here, the configuration of the reversing unit and the reticle changer of the exposure apparatus of the present embodiment will be described in detail with reference to FIG.
A transfer arm (not shown) is provided between the reversing unit 30 and the reticle stage RS, and the reticle R is transferred by this transfer arm.

  The reticle changer 32 takes out one of the reticles R from the reticle cases RC1 to RC8 housed in the reticle cassette library 34, and conveys it to the reticle stage RS. In addition, the reticle R placed on the reticle stage RS is stored in one of the reticle cases RC1 to RC8, and the reticle R is stored in the reticle cassette library 34.

The reticle changer 32 has opening / closing means (not shown) for opening and closing the reticle cases RC1 to RC8, and reticle transport means (not shown).
This reticle transport means takes out the reticle R from the reticle cases RC1 to RC8 opened by the opening / closing means, and places the reticle R on the reticle stage. The reticle R placed on the reticle stage is also stored in the reticle cases RC1 to RC8.

  As shown in FIG. 4, the reticle cassette library 34 stores and stores a plurality of reticle cases RC1 to RC8. For example, the reticle cases RC1 to RC8 are stacked and stored in the vertical direction. In the present embodiment, for example, eight reticle cases RC1 to RC8 are stacked and stored in the vertical direction.

  The reticle cassette library 34 is provided with a reticle case outlet 36. A transfer arm (not shown) is provided between the reticle case outlet 36 and the reticle cassette library 34. The reticle case is transported to the reticle case outlet 36 by the transport arm. In this embodiment, when the number of reticle cases is reduced or newly added, the reticle case is conveyed by the conveyance arm. The reticle case taken out from the reticle case outlet 36 is stored in a reticle storage outside the exposure apparatus until it becomes necessary next time.

FIGS. 6A and 6B and FIGS. 7A and 7B are schematic perspective views showing the operation of the reversing unit of the exposure apparatus of this embodiment in the order of steps. In these figures, the display of the pellicle is omitted.
As shown in FIG. 6A, the reversing unit 30 holds the reticle R transported from the reticle stage RS by the transport arm 50 and reverses it while maintaining the retained state.
The reversing unit 30 includes a rotating unit 60 and a holding unit.

  The rotating part 60 is configured by a rectangular base. At the end portions of the four corners of the rotating portion 60, holding means are provided. The holding means includes arm members 62a to 62d, moving members 64a to 64d for moving the arm members 62a to 62d, and holders 66a to 66d.

  Each of the arm members 62a to 62d is a rod-like member extending in one direction, and one end thereof is rotatably provided at a corner portion of the rotating unit 60, and the holders 66a to 66d are provided at the other end. The arm members 62a to 62d are connected to movable members 64a to 64d that are provided at the edges of the respective corners on the surface 60a side of the rotating portion 60 so as to be extendable and contractible.

The holders 66a to 66d hold the corners of the reticle R so as to wrap around the corners. One side of the triangular prism having a shape substantially similar to the corner of the reticle R is removed.
In addition, a rotating shaft 68 is provided on the side surface 60b of the rotating portion. Rotation driving means (not shown) such as a motor is connected to the rotation shaft 68. The rotating unit 60 is rotated by the rotation driving unit.

Next, a method for reversing the reticle R will be described.
First, as shown in FIG. 6A, for example, the reticle R after exposure irradiation is transported from the reticle stage RS by the transport arm 50. At this time, the moving members 64 a to 64 d are in a state of protruding to the outside of the rotating unit 60.
The transfer arm 50 includes, for example, a base 52 having a rectangular shape, and arm portions 54 and 56 provided at both ends on one long side of the base 52. The reticle R is supported by the arm portions 54 and 56.

  Next, as shown in FIG. 6B, the moving members 64a to 64d are drawn into the rotating portion 60, and the corners of the reticle R are held by the holding tools 66a to 66d. Then, the transfer arm 50 is retracted. In this way, the reticle R is held above the surface 60a of the rotating unit 60.

  Next, as shown in FIG. 7A, the rotating unit 60 is rotated 180 ° in the α direction by the rotation driving means.

Next, as shown in FIG. 7B, the reticle R is held by the arms 54 and 56 of the transfer arm 50, and in this state, the moving members 64a to 64d are projected to release the holding of the reticle R. Next, the reticle R is transferred to the wafer stage RS. In this way, the reticle R is inverted.
Next, the rotating unit 60 rotates the rotating unit 60 by 180 ° in the β direction, and waits until the reticle R to be reversed next is conveyed.

Next, an exposure apparatus according to another embodiment of the present invention and a foreign matter generation preventing method using the exposure apparatus will be described.
FIG. 8 is a schematic view showing an exposure apparatus according to another embodiment of the present invention. The same components as those of the exposure apparatus according to the embodiment of the present invention shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The exposure apparatus 21 shown in FIG. 8 is different from the exposure apparatus 20 shown in FIGS. 3 and 4 in place of the reversing unit 30 and a reflection mirror M that is moved below the reticle R, and the reflection mirror M as a reticle. The other difference is that a drive mechanism for moving below R is provided, and the rest of the configuration is the same as that of the exposure apparatus shown in FIGS. 3 and 4, and a detailed description thereof will be omitted.

In the present embodiment, by moving the reflection mirror M between the projection optical system 28 and the reticle R, the exposure light can be irradiated from the pattern surface 102b side of the reticle R without inverting the reticle R. it can. That is, cleaning can be performed by reversing the exposure light.
For this reason, the structure of the exposure apparatus 21 can be simplified more than the exposure apparatus shown in FIG. 3 and FIG. The reflecting mirror M may be at least as large as the effective area S. As the reflection mirror M, for example, a total reflection type mirror such as an aluminum mirror or a cold mirror can be suitably used.

Next, the foreign matter generation preventing method of the present embodiment will be described.
In the present embodiment, for example, a reticle R having an effective area of 20 mm □ is used. At this time, the exposure condition is set such that, for example, a light source having a wavelength of 365 nm (i-line) is used and an exposure amount is 100 mJ / cm ² . The exposure processing is performed by processing 25 wafers as one lot. There are 60 shots per wafer.

First, the first shot exposure is performed on the wafer. Next, the reflecting mirror M is moved below the reticle R to block exposure light to the wafer (not shown). At this time, the exposure light is reflected, that is, reversely, the exposure light is irradiated from the pattern surface side of the reticle R. At the same time, the wafer is moved by a wafer stage (not shown), and the next exposure position is adjusted to the image plane of the projection lens.
As described above, the reflection mirror M is used to reverse the exposure light and is also used as a shutter that blocks the exposure light to the wafer. When the time required for moving the wafer is longer than the time required for cleaning the reticle R, the cleaning of the reticle R using the reflecting mirror M is completed only in the required time, and thereafter The exposure light to the wafer may be blocked using a shutter (not shown).

Next, the reflection mirror M is moved to perform the second shot exposure. Next, when the reflection mirror M is moved again, exposure light is irradiated from the pattern surface side of the reticle R.
In this way, the reticle R can be cleaned using the reflection mirror M for each shot. Thereby, generation | occurrence | production of a foreign material can be prevented further.
After the exposure and cleaning processes for one lot are completed, the reticle R is stored in a reticle cassette library and stored.

  In the present embodiment, the timing for performing the cleaning process is not particularly limited. For example, the cleaning may be performed by moving the reflection mirror M after processing one wafer, that is, after the exposure of 60 shots is completed. In this case, for example, similarly to the above-described embodiment, cleaning is performed by irradiating the exposure light EL with the same total dose as the total dose for the exposure process. Alternatively, the irradiation is performed with the total irradiation amount appropriately set according to the foreign substance occurrence state. Minimize wafer throughput degradation by measuring wafer conditions such as wafer transport and alignment required for exposure, focus sensor correction factor, and tilt while cleaning. Can do.

  Further, after the one lot processing, the reflection mirror M may be moved for cleaning, and the timing for cleaning is not particularly limited.

  In any of the above-described foreign matter generation prevention methods, the cleaning time is not particularly limited. For example, every shot, every 1 shot, or every 100 shots. It may be once per hour, once per day, or once every two days. Furthermore, it may be one hour after the start of use, two hours after the start of use, or the like after the use of the exposure apparatus.

  Next, a reticle according to an embodiment of the present invention will be described. As shown in FIG. 9, the reticle 100a is preferably formed with uneven portions 70 to 76 outside the effective area S and in the pellicle frame 112b. The reticle 100a shown in FIG. 9 differs from the reticle 100 shown in FIG. 10 in that uneven portions 70 to 76 are formed outside the effective area S and in the pellicle frame 112b. Since the configuration is the same as that of reticle 100 shown in FIG. 10, detailed description thereof is omitted.

The concavo-convex portions 70 to 76 are dedicated for adsorbing a substance serving as a nucleus for generating foreign matter, and concavo-convex portions are formed on the surface thereof. An identification pattern and a measurement pattern are formed on the reticle 100a. These are usually provided outside the pellicle frame, but may be provided outside the effective area S and inside the pellicle frame 112b. However, the uneven portions 70 to 76 are different from these.
The identification pattern includes, for example, identification information (ID) or a production number. The measurement patterns include, for example, those for positioning in an exposure apparatus, for measuring the focal position of a projection optical system, or for measuring accuracy used in a reticle inspection apparatus.

As in the reticle 100a shown in FIG. 9, by forming the uneven portions 70 to 76 outside the effective area S and in the reticle frame 112b, the substance that has been sublimated by exposure light is applied to the uneven portions 70 to 76. Since it pre-adsorbs preferentially, it becomes difficult to re-adsorb to the chromium film forming the pattern 108 in the effective area S.
By using the reticle 100a provided with such concavo-convex portions 70 to 76, the effect of the foreign matter generation preventing method described above can be further enhanced. That is, the generation of foreign matter in the effective area S can be further prevented.
The concavo-convex portions 70 to 76 can be formed, for example, by patterning a chromium film common to the chromium film for forming the pattern 108 for projecting the wafer into the effective area S into an appropriate shape. Further, it may be formed of a film made of a material different from the pattern in the effective area S, or may be formed by selectively etching the surface of the reticle substrate 102 itself.
In the present embodiment, the formation position of the concavo-convex portion is not particularly limited as long as it is outside the effective area S and within the pellicle frame 112b. For example, the uneven portion may be formed on the inner surface of the pellicle frame 112b on the pattern surface 104b (see FIG. 10C) side. Further, the shape and form of the concavo-convex portion is not particularly limited as long as nucleation is likely to occur, and it is provided outside the region of the effective area S and within the pellicle frame 112b. It may be a rough surface having no specific pattern shape.

  In any of the foreign matter prevention methods described above, the effective particle size measured by, for example, a foreign matter inspection apparatus, which hinders the projection of the pattern 108 in the effective area even for a long period of time, for example, five years of continuous use. Generation | occurrence | production of the foreign material of 1.5 micrometers or more can be suppressed.

  In any of the above-described foreign matter generation preventing methods, the cleaning process is performed using the exposure light of the exposure apparatus, but the present invention is not limited to this. For example, a reticle cleaning process, that is, irradiation from the pattern surface side may be performed using a dedicated irradiation apparatus. In this case, the wavelength of the ultraviolet light to be irradiated is preferably suitable for the pellicle film. For example, since absorption of light leads to deterioration of the pellicle film, it is preferable to use light having a wavelength with the least absorption by the pellicle film, that is, the highest transmittance.

  For example, in the case of a pellicle film for both g-line and i-line manufactured by Mitsui Chemicals, the wavelength of ultraviolet light to be cleaned is set to 365 nm (i-line), for example. However, depending on the spectral transmission characteristics of the pellicle film, for example, light having a wavelength such as 400, 435, and 480 nm, which is longer than the i-line, may be used. Since the transmittance of light having these wavelengths is higher than that of ultraviolet light having a wavelength of 365 nm, the deterioration of the reticle film can be suppressed.

  In any of the above-described exposure apparatuses, the step-and-repeat method has been described. However, the present invention is not limited to this. For example, the present invention can be applied to a step and scan method. In this case, the illumination optical system causes the exposure light to pass through the entire length of the first side of the effective area S (see FIG. 10C) in the direction of the first side (for example, in the lateral direction). The second side of the effective area S is shaped into a strip shorter than the length of the second side of the effective area S in the direction of the second side (eg, the vertical direction) orthogonal to the side. While irradiating the strip-shaped exposure light, the reticle and the wafer are synchronized and moved in the second direction at a constant speed, thereby projecting and exposing the pattern formed in the effective area S onto the wafer.

  The present invention is basically as described above. Although the foreign matter generation preventing method, reticle, and exposure apparatus have been described in detail, the present invention is not limited to the above-described embodiment, and various modifications or changes may be made without departing from the spirit of the present invention. It is.

It is a typical perspective view for demonstrating the principle of the foreign material generation | occurrence | production prevention which concerns on this invention to process order. It is a typical perspective view for demonstrating the next process of FIG. It is a schematic diagram which shows the exposure apparatus which concerns on the Example of this invention. It is a schematic diagram explaining the foreign material generation | occurrence | production prevention method using the exposure apparatus which concerns on the Example of this invention. It is a schematic diagram which shows the structure of the inversion unit and reticle changer of the exposure apparatus of a present Example in detail. (A) And (b) is a typical perspective view which shows operation | movement of the inversion unit of the exposure apparatus of a present Example in order of a process. (A) And (b) is a typical perspective view which shows operation | movement of the inversion unit of the exposure apparatus of a present Example in order of a process. It is a schematic diagram which shows the exposure apparatus which concerns on the other Example of this invention. It is a schematic diagram which shows the reticle which concerns on the Example of this invention. (A) is a top view which shows a reticle, (b) is sectional drawing by the AA of (a), (c) is a back view of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 Reticle 12 Glass substrate 14a, 14b Chromium film | membrane 16a, 16b Chromium film | membrane 20, 21 Exposure apparatus 22 Light source 24 Illumination optical system 27 Reticle blind 28 Projection lens 30 Reversing unit 32 Reticle changer 34 Reticle cassette library 36 Reticle case exit 50 Transfer arm 60 Rotating part 62a to 62d Arm member 64a to 64d Moving member 66a to 66d Holding tool 70 to 76 Uneven part b Effective area D Deposit EL Exposure light M Reflecting mirror S Effective area R Reticle RS Reticle stage RC1 to RC8 Reticle case W Wafer WS Wafer stage

Claims (5)

In the effective area of the pattern surface of the reticle substrate, a pattern for projecting onto the wafer by irradiating exposure light as ultraviolet light from the glass surface side opposite to the pattern surface is formed, and the effective area The pellicle that covers the pattern surface is at least on the opposite side of the pattern surface of the substance adsorbed by the portion outside the chromium film of the pattern surface in the effective area of the pattern surface of the reticle mounted on the pattern surface side. Sublimation by the energy of exposure light, which is ultraviolet light irradiated from the glass surface side, and adsorption of the sublimated substance on the surface of the chromium film are repeated for each exposure, thereby branching from the edge of the chromium film. A method of preventing the generation of foreign matter that is generated and grows and becomes an obstacle to the projection of the pattern,
The projected pattern onto the wafer, and before the foreign matter is generated by irradiating the exposure light is ultraviolet light exposure apparatus that performs projection of the pattern from the pattern surface side to said reticle, said A foreign matter generation prevention method, characterized by preventing the generation of foreign matter. The exposure apparatus projects the pattern by irradiating the reticle held on a reticle stage with the exposure light from a surface opposite to the pattern surface,
The irradiation of ultraviolet light from the pattern surface side, the reticle to the reticle stage, occurrence of foreign matters according to claim 1, characterized in that by mounting in the opposite direction to the case of performing the projection of the pattern Prevention method. The exposure apparatus projects the pattern by irradiating the reticle held on a reticle stage with the exposure light from a surface opposite to the pattern surface,
Irradiation of ultraviolet light from the pattern surface side is performed by reversing the exposure light transmitted through the reticle while holding the reticle on the reticle stage in a direction in which the pattern is projected. The foreign matter generation | occurrence | production prevention method of Claim 1 . The reticle is mounted on a reticle stage of an exposure apparatus when performing the pattern projection, and then removed from the reticle stage and stored until the next projection.
After pattern projection and mounted on the reticle stage, before the storage, the foreign matter according to any one of claims 1 to 3, characterized in that the irradiation of the ultraviolet light from the pattern surface side Occurrence prevention method. The pellicle is obtained by mounting a pellicle film on a pellicle frame provided outside the effective area of at least the pattern surface of the reticle substrate,
Irradiation of ultraviolet light from the pattern surface side is performed selectively with respect to the effective area,
An uneven portion that is neither a measurement mark nor an identification mark is formed outside the effective area of the pattern surface and inside the pellicle frame, or on the inner surface of the pellicle frame on the pattern surface side 5. A foreign matter generation preventing method according to any one of claims 1 to 4 , wherein an uneven portion is formed.

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