JP2006093318A - EUV exposure apparatus, EUV exposure method, and reflective mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power of EUV light necessary for a mass production EUV exposure machine.
By irradiating EUV light X1 onto an irradiation area 3 of a reflective cylindrical mask 1 and irradiating a pattern of the irradiation area 3 onto a wafer 2 via a plurality of reflecting mirrors M1 to M6. The EUV exposure apparatus 100 performs projection projection exposure of the entire pattern on the mask 1 onto the wafer 2, and a cylindrical mask is used as the reflective cylindrical mask 1.
[Selection] Figure 1

Description

  The present invention relates to an exposure apparatus, an exposure method, and a reflective mask used at the time of manufacturing a semiconductor. Called an exposure machine).

  At present, as an exposure apparatus, an ArF exposure machine using an ArF excimer laser as an exposure light source is widely used. In the ArF exposure machine, when a pattern on a mask is reduced and projected onto a wafer, exposure is performed while scanning the mask and the wafer on opposite sides, which is called a scanning exposure machine. . An exposure method using this scanning type exposure machine will be described with reference to FIG.

  In the general scanning exposure apparatus 200 (which may be a KrF exposure apparatus or an ArF exposure apparatus) shown in FIG. 6, for example, a letter “A” is formed on the transmission mask 202 placed on the mask stage 201. When the pattern is applied, the light image of the exposure laser beam L1 irradiated here is projected onto the wafer 205 on the wafer stage 204 by the reduction projection optical system 203, and the letter “A” is formed. The pattern is reduced in the opposite direction and projected.

  The entire exposure area 208 is projected and exposed by scanning the irradiation area 206 a (that is, the slit-shaped area that is instantaneously projected) irradiated to the transmissive mask 202 over the entire pattern area 207. It becomes like this. Therefore, during exposure, the transmission mask 202 and the wafer 205 are scanned in synchronization with each other in the opposite directions with respect to the X direction. When the exposure area 208 is moved in the direction (Y direction) orthogonal to the scanning direction (X direction) on the wafer 205, the wafer 205 is stepped in the Y direction by the wafer stage 204. Note that the scan type exposure apparatus is disclosed in Non-Patent Document 1, for example.

  On the other hand, the use of an EUV exposure machine is widely studied as a next-generation exposure machine for ArF exposure machines. Similarly to the ArF exposure machine, the EUV exposure machine uses a scanning type because the size of the image (irradiation area on the wafer) projected on the wafer at a certain moment is smaller than the exposure area. However, the EUV exposure machine is greatly different from an exposure apparatus using ultraviolet light such as an ArF exposure machine in that the reduction projection optical system is entirely composed of a reflecting mirror and the mask is also of a reflective type. The EUV exposure apparatus is disclosed in Patent Document 1 or Non-Patent Document 2.

JP 2004-170869 A Journal of Precision Engineering, Vol. 61, no. 12, pp. 1676 to 1680, 1995 OPTRONICS, no. 4, pp. 122-127, 2003

  The biggest problem with the EUV exposure machine is that the power of the EUV light that is the exposure light is insufficient, and in the current experimental machine, only an average of about 20 W is obtained at the emission point of the EUV light. Under such circumstances, it is said that the EUV light power needs to be 115W or more at the light emitting point to realize a mass production machine capable of exposing 80 wafers or more of 300mm wafers per hour. It was difficult to improve the output.

  Accordingly, an object of the present invention is to reduce the power of EUV light necessary for an EUV exposure machine for mass production, and to realize a practical mass production machine at an early stage.

  In the present invention, the entire pattern on the reflective mask is reduced on the substrate by irradiating the irradiation area of the reflective mask with the exposure light and irradiating the substrate with the pattern of the irradiated area via a plurality of reflecting mirrors. In the exposure apparatus for projection exposure, the reflective mask is formed in a cylindrical shape.

  Here, the entire pattern is formed on a cylindrical surface of the reflective mask, and the substrate is scanned at a constant speed in a predetermined direction while rotating the cylindrical reflective mask at a constant speed. The entire pattern is exposed on the substrate. The exposure of the entire pattern is performed without inverting the cylindrical reflective mask. Preferably, the exposure light is EUV light.

  Moreover, it is preferable to have a gas discharge port which blows gas with respect to the irradiation area vicinity of the said cylindrical reflective mask.

  Moreover, it is preferable to have a cover that covers the entire periphery of the cylindrical reflective mask. Preferably, the cover is provided with a shutter that exposes only a peripheral portion of the irradiation area during exposure. Moreover, it is preferable that the adhesive material is apply | coated to the inner surface of the said cover.

  As described above, in the present invention, a cylindrical mask is used as a mask of an EUV exposure machine. Unlike a conventional ArF exposure machine or the like, the mask of the EUV exposure machine is a reflection type. Therefore, even if the mask is cylindrical, a reflective mask necessary for the EUV exposure apparatus can be configured by forming a pattern on the cylindrical surface.

  According to the present invention, by rotating the cylindrical reflective mask during exposure, the entire pattern to be exposed can be projected on the wafer, and the projection of the entire pattern is finished by rotating the mask once. When exposure is performed, it is not necessary to invert the mask or wafer as in the prior art, so that the inversion time of these stages is not required.

  As a result, one wafer can be exposed in a shorter time than before. In addition, in order to expose the wafer in the same time as the conventional method, it is only necessary to scan the wafer later than the conventional method, and as a result, an equivalent throughput can be obtained with the power of EUV light that is about 1/2 of the conventional method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view centering on a projection optical system of an EUV exposure apparatus 100 according to an embodiment of the present invention.

  The EUV light X1, which is an exposure light source of the EUV exposure apparatus 100, is irradiated to the elongated irradiation region 3 on the surface of the reflective cylindrical mask 1 (however, the elongated direction is a direction perpendicular to the paper surface). A pattern to be projected is attached to the cylindrical surface of the reflective cylindrical mask 1. The EUV light X2 reflected by the reflective cylindrical mask 1 is sequentially reflected by the six aspherical mirrors M1, M2, M3, M4, M5, and M6 to irradiate the irradiation area 4 of the wafer 2. These six aspherical mirrors form a reflective reduction projection optical system. As a result, the pattern of the irradiation area 3 of the reflective cylindrical mask 1 is reduced and projected onto the irradiation area 4 on the wafer 2.

  The first aspherical mirror M1 has one direction as compared with the first aspherical mirror of a conventional EUV exposure machine having a reduction projection optical system composed of similar six aspherical mirrors. The curvature of is shorter. The reason is that since the irradiation area 3 is a cylindrical surface, the reflected light travels while spreading more than in the case of a conventional flat reflective mask.

  In order to reduce and expose the entire pattern formed on the cylindrical surface of the reflective cylindrical mask 1 onto the wafer 2, the wafer 2 is moved in the direction of the arrow while the reflective cylindrical mask 1 is rotated at a constant speed in the direction of the arrow. Can be scanned at a constant speed.

  As described above, in the EUV exposure apparatus 100 of the present invention, when the reflection type cylindrical mask 1 completes one rotation, the same pattern is projected again. Therefore, there is an inversion operation on the reflection type cylindrical mask 1 itself. It is not necessary to invert the wafer 2 for each LSI chip exposure. As a result, even when exposure is performed with the same EUV light power as in the prior art, the total processing time required for exposing the entire surface of the wafer 2 is shortened.

  In the EUV exposure apparatus 100, clean helium gas is discharged from the gas discharge port 5 during exposure, and the vicinity of the irradiation region 3 in the reflective cylindrical mask 1 is blown. As a result, even if particles adhere to the vicinity of the irradiation region 3, they are blown off.

  In addition, as shown in FIG. 2, the reflective cylindrical mask 1 may be mounted on the EUV exposure apparatus 100 with the cover 6 covering the whole mounted. In that case, it suffices to provide the shutter 7 so that the cylindrical surface of the reflective cylindrical mask 1 is exposed only in the periphery of the irradiation region 3 irradiated with the EUV light X1. That is, while not being exposed, the shutter 7 slides to close the opening of the cover 6. Further, when the reflective cylindrical mask 1 is removed from the EUV exposure apparatus 100 and carried, the reflective cylindrical mask 1 can be kept in the cover 6. This prevents surrounding particles from adhering to the cylindrical surface of the reflective cylindrical mask 1 even during transportation of the reflective cylindrical mask 1.

  An adhesive material is applied to the inner surface of the cover 6. Thereby, when the particles adhering to the surface of the reflective cylindrical mask 1 during the exposure are blown off by the centrifugal force of the rotation, they can be caught. 1 does not adhere to the surface.

  Next, since the conventional EUV exposure apparatus (however, the general scanning type exposure apparatus 200 shown in FIG. 6 is the same, the number of FIG. 6 is also shown) and the EUV of the present invention shown in FIG. Differences in how the wafer is exposed with respect to the exposure apparatus 100 will be described with reference to FIGS.

  FIG. 3 shows an operation in the case where a portion of each exposure area 208 that is filled with diagonal lines is exposed on the wafer 205. In the conventional EUV exposure machine, the irradiation area 206b is irradiated along the exposure direction indicated by the solid arrow. A dotted arrow indicates a step operation for moving the irradiation region 206b. At this time, the mask stage 201 and the wafer stage 204 are reversed with respect to the scanning direction. As can be seen from FIG. 3, every time each exposure region 208 is exposed, the reversing operation of the mask stage 201 and the wafer stage 204 is required.

  On the other hand, when the wafer 2 is exposed by the EUV exposure apparatus 100 of the present invention shown in FIG. 4, the irradiation region 4 continuously moves in the portion indicated by the oblique lines in the exposure region 10. The wafer 2 may be scanned at a constant speed. That is, it is not necessary to perform a step operation or a stage reversal operation every time one exposure area 10 is exposed. These are performed once when exposure of one row of exposure areas 10 arranged in the wafer 2 is completed. Just do it.

  As described above, in the EUV exposure apparatus 100 of the present invention, the ratio of the time required to move the stage without actually irradiating the wafer with the EUV light as the exposure light in the time for processing one wafer. Can be greatly reduced.

  Therefore, the throughputs of the EUV exposure apparatus 100 of the present invention and the conventional EUV exposure apparatus were compared. The calculation results of these throughputs are shown in FIG.

  The calculation conditions are that when a wafer with a diameter of 300 mm is exposed to 111 LSI chips of 24 mm square, the scanning speed of the wafer stage is a maximum of 500 mm / second, the acceleration of the wafer stage is 10 m / s ^ 2, and the overscan distance. (It is a running distance for scanning the LSI chip to be exposed and moves at the same scanning speed as the exposed portion) was assumed to be 8 mm, and the time to replace and align the wafer was 10 seconds. The arrival rate from the EUV light emission point to the wafer was 0.127%. As is clear from FIG. 5, when the EUV light power is the same as 115 W, the EUV exposure apparatus of the present invention improves the throughput by 50 to 60% when the resist sensitivity is 3 mJ / cm 2 or more compared to the conventional apparatus. did.

  In the exposure apparatus of the present invention, when the EUV light power is 57.5 W, which is half of 115 W, when the resist sensitivity is about 3 mJ / cm 2, the EUV light power is 115 W with a conventional EUV exposure machine. Became equivalent. That is, in the EUV exposure apparatus of the present invention, the required power of EUV light can be halved.

  Note that the EVU exposure apparatus of the present invention described above may be applied not only to EUV but also to an exposure apparatus using ultraviolet light such as an ArF exposure machine. In that case, a reflective mask may be used instead of the conventional transmissive mask used for these.

  By the way, as a pattern drawing device for applying a pattern to the cylindrical surface of the reflective cylindrical mask 1 as in the present invention, the entire cylindrical surface can be exposed while rotating the reflective cylindrical mask 1 during pattern exposure. A raster scanning pattern drawing apparatus is preferable, and for example, an exposure apparatus using a micromirror device can be used.

  That is, the raster scan is a method of irradiating the exposure beam linearly only in one direction when exposing the inside of the substrate. Therefore, the exposure beam is applied in the linear direction of the cylinder of the reflective cylindrical mask 1. This is because a pattern can be drawn on the entire surface of the cylindrical surface simply by reciprocating.

It is sectional drawing of the EUV exposure machine 100 by embodiment of this invention. It is explanatory drawing of the reflection type cylindrical mask in the EUV exposure machine 100 of this invention. It is explanatory drawing of the wafer exposure by the conventional EUV exposure machine. It is explanatory drawing of the wafer exposure by the EUV exposure machine 100 of this invention. It is a comparison figure of the throughput of EUV exposure machine 100 of the present invention and the conventional EUV exposure machine. It is explanatory drawing of the general scanning type exposure machine 200. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflective cylindrical mask 2,205 Wafer 3,4,206a, 206b Irradiation area 5 Gas discharge port 6 Cover 7 Shutter 10, 208 Exposure area 11,210 Exposure direction 12,212 Stage reversal 100 EUV exposure machine 200 of this invention General Scan type exposure machine 201 Mask stage 202 Transmission type mask 203 Reduction projection optical system 204 Wafer stage L1 Laser light X1, X2 EUV light

Claims (17)

Exposure that irradiates the irradiation area of the reflective mask with the exposure light and irradiates the pattern of the irradiation area onto the substrate through a plurality of reflecting mirrors, thereby reducing and exposing the entire pattern on the reflective mask onto the substrate. In the device
An exposure apparatus characterized in that the reflective mask is formed in a cylindrical shape.   The overall pattern is formed on a cylindrical surface of the reflective mask, and the substrate is scanned at a constant speed in a predetermined direction while rotating the cylindrical reflective mask at a constant speed. The exposure apparatus according to claim 1, wherein exposure is performed on the substrate.   2. The exposure apparatus according to claim 1, wherein the exposure of the entire pattern is performed without inverting the cylindrical reflective mask.   The exposure apparatus according to claim 1, wherein the exposure light is EUV light.   The exposure apparatus according to claim 1, further comprising a gas discharge port that blows gas toward an irradiation region in the vicinity of the cylindrical reflective mask.   2. The exposure apparatus according to claim 1, further comprising a cover that covers the entire periphery of the cylindrical reflective mask.   The exposure apparatus according to claim 6, wherein the cover is provided with a shutter that exposes only a peripheral portion of the irradiation area during exposure.   The exposure apparatus according to claim 6, wherein an adhesive material is applied to an inner surface of the cover. Exposure that irradiates the irradiation area of the reflective mask with the exposure light and irradiates the pattern of the irradiation area onto the substrate through a plurality of reflecting mirrors, thereby reducing and exposing the entire pattern on the reflective mask onto the substrate. In the method
An exposure method using a cylindrical mask as the reflective mask.   The overall pattern is formed on a cylindrical surface of the reflective mask, and the substrate is scanned at a constant speed in a predetermined direction while rotating the cylindrical reflective mask at a constant speed. The exposure method according to claim 9, wherein exposure is performed on the substrate.   The exposure method according to claim 9, wherein the exposure of the entire pattern is performed without inverting the cylindrical reflective mask.   The exposure method according to claim 9, wherein EUV light is used as the exposure light.   A cylindrical reflective mask used in an exposure apparatus that irradiates an irradiation area with exposure light to reduce and project a pattern onto a substrate through a plurality of reflecting mirrors.   The reflective mask according to claim 13, wherein the exposure light is EUV light.   The reflective mask according to claim 13, further comprising a cover that covers the entire periphery.   The reflective mask according to claim 15, wherein the cover is provided with a shutter that exposes only a peripheral portion of the irradiation area during exposure. The reflective mask according to claim 15, wherein an adhesive material is applied to an inner surface of the cover.

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