JP4615210B2 - Immersion exposure equipment - Google Patents

Description

  The present invention relates to an exposure apparatus used in an exposure process when manufacturing a semiconductor integrated circuit, and more particularly to an immersion type exposure apparatus using an immersion optical system.

  In general, in an exposure apparatus used in an exposure process at the time of manufacturing a semiconductor integrated circuit, in order to improve resolution performance, a lens closest to a wafer (hereinafter referred to as the final lens) among many lenses constituting a reduction projection optical system of an exposure apparatus. A method called an immersion optical system has been proposed that improves the resolution performance by filling the space between the lens and the wafer with a liquid and increasing the numerical aperture (NA) of the reduction projection optical system. Yes. For example, what is applied to an exposure apparatus using an ArF excimer laser with a wavelength of 193 nm as a light source (hereinafter referred to as an ArF exposure machine) is called an ArF immersion optical system, and is filled with water between a lens and a wafer. It is known that the resolution performance can be improved. That is, since the refractive index of water is 1.3 to 1.4, the NA is 1.3 to 1.4 times larger than when the working distance is filled with air. It has been pointed out that it becomes smaller (resolution performance becomes higher). For example, in the ArF exposure apparatus 100 having the configuration shown in FIG. 1, it is considered that water 6 is filled between the reduction projection optical system 3 and the wafer 4 during exposure, as shown in FIG. Yes.

  This technique is described in, for example, SEMICON Japan 2002, Technical programs for the semiconductor equipment and materials industries, Nos. 3-15 to 3-16 (Non-Patent Document 1).

By the way, the exposure apparatus is an apparatus for transferring a circuit pattern drawn on a mask (sometimes called a reticle) onto a wafer. To manufacture a semiconductor integrated circuit, about 30 different masks are required. Therefore, the positional accuracy of pattern transfer onto the wafer is very high so that these exposure patterns overlap with high accuracy, and it is necessary to be one digit smaller than the minimum line width. For example, when the minimum line width is 100 nm, it is necessary to set the error as the position accuracy to 10 nm or less. For this reason, many parts constituting the apparatus, such as a wafer stage for moving the wafer in particular, need to suppress thermal expansion to a minimum. Therefore, ceramics having a very low thermal expansion coefficient (low thermal expansion ceramic) and generally low thermal expansion alloys called invar or super invar are widely used as these materials. However, both the low thermal expansion ceramic and the low thermal expansion alloy are generally used, and it is preferable to use the low thermal expansion alloy particularly for a portion requiring rigidity.
SEMICON Japan 2002, Technical programs for the semiconductor equipment and materials industries, 3-15-3-16

  A problem in configuring the immersion optical system is that the water filled between the final lens and the wafer overflows from the wafer, and the movable part of the wafer stage is covered with water. In particular, when exposing a portion close to the periphery of the wafer, water often protrudes from the wafer and is applied to the wafer stage. Moreover, since the exposure apparatus is often operated continuously for a long period of time at a high operating rate particularly in a mass production factory, the problem is that the metal parts constituting the wafer stage are rusted by water. In addition, although there exists stainless steel as a metal which is hard to rust, it has a thermal expansion coefficient of about minus 10 to the power of about 17 × 10, making it difficult to use it as a component material for the wafer stage.

  Especially in the wafer stage, invar or super invar, which is a low thermal expansion alloy, is widely used as the material of the component parts. However, since these are very rusting, it has become a problem when applying an immersion optical system. . That is, invar is about 42% nickel (the rest is iron), super invar is an alloy with about 31 to 32% nickel, about 5% cobalt and about 62% iron, with a low nickel content, Since the content is large, it becomes very easy to rust. Therefore, when the immersion optical system is applied to an exposure apparatus using a wafer stage made of such a low thermal expansion alloy, the wafer stage gradually rusts. May become particles and contaminate the wafer.

  In addition, in nickel alloys such as Invar and Super Invar, on the contrary, Monel, which is known to be extremely resistant to rust, contains 63% or more of nickel, and Inconel contains 72% or more of nickel. The rate is low. However, the coefficient of thermal expansion is 15.8 × 10 minus 6th power for Monel, and 14.4 × 10 minus 6th power for Inconel, compared to about 0.5 × 10 minus 6th power for Super Inver. Since it is extremely large, it is difficult to use as a wafer stage member.

  An object of the present invention is to provide an exposure method and an exposure apparatus that do not rust at all even when water is applied to a wafer stage made of a low thermal expansion alloy in an exposure apparatus to which an immersion optical system is applied.

In order to achieve the object, in the present invention, hydrogen is dissolved in water filled between the final lens and the wafer. According to this, this water is called so-called hydrogen water, and the water itself has reducibility, so that the metal in contact does not rust. As the particular dissolved concentration of hydrogen, 0 .1～1.6Ppm, preferably, preferably those including about 1.2～1.4Ppm, below the saturation concentration is preferred. This is because if the dissolved concentration of hydrogen is too high, hydrogen may be generated as bubbles.

  According to the present invention, since all the metal materials in the components of the wafer stage are not rusted at all, even if an immersion optical system having a structure in which the entire wafer and further the wafer stage itself is immersed in water is configured, it can be operated without a long-term problem. Can do.

  As described above, according to the scanning exposure apparatus to which the immersion optical system of the present invention is applied, a super invar that is very rustable is formed on many exposed parts in contact with the ambient atmosphere in many of the members constituting the wafer stage. It can be used now.

  In addition, this makes it unnecessary to use a low thermal expansion ceramic that has been used frequently in the past, and as a result, the rigidity is higher than that of the case of being made of ceramic, so even if the stage is scanned at high speed, Deformation caused by reaction force has been greatly reduced.

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

  FIG. 1 is a block diagram of an ArF exposure apparatus 100 as a first embodiment of the present invention. Laser light L1 that is exposure light irradiates the irradiation region R1 of the mask 1. The laser beam L2 that has passed through the mask 1 enters the reduction projection optical system 3 having a reduction magnification of 1/4, and irradiates the irradiation region R2 on the wafer 4. That is, the reduction projection optical system 3 reduces and projects the pattern in the irradiation region R1 of the mask 1 onto the irradiation region R2 of the wafer 4.

The mask 1 is placed on the Y stage 2a in the mask stage 2, and can reciprocate (that is, reciprocating scan) in the Y direction (scanning direction S1 in the figure). On the other hand, the wafer 4 is placed on the Y stage 5c in the wafer stage 5, and can be reciprocally scanned in the Y direction (scanning direction S2 in the figure). A reciprocating scan is performed in synchronization with the opposite direction.

  The Y stage 5c of the wafer stage 5 on which the wafer 4 is placed is placed on the X stage 5b that can move in the X direction, whereby the wafer 4 can also be stepped in the X direction (step direction S3 in the figure). It is like that.

  In the present embodiment, water 6 is supplied between the irradiation region R2 on the wafer 4 and the reduction projection optical system 3, so that an immersion optical system can be applied. However, in FIG. 1, the wafer 4 and the reduction projection optical system 3 are drawn somewhat apart from each other, but in reality, the distance between them is as small as about 1 mm. The relationship between the wafer 4 and the reduction projection optical system will be described below with reference to FIG.

  FIG. 2 is a cross-sectional view when water 6 is supplied between the reduction projection optical system 3 and the wafer 4 in the ArF exposure apparatus 100 in the first embodiment shown in FIG. The water 6 is discharged from the discharge nozzle 7 and supplied between the wafer 4 and the final lens 9 mounted at the bottom of the reduction projection optical system 3. Further, water filled between the final lens 9 and the wafer 4 is sucked from the suction nozzle 8. That is, new water 6 is always supplied from the discharge nozzle 7 during exposure. Here, for the discharge nozzle 7 and the suction nozzle 8, the combination of the discharge nozzle and the suction nozzle shown in FIG. 3B of Japanese Patent Application No. 2003 149375 can be used. More specifically, the discharge nozzle 7 and the suction nozzle 8 cross the scan direction Y of the reduction projection optical system 3 with the final lens 9 so as to cross the scan direction Y, that is, parallel to the step direction X. The final lens 9 is positioned therebetween. Furthermore, in the illustrated example, actually, a plurality of discharge nozzles 7 and suction nozzles 8 are alternately arranged on the right side (or left side) of the final lens 9 in a direction perpendicular to the paper surface of FIG. Further, a discharge nozzle and a suction nozzle (not shown) extending in the X direction are provided at the center of the final lens 9 in the Y direction. In this example, while the wafer 4 is being scanned in the + Y or −Y direction of the scan direction, hydrogen water is discharged from the discharge nozzle 7 and the hydrogen water is sucked by the suction nozzle 8. Instead of the combination of the discharge nozzle 7 and the suction nozzle 8, a configuration in which only the discharge nozzle is arranged may be employed.

  In the present invention, this water 6 is generally called hydrogen water, and in this embodiment, hydrogen is contained in 1.5 liters (1.5 ppm) in 1 liter of water as the concentration of hydrogen contained, and is highly reducible. You are using water. As a result, even if the water 6 contacts the metal for a long time, the metal does not rust at all. As a result, a super invar can be used for the material of most of the parts constituting the wafer stage 5 shown in FIG. 1, and a wafer stage having a low thermal expansion coefficient can be constituted.

  In addition, although it is pointed out also in Japanese Patent Application No. 2003-038941 concerning the application of the present inventors about adding hydrogen gas with respect to pure water and preventing a metal rust, immersion type It is not pointed out that the exposure apparatus is composed of a low thermal expansion alloy.

  The present invention can be used for exposure of masks and wafers used in the manufacture of semiconductor devices, and can also be applied to exposure apparatuses such as LEEPL.

It is a figure which shows schematically the structure of the ArF exposure apparatus 100 used for this invention. It is a figure which shows roughly the cross section of the immersion optical system used in this invention. It is sectional drawing which illustrates an immersion optical system roughly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mask 2 Mask stage 2a Y stage 3 Reduction projection optical system 4 Wafer 5 Wafer stage 5a Stage base 5b X stage 5c Y stage 6 Water 7 Discharge nozzle 8 Suction nozzle 9 Final lens 100 ArF exposure apparatus L1, L2 Laser light R1, R2 Irradiation area S1, S2 Scan direction S3 Step direction

Claims (4)

In an immersion type exposure apparatus in which the space between the optical member closest to the wafer side in the reduction projection optical system and the wafer is filled with water to increase the numerical aperture of the reduction projection optical system,
The wafer stage having a portion in contact with water is made of a low thermal expansion alloy containing iron,
An immersion type exposure apparatus, wherein the water contains hydrogen.   2. The immersion type exposure apparatus according to claim 1, wherein the low thermal expansion alloy is Super Invar.   3. The immersion type exposure apparatus according to claim 1, further comprising means for discharging the water containing hydrogen between the optical member and the wafer.   4. The immersion type exposure apparatus according to claim 3, further comprising means for sucking water containing hydrogen.

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