1. Field of the Invention
The present invention relates to an exposure apparatus that exposes a substrate through liquid and a method for manufacturing a device using the exposure apparatus.
2. Description of the Related Art
Referring to
A liquid recovery mechanism is disposed in a lower part of a space 800. The liquid recovery mechanism includes a recovery port 804, a recovery pipe 805, and a suction device 806. The recovery port 804 serves to drain liquid LW that has dropped into the space 800 as shown in
Japanese Patent Laid-Open No. 2006/186112 describes controlling of spattering and flow of liquid by providing a hydrophilic area on a surface of a support plate. International Publication No. WO 2004/112108 pamphlet and International Publication No. WO 2006/049134 pamphlet describe a liquid recovery mechanism for recovering liquid that has dropped into a gap between the wafer and the support plate.
Referring to
Referring to
As heretofore described, it is important to rapidly recover liquid d divided at gap g without allowing the liquid d to spatter in the exposure apparatus, and to prevent liquid LW that has dropped into the space 800 from overflowing when the stage moves.
The present invention provides an exposure apparatus with which one or both of the first problem and the second problems is solved and light exposure is performed with excellent precision.
According to an aspect of the present invention, an exposure apparatus for exposing a substrate through liquid includes a stage for holding and moving the substrate. The stage includes a holding section for holding the substrate and a supporting section disposed around the holding section. The supporting section includes a recovery port including a gap between the substrate held by the holding section and the supporting section, the recovery port for recovering the liquid, a space for storing the liquid recovered through the recovery port, a liquid recovery mechanism for draining the liquid that has collected in a lower part of the space, and a sloshing reduction member disposed in the space, the sloshing reduction member for reducing sloshing of the liquid.
Further aspects of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, various embodiments of the present invention are described in detail with reference to the attached drawings.
The exposure apparatus 1 is an immersion exposure apparatus that exposes a pattern of a reticle (mask) 20 onto a wafer 40 through liquid (immersion liquid) LW that is supplied between a final surface 30a of a projection optical system 30 and the wafer 40. The exposure apparatus 1 exposes the wafer 40 to light by a step-and-scan method. However, an exposure apparatus that exposes the wafer 40 to light by a step-and-repeat method can also be used.
As shown in
The illumination unit 10 includes a light source 11 and an illumination optical system 12. In this embodiment, ArF excimer lasers with a wavelength of 193 nm are used as the light source 11. However, KrF excimer lasers of a wavelength of about 248 nm or F2 lasers with a wavelength of about 157 nm can be used as the light source 11. The illumination optical system 12 illuminates the reticle 20 with light from the light source 11.
The reticle stage 21 is mounted on a base 22 for fixing the reticle stage 21. The reticle stage 21 holds the reticle 20 with a reticle chuck (not shown). The reticle stage 21 is controlled by a movement mechanism (not shown) and a control unit described below. The reticle 20, which is made of quartz, is an original having a circuit pattern formed thereon. Diffracted light that has passed through the circuit pattern of the reticle 20 is projected onto the wafer 40 with the projection optical system 30.
The projection optical system 30 projects the pattern of the reticle 20 onto the wafer 40. A dioptric system or a catadioptric system can be used for the projection optical system 30.
The wafer stage 41 is mounted on a base 42 for fixing the wafer stage 41. The wafer stage 41 holds the wafer 40 on a wafer holding section. The wafer stage 41 functions to adjust the up-and-down (vertical) position, the orientation, and the inclination of the wafer 40. The wafer stage 41 is controlled by a stage control unit. While the wafer 40 is being exposed to light, the stage control unit controls the wafer stage 41 so that the focal plane of the projection optical system 30 coincides with the upper surface of the wafer 40 with high precision. The wafer 40 is conveyed into the exposure apparatus 1 with a wafer conveying system (not shown). The wafer 40 is supported on and moved with the wafer stage 41. Although the wafer 40 is used as a substrate in this embodiment, a liquid crystal substrate or the like can be also used as the substrate. The wafer 40 is coated with a photoresist.
The support plate 43 surrounds the wafer 40. The height of the upper surface of the support plate 43 is adjusted so as to be substantially the same height as the upper surface of the wafer 40. The support plate 43 and the wafer 40 support the liquid LW when an edge of the wafer 40 is exposed to light.
The distance measuring unit 50 measures in real time the position of the reticle stage 21 and the three-dimensional position of the wafer stage 41 using reference mirrors 51 and 52 and laser interferometers 53 and 54. Measurements made by the distance measuring unit 50 are transmitted to a control unit 130 described below. The reticle stage 21 and the wafer stage 41 are driven and positioned under control by the control unit 130.
The liquid LW can be selected, for example, from substances having a low absorptance for the light used for exposure and having a refractive index as high as possible. As more specific examples, pure water, functional water, a fluoridized liquid (for example, a fluorocarbon), an organic liquid, or the like may is used as the liquid LW. Dissolved gas in the liquid LW can be sufficiently removed using a degassing apparatus. As the liquid LW, liquid including water with a very small amount of additives or hydrocarbon organic liquid can also be used.
The exposure apparatus 1 further includes a supply/recovery unit 110 and the control unit 130.
The supply/recovery unit 110 supplies the liquid LW to and recovers the liquid LW from between the wafer 40 and the final surface 30a of the projection optical system 30 through a supply pipe 111, a recovery pipe 112, a supply nozzle 113, and a recovery nozzle 114. The supply/recovery unit 110, which has a structure for supplying and recovering the liquid LW, is controlled by the control unit 130. The supply/recovery unit 110 also supplies and recovers the liquid LW when the wafer stage 41 moves. With the above-described structure, the supply/recovery unit 110 can remove dissolved gas and impurities from the liquid LW, and the liquid LW is maintained in a homogeneous state.
The control unit 130, which includes a CPU (not shown) and a memory, controls the exposure apparatus 1. The control unit 130 is electrically connected to the illumination unit 10, the movement mechanism (not shown) for the reticle stage 21, a movement mechanism (not shown) for the wafer stage 41, and the supply/recovery unit 110. For example, the control unit 130 may be configured to supply and recover the liquid LW by switching the flow direction of the liquid LW in accordance with the wafer stage 41 when light exposure is performed. Alternatively, the control unit 130 may be configured to supply and recover the liquid LW in a constant amount when light exposure is performed.
Referring to
First, a structure around the periphery of the wafer 40 in this embodiment is described. A surface of the support plate 43 includes a first area 43a that is hydrophilic and a second area 43b that is hydrophobic (liquid-repellent). The first area 43a is made of hydrophilic material (for example, SiO2, SiC, or a metal oxide such as titanium oxide). Lateral sides of the first area are also hydrophilic. The first area 43a surrounds the wafer 40. The first area 43a has a width w in the range of several millimeters to several tens of millimeters. The width of a gap g between the wafer 40 and the first area 43a is adjusted so as to be approximately between 0.1 mm to 2 mm. The second area 43b surrounds the first area 43a. A gap g2 is formed between the first area 43a and the second area 43b. The second area 43b is coated with Teflon or treated by a hydrophobic treatment such as PFA.
The gap g2 and the gap g provide recovery ports 109 for recovering the liquid d and allow the liquid d to be recovered from the surface of the support plate 43 to the space 100 therethrough. A side surface 43c of the support plate 43 is made hydrophilic so that the liquid d can be smoothly recovered to the space 100. As hydrophilic treatment, titanium oxide coating, for example, can be used. Moreover, a side surface of the wafer 40 and a side surface 802a of the wafer holding section 802 may be made hydrophilic. Furthermore, the liquid d can be recovered more effectively by disposing a recovery port for recovering the liquid d in the first area 43a. For example, slits, pinholes, or a porous body may be formed in the first area 43a.
The space 100 is formed in the support plate 43 in a ring shape so as to surround the wafer 40 so that liquid recovered through the recovery ports 109 can be temporarily stored therein.
A porous body 101, which serves as a sloshing reduction member, has a ring shape so as to surround the wafer 40 and has a volume equal to or larger than half the volume of the space 100. In this embodiment, the porous body 101 occupies a space from a space bottom 100a to near the first area 43a. As the porous body 101, for example, SiO2, SiC, or a sintered compact of metal such as stainless steel or titanium can be used. Hydraulic conductivity is an indicator of the permeability of a porous body. Hydraulic conductivity is a coefficient defined by Darcy's law expressed by equation 1. Here, v is apparent seepage flow velocity (cm/sec), k is hydraulic conductivity (cm/sec), and i is hydraulic gradient.
v=ki (1)
The porous body 101 in this embodiment has a hydraulic conductivity equal to or lower than 1000 cm/sec for the reasons described below.
A liquid recovery mechanism 104 is a mechanism for draining liquid that has collected in the space 100. In this embodiment, the liquid recovery mechanism 104 includes a groove 102 and pinholes 103 disposed in the lower part of the space 100. The groove 102, which is formed in the space bottom 100a, has a ring shape so as to surround the wafer 40. The groove 102 serves to guide the liquid LW that has infiltrated into the porous body 101 to the pinholes 103. The pinholes 103 have a diameter in the range from several hundred micrometers to several tens of millimeters. The pinholes 103 are disposed in the groove 102. In this embodiment, the pinholes 103 are disposed at equally spaced intervals along the circumference of the wafer 40. The groove 102 is not necessary when a large number of the pinholes 103 are provided, because the liquid LW that has infiltrated into the porous body 101 is easily drained to the pinholes 103 in this case. The liquid recovery mechanism 104 is disposed near the center of the space bottom 100a or below the recovery ports 109. In order to effectively drain the liquid LW, the space bottom 100a may be inclined downward toward the liquid recovery mechanism 104.
As shown in
A recovery pipe 105 guides liquid from the liquid recovery mechanism 104 to a suction device 108. The suction device 108 includes a gas-liquid separation unit 106 and a decompressor 107.
Next, some of the advantages of this embodiment are described.
While a periphery of the wafer 40 is being exposed to light (edge shot), liquid may be divided when an immersion area spreads over the gap g. However, in this embodiment, the liquid d that has been divided remains on the first area 43a because the first area 43a is hydrophillic, whereby spattering of the liquid d is reduced. Therefore, corrosion of peripheral components and formation of water marks resulting from spattering of the liquid d can be reduced.
Moreover, the liquid d on the first area 43a is drained to the space 100 through the recovery ports 109. Therefore, evaporation of the liquid d on the first area 43a and the formation of water marks resulting therefrom can be reduced.
Although the first area 43a is made hydrophilic in this embodiment, the first area 43a may be made hydrophobic in a case when liquid is not divided or in a case when only a small amount of liquid is divided. In this case, the contact angle between the first area 43a and the surface of liquid is equal to the contact angle between the second area 43b and the surface of liquid. Moreover, the surface of the support plate 43 may be constituted by a single region without the gap g2.
As shown in
The liquid LW enters from the recovery ports 109, passes through the porous body 101, and collects in the space 100. A material having a sufficiently high permeability is used for the porous body 101.
The liquid LW that has collected in the space 100 may overflow through the recovery ports 109 when the wafer stage 41 moves. However, sloshing of the liquid LW is reduced in this embodiment since the porous body 101 is disposed in the space 100. As a result, overflow of the liquid LW from the recovery ports 109 can be reduced. Actually, overflow of the liquid LW is reduced when hydraulic conductivity of the porous body 101 is equal to or less than 1000 cm/sec. In particular, it is beneficial to reduce overflow of the liquid LW for this embodiment, because the liquid easily drops into the space 100 since the first area 43a is hydrophilic.
Next, referring to equations 2 to 5 and
When the Z coordinate is taken as shown in
Here, maximum value of Z is expressed by equation 4. The maximum rise value Δz of the liquid LW resulting from sloshing of the liquid caused by the movement of the wafer stage 41 is expressed by equation 5.
The relation between hydraulic conductivity k and a rise value of the liquid Δz is illustrated in the graph of
In this embodiment, it is not necessary to continuously suck and recover the liquid LW through the liquid recovery mechanism 104, because the liquid LW collected in the space 100 does not overflow. For example, suction recovery of the liquid LW may be stopped by closing a valve 105a shown in
As heretofore described, since the exposure apparatus 1 of this embodiment has the first area 43a that is hydrophilic and the recovery ports 109 on the surface of the support plate 43, the liquid d can be recovered to the space 100 without allowing the liquid d to spatter in the exposure apparatus 1. Moreover, since the porous body 101 is disposed in the space 100, the liquid LW is prevented from overflowing from the space 100 as the stage moves. As a result, corrosion of components near the wafer and formation of water marks can be suppressed, and staining of the exposure apparatus 1 can be reduced. Moreover, since it is not necessary to constantly suck the liquid that has collected in the space 100, heat of vaporization can be reduced, whereby decline of exposure accuracy caused by the heat of vaporization can be suppressed.
Referring to
In
Although the porous body 501 is used as a sloshing reduction member in the foregoing description, a porous plate having pinholes therein can also be used as a sloshing reduction member. The porous plate has a thickness of several millimeters, and the diameter of the pinholes is in the range from several hundred micrometers to several millimeters. By treating the porous plate by hydrophilic treatment, liquid can be easily drained to the space 100 through the pinholes.
As described above, since an exposure apparatus of this embodiment has a porous body or a porous plate as a sloshing reduction member in the upper part of the space 100, liquid d can be recovered through the recovery ports 109 and sloshing of the liquid LW in the space 100 can be reduced. As a result, the liquid LW is prevented from overflowing from the recovery ports 109, and spattering of liquid in the exposure apparatus can be suppressed.
Referring to
As shown in
In the foregoing description, the plates 602 with the pinholes 601 are used as multi-tiered plates so as to reduce sloshing of liquid. However, as shown in
In this embodiment, the plates 602 may be hydrophilic. In this case, liquid d recovered through the recovery ports 109 can be quickly drained to the lower part of the space 100.
As heretofore described, since the exposure apparatus of this embodiment has the multi-tiered plates 602 with openings in the space 100 as a sloshing reduction member, liquid d can be recovered through the recovery ports 109 and sloshing of liquid LW in the space 100 can be reduced. As a result, overflow of liquid LW through the recovery ports 109 and spattering of liquid LW in the exposure apparatus can be suppressed.
Referring to
In this embodiment, partition plates 701 serving as a sloshing reduction member divides the space 100 into a plurality of spaces 702. As shown in
When the wafer stage 41 moves, the partition plates 701 serve to reduce sloshing of the liquid and suppress overflow of the liquid through the recovery ports 109.
Although the partition plates 701 are disposed in the radial direction and the circumferential direction of the wafer 40 in this embodiment, the partition plates 701 may be disposed in only one of the directions. It is not necessary that the partition plates 701 be disposed in the radial direction or in the circumferential direction as long as the space 100 is divided into a plurality of spaces.
As heretofore described, since the exposure apparatus of this embodiment has the partition plates 701 serving as a sloshing reduction member in the space 100, liquid d can be recovered through the recovery ports 109, and sloshing of liquid LW in the space 100 can be reduced. As a result, overflow of liquid LW through the recovery ports 109 and spattering of liquid LW in the exposure apparatus can be suppressed.
Next, a method for manufacturing a device (semiconductor device, liquid crystal display device, or the like) according to another embodiment of the present invention is described. A method for manufacturing a semiconductor device is used as an example here.
A semiconductor device is manufactured by a front-end process by which an integrated circuit is formed on a wafer and a back-end process by which chips of the integrated circuit formed by the front-end process are finished into a product. The front-end process includes a process for exposing a substrate coated with a photoresist to light using any of the above-described exposure apparatuses of the present invention and a process for developing the substrate. The back-end process includes an assembly process (dicing and bonding) and a packaging process.
With the device manufacturing method of this embodiment, a device having a quality higher than the existing device can be manufactured.
While the present invention has 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. 2008-076891 filed Mar. 24, 2008 and No. 2009-016217 filed Jan. 28, 2009, which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | Kind |
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2008-076891 | Mar 2008 | JP | national |
2009-016217 | Jan 2009 | JP | national |