JP2006120878A - Liquid-immersion exposure device and device manufacturing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid-immersed exposure device which can be kept stable in performance for a longer period than normally. <P>SOLUTION: The liquid-immersed exposure device is equipped with a projection optical system which projects a pattern provided on a reticle onto a substrate, and a liquid feeder which feeds liquid to, at least a part of space between the projection optical system and the substrate. Furthermore, the liquid-immersed exposure device is configured so as to be equipped with a unit which introduces a reducing agent into the liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to an exposure apparatus, and more particularly, to an immersion exposure apparatus for exposing and transferring a device pattern onto a substrate in a lithography process when manufacturing a semiconductor device, and a device manufacturing method using the same.

  In recent years, the demand for miniaturization of semiconductor devices is increasing, and the demand for improving the resolution of projection exposure apparatuses is increasing. In order to improve the resolving power of the projection exposure apparatus, a higher NA of the projection lens and a shorter wavelength of the exposure light have been accelerated in recent years. The shortening of the wavelength has progressed from 248 nm using a KrF excimer laser as a light source to 193 nm using an ArF excimer laser as a light source.

  On the other hand, one technique for improving the resolution of an optical microscope is an immersion method in which a liquid with a high refractive index is filled between an objective lens and an observation sample.

There is also a proposal to apply this effect for miniaturization of a semiconductor device (see, for example, Patent Document 1), and the space between the lens (final lens) on the most wafer side of the projection optical system and the wafer is more than air. There has been proposed an immersion exposure apparatus that can obtain the same effect of using light having a wavelength 1 / n of that in air as exposure light by filling with a liquid having a high refractive index n (Patent Document). 2).
US Pat. No. 5,121,256 Japanese Patent Laid-Open No. 06-124873

  Conventionally, when the wavelength of the exposure light is shortened and the energy of the exposure light is increased, the exposure light is converted into a glass material (lens, mirror, etc.) of the exposure apparatus, an antireflection film formed on the glass material, and members around the glass material. It was known to cause damage.

  However, as a result of the inventor's investigation, in the case of an immersion exposure apparatus, the damage is greater than that of a dry exposure apparatus that does not use a conventional immersion method, particularly the final lens and members around the final lens. It has been found that this occurs in the wafer and members around the wafer (members for holding the wafer, etc.). The damage becomes more prominent as the exposure wavelength becomes shorter.

  Due to the occurrence of such damage, there may be a problem that the resolution performance of the exposure apparatus is slightly lowered, and the glass material must be replaced frequently, so that the throughput is deteriorated.

  Accordingly, an exemplary object of the present invention is to provide an immersion exposure apparatus capable of maintaining stable performance for a longer period of time.

  In order to achieve the above object, an immersion exposure apparatus according to one aspect of the present invention includes a projection optical system that projects a reticle pattern onto a substrate, and a liquid that is applied to at least a portion between the projection optical system and the substrate. An immersion exposure apparatus comprising a supply unit for supplying a supply unit, wherein the apparatus includes a device for introducing a reducing agent into the liquid.

  A device manufacturing method according to one aspect of the present invention includes a step of exposing a substrate using the immersion exposure apparatus, and a step of developing the exposed substrate.

  Furthermore, an exposure system according to an aspect of the present invention includes a projection optical system that projects a reticle pattern onto a substrate, and a liquid supply unit that supplies liquid to at least a part between the projection optical system and the substrate. An immersion exposure apparatus and an apparatus for introducing the reducing agent into the liquid are provided.

  Furthermore, an exposure method according to one aspect of the present invention is an exposure method in which the substrate is exposed via a projection optical system that projects a reticle pattern onto the substrate and a liquid filled in at least a portion between the substrates. It has a step of introducing a reducing agent into the liquid.

  Further objects and other features of the present invention will be made clear by the preferred embodiments described below with reference to the accompanying drawings.

  It is possible to provide an immersion exposure apparatus that can maintain stable performance for a long period of time compared to the prior art.

In the immersion exposure apparatus, a liquid having a refractive index higher than that of air is used as a liquid (immersion liquid) filled between the optical element (final lens) on the most substrate side of the projection optical system and the substrate. However, when water or an aqueous solution is used as the immersion liquid, O (oxygen element) is contained as O in H ₂ O, and even when an organic liquid is used, O is contained in the structure. There are many that have been done. Further, even if the immersion liquid itself does not have O, oxygen in the atmosphere may be mixed into the immersion liquid and contain oxygen.

  Accordingly, when a liquid containing oxygen (including a liquid containing O) is used as the immersion liquid, the liquid containing oxygen and the exposure light are simultaneously placed between the final lens and the wafer during wafer exposure. Will exist.

  As a result of further diligent examination by the inventor, the damage of the final lens, the member around the final lens, the wafer or the member around the wafer generated in the above-described immersion exposure apparatus is “between the final lens and the wafer. It has been found that this is caused by the fact that a liquid containing oxygen and exposure light exist simultaneously.

  In the case where a liquid containing oxygen and light are present at the same time, the liquid and oxygen in the liquid are excited by light, and excited species having a very strong oxidizing power are generated. Due to the oxidizing power of the excited species, each member is denatured, and its performance cannot be maintained, or particles are generated.

For example, hydroxyl ion H ₃ O ₂ ^— is one of ions having strong oxidizing power generated by exposure to water, but reacts with organic substances, metals, and the like to cause damage. Therefore, the lens and the member around the lens, or the wafer and the member around the wafer are greatly damaged.

  Furthermore, the liquid in which the excited species having a strong oxidizing power is present flows downstream of the exposure area (a position adjacent to the exposure area), thereby damaging a member that is not directly exposed to light for exposing the wafer. Also turned out.

Therefore, in this embodiment, by introducing a reducing agent such as hydrogen, carbon monoxide, methane, or a mixture of these substances into the immersion liquid, the following reaction formulas (1) to (3) are expressed. Thus, the hydroxyl ion H ₃ O ₂ ^— was reduced to reduce the oxidizing power.

2H ₃ O ₂ ⁻ + H ₂ → 4H ₂ O + 2e ⁻ (1)
^{_{H 3 O 2 - + CO →}} H 2 O + CO 2 + e - ··· (2)
8H ₃ O ₂ ⁻ + CH ₄ → 14H ₂ O + CO ₂ + 8e ⁻ (3)
A reducing agent is a substance that easily gives electrons, and is an element having a valence lower than the normal valence, such as hydrogen compounds such as hydrogen, hydrogen sulfide, and hydrogen iodide, carbon monoxide, sulfurous acid, and nitrous acid. Oxides, hydrocarbon compounds such as methane and ethane, organic substances such as oxalic acid and glucose, or mixtures of the above substances, but are not limited to these as long as they do not adversely affect the exposure. .

  As described above, by reducing ions having strong oxidizing power and other excited species in the immersion liquid, the immersion lens can be applied to the final lens and the members around the final lens or the wafer and the members around the wafer. The performance of these members can be maintained stably for a long time without giving damage. Therefore, it is possible to provide an immersion exposure apparatus that is stable for a long time and can maintain high resolution.

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

  1 and 2 are diagrams for explaining an immersion exposure apparatus according to the first embodiment.

  In FIG. 1, reference numeral 1 denotes a substrate such as a wafer or a glass plate, and 2 denotes a substrate chuck for holding the substrate 1. Reference numeral 3 denotes a substrate stage, which has a substrate 1 having axes parallel to the X, Y, and Z directions and six driving shafts around each axis. Reference numeral 4 denotes a stage surface plate, and the substrate stage 3 is driven by air levitation or magnetic levitation on the stage surface plate 4. A projection optical system 5 projects a transfer pattern drawn on the reticle (mask) 6 onto the substrate 1. Note that a reticle 6 is provided above the projection optical system 5, and the reticle 6 is mounted on a reticle stage (not shown) and is driven to scan the exposure light in synchronization with the substrate stage 3. In addition, an illumination optical system 7 is further arranged on the upper part, and illuminates the reticle 6 with exposure light from a light source (not shown). Reference numeral 9 denotes an immersion liquid, which is filled in at least a part between the substrate 1 and the optical element (final lens) closest to the substrate 1 of the projection optical system 5 in the immersion exposure apparatus. When the exposure light is a KrF or ArF excimer laser, a liquid having a refractive index larger than that of air, mainly water, is used as the liquid 9. A liquid nozzle 13 serves as a supply unit and a recovery unit for the liquid 9, and supplies the liquid 9 to at least a part between the substrate 1 and the final lens of the projection optical system 5, and collects the liquid 9. is there. 10 is a pure water production apparatus, and 11 is a deaeration apparatus. Reference numeral 12 denotes a reducing agent introduction device. Water produced by the pure water production device 10 is degassed by the degassing device 11, and the reducing agent is introduced by the reducing agent introduction device 12 and connected to the supply system of the liquid nozzle 13. ing. The installation locations of the pure water production apparatus 10, the deaeration apparatus 11, and the reducing agent introduction apparatus 12 may be inside or outside the exposure apparatus, respectively.

  In this example, hydrogen as a reducing agent was introduced into water as an immersion liquid through a gas introducing membrane module (not shown) connected to a hydrogen gas cylinder in the reducing agent introduction device 12. Note that hydrogen may be supplied by a hydrogen gas cylinder as in this embodiment, or may be supplied by electrolyzing water. Furthermore, water having a higher hydrogen content that has been produced by electrolysis may be used as it is as an immersion liquid. In the reducing agent introduction device 12, various methods such as use of a membrane module, dropping, and stirring are taken depending on whether the reducing agent is gas, liquid, or solid, but the reducing agent is introduced into the immersion liquid. Any method may be adopted as long as it exists.

  FIG. 2 is an enlarged view of the periphery of the liquid 9 in the immersion exposure apparatus of FIG.

  Reference numeral 16 denotes a final lens of the projection optical system 5. Reference numeral 17 denotes a lens holding member of the final lens. The lens holding member 17 is processed with high accuracy. Further, an adhesive or a sealing material 18 such as an O-ring may be used between the lens holding member 17 and the final lens 16.

  An immersion liquid holding plate 19 for holding the immersion liquid 9 having the same surface as the substrate 1 is provided on the outer periphery of the substrate 1. In order to detect the focal position of the projection optical system 5, a mark 20 and a sensor 22 for detecting the amount of light passing through the mark 20 are provided. Even in this case, an adhesive or a sealing material 18 such as an O-ring may be used.

  The sealing material 18 is more advantageous in terms of workability if an organic material such as an adhesive or an O-ring is used. However, as described above, when there is an excited species having strong oxidizing power generated by the interaction between the liquid 9 and the light 8, the sealing material 18 is denatured by oxidative decomposition or the like, and the physical property value such as Young's modulus is changed. Or cause particles. In this embodiment, when the immersion liquid is mixed with hydrogen as a reducing agent and introduced between the final lens 16 and the substrate 1, the redox potential is measured by an ORP meter (redox potential meter). It could be reduced to −100 mV (normal water redox potential is +250 mV). Since the oxidizing power was reduced, organic substances such as adhesives and O-rings could be used stably over a long period of time. Therefore, it was possible to provide a long-term stable immersion exposure apparatus manufactured with good workability.

  The immersion exposure apparatus of Example 2 will also be described with reference to FIGS.

Since the configuration of the immersion exposure apparatus in FIG. 1 is substantially the same as that of the first embodiment, the following description will mainly focus on the differences from the first embodiment. In addition, the same number is attached | subjected about the member similar to Example 1. FIG. In this example, water was used as the immersion liquid and methane was used as the reducing agent. Hydrocarbon compounds such as methane generate CO ₂ when acting as a reducing agent. Since the CO ₂ is soluble in water, the immersion liquid can be made conductive, and the static electricity generated on the substrate 1 can be suppressed as described in Japanese Patent Application No. 2003-422932. Therefore, it is possible to suppress the occurrence of device defects due to static electricity. Even when carbon monoxide is used as the reducing agent, CO ₂ can be generated in the same manner.

  In FIG. 2, the lens holding member 17 can be made of ceramics or the like, but if it can be made of metal, it is advantageous in terms of processing accuracy, and SUS or the like may be used. Also, the mark 20 is often formed by a metal pattern on a glass material such as quartz. Cr or the like is often used because it can be manufactured by the same processing as the reticle.

  However, when there is an excited species having a strong oxidizing power generated by the interaction between water and light, the metal that is the material of the holding member 17 is oxidized or denatured and dissolved in water as a contaminant (impurity). It was sticking out and causing particles. In addition, the metal of the alignment mark 20 is changed to an oxide, and the optical characteristics necessary for the mark cannot be maintained. In this embodiment, a hydrocarbon compound such as methane or carbon monoxide is mixed in the immersion water as a reducing agent to reduce the oxidizing power, and even a metal member can be used stably over a long period of time. Therefore, it is possible to provide a long-term stable immersion exposure apparatus manufactured with high processing accuracy.

Further, by simultaneously generating CO ₂ , the pure water can be made conductive, and the occurrence of device failure due to static electricity can be suppressed.

  The immersion exposure apparatus of Example 3 will be described with reference to FIG.

  The configuration of the immersion exposure apparatus is almost the same as that of the first embodiment, and the same members as those of the first embodiment are denoted by the same reference numerals.

  In this embodiment, the reducing agent introduction device 12 is linked to the control unit 15 of the immersion exposure apparatus, and introduces the reducing agent into the liquid 9 according to the exposure of the substrate 1. Here, the reducing agent is controlled to be introduced only into the immersion liquid 9 that is actually irradiated with the exposure light 8. That is, a reducing agent is introduced into the immersion liquid injected between the substrate 1 and the projection optical system 5 when each exposure area (shot) on the substrate 1 is scanned with the exposure light 8, so Is not introduced into the immersion liquid injected between the substrate 1 and the projection optical system 5 during the step movement. Thereby, the usage-amount of a reducing agent can be reduced and cost can be reduced.

  The immersion exposure apparatus of Example 4 will be described with reference to FIG.

  The configuration of the immersion exposure apparatus is almost the same as that of the first embodiment, and the same members as those of the first embodiment are denoted by the same reference numerals.

  In this embodiment, the measuring device 14 measures the oxidizing / reducing power of the immersion liquid collected by the liquid nozzle 13. As the measuring means, the oxidation-reduction potential may be measured, or any other device that can measure the oxidation / reduction power may be used. The measurement result of the measuring instrument 14 is sent to the control unit 15. The twelve reducing agent introduction devices are interlocked with the control unit 15 of the immersion exposure apparatus, and are controlled so that the amount of the reducing agent is adjusted in accordance with the measured value and introduced into the immersion liquid. Thereby, the usage-amount of a reducing agent can be made appropriate and cost can be reduced.

  Next, an embodiment of a method for manufacturing a semiconductor device (semiconductor element) using the above-described immersion exposure apparatus will be described.

  FIG. 5 is a flowchart for manufacturing a semiconductor device (a semiconductor chip such as an IC or LSI, or a liquid crystal panel or CCD). In this embodiment, in step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (reticle fabrication), a reticle (mask) on which the designed circuit pattern is formed is fabricated. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by the prepared semiconductor exposure apparatus.

  The next step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer manufactured in step 4, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including.

  In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 6 is a detailed flowchart of the wafer process in Step 4 above. First, in step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface.

  In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a resist is applied to the wafer.

  In step 16 (exposure), the circuit pattern of the reticle is printed on the wafer by exposure using the above-described immersion exposure apparatus. The wafer is loaded, the wafer is opposed to the reticle, and exposure is performed while supplying and recovering the immersion liquid into which the reducing agent is introduced. After the exposure is completed, the wafer is stepped to the next shot and the operation is repeated.

  In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

  If the manufacturing method of this embodiment is used, it is possible to cope with mass production of highly integrated semiconductor devices that have been difficult to manufacture.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

1 is a schematic diagram of an immersion exposure apparatus of Example 1. FIG. FIG. 2 is an enlarged view of a part of the immersion exposure apparatus of FIG. 1. 6 is a schematic view of an immersion exposure apparatus according to Embodiment 3. FIG. 6 is a schematic view of an immersion exposure apparatus according to Embodiment 4. FIG. FIG. 10 is a diagram illustrating a flow of a device manufacturing method of Example 5. FIG. 10 is a diagram illustrating a detailed flow of a wafer process in the device manufacturing flow of Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate chuck 3 Substrate stage 4 Stage surface plate 5 Projection optical system 6 Reticle 7 Illumination optical system 8 Exposure light 9 Liquid 10 Pure water production apparatus 11 Deaeration apparatus 12 Reducing agent introduction apparatus 13 Liquid nozzle (supply part, recovery part) )
DESCRIPTION OF SYMBOLS 14 Measuring instrument 15 Control part 16 Final lens 17 Lens holding member 18 Seal material 19 Immersion liquid holding plate 20 Mark 22 Sensor (CCD etc.)

Claims (9)

In an immersion exposure apparatus comprising: a projection optical system that projects a reticle pattern onto a substrate; and a supply unit that supplies liquid to at least a portion between the projection optical system and the substrate.
An immersion exposure apparatus comprising an apparatus for introducing a reducing agent into the liquid.   The measuring device for measuring the oxidizing / reducing power of the liquid, and a control unit for determining the amount of reducing agent to be introduced into the liquid based on the measurement result of the measuring device. Immersion exposure equipment.   The exposure apparatus according to claim 1, further comprising a control unit for introducing the reducing agent into the liquid according to exposure of the substrate.   2. The immersion exposure apparatus according to claim 1, wherein the reducing agent is a hydrogen compound, an oxide of an element having a valence lower than a normal valence, a hydrocarbon compound, an organic substance, or a mixture thereof.   The immersion exposure apparatus according to claim 1, wherein the liquid is hydrogen water until at least the liquid is supplied between the projection optical system and the substrate.   2. The immersion exposure apparatus according to claim 1, wherein the oxidation-reduction potential of the liquid is lower than the standard oxidation-reduction potential of water until it is supplied at least between the projection optical system and the substrate. Exposing a substrate using the immersion exposure apparatus according to any one of claims 1 to 6;
And developing the exposed substrate. A device manufacturing method comprising: An immersion exposure apparatus comprising: a projection optical system that projects a pattern of a reticle onto a substrate; and a supply unit that supplies liquid to at least a part between the projection optical system and the substrate;
An exposure system comprising: an apparatus for introducing the reducing agent into the liquid. In an exposure method for exposing a substrate through a projection optical system that projects a pattern of a reticle onto the substrate and a liquid filled in at least a portion between the substrate,
An exposure method comprising a step of introducing a reducing agent into the liquid.

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