JP2009009954A - Aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner and an exposure method capable of effecting exposure of a substrate with desired performance even if a liquid immersion method for exposing the substrate via liquid is applied. <P>SOLUTION: The aligner exposes the substrate to light by irradiating the substrate with exposure beams via liquid, and has an impurity removal mechanism for removing impurities contained in the liquid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an exposure method in a lithography process for manufacturing a device such as a semiconductor element, an imaging element (CCD, etc.), a liquid crystal display element, or a thin film magnetic head.

  When manufacturing a semiconductor element or the like, an image of a reticle pattern as a mask is transferred to each shot area on a wafer (or glass plate or the like) coated with a resist as a photosensitive substrate via a projection optical system. A projection exposure apparatus is used. Conventionally, a step-and-repeat reduction projection type exposure apparatus (stepper) has been widely used as a projection exposure apparatus, but recently, a step-and-scan system that performs exposure by synchronously scanning a reticle and a wafer. The projection exposure apparatus is also attracting attention.

  The resolution of the projection optical system provided in the projection exposure apparatus becomes higher as the exposure wavelength used becomes shorter and the numerical aperture of the projection optical system becomes larger. For this reason, with the miniaturization of integrated circuits, the exposure wavelength used in the projection exposure apparatus has become shorter year by year, and the numerical aperture of the projection optical system has also increased. The mainstream exposure wavelength is 248 nm for a KrF excimer laser, but 193 nm for a shorter wavelength ArF excimer laser is also in practical use.

Also, when performing exposure, the depth of focus (DOF) is important as well as the resolution. The resolution R and the depth of focus δ are each expressed by the following equations.
_{R = k 1 · λ / NA} (1)
δ = k ₂ · λ / NA ² (2)
Here, λ is the exposure wavelength, NA is the numerical aperture of the projection optical system, and k ₁ and k ₂ are process coefficients. From the equations (1) and (2), it can be seen that the depth of focus δ becomes narrower when the exposure wavelength λ is shortened and the numerical aperture NA is increased in order to increase the resolution R.

Therefore, a projection exposure apparatus using an immersion method that substantially shortens the exposure wavelength and increases the depth of focus has been proposed (see, for example, Patent Document 1). This is because the space between the lower surface of the projection optical system and the wafer surface is filled with water or a liquid such as an organic solvent, and the wavelength of exposure light in the liquid is 1 / n times that in air (n is the refractive index of the liquid). This is a projection exposure apparatus that improves the resolution by utilizing the fact that it is usually about 1.2 to 1.6, and expands the depth of focus by about n times.
JP-A-10-303114

Here, in the immersion type exposure apparatus, there is a problem that if the liquid transmittance is reduced, the exposure apparatus does not exhibit desired performance.
An object of the present invention is to provide an exposure apparatus and an exposure method capable of exposing a substrate with a desired performance even when an immersion method for exposing the substrate through a liquid is applied.

  The exposure apparatus according to claim 1 is an exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through a liquid, and has an impurity removal mechanism that removes impurities contained in the liquid. It is provided.

According to the projection exposure apparatus of the first aspect, since impurities contained in the liquid can be removed, desired exposure can be performed.
The exposure apparatus according to claim 2 is characterized in that the liquid is decahydronaphthalene (C ₁₀ H ₈ ).

The exposure apparatus according to claim 3 is characterized in that the impurity is oxygen.
An exposure apparatus according to claim 4 is characterized in that the impurity removal mechanism is an oxygen removal filter.
The exposure method according to claim 5 is an exposure method for exposing the substrate by irradiating the substrate with an exposure beam through a liquid, the impurities contained in the liquid being removed, and the impurities The substrate is exposed by irradiating the substrate with the exposure beam through the liquid from which the substrate is removed.

The exposure method according to claim 6 is characterized in that the liquid is decahydronaphthalene (C ₁₀ H ₈ ).
The exposure method according to claim 7 is characterized in that the impurity is oxygen.

  The exposure apparatus according to claim 8 is an exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through a liquid, a chamber that substantially seals the substrate, and a rare atmosphere in the chamber. A rare gas inlet for introducing gas and a rare gas outlet for discharging the rare gas in the chamber are provided.

  According to the projection exposure apparatus of the eighth aspect, since the liquid can be used in an environment where the oxygen concentration is extremely low, it is possible to suppress a decrease in the transmittance of the liquid and perform desired exposure.

The exposure apparatus according to claim 9 is characterized in that the rare gas is nitrogen gas, helium gas, argon gas, or a mixed gas thereof.
The exposure method according to claim 10, wherein the substrate is exposed by irradiating the substrate with an exposure beam through a liquid, the substrate being carried into a substantially sealed chamber, and A rare gas is introduced into the chamber, and the rare gas in the chamber is discharged.

An exposure method according to an eleventh aspect is characterized in that the rare gas is nitrogen gas, helium gas, argon gas, or a mixed gas thereof.
13. The exposure apparatus according to claim 12, further comprising a transmittance suppressing mechanism that suppresses a decrease in the transmittance of the liquid with respect to the exposure beam in the exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through the liquid. It is characterized by that.

The exposure apparatus according to claim 13 is characterized in that the liquid is decahydronaphthalene (C ₁₀ H ₈ ).
15. The exposure apparatus according to claim 14, further comprising a liquid supply mechanism that supplies the liquid, wherein the transmittance suppression mechanism includes an oxygen device that removes oxygen in the liquid supplied from the liquid supply mechanism. To do.

  16. The exposure apparatus according to claim 15, wherein the transmittance suppressing mechanism includes a gas supply mechanism that supplies a predetermined gas around the liquid on the substrate so that the liquid on the substrate does not come into contact with oxygen. And

  According to the exposure apparatus and the exposure method of the present invention, the substrate can be exposed in an optimum state even when the liquid immersion method is applied.

  A projection exposure apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a step-and-repeat projection exposure apparatus according to the first embodiment. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward.

  As shown in FIG. 1, the projection exposure apparatus according to this embodiment includes an ArF excimer laser light source as an exposure light source, and includes an illumination optical system 1 including an optical integrator (homogenizer), a field stop, a condenser lens, and the like. It has. Exposure light (exposure beam) IL made up of ultraviolet pulsed light having a wavelength of 193 nm emitted from a light source passes through the illumination optical system 1 and illuminates a pattern provided on a reticle (mask) R. The light that has passed through the reticle R passes through the telecentric projection optical system PL on both sides (or one side on the wafer W side) and is projected to a predetermined projection magnification β (for example, on an exposure region on the wafer (substrate) W coated with photoresist. , Β is 1/4, 1/5, etc.) and reduced projection exposure is performed.

As the exposure light IL, KrF excimer laser light (wavelength 248 nm), F ₂ laser light (wavelength 157 nm), i-line (wavelength 365 nm) of a mercury lamp, or the like may be used.
The reticle R is held on a reticle stage RST, and a mechanism for finely moving the reticle R in the X direction, the Y direction, and the rotation direction is incorporated in the reticle stage RST. The positions of the reticle stage RST in the X direction, the Y direction, and the rotational direction are measured and controlled in real time by a reticle laser interferometer (not shown).

  The wafer W is fixed on the Z stage 9 via a wafer holder (not shown). The Z stage 9 is fixed on an XY stage 10 that moves along an XY plane substantially parallel to the image plane of the projection optical system PL, and the focus position (position in the Z direction) and tilt angle of the wafer W are set. Control. The positions of the Z stage 9 in the X direction, the Y direction, and the rotation direction are measured and controlled in real time by a wafer laser interferometer 13 using a moving mirror 12 positioned on the Z stage 9. The XY stage 10 is placed on the base 11 and controls the X direction, Y direction, and rotation direction of the wafer W.

  The main control system 14 provided in the projection exposure apparatus adjusts the position of the reticle R in the X direction, the Y direction, and the rotational direction based on the measurement values measured by the reticle laser interferometer. That is, the main control system 14 adjusts the position of the reticle R by transmitting a control signal to a mechanism incorporated in the reticle stage RST and finely moving the reticle stage RST.

  Also, the main control system 14 adjusts the focus position (position in the Z direction) and the tilt angle of the wafer W in order to adjust the surface on the wafer W to the image plane of the projection optical system PL by the auto focus method and the auto leveling method. To do. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the Z stage 9 by the wafer stage drive system 15 to adjust the focus position and the tilt angle of the wafer W. Further, the main control system 14 adjusts the position of the wafer W in the X direction, the Y direction, and the rotation direction based on the measurement values measured by the wafer laser interferometer 13. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to adjust the position of the wafer W in the X direction, Y direction, and rotation direction. .

  At the time of exposure, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to sequentially step each shot area on the wafer W to the exposure position. . That is, the operation of exposing the pattern image of the reticle R onto the wafer W by the step-and-repeat method is repeated.

  In this projection exposure apparatus, an immersion method is applied to substantially shorten the exposure wavelength and improve the resolution. Here, in the immersion type projection exposure apparatus to which the immersion method is applied, at least while the pattern image of the reticle R is transferred onto the wafer W, the surface of the wafer W and the side of the projection optical system PL on the wafer W side. A predetermined liquid 7 is filled in between the transmissive optical element 4. The projection optical system PL includes a lens barrel 3 that houses a plurality of optical elements formed of synthetic quartz glass or the like that constitutes the projection optical system PL. In this projection optical system PL, the transmissive optical element 4 closest to the wafer W is formed of synthetic quartz glass, and only the surface of the transmissive optical element 4 is in contact with the liquid 7. As a result, corrosion of the lens barrel 3 made of metal is prevented.

As the liquid 7, decahydronaphthalene (C ₁₀ H ₁₈ ) (hereinafter referred to as decalin) which is a high refractive index liquid is used.
The projection exposure apparatus according to this embodiment includes a liquid supply device 5 that controls the supply of decalin 7 and a liquid recovery device 6 that controls the discharge of decalin 7.

  The liquid supply device 5 includes a decalin 7 tank (not shown), a pressure pump (not shown), a temperature control device (not shown), an oxygen removal filter 55, and the like. In addition, a discharge nozzle 21 a having a thin tip on the wafer W side is connected to the liquid supply device 5 via a supply pipe 21. The liquid supply device 5 adjusts the temperature of the decalin 7 by the temperature control device, and supplies the decalin 7 whose temperature is adjusted from the discharge nozzle 21 a via the supply pipe 21 onto the wafer W. Note that the temperature of the decalin 7 is set by the temperature control device, for example, to the same level as the temperature in the chamber in which the projection exposure apparatus according to this embodiment is accommodated.

  The liquid recovery device 6 includes a decalin 7 tank (not shown), a suction pump (not shown), and the like. In addition, an inflow nozzle 23 a having a wide tip is connected to the liquid recovery apparatus 6 via a recovery pipe 23.

The liquid recovery apparatus 6 recovers the decalin 7 from the wafer W through the recovery tube 23 from the inflow nozzle 23a.
In the projection exposure apparatus according to the first embodiment, since the oxygen removing filter 55 for removing oxygen contained in the decalin 7 is provided in the liquid supply apparatus 5, the transmittance of the decalin 7 is reduced due to oxygen absorption. Can be prevented.

In the present embodiment, the oxygen removal filter is provided in the liquid supply device 5, but it goes without saying that it may be provided in the supply pipe 21.

Next, a projection exposure apparatus according to a second embodiment will be described with reference to the drawings. FIG. 2 is a front view showing the lower part of the projection optical system PLA of the step-and-scan projection exposure apparatus according to the second embodiment, the liquid supply device 5, the liquid recovery device 6, and the like.

In the wafer chamber 101, the wafer, the Z stage 9, the XY stage 10, the wafer W, the supply pipe 21, or the recovery pipe 23 are arranged to be effectively sealed.
A rare gas inlet 102 for introducing nitrogen gas into the wafer chamber 101 and a rare gas outlet 103 for discharging nitrogen gas are provided. The rare gas inlet 102 is connected to a nitrogen tank (not shown), and the rare gas outlet is exhausted through a filter (not shown).

  According to the projection exposure apparatus according to the second embodiment, the decalin 7 is filled between the wafer W and the projection optical system PL in a nitrogen atmosphere, so that a decrease in transmittance due to oxygen absorption of decalin is prevented. be able to.

  In the second embodiment described above, the wafer chamber 101 is provided so that the decalin 7 fills the space between the wafer 7 and the projection optical system PL in a nitrogen atmosphere. For example, Japanese Patent Application Laid-Open No. 2004-289126. As disclosed in the publication, nitrogen may be used as a gas used in a gas seal mechanism for containing the liquid (decalin) 7 in a predetermined region.

In this embodiment mode, nitrogen is used as a rare gas, but it goes without saying that helium gas, argon gas, or a mixed gas thereof may be used.
In the first and second embodiments, with decahydronaphthalene (C ₁₀ H ₁₈₎ as the high refractive index liquid, cis-decahydronaphthalene (C ₁₀ H _18), trans- decahydronaphthalene ( Needless to say, C ₁₀ H ₁₈ ) and mixtures thereof may be used.

It is a figure which shows schematic structure of the projection exposure apparatus used in the 1st Embodiment of this invention. It is a figure which shows schematic structure of the projection exposure apparatus used in the 2nd Embodiment of this invention.

Explanation of symbols

R ... reticle PL ... projection optical system W ... wafer 1 ... illumination optical system 5 ... liquid supply device 6 ... liquid recovery device 7 ... liquid (decalin)
DESCRIPTION OF SYMBOLS 9 ... Z stage 10 ... XY stage 14 ... Main control system 21 ... Supply pipe 21a ... Discharge nozzle 23 ... Recovery pipe 23a ... Inflow nozzle 55 ... Oxygen removal filter 101 ... Wafer chamber 102 ... Noble gas inlet 103 ... Noble gas outlet

Claims (15)

An exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through a liquid,
An exposure apparatus comprising an impurity removal mechanism for removing impurities contained in the liquid. The exposure apparatus according to claim 1, wherein the liquid is decahydronaphthalene (C ₁₀ H ₈ ).   The exposure apparatus according to claim 1, wherein the impurity is oxygen.   The exposure apparatus according to claim 1, wherein the impurity removal mechanism is an oxygen removal filter. An exposure method for exposing the substrate by irradiating the substrate with an exposure beam through a liquid,
Removing impurities contained in the liquid;
An exposure method in which the substrate is exposed by irradiating the substrate with the exposure beam through the liquid from which the impurities have been removed. The exposure method according to claim 5, wherein the liquid is decahydronaphthalene (C ₁₀ H ₈ ).   The exposure method according to claim 5, wherein the impurity is oxygen. An exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through a liquid,
A chamber that substantially seals the substrate;
A rare gas inlet for introducing a rare gas into the chamber;
An exposure apparatus comprising: a rare gas discharge port for discharging a rare gas in the chamber.   9. The exposure apparatus according to claim 8, wherein the rare gas is nitrogen gas, helium gas, argon gas, or a mixed gas thereof. An exposure method for exposing the substrate by irradiating the substrate with an exposure beam through a liquid,
Carrying the substrate into a substantially sealed chamber;
Introducing a rare gas into the chamber;
An exposure method comprising discharging a rare gas in the chamber.   The exposure method according to claim 10, wherein the rare gas is nitrogen gas, helium gas, argon gas, or a mixed gas thereof. In an exposure apparatus that exposes the substrate by irradiating the substrate with an exposure beam through a liquid,
An exposure apparatus provided with a transmittance suppressing mechanism that suppresses a decrease in the transmittance of the liquid with respect to the exposure beam. The exposure apparatus according to claim 12, wherein the liquid contains decahydronaphthalene (C ₁₀ H ₈ ). A liquid supply mechanism for supplying the liquid;
The exposure apparatus according to claim 13, wherein the transmittance suppression mechanism includes an oxygen device that removes oxygen in the liquid supplied from the liquid supply mechanism.   15. The exposure apparatus according to claim 13, wherein the transmittance suppressing mechanism includes a gas supply mechanism that supplies a predetermined gas around the liquid on the substrate so that the liquid on the substrate does not come into contact with oxygen.