JP2007294691A - Liquid immersion aligner, and method of manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid immersion aligner which suppresses the reduction of the contact angle of an auxiliary member, does not make a drop remain on the auxiliary member after exposure, and also can reduce wafer electrification; and to provide a method of manufacturing a device. <P>SOLUTION: The liquid immersion aligner comprises: a projection optical system 3 for carrying out exposure transfer of the pattern on a reticle 2 on a wafer 5, and a liquid feeder for supplying liquid immersion liquid to both a lens surface (the last surface) which approaches the wafer 5 of the projection optical system 3 most closely and a gap of the wafer 5. The liquid immersion aligner which carries out exposure by holding liquid immersion liquid in at least one part of the gap comprises also an auxiliary member provided around a wafer chuck 20 for holding the wafer 5. The auxiliary member holds the liquid immersion liquid together with the wafer chuck 20, and its material should be composed of graphite in surface material quality at least. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure apparatus mainly used for exposure of a semiconductor integrated circuit or the like, and in particular, an immersion liquid that exposes a pattern on a wafer by filling at least a part between the projection optical system and the wafer with the immersion liquid. The present invention relates to an exposure apparatus and a device manufacturing method.

With the progress of miniaturization of semiconductor element circuit patterns, techniques such as phase shift masks and modified illumination have been put into practical use in addition to shortening the exposure wavelength used to improve the miniaturization performance of exposure apparatuses.
However, in the conventional design, since a gas layer having a refractive index of about 1 is interposed between the projection optical system and the substrate, it is impossible in principle to make NA (numerical aperture) 1 or more. It was.

On the other hand, as one of the techniques for improving the resolving power of an optical microscope, there is an immersion method in which a high refractive index liquid having a higher refractive index than gas (generally air) is filled between an objective lens and an observation sample.
As an application of this principle to an exposure apparatus for manufacturing semiconductor elements, projection exposure is performed while filling a space, which has been filled with gas, between the final surface of the projection optical system and the substrate, with an immersion liquid. There is a so-called immersion exposure method.

The advantage of the immersion method is that the equivalent exposure wavelength is 1 / n of the wavelength of the light source, where n is the refractive index of the liquid used.
This means that the resolution can be improved to 1 / n of the conventional method even if a light source of the same wavelength is used, assuming that the maximum incident angle of the light beam imaged on the wafer is the same between the immersion method and the conventional method. Means.
For example, when the wavelength of the light source is 193 nm and the immersion liquid is water, the refractive index of water is about 1.44. Therefore, by using the immersion method using the water immersion liquid, the resolution is higher than that of the conventional method. Can be reduced to 1 / 1.44.

In a projection exposure apparatus using an immersion method, the following two methods are roughly devised as a method for filling the space between the final surface of the projection optical system and the substrate with an immersion liquid.
One is a method of immersing the entire substrate in the liquid tank together with the final surface of the projection optical system.
However, the method of immersing the entire substrate in the liquid tank together with the final surface of the projection optical system has a disadvantage that the container for holding the immersion liquid is large, the drive mechanism is large to drive the stage at high speed, and the apparatus is large. There is.
Further, since the wafer is completely immersed in the immersion liquid, the wafer must be moved in the exposure apparatus with the immersion liquid attached to the back surface of the wafer, and the immersion liquid is scattered in the exposure apparatus. There are drawbacks.
The scattering of the immersion liquid causes a problem of causing rust and the like on the metal components in the exposure apparatus.
In order to solve the problem of causing rust and the like, there is a problem that the exposure apparatus is not practical because it increases the apparatus cost.

Another method for filling the space between the final surface of the projection optical system and the substrate with the immersion liquid is to supply the immersion liquid only to the gap between the projection optical system and the substrate to form a liquid film. There is a local fill method.
FIG. 6 schematically shows the positional relationship between the projection optical system 103 and the wafer 105 when exposing a shot ES (edge shot) at the periphery of the wafer.
In the local fill method, it is necessary to hold the liquid film 104 in the gap between the projection optical system 103 and the wafer 105 on the wafer chuck 120.
The liquid film 104 is configured to flow by supplying the immersion liquid to the gap from the liquid supply apparatus 110 and continuing the recovery of the immersion liquid by the liquid recovery apparatus 111.
However, it is obvious that if there is nothing around the wafer 105, the liquid film 104 cannot be held in the gap and flows out without being recovered. Of course, the shot ES cannot be immersed.

  In the conventional technique (for example, see Patent Documents 1 and 2), as shown in FIGS. 7a and 7b, an annular member (so-called auxiliary member) 100 is provided around the wafer 105, and the annular member (so-called auxiliary member) is provided. A means is disclosed in which the upper surface of 100 and the surface of the wafer 205 are substantially flush with each other.

When attention is paid to the local fill method of the above-described immersion type exposure apparatus, the above-described conventional technique has the following problems.
That is, according to our previous studies, it has been found that the use of the annular member (so-called auxiliary member) 100 causes the following adverse effects.
That is, when exposure light having high energy such as KrF or ArF laser and immersion liquid (pure water here) simultaneously act on the surface of the annular member (so-called auxiliary member) 100 or the like, the surface state of SiC or the like changes.
As a result, there arises a serious problem that the contact angle, which is one of the important functions of the annular member (so-called auxiliary member) 100, is lowered.

In general, the contact angle of the immersion liquid is greatly reduced in ceramics that can be used for the annular member (so-called auxiliary member) 100. For example, in SiC, the contact angle decreases from an initial value of about 50 ° to about 10 ° after irradiation.
If the contact angle of the immersion liquid with respect to the annular member (so-called auxiliary member) 100 is extremely small, the immersion liquid remains as droplets on the annular member 100 when the liquid film moves on the annular member 100. There is a case.
If the liquid droplets remain on the annular member (so-called auxiliary member) 100, there is a problem that the portion causes contamination and causes wafer contamination.
In addition, there is a problem that the remaining droplets move on the wafer and cause pattern defects when the stage moves.
In addition, the remaining droplets are scattered when the stage is moved, causing problems such as contamination or corrosion of surrounding components and short-circuiting of electric circuits.

On the other hand, the immersion exposure apparatus has a problem in that static electricity is generated due to friction because the wafer moves while the wafer and the immersion liquid are in contact with each other during the immersion exposure, and the wafer surface is charged.
For example, a wafer coated with pure water and a resist (photosensitive resin) has been confirmed to have a charge of +100 V to +200 V as the wafer surface potential.
When such a state occurs, there is a concern that a semiconductor element formed in the wafer is destroyed due to discharge due to charging.
That is, when the immersion liquid contacts the annular member (that is, the auxiliary member) 100 and exposure light irradiation occurs at the same time, the contact angle between the annular member 100 and the immersion liquid decreases, and the immersion liquid droplets remain. There was a need to improve the points.
JP 2004-207696 A JP 2004-207710 A

  The present invention has been made in view of the above-mentioned problems, and in an immersion exposure apparatus using a local fill immersion exposure method, an immersion exposure apparatus that can reduce the remaining of droplets on an auxiliary member. For the purpose of provision.

  In order to solve the above problems, an immersion exposure apparatus according to one aspect of the present invention includes a projection optical system that exposes and transfers a pattern on a reticle onto a wafer, and a lens surface that is closest to the wafer of the projection optical system. A liquid supply device for supplying an immersion liquid to a gap between the wafer and a liquid exposure apparatus for performing exposure while holding the liquid in at least a part of the gap, around the wafer chuck holding the wafer A material of at least the surface of the auxiliary member that is provided and holds the immersion liquid together with the wafer chuck is made of graphite.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

According to the immersion exposure apparatus of the present invention, since the material of at least the surface of the auxiliary member that holds the immersion liquid together with the wafer chuck is made of graphite, the following effects can be obtained.
That is, since the surface of the auxiliary member is made of a graphite material, even if the auxiliary member is exposed to the exposure light, the immersion liquid irradiated with the exposure light, or the immersion liquid, the decrease in the contact angle of the liquid droplet of the auxiliary member can be suppressed. In addition, no remaining droplets are generated on the auxiliary member, and the stability of immersion exposure can be improved.
In particular, the graphite material constituting the surface of the auxiliary member contacts at least a part of the wafer mounted on the wafer chuck, thereby reducing the wafer charging during immersion exposure and preventing the adverse effect of charging. can do.
On the other hand, according to the device manufacturing method of the present invention, since the auxiliary member having the above-described configuration is used, liquid droplet exposure is stable without generating residual droplets on the auxiliary member, and wafer charging during liquid immersion exposure is reduced. In addition, there is an advantage of improving the quality reliability of the manufacturing device.

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

FIG. 1 is a schematic diagram schematically illustrating a configuration of an immersion exposure apparatus according to the first embodiment.
In the immersion exposure apparatus of this example, as an example of exposure light and immersion liquid, ArF laser light is used as exposure light and water (pure water) is used as immersion liquid.
The immersion exposure apparatus of this example is not limited to ArF laser light and water, but can be similarly applied to an immersion exposure apparatus using light of other wavelengths and an immersion liquid usable at that wavelength.
Further, the immersion liquid may be a liquid containing water with a small amount of additive or a hydrocarbon-based organic liquid.

The illumination system 1 includes, for example, a laser output device (not shown) that outputs an ArF excimer laser (wavelength 193 nm), a known optical system (not shown), and the like.
The illumination system 1 illuminates a reticle (mask) 2 on which a device pattern (for example, a circuit pattern) is formed with laser light from a laser output device.

  The projection optical system 3 is a refraction type or a catadioptric system, and projects the circuit pattern of the reticle 2 illuminated by the illumination system 1 onto a wafer 5 (substrate) as a second object.

The distance measuring laser interferometer 15 measures the two-dimensional position of the reticle stage 12 and the wafer stage 13 in the horizontal plane via the reference mirror 14.
Based on this measurement value, the stage control device 17 performs positioning and synchronous control of the reticle 2 and the wafer 5.

The wafer stage 13 includes a wafer chuck 22 for fixing the wafer 5 and has a function of adjusting the vertical position, rotation angle, and tilt of the wafer 5.
The wafer stage 13 matches the surface of the wafer 5 with the image plane of the projection optical system 3 during exposure.
Further, the wafer stage 13 is provided with an auxiliary member (so-called same surface plate) 21 surrounding the chuck 20 around a main portion (or bottom surface and side surface) of the surface of the wafer 5 fixed on the wafer chuck 20 in immersion exposure. Have.

The height of the auxiliary member 21 and the height of the surface of the wafer 5 are substantially flush with each other.
In this example, even if the height of the auxiliary member 21 and the height of the wafer 5 are different from each other by, for example, several hundred μ, for example, about 100 μ (microns), they are defined as substantially the same surface.
Since the auxiliary member 21 forms substantially the same surface, the liquid film 4 is held so that the liquid film 4 does not flow down from the wafer 5 or the droplets scatter to the periphery when the edge shot ES is exposed. Is possible.

On the other hand, a layer (not shown) made of a graphite material is formed on at least the surface of the auxiliary member 21.
At least a part of the graphite material layer constituting the auxiliary member 21 is in contact with the back surface of the wafer 5 mounted on the wafer chuck 20.

The auxiliary member 21 has a layer of graphite material at least on the surface, so that a decrease in the contact angle of the immersion liquid on the surface of the auxiliary member 21 is suppressed, and there is no generation of residual droplets on the auxiliary member 21 and the stability is improved. A good liquid film 4 can be held.
That is, even if the surface of the auxiliary member 21 receives exposure light, or the auxiliary member 21 is exposed to the immersion liquid that has received exposure light or is simply exposed to the immersion liquid, the immersion liquid contacts the surface of the auxiliary member 21. Reduction in corners is suppressed.
As a result, it is possible to hold the stable liquid film 4 with no residual liquid droplets on the auxiliary member 21, and the conventional problems are solved.

Further, at least a part of a layer (not shown) made of the graphite material of the auxiliary member 21 comes into contact with the back surface of the wafer 5 mounted on the wafer chuck 20.
As a result, electrical continuity between the wafer 5 and the auxiliary member 21 is obtained, and charging of the wafer 5 due to static electricity generated by friction between the immersion liquid and the wafer 5 is reduced.
For this reason, it is possible to improve the stability of the performance of the exposure process without electrically destroying the semiconductor elements in the wafer 5 during the immersion exposure.

On the other hand, in the first embodiment, there is one gist in improving the resolution in exposure by shortening the equivalent exposure wavelength by using the liquid immersion method.
In the immersion exposure apparatus of this example, an immersion liquid supply port 10 and an immersion liquid recovery port 11 are arranged around the final surface of the projection optical system 3 to improve resolution, and the final surface of the projection optical system 3 ( The liquid film 4 is formed by supplying an immersion liquid of water to the gap between the lens surface) and the wafer 5.

It is desirable that the distance between the final surface (lens surface) of the projection optical system 3 and the wafer 5 be small enough to form and remove the liquid film 4 stably, for example, 1.0 mm.
The supply port 10 is connected to the pure water supply device 6 through the immersion liquid supply pipe 8, and the recovery port 11 is connected to the water recovery device 7 through the recovery pipe 9.

The pure water supply device 6 includes a deaeration device 18 and a temperature control device 19 as a part thereof.
The deaeration device 18 includes, for example, a known membrane module (not shown) and a vacuum pump (not shown).

The immersion control device 16 transmits and receives data to and from the stage control device 17 at the same time as sending control signals to the pure water supply device 6 and the water recovery device 7.
Thereby, the immersion control device 16 adjusts the pure water supply amount and the recovery amount according to the moving direction and speed of the wafer 5.

Here, it supplements about some outline | summarys of the function of the auxiliary member 21 shown in FIG.
That is, the auxiliary member 21 maintains the liquid film 4 when the edge shot ES shown in FIG. 1 is exposed, and achieves good immersion exposure performance.
Furthermore, as a necessary function, there is an action and an effect of eliminating the remaining of the droplet when the liquid film 4 moves on the surface of the auxiliary member 21 (the layer made of the graphite material).
Even after the edge shot (see FIG. 1) ES around the periphery of the wafer 5 is exposed, the generation of droplets remaining on the auxiliary member 21 can be prevented.

  In order to achieve this effect, there is provided an auxiliary member 21 having an exposure light, an immersion liquid irradiated with the exposure light, and a surface capable of maintaining the contact angle of the immersion liquid even when exposed to the immersion liquid. What should I do?

Further, the auxiliary member 21 is preferably a material that does not elute metal, graphite is suitable as a material having the above-mentioned conditions, and an example in which the entire auxiliary member 21 is made of a graphite material is also preferable.
According to our study, it was found that the initial value of the contact angle of the graphite immersion liquid (for example, water) is about 100 °, and the contact angle of about 70 ° is maintained after exposure light exposure.

According to the immersion exposure apparatus having the above-described configuration, it is possible to provide an immersion exposure apparatus that has no droplets remaining on the auxiliary member 21, is highly stable, and can form a highly accurate circuit pattern. .
In particular, since at least a part of the layer made of the graphite material of the auxiliary member 21 is in contact with the back surface of the wafer 5, electrical continuity between the wafer 5 and the auxiliary member 21 can be taken, and charging of the wafer 5 can be reduced. It was.
Therefore, during the immersion exposure, it is possible to improve the stability of the performance of the exposure process without electrically destroying the semiconductor elements in the wafer 5.

Next, a second embodiment of the present invention will be described. FIG. 2 is a schematic diagram schematically showing a configuration between the auxiliary member 21 and the wafer 5 for developing an antistatic function in the second embodiment of the present invention.
When the wafer 5 is mounted on the wafer chuck 20, a gap L exists between the wafer 5 and the auxiliary member 21 as shown in FIGS. 2 a and 2 b. The gap L is, for example, about 1 to 2 mm.

The auxiliary member 21 is made of graphite, and includes a conductive contact body (contact bar) 31 formed at a height and length so as to contact the lower surface of the wafer 5 mounted on the wafer chuck 20. ing.
Further, the auxiliary member 21 is configured to release the charging of the wafer 5 by grounding the contact body 31 (not shown).

More specifically, the contact body 31 is provided at a position slightly higher than the lower surface of the wafer 5 so that the contact with the wafer 5 is reliably performed when the wafer 5 is mounted on the wafer chuck 20.
Further, the contact body 31 is made of a flexible material and has a predetermined shape and thickness for effectively exhibiting the flexibility so that the wafer 5 does not cause an adsorption error to the wafer chuck 20. It is desirable.
Here, the number and shape of the contact bodies 31 are not limited to the illustrated configuration, and may be appropriately selected in order to obtain reliable contact between the wafer 5 and the auxiliary member 21.

By the way, since graphite has higher conductivity than metal (graphite: about 10,000 S / cm), the antistatic effect is large.
In the immersion exposure, the wafer 5 may move while being in contact with the immersion liquid during exposure, and charging may occur on the wafer 5 in some cases.
In particular, in the case of an immersion liquid having a low electrical conductivity and a high charging ability, such as a hydrocarbon-based organic liquid, the charged voltage of the wafer 5 is several hundred volts or more.
When such a state occurs, there is a possibility that the semiconductor element formed in the wafer 5 is destroyed due to discharge due to charging.
However, when the graphite material of the auxiliary member 21 and the wafer 5 come into contact with each other, the conductive member 21 is electrically connected. Therefore, the installation of the auxiliary member 21 can suppress the occurrence of charging of the wafer 5 and prevent the semiconductor element from being destroyed.

The main point of the second embodiment is that the auxiliary member 21 is provided with a conductive contact 31 for grounding the wafer 5 mounted on the wafer chuck 20.
For this reason, generation | occurrence | production of the charge of the wafer 5 can be suppressed and destruction of the semiconductor element on the wafer 5 can be prevented more effectively.

Next, a third embodiment of the present invention will be described. FIG. 3 is a schematic diagram schematically illustrating a configuration of a main part of the immersion exposure apparatus according to the third embodiment.
The auxiliary member 21 shown in the figure has a base 51 formed of ceramics such as SiC, SiO2, SiN, A12O3, etc., and a sheet-like graphite sheet 52 is formed on the base 51.

  The thickness of the graphite sheet 52 should just exhibit the water-repellent function, for example, about 100 nm is suitable.

The third embodiment is different from the first embodiment only in that the surface of the auxiliary member 21 has a structure of a graphite sheet 52 for expressing a water repellency function.
Other configurations are exactly the same as those of the first embodiment, and the operations and effects are also the same.

(Example of micro device manufacturing)
Next, an example of a device manufacturing method using the above-described immersion exposure apparatus will be described.
FIG. 4 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.).
First, in step 1 (circuit design), a device pattern is designed. In step 2 (mask fabrication / reticle fabrication), a reticle 2 having a designed device pattern is fabricated.

On the other hand, in step 3 (wafer manufacture), the wafer 5 is manufactured using a material such as silicon or glass.
Step 4 (wafer process) is called a pre-process, and an actual circuit pattern is formed on the wafer 5 by lithography using the prepared reticle 2 and wafer 5.
During the wafer process, at least the exposure position of the wafer 5 is protected by an auxiliary member 21 provided with a layer made of a graphite material.

The actual formation of the circuit pattern on the wafer 5 includes measurement of the two-dimensional position of the reticle stage 12 and the wafer stage 13 in the horizontal plane by the distance measuring laser interferometer 15 of the immersion exposure apparatus.
Based on this measurement value, positioning and synchronous control of the reticle 2 and the wafer 5 are possible, and under this control, the circuit pattern of the reticle 2 illuminated by the illumination system 1 of the projection optical system 3 is the wafer 5 as the second object. Projected on.
In the exposure, the immersion exposure apparatus supplies the immersion liquid from the supply port 10 to form the liquid film 4 at the interval between the final surface of the projection optical system 3 and the wafer 5 in order to improve the resolution.
At this time, since the graphite layer is formed on the surface of the auxiliary member 21, no droplets remain, and adverse effects due to charging of the wafer 5 are reliably prevented.

The next step 5 (assembly process) is called a post-process, and is a process for forming a semiconductor chip using the substrate (wafer 5) manufactured in step 4.
The assembly process includes processes such as an assembly process (dicing, bonding) and a packaging process (chip encapsulation).
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. 5 shows a detailed flow of the substrate process.
In step 11 (oxidation), the surface of the wafer 5 is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer 5. In step 13 (electrode formation), an electrode is formed on the wafer 5 by vapor deposition.
In step 14 (ion implantation), ions are implanted into the wafer 5. In step 15 (resist process), a resist is applied to the wafer 5.
In step 16 (exposure), the circuit pattern of the reticle 2 is arranged in a plurality of shot areas of the wafer 5 by the immersion exposure apparatus described above, and printing exposure is performed. In step 17 (development), the exposed substrate is developed.
Next, in step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed.

By repeatedly performing these steps, multiple circuit patterns are formed on the wafer 5.
If the device manufacturing method of the present embodiment is used, it is possible to prevent residual droplets, charging abnormalities, and the like during immersion exposure in advance, and it is possible to stably manufacture high-quality devices.

It is a schematic diagram which shows typically the structure of Example 1 of this invention. FIG. 2a is a side view schematically showing a main configuration of the second embodiment of the present invention. FIG. 2B is a top view schematically showing the main configuration of the second embodiment of the present invention. It is sectional drawing which shows typically the principal part structure of Example 3 of this invention. It is a flowchart for demonstrating manufacture of the device using an exposure apparatus. 5 is a detailed flowchart of the wafer process in Step 4 of the flowchart shown in FIG. 4. It is a side view which shows the prior art. FIG. 7a is a top view showing a concept of a main part of another conventional technique. FIG. 7 b is a cross-sectional view showing the configuration of another conventional technique.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination system 2 Reticle 3 Projection optical system 4 Liquid film 5, 105 Wafer (substrate)
6 Immersion liquid supply device 7 Immersion liquid recovery device 8 Immersion liquid supply pipe 9 Immersion liquid recovery pipe 10, 110 Supply port 11, 111 Recovery port 12 Reticle stage 13 Wafer stage 14 Mirror 15 Distance measuring laser interferometer 16 Immersion control device 17 Stage control device 18 Deaeration device 19 Temperature control device 20, 120 Chuck 21 Auxiliary member 31 Contact body 51 Base material 52 Graphite sheet

Claims (3)

A projection optical system for exposing and transferring a pattern on a reticle onto a wafer; a liquid supply device for supplying an immersion liquid to a gap between the lens surface closest to the wafer of the projection optical system and the wafer; In an immersion exposure apparatus that performs exposure while holding at least part of the liquid,
An immersion exposure apparatus, wherein a material of at least a surface of an auxiliary member provided around the wafer chuck for holding the wafer and holding the immersion liquid together with the wafer chuck is made of graphite.   2. The immersion exposure apparatus according to claim 1, wherein the graphite material constituting the surface of the auxiliary member contacts at least a part of the wafer mounted on the wafer chuck. A step of exposing the wafer using the immersion exposure apparatus according to claim 1;
And a step of developing the wafer.

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