JPH08124822A - Projection exposure device - Google Patents

Abstract

PURPOSE: To prevent dust from adhering to the surface of a mask pattern by a method wherein a glass plate is used in place of a pellicle formed of thin film. CONSTITUTION: A projection light exposure device is composed of a light irradiation section 1, a mask M, a mask stage 2, a projection lens 3, and a work W, wherein a double telecentric lens is used as the projection lens 3, and a glass plate 11 is disposed on the mask stage 2 in parallel with the mask M so as to form a closed space surrounded with the glass plate 11 and the surface of the mask M where a pattern is provided to prevent dust from being attached to the surface of the mask pattern. As a double telecentric lens is made to serve as the projection lens 3, primary light rays pass through the glass plate 11 vertically, so that no optical aberration is induced even if a thick glass plate is used. Another means that gas is made to flow through the closed space or ionized gas is introduced into the closed space to prevent the mask from being charged with electricity is jointly used, whereby dust attached to the surface of a mask pattern is much lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus which irradiates a work with light through a mask, and more specifically, it projects and exposes an image of a mask pattern using ultraviolet rays onto a work coated with a photoresist by a projection lens. The present invention relates to a projection exposure apparatus that does.

[0002]

2. Description of the Related Art Micron-sized processing is required for semiconductor elements, liquid crystal screens, ink jet printer heads, multichip modules that produce a large number of various electrical elements on a single substrate into a single module. An exposure process is used in a process of manufacturing a variety of electric parts.

This exposure process uses a mask in which a metal such as chrome is vapor-deposited and etched on a transparent substrate such as glass to form a pattern, and the work is irradiated with ultraviolet rays through the mask to be applied on the work. The mask pattern is transferred to the existing photoresist. The exposure method is a projection exposure method in which the image of the mask is formed on the work with a projection lens, a contact exposure method in which parallel light is emitted while the mask and the work are in close contact, and a slight gap is provided between the mask and the work. It is roughly classified into a proximity exposure method in which parallel light is emitted in a state.

The projection exposure method has an advantage that it has a better resolution than the contact exposure method and the proximity exposure method. Further, as compared with the contact exposure method, the mask and the work do not come into contact with each other, so that the mask is less likely to be contaminated and the mask has a long life. FIG. 6 is a diagram showing the configuration of the projection exposure apparatus described above. In the figure, 1 is a light irradiation device, 1a is a shutter, 1b is an optical filter, 1
c is a condenser lens, 1d is a lamp, and 1e is a condenser mirror.

A mask stage 2 has a mask M fixed to the mask stage 2 by a vacuum chuck or the like.
It is driven by Y, Z, θ (X, Y axes: orthogonal axes on a plane parallel to the mask surface, Z axis: vertical axis in the figure, θ: rotation axis about Z axis). 3 is a projection lens, W is a work,
Reference numeral 4 denotes a work stage. The work W is fixed to the work stage 4 by a vacuum chuck or the like, and the work drive stage 4 is driven by a drive device (not shown).

Reference numeral 5 denotes an alignment unit, and the alignment unit 5 observes an alignment mark on the work W and an alignment mark (not shown) on the mask. The alignment unit may be provided at the position B or C in the figure other than the position A in the figure. In the figure, when performing the exposure process on the work W, first, the alignment unit 5
Observe the alignment marks of the work and the mask by using the mask M or work W
Are moved in the X, Y, and θ directions. After the alignment is completed, the light irradiation device 1 irradiates ultraviolet rays to project the mask pattern MP on the work W for exposure.

By the way, a glass plate is often used as the material of the mask M in the projection exposure apparatus. Since the glass plate is an insulator, it is easily charged with static electricity. For this reason, there is a problem in that dust floating in the air is attracted by static electricity charged during use, and the mask becomes dirty. The dirt on the mask, especially the dirt attached to the surface on which the pattern is formed, causes an image thereof to be directly projected onto the work, which causes a defective product.

As a method for solving this problem, a technique has been developed for covering the surface on which the mask pattern is formed with a transparent thin film called a pellicle. This utilizes the extremely shallow depth of focus of the projection lens for micron-sized fine pattern exposure. FIG. 7 is a diagram showing a mask covered with the above pellicle. In the figure, 2 is a mask stage on which the mask M is placed, and M is a mask.
Spacer SP is formed so as to surround the pattern MP of the mask M, and a pellicle P made of a transparent thin film of nitrocellulose or the like is covered on the spacer SP to seal it. This can prevent dust from directly adhering to the pattern surface of the mask M.

Further, even if dust adheres to the pellicle surface, the depth of focus of the projection lens is extremely shallow, so the dust on the pellicle several mm away from the pattern forming surface of the mask is blurred and forms an image on the work surface. do not do.

[0010]

However, the conventional method using the pellicle has a problem that the thickness of the pellicle is thin and highly accurate thickness uniformity is required, which is very expensive. This is because when a one-telecentric lens is used as the projection lens, the principal ray passes obliquely through the pellicle, and optical aberration occurs if the pellicle is thick or not uniform in thickness.

The one-telecentric lens is a lens usually used for a projection lens, and as shown in FIG.
The chief ray of the projection lens 3 is parallel on the exit side (work side),
9 is a non-parallel lens on the incident side (mask side), and when a one-telecentric lens is used, each optical axis of the principal ray passing through the mask M is considered to be non-parallel, and therefore the thick pellicle is shown in FIG. Thus, the light passing through the pellicle is shifted by d, and the image projected on the work W is displaced.

To avoid this, an extremely thin pellicle having a thickness of several μm is required, and a thick pellicle such as a glass plate cannot be used. As described above, since the pellicle has a very small thickness, it is easily damaged and difficult to handle. In addition, since the pellicle is made of an organic thin film such as nitrocellulose, it deteriorates due to ultraviolet rays and chemical substances contained in the atmosphere (mainly chemicals used in the factory volatilized in the air), and There was a problem that it had to be replaced with a new one.

Further, even if the pattern surface of the mask is sealed in the closed space by the pellicle, it is practically difficult to reduce the dust existing in the closed space to zero, and a small amount of dust enters when the pellicle is replaced. In some cases, the static electricity of the mask is attracted and adheres to the mask surface, which may cause product defects. The present invention has been made in consideration of the above-mentioned problems of the prior art, and the first object of the present invention is to replace the pellicle formed from the above-mentioned thin film with
It is an object of the present invention to provide a projection exposure apparatus which can use a glass plate and can solve the above-mentioned various problems that occur when a pellicle formed of a thin film is used.

A second object of the present invention is to provide a projection exposure apparatus capable of greatly reducing the influence of dust entering the closed space.

[0015]

In order to solve the above problems, the invention of claim 1 of the present invention is directed to a mask stage section including a light irradiation section for irradiating ultraviolet rays, a mask, and a mask stage for holding the mask. ,, projection lens, work,
In a projection exposure apparatus comprising a work stage section including a work stage for holding the work, the projection lens is a both telecentric lens, and the mask stage is provided with a glass plate arranged in parallel with the mask. A closed space is formed by the patterned surface, the mask stage and the glass plate.

According to a second aspect of the present invention, in the first aspect of the invention, air or an inert gas is contained in the mask stage, the surface on which the pattern of the mask is formed, and the closed space formed by the mask stage and the glass plate. Gas inlet for supplying
A gas exhaust port for discharging the introduced air or inert gas is provided. According to a third aspect of the present invention, in the second aspect of the invention, a pair or a plurality of pairs of discharge electrodes are provided in a flow path for introducing air or an inert gas into the gas inlet, and the discharge electrodes are AC or DC. A voltage is applied to ionize air or an inert gas.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the shape of the holes on the closed space side of the gas inlet and the gas outlet is slit-like, and the long sides of the slits are defined. It is parallel to the mask surface.

[0018]

According to the first aspect of the present invention, as described above, the projection lens is the both telecentric lenses, and the mask stage is provided with the glass plate arranged in parallel with the mask, and the pattern of the mask is formed. Since the closed space is formed by the formed surface, the mask stage, and the glass plate, dust can be attached to the pattern surface of the mask without using an expensive pellicle that needs to be thin and uniform in thickness. Can be prevented.

In particular, the glass plate is thicker than the pellicle and less likely to be damaged, and is easy to handle. Further, since the glass plate is less likely to deteriorate due to ultraviolet rays and chemical substances contained in the atmosphere, it does not need to be replaced periodically. Further, by using quartz glass, it becomes possible to use ultraviolet rays having a wavelength shorter than 300 nm for exposure. In the invention of claim 2 of the present invention, the closed space is provided with a gas inlet for supplying air or inert gas and a gas outlet for discharging the introduced air or inert gas. Even a small amount of existing dust can be washed away, and the adhesion of dust to the mask surface can be greatly improved.

According to the third aspect of the present invention, a pair of or a plurality of pairs of discharge electrodes are provided in the flow path of air or an inert gas, and AC or DC voltage is applied to the discharge electrodes so that air or Since the inert gas is ionized, the charge on the mask can be eliminated, and the probability that dust adheres to the mask can be reduced. Moreover, since a dry gas can be used, there is no fear of condensation or corrosion of metal parts.

According to the fourth aspect of the present invention, since the shape of the holes on the closed space side of the gas inlet and the gas outlet is slit-like and the long side of the slit is parallel to the mask surface, the closed space is closed. It is possible to make the flow of gas uniform and to prevent dust from accumulating, so that the adhesion of dust to the mask can be reduced.

[0022]

1 is a diagram showing the construction of a projection exposure apparatus according to a first embodiment of the present invention. In the figure, the same components as those shown in FIG. 6 are designated by the same reference numerals, 1 is a light irradiation device, 1a is a shutter, 1b is an optical filter, and 1c.
Is a condenser lens, 1d is an ultra-high pressure mercury lamp, and 1e is a condenser mirror.

Reference numeral 2 denotes a mask stage. The mask M is fixed to the mask stage 2, and light is incident on the mask M from the light irradiation device 1 in parallel. A glass plate 11 made of quartz glass or the like is attached to the mask stage 2 on the mask pattern MP side of the mask M parallel to the mask, and a closed space is formed by the mask pattern surface of the mask M, the mask stage 2 and the glass plate 11. Is forming.

Reference numeral 3 denotes a projection lens, and both telecentric lenses are used as the projection lens 3 in this embodiment. As shown in the figure, both telecentric lenses are lenses in which the principal ray of the lens is parallel on both the emission side (work side) and the incident side (mask side), and both telecentric lenses should be used as the projection lens 3. Thus, the chief ray passes through the glass plate 11 vertically, and even if the glass plate 11 is thick, the image projected on the work W is not displaced due to optical aberration.

W is a work, 4 is a work stage,
Reference numeral 5 denotes an alignment unit, and the alignment unit 5 observes an alignment mark on the work W and an alignment mark (not shown) on the mask, and positions the both as described in FIG. Matching is done. In this embodiment, both telecentric lenses are used as the projection lens as described above, and
Since a glass plate is used instead of the thin film pellicle, dust is not generated on the pattern surface of the mask M without using a very expensive pellicle that requires a thin and highly accurate thickness uniformity as in the conventional example. Can be prevented.

Further, since the glass plate is thick, it is hard to break,
It is easy to handle and does not need to be replaced periodically because it is less susceptible to deterioration due to ultraviolet rays and chemical substances contained in the atmosphere. Especially when quartz glass is used,
Ultraviolet rays having a wavelength shorter than 300 nm can be used for exposure. FIG. 2 is a diagram showing a second embodiment of the present invention.

In this embodiment, the gas introduction pipe 2a and the gas discharge pipe 2b are attached to the mask stage 2 in the first embodiment, and the mask pattern surface, the mask stage 2 and the glass are inserted through the holes provided in the mask stage 2. The gas is introduced into the closed space formed by the plate. That is, even if the mask pattern surface is sealed in the closed space as in the first embodiment, it is practically difficult to completely eliminate the dust existing in the closed space. Dust will get in. Then, the dust that has entered will eventually adhere to the mask surface that is attracted to the static electricity of the mask.

Therefore, as shown in FIG. 2, clean air or an inert gas is flown into the closed space through the gas introduction pipe 2a and is discharged through the gas discharge pipe 2b. As a result, a small amount of dust that has entered the closed space can be washed away, and the adhesion of dust to the mask surface can be greatly improved. By the way, as in the second embodiment, by introducing gas into the closed space formed by the mask pattern surface, the mask stage and the glass plate, the influence of dust can be greatly reduced. If the gas introduced into the space is dry, the mask is charged by the friction between the gas and the mask.

Normally, clean air or an inert gas such as nitrogen or argon used in a factory for manufacturing electronic devices or semiconductor devices is a very dry one having a dew point of about -40 ° or lower, When such a dry gas is flowed, static electricity is generated due to friction with the mask, and even if the amount of dust contained in the gas is extremely small, if the mask is charged, the probability of dust attachment increases. On the other hand, moist gas cannot be used because it causes condensation and corrosion of metal parts.

The third embodiment of the present invention is designed to prevent the adhesion of dust due to the charging of the mask described above. In this embodiment, the gas introduction pipe 2a shown in FIG. 2 is used.
In the gas flow path to the
2, 23 are provided. Then, an AC or DC voltage is applied from the power source 21 to the discharge electrodes 22 and 23 to generate corona discharge and ionize the gas in the flow path.

As a result, the ionized gas is introduced into the closed space, and static electricity is not generated by the mask M and the gas. Further, even if the mask M is charged from the beginning, it can be removed. Therefore, even if the gas introduced into the closed space contains a very small amount of dust, it is possible to reduce the probability of adhering to the mask. Moreover, since a dry gas can be used, there is no concern about dew condensation or metal corrosion.

Although FIG. 3 shows an example in which a pair of electrodes is provided, a plurality of pairs of electrodes may be provided. FIG. 4 is a diagram showing a fourth embodiment of the present invention. This embodiment is the same as the second or third embodiment, except that a gas inlet to the closed space,
In addition, the gas discharge port is formed in a slit shape, and a gas reservoir is provided in the gas introduction flow path to make the gas flow in the closed space uniform.

In FIG. 4, the same components as those shown in FIG. 2 are designated by the same reference numerals, and in this embodiment, as shown in the diagram, the gas flow passages provided in the mask stage 2 are provided. Further, a gas reservoir 2c that makes the flow velocity distribution of the gas discharged from the slit uniform is provided, and a gas inlet and a gas outlet to the closed space are formed in a slit shape.

FIG. 5 is a perspective view of the mask stage 2 (the state in which the mask M is not placed is shown in FIG. 5). As shown in FIG. 5, the long side of the slit 2d is the mask. It is parallel to the surface and its length is approximately equal to the length of one side of the closed space. In this embodiment, as described above, since the gas reservoir 2c is provided and the gas inlet and the gas outlet to the closed space are formed in a slit shape, the gas flow in the closed space is not stagnant. . Therefore, the dust does not stay in the stagnation portion and a portion having a high dust concentration is not generated locally, and the adhesion of the dust to the mask can be reduced.

[0035]

As described above, in the present invention,
The following effects can be obtained. (1) The projection lens is a bi-telecentric lens, and the mask stage is provided with a glass plate arranged in parallel with the mask, and the mask pattern-formed surface, the mask stage and the glass plate form a closed space. Since it is formed, it is possible to prevent dust from adhering to the pattern surface of the mask without using an expensive pellicle that is thin and requires uniform thickness. Further, the glass plate is thicker than the above pellicle and less likely to be damaged, and is easy to handle. Further, since it is less likely to be deteriorated by ultraviolet rays and chemical substances contained in the atmosphere, it is not necessary to replace it regularly.

Therefore, maintenance and management can be facilitated and costs can be reduced as compared with the conventional ones. (2) A gas inlet for supplying air or an inert gas to the closed space and a gas outlet for discharging the introduced air or an inert gas are provided, and by flowing a gas into the closed space,
Even a small amount of dust existing in the closed space can be washed away, and the adhesion of dust to the mask surface can be greatly improved. (3) In the flow path of air or an inert gas, a pair of or a plurality of pairs of discharge electrodes are provided, and an AC or DC voltage is applied to the discharge electrodes to ionize the air or the inert gas. The charge can be removed, and the probability that dust adheres to the mask can be reduced. Moreover, since a dry gas can be used, there is no fear of condensation or corrosion of metal parts. (4) By making the shape of the holes on the closed space side of the gas inlet and gas outlets slit-shaped and making the long sides of the slits parallel to the mask surface, the accumulation of dust is prevented and the dust on the mask is prevented from adhering. Can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

FIG. 5 is a perspective view of a mask stage according to a fourth embodiment.

FIG. 6 is a diagram showing a configuration of a projection exposure apparatus.

FIG. 7 is a diagram showing a conventional dustproof method for a mask using a pellicle.

FIG. 8 is a diagram illustrating characteristics of a one-side telecentric lens.

FIG. 9 is a diagram illustrating optical aberration caused by oblique incidence of light.

[Explanation of symbols]

 1 Light Irradiation Device 1a Shutter 1b Optical Filter 1c Condenser Lens 1d Lamp 1e Condensing Mirror 2 Mask Stage 2a Gas Introducing Tube 2b Gas Discharge Tube 2c Gas Reservoir 2d Slit 3 Projection Lens 4 Work Stage 5 Alignment Unit 11 Glass Plate 21 Power Supply 22 , 23 Discharge electrode M mask MP mask pattern W work P pellicle SP spacer

Claims (4)

[Claims] 1. A light irradiation unit that irradiates ultraviolet rays, a mask, a mask stage unit that includes a mask stage that holds the mask, a projection lens, a work, and a work stage unit that includes the work stage that holds the work. In the projection exposure apparatus, the projection lens is a bi-telecentric lens, the mask stage includes a glass plate arranged in parallel with the mask, the mask pattern surface, and the mask stage, A projection exposure apparatus, wherein a closed space is formed with the glass plate. 2. The mask stage is provided with a gas inlet for supplying air or an inert gas to a closed surface formed by the mask stage, the mask stage and the glass plate, and the introduced air or the inert gas. The projection exposure apparatus according to claim 1, further comprising a gas exhaust port for exhausting gas. 3. A pair of or a plurality of pairs of discharge electrodes are provided in a flow path for introducing air or an inert gas into the gas inlet, and an AC or DC voltage is applied to the discharge electrodes to remove the air or the inert gas. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is ionized. 4. The gas inlet and the gas outlet on the closed space side are shaped like slits, and the long sides of the slits are parallel to the mask surface. Projection exposure equipment.