JPH07201702A - Exposure method and exposure apparatus - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a lens due to the atmosphere by performing lens exposure by permitting at least one plane of the lens to make contact with the non-oxidizing atmosphere. CONSTITUTION:Lenses L1-L10 are permitted to form a high-resolution reducing lens system as a whole and are held in a lens-barrel 1. Spaces S1-S9 are formed between the ten lenses L1-L10. Through holes H1-H9 are formed on the lens- barrel 1 so as to connect the spaces S1-S9 with the external. The four through holes H1-H9 are formed in the spaces S1-S9 between the lenses at the intervals of approximately 90 degrees. The through holes are used for the intake and exhaustion for gas replacement so as to have the non-oxidizing atmosphere in the space between the lenses, exposure is performed permitting at least one plane of the lens to make contact with the non-oxidizing atmosphere and the deterioration of a lens due to the atmosphere is prevented even when ultraviolet rays are transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure technique used for manufacturing a semiconductor device or the like, and more particularly to an exposure technique using a stepper exposure apparatus including a reduction exposure system.

[0002]

2. Description of the Related Art A stepper exposure apparatus reduces the pattern on a reticle or mask (collectively referred to as a reticle in this specification) to 1/10 to 1/5 and exposes an object to be exposed such as a photoresist film on a semiconductor wafer. Focus on top.

With the high integration and miniaturization of semiconductor devices, the exposure wavelength of a stepper exposure device has been shortened from the g-line of a mercury lamp to the i-line, and further, KrF laser light or ArF laser light of an excimer laser is used. We are promoting shorter wavelengths.

The ultraviolet light used for these exposures has a high photon energy and causes a chemical change in the exposed photoconductor such as photoresist. By the way, there is no guarantee that these ultraviolet rays will not affect anything other than the photoconductor.

When the stepper exposure apparatus is used for a long period of time, the illuminance on the exposure surface is lowered and scattered light is generated as it is used. These disorders are only confirmed by continued use.

FIGS. 7A and 7B show a stepper exposure system according to the prior art. FIG. 7A shows the stepper in a new state, and FIG. 7B shows the stepper which has been used for a long period of time.
In FIG. 7A, a lamp 20 that emits ultraviolet rays and a condenser lens 12 that irradiates the reticle 13 with the light emitted from the lamp 20 are arranged in a lens barrel 11 of the illumination system. The light emitted from the lamp 20 and condensed by the condenser lens 12 illuminates the reticle 13.

The photoresist film, which has passed through the opening of the reticle 13 and the inside of the projection system lens barrel 14 and has been focused by the reduction lens group 15 and applied on the semiconductor wafer 16, is exposed. The semiconductor wafer 16 is mounted on the XY stage 17 fixed on the base 18.

When such a stepper is used for a long period of time,
As shown in FIG. 7B, the cloudy surface 3 on the lens surface of the condenser lens group 12 of the illumination system and the reduction lens group 15 of the projection system.
0 is deposited. If the haze 30 blocks or scatters the transmitted light and deteriorates the performance of the entire optical system, the performance of the stepper is deteriorated as a whole.

[0009]

The reduction lens system of the g-line stepper exposure apparatus, which the applicant has been using for about 10 years, is fogged, and the transmittance is extremely reduced (therefore, the illuminance on the exposed surface is lowered. ) Has occurred. When such deterioration of the lens system occurs, the exposure performance deteriorates, and it is difficult to continue using this lens system.

It is an object of the present invention to provide an exposure method and an exposure apparatus which have little deterioration in performance even when used for a long period of time.

[0011]

An exposure method of the present invention is an exposure method in which light emitted from a light source is passed through an optical path including a lens, and an object to be exposed is exposed through a mask. Exposure is performed while contacting at least one surface of the existing lens with a non-oxidizing atmosphere.

[0012]

Since the exposure is performed while at least one surface of the lens is brought into contact with the non-oxidizing atmosphere, the atmosphere is less likely to deteriorate the lens even when ultraviolet rays are transmitted.

[0013]

EXAMPLES The present inventors analyzed an exposure lens having deteriorated performance with an X-ray photoelectron spectroscope, and analyzed C, S, Sn, M
It was discovered that oxides of g, Si, etc. were deposited on the lens surface. When analyzing the same unused lens system,
No such oxide was found other than the oxide of Si. Therefore, it can be judged that these oxides are oxidized in the components in the atmosphere or the outgas components from the lens assembly. In addition, nitrides of these elements were not found.

It is considered that if the oxidation reaction can be prevented, the deterioration of the exposure optical system can be prevented. In order to prevent the oxide from accumulating, the surface of the lens may be covered with a non-oxidizing gas, or oxygen may be removed from the atmosphere gas surrounding the lens.

The non-oxidizing gas includes, for example, nitrogen gas, an inert gas such as argon and helium, a reducing gas such as hydrogen, and the like, and the oxygen-depleted atmosphere includes a reduced pressure atmosphere other than the above. Among these, reducing gas such as hydrogen has a risk of ignition. Also, the reduced pressure atmosphere can create new problems with respect to the mechanical stability of the device. Nitrogen gas and inert gas do not have these problems.

Further, from the point of not changing the design of the currently used lens system, nitrogen gas having a molecular weight (28) substantially equal to the molecular weight (29) of air does not substantially change the optical performance of the lens. preferable.

The inert gas is superior to the nitrogen gas in that the possibility of chemical reaction is extremely small, but as a result of analyzing the deposits on the lens by the present inventors, formation of nitrides was not found. Therefore, it is considered that even if nitrogen is used, the same stability as when an inert gas is used can be obtained.

By the way, the high resolution lens system is assembled while being adjusted. The lens system after assembly contains air between the lenses. It is difficult to completely replace the air contained between the lenses with another gas after assembly.

FIG. 1 shows a lens system having a structure capable of easily replacing the atmospheric gas between the lenses. The lenses L1 to L10 form a high resolution reduction lens system as a whole and are held by the lens barrel 1. 10 lenses L
Spaces S1 to S9 are formed between 1 to L10, respectively.

In this structure, the through holes H1 for connecting the spaces S1 to S9 between the adjacent lens pairs to the outside.
To H9 are formed on the lens barrel 1. In the space S between each lens pair, four through holes H are formed at intervals of approximately 90 degrees. By using these through holes H for supplying and exhausting gas for gas replacement, the space S between each adjacent lens pair is formed.
Can be replaced with a desired atmosphere.

The number of through holes is not limited to four. If there is at least one through hole, the atmosphere inside can be replaced. However, it is preferable that there are a plurality of through holes for efficient replacement.

FIGS. 2A to 2C show a mode in which the atmosphere gas in each space S between the lenses is replaced. Figure 2 (A)
The pipes Pa to Pd are connected to the through holes Ha to Hd, respectively, and the two pipes Pa and Pb are used for air supply, and the remaining two pipes Pc and Pd are used as exhaust pipes. When using the exposure optical system, a desired gas such as nitrogen gas is supplied from the pipes Pa and Pb, and the atmospheric gas is exhausted from the pipes Pc and Pd, so that the space S between the lenses is changed to the desired atmospheric gas. Can be replaced.

According to the structure of FIG. 2A, the pipe is connected to each through hole. In the case of a lens group of 10 lenses, if four through holes are provided in the space between the lenses, the total number of through holes will be 36. Therefore, the number of pipes is 36.

FIG. 2B shows another structure in which the piping can be simplified. In the figure, the right part of the lens barrel 1,
The left side portions are covered with outer jackets 2a and 2b, respectively, and form a gas passage between them and the lens barrel. The through holes Ha and Hb formed in the lens barrel 1 communicate with the space defined by the outer jacket 2a,
The through holes Hc and Hd communicate with the space defined by the outer jacket 2b. The jackets 2a and 2b may have a common configuration in the spaces S1 to S9 between the lenses.

A pipe Pin is connected to the outer jacket 2a, and a pipe Pout is connected to the outer jacket 2b. When a desired gas is supplied from the pipe Pin and exhausted from the pipe Pout,
The atmosphere in the space S in the lens barrel can be replaced with a desired atmosphere. According to this configuration, the number of pipes is two.

FIG. 2C shows another structure which can simplify the piping. The lens barrel 1 is surrounded by one outer jacket 2. The point that the pipes Pin and Pout are connected to the jacket 2 is similar to the case of FIG. 2 (B). Space S in lens barrel 1
Is connected to the space in the outer jacket 2 through the through holes Ha to Hd, so that a desired atmosphere gas is supplied from the pipe Pin and exhausted from the pipe Pout, so that a desired atmosphere in the space S in the lens barrel is obtained. Can be replaced. In this case, the atmospheric gas supplied from the pipe Pin does not flow into the space S in the lens barrel 1 but passes through the space between the outer jacket 2 and the lens barrel 1 and the exhaust side pipe P
There is a possibility that it will flow out. In order to reduce this possibility, it is preferable to provide a baffle B in the outer jacket 2 to limit the gas flowing from the air supply side Pin to the exhaust side Pout.

In order to prevent an unintended force from acting on the lens system, a baffle B as shown in FIG.
Is preferably not used. In the configuration of FIG. 2C, the outer jacket 2 and the lens barrel 1 may be opened without contacting each other. In such a configuration, the gas in the lens group diffuses and after a certain period of time, it is replaced with gas in which oxygen is reduced to a predetermined level or less or pure nitrogen. It is possible to flow about several liters / min of nitrogen during the replacement and about several tens of cc / min of nitrogen after the replacement.

FIG. 3 shows another form of atmosphere gas replacement. FIG. 3A shows each pipe P in the configuration of FIG.
Is connected to the valve V. Space S between lenses
After replacing the atmosphere inside with a desired atmosphere, each valve V is closed and the space S is sealed. By closing the valve V, the space S between the lenses is sealed while being replaced with the desired atmosphere.

In this structure, it is preferable that the member for sealing the gas has a sufficiently high airtightness against the invasion of air. It is not necessary to replace the atmosphere gas once after replacement. The atmosphere gas may be replaced every predetermined time.

FIG. 3B shows a pipe P having the structure shown in FIG. 2B.
The configuration in which the valve V is attached is shown in FIG. As in the case of FIG. 3A, after replacing the space S between the lenses with a desired atmosphere, the valve V is closed to seal the space S.

3 (C) and 3 (D) are shown in FIG.
The structure which attached the valve V to the piping P of a structure of (D) is shown. Also in this case, after replacing the space S between the lenses with a desired atmosphere, the valve V is closed to seal the atmosphere in the space S.

In FIGS. 3 (A) to 3 (C),
The case where the valve is provided in the pipe and the space S between the lenses is replaced with a desired atmosphere and then the valve is closed to seal the space S has been described. However, instead of providing the valve, the atmosphere of the space S is replaced and then the pipe The through holes H themselves may be closed by blocking the above, sealing with a sealing material, or the like.

With such a structure, the inter-lens space of the lens group can be filled with a non-oxidizing atmosphere, or exposure can be performed while flowing a non-oxidizing atmosphere gas. The configuration described above can be applied not only to the reduction lens system but also to a lens group having a plurality of lenses.

FIG. 4 shows a case where the above-mentioned configuration is applied to an illumination system lens of a stepper exposure system. FIG. 4A shows a configuration in which the inter-lens space of the condenser lens group 12 of the stepper exposure system is filled with nitrogen gas.

The light emitted from the lamp 20 passes through the condenser lens group 12 and illuminates the reticle 13. The light transmitted through the reticle 13 passes through the reduction lens group 15 and forms an image on the photoresist film on the semiconductor wafer 16 mounted on the XY stage 17. In the figure, 18 denotes a base for supporting the XY stage 17, and 11 and 14 denote lens barrels for holding the condenser lens group and the reduction lens group.

The space between each adjacent lens pair of the condenser lens group 12 is filled with nitrogen gas N ₂ . Lamp 20
Even if the ultraviolet ray from passes through the condenser lens group 12,
Since the atmosphere is nitrogen gas, no oxidation reaction occurs in the space between each pair of adjacent lenses, and no oxide is deposited on the lens surface in contact with nitrogen gas.

In this structure, oxide may be deposited on the outermost lens surface of the condenser lens group 12, but the outermost lens surface can be accessed from the outside, and the deposit is Cleaning can occur when it occurs.

On the other hand, the lens surface in contact with the space between the lenses cannot be accessed once the lens groups have been assembled. If oxide is deposited on the lens surface between the lenses, it cannot be cleaned, and the lens life will end when the lens performance deteriorates.

In this structure, since the space between each pair of adjacent lenses is filled with nitrogen gas, the life of the lens group can be extended without depositing oxides.
FIG. 4B shows a configuration in which nitrogen gas is caused to flow in the space between each pair of adjacent lenses of the condenser lens group of the illumination system. With the configuration as shown in FIG. 2, nitrogen gas can be made to flow inside the condenser lens group 12.

The circumference of the lens barrel 11 is surrounded by the outer jacket 2,
The nitrogen gas discharged from the jacket 2 flows into the space that houses the lamp 20, and also prevents the oxide from being deposited in this space. The nitrogen gas is supplied from the air supply port 21, passes through the space inside the condenser lens group 12, passes through the space surrounding the lens 20, and is exhausted through the exhaust port 22.

According to the configuration of FIGS. 4A and 4B, the lens surface exposed in the inter-lens space of the condenser lens group in the stepper exposure system can be protected and the life of the condenser lens can be extended. According to the configuration of FIG. 4B, it is possible to further reduce the oxide deposition in the entire illumination system.

FIG. 5 shows a case where the configuration of FIG. 3 is applied to a projection optical system. The illumination system of the stepper exposure system is the lens 20.
The reticle 13 is irradiated with the light emitted from the reticle 13 through the condenser lens group 12 held by the lens barrel 11. Reticle 13
The light that has passed through is the reduction lens system 1 held by the lens barrel 14.
An image is formed on the photoresist film on the semiconductor wafer 16 through 5.

In this structure, the space between each pair of adjacent lenses of the reduction lens group 15 of the projection system is filled with nitrogen gas. The lens surface in contact with nitrogen gas is prevented from oxide deposition and keeps its performance good for a long time.

The configuration of FIG. 5A does not protect the outermost lens surface of the reduction lens system from oxide buildup. The outermost lens surface is washable but more preferred if no oxide deposits.

FIG. 5B shows a structure in which the outermost lens surface of the reduction lens system 15 is also protected. Reduction lens system 15
Thin film pellicles 24 and 25, which hardly change the optical characteristics of the optical path, are arranged on the upstream side and the downstream side, and seal the space between them and the outermost lens. In this configuration, the space between the outermost lens surface of the reduction lens system 15 and the pellicles 24 and 25 is also filled with nitrogen gas.
With such a configuration, the entire lens surface of the reduction lens system 15 is protected from oxide deposition. The pellicle 24,
25 shall be exchanged as needed.

FIGS. 6 (A) and 6 (B) show configurations in which the configuration of FIG. 2 is applied to the projection lens system. In FIG. 6A, the nitrogen gas supplied through the space between the lens barrel 14 and the outer jacket 2 is supplied to the inter-lens space of the reduction lens system 15 held by the lens barrel 14. The nitrogen gas that has passed through the space between the lenses is exhausted from the exhaust side pipe Pout.

FIG. 6B further shows pellicles 24 and 25.
Is used to protect the outermost lens surface of the reduction lens system 15 as well. Pellicles 24 and 25 are arranged further outside the outermost lens of the reduction lens system 15 to form a semi-enclosed space with the outermost lens.

The nitrogen gas supplied from the air supply side pipe Pin flows through the space between the pellicles 24 and 25 and the outermost lens similarly to the inter-lens space, and is exhausted from the exhaust side pipe Pout. With this configuration, the entire lens surface of the reduction lens system 15 is protected from oxide deposition. Note that FIG.
Similar to the configuration of (B), the pellicles 24 and 25 are exchanged as needed.

The reduction lens system has a high resolution, and if the refractive index of the space is disturbed, the performance is deteriorated. Therefore, FIG.
In the configurations of (A) and 6 (B), it is preferable that a fixed amount of gas (for example, several tens of cc / min) is allowed to flow stably.

Although the case where the space surrounding the lens is replaced with nitrogen gas has been described, other non-oxidizing gas may be used instead of nitrogen gas. For example, an inert gas can be used. However, when an inert gas is used, the refractive index of the inert gas is different from the refractive index of air, so it is necessary to adjust the characteristics of the optical system according to the replacement gas.

If the space surrounding the lens is made to have a reduced pressure atmosphere, the amount of oxygen itself, which is the cause of the generation of oxide, is reduced, so that the deposition of oxide is also reduced. A reducing gas can also be used as the non-oxidizing atmosphere. For example, hydrogen gas can be used as the reducing gas.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
The present invention can be applied to any high-performance lens group using ultraviolet rays, not limited to the reduction projection exposure system. Other,
It will be apparent to those skilled in the art that various changes, improvements, combinations and the like can be made.

[0053]

As described above, according to the present invention,
The life of the exposure system using ultraviolet rays can be extended.

Further, according to the present invention, it is possible to prevent performance deterioration of the exposure system using ultraviolet rays.

[Brief description of drawings]

FIG. 1 is a sectional view showing a lens system according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining atmosphere replacement in the space between lenses according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view for explaining atmosphere replacement in the space between lenses according to an embodiment of the present invention.

FIG. 4 is a schematic sectional view showing an exposure optical system according to an example of the present invention.

FIG. 5 is a schematic sectional view showing an exposure optical system according to an example of the present invention.

FIG. 6 is a schematic sectional view showing an exposure optical system according to an example of the present invention.

FIG. 7 is a sectional view schematically showing an optical system of a reduction projection exposure system according to a conventional technique.

[Explanation of symbols]

 S space H through hole L lens 1 lens barrel 2 jacket 11 lens barrel 12 condenser lens 13 reticle 14 lens barrel 15 reduction lens 16 wafer 20 lamp 21 air supply port 22 exhaust port

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location 7352-4M H01L 21/30 516 F (72) Inventor Shiwakazu 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Incorporated (72) Inventor Tadahiro Hayashi 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (10)

[Claims] 1. An exposure method in which light emitted from a light source is passed through an optical path including a lens, and an object to be exposed is exposed through a reticle, wherein at least one surface of the lens existing on the optical path is non-oxidized. An exposure method in which exposure is performed while contacting with a volatile atmosphere. Exposure method. 2. The exposure method according to claim 1, wherein the non-oxidizing atmosphere contains nitrogen gas as a main component. 3. The exposure method according to claim 1, wherein the non-oxidizing atmosphere contains a Group VIII element gas as a main component. 4. The exposure method according to claim 1, wherein the non-oxidizing atmosphere contains hydrogen gas as a main component. 5. An exposure method in which light emitted from a light source is passed through an optical path including a lens, and an object to be exposed is exposed through a mask, wherein at least one surface of the lens existing on the optical path is under a reduced pressure atmosphere. An exposure method in which exposure is performed while contacting the substrate. 6. A first lens group including a plurality of lenses for condensing light emitted from a light source and irradiating the light onto a predetermined surface, and a first mirror surrounding and holding the first lens group. A second lens group including a cylinder, a plurality of lenses for forming an image of light transmitted through a reticle arranged on the predetermined surface on a target surface, and a second lens group surrounding and holding the second lens group. An exposure apparatus comprising: a lens barrel; a space between at least one pair of adjacent lenses in the first or second lens group; and a non-oxidizing gas sealed by the first or second lens barrel. 7. Further, it is held in the second lens barrel,
A pair of pellicles arranged at positions sandwiching the second lens group, and a non-oxidizing member enclosed in a space sandwiched between each of the pellicles and the second lens group in the second lens barrel. The exposure apparatus according to claim 6, further comprising a gas. 8. A first lens group including a plurality of lenses for collecting light emitted from a light source and irradiating the light on a predetermined surface, and a first mirror surrounding and holding the first lens group. A second lens group including a cylinder, a plurality of lenses for forming an image of light transmitted through a reticle arranged on the predetermined surface on a target surface, and a second lens group surrounding and holding the second lens group. Lens barrel and at least two gases formed in the first or second lens barrel for flowing a non-oxidizing gas between at least one pair of adjacent lenses in the first or second lens group. An exposure apparatus having a through hole. 9. Further, the second lens barrel is held in the second lens barrel,
A pair of pellicles arranged at positions sandwiching the second lens group, and a non-oxidizing gas flowing in a space sandwiched between each of the pellicles and the second lens group in the second lens barrel. 9. The exposure apparatus according to claim 8, further comprising: at least two gas passage holes formed in the second lens barrel. 10. A plurality of lenses arranged on the optical axis, a lens barrel for holding the plurality of lenses from the surroundings, and an outside and an inside of the lens barrel connected between each adjacent pair of the plurality of lenses. An exposure lens system having a plurality of through holes.