JPH10289853A - Exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to lessen the deterioration of the performance of an exposure device for a long period even in any exposure wavelength by a method wherein while one part of the interior of an optical system is held in an oxidizing atmosphere, from which Si, Al, Mg and NH4 , which produce a solid material by an oxidation, and these compounds and the like are removed, an exposure is performed on an object of exposure. SOLUTION: A laser beam radiated from an excimer laser 11, which is used as a light source, is adjusted so that a reticle 14 is uniformly illuminated by optical components 13, such as a mirror 12, an capacitor lens and a zoom lens, to make the laser beam, which is made to pass through the reticle 14, incide in a sealing box 102 for sealing a group 15 of reduced exposure lenses housed in a lens barrel 16 and the laser beam transfers a reticle pattern on a wafer 17 via the group 15. At this time, ozone gas, which is oxidizing gas purified by an oxygen gas bomb 103 and an ozone generator 104, is introduced in the box 102 to perform an exposure on an object of exposure while one part of the interior of the lens barrel 16 is held in an oxidizing atmosphere, from which Si, Al, Mg and NH4 and these compounds are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A stepper reduces a pattern on a reticle or mask (hereinafter collectively referred to as a reticle) by 1/10.
The image is reduced to 1/5 and focused on an exposure object such as a photoresist film on a semiconductor wafer.

With the increase in the degree of integration and miniaturization of semiconductor devices, the exposure wavelength of a stepper exposure apparatus has been shortened from a g-line of a mercury lamp to an i-line, and further to a KrF laser beam and an ArF laser beam of an excimer laser. We are working to shorten the wavelength.

[0004] The ultraviolet light used for these exposures has high photon energy, and causes a chemical change in the irradiated photoreceptor such as a photoresist to form a reticle pattern on an object to be exposed.

FIG. 6 shows a conventional stepper exposure apparatus. In FIG. 6, a lamp 61 that emits ultraviolet light and a condenser lens 62 for irradiating light emitted from the lamp 61 onto a reticle 64 are arranged in a lens barrel 601 of an illumination system. Emitted from lamp 61, condenser lens 62
The light converted into a parallel light beam at irradiates the reticle 64.

Further, the ultraviolet light passing through the opening of the reticle 64 passes through the projection system lens barrel 602, is focused by the reduction projection system lens group 65, and exposes the photoresist film applied on the semiconductor wafer 67. . The semiconductor wafer 67 is mounted on an XY stage 69 fixed on a base 68.
It is placed on.

After exposing at an appropriate illuminance using a shutter, a diaphragm, and the like, which are omitted in the drawing showing the conventional exposure apparatus, the XY69 stage is moved, and exposure is repeatedly performed in the same procedure.

In order to increase the processing speed of the stepper, it is necessary to increase the amount of light transmitted through all the lens groups of the illumination system and the exposure system, and flare and illuminance unevenness on the object to be exposed must be minimized. No.

Usually, an antireflection film for an exposure wavelength is formed on the lens surface in order to increase transmittance and suppress flare.

[0010]

If the g-line and i-line steppers are used for a long time, clouding and organic substances accumulate on the lens surfaces of the illumination system lens group 62 and the projection system reduction lens group 65 in FIG. Generally, the surface of these lens groups is coated with an anti-reflection film for the exposure wavelength, and the reflectance changes due to cloudiness and the deposition of organic substances, which reduces the transmittance and reduces the scattering of the exposure light. Had also occurred.

[0011] If the accumulation of fogging and the adhesion of organic substances are uneven over the entire surface of the lens constituting the optical system, the illuminance may be uneven on the object to be exposed. Also, when the deposit adhering to the lens group surface absorbs the exposure light, similarly, the transmittance of the lens decreases and the transmittance in the lens surface becomes uneven. In such a state, the projection illuminance of the stepper decreases, illuminance unevenness occurs, flare and the like increase, and the performance deteriorates as a whole.

On the other hand, the exposure wavelength is excimer KrF laser (2
48nm) and ArF laser (193nm), and when the photon energy and energy density increase, organic substances and the like attached in the clean room and in the lens barrel are removed, and the illuminance on the exposed surface can be reduced even in a short period. There were problems such as changes.

To solve the above problems, Japanese Patent Laid-Open No.
The -201702 discloses improvements are disclosed for filling the barrel with gas such as N ₂ is a non-oxidizing gas. Further, Japanese Patent Application Laid-Open No. 7-273016 discloses an improvement measure for preventing performance deterioration by preventing sticking to a lens or the like with a seal glass and making the seal glass replaceable.

However, in the lens barrel, there are adhesives for fixing the lens and the lens barrel, and contaminants such as organic substances attached to the inner surface of the lens barrel. These contaminants are decomposed or decomposed by the energy of ultraviolet rays. Upon reaction, decomposition products or reaction products adhere to the lens surface. Further, the organic matter adheres to the lens surface without irradiating ultraviolet rays. Therefore, the above measures are not enough to prevent the deterioration of the optical performance due to the adhesion of the organic substance.

Further, there is a problem that conventional measures cannot cope with the problem, for example, it is very difficult to replace the reduction exposure system lens group.

An object of the present invention is to provide an exposure method in which the performance is not deteriorated for a long time at any exposure wavelength.

[0017]

The above object is achieved by the present invention described below. That is, the present invention provides an exposure method in which a light beam from a light source is passed through an optical system including a lens, and is exposed on an object to be exposed through a reticle, wherein at least a part of the optical system forms a solid by oxidation. An exposure method is disclosed in which exposure is performed while maintaining an oxidizing atmosphere in which Al, Mg, NH ₄ and compounds thereof have been removed.

According to the present invention, there is provided an exposure method for passing a light beam from a light source through an optical system including a lens, and exposing the exposed object through a reticle. Si, A generated
Exposure is performed while maintaining the atmosphere in which l, Mg, NH ₄ and their compounds have been removed, and thereafter, at least a part of the optical system is maintained in an oxidizing atmosphere to remove organic substances attached to the lens surface. The present invention discloses an exposure method characterized by introducing.

Further, the present invention provides an exposure method of passing a light beam from a light source through an optical system including a lens and exposing the object to an exposure object through a reticle. Generated Si,
Exposure is performed while maintaining the atmosphere from which Al, Mg, NH ₄ and these compounds have been removed, and thereafter, at least a part of the optical system is irradiated with ultraviolet light other than the exposure wavelength, and the energy of ultraviolet light or ultraviolet light is irradiated. Also disclosed is an exposure method characterized by introducing a step of removing an organic substance attached to the lens surface with an oxidizing gas such as ozone generated by light.

According to the exposure method of the present invention, the light emitted from the light source passes through an optical path including a lens, and is exposed on an object to be exposed through a mask. Keep in an environment where impurities such as oxide film formed on the surface are removed,
At least one surface of the lens is exposed to an oxidizing atmosphere to perform exposure while removing organic substances and the like adhering to the lens surface.

Alternatively, exposure is performed while maintaining the lens atmosphere present on the optical path in an environment such as a nitrogen or oxygen atmosphere from which an impurity substance that forms an oxide film on the lens surface by oxidation is removed. At this point, the contaminated lens surface is replaced with an oxidizing atmosphere to remove contaminants.

In order to prevent clouding of the lens surface due to substances generated by oxidation and decomposition and synthesis of organic gas molecules, change in reflectance due to attached matter, and change in transmittance due to change in absorption, metal elements and metal compounds, organic impurities By keeping at least one surface of the lens in an oxidizing gas environment from which oxidization has been removed, lens contamination due to oxidation is prevented, and exposure is performed while being brought into contact with an oxidizing atmosphere, or at least one contaminated lens is exposed. Is exposed to an oxidizing atmosphere to remove organic substances adhered to the lens surface by ultraviolet rays, thereby stabilizing the optical performance of the exposure system.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.

[0024]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[Example 1] A lens left in a clean room environment was replaced with a Fourier transform infrared spectrometer (hereinafter referred to as FTI).
R) to confirm that various organic compounds such as hydrocarbons were deposited on the lens surface. It is known that various hydrocarbons adhere to a sample which is usually left in the atmosphere, and it has been found that the hydrocarbon adheres to the lens surface during a normal lens preparation process or after cleaning.

In an excimer (KrF, ArF) laser,
Since the photon energy is large, these organic compounds are removed.

The organic compound adhered to the lens surface has various refractive indexes ranging from about 1.3 to 1.7, but when such contaminants adhere to the surface, the reflectance of the lens surface changes,
The transmittance decreases. Also, as the exposure wavelength becomes shorter, absorption of contaminants also becomes a problem.

FIG. 1 is a schematic view of a main part of an excimer (KrF) exposure apparatus according to the present invention. In the figure, 101 is an illumination lens sealing chamber, 102 is a projection lens sealing chamber, 103 is an oxygen gas cylinder, 104 is an ozone generator, and 105 is an ozone treatment apparatus.

Hereinafter, the present invention will be described in detail with reference to FIG. 11 is an excimer laser as a light source, 248n
m laser light is pulsed. The laser light emitted from 11 is adjusted to uniformly illuminate the reticle 14 by optical components such as 12 mirrors, 13 condenser lenses, and optical integrators and zoom lenses (not shown).

The laser beam that has passed through the reticle 14 is
The reticle pattern enters the sealing box (chamber) 102 that seals the reduction exposure system lens group 15 housed in 6, and is transferred to the wafer 17 through the reduction exposure lens group 15. The lens barrel 16 includes an adhesive for bonding the reduction exposure lens group 15 and the lens barrel 16, a lens fixing jig, and the like, but is omitted.

Since various gases such as various solvents in a clean room and organic gases are mixed in the lens barrel, various exposures such as various hydrocarbons, etc. Organic compounds are deposited.

Here, ozone gas is introduced into the sealed box 102 by the oxygen gas cylinder 103 and the ozone generator 104. The oxygen gas used for generating ozone gas used here is an organic solvent and an organic metal-based gas mixed in a clean room, and a gas that generates a solid by a photochemical reaction is removed, and the oxygen gas is purified to a state where deposition does not occur.
In order to improve the ozone generation efficiency, several percent of N ₂
Gas is added.

A through-hole 105 is formed in the lens barrel 16 in the sealing box 102 so that the ozone gas can efficiently reach the reduction exposure system lens group 15.

The ozone gas is allowed to flow for a while into the sealing box 102 to sufficiently replace the impurity gas in the lens barrel.
Thereafter, exposure is performed while flowing ozone gas.

During exposure, organic substances deposited on the lens surface are removed by intense laser light and are always cleaned.

At the same time as the completion of the exposure, an organic substance adheres to the lens surface. The organic substance changes into a gaseous substance having a high vapor pressure by the ozone gas introduced into the lens barrel, and is removed from the lens together with the ozone gas. It is discharged outside. The discharged gas is decomposed into harmful ozone, the other gas components are detoxified, and further discharged through a particle removal filter into a clean room.

It is desirable to use a material having a high resistance to ozone, such as an adhesive for adhering the lens barrel and the lens and the inner surface of the barrel, or to coat a protective film so as not to be exposed to ozone gas.

In this embodiment, an excimer laser exposure apparatus has been exemplified and the exposure method has been described.
Also in the exposure apparatus such as F, if the exposure method of this embodiment is executed, the optical performance is stabilized by the cleaning effect of the organic substances attached to the lens surface.

Although ozone is used as the oxidizing gas in this embodiment, the same effect can be obtained by using a gas having an organic film removing effect such as N ₂ O or H ₂ O ₂ other than ozone. In addition to these oxidizing gases, active molecules such as oxygen radicals and N ₂ O radicals may be supplied. However, in this case, the inside of the sealing chamber must be made of a material having high resistance to these oxidizing gases.

In this embodiment, the embodiment in which only the reduction exposure system lens is cleaned has been described, but it goes without saying that the same processing can be performed for the illumination system lens.
Although organic substances also adhere to the atmosphere side of the exposure light irradiation sections of the sealing chambers 101 and 102, an adhesion glass or the like is arranged in this portion to facilitate attachment and detachment and replacement.

When the exposure method shown in FIG. 1 according to the present invention is used, it is possible to change the reflectance by adhering to the lens surface, and to always remove organic substances that absorb the excimer laser, thereby improving the transmittance, Irradiation unevenness does not change, and stable exposure can be performed for a long time. Also, the apparatus can be used efficiently without the need for disassembling and cleaning the lens group.

[Embodiment 2] FIG. 2 is a schematic view showing a main part of an excimer exposure apparatus according to a second embodiment of the present invention. In the figure, 201 is an N ₂ gas, and 202 is a gas switch.

Hereinafter, the present invention will be described in detail with reference to FIG. Before irradiating the lens group 15 with ultraviolet rays for exposure, the gas switching device 202 allows the N ₂ gas 201 to flow into the lens barrel, and sufficiently purges the lens barrel with the N ₂ gas. The N ₂ gas used here is one from which impurities causing deposition such as organic metal and NH ₄ have been removed. Although N ₂ gas is used here, an inert gas such as Ar or Ne may be used, or air from which metal impurities and organic impurities have been removed may be used. Desirably, it is available and has a refractive index similar to that of the atmosphere.

After purging with N ₂ gas, exposure is performed while flowing the gas at a very small flow rate. The laser removes organic deposits during exposure, but after exposure, organic films such as hydrocarbons adhere to the lens surface due to organic contaminants such as gases released from the lens barrel and adhesives. I do.

After the exposure, the gas switch 202 is switched, and ozone gas is introduced into the lens barrel by the oxygen gas 103 and the ozone generator 104. The ozone gas prevents organic contaminants from adhering to the lens surface after exposure. By doing so, it is possible to suppress the deterioration of the optical performance of the reduction exposure system.

Since the oxidizing gas is replaced with a stable gas during laser irradiation, there is an advantage that the life of an adhesive or the like installed in the lens barrel can be extended.

In this embodiment, the reduction exposure system has been described. However, it is needless to say that the invention can be applied to an illumination system.

Although ozone was used as the oxidizing gas in this embodiment, the same effect can be obtained by using a gas having an organic film removing effect such as N ₂ O and H ₂ O ₂ other than ozone. In addition to these oxidizing gases, active molecules such as oxygen radicals and N ₂ O radicals may be supplied. However, in this case,
The inside of the sealed chamber must be made of a material having high resistance to these oxidizing gases.

Although organic substances also adhere to the atmosphere side of the exposure light irradiation sections of the sealing chambers 101 and 102, anti-adhesion glass or the like is disposed at this portion to facilitate replacement and replacement.

[Embodiment 3] FIG. 3 is a schematic view showing a main part of an excimer exposure apparatus according to a third embodiment of the present invention. In the figure, 301 is N ₂ gas, 302 is oxygen gas, 30
3 is an electrode, 304 is a high-frequency power supply and a matching box, and 305 is an exhaust system.

In the lens barrel 16, N ₂ / O _{2 of} 301 and 302
( _20% ) After sufficiently purging with mixing gas, exposure is performed. This gas removes metals and metallic compounds, impurities such as NH ₄ as much as possible. After the completion of the exposure, the organic matter adheres, and the illuminance and the illuminance distribution on the wafer 17 change.
Therefore, after the exposure is completed, the pressure in the exhaust system 305 is reduced to an appropriate pressure. Here, high-frequency power is applied from the high-frequency power source 304 to the electrode 303 to form oxygen and nitrogen plasma. Organic substances on the lens are removed by oxygen radicals, ozone and the like formed in the plasma. The removed organic matter is discharged from the lens barrel 16 by the exhaust system 305, is rendered harmless by the processing system 105, and is discharged.

Since the discharge can be formed and removed only at the portion where the organic substance adheres frequently, the deterioration of the adhesive, the inner surface of the sealing chamber, etc. can be prevented.

Also, since ozone and the like can be efficiently supplied to the lens, the organic matter removal rate is very high.

In this embodiment, the supply gas is N_TwoAnd O_TwoUsing
Is N_Two/ O_TwoFor mixed gas, CR (clean room)
There is an advantage that can be discharged into. But to discharge
Therefore, a gas that generates an active substance having an organic film removing effect
Then N_TwoO, H_TwoO, H_Two O _TwoEtc., in this case,
The exclusion system is installed on the atmosphere side of the exhaust system 305. Especially active
Safe gas before generating oxygen atoms and becoming active species
Is desirable.

[Embodiment 4] FIG. 4 is a schematic view showing a main part of an excimer KrF exposure apparatus according to a fourth embodiment of the present invention. In the figure, 11 is an excimer laser, 12 is a mirror, 401 is a shutter, 402 is a shutter drive mechanism, 403 is a high-pressure mercury lamp, 404 is an N ₂ / O ₂ mixed gas from which metal impurities, organic impurities and the like have been removed.

Before the exposure, the inside of the lens barrel 16 is sufficiently replaced with the gas 404. During exposure, the wafer is baked while flowing a gas at a sufficient flow rate. This prevents adhesion of metal oxides and the like. After the exposure, the mirror 12 is moved, and the shutter 401 is opened by the drive mechanism 402.

In this way, the reduction exposure lens group 15 is irradiated with ultraviolet light from the light source 11. The light source 11 has many bright lines other than the i-line of the printing wavelength, and emits ultraviolet rays of shorter wavelength. Oxygen in the lens barrel 16 is activated by the ultraviolet rays, generates active species such as ozone, and removes organic substances attached to the lens.

Ultraviolet rays are effective for the generation of active species, and the effect of removing organic substances hardly changes even when irradiation is performed through an infrared cut filter in order to prevent heating of the exposure system. When removing organic matter, it is desirable to remove the reticle 14 in order to increase the illuminance as much as possible.

The shorter the wavelength of the ultraviolet light used for removing organic substances, the better the ozone generation efficiency and organic substance decomposition efficiency, and desirably 160 to 350 nm.

[Embodiment 5] FIG. 5 is a schematic view showing a main part of an i-line exposure apparatus according to a fifth embodiment of the present invention. In the same figure, reference numeral 16 denotes a sealed lens barrel filled with ozone gas,
501 is an N ₂ / O ₂ mixed gas from which metals and metal compounds, organic impurities and the like have been removed, 502 is a stop valve, 503
Is a gas exhaust hole, 504 is an i-line filter, and 505 is a filter transfer mechanism.

In order to prevent deposits such as metal oxides, which cannot be easily removed, from depositing on the reduced exposure system, N ₂ from which metals and metal compounds, organic impurities, etc. are removed from a cylinder or the like.
Exposure is performed while purging with the / O ₂ mixed gas 501.

The lens barrel is filled with a high concentration of ozone gas, which removes organic substances adhering to the lens surface during exposure and during standing, and changes them into CO ₂ , H ₂ O or the like.
These gases do not decompose by i-rays and exist stably in gaseous form. Organic substances in the lens barrel are mainly composed of gas released from hydrocarbons, adhesives, and the like attached to the lens barrel during manufacture, but wither over a long period of use. Therefore, by converting the organic deposits due to the initially released gas into a gas state that does not re-adhere, it is possible to maintain stable optical performance for a long time.

When used for a very long time, the ozone filled in the lens barrel is decomposed and changes into oxygen, and this effect gradually diminishes. Here, the i-line filter 504 is removed by the transfer mechanism 505, and the light source 11 emits ultraviolet light to the reduction exposure lens group 15 without passing through the filter. Ultraviolet light emitted from the light source 11 also emits light having a very short wavelength of 200 nm or less, and activates oxygen filled in the lens group 15.

Therefore, the organic impurities attached to the lens surface can be removed by the active oxygen such as ozone.

In the present embodiment, the light source used for exposure can be used as it is, and it is efficient, and it is easy to use, inexpensive, and long in terms of the need for an oxide gas treatment system and an oxide gas supply system. There is an advantage that an exposure apparatus having stable optical performance for a long period can be provided.

[0066]

As described above, according to the present invention, there is provided an exposure method capable of operating an exposure apparatus using ultraviolet light stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to a third embodiment of the present invention.

FIG. 4 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to Embodiment 4 of the present invention.

FIG. 5 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to Embodiment 5 of the present invention.

FIG. 6 is a schematic sectional view showing an outline of a lens system of an exposure apparatus according to a conventional technique.

[Explanation of symbols]

11,61 light source (lamp), excimer laser 12 mirror 13,62 condenser lens 14,64 reticle 15,65 reduction exposure system lens group 16 lens barrel 17,67 silicon wafer (semiconductor wafer) 68 base 69 XY stage 101 illumination system lens Sealing chamber 102 Projection system lens sealing chamber (sealing box) 103 Oxygen gas cylinder 104 Ozone generator 105 Ozone treatment unit 106 Through hole 201,301 N ₂ gas 202 Gas switch 302 Oxygen gas 303 Electrode 304 High frequency power supply and matching box 305 exhaust system 401 shutter 402 Shiyatsuta drive mechanism 403 high pressure mercury lamp 404,501 N ₂ / O ₂ mixed gas 502 stop valve 503 gas outlets 504 i-ray filter 505 filters transferor 601 illumination system lens barrel 602 projection system lens barrel

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryuji Bilo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hidehiro Kanazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Non Corporation

Claims (7)

[Claims] 1. An exposure method in which a light beam from a light source passes through an optical system including a lens and is exposed on an object to be exposed through a reticle, wherein at least a part of the optical system is oxidized to form a solid by oxidation. , Al, Mg, NH
_4. An exposure method, wherein exposure is carried out while maintaining the composition in an oxidizing atmosphere from which these compounds and the like have been removed. 2. An exposure method for passing a light beam from a light source through an optical system including a lens and exposing the object on an exposure object through a reticle, wherein at least a part of the optical system forms a solid by oxidation. , Al, Mg, NH
₄ and performing exposure while maintaining the atmosphere in which these compounds and the like have been removed, and then introducing a process of maintaining at least a part of the optical system in an oxidizing atmosphere and removing organic substances attached to the lens surface. Characteristic exposure method. 3. The method according to claim 1, wherein the main component of the oxidizing atmosphere is ozone,
_{2. A} gas according to claim 1, which is N ₂ O, H ₂ O ₂ or a mixed gas thereof.
Or the exposure method according to 2. 4. The exposure according to claim 1, wherein a main component of the oxidizing atmosphere is an active species having an oxidizing property such as an oxygen radical, a N ₂ O radical, a H ₂ O ₂ radical, and a mixed gas thereof. Method. 5. An exposure method for passing a light beam from a light source through an optical system including a lens and exposing the object on an exposure object through a reticle, wherein at least a part of the optical system is oxidized to form a solid by oxidation. , Al, Mg, NH
₄ and exposure was performed while maintaining the atmosphere in which these compounds and the like were removed, and thereafter, at least a part of the optical system was irradiated with ultraviolet light other than the exposure wavelength, and was generated by ultraviolet light energy or ultraviolet light. An exposure method characterized by introducing a step of removing organic substances attached to the lens surface with an oxidizing gas such as ozone. 6. The wavelength of the ultraviolet light is 160 to 35.
The exposure method according to claim 5, wherein the wavelength is in a range of 0 nm. 7. The exposure method according to claim 5, wherein the ultraviolet light source is a light source used in an exposure apparatus.