JP2005142488A - Aligner and method for exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner that can prevent the adhesion of organic substances having large molecular weights of gases deaerated from a resist to a projection lens etc., by decomposing the organic substances, at the same time, can remove contaminants already adhering to the surface of the projection lens during the course of exposure, accordingly, can be extended in service life, and can be reduced in the number of maintenance times; and to provide a method for exposure. <P>SOLUTION: The aligner has the projection lens 2 which projects the exposing light emitted from an exposing light source and passed through a reticle 6 upon a wafer 4; a wafer stage 3 on which the wafer 4 is disposed; and a gas supply system 1 which supplies a prescribed gas prepared by adding an active gas to an inert gas to the space between the lens 2 and stage 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor manufacturing apparatus, and more particularly to an exposure apparatus and an exposure method for manufacturing a semiconductor device. As a specific application, degassing from the resist is decomposed into a substance having a low molecular weight by making the vicinity of the wafer to be exposed an atmosphere containing a small amount of active gas, and then to the projection lens or projection lens cover of the exposure apparatus. The present invention relates to an exposure apparatus and an exposure method that prevent the adhesion of contamination and promote the life of the exposure apparatus.

Along with the miniaturization of patterns in semiconductor processes in recent years, the exposure wavelength has been shortened, and research is currently being conducted on the use of an F ₂ laser beam having a wavelength of 157 nm as an exposure light source.

The light of the F ₂ laser is absorbed by carbon monoxide, carbon dioxide, organic substances, etc. in addition to oxygen molecules and water molecules, and sufficient transmittance cannot be obtained in the atmosphere. When the oxygen molecule concentration is 10 ppm, the transmittance decreases to 90% at an optical path length of about 0.7 m, and when the water molecule concentration is 10 ppm, the transmittance decreases to 90% at an optical path length of about 1.1 m. I know. Therefore, the exposure optical path is purged with an inert gas such as nitrogen or helium. If the purge is insufficient, the exposure light is not sufficiently irradiated on the wafer surface, the illuminance uniformity is deteriorated, and variations in pattern size are caused. Therefore, in the exposure optical path from the F ₂ laser oscillation device to the wafer surface to which the exposure light is irradiated, the oxygen concentration is measured at several locations. If the measurement result is not below a certain threshold value, that is, the exposure light is sufficiently If the wafer surface is not irradiated, the system does not perform exposure.

Further, Patent Documents 1, 2, and 3 describe conventional techniques for supplying an inert gas to which an active gas is added.
JP 2002-280284 A JP 2002-196478 A JP-A-11-195585

As described above, when the light of the F ₂ laser is used as the exposure light source, purging with an inert gas is required to control the oxygen concentration in order to prevent the exposure light from being attenuated. However, in the case of exposure in an environment where the oxygen concentration is low, if degassing of an organic substance having a large molecular weight occurs from the resist, the organic substance does not decompose, and the organic substance is not present on the surface of the glass material such as a projection lens or a projection lens cover. There is a problem that adheres. Due to the adhesion of the organic matter, the illuminance uniformity of the exposure light and the resolution are deteriorated, and the yield of the product is reduced.

FIG. 5 is a diagram showing types of degassing by irradiation with F ₂ laser light of a resist for F ₂ lithography.

As shown in FIG. 5, it has been found that the resist for F ₂ lithography generates various organic substance gases upon exposure. Therefore, it can be considered that these organic substances adhere to the surface of a glass material such as a projection lens as contamination.

  An object of the present invention is to decompose an organic substance having a large molecular weight out of degassing from a resist to prevent adhesion to a projection lens or the like.

An exposure apparatus according to the present invention comprises: a projection optical system that projects exposure light irradiated from an exposure light source and passed through a mask onto a wafer;
A wafer stage for placing the wafer;
A gas supply unit that supplies a predetermined gas obtained by adding an active gas to an inert gas is provided in the space between the projection optical system and the wafer stage.

  The gas supply unit supplies the predetermined gas whose concentration of the active gas is controlled from 20 ppm to 10000 ppm.

The gas supply unit supplies the predetermined gas controlled from 0.3 L · min ⁻¹ to 10 L · min ⁻¹ .

  The exposure apparatus uses light having a wavelength of 200 nm or less absorbed in air as exposure light.

  As the inert gas, nitrogen or any gas belonging to a rare gas group in the periodic table is used.

  As the active gas, any one of gaseous substances containing oxygen atoms is used.

An exposure method according to the present invention includes a projection step of projecting exposure light irradiated from an exposure light source and passing through a mask onto a wafer via a projection optical system
A gas supply step of supplying a predetermined gas obtained by adding an active gas to an inert gas to a space between the projection optical system and the wafer stage on which the wafer is disposed;
An exposure step of exposing the wafer disposed on the wafer stage in a state where the predetermined gas is supplied to a space between the projection optical system and the wafer stage by the gas supply step. And

  According to the present invention, among the degass generated from the resist by exposure, an organic substance having a large molecular weight is decomposed into carbon dioxide, carbon monoxide, and water by reacting with the active gas by the energy of exposure light. Make it possible. As a result, contamination of organic substances on the surface of a glass agent such as a projection lens is prevented. Further, it can be expected to remove contamination on the surface of the projection lens that has already adhered during exposure. Therefore, the effect of extending the life of the exposure apparatus can be obtained, or the number of maintenance of the exposure apparatus can be greatly reduced.

Embodiment 1 FIG.
The first embodiment will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.

  FIG. 1 is a simplified diagram for explaining an exposure apparatus according to the first embodiment.

  FIG. 2 is a diagram for explaining the gas supply system according to the first embodiment.

As shown in FIG. 1, an exposure apparatus 100 includes a gas supply system 1, a projection lens 2, a wafer stage 3, a reticle stage 5, illumination system optics 7, and an F ₂ laser oscillator (not shown) as an exposure light source. )). The casing of the exposure apparatus 100 is omitted.

As the projection optical system, the projection lens 2 projects the exposure light irradiated from the F ₂ laser oscillator serving as the exposure light source and passed through the reticle 6 (an example of a mask) onto the wafer 4. During exposure, the wafer 4 is set on the wafer stage 3 and the reticle 6 is set (arranged) on the reticle stage 5. 2, the gas supply system 1 includes a gas supply line 11, a gas exhaust line 12, a gas mixing tank 13 (reservoir tank), a high-purity nitrogen supply line 14, an oxygen supply line 15, an oxygen cylinder 16, Two mass flow controllers 17 are provided, and high purity nitrogen supplied from the factory and oxygen supplied from the oxygen cylinder 16 are mixed to a predetermined amount of oxygen concentration in the gas mixing tank 13, and from the gas supply line 11. A mixed gas is supplied and exhausted from the gas exhaust line 12. Note that the presence or absence of the gas exhaust line 12 may be either. Further, a vacuum pump may be connected to the gas exhaust line 12. In other words, the gas supply system 1 as an example of the gas supply unit has a high purity nitrogen (which is an example of an inert gas) and oxygen (active gas) in the space between the projection lens 2 and the wafer stage 3. A predetermined gas (mixed gas) to which is added) is supplied.

  Next, the operation of the exposure apparatus will be described.

  FIG. 3 is a flowchart showing the operation of the exposure apparatus in the first embodiment.

  The first embodiment is particularly effective for the exposure apparatus 100 that uses light having a wavelength of 200 nm or less absorbed by air as exposure light.

  First, the resist-coated wafer 4 (photosensitive substrate) is transferred to the wafer stage 3 via a wafer transfer arm (not shown).

In S (step) 301, as an inert gas supply step, F ₂ laser oscillator internal, F ₂ (not shown) the beam line from the laser oscillator to the illumination optical system 7 inside, inside the illumination optical system 7, the reticle stage 5 near In this space, the inside of the projection lens 2 is purged with high-purity nitrogen. After that, it is constantly purged to prevent oxygen and water molecules from entering.

In S302, as a mixed gas supply step, a space (in other words, a wafer region) between the surface of the projection lens 2 (which is an example of a lens immediately above the wafer) facing the wafer stage 3 and the wafer stage 3 is provided. The gas supply system 1 starts supplying a mixed gas (nitrogen + oxygen) controlled to a predetermined amount of oxygen concentration and controlled to a predetermined amount of flow rate. Thereafter, a mixed gas is always supplied. A suitable concentration of oxygen is 20 to 10,000 ppm. In other words, the gas supply system 1 which is an example of the gas supply unit supplies the predetermined gas in which the concentration of the active gas is controlled from 20 ppm to 10,000 ppm. A higher oxygen concentration promotes degassing decomposition from the resist, but the exposure light transmittance decreases. Further, the flow rate of the supplied mixed gas is suitably in the range of 0.3 L · min ⁻¹ to 10 L · min ⁻¹ . In other words, the gas supply system 1 which is an example of the gas supply unit supplies the predetermined gas controlled from 0.3 L · min ⁻¹ to 10 L · min ⁻¹ .

  In S303, it is determined whether the inert gas supply step and the mixed gas supply step have been sufficiently performed. In other words, whether or not the oxygen concentration in the space between the surface of the projection lens 2 and the wafer stage 3 is equal to the oxygen concentration of the supply gas is determined, for example, by measuring with a densitometer. The oxygen concentration is measured as follows. First, gas in a space is sucked from a location where oxygen concentration is measured using piping, and the oxygen concentration of the sucked gas is measured by an oxygen concentration meter. By actually measuring, more accurate oxygen concentration management becomes possible.

In S304, as an exposure process, the wafer 4 coated with the resist transported to the wafer stage 3 is exposed. The light oscillated from the F ₂ laser oscillator passes through the illumination optical system 7 and the reticle 6, and further passes through the projection lens 2 to expose the resist applied to the wafer 4. Thereafter, the wafer 4 is unloaded via the wafer transfer arm. Subsequently, the next exposure process is performed through the same operation. The active gas is activated by the light oscillated from the F ₂ laser oscillator, and the exposure apparatus 100 can decompose the degassing from the resist using the activated active gas.

In this example, the projection lens 2 has no cover. However, when the projection lens 2 is installed, the F ₂ laser oscillator, the beam line from the F ₂ laser oscillator to the illumination optical system 7, the illumination Purge with nitrogen is performed inside the optical system 7, the space near the reticle stage 5, and the inside of the projection lens 2 up to the cover of the projection lens 2 (an example of the cover of the lens directly above the wafer). Further, in a space between the surface of the cover of the projection lens 2 facing the wafer stage 3 and the wafer stage 3, a mixed gas controlled by the gas supply system 1 to a predetermined amount of oxygen concentration and a predetermined amount of flow. Supply.

Here, the purge gas inside the F ₂ laser oscillator, inside the beam line from the F ₂ laser oscillator to the illumination optical system 7, inside the illumination optical system 7, near the reticle stage 5, and inside the projection lens 2 is nitrogen, An inert gas such as He may be used. As the inert gas, any gas belonging to a rare gas group in the periodic table of elements may be used.

Here, the mixed gas supplied to the space between the surface of the projection lens 2 and the wafer stage 3 by the gas supply system 1 is a mixed gas of nitrogen and oxygen, but inert such as He instead of nitrogen. Gas may be used. As described above, the inert gas may be any gas belonging to the rare gas group in the periodic table. Further, ozone, nitrogen oxides (NO _x ), sulfur oxides (SO _x ), and other gaseous substances containing oxygen atoms may be used instead of oxygen. In other words, the active gas may be any gas substance containing oxygen atoms.

Embodiment 2. FIG.
In the first embodiment, the gas supply system 1 always supplies the mixed gas supplied to the space between the surface of the projection lens 2 and the wafer stage 3. However, in the second embodiment, the wafer 4 is attached to the wafer stage 3. It may be until the exposure of one wafer 4 is completed after being conveyed upward. However, in this case, after supplying the mixed gas, the next exposure process is performed as compared with the first embodiment until the oxygen concentration in the space between the surface of the projection lens 2 and the wafer stage 3 becomes equal to the oxygen concentration of the supply gas. I need to wait a long time.

Embodiment 3 FIG.
FIG. 4 is a flowchart showing the operation of the exposure apparatus in the third embodiment.

  Except for S403, the process is the same as in FIG. In the first and second embodiments, whether or not the oxygen concentration in the space between the surface of the projection lens 2 and the wafer stage 3 is equal to the oxygen concentration of the supply gas in S303 in FIG. Although it is determined by measurement, in S403 instead of S303, the inert gas supply step and the mixed gas supply step are started to determine whether the inert gas supply step and the mixed gas supply step are sufficiently performed. Thereafter, if the predetermined period T has elapsed, it is determined that the inert gas supply step and the mixed gas supply step have been sufficiently performed. By managing with the purge time, simple oxygen concentration management becomes possible. In such a case, when the wafer 4 is transported and replaced, the space between the surface of the projection lens 2 and the wafer stage 3 is opened to the external space even when the wafer 4 is constantly purged and the entry of oxygen and water molecules is prevented. In some cases, the oxygen concentration increases. Therefore, in the second and subsequent exposures to the wafer 4, after the space between the surface of the projection lens 2 and the wafer stage 3 and the external space are closed, the inert gas supply step and the mixed gas supply step are performed. It is preferable that the process proceeds to S304 after a predetermined period Ti in which it can be determined that the above has been sufficiently performed.

  As described above, the gas supply system 1 installed in the exposure apparatus 100 according to the above-described embodiment is an inert gas containing a predetermined amount of active gas between the projection lens 2 or the projection lens cover and the wafer stage. It is characterized by introducing gas.

  In addition, the gas supply system 1 can mix an active gas into a pure inert gas and can control the active gas concentration to be uniform, and can introduce the gas at a constant flow rate. It is characterized by that.

  The gas supply system 1 is controlled to have an active gas concentration of 20 ppm to 10,000 ppm.

The gas supply system 1 is controlled to have a gas flow rate of 0.3 L · min ⁻¹ to 10 L · min ⁻¹ .

  The exposure apparatus 100 is an exposure apparatus that uses light having a wavelength of 200 nm or less, which is absorbed into the normal atmosphere, as exposure light, and exposes the exposure light source to the inside of the projection lens through the beam line, illumination optical system, and mask. An inert gas whose air path is hermetically sealed with an inert gas and the active gas is mixed in a uniform concentration by the gas supply system on the surface of the projection lens with respect to the wafer or the exposure optical path between the projection lens cover and the wafer stage. The gas is supplied at a constant flow rate.

  Further, the exposure apparatus 100 does not provide an exposure optical path from the exposure light source to the inside of the projection lens through the beam line, illumination optical system, and mask in exposure using light having a wavelength of 200 nm or less, which is absorbed in normal air. An inert gas mixed with an active gas at a uniform concentration in the gas supply system is hermetically sealed with an active gas, and the projection lens surface with respect to the wafer or an exposure optical path between the projection lens cover and the wafer stage. It is characterized by being carried out while supplying at a constant flow rate.

Further, the gas supply system 1, the exposure apparatus 100, and the exposure method using these use either N ₂ or a rare gas such as He as the inert gas.

The gas supply system 1, the exposure apparatus 100, and the exposure method using them include oxygen, ozone, nitrogen oxides (NO _x ), sulfur oxides (SO _x ), and other oxygen atoms as the active gas. Any of the gaseous substances to be contained is used.

  Further, the wafer 4 is processed into a semiconductor device by the above exposure method.

1 is a simplified diagram for explaining an exposure apparatus according to Embodiment 1. FIG. It is a figure for demonstrating the gas supply system by Embodiment 1. FIG. FIG. 7 is a flowchart showing the operation of the exposure apparatus in the first embodiment. FIG. 10 is a flowchart showing the operation of the exposure apparatus in the third embodiment. F ₂ is a diagram illustrating a degassing type by irradiation of F ₂ laser lithography resist.

Explanation of symbols

  1 gas supply system, 2 projection lens, 3 wafer stage, 4 wafer, 5 reticle stage, 6 reticle, 7 illumination optical system, 11 gas supply line, 12 gas exhaust line, 13 gas mixing tank, 14 high purity nitrogen supply line, 15 oxygen supply line, 16 oxygen cylinder, 17 mass flow controller, 100 exposure apparatus.

Claims (7)

A projection optical system that projects the exposure light irradiated from the exposure light source and passed through the mask onto the wafer;
A wafer stage for placing the wafer;
An exposure apparatus comprising: a gas supply unit that supplies a predetermined gas obtained by adding an active gas to an inert gas into a space between the projection optical system and the wafer stage.   2. The exposure apparatus according to claim 1, wherein the gas supply unit supplies the predetermined gas whose concentration of the active gas is controlled from 20 ppm to 10000 ppm. 2. The exposure apparatus according to claim 1, wherein the gas supply unit supplies the predetermined gas controlled from 0.3 L · min ⁻¹ to 10 L · min ⁻¹ .   2. The exposure apparatus according to claim 1, wherein the exposure apparatus uses light having a wavelength of 200 nm or less absorbed by air as exposure light.   2. The exposure apparatus according to claim 1, wherein the inert gas is nitrogen or any gas belonging to a rare gas group in the periodic table.   2. The exposure apparatus according to claim 1, wherein the active gas uses any one of gaseous substances containing oxygen atoms. A projection step of projecting exposure light irradiated from an exposure light source and passing through a mask onto a wafer via a projection optical system;
A gas supply step of supplying a predetermined gas obtained by adding an active gas to an inert gas to a space between the projection optical system and the wafer stage on which the wafer is disposed;
An exposure step of exposing the wafer disposed on the wafer stage in a state where the predetermined gas is supplied to a space between the projection optical system and the wafer stage by the gas supply step. Exposure method.

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