JP4366990B2 - Projection optical system, exposure apparatus and exposure method - Google Patents

Description

この投影露光装置による最大像高Ｙは、当該投影露光装置固有の値であり、１３．７３ｍｍである。又、最も基板側のレンズ面の曲率半径（Ｇ２３−Ｒ２）は、５２．０５７ｍｍである。よって、Ｒ／Ｙの値は、３．７９１となる。
また、この投影露光装置において用いられる液浸用液体１ｃｍあたりの光の透過率Ｔ１は、０．９０であり、液体中の光路のうち短いものの距離Ｕ１は、０．３５６ｃｍであり、長いものの距離Ｌ１は、０．５９８ｃｍである。又、投影光学系内の吸収率の高いレンズ硝材１ｃｍあたりの光の透過率Ｔ２は、０．９８であり、Ｕ１の光路を投影光学系内でたどる光線の当該レンズ内を透過する光路の距離Ｕ２は、５．０４９ｃｍ、Ｌ１の光路を投影光学系内でたどる光線の当該レンズ内を透過する光路の距離Ｌ２は、２．５０５ｃｍである。このＵ２、Ｕ２の値はＬ１、Ｌ１の投影光学系内の光路を計算することにより求めることができる。よって、｛１−（Ｔ１＾Ｕ１）＊（Ｔ２＾Ｕ２）｝／｛１−（Ｔ１＾Ｌ１）＊（Ｔ２＾Ｌ２）｝の値は、１．２１２となり、結像性能に悪影響を与えることはない。
ここで、比較として、このような吸収率の高いレンズを入れない場合、即ち、前記において吸収率の高いとされたレンズが他のレンズと同様に光をほとんど吸収せず透過する場合、近似的にＴ２を１と考えることができるため、｛１−（Ｔ１＾Ｕ１）＊（Ｔ２＾Ｕ２）｝／｛１−（Ｔ１＾Ｌ１）＊（Ｔ２＾Ｌ２）｝の値は、０．６０３となり、光の強度差が大きく、結像性能に悪影響を与える。
【００１９】
本発明に基づく具体的な第２実施例を説明する。
第２実施例は図４の構成に基づくもので、表２のレンズデータを有した投影光学系である。
【００２０】
【表２】

この投影露光装置による最大像高Ｙは、当該投影露光装置固有の値であり、１３．７３ｍｍである。又、最も基板側のレンズ面の曲率半径（Ｇ２７−Ｒ２）は、４２．１８６ｍｍである。よって、Ｒ／Ｙの値は、３．０７３となる。
また、この投影露光装置において用いられる液浸用液体１ｃｍあたりの光の透過率Ｔ１は、０．９０であり、液体中の光路のうち短いものの距離Ｕ１は、０．７６４ｃｍであり、長いものの距離Ｌ１は、１．３７７ｃｍである。又、投影光学系内の吸収率の高いレンズ硝材１ｃｍあたりの光の透過率Ｔ２は、０．９８であり、計算によりＵ１の光路を投影光学系内でたどる光線の当該レンズ内を透過する光路の距離Ｕ２は、４．３１５ｃｍ、Ｌ１の光路を投影光学系内でたどる光線の当該レンズ内を透過する光路の距離Ｌ２は、１．１４６ｃｍである。
よって、｛１−（Ｔ１＾Ｕ１）＊（Ｔ２＾Ｕ２）｝／｛１−（Ｔ１＾Ｌ１）＊（Ｔ２＾Ｌ２）｝の値は、０．９９７となり、結像性能に悪影響を与えることはない。
【００２１】
ここで、比較として、このような吸収率の高いレンズを入れない場合、即ち、前記において吸収率の高いとされたレンズが他のレンズと同様に光をほとんど吸収せず透過する場合、近似的にＴ２を１と考えることができるため、｛１−（Ｔ１＾Ｕ１）＊（Ｔ２＾Ｕ２）｝／｛１−（Ｔ１＾Ｌ１）＊（Ｔ２＾Ｌ２）｝の値は、０．５７３となり、光の強度差が大きく結像性能に悪影響を与える。
【００２２】
【発明の効果】
本発明では、液浸の露光装置であっても収差や結像性能を劣化させることなく結像可能とすることができる。
特に、液浸に用いる液体が光を吸収する場合には、結像性能の劣化を回避することができ、所望の微細パターンを正確に焼き付けることができる。
【図面の簡単な説明】
【図１】は、液浸投影露光装置の概要図である。
【図２】は、液浸投影露光装置のうち、液浸となる部分の構成図である。
【図３】は、本発明の第１実施例による投影露光装置の光学系の構成図である。
【図４】は、本発明の第２実施例による投影露光装置の光学系の構成図である。
【符号の説明】
１・・・光源
２・・・照明光学系
３・・・レチクル
４・・・レチクルステージ
５・・・投影光学系
６・・・液体遮断板
７・・・ウエハステージ
８・・・ウエハ
８ａ・・・像面
９・・・投影光学系の最もウエハ側のレンズ
Ａ・・・光線
Ｂ・・・液体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection exposure apparatus and an exposure method having a projection optical system that prints and transfers a pattern drawn on an original onto a substrate.
[0002]
[Prior art]
In recent years, miniaturization of a pattern transferred to a wafer as a photosensitive substrate has been desired. In order to achieve this, two methods are conceivable: shortening the exposure wavelength or increasing the numerical aperture of the projection optical system. Conventionally, an immersion type projection exposure apparatus has been proposed as one of the methods for increasing the numerical aperture of the projection optical system. The immersion type projection exposure apparatus includes a space between the lens surface on the most wafer side of the projection optical system and the wafer, that is, a working distance (working distance) space (hereinafter referred to as working space) or the wafer side. It is a device that fills the space with a liquid such as water or oil. For example, the refractive index of oil is about 1.6, while the refractive index of air that occupies the operating space during normal use is 1.0. Therefore, if the entire working space or the wafer-side space is replaced with such a liquid having a high refractive index, the numerical aperture on the wafer side of the projection optical system can be increased and the exposure pattern can be miniaturized. .
[0003]
[Patent Document 1]
JP 2000-58436 A
[0004]
[Problems to be solved by the invention]
In the conventional immersion type projection exposure apparatus, when the entire working space is replaced with a liquid having a high refractive index, the refractive index value of the lens closest to the wafer in the projection optical system and the refractive index of the liquid If the values are the same, there is no problem, but in general, the refractive index value of the lens glass material is different from the refractive index value of the liquid used for immersion. Will occur.
By the way, in general, an immersion optical system does not assume that light emitted from a lens forms an image in the air, but aims to form an image in a liquid. Therefore, the generated aberration is different from that in the case of using in normal air.
[0005]
When aberration occurs in such an immersion optical system, it can be corrected, but depending on the shape of the lens, it may not be able to be eliminated by correction. There is a problem of being forced, and it becomes a problem to solve this problem.
In general, in a liquid immersion type projection optical system, the light transmittance of a lens used for this is often different from the light transmittance of a liquid used for liquid immersion. This tendency is particularly noticeable in the short wavelength region. In vacuum ultraviolet light such as excimer light represented by ArF, the transmittance of the glass material of the lens is high, but the liquid used for immersion absorbs light. Therefore, the transmittance is lower than that of the glass material.
[0006]
For this reason, if the optical path of the light beam that is imaged on the wafer is different, the amount of light absorbed in the liquid is different, which adversely affects the imaging performance. In other words, light rays that are imaged on the wafer are focused on a single point on the wafer through the projection optical system, and the light rays that pass through this projection optical system are projected. Rather than following the same optical path in the optical system, the light rays that follow various optical paths are condensed and imaged on the wafer. For this reason, when the immersion liquid absorbs light, the distance through which the liquid passes depends on the optical path followed by the light, and the amount of transmission of each light also differs. As a result, the intensity of the light is caused by the difference in the optical path followed by the light beam, which adversely affects the imaging performance.
More specifically, referring to FIG. 3, the light path length that passes through the liquid for immersion in the light beam formed at the position of the maximum image height has the shortest distance U1 and the longest distance L1. The distances that pass through it vary greatly. When this liquid absorbs light, the intensity of each light beam is increased and decreased, and the imaging performance is deteriorated. For this reason, it becomes a subject to prevent deterioration of imaging performance.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, according to a first aspect of the present invention, there is provided a projection optical system for transferring a pattern drawn on an original to a photosensitive surface of a substrate, the lens surface closest to the substrate of the projection optical system. In the projection optical system in which a predetermined liquid can be inserted into the space between the substrate and the photosensitive surface of the substrate, the radius of curvature of the lens surface closest to the substrate of the projection optical system is R and the projection is projected onto the photosensitive surface of the substrate. If the maximum image height is Y,
1 <R / Y <7
It is characterized by satisfying.
Here, immersion refers to filling a space between the lens surface closest to the substrate of the projection optical system and the photosensitive surface with a liquid.
The maximum image height Y indicates the distance to the imaging position farthest from the imaging center on the photosensitive surface. This maximum image height is a value unique to the projection exposure apparatus, and means the maximum distance from the imaging center at which an image can be formed without being adversely affected by aberrations or the like. For this reason, if this value becomes too small, the exposure area of one time becomes narrow, the production efficiency is remarkably lowered, and the significance as a production apparatus is lost.
[0008]
According to a second aspect of the present invention, there is provided a projection optical system for transferring a pattern drawn on an original plate onto a photosensitive surface of a substrate, the lens surface closest to the substrate of the projection optical system and the photosensitive surface of the substrate. In a projection optical system in which a predetermined liquid can be inserted in a space between them, all or a part of the glass material used in the projection optical system is formed of a light-absorbing glass material, and one of the light rays transmitted through the liquid is wherein the other light beam long a distance transmitted through the glass material with the light absorption of the distance which passes the liquid than the one light beam than the distance transmitted through the glass material with the light absorption was increased And
This makes it possible to reduce the amount of light absorbed by each light beam even when the immersion liquid absorbs light or when the optical path is different, and forms an image on the photosensitive surface of the substrate. Performance degradation can be avoided.
[0009]
According to a third aspect of the present invention, there is provided a projection optical system for transferring a pattern drawn on an original plate onto a photosensitive surface of a substrate, and comprising a lens surface closest to the substrate of the projection optical system and a photosensitive surface of the substrate. In the projection optical system in which a predetermined liquid can be inserted into the space between the optical paths for forming an image at a position where the maximum image height is projected onto the photosensitive surface of the substrate, the most of the projection optical system The optical path having the shortest optical path length between the lens surface on the substrate side and the photosensitive surface of the substrate is KU, where the light absorption rate in the optical path in the projection optical system traced between the original plate and the substrate is KU. The optical path having the longest optical path length between the lens surface on the most substrate side of the optical system and the photosensitive surface of the substrate is defined as KL in the optical path in the projection optical system that is traced between the original plate and the substrate. Glass materials used in the projection optical system All or part of it is made of a light-absorbing glass material, and the light beam that follows the short optical path that passes through the liquid increases the distance that passes through the light-absorbing glass material and passes through the liquid. By shortening the distance that the light beam that follows the long optical path passes through the light-absorbing glass material,
0.8 <KU / KL <1.25
It is characterized by satisfying.
[0010]
According to a fourth aspect of the present invention, in the third aspect, the transmittance per unit of the liquid medium immersed in the space is T1, and the image is at a position where the maximum image height is projected onto the photosensitive surface. The optical path length between the lens surface on the most substrate side of the projection optical system and the photosensitive surface is U1, and the longest optical path distance is L1. T2 is the transmittance per unit of the light-absorbing glass material in the projection optical system, and U2 is the length of the light beam that passes through the shortest optical path distance U1, and the longest optical path distance. When the length of the light beam that follows L1 passes through the glass material is L2,
0.8 <{1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} <1.25 is satisfied.
Here, * means a product, ^ means a power, and (T1 ^ U1) means U1 of T1.
[0011]
According to a fifth aspect of the present invention, there is provided a projection exposure apparatus having the projection optical system according to any one of the first to fifth aspects, wherein the lens surface closest to the substrate of the projection optical system and the photosensitive of the substrate. A predetermined liquid is inserted into a space between the substrate and a pattern drawn on the original plate is transferred to the photosensitive surface of the substrate.
Further, according to a sixth aspect of the present invention, in the exposure method using the projection exposure apparatus according to the fifth aspect, an illumination step of illuminating the original with predetermined exposure light, and the original via the projection optical system 5 And an exposure step of exposing the pattern image to the photosensitive surface of the substrate.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a projection exposure apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a view showing a projection exposure apparatus according to the present invention.
In the present embodiment, in an exposure method including an illumination process and an exposure process, a pattern image of the reticle 3 as an original is formed on the photosensitive surface 8a of the wafer 8 as a substrate. That is, a light beam emitted from a light source 1 such as an ArF excimer laser light source uniformly irradiates a pattern surface of a reticle 3 as an original placed on a reticle stage 4 through an illumination optical system 2. The exposure light emitted from the pattern surface of the reticle 3 forms an image of the pattern surface of the reticle 3 on the photosensitive surface 8 a of the wafer 8 placed on the XY stage 7 via the projection optical system 5.
A box-shaped liquid blocking plate 6 is installed on the XY stage 7. For the sake of simplicity, only the cross section of the liquid blocking plate 6 is shown in FIG. Then, a liquid such as water or oil can be put into the space surrounded by the liquid blocking plate 6 to make the working space a liquid. When the projection exposure apparatus of the present invention is used in a liquid immersion state, the liquid B is filled up to the broken line portion in FIG. 1 so that the entire space between the wafer 8 and the surface of the projection optical system 5 on the wafer 8 side is immersed in the liquid. The Rukoto.
[0013]
Here, the maximum image height formed on the exposure surface in FIG. 3 is Y (Y indicates the distance from the image formation center to the image formation position furthest away on the photosensitive surface), the most substrate side of the projection optical system. When the radius of curvature R of the lens surface is
1 <R / Y <7
By forming so as to satisfy the above, it is possible to easily correct aberrations without increasing the size of the lens.
[0014]
When R / Y is 1 or less, the maximum image height formed on the exposure surface is larger than the radius of curvature, and it is difficult to eliminate the aberration by correction or the like. In particular, in the case of a concave lens having a large aperture and a radius close to the curvature radius, a part of the light beam emitted from the lens may enter the lens again, and in this case, the imaging performance is extremely deteriorated. Further, in a lens having a small radius of curvature, it is difficult to supply and discharge liquid in the space between the lens and the substrate in a short time, which causes a reduction in throughput and impairs the function as a production apparatus. Further, when R / Y is 7 or more, it is difficult to correct the field aberration, and it is necessary to increase the lens outer diameter. Therefore, in order to ensure the function as a production apparatus without increasing the size of the lens, R / Y needs to be within the above range.
In particular, if attention is paid to the improvement of the throughput of the production apparatus, it is desirable that the range of 2 <R / Y <7.
Further, in the projection optical system, the light absorption amount is substantially the same between the reticle 3 serving as the original and the wafer 8 serving as the substrate, regardless of the optical path followed by the light, so that the liquid light used for the immersion can be obtained. This eliminates the deterioration of the imaging performance caused by the absorption of light. Specifically, a part of the glass material used in the projection optical system is formed of a glass material with a low transmittance, and the light beam in the optical path having a long distance transmitting through the liquid has a short distance to transmit through the glass material with a low transmittance. However, the light beam having a short distance that passes through the liquid has a longer distance through the glass material having a low transmittance.
[0015]
In the projection optical system having such a configuration, even if light rays emitted from the same starting point follow different optical paths, the amount of light absorption is almost the same, and light of the same intensity reaches the wafer 8, so that imaging performance is achieved. Will not be adversely affected.
The amount of light absorption is adjusted by using a glass material with low light transmittance, but a gas that absorbs light, for example, part of the atmosphere, is introduced into the lens and the lens space in the projection optical system. Therefore, it is possible to desire the same effect. However, such a gas causes fogging of the lens surface, and the imaging performance is deteriorated due to the fluctuation of the gas, and this solution is not found. It is not a solution.
[0016]
What can be used as a lens that absorbs light as described above is also limited in the projection optical system, and it is difficult to make the amount of absorption completely the same regardless of the optical path, but this value is 0.8 to 1 If it is within the range of .25, the imaging performance is hardly affected. In other words, if it is out of this range, the amount of light absorption differs depending on the optical path, and the imaging performance is significantly deteriorated. Will not deteriorate.
[0017]
A specific first embodiment according to the present invention will be described.
The first embodiment is based on the configuration of FIG. 3 and is a projection optical system having the lens data shown in Table 1. Here, r is a radius of curvature, d is a center thickness / surface interval, and n is a refractive index.
[0018]
[Table 1]

The maximum image height Y by this projection exposure apparatus is a value unique to the projection exposure apparatus, and is 13.73 mm. Further, the radius of curvature (G23-R2) of the lens surface closest to the substrate is 52.057 mm. Therefore, the value of R / Y is 3.791.
The light transmittance T1 per 1 cm of the immersion liquid used in this projection exposure apparatus is 0.90, and the distance U1 of the short one of the optical paths in the liquid is 0.356 cm, which is a long distance. L1 is 0.598 cm. The light transmittance T2 per 1 cm of the lens glass material having a high absorptance in the projection optical system is 0.98, and the distance of the light path that passes through the lens in the projection optical system through the optical path U1. U2 is 5.049 cm, and the distance L2 of the optical path that passes through the lens of the light beam that follows the optical path of L1 in the projection optical system is 2.505 cm. The values of U2 and U2 can be obtained by calculating the optical paths in the L1 and L1 projection optical systems. Therefore, the value of {1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} is 1.212, which adversely affects the imaging performance. There is no.
Here, as a comparison, when such a lens with high absorptance is not inserted, that is, when a lens with a high absorptance in the above does not absorb light like other lenses and transmits, it is approximate. Since T2 can be considered as 1, the value of {1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} is 0.603. The light intensity difference is large, which adversely affects the imaging performance.
[0019]
A specific second embodiment based on the present invention will be described.
The second embodiment is based on the configuration of FIG. 4 and is a projection optical system having the lens data shown in Table 2.
[0020]
[Table 2]

The maximum image height Y by this projection exposure apparatus is a value unique to the projection exposure apparatus, and is 13.73 mm. The curvature radius (G27-R2) of the lens surface closest to the substrate is 42.186 mm. Therefore, the value of R / Y is 3.073.
Further, the light transmittance T1 per 1 cm of immersion liquid used in this projection exposure apparatus is 0.90, and the distance U1 of the short one of the optical paths in the liquid is 0.764 cm, which is a long distance. L1 is 1.377 cm. The light transmittance T2 per 1 cm of the lens glass material having high absorptance in the projection optical system is 0.98, and the optical path through which the light beam tracing U1 in the projection optical system is calculated is calculated. The distance U2 is 4.315 cm, and the distance L2 of the optical path that passes through the lens of the light beam that follows the optical path of L1 in the projection optical system is 1.146 cm.
Therefore, the value of {1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} is 0.997, which adversely affects the imaging performance. There is no.
[0021]
Here, as a comparison, when such a lens with high absorptance is not inserted, that is, when a lens with a high absorptance in the above does not absorb light like other lenses and transmits, it is approximate. Since T2 can be considered as 1, the value of {1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} is 0.573. The light intensity difference is large and adversely affects the imaging performance.
[0022]
【The invention's effect】
In the present invention, even an immersion exposure apparatus can form an image without deteriorating aberration and image formation performance.
In particular, when the liquid used for immersion absorbs light, it is possible to avoid deterioration of the imaging performance and to print a desired fine pattern accurately.
[Brief description of the drawings]
FIG. 1 is a schematic view of an immersion projection exposure apparatus.
FIG. 2 is a configuration diagram of a portion of the immersion projection exposure apparatus that is to be immersed.
FIG. 3 is a block diagram of an optical system of the projection exposure apparatus according to the first embodiment of the present invention.
FIG. 4 is a block diagram of an optical system of a projection exposure apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Illumination optical system 3 ... Reticle 4 ... Reticle stage 5 ... Projection optical system 6 ... Liquid blocking plate 7 ... Wafer stage 8 ... Wafer 8a ..Image surface 9 ... Lens A on the most wafer side of the projection optical system ... Light beam B ... Liquid

Claims (5)

A projection optical system for transferring a pattern drawn on an original to a photosensitive surface of a substrate, wherein a predetermined liquid is applied to a space between the lens surface closest to the substrate of the projection optical system and the photosensitive surface of the substrate. In an insertable projection optical system,
All or a part of the glass material used in the projection optical system is formed of a light-absorbing glass material, and the distance that one of the light rays transmitted through the liquid passes through the glass material having the light absorption is determined by the one light beam. A projection optical system characterized in that the light beam having a longer distance to transmit through the liquid is longer than the distance to transmit through the glass material having light absorption. Of the optical paths for forming an image at a position where the maximum image height is projected onto the photosensitive surface of the substrate, the optical path length between the lens surface closest to the substrate of the projection optical system and the photosensitive surface of the substrate The optical absorptance of light in the optical path in the projection optical system traced between the original plate and the substrate is KU, and the lens surface on the most substrate side of the projection optical system and the photosensitive surface of the substrate When the optical path having the longest optical path length between the original plate and the substrate is KL, the absorption rate in the optical path in the projection optical system
0.8 <KU / KL <1.25
The projection optical system according to claim 1, wherein: Of the optical path for forming an image at a position where the maximum image height projected onto the photosensitive surface of the substrate is T1, where the transmittance per unit of the liquid medium immersed in the space is T1, the projection optical system The optical path length between the lens surface closest to the substrate and the photosensitive surface of the substrate is U1, where the distance of the shortest optical path is L1, the distance of the longest optical path is L1, and a glass material having light absorption in the projection optical system. The transmissivity per unit is T2, the length that the light ray that follows the shortest optical path distance U1 passes through the glass material is U2, and the light ray that follows the longest light path distance L1 passes through the glass material. If the power is L2, and the power is represented by ^,
3. It satisfies 0.8 <{1- (T1 ^ U1) * (T2 ^ U2)} / {1- (T1 ^ L1) * (T2 ^ L2)} <1.25. The projection optical system described. A projection optical system according to claim 1 , wherein a predetermined liquid is inserted into a space between the lens surface closest to the substrate of the projection optical system and the photosensitive surface of the substrate. A projection exposure apparatus for transferring a pattern drawn on an original to a photosensitive surface of a substrate. In the method of exposing using the projection exposure apparatus according to claim 4 , an illuminating step of illuminating the original with predetermined exposure light;
And an exposure step of exposing the pattern image of the original on the photosensitive surface of the substrate through the projection optical system.

Images