JP2010232242A - Reflection type projection optical system, and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type projection optical system and an exposure device that easily achieve a high NA. <P>SOLUTION: The reflection type projection optical system which has an object plane side made non-telecentric and projects an image of an object plane MS on an image plane W includes a plurality of reflecting mirrors M1 to M6, and a diaphragm member AS inclined to a plane perpendicular to an optical axis AX. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflective projection optical system and an exposure apparatus.

  Patent Document 1 discloses a reflection type projection optical system including six reflecting mirrors in an exposure apparatus that uses extreme ultraviolet light. Patent Document 2 discloses a reflection type projection optical system including six reflecting mirrors having a relatively large numerical aperture (NA) on the image side and an aperture stop disposed between a first reflecting surface and a second reflecting surface. The system is disclosed.

International Publication No. 02/48796 JP 2005-101591 A

  High NA is effective in achieving high resolution, but conventionally, even if an attempt was made to increase NA, the luminous flux was vignetted in the vicinity of the aperture stop, so that the NA could not be sufficiently increased.

  An object of the present invention is to provide a reflective projection optical system and an exposure apparatus that can easily achieve a high NA.

  A reflective projection optical system according to one aspect of the present invention is a reflective projection optical system in which an object plane side is configured to be non-telecentric and projects an image of an object plane onto an image plane. And a diaphragm member inclined with respect to a plane perpendicular to the surface.

  The present invention can provide a reflective projection optical system and an exposure apparatus that can easily achieve a high NA.

It is an optical path figure of the projection optical system of a present Example. It is the elements on larger scale of FIG.

  FIG. 1 is an optical path diagram in the vicinity of the reflective projection optical system of the exposure apparatus of the present embodiment. The exposure apparatus is an exposure apparatus that exposes an image of an original (mask or reticle) pattern onto a substrate (wafer or liquid crystal substrate) using EUV light. The exposure apparatus includes a light source, an illumination optical system, an original stage, a reflective projection optical system, and a substrate stage.

  The light source emits EUV light, and a laser plasma light source or a discharge plasma light source can be used. The illumination optical system uniformly illuminates the original, and has a condensing reflector and an optical integrator. The original is a reflective original having a pattern to be transferred and disposed on the object surface MS. The original stage supports and drives the original. The substrate is placed on the image plane W and is coated with a photoresist. The substrate stage supports and drives the substrate.

  The reflective projection optical system maintains a conjugate relationship between the object plane MS and the image plane W, and reduces and projects a pattern image of the original (mask or reticle) onto the substrate (wafer or liquid crystal substrate). The illumination area on the object plane and the exposure area on the image plane are not on the optical axis AX. This is to prevent the light flux from being vignetted by the reflective optical element or the diaphragm member. In addition, since the reflective master is used, the reflective projection optical system is non-telecentric on the object plane side.

  The reflective projection optical system has a plurality of reflecting mirrors. Each reflecting mirror is provided with a multilayer film that reflects EUV light. The plurality of reflecting mirrors are six reflecting mirrors in this embodiment, but the present invention is not limited to six such as four to eight.

  In the present embodiment, the plurality of reflecting mirrors reflect the first reflecting mirror M1, the second reflecting mirror M2, the third reflecting mirror M3, and the fourth reflecting in the order in which light is reflected from the object plane MS along the optical path. It comprises a mirror M4, a fifth reflecting mirror M5, and a sixth reflecting mirror M6. An intermediate image IM is formed between the fourth reflecting mirror M4 and the fifth reflecting mirror M5 along the optical path. The reflective projection optical system is arranged so as to form a coaxial system, but the reflecting mirror may be decentered or rotated.

If the radius of curvature of each reflecting mirror is r _i , the sum of Petzval terms expressed by the following equation must be zero or almost zero.

  At least one of the plurality of reflecting mirrors includes an aspherical surface. The aspheric shape is defined by the following equation. From the viewpoint of aberration correction, it is better to have as many aspheric surfaces as possible.

  In Equation 3, Z is the coordinate in the optical axis direction, c is the curvature (the reciprocal of the radius of curvature r), h is the height from the optical axis, k is the cone coefficient, A, B, C, D, E, F, G, H, J... Are aspherical coefficients of 4th order, 6th order, 8th order, 10th order, 12th order, 14th order, 16th order, 18th order, 20th order,.

  A diaphragm member (aperture diaphragm) AS is disposed between the first reflecting mirror M1 and the second reflecting mirror M2. The aperture member AS is inclined with respect to a plane perpendicular to the optical axis AX (that is, not perpendicular to the optical axis AX). The light beam traveling from the first reflecting mirror M1 toward the second reflecting mirror M2 is directed from the upper right to the lower left (from the image plane side to the object plane side) in FIG. 1, and in this case, the diaphragm member AS will be described later. It tilts counterclockwise around the point O shown in FIG. By tilting the aperture member AS in this direction, the vignetting of the light beam can be reduced and the NA can be increased. This will be described in more detail later.

  The diameter of the aperture member AS may be fixed or variable. In the case of being variable, the NA of the reflective projection optical system can be changed by changing the diameter of the aperture member. The shape of the aperture member AS may be circular or elliptical.

  FIG. 2 is a partially enlarged view of FIG. 1 and an enlarged view of the meridional surface in the vicinity of the aperture member AS. FIG. 2 shows an outer edge ray (or marginal ray) R1 passing through the upper end of the aperture stop AS, a principal ray PR, and an outer edge ray (or marginal ray) R2 passing through the lower end of the aperture stop AS. Show. Further, AS1 is a diaphragm member arranged perpendicular to the optical axis AX as in the prior art. Point O is the intersection of principal ray PR and optical axis AX. A pair of thick lines of the diaphragm member AS and the diaphragm member AS1 are light shielding portions, and an opening is provided between them.

In FIG. 2, the angles at which the pair of outer edge rays R1 and R2 enter the diaphragm member AS1 are α (°) and β (°), respectively. That is, the angle at which the outer edge ray R1 is incident on the aperture member AS1 is α (°). Further, an angle at which the outer edge ray R2 is incident on the aperture member AS1 is β (°). The numerical aperture on the image side of the outer edge ray R1 is NA _a (= n · sin α _img ), and the numerical aperture on the image side of the outer edge ray R1 is NA _b (= n · sin β _img ). However, n is a refractive index, α _img (°) is an angle at which the outer edge ray R 1 is incident on the image plane W, and β _img (°) is an angle at which the outer edge ray R 2 is incident on the image plane W. Furthermore, A, B, and S are defined as the following formulas.

  Assuming that the inclination angle with respect to the surface perpendicular to the aperture member AS and the optical axis AX (or the aperture member AS1) is θ (°), θ satisfies the following equation.

  Formula 8 represents the angular relationship between the aperture member AS and the object plane MS. When the upper limit or lower limit is exceeded, the NA difference between the upper line and the lower line increases on the image side. As described above, since the reflection type projection optical system is non-telecentric on the object plane side in order to use the reflection type master, the numerical aperture of the light beam has directionality for each image height. The anisotropy has directionality in the resolving power, and nonuniformity occurs in the pattern formed on the substrate. Equation 8 is a condition for reducing the pattern non-uniformity within a practical range.

  In exposure, EUV light illuminates the original and forms an original pattern on the substrate. The image surface becomes an arc-shaped image surface, and the entire surface of the original is exposed by scanning the original and the substrate at a reduction ratio.

Tables A and B show the specifications of the reflective projection optical system (curvature radius R, surface interval D, aspheric coefficient).
(Table A)
Mirror number Curvature radius (mm) Surface spacing (mm)
M (mask) 0 694.84276
M1 -716.2476 -219.13081
Aperture stop 0 -114.33524
M2 -1550 241.59945
M3 721.61644 -261.49378
M4 586.31403 817.09236
M5 296.69119 -353.73198
M6 430.1551 401.2495
W (wafer) 0 0
(Table B)
Aspheric coefficient K A B C
M1 -1.92463E + 00 8.59913E-10 -2.03466E-14 4.62151E-19
M2 -2.88259E-01 -2.29465E-09 8.45007E-14 -1.61951E-17
M3 1.17791E + 00 -1.85904E-09 -8.39806E-14 1.11840E-17
M4 -3.00880E-02 2.80737E-11 -1.37915E-15 2.11145E-20
M5 3.12023E-01 -1.03445E-09 1.58463E-12 -8.00021E-17
M6 3.02209E-02 4.87630E-11 3.48587E-16 5.93966E-22
Aspheric coefficient D E F G
M1 -8.54869E-24 -2.76473E-28 3.16917E-32 -7.82844E-37
M2 7.60003E-21 -1.92909E-24 2.47481E-28 -1.19995E-32
M3 -8.47167E-22 3.85393E-26 -9.68293E-31 1.03379E-35
M4 -9.66767E-26 -1.37500E-30 1.93512E-35 -6.99842E-41
M5 2.19921E-21 8.72805E-24 -3.83620E-27 5.39287E-31
M6 1.37823E-25 -5.78066E-30 1.46588E-34 -1.55827E-39
In the first embodiment, the diaphragm member AS is inclined by 20 degrees with respect to a plane perpendicular to the optical axis AS. Table C shows the lengths a to d in FIG. By tilting the aperture member AS, there is a margin for light beam interference, which is advantageous for increasing the NA. In addition, there is room for the arrangement of the apparatus.
(Table C)
Clearance (mm)
a 9.642
b 4.034
c 17.55
d 12.44
In Example 1, the distance (full length) between the object plane MS and the image plane W on the optical axis is 1206.0092 mm. The numerical aperture on the image side is 0.27, the magnification is 1/4, and the object height is 126 to 134 mm (arc-shaped field of view with a width of 2 mm on the image side). The RMS of wavefront aberration is 14.4 mλ, and the static distortion is 2.3 nm in range.

On the other hand, when the aperture stop AS1 shown in FIG. 2 is used, NA _a is 0.2642, NA _b is 0.2758, and an NA difference is generated. Since NA _a is the numerical aperture on the image side of the outer edge ray R1, the difference between NA _a and NA _b can be reduced by making the upper diameter of the diaphragm member AS1 larger than the diameter of the lower side of the diaphragm member AS1. it can.

In order to perform this correction, when α> β, as shown in FIG. 2, the aperture member AS1 is tilted like the aperture member AS in the direction to avoid the vignetting of the light beam so that the upper diameter of the aperture member is reduced. It can be larger than the lower diameter. In FIG. 2, since α = 18.27 ° and β = 11.31 °, the condition is satisfied, and from Equation 7, θ _opt = 19.64 °. −5 ° <0.36 ° <5 °, which satisfies Expression 7.

Table D shows the NA for each image height when the aperture member AS1 is used. Table E shows the NA for each image height when the aperture member AS is used. In Tables D and E, the “NA upper line” is the NA calculated from the angle at which the upper outer edge ray R1 is incident on the image plane W. The “NA underline” is an NA calculated from an angle at which the lower outer edge ray R2 enters the image plane W.
(Table D)
Object height (mm) NA overline NA underline NA overline-NA underline NA meli NA saji
126 0.265176 -0.27629 -0.011114 0.270733 0.278261
130 0.264197 -0.2758 -0.011606 0.27 0.277993
134 0.263187 -0.27531 -0.012123 0.2692485 0.277718
(Table E)
Object height (mm) NA overline NA underline NA overline-NA underline NA meli NA saji
126 0.270213 -0.26976 0.000454 0.269986 0.270474
130 0.269949 -0.27005 -0.000102 0.27 0.270215
134 0.269652 -0.27034 -0.000688 0.269996 0.26995
As can be seen from the above table, the NA difference between the outer edge rays R1 and R2 is reduced by the total image height by tilting the diaphragm member from the plane perpendicular to the optical axis AX. Further, the NA difference between the meridional direction and the sagittal direction is also reduced, and the anisotropy of NA is reduced.

  As described above, the reflection type projection optical system of the present embodiment can increase the NA by allowing the clearance of the light beam in the vicinity of the diaphragm member to be increased, can reduce the anisotropy of the NA for each image height, and can achieve high resolution. Good image performance can be achieved.

  Devices (semiconductor integrated circuit elements, liquid crystal display elements, etc.) use an exposure apparatus to expose a substrate (wafer, glass plate, etc.) coated with a photosensitive agent, develop a substrate, and other well-known methods And a process (device manufacturing method).

  The reflective projection optical system can be applied to an exposure apparatus. The exposure apparatus can be applied to an application for manufacturing a device.

MS Object surface W Image surface AS Aperture member M1 to M6 Reflector AX Optical axis

Claims (4)

A reflection type projection optical system configured such that the object plane side is non-telecentric and projects an image of the object plane onto the image plane;
Multiple reflectors,
A diaphragm member inclined with respect to a plane perpendicular to the optical axis;
A reflective projection optical system comprising: The angles at which a pair of outer edge rays are incident on the plane perpendicular to the optical axis on the meridional plane are α and β, respectively, and the numerical apertures on the image side of the pair of outer edge rays are NA _a and NA _b , respectively. The reflective projection optics according to claim 1, wherein θ satisfies the following equation, where θ is defined as the following equation, and an inclination angle with respect to a plane perpendicular to the diaphragm member and the optical axis is θ. system.




  An exposure apparatus comprising the reflective projection optical system according to claim 1. Exposing the substrate using the exposure apparatus of claim 3;
Developing the exposed substrate;
A device manufacturing method comprising: