JP2006269462A - Exposure apparatus and illuminating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus, having an illumination system for imparting an arbitrary polarization distribution to the light for illuminating masks. <P>SOLUTION: The exposure apparatus comprises a fly-eye lens array 104 arranged with fly eyes in a matrix form, in order to equalize the intensity of light being emitted from a light source, and an optical rotation element array 102, consisting of a plurality of optical rotation elements, arranged in correspondence with respective lens element of the fly-eye lens array 104, while having an optical axis parallel with the traveling direction of the light emitted from the light source and making the oscillation plane of passing light rotate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an illumination apparatus having an illumination optical system that controls a vibration plane of light, and more particularly to an exposure apparatus and an illumination apparatus used in a lithography process in a semiconductor device manufacturing process.

  In recent years, in the lithography process in the manufacturing process of semiconductor devices, high resolution exceeding the resolution limit determined from the wavelength of light is required as the pattern to be formed is miniaturized. Various super-resolution techniques that enable pattern formation have been applied.

  Recently, immersion exposure has been proposed that makes it possible to make the numerical aperture (NA) of the projection lens 1 or more by filling the space between the final surface of the projection lens and the exposure wafer with a liquid such as water. Even with an exposure apparatus using a 193 nm ArF laser as a light source, a semiconductor of 32 nm node (half pitch 45 nm) can be manufactured by immersion exposure of one or more NAs.

  Here, NA exceeding 1 is called Hyper-NA or the like, and development for manufacturing a device of 32 nm node (half pitch 45 nm) by ArF immersion is being studied.

  In such a Hyper-NA region, it is pointed out that the incident angle of the exposure light to the resist and the incident angle of the exposure light in the resist layer also increase, and in particular, the reduction of the image contrast due to the TM polarization component (P polarization component) becomes a problem. Yes. This is discussed in detail in Non-Patent Document 1 and the like.

  Furthermore, recently, a proposal has been proposed to improve image contrast by positively controlling the polarization of illumination light on a mask that has not been conventionally polarized. This is discussed in detail in Non-Patent Document 2 and the like.

T.A.Brunner, “High NA lithographic imagery at Brewster ’s angle” (SPIE Proceeding vol. 4691, pp1-10 B. Smith, “Benefiting form polarization-effects on high-NA imaging” (SPIE Proceeding vol.5377 part1, pp68-79

  However, although the above-mentioned document introduces azimuthal polarization illumination, radial polarization illumination, quadrupole linear polarization illumination, etc., no specific optical system for actually forming these polarization illuminations in an exposure apparatus has been proposed. .

  The present invention has been made to solve the above problems. That is, the present invention provides a fly-eye lens array in which lenses are arranged in a matrix to make the intensity of light emitted from the light source uniform, and is arranged corresponding to each lens element of the fly-eye lens array. The exposure apparatus includes an optical rotation element array having a plurality of optical rotation elements that have an optical axis parallel to the traveling direction of emitted light and rotate a vibrating surface of the passing light in proportion to its thickness.

  In the present invention as described above, a plurality of vibrating surfaces of light passing therethrough are rotated in proportion to the thickness corresponding to each lens element of the fly-eye lens array that equalizes the intensity of light emitted from the light source. Since the optical rotation element array including optical rotation elements is provided, the vibration plane orientation with respect to the angle of the light irradiated on the mask surface can be arbitrarily set.

  For example, if a quartz plate is used as the optical rotation element, the rotation angle of the vibration plane direction of the light can be controlled according to the thickness of the quartz plate in the optical axis direction, so that the quartz plate array corresponding to each lens element of the fly-eye lens array And the thickness thereof is controlled for each quartz plate element, so that the vibration plane of the light passing through corresponding to the element unit of the fly-eye lens, that is, the position in the equivalent light source, that is, the polarization direction can be controlled. .

  Therefore, according to the present invention, it is possible to form an arbitrary vibration azimuth distribution for each element of the fly-eye lens as the polarization state in the equivalent light source, and exposure that increases the incident angle to the resist in the Hyper-NA region. Even so, it is possible to appropriately control the vibration azimuth of the light that forms the image of the mask pattern in the resist, so that it is possible to suppress image contrast reduction. Thereby, the process margin of the lithography process can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a schematic configuration of an exposure apparatus according to the present embodiment. The illumination system applied in the exposure apparatus according to the present embodiment has a configuration in which the optical rotation element array 102 is arranged on the incident surface of the fly-eye lens array 104 that is an intensity uniformizing unit.

  The optical rotatory element array 102 has a configuration in which a plurality of optical rotatory elements are arranged in an array corresponding to each of a plurality of lens elements arranged in a matrix constituting the fly-eye lens array 104. It is characterized in that the rotation angle of the vibration surface of light passing therethrough is set by setting the thickness of the optical rotatory element in the optical axis direction. The incident light to the optical rotatory element array 102 is linearly polarized light, and the element material is, for example, quartz that is transparent to DUV (far ultraviolet) laser light such as ArF or KrF as exposure light.

  Here, when the optical axis of the optical rotatory element is arranged so as to be parallel to the light traveling direction (optical axis), and linearly polarized light is incident on the optical rotatory element, the polarization plane (vibration plane) rotates in proportion to the thickness. (For example, see Norito Suzuki and Takafumi Koshio, Applied Optics II, p.20).

  By utilizing this characteristic and controlling the thickness of each element of the optical rotation element array 102, an arbitrary vibration plane orientation can be formed for each element of the fly-eye lens array 103, and the light at each location in the equivalent light source can be formed. It is possible to obtain an arbitrary “polarized light source” whose vibration direction is arbitrarily controlled.

  Next, FIG. 1 shows an optical system from the equivalent light source surface 105 to the mask surface 108. In this optical system, the equivalent light source surface 105 and the mask surface 108 are in a Fourier transform relationship by the condenser lens 106. That is, position information in the equivalent light source surface 105 is converted into angle information on the mask surface 108. When the direction of the vibration surface of light is controlled on the fly-eye lens entrance surface 103 in element units, the orientation distribution of the light vibration surface is also maintained on the fly-eye lens exit surface 105 that is the pupil plane of the illumination optical system. Then, the photomask 108 serving as the original plate is illuminated through the condenser lens 106. Here, the azimuth distribution of the light vibration plane with respect to the angle in the light 107 that illuminates the mask corresponds to the azimuth distribution of the light vibration plane set for each element of the fly-eye lens array 102. This makes it possible to obtain a desired polarized illumination.

  Hereinafter, an exposure apparatus and a method for manufacturing a semiconductor device according to the present embodiment will be described in detail. Note that the exposure apparatus described here is an example used in a semiconductor device manufacturing process, and more specifically, on a wafer substrate by a projection mapping using a photomask in a lithography process in the semiconductor device manufacturing process. It is used to form a desired pattern on the applied photoresist.

  Next, a schematic configuration of the exposure apparatus will be described. FIG. 2 is a schematic diagram showing an example of the overall configuration of the exposure apparatus according to the present embodiment. First, a DUV laser (ArF excimer laser, wavelength 193 nm) serving as a light source will be described. Usually, the ArF excimer laser 200 used for the light source of the semiconductor exposure apparatus has a rectangular output beam shape 201, and the half-value width of the wavelength of the emitted light is narrowed to 1 pm or less. The polarization in the beam is typically about 98% or more polarized in the direction of the short side of the beam, and can be regarded as almost linearly polarized light.

  Reference numeral 202 in the figure denotes a beam shaping unit, which includes a cylindrical lens, a zoom lens, a DOE (Diffractive Optical Element), and the like, and shapes the beam into a predetermined size and shape. In this embodiment, it is assumed that the beam is shaped into a shape and size that match the outer shape of the fly-eye lens array 104 that is an intensity uniformizing element.

  Reference numeral 102 in the figure denotes an optical rotation element array which is a main configuration of the present embodiment. The material is, for example, quartz having a high transmittance in the DUV region. The optical axis is arranged in parallel with the light traveling direction (optical axis). More specifically, in this embodiment, it is assumed that the quartz crystal is a left quartz crystal whose polarization plane rotates counterclockwise when viewed from the near side in the light traveling direction.

In the arrangement as described above, when linearly polarized light enters the optical rotatory element array 102, the plane of polarization rotates in proportion to the thickness. The rotation angle ρ per unit length is called the optical rotation power. The value of quartz is 201.9 ° / mm (wavelength 226.) shown in Tsuruta, Applied Optics II, p167, Baifukan. 5 nm) and wavelength dependency (optical rotation dispersion) are proportional to 1 / wavelength ^2, and the optical rotation power ρ at an exposure wavelength of 193 nm is assumed to be 275 ° / mm.

  As a result, the optical rotation elements are arrayed in accordance with the fly-eye lens array, and the thickness of the crystal is changed for each element. In the present embodiment, azimuthal polarization in which the vibration plane orientations are distributed concentrically as shown in FIG. Here, the arrow in FIG. 3A represents the direction of the vibration plane of the light viewed from the incident surface side of the fly-eye lens array, and FIG. 3B shows the element arrangement of the fly-eye lens array and the optical rotation element array. It is a conceptual diagram. In this embodiment, since a scanning type exposure apparatus is assumed, the exposure field on the mask and the wafer is rectangular, and the lens elements constituting the fly-eye lens array are also rectangular.

  3 (a) and 3 (b), the dimensions of the unit elements of the optical rotation element array and the fly-eye lens array are X * Y = (2M + 1) * (2N + 1) arrays where the major axis L and the minor axis W are used. Assume. Further, it is assumed that the vibration surface of incident light is polarized in an azimuth direction of 90 ° as viewed from the incident side as shown in FIG.

  Assuming this as a reference for the optical rotation element array 102, the thickness of the optical rotation element of the center element (0, 0) is 360 ° / ρ = 1.31 mm. This is the reference thickness (Dc) of the optical rotation element array 303.

  The target vibration plane orientation θij in the element (i, j) is expressed by the following formula 1. Here, i is an integer from −M to M, and j is an integer from −N to N.

  Therefore, the thickness Dij in the optical rotatory element (i, j) is expressed by Equation 2.

  In this way, by using an optical rotatory element array with each element thickness changed, it becomes possible to change the orientation of the vibration surface in units of fly-eye lens elements, and the azimuthal polarization as shown in FIG. Can be formed on the surface. Since the thickness range of the optical rotatory element is about 1.31 mm at 360 °, actual processing is possible.

  As a result, polarized light having a vibration plane orientation of θij can be formed on each element ij of the fly-eye lens array 104, and the vibration plane orientation is maintained on the exit surface 105 of the fly-eye lens array 104 as shown in FIG. Yes. Since the exit surface 105 is a so-called equivalent light source surface (a conjugate surface of the projection lens pupil), the final goal is to form a desired polarization state on this surface.

  In addition, by installing an aperture serving as a light shield on the emission surface 105, the shape can be shaped into, for example, a circle, an annular zone, or a quadrupole.

  Each element of the fly-eye lens array 104 can improve intensity uniformity on the photomask 108 by subjecting the photomask 108 to wavefront division through the condenser lens 106 and then superimposing and illuminating. Further, as described in paragraph “0017”, since the equivalent light source surface 105 has a Fourier transform relationship with the mask surface 108, each point of the mask is illuminated at this time as indicated by reference numeral 207 in FIG. The vibration azimuth distribution with respect to the angle in the illumination light 107 corresponds to that of the exit surface 105.

  Further, the light illuminating the mask with a desired polarization distribution passes through the projection lens 209 and forms an image of the device pattern on the photomask on a photoresist (not shown) applied to the wafer 211 to be transferred. In this manner, polarized illumination having an arbitrary polarization distribution can be formed using Equations 1 and 2.

  Here, as a second embodiment, an illumination optical system combined with a DOE (Diffractive Optical Element) will be described. FIG. 4 is a schematic diagram for explaining the second embodiment. It is assumed that the incident laser beam LB is linearly polarized light with a 90 ° azimuth as shown in the figure.

  In the figure, reference numeral 400 denotes a DOE, which can form an arbitrary intensity distribution with respect to the angular direction while substantially maintaining the polarization state. This DOE design itself is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-242414. That is, a step of generating an initial solution of the phase function of the diffractive optical element, a step of calculating a point spread function by the initial solution of the phase function, a distribution of the point spread function, and the point spread function are determined. The target function may be designed based on a beam shaping element design method having a process of converging the solution of the phase function so as to be closest to the evaluation function by an optimization algorithm. By using DOE, an arbitrary intensity distribution light source can be configured with low loss. Reference numeral 401 in the figure denotes a collimating optical system, which converts an arbitrary intensity distribution formed by the DOE 400 into parallel rays.

  On the incident surface 402 of the optical rotatory element array 102, the vibration plane orientation of the original incident laser beam LB is substantially preserved, and is linearly polarized light of 90 ° orientation.

  As described in the first embodiment, by passing through the optical rotatory element array 102, the vibration surface of the incident light is rotated for each optical rotatory element, and the fly-eye lens element incident surface 404 has an element unit of the fly-eye lens. It is possible to have a distribution with different vibration plane orientations. Accordingly, it is possible to form an equivalent light source having an arbitrary intensity distribution and an arbitrary vibration plane orientation distribution on the fly-eye lens exit surface 406, that is, the equivalent light source surface (the conjugate surface of the projection lens pupil).

  FIG. 5 is a diagram illustrating an example in which the effect of azimuthal polarization is calculated by simulation. A mask pattern to be transferred is a 55 nm line and space on the wafer. This is a simulation result in the case of immersion exposure with NA 1.2 (immersion material = water, n = 1.44), σ0.9, and annular ratio 0.75. The simulation uses resist parameters calibrated in advance with experimental data, and the analysis sets the allowable dimension error to 55 nm ± 5.5 nm, and uses the calculation result of the resist dimension when the exposure amount and focus are used, and the allowable dimension error described above is used. The exposure amount and focus range in which the inner dimensions are obtained are defined by a rectangular window, and the relationship between DOF and exposure amount tolerance as shown in FIG. 5 is obtained.

  From this result, the exposure margin for obtaining DOF of 0.2 μm is 4.6% for the conventional non-polarized light, but is improved to 7% for the annular azimuthal illumination formed using this embodiment. I understand.

  In the above-described embodiments, the example in which the optical rotation element array is arranged on the incident surface side of the fly-eye lens array has been shown, but the present invention is not limited to this, and the light-emitting element array is arranged on the emission surface side of the fly-eye lens array An optical rotation element array may be arranged. Further, the vibration plane orientation distribution generated using the optical rotation element array can be realized by other distributions such as radial polarization and quadrupole linear polarization other than azimuthal polarization.

It is a schematic diagram explaining schematic structure of the exposure apparatus which concerns on this embodiment. It is a schematic diagram which shows an example of the whole structure of the exposure apparatus which concerns on this embodiment. It is a schematic diagram explaining the vibration surface orientation and the arrangement of the fly-eye lens array. It is a schematic diagram explaining 2nd Embodiment. It is a figure which shows the example which calculated the effect of the azimer mon polarization by simulation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 102 ... Optical rotation element array, 103 ... Fly eye lens array entrance surface, 104 ... Fly eye lens array, 105 ... Fly eye lens array exit surface, 106 ... Condenser lens, 108 ... Photomask

Claims (7)

A fly-eye lens array in which fly-eye lenses are arranged in a matrix to equalize the intensity of light emitted from the light source;
It is arranged corresponding to each lens element of the fly-eye lens array, has an optical axis parallel to the traveling direction of the light emitted from the light source, and comprises a plurality of optical rotation elements that rotate the vibration surface of the passing light. An optical rotatory element array;
And a condenser lens that irradiates the mask with light having a vibration plane rotated in a desired direction with respect to an incident angle on the mask surface via the fly-eye lens array and the optical rotation element array. apparatus. The exposure apparatus according to claim 1, wherein each optical rotation element of the optical rotation element array has a rotation angle of the vibration surface different depending on a thickness along the optical axis direction. The exposure apparatus according to claim 1, wherein the optical rotation element is made of quartz. The exposure apparatus according to claim 1, wherein the vibration direction of light passing through the optical rotation element array is azimuthal polarization. The optical rotation element array and the fly-eye lens array form an equivalent light source having a predetermined vibration azimuth distribution on an equivalent light source surface in a conjugate relationship with the projection lens pupil, and further, an arbitrary shape serving as a light shield on the equivalent light source surface The exposure apparatus according to claim 1, wherein an equivalent light source having an arbitrary shape and an arbitrary vibration plane orientation distribution is formed by disposing the aperture stop. The optical rotation element array and the fly-eye lens array form an equivalent light source having a predetermined vibration azimuth distribution on the equivalent light source surface, and a diffractive optical element capable of forming an arbitrary intensity distribution on the light source side from the optical rotation element array. The exposure apparatus according to claim 1, wherein an equivalent light source having an arbitrary intensity distribution and an arbitrary vibration plane orientation distribution is formed on the equivalent light source surface. A fly-eye lens array in which fly-eye lenses are arranged in a matrix to equalize the intensity of light emitted from the light source;
It is arranged corresponding to each lens element of the fly-eye lens array, has an optical axis parallel to the traveling direction of the light emitted from the light source, and comprises a plurality of optical rotation elements that rotate the vibration surface of the passing light. An illumination device comprising: an optical rotation element array.

Images