JP2006269853A - Exposure apparatus and method of exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polarization illumination of an exposure apparatus with which resolution property can be enhanced, in exposure of gate lines, or the like, having strict dimensional rules, when a desired pattern is obtained by projection mapping that uses a phase shift mask. <P>SOLUTION: The exposure apparatus comprises a fly-eye lens array 304 arranged with fly-eye lenses in a matrix form, in order to equalize the intensity of light emitted from a light source, a rotation element array 302 consisting of a plurality of rotation elements for making the plane of vibration of passing light, arranged in correspondence with respective lens elements of the fly-eye lens array 304 rotate and having an optical axis parallel with the traveling direction of the light emitted from a light source, and a condenser lens 306 for irradiating a phase shift mask 308 with a light, having an orientation distribution of the plane of vibration in the plane of an equivalent light source via the fly-eye lens array 304 and the rotation element array 302, wherein the equivalent light source has a cross or radial cross shape and orientation distribution of the plane of vibration of light in the equivalent light source has a cross or radial cross shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an exposure method 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. A phase shift mask (reticle) that enables pattern formation is widely used.

  The phase shift mask obtains high resolution by using the phase difference of transmitted light, and for example, a Shibuya-Levenson type is well known (see Patent Document 1 and Non-Patent Document 1). When this Shibuya-Levenson type phase shift mask is used, it is usual to use small circular illumination, that is, small σ illumination in order to put ± 1st order diffracted light as much as possible into the aperture (NA) of the projection lens.

  When such a phase shift mask is used, conventionally, non-polarized light is used as illumination light for the mask in order to avoid the orientation dependency of the pattern resolution. On the other hand, it is known that if the illumination light for the mask is polarized in a direction parallel to the side of the pattern formed on the mask, the image quality of the transferred image is improved. As disclosed, a technique combining this with a phase shift mask has also been proposed.

JP-A-57-62052 JP-A-5-88356 M.D.Levenson et al: IEEE Trans. Electron Device, ED-29, p1828 (1982)

  However, in order to obtain polarized light having an azimuth parallel to the pattern constituent side on the mask, for example, TE (transverse electric) transmission or TM is applied to each shifter that generates a phase difference of light in the phase shift mask depending on the azimuth. It is necessary to install a translucent polarizing element. However, it is very difficult to create a phase shift mask having such a complicated structure. Note that the difference between TE transmission and TM transmission here is due to the difference in whether the light oscillation direction is the y direction or the x direction on the incident surface. The TE polarized light is polarized light whose electric field vector is parallel to the pattern, and TM polarized light is polarized light whose direction is perpendicular to the pattern direction.

  The inventor of the present application has also proposed a multiple exposure method in which a mask pattern is divided according to the orientation of the pattern and the polarization orientation for illuminating the mask is changed for each orientation of the pattern (Japanese Patent Application No. 2001-388984). However, since one layer exposure process is a multiple exposure method using a plurality of masks, there are problems such as cost of an expensive phase shift mask and an increase in exposure TAT (Turn Around Time).

Furthermore, recently, immersion exposure has been proposed that allows the numerical aperture (NA) of the projection lens to be 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. For example, even with an exposure apparatus that uses a 193 nm ArF laser as a light source, a 32 nm node (half pitch 45 nm) semiconductor 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. However, in such a Hyper-NA region, the incident angle of the exposure light to the resist and the incident angle of the exposure light in the resist layer also become large, and in particular, there is a problem of image contrast reduction due to the TM polarization component. This is discussed in detail in, for example, T. A. Brunner, “High NA lithographic imagery at Brewster ’s angle” (SPIE Proceeding vol. 4691, pp 1-10).

  The present invention has been made to solve such problems. That is, the present invention is an exposure apparatus for obtaining a desired pattern by projection mapping using a phase shift mask, wherein the equivalent light source has a cross shape or a radiation cross shape. Furthermore, the distribution of the vibration plane orientation of the light in the cross-shaped or radiant cross-shaped light source is also a cross shape or a radiation cross shape.

  In the present invention as described above, the shape of the equivalent light source is a cross shape or a radiation cross shape along the direction of the constituent side of the pattern of the phase shift mask, that is, the vertical direction and the horizontal direction, and the light source shape is in both x and y positions. The Shibuya-Levenson-type phase shift mask with this pattern is optimal, and the vibration plane orientation of the light in the light source is the one that eliminates the TM polarization component as much as possible at the stage of illuminating the mask. Therefore, a good image contrast can be obtained for each of the vertical and horizontal patterns.

  Further, the present invention is arranged corresponding to each lens element of the fly-eye lens array in which fly-eye lenses are arranged in a matrix to make the intensity of light emitted from the light source uniform, An optical rotatory element array having a plurality of optical rotatory elements having an optical axis parallel to the traveling direction of the light emitted from the light source and rotating a vibrating surface of the passing light in proportion to its thickness; a fly-eye lens array; A condenser lens that irradiates the phase shift mask with light whose rotational plane direction with respect to the angle of light incident on the mask surface via the optical rotation element array is rotated in a desired direction is provided. The shape of an equivalent light source composed of an element array and a condenser lens, and the vibration plane orientation distribution of light in the equivalent light source is a cross shape or a radiation cross It is to have an exposure apparatus becomes Jo. In addition, when a Shibuya-Levenson type phase shift mask is used as the mask, the shape of the equivalent light source surface composed of the optical rotation element array and the condenser lens is made circular, and the orientation distribution of the vibration plane of the light within the equivalent light source surface is obtained. It is also an exposure device that makes a cross or a radiation cross.

  In the present invention, the shape of the equivalent light source is a cross shape or a radiation cross shape along the direction of the constituent side of the pattern of the phase shift mask, that is, the vertical direction and the horizontal direction, and the light source shape is both x and y. It is optimal for Shibuya-Levenson type phase shift mask with a pattern of the position, and the vibration plane orientation of the light in the light source is the one that eliminates the TM polarization component as much as possible at the stage of illuminating the mask. Therefore, good image contrast can be obtained for each of the vertical and horizontal patterns.

  The present invention also relates to an exposure method in which a pattern is formed by exposure using a phase shift mask and exposure using a trim mask. In exposure using a phase shift mask, the shape of the equivalent light source is the main of the phase shift mask. It is a cross shape or a radiation cross shape with directions of 0 °, 90 °, 180 °, 270 ° with respect to the side direction (longitudinal direction) of the pattern, and the distribution of the vibration plane direction of light is a cross shape or a radiation cross shape. In the exposure using a trim mask using non-polarized illumination, a non-polarized illumination is used. Further, when a Shibuya-Levenson type phase shift mask is used, it is also an exposure method in which the shape of the equivalent light source surface is circular and the orientation distribution of the vibration surface of the light in the light source surface is made a cross or a radiation cross.

  In the present invention as described above, in the exposure using the phase shift mask, it is possible to obtain a good image contrast for each pattern in the pattern direction, that is, the vertical direction and the horizontal direction, with respect to a pattern having a strict design rule. . In particular, the light source shape is optimal for a Shibuya-Levenson type phase shift mask having a pattern with both x and y positions. Further, in the exposure using the trim mask, it is possible to perform the exposure without depending on the orientation of the pattern on the imaging performance with a simple light source configuration by the non-polarized illumination with respect to the pattern having a relatively loose design rule.

  Therefore, according to the present invention, it is possible to obtain a good image contrast with respect to the vertical pattern and the horizontal pattern formed on the phase shift mask during the projection mapping. Thereby, a large process margin can be obtained in the exposure using the phase shift mask, and the line width can be controlled with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the outline of the present invention will be described. That is, the present invention is an exposure apparatus and an exposure method using a phase shift mask, and the shape of the equivalent light source is a cross shape or a radiation cross shape during projection mapping. As shown in FIG. 1, the cross-shaped direction has strengths in directions of 0 °, 90 °, 180 °, and 270 ° with respect to the side direction (longitudinal direction) of the vertical pattern, and the X direction side of the cross Use a modified polarization illumination in which the polarization direction in the inside (A part and C part in the figure) is X-polarized light and the polarization direction in the Y direction side of the cross (B part and D part in the figure) is Y-polarized light It is characterized by.

  In FIG. 1, the vibration direction of light is 0 ° in the A portion, 90 ° in the B portion, 180 ° in the C portion, and 270 ° in the D portion. In the E portion of the cross portion, the ratio of X-polarized light and Y-polarized light is equal, and is 45-degree linearly polarized light or non-polarized light.

  The B part and the D part have a polarization component parallel to the pattern constituent side direction (longitudinal direction) with respect to the vertical pattern on the phase shift mask (vertical pattern (hereinafter referred to as “V pattern”)), Since the image formation in the photoresist applied to the substrate wafer is almost TE-polarized light and rectangular illumination with a small width in the X direction, that is, a σ value in the X direction, the contrast of the vertical pattern is reduced. Increase greatly.

  On the other hand, the A part and the C part are orthogonal polarization components, and the contrast is zero, or the contrast is slightly increased when the pattern pitch is increased. Basically, it only gives a DC component and has the effect of reducing the image contrast.

  Here, FIG. 6C shows the diffracted light on the pupil plane of the vertical pattern of the phase shift mask of pitch P. As shown here, since the illumination shape is a cross shape in the present invention, in the narrow pitch pattern, most of the C part shown in FIG. Become. As a result, the contribution of image formation by illumination light that increases the image contrast in the B and D portions shown in FIG. 1 is increased, and the overall image contrast is improved. The same applies to the + first-order diffracted light 608.

  A similar effect can be obtained with a horizontal pattern on the mask (horizontal pattern (hereinafter referred to as “H pattern”). Since the E portion which is a cross-shaped cross portion shown in FIG. , It contributes to obtain equivalent contrast to the H pattern.

  Further, according to the present invention, in the case of projection mapping using a phase shift mask, the radiation cross has intensities of 0 °, 90 °, 180 °, 270 ° azimuth as shown in FIG. Modified polarized illumination in which the polarization direction (see the arrow in the figure) is radial may be used. Even with this polarized illumination, it is possible to obtain the same or higher contrast improvement effect as the cross-shaped polarized illumination in FIG.

  That is, the B part and the D part have a polarization component substantially parallel to the pattern constituent side (longitudinal direction) with respect to the vertical pattern on the phase shift mask, and the result is a result in the photoresist applied to the substrate wafer. Since the image is substantially TE-polarized and the fan illumination has a small σ value in the X direction, the contrast of the vertical pattern is increased.

  On the other hand, the A part and the C part are polarization components that are almost orthogonal to the vertical pattern, and the contrast is zero or the contrast becomes higher when the pattern pitch is increased, but this image contrast value is very low. . However, since the illumination shape is a radiation cross shape, as described in the paragraph number “0021”, most of A part and C part shown in FIG. 2 are blocked by NA, and A, B, The contrast of the vertical pattern in the C and D portions is improved. Similar effects can be obtained with a horizontal pattern on the mask.

  Furthermore, the exposure apparatus of the present invention uses the following configuration in order to obtain the modified polarized illumination described above by a projection map using a phase shift mask. That is, as shown in FIG. 3, an optical rotation element array 302 having a different thickness for each element is arranged on the incident surface of the fly-eye lens array 304, which is an intensity uniformizing optical element. The polarization orientation can be formed.

  Here, reference numeral 302a in the figure denotes an optical rotator, and the material is a crystal having transparency to a wavelength of 193 nm and is an active crystal, and the optical axis is the optical axis (light traveling direction). To be parallel to

  When linearly polarized light is incident on the optical rotator 302a, the polarization plane rotates in proportion to the thickness. F. Arago's experiment (for example, see Norito Suzuki, Takafumi Koshio, Applied Optics IIp20, Asakura Shoten).

  Therefore, by changing the thickness in the optical axis direction for each element of the optical rotation element array 302 for each element of the corresponding fly-eye lens using incident light as linearly polarized light, the vibration plane orientation of the light is controlled for each element of the optical rotation element 302a. The focal point of the fly-eye lens array exit surface 305 (that is, the equivalent light source plane or the pupil conjugate plane) on which the vibration plane orientation of the controlled light is incident is also controlled by the vibration plane orientation distribution (polarization distribution) of the controlled light. Will have. That is, an equivalent light source having an arbitrary polarization distribution is obtained.

  Furthermore, it is possible to make the light source shape into an arbitrary shape by installing an unillustrated light-shielding body stop (not shown) on the fly-eye lens array emission surface 305. Each element of the fly-eye lens array 304 improves the intensity uniformity on the photomask 308 by subjecting the photomask 308 through the condenser lens 306 to wavefront division and then superimposing and illuminating. The condenser lens 306 has an equivalent light source surface 305 and a mask surface 308 in a Fourier transform relationship. That is, position information in the equivalent light source surface 306 is converted into angle information on the mask surface 308. As described above, when the direction of the vibration plane of the light is controlled in units of elements on the entrance surface of the fly-eye lens array 304, this light vibration plane is also generated on the fly-eye lens exit surface 305 that becomes the pupil plane of the illumination optical system. The azimuth distribution is maintained, and the photomask 308 serving as the original plate is illuminated through the condenser lens 306. Here, as shown in FIG. 3, the orientation distribution of the vibration plane of the light with respect to the angle in the light 307 illuminating the mask corresponds to the orientation distribution of the vibration plane of the light set in units of elements of the fly-eye lens array 304. It has become. This makes it possible to obtain a desired polarized illumination.

  Next, the present invention will be described in detail. The exposure apparatus and the exposure method described here are mainly used in a semiconductor device manufacturing process. More specifically, it is used for forming a desired pattern in a photoresist applied on a wafer as a substrate by a projection mapping using a phase shift mask in a lithography process in a semiconductor device manufacturing process.

  First, a schematic configuration of the exposure apparatus will be described. FIG. 4 is an explanatory view showing an example of a schematic configuration of an exposure apparatus according to the present invention. The exposure apparatus described here includes a phase shift mask 308, a light source of illumination light for the phase shift mask 308 (corresponding to the surface of the condenser lens 306), and an optical rotation element array 302 that is a polarization state control unit positioned therebetween. And a light source shape control unit 406.

  Of these, the phase shift mask 308 can be arbitrarily selected and replaced in accordance with a pattern to be formed on a photoresist (not shown) applied on the wafer 410 as a substrate. However, in this embodiment, as will be described in detail later, the phase shift mask 308 is considered to be applied to transfer of a gate pattern of V (vertical) orientation and H (horizontal) orientation.

  Originally, the gate layer pattern is a two-dimensional pattern including a wire pattern, but the transfer dimension accuracy of the gate portion overlapping the active layer is important, and the transfer of the gate portion will be mainly described below. The wire pattern other than the gate portion is usually formed by trimming exposure performed after the gate transfer, and a mask different from the above-described phase shift mask is used, but this portion will be described later.

  First, the modified polarized illumination that is the main configuration of the present invention will be described. Here, as an example of applying Shibuya-Levenson-type phase shift mask exposure to gate lithography in the Hyper-NA region, a case where pattern transfer with a half pitch of 45 nm is performed by ArF immersion exposure with NA 1.2 is treated as follows. To do. It is assumed that water having a refractive index of 1.44 is used as the immersion liquid material.

  First, an optimal illumination shape will be described without considering polarization. Conventionally, in the Shibuya-Levenson-type phase shift mask exposure, a small σ illumination is used. This is because, as shown in FIG. 6A, ± 1st-order diffracted light is taken into the aperture (NA) of the projection lens as much as possible. It is. When the projection lens is regarded as a mask information transmission means, the mask pattern transfer fidelity is improved and the image contrast is improved by minimizing the blockage of information at NA.

  Now, assuming that the pattern to be transferred is a V pattern, when transferring a pattern with a pitch P using Shibuya-Levenson type phase shift, an ideal light source shape is V direction as indicated by 601 in FIG. This is a linear light source. Here, FIG. 6A shows the pupil plane of the projection lens, 601 represents a linear light source, 602 and 603 are 601 linear light sources, and the projection when the pattern pitch P in the V direction on the mask is illuminated. The first-order diffracted light on the pupil plane of the lens is shown.

  However, with a linear light source, as a practical problem, sufficient mask illumination intensity uniformity cannot be obtained. In addition, since there is a problem that the sensitivity of the projection lens to a specific aberration component is increased, the light source needs to have a predetermined size or more. Here, if the light source is as indicated by reference numeral 604 in FIG. 6B, ± first-order diffracted light enters the NA. Here, the condition for all the ± first-order diffracted lights to enter the NA is expressed by the following equation (1).

  In Equation 1, P represents the pattern pitch on the wafer, λ represents the exposure wavelength, and σx and σy represent the X size and Y size of the linear light source, respectively, and are defined by being normalized by NA. For example, the light source 604 in FIG. 6B has σy = 0.3 and σx = 0.05, which satisfies Equation 1.

  As σx and σy, as σx increases, the oblique incident illumination component increases. Therefore, the illumination intensity uniformity and aberration sensitivity are set as small as possible within the range satisfying the desired level, and σy is derived within the range satisfying Equation 1. To do. In the present embodiment, a linear light source satisfying Equation 1 is handled, but a policy may be adopted in which σx and σy are increased within a range in which desired imaging performance can be obtained without satisfying Equation 1.

  In the present embodiment, the target is to transfer both VH positions in a single exposure. Therefore, as the illumination shape, the light source 604 shown in FIG. The cross shape is the optimal illumination shape. The polarized light in the illumination shape is first unpolarized.

  Under these conditions, FEM calculation (Focus-Exposure-Matrix calculation) is performed using a commercially available lithography simulator for the light source having the shape shown in FIG. 1 and the size of σy = 0.3 and σx = 0.05. FIG. 7 shows the result of calculating the exposure process margin. In FIG. 7, as a typical example of the prior art, it is shown together with circular non-polarized illumination with σ0.3. Here, the mask pattern is 50 nm LS, the target line width is 45 nm ± 4.5 nm, and the analysis is performed with the maximum elliptical window. From this result, it can be confirmed that the exposure process margin is greatly improved with the cross-shaped illumination (solid line) compared to the conventional small σ illumination (broken line).

  In addition, the FEM calculation in the present embodiment uses not a spatial image but a resist model (Lumped-Parameter-Model = LPM model) using aggregate parameters calibrated in advance with respect to experimental data.

  Furthermore, the polarization in the cross-shaped illumination described above is optimized. When the formation pattern of interest is a V line, it is desirable that the polarization directions of the B and D portions in FIG. 1 that play the main role in the image formation are parallel to the longitudinal direction of the pattern, and Y polarization is optimal. . Similarly, when the mask pattern of interest is an H line, it is desirable that the polarization orientations of the A and C portions in FIG. 1 that play the main role in the image formation are parallel to the longitudinal direction of the pattern, and the X polarization is Is optimal.

  In addition, since the overlap portion E contributes to both VH patterns, non-polarized light or polarized light of 45 ° azimuth is desirable. As described above, the optimal modified polarized illumination for the VH line pattern is as shown in FIG. The size of each side was set to σx = 0.05 and σy = 0.30.

  This is simulated in the same manner as described above, and the result of calculating the exposure process margin is shown in FIG. 8 (solid line). This is shown together with the results of the conventional small σ non-polarized light (dashed line) and cross non-polarized illumination (one-dot broken line) shown in FIG. 7 (solid line 05sx30sy / pol in the graph). From this result, it can be confirmed that a larger process margin can be obtained by optimizing the polarization in the light source in addition to the light source shape.

  Next, as another embodiment of the present invention, a description will be given of illumination that combines cross-radial illumination as shown in FIG. 2 with Radially polarized light whose polarization direction in the light source is also radial. The concept is the same as the cross illumination described so far, the shape is substantially cross-shaped, and the polarization direction is radial, and almost the same effect as the cross-shaped polarization illumination of FIG. 1 can be obtained.

  Since the distribution of the vibration plane orientation of the light in the cross-radial light source is radial, there is a slight deviation between the orientation of the mask pattern except for the 0 ° orientation and the 90 ° orientation, and there is a slight deterioration in contrast. By suppressing the opening angle (θ) of the four fans within an appropriate range, it is possible to suppress deterioration in contrast.

  Further, the cross portion E of the cross-shaped illumination in FIG. 1 is non-polarized, but in the cross-shaped radial illumination in FIG. 2, the radiation direction (almost 0 ° (180 °), 90 ° (270 °) azimuth) to the light source center. Since it is a polarization component, the polarization component in this portion enhances the contrast of the H direction pattern and the V direction pattern, respectively.

  Here, in FIG. 2, Radially polarized illumination with σ = 0.3 and θ = 15 degrees is taken as one of the optimal solutions, and the FEM simulation is similarly performed to calculate the exposure process margin. The result is shown in FIG. 9 (solid line). This is shown together with the results of the conventional small σ non-polarized light (dashed line) and cross-polarized illumination (one-dot broken line) shown in FIG. From this result, it can be confirmed that a greater process margin improvement can be obtained than the cross-shaped polarized illumination as shown in FIG.

  Next, a method for realizing the polarized illumination described above on the exposure apparatus will be briefly described. FIG. 4 shows a conceptual diagram of an exposure apparatus / illumination optical system for obtaining polarized illumination having the cross shape of FIG. 1 and the radiation cross shape of FIG.

  The beam of the excimer laser 400 has a rectangular shape with an aspect ratio of around 5, and the excimer laser beam whose wavelength is narrowed is strongly polarized in the short side direction. Typically, the degree of polarization is 98% or more, and can be regarded as almost linearly polarized light.

  The illumination optical system is capable of forming the light source shape shown in FIGS. 1 and 2 and the vibration plane distribution of the light in the light source on the fly-eye incident surface for obtaining the intensity uniformity of the mask illumination light by making good use of this polarized beam. This is a required function.

  First, the narrow band excimer laser beam 401 emitted from the excimer laser 400 is strongly polarized in the beam short side direction. The beam shaping optical system 402 includes a cylindrical lens, a zoom lens, a DOE (Diffractive Optical Element), and the like, and is an optical system that shapes the shape and size according to the outer shape of the fly-eye lens 304 that is an intensity uniformizing optical element.

  Further, reference numeral 302 denotes an optical rotatory element array, and as described above, the vibration direction of the linearly polarized light that is incident can be rotated depending on the thickness thereof. As a result, as indicated by reference numeral 404, it is possible to give an arbitrary distribution to the vibration surface rotation amount of the emitted light in units of elements. Thereby, the vibration plane orientation distribution of light as shown in FIGS.

  Reference numeral 304 denotes an intensity uniformizing optical element, which is a fly-eye lens array. Reference numeral 406 denotes an aperture stop that serves as a light shielding body, which can limit and shape the size and shape of the light source (circular, annular, quadrupole, cross, etc.). Reference numeral 406 has a conjugate relationship with the pupil plane of the projection lens, and this plane is called an equivalent light source plane.

  Reference numeral 306 denotes a condenser lens, which converts position information in the equivalent light source plane into angle information in the mask incident angle, as described in paragraph “0030”. Further, light from each lens element of the fly-eye lens array 304 is superimposed on the photomask 308. Reference numeral 409 denotes a projection lens that images the pattern of the photomask 308 on a photoresist (not shown) on the wafer 410 as a substrate.

Next, the optical rotation element array 302 that forms the vibration direction distribution of FIGS. 1 and 2 will be described with reference to FIG. When linearly polarized light enters the optical rotation element array 302 arranged so that the optical axis is parallel to the optical axis, the plane of polarization rotates in proportion to the thickness. The rotation angle ρ per unit length is called optical rotation, but the value of quartz is 201.9 ° / mm (wavelength shown in “Tsuruta, Applied Optics II, p167, Baifukan”). 226.5 nm) and the wavelength dependence (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.

First, the formation of the radial vibration surface distribution of FIG. 2 will be described. An object is to form radial polarized light in which the vibration plane orientations are distributed radially as shown in FIG. Here, FIG. 5B is an array diagram of the fly-eye lens array. From FIGS. 5 (a) and 5 (b), it is assumed that the dimensions of the unit elements of the optical rotation element array and the fly-eye lens array are (2M + 1) × (2N + 1) arrays with the major axis L and the minor axis W. Consider the thickness of the array (i, j). Assume that (0, 0) is a fly-eye lens center element.
In this embodiment, since a scan 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.

  Now, it is assumed that the vibration plane of the incident light is polarized in an azimuth of 90 ° as viewed from the incident side as shown in FIG. Assuming that this is the reference of the optical rotation element array 302, the thickness of the optical rotation element of the central element (0, 0) is assumed to be 360 ° / ρ = 1.31 mm, and this is referred to as the reference thickness (Dc) of the optical rotation element array 302. To do.

  The target vibration plane orientation θij in the element (i, j) for obtaining the above-mentioned radial polarization is expressed by the following formula 2.

  Therefore, the thickness Dij in the optical rotatory element (i, j) is expressed by the following formula 3.

  Thus, by using an optical rotation element array in which each element thickness is changed, it becomes possible to have a distribution in the vibration plane orientation in units of fly-eye lens elements, and a light-shielding diaphragm (not shown) is provided on the surface indicated by reference numeral 305. By shaping into a radiation cross shape, it is possible to form the radial cross illumination of the radiation cross shape of FIG.

  The variable thickness range of the optical rotatory element 302 is about 1.31 mm at 360 °, which is a level that can be realized in processing.

  Next, a method for obtaining the cross-shaped polarized illumination in FIG. 1 will be described. This also allows the design of the optical rotator array described above based on the same concept as described above. The portion E shown in FIG. 1 has a vibration plane orientation = 45 °, and the thickness of the element corresponding to this portion is 1.15 mm including θ = 45 ° from Equation 2. In the same way, A part (180 °) = 1.64 mm, B part (270 °) = 1.96 mm, C part (0 °) = 0.98 mm, and D part (90 °) = 1.31 mm. Thus, it is only necessary to design each element thickness in the fly-eye lens array corresponding to the A-E portion.

  The combination of the optimized polarized illumination described above and the Shibuya-Levenson type phase shift mask provides a good resolution, and the gate lines in the V and H directions can be formed with high accuracy in a single exposure. . In the case of exposure using the Shibuya-Levenson-type phase shift mask, the distribution of the vibration plane orientation of light within the light source plane is a cross or a radiation cross even if the equivalent light source shape is circular as usual. Even in some cases, it is readily understood that a larger exposure process margin is obtained than conventional circular + non-polarized illumination.

  After this gate line formation exposure, the phase shift mask for gate line exposure is replaced with a trim mask in order to form a wire pattern other than the gate V line and H line, and exposure using the trim mask is performed. In the case of this trim mask, the pitch is not as narrow as when forming the gate line, and the tolerance of variation in the formation line width is also large, so there is no need to use a phase shift mask, usually a binary mask or halftone type A phase shift mask is used.

  When the trim mask is exposed, the illumination condition does not have to be polarized illumination. Therefore, the optical rotation device array 302 is removed from the optical path, and a depolarizer (depolarization element) (not shown) is placed in the optical path instead. As the non-polarized illumination, the diaphragm 406 is also switched to a normal circular or annular shape. As a result, the wire pattern other than the gate pattern is exposed with non-polarized illumination having no azimuth dependency, and the conventional technique can be used.

It is a schematic diagram explaining a cross-shaped polarized light source. It is a schematic diagram explaining the polarization | polarized-light deformation light source of a radiation cross shape. It is a schematic diagram explaining the illumination system schematic structure of the exposure apparatus which concerns on this embodiment. It is a schematic diagram explaining the structure of the exposure apparatus which concerns on this embodiment. It is a schematic diagram explaining radial polarization illumination. It is a schematic diagram explaining optimization of a light source shape. It is a figure of the simulation result which shows the comparison of the process margin of a cross-shaped light source and a circular light source. It is a figure of the simulation result which shows the comparison of the process margin at the time of optimizing polarization with a cross shape light source. It is a figure of the simulation result which shows the comparison of the process margin at the time of optimizing polarization with a radiation cross shape light source.

Explanation of symbols

  302 ... Optical rotation element array, 304 ... Fly eye lens array, 305 ... Fly eye lens array exit surface, 306 ... Condenser lens, 308 ... Phase shift mask

Claims (7)

An exposure apparatus that obtains a desired pattern by projection mapping using a phase shift mask,
An exposure apparatus characterized in that the shape of the equivalent light source is a cross shape or a radiation cross shape. The direction of the cross shape or the radiation cross shape of the equivalent light source is an orientation of 0 °, 90 °, 180 °, 270 ° with respect to the longitudinal direction of the pattern of the phase shift mask. Exposure equipment. The exposure apparatus according to claim 1, wherein the orientation distribution of the vibration plane of the light in the equivalent light source is a cross or a radiation cross. 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;
A condenser lens that irradiates the phase shift mask with the light whose plane of vibration is rotated in a desired direction with respect to the incident angle to the mask surface via the fly-eye lens array and the optical rotation element array. ,
An exposure apparatus, wherein the orientation distribution of the vibration plane of light within the equivalent light source plane constituted by the fly-eye lens array, the optical rotation element array, and the condenser lens is a cross or a radiation cross. 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;
A condenser lens that irradiates the phase shift mask with the light whose plane of vibration is rotated in a desired direction with respect to the incident angle to the mask surface via the fly-eye lens array and the optical rotation element array. ,
When a Shibuya-Levenson-type phase shift mask is used as the mask, the shape of the equivalent light source surface constituted by the optical rotation element array and the condenser lens is circular, and the orientation of the vibration plane of light within the equivalent light source surface An exposure apparatus characterized in that the distribution is a cross or a radial cross. In an exposure method in which a pattern is formed by exposure using a phase shift mask and exposure using a trim mask,
In the exposure using the phase shift mask, the shape of the equivalent light source is a cross shape or a radiation cross shape in which the orientation of the main pattern of the phase shift mask is 0 °, 90 °, 180 °, 270 °. , Using light in which the orientation distribution of the vibration plane of light within the equivalent light source plane is a cross or a radiation cross,
In the exposure using the trim mask, non-polarized illumination is used. In the exposure method using Shibuya-Levenson type phase shift mask,
An exposure method, wherein the shape of the equivalent light source surface is circular, and the orientation distribution of the vibration surface of the light in the light source surface is a cross or a radiation cross.

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