JP2007189079A - Illuminating optical system, exposure device having it, and manufacturing method of device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminating optical system capable of correcting the polarization state of a luminous flux with high precision, and maintaining the polarization state at the illuminated surface in the desired state. <P>SOLUTION: This illuminating optical system for illuminating the illuminated surface with the luminous flux from a light source comprises a beam shaping unit for shaping the cross-sectional shape of the luminous flux from the light source; an integrator for dividing the luminous flux from the beam shaping unit; a condenser system for superposing the luminous flux divided by the integrator and guiding it to the illuminated surface; and an optical member arranged in the plane of incidence for the integrator or in the plane between the beam shaping unit and the integrator, and conjugated with the plane of incidence for the integrator and having a birefringence distribution in the cross-section orthogonal to the optical axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to an illumination optical system, and more particularly to an illumination optical system used in an exposure apparatus that exposes an object to be processed such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD). .

  When manufacturing semiconductor elements using photolithography (baking) technology, a projection exposure system that projects a circuit pattern drawn on a reticle (mask) onto a wafer or the like by a projection optical system and transfers the circuit pattern has been used. Has been.

  In recent years, along with a demand for miniaturization of semiconductor elements, an exposure apparatus that exposes a pattern having a size less than half of the exposure wavelength (that is, achieves high resolution) has been developed. Such high resolution is generally achieved by shortening the wavelength of exposure light and increasing the numerical aperture (NA) of the projection optical system. Increasing the NA of the projection optical system means increasing the angle between the perpendicular from the image plane and the traveling direction of the incident light, which is called high NA imaging.

  In high NA imaging, the polarization of exposure light becomes a problem. For example, consider the case of exposing a so-called line and space (L & S) pattern in which lines and spaces are repeated. The L & S pattern is formed by plane wave two-beam interference. A plane including the incident direction vector of two light beams is defined as an incident plane, polarized light perpendicular to the incident plane is defined as S-polarized light, and polarized light parallel to the incident plane is defined as P-polarized light. Note that simply polarized light perpendicular to the paper surface may be referred to as S-polarized light, and simply polarized light parallel to the paper surface may be referred to as P-polarized light. When the angle formed between the incident vectors of the two light beams is 90 degrees, the S-polarized light interferes, so that a light intensity distribution according to the L & S pattern is formed on the image plane. On the other hand, since the P-polarized light does not interfere (the effect of interference is canceled), the light intensity distribution is constant, and the light intensity distribution corresponding to the L & S pattern is not formed on the image plane. When S-polarized light and P-polarized light coexist, a light intensity distribution having a poorer contrast than when only S-polarized light is formed on the image plane. When the ratio of P-polarized light is increased, the contrast of the light intensity distribution on the image plane is increased. In the end, the pattern is not formed.

  For this reason, it is necessary to control the polarization of exposure light, and basic experiments have been conducted. Note that the polarization control of the exposure light is generally performed on the pupil plane of the illumination optical system or the projection optical system. The exposure light whose polarization is controlled by the pupil plane of the illumination optical system is irradiated onto the reticle via the optical system after the pupil plane of the illumination optical system, and is further condensed by the projection optical system to form an image on the image plane. . The exposure light whose polarization is controlled can form a light intensity distribution with sufficient contrast on the image plane, and a finer pattern can be exposed.

  On the other hand, there are many error factors in the actual exposure optical system that break the ideal polarization state. Such error factors include the residual birefringence of glass materials (quartz and fluorite) used in illumination optical systems and projection optical systems, stress birefringence generated by mechanical suppression, optical properties such as mirrors and antireflection films, etc. The phase characteristics and reflection characteristics of the coating. Due to such error factors, for example, even if the light beam from the laser light source is linearly polarized light that is close to ideal, the polarization state of each light beam is destroyed when it reaches the wafer surface.

Therefore, an exposure apparatus has been proposed in which a birefringent member having a phase distribution is arranged at the pupil position of the projection optical system or illumination optical system in order to adjust (correct) the polarization state (see, for example, Patent Documents 1 and 2). ). For example, Patent Document 1 discloses an exposure apparatus in which an Alvarez lens that adjusts the polarization state of exposure light is arranged on the pupil plane of a projection optical system. Patent Document 2 discloses an exposure apparatus in which a phase plate for adjusting the polarization state of exposure light is arranged in an illumination optical system and / or a projection optical system.
Japanese Patent Laid-Open No. 11-271680 International Publication No. 2005/031467 Pamphlet

  However, these conventional techniques, in principle, can correct the degree of polarization (polarization state) for only one point on the optical axis, but light is incident on the phase plate obliquely outside the optical axis. Therefore, the degree of polarization is lost (that is, cannot be corrected).

  In Patent Documents 1 and 2, by arranging a phase plate on the pupil plane of the projection optical system, or its conjugate plane in the illumination optical system or the pupil plane of the imaging system of the illumination optical system, it is as if the entire illuminated surface Are described so that a common phase difference can be given. Hereinafter, with reference to FIG. 21, the problem of this arrangement will be described.

  FIG. 21 is a diagram showing an arrangement example of the phase plate in the prior art and the polarization degree in that case, and shows an optical path from the masking blade MB to the reticle RT (illuminated surface) in the illumination optical system. As shown in FIG. 21, the phase plate PB is disposed between the imaging system IS1 and the imaging system IS2, specifically, the pupil plane IPS of the imaging system IS1.

  The phase plate PB is generally a biaxial crystal having a main axis in a cross section orthogonal to the optical axis. When a light beam having a certain orientation (vibration direction) is incident on such a phase plate PB, the crystal has a different refractive index between the principal axis and the direction perpendicular thereto (that is, has birefringence). Are subject to different phase differences. In the case of light traveling perpendicularly to the phase plate PB (that is, parallel to the optical axis), the phase difference amount φ1 is that the refractive index in the main axis direction is No, the refractive index in the direction orthogonal thereto is Ne, and the thickness of the phase plate PB. Where d is expressed by Equation 1 below. Note that λ is the wavelength of exposure light.

  The light traveling perpendicularly to the phase plate PB is a light beam group Lc1, Lc2, and Lc3 passing through the center point C of the masking blade MB. After passing through the phase plate PB, they are condensed on the optical axis on the reticle RT by the action of the imaging system IS2. Therefore, when the cross-sectional distribution F2 of the light beam condensed on the optical axis is viewed, the degree of polarization changes uniformly by the amount caused by the phase difference amount φ1 described above. This is shown in FIG. 21 as τ1. There are various definitions of the degree of polarization, for example, the distribution ratio S / (S + P) between S-polarized light and P-polarized light.

  On the other hand, the light groups Lu1, Lu2, and Lu3 from the off-axis point U on the masking blade MB are incident on the phase plate PB obliquely by the action of the imaging system IS1. Therefore, the light beam groups Lu1, Lu2, and Lu3 are substantially different from the light beams incident in parallel at a distance passing through the phase plate PB. The emitted light groups of the light groups Lu1, Lu2, and Lu3 are condensed off-axis on the reticle RT, and the light beam cross-sectional distribution F3 at the light condensing point has a polarization degree different from that of the light beam cross-sectional distribution F2 on the axis. Will have. This is shown in FIG. 21 as τ2.

  Referring to FIG. 21, τ1 ≠ τ3. This causes variations in the degree of polarization within the surface to be illuminated, resulting in variations in the contrast of the exposure light on the wafer surface. Eventually, variations in the burn-in line width in the semiconductor element occur, causing frequent chip failures. This is the phenomenon most disliked in the manufacturing process of semiconductor elements. A similar phenomenon occurs when the phase plate PB is arranged in the vicinity of the pupil plane of the projection optical system.

  Accordingly, an exemplary object of the present invention is to provide an illumination optical system capable of correcting the polarization state of a light beam with high accuracy and maintaining the polarization state on a surface to be illuminated in a desired state. To do.

  In order to achieve the above object, an illumination optical system according to one aspect of the present invention is an illumination optical system that illuminates a surface to be illuminated with a light beam from a light source, and a beam that shapes a cross-sectional shape of the light beam from the light source. A shaping unit; an integrator that divides the light beam from the beam shaping unit; a condenser system that superimposes the light beam divided by the integrator and guides it to the illuminated surface; and an incident surface of the integrator or the beam shaping unit And an optical member having a birefringence distribution in a cross section orthogonal to the optical axis. The optical member is disposed on a plane conjugate with the incident surface of the integrator.

  An exposure apparatus according to another aspect of the present invention is an exposure apparatus that exposes a reticle pattern onto an object to be processed, the illumination optical system that illuminates the reticle, and the reticle pattern onto the object to be processed. A projection optical system for projecting.

  According to still another aspect of the present invention, there is provided a device manufacturing method comprising: exposing a target object using the above-described exposure apparatus; and developing the exposed target object.

  An exposure apparatus according to still another aspect of the present invention is characterized in that the polarization control member is adjusted in accordance with a change in illumination mode.

  An exposure apparatus according to still another aspect of the present invention is characterized by measuring a polarization state on a reticle surface or a wafer surface and adjusting a polarization control member in accordance with a change in illumination mode.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to correct | amend the polarization state of a light beam with high precision, and the illumination optical system which can maintain the polarization state in a to-be-illuminated surface in a desired state can be provided.

  Hereinafter, an exposure apparatus according to one aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted. Here, FIG. 1 is a schematic sectional view showing the structure of the exposure apparatus 1 of the present invention.

  The exposure apparatus 1 is a projection exposure apparatus that exposes the pattern of the reticle 20 onto the object to be processed 40 by a step-and-scan method or a step-and-repeat method. The exposure apparatus 1 is suitable for sub-micron and quarter-micron lithography processes, and in the present embodiment, a step-and-scan exposure apparatus (also referred to as a “scanner”) will be described as an example. Here, the “step and scan method” means that the wafer is continuously scanned (scanned) with respect to the reticle to expose the reticle pattern onto the wafer, and the wafer is stepped after completion of one shot of exposure. The exposure method moves to the next exposure area. The “step-and-repeat method” is an exposure method in which the wafer is stepped and moved to the next exposure area for every batch exposure of the wafer.

  As shown in FIG. 1, the exposure apparatus 1 includes an illumination apparatus 10, a reticle stage (not shown) on which the reticle 20 is placed, a projection optical system 30, a wafer stage (not shown) on which the object to be processed 40 is placed, and a polarization. A measurement unit 50 and a control unit 60 are included.

  The illumination device 10 illuminates a reticle 20 (illuminated surface) on which a transfer circuit pattern is formed, and includes a light source unit 12 and an illumination optical system 14.

For the light source unit 12, for example, an ArF excimer laser having a wavelength of about 193 nm and a KrF excimer laser having a wavelength of about 248 nm can be used as the light source. However, the type of the light source is not limited to the excimer laser. For example, an F ₂ laser having a wavelength of about 157 nm may be used, and the number of the light sources is not limited. The light source that can be used for the light source unit 12 is not limited to a laser, and one or a plurality of lamps such as a mercury lamp and a xenon lamp can be used.

  The illumination optical system 14 is an optical system that illuminates the reticle 20. In this embodiment, the illumination optical system 14 includes a beam shaping unit 141, bending mirrors 142a and 142b, effective light source forming means 143, and condenser lenses 144a and 144b. Further, the illumination optical system 14 includes an integrator 145, an aperture stop 146, a masking blade 147, imaging systems 148 a and 148 b, a collimator system 149, and a polarization degree adjusting unit 16.

  Referring to FIG. 1, the light beam emitted from the light source unit 12 is processed by the beam shaping unit 141 and drawn. Here, the processing means an action of enlarging or reducing the light beam diameter or uniforming the cross-sectional distribution of the light beam. The light beam emitted from the beam shaping unit 141 has its path changed by the bending mirror 142 a and enters the effective light source forming unit 143.

  The effective light source forming unit 143 includes a stop, a prism, and CGH (a diffractive optical element formed by a computer generated hologram). The effective light source forming unit 143 has a function of forming an arbitrary effective light source shape on the incident surface of the integrator 145 in cooperation with the subsequent first condenser lens 144a. The effective light source shape (illumination distribution) can be arbitrarily switched every time the exposure process during semiconductor manufacturing is changed. In an actual illumination optical system, the beam shaping unit 141, the bending mirror 142a, the effective light source forming unit 143, and the first condenser lens 144a may be referred to as a beam shaping unit.

  The integrator 145 is a wavefront division type integrator. An aperture stop 146 is disposed at the exit of the integrator 145. The aperture stop 146 regulates the light flux. The light beam that has passed through the aperture stop 146 is condensed on the masking blade 147 by the action of the second condenser 144b. The light beam that has passed through the masking blade 147 passes through the first imaging system 148a, the pupil plane IPS of the first imaging system 148a, the second imaging system 148b, the folding mirror 142b, and the collimator system 149, and the reticle 20 Condensed on the lower surface (circuit pattern surface).

  In the configuration of the illumination optical system 14, the polarization degree adjusting unit 16 is disposed immediately before the integrator 145. FIG. 2 is an optical path diagram showing the vicinity of the polarization degree adjusting means 16 in an enlarged manner, and shows the traveling state of light rays from the polarization degree adjusting means 16 to the masking blade 147.

  Referring to FIG. 2, in the optical arrangement of the present embodiment, the exit end face Ho of the integrator 145 is arranged on the front focal plane of the second condenser 144b, and the illuminated surface is set on the rear focal plane. In this embodiment, the integrator 145 is configured by a fly-eye lens, and each fly-eye lens is configured such that the entrance surface and the exit surface face each other with a focal distance f3 therebetween. As shown in FIG. 2, the fly-eye lens which is the integrator 145 of the present embodiment is manufactured by integrating the individual fly-eye lenses H1 to H3 (that is, as an integral lens).

  Light rays Lc21, Lc2 and Lc23 that are condensed on the fly-eye lens H2 on the optical axis become parallel rays by the refraction action of the exit-side lens of the fly-eye lens H2, and further, the light collection action of the second condenser lens 144b. Thus, an image is formed at a point C on the axis of the masking blade 147.

  Here, the polarization degree distribution of the light beams Lc21, Lc2, and Lc23 will be described. The light beams Lc21, Lc2, and Lc23 pass through a polarization plate adjusting means 16, for example, a phase plate made of a birefringent member, before entering the fly-eye lens H2. When passing through the phase plate, only the light beam Lc2 on the optical axis obtains a phase difference due to birefringence by the amount expressed by Equation 1. On the other hand, the peripheral light beams Lc21 and Lc23 pass through the phase plate obliquely, and thus a phase difference larger than the amount expressed by Equation 1 is obtained. A similar relationship holds for light rays that pass through off-axis fly-eye lenses H1 and H3.

  The cross-sectional distribution of the light beam that has passed through the point C on the axis of the masking blade 147 shown in FIG. 2 will be described. In FIG. 2, F2 indicates the light beam cross-sectional distribution of the light beam that has passed through the point C, and referring to the enlarged view, in the light beam group H2D that has passed through the fly-eye lens H2, the degree of polarization of the light beam Lc2 is small. (Τ3), the degree of polarization of the light beams Lc21 and Lc23 is large (τ2). A similar degree of polarization occurs in the light groups H3D and H1D that have passed through the off-axis fly-eye lenses H1 and H3.

  In the above description, it is assumed that the light beam incident on the fly-eye lens is telecentric, that is, the principal ray of the light beam condensed off-axis is parallel to the optical axis. When such a condition is broken, the off-axis principal ray also enters the phase plate at a slight angle, so that the ray groups H1D and H3D obtain a slightly larger degree of polarization than the ray group H2D. Become. However, even in this case, the effects of the present invention can be obtained without problems. The polarization degree distribution of the light beam focused on the point C on the axis of the masking blade 147 has been described above.

  Next, the polarization degree distribution of the light beam focused on the off-axis point U of the masking blade 147 will be described. As a conclusion, the polarization degree distribution of the light beam focused on the off-axis point U is the same as the polarization degree distribution focused on the point C on the axis.

  In the optical arrangement shown in FIG. 2, the incident surface of each fly-eye lens and the masking blade surface are optically conjugate (image relationship). For example, the uppermost point U1 of the fly-eye lens H2 is conjugate with the lowermost point U on the masking blade 147. Similarly, the uppermost points (not shown) of the fly-eye lenses H1 and H3 are also in a conjugate relationship with the lowermost point U on the masking blade 147, and a light ray group emitted from these conjugate points is collected at the U point. The light beams Lc11, Lu2 and Lc13 that are focused on the uppermost point U1 of the fly-eye lens H2 are simply about half the effective diameter of the fly-eye lens compared to the light beam groups Lc21, Lc2, and Lc23 that are focused on the point C1. Only parallel shift. Therefore, the light beams Lc21 and Lc11, the light beams Lc2 and Lu2, and the light beams Lc23 and Lc13 are incident on the fly-eye lens at substantially the same angle.

  As described above, the optical arrangement shown in FIG. 2 (that is, the degree of polarization adjusting means 16 is arranged immediately in front of the integrator 145) can provide an on-pupil degree of polarization distribution common to each point on the illuminated surface. The polarization degree distribution can be controlled.

  Here, the magnitude relationship between the polarization degree residue τ2 shown in FIG. 2 and the polarization degree error τ1 shown in FIG. 21 will be described. Note that τ3 is the degree of polarization received by the polarization degree adjusting means 16 or the phase plate PB when the light beam traveling straight on the optical axis in FIGS. 2 and 21 is shown in FIGS. 2 and 21 in order to simplify the explanation. Assume the same value. In general, in order for the illumination light beam to pass through the fly-eye lens without fail, the maximum incident angle of the light beam incident on the fly-eye lens is equal to or the maximum emission angle of the light beam emitted from the fly-eye lens. Must be smaller than.

  For example, in FIG. 2, the maximum incident angle θ1 of the light beam incident on the center C1 of the fly-eye lens H2 is set so that the light beam is not scattered on the exit surface Ho of the fly-eye lens H2. It is expressed by Formula 2. Sh is the effective diameter of one fly-eye lens.

  On the other hand, the maximum emission angle θ3 of the light beam emitted from the fly-eye lens is expressed by the following Equation 3. As shown in FIG. 2, the light beam Lu2 parallel to the optical axis incident on the outermost point U1 of the fly's eye lens H2 is emitted from the fly's eye lens H2 by the condensing action of the fly's eye lens H2. This is because it passes through the point Co on the optical axis on the surface and reaches the most off-axis point U as it is.

  When Equation 2 and Equation 3 are compared, the following Equation 4 is established.

  In other words, in the illumination optical system 14, in order to effectively use the light beam (energy) from the light source unit 12 without being lost, the maximum incident angle to the fly-eye lens is the emission from the fly-eye lens. It must be equal to the maximum angle or smaller than the maximum injection angle.

  In particular, in the case of a scanner, the optical illumination area currently has a rectangular shape of 8 mm to 13 mm in the scanning direction and 26 mm in the direction orthogonal to the scanning direction on the wafer surface. On the other hand, the light beam emitted from the light source unit is formed into a rotationally symmetric shape (substantially circular shape) on the incident surface of the fly-eye lens as an effective light source by the action of the beam shaping unit. Therefore, when comparing the margin of the light flux in the fly-eye lens between the cross section in the scanning direction and the cross section orthogonal to the cross section in the scanning direction, the incident light flux is rotationally symmetric, and thus the maximum in both cross sections. The incident angle θ1 is the same value. On the other hand, the maximum emission angle θ3 is about 2 to 3 times larger in the cross section perpendicular to the scanning direction.

  In order to effectively use the light beam (energy) from the light source unit without losing it, the optical system must be set so that the light beam cannot be lost even in a cross section in the scanning direction where the light beam margin is small. As a result, the cross-section perpendicular to the scanning direction with a large beam margin becomes a condition that is less likely to occur, and the maximum incident angle θ1 is reduced to 1/2 to 1/3 or less of the maximum emission angle θ3.

  In the prior art, the exit surface of the integrator (fly eye lens) (such a surface generally coincides with the diaphragm surface) and the pupil plane of the imaging system are optically conjugate. The effective diameter is a substantially equal dimension. Therefore, in the prior art, that is, the angle θ2 shown in FIG. 21 is substantially equal to the maximum injection angle θ3 shown in FIG. This is because from Helmholtz Lagrange's theorem, there is a relationship that the product of the irradiation screen size and the aperture angle on each surface is invariable (constant) between the object plane and the image plane that are in an imaging relationship. is there.

  Both the polarization degree residue τ2 and the polarization degree error τ1 are generated when passing through the phase plate (polarization degree adjusting means 16) obliquely, and the amount of generation increases as the angle of incidence on the phase plate increases. . Therefore, it can be seen that the polarization degree residue τ2 generated in this embodiment (FIG. 2) is smaller than the polarization degree error τ1 in the prior art (FIG. 21). In particular, in a cross section perpendicular to the scanning direction, the amount is reduced to 1/2 to 1/3 or less.

  FIG. 3 is an optical path diagram showing, in an enlarged manner, the vicinity of the phase distribution element 16A when the polarization adjusting unit 16 is replaced with a phase distribution element 16A having a quadratic function distribution as a specific example. With respect to all the light rays incident on the fly-eye lens H2, the light rays incident on the fly-eye lenses H1 and H3 located off-axis obtain a large degree of polarization by the action of the phase distribution element 16A. Therefore, in the present embodiment, the distribution on the pupil of the light beam condensed at the point C and the point U has a quadratic function-like distribution (see the F2 enlarged view shown in FIG. 3).

  In this way, by forming an arbitrary phase distribution in the polarization degree adjusting means 16, it becomes possible to control the polarization degree distribution on the pupil common to each point on the illuminated surface. The phase distribution element 16A has a quadratic function surface shape, but this is for clearly explaining the effect of the present invention, and is not limited to such a shape. For example, even if the phase distribution element 14A is a parallel plate, the effect of the present invention can be obtained if the birefringence distribution is a quadratic function.

  FIG. 4 is a schematic cross-sectional view showing a phase plate 160A which is a specific configuration of the polarization degree adjusting means 16. The phase plate 160A has a configuration of a phase plate known as a Babinet Soleil plate, and two crystal plates (adjustment plates 162A and 164A) whose main axes of birefringence are orthogonal to each other are processed into a wedge shape, and the unevenness is complementary. It has the structure combined so that it may become. In the present embodiment, as shown in FIG. 4, the wedge surfaces of the adjusting plates 162A and 164A are arranged in a cross section orthogonal to the optical axis Z (in the Y-axis direction in FIG. 4). The birefringence amount Δε generated in the Y-axis direction by the phase plate 160A shown in FIG. 4 becomes a linear function as shown by a solid line in FIG.

When the two adjustment plates 162A and 164A are slightly shifted from each other in the Y-axis direction,
A certain amount of birefringence expressed by a differential function of a surface shape (in this embodiment, wedge-shaped and linear function) is further added. The added birefringence amount (addition amount) is indicated by a dotted line in FIG.

  When the difference between the thicknesses of two phase plates whose main axes are orthogonal to each other is Δd, the birefringence change φ2 received by the light beam passing through the phase plate is expressed by the following Equation 5.

  Furthermore, it has been found that the amount of wavefront aberration that occurs when curved surfaces having a pair of concave and convex shapes that are complementary to each other relatively translates follows a differential function of such curved surfaces. The physical quantity called the wavefront aberration amount is defined by the product of the refractive index of the material through which the light beam propagates and the optical path length (strictly, the optical path length difference between the principal ray and the peripheral ray). It is none other than the difference Δd.

  Therefore, in FIG. 5, by moving the adjustment plates 162A and 164A relatively in the Y-axis direction (both positive and negative directions), it is possible to correct a wide range of birefringence distribution as shown by the dotted line. The solid line is a birefringence in the form of a linear function generated by introducing this optical element.

  FIG. 6 is a schematic cross-sectional view showing an optical member 160 </ b> B that is a specific configuration of the polarization degree adjusting means 16. The optical member 160B is composed of two adjustment plates 162B and 164B having concavities and convexities facing each other. The surface shapes of the adjustment plates 162B and 164B are formed in a quadratic curve. The birefringence amount Δε generated in the Y-axis direction by the optical member 160B shown in FIG. 6 is a quadratic function as shown by the solid line in FIG. Further, when the two adjusting plates 162B and 164B are slightly shifted in the Y-axis direction, the birefringence amount of a linear function is further added as shown by a dotted line in FIG.

  FIG. 8 is a schematic sectional view showing an optical member 160 </ b> C that is a specific configuration of the polarization degree adjusting means 16. The optical member 160C is composed of two adjustment plates 162C and 164C having concavities and convexities facing each other. The surface shapes of the adjustment plates 162C and 164C are formed in a quadratic curve shape. The birefringence amount Δε generated in the Y-axis direction by the optical member 160C shown in FIG. 8 becomes a cubic function as shown by a solid line in FIG. When the two adjustment plates 162C and 164C are slightly shifted in the Y-axis direction, the birefringence amount of a quadratic function is further added as shown by the dotted line in FIG.

  In the present embodiment, the adjustment plates 164A, 164B, and 164C are exemplarily shifted, but the same effect can be obtained by shifting the adjustment plates 162A, 162B, and 162C. Further, the same effect can be obtained even if the pair of adjusting plates are displaced in the opposite directions (the + direction and the − direction in the Y-axis direction). The physical quantity that determines the adjustment range is the product of the coefficient of the degree of the curve that defines the surface shape of the adjustment plate and the movement amount d of the adjustment plate. However, the polarization degree adjusting means 16 is not limited to the phase plate 160A and the optical members 160B and 160C, but includes a complementary phase plate having any phase distribution or any shape.

  FIG. 10 is a schematic cross-sectional view showing an optical member 160 </ b> D that is a specific configuration of the polarization adjusting unit 16. The optical member 160D has a configuration in which a pair of adjustment plates 166D and 168D are further added to the phase plate 160A shown in FIG. The adjusting plates 166D and 168D are arranged in the phase plate 160A by disposing the adjusting plates 162A and 164A in the optical path, so that the degree of polarization originally generated before the adjusting plates 162A and 164A are driven eccentrically (the solid line shown in FIG. 5). Distribution).

  Adjustment plates 166D and 168D are configured such that the amount of birefringence cancels out light rays passing through respective heights on the Y axis. In other words, the shapes of the adjusting plates 166D and 168D are configured to be the same as the shapes of the adjusting plates 162A and 164A, and the birefringence amount is reversed. In the present embodiment, the adjustment plates 166D and 168D are illustrated so as to correct the optical axis deviation caused by the (own) wedge shape, but are not necessarily limited to this shape. The adjustment plates 166D and 168D allow any shape as long as they are optical members that cancel the amount of birefringence generated by the adjustment plates 162A and 164A.

  As a result, the birefringence amount Δε generated in the Y-axis direction by the optical member 160D becomes 0 as shown by the solid line in FIG. 11, as shown in FIG. 11, and is generated by the eccentric movement of the adjusting plates 162A and 164A. Only the amount of birefringence (dotted line shown in FIG. 11) is effective.

  FIG. 12 is a schematic cross-sectional view showing an optical member 160 </ b> E that is a specific configuration of the polarization adjusting unit 16. The optical member 160E has a configuration in which a pair of adjustment plates 166E and 168E are further added to the optical member 160B shown in FIG. The adjusting plates 166E and 168E are arranged in the optical member 160B by arranging the adjusting plates 162B and 164B in the optical path, so that the degree of polarization that is originally generated before the adjusting plates 162B and 164B are eccentrically driven (the solid line shown in FIG. 7). Distribution).

  The adjusting plates 166E and 168E are configured such that the birefringence amount cancels out the light rays passing through the respective heights on the Y axis. In other words, the shapes of the adjustment plates 166E and 168E are configured to be the same as the shapes of the adjustment plates 162B and 164B, and the birefringence amount is reversed. In the present embodiment, the adjustment plates 166E and 168E are illustrated so as to correct the optical axis deviation caused by the quadratic curve shape, but are not necessarily limited to this shape. The adjustment plates 166E and 168E allow any shape as long as they are optical members that cancel the amount of birefringence generated by the adjustment plates 162B and 164B.

  As a result, as shown in FIG. 13, the birefringence amount Δε generated in the Y-axis direction by the optical member 160E becomes 0 as shown by the solid line in FIG. 13, and is generated by the eccentric movement of the adjusting plates 162B and 164B. Only the amount of birefringence (dotted line shown in FIG. 13) is effective.

  FIG. 14 is a schematic cross-sectional view showing an optical member 160 </ b> F that is a specific configuration of the polarization adjusting unit 16. The optical member 160F has a configuration in which a pair of adjustment plates 166F and 168F are further added to the optical member 160C shown in FIG. The adjusting plates 166F and 168F are arranged in the optical member 160C by arranging the adjusting plates 162C and 164C in the optical path, so that the degree of polarization that is originally generated before the adjusting plates 162C and 164C are eccentrically driven (the solid line shown in FIG. 9). Distribution).

  The adjusting plates 166F and 168F are configured such that the birefringence amount cancels out the light beam passing through the respective heights on the Y axis. In other words, the shapes of the adjustment plates 166F and 168F are configured to be the same as the shapes of the adjustment plates 162C and 164C, and the birefringence amount is reversed. In the present embodiment, the adjustment plates 166F and 168F are illustrated so as to correct the optical axis deviation caused by the quadratic curve shape, but are not necessarily limited to this shape. The adjustment plates 166F and 168F allow any shape as long as they are optical members that cancel the amount of birefringence generated by the adjustment plates 162C and 164C.

  As a result, the birefringence amount Δε generated in the Y-axis direction by the optical member 160F is 0 as shown by the solid line in FIG. 15, as shown in FIG. 15, and is generated by the eccentric movement of the adjusting plates 162C and 164C. Only the amount of birefringence (dotted line shown in FIG. 15) is effective.

  FIG. 16 is a schematic cross-sectional view showing an optical member 160G having a polarization adjusting means configuration. The optical member 160G is composed of a pair of phase plates 162G and 164G in which the unevenness formed by a two-dimensional curved surface has a complementary relationship.

  The adjustment plates 162A and 164A, 162B and 164B, 162C and 164C shown in FIGS. 4, 6 and 8 have a one-dimensional curved surface shape, and are moved in the Y-axis direction to thereby change the one-dimensional polarization. The degree is corrected. On the other hand, the optical member 160G can decenter the phase plates 162G and 164G by a predetermined amount (dx, dy) in two directions of the X-axis direction and the Y-axis direction, respectively, as shown in FIG. Thereby, the optical member 160G can two-dimensionally correct the degree of polarization distribution on the pupil plane at each point on the illuminated surface. It should be noted that the principle of such correction is the same as the one-dimensional correction, and is omitted.

  As shown in FIG. 17, the illumination optical system 14 can also include an illumination optical system 18. The illumination optical system 18 is the same in that the polarization degree adjusting means 16 is disposed on the illuminated surface of the first condenser 144a in the illumination optical system 14. However, the illumination optical system 18 uses the polarization degree adjusting unit 16 as an object plane, and the luminous flux emitted from the polarization degree adjusting unit 16 on the incident surface of the integrator 145 by the action of the condenser 181 and the field lens 182 newly disposed. Form an image. Here, FIG. 17 is a schematic sectional view showing the configuration of the exposure apparatus 1 as one aspect of the present invention.

  The light beam emitted from the integrator 145 travels on the same optical path as that of the illumination optical system 14 shown in FIG. The field lens 182 makes the light beam incident on the integrator 145 close to telecentric (the principal ray is parallel to the optical axis). As a result, as described above, the birefringence amount generated in the light ray group incident on the on-axis fly-eye lens and the birefringence amount generated in the light ray group incident on the off-axis fly-eye lens are the same amount. Thus, the polarization degree correction residue can be kept small.

  In the illumination optical system 18, since the polarization degree adjusting means 16 is disposed at a position away from the integrator 145, the spatial restriction of the optical system can be released. In addition, the illumination optical system 18 may use a phase plate having a larger diameter than the integrator 145 as the polarization degree adjusting means 16, and reduce the light beam from the phase plate on the integrator incident surface. Accordingly, from the Helmholtz Lagrange's theorem, the angle of the light beam incident on the phase plate can be suppressed to be smaller than that in the configuration of FIG. 1, and the polarization degree residue τ 2 in FIG. 2 can be further reduced.

  Returning to FIG. 1, the reticle 20 is made of, for example, quartz, and a circuit pattern (or image) to be transferred is formed on the lower surface thereof, and is supported and driven by a reticle stage (not shown). The diffracted light emitted from the reticle 20 passes through the projection optical system 30 and is projected onto the object to be processed 40. The reticle 20 and the workpiece 40 are arranged in an optically conjugate relationship. Since the exposure apparatus 1 is a scanner, the pattern of the reticle 20 is transferred onto the object to be processed 40 by scanning the reticle 20 and the object to be processed 40 at the speed ratio of the reduction magnification ratio. During such scanning, the masking blade 147 of the illumination optical system 14 defines an illuminated area on the reticle surface. In the case of a step-and-repeat type exposure apparatus (also called “stepper”), exposure is performed with the reticle 20 and the object to be processed 40 being stationary.

  The projection optical system 30 has a function of forming an image of the diffracted light that has passed through the pattern formed on the reticle 20 on the workpiece 40. The projection optical system 30 can use a catadioptric optical system having a plurality of lens elements and at least one reflecting mirror, a refractive optical system consisting of only a plurality of lens elements, and the like. In the present embodiment, the projection optical system 30 includes a first projection lens group (front lens) 32 and a second projection lens group (rear lens) 34, and the first projection lens group 32 and the second projection lens group 32 are connected to each other. A pupil plane PPS exists between the projection lens group 34 and the projection lens group 34.

  The workpiece 40 is supported and driven by a wafer stage (not shown). The object to be processed 40 is a wafer in the present embodiment, but widely includes liquid crystal substrates and other objects to be processed. A photoresist is applied to the object to be processed 40.

  The polarization measuring unit 50 measures the polarization state of the light beam that has passed through the illumination optical system 14 emitted from the light source unit 12. In the present embodiment, the polarization measuring unit 50 includes a polarization degree sensor 52 disposed on a surface equivalent to the workpiece 40 and a polarization degree sensor 54 disposed on a surface equivalent to the reticle 20.

  Since any configuration known in the art can be applied to the configurations of the polarization degree sensors 52 and 54, a detailed description of the structure and operation is omitted here. For example, the rotatable phase plate proposed by the present applicant is arranged in combination with an analyzer, and transmitted light at a plurality of rotational positions of the phase plate is received and calculated by a photoelectric sensor (photo pin sensor or CCD sensor). Applying the method to obtain the degree of polarization.

  The control unit 60 includes a CPU and a memory (not shown) and controls the operation of the exposure apparatus 1. The controller 60 is electrically connected to the illumination device 10, a reticle stage and wafer stage (not shown), and the polarization measuring unit 50. The CPU includes any processor of any name such as MPU and controls the operation of each unit. The memory is composed of ROM and RAM, and stores firmware that operates the exposure apparatus 1.

  In the present embodiment, the control unit 60 acquires information such as the polarization state of the exposure light, and controls the polarization state of the exposure light based on the information. Outputs of the polarization degree sensors 52 and 54 are input to the control unit 60, and when a polarization degree error exceeding an allowable value is detected as a result of the calculation, a command for adjusting this is given to the polarization degree adjustment means 16. Sent. Further, the control unit 60 transmits the command to the effective light source forming unit 143 when switching the illumination mode of the illumination device 10. In other words, this embodiment suggests that the degree of polarization under a new illumination mode is measured and the degree of polarization is adjusted automatically based on the measurement result.

  Here, the polarization degree adjustment by the control unit 60 will be described with reference to FIG. FIG. 18 is a flowchart for explaining the polarization degree adjustment in the exposure apparatus 1. Referring to FIG. 18, first, when the illumination mode is set (step 1002), the polarization degree is measured at each point on the object surface and the reticle surface by the polarization measuring unit 50 (polarization degree sensors 52 and 54). (Step 1004).

Next, the measured value of the measured degree of polarization is compared with a preset allowable value of the degree of polarization (step 1006). When the measured degree of polarization exceeds the allowable value, the degree of polarization adjusting means 16 (for example, the phase plate 164A) necessary for correcting the degree of polarization (that is, within the allowable value range). Is calculated (step 1008). Next, the polarization degree adjusting means 16 is driven based on the driving amount (step 10010). Further, the degree of polarization is measured again at each point on the object surface and the reticle surface (step 1012), and the process returns to step 1006 to compare the measured value of the degree of polarization with the allowable value of the degree of polarization. On the other hand, when the measured polarization degree does not exceed the allowable value, the polarization degree adjustment is terminated. Such polarization degree adjustment is performed every time the illumination mode is switched (reset). (When the illumination mode is switched, the position where the illumination light beam passes through the optical system changes, and the influence of the birefringence index of the optical system also changes. Therefore, by adjusting the polarization state for each illumination mode in this way, (It can be said that the effect of optimizing the resolution performance is very great.)
As described above, the exposure apparatus 1 is configured so that the illumination optical system 14 or 18 (polarization degree adjusting means disposed immediately in front of the integrator) causes a screen on the illuminated surface even if an error in the polarization degree occurs in the exposure optical system. It is possible to accurately control the polarization distribution on the pupil common to each point. Therefore, the exposure apparatus 1 can correct the polarization degree error and improve the contrast of the optical image formed on the surface of the object to be processed. Further, when there is a difference in optical image contrast among a plurality of exposure apparatuses, the difference in contrast between the exposure apparatuses can be made the same. Thereby, it becomes possible to expose the same reticle under the same exposure conditions using a plurality of exposure apparatuses, and it is possible to greatly improve the process and reduce the cost of the semiconductor manufacturing process.

  In the exposure, the light beam emitted from the light source unit 12 illuminates the reticle 20 by the illumination optical system 14, for example, Koehler illumination. The light that passes through the reticle 20 and reflects the circuit pattern is imaged on the object 40 by the projection optical system 30. As described above, the exposure apparatus 1 can make the exposure light have a desired (optimal) degree of polarization, that is, can be exposed using exposure light having a desired polarization state. As a result, the exposure apparatus 1 can provide a high-quality device (semiconductor element, LCD element, imaging element (CCD, etc.), thin film magnetic head, etc.) with high throughput and high economic efficiency.

  Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 1 will be described with reference to FIGS. FIG. 19 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), a device circuit is designed. In step 2 (reticle fabrication), a reticle on which the designed circuit pattern is formed is fabricated. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the reticle and wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 20 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a reticle circuit pattern onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using the exposure apparatus 1 and the resulting device also constitute one aspect of the present invention.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. It is an optical path diagram which expands and shows the vicinity of the polarization degree adjusting means shown in FIG. FIG. 2 is an enlarged optical path diagram showing the vicinity of a phase distribution element when the polarization adjusting unit shown in FIG. 1 is replaced with a phase distribution element as a specific example. It is a schematic sectional drawing which shows the phase plate which is a specific structure of the polarization degree adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the phase plate shown in FIG. 4 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization degree adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the optical member shown in FIG. 6 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization degree adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the optical member shown in FIG. 8 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the optical member shown in FIG. 10 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the optical member shown in FIG. 12 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization adjustment means shown in FIG. It is a figure which shows the amount of birefringence which the optical member shown in FIG. 14 generate | occur | produces in a Y-axis direction. It is a schematic sectional drawing which shows the optical member which is a specific structure of the polarization adjustment means shown in FIG. It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. 3 is a flowchart for explaining polarization degree adjustment in the exposure apparatus shown in FIG. 1. It is a flowchart for demonstrating manufacture of devices (semiconductor chips, such as IC and LSI, LCD, CCD, etc.). 20 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 19. It is a figure which shows the example of arrangement | positioning of the phase plate in a prior art, and the polarization degree in that case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 Illumination device 12 Light source part 14 Illumination optical system 143 Effective light source formation means 147 Masking blade 16 Polarization degree adjustment means 16A Phase distribution element 160A Phase plate 162A and 164A Adjustment plate 160B Optical member 162B and 164B Adjustment plate 160C Optical member 162C And 164C Adjustment plate 160D Optical member 166D and 168D Adjustment plate 160E Optical member 166E and 168E Adjustment plate 160F Optical member 166F and 168F Adjustment plate 160G Optical member 162G and 164G Adjustment plate 18 Illumination optical system 181 Condenser 182 Field lens 20 Reticle 30 Projection optical System 40 Object 50 Polarization Measurement Units 52 and 54 Polarization Sensor 60 Control Unit

Claims (14)

An illumination optical system that illuminates a surface to be illuminated with a light beam from a light source,
A beam shaping unit for shaping a cross-sectional shape of a light beam from the light source;
An integrator for splitting the light beam from the beam shaping unit;
A condenser system that superimposes the luminous flux divided by the integrator and guides it to the illuminated surface;
An optical member having a birefringence distribution in a cross section orthogonal to the optical axis, which is disposed between the incident surface of the integrator or the beam shaping unit and the integrator and in a plane conjugate with the incident surface of the integrator. An illumination optical system.   2. The illumination optical system according to claim 1, wherein the birefringence distribution is one-dimensionally or two-dimensionally continuous.   The illumination optical system according to claim 1, wherein a maximum incident angle of a light beam incident on the integrator is smaller than a maximum emission angle of a light beam emitted from the integrator. The optical member has a pair of optical elements having planes in which the one-dimensional or two-dimensional irregularities of the surface shapes are complementary to each other,
2. The illumination optical system according to claim 1, wherein the pair of optical elements are birefringence generating elements, and their principal axes are shifted in a cross section perpendicular to the optical axis. The optical member has a pair of optical elements having planes in which the one-dimensional or two-dimensional irregularities of the surface shapes are complementary to each other,
The illumination optical system according to claim 1, wherein at least one of the optical elements is a birefringence generating element.   6. The illumination optical system according to claim 4, wherein the pair of optical elements can move in parallel with each other within a cross section perpendicular to the optical axis.   6. The illumination optical system according to claim 4, wherein the optical member includes a canceling member having birefringence that cancels the birefringence of the pair of optical elements.   The illumination optical system according to claim 1, wherein the light beam incident on the integrator is telecentric. An exposure apparatus that exposes a reticle pattern onto an object to be processed,
The illumination optical system according to any one of claims 1 to 8, which illuminates the reticle;
An exposure apparatus comprising: a projection optical system that projects the reticle pattern onto the object to be processed. A polarization measuring means for measuring a polarization state of the light beam on the surface of the object or the reticle;
The exposure apparatus according to claim 9, further comprising a control unit that adjusts the optical member based on a polarization state of the light beam measured by the polarization measuring unit.   The exposure apparatus according to claim 10, wherein the controller adjusts the optical member every time an illumination mode of the illumination optical system is changed. Exposing the object to be processed using the exposure apparatus according to any one of claims 9 to 11,
And developing the exposed object to be processed.   An exposure apparatus that adjusts a polarization control member in accordance with a change in illumination mode.   An exposure apparatus that measures a polarization state on a reticle surface or a wafer surface and adjusts a polarization control member in accordance with a change in illumination mode.