WO1999065066A1

WO1999065066A1 - Transfer method and aligner

Info

Publication number: WO1999065066A1
Application number: PCT/JP1999/002941
Authority: WO
Inventors: Naomasa Shiraishi
Original assignee: Nikon Corporation
Priority date: 1998-06-10
Filing date: 1999-06-02
Publication date: 1999-12-16
Also published as: AU4058599A; TW417164B; JP4465644B2

Abstract

A transfer method for exposing with high accuracy an image of a circuit pattern consisting of a gate-pattern-like linear pattern and a wide pattern at the end of the linear pattern, wherein a first reticle pattern, in which light shielding patterns (A1 to A3) having substantially the same shape as an original pattern are formed in a transmission unit (35), and a second reticle pattern, in which transmission patterns (B1 to B3) are formed periodically in a light shielding unit (32) so as to sandwich portions corresponding to patterns (A1a, A2a, A3a, A3b) which are as wide as the resolution limit of a projection optical system in light shielding patterns (A1 to A3), are formed from the original pattern of the circuit pattern to be transferred. After an image of the first reticle pattern is exposed onto a wafer via the projection optical system by using an illuminating light from a circular aperture stop, an image of the second reticle pattern is superposingly exposed onto the wafer under a deformed illumination.

Description

Description Transfer method and exposure apparatus

The present invention transfers a mask pattern image onto a substrate such as a wafer during a lithography process for forming a fine pattern of an electronic device such as a semiconductor integrated circuit, an image pickup device (CCD or the like), or a liquid crystal display device. The present invention relates to a transfer method and an exposure apparatus used for the transfer. Background art

Conventionally, a fine pattern of a semiconductor integrated circuit or the like is obtained by using a projection exposure apparatus (stepper or the like) to apply an image of an original pattern drawn on a reticle as a mask to a wafer coated with a photoresist as a photosensitive film. It is formed by subjecting a photosensitive resist film to a positive resist by development after projecting and exposing it to a substrate such as the above, followed by a predetermined processing step. In order to miniaturize the pattern of the semiconductor integrated circuit or the like, that is, to improve the degree of integration, it is necessary to improve the resolution of the projection optical system provided in the projection exposure apparatus. The resolution of a projection optical system is generally proportional to λ / Α 、, assuming the wavelength of illumination light (exposure light) and the numerical aperture as NA. The currently mainstream exposure wavelength λ is 248 nm of KrF excimer laser light, but the use of ArF excimer laser light (wavelength: 193 nm) will be considered in the future. ing. However, if the wavelength is further shortened, it is difficult to construct a projection optical system using a refraction system because there is no suitable glass material that can be used as a lens constituting the projection optical system. On the other hand, since the numerical aperture NA of the current projection optical system is as large as about 0.7, further improvement of the numerical aperture NA cannot be expected. Depth of focus (DOF) is also important when actually transferring a fine pattern, but the depth of focus is reduced by either shortening the exposure wavelength λ or improving the numerical aperture NA. Although the depth of focus varies depending on the type of the pattern to be transferred, in the case of a dense pattern (periodic pattern) in which the patterns are arranged relatively close to each other, Japanese Patent Application Laid-Open No. H11-111408 and As disclosed in the corresponding U.S. Pat.No. 5,638,211, Japanese Patent Application Laid-Open No. H5-20607, and the corresponding U.S. Pat.No. 5,719,704, On the optical Fourier transform surface for the reticle pattern in the illumination optical system, by controlling the shape of the distribution of the amount of illumination light, that is, by performing modified illumination to control the angle of incidence of the illumination light on the reticle, Its resolution and depth of focus can be greatly improved.

On the other hand, a linear pattern (fine line pattern) with a fine line width, which is called an isolated line and is relatively isolated from other patterns, is a pattern in which it is particularly difficult to obtain a focal depth. In electronic devices such as semiconductor integrated circuits and liquid crystal display elements, patterns called gate patterns that determine the performance of the devices include isolated lines.

Techniques for improving the resolution and depth of focus for isolated lines are disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 4-268781 and the corresponding U.S. Patent No. 5,357,311. As described above, there is a method (hereinafter referred to as “auxiliary pattern method”) in which auxiliary patterns are added to both ends of the isolated line, and deformed illumination (including annular illumination) is also used. By this method, the imaging characteristics of the isolated line can be improved to some extent. Further, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-2743427, a method for forming an isolated line by composite exposure (multiple exposure) of an isolated line and a periodic pattern (hereinafter referred to as “synthetic exposure”) Law). Also in this method, the resolution and the depth of focus are improved by using deformed illumination when exposing the periodic pattern. Therefore, the resolution and depth of focus of the isolated line image are greatly improved.

As described above, conventionally, methods for improving the resolution and depth of focus of an image of an isolated line included in a gate pattern or the like have been proposed. However, in the former auxiliary pattern method, the resolution of the isolated line image and the depth of focus may not be sufficiently improved. In addition, the latter synthetic exposure method was able to almost cope with the imaging characteristics required in the past, but in order to perform high-precision exposure of circuit patterns that will be further miniaturized in the future, the following methods are required. There is a problem. One is that the actual gate pattern is not just an isolated line, but has a wide overlapping pattern at either or both ends of the isolated line for connection with the wiring pattern. Therefore, it is not easy to disassemble the gate pattern, which will be further miniaturized, into an isolated line and a periodic pattern.

Another problem is that when exposing one periodic pattern of the two types of patterns to be synthesized, modified illumination is used to further improve the resolution and depth of focus. It is necessary to limit the luminous flux on the optical Fourier transform surface in the optical system to a small area as far away from the optical axis as possible. Thus, if the illumination light beam is narrowed down on the Fourier transform surface in the illumination optical system, the spread of the light beam in the projection optical system is correspondingly reduced, and as a result, the projection optical system is affected by the exposure light beam. Local heating causes local thermal expansion and changes in the refractive index, and the imaging characteristics of the projection optical system gradually degrade slightly.

In view of the above, the present invention provides a transfer method capable of transferring a circuit pattern image composed of a linear pattern such as a gate pattern and a pattern having a wide end portion onto a substrate such as a wafer with high accuracy. The primary purpose is to provide.

Furthermore, the present invention transfers a pattern image such as an isolated line onto a substrate with high accuracy. A second object is to provide a transfer method that can be used.

A third object of the present invention is to provide a transfer method capable of suppressing deterioration of the imaging characteristics of the projection optical system when deformed illumination is used as part of the illumination conditions.

Further, the present invention provides an exposure apparatus that can use such a transfer method, an efficient manufacturing method of the exposure apparatus, and a device manufacturing method that can manufacture a device with high accuracy using such a transfer method. It is also intended. Disclosure of the invention

A first transfer method according to the present invention is a transfer method that transfers an image of a pattern (P 1) having a predetermined shape including a predetermined linear pattern (P la) onto a substrate (16) via its projection optical system. A first mask pattern (9A) in which a portion (A1) corresponding to the pattern having a predetermined shape is a light-reducing portion, and the other portion (35) is a transmissive portion; A plurality of transmission patterns (B 1) each having substantially the same line width as the linear pattern are formed in the width direction of the linear pattern so as to contact the portion (P la ′) corresponding to the linear pattern. A second mask pattern (9B) that is periodically arranged and at least a region other than the transmission pattern in the vicinity of a portion corresponding to the linear pattern is used as a light-reducing portion (32) is used. The images of the two masks are sequentially placed on the substrate via the projection optical system. Next, the light is transferred while being aligned with each other, and the illumination conditions for exposing the image of the second mask pattern are determined by the intensity distribution on the optical Fourier transform plane (5) for the pattern to be exposed by the illumination optical system. However, in this region outside the vicinity of the optical axis, strong deformed illumination is used.

In the present invention, by using the modified illumination, Since an image of a periodic pattern finer than the resolution limit under illumination can be projected with a high depth of focus with high precision, when dividing the pattern of the predetermined shape into the first and second mask patterns, In this mask pattern, a transmission pattern (B 1) that is periodically arranged only at a position corresponding to the vicinity of the linear pattern was formed, and the other portions were light reduction portions.

As a result, the shape of the first mask pattern may be substantially the same as the pattern of the predetermined shape to be transferred, and there is almost no pattern data to be newly created, while the second mask pattern has a line shape. It is only necessary to arrange them around the shape pattern, and the amount of creation for each day is small as a whole. Further, when the pattern having the predetermined shape is a gate pattern, it is not necessary to form a wide pattern such as a pattern for superimposing the end of the linear pattern on the second mask pattern, and the second mask pattern is substantially formed. This means that the gate pattern is easily and easily decomposed into isolated lines and periodic patterns.

Also, the transmission pattern included in the second mask pattern is only a minute periodic pattern portion around the linear pattern, and the transmittance (the ratio of the transmission pattern) of the entire pattern is low. When performing deformed illumination using a mask pattern, the amount of light transmitted through the projection optical system is reduced. Therefore, even if the imaging light flux is locally concentrated in the projection optical system due to the deformed illumination, there is no danger that the optical system will be locally heated and deformed, and the high-resolution deformed illumination should be used stably. Becomes possible.

Further, it is desirable that the exposure amount when transferring the second mask pattern is set to be larger than the exposure amount when transferring the first mask pattern.

Next, a second transfer method according to the present invention is a transfer method for transferring an image of an isolated linear pattern onto a substrate via a projection optical system, wherein the linear pattern is used as a light-reducing portion. Isolated first pattern (A 1) and multiple transparent patterns The periodic second pattern (B 1) consisting of the pattern is illuminated with the illumination light, and the dimming part of the first pattern and one dimming sandwiched between the plurality of transmission patterns on the substrate. The substrate is subjected to multiple exposure using the first and second patterns so that the portions overlap.

According to the present invention, the final line width of the isolated linear pattern is accurately defined by the periodic transfer of the second pattern, and unnecessary periodic patterns are covered by the transfer of the first pattern. It can transfer isolated linear patterns with high accuracy.

It is desirable that the exposure amount when transferring the first pattern and the exposure amount when transferring the second pattern be different.

Further, the line width of the first pattern is approximately 1 to 2 times the line width of the linear pattern, and the line width of the second pattern is desirably about the same as the line width of the linear pattern. .

Next, a third transfer method according to the present invention is a transfer method for transferring an image of an isolated linear pattern onto a substrate via a projection optical system, wherein the transfer pattern has substantially the same shape as the linear pattern. A first pattern (A 1) of the above and a periodic second pattern (B 1) including a linear portion having substantially the same line width as the linear pattern are illuminated with illumination light, respectively. The substrate is subjected to multiple exposure using the first and second patterns so that the first pattern and the linear portion of the second pattern overlap. According to the third transfer method of the present invention, as in the second transfer method of the present invention, an isolated linear pattern can be transferred with high accuracy.

In addition, it is desirable that the exposure condition of the substrate when transferring the first pattern and the exposure condition of the substrate when transferring the second pattern be different.

Also, the exposure condition is applied to the first and second patterns, respectively. When the substrate is exposed using the second pattern, the illumination optical system includes the intensity distribution of the illumination light on the optical Fourier transform plane for the pattern in the illumination optical system that emits bright light. It is desirable to increase the intensity distribution of the illumination light outside the region including the optical axis of the illumination light.

It is desirable that the exposure conditions include the exposure amount of the substrate.

The second pattern preferably includes a transmissive portion that shifts the phase of the illumination light by approximately 180 °, and the transmissive portion is desirably a translucent portion that reduces the illumination light.

Further, it is desirable that the line pattern has a line width at least at one end larger than that at the center. The linear pattern is, for example, a gate electrode pattern.

In each of the above inventions, the line width of the linear pattern is, for example, substantially equal to the resolution limit of the projection optical system. Such a linear pattern is, for example, when illuminated under illumination conditions (normal illumination) using illumination light passing through a substantially circular area centered on the optical axis on the optical Fourier transform surface with respect to the mask pattern. A pattern whose ideal projected image width is about 12 to 5 times the theoretical resolution limit of the projected optical system. Next, the exposure apparatus according to the present invention comprises an illumination optical system (1 to 4, 6A, 6B, 7) for illuminating a predetermined mask, and a projection optical system for transferring an image of a pattern of the mask onto a substrate. In the exposure apparatus having (1) and (2), the illumination conditions of the illumination optical system are set such that the intensity distribution of the pattern to be exposed on the optical Fourier transform plane (5) is stronger in a region outside the vicinity of the optical axis than in the vicinity of the optical axis. An illumination condition control system (2 3, 4 2, 4 3) that switches between deformed illumination and other illumination, and a plurality of mask patterns (9 A, 9 B) A pattern selecting device (11 to 13) for selecting one of the mask patterns and a mutual position of a plurality of mask patterns sequentially selected by the pattern selecting device; An alignment system (8A, 8B, 25) that performs alignment, and an exposure system that switches the illumination conditions via the illumination condition control system according to the pattern selected by the pattern selection device to perform multiple exposure. Control system (27) and With this exposure apparatus, the first and second transfer methods of the present invention can be performed.

Next, the method of manufacturing an exposure apparatus according to the present invention includes an illumination optical system (1 to 4, 6A, 6B, 7) for illuminating a predetermined mask, and a projection for transferring an image of a pattern of the mask onto a substrate. The illumination conditions of the optical system (14) and its illumination optical system are defined as follows: the intensity distribution of the pattern to be exposed on the optical Fourier transform surface (5) is higher than that of the vicinity of the optical axis. , An illumination condition control system (23, 42, 43) that switches to one of the other illuminations, and one of a plurality of mask patterns (9A, 9B) as the mask pattern A pattern selection device (11 to 13), an alignment system (8A, 8B, 25) for mutually aligning a plurality of mask patterns sequentially selected by the pattern selection device, and the pattern The lighting condition control system according to the pattern selected by the selection device An exposure control system for performing multiple exposure (2 7) is switched the lighting conditions through, the one in which assembled in a predetermined positional relationship.

Further, the device manufacturing method according to the present invention includes, in a certain layer, a pattern having a line width substantially equal to a resolution limit of a projection image of a projection optical system (14) of an exposure apparatus to be used. A method for manufacturing a device in which a circuit pattern having a predetermined shape is formed, wherein the exposure apparatus exposes the layer using the exposure method according to the present invention. As a result, a pattern having a line width approximately equal to the resolution limit of the projection optical system can be formed with high accuracy. Also, for example, the linear pattern is a gate electrode pattern of a field-effect transistor. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing a projection exposure apparatus used in an example of an embodiment of the present invention. FIG. 2 is a partially enlarged view showing an example of a circuit pattern of a certain layer of the device formed in the embodiment. FIG. 3 is a diagram showing a pattern configuration of two reticles used to project an image of the circuit pattern of FIG. FIG. 4A is a diagram showing a pattern of a second reticle used in another example of the embodiment of the present invention, and FIG. 4B is a diagram showing a third reticle used in the embodiment. FIG. FIG. 5 (A) is a cross-sectional view taken along line ΑΑ of FIG. 5 (Β) showing a state where the σ stop 44 is arranged on the exit surface of the fly-eye lens 41 of FIG. 1, and FIG. 5 (Β) is a modified illumination 5 (C) is a diagram showing a diaphragm 45 having a circular aperture, and FIGS. 5 (D) and 5 (Ε) are σ diaphragms 46 and 47 for deformed illumination, respectively. FIG. FIG. 6 is a diagram showing a reticle in which only a periodic transmission pattern is configured by a transmission unit, only a portion between the transmission patterns is configured by a dimming type phase shift unit, and the other part is configured by a light shielding unit. FIG. 7 is a flowchart showing an exposure operation according to an example of the embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a projection exposure apparatus used in this example. In FIG. 1, illumination light IL 0 as exposure light emitted from an exposure light source 1 is adjusted after a beam shape is adjusted by a relay optical system 2. Then, the light is reflected by the mirror 13 as illumination light IL 1 and enters the illuminance distribution shaping optical system 4. As the exposure light source 1, an ArF excimer laser light source (wavelength: 193 nm) is used in this example. Otherwise the K r F excimer laser (wavelength 248 nm), F ₂ laser (wavelength 1 57 nm), A r ₂ laser (wavelength 1 26 nm), or harmonic generator such as a Y AG laser can also be used.

The illuminance distribution shaping optical system 4 of this example is provided with a fly-eye lens 41 as an optical integrator (homogenizer), and is rotatably disposed on the exit surface 5, and has a plurality of aperture stops ( A rotating plate 42 on which a rotating plate 42 is disposed, and a driving module 43 for rotating the rotating plate 42. The exit surface 5 of the fly-eye lens 41 has an optical Fourier transform relationship with the pattern surface of the reticle as a mask to be exposed, and the center of the desired σ stop is turned by rotating the rotating plate 42. By setting the σ stop on the exit surface 5 so as to match the optical axis AX 1, a desired illumination condition can be set.

As shown in FIGS. 5 (Α) to (Ε), the rotating plate 42 has four light-shielding plates formed at equal angular intervals around the optical axis AX 1 while being installed on the emission surface 5 respectively. Aperture 44 with circular apertures 44a to 44d, σ stop 45 with a circular aperture 45a centered on optical axis ΑΧ1, two formed to sandwich optical axis AX1 in a predetermined direction A σ stop 46 having small circular openings 46 a and 46 b, and a σ stop 47 having openings 47 a and 47 b formed by rotating the σ stop 46 by 90 ° are arranged. FIG. 5 (Α) is a sectional view taken along the line ΑΑ of FIG. 5 (5). The intensity distribution of the illumination light when passing through the optical Fourier transform surface of the reticle pattern to be exposed, that is, the illumination conditions, is defined by the positions of the apertures of the σ stops 44 to 47, and the reticle pattern is incident on the reticle pattern. The distribution of the incident angle and direction of the illumination light is specified. The σ stops 44, 46, and 47 are σ stops for performing modified illumination, which is an illumination condition in which the illumination light passes through a region not including the optical axis AX1, on the optical Fourier transform plane. Returning to Fig. 1, the main control system 27, which supervises and controls the operation of the entire apparatus, has an optimal σ stop among σ stops 44 to 47, depending on the period direction and fineness of the reticle pattern to be exposed. The information is stored as a table. Therefore, before exposure, the main control system 27 supplies information of the σ stop which is optimal for the reticle pattern to be exposed to the exposure control system 23, and the exposure control system 23 is optimized via the driving mode 43. Set the appropriate σ stop on the exit surface 5 of the fly-eye lens 4 1. The exposure control system 23 also controls the light emission state of the exposure light source 1. It should be noted that the optimum shape of the σ stop for various reticle patterns is described in, for example, Japanese Patent Application Laid-Open No. Hei 4-111, U.S. Pat. No. 5,638,211 and U.S. Pat. No. 5,335,044, the disclosures of the above-mentioned publications and U.S. patents are hereby incorporated by reference, to the extent permitted by the national laws of the designated State designated in this International Application, or of the chosen elected State. Part of the text.

The illumination light IL 2 emitted from the illuminance distribution shaping optical system 4 passes through a condenser lens system 6 mm, a mirror 7 and a condenser lens 6 mm, and in the state of FIG. 1, the pattern of the first reticle 9 mm as a mask in FIG. Illuminates the illumination area of the surface. Under the illumination light IL 2, an image of the pattern of the reticle 9A is projected through the projection optical system 14 at a projection magnification of 3 (for example, 1/4, 1/5, etc.), and the photoresist as a substrate is formed. The surface of the wafer 16 coated with the wafer is projected and exposed. Note that the condenser lens system 6A actually includes a field stop (reticle blind) that defines the illumination area. The exit surface 5 of the fly-eye lens 41 is an optical Fourier transform surface of the pattern surface of the reticle to be exposed with respect to the optical system including the condenser lens system 6A, the mirror 7, and the condenser lens 6B. I have. An aperture stop 15 is arranged on an optical Fourier transform plane (pupil plane) for the pattern surface of the reticle 9A in the projection optical system 14.

The reticle 9 A is a reticle holder 10 A on the reticle stage 11, Adsorbed and held on 10 B. As described later, in this example, exposure of a predetermined pattern image onto the wafer 16 is performed by composite exposure (multiple exposure) of a plurality of reticle patterns. Therefore, the second reticle 9B is sucked and held via the reticle holders 10B and 10C in an area near the reticle 9A on the reticle stage 11, and exposure is performed while exchanging these reticles. This is possible. In the following, a description will be given taking an X axis parallel to the plane of FIG. 1 and a Y axis perpendicular to the plane of FIG. 1 in a plane perpendicular to the optical axis AX 2 of the projection optical system 14.

First, the reticles 9A and 9B are mounted on the reticle stage 11 in close proximity in the X direction. The reticle stage 11 can be moved on the reticle base 12 with a long stroke in the X direction, and can be positioned in a predetermined range in the X direction, the Y direction, and the rotation direction. The two-dimensional position of the reticle stage 11 is measured by a movable mirror 13 m and a laser interferometer 13 disposed opposite thereto, and based on the measured values and control information from the main control system 27. The reticle stage drive system 21 controls the operation of the reticle stage 11.

A pair of reticle alignment microscopes (hereinafter referred to as “RA microscopes”) 8A and 8B are installed below the periphery of the condenser lens 6B, and the imaging signals of the RA microscopes 8A and 8B are transferred to an alignment signal processing system. Supplied to 26. At the time of reticle alignment, the RA microscopes 8A and 8B capture images of the alignment marks of the reticle 9A (or reticle 9B) and the corresponding reference marks on the wafer stage, respectively, and the alignment signal processing system 26 Then, the position shift amount of the two pairs of marks is calculated and supplied to the main control system 27. The main control system 27 maintains the positional relationship between the reticle images of both reticles 9A and 9B by, for example, positioning the reticle stage 11 so that the amount of displacement is symmetrically minimized. And with high precision Can be aligned. However, in this example, even when the reticles 9A and 9B are exchanged, the position (including the X coordinate) of the reticle stage 11 is measured with high accuracy by the laser interferometer 13; The reticle alignment of the reticle 9A, 9B need only be performed once when these reticles 9A, 9B are loaded onto the reticle stage 11 from a reticle opening system (not shown). When performing exposure by exchanging, the reticle stage 11 may be simply positioned based on the measurement value of the laser interferometer 13.

On the other hand, the wafer 16 is held on a wafer stage 17 via a wafer holder (not shown), and the wafer stage 17 moves the wafer 16 stepwise in the X direction and the Y direction on the platen 18. The focus position (position in the Z direction) and the tilt angle of the surface of the wafer 16 are adjusted to the image plane of the projection optical system 14 by an autofocus method based on the measurement values of an autofocus sensor (not shown). The two-dimensional position of the wafer stage 17 is measured by a moving mirror 19 m and a laser interferometer 19, and based on the measured values and control information from the main control system 27, a wafer stage drive system 2 2 Controls the operation of wafer stage 17. At the time of exposure, when the exposure (or double exposure) of the reticle pattern image to one shot area on the wafer 16 is completed, the next shot area is moved to the exposure position by the step movement of the wafer stage 17. The operation of performing exposure is repeated in a step-and-repeat manner. As described above, the projection exposure apparatus of this example is a stepper type (collective exposure type), but the present invention can be applied to a case where a scanning exposure type such as a step-and-scan method is used as the projection exposure apparatus. Needless to say.

In addition, in order to perform alignment at the time of overlay exposure on each shot area of the wafer 16, an image processing type alignment cell using an off-axis method is used. A sensor 25 is provided, and an imaging signal of the alignment sensor 25 is also supplied to the alignment signal processing system 26. A reference mark used for performing reticle alignment via the RA microscopes 8 A and 8 B and a reference mark for the alignment sensor 25 are formed on the wafer stage 17. A marking member 20 is also provided.

Next, an example of an operation when exposing an image of a predetermined pattern using the projection exposure apparatus of the present embodiment will be described. In this example, double exposure is performed for each shot area on the wafer 16 while exchanging two reticles. First, the first reticle 9A is used to perform an entire shot area on the wafer 16. Exposure, followed by exchanging the reticle for the second reticle 9B and again exposing the entire shot area on the wafer 16 would be better for the reticle 9A, 9B for each shot area. The throughput is higher than when exposing by changing the exposure. Therefore, an operation for continuously exposing the entire shot area of the wafer for each reticle will be described below.

FIG. 2 is a partially enlarged view of a circuit pattern 31 of a certain layer of an electronic device formed in each shot area of a wafer in this example. In FIG. The overlapping pattern P 1 c, P 1 d with a wider width dY2 (dY2 is about 1.5 times dY1) is arranged at both ends of the thin line pattern P1a A first gate pattern P1 is formed. Similarly, at the end of a thin line pattern P2a elongated in the Y direction with a width dX1, a superposition pattern P of a wider width dX2 (dX2 is approximately 1.5 times dXl) is provided. 2 The second gate pattern P2 in the shape of c, and the thin wire pattern P3a, P3b with width dX1 extending in the Y direction. Gate patterns P 3 A and P 3 B with overlapping patterns P 3 c and P 3 d of width dX2 are arranged at center distance e X 1 (e X 1 = 2 · dX 1 in this example) The first Three gate patterns P3 are formed. In this case, dXl = dY1.

The width dYl (i.e., dXl) of these isolated linear thin line patterns P1a, P2a, P3a, P3b is the solution of the projection optical system 14 of this example when no modified illumination is used. The width is about the image limit or slightly smaller than the resolution limit, and the fine line patterns P la, P 2a, P 3a, and P 3b correspond to the linear pattern of the present invention. That is, assuming that the exposure wavelength is obtained and the numerical aperture of the projection optical system 14 is NA, the resolution limit of the projection optical system 14 when the modified illumination is not used is approximately k 1 ··· using a predetermined process coefficient k 1. λ / ΝΑ, and the width d Υ 1 (dX 1) is of the order of kl ′ AZNA or slightly smaller. On the other hand, the width dY2 (ie, dX2) of the superposition patterns P1c, P2c, etc. is set to be about 1.5 times as large as the resolution limit k1 · λΖΝΑ.

The thin line patterns Ρ 1 a, P 2 a, P 3 a, and P 3 b of the gate patterns P l, Ρ 2, and Ρ 3 are patterns that become gate electrodes of, for example, field-effect transistors, It is necessary to form the gate patterns P1, P2, and P3 on the relevant layer in each shot area as a pattern (a pattern in which a metal film or the like remains only in that part). In actual devices, tens of millions or more of such gate patterns may be formed, but as the gate electrode becomes thinner and the line width becomes constant at all parts of the device, The electronic device can be operated at high speed.

To form such gate patterns P1, P2, and P3, a reticle having an enlarged light-shielding pattern (original pattern) having a similar shape to that of the reticle is created, and a reduced image thereof is formed on a wafer by a projection exposure apparatus. However, with an exposure method that does not use deformed illumination, a pattern image that is smaller than the resolution limit of about k1λm can be exposed with high accuracy while maintaining an appropriate depth of focus. It is difficult to do. Therefore, in this example, two reticle patterns are generated from the original pattern obtained by enlarging the circuit pattern 31 in FIG. 2 by the reciprocal (1 // 3) times the projection magnification 3 of the projection optical system 14 in FIG. These reticle patterns are separately formed on reticles 9A and 9B in FIG. The actual length of the reticle pattern is a value obtained by multiplying the target value of the length on the wafer by (1Z / 3) times. For convenience of explanation, the length of each part of the reticle pattern will be described below. Is displayed as a value converted to the length on the wafer. Further, the projection optical system 14 in FIG. 1 performs, for example, reverse projection, but for the sake of simplicity, a description will be given assuming that the reticle pattern and the projected image have the same direction.

FIGS. 3A and 3B show the reticle patterns drawn on the first reticle 9A and the second reticle 9B, respectively, and are drawn on the first reticle 9A. As the reticle pattern, light-shielding patterns A1 to A3 each formed of a light-shielding film having the same shape as the gate patterns P1 to P3 in FIG. It was done. That is, the light-shielding pattern A1 is composed of the patterns A1a, Alc, and Aid having the same shape as the fine line pattern P1a and the overlapping patterns P1c and P1d in FIG. In this case, the width of the patterns A le and A id is d Y 2 which is the same as the width of the overlapping patterns P 1 c and P 1 d, but the width of the central pattern A 1 a is the width of the fine line pattern P 1 a It is represented by d Y 3 with respect to d Y 1.

This means that the width dY3 of the pattern A1a corresponding to the fine line pattern P1a may be the same as the width dY1, but may be set between 1 and 2 times the width dY1. are doing. By setting the width dY3 of the pattern A la to be large in this manner, is it possible to reduce the line width of the image of the pattern A1a by exposing the image near the resolution limit under illumination conditions without using modified illumination? Or narrow line width due to slight misalignment of two reticle patterns. Is stopped. Even if the width dY3 of the pattern A la is set to be large, there is no problem because the final line width of the image of the pattern A1a is determined by the exposure of the pattern image of the second reticle 9B.

Similarly, the light-shielding pattern A2 is a pattern A2 having a width dX3 (= dY3) and a pattern A2 having a width dX3 (= dY3) each having the same shape as the fine line pattern P2a and the overlapping pattern P2c in FIG. Consists of c. Further, the light-shielding pattern A3 is composed of a first light-shielding pattern A3A composed of patterns A3a and A3c having the same shape as the thin line pattern P3a and the overlapping pattern P3c in FIG. And a second light-shielding pattern A 3 B composed of a pattern A 3 b and A 3 having the same shape as the fine line pattern P 3 b and the overlapping pattern P 3 d, and a pattern A 3 a having a width dX 3. , A3b are the same as the center intervals e X 1 of the thin line patterns P3a, P3b.

Next, the pattern drawn on the second reticle 9B in FIG. 3B is an original of the fine line pattern P1a, the fine line pattern P2a, and the fine line patterns P3a and P3b in FIG. A plurality of transmissive patterns Bl, B2, and B3 are arranged in predetermined directions at positions corresponding to the patterns, respectively, and the other areas are light-shielding portions 32. Then, the first transmission pattern B 1 sandwiches the original pattern P 1 a ′ which is elongated in the X direction shown by a dotted line obtained by accurately multiplying the thin line pattern PI a of FIG. 2 by the reciprocal (1 // 3) of the projection magnification ( So that four transparent patterns of the same shape as the original pattern P la 'and whose width is almost dY 1 are orthogonal to the Y direction (that is, the long side direction (longitudinal direction) of the original pattern P la'). (In the direction) The pattern is arranged at a pitch of approximately 2 · dY 1 (In addition, the second transmission pattern B 2 sandwiches the original pattern P 2 a ′ which is elongated in the Y direction of the thin line pattern P 2 a in FIG. In this way, four transmission patterns of the same shape as the original plate P 2 a 'and having a width of approximately dX 1 are arranged at a pitch of approximately 2 · d X 1 in the X direction. Similarly, The third transmission pattern B 3 is an original pattern P 3 a ′ so that the original pattern P 3 a ′ and P 3 b ′ of the fine line pattern P 3 a, P 3 b ′ shown in FIG. This is a pattern in which six transmissive patterns having the same shape as that of the above and having a width of approximately dX1 are arranged at a pitch of approximately 2 · dX1 in the X direction. Note that, as the transmission patterns Bl and B2, a pattern in which about 2 to 8 rectangular transmission patterns are periodically arranged can be used. Similarly, as the transmission pattern B3, a pattern in which about 3 to 9 rectangular transmission patterns are periodically arranged can be used.

As can be seen from FIG. 3 (B), the long side direction of each transmission pattern B 1 to B 3 is the long side direction of the original pattern corresponding to each of the fine line patterns P 1 a to P 3 a and P 3 b (Y direction, Or the X direction), and the periodic direction of each of the transmission patterns B1 to B3 is a direction orthogonal to the long side direction of each corresponding thin line pattern. Further, the portions of the fine line patterns Pla to P3a and P3b in FIG. 2 corresponding to the original patterns Pla 'to P3a, Ρ3b' are light-shielding patterns. The positional relationship between each of the light-shielding patterns A1 to A3 included in the first reticle 9A and each of the transmission patterns B1 to B3 included in the second reticle 9B, They are arranged so that they overlap exactly. Therefore, although not shown, a pair of alignment marks are formed at predetermined intervals in the X direction in the pattern regions of the reticles 9A and 9B, respectively.

Then _c will be described first with reference to the flowchart of FIG. 7 per exposure operation of the present embodiment, in step 10 1 of Figure 7, a positive type photoresist Bok is applied to one lots of wafers. A predetermined circuit pattern is formed on the underlying layer of each shot area of the one-lot wafer in the steps up to that. Thereafter, the wafers of the one lot are transferred to a wafer cassette (not shown) near the projection exposure apparatus of FIG. Next, one lock One of the wafers is loaded on the wafer stage 17 in FIG. 1, and the wafer is aligned via the alignment sensor 25 (step 102). After that, the reticle stage 11 is driven to move the first reticle 9A to the illumination area by the illumination light IL2, and the reticle alignment is performed using the RA microscope 8A, 8B or the laser interferometer 13. Do (Step 103).

In the subsequent step 104, the illuminating conditions are optimized for the reticle 9 mm by rotating the rotating plate 42 and setting the corresponding σ stop on the exit surface 5 of the fly-eye lens 41. Since the light-shielding patterns A1 to A3 shown in FIG. 3A drawn on the reticle 9A have low periodicity, it is not necessary to use a deformed illumination, and the circular aperture shown in FIG. 5C is used. A squeeze aperture 45 having 45 a is installed on its exit surface 5. The opening 45a is, for example, a normal circular opening having a coffee reference factor (σ value) of about 0.3 to 0.7. The illumination condition using the σ-stop 45 is called “normal illumination” here. However, other shapes of apertures may be used if necessary. Under the illumination conditions, a pattern image of a reticle 9 レ is projected and exposed on each shot area of the wafer.

Next, in step 105, the reticle stage 11 is driven to move the second reticle 9B to the illumination area, and reticle alignment is performed. In the subsequent step 106, the illumination conditions are optimized to the periodic transmission patterns B1 to B3 of the reticle 9B in FIG. 3 (B). In this case, the four apertures 44a to 44d shown in Fig. 5 (B) are used in order to obtain deformed illumination suitable for forming a pattern having periodicity in two orthogonal directions (X and Y directions). Is set to the exit surface 5. The X direction and the Υ direction in FIGS. 5 (Β) to (Ε) are directions corresponding to the X direction and the Υ direction on the wafer stage 17 in FIG. 1, respectively. squeezing aperture 44 aperture 4 4a to 44d are centered on the optical axis AX1 with respect to the periodic direction (Y direction) of the transmission pattern B1 in FIG. 3B and the periodic direction (X direction) of the transmission patterns B2 and B3. It is a small circle centered on a position equidistant from the optical axis AX 1 along four directions rotated by 45 ° each. The use of the σ stop 44 can improve the resolution and the depth of focus of a pattern having periodicity in the X direction and the 、 direction. The details are described in US Pat. No. 7,007,704 and U.S. Pat.No. 5,719,704, and the description here is omitted, but the designated country specified in this international application or the selected selected country To the extent permitted by Japanese law, the disclosures of the above-mentioned publications and US patents are incorporated herein by reference.

Since the exit surface 5 on which the σ stop 44 is disposed is an optical Fourier transform surface with respect to the pattern surface of the reticle 9 Β as described above, the exit surface 5 is provided with an aperture stop 1 in the projection optical system 14. It is conjugate (imaging relationship) with the arrangement plane of 5. Then, the images of the apertures 44a to 44d of the σ stop 44 in FIG. 5 (Β) should be located as far as possible in the corresponding aperture stop 15 aperture, that is, as far away from the optical axis as possible. And the inner diameters of the openings 44a to 44d are made as small as possible, so that the transmission corresponding to the finer linear patterns Pla, P2a, P3a, P3b It is possible to transfer images of patterns B1 to B3 with high accuracy.

However, if the line width of the linear pattern to be transferred is larger than the exposure wavelength and the numerical aperture NA of the projection optical system is about 0.4 λ λ / Α 変, the deformed illumination used will be as described above. As described above, the illumination optical system pupil plane is not limited to deformed illumination that is as far away from the optical axis as possible and uses an aperture as small as possible, and the intensity distribution of the illumination light on the illumination optical system pupil plane is close to the optical axis. It is also possible to use deformed illumination with relatively low concentration, which is weak and strong in other (outside) areas. Alternatively, annular illumination can be used. Of course, transcription If the line width of the linear pattern to be formed is smaller than about 0.4 X Λ ΖΝ 用いる, use an aperture as far as possible from the optical axis and as small as possible on the pupil plane of the illumination optical system as described above. It is desirable to use modified illumination.

Under the deformed illumination, a pattern image of a reticle 9 mm is projected and exposed on each shot area of the wafer. Steps 102 to 106 are repeated until there are no unexposed wafers in step 107, and images of two reticles 9 9 and 9Β are combined and exposed on all wafers in one lot. (Double exposure).

By the way, when deformed illumination is used, the imaging light flux that has passed through the reticle usually passes while being focused on a specific location in the projection optical system. The projection optical system is locally heated by the absorption of light, causing local deformation and a change in the refractive index, which may deteriorate the imaging characteristics. However, in this example, the second reticle 9 使用 used for performing the deformed illumination only has a linear pattern 転写 1 a, P 2 a, P 3 a, P 3 b near the portion corresponding to P 3 b. In addition, only the periodic transmission patterns B 1, B 2, and B 3 are provided, and the other portions are all light shielding portions 32. Therefore, most of the illuminating light beam is shielded by the reticle 9B and the amount of the image forming light beam transmitted through the projection optical system 14 is small, and there is no possibility that the above-described deterioration of the image forming characteristics occurs.

By performing two exposures for each wafer described above, the images of the patterns of the two reticles 9A and 9B are logically recorded on the photoresist on each shot area of each wafer. That is, the bright portion photoresist (transmission pattern) in a region is exposed to light at least one of the exposure, both times喑部photoresist (light-shielding pattern) at a region not exposed to light _c then Proceeding to step 108, one lot of wafers after double exposure are imaged. Since the photoresist in this example is a positive type, it is insensitive after development. Only the light portions remain, and as a result, portions corresponding to the gate patterns P 1, P 2, and P 3 in FIG. 2 are formed as resist patterns. At this time, many light-shielding portions 32 existing on the reticle 9B are formed on the reticle 9A corresponding to the light-transmitting portions 3A except for areas corresponding to the gate patterns P1, P2, and P3 to be transferred. Since the value is 5, the resist does not remain (is erroneously transferred).

In this example, the second reticle 9B is used in comparison with the conventional one-time exposure method, ie, the exposure method using only the first reticle 9A. In the exposure, the resolution and the depth of focus of the fine line patterns P1a, P2a, P3a, P3b in the gate patterns P1, P2, P3 can be remarkably improved. Therefore, this characteristic is utilized even after the synthetic exposure, and the resolution and depth of focus of the images of the fine line patterns Pla, P2a, P3a, and P3b are achieved. Each exposure amount in the above two exposures does not have to be equally divided into appropriate exposure amounts determined by the sensitivity of the photoresist, that is, it does not have to be half of the appropriate exposure amount, and the exposure amount at the time of exposure using the reticle 9B is larger. Setting it is more effective.

Thereafter, in a processing step of step 109, etching and the like are performed on one lot of wafers using the resist pattern left after development as a mask, whereby the gate pattern of FIG. 2 is formed on the layer. Then, after going through a resist removal step to remove unnecessary resist after the processing step, by repeating the steps of resist application, exposure, imaging, processing, resist removal, etc., sequentially to the layer further above the wafer The wafer process ends. When the wafer process is completed, in the actual assembling process, a dicing process in which the wafer is cut into chips for each printed circuit, a bonding process in which wiring is performed on each chip, and a packaging process in which each chip is packaged The semiconductor device is finally manufactured through the process You.

Next, another example of the embodiment of the present invention will be described with reference to FIGS.

FIGS. 4A and 4B respectively show a second reticle 9C and a third reticle 9D used in this example instead of the second reticle 9B of FIG. 3B. I have. In this example, triple exposure (synthetic exposure) is performed while sequentially aligning the pattern images of reticle 9A in FIG. Form P1-P3.

As shown in FIG. 4 (A), the reticle 9C has a periodic transmission pattern B which is a pattern having a periodicity in the Y direction among the patterns drawn on the reticle 9B in FIG. 3 (B). Only one is drawn. As shown in FIG. 4B, the reticle 9D has only the periodic transmission patterns B2 and B3, which are patterns having periodicity in the X direction, of the pattern drawn on the reticle 9B. Is drawn. The portions other than the transmission patterns of both reticles 9 C and 9 D are light shielding portions 33 and 34.

As described above, when exposing the reticles 9C and 9D in which the periodic direction of the periodic transmission pattern is limited to only the Y direction and the X direction, the illumination conditions are as shown in FIGS. 5D and 5E, respectively. ), The use of modified illumination in which two apertures σ diaphragms 46 and 47 are installed on the exit surface 5 of the fly-eye lens 41 in Fig. 1 can further improve resolution and depth of focus. It is. This principle is also described in detail in the above-mentioned Japanese Patent Application Laid-Open No. HEI 4-111148.

That is, when exposing the reticle 9C having the transmission pattern Β1 having a periodicity in the Υ direction, the reticle 9C on the Υ axis (the 直線 direction straight line passing through the optical axis AX1 of the illumination optical system) in FIG. It is preferable to use a diaphragm 46 having openings 46a and 46b at two locations equidistant from the optical axis AX1. On the other hand, in the X direction When exposing reticle 9D having periodic transmission patterns B2 and B3, the light on the X-axis (a straight line in the X-direction passing through optical axis AX1 of the illumination optical system) shown in FIG. It is preferable to use a σ stop 47 having openings 47a and 47b at two places equidistant from the axis AX1.

In this example, since the optimal illumination conditions differ between the transmission pattern Β1 and the transmission patterns Β2 and Β3, the wafer is triple-exposed using three reticles 9Α, 9C and 9D. However, triple exposure may be performed using the two reticles 9 # and 9 # used in the above-described embodiment. That is, before performing exposure by the reticle 9B to the wafer exposed by the reticle 9 °, the illumination light IL2 is applied to only a predetermined area including the transmission pattern B1 on the reticle 9B. As described above, the illumination area of the reticle 9B by the illumination light IL 2 is adjusted by the field stop (reticle blind) placed on the surface almost conjugate with the reticle plane in the illumination optical system. I do. This is performed, for example, in parallel with the exchange of the σ stop. Then, the illuminating light IL2 is applied to the transmission pattern # 1 through the σ stop 46, and the image of the transmission pattern # 1 is superimposed on the image of the light-shielding pattern A1 on the wafer W and transferred. Next, the illumination area on the reticle 9B is adjusted by the field stop so that the σ stop is exchanged so that the illumination light IL is emitted only to the predetermined area including the transmission patterns B 2 and B 3. Thereafter, the illuminating light IL 2 is applied to the transmission patterns Β 2 and Β 3 through the σ stop 47, and the images of the transmission patterns B 2 and B 3 are superimposed on the images of the light shielding patterns A 2 and A 3 and transferred. . As a result, even if a plurality of transmission patterns with different optimum illumination conditions are mixed on the reticle 9B, the reticle is not replaced, and the optimum illumination conditions are set for each of the one or more transmission patterns. A transfer image can be formed on the wafer.

In the above embodiment, the wafer is exposed using the reticle 9A, and then the wafer is exposed using the reticle 9B (or the reticle 9C, 9D). Although the eight exposures are performed, the order may be reversed. That is, the order of use of a plurality of reticles used for multiple exposure may be arbitrary.

In the above embodiment, small circular apertures 44 a to 44 d, 46 a, 46 b, 47 a, 47 of the σ diaphragms 44, 46, 47 for the deformed illumination are used. When the inner diameter of b is small as described above, when the combination of the fly-eye lens 41 and the σ stop as shown in FIG. 1 is used as the illuminance distribution shaping optical system 4, the σ stop for deformed illumination can be obtained. The efficiency (transmittance) of the illumination light passing through each small aperture is greatly reduced. In order to avoid this, for example, a combination of a light beam splitting system, a condensing optical system, and an illuminance uniforming optical system as disclosed in Japanese Patent Application Laid-Open No. 5-206007 is used. Alternatively, a glass rod can be used as the illumination uniforming optical system (optical, integrator). Furthermore, a pair of axicons may be used as a light beam splitting system, and the light amount distribution of the illumination light IL 2 on the Fourier transform surface in the illumination optical system may be formed in an annular shape, and the distance between the pair of axicons may be adjusted. The size can be changed. At this time, when the σ stop 44 shown in FIG. 5 (Β) is used together, the loss of light amount can be suppressed smaller than the combination of the fly-eye lens 41 and the σ stop 44 described above. As described above, a mechanism for changing the illumination condition, that is, the light amount distribution (at least one of the shape and the size) of the illumination light IL2 on the Fourier transform plane in the illumination optical system may have any configuration.

Further, in the above embodiment, all the reticle patterns are composed of the transmissive portion and the light shielding portion. However, instead of the light shielding portion, the phase of the transmitted light is shifted by 180 ° with respect to the transmissive portion. Alternatively, a reticle plate may be employed as a dimming type (halftone type) phase shift unit having a transmittance of, for example, about 3 to 10%. In this case, the resolution of the periodic pattern as shown in reticles 9 #, 9C, 9D can be further improved. this Sometimes, modified lighting (including annular lighting) is used in combination.

However, assuming that the light-shielding portions (non-pattern portions) of reticles 9B, 9C, and 9D are all dimming type phase shift portions, the thin line patterns in gate patterns P1, P2, and P3 shown in FIG. The portions corresponding to the overlapping patterns P 1 c, P 1 d, P 2 c, P 3 c, and P 3 d at the ends are slightly exposed by the transmitted light from the extinction type phase shift unit. The Rukoto. However, the amount of exposure is small due to the dimming action of the dimming type phase shift unit. However, if that becomes a problem, instead of reticles 9B, 9C, and 9D, reticle 9E shown in FIG. May be used.

In the pattern of reticle 9E in FIG. 6, only each of the periodic transmission pattern portions is constituted by transmission portion 91, only the portion between them is constituted by dimming type phase shift portion 92, and the other portions are shielded portions 9 It is composed of 3. By using this reticle pattern, it is possible to completely prevent adverse effects on the above-mentioned superimposition patterns P1c, Pld, P2c, P3c, P3d and the like. In addition, for example, Japanese Patent Application Laid-Open No. 5-133505 and corresponding US Pat. No. 5,334,270, Japanese Patent Application Laid-Open No. 412,776,1212 and the corresponding U.S. Pat. As disclosed in Japanese Patent No. 51944983, while exposing one shot area on a wafer using a reticle 9A, it is parallel to the optical axis AX2 of the projection optical system 14 The wafer may be moved in any Z direction. In conjunction with this method or alone, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-179958 and the corresponding US Pat. On the Fourier transform plane (pupil plane) in the optical system 14, an optical filter that blocks illumination light distributed in a circular area centered on the optical axis, a so-called pupil filter may be used. Designated states in this international application, or the extent permitted by the national laws of elected states, _t to are incorporated herein by reference for the disclosure of the 3 above, and of 3 U.S. For example, the reticles 9B to 9D may be phase shift reticles of the spatial frequency modulation type. In this case, modified illumination (including annular illumination) is not used, and the coherence factor (σ value) is 0. Ordinary illumination using a σ stop having a circular aperture of about 1 to 0.4 is adopted.

Further, in the above-described embodiment, the long side direction of the pattern requiring more resolution is limited to the X direction or the Υ direction, but the long side direction is any direction other than the X direction and the Υ direction. There may be. Also, for example, the long sides are 90 in each other. Two patterns that intersect at an angle other than the above may be set as exposure targets. In these cases, the periodic direction of each periodic transmission pattern in the reticles 9Β, 9C, and 9D and the conditions of the deformed illumination should also be changed to the direction perpendicular to the long side direction in accordance with that. Is desirable. Further, for example, at least three patterns whose long sides intersect each other may be used as exposure targets. In this case, annular illumination may be used.

Further, in the above embodiment, the pattern to be multiple-exposed is drawn on different reticles, but the pattern to be multiple-exposed is drawn on different areas of the pattern surface of one reticle, and is exposed by a field stop at the time of exposure. The pattern to be defined may be defined, and the wafer stage may be moved to perform the alignment.

In the above embodiment, a gate pattern is assumed as an example of a pattern to which the present invention is applied. However, the present invention can be applied to other patterns and other steps.

Note that if using a deep UV excimer laser or the like as illumination light for exposure, transmits far ultraviolet such as quartz as a glass material for a projection optical system (S i 0 ₂₎ and fluorite (CaF ₂₎ material Is used. Further, the projection optical system may be any one of a refraction system, a reflection system, and a catadioptric system.

In addition, the infrared region oscillated from a DFB semiconductor laser or fiber laser Alternatively, a single wavelength laser in the visible region is amplified with a fiber amplifier doped with, for example, erbium (Er) (or both erbium and ytterbium (Yb)), and ultraviolet light is applied using a nonlinear optical crystal. A harmonic converted into light may be used as illumination light for exposure. Further, for example, a bright line generated from a mercury lamp (eg, g-line, i-line, etc.), or a soft X-ray region (wavelength of about 5 to 50 nm) generated from a laser-excited plasma light source or SOR, for example, a wavelength of 13 EUV (Extreme Ultra Violet) light of 4 nm or 11.5 nm may be used as illumination light for exposure. That is, the wavelength of the illumination light for exposure used in the projection exposure apparatus to which the present invention is applied may be arbitrary. In an exposure apparatus using EUV light, a reflective reticle is used, and a projection optical system is used. It consists of only a plurality of, for example, 3 to 8 reflective optical elements (mirrors). Further, as described above, the present invention can be applied to a scanning projection exposure apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 4-19613 and corresponding US Pat. No. 5,473,410. To the extent permitted by the laws of the designated country designated in this international application or of the selected elected country, the disclosure of the above gazette and US patent shall be incorporated herein by reference.

Then, the illumination optical system including the illuminance distribution shaping optical system 4 of this example, and the projection optical system are incorporated in the main body of the projection exposure apparatus to perform optical adjustment, and the reticle stage and the wafer stage, which are composed of a large number of mechanical parts, are connected to the projection exposure apparatus. The projection exposure apparatus of the present embodiment can be manufactured by attaching to a main body, connecting wiring and piping, and further performing overall adjustment (electrical adjustment, operation confirmation, and the like). It is desirable to manufacture the projection exposure apparatus in a clean room where the temperature, cleanliness, etc. are controlled.

The application of the projection exposure apparatus is not limited to a projection exposure apparatus for semiconductor manufacturing. For example, a projection exposure apparatus for a liquid crystal for exposing a liquid crystal display element panel to a square glass plate, For manufacturing thin-film magnetic heads Can be widely applied to projection exposure apparatuses. Further, the present invention can be applied to a step-and-stitch type reduction projection exposure apparatus which is used for manufacturing a photomask reticle and uses, for example, far ultraviolet light or vacuum ultraviolet light as exposure illumination light. .

As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention. In addition, all disclosures in Japanese Patent Application No. 10--16 1896, filed on June 10, 1998, including the specification, claims, drawings, and abstract. Is incorporated here as it is. Industrial applicability

According to the first transfer method of the present invention, a first mask pattern on which a pattern to be transferred is formed and a second mask pattern in which a portion corresponding to the linear pattern is a periodic transmission pattern are used. Has the advantage that a circuit pattern image consisting of a linear pattern like a gate pattern and a pattern with a wide end portion can be exposed with high precision. .

Further, in the second mask pattern for performing the deformed illumination, an area other than the transmission pattern is used as a dimming part, and the amount of the image forming light flux passing through the projection optical system is small. When such a method is used, it is possible to suppress the deterioration of the imaging characteristics of the projection optical system.

Next, according to the second and third transfer methods of the present invention, a pattern image such as an isolated line can be transferred with high accuracy.

According to the exposure apparatus of the present invention, such an exposure method can be used, and according to the device manufacturing method of the present invention, there is an advantage that a device can be manufactured with high accuracy using such an exposure method. is there.

Claims

Range of request

1. A transfer method for transferring an image of a pattern having a predetermined shape including a linear pattern onto a substrate via a projection optical system,

A first mask pattern in which a portion corresponding to the pattern of the predetermined shape is a light-reducing portion, and the other portion is a transmission portion;

A plurality of transmission patterns each having substantially the same line width as the linear pattern are periodically arranged in the width direction of the linear pattern so as to be in contact with a portion corresponding to the linear pattern; and A second mask pattern in which at least a region other than the transmission pattern near a portion corresponding to the linear pattern is a light-reducing portion;

Images of the two mask patterns are sequentially transferred onto the substrate via the projection optical system while being aligned with each other, and

The illumination conditions when transferring the image of the second mask pattern are as follows: the intensity distribution on the optical Fourier transform plane for the pattern to be transferred of the illumination optical system is strongly deformed in a region outside the vicinity of the optical axis outside the vicinity of the optical axis. A transfer method, characterized in that:

2. The transfer according to claim 1, wherein a line width of a portion corresponding to the linear pattern in the first mask pattern is 1 to 2 times a line width of the linear pattern. Method.

3. When the linear pattern is a first linear pattern, the pattern having the predetermined shape is a second linear pattern having a direction orthogonal to a long side direction of the first linear pattern as a long side direction. Further include a pattern,

The second mask pattern has a line width substantially equal to that of the second linear pattern so as to be in contact with a portion corresponding to the second linear pattern. A plurality of periodically arranged in the width direction of Further including a transmission pattern,

The conditions of the deformed illumination when transferring the image of the second mask pattern are as follows: the intensity distribution of the illumination light on the optical Fourier transform surface is the first and second with the optical axis as the center. Claims characterized in that the distribution has a distribution centered at four positions along a direction substantially 45 ° rotated from the direction corresponding to the long side direction of the linear pattern. The transfer method described in 1 or 2.

4. The transfer method according to claim 3, wherein an exposure amount when transferring the second mask pattern is set to be larger than an exposure amount when transferring the first mask pattern.

5. When the linear pattern is a first linear pattern, the pattern having the predetermined shape is a second linear pattern in which a direction crossing a long side direction of the first linear pattern is a long side direction. Further include a pattern,

A plurality of transmission patterns each having substantially the same line width as that of the second linear pattern are formed on the second line so as to be in contact with a portion corresponding to the second linear pattern. A third mask pattern that is periodically arranged in the width direction of the linear pattern, and in which at least a region other than the transmission pattern near a portion corresponding to the second linear pattern is a light-reducing portion. The images of the three mask patterns are sequentially transferred onto the substrate via the projection optical system while being aligned with each other, and

Illumination conditions when transferring the image of the second mask pattern and the image of the third mask pattern are respectively described as follows. The intensity distribution of the illuminating light on the optical Fourier transform surface is defined as the first linear pattern. A modified illumination having a distribution centered on two positions away from the optical axis in a direction perpendicular to the long side direction of the second linear pattern and in a direction corresponding to a direction perpendicular to the long side direction of the second linear pattern. 3. The transfer method according to claim 1, wherein the transfer method is performed.

6. The transfer method according to claim 5, wherein an exposure amount when transferring the second mask pattern is set to be larger than an exposure amount when transferring the first mask pattern.

7. In a transfer method for transferring an image of an isolated linear pattern onto a substrate via a projection optical system,

Irradiating the isolated first pattern with the linear pattern as the dimming portion and the periodic second pattern including a plurality of transparent patterns with illumination light respectively, reducing the first pattern on the substrate. A transfer method, wherein the substrate is subjected to multiple exposure using the first and second patterns so that a light portion and one light-reducing portion sandwiched between the plurality of transmission patterns overlap.

8. In the illumination optical system that irradiates the first and second patterns with the illumination light, the intensity distribution of the illumination light on an optical Fourier transform plane for the pattern is represented by the first pattern and the first pattern. 8. The transfer method according to claim 7, wherein the transfer method is different from the second pattern.

9. The method according to claim 8, wherein, when exposing the substrate using the second pattern, the intensity distribution of the illumination light is increased outside a region including an optical axis of the illumination optical system. Transfer method.

10. The exposure amount when transferring the first pattern and the exposure amount when transferring the second pattern are different from each other, according to any one of claims 7 to 9, wherein Transfer method.

11. The transfer method according to claim 10, wherein the exposure amount when transferring the second pattern is larger than the exposure amount when transferring the first pattern.

12. The line width of the linear pattern is about the resolution limit of the projection optical system, and the line width of the first pattern is approximately 1 to 2 times the line width of the linear pattern. The line width of the second path is substantially the same as the line width of the linear path. The transfer method according to claim 11, wherein the transfer method is performed.

13. The light-reducing portion of the first and second patterns is a light-shielding portion or a translucent portion for shifting the phase of transmitted light by approximately 180 °, respectively. The transfer method according to claim 1.

14. The line width of the linear pattern is about the resolution limit of the projection optical system, the line width of the first pattern is approximately 1 to 2 times the line width of the linear pattern, 10. The transfer method according to claim 7, wherein a line width of the two patterns is substantially equal to a line width of the linear pattern.

15. The first and second patterns are respectively formed on different masks, and the two masks are arranged so that a longitudinal direction of the first pattern and a periodic direction of the second pattern are substantially orthogonal to each other. The transfer method according to any one of claims 7 to 9, wherein the transfer method is sequentially arranged on the object plane side of the projection optical system.

16. A transfer method for transferring an image of an isolated linear pattern onto a substrate via a projection optical system,

A first pattern having substantially the same shape as the linear pattern and a periodic second pattern including a linear portion having substantially the same line width as the linear pattern are irradiated with illumination light. Transferring the substrate by multiple exposure using the first and second patterns so that the first pattern and the linear portion of the second pattern overlap on the substrate. .

17. The exposure condition of the substrate when transferring the first pattern and the exposure condition of the substrate when transferring the second pattern are different from each other. Transfer method.

18. The exposure condition includes an intensity distribution of the illumination light on an optical Fourier transform plane for the pattern in an illumination optical system that irradiates the first and second patterns with the illumination light, respectively. Claims characterized by 17. The transfer method according to 17.

19. When exposing the substrate using the second pattern, the intensity distribution of the illumination light is increased outside a region including an optical axis of the illumination optical system. 18. The transfer method according to item 18.

20. The exposure condition includes an exposure amount of the substrate, and an exposure amount when transferring the second pattern is larger than an exposure amount when transferring the first pattern. 18. The transfer method according to claim 17.

21. The transfer method according to claim 17, wherein the line width of the first pattern is approximately 1 to 2 times the line width of the linear pattern.

22. The transfer method according to claim 21, wherein the second pattern includes a transmission portion that shifts the phase of the illumination light by approximately 180 °.

23. The transfer method according to claim 22, wherein the transmission portion is a translucent portion that reduces the illumination light.

24. The transfer method according to any one of claims 16 to 23, wherein the linear pattern has a line width at least at one end larger than a central portion.

25. The transfer method according to claim 24, wherein the linear pattern is a gate electrode pattern.

26. An exposure apparatus comprising: an illumination optical system that illuminates a predetermined mask; and a projection optical system that transfers an image of the pattern of the mask onto a substrate. The illumination condition of the illumination optical system is set to a pattern to be exposed. An intensity distribution on the optical Fourier transform plane, an illumination condition control system that switches to one of a deformed illumination that is stronger in an area outside the vicinity of the optical axis than this and an illumination other than the illumination, and a plurality of mask patterns. A pattern selection device for selecting any one of the mask patterns;

The mutual selection of a plurality of mask patterns sequentially selected by the pattern selection device Alignment and alignment

An exposure apparatus, comprising: an exposure control system that performs the multiple exposure by switching the illumination condition via the illumination condition control system in accordance with the pattern selected by the pattern selection device.

27. An illumination optical system for illuminating a predetermined mask, a projection optical system for transferring an image of a pattern of the mask onto a substrate,

The illumination conditions of the illumination optical system are as follows: the intensity distribution on the optical Fourier transform surface of the pattern to be exposed is one of a deformed illumination that is stronger in a region outside the vicinity of the optical axis than the vicinity of the optical axis; An illumination condition control system for switching to any one of: a pattern selection device for selecting any one of a plurality of mask patterns as the mask pattern;

An alignment system for mutually aligning a plurality of mask patterns sequentially selected by the pattern selection device; and the illumination condition control system via the illumination condition control system in accordance with the pattern selected by the pattern selection device. An exposure control system for performing multiple exposure by switching,

Are assembled in a predetermined positional relationship.

28. A method of manufacturing a device in which a circuit pattern having a predetermined shape including a linear pattern is formed in a certain layer,

A method for manufacturing a device, comprising transferring the circuit pattern to the layer by using the transfer method according to any one of claims 1, 2, 7 to 9, and 16 to 23.

29. The method for manufacturing a device according to claim 28, wherein said linear pattern is a gate electrode pattern of a field effect transistor.