JP2015079807A - Projection exposure device and projection condition calculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply an exposure device that controls a longitudinal/lateral error (line width HV difference) in printing line width of an exposure substrate due to a process factor outside the exposure device, especially, a pattern line width drawing error of a mask to within a proper range according to the mask.SOLUTION: Horizontal and vertical line width errors (line width HV differences) of a printing pattern of a photosensitive substrate are measured for each mask according to a pattern drawing region in the mask. According to the pattern drawing region in the mask, a light intensity distribution value of illumination light for correcting the line width HV differences to within a proper range is measured, and the light intensity distribution value is set as a correction parameter to the exposure device. When the photosensitive substrate is exposed by the exposure device, the light intensity distribution value is controlled according to the set correction parameter once the illumination light reaches a pattern drawing region in each mask during scanning exposure so as to control line width HV differences corresponding to the pattern drawing region in the mask to within the proper range.

Description

  The present invention relates to a projection exposure apparatus for manufacturing microdevices such as semiconductor elements such as ICs and LSIs, liquid crystal substrates, CCDs, thin film magnetic heads, and in particular, device line width control in such projection exposure apparatuses. Alternatively, the present invention relates to a technique related to light intensity distribution adjustment (correction) of illumination light.

  Conventionally, in the manufacturing process of semiconductor elements formed from ultrafine patterns such as LSI or VLSI, a circuit pattern drawn on a mask is reduced and exposed on a substrate coated with a photosensitive agent (hereinafter referred to as “wafer”). Reduction projection exposure apparatuses that perform printing and baking are used (see Patent Documents 1 and 2). As the mounting density of semiconductor elements increases, further miniaturization of patterns is required, and higher resolution is required. As one of the techniques for increasing the resolving power, a super-resolution imaging technique called oblique incidence illumination for illuminating a mask with oblique incidence has been proposed. In such an illumination method, a secondary light source distribution (hereinafter referred to as “effective light source distribution”) having a special shape such as an annular shape or a quadrupole shape is formed.

  Especially when forming an effective light source distribution of a special shape, the pattern of the pattern transferred to the wafer is affected by the non-uniform (asymmetric) light intensity of the effective light source distribution caused by the manufacturing error of the optical member. A direction error (line width HV difference) different from the design line width occurs in the horizontal direction (H direction) and the vertical direction (V direction), which may cause a disadvantage that the yield is lowered. In order to reduce such inconvenience, it is required to form a good effective light source distribution according to the circuit pattern of the mask, and it is necessary to adjust the light intensity of the effective light source distribution to be uniform (symmetric). . The conventional method for adjusting the light intensity non-uniformity (asymmetrical) of the effective light source distribution is to measure the light intensity of the effective light source distribution with an effective light source measuring device arranged on the wafer stage, and can be independently driven on a plane perpendicular to the optical axis. There has been proposed a method for adjusting symmetry by using a plurality of light shielding plates and shielding a part of the light intensity of the effective light source distribution outline.

  Even if the light intensity of the effective light source distribution is adjusted to be uniform (symmetric), the vertical and horizontal errors (line width) of the pattern transferred to the wafer due to manufacturing errors in the circuit pattern line width drawn on the mask, etc. There is a problem that HV difference) occurs. Patent Document 3 has been proposed as a conventional technique for compensating for fluctuations in the line width HV difference, and discloses a method in which an aperture device is disposed in an illumination optical system and the angular distribution of illumination light is controlled by the aperture device. According to this method, the shape of the aperture device is adjusted based on the detected variation of the pattern line width transferred to the wafer.

Japanese Unexamined Patent Publication No. 2004-247527 Japanese Unexamined Patent Publication No. 2006-19702 Japanese Patent Laid-Open No. 2003-338459

  However, since the mask pattern drawing error tends to occur at random, it is necessary to control the line width HV difference to an appropriate range with higher accuracy in accordance with the pattern drawing region (pattern drawing position) in the mask. Further, since the pattern drawing error differs for each mask, there is a problem of calculating correction parameters for each mask in a short time according to the mask to be used.

  In view of the above-mentioned problems in the prior art, the present invention eliminates vertical and horizontal errors (line width HV difference) in the printing pattern line width of the photosensitive substrate caused by process factors outside the exposure apparatus, particularly mask pattern line width drawing errors. In order to reduce, for each mask, according to the pattern drawing area (pattern drawing position) in the mask, the light intensity distribution value of the illumination light is adjusted and controlled in a short time and with high accuracy, and the line width HV difference is in an appropriate range. The present invention provides a projection exposure apparatus that controls the above and a device manufacturing method using the same.

  In order to achieve the above object, a projection exposure apparatus of the present invention comprises a light intensity distribution setting means for setting a light intensity distribution value of illumination light corresponding to a mask pattern drawing region, and light for adjusting the light intensity distribution of illumination light. An intensity distribution adjusting means, monitoring a position where the illumination light irradiates the mask during scanning exposure of the photosensitive substrate, and based on the light intensity distribution value immediately before irradiating the pattern drawing region with the illumination light. The light intensity distribution adjusting means controls the light intensity distribution value, and the pattern line width HV difference is controlled within an appropriate range.

  In a preferred embodiment of the present invention, by measuring the line width HV difference of the photosensitive substrate pattern subjected to test exposure while changing the light intensity distribution value by the intensity distribution adjusting means in advance, the optimum light according to the pattern drawing area of the mask. After obtaining the intensity distribution value, the light intensity distribution value corresponding to the pattern drawing area of the mask is recorded in the storage unit together with the mask identifier. The light intensity distribution value is retrieved from a mask ID (identifier) that uses the photosensitive substrate for exposure, and the light intensity distribution value is controlled according to the pattern drawing area of the mask based on the retrieved light intensity distribution value.

  In a preferred embodiment of the present invention, the light intensity adjustment plate (light-shielding plate) for adjusting the light intensity distribution value of the illumination light can be independently driven in a plurality of positions arranged in the vicinity of the surface forming the basic shape of the illumination light. It is constituted by a light shielding plate, and is characterized in that a light shielding plate corresponding to a light intensity distribution value is selected from a plurality of light shielding plates and position control is performed.

  In a preferred embodiment of the present invention, an exposure condition calculation device that calculates a light intensity distribution value of illumination light corresponding to a pattern drawing region of a mask is configured to be connected to a plurality of exposure devices and a plurality of line width measuring devices via a network. It is. The exposure condition calculation device receives the light intensity distribution value data subjected to the test exposure and the line width HV data of the photosensitive substrate pattern measured by the line width measuring device, and the optimum line width HV difference according to the pattern drawing area of the mask. The light intensity distribution value is automatically calculated to simplify complicated work by manpower.

  According to the present invention, it is possible to satisfactorily adjust the light intensity distribution value of illumination light for each mask even when a vertical / horizontal difference (line width HV difference) in the printing pattern line width occurs due to a process factor outside the exposure apparatus. The difference in line width HV can be reduced, and in particular, there is an effect of increasing the resolution of a very fine pattern.

  Also, by controlling the light intensity distribution value of the illumination light according to the pattern drawing area (pattern drawing position) in the mask, the line width HV difference can be reduced with high accuracy, and in particular, the resolving power of extremely fine patterns can be reduced. There is an effect to increase.

  Furthermore, by automating the calculation of the light intensity distribution value (correction parameter) according to the mask, it is possible to simplify complicated manual operations and to accurately and accurately adjust the line width HV difference according to the pattern drawing area in a short time. The range can be controlled.

Schematic block diagram of exposure equipment Partial explanatory diagram of the embodiment of FIG. Explanatory diagram forming effective light source distribution Schematic configuration of effective light source measuring instrument Explanatory drawing showing light intensity distribution amount change and line width HV difference change by light intensity adjustment plate Explanatory diagram showing the relationship between X / Y light quantity ratio of effective light source distribution and line width HV difference Explanatory drawing showing the relationship between X / Y light quantity ratio of mask area and line width HV difference Explanatory drawing which shows the correction parameter setting of a mask area | region Explanatory drawing which shows the exposure direction at the time of mask exposure Flow explaining the exposure operation according to the mask area correction parameter System configuration diagram of exposure condition calculator

[Example]
First Embodiment FIG. 1 shows a schematic configuration of a step-and-scan exposure apparatus according to an embodiment of the present invention. In the figure, a pulse laser light source 101 is filled with a gas such as ArF and emits laser light. This light source emits light having a wavelength of 193 nm in the far ultraviolet region. The laser light source also includes a front mirror that constitutes a resonator, a diffraction grating for narrowing the exposure wavelength, a narrowing module composed of a prism, etc., a spectrometer for monitoring wavelength stability and spectral width And a monitor module including a detector, a shutter, and the like. The gas exchange operation of the laser light source, the control for stabilizing the wavelength, the control of the discharge applied voltage, and the like can be controlled by a command from the main controller 130 of the exposure apparatus connected by the interface cable.

  The λ / 2 phase plate 102 is made of a glass material having birefringence such as quartz or magnesium fluoride, and converts the beam emitted from the pulse laser light source 101 into polarized light whose electric field vector is directed in a predetermined direction. By moving the λ / 2 phase plate 102 to the optical path, the surface to be illuminated can be switched between illumination with X-polarized light and illumination with Y-polarized light. The neutral density filter 103 is configured to be switchable in order to change the illuminance of the illumination light in accordance with the exposure amount. The microlens array 104 is incident on the optical system after the microlens array 104 even if the light from the laser light source 101 is shifted or decentered with respect to the optical axis of the illumination optical system due to floor vibration or exposure apparatus vibration. Light is emitted with a specific angular distribution so that the characteristics of the light do not change.

  The first condenser lens 105 guides the light from the microlens array 104 to the diffractive optical element 106. The diffractive optical element 106 is mounted on a turret 107 having a plurality of slots, and an arbitrary element can be moved on the optical axis by an actuator. The light emitted from the diffractive optical element 106 is collected by the second condenser lens 108 and forms a diffraction pattern on the diffraction pattern surface A. If the diffractive optical element 106 mounted on the turret 107 is moved on the optical axis, the shape of the diffracted light pattern can be changed.

  In the diffraction pattern formed on the diffraction pattern surface A, the prism 109 and the first zoom lens 111 adjust the parameters of the effective light source distribution of illumination light such as the annular ratio and the σ value. The effective light source distribution is a non-light intensity distribution on the pupil plane of the projection optical system 121. The prism 109 forming the effective light source distribution shape is mounted on the turret 110 having a plurality of slots, and an arbitrary prism can be moved on the optical axis by an actuator. The σ value is the value of the ratio of the illumination optical system numerical aperture (effective light source distribution diameter) to the projection lens 121 numerical aperture, and the first zoom lens 111 is controlled to enlarge or reduce the effective light source distribution diameter. The σ value is controlled to a desired value.

  FIG. 3 shows a schematic diagram for forming the shape of the effective light source by the prism. FIG. 3 (a) shows a case where a ring-shaped effective light source distribution is formed. A prism having a concave conical surface (or plane) 301 on the incident side indicated by an arrow and a convex conical surface 302 on the exit side is shown. A ring-shaped effective light source distribution is formed. FIG. 3B shows a case where a quadrupole effective light source distribution is formed. A concave quadrangular pyramid surface (or plane) 303 is provided on the incident side indicated by an arrow, and a convex quadrangular pyramid surface 304 is provided on the exit side. An effective light source distribution is formed by the provided prism. Furthermore, if it is configured by a pair of prisms as shown in FIGS. 3C and 3D and the interval of the prism can be moved relative to the optical axis direction, a wider variety of effective light source distributions can be formed. 3 (c) and 3 (d) show a pair of prisms that form a ring-shaped effective light source distribution. When the prism interval 305 is small as shown in FIG. 3 (c), the width of the light emitting part 306 is wide. When the prism interval 307 is large as shown in FIG. 3D, an annular effective light source distribution with a narrow width 308 of the light emitting portion can be formed.

  Returning to FIG. 1, the σ value of the effective light source distribution is adjusted by enlarging / reducing the first zoom lens 111 while the diffraction pattern on the diffraction pattern surface A is maintained in a substantially similar shape. After the polarization state is shaped in a desired direction by the polarization optical element 112, an image is formed on the incident surface of the fly-eye lens 114. The second zoom lens 115 superimposes and superimposes the light beams divided by the fly-eye lens 114 and forms a substantially uniform light distribution on the B surface. The half mirror 116 on the optical path extracts a part of the exposure light that irradiates the mask (or “reticle”) 120 and branches it to the light amount detector 117. The relay optical system 119 projects a substantially uniform effective light source distribution formed on the B surface onto the mask 120.

  The mask 120 is formed with a circuit pattern of a semiconductor element to be baked. In the variable blind 118, a light shielding plate is disposed on a surface orthogonal to the optical axis, and an irradiation area on the circuit pattern surface of the mask 120 can be arbitrarily set. FIG. 2 shows a state where the mask 120 is illuminated. A part of the circuit pattern 202 of the mask 201 is slit-lit with a slit-shaped light beam 203, and a part of the circuit pattern 202 is reduced on the wafer 122 coated with the photoresist by the projection lens 121 shown in FIG. β is reduced exposure by 1/4), for example. At this time, as shown by the arrows in FIG. 1, the mask 120 and the wafer 122 are scanned in opposite directions at the same speed ratio as the reduction ratio β of the projection lens 121 with respect to the projection lens 121 and the slit-shaped light beam 203. By repeating multi-pulse exposure by pulse light emission from the laser light source 101, the circuit pattern 202 on the entire mask surface 201 is transferred to one chip region or a plurality of chip regions on the wafer 122.

  The light quantity detector 117 generates an output corresponding to the intensity (exposure energy) of the exposure light. The output of the light amount detector 117 is converted into exposure energy per pulse by an integration circuit (not shown) that performs integration for each pulse emission of the pulse laser light source 101, and is input to the main controller 130 that controls the exposure apparatus. Yes. The main controller 130 feedback-controls the amount of light emitted from the pulse laser light source 101 while sequentially measuring the exposure light with the light amount detector 117 so as to match the appropriate exposure amount determined by the photosensitive material applied to the wafer 122. Thus, the exposure amount is controlled.

  On the pupil plane of the projection lens 121 (Fourier transform plane with respect to the mask), an aperture stop (not shown) of the projection lens having a substantially circular aperture is disposed, and the diameter of the aperture is controlled by driving means such as a motor. Thus, it can be set to a desired value. The field lens 123 constitutes a part of the lens system in the projection lens 121, and is moved on the optical axis of the projection lens by using air pressure or a piezoelectric element. The projection magnification and the distortion error are improved while preventing the aberration from decreasing.

  The wafer stage 125 can move in a three-dimensional direction, and can move in the optical axis direction (Z direction) of the projection lens 121 and in a plane (XY plane) orthogonal to this direction. By measuring the distance between the moving mirror fixed to the wafer stage and the laser interferometer 126, the position of the XY plane of the wafer stage 125 is detected. The main controller of the exposure apparatus detects the position of the wafer stage 125 with the laser interferometer 126 and controls the driving means such as a motor to move the wafer stage to a predetermined XY plane position.

  In this embodiment, after positioning the mask 120 and the wafer 122 so as to have a predetermined relationship, the pulse laser light source 101, the wafer stage 125, and the mask stage 124 are synchronously controlled based on a synchronization signal from the main controller 130. Then, scan exposure is performed to transfer the circuit pattern 202 on the entire surface 203 to the chip area of the wafer 122. Thereafter, a so-called step-and-scan method is adopted in which the wafer 122 is driven in the XY plane by a predetermined amount by the wafer stage 125 and the other areas of the wafer 122 are sequentially projected and exposed in the same manner. .

  An illuminance detector 128 disposed on the wafer stage 125 detects the illuminance of exposure light (illumination light) reaching the wafer surface (image surface). The exposure light (illumination light) that has passed through the projection lens 121 passes through a pinhole (not shown) having a diameter of several hundreds μm disposed inside the illuminance detector 128 and is incident on the light receiving portion of the illuminance detector 128. For example, a photodiode is used as the light receiving portion, and a current amount corresponding to the intensity (exposure energy) of the exposure light is output, so that the exposure energy on the wafer surface (image surface) can be measured. By measuring the illuminance on the wafer surface (image surface) prior to wafer exposure, the appropriate exposure amount of the wafer can be controlled with high accuracy.

  The effective light source measuring device 129 arranged on the wafer stage 125 measures the effective light source distribution of the exposure light (illumination light). The configuration and measuring method of the effective light source measuring device 129 will be described with reference to FIG. FIG. 4A is an explanatory diagram of an imaging state when the effective light source distribution is measured by the effective light source measuring device 129. FIG. The effective light source measuring device 129 arranges a minimal pinhole 403 having a diameter of several tens of μm on the imaging surface 402 of the pupil effective light source distribution 401 of the projection lens 121, and exposure light (illumination light) that has passed through the projection lens 121 is a minimal pin. After passing through the hole 403, the light is incident on the light receiving unit 405 with a light intensity distribution equivalent to the effective light source distribution 401. For example, a two-dimensional CCD sensor is used for the light receiving unit 405, and the effective light source distribution 404 of the exposure light (illumination light) can be measured by photoelectric conversion according to the light intensity of the light source and output. In the embodiment of the present invention, a 512 × 512 two-dimensional CCD image sensor arranged in a lattice pattern as shown by 406 in FIG. 4B is used. Reference numeral 407 represents the effective light source distribution by a position function (map) of a two-dimensional CCD pixel (a minute point light source), and the light intensity at an arbitrary coordinate (x, y) is represented by A (x, y). A (x, y) value of 0 means no exposure light (illumination light). By measuring and adjusting the effective light source distribution on the wafer surface (image surface) prior to wafer exposure, the line width of the device pattern transferred onto the wafer can be controlled with high accuracy.

  Based on the schematic configuration of the exposure apparatus described above, the light intensity distribution of the effective light source distribution of the illumination light when the line pattern transferred onto the wafer has a direction error (line width HV difference) in the horizontal and vertical directions. An embodiment in which the value is adjusted to reduce the line width HV difference will be described. In order to control the light intensity distribution value of the effective light source distribution, the light intensity adjusting plate 131 disposed in the vicinity of the diffraction pattern surface A in FIG. 1 is used. FIGS. 5A to 5A show a schematic configuration of the light intensity adjustment plate 131 on a plane (X-Y plane) perpendicular to the optical axis 505. FIG. Four light shielding plates XR501, XL502, YU503, and YD504 are connected to an actuator (not shown), and can be driven independently in the direction indicated by the arrow in response to a command from the main controller 130.

  The four light shielding plates 501 to 504 in FIGS. 5 (a) to (1) show an initial state where the outer shape of the effective light source distribution 506 is not shielded. In this state, FIG. 5 (a)- The light intensity distribution of the effective light source shown in (2). The upper diagram in FIGS. 5A to 5B schematically illustrates the light intensity distribution of the effective light source X section, and the lower diagram illustrates the effective light source Y section. The horizontal axis indicates the radial size (σ value) of the effective light source distribution around the optical axis 505, and the vertical axis indicates the light intensity of the effective light source. In the initial state where the light shielding plate is opened, the light intensity area 507 of the X section and the light intensity area 508 of the Y section are equal, and the light intensity of the XY section is adjusted uniformly.

  5 (b)-(1) shows a case where the X-direction light shielding plate (XR, XL) is moved in the optical axis direction, and the X-direction outer shape part 509 of the effective light source distribution is equally shielded from the left and right. The light intensity distribution at this time is shown in Fig. 5 (b)-(2). The light intensity distribution 510 in the X section is lower than the light intensity distribution 507 in the open state in accordance with the X light shielding amount. On the other hand, the light intensity distribution 511 of the Y cross section that is not shielded from light has the same light intensity as that in the opening state 508.

  FIG. 5 (c)-(1) shows a case where the Y-direction light shielding plate (YU, YD) is moved in the optical axis direction and the Y-direction outer shape part 512 of the effective light source distribution is equally shielded from the left and right. The light intensity distribution at this time is shown in Fig. 5 (c)-(2). The light intensity distribution 514 in the Y cross section is lower than the light intensity distribution 508 in the open state in accordance with the Y light shielding amount. On the other hand, the light intensity distribution 513 of the X cross section that is not shielded can obtain the same light intensity as that of the aperture state 507. In FIG. 5 (1), for the sake of explanation, a part of the outer shape of the effective light source distribution 506 having a ring shape is shown to be missing, but the effective light source distribution maintained the ring shape in the A plane of FIG. The light intensity (energy) is controlled in the state.

  The change in the light intensity of the effective light source distribution and the change in the horizontal direction (H direction) and the vertical direction (V direction) of the printing pattern line width transferred to the wafer will be described with reference to FIG. 5A to 5C, the light intensities 507 and 508 of the effective light source distribution are uniformly adjusted in the XY directions, and the line widths of the H direction pattern 515 and the V direction pattern 516 are transferred equally. Figures 5 (b)-(3) show that the exposure energy irradiated to the wafer is uniformly reduced in the X direction by reducing the X light intensity 510 with the light shielding plates (XR, XL) in the X direction. The V direction pattern 518 is transferred thickly with respect to the state 516 of uniform light intensity. Similarly, when the Y-light intensity 514 is reduced by the Y-direction light shielding plates (YU, YD) shown in FIGS. 5 (c) to (3), the H-direction pattern line width 519 is changed to the state 515 in which the light intensity is uniform. On the other hand, it is transcribed thickly. As described above, the light intensity adjusting plate 131 shields a portion of the effective light source distribution in the X direction or the Y direction, thereby generating a light intensity distribution value (bias amount) in the effective light source distribution, and exposure energy to the wafer. The pattern line width can be adjusted by controlling the HV direction difference.

  Next, a method for quantifying the relationship between the line width HV difference of the actual wafer printing pattern line width and the light intensity distribution value (bias amount) of the effective light source distribution will be described with reference to FIG. The vertical axis in Fig. 6 (1) shows the line width difference (H-V) between the horizontal direction (H direction) and vertical direction (V direction) of the actual pattern line width, and the horizontal axis shows the light intensity distribution value of the effective light source distribution. (X / Y light quantity ratio). The origin in FIG. 6 (1) indicates that there is no deviation in the X / Y light intensity of the effective light source distribution, and there is no difference in line width HV when the wafer printing pattern line width is measured. The light intensity distribution value (X / Y light quantity ratio) on the horizontal axis is measured by the effective light source measuring device 129 arranged on the wafer stage 125 described above. FIG. 6 (2) is a schematic diagram in which the light source intensity distribution of the annular illumination is measured by the two-dimensional CCD 601 of the effective light source measuring device 129. The light intensity of the CCD pixel (small point light source) is integrated for each of the four areas AXL (602), AXR (603), AYU (604), and AYD (605) divided diagonally around the optical axis (AX). , (Expression 1) to obtain the light intensity distribution value (X / Y light quantity ratio) in the XY direction.

X / Y light intensity ratio [%] = (AXL light intensity + AXR light intensity) / (AYU light intensity + AYD light intensity) (Formula 1)
When the light intensity in the X direction is lowered, it becomes smaller than 100%, and the line width in the H direction becomes thicker (or thinner). On the other hand, when the light intensity in the Y direction is lowered, it becomes larger than 100%, and the line width in the V direction becomes thicker (or thinner).

  The relationship between the change in the line width HV difference and the X / Y light quantity ratio (light intensity distribution value) shown in FIG. 6 (1) is quantified (coefficientized) by test exposure and stored in the exposure apparatus. First, the X / Y light quantity ratio (Formula 1) is measured in a state where the light shielding plate position of the light intensity adjustment plate 131 is positioned at a specific position. By repeatedly measuring the X / Y light amount ratio (Equation 1) while changing the predetermined range of the light shielding plate position at a predetermined pitch, the relationship of the X / Y light amount ratio (Equation 1) corresponding to the light shielding plate position is quantified ( Coefficient) and store it in the exposure apparatus.

  Next, with the X / Y light amount ratio of 100% as the center, the X / Y light amount ratio changes within a predetermined range at a predetermined pitch based on the coefficient of the X / Y light amount ratio (Equation 1) according to the light shielding plate position described above. The wafer is test-exposed. A line 608 is a graph obtained by measuring and plotting the line width HV difference of the printing pattern for each X / Y light quantity ratio (light intensity distribution value) with a line width measuring device. In this case, if exposure is performed with an X / Y light quantity ratio of 98% (607) at which the line width HV difference is close to 0, the line width HV difference can be uniformly printed. As described above, the relationship (coefficient) between the light shielding plate position and the X / Y light quantity ratio measured by the effective light source measuring device (129) and the relation (coefficient) between the X / Y light quantity ratio and the line width HV difference measured by the test exposure are previously determined. By memorizing, the relationship between the line width HV difference and the light intensity distribution value (X / Y light quantity ratio) of the effective light source distribution can be quantified, and the light shielding plate position that makes the line width HV difference uniform can be obtained.

  Next, a method of controlling the line width HV difference within an appropriate range according to the mask, which is one of the features of the present invention, will be described. FIG. 7 is an explanatory diagram showing the relationship between the X / Y light quantity ratio and the HV line width difference in the pattern drawing area in the mask. FIG. 7 (1) is a schematic view of the mask as seen from the direction of irradiation of exposure light (upper surface). The pattern drawing area (circuit pattern surface) of one mask is divided into four areas (701, 702, 703, 704). The example divided into is shown. In the present embodiment, a method of dividing the circuit pattern surface of the mask into regions according to the coordinates in the scanning direction Y and correcting the line width HV difference according to the mask regions 701 to 704 is illustrated.

  Figure 7 (2) is a schematic diagram quantifying (coefficientizing) the relationship between the line width HV of the actual wafer printing pattern line width and the light intensity distribution value (X / Y light intensity ratio) of the effective light source distribution for each mask area. The figure is shown. In the same procedure as in FIG. 6 described above, the relationship between the light shielding plate position measured by the effective light source measuring device 129 and the X / Y light quantity ratio (light intensity distribution value) is stored for each of the mask areas 701 to 704, and a line is obtained after the test exposure. Stores the relationship between the line width HV difference measured by the width measuring instrument and the X / Y light quantity ratio (light intensity distribution value) at that time.

  A line L701 in FIG. 7 (2) shows a correlation obtained by performing test exposure on the mask area 701. The line L701 is exposed at a point P701 with an X / Y light quantity ratio of 95% at which the line width HV difference is close to zero. For example, the pattern line width HV difference can be burned uniformly. Similarly, the correlation is illustrated with the mask area 702 as a line L702, the mask area 703 as a line L703, and the mask area 704 as a line L704. The mask regions 702 and 703 are points P702 and P703 having an X / Y light amount ratio of 100% at which the line width HV difference is close to 0, and the mask region 704 is an X / Y light amount ratio of 97% at which the line width HV difference is near 0. If exposure is performed at point P704, the pattern line width HV difference can be uniformly printed. As described above, the burn-in line width HV difference that occurs randomly for each mask is obtained by calculating the X / Y light quantity ratio (light intensity distribution value) as a correction parameter according to the pattern drawing area (701 to 704) in the mask. The pattern line width HV difference can be suppressed with high accuracy.

  The X / Y light quantity ratio (light intensity distribution value) corresponding to the mask areas 701 to 704 obtained in FIG. 7 is input to the exposure apparatus as a correction parameter. FIG. 8 shows an example in which correction parameters corresponding to the mask areas 701 to 704 are set in the exposure apparatus. Set 95% of the X / Y light quantity ratio of the mask area 701 to the correction parameter 801, 100% of the X / Y light quantity ratio of the mask areas 702 and 702 to the correction parameter 802 and 803, and 97% of the X / Y light quantity ratio of the mask area 704 The correction parameters 804 are respectively set and recorded in a storage device (not shown). The exposure apparatus controls the line width HV difference to an appropriate range by controlling the position of the light shielding plate of the light intensity adjusting plate 131 during wafer exposure according to the set X / Y light quantity ratio (light intensity distribution value) correction parameter. Is possible.

  Next, the exposure operation of the exposure apparatus will be described in detail using the flow of FIG. When the wafer exposure operation of the exposure apparatus is started, in step S1001, the X / Y light quantity ratio parameter corresponding to the mask ID (mask identifier) used for exposure (described above with reference to FIG. 8) is stored from the storage device (not shown). read out. In step S1002, the illumination condition of the illumination light of the mask circuit pattern is controlled. For example, when illuminating a reticle with an annular-shaped effective light source distribution, a desired σ value is controlled by the first zoom lens 111 and the annular width is controlled by the interval of the prism lens 109. At this time, the four light shielding plates of the light intensity adjusting plate 131 are controlled to be opened.

  In step S1003, the wafer carried in the exposure apparatus is moved on the wafer stage 125 to the start position of one chip area (exposure shot). In step S1004, the exposure direction is determined prior to exposure. The exposure direction refers to the direction in which slit-shaped exposure light scans the mask surface when performing scan exposure by the step-and-scan method.

  FIG. 9 shows a schematic diagram of the exposure direction when irradiating the mask surface with exposure light. The case where the slit exposure light 203 shown in FIG. 9 (1) scans upward is the Up direction, and the case where the slit exposure light 203 shown in FIG. 9 (2) scans downward is the Down direction. In the case of the step-and-scan method, the entire wafer surface is usually exposed while alternately repeating shot exposure in the Up direction and Down direction. When the exposure direction in FIG. 9 (1) is Up, the mask areas 704, 703, 702, and 701 are exposed in the order, and when the exposure direction in FIG. 9 (2) is Down, the mask areas 701, 702, 703, and 704 are exposed. The exposure is performed in the order of. Returning to the flow of FIG. 1, the exposure direction of the first exposure shot of this embodiment is set to Down, and the process proceeds to the start of exposure in step S1005.

  In step S1006, the light intensity distribution value (X / Y light amount ratio) of the effective light source corresponding to the mask area is controlled to start scanning exposure. When the exposure direction is Down, the light shielding plate of the light intensity adjusting plate 131 is positioned so that the exposure light in the mask area 701 has an X / Y light quantity ratio of 95% (801). FIG. 10 (a) shows a schematic diagram of the light shielding plate of the light intensity adjusting plate (131) viewed on a plane (XY plane) perpendicular to the optical axis AX at this time. The X light shielding plate (XL, XR) is driven in the direction toward the optical axis AX, and the X light quantity is reduced by 5% with respect to the Y light quantity. The position of the X light shielding plate (XL, XR) at which the X / Y light quantity ratio is 95% is determined based on the coefficients stored in the test exposure of FIGS. As soon as the light shielding plate is positioned, the process proceeds to step S1007 to monitor whether the exposure of the mask area 701 is completed. The position of the mask subjected to scanning exposure is determined by constantly measuring the position of the mask stage 124 that is moved by the mask stage laser interferometer (127) and converting it to the position of the mask area by the main controller 130.

  When the exposure of the mask area 701 is completed, the process proceeds to step S1008, and the light shielding plate of the light intensity adjusting plate 131 is positioned so that the exposure light of the mask area 702 has an X / Y light quantity ratio of 100% (802). FIG. 10B is a schematic diagram showing a light shielding plate state in which the mask region 702 is exposed with an X / Y light quantity ratio of 100%, as in FIG. 10A.

  From the state of FIG. 10 (a), the X light shielding plates (XL, XR) are driven in the direction opposite to the optical axis AX and positioned so that the ratio of the X light quantity and the Y light quantity is equal. As soon as the light shielding plate is positioned, it is monitored whether or not the exposure of the mask area 702 has been completed. Like the mask area 702, the mask area 703 has an X / Y light quantity ratio of 100% (803), and the light intensity adjusting plate 131 is positioned so that the exposure light has an X / Y light quantity ratio of 100% (803). .

  In this case, the position of the light shielding plate does not change between FIG. 10 (b) and FIG. 10 (c). When the mask region 703 ends, the process proceeds to step S1010, and the light shielding plate of the light intensity adjustment plate 131 is positioned so that the exposure light in the mask region 704 has an X / Y light amount ratio of 97% (804). In FIG. 10D, the X light shielding plate (XL, XR) is driven in the direction toward the optical axis AX from the opening state of FIG. 10C, and the X light amount is reduced by 3% with respect to the Y light amount. The position of the X light shielding plate (XL, XR) at which the X / Y light quantity ratio is 97% is determined based on the coefficients stored in the test exposure of FIGS. As soon as the light shielding plate is positioned, it is monitored whether the exposure of the mask area 704 has been completed. When the exposure is completed, the exposure shot (exposure of one chip area) is completed.

  In step S1012, it is determined whether all shots of the wafer have been completed. If not, the process returns to step S1003, and the wafer stage 125 is moved to the start position of the second exposure shot. The exposure direction of the second exposure shot is switched to the Up direction, and in step S1004, the process proceeds to the Up direction. When the exposure direction is Up, the mask areas are exposed in the order of 704, 703, 702, and 701 as shown in FIG. 9 (1). The exposure shot is controlled by controlling the corresponding X / Y light quantity ratio. Thereafter, the entire wafer surface is exposed while alternately repeating shot exposure in the Up direction and Down direction. When the exposure of the entire wafer surface is completed, the process proceeds to step S1013. In step S1014, the wafer is loaded and the wafer exposure is repeated until the predetermined number of wafers is completed.

  As described above, the light intensity distribution value (X / Y light amount ratio) that suppresses the line width HV difference to an appropriate range is quantified as a correction parameter for each mask according to the pattern drawing area in the mask, and is exposed by the exposure device. When exposing the substrate, when the illumination light reaches the pattern drawing area in the mask during scanning exposure, the light intensity distribution value of the illumination light is controlled according to the set light intensity distribution value. The line width HV difference according to the pattern drawing area can be controlled within an appropriate range.

Second Embodiment In the first embodiment, an exposure apparatus correction method for controlling the line width HV difference to an appropriate range by the light intensity distribution value (X / Y light amount ratio) according to the pattern area in the mask is exemplified. . In the second embodiment, a method of automating the calculation of different light intensity distribution values (correction parameters) for each mask and obtaining it in a short time according to the mask to be used will be described. FIG. 11 shows a system configuration for automating the calculation of the light intensity distribution value (correction parameter) for each mask.

  The exposure condition calculation device 1101 for calculating the light intensity distribution value is connected to N exposure devices 1103 and a plurality of M line width measuring instruments 1106 via a network capable of bidirectional communication, and can transmit and receive desired data. It is possible. Further, a storage device 1102 for recording correction parameters for each mask is connected to the exposure condition calculation device 1101, and a correction parameter is obtained according to a numerically / symbolized mask identifier (mask ID) for identifying a mask solid. Can be stored.

  The flow of automatically calculating the light intensity distribution value (correction parameter) by the exposure condition calculation device 1101 will be described with reference to FIG. When device production using a new mask 1104 is planned by the exposure apparatus 1103, test exposure is generally performed for the purpose of determining exposure conditions such as exposure amount and focus amount.

  At that time, test exposure is also performed in which the light intensity distribution value (X / Y light quantity ratio) described in FIGS. 6 and 7 is repeated at a predetermined pitch while changing a predetermined range. When the test exposure of the exposure apparatus 1101 is completed, the exposure condition calculation apparatus 1101 receives the test exposure condition data 1105, the light intensity distribution value (X / Y light quantity ratio) measured by the effective light source measuring instrument, and the mask identifier. As the mask identifier, for example, there is a method in which a different barcode is attached to each mask, the exposure apparatus 1101 reads the barcode information, and the exposure condition calculation apparatus 1101 receives the barcode information.

  The test-exposed wafer 1105 is transferred from the exposure apparatus 1103 to the line width measuring device 1106, and the printing line width HV transferred to the wafer by the line width measuring device 1106 is measured. When the line width measurement is completed by the line width measuring device 1106, the exposure condition calculation apparatus 1101 receives the measurement result data 1107 and the line width measurement results in the horizontal direction (H direction) and the vertical direction (V direction).

  The exposure condition calculation device 1101 performs function approximation on the relationship between the change in the line width HV difference and the X / Y light quantity ratio (light intensity distribution value) in accordance with the mask areas 701 to 704 described in FIGS. Stored in device 1102 along with the mask identifier. When mass production of a device using the new mask 1104 is started in the exposure apparatus 1103, the exposure apparatus 1103 receives the light intensity distribution value 1108 corresponding to the mask identifier from the storage device 1102 of the exposure condition calculation apparatus 1101, and in FIG. Corrected exposure is performed by the described exposure operation.

  As described above, by automating the calculation of light intensity distribution values (correction parameters) for pattern drawing errors that occur randomly for each mask, it is possible to simplify manual operations and to shorten the pattern drawing area (pattern drawing) in a short time. The line width HV difference according to the position) can be controlled within an appropriate range with high accuracy.

101 ... Pulse laser light source 102 ... λ / 2 phase plate
103 ... Needing filter 104 ... Micro lens array
105 ... 1st condenser lens 106 ... Diffractive optical element
107 ... Turret 108 ... Second condenser lens
109 ... Prism 110 ... Turret
111 ... first zoom lens 112 ... polarizing optical element
113 ... Turret 114 ... Fly Eye Lens
115 ... second zoom lens 116 ... half mirror
117 ... Light intensity detector 118 ... Variable blind
119 ... Relay optical system 120 ... Mask (reticle)
121 ... Projection lens 122 ... Substrate (wafer)
123 ... Field lens 124 ... Mask stage
125 ... Wafer stage 126 ... Wafer stage laser interferometer
127 ... Mask stage laser interferometer 128 ... Illuminance detector
129 ... Effective light source measuring instrument 130 ... Main controller
131… Light intensity adjustment plate
201 ... Mask (reticle) 202 ... Circuit pattern
203 ... Slit beam

Claims (7)

An illumination optical system that illuminates a mask with illumination light from a light source, a projection optical system that projects a pattern of the mask onto a predetermined imaging plane, and a light intensity distribution adjustment unit that adjusts the light intensity distribution of the illumination light; A light intensity distribution setting means for setting a light intensity distribution value of the illumination light according to the pattern drawing region of the mask,
In a projection exposure apparatus that exposes a photosensitive substrate at a conjugate position with the mask via the projection optical system, the light intensity distribution of the illumination light according to the pattern drawing area of the mask during scanning exposure of the photosensitive substrate A projection exposure apparatus, wherein the light intensity distribution value is controlled by the light intensity distribution adjusting means based on the value.   The light intensity distribution value of the illumination light corresponding to the pattern drawing region of the mask corrects a line width error due to a direction difference between a horizontal pattern line width and a vertical pattern line width on the photosensitive substrate. The projection exposure apparatus according to claim 1.   The projection exposure apparatus according to claim 1, wherein a light intensity distribution value of the illumination light corresponding to a pattern drawing region of the mask is recorded according to a two-dimensional coordinate position of the mask.   The light intensity distribution value of the illumination light corresponding to the pattern drawing area of the mask is recorded for each mask using a mask identifier, and a value corresponding to the mask identifier used for exposure is searched and used. The projection exposure apparatus according to any one of claims 1 to 3.   The light intensity distribution adjusting means is composed of a plurality of independently driveable light shielding plates arranged in the vicinity of the surface forming the basic shape of the illumination light, and according to the light intensity distribution amount from the plurality of light shielding plates. 5. The projection exposure apparatus according to claim 1, wherein the position is controlled by selecting a light shielding plate.   The horizontal and vertical pattern line widths on the photosensitive substrate from the measured values of the light intensity distribution of the plurality of illumination lights and the measured values of the horizontal and vertical pattern line widths of the photosensitive substrate exposed with the light intensity distribution. An exposure condition calculation apparatus for calculating a light intensity distribution value of the illumination light that minimizes a line width error due to a difference in direction of the illumination light.   The exposure condition calculation apparatus according to claim 6, wherein the light intensity distribution value is a light intensity distribution value of the illumination light corresponding to a pattern drawing region.