JP2006059860A - Immersion aligner and its method, and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize highly accurate levelling measurement in the following exposure area adjacent to an immersion lithography area by one shot. <P>SOLUTION: In immersion lithography, an image projecting from a reticle is transferred onto a photosensitive surface 20A while a liquid 40 is held between a projection optics and the photosensitive surface 20A on a substrate 20. When the immersion lithography is repeated while changing an exposure area sequentially within the photosensitive surface 20A, a liquid holding frame 30 is provided to hold a liquid 40 for a part of a substrate facing surface 5A of a projection optics 5B. Thus, one exposure area EAx is included in a portion being in contact with the liquid 40 of the photosensitive surface 20A, and at least a part of a following exposure area EAx+1 adjacent to the exposure area becomes in non-contact with the liquid 40. Therefore, pre-read levelling in air is made possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an immersion exposure apparatus that repeats so-called immersion exposure (Immersion Lithography) while sequentially changing the exposure area within a photosensitive surface on a substrate, a method thereof, and a semiconductor device that performs pattern transfer using immersion exposure. It relates to the manufacturing method.

  In recent years, circuit patterns have been miniaturized at a rapid pitch for the purpose of increasing the degree of integration of LSIs and improving performance. As a result, the minimum dimension of the line width used for the LSI circuit pattern approaches the resolution limit of the lithography process, resulting in a serious shortage of process margin.

  An immersion exposure apparatus has been proposed as a solution to this problem. Immersion exposure is a technique for improving the resolution of lithography by filling the space between the optical components closest to the wafer of the projection optical system (Projection Optics) and the wafer with water. Lithographic resolution R is determined by the Rayleigh equation shown below, as is well known.

[Equation 1]
R = k1 · (λ / NA) (1)

  Here, “k1” represents a process-dependent constant, and “λ” represents the wavelength of light used for exposure. “NA” is a parameter indicating the numerical aperture of the projection optical system of the exposure apparatus, and is defined by the following equation.

[Equation 2]
NA = n · sin θ (2)

  Here, “θ” represents the angle at which the lens is viewed from the image plane by the projection optical system, and this corresponds to the size of the projection lens.

In a conventional exposure apparatus, a method has been employed in which the angle θ is increased by increasing the lens diameter to increase the numerical aperture NA, and as a result, the resolution is improved. However, there is a physical limit to increasing the lens diameter.
At present, a projection lens of sin θ = 0.85 has already been introduced as a projection exposure apparatus for mass production with a minimum resolution width of 65 nm class, and sin θ = 0.93 for a projection exposure apparatus with a minimum resolution width of 45 nm class. Development of a projection lens is underway. Up to this point, it is said that the projection lens has a large aperture.

On the other hand, “n” in the equation (2) represents the refractive index of the medium that fills the imaging space.
In the conventional exposure apparatus, since the medium between the lens and the wafer is air, the refractive index n is 1. In an immersion exposure apparatus, water or a liquid having a refractive index n higher than water is filled between the wafer and the surface facing the substrate of the projection optical system, that is, the final lens or optical plate (parallel plane plate, etc.). The numerical aperture NA is increased, and as a result, the resolution is improved.

  By the way, in the step movement type exposure apparatus currently in operation, the area where the pattern on the photomask is transferred by one shot exposure is limited, and the table on which the wafer is placed is driven to The exposure is repeated while sequentially moving the exposure area. At this time, an exposure apparatus used in a state-of-the-art semiconductor manufacturing process requires highly accurate focus control.

For high-precision focus control, an autofocus mechanism called “look ahead type” is generally used.
This is an autofocus method suitable for an exposure sequence using, for example, a step-and-scan exposure apparatus (scanner). In the step-and-scan type exposure apparatus, light hits a part of a reticle by an elongated illumination light slit (illumination field stop opening) elongated in a direction orthogonal to the scanning direction, and the pattern of the reticle part Is projected. Next, the reticle and wafer are stepped in a direction different from the scanning direction, and a pattern next to the already projected pattern of the reticle is projected. At this time, since the wafer is stepped in the opposite direction to the reticle, the pattern is transferred to an area adjacent to the already exposed area on the wafer. In scanning exposure, by repeating such an operation, it becomes possible to perform exposure of a large area that cannot be realized by a normal step-and-repeat exposure apparatus (stepper) due to lens diameter restrictions.

  In read-ahead autofocus, so-called leveling measurement is performed on a wafer area (next exposure area) that is adjacent along the scanning direction and is planned for the next exposure while a certain area on the wafer is being exposed. . In the leveling measurement, it is checked how much the photosensitive surface (resist layer surface) of the exposure area of the wafer is displaced as a relative position from the surface (image surface by the projection optical system) that becomes the just focus. The leveling measurement value is fed back to the control of the table holding the wafer, and after the height and tilt (Tilt) are corrected, the next exposure is performed. Strictly speaking, since there is a mechanical accuracy error in table movement, a certain degree of focus deviation usually occurs. However, in the read-ahead autofocus, the relative position of the wafer with respect to the projection optical system is always adjusted to a state close to the best focus for each exposure shot as described above. Absorb and achieve almost optimal exposure in all areas.

  7A to 7D are conceptual diagrams of a method for performing pre-read autofocus simultaneously with exposure. Here, as an example of the case where the pattern on one reticle is transferred to the photosensitive surface on the wafer by 6-shot exposure, in each drawing, there are six continuous exposure areas EA1, EA2, EA3, EA4 on the wafer. EA5 and EA6 are shown.

In the first step shown in FIG. 7A, leveling measurement is performed on the first exposure area EA1 as an initial stage before the start of exposure.
In the leveling measurement, a plurality of spot lights (measurement lights) are applied in the longitudinal direction of a rectangular exposure area (here, EA1), for example, at equal intervals, and the positional deviation from the prescribed value of the reflected spot light is measured. Based on the measured values, deviations such as the position of the wafer in the Z direction (optical axis direction of the projection optical system) and the inclination of the wafer in the longitudinal direction of the exposure area are calculated, and the table is set so as to cancel these deviations. Moving in the Z direction and rotating about the axis in the scanning direction, the relative positions of the photosensitive surface of the exposure area EA1 and the image plane of the projection optical system are substantially matched.

  In the next step shown in FIG. 7B, the first exposure area EA1 that has already been subjected to relative position correction for autofocus is exposed. During this exposure period, a pre-read autofocus operation, that is, a relative position correction for leveling measurement and autofocus is performed on the next exposure area EA2 as in the case of FIG.

Thereafter, similarly, the exposure and the pre-read autofocus operation are executed while sequentially sending the exposure area in the scanning direction. FIG. 7C shows a state in which leveling measurement is being performed for exposure on the fourth exposure area and prefetching on the fifth exposure area.
In the final step shown in FIG. 7D, the sixth exposure area EA6 is exposed. At this time, the prefetch autofocus operation is not performed.

  In the immersion exposure apparatus, as illustrated in FIG. 8A, the liquid 102 is applied to the entire surface of the wafer 100 or at least the entire lower surface of the lens barrel (barrel 101) of the projection optical system. Supplied. For this reason, as shown in FIG. 8B, the next exposure area EA5 to be leveled is always immersed in the liquid 102. Therefore, it is necessary to perform the above-described multipoint (multipoint) leveling measurement on the next exposure area EA5 in a state immersed in the liquid 102.

  When leveling measurement is performed in the liquid as described above, the reflection angle of the leveling light fluctuates due to fluctuations in the liquid level, or the reflectance decreases. For this reason, the accuracy of the level link measurement is lowered, and in addition to this, the intensity of the reflected spot light is weakened, resulting in a problem that the accuracy of the autofocus is lowered. In addition, since the liquid is warmed by the spot light, the refractive index of the liquid changes, which adversely affects not only leveling measurement but also immersion exposure itself.

  The problem to be solved by the present invention is to enable highly accurate leveling measurement in the next exposure area adjacent to the immersion exposure area by one shot.

The immersion exposure apparatus according to the present invention performs immersion exposure in which a projection image from a mask irradiated with light is transferred to the photosensitive surface in a state where liquid is held between the projection optical system and the photosensitive surface on the substrate. An immersion exposure apparatus that repeats while sequentially changing exposure areas within the photosensitive surface, and includes a single exposure area at a location in contact with the liquid within the photosensitive surface and is adjacent to the exposure area. Liquid holding means for holding the liquid with respect to a part of the projection optical system in the substrate facing surface so that at least a part of the projection optical system is not in contact with the liquid.
In the immersion exposure apparatus, it is preferable that the liquid holding unit includes an annular frame body in which one annular frame end surface is fixed to the substrate facing surface and holds the liquid.
Preferably, an illumination light slit that allows a part of the light that illuminates the mask to pass during immersion exposure is provided, and the liquid holding unit is a surface of the substrate facing surface that corresponds to the shape of the opening surface of the illumination light slit. The liquid holding area is limited to the portion.

The immersion exposure apparatus of the present invention preferably measures a relative positional deviation between the projection optical system and the substrate at a position that is not in contact with the liquid in the next exposure area, and the projection optical system in the next exposure area. It further has a pre-read autofocus unit that adjusts the relative position between the image plane by the system and the substrate based on the measurement result.
More preferably, in this case, the pre-read autofocus unit includes a plurality of spotlights obliquely with respect to a portion that is not in contact with the liquid in the next exposure area from a direction different from a direction in which the exposure area moves within the photosensitive surface. , Each spot light reflected in the next exposure area is received, and an adjustment amount of the relative position between the projection optical system and the substrate is obtained from the position information of the received light.

In the immersion exposure method according to the present invention, immersion exposure is performed in which a projection image from a mask irradiated with light is transferred to the photosensitive surface in a state where the liquid is held between the projection optical system and the photosensitive surface on the substrate. In the immersion exposure method, the exposure area is repeatedly changed while sequentially changing the exposure area in the photosensitive surface, the exposure surface including one exposure area at a position in contact with the liquid and adjacent to the exposure area. The immersion exposure is performed in a state where the liquid is held on a part of the projection optical system in the substrate facing surface so that at least a part thereof is not in contact with the liquid.
Preferably, in the immersion exposure method, in the immersion exposure step, a relative positional shift between the projection optical system and the substrate is measured in one exposure area in the photosensitive surface, and the projection is performed in the exposure area. An autofocus step for adjusting the relative position between the image plane by the optical system and the substrate based on the result of the measurement, and an exposure for moving the exposure area used for the measurement directly below the liquid and performing the immersion exposure And performing the autofocus step on the next exposure area by performing the measurement at a location not in contact with the liquid in the next exposure area during execution of the exposure step.

  According to the immersion exposure apparatus and the immersion exposure method having such a configuration, at each immersion exposure, the area (exposure area) to be exposed on the photosensitive surface on the wafer is the exposure area and the projection optical system. The liquid is filled between the substrate facing surface. However, at the next exposure area that is adjacent to the exposure area and the front surface will be in contact with the liquid when the wafer is next moved stepwise, at least a part of the exposure area will not be in contact with the liquid, and leveling measurement in air will be performed. It is possible.

In the immersion exposure apparatus, the above state is always maintained by the liquid holding means, that is, in each exposure.
In the immersion exposure method, so-called pre-read autofocus operation and immersion exposure are performed in parallel, and at this time as well, the entire area to be exposed (exposure area) is in contact with the liquid, but adjacent to it. A state in which at least a part of the next exposure area is not in contact with the liquid, for example, a state in which leveling measurement in air can be performed is always maintained in each exposure.

In the method of manufacturing a semiconductor device according to the present invention, when a semiconductor device is formed on a semiconductor substrate, a projection image from a mask irradiated with light is held between the projection optical system and the photosensitive surface on the semiconductor substrate. A method of manufacturing a semiconductor device in which immersion exposure to be transferred to the photosensitive surface is repeated while sequentially changing the exposure area within the photosensitive surface, wherein the photo resist forming the photosensitive surface is an element of the semiconductor substrate. A pre-processing step including application to the uppermost surface of the formation surface; and a portion of the photosensitive surface that is in contact with the liquid includes one exposure area, and at least a part of the next exposure area adjacent to the exposure area is The immersion exposure is performed while the liquid is held on a part of the surface of the projection optical system facing the substrate so as not to contact the liquid, and the exposure area is sequentially changed within the photosensitive surface. Developed an exposure step of repeating al, the photoresist after the exposure, the formed resist pattern and a step of post-processing to be used for formation of the semiconductor device.
In this manufacturing method, preferably, the immersion exposure measures a relative positional shift between the projection optical system and the substrate in one exposure area in the photosensitive surface, and the image by the projection optical system in the exposure area. An autofocus step of adjusting the relative position of the surface and the substrate based on the measurement result, and an exposure step of moving the exposure area used for the measurement directly below the liquid and performing the immersion exposure. During the exposure step, the autofocus step is performed on the next exposure area by performing the measurement at a location that is not in contact with the liquid in the next exposure area.

  This manufacturing method is similar to ordinary photolithography in that it includes steps of preprocessing including application of a photoresist, post-processing including exposure and development. However, the exposure step is immersion exposure in which immersion exposure is repeated while moving the relative position of the wafer stepwise, and a so-called pre-read autofocus operation is performed in parallel with each exposure. At this time, as in the above-described immersion exposure apparatus and method, the entire area to be exposed (exposure area) is in contact with the liquid, but at least a part of the adjacent next exposure area is not in contact with the liquid. For example, a state in which leveling measurement in the air is possible is always maintained in each exposure.

According to the immersion exposure apparatus and the method thereof according to the present invention, leveling measurement in so-called pre-read autofocus is possible in the air, and in that case, the accuracy of focusing is increased due to the high measurement accuracy. There is.
In addition, according to the semiconductor device manufacturing method of the present invention, leveling measurement can be performed in the air or the like. In that case, the accuracy of focusing is increased due to the high measurement accuracy. Further, as a result, the pattern transfer accuracy (resolution and depth of focus) to the semiconductor device is increased, which has the advantage that the characteristics and yield of the semiconductor device are improved.

  Hereinafter, an embodiment of an immersion exposure apparatus and an immersion exposure method will be described with reference to the drawings, taking as an example the case of use in manufacturing a semiconductor device.

FIG. 1 shows the overall configuration of the immersion exposure apparatus. FIG. 2 shows a more detailed configuration diagram of the means for leveling measurement in the step-and-scan exposure.
An immersion exposure apparatus 1 shown in FIG. 1 includes an illumination system 2 incorporating a KrF excimer laser light source as an exposure light source, an illumination field stop 3 having an illumination light slit 3A, a reticle table 4, a projection optical system 5, A Z table 6, an XY table 7, a prefetch autofocus (AF) unit 8, and a scanning unit 9 are provided.

  The scanning unit 9 includes means for detecting positions of the reticle table 4 and the XY table 7 in the X direction and the Y direction, for example, laser interferometers 9B and 9C. The scanning unit 9 controls the reticle table 4 and the XY table 7 by controlling driving means such as an actuator (not shown) or a linear motor based on the outputs (position detection results) of the two laser interferometers 9B and 9C. It has a scan controller 9A that controls the relative positions in the X direction and the Y direction.

  In FIG. 1, a reticle 10 on which a pattern for manufacturing a semiconductor device is formed is fixed to a reticle table 4 by vacuum suction or the like. A wafer (semiconductor substrate) 20 is fixed to the Z table 6 by vacuum suction or the like. It is assumed that several layers of insulating films are already formed on the element forming surface of the wafer 20, and a photoresist layer 20A is applied on the uppermost layer.

  Light from the light source (for example, KrF excimer laser light) passes through optical components (not shown) in the illumination system 2 and is limited to a part by an opening provided in the illumination field stop 3, that is, the illumination light slit 3A. . Then, the light passing through the illumination light slit 3 A illuminates a predetermined range of the reticle 10 determined by the control of the scanning unit 9, and a projection image from the reticle is input to the projection optical system 5. The projection optical system 5 accommodates a large number of optical components, such as a projection lens and an objective lens, in a lens barrel, reduces the projected image with a predetermined reduction magnification by these optical components, and also forms a photoresist layer ( The reduced projection image is formed on the photosensitive surface 20A.

  More precisely, the position of the exposure target portion of the wafer 20 in the Z direction (height) and the level of the reticle 10 and the projection optical system 5 are precisely controlled under the control of the scanning unit 9 at this time. The projection image is formed on the photosensitive surface 20A. This control is called leveling, and is executed by the prefetch AF unit 8 in this example.

The prefetch AF unit 8 includes an autofocus control unit (AF.CONT) 8A and a leveling measurement unit (LEV) 8B.
As shown in FIG. 2, the leveling measurement unit 8B includes a broadband illumination 81, a multi slit 82, an irradiation optical component 83, a light receiving optical component 84, reflection mirrors 85A and 85B, a condensing optical component 86, and a multi AF light receiving position sensor 87. Have. A predetermined number of spot lights are generated by the multi slit 82 from the measurement light from the broadband illumination 81. The spot light is irradiated on the photosensitive surface 20 </ b> A on the wafer 20 on the Z table 6 by reducing the diameter by the irradiation optical component 83 and adjusting the position between them. The reflected light (reflected spot light) is adjusted by the light receiving optical component 84, passes through the reflection mirrors 85 </ b> A and 85 </ b> B, is adjusted again by the condensing optical component 86, and enters the multi-AF light receiving position sensor 87. .
The multi-AF light receiving position sensor 87 photoelectrically converts the input spot light and outputs, for example, received light intensity distribution information in two dimensions. At this time, in order to increase the distribution accuracy in the detection direction, it is desirable to generate the spot light shape in a predetermined shape by the multi slit 82 in advance.

  The autofocus control unit 8A inputs a signal of the received light intensity distribution in each direction of a two-dimensional direction of a predetermined number of spot lights, and detects the peak point, for example. The autofocus control unit 8A detects how much the measurement result deviates from the reference value at the time of just focus, and from the result, the control amount of the Z table 6, that is, the direction and magnitude of the adjustment amount in the Z direction, The direction and magnitude of the tilt adjustment amount are calculated. The autofocus control unit 8A having such a function can be constituted by computer-based control means such as a microcomputer and CPU.

  The number of spot lights and the arrangement of irradiation points on the wafer are arbitrary, but at least two points are required to detect the inclination, and three to six points or more are desirable. In the embodiment of the present invention, the case of all three points is illustrated for simplification of the drawings, but the present invention is not limited to this.

FIG. 2 further shows the relationship between the pattern area PA on the reticle and the exposure area EA on the wafer 20.
In the scan exposure, the pattern area PA on one reticle is transferred to the photosensitive surface of the wafer 20 by multiple shot exposures. The one-shot exposure area PAx at this time is defined by the opening shape (see FIG. 1) of the illumination light slit 3A described above, and is usually a rectangle that is long in the direction orthogonal to the moving direction of the wafer 20 and the reticle, for example, 1: 3. It is a rectangle having an aspect ratio of more than about. This is to increase the resolution by effectively using the radial direction of the projection lens in the projection optical system 5 shown in FIG. 1 and increasing the effective use angle of the angle θ in the equation (2). In addition, this makes it possible to expose a device block having a diagonal distance larger than the diameter of the projection lens.

In the conventional scanning immersion exposure apparatus, the entire area between the substrate facing surface of the lowermost optical component of the projection optical system and the photosensitive surface on the wafer is filled with a liquid such as pure water.
On the other hand, in the present embodiment, the liquid supply area is limited to the minimum necessary area including the one-shot exposure area PAx (FIG. 2) defined by the illumination light slit. Thereby, the next exposure area where the leveling measurement is performed is maintained in a state where no liquid exists.

As a configuration for this, as shown in FIG. 1, for example, a liquid holding frame 30 is provided as a liquid holding means on the substrate facing surface 5A of the lowermost optical component (optical plate 5B) of the projection optical system 5.
The optical component on which the liquid holding frame 30 is provided may be a positive lens (objective lens) having a flat bottom surface, but preferably an optical plate (parallel plane plate) that can be easily replaced or cleaned as in this example. Etc.) 5B is desirable. Further, the liquid holding frame 30 may be formed separately from the optical plate and firmly fixed, or may be integrally formed of the same material (for example, quartz glass) as the optical plate 5B.

  FIG. 3A is a plan view of one configuration example of the liquid holding frame viewed from the optical plate side. The liquid holding frame 30 of this example is formed of a thin-width annular frame, and one end of the annular frame (shaded portion in the figure) is fixed to or integrally formed with the optical plate. The inner area of the annular frame includes an exposure area EAx for one shot indicated by a broken line in the drawing, and does not include at least a part of the next exposure area EAx + 1 adjacent to the scan direction to enable leveling measurement. Have a size.

3B is a cross-sectional view taken along line BB in FIG. 3A, and FIG. 3C is a cross-sectional view taken along line CC in FIG. 3A.
As is clear from both cross-sectional views, the liquid holding frame 30 is filled with a liquid 40, for example, pure water, or other liquid having a higher refractive index than that of pure water. The height of the liquid holding frame 30 is set so that the frame does not contact the photosensitive surface 20A of the wafer when the maximum height control of the Z table 6 is performed. The liquid is also filled in the gap between the liquid holding frame 30 and the photosensitive surface 20A, and the liquid 40 does not leak to the outside due to the surface tension even when the wafer 20 is stepped.
Further, when the temperature of the liquid increases due to exposure and the refractive index may change, or when it is necessary to keep the photosensitive surface constantly washed, it is desirable to circulate the liquid constantly or periodically. As a configuration for that purpose, although not particularly shown, it is preferable that the liquid can be circulated by a tube along the substrate facing surface 5A of the optical plate 5B, or an internal groove or piping of the optical plate 5B.

Next, procedures for immersion exposure and pre-read autofocus operation will be described.
4A to 4D are conceptual diagrams of a method for performing pre-read autofocus simultaneously with exposure. Here, as an example of the case where the pattern on one reticle is transferred to the photosensitive surface on the wafer by 6-shot exposure, in each drawing, there are six continuous exposure areas EA1, EA2, EA3, EA4 on the wafer. EA5 and EA6 are shown.

In the first step shown in FIG. 4A, leveling measurement is performed on the first exposure area EA1 as an initial stage before the start of exposure.
In the leveling measurement, as shown in FIG. 2, a plurality of spot lights (measurement lights) are applied in the longitudinal direction of a rectangular exposure area (here, EA1), for example, at equal intervals, and the position from the prescribed value of the reflected spot light. The shift is obtained from the information of the received light intensity distribution from the multi-AF position detection sensor 87 by the autofocus control unit (AF.CONT) 8A. Further, the autofocus control unit 8A determines the deviations such as the position of the wafer in the Z direction (the optical axis direction of the projection optical system 5) and the inclination of the wafer in the longitudinal direction of the exposure area EA1 based on the measurement value of the positional deviation. The Z table 6 is moved in the Z direction so as to cancel these deviations and rotated about the axis in the scanning direction, so that the relative position between the photosensitive surface of the exposure area EA1 and the image plane of the projection optical system is approximately Match.

  In the next step shown in FIG. 4B, the first exposure area EA1 that has already been subjected to relative position correction for autofocus is exposed. During this exposure period, the pre-read autofocus operation, that is, the relative position correction for leveling measurement and autofocus is performed on the next exposure area EA2 as in the case of FIG. At this time, since the liquid 40 exists only in an area centered on the exposure area EA1, leveling measurement is performed in the air.

Thereafter, similarly, the exposure and the pre-read autofocus operation are executed while sequentially sending the exposure area in the scanning direction. FIG. 4C shows a state in which leveling measurement is being performed for exposure to the fourth exposure area EA4 and prefetching for the fifth exposure area EA5.
In the final step shown in FIG. 4D, the sixth exposure area EA6 is exposed. At this time, the prefetch autofocus operation is not performed. However, if the exposure areas for six shots are adjacent, pre-read autofocus may be performed for the first exposure area at the stage shown in FIG.

In any case after FIG. 4B, as the exposure area is stepped, the liquid 40 also moves so as to cover the exposure area but enable leveling measurement in the next exposure area.
For this reason, the measurement light (spot light) in the liquid 40 does not pass, the measurement accuracy is high, and the temperature of the liquid 40 does not increase due to the spot light, so that the accuracy of the immersion exposure itself can be maintained high. Is obtained.

  Note that the X direction and the Y direction are usually not subject to leveling measurement because feedback control is performed using a laser interferometer so that the relative positions of the reticle and wafer are matched. Further, the rotation correction in the width direction of the exposure area EA1 may be obtained by applying a plurality of spot lights in that direction or by calculating the leveling measurement values in the plurality of exposure areas from the values. Good.

A semiconductor device was actually formed using immersion exposure.
After a film for forming a fine pattern was deposited on the top of the semiconductor substrate, as a pretreatment step, after cleaning and pre-baking, a photoresist was applied to the surface and post-baking was performed.
Next, the immersion exposure step is executed by the above-described method, and development, curing (rinsing) and drying are performed as post-processing steps, the base is processed by anisotropic dry etching, the resist is peeled off, and the substrate is washed. Thus, the desired fine pattern was formed.

When such a semiconductor manufacturing method is used, in the lithography process on the substrate having the unevenness of 0.1 μm, the immersion agent supply area is limited to only the slit portion (23 mm × 8 mm) of the exposure apparatus, and the leveling measurement is performed by the immersion agent. By performing autofocusing in the air in which no air is present, a highly accurate LSI pattern can be formed with a sufficiently large exposure margin.
In this LSI, the resolution R is improved by applying the liquid immersion exposure method described above, and exposure with a higher focus is possible because of the high relevance accuracy at this time. As a result, the resolution R and the depth of focus (DOF) were improved, and the process margin was improved, and the device characteristics and yield were improved.

Finally, a device using a scanner having the same performance as that of the same photomask (reticle) was manufactured by immersion exposure and dry exposure without immersion.
5 and 6 are graphs showing the relationship between the exposure margin and the depth of focus (DOF). FIG. 5 is a graph when an 80 nm wide isolated line is formed, and FIG. 6 is a graph when a 120 nm diameter contact hole is formed.

The conditions at the time of forming the isolated line in FIG.
(1) Illumination conditions: 0.75 numerical aperture NA / 0.75 sigma (1/2 annular illumination),
(2) Line size: 80 nm isolated line,
(3) CD (short dimension or minute dimension) margin: ± 8 nm,
(4) Photomask type: halftone phase shift mask (transmittance 6%),
(5) Photoresist: Tokyo Ohka TArF5068 (film thickness 225 nm),
(6) BARC: Nissan Chemical ARC28 (film thickness 37 nm),
(7) TARC: Tokyo Ohka TSP-3A (film thickness 41 nm).

The conditions at the time of forming the contact hole in FIG.
(1) Illumination conditions: 0.75 numerical aperture NA / 0.85 sigma (normal illumination),
(2) Hole size: 120 nm (pitch 220 nm),
(3) CD margin: ± 10 nm
(4) Photomask type: halftone phase shift mask (transmittance 6%),
(5) Photoresist: Tokyo Ohka P7047 (film thickness 300 nm),
(6) BARC: Nissan Chemical ARC28 (film thickness 37 nm),
(7) TARC: Tokyo Ohka TSP-3A (film thickness 41 nm).

  5 and 6 that the exposure margin is remarkably expanded by the immersion exposure.

  According to the embodiment described above, the immersion type exposure apparatus can obtain a focus accuracy comparable to that of the conventional exposure apparatus, so that a stable pattern can be formed. For this reason, the margin of the semiconductor manufacturing process is increased and the manufacturing yield is improved. Further, since the LSI circuit pattern can be formed with high accuracy, the performance of the semiconductor device is improved.

It is a figure which shows the whole structure of the immersion exposure apparatus which concerns on embodiment of this invention. It is a more detailed block diagram of a means for leveling measurement in step-and-scan exposure. (A) is the top view which looked at the example of 1 structure of the liquid holding frame in this Embodiment from the optical plate side, (B) is sectional drawing along the BB line of (A), (C) is It is sectional drawing along CC line of (A). (A)-(D) are the conceptual diagrams of the method of performing prefetch autofocus simultaneously with exposure in this Embodiment. It is a graph which shows the relationship between the exposure margin at the time of formation of an isolated line of 80 nm width, and a depth of focus (DOF). It is a graph which shows the relationship between the exposure margin at the time of formation of a 120 nm diameter contact hole, and a depth of focus (DOF). (A)-(D) are the conceptual diagrams of the method of performing the conventional prefetch autofocus simultaneously with exposure. (A) And (B) is a figure which shows typically the mode at the time of the measurement at the multipoint (three points) with respect to the next exposure area from the cross-sectional direction and the upper surface used in order to demonstrate the conventional subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Immersion exposure apparatus, 2 ... Illumination system, 3 ... Illumination field stop, 3A ... Illumination light slit, 4 ... Reticle table, 5 ... Projection optical system, 5A ... Substrate facing surface, 5B ... Optical plate, 6 ... Z table , 7 ... XY table, 8 ... Prefetch AF section, 8A ... Autofocus control section, 8B ... Leveling measurement section, 9 ... Scan section, 9A ... Scan control section, 9B, 9C ... Laser interferometer, 10 ... Reticle, 20 ... Semiconductor substrate, 20A ... photosensitive surface, 30 ... liquid holding frame, 40 ... liquid, EA ... exposure area (next exposure area)

Claims (9)

Immersion exposure in which a projection image from a mask irradiated with light is transferred to the photosensitive surface in a state where liquid is held between the projection optical system and the photosensitive surface on the substrate, and the exposure area is sequentially changed in the photosensitive surface. An immersion exposure apparatus that repeats while
The projection optical system includes a single exposure area at a position in contact with the liquid in the photosensitive surface, and at least a part of a next exposure area adjacent to the exposure area is not in contact with the liquid. An immersion exposure apparatus, comprising: a liquid holding unit that holds the liquid with respect to a part of the substrate facing surface. The immersion exposure apparatus according to claim 1, wherein the liquid holding unit includes an annular frame body having one annular frame end face fixed to the substrate facing surface and holding the liquid. An illumination light slit for passing a part of the light that illuminates the mask during immersion exposure;
The immersion exposure apparatus according to claim 1, wherein the liquid holding unit limits the liquid holding area to a part of the substrate facing surface corresponding to the shape of the opening surface of the illumination light slit. The relative positional deviation between the projection optical system and the substrate is measured at a position that is not in contact with the liquid in the next exposure area, and the relative position between the image plane and the substrate by the projection optical system is measured in the next exposure area. The immersion exposure apparatus according to claim 1, further comprising a prefetch autofocus unit that adjusts based on a result of the measurement. The pre-read autofocus unit applies a plurality of spot lights obliquely to a portion of the next exposure area that is not in contact with the liquid from a direction different from a direction in which the exposure area moves in the photosensitive surface, and the next exposure area The liquid immersion exposure apparatus according to claim 4, wherein each spot light reflected by the step is received, and an adjustment amount of a relative position between the projection optical system and the substrate is obtained from position information of the received light. Immersion exposure in which a projection image from a mask irradiated with light is transferred to the photosensitive surface in a state where liquid is held between the projection optical system and the photosensitive surface on the substrate, and the exposure area is sequentially changed in the photosensitive surface. While repeating immersion exposure method,
The substrate of the projection optical system includes one exposure area at a location in contact with the liquid on the photosensitive surface, and at least a part of the next exposure area adjacent to the exposure area is not in contact with the liquid. A liquid immersion exposure method in which the liquid immersion exposure is performed in a state where the liquid is held on a part of an opposing surface. The immersion exposure process includes:
The relative displacement between the projection optical system and the substrate is measured in one exposure area in the photosensitive surface, and the relative position between the image plane and the substrate by the projection optical system in the exposure area is a result of the measurement. An autofocus step to adjust based on
An exposure step of moving the exposure area used for the measurement directly below the liquid and performing the immersion exposure,
The immersion exposure method according to claim 6, wherein during the exposure step, the autofocus step is performed on the next exposure area by performing the measurement at a location not in contact with the liquid in the next exposure area. . When forming a semiconductor device on a semiconductor substrate, an immersion image is transferred to the photosensitive surface while a liquid is held between the projection optical system and the photosensitive surface on the semiconductor substrate. A method for manufacturing a semiconductor device in which exposure is repeated while sequentially changing exposure areas within the photosensitive surface,
A pretreatment step including application of a photoresist constituting the photosensitive surface to the uppermost surface of an element formation surface of the semiconductor substrate;
The substrate of the projection optical system includes one exposure area at a location in contact with the liquid on the photosensitive surface, and at least a part of the next exposure area adjacent to the exposure area is not in contact with the liquid. An exposure step of repeating the immersion exposure while holding the liquid with respect to a part of the opposing surface while sequentially changing the exposure area in the photosensitive surface;
A post-processing step of developing the exposed photoresist and utilizing the formed resist pattern for forming the semiconductor device. The immersion exposure is
The relative displacement between the projection optical system and the substrate is measured in one exposure area in the photosensitive surface, and the relative position between the image plane and the substrate by the projection optical system in the exposure area is a result of the measurement. An autofocus step to adjust based on
An exposure step of moving the exposure area used for the measurement directly below the liquid and performing the immersion exposure,
9. The semiconductor device manufacturing according to claim 8, wherein during the exposure step, the autofocus step is performed on the next exposure area by performing the measurement at a location not in contact with the liquid in the next exposure area. Method.

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