JP2002164276A - Focusing method, aligning method, exposing method, aligner, and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing method and an aligning method, whereby the focusing can be made in a short time. SOLUTION: A relative positional relation ΔZdi in an optical axis direction between a non-mark stop MS and a mark Mn on a substrate W is previously stored, position information of the non-mark spot MS in the optical axis direction are measured with the substrate W being moved, in a direction perpendicular to the optical axis and a required travel distance Za' of the substrate in the optical axis direction for focusing, is calculated, based on this measurement result Zm' and the stored relative positional relation ΔZdi.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing method for aligning a mark provided on a substrate with respect to a predetermined optical system in an optical axis direction, and an alignment method for aligning a substrate using the mark. ,In particular,
The present invention relates to a focusing method and an alignment method used in an exposure apparatus for manufacturing a device such as a semiconductor element.

[0002]

2. Description of the Related Art Conventionally, semiconductor devices (such as integrated circuits)
When forming a fine pattern in the manufacturing process of a device such as a liquid crystal display, a mask (photomask or reticle) pattern is formed on a substrate (wafer, glass plate, etc.) coated with a photosensitive material via a projection optical system. An exposure device for transferring is used. In the exposure equipment,
In order to transfer the mask pattern onto the substrate with high accuracy,
A mark formed on the substrate is detected via a predetermined optical system, and the substrate is positioned (aligned) at a desired position based on the detection result.

[0003] In such alignment of the substrate,
For the purpose of accurately detecting a mark, focusing (alignment AF) for positioning the mark within the depth of focus of the optical system is often performed. In this alignment AF, generally, the substrate is moved in a direction orthogonal to the optical axis direction of the optical system, and the mark is arranged in the field of view of the optical system. The position is measured, and the amount of movement of the substrate in the optical axis direction necessary for focusing is calculated based on the measurement result.

[0004]

However, in such substrate alignment, the above-described alignment AF operation is performed for each mark to be detected. Therefore, when aligning the substrate using a plurality of marks, the alignment AF operation is performed. Spend a lot of time. Therefore, one of the issues is to shorten the processing time required for the alignment AF in order to improve the throughput.

The present invention has been made in view of the above circumstances, and has as its object to provide a focusing method and an alignment method capable of performing focusing in a short time. It is another object of the present invention to provide an exposure method, an exposure apparatus, and a device manufacturing method capable of improving throughput.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 is to move a substrate in a direction orthogonal to an optical axis direction (AX) of a predetermined optical system (41), (W) The mark (Mn) formed on the optical system (41) is arranged within the field of view of the optical system (41), and the substrate is moved in the optical axis direction to move the mark (Mn) relative to the optical system (41). Mn) in a focusing method for aligning
The relative positional relationship (ΔZdi) in the optical axis direction between the non-marked portion (MS) on the substrate (W), which is different from the mark (Mn), and the mark (Mn) is stored in advance. Measuring the position information (Zm ′) of the non-mark portion (MS) in the optical axis direction while moving the substrate (W) in a direction perpendicular to the optical axis direction, and measuring the measurement result (Zm ′) Relative positional relationship (ΔZdi)
Then, the amount of movement (Za ') of the substrate in the optical axis direction required for the focusing is calculated based on In this focusing method, the position information of a non-mark portion is measured while moving the substrate in a direction orthogonal to the optical axis direction, and the measurement result is used to align the substrate in the optical axis direction necessary for focusing the mark. Since the movement amount is calculated, it is possible to reduce the time required for measuring the position information out of the processing time required for focusing. In this case, as in the invention described in claim 2, the relative positional relationship is determined by the non-mark portion (MS) on another substrate (W).
And the position information (Zm, Za) of the mark (Mn) in the optical axis direction may be calculated. In this case, for example, by using the relative positional relationship measured with respect to one substrate, it is possible to focus on a plurality of other substrates in a short time.

According to a third aspect of the present invention, a mark (Mn) formed on the substrate (W) is detected by a predetermined optical system (41), and the substrate (W) is detected based on the detection result. In the alignment method, the optical system (4) is formed by using the focusing method according to claim 1 or 2.
The mark (Mn) is aligned with respect to 1). According to a fourth aspect of the present invention, there is provided an exposure method for transferring a pattern of a mask (R) onto a substrate to be exposed (W) by an energy beam from a light source. The substrate (W) is aligned. According to a fifth aspect of the present invention, there is provided the exposure apparatus (10), wherein the illumination system (21) for illuminating the mask (R) on which the pattern is formed with an energy beam, and a pattern of the mask (R). A projection optical system (P) for transferring onto a substrate to be exposed (W)
L) and an alignment system (41) for aligning at least one of the mask (R) and the substrate to be exposed (W) using the alignment method according to claim 3. According to a sixth aspect of the present invention, there is provided a method for manufacturing a device including a lithography step, wherein the lithography step uses the exposure method according to the fourth aspect. In the present invention, positioning the mark (Mn) with respect to the optical system (41) means not only arranging the mark (Mn) within the depth of focus of the optical system (41), The optical system (4
The method also includes defocusing the mark (Mn) with respect to 1), that is, arranging the mark (Mn) outside the depth of focus.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a focusing method and an alignment method according to the present invention will be described.
FIG. 2 schematically shows a configuration of a reduction projection type exposure apparatus 10 for manufacturing a semiconductor device which is preferably used in this embodiment. The exposure apparatus 10 transfers a circuit pattern formed on the reticle R to each shot area on the wafer W while synchronously moving a reticle R as a mask and a wafer W as a substrate in a one-dimensional direction. An AND-scan type scanning exposure apparatus, that is, a so-called scanning stepper. First, the overall configuration of the exposure apparatus 10 will be described below.

The exposure apparatus 10 uses a reticle R by an energy beam (exposure illumination light) from an exposure light source (not shown).
, A projection optical system PL for projecting exposure light emitted from the reticle R onto the wafer W, and a reticle R
A reticle stage 22 for holding the wafer W, a wafer stage 23 for holding the wafer W, and a main control unit 24 for integrally controlling the entire apparatus.

The illumination system 21 includes a relay lens (not shown),
Illumination light from an exposure light source, which includes various lens systems such as a fly-eye lens (or lot integrator), a condenser lens, etc., and a blind disposed at a position conjugate with the pattern surface of the aperture stop and reticle R. Is irradiated in a predetermined illumination area on the reticle R with a uniform illuminance distribution.

The projection optical system PL includes a plurality of lenses (not shown) and the like, and converts the illumination light transmitted through the reticle R into a predetermined reduction magnification 1 / β (β is, for example, 1/4, 1
/ 5) and is exposed on a wafer W coated with a photosensitive material (photoresist or the like). Here, a direction parallel to the optical axis AX of the projection optical system PL is defined as a Z direction, and the optical axis AX
The direction of relative scanning between the reticle R and the illumination area (the direction parallel to the paper surface) in the plane perpendicular to the X direction is the X direction, the direction perpendicular thereto is the Y direction, and the axis parallel to the optical axis AX of the projection optical system PL is The rotation direction about the center is defined as the θ direction.

The reticle stage 22 is one-dimensionally scanned and moved in the X direction by a driving device (not shown).
It is configured to perform minute driving in the Y direction and the θ direction. The positions of the reticle stage 22 in the X direction, the Y direction, and the θ direction are constantly monitored by a measuring device (not shown) such as a laser interferometer, and the obtained position information is supplied to the main control unit 24.

The wafer stage 23 includes an XY stage 30 which can be driven in a two-dimensional plane (XY plane in FIG. 2),
A Z-leveling stage 31 that holds the wafer W by suction and is finely driven and tiltable on the XY stage 30 in the Z direction.
And disposed on a base (not shown). The XY stage 30 has a driving device 32 composed of, for example, a magnetic levitation type two-dimensional linear actuator or the like, and performs positioning and movement of the wafer W to a predetermined position under an instruction from the main control unit 24. Further, the Z leveling stage 31 has a drive mechanism (not shown) including, for example, three actuators for driving the wafer holder, and moves the wafer W minutely in the Z direction under a command from the main control unit 24. And at the same time, relative to the XY plane. The positions of the Z leveling stage 31 in the X direction, the Y direction, and the θ direction are constantly monitored by a measuring device 33 such as a laser interferometer, and the obtained position information is supplied to the main control unit 24.

A focus position detection system 34 (hereinafter, referred to as a main AF sensor) for measuring the position in the Z direction of the surface (exposure surface) of the wafer W is provided above the wafer stage 23. . This main AF sensor 3
4 includes a light transmission system 35 for irradiating the surface of the wafer W with spot light from an oblique direction, and a light receiving system 36 for receiving the light reflected on the surface of the wafer W through a predetermined slit. Based on the detection signal obtained from the reflected light from the surface of the wafer W, the height position (focus amount) of the surface of the wafer W in the Z direction with respect to the imaging plane of the projection optical system PL and the two-dimensional inclination amount are calculated. It is configured to be.

In the exposure apparatus 10, when the circuit pattern of the reticle R is transferred onto the wafer W, Z is calculated based on the focus amount and the tilt amount calculated by the main AF sensor 34.
The leveling stage 31 is driven to position (focus) the surface of the wafer W within the depth of focus of the projection optical system PL. Further, the XY stage 30 is driven to move the wafer W by a predetermined amount in the XY plane perpendicular to the optical axis AX of the projection optical system PL in the X direction and the Y direction by a predetermined amount. An image of the circuit pattern of the reticle R is sequentially transferred to each of the regions.

At this time, the exposure apparatus 10 performs an alignment operation for aligning the center of each shot area of the wafer W with the optical axis AX of the projection optical system PL. This alignment operation is performed based on position information of alignment marks formed on reticle R and wafer W. Further, the mark of reticle R is indicated by reticle alignment system 40.
The mark on the wafer W is detected by the wafer alignment system 41. In this embodiment, the focusing method and the alignment method according to the present invention are applied to this alignment operation.

Next, a configuration example of the reticle alignment system 40 and the wafer alignment system 41 will be described.
As the reticle alignment system 40, in the present embodiment,
A so-called TTR method (through-the-track) in which a reticle mark RM formed on a reticle R and a reference mark FM provided on a Z leveling stage 31 are simultaneously detected.
A reticle type optical system is used. Reticle R is
Based on the position information (X coordinate, Y coordinate) of the reticle mark RM measured by the reticle alignment system 40, alignment is performed so that the center of the reticle R matches the optical axis AX of the projection optical system PL (that is, the reticle stage 22). The measurement value is associated with the measurement device of the wafer stage 30 and the measurement device 33 of the wafer stage 30. Note that the distance between the reticle mark RM and the center of the reticle R is a predetermined value in design, and this value is calculated based on the reduction magnification of the projection optical system PL, thereby obtaining the image plane side of the projection optical system PL. The distance between the projection point of the reticle mark RM on the (wafer side) and the center of the projection optical system PL can be calculated. This distance is used as a correction value when each shot area on the wafer W is arranged within the field of view of the projection optical system PL. The reference mark FM is formed, for example, in the same shape as the alignment mark (wafer mark) formed on the wafer W, and has the same height as that of the wafer W surface.
It is formed on a reference mark plate provided on the leveling stage 31.

On the other hand, as the wafer alignment system 41, in this embodiment, an off-axis type optical system that detects a wafer mark for alignment at a position distant from the optical axis of the projection optical system PL is used. The wafer alignment system 41 illuminates the wafer W illuminated with light having a wide wavelength bandwidth.
The FIA (Field Imag) performs position measurement by taking an image of the mark of
e Alignment) type alignment system.

FIG. 3 shows a configuration example of the wafer alignment system 41. In the wafer alignment system 41 of FIG.
Broadband illumination light insensitive to the photoresist on the wafer W is emitted from the optical fiber 51, and the illumination light is transmitted through a condenser lens 52 to a field stop plate 53.
Is illuminated with uniform illumination. The illumination light restricted by the field stop plate 53 is reflected by the dichroic mirror 54, passes through the lens system 55, and enters the beam splitter 56.
The illumination light reflected by the beam splitter 56 illuminates a predetermined area on the wafer W via the objective lens 57 and the prism mirror 58. In the wafer alignment system 41, the field stop plate 53 has a conjugate relationship (image formation relationship) with the wafer W with respect to the lens system 55 and the objective lens 57. The illumination area for the wafer W is uniquely determined by the shape and size of the opening formed in the field stop plate 53.

The light reflected on the surface of the wafer W passes through a prism mirror 58 and an objective lens 57, and is split by the beam splitter 5
Return to 6. Further, the light transmitted through the beam splitter 56 enters the dichroic mirror 61 via the lens system 60. The light from the dichroic mirror 61 forms an image of the wafer mark on the index plate 63 via the mirror 62. The light from this image and the index mark on the index plate 63 is
The relay lens 64, mirror 65, relay lens 66, and beam splitter 67
A two-dimensional image sensor 68X for the X-axis, such as a two-dimensional CCD,
Then, images of the wafer mark and the index mark are formed on the imaging surface of the two-dimensional imaging element 68Y for the Y axis.

Here, in a focused state where the surface of the wafer W matches the image plane of the objective lens 57, the index plate 63
The composite system of the objective lens 57 and the lens system 60 is disposed conjugate with the surface of the wafer W, and the index plate 63 and the imaging surfaces of the imaging devices 68X and 68Y are connected to the relay lens 64,
66 are conjugated to each other. The indicator plate 63 is
An index mark is formed by a chrome layer or the like on a transparent plate, and a portion where an image of a wafer mark is formed remains a transparent portion. The index mark includes an X-axis index mark serving as a position reference in a direction conjugate to the X direction on the wafer W, and a Y-axis index mark serving as a position reference in a direction conjugate to the Y direction. By imaging the wafer mark and the image of the index mark by the imaging devices 68X and 68Y and performing image processing on the imaging signals of the imaging devices 68X and 68Y, it becomes possible to obtain the X coordinate and the Y coordinate of the wafer mark. . In practice, an illumination system (not shown) for independently illuminating the index plate 63 may be provided.

In FIG. 2, the optical axis AXa on the projection image plane side (wafer side) of the wafer alignment system 41 is:
It is arranged parallel to the optical axis AX of the projection optical system PL. Therefore, the reference mark FM on the wafer stage 23 is arranged in the field of view (illumination area) of the wafer alignment system 41, the position information (X coordinate, Y coordinate) is measured, and the reference mark FM is transferred to the reticle alignment system 40. Of the wafer alignment system 41 and the optical axis AX of the projection optical system PL
, The so-called baseline amount can be calculated. This baseline amount is a reference amount when each shot area on the wafer W is arranged within the field of view of the projection optical system PL. That is, the X- and Y-coordinates of the alignment wafer mark are measured by the wafer alignment system 41, and the wafer stage 23 is driven based on a value obtained by adding the baseline amount to the measurement result, and the wafer W is moved. By performing the stepping movement in the X direction and the Y direction, the center of each shot area of the wafer W can be aligned with the optical axis AX of the projection optical system PL.

The wafer alignment system 41 has a height (Z direction) of the surface of the wafer W in order to position the surface (exposure surface) of the wafer W within the depth of focus of the wafer alignment system 41 (alignment AF). A focus position detection system 70 (hereinafter, referred to as an alignment AF sensor) for measuring a position is provided. Specifically, in the wafer alignment system 41 shown in FIG. 3, apart from the illumination light for detecting the above-described wafer mark, the alignment A
Light source 71 such as LED or laser diode for F
Is provided. The detection light emitted from the light source 71 illuminates the slit plate 73 via the condenser lens 72. A focus detection pattern having a predetermined shape is formed on the slit plate 73. The detection light that has passed through the focus detection pattern of the slit plate 73 passes through the dichroic mirror 54 and then passes through the lens system 55 to the beam splitter 5.
Go to 6. Here, as the detection light for alignment AF, light in a wavelength band (for example, red light to near infrared light) that is insensitive to the photoresist on the wafer W is used.
In addition, the wavelength selectivity of the dichroic mirror 54 is such that the light in the wavelength band used for detecting the position of the wafer mark in the illumination light from the optical fiber 51 is reflected and is used for alignment AF in the detection light from the light source 71. The characteristic is set so as to transmit light in a wavelength band to be used. That is, the light for position detection and the light for focus detection applied to the wafer W have different wavelength bands, and do not adversely affect each other. The light for focus detection reflected by the beam splitter 56 is supplied to an objective lens 57 and a prism mirror 58.
Is irradiated onto the wafer W through The slit plate 73
Is the wafer W with respect to the lens system 55 and the objective lens 57.
An image (or a defocused image) of the focus detection pattern of the slit plate 73 is projected on the surface of the wafer W substantially conjugate with the surface.

The light reflected on the surface (exposure surface) of the wafer W returns to the beam splitter 56 through the prism mirror 58 and the objective lens 57, and the light transmitted through the beam splitter 56 passes through the lens system 60 to the dichroic mirror 61. Heading. Here, the wavelength selectivity of the dichroic mirror 61 is different from that of the dichroic mirror 54 in that the light for position detection emitted from the optical fiber 51 is transmitted through the light source 7.
1 has a characteristic of reflecting the light for focus detection emitted from 1. The light for focus detection reflected by the dichroic mirror 61 passes through a light-shielding plate 74 for restricting the pupil provided on the image side to degrade the telecentricity on the image side, and is transferred onto a line sensor 75 composed of a one-dimensional CCD or the like. The image (or defocused image) of the focus detection pattern projected above is re-imaged. The surface (exposure surface) of the wafer W and the light receiving surface of the line sensor 75 correspond to the objective lens 57 and the lens system 6.
0 is almost conjugate.

FIG. 4 shows an essential part of the alignment AF sensor 70 of the wafer alignment system 41. In FIG. 4, a plurality of focus detection patterns (here, focus detection patterns 80A
And 80B are shown). In addition, the pupil-limiting light-shielding plate 74 shields a lower half region in the U direction from the optical axis AXa. Lens system 55 for focus detection patterns 80A and 80B, and objective lens 57
81A, 81B are projected onto the wafer W, and the objective lens 57, the lens system 60, the dichroic mirror 6
1 and images 82A and 8 re-imaged via the light shielding plate 74
2B is projected on the line sensor 75. The images 81A and 81B of the focus detection pattern projected on the wafer W are arranged substantially on a straight line, and the images 82A and 82B re-imaged on the line sensor 75 are arranged in a predetermined direction (U direction). Along with each other. At this time, although the wafer W side from the objective lens 57 is telecentric, the line sensor 75 side from the lens system 60 is non-telecentric due to the action of the light shielding plate 74. Therefore, when the wafer W is displaced in the Z direction parallel to the optical axis AXa, the image 81 of the focus detection pattern is formed on the wafer W.
The positions of the images 82A and 82B of the focus detection pattern on the line sensor 75 are shifted in the U direction while the positions of A and 81B are kept as they are (the image is defocused).
Therefore, based on the positions of the images 82A and 82B when the surface of the wafer W matches the image forming plane of the objective lens 57 (in a focused state), the deviation amount of the images 82A and 82B from the reference position is determined by the line sensor 75. Thus, the height position (focus amount) of the surface of the wafer W in the Z direction with respect to the image forming plane of the objective lens 57 (wafer alignment system 41) can be measured.

FIG. 5 shows shot areas ES1 to ESn (generally shot areas ESi) to which the pattern of reticle R is to be transferred, arranged along the coordinate system (X, Y) of wafer W.
). In FIG. 5, on a scribe line adjacent to each shot area ESi, a wafer mark Mn having an X-direction alignment wafer mark and a Y-direction alignment wafer mark is formed. The wafer mark for alignment in the X direction is composed of, for example, a plurality of patterns arranged at a predetermined pitch in the X direction, and the wafer mark My for alignment in the Y direction is, for example, a plurality of patterns arranged at a predetermined pitch in the Y direction. Consists of In the present embodiment, for example,
No. 29, an EGA (Enhanced Global Alignment) method is used to align a reticle pattern with each shot area ESi on the wafer W.

That is, in the above-described EGA type alignment, the main control unit 24 (see FIG. 2) determines at least three shot areas (here, nine alignment shots) selected as alignment shot areas among all shot areas ESi. Areas SA1 to SA9)
The wafer mark Mn in the wafer alignment system 41
(See FIG. 2), and each of the shot areas SA1 to SA1 is detected.
The coordinate position of SA9 is obtained. Next, the obtained coordinate position and a known coordinate position (design value, etc.) are substituted for the model function representing the shot arrangement on the wafer W for each alignment shot, and the parameters of the model function are changed by, for example, statistical calculation. decide. Then, by substituting the known coordinate position for each shot area ESi on the wafer W into the model function, the coordinate positions (X coordinate, Y coordinate) of all the shot areas are calculated. By driving the wafer stage 23 (see FIG. 2) in the X and Y directions based on the calculated coordinate position and the above-described baseline amount of the wafer alignment system 41, the center of each shot area ESi of the wafer W is Can be accurately aligned with the optical axis AX of the projection optical system PL.

FIG. 6 shows an example of a locus that the illumination area of the wafer alignment system 41 virtually draws on the wafer W in the above-described EGA type alignment. As shown in FIG. 6, as the wafer stage moves in the XY plane, the illumination area of the wafer alignment system 41 (the observation field area of the objective lens 57 shown in FIG. 3)
Alignment shot area SA1 → SA2 → SA3 ... →
It moves relatively on the wafer W in the order of SA9. That is, the wafer alignment system 41 first relatively moves on the trajectory LC1 to the alignment shot area SA1, where the wafer mark Mn (see FIG. 5) is detected. Subsequently, the wafer is relatively moved on the trajectory LC2 from the alignment shot area SA1 to SA2, and the wafer mark Mn is detected there. Thereafter, similarly, the wafer alignment system 41
, The relative movement on each of the trajectories LC3, LC4... LC9 and the detection of the wafer mark are sequentially repeated.

The focusing method (alignment AF) of this embodiment measures position information of a portion (non-mark portion) different from the wafer mark Mn to be detected in this EGA type alignment, and the measurement result is obtained. Is used to align the wafer mark Mn formed on the wafer W within the depth of focus of the wafer alignment system 41. Here, the “non-mark portion” in the present embodiment
Are the alignment shot areas SA1 to SA described above.
A predetermined section MS (hereinafter, referred to as a measurement section MS) set on the trajectories LC1 to LC9 toward 9 and a coordinate position (a start position, a section length, and the like) representing the measurement section MS.
Are stored in the main control unit 24 together with information on the trajectories LC1 to LC9. In addition, this measurement section MS
Are the target alignment shot areas SA1 to SA
9 is preferably set as close as possible. Furthermore, the main control unit 24 may determine the measurement section MS for each mark using the signal strength of the alignment AF sensor 70 on the trajectories LC1 to LC9. The measurement section MS determined here may be determined for each alignment shot area (or its mark) on the same wafer, or 1 to be measured first on the same wafer.
The value determined in the second alignment shot area may be used in the second and subsequent alignment shot areas. In particular, in the latter, not only the first alignment shot area, but also the average value of the measurement sections MS determined in the m-th alignment shot area may be used in the (m + 1) -th and subsequent alignment shot areas. At this time, in the (m + 1) th and subsequent alignment shot areas, it is not necessary to use all the measurement sections MS determined in the 1st to mth alignment shot areas.
The measurement section MS determined in at least one of the m-th alignment shot areas may be used as it is, or an average value thereof may be used. Note that m is 1 or more, and the total number of alignment shot areas on the wafer (9 in this example).
) Is a natural number smaller by one. When each of a plurality of wafers in the same lot is exposed, the measurement section MS may be determined for each wafer, or the measurement section MS determined for the first (first) wafer in the lot may be determined by two. It may be used for the second and subsequent wafers. Especially in the latter, 1
The average value obtained by averaging the measurement sections MS determined not only for the first wafer but also for the t-th wafer, for example, in units of the alignment shot area may be used for the (t + 1) -th and subsequent wafers. At this time, for the (t + 1) th and subsequent wafers, all of the measurement sections MS determined for the first to tth wafers need not be used, and the measurement interval MS is determined for at least one of the first to tth wafers. The measured section MS may be used as it is, or an average value thereof may be used. Note that t is 1 or more, and the number of wafers in a lot is also 1
It is only a small natural number. Further, the method may be combined with the above-described method of determining a measurement section in the same wafer.

FIG. 1 is a flowchart showing a typical sequence of the alignment AF according to the present embodiment, and the following description will be made with reference to this flowchart. This sequence is mainly controlled by the main control unit 24.

First, the main control unit 24 stores the relative positional relationship between the non-mark portion (measurement section MS) and the wafer mark Mn in the Z direction (step 100).
In the present embodiment, the relative positional relationship of the leading wafer in a predetermined lot consisting of a plurality of wafers having the same processing process is measured and stored. That is, in the above-described EGA alignment with respect to the wafer at the beginning of the lot, the main control unit 24 uses the alignment AF sensor 70 to control the alignment shot areas SA1 to SA1.
On the trajectories LC1 to LC9 toward SA9, the measurement section MS
The height position (focus amount) Zm in the Z direction is measured and the alignment shot areas SA1 to SA
In A9, the height position (focus amount) Za of the wafer mark Mn is measured. Then, for each alignment shot, the height difference ΔZdi (Zdi = Zm−
Za, i = 1 to 9) are calculated, and they are stored as the relative positional relationship. Note that the height position Zm in the measurement section MS may be an average value of the height positions (focus amounts) of the entire measurement section MS, or may be a height position at a predetermined coordinate position. The alignment AF for the wafer at the head of the lot is performed based on the height position Za of the wafer mark measured here.

Next, the main control unit 24 measures the position information of the measurement section MS on another wafer W of the same lot (step 101). This measurement is based on E
In the GA system alignment, the trajectories LC1 to L
This is performed in parallel with the relative movement of the wafer alignment system 41 on C9. That is, the main control unit 24
Is the height position (focus amount) Zm of the measurement section MS on the trajectories LC1 to LC9 in the Z direction by the alignment AF sensor 70 while moving the wafer W in the XY directions by the wafer stage 23 (XY stage 30). 'Measure.

Subsequently, the main control unit 24 determines the wafer mark Mn of the wafer alignment system 41 based on the measurement result (height position Zm ') of step 101 and the stored relative positional relationship ΔZdi. Positioning is performed within the depth of focus (steps 102 and 103). At this time, the main control unit 24 first determines the measured height position Zm ′ of the measurement section MS and the relative positional relationship ΔZ stored in advance.
di, the amount of movement of the wafer W in the Z direction required for focusing, that is, the amount of focus Za ′ (Za ′ = Zm ′ + Δ) with respect to the imaging plane of the wafer alignment system 41.
Zdi) is calculated. And the main control unit 24
The wafer W is moved in the Z direction by the focus amount Za 'by the wafer stage 23 (Z leveling stage 31). At this time, as in the present embodiment, within the same lot of the processing process, the surface characteristics of each wafer W such as the step and the reflectance are almost the same between the wafers. Therefore, Z between one predetermined location and another predetermined location in wafer W
It is considered that the relative positional relationship in the direction (difference in height position in Z direction, step) is substantially the same between wafers W in the same lot. Therefore, the relative positional relationship (step information) in the Z direction between a plurality of predetermined portions of the first wafer (the first wafer in this embodiment) serving as a reference is stored, and the second wafer in the same lot is stored. By measuring the height position in the Z direction of one of the predetermined plurality of positions on the wafer and correcting the measurement result based on the relative positional relationship, the Z position of the other position of the second wafer is measured. The height position in the direction can be calculated.

That is, in the present embodiment, the relative positional relationship between the measurement section MS and the wafer mark Mn in the Z direction is stored in advance, so that the coordinate position is different from that of the wafer mark Mn during the alignment operation. Just by measuring the position information (height position in the Z direction) of a certain non-mark portion (measurement section MS), using the measurement result, align the wafer mark Mn within the depth of focus of the wafer alignment system 41. Can be. Moreover, the height position Zm 'of the measurement section MS provided near the shot areas SA1 to SA9 is measured for each alignment shot, and the above-described correction is performed on the measurement result. Even if they occur slightly, their errors are not integrated. And the measurement of the position information is
As described above, this is performed while the wafer W is being moved in the XY directions. Therefore, of the processing time required for the alignment AF operation, the time required for measuring the position information is saved, and focusing (alignment AF) is performed in a short time.
It can be performed. Further, the wafer W in the XY directions
By calculating the amount of movement (focus amount) of the wafer W in the Z direction during the movement of the wafer W and performing the movement of the wafer W in the Z direction in parallel, the processing time of the alignment AF can be further reduced. it can. Thus, according to the present embodiment,
By performing each alignment AF operation on a plurality of wafer marks in a short time, the processing time required for the alignment operation can be significantly reduced.

In the above embodiment, when measuring the relative positional relationship in the Z direction (step 100), the Z direction of the measurement section MS on all the trajectories LC1 to LC9 toward each of the alignment shot areas SA1 to SA9. The height position of is measured. This is because in the above embodiment, as shown in FIG.
The directions of the trajectories LC1 to LC9 toward 9 are not uniform,
This is because the relative positional relationship in the Z direction described above differs for each alignment shot. Therefore, as shown in FIG. 7, each of the alignment shot areas SA1 to SA
9, the directions of the trajectories LC1 to LC9, that is, the wafer (wafer stage) for each alignment shot
By partially aligning the movements in the X and Y directions, the relative positional relationship for each alignment shot can be made substantially the same. In this case, by measuring the height position in the Z direction of the measurement section MS on the trajectory (for example, the trajectory LC1) for at least one alignment shot area, the measurement operation on the trajectory toward another alignment shot area is omitted, Processing time can be reduced.

Also, even when the directions of the trajectories LC1 to LC9 are not uniform, the trajectories LC1 to LC9 are set so that at least a part thereof is along a scribe line (see FIG. 5) adjacent to the shot area ESi, for example. By setting the above-described measurement section MS on the scribe line, the relative positional relationship for each alignment shot is made substantially the same, and the processing time can be reduced.

Further, as shown in FIG.
1 to LC9 are partially aligned with the alignment shot areas SA1 to SA9.
When the alignment is performed for each SA9, the relative positional relationship is measured with respect to a plurality of alignment shot areas, and the average value is calculated for the subsequent movement amount in the Z direction (step 10).
You may make it use for 2). Further, the relative positional relationship used for calculating the movement amount may be obtained by measuring the relative positional relationship for each alignment shot and using a statistical method (such as a standard deviation). .

When detecting a plurality of wafer marks for one alignment shot, moving a wafer (wafer stage) in the XY directions for each of the plurality of wafer marks within one alignment shot area. There is. In such a case, the height position in the Z direction may be further measured on each trajectory toward each wafer mark, and the above-described relative positional relationship in the Z direction may be obtained for each wafer mark. However, in this case, the movement of the wafer (wafer stage) in the XY directions with respect to the second and subsequent wafer marks is often the same for each alignment shot. Therefore, when measuring the relative positional relationship in the Z direction (step 100), the height position in the Z direction is measured on a trajectory toward each wafer mark in at least one alignment shot area, thereby obtaining another position. The above measurement for the second and subsequent wafer marks in the alignment shot area can be omitted.

In measuring the relative positional relationship in the Z direction, not only the first wafer in the lot but also a plurality of wafers (for example, a predetermined number of wafers from the first wafer) are used, as in the above embodiment. The relative positional relationship may be measured with respect to a plurality of wafers or a plurality of wafers selected at predetermined intervals, and the result of, for example, averaging the measured values may be used.

Further, in the above embodiment, an example is described in which the present invention is applied to a wafer alignment system of the FIA system for detecting a wafer mark. However, the alignment system used for mark detection is not limited to this. LSA method and LI for detecting diffracted light generated from marks
Any method such as the A method may be used. Also, FI
In the A-type alignment system, the zero-order light out of the light generated from the wafer mark may be cut and detected by the image sensor, or the phase may be changed by a part of the light generated from the wafer mark.

The method of determining the height position in the Z direction of the surface of the wafer W with respect to the image plane of the wafer alignment system 41 (objective lens 57), that is, the method of measuring the amount of focus on the wafer surface (or wafer mark) is as follows.
Not limited to the above embodiment, various ones can be applied. For example, an oblique incidence method such as the main AF sensor 34 shown in FIG. 2 may be used, a charge accumulation method that accumulates charges detected in a predetermined section and measures a focus amount based on the amount, or a wafer mark. The maximum contrast may be found by shaking the focus.
When the charge storage method is used, it is preferable to use an automatic gain controller (AGC) so that a sufficient dynamic range can be obtained by adjusting the gain at the time of photoelectric conversion.

Further, when measuring the relative positional relationship in the Z direction (step 100), an apparatus different from the wafer alignment system 41 (for example, the main AF shown in FIG. 2)
Sensor 34) may be used. In this case, the offset amount generated between the devices may be measured and stored in advance.

In the above embodiment, the relative positional relationship is measured and stored with respect to a reference wafer (a wafer at the head of the lot, etc.). Can be omitted. That is, the surface characteristics of the wafer conveyed to the exposure apparatus are controlled to a desired state by the processing process up to that time. Therefore, if the relative positional relationship is stored in the main control unit in association with each processing condition,
By selectively using the relative positional relationship according to the processing process of the target wafer, the measurement operation of the relative positional relationship can be omitted. As a method of storing the relative positional relationship, for example, the relative positional relationship in the Z direction measured in one lot is stored in the main control unit together with information on a processing process performed on the wafer lot. . As a result, when a new wafer lot that has undergone the same processing process flows,
The alignment AF operation can be performed quickly. At this time, the stored relative positional relationship may be measured in a predetermined wafer lot, or may be obtained by averaging with a value stored in a past lot of the same processing process.

Further, when performing the alignment AF without performing the relative positional relationship measurement operation, the surface condition of the wafer is detected at a predetermined timing, and the relative positional relationship is corrected based on the detection result. Alternatively, the relative positional relationship may be corrected in accordance with the processing conditions of the wafer. FIG. 8 is a flowchart showing a sequence of the alignment AF operation. That is, the main control unit 24 has the relative positional relationship Δ
Along with Zdi (step information on the wafer surface), information on the trajectory drawn by the wafer alignment system 41 on the wafer W during alignment and information on the surface characteristics of the wafer such as the type of photoresist are stored (step 2).
00). When starting the alignment operation, the main control unit 24 uses a predetermined detection system (the wafer alignment system 41, the main AF sensor, etc.) to output information such as the reflectance of the wafer surface, the undulation and inclination of the entire wafer surface, and errors in the wafer stage. 34, another detection system, etc.), and based on the detection result, the stored relative positional relationship is corrected and a new relative positional relationship ΔZdi ′ is obtained.
(Step information) is calculated. Alternatively, the relative positional relationship stored in accordance with the processing conditions of the target wafer W (for example, the type of photoresist used) is corrected to calculate a new relative positional relationship ΔZdi ′. (Step 201). Then, using the corrected relative positional relationship ΔZdi ′, similarly to the above-described sequence (see FIG. 1), detection of the position information Zm ′ of the non-mark portion (step 202), the wafer in the Z direction W
Is calculated (step 203), and the wafer W is moved in the Z direction (step 204). As described above, by correcting the stored relative positional relationship at a predetermined timing, the alignment A can be accurately performed even when the measurement operation of the relative positional relationship is omitted.
F can be implemented. In addition, even when the alignment AF is performed by measuring the relative positional relationship, the accuracy of the processing can be improved by performing the correction processing at a predetermined timing.

The operation procedure shown in the above-described embodiment or various shapes and combinations of the constituent members are merely examples, and various changes may be made based on process conditions and design requirements without departing from the gist of the present invention. It is possible. The present invention includes, for example, the following modifications.

The focusing method and alignment method according to the present invention can be applied not only to the method for detecting a wafer mark, but also to the method for detecting a mark formed on a reticle or a mark formed on a stage.

The focusing method according to the present invention can be applied not only to the alignment operation but also to the focusing of the wafer surface with respect to the projection optical system PL by the main AF sensor 34. For example, the present invention is also applied to a case where exposure is performed with the optical axis of the projection optical system PL shifted from the center of the reticle R, or a case where leveling is measured.

Further, the number, arrangement position, and shape of the marks formed on the substrate (eg, wafer or reticle) may be arbitrarily determined. In particular, at least one wafer mark may be provided in each shot area, or a wafer mark may be formed at a plurality of points on a wafer without providing a wafer mark for each shot area. Further, the mark on the substrate may be either a one-dimensional mark or a two-dimensional mark. In the above-described embodiment, the focusing has been described in which the mark Mn on the wafer W is arranged within the depth of focus with respect to the optical system (such as the wafer alignment system 41). ,
In the wafer alignment system 41, the mark Mn is defocused, that is, the mark Mn is detected in a state where the mark Mn is arranged within the depth of focus, and the contrast of the mark image may be improved. It is possible to apply That is, focusing in the present invention is a broad concept of arranging the mark Mn at a predetermined target position in the optical axis direction of the optical system regardless of the inside and outside of the focal depth of the optical system. Here, the target position is a value stored in the main control unit 24 as a device constant.

An exposure apparatus to which the present invention is applied is a scanning exposure method (for example, a method in which a mask (reticle) and a substrate (wafer) are relatively moved with respect to exposure illumination light.
The method is not limited to the step-and-scan method, but may be a static exposure method in which the mask pattern is transferred onto the substrate while the mask and the substrate are almost still, for example, a step-and-repeat method. Furthermore, the present invention can be applied to a step-and-stitch type exposure apparatus that transfers a pattern to each of a plurality of shot areas whose peripheral portions overlap on a substrate. Further, the projection optical system PL may be any of a reduction system, an equal magnification system, and an enlargement system, and may be any of a refraction system, a catadioptric system, and a reflection system. Further, the present invention can be applied to, for example, a proximity type exposure apparatus that does not use a projection optical system.

In the exposure apparatus to which the present invention is applied, g-rays, i-rays, KrF excimer laser light, ArF excimer laser light, F ₂ laser light, and Ar light are used as illumination light for exposure.
₂ Not only ultraviolet light such as laser light, but also EUV light,
X-rays or charged particle beams such as electron beams and ion beams may be used. Further, the light source for exposure is not limited to a mercury lamp or an excimer laser, but may be a harmonic generator such as a YAG laser or a semiconductor laser, an SOR, a laser plasma light source, an electron gun, or the like.

The exposure apparatus to which the present invention is applied is not limited to semiconductor device manufacturing, but includes a liquid crystal display device, a display device, a thin-film magnetic head, an imaging device (such as a CCD), a micromachine, and a DNA chip. For manufacturing microdevices (electronic devices), and for manufacturing photomasks and reticles used in exposure apparatuses.

The present invention can be applied not only to an exposure apparatus, but also to other manufacturing apparatuses (including an inspection apparatus) used in a device manufacturing process.

When a linear motor is used for the wafer stage or reticle stage, either an air levitation type using an air bearing or a magnetic levitation type using Lorentz force or reactance force may be used. Also, the stage may be a type that moves along a guide,
A guideless type without a guide may be used. further,
When a planar motor is used as the stage driving device, one of the magnet unit (permanent magnet) and the armature unit is connected to the stage, and the other of the magnet unit and the armature unit is connected to the stage moving surface side (base). May be provided.

Further, the reaction force generated by the movement of the wafer stage is mechanically moved to the floor (ground) by using a frame member, as described in JP-A-8-166475.
You may escape to The present invention is also applicable to an exposure apparatus having such a structure.

Further, the reaction force generated by the movement of the reticle stage may be mechanically released to the floor (ground) using a frame member as described in JP-A-8-330224. The present invention is also applicable to an exposure apparatus having such a structure.

Further, the exposure apparatus to which the present invention is applied controls various subsystems including the respective components described in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. And manufactured by assembling. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electric systems to ensure these various accuracy Are adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus from various subsystems includes mechanical connections, wiring connections of electric circuits, and piping connections of pneumatic circuits among the various subsystems. It goes without saying that there is an assembling process for each subsystem before the assembling process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, comprehensive adjustment is performed, and various precisions of the entire exposure apparatus are secured. It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

For a semiconductor device, a step of designing the function and performance of the device, a step of manufacturing a mask (reticle) based on the design step, a step of manufacturing a wafer from a silicon material, and the exposure apparatus of the above-described embodiment The wafer is manufactured through a wafer processing step of exposing a reticle pattern to a wafer, a device assembling step (including a dicing step, a bonding step, and a packaging step), an inspection step, and the like.

[0058]

As described above, according to the focusing method and the alignment method according to any one of the first to third aspects, the use of the position information of the non-marked part in the calculation of the amount of movement of the substrate enables the short-circuiting. Focusing can be performed in time. Further, the exposure method according to any one of claims 4 to 6,
According to the exposure apparatus and the device manufacturing method, it is possible to improve the throughput by performing the alignment in a short time.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a sequence of an embodiment of a focusing method according to the present invention.

FIG. 2 is a configuration diagram schematically showing an embodiment of an exposure apparatus according to the present invention.

FIG. 3 is a perspective view schematically showing a configuration of a wafer alignment system 41.

FIG. 4 is a diagram schematically showing a configuration of a main part of an alignment AF sensor 70;

FIG. 5 is a diagram showing an example of an arrangement of shot areas.

FIG. 6 is a diagram illustrating an example of a locus that an illumination area of a wafer alignment system 41 virtually draws on a wafer W;

FIG. 7 is a diagram showing another example of a locus that an illumination area of a wafer alignment system 41 virtually draws on a wafer W.

FIG. 8 is a flowchart showing another sequence of the focusing method according to the present invention.

[Explanation of symbols]

Mn Wafer mark (mark) RM Reticle mark (mark) R Reticle (mask) W Wafer (substrate) PL Projection optical system ES1 to ESn Shot area SA1 to SA9 Alignment shot area LC1 to LC9 Trace drawn by illumination area of wafer alignment system MS Measurement section (non-mark location) 10 Exposure device 21 Illumination system 23 Wafer stage 24 Main control unit 34 Main AF sensor 40 Reticle alignment system (alignment system) 41 Wafer alignment system (alignment system) 70 Alignment AF sensor

Claims (6)

[Claims] 1. A substrate is moved in a direction orthogonal to an optical axis direction of a predetermined optical system to dispose a mark formed on the substrate within a visual field of the optical system, and to move the substrate in the optical axis direction. In a focusing method of moving and aligning the mark with respect to the optical system, a relative positional relationship between a non-mark part on a substrate, which is a part different from the mark, and the mark in the optical axis direction. Is stored in advance, and while the substrate is moved in a direction perpendicular to the optical axis direction, the position information of the non-mark portion in the optical axis direction is measured, and based on the measurement result and the relative positional relationship. hand,
A focusing method comprising calculating an amount of movement of the substrate in the optical axis direction required for the focusing. 2. The method according to claim 1, wherein the relative positional relationship is calculated by measuring positional information of the non-mark portion and the mark on another substrate in the optical axis direction. Focusing method as described. 3. A method for detecting a mark formed on a substrate with a predetermined optical system and aligning the substrate based on the detection result, wherein the focusing method according to claim 1 or 2 is used. And positioning the mark with respect to the optical system. 4. An exposure method for transferring a pattern of a mask onto a substrate to be exposed using an energy beam from a light source, wherein the substrate is aligned using the alignment method according to claim 3. . 5. An alignment system for illuminating a mask on which a pattern is formed with an energy beam, a projection optical system for transferring a pattern of the mask onto a substrate to be exposed, and the alignment method according to claim 3. An exposure apparatus comprising: a mask and an alignment system for aligning at least one of the substrate to be exposed. 6. A device manufacturing method including a lithography step, wherein the lithography step uses the exposure method according to claim 4. Description: