JPS5974625A - Projection type exposure device - Google Patents

Abstract

PURPOSE:To position a mask and a wafer relatively and extremely accurately by directly detecting the projected image of a mark formed on the mask by an optoelectric element set up to a stage. CONSTITUTION:Light beams emitted from an illumination system 4 for exposure uniformly illuminate the whole surface of a mask 5, and an image to be transferred to a circuit pattern formed to the lower surface of the mask 5 is imaged on the wafer 7 through a projecting lens 6. On the other hand, laser luminous flux from a light source 11 is beam-expanded 12, deflected in a surface parallel with a paper surface by a vibrating mirror 13, focused by a focusing lens 15 through a beam splitter 14, reflected to the lower side of a dichroic mirror 10 through a reflecting mirror 17, and imaged on the surface of the wafer through the projecting lens 6. The image on the wafer is detected by the optoelectric element 28. Optical path lengths up to the entrance pupil of the lens 6 are each made differ from the mask 5 and the lens 15, and the mask 5 and a laser light spot are imaged on the same plane.

Description

[Detailed description of the invention]

The present invention relates to an exposure apparatus for optically transferring a pattern of a proven circuit (IC), etc., and a projection apparatus that allows accurate alignment of a mask or reticle and a wafer as an object to be exposed on a TP. It relates to a mold exposure device. In recent years, the pattern miniaturization of large-scale integrated circuits (LSI) has progressed rapidly.
Reduction projection type exposure equipment is becoming popular as a device for printing circuit patterns that can also increase productivity.
This device uses a mask (reticle) on which a circuit pattern that is several times (for example, 10 times) larger than the circuit pattern to be transferred onto a silicon wafer is used. is scaled down and projected onto the wafer. Therefore, the area that can be exposed in one day is a square area on the wafer with a size of approximately 10×ID+nm. Therefore, in order to print a circuit pattern on the entire surface of a wafer with a diameter of about 125 mm, the so-called step-and-repeat method is used, in which the stage on which the wafer is placed is moved two-dimensionally by a fixed distance and exposure is repeated. It has been adopted. For this reason, this type of exposure equipment is sometimes called a stepper.Furthermore, in LSI manufacturing, several layers or more of patterns are printed overlappingly, but at this time, the overlay error between layers must be kept below a certain value. For example, for a pattern with a minimum line width of 1 μm, there is an overlay error of about 0.2 μm at most! F Not served. In order to achieve such high-precision alignment, there are conventionally two methods: the on-axis (Jn Axis) method and the off-axis (0ffAxis) method. Of these, the on-axis method Through-the-lens (TTL) is used to simultaneously observe the mask (reticle) and wafer alignment marks through a projection lens.
) method, and has the characteristic that alignment accuracy is generally improved compared to the off-axis method that does not involve a photographic lens. Incidentally, 1. Projection lenses required to provide resolution down to submicrons are designed to have the smallest chromatic aberration with respect to the wavelength of light used for printing. For this reason, if a source with a wavelength different from the light used for printing (printing is light) is used to detect the alignment mark, the imaging position will be significantly shifted due to strong chromatic aberration. - As an example, let us consider a case where the original wavelength for printing is set to 466 and the wavelength of light for alignment mark detection is set to 633. In order to combine the f-elements of the two lights on the same plane on the wafer side, the mask or reticle (object plane) must be moved in the optical axis direction by about 200 times the depth of focus of the projection lens. Therefore, in order to simultaneously observe the mask (reticle) and the wafer using the TTL force method, it is best to observe the printing using light or light with a wavelength close to it. However, in this type of observation, the unevenness of the circuit pattern formed on the wafer in the previous stage exceeds the depth of focus of the projected image, and the printing toward the wafer is caused by light and reflected light from the wafer surface. Due to the interference effect, there was a drawback that the condition deteriorated. Therefore, a thick first layer was provided on the surface of the wafer to make the surface smooth, and then the printing was done using a pigment that absorbs light. A multi-layer resist method has been considered in which a second layer containing 4C is formed, and a t-resist is formed on top of it as a sixth layer. However, even in this method, alignment When using light or light with a wavelength similar to that wavelength for the actual observation, it is difficult to observe the 9 budai (the alignment mark) on the 11111 mark due to the dye in the second layer. In addition, when observed with a TTL method using a source with a wavelength different from that of light, it can be seen that the burn-in is caused by the pigment in the second layer. Although absorption does not occur, as mentioned above, due to the strong chromatic aberration of the projection lens, it has been pointed out that accurate positioning cannot be achieved as it is.The present invention has been developed using a wafer and a mask as the exposed object.
In order to align the relative position with the wafer (reticle), one alignment mark on the wafer, which is back-projected by the projection optical system, and the alignment mark on the mask (reticle) are overlapped at the same time! Another object of the present invention is to provide a projection exposure apparatus that enables highly accurate correspondence between a stage on which a wafer is placed and a mask (reticle). Furthermore, it is an object of the present invention to provide an exposure device that can automatically and accurately align the projection optical system even if there is chromatic aberration due to a difference in wavelength between the printing light and the alignment light for alignment. This is the purpose. In other words, in the invention, there is provided a stage on which an object to be exposed is placed and can be moved two-dimensionally, and a mask (reticle) on which marks are drawn.
an illumination means for illuminating the stage and the mask (reticle) with light of a predetermined exposure wavelength; and a projection optical system for projecting the illuminated image of the mask (reticle) onto the object to be exposed. In order to correlate the relative position with the mask (reticle), a photoelectric detector is installed on the mask (reticle) to detect a mark image on the mask (reticle) projected with light having a wavelength substantially equal to the exposure wavelength through the projection optical system. In one embodiment, the stage has a reference mark consisting of a light transmitting part and a light reflecting part, and the photoelectric detector detects a mask that passes through the light transmitting part of the reference mark. According to the present invention, the projected image of the marks provided on the mask (reticle) is detected by a photoelectric detector provided on the stage. Since the mark is directly detected by the OT F (0pical tra
The position of the mask (reticle) and the stage can be matched extremely accurately without being affected by the influence of the nsfer function or the flare that does not collect dust, and the relative relationship between the mask (reticle) and the exposed object can be made extremely accurately. The positioning can be performed extremely precisely.The present invention will be explained as follows with reference to the drawings of the embodiments.Fig. In Fig. 1, the burning from light source 1 is caused by light (in this example, g
The line light) passes through the condenser lens 2 and reaches the exposure illumination optical system 4 via the shutter 6. The printing light emitted from the exposure illumination optical system 4 uniformly illuminates the entire surface of the reticle 5. A circuit pattern made of chrome or the like is formed on the lower surface of the reticle 5, and this circuit pattern surface (object surface) is a reduction projection lens 6 (hereinafter simply referred to as the projection lens 6).
An image is formed on the wafer 7 as the transferred object. This projection lens 6 has a telecentric optical system only on the image side (exit side). Two-dimensional movement of the 7 wafers, that is, the left and right force direction (X
The stage 8 is placed on a stage 8 that is movable in the forward and backward direction (y direction) and the front and back directions (y direction) of the paper.The two-dimensional position (coordinate values) of the stage 8 is sequentially measured by a laser interferometer 9. Although only the laser interferometer 9 in the X direction is shown in FIG. 1, laser interferometers are similarly provided in the y''5 direction. The surface of the projection lens A is arranged so that it is conjugate with respect to the projection lens A, but this conjugate relationship holds true only for the light (0g line) or its approximate wavelength, that is, the source of the wavelength λl. Since alignment is performed using light of a wavelength other than light during printing, a dichroic mirror 10 approximately the same size as the reticle 5 is installed between the reticle 5 and the projection lens 6. The dichroic mirror 10 is arranged perpendicular to the optical axis.This dichroic mirror 10 reflects red light as alignment light, such as helium neon laser light (light with wavelength λ2), and transmits printing light (g-line). In order to perform alignment using the TTL force method via the dichroic mirror 10, a laser beam source 11, a beam expander 12 that expands the beam diameter of the laser beam, and a single laser beam A vibrating mirror 13 that deflects vibrationally, a beam splitter 14, a focusing lens 15, a parallel flat glass 16 (burping glass), and a reflecting mirror 17 are provided.Therefore, the laser beam from the light source 11 is transmitted to the beam expander. After being made into a parallel beam with a large beam diameter by -12,
It is deflected by the vibrating mirror 16 in a plane parallel to the plane of the paper, passes through the beam splitter 14, and is focused by the focusing lens 15 into a minute spot. This spot light is then reflected by a reflecting mirror 17 via a parallel flat glass plate 16 toward the lower surface of the dichroic mirror 10. Since the dichroic mirror 10 reflects the helium-neon laser beam, the spot light from the reflecting mirror 17 enters the projection lens B. At this time, it is assumed that the spot light focused by the focusing lens 15 is imaged at the position of the reflecting mirror 17, and 1. This spot light is re-imaged on the surface of the way 7 by the projection lens B. Here, as mentioned above, the projection lens 6 has strong chromatic aberration, so the optical path length for the g-ray light from the reticle 5 to the entrance pupil of the projection lens 6 and the imaging position of the spot light by the focusing lens 15 (reflection mirror -17) to the entrance pupil of the projection lens B, the pattern image of the reticle 5 and the laser spot light are formed on the same plane on the exit pupil side of the projection lens B. It is determined that Note that the beam splitter 14 is used to take out the original information that is returned after entering the projection lens 6 in the opposite direction. The optical information reflected by the beam splitter 14 is converted into one or more dimensional components by a spatial filter 18 that cuts specularly reflected light (10 dimensions), and passes through a lens 19 to reach a photoelectric element 20.This photoelectric element 20 is provided mainly to detect alignment marks on the wafer 7. Furthermore, the spatial filter 1
An exit pupil image of the projection lens B is formed on the photoelectric element 8, and high-order diffracted light is focused on the photoelectric element 20 by the lens 19. Further, the reticle 5 is provided with a mark 21 in which a slit-shaped light transmitting portion is formed for alignment. The lamp 22 generates light of the same or similar wavelength to the printing light, and the light passes through a half mirror 23, a shutter 24, and a lens 25, and is bent by a reflecting mirror 26 to illuminate a local area including the mark 21. to illuminate. Furthermore, lamp 22
Alternatively, the light from the light source 1 may be guided by an optical fiber. Now, a reference mark 27 as described later is provided on the stage 8 in order to detect the image of the mark 21 projected by the projection lens B or the spot light of the laser. (7) Standard 7-ri 27 is chromium etc. on the glass plate (7)
A light-shielding material is vapor-deposited, and a portion thereof is provided with minute slit openings or lattice-shaped openings that transmit light. A photoelectric element 28 is embedded below the reference mark 27 to receive light transmitted through the slit or grating. Further, the surface of the reference mark 27 other than the opening is subjected to surface treatment to increase the reflectance. Further, the surface of the reference mark 27 is set to match the surface of the wafer 7 placed on the stage 8 in height. Further, between the base mark 27 and the photoelectric element 28, He
- A colored glass filter 29 is provided to cant the N6 laser light (red light) and prevent the printing from passing light of the original or approximate wavelength.

[It may be the same as Gosoku Mirror 10. The above-mentioned laser scanning optical system (vibrating mirror 13, beam brick 14, focusing lens 15, parallel flat glass 16, and reflecting mirror 17) scans the spot light in the X direction, and the detection system (filter 18, lens 19 and the photoelectric element 20) are for detecting the higher-order diffracted light that has entered in the opposite direction from the projection lens 6, and in reality, in order to combine scanning and detection in the y direction, they are shown on the front and back of the paper in FIG. A similar laser scanning optical system and detection system (not shown) are also provided in the direction. Furthermore, the mark 21 is not limited to just one place on the reticle 5, but marks similar to the mark 21 are also provided around the periphery in the direction perpendicular to the plane of the paper so that the reticle 5 can be positioned in the X and Y directions. There is. As will be described later, an observation illumination optical system composed of a lamp 22, a half mirror 26, a shutter 24, a lens 25, and a reflecting mirror 26 is also provided to illuminate each mark. -1: Way 7 for stage 8
is capable of minute rotation on its plane l1ii, and also moves up and down to keep the projection lens 6 in focus. In addition, a reference mark 27, a colored glass filter 29, and a photoelectric element 28
move upward together with the wafer 7 as one unit. FIG. 2 is a plan view of the reticle 5 shown in FIG. 1, in which the surrounding hatched area represents a light-shielding area made of chrome, etc., and the internal rectangular area is an exposure area 5a on which a circuit pattern is drawn.
represents. The aforementioned mark 21 (for the X direction) and mark 21
'(for the y direction) is an exposure area 5a0 of the reticle 5) provided in the light-shielding part as a slit opening extending thin and thin along the edge of the reticle 5.
It can also be something that extends radially from the center. In any case, marks are provided at at least two locations on the reticle 5 that are separated from each other. 6 is an enlarged partial view showing the reference mark 27 in detail, FIG. 6(a) is a plan view, and FIG.
Fig. 6 (a)
) In (b), the reference mark 27 is the transparent glass plate 2.
X marks 27a and Y marks 27b, which are formed by regularly arranging fine rectangular lattice elements, are formed on a part of the chromium layer 27 formed on the entire surface of 7'. The X mark 27a and the Y mark 27b are set so that the arrangement directions of the lattice elements are perpendicular to each other, and the arrangement directions are set to coincide with the inward direction of the xy movement of the stage 8, respectively. Furthermore, when the mark 21 of the reticle 5 is reduced and projected onto the reference mark 27 through the projection lens 6, the image of the mark 21 is approximately the same size as the X mark 27a. The size of each mark is determined to match the shape. Of course, the sizes of the image of the mark 21' and the Y mark 27b are similarly determined. FIG. 4 is a block diagram of a device for controlling the exposure apparatus according to this embodiment. The entire device is a CP such as a microprocessor.
It is centrally controlled by U100. The CPU 100 controls the reticle alignment control system (hereinafter referred to as IFIU 1) via an interface 101 (hereinafter referred to as IFIU 1).
The X-axis alignment system (hereinafter referred to as RAC) 1o2, which includes the shutters 3 and 24 shown in FIG.
(hereinafter referred to as X-7-ALG) 103, Y-axis alignment system (hereinafter referred to as Y-ALG) if] 4, X @ drive unit that drives the stage 8 in the X direction (hereinafter referred to as X-ACT) 105 , a Y-axis drive unit (hereinafter referred to as Y-ACT) 106 that similarly drives the stage 8 in the y direction, and a θ rotation drive unit (hereinafter referred to as Y-ACT) that slightly rotates the sea urchin 7.7 relative to the stage 8.
0w A CT) 107, the z-axis to move the wafer 7 and the reference mark 27 up and down with respect to the stage 8.
rM (hereinafter referred to as Jy lower Z-ACT) 10B, a focus detection system (hereinafter referred to as AF) 109 that detects the focal point position so that the focus of the projection lens B is focused on the wafer 7, and the X direction of the stage 8. An X-axis interferometer 110 (same as the laser interferometer 9 in FIG. 1) that measures the position in the open side, a Y-axis interferometer 111 that measures the position in the y direction, and a photoelectric element 28 embedded in the stage 8. Various detection information and control information are exchanged between them. In addition, X-ALGl[]3 and Y-ALG1
04 consists of an optical system and a detection system, each of which transmits the Rayleigh 4 spot beams as described above. The 5th comb ζ is the 1st (flat plate with 7J combs on the 1st plate) by controlling the inclination of the lath 16 to vibrate the laser beam 1]
FIG. 3 is a process diagram showing a control system for deflecting the I-axis. Of course, this control system also controls I Ii"'+01.
It operates under the CP Uioo. Oscillator (JR, -
The AC output signal of 300 is input to the drive circuit 301 that drives the vibrating mirror 13, and
Synchronous detection circuit (hereinafter referred to as PSD) 3 Ll 2'
TC man sawed. - The output signals of the electronics 20 are also input to 1) S1) 302, and the servo circuit 303 is operated based on the detected signal of p31) 302. The sensor circuit 303 looks up at the flat glass 16 so that the detected signal becomes zero. Next, the operation of this embodiment will be explained with reference to the above-mentioned figures. o> First, the alignment thread is calibrated for the chromatic aberration of the projection lens 6.The reticle 5 as shown in FIG. 2 is set at a predetermined position during exposure using the RA c1 port 2. After that, AF109
The Z-ACT 10 detects the focal position of the projected image of the mark 21 or mark 21' on the reticle 5 by the projection lens B, and moves the Z-ACT 10 so that the image is focused on the reference mark 27.
Activate 8. Next, the shutter 24 is opened, the mark 21 is illuminated with light from the lamp 22, and the stage 8 is moved by operating the X-ACT 105 and y-ACT 106 so that the projected image of the mark 21 overlaps the X mark 27a. At this time, the stage 8 is sent at a constant speed in the X direction, and the light transmitted through the X mark 27a is detected by the photoelectric element 28 to measure the light intensity distribution of the projected image of the mark 21. This intensity distribution has a waveform as shown in FIG. 6(a), for example. FIG. 6(a) shows the magnitude of the photoelectric signal (2) of the photoelectric element 28 with respect to the position of the stage 8 in the X direction. Therefore, while moving the stage 8 in the χ direction, the X-axis interferometer 11
0, the position in the x75 direction is measured, and the positions Xi and x2 when the photoelectric signal I intersects with a predetermined level Ir are determined. Then, CPUID0 is located at the center position XO of these positions x1 and X2.
%, that is, the peak position of the photoelectric signal 1, and calculate its position or value. The X-ACT 105 is controlled so that the stage 8 stops at . As a result, the projected position of the mark 21 and the position of the stage 8 in the X direction are associated with each other. position x. After stage 8 stopped, X-ALG103
Align the vibration center of the laser spot light with the X mark 27a. In this case, as shown in FIG.
The laser beam emitted from the reflecting mirror 17 is reflected by the dichroic mirror 10 to the projection lens 2, and is focused as a spot light on the surface of the way 7 or the surface of the reference mark 270. This spot light is scanned by the vibrating mirror 16 in a direction perpendicular to the direction in which the X mark 27a extends. Therefore, the parallel plate glass 16 is tilted by a servo control system using synchronous detection shown in FIG. At this time, when the spot light irradiates the X mark 27a, diffracted light is generated from the grating element, and the photoelectric element 20 receives only the higher-order diffracted light. Note that the thickness of the spot light on the reference mark 27 is the same as that of the X mark 27a (or Y mark 27b).
) is set to be approximately equal to the width of the At this time, the detection signal S of PSD302 in FIG. 5 is as shown in FIG. 6(b).
It can take a waveform like this. Therefore, if the detection signal S is set to the zero point P, the position of the projection image of the mark 210g line of the reticle 5 or light of an approximate wavelength and the detection center of the TTL force type laser beam alignment system, that is, the X-ALG 106 This means that the correspondence has been completely calibrated (adjusted). Then, when the detected signal S reaches the zero point P, the inclination of the parallel flat glass 16 is fixed. Mark 21 on the reticle 5 for alignment in the X direction by the movement above the eyebrows
The center of vibration of the laser scanning optical system is aligned to a position that is optically conjugate.Also, the calibration in the y7i direction is completely performed using the mark 21' of the reticle 5 and the Y mark 27b of the reference mark 27. It is done in the same way. In this case, the stage 8 moves in the y direction. According to the above, px-ALG103, Y-ALG
104 proofreading 〃5 thread winter 1-ru. (2) Next, the case of frying sea urchins 1 to 7 by passing them through 5v of revuccle will be described. At this stage, Uenohe 7 is moved to stage 8 by an off-axis θ-axis alignment system (not shown).
A rotation error of 75 balls was detected, and the rotation error was 0-
Assume that it has been corrected by ACTl (:17. Furthermore, as shown in FIG. 7, there is an Assume that marks 3 [ ] and 31 provided as a set of lattice elements are marked in the same manner as a + Y mark 2 f b. The mark 30 is the circuit pattern area 7a
On the right side (l1111 edge 'fn part), lattice elements are arranged in the y15 direction and are used for alignment of the X force 1. Mark 31 is a circuit) at the lower edge of the turn area 7a. Grid elements are arranged in the X direction and used for alignment in the Y direction. In addition, the surface of the reticle 7 is coated with a photoresist, and in order to prevent the photoresist from being exposed to light, the shutters 6 and 24 are both bent. Now, the reticle 5 and the reticle 7 To align the upper circuit/turn area 7a, first move the stage 8 based on the distance from the reference mark 27 to the circuit to be exposed (turn area 7a). It is assumed that the position relative to stage 8 is reproduced almost constant.When the vibration center of the laser scanning optical system is calibrated, the CPU 100 adjusts the position of stage 8 to X and y7.
X-axis interference in the j direction! tl'iio and Y-axis interferometer 11
1, the distance from that position to the circuit pattern area 7a to be exposed can be easily determined. It is the position of Ueno 7 with respect to the reference mark 27, and the arrangement of the circuit area on Ueno 7).
This is because S is known in advance. When the stage 8 is sent in this way, the circuit pattern image by the projection lens B and the circuit pattern image on the Uni-No 7 (turn area 7
& will overlap with an error of several tens of μm or less. Next, X-ALGl[13, Y
- Activate the ALG 104 and use the PSD 3 shown in FIG.
[The deviation between the detection signal S of J2 and the zero point P is determined, and the Breimen l-error between the circuit pattern area of the reticle 50 and the wafer 7 is measured. t, that is, the relative positional deviation between the reticle 5 and the wafer 7 is detected. At this time, X-ALG1
The laser spot light of 03 scans the mark 3o back and forth in the x5 direction, and the laser spot light of Y-ALG 104 scans the mark 61 back and forth in the y73 direction. Now, based on the measured error (J y ),
The X-ACT 105 and Y-ACT 106 are driven, and the stage 8 is slightly moved to eliminate this error. Then, at that position, the shutter is opened for a certain period of time, and the circuit pattern image on the reticle 5 is transferred to the circuit on the wafer 7. It is transferred onto the photoresist in a state that matches the pattern area 7a.Then, the stage 8 is moved to the position on the wafer 7 to be exposed next according to the position measurements of the X-axis interferometer 110 and the Y-axis interferometer 111.Here also. Similarly, X-ALG103, Y
-Measure the alignment error using ALGICJ4,
Align the stage 8 by slightly moving it. In this way, alignment is performed one after another for each exposure area, and printing is completed for the entire surface of the Unihaf. Note that if the surface of the wafer 7 has a taper, AF109. Focus adjustment may be performed using Z-ACT 108. As described above, according to this embodiment, the reference marks 27 (X mark 27a, Y mark 27b) provided on the stage 8
is an assembly of grating elements like the marks 30 and 31 on the wafer 7, and a photoelectric element 28 for detecting light transmitted through the reference mark 27 is embedded, so that g-line light or light of a similar wavelength can be used. The mark image on the reticle is accurately detected by the photoelectric element 28, and the relative positions of the reticle 5 and the stage 8 are accurately correlated. Detection using a laser beam spot can also be accurately performed from higher-order diffracted light. For this reason, even though there are changes in vertical and horizontal magnification due to chromatic aberration (projection laser): B, the projection position by G-ray light and the alignment center using laser light, that is, the light beam There is an advantage that the reticle 5 can be adjusted to correspond to the vibration center as the irradiation position.
When the marks 21 and 21' are extended radially from the center of the reticle 5 as shown in FIG. 8(a), marks 30 and 31 provided around one circuit pattern area 7a on the wafer 7 also It is preferable to arrange them radially as shown in FIG. 8(b). In FIG. 1, while the shutter 24 is open, the mark 21 on the reticle 5 is visible through the half mirror 26.
(21') and the X mark 27a (Y mark 27b) of the reference mark 27 can also be observed at the same time. As a result, when calibrating the vibration center of the laser spot light, it becomes possible to check it with the naked eye using a microscope, a television camera, etc., and also to perform fine adjustment manually. A second embodiment of the invention will be described below. The overall configuration of the exposure apparatus according to the second embodiment is almost the same as that in FIG. 1, but an optical system (lamp 22, half mirror 23, shutter in FIG. 24, lens 25, and reflection mirror 26] are all removed. Then, the exposure illumination optical system 4 is configured to simultaneously illuminate the area of the reticle 5 including the mark 21 (21'). The shape of the reference mark 27 fixed to is also as shown in Fig. 9. In Fig. 9, the shaded part indicates the light shielding part, and the grating elements are arranged in the X direction and the y force direction as in the first embodiment. Arranged X
In addition to the mark 27a and the Y mark 27b, there is a slit-like mark 27c and a mark 2 that are elongated in the [direction] and the y force direction.
7d is provided. The marks 27c and 27d are both set to approximately the same size as the projected images of the marks 21 and 21/ on the reticle 5, the mark 27c detects the position of the projected image of the mark 21 in the X direction, and the mark 27d detects the position of the projected image of the mark 21/21/ on the reticle 5.
The position of the projected image in the y force direction is detected. The center line (width center) of the X mark 27a extending in the y''5 direction coincides with the center line of the mark 27c extending in the y7j direction, and the center line of the Y mark 27b extending in the X direction also coincides with the center line of the mark 27c.
The center line extending in the direction of the 7dOX force also includes the exposure illumination optical system 4.
Since the marks 21, 21' on the reticle 5 are illuminated using the illumination mark 21, 21', the marks 21, 21' are actually located inside 1, that is, at the periphery of the exposure area 5a, from the position shown in FIG. 8(a). To position. Now, the procedure for correcting the correspondence between the imaging center of the laser scanning optical system and the mark 21, 21' using this reference mark 27 is as follows. The stage 8 is moved so that the reference mark 27 is directly below the projection lens B, the shutter 6 is opened, and the reticle 5 is illuminated. The stage 8 is then moved so that the projected image of the mark 21 on the reticle 5 scans the mark 27c at a constant speed. Thereafter, as in the embodiment of the cylinder 1, the stage 8 is moved based on the output signal of the photoelectric element 28 so that the center of the projected image coincides with the center of the mark 27c, and is stopped at that position. Next, the laser spot light from the X-ALG 103 shown in FIG.
The servo control system shown in FIG. 5 is operated so as to coincide with the center of . As a result, the vibration center of the spotlight of the X-ALG 103 is calibrated in the X direction1, and the vibration center of the Y-ALG 104 is also calibrated using the mark 21', the Y mark 27b, and the mark 27d of the reticle 5. , are calibrated in the X direction by a similar procedure. After the calibration is completed through the above operations, printing is performed using the step-and-repeat method as in the first embodiment. In this case, each circuit pattern area 7 on the wafer 7
Radial marks 30 and 31 as shown in FIG. 8(b) have already been provided around point a, and this mark 30
．． Alignment is performed by scanning filter 1 with a laser spot light. In this manner, according to the second embodiment, the projected image of the mark 21.21' on the reticle 5 is the slit-shaped mark 27c.
, 27d, the S/N ratio of the photoelectric signal is improved compared to the first embodiment, and the alignment detection center can be accurately adjusted. Also mark 27
Since slits c and 27d are simply slits, even if minute dust is clogged, the S/N ratio will not decrease at all, and the position of the projected image of mark 21. = Possible. Of course, since there is no need for an optical system to independently illuminate the marks 21 and 21', there is an advantage that the configuration becomes simpler.On the other hand,
One exposure (one shot) NJ7. Then, the marks 21, 21' of the reticle 5 are transferred as mark images 32, 33 into the circuit pattern area 7a on the wafer 7 as shown in FIG. The mark images 32 and 33 need to have a length of several tens of micrometers, and are placed in the exposure area 5a of the reticle 5.
A prohibition heading prohibiting the formation of circuit patterns shall be provided. Therefore, a sixth embodiment was developed to prevent the mark images 32 and 33 from being transferred into the circuit pattern area 7a.
This will be explained using figures. In this case, the X mark 27a in the reference mark 27 shown in FIG. The arrangement of the Y mark 27b, mark 27c and mark 27d is changed as shown in FIG. In this way, the marks 21, 21' of the reticle 5 can be provided on the outer periphery of the exposure area 5a as shown in FIG. 8(a). Now, the first
In FIG. 1, slit-shaped marks 27c and 27d are each an X mark 27a. It is located parallel to Y mark 27b, and its opening is xd
, xy. When calibrating the vibration center of the laser scanning optical system, the stage 8 is moved by 1.7 degrees so that the projected image of the mark 21 on the reticle 5 overlaps the mark 27c. Then, the laser spot light scans the X mark 27a back and forth in the X direction, and the center of vibration is aligned with the center of the X mark 27a. This completes the calibration in the X direction. The X direction is similarly calibrated using the mark 21', mark 27a, and Y mark 27b of the reticle 5. Now, when printing using the step-and-repeat method, x-ALc103. Y-ALG104 tD Marks 3.0.31 corresponding to one circuit pattern area 7a on the wafer 7 are detected and aligned using each spot light. When the alignment is completed and nine exposures are performed, a projected image 64.6s of the mark 21.21' on the reticle 5 is placed on the outside of the circuit pattern area 7a as shown in FIG. For this reason, on the evaporator 7, there is a
The pattern of the projected image 34 remains at a distance d, and the projected image 3 remains at a distance yd from the mark 31 in the X direction.
Therefore, the mark 21 for the exposure area 5a of the reticle 5 remains.
, 21' is arranged in the circuit pattern area 7a of the wafer 7.
If it is similar to the arrangement of marks 30 and 31 for They are shifted by xd and yd in the directions, respectively. Therefore, exposure must be performed after the stage 8 has been advanced by xd and yd. If you still wish to make this feeding operation unnecessary, you can set the mark 21 shown in FIG. 8(a) by shifting it by xd- in the X direction, and by shifting the mark 21' by only yd- in the X direction. . However, K
is the reciprocal of the magnification of the projection lens B (K=10 in the case of a 1/10 reduction lens). According to this sixth embodiment, the images of the marks 21 and 21' of the alignment stopper reticle 5 are not transferred into one circuit pattern area 7a on the circuit pattern 7, and the image of the mark 21, 21' of the alignment stopper reticle 5 is not transferred into one circuit pattern area 7a on the pattern area. Since the pattern is transferred onto a so-called street line, there is an advantage that there is no need to secure a prohibited area for the circuit pattern on the reticle 5. As explained in each of the above examples, X-ALG103 and Y-A
An alignment method can also be implemented in which the LG 104 is used to detect alignment marks 30, 51, etc. on the wafer 7, and then the stage 8 is moved from that position by a certain distance ΔX, Δy in the x, y, and X directions to perform exposure printing. To do this, the positions of the photographed images of the marks 21 and 21' provided on the reticle 5 are set using an opening (X mark 2) fixed to the stage 8.
7a, Y mark 27b, etc.) is used for detection. Then move the stage 8 a distance ΔX from that position. At the position moved by Δy, use the reference mark 27 to
The detection center of ALσ10 and Y −ALG104 may be adjusted. Therefore, the position of the alignment mark provided on the wafer is virtually unlimited. In the second embodiment described above, the slit-shaped mark 27c and the X mark'/! shown in FIG. 7a in the X direction, or center deviations in the X direction between the mark 27d and the Y mark 27b, or in the sixth embodiment, the slit-shaped mark 27c and the X mark 27
．． Sa, the distance between marks 27d and Y was off from xd.
The 1111 distance with mark 27b is off from yd.
j-, the following procedure may be performed assuming that the amount of deviation (error) is known in advance. That is, mark 27
c, Detect the image position of the mark on the reticle 5 using 27a.
j31. After correcting the movement of the stage 8 by the amount of error from the X-ALG103. Y-ALGI04
Adjust the detection center. In this way, the X mark 27a and Y mark 27 that were generated when the reference mark 27 was manufactured
b. The errors of the marks 27e and 27d by the own device do not cause any trouble, and accurate alignment of 75 balls is achieved. In each of the embodiments of the present invention, the printing was performed using violet light or ultraviolet light, and the explanation was limited to using He-Ne laser light with a wavelength of 633 nm for TTL alignment. It is not necessarily necessary to use laser light for this purpose; it is only necessary to use a strong light source. However, the wavelength of the alignment stopper is not limited to red; it may be any wavelength to which the photoresist is not sensitive, or it may be, for example, a semiconductor diode in the infrared region. Although a colored glass filter 29 is provided between the photoelectric element 28 and the laser scanning optical system of the For example, the center of the projected image of the mark 21, 21' on the reticle 5 is detected by comparing it with a certain level of the light intensity distribution. However, the same effect can be obtained by using other methods such as finding the center of gravity of the image intensity distribution, or finding the peak value by differentiation.The alignment optical system also uses a gicroic mirror. There is no need to limit the method to using 10, and it is also possible to use an imaging lens, prism, optical path length correction optical system, etc. that corrects chromatic aberration with the projection lens 6.The laser spot light on the wafer is scanned by simple harmonic scanning. Although this is explained in the case of X mark 27a,
It is preferable to use an elongated strip-shaped spot light to match the overall shape of the X mark 27b, mark 30°61, etc., because this improves the S/N ratio of the photoelectric element 20.28 and achieves alignment with high resolution. be. Furthermore, the method is not limited to vibrating and scanning the laser spot light; it is also possible to detect alignment marks, X marks, and X marks on the wafer by scanning (sweeping) the stage 8 without vibrating the spot light itself. ,
In this case, each mark will be detected by detecting the maximum value of the output signal of the photoelectric element 20. In each of the above embodiments, the relative positions of the reticle 5 and the projection lens 6 are assumed to be immovable. By the way, some projection exposure apparatuses have a method of aligning the wafer and the reticle by slightly moving the reticle in the x and y directions with respect to the optical axis of the projection lens. An embodiment in which the present invention is applied to a device of this type will be described below with reference to FIG. 13. FIG. 16 shows that the reticle 5 is set on a movable holder 203 and the holder 206 is moved between an
This is a schematic diagram showing an embodiment in which positioning is performed by slight movement in the x and y directions. ing. In FIG. 13, the interface 101 is the same as the interface 101 in FIG. 4, and only the portion that provides a control signal for driving the reticle x and y to the servo circuit 204 based on the detection input from the photoelectric element 28 is shown. This is an indication. In this embodiment, first, the stage 8 (Ueno 7) and the reticle 5 are pre-aligned so that the projected image of the exposure area 5a of the reticle 5 and each circuit pattern area 7a on the Ueno Z are almost aligned. state. Next, the control system X-ALG103 (Y-AL
The vibration center of the laser spot light of G104:) is located at the X-mark 27a (X-mark 27b
) move stage 8 so that it matches The stage 8 digit IW at that time becomes the reference position. Assuming that the reference mark 27 is of the first embodiment, the holder supporting the reticle 5 is slightly moved in the X direction so that the image projected by the mark 210 of the reticle 5 and the X mark 27a coincides with the X mark 27a. Once they match, the servo system is turned off to fix the position of the holder 206 in the X direction (2), and then the servo control is performed in the same manner so that the image of the mark 21' and the X mark 27b match to determine the position in the Y direction. By the above procedure, X-AL as an alignment means
Detection center by alignment light (laser spot light) of GI03 and Y-ALG104 and mark 2 of reticle 5
In the printing of 1.21', the relative positional relationship with the projected image is adjusted using light or light having an approximate wavelength. Thereafter, the stage 8 is moved, and the relative positions of the reticle 5 and the wafer 7 are aligned using each alignment mark on the wafer 7, and printing is performed using a step-and-repeat method. If the reticle 5 is moved slightly in this way to calibrate the detection center of the alignment using the laser beam, the advantage is that the precision of the actuator of the reticle 5 and its servo system is not required as strictly as long as the reduction projection method is used. can get. To summarize each of the embodiments of the present invention, a projection optical system is provided on the stage 8 and is used as a projection optical system using light of an exposure wavelength (the wavelength of light for printing) or a wavelength approximately equal to it (wavelength: 1.). a photoelectric detector (photoelectric element 28) that detects the image of the mark 21, 21' on the mask (reticle 5) projected through the projection lens 6; a reference mark 27 (provided on the stage 8);
X mark 27a,
Irradiate 30 and 31 (key marks), and 8 mark 3
0.31 for alignment (vibration mirror 16, beam splitter 14
．． Converging lens 15. Horizontal flat glass 16, reflective mirror 1
7. Filter 18. Including lens 19° and photoelectric element 20 tr X -ALG 103. Y-ALG104
) and ; The position of the stage 8 when the photoelectric element 28 detects the image of the mark 21.21' is set as the reference position, and the laser beam of wavelength "2 and the mark 27 are A tilt control system (driving circuit 3
01. PSD302. A servo circuit 606) is provided. As a result, with respect to the position of the image of the mark 21° 21' detected by the light of wavelength λ1, that is, Ice-N, the light of wavelength λ2, that is, Ice-N
The alignment detection center (vibration center) matched by the e-laser light spot is associated with the projection lens 6 by correcting the chromatic aberration. Further, as the correction means, a laser beam of wavelength λ2 and reference marks 27 (X mark 27a, Y mark 27b) are used.
) so that the photoelectric element 28 detects the image of the mark 21.21' using the position of the stage 8 when the reference mark 27 matches the detection center for alignment as the reference position. Even if (the reticle 5) is slightly moved, the position of the image of the mark 21, 21' and the detection center for alignment can be correlated by correcting the chromatic aberration of the projection lens 6. As described above, according to the present invention, the projected image of the mark provided on the mask is detected by the photoelectric detector (
Since it is directly detected by the photoelectric probe 28), there is no need for an optical system that detects the projected image of the mark as a reflected image via a projection optical system. Therefore, the positions of the mask and the stage can be correlated extremely accurately without the influence of the OTF of the detection optical system or the influence of flare caused by design dust, etc. I am impressed by the effect of extremely precise positioning. It goes without saying that similar effects can be obtained even when the present invention is applied to a projection exposure apparatus equipped with off-axis alignment means.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an I1N configuration of an optical system according to an embodiment of the present invention, FIG. 2 is a plan view showing an example of a reticle, and FIG.
a) (b) is a plan view showing the fiducial mark portion on the stage and a sectional view taken from the person-A' arrow, FIG. 4 is a block diagram showing an example of the exposure apparatus control system, and FIG. A block diagram of the vibration control system, Figures 6(a) and 6(b) are detection characteristic diagrams of the photoelectric element, and Figure 7 is an enlarged view showing marks on the wafer.
Fig. 8(a) is a plan view showing another example of the mark on the reticle, Fig. 8(b) is an enlarged view showing the mark on the urchin/・ corresponding to the previous mark, and Fig. 9 is a plan view showing another example of the mark on the reticle. FIG. 10 is a plan view showing another example of the reference mark; FIG. 10 is an enlarged view showing an example of the formation of a mark image on the wafer; FIG. 11 is a plan view showing still another example of the reference mark on the stage; FIG. 12 is an enlarged view showing another example of forming a mark image on a wafer, and FIG. 16 is a schematic view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Light source, 2... Condenser lens, 6... Shutter, 4... Illumination optical system for exposure, 5... Reticle, 6... Projection lens, 7... Wafer, 8... ... Stage, 9... Laser interferometer, 10... Guicroic mirror, 11... Tar-1'l, 12... Beam extractor, 13... Oscillating mirror, 14... - Beam splitter, 15... Converging lens, 16... Parallel flat glass, 17... Reflection mirror, 18... Spatial filter, 19... Lens, 20... Photoelectric element,
21...Mark, 22...Lamp, 26...Half mirror 124...Shutter, 25...Lens,
26... Reflection mirror, 27... Reference mark, 28.
...Photoelectric element, 29...Colored glass filter, 100.
...Microprocessor (CPU), 101...Interface, 102...Reticle alignment control system, 106...Y-axis alignment system, 104...X
Axial element system, 105...X-axis drive unit, 106...Y
Shaft, drive unit, 107...θ rotation drive unit, 10B...
Z-axis drive unit, 109...Focus detection system, 110...X
1lilj interferometer, 111...Y-axis interferometer, 201
...X-axis drive section, 202...X-axis drive section, 203.
...Σ) Kuruda, 204...Surf 1ζ circuit, 500
...Oscillator, 7IO1...Drive circuit, Ro02...
11J] Detection circuit, Ro06... Servo circuit. Agent Patent Attorney Sanro Kimura 1st Ward □2 24th Figure 3/F = 4 Figure 13, +5 Figure 13 O Figure 6 Off Figure n, +8 Figure O 9 Figure 11

Claims (1)

[Scope of Claims] <1) A stage capable of two-dimensional movement on which a W exposure object is placed; illumination means for illuminating a mask on which a mark is drawn with light of a predetermined exposure wavelength; and the illuminated mask. In an exposure apparatus having a projection optical system for projecting an image of an image onto an object to be exposed, in order to associate the relative positions of the stage and the mask, the exposure wavelength and substantially 1. A projection type exposure apparatus characterized in that the stage is provided with a photoelectric detector for detecting a mark image of a mask projected with light having a wavelength equal to . (2) The stage has a reference mark consisting of a light transmitting part and a light reflecting part, and the photoelectric detector is configured to detect the mark image of the mask that has passed through the light transmitting part of the reference mark. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is embedded in a stage.