JPH0513304A - Projection aligner and method for manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To align the positions of a mask and a wafer with a high precision by detecting with an off axis microscope the alignment marks which are formed by the utilization of a phase shifting method. CONSTITUTION:Reticle alignment marks 105L and 105R provided with an area where the phase of transmittable beams is inverted are arranged in a given position on a reticle 11 and also a reticle set mark 12 is arranged on a reticle 11 when a semiconductor circuit pattern on the reticle 1 is projected by a projection lens 4 onto the photosensitive layer on a wafer 2 for exposure. The reticle alignment marks illuminated by the projection lens 4 are formed as a latent image on the photosensitive layer arranged in a given position of a stage 5 where the wafer 2 is mounted, or as the respective images of the marks on the wafer 2, through a reticle illuminating optical system 13. Then, these images are detected by a CCD 48. In accordance with the result of such detection, the reticle 1 is shifted to a reticle stage. Thus, the reticle alignment marks 105L and 105R are aligned with respect to a reticle set 121.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for manufacturing semiconductor elements such as ICs and LSIs, and more particularly to a projection exposure apparatus having a relative alignment function between a reticle (mask) and a wafer. .

[0002]

2. Description of the Related Art The miniaturization and high integration of semiconductor devices continue to progress day by day. DRAM (Dynamic Random Access Memory), which plays a leading role in miniaturization, is already in the sub-micron area at the product level, and half-micron (0.5 μm) at the research level.
Patterning with the following accuracy is discussed.

A reduction type projection exposure apparatus called a stepper, which appeared in the era of 256 Kbit DRAM, has a size of 1M to 4M.
It has become the main model in the production of bit DRAMs, and is expected to be a promising future ultra-fine device.

Although resolution is always a topic of discussion in terms of miniaturization, the overlay accuracy of the mask and the wafer is also as important as resolution or more. In this case, the required accuracy of superposition is generally set to about 1/3 to 1/5 of the resolution.

The alignment systems in the steppers proposed so far are roughly classified into the following three types. (A) TTL ON AXIS system: The wavelength of the alignment light is the same as the wavelength of the exposure light, and the reticle and the wafer are simultaneously observed through the projection lens. (B) TTL NON AXIS system: The wavelength of the alignment light is different from the wavelength of the exposure light, but the wafer is observed through the projection lens. (C) Off-axis system: The wafer is observed by an alignment system that is provided separately from the projection lens.

Among them, the TTL ON AXIS stepper uses light having the same wavelength as the exposure light as alignment light, so that the photosensitive layer at the alignment mark portion of the wafer is exposed and the alignment mark on the wafer is exposed only once. Currently, it is not used much because it cannot be used, the photosensitive layer is exposed to light, the physical properties of the photosensitive layer are changed, and an alignment error occurs.

In addition, the off-axis type stepper has many indirect error factors that intervene in the relative alignment between the reticle and the wafer, and since the time from the alignment to the exposure and the moving distance are long, the change with time of the error component is large.
As a result, it is difficult to obtain high overlay accuracy. Therefore, it is not used much at present. Therefore TTLN
The ON AXIS method is currently the mainstream.

On the other hand, the resolving power of the projection lens follows the Rayleigh equation of Re = k × (λ / NA), and the exposure wavelength is g-line (wavelength 4
36 nm) to increase the numerical aperture (NA) of the projection lens to improve the resolving power Re.

However, as is apparent from Rayleigh's equation DOF = ± λ / 2NA ² , this also causes the depth of focus DOF to decrease with an increase in NA, while the design and manufacture of the projection lens has reached its limit. Therefore, it is required to shorten the exposure wavelength in order to support the sub-micron generation in the future.

At present, various steppers using i-line (wavelength 365 nm) light have been proposed. On the other hand, a so-called excimer stepper using a KrF excimer laser (wavelength 248 nm) as a light source is also considered promising.

To manufacture a semiconductor device using an excimer stepper, it is difficult to use the TTL NONAXIS alignment system as it is. This is because the glass materials that allow the light of the KrF excimer laser (wavelength 248 nm) to pass through are currently only slightly limited to quartz and fluorite, and it is very difficult in design to correct chromatic aberration with respect to light other than the exposure wavelength.

FIG. 6A shows the axial chromatic aberration characteristic of a conventional projection lens for g-line. FIG. 6B shows the axial chromatic aberration characteristic of the conventional projection lens using a single glass material of quartz for excimer laser. 6A and 6B, the horizontal axis represents wavelength and the vertical axis represents axial chromatic aberration.

In the case of the g-line projection lens of FIG. 6A,
Usually, the combination of glass materials can be designed so that the chromatic aberration characteristic curves are in contact with each other at the target wavelength at the zero point.

On the other hand, in the excimer projection lens of FIG. 6B, since there is no degree of freedom of the glass material, the chromatic aberration becomes almost a straight line crossing at one point of the target wavelength.

When laser light from a He-Ne laser (wavelength 633 nm) is selected as alignment light for the projection lens for the g-line, the axial chromatic aberration is about ten and several .mu.m.
m. On the other hand, for example, an Ar laser (wavelength 500 n
When the laser light from m) is selected, its axial chromatic aberration reaches the order of mm. Therefore, it is very difficult to realize the TTL NON AXIS (non-exposure) alignment system in the projection lens for the excimer unless the characteristic curve of the axial chromatic aberration is improved.

Based on this recognition, attention is paid again to the off-axis method, and a method using a dummy wafer as a proposal for improving the above-mentioned drawbacks to the off-axis type alignment system (Japanese Patent Laid-Open No. 120820/1989) or a chuck on which a recording material is mounted. Using the method (Japanese Patent Application Laid-Open No. 1-286630
Various steppers such as Japanese Patent No. 9) have been proposed.

[0017]

In the method of using the alignment mark formed on the dummy wafer or the recording material among the above-mentioned steppers, if the contrast of the alignment mark is poor or the resolution is poor, the detection accuracy of the alignment mark decreases. There was a problem.

For example, when the contrast of the alignment mark is poor, the S / N ratio of the detection system for detecting the alignment mark becomes poor, and the detection accuracy decreases. When the resolution for detecting the alignment mark is poor, the edge portion of the alignment mark is generally unclear, so that the S / N ratio of the detection system decreases as in the case of poor contrast.

As a conventional method for improving the contrast and resolution of an exposed pattern, there is a method using a phase shift method.

In the present invention, the phase shift method is applied to the wafer for aligning the mask and the wafer, the photosensitive layer provided on the wafer mounting table, and the alignment marks formed on the dummy wafer and the recording material (photosensitive layer). An object of the present invention is to provide a projection exposure apparatus capable of forming an alignment mark with high contrast and high resolution and improving alignment detection accuracy.

[0021]

In the projection exposure apparatus of the present invention, the pattern on the original plate is projected through a projection optical system onto a photosensitive layer on a substrate to be exposed mounted on the surface of a movable stage means. In the exposure apparatus, a specific mark having a region for inverting the phase of the passing light beam is provided at a predetermined position on the original plate, and the specific mark illuminated by illumination means is exposed through the projection optical system. A latent image or a specific mark image is formed on a photosensitive layer provided at a predetermined position on a mounting table on which a substrate is placed, or as a specific mark image on a part of the exposed substrate, and the latent image or the specific mark image is detected by a detection unit. The control means controls the movement of the stage means based on the detection result from the detection means.

Further, in the invention, the projection exposure apparatus has an erasing means for erasing a latent image formed on a photosensitive layer provided at a predetermined position on a mounting table on which the substrate to be exposed is mounted. I am trying.

In addition, as a method of manufacturing a semiconductor device of the present invention, when aligning a pattern area of a wafer with a circuit pattern of a mask, an image of an alignment mark of the mask is formed on the wafer by a projection optical system. Projecting and transferring, and detecting the alignment mark image transferred onto the wafer without developing, and the projection optical system to form an image of the circuit pattern of the mask on a pattern area of the wafer. In the method of manufacturing a semiconductor device from a wafer by chemically processing the wafer after projecting onto the wafer and transferring the wafer, a grid pattern in which the alignment marks of the mask are alternately arranged with light-shielding portions and light-transmitting portions. And a phase member that gives a phase difference to light passing through adjacent light-transmitting portions with a light-shielding portion sandwiched therebetween in the lattice pattern, and the grating in which the phase member is formed It is characterized by projecting the turn image of.

[0024]

Embodiment 1 FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention. This embodiment shows a case where the invention is applied to a reduction projection exposure apparatus for manufacturing a step-and-repeat type semiconductor device using an excimer laser as a light source.

In the figure, 1 is an original plate (hereinafter referred to as "reticle") as a photomask, and 2 is a semiconductor substrate (hereinafter referred to as "wafer"). The light beam 31 emitted from the excimer laser 30 passes through the illumination optical system 3 and illuminates the reticle 1. At this time, the projection lens 4 causes the circuit pattern of the semiconductor element on the reticle 1 to be the wafer 2 to be exposed.
The image is reduced and projected upward, and transferred onto the photosensitive layer on the wafer 2.

Reference numeral 98 denotes a variable NA diaphragm having a variable aperture diameter,
The NA of the projection lens 4 is changed. The configuration of the illumination optical system 3 has already been proposed by many steppers, and therefore will be simply described below.

The beam 31 directed upward (in the z direction) by the mirror 41 sequentially passes through an incoherent optical system 32, a fly-eye lens 33, a variable σ diaphragm 99 having a variable aperture diameter, condenser lenses 34a and 34b, and a mirror 35. It reaches the masking image plane. Reference numeral 36 is a masking blade arranged on the masking image forming plane, and 37a and 37b are masking image forming lenses for forming an image of the masking blade 36 on the reticle 1 via a mirror 38.

The reticle 1 is supported by a reticle holding table 11. The reticle holder 11 is a stage (not shown)
Is supported so as to move in the X, Y, and θ directions.
The wafer 2 is projected and exposed while being vacuum-adsorbed by a wafer chuck 21 as a mounting table, but in FIG. 1, it is shown as being supported by a support chuck 22 and separated from the wafer chuck 21. A pattern recording material (photosensitive layer, eg, magneto-optical recording material, photochromic material) 23 and a coated glass plate 24 are arranged around the wafer chuck 21. Although two sets of glass plates 24 are shown in the same drawing, actually, reference numerals 113, 114, 115 and 11 are shown in FIG.
As shown by 6, four sets are arranged around the wafer chuck 21.

The wafer chuck 21 is moved by the movable stage 5 by X, Y, Z, θ, ω _X (rotation component around the X axis), ω.
Move in each direction of _Y (rotational component around Y axis). The stage 5 is supported on the stage surface plate 50.

The stage 5 is Y with respect to the stage surface plate 50.
It has a Y stage 51 that moves in the axial direction and an X stage 52 that moves in the X axis direction with respect to the Y stage 51, on which leveling (ω _X , ω _Y ) by, for example, three piezoelectric elements (piezo elements) 53 is provided. ) And a leveling stage 54 that moves in the Z-axis direction are further mounted thereon with a rotary (θ) fine movement stage 55 and a vertical (Z) fine movement stage 56.
The wafer chuck 21 is mounted on the Z fine movement stage 56.

On the leveling stage 54, mirrors 85, which serve as a reference for the position coordinates of the stage 5, are mounted in the X and Y directions, respectively, and by reflecting the beam that has passed through the laser interferometer 86, the stage 5 It detects the position and the distance traveled.

A receiver 87 converts the optical signal from the laser interferometer 86 into an electric signal. Further, a θ coarse movement mechanism 57 and a Z coarse movement mechanism 58 are provided on the leveling stage 54, and the support chuck 22 is placed on the surface thereof.

Above the reticle 1, a reticle optical system 6 is arranged so as to have a fixed positional relationship with the projection lens 4. The reticle optical system 6 includes a reticle set mark 12 and a reticle 1 provided on a reticle holding table 11.
The reticle alignment mark (105 in FIG. 2) provided above
L, 105R) relative position is detected.

The light from a light source (not shown) is fed into the fiber 1
4. The reticle set mark 12 and the reticle alignment marks 105L and 10L via the reticle illumination optical system 13.
5R is irradiated, and the image of each irradiated mark is detected by the CCD 48 via the beam splitter 47, the objective lens 46, the relay lens 45, and the beam splitter 44.

From the image of the mark detected by the CCD 48,
The relative position between the reticle set mark 12 and the reticle alignment marks 105L and 105R is calculated, and the reticle 1
The reticle alignment marks 105L and 105R are aligned with the reticle set mark 12 by a reticle stage (not shown) that moves in the X, Y, and θ directions. This allows the reticle 1 to have a predetermined positional relationship with the projection lens 4.

An off-axis microscope 7 is arranged above the stage 5 in a space adjacent to the projection lens 4. The off-axis microscope 7 is composed of a monocular microscope using non-exposure light (white light), and detects the relative position between the internal reference mark 70 and the alignment mark on the wafer 2.

The objective lens 71 and the relay lens 72 enlarge the alignment mark on the wafer 2 and project it on the image plane 74. The erector lenses 77 and 78 act as a low-magnification erector lens when both are inserted on the optical axis, and act as a high-magnification erector lens when the erector lens 78 recedes from the optical axis, and the aerial image plane 74 The image is projected on the light receiving surface of the CCD camera 79.

Reference numeral 25 denotes an optical fiber that guides light from a light source (not shown), and the light from this becomes illumination light for the wafer 2 via the illumination lens 26, the beam splitter 73, the relay lens 72, and the objective lens 71. .

Similarly, 27 is an optical fiber for guiding light from a light source (not shown), and the light from this illuminates the reference mark 70 via the illumination lens 28. Beam splitter 7
5, the pattern surface of the reference mark 70 and the image plane 74 are CCDs.
It is arranged so that the same optical path length from the light receiving surface of the camera 79 is obtained. As a result, the reference mark 70 is attached to the erector lens 7
The images are projected and imaged on the light receiving surface of the CCD camera 79 by 7, 78.

The off-axis microscope 7 has a focus detection function. This can be performed, for example, by detecting the blur amount using the output signal of the CCD camera 79.

Further above the stage 5, the projection lens 4
An erasing means 80 for erasing the pattern written on the pattern recording material surface 23 is arranged in the vicinity of. The erasing means 80 specifically introduces light through a fiber 81 and epi-illuminates the light onto the pattern recording material surface 23 through a prism 82 and a lens 83, thereby erasing the pattern formed on the pattern recording material surface 23.

The control circuit 9 is used to control the above-mentioned components. The CPU 91 issues a command to each element according to the predetermined sequence software, and determines the data from each element to determine the next procedure.

The arithmetic circuit 92 mainly uses the reticle 1 based on the coordinate position of the stage 5 and the detection result of the off-axis microscope 7.
It is used for calculation processing that requires high speed and high accuracy, such as calculating the pattern arrangement of the recording circuit 93, and the recording circuit 93 stores the measurement data and calculation data. Although a partial detailed structure will be described later, the above is the basic configuration of the present embodiment.

FIG. 2 is a front view of the main parts of the reticle 1 used in the present invention. In FIG. 2, reference numeral 101 denotes a projection transferable area by the projection lens 4, reference numeral 102 denotes an area in which an actual element pattern for a semiconductor element is formed, and precise alignment marks 103L and 103R are provided in a scribe line area in contact with this area. And a coarse alignment mark 104 is arranged above the drawing. Further, reticle alignment marks 105L and 105R for measuring relative positions with respect to the reticle set mark 12 are arranged on the left and right on the X axis.

Precision alignment marks 103L, 103
R is exposed and transferred to the image recording surface on the chuck described later.
It is also a mark for performing GA (advanced gloval alignment), and is also a mark used for AGA of a wafer in the next process after being exposed and transferred onto the wafer.

FIG. 3 is a principal plan view showing the wafer chuck 21 and the wafer 2 according to the present invention. Wafer chuck 2
1 is an image recording surface 1 so that the four corners have substantially equal intervals.
13, 114, 115 and 116 are arranged. The surfaces of the image recording surfaces 113, 114, 115 and 116 are set to be substantially flush with the surface of the wafer 2 held by the wafer chuck 21 in the Z direction.

4A and 4B show precision alignment marks 103L (103) in the reticle 1 of this embodiment.
It is a detailed explanatory view of R). 4A is a schematic plan view and FIG. 4B is a schematic cross-sectional view. The mark 103L includes a light-shielding portion 111 (for example, a chrome film portion), and a transmitting portion 110 through which exposure light is transmitted (in this embodiment, there are three portions in each of the X direction and the Y direction).
Formed of a lattice pattern.

As shown in FIG. 4B, a member (phase shift film) 112 for inverting the phase of passing light is formed in the adjacent transmissive portions of the transmissive portion 110. Reference numeral 119 is glass (quartz or the like) which is a substrate of the reticle. By providing a member (phase shift film) 112 for reversing the phase of light in the adjacent transmitting portions, a high-contrast and high-resolution mark is formed on the image recording material surface on the wafer chuck.

Next, an operation procedure for aligning the reticle and the wafer in this embodiment will be described with reference to the flowchart of FIG. The operation is started (step 15)
0) and the reticle 1 as shown in FIG.
It is set to 1 (step 151). After that, the reticle set mark 1 is set by the reticle optical system 6 and the control circuit 9.
The relative position between the reticle alignment marks 105L and 105R is measured, and the reticle alignment marks 105L and 105R are aligned with the reticle set mark 12 by a reticle stage (not shown) (step 151).

As a result, the reticle 1 is set at a predetermined position with respect to the projection lens 4. Reticle 1 for example
The center of is located on the optical axis of the projection lens 4. After the reticle alignment is completed, the wafer 2 is carried into the wafer chuck 21 (step 152).

Next, excimer laser light 31 is generated, and the pattern and precision alignment marks 103L and 103R on the reticle 1 are exposed and transferred onto the image recording surfaces 113, 114, 115 and 116 of the wafer chuck 21 via the illumination optical system 3. To do. Precision alignment mark 10 on reticle 1
Members for shifting the phase of the passing light beam are formed on the 3L and 103R as shown in FIG. Image recording surface 113, 1
AGA is performed on the precision alignment marks 103L and 103R exposed and transferred to 14, 115 and 116 through the off-axis microscope 7 (step 155). With this, a so-called baseline is obtained.

Next, at step 156, shot numbers 7, 12, 18, 43, 47 on the wafer shown in FIG.
AGA is performed on the precision alignment marks of the shots 51, 76, 82, and 87.

In step 157, step 15
5, 156, the array coordinates at the time of wafer exposure are determined from the alignment detection data and the stage position data obtained by the AGA.

From the data obtained in step 155, the baseline length, stage magnification component, orthogonality component, projection lens magnification component, etc. are calculated.

From the data obtained in step 156, the X-axis and Y-axis components of the shot array in the wafer and the respective magnification components and the chip rotation amount in the X and Y directions are calculated. The array coordinates at the time of exposure are determined from the above results.

In step 158, step-and-exposure of the wafer is performed according to the array coordinates calculated in step 157. The step-and-exposure wafer is unloaded from the wafer chuck 21 (step 159).

Next, if it is not judged whether or not there is an area for exposing and transferring the next precise alignment mark on the image recording surface, the image on the image recording surface is brought under the erasing means 80 and erased (step 160, 161).

It is judged whether or not the next wafer is on standby. If it is on standby, the wafer is loaded into the wafer chuck 21, and the process is repeated from step 153. If not, it ends. (Steps 162 and 163).

Here, in this embodiment, steps 154 and 15 are performed.
5 is performed for each wafer, but it is not necessary to perform it for each wafer as long as the baseline length, stage magnification component, orthogonality component, projection lens magnification component, etc. are stable.

In this embodiment, the off-axis alignment system of the excimer stepper is described.
The light to be exposed and transferred to the photosensitive layer on the image recording surface or the dummy wafer surface may be g-line or i-line other than the excimer as long as it can expose and transfer the alignment mark.

Although the off-axis system is described as the alignment system, if it is a system capable of detecting the marks transferred by exposure to the photosensitive layer on the image recording surface or the dummy wafer surface, TTL ON AXIS or TTL NON.
The AXIS method may be used.

[0062]

According to the present invention, by forming the alignment mark for aligning the mask and the wafer by the phase shift method, it is possible to easily obtain an alignment mark with high contrast and high resolution, and to perform highly accurate alignment. A projection exposure apparatus that can be implemented can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory view of an alignment mark on the mask surface of FIG.

FIG. 3 is an explanatory view of the wafer and wafer chuck surface of FIG.

FIG. 4 is an explanatory view of an alignment mark on the mask surface of FIG.

FIG. 5 is a flowchart of the alignment according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram regarding chromatic aberration of the projection lens.

[Explanation of symbols]

1 mask 2 wafers 3 Illumination optical system 4 Projection lens 5 stages 6 Reticle optical system 7 Off-axis microscope 9 Control circuit 21 Wafer chuck 22 Support chuck 23 Pattern recording material 24 glass plate 80 Erasing means 104 Coarse alignment mark 105L, 105R reticle alignment mark

Claims (13)

[Claims] 1. A projection exposure apparatus for projecting and exposing a pattern on an original plate onto a photosensitive layer on a substrate to be exposed, which is placed on a movable stage means surface via a projection optical system, and passes through a predetermined position on the original plate. A specific mark having a region for inverting the phase of the light flux is provided, and the specific mark illuminated by the illumination means is placed at a predetermined position on the mounting table on which the substrate to be exposed is mounted via the projection optical system. Formed as a latent image on the provided photosensitive layer or as a specific mark image on a part of the substrate to be exposed, the latent image or the specific mark image is detected by detection means, and control is performed based on the detection result from the detection means. A projection exposure apparatus characterized in that the movement of the stage means is controlled by means. 2. The projection exposure apparatus has erasing means for erasing a latent image formed on a photosensitive layer provided at a predetermined position on a mounting table on which the substrate to be exposed is mounted. Item 1. The projection exposure apparatus according to item 1. 3. A projection exposure apparatus for projecting a pattern on an original plate onto a photosensitive layer on a surface of a substrate to be exposed, which is placed on a movable stage means surface via a projection optical system, at a predetermined position on the original plate. By providing a specific mark having a region for inverting the phase of the passing light beam, and using the specific mark, relative alignment between the original plate and the exposed substrate is performed through the projection optical system. A projection exposure apparatus characterized in that 4. When aligning a pattern area of a wafer with a circuit pattern of a mask, an image of an alignment mark of the mask is projected and transferred onto the wafer by a projection optical system, and transferred onto the wafer. The step of detecting the aligned alignment mark image formed without development, projecting and transferring the image of the circuit pattern of the mask onto the pattern area on the wafer by the projection optical system, In the method of manufacturing a semiconductor device from the wafer by chemically processing, the alignment mark of the mask is formed by a grid pattern in which light-shielding portions and light-transmitting portions are alternately arranged, and the light-shielding portion is formed on the lattice pattern. A semiconductor device characterized by forming a phase member for imparting a phase difference to light passing through adjacent light-transmitting portions, and projecting an image of a lattice pattern on which the phase member is formed. Chair manufacturing method. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the phase member imparts a phase difference of approximately 180 degrees to the light passing through the adjacent light transmitting portions. 6. When aligning a pattern area of a wafer with a circuit pattern of a mask, an image of an alignment mark of the mask is projected and transferred onto a recording member by a projection optical system and recorded on the recording member. A step of detecting the registration mark image formed by the projection optical system, projecting an image of the circuit pattern of the mask onto a pattern area on the wafer by the projection optical system, and then chemically processing the wafer. Thus, in the method of manufacturing a semiconductor device from the wafer, the alignment mark of the mask is formed by a grid pattern in which light-shielding portions and light-transmitting portions are alternately arranged, and the light-shielding portions are sandwiched by the lattice patterns and are adjacent to each other. Manufacturing of a semiconductor device characterized by forming a phase member for imparting a phase difference to light passing through the light transmitting portion, and projecting an image of a lattice pattern on which the phase member is formed. Method. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the phase member imparts a phase difference of approximately 180 degrees to the light passing through the adjacent light transmitting portions. 8. The method of manufacturing a semiconductor device according to claim 6, wherein the recording member includes a substrate and a magneto-optical recording material formed on the substrate. 9. The method of manufacturing a semiconductor device according to claim 6, wherein the recording member includes a substrate and a photochromic material formed on the substrate. 10. The method of manufacturing a semiconductor device according to claim 6, wherein the substrate is a dummy wafer. 11. The method of manufacturing a semiconductor device according to claim 10, wherein the dummy wafer comprises a magneto-optical recording material. 12. The method of manufacturing a semiconductor device according to claim 10, wherein the dummy wafer comprises a photochromic material. 13. The method of manufacturing a semiconductor device according to claim 10, wherein the dummy wafer comprises a resist material.