JPH0287346A - Magneto-optical recording medium for registration of exposing device - Google Patents

Abstract

PURPOSE:To allow accurate monitoring of the distance between the optical axes of an optical system for projection and an optical system for registration by forming the recording medium of a rare earth transition metal alloy contg. light rare earths. CONSTITUTION:This magneto-optical recording medium 6 is formed of the rare earth transition metal alloy contg. the light rare earth elements. The light rare earth are preferably selected form Ce, Pr, Nd, and Sm. Saturation magnetization is lowered and the stability of recording and the reproducing contrast at the wavelengths shorter than a visible region are assured by properly combining the light rare earths and the heavy rare earths. The accurate monitoring of the distance between the optical axes of the optical system 3 for projection and the optical system 9 for registration provided to the exposing position is executed in this way.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention projects and transfers an image of the first object onto an object 'fcK2 in a state in which a first object and a second object are aligned in position. In an exposure apparatus equipped with an alignment optical system that detects the positional relationship between a first object and a second object at a position different from the exposure position, the projection optical system and the projection optical system provided at the exposure position are used. The present invention relates to a magneto-optical recording medium used for monitoring the distance between optical axes of the alignment optical system.

[Conventional technology]

This type of exposure apparatus is mainly used to print fine patterns on semiconductor integrated circuits.

In such a device for printing semiconductor integrated circuits, in order to form a complex semiconductor integrated circuit structure, it is usually necessary to print a combination of several types of patterns in order to manufacture one semiconductor integrated circuit. The required overlay accuracy is becoming increasingly strict as the mother turns become finer. For this superposition, there is an off-axis method in which the position is detected using an optical system such as a microscope installed at a fixed position from the optical axis of the projection optical system.

However, there is a problem that the distance between the optical axes of the projection optical system and the alignment microscope changes over time. Accuracy must be maintained by doing this.

For this reason, the relative positioning of the first and second objects when exposing the pattern drawn on the first object to the second object placed on the movable stage via the projection optical system is controlled by the Writing/writing on the outside of the second object on the movable stage
This is done by arranging an erasable magneto-optical recording medium.

That is, a mechanism is disposed on the movable stage to apply a magnetic field to the magneto-optical recording medium in the same direction as the optical axis of the projection optical system, that is, in a direction perpendicular to the recording medium. When monitoring the distance between the optical axes of the projection optical system and the alignment microscope, the magnetic field is applied to the magneto-optical recording medium by the magnetic field applying mechanism, and the predetermined portion is raised to a temperature higher than the Curie temperature of the t-exposure light. to form a mark image, move the stage a certain amount to bring the image forming part under the alignment optical system, detect the position of the image, and set it as a reference position in the alignment optical system. Sequence control is performed to measure the deviation. Further, at the end of the sequence control, a reverse magnetic field is applied to the magneto-optical recording medium to erase the mark image.

The magneto-optical recording medium used in this method is a magneto-optical recording medium made of a rare earth transition metal alloy, which is used as a high-density, large-capacity memory due to its high exposure sensitivity, repeated use, durability, and resolution. suitable. When used as a memory etc., Gd and Tb are used as rare earth elements.
Heavy rare earths such as #Dy and Ho are used, and transition metals such as F's and Co are used, and a magneto-optical recording medium made of a rare earth-transition metal alloy is formed by a combination of these.

[Problem to be solved by the invention]

However, the above-mentioned magneto-optical recording medium is memo IJ- and (-
When used in the optical system, the wavelength of the reproduction light is usually in the infrared region (780 to 830 nm) of a semiconductor radar, but the wavelength of the reproduction light in the alignment optical system of the exposure device is in the visible region of a halogen lamp, xenon lamp, etc. The magneto-optic recording medium made of the rare earth transition metal alloy has a tendency for the magneto-optic effect, that is, the Kerr rotation angle, to decrease as the wavelength becomes shorter, so that sufficient contrast cannot be obtained for reproduction. There was a problem in that the mark image could not be detected with high precision.

In view of these problems, an object of the present invention is to provide a magneto-optical recording medium for aligning an exposure device, which can obtain a sufficient contrast in reading mark images, and therefore can detect mark images with high precision. do.

[Means to solve the problem]

The above purpose is to provide an illumination optical system that irradiates exposure light to a first object, a movable stage, and a mother turn drawn on the first object onto a second object placed on the movable stage. a projection optical system for projecting, an alignment optical system for detecting the relative positional relationship between the first and second objects at a position apart from the optical axis of the projection optical system, and a positioning optical system disposed on the movable stage. A magneto-optical recording medium used as a writable/erasable recording medium in an exposure apparatus equipped with a writable/erasable recording medium, the medium comprising a light rare earth element? This is achieved by providing a magneto-optical recording medium for aligning an exposure apparatus, characterized in that it is made of a rare earth transition metal alloy containing:

[Effect]

In rare earth transition metal alloys containing light rare earth metals, the Kerr rotation angle increases as the wavelength of the reproduction light becomes shorter.

〔Example〕 Examples of the present invention will be described in detail below.

A typical composition according to an embodiment of the magneto-optical recording medium of the present invention can be expressed by the following formula.

HRX L% (F61-zcoz) 1~
x - yHowever, 0 x x 0.45, 0 x y≦0.5, 0
Rizuri 1.

LRFi is a light rare earth element with magnetic properties F) C@e Pr
, Nd *Sm is preferably selected. HR
It is preferable to select heavy rare earths among Gd, Tb, Dy, and Ho.

The reason why light rare earths and heavy rare earths are combined here is that if only light rare earths are used, the saturation magnetization Ms will be large and the coercive force will be small, so that recording will not be stable, but by appropriately combining them with heavy rare earths, it will be possible to achieve saturation. This is to lower the magnetization Ms to ensure recording stability and reproduction contrast at wavelengths shorter than the visible range.

1 to 3 show a recording layer 2 having a complete structure according to the present invention.
2 shows an example of a configuration in which a magneto-optical recording medium is configured using 2.

The magneto-optical recording medium shown in FIG. 1 has a recording layer 22 formed on a substrate 21 and a protective rfJ23'e shaped bottom formed thereon. The exposure beam or reproduction light 24 is irradiated onto the protective layer 23 side.

In the magneto-optical recording medium shown in FIG. 2, a substrate 21' is formed of a light-transmitting material, and an antireflection film 25°, a recording layer 22, and a protective layer 23fr are sequentially formed under the substrate 21'. The exposure beam or reproduction light 24 is irradiated from the substrate 21' side by passing through the substrate 21'.

The magneto-optical recording medium shown in FIG. 3 has a reflective film 26 on a substrate 2. Interference film 27. Recording layer 22. The protective layer 23 is formed sequentially, and the exposure beam or reproduction light 24 is formed on the protective layer 2.
Irradiated from the 3rd side.

Next, FIG. 4 shows an example of an exposure apparatus to which the magneto-optical recording medium according to the present invention is applied.

In the figure, light emitted from an illumination optical system 1 illuminates a chip 2, and the pattern is transferred onto a wafer 4 by a projection optical system 3. The wafer 4 is fixed on a movable stage 5 placed on a surface plate 10.

The movable stage 5 can be moved in X and Y directions by a vehicle drive system (not shown), and the movement # is X.
It is monitored with a laser length measuring device for each direction. In FIG. 4, the laser sub-length measuring device 8 for the X direction appears, but the laser length measuring device for the X direction does not appear. The height of the optical axis of this laser length measuring device 8 is set at the same height as the surface of the wafer 4 in order to eliminate Atsube's error.

Furthermore, a magneto-optical recording medium 6 is arranged outside the wafer 4 on the movable stage 5, and the height of its surface is made to match the height of the wafer 4. Further, if necessary, an adjustment mechanism is provided to match the height of the surface of the magneto-optical recording medium 6 with the height of the wafer 4. An electromagnet 7 is embedded below this magneto-optical recording medium 6, so that a magnetic field can be applied in any direction above or below the optical axis direction of the projection optical system 3.

Reference numeral 9 denotes an optical system for positioning, which includes a rung 14 that emits light of a wavelength that is not substantially sensitive to the resist, a beam smitter 15 for controlling the optical path, an objective lens 16, a television camera 17 for observation, and the like. The image taken by the television camera 17 is sent to a computer (not shown), where it is processed and the position is detected.

Further, 11 is an optical system for irradiating the alignment mark 18 on the reticle, which takes out a part of the exposure light from the illumination optical system 1.
It has a functional metal that illuminates the slit 12 and forms an image of the slit 12 on two surfaces of the reticle. The light from the illumination optical system 1 to the mark irradiation optical system 11 is guided to the shutter 1.
It is turned on/off by 3.

FIG. 5 shows an explanatory diagram of the state near the magneto-optical recording medium 6,
A method of monitoring the distance between the optical axes of the projection optical system 3 and the positioning optical system 9 in the apparatus shown in FIG. 4 will be described.

a) Referring to FIG. 5(&)', first, the medium 6, which has been magnetized downward in advance, is moved to a position directly below the projection optical system 3 where the alignment mark 18 on the reticle is imaged. Stage 5FJR: Bring it. Next, the shutter 13 is opened and the alignment mark 18 is exposed by the mark irradiation optical system 11, and an image of the mark 18 is formed on the medium 6. At this time, for example, the electromagnet 7 causes the magnetic *t-
When exposed to light, only the portion of the medium 6 that is hit by the light absorbs the light, and the resulting heat reaches the Curie point, reversing the direction of magnetization. As a result, a portion with reversed magnetization is created in the shape of the alignment mark 18. When the exposure of the mark 18 is completed, the shutter 13 is closed.

b) Referring to FIG. 5(b)k, next move the movable stage 5 by a vector that is approximately the same as the vector from the exposure position of the mark 18 by the projection optical system 3 to the optical axis of the alignment optical system 9. so that the medium 6 is located almost directly below the objective lens 16 of the alignment optical system. During this time, X, Y
The moving eclipse of is accurately measured by a laser length measuring device 8. Therefore, the alignment mark made in step 1) above is observed, and the position of the mark is detected based on the difference in polarization state caused by the difference in the direction of magnetization. In this way, the distance between the optical axes of the projection optical system 3 and the alignment optical system 9 or the amount of deviation α from the predetermined value can be accurately determined based on the amount of movement of the stage measured by the laser length measuring device and the detected mark position. You can know. Based on the measured values, using the optical system 9, the alignment mark of a predetermined shot of the wafer is brought under the optical system 9, and the position of the 7 alignment mark of the wafer with respect to 9 and the stage coordinates at that time are measured. In this case, a die-by-die method is used to measure each shot and align all shots on the wafer 4, or from the measured values of the 7 alignment marks on the wafer and the optical system 9 in several shots and the coordinates of the stage at that time. Exposure can be performed by selecting the Daropal method of positioning, in which the stage is sent to the position of the calculated reference grid for positioning.

C) Referring to FIG. 5(c), move the movable stage 5 to any position! When a strong downward magnetic field is applied by magnet 7,
The entire surface of the medium 6 is magnetized downward, the marks are erased, and the medium 6 can be reused.

An example of the above sequence is shown in detail in the flowchart of FIG.

Next, we will show the results of an experiment in which a magneto-optical recording medium according to the present invention was actually manufactured and applied to an exposure apparatus.

The exposure device shown in FIG. 4 was used.

◎Specific Example 1 A magneto-optical recording medium having the structure shown in FIG. 1 was used. An S1 wafer is used as the substrate 21, and NdT is deposited on it.
A recording layer 22 of bFe was provided at a thickness of 300X, and a protective layer 23 of SiN was further provided thereon at a thickness of 250X.

The NdTbFe layer was created by simultaneously sputtering Ndo, 5Tbo, 5 targets and Fe target. The composition of the layer was NdO, 18TbO, 18'' OJ4.

This is the wavelength of 248 with an exposure energy of 0.5mJ/1M2.
The alignment mark was exposed to t-10 pulses using a KrF excimerode nozzle. The magnetic field is directed upward (
2000 @ was applied to the optical axis (facing the light source direction).

This was set under a polarizing microscope as an alignment optical system, and illuminated with a xenon lamp, resulting in a contrast of 0.
．． 45 was obtained.

Erasing is a downward magnetic field '5! :2 KOa was applied.

Comparative Example For comparison, a recording layer having the same structure as in Example 1 was prepared by simultaneously sputtering a Tb target and an Fe target. The composition of the recording layer is Tb0.16''
It was 0.84.

Using this magneto-optical recording medium, alignment marks were exposed and reproduced using a xenon rung under the same conditions as in Example 1, and the contrast was 0.2.

A comparison between Example 1 and Comparative Example shows that the reproduction contrast is increased by including a light rare earth Nd in a magneto-optical recording medium made of a rare earth transition metal alloy.

◎Specific Examples 2 to 5 A magneto-optical recording medium having the structure shown in FIG. 2 was used. Polished quartz glass is used as the substrate 21', and At203't300X is provided thereon as an antireflection film 25.
Thereon is a recording layer 22't30 having the composition shown in Table 1 below.
01 was formed. Furthermore, SIN 3001 was formed as a protective layer 23 on top of this, and was coated with a 'ft UV curing resin. The recording layer 22 was created by simultaneous sputtering. Using these recording media, alignment mark exposure and reproduction with a xenon lamp were carried out under the same conditions as in Specific Example 1 (however, the exposure energy in each specific example was as shown in Table 1). When all the steps were carried out, the contrast shown in Table 1 was obtained.In addition, both exposure and reproduction were carried out through the quartz glass from the quartz glass side.

Table 1 Example composition s-x Light energy Contrast 2; Ndo, osTbo, 1o”o, so”o, o
s 1-OmJ/m2O-33; Nd0018Dy0
．． 18F@0.54C00,100.70.5';
Ndo, +aGdo, osTbo, 1z”oaz O
・70.455: Ndo, 2oDYo & 2oHoo
, toFeo, so (140,3oSpecific Examples 6 to 9 A magneto-optical recording medium having the structure shown in FIG. 200X was formed, and kt203'e 350X was formed thereon as an interference film 27.

On top of that, a recording layer 22 having the composition shown in Table 2 below is formed at 150 mL.
X is formed, and At is formed thereon as a protective film and anti-reflection film
20. t 300 X was formed. The recording layer 22 was formed by the simultaneous double layer 9-vine method. Using these recording media, alignment mark exposure and xenon lamp exposure were performed under the same conditions as in Specific Example 1 (however, the exposure energy in each specific example was as shown in Table 2). When reproduced, the contrast shown in Table 2 was obtained.

Table 2 Examples Composition Required exposure
1.Contrast"NdO,18Tb0.18"0
,64 0.5mJ/crn20.57: S
mo, 1. Tbo,,6Feo,,1o,5
0.58: ”o,,sD)'o,+6”o,71
0.4 0.59: P”a, 1sDVa
, taHoo, aa"a, 6q O, 30, 4 As is clear from Examples 2 to 5. 6 to 9, when a light rare earth is included in a magneto-optical recording medium made of a rare earth-X1 transfer metal, during reproduction. The contrast of the mark image can be increased.

An example of an exposure apparatus to which the magneto-optical recording medium according to the present invention shown in FIG. For example, the mark can be erased by applying a gi field of about the same strength as the gi field applied during mark exposure. Further, an exposure apparatus using a permanent matrix that can be turned upside down without using one magnet 7 may be used. Furthermore, the illumination optical system 1 may be used directly for irradiating the alignment mark 18 on the reticle, instead of using the mark irradiation optical system 11 shown in FIG. Furthermore, as a light source for irradiating the mark 18, the exposure light may not be extracted from the illumination optical system 1, but a separate light source having substantially the same wavelength may be used.

As described above, various types of exposure apparatuses can be considered to be applied to the present invention.

〔Effect of the invention〕

Since the magneto-optical recording medium for exposure device alignment according to the present invention is made of a rare-earth transition metal alloy containing light rare earth elements, sufficient mark image reading contrast can be obtained, and therefore the mark image can be read with high precision. It is possible to detect
The distance between the optical axes of the projection optical system and the alignment optical system of the exposure apparatus can be monitored with high accuracy.

[Brief explanation of drawings]

1 to 3 are side views showing an example of the structure of a magneto-optical recording medium in which a recording layer having a composition according to the present invention is used, and FIG. 4 is a side view showing a configuration example in which a magneto-optical recording medium according to the present invention is applied. FIG. 5 is an explanatory diagram showing an example of the exposure apparatus shown in FIG. 4, and FIG.
This figure is a flowchart showing an example of the sequence of the exposure apparatus of FIG. 4. 1: illumination optical system, 2 reticle (first object), 3: projection optical system, 4: wafer (second object), 5: movable stage, 6: magneto-optical recording medium, 7: electromagnet, 8 reticle 9: positioning optical system, 11: mark irradiation optical system, 21.21': substrate, 22: recording layer, 23: protective layer. Agent: Patent Attorney Yohei Yamashita

Claims (2)

[Claims] (1) An illumination optical system that irradiates a first object with exposure light, a movable stage, and a projection that projects a pattern drawn on the first object onto a second object placed on the movable stage. an optical system, an alignment optical system that detects the relative positional relationship between the first and second objects at a position distant from the optical axis of the projection optical system, and a writing/erasing system arranged on the movable stage. A magneto-optical recording medium used as the writable/erasable recording medium in an exposure apparatus equipped with a recording medium that can be written to and erased from, the exposure apparatus position being characterized by being made of a rare earth transition metal alloy containing a light rare earth element. Magneto-optical recording medium for alignment. (2) The magneto-optical recording medium for aligning an exposure apparatus according to claim 1, wherein the light rare earth element is selected from Ce, Pr, Nd, and Sm. 3. The magneto-optical recording medium for aligning an exposure apparatus according to claim 1 or 2, further comprising: a magneto-optical recording medium for aligning an exposure apparatus.