JPH02126627A - Exposure device - Google Patents

Abstract

PURPOSE:To increase the quantity of light projected to a mark and perform writing in a recording medium having high light exposure as well as rapid writing by making use of auxiliary lighting system at the time of writing to the photoelectric magnetic recording medium of a mark for detecting positions. CONSTITUTION:A photoelectric magnetic recording medium 6 is positioned in the vicinity of an optical axis of a projection optical system 3 by moving a movable state 5. A mark 18 for detecting positions on the face of a reticle 2 is transferred on the photoelectric magnetic recording medium 6 and writing is performed. In such a case, an auxiliary lighting system 110 is moved to a place in the vicinity of the optical axis of the projection optical system 3 and its system allows exposure light from a lighting optical system 1 to be condensed and then a great deal of light is irradiated to the mark 18 by increasing flux density. The light irradiated to the mark 18 is established so that the mark 18 for detecting positions becomes strong enough to be recorded magnetically on the photoelectric magnetic recording medium 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an exposure apparatus, and particularly in the production of integrated circuits such as ICs and LSIs, a pattern on a first object surface such as a mask or a reticle is projected by a projection optical system. The present invention relates to an exposure apparatus that uses a position detection system to detect the positional relationship between a first object and a second object at a position different from the exposure position on a second object surface such as a wafer, and performs projection exposure. .

(Prior Art) Recently, reduction projection type exposure devices (so-called steppers) have been used as devices for exposing and transferring fine circuit patterns to ICs and LSIs.
It is widely used in the production of semiconductor devices such as In this reduction projection type exposure apparatus, an image of a circuit pattern drawn on a reticle (mask) is reduced by a projection optical system and is repeatedly exposed to a photoresist (photosensitive agent) layer on a semiconductor wafer.

At this time, as the precision of integrated circuits increases, there is a demand for higher precision in overlapping the mask and the wafer.

In general, the optical system for detecting the relative positional relationship between the mask and the wafer is TTL (Thr
There are two methods: an out-of-the-lens method, and an off-axis method, which uses a position detection system consisting of a microscope or the like located at a certain distance from the optical axis of the projection optical system.

Among these methods, the off-axis method generally has the advantage of being able to use non-exposure light at a wavelength other than the exposure light and has a fast detection speed. However, the disadvantages are that movement errors occur and the distance between the optical axes of the projection optical system and the alignment microscope changes over time.

For example, in the previous Japanese Patent Application No. 62-245244 and Japanese Patent Application No. 1i2-278706, the applicant used a recording medium such as a writable and erasable magneto-optical recording medium to connect a projection optical system to a microscope for positioning. We are proposing a high-speed and highly accurate off-axis exposure system that measures the change in the distance between the optical axes over time. FIG. 7 is an example of a sequence flowchart at that time.

Generally, when writing on a writable and erasable recording medium using exposure light, due to the sensitivity of the recording medium, chemical reaction characteristics, etc.
Exposure often requires a large amount of energy.

For example, when a magneto-optical recording medium is used as the recording medium and a pulsed exposure light such as an excimer laser is used as the exposure light source, the magneto-optical recording medium undergoes magnetic field reversal when the magnetic domain reaches the Curie temperature due to the magneto-optical effect. Things are looking good.

However, since the heat spreads very quickly compared to the time between pulses, energy is not accumulated over time very much. Therefore, it was necessary to increase the amount of energy in one pulse to an amount sufficient to reach the Curie temperature.

(Problems to be solved by the invention) The present invention uses a recording medium such as a magneto-optical recording medium or a photochromic recording medium, forms a predetermined mark for alignment on its surface, and uses the mark to align a mask and a wafer. When detecting the relative positional relationship between The purpose is to provide an exposure apparatus that can

(Means for solving the problem) An illumination system that irradiates a first object with exposure light, and projects a pattern of the first object illuminated with the exposure light onto a second object placed on a movable stage. and an observation optical system provided at a predetermined distance from the projection optical system, wherein a writable and erasable recording medium is provided on the movable stage, and a mark pattern is formed on the first object. is projected onto the recording medium via the projection optical system to record an image of the mark pattern on the recording medium, a condensing optical system is inserted between the auxiliary illumination system and the first object; The purpose of this method is to focus exposure light on the mark pattern.

(Embodiment) FIG. 1 is a schematic diagram of the entire main part of an exposure apparatus according to an embodiment of the present invention. In the figure, light emitted from an illumination optical system 1 illuminates a reticle 2 as a first object, and the pattern is transferred onto a wafer 4 as a second object by a projection optical system 3.Wafer 4 is fixed on a movable stage 5 placed on a surface plate 10-H.

The projection optical system 3 is supported by a lens barrel (not shown), and in some cases, a lens driving means is provided so that a predetermined lens of a plurality of lenses constituting the projection optical system 3 can be moved.

Also, reticle 2 is secured to the reticle stage,
The reticle stage is moved x by the reticle drive means 102.
It is moved in the y, z, and θ directions.

The movable stage 5 can be moved in the X and Y directions by a drive system 101, and the amount of movement thereof is monitored by a laser length measuring device for each of the X and Y directions. Moreover, this movable stage 5 is movable in the direction of arrow X,
The position of the movable stage 5 in the Z direction is also monitored by a Z direction position detection means (not shown).

In FIG. 1, the laser length measuring device 8 for the X direction appears, but the laser length measuring device for the Y 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 errors in irregularities.

Further, a magneto-optical recording medium 6 as a recording medium is arranged outside the wafer 4 on the movable stage 5, and the height of its surface is made to substantially match the height of the wafer 4. Also, if necessary,
An adjustment mechanism is provided to match the height of the surface of the magneto-optical recording medium 6 and the height of the wafer 4. An electromagnet 7 as a magnetic field applying means is embedded below the 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.

Further, a magnetic shield 22 is provided around the electromagnet 7 so that the magnetic field generated by the electromagnet 7 does not adversely affect other members.

It also prevents magnetic fields from reaching the magneto-optical recording member 6 from other members. Reference numeral 9 denotes a position detection system which is located parallel to and away from the optical axis of the projection optical system 3, and includes a lamp 14, a beam splitter 15 for optical path distribution, an objective lens 16, a television camera 17 for observation, etc. including. Further, the position detection system may use, for example, a light beam of a non-exposure wavelength or may include a polarizing microscope. The image taken by the television camera 17 is sent to the computer 100 and subjected to image processing to perform position detection, contrast detection, etc. 18 is a mark on the reticle 2 for position detection.

For example, one or two marks 18 are arranged outside the area where the actual element pattern is drawn on the two surfaces of the reticle, and inside both effective surfaces of the projection optical system 3.

In addition, in this embodiment, if one mark 18 for position detection is provided, the distance between the optical axes of the projection optical system 3 and the position detection system 9 can be determined, and the distance between the optical axes of the projection optical system 3 and the position detection system 9 can be determined. The amount of feed of the stage 5 can be determined, but if two stages are provided, for example, information regarding the rotation of the reticle 2 can also be obtained, and the accuracy of alignment between the reticle and the wafer can be further improved.

Reference numeral 110 denotes an auxiliary illumination system (condensing optical system), which can be moved from the optical axis of the projection optical system 3, where the mark 18 is located between the illumination optical system 1 and the reticle 2, to a position where it does not interfere with the exposure light. It is configured so that

In this embodiment, the auxiliary lighting system +1 is controlled by the drive system (not shown).
0 is set to be moved to an arbitrary position above the two surfaces of the reticle depending on the location of the position detection mark 18.

In this embodiment, as will be described later, the movable stage 5 is moved to position the magneto-optical recording medium 6 near the optical axis of the projection optical system 3. And mark 1 for position detection on the 2nd surface of the reticle.
8 onto the magneto-optical recording medium 6 for writing. At this time, as shown in FIG. 2(A), the auxiliary illumination system 110 is moved near the optical axis of the projection optical system 3, The exposure light from the laser beam is focused to increase the luminous flux density and irradiate the mark 18 with a large amount of light.

The intensity of the light irradiated to the mark 18 at this time is set to be such that the mark 18 for position detection is magnetically recorded on the magneto-optical recording medium 6.

FIG. 2(B) shows a case where a pattern on two surfaces of the reticle is illuminated by the illumination optical system 1 in a normal state, and at this time, the auxiliary illumination system! 10 is retracted to a position where it does not interfere with the exposure light.

In this embodiment, for example, suppose that the required occupied area of the alignment mark 18 is a (c+n2) and the normal exposure amount is E (mJ/cm2) (the auxiliary illumination system 110 has an area b on the optical system entrance side). (cm2) shall be focused on the occupied area a (cm2) of the alignment mark 18. At this time, the exposure amount per unit area of irradiating the mark 18 is E ・-(mJ/cm2 )
(b > a), and it becomes possible to increase the exposure amount by a factor of b/a. Due to this increased exposure, the alignment mark 18 is transferred to the magneto-optical recording medium 6 via the projection optical system 3, and the amount of exposure is sufficient to easily cause the magnetic field reversal reaction. .

Assist in determining the amount of luminous flux to be focused at this time! ! - The area b (cm2) representing the size of the bright system 110 is the minimum exposure amount Eff1ln (m2) for writing on the magneto-optical recording medium 6.
J/cm2), the normal exposure amount E (mJ/cm2), and the area occupied by the alignment mark 18 a (am2
)E l1lin, resulting in the relationship b>a・.

From this equation, the optimal size of the auxiliary lighting system +10 is determined, and the auxiliary lighting system +10 is set to satisfy this condition.

Normally, in the case of photolithography baking as in the present invention,
A parameter called sigma in the lighting system is often set around 0.5. Therefore, the sigma can be expanded to 1 by using the auxiliary lighting according to the present invention, ¥-110. The amount of light becomes '1 ('1). This value of 4 times is not just 4 times, but has the dramatic effect of making it possible to perform transfers that were previously impossible.

Using the magneto-optical recording medium 6 on which writing has been completed in this way, the distance between the optical axes of the projection optical system 3 and the position detection system 9 is determined,
Using this value, the reticle 2 and wafer 4 are aligned with high precision.

FIG. 3 is a sequence flowchart of a specific example at this time.

Next, in this embodiment, a mark 18 for position detection is recorded on the magneto-optical recording medium 6, and the projection optical system 3 is connected using the magneto-optical recording medium (hereinafter referred to as "medium") 6 on which the mark is recorded. An example of determining the distance between the optical axes and the position detection system 9 will be described with reference to FIGS. 4 to 6.

As shown in FIG.
8. The movable stage 5 is brought to a position where the image is formed. Next, the exposure light from the illumination optical system 1 is focused by the auxiliary illumination system 110 to expose the mark 18, and an image of the mark 18 is formed on the medium 6.

At this time, when an upward magnetic field is applied by the electromagnet 7, 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.

This creates a part with reversed magnetization in the shape of the mark day. The resolution of the medium 6 is determined by the magnitude of the magnetic field and is approximately 0.0
The thickness is 2 μm, which is sufficient for the purpose of this embodiment. Furthermore, ultraviolet light, which is normally used for semiconductor exposure, has a high absorption rate in the medium 6 and a high photon energy, so it is effective. When the exposure of the mark 18 is completed, the illumination from the illumination optical system 1 is stopped.

Next, as shown in FIG.
The movable stage 5 is moved by a vector b that is approximately the same as the vector from the exposure position to the optical axis of the position detection system 9, so that the medium 6 is located almost directly below the objective lens 16 of the position detection system.

Then, the magnetized image of the mark on the medium 6 is observed using the position detection system 9, and the image of the mark is formed on the television force memella 17 due to the difference in the polarization state of the light from the medium 6 caused by the difference in magnetization. At this time, the amount of deviation of the mark formed on the medium 6 from the predetermined position and the movable stage 5
The distance between the optical axes of the projection optical system 3, position detection, and f-9 is determined from the feed amount and the like.

Thereafter, as shown in FIG. 6, a strong downward magnetic field is applied to the medium 6 by an electromagnet 7 at an arbitrary position on the movable stage 5.
As a result, the entire surface of the medium 6 is magnetized downward, erasing the marks, and making it reusable.

In this embodiment, the object of the present invention can be similarly achieved even if a photochromic material is used instead of the magneto-optical recording medium. In the case of photochromic material, electromagnet 7,
Others are no longer needed.

(Effects of the Invention) According to the present invention, as described above, by using the auxiliary illumination system when writing marks for position detection on a recording medium,
It is possible to achieve an exposure apparatus that increases the amount of light irradiated to a mark, enables writing on a recording medium with a high exposure amount and speedy writing, and prevents the overall complexity of the apparatus.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the main parts of an embodiment of the present invention, Figure 2 (A)
, (B) is an explanatory diagram of a part of FIG. 1, FIG. 3 is a sequence flowchart of an embodiment of the present invention, 'fJ7
The figure is a sequence flowchart in an off-axis type exposure apparatus, and FIGS. 4 to 6 are schematic diagrams of an embodiment of writing and erasing marks on a magneto-optical recording medium according to the present invention. In the figure, 1 is an illumination optical system, 2 is a reticle, 3 is a projection optical system, 4 is a wafer, 5 is a movable stage, 6 is a magneto-optical recording member, 7 is an electromagnet, 9 is a position detection system, 10 is a surface plate, 18 is a mark for position detection, 110 is an auxiliary illumination system, and 101 is a drive system. Patent applicant: Canon Co., Ltd. Figures (A) (B)

Claims (3)

[Claims] (1) an illumination system that irradiates a first object with exposure light; a projection optical system that projects a pattern of the first object illuminated with the exposure light onto a second object placed on a movable stage; In an apparatus having an observation optical system provided at a predetermined distance from a projection optical system, a writable/erasable recording medium is provided on the movable stage, and a mark pattern formed on the first object is transmitted through the projection optical system. When recording an image of the mark pattern on the recording medium by projecting it onto the recording medium, a condensing optical system is inserted between the auxiliary illumination system and the first object, and the exposure light is directed onto the mark pattern. An exposure device characterized by focusing light on. (2) The exposure apparatus according to claim 1, wherein the recording medium is made of a magneto-optical recording medium or a photochromic material. (3) The exposure apparatus according to claim 1, wherein the second object is a wafer coated with a photoresist, and the recording medium is coated on the wafer instead of the photoresist.