JPS62222636A - Exposure unit and exposure method - Google Patents

Abstract

PURPOSE:To enable a wafer to be exposed in a correctly registered position, by irradiation registering marks by means of a light irradiating means for eliminating errors in detecting positions of marks caused by the presence of photoresist. CONSTITUTION:Light from an excimer laser source 11 travels via an aperture member 12, a luminous energy regulating mechanism 17 provided by a switchable ND filter and relay lens 13 and enters a roof prism 5 through a retractable mirror 8. The light is divided by the roof prism 5 into two oppositely directed rays and applied to registering marks 16a-1 and 16a-2 on the top face of a wafer 16. The luminous energy of the light from the light source 11 is regulated by a luminous energy regulating mechanism 17 for each resist. Photoresist applied on the registering marks and on the periphery thereof can be removed thereby. Since photoresist in the proximity of the registering marks has been removed, the wafer can be scanned by an argon ion laser beam 1 with the retractable mirror positioned as indicated by the broken lines without errors in detecting positions due to nonuniformity in the photoresist layer and without shortage of scattered light due to the photoresist absorbing light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to an exposure apparatus for exposing a photoreceptor after alignment, and particularly to a semiconductor exposure apparatus.

(Prior art) Conventionally, in this type of exposure apparatus, alignment light is applied to alignment marks with a step structure on the top surface of a semiconductor wafer coated with a photoconductor, and the diffraction and scattered light at this time is emitted. The system receives light and performs alignment based on the positional information obtained from it.However, the photoreceptor layer, for example, a photosensitive resin (photoresist) layer coated on the alignment mark, If the mark is asymmetrical, when light is applied to this mark, the direction of the diffracted and scattered light will be deflected in different directions on the left and right, which could lead to errors in position detection.Also, when aligning the mark, If the alignment moonlight to be applied has almost the same wavelength as the exposure light, even if the alignment moonlight is applied to this mark, the light will be absorbed by the photosensitive resin and the amount of diffracted and scattered light for position detection will decrease. There was also the problem of shortages.

(Object of the Invention) An object of the present invention is to eliminate the adverse effects of the photosensitive resin during alignment in an exposure apparatus, as described above.

[Example] 1 is an argon ion laser light source, 2 is a 5HG (5eco
nd llarmanics Generator = second harmonic generation element), 3 is a polygon mirror, 4 is f・θ
Lens, 5 is a roof prism, 6-1.6-2 is a 1-plane beam splitter, 7-1.7-2 is an objective lens, 8 is a foldable mirror, 9-1.9-2 is a stopper, 10- 1.10
-2 is a photodetector, 11 is a KrF excimer laser light source, 12 is an aperture member, 13 is a relay lens, 14 is a substrate, 15 is a projection optical system, 16 is a wafer, +4a-1, 1
4a-2, 16a-1, 16a-2 are alignment marks, and 17 is a light amount adjustment mechanism. The beam emitted from the argon ion laser light source 1, which oscillates at a wavelength of around 496.5 mm, passes through 5HG2 and has a wavelength halved to approximately 248.5 mm.
The light has a wavelength around 2 mm. This laser beam passes through a rotating polygon mirror 3 and an f/θ lens 4, and is temporally distributed to the left and right by a roof prism 5 by the action of both, and then is sent to a polarizing beam splitter 6-1, 6-2 and an objective lens 7. -1.7-2, the substrate 14# is scanned, and then the wafer 16, which is roughly aligned and placed via the projection optical system 15, is scanned. At this time, the foldable mirror 8
is located at the position of the broken line in the figure. Each chip area on the substrate 14 and wafer 16 has a positioning mark 14a, +6a with a stepped structure, and only the scattered light at the stepped portion passes through the stopper 9-1, 9-2 and reaches the photodetector 10. -1.10-2, the position of the mark is detected, and automatic alignment is performed by moving the relative positions of the substrate and wafer under the control of a computer (not shown).

Before performing this automatic positioning described above, the collapsible mirror 8 is placed at the solid line position in the figure, and the KrF excimer laser light source 11 (wavelength 248. The wafer 16 is irradiated with light from a distance of about 5 mm). Excimer laser light source 1
The light from 1 passes through an aperture member 12, a light amount adjustment mechanism 17 such as a switchable ND filter, a relay lens 13, etc., passes through a collapsible mirror 8, enters a roof prism 5, and is distributed to the left and right, and is divided into alignment marks. irradiate. An example of the structure of the opening member 12 is shown in FIG. 18-1.18-2
is the opening above the opening 12. In this way, the frontage member 12
The beams are divided by a roof prism into two beams each.
Two openings are provided. Here, the opening 12 and the upper surface of the wafer 16 are in an imaging relationship. Therefore, on the upper surface of the wafer, the openings are aligned with the alignment marks 16a-1 and 16a.
By forming an image on -2, it is possible to irradiate only the alignment mark and its surroundings with excimer laser light. Since part of the positioning optical system is also used for excimer laser beam irradiation, the device can be made smaller. Frontage portion on opening member 12 +8-1.
The size of 18-2 should be large enough so that the image area of the opening on the wafer 16 can sufficiently include the alignment marks 16a-1 and 16a-2, but does not include the part where the pattern etc. will be printed. It is desirable to limit the size. When creating an aperture image on a wafer in a roughly aligned state, the position and size of the aperture are adjusted so as to always include the alignment mark +6a-1°16a-2. The amount of light irradiated by the excimer laser light source 11 is adjusted by the light amount adjustment mechanism 1 for each resist.
Adjust by 7. Irradiating a photoresist such as PMMA with short-wavelength electromagnetic waves such as excimer laser light used as light for printing exposure at high irradiation power density has the effect of removing the photoresist. Therefore, the light intensity of the excimer laser beam is adjusted to an appropriate level by the light intensity adjustment mechanism 17, and the wafer 16-' is exposed to the excimer laser beam τ source 11 via the above-mentioned optical system, thereby aligning the upper surface of the wafer 16. The photoresist coated on the marks 16a-1, +6a-2 and their surroundings can be removed.For this reason, even if the collapsible lens 8 is then placed at the position indicated by the broken line in the figure and argon ion laser beam scanning is performed, Since the photoresist is removed near the alignment mark on the top surface of the wafer 16, there is no problem of position detection errors due to non-uniformity of the photoresist layer or lack of scattered light due to light absorption by the photoresist as described above.The excimer laser beam irradiation area is Since it is located at almost the same position as the scanning area of the argon ion laser beam, the alignment optical system and the resist removal optical system using an excimer laser or the like can be used in common, as in this embodiment, and the apparatus can be simplified. Possible. The tilting mirror 8 may be replaced with a half mirror.In this embodiment, light with a wavelength similar to that of alignment light (about 248.2 mm) and resist removal light (about 248.5+nm) is used. Therefore, during resist removal irradiation, if the alignment marks 14a-1 and 14a-2 are included in the photoresist removal light irradiation area on the substrate, the projected images of alignment marks +4a-1 and 14a-2 is formed on the wafer 16, and the photoresist in that part is not removed, and this remaining photoresist part becomes a noise component of position information during alignment.Therefore, when irradiating light for photoresist removal, the position Alignment mark 14a-
The substrate 14 is shifted or completely removed so that the optical system and the alignment marks 14a-1 and 14a-2 do not come into the light irradiation area for photoresist removal on the substrate. , 16a-1゜16a-
The substrate 14 is moved to a position where alignment according to 2 is possible. During this time, the substrate is moved by a substrate moving mechanism (not shown). If an XY interferometer is used to measure the substrate position, it is possible to control substrate movement with sufficient accuracy for positioning after resist removal light irradiation. Another way to prevent the projection images of the alignment marks +4a-1 and 14a-2 on the substrate from occurring on the wafer when removing the photoresist is to change the wavelength of the excimer laser light from that of the alignment moonlight and to create a projected image of the alignment marks +4a-1 and 14a-2 on the substrate. Positioning marks 14a-1, 14a-2
There is also a method of defocusing so as not to form an image on the wafer 16. In this case, the resist removal optical system, for example, the relay lens 13, is configured to use excimer laser light with a different wavelength to form an image of the aperture 18 on the wafer 16 via a part of the alignment optical system. Adjust.

Photodetector 10 when irradiating light for photoresist removal
-1.10-2 may be provided with a shutter or a portion of the detection optical system may be blocked to prevent scattered light from damaging the photodetector.

FIG. 3 is a schematic diagram of a positioning optical system of a second embodiment of an exposure apparatus to which the present invention is applied. 19 in the diagram is acceptable 151
The foldable mirrors 8 and 19 are interlocked to take the position shown by the solid line and the position shown by the broken line.

The difference between the second embodiment and the first embodiment is that the substrate 14 and the wafer 16 are aligned using reflected light rather than transmitted light from alignment marks +4a-1 and 14a-2 on the substrate 14. The point is that there is. As shown in FIG. 3, during alignment and photoresist removal, the light does not pass through the substrate 14 and is irradiated onto the wafer 16 through a detour. When performing alignment, the collapsible mirrors 8 and 19 are at the position indicated by the broken line in the figure, and the alignment light (alignment light)
After bypassing the substrate 14, the light is incident near the alignment marks 14a-1 and 14a'-2 on the substrate by the mirror 19, and the reflected light hits the alignment marks 16a-1 and 14a'-2 on the wafer.
It is incident near 1, 16a-2. At this time, only the scattered light at the stepped portions of the alignment marks 14a and 16a enters the photodetector 0-1.10-2.
This is the same as the embodiment.

Before performing this positioning, place the collapsible lenses 8 and 19 at the positions indicated by the solid lines in the figure, and use KrF for photoresist removal.
The light from the excimer laser light source 11 is made to irradiate the wafer 16. If the collapsible mirror 19 is at the solid line position, the photoresist removal light will be directed to the alignment marks 14a-1,
14a-2, the projected image of alignment marks +4a-1 and 14a-2 cannot be formed on the wafer 16, and therefore, the remaining portion of the photoresist is left in the photoresist removal light irradiation area. Does not occur.

In the first and second embodiments, a part of the alignment optical system and a part of the photoresist removal optical system are used together, but the two may be provided completely separately. In this case, as shown in FIG. 4, a collapsible mirror 20 may be provided on the alignment mark of the wafer 16 to irradiate the wafer 16 with photoresist removal light. In addition, with the recent miniaturization of ultra-LSI,
Various places are researching the use of high-output excimer lasers in the far ultraviolet region for transfer exposure;
The excimer laser light source 11 in FIG. 3 is used as a light source for substrate pattern baking exposure, and a collapsible mirror is provided in the baking exposure optical system. It may be introduced into an optical system for resist removal, and in this case, it is more preferable in terms of economy, space factor, etc. Figures 1 and 3
The figure shows a case in which the invention is applied to a lens reduction projection exposure apparatus, but the invention can also be applied to other mirror projection exposure apparatuses, contact 1'
i! l! It is obvious that the present invention can be applied to exposure apparatuses, and also to X-ray exposure apparatuses, EB exposure apparatuses, etc. other than optical exposure apparatuses.

In this embodiment, excimer laser light was used as the photoresist removal light to remove the photoresist near the alignment mark, but the same effect can be obtained even if this light is replaced with other short wavelength electromagnetic waves. Further, the photoresist may be removed by irradiation with an electron beam or an ion beam, or by using other etching means.

〔Effect of the invention〕

As described above, by using the present invention, even if light is irradiated onto the alignment mark during alignment, position detection errors due to the photoresist of the mark will not occur, the amount of diffracted scattered light for position detection will not decrease, and accurate It is now possible to perform exposure while positioning.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a positioning optical system of an exposure apparatus showing one embodiment of the present invention, FIG. 2 is a diagram showing the shape of an aperture member 12, and FIG. 3 is an exposure diagram showing another embodiment of the present invention. FIG. 4 is a partial schematic diagram of the alignment optical system of an exposure apparatus showing still another embodiment of the present invention. In the figure: l: Argon ion laser light source 3: Polygon mirror 8: Foldable mirror 10-1, 10-2: Photodiactor +1: KrF excimer laser light source 12: Aperture member 14: Reticule 14a-1, 14a-2 Ni reticle Alignment mark 15: Projection optical system 16: Wafer 16a-1, 16a-2: On-wafer alignment mark.

Claims (7)

[Claims] (1) An exposure device for exposing a photoreceptor, characterized by having a light irradiation means for removing a specific area of the photoreceptor. (2) The photoreceptor is located on an object having a mark for detecting its position, and the photoreceptor to be removed is present in and around the mark. exposure equipment. (3) The exposure apparatus according to claim 2, wherein the light irradiation means includes a far ultraviolet light source. (4) The exposure apparatus according to claim 3, wherein the far-ultraviolet light source is an excimer laser light source. (5) A device that exposes an object having a photoreceptor and a mark for position detection, which includes an optical system for positioning that irradiates the mark and its surroundings with light and receives an optical signal from the mark; a light source that emits light capable of removing the photoreceptor;
An exposure apparatus comprising means for introducing light from the light source into part or all of the alignment optical system. (6) The exposure apparatus according to claim 5, wherein the light source also serves as an exposure light source. (7) An exposure method characterized by removing a photoreceptor near an alignment mark on an object having a photoreceptor, aligning the object using the mark, and exposing the object.