JPS61111530A - Exposure device - Google Patents

Abstract

PURPOSE:To enable the accurate positioning of circuit patterns to wafers by varying the oscillation wavelength from a light source for alignment in the presence of step structure on the wafer surface. CONSTITUTION:In the presence of step structure 10 on the wafer surface 9, reflection light fluxes on the top and bottom of the step structure 10 interfere with each other and make difficulty in observation on the wafer surface, or the S/N ratio of signals from a TV camera, a photo receiving means, etc. decreases when they are used. Therefore, in this case, interference is prevented by varying the oscillation wavelength by moving the wavelength-selecting elements such as rhythm and grating in a color element laser 3 with a wavelength controller 3 manually or automatically. In place of exciting the color element laser with an excimer laser 1 in such a manner, a Raman shifter or the harmonic of the crystal of KDP or the like can be utilized as the wavelength converting means.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure apparatus for projecting and exposing a fine circuit pattern of an electronic circuit such as an IC or LSI onto a substrate made of silicon or the like to be exposed.

In particular, the present invention divides the light beam from one light source into multiple parts, uses one light beam to project and expose the circuit pattern on the entire wafer surface, and converts the other light beam into a wavelength suitable for observation on the wafer surface. The present invention relates to an exposure apparatus suitable for manufacturing literary conductors that aligns circuit patterns and wafers.

In recent years, semiconductor technology has continued to increase the integration and miniaturization of electronic circuits, and optical exposure methods are also expanding their scope further with the development of crystal-resolving lenses. In such exposure equipment for semiconductor manufacturing, when transferring and printing the circuit pattern of a mask or reticle onto the wafer surface,
The resolution line width of the circuit pattern printed on the wafer surface is proportional to the wavelength of the light source.
Short wavelength light sources in the UV) region are used.

Conventionally, the far ultraviolet light source for this plum tree was a deuterium lamp or Xs.
-Hg lamps are known.

However, these light sources have low output in the deep ultraviolet region, and the photoresist material coated on the wafer surface has low photosensitivity, resulting in long exposure times and small throughput. .

On the other hand, in recent years, excimer (s+xe1 mor) lasers, which are high-output light sources whose oscillation wavelength is in the deep ultraviolet region, have been used in various fields.

This excimer laser is very effective in exposure equipment for semiconductor manufacturing because of its high brightness, monochromaticity, and excellent coherence. When used in an excimer laser t-exposure system, the excavation wavelength of the excimer laser is invisible light, so it is used as a device for aligning the circuit pattern of a mask or reticle with the wafer in the same way as a conventional exposure system. equipment will be required.

Generally, when forming circuit patterns such as LSI on the surface of a wafer as a semiconductor substrate using gold photolithography technology, the method of repeatedly projecting and exposing various circuit patterns on the surface of the wafer and photo-etching the wafer is generally used. taken. For this reason, normally, in the second and subsequent projection exposure processing steps, a stepped structure of the photo-etched circuit pattern has already been formed on the wafer surface.

For this reason, for example, when a light beam is irradiated onto the surface of a sea urchin and the reflected light beam is used to view and worship the sea urchin surface, the light beams reflected from the top and bottom surfaces of the stepped structure on the wafer surface interfere, making observation difficult. It may become a scar.

That is, if the oscillation wavelength of the light source for prefecture viewing is λ, and the step t between the top and bottom surfaces of the step structure is d, then when the step id is in the wavelength order and coincides with the coherence distance, za, (n+4)λ ・・・・−・(1 ) (however, n-0, 1, 2, =.), the reflected light beams from the top and bottom surfaces of the stepped structure on the wafer surface interfere with each other and cannot be observed.

As a result, it becomes difficult to align the circuit pattern and the wafer.

Furthermore, even in so-called auto-alignment, which automatically aligns the circuit pattern and the wafer using a light-receiving means, a TV camera, etc., if the reflected light beam interferes, the S/N ratio of the light-receiving means decreases, making it difficult to achieve high-precision alignment. It's getting difficult. This is particularly likely to occur when a monochromatic light source with a long coherence length, such as a laser, is used as the high-brightness light source.

In recent years, the depth of focus of printing has become shallower due to the higher resolution of the projection light beam of exposure equipment as LSIs have become more highly integrated, but multilayer resist technology has been developed as a solution to this problem. When this technique is used, the resist layer absorbs the printing light and there is almost no reflected light, making it impossible to perform alignment based on the printing wavelength. Therefore, in multilayer resist technology, it is necessary to use alignment light with a wavelength different from that for printing.

The present invention is applicable to semiconductor manufacturing in which the circuit pattern and the wafer can be aligned with perfect precision even if there is any step structure due to the circuit pattern on the wafer surface when projecting and exposing the circuit pattern onto the wafer surface that is the object to be exposed. The purpose of the present invention is to provide a suitable exposure apparatus.

Another object of the present invention is to enable full alignment of circuit patterns and wafers even in multi-no-resist technology.

The main features of the exposure apparatus for achieving the purpose of the present invention are as follows:
An observation optical system that aligns the object by continuously varying the wavelength of the light irradiated onto the object according to the amount of step difference in the fine step structure of the object, and an exposure system that exposes the object. an optical system, a light source that emits a light flux that is guided to the observation optical system and the exposure optical system, and a ninth light splitting means that guides the light flux emitted from the light source to the observation optical system and the exposure optical system. It is a biased thing.

In this way, in the present invention, the interference caused by the light beams reflected from the top and bottom surfaces of the step structure on the wafer surface is avoided by changing the wavelength of the light irradiated onto the exposed object, and the alignment of the circuit pattern and the wafer is completely controlled. This makes it possible to do this with high precision. Furthermore, by using a dye laser, the wavelength of the alignment source is separated from the wavelength for printing.

Next, the implementation of the present invention will be explained with reference to each figure.

FIG. 1 is a schematic diagram of one implementation of the present invention. In the figure, 1 is an excimer laser as a light source whose excavation wavelength is variable. A light beam emitted from the excimer laser 1 (for example, a light beam having a wavelength of 308 tLm or 248nrrL) is split into two beams by a half mirror 2.

Of these, the light beam reflected by the half mirror 2 is guided to the illumination optical system 5.

Illumination is incident on the optical system 5, and the subsequent light flux has a predetermined numerical aperture and illuminance distribution due to the light inch grater and the condenser lens, and illuminates a circuit pattern 7 such as a mask or reticle. The circuit pattern 7 is then projected onto the wafer If19 by the projection optical system 8 and exposed.

On the other hand, the light beam that passes through the half mirror 2 enters the dye laser 3 and serves as the excitation light for the dye laser 3.
The light beam enters the dye cell inside and oscillates in its entirety at a predetermined wavelength.

Figure 2 shows an example of the oscillation wavelength and oscillation efficiency of an allyochrome laser excited with a 308 nm XaCl V-laser (a type of ex-7 laser), and each chevron curve shows the oscillation efficiency when the dye is changed. .

In this way, the dye laser can produce tens of n1rL even with a single dye.
It oscillates with a wavelength width of . By changing the pigment gold, the wavelength can be changed several times within the range of n1rL. In addition, these wavelengths of XeCt laser 308
It is a different wavelength from nm.

Generally, a laser having high output in the ultraviolet region, such as an excimer laser, is suitable as a light source for excitation of a dye laser. The excimer laser excites and oscillates, and the visible light beam from the fixed dye laser 3 enters an alignment optical system 6 for aligning the circuit pattern and the wafer.

Thereafter, it is converted into a light beam suitable for alignment and irradiates the circuit pattern 7.

Since the circuit pattern 7 is projected onto the wafer surface 9 by the projection optical system 8, the alignment between the circuit pattern 7 and the wafer 9 is performed by the naked eye or by using a TV camera, light receiving means, etc. in the alignment optical system 6. Automatically using signal °C
This can be done by moving the stage 11i.

At this time, as mentioned above, if there is a step structure 10 on the surface 9, the reflected light beams on the top and bottom surfaces of the step structure 10 will interfere, and the observation on the surface will become a tabata *D, TV When using a camera, light receiving means, etc., the S/N of the future signal
As this decreases, it becomes difficult to accurately align the circuit pattern and the wafer with the naked eye or automatically.

In this embodiment, in such a case, for example, the wavelength controller 4 manually or automatically activates a wavelength selection element such as a prism or grating in the dye laser 3 to change the oscillation wavelength so that interference does not occur, or to avoid interference as described above. (It consists of 11 types) and is made to come off.

The oscillation wavelength from the dye laser may also be varied by changing the output energy of the excimer laser, or by changing the dye if the oscillation wavelength is to be changed significantly.

In this embodiment, an excimer laser is used for projection exposure of a circuit pattern and is further used as a light source for excitation of a dye laser, thereby making the entire semiconductor device smaller and cheaper.

Furthermore, in this embodiment, the wavelength of the alignment light is set to be different from the wavelength for full baking, thereby making alignment possible even in multilayer resist technology.

In this embodiment, since the output of the excimer laser is large, even if the luminous flux from the excimer laser is divided into a plurality of parts, the amount of exposure is unlikely to be insufficient.

In this embodiment, instead of exciting the dye laser with an excimer laser, a Raman shifter or harmonics of a crystal such as KDP may be used as a wavelength conversion means. Further, instead of the wavelength conversion means, a wavelength selection means such as a spectroscope or a filter for selecting the wavelength of light emitted from the light source may be used.

Furthermore, in this embodiment, a light source having an emission spectrum of the mantissa of a supercommercial pressure mercury lamp was used instead of the laser light source,
The emission spectra of these may be selected as appropriate.

As described above, according to the present invention, when projecting a circuit pattern onto a wafer l, even if there is a stepped structure on the wafer l,
By changing the oscillation wavelength from the alignment light source, it is possible to align the circuit pattern and the wafer with high precision.In addition, it is a compact and low-cost exposure device that guides the light flux from the exposure light source to the observation optical system. can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a diagram of the oscillation wavelength and excavation efficiency of a conventional dye laser. In the figure, 1 is an excimer laser and 12 is a half mirror 151d.
5 is an illumination optical system, 6 is an alignment optical system, 7 is a circuit pattern, 8 is a projection optical system, 9 is a wafer, 10 is a stepped structure, and 11 is a °C stage.

Claims (4)

[Claims] (1) An observation optical system that aligns the exposed object by continuously varying the wavelength of the irradiation light on the exposed object according to the amount of step difference in the fine step structure of the exposed object; an exposure optical system that performs exposure; a light source that emits a light flux that is guided to the observation optical system and the exposure optical system; and a light splitter that guides the light flux emitted from the light source to the observation optical system and the exposure optical system. An exposure apparatus characterized by comprising means. (2) The exposure apparatus according to claim 1, wherein the observation optical system includes wavelength changing means for changing the wavelength of the light emitted from the light source. (3) The exposure apparatus according to claim 2, wherein the light source is an excimer laser, and the wavelength changing means is a dye laser excited by the excimer laser. (4) The exposure apparatus according to claim 1, wherein the observation optical system includes wavelength selection means for selecting the wavelength of the light emitted from the light source.