JPH11212021A - Laser light radiating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the laser beam of high uniformity removing the effect of interference fringes generated at the exit of a kaleidoscope by arranging a mask for selectively transmitting laser light outputted from the kaleidoscope for making uniform laser light intensity. SOLUTION: The laser light made incident through an incident lens 7 into a kaleidoscope 8 is repeatedly reflected inside of the kaleidoscope 8 and reaches an exit 8E. At the exit 8E of this kaleidoscope 8, the laser light has the distribution of light intensity generating interference fringes (b). When the laser light having this intensity distribution is passed through a mask 20, since a light transmissible part is formed only at the center of the mask 20, the peripheral part having the interference fringes is cut and only the beam center having the high uniformity of light intensity is transmitted. Therefore, the light intensity distribution of laser beams transmitted through the mask 20 becomes in a uniform rectangular from (c). The image of this laser beam is formed into spot and an object W to be irradiated is uniformly irradiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing technique, for example, in which Cu is deposited on fine holes or grooves by a sputtering method, and is irradiated with an energy beam to be melted. The present invention relates to an apparatus for spatially uniformizing the intensity distribution of a laser beam, which is used when forming the laser beam.

[0002]

2. Description of the Related Art Generally, an aluminum alloy is used as a wiring material of a semiconductor device. However, in recent years, especially for semiconductor devices that require ultra-high-speed operation with fine patterns, (a) increase in current density due to miniaturization of wiring, (b) increase in wiring resistance, (c) problems of electromigration, (D) There is a concern that the operating speed may be reduced due to an increase in wiring delay.

For this reason, wiring using Cu, which has high electromigration resistance and lower electric resistance than aluminum, has been attempted. When forming a Cu wiring, it is required to form a wiring having a buried structure because Cu has no compound having a low vapor pressure and dry etching is difficult.

[0004] One of the methods of forming a wiring having a buried structure is to form Cu on a hole or a groove pattern formed on an insulating film by a sputtering method and irradiate an excimer laser beam to melt the Cu film to form a hole or a groove. Embedded in the groove pattern, leaving the Cu in the wiring by the subsequent chemical mechanical polishing technique (CMP),
The Cu wiring film on the other insulating film is polished and removed, and an interlayer insulating film is deposited on the entire surface of the substrate.

[0005] In particular, by excimer laser light irradiation, Cu
In order to reliably bury the hole or groove pattern, it is necessary to uniformly heat the space, and for that purpose, it is necessary to make the laser beam spatially uniform.

A kaleidoscope-type beam homogenizer is often used as an optical system for homogenizing the spatial intensity distribution of the laser light.

As shown in FIG. 11, the kaleidoscope-type beam homogenizer is arranged in the order of an incident lens 7, a kaleidoscope 8, and an imaging lens 9 in front of an optical axis of a laser oscillator (not shown). The laser light L oscillated from the laser oscillator by the incident lens 7 is condensed and incident on the kaleidoscope 8, and the incident laser light L is repeatedly reflected in the kaleidoscope 8 and
At the outlet 8E. Then, the uniformized beam is imaged on the irradiation target W by the imaging lens 9, and the irradiation target W
The desired processing is performed.

The kaleidoscope 8 has the shape of a quadrilateral cylinder or a quadrangular prism. The quadrilateral cylinder has four inner surfaces formed by reflection mirrors, and the laser light L incident from the entrance of the kaleidoscope 8 is provided inside the cylinder. By repeating the reflection with the four reflection mirrors, a uniform laser beam is obtained at the exit. The rectangular prism is a quadrangular prism made of optical glass, and the laser beam L incident from the entrance repeatedly reflects on the optical glass wall surface and outputs a laser beam uniform at the exit.

At this time, the uniformity of the laser beam LB at the output end is determined by the focal length of the incident lens 7 constituting the optical system, the diameter of the optical waveguide of the kaleidoscope 8, and the length of the kaleidoscope 8. It depends on the number of reflections. Of course, the greater the number of reflections on the kaleidoscope 8, the better the uniformity.

Further, as shown in FIG. 12 (a), the diameter of the exiting optical waveguide 8d of the kaleidoscope 8 is about 1/45 of the output from the incident lens when no kaleidoscope is present. .

At the output end which is the exit 8E of the kaleidoscope 8, interference fringes are generated due to the interference effect of the laser light L as shown in FIG. The region where the interference fringes occur depends on the spatial phase of the laser light L incident on the kaleidoscope 8.

For example, when the spatial phase of the excimer laser light L in the X direction and the Y direction is measured as shown in FIG. 13, the interference intensity is reduced to 5% or less in a space of about 400 μm in the X direction and about 200 μm in the Y direction. Interference fringes occur in the inside. The generated interference fringes naturally lower the uniformity of the uniformized beam.

The spatial phase can be measured by an interference fringe measuring optical system as shown in FIG. This optical system includes two half mirrors 15 and 16 and a total reflection mirror 1.
7, a mirror M, and a screen 18. By shifting the mirror M in the X and Y directions in this configuration,
The degree of the spatial phase can be measured.

An application example of this method is disclosed in Japanese Patent Application Laid-Open No. H6-111001.
No. 0 discloses this. That is, as shown in FIG. 15, the laser light L passes through the prism P and the incident lens 7 arranged on the optical axis and enters the kaleidoscope 8.
Since the kaleidoscope 8 has a rectangular cylindrical shape such that its inner surface reflects the incident laser light L, the incident laser light L is repeatedly reflected on the inner surface of the kaleidoscope 8 to make the intensity distribution uniform. Out of the callide scope 8.

The laser light L emitted from the kaleidoscope 8 forms an image as a spot S on the surface of the irradiated portion W through the imaging lens 9 and accurately irradiates a predetermined portion of the irradiated object W.

The reason why the prism P is used in this method is that when the laser beam L is condensed near the entrance of the kaleidoscope 8 by the incident lens 7, the air breakdown due to the concentration of the laser beam L In order to prevent the occurrence of the laser beam L, a plurality of laser light condensing portions are provided.

[0017]

In the homogenizer of the kaleidoscope system, the laser beam incident in the kaleidoscope is made to be uniform at the output end by being repeatedly reflected. The number of repetitions of this reflection is shown in FIG. ),
The beam size at the exit end of the kaleidoscope is subdivided into the size of the optical waveguide diameter of the kaleidoscope and folded at one location.

For this reason, since the phase of the laser beam is equal at the edge of the obtained uniform beam, interference fringes occur when the edge of the uniform beam is enlarged as shown in FIG. For this reason, high uniformity cannot be obtained.

Since the laser light has a property called spatial coherence, the interference effect is enhanced when lights close to each other in the beam interfere with each other. Further, in the vicinity of the reflection surface, the spatial coherence of the reflected light and the unreflected light increases, so that the interference effect is high.

Further, the occurrence of interference fringes due to the overlapping of the laser beams becomes more pronounced as the light intensity of the overlapping laser beams becomes equal, and the interference effect becomes smaller as the light intensity difference between the overlapping laser beams becomes larger.

Therefore, in the method of making the light intensity distribution of the laser light uniform with the kaleidoscope, when the light intensity distribution of the incident laser light is smooth, the light intensity of the overlapping laser light is more equal to the reflection surface, that is, the side surface. Close to
Interference fringes at the exit of the kaleidoscope are also likely to occur around the beam.

Note that the intensity distribution generated by the interference fringes is maintained even when an image is formed on an object to be illuminated, thereby affecting the reduction in the uniformity of the laser irradiation intensity.

[0023]

According to the present invention, an incident lens provided on an optical axis of a laser beam oscillated from a laser oscillator, and a laser provided in front of the incident lens on the optical axis. A ride scope, a mask provided at an end of the kaleidoscope or on an emission side of the laser light on the optical axis, and selectively transmitting laser light output from the kaleidoscope; An imaging optical system provided on the emission side of the laser light on the optical axis.

According to the invention, there is provided a laser beam irradiation apparatus, wherein the mask is a mask having a tapered opening cross section.

According to the present invention, there is provided a laser beam irradiation apparatus, wherein the mask is a mask having a portion for scattering the laser beam.

According to the present invention, the mask having the scattered portion is a mask in which the emission portion of the laser light is formed by frosted glass, and the mask having the frosted glass is an optical waveguide of the kaleidoscope. A laser beam irradiation apparatus is characterized in that a portion having a diameter smaller than the optical waveguide diameter with respect to the center position of the path diameter has a transmittance higher than that of the ground glass.

According to the present invention, the ground glass is made of amorphous silicon dioxide or borosilicate crown glass, and the ground glass has a surface roughness of 0.5 μm.
There is provided a laser beam irradiation apparatus characterized by the above.

Further, according to the present invention, the mask is a mask formed of metal, and the mask formed of metal is based on the center position of the optical waveguide diameter of the kaleidoscope. The laser light irradiation device is characterized in that an opening having a diameter smaller than the diameter of the optical waveguide is provided.

According to the present invention, the material of the mask formed of the metal has a reflectance of 80% or more or a reflectance of 2% or more.
A laser light irradiation apparatus characterized by having a melting point of 500 ° C. or higher.

Further, according to the present invention, a light-transmitting portion provided on the mask and having a diameter smaller than the diameter of the optical waveguide with respect to the center position of the optical waveguide diameter of the kaleidoscope is formed around the optical waveguide. A laser beam irradiation device is characterized by being separated from each of the sides by 200 μm or more.

Further, according to the present invention, the kaleidoscope has a hermetically shielded pinhole plate at a laser beam entrance, and a hermetically shielded mask at a laser beam exit. The light-shielding portion of each of the pinhole plate and the mask is subjected to a reflection process with respect to a laser beam.

According to the present invention, the kaleidoscope is a polygonal cylinder or a polygonal column.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

First, an outline of a manufacturing process of a semiconductor device according to the present invention will be described with reference to FIG. 1. FIG. 1 shows a cross-sectional structure of a substrate and respective layers formed thereon in each manufacturing process. is there.

As shown in FIG. 1A, a silicon substrate 1
The wiring groove 3 (having a width of 0.6) is formed on the insulating film 2 formed thereon.
μm, a depth of 0.3 μm, and a total extension of the groove of about 50 mm). Next, as shown in FIG. 1B, a Cu film 4 having a thickness of about 0.3 μm is formed on the insulating film 2 by a sputtering method. Thereafter, as shown in FIG. 1C, the Cu film 4 is irradiated with XeCl excimer laser light L to melt the Cu film, thereby burying Cu in the wiring groove 3. In the state where the Cu is embedded, as shown in FIG.
To leave the Cu in the wiring groove 3 and the other insulating film 2
Is polished and removed. Next, FIG.
(E), an interlayer insulating film 6 is formed on the entire surface of the substrate 1 by the CVD method.

Thereafter, an interlayer connection port (not shown) is opened in the interlayer insulating film 6, and a second-layer Cu wiring is formed thereon. Further, a passivation film is formed thereon to form a pad.

The Cu of the above-described XeCl excimer laser beam L
When irradiating the film 4, it is required that the spatial intensity distribution of the irradiating laser beam LB be uniform. In order to satisfy this requirement, a means for making the laser beam LB uniform by a kaleidoscope is used.

Hereinafter, each embodiment will be described in more detail.

(Embodiment 1) Referring to FIGS. 2A to 2C, a laser beam L oscillated from a laser oscillator (not shown) is provided with an incident lens 7 and a laser beam sequentially arranged on an optical axis. A predetermined position of the irradiation object W is irradiated via the ride scope 8, the mask 20 and the imaging lens 9.

Callide scope 8 through incident lens 7
The laser light L incident on the inside repeatedly reaches the outlet 8E of the kaleidoscope 8 repeatedly in the kaleidoscope 8. At the exit 8E of the kaleidoscope 8, the light intensity distribution of the laser light L becomes the intensity distribution shown in FIG. 2B due to the generated interference fringes.

The laser beam L having this intensity distribution is applied to the mask 2
When the light passes through 0, the mask 20 has a light-transmitting portion formed only in the central portion, so that the peripheral portion having the interference fringes is cut, and only the central portion of the beam having a high degree of uniformity of the light intensity is transmitted.

Accordingly, the light intensity distribution of the laser beam LB transmitted through the mask 20 becomes a rectangular shape having a uniform light intensity distribution as shown in FIG. The laser beam LB is focused on a spot at a predetermined magnification to uniformly irradiate the irradiation object W.

FIG. 3 shows an example in which a metal mask 20m is used as the mask 20. In this case, assuming that the diameter of the optical waveguide of the kaleidoscope 8 is d × d, the metal mask 20m is smaller than the diameter of the optical waveguide 8d of the kaleidoscope 8. (D-
a) A metal mask 20m having an opening H of × (da). However, d> a, and a / 2 is an interference fringe generation area. Therefore, the interference fringe generating portions a / 2 at both ends are cut off from each side d of the optical waveguide by the metal mask 20m, and the laser light transmitted through the metal mask 20m is only uniform light without interference fringes.

Incidentally, both surfaces of the metal mask 20m are mirror-finished, and the luminous flux of the interference fringe region generated at the end of the exit 8E of the optical waveguide of the kaleidoscope 8 is absorbed by the metal mask 20m so that a uniform beam is formed. Occurrence was avoided. However, since the metal mask 20m absorbs the laser beam L, it is needless to say that the energy of the laser must be suppressed to a level that does not melt the metal mask 20m. FIG.
FIG. 4A shows a beam profile of a uniform beam obtained in this embodiment, and FIG. 4B shows a profile of a conventional uniform beam.

(Embodiment 2) The basic structure of the entire optical system is the same as that of Embodiment 1 as shown in FIG. In this embodiment, a tapered mask 20t having a tapered hole Ht at the center is used as a mask.

The laser light L incident on the kaleidoscope 8
The light intensity distribution at the exit 8E becomes the intensity distribution shown in FIG. 5B due to the generated interference fringes. When the laser beam L having this intensity distribution passes through the tapered mask 20t, the peripheral portion of the beam having the interference fringes is cut, and only the central portion of the beam having a high degree of uniformity of the laser beam L intensity is transmitted.

Accordingly, the light intensity distribution of the laser light L after passing through the tapered mask 20t is as shown in FIG. 5C, and the laser light L having this distribution is supplied to the pot at a predetermined magnification by the imaging lens 9. An image is formed and the object to be irradiated W is uniformly irradiated.

The use of the tapered mask 20t made it possible to clarify the image plane and obtain a sharp image at the spot.

(Embodiment 3) The basic structure of the entire optical system is the same as that of Embodiment 1 as shown in FIG. In this embodiment, a scattering mask 20d is used as a mask. The scattering mask 20d is entirely formed of a scattering plate, and has a hole Hd for transmitting the laser beam L at the center.

The laser light L incident on the kaleidoscope 8
The light intensity distribution at the exit 8E becomes the intensity distribution shown in FIG. 5B due to the generated interference fringes. When the laser beam L having this intensity distribution passes through the scattering mask 20d, the peripheral portion of the beam having the interference fringes is scattered, and only the central portion of the beam having a high degree of uniformity of the laser beam L intensity is transmitted. Therefore, the light intensity distribution of the laser beam L after passing through the scattering mask 20 is shown in FIG.
The result is as shown in FIG. The laser beam L having this distribution is imaged on the pot at a predetermined magnification by the imaging lens 9 to uniformly irradiate the irradiation object W.

When the scattering mask 20 is used, if the scattering is sufficiently large, the ratio of the scattered laser light L that passes through the imaging lens 9 is small. The strength is weak. On the other hand, the laser light L transmitted through the hole of the mask 20 has a high light intensity uniformity and a high laser light L intensity.

FIG. 7 shows an example in which ground glass is used as the scattering mask 20d. In this case, if the diameter of the optical waveguide of the kaleidoscope 8 is d × d, the ground glass mask 20
g is a ground glass mask 20g that is (da) × (da) transparent to the center position of the kaleidoscope 8 optical waveguide diameter 8d. However, d> a, and a / 2 is an interference fringe generation area.

The surface roughness of the ground glass part is 0.5 μm or more, and only the contacted surface of the kaleidoscope 8 is ground glass. The material is amorphous silicon nitrate or borosilicate crown glass. According to this, it is possible to obtain a high transmittance for ultraviolet rays.

The thickness of the ground glass mask 20 g is 1 m
m, 2 mm and 5 mm were used. As a result, the luminous flux in the interference fringe region generated at the exit 8E of the optical waveguide of the kaleidoscope 8 is diffused by frosted glass to avoid the occurrence of interference fringes in the uniform beam. FIG.
FIG. 8A shows a beam profile of a uniform beam obtained in this embodiment, and FIG. 8B shows a profile of a conventional uniform beam.

FIG. 9 shows that the exit end face of the kaleidoscope 8 is selectively ground glass processing. In this case, it is not necessary to separately provide a ground glass mask 20g.

This ground glass processing is also performed with respect to the center of the diameter of the optical waveguide 8d of the kaleidoscope 8 (d−a) × (d
-A) is a transparent ground glass mask 20. However,
Let d> a and a / 2 is the interference fringe generation area.

Thus, the luminous flux of the interference fringe region generated at the exit 8E of the optical waveguide of the kaleidoscope 8 is diffused by frosted glass to avoid the occurrence of interference fringes in the uniform beam.

(Embodiment 4) The basic structure of the entire optical system is the same as that of Embodiment 1 as shown in FIG. In this embodiment, a pinhole 31 is provided on the incident side of the kaleidoscope 8, and a mask 20 is provided on the exit 8E side. The inside of the surface of the pinhole 31 and the inside of the surface of the mask 20 are subjected to a process for highly reflecting the laser beam L.

Laser light L oscillated from a laser oscillator (not shown) passes through a pinhole via an incident lens 7 and enters a kaleidoscope 8. Callide scope 8
The reflection is repeated on the inner surface of the light emitting device and reaches the outlet 8E. At the exit 8E, the light intensity distribution is changed by the generated interference fringes as shown in FIG.
The intensity distribution shown in FIG. When the laser beam L having this intensity distribution passes through the mask 20, the peripheral portion of the beam having the interference fringes is scattered, and only the central portion of the beam having a high degree of uniformity of the laser beam L intensity is transmitted.

Accordingly, the laser beam L transmitted through the mask 20
Is as shown in FIG. 10 (c). The laser beam L having this distribution is imaged on a pot at a predetermined magnification by the imaging lens 9 to uniformly irradiate the irradiation object W.

On the other hand, the laser beam L reflected on the mask 20 surface of the kaleidoscope 8 returns to the entrance side while repeating reflection in the kaleidoscope 8, but is reflected on the pinhole surface at the entrance and again The reflection repeatedly reaches the mask 20 inside the scope 8, and a part of the light reaches the mask 2.
0 is transmitted through the imaging lens 9 to form an image on a spot, and the rest is reflected by the mask 20 to perform the same repetition.

Thus, the laser beam L that has been processed in the non-transmissive portion of the mask 20 can be effectively used.

[0063]

As described above, the present invention relates to an optical system using a kaleidoscope for equalizing the intensity of a laser beam.
By arranging various masks and the like that selectively transmit the laser light output from the kaleidoscope, a highly uniform laser beam LB free of the influence of interference fringes generated at the outlet of the kaleidoscope is obtained. I was able to do it.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cross-sectional structure of a substrate and respective layers formed thereon in respective manufacturing steps of a semiconductor manufacturing apparatus according to the present invention.

FIG. 2A is a configuration diagram illustrating an embodiment of the present invention.
(B) Waveform diagram at the exit of the kaleidoscope affected by the interference fringes in which the light intensity distribution of the laser light has occurred. (C) Waveform diagram showing the light intensity distribution of the laser beam transmitted through the mask.

FIG. 3 is an explanatory view showing an example in which a metal mask is used as a mask.

FIG. 4A shows a beam profile of a uniformized beam when a metal mask is used. (B) is a profile of a conventional uniform beam.

FIG. 5 (a) is a configuration diagram showing another embodiment of the present invention. (B) Waveform diagram at the exit of the kaleidoscope affected by the interference fringes in which the light intensity distribution of the laser light has occurred.
(C) Waveform diagram showing the light intensity distribution of the laser beam transmitted through the mask.

FIG. 6 (a) is a configuration diagram showing another embodiment of the present invention. FIG. 3B is a waveform diagram showing a light intensity distribution of the laser beam transmitted through the mask.

FIG. 7 is an explanatory view showing an example in which ground glass is used as a scattering mask.

FIG. 8A shows a beam profile of a uniform beam obtained when frosted glass is used as a mask. (B) is a profile of a conventional uniform beam.

FIG. 9 is an explanatory view showing an example in which a ground glass processing is selectively performed on an emission end face of a kaleidoscope.

FIG. 10A is an explanatory view of an example in which a pinhole is provided on the incident side of the kaleidoscope and a mask is provided on the exit side.
(B) Waveform diagram at the exit of the kaleidoscope affected by the interference fringes in which the light intensity distribution of the laser light has occurred. (C) Waveform diagram showing the light intensity distribution of the laser beam transmitted through the mask.

FIG. 11 is a configuration diagram of a kaleidoscope type beam homogenizer.

FIG. 12A is an explanatory diagram showing a comparison between the diameter of an optical waveguide emitted from a kaleidoscope and the diameter of an output from an incident lens in the absence of a kaleidoscope. (B) An enlarged view of a waveform in which interference fringes occur due to the interference effect of laser light.

FIG. 13 is a graph showing the occurrence of interference fringes in space by measuring the spatial phase of the excimer laser light in the X and Y directions.

FIG. 14 is a configuration diagram of an interference fringe measurement optical system.

FIG. 15 is a configuration diagram showing a conventional example of a kaleidoscope type beam homogenizer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... substrate, 2 ... insulating film, 3 ... wiring groove, 4 ... Cu film, 6 ...
Interlayer insulating film, 7: incident lens, 8: kaleidoscope,
9: imaging lens, 20: mask, 20m: metal mask, 20t: tape mask, 20d: scattering mask, 2
0g: ground glass mask

Claims (10)

[Claims] 1. An incident lens provided on an optical axis of a laser beam oscillated from a laser oscillator, a kaleidoscope provided in front of the incident lens on the optical axis, and an end of the kaleidoscope A mask provided on a portion or on the optical axis on the emission side of the laser beam, for selectively transmitting the laser beam output from the kaleidoscope; and an emission side of the laser beam on the optical axis of the mask And an imaging optical system provided in the laser beam irradiation apparatus. 2. The laser beam irradiation apparatus according to claim 1, wherein said mask is a mask having a tapered opening section. 3. The laser beam irradiation apparatus according to claim 1, wherein the mask is a mask having a portion that scatters the laser beam. 4. A mask having the scattered portion is a mask in which the laser light emitting portion is formed by frosted glass, and the mask having the frosted glass has a center position of an optical waveguide diameter of the kaleidoscope. The laser beam irradiation device according to claim 3, wherein a portion having a diameter smaller than the diameter of the optical waveguide has a transmittance higher than that of the ground glass. 5. The material of the ground glass is amorphous silicon dioxide or borosilicate crown glass, and
4. The laser beam irradiation device according to claim 3, wherein the surface roughness of the ground glass portion is 0.5 μm or more. 6. The mask formed of a metal, and the mask formed of the metal is smaller than the diameter of the optical waveguide with respect to the center position of the optical waveguide diameter of the kaleidoscope. The laser beam irradiation device according to claim 1, wherein an opening having a diameter is provided. 7. The laser beam irradiation apparatus according to claim 6, wherein a material of the mask formed of the metal has a property of a reflectance of 80% or more or a melting point of 2500 ° C. or more. 8. A light-transmitting portion provided on the mask and having a diameter smaller than the diameter of the optical waveguide of the kaleidoscope based on the center position of the optical waveguide of the kaleidoscope is 200 μm from each of four sides around the optical waveguide. 7. The laser beam irradiation device according to claim 4, wherein the laser beam irradiation devices are separated from each other. 9. The kaleidoscope has a hermetically sealed light-shielded pinhole plate at a laser light entrance, and a hermetically sealed light-shielded mask at a laser light emission opening. 2. The laser beam irradiation apparatus according to claim 1, wherein each light shielding portion of the mask is subjected to a reflection process with respect to a laser beam. 10. The laser beam irradiation apparatus according to claim 1, wherein said kaleidoscope is a polygonal cylinder or a polygonal column.