JP4302810B2 - Laser oscillation apparatus, exposure apparatus, and device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser oscillation device that generates laser light by introducing electromagnetic waves into a laser tube through a plurality of minute gaps formed on a waveguide wall from the waveguide, and particularly as an electromagnetic wave for laser gas excitation. It is suitable for application to a laser oscillation apparatus using a microwave, an exposure apparatus provided with the same, and a device manufacturing method.
[0002]
[Prior art]
In recent years, so-called excimer lasers have attracted attention as the only high-power lasers that oscillate in the ultraviolet region. Specifically, in the electronics industry, chemical industry, energy industry, etc., specifically metals, resins, glass, ceramics, semiconductors, etc. Applications are expected for processing and chemical reactions.
[0003]
The functional principle of the excimer laser oscillation device will be described. First, a laser gas such as Ar, Kr, Ne, or F ₂ filled in the manifold is brought into an excited state by electron beam irradiation or discharge. At this time, the excited F atoms are combined with inactive Kr and Ar atoms in the ground state to generate KrF ^* and ArF ^* which are molecules existing only in the excited state. This molecule is called an excimer. Excimer is unstable and immediately emits ultraviolet light and falls to the ground state. This is called bond-free transition or spontaneous light emission. Excimer laser oscillation device uses this excited molecule to amplify it as light with the same phase in an optical resonator composed of a pair of reflectors and extract it as laser light. It is.
[0004]
[Problems to be solved by the invention]
When excimer laser light is emitted, a microwave is mainly used as a laser gas excitation source as described above. The microwave is an electromagnetic wave having an oscillation frequency of several hundred MHz to several tens GHz. In this case, a microwave is introduced into the laser tube through a gap (slot) formed in the waveguide wall from the waveguide, thereby exciting the laser gas in the laser tube into a plasma state.
[0005]
However, although plasma is generated in the vicinity of the microwave emission surface on the slot, in the plasma sheath formed on the slot, the microwave can be propagated, and as a result, the microwave is short in the slot through the sheath region. Since it spreads in the axial direction and the input power is dispersed, the energy density required for excimer laser excitation cannot be satisfied. This is because when the plasma is diffused in a wide space, it is difficult to realize an energy density sufficient to excite the excimer by dispersing the energy used for generating the plasma.
[0006]
FIG. 8 is a schematic view showing a state in which microwaves propagate through the plasma sheath, and shows a cross section along a direction perpendicular to the longitudinal direction of the slot.
[0007]
The plasma is not electrically grounded on the slot, but the outside thereof is basically directly grounded to the waveguide 1, and the potential difference in the sheath, the sheath width, and the like are different between the two. For this reason, when the plasma density is not sufficient, the sheath becomes thick, and the microwave easily leaks to the outside unevenly. As a result, a phenomenon occurs in which the plasma is thin immediately above the slot opening end and becomes high density outside.
[0008]
The present invention has been made to solve such a problem, and adopts a slot array structure, but suppresses diffusion of plasma generated on the slot and suppresses energy loss as much as possible. It is an object of the present invention to provide a laser oscillation apparatus that can emit light, a high-performance exposure apparatus including the laser oscillation apparatus, and a high-quality device manufacturing method using the exposure apparatus.
[0009]
[Means for Solving the Problems]
The laser oscillation device of the present invention generates plasma by exciting a laser gas in the laser tube by introducing a microwave into the laser tube through a plurality of slots formed on the waveguide wall from the waveguide, A laser oscillation device for generating laser light by resonating light emitted from the plasma, wherein the plurality of slots are arranged in a line along a longitudinal direction of the waveguide, and the longitudinal direction of the slots is Shielding structures that are arranged to coincide with the longitudinal direction of the waveguide and suppress the diffusion of the plasma are provided on both sides of the slot in parallel to the longitudinal direction of the slot , and each of the slots has a plurality of rows. It consists of a slit, the slit has an opening so that its longitudinal direction coincides with the longitudinal direction of the slots, slits in the column of the end portion of the plurality of rows The width of the short-side direction is smaller than the short-side direction of the width of the slit in the column near the center of the plurality of rows of.
[0013]
In an embodiment of a laser oscillating apparatus of the present invention, the in plurality of rows of slits, the length of the longitudinal slits in the column of the end portion is smaller than the longitudinal length of the slit in the column near the center.
[0015]
The exposure apparatus of the present invention is a light source that emits illumination light, and the laser oscillation device according to claim 1 or 2, and a first optical system that irradiates the reticle on which a predetermined pattern is formed with illumination light from the laser oscillation device. And a second optical system that irradiates the surface to be irradiated with illumination light through the reticle, and performs exposure by projecting a predetermined pattern of the reticle onto the surface to be irradiated.
[0016]
The device manufacturing method of the present invention includes a step of applying a photosensitive material to an irradiated surface, a step of exposing a predetermined pattern on the irradiated surface applied with the photosensitive material using the exposure apparatus, Developing the photosensitive material that has been exposed in a predetermined pattern.
[0017]
In one embodiment of the device manufacturing method of the present invention, the irradiated surface is a wafer surface, and a semiconductor element is formed on the wafer surface.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.
[0019]
(First embodiment)
First, the first embodiment will be described. In the present embodiment, an excimer laser oscillation device that emits so-called excimer laser light is exemplified. FIG. 1 is a schematic diagram showing the main configuration of the excimer laser oscillation apparatus of the present embodiment.
[0020]
As shown in FIG. 1, the excimer laser oscillation apparatus is configured to excite an excimer laser gas in a laser tube 2 that emits laser light by resonating light emitted by excitation of an excimer laser gas, and to make a plasma state. In order to cool the waveguide 1 and the waveguide 1, a cooling vessel 7 having a cooling water inlet / outlet 9 is provided.
[0021]
The excimer laser gas used as a raw material for generating excimer laser light is one or more inert gases selected from Kr, Ar, and Ne, or a mixed gas of the one or more inert gases and F ₂ gas. is there. Of these, the gas species may be appropriately selected and combined depending on the wavelength to be used. For example, when it is desired to generate a laser beam having a wavelength of 248 nm, Kr / Ne / F ₂ is used. For a wavelength of 193 nm, Ar / Ne / F _{2 is used} . For a wavelength of 157 nm, Ne / F ₂ is used. do it.
[0022]
The laser tube 2 is provided with a laser gas inlet / outlet 8 serving as a portion for introducing an excimer laser gas into the tube, and reflection structures 5 and 6 at each end, respectively. Are aligned and laser light is generated.
[0023]
The waveguide 1 is means for supplying microwaves to the laser gas in the gas supply path structure 11, and a plurality of elongated slots 10 are formed on the upper surface portion in FIG. When a microwave having a frequency of several hundred MHz to several tens GHz is introduced from the upper part of the waveguide 1, the microwave is emitted from the slot 10 to the outside of the waveguide 1 while propagating through the waveguide 1. Is done. The emitted microwave is introduced into the laser tube 2. The excimer laser gas in the laser tube 1 is excited by the introduced microwave and resonates to generate excimer laser light.
[0024]
A specific state of the waveguide 1 is shown in FIG. Here, FIG. 2A is a schematic perspective view of the waveguide 1, and FIG. 2B is a plan view thereof.
[0025]
As shown in FIG. 2B, the slots 10 are arranged in a row so that the longitudinal direction thereof coincides with the longitudinal direction of the waveguide 1. The slots 10 are arranged along the longitudinal direction of the waveguide 1 , and each has a shape extending in the longitudinal direction of the waveguide 1 .
[0026]
FIG. 3 shows a cross section of the waveguide 1 in the vicinity of the laser tube 2 in the first embodiment. Here, FIG. 3 shows a cross section along a direction perpendicular to the longitudinal direction of the slot 10.
[0027]
Microwaves are radiated from the slot 10 formed in the waveguide 1 to generate plasma on the slot 10. A sheath is formed between the plasma and the open end of the slot 10. In the present embodiment, considering the uniform propagation of microwaves, the diameter (width) of the slot 10 is set to be equal to or less than the thickness of the sheath (10 μm to 100 μm). Therefore, it is possible to suppress the propagation of the microwave to the side of the slot 10 and generate plasma only on the slot 10. Here, it is preferable that the magnitude of the plasma protrusion on the slot 10 is, for example, 1/10 or less of the laser beam diameter and has little influence on the laser oscillation.
[0028]
As described above, according to the first embodiment of the present invention, by making the width of the slot 10 smaller than the wavelength of the microwave, the plasma diffuses from the slot 10 to the side through the sheath. Can be suppressed.
[0029]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings.
In the second embodiment, the slot 10 is configured by a plurality of slits 11. In addition, since the whole structure of the excimer laser oscillation apparatus in 2nd Embodiment is the same as that of the 1st Embodiment, description is abbreviate | omitted. In the drawings for explaining the second embodiment, components substantially the same as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0030]
As described in the first embodiment, when the width of the slot 10 is an ultrafine shape that is equal to or smaller than the wavelength of the microwave, the width in the short side direction of the slot 10 is narrow, so that the aperture ratio cannot be obtained and the emission efficiency is high. The case where it falls is assumed. The second embodiment is different from the first embodiment in that the slot 10 has a configuration in which a plurality of slits 11 are arranged in parallel to prevent this, and the emission efficiency is increased.
[0031]
FIG. 4 shows a plan view of the waveguide 1 in which a slot 10 composed of a plurality of slits 11 is formed. FIG. 5 is a schematic diagram showing a cross section perpendicular to the longitudinal direction of the slit 11.
[0032]
In this way, by arranging a plurality of the ultrathin slits 11 in parallel, a desired aperture ratio can be obtained, and plasma can be generated uniformly on the slots 10 arranged in parallel.
[0033]
FIG. 6 shows an example in which the width of the slit 11a at the end is made narrower than the width of the slit 11 at the center when the slits 11 are arranged in parallel.
[0034]
When the metal wall 15 or the like is formed in the short side direction of the opening end of the slot 10 (slit 11) for the purpose of preventing the plasma generated in the short side direction of the slit 11 from diffusing, Since more plasma is generated along the position, there may be a problem in ensuring the uniformity of the plasma. As shown in FIG. 6, the microwave radiated from the slit 11a is made narrower than the width of the slit 11 located at the end in the short side direction than the width of the slit 11 located at the center. Therefore, the plasma generated on the slot 10 can be made uniform as a whole.
[0035]
In addition, as shown in FIG. 7, the generation of uniform plasma on the slot 10 is realized by suppressing the generation of plasma near the metal wall 15 by shortening the length of the slit 11 b at the end. can do. Needless to say, this effect is the same as that of a metal wall for a microwave, that is, a similar result can be obtained if the structure enables microwave confinement.
[0036]
As described above, according to the second embodiment, by arranging the ultrafine slits 11a in parallel, the microwave emission efficiency can be increased, and plasma can be generated uniformly on the slot 10. Become.
[0037]
(Third embodiment)
Hereinafter, a third embodiment will be described. In the third embodiment, an exposure apparatus (stepper) having the excimer laser oscillation apparatus described in the first embodiment as a laser light source is exemplified. FIG. 9 is a schematic diagram showing the main configuration of this stepper.
[0038]
The stepper includes an optical system 111 for irradiating illumination light onto a reticle 101 on which a desired pattern is drawn, and illumination light incident through the reticle 101, and the pattern of the reticle 101 is reduced and projected onto the surface of the wafer 102. A projection optical system 112, a wafer chuck 113 on which the wafer 102 is placed and fixed, and a wafer stage 114 on which the wafer chuck 113 is fixed.
As the reticle, not only a transmission type (reticle 101) but also a reflection type can be applied as shown in the figure.
[0039]
The optical system 111 converts the excimer laser oscillation device 121 according to the first embodiment, which is a light source that emits high-intensity excimer laser light as illumination light, and the illumination light from the excimer laser oscillation device 121 into a desired light beam shape. The beam shape converting means 122, an optical integrator 123 in which a plurality of cylindrical lenses and microlenses are two-dimensionally arranged, and a switching means (not shown) can be switched to an arbitrary aperture, and formed by the optical integrator 123. The diaphragm member 124 is disposed near the position of the secondary light source, the condenser lens 125 that collects the illumination light that has passed through the diaphragm member 124, and four variable blades, for example, and is disposed on the conjugate surface of the reticle 101. Blind 12 for arbitrarily determining the illumination range on the surface of the reticle 101 And an imaging lens 128 for projecting the illumination light determined in a predetermined shape by the blind 127 onto the surface of the reticle 101, and a bending mirror 129 for reflecting the illumination light from the imaging lens 128 in the direction of the reticle 101. It is configured.
[0040]
An operation for reducing and projecting the pattern of the reticle 101 onto the surface of the wafer 102 using the stepper configured as described above will be described.
[0041]
First, the illumination light emitted from the light source 121 is converted into a predetermined shape by the beam shape conversion unit 122 and then directed to the optical integrator 123. At this time, a plurality of secondary light sources are formed in the vicinity of the emission surface. Illumination light from the secondary light source is collected by the condenser lens 125 through the diaphragm member 124, and after being determined to have a predetermined shape by the blind 127, is reflected by the bending mirror 129 through the imaging lens 128 and reflected by the reticle 101. Is incident on. Subsequently, the light passes through the pattern of the reticle 101 and enters the projection optical system 122. Then, the pattern passes through the projection optical system 122, is reduced to a predetermined size, projected onto the surface of the wafer 102, and exposed.
[0042]
According to the stepper of the present embodiment, since the excimer laser oscillation apparatus of the first embodiment is used as a laser light source, high-power and uniform excimer laser light can be emitted for a relatively long time, and exposure to the wafer 102 can be performed. The exposure can be performed quickly and accurately.
[0043]
Next, an example of a method for manufacturing a semiconductor device (semiconductor device) using the projection exposure apparatus described with reference to FIG. 10 will be described.
[0044]
FIG. 10 shows a flow of a manufacturing process of a semiconductor device (a semiconductor chip such as an IC or LSI, or a liquid crystal panel or a CCD). First, in step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by photolithography using the mask and wafer prepared as described above. The next step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), etc. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).
[0045]
FIG. 11 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), a conductive film or an insulating film is formed on the wafer surface using a vapor phase reaction. In step 13 (PVD), a conductive film or an insulating film is formed on the wafer by sputtering or vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed on the wafer by exposure using the projection exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
[0046]
By using this manufacturing method, it is possible to easily and surely manufacture a highly integrated semiconductor device that has been difficult to manufacture with high yield.
[0047]
【The invention's effect】
According to the present invention, it is possible to prevent plasma from diffusing out of a predetermined range from the individual slots. Accordingly, it is possible to provide a laser oscillation apparatus that enables uniform laser emission with as little energy loss as possible, a high-performance exposure apparatus including the laser oscillation apparatus, and a method for manufacturing a high-quality device using the exposure apparatus. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the main configuration of an excimer laser oscillation apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a specific state of the waveguide of the excimer laser oscillation apparatus according to the first embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing a slot in the laser oscillation apparatus according to the first embodiment of the present invention.
FIG. 4 is a schematic plan view showing slots in the laser oscillation apparatus according to the first embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing a slot in a laser oscillation device according to a second embodiment of the present invention.
FIG. 6 is a schematic diagram showing slots in a laser oscillation apparatus according to a second embodiment of the present invention.
FIG. 7 is a schematic plan view showing slots in a laser oscillation apparatus according to a second embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view for explaining a sheath formed on a slot in a conventional laser oscillation device.
FIG. 9 is a schematic view showing a stepper according to a third embodiment of the present invention.
FIG. 10 is a flowchart of manufacturing steps of a semiconductor device using a stepper according to a third embodiment of the present invention.
11 is a flowchart showing the wafer process in FIG. 10 in detail.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Waveguide 2 Laser tube 5, 6 Reflective structure 7 Cooling container 8 Laser gas introduction exit 9 Cooling water introduction exit 10 Slot 11, 11a, 11b Slit 15 Metal wall 101 Reticle 102 Wafer 111 Optical system 112 Projection optical system 113 Wafer chuck 114 Wafer stage 121 Excimer laser oscillation device 122 Beam shape conversion means 123 Optical integrator 124 Aperture member 125 Condenser lens 127 Blind 128 Imaging lens 129 Bending mirror

Claims (5)

A microwave is introduced into the laser tube from the waveguide through a plurality of slots formed on the waveguide wall to excite the laser gas in the laser tube to generate plasma, and the light emitted from the plasma is resonated. A laser oscillation device for generating laser light,
The plurality of slots are arranged in a line along the longitudinal direction of the waveguide,
The slot is arranged such that its longitudinal direction coincides with the longitudinal direction of the waveguide;
Shielding structures that suppress the diffusion of the plasma are provided on both sides of the slot in parallel with the longitudinal direction of the slot,
Each of the slots is composed of a plurality of rows of slits, and the slits have openings so that the longitudinal direction thereof coincides with the longitudinal direction of the slots, and the slots are arranged in the short side direction of the slits in the end rows of the plurality of rows . A laser oscillation device characterized in that a width is smaller than a width in a short side direction of a slit in a row near the center of the plurality of rows . Wherein the plurality of rows of slits, the longitudinal length of the slit in the column of the end, the laser oscillation apparatus according to claim 1, characterized in that less than the longitudinal length of the slit in the column near the center. The laser oscillation device according to claim 1 or 2, which is a light source that emits illumination light;
A first optical system that irradiates illumination light from the laser oscillation device onto a reticle having a predetermined pattern;
A second optical system for irradiating the illuminated surface with illumination light via the reticle,
An exposure apparatus that performs exposure by projecting a predetermined pattern of the reticle onto the irradiated surface. Applying a photosensitive material to the irradiated surface;
Using the exposure apparatus according to claim 3 to perform a predetermined pattern exposure on the irradiated surface to which the photosensitive material is applied;
And a step of developing the photosensitive material that has been exposed to the predetermined pattern.   The device manufacturing method according to claim 4, wherein the irradiated surface is a wafer surface, and a semiconductor element is formed on the wafer surface.

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