JP4204689B2 - 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, it is difficult to make the radiation characteristic of the electromagnetic wave from the slot formed in the waveguide wall uniform in the entire region on the slot, and usually has a sinusoidal or similar distribution in the slot long axis direction. . That is, as shown in FIG. 9A, the electric field strength distribution at the center in the slot major axis direction is the largest, and the electric field strength distribution at the end in the slot major axis direction is the smallest.
[0006]
Furthermore, as shown in FIG. 9B, the microwave electric field strength distribution has a property that the excited plasma gathers at the center in the slot major axis direction, and the electric field strength in the slot major axis direction is not uniform. Distribution is encouraged. This is a major factor that makes it impossible to make the plasma excited in the longitudinal direction of the slot uniform.
[0007]
This phenomenon is characterized in that the intensity of the electromagnetic wave, which is the excitation source, is strongest at the central position in the longitudinal direction of the slot, so that the plasma is easily excited at the central position, and the excited plasma is likely to gather in a spherical shape with a minimum surface area. This is due to the nature. The plasma excited at the center position forms a low-impedance region in the center of the slot, where energy is preferentially consumed, and the plasma acts as a shield and is designed to emit microwaves. The slot length that has been set is half that of the microwave, and the microwave is not emitted outside the slot. Due to these two factors, the plasma is easily formed only at the center of the slot, and it is extremely difficult to excite a uniform plasma on the slot.
[0008]
The present invention has been made to solve such a problem, and adopts a slot array structure, but realizes uniform plasma excitation over the longitudinal direction of each slot, thereby reducing energy loss. It is an object of the present invention to provide a laser oscillation apparatus capable of uniform laser emission with as much suppression as possible, a high-performance exposure apparatus equipped with the laser oscillation apparatus, and a method for manufacturing a high-quality device using the exposure apparatus. .
[0009]
[Means for Solving the Problems]
The laser oscillation device of the present invention excites a laser gas in the laser tube by introducing electromagnetic waves into the laser tube through a plurality of minute gaps formed on the waveguide wall from the waveguide, and emits light from the laser gas. In the laser oscillation device that resonates and generates laser light, each of the micro gaps is a portion where the emission characteristics of the electromagnetic waves depending on the micro gaps conflict with the intensity distribution of the electromagnetic waves propagated in the waveguide, It is formed so that the minimum value of the intensity distribution of the electromagnetic wave propagating in the waveguide is located at a substantially central portion of the minute gap.
[0011]
In one aspect of the laser oscillation device of the present invention, the minute gaps are formed in a row with the guide wavelength or half wavelength in the waveguide of electromagnetic waves as a pitch.
[0012]
In one aspect of the laser oscillation device of the present invention, the electromagnetic wave introduced from the waveguide is a microwave.
[0013]
In one aspect of the laser oscillation device of the present invention, the laser gas may be at least one inert gas selected from Kr, Ar, Ne, or a mixed gas of the at least one inert gas and F ₂ gas. An excimer laser oscillation device.
[0014]
The exposure apparatus of the present invention includes the laser oscillation device that is a light source that emits illumination light, a first optical system that irradiates illumination light from the laser oscillation device to a reticle on which a predetermined pattern is formed, and the reticle. A second optical system that irradiates the irradiated surface with illumination light, and projects a predetermined pattern of the reticle onto the irradiated surface for exposure.
[0015]
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.
[0016]
In one aspect 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.
[0017]
[Action]
In the laser oscillation device of the present invention, each minute gap is formed at a site where the emission characteristics of the electromagnetic wave in the minute gap conflict with the intensity distribution of the electromagnetic wave propagated in the waveguide. Here, the electromagnetic wave emission characteristics depending on the minute gap show a distribution in which the electromagnetic wave intensity has the maximum value at the central part of the minute gap and becomes smaller as it approaches the end of the minute gap as described above. If a minute gap is formed at a position where the intensity distribution of the propagating electromagnetic wave is opposite to this, the intensity distribution of the electromagnetic wave propagating in the waveguide is affected by the intensity distribution due to the electromagnetic wave emission characteristics depending on the minute gap. As a result, the uniformity of the intensity distribution of the electromagnetic waves actually emitted from each minute gap is enhanced over the entire area of each minute gap.
[0018]
Specifically, assuming an E-plane antenna, for example, if each minute gap is formed in a line with the wavelength in the waveguide of the electromagnetic wave or the half wavelength thereof as a pitch, the intensity distribution of the electromagnetic wave propagated in the waveguide Each minute gap is formed so that the minimum value is located at a substantially central portion of the minute gap. That is, according to the intensity distribution of the electromagnetic wave propagating in the waveguide, each micro gap is uniformly λg from the position corresponding to the maximum value of the electromagnetic wave emission intensity distribution at the central portion of each micro gap. The minute gap is formed at a position shifted by / 4 (λg: in-tube wavelength). By such a method relatively easily, it is possible to further uniform the intensity distribution of the electromagnetic wave emitted from each minute gap.
[0019]
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.
[0020]
(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.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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 introduced into the laser tube 2 from the slot 10 while propagating through the waveguide 1. . The excimer laser gas in the laser tube 2 is excited by the introduced microwave and resonates to generate excimer laser light.
[0025]
In this embodiment, on the E plane of the waveguide 1, the slots 10 are formed in a line in the longitudinal direction at a pitch of λg (λg: guide wavelength), and each slot 10 depends on the slot 10. It is formed at a site where the microwave emission characteristics conflict with the intensity distribution of the microwave propagated in the waveguide 1.
[0026]
A specific state of each slot 10 is shown in FIG.
As shown in FIG. 2, in the comparative example (a), the microwave intensity distribution (in the example shown in the figure, the density distribution of the current flowing through the wall surface of the waveguide 1 is represented by the microwave intensity distribution in the central portion of the slot 10. Each slot 10 is formed at a position corresponding to the maximum value of the same). In this case, as described above, the intensity distribution due to the microwave emission characteristic depending on the slot 10 is Since the intensity distribution of the microwave propagated in the waveguide 1 is substantially the same, the intensity distribution of the microwave is as shown in FIG.
[0027]
On the other hand, in the embodiment (b) of FIG. 2, each slot 10 is uniformly arranged from the position corresponding to the central portion of the slot 10 of the comparative example (a) so that the maximum value of the intensity distribution of the microwaves matches. The slot 10 is formed at a position shifted by λg / 4.
[0028]
As a result, each slot 10 exists so that the minimum value of the intensity distribution of the microwave propagated in the waveguide 1 is located at a substantially central portion of the slot 10. The intensity distribution of the microwaves affected by the intensity distribution due to the emission characteristics of the microwaves depending on the slot 10, and as shown in FIG. 3, the uniformity of the intensity distribution of the microwaves actually emitted from each slot 10 Will increase.
[0029]
In this example, the case where the slot 10 is formed on the so-called E-plane of the waveguide 1 is illustrated, and the same argument holds even when a so-called H-plane antenna having the slot 10 formed on the H-plane is used. Needless to say.
[0030]
Further, as shown in FIG. 4, the present invention is also applicable to the case where the slots 10 are formed in a line in the longitudinal direction at a pitch of λg / 2. Here, as in FIG. 2, an example (b) for the comparative example (a) is shown. Similarly in this case, as shown in FIG. 3, the uniformity of the intensity distribution of the microwaves actually emitted from each slot 10 is increased.
[0031]
Specifically, microwave irradiation of an aluminum alloy housing of 2.45 GHz using an E-plane emission antenna having a size of a = 42 mm and b = 21 mm and a waveguide resonator length of 220.8 mm (length in the laser oscillation direction). I made an antenna. The waveguide resonator length is filled with alumina having a dielectric constant of 9.8. At this time, the guide wavelength in the waveguide resonator is 44.2 mm. Accordingly, the slot pitch is set to 44.2 mm and 22.1 mm in the case of λg pitch and λg / 2 pitch, respectively.
[0032]
When the slot is formed at a position corresponding to the current density antinode (the strongest part), sin-shaped irradiation as shown in FIG. 5A is obtained.
[0033]
On the other hand, when the slot is formed by shifting by λg / 4, the standing wave intensity distribution as shown in FIG. 5B is obtained.
[0034]
Accordingly, the intensity distribution of the microwaves emitted from the slots by this excitation is as shown in FIG. 5C, and irradiation with higher uniformity than in the case of FIG. 5A can be realized. Recognize.
[0035]
Note that this radiation characteristic is a characteristic of the slot alone in the absence of plasma, and since plasma is actually present, more uniform excitation occurs when propagation in the sheath portion is taken into consideration. I can expect that.
[0036]
As described above, according to the excimer laser oscillation device of the present embodiment, even though the slot array structure is adopted, uniform plasma excitation is realized over the longitudinal direction of each slot, and energy loss is suppressed as much as possible. And uniform laser emission.
[0037]
(Second Embodiment)
Hereinafter, the second embodiment will be described. In the second embodiment, an exposure apparatus (stepper) having the excimer laser oscillation apparatus described in the first embodiment as a laser light source is exemplified. FIG. 6 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 includes the excimer laser oscillation device 121 according to the first embodiment, which is a light source that emits high-luminance excimer laser light as illumination light, and beam shape conversion that converts illumination light from the light source 121 into a desired light beam shape. A secondary light source formed by the optical integrator 123, which can be switched to an arbitrary aperture by 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). The diaphragm member 124 is arranged near the position of the lens, the condenser lens 125 that collects the illumination light that has passed through the diaphragm member 124, and four variable blades, for example. Blind 127 that arbitrarily determines the illumination range on the surface of the screen, and Blind 1 7 has an imaging lens 128 for projecting the illumination light determined in a predetermined shape onto the surface of the reticle 101, and a folding 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. 6 will be described.
[0044]
FIG. 7 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. 8 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, even when the slot array structure is adopted, uniform plasma emission can be realized with the energy loss suppressed as much as possible by realizing uniform plasma excitation over the longitudinal direction of each slot.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a main configuration of an excimer laser oscillation device according to a first embodiment.
FIG. 2 is a schematic diagram showing the relationship between a slot formation site in a waveguide and the density of current flowing through the wall surface of the waveguide.
FIG. 3 is a characteristic diagram showing an intensity distribution of microwaves emitted from slots in the present embodiment.
FIG. 4 is a schematic diagram showing a relationship between a slot formation site in a waveguide and the density of current flowing through the wall surface of the waveguide in another example of the present embodiment.
FIG. 5 is a characteristic diagram showing the relationship between the slot position and the radiant energy or standing wave intensity for the slot formed in the waveguide according to the present embodiment.
FIG. 6 is a schematic diagram showing a stepper according to a second embodiment.
FIG. 7 is a flowchart of a semiconductor device manufacturing process using the stepper of the second embodiment.
FIG. 8 is a flowchart showing the wafer process in FIG. 7 in detail.
FIG. 9 is a characteristic diagram showing the intensity distribution of microwaves emitted from slots in a conventional waveguide.
[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 Passage 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 (7)

The laser gas in the laser tube is excited by introducing electromagnetic waves into the laser tube through a plurality of minute gaps formed on the waveguide wall from the waveguide, and the laser beam is generated by resonating the light emitted from the laser gas. In the laser oscillation device to be
Each of the micro gaps is a portion where the emission characteristic of the electromagnetic wave depending on the micro gap is opposite to the intensity distribution of the electromagnetic wave propagated in the waveguide, and the minimum of the intensity distribution of the electromagnetic wave propagated in the waveguide A laser oscillation device, wherein the value is formed so that the value is located at a substantially central portion of the minute gap.   2. The laser oscillation device according to claim 1, wherein each of the minute gaps is formed in a line with an in-tube wavelength or a half wavelength thereof in a waveguide of electromagnetic waves as a pitch.   The laser oscillation apparatus according to claim 1 or 2, wherein the electromagnetic wave introduced from the waveguide is a microwave. It is an excimer laser oscillation device using the laser gas as at least one inert gas selected from Kr, Ar, Ne or a mixed gas of the at least one inert gas and F ₂ gas. The laser oscillation device according to any one of claims 1 to 3. It is a light source which emits illumination light, The laser oscillation apparatus of any one of Claims 1-4,
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 5 to perform exposure of a predetermined pattern on the irradiated surface to which the photosensitive material is applied; and
And a step of developing the photosensitive material that has been exposed to the predetermined pattern.   7. The device manufacturing method according to claim 6, wherein the irradiated surface is a wafer surface, and a semiconductor element is formed on the wafer surface.

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