JPS60202936A - Radiation source used for optical device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention-91-1
The present invention relates to a radiation source for use in a photolithographic exposure system, such as for exposing a photosensitive layer on a semiconductor wafer using a radiation source with a radiation power higher than that of a high pressure mercury lamp.

A large number of radiation sources are known whose properties are adapted to the conditions of the equipment in which they are to be used.

Such conditions include the spectral distribution of the radiation,
The maximum width side density and the spectral and angular distribution of the generated radiation are mentioned.The spectral radiation output exceeds the spectral radiation output of a black body and is above the melting point of various solid trees. can only be realized with plasma.

Generally, plasmas are created, for example, by applying a high frequency electromagnetic field to a medium or passing an electric current through it.

The spectral radiation density reached is the tl of the excited medium 4. :Due to the maximum power available per l-volume ram,
It is also limited by the electrode capacity, or even by the fact that the cavity wall material must be able to withstand it thermally.

When using radio-frequency heating, the various limitations imposed by the electrodes that would otherwise be used do not exist; however, concentrating the radio-frequency energy within a limited space is a major problem. It is.

If the radiation source is not operated continuously, an increase in power of up to several tens of degrees will be more than enough if the energy delivered has an adverse effect on the walls of the launch vessel and its ripolar poles, if present. If it is converted into radiation very quickly, it is possible for a very short period of time. Apart from the various disadvantages of mechanical stresses on the %p plane of the launch vessel, which are fatal only under unfavorable conditions, due to the regular shock waves of this type of operation, the wall material Evaporation and wear of the electrode material must meet the specified lifetime of the radiation source, which is a minor obstacle to producing a dense radiation flux.

Radiation t of both classes, i.e. continuous radiation and pulsed radiation
When using a radiant FA source that exceeds a certain power level, which depends on its particular type as a J4 source and which in practice is achieved with all technical means developed so far, its radiant power can be further increased. - can only be achieved at the expense of a very significant reduction in the longevity of the equipment.

However such a short lifespan! ) sources are unsuitable for many applications, for example because replacing a single lamp generally requires a great deal of adjustment effort, and the optical system is not suitable for each individual lamp. For the operation and maintenance of the various equipment in which such radiation sources are employed, given the lengthy work that must be carried out to adapt the respective radiation fluxes, This is because the work will increase excessively.

The desired radiation wavelength comprising the supplied electrical energy and 1
) (By selectively converting the desired direction of propagation, the radiation output can be increased within certain limits without exceeding the maximum load of the axial source).

This is due to the optimal composition of the medium and /19 of the plasma.
．． It is possible to set the pressure and temperature to the optimum conditions during use.

However, different working media of electrode material J3 and electrode material (
Δ 31st, due to the incompatibility with its operating temperature.
; it is necessary to take into account the various limitations introduced by . Still other limitations result from the dual functionality of the radiation source in pulsed operation, both as a high-power electrical switch and as a converter for converting electrical energy into radiation.

Again, the optimum range for effective radiation generation is limited because reliable ignition and maintenance of continuity is dependent on the specific conditions of the plasma. A disadvantage of radiation sources using various electrodes in continuous and pulsed operation is that certain parts of the discharge space are shadowed and the radiation therefore ages and cannot be fully developed.

Furthermore, for example, the magazine SP [E Vol. 174, No. 28-3
M 1chcl l acomba on page 6 (1979)
Since "coherent irradiation improves step-and-repeat printing on wafers" has been reported by T et al., each optical system is sufficiently illuminated during the process of forming fine structures on a wafer by microlithography. It is known to use lasers to

This J:una light source is disadvantageous due to the inclusion of a very high spatial coherence, which leads to structural distortions, and also has a high monochromaticity (monochromaticity).
cy) is raw and the other is ni#i1" so (7) photosensitive 1
JII standing wave breakwater effect standing-
wave ef-fcct).

High power and high efficiency laser devices are generally not available on the market for the most advantageous spectral ranges.

The use of "E This is because the necessary degree of spatial incoherence cannot be achieved in a culm sufficient for its technical use (Magazine 5PIE Vol. 334, 259-282)
(1982), Jain et al.
(See "Ultrahigh-speed F/i' image contact lithography using r l-asOr").

Excuse attempts to resolve. 1. One of the objects of the present invention is to overcome the above-mentioned drawbacks.

A further object of the present invention is to cover a wide spatial angle and ensure rapid exposure of the photosensitive material in a photolithographic exposure system, thereby achieving a significantly high working efficiency in the photolithographic apparatus. The purpose of the present invention is to provide a radiation OA radiation source that does not require any radiation.

Yet another object of the present invention is to provide a plasma-based radiation source for optical devices, particularly photolithographic exposure systems.

A further object of the invention is to spatially isolate the plasma from the walls or other various members of the launch vessel and to eliminate the use of high frequency type R415 electrodes in the launch vessel. It is an object of the present invention to provide a radiation source with a long life and high energy density based on the above.

Yet another object of the present invention is to provide a radiation source that allows pulsed operation after a reduction in the rate of stress on the launch vessel due to the impact waves.

Another object of the invention is to provide a radiation source which allows a wide optimum range in the desired wavelength of the radiation IJJt5jl with respect to the parameters of plasma generation medium, pressure and temperature.

Still another object of the present invention is to provide a photosensitive layer which exhibits high spatial incoherence and has weakly monochromatic radiation compared to a laser radiation source, and which when used in a photolithographic exposure system. The object of the present invention is to provide a radiation OA radiation source that practically eliminates the vertical wave effect within the radiation source.

Structure of the Invention Measures for Solving the Problems These and other objects are realized in a radiation source consisting of an airtight launch vessel filled with light *'j'R bodies that make it possible to generate plasma. be done.

The launch vessel has at least one light inlet gap sealed by a material 1 transparent to laser radiation, and at least one +Δ diagonal sealed by a material 1 transparent to plasma radiation. The light exit gap 11 described above is provided.

At least one laser device is installed on the exterior of the launch vessel for producing a laser beam. The laser beam is focused through the inlet opening into the launch medium, thereby causing the laser beam to be focused into the launch medium through the inlet opening. , are provided with optical means for generating and maintaining a radiant plasma in the launch medium at a location spaced apart from the vessel wall.

This plasma radiation *J 11!2 is radiated through the exit opening towards the subsequent optical system.

Advantageously, another pulsed laser device is provided outside the launch vessel and this is used if the radiant energy of the first laser is insufficient to generate a breakthrough in the plasma. It is advantageous to bring about the ignition of the launch medium at a time when this second laser is mounted on the wall of the launch vessel at the same position of the launch medium (
is focused by optical means through another inlet 1].

It is further advantageous if means are provided external to the launch vessel for focusing the laser radiation into the plasma and for changing the focal position within the plasma.

It is advantageous to provide means for adjusting this focusing means.

One simple example of a radiation source is laser radiation! Means for focusing the J4 beam may be located within the walls of the launch vessel and/or within the launch vessel.
There is.

b Schife C) I Part of the inner wall of the vessel focuses the laser 1lili line from the outside into the interior of the launch vessel! It is even more advantageous if it is designed as a means of replenishment.

At least a part of the inner wall of the launch vessel constitutes an optical means for directing radiation directed into the plasma, which ensures a wide spatial angle sweep. If there is, it is even more right-handed. For this purpose, light (1.
The inner wall of one container is in the shape of a concave reflector. One specific example of this concave reflector is an ellipsoidal reflector.

To increase the life of the launch vessel, the launch vessel is provided with an external cooling system, which also allows operation at significantly higher shaft densities of 8'F.

In order that the invention may be more easily understood, reference is made to the accompanying drawings, which represent examples diagrammatically illustrating four embodiments of the invention.

In FIG. 1, a gas-tight container 1 of rectangular cross section contains an interior chamber 1', in which a gaseous medium 2, for example argon, is contained. The container 1 has adjacent walls 3' and 4'.
A first inlet space [Tl 3 d3] and a second artificial opening 4 are provided inside, and these are sealed by an infrared-transparent window 6 and an ultraviolet-transparent lens 7, respectively. An outlet opening 5 is provided in the wall opposite the inlet opening 4, which is closed off by a window 8 which is transparent to the plasma radiation.

A laser device 9 is arranged on the outside of the container 1, facing the opening 3, and a laser device 1o is arranged facing the opening 4, respectively. The laser device 9 is the window 6
The laser beam 11 is emitted substantially at right angles to the A concave 01 mirror 12 is disposed on the wall 12' of the container 1 on the opposite side to the window 6, facing the window 6. This concave reflecting mirror 12 serves to receive the laser beam 11 and focus it onto an excitation focal point 14 to create a plasma torch. The laser device 10 emits a laser beam 13 along an axis 0-0 that substantially coincides with the optical axis (not shown) of the lens 7 in the aperture 4. This laser beam 13 is also passed through the lens 7 to the excitation focus 1
The focus is on 4.

In operation, the continuous emitting C02 laser Komoda 9 emits a laser beam 11, which belongs to the infrared region of the spectrum. This laser beam 11 passes through an infrared-transmissive window 6, for example a N a (:, l filter), and passes through an earthen concave surface Q [
Collision on top of 12. Reflector 12 emits laser beam 11
into the excitation point 14), which is in the container 1
located away from each inner wall. At this focal point 14, the argon plasma medium is heated by the approximately 1 kW radiation output of this beam to a temperature near the point of plasma generation.

The container was prefilled with gas at a pressure of 10'pa. For reasons of simplicity, the corresponding pressure introduction is not shown.

The laser device 10 is a pulsed N2 laser') A ii, and the laser beam 13 produced therefrom is also focused by the lens 7 through the entrance aperture 4 into the excitation focus 14 . Whenever plasma radiation 15 is required, for example for photocopying, this laser device 10 emits a flash of laser light, which is focused through an ultraviolet-transmissive lens 7 to an excitation focal point 14, where a plasma is created. The plasma radiation 15 is then emitted through the window 8 into a projection lens (not shown) and used for photolithography.

The plasma medium may be helium, but it is also possible to use xenon. Windows 6 and 8 and lens 7 are each seated in flexible sealing means, not shown for simplicity, thereby providing approximately 10'pa.
Due to the internal pressure of the container 1, the windows 6, ε3 and the lens 7
are pressed against the flange parts 50, 51, 52 of the walls, respectively, thereby ensuring the tightness of the container 1.

In order to achieve a hermetically sealed seal of the transparent members to the wall of the container 1, screw-type attachment means can also be used. The radiation source shown in FIG. 1 is also such that the output power of the pulsed CO2 laser device is higher than that of the continuous CO2 laser device and is sufficient to create a plasma, i.e. to cause radiation to be emitted from the plasma torch 14. If the pulsed laser device 10 is omitted and the C02 laser device is used as a pulsed laser device, the radiation source shown in FIG. 1 will work well.

The laser beam 11 is recorded using argon or xenon as a plasma medium at a pressure of 10'pa.
to 18,000”k by laser beam 11;
When heated, a plasma torch 14 having a diameter of 4 mm to 5111111 mm is formed. The dimensions of the plasma torch and the temperature of the radiation-generated plasma can be varied, and thus the emission wavelength of the radiation can be varied by changing the pressure within the vessel of the radiation source: increase in pressure. As the temperature decreases, the spectral distribution of the plasma radiation approaches a blank function. As the pressure is lowered, the temperature rises and the radiation of the radiant plasma approaches the line. It is self-evident that the radiation source according to the invention operates at the pressures mentioned above, and therefore such a pressure generating device is not shown in FIG.

Of course, for special applications it is possible for the container 1 to be equipped with a pressure outlet valve in order to achieve a change in the spectral distribution during operation.

When using helium as the gas for generating the plasma in vessel 1, temperatures in excess of 20,000°K are created, and this gas has a wider radiation density and spectral distribution than conventional radiation sources. Allow for change. It should be pointed out that helium was not always very suitable in conventional electrically pulsed light sources to attack the electrode material.

FIG. 2 shows a launch vessel for a radiation O1 source in which a portion of the inner wall constitutes an optical element.

The launch container consists of a housing 30 of rectangular cross-section, which includes an interior chamber consisting of a tubular shell 16 and front and rear openings, each of which is hermetically sealed by a concave reflector 11 and a window 1.8. , in which case the above window 18
is made of quartz.

The interior chamber (1G, 17.18) has an axis of symmetry X-X located substantially centrally within the housing 30.

For example, argon,
Kihinon, Iζ is iJ that generates plasma like helium.
Contains a capable medium 19.

The housing 30/inner chamber (16, 17, 18) arrangement forms a cavity 31 between them, in which coolant 32 circulates from inlet valve 33 to outlet valve 34 for heat dissipation. An opening 23' is provided through the housing 30 and the interior 16 around an axis x'-x' perpendicular to the X-X axis, which is sealed and enclosed by an infrared transparent window 23. . Sealing elements for both windows 18 and 23 are not shown because they are in the cylinder. A CO2 pulse laser device 21 is installed in the housing 3 around the X'-X' axis.
It is located away from 0.

This laser device 21 emits a laser beam 20 substantially coaxially with the axis xl-x# intersecting the axis X-X in the interior chamber (1G, 17.18).

A focusing lens 22 that is transparent to infrared radiation is arranged between the laser device @ 21 and the window 23 on the axis x I -x.
The laser beam 20 is located around the laser beam 20. The laser device 21 is operated by an x-y table 24' and micrometer screws 25°
- It is adjustable in the y direction (24, 25).

The lens 22 is adjustable in the Z direction (2G) by a carriage support member fixed to the housing 30 by 26°. Other mechanical coupling means between the sliding device of the laser device 21 and the sliding device of the lens 22 and respectively with the housing 30 are suggested.

In operation, the pulsed CO2 laser device @ 21 is emitted through the lens 22 and the window 23 in the axis x1-x' to the width of the plasma medium 19, which is heated at 27 to generate a plasma and generate a plasma. It reaches a temperature that emits plasma radiation.

'823 and lens 22 select the desired laser beam wavelength portion; in addition, lens 221.1
This ray portion is directed into a region 27 substantially represented by the intersection of the x-x and xl-xl axes.

The blown plasma radiation 28 is reflected directly and reflected at the concave reflector 17 through the quartz window 18 located in the exit opening 18' to the condenser lens 29 of the housing 30 along the X-X axis. The condenser lens is symmetrically oriented with respect to the plasma width! lF1
% 12B is directed to a role lens (not shown), such as a lithographic exposure apparatus (not shown).

Laser beam sliding means 24' and 25', 2
5'' in combination with the l axial slide of the lens 22, the position of the focal point of the laser beam 2° is adjusted relative to the axis x-x in the gas medium 19.

The biaxial sliding means of lens 22 adjusts the focal point.

It is also possible to replace the window 23 by a lens 22 which is to be arranged in the interior chamber 16 in a seven-way adjustable manner and in a gas-tight manner.

The circulation of the coolant 32 in the cavity 31 causes the inner chamber (16,1
7, 18) is dissipated. Hermetic sealing of the windows 23 and 18 in the interior chamber 1G is likewise obtained by the flanges 18'' and 23', respectively. The contact parts 18 and 18° of the windows 18,
and a flexible member located between 23 and 23' (not shown).

3 and 4, a radiation source for high power radiation emission includes a launch vessel consisting primarily of a parabolic reflector. In FIG. 3, the laser beam 37 emitted by the CO2 laser 1 and 38 has a parabolic reflection $14
The exit window 49 passes through a selective window 40 in which the acid 1 is added to the concave reflector 39, which seals the cavity formed by the ellipsoidal reflector 43.
Fixed. The anti[1][39 directs the laser beam to the first focal point 41 of the ellipsoidal antiq'' mirror 43, where the lζ gas suitable for plasma generation is excited and emits a plasma width line, which is reflected by the reflecting mirror 43. Second focus 4:)
and the plasma width line is then focused by an =I indenzer lens 47 and used for further processing in an optical system, not shown.

In the case of J3 shown in Fig. 4, the reflector 31) in Fig. 3 is replaced by the lens 40.
This lens [,1 transmits infrared rays, and is inserted into the elliptical mirror 44 in place of the window 40 in FIG.

As in the case of FIG. 3, the laser beam 37 is 411
It is focused on the first focal point 42 of the ellipsoidal mirror 44, where the scum is excited and generates plasma, and the radial 0=1 line of this plasma is directed to the second focal point 46 of the ellipsoidal mirror 44. The light is condensed by a condenser lens 48.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a first example of an alpine horn radiation source according to the invention, FIG. 2 is a schematic sectional view of a second example, and FIGS. 3 and 4 are third and fourth examples, respectively. FIG. 119. Whitening/1 container 2.19. , , light emitting medium 3.
400. Entrance frontage 589. Exit frontage 6.8.23. , , window 7.22
．． 29. , , Lens 9.10.21. , , Laser device 11.13.2
0.37. , , Laserbee 1112.17.39
．． 43.44. , 9 reflector 14.27. , , excitation focus 15.28. , , Plasma width line 24' , , , x-y table procedure nJ formal writing (method) April 24, 1985 Special Agent at the Special Agents' Office 1, Indication of the case 1982 Patent Application No. 229035 2. Name of the invention: Width line source used in optics 1. 3. Who makes the correction? What is the relationship?
llj person 11 Location 5 Toranomon Minami Building, 3-3-3 Toranomon, Minato-ku, Tokyo
Floor Tel: 438-91886, Subject of amendment Specification and drawing 7, Contents of amendment clarified i'! 1 is as per Koriyama/Attachment of the original attached to the application (no change in content) The drawing is corrected as attached.

Claims (1)

Claims: (1) A radiation source emitting selective radiation of significantly high intensity for use in particular, but not exclusively, in photolithographic apparatus, the launch vessel containing a gaseous medium suitable for plasma generation; a first laser device for emitting a laser beam (provided that the first laser beam is disposed outwardly on one side of the launch vessel and is connected to the emission vessel); - a first radiation inlet opening provided in the wall of the launch vessel (operably connected to the gaseous medium within the vessel), the radiation inlet opening being hermetically sealed by a first optical means; and the intensity tAtf of the laser beam is
A) for focusing the laser beam through the first radiation inlet opening into a volume of the gaseous medium within the launch vessel, provided that the volume extends within the eight walls of the launch vessel. ), and a plasma within another wall of the launch vessel! @
A radiation exit opening, wherein said radiation exit opening is hermetically sealed by a second optical means transparent to said plasma radiation. (2) A single stage for focusing the laser beam within the volume range within the launch container is a four-sided mirror (J4 mirror) mounted on the inner wall of the launch container facing the first port. [The radiation source according to claim 1. (3) A second radiation tJJ line inlet opening is provided in the wall of the launch vessel facing the body 1 area, A radiation source according to claim 2. (4) A radiation source according to claim 3, wherein the second radiation entrance aperture is hermetically sealed by a first force lens. (5) A second laser device is provided for directing the laser beam focused into the volumetric range by the first focusing lens. A radiation source. (6) The radiation source according to claim 5, wherein the first laser device is a continuous wave CO2 laser device Fl. (7) The second laser device is a pulsed laser device. The radiation source according to claim 6, which is a device for increasing the temperature of the gas medium within the volume range of (1) to near the plasma generation humidity. , and the pulse laser device is
7. The method according to claim 7, wherein plasma radiation is generated in a gaseous medium at an elevated temperature in the range Ii, the plasma radiation being emitted from the outlet opening through the second optical means. radiation source. (9) The radiation source according to claim 1, wherein the first laser device is a pulsed CO2 laser device. (10) The above pulse CO2 laser! 12. The A-neck is used to generate plasma radiation of the gaseous medium within the volumetric range, and the plasma radiation is emitted from the plasma radiation exit aperture through the second optical means. A radiation source according to paragraph 9. (11) Claim 10, wherein the focusing means is a second focusing lens installed in the laser beam between the first optical means and the first laser device. 12. The radiation source according to claim 10, wherein the first optical means is third focusing means. (13) The radiation ray according to claim 12, wherein means for displacing the second focusing lens parallel to the first beam and at right angles are provided. source. (14) means are provided for displacing the first laser device perpendicular to the axis defined by the first laser beam in alignment with the orthogonal displacement of the second focusing lens; Patent' [Claim I7'
ll. The radiation source according to No. 13 Jji. (15) The wall portion facing the plasma radiation exit opening is a concave reflective mirror, the focal point of which substantially coincides with the volume range in the vicinity of the axis; 15. A radiation source according to claim 14, which is used to reflect at least a portion of the plasma radiation into a condenser lens through a plasma radiation exit aperture. (46>, J- The radiation source 3° according to claim 8, wherein means for cooling the light ray container are provided. (17) Means for cooling the light q1 container is provided. A radiation source according to claim 15, provided: (18) In particular, but not exclusively, in photolithography f
A radiation source that emits a selective radiation line of extremely high intensity for use in the device (h) is placed in a gas-tight launch vessel ((l:i L, u-recording) containing a gaseous medium suitable for plasma generation. (the split container has a reflective inner surface), a laser device for emitting a laser beam (provided that the laser beam has a defined axis, and the shape of the launch container is substantially a half of an ellipsoid; (the principal axis of the ellipsoid coincides with the axis, and one apex of the ellipsoid faces the laser device), and a laser is provided in the wall of the launch vessel symmetrically with respect to the apex. a radiation inlet aperture, provided that the laser radiation inlet aperture is hermetically sealed by a first optical means transparent to the laser radiation, and symmetrically about the principal axis the laser radiation inlet aperture; one opening for plasma radiation disposed in the wall of the launch vessel opposite to the plasma radiation outlet opening, wherein said plasma radiation exit opening is hermetically sealed by a second optical means transparent for said plasma generation; ). (19) The first optical means comprises the laser radiation source.
a focusing lens for focusing into a first focal range of the ellipsoid for the generation of plasma radiation of the gaseous medium (provided that the plasma radiation is directed to -F by the reflective surface);
It! (reflected to a second focal point of the ellipsoid outside the launch vessel) and about the axis behind the second focal point, looking in the direction of propagation of the rays, to direct the plasma radiation. Radiation source according to claim KB 18, in which the condensing lens is arranged symmetrically to . (20) A concave reflecting mirror is provided facing the first optical means and attached to the second optical means, and this concave anti-OA mirror converts the laser radiation into the plasma radiation of the gas medium. into a first focal range of the ellipsoid for the generation of a beam, wherein the plasma radiation is directed onto the reflective surface into the second focal point of the ellipsoid outside of the launch vessel. A condensing lens is arranged symmetrically about the axis behind the second focal point, viewed in the direction of propagation of the radiation, for reflecting and thereby directing the plasma radiation. The radiation source according to paragraph 181r3.