JP5162365B2 - Light source for semiconductor lithography - Google Patents

Description

  The present invention relates to a light source for semiconductor lithography that generates short-wavelength light for forming a circuit pattern on a semiconductor wafer.

  Conventionally, as a method of manufacturing a semiconductor integrated circuit used as a storage element or an information processing element for various electric devices such as a personal computer, a mobile phone, and a navigation system, light from a light source is irradiated onto a mask on which a circuit pattern is formed. Lithography is known in which a circuit pattern of a mask is transferred to a photosensitive resin (photoresist) on a semiconductor wafer.

  At present, the wavelength of light used for lithography is g-line (wavelength: 436 nm), i-line (wavelength: 365 nm), KrF excimer laser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm) of a high-pressure mercury lamp. However, when the wavelength of light is long, the resolution of the circuit pattern on the photoresist tends to be low. Therefore, the light with the above wavelength is used for high integration of semiconductors (miniaturization of circuit patterns). A laser-produced plasma (LPP) light source and a discharge-produced plasma (DPP) light source that generate light having a shorter wavelength (EUV light) are provided (for example, see Patent Document 1).

  By the way, short wavelength light (EUV light) has the property of being absorbed by glass, and therefore, it is not possible to change the path of light using a glass optical system (lens or the like). A Mo / Si multilayer film having a peak in reflectance at a wavelength of 13.5 nm is being adopted as an optical system (reflecting mirror) for changing the path of light.

Accordingly, both the laser-generated plasma light source and the discharge-generated plasma light source can generate light having a wavelength that matches the characteristics of the optical system (light having a wavelength of 13.5 nm with little loss of reflection in the optical system). It is configured. Specifically, a laser-produced plasma light source emits a strong laser (YAG (Gauss) laser) to a tin (Sn) or tin (Sn) compound as a target material and emits a strong emission peak near 13.5 nm. Is configured to generate a plasma light. On the other hand, the discharge-generated plasma light source is configured to generate plasma light including a light component having a wavelength of 13.5 nm between the electrodes by causing a high current of a steady frequency to flow between the pair of electrodes for discharge. .
JP 2008-130230 A

  However, any of the above light sources has a problem in that debris (impurities) are generated with the generation of plasma and the transfer of the circuit pattern to the semiconductor wafer is hindered. That is, in the laser-generated plasma light source, debris is generated from the target material (tin, which is solid at room temperature) as the plasma is generated, and in the discharge-generated plasma, debris is generated from the electrode as the plasma is generated. There is a problem that it adheres to an optical system, a mask, a semiconductor wafer, etc., and hinders transfer of a circuit pattern to the semiconductor wafer.

  Therefore, in view of such circumstances, the present invention generates light having a short wavelength that is optimal for forming highly integrated circuits on a semiconductor wafer without generating debris that hinders transfer of a circuit pattern to the semiconductor wafer. It is an object of the present invention to provide a light source for semiconductor lithography that can be used.

  A light source for semiconductor lithography according to the present invention is a light source for semiconductor lithography that generates short-wavelength light for forming a circuit pattern on a semiconductor wafer, and is mixed with a rare gas or a rare gas in a negative pressure state. A light source body having an outer peripheral wall defining an internal space filled with gas; and a magnetic field generating means for generating a rotating magnetic field around a predetermined axis in the inner space, wherein the light source main body includes at least the outer peripheral wall. Is made of a non-magnetic material having electrical insulation, and at least a light emitting portion for emitting a light component having a short wavelength or light containing the light component from the internal space to the outside is formed. It is characterized by.

  The light source for semiconductor lithography having the above structure is configured such that the magnetic field generating means generates a rotating magnetic field around a predetermined axis in an internal space filled with a rare gas or a mixed gas containing a rare gas in a negative pressure state. Therefore, it is possible to generate plasma that emits light components having a short wavelength corresponding to the filled rare gas. As a result, the light source for semiconductor lithography having the above configuration forms a highly integrated circuit (miniaturized circuit) on the semiconductor wafer from the light generated by the plasma without generating debris that hinders the formation of the circuit pattern. It is possible to irradiate the semiconductor wafer directly or indirectly by emitting a light component having a short wavelength optimum for the semiconductor wafer.

  As one aspect of the present invention, the magnetic field generating means is preferably configured to generate a rotating magnetic field while generating an axial magnetic field in the axial direction in an internal space. In this way, out of the axial magnetic field formed in the predetermined axial direction, the region where the rotating magnetic field is generated becomes the magnetic field in the opposite direction to the other region, and the magnetic field lines confining the plasma generated around the axial line are formed. Is done. As a result, it is possible to generate a plasma with a very high density, and thus it is possible to obtain a plasma with a low input and a high output (light of short wavelength).

  In this case, the light source main body has an outer peripheral wall portion formed in a cylindrical shape, and the magnetic field generating means includes a plurality of first coils arranged at intervals around the outer peripheral wall portion and an axial direction of the outer peripheral wall portion. A plurality of second coils that are externally fitted to the outer peripheral wall with a space therebetween, and a configuration in which an alternating magnetic field is generated by the first coil while an axial magnetic field is generated by the second coil to generate a rotating magnetic field It is preferable that In this way, since no configuration of the magnetic field generating means is arranged in the internal space, the internal space can be made only for plasma generation, and good plasma can be generated.

  As another aspect of the present invention, the rare gas is preferably xenon (Xe) gas or neon (Ne) gas. By doing so, it is possible to generate plasma that emits light containing a large amount of light components having a wavelength of 13.5 nm. Therefore, it is an optimal light source for an optical system composed of a Mo / Si multilayer film (reflector having a reflectance peak of 13.5 nm).

  As still another aspect of the present invention, it is preferable that at least the outer peripheral wall of the light source body is made of heat-resistant glass. In this way, it is possible to confirm the generation state of plasma in the internal space from the outside. In addition, the heat resistance can withstand the heat generated by the generation of plasma, and can be excellent in durability.

  As described above, according to the light source for semiconductor lithography according to the present invention, the shortest optimum for forming a highly integrated circuit on a semiconductor wafer without generating debris that hinders transfer of the circuit pattern to the semiconductor wafer. An excellent effect that light having a wavelength can be generated can be obtained.

  Hereinafter, a light source for semiconductor lithography according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  The light source for lithography according to the present embodiment (hereinafter simply referred to as the light source) is a short wavelength light (in this embodiment, the wavelength is 13.5 nm) that is applied to the semiconductor wafer to form a circuit pattern on the semiconductor wafer. Light component: hereinafter referred to as EUV light). The light source according to the present embodiment is incorporated as one configuration of a semiconductor lithography apparatus U that transfers a circuit pattern onto a semiconductor wafer W, as shown in FIG. That is, the semiconductor lithography apparatus U includes the light source 1, a stage S on which the semiconductor wafer W is disposed, a mask (not shown) on which a circuit pattern to be transferred to the semiconductor wafer W on the stage S is formed, And an optical system M for guiding light to a mask. In the semiconductor lithography apparatus U according to this embodiment, the stage S, the mask, and the optical system M are housed in a sealed casing C, and the light source 1 is connected to the casing C on the outer surface.

  The light source 1 includes a light source body 10 having an outer peripheral wall portion 101 defining an internal space 100 filled with a rare gas or a mixed gas containing a rare gas in a negative pressure state, and a predetermined axis in the internal space 100. Magnetic field generating means 20 configured to generate a rotating magnetic field around (center line CL of outer peripheral wall 101 in the present embodiment) is provided.

  In the light source body 10, at least the outer peripheral wall portion 101 is made of a nonmagnetic material having electrical insulation. In addition, the light source body 10 is formed with a light emitting portion 102 capable of emitting a light component of light emission accompanying the generation of plasma to the outside at least partially. The light source body 10 has an outer peripheral wall portion 101 formed in a cylindrical shape, an opening at one end thereof is set to the light emitting portion 102, and the opening at one end is connected to the opening formed in the casing C. That is, the light source body 10 has one end portion of the outer peripheral wall portion 101 with respect to the casing C such that the inside of the outer peripheral wall portion 101 (inner space 100) and the inside of the casing C communicate with each other via the light emitting portion 102. Airtight connection. In the light source body 10, the other end opening of the outer peripheral wall portion 101 is closed by a lid member 104 having a cylindrical nozzle 103 protruding in part (center portion). In the light source body 10, at least the outer peripheral wall portion 101 is preferably made of heat-resistant glass so that the internal state can be confirmed. In the present embodiment, the outer peripheral wall portion 101 is made of heat-resistant glass, and the lid The member 104 and the nozzle 103 are made of nonmagnetic metal (for example, stainless steel or aluminum alloy).

The light source 1 according to the present embodiment employs xenon (Xe) gas as a rare gas filled in the internal space 100 defined by the outer peripheral wall portion 101, and is set to a negative pressure (10 ⁻⁴ Pa). The internal space 100 is filled with a pressure of 3 Pa to 15 Pa, preferably 5 to 10 Pa.

The light source 1 according to the present embodiment includes a suction pump (not shown) that makes the internal space 100 a negative pressure, and a rare gas filling source (not shown) that fills the internal space 100 with a predetermined pressure. The suction pump and the rare gas filling source are fluidly connected to the light source body 10 directly or indirectly. Specifically, in the light source 1 according to the present embodiment, the rare gas filling source is fluidly connected to the nozzle 103 of the light source body 10, while the suction pump is fluidly connected to the casing C. The suction pump sucks the inside of the casing C, whereby the internal space 100 is made negative pressure (10 ⁻⁴ Pa to 10 ⁻⁶ Pa, preferably 10 ⁻⁵ Pa to 10 ⁻⁶ Pa) through the inside of the casing C. It is like that. The light source 1 according to the present embodiment employs a rotary pump and a turbo molecular pump as suction pumps, and by arranging these pumps in series, the pressure of the internal space 100 can be set to 10 ⁻⁴ Pa. It is configured.

  The magnetic field generation means 20 according to the present embodiment is configured to generate an axial magnetic field in the predetermined axial line CL direction in the internal space 100, and configured to generate a rotating magnetic field in a state where the axial magnetic field is generated. ing.

  Specifically, the magnetic field generating means 20 is externally fitted to the outer peripheral wall portion 101 with a plurality of first coils 200 arranged at intervals around the outer peripheral wall portion 101 at intervals in the axis CL direction. Are generated, and an alternating magnetic field is generated by the first coils 200 while generating the axial magnetic field AM in the direction of the axis CL in the internal space 100 filled with the rare gas by the second coils 201. By generating the rotating magnetic field RM, the plasma P is generated (see FIG. 2).

  Each of the first coils 200 is formed in a frame shape (a frame shape whose outer shape forms a square shape), and is attached to the outer surface of the outer peripheral wall portion 101 at intervals of 90 ° in the circumferential direction of the outer peripheral wall portion 101. Yes. That is, two pairs of first coils 200... Arranged at intervals of 180 ° are provided with a phase of 90 ° with respect to the center line (axis line CL) of the outer peripheral wall portion 101.

  In the magnetic field generation means 20 according to the present embodiment, the frequency at which current is applied to each set of the first coils 200 is set to 100 Hz to 1 MHz, preferably 200 Hz to 400 Hz, and the applied current is 200 A to 2 KA, Preferably, it is set to 400A to 2KA.

  The magnetic field generating means 20 applies a current at the above-described frequency to each of the first coils 200... So that the application timing (cycle) of the current to each of the first coils 200. A rotating magnetic field is formed. For example, a sinusoidal alternating current is applied to one set of first coils 200 of two sets of first coils 200 provided at a position rotated by 90 ° with respect to the axis CL, and an alternating magnetic field is continuously applied. A rotating magnetic field is generated by applying a current having a phase difference of 90 ° to that of the first coil 200 of one set to the first coil 200 of the other set. When a current of 400 A is applied to each of the two sets of first coils 200..., A rotating magnetic field RM of 200 KHz is generated with a magnetic flux density of 130 G (Gauss).

  On the other hand, each of the second coils 201 is formed in an annular shape and is externally fitted to the outer peripheral wall portion 101, and an axial magnetic field AM extending in the direction of the axis CL in the internal space 100 by simultaneously applying current to them. (See FIG. 2). In the present embodiment, an axial magnetic field AM having a magnetic flux density of 60 gauss at maximum is generated.

  The optical system M is composed of a Mo / Si multilayer M. In this embodiment, the Mo / Si multilayer M is formed in a curved shape and is formed like a concave mirror. The optical system M is arranged so that the reflection surface corresponds to the optical axis of the light source 1, and can irradiate the semiconductor wafer W on the stage S arranged on a line substantially parallel to the optical axis with EUV light. It has become. Since the stage S and the mask have a general configuration, description thereof is omitted here.

  The casing C is provided with a door (not numbered) that can be opened and closed in order to replace the semiconductor wafer W to be processed. The casing C is formed so that the inside can be kept airtight with the door closed. Thereby, when the inside is sucked by the suction pump, the inside can be maintained in a negative pressure state.

  The semiconductor lithography apparatus U (light source 1) according to the present embodiment has the above configuration, and the operation will be described next.

First, the semiconductor wafer W is disposed on the stage S, and the mask is disposed in a state of facing the semiconductor wafer W. After that, as shown in FIG. 2, after the internal space 100 of the light source body 10 (outer peripheral wall portion 101) is made negative pressure, it is filled with xenon (Xe) gas and then rotated into the internal space 100 by the first coils 200. A magnetic field RM is generated. Then, a plasma current is induced by the rotating magnetic field RM, whereby the rare gas is ionized. In the case of xenon (Xe) gas, light (EUV light) emitted by the 4d-5p transition of the xenon gas (Xe ⁺¹⁰ ). A light component having a wavelength of 13.5 nm) is generated.

  In the present embodiment, since the rotating magnetic field RM is generated by the first coils 200... While generating the axial magnetic field AM by the second coils 201. While the direction of the nearby axial magnetic field AM (magnetic line ML1) remains as it is, the axial magnetic field AM (magnetic line ML2) on the axial line CL is reversed, and this magnetic field ML2 on the inner side (on the axial line CL) and the outer side (outer periphery). The magnetic force line ML3 between the magnetic force line ML1 on the wall portion 101 side) is closed in an annular shape, and the plasma P generated as described above is supplemented by the annular magnetic force line ML3, and a high density plasma is confined. .

  Then, the plasma is heated to a high temperature (> 20 eV) necessary for generation of EUV light by Joule heating with a current (plasma current) induced in the rotating magnetic field.

  When the plasma P is generated in this way, light emission including a light component having a wavelength of 13.5 nm is generated as described above. Therefore, the light passes through the light emitting portion 102 formed in the light source body 10 and goes out. And In the present embodiment, since the outer peripheral wall portion 101 of the light source body 10 is made of heat-resistant glass, the light emitted in all directions along with the generation of the plasma P is emitted toward other than the light emitting portion 102. EUV light will be absorbed. Therefore, only the EUV light emitted toward the light emitting portion 102 (opening) where no glass exists can be emitted to the outside.

  As the EUV light is emitted from the light emitting unit 102 to the outside, light components other than 13.5 nm also exit to the outside (in the casing C in the present embodiment) through the light emitting unit 102. Light components other than 5 nm are transmitted through the optical system M or absorbed by the optical system M. As a result, only EUV light is reflected by the optical system M (Mo / Si multilayer film M) and guided to the mask. As a result, the circuit pattern formed on the mask is transferred to the photoresist of the semiconductor wafer W on the stage S.

  As described above, the light source 1 according to the present embodiment defines the internal space 100 filled with a rare gas or a mixed gas containing a rare gas and is made of a nonmagnetic material having electrical insulation. A light source body 10 having a configured outer peripheral wall portion 101; and a magnetic field generation means 20 configured to generate a rotating magnetic field RM around a predetermined axis CL in the internal space 100, the light source body 10 includes: Since the light emitting portion 102 capable of emitting the light component of the light emission accompanying the generation of the plasma P to the outside is formed at least in part, the plasma P including EUV light can be generated. Thereby, the highly integrated (miniaturized) circuit pattern can be appropriately and continuously transferred to the semiconductor wafer W by the EUV light contained in the plasma P. Further, as described above, since no solid target or electrode is used, debris that inhibits the formation of the circuit pattern is not generated, and the circuit pattern can be satisfactorily formed on the semiconductor wafer W.

  Further, in the conventional discharge generated plasma (DPP) light source 1, since the plasma P is generated by pulse discharge in a short time (μ seconds), the stable plasma P can be generated for a long time due to intermittent discharge. However, since the light source 1 according to the present embodiment forms a magnetic field by supplying power with a steady frequency (several hundred kHz), it is possible to generate a stable plasma P over a long period of time. Therefore, the semiconductor wafer W can be continuously exposed with high quality.

  Further, the magnetic field generation means 20 is configured to generate an axial magnetic field AM in a predetermined axis CL direction in the internal space 100, and configured to generate a rotating magnetic field RM in a state where the axial magnetic field AM is generated. Therefore, it is possible to generate a plasma P having a very high density and to obtain a plasma P (EUV light) with a low input and a high output.

  In particular, the light source body 10 has an outer peripheral wall portion 101 formed in a cylindrical shape, and the magnetic field generating means 20 includes a plurality of first coils 200 arranged around the outer peripheral wall portion 101 at intervals, and an axis line. A plurality of second coils 201 externally fitted to the outer peripheral wall portion 101 at intervals in the CL direction, and an alternating magnetic field is generated by the first coils 200 while generating the axial magnetic field AM by the second coils 201. Thus, the configuration is such that the plasma P is emitted by generating the rotating magnetic field RM. Therefore, any configuration of the magnetic field generating means 20 is not disposed in the internal space 100. For this reason, the internal space 100 can be made only for plasma generation, and good plasma can be generated.

  Further, since the xenon (Xe) gas is adopted as the rare gas, it is possible to generate the plasma P that emits a lot of EUV light. Accordingly, the light source 1 that is optimal for the reflector M (reflector having a reflectivity peak of 13.5 nm) M composed of a Mo / Si multilayer film can be obtained.

  Furthermore, a suction pump that makes the internal space 100 have a negative pressure and a rare gas filling source that fills the inner space 100 with a rare gas are provided. The suction pump and the rare gas filling source are fluidly connected to the light source body 10. Since it is connected, the pressure of the internal space 100 can be adjusted with a suction pump, and the concentration and pressure of the rare gas in the internal space 100 can be adjusted. ) Can be stably generated.

  Further, since at least the outer peripheral wall portion 101 of the light source body 10 is made of heat-resistant glass, the generation state of the plasma P in the internal space 100 can be confirmed from the outside. In addition, the heat resistance can withstand the heat generated by the generation of plasma, and can be excellent in durability.

  In order to confirm the performance of the light source according to the present invention, the inventor produced an experimental apparatus described below and conducted an experiment.

  As shown in FIG. 3, the experimental apparatus includes a light source 1 ′, an electrostatic probe 5 ′ for measuring the density and electron temperature of plasma generated in the light source 1 ′ (internal space 100 ′), and a light source 1 ′. And a sensor 6 ′ for measuring EUV light (light component having a wavelength of 13.5 nm).

  In the light source 1 ′, an outer peripheral wall portion 101 ′ of a light source body 10 ′ is formed in a cylindrical shape, and one end opening of the outer peripheral wall portion 101 ′ is set as a light emitting portion 102 ′. The outer peripheral wall portion 101 ′ of the light source body 10 ′ is made of heat-resistant glass, and has a diameter of 70 mm and a length of 600 mm. The light source 1 ′ has a rare gas filling source connected to the other end of the outer peripheral wall portion 101 ′, and can fill the internal space 100 ′ with a rare gas (xenon (Xe) gas) at 1 Pa to 20 Pa. Yes.

  In the light source 1 ′, two pairs of first coils 200 ′ that are opposed to each other with the outer peripheral wall portion 101 ′ interposed therebetween are arranged with a 90 ° phase shift in the circumferential direction of the outer peripheral wall portion 101 ′. Each first coil 200 ′ is formed in a frame shape (square shape) having a side of 75 mm. A current of 400 A is supplied to each first coil 200 ′ by a 200 kHz vibrator, and a magnetic field is alternately generated by each set of first coils 200 ′, that is, an alternating magnetic field is generated around the axis CL. As a result, a rotating magnetic field of 130 gauss at the center is generated around the axis CL. The maximum output from each transducer is 40 kW and is maintained at a maximum of 5 milliseconds. A suitable capacitor for forming a series resonant circuit is connected in series to each first coil 200 '.

  In the light source 1 ′, a plurality of second coils 201 ′ are externally fitted to the outer peripheral wall portion 101 ′ with an interval in the direction of the axis CL of the outer peripheral wall portion 101 ′. Six second coils 201 'are provided, and an axial magnetic field of up to 60G (Gauss) is generated along the axis CL.

  The light source 1 ′ is airtightly connected to the other end of the outer peripheral wall portion 101 ′ so that the case 7 ′ having a space formed therein communicates with the inner space 100 ′ of the outer peripheral wall portion 101 ′. Yes.

The case 7 'is made of a non-magnetic material (SUS304), and a suction pump is fluidly connected to the case 7'. Thereby, the inside of case 7 'and the inside of light source main body 10' (internal space 100 ') can be made into a negative pressure. In this experimental apparatus, a rotary pump and a turbo molecular pump are adopted as the suction pump, and these are arranged in series, so that the pressure in the internal space 100 ′ can be reduced to 10 ⁻⁴ Pa or less in 10 minutes. Yes.

  The electrostatic probe 5 ′ is spaced from the outer peripheral wall portion 101 ′ in the direction of the axis CL so that the detection portion (not numbered) is positioned in the outer peripheral wall portion 101 ′ (internal space 100 ′). It is attached to the three ports 105a, 105b, 105c provided. In this experimental apparatus, plasma P ′ is generated in a region corresponding to the middle port 105b among the three ports 105a, 105b, and 105c. Therefore, measurement is performed with the electrostatic probe 5 ′ of the middle port 105b. It was decided.

  The sensor 6 ′ is provided in the case 7 ′ so that the center of the detection unit 60 ′ is located on an extension line of the axis CL of the outer peripheral wall 101 ′. In the present experimental apparatus, the sensor 6 ′ is provided such that the detection unit 60 ′ is located at a position 750 mm away from the center of the plasma P ′ generated in the internal space 100 ′.

The sensor 6 ′ employs a photodiode, and this experimental apparatus includes a SHUV20HS1 photodiode (Mo: 500 nm, Si: 500 nm, Sic: 50 nm, pn junction having a thin film filter manufactured by IRD, USA). Silicon diode) was adopted. In the photodiode 6 ′, the detection effective area of the detection unit 60 ′ is 20 mm ² , and the spectral response of EUV light is 13.3 mA / W. In order to guarantee the detection accuracy by the detection unit 60 ′, the detection unit 60 ′ is covered with an aluminum cover 8 ′ having a thickness of 0.5 mm in which a circular hole 80 ′ having a diameter of 5 mm is formed, and the circular hole 80 ′ is covered. The light can be guided to the detection unit 60 ′.

  An optical filter 30 'that allows only EUV light (a light component having a wavelength of 13.5 nm) to pass therethrough is disposed in front of the detection unit 60' so as to close the hole 80 'of the cover 8'. Thereby, only the EUV light is detected by the photodiode 6 ′ from the light that has passed through the light emitting portion 102 ′. The optical filter 30 'is made of aluminum having a thickness of 5 nm and zirconium having a thickness of 150 nm, and the loss at a wavelength of 13.5 nm is about 0.5. In this experimental apparatus, L05 manufactured by LEBOW of the United States was used as the optical filter 30 '.

  In the circuit for connecting the photodiode 6 ', as shown in FIG. 4, the reverse bias is blocked by a 0.82 .mu.F capacitor, and the terminal voltage of 1 M.OMEGA. Of the input impedance of the oscilloscope can be measured. . Since it is difficult to measure the signal of the photodiode 6 ′ whose time constant is about 300 μs and constant for several milliseconds, the cable connecting the photodiode 6 ′ to the oscilloscope is 50Ω. Not terminated by a resistor.

  The output of the total EUV light emitted from the plasma P ′ by the experimental apparatus having the above configuration is roughly estimated by assuming that the plasma P ′ is an isotropic light source point.

That is, since the input (output of the EUV light on the detection unit 60 ′) P _{d to the} photodiode 6 ′ is related to the total output of the plasma P ′, the total output of the plasma P ′ is detected as P _r . When the effective detection area of the part 60 ′ is A _p and the distance from the center of the plasma P ′ to the detection part 60 ′ is L, Expression (1) is obtained.

A conversion formula for converting the output of the EUV light by the experimental apparatus having the above configuration into the output of the oscilloscope (output per 1 V of the oscilloscope output) is expressed by the formula (2) based on the formula (1).

Moreover, the conversion formula in the case of using the optical filter (a filter made of aluminum / zirconium) 30 ′ is expressed by the formula (3) by reflecting the efficiency of the optical filter 30 ′.

  Based on the above assumptions, the signal of the photodiode 6 ′ (the EUV light generation state), the coil current of the first coil 200 ′, and the axial magnetic field were measured. As shown in FIG. The axial magnetic field (CH5 signal) was 20 G (Gauss). Immediately after generating the rotating magnetic field, the xenon (Xe) gas is ionized by the alternating magnetic field (alternate electric field), so that the coil current (CH4 signal) of the first coil 200 ′ that generates the rotating magnetic field is generated. Decrease. The presence of the plasma P 'increases resistance and decreases the inductance of the first coil 200'. That is, as the inductance of the first coil 200 'decreases, the coil current of the first coil 200' decreases.

  When the rotating magnetic field enters the plasma P ′, the inductance of the first coil 200 ′ increases, the coil current of the first coil 200 ′ returns to the initial value, and at the same time, the axial magnetic field is reversed (reverse). ) To form a magnetic field in the opposite direction (magnetic field reversal configuration) on the axis CL. This is because 1) W.W. N. Hugrass, I.M. R. Jones, K.M. F. McKenna, M .; G. R. Phillips, R.D. G. Storer and H.C. Tuczek: Phys. Rev. Lett. 44 (1980) 1676.2) H. Y. Guo, A .; L. Hoffman, R.M. D. Brooks, A.M. M.M. Peter, Z .; A. Pietrzyk, S.M. J. et al. Tobin, and G.G. R. Votrobek, Physics of Plasmas, 9, 185 (2003), and 3) N. Hugrass, T.W. Okada, and M.M. Ohnishi, Plasma Phys. Control. Fusion, 50, 055008 (2008). Etc.

  When a reverse magnetic field (magnetic field reversal configuration) was formed on the axis CL, the EUV signal (ch1) reached 400 mV, and gradually increased to record 440 mV. The plasma disappears with the end of the rotating magnetic field, and the generation of EUV eventually becomes zero as the circuit constant is attenuated. According to equation (3), 19 W EUV radiation is observed.

  The inventor calculated the energy conversion efficiency from the relationship between the input to the experimental apparatus (power supplied to the first coil 200 ′ and the second coil 201 ′) and the output of the EUV light, and the result was about 0.03%. The output of EUV light was obtained with the efficiency of The light source according to the present invention is currently low compared to a conventional laser generated plasma (LPP) light source with an energy conversion efficiency of 1% and a discharge generated plasma (DPP) light source with an energy conversion efficiency of 0.5%. Although it is a value, it can be increased in the future by optimizing the device and operating conditions. Also, the output of EUV light is limited by the high-frequency power capability used, but by using a power source with a higher output, the EUV light required for practical use can be used without changing the device or operating principle. An output is obtained.

  The light source for semiconductor lithography of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the present invention.

  In the above embodiment, xenon (Xe) gas is filled as the rare gas filling the internal space 100 of the light source body 10, but the present invention is not limited to this. For example, neon (Ne) gas is used. You may make it fill. Further, the internal space 100 is not limited to the one in which only the rare gas is filled, and a mixed gas containing xenon (Xe) gas or neon (Ne) gas as described above is added to the internal space 100. You may make it fill. Even in this case, plasma P that emits EUV light (light component of 13.5 nm) can be generated in the same manner as when xenon (Xe) gas is filled.

  In the above embodiment, the outer peripheral wall portion 101 is made of heat resistant glass, and the other portions are made of nonmagnetic material such as stainless steel. However, the present invention is not limited to this. For example, the entire light source body 10 is made of heat resistant glass. May be formed. Moreover, the outer peripheral wall part 101 is not limited to what was comprised with heat-resistant glass, For example, you may comprise with nonmagnetic materials which have electrical insulation, such as a ceramic, earthenware, and resin. That is, the light source body 10 only needs to be made of a nonmagnetic material having at least the outer peripheral wall portion 101 having electrical insulation. In the case where the outer peripheral wall portion 101 is made of a material other than glass, it is preferable to provide a window except that a transparent material such as heat-resistant glass is fitted so that the internal space 100 can be confirmed from the outside.

  In the said embodiment, although the outer peripheral wall part 101 of the light source main body 10 was formed in the cylindrical shape, it is not limited to this, If the internal space 100 can be demarcated, it can be changed into various forms. However, it is preferable to prevent the inner circumference from being distorted due to the magnetic field generated in the internal space 100.

  In the above embodiment, the light source 1 has been described as one configuration of the semiconductor lithography apparatus U. However, the present invention is not limited to this. For example, the light source 1 may be configured as an independent component of the semiconductor lithography apparatus U. In this case, the light source body may be configured so that the inside of the casing C and the internal space 100 communicate with each other via the light passage portion 102 when assembled to the semiconductor lithography apparatus U.

  In the above embodiment, the light source 1 is arranged outside the casing C of the semiconductor lithography apparatus U. However, the present invention is not limited to this. For example, the stage S, the mask, and the optical system on which the semiconductor wafer W is arranged. The light source body 10 and the magnetic field generation means 20 may be arranged in a casing C in which M (a multilayer film of Mo / Si) is housed. Specifically, as shown in FIG. 6, the outer peripheral wall portion 101 of the light source body 10 is formed in a cylindrical shape with both ends open, and at least the first coil 200 (or the second coil 201) around the outer peripheral wall portion 101. ... and the first coil 200 ...) are arranged to constitute the light source 1, and the light source 1 may be arranged in the casing C.

  Even in this case, since the rare gas is filled in the internal space 100 of the light source body 10 by filling the casing C with the rare gas, the magnetic field generating means 20 (second coil 201... First coil 200...) Due to the generation of a magnetic field in the outer peripheral wall portion 101 (internal space 100), plasma P can be generated in the internal space 100. Therefore, the EUV light can be guided to the mask (semiconductor wafer W on the stage S) by arranging the optical system M on both sides of the light source body 10. However, since the magnetic field generating means 20 is arranged in the casing C in this way, dust or the like attached thereto may hinder exposure to the semiconductor wafer W. Therefore, the light source 1 is not used as in the above embodiment. Needless to say, it is preferable to dispose the casing C outside.

  In the above embodiment, the magnetic field generation unit 20 is configured to generate the axial magnetic field AM, but the present invention is not limited to this. For example, the magnetic field generation unit 20 is configured to generate only the rotating magnetic field RM. It may be. That is, the magnetic field generating means 20 may be constituted by only the second coils 201.

  In the above embodiment, six second coils 201 are provided. However, the present invention is not limited to this. For example, the number of second coils 201 can be appropriately changed as long as an axial magnetic field AM can be formed. Also, the first coils 200 are provided with two sets with a 90 ° phase shift. However, the present invention is not limited to this, and three sets or more are provided with a predetermined angle phase shifted around the axis CL. Also good. Alternatively, the pair of first coils 200 may be arranged to be rotatable around the outer peripheral wall portion 101, and the rotating magnetic field RM may be formed by the rotation of the first coils 200. Moreover, you may make it form the rotating magnetic field RM by rotating these around the outer peripheral wall part 101, generating an alternating magnetic field with respect to two or more sets of 1st coils 200 ....

  In the above embodiment, on the premise that a Mo / Si multilayer film is adopted for the optical system M that reflects EUV light, light of 13.5 nm is emitted from the light source 1 as short-wavelength light (EUV light). However, the present invention is not limited to this, and a short wavelength light component corresponding to the characteristics of the employed optical system M or a short wavelength light component preferable for forming a circuit pattern on the semiconductor wafer W (for example, The rare gas may be selected so that the light component having a wavelength of 13 nm to 14 nm is generated as EUV light.

  In the above embodiment, the EUV light from the light source 1 is indirectly guided to the semiconductor wafer W through the Mo / Si multilayer film. However, the present invention is not limited to this. For example, the EUV light from the light source 1 is used. The light source 1 may be arranged so that light can be guided directly to the semiconductor wafer W. In this case, an optical filter that passes only a light component having a predetermined short wavelength may be provided so as to correspond to the arrangement of the light emitting unit 102. Such an optical filter is selected according to the wavelength of light to be transmitted, and an aluminum / zirconium film is employed when only EUV light is allowed to pass as in the above embodiment. Further, as in the above-described embodiment, the optical system M is provided, and of course, an optical filter may be provided between the optical system M and the light source 1 (plasma P).

1 shows a schematic block diagram of a semiconductor lithography apparatus including a light source for semiconductor lithography according to an embodiment of the present invention. An explanatory view for explaining a generation mechanism of plasma in a light source for semiconductor lithography according to the embodiment is shown. The schematic block diagram of the experimental apparatus which concerns on the Example of this invention is shown. The electrical circuit diagram used for the experimental apparatus which concerns on the Example is shown. The output screen of an oscilloscope is shown by the experimental result by the experimental apparatus which concerns on the Example. FIG. 2 shows a schematic configuration diagram of a semiconductor lithography apparatus including a light source for semiconductor lithography according to another embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 10 ... Light source main body, 20 ... Magnetic field generating means, 100 ... Internal space, 101 ... Outer peripheral wall part, 102 ... Light emission part, 103 ... Nozzle, 104 ... Lid member, 200 ... First coil, 201 ... First Two coils, C ... casing, M ... optical system (reflecting mirror: multilayer film), P ... plasma, AM ... axial magnetic field, RM ... rotating magnetic field, S ... stage, W ... semiconductor wafer, U ... semiconductor lithography apparatus

Claims (5)

  A light source for semiconductor lithography that generates short-wavelength light for forming a circuit pattern on a semiconductor wafer, and defines an internal space filled with a rare gas or a mixed gas containing a rare gas in a negative pressure state A light source body having an outer peripheral wall portion; and a magnetic field generating means for generating a rotating magnetic field around a predetermined axis in the internal space, wherein the light source body is a nonmagnetic material having at least an outer peripheral wall portion having electrical insulation. A light source for semiconductor lithography, characterized in that a light emitting part for emitting a light component having a short wavelength or light containing the light component to at least a part from the internal space to the outside is formed.   The light source for semiconductor lithography according to claim 1, wherein the magnetic field generating unit is configured to generate a rotating magnetic field while generating an axial magnetic field in the axial direction in an internal space.   The light source body has an outer peripheral wall portion formed in a cylindrical shape, and the magnetic field generating means is spaced apart from the plurality of first coils arranged around the outer peripheral wall portion in the axial direction of the outer peripheral wall portion. A plurality of second coils externally fitted to the outer peripheral wall, and configured to generate a rotating magnetic field by generating an alternating magnetic field with the first coil while generating an axial magnetic field with the second coil. The light source for semiconductor lithography according to claim 2.   4. The light source for semiconductor lithography according to claim 1, wherein the rare gas is either xenon (Xe) gas or neon (Ne) gas. 5.   The light source for semiconductor lithography according to claim 1, wherein at least an outer peripheral wall portion of the light source body is made of heat resistant glass.