JP2009105307A - Extreme ultraviolet light source device and method for removing deposits in extreme ultraviolet light source - Google Patents

Abstract

When tin is used to generate extreme ultraviolet light, a tin compound is sufficiently removed.
A chamber (2) evacuated inside and a plasma generator for generating plasma by heating and exciting tin introduced into a plasma generation region (2b) set in the chamber (2). 6), an extreme ultraviolet light deriving portion (11) from which extreme ultraviolet light (9) emitted from the tin plasma is derived, and an adhesion portion (10a) to which tin oxide generated from the tin plasma is adhered A vacuum ultraviolet light source device (15) that irradiates vacuum ultraviolet light (15a) with respect to, and reducing the tin oxide adhering to the adhesion part (10a) to tin by the vacuum ultraviolet light (15a) An extreme ultraviolet light source device (1) characterized by
[Selection] Figure 1

Description

  The present invention relates to an extreme ultraviolet light source device that generates extreme ultraviolet light having a wavelength of 20 nm or less, and a deposit removal method in the extreme ultraviolet light source. The present invention relates to a method for removing deposits in a light source.

  Research on a light source using extreme ultraviolet light (EUV: Extreme Ultraviolet) having a wavelength of 13.5 nm is being conducted as an exposure light source for next-generation semiconductor lithography in which process rules are miniaturized. EUV having a wavelength of 13.5 nm is emitted by generating plasma by irradiating a medium called a target with laser light for generating plasma. As targets for generating EUV having a wavelength of 13.5 nm, xenon (Xe), tin (Sn), and lithium (Li) are known. Among these targets, lithium (Li) is highly reactive, so the wall surface of the room where the plasma is generated may be altered or corroded by the reaction. Special processing to withstand the reaction with lithium, etc. There was a need to do. In addition, xenon has a problem that the energy conversion efficiency, which is the ratio between the energy of laser light for plasma excitation and the energy of the obtained extreme ultraviolet light, is as low as about 0.5%. Therefore, at present, research on EUV high-efficiency light emission has been focused on those using tin-based metals.

When tin-based metal is used as a target, tin is solid at room temperature. Therefore, when solid tin is irradiated with laser light, dust or dusty tin is scattered and a large amount of so-called debris is generated. It is known that when the debris collides with an optical system or the like, tin adheres to the optical system (reflecting mirror or the like), thereby changing the reflectance or damaging the optical system. Energies are directed at research to reduce flying objects.
As a technique for removing the debris, for example, techniques described in Patent Documents 1 and 2 are known.
Patent Document 1 (Japanese Patent Laid-Open No. 2006-222426) and Patent Document 2 (Japanese Patent Laid-Open No. 2007-220949) describe tin and tin compounds contained in debris as hydrogen ions in an extreme ultraviolet light source targeting tin. Describes a technique of producing gaseous tin hydride (stannane: SnH ₄ ) or tin halide (SnCl ₄ ) by reacting them with hydrogen radicals, halogen ions, halogen radicals, etc., and exhausting them with a vacuum pump. .

JP 2006-222426 A (“0065” to “0076”) JP 2007-220949 A ("0017" to "0022", "0045" to "0048")

(Problems of conventional technology)
In the conventional extreme ultraviolet light source, debris contains not only metallic tin (Sn) but also a tin compound. In general, an oxide has a large electronic band gap (energy gap: the size of a gap of an energy value that an electron can take in a steady state), is chemically stable, and tin oxide (SnO ₂ or the like). Is also chemically stable.
In the methods using hydrogen radicals and the like described in Patent Documents 1 and 2, a technique has been established to some extent for the removal of metallic tin (Sn), but for a stable tin compound such as tin oxide. Has not been sufficiently removed. Therefore, in the techniques described in Patent Documents 1 and 2, with respect to tin deposits, the chemical reaction of metallic tin with hydrogen radicals or the like is performed in a situation where an oxygen-free environment is maintained with little oxygen and no oxide is generated. It was being removed.
However, metal tin (Sn) is highly reactive and has a high rate of oxide formation. Therefore, the generation of tin oxide is inevitable, and it is oxidized during the cleaning process of the optical system to which metal tin (Sn) is attached. Is unavoidable. Therefore, a method that can sufficiently remove a tin compound such as tin oxide by a simple method is desired.

  This invention makes it the 1st technical subject to enable removal of a tin oxide by a simple method, when generating extreme ultraviolet light using tin.

In order to solve the technical problem, the extreme ultraviolet light source device of the invention according to claim 1,
A chamber whose interior is exhausted,
A plasma generator for generating plasma by heating and exciting tin introduced into a plasma generation region set in the chamber;
An extreme ultraviolet light deriving unit from which extreme ultraviolet light emitted from the tin plasma is derived;
A vacuum ultraviolet light source device that irradiates vacuum ultraviolet light to an adhesion portion to which tin oxide generated from the tin plasma is attached;
And tin oxide attached to the attachment portion by the vacuum ultraviolet light is reduced to tin.

The invention according to claim 2 is the extreme ultraviolet light source device according to claim 1,
An optical system for guiding the extreme ultraviolet light emitted from the tin plasma to the extreme ultraviolet light deriving section;
The adhering part constituted by the surface of the optical system;
It is provided with.

The invention according to claim 3 is the extreme ultraviolet light source device according to claim 1 or 2,
A tin reactive gas generator that generates a tin reactive gas that reacts with the reduced tin to produce a tin compound gas;
It is provided with.

The invention according to claim 4 is the extreme ultraviolet light source device according to claim 3,
A gas supply device for supplying a gas containing hydrogen or halogen gas into the chamber; and an energy supply device for supplying energy to the gas supplied by the gas supply device. The tin reactive gas generator for generating the tin reactive gas by ionizing or radicalizing gas;
It is provided with.

In order to solve the technical problem, the deposit removal method in the extreme ultraviolet light source of the invention according to claim 5,
In the method for removing deposits in an extreme ultraviolet light source device in which extreme ultraviolet light is emitted from plasma in which tin is heated and excited,
The tin oxide scattered from the plasma and adhered to the adhering portion is irradiated with vacuum ultraviolet light to reduce the tin oxide to tin, thereby facilitating removal of tin.

According to the invention described in claim 1, when tin is used to generate extreme ultraviolet light, the tin compound, at least tin oxide, can be reduced with vacuum ultraviolet light, and tin oxide can be reduced by a simple method. It can be made removable.
According to invention of Claim 2, the tin compound adhering to an optical system can fully be removable.
According to the invention described in claim 3, the reduced tin can be removed by exhausting with tin reactive gas as tin compound gas.
According to invention of Claim 4, tin can be exhausted and removed with the ionized or radicalized tin reactive gas.
According to the invention described in claim 5, when tin is used to generate extreme ultraviolet light, the tin compound, at least tin oxide, can be reduced with vacuum ultraviolet light, and tin oxide can be reduced by a simple method. It can be made removable.

Next, examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an extreme ultraviolet light source device according to a first embodiment of the present invention.
In FIG. 1, an extreme ultraviolet light source device 1 according to a first embodiment of the present invention is configured by a so-called laser-produced plasma type extreme ultraviolet light source device. The extreme ultraviolet light source device 1 has a chamber 2. A vacuum chamber 2a is provided inside the chamber 2, and a plasma generation region 2b is set at the center of the vacuum chamber 2a. A vacuum pump 3 as an example of an exhaust device is connected to the chamber 2 and the vacuum chamber 2a is exhausted.
A target material supply device 4 is supported above the plasma generation region 2b. The target material supply device 4 has a supply nozzle 4a extending to above the plasma generation region 2b, and supplies the target material to the plasma generation region 2b at a predetermined timing and amount. In Example 1, as an example of the target material, tin oxide (SnO ₂ ) fine particles 5 containing tin are used.

A plasma generator 6 is disposed on the left side of the plasma generation region 2b. The plasma generator 6 of Example 1 is configured by a conventionally known Nd: YAG laser light source device, and irradiates a laser beam 6a for generating plasma. The plasma generating laser light 6 a is condensed by a condensing lens 7 and irradiated to the plasma generating region 2 b in the chamber 2 through the plasma generating laser light introducing window 8. Therefore, the tin oxide supplied by the target material supply device 4 is irradiated with the laser beam 6a, the tin is heated and excited, plasma is generated, and extreme ultraviolet light (EUV) 9 having a wavelength of about 13.5 nm is generated. Released.
An optical system 10 is disposed on the lower right side of the plasma generation region 2b. The optical system 10 of Example 1 is configured by a so-called concave mirror, and condenses the extreme ultraviolet light 9 emitted from the plasma generation region 2b on the extreme ultraviolet light deriving unit 11 to derive vacuum ultraviolet light to the outside. To do. The optical system 10 can be constituted by, for example, a multilayer film reflecting mirror in which molybdenum (Mo) and silicon (Si) films are laminated in multiple layers, and the attachment portion 10a of Example 1 is constituted by the reflecting mirror surface. Has been.

A gas supply device 12 is disposed on the lower left side of the chamber 2. The gas supply device 12 includes a gas supply nozzle 12a extending between the plasma generation region 2b and the optical system 10 to the vicinity of the plasma generation region 2b. The gas supply device 12 of Example 1 supplies hydrogen gas 12b as an example of supply gas.
An energy supply device 13 is disposed on the upper right side of the chamber 2. The energy supply device 13 according to the first embodiment includes an ion / radical generation laser light source device 13 and irradiates an ion / radical generation laser beam 13a. The ion / radical generating laser light 13a is condensed by the condensing lens 14 and irradiated to the hydrogen gas 12b.

Therefore, the hydrogen gas supplied by the gas supply device 12 forms a so-called gas curtain by the flow of the hydrogen gas, and debris of metal tin or tin compound generated in the plasma generation region 2b is converted into the optical system 10 by the gas curtain. The movement to the side is hindered, and the adhesion of debris to the optical system 10 is reduced. Further, the hydrogen gas irradiated with the ion / radical generation laser beam 13a receives energy and is ionized or radicalized to generate a tin reactive gas such as hydrogen ion or hydrogen radical. The generated hydrogen radicals and the like chemically react with metallic tin (Sn) attached to the optical system 10 through the gas curtain to become gaseous tin hydride (SnH ₄ or the like).
The gas supply device 12, the energy supply device 13, the condenser lens 14 and the like constitute the tin reactive gas generator (12 to 14) of Example 1. As the tin reactive gas generator (12 to 14), a conventionally known device can be used. For example, the devices described in Patent Documents 1 and 2 can be used.

A vacuum ultraviolet light source device 15 is disposed above the optical system 10. The vacuum ultraviolet light source device 15 of the first embodiment is composed of an argon excimer lamp, and is irradiated with vacuum ultraviolet light (VUV: Vacuum Ultraviolet) 15a having a wavelength of 126 nm. The vacuum ultraviolet light 15 a is introduced into the chamber 2 and is applied to the adhesion portion 10 a on the surface of the optical system 10.
In addition, the said excimer lamp can use a conventionally well-known thing, for example, it is also possible to use the excimer lamp of Unexamined-Japanese-Patent No. 2007-128924, and it replaces with this, for example, Unexamined-Japanese-Patent No. 2007- It is also possible to use an excimer laser light source device described in Japanese Patent No. 88384.

(Operation of Example 1)
In the extreme ultraviolet light source device 1 of Example 1 having the above-described configuration, the metal tin supplied to the plasma generation region 2b is irradiated with the plasma generating laser light 6a to form plasma, and the extreme ultraviolet light having a wavelength of about 13.5 nm. 9 is emitted, reflected and condensed by the optical system 10, and irradiated from the extreme ultraviolet light deriving unit 11 to the outside. At this time, a part of debris formed by the scattered metal tin or tin compound generated in the plasma generation region 2b is blocked from moving to the optical system 10 side by the gas curtain, and tin reactivity such as hydrogen radical is performed. The gas turns into gaseous tin hydride (tin compound gas) and is exhausted by the vacuum pump 3.

A relatively stable substance such as tin oxide contained in the debris that does not react with hydrogen radicals may adhere to the optical system 10. Tin oxide or the like attached to the surface 10 a of the optical system 10 is reduced to metallic tin by the vacuum ultraviolet light 15 a irradiated by the vacuum ultraviolet light source device 15. In the reduction of tin oxide to metallic tin, when the tin oxide is irradiated with relatively high energy vacuum ultraviolet light, excitons are induced via defects in the oxide, and oxygen is released through this exciton reaction. It is considered that tin is separated and precipitates.
The metallic tin reduced and deposited by the vacuum ultraviolet light 15 a has high reactivity, reacts with hydrogen radicals and the like existing in the vicinity, becomes tin hydride, and is exhausted by the vacuum pump 3. Therefore, in the extreme ultraviolet light source device 1 of Example 1, the tin oxide can be decomposed and reduced to metallic tin only by irradiating the vacuum ultraviolet light 15a. It can be gasified and exhausted with a tin reactive gas. That is, tin oxide can be reduced efficiently and stably with only light energy and without using other gases.

(Experimental example)
An experiment for confirming the effect of Example 1 was performed.
(Experimental example 1)
In Experimental Example 1, when the number of times of irradiation with the plasma generating laser beam 6a is 0, 10,000, 20,000, and 30,000 times in the extreme ultraviolet light source device 1, the debris adhered and deposited is 126 nm. After irradiating the excimer lamp with an irradiation intensity of 3 mW / cm ² for 5 hours, the surface was analyzed by XPS (X-ray photoelectron spectroscopy). The analysis by XPS measured the XPS spectrum corresponding to the 3d orbital (Sn-3d) of tin and the XPS spectrum corresponding to the 1s orbital (O-1s) of oxygen.
(Comparative Example 1)
In Comparative Example 1, the experiment was performed under the same conditions as in Experimental Example 1 except that the excimer lamp was not irradiated.
The experimental results are shown in FIG.

FIG. 2 is a graph of experimental results of the experimental example, FIG. 2A is a graph of the XPS spectrum of Sn-3d, and FIG. 2B is a graph of the XPS spectrum of O-1s.
In the graph of FIG. 2, the horizontal axis represents the number of times of irradiation (the number of laser shots), and the vertical axis represents the XPS signal intensity.
In FIG. 2A, the signal from the tin atom of the deposit (tin oxide or the like) is proportional to the number of times of irradiation regardless of whether or not the excimer lamp is irradiated, and is proportional to the number of times of irradiation of the plasma generating laser beam 6a. As a result, the deposits increase.
In FIG. 2B, when the excimer lamp is not irradiated, the oxygen atom component from the deposit increases oxygen as in Comparative Example 1 (see Δ in the graph), and tin oxide adheres and deposits. It can be seen that it has increased. On the other hand, when the excimer lamp is irradiated, as shown in Experimental Example 1 (see ○ in the graph), oxygen is reduced compared to Comparative Example 1 with the same number of irradiations, and oxygen is desorbed from the deposits. It was confirmed that tin oxide was reduced, and deposition of metallic tin was confirmed.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible.
For example, in the above-described embodiment, the configuration of a laser generated plasma (LPP) system is exemplified as a method for generating plasma for generating extreme ultraviolet light. However, the present invention is not limited to this, and DPP (discharge generated plasma) is not limited thereto. , Discharge Produced Plasma) and other plasma generation methods.
In the above embodiment, fine particle tin as a target material was supplied. However, the present invention is not limited to this method, and a fixed plate-shaped tin target, a liquid or gaseous tin compound as a target, or The shape of the target can be arbitrarily changed, such as a droplet containing tin fine particles. Moreover, although the easily available tin oxide was illustrated as a target material, it is not limited to this, It is also possible to use metallic tin and another tin compound.

Furthermore, in the said Example, it can change arbitrarily about the concrete material name and numerical value which were illustrated according to a design, a specification, etc. For example, the laser light source devices 6 and 13 can use known laser light source devices that can be used. Further, the positional relationship of the devices 4, 6, 10, 12, 13 and the like is not limited to the positional relationship illustrated in the embodiment, and can be changed.
Moreover, although hydrogen was illustrated as gas for gas curtain, it is not limited to this, Arbitrary gas which can react with tin and can be made into a gaseous state, for example, halogen gas (chlorine gas) etc. are used. It is also possible. Further, although hydrogen radicals and the like are generated by laser light irradiation, the present invention is not limited to this method, and it can be generated by a method such as bringing hydrogen gas into contact with a heated metal (tungsten or the like).
Furthermore, in the said Example, although the structure which irradiates vacuum ultraviolet light with respect to the surface 10a of the optical system 10 as an adhesion part to which a debris adheres, it is not limited to this, Arbitrary arbitrary which needs to remove a debris The member can be irradiated with vacuum ultraviolet light.

  The extreme ultraviolet light source device of the present invention can be suitably used in the lithography field in which a fine circuit pattern is created using extreme ultraviolet light.

FIG. 1 is an overall explanatory view of an extreme ultraviolet light source device according to a first embodiment of the present invention. FIG. 2 is a graph of experimental results of the experimental example, FIG. 2A is a graph of the XPS spectrum of Sn-3d, and FIG. 2B is a graph of the XPS spectrum of O-1s.

Explanation of symbols

1 ... Extreme ultraviolet light source device,
2 ... Chamber,
2a ... vacuum chamber,
2b ... plasma generation region,
3 ... Vacuum pump
4 ... Target material supply device,
4a ... supply nozzle,
5 ... fine particles,
6 ... Plasma generator,
6a ... laser light for plasma generation,
7 ... Condensing lens,
8 ... Laser light introduction window for plasma generation,
9 ... Extreme ultraviolet light,
10 ... Optical system,
10a: adhesion part,
11 ... Extreme ultraviolet light deriving part,
12 ... Gas supply device,
12-14 ... tin reactive gas generator,
12a ... Gas supply nozzle,
12b ... hydrogen gas,
13 ... Energy supply device,
13a: Laser light for generating ions and radicals,
14 ... Condensing lens,
15 ... Vacuum ultraviolet light source device,
15a ... Vacuum ultraviolet light.

Claims (5)

A chamber whose interior is exhausted,
A plasma generator for generating plasma by heating and exciting tin introduced into a plasma generation region set in the chamber;
An extreme ultraviolet light deriving unit from which extreme ultraviolet light emitted from the tin plasma is derived;
A vacuum ultraviolet light source device that irradiates vacuum ultraviolet light to an adhesion portion to which tin oxide generated from the tin plasma is attached;
And an ultra-violet light source device that reduces the tin oxide adhering to the adhering portion to tin by the vacuum ultraviolet light. An optical system for guiding the extreme ultraviolet light emitted from the tin plasma to the extreme ultraviolet light deriving section;
The adhering part constituted by the surface of the optical system;
The extreme ultraviolet light source device according to claim 1, comprising: A tin reactive gas generator that generates a tin reactive gas that reacts with the reduced tin to produce a tin compound gas;
The extreme ultraviolet light source device according to claim 1, wherein the extreme ultraviolet light source device is provided. A gas supply device for supplying a gas containing hydrogen or halogen gas into the chamber; and an energy supply device for supplying energy to the gas supplied by the gas supply device. The tin reactive gas generator for generating the tin reactive gas by ionizing or radicalizing gas;
The extreme ultraviolet light source device according to claim 3, comprising: In the method for removing deposits in an extreme ultraviolet light source device in which extreme ultraviolet light is emitted from plasma in which tin is heated and excited,
Irradiation with vacuum ultraviolet light to the tin oxide scattered from the plasma and adhering to the adhering portion, and reducing tin oxide to tin facilitates removal of tin. A method for removing deposits in a light source.

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