JP2008041391A - Light source device, exposure system, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device which can achieve superior debris removal and supply the EUV light with high stability. <P>SOLUTION: The light source device generates a plasma, supplies the light radiated from the plasma to an optical system, includes a chamber for housing the plasma, a gas supply means for supplying the buffer gas into the chamber, a detection means for detecting the environmental conditions within the chamber, and a control means for controlling the buffer gas pressure within the chamber in accordance with the detection result found by the detection means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to a light source device, and more particularly to a light source device that emits extreme ultraviolet (EUV) light. The present invention is suitable for a light source of an exposure apparatus that exposes an object to be processed such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD).

  2. Description of the Related Art A projection exposure apparatus has been conventionally used when manufacturing a fine semiconductor element such as a semiconductor memory or a logic circuit by using a photolithography technique. The projection exposure apparatus transfers a circuit pattern drawn on a mask (reticle) to an object to be processed such as a wafer via a projection optical system.

  The minimum dimension (resolution) that can be transferred by the projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength, the better the resolution. For this reason, with the recent demand for miniaturization of semiconductor elements, the exposure light has been shortened in wavelength. Specifically, the ultra high pressure mercury lamp (i-line (wavelength: about 365 nm)), KrF excimer laser (wavelength: about 248 nm), ArF excimer laser (wavelength: about 193 nm), and the wavelength of ultraviolet light used as exposure light are shortened. I came.

  In recent years, semiconductor elements have been miniaturized rapidly, and there is a limit in lithography using ultraviolet light. Therefore, in order to efficiently transfer a very fine circuit pattern of 0.1 μm or less, a projection exposure apparatus (hereinafter referred to as “EUV exposure”) using EUV light having a wavelength shorter than that of ultraviolet light and having a wavelength of about 10 nm to 15 nm. Has been developed.

  An EUV exposure apparatus typically uses a laser plasma (LPP) light source or a discharge plasma (DPP) light source as an EUV light source. The laser plasma light source generates EUV light by irradiating a target material with laser light to generate plasma. On the other hand, a discharge-type plasma light source generates plasma by generating a EUV light by flowing a gas between electrodes and discharging it.

  Such an EUV light source generates scattered particles called debris (for example, gasified, liquefied, ionized target material, high-speed electrons and ions, etc.) together with EUV light. Such debris contaminates and damages optical elements (such as a condensing mirror for condensing light from plasma and a mirror included in a subsequent optical system), and causes a decrease in reflectance.

  Accordingly, various proposals have been made to mitigate the influence of debris (to remove debris) (see, for example, Patent Documents 1 and 2). For example, a debris blocking member is disposed around the plasma, filled with a buffer gas (for example, an inert gas such as Ar or He) having a high transmittance with respect to EUV light, or caused to collide with debris. A gas flow (gas molecules) is formed by a buffer gas.

When the gas flow collides with the debris, the debris loses energy when jumping out of the plasma or the target material (that is, the velocity is attenuated) and is trapped in the gas flow. The debris trapped in the gas flow adheres to a debris filter disposed around the plasma, or is exhausted together with gas molecules by a vacuum pump or the like. The rate of decay of the debris velocity due to gas molecules is proportional to the product of the gas pressure and the gas thickness (where “gas thickness” is the flight distance of the gas molecules). The attenuation factor of EUV light is also proportional to the product of the gas pressure and the gas thickness. Thus, increasing the gas pressure or thickness to mitigate the effects of debris also greatly attenuates EUV light.
Japanese Unexamined Patent Publication No. 63-292553 Japanese Patent Laid-Open No. 9-320794

  However, an EUV light source that removes debris by introducing a buffer gas has various problems as follows.

  When the temperature of the buffer gas rises as the ambient temperature changes due to plasma emission, the molecular density of the buffer gas decreases. Therefore, the number of collisions between the debris and the gas molecules is reduced, resulting in a problem that the debris suppression effect is rapidly reduced. The debris velocity decay rate by gas molecules is as follows: gas thickness L, gas pressure P, gas molecular weight M, debris diameter α, debris density ρ, mass of substance n, gas density When d and the volume of gas are V, it is expressed by the following formula 1.

  Referring to Equation 1, when the gas density is decreased and the debris density is increased, the attenuation rate is rapidly decreased. This is a problem that affects the lifetime of the optical element.

  In addition, since the change in the density of the buffer gas also changes the EUV light absorption rate, there is a problem that the power of the EUV light that can be extracted (supplied) becomes unstable.

  Therefore, an object of the present invention is to provide a light source device that realizes good debris removal and can stably supply EUV light.

  In order to achieve the above object, a light source device according to one aspect of the present invention is a light source device that generates plasma and supplies light emitted from the plasma to an optical system, and includes a chamber that stores the plasma. A gas supply means for supplying a buffer gas into the chamber; a detection means for detecting an environmental condition in the chamber; and a pressure of the buffer gas in the chamber based on a detection result of the detection means. And a control means.

  A light source device according to another aspect of the present invention is a light source device that generates plasma and supplies light emitted from the plasma to an optical system, the chamber containing the plasma, and a buffer gas in the chamber And a control means for controlling the pressure of the buffer gas in the chamber based on the light emission setting of the plasma.

  An exposure apparatus according to still another aspect of the present invention is an exposure apparatus that exposes a mask pattern onto an object to be processed, and an illumination optical system that illuminates the mask using light supplied from the light source device described above. And a projection optical system for projecting the pattern onto the object to be processed.

  According to still another aspect of the present invention, there is provided a device manufacturing method comprising: exposing a target object using the above-described exposure apparatus; and developing the exposed target object. The device manufacturing method claims also apply to the intermediate and final device itself. Such devices include semiconductor chips such as LSI and VLSI, CCDs, LCDs, magnetic sensors, thin film magnetic heads, and the like.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the light source apparatus which implement | achieves favorable debris removal and can supply EUV light stably can be provided.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  The light source device of the present invention is a light source device that generates plasma and supplies EUV light (light having a wavelength of 20 nm or less, preferably light having a wavelength of 13 nm to 15 nm) emitted from the plasma to a subsequent optical system. . In the present embodiment, the light source device of the present invention is embodied as a laser plasma (LPP) light source. However, the light source device of the present invention is not limited to the LPP light source, and may be a discharge plasma (DPP) light source or other types of light sources.

  The light source device of the present invention has a chamber for storing plasma and a gas supply means for supplying a buffer gas for removing debris generated in the chamber. Here, the removal of debris means that the light source device suppresses the debris from reaching the optical system that supplies the EUV light, and the debris reaches the condensing mirror that collects the EUV light from the plasma. Including suppression.

  Furthermore, the light source device of the present invention has a detection means for detecting an environmental state in the chamber and a control means for controlling the pressure of the buffer gas in the chamber based on the detection result of the detection means. Here, the environmental condition in the chamber, that is, the object to be detected by the detection means is, for example, the density of the buffer gas, the temperature and pressure of the buffer gas, and the transmittance of light (EUV light or infrared light) to the buffer gas. is there. The control means controls the pressure of the buffer gas in the chamber by controlling the supply amount of the buffer gas supplied by the gas supply means into the chamber and / or the exhaust amount by the exhaust means for exhausting the atmosphere in the chamber. .

  In the light source device of the present invention, the above-described control means can be replaced with a control means for controlling the pressure of the buffer gas in the chamber based on the plasma emission setting.

  Hereinafter, the light source device of the present invention will be specifically described.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration of a light source device 1 according to the first embodiment. The light source device 1 supplies the EUV light EL to the subsequent optical system OP. As illustrated in FIG. 1, the light source device 1 includes a chamber 10, an exhaust pump 11, a pump control unit 12, a target supply mechanism 13, a target recovery mechanism 14, and a laser light source unit 15. In addition, the light source device 1 includes a condenser mirror 16, a debris filter 17, a buffer gas supply mechanism 18, a gas control unit 19, and a gas density detector 20.

  The chamber 10 maintains a vacuum or reduced pressure environment formed by an exhaust pump 11 to be described later, and stores the plasma PL generated by the light source device 1. Moreover, the chamber 10 accommodates the target supply mechanism 13, the target collection | recovery mechanism 14, the laser light source part 15, the condensing mirror 16, the debris filter 17, the buffer gas supply mechanism 18, and the gas density detector 20 in this embodiment.

  The exhaust pump 11 is controlled by a pump control unit 12 to be described later, and exhausts the chamber 10 to form a vacuum or reduced pressure environment. In other words, the exhaust pump 11 functions as an exhaust means. The exhaust pump 11 is composed of, for example, a turbo molecular pump.

  The pump control unit 12 controls the exhaust pump 11 based on a detection result of a gas density detector 20 described later, and in this embodiment, controls the exhaust amount (exhaust speed) of the exhaust pump 11. The pump control unit 12 functions as a control unit that controls the pressure (density) of the buffer gas supplied from the gas supply mechanism 18 in the chamber 10 by controlling the exhaust amount of the exhaust pump 11.

  The target supply mechanism 13 supplies a target to a predetermined position of the chamber 10 maintained in a vacuum or reduced pressure environment via a gas jet (not shown). The target supply mechanism 13 supplies a target intermittently in synchronization with light emission of a laser beam LL from a laser light source unit 15 described later. The target is, for example, a metal thin film such as copper, tin, or aluminum, a gas such as xenon (Xe), or a cluster.

  The target recovery mechanism 14 recovers the target supplied from the target supply mechanism 13. The target recovery mechanism 14 recovers not only the target (that is, the surplus target) supplied from the target supply mechanism 13 and not used for generating the plasma PL but also the target after being used for generating the plasma PL. Can do.

  The laser light source unit 15 irradiates the laser beam LL toward the target supplied from the target supply mechanism 13. Specifically, the laser beam LL is a pulse laser, and in order to increase the average intensity of the EUV light EL emitted from the plasma PL (target), the repetition frequency of the pulse laser is preferably high. The laser light source unit 15 is operated at a repetition frequency of several kHz, for example.

  In this embodiment, the condensing mirror 16 is composed of a multilayer mirror and has a function of condensing the EUV light EL emitted from the plasma PL. In other words, the condensing mirror 16 collects the EUV light EL from the plasma PL to form a condensing point IF. In addition, the condensing mirror 16 supplies the EUV light EL to a subsequent optical system OP (for example, an illumination optical system in the case of an exposure apparatus).

  The debris filter 17 is disposed around the plasma PL, and collects debris emitted from the plasma PL together with the EUV light EL. In other words, the debris filter 17 removes the debris generated in the chamber 10 in cooperation with a buffer gas supply mechanism 18 (buffer gas supplied from) described later.

  As shown in FIG. 2, the debris filter 17 includes a hollow spherical metal body 171 and a thin plate-like debris attachment member 172 such as aluminum. Specifically, the debris filter 17 is configured by arranging a plurality of debris adhesion members 172 radially on the spherical metal body 171 around the plasma PL (light emission point) so as not to block the EUV light EL. As shown by MD in FIG. 2, debris (unnecessary substance) collides with the gas molecules (or gas flow) of the buffer gas filled in the chamber 10, and the movement direction (movement direction) becomes irregular, and the debris adheres. It adheres and accumulates on the member 172. Here, FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the debris filter 17.

  The buffer gas supply mechanism 18 is controlled by a gas control unit 19 described later, and supplies the buffer gas into the chamber 10 via a supply nozzle (not shown). In other words, the buffer gas supply mechanism 18 functions as a gas supply unit. The buffer gas supply mechanism 18 fills the chamber 10 with the buffer gas and forms a buffer gas flow in the chamber 10. The buffer gas is a gas for removing debris generated in the chamber 10 by colliding with the debris, and is, for example, an inert gas such as argon gas or helium.

  The gas control unit 19 controls the buffer gas supply mechanism 18 based on the detection result of the gas density detector 20 described later. In this embodiment, the supply amount (supply speed) of the buffer gas by the buffer gas supply mechanism 18 is controlled. Control. The gas control unit 19 functions as a control unit that controls the pressure (density) of the buffer gas supplied from the gas supply mechanism 18 in the chamber 10 by controlling the supply amount of the buffer gas. However, the gas control unit 19 can also control the temperature and pressure of the buffer gas by the buffer gas supply mechanism 18.

  The gas density detector 20 is disposed inside the debris filter 17 and detects the environmental state in the chamber, specifically, the gas density of the buffer gas. In other words, the gas density detector 20 functions as detection means. In the present embodiment, the gas density detector 20 uses the property that the resonance frequency of the thin cylinder changes depending on the fluid density. This property is that when the cylinder is vibrated in the fluid, the surrounding fluid also vibrates, the flow of the surrounding fluid seen from the cylinder becomes an inertial load, the apparent mass of the cylinder increases, and the resonance frequency changes. It is. Since the amount of change is a function of the fluid density, the density of the fluid (that is, the density of the buffer gas) can be detected by measuring the resonance frequency. Here, the buffer gas may simply be the atmosphere in the chamber.

  In the light source device 1, plasma PL is generated by irradiating the target material supplied from the target supply mechanism 13 with the laser light LL emitted from the laser light source unit 15. EUV light EL is emitted from the plasma PL, and is collected by the collector mirror 16. The EUV light EL condensed by the condensing mirror 16 forms a condensing point IF via the bellows BL disposed in the chamber 10. At this time, the gas control unit 19 uses the buffer gas supply mechanism 13 so that the pressure (density) of the buffer gas in the chamber 10 is constant based on the detection result (buffer gas density) of the gas density detector 20. The supply amount of the buffer gas from is controlled. Thereby, the debris removal effect (debris suppression effect) by the debris filter 16 and the buffer gas supply mechanism 18 can be obtained reliably. Instead of the gas control unit 19 controlling the supply amount of the buffer gas, the pump control unit 12 may maintain the pressure (density) of the buffer gas constant by controlling the exhaust amount by the exhaust pump 11. And you may combine both. For example, the gas control unit 19 compares the buffer gas density (detected value) detected by the gas density detector 20 with a preset set value (initial set value), and detects a change in the buffer gas density. To do. When a change in the density of the buffer gas is detected, the gas control unit 19 controls the supply amount of the buffer gas by the buffer gas supply mechanism 18, and then the pump control unit 11 controls the exhaust amount by the exhaust pump 11. Here, the exhaust pump mainly discharges the buffer gas from the inside of the chamber, but of course, the buffer gas is not selected and discharged, but only the atmosphere in the chamber is discharged.

  FIG. 3 is a diagram for explaining specific control (control by the pump control unit 12 and the gas control unit 19) of the density of the buffer gas in the chamber 10 according to the first embodiment. FIG. 3 is a graph showing the density of the buffer gas in the chamber 10 in Example 1, with the horizontal axis representing time and the vertical axis representing the buffer gas density (normalized).

  Referring to FIG. 3, first, the buffer gas is supplied so that the buffer gas density in the chamber 10 becomes the initial setting value, and the detection of the buffer gas density by the gas density detector 20 is started (step). 1001). The initial set value here is a value set so that the energy of the EUV light EL continuously emitted for 1 second at a predetermined frequency (1 kHz) at the condensing point IF is maximized. In addition, the supply of the target from the target supply mechanism 13 is also started.

  Next, light emission of the plasma PL is started (step 1002). Specifically, the irradiation of the laser beam LL from the laser light source unit 15 is started.

  When the density of the buffer gas in the chamber 10 decreases due to the light emission of the plasma PL and falls below a preset threshold value, the supply amount of the buffer gas supplied from the buffer gas supply mechanism 13 is increased (step 1003). The threshold here is 1 × 0.7.

  Then, when the density of the buffer gas in the chamber 10 returns to the initial setting value, the increase in the supply amount of the buffer gas is stopped, and the supply of the buffer gas is continued while maintaining the supply amount when the increase is stopped (step). 1004). When the density of the buffer gas in the chamber 10 exceeds the initial set value, the exhaust amount (exhaust speed) by the exhaust pump 11 is controlled.

  Finally, the density of the buffer gas in the chamber 10 when the emission of the plasma PL is finished is stored as an initial set value (step 1005).

  As described above, in the light source device 1, the supply amount and / or the exhaust amount of the buffer gas is controlled from the detection result by the gas density detector 20 arranged inside the debris filter 17, and the density of the buffer gas in the chamber 10 is controlled. Is controlled to be constant. Thereby, the light source device 1 can maintain the lifetime of the optical elements disposed in the chamber 10 and the optical elements constituting the subsequent optical system OP for a long period without reducing the debris removal effect. Moreover, the light source device 1 can reduce the fluctuation of the debris removal effect and can stabilize the EUV light EL to be extracted. In other words, the light source device 1 can achieve good debris removal, and can stably supply the EUV light EL to the subsequent optical system OP.

  FIG. 4 is a schematic cross-sectional view illustrating the configuration of the light source device 1A according to the second embodiment. Compared with the light source device 1, the light source device 1 </ b> A has a gas temperature detector 21 and a pressure gauge 22 as detection means instead of the gas density detector 20.

  The gas temperature detector 21 is disposed inside the debris filter 17 and detects the environmental state in the chamber, specifically, the temperature of the buffer gas. The pressure gauge 22 detects the pressure of the buffer gas. Since the gas temperature detector 21 and the pressure gauge 22 can employ any configuration known in the art, a detailed description of the structure and operation is omitted here.

  In the second embodiment, the gas control unit 19 determines that the pressure (density) of the buffer gas in the chamber 10 is constant based on the detection results (buffer gas pressure / temperature) of the gas temperature detector 21 and the pressure gauge 22. Thus, the supply amount of the buffer gas from the buffer gas supply mechanism 13 is controlled. Thereby, the debris removal effect (debris suppression effect) by the debris filter 16 and the buffer gas supply mechanism 18 can be obtained reliably.

  For example, the gas control unit 19 compares the detection result (buffer gas pressure / temperature) detected by the gas temperature detector 21 and the pressure gauge 22 with a preset setting value (initial setting value), and the buffer gas. Detects changes in density. When a change in the density of the buffer gas is detected, the gas control unit 19 simultaneously controls the supply amount of the buffer gas by the buffer gas supply mechanism 18 and the pump control unit 11 simultaneously controls the exhaust amount by the exhaust pump 11.

  FIG. 5 is a diagram for explaining specific control (control by the pump control unit 12 and the gas control unit 19) of the density of the buffer gas in the chamber 10 in the second embodiment. FIG. 5 is a graph showing the density of the buffer gas in the chamber 10 in Example 2, with the horizontal axis representing time and the vertical axis representing buffer gas pressure / temperature (normalized).

  Referring to FIG. 5, first, the buffer gas is supplied so that the pressure / temperature of the buffer gas in the chamber 10 becomes the initial set value, and the temperature of the buffer gas by the gas temperature detector 21 and the pressure gauge 22 Pressure detection is started (step 1001A). In addition, the supply of the target from the target supply mechanism 13 is also started.

  Next, emission of plasma PL is started (step 1002A). Specifically, the irradiation of the laser beam LL from the laser light source unit 15 is started.

  The pressure / temperature of the buffer gas in the chamber decreases due to the light emission of the plasma PL, and when the pressure falls below the threshold, the exhaust amount by the exhaust pump 11 is controlled so that the pressure in the chamber 10 increases, and the supply amount of the buffer gas is reduced. Increase (step 1003A). The threshold here is 1 × 0.8.

  Then, when the pressure / temperature of the buffer gas in the chamber 10 returns to the initial set value, the increase in the supply amount of the buffer gas is stopped, and the supply of the buffer gas is continued while maintaining the supply amount when the increase is stopped. (Step 1004A). If the pressure / temperature of the buffer gas in the chamber 10 exceeds the initial set value, the exhaust amount (exhaust speed) by the exhaust pump 11 is controlled.

  Finally, the pressure / temperature of the buffer gas in the chamber 10 when the emission of the plasma PL is completed is stored as an initial set value (step 1005A).

  Thus, in the light source device 1A, the supply amount and / or the exhaust amount of the buffer gas is controlled from the detection result by the gas temperature detector 21 and the pressure gauge 22 arranged inside the debris filter 17, and the chamber 10 The density of the buffer gas is controlled to be constant. Thereby, the light source device 1A can maintain the lifetime of the optical elements disposed in the chamber 10 and the optical elements constituting the subsequent optical system OP for a long period without reducing the debris removal effect. Further, the light source device 1A can reduce the fluctuation of the debris removal effect and can stabilize the EUV light EL to be extracted. In other words, the light source device 1A can achieve good debris removal and stably supply the EUV light EL to the optical system OP at the subsequent stage.

  FIG. 6 is a schematic cross-sectional view illustrating the configuration of the light source device 1B according to the third embodiment. Compared with the light source device 1, the light source device 1 </ b> B has photodetectors 23 and 24 as detection means instead of the gas density detector 20. Further, the light source device 1B includes reflection mirrors 25 and 26 that reflect the EUV light EL. In the present embodiment, the reflection mirrors 25 and 26 are formed of multilayer mirrors.

  The photodetectors 23 and 24 are constituted by, for example, a photodiode or a CCD, and are arranged in the chamber 10. The photodetector 23 detects the amount of EUV light EL reflected by the reflection mirror 25 and not passing through the buffer gas supplied from the buffer gas supply mechanism 18. On the other hand, the photodetector 24 detects the amount of EUV light EL reflected by the reflecting mirror 25 and the reflecting mirror 26 and passing through the buffer gas. Therefore, the photodetectors 23 and 24 detect the transmittance of the EUV light EL with respect to the buffer gas by comparing the detection value (light amount) in the photodetector 23 with the detection value (light amount) in the photodetector 24. be able to. The light source device 1 uses the transmittance (detected value in the light detector 24 / detected value in the light detector 23) as a parameter representing the pressure (density) of the buffer gas.

  In the third embodiment, the gas control unit 19 determines the pressure of the buffer gas in the chamber 10 based on the detection results of the photodetectors 23 and 24 (detection value in the photodetector 24 / detection value in the photodetector 23). The supply amount of the buffer gas is controlled so that (density) is constant. Thereby, the debris removal effect (debris suppression effect) by the debris filter 16 and the buffer gas supply mechanism 18 can be obtained reliably.

  For example, the gas control unit 19 compares the detection results of the photodetectors 23 and 24 (detection value in the photodetector 24 / detection value in the photodetector 23) with a preset setting value (initial setting value). Detect changes in the density of the buffer gas. When a change in the density of the buffer gas is detected, the gas control unit 19 simultaneously controls the supply amount of the buffer gas by the buffer gas supply mechanism 18 and the pump control unit 11 simultaneously controls the exhaust amount by the exhaust pump 11.

  As described above, in the light source device 1B, the supply amount and / or exhaust amount of the buffer gas is controlled from the detection results of the photodetectors 23 and 24, and the density of the buffer gas in the chamber 10 is controlled to be constant. . Thereby, the light source device 1B can maintain the lifetime of the optical elements arranged in the chamber 10 and the optical elements constituting the subsequent optical system OP for a long time without reducing the debris removal effect. In addition, the light source device 1B can reduce the fluctuation of the debris removal effect and can stabilize the EUV light EL to be extracted. In other words, the light source device 1B can achieve good debris removal and stably supply the EUV light EL to the subsequent optical system OP. In the third embodiment, the transmittance of the EUV light EL is used. However, the transmittance of the infrared light emitted from the plasma PL may be used as in the case of the EUV light EL.

  FIG. 7 is a schematic cross-sectional view illustrating the configuration of the light source device 1 </ b> C according to the fourth embodiment. Compared with the light source device 1, the light source device 1 </ b> C does not have the detection means (gas density detector 20) but has the light source control unit 27.

  The light source control unit 27 uses the buffer gas in the chamber 10 based on the emission setting of the plasma PL (EUV light EL) (for example, the emission frequency of the plasma PL (frequency of the laser light LL), the target supply interval, etc.). To control the pressure. Specifically, the light source control unit 27 has a table of buffer gas supply amount and exhaust amount corresponding to the light emission setting of the plasma PL. The light source control unit 27 controls the exhaust pump 11 (pump control unit 12) and the buffer gas supply mechanism 18 (gas control unit 19) using the table.

  In the third embodiment, the light source control unit 27 has a buffer gas supply amount and exhaust amount table corresponding to the emission frequency of the plasma PL, and controls the buffer gas supply amount and exhaust amount according to the table. In the third embodiment, a table corresponding only to the light emission frequency of the plasma PL is used, but the present invention is not limited to this. There may be a plurality of light emission settings for the plasma PL. For example, a buffer gas supply amount and exhaust amount table corresponding to parameters of the light emission frequency and the drive duty may be used.

  In this way, in the light source device 1C, the exhaust pump 11 and the buffer gas supply mechanism 18 are controlled based on the buffer gas supply amount and exhaust amount table corresponding to the light emission setting of the plasma PL (EUV light EL). Thereby, the light source device 1 </ b> C can keep the density of the buffer gas in the chamber 10 constant. Therefore, the light source device 1C can maintain the lifetime of the optical elements arranged in the chamber 10 and the optical elements constituting the subsequent optical system OP for a long period without reducing the debris removal effect. In addition, the light source device 1C can reduce the fluctuation of the debris removal effect and can stabilize the EUV light EL to be extracted. In other words, the light source device 1C can achieve good debris removal, and can stably supply the EUV light EL to the optical system OP at the subsequent stage.

  Hereinafter, an exposure apparatus 300 to which the light source devices 1 to 1C of the present invention are applied will be described with reference to FIG. Here, FIG. 8 is a schematic sectional view showing a configuration of an exposure apparatus 300 as one aspect of the present invention.

  The exposure apparatus 300 of the present invention uses EUV light (for example, a wavelength of 13.4 nm) as exposure light, and is a projection that exposes the pattern of the mask 320 onto the object 340 by the step-and-scan method or the step-and-repeat method. It is an exposure apparatus. Such an exposure apparatus is suitable for a lithography process of sub-micron or quarter micron or less, and in the present embodiment, a step-and-scan type exposure apparatus (also referred to as “scanner”) will be described as an example. Here, the “step-and-scan method” is a method in which a wafer is exposed to a mask pattern by continuously scanning the wafer with respect to the mask. In the “step-and-scan method”, the wafer is stepped after the exposure of one shot is completed, and is moved to the next exposure area. The “step-and-repeat method” is a method in which the wafer is moved stepwise for each batch exposure of the wafer and moved to the exposure area of the next shot.

  The exposure apparatus 300 includes an illumination device 310, a mask stage 335 on which a mask 330 is placed, a projection optical system 340, a wafer stage 355 on which an object 350 is placed, an alignment detection mechanism 360, and a focus position detection mechanism. 370.

  In addition, as shown in FIG. 8, the exposure apparatus 300 is provided with a vacuum chamber VC so that at least the optical path through which the EUV light EL passes is a vacuum environment. This is because EUV light EL has a low transmittance to the atmosphere and generates contaminants due to a reaction with a residual gas (polymer organic gas or the like) component.

  The illumination device 310 is an illumination device that illuminates the mask 330 with an arc-shaped EUV light (for example, a wavelength of 13.4 nm) EL corresponding to the arc-shaped field of view of the projection optical system 340. And an optical system 314.

  The light source device 1 can be applied in any form as described above, and a detailed description thereof is omitted here. Moreover, although the light source device 1 shown in FIG. 1 is used in FIG. 8, this form is illustrative and the present invention is not limited to this. For example, the light source devices 1A, 1B, and 1C shown in FIGS. 4, 6, and 7 may be used.

  The illumination optical system 314 includes a reflection mirror 314a and an optical integrator 314b. The reflection mirror 314a reflects the EUV light EL supplied from the light source device 1 and plays a role of guiding it to the optical element (optical system) at the subsequent stage. The optical integrator 314b has a role of uniformly illuminating the mask 330 with a predetermined numerical aperture. Further, the illumination optical system 314 may have an aperture for limiting the illumination area of the mask 330 to an arc shape at a position conjugate with the mask 330.

  The mask 330 is a reflective mask, on which a circuit pattern (or image) to be transferred is formed, and is supported and driven by a mask stage 335. Diffracted light emitted from the mask 330 is reflected by the projection optical system 340 and projected onto the object 350. The mask 330 and the target object 350 are arranged in an optically conjugate relationship. Since the exposure apparatus 300 is a step-and-scan exposure apparatus, the pattern of the mask 330 is reduced and projected onto the object 350 by scanning the mask 330 and the object 350.

  The mask stage 335 supports the mask 330 and is connected to a moving mechanism (not shown). Any structure known in the art can be applied to the mask stage 335. A moving mechanism (not shown) is composed of a linear motor or the like, and can move the mask 330 by driving the mask stage 335 at least in the X direction. The exposure apparatus 300 scans the mask 330 and the workpiece 350 in a synchronized state. Here, the scanning direction in the surface of the mask 330 or the object to be processed 350 is X, the direction perpendicular to the scanning direction is Y, and the direction perpendicular to the mask 330 or the object to be processed 350 is Z.

  The projection optical system 340 uses a plurality of reflection mirrors (that is, multilayer mirrors) 342 to reduce and project the pattern on the mask 330 onto the object 350 to be processed, which is an image plane. The number of the plurality of reflecting mirrors 342 is about 4 to 6. In order to realize a wide exposure area with a small number of mirrors, the mask 330 and the object 350 are scanned simultaneously using only a thin arc-shaped area (ring field) separated from the optical axis by a certain distance. Transfer the area. The numerical aperture (NA) of the projection optical system 340 is about 0.2 to 0.3.

  The object to be processed 350 is a wafer in this embodiment, but widely includes liquid crystal substrates and other objects to be processed. A photoresist is applied to the object to be processed 350.

  Wafer stage 355 supports object 350 to be processed via a wafer chuck. For example, the wafer stage 355 moves the workpiece 350 in the XYZ directions using a linear motor. The mask 330 and the workpiece 350 are scanned synchronously. Further, the position of the mask stage 335 and the position of the wafer stage 355 are monitored by a laser interferometer, for example, and both are driven at a constant speed ratio.

  The alignment detection mechanism 360 measures the positional relationship between the position of the mask 330 and the optical axis of the projection optical system 340, and the positional relationship between the position of the object 350 and the optical axis of the projection optical system 340. Based on the measurement result, the positions and angles of the mask stage 335 and the wafer stage 355 are set so that the projected image of the mask 330 coincides with a predetermined position of the workpiece 350.

  The focus position detection mechanism 370 measures the focus position on the surface of the object 350 to be processed, and controls the position and angle of the wafer stage 355 so that the surface of the object 350 is always imaged by the projection optical system 340 during exposure. Keep on.

  In the exposure, the EUV light EL emitted from the illumination device 310 illuminates the mask 330, and the projection optical system 340 forms an image of the pattern on the mask 330 surface on the surface of the object 350 to be processed. In the present embodiment, the exposure field on the image plane has an arc shape (ring shape). Then, the entire pattern of the mask 330 is transferred to the object 350 by scanning the mask 330 and the object 350 to be processed at the same speed ratio as the reduction magnification ratio of the projection optical system 340. The light source device 1 used in the exposure apparatus 300 can achieve good debris removal, stably supply the EUV light EL to the illumination optical system 314, and reflect the optical elements that constitute the illumination optical system 314 by debris. A decrease in rate can be prevented. Thereby, the exposure apparatus 300 can provide a high-quality device (semiconductor element, LCD element, imaging element (CCD, etc.), thin film magnetic head, etc.) with high throughput and high cost efficiency.

  Hereinafter, an embodiment of a device manufacturing method using the above-described exposure apparatus 300 will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), a device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 10 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 300 to expose a circuit pattern on the mask onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using the exposure apparatus 300 and the resulting device also constitute one aspect of the present invention.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic sectional drawing which shows the structure of the light source device in Example 1 of this invention. It is a schematic sectional drawing which shows an example of a structure of the debris filter of the light source device shown in FIG. It is a figure for demonstrating the concrete control (control by a pump control part and a gas control part) of the density of the buffer gas in the chamber in Example 1. FIG. It is a schematic sectional drawing which shows the structure of the light source device in Example 2 of this invention. It is a figure for demonstrating the concrete control (control by a pump control part and a gas control part) of the density of the buffer gas in the chamber in Example 2. FIG. It is a schematic sectional drawing which shows the structure of the light source device in Example 3 of this invention. It is a schematic sectional drawing which shows the structure of the light source device in Example 4 of this invention. It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. It is a flowchart for demonstrating manufacture of devices (semiconductor chips, such as IC and LSI, LCD, CCD, etc.). 10 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source device 10 Chamber 11 Exhaust pump 12 Pump control part 13 Target supply mechanism 14 Target collection | recovery mechanism 15 Laser light source part 16 Condensing mirror 17 Debris filter 171 Debris adhesion member 18 Buffer gas supply mechanism 19 Gas control part 20 Gas Density detector 1A Light source device 21 Gas temperature detector 22 Pressure gauge 1B Light source device 23 and 24 Light detectors 25 and 26 Reflection mirror 1C Light source device 27 Light source control unit PL Plasma EL EUV light IF Condensing point OP Optical system 300 Exposure device 310 Illumination Device 314 Illumination Optical System 330 Mask 340 Projection Optical System 350 Object to be Processed 360 Alignment Detection Mechanism 370 Focus Position Detection Mechanism

Claims (10)

A light source device that generates plasma and supplies light emitted from the plasma to an optical system,
A chamber for storing the plasma;
Gas supply means for supplying a buffer gas into the chamber;
Detecting means for detecting an environmental state in the chamber;
And a control unit configured to control the pressure of the buffer gas in the chamber based on a detection result of the detection unit.   The light source device according to claim 1, wherein the detection unit detects a density of the buffer gas.   The light source device according to claim 1, wherein the detection unit detects a temperature and a pressure of the buffer gas.   The light source device according to claim 1, wherein the detection unit detects light transmittance with respect to the buffer gas.   The light source device according to claim 4, wherein the light is EUV light or infrared light.   The light source device according to claim 1, wherein the control unit controls a supply amount of the buffer gas by the gas supply unit. An exhaust means for exhausting the atmosphere in the chamber;
The light source apparatus according to claim 1, wherein the control unit controls an exhaust amount by the exhaust unit. A light source device that generates plasma and supplies light emitted from the plasma to an optical system,
A chamber for storing the plasma;
Gas supply means for supplying a buffer gas into the chamber;
And a control means for controlling the pressure of the buffer gas in the chamber based on the light emission setting of the plasma. An exposure apparatus that exposes an object to be processed with a mask pattern,
An illumination optical system that illuminates the mask using light supplied from the light source device according to any one of claims 1 to 8,
An exposure apparatus comprising: a projection optical system that projects the pattern onto the object to be processed. Exposing a workpiece using the exposure apparatus according to claim 9;
And developing the exposed object to be processed.