WO2003036696A1

WO2003036696A1 - Method and instrument for measuring concentration, method and unit for exposure to light, and method for manufacturing device

Info

Publication number: WO2003036696A1
Application number: PCT/JP2002/011044
Authority: WO
Inventors: Takashi Aoki
Original assignee: Nikon Corporation
Priority date: 2001-10-24
Filing date: 2002-10-24
Publication date: 2003-05-01
Also published as: JPWO2003036696A1

Abstract

A method for measuring the concentration of a substance contained in a gas discharged from the space being subjected to gas substitution, which comprises controlling at least one of the flow rate and the pressure of the gas discharged from the space being subjected to gas substitution to a constant value by means of a gas control device and measuring the concentration of the substance contained in the controlled gas. The method allows the measurement with improved precision for the concentration of a substance contained in a gas discharged from the space being subjected to gas substitution.

Description

Description Density Measurement Method and Apparatus, Exposure Method and Apparatus, and Device Manufacturing Method Background of the Invention

1. Field of application of the invention

The present invention relates to a method and an apparatus for measuring the concentration of an arbitrary substance contained in a gas discharged from a space to be replaced with a gas, and particularly to a semiconductor element, a liquid crystal display element, an image pickup element (CCD, etc.). The present invention relates to an exposure method for manufacturing an electronic device such as a thin film magnetic head and a technique used for the apparatus.

2. Description of the prior art

When manufacturing an electronic device such as a semiconductor device or a liquid crystal display device by photolithography, a pattern image of a mask or reticle (hereinafter, referred to as a reticle) having a pattern formed thereon is exposed to a photosensitive material (hereinafter referred to as a reticle) through a projection optical system. A projection exposure apparatus is used to project each shot (shot) area on a substrate coated with a resist. The circuit of the electronic device is transferred by exposing a circuit pattern on a substrate to be exposed by the projection exposure apparatus, and is formed by post-processing.

In recent years, high-density integration of integrated circuits, that is, miniaturization of circuit patterns, has been promoted. Along with this, the exposure illumination beam (exposure beam) in the projection exposure apparatus tends to be shorter in wavelength. Specifically, a short-wavelength light source such as a KrF excimer laser (wavelength: 248 nm) has been used in place of the mercury lamp that has been the mainstream until now, and an even shorter-wavelength ArF excimer laser has been used. Exposure systems using (193 nm) are also entering the practical stage. In addition, with the aim of achieving further high-density integration, research on exposure systems using lasers (157 nm) has been advanced.

Beams having a wavelength of about 190 nm or less belong to the vacuum ultraviolet region, and these beams do not pass through air. This is because the energy of the beam is absorbed by substances such as oxygen molecules 'water molecules' and carbon dioxide molecules (hereinafter referred to as light absorbing substances) contained in the air.

For this reason, a projection exposure apparatus using an exposure beam in the vacuum ultraviolet region In order for the exposure beam to reach the plate with sufficient illuminance, the gas in the space on the optical path of the exposure beam is replaced with a gas that absorbs less energy than the light-absorbing substance in the vacuum ultraviolet region of the beam. There is a need to reduce the light absorbing material on the optical path.

For example, in a projection exposure apparatus using F ₂ laser, it is necessary to gas replacement gas in the space in the high-purity inert gas Te to Pa on the optical path of the exposure beam. In this case, for example, assuming that the total optical path length is 100 O mm, the concentration of the light absorbing substance in the space on the optical path is preferably about 1 ppm or less. The management of the concentration of the light-absorbing substance in the optical path space is usually performed by measuring the concentration of the light-absorbing substance contained in the gas discharged from the space using a predetermined concentration measuring device.

However, the gas discharged from the space to be replaced is liable to change in flow rate, pressure, etc. as the gas replacement proceeds. In a concentration measuring device that measures the concentration of a substance in a gas, if the measurement environment such as the gas flow rate and pressure is greatly disturbed, the measurement accuracy may be reduced due to a change in response characteristics and the like. · Summary of the invention

The present invention has been made in view of the above-described circumstances, and provides a concentration measuring method and an apparatus therefor capable of accurately measuring the concentration of a substance contained in a gas discharged from a space to be replaced with a gas. The purpose is to:

It is another object of the present invention to provide an exposure method and apparatus capable of improving exposure accuracy, and a method of manufacturing a device capable of improving accuracy of a pattern to be formed.

In order to solve the above problems, the present invention provides a concentration measuring method for measuring the concentration of an arbitrary substance contained in gas discharged from a space to be replaced with a gas, wherein a flow rate and a pressure of the gas discharged from the space are measured. At least one of them is controlled to be substantially constant, and the concentration of an arbitrary substance contained in the controlled gas is measured.

In this concentration measurement method, by controlling at least one of the flow rate and the pressure of the gas discharged from the space to be replaced with gas to be substantially constant, disturbance in the measurement environment is reduced, and the measurement accuracy is reduced. Is suppressed. As a result, the concentration of the substance contained in the gas can be accurately measured. In this case, the space is a space in which a gas atmosphere containing oxygen is replaced with an inert gas such as a nitrogen gas or a helium gas, and the arbitrary substance may be oxygen. In this case, based on the measurement result of the oxygen concentration, it is possible to confirm the progress state of the gas replacement such as whether or not the gas replacement for the space is completed. Further, the above concentration measuring method is a concentration measuring device including a measuring unit for measuring the concentration of an arbitrary substance contained in a gas discharged from a space to be replaced with a gas. The present invention can be implemented by a concentration measuring device that includes a gas control device that controls at least one of the flow rate and the pressure of the discharged gas to be substantially constant.

The present invention is also an exposure method for transferring a mask pattern onto a substrate by using a beam, wherein a specific gas having reduced beam absorption with respect to a light-absorbing substance that absorbs the beam is placed in a space including the optical path of the beam. At least one of the flow rate and the pressure of the gas supplied and discharged from the space is controlled to be substantially constant, the concentration of the light absorbing substance contained in the controlled gas is measured, and the transfer process is performed according to the measurement result. It is characterized by performing. In this exposure method, at least one of the flow rate and the pressure of the gas discharged from the space including the beam optical path is controlled to be substantially constant, so that the disturbance of the measurement environment is reduced, and the absorption contained in the gas is reduced. The concentration of the substance is accurately measured. Therefore, by using this measurement result, the transfer treatment can be performed in a state where the light absorbing substance is sufficiently reduced.

In the above exposure method, in an exposure apparatus for transferring a mask pattern to a substrate by using a beam, a specific gas in which a beam is reduced with respect to a light absorbing substance absorbing the beam is supplied to a space including an optical path of the beam. A gas supply device, a measuring unit for measuring the concentration of the light-absorbing substance contained in the gas, and at least one of the flow rate and the pressure of the gas discharged from the space disposed upstream of the measuring unit. The present invention can be implemented by an exposure apparatus including a gas control device for performing constant control. According to the exposure method and the exposure apparatus according to the present invention, the exposure accuracy can be improved by reliably reducing the light absorbing material from the space including the optical path of the exposure beam based on the accurately measured concentration of the light absorbing material in the gas. Can be improved.

Further, the present invention relates to a method for manufacturing a device including a lithographic process, In the graphing process, a device is manufactured using the above-described exposure method.

According to this device manufacturing method, it is possible to improve the accuracy of a formed pattern by improving the exposure accuracy. As a result, it is possible to provide a device having a pattern with improved accuracy. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a piping system of one embodiment of a concentration measuring device according to the present invention. FIG. 2 is a diagram showing an overall configuration of an embodiment of an exposure apparatus according to the present invention.

FIG. 3 is a diagram showing a piping system according to another embodiment of the concentration measuring device.

FIG. 4 is a flowchart showing a manufacturing process of the semiconductor device according to the present invention. Preferred embodiment

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a concentration measuring device 10 according to the present invention. The concentration measuring device 10 measures the concentration of a predetermined substance contained in the gas discharged from the space 11 to be replaced with gas, and the concentration sensor 12 as a measuring unit and the concentration from the space 11 are measured. Gas supply device 13 that supplies the sampled gas to the concentration sensor 12, clean gas supply device 14 that supplies a clean predetermined gas to the concentration sensor 12, and gas that supplies the concentration sensor 12 And a control device 16 that controls these devices as a whole. The space 11 to be replaced with gas is replaced with a predetermined gas (atmosphere) such as helium gas from a state containing air (gas atmosphere). It is desirable that the space 11 be maintained in a positive pressure state. The concentration measuring device 10 measures the concentration of a predetermined substance contained in the gas discharged from the space 11 to determine whether the gas replacement is in progress or not. It is used to confirm whether the state is maintained.

In the present embodiment, an oxygen sensor capable of measuring the oxygen concentration in the gas is used as the concentration sensor 12. Examples of oxygen sensors include zirconia oxygen Various types including sensors can be used. The zirconium oxide sensor detects the oxygen concentration by utilizing the properties of zirconia as a solid electrolyte having high conductivity based on the movement of ions. That is, if the oxygen concentration of the gas on both sides of the zirconia (stabilized zirconia, zirconia ceramic) with electrode processing on both sides is different, oxygen molecules are ionized on one electrode and oxygen ions on the other electrode. Is returned to oxygen molecules, and electrons are exchanged between both electrodes (ion conduction). At this time, the degree of ionic conductivity increases as the difference in the oxygen concentration of the gas increases. Therefore, the degree of ionic conductivity, that is, the difference between the oxygen concentrations on both sides of the zirconia can be extracted as the magnitude of the electromotive force between both electrodes. More specifically, for example, a gas having a constant oxygen concentration is placed as a reference gas (for example, the atmosphere) outside the tube of a zirconia formed into a tube, and a gas to be measured (a sample gas) is placed inside the tube. As a result, ionic conductivity is generated between the inner side and the outer side of the tube from the high oxygen concentration side to the low oxygen concentration side, and the oxygen concentration can be measured. The oxygen sensor is not limited to the solid electrolyte sensor described above, but may be a constant potential electrolytic type or battery type oxygen sensor using an electrochemical reduction current of oxygen. In addition, the electromotive force of the oxygen sensor may vary depending on the ambient temperature and the oxygen concentration of the reference gas, so the oxygen sensor should be installed in a constant temperature furnace. The measurement result of the oxygen concentration measured by the oxygen sensor (concentration sensor 12) is sent to the control device 16.

The sample gas supply device 13 is provided with a pipe 20 for supplying the gas discharged from the space 11 to the concentration sensor 12 (oxygen sensor) and a substantially constant flow rate of the gas discharged from the space 11. It is configured to include a mass flow controller (MFC) 21 as a gas control device for controlling. Here, the response characteristics of the concentration sensor 12 such as the oxygen sensor described above may show characteristics that differ greatly from the theoretical curve depending on the measurement environment (for example, gas flow rate and pressure). For example, in the above-described zirconia oxygen sensor, if the ionization of oxygen molecules at one electrode or the release of oxygen molecules at the other electrode cannot keep up with the speed of ion conduction between the two electrodes, the output voltage of the sensor However, it tends to be affected by the gas flow rate (or flow velocity) in contact with the electrode. Such non-ideal behavior is likely to occur, for example, when the analyte concentration is low (eg, a few ppm). In this embodiment. As described above, it is necessary to detect the progress of gas replacement and whether or not gas replacement has been completed. Therefore, it is necessary to reliably measure the oxygen concentration to a relatively low concentration level. For this reason, in the sample gas supply device 13, the size (inner diameter, etc.) of the pipe 20 is determined in consideration of the response speed of the system due to the internal volume of the pipe, and the concentration sensor 12 is controlled by the mass flow controller 21. The flow rate of the flowing sample gas is controlled to be constant.

Here, the flow rate of the sample gas controlled to be constant by the mass flow controller 21 is preset according to the characteristics of the concentration sensor 12. This set flow rate can be determined by a test using a calibration gas having a predetermined oxygen concentration. When measuring the concentration of a substance (here, oxygen concentration) contained in the exhaust gas from the space 11 to be replaced with gas, the oxygen concentration is measured between immediately after the start of the gas replacement and when the gas replacement is completed. The difference may be relatively large. For this reason, an appropriate set flow rate may be determined stepwise according to the progress of gas replacement.

That is, the flow rate of the sample gas may be set to be substantially constant at all times, or the flow rate of the sample gas may be set to be substantially constant during an arbitrary time. For example, during a predetermined time before and after the start of gas replacement, the mass flow controller 21 sets the flow rate of the sample gas to a value corresponding to the first flow rate so that the flow rate of the sample gas becomes a substantially constant first flow rate. During a predetermined period of time before and after the completion of the gas replacement, the mass flow controller 21 adjusts the flow rate of the sample gas to the second flow rate so that the flow rate of the sample gas becomes a substantially constant second flow rate smaller than the first flow rate. May be set to a value corresponding to. In this case, the predetermined time before and after the start of the gas replacement and the predetermined time before and after the completion of the gas replacement may be the same time or different. Whether or not the gas replacement is completed may be determined based on whether a predetermined time has elapsed from immediately after the gas replacement is started, or may be determined based on the measurement result of the concentration sensor 12. Is also good. Furthermore, in addition to setting the sample gas flow rates to different values before and after the start of gas replacement and before and after the completion of gas replacement, the flow rate of the sample gas is also, for example, before and after the start of gas replacement and before and after the completion of gas replacement. The value of the mass flow controller 21 d may be set so as to be substantially constant between and, or to vary step by step between them. Further, in this embodiment, when the space 11 from which the gas is discharged has a positive pressure, the sample gas is transferred to the concentration sensor 12 using the pressure. For this reason, a low differential pressure type that can reliably set the flow rate even when the pressure difference between the primary side (upstream side) and the secondary side (downstream side) is relatively small, is used as the controller unit 21. It is preferable to use it.Moreover, since the pressure in the space 11 to be replaced with gas is expected to fluctuate to some extent, even if the pressure on the primary side fluctuates slightly, a configuration that can maintain the set flow rate on the secondary side may be used. It is preferred to use

Further, in the present embodiment, the mass flow controller 21 controls the flow rate of the sample gas to be constant. However, the flow rate of the sample gas is not necessarily strictly constant. That is, a certain degree of variation according to the response characteristics of the concentration sensor 12 is allowed.

The clean gas supply device 14 supplies the concentration sensor 12 with a clean gas containing a substance (oxygen in this case) measured by the concentration sensor 12 and an impurity having a sufficient adverse effect on the concentration sensor 12. It is configured to include a clean gas storage section 30 containing gas, and a pipe 31 for guiding the clean gas from the clean gas storage section 30 to the concentration sensor 12 (oxygen sensor). The clean gas is mainly used for cleaning the concentration sensor 12. Therefore, the same gas as the gas (replacement gas) supplied to the space 11 for gas replacement may be used as the clean gas. In the present embodiment, the same helium gas as the replacement gas is used as the cleaning gas.

Helium gas is compressed or liquefied and stored in a high purity state. In addition, the pressure of the clean gas is supplied to the outlet of the clean gas storage unit 30 at a predetermined pressure.

(For example, a pressure approximately equal to the pressure in the space 11), a pressure reducing valve 32 that can be adjusted to reduce the pressure may be attached.

The switching device 15 is used to switch the gas supplied to the concentration sensor 12 between the sample gas and the clean gas. Therefore, for example, a three-way solenoid valve is used as the switching device 15, and the switching device 15 is configured to perform a switching operation according to a command from the control device 16. The timing of supplying the sample gas to the concentration sensor 12 is, for example, immediately before the oxygen concentration is measured by the concentration sensor 12. This enables accurate density measurement by the cleaned density sensor 12. Also, the supply of sample gas and the supply of clean gas to the concentration sensor 12 are alternately performed. Thus, the concentration sensor 12 is cleaned as needed as the gas replacement progresses, and it is possible to reduce the time for one cleaning and stabilize the measurement accuracy. When measuring the oxygen concentration using the concentration measuring device 10 having the above configuration, the calibration of the concentration sensor 12 and the setting of the flow rate of the sample gas to be supplied to the concentration sensor 12 are performed in advance. The calibration of the concentration sensor 12 may be performed using the air or a calibration gas having a predetermined oxygen concentration. When a calibration gas is used, only a calibration gas having a low oxygen concentration of about several ppm level or less when judging that gas replacement is completed may be used, or air (air) may be used to improve measurement accuracy over a wide range. A plurality of calibration gases having different oxygen concentrations may be used, such as a calibration gas having an oxygen concentration close to the above and a calibration gas having a low oxygen concentration of several ppm level. As a method of determining the flow rate of the sample gas, for example, a calibration gas having a predetermined oxygen concentration is supplied to the concentration sensor via the mass flow controller 21 (a new mass flow controller may be provided for the calibration gas). While supplying to 12, the fluctuation of the output voltage (or current) from the concentration sensor 12 is measured while changing the flow rate. Then, the flow rate at which the output voltage of the concentration sensor 12 stabilizes and keeps substantially constant with respect to the flow rate change is set as the flow rate of the sample gas when supplied to the concentration sensor 12.

At the time of measuring the oxygen concentration, the concentration measuring device 10 controls the flow rate of the sample gas discharged from the space 11 to be replaced with the gas to a predetermined set flow rate by the mass flow controller 21. By controlling the flow rate of the gas supplied to the concentration sensor 12 to be constant, disturbance in the measurement environment of the concentration sensor 12 is suppressed. Therefore, it is possible to accurately measure the oxygen concentration based on the ideal response characteristics of the concentration sensor 12.

In this case, it is considered that the concentration of oxygen contained in the gas discharged from the space 11 changes greatly with the progress of gas replacement, so the sample gas is controlled to the same flow rate at all stages during gas replacement. By controlling the sample gas flow rate step by step at multiple stages during gas replacement, the oxygen concentration can be measured immediately after the start of gas replacement and before and after the completion of gas replacement. Accuracy can be improved. By accurately measuring the oxygen concentration in this way, it is possible to accurately detect whether the gas replacement is in progress, whether the gas replacement has been completed, or whether the gas replaced state is maintained. It becomes possible.

The above-described density measuring method and apparatus of the present invention can be suitably used for a reduced projection type exposure apparatus for manufacturing a semiconductor device as shown in FIG. This exposure apparatus transfers the circuit pattern formed on the reticle R to each shot area on the wafer W while synchronously moving the reticle R as a mask and the wafer W as a substrate. This is a scanning type scanning exposure apparatus, so-called scanning-stepper. Hereinafter, a configuration example of the exposure apparatus will be described.

This exposure apparatus includes a light source 40, an illumination system 41 for illuminating the reticle R with an energy beam (exposure beam IL) from the light source 40, a reticle chamber 42 for accommodating the reticle R, and an exposure beam emitted from the reticle R. It comprises a projection optical system PL for projecting the IL onto the wafer W, a wafer chamber 43 for accommodating the wafer W, and a main control system 44 for overall control of the entire apparatus.

As the light source 40, here, a light source that emits light belonging to the vacuum ultraviolet light region with a wavelength of about 120 nm to about 180 nm, such as a fluorine laser (F laser) with an oscillation wavelength of 157 nm, A krypton dimer laser (Kr laser) with a wavelength of 146 nm and an argon dimer laser (Ar laser) with an oscillation wavelength of 126 nm are used. Note that an ArF excimer laser having an oscillation wavelength of 193 nm may be used as a light source. The illumination system 41 includes a mirror 50 that bends a light beam (laser beam) IL emitted from the light source 40 in a predetermined direction, and adjusts the light beam IL guided by the mirror 50 to a light beam having a substantially uniform illuminance distribution. Optical integrator 51, beam splitter 53 that transmits most (eg, 97%) of exposure beam IL and guides the remaining portion (eg, 3%) to integrator sensor 52, and beam splitter 53 A reticle blind 56 that passes through the splitter 53 and regulates the exposure beam IL guided by the mirror 54 and the relay lens 55 to a predetermined illumination range, and passes through an opening of the reticle blind 56. It is configured to include a relay lens 57, a mirror 58, and the like for guiding the exposure beam IL to the reticle chamber 52.

The integrator sensor 52 includes a photoelectric conversion element and the like, and the beam splitter 53 A part of the exposure beam IL guided by the photoelectric conversion is photoelectrically converted, and the photoelectric conversion signal is supplied to the main control system 54. The main control system 54 drives and stops the light source 40 based on information from the integrator sensor 52, whereby the exposure amount (irradiation amount of the exposure beam) to the wafer W is controlled. . The output signal of the integrator sensor 52 is, before the exposure operation, an output obtained by receiving the exposure beam IL that has passed through the projection optical system with a radiation amount monitor attached to the wafer stage WST described later. Associated with the signal.

The reticle blind 56 includes, for example, a pair of blades (not shown) that are bent into a plane L shape and are combined in a plane orthogonal to the optical axis of the exposure beam IL to form a rectangular opening. A light-shielding unit displacement device (not shown) for displacing these blades in a plane orthogonal to the optical axis based on an instruction from the main control system 44 is provided. At this time, the blade is arranged on a plane conjugate with the pattern plane of reticle R. In addition, the size of the opening of the reticle blind 56 changes with the displacement of the blade, and the exposure beam IL defined by this opening transmits the reticle placed in the reticle chamber 42 via the relay lens 57. A specific area of R is illuminated with substantially uniform illuminance.

The reticle chamber 42 is formed by a partition wall 60 bonded to the housing of the illumination system 41 and the housing of the projection optical system PL without any gap, and has a reticle stage RST for adsorbing and holding the reticle R in its internal space. ing. The reticle stage RST is arranged on a reticle base (not shown). The RST is moved by a predetermined stroke in the Y direction (scan direction) on the reticle base by a stage drive system (not shown), and is moved in the X direction. , Y direction, and Θ direction (rotation direction). The stage drive system includes, for example, a linear guide disposed parallel to the Y axis to guide the reticle stage RST in the Y direction, a scanning linear motor (voice coil motor), and the like. The position and rotation angle of the reticle stage RST are measured with high precision by a laser interference system (not shown), and based on the measured values and control information from a main control system 44 composed of a computer that controls the overall operation of the entire device. The reticle stage RST is driven. The projection optical system PL accommodates a plurality of optical members such as lenses and reflectors made of fluoride crystals such as fluorite and lithium fluoride in a housing (barrel) and hermetically seals them. It is a higher degree. In the present embodiment, a reduction optical system having a projection magnification of, for example, 14 or 15 is used as the projection optical system PL. When the reticle R is illuminated by the exposure beam IL from the illumination system 41, the pattern formed on the reticle R is reduced and projected onto a specific area (shot area) on the wafer W by the projection optical system PL. .

The wafer chamber 43 is formed by a partition wall 67 bonded to the housing of the projection optical system PL without any gap. In the internal space, a wafer holder 68 for holding the wafer W by vacuum suction, and a wafer holder 68 are provided. And a wafer stage WST to be supported. '

The wafer stage WST is moved along the XY plane (in the direction perpendicular to the optical axis of the projection optical system PL) by a drive system (not shown) including, for example, a magnetic levitation type two-dimensional linear actuator (plane motor). It is configured to be driven freely in the horizontal direction. The position of the wafer stage WST is adjusted by a laser interference system including an optical member such as a laser light source and a prism and a detector. The members constituting this laser interference system are arranged outside the wafer chamber 43 in order to prevent foreign matter generated from the members from adversely affecting exposure. If the generation of the light-absorbing substance from each component constituting each laser interference system is sufficiently suppressed, these components may be arranged in the wafer chamber 43.

In the wafer chamber 43, an arbitrary shot area on the wafer W is positioned at the projection position (exposure position) of the reticle R pattern by moving the wafer stage WST in the XY plane. ing. Thus, in this exposure apparatus, the main control system 44 moves the wafer stage WST so as to sequentially position each shot area on the wafer W to the exposure start position, and a shot-to-shot stepping operation; The scan exposure operation of transferring the pattern of the reticle R to the shot area of the wafer W while synchronizing the movement of W with the horizontal direction along the XY plane is repeatedly performed.

The main control system 44 includes a microcomputer (or a microcomputer) including a CPU (central processing unit), a ROM (read “only” memory), a RAM (random “access” memory), and the like. Also, the main control system 4 4 The position of each stage is controlled while monitoring the wafer stage RST and wafer stage WST via a laser interference system. The control device 16 in the concentration measuring device 10 described above is included in the main control system 44.

In the case where a beam having a wavelength in the vacuum ultraviolet region is used as an exposure beam as in this exposure apparatus, a substance having a strong absorption characteristic for light in this wavelength band (hereinafter, referred to as a light absorbing substance) is excluded from the optical path. There is a need to. The absorption substance on the beam in the vacuum ultraviolet region, oxygen (0 _2), water (water vapor: H ₂ 0), carbon dioxide (carbon dioxide:. CO, some organic matter, and halide etc. Meanwhile, exposure beam IL is Permeable gases (substances with little energy absorption) include nitrogen (N ₂ ), helium (He), neon (Ne), argon (Ar), krypton (Kr). ), Xenon (X e), and radon (Rn), which are referred to hereinafter as “permeated gas”.

Here, nitrogen gas acts as a light-absorbing substance with respect to light having a wavelength of about 150 nm or less, and helium gas acts as a transparent gas up to a wavelength of about 100 nm. In addition, helium gas has a thermal conductivity that is about six times that of nitrogen gas, and the amount of change in the refractive index with respect to changes in atmospheric pressure is about 1/8 that of nitrogen gas. Excellent in stability and cooling performance. Since helium gas is expensive, if 1 50 nm or more as the wavelength of the exposure light beam is an F ₂ laser, to use nitrogen gas as its gas permeability in order to reduce the operating costs It may be. In this example, from the viewpoints of the stability of the imaging characteristics and the cooling property, it is assumed that a gas that allows the exposure beam IL to pass therethrough is a Helium gas.

Vacuum pumps for exhausting gas containing light-absorbing substances inside through piping 70 and the like are provided in the internal spaces of the illumination system 41, the reticle chamber 42, the projection optical system PL, and the wafer chamber 23 according to the present embodiment. 71 A, 71 B, 71 C and 71 D are connected. Also, for example, a gas in a gas supply device 72 installed outside a chamber (not shown) in which the entire exposure apparatus of the present embodiment is housed is compressed or pumped in a high-purity state by a high-purity helium gas. Liquefied and stored. The helium gas extracted from the cylinder as needed is supplied to the lighting system via valves 73A, 73B, 73C, 73D and piping 74A, 74B, 74C, 74D. 4 1, reticle room 4 2. It is supplied to each internal space of the projection optical system PL and the wafer chamber 43. There is a HEPA finoleta (High Efficiency Particulate Air Filter) in the cylinder or in the middle of the piping to each space, and a dust such as ULPA finoleta (Ultra Low Penetration Air Filter).

An air filter (not shown) that removes (particles) and a chemical filter (not shown) that removes light-absorbing substances such as oxygen are provided.

Further, in each of the internal spaces of the illumination system 41, the reticle chamber 42, the projection optical system PL, and the wafer chamber 43, the concentration measuring device 1 shown in FIG. 0 is connected to each. As shown in Fig. 1, the concentration measuring device 10 is equipped with a concentration sensor 12 (oxygen sensor) that can measure the oxygen concentration in the gas. 4 (control device 16).

Under the control of the main control system 44, the gas atmosphere in the illumination system 41, reticle chamber 42, projection optical system PL, and wafer chamber 43 is replaced with helium gas under the control of the main control system 44. Is done. Specifically, at the time of gas replacement, the main control system 44 operates the vacuum pumps 71A, 71B, 71C or 71D to operate the illumination system 41, the reticle chamber 42, and the projection system. Exhaust the gas and light-absorbing substance in the optical system PL or the wafer chamber 43, and open the valve 73A, 73B, 73C or 73D to operate the gas supply device 72. A high-purity, high-temperature, hemi-gas is supplied to the illumination system 41, the reticle chamber 42, the projection optical system PL, or the internal space of the wafer chamber 43 via the pipes 74A to 74D. At this time, the progress of the gas replacement can be confirmed by the measurement result of the concentration measuring device 10, that is, the oxygen concentration measured by the concentration sensor 12. When the oxygen concentration measured by the concentration sensor 12 becomes equal to or less than a preset allowable concentration, the main control system 44 causes the vacuum pumps 71A, 71B, 71C or 71D. To stop. As a result, the interior of the illumination system 41, the reticle chamber 42, the projection optical system PL, or the wafer chamber 43 is filled with a helium gas, which has less energy absorption than a light-absorbing substance with respect to a vacuum ultraviolet beam, The pressure is equal to or higher than the atmospheric pressure (for example, about 1 to 10% higher than the atmospheric pressure). When the gas replacement is completed, the main control system 44 continuously outputs a predetermined flow rate from the gas supply device 72 so that the oxygen concentration measured by the concentration sensor 12 does not exceed the preset allowable concentration. Supply Helium gas. At the time of gas replacement and after completion of the gas replacement, the main control system 44 monitors residual air and leaks in each of the above-mentioned spaces using the measurement result of the oxygen concentration by the concentration sensor 12. As described above, the concentration measuring device 10 measures the flow rate of the sample gas discharged from the gas replacement space 11 by controlling the flow rate of the sample gas to a predetermined set flow rate by the mass flow controller 21 (see FIG. 1). The disturbance of the environment is suppressed, and the oxygen concentration is accurately measured. Therefore, this exposure apparatus accurately detects the progress of gas replacement, whether or not the gas replacement has been completed, or whether or not the gas replacement state is maintained, based on the accurately measured oxygen concentration. can do.

In addition, in the illumination system 41, the reticle chamber 42, the projection optical system PL, and the space including the exposure beam IL, which is the internal space of each of the wafer chambers 43, the internal oxygen concentration is measured using the concentration measurement device 10. The condition where the light-absorbing substances are monitored and removed is stably maintained. Therefore, in this exposure apparatus, the energy of the exposure beam IL from the light source 40 reaches the wafer W with sufficient illuminance without being largely absorbed in these spaces, and the pattern image of the reticle R is accurately displayed on the wafer W. Transcribed well.

The operation procedure described in the above embodiment, or the various shapes and combinations of the constituent members are merely examples, and various changes can be made based on process conditions and design requirements without departing from the gist of the present invention. It is. The present invention includes, for example, the following changes.

In the above embodiment, since the space from which the gas for the sample is discharged has a positive pressure, the sample gas is transferred to the concentration sensor by using the pressure. However, the method of transferring the sample gas to the concentration sensor is as follows. It is not limited to this. That is, as shown in FIG. 3, the concentration measuring device may be provided with a pressure-increasing device (for example, a vacuum pump) 80 for increasing the pressure of the sample gas. The booster 80 may be disposed between the space in which the gas is replaced and the mass flow controller 81, that is, upstream of the concentration sensor 82. As the booster 80, for example, a diaphragm pump using a diaphragm valve that generates less pollutants may be used. The configuration of the concentration measuring device including the pressure-increasing device 80 ensures that the sample gas is supplied to the concentration sensor 82 even when the pressure of the space to be replaced with gas is low. In particular, the concentration sensor 82 When the pressure of the supplied sample gas decreases, the response characteristics may become unstable. Even in such a case, the pressure of the gas supplied to the concentration sensor 82 is stably ensured by the booster 80, so that a decrease in the measurement accuracy of the concentration sensor 82 due to the pressure decrease can be suppressed. The device for increasing the pressure of the sample gas supplied to the concentration sensor is not limited to the pressure increasing device, but may be configured to include a suction device on the downstream side of the concentration sensor.

When such a booster is used, a pressure sensor is provided in the space to be replaced with gas or in the middle of the pipe between this space and the booster, and based on the detection result of the pressure sensor, the pressure sensor is used. The operation, that is, the pressure of the sample gas may be controlled. Furthermore, when controlling the pressure of the sample gas, similarly to the case of controlling the flow rate of the sample gas, the pressure of the sample gas is substantially constant for a predetermined time before and after the start of gas replacement. The pressure of the sample gas is set to a value corresponding to the first pressure so that the pressure of the sample gas is smaller than the first pressure for a predetermined time before and after the completion of the gas replacement. The booster may be set to a value corresponding to the second pressure so that the pressure is two.

In the above embodiment, the mass flow controller (MFC) is used to control the gas flow rate, but the means for controlling the gas flow rate is not limited to this. For example, it is possible to use a needle valve for flow control and a flow meter for flow measurement (for example, a float flow meter with contacts), and control the needle valve based on a signal from the flow meter by a controller. Good.

In the above embodiment, the gas flow rate is controlled to be constant in order to suppress the disturbance of the measurement environment. However, instead of controlling the flow rate, the pressure may be controlled to be constant. In this case, the concentration measuring device may include, for example, a pressure increasing device and a pressure gauge, and may be configured to control the pressure increasing device so that the gas supplied to the concentration sensor has a constant pressure. If the device has a function to control the pressure on the secondary side (downstream side), a configuration without the booster can be adopted. Furthermore, instead of controlling only one of the flow rate and the pressure, both may be controlled to a predetermined value.

Also, when the sample gas is pressurized or changes in temperature, If there is a risk of generating water vapor in the above, a dehumidifier should be provided upstream of the concentration sensor to prevent the liquid from lowering the measurement accuracy of the concentration sensor. Furthermore, if impurities are mixed in the gas discharged from the gas replacement space and the impurities may adversely affect the concentration sensor, a filter corresponding to the impurities may be provided upstream of the concentration sensor. Les ,.

Further, in the above embodiment, oxygen is a measurement target, but it goes without saying that the measurement target of the present invention is not limited to this. For example, the present invention is applicable to the measurement of other substances such as water (water vapor), carbon dioxide (carbon dioxide), organic substances and halides, which are the above-mentioned light-absorbing substances. In this case, sensors that measure each substance are used.

Further, in the above-described embodiment, the inert gas such as helium (H e) as a permeated gas; nitrogen (N 2), or a rare gas (argon (Ar), etc.) is a vacuum. small amount of absorption of light in the ultraviolet region, small enough in particular almost negligible absorption amount with respect to the F ₂ laser beam Le. Therefore, any inert gas may be used.

In the above-described exposure apparatus, for example, in each of the internal spaces of the illumination system, the reticle chamber, the projection optical system, and the wafer chamber, the concentration of the light absorbing substance may be controlled with different values.

Further, a purge pipe may be provided by providing a permeated gas supply pipe and an exhaust pipe for each space of the optical elements constituting the illumination optical system and the projection optical system. Furthermore, the concentration of the light-absorbing substance may be controlled for each space of the optical element constituting the illumination system or the projection optical system.

In addition, each housing (including the cylindrical body etc.) of the wafer chamber from the illumination system, and the piping for supplying helium gas, etc., are made of a material with low impurity gas (degassing), such as stainless steel, tetrafluoroethylene, tetrafluoroethylene. It is desirable to form with various polymers such as norroethylene-tenorefnoleo mouth (alkyl vinyl ether) or tetrafluoroethylene-hexafluoropropene copolymer.

The reticle chamber partition, wafer chamber partition, illumination system housing, projection optical system housing (barrel), sample gas (permeate gas) and clean gas supply piping, etc. are processed by polishing, etc. to obtain a rough surface. By using a material such as stainless steel (SUS) with reduced strength, it is possible to suppress the generation of degassing. Further, in order to remove the light absorbing substance from the optical path, it is preferable to perform a treatment for reducing the amount of outgas from the surface of the structural material in advance. For example, (1) the surface area of the structural material is reduced, (2) the surface of the structural material is polished by a method such as mechanical polishing, electrolytic polishing, ball polishing, chemical polishing, or GBB (Glass Beads Blasting). (3) Clean the surface of structural materials by techniques such as ultrasonic cleaning, spraying a fluid such as clean dry air, and vacuum degassing (baking). (4) Hydrocarbons and halogens Wire coating materials containing oxides, sealing members (such as O-rings), adhesives, etc., should not be installed in the optical path space as much as possible.

The exposure apparatus to which the present invention is applied is a scanning exposure method (for example, a step-and-scan method) in which a mask (reticle) and a substrate (wafer) are relatively moved with respect to an exposure illumination beam. However, the present invention is not limited to this, and a static exposure method in which a mask pattern is transferred onto a substrate while the mask and the substrate are almost stationary, for example, a step-and-repeat method may be used. Further, the present invention can be applied to a step-and-stitch type exposure apparatus that transfers a pattern to a plurality of shot areas whose peripheral portions overlap each other on a substrate. Further, the projection optical system PL may be any one of a reduction system, an equal magnification system, and an enlargement system, and may be any one of a refraction system, a reflection refraction system, and a reflection system. Further, the present invention can be applied to an exposure apparatus that does not use a projection optical system, for example, a proximity type exposure apparatus.

The exposure apparatus to which the present invention is applied, g-ray as the exposure illumination light, i line, K r F excimer laser light, A r F excimer one laser light, F ₂ laser beam, and A r ₂ laser beam such as Not only ultraviolet light but also EUV light, X-ray, or charged particle beam such as electron beam or ion beam may be used. Furthermore, the light source for exposure is not limited to a mercury lamp or excimer laser, but may be a harmonic generation device such as a YAG laser or a semiconductor laser, an SOR, a laser plasma light source, an electron gun, or the like.

Also, the exposure apparatus to which the present invention is applied is not limited to semiconductor device manufacturing, but may be a liquid crystal display device, a display device, a thin-film magnetic head, an imaging device (such as a CCD), a micromachine such as a micromachine, and a DNA chip. It may be used for manufacturing a device (electronic device) or for manufacturing a photomask / reticle used in an exposure apparatus. Further, the present invention can be applied not only to an exposure apparatus, but also to another manufacturing apparatus (including an inspection apparatus) used in a device manufacturing process.

When a linear motor is used for the wafer stage / reticle stage described above, either an air levitation type using an air bearing or a magnetic levitation type using a Lorentz force or a reactor tanker may be used. Also, the stage may be of a type that moves along a guide or a guideless type that does not have a guide. Furthermore, when a planar motor is used as the stage drive system, one of the magnet unit (permanent magnet) and the armature unit is connected to the stage, and the other of the magnet unit and the armature unit moves the stage. It may be provided on the surface side (surface plate, base). Also, the reaction force generated by the movement of the wafer stage is mechanically released to the floor (ground) using a frame member as described in JP-A-8-166475. Is also good. The present invention is also applicable to an exposure apparatus having such a structure.

Further, the reaction force generated by the movement of the reticle stage may be mechanically released to the floor (ground) using a frame member as described in JP-A-8-330224. . The present invention is also applicable to an exposure apparatus having such a structure.

Further, the exposure apparatus to which the present invention is applied is configured such that various subsystems including the respective constituent elements recited in the claims of the present application maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. It is manufactured by assembling. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electrical For, adjustments are made to achieve electrical accuracy. The process of assembling the exposure apparatus from various subsystems includes mechanical connections, wiring connections of electric circuits, and piping connections of pneumatic circuits among the various subsystems. It goes without saying that there is an assembly process for each subsystem before the assembly process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, a comprehensive adjustment is performed to ensure various precisions of the entire exposure apparatus. It is desirable to manufacture the exposure apparatus in a clean room where the temperature, cleanliness, etc. are controlled. For semiconductor devices, as shown in Fig. 4, a process 201 for designing the function and performance of the device, a process 202 for manufacturing a mask (reticle) based on the design steps, and a wafer made of silicon material are used. , A wafer processing step of exposing a reticle pattern to a wafer by the above-described exposure apparatus, a device assembling step 205 (including a dicing step, a bonding step, and a package step). It is manufactured through an inspection process 206 and the like.

Claims

The scope of the claims

1-In a concentration measurement method for measuring the concentration of any substance contained in a gas discharged from a space to be replaced with a gas,

A concentration measuring method for controlling at least one of a flow rate and a pressure of a gas discharged from the space to be substantially constant, and measuring a concentration of the arbitrary substance contained in the gas.

2. The concentration measuring method according to claim 1, wherein the space is a space in which a gas atmosphere containing oxygen is replaced with an inert gas such as a nitrogen gas or a helium gas, and the arbitrary substance is oxygen.

3. At least one of the flow rate and the pressure of the gas is substantially constant for a first predetermined time before and after the start of the gas replacement, and for a second predetermined time before and after the completion of the gas replacement. 2. The concentration measuring method according to claim 1, which is controlled.

4. At least one of the flow rate and the pressure of the gas before and after the start of the gas replacement and at least one of the flow rate and the pressure of the gas before and after the completion of the gas replacement are controlled to values different from each other. 4. The method according to claim 3, wherein the concentration is measured.

5. At least one of the flow rate and the pressure of the gas before and after the start of the gas replacement is controlled to be smaller than at least one of the flow rate and the pressure of the gas before and after the completion of the gas replacement. The concentration measurement method described in Item 4.

6. In a concentration measuring device provided with a measuring unit for measuring the concentration of an arbitrary substance contained in a gas discharged from a space to be replaced with a gas,

A concentration measuring device provided upstream of the measuring unit and comprising a gas control device for controlling at least one of a flow rate and a pressure of a gas discharged from the space to be substantially constant.

7. The gas control device controls at least one of the flow rate and the pressure of the gas during a first predetermined time before and after the start of the gas replacement, and a second predetermined time before and after the completion of the gas replacement. 7. The concentration measuring apparatus according to claim 6, wherein the apparatus is controlled to be substantially constant during the period.

8. The gas control device determines at least one of the flow rate and the pressure of the gas before and after the start of the gas replacement and at least one of the flow rate and the pressure of the gas before and after the completion of the gas replacement. Claim 7 which is controlled to be different from each other The concentration measuring device according to 1.

9. The gas control device sets at least one of the flow rate and the pressure of the gas before and after the start of the gas replacement to be smaller than at least one of the flow rate and the pressure of the gas before and after the completion of the gas replacement. 9. The concentration measurement device according to claim 8, wherein the concentration measurement device performs control.

10. An exposure method for transferring a pattern of a mask onto a substrate by a beam, comprising: supplying a specific gas having a reduced absorption of the beam to a space including an optical path of the beam; At least one of the flow rate and the pressure of the gas discharged from the space is controlled to be substantially constant, and the concentration of the light absorbing substance contained in the gas is measured. Exposure method.

11. An exposure apparatus for transferring a mask pattern onto a substrate by a beam, wherein a specific gas having a reduced absorption of the beam with respect to a light absorbing material absorbing the beam is supplied to a space including an optical path of the beam. A gas supply device;

A measuring unit for measuring the concentration of the light absorbing substance contained in the gas,

An exposure apparatus, comprising: a gas control device disposed upstream of the measurement unit and configured to control at least one of a flow rate and a pressure of the gas discharged from the space to be substantially constant.

1 2. A method for manufacturing a device including a lithographic process,

A method for producing a device using the exposure method according to claim 10 in the lithographic process.