Patent ID: 12207382

DESCRIPTION OF EMBODIMENTS

Contents

1. Overall description of EUV light generation system11

1.1 Configuration1.2 Operation
2. Comparative example2.1 Configuration2.1.1 Reservoir tank C12.1.2 Load lock chamber C22.1.3 Target generation unit2602.1.4 Detail of load lock chamber C2and solid target supply valve VT22.2 Operation2.2.1 Operation of EUV light generation processor52.2.2 Input control of solid target substance27a2.2.3 Temperature control of large tank71t2.2.4 Temperature control of small tank7st2.2.5 Temperature control of nozzle7nz2.2.6 Block diagram2.3 Problem of comparative example
3. Suppression of temperature decrease by feedforward control3.1 Operation3.1.1 Input control of solid target substance27a3.1.2 Temperature control of large tank71t3.1.3 Temperature control of small tank7st3.1.4 Temperature control of nozzle7nz3.1.5 Block diagram3.2 Simulation result3.3 Effect
4. Example in which feedforward control is selectable4.1 Operation4.1.1 Input control of solid target substance27a4.1.2 Temperature control of large tank71t4.1.3 Temperature control of small tank7st4.1.4 Temperature control of nozzle7nz4.1.5 Block diagram4.2 Effect
5. Example of performing feedforward control on temperatures of small tank7stand nozzle7nz5.1 Operation5.1.1 Input control of solid target substance27a5.1.2 Temperature control of large tank71t5.1.3 Temperature control of small tank7st5.1.4 Temperature control of nozzle7nz5.1.5 Block diagram5.2 Simulation result5.3 Effect
6. Example of performing feedforward control using correction value fcst(t) of current6.1 Operation6.1.1 Input control of solid target substance27a6.1.2 Temperature control of large tank71t6.1.3 Temperature control of small tank7st6.1.4 Temperature control of nozzle7nz6.1.5 Block diagram6.2 Simulation result6.3 Effect
7. Example in which waveform of correction value fcst (t) of current is rectangular wave
8. Others

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the contents of the present disclosure. Also, all configurations and operation described in the embodiments are not necessarily essential as configurations and operation of the present disclosure. Here, the same components are denoted by the same reference numerals, and duplicate description thereof is omitted.

1. Overall Description of EUV Light Generation System11

1.1 Configuration

FIG.1schematically shows the configuration of an LPP EUV light generation system11. An EUV light generation apparatus1is used together with a laser device3. In the present disclosure, a system including the EUV light generation apparatus1and the laser device3is referred to as the EUV light generation system11. The EUV light generation apparatus1includes a chamber2and a target supply system26. The chamber2is a sealable container. The target supply system26supplies a target27containing a target substance into the chamber2. The material of the target substance may include tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more thereof.

A through hole is formed in a wall of the chamber2. The through hole is blocked by a window21and pulse laser light32output from the laser device3passes through the window21. An EUV light concentrating mirror23having a spheroidal reflection surface is arranged in the chamber2. The EUV light concentrating mirror23has first and second focal points. A multilayer reflection film in which molybdenum and silicon are alternately stacked is formed on a surface of the EUV light concentrating mirror23. The EUV light concentrating mirror23is arranged such that the first focal point is located in a plasma generation region25and the second focal point is located at an intermediate focal point292. A through hole24is formed at the center of the EUV light concentrating mirror23, and pulse laser light33passes through the through hole24.

The EUV light generation apparatus1includes an EUV light generation processor5, a target sensor4, and the like. The EUV light generation processor5is a processing device including a memory501in which a control program is stored and a central processing unit (CPU)502which executes the control program. The EUV light generation processor5is specifically configured or programmed to perform various processes included in the present disclosure. The target sensor4detects at least one of the presence, trajectory, position, and velocity of the target27. The target sensor4may have an imaging function.

Further, the EUV light generation apparatus1includes a connection portion29providing communication between the internal space of the chamber2and the internal space of an EUV light utilization apparatus6. An example of the EUV light utilization apparatus6will be described later with reference toFIGS.27and28. A wall291in which an aperture is formed is arranged in the connection portion29. The wall291is arranged such that the aperture is located at the second focal point of the EUV light concentrating mirror23.

Further, the EUV light generation apparatus1includes a laser light transmission device34, a laser light concentrating mirror22, a target collection unit28for collecting the target27, and the like. The laser light transmission device34includes an optical element for defining a transmission state of the pulse laser light32, and an actuator for adjusting the position, posture, and the like of the optical element.

1.2 Operation

Operation of the EUV light generation system11will be described with reference toFIG.1. Pulse laser light31output from the laser device3enters, via the laser light transmission device34, the chamber2through the window21as the pulse laser light32. The pulse laser light32travels along a laser light path in the chamber2, is reflected by the laser light concentrating mirror22, and is radiated to the target27as the pulse laser light33.

The target supply system26outputs the target27toward the plasma generation region25in the chamber2. The target27is irradiated with the pulse laser light33. The target27irradiated with the pulse laser light33is turned into plasma, and radiation light251is radiated from the plasma. EUV light included in the radiation light251is reflected by the EUV light concentrating mirror23with higher reflectance than light in other wavelength ranges. Reflection light252including the EUV light reflected by the EUV light concentrating mirror23is concentrated at the intermediate focal point292and output to the EUV light utilization apparatus6. Here, one target27may be irradiated with a plurality of pulses included in the pulse laser light33.

The EUV light generation processor5controls the entire EUV light generation system11. The EUV light generation processor5processes a detection result of the target sensor4. Based on the detection result of the target sensor4, the EUV light generation processor5controls the timing at which the target27is output, the output direction of the target27, and the like. Further, the EUV light generation processor5controls an oscillation timing of the laser device3, the travel direction of the pulse laser light32, the concentration position of the pulse laser light33, and the like. Such various kinds of control described above are merely exemplary, and other control may be added as necessary.

2. Comparative Example

2.1 Configuration

FIG.2schematically shows the configuration of the target supply system26according to a comparative example. The comparative example of the present disclosure is an example recognized by the applicant as known only by the applicant, and is not a publicly known example admitted by the applicant. As shown inFIG.2, the target supply system26according to the comparative example includes a reservoir tank C1, a load lock chamber C2, a target generation unit260, a target supply processor60, a measuring instrument61, a pressure regulator62, a temperature control processor63, and an input control processor64.

The target supply processor60is a processing device including a memory601in which a control program is stored and a CPU602which executes the control program. The target supply processor60is specifically configured or programmed to perform various processes included in the present disclosure. The target supply processor60transmits a control signal to the pressure regulator62and the temperature control processor63.

2.1.1 Reservoir Tank C1

The reservoir tank C1is a container containing the solid target substance27asuch as tin. The solid target substance27amay be, for example, spherical particles of substantially the same size. Alternatively, the particles may have a shape other than a spherical shape. The temperature in the reservoir tank C1is lower than the melting point of the target substance. The gas pressure in the reservoir tank C1is substantially equal to the atmospheric pressure.

The measuring instrument61is arranged at the lower end of the reservoir tank C1in the gravity direction. The reservoir tank C1is connected to the solid target supply pipe41via the measuring instrument61, and the solid target supply pipe41is connected to the load lock chamber C2. A solid target supply valve VT1is arranged at the solid target supply pipe41.

The measuring instrument61normally stops the supply of the solid target substance27ato the solid target supply pipe41. The measuring instrument61can pass the solid target substance27asupplied from the reservoir tank C1to the load lock chamber C2while measuring the amount of the solid target substance27a. Measuring the amount of the solid target substance27aincludes counting the number of particles of the solid target substance27a. The measured solid target substance27ais moved by gravity to the load lock chamber C2as passing through the solid target supply pipe41and the solid target supply valve VT1. After a predetermined amount of the solid target substance27apasses, the measuring instrument61stops passing of the solid target substance27a.

2.1.2 Load Lock Chamber C2

The load lock chamber C2is a container configured capable of containing the solid target substance27asupplied from the reservoir tank C1. The temperature in the load lock chamber C2is lower than the melting point of the target substance.

The load lock chamber C2is connected to the solid target supply pipe42, and the solid target supply pipe42is connected to the target generation unit260. A solid target supply valve VT2is arranged at the solid target supply pipe42. The configurations of the load lock chamber C2and the solid target supply valve VT2will be described later with reference toFIGS.3and4.

The solid target supply valves VT1, VT2are normally closed, and only when one of them is closed, the other is to be opened. That is, when the solid target substance27ais moved from the reservoir tank C1to the load lock chamber C2avia the measuring instrument61, the solid target supply valve VT2is temporarily opened while the solid target supply valve VT1is closed. Further, when the solid target substance27ais introduced from the load lock chamber C2to the target generation unit260, the solid target supply valve VT2is temporarily opened while the solid target supply valve VT1is closed. Thus, the gas in the target generation unit260is suppressed from flowing toward the reservoir tank C1.

The input control processor64is a processing device including a memory641in which a control program is stored and a CPU622which executes the control program. The input control processor64configures the processor in the present disclosure. The input control processor64is specifically configured or programmed to perform various processes included in the present disclosure. The input control processor64controls the measuring instrument61, the solid target supply valves VT1, VT2, and an adjustment mechanism66, which will be described later, provided in the load lock chamber C2. The measuring instrument61, the solid target supply valves VT1, VT2, and the adjustment mechanism66configure the input mechanism in the present disclosure.

2.1.3 Target Generation Unit260

The target generation unit260is a device that generates a liquid target substance27bby melting, at the inside thereof, the solid target substance27aintroduced from the load lock chamber C2through the solid target supply pipe42, and outputs the liquid target substance27bas the target27.

The target generation unit260includes a large tank71t, a small tank7st, and a nozzle7nz. The large tank71tmelts the solid target substance27atherein to generate the liquid target substance27b. The small tank7stpasses the liquid target substance27bgenerated in the large tank71ttoward the nozzle7nz. The nozzle7nzoutputs the liquid target substance27bgenerated in the large tank71t. A filter F is arranged between the large tank71tand the small tank7st. The filter F is a plate having a large number of fine through holes, and suppresses solid matters mixed to the inside of the large tank71tfrom flowing into the small tank7st. The large tank71tcorresponds to the first tank in the present disclosure, and the small tank7stcorresponds to the second tank in the present disclosure. Here, the large tank71tmay not be larger than the small tank7st.

In the present disclosure, a region including the large tank71tin the target generation unit260may be referred to as the first region, and a region including the nozzle7nzin the target generation unit260may be referred to as the second region.

The boundary between the first region and the second region may be defined by the position of the filter F. In this case, the small tank7stis included in the second region, but the present disclosure is not limited thereto.

Heaters81t,8st,8nzare arranged at the large tank71t, the small tank7st, and the nozzle7nz, respectively. The heaters81t,8st,8nzare connected to power sources821t,82st,82nz, respectively, and heat the inside of the target generation unit260to a predetermined temperature higher than the melting point of the target substance. The temperature of the inside of the target generation unit260is controlled by controlling the power sources821t,82st,82nzbased on the outputs of sensors801t,80st,80nzarranged at the heaters81t,8st,8nz, respectively. The sensor80ltis arranged at the heater81tand is not in contact with the large tank71tand the liquid target substance27btherein. However, since the thermal conductivity of each of the large tank71tand the liquid target substance27bis high enough so that the temperature of the large tank71tand the temperature of the liquid target substance27btherein can be regarded as being substantially the same as the temperature of the heater81t, these temperatures may be measured by the sensor80lt. The sensors80st,80nzare arranged at the heaters8st,8st, respectively, and are not in contact with the small tank7st, the nozzle7nz, and the liquid target substance27btherein. However, the above is the same for the thermal conductivity of the small tank7stand the nozzle7nz, and the temperatures may be measured by the sensors80st,80nz, respectively. The sensors801t,80st,80nzmay also be attached directly to the large tank71t, the small tank7st, and the nozzle7nz, respectively.

In the present disclosure, one heater arranged in the first region among the heaters81t,8st,8nzis referred to as the first heater, and one heater arranged in the second region among the heaters81t,8st,8nzis referred to as the second heater. For example, the heater81tcorresponds to the first heater, and one of the heater8stand the heater8nzcorresponds to the second heater. Alternatively, one of the heater81tand the heater8stcorresponds to the first heater, and the heater8nzcorresponds to the second heater. Alternatively, the heater81tcorresponds to the first heater, the heater8stcorresponds to the second heater, and the heater8nzcorresponds to the third heater.

The large tank71tis connected to the pressure regulator62via a gas pipe. The pressure regulator62is connected to a gas cylinder G1. The gas cylinder G1contains a high-pressure rare gas such as an argon gas or a helium gas as a pressurized gas. The pressure regulator62regulates the pressure of the gas supplied from the gas cylinder G1and supplies the gas to the large tank71t. The gas pressure in the large tank71tis lower than the gas pressure supplied from the gas cylinder G1and higher than the atmospheric pressure.

The small tank7stis located between the large tank71tand the nozzle7nz. The nozzle7nzis arranged at a lower end portion of the target generation unit260in the gravity direction. The tip of the nozzle7nzis opened to the inside of the chamber2(seeFIG.1). The liquid target substance27bin the target generation unit260is output from the opening at the tip of the nozzle7nzowing to the difference between the gas pressure supplied from the pressure regulator62and the gas pressure in the chamber2. When vibration is applied to the nozzle7nzby a piezoelectric element (not shown), the jet-like liquid target substance27boutput from the nozzle7nzis separated into droplets to form the target27.

The temperature control processor63is a processing device including a memory631in which a control program is stored and a CPU632which executes the control program. The temperature control processor63configures the processor in the present disclosure. The temperature control processor63is specifically configured or programmed to perform various processes included in the present disclosure. The temperature control processor63determines current values of the heaters81t,8st,8nzbased on the temperature of the target generation unit260detected by the sensors801t,80st,80nz, and controls the power sources821t,82st,82nz.

2.1.4 Detail of Load Lock Chamber C2and Solid Target Supply Valve VT2

Each ofFIGS.3and4shows the configuration of the load lock chamber C2and the solid target supply valve VT2, and their operation is shown in combination ofFIGS.3and4.

The adjustment mechanism66included in the load lock chamber C2includes a receiving plate66aand an actuator66b. The receiving plate66ais located near the lower end of the load lock chamber C2in the gravity direction. The actuator66bis configured to switch the adjustment mechanism66between a first state shown inFIG.3and a second state shown inFIG.4by moving the receiving plate66a.

In the first state, the receiving plate66ais arranged to block a connection portion between the load lock chamber C2and the solid target supply pipe42. Thus, the movement of the solid target substance27atoward the solid target supply valve VT2is suppressed.

In the second state, the receiving plate66ais arranged at a position away from the connecting portion between the load lock chamber C2and the solid target supply pipe42. Thus, the movement of the solid target substance27atoward the solid target supply valve VT2is allowed.

The adjustment mechanism66is normally set in the first state, and is temporarily set in the second state when the solid target substance27ais to be moved toward the solid target supply valve VT2.

The solid target supply valve VT2includes, for example, a ball valve including a ball portion V2aand a body portion V2b. By rotating the ball portion V2ainside the body portion V2bin the direction of an arrow R, switching is performed between the closed state shown inFIG.3and the open state shown inFIG.4. In the closed state, the flow of gas from the target generation unit260to the load lock chamber C2is suppressed, and in the open state, the solid target substance27ais allowed to be introduced from the load lock chamber C2to the target generation unit260.

2.2 Operation

2.2.1 Operation of EUV Light Generation Processor5

FIG.5is a flowchart for the EUV light generation processor5in the comparative example. The EUV light generation processor5operates the EUV light generation system11in the following manner to generate EUV light.

In S1, the EUV light generation processor5activates the EUV light generation system11. The activation of the EUV light generation system11includes activation of various power sources included in the EUV light generation system11, activation of various processors, gas purging and vacuuming of various devices, and the like.

In S2, the EUV light generation processor5causes the input control processor64to start input control of the solid target substance27a. After being started in S2, the input control of the solid target substance27ais repeated until, for example, the EUV light generation is completed. The input control of the solid target substance27awill be described later with reference toFIG.6.

In S3, the EUV light generation processor5transmits a control signal to the target supply processor60to cause the temperature control processor63to start temperature control of the large tank71t, the small tank7st, and the nozzle7nz. After being started in S3, the temperature control is repeated until, for example, the EUV light generation is completed. The temperature control will be described later with reference toFIGS.7to9.

In S4, the EUV light generation processor5causes the target supply processor60to start the target supply. The target supply is started, for example, by the pressure regulator62adjusting the gas pressure in the large tank71tto a high pressure.

In S5, the EUV light generation processor5performs processing for EUV light generation. The EUV light generation is performed by controlling the laser device3, the laser light transmission device34, and the like so that the target27is irradiated with the pulse laser light33at a timing when the target27reaches the plasma generation region25(seeFIG.1).

In S6, the EUV light generation processor5determines whether or not to continue the EUV light generation. When the EUV light generation is to be continued (S6: YES), the EUV light generation processor5returns processing to S5. When the EUV light generation is not to be continued (S6: NO), the EUV light generation processor5ends processing of the present flowchart.

2.2.2 Input Control of Solid Target Substance27a

FIG.6is a flowchart for the input control processor64in the comparative example. The solid target substance27ais introduced to the target generation unit260in the following manner.

In S21, the input control processor64determines whether or not the amount of the liquid target substance27bin the large tank71tis equal to or less than a set value. The amount of the liquid target substance27bis determined by the output of a liquid level sensor (not shown) arranged in the large tank71t. When the amount of the liquid target substance27bis equal to or less than the set value (S21: YES), the input control processor64advances processing to S22. When the amount of the liquid target substance27bis larger than the set value (S21: NO), the input control processor64advances processing to S26. The input timing is controlled by waiting without introducing the solid target substance27auntil the amount of the liquid target substance27bbecomes equal to or less than the set value.

In S22, the input control processor64controls the measuring instrument61and the solid target supply valve VT1so as to measure the solid target substance27aone by one and move the solid target substance27ato the load lock chamber C2.

In S23, the input control processor64determines whether or not a predetermined amount of the solid target substance27ahas moved to the load lock chamber C2. When the predetermined amount of the solid target substance27ahas not moved (S23: NO), the input control processor64returns processing to S22. When the predetermined amount of the solid target substance27ahas moved (S23: YES), the input control processor64advances processing to S25. By continuing the measurement until the predetermined amount of the solid target substance27amoves, the input amount of the solid target substance27ais controlled.

In S25, the input control processor64controls the adjustment mechanism66in the load lock chamber C2and the solid target supply valve VT2so as to introduce the solid target substance27ato the load lock chamber C2.

In S26, the input control processor64determines whether or not the input control of the solid target substance27ais to be continued. For example, when the EUV light generation processor5determines that the EUV light generation is to be continued, it is also determined that the input control of the solid target substance27ais to be continued. When the input control of the solid target substance27ais to be continued (S26: YES), the input control processor64returns processing to S21. When the input control of the solid target substance27ais not to be continued (S26: NO), the input control processor64ends processing of the present flowchart.

By such operation, the solid target substance27acontained in the reservoir tank C1, which is substantially at the atmospheric pressure, is introduced to the target generation unit260having a high pressure. Even when the liquid target substance27bin the target generation unit260is consumed, the target substance can be replenished without replacing the target generation unit260, so that the downtime of the EUV light generation apparatus1can be reduced.

2.2.3 Temperature Control of Large Tank71t

FIG.7is a flowchart of the temperature control of the large tank71tby the temperature control processor63in the comparative example. The temperature of the large tank71tis feedback controlled as follows.

In S301, the temperature control processor63determines whether or not a control cycle of the temperature of the large tank71thas elapsed. When the control cycle has elapsed (S301: YES), the temperature control processor63advances processing to S302. When the control cycle has not elapsed (S301: NO), the temperature control processor63advances processing to S312.

In S302, the temperature control processor63reads a target temperature SVlt of the large tank71tfrom the memory631.

In S306, the temperature control processor63reads a present temperature PVlt of the large tank71tdetected by the sensor80lt.

In S307, the temperature control processor63calculates a temperature deviation elt between the target temperature SVlt and the present temperature PVlt by the following equation.
elt=SVlt−PVlt
In S308, the temperature control processor63performs PID control calculation to calculate a current value Clt of the heater81t.

In S311, the temperature control processor63outputs a heater control signal for the heater81tusing the current value Clt.

In S312, the temperature control processor63determines whether or not to continue the temperature control of the large tank71t. For example, when the EUV light generation processor5determines that the EUV light generation is to be continued, it is also determined that the temperature control is to be continued. When the temperature control is to be continued (S312: YES), the temperature control processor63returns processing to S301. When the temperature control is not to be continued (S312: NO), the temperature control processor63ends processing of the present flowchart.

2.2.4 Temperature Control of Small Tank7st

FIG.8is a flowchart of the temperature control of the small tank7stby the temperature control processor63in the comparative example. The temperature control of the small tank7stcorresponds to the temperature control of the large tank71tdescribed with reference toFIG.7with the following points replaced.Step numbers starting from “S3” are replaced with step numbers starting from “S4.”The target temperature SVlt of the large tank71tis replaced with the target temperature SVst of the small tank7st. Specific numerical values of the target temperatures SVlt, SVst may be the same as each other.The present temperature PVlt of the large tank71tis replaced with the present temperature PVst of the small tank7st.The temperature deviation elt is replaced with the temperature deviation est.The current value Clt of the heater81tis replaced with the current value Cst of the heater8st.

2.2.5 Temperature Control of Nozzle7Nz

FIG.9is a flowchart of the temperature control of the nozzle7nzby the temperature control processor63in the comparative example. The temperature control of the nozzle7nzcorresponds to the temperature control of the large tank71tdescribed with reference toFIG.7with the following points replaced.Step numbers starting from “S3” are replaced with step numbers starting from “S5.”The target temperature SVlt of the large tank71tis replaced with the target temperature SVnz of the nozzle7nz. Specific numerical values of the target temperatures SVlt, SVnz may be the same as each other.The present temperature PVlt of the large tank71tis replaced with the present temperature PVnz of the nozzle7nz.The temperature deviation elt is replaced with the temperature deviation enz.The current value Clt of the heater81tis replaced with the current value Cnz of the heater8nz.

2.2.6 Block Diagram

FIG.10is a block diagram of the temperature control in the comparative example. The temperature control is performed for each of the large tank71t, the small tank7st, and the nozzle7nzin a mutually independent manner. The temperature deviations elt, est, enz of the large tank71t, the small tank7st, and the nozzle7nzare calculated from the target temperatures SVlt, SVst, SVnz and the present temperatures PVlt, PVst, PVnz, respectively. The current values Clt, Cst, Cnz of the heaters81t,8st,8nzare calculated by the PID control calculation using the temperature deviations elt, est, enz. The heaters81t,8st,8nzconvert electric energy corresponding to the current values Clt, Cst, Cnz to thermal energy, respectively. The thermal energy and disturbance when the solid target substance27ais introduced to the large tank71taffect the present temperatures PVlt, PVst, PVnz. The present temperatures PVlt, PVst, PVnz are detected by the sensors801t,80st,80nzand feedback is performed.

2.3 Problem of Comparative Example

FIG.11shows a simulation result of a temperature change of the liquid target substance27bin the small tank7stin the comparative example. The horizontal axis represents the elapsed time from the input timing of the solid target substance27a, and the vertical axis represents the temperature deviation with respect to the temperature of the liquid target substance27bat the input timing of the solid target substance27a. The remaining amount of the liquid target substance27bin the target generation unit260before introducing the solid target substance27awas 50 cm3, and the input amount of the solid target substance27awas 0.35 cm3.

The liquid target substance27bis deprived of fusion heat by the solid target substance27a, so that the temperature of the liquid target substance27bdecreases. Then, the temperature of the liquid target substance27bis recovered by feedback control on the heaters81t,8st,8nz. When the decrease in temperature is within an allowable range, the liquid target substance27boutput from the nozzle7nzbecomes ideal targets27each in the form of a droplet. However, when the decrease in temperature is out of the allowable range, a target formation failure may occur. For example, a decrease of 0.1° C. may cause a target formation failure.

3. Suppression of Temperature Decrease by Feedforward Control

A first embodiment will be described in the following. The configuration of the target supply system26according to the first embodiment may be similar to that described with reference toFIG.2.

3.1 Operation

3.1.1 Input Control of Solid Target Substance27a

FIG.12is a flowchart for the input control processor64in the first embodiment. The process shown inFIG.12differs from the process shown inFIG.6in the following points.

When the predetermined amount of the solid target substance27ahas moved to the load lock chamber C2(S23: YES), the input control processor64advances processing to S24a. In S24a, the input control processor64notifies the temperature control processor63of the input timing and the input amount of the solid target substance27a. Then, in S25, the solid target substance27ais introduced to the large tank71t.

3.1.2 Temperature Control of Large Tank71t

The temperature control of the large tank71tmay be feedback control similar to that shown inFIG.7.

3.1.3 Temperature Control of Small Tank7st

FIG.13is a flowchart of the temperature control of the small tank7stby the temperature control processor63in the first embodiment. The process shown inFIG.13differs from the process shown inFIG.8in the following points.

After reading the target temperature SVst of the small tank7stin S402, in S404a, the temperature control processor63calculates a correction value fst(t) of the temperature of the small tank7stby feedforward control calculation. The correction value fst(t) is calculated based on the input timing and the input amount of the solid target substance27areceived from the input control processor64. The correction value fst(t) is a function of time represented by the following equation.
fst(t)=N·Ast·exp(−t/τst)

Here, N is an input amount of the solid target substance27a, Ast is a control gain, t is an elapsed time from the input timing of the solid target substance27a, and τst is a time constant. The correction value fst(t) is a function that attenuates and approaches 0 in accordance with the elapsed time t.

In S405a, the temperature control processor63calculates a corrected target temperature SVstr by adding the correction value fst (t) to the target temperature SVst of the small tank7st. The target temperature SVst is an example of the first target value in the present disclosure, and the corrected target temperature SVstr is an example of the second target value in the present disclosure.

Feedback control is performed in S406to S411. At this time, since the corrected target temperature SVstr is used to calculate the temperature deviation est in S407a, feedforward control is performed together with feedback control. Feedforward control is performed in accordance with the control cycle of feedback control.

3.1.4 Temperature Control of Nozzle7nz

The temperature control of the nozzle7nzmay be feedback control similar to that shown inFIG.9.

3.1.5 Block Diagram

FIG.14is a block diagram of the temperature control in the first embodiment. In the first embodiment, the input control processor64transmits the input timing and the input amount of the solid target substance27ato the temperature control processor63. The temperature control processor63calculates the correction value fst (t) by feedforward control calculation based on the input timing and the input amount, and calculates the corrected target temperature SVstr by adding the correction value fst(t) to the target temperature SVst of the small tank7st. Feedback control and feedforward control are performed by performing feedback control on the heater8thof the small tank7thbased on the corrected target temperature SVstr.

With respect to the temperature of the large tank71tand the temperature of the nozzle7nz, feedforward control based on the input timing and the input amount may not be performed, and feedback control may be performed similarly to the comparative example.

3.2 Simulation Result

FIG.15shows a simulation result of the temperature change of the liquid target substance27bin the small tank7stin the first embodiment. The temperature of the liquid target substance27bdecreases after the solid target substance27ais introduced, and is then recovered by feedback control.

InFIG.15, the correction value fst(t) of the temperature of the small tank7stis shown together. The time constant τst of the correction value fst(t) is set to, for example, about 10 seconds, and after the correction value fst(t) becomes substantially 0, the temperature of the liquid target substance27bbecomes the lowest. The next introduction of the solid target substance27ato the target generation unit260is performed thereafter

The decrease of the temperature of the liquid target substance27bis 0.1° C. or more in the comparative example, whereas it is less than 0.1° C. in the first embodiment due to feedforward control. Since the decrease of the temperature is within the allowable range, the occurrence of the target formation failure is suppressed. Thus, the EUV light generation can be stabilized.

3.3 Effect

(1) According to the first embodiment, the target supply system26includes the target generation unit260, the input mechanism, the heater8st, the sensor80st, the input control processor64, and the temperature control processor63. The target generation unit260generates the liquid target substance27bby melting the solid target substance27aat the inside thereof, and outputs the liquid target substance27b. The input mechanism includes, for example, the measuring instrument61, the solid target supply valves VT1, VT2, and the adjustment mechanism66, and introduces the solid target substance27ato the target generation unit260. The heater8stis arranged at the target generation unit260. The sensor80stdetects the temperature of the target generation unit260. The input control processor64controls the input timing at which the solid target substance27ais introduced to the target generation unit260. The temperature control processor63performs feedforward control on the heater8stbased on the input timing while performing feedback control on the heater8stbased on the present temperature PVst detected by the sensor80st.

According to this, feedforward control is performed, on the heater8st, based on the input timing of the solid target substance27awhile feedback control is performed, so that the temperature fluctuation when the solid target substance27ais introduced can be suppressed and the formation of the target27can be stabilized.

(2) According to the first embodiment, the temperature control processor63performs feedforward control on the heater8stso that the decrease in the temperature of the target generation unit260is less than 0.1° C.

According to this, it is possible to suppress the occurrence of the target formation failure.

(3) According to the first embodiment, the temperature control processor63performs feedforward control on the heater8stin accordance with the control cycle of feedback control on the heater8st.

According to this, it is possible to suppress an increase in the calculation amount of the control calculation by adjusting the control cycle.

(4) According to the first embodiment, the temperature control processor63reads the target temperature SVst of the target generation unit260, and adds the correction value fst (t) including a feedforward factor to the target temperature SVst to calculate the corrected target temperature SVstr. The temperature control processor63further performs feedback control on the heater8stbased on the corrected target temperature SVstr and the present temperature PVst.

According to this, by performing feedback control with the correction value fst(t) added to the target temperature SVst, it is possible to suppress an increase in the calculation amount due to the addition of feedforward control.

(5) According to the first embodiment, the input control processor64controls the input amount of the solid target substance27aintroduced to the target generation unit260, and the temperature control processor63calculates the correction value fst(t) based on the input amount.

According to this, the input amount of the solid target substance27acan be known before the introduction of the solid target substance27a, and the correction value fst(t) can be calculated in a timely manner. Further, it is possible to avoid a case in which the temperature fluctuation cannot be suppressed due to an excessively large input amount, or a case in which the life of the solid target supply valve VT2is shortened due to frequent opening and closing of the solid target supply valve SL caused by an excessively small input amount.

(6) According to the first embodiment, the temperature control processor63causes the correction value fst(t) to approach 0 while performing feedback control on the heater8st.

According to this, feedforward control can be performed, on the heater8st, only for a required period while feedback control is performed.

(7) According to the first embodiment, the input control processor64controls the input timing so that the solid target substance27ais introduced to the target generation unit260in a state that the correction value fst(t) is substantially 0.

According to this, since the next feedforward control is started in a state in which the correction value fst(t) is substantially 0, it is possible to avoid complication of the feedforward control calculation.

(8) According to the first embodiment, the target generation unit260includes the first region in which the solid target substance27ais melted at the inside thereof to generate the liquid target substance27b, and the second region including the nozzle7nzfor outputting the liquid target substance27bgenerated in the first region. The target generation unit260includes the heater81tarranged at the first region, and the heater8starranged at the second region. The temperature control processor63performs feedforward control while performing feedback control on at least one of the heaters81t,8st.

According to this, it is possible to select the optimum control for each region in the target generation unit260.

In the first embodiment, description has been provided on a case in which feedforward control is performed, on the heater8stof the small tank7st, while feedback control is performed, and feedback control is performed on the heater81tof the large tank71tand the heater8nzof the nozzle7nz, but the present disclosure is not limited thereto. Feedforward control may be performed while performing feedback control on at least one of the heaters81t,8st,8nz, and feedback control may be performed on the other heaters.

Further, the small tank7stmay not be provided, and in this case, for example, feedback control may be performed on the heater81tof the large tank71t, and feedforward control may be performed while feedback control is performed on the heater8nzof the nozzle7nz.

(9) According to the first embodiment, the temperature control processor63performs feedback control on the heater81tand performs feedforward control while performing feedback control on the heater8st.

According to this, the formation of the target27can be stabilized by stabilizing the temperature of the small tank7stnear the nozzle7nz.

(10) According to the first embodiment, the filter F is arranged between the first region and the second region.

According to this, it is possible to stabilize the temperature of the second region when the solid target substance27ais introduced to the first region.

In other respects, the first embodiment is similar to the comparative example.

4. Example in which Feedforward Control is Selectable

A second embodiment will be described in the following. The configuration of the target supply system26according to the second embodiment may be similar to that described with reference toFIG.2.

4.1 Operation

4.1.1 Input Control of Solid Target Substance27a

FIG.16is a flowchart for the input control processor64in the second embodiment. The process shown inFIG.16differs from the process shown inFIG.12in the following points.

When the predetermined amount of the solid target substance27ahas moved to the load lock chamber C2(S23: YES), the input control processor64advances processing to S24c.

In S24c, the input control processor64notifies the temperature control processor63of the input timing and the input amount of the solid target substance27aand also notifies the temperature control processor63of the target portion of feedforward control. Then, in S25, the solid target substance27ais introduced to the large tank71t.

The target portion of feedforward control may be determined according to the input amount of the solid target substance27a, or may be selected by a user. In the second embodiment, the heater8stof the small tank7stis subjected to feedforward control, and it is possible to select whether or not to perform feedforward control on each of the heater81tof the large tank71tand the heater8nzof the nozzle7nz.

4.1.2 Temperature Control of Large Tank71t

FIG.17is a flowchart of the temperature control of the large tank71tby the temperature control processor63in the second embodiment. The process shown inFIG.17differs from the process shown inFIG.7in the following points.

After reading the target temperature SVlt of the large tank71tin S302, in S303c, the temperature control processor63determines whether or not to perform feedforward control on the heater81tof the large tank71t. In the process ofFIG.16, when the large tank71tis set as the target portion of feedforward control, the temperature control processor63determines that feedforward control is to be performed (S303c: YES), and processing proceeds to S304b. When the large tank71tis not set as the target portion of feedforward control, the temperature control processor63determines that feedforward control is not to be performed (S303c: NO), and processing proceeds to S306.

In S304b, the temperature control processor63calculates a correction value flt(t) of the temperature of the large tank71tby feedforward control calculation. The correction value flt(t) is calculated based on the input timing and the input amount of the solid target substance27areceived from the input control processor64. The correction value flt(t) is a function of time represented by the following equation.
flt(t)=N·Alt·exp(−t/τlt)

Here, Alt is a control gain and τlt is a time constant. The correction value flt(t) is a function that attenuates and approaches 0 in accordance with the elapsed time t.

In S305b, the temperature control processor63calculates a corrected target temperature SVltr by adding the correction value flt(t) to the target temperature SVlt of the large tank71t. The target temperature SVlt is an example of the first target value in the present disclosure, and the corrected target temperature SVltr is an example of the second target value in the present disclosure.

The corrected target temperature SVltr is used to calculate the temperature deviation elt in S307b.

4.1.3 Temperature Control of Small Tank7st

The temperature control of the small tank7stmay be a combination of feedback control and feedforward control similar to that shown inFIG.13.

4.1.4 Temperature Control of Nozzle7nz

FIG.18is a flowchart of the temperature control of the nozzle7nzby the temperature control processor63in the second embodiment. The temperature control of the nozzle7nzcorresponds to the temperature control of the large tank71tdescribed with reference toFIG.17with the following points replaced.Step numbers starting from “S3” are replaced with step numbers starting from “S5.”The target temperature SVlt of the large tank71tis replaced with the target temperature SVnz of the nozzle7nz.The correction value flt(t) of the temperature of the large tank71tis replaced with a correction value fnz(t) of the temperature of the nozzle7nz.The corrected target temperature SVltr of the large tank71tis replaced with the corrected target temperature SVnzr of the nozzle7nz.The present temperature PVlt of the large tank71tis replaced with the present temperature PVnz of the nozzle7nz.The temperature deviation elt is replaced with the temperature deviation enz.The current value Clt of the heater81tis replaced with the current value Cnz of the heater8nz.

The correction value fnz(t) is a function of time represented by the following equation.
fnz(t)=N·Anz·exp(−t/τnz)

Here, Anz is a control gain and τlt is a time constant. The correction value fnz(t) is a function that attenuates and approaches 0 in accordance with the elapsed time t.

The set values of the control gains Alt, Ast, Anz for calculating the correction values flt(t), fst(t), fnz(t) may be different from each other. The set values of the time constants τlt, τst, τnz for calculating the correction values flt(t), fst(t), fnz(t) may be different from each other.

4.1.5 Block Diagram

FIG.19is a block diagram of the temperature control in the second embodiment. In the second embodiment, the input control processor64notifies the temperature control processor63of the target portion of feedforward control.

When the large tank71tis set as the target portion of feedforward control, the temperature control processor63performs feedback control on the heater81tof the large tank71tusing the corrected target temperature SVltr corrected by the correction value flt(t). When the large tank71tis not set as the target portion of feedforward control, feedback control is performed similarly to the comparative example.

When the nozzle7nzis set as the target portion of feedforward control, the temperature control processor63performs feedback control on the heater8nzof the nozzle7nzusing the corrected target temperature SVnzr corrected by the correction value fnz(t). When the nozzle7nzis not set as the target portion of feedforward control, feedback control is performed similarly to the comparative example.

The small tank7stis always set as the target portion of feedforward control, and the temperature control processor63performs feedback control on the heater8stof the small tank7stusing the corrected target temperature SVstr corrected by the correction value fst(t).

4.2 Effect

(11) According to the second embodiment, at least one of the heaters81t,8nzcan be selected whether or not feedforward control is performed thereon while feedback control is performed. According to this, it is possible to select the optimum control in accordance with conditions such as the input amount of the solid target substance27a.

In the second embodiment, description has been provided on a case in which the heater8stof the small tank7stis always subjected to feedforward control, but the present disclosure is not limited thereto. It may be possible to select whether or not to perform feedforward control on the heater8stof the small tank7st.

(12) According to the second embodiment, the temperature control processor63performs, on the heater81t, feedforward control using a first set value, such as the time constant τlt while performing feedback control. Further, feedforward control is performed, on the heater8st, using a second set value, such as the time constant τst which is different from the first set value, while performing feedback control.

According to this, since the set value of feedforward control can be changed for each region, fine temperature control can be performed.

In other respects, the second embodiment is similar to the first embodiment.

5. Example of Performing Feedforward Control on Temperatures of Small Tank7stand Nozzle7nz

A third embodiment will be described in the following. The configuration of the target supply system26according to the third embodiment may be similar to that described with reference toFIG.2.

5.1 Operation

5.1.1 Input Control of Solid Target Substance27a

The input control of the solid target substance27amay be similar to that inFIG.12.

5.1.2 Temperature Control of Large Tank71t

The temperature control of the large tank71tmay be feedback control similar to that shown inFIG.7.

5.1.3 Temperature Control of Small Tank7st

The temperature control of the small tank7stmay be a combination of feedback control and feedforward control similar to that shown inFIG.13.

5.1.4 Temperature Control of Nozzle7nz

FIG.20is a flowchart of the temperature control of the nozzle7nzby the temperature control processor63in the third embodiment. The process shown inFIG.20differs from the process shown inFIG.9in the following points.

After reading the target temperature SVnz of the nozzle7nzin S502, in S504b, the temperature control processor63calculates the correction value fnz(t) of the temperature of the nozzle7nzby feedforward control calculation. The correction value fnz(t) is calculated based on the input timing and the input amount of the solid target substance27areceived from the input control processor64. The correction value fnz(t) may be similar to that described in the second embodiment.

The set values of the time constant τnz and the control gain Anz for calculating the correction value fnz (t) of the temperature of the nozzle7nzmay be larger than the set values of the time constant τst and the control gain Ast for calculating the correction value fst (t) of the temperature of the small tank7st, respectively. The correction value fnz(t) may be a function that attenuates slower than the correction value fst(t).

In S505b, the temperature control processor63calculates the corrected target temperature SVnzr by adding the correction value fnz(t) to the target temperature SVnz of the nozzle7nz. The target temperature SVnz is an example of the first target value in the present disclosure, and the corrected target temperature SVnzr is an example of the second target value in the present disclosure.

The corrected target temperature SVnzr is used to calculate the temperature deviation enz in S507b.

5.1.5 Block Diagram

FIG.21is a block diagram of the temperature control in the third embodiment. In the third embodiment, the temperature control processor63adds the correction value fnz(t) calculated by the feedforward control calculation based on the input timing and the input amount to the target temperature SVnz of the nozzle7nz. Feedback control on the heater8nzof the nozzle7nzis performed based on the corrected target temperature SVnzr having the correction value fnz(t) added.

With respect to the temperature of the large tank71t, feedforward control based on the input timing and the input amount may not be performed, and feedback control may be performed similarly to the comparative example.

5.2 Simulation Result

FIG.22shows a simulation result of the temperature change of the liquid target substance27bin the small tank7stin the third embodiment. The temperature of the liquid target substance27bdecreases after the solid target substance27ais introduced, and is then recovered by feedback control.

InFIG.22, the correction value fst(t) of the temperature of the small tank7stand the correction value fnz(t) of the temperature of the nozzle7nzare shown together. The time constant τst of the correction value fst(t) is set to, for example, about 10 seconds, and the time constant τnz of the correction value fnz(t) is set to, for example, about 20 seconds. After both of the correction values fst(t), fnz(t) become substantially 0, the temperature of the liquid target substance27bbecomes the lowest. The next introduction of the solid target substance27ato the target generation unit260is performed thereafter.

The decrease of the temperature of the liquid target substance27bis small compared to the decrease of the temperature in the first embodiment. Since the decrease of the temperature is small, the occurrence of the target formation failure is suppressed. Thus, the EUV light generation can be stabilized.

5.3 Effect

(13) According to the third embodiment, the target generation unit260includes the large tank71t, the nozzle7nz, and the small tank7sttherebetween. The heater81tis arranged at the large tank71t, the heater8stis arranged at the small tank7st, and the heater8nzis arranged at the nozzle7nz. According to this, by arranging the heater at each of the large tank71t, the small tank7st, and the nozzle7nz, it is possible to perform fine temperature control. In other respects, the third embodiment is similar to the first embodiment.

As described in the first to third embodiments, the small tank7stmay always be set as the target portion of feedforward control.

With respect to the nozzle7nz, only feedback control may be performed as described in the first embodiment, feedforward control may be selectable as described in the second embodiment, or the nozzle7nzmay always be set as the target portion of feedforward control as described in the third embodiment.

6. Example of Performing Feedforward Control Using Correction Value fcst(t) of Current

A fourth embodiment will be described in the following. The configuration of the target supply system26according to the fourth embodiment may be similar to that described with reference toFIG.2.

6.1 Operation

6.1.1 Input Control of Solid Target Substance27a

The input control of the solid target substance27amay be similar to that inFIG.12.

6.1.2 Temperature Control of Large Tank71t

The temperature control of the large tank71tmay be feedback control similar to that shown inFIG.7.

6.1.3 Temperature Control of Small Tank7st

FIG.23is a flowchart of the temperature control of the small tank7stby the temperature control processor63in the fourth embodiment. The process shown inFIG.23differs from the process shown inFIG.8in the following points.

After calculating the current value Cst of the heater8stby PID control calculation using the target temperature SVst and the present temperature PVst in S408, the temperature control processor63calculates a correction value fcst(t) of the current of the heater8stby feedforward control calculation in S409d. The correction value fcst(t) is calculated based on the input timing and the input amount of the solid target substance27areceived from the input control processor64. The correction value fst(t) is a function of time represented by the following equation.
fcst(t)=N·Acst·exp(−t/τcst)
Here, Acst is a control gain and τlt is a time constant. The correction value fcst(t) is a function that attenuates and approaches 0 in accordance with the elapsed time t.

In S410d, the temperature control processor63calculates a corrected current value Cstr by adding the correction value fcst(t) to the current value Cst of the heater8st. The current value Cst corresponds to the first current value in the present disclosure, and the corrected current value Cstr corresponds to the second current value in the present disclosure. When the heater control signal is output in S411, the corrected current value Cstr is used.

6.1.4 Temperature Control of Nozzle7nz

The temperature control of the nozzle7nzmay be feedback control similar to that shown inFIG.9.

6.1.5 Block Diagram

FIG.24is a block diagram of the temperature control in the fourth embodiment. In the fourth embodiment, the temperature control processor63adds the correction value fcst(t) calculated by feedforward control calculation based on the input timing and the input amount to the current value Cst of the heater8stcalculated by PID control calculation. The control of the heater8stis performed using the corrected current value Cstr having the correction value fcst(t) added.

With respect to the temperature of the large tank71tand the temperature of the nozzle7nz, feedforward control based on the input timing and the input amount may not be performed, and feedback control may be performed similarly to the comparative example.

6.2 Simulation Result

FIG.25shows a simulation result of the temperature change of the liquid target substance27bin the small tank7stin the fourth embodiment. The temperature of the liquid target substance27bdecreases after the solid target substance27ais introduced, and is then recovered by feedback control.

InFIG.25, the correction value fcst(t) of the current of the heater8stis shown together. The time constant τcst of the correction value fcst(t) is set to, for example, about 100 seconds, and the decreased temperature of the liquid target substance27brecovers after the correction value fcst(t) becomes substantially 0. The next introduction of the solid target substance27ato the target generation unit260is performed thereafter.

The decrease of the temperature of the liquid target substance27bis 0.1° C. or more in the comparative example, whereas it is less than 0.1° C. in the fourth embodiment. Since the decrease of the temperature is within the allowable range, the occurrence of the target formation failure is suppressed. Further, in the fourth embodiment, it is possible to reduce overshoot after the temperature is once decreased and recovered. Thus, the EUV light generation can be stabilized.

6.3 Effect

(14) According to the fourth embodiment, the temperature control processor63reads the target temperature SVst of the target generation unit260, and calculates the current value Cst of the heater8stby feedback control calculation based on the target temperature SVst and the present temperature PVst. The temperature control processor63calculates the corrected current value Cstr by adding the correction value fcst(t) including a feedforward element to the current value Cst, and controls the heater8stin accordance with the corrected current value Cstr.

According to this, by performing feedback control with the correction value fst(t) added to the current value Cst, it is possible to suppress an increase in the calculation amount due to the addition of feedforward control.

(15) According to the fourth embodiment, the input control processor64controls the input amount of the solid target substance27aintroduced to the target generation unit260, and the temperature control processor63calculates the correction value fcst(t) based on the input amount.

According to this, the input amount of the solid target substance27acan be known before the introduction of the solid target substance27a, and the correction value fcst(t) can be calculated in a timely manner. Further, it is possible to avoid a case in which the temperature fluctuation cannot be suppressed due to an excessively large input amount, or a case in which the life of the solid target supply valve VT2is shortened due to frequent opening and closing of the solid target supply valve SL caused by an excessively small input amount.

(16) According to the fourth embodiment, the temperature control processor63causes the correction value fcst(t) to approach 0 while performing control of the heater8stin accordance with the corrected current value Cstr.

According to this, the feedforward control can be performed, on the heater8st, only for a required period while feedback control is performed.

(17) According to the fourth embodiment, the input control processor64controls the input timing so that the solid target substance27ais introduced to the target generation unit260in a state that the correction value fcst(t) is substantially 0.

According to this, since the next feedforward control is started in a state in which the correction value fcst(t) is substantially 0, it is possible to avoid complication of the feedforward control calculation.

In the fourth embodiment, description has been provided on a case in which feedforward control is performed on the heater8stthe small tank7st, but the present disclosure is not limited thereto. Feedforward control may be performed on the heater81tof the large tank71tor the heater8nzof the nozzle7nzusing the correction current value. It may be possible to select whether or not to perform feedforward control on each of the heaters81t,8st,8nz.

In other respects, the fourth embodiment is similar to the first embodiment.

7. Example in which Waveform of Correction Value fcst (t) of Current is Rectangular Wave

FIG.26shows a simulation result of the temperature change of the liquid target substance27bin the small tank7stin a fifth embodiment.

InFIG.26, the correction value fcst(t) of the current of the heater8stis shown together. In the fifth embodiment, the correction value fcst(t) is not an attenuating function, but is a rectangular wave represented by the following equations.
fcst(t)=N·Ac(0≤t≤T)
fcst(t)=0 (t<0,T<t)
Here, Ac is a control gain and T is a time width of the rectangular wave. Due to the rectangular wave, it may be easy to calculate the corrected value fcst(t). The time width T is set to, for example, about 200 seconds, and after the correction value fcst(t) becomes substantially 0, the temperature of the liquid target substance27bbecomes the lowest. The next introduction of the solid target substance27ato the target generation unit260is performed thereafter.

The temperature of the liquid target substance27bdoes not significantly decrease during the period in which the correction value fcst(t) is a constant value N·Ac, but may rapidly increase. However, the temperature of the liquid target substance27bmay decrease when the correction value fcst(t) is switched to 0. By changing the control gain Ac and the time width T of the rectangular wave, the temperature change of the liquid target substance27bcan be adjusted.

In other respects, the fifth embodiment is similar to the first embodiment.

8. Others

FIG.27schematically shows the configuration of an exposure apparatus6aconnected to the EUV light generation system11.

InFIG.27, the exposure apparatus6aas the EUV light utilization apparatus6(seeFIG.1) includes a mask irradiation unit608and a workpiece irradiation unit609. The mask irradiation unit608illuminates, via a reflection optical system, a mask pattern of a mask table MT with the EUV light incident from the EUV light generation system11. The workpiece irradiation unit609images the EUV light reflected by the mask table MT onto a workpiece (not shown) arranged on a workpiece table WT via a reflection optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer on which photoresist is applied. The exposure apparatus6asynchronously translates the mask table MT and the workpiece table WT to expose the workpiece to the EUV light reflecting the mask pattern. Through the exposure process as described above, a device pattern is transferred onto the semiconductor wafer, thereby an electronic device can be manufactured.

FIG.28schematically shows the configuration of an inspection apparatus6bconnected to the EUV light generation system11.

InFIG.28, the inspection apparatus6bas the EUV light utilization apparatus6(seeFIG.1) includes an illumination optical system603and a detection optical system606. The illumination optical system603reflects the EUV light incident from the EUV light generation system11to illuminate a mask605placed on a mask stage604. Here, the mask605conceptually includes a mask blanks before a pattern is formed. The detection optical system606reflects the EUV light from the illuminated mask605and forms an image on a light receiving surface of a detector607. The detector607having received the EUV light obtains the image of the mask605. The detector607is, for example, a time delay integration (TDI) camera.

Defects of the mask605are inspected based on the image of the mask605obtained by the above-described process, and a mask suitable for manufacturing an electronic device is selected using the inspection result. Then, the electronic device can be manufactured by exposing and transferring the pattern formed on the selected mask onto the photosensitive substrate using the exposure apparatus6a.

The description above is intended to be illustrative and the present disclosure is not limited thereto. Therefore, it would be obvious to those skilled in the art that various modifications to the embodiments of the present disclosure would be possible without departing from the spirit and the scope of the appended claims. Further, it would be also obvious to those skilled in the art that embodiments of the present disclosure would be appropriately combined.

The terms used throughout the present specification and the appended claims should be interpreted as non-limiting terms unless clearly described. For example, terms such as “comprise”, “include”, “have”, and “contain” should not be interpreted to be exclusive of other structural elements.

Further, indefinite articles “a/an” described in the present specification and the appended claims should be interpreted to mean “at least one” or “one or more.” Further, “at least one of A, B, and C” should be interpreted to mean any of A, B, C, A+B, A+C, B+C, and A+B+C as well as to include combinations of any thereof and any other than A, B, and C.