WO2008075841A1

WO2008075841A1 - Device for generating haze on a photomask

Info

Publication number: WO2008075841A1
Application number: PCT/KR2007/006145
Authority: WO
Inventors: Dae-Jin Kim; Gun-Sup Go; Hyun-Jung Kim; Seung-Hwan Eom; Kwang-Jae Lee
Original assignee: Kornic Systems Co. Ltd.
Priority date: 2006-12-18
Filing date: 2007-11-30
Publication date: 2008-06-26
Also published as: KR100793085B1; TWI352260B; TW200832052A

Abstract

Provided is a device for generating haze on a photomask having an improved structure capable of irradiating a laser beam of predetermined energy intensity onto a photomask until haze is generated, accurately obtaining the amount of laser beam energy accumulated on the photomask, and controlling an environment in a process chamber. The haze generating device includes: a laser emission unit for emitting a laser beam; an attenuator for controlling energy intensity of the laser beam; an optical system for processing the laser beam so that the laser beam has a predetermined shape and energy distribution; a process chamber having a window installed at an upper portion thereof and formed of a transparent material, through which the laser beam passes, and a space formed therein to dispose the photomask and fill a process gas, the space being separated from the outside; and an attenuator control unit for controlling the attenuator so that the laser beam of predetermined reference energy intensity is irradiated onto the photomask based on incident energy intensity of a laser beam incident to the window.

Description

DEVICE FOR GENERATING HAZE ON A PHOTOMASK

Technical Field

[1] The present invention relates to a device for generating haze on a photomask, and more particularly, to a device for generating haze on a photomask, in which haze that is a growth defect is artificially generated on a surface of a photomask to find out a cause of haze generation. Background Art

[2] Currently, as semiconductor devices are highly integrated, a light source emitting a laser beam having a wavelength of 200nm or less is used in a photolithography process. For example, an ArF excimer laser emitting a laser beam having a wavelength of 193nm is widely used. However, when a laser beam having a wavelength of 200nm or less is irradiated onto a photomask, haze that is a growth defect is generated on a surface of the photomask. As a result, performance of the photomask is deteriorated and the life span of the photomask is also reduced. Therefore, to meet demand for research into a cause of haze generation and a method of preventing the haze from being generated, a device for artificially generating haze on a photomask is required.

[3] FIG. 1 illustrates a device 100' for generating haze on a photomask according to a conventional art. Referring to FIG. 1, the haze generating device 100' includes a laser emission unit 10' emitting an excimer laser beam having a wavelength of 193nm, an optical system for processing a laser beam so that the laser beam has a predetermined shape and energy distribution, and a process chamber 40' in which a photomask 1 is disposed. The optical system includes a plurality of mirrors 31', 32' and 33', a telescope 34' for processing the shape of a laser beam, a homogenizer 35' for uniformly processing energy of the laser beam, and a focus lens 36' for adjusting the focus and size of the laser beam. Windows 41' and 42', through which the laser beam passes, are installed at upper and lower portions of the process chamber 40'. Beam splitters 501' and 511' and energy meters 502' and 512' for measuring the energy of laser beams reflected from the beam splitters are respectively disposed over and under the process chamber 40'. A charge-coupled device camera 49' for monitoring whether haze is generated on a surface of the photomask or not is disposed over the process chamber 40'. Also, the process chamber 40' is connected to a gas supplier 45' for supplying gas and a moisture supply unit 60' for controlling humidity.

[4] Also, net energy of a laser beam irradiated onto the photomask is determined by the energy of the laser beam, which is measured by the energy meter 502' and trans- mittance of the beam splitter 501', and accumulated energy of the laser beam irradiated onto the photomask until haze is generated is obtained by adding each net energy of the laser beam irradiated until haze is generated.

[5] Meanwhile, examples of variables having an effect on the generation of haze are known to be the amount of the energy of a laser beam accumulated on a photomask until haze is generated, environmental conditions such as temperature and humidity in the process chamber, etc. Therefore, these variables should be controlled by a researcher as desired.

[6] However, in the haze generating device, a researcher cannot irradiate a laser beam of desired energy intensity onto the photomask until haze is generated. That is, when the laser beam reacts with oxygen, the energy of the laser beam is reduced. However, conventionally, the net energy of the laser beam and the accumulated energy of the laser beam until haze is generated are determined without taking into account an energy loss rate of the laser beam, which is caused by oxygen in the process chamber, and thus errors are found in the net energy and accumulated energy of the laser beam.

[7] Further, while a laser beam of predetermined energy intensity should be irradiated onto the photomask 1 until haze is generated, in the conventional device, a laser beam emitted from the laser emission unit 10' is processed by the optical system to be irradiated to the process chamber 40' without any constitution, by which the energy intensity of the laser beam is adjusted. As a result, even when the energy of the laser beam incident to the photomask is changed over time by a change in efficiency of the optical system, no method for preventing the energy of the laser beam from being changed is suggested.

[8] In addition, while the energy loss of the laser beam is caused by environmental factors in the process chamber, e.g., the temperature, humidity and the composition of the gas in the process chamber, the net energy and the accumulated energy of the laser beam are not precisely determined since these environmental factors in the process chamber are not considered in the conventional art. Furthermore, a researcher cannot control the environmental factors in the process chamber 40' as desired until haze is generated.

[9] When a laser beam is irradiated onto the optical system, the windows 41' and 42' and the beam splitters 501' and 511', which are exposed to air, the laser beam reacts with the optical system, the windows and the beam splitters, respectively. As a result, the optical system, the windows and the beam splitters are contaminated, and the energy of the laser beam passing through the contaminated optical system, windows and beam splitters is reduced. Therefore, the net energy and accumulated energy of the laser beam may not be accurately measured, and the energy intensity of the laser beam may not be constantly maintained. Disclosure of Invention Technical Problem

[10] T he present invention is directed to a device for generating haze on a photomask having an improved structure capable of irradiating a laser beam of predetermined energy intensity onto the photomask until haze is generated, accurately measuring an amount of laser beam energy which is accumulated on the photomask, and controlling environmental factors in a process chamber. Technical Solution

[11] One aspect of the present invention provides a device for generating haze on a photomask comprising: a laser emission unit for emitting a laser beam; an attenuator for controlling energy intensity of the laser beam; an optical system for processing the laser beam so that the laser beam has a predetermined shape and energy distribution; a process chamber having a window installed at an upper portion thereof and formed of a transparent material, through which the laser beam passes, and a space formed therein to dispose the photomask and fill a process gas, the space being separated from the outside; and an attenuator control unit for controlling the attenuator so that a laser beam of predetermined reference energy intensity is irradiated onto the photomask based on incident energy intensity of the laser beam incident to the window. Advantageous Effects

[12] According to the present invention, net energy intensity of a laser beam irradiated onto a photomask and accumulated energy of the laser beam irradiated onto the photomask until haze is generated can be accurately measured.

[13] Also, a laser beam of predetermined energy intensity can be continuously irradiated onto the photomask.

[14] Furthermore, humidity in a process chamber can be controlled as desired.

Description of Drawings

[15] FIG. 1 schematically illustrates the configuration of a conventional device for generating haze on a photomask;

[16] FIG. 2 schematically illustrates the configuration of a device for generating haze on a photomask according to an exemplary embodiment of the present invention;

[17] FIG. 3 is a block diagram schematically illustrating a process of controlling an attenuator in the device for generating haze on a photomask illustrated in FIG. 2;

[18] FIG. 4 is a block diagram schematically illustrating an alarm unit for sounding an alarm when haze is generated in the device for generating haze on a photomask illustrated in FIG. 2;

[19] FIG. 5 is a block diagram schematically illustrating a humidity control unit for controlling humidity in a process chamber illustrated in FIG. 2; and

[20] FIG. 6 is a block diagram schematically illustrating a control process of an attenuator control unit according to another exempl ary embodiment of the present invention. Mode for Invention

[21] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[22] FIG. 2 schematically illustrates the configuration of a device for generating haze on a photomask according to an exemplary embodiment of the present invention, FIG. 3 is a block diagram schematically illustrating a process of controlling an attenuator in the device for generating haze on a photomask illustrated in FIG. 2, FIG. 4 is a block diagram schematically illustrating an alarm unit for sounding an alarm when haze is generated in the device for generating haze on a photomask illustrated in FIG. 2, and FIG. 5 is a block diagram schematically illustrating a humidity control unit for controlling humidity in a process chamber illustrated in FIG. 2.

[23] Referring to FIGS. 2 to 5, a device 100 for generating haze on a photomask according to an exemplary embodiment of the present invention includes a laser emission unit 10, an attenuator 20, an optical system 30, a process chamber 40, a monitoring unit 49, energy measuring units 50 and 51, and a moisture supply unit 60.

[24] The laser emission unit 10 generates and emits a laser beam. The laser emission unit

10 generates and emits a laser beam having a wavelength of 200nm or less, e.g., an excimer laser beam having a wavelength of 193nm.

[25] The attenuator 20 attenuates and controls the energy of the laser beam emitted from the laser emission unit 10. The energy intensity of the laser beam is controlled by adjusting an angle of the attenuator 20.

[26] The optical system 30 processes the laser beam, so that the laser beam has a predetermined shape and energy distribution. The optical system 30 includes a first mirror 31, a second mirror 32 and a third mirror 33, each of which reflects the laser beam, a telescope 34 disposed between the first mirror 31 and the second mirror 32 to process the shape of the laser beam, a homogenizer 35 disposed between the second mirror 32 and the third mirror 33 to uniformly process the energy of the laser beam, a field lens 36 disposed between the homogenizer 35 and the third mirror 33, a mask 37 disposed between the field lens 36 and the third mirror 33 to prevent a beam formed by diffraction of a laser beam, and a projection lens 38 for adjusting a focus of the laser beam. In the present exemplary embodiment, a laser beam of which energy intensity is adjusted by the attenuator 20 is incident to the optical system 30 to be processed and emitted toward the process chamber 40.

[27] A space separated from the outside is formed in the process chamber 40. A stage (not shown), on which a photomask 1 is mounted, is installed in the process chamber 40. Windows 41 and 42 are respectively installed at upper and lower portions of the process chamber 40. Each of the windows 41 and 42 is formed of a transparent material through which a laser beam can pass, such as glass. Therefore, a laser beam processed by the optical system 30 passes through the upper window 41 to be irradiated onto the photomask 1. Also, the process chamber 40 is filled with a process gas, e.g., a mixture of NH₃, O₂, N₂, SO₂, etc. A gas sensor 43 for measuring a composition ratio of the process gas in the process chamber and a humidity sensor 44 for measuring humidity in the process chamber are installed in the process chamber 40.

[28] The monitoring unit 49 is installed over the process chamber 40. The monitoring unit

49 monitors whether haze is generated on a surface of the photomask 1. In the present exemplary embodiment, a charge-coupled device camera is used as the monitoring unit 49.

[29] The energy measuring units 50 and 51 are respectively installed over and under the process chamber 40. The energy measuring unit 50 includes a beam splitter 501 and an energy meter 502for measuring the energy of the laser beam reflected from the beam splitter 501, and the energy measuring unit 51 includes a beam splitter 511 and an energy meter 512 for measuring the energy of the laser beam reflected from the beam splitter 511. The energy meter 502 disposed over the process chamber 40 measures the energy of a laser beam incident to the upper window 41, and the energy meter 512 disposed under the process chamber 40 measures the energy of a laser beam emitted from the lower window 42.

[30] The moisture supply unit 60 supplies the moisture to the space in the process chamber 40. The moisture supply unit 60 includes a water tub 61, in which water is stored and a heating element 62 that generates heat when power is applied to heat the water tub 61. The water tub 61 is connected to the process chamber 40 by a moisture supply pipe 63. The water tub 61 is connected to a gas supplier 65 for supplying an inert gas, such as nitrogen, by a gas supply pipe 64. When the inert gas is supplied to the water tub 61 through the gas supply pipe 64, moisture formed by the heat of the heating element 62 is supplied to the space in the process chamber 40 through the moisture supply pipe 63. Further, the amount of the moisture supplied to the process chamber 40 is changed depending on the amount of the inert gas introduced into the water tub 61. That is, the more the inert gas is supplied to the water tub 61, the more the moisture is supplied to the process chamber 40. Meanwhile, a heater 67 that generates heat when power is applied is installed on an outer surface of the moisture supply pipe 63. In addition, the heat of the heater 67 prevents dew from being formed on an inner wall of the moisture supply pipe 63. The moisture supply pipe 63 is connected to an exhaust pipe 66, and a first valve 631 and a second valve 661 are respectively installed on the moisture supply pipe 63 and the exhaust pipe 66. A flow controller 641 for controlling a flow of the inert gas and a third valve 642 are installed on the gas supply pipe 64. In the present exemplary embodiment, a mass flow controller is used as the flow controller 641.

[31] The process chamber 40 is connected to a gas supplier 45 for supplying a process gas to the interior of the process chamber. One side of the process chamber 40 is connected to a gas supply pipe 46 connected to the gas supplier 45, and the other side of the process chamber 40 is connected to a gas exhaust pipe 47 for exhausting the gas in the process chamber. A fourth valve 461 is installed on the gas supply pipe 46, and an auto pressure controller 48 for controlling the volume of exhaust gas to constantly maintain pressure in the process chamber 40 is installed on the gas exhaust pipe 47.

[32] The attenuator 20, the optical system 30, and the upper beam splitter 501 are arranged in a case 39, on which an inflow port 391 and an outflow port 392 are formed. When the inert gas, e.g., nitrogen gas, is introduced through the inflow port 391 to be exhausted through the outflow port 392, the attenuator 20, the optical system 30, and the upper beam splitter 501 are exposed to an inert gas atmosphere, respectively, so that the attenuator 20, the optical system 30, and the upper beam splitter 501 are prevented from contamination caused by a laser beam. Therefore, the energy of the laser beam is not reduced, which was impossible to anticipate in the conventional art. Also, since the lower beam splitter 511 is arranged in a separate case 513 on which an inflow port 514 and an outflow port 515 are formed and the inert gas is introduced through the inflow port 514 to be exhausted through the outflow port 515, the lower beam splitter 511 may be prevented from contamination caused by the laser beam. Gas emitters 11, which respectively emit the inert gas toward the windows 41 and 42, are installed adjacent to the upper and lower windows 41 and 42 so that the windows 41 and 42 can be prevented from contamination caused by the laser beam when the laser beam is irradiated.

[33] Furthermore, the haze generating device 100 according to an exemplary embodiment of the present invention further includes a storage unit 71, a calculation unit 72, an attenuator control unit 73 and an alarm unit 80.

[34] The storage unit 71 stores an energy loss rate of a laser beam corresponding to each composition ratio of the process gas. Here, the energy loss rate of the laser beam refers to a numerical value indicating the degree of decrease in the energy of the laser beam when the laser beam reacts with the process gas, and as a result, the energy of the laser beam is reduced. While the energy loss of the laser beam is largely caused by oxygen, gases other than oxygen may cause the loss as well. Accordingly, the energy loss rate of the laser beam is changed by the composition ratio of the process gas. The energy loss rate of the laser beam may be empirically obtained through experiment.

[35] The calculation unit 72 receives incident energy intensity of the laser beam, which is measured by the energy meter 502 and the energy loss rate of the laser beam, which is read from the storage unit 71 to calculate net energy intensity of the laser beam ir- radiated onto the photomask 1. Here, the read energy loss rate of the laser beam refers to an energy loss rate of the laser beam corresponding to the composition ratio of the process gas in the process chamber, which is measured by a gas sensor 43 and in particular, the calculation unit 72 reads the energy loss rate of the laser beam in the present exemplary embodiment. Further, the calculation unit 72 calculates the net energy intensity of the laser beam by Equation 1.

[36] [ Equation 1 ]

[37] [Math.l]

[38] wherein E_p denotes net energy intensity of a laser beam irradiated onto the photomask 1, E₁ denotes incident energy intensity of the laser beam, which is measured by the energy meter 502, T₁ denotes transmittance of the beam splitter 501, T₂ denotes transmittance of the upper window 41, and α denotes calculated energy loss rate of the laser beam.

[39] As described above, the calculation unit 72 calculates the net energy of the laser beam by taking into account a decrease in the energy of the laser beam, which is caused by the process gas in the process chamber 40, and thus more precise net energy of the laser beam than that in the conventional art may be obtained.

[40] The attenuator control unit 73 controls the attenuator 20 based on the incident energy intensity of the laser beam, which is measured by the energy meter 502. In the present exemplary embodiment, the attenuator control unit 73 controls the attenuator 20 based on the calculated net energy intensity of the laser beam. That is, the attenuator control unit 73 compares the net energy intensity of the laser beam with predetermined reference energy intensity, and adjusts an angle of the attenuator 20, so that the net energy intensity of the laser beam becomes the same as the reference energy intensity. Therefore, a laser beam having the reference energy intensity is irradiated onto the photomask 1 until haze is generated. Also, accumulated energy of the laser beam irradiated onto the photomask 1 until haze is generated can be accurately measured.

[41] The alarm unit 80 sounds an alarm at a point in time when haze is generated based on the emission energy intensity of the laser beam, which is measured by the energy meter 512. The alarm unit 80 includes a memory 81, a determinator 82, and an alarm 83.

[42] In the memory 81, a reference value corresponding to each of process conditions is stored. Here, the process conditions are determined by the composition ratio of the process gas and humidity in the process chamber 40, and the net energy intensity of the laser beam irradiated onto the photomask 1, and the reference value refers to the emission energy intensity of the laser beam when haze is generated on a surface of the photomask 1 under each of various process conditions. The process conditions and reference value are obtained by experiment, and the reference value may vary depending on the process conditions.

[43] The determinator 82 receives the composition ratio of the process gas and the humidity in the process chamber 40 and the net energy intensity of the laser beam, reads a reference value corresponding to the process condition of the process chamber from the memory 81, and determines a time when the emission energy of the laser beam becomes the same as the read reference value as a time when haze is generated. That is, when haze is generated on a surface of the photomask 1, the emission energy intensity of the laser beam that passes through the photomask 1 and is emitted from the lower window 42 is changed to become the same as the reference value.

[44] The alarm 83 alerts a researcher when haze is generated. In the present exemplary embodiment, a speaker is used as the alarm 83. The determinator 82 outputs an alarm signal to the speaker when haze is generated, so that the speaker makes a sound.

[45] The haze generating device 100 according to the present exemplary embodiment further includes a humidity control unit 90.

[46] The humidity control unit 90 maintains humidity in the process chamber based on the humidity in the process chamber 40 at predetermined reference humidity. The humidity control unit 90 includes a valve control unit 91 for controlling the first valve 631, the second valve 661 and the third valve 642, and a flow controller control unit 92 for controlling the flow controller 641.

[47] When the humidity measured by the humidity sensor 44 is equal to or less than the predetermined reference humidity, the valve control unit 91 controls the first and second valves 631 and 661 to be open and closed respectively, so that moisture is supplied to the space in the process chamber 40. Alternatively, when the humidity measured by the humidity sensor 44 exceeds the predetermined reference humidity , the valve control unit 91 controls the first and second valves 631 and 661 to be closed and open respectively, so that moisture in the water tub 61 is exhausted through the exhaust pipe 66 to prevent moisture from being supplied to the space in the process chamber 40. In addition, when the haze generating device 100 is operated, the valve control unit 91 controls the third valve 642 to be always open, so that the inert gas is supplied to the water tub 61 of a moisture supply unit.

[48] Before the haze generating device 100 is operated, the third valve 642may be open while the first and second valves 631 and 661 are closed and open respectively, so that the inert gas is exhausted through the exhaust pipe 66 to thereby remove dew formed on an inner wall of the water tub 61 of the moisture supply unit and on internal walls of the moisture supply pipe 63 and the exhaust pipe 66 . Thus, a fixed amount of moisture is supplied to the process chamber 40 to maintain desired humidity.

[49] The moisture supplied to the process chamber 40 may be increased or decreased by the flow controller control unit 92. The flow controller control unit 92 controls the flow controller 641 based on the humidity measured by the humidity sensor 44 to increase or decrease the amount of moisture supplied to the process chamber 40. Accordingly, it enables the humidity in the process chamber 40 to be the same as the reference humidity in a short period.

[50] As described above, in the present exemplary embodiment, the energy loss of a laser beam, which is caused by the process gas, is considered to calculate the net energy of the laser beam. As a result, the net energy of a laser beam irradiated onto the photomask and the accumulated energy of a laser beam irradiated onto the photomask until haze is generated can be accurately obtained, which was impossible to anticipate in the conventional art.

[51] Further, unlike the conventional art, since an angle of the attenuator is adjusted, a laser beam of reference energy intensity may be continuously irradiated onto the photomask until haze is generated.

[52] In addition, since humidity in the process chamber may be controlled by a researcher as desired, the energy loss of a laser beam, which may be caused by a change in humidity, can be minimized. Also, the heater installed on an outer side of the moisture supply pipe prevents dew formed on an inner wall of the moisture supply pipe from being introduced into the process chamber to accurately control humidity in the space of the process chamber.

[53] Furthermore, since the optical system, the windows, the attenuator, and the beam splitters are exposed to an inert gas atmosphere, the optical system, the windows and the beam splitters are prevented from contamination caused by a laser beam to minimize energy dissipation of the laser beam.

[54] Meanwhile, in the present exemplary embodiment, while the attenuator control unit and the humidity control unit are separate components, they may be integrally formed.

[55] Also, in the present exemplary embodiment, while the energy loss of the laser beam caused by the process gas in the process chamber is considered to determine the net energy intensity of the laser beam irradiated onto the photomask, and the attenuator is controlled so that the determined net energy intensity becomes the same as the reference energy intensity, other factors having an effect on the energy loss of the laser beam as well as the process gas in the process chamber may be considered so that the net energy intensity is determined by an calculation unit 72a as illustrated in FIG. 6.

[56] Generally, the energy loss of a laser beam is caused by various factors including environmental conditions besides a process gas, such as temperature and humidity in a process chamber, and a change in property of an optical system caused by use over a long time. Therefore, when only the energy loss of a laser caused by the process gas is taken into account, the net energy of a laser beam irradiated onto the photomask cannot be accurately measured. Thus, in the present exemplary embodiment, a correcting unit 75 is further included so that emission energy of a laser beam, which is measured by an energy meter 512 is used to correct the energy loss caused by environmental conditions in a process chamber 40 besides the process gas, e.g., temperature and humidity in the process chamber to thereby control an attenuator 20.

[57] The correcting unit 75 corrects the energy loss caused by the environmental conditions in the process chamber besides a composition ratio of the process gas. The correcting unit 75 outputs a correction signal to a calculation unit 72a when the emission energy intensity of the laser beam, which is measured by the energy meter 512, is equal to or less than a predetermined standard value. The calculation unit 72a that receives the correction signal corrects an energy loss rate of the laser beam, which is read from a storage unit 71. For example, based on a difference between the emission energy and the standard value, a proportional constant corresponding to each difference is set, and the proportional constant is multiplied by the read energy loss rate of the laser beam to correct the read energy loss rate of the laser beam. Here, the standard value is set based on a difference between the incident energy of the laser beam and the reduced amount of laser beam energy, which is caused by the process gas in the process chamber, and is generally set within a range less than the difference.

[58] As described above, when the measured emission energy intensity of the laser beam is equal to or less than the standard value, the correction signal is input into the calculation unit 72a, and the calculation unit 72a compensates for the read energy loss rate of the laser beam to calculate the net energy intensity of the laser beam irradiated onto the photomask 1 based on the compensated energy loss rate and the incident energy intensity of the laser beam. Meanwhile, when the measured emission energy intensity of the laser beam exceeds the standard value, the correction signal is not output, and the calculation unit 72a calculates the net energy intensity of the laser beam irradiated onto the photomask 1 based on the read energy loss rate of the laser beam and the incident energy intensity of the laser beam. Further, in the process of calculation by the calculation unit 72a, Equation 1 is applied. In Equation 1, α denotes the corrected energy loss rate of the laser beam when the emission energy intensity is equal to or less than the standard value, and denotes the read energy loss rate of the laser beam when the emission energy intensity exceeds the standard value.

[59] The calculated net energy intensity of the laser beam is input into the attenuator control unit 73a, and the attenuator control unit 73a controls the attenuator 20 so that the calculated net energy intensity of the laser beam becomes the same as the reference energy intensity. [60] As described above, in the present exemplary embodiment, a decrease in energy of a laser beam caused by environmental conditions in the process chamber, e.g., temperature and humidity in the process chamber as well as a decrease in energy of a laser beam, which is caused by the process gas in the process chamber, are taken into account to calculate the net energy of the laser beam, and the attenuator is controlled so that the calculated net energy is irradiated onto the photomask. Therefore, the net energy of the laser beam irradiated onto the photomask and the accumulated energy of the laser beam irradiated onto the photomask until haze is generated are more accurately obtained compared to the conventional art.

[61] While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims .

Claims

[1] A device for generating haze on a photomask, comprising: a laser emission unit for emitting a laser beam; an attenuator for controlling energy intensity of the laser beam; an optical system for processing the laser beam so that the laser beam has a predetermined shape and energy distribution; a process chamber having a window installed at an upper portion thereof and formed of a transparent material , through which the laser beam passes, and a space formed therein to dispose the photomask and fill a process gas, the space being separated from the outside; and an attenuator control unit for controlling the attenuator so that a laser beam of predetermined reference energy intensity is irradiated onto the photomask based on incident energy intensity of the laser beam incident to the window.

[2] The device of Claim 1, further comprising: a storage unit for storing an energy loss rate of the laser beam corresponding to each composition ratio of the process gas; and a calculation unit for calculating net energy intensity of the laser beam irradiated onto the photomask based on the incident energy intensity of the laser beam and the energy loss rate of the laser beam corresponding to the composition ratio of the process gas in the process chamber, which is read from the storage unit, wherein the attenuator control unit controls the attenuator so that the calculated net energy intensity of the laser beam becomes the same as the reference energy intensity.

[3] The device of Claim 2, further comprising: an energy measuring unit disposed over the process chamber to measure the incident energy intensity of the laser beam incident to the window of the process chamber, and including a beam splitter and an energy meter for measuring energy intensity of the laser beam reflected from the beam splitter, wherein the calculation unit calculates the net energy intensity of the laser beam by Equation 1 :

[Math.2]

wherein E_p denotes net energy intensity of the laser beam irradiated onto the photomask, Ei denotes incident energy intensity of the laser beam, which is measured by the energy meter, T₁ denotes transmittance of the beam splitter of the energy measuring unit, T₂ denotes transmittance of the window, and α denotes the read energy loss rate of the laser beam.

[4] The device of Claim 1, wherein a window formed of a transparent material, through which the laser beam passes, is installed at a lower portion of the process chamber; and the haze generating device further comprising an alarm unit for comparing emission energy intensity of the laser beam emitted from the lower window with a predetermined reference value to determine a time when the emission energy intensity becomes the same as the reference value as a haze generation time, and to sound an alarm.

[5] The device of Claim 4, wherein the alarm unit comprises: a memory for storing reference values corresponding to each process condition; a determinator for reading a reference value corresponding to a process condition formed by a composition ratio of the process gas and humidity in the process chamber and net energy intensity of the laser beam irradiated onto the photomask from the memory, and determining a time when the emission energy of the laser beam becomes the same as the read reference value as a haze generation time to output an alarm signal; and an alarm for receiving the alarm signal to sound an alarm when the haze is generated.

[6] The device of Claim 1, wherein a window formed of a transparent material, through which the laser beam passes, is installed at a lower portion of the process chamber; and the attenuator control unit controls the attenuator based on the incident energy intensity and emission energy intensity when the emission energy intensity of the laser beam emitted from the lower window is equal to or less than a predetermined standard value, and controls the attenuator based on the incident energy intensity when the emission energy intensity of the laser beam exceeds the standard value.

[7] The device of Claim 6, further comprising: a storage unit for storing an energy loss rate of the laser beam corresponding to each composition ratio of the process gas; and a calculation unit for calculating net energy intensity of the laser beam irradiated onto the photomask based on the incident energy intensity of the laser beam and the energy loss rate of the laser beam corresponding to the composition ratio of the process gas in the process chamber, which is read from the storage unit, when the emission energy intensity exceeds the standard value, and correcting the read energy loss rate of the laser beam to calculate net energy intensity of the laser beam irradiated onto the photomask based on the corrected energy loss rate and the incident energy intensity of the laser beam when the emission energy intensity is equal to or less than the standard value, wherein the attenuator control unit controls the attenuator so that the calculated net energy intensity of the laser beam becomes the same as the reference energy intensity.

[8] The device of Claim 1, further comprising: a moisture supply unit for supplying the space of the process chamber with moisture; a moisture supply pipe for connecting the process chamber to the moisture supply unit; and a heater for heating the moisture supply pipe.

[9] The device of Claim 8, wherein the moisture supply unit is connected to a gas pipe, to which an inert gas is supplied, the moisture supply pipe is communicated with an exhaust pipe, and the moisture generated by the moisture supply unit is introduced into the space of the process chamber by the inert gas.

[10] The device of Claim 9, wherein a flow controller for controlling a flow of the inert gas is installed on the gas pipe, and a first valve and a second valve are installed on the moisture supply pipe and the exhaust pipe, respectively.

[11] The device of Claim 10, further comprising a humidity control unit for controlling the flow controller, the first valve and the second valve so that humidity in the process chamber is maintained at predetermined reference humidity based on the humidity in the process chamber.

[12] The device of Claim 11, wherein the humidity control unit comprises: a valve control unit for controlling the first and second valves to be respectively open and closed when the humidity in the process chamber exceeds the predetermined reference humidity, and to be respectively closed and open when the humidity in the process chamber is lower than the predetermined reference humidity; and a flow controller control unit for controlling the flow controller to increase or decrease the amount of moisture exhausted from the moisture supply unit.

[13] The device of any one of Claims 1 to 12, wherein the attenuator, the optical system, and the window are exposed to an inert gas atmosphere, respectively.