JP2016180976A - Photomask inspection apparatus and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask inspection apparatus and inspection method for inspecting the presence or absence of contamination or particles on a photomask before the photomask is introduced into a vacuum chamber.SOLUTION: A photomask inspection apparatus according to the present invention comprises: a main chamber for projecting light onto a photomask to perform patterning on a wafer, the main chamber keeping a high vacuum state; a subchamber which is provided in a front stage of the main chamber and receives a photomask to be introduced into the main chamber, the subchamber keeping a vacuum state lower than that of the main chamber; and an inspection unit which is provided in the front stage of the main chamber and inspects whether or not particles are present on the photomask, and which if particles are present on the photomask, determines whether or not the presence is equal to or greater than an allowable reference value. The photomask inspection apparatus is characterized in that existence of particles on a photomask is detected, and if particles are determined to be present, the photomask is unloaded for cleaning to prevent errors caused by the photomask.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photomask inspection apparatus and inspection method, and more specifically, before being drawn into a photomask process chamber, the presence or absence of contamination of the photomask in the sub-chamber or the presence or absence of particles, and the particles drawn into the process chamber (so-called Photomask inspection system that monitors the size and number of “dust” such as particles, and removes any foreign matter found as a result of monitoring, thereby preventing the occurrence of serious defects And an inspection method.

  During photomask manufacturing, the number and size of the remaining particles are constantly monitored while the particles are removed at a high level. During each process in a semiconductor manufacturing processing line, contamination of the photomask may cause a serious error. In particular, when foreign matter exists on the pattern surface of the photomask, there is a problem that a serious defect occurs and a high cost loss occurs.

  In general, a process of transferring a pattern formed on a photomask onto a wafer in a process of manufacturing a semiconductor element is called a lithography process. By repeating the lithography process several to several tens of times, a semiconductor element including a transistor, a capacitor, and a resistor is manufactured.

  In order to perform the lithography process, a reticle or a photomask having a semi-transparent or opaque exposure pattern is manufactured using a metal material such as chromium (Cr) or a silicon compound (MoSi). After the reticle is prepared, a photoresist film containing a photosensitive material is formed on the wafer on which the thin film is formed, and the photoresist film is irradiated with light using the reticle, so that the exposure pattern of the reticle is formed on the photoresist film. A photoresist pattern is formed on the wafer by transferring and developing the photoresist film with a developer. Thereafter, impurities are implanted into the photoresist pattern by ion implantation or the like, or the thin film on the wafer is etched and patterned using the photoresist pattern.

  The photomask is formed as a molybdenum (Mo), chromium (Cr) EBR (Electric Beam Resist) layer on the surface of a highly transparent square quartz (Qz) at the time of manufacture, and a pattern is drawn on the surface of the EBR using an electron beam. . By development, the pattern is developed using a developing solution for the exposed portion and the non-exposed portion.

  If the surface of the photomask is contaminated with foreign matter or the like, the beam (Beam) is not irradiated on the portion contaminated with foreign matter or the like. Short circuit or deformation may occur.

  In addition, with the advancement of semiconductor chips, there is also a problem that it takes a very long time for pattern exposure.

  At this time, if a foreign substance or a contamination source is present in a blank mask (clean mask before pattern exposure), a large loss is caused. Severe damages such as loss of raw material prices, exposure time, and development opportunities occur.

  On the other hand, the reticle loaded / unloaded from the reticle loading / unloading equipment to the stepper is contaminated with particles and the like as it is repeatedly used. Therefore, in order to remove particles attached to the reticle, the reticle loaded on the reticle loading / unloading equipment is periodically cleaned. At this time, the reticle is generally cleaned with nitrogen gas injected at a high speed.

Therefore, the present invention is for solving the above-described problems of the prior art, and detects whether or not a photomask particle is present, and if it is determined that a particle is present, the photomask can be unloaded. An object of the present invention is to provide a mask inspection apparatus and an inspection method. (Currently: Photomask box → Load / unload section → Mask movement → Fixing to process chamber → Process progress)
(Solution: Photomask box → Load / unload section → Mask movement → Process chamber entrance inspection device → Fixation to process chamber → Process progress)

It is another object of the present invention to provide a photomask inspection apparatus and inspection method in a sub-chamber before the photomask is drawn into the main chamber in the case of a process performed in a vacuum chamber.
(Currently: Photomask box → Load / unload section → Mask movement → Sub-chamber pulling → Main chamber movement → Main chamber fixing → Process progress)
(Solution: Photomask box → Load / unload section → Mask movement → Pulling into sub-chamber → Particle inspection using inspection device configured at top of sub-chamber → Transfer to main chamber → Fixing to main chamber → Process progress)

  In addition, the present invention detects the size of the particles, counts the number of particles, and if the count result is equal to or greater than a reference value, informs the operator of this and enables the operator to take appropriate measures. An object is to provide a photomask inspection apparatus and an inspection method.

  The photomask inspection apparatus of the present invention for achieving the above object is provided with a main chamber that is irradiated with light on a photomask to perform patterning on a wafer and maintained in a high vacuum state, and in front of the main chamber, A sub-chamber for accommodating the photomask to be drawn in and maintaining a vacuum state lower than the vacuum state of the main chamber; provided in a front stage of the main chamber; whether or not particles are present on the photomask; and And an inspection unit that inspects whether or not the particle is greater than or equal to an allowable reference value when particles are present.

  The inspection unit may be fixed to an upper part in the sub chamber.

  The inspection unit may be fixed to an upper portion of a transfer unit provided in a front stage of the sub chamber.

  The cleaning unit further includes a cleaning unit provided in an upper part of the transfer unit provided in the front stage of the sub-chamber, and the transfer unit cleans the photomask when the inspection result of the inspection unit indicates that the particles are greater than or equal to an allowable reference value. The cleaning unit can remove the gas by injecting gas into the photomask or sucking particles.

  It further includes a cleaning unit provided between the inspection unit and the sub-chamber and provided above the transfer unit. The inspection unit determines whether or not the particle is an allowable reference value or more, and the particle When the particle size is greater than or equal to the allowable reference value, the sample is transferred to the cleaning unit for cleaning, and when the particle is less than the allowable reference value, the cleaning unit is allowed to pass through.

  The inspection unit may be configured to determine the presence / absence of particles using at least one of a bright field inspection reaction and a dark field inspection reaction.

  In order to achieve the above object, a photomask inspection apparatus according to the present invention includes a gas pipe that extends from the main chamber and forms a passage for a gas stream flowing out from the main chamber; the gas pipe and the main chamber A sensor for measuring the velocity of the gas stream, a laser emission unit installed on one side of the gas pipe, generating a plane beam and entering the gas pipe, and the gas A laser receiving unit installed on the other side of the tube and receiving a plane beam emitted from the gas tube, and receiving information on the plane beam scattered by particles contained in the gas stream from the laser receiving unit, The velocity of the gas stream from the sensor is received and a plane beam is passed through the gas pipe per unit time. A control unit that calculates the number of particles and the particle size of the particles, and calculates a particle change amount; and when the calculation result of the control unit and the particle change amount per unit time are equal to or greater than a predetermined reference value And an alarm unit for generating an alarm.

The control unit can calculate the volume of particles contained in the gas stream flowing out of the main chamber by the following formula:
V = N × d ³
In the formula, V represents the volume of the particles, N represents the number of particles, and d represents the average particle diameter of the particles.

The control unit can calculate the amount of particle change per unit time t by the following equation:
m = V / vt
In the equation, m represents the amount of particle change, v represents the speed of the gas stream, t represents the unit time when the gas stream is injected through the injector, or the unit time when the pump is operated.

In order to achieve the above object, a photomask inspection method according to the present invention calculates a volume V of particles contained in a gas stream flowing out from a main chamber,
When the particle change amount is greater than or equal to the reference value as a result of comparison in the process of calculating the particle change amount m per unit time t, the process of comparing the predetermined reference value with the particle change amount, and the comparison process. Includes a step of determining that the main chamber is contaminated and generating an alarm.

The volume of the particles in the process of calculating the volume can be calculated using the following formula:
V = N × d ³
In the formula, V represents the volume of the particles, N represents the number of particles, and d represents the average particle diameter of the particles.

The particle change amount in the process of calculating the particle change amount m can be calculated using the following equation:
m = V / vt
In the equation, m represents the amount of particle change, v represents the speed of the gas stream, t represents the unit time when the gas stream is injected through the injector, or the unit time when the pump is operated.

  The photomask inspection apparatus and inspection method of the present invention having the above-described configuration detects whether or not a photomask particle is present, and when it is determined that a particle is present, the photomask can be unloaded, This has the effect of preventing errors caused by foreign matters such as particles on the mask.

  Also, the photomask inspection apparatus and inspection method of the present invention detects the presence or absence of particles in the photomask, and when it is determined that particles are present, removes the photomask particles and loads them again into the sub chamber and the main chamber. There is an effect of providing a photomask inspection apparatus and an inspection method that can be used.

  Further, the photomask inspection apparatus and inspection method of the present invention have an effect that the size of particles can be detected and the number of particles can be counted.

  In addition, the photomask inspection apparatus and inspection method of the present invention detects the size of particles, counts the number of particles, and if it is determined that the reference contamination value has been exceeded as a result of the count, informs the operator of this, There is an effect that the operator can take appropriate measures.

It is a block diagram which shows schematically the structure of the photomask inspection apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the photomask inspection apparatus which concerns on other embodiment of this invention. It is a block diagram which shows schematically the structure of the photomask inspection apparatus which concerns on other embodiment of this invention. It is a block diagram which shows schematically the structure of the particle counter of FIG. 3 which concerns on other embodiment of this invention. 5 is a flowchart illustrating a process of inspecting a photomask according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

  FIG. 1 is a block diagram schematically showing the configuration of a photomask inspection apparatus according to an embodiment of the present invention.

  Referring to FIG. 1, the photomask inspection apparatus and inspection method of the present invention includes a main chamber 110, a subchamber 120, a photomask stage 130, a wafer stage 140, a high vacuum pump 150, a low vacuum pump 160, and a first inspection unit 121. Consists of

  The high vacuum pump 150 of the two pumps 150 and 160 is connected to the main chamber 110 in order to make the inside vacuum. A switch (not shown) may also be provided between the high vacuum pump 150 and the main chamber 110. A second opening / closing means 126 is provided between the main chamber 110 and the sub chamber 120, and is opened when the photomask 132 is drawn from the subchamber 120 to the main chamber 110. When the pull-in is completed, the second opening / closing means 126 is closed. After the second opening / closing means 126 is closed, the high vacuum pump 150 is further activated to increase the vacuum state of the main chamber 110. When the photomask 132 is thus fixed to the photomask stage 130, a pattern can be formed on the wafer 142 by irradiating the photomast 132 with light. At this time, the wafer 142 is fixed to the wafer stage 140.

  The sub-chamber 120 is provided in front of the main chamber 110 in a high vacuum state, and receives and accommodates the transfer of the photomask 132 through the transfer unit 122 and the first opening / closing means 124 in a low vacuum state. The sub-chamber 120 can accommodate the photomask 132 in a low vacuum state before accommodating the photomask 132 in the main chamber 110. That is, the photomask 132 drawn into the main chamber 110 that is in a high vacuum state is prevented from being generated due to shaking due to strong suction due to the high vacuum pressure. That is, the photomask 132 transferred by the transfer unit 122 is drawn into the sub-chamber 120 when the first opening / closing means 124 is opened, and is further reduced to a vacuum state when the first opening / closing means 124 is closed again. Therefore, the low vacuum pump 160 is activated to bring the inside of the sub chamber 120 into a desired low vacuum state. When the sub-chamber 120 is in a low vacuum state, whether or not particles exist in the photomask 130 by the first inspection unit 121 configured to be attached to the upper portion of the sub-chamber 120, or an acceptance criterion when particles exist. Check if it is greater than or equal to the value. As a result of the inspection by the first inspection unit 121, if the particles are detected within the allowable reference value or if no particles are detected, the second opening / closing means 126 is opened and the photomask 132 is drawn into the main chamber 110. The second opening / closing means 126 can be closed by being fixed to the photomask stage 130. After closing, as described above, the high vacuum pump 150 can be operated to maintain the inside of the main chamber 110 in a high vacuum state.

  The high vacuum pump 150 is connected to the main chamber 110 via the first gas pipe 152 in order to maintain the inside of the main chamber 110 in a high vacuum state. The high vacuum pump 150 sucks the atmosphere in the main chamber 110 through the first gas pipe 152 and maintains the high vacuum state in order to maintain the set high vacuum state.

  The sub-chamber 120 is connected to the low vacuum pump 160 of the two pumps 150 and 160 at the end thereof in order to make the inside of the sub-chamber 120 into a vacuum state. Therefore, the second gas pipe 162 communicating with the sub chamber 120 extends, and the low vacuum pump 160 is connected to the end of the extended second gas pipe 162. A switch (not shown) may also be provided between the low vacuum pump 160 and the sub chamber 120.

  The low vacuum pump 160 is connected to the sub-chamber 120 via the second gas pipe 162 in order to maintain the inside of the sub-chamber 120 at a pressure state lower than the high vacuum state. The low vacuum pump 160 sucks the atmosphere in the sub-chamber 120 through the second gas pipe 162 and maintains the low vacuum state in order to maintain the set low vacuum state.

  The first inspection unit 121 is configured to be attached to the upper portion of the sub chamber 120. The first inspection unit 121 uses an optical microscope camera to acquire an image of the photomask 132 or a pod that houses the photomask using the optical microscope camera, and detects whether or not particles are detected from the acquired image. Check if the particle is above the acceptable reference value. The first inspection unit 121 can employ a bright field inspection reaction or a dark field inspection reaction. At this time, the bright field inspection reaction may be performed by imaging the photomask 132 with a bright field camera. Here, in the case of transparent particles, the image may not be captured by the bright field camera. Thus, a dark field inspection reaction can be employed. The dark field inspection reaction may be to image the photomask 132 with a dark field camera. Bright field inspection reactions and dark field inspection reactions can also be employed together. That is, the particles can be detected by adding the number of particles acquired by the dark field camera to the number of particles acquired by the bright field camera. Alternatively, particles can be detected using a bright field camera or a dark field camera individually.

  When particles are detected from the photomask 132 inspected by the first inspection unit 121 or when the particles are detected exceeding the allowable reference value, the first opening / closing means 124 is opened and the photomask 132 is transferred. To the section 122. The transported photomask 132 is cleaned using the cleaning unit 125 disposed at the upper end of the transfer unit 122. The cleaning unit 125 is configured to remove particles by injecting an inert gas at high speed or sucking air. After the cleaning by the cleaning unit 125 is completed, the first opening / closing means 124 is opened, and the photomask 132 is transferred to the sub-chamber 120 via the transfer unit 122. The first inspection unit 121 re-inspects the photomask 132, and when particles are detected or the particles exceed the allowable reference value, the cleaning process by the cleaning unit 125 described above is performed again and no particles are detected. Alternatively, when the particles are detected within the allowable reference value, the second opening / closing means 126 is opened and the photomask 132 is transferred to the main chamber 110. The photomask 132 transferred in the main chamber 110 can be fixed to the photomask stage 130 and the second opening / closing means 126 can be closed. After the photomask 132 is mounted on the main chamber 110, as described above, the high vacuum pump 150 can be further operated to maintain the inside of the main chamber 110 in a high vacuum state.

  FIG. 2 is a configuration diagram showing a configuration of a photomask inspection apparatus according to another embodiment of the present invention.

  Referring to FIG. 2, whether or not particles are detected from the photomask 132 disposed at the top of the transfer unit 122 and temporarily stopped at the bottom of the second check unit 123 during the transfer. Check. As a result of the confirmation, if the particles are detected or if the particles exceed the allowable reference value, the photomask 132 is transferred to the cleaning unit 125 installed at the subsequent stage of the second inspection unit 123, and gas, particularly nitrogen The first opening / closing means 124 is opened and the photomask 132 is transferred to the sub-chamber 120 through a cleaning process by spraying or a cleaning process for sucking air around the photomask 132. After that, the process of transferring the photomask 132 disposed in the sub-chamber 120 to the main chamber 110 is the same as that described with reference to FIG.

  In FIG. 2, the cleaning unit 125 and the second inspection unit 123 are fixed to the upper part of the transfer unit 122, and the cleaning unit 125 is located at the subsequent stage of the second inspection unit 123, that is, between the second inspection unit 123 and the sub-chamber 120. Connected between. However, the cleaning unit 125 may be configured upstream of the second inspection unit 123 in order to increase reliability. That is, the cleaning unit 125 and the second inspection unit 123 are fixed to the upper portion of the transfer unit 122, but the second inspection unit 123 is disposed between the cleaning unit 125 and the sub-chamber 120, and the second inspection unit 123 is arranged. When particles are detected via the photomask or when the particles exceed the allowable reference value, the photomask 132 can be transported to the cleaning unit 125 again to repeatedly clean the photomask 132.

  FIG. 3 is a block diagram schematically showing the configuration of a photomask inspection apparatus according to another embodiment of the present invention. Referring to FIG. 3, the particle monitoring apparatus of the present invention mainly includes a main chamber 110, a particle counter 170, a low vacuum pump 160 and a high vacuum pump 150. Furthermore, each switch 112,155,163 which interrupts the channel | path between each pump 150,160 and the main chamber 110 is included. On the other hand, although the sub chamber 120 is not shown, the sub chamber 120 may be provided in front of the main chamber 110.

  As described above, the two pumps 150 and 160 are used to bring the inside of the main chamber 110 into a vacuum state. For this reason, the gas pipe 154 communicated with the main chamber 110 extends, and the extended gas pipe 154 is branched into two gas pipes 152 and 162, respectively. In particular, a low vacuum pump 160 for making the inside of the main chamber 110 into a low vacuum state is connected to one side of the second gas pipe 162, and the inside of the main chamber 110 is connected to one side of the first gas pipe 152. A vacuum pump 150 for connecting to a vacuum state is connected.

  The third switch 155 that operates to open and close the gas pipe 154 and the high vacuum pump 150 is closed, and the second switch 163 that operates to open and close the second gas pipe 162 branched to one side and the low vacuum pump 160. Is released. The low vacuum pump 160 is operated with the second switch 163 opened. At this time, a gas stream is generated by the low vacuum pump 160, and the sensor 114 detects the velocity v of the gas stream sucked through the gas pipe 154.

  By operating the low vacuum pump 160, the inside of the main chamber 110 is brought into a low vacuum state. When the inside of the main chamber 110 is in a low vacuum state, the second switch 163 is closed, and the third switch 155 and the first switch 112 that opens and closes between the high vacuum pump 150 and the low vacuum pump 160 are opened. To do. The high vacuum pump 150 is operated with the first switch 112 and the third switch 155 opened. At this time, a gas stream is generated by the high vacuum pump 150, and the sensor 114 detects the velocity v of the gas stream sucked through the gas pipe 124.

  When the inside of the main chamber 110 is set to a low vacuum state without operating the low vacuum pump 160 and the high vacuum pump 150 together, the high vacuum state is set to a high vacuum state without passing through the low vacuum state. This is because there is a risk that the equipment, particularly the pumps 150 and 160, may be overwhelmed and a failure may occur. For example, when the high vacuum pump 150 is operated without first operating the low vacuum pump 160 in the atmospheric pressure state, damage such as bending of the rotary blades constituting the vacuum pump 150 may occur.

  FIG. 4 is a block diagram schematically showing the configuration of the particle counter of FIG. 3 according to another embodiment of the present invention. Referring to FIG. 4, the laser receiving unit 230 receives information that the plane beam 220 emitted from the laser emitting unit 210 scatters while passing through the particles included in the gas stream and receives the number of particles. And can recognize the size. The width of the planar beam 220 is the same size as the diameter of the gas tube 154. If the width of the planar beam 220 is larger, an error may occur. Therefore, the planar beam 220 having a width corresponding to the diameter of the gas tube 154 is generated.

  The controller 240 may calculate the number of particles that have passed through the plane beam while flowing through the gas pipe per unit time and the particle size of the particles. At this time, the laser emitting unit 210 operates based on the Mie scattering theory. When the plane beam 220 touches the particle particle, the particle scattering spectrum is formed on the focal plane of a Fourier lens that is not affected by the particle motion, and the particle size is determined by analyzing the scattering spectrum. be able to. Considering that there are spherical particles having the same particle size, the scattered light energy has a distribution along the Elie circle. In other words, a series of concentric circles are formed on the focal plane of the lens. The diameter of the concentric circle is related to the particles that cause scattering, but when the particle size is small, the scattering angle and the diameter of the concentric circle increase, and when the particle size is large, the scattering angle and the diameter of the concentric circle decrease. The particle size can be measured. The number of particles may be determined by measuring the number of analyzed particle particles. Such concentric circle information and particle particle number information are transmitted to the control unit 240.

  The control unit 240 receives the planar beam 220 emitted from the laser emitting unit 210 via the laser receiving unit 230 in order to measure the number of particles and the particle size of each particle. The average particle diameter of the particles is calculated from the concentric circle information. The controller 240 calculates the total particle volume using the calculated average particle diameter information of the particles and the total number of particles.

The total particle volume calculated by the control unit 240 can be expressed by the following Equation 1.
[Equation 1]
V = N × d ³
In the equation, N is the number of particles analyzed by analyzing information received by the laser receiving unit 230, and d is the average particle diameter of particles calculated from concentric circle information received by the laser receiving unit 230. An average value of particle diameters calculated from the concentric circle information is calculated and set as d value.

  V indicates the volume (volume) of the total particles, and can be obtained using a value obtained by multiplying the average volume d3 of each particle by the number of particles.

On the other hand, the control unit 240 determines the total particle volume calculated by Equation 1 above, the velocity v of the gas stream received from the sensor 114, and the unit time when the gas stream is drawn or the unit time when the pumps 150 and 160 are operated. Using t, the amount of particle change per unit time t can be measured by the following formula 2. Formula 2 is as follows.
[Equation 2]
m = V / vt
In the equation, m is the amount of particle change, v is the velocity of the gas stream, and t is the unit time. On the other hand, the variables in Equation 2 described above are V indicating the volume of the particle and the velocity v of the gas stream, and the volume of the particle is detected corresponding to a change in time in real time. Therefore, the amount of particle change can be detected in real time. That is, the degree of contamination per unit time can be measured. If the unit time is set short, the degree of contamination can be measured even in a short time.

  The control unit 240 measures the particle change amount m per unit time t, and when the particle change amount m per unit time is equal to or greater than a predetermined reference value, the control unit 240 controls the alarm unit 250 to sound an alarm. it can.

  FIG. 5 is a flowchart illustrating a process of inspecting a photomask according to an embodiment of the present invention. Referring to FIG. 5, in step S <b> 302, the controller 240 calculates a volume V of particles contained in the gas stream flowing out from the main chamber 110. The volume V of the particles can be obtained by the above-described formula 1.

  In step S <b> 304, the control unit 240 calculates the particle change amount m per unit time t according to Equation 2 described above. Using the amount of particle change per unit time, it is possible to recognize the degree of contamination of the main chamber 110 per unit time, that is, during the set time t.

  In step S306, the control unit 240 compares a predetermined reference value with the amount of particle change.

  As a result of the comparison in step S306, if the amount of particle change is greater than or equal to the reference value, the control unit 240 determines that the main chamber 110 is contaminated and controls the alarm unit 250 to sound an alarm (S308).

  As a result of the comparison in step S306, if the particle change amount is less than the reference value, the process returns to step S306.

For example, the time is set to 10 seconds, the speed of the gas stream drawn by the low vacuum pump 160 is detected by the sensor 114 as 50 m / s, and the total volume of particles drawn for 10 seconds is 2 × 10 ⁻⁷ m ³ . In some cases, a value of 4 × 10 ⁻¹⁰ is output as the particle change amount. At this time, if the user sets the reference value of the contamination level to 2 × 10 ⁻¹⁰ , the amount of particle change is larger than the reference value, so the control unit 240 controls the alarm unit 250 to sound an alarm. Can do.

  The above-described contents of the present invention have been described with reference to the illustrated embodiments. However, these embodiments are merely illustrative, and various modifications and changes may be made by those having ordinary skill in the art. It will be understood that other equivalent implementations are possible. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the appended claims.

DESCRIPTION OF SYMBOLS 110 Main chamber 112,155,163 Switch 114 Sensor 120 Sub chamber 121 1st inspection part 122 Transfer part 123 2nd inspection part 124 1st opening / closing means 125 Cleaning part 126 2nd opening / closing means 130 Photomask stage 132 Photomask 140 Wafer Stage 142 Wafer 150 High vacuum pump 152 First gas pipe 154 Gas pipe 160 Low vacuum pump 162 Second gas pipe 170 Particle counter 210 Laser emitting section 220 Planar beam 230 Laser receiving section 240 Control section 250 Alarm section

Claims (12)

A main chamber that is irradiated with light on the photomask to pattern the wafer and maintained in a high vacuum state;
A sub-chamber that is provided in the front stage of the main chamber, accommodates the photomask to be pulled in, and maintains a vacuum state lower than the vacuum state of the main chamber;
An inspection unit that is provided in a front stage of the main chamber and inspects whether or not particles are present on the photomask and whether or not an allowable reference value is exceeded if the particles are present. A photomask inspection apparatus characterized by comprising:   The photomask inspection apparatus according to claim 1, wherein the inspection unit is fixed to an upper part of the sub chamber.   The photomask inspection apparatus according to claim 1, wherein the inspection unit is fixed to an upper portion of a transfer unit provided in a front stage of the sub-chamber. It further includes a cleaning unit provided at an upper part of the transfer unit provided in the previous stage of the sub-chamber,
The transfer unit, the inspection result of the inspection unit, if the particles exceed the allowable reference value, to transport the photomask to the cleaning unit,
The photomask inspection apparatus according to claim 2, wherein the cleaning unit removes the particles by injecting gas or inhaling particles to the transported photomask. It further includes a cleaning unit provided at an upper part of the transfer unit which is a subsequent stage of the inspection unit,
The transfer unit transfers the photomask to the cleaning unit when the particle exceeds an allowable reference value as a result of the inspection by the inspection unit, and the cleaning unit is moved when the particle is less than the allowable reference value. Let it pass,
The photomask inspection apparatus according to claim 3, wherein the cleaning unit removes the particles by injecting gas or inhaling particles to the transferred photomask. The inspection unit
2. The photomask inspection apparatus according to claim 1, wherein the presence or absence of particles is determined using a bright field inspection reaction or a dark field inspection reaction. Forming a passage for the gas stream flowing out from the main chamber, and a gas pipe provided extending from the main chamber;
A sensor installed at a connection point between the gas pipe and the main chamber for measuring the speed of the gas stream;
A laser emitting unit installed on one side of the gas pipe to generate a plane beam and enter the gas pipe;
A laser receiver installed on the other side of the gas pipe and receiving a planar beam emitted from the gas pipe;
The information on the plane beam scattered by the particles included in the gas stream is received from the laser receiver, the velocity of the gas stream from the sensor is received, and the plane beam flows while flowing in the gas pipe per unit time. A control unit that calculates the number of particles that have passed through and the particle size of the particles, and calculates the amount of particle change;
A photomask inspection apparatus comprising: an alarm unit that generates an alarm when a calculation result of the control unit and a particle change amount per unit time is equal to or greater than a predetermined reference value. The controller is
The volume of particles contained in the gas stream flowing out from the main chamber is calculated by the following formula:
V = N × d ³
8. The photomask inspection apparatus according to claim 7, wherein V represents the volume of the particles, N represents the number of particles, and d represents the average particle diameter of the particles. The control unit calculates the particle change amount per unit time t by the following formula:
m = V / vt
Where V is the volume of the particle, m is the amount of particle change, v is the velocity of the gas stream, t is the unit time when the gas stream is injected through the injector, or the unit time when the pump is activated. The photomask inspection apparatus according to claim 7. Calculating the volume V of particles contained in the gas stream flowing out of the main chamber;
A process of calculating a particle change amount m per unit time t;
A process of comparing a predetermined reference value with the amount of particle change;
A photomask comprising: a step of determining that the main chamber is contaminated and sounding an alarm when the amount of change in the particles is equal to or greater than a reference value as a result of the comparison in the comparison process. Inspection method. The volume of the particles in the process of calculating the volume is
Calculate using the following formula:
V = N × d ³
11. The photomask inspection method according to claim 10, wherein V represents the volume of the particles, N represents the number of particles, and d represents the average particle diameter of the particles. The particle change amount in the process of calculating the particle change amount m is:
Calculate using the following formula:
m = V / vt
Where V is the volume of the particle, m is the amount of particle change, v is the velocity of the gas stream, t is the unit time when the gas stream is injected through the injector, or the unit time when the pump is activated. The photomask inspection method according to claim 10.

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