Method and device for removing stubborn dirty points on tiny gaps of mask

Abstract

The invention discloses a method and a device for removing stubborn dirty points on tiny gaps of a mask, and the method comprises the following steps: selecting an abnormal mask of which tiny dirty points are difficult to remove from mask plates of which nodes are smaller than or equal to 180nm, and placing the abnormal mask on a fixed clamping groove in a soaking tank; a KOH cleaning agent added with an active agent with a certain concentration is conveyed to the soaking tank through a diaphragm pump, and the full soaking time is T1; after soaking is completed, a liquid drainage ball valve is opened, and after the cleaning agent in the soaking tank is emptied, the soaked abnormal mask is washed with a deionized pure water gun for time T2; the mask is placed on a chuck of a cleaning machine, washed clean with hot and cold deionized ultrapure water and spin-dried; the size of the micro gap is less than or equal to 0.72 mu m; according to the method, the problems that stubborn dirty points on the tiny gaps of the mask with technical nodes below 180nm are difficult to remove, so that products are scrapped and the cleaning process is abnormal can be solved, and the one-time cleaning passing rate of the cleaning process of the mask is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photomasks, and particularly to a method and device for removing stubborn dirt on minute gaps of a photomask. Background Art

[0002] Photomask cleaning is mainly to remove various contamination impurities generated during the production process of the photomask. It is the process with the most steps in the photomask manufacturing process and almost runs through the entire production process. Since the processing of the photomask has very high requirements for cleanliness, all media in contact with the photomask may cause contamination to the photomask. The atomic bonding between the contaminants and the photomask forms dirt, and the purpose of cleaning is to effectively eliminate this phenomenon.

[0003] The high-node order is a photomask with a 180nm technology node, and the minimum line gap of the designed pattern is 0.72um.

[0004] In the actual production process of mass-producing photomasks with a 180nm technology node, the cleaning process is a bottleneck. Often, one or several dirt points ≥0.2um fall on the minute gap of 0.72um. The smaller the dirt point, the more difficult it is to remove. After repeated cleaning three times, it still cannot be removed, and we call it stubborn "dirt point", which ultimately leads to product scrapping and shipment delays.

[0005] The reasons why the dirt points on the 0.72um minute gap cannot be removed 100% are as follows:

[0006] The current mainstream cleaning equipment cleans in a Spin manner: simply put, the photomask is placed on a chuck and rotated at a set speed, and the process arm is on the photomask, generally 10 - 15mm away from the mask surface, and scans back and forth at a set speed. There are blind spots where the liquid medicine is not sprayed sufficiently or not wetted sufficiently. If there are dirt points in these blind spots, it will result in incomplete cleaning of the photomask.

[0007] Due to the surface tension of the chemical agent during the cleaning process, it directly affects the wetting ability of the chemical agent on the surface of the photomask. The smaller the line gap, the more difficult it is for the chemical agent to fully penetrate into the micro-structure gap, resulting in the dirt points in the micro-structure gap being difficult to completely remove. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to propose a method for removing stubborn dirt points on minute gaps of a photomask. This method can solve the problem that the stubborn dirt points on the minute gaps of photomasks with technology nodes below 180nm are difficult to remove, ultimately leading to product scrapping and abnormal cleaning processes, and improve the first-pass cleaning rate of the photomask cleaning process. The size of the minute gap is ≤0.72um.

[0009] To solve the above technical problems, the present invention provides a method for removing stubborn dirt spots on minute gaps of a photomask, which is characterized by comprising:

[0010] Select an abnormal photomask with difficult-to-remove minute dirt spots from the photomasks of specific nodes, place the abnormal photomask on the fixed card slot in the immersion tank using a fixture, and then convey a KOH cleaning agent added with an active agent at a certain concentration to the immersion tank through a diaphragm pump for sufficient immersion time T1;

[0011] After the immersion is completed, open the drain ball valve, empty the cleaning agent in the immersion tank, and then rinse the immersed abnormal photomask with a deionized pure water water gun for time T2;

[0012] Use the fixture to take out the abnormal photomask and place it on the chuck of the cleaning machine, select a specific cleaning program to rinse it clean with hot and cold deionized ultrapure water and spin-dry it to obtain a normal photomask;

[0013] Among them, the photomask of the specific node is a photomask of a node ≤ 180 nm, and the size of the minute gap is ≤ 0.72 um.

[0014] Preferably, the delivery amount of the cleaning agent in the step of "conveying a KOH cleaning agent added with an active agent at a certain concentration to the immersion tank through a diaphragm pump" stops when the upper surface of the photomask is completely immersed.

[0015] Preferably, the abnormal photomask with difficult-to-remove minute dirt spots is a photomask whose dirt spots on the minute gaps cannot be removed clean after being continuously cleaned twice.

[0016] Preferably, the diaphragm pump is a PFA diaphragm pump, the time T1 is 30 minutes, and the time T2 is 3 minutes.

[0017] Preferably, the KOH cleaning agent added with an active agent at a certain concentration is a KOH cleaning agent added with an active agent at a concentration of 10%.

[0018] To solve the above technical problems, the present invention also discloses a device adopting the method for removing stubborn dirt spots on minute gaps of a mask plate as described above, which includes an air source, a pressure reducing valve, a gas control valve, a diaphragm pump, a soaking tank main body, a first control valve, a chemical filter, a chemical accommodating main body and a deionized pure water water gun. The air source is connected to the gas inlet valve of the diaphragm pump through the pressure reducing valve, the gas control valve and a pipeline. The cleaning agent is arranged in the chemical accommodating main body. The chemical accommodating main body is connected to the liquid inlet valve of the diaphragm pump through the chemical filter and a pipeline. An immersion tank is arranged at the upper part of the soaking tank main body. The liquid outlet valve of the diaphragm pump is connected to the immersion tank through the first control valve and a pipeline. A plate placing rack assembly suitable for fixedly placing a plurality of mask plates is arranged at the bottom of the immersion tank. A liquid discharge port for draining the waste cleaning agent liquid is arranged at the bottom of the immersion tank. The deionized pure water water gun is connected to a deionized pure water water source through a pipeline.

[0019] Preferably, the gas control valve is used to control the on-off of the gas. When it is necessary to convey the cleaning agent from the diaphragm pump to the immersion tank, the gas control valve is opened. When it is necessary to stop the diaphragm pump from conveying the cleaning agent, the gas control valve is closed.

[0020] The diaphragm pump is used to convey the cleaning agent to the immersion tank. When the gas control valve is opened, the gas enters the pump chamber of the diaphragm pump to push the diaphragm to reciprocate. When the diaphragm of the diaphragm pump moves towards the side close to the air source, a negative pressure is formed in the pump chamber of the diaphragm pump, and the cleaning agent is sucked into the pump chamber of the diaphragm pump from the chemical accommodating main body through the chemical filter and a pipeline. When the diaphragm of the diaphragm pump moves towards the side away from the air source, a positive pressure is formed in the pump chamber of the diaphragm pump, and the liquid is discharged from the pump chamber through the outlet valve. By opening the first control valve, the cleaning agent is conveyed to the immersion tank.

[0021] Preferably, an immersion tank cover for sealing the immersion tank is arranged on the immersion tank.

[0022] A pressure reducing valve and a filter are further arranged on the pipeline between the air source and the gas control valve.

[0023] The filter is used to filter the oil mist and particles of the gas.

[0024] The pressure reducing valve is used to ensure that the gas pressure is stabilized at a certain value. A throttle valve and a muffler are also arranged on the diaphragm pump.

[0025] Preferably, the plate placing rack assembly includes four composite plate placing racks made of Teflon material arranged at the bottom of the immersion tank. The steps of the composite plate placing rack from top to bottom respectively correspond to mask plates of 7 inches, 6 inches, 5 inches and 4 inches. The composite plate placing rack is installed at a certain inclination angle with the bottom plane of the immersion tank to facilitate draining the waste liquid.

[0026] Preferably, the drain port at the bottom of the soaking tank is connected to a waste liquid recovery barrel through a second control valve and a pipeline, and the waste liquid recovery barrel is arranged on a layer below the medicine accommodating main body.

[0027] After adopting the above method and device, the method for removing stubborn dirt spots on the tiny gaps of a mask plate includes: selecting an abnormal mask plate with difficult-to-remove tiny dirt spots from the mask plates at specific nodes, placing the abnormal mask plate on the fixed card slot in the soaking tank using a fixture, and then conveying a KOH cleaning agent added with a certain concentration of surfactant to the soaking tank through a diaphragm pump for sufficient soaking for a time T1; after the soaking is completed, opening the drain ball valve, emptying the cleaning agent in the soaking tank, and rinsing the soaked abnormal mask plate with a deionized pure water water gun for a time T2; taking out the abnormal mask plate using the fixture and placing it on the chuck of a cleaning machine, and selecting a specific cleaning program to rinse it clean with hot and cold deionized ultrapure water and spin-dry it to obtain a normal mask plate; wherein, the mask plate at the specific node is a mask plate with a node of ≤ 180 nm, and the size of the tiny gap is ≤ 0.72 um; this method can solve the problem that the stubborn dirt spots on the tiny gaps of the mask plate at a technical node below 180 nm are difficult to remove, ultimately resulting in product scrapping and abnormal cleaning processes, and improve the one-time cleaning passing rate of the mask plate cleaning process. Description of the Drawings

[0028] Figure 1 It is the overall structure diagram of the device for the method of removing stubborn dirt spots on the tiny gaps of a mask plate adopted by the present invention;

[0029] Figure 2 It is the structure diagram of the plate placing frame assembly of the device for the method of removing stubborn dirt spots on the tiny gaps of a mask plate adopted by the present invention. Detailed Description of the Invention

[0030] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Embodiment 1

[0032] This embodiment discloses a method for removing stubborn dirt spots on the tiny gaps of a mask plate, including: selecting an abnormal mask plate with difficult-to-remove tiny dirt spots from the mask plates at specific nodes, placing the abnormal mask plate on the fixed card slot in the soaking tank using a fixture, and then conveying a KOH cleaning agent added with a certain concentration of surfactant to the soaking tank through a diaphragm pump for sufficient soaking for a time T1;

[0033] After the soaking is completed, opening the drain ball valve, emptying the cleaning agent in the soaking tank, and rinsing the soaked abnormal mask plate with a deionized pure water water gun for a time T2;

[0034] Use a fixture to take out the abnormal mask plate and place it on the chuck of the cleaning machine. Select a specific cleaning program and rinse it thoroughly with hot and cold deionized ultrapure water and spin-dry it to obtain a normal mask plate;

[0035] Among them, the mask plate of the specific node is a mask plate of ≤180nm node, and the size of the micro-gap is ≤0.72um.

[0036] Due to the lower surface tension, the chemical liquid can spread more evenly on the surface of the mask plate and is more likely to penetrate into the micro-structure gaps, thus effectively removing dirt such as particulate matter and organic matter. For example, in the wet cleaning process, by adjusting the surface tension of the cleaning liquid, such as using surfactants, the wrapping and peeling efficiency of the solution for the dirt in the micro-structure gaps of the mask plate can be optimized.

[0037] Therefore, in order to solve the problem that it is difficult to remove dirt on the micro-gaps (≤0.72um) of the high-node mask plate, it is necessary to make full use of surfactants to adjust the liquid surface tension. During the cleaning process, the surfactant concentration needs to be strictly controlled within an appropriate range: too low concentration may lead to too high surface tension and reduce the cleaning effect; too high concentration may affect subsequent processes (such as lithography or bonding) due to the residual surfactant; and during the cleaning process, it is necessary to ensure that the cleaning agent liquid spreads quickly and evenly covers the surface.

[0038] Example Two

[0039] This example is based on Example One. In this example,

[0040] The abnormal mask plate with difficult-to-remove small dirt is a mask plate that still cannot remove the dirt on the micro-gaps after being continuously cleaned twice.

[0041] For the "delivery of the KOH cleaning agent added with a certain concentration of surfactant to the immersion tank through a diaphragm pump", the delivery volume of the cleaning agent stops when the upper surface of the mask plate is completely immersed.

[0042] Example Three

[0043] This example is based on Example One. In this example,

[0044] The diaphragm pump is a PFA diaphragm pump, the time T1 is 30 minutes, and the time T2 is 3 minutes.

[0045] A KOH cleaning agent with a surfactant concentration of X% was formulated. Through continuous experiments, the cleaning effect was verified and the influence of the residual surfactant on subsequent processes was comprehensively evaluated to determine the appropriate cleaning agent concentration; ensuring both a high removal ability for the dirt on the micro-structure gaps of the mask plate and avoiding the influence of the residual surfactant on subsequent processes, and at the same time, a supporting device was made.

[0046] In this embodiment, preferably, the KOH cleaning agent added with a certain concentration of surfactant is a KOH cleaning agent added with 10% surfactant; this can ensure that there is a high removal ability for the dirt spots on the microstructural gaps of the mask plate and can avoid the influence of the residual surfactant on the subsequent processes.

[0047] Example 4

[0048] Please refer to Figure 1 , Figure 1 , which is the overall structure diagram of the device for the method of removing stubborn dirt spots on the micro gaps of the mask plate according to the present invention;

[0049] This embodiment discloses a device for the method of removing stubborn dirt spots on the micro gaps of the mask plate according to any one of Embodiments 1 to 3, including a gas source 11, a gas control valve 14, a diaphragm pump 15, an immersion tank main body 18, a first control valve 16, a chemical agent accommodating main body 22, and a deionized pure water water gun 24. The gas source 11 is connected to the gas inlet valve of the diaphragm pump 15 through the gas control valve 14 and a pipeline. The cleaning agent is disposed in the chemical agent accommodating main body 22. The chemical agent accommodating main body is connected to the liquid inlet valve of the diaphragm pump 15 through a chemical agent filter 25 and a pipeline. An immersion tank 17 is provided at the upper part of the immersion tank main body 18. The liquid outlet valve of the diaphragm pump 15 is connected to the immersion tank 17 through the first control valve 16 and a pipeline. A plate placing rack assembly suitable for fixedly placing a plurality of mask plates is provided at the bottom of the immersion tank 17. A liquid discharge port for emptying the cleaning agent waste liquid is provided at the bottom of the immersion tank 17. The deionized pure water water gun 24 is connected to a deionized pure water water source through a pipeline.

[0050] It is necessary to fabricate a device, configure a cleaning agent with a certain concentration and added with surfactant, quickly and evenly cover the surface of the mask plate, make the cleaning agent fully wet each microstructural gap on the mask plate and maintain a certain sufficient infiltration time, enable the dirt spots in the microstructural gaps on the mask plate to be fully infiltrated and absorb heat, effectively break the chemical bond binding force between the dirt spots and the microstructural gaps of the mask plate, so as to separate the dirt spots, and finally take the mask plate to a cleaning device to rinse it clean with hot and cold deionized ultrapure water and spin-dry it.

[0051] Select an abnormal mask plate with difficult-to-remove micro dirt spots from the mask plates at specific nodes, use a fixture to place the abnormal mask plate on the fixed card slot in the immersion tank. When the diaphragm of the diaphragm pump moves away from the gas source side, a positive pressure is formed in the pump chamber of the diaphragm pump, and the liquid is discharged from the pump chamber through the outlet valve. Open the manual ball valve, and the cleaning agent is transported to the immersion tank and soaked for 30 minutes. After the soaking is completed, open the drain ball valve, empty the cleaning agent in the tank, and then rinse the soaked abnormal mask plate with the deionized pure water water gun for 3 minutes.

[0052] Example 5

[0053] This embodiment is based on Embodiment 4. In this embodiment, the gas control valve 16 is used to control the on-off of the gas. When it is necessary to use the diaphragm pump 15 to transport the cleaning agent to the immersion tank 17, the gas control valve 16 is opened. When it is necessary to stop the diaphragm pump 15 from transporting the cleaning agent, the gas control valve 16 is closed.

[0054] The diaphragm pump 15 is used to transport the cleaning agent to the immersion tank 17. When the gas control valve 16 is opened, the gas enters the pump chamber of the diaphragm pump 15 to push the diaphragm to move reciprocally. When the diaphragm of the diaphragm pump 15 moves towards the side close to the gas source, a negative pressure is formed in the pump chamber of the diaphragm pump. The cleaning agent is sucked into the pump chamber of the diaphragm pump from the chemical agent accommodating main body 22 through the pipeline. When the diaphragm of the diaphragm pump 15 moves towards the side away from the gas source, a positive pressure is formed in the pump chamber of the diaphragm pump 15, and the cleaning agent is discharged from the pump chamber through the liquid outlet valve. When the first control valve 16 is opened, the cleaning agent is transported to the immersion tank 17.

[0055] Embodiment 6

[0056] This embodiment is based on Embodiment 4. In this embodiment,

[0057] An immersion tank cover for sealing the immersion tank is provided on the immersion tank 17. Preferably, the materials used for the immersion tank and the immersion tank cover are Teflon, which can better seal the immersion tank when immersing the mask plate.

[0058] A pressure reducing valve 13 and a filter 12 are further provided on the pipeline between the gas source 11 and the gas control valve 14;

[0059] The chemical agent filter 25 is used to filter impurities and particles in the cleaning agent, and the filtering specification is 30 nm;

[0060] The pressure reducing valve 13 is used to ensure that the gas pressure is stable at a certain value. The diaphragm pump 15 is further provided with a throttle valve 21 and a muffler 20.

[0061] Embodiment 7

[0062] This embodiment is based on Embodiment 4. In this embodiment,

[0063] Please refer to Figure 2 , Figure 2 which is the structural diagram of the plate placing frame assembly of the device for the method adopted by the present invention for removing stubborn dirt spots on the tiny gaps of the mask plate;

[0064] The plate placing frame assembly includes four composite plate placing frames made of Teflon material arranged at the bottom of the immersion tank. The steps 26, 27, 28, and 29 of the composite plate placing frame from top to bottom respectively correspond to mask plates of 7 inches, 6 inches, 5 inches, and 4 inches. The composite plate placing frame is installed at a certain inclination angle with the bottom plane of the immersion tank 17 to facilitate the drainage of waste liquid.

[0065] The liquid discharge port 30 at the bottom of the immersion tank 17 is connected to the waste liquid recovery barrel 23 through the second control valve 19 and a pipeline, and the waste liquid recovery barrel 23 is arranged on a layer below the medicine accommodating main body 22.

[0066] This method can solve the problems that stubborn dirt spots on the tiny gaps of the mask below the 180nm technology node are difficult to remove, ultimately leading to product scrapping and abnormal cleaning processes, and improve the first-pass cleaning rate of the mask cleaning process.

[0067] It should be understood that the above are only the preferred embodiments of the present invention, and the patent scope of the present invention cannot be limited thereby. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for removing stubborn dirt spots on tiny gaps of a mask, characterized in that: include: Select the abnormal mask with tiny dirty spots that are difficult to remove from the mask plate of a specific node, use a fixture to place the abnormal mask on the fixed card slot in the immersion tank, and then use a diaphragm pump to transport KOH cleaning agent with a certain concentration of active agent to the immersion tank for a sufficient immersion time T1; After the soaking is completed, open the drain ball valve, drain the cleaning agent in the soaking tank, and use a deionized pure water gun to rinse the abnormal mask after soaking for a period of time T2; Use a fixture to take out the abnormal mask and place it on the chuck of the cleaning machine. Select a specific cleaning program and use hot and cold deionized ultrapure water to rinse it and spin dry it to get a normal mask. The mask of the specific node is a mask of a node ≤180nm, and the size of the tiny gap is ≤0.72um.

2. The method for removing stubborn dirt spots on tiny gaps of a mask according to claim 1, characterized in that: In the "delivering KOH cleaning agent added with a certain concentration of an active agent to the immersion tank through a diaphragm pump", the delivery amount of the cleaning agent is to stop after the upper surface of the mask is completely immersed.

3. The method for removing stubborn dirt spots on tiny gaps of a mask according to claim 1, characterized in that: The abnormal mask from which it is difficult to remove tiny dirty spots is a mask from which the dirty spots on the tiny gaps cannot be removed even after two consecutive cleanings.

4. The method for removing stubborn dirt spots on tiny gaps of a mask according to claim 1, characterized in that: The diaphragm pump is a PFA diaphragm pump, the time T1 is 30 minutes, and the time T2 is 3 minutes.

5. The method for removing stubborn dirt spots on tiny gaps of a mask according to claim 1, characterized in that: The KOH cleaning agent with a certain concentration of active agent added thereto is a KOH cleaning agent with a concentration of 10% of active agent added thereto.

6. A device using the method for removing stubborn dirt spots on tiny gaps of a mask plate according to any one of claims 1 to 5, comprising an air source, a pressure reducing valve, a gas control valve, a diaphragm pump, a soaking tank body, a first control valve, a reagent filter, a reagent containing body and a deionized pure water gun, wherein the air source is connected to the gas inlet valve of the diaphragm pump via the pressure reducing valve, the gas control valve and a pipeline, the cleaning agent is arranged in the reagent containing body, the reagent containing body is connected to the liquid inlet valve of the diaphragm pump via the reagent filter and a pipeline, a soaking tank is arranged on the upper part of the soaking tank body, the liquid outlet valve of the diaphragm pump is connected to the soaking tank via the first control valve and a pipeline, a plate placing rack assembly suitable for fixing and placing a variety of mask plates is arranged at the bottom of the soaking tank, a liquid discharge port for draining the cleaning agent waste liquid is arranged at the bottom of the soaking tank, and the deionized pure water gun is connected to the deionized pure water source via a pipeline.

7. The device according to claim 6, characterized in that The gas control valve is used to control the on and off of the gas. When the diaphragm pump is needed to deliver the cleaning agent to the soaking tank, the gas control valve is opened. When the diaphragm pump needs to stop delivering the cleaning agent, the gas control valve is closed. The diaphragm pump is used to convey the cleaning agent to the soaking tank. When the gas control valve is opened, the gas enters the pump chamber of the diaphragm pump and pushes the diaphragm to reciprocate. When the diaphragm of the diaphragm pump moves toward the side close to the gas source, a negative pressure is formed in the pump chamber of the diaphragm pump, and the cleaning agent is sucked into the pump chamber of the diaphragm pump from the agent containing body through the agent filter and the pipeline. When the diaphragm of the diaphragm pump moves toward the side away from the gas source, a positive pressure is formed in the pump chamber of the diaphragm pump, and the liquid is discharged from the pump chamber through the outlet valve. The first control valve is opened, and the cleaning agent is conveyed to the soaking tank.

8. The device according to claim 6, characterized in that The soaking tank is provided with a soaking tank cover for sealing the soaking tank; A pressure reducing valve and a filter are also provided on the pipeline between the gas source and the gas control valve; The filter is used to filter oil mist and particles in the gas; The pressure reducing valve is used to ensure that the gas pressure is stable at a certain value, and the diaphragm pump is also provided with a throttle valve and a muffler.

9. The device according to claim 6, characterized in that The plate rack assembly includes four composite plate racks made of Teflon material and arranged at the bottom of the immersion tank. The steps of the composite plate rack from top to bottom correspond to 7-inch, 6-inch, 5-inch and 4-inch mask plates respectively. The composite plate rack is installed at a certain inclination angle to the bottom plane of the immersion tank to facilitate the emptying of waste liquid.

10. The device according to claim 6, characterized in that The liquid discharge port at the bottom of the soaking tank is connected to a waste liquid recovery barrel through a second control valve and a pipeline, and the waste liquid recovery barrel is arranged in a layer at the lower part of the medicine containing body.

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