Photomask processing method and apparatus

Abstract

A method and apparatus for treating a sample for surface modification prior to photomask application and photomask cleaning using a dielectric barrier discharge (DBD) plasma. In some embodiments, the method for treating a surface with AP plasma includes igniting a plasma on an ignition plate, where the AP plasma is formed by one or more plasma heads of an AP plasma reactor positioned above the ignition plate, monitoring a characteristic of the AP plasma using an optical emission spectroscopy (OES) sensor to determine whether a stable AP plasma is obtained, and when a stable AP plasma is obtained, moving the AP reactor over a central opening of an auxiliary plate, where the central opening contains the sample being treated and the auxiliary plate reduces AP plasma arcing on the sample being treated. The AP reactor scans back and forth over the central opening of the auxiliary plate while maintaining a stable AP plasma to treat the sample.

Description

[Technical field]

[0001]

[0001] Embodiments of the present principles relate generally to semiconductor manufacturing. [Background technology]

[0002] During the manufacturing process of semiconductor circuits, photomasks are used to develop a photoresist layer deposited on a wafer. Typically, the wafer surface is prepared before the photoresist layer is deposited on the wafer. The photomask is then used to project the desired circuit layout onto the photoresist layer on the wafer. When photomasks are used to create very fine features, any particles or defects on the photomask will cause defects in the features in the photoresist layer, reducing yield. To reduce defects, photomasks are often cleaned in tools designed for photomask cleaning before use. Photomasks must be cleaned frequently to maintain optimal performance, so the amount of time it takes to clean the photomask can significantly affect the throughput of the manufacturing process.

[0003] Accordingly, the present inventors have provided a method and apparatus for more efficiently cleaning photomasks, resulting in significant improvements in throughput and photomask performance. Summary of the Invention

[0004]

[0004] Provided herein are methods and apparatus for AP plasma treatment of a specimen.

[0005]

[0005] In some embodiments, an apparatus for treating a surface with atmospheric pressure (AP) plasma may include a pedestal having a sample support region configured to hold a sample for plasma processing, an auxiliary plate surrounding the sample support region and having a central opening configured to expose the sample support region to the plasma, and an ignition plate adjacent to the auxiliary plate, the ignition plate having a solid upper surface configured to interact with the plasma during plasma ignition, and a plasma reactor configured to generate an AP plasma, positioned above the pedestal, having one or more plasma heads extending wider than the central opening of the auxiliary plate, and positionable above the ignition plate and auxiliary plate.

[0006]

[0006] In some embodiments, the apparatus may further include a plurality of gas nozzles configured to flow one or more gases around the one or more plasma heads, the plurality of gas nozzles configured to flow a mixture of argon gas and an oxygen-based gas and configured to flow a mixture of argon gas and a hydrogen-based forming gas, and an optical emission spectroscopy sensor configured to monitor a characteristic of the plasma during ignition and surface treatment, the one or more plasma heads being positioned about 1 mm to about 2 mm above the ignition plate and about 1 mm to about 2 mm above a top surface of the auxiliary plate, the plasma reactor comprising: the plasma heads are configured to scan back and forth over a central opening of the auxiliary plate during plasma processing, at least one of the plurality of plasma heads is configured to extend over at least one edge of the auxiliary plate during plasma processing, the auxiliary plate is configured to reduce plasma arcing in the sample support region during plasma processing, the one or more plasma heads have a central RF electrode surrounded by a dielectric material and have one ground electrode on each side of the central RF electrode, and / or the apparatus is configured to modify a surface of a photomask, remove a photoresist layer overlying a photomask, or remove organic defects.

[0007]

[0007] In some embodiments, a method for treating a surface with an atmospheric pressure (AP) plasma may include igniting an AP plasma on an ignition plate, the AP plasma being formed by one or more plasma heads of a plasma reactor positioned above the ignition plate; monitoring a characteristic of the AP plasma using an optical emission spectroscopy (OES) sensor to determine whether a stable AP plasma has been obtained; moving the plasma reactor over a central opening of an auxiliary plate when the AP plasma is stable, the central opening containing a sample being processed, the auxiliary plate reducing AP plasma arcing on the sample being processed; moving the plasma reactor over the central opening of the auxiliary plate when the AP plasma is stable; and scanning back and forth over the central opening of the auxiliary plate while maintaining the stable AP plasma to treat the sample.

[0008] In some embodiments, the method may further include monitoring the AP plasma during the processing of the specimen to determine a processing end point based on the oxygen peak level, and scanning back and forth over the central opening of the auxiliary plate such that at least one of the plasma heads extends over the auxiliary plate at the end of one scan to obtain the same AP plasma residence time on the top surface of the specimen during processing, the specimen being a photomask, and the specimen during processing has a top surface to be modified, where a photoresist layer is removed or organic defects are removed. The method may further include flowing a mixture of argon gas and an oxygen-based gas around the RF electrodes of the one or more plasma heads during processing, flowing water vapor with the mixture to generate hydroxyl during the processing of the specimen, and / or flowing a mixture of argon gas and a hydrogen-based forming gas around the RF electrodes of the one or more plasma heads during processing.

[0009]

[0009] In some embodiments, a non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method of treating a surface with an AP plasma to be performed, the method may include igniting an AP plasma on an ignition plate, the AP plasma being formed by one or more plasma heads of a plasma reactor positioned above the ignition plate; monitoring a characteristic of the AP plasma using an optical emission spectroscopy (OES) sensor to determine if a stable AP plasma has been obtained; moving the plasma reactor over a central opening of an auxiliary plate when the AP plasma is stable, the central opening containing a sample being processed, the auxiliary plate reducing AP plasma arcing on the sample being processed; moving the plasma reactor over the central opening of the auxiliary plate when the AP plasma is stable; and scanning back and forth over the central opening of the auxiliary plate while maintaining the stable AP plasma to treat the sample.

[0010]

[0010] Other further embodiments are disclosed below.

[0011]

[0011] The embodiments of the present principles summarized above and described in more detail below can be understood by reference to exemplary embodiments of the present principles illustrated in the accompanying drawings, which, however, merely illustrate exemplary embodiments of the present principles and should not be considered as limiting the scope thereof, as the present principles may admit of other equally effective embodiments. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 shows a cross-sectional view of an AP plasma reactor according to some embodiments of the present principles. [Diagram 2] FIG. 1 shows an isometric view of an AP plasma reactor according to some embodiments of the present principles. [Diagram 3] FIG. 1 illustrates an isometric view of an ignition plate and a back-up plate in accordance with some embodiments of the present principles. [Figure 4]FIG. 1 shows an isometric view of a plasma reactor on an ignition plate in accordance with some embodiments of the present principles. [Diagram 5] FIG. 1 shows an isometric view of an AP plasma reactor on a photomask and backing plate in accordance with some embodiments of the present principles. [Figure 6] FIG. 1 shows an isometric view of an AP plasma reactor for scanning a sample according to some embodiments of the present principles. [Figure 7] 11A-11C are top view illustrations of the plasma region on the auxiliary plate during scanning in accordance with some embodiments of the present principles; [Figure 8] 1 illustrates a cross-sectional view of an AP plasma processing system according to some embodiments of the present principles. [Figure 9] 1 is a method for treating a specimen with an AP plasma according to some embodiments of the present principles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]

[0021] To facilitate understanding, the same reference numbers have been used, wherever possible, to designate identical elements common to the drawings. The drawings are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further detail.

[0014]

[0022] The method and apparatus allows for highly efficient photomask processing, dramatically increasing throughput and reducing manufacturing costs. The techniques of the present principles utilize atmospheric pressure (AP) plasma to effectively clean photomasks. The apparatus has the advantages of a simplified structure (no vacuum used), large plasma area, and high throughput for cleaning organic contamination that can also be used to perform surface modification before photomask use. The apparatus also has the flexibility to be used for other semiconductor manufacturing processes. In some embodiments, the apparatus may include multiple plasma heads to increase plasma coverage during one pass and ensure equal plasma residence time for all areas of the photomask. In some embodiments, the apparatus utilizes argon gas during processing, along with optical emission data for plasma characterization and control, resulting in low cost of ownership, high throughput, and a stable plasma that reduces damage to the photomask. With the use of multiple plasma heads to increase plasma coverage and throughput, and the use of argon instead of helium to reduce operational costs, the method and apparatus can dramatically improve the cost-effectiveness of the photomask cleaning process.

[0015]

[0023] In some embodiments, the AP plasma device provides a dielectric barrier discharge (DBD) plasma cleaning device for photomask cleaning. The AP plasma device can be ignited on an ignition plate to avoid an unstable plasma damaging the photomask. The plasma is monitored with an optical emission spectroscopy (OES) sensor to ensure the plasma is stable before moving the plasma head over the photomask for cleaning or preparation. An auxiliary plate surrounds the photomask to prevent unwanted arcing or discharge that would damage the photomask during cleaning or preparation. In some embodiments, an OES sensor monitors the processing of the photomask and determines when the processing of the photomask is complete, allowing for automatic termination of the process along with improved plasma stability and reduced arcing. The multiple plasma heads of the AP plasma device scan back and forth across the photomask during processing to obtain the same plasma dwell time on the photomask. The spacing between the plasma heads allows for overscanning to completely cover the photomask during processing.

[0016]

[0024] DBD is an electrical discharge between two electrodes separated by an insulating dielectric barrier. The dielectric barrier generates a self-pulsing plasma action, establishing a non-thermal plasma at atmospheric pressure. The inventors have discovered that AP plasma can be used for surface treatment. Often the surface is hydrophobic (water resistant) and the surface modification is treated until the surface becomes hydrophilic (water absorbing). The hydrophilic surface enhances the bond strength between the surface and the photoresist layer. The inventors have also discovered that AP plasma can be used to treat photomasks to remove contaminants such as organic contaminants. The inventors have discovered an AP plasma method and apparatus that can be used for both surface modification and photomask cleaning, as well as other operations. The AP plasma method and apparatus has low operating costs and high throughput, resulting in savings in both capital costs (reducing the number of equipment to one type) and recurring costs.

[0017]

[0025] FIG. 1 shows a diagram 100 of an AP plasma reactor 102 for generating DBD plasma according to some embodiments. The AP plasma reactor 102 has an RF electrode 104 surrounded by a dielectric layer 106 and powered by an RF power supply 110 that also interfaces with a ground 112. The RF electrode 104 generates a plasma 128 for processing a specimen 126, which may be a photomask to be cleaned or a surface to be modified, etc. The plasma 128 is generated between the RF electrode 104 and a first grounded electrode 108A and a second grounded electrode 108B. The first grounded electrode 108A and the second grounded electrode 108B are electrically connected to the ground 112. The RF electrode 104 (with the dielectric layer 106), the first grounded electrode 108A, and the second grounded electrode 108B form an AP plasma head. In some embodiments, RF power may be supplied to the AP plasma head at a total power of about 100 Watts to about 700 Watts during specimen processing. In some embodiments, RF power may be provided to the AP plasma during sample processing at a total power of about 500 Watts to about 700 Watts. In some embodiments, RF power may be provided at a frequency such as about 13.56 MHz. During processing of the sample 126, a mixed gas is flowed around the outside of the dielectric layer 106 between the dielectric layer 106 and the first and second grounded electrodes 108A and 108B toward the sample 126. In some embodiments, the mixed gas may be generated from the first and second gas supplies 118 and 120, mixed by the mixer 122, and flowed through the gas lines 124 from the multiple nozzles 134.

[0018]

[0026] In some embodiments, the first gas supply 118 provides a carrier gas, such as argon gas, and the second gas supply 120 provides a reactive gas, such as oxygen gas. In some embodiments, water vapor may be combined into the gas mixture by the mixer 122 during processing of the sample 126. The oxygen gas dissociates in the plasma 128 to form atomic oxygen. In some embodiments, the reactive gas may be flowed at a rate of about 30 sccm to about 60 sccm. In some embodiments, the flow rate of the reactive gas may be about 40 sccm. In some embodiments, the carrier gas may be flowed at a rate of about 10 liters per minute to about 60 liters per minute. In some embodiments, the carrier gas may be flowed at a rate of about 50 liters per minute. When water vapor is added to the mixture, the water vapor forms hydroxyl (OH) radicals in the plasma. A reactive gas such as oxygen gas generates atomic oxygen in the plasma, and when stripping the photoresist layer on the photomask, excess atomic oxygen may be generated to rapidly deplete hydrogen in the photoresist layer of the photomask and form a carbon-rich organic layer. By controlling the oxygen gas peak and the hydroxyl peak (from water vapor), the rate of hydrogen depletion during the photomask process can be controlled. The reactive gas can be a forming gas composed of an inert gas such as argon and / or hydrogen. The hydrogen concentration is 1% to 5% for safety reasons. The reason for using forming gas as a reactive gas is to remove photoresist or other organics in a reducing atmosphere in order to oxidize the layers on the photomask.

[0019]

[0027] The ventilation system 114 removes by-products resulting from the processing of the specimen 126 using a duct system 116. In some embodiments, the ventilation system 114 may include a blower system or the like. The ventilation flow 136 is outside the first ground electrode 108A and outside the second ground electrode 108B. The plasma 128 may be monitored by an optical emission spectroscopy (OES) sensor 132 via a fiber optic input 142 to determine characteristics of the plasma 128 during ignition and also during processing of the specimen 126. The OES sensor 132 may monitor different wavelength peaks associated with different gases to determine characteristics of the plasma. The plasma characteristics may be used to adjust the plasma during ignition and also during processing to determine plasma stability, improve the plasma, and determine the processing end point. For example, the oxygen level in the plasma increases as the photomask approaches completion of the process due to the need for less oxygen. When the oxygen level peaks become constant, the end point of the process may be determined and the processing may be automatically stopped. The spacing 130 from the bottom of the RF electrode 104, the first ground electrode 108A, and the second ground electrode 108B to the top surface 138 of the sample 126 is about 1 to about 2 millimeters.

[0020]

[0028] FIG. 2 is a diagram 200 illustrating an AP plasma reactor 202 for generating DBD plasma according to some embodiments. The AP plasma reactor 202 incorporates multiple AP plasma heads 204A-204D that generate multiple plasma regions 228A-228D to increase the overall plasma coverage area and improve throughput. The AP plasma reactor 202 may have any number of AP plasma heads. Spacing 206 between the multiple AP plasma heads 204A-204D allows for ventilation of by-products that occur during processing of the specimen. The specimen and / or the AP plasma reactor 202 may move back and forth relative to each other in a scanning manner, so that the spacing 206 between the multiple plasma regions 228A-228D is compensated for by the movement 208.

[0021]

[0029] FIG. 3 illustrates a diagram 300 of an ignition plate 304 and an auxiliary plate 306 according to some embodiments. In some embodiments, the ignition plate 304 and the auxiliary plate 306 may be supported by a pedestal arrangement 302, which may be stationary and / or movable relative to the AP plasma reactor 412 (see FIG. 4). In some embodiments where the pedestal arrangement 302 is stationary, the AP plasma reactor 412 is movable and vice versa. In some embodiments, the ignition plate 304 and the auxiliary plate 306 may be formed together as a unitary structure. In other embodiments, the ignition plate 304 and the auxiliary plate 306 may be formed separately and positioned adjacent to one another with or without an intervening space or gap (not shown). The interface between the ignition plate 304 and the auxiliary plate 306 is indicated by dashed line 318. The ignition plate 304 and the auxiliary plate 306 may be formed from a photomask-like material, such as a fused silica material with a metal coating. In some embodiments, the metallic coating of the ignition plate 304 and / or the back-up plate 306 may or may not be coupled to an electrical ground.

[0022]

[0030] The ignition plate 304 provides an area for igniting the plasma generated by the AP plasma reactor 412 without damaging the specimen. When the AP plasma is generated, arcing may occur. The ignition plate 304 is used to prevent arcing damage to the specimen being processed during plasma ignition, and the auxiliary plate 306 is used to prevent arcing damage to the specimen being processed. The auxiliary plate 306 has a central opening 308 to receive the specimen. The central opening 308 may be any shape, such as circular, rectangular, or other shape that accommodates the specimen. In some embodiments, the central opening 308 has a bottom 312 that is recessed below the top surface 314 of the auxiliary plate 306. In some embodiments, the dimensions (width and length) of the central opening 308 may be about 6 inches wide by about 6 inches long for a photomask specimen. In some embodiments, the recess depth 310 may be about 0.05 inches to about 0.375 inches to accommodate the thickness of the photomask. In some embodiments, the recess depth 310 may be about 0.25 inches to accommodate the thickness of the photomask. The recess depth 310 forms a step to accommodate the thickness of the specimen such that the top surface of the specimen is flush with or below the top surface of the auxiliary plate 306. If a plasma arc were to occur, the arc would cross the edge of the plasma head on the edge of the auxiliary plate 306, not on the specimen being processed. In some embodiments, the bottom 312 of the central opening 308 may be formed by the top surface 316 of the pedestal device 302.

[0023]

[0031] FIG. 4 shows a diagram 400 of an AP plasma reactor 412 on an ignition plate 304 according to some embodiments. The AP plasma reactor 412 is moved onto the ignition plate 304 during plasma ignition. If the AP plasma reactor 412 is placed on the specimen 420 during plasma ignition (when the plasma is unstable), the specimen 420 is likely to be damaged by plasma arcing during ignition. In the example of FIG. 4, the AP plasma reactor 412 has four AP plasma heads 404A-404D, each generating a respective plasma. The number of AP plasma heads can be from one to any number and is selected to ensure high coverage of the specimen during processing and improve throughput. The throughput is improved due to the high coverage percentage of the specimen by the plasma and the way the AP plasma heads are positioned on the specimen (giving the same dwell time to all areas of the specimen on each pass). The OES sensor 432 has multiple fiber optic inputs 442A-442D to monitor the plasma of each of the four AP plasma heads 404A-404D. The OES sensor 432 receives wavelength information from each plasma to determine if the plasma is stable. If the plasma is stable, the detected wavelength peak does not vary over time. In some embodiments, once each plasma is stable, the AP plasma reactor automatically begins processing the sample 420. The OES sensor 432 may move with the AP plasma reactor 412 to characterize each plasma during ignition and also during processing of the sample 420.

[0024]

[0032] FIG. 5 is a diagram 500 showing an AP plasma reactor 412 on a backing plate 306 according to some embodiments. Once the plasma of each of the AP plasma reactors 412 is stable, the AP plasma reactors 412 are moved 502 over the specimen 420 (below the AP plasma reactor 412 in FIG. 5). The multiple AP plasma heads 404A-404D are wider than the central opening 308 of the backing plate 306 to reduce plasma arcing and protect the specimen 420 during processing. FIG. 6 shows a diagram 600 of the AP plasma reactor 412 scanning the specimen 420 according to some embodiments. The AP plasma reactor 412 moves back 602 and forward 604 over the specimen 420 to obtain the same residence time of the plasma on the specimen 420 during processing. In some embodiments, the speed of scanning over the specimen can be about 5 mm per second to about 20 mm per second. In some embodiments, the AP plasma reactor 412 can be scanned back and forth about 50 to about 100 times during processing of the sample 420. The OES sensor 432 can move in conjunction with the AP plasma reactor 412 so that the plasma maintains optimal properties. In some embodiments, the OES sensor 432 can be used during processing to determine the processing end point. The OES sensor 432 can detect peak levels of oxygen and argon in the plasma. When the peak oxygen level remains constant during processing of the photomask sample, the processing of the photomask sample is complete and the scan can automatically stop.

[0025]

[0033] 7 shows a top view 700 of plasma regions 704A-D on the specimen 420 and auxiliary plate 306 during scanning according to some embodiments. The plasma regions 704A-D can be generated by respective AP plasma heads 404A-D of the AP plasma reactor 412. To obtain the same residence time of the plasma on the specimen 420, the plasma regions 704A-D can overlap the top surface 314 of the auxiliary plate 306 at a first end 710 of the auxiliary plate 306 when the AP plasma reactor moves backward 602 (plasma region 704A is above the top surface 314 of the auxiliary plate 306 at the first end 710) and can overlap the top surface 314 of the auxiliary plate 306 at a second end 712 of the auxiliary plate 306 when the AP plasma reactor moves forward 604 (plasma region 704D is above the top surface 314 of the auxiliary plate 306 at the second end 712).

[0026]

[0034] 8 illustrates an AP plasma processing system 800 for generating a DBD plasma according to some embodiments. The AP plasma processing system 800 includes an AP plasma reactor 802 having one or more AP plasma heads 804. The AP plasma reactor 802 is positioned above an ignition plate 808 and an auxiliary plate 810 that reside on an optional support pedestal 806. In some embodiments, the AP plasma reactor 802 moves relative to the ignition plate 808 and the auxiliary plate 810. In some embodiments, the ignition plate 808 and the auxiliary plate 810 move relative to the AP plasma reactor 802. An optional actuator 824 can be used to move the ignition plate 808 and the auxiliary plate 810 to ignite a plasma on the ignition plate 808 and to scan a sample on the auxiliary plate 810. The optional actuator 824 can be controlled by and provide feedback to a controller 826. The AP plasma reactor 802 may be interfaced with an RF power source 820 to facilitate plasma generation beneath the one or more AP plasma heads 804. The RF power source 820 and a ground electrode (not shown) of the one or more AP plasma heads 804 may also be electrically connected to a system ground (not shown).

[0027]

[0035] The first gas supply 814 and the second gas supply 816 may be mixed in a gas mixer 818 and flowed onto the RF electrodes of the AP plasma head(s) 804. In some embodiments, an optional water vapor supply 834 may also be mixed with the mixed gas and flowed onto the RF electrodes of the AP plasma head(s) 804. A ventilation system 822 may also be used in the AP plasma processing system 800 to remove by-products generated during processing of the specimen. The OES sensor 812 may also provide plasma characterization of the AP plasma processing system 800 during ignition of the plasma and during processing of the specimen. A controller 826 interacts with one or more devices of the AP plasma processing system 800 to automate and / or regulate processes and timing to ensure optimal performance of the AP plasma processing system 800. The controller 826 can vary the power level of the RF power source 820, the ventilation speed of the ventilation device 822, the gas mix levels of the first and second gas supplies, the water vapor supply level, and the movement of the AP plasma reactor 802 and / or the ignition plate 808 / back-up plate 180 based on the process recipe and / or feedback from the OES sensor 812, etc.

[0028]

[0036] The controller 826 controls the operation of the AP plasma processing system 800 using direct control or alternatively by controlling computers (or controllers) associated with the devices of the AP plasma processing system 800. In the process, the controller 826 enables data collection and feedback from each device and system to optimize the performance of the AP plasma processing system 800. The controller 826 generally includes a central processing unit (CPU) 828, a memory 830, and support circuits 832. The CPU 828 may be any form of general-purpose computer processor that may be used in an industrial environment. The support circuits 832 are conventionally coupled to the CPU 828 and may include cache, clock circuits, input / output subsystems, power supplies, etc. Software routines, such as the methods described below, can be stored in the memory 830 and, when executed by the CPU 828, transform the CPU 828 into a special purpose computer (controller 826). The software routines may also be stored and / or executed by a second controller (not shown) located remotely from the AP plasma processing system 800.

[0029]

[0037] The memory 830 is in the form of a computer-readable storage medium that includes instructions that, when executed by the CPU 828, facilitate the operation of semiconductor processes and equipment. The instructions in the memory 830 are in the form of a program product, such as a program that implements the methods of the present principles. The program code may conform to any one of a number of different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program(s) of the program product define the functions of the aspects (including the methods described herein). Exemplary computer-readable storage media include, but are not limited to, non-writable storage media in which information is permanently stored (e.g., a read-only memory device in a computer, such as a CD-ROM disk readable by a CD-ROM drive, a flash memory, a ROM chip, or any type of solid-state non-volatile semiconductor memory), and writeable storage media in which changeable information is stored (e.g., a floppy disk in a diskette drive or hard disk drive, or any type of solid-state random access semiconductor memory). Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are aspects of the present principles.

[0030]

[0038] FIG. 9 illustrates a method 900 for processing a specimen with an AP plasma according to some embodiments. In block 902, a gas mixture and / or water vapor is flowed into the AP plasma during processing. The gas mixture includes a carrier gas and a reactive gas, as described above. The carrier gas may be, for example, but is not limited to, argon gas, etc. Argon gas is less expensive and advantageous than using a carrier gas such as helium. The reactive gas may be oxygen gas, which produces atomic oxygen in the plasma. In some embodiments, water vapor may also be used to produce hydroxyl radicals in the plasma, as described above, to better control the hydrogen depletion rate of the specimen. In block 904, the AP plasma is ignited on an ignition plate. If the plasma is ignited on the ignition plate rather than on the specimen, any arcing that occurs during ignition will not damage the specimen. In block 906, the characteristics of the AP plasma are monitored by an OES sensor. The OES sensor monitors the ignition process to determine the characteristics of the plasma and determine when the plasma is stable before it is moved onto the specimen for processing. When the plasma is stable, the detected parameters of the plasma do not vary over time. In block 908, the AP plasma is moved onto the sample in the opening of the auxiliary plate after the AP plasma is stable. In some embodiments, the movement from the ignition plate to the auxiliary plate can be automated based on the stability of the plasma detected by the OES sensor. The edge of the auxiliary plate provides a path for AP plasma arcing that may occur during processing, eliminating / reducing damage to the sample.

[0031]

[0039] In block 910, the sample is treated with the AP plasma by scanning the AP plasma back and forth over the sample. The scanning is performed so that the AP plasma overlaps at both ends of the auxiliary plate to ensure that the same AP plasma residence time occurs over the area of ​​the sample. The OES sensor can be used to monitor the characteristics of the AP plasma during processing to ensure that the AP plasma remains stable and also to monitor oxygen levels, etc. In some embodiments, the AP plasma is used to modify a surface before applying a photomask. In some embodiments, the AP plasma is used to clean the surface of the photomask. In optional block 912, an end point of the sample processing can be determined based on the oxygen peak level. Oxygen may be utilized during the processing of the sample, and when processing is completed, the oxygen level in the plasma increases. When the oxygen peak level becomes constant, it can be determined that the processing is complete. In some embodiments, after the end point is detected by the OES sensor, the plasma can be automatically removed and the next sample can be automatically processed.

[0032]

[0040] Embodiments according to the present principles may be implemented in hardware, firmware, software, or any combination thereof. Also, embodiments may be implemented as instructions that may be stored using one or more computer-readable media and read and executed by one or more processors. A computer-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform or a "virtual machine" running on one or more computing platforms). For example, a computer-readable medium may include any suitable form of volatile or non-volatile memory. In some embodiments, a computer-readable medium may include a non-transitory computer-readable medium.

[0033]

[0041] While the forgoing is directed to embodiments of the present principles, other and further embodiments of the present principles may be devised without departing from the basic scope thereof.

Claims

1. 1. An apparatus for treating a surface with a plasma, comprising: a pedestal having a specimen support region configured to hold a specimen for plasma processing; a support plate having a metal top surface surrounding the sample support area and having a central opening configured to contain the sample; an ignition plate adjacent the auxiliary plate, the ignition plate having a solid metal upper surface configured to interact with the plasma during plasma ignition; a plasma reactor configured to generate the plasma and positioned above the pedestal, the plasma reactor having one or more plasma heads extending wider than a central opening of the backing plate and positionable above the ignition plate and the backing plate; An apparatus comprising:

2. The apparatus of claim 1 , wherein the plasma is an atmospheric pressure (AP) plasma.

3. an optical emission spectroscopy (OES) sensor configured to monitor a characteristic of the plasma; The apparatus of claim 1 further comprising:

4. a controller configured to: (a) ignite the plasma on the ignition plate, the plasma being formed by the one or more plasma heads of the plasma reactor positioned above the ignition plate; and (b) move the plasma reactor over the central opening of the auxiliary plate while maintaining the plasma. The apparatus of claim 1 further comprising:

5. 5. The apparatus of claim 4, wherein the controller is configured to monitor the plasma during processing of the specimen to determine a processing endpoint based on a peak oxygen level.

6. The apparatus of claim 4 , wherein the controller is configured to scan the plasma reactor back and forth over the central opening of the backing plate.

7. a plurality of gas nozzles configured to flow one or more gases around the one or more plasma heads; The apparatus of claim 1 further comprising:

8. 2. The apparatus of claim 1, wherein the one or more plasma heads are positioned 1 to 2 mm above the ignition plate and 1 to 2 mm above a top surface of the back-up plate.

9. The apparatus of claim 1 , wherein at least one of the plurality of plasma heads is configured to extend over at least one end of the backing plate during plasma processing.

10. 10. The apparatus of claim 1, wherein the one or more plasma heads have a central RF electrode surrounded by a dielectric material and a ground electrode on either side of the central RF electrode.

11. 10. The apparatus of claim 1 , wherein the specimen is a photomask, and the apparatus is configured to modify a surface of the photomask, remove a photoresist layer overlying the photomask, or remove organic defects.

12. 1. A method for treating a surface with a plasma, comprising the steps of: igniting the plasma on an ignition plate having a metallic upper surface, the plasma being formed by one or more plasma heads of a plasma reactor positioned above the ignition plate; moving the plasma reactor over a central opening of an auxiliary plate having a metal top surface while maintaining the plasma, the one or more plasma heads of the plasma reactor being wider than the central opening of the auxiliary plate; and moving the plasma reactor over the central opening of the auxiliary plate while maintaining the plasma. The method includes:

13. monitoring the plasma to determine a process endpoint based on an oxygen peak level. The method of claim 12 further comprising:

14. scanning back and forth over the central opening of the auxiliary plate such that at least one of the plasma heads extends over the auxiliary plate at the end of one scan to obtain the same plasma residence time on the surface located at the central opening. The method of claim 12 further comprising:

15. The method of claim 12 , wherein the sample disposed in the central opening is a photomask.

16. modifying a surface of the photomask; removing the photoresist layer overlying the photomask; or Removing organic defects The method of claim 15 further comprising:

17. A mixture of argon gas and oxygen-based gas is flowed around the RF electrodes of one or more plasma heads. The method of claim 12 further comprising:

18. flowing water vapor with said gas mixture to produce hydroxyl; 20. The method of claim 17, further comprising:

19. A mixture of argon gas and hydrogen-based forming gas is flowed around the RF electrodes of one or more plasma heads. The method of claim 12 further comprising:

20. 1. A non-transitory computer readable medium having stored thereon instructions that, when executed, cause a method of treating a surface with a plasma, the method comprising: igniting the plasma on an ignition plate having a metallic upper surface, the plasma being formed by one or more plasma heads of a plasma reactor positioned above the ignition plate; moving the plasma reactor over a central opening of an auxiliary plate having a metal top surface while maintaining the plasma, the one or more plasma heads of the plasma reactor being wider than the central opening of the auxiliary plate; and moving the plasma reactor over the central opening of the auxiliary plate while maintaining the plasma.

16. A non-transitory computer readable medium comprising:

21. The method of claim 12, further comprising modifying the surface of the sample from hydrophobic to hydrophilic by treatment.

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