JP2008173728A - Atomic force microscope microprocessing device and microprocessing method using atomic force microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high accuracy of processing of an atomic force microscope microprocessing device and to make it possible to remove process waste produced in a cutting step by a process probe. <P>SOLUTION: The atomic force microscope microprocessing device is wholly or partially, in a portion including a cantilever 2 and a processing region, evacuated to be in a vacuum atmosphere to reduce the resistance of air and to improve the Q value of resonance, so that the cantilever 2 having a high spring constant and less torsion or bend which can not be conventionally used because of damages induced even only upon imaging, can be used for observation an processing, and thereby, controllability of a probe 1 during processing is improved to achieve high accuracy processing. Further, process waste produced during cutting with the process probe 1 is sucked and removed by the device evacuating system or the local evacuating system 3A. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an atomic force microscope fine processing apparatus and a fine processing method using an atomic force microscope used for defect correction of a photomask.

  Nanometer-order microfabrication technology is required for advanced functions and high integration, and research and development of processing technologies such as local anodization and microscratch processing using a scanning probe microscope (SPM) is actively pursued. Has been done. Recently, not only the pursuit of the possibility of fine processing, but also a precise shape and high-precision processing are required as a practical processing machine.

In recent years, as an example in which an accurate shape and high-precision processing are required in an apparatus based on an atomic force microscope (AFM), there is correction of a photomask pattern surplus defect (Non-patent Document 1). Photomask surplus defect correction using an atomic force microscope is currently using an atomic force microscope probe that is harder than the material to be processed (the material of the surplus defect). Alternatively, imaging is performed in intermittent contact mode to recognize defective parts, and during processing, the high-weight contact mode or feedback is turned off and the hard probe is fixed at the same height as the underlying glass surface and placed on the glass surface. This is performed by scanning and physically removing a certain excess defect portion.
Photomask surplus defect correction using an atomic force microscope has recently been able to correct isolated defects that are difficult to observe and process due to charge-up using a focused ion beam defect correction apparatus that has been used as a correction apparatus for fine defects in conventional masks. It is also being used at mask manufacturing sites. Since the mask serves as the master for wafer transfer, if the processing accuracy at the correction location is poor, or overetching or uncut parts, the transfer characteristics will be adversely affected, causing device defects on all transferred wafers. Accurate shape and high-precision processing are required by mechanical removal processing with a microscope.

  In order to achieve high accuracy by mechanical processing, it is necessary to have a structure with little twist and deflection so that the cutting edge does not deviate from the target processing position even if there is processing resistance. If a cantilever with little twist or deflection is used, the sensitivity of force detection is lowered, and there is a problem that a hard probe damages the image just by imaging. Intermittent contact mode (dynamic mode) is used for imaging to reduce damage, but there is still a trade-off between processing performance and sensitivity, and the cantilever shape is optimized within a range that does not cause damage in imaging. However, there is a problem that a certain degree of twisting and deflection remain, and high processing accuracy cannot be obtained.

Further, machining waste is generated in mechanical processing, and removal of the machining waste is necessary to ensure the transmittance of the photomask. In addition, it is necessary to remove the processing waste because it becomes an obstacle when performing additional processing, or it interferes with processing with good reproducibility. Conventionally, processing scrap removal has been performed by wet cleaning or dry ice cleaner (Non-patent Document 2), but both are off-line cleaning, and repeated processing and cleaning have increased man-hours and reduced throughput. There is a need for a method that can clean processing waste in-line.
Y. Morikawa, H. Kokubo, M. Nishiguchi, N. Hayashi, R. White, R. Bozak, and L. Terrill, Proc. Of SPIE 5130 520-527 (2003) WV Brandt, Proc. Of SPIE 4562 600-608 (2002)

An object of the present invention is to increase the resonance Qa value and increase the sensitivity of the dynamic mode when using a cantilever having a high spring constant, thereby improving processing accuracy.
Another object is to remove processing waste generated during processing in real time.

It is known that the Q value of resonance of a probe having a low spring constant used for observation is orders of magnitude higher because air resistance is reduced in a vacuum than in the atmosphere. The present invention utilizes this finding.
That is, in the atomic force microscope micromachining apparatus of the present invention, in the atomic force microscope micromachining apparatus that performs micromachining on a sample by bringing the cantilever into contact with the sample, at least the cantilever and the processing area of the sample are surrounded. In addition, a partition wall is provided, and an evacuation system for evacuating an internal space surrounded by the partition wall is provided.

  According to the atomic force microscope microfabrication apparatus of the present invention, a cantilever having a high spring constant (herein, a spring constant in the range of 500 N / m to 3500 N / m) and a processing region of the sample are surrounded. A partition wall is provided, and the internal space surrounded by the partition wall is set to a vacuum atmosphere. Thereby, the Q value of the vibration of the cantilever can be increased. Therefore, by increasing the sensitivity of the dynamic (non-contact or intermittent contact) mode, it is possible to observe and process cantilevers with high spring constants that could not be used because damage occurred just by imaging so far. As a result, it became possible to improve the processing accuracy.

In the atomic force microscope microfabrication apparatus of the present invention, it is preferable that the suction opening of the evacuation system is disposed near the tip of the cantilever.
Thereby, in this case, machining waste is generated by machining with a cantilever machining probe, but the generated machining waste can be sucked and removed by a vacuum exhaust system. If the processing debris can be removed in the apparatus, there is no step for taking out the photomask for cleaning and confirming the processing result and performing additional processing, and returning it to the apparatus for positioning, thereby improving the throughput. Since it is not obstructed by the processing waste, the reproducibility of processing is also improved.

In the atomic force microscope microfabrication apparatus of the present invention, it is preferable that the partition wall surrounds only the local region including the cantilever and the sample processing region.
By evacuating only the local region in this manner, the time required for evacuation can be shortened compared to evacuating the entire apparatus as a vacuum target.

In the atomic force microscope microfabrication apparatus of the present invention, a multi-stage vacuum exhaust system is employed in which a plurality of the partition walls are arranged from the inside to the outside, and each internal space surrounded by the multi-structure partition walls is individually evacuated. A system is preferably provided.
In this way, by providing a multi-stage evacuation system for individually evacuating each internal space surrounded by the multi-structure partition walls, the innermost internal space, that is, the interior surrounding the cantilever and the sample processing region The amount of air leakage in the space can be reduced and the degree of vacuum can be increased.

Further, the micromachining method using the atomic force microscope of the present invention is a micromachining using an atomic force microscope that performs micromachining on a sample by bringing a cantilever having a spring constant of 500 N / m or more into contact with the sample. In the method, a partition wall is provided so as to surround at least the cantilever and the sample processing region, an internal space surrounded by the partition wall is evacuated to form a vacuum atmosphere, and a resonance Q value of the cantilever is increased. It is characterized by performing fine processing.
According to the microfabrication method using the atomic force microscope of the present invention of the present invention, the same operational effects as the above-described operational effects of the atomic force microscope microfabrication apparatus of the present invention are exhibited.

  According to the present invention, by increasing the resonance Q value to increase the sensitivity, a cantilever having a high spring constant with less twisting and deflection can be used for observation and processing, so that the processing resistance is higher than before. However, the controllability of the cutting edge is improved and machining can be performed at the target position. Therefore, the machining accuracy of machining by the machining probe can be improved more than before.

Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a side view showing a main part of an atomic force microscope microfabrication apparatus according to the present invention, which is an example using a two-stage local vacuum exhaust system. A single-stage local evacuation system may be used, but using a two-stage local evacuation system is advantageous in that it is easy to maintain a better degree of vacuum. In the figure, reference numeral 12 denotes an XY stage, on which a glass substrate 6 on which a predetermined pattern is formed is placed. In addition to the normal pattern 5, the black defect 4 may be formed on the glass substrate 6. Reference numeral 9 denotes a Z stage. A scanner 8 is provided on the Z stage 9, and a cantilever 2 having a machining probe 1 is attached to the scanner 8. The cantilever 2 has a spring constant of 500 N / m to 3500 N / m, which is higher than that of a normal cantilever, and is less twisted or bent. Incidentally, the spring constant of the cantilever 2 generally used is about 0.02 N / m to 50 N / m.

A first partition wall 17 is provided so as to surround the cantilever 2 and a processing region including the black defect 4 of the sample, and a second partition wall 18 is provided outside the first partition wall 17 so as to surround the first partition wall 17. ing. That is, in this embodiment, the partition wall has a multiple structure in which a plurality of partitions are arranged from the inside to the outside with reference to the cantilever 2 and the processing region of the sample. A first local evacuation system 3A including a vacuum pump 10 and a gate valve that evacuates the internal space corresponding to the first partition wall 17 is provided. A second local evacuation system 3B including a vacuum pump 10 and a gate valve for evacuating the space between the first partition wall 17 and the second partition wall 18 is provided corresponding to the second partition wall 18. It has been.
The suction opening 3AA of the first evacuation system 3A is arranged in the vicinity of the processing probe 1 at the tip of the cantilever 2 so as to point to the processing probe 1.

  Further, the atomic force microscope microfabrication apparatus is provided with an optical lever detection system for detecting the deflection of the cantilever 2. The optical lever detection system causes the laser light 15 emitted from the laser light source 14 to enter the space in the first partition wall 17 through the view port 13 made of glass of the first and second local evacuation systems 3A and 3B. The incident laser beam 15 is reflected by the back surface of the cantilever 2, and the reflected laser beam 15 is detected by the position sensitive detector 16 through the view port 13.

Next, a micromachining method using the atomic force microscope micromachining apparatus having the above configuration will be described. First, a photomask having a black defect 4 is introduced into an atomic force microscope fine processing apparatus equipped with local vacuum exhaust systems 3A and 3B, and the cantilever 2 is processed at a position 4 where the black defect 4 found by the defect inspection apparatus is present. The XY stage 12 is moved and adjusted so that the vicinity of the tip of the probe 1 is located.
In this example, local evacuation is adopted for evacuation. However, the evacuation is not limited to this, and it may be performed for the entire apparatus (a system for evacuating the entire apparatus is an apparatus exhaust system). Called). In this case, the floor, the wall, and the ceiling that define the internal space in which the main components of the atomic force microscope microfabrication apparatus are housed constitute a partition wall. When the apparatus exhaust system is employed, evacuation is performed after the photomask is introduced, and the process waits until the degree of vacuum reaches a predetermined value. As shown in FIG. 1, in the case of the two-stage local evacuation systems 3A and 3B, it has a plurality of differential evacuations drawn by the vacuum pump 10 and is easily set so that the innermost degree of vacuum becomes high. This is advantageous compared to a single-stage local vacuum exhaust system. That is, the degree of vacuum is determined by the amount of leakage within the range of the pumping capacity of the vacuum pump. However, when the local vacuum pumping system has two stages of 3A and 3B, the locality is generated when the atmosphere and the leak source are outside the local vacuum pumping system 3B. Since a vacuum is drawn in the local exhaust system 3B outside the exhaust system A, the amount of leak flowing inward from the atmosphere or a leak source is reduced, and the degree of vacuum of the inner local exhaust system 3A can be easily kept high.
When a self-detecting cantilever that detects the deflection of the cantilever 2 as a change in resistance value by the piezo effect is used, the viewport 13 is not required for the local evacuation systems 3A and 3B.

  In the case of a local exhaust system, the gate valve 11 of the vacuum pump 10 is opened at a position where the black defect 4 exists, and the vicinity of the processing region (black defect), the processing probe 1 of the atomic force microscope, and the cantilever 2 with less twist and deflection. The area containing the is exhausted locally. By making a vacuum, the air resistance is reduced, the resonance Q value is improved, and the sensitivity of the cantilever 2 is increased. After vacuum evacuation, use a processing probe (for example, a diamond probe) 1 that is harder than the material to be processed (pattern material of the photomask). In the dynamic mode, the damage to the mask is suppressed as much as possible, and an atomic force microscope image is acquired with a visual field of about 10 μm to search for the black defect 4. If the black defect 4 is found, an offset of the scanner 8 is applied so that the black defect 4 is in the middle, and a high resolution image is obtained again with a field of view of about 2 μm. The area of the black defect 4 is recognized by comparing with a normal pattern 5 having no defect by pattern matching or the like. After measuring the height of the reference point (glass substrate 6), only the processing region (black defect) 4 is selectively scanned with the height of the constant height mode with feedback turned off, and processed by physical removal (black Perform defect correction).

  At this time, as shown in FIG. 2, machining waste 7 generated by machining with the machining probe 1 is sucked by the local vacuum exhaust system 3 </ b> A or the apparatus exhaust system and removed in-line. When the machining waste 7 remains, the probe 1 is scanned in the dynamic mode used for observation, or the probe 1 is set to a height that does not cut the ground pattern in the constant height mode with feedback turned off. Then, the machining waste 7 is moved by making it scan, so that the machining waste is made finer and is easily sucked into the apparatus exhaust system or the local vacuum exhaust system 3A. The height at which the ground pattern is not cut is the height of the ground pattern or a little higher than that. If the probe 1 is scanned at this height, it can be moved by applying force only to the processing scraps on the base without damaging the base. When the base is hard to some extent and the sensitivity of the cantilever is low, observation of a dynamic mode with little damage to the base may move the processing scrap by interacting with the base by piercing or scraping soft processing scraps. When the height of the machining waste is higher than the amplitude in the dynamic mode, the lateral force accompanying the scanning acts on the machining waste, and it becomes easier to move.

  In this way, the processing waste 7 can be removed in the equipment, so there is no need to take out the photomask in the middle of correction and apply it to wet cleaning or dry ice cleaner as before, and continue processing result confirmation and additional processing as it is. Can do.

  If there are a plurality of black defects 4 to be corrected by the local evacuation system, after one defect correction is completed, the processing probe 1 is moved away from the photomask surface, the gate valve 11 of the vacuum pump 10 is closed, and the local evacuation system is closed. 3A and 3B are returned to the atmosphere, the XY stage 12 is moved to the next defect position, the gate valve 11 of the vacuum pump 10 is opened again at that position, and local evacuation is performed, and defect correction is performed in the same manner as described above. . This procedure is repeated until there are no black defects to be corrected. When the entire apparatus is evacuated, all the defects are corrected in a vacuum, and then the mask is taken out to the atmosphere.

Of course, in the present invention, not only defective machining scraps but also shavings generated when foreign particles with strong adhesive force are removed by the processing probe 1 can be removed in-line by the local vacuum exhaust system 3A, and offline after the foreign matter removal. No need for cleaning.
In the above-described embodiment, the partition wall has a double structure, and the two-stage local evacuation systems 3A and 3B are provided to individually evacuate each internal space surrounded by the double structure partition wall. However, the present invention is not limited to this, and the partition wall has a multiple structure of three or more, and correspondingly there are provided three or more multi-stage local vacuum exhaust systems that individually evacuate each internal space surrounded by the multiple structure partition wall. It may be configured.

It is a schematic sectional drawing which shows the example using the local vacuum exhaust system which best expresses the characteristic of this invention. It is a schematic sectional drawing which shows the example which sucks and removes processing waste with a local vacuum exhaust system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing probe 2 Cantilever 3A, 3B Local evacuation system 4 Black defect 5 Normal pattern 6 Glass substrate 7 Processing waste 8 Scanner 9 Z axis stage 10 Vacuum pump 11 Gate valve 12 XY stage 13 Viewport 14 Laser light source 15 Laser light 16 Position sensitive detector 17 First partition 18 Second partition

Claims (5)

In atomic force microscope microfabrication equipment that performs microfabrication on a sample by bringing the cantilever into contact with the sample,
While providing a partition so as to surround at least the processing region of the cantilever and the sample,
An atomic force microscope microfabrication apparatus provided with an evacuation system for evacuating an internal space surrounded by the partition walls.   2. The atomic force microscope microfabrication apparatus according to claim 1, wherein the suction opening of the vacuum exhaust system is disposed in the vicinity of the tip of the cantilever.   The atomic force microscope fine processing apparatus according to claim 1, wherein the partition wall surrounds only a local region including the processing region of the cantilever and the sample.   4. A multi-layered structure in which a plurality of the partition walls are arranged from the inside to the outside, and a multistage vacuum exhaust system for individually evacuating each internal space surrounded by the multi-structure partition walls is provided. An atomic force microscope microfabrication apparatus described in 1. In a micromachining method using an atomic force microscope that performs micromachining on a sample by bringing a cantilever having a spring constant of 500 N / m or more into contact with the sample,
A partition is provided so as to surround at least the cantilever and the processing region of the sample,
The internal space surrounded by the partition is evacuated to form a vacuum atmosphere,
A fine processing method using an atomic force microscope, characterized in that the fine processing is performed by increasing the Q value of resonance of the cantilever.

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