JP2010251131A - Processing method of solid surface, and device for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method of a solid surface with improved processing speed, and to provide a device for the method. <P>SOLUTION: In a processing method of the solid surface using a gas cluster ion beam which converges with lens, while obtaining actual measurement data of changes with respect to coordinate in an irradiation axis direction, on a current density distribution of the gas cluster ion beam in an in-plane direction which is perpendicular to an irradiation axis, based on the change data with respect to the coordinate in the irradiating axis direction of an etching process speed by each area of a processing object region acquired in a range shorter than a focal distance of the gas cluster ion beam fixed by the current density distribution data actually measured, the coordinate in the irradiation axis direction installing the solid surface of the object to be processed is fixed by each areas of the region for the object to be processed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention can be used, for example, for etching and planarizing the surface of semiconductors and other electronic device materials, and for etching and planarizing various device surfaces, pattern surfaces, and complex structure surfaces such as molds. The present invention relates to a method and apparatus for processing a solid surface by irradiation with a cluster ion beam.

  In recent years, a solid surface processing method using a gas cluster ion beam has attracted attention because it has little surface damage and can extremely reduce the surface roughness. In processing using a gas cluster ion beam, generally, a beam size of about several tens of millimeters is often used. By scanning a beam with such a beam size, for example, a wafer having a diameter of about 100 mm or more is planarized. Has been done. On the other hand, in order to cope with a case where the processing area is smaller than the beam size as described above, a beam is converged using a lens.

  Patent Document 1 describes the configuration of a processing apparatus that performs processing using such a gas cluster ion beam. Main components include ionizers for ionizing neutral clusters generated from nozzles, electrodes for accelerating cluster ions, lenses for focusing accelerated cluster ions, and for removing monomer ions. A permanent magnet beam filter and a scanning plate for irradiating the workpiece with cluster ions are provided. Here, the lens allows for a small beam spot at the workpiece target, so that a long focal length (up to 1.5 meters) can be achieved.

  On the other hand, Patent Document 2 discloses a nitride forming method using a gas cluster ion beam, and describes that the gas cluster ion beam is converged to a small area using an electrostatic lens.

JP-T-2003-521812 JP 2000-87227 A

  In Patent Document 1 and Patent Document 2, a lens is used for the purpose of focusing on a gas cluster ion beam, thereby enabling a small beam spot size on the surface of the workpiece. By using such a lens, it is considered that an effect that only a minute region to be processed can be processed is expected. In addition, there is a possibility that the effect of improving the beam current density by beam convergence and improving the processing speed in a minute region may be expected, but it is not clearly described.

  By the way, since the gas cluster ion beam is composed of clusters having a wide size distribution, the convergence situation varies depending on the size, and the position where the beam is focused like the monomer ion (position where the beam size is the smallest) However, the processing speed is not always improved. In other words, the purpose of using the conventional lens is mainly to adjust the beam size for processing only the target minute region, and the lens for the gas cluster ion beam and the processing using the same for improving the processing speed. The optimum design of the method (apparatus) was not clear.

  Assuming that the beam current is constant, the current density in the irradiation region increases when the beam is converged using a lens. Usually, the improvement of the processing speed by using a lens means the effect of increasing the current density, that is, the number of atoms sputtered per unit time as a result of increasing the number of ions irradiated within the unit time.

  On the other hand, there is a method of improving the sputtering rate in order to improve the processing speed. The sputtering rate is defined as atoms / ion, and is an amount indicating how many constituent atoms of the solid surface can be sputtered per cluster ion. It is known that the sputtering rate varies depending on, for example, the cluster size and is small for cluster ions having a large size.

  From the above, in the method (apparatus) for processing using a gas cluster ion beam, if the optimum irradiation conditions can be found from the two viewpoints of improving the current density and improving the sputtering rate, the processing speed can be increased. This can be improved over the prior art. However, the processing method (apparatus) from such a viewpoint has not been clarified so far.

  In view of such circumstances, an object of the present invention is to provide a solid surface processing method and apparatus capable of improving the processing speed as compared with the prior art.

  According to the first aspect of the present invention, there is provided a method of processing a solid surface using a gas cluster ion beam focused by a lens, wherein the irradiation of current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam is performed. Etching processing for each area of the processing target area acquired in the range of the irradiation axis direction shorter than the focal length of the gas cluster ion beam determined from the data of the current density distribution by acquiring change data with respect to the axial coordinate Based on the change data of the velocity with respect to the coordinate in the irradiation axis direction, the coordinate in the irradiation axis direction for setting the solid surface to be processed is determined for each area of the processing target region.

  In the invention of claim 2, in the invention of claim 1, before processing the solid surface, the current density distribution data is re-measured, and the coordinates in the irradiation axis direction where the solid surface is installed are converted into the result of the re-measurement. Correct based on.

  According to the invention of claim 3, a method of processing a solid surface by using a gas cluster ion beam focused by a lens is an irradiation of a current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam. Measure the change data with respect to the axial coordinates, determine the focal length of the gas cluster ion beam and the cross-sectional area of the beam size defined by the half value of the maximum value of the current density at the position of the focal length. When the area of the target region is smaller than the cross-sectional area of the beam size, processing is performed by selecting the coordinates in the irradiation axis direction where the solid surface to be processed is set within the range of 60% to 70% of the focal length. .

  According to the invention of claim 4, an apparatus for processing a solid surface using a gas cluster ion beam includes a gas cluster ion beam generator for emitting the gas cluster ion beam, and a lens for focusing the gas cluster ion beam. A 3-axis stage capable of moving the solid surface to be processed in the gas cluster ion beam irradiation axis direction and two orthogonal directions perpendicular to the irradiation axis, and a beam current detector mounted on the 3-axis stage. The gas defined by the data of the change in the current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam detected by the beam current detector and the current density distribution data. For each area of the processing target area acquired in the irradiation axis direction range shorter than the focal length of the cluster ion beam It has a database that includes data on changes in etching processing speed relative to the coordinates in the irradiation axis direction, and refers to the database to calculate the coordinates in the irradiation axis direction for setting the solid surface to be processed for each area of the processing target area. In addition, the three-axis stage is positioned.

[Action]
The gas cluster ion beam includes cluster ions having different sizes. Generally, when the average cluster size is 2000, the peak is 2000 and includes cluster sizes from several to tens of thousands. Depending on the size, even with the same acceleration energy, the energy per atom constituting the cluster is different, and the sputtering capability is also different. The size that contributes most to sputtering is said to be about 100. Although the sputtering rate increases in that the number of atoms that contribute to sputtering increases when a large number of atoms are included per cluster ion, the energy per atom is reduced, so in this respect the sputtering rate is From the balance between the two, the size of this region is considered to have the highest sputtering rate.

  Therefore, in order to increase the processing speed of a minute region (a region smaller than the beam size, where the beam size is defined at a position where the beam current density is half of the peak position), cluster ions of a size that maximizes the sputtering rate are used. It is desirable to perform the processing under conditions that allow the cluster region to converge on the minute region and increase the contribution of other sizes of cluster ions to the sputtering (conditions that reduce the loss of energy of these sizes).

  In order to perform processing under such conditions, the relationship between the beam convergence and the distance between the lens and the object to be processed and the sputtering rate was examined (see FIG. 2). The distance direction (beam irradiation axis direction) between the lens and the object to be processed is the Z direction, the distance from the lens in the Z direction is z, and the distance (focal length) at which the beam size is minimized (converged) is z =. It was found that the sputtering rate near the center of the beam becomes higher at a distance shorter than zf when zf is used. This is because it is considered that the cluster ions having a high sputtering rate of about 100 sizes are converged at a distance shorter than zf, and the distance between the lens and the object to be processed is made closer than zf. It is considered that the sputtering rate is larger than the position of z = zf from the two viewpoints that the energy loss of the cluster ions of the size is reduced. The energy decreases as the distance z from the lens increases because the kinetic energy decreases because the cluster decomposes due to collision with the residual gas and the size (mass) decreases.

  On the other hand, it is known that the current value of the entire beam (total beam current value) decreases as the distance z from the lens increases. This is because cluster ions are scattered by collision with the residual gas. Therefore, from the viewpoint of the total beam current value, it is advantageous to improve the processing speed to process at a position as close as possible to the lens.

  As described above, when processing a minute region, that is, when only the vicinity of the center of the beam converged by the lens is used, z is selected near the irradiation position where the sputtering rate increases, and when the processing region is large, that is, the beam In the case of using not only the central portion but also the entire portion, it is considered necessary to select z at a position where the total beam current value becomes high in order to improve the processing speed. In any case, it can be seen that the processing position may be smaller than the focal length of the beam.

  The above holds regardless of the material to be processed. That is, regardless of the material, it is known that the sputtering rate increases as the energy per atom increases, and the sputtering rate increases as the beam current value increases. The relationship between z and z shows the same curve for any material, although the absolute value of the sputtering rate is different. Therefore, the processing position can be set smaller than the focal length of the beam in processing any material.

  According to the present invention, it is possible to select and process the position that can be processed at the highest speed according to the size of the processing target region, and thus it is possible to improve the processing speed as compared with the conventional method.

The figure which shows the basic composition of the gas cluster ion beam processing apparatus which implement | achieves the processing method of the solid surface of this invention. The graph which shows the relationship between the distance from a lens, beam size, and a sputtering rate. A table showing the relationship between the distance from the lens, the total beam current value, and the processing speed. The graph which shows the relationship between the distance from a lens, and a processing speed. The figure for demonstrating an example of the scanning method in the case of etching a 50 square mm area | region. The figure which shows an example of beam profile data. The perspective view which shows an example of the shape of a process target object, and a process area | region.

Embodiments of the present invention will be described below.
FIG. 1 shows the basic configuration of a solid surface processing apparatus using a gas cluster ion beam according to the present invention. First, the basic configuration of the processing apparatus will be described with reference to FIG.

  The source gas is ejected from the nozzle 11 into the vacuum cluster generation chamber 12 to aggregate the gas molecules and generate clusters. The cluster is guided to the ionization chamber 14 through the skimmer 13 as a gas cluster beam. In the ionization chamber 14, the neutral cluster is ionized by irradiating an electron beam, for example, thermal electrons, from the ionizer 15. The ionized gas cluster ion beam is accelerated by the acceleration electrode 16. The accelerated gas cluster ion beam is adjusted in focal length by a beam focusing lens 17 and is incident on a process chamber 18.

  An Einchel lens was used as the lens 17 for beam convergence. The Einchel lens has a two-tiered basic structure for providing a convergence function. The convergence performance can be controlled by adjusting the first-stage and second-stage lens applied voltages (E1, E2).

  In the process chamber 18, a three-axis stage 21 for controlling the position x, y in the in-plane direction perpendicular to the irradiation axis of the workpiece 19 and the distance z from the lens 17 is provided. The workpiece 19 is attached to the support 22 on the three-axis stage 21, and the incident gas cluster ion beam 23 is irradiated on the surface of the workpiece 19. When the surface of the electrical insulator 19 is processed, the gas cluster ions may be neutralized by electrons in advance. A beam current detector 24 is mounted on the support base 22, and the beam current detector 24 can change the relative position with respect to the gas cluster ion beam 23 by moving the triaxial stage 21.

  Here, in order to clarify the convergence characteristics of the lens 17, the relationship between the distance z from the lens 17 and the beam size was examined. As the beam condition, Ar clusters accelerated to 20 kV were used, and the applied voltage of the lens 17 was set to the first stage E1 = 18 kV and the second stage E2 = 15 kV. A Faraday cup was used as the beam current detector 24, an aperture having a 1 mm square opening was attached to the entrance of the Faraday cup, and the Faraday cup was subjected to XY scanning to map the current density distribution of the beam. Thereby, the beam profile is known. The distance between the positions where the current density is half that of the portion where the beam current density is the highest (center portion) (half-value width) was defined as the beam size.

  Next, the workpiece 19 was made of silicon, and the relationship between the distance z from the lens 17 and the sputtering rate of silicon was examined. The sputtering rate can be obtained from the relationship between the current density and the average processing depth per unit area. The sputtering rate was examined for a 1 mm square region near the center of the beam. The relationship between the obtained distance z from the lens 17, the beam size, and the sputtering rate is shown in FIG. The focal length was z = 50 mm.

  Next, in the range of z = 10 mm to 50 mm where z is smaller than the focal length, the processing speed in the 1 mm square region at the center of the beam, that is, the average processing depth per unit beam irradiation time was examined. Further, with a Faraday cup having an opening diameter of 50 mm, the total beam current value in the region of φ50 mm was measured around the point where the beam current density was the largest. The results are shown in Table 1 in FIG. The machining speed became the largest at z = 35 mm.

  Next, the processing speed in the region of 50 mm square in the range of z = 10 mm to 50 mm was examined. In order to etch (sputter) a 50 mm square region with a uniform depth, an XY scan was performed on the region including the 50 mm square region. FIG. 5 shows this state, and the three-axis stage 21 was controlled so that the center of the beam was scanned at a constant speed in a scan area 31 of 100 mm × 100 mm. In FIG. 5, 32 indicates a 50 mm square region, and 33 indicates a beam spot of the gas cluster ion beam.

  As indicated by the arrows in FIG. 5, scanning from point a to b was performed, and after reaching point b, scanning was performed in the reverse direction toward point a. By repeating this, the 50 mm square region 32 can be etched almost uniformly regardless of the intensity distribution of the beam. The moving speed of the triaxial stage 21 in the X-axis direction was 50 mm / s, and the 100 mm × 100 mm scan region 31 was scanned while shifting by 1 mm in the Y-axis direction. The results are shown in Table 1 in FIG. The machining speed became the largest at z = 10 mm.

  Further, a 40 mm × 40 mm region was scanned for a 20 mm square region by the same method, and the relationship between z and the processing speed was examined. The results are shown in Table 1 in FIG. The machining speed became the largest at z = 20 mm.

  The relationship between the distance z from the lens 17 and the beam profile (mapping data of beam current density: illustrated in FIG. 6) was examined for the generation conditions of each cluster ion beam, and a database was created. As conditions for generating the beam, parameters of gas type, introduction pressure P, neutral cluster ionization conditions (acceleration voltage Ve of thermoelectrons used for ionization and thermoelectron current Ie detected at the anode) and acceleration voltage Va are used as parameters. did. Since the cluster ion size distribution changes depending on the beam generation conditions, the beam convergence state changes even if the parameters of the lens 17 are the same. For this reason, it is desirable to create a database of the above relationship under the generation conditions for each beam.

  Next, in a region of z shorter than the focal length of the lens, the relationship between z and processing speed was examined for various processing region sizes, and a database was created. Silicon was used as the material. FIG. 4 shows data when the processing region size is 1 mm square and 50 mm square.

  By accurately grasping the relative position of the Faraday cup and the sample in advance, the beam profile can be accurately associated with the processing speed.

  Next, with respect to a sample chip of SKD11 (die steel), which is a material to be processed, the processing speed at z = 35 mm when the processing region was 1 mm square was examined. As a result, the processing speed was 28 nm / min. The processing speed ratio with silicon was 0.67, and this value was registered in the database.

  By measuring the beam profile with respect to the value of z, the relationship between z and the beam size and the relationship between z and the total beam current value can be obtained. These secondary relations are also stored in the database. The graph of the relationship between z and beam size shown in FIG. 2 and the relationship between z and the total beam current value shown in Table 1 of FIG. 3 are obtained in the process of creating such a database. Are gas types Ar, P = 0.6 Mpa, Va = 20 kV, E1 = 18 kV, E2 = 15 kV, Ve = 300 V, Ie = 300 mA.

  The workpiece 19 having the shape shown in FIG. 7 was processed according to the following procedure. The constituent material of the workpiece 19 was SKD11 (die steel). The region A and the region B of the processing object 19 are etched by an average depth of 100 nm and flattened. The size of the region A is 50 mm square, and the size of the region B is 1 mm square.

(1) Referring to the database, the distance z at which the average machining speed in the region A is the largest is calculated from z and machining speed distribution data. As a result, z = 10 mm is obtained. Similarly, it calculates also about the area | region B, and obtains z = 35mm as a result.
(2) Referring to the database, the time required for 100 nm etching at the position of z = 10 mm (processing position in region A) is calculated from the z and processing speed distribution data and the ratio of the processing speed of silicon and SKD11. To do. As a result, an irradiation time of 20.0 minutes is obtained. Similarly, a position where z = 35 mm (processing position in region B) is calculated, and 3.63 minutes are obtained as a result. The current beam current value at z = 10 mm and 35 mm is monitored, and if there is a deviation between z on the database and the data value of the total beam current value, the irradiation time is corrected by proportional calculation.
(3) Subsequently, the triaxial stage 21 is moved so that the center of the region A is located at a position where z = 10 mm.
(4) Irradiate the gas cluster ion beam for 20.0 minutes.
(5) Next, the triaxial stage 21 is moved so that the center of the region B is located at a position where z = 35 mm.
(6) Irradiate the gas cluster ion beam for 3.63 minutes.
Thus, the processing is completed.

  Referring to Table 1 in FIG. 3, it can be seen that the processing speed in the 1 mm square region of the center of the beam is the shortest when z = 35 mm. The processing speed depends on the beam current value as well as the magnitude of the sputtering rate, but in the measured z range, the change in the beam current value is smaller than the difference in the sputtering rate, and as a result, the sputtering rate becomes the largest z = 35 mm. It is considered that the processing time was the shortest in (see FIG. 2).

  On the other hand, when the 50 mm square region is etched at a uniform depth, the position at z = 10 mm has the highest processing speed. This is because the irradiation area is larger than the beam size, so that the processing speed was the highest at the distance where the beam current value (total beam current value) of the entire irradiation area was larger than the height of the sputtering rate at the center position of the beam. It is done.

  When a 20 mm square region is machined, it is intermediate between the 1 mm square and the 50 mm square, and the machining speed is considered to be maximized at z = 20 mm.

  As described above, it can be seen that the position of z at which the processing speed is maximized differs depending on the size of the irradiation region. That is, the processing speed can be maximized by adjusting the position of z according to the size of the irradiation area.

  Further, referring to FIG. 4, when the processing area is about 1 mm square and smaller than the beam size, the processing speed becomes the largest in the range of z = 30 to 35 mm with respect to the focal length of the beam of 50 mm, and the change thereof. Is relatively small. That is, it can be seen that the processing speed can be increased by performing processing by selecting the irradiation position within the range of 60% to 70% of the focal length.

  As described above, in the present invention, data of change in the current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam focused by the lens with respect to the coordinates in the irradiation axis direction is obtained by actual measurement. The change in the etching speed for each area of the processing target area in the irradiation axis direction range shorter than the focal length of the gas cluster ion beam determined from the current density distribution data with respect to the coordinates in the irradiation axis direction. Based on this, the coordinates in the direction of the irradiation axis where the solid surface to be processed is set are determined for each area of the processing target area, and this enables irradiation that can be processed at the highest speed according to the size of the processing target area. The position can be selected and processed, and therefore the processing speed can be improved as compared with the conventional method.

  In addition, if the current density distribution data is measured again before processing the solid surface, and the coordinates in the irradiation axis direction where the solid surface is installed are corrected based on the result of the re-measurement, it is more accurate. The optimum processing position can be obtained.

  On the other hand, in order to perform processing more simply than the method described above, only the data on the change of the current density distribution with respect to the coordinates in the irradiation axis direction is measured, and the focal length of the gas cluster ion beam and its focal length are measured. When the area of the region to be processed is smaller than the cross-sectional area of the beam size, the coordinates in the irradiation axis direction where the solid surface to be processed is set are 60% to 70% of the focal length. % May be selected for processing.

  As described above, the example of measuring the etching depth distribution has been described as a specific example of processing. As an evaluation index after processing, not only etching depth but also surface roughness distribution and surface damage depth can be measured and databased. Thereby, in order to set the average surface roughness and the processing damage depth of the processing target region to the optimum values, the present invention can be applied to the case where the irradiation position where the processing speed is maximized is set.

  In addition, in the database, for materials considered as processing targets, the processing speed is checked only at a specific z for a certain processing area size, and the ratio of the processing speed of silicon is registered in the database to determine what kind of material. Also, by referring to the database, it is possible to determine the irradiation position at which the processing speed is maximized.

Claims (4)

A method of processing a solid surface using a gas cluster ion beam focused by a lens,
Data of the change in the current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam with respect to the coordinates in the irradiation axis direction is obtained by actual measurement,
Data on the change in the etching processing speed for each area of the processing target region acquired in the irradiation axis direction range shorter than the focal length of the gas cluster ion beam determined from the current density distribution data with respect to the coordinates in the irradiation axis direction A solid surface processing method characterized in that, based on the area of the region to be processed, coordinates in the irradiation axis direction for setting the solid surface to be processed are determined. The solid surface processing method according to claim 1,
Before processing the solid surface, the current density distribution data is re-measured, and the coordinates in the irradiation axis direction where the solid surface is installed are corrected based on the result of the re-measurement. Processing method. A method of processing a solid surface using a gas cluster ion beam focused by a lens,
Measured data of the current density distribution in the in-plane direction perpendicular to the irradiation axis of the gas cluster ion beam with respect to the coordinates in the irradiation axis direction, and the focal length of the gas cluster ion beam and the position of the focal length And the cross-sectional area of the beam size defined by half the maximum value of the current density in
If the area of the region to be processed is smaller than the cross-sectional area of the beam size, processing is performed by selecting the coordinates in the irradiation axis direction where the solid surface to be processed is set within the range of 60% to 70% of the focal length. A method of processing a solid surface, characterized in that: An apparatus for processing a solid surface using a gas cluster ion beam,
A gas cluster ion beam generator for emitting a gas cluster ion beam;
A lens for focusing the gas cluster ion beam;
A three-axis stage capable of moving the solid surface to be processed in the irradiation direction of the gas cluster ion beam and in two orthogonal directions perpendicular to the irradiation axis;
A beam current detector mounted on the 3-axis stage,
The gas cluster ion beam detected by the beam current detector is determined from the change data of the current density distribution in the in-plane direction perpendicular to the irradiation axis with respect to the coordinates in the irradiation axis direction and the data of the current density distribution. It has a database including data on changes in etching processing speed for each area of the processing target region acquired in a range in the irradiation axis direction shorter than the focal length of the gas cluster ion beam in the previous period, with respect to coordinates in the irradiation axis direction,
Referring to the database, the coordinates in the irradiation axis direction for setting the solid surface to be processed are calculated for each area of the processing target region, and the three-axis stage is positioned. Solid surface processing equipment.

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