JP4220156B2 - Surface planarization of silicon films during and after processing by sequential lateral crystallization. - Google Patents

Description

[0001]
(Background of the Invention)
I FIELD OF THE INVENTION The present invention relates to semiconductor processing technology, and more particularly to semiconductor processing that can be performed at low temperatures.
[0002]
II Description of Related Art In the field of semiconductor processing, there have been several attempts to use lasers to convert thin amorphous silicon films into polycrystalline films. An overview of conventional excimer laser annealing (heat treatment) technology is disclosed in James Im et al., "Crystalline Si Films for Integrated Active-Matrix Liquid-Crystal Displays", 11 MRS Bulletin 39 (1996). In systems used to perform excimer laser annealing, the excimer laser beam is shaped into a long beam, typically up to 30 cm long and 500 μm wide or wider. The shaped beam is scanned over a sample of amorphous silicon to promote melting of the sample and formation of polycrystalline silicon as the sample resolidifies.
[0003]
The use of conventional excimer laser annealing techniques to produce polycrystalline or single crystal silicon is problematic for several reasons. First, the silicon produced by the process is usually a random microstructure with small grain size and / or non-uniform grain size, resulting in poor and non-uniform devices. This can reduce the manufacturing yield. Second, the processing technology required to obtain an acceptable level of performance requires that manufacturing throughput to produce polycrystalline silicon remain low. Also, these processes generally require a controlled environment and pre-heating of the amorphous silicon sample, further reducing the processing rate. Lastly, the fabricated films generally have an unacceptable degree of surface roughness, which can be a problem for the performance of microelectronic devices.
[0004]
There is a need in the field to produce higher quality polycrystalline and single crystal silicon at higher processing speeds. There is also a need for manufacturing techniques that reduce the surface roughness of such polycrystalline and single crystal silicon thin film films used in the fabrication of higher quality devices such as flat panel displays.
[0005]
(Summary of Invention)
An object of the present invention is to provide a technique for planarizing the surface of polycrystalline and single crystal thin film semiconductors.
[0006]
It is a further object of the present invention to provide a surface planarization technique that can be applied as a post-processing step for polycrystalline and single crystal thin film semiconductors produced during a sequential lateral crystallization (SLS) process. There is.
[0007]
It is a further object of the present invention to provide a surface planarization technique that can be applied as a processing step during the production of polycrystalline and single crystal thin film semiconductors in a sequential lateral crystallization process.
[0008]
It is a further object of the present invention to provide techniques for producing high quality semiconductor devices that are useful in the production of displays and other products.
[0009]
In order to achieve these objectives, as well as other objectives that will become apparent with reference to the following description, the present invention provides surface roughness of polycrystalline and single crystal thin film previously produced by a sequential lateral crystallization process. A system and method for reducing the likelihood is provided. In one configuration, the system causes an excimer laser that generates a plurality of excimer laser pulses of a predetermined flux amount (fluence) and the flux amount of the excimer laser pulses to completely melt the thin film in the thickness direction. A beam attenuator that can be controlled in a controlled manner so that the amount of flux is equal to or less than the amount of flux required for the above, a beam homogenizer that homogenizes the modulated laser pulse in a predetermined plane, and the uniform A sample stage (sample stage) for performing partial melting in a thickness direction of a portion corresponding to the laser pulse of a polycrystalline or single crystal thin film upon receiving a laser pulse, and the laser on the sample stage Translation means for controllably translating the relative position with respect to the pulse, and generating the excimer pulse and modulating the flux amount relative to the sample stage. Performed together, therefore, by sequentially translating the sample stage relative to the laser pulse, which comprises a computer for processing polycrystalline or single crystal thin film. The excimer laser is preferably an ultraviolet excimer laser that generates ultraviolet excimer laser pulses.
[0010]
In one configuration, the beam homogenizer is operable to shape a laser pulse with top-hat characteristics in both the x and y directions. The beam attenuator operates to attenuate the flux amount of the excimer laser pulse from about 25% to 75% of a threshold value for completely dissolving the polycrystalline or single crystal thin film in the thickness direction. enable.
[0011]
(Description of preferred embodiments)
The translation stage includes a translation unit in the X direction and a translation unit in the Y direction. These units are coupled to the computer and coupled to each other, and two perpendicular to the path formed by the laser pulse. It is advantageous to be able to move in orthogonal directions and be controllable by the computer, the computer controllably translating the sample in both directions which can be translated under the control of the computer. . Further, the beam homogenizer is operable to shape the laser pulse in a top hat type characteristic in both the x and y directions, and the translation means includes the polycrystalline or single crystal thin film, Operable to translate in two directions perpendicular to the direction of the laser pulse, so that the homogenized laser pulse overlaps little by little in the two directions of the polycrystalline or single crystal thin film. Incidently enter the region.
[0012]
The modified configuration of the present invention provides a system and method for processing an amorphous silicon thin film sample into a single crystal or polycrystalline silicon thin film with reduced surface roughness. In one configuration, the method is performed on an amorphous silicon thin film sample having a thickness sufficient to withstand shrinkage and expansion during melting and resolidification of the thin film silicon during a sequential lateral crystallization process. Forming a rigid cap layer. The method includes the steps of generating an excimer laser pulse train, modulating each excimer laser pulse in the pulse train to a predetermined flux amount in a controllable manner, and modulating and controlling the flux amount in the pulse train. A step of uniformizing each laser pulse in a predetermined plane, and masking a part of each laser pulse in the pulse train that has been uniformized to control the flux amount, thereby patterning and controlling the flux amount. Generating a pulse train of beams, irradiating an amorphous silicon thin film sample with a pulse train of small beams patterned by controlling the amount of flux, and performing partial melting in the thickness direction of the sample; The sample is sequentially translated in a controllable manner with respect to each pulse of a small beam patterned by controlling the amount of the flux. Treating a silicon thin film sample into a single crystal or polycrystalline silicon thin film with reduced surface roughness; removing the cap layer from the treated single crystal or polycrystalline silicon thin film; and It has.
[0013]
The accompanying drawings constitute a part of this specification and illustrate the preferred embodiment of the present invention and serve to explain the principles of the invention.
[0014]
Embodiments of the present invention will be described below with reference to the drawings.
The present invention provides a technique for planarizing the surface of polycrystalline and single crystal thin film semiconductors. In a preferred embodiment, this surface planarization technique is applied as a post-processing step to polycrystalline and single crystal thin film semiconductors produced during the sequential lateral crystallization process, or in the sequential lateral crystallization process. Applicable as a processing step in the production of polycrystalline or monocrystalline thin film semiconductors. Therefore, to fully understand these techniques, the sequential lateral crystallization process must first be understood.
[0015]
The sequential lateral crystallization process is a technique that produces a large grain silicon structure by unidirectional narrow translation of a silicon sample between successive pulses emitted by an excimer laser. As each pulse is absorbed by the sample, a small region of the sample is completely melted in the thickness direction and enters the crystal region produced by the previous pulse in the pulse set and resolidifies.
[0016]
A particularly advantageous sequential lateral crystallization process and apparatus for carrying out this process are disclosed in the Applicant's co-pending patent application, Ser. No. 09 / 390,537, filed Sep. 3, 1999, entitled “Systems and Methods using Sequential Lateral Solidification for Producing Single or Polycrystalline Silicon Thin Films at Low Temperatures ", which is incorporated herein by reference. Although the foregoing disclosure has been made with reference to a specific technique described in the applicant's co-pending patent application, other sequential lateral crystallization techniques are readily applicable for the present invention. Is clear.
[0017]
FIG. 1 illustrates a system described as a preferred embodiment in the applicant's co-pending patent application, which includes an excimer laser 110, an energy density modulator 120 that rapidly changes the energy density of the laser beam 111, and Beam attenuator / shutter 130, optical devices 140, 141, 142, and 143, beam homogenizer 144, lens systems 145, 146, and 148, masking system 150, and lens systems 161, 162, and 163 An incident laser pulse 164, a thin film silicon film sample 170, a sample translation stage (stage) 180, a graphite block 190, support systems 191, 192, 193, 194, and a management computer 100. Mask in masking system 150 under 100 instructions 10 movement of, either by movement of the sample translation stage 180 performs parallel movement in the X and Y directions of the silicon sample 170.
[0018]
As described in more detail in the applicant's co-pending application, a plurality of excimer laser pulses of a predetermined flux amount are generated and the flux amount of the excimer laser pulses is modulated in a controllable manner. Then, the modulated laser pulse is made uniform in a predetermined plane, and a part of the modulated and uniform laser pulse is masked to form a patterned small beam, and the amorphous silicon thin film sample is patterned. Irradiating with a beam to melt the portion of the sample corresponding to the small beam and translating the sample in a controllable manner with respect to the patterned small beam and the controlled modulation. A silicon thin film sample is processed into a single crystal or polycrystalline silicon thin film, so that the patterned small beam The sample pattern amorphous silicon thin film sample is processed by sequentially translating the sample and sequentially irradiating the corresponding position on the sample with a patterned beam of variable flux. Crystalline silicon thin film.
[0019]
For the production of single crystal or large polycrystalline silicon thin film films, sequential lateral crystallization processes are very advantageous, but the crystals produced are often melted and regenerated, characteristic of the crystal growth process. The surface roughness due to repeated solidification is shown. For this reason, as shown in FIG. 2, a crystal having a thickness of 200 nm exhibits a variation in height throughout the length of the crystal. In FIG. 2, a height of 0 indicates the optimum height for a 200 nm thick crystal, and a height varying from 175 nm to 225 nm is shown as normal throughout the length of the crystal. In the large protrusion 210 near the crystal boundary, the thickness of the crystal exceeds the optimum thickness of 200 nm by 350 nm.
[0020]
A first embodiment of the present invention will now be described with reference to FIGS. FIG. 3 illustrates an embodiment of a post-processing system for planarizing polycrystalline and single crystal thin film semiconductors produced by a sequential lateral crystallization process. This system includes an excimer laser 310, a beam attenuator / shutter 320, a reflecting plate 330, telephoto lenses 331 and 332, a reflecting plate 333, a beam uniformizer 340, a condenser (condensing) lens 345, A reflection plate 347, a field (field of view) lens 350, a sample 360, a sample translation table 370, an optical table 380, and a management computer 300 are provided. Each of the preferred laser 310, attenuator 320, telephoto lenses 331, 332, homogenizer 340, and sample translation table 370 movable in two orthogonal directions is a co-pending patent application Ser. No. 09 / 390,537. It is described in the application. The table 380 can be as described in this patent application or can be a normal table. Preferably, the homogenized beam 346 is shaped to a top hat shape in both the x and y directions, and the beam energy density is less than or equal to the energy density required to completely melt the sample 360 in the thickness direction. This is very important.
[0021]
The sample 360 will be described in detail with reference to FIGS. 4a and 4b. Since the sample of this example has already been processed, it already contains a number of crystal regions, which are shown schematically as chevron-shaped (mountain) crystals 365. A state in which the homogenized beam 346 is incident on a part 361 of the sample 360 and induces partial melting in the thickness direction thereof is shown.
[0022]
For a 200 nm thick silicon thin film, the threshold for complete melting in the thickness direction is about 600 mJ / cm ² . Therefore, in order to derive a sufficient thickness direction of the partial melting of the portions 361 should utilize beam 346 with an energy of about 25% to 75% of the threshold of complete melting of the thickness direction. If the energy of the beam is larger, the energy fluctuation inherent in the excimer laser can cause complete melting of the sample region 361 in the thickness direction . If the energy of the beam is smaller, the sample portion 361 will not melt sufficiently to be satisfactorily flattened.
[0023]
As shown in FIG. 4 b, the sample 360 includes a silicon oxide base layer 400 and a silicon layer 410. According to the present invention, the outer surface of the silicon layer 410 is melted to a depth 420. Upon resolidification, the rough surface 430 is modified to become more flat.
[0024]
A homogenized single beam pulse having an energy of about 25% to 75% of the full melt threshold in the thickness direction is sufficient to induce partial melt in the thickness direction of region 361, but multiple beams It is preferred to irradiate all of these areas with a pulse. Each subsequent beam pulse leads to partial melting of the region 361 in the thickness direction , which when resolidified results in a more planar surface. Thus, the use of 10 beams per region 361 produces a much smoother surface 430 than with a single pulse.
[0025]
Returning to FIG. 4 a, the sample stage 370 is translated from right to left under the control of the computer 300, and the uniformed beam 346 is scanned from the left to the right 450 on the upper portion of the sample 360. Then, the table 370 is moved in the orthogonal direction (shown as the Y direction), the sample is aligned with the new position 460, and the parallel translation 470 in the reverse direction is started. This process is repeated until the entire surface of the sample 360 has been scanned with the homogenized beam 346.
[0026]
When the sample stage is translated in the Y direction, it is advantageous to match the homogenized beam so that it slightly overlaps the area scanned before the sample 360. For this reason, if the region 361 is 1.2 × 1.2 cm, then a Y-direction translation of 1.15 cm can be used to avoid edge effects caused by uniform beam irregularities. Similarly, it is advantageous to produce a slight overlap during the execution of the translation in the X direction.
[0027]
The above has been described with reference to a beam that is uniformed into a square with a top-hat type characteristic, but beams of other shapes can also be used. For this reason, as shown in FIG. 5, it is possible to use a uniform beam that is sufficiently wide to eliminate the need for translation in the X direction, and the advantage that the need for movement by the translation table 370 is reduced. And thus a greater production capacity is obtained. Similarly, when performing greater overlap between translations in the X direction, a beam shaped with Gaussian characteristics in the X direction can be used.
[0028]
6 and 7 show the results of the process described with reference to FIGS. 3 and 4a. The characteristics of the sample 360 produced by the sequential lateral crystallization process are shown in FIG. 6a. This sample shows surface irregularities with an optimum height of 200 nm to ± 25 nm. As shown in FIG. 6b, these surface irregularities can be significantly reduced after post-treatment with a single laser pulse according to the invention. These results are shown in FIG. 7, which shows a surface roughness reduction of less than 100% caused by the post-treatment according to the invention.
[0029]
Next, a second embodiment of the present invention will be described with reference to FIG. In this example, the surface of the silicon thin film is planarized by employing a rigid cap layer during the sequential lateral crystallization process. Accordingly, FIG. 8 shows a thin film silicon sample formed of an amorphous silicon layer 810 having a thickness of about 50 nm to 200 nm deposited on the base layer 800 of silicon oxide. The sample is covered with a thick second silicon oxide layer 820 having a thickness of about 2 microns, which is substantially rigid. This cap layer must be thick enough to withstand the shrinkage and expansion during melting and resolidification of the silicon layer during the sequential lateral crystallization process.
[0030]
Thus, in a sequential lateral crystallization process, a sample having a cap layer 820 is used instead of sample 170, and a complete description thereof is included in the above-mentioned patent application No. 09 / 390,537. After such processing, cap layer 820 is removed from the sample by conventional wet or dry etching techniques. FIG. 9 shows the results of the process described with reference to FIG.
[0031]
Referring to FIG. 10, the steps performed by computer 300 to control both the sequential lateral crystallization process of FIG. 1 and the surface planarization process realized with respect to FIG. 3 will be described. Various electronic circuits of the system are initialized by computer 300 (1000) to begin the process. Then, the sample is loaded on the sample translation table (1005). Such loading can be performed manually or robotically under the control of the computer 300. Next, the sample is processed 1010 by a sequential lateral crystallization process using the apparatus of FIG. Then, the processed sample is positioned (1015). If necessary, the various optical components of the system are focused (1020). The laser is then stabilized (1025) to the desired energy level and repeatability required to partially melt the sample in the thickness direction in accordance with the teachings of the present invention. If necessary, finely adjust the attenuation of the laser pulse (1030).
[0032]
Next, in parallel with the region of the sample that has been subjected to the sequential lateral crystallization process, the sample starts to move in a predetermined direction at a predetermined speed (1035). The shutter is then opened (1040) and the sample is exposed by irradiation, thereby starting the planarization process.
[0033]
Until flattening is completed (1045), the sample continues to be translated and irradiated (1050), at which point the computer closes the shutter (1055) and stops the translation (1060). If another region on the sample is selected for flattening (1065), the sample is repositioned (1066) and the process is repeated with the new region. If an area for further planarization has not been selected, the laser is turned off (1070), the hardware is turned off (1075), and the process is terminated (1080).
[0034]
Referring to FIG. 11, the steps performed by computer 100 along with the surface planarization steps performed with respect to FIG. 1 to control the crystal growth process will be described. FIG. 10 is a flow diagram showing the basic steps performed in the system of FIG. 1 using a capped sample as shown in FIG. An oxide layer is deposited on the base (1100). Then, a silicon layer is deposited on the oxide buffer layer (1110), and a cap oxide is deposited on the upper layer portion of the sample (1120).
[0035]
The sample of FIG. 1 is then used to process the sample according to a sequential lateral crystallization process. After the treatment, the cap oxide is removed, for example, by dissolution with dilute hydrofluoric acid.
The foregoing merely illustrates the principles of the invention. Various modifications and alternatives to the described embodiments will be apparent to those skilled in the art in light of the teachings herein. For example, the removal of the cap layer is disclosed with respect to the use of dissolution in dilute hydrofluoric acid, but the cap layer can be removed by any conventional technique such as dry etching. Thus, although not explicitly described herein, it will be apparent to those skilled in the art that the principles of the present invention may be embodied and thus numerous systems and methods within the scope of the present invention may be implemented by those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a functional diagram of a system that performs a sequential lateral crystallization process suitable for implementing the preferred process of the present invention.
2 shows the surface properties of a conventional film processed by the sequential lateral crystallization process of FIG.
FIG. 3 is a functional diagram of a preferred system for planarizing the surface of a polycrystalline or single crystal thin film semiconductor produced during a sequential lateral crystallization process according to the present invention.
4a and 4b schematically show a crystalline silicon film to be processed by the system of FIG. 3 using a narrow beam.
FIG. 5 schematically illustrates a crystallized silicon film to be processed by the system of FIG. 3 using a broad beam.
FIG. 6 is a diagram showing surface characteristics of a normal film before processing by the system of FIG. 3;
FIG. 7 is a diagram showing surface characteristics of a normal film after processing by the system of FIG. 3;
8 schematically shows a cross-section of a crystallized silicon film processed by the system of FIG. 1, according to a second embodiment of the present invention.
FIG. 9 shows the characteristics of a normal film processed according to the second embodiment of the present invention.
10 is a flow diagram illustrating steps performed in the system of FIG. 3 according to a first embodiment of the present invention.
11 is a flow diagram illustrating steps performed in the system of FIG. 1 according to a second embodiment of the present invention.

Claims (17)

In a system for reducing the surface roughness of a polycrystalline or monocrystalline thin film produced by a sequential lateral crystallization process by performing partial melting of the polycrystalline or monocrystalline thin film,
(a) an excimer laser that generates a plurality of excimer laser pulses of a predetermined flux amount;
(b) optically coupled to the excimer laser, and the excimer laser is such that the flux is a flux required to partially melt the polycrystalline or single crystal thin film. A beam attenuator that controllably modulates the flux of the excimer laser pulse to be emitted;
(c) a beam homogenizer optically coupled to the beam attenuator and homogenizing the modulated laser pulse in a predetermined plane;
(d) a sample stage optically coupled to a mask, on which the polycrystalline or single-crystal thin film is placed to receive the uniformed laser pulse, and the polycrystalline or single-crystal thin film The part of the film corresponding to the homogenized laser pulse is the part that was previously completely melted and re-solidified into a crystalline region, partially melted by the homogenized laser pulse,
The system further includes:
(e) parallel movement means coupled to the sample stage and for controllably translating the relative position of the sample stage with respect to the homogenized laser pulse;
(f) Coupled to the excimer laser, the beam attenuator , and the translation means, the controllable modulation of the flux amount of the excimer laser pulse, and the sample stage and the uniformized laser pulse Controlling the controllable relative position, and generating the excimer laser pulse and modulating the flux amount according to the relative position of the sample stage and the homogenized laser pulse, A computer that sequentially processes positions corresponding to the laser pulses on the polycrystalline or single crystal thin film by sequentially translating the sample stage with respect to the homogenized laser pulses. Feature system.   The system of claim 1, wherein the excimer laser is an excimer laser that generates ultraviolet excimer laser pulses.   The system of claim 1, wherein the beam homogenizer is operable to shape the laser pulse to top-hat characteristics in both the x and y directions. The beam attenuator operates to attenuate the flux amount of the excimer laser pulse from 25% to 75% of a threshold value for completely melting the polycrystalline or single crystal thin film in the thickness direction. The system of claim 1, wherein the system is possible.   The translation means comprises the sample stage, the sample stage comprises a Y-direction translation unit, and the Y-direction translation unit is coupled to the computer in the direction of the uniform laser pulse. By the computer to enable translation in one orthogonal direction and to controllably translate the polycrystalline or monocrystalline thin film in the translatable direction under the control of the computer. The system of claim 1, wherein the system is controllable.   The beam homogenizer is operable to shape the laser pulse into a top-hat characteristic in at least the direction orthogonal to the laser pulse, and the homogenized laser pulse is formed from the polycrystalline or single crystal thin film The parallel movement means is operable to translate the polycrystalline or single crystal thin film in the direction perpendicular to the direction of the uniformized laser pulse so that the light beams are sequentially incident on the overlapping regions. 6. The system of claim 5, wherein there is a system.   The translation means comprises the sample stage, the sample stage comprises a translation part in the X direction and a translation part in the Y direction, each of the translation parts being coupled to the computer and mutually Combined, the X-direction and Y-direction translation units are movable in two orthogonal directions perpendicular to the path formed by the uniformized laser pulse, and the sample stage is controlled by the computer. 2. The system of claim 1, wherein the system is controllable by the computer to controllably translate in both the translatable directions.   The beam homogenizer is operable to shape the modulated laser pulse in a top hat shape in both the x and y directions, and the homogenized laser pulse is applied to the polycrystalline or single crystal thin film film. The parallel movement means should translate the polycrystalline or single crystal thin film in two directions orthogonal to the direction of the uniformized laser pulse so as to sequentially enter a region that overlaps little by little in two directions. The system of claim 7, wherein the system is operable. In a method for reducing the surface roughness of a polycrystalline or single crystal thin film produced by a sequential lateral crystallization process
(a) generating a plurality of excimer laser pulses of a predetermined flux amount;
(b) The flux of the excimer laser pulse emitted by the excimer laser so that the flux amount becomes a flux amount necessary for partially melting the polycrystalline or single crystal thin film. Modulating the quantity controllably;
(c) homogenizing the modulated laser pulse in a predetermined plane;
(d) partially melting the portion corresponding to the homogenized laser pulse of the polycrystalline or single crystal thin film with the homogenized laser pulse, wherein the portion was previously completely melted; A step that is the part that has re-solidified into a crystalline region;
(e) Controllably translating the relative position of the polycrystalline or single crystal thin film with respect to the homogenized laser pulse, so that the homogenized laser pulse is converted into the polycrystal or single crystal thin film. By sequentially translating the polycrystalline or single crystal thin film with respect to the homogenized laser pulse so as to correspond to the positions arranged in order on the film, And sequentially processing corresponding positions.   The method of claim 9, wherein the excimer laser pulse comprises an ultraviolet excimer laser pulse. 10. The method of claim 9 , wherein the step of homogenizing comprises the step of homogenizing the laser pulse to a top-hat type characteristic in both the x and y directions. The step of modulating attenuates the flux of the excimer laser pulse from 25% to 75% of a threshold value for completely melting the polycrystalline or single crystal thin film in the thickness direction ; The method according to claim 9 , comprising: The step of translating comprises the step of controllably translating the polycrystalline or single crystal thin film in one direction orthogonal to the direction of the homogenized laser pulse. Item 10. The method according to Item 9 .   The step of homogenizing comprises the step of homogenizing the laser pulse to a top hat type characteristic at least in the direction orthogonal to the direction of the laser pulse, and the step of translating comprises the step of: Translating the polycrystalline or single crystal thin film in the direction perpendicular to the direction of the uniformized laser pulse so as to sequentially enter a region where the polycrystalline or single crystal thin film overlaps little by little. 14. The method of claim 13, comprising: The step of translating comprises the step of controllably moving the polycrystalline or single crystal thin film in two orthogonal directions perpendicular to the path formed by the homogenized laser pulse. 10. A method according to claim 9 , characterized in that   The step of homogenizing comprises the step of homogenizing the laser pulse into a top hat type characteristic in the two directions orthogonal to the direction of the laser pulse, and the step of translating comprises the step of: Translating the polycrystal or single crystal thin film in the two directions so as to sequentially enter the regions of the polycrystal or single crystal thin film that are slightly overlapped in the two directions. The method according to claim 15. The step of translating includes irradiating at least two beams corresponding to the homogenized laser pulse of the polycrystalline or single crystal thin film, and then paralleling the polycrystalline or single crystal thin film. The method of claim 9 , comprising the step of moving.

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