KR101352452B1 - Systems and methods for implementing an interaction between a laser shaped as a line beam and a film deposited on a substrate - Google Patents

Abstract

Disclosed are a laser crystallization apparatus and method for selectively dissolving a film such as amorphous silicon deposited on a substrate. The apparatus may include an optical system for calculating a stretched laser pulse for use in dissolving the film. In another form of embodiment of the present invention, a system and method for stretching a laser pulse are provided. In another form, a system is provided for maintaining the spread of a pulsed laser beam (stretched or not stretched) within a predetermined range at a location along the beam path. In another form, a system is provided for maintaining energy density in a film within a predetermined range during interaction of the film and forming line beams.

Molded optics, light source, molded line beam, film, energy density, focusing lens, autofocus sensor, light source parameters, controller.

Description

SYSTEM AND METHOD FOR IMPLEMENTING AN INTERACTION BETWEEN A LASER SHAPED AS A LINE BEAM AND A FILM DELAYED ON A SUBSTRATE {SYSTEMS AND METHODS FOR IMPLEMENTING AN INTERACTION BETWEEN A LASER SHAPED A

The present invention claims priority of US patent application Ser. No. 11 / 138,100, filed May 26, 2005, and entitled U.S. Patent No. 6,693,939, entitled "LASER LITHOGRAPHY LIGHT SOURCE WITH BEAM DELIVERY," May 2002. Partially filed in US Patent Application No. 10 / 712,545, filed November 13, 2003, filed November 13, 2003, entitled "LONG DELAY AND HIGH TIS PULSE STRETCHER" And each disclosure is incorporated herein by reference.

The present invention is also part of US Patent Application No. 10 / 781,251 filed on February 18, 2004 entitled "VERY HIGH ENERGY, HIGH STABILITY GAS DISCHARGE LASER SURFACE TREATMENT SYSTEM."

The present invention is also filed on April 29, 2003, entitled " LITHOGRAPHY LASER WITH BEAM DELIVERY AND BEAM POINTING CONTROL. &Quot; Some ongoing applications of 10 / 425,361.

The present invention relates to film crystallization for thin film transistor (TFT's) fabrication purposes, e.g., for the purpose of controlling amorphous silicon film dissolution, e. It relates to a method and system for positioning.

Laser crystallization of amorphous silicon films deposited on substrates, such as glass, is a representative promising technique for the production of material films with relatively high electron mobility. After crystallization, these materials can be used to make thin film transistors (TFT's), and in one particular application TFT's are suitable for use in relatively large liquid crystal displays (LCD's). Other applications of crystallized silicon films include organic LEDs (OLEDs) and system on a panels (SOPs). More specifically, a high volume production system capable of quickly crystallizing a film having a thickness of about 90 nm and a width of about 700 mm or more will be commercially available in the near future. Such a process can be performed using a pulsed laser, for example focused on a first axis, for example a short axis, and optically shaped into a line beam, such as a laser extending on a second axis, for example a long axis. Typically the first and second axes are orthogonal to each other and the two axes are substantially orthogonal to the central ray running toward the film. Exemplary line beams for laser crystallization may have a beam length of about 700 mm and a beam width of about 20 micrometers or less. With this arrangement, the film can be scanned and stepped in a direction parallel to the beam width, for example, to sequentially dissolve and crystallize a film having a substantial length of at least 700 mm.

In some cases, during dissolution it may be desirable to ensure that each portion of the silicon film is exposed to a controlled laser energy density within a preselected energy density range. In particular, it is typically desirable to control the energy density within a preselected range with respect to the position along the forming line beam, and when the line beam is scanned against the silicon film, it is desirable to have a somewhat constant energy density. High energy density levels can cause the film to run down, resulting in undesirable "thin spots", uneven surface profiles, and poor tissue quality. This non-uniform distribution of film materials is often referred to as "agglomeration" and may render the crystallized film unsuitable for a particular application. Low energy density levels, on the other hand, can cause incomplete dissolution and lead to poor tissue quality. By controlling the energy density, films with substantially uniform properties can be achieved.

One factor that can affect the energy density in the exposed film is the spatial relationship of the thin film to the DOF (focal depth) of the pulsed laser. This DOF depends on the focusing lens, but for a typical lens system configured to produce a line beam with a beam width of 20 micrometers, a good estimated DOF may be about 20 micrometers.

In view of the foregoing, it should be understood that a portion of the silicon film that fully belongs to the DOF of the laser will experience a different energy density than the portion of the silicon film that is only partially within the DOF of the laser. Therefore, the surface deviation of the silicon film, the glass substrate, and the vacuum junk surface holding the glass substrate can cause unwanted energy density variations between one film position and the other film position, even if not considered, even deviations as small as a few micrometers. have. In addition, even under controlled manufacturing conditions, the overall surface deviation (ie, vacuum junk + glass substrate + film) can be about 35 micrometers. It should be understood that such surface deviation may be an inherent problem for a focused thin beam with a DOF of only about 20 micrometers.

In addition to surface deviations, unwanted movement of the film with respect to the forming line beam can cause variations in energy density. For example, small movements can occur during stage vibrations. In addition, an inappropriate arrangement of the stage with respect to the shaping beam and / or an inappropriate arrangement of the stage with respect to the scan plane can cause unwanted energy density variations.

Other factors that cause an energy density deviation between one film and another film may include variations in laser output characteristics (eg, pulse energy, beam pointing, beam spread, wavelength, bandwidth, pulse duration, etc.) during the scan. In addition, the position and stability of the shaping line beam during the scan, and the quality of the beam focus can affect the energy density constant.

In view of the above, Applicant discloses several systems and methods for implementing the interaction between a forming line beam and a film deposited on a substrate.

A system and method are disclosed for producing pulses having pulse characteristics suitable for interacting with a film deposition substrate when the forming beam forms a short axis and a long axis. In one form of embodiment of the present invention, a system and method for stretching a laser pulse are provided. The system includes a beam splitter for directing a first portion of a pulse along a first beam path and a second portion of a pulse along a second delayed beam path; And a plurality of positions positioned along the delay beam path, arranged to invert the second beam portion, and cooperating with the beam splitter to place at least a portion of the inverted second beam portion to travel the first beam path. It may include a reflective element.

In another form of embodiment of the present invention, a system and method are provided for maintaining the spread of a pulsed laser beam within a predetermined range at a location along a beam path. The system includes an adaptive beam expander; An apparatus for measuring spread and generating a signal indicative of the spread; And a controller responsive to the signal to adjust the beam expander and maintain the spread of the pulsed laser beam within a predetermined range.

In another form of embodiment of the present invention, a laser crystallization apparatus or method is provided for selectively dissolving a film deposited on a substrate. The apparatus comprises a laser source for producing a pulsed laser output beam; An optical system for stretching a pulse in the laser output beam to produce a pulse stretcher output; And an optical arrangement for calculating the line beam from the pulse stretcher output.

In yet another aspect of an embodiment of the present invention, a system and method are provided for maintaining energy density in a film within a predetermined range during interaction of a forming beam and a film. The system includes an autofocus sensor for measuring the distance between the film and the focusing lens; And a controller used for the measurement to adjust the light source parameter to maintain the energy density in the film in a predetermined range.

1 shows a schematic diagram of the main components of an exemplary production system for crystallizing an amorphous silicon film;

2 shows an apparatus for determining whether a line beam is focused on a film deposited on a substrate;

3A is a first beam having the best focus in the sampled plane, a second beam having the best focus at 10 micrometers from the sampled plane, and a third beam having the best focus at 15 micrometers from the sampled plane. Shows a plot of intensity deviations as a function of uniaxial beam width for three exemplary beams;

FIG. 3B is a diagram showing energy density as a function of lateral growth length, showing areas where partial dissolution and agglomeration can occur;

4 shows a perspective view of a vacuum junk assembly for holding a workpiece during interaction with a line beam;

5A-5Q are schematic plan views illustrating a system and illustrating its use for positioning a silicon film to interact with a line beam;

FIG. 6 shows a schematic diagram of a portion of the system shown in FIG. 1, showing the form of an embodiment of the present invention; FIG.

7 shows a detailed view of a six-mirror pulse stretcher;

8 shows a plot of intensity versus time for stretched and unstretched pulses;

9 shows a plot of intensity vs. vertical width showing an increase in the vertical constant of stretched pulses as compared to unstretched pulses;

10 shows an active controllable beam expander that is adjustable independently of two axes.

Referring first to FIG. 1, there is shown a schematic non-scale view of the major components of an exemplary production system designated generally as system 10 for crystallizing amorphous silicon film 12. As shown, system 10 actively steers a laser source 20 for generating a pulsed laser beam, a pulse stretcher 22 for increasing pulse duration, and a beam and / or beam expander. It may include a beam delivery unit 24 that may include a mechanism for). System 10 further includes a stability measurement module 26 for measuring one or more beam characteristics, such as wavefront and / or beam pointing, and for generating control signals for use by the active steering unit and / or active beam expander. It may include. System 10 also holds optical module 28 for beam homogenization, beam shape, and / or beam focusing, and silicon film 12 deposited on substrate 32, which may be, for example, glass. And a movable stage system 30 for positioning.

Schematically, the system 10 shown in FIG. 1 and described in more detail below has a film 12 thickness (short) of less than about 20 micrometers, a length (longer axis) of greater than 700 nm, and about 10-20 microns. It can be configured to generate a focused thin beam 34, eg a line beam, with a depth of field (DOF) of meters. Each pulse of the focused thin beam can be used to dissolve a strip of amorphous silicon. Thereafter, the strip is crystallized. In particular, the strip crystallizes in a side growth process in which grain grows in a direction parallel to the minor axis. The grain grows inwardly (parallel to the short axis) from the edge and creates a ridge (so-called grain boundary protrusion) along the center of the strip extending out of the plane of the silicon film. The stage is moved gradually or continuously to overlap a portion of the first strip and to expose a second strip parallel to the first strip. During exposure, the second strip is dissolved and then recrystallized. Sufficient overlap may be used to remelt the ridge. By re-dissolving the ridges, a flat film surface (eg, having a peak-to-peak value of ˜15 nm) can be maintained. This process, referred to herein as tb-SLS (thin-beam, sequential lateral solidification), is typically repeated until the entire film has crystallized.

2 shows an apparatus for determining whether a thin beam pulse laser 34 is properly focused on a silicon film 12 deposited on a substrate 32. A portion of the optical module 28 may include a uniaxial field stop 35 and a uniaxial focusing optical member 37. Typically, the beam is first focused at field stop 36 and then imaged in film 12 to yield an intensity profile as shown in FIG. 3A (plot 62). 3A shows a profile (plot 62) for a field stop 36 consisting of slits with small dimensions on the short axis. This arrangement has a beam width (FWHM) of about 13 μm, a strength constant better than 5% along the flat top of the profile, and a steep edge slope that can be less than about 3um between 10% and 90% of the full intensity. It is used to calculate the profile shown in. In addition, a beam with a width of about 5-10 μm can be used. To produce a beam profile with a steep trailing edge slope (i.e., an edge corresponding to a material that does not redissolve during the tb-SLS process), with a single-edge (i.e. blade) leaving the leading edge unaffected Can be used to make slits in field stops. While a single lens is shown, it should be understood that the focusing optical element 37 may include a plurality of optical components, including but not limited to various types of lenses.

2 shows that the beam 36 is not aimed and spreads from the field stop 36 to the film 12 of the long axis 38. As described above, the length of the beam 36 in the long axis 38 may be about 700 nm or more. On the other hand, as shown in FIG. 1, the beam 36 is focused on the minor axis 40 by the optical module 28, which may include the focusing optical member 38. With this arrangement of structures, the light 42 reflected from the film 12 continues to spread out of the optical axis 44 and to a detection system for determining whether the beam 36 is focused properly on the axis 40. Can be analyzed (see FIG. 1).

With continued reference to FIG. 2, the detection system may include a fully reflective mirror 46 that directs reflected light 42 to the image plane 48. Magnification lens 50 is arranged to provide an enlarged image of image plane 48 to camera 52. With respect to the detection system, the image plane 48 is roughly the distance traveled by the reflected light 42 from the film 12 to the image plane 48 and the distance traveled by the same light from the short field stop 36 to the film. Are positioned to be the same (e.g., to the same within acceptable tolerances in the art). The camera output may then be used to adjust one or more system parameters to improve focus at film 12 or to change energy density in film 12, as described in more detail below. . For example, the stage 30 can be moved relative to the focusing optical member 37 to adjust the focus.

In some cases, as shown in FIG. 2, it may be desirable to include a second detection system, similar to the detection system described above, with a mirror 54, a magnification lens 56, and a camera 58. . In this combination, these two detection systems can be used to simultaneously determine whether the light is focused (in short axis) at both ends of the beam in long axis 44. One notable functional form for the detection system shown in FIG. 2 is that the detection system, and in particular the mirrors 46, 54, are positioned so as not to disturb the light traveling from the uniaxial field stop 36 to the substrate 12. . This arrangement also allows the focus of the thin beam to be analyzed and adjusted during exposure of the film 12.

3A shows a plot showing intensity variation as a function of shortened beam width for a focused beam (plot 62), a 10 micrometer out of focus beam (plot 64), and a 15 micrometer out of focus beam (plot 66). do. The plot shown for reference is for a focusing lens with a numerical aperture (NA) of approximately 0.15. An interesting feature of these plots is that all plots 62, 64, 66 have relatively steep sidewalls. This steep sidewall is the result of the optical arrangement shown in FIG. 2 where a uniaxial field stop 36 is used. As such, FIG. 3A shows that the change in beam intensity is more pronounced than the corresponding change in beam width when the beam is out of focus. As already described in the Background section of this specification, it may be desirable to maintain the energy intensity within the predetermined range in the film 12. More specifically, energy density control in the film 12 can be achieved over a range of focus conditions by allowing the characteristics of the laser pulse, such as pulse energy, to change only with small variations within the beam width.

In view of the foregoing, Applicants disclose systems and methods for maintaining energy density within a predetermined range in film 12, for example, by changing pulse characteristics to compensate for changes in focus conditions. Such a change in focus condition may occur, for example, during the scan movement of the stage 30 with respect to the laser beam. More specifically, the energy density obtained with a slightly out of focus beam (eg, plot 66) can be selected as the target energy density. With this target, focus conditions are measured using, for example, the detection system shown in FIG. 2. It should be understood that alternative methods for determining focus conditions may be used to include an autofocus sensor or other suitable technique capable of measuring the distance between the film 12 and the focusing optics 37 (FIG. 2). After the focus condition is measured, pulse characteristics such as pulse energy can be changed to reach the targeted energy density. Therefore, if the measurement indicates that a condition out of focus exists, the first pulse energy E1 corresponding to the target energy density for the out of focus condition is used. On the other hand, if the measurement indicates that the film 12 is in the DOF, the second pulse energy E2 corresponding to the target energy density for the focus condition is used, and E1 < E2.

3B shows a plot showing energy density as a function of side growth length for a 50 nm thick Si film and shows the areas where partial dissolution and agglomeration can occur. 3 also shows that the energy range for side growth can be very wide (approximately 450 mJ / cm 2 and 820 mJ / cm 2), with the side growth length increasing in proportion to the energy density. The larger side growth length then has the advantage of allowing a larger scan pitch while re-dissolving the center ridges.

Several methods can be used to adjust the pulse energy when desired, on a pulse-to-pulse basis in some cases. For example, for an excimer laser source, the discharge voltage can be changed to achieve the desired pulse energy. Alternatively, an adjustable attenuator can be positioned along the beam path of the laser beam to selectively change the pulse energy. For this purpose, any device known in the art for reducing pulse energy can be used, including but not limited to filters and pulse trimmers. Other pulse characteristics that may be altered to compensate for focus conditions to maintain energy density within a preselected range at different locations of the film 12 may be, for example, pulse streams using an adjustable line narrowing module or a line selection module. Ie, wavelength), but is not necessarily limited thereto. Alternatively, an adaptive optical element capable of high speed focus control can be used as the focusing optical element 37 responsive to the focus conditions measured in the controlled feedback loop.

4 and 5A-Q show a system for positioning film 12 for interaction with a focused line beam from a laser source and a corresponding method of use. As shown in FIG. 4, the exemplary positioning arrangement is substantially flat, formed or located as an integral part of a so-called ZRP table 102 (see FIG. 5A), which may include a movable wedge assembly. For example, it may include a vacuum junk 100 having a flat surface 101 (also shown in FIG. 5A) within manufacturing errors in the art.

As best seen with cross reference to FIGS. 4 and 5A, the ZPR table 102 moves the vacuum junk 100 back and forth in the Z direction, the pitch direction in which the junk 100 is rotated about the X axis, and the junk 100. ) May have a function of independently moving in the rotation direction rotated about the Y axis. 5A may also include an X-stage 104 for moving the vacuum junk 100 back and forth in the X direction and a Y-stage 106 for moving the vacuum junk 100 back and forth in the Y direction. It is shown schematically. Typically in an exemplary setup, X, Y, and Z are three mutually orthogonal axes. As shown, the two stages 104, 106 may be movable relative to a stable reference block 108, such as a granite block, that forms a reference surface 110 that is substantially flat (eg, flat within the manufacturing error of the industry). Can be. Typically, air bearings may be employed between the stages 104 and 106 and the granite block 108.

As best seen in FIG. 5B, the system includes, for the illustrated embodiment, three autofocus sensors 112a-c fixedly mounted to the granite block 108 via the overhead housing 114, For example, it may include a plurality of optical sensors that are active or passive autofocus sensors. As shown, the three autofocus sensors 112a-c are spaced apart along the X axis. Typically, these sensors can be located on the X axis or along a line parallel to the X axis. In addition, as shown, each autofocus sensor 112a-c may provide a distance between each autofocus sensor 112a-c and the surface 101, such as distance 116, parallel to the Y axis. Direction for measurement. This then provides a distance, parallel to the Y axis, between the surface 101 and the reference plane 110. While three optical sensors are shown, it should be understood that more than three optical sensors may be used and one optical sensor may be employed to perform all or some of the functional forms detailed above.

5B-5E show how the system can determine the angle of rotation α between the surface 101 and the reference plane 110. More specifically, starting with FIG. 5B, a first measurement (distance 116) can be made between the surface 101 with the table 102 at the first position along the X axis and the autofocus sensor 112A. Can be seen. Next, as shown in FIG. 5C, the table 102 moves along the X axis by moving the X-stage to position the table at a second position along the X axis. In this second position, a second distance measurement is made between the autofocus sensor 112A and the surface 101. Although both measurements are sufficient, FIG. 4D shows that the system can make a third measurement with the table at a third position along the X axis. This measurement can then be processed in an algorithm for determining the angle of rotation α between the surface 101 and the reference plane 110, as shown in FIG. 5E. For reference, a similar procedure (not shown) may be performed by moving the table 102 along the Y-axis to determine the tilt angle of the surface 101 with respect to the reference plane.

After the rotation angle α (and, if desired, the tilt angle) is determined, as shown in FIG. 5F, the ZRP table 102 is surface 101 until it is substantially parallel to the reference plane 110. It is optionally activated to move. At this point, a stage coordinate system can be established. In addition, as shown in FIG. 5G, the three autofocus sensors 112a-c may be calibrated for linearity and distance to the surface 101 over the measurement range. With this calibration, surface 101 can be used as a reference for future measurements (eg, autofocus reference planes).

In one embodiment of the system, the spatial position and direction of the focused line beam of the laser can be determined. An exemplary focused beam that can be characterized by the substantially linear beam axis 118 is shown in phantom in FIG. 5H. For the system shown, pulsed laser light reaches beam axis 118 from above and in front of overhead housing 114. In addition, a portion of the ZRP table 102 extends outwardly along the Y-axis from the overhead housing 114 so that a portion of the surface 101 of the table 102 can be exposed to the pulsed laser.

As shown in FIG. 5H, the system is, in the illustrated embodiment, a detector, which may be a line beam camera 120, for measuring a position relative to a plurality of thin beam focus positions (eg, the best focus position). It may include. More specifically, as shown, a line beam camera 120 can be installed in the line ZRP table 102 and, thus, is movable like that table. It should be understood that an arrangement with a plurality of line beam cameras (not shown) may be used to measure the plurality of line beam focal positions without movement of the X-stage.

5I-5L show how a system with a camera 120 can determine the spatial position of the beam axis 118 and the relative angle φ between the surface 101 and the beam axis 118. More specifically, beginning with FIG. 5I, the first measurement is parallel to the Y-axis, between the beam axis 118 and the reference plane 110, with the table 102 in a first position along the X-axis, It can be seen that it is performed by the camera 120 (representing the distance 122a). Then, as shown in FIG. 5J, the table 102 can be moved along the X-axis by activation of the X-stage 104 to position the table in a second position along the X-axis. In this second position, a second distance measurement 122a, parallel to the Y-axis, may be performed by the camera 120. In some cases two measurements are sufficient, but FIG. 5K shows that the system can perform a third measurement (distance 122c), for example with table 102 at a third position along the X-axis. This measurement can then be processed in an algorithm for determining the angle of rotation α between the surface 101 and the beam axis 118, as shown in FIG. 5L.

After the angle of rotation α between the surface 101 and the beam axis 118 is determined, as shown in FIG. MF, the ZRP table 102 shows that the surface 101 is substantially parallel to the beam axis 118. In one arrangement, the table 102 may be selectively activated to move and orient the table. After being arranged, FIG. 5N shows that autofocus sensors 112a-c can be used to measure the position of surface 101 and calibrate autofocus sensors 112a-c on an autofocus reference plane. This then establishes a laser / stage coordinate system.

5O shows that the glass substrate 32 and the deposition film 12 can be placed on a vacuum junk (ie, surface 101). As shown, the X-stage 104 may be activated to move the table 12 to a suitable position to facilitate positioning of the film 12 on the surface 101. With the film located on the table 102, the table 102 can be moved to interact with the autofocus sensors 112a-c as shown in FIG. 5P. Autofocus sensors 112a-c may be used to determine the height of film 12. With the height of the film 12 found, the ZRP table 102 can be activated to move the film 12 into the depth of focus (DOF) of the focused line beam as shown in FIG. 5Q. Along with the film 12 in the DOF of the laser, the laser can be activated to expose and dissolve the strip of film 12, eg, as part of the tb-SLS process described above.

In another form of embodiment of the present invention, the system shown in FIGS. 5A-5Q may be used to compensate for a film 12 having an incomplete, non-planar surface. This deviation in surface profile may be due to the dimensional imperfections of the film 12, the glass substrate 32, and / or the vacuum junk surface 101. By compensating for the deviation of the surface profile, a substantially constant energy density can be maintained at different locations of the film 12. For this purpose, as shown in FIG. 5P, the method uses three autofocus sensors 112a-c to determine each of the three distances, parallel to the Y-axis, between the sensor and the film 12. It may include a second step using. Using the line beam camera 120, the ZRP table 102 is adapted by varying (Z, pitch, and roll) to position the surface 101 along the line of best focus (eg, beam axis 118). Can be adjusted manually. Then, each distance between each sensor 112a-c and the film 12 may be stored as a reference distance resulting in three coordinate points on the film 12. A linear fit through these three coordinate points can be used to determine the best focal line (axis 118) that has been calculated. During exposure, when the film 12 is scanned along the Y-axis, the distance to the film 12 can be measured by, for example, three autofocus sensors 112a-c resulting in three new coordinate points. have. Then, the best fit line passing through the new coordinate point can be calculated, and the ZRP table 102 allows the best fit line and the calculated best focal line (axis 118) to be substantially the same (e.g., Can be adjusted via computer control to arrange the table 102, to match within acceptable tolerances in the industry.

FIG. 6 shows a portion of the system 10 shown in FIG. 1 in more detail. More specifically, FIG. 6 shows an exemplary embodiment with two chambers, an excimer laser 20. Seeding a solid state laser, an excimer laser with one chamber, an excimer laser with two or more chambers, such as an oscillator chamber and two amplification chambers (with parallel and series amplification chambers), or one or more excimer amplification chambers. It is to be understood that other types of laser sources can be used in the system 10, including solid state lasers. Other designs are possible. A more detailed description of the two chamber laser sources 20 shown in FIG. 6 is described in US Application No. 10 / 631,349, 2003, filed July 30, 2003 entitled “CONTROL SYSTEM FOR A TWO CHAMBER GAS DISCHARGE LASER”. US Application No. 10 / 356,168, filed Jan. 31, 2013, filed "METHOD AND APPARATUS FOR CONTROLLING THE OUTPUT OF A GAS DISCHARGE", filed Dec. 18, 2003. United States Application No. 10 / 740,659, filed September 30, 2003, filed US Application No. 10 / 676,907, September 30, 2003, filed GAS DISCHARGE MOPA LASER SPECTRAL ANALYSIS MODULE. U.S. Application No. 10 / 676,224 entitled "OPTICAL MOUNTINGS FOR GAS DISCHARGE MOPA LASER SPECTRAL ANALYSIS MODULE", US Application No. 10 / 676,175, filed September 30, 2003 , Filed June 30, 2003, filed "CONTROL SYSTEM FOR U.S. Application No. 10 / 631,349, filed on June 24, 2003, entitled "TWO CHAMBER GAS DISCHARGE LASER," US Application No. 10 / entitled "VERY NARROW BAND, TWO CHAMBER, HIGH REP-RATE GAS DISCHARGE LASER." 631,349, filed on June 25, 2003, entitled "METHOD AND APPARATUS FOR COOLING MAGNETIC CIRCUIT ELEMENTS," US Patent No. 10 / 607,407, filed August 20, 2004, entitled "TIMING CONTROL FOR TWO-CHAMBER GAS DISCHARGE LASER." US Patent No. 6,625,191 entitled "HIGH REP RATE MOPA LASER SYSTEM" and US Patent No. 6,567,450 entitled "BASIC MODULAR MOPA LASER SYSTEM". And all of these disclosures are incorporated herein by reference.

6 schematically shows that two chamber laser sources 20 may include a master oscillator 208 and a power amplifier 210, and thus are often referred to as a so-called MOPA laser source. In the implementation of the tb-SLS process described above, a 6Khz (6000 pulses per second) MOPA laser can be used with a pulse energy of approximately 150mJ. With this arrangement, a 730 mm x 920 mm film can be processed (with 60 percent overlap) in about 75 seconds.

The master oscillator 208 and the power amplifier 210 each comprise two elongated electrodes, a laser gas such as XeCl, XeF, ArF, KF, a vertical fan for circulating the gas between the electrodes, and one or more (not shown). A discharge chamber, which may include a water cooled fin heat exchanger. The master oscillator 208 produces a first laser beam 214A that can be amplified through the power amplifier 210, for example by two passing, to produce the laser beam 214B. The master oscillator 208 may include a resonant cavity formed by the output coupler 208A, and a line narrowing module 208B, all of which are described in detail in the above referenced patents and applications. The gain medium for the master oscillator 208 is approximately 30-50 cm long, respectively, and can be calculated between two electrodes housed within the master oscillator discharge chamber.

The power amplifier 210 may include a discharge chamber similar to the discharge chamber of the master oscillator 208 to provide a gain medium between two elongated electrodes. However, unlike the master oscillator 208, the power amplifier 210 typically does not include a resonant cavity, and generally the gas pressure is maintained higher than the pressure of the master oscillator 208. The MOPA structure shown in FIG. 6 allows the master oscillator 208 to be designed and operated to maximize beam quality parameters such as wavelength stability and provide very narrow bandwidths, while the power amplifier 210 maximizes power output. Can be designed and operated.

The output beam 214A of the master oscillator 208 can be amplified by, for example, passing through the power amplifier 210 twice to yield the output beam 214B. The optical components to achieve this are three, which Applicants name Master Oscillator Wavefront Engineering Box (MO WEB 224), Power Amplifier Wavefront Engineering Box (PA WEB 226), and Beam Inverter (BR 228). Can be housed in a module. Together with the line narrowing module 208B and the output coupler 208A, these three modules can be installed on a single vertical optical table independent of the discharge chamber 208C and the discharge chamber of the power amplifier 210. With this arrangement, chamber vibrations caused by acoustic shock and fan rotation can be substantially isolated from the optical component.

The optical components in line narrowing module 208B and output coupler 208A are described in more detail in the above referenced applications and patents. In general, the line narrowing module (LNM) 208B may include three or four prism beam expanders, ultrafast response tuning mirrors, and gratings disposed in a litrow structure. The output coupler 208A can typically include a partially reflective mirror that reflects about 20 percent of the output beam for the KrF system and about 30 percent for the ArF system. The remaining unreflected light passes through output coupler 208 and passes to line center analysis module (LAM) 207. From the LAM 207, light can pass to the MO WEB 24. The MO WEB may include an internal total reflection (TIR) prism (or a first surface mirror with a high reflective coating), and an arrangement component for precisely directing the output beam 214A to the PA WEB 226.

PA WEB 226 may include an array component for directing the TIR prism (or first surface mirror with high reflective coating) and the laser beam 214A through the power amplifier gain medium to the first pass. The beam inversion module 228 may include a double-reflection beam inversion prism that relies only on total internal reflection and thereby does not require optical coating. Alternatively, the beam inverter 228 may be a fully reflective mirror. In this case, the beam inverter 228 is in response to a control signal from the measurement device, eg, the SMM 26, to direct the partially amplified beam onto the preselected beam path through the power amplifier gain medium. It may be adjustable. In particular, the beam inverter may be adjusted to correct for beam pointing errors and to reduce beam spread of the beam exiting the pulse stretcher 22, as described below.

After inversion in the beam reversal module 228, the partially amplified beam 214A may make another pass through the gain medium in the power amplifier 210, and may cause the spectral analysis module 209 and the PA WEB 226 to pass through. Through the power amplifier output beam 214B. From PA WEB 226, the beam increases the pulse duration, reduces beam intensity fluctuations (ie, smooths or averages the intensity profile) across the beam section, as described below, and beam coherence. ), For example, enters the 6-mirror pulse stretcher 22. By increasing the pulse duration, the peak intensity of each laser pulse is reduced while maintaining the pulse energy. For the system 10 shown in FIG. 1, the optical components in the optical module 28 include relatively large lenses that are difficult and expensive to manufacture. These expensive components are often prone to degradation due to billions of high intensity ultraviolet pulses. It is also known that optical damage increases the intensity of laser pulses (ie, optical power (energy / hour) per cm.sup. 2 or mJ / ns-cm.sup. 2). Therefore, reducing the pulse intensity by increasing the pulse duration can increase the lifetime of these optical components. Increasing the pulse duration may also be advantageous in the crystallization process. One disclosed in co-pending US application Ser. No. 10 / 712,545 entitled “LONG DELAY AND HIGH TIS PULSE STRECHER,” filed November 13, 2003, with or instead of 6-mirror pulse stretcher 22. The above pulse stretchers can be used to generate stretched pulses for use in the tb-SLS process described herein, in particular pulse stretchers with output pulses of 200 ns TIS. US Application No. 10 / 712,545 is hereby incorporated by reference.

FIG. 7 shows a more detailed view of the six-mirror pulse stretcher 22 showing the beam path through the pulse stretcher 22. Beam splitter 216 may be selected to reflect a percentage of power amplifier output beam 214B in the delay paths generated by six focusing mirrors 320A, 320B, 320C, 320D, 320E, 320F. The remaining light is transmitted through the beam splitter 216. It should be understood that the reflection / pass characteristics of the beam splitter may affect the output pulse duration and / or output pulse shape. For the stretcher 22, each mirror 320A-F may be a focusing mirror, such as a convex spherical mirror. Typically, to facilitate the arrangement of the pulse stretcher 22, one or more of the six mirrors may be capable of, for example, tip / tilt adjustment.

As shown in FIG. 7, the light reflected from the beam splitter 216 travels unfocused (ie, substantially parallel) along the path 301A to the mirror 320A, and then with the mirror 320A. A portion of the reflection along the path 301B may be focused to a point 302 located midway between the mirrors 320B. This beam then spreads and is reflected from the mirror 302B, and the spreading beam is converted into a parallel (ie substantially parallel) beam and directed along the path 301C to the mirror 320C. Mirror 320C may then focus the reflected portion along path 301D to point 304 located midway between mirror 320C and mirror 320D. This beam can then spread and be reflected from the mirror 320D, which spreads the beam into a parallel (ie substantially parallel) beam and is directed along the path 301E to the mirror 320E. . Mirror 320E may then focus the reflected portion along path 301F to point 306 located midway between mirror 320E and mirror 320F. This beam can then spread out and be reflected from the mirror 320F, and the spreading beam is converted into a parallel (ie substantially parallel) beam and directed along the path 301G with the beam splitter 216 do. In beam splitter 216, the beam from mirror 320F may be reflected in a path 301H that merges the portion of the pulse transmitted through beam splitter 216 with it. Together, some of the transmitted and delayed pulses make up the pulse stretcher beam output 214C, as shown. The stretched pulse 400 is shown as intensity vs time in FIG. 8 and can also be compared to the shape of the power amplifier output pulse 402 (not stretched) shown in FIG. 8. For the stretched pulses shown, these pulses may be shaped with two large, approximately identical peaks, with peaks that follow a smaller decrease in time following the first two peaks. It should be understood that the shape of the stretched pulse can be changed by using beam splitters with different reflectances.

7 shows that the delayed beam can be focused and spread three times. The number of such focusing steps is odd (i.e. not even) because the delayed beam is inverted (both vertically and horizontally) for the portion of the pulse transmitted through the beam splitter 216. Therefore, the output beam 214C from the six-mirror pulse stretcher 22 may comprise a combined or mixed beam. This mixing reduces the intensity change. Pulse stretcher 22 can also reduce beam coherence because different coherent cells from the top portion of the beam can be mixed. The impact on the vertical constant of the exemplary beam is shown in FIG. 9. More specifically, the stretched pulse 404 is shown in FIG. 9 with intensity vs. intensity. It is shown as the vertical width and can also be compared with the shape of the power amplifier output pulse 406 shown in FIG. If the beam is often close to a typical Gaussian when using an excimer laser source in the horizontal axis, the impact of the pulse stretcher 22 on the horizontal intensity change can be ignored.

As mentioned above, the performance of the laser crystallization process depends on a certain degree of energy density. Unlike lithography, which is a multi-shot process and requires an average shot-to-shot during exposure, laser crystallization is, for the most part, a single shot process, and therefore the average can be limited to the intensity average in a single pulse. . Several factors that determine the energy density constant are laser beam constant and beam spatial coherence. Typically, optical members may be included in optical module 28 (FIG. 1) to homogenize the beam. Such optical members can include the use of an array of micro lenses to split the beam into beamlets. Large aperture lenses can be used to direct the beamlets so that they precisely overlap each other in the focal plane of the spherical lens. The integration of such beamlets can effectively smooth out any intensity fluctuations that yield a flat-top beam profile. The more beams are divided into more beamlets, the better the mean. However, if the micro lens aperture is too small, for example smaller than one interference region of the laser beam, the intersecting region experiences a repeated pattern of microlenses, which can cause undesirable results. In short, the degree of uniformity achieved using an array of micro lenses can be limited. With this in mind, the averaging of the spatially coherent cells in the pulse stretcher 22 allows for less coherent beams to be delivered to the microlens array, then minimizing intensity variations due to interference, and / or smaller Allow the use of microlens arrays.

One feature of the pulse stretcher 22 shown in FIG. 7 is that when the beam pointing error of the input beam (i.e., beam 214B) increases, the beam spread of the output beam (i.e., beam 214C) may increase. Indicates that it can. This increase in beam spread is often undesirable for laser crystallization, and therefore it is desirable to minimize beam pointing errors of the beam entering the pulse stretcher (eg, beam 214B). 6 shows an active beam steering unit 500 that may be located upstream of the pulse stretcher 22 to minimize beam pointing errors of the beam 214B entering the pulse stretcher. Such an active beam steering unit may respond to beam pointing measurements made upstream of the pulse stretcher 22 and / or spread measurements made downstream of the pulse stretcher 22, for example, the spread measurements may be SMM ( 26), and may be used to control the active beam steering unit 500. Structurally, the active beam steering unit 500 is a mirror 240A, 240B described in more detail below and in some applications, incorporated by reference above, for actively controlling beam steering in the beam delivery unit 238. It may include one or more adjustable mirrors similar to the. In addition to or as an alternative to the active beam steering unit 500, the direction of the beam inverter 228 can be actively adjusted to control beam pointing upstream of the pulse stretcher 22. More specifically, the adjustable beam inverter 228 may respond to beam pointing measurements performed upstream of the pulse stretcher 22 and / or spread measurements performed downstream of the pulse stretcher 22. have.

6 shows that the system 10 may include a beam delivery system 24 and a stability measurement module (SSM 26). Functionally, these elements can cooperate with the laser source 20 and the pulse stretcher 22 to supply a pulsed beam to the SMM 26 output that meets a set of beam specifications for the application. In practice, the beam specification at the input of the optical module 28 (see FIG. 1) may depend on the design of the optical module 28 (ie, illuminator). Specific beam parameters include, but are not limited to intensity, wavelength, bandwidth, wavefront (eg, wavefront curvature, also referred to as beam spread), polarization, intensity profile, beam size, beam pointing, dose stability, and wavelength stability. For example, for an optical module capable of producing the above-described line beam for laser crystallization of 20 micrometers by 700 mm, the pointing stability is within 20 μrad, the wavefront bending change is less than 10%, and the energy stability is +/- Maintaining within 2% may be required. In addition, to avoid wasting shots, it may be desirable to obtain this property without requiring the laser to operate continuously for a relatively long period of time until the laser is “stabilized”.

The SMM 26 monitors the incoming beam and provides a feedback signal to the control system to ensure that the light is provided to the optical module 28 with desired parameters including beam pointing, beam position, beam size, wavefront, and pulse energy. May be located upstream of the input port of the optical module 28. For example, pulse energy, beam pointing, and beam position may be measured using a SMM (on a pulse-to-pulse basis) using the techniques described in U.S. Patent Application No. 10 / 425,361 (the '361 application), which is previously incorporated herein by reference. 26) can be monitored by the measuring device. More specifically, FIG. 10B of the '361 application shows a structural arrangement for measuring pulse energy, beam pointing, and beam position on a pulse-to-pulse basis. As described in more detail below, SMM 26 may also be configured to monitor wavefront flexure and beam size. The use of a DSP-based processor, combined with a high-speed CMOS linear photo-diode array, enables fast calculation of beam characteristics up to 8kHz as well as fast feedback to stabilize beam characteristics.

Vertical and horizontal beam pointing and position errors can be evaluated at SMM 26 for the light of every pulse generated by the laser. In total, there are four independent sensor measurements: vertical pointing error, horizontal pointing error, vertical position error, and horizontal position error. In an exemplary implementation, vertical and horizontal pointing is far-field on a linear photodiode array (PDA) such as the 'S903 NMOS Linear Image Sensor' provided by 'Hamamatsu Corporation' with offices in NJ Bridgewater. It can be measured by dropping the image. Typically, the pointing error may be formed from a target location formed at the exit of the SMM 26. Vertical and horizontal positions can be measured by placing a reduced image of the beam near the BDU exit on the linear PDA element. The pulse energy of the beam can be measured at the SMM 26 with a calibrated photo-cell connector. The signal from the sensor in the SMM 26 may be sent via an electrical connector to a stabilization controller that forms part of the SMM 26.

The beam pointing control selectively adjusts the direction of the beam inverter 228 (as described above), thereby upstream of the pulse stretcher 22 (also described above) and / or within the BDU 24. This can be accomplished by using the steering unit 500. More specifically, the BDU 24 may include two beam pointing mirrors 240A and 240B, one or both of which may be controlled to provide tip or tilt correction for changing the beam pointing. Beam pointing may be monitored at SMM 26 providing feedback control to one or both of pointing mirrors 240A and 240B. For example, the error signal may be sent to a stabilization controller in the SMM 26 that processes raw sensor data and generates commands to drive the high speed steering turning mirrors 40A and 40B. These two high speed steering turning mirrors, each with two axes of control, can be installed upstream of the SMM 26, as shown. The turning mirrors may each be installed on a high speed steering motor. In certain embodiments, piezoelectric mirror drivers may be provided to allow high speed (200 Hz) beam pointing and position correction.

This motor activates the mirror angle in both axes, thereby directing the path of the laser beam again. Two motors with two control axes allow the BDU stabilization controller to independently control vertical and horizontal beam pointing and position errors. Such a control system can correct for pulse-to-pulse beam errors. That is, the beam error from each laser pulse can be supplied to the feedback control system to generate a command for the steering motor. The electronics used to drive the feedback control system can be located in the stabilization controller. By placing the mirror as shown in FIG. 6, drift due to the laser, attenuator (if provided), and other optical members can be corrected. Therefore, a stable beam (in position and pointing) can, in some cases, be projected at the entrance of the optical module 28, with stability within 10 μrad.

The pulse energy monitored at the SMM 26 may be used as a feedback signal and input to the laser's energy control algorithm. For a gas discharge laser, the discharge voltage of the laser can be adjusted to change the pulse energy. Since the energy control algorithm can stabilize the energy in the SMM 26, any short or long term drift in pulse energy due to optical absorption or other causes can be compensated for.

As discussed above, the SMM 26 may also measure beam size and beam spread (ie, wavefront bending). Typically, an aperture at the laser exit can be used to fix the beam size from the laser. However, the beam spread from the laser can change due to the heating of the optical member, the laser energy, the laser voltage, and the F2 concentration in the discharge gas when using a fluoride excimer laser.

As shown in FIGS. 6 and 7, beam spread and beam size may be actively controlled using an adjustable beam expander 502 that may be disposed along the BDU 24. As shown in FIG. 7, the beam expander 502 may include four lenses, two horizontal lenses 504A and 504B, and two vertical lenses 504C and 504D. In one setup, the beam expander 502 may have a length L of about 0.30 m and is sized to have a nominal input of 12 mm on the horizontal axis and 9 mm on the vertical axis, and a nominal output of 5 mm on the vertical axis and 18 mm on the vertical axis. . In an exemplary arrangement, lens 504A is a cylindrical plano-convex with f = 507.0 mm, lens 504B is a cylindrical flat convex lens with f = 202.8 mm, and lens 504C is f A cylindrical flat convex lens of = 202.8 mm, and lens 504D may be a cylindrical flat convex lens of f = 405.6 mm. In alternative arrangements, lenses 504A and 504C may be replaced by a single lens. The change in beam spread and beam size can be achieved by adjusting the space of the beam expander lens. More specifically, the space between the lenses 504A and 504B may change to change the beam to the horizontal axis, and the space between the lenses 504C and 504D may change to change the beam to the vertical axis. In one embodiment, the movable lens can be mounted on a linear motor driver. The dilator 504 may then enable independent control of the horizontal and vertical beam wavefronts.

Those skilled in the art will understand that the forms of the embodiments of the invention described above are merely preferred embodiments, and do not in any way limit the scope of the invention to any particular preferred embodiment. Those skilled in the art will appreciate that many variations and modifications may be made to the forms of the disclosed embodiments. The appended claims are intended to cover the forms of embodiments of the present invention as well as to cover equivalents, other variations, and modifications apparent to those skilled in the art. 35 U.S.C. Embodiments in which particular forms of embodiments of systems and methods for implementing interactions between lasers shaped on a substrate and films formed on substrates, such as the line beams described and described in detail herein, required to meet § 112 are described. Although the purpose of the examples forms, or any other reason, or any of the foregoing objects for the problem to be solved may be fully achieved, those skilled in the art will recognize that the forms described herein of the described embodiments of the invention are It should be understood that this is an exemplary, explanatory and representative problem that is widely considered. The scope of the forms of the embodiments described and claimed herein includes all other embodiments that may be apparent to those skilled in the art upon reading this specification. The scope of systems and methods for implementing interactions between lasers shaped like line beams and films deposited on substrates is limited solely and completely by the appended claims, except as not set forth in the appended claims. do. Reference to an element in this claim alone is not intended to mean "one and only one" of the claim element, and "one or more" if nothing is specified. All equivalents, structural and functional, to any element of the above-described form of the embodiment which will be appreciated by those skilled in the art, or which will be appreciated later, are expressly incorporated herein by reference and are incorporated herein by reference. Any term used herein and / or within a claim, and the meanings explicitly given in the specification and / or claims, should have such meaning, regardless of the dictionary meaning of the term or the meaning generally used. Any form of embodiment is not a prerequisite for the device or method described herein to cover each and every problem that has been sought to be solved by the form of the embodiments described herein, but is included in the claims. The elements, components, or method steps in this specification are not intended to inform the public regardless of whether the elements, components, or method steps are expressly mentioned in the claims. Claim elements in the appended claims are not explicitly mentioned using the phrase "by means of" or if the element is not referred to as "step" in place of "action" in the case of a method claim. , 35 USC It should not be interpreted in accordance with the provisions of § 112, paragraph 6.

Claims (20)

An apparatus for focusing beams for interaction with a film, the beams forming short and long axes orthogonal to each other, A _single field stop located at a distance d ₁ from the film; A first optical member for focusing a laser beam on the field stop; A second optical member positioned between the field stop and the film to focus the beam at the short axis for interaction with the film; And Along the beam path reflected from the film, analyze the light reflected from the film on an image plane located at d ₂ , which is substantially the same distance as d _1, and determine whether the beam is focused at the short axis in the film. A detection system for analyzing the reflected light to And the beam is not collimated in the film in the long axis, wherein the beams forming mutually orthogonal short and long axes are focused for interaction with the film. The method of claim 1, wherein the detection system includes a mirror disposed along the reflected beam path between the film and the image plane, wherein the beams form beams that form a short axis and a long axis perpendicular to each other. A device for focusing for. 3. The system of claim 2, wherein the detection system further comprises a camera and a lens, wherein the lens is positioned to project and magnify an image from the image plane to the camera. A device for focusing a beam for interaction with a film. The system of claim 1, wherein the detection system is a first detection system for determining whether the beam is focused at the short axis at a first position along the long axis of the film, and wherein the apparatus is configured to determine the long axis of the film. And a second detection system for determining whether or not the focus is at the short axis at a second location according to the present invention. 5. The apparatus of claim 4, wherein each detection system comprises a respective mirror, a magnification lens, and a camera, wherein the beams forming mutually orthogonal short and long axes are focused for interaction with the film. The method of claim 1, wherein the film is made of an amorphous silicon material, and the beam is a pulsed laser focused to dissolve the film. A device for focusing for. delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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