Patent Publication Number: US-2015075426-A1

Title: Pulsed laser deposition system

Description:
CROSS REFERENCE 
     This application claims priority from Taiwan Patent Application No. 102133097, filed Sep. 13, 2013, the content of which are hereby incorporated by reference in their entirety for all purposes. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pulsed laser deposition system, and particularly relates to a pulsed laser deposition system capable of using several different targets. 
     2. Description of the Prior Art 
     Referring to  FIG. 1 , it illustrates a conventional pulsed laser deposition system  1  which is commonly used in pulsed laser deposition. The pulsed laser deposition system  1  uses an excimer laser including various visible light bands and UV bands as laser source  10 . The pulsed laser deposition system  1  has a chamber  20 , and there are a chamber door  22  for putting a substrate  29  and a target  27  into the chamber  20  and for taking the substrate  29  and the target  27  out the chamber  20 , a single laser input window  24  for the excimer laser passing through, and a port  26  for connecting a vacuum pump  32  on the chamber  20 . There are a target stage  28  for carrying or holding single target  27 , and a carrier stage  30  for carrying or holding single substrate  29  inside the chamber  20 . When pulsed laser deposition is performed by the pulsed laser deposition system  1 , the excimer laser provided by the laser source  10  passes through the laser input window  24  to irradiate the target  27 . The surface of the target absorbs the high energy of the excimer laser, and then, the surface of the target is gasified (or plasma-ized) by the high energy to form a clustered plasma gas having high kinetic energy. The clustered plasma gas having high kinetic energy is jetted to the substrate  29  to form a thin film (such as a III-V compound semiconductor film) on the substrate  29 . 
     However, the conventional pulsed laser deposition system  1 , can fabricate a III-V compound semiconductor film, but it can&#39;t fabricate a doped epitaxial layer or a ternary or more epitaxial layer. It is because the conventional pulsed laser deposition system  1  only can use one target once to perform pulsed laser deposition and the target is commonly composed of single material. Therefore, the conventional pulsed laser deposition system  1  can&#39;t fabricate a doped epitaxial layer or a ternary or more epitaxial layer. Although, in recent years, the target fabricated by mixing and pressure molding several different materials is developed for performing pulsed laser deposition to fabricate a doped epitaxial layer or a ternary or more epitaxial layer, but this method has following limitations and shortcomings. First, if an user wants to use the target composed of several different materials, the powders of the materials need to be pressed to form an ingot by a pressing machine. And then, the ingot composed of the several different materials is sintered to form a target composed of several different materials. However, not all kinds of materials can be pressed by the pressing machine or sintered. Once one of the materials (using to fabricate the target) can&#39;t be pressed by the pressing machine or sintered, the target can&#39;t be fabricated for performing pulsed laser deposition. Therefore, the epitaxial layer containing the material, which can&#39;t be pressed by the pressing machine or sintered, can&#39;t be formed by pulsed laser deposition, and the doped epitaxial layer or the ternary or more (such as quaternary) epitaxial layer containing the material, which can&#39;t be pressed by the pressing machine or sintered, can&#39;t be formed by pulsed laser deposition, either. Second, although the target can be fabricated by mixing, pressing and sintering several different materials with a certain ratio, but the materials are not distributed in the target uniformly. Therefore, in pulsed laser deposition process, the ratio of the compositions of plasma gas formed by the target can&#39;t be predicted and confirmed and it results in uncontrollable ratio of the compositions of the epitaxial layer fabricated by pulsed laser deposition with the target composed of several different materials. Third, it has a need of using a target composing a doped material for doping the epitaxial layer and an epitaxial material for forming the epitaxial layer, and the concentration of the doped material is much lower than the concentration of the epitaxial material. It means that the difference between the concentration of the doped material and the concentration of the epitaxial material is very large. However, the target composed of different materials, in which the difference between the concentration of the different materials is very large, can&#39;t be formed by current target fabricating technology. Therefore, the conventional pulsed laser deposition system (such as the pulsed laser deposition system  1  illustrated in  FIG. 1 ) can&#39;t fabricate a doped epitaxial layer. 
     Besides, the area of the epitaxial layer fabricated by the conventional pulsed laser deposition system (such as the pulsed laser deposition system  1  illustrated in  FIG. 1 ) is limited by the size of the conventional pulsed laser deposition system. Therefore, the conventional pulsed laser deposition system only can perform pulsed laser deposition to a substrate with small size (≦4 inches) but it can&#39;t perform pulsed laser deposition to a substrate with big size (&gt;4 inches). 
     Therefore, it has a need of a pulsed laser deposition system capable of fabricating a doped epitaxial layer or a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film). This pulsed laser deposition system also can control the doped concentration and the ratio of the compositions in the epitaxial layer efficiently and precisely, and it can perform pulsed laser deposition to a substrate with big size (&gt;4 inches). 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, one object of the present invention is to provide a pulsed laser deposition system for overcoming above-mentioned shortcomings. This pulsed laser deposition system is capable of using one target or simultaneously using several different targets to perform pulsed laser deposition for fabricating a doped epitaxial layer or a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film), and it can perform pulsed laser deposition to a substrate with big size (&gt;4 inches). 
     According to one of the objects above, a pulsed laser deposition system is disclosed herein. The pulsed laser deposition system comprises a UV laser source, a chamber, a beam-splitting device, a target stage, and a carrier stage. The UV laser source and the beam-splitting device are deposed outside the chamber, and the target stage and the carrier stage are deposed inside the chamber. The UV laser source is capable of emitting an excimer laser including various UV bands for providing a UV laser to the pulsed laser deposition system. The beam-splitting device is used for splitting the UV laser provided by the UV laser source into a plurality of UV laser beams. The chamber has a plurality of laser input windows. The UV laser beams split by the beam-splitting device are respectively directed into different laser input windows at the same time by the beam-splitting device. And then, the UV laser beams respectively directed into different laser input windows are directed into the chamber through the laser input windows at the same time. The target stage is constructed of a plurality of target holding stages for carrying or holding one or more targets to perform pulsed laser deposition. The carrier stage is a carrier stage with big size (≧6 inches) and it is capable of carrying or holding substrates with big size (≧6 inches). The carrier stage is used for carrying or holding one or more substrates to perform pulsed laser deposition to the substrates. In the pulsed laser deposition system, the UV laser provided by the UV laser source is split into a plurality of UV laser beams through the beam-splitting device, and the UV laser beams enter into the chamber respectively through the laser input windows for respectively irradiating the different targets on the target stage. The different targets on the target stage are simultaneously gasified (or plasma-ized) by the UV laser beams to form a plasma (gas), and the plasma (gas) is jetted to the substrate(s) on the carrier stage for performing pulsed laser deposition to the substrate(s). Therefore, a doped epitaxial layer or a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film) can be formed by this pulsed laser deposition system. The doped concentration and the ratio of the compositions in the epitaxial layer can be efficiently and precisely controlled by controlling the intensity of the UV laser beams which are directed into different laser input windows respectively. 
     Therefore, the present invention provides a pulsed laser deposition system. In the pulsed laser deposition system, by the beam-splitting device, a plurality of laser input windows deposed on the chamber, and the target stage constructed of a plurality of target holding stages, the UV laser provided by the UV laser source is split into a plurality of UV laser beams, and the UV laser beams simultaneously enter into the chamber and simultaneously irradiate on different targets respectively through different laser input windows. Therefore, the pulsed laser deposition system is capable of fabricating a doped epitaxial layer or a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film). Furthermore, the pulsed laser deposition system is capable of perform pulsed laser deposition to a substrate with big size (&gt;4 inches) because the carrier stage is a carrier stage with big size (≧6 inches). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a drawing illustrating a conventional pulsed laser deposition system. 
         FIG. 2A  to  FIG. 2C  are drawings respectively illustrating a pulsed laser deposition system in different view in accordance with one embodiment of the present invention. 
         FIG. 3A  to  FIG. 3B  are drawings illustrating the target stage of the pulsed laser deposition system in accordance with one embodiment of the present invention. 
         FIG. 4A  to  FIG. 4C  are drawings respectively illustrating different kinds of the carrier stage of the pulsed laser deposition system in accordance with another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The detailed description of the present invention will be discussed in the following embodiments, which are not intended to limit the scope of the present invention, but can be adapted for other applications. While drawings are illustrated in details, it is appreciated that the quantity of the disclosed components may be greater or less than that disclosed, except expressly restricting the amount of the components. Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims. 
     Referring to  FIG. 2A ,  FIG. 2B , and  FIG. 2C  simultaneously,  FIG. 2A  is stereo drawing illustrating a pulsed laser deposition system  100  in accordance with one embodiment of the present invention,  FIG. 2B  is drawing in top view of the pulsed laser deposition system  100 , and  FIG. 2C  is stereo drawing illustrating a chamber  300  of the pulsed laser deposition system  100 . The pulsed laser deposition system  100  comprises a UV laser source  102 , a chamber  300 , a beam-splitting device  200 , a target stage  400 , and a carrier stage  500 . The UV laser source  102  and the beam-splitting device  200  are deposed outside the chamber  300 . The UV laser source  102  is a laser source capable of providing or emitting an excimer laser including various UV bands, and the UV laser source  102  is used to provide a UV laser to the pulsed laser deposition system  100  for performing pulsed laser deposition. The beam-splitting device  200  is used for splitting the UV laser provided by the UV laser source  102  into a plurality of UV laser beams and for directing these split UV laser beams into the chamber  300  to perform pulsed laser deposition. The chamber  300  provides a confined space for performing pulsed laser deposition. The target stage  400  deposed inside the chamber  300  for carrying or holding one or more targets to perform pulsed laser deposition. The carrier stage  500  deposed inside the chamber  300  for carrying or holding one or more substrates  508  to perform pulsed laser deposition to the substrates  508 . 
     The chamber  300  comprises a chamber door  302 , a plurality of laser input windows  304   a ,  304   b ,  304   c ,  304   d , a vacuum pump port  306 , and a view port  308 . The target(s) and the substrate(s)  508  are put into the chamber  300  and taken out the chamber  300  through the chamber door  302 . The laser input windows  304   a ,  304   b ,  304   c ,  304   d  are used to direct these split UV laser beams to enter the chamber  300 , and these split UV laser beams enter the chamber  300  respectively through the laser input windows  304   a ,  304   b ,  304   c ,  304   d . The view port  308  is a window made of a glass or other transparent materials. Therefore, the user can observe laser deposition condition in the chamber  300  through the view port  308 . A vacuum pump  600  (for example a turbine pump or other vacuum pump) is connected with the chamber  300  by the vacuum pump port  306  for vacuuming the chamber  300  to control the pressure in the chamber  300 . Therefore, the vacuum or pressure in the chamber  300  can achieve the required vacuum degree or pressure of pulsed laser deposition. Besides, in other embodiments of the present invention, there is a flange deposed one side of the chamber  300  for loading or equipping an additional device. The additional device may be a plasma gun or a RHEED gun, but it is not limit. Therefore, a plasma gun or a RHEED gun can directly configure on the pulsed laser deposition system  100  (or the chamber  300 ) of the present invention by the flange for observing the crystal of the epitaxial layer which is formed on the substrate by the laser deposition system of the present invention. Besides, according to requirements of pulsed laser deposition, other additional device also can configure on the pulsed laser deposition system (or the chamber) of the present invention by the flange. Although, in the pulsed laser deposition system  100  illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 2C , the chamber  300  comprises four laser input windows  304   a ,  304   b ,  304   c ,  304   d , but it is not limit. In other embodiments of the present invention, according to requirements of pulsed laser deposition, the laser input windows can be increased, for example five, six, or more laser input windows, or the laser input windows can be decreased, for example two or three laser input windows. 
     The beam-splitting device  200  comprises a beam-splitting lens  201  and a plurality of directing lenses  202   a ,  202   b ,  202   c ,  202   d . The beam-splitting lens  201  is used to split the UV laser emitted from the UV laser source  102  into several UV laser beams and to adjust the intensity of the UV laser beams. Each of the directing lenses  202   a ,  202   b ,  202   c ,  202   d  is corresponded to one of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  for respectively directing the UV laser beams to different laser input windows  304   a ,  304   b ,  304   c ,  304   d  so the UV laser beams can simultaneously enter the chamber  300  respectively through different laser input windows  304   a ,  304   b ,  304   c ,  304   d . In the present invention, each of the directing lenses must be corresponded to at least one of the laser input windows. Taking the pulsed laser deposition system  100  illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 2C  for example, the directing lenses  202   a  is corresponded to the laser input window  304   a  for directing one of the UV laser beams to the laser input window  304   a  to enter the chamber  300  through the laser input window  304   a , the directing lenses  202   b  is corresponded to the laser input window  304   b  for directing one of the UV laser beams to the laser input window  304   b  to enter the chamber  300  through the laser input window  304   b , the directing lenses  202   c  is corresponded to the laser input window  304   c  for directing one of the UV laser beams to the laser input window  304   c  to enter the chamber  300  through the laser input window  304   c , and the directing lenses  202   d  is corresponded to the laser input window  304   d  for directing one of the UV laser beams to the laser input window  304   d  to enter the chamber  300  through the laser input window  304   d . Although, in the pulsed laser deposition system  100  illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 2C , the beam-splitting device  200  comprises four directing lenses  202   a ,  202   b ,  202   c ,  202   d , but it is not limit. In other embodiments of the present invention, according to requirements of pulsed laser deposition, the directing lenses can be increased, for example five, six, or more directing lenses, or the directing lenses can be decreased, for example two or three directing lenses. Or, the directing lenses may be increased or decreased following change of the number of the laser input windows. 
     Each of the directing lenses  202   a ,  202   b ,  202   c ,  202   d  has a reflecting lens  204   a ,  204   b ,  204   c ,  204   d  and a focusing lens  206   a ,  206   b ,  206   c ,  206   d . The reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  are respectively deposed between the beam-splitting lens  201  and the laser input windows  304   a ,  304   b ,  304   c ,  304   d , and each of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  is corresponded to at least one of the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d . The laser input windows  304   a  is corresponded to the reflecting lens  204   a , the laser input windows  304   b  is corresponded to the reflecting lens  204   b , the laser input windows  304   c  is corresponded to the reflecting lens  204   c , the laser input windows  304   d  is corresponded to the reflecting lens  204   d . The reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  are used to respectively reflect at least one of the UV laser beams and to direct the UV laser beam into the corresponded laser input window  304   a ,  304   b ,  304   c ,  304   d . Each of the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  is corresponded to one of the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  and one of the laser input window  304   a ,  304   b ,  304   c ,  304   d , and each of the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  is deposed between the corresponded reflecting lens  204   a ,  204   b ,  204   c ,  204   d  and the corresponded laser input window  304   a ,  304   b ,  304   c ,  304   d . The focusing lens  206   a  is deposed between the reflecting lens  204   a  and the laser input window  304   a  and is corresponded to both of the reflecting lens  204   a  and the laser input window  304   a . The focusing lens  206   b  is deposed between the reflecting lens  204   b  and the laser input window  304   b  and is corresponded to both of the reflecting lens  204   b  and the laser input window  304   b . The focusing lens  206   c  is deposed between the reflecting lens  204   c  and the laser input window  304   c  and is corresponded to both of the reflecting lens  204   c  and the laser input window  304   c . The focusing lens  206   d  is deposed between the reflecting lens  204   d  and the laser input window  304   d  and is corresponded to both of the reflecting lens  204   d  and the laser input window  304   d . The focusing lenses  206   a ,  206   b ,  206   c ,  206   d  are used to focus the UV laser beams which are split by the beam-splitting lens  201  and respectively reflected by the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  for being desired to directed into the corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d.    
     Besides, for controlling and adjusting intensity of the UV laser beams directed to the laser input windows  304   a ,  304   b ,  304   c ,  304   d  more efficiently, the beam-splitting device  200  maybe comprises one or more density filter lenses  208   a ,  208   b ,  208   c ,  208   d  for controlling and adjusting the intensity of the UV laser beams directed into the laser input windows  304   a ,  304   b ,  304   c ,  304   d . Although, in the pulsed laser deposition system  100  illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 2C , each of the directing lenses  202   a ,  202   b ,  202   c ,  202   d  comprises a density filter lens  208   a ,  208   b ,  208   c ,  208   d , and each of the directing lenses  202   a ,  202   b ,  202   c ,  202   d  is deposed between one of the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  and one of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  for being corresponded to the focusing lens and the laser input window, but it is not limit. In other embodiments of the present invention, people can determine whether it is necessary to add a density filter lens into each of the directing lenses, which directing lenses has need of adding a density filter lens into, or how much density filter lens need to be added into each of the directing lenses for making the intensity of different UV laser beams directed into different laser input windows to have different intensity or respectively have certain intensity, according to the desired intensity of the UV laser beam directed to each of the directing lens or each of the laser input window or according to desired intensity of the UV laser beam for different targets. Although, in the pulsed laser deposition system  100  illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 2C , each of the density filter lenses  208   a ,  208   b ,  208   c ,  208   d  is deposed between one of the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  and one of the laser input windows  304   a ,  304   b ,  304   c ,  304   d , but it is not limit. In other embodiments of the present invention, the density filter lenses  208   a ,  208   b ,  208   c ,  208   d  can be deposed between the beam-splitting lens  201  and the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d , between the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  and the focusing lenses  206   a ,  206   b ,  206   c ,  206   d , or between the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  and the laser input windows  304   a ,  304   b ,  304   c ,  304   d  according to requirements. Furthermore, other embodiments of the present invention, baffles maybe adopted instead of the density filter lenses for controlling and adjusting the intensity of the UV laser beams directed into the laser input windows. The baffles can be deposed between the beam-splitting lens and the reflecting lenses, between the reflecting lenses and the focusing lenses, or between the focusing lenses and the laser input windows according to requirements. 
     Referring to  FIG. 2A ,  FIG. 2B ,  FIG. 2C ,  FIG. 3A , and  FIG. 3B  simultaneously, the target stage  400  comprises a base  402 , a plurality of pillars  406  deposed on the base  402 , a plurality of target holding stages  404   a ,  404   b ,  404   c ,  404   d , and a target inclination controlling device  411 . Each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  is deposed between two adjacent pillars  406  and Each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  is pinjointed to the two adjacent pillars  406 . Therefore, each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  is indirectly deposed on the base  402  through the pillars  406  and each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  is able to rotate between the two adjacent pillars  406 . The target holding stages  404   a ,  404   b ,  404   c ,  404   d  are used for holding or carrying targets thereon to perform pulsed laser deposition. The target inclination controlling device  411  is used for controlling and adjusting inclination angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to make the targets held on the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to be scanned back and forth by the UV laser beams with different inclination angles. 
     The target inclination controlling device  411  comprises an inclination angle controlling column  409  and a plurality of inclination angle spindles  408 . The inclination angle controlling column  409  is deposed on the base  402  and it is able to move up and down (or rise and descend) on the base  402 . The inclination angle spindles  408  are connections between the inclination angle controlling column  409  and the target holding stages  404   a ,  404   b ,  404   c ,  404   d . Each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  is corresponded to one of the inclination angle spindles  408 . One end of each of the inclination angle spindles  408  is hinge connected to one of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  (or the corresponded target holding stages) for driving the target holding stage  404   a ,  404   b ,  404   c ,  404   d  to rotate up and down. Therefore, each of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  can be inclined with a predetermined angle by the corresponded inclination angle spindle  408 . Another end of each of the inclination angle spindles  408  is hinge connected to the inclination angle controlling column  409  so that each of the inclination angle spindles  408  is able to move up and down following moving (or rising and descending) of the inclination angle controlling column  409  for driving corresponded target holding stage  404   a ,  404   b ,  404   c ,  404   d  to rotate upward or downward. Therefore, the inclination angle of the corresponded target holding stage  404   a ,  404   b ,  404   c ,  404   d  can be controlled by this way. When the inclination angle controlling column  409  moves up (or rises), the inclination angle controlling column  409  drives the inclination angle spindles  408  to move down (or descend). And then, following the downwardly moving (or descend) of the inclination angle spindles  408 , the inclination angle spindles  408  drive the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to rotate downward so that the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are inclined downward at a certain or predetermined angle (as showed in  FIG. 3A ). When the inclination angle controlling column  409  moves down (or descends), the inclination angle controlling column  409  drives the inclination angle spindles  408  to move up (or rise). And then, following the upwardly moving (or rising) of the inclination angle spindles  408 , the inclination angle spindles  408  drive the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to rotate upward so that the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are inclined upward at a certain or predetermined angle or the target holding stages  404   a ,  404   b ,  404   c ,  404   d  come back to the horizontal positions. The upwardly moving (or rising) distances and the downwardly moving (or descending) distances of the inclination angle spindles  408  can be controlled and adjusted respectively by controlling and adjusting the downwardly moving (or descending) distance and the upwardly moving (or rising) distance of the inclination angle controlling column  409 . Further, the downwardly rotation angles (or the downwardly inclination angles) and the upwardly rotation angles (or the upwardly inclination angles) of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  can be controlled and adjusted respectively by controlling and adjusting the upwardly moving (or rising) distance and downwardly moving (or descending) distance of the inclination angle controlling column  409 . The downwardly rotation angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  means the downwardly inclination angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d , and the upwardly rotation angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  means the upwardly inclination angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d . Therefore, the pulsed laser deposition system  100  of the present invention can control the targets to perform pulsed laser deposition with different inclination angles by the target inclination controlling device  411 . 
     Besides, there is a rotating device  410  deposed under the target stage  400  for rotating the target stage  400  and thereby the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are able to be revolved or rotated back and forth around center of the target stage  400 . By this revolving or rotating, the target holding stage  404   a ,  404   b ,  404   c ,  404   d  corresponded to each of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  can be changed from one to another. Therefore, the pulsed laser deposition system  100  can change targets of laser deposition form one to another during laser deposition by the rotating device  410 . Furthermore, the rotating device  410  can rotate the target stage  400  and thereby the targets put in the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are able to be horizontally scanned back and forth by the UV laser beams. Therefore, the pulsed laser deposition system  100  of the present invention can control the targets put in the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to be scanned back and forth with different inclination angles by the target inclination controlling device  411  and the rotating device  410 . Although, the target stage  400  illustrated in  FIG. 2A  and  FIG. 3A  has four target holding stages  404   a ,  404   b ,  404   c ,  404   d , but it is not limit. In other embodiments of the present invention, the target holding stages  404   a ,  404   b ,  404   c ,  404   d  can be increased or decreased according to requirements, but the number of the target holding stages must be much than the number of the laser input windows or equal to the number of the laser input windows. Preferably, the number of the target holding stages is a multiple of the number of the laser input windows because it is useful and convenient for changing the targets during pulsed laser deposition. Therefore, the pulsed laser deposition system  100  of the present invention can change different targets to perform pulsed laser deposition during pulsed laser deposition for forming a epitaxial layer (or III-V compound semiconductor film) which is more than ternary. 
     Referring to  FIG. 2A  and  FIG. 4A  simultaneously, the carrier stage  500  is a carrier stage with big size (≧6 inches). The size of the carrier stage  500  is 6 inches to 12 inches but it is not limit. In some embodiments of the present invention, the size of the carrier stage  500  maybe bigger than 12 inches. The carrier stage  500  comprises a cavity  502  capable of putting or holding a substrate having a size of 6 inches to 12 inches thereon (as showed in  FIG. 4A ). Therefore, the pulsed laser deposition system  100  of the present invention can perform pulsed laser deposition to the substrates with big size (6 inches-12 inches) by the carrier stage  500 . Referring to  FIG. 4B , it is a drawing illustrating another kind of the carrier stage  500 A of the pulsed laser deposition system in accordance with another embodiment of the present invention. The carrier stage  500 A comprises a cavity  502  capable of putting or holding a substrate having a size of 6 inches to 12 inches thereon and several small substrate containing pits  504   a ,  504   b ,  504   c ,  506  deposed in the cavity  502  for putting or holding one or more substrates having small size (&lt;6 inches) thereon to perform laser deposition. The small substrate containing pits  504   a ,  504   b ,  504   c  is used for putting or holding substrates having size of 2 inches to 4 inches thereon to perform laser deposition. The small substrate containing pits  506  is used for putting or holding substrates having smaller size than of 2 inches thereon to perform laser deposition. Therefore, by the carrier stage  500 A, the pulsed laser deposition system  100  of the present invention can perform pulsed laser deposition to the substrates with big size (&gt;6 inches), and also can perform pulsed laser deposition to the substrates with small size (&lt;6 inches). Further, the pulsed laser deposition system  100  of the present invention can simultaneously perform pulsed laser deposition to the substrates with different small sizes. Although the carrier stage  500 A illustrated in  FIG. 4B  has three small substrate containing pits  504   a ,  504   b ,  504   c  (for substrates having size of 2 inches to 4 inches) and one small substrate containing pits  506  (for substrates having smaller than 2 inches), but it is not limit. In other embodiments of the present invention, the size and the number of the small substrate containing pits can be changed according to requirements. 
     Referring to  FIG. 4C , it is a drawing illustrating still another kind of the carrier stage  500 B of the pulsed laser deposition system in accordance with still another embodiment of the present invention. There is no cavity, which is capable of putting or holding a substrate thereon, on the carrier stage  500 B. On the contrary, there is a carrier  512 , which is capable of putting or holding a substrate thereon, deposed on the carrier stage  500 B. The carrier  512  may comprise a cavity capable of putting or holding a substrate having a size of 6 inches to 12 inches thereon as showed in  FIG. 4A . Or, the carrier  512  may comprise a cavity capable of putting or holding a substrate having a size of 6 inches to 12 inches thereon and several small substrate containing pits deposed in the cavity for putting or holding one or more substrates having small size (&lt;6 inches) thereon as showed in  FIG. 4B . The carrier  512  may be a carrier fixed on the carrier stage or a movable carrier which can be taken from the carrier stage for changing the carrier with different sizes and designs. 
     Besides, referring  FIG. 2A , the carrier stage  500  comprises a rotation-and-rise controlling device  510  for controlling the carrier stage  500  to rotate in order to perform laser deposition to all of the substrates  508  put on the carrier stage  500  uniformly and for rising and descending the carrier stage  500  to control the work distance between the carrier stage  500  and the target stage  400 . The rotation-and-rise controlling device  510  may control the carrier stage  500  to rise and descend by a manual way (for example manually rotating a turntable by hands) or a mechanical way (for example using a lifting mechanism). Therefore, the work distance between the carrier stage  500  and the target stage  400  can be adjusted within a range of 10 centimeter (cm) to 40 centimeter (cm) by the rotation-and-rise controlling device  510  according to requirements. In the pulsed laser deposition system of the present invention, a heating device equipped above, beside, or around the carrier stage for heating the substrate put on the carrier stage to perform laser deposition. 
     Although, the pulsed laser deposition system  100  illustrated in  FIG. 2B  has only one beam-splitting lens  201 , but in the other embodiments of the present invention, one or more beam-splitting lenses can be added into the pulsed laser deposition system according to the desired number of the UV laser beams. Therefore, the UV laser provided by laser source can be split into more UV laser beams by additional beam-splitting lens(es) and a epitaxial layer (or III-V compound semiconductor film) which is more than ternary or has more dopants can be formed by the pulsed laser deposition system having a plurality of the beam-splitting lenses. 
     Referring  FIG. 2A ,  FIG. 2B , and  FIG. 2C  simultaneously, the process and operation of pulsed laser deposition by using the pulsed laser deposition system is detailed as following: After the laser source  102  emits a UV laser, the beam-splitting lens  201  in the beam-splitting device  200  splits the UV laser into several UV laser beams. After the UV laser is split into several UV laser beams, the directing lenses  202   a ,  202   b ,  202   c ,  202   d  in the beam-splitting device  200  direct several UV laser beams to corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d  wherein each of laser input windows  304   a ,  304   b ,  304   c ,  304   d  is corresponded to one of the directing lenses  202   a ,  202   b ,  202   c ,  202   d  and each of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  has one of the UV laser beams directed thereto by the corresponded directing lenses  202   a ,  202   b ,  202   c ,  202   d . Before the UV laser beams enter the chamber  300  through the laser input windows  304   a ,  304   b ,  304   c ,  304   d , the intensity of the of the UV laser beams are adjusted by the beam-splitting lens  201  and the density filter lenses  208   a ,  208   b ,  208   c ,  208   d  (or baffles). After the UV laser beams are directed to corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d , the UV laser beams enter the chamber  300  respectively through the laser input windows  304   a ,  304   b ,  304   c ,  304   d , and then the UV laser beams passed through different laser input windows  304   a ,  304   b ,  304   c ,  304   d  simultaneously irradiate on the targets put on different the target holding stages  404   a ,  404   b ,  404   c ,  404   d  for gasifying (or plasma-izing) the targets to perform the pulsed laser deposition wherein the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are corresponded to different laser input windows  304   a ,  304   b ,  304   c ,  304   d . When the UV laser beams irradiate on the targets, the inclination angles of the target holding stages  404   a ,  404   b ,  404   c ,  404   d  and the target put on the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are controlled and adjusted by the target inclination controlling device  411 , and the rotating device  410  controls the target holding stages  404   a ,  404   b ,  404   c ,  404   d  and the target put on the target holding stages  404   a ,  404   b ,  404   c ,  404   d  to horizontally rotate back and forth. Therefore, the UV laser beams irradiating on the targets can scan the targets back and forth with different (inclination) angles according requirements. During the pulsed laser deposition, each of the laser input windows  304   a ,  304   b ,  304   c ,  304   d  can be changed to be corresponded to different target holding stages by the rotating device  410 . It means that each of the UV laser beams can be changed to irradiate on different the target holding stages and targets by the rotating device  410  for forming a epitaxial layer (or III-V compound semiconductor film) which is more than ternary or quaternary. Besides, a substrate with big size or several substrates with small size can be put on the carrier stage  500  for being performed pulsed laser deposition thereon. During the pulsed laser deposition, the rotation-and-rise controlling device  510  controls the carrier stage  500  and the substrate(s) put on the carrier stage  500  to rotate for uniformly performing pulsed laser deposition on the substrate(s), and the work distance between carrier stage  500  and the target stage is controlled and adjusted by the rotation-and-rise controlling device  510 . Therefore, the pulsed laser deposition system  100  of the present invention can simultaneously gasify (or plasma-ize) several targets to perform pulsed laser deposition. Furthermore, in the pulsed laser deposition system  100  of the present invention, the ratio of the compositions of a epitaxial layer (or III-V compound semiconductor film) or the doped concentration of the a epitaxial layer (or III-V compound semiconductor film) can be precisely controlled by adjusting the intensity of the UV laser beams and controlling the sizes of the targets. 
     Referring  FIG. 2A ,  FIG. 2B , and  FIG. 2C  simultaneously, the process and operation of forming a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film) by using the pulsed laser deposition system is detailed as following: First, the laser source  102  is turned on to emit a UV laser. After, the beam-splitting lens  201  in the beam-splitting device  200  splits the UV laser into several UV laser beams, and then, the beam-splitting lens  201  adjusts the intensity of the UV laser beams. After, the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  reflect the UV laser beams to the corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d  respectively. And then, the UV laser beams are respectively focused at the corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d  by the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  before the UV laser beams enter the chamber  300  through the laser input windows  304   a ,  304   b ,  304   c ,  304   d . After the UV laser beams are focused, intensity of each of the UV laser beams is precisely adjusted by the density filter lenses  208   a ,  208   b ,  208   c ,  208   d  (or baffles) according to the energy for gasifying (or plasma-izing) the target put on the target holding stage  404   a ,  404   b ,  404   c ,  404   d  corresponded to the laser input window  304   a ,  304   b ,  304   c ,  304   d  which the UV laser beam passes through. After, the UV laser beams simultaneously enter the chamber through different laser input windows  304   a ,  304   b ,  304   c ,  304   d , and then, the UV laser beams respectively irradiate on different target holding stages  404   a ,  404   b ,  404   c ,  404   d  on the target stage  400 . Next, a substrate or substrates are put on the carrier stage  500  and the different targets are put one different target holding stages  404   a ,  404   b ,  404   c ,  404   d . After, the chamber door  302  is closed and the vacuum pump  600  is turned on to vacuum the chamber  300  for achieving the required vacuum degree or pressure of pulsed laser deposition. And then, the chamber  300  is heated to the required temperature and the reaction gases are introduced into the chamber  300 . Next, the UV laser beams simultaneously enter the chamber through different laser input windows  304   a ,  304   b ,  304   c ,  304   d  and simultaneously irradiate on different targets put on different target holding stages  404   a ,  404   b ,  404   c ,  404   d  for gasifying (or plasma-izing) the targets to perform the pulsed laser deposition wherein the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are corresponded to different laser input windows  304   a ,  304   b ,  304   c ,  304   d . By splitting a UV laser into several UV laser beams and precisely controlling and adjusting intensity of the UV laser beams, several targets can be simultaneously gasified (or plasma-ized). Therefore, the ratio of the compositions of a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film) can be precisely controlled. 
     Referring  FIG. 2A ,  FIG. 2B , and  FIG. 2C  simultaneously, the process and operation of forming a doped epitaxial layer (or III-V compound semiconductor film) by using the pulsed laser deposition system is detailed as following: First, the laser source  102  is turned on to emit a UV laser. After the laser source  102  emits a UV laser, the beam-splitting lens  201  splits the UV laser into several UV laser beams, and then, the beam-splitting lens  201  adjusts the intensity of the UV laser beams. After, the reflecting lenses  204   a ,  204   b ,  204   c ,  204   d  reflect the UV laser beams to the corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d  respectively. And then, the UV laser beams are respectively focused at the corresponded laser input windows  304   a ,  304   b ,  304   c ,  304   d  by the focusing lenses  206   a ,  206   b ,  206   c ,  206   d  before the UV laser beams enter the chamber  300  through the laser input windows  304   a ,  304   b ,  304   c ,  304   d . After the UV laser beams are focused, intensity of each of the UV laser beams is precisely adjusted by the density filter lenses  208   a ,  208   b ,  208   c ,  208   d  (or baffles) according to the energy for gasifying (or plasma-izing) the target put on the target holding stage  404   a ,  404   b ,  404   c ,  404   d  corresponded to the laser input window  304   a ,  304   b ,  304   c ,  304   d  which the UV laser beam passes through. The energy of the UV laser beam(s) used to gasify (or plasma-ize) the doping target(s), which is used to dope the epitaxial layer, is much weaker than the energy of the UV laser beam(s) used to gasify (or plasma-ize) the other target(s) which is used to form the epitaxial layer. Therefore, more additional density filter lenses or one or more additional baffles can be added for further weakening the energy of the UV laser beam(s) used to gasify (or plasma-ize) the doping target(s). After, the UV laser beams simultaneously enter the chamber through different laser input windows  304   a ,  304   b ,  304   c ,  304   d , and then, the UV laser beams respectively irradiate on different target holding stages  404   a ,  404   b ,  404   c ,  404   d . It is noticed that the weakened UV laser beam(s) must irradiate on the target holding stage(s) which is used to hold or carry the doping target. Next, a substrate or substrates are put on the carrier stage  500  and the different targets are put one different target holding stages  404   a ,  404   b ,  404   c ,  404   d . It is noticed that the doping target must be put on the target holding stage(s) which will be irradiated by the weakened UV laser beam(s) and is corresponded to the laser input window for the weakened UV laser beam pass through. After, the chamber door  302  is closed and the vacuum pump  600  is turned on to vacuum the chamber  300  for achieving the required vacuum degree or pressure of pulsed laser deposition. And then, the chamber  300  is heated to the required temperature and the reaction gases are introduced into the chamber  300 . Next, the UV laser beams simultaneously enter the chamber through different laser input windows  304   a ,  304   b ,  304   c ,  304   d  and simultaneously irradiate on different targets put on different target holding stages  404   a ,  404   b ,  404   c ,  404   d  for gasifying (or plasma-izing) the targets to perform the pulsed laser deposition wherein the target holding stages  404   a ,  404   b ,  404   c ,  404   d  are corresponded to different laser input windows  304   a ,  304   b ,  304   c ,  304   d . By splitting a UV laser into several UV laser beams, which have much difference between their intensity, and by precisely controlling and adjusting intensity of the UV laser beams, several targets (including the doping targets and the targets for forming the epitaxial layer) can be simultaneously gasified (or plasma-ized). Therefore, the ratio of the compositions of a doped epitaxial layer (or III-V compound semiconductor film) and the doping concentration of a doped epitaxial layer (or III-V compound semiconductor film) can be precisely controlled. 
     According to foregoing embodiments, the present invention provides a pulsed laser deposition system. In the pulsed laser deposition system, by the beam-splitting device, a plurality of laser input windows deposed on the chamber, and the target stage constructed of a plurality of target holding stages, the UV laser provided by the UI laser source is split into a plurality of UV laser beams, and the UV laser beams simultaneously enter into the chamber and simultaneously irradiate on different targets respectively through different laser input windows. Therefore, the pulsed laser deposition system is capable of fabricating a doped epitaxial layer or a ternary or more (such as quaternary) epitaxial layer (or III-V compound semiconductor film). Furthermore, the pulsed laser deposition system is capable of perform pulsed laser deposition to a substrate with big size (&gt;4 inches) because the carrier stage is a carrier stage with big size (≧6 inches).