Patent Document

CROSS REFERENCE 
     This patent is a continuation-in-part of U.S. patent Ser. No. 09/712,730 filed Nov. 14, 2000, and is a continuation-in-part of U.S. patent Ser. No. 09/728,691 filed Dec. 1, 2000, and claims the benefit of U.S. Provisional Patent Ser. No. 60/257824 filed Dec. 22, 2000, all of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to lithographic exposure equipment, and more particularly, to a photolithography system and method, such as can be used in the manufacture of semiconductor integrated circuit devices. 
     In conventional analog photolithography systems, the photographic equipment requires a mask for printing an image onto a subject. The subject may include, for example, a photo resist coated semiconductor substrate for manufacture of integrated circuits, metal substrate for etched lead frame manufacture, conductive plate for printed circuit board manufacture, or the like. A patterned mask or photomask may include, for example, a plurality of lines or structures. During a photolithographic exposure, the subject must be aligned to the mask very accurately using some form of mechanical control and sophisticated alignment mechanism. 
     U.S. Pat. No. 5,691,541, which is hereby incorporated by reference, describes a digital, reticle-free photolithography system. The digital system employs a pulsed or strobed excimer laser to reflect light off a programmable digital mirror device (DMD) for projecting a component image (e.g., a metal line) onto a substrate. The substrate is mounted on a stage that is moves during the sequence of pulses. 
     U.S. Pat. Ser. No. 09/480,796, filed Jan. 10, 2000, now U.S. Pat. No. 6,379,867, and hereby incorporated by reference, discloses another digital photolithography system which projects a moving digital pixel pattern onto specific sites of a subject. A “site” may represent a predefined area of the subject that is scanned by the photolithography system with a single pixel element. 
     Both digital photolithography systems project a pixel-mask pattern onto a subject such as a wafer, printed circuit board, or other medium. The systems provide a series of patterns to a pixel panel, such as a deformable mirror device or a liquid crystal display. The pixel panel provides images consisting of a plurality of pixel elements, corresponding to the provided pattern, that may be projected onto the subject. 
     Each of the plurality of pixel elements is then simultaneously focused to different sites of the subject. The subject and pixel elements are then moved and the next image is provided responsive to the movement and responsive to the pixel-mask pattern. As a result, light can be projected onto or through the pixel panel to expose the plurality of pixel elements on the subject, and the pixel elements can be moved and altered, according to the pixel-mask pattern, to create contiguous images on the subject. 
     With reference now to FIG. 1 a , a conventional analog photolithography system that uses a photomask can easily and accurately produce an image  10  on a subject  12 . The image  10  can have horizontal, vertical, diagonal, and curved components (e.g., metal conductor lines) that are very smooth and of a consistent line width. 
     Referring also to FIG. 1 b , a conventional digital photolithography system that uses a digital mask can also produce an image  14  on a subject  16 . Although the image  14  can have horizontal, vertical, diagonal, and curved components, like the analog image  12  of FIG. 1 a , some of the components (e.g., the diagonal ones) are neither very smooth nor of a consistent line width. 
     Certain improvements are desired for digital photolithograph systems, such as the ones described above. For one, it is desirable to provide smooth components, such as diagonal and curved metal lines, like those produced with analog photolithography systems. In addition, it is desired to have a relatively large exposure area, to provide good image resolution, to provide good redundancy, to use a relatively inexpensive incoherent light source, to provide high light energy efficiency, to provide high productivity and resolution, and to be more flexible and reliable. 
     SUMMARY 
     A technical advance is provided by a novel method and system for performing digital lithography onto a subject. In one embodiment, the system includes a light source for producing a first light and an optical diffraction element for individually focusing the first light into a plurality of second lights. The system also includes a pixel panel for generating a digital pattern, the pixel panel having a plurality of pixels corresponding to the plurality of second lights. A lens system may then direct the digital pattern to the subject, thereby enabling the lithography. 
     In some embodiments, the pixel panel is a spatial light modulator. 
     In some embodiments, the system also includes a beam splitter for directing the plurality of second lights to the pixel panel and for directing the digital pattern to the lens system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a  and  1   b  are images produced by a conventional analog photolithography system and a conventional digital photolithography system, respectively. 
     FIG. 2 is a block diagram of an improved digital photolithography system for implementing various embodiments of the present invention. 
     FIGS. 3 a  and  3   b  illustrate various overlay arrangement of pixels being exposed on a subject. 
     FIGS. 4 a  and  4   b  illustrate the effect of overlaid pixels on the subject. 
     FIG. 5 illustrates a component exposure from the system of FIG. 2, compared to conventional exposures from the systems of FIGS. 1 b  and  1   a.    
     FIGS. 6 a  and  6   b  illustrate component exposures, corresponding to the images of FIGS. 1 a  and  1   b , respectively. 
     FIG. 7 illustrates various pixel patterns being provided to a pixel panel of the system of FIG.  2 . 
     FIGS. 8,  9 , and  10 . 1 - 10 . 20  provide diagrams of a subject that is positioned and scanned at an angle on a stage. The angle facilitates the overlapping exposure of a site on the subject according to one embodiment of the present invention. 
     FIG. 11 is a block diagram of a portion of the digital photolithography system of FIG. 2 for implementing additional embodiments of the present invention 
     FIGS. 12-13 provide diagrams of a subject that is positioned and scanned at an angle on a stage and being exposed by the system of FIG.  11 . 
     FIG. 14 illustrates a site that has been overlapping exposed 600 times. 
     FIGS. 15-25 are block diagrams of several different digital photolithography systems for implementing various embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to exposure systems, such as can be used in semiconductor photolithographic processing. It is understood, however, that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention from that described in the claims. 
     Maskless Photolithography System 
     Referring now to FIG. 2, a maskless photolithography system  30  includes a light source  32 , a first lens system  34 , a computer aided pattern design system  36 , a pixel panel  38 , a panel alignment stage  39 , a second lens system  40 , a subject  42 , and a subject stage  44 . A resist layer or coating  46  may be disposed on the subject  42 . The light source  32  may be an incoherent light source (e.g., a Mercury lamp) that provides a collimated beam of light  48  which is projected through the first lens system  34  and onto the pixel panel  38 . 
     The pixel panel  38  is provided with digital data via suitable signal line(s)  50  from the computer aided pattern design system  36  to create a desired pixel pattern (the pixel-mask pattern). The pixel-mask pattern may be available and resident at the pixel panel  38  for a desired, specific duration. Light emanating from (or through) the pixel-mask pattern of the pixel panel  38  then passes through the second lens system  40  and onto the subject  42 . In this manner, the pixel-mask pattern is projected onto the resist coating  46  of the subject  42 . 
     The computer aided mask design system  36  can be used for the creation of the digital data for the pixel-mask pattern. The computer aided pattern design system  36  may include computer aided design (CAD) software similar to that which is currently used for the creation of mask data for use in the manufacture of a conventional printed mask. Any modifications and/or changes required in the pixel-mask pattern can be made using the computer aided pattern design system  36 . Therefore, any given pixel-mask pattern can be changed, as needed, almost instantly with the use of an appropriate instruction from the computer aided pattern design system  36 . The computer aided mask design system  36  can also be used for adjusting a scale of the image or for correcting image distortion. 
     In the present embodiment, the pixel panel  38  is a digital light processor (DLP) or digital mirror device (DMD) such as is illustrated in U.S. Pat. No. 5,079,544 and patents referenced therein. Current DMD technology provides a 600×800 array of mirrors for a set of potential pixel elements. Each mirror can selectively direct the light  48  towards the subject  42  (the “ON” state) or away from the subject (the “OFF” state). Furthermore, each mirror can alternate between ON and OFF for specific periods of time to accommodate variations in light efficiency. For example, if the second lens system  40  has a “darker” area (e.g., a portion of the lens system is inefficient or deformed), the DMD can alternate the mirrors corresponding with the “brighter” areas of the lens, thereby equalizing the overall light energy projected through the lens. For the sake of simplicity and clarity, the pixel panel  38  will be further illustrated as one DMD. Alternate embodiments may use multiple DMDs, one or more liquid crystal displays and/or other types of digital panels. 
     In some embodiments, the computer aided mask design system  36  is connected to a first motor  52  for moving the stage  44 , and a driver  54  for providing digital data to the pixel panel  38 . In some embodiments, an additional motor  55  may be included for moving the pixel panel, as discussed below. The system  36  can thereby control the data provided to the pixel panel  38  in conjunction with the relative movement between the pixel panel  38  and the subject  42 . 
     Pixel Overlay 
     The amount of exposure time, or exposure intensity, of light from the pixel panel  38  directly affects the resist coating  46 . For example, if a single pixel from the pixel panel  38  is exposed for a maximum amount of time onto a single site of the subject  42 , or for a maximum intensity, then the corresponding portion of resist coating  46  on the subject would have a maximum thickness (after non-exposed or under exposed resist has been removed). If the single pixel from the pixel panel  38  is exposed for less than the maximum amount of time, or at a reduced intensity, the corresponding portion of resist coating  46  on the subject  42  would have a moderate thickness. If the single pixel from the pixel panel  38  is not exposed, then the corresponding portion of resist coating  42  on the subject  42  would eventually be removed. 
     Referring now to FIGS. 3 a  and  3   b , it is desired that each pixel element exposed onto a site overlap previous pixel element exposures. FIG. 3 a  shows a one-direction overlay scenario where a pixel element  80 . 1  is overlapped by pixel element  80 . 2 , which is overlapped by pixel element  80 . 3 , . . . which is overlapped by pixel element  80 .N, where “N” is the total number of overlapped pixel elements in a single direction. It is noted that, in the present example, pixel element  80 . 1  does not overlay pixel element  80 .N. 
     FIG. 3 b  is a two-dimensional expansion FIG. 3 a . In this example, pixel element  80 . 1  is overlapped in another direction by pixel element  81 . 1 , which is overlapped by pixel element  82 . 1 , . . . which is overlapped by pixel element  8 M.N, where “M” is the total number of overlapped pixel elements in a second direction. As a result, a total of M×N pixel elements can be exposed for a single site. 
     Referring now to FIG. 4 a , consider for example a site that has the potential to be exposed by (M,N)=(4,4) pixel elements. In this example, only four of the 16 possible pixel elements are actually “ON”, and therefore expose portions of the subject  42 . These four pixel elements are designated:  100 . 1 ,  100 . 2 ,  100 . 3 ,  100 . 4 . The four pixel elements  100 . 1 - 100 . 4  are exposed onto the photo resist  46  of the subject  42 . All four pixel elements  100 . 1 - 100 . 4  overlap with each other at an area  102 ; three of the pixel elements overlap at an area  104 ; two of the pixel elements overlap at an area  106 ; and an area  108  is only exposed by one pixel element. Accordingly, area  102  will receive maximum exposure (100%); area  104  will receive 75% exposure; area  106  will receive 50% exposure; and area  108  will receive 25% exposure. It is noted that the area  102  is very small, {fraction (1/16)}th the size of any pixel element  100 . 1 - 100 . 4  in the present example. 
     Referring now to FIG. 4 b , the example of FIG. 4 a  can be expanded to (M,N)=(6,6) pixel elements, with two more overlapping pixel elements  100 . 5 ,  100 . 6  in the ON state. The pixel elements  100 . 5 ,  100 . 6  are therefore exposed onto the photo resist  46  of the subject  42  so that they overlap some of the four pixel elements  100 . 1 - 100 . 4 . In this expanded example, the pixel elements  100 . 1 - 100 . 4  overlap with each other at area  102 ; the four pixel elements  100 . 2 - 100 . 5  overlap each other at an area  110 ; and the four pixel elements  100 . 3 - 100 . 6  overlap each other at an area  112 . In addition, area  114  will receive 75% exposure; area  116  will receive 50% exposure; and area  118  will receive 25% exposure. As a result, a very small ridge is formed on the photo resist  46 . 
     In one embodiment, the pixel panel  32  of the present invention may have a 600×800 array of pixel elements. The overlapping is defined by the two variables: (M, N). Considering one row of 600 pixels, the system overlaps the 600 pixels onto an overlay area  184  of: 
     
       
         ( M,N )=20 pixels×30 pixels.  (1) 
       
     
     Referring also to FIG. 5 a , the process of FIGS. 4 a  and  4   b  can be repeated to produce a diagonal component  150  on the subject  42 . Although the example of FIGS. 4 a  and  4   b  have only four potential degrees of exposure (100%, 75%, 50%, 25%), by increasing the number of overlaps (such as is illustrate in FIG. 3 b ), it is possible to have a very fine resolution of desired exposure. 
     The diagonal component  120  appears as a prism-shaped structure having a triangular cross-section. If the subject  42  is a wafer, the component  120  may be a conductor (e.g., a metal line), a section of poly, or any other structure. The top most portion  120   t  of the component is the portion of photo resist  46  that is overlapped the most by corresponding pixel elements, and therefore received the maximum exposure. 
     The component  120  is contrasted with a component  122  of FIG. 5 b  and a component  124  of FIG. 5 c . The component  122  of FIG. 5 b  illustrates a conventional digital component. The component  124  of FIG. 5 c  illustrates a conventional analog component. 
     Overlay Methods 
     Referring again to FIG. 2, the above-described overlays can be implemented by various methods. In general, various combinations of moving and/or arranging the pixel panel  38  and/or the subject  42  can achieve the desired overlap. 
     In one embodiment, the maskless photolithography system  30  performs two-dimensional digital scanning by rapidly moving the image relative to the subject in two directions (in addition to the scanning motion). The panel motor  55  is attached to the pixel panel  38  to move the pixel panel in two directions, represented by an x-arrow  132  and a y-arrow  134 . The panel motor  55  may be a piezo electric device (PZT) capable of making very small and precise movements. 
     In addition, the scanning motor  55  scans the stage  44 , and hence the subject  42 , in a direction  136 . Alternatively, the stage  44  can be fixed and the panel motor  55  can scan the pixel panel  38  (and the lenses  40 ) opposite to direction  136 . 
     Referring also to FIG. 7, corresponding to the image scanning described above, the pixel-mask pattern being projected by the pixel panel  38  changes accordingly. This correspondence can be provided, in one embodiment, by having the computer system  36  (FIG. 2) control both the scanning movement  70  and the data provided to the pixel panel  38 . The illustrations of FIG.  7  and the following discussions describe how the data can be timely provided to the pixel panel. 
     FIG. 7 shows three intermediate patterns of pixel panel  38 . Since the pattern on the pixel panel  38  and the data on the signal lines  50  change over time, the corresponding patterns on the pixel panel and data on the signal lines at a specific point in time are designated with a suffix “0.1”, “0.2”, or “0.3”. In the first intermediate pattern, the pattern of pixel panel  38 . 1  is created responsive to receiving data DO provided through the signal lines  50 . 1 . In the present example, the pattern is created as a matrix of pixel elements in the pixel panel  38 . 1 . After a predetermined period of time (e.g., due to exposure considerations being met), the pattern is shifted. The shifted pattern (now shown as pixel panel  38 . 2 ) includes additional data D 1  provided through the signal lines  38 . 2 . The shifting between patterns may also utilize a strobing or shuttering of the light source  32 . 
     In the second intermediate pattern of FIG. 7, D 1  represents the left-most column of pixel elements in the pattern of DMD 38 . 2 . After another predetermined period of time, the pattern (now shown as pixel panel  38 . 3 ) is shifted again. The twice-shifted pattern includes additional data D 2  provided through the signal lines  38 . 2 . In the third intermediate pattern of FIG. 7, D 2  now represents the left-most column of pixel elements in the pattern of the DMD 38 . 3 . Thus, the pattern moves across the pixel panel  38  in a direction  138 . It is noted that the pattern direction  138 , as it is being provided to the pixel panel  38  from the signal lines  50 , is moving opposite to the scanning direction  136 . In some embodiments, the pattern may be shifted in additional directions, such as perpendicular to the scanning direction  136 . 
     Referring now to FIG. 8, in some embodiments, the maskless photolithography system  30  performs two-dimensional digital scanning by rapidly moving the image relative to the subject  42  in one direction (in addition to the scanning motion) while the subject is positioned on the stage  44  to accommodate the other direction. The panel motor  55  moves the pixel panel  38  in one direction, represented by the y-arrow  134 . The scanning motor  55  scans the stage  44 , and hence the subject  42  in a direction  136 . Alternatively, the stage  44  can be fixed and the panel motor  55  can scan the pixel panel  38  (and the lenses  40 ) opposite to direction  136 . 
     The image from the pixel panel  38  and/or the subject  42  is aligned at an angle θ with the scan direction  136 . Considering that each pixel projected onto subject  42  has a length of l and a width of w, then θ can be determined as:              θ   =         tan     -   1            (       w   -     1   /   M         N   ×   l       )       .             (   2   )                                
     In another embodiment, the offset may go in the opposite direction, so that θ can be determined as:              θ   =         tan     -   1            (       w   +     1   /   M         N   ×   l       )       .             (   3   )                                
     Referring to FIGS.  9  and  10 . 1 , consider for example two sites  140 . 1 ,  142 . 1  on the subject  42 . Initially, the two sites  140 . 1  and  142 . 1  are simultaneously exposed by pixel elements P 1  and P 50 , respectively, of the pixel panel  38 . The pixel elements P 1  and P 50  are located at a row R 0  and columns C 1  and C 0 , respectively, of the pixel panel  38 . This row and column designation is arbitrary, and has been identified in the present embodiment to clarify the example. The following discussion will focus primarily on site  140 . 1 . It is understood, however, that the methods discussed herein are typically applied to multiple sites of the subject, including the site  142 . 1 , but further illustrations and discussions with respect to site  142 . 1  will be avoided for the sake of clarity. 
     As can be clearly seen in FIG. 9, the pixel panel  38  is angled with respect to the subject  42  and the scan direction  136 . As the system  30  scans, pixel element P 11  would normally be projected directly on top of site  140 . 1 . However, as shown in FIG. 10.2, the pixel element P 11  exposes at a location  140 . 11  that is slightly offset in the y direction (or −y direction) from the site  140 . 1 . As the system  30  continues to scan, pixel elements P 12 -P 14  are exposed on offset locations  140 . 12 - 140 . 14 , respectively, shown in FIGS.  10 . 3 - 10 . 5 , respectively. Pixel elements P 11 -P 14  are on adjacent consecutive rows R 1 , R 2 , R 3 , R 4  of column C 1  of the pixel panel  38 . 
     In the present embodiment, the scanning motor  52  moves the stage  44  (and hence the subject  42 ) a distance of l, the length of the pixel site  140 . 1 , for each projection. To provide the offset discussed above, the panel motor  55  moves the pixel panel  38  an additional distance of l/(N−1) for each projection. (N=5 in the present example). Therefore, a total relative movement SCAN STEP for each projection is: 
     
       
         SCAN STEP= l+l /( N− 1).  (4) 
       
     
     In another embodiment, the offset may go in the opposite direction, so that the total relative movement SCAN STEP for each projection is: 
     
       
         SCAN STEP= l−l /( N− 1).  (5) 
       
     
     In some embodiments, the panel motor 55 is not needed. Instead, the scanning motor  52  moves the stage the appropriate length (equation 4 or 5, above). 
     Once N locations have been exposed, the next pixel elements being projected onto the desired locations are of an adjacent column. With reference to FIG. 10.6, in the present example, a pixel element P 2  at row RS, column C 2  exposes a location  140 . 2  that is slightly offset in the x direction (or −x direction, depending on whether equation 4 or 5 is used) from the site  140 . 1 . As the system  30  continues to scan, pixel elements P 21 -P 24  are exposed on offset locations  140 . 21 - 140 . 24 , respectively, shown in FIGS.  10 . 7 - 10 . 10 , respectively. Pixel elements P 21 -P 24  are on adjacent consecutive rows R 6 , R 7 , R 8 , R 9  of column C 2  of the pixel panel  38 . 
     Once N more pixel locations have been exposed, the next pixel elements being projected onto the desired locations are of yet another adjacent column. With reference to FIG. 10.11, in the present example, a pixel element P 3  at row R 10 , column C 3  exposes a location  140 . 3  that is slightly offset in the x direction (or −x direction, depending on whether equation 4 or 5 is used) from the location  140 . 2 . As the system  30  continues to scan, pixel elements P 31 -P 34  are exposed on offset locations  140 . 31 - 140 . 34 , respectively, shown in FIGS.  10 . 12 - 10 . 15 , respectively. Pixel elements P 31 -P 34  are on adjacent consecutive rows R 11 , R 12 , R 13 , R 14  of column C 3  of the pixel panel  38 . 
     The above process repeats to fully scan the desired overlapped image. With reference to FIG. 10.16, in the present example, a pixel element P 4  at row R 15 , column C 4  exposes a location  140 . 4  that is slightly offset in the x direction (or −x direction, depending on whether equation 4 or 5 is used) from the location  140 . 3 . As the system  30  continues to scan, pixel elements P 41 -P 44  are exposed on offset locations  140 . 41 - 140 . 44 , respectively, shown in FIGS.  10 . 17 - 10 . 20 , respectively. Pixel elements P 41 -P 44  are on adjacent consecutive rows R 16 , R 17 , R 18 , R 19  of column C 4  of the pixel panel  38 . 
     Point Array System and Method 
     Referring now to FIG. 11, in another embodiment of the present invention, the photolithography system  30  utilizes a unique optic system  150  in addition to the lens system  40 . The optic system  150  is discussed in detail in U.S. Pat. Ser. No. 09/480,796, which is hereby incorporated by reference. It is understood that the lens system  40  is adaptable to various components and requirements of the photolithography system  30 , and one of ordinary skill in the art can select and position lenses appropriately. For the sake of example, a group of lenses  40   a  and an additional lens  40   b  are configured with the optic system  150 . 
     The optic system  150  includes a grating  152  and a point array  154 . The grating  152  may be a conventional shadow mask device that is used to eliminate and/or reduce certain bandwidths of light and/or diffractions between individual pixels of the pixel panel  38 . The grating  152  may take on various forms, and in some embodiments, may be replaced with another device or not used at all. 
     The point array  154  is a multi-focus device. There are many types of point arrays, including a Fresnel ring, a magnetic e-beam lens, an x-ray controlled lens, and an ultrasonic controlled light condensation device for a solid transparent material. 
     In the present embodiment, the point array  154  is a compilation of individual microlenses, or microlens array. In the present embodiments, there are as many individual microlenses as there are pixel elements in the pixel panel  38 . For example, if the pixel panel  38  is a DMD with 600×800 pixels, then the microlens array  154  may have 600×800 microlenses. In other embodiments, the number of lenses may be different from the number of pixel elements in the pixel panel  38 . In these embodiments, a single microlens may accommodate multiple pixels elements of the DMD, or the pixel elements can be modified to account for alignment. For the sake of simplicity, only one row of four individual lenses  154   a ,  154   b ,  154   c ,  154   d  will be illustrated. In the present embodiment, each of the individual lenses  154   a ,  154   b ,  154   c ,  154   d  is in the shape of a rain drop. It is understood, however, that shapes other than those illustrated may also be used. 
     Similar to the lens system  40  of FIG. 2, the optic system  150  is placed between the pixel panel  38  and the subject  42 . For the sake of example, in the present embodiment, if the pixel panel  38  is a DMD device, light will (selectively) reflect from the DMD device and towards the optic system  150 . If the pixel panel  38  is a liquid crystal display (“LCD”) device or a transparent spatial light modulator (“SLM”), light will (selectively) flow through the LCD device and towards the optic system  150 . To further exemplify the present embodiment, the pixel panel  38  includes one row of elements (either mirrors or liquid crystals) for generating four pixel elements. 
     In continuance with the example, four different pixel elements  156   a ,  156   b ,  156   c ,  156   d  are projected from each of the pixels of the pixel panel  38 . In actuality, the pixel elements  156   a ,  156   b ,  156   c ,  156   d  are light beams that may be either ON or OFF at any particular instant (meaning the light beams exist or not, according to the pixel-mask pattern), but for the sake of discussion all the light beams are illustrated. 
     The pixel elements  156   a ,  156   b ,  156   c ,  156   d  pass through the lens system  40   a  and are manipulated as required by the current operating conditions. As discussed earlier, the use of the lens system  40   a  and  40   b  are design options that are well understood in the art, and one or both may not exist in some embodiments. The pixel elements  156   a ,  156   b ,  156   c ,  156   d  that are manipulated by the lens system  40   a  are designated  158   a ,  158   b ,  158   c ,  158   d , respectively. 
     The pixel elements  158   a ,  158   b ,  158   c ,  158   d  then pass through the microlens array  154 , with each beam being directed to a specific microlens  154   a ,  154   b ,  154   c ,  154 d, respectively. The pixel elements  158   a ,  158   b ,  158   c ,  158   d  that are manipulated by the microlens array  154  are designated as individually focused light beams  160   a ,  160   b ,  160   c ,  160   d , respectively. As illustrated in FIG. 11, each of the light beams  160   a ,  160   b ,  160   c ,  160   d  are being focused to focal points  162   a ,  162   b ,  162   c ,  162   d  for each pixel element. That is, each pixel element from the pixel panel  38  is manipulated until it focuses to a specific focal point. It is desired that the focal points  162   a ,  162   b ,  162   c ,  162   d  exist on the subject  42 . To achieve this goal, the lens  40   b  may be used in some embodiments to refocus the beams  160   a ,  160   b ,  160   c ,  160   d  on the subject  42 . FIG. 11 illustrates focal points  162   a ,  162   b ,  162   c ,  162   d  as singular rays, it being understood that the rays may not indeed be focused (with the possibility of intermediate focal points, not shown) until they reach the subject  42 . 
     Continuing with the present example, the subject  42  includes four exposure sites  170   a ,  170   b ,  170   c ,  170   d . The sites  170   a ,  170   b ,  170   c ,  170   d  are directly associated with the light beams  162   a ,  162   b ,  162   c ,  162   d , respectively, from the microlenses  154   a ,  154   b ,  154   c ,  154   d , respectively. Also, each of the sites  170   a ,  170   b ,  170 c,  170   d  are exposed simultaneously. However, the entirety of each site  170   a ,  170   b ,  170   c ,  170   d  is not exposed at the same time. 
     Referring now to FIG. 12, the maskless photolithography system  30  with the optic system  150  can also performs two-dimensional digital scanning, as discussed above with reference to FIG.  8 . For example, the image from the pixel panel  38  may be aligned at the angle θ (equations 2 and 3, above) with the scan direction  136 . 
     Referring also to FIG. 13, the present embodiment works very similar to the embodiments of FIGS. 9-10. However, instead of a relatively large location being exposed, the pixel elements are focused and exposed to a relatively small point (e.g., individually focused light beams  162   a ,  162   b ,  162   c ,  162   d  from FIG. 11) on the sites  170   a ,  170   b ,  170   c ,  170   d.    
     First of all, the pixel element  156   a  exposes the individually focused light beam  162   a  onto the single site  170   a  of the subject  42 . The focused light beam  162   a  produces an exposed (or unexposed, depending on whether the pixel element  156   a  is ON or OFF) focal point PT 1 . As the system  30  scans, pixel element  156   b  exposes the individually focused light beam  162   b  onto the site  170   a . The focused light beam  162   b  produces an exposed (or unexposed) focal point PT 2 . Focal point PT 2  is slightly offset from the focal point PT 1  in the y direction (or −y direction). As the system  30  continues to scan, pixel elements  156   c  and  156   d  expose the individually focused light beams  162   c  and  162   d , respectively, onto the site  170   a . The focused light beams  162   c  and  162   d  produce exposed (or unexposed) focal points PT 3  and PT 4 , respectively. Focal point PT 3  is slightly offset from the focal point PT 2  in the y direction (or −y direction), and focal point PT 4  is similarly offset from the focal point PT 3 . 
     Once N pixel elements have been projected, the next pixels being projected onto the desired sites are of an adjacent column. This operation is similar to that shown in FIGS.  10 . 6 - 10 . 20 . The above process repeats to fully scan the desired overlapped image on the site  170   a.    
     It is understood that while light beam  162   a  is being exposed on the site  170   a , light beam  162   b  is being exposed on the site  170   b , light beam  162   c  is being exposed on the site  170   c , and light beam  162   d  is being exposed on the site  170   d . Once the system  30  scans one time, light beam  162   a  is exposed onto a new site (not shown), while light beam  162   b  is exposed on the site  170   a , light beam  162   c  is exposed on the site  170   b , and light beam  162   d  is exposed on the site  170   c . This repeats so that the entire subject can be scanned (in the y direction) by the pixel panel  38 . 
     It is further understood that in some embodiments, the substrate  42  may be moved rapidly while the light beams (e.g.,  162   a-d ) transition from one site to the other (e.g.,  170   a-   170   d , respectively), and slowly while the light beams are exposing their corresponding sites. 
     By grouping several pixel panels together in the x−direction, the entire subject can be scanned by the pixel panels. The computer system  36  can keep track of all the data provided to each pixel panel to accommodate the entire scanning procedure. In other embodiments, a combination of scanning and stepping can be performed. For example, if the subject  42  is a wafer, a single die (or group of die) can be scanned, and then the entire system  30  can step to the next die (or next group). 
     The example of FIGS. 11-13 are limited in the number of pixel elements for the sake of clarity. In the figures, each focal point has a diameter of about ½ the length l or width w of the site  170   a . Since N=4 in this example, the overlap spacing is relatively large and the focal points do not overlap very much, if at all. As the number of pixel elements increase (and thus N increases), the resolution and amount of overlapping increase, accordingly. 
     For further example, FIG. 14 illustrates a site  220  that has been exposed by 600 pixel elements with focal points PT 1 -PT 600  (e.g., from a 600×800 DMD). As can be seen, the focal points PT 1 -PT 600  are arranged in an array (similar to equation 1, above) of: 
     
       
         ( M,N )=20 focal points×30 focal points.  (6) 
       
     
     By selectively turning ON and OFF the corresponding pixel elements, a plurality of structures  222 ,  224 ,  226  can be formed on the site  220 . It is noted that structures  222 - 226  have good resolution and can be drawn to various different shapes, including diagonal. It is further noted that many of the focal points on the periphery of the site  220  will eventually overlap with focal points on adjacent sites. As such, the entire subject  42  can be covered by these sites. 
     Alternatively, certain focal points or other types of exposed sites can be overlapped to provide sufficient redundancy in the pixel panel  38 . For example, the same 600 focal points of FIG. 14 can be used to produce an array of: 
     
       
         ( M,N )=20 focal points×15 focal points.  (7) 
       
     
     By duplicating the exposure of each focal point, this redundancy can accommodate one or more failing pixel elements in the pixel panel  38 . 
     Additional Embodiments of the Point Array System 
     FIGS. 15-25, below, describe additional configurations of the point array system that can be implemented, each providing different advantages. To the extent that similar components are used as those listed in FIGS. 2 and 11, the same reference numerals will also be used. 
     Referring now to FIG. 15, a maskless photolithography system  300  is similar to the systems of FIGS. 2 and 11. The system  300  includes a transparent spatial light modulator (“SLM”) as the pixel panel  38 . The light  48  passes through the SLM  38  and, according to the pixel pattern provided to the SLM, is selectively transmitted towards the substrate  42 . 
     Referring now to FIG. 16, a maskless photolithography system  320  is similar to the system  300  of FIG. 15, except that it positions the micro-lens array  154  and the grating  152  before (as determined by the flow of light  48 ) the SLM  38 . 
     Referring now to FIG. 17, a maskless photolithography system  340  is similar to the system  320  of FIG. 16, except that it uses an optical diffraction element  342  instead of the micro-lens array  154  and grating  152 . The optical diffraction element  342  may be of the type used for holograms, or a binary diffraction component. 
     Referring now to FIG. 18, a maskless photolithography system  360  is similar to the system  320  of FIG. 16, except that the SLM  38  is non-transparent. For this system  360 , a beam splitter  362  is used to direct the incoming light  48  towards the SLM  38 , and the reflected image towards the lens system  40   a.    
     Referring now to FIG. 19, a maskless photolithography system  380  is similar to the system  360  of FIG. 18, except for the location of the components. The incoming light  48  first passes through the microlens array  154 , the grating  152 , and then through the beam splitter  362 . At this time, the light is separately focusable into individual pixels. The pixelized light then reflects off the SLM  38  and the resulting image passes back through the beam splitter  362  and onto the subject  42 . 
     Referring now to FIG. 20, a maskless photolithography system  400  is similar to the system  380  of FIG. 19, except that the beam splitter  382  is positioned adjacent to the SLM  38 . 
     Referring now to FIG. 21, a maskless photolithography system  420  is similar to the system  400  of FIG. 20, except that instead of a microlens array and grating, the system uses the optical diffraction component  342 . 
     Referring now to FIG. 22, a maskless photolithography system  440  is similar to the system  400  of FIG. 20, except that the image lens  40   b  is positioned on both sides of the beam splitter  382 . 
     Referring now to FIG. 23, a maskless photolithography system  460  is similar to the system  420  of FIG. 21, except that the image lens  40   b  is positioned on both sides of the beam splitter  382 . 
     Referring now to FIG. 24, a maskless photolithography system  480  is similar to the system  320  of FIG. 16, except that the pixel panel  38  is a DMD, and the light reflects off the individual micro mirrors of the DMD at a predetermined angle. 
     Referring now to FIG. 25, a maskless photolithography system  500  is similar to the system  340  of FIG. 17, except that the pixel panel  38  is a DMD, and the light reflects off the individual micro mirrors of the DMD at a predetermined angle. 
     While the invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing form the spirit and scope of the invention. For example, multiple DMD pixel panels can be configured in a serial orientation. In this manner, light from the light source  32  can be projected to the first DMD, where it is reflected to the second DMD, where it is further reflected onto the subject  42 . In this scenario, the second DMD can be used to generate the image to be exposed while the first DMD controls light uniformity according to simultaneous or previously mapped data. Therefore, the claims should be interpreted in a broad manner, consistent with the present invention.

Technology Category: 3