Patent Document

BACKGROUND 
     Technical Field 
     The disclosure concerns a method of forming layered structures by atomic layer deposition of materials, in accordance with a predetermined pattern of different materials in an integrated circuit. 
     Background Discussion 
     In some fabrication processes for forming integrated circuits, it is desirable to deposit thin films by atomic layer deposition (ALD) in accordance with a predetermined pattern. The pattern defines selective areas on a workpiece surface for deposition by an ALD process, while ALD is prevented in the other areas. Such a process is referred to herein as selective area atomic layer deposition. The problem is how to accurately govern the boundaries of the selective areas. 
     SUMMARY 
     A first method of performing atomic layer deposition in selected zones of a workpiece comprises: (a) providing a surface in each of the selected zones of a first material of a first type that is initially hydrophilic and that becomes hydrophobic upon treatment with a fluoro-carbon plasma or fluoro-carbon ion beam; (b) providing a surface of a second material in other zones of the workpiece that remains hydrophilic upon treatment with a fluoro-carbon plasma or fluoro-carbon ion beam; (c) performing a plasma treatment on the workpiece using a plasma derived from a fluoro-carbon species; and (d) performing an atomic layer deposition process on the workpiece, and growing an atomic layer of a growth material on surfaces of the selected zones while generally avoiding growth of an atomic layer of the growth material in the other zones. 
     In one embodiment, the first material comprises any material that becomes hydrophilic upon treatment with a fluoro-carbon plasma or fluoro-carbon ion beam, such as (but not limited to) for example one of W, Co, SiN, T-oxide, TEOS or Si. In one embodiment, the second material comprises any material that remains hydrophilic upon treatment with a fluoro-carbon plasma or fluoro-carbon ion beam, such as (but not limited to) one of Cu or TiN. In one embodiment, the growth material comprises a metal or an oxide of a metal. 
     In one embodiment, the method is repeated until a desired thickness of the growth material is reached. 
     In one embodiment, the method further comprises removing growth material defects in the other zones. 
     A second method of performing atomic layer deposition in selected zones of a workpiece comprises: (a) depositing a first photolithographic mask on the workpiece comprising first openings corresponding to portions of the selected zones; (b) treating the workpiece by exposure to species derived from a fluoro-carbon plasma; (c) removing the first photolithographic mask; (d) depositing a second photolithographic mask on the workpiece comprising second openings corresponding to remaining portions of the selected zones; (e) treating the workpiece by exposure to species derived from a fluoro-carbon plasma; (f) removing the second photolithographic mask; and (g) performing an atomic layer deposition process. 
     In one embodiment, the method further comprises removing growth material from areas outside of the selected zones. 
     In one embodiment, the treating the workpiece comprises forming a fluoro-carbon plasma and exposing the workpiece to the plasma. In one embodiment, the treating the workpiece comprises forming an ion beam from a fluoro-carbon plasma and directing the ion beam to the workpiece. 
     In one embodiment, the atomic layer deposition process produces a growth material. The growth material may be any material that can be formed by atomic layer deposition such as (but not limited to) metal, a non-metal or a metal oxide. 
     A third method of performing atomic layer deposition in selected zones of a workpiece comprises: (a) depositing a first photolithographic mask on the workpiece comprising first openings corresponding to portions of the selected zones; (b) treating the workpiece by exposure to species derived from a fluoro-carbon plasma; (c) removing the first photolithographic mask; (d) performing a first atomic layer deposition process on the workpiece; (e) depositing a second photolithographic mask on the workpiece comprising second openings corresponding to remaining portions of the selected zones; (f) treating the workpiece by exposure to species derived from a fluoro-carbon plasma; (g) removing the second photolithographic mask; and (h) performing a second atomic layer deposition process. 
     In one embodiment, the first and second atomic layer deposition processes deposit different growth materials on the workpiece. 
     In one embodiment, the treating the workpiece comprises forming a fluoro-carbon plasma and exposing the workpiece to the plasma. In one embodiment, the treating the workpiece by exposure to species derived from a fluoro-carbon plasma comprises forming an ion beam from a fluoro-carbon plasma and directing the ion beam to the workpiece. 
     In one embodiment, the first and second atomic layer deposition process produce on the workpiece different respective growth materials. 
     A first method of performing atomic layer deposition in selected zones of a workpiece having 3-dimensional structures on a surface thereof comprising vertical walls separated by trenches, comprises: (a) providing a directional plasma source emitting ions along an ion propagation direction toward the workpiece; (b) orienting the ion propagation direction relative to the vertical walls to enable the vertical walls to mask the selected zones from the ions emitted by the directional plasma source; and (c) performing an atomic layer deposition process on the workpiece. 
     In one embodiment, the directional plasma source emits ions in two beams tilted relative to the vertical walls through opposing angles and the two beams strike opposing ones of the vertical walls. 
     In one embodiment, the directional plasma source emits a beam tilted relative to the vertical walls and the beams strikes one of the vertical walls. 
     In one embodiment, the directional plasma source emits ions in one beam parallel to the vertical walls. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the exemplary embodiments of the present invention are attained can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be appreciated that certain well known ‘processes are not discussed herein in order to not obscure the invention. 
         FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G and 1H  depict successive operations of a process performed on a workpiece in accordance with a first embodiment. 
         FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H  depict successive operations of a process performed on a workpiece in accordance with a second embodiment. 
         FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G and 3H  depict successive operations of a process performed on a workpiece, in accordance with a third embodiment 
         FIGS. 4A and 4B  depict successive operations of a process performed on a workpiece in accordance with a fourth embodiment. 
         FIGS. 5A and 5B  depict successive operations of a process performed on a workpiece in accordance with a fifth embodiment. 
         FIGS. 6A and 6B  depict successive operations of a process performed on a workpiece in accordance with a fifth embodiment. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     DETAILED DESCRIPTION 
     Selective ALD formation of a deposited film employs plasma poisoning of the workpiece surface in accordance with a desired pattern. A fluoro-carbon plasma treats selected areas of the workpiece surface to transform those selected areas from a hydrophilic state to a hydrophobic state. Certain ALD processes are enabled on hydrophilic surfaces and disabled on hydrophobic surfaces. In essence, the fluoro-carbon plasma treatment altered (poisoned) the surface to prevent ALD formation of deposited films. 
     The pattern may be established in various ways. One way (Method I) is to provide a first material only in selective surface areas, the first material being one that becomes hydrophobic upon exposure to a fluoro-carbon. The remaining areas consist of a second material that remains hydrophilic. Another way (Method II) is to provide a material that is hydrophilic unless treated by a fluoro-carbon plasma, in which case it becomes hydrophobic. In this latter case, the desired pattern is realized by masking the selected surface areas during the plasma treatment. This masking may employ photoresist, for example. Yet another way (Method C) is to employ a directional plasma beam so as to exploit 3-dimensional features on the surface to shadow the plasma beam from selected portions of the surface. 
       FIGS. 1A  though  1 H depict a first embodiment that employs Method I.  FIG. 1A  depicts a workpiece surface  100  having two or more zones  105 - 1  (Material A),  105 - 2  (Material B),  105 - 3  (Material C) of different characteristics. In  FIG. 1B , the workpiece is subjected to a plasma treatment. The plasma treatment may be carried out by ion implantation of a fluoro-carbon species, or by exposure to an ion beam from a fluoro-carbon plasma (e.g., CF4). The plasma treatment forms a plasma treated surface layer  170 . In the illustrated example, Materials A and C become hydrophobic upon plasma treatment by a fluoro-carbon plasma, while material B remains hydrophilic, as indicated symbolically in  FIG. 1C . Next, as depicted in  FIG. 1D , an ALD process is performed. The result is depicted in  FIG. 1E , in which ALD deposition occurs only on Material B in zone  105 - 2 . This is because Material B is hydrophilic, while Materials A and C are hydrophobic.  FIG. 1F  depicts an example in which the operation of  FIG. 1D  left small ALD deposits  115  in unselected areas. In this case, an ALD clean-up step depicted in  FIG. 1G  is performed, which removes the unwanted ALD deposits, and the thickness of the ALD deposited film in zone  105 - 2  is slightly reduced, as depicted in  FIG. 1H . 
     Materials A and C, which become hydrophobic upon exposure to a fluoro-carbon plasma, can be selected from a wide range of materials, such as (but not limited to) W, Co, SiN, T-oxide, TEOS, a nitride, a metal, a metal oxide, a semiconductor or Si. Material B, which remains hydrophilic after exposure to a fluoro-carbon plasma, may be selected from a group of materials including Cu and TiN, for example. 
     The operations of  FIGS. 1A through 1H  may be repeated on the workpiece by a number of times until a desired thickness of ALD deposited film is reached. Prior to each repetition, an anneal process may be performed to remove the effects of the plasma treatment. Another way to remove the effect of fluorocarbon plasma treatment is by exposing the surface to another type of plasma such as, for example, an Ar plasma or a N plasma. 
       FIGS. 2A through 2H  depict a process in accordance with a second embodiment. In  FIG. 2A , a workpiece surface  200  is patterned by a photoresist layer  205  using photolithography, leaving portions of the workpiece surface  200  exposed. In the next operation, a plasma treatment operation depicted in  FIG. 2B , the workpiece surface  200  is exposed to a fluoro-carbon plasma, forming a plasma treated surface layer  270  shown in  FIG. 2C . The plasma treated surface layer  270  is formed in areas aligned with openings in the photoresist layer  205 . Then, the photoresist layer  205  is removed and replaced by a new photoresist layer  210 , as depicted in  FIG. 2C . The pattern of the new photoresist layer  210  may be slightly shifted relative to the previous photoresist layer  205  (now removed), as shown in  FIG. 2C . A second plasma treatment is performed as depicted in  FIG. 2D , forming an additional plasma treated surface layer  271  extending beyond the first plasma treated surface layer  270 , as shown in  FIG. 2E . The plasma treated surface layers  270  and  271  are hydrophobic while the remainder of the workpiece surface  200  is hydrophilic. The second photoresist layer  210  is removed and an ALD process is performed, as indicated in  FIG. 2E . The resulting ALD growth  240  shown in  FIG. 2F  occurs on the hydrophilic surfaces and has a narrow width W determined by the shift between the first and second photoresist layers  205 ,  210 . 
       FIG. 2G  illustrates an example in which defects  250 , such as unwanted ALD growth nodules, are formed. The defects  250  are removed in an etch operation, which decreases the thickness of the ALD growth  240 , as depicted in  FIG. 2H . 
     The process of  FIGS. 2A through 2H  may be repeated a number of times to increase the thickness of the ALD growth  240 . Prior to each such repeat, an anneal operation may be performed to remove the effects of the previous plasma treatments. 
       FIGS. 3A through 3H  depict a process in accordance with a third embodiment. In  FIG. 3A , a workpiece surface  300  is patterned by a photoresist layer  305  using photolithography, leaving portions of the workpiece surface  300  exposed. In the next operation, which is depicted in  FIG. 3B , a first plasma treatment is performed by exposing the workpiece surface  300  to a fluoro-carbon plasma. This produces a plasma treated surface layer  370  indicated in  FIG. 3C . Then, the photoresist layer  305  is removed and a first ALD process is performed, as indicated in  FIG. 3C . The resulting ALD growth  340  shown in  FIG. 3C  coincides with locations on the workpiece surface  300  not treated by the plasma and which are hydrophilic. Thereafter, the workpiece surface  300  is subjected to an anneal procedure ( FIG. 3D ) to remove the effects of the plasma treatment previously performed in  FIG. 3B . This renders the exposed portions of the workpiece surface  300  hydrophilic. Next, as indicated in  FIG. 3E , a second photoresist layer  310  is deposited on the workpiece surface  300  as shown in  FIG. 3E . The pattern of the new photoresist layer  310  may be shifted relative to the previous photoresist layer  305  (now removed), as shown in  FIG. 3E . A second plasma treatment is performed as depicted in  FIG. 3F , which produces a plasma treated surface layer  371  extending beyond the plasma treated surface layer  370 , as indicated in  FIG. 3G . Then the second photoresist layer  310  is removed and a second ALD process is performed, as indicated in  FIG. 3G . This second ALD process results in a second ALD growth layer  341 . The ALD growth layers  340  and  341  may be of the same or different materials, depending upon the ALD processes employed. Next, the workpiece surface  300  is subjected to an anneal procedure ( FIG. 3H ) to remove the effects of the fluoro-carbon plasma treatment of  FIG. 3F . Another way to remove the effect of fluorocarbon plasma treatment is by exposing the surface to another type of plasma such as, for example, an Ar plasma or a N plasma. 
     The foregoing process of  FIGS. 3A through 3H  may be repeated for multi-zone patterning of several or many different materials. The materials may include any material that can be formed by ALD, such as (but not limited to metals, non-metals, nitrides, metal oxides, HfO2, ZrO2, TiO2, SiO2, ZnO, and other similar materials, as some examples. 
       FIGS. 4A and 4B  depict a process for ALD in selected areas, by employing shadowing effects of three-dimensional structures on the workpiece surface. In  FIG. 4A , a workpiece  400  has vertical surfaces  410  spaced apart by trenches  420 , the vertical surfaces  410  comprising a hydrophilic material. Selected portions of the vertical surfaces  410  are changed from hydrophilic to hydrophobic by treatment with a directional plasma or plasma beam of a fluoro-carbon species. Also, the vertical surfaces  410  are similarly treated. The plasma treatment forms plasma treated surface layers  470 . 
     The plasma beam includes two beams  461 ,  462 , of respective beam directions tilted through different angles, such as (for example) equal and opposite angles relative to the vertical surfaces  410 . The tilt angle, the width of trench  420  and the depth of the trench  420  are such that the plasma beams  461 ,  462  do not reach bottom surface  460  of the trench  420 . The plasma-treated surface layers  470  extend partially toward the bottom surface  460 . 
     Next, an ALD process is performed as depicted in  FIG. 4B . The growth of ALD material  480  occurs inside the trench  420  starting at the bottom surface  460  and progresses upwardly from the bottom surface  460 . The plasma-treatment changes the exposed surfaces from hydrophilic to hydrophobic, preventing ALD growth on the exposed surfaces. 
       FIGS. 5A and 5B  depict a modification of the process of  FIGS. 4A and 4B . In  FIGS. 5A and 5B , only a single tilted plasma beam  560  is needed. In  FIG. 5A , only one side (e.g., vertical surface  410   a ) of each vertical feature is exposed to plasma treatment to form a plasma-treated surface layer  471 . The vertical surface  410   b  is untreated and remains hydrophilic. As depicted in  FIG. 5B , an ALD process is performed and produces growth material  485  on the vertical surface  410   b.    
     In  FIG. 6A , an untilted (vertical) plasma beam  660  is employed to perform plasma treatment. The result is that only horizontal surfaces (i.e., top surfaces  412  and bottom surfaces  460 ) are rendered hydrophobic by the formation of plasma treated surface layer  472 . Next, an ALD process is performed as depicted in  FIG. 6B , depositing an ALD growth material  490  on the vertical surfaces  410  only. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Technology Category: 5