Patent Publication Number: US-2017369366-A1

Title: Scratch-resistant windows with small polycrystals

Description:
PRIORITY 
     This patent application is a continuation of U.S. patent application Ser. No. 15/193,868, filed on Jun. 27, 2016, entitled, “SCRATCH-RESISTANT WINDOWS WITH SMALL POLYCRYSTALS,” attorney docket number 4217/1038, and naming John P. Ciraldo as inventor, the disclosure of which, is incorporated herein, in its entirety, by reference. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is related to the following patent applications: U.S. patent application Ser. No. 14/101,957, filed on Dec. 10, 2013, entitled, “METHOD OF GROWING ALUMINUM OXIDE ONTO SUBSTRATES BY USE OF AN ALUMINUM SOURCE IN AN ENVIRONMENT CONTAINING PARTIAL PRESSURE OF OXYGEN TO CREATE TRANSPARENT, SCRATCH-RESISTANT WINDOWS,” attorney docket number 4217/1018, and naming Jonathan Levine and John Ciraldo as inventors, and 
     U.S. patent application Ser. No. 14/101,980, filed on Dec. 10, 2013, entitled, “METHOD OF GROWING ALUMINUM OXIDE ONTO SUBSTRATES BY USE OF AN ALUMINUM SOURCE IN AN OXYGEN ENVIRONMENT TO CREATE TRANSPARENT, SCRATCH-RESISTANT WINDOWS,” attorney docket number 4217/1023, and naming Jonathan Levine and John Ciraldo as inventors. 
     The disclosures of both above noted patent applications are incorporated herein, in their entireties, by reference. 
     BACKGROUND OF THE INVENTION 
     1.0 Field of the Disclosure 
     Illustrative embodiments relate to a system, method, and device for coating a material (e.g., a substrate) with a layer of aluminum oxide to provide a transparent, scratch-resistant surface. 
     2.0 Related Art 
     There are many applications for use of glass, including applications in, e.g., the electronics area. Mobile devices, such as cell phones and computers, may employ glass screens configured as a touch screen. Undesirably, these glass screens can be prone to breakage or scratching. 
     The following patent documents provide informative disclosures: WO 87/02713; U.S. Pat. No. 5,350,607; U.S. Pat. No. 5,693,417; U.S. Pat. No. 5,698,314; and U.S. Pat. No. 5,855,950. 
     Xinhui Mao et al., in their article titled “Deposition of Aluminum Oxide Films by Pulsed Reactive Sputtering,” J. Mater. Sci. Technol., Vol. 19, No. 4, 2003, describe a pulsed reactive sputtering process that may be used to deposit some compound films, which are not easily deposited by traditional direct current (D.C.) reactive sputtering. 
     P. Jin et al., in their article “Localized epitaxial growth of α-Al 2 O 3  thin films on Cr 2 O 3  template by sputter deposition at low substrate temperature,” Applied Physics Letters, Vol. 82, No. 7, Feb. 17, 2003, describe low-temperature growth of α-Al 2 O 3  films by sputtering. 
     SUMMARY OF ILLUSTRATIVE EMBODIMENTS 
     In accordance with one embodiment of the invention, a window has an ion exchange substrate with a top surface. To improve robustness, the top surface has a polycrystalline aluminum oxide film formed from a plurality of crystals. At least 95% of the plurality of crystals in the aluminum oxide film has a largest dimension of no greater than about 10 nanometers. In addition, both the ion exchange substrate and aluminum oxide film are transparent or translucent. 
     Among other things, the ion exchange substrate may include glass, such as boron silicate glass, or aluminum-silicate glass. The substrate and film may have an aggregate Young&#39;s Modulus of less than about 350 Gigapascals. 
     The film may include sapphire. Moreover the film may have a film hardness that is greater than the substrate hardness. The film, which may have a thickness of between 10 nanometers and 10 microns, may be chemically adhered to the top surface of the substrate, or mechanically adhered to the top surface of the substrate. For example, the film may be conformal to top surface of the substrate. 
     In some embodiments, at least 98 percent of the plurality of crystals may have a maximum dimension that is no greater than about 10 nanometers. In other embodiments, at least 95 percent of the plurality of crystals may have a maximum dimension that is no greater than about 5 nanometers. 
     In accordance with another embodiment of the invention, a window has a quartz substrate with a top surface. To improve robustness, the top surface has a polycrystalline aluminum oxide film formed from a plurality of crystals. At least 95% of the plurality of crystals in the aluminum oxide film has a largest dimension of no greater than about 10 nanometers. In addition, both the quartz substrate and aluminum oxide film are transparent or translucent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of various embodiments, are incorporated in and constitute a part of this specification, illustrate embodiments and together with the detailed description serve to explain the illustrative embodiments of the invention. No attempt is made to show structural details in more detail than may be necessary for a fundamental understanding of illustrative embodiments and the various ways in which it may be practiced. In the drawings: 
         FIG. 1  is a block diagram of an example of a system for coating a material with a layer of aluminum oxide, the system configured according to illustrative embodiments of the invention; 
         FIG. 2  is a block diagram of an example of a system for coating a material with a layer of aluminum oxide, the system configured according to illustrative embodiments of the invention; 
         FIG. 2A  schematically shows a top/plan view of window produced in accordance with illustrative embodiments of the invention. 
         FIG. 2B  schematically shows a cross-sectional view of the window of  FIG. 2A  across line B-B. 
         FIG. 3  is a flow diagram of an example process for creating an aluminum oxide enhanced substrate, the process performed according to illustrative embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Various features and advantageous details of illustrative embodiments are explained more fully with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features in the drawings are not necessarily drawn to scale, and features of one embodiment may be employed with other embodiments as the skilled artisan would recognize, even if not explicitly stated herein. In fact, some features of the incorporated patent applications may be added to illustrative embodiments of the invention as described below. 
     Descriptions of well-known components and processing techniques may be omitted to not unnecessarily obscure the embodiments. The examples used herein are intended merely to facilitate an understanding of ways in which illustrative embodiments may be practiced and to further enable those of skill in the art to practice various embodiments of the invention. Accordingly, the examples and various embodiments described in this description should not be construed as limiting the scope of the many embodiments. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings. 
     The terms “including”, “comprising” and variations thereof, as used in this description, mean “including, but not limited to”, unless expressly specified otherwise. 
     The terms “a”, “an”, and “the”, as used in this description, means “one or more”, unless expressly specified otherwise. 
     Although process steps, method steps, algorithms, or the like, may be described in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of the processes, methods or algorithms described may be performed in any order practical. Further, some steps may be performed simultaneously. Moreover, not all steps may be required for every implantation. 
     When a single device or article is described, it will be readily apparent that more than one device or article may be used in place of a single device or article. Similarly, where more than one device or article is described herein, it will be readily apparent that a single device or article may be used in place of the more than one device or article. The functionality or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality or features. 
       FIG. 1  is a schematic block diagram of an example of a system  100  for coating a material (e.g., a substrate  120 , such as glass) with a layer  121  of aluminum oxide, according to illustrative embodiments of the invention. The system  100  may be employed to produce a very hard and superior scratch-resistant surface on glass, or other type of substrates. For example, the substrate may include an ion-exchange glass. The substrate may also be a boron silicate glass, quartz, or plastic. Coating the substrate with aluminum oxide (e.g., sapphire) has been found to produce a high quality product for use in applications where a hard, scratch-resistant surface is beneficial, such as glass windows useable, e.g., in electronic devices or scientific instruments, and the like. 
     As shown in  FIG. 1 , system  100  may include an evacuation chamber  102  with partial pressure of process gas  135  created therewithin, including molecular or atomic oxygen. The device  100  may further include an aluminum source  105 , a stage  110 , a process gas inlet  125 , and a gas exhaust  130 . The stage  110  may be configured to be heated (or cooled). The stage  110  may be configured to move in any one or more dimensions of 3-D space, including configured to be rotatable, movable in a x-axis, movable in a y-axis and/or movable in a z-axis. 
     The substrate  120  (e.g., chemically treated glass, such as ion-exchange glass) may be a planar material or a non-planar material, and preferably is transparent or translucent. The substrate  120  may be placed on the stage  110  so that one or more of its surfaces that may be subject to treatment. The substrate  120  may be a boron silicate glass, quartz, or plastic. The substrate may be chemically strengthened prior to coating. In some applications, the substrate  120  may be embodied in multiple dimensions, e.g., to include surfaces oriented in three dimensions that may be coated by the coating process. The aluminum source  105  is configured to produce a controlled deposition beam  115  comprising aluminum atoms and/or aluminum oxide molecules. The deposition beam  115  may be a cloud-like beam. The aluminum source  105  may comprise a sputtering mechanism (e.g., traditional sputtering), or a mechanism as described in incorporated U.S. patent application Ser. No. 14/101,980. In addition, the aluminum source  105  may include a device to heat aluminum. The targeting of the aluminum atoms and/or aluminum oxide molecules may include adjusting the location of the aluminum source  105  and/or adjusting the orientation of the stage  110 . Adjusting an orientation or position of the substrate  120  relative to the aluminum ions  115  may adjust an exposure amount of the aluminum ions to the substrate  120 . This adjusting may also permit coating of the aluminum oxide to particular or additional sections of the substrate  120 . 
     The system  100  may be used to coat a layer of aluminum oxide on the target substrate  120  (e.g., such as glass) to provide a matrix layer (referred to as a “matrix  121 ” or “layer  121 ”) having a transparent, scratch resistant surface  122 . This coat/layer  121  thus may be considered to form a film on the substrate  120 , producing a scratch-resistant window  119 . To that end,  FIG. 2A  schematically shows a plan view of the window  119  in illustrative embodiments of the invention.  FIG. 2B  schematically shows a cross-sectional view of the window  119  of  FIG. 2A  across line B-B. As shown, the layer  121  forms a substantially unitary, continuous film across the top of the substrate  120 . 
     In illustrative embodiments, the film/layer  121  is a polycrystalline structure—a plurality of crystals domains. Specifically, as known by those in the art, a polycrystalline structure has local order across the majority of the material (e.g., sixty percent), but lacks that same order across the entire crystal. 
     The material has plurality of poly-crystals that, as known by those in the art, are known to have sizes—i.e., their largest dimension. In illustrative embodiments, this largest dimension is no greater than about 10 nanometers. For example, this generally unitary film may be formed so that each one of at least 95 percent of the crystals has a largest dimension of no greater than about 10 nanometers. That dimensional limit can be smaller for the 95 percent of crystals. Specifically, each of at least 95 percent of the crystals may have a largest dimension of less than or equal to any one of 9, 8, 7, 6, 5, 4, 3, or 2 nanometers. For example, at least 95 percent of the crystals can have a largest dimension that is less than or equal to about 3 nanometers. In some embodiments, the percentage of crystals having the maximum size can be greater. In that case, at least 96, 97, 98 or even 99 percent of the plurality of crystals can have largest dimensions of less than or equal to about 10, 9, 8, 7, 6, 5, 4, 3, or 2 nanometers, whichever the case may be. For example, 98 percent of the crystals may have largest dimensions of no greater than about 3 nanometers. 
     In some embodiments, the overall film structure possesses small crystallites combined with amorphous aluminum-oxide to provide mechanical advantages over amorphous or single-crystal films. Such a structure is analogous to a nanoscale concrete where the polycrystalline material serves as the aggregate, strongly bound together by the cement-like amorphous content. Moreover, the small crystal domains provide optical advantages for the final film as the domain sizes have much smaller dimensions that the wavelengths of visible light, effectively mitigating optical interference. 
     The resultant scratch resistant surface  122  produces the noted window  119 , which may be further processed (e.g., by cutting and/or polishing steps) to have applications for a wide variety of products including, e.g., a watch crystal, a camera lens, and e.g., touch screens for use in e.g., mobile phones, tablet computers, scanners (e.g., a grocery store scanner) and laptop computers, where maintaining a scratch-free or break-resistant surface may be of primary importance. The thin window  119  may have a thickness of about 2 mm or less. In some embodiments, the window  119  may have a thickness that is greater than 5 mm in thickness, but less than 6 mm (e.g., about 5.6 mm). The thin window  119  is configured and characterized as having a shatter resistance with a Young&#39;s Modulus value that is less than sapphire, which may be less than about 350 gigapascals (GPa). Moreover, it should be understood that, in the case that there are different values for the Young&#39;s Modulus based on a testing method or region of material tested (e.g., ion-exchange glass, which may have different values for the surface and the bulk), that the lowest value is the applicable value. 
     A benefit provided by the resultant matrix  121  at surface  122  includes improved mechanical performance, such as, e.g., improved scratch resistance, greater resistance to cracking compared to currently used materials such as traditional untreated glass, plastic, and the like. Additionally, by using aluminum oxide (e.g., sapphire) coated on glass (e.g., ion exchange glass) rather than an entire aluminum oxide window (i.e., a window comprising all sapphire), the cost may be reduced substantially, making the product available for widespread consumer usage. Moreover, the use of aluminum oxide films, as opposed to full sapphire windows, offers additional cost savings by eliminating the need to cut, grind, and/or polish sapphire, which may be difficult and costly. 
     According to an embodiment of the invention, a substrate  120 , such as, e.g., glass, quartz, or the like, may be placed onto a stage  110 , which may be heated within an evacuated chamber  102 . Process gases are permitted to flow into the evacuation chamber  102  such that a controlled partial pressure is achieved. This gas may contain oxygen either in atomic or molecular form, and may also contain inert gases such as argon. After achieving the desired partial pressure, a deposition beam comprising energized aluminum atoms and/or aluminum oxide molecules  115  may be introduced such that the substrate  120  is exposed to an aluminum oxide deposition beam  115 . Being exposed to oxygen within the evacuation chamber  102 , the aluminum atoms may form aluminum oxide (Al 2 O 3 ) molecules, which adhere to the substrate surface  122 . The combination thus forms the noted matrix  121 , which provides exceptional useful qualities including, e.g., improved scratch resistance and greater resistance to cracking. 
     If the deposition beam  115  is not sufficiently large enough to homogeneously cover the substrate surface  122 , the substrate  120  itself may be moved in the deposition beam, such as, e.g., through movement of the stage  110 , which may be controlled to move up, down, left, right, and/or to rotate, to allow an even coating. In some implementations, the aluminum source  105  may be moved. Moreover, the substrate  120  may be heated by a heating device  123  sufficiently to allow mobility of ablated particles on the surface  122  of the substrate  120 , allowing for improved quality of the coating agent. The matrix  121  chemically and/or mechanically adheres to the substrate surface  122  to form a bond sufficiently strong enough to substantially prevent delamination of the aluminum oxide (Al 2 O 3 ) with the substrate  120 . Accordingly, this process creates a hard and strong surface  122  that is resistant to breaking and/or scratching. In illustrative embodiments, the hardness of the matrix  121 /film is greater than the hardness of the substrate  120 , thus protecting the surface of the substrate  120  from scratches and the like. 
     The growth rate of the aluminum oxide (Al 2 O 3 ) layer forming matrix  121  at the surface  122  may be tunable. The growth rate of the aluminum oxide (Al 2 O 3 ) layer forming matrix  121  may be enhanced by reducing the distance between the aluminum source  105  and the substrate  120 . The growth rate may be further enhanced by optimizing sputter power, as well as ambient gas pressure and composition. 
     The substrate  120  may be exposed to the aluminum oxide deposition beam, and the exposure stopped based on a predetermined parameter, such as, e.g., a predetermined time period and/or a predetermined depth of layering of aluminum oxide on the substrate  120  being achieved. The predetermined parameter may include a predetermined amount of aluminum oxide deposited such that the amount is sufficient to achieve a desired amount of scratch resistance, but not thick enough to affect the shatter resistance of the substrate  120 . In some applications, the amount of aluminum oxide deposited may have a thickness less than about 1% of the thickness of the substrate  120 . Moreover, the amount of aluminum oxide deposited may range between about 10 nm and 10 microns (e.g., 5 microns). 
     Illustrative embodiments may use a radio frequency (RF) or pulsed direct current (DC) sputtered power source to counteract charge accumulation that may result from the dielectric nature of aluminum oxide. Coated layers 2-3 nanometers to 300 microns thick can be achieved depending on the process parameters and duration. 
     Process duration can range from several minutes to several hours. By controlling the aluminum atom and/or aluminum oxide flux and oxygen partial pressure, the properties of the coated film (i.e., the aluminum oxide) can be tailored to maximize the films scratch resistance and mechanical adhesion of the grown film. The film on the substrate  120  results in a strong matrix that is very difficult to separate. The film preferably is conformal to the surface of the substrate  120 . This conformance characteristic may be useful and advantageous to coat irregular surfaces, non-planar surfaces, or surfaces with deformities. Moreover, this conformance characteristic may result in a superior bond over, for example, a laminate technique, which typically does not adhere well to irregular surfaces, non-planar surfaces, or surfaces with certain deformities. 
       FIG. 2  is a schematic block diagram of an example of a similar system  101  to form the window  119  according to alternative embodiments of the invention. The system  101  is similar to the system of  FIG. 1  and works principally the same way, except that the substrate  120  may be oriented differently, which in this example, is oriented above the aluminum source  105 . The deposition beam  115  may be controlled to direct the atoms upwardly towards the suspended substrate  120 . Adjusting an orientation or position of the substrate  120  relative to the aluminum atoms  115  may adjust an exposure amount of the aluminum atoms to the substrate  120 . This may also permit coating of the aluminum oxide to particular or additional sections of the substrate  120 . Traditional sputtering may be employed. 
     The system of  FIG. 2  may also generally illustrate that the relationship of the substrate  120  and the aluminum source  105  might be in any practical orientation. An alternate orientation may include a lateral orientation wherein the substrate  120  and the aluminum source may be laterally positioned relative to each other. 
     In  FIG. 2 , the substrate  120  may be held in position by a securing mechanism  126 . The securing mechanism  126  may include an ability to move in any axis. Moreover, the securing mechanism  126  may include a heater  123  configured to heat the substrate  120 . 
     The substrate  120  may be exposed to the aluminum and aluminum oxide deposition beam, and the exposure stopped based on a predetermined parameter such as, e.g., a predetermined time period and/or a predetermined depth of layering of aluminum oxide on the substrate  120  being achieved. 
     As noted, the thin window  119  formed by the systems of  FIG. 1  and  FIG. 2  to have a thickness of about 2 mm or less. The thin window  119  may be configured and characterized as having a shatter resistance with a Young&#39;s Modulus value that is less than that of sapphire, i.e., less than about 350 gigapascals (GPa). In other words, the substrate  120  and top surface film, in this example, have an aggregate Young&#39;s Modulus of less than about 350 GPa. Moreover, it should be understood that, in the case that there are different values for the Young&#39;s Modulus based on a testing method or region of material tested (e.g., ion-exchange glass, which may have different values for the surface and the bulk), that the lowest value is the applicable value. 
     In some implementations, the systems  100  and  101  may include a computer  205  to control the operations of the various components of the systems  100  and  101 . For example, the computer  205  may control the heater  123  for heating of the aluminum source. The computer may also control the motion of the stage  110  or the securing mechanism  126  and may control the partial pressures of the evacuation chamber  102 . The computer  205  may also control the tuning of the gap between the aluminum source and the substrate  120 . The computer  205  may control the amount of exposure duration of the deposition beam  115  with the substrate  120 , perhaps based on, e.g., a predetermined parameter(s) such as time, or based on a depth of the aluminum oxide formed on the substrate  120 , or amount/level of pressure of oxygen, or any combination therefore. The gas inlet  125  and gas outlet may include valves (not shown) for controlling the movement of the gases through the systems  100  and  200 . The valves may be controlled by computer  205 . The computer  205  may include a database for storage of process control parameters and programming. 
       FIG. 3  is a flow diagram of an illustrative process of creating the window  119  of  FIGS. 2A and 2B . The process of  FIG. 3  may include a traditional type of sputtering, and may form the film  121  on one or both surfaces of the underlying substrate  120 . The process of  FIG. 3  may be used in conjunction with the systems  100  and  101 . At step  305 , a chamber, e.g., evacuation chamber  102 , may be provided that is configured to permit a partial pressure to be created therein, and configured to permit a target substrate  120  such as, e.g., glass or boron silicate glass to be coated. At step  310 , a source of aluminum  105  may be provided that enables energized aluminum atoms  115  to be generated in the evacuation chamber  102 . This may comprise a sputtering technique. At step  315 , a support securing mechanism  126  or stage such as, e.g., stage  110 , may be configured within the chamber  102 , depending on the type of system employed. The stage  110  and/or securing mechanism  126  may be configured to be rotatable. The stage  110  and securing mechanism  126  may be configured to be moved in an x-axis, a y-axis and a z-axis. 
     At step  320 , a target substrate  120  having one or more surfaces such as, e.g., glass, borosilicate glass, aluminum-silicate glass, plastic, or yttria-stabilized zirconia (YSZ), may be placed on the stage  110 , or alternatively by the securing mechanism  126 . At optional step  325 , the target substrate  120  may be heated. At step  330 , a deposition beam  115  may be created which comprises aluminum atoms and/or aluminum oxide molecules. At step  335 , a partial pressure may be created within the chamber. This may be achieved by permitting oxygen to flow into the evacuation chamber  102 . At step  340 , the substrate  120  is exposed to the deposition beam  115  of aluminum atoms and/or aluminum oxide molecules to coat the substrate  120 . The exposure may be based on one or more predetermined parameter(s) such as, e.g., a depth of the aluminum oxide being formed on the target substrate surface(s), time duration, or a pressure level of the oxygen in the evacuation chamber  102 , or combinations thereof. The aluminum atoms and aluminum oxide molecules may form the deposition beam  115  directed towards the target substrate  120 . 
     At optional step  345 , a gap or distance between the aluminum source  105  and the target substrate  120  may be adjusted to increase or decrease a rate of coating the target substrate  120 . At optional step  350 , the target substrate  120  may be re-positioned by adjusting the orientation of the stage  110 , or adjusting the orientation of the securing mechanism  126 . The stage  110  and/or securing mechanism  126  may be rotated or moved in any axis. At step  360 , a matrix  121  may be created at one or more surfaces of the target substrate  120  as the aluminum atoms and aluminum oxide molecules coat and bond with the one or more surfaces of the substrate  120 . At step  365 , the process may be terminated when one or more predetermined parameter(s) are achieved such as time, or based on a depth/thickness of the aluminum oxide formed on the substrate  120 , or amount/level of pressure of oxygen, or any combination therefore. Moreover, a user may stop the process at any time. 
     The process of  FIG. 3  produces the noted window  119 , which preferably is lightweight, and has substantial resistance to breakability and scratches. In illustrative embodiments, the window  119  has a thickness of about 2 mm or less, although some embodiments may form the window  119  to have a greater thickness, such as those used in grocery store scanners (e.g., point of sale scanners), which may be more than 5.5 mm thick, or dozens of mm thick. The window  119  may be configured and characterized as having a shatter resistance with a Young&#39;s Modulus value that is less than that of sapphire, i.e., less than about 350 gigapascals (GPa). Moreover, it should be understood that, in the case that there are different values for the Young&#39;s Modulus based on a testing method or region of material tested (e.g., ion exchange glass which may have different values for the surface and the bulk), that the lowest value is the applicable value. The window  119  produced by the process of  FIG. 3  may be used to produce transparent thin windows including, e.g., watch crystals, lenses, touch screens in, e.g., mobile phones, smart phones, tablet computers, and laptop computers, where maintaining a scratch-free or break-resistant surface may be of primary importance. As such, the window  119  should be transparent at least to visible light. The process also may be used on translucent types of substrate materials. 
     The steps of  FIG. 3  may be performed by or controlled by a computer, e.g., computer  205  that is configured with software programming to perform the respective steps. The computer  205  may be configured to accept user inputs to permit manual operations of the various steps. 
     While the description includes examples, those skilled in the art will recognize that illustrative embodiments can be practiced with modifications in the spirit and scope of the appended claims. These examples are merely illustrative and are not meant to be an exhaustive list of all possible designs, embodiments, applications or modifications of various embodiments.