PRIORITY CLAIM AND CROSS-REFERENCE

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 62/880,261 filed on July 30, 2019, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The disclosure relates to the use of atmospheric pressure plasma etching (APPE) processes on glass surfaces to reduce electrostatic charging that otherwise may occur during processing of the glass.

BACKGROUND

[0003] Flat or curved substrates made of an optically transparent material such as glass are often used for flat panel displays, photovoltaic devices, and other suitable applications.

These displays and devices are made through a series of manufacturing steps in which the glass material is handled in various processing steps. The interaction between the glass and the processing equipment can cause a charge to be imparted on or to otherwise accumulate on one or more of the glass surfaces. It can be desirable to minimize the charge that is imparted on or otherwise accumulates on glass surfaces.

SUMMARY OF THE INVENTION

[0004] The present disclosure provides a treated glass substrate with a surface roughness and surface composition that reduces the electrostatic charging of the glass surface.

[0005] In one example, a treated glass substrate for use in a flat panel display may include a first side configured to hold a plurality of thin-film transistors and a second side positioned on a side of the glass substrate opposite to the first side. The second side may be treated using a dry etching process to change a surface composition of the second side. The surface composition of the second side may include a first Al/Si ratio to a first depth of about 1 nm in a range of about 38% to about 42% of a surface composition of an untreated glass substrate to the first depth, and a second Al/Si ratio to a second depth of about 10 nm in a range of about 71% to about 73% of the surface composition of the untreated glass substrate to the second depth.

[0006] In one aspect, the glass substrate may comprise a boro-aluminosilicate glass.

[0007] In another aspect, the dry etching process may be an atmospheric pressure plasma etching (APPE) process.

[0008] In another aspect, a surface composition of the first side may be substantially similar to the surface composition of the untreated glass substrate.

[0009] In another aspect, the surface composition of the second side may include a first

Mg/Si ratio to the first depth in a range of about 72% to about 81% of the surface composition of the untreated glass substrate to the first depth, and the surface composition of the second side may include a second Mg/Si ratio to the second depth in a range of about 72% to about 81% of the surface composition of the untreated glass substrate to the second depth.

[0010] In another aspect, the surface composition of the second side may include a first

Ca/Si ratio to the first depth in a range of about 33% to about 34% of the surface composition of the untreated glass substrate to the first depth, and the surface composition of the second side may include a second Ca/Si ratio to the second depth in a range of 77% to about 99% of the surface composition of the untreated glass substrate to the second depth.

[0011] In another aspect, the surface composition of the second side may include a concentration of fluorine to the first depth in a range of about 290% to about 330% of the concentration of fluorine of the surface composition of the untreated glass substrate to the first depth.

[0012] In another aspect, an average roughness Ra of the second side may be in a range of about 0.6 nm to about 1 nm.

[0013] In another aspect, a mean glass voltage of the glass substrate may be reduced by at least about 50% over a mean glass voltage of the untreated glass substrate when Lift Tested from a vacuum chuck.

[0014] In another aspect, the reduction in mean glass voltage of at least 50% over that of the untreated glass substrate is exhibited after the treated glass substrate is packed adjacent to interleaf paper, vibrated for at least two hours and washed using a solution comprising about 1% detergent.

[0015] In another aspect, a haze of the treated glass substrate is not more than about 10% greater than a haze of the untreated glass substrate.

[0016] In one example method in accordance with the present disclosure, a method of producing a treated glass substrate for use in a flat panel display is provided. The method may include heating the glass substrate to a predetermined treatment temperature and exposing a first side of the heated glass substrate to air while exposing a second side of the heated glass substrate to a HF plasma to etch the second side of the glass substrate and change a surface composition of the second side to form a treated glass substrate. The surface composition of the second side of the treated glass substrate may include a first Al/Si ratio at a first depth of about 1 nm in a range of about 38% to about 42% of a surface composition of an untreated glass substrate to the first depth, and the surface composition of the second side of the treated glass substrate may include a second Al/Si ratio to a second depth of about 10 nm in a range of about 71% to about 73% of the surface composition of the untreated glass substrate to the second depth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like reference numerals denote like features throughout specification and drawings.

[0018] FIG. 1 is a perspective view illustrating an exemplary treated glass substrate in accordance with some embodiments of the present disclosure.

[0019] FIG. 2 is a cross-sectional view illustrating various exemplary layers of the treated glass substrate of FIG. 1

[0020] FIG. 3 is a flow chart illustrating an exemplary method of producing the treated glass substrate of FIGs. 1 & 2.

[0021] FIG. 4 is a flow chart illustrating an exemplary method of etching the glass substrate of FIGs. 1 & 2. [0022] FIG. 5 is a schematic illustrating an exemplary etching zone that can be used to produce the treated glass substrate of FIGs. 1 & 2.

[0023] FIG. 6 is a graphical illustration showing a PSD versus Frequency plot showing a vibration profile used to vibrate test samples before lift testing.

[0024] FIG. 7 is a plot showing a glass voltage of treated glass test samples showing a reduction in glass voltage for samples using the etching process of the present disclosure.

DETAILED DESCRIPTION

[0025] The present disclosure provides methods for producing a glass substrate that have improved electrostatic charge (ESC) performance over those substrates that do not employ the methods of the present disclosure. The glass substrates of the present disclosure may be configured to be used for manufacturing a flat panel display device such as a liquid crystal display (LCD), light emitting diode (LED) display or an organic light emitting diode (OLED) display. In some embodiments, the glass substrate is optically transparent. Examples of a substrate include, but are not limited to, a flat or curved glass panel.

[0026] Unless expressly indicated otherwise, the term“glass substrate” or“glass” used herein is understood to encompass any object made wholly or partly of glass. Glass substrates include monolithic substrates, or laminates of glass and glass, glass and non-glass materials, glass and crystalline materials, and glass and glass-ceramics (which include an amorphous phase and a crystalline phase).

[0027] The glass substrate such as a glass panel may be flat or curved, and is transparent or substantially transparent. As used herein, the term“transparent” is intended to denote that the article, at a thickness of approximately 1 mm, has a transmission of greater than about 85% in the visible region of the spectrum (400-700 nm). For instance, an exemplary transparent glass panel may have greater than about 85% transmittance in the visible light range, such as greater than about 90%, greater than about 95%, or greater than about 99% transmittance, including all ranges and subranges therebetween. According to various embodiments, the glass article may have a transmittance of less than about 50% in the visible region, such as less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, or less than about 20%, including all ranges and subranges therebetween. In certain embodiments, an exemplary glass panel may have a transmittance of greater than about 50% in the ultraviolet (UV) region (100-400 nm), such as greater than about 55%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95%, or greater than about 99% transmittance, including all ranges and subranges therebetween.

[0028] Exemplary glasses can include, but are not limited to, aluminosilicate, alkali- aluminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali- aluminoborosilicate, and other suitable glasses. Non-limiting examples of available glasses suitable for use as a glass substrate in the teachings of the present disclosure include, for instance, LOTUS™ NXT,

IRIS™, GORILLA ^® , ASTRA™ and Eagle XG ^® glasses from Corning Incorporated. While various principles and teachings of the present disclosure may be used in connection with other types of glass substrates, the glass substrate used can preferably be an alkaline earth boro- aluminosilicate fusion drawn glass such as, LOTUS™ NXT glass from Corning Incorporated.

[0029] Thin glass substrates that can be used in flat panel displays can have a functional

A-side surface. Thin-film transistors can be fabricated on the functional A-side surface. On a side of the glass substrate opposite to the A-side surface, the glass substrate can include a non functional side or B-side. During various stages of manufacturing a flat panel display or other display device, the B-side surface of the glass substrate may come into contact with conveyance and/or handling equipment. Such conveyance and/or handling equipment can be made of various types of materials including, metals, ceramics, polymeric materials and the like. The interaction between these various types of dissimilar materials and the glass substrate can result in charging of the glass substrate through the triboelectric effect or contact electrification, for example. The charge that is transferred to the glass surface of the glass substrate can accumulate on the glass substrate. As the charge accumulates on the surface of the glass substrate, the surface voltage of the glass substrate can also change. Such accumulation of charge on one or more surfaces of the glass substrate can be termed electrostatic charging (ESC).

[0030] Electrostatic charging of the B-side surface of the glass substrate can be undesirable because such electrostatic charging can degrade the performance of the glass substrate and/or damage the glass substrate. Lor example, electrostatic charging of the B-side of the glass substrate may cause gate damage to the thin film transistor (TET) devices that may be deposited on the A-side (or functional) surface of the glass substrate. Such gate damage can be caused through dielectric breakdown and/or electric field induced charging. [0031] Electrostatic charging of the glass substrate can also be undesirable because such charging can attract particles, such as dust, particulate debris or other contaminants to the glass surface. This attraction and/or accumulation of dust and particulate debris can damage the glass substrate or degrade the surface quality of the glass substrate.

[0032] In one exemplary embodiment of the present disclosure, the B-side surface of the glass substrate can be etched using one or more of the methods described below in order to increase the surface roughness of the B-side surface and change the surface chemistry in one or more regions on the B-side surface. An increased surface roughness and the change in chemistry in the one or more surface layers of the B-side surface can reduce the accumulation of an electrostatic charge on the B-side surface. Furthermore, the increased surface roughness and/or the change in chemistry can also reduce the friction between the glass substrate and the handling and/or conveyance equipment that is used during processing of the glass substrate. A reduction in friction can reduce wear on such equipment. This reduction in wear can increase the service life of the handling and/or conveyance equipment and can decrease the required maintenance to such equipment. This, in turn, can increase process up-time, increase manufacturing yields and reduce costs for the overall flat panel display manufacturing process.

[0033] Referring now to FIGs. 1 and 2, an exemplary glass substrate 20 is shown. The glass substrate can be formed using any suitable glass fabrication process. In one example, the glass substrate 20 is formed using a fusion drawing process. The glass substrate 20 can include a first side (or A-side) 22. The first side 22 can be the side of the glass substrate 20 on which the thin-film transistors (TFT) can be fabricated. Opposite to the first side 22, the glass substrate 20 can also include a second side (or B-side) 24. The second side 24 is the side of the glass substrate 20 that may come into contact with one or more pieces of conveyance or handling equipment during the processing and/or fabrication of a flat panel display.

[0034] The glass substrate 20 can be treated using an etching process, as will be further described below, to cause the second side 24 to have one or more characteristics that result in reduced electrostatic charging over an untreated glass substrate or over a glass substrate having traditional surface treatments. One such characteristic that is changed using one or more etching processes of the present disclosure is a surface composition of the second side 24 of the glass substrate 20. As shown in FIG. 2 (but not shown to scale), the surface composition of the second side 24 can be measured using any suitable technique to one or more depths from an external surface 26 of the second side 24. Such techniques can measure the surface composition of the second side 24 of one or more compositional elements (or a ratio thereof) that is expressed as an average value of the compositional element (or ratio of elements) from the external surface 26 to a particular depth. Some example techniques include time-of-flight secondary ion mass spectrometry (TOF-SIMS) and x-ray photoelectron spectroscopy (XPS). In view of these measurement techniques, measurements may be described in the present disclosure as“to” a particular depth. For example, the surface composition of the second side 24 can be measured to a first depth Dl. The surface composition of the second side 24 can also be measured to a second depth D2 from the external surface 26. In one example, the surface composition of the second side 24 can be measured to a first depth Dl of about 1 nm and to a second depth D2 of about 10 nm. In other examples, the first depth Dl and the second depth D2 can be other depths measured from the external surface 26.

[0035] The etching processes of the present disclosure may cause the surface

composition, for some elements present in the glass substrate 20, to be different to the first depth Dl and to the second depth D2. For other elements that may be present in the glass substrate 20, the surface composition may be the same or substantially the same to the first depth Dl and to the second depth D2.

[0036] In one example, the surface composition of the second side 24 can be measured to determine its Aluminum/Silicon (Al/Si) ratio. This ratio can be determined using any suitable technique such as time-of-flight secondary ion mass spectrometry (TOF-SIMS), x-ray photoelectron spectroscopy (XPS), or x-ray fluorescence (XRF). X-ray fluorescence can be used to determine a bulk composition of the glass substrate 20 and time-of-flight secondary ion mass spectrometry (TOF-SIMS) and x-ray photoelectron spectroscopy (XPS) can be used to determine surface compositions of the glass substrate 20. Such techniques can be used to measure the surface composition of the second side 24 at the first depth Dl and at the second depth D2. The surface composition of the second side 24 after treatment with the etching processes of the present disclosure can be compared to a surface composition of the second side 24 in which no treatment has been made. In such a manner, the difference between the surface compositions of the treated versus untreated second sides 24 can be measured.

[0037] In one example, the second side 24 can have a surface composition having a Al/Si ratio in the range of 38 - 42 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Al/Si ratio in the range of 71 - 73 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm. In another example, the second side 24 can have a surface composition having a Al/Si ratio in the range of 35 - 45 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Al/Si ratio in the range of 70 - 74 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm. In still another example, the second side 24 can have a surface composition having a Al/Si ratio in the range of 30 - 50 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Al/Si ratio in the range of 65 - 75 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm.

[0038] In some examples, the surface composition of the second side 24 can be measured to determine its Magnesium/Silicon (Mg/Si) ratio. The Mg/Si ratio can be measured using one or more of the techniques described above with respect to the Al/Si ratio. The second side 24 can have a surface composition having a Mg/Si ratio in the range of 72 - 81 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Mg/Si ratio in the range of 72 - 81 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm. In this example, the Mg/Si ratio can be substantially the same at the first depth D1 of 1 nm and at the second depth D2 of 10 nm. In another example, the second side 24 can have a surface composition having a Mg/Si ratio in the range of 70 - 83 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and to a second depth D2 of 10 nm. In still another example, the second side 24 can have a surface composition having a Mg/Si ratio in the range of 65 - 88 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and to a second depth D2 of 10 nm.

[0039] In some examples, the surface composition of the second side 24 can be measured to determine its Calcium/Silicon (Ca/Si) ratio. The Ca/Si ratio can be measured using one or more of the techniques described above with respect to the Al/Si ratio. The second side 24 can have a surface composition having a Ca/Si ratio in the range of 33 - 34 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Ca/Si ratio in the range of 77 - 99 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm. In another example, the second side 24 can have a surface composition having a Ca/Si ratio in the range of 31 - 35 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Ca/Si ratio in the range of 75 - 99 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm. In still another example, the second side 24 can have a surface composition having a Ca/Si ratio in the range of 30 - 36 % of a surface composition of an untreated glass substrate 20 to a first depth D1 of 1 nm and a Ca/Si ratio in the range of 72 - 99 % of a surface composition of an untreated glass substrate 20 to a second depth D2 of 10 nm.

[0040] The surface composition of the second side 24 can also be measured to determine a concentration of fluorine (F) at one or more depths. The measurement techniques described above can be used to determine the concentration of F in the surface composition of the second side 24. In one example, the concentration of F at the second side 24 at the first depth D1 of 1 nm can be 290 - 330 % of a concentration of F in an untreated glass substrate 20. In another example, the concentration of F at the second side 24 at the first depth D1 of 1 nm can be 270 - 350 % of a concentration of F in an untreated glass substrate 20.

[0041] As described above, the surface compositions are described separately but it should be appreciated that the surface composition of the second side 24 can have more than one or all of the characteristics described above. For example, the surface composition of the second side 24 can have one or all of the Al/Si ratio, the Mg/Si ratio, the Ca/Si ratio and F concentration described above. In one example, the surface composition of the second side 24 can have a Al/Si ratio of 38 - 42 %, a Mg/Si ratio of 72 - 81%, and a Ca/Si ratio of 33 - 34% of a surface composition of an untreated glass substrate to a first depth of 1 nm and a Al/Si ratio of 71 - 73 %, a Mg/Si ratio of 72 - 81 %, and a Ca/Si ratio of 77 - 99% of an untreated glass substrate to a second depth of 10 nm. This same example can also have a F concentration in a range of 290 - 330 % of a surface concentration of the untreated glass substrate.

[0042] The etching processes of the present disclosure may also cause the external surface 26 of the second side 24 to have a predetermined roughness. The roughness of the second side 24 can have a roughness (after etching) that is greater than a roughness of the first side 22. In one example, the roughness of the second side 24 can have a roughness value Ra in range of 0.6 - 1.0 nm. In another example, the second side 24 can have a roughness value Ra in the range of 0.5 - 1.2 nm. In other examples, other suitable roughness values can also be produced. The roughness can be measured to determine the above ranges using any suitable technique including a profilometer or the like. [0043] The etching processes of the present disclosure and the accompanying changes to surface compositions and/or roughness of the second side 24 can result in a reduced amount of electrostatic charging that occurs to the glass substrate 20. In one example, the treated glass substrates can have at least a 50% reduction in glass voltage over that of untreated glass substrates. In another example, the treated glass substrates can have at least a 60% reduction in glass voltage over that of untreated glass substrates. In still other examples, the treated glass substrates can have at least a 65% reduction in glass voltage over that of untreated glass substrates.

[0044] It is also desirable that the etching processes of the present disclosure does not result in adverse effects on the glass substrate 20. Some etching processes can result in the treated glass substrate having an unacceptable amount of haze to the treated glass substrate. The etching processes of the present disclosure does not result in an excessive amount of haze to the treated glass substrate. That is, the etching processes do not impart haze that would negatively result in the use of the glass substrate in a flat panel display.

[0045] FIG. 3 illustrates one example method 300 of processing a glass substrate using the principles and teachings of the present disclosure. Prior to the steps shown in FIG. 3 a glass substrate can be produced using any suitable method. In one example, a glass substrate can be formed using a fusion drawing process. The glass substrate can be any suitable glass substrate for use in a flat panel display. The glass substrate, for example, can be an Alkaline Earth Boro- Aluminosilicate glass such as Coming’s Lotus™ NXT glass.

[0046] At step 304, the glass substrate can be pre-heated to a predetermined etching temperature. Any suitable oven or heating source can be used at step 304 to heat the glass substrate to the predetermined etching temperature.

[0047] At step 306, the glass substrate is etched using one of the etching processes of the present disclosure as will be further described below. In one example, the etching process at step 306 is an atmospheric pressure plasma etching (APPE) process in which HF plasma is used to etch the second side 24 of the glass substrate 20. . In such a process, CF4 and H2O can be used as precursors to produce a glass substrate 20 with the characteristics of the second side 24 previously described. During step 306, and as further described below, the first side of the heated glass substrate can be exposed to air while exposing a second side of the heated glass substrate to a HF plasma to etch the second side of the glass substrate and change a surface composition of the second side to form a treated glass substrate.

[0048] After etching, at step 308, the glass substrate can be rinsed and dried. Any suitable rinsing and drying process can be used such as the processes described above or the processes described below with respect to the performance testing.

[0049] FIG. 4 illustrates an example method 400 of etching a glass substrate 20. The method 400 can further detail one or more steps that may occur during step 306 of method 300. The etching apparatus 500 depicted in FIG. 5 can be used during one or more steps of the method 400 as will be described. It should be understood, however, that FIGs. 4 and 5 are discussed together for illustration purposes only. The method 400 and the etching apparatus 500 illustrated in FIGs. 4 and 5, respectively, can be used in implementations other than the specific example described below.

[0050] At step 402, HF plasma can be generated by one or more plasma generators. Any suitable generator can be used. In addition, there can be two or more plasma generators that can be fluidly coupled to mix the HF plasma. At step 404, the plasma can be transferred into an etching zone. At step 406, the plasma can contact the glass substrate in the etching zone. While the plasma is contacting the glass substrate, the plasma can interact with the glass substrate to cause the changes to the surface composition of the glass substrate as previously described. In addition, the surface of the glass substrate that is contacted by the plasma can be roughened to have the roughness characteristics previously described. At step 406, the etching zone can be configured, for example, to cause the second side 24 of the glass substrate 20 to be contacted by the plasma to cause the changes to the surface composition and to the roughness of the surface while preventing or limiting a substantial amount of plasma from contacting the first side 22 of the glass substrate 20. In this manner, the second side 24 undergoes the changes previously described while the first side 22 is largely unimpacted by plasma such that the first side 22 remains suitable for the fabrication of the thin-film transistors to fabricate a flat panel display.

[0051] At step 408, the plasma is removed from the etching zone. For example, the etching zone can have an exit channel through which the plasma can be drawn from the etching zone and away from the glass substrate. In this manner, the plasma can be circulated through the etching zone (and in contact with the glass substrate) to cause the etching of the glass substrate to occur. [0052] At step 410, plasma exit data can be collected from the plasma that is removed from the etching zone. Any suitable sensor or data processing equipment can be used. In one example, a Fourier-transform infrared (FT-IR) spectrometer can be used to collect and process data about the characteristics of the plasma that exits the etching zone. This data and

information can be used to monitor the process and make adjustments to the flow rates, the plasma, the conveyance speed of the glass substrate or other process attributes. While not shown, the method 400 can include other steps as well. Such additional steps may include collecting data at other points in the process or scrubbing or otherwise processing the plasma that may exit the etching zone.

[0053] The steps of method 300 and/or method 400 may be performed by a computer implemented program or other processing device. The data collection and analysis can also be output to screen or other output device. The methods and system described herein may be at least partially embodied in the form of computer-implemented processes and apparatus for practicing those processes. The disclosed methods may also be at least partially embodied in the form of tangible, non-transient machine readable storage media encoded with computer program code. The media may include, for example, RAMs, ROMs, CD-ROMs, DVD-ROMs, BD- ROMs, hard disk drives, flash memories, or any other non-transient machine-readable storage medium, or any combination of these mediums, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the method. The methods may also be at least partially embodied in the form of a computer into which computer program code is loaded and/or executed, such that, the computer becomes an apparatus for practicing the methods. When implemented on a general-purpose processor, the computer program code segments configure the processor to create specific logic circuits. The methods may alternatively be at least partially embodied in a digital signal processor formed of application specific integrated circuits for performing the methods.

[0054] FIG. 5 illustrates an example etching apparatus 500. As shown, the etching apparatus 500 can include a generator 502, a nozzle 504 and a detector 508. The etching apparatus 500 can be used, in one example, in the method 400 previously described. The generator 502 can be any suitable generator such as a plasma generator for generating HF plasma. In other examples, other devices for generating an HF vapor can also be used. The generator 502 can be fluidly connected to the nozzle 504 by an input channel 512. The input channel 512, as shown, can permit the plasma to move from the generator 502 and into the nozzle 504 as indicated by the arrows in FIG. 5. The plasma can move toward the glass substrate 20 that is positioned in the nozzle 504. In the example shown, the glass substrate 20 can be positioned such that the second side 24 of the glass substrate is located opposite to the input channel 512. As such, the plasma can contact the second side 24 of the glass substrate 20 when it flows into the etching chamber 516.

[0055] As further shown, the nozzle is also fluidly connected to an exit channel 514. The plasma can exit the etching chamber 516 through the exit channel 514. In one example, a vacuum can be applied at the exit channel 514 to cause the plasma to flow from the input channel 512 through the etching chamber 516 and out the exit channel 514. In this configuration, the second side 24 of the glass substrate 20 is exposed to the plasma to cause the etching of the second side 24 to occur. In the example shown, the glass substrate 20 can be supported in the etching chamber 516 by the rollers 510. The rollers 510 can be positioned at opposite ends of the etching chamber 516 and can seal the ends of the etching chamber 516 to prevent and/or limit the plasma from escaping the etching chamber. As further shown, the portion of the second side 24 between the rollers 510 is exposed to the plasma for etching without being supported or without having other intermediate members contacting the second side 24. Such configuration can result in a consistent etching and consistent surface characteristics of the second side 24.

[0056] The configuration of the etching apparatus 500 previously described also limits and/or prevents the first side 22 of the glass substrate 20 from being exposed to a significant amount of plasma or HF vapor. The first side 22 of the glass substrate 20 is exposed to the air. While some air may flow from the first side 22 toward the second side 24 (and out through the exit channel 514), the plasma is limited from moving toward the first side 22 in light of the pressure differential between the regions of the nozzle 504 above the first side 22 and below the second side 24.

[0057] As further shown, the exit channel 514 can be connected to the detector 508. The detector 508 can be any suitable sensor and/or data collection or analyzer unit. For example, the detector 508 can be a Fourier-transform infrared (FT-IR) spectrometer which can be used to collect and process data about the characteristics of the plasma that exits the etching chamber 516. In other examples, other sensors or data collection units can be used. [0058] The implementation of the methods and apparatus described above can result in a glass substrate having the characteristics previously described. The surface composition and the increased roughness can result in a glass substrate 20 that has reduced electrostatic charging over glass substrates that have not been etched using the principles and teachings of the present disclosure. The etched glass substrates 20 of the present disclosure also exhibit reduced electrostatic charging and reduced friction over glass substrates that are etched using traditional wet etching processes. One such wet etching process is a process that uses NaF and H3PO4 as described in U.S. Patent No. 5,792,327 to Belscher et al.

[0059] EXAMPLE GLASS SUBSTRATES - PERFORMANCE TESTING

[0060] Exemplary glass substrates were etched using the dry etching, APPE process of the present disclosure and tested to determine the change in surface characteristics and the resulting improvements in electrostatic charging. The test samples were prepared using

Coming’s Lotus™ NXT glass that is an Alkaline Earth Boro- Aluminosilicate glass. The samples were manually input through a dry etching, APPE process substantially similar to the process previously described and rinsed and air knife dried without detergent. For purposes of the description below, these samples are described as“APPE” samples. The APPE samples were processed such that some of the samples exhibited a roughness Ra of about 1.0 nm (described as “APPE TO”). Other APPE samples were processed that exhibited a roughness Ra of about 0.6 nm (described as“APPE 0.6”).

[0061] Other comparison samples of the glass were processed as described above without being treated using the dry etching process. Such samples are described as“untreated” samples for the purposes of the description below. Other comparison samples of the glass were processed as described above but were etched using a wet etching process described in U.S. Patent No. 5,792,327 to Belscher et al. For purposes of the description below, these samples are described as“wet etched” samples.

[0062] The APPE samples, the untreated samples and the wet etched samples were packed and vibrated in order to simulate the packing and transportation that normally occurs during the shipment of glass substrates from a glass manufacturing facility to a subsequent manufacturing facility during the fabrication of a flat panel display. The samples were packed next to an interleaf packing paper (e.g. GCIP D paper manufactured by Tokushu Tokai Paper Co.) and then vibrated for two hours using a Telecordia GR-63 standard (e.g. Telecordia GR-63 Transportation Vibration from Section 4.4.5) at ambient humidity and using pressures developed to simulate pressures typically seen in normal packing and transportation. Further details of the vibration testing can be seen in FIG. 6 showing the power spectral density (PSD) versus frequency.

[0063] The APPE sample, the untreated sample and the wet etched samples were then unpacked and washed, and then spun, rinsed, and dried. The washing process included washing the samples with a wash chemistry of 1% Semiclean KG detergent (produced by Yokohama Oils and Fats Industry Co., Ltd.) for 10 minutes at 50 degrees Celsius with ultrasonics followed by a deionized water rinse. It should be noted that the wash chemistry can change the surface chemistry of the samples.

[0064] The samples were then lift tested to determine the surface charge characteristic of the samples. As used herein, a Lift Test refers to the testing process of a glass substrate or glass sample as described below. The Lift Test occurred on a vacuum chuck table that is a common device used during the conveyance and/or processing of glass substrates in a flat panel display manufacturing process. The lift testing apparatus was made of aluminum with an insulative anodized coating and included a square perimeter vacuum channel with a smaller square inner vacuum channel. The vacuum level achieved when the glass samples were in contact with the vacuum chuck was about -83 kPA. The glass samples were 4 inches by 4 inches in size and were lowered onto the vacuum chuck and raised from the vacuum chuck using rounded insulative Vespel pins.

[0065] Electrostatic charge is commonly generated when a glass substrate is raised and lowered from a vacuum chuck. Charge can also be generated by tribo-electrification when the glass is being pulled against the chuck, deforms near the vacuum channel edges, and rubs against the edges of the chuck. To simulate this effect during processing, the glass samples were lowered and lifted from the vacuum chuck six times at a rate of 10 mm/second. A glass voltage measurement sensor was used to measure the voltage of the glass 60 seconds after contact separation. The glass voltage sensor was located at 10mm distance from the glass and tracked with the movement of the glass as it was raised and lowered from the vacuum chuck. The glass voltage was recorded during each cycle of the glass sample. The mean glass voltage was then calculated using the voltages recorded during each cycle. The mean glass voltage for each glass sample is shown in Table 1 below. In addition, the statistical analysis of the glass sample voltages is shown in FIG. 7 and shows that the APPE samples, the wet etched samples and the untreated samples are statistically significant from each other.

[0066] TABLE 1 - MEAN GLASS VOLTAGE OF TEST SAMPLES

[0067] As can also be seen, the APPE sample treated using the etching process of the present disclosure demonstrated significant improvement in electrostatic charging over both the wet etched and the untreated samples. The APPE sample shows a 66 % improvement over the untreated sample and a 38 % improvement over the wet etched sample.

[0068] The surface compositions of the APPE sample, the wet etched sample and the untreated sample were also analyzed using XPS and TOF SIMS to determine the composition of the glass surfaces for the major glass element rations compared to silicon and for the

concentration of fluorine. The TOF SIMS characterization method was used to determine the surface composition of the test sample to a depth of 1 nm. The XPS characterization method was used to determine the surface composition of the test sample to a depth of 10 nm. The results of the surface composition testing is shown below in Table 2. The values of the element ratios and F concentration were also normalized to the untreated sample to show the difference from the untreated sample.

[0069] TABLE 2 - SURFACE COMPOSITIONS OF TEST SAMPLES

[0070] As can be seen, the APPE samples show changes in the Al/Si, Mg/Al, Ca/Si ratios and the F concentration over that of the untreated samples. Such compositional changes as well as the increased roughness of the glass surface can be seen to demonstrate the reduction in electrostatic charging previously described in Table 1.

[0071] The test samples were also tested to determine whether a haze of the test samples was increased after being subjected to the dry etching, APPE process of the present disclosure. The haze was subjectively determined to be very low and/or non-existent for all samples. The samples were also measured using an RKY Haze Gard Plus, Model 4725. The measurements are shown in Table 3 below.

[0072] TABLE 3 - HAZE MEASUREMENTS OF TEST SAMPLES

[0073] As shown, the haze did not significantly increase. The haze for the APPE samples did not increase by more than 4%.

[0074] This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as“lower,”“upper,”“horizontal,” “vertical,”,“above,”“below,”“up,”“down,” “top” and“bottom” as well as derivative thereof (e.g.,“horizontally,”“downwardly,”“upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as“connected” and“interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

[0075] For purposes of the description hereinafter, it is to be understood that the embodiments described below may assume alternative variations and embodiments. It is also to be understood that the specific articles, compositions, and/or processes described herein are exemplary and should not be considered as limiting.

[0076] In the present disclosure the singular forms“a,”“an,” and“the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. When values are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms another embodiment. As used herein,“about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase“about 8” preferably refers to a value of 7.2 to 8.8, inclusive. As used herein,“substantially similar to” preferably refers to ±10% of a value used to characterize the compared characteristics. Where present, all ranges are inclusive and combinable. For example, when a range of“1 to 5” is recited, the recited range should be construed as including ranges“1 to 4”,“1 to 3”,“1-2”,“1-2 & 4-5”,“1-3 & 5”,“2-5”, and the like. In addition, when a list of alternatives is positively provided, such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of“1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of“1 to 5” may be construed as“1 and 3-5, but not 2”, or simply“wherein 2 is not included.” It is intended that any component, element, attribute, or step that is positively recited herein may be explicitly excluded in the claims, whether such components, elements, attributes, or steps are listed as alternatives or whether they are recited in isolation.

[0077] Although the subject matter has been described in terms of exemplary

embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.