WO2018226513A1 - Methods of etching glass articles - Google Patents

Abstract

Methods of etching of glass articles are disclosed that provide display glass articles with low haze. A specific method etching an aluminosilicate glass article comprising at least one of barium oxide and magnesium oxide in a range of from about 1 mol% to about 10 mol% is provided, the method comprising contacting the glass article with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from about 1:3 to about 1:12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution.

Description

METHODS OF ETCHING GLASS ARTICLES

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S.

Provisional Application Serial No. 62/649,745 filed on March 29, 2018 and U. S. Provisional Application Serial No. 62/515,207 filed on June 5, 2017, the contents of each of which are relied upon and incorporated herein by reference in their entireties.

BACKGROUND

[0002] The present disclosure relates generally to a glass articles which can be used in a display applications and methods of etching glass articles that result in low haze.

[0003] Display glass may be subjected to a variety of fluorinated etching chemistries during thin-film-transistor (TFT) fabrication processes. During TFT fabrication processes, insulator films may be etched, for example, to create vias for electrical contact formation. In these sensitive etch steps where etch depth may need to be controlled at the sub-micron scale, buffered hydrofluoric acid (BUF) etchants are often used to provide a controlled and repeatable etch rate. The most common buffering agents are ammonium compounds, often added to the etchant mixtures in the form of NH4F (ammonium fluoride) or NH HF2 (ammonium bifluoride). After a display glass panel has been assembled into a full package (such as a liquid crystal display (LCD) or organic light emitting diode (OLED)), some displays are then etched again using a faster etching chemistry to thin the panel down to a desired thickness, for example for mobile device applications where thickness is critical. These faster etching chemistries are often non-buffered.

[0004] During TFT fabrication, the general industry practice for wet chemical etching of display glass usually involves the use of a binary mixture of 1 : 10 BUF. HF dissolved in water is a weak acid. Solutions of HF contain H⁺, F^", tJTV ions and un-dissociated HF molecules. HF is generally considered one of the best performing chemicals in terms of the ability to appreciably dissolve silica-containing materials such as glass. As a result, and despite the expense and effort necessary to successfully manage the significant and well- known environmental and health risks associated with its use, HF is widely utilized for many applications where silica and other like materials are to be cleaned or dissolved.

[0005] For a given glass composition, factors that affect the rate of etching of glass include the concentration of HF acid, the etchant temperature, and the presence and amount of physical agitation (whether by flow, stirring, application of acoustic energy, or other means).

1 Increasing HF acid concentration generally increases the etch rate at a given constant temperature. In most industrial applications, a high etch rate is usually necessary to enable an acceptably high throughput to be achieved. This is usually accomplished by using an elevated process temperature (a heated etchant) and/or by using an etchant with relatively high HF concentration.

[0006] Etchants with higher HF concentration increase the corrosion rate of most metal alloys, namely, bolts, rivets and any other similar degradable components within etch systems and within associated vapor recovery systems. In some cases, certain types of heaters and/or chillers, which have to be immersed in the etching solution to enhance their heat transfer effectiveness, are chemically attacked by the harsh acid concentration, resulting in the need for frequent system maintenance to ensure that equipment integrity is not compromised. Also, at increased HF concentrations, the rate of evaporation of HF increases. This requires the use of enhanced-performance vapor recovery and safety systems to prevent hazardous gasses from escaping.

[0007] Similar issues arise if etchant temperature is increased. In addition to increased rate of corrosion of degradable components of the system, the rate of evaporation of gases increases with increase in temperature, requiring enhanced vapor recovery and safety units and more frequent maintenance in order to ensure continuous and safe operation.

[0008] It would be desirable provide alternatives to the currently used aqueous hydrofluoric (HF) acid solutions. It also would be desirable to methods of etching glass articles comprising barium oxide and etched glass articles having low haze.

SUMMARY

[0009] A method of etching an aluminosilicate glass article comprising at least one of barium oxide and magnesium oxide in a range of from about 1 mol% to about 10 mol% is disclosed. In a first embodiment, the method comprises etching the aluminosilicate glass article by contact thereof with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from about 1 :3 to about 1 : 12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution, wherein the buffered HF solution corresponds to a volumetric mixture of a 47 vol% HF aqueous solution and 40 vol% NH4F aqueous solution in a volume ratio of (HF aqueous solution):(NH4F aqueous solution) of from about 1 :4 to about 1 : 12, and the mineral acid is selected from the group consisting of H3PO4, H2SO4, HC1 and mixtures thereof, the concentration of the mineral acid in the mixed acid being in the range of about 10-40 vol%.

[0010] In a second embodiment, the etchant mixture of the first embodiment comprises a mixture of 1 : 10 buffered HF solution and 3.6M H3PO4. In a third embodiment, the etchant mixture of the first embodiment comprises a mixture of 1 : 1 buffered HF solution diluted within a range of about 1 :4 to about 1 : 10 parts water on a volume basis. In a fourth embodiment, the etchant mixture of the first embodiment comprises a mixture of about 1 : 10 buffered HF solution and HC1 or H2SO4, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

[0011] In a fifth embodiment, the etching of the first through fourth embodiments is performed with an etchant mixture to glass article contact time in a range of from about 1 minute to about 10 minutes. In a sixth embodiment, the etching of the first through fifth embodiments is with the etchant mixture at a temperature within the range of about 22-28° C.

[0012] In a seventh embodiment, the etching of the first through sixth embodiments is performed with the etchant mixture at a temperature within the range of about 22-28° C.

[0013] In an eighth embodiment, the etching of the first through seventh embodiments results in an etching rate that is equal to or greater than the etching rate achieved by etching a glass article with a 1 : 10 buffered HF solution for a contact time in a range of from about 1 minute to about 10 minutes at a temperature within the range of about 22-28° C.

[0014] In a ninth embodiment, the etchant mixture of the first embodiment comprises a mixture of 1 : 1 buffered HF solution diluted with 1 :9 parts water on a volume basis. In a tenth embodiment, the etchant mixture of the first embodiment comprises a mixture of 1 : 10 buffered HF solution and HC1, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

[0015] In an eleventh embodiment, the etchant mixture of the first embodiment comprises a mixture of 1 : 10 buffered HF solution and H2SO4, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

[0016] In a twelfth embodiment, the alummosilicate glass article of the first through eleventh embodiments comprises, in mole percent on an oxide basis in ranges: S1O2 60.0-75.0, AI2O3 13.0-20.0, B2O3 0.01-2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01-4.5, and BaO 0.01-9.

[0017] A thirteenth embodiment pertain to a method of manufacturing a thin film transistor comprising etching an aluminosilicate glass sheet comprising barium and having a thickness in a range of from about 0.2 mm to about 1.7 mm and having a dielectric layer selected from SiOx or SiNx, the dielectric layer having a via therein, the etching comprising contacting the aluminosilicate glass sheet with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from aboutl :3 to about 1 : 12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution, wherein the buffered HF solution corresponds to a volumetric mixture of a about 47 vol% HF aqueous solution and about 40 vol% NHtF aqueous solution in a volume ratio of (HF aqueous solution): ( H₄F aqueous solution) of from about 1 :4 to about 1 : 12, and the mineral acid is selected from the group consisting of H3PO4, H2SO4, HC1 and mixtures thereof, the concentration of the mineral acid in the mixed acid being in the range of about 10-40 vol%.

[0018] In a fourteenth embodiment, the etchant mixture of the thirteenth embodiment comprises a mixture of 1 : 10 buffered HF solution and 3.6M H3PO4. In a fifteenth embodiment, the etchant mixture of the thirteenth embodiment comprises a mixture of 1 : 1 buffered HF solution diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis. In a sixteenth embodiment, the etchant mixture of the thirteenth embodiment comprises a mixture of about 1 : 10 buffered HF solution and HC1 or H2SO4, the mixture diluted with a range of 1 :4 to 1 : 10 parts water on a volume basis.

[0019] In a seventeenth embodiment, the contacting in the thirteenth through sixteenth embodiments is performed with an etchant mixture to glass sheet contact time of from about 1 minute to about 10 minutes. In an eighteenth embodiment, the contacting in the thirteenth through seventeenth embodiments is performed with the etchant mixture at a temperature within the range of about 22-28° C. In a nineteenth embodiment, the glass sheet of the thirteenth through eighteenth embodiments comprises, in mole percent on an oxide basis in ranges: S1O2 60.0-75.0, AI2O3 13.0-20.0, B₂0₃ 0.01-2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01-4.5, and BaO 0.01-9.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 a graph showing the performance low-haze etchant mixtures compared to 1 : 10 BHF for a TFT on a glass substrate; and

[0021] FIG. 2 is a graph showing the performance low-haze etchant mixtures compared to 1 : 10 BHF for a TFT on a glass substrate. DETAILED DESCRIPTION

[0022] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0023] During TFT fabrication, contact of the buffered etchants with the display glass substrate has been observed to cause haze or precipitate formation under certain conditions. It should be noted that in most TFT fabrication processes, the TFT side of the glass will first be coated with a relatively thick (0.5-1 micron) layer of oxide and/or nitride barrier layers, which have traditionally been used to isolate the TFT electrical properties from potential glass substrate variations. These buffer layers are not fully etched away, as they protect the glass during BHF etching. Haze formation does not occur when buffered etchants contact these barrier layers, but when the etchants contact the glass substrate.

[0024] Buffered etchant mixtures are described that reduce or eliminate haze formation, while exhibiting similar TFT oxide/nitride dielectric layer etch rate as 1 : 10 BHF solution (a 1 : 10 volumetric mixture of 47 wt. % HF : 40 wt% N¾F in water) at room temperature (room temperature refers to a temperature of about 22° C) for 3 to 5 minutes. As used herein, the designation of a buffered HF solution 1 : 10, or BHF solution 1 : 10 (and similar numerical designation such as BHF solution 1 : 1 and BHF solution 1 :5) with respect to etchant mixtures described herein refers to a volumetric mixture of the acid component to the buffering agent, which for buffered HF is NH4F in water. For buffered HF solution, 1 : 10 represents an etchant comprised of 1 part by volume HF and 10 parts by volume buffer.

[0025] Etching experiments were conducted on aluminosilicate glass articles, and chemical analysis revealed that during etching of aluminosilicate glasses comprising barium (Ba) and magnesium (Mg), insoluble Ba-and Mg-containing minor phase precipitates form first, acting as nucleating sites for Al- and Si-containing major phase precipitates. Several dilute buffered etchant compositions were tested that exhibited minimal haze formation on aluminosilicate glasses comprising Ba and Mg, as well as exhibiting comparable TFT oxide/nitride dielectric film etching rates compared with 1 : 10 BHF.

[0026] Experiments showed that aluminosilicate display glasses containing a barium content in a range of about 1-10 mol. % on an oxide basis and/or a magnesium content in a range of about 1-10 mol% on an oxide basis that were etched with 1 : 10 BHF etchant solution at room temperature exhibited high haze compared with aluminosilicate glasses having similar amounts of alumina and silica, but no barium content, which exhibited low haze.

[0027] It was initially believed that etch rate differences between the glasses could be correlated with haze formation tendency, through a mechanism of faster etch rate in the buffered solutions providing more elements from the glass for precipitate formation.

However, etching experiments conducted with aluminosilicate glasses containing no barium and aluminosilicate glasses comprising barium indicated that not all glasses that could be etched quickly necessarily exhibited high haze formation. It was determined that high haze formation was primarily due to the presence of barium in the glass. X-ray diffraction (XRD) analysis of aluminosilicate glass articles containing a range of from about 1 mol% to 5 mol% barium on an oxide basis exposed to 1 :5 BHF droplets for 2 to 10 minutes and then gently rinsed contained major phases precipitated on the surface of the glass article. The major phases precipitated on the surface included ammonium aluminum fluoride (N1¾)3A1F6 and cryptohalite ( H^SiFe. Scanning electron microscopy (SEM) with energy dispersive X-ray analysis (SEM-EDX) confirmed the presence of the same major precipitate phases. SEM- EDX with background subtraction is a semi-quantitative method for analyzing enrichment of small or thin surface species relative to a substrate. Since the electron beam of the SEM- EDX has a penetration depth on the order or microns which contributes to the EDX signal, subtracting the substrate background is helpful to analyze the composition of surface objects or layers that are less than a few microns in size.

[0028] SEM-EDX of aluminosilicate glass article samples exposed to 1 :5 BHF solution and 1 : 10 BHF solution droplets for 10 minutes confirmed the presence of minor precipitate phases that appeared to form closer to the exposed glass surface and were enriched in Ba, Mg, and Ca relative to the composition of the glass article. However, aluminosilicate glass article samples that did not contain any barium in the composition that were exposed to 1 : 10 BHF for 2 minutes that were analyzed with SEM-EDX showed minor phases that did not contain barium. Therefore, aluminosilicate glasses that contained barium and were exposed to BHF included precipitates having minor phases enriched in Ba, Mg, and Ca species relative to the glass composition. While the present disclosure should not be limited by a particular principle or theory of operation, it is believed that Ba, Mg, and Ca are likely to play an important role in nucleating minor phases close to the glass surface, which then can promote more rapid formation of major phase precipitates. This formation of major phase precipitates was identified as the major contributor to the formation of haze after exposure to acid. While display glasses could be produced that do not contain barium, the presence of barium provides certain beneficial properties in display glasses, and it may not be desirable to eliminate barium from display glass compositions. Accordingly, etchants were investigated that provided an equivalent etching rate compared with 1 : 10 HF and that did not produce haze after etching.

[0029] One or more embodiments of the disclosure provides methods of etching an aluminosilicate glass article comprising at least one of barium oxide and magnesium oxide in a range of from about 1 mol% to about 10 mol%, the method comprising etching the aluminosilicate glass article by contact thereof with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from about 1 :3 to about 1 : 12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution, wherein the buffered HF solution corresponds to a volumetric mixture of a 47 vol% HF aqueous solution and 40 vol% N¾F aqueous solution in a volume ratio of (HF aqueous solution): ( H4F aqueous solution) of from about 1 :4 to about 1 : 12, and the mineral acid is selected from the group consisting of H3PO4, H2SO4, HC1 and mixtures thereof, the concentration of the mineral acid in the mixed acid being in the range of about 10-40 vol%.

[0030] The method may be performed with an etchant to glass article contact time in a range of from about 1 minute to about 10 minutes, or from about 1 minute to about 8 minutes, or from about 1 minute to about 5 minutes or from about 1 minute to about 3 minutes, with the etchant temperature at a temperature within the range of about 22-28° C during the contact with the glass article. The disclosed methods allow for etching at an etching rate that is equal to or greater than etching a glass article with a 1 : 10 BHF (a 1 : 10 volumetric mixture of 47 wt. % HF : 40wt% H4F in water) under the same etching conditions (i.e., for the same etchant contact time and same etchant temperature). Etching rate is determined by the change in mass per unit time for the etching. The etching rate is calculated by subtracting the mass of the glass article after etching from the mass of the glass article prior to etching, and then dividing the change in mass by the etching time. For example, a glass article having a mass of 10 grams prior to etching and 9 grams after etching for 1 minute has been etched at an etching rate of 1 gram/minute.

[0031] The methods described herein can be used to etch glass articles comprising, in mole percent on an oxide basis, in the ranges: S1O2 60.0-75.0, AI2O3 13.0-20.0, B2O3 0.01 -2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01-4.5, BaO 0.01 -9. The methods described herein can be used to etch glass articles comprising, in mole percent on an oxide basis in the ranges: S1O2 68.5-72.0, AI2O3 greater than or equal to about 13.0, B2O3 less than or equal to about 2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01 -4.5, BaO 0.01-4.5, such that

(MgO+CaO+SrO+BaO)/Ah03 is less than or equal to about 1.6. The methods described herein can be used to etch glass articles comprising, in mole percent on an oxide basis in the ranges: S1O2 63.0-71.0, AI2O3 13.0-14.0, B2O3 >0-3.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO >0- 6.0, BaO 1.0-9.0, the glass substantially free of alkalis (Ca, Li, Na, K).

[0032] The methods described herein can be used to etch glass substrates comprising, in mole percent on an oxide basis in the ranges: S1O2 68.0-70.5, AI2O3 13.0-14.0, B2O3 >0-3.0, MgO 0.9-9.0, CaO 5.25-11, SrO >0-6.0, BaO 1.0-9.0, the glass substantially free of alkalis.

[0033] The methods described herein can be used to etch glass articles comprising, in mole percent on an oxide basis in the ranges: S1O2 63.0-75.0, AI2O3 13.0-14.0, B2O3 >0-3.0, MgO 0.9-9.0, CaO 5.25-11, SrO >0-6.0, BaO 3.0-5.4, the glass substantially free of alkalis.

[0034] The methods described herein can be used to etch glass articles comprising, in mole percent on an oxide basis in the ranges: S1O2 63.0-71.0, AI2O3 13.0-14.0, B2O3 >0-2.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO >0-6.0, BaO 1.0-9.0, the glass substantially free of alkalis.

[0035] The glass articles in one or more embodiments are glass sheets having a first major surface, a second major surface and a thickness between the first major surface and the second major surface. The thickness in one or more embodiments is in a range of from 0.2 mm to 1.7 mm. In one or more embodiments, the glass articles comprise a glass sheet with a SiOx or SiNx dielectric layer having a via in the dielectric layer. Thus, in one or more embodiments, a method of manufacturing a thin film transistor comprises etching an aluminosilicate glass sheet comprising barium and having a thickness in a range of from 0.2 mm to 1.7 mm an having a dielectric layer selected from SiOx or SiNx, the dielectric layer having a via therein. The etching comprises contacting the glass sheet with an etchant as described herein.

[0036] As used herein, the terms "haze" and "transmission haze" refer to the percentage of transmitted light scattered outside an angular cone of± 4.0° in accordance with ASTM procedure D1003. In the Examples, haze was observed by human visual inspection of images as explained below, and can also be quantified using known methods such as measurement on a BYK Gardner Haze-meter. "Low haze" conditions result in letting most light pass through the samples without scattering with only a small amount of visible haze or precipitate formed on the surface of the glass. "Medium haze" appears as an increase in the amount of precipitate and/or haze observed but some light is still transmitted through the specimen without scattering. "High haze" is greatly increased haze or precipitates observed allowing little light to be transmitted without scattering.

[0037] EXAMPLES

[0038] Alternative etchant mixtures were tested for their haze formation tendency, primarily using a droplet test and human visual rankings of haze severity (high, medium, low). The droplet test was used to qualitatively evaluate haze formation tendency. In this test, a droplet of about 1 ml etchant was dropped onto glass that had been previously cleaned in a 4% Semiclean KG (KOH detergent) solution at 70° C using an ultrasonic cleaner. The droplet was allowed to sit on the glass surface, typically for 2 minutes or 10 minutes, then gently rinsed off for 1-2 seconds under flowing deionized water and then dried in air. Images were taken under controlled and repeated lighting conditions to compare the haze level. The images were obtained using a digital camera, a Cannon Powershot S3 IS, in manual mode. Settings were kept constant for all photographs (ISO: 800, F (shutter speed): 1/50, Aperture: 3.2). Additionally, samples were placed on a dark black background and the distance from camera lens to samples was kept as consistent as possible.

[0039] As summarized in the tables below, several general observations of haze formation tendency on glass samples as a function of etchant chemistry were found. Lowering L content of the etchant reduced haze. Dilution of etchant with water also reduced haze.

Addition of certain mineral acids, such as HCl, H2SO4, and to a lesser extent, H3PO4, were shown to reduce haze.

[0040] More specifically, 1 : 1 BHF solution and diluted 1 : 1 BHF solution were effective in most cases to reduce or eliminate haze on glass samples comprising barium. 1 :5 BHF + 3.6M HCl was effective to reduce haze, and 1 : 10 BHF + 3.6M H2SO4 was effective to reduce haze. These results are summarized in Table 1.

[0041] Table 2 includes glass etching rate information for selected etchant mixtures from Table 1, including some different dilute buffered etchant mixtures. The addition of mineral acids, without dilution, showed a tendency to increase the glass etching rate, which may not be practical for finely controlled TFT fabrication processes. Dilute buffered etchant mixtures based on 1 : 10 or 1 :5 BHF with ¾Ρ04, HCl, or H2SO4 added were shown to be effective to reduce or eliminate haze, as well as have comparable glass etching rates compared with 1 : 10 BHF. 1 : 10 BHF was chosen as the primary standard for comparison since this is the most common buffered etchant used in industry. [0042] The etching rate for various glass and etchant combinations was measured by static immersion of three pieces of 50 x 50 mm glass into 500 ml of etchant solution. After etching, the glass samples were thoroughly rinsed for about 1 minute under immersion with agitation and flowing deionized water to remove precipitates and then dried. Samples were weighed before and after etching to determine weight loss. In the case of TFT dielectric film etch rate, a different procedure was used. TFT films were masked using Kapton tape and etched by static immersion of four 50 x 50 mm glass samples in 500 ml of etchant for 2-30 minutes, then rinsed in deionized water. The tape was removed and tape residue remove with acetone, and etch depth was measured at the edge of the tape mask using stylus profilometry. Care was taken to avoid transistor areas of the TFT panel, so that etch depth measured was in the dielectric film regions only (avoiding metal and semiconductor areas)

[0043] The mechanisms of haze reduction through acid addition or water dilution are believed to be related in both cases due to increasing the solubility or reducing the concentration of the precipitate components in solution. Experiments were also conducted with additives that may operate through alternate or modified mechanisms such as the addition of surfactants to modify surface energy and precipitate nucleation and the addition of chelating agents which are known to solubilize aluminum (a major precipitate component) in fluorinated solutions. These alternate additives (not shown in Tables 1 and 2) included fluorinated, low-foaming surfactants (Dupont Zonyl FS-610 and Capstone FS-61) as well as chelating agents for aluminum (EDTA, HEDTA, citric acid, malic acid, tartaric acid, and low-molecular polyacrylic acid). None of these surfactants or chelating agents showed any apparent benefit of haze reduction when combined with 1 : 10 or 1 :5 BHF.

[0044] Selected etchant formulation examples are described below to provide an

understanding of the etchant formulations utilized in Tables 1 and 2 and FIGS. 1 and 2.

[0045] Comparative Example 1

[0046] 1 : 10 BHF = 1 : 10 (47% HF (aqueous) : 40%NH₄F (aqueous) mix by volume = 192 grams NH₄F (solid) + 288 ml deionized (DI) Water + 43 ml HF(47%).

[0047] Comparative Example 3

[0048] 1 :5 BHF = 1 :5 (47% HF (aqueous) : 40% NH₄F (aqueous)) mix by volume = 185 grams NH₄F (solid) + 277.5 ml DI Water + 83 mL 47% HF.

[0049] Comparative Example 4

[0050] Utilized an etchant designated Etchant 50A, which was 1 : 1 BHF diluted in 1 :9 parts water 10.6 grams NH₄F (solid) + 445 ml DI Water + 23.9 ml HF (47%) [0051] Example 1

[0052] 1 : 1 BHF = 1 : 1 (47% HF (aqueous) : 40% NH₄F (aqueous)) mix by volume = 844 grams NH₄F + 1266 ml DI Water + 1900 ml 47% HF

[0053] Example 2 A

[0054] Utilized an etchant designated Etchant 21 A in FIG. 1 , which was 1 : 10BHF + 3.6M H2SO4 diluted 1 :9 parts water = 9.5 ml H2SO4 (96-99%) + 451 ml DI Water + 15.4 grams NH₄F (solid) + 3.5 ml HF (47%)

[0055] Example 3 A

[0056] Utilized an etchant designated Etchant 22A, which was 1 :5 BHF + 3.6M HCl diluted 1 :9 parts water = 14.3 ml HC 1(37%) + 446 ml DI Water + 12.3 grams NH₄F (solid) + 5.6 ml HF (47%)

[0057] Example 4 A

[0058] Utilized an etchant designated Etchant 20A in FIG. 2, which was 1 : 10 BHF + 3.6M H₃P0₄ diluted 1 :4 parts water = 23 ml H3PO4 (85%) + 424 ml DI Water + 29.1 grams H₄F (solid) + 6.6 ml HF (47%)

[0059] Table 1 shows etchant mixtures tested with barium free aluminosilicate glasses and aluminosilicate glasses that contain 1-5 mol% barium. Examples 1-4 and 10 showed the best results.

[0060] TABLE 1

Comp.10B 1:5BHF + 3.6M HC1 Low Low Low Low Low

Comp.11B 1:5BHF+ 1.8M HC1 Low High High High High

Comp.12B 1:5 BHF+ I.8MH2SO4 Low Med Med Med Med

Comp.13B 1:5 BHF + 0.9M H2SO4 Low High High High High

Comp.14B 1:5 BHF + 18MH3PO4 Low High High High High

Comp.15B 1:5 BHF + 0.9M H3PO4 Low High High High High

[0061] The etching rate was not optimal for Comparative Examples 1 and 1B-15B, and as can be seen from Table 1, several Comparative Examples had high haze values. A second series of alternate etchant mixtures was tested with various aluminosilicate glasses.

[0062] Examples 23-27 showed the best results.

[0063] TABLE 2

27 11BHF dilute 1/15 0.3/L 0.5/L 0.2/L

Comp. 28B 10wt% HF + 5wt% 3.4/L 3.4/L 3.2/L

H₂S0₄

Comp. 29B 10wt% HF + 5wt% HCl 4.8/L 4.4/L 4.4/L

[0064] Since glass etching rate is a proxy for TFT dielectric layer etching rate, samples comprising TFT dielectric layer films on a glass substrate were tested. Etch rate of selected low-haze-forming dilute buffered etchant mixtures were tested in an attempt to match the TFT dielectric layer etching rate of 1 : 10 BHF with some of the alternative etchant mixtures in Tables 1 and 2. The components of the TFT film were an approximately 300 nm layer of SiOx material adjacent to the glass, followed by a second layer of about 330 nm of SiNx, followed by a third and final layer of about 290 nm of SiOx. These three layers are shown schematically in Figs. 9 and 10 which depict etching depth vs. etching time of the same TFT dielectric layer structure for selected etchant mixtures. As shown in FIG. 1 and FIG. 2, low- haze etchant mixtures of Example 4A (etchant mixture 20A) (1 : 10 BHF + 3.6M H3PO4 diluted 1 :4 parts with water) and Comparative Example 4 (etchant mixture50A), (1 : 1 BHF diluted 1 :9 parts with water) provided nearly identical TFT dielectric layer etch rate as standard 1 : 10 BHF. In addition, Example 2 A (using etchant mixtures 21 A (1 : 10BHF + 3.6M H2SO4 diluted 1 :9 parts with water)) and Example 3A (Using Etchant 22A (1 :5BHF + 3.6M HC1 diluted 1 :9 parts with water)) provided comparable etch rate to 1 : 10 BHF. It is believed that slight modifications of etchant 21 A and 22A (for example, slightly less dilution with water, or slightly more mineral acid addition) could be used to more exactly match the TFT dielectric layer etching rate of 1 : 10 BHF.

[0065] The above experiments identified dilute low-haze buffered etchant mixtures having similar TFT dielectric layer etch rate as 1 : 10 BHF. General observations included that water dilution, selected mineral acid addition (especially HC1 or H2SO4), and NH4 content reduction can all reduce haze and precipitate formation. It is believed that the mechanism for haze reduction is increased solubility or lower concentration of precipitate components in solution. Surfactants and chelating agents were not shown to reduce haze or precipitates. The following low-haze dilute buffered etchant mixtures were shown to have nearly identical TFT dielectric layer etching rate as standard 1 : 10 BHF: 1) 1 : 10 BHF + 3.6M H3PO4 diluted 1 :4 parts with water, and 2) 1 : 1 BHF diluted 1 :9 parts water. It is believed that similar results can be achieved based on diluted 1 : 10 or 1 :5 BHF with HC1 or H2SO4 addition. [0066] Ranges expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0067] Directional terms as used herein, for example up, down, right, left, front, back, top, bottom are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0068] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0069] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0070] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method of etching an aluminosilicate glass article comprising at least one of barium oxide and magnesium oxide in a range of from about 1 mol% to about 10 mol%, the method comprising etching the aluminosilicate glass article by contact thereof with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from about 1 :3 to about 1 : 12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution, wherein the buffered HF solution corresponds to a volumetric mixture of about 47 vol% HF aqueous solution and about 40 vol% NH F aqueous solution in a volume ratio of (HF aqueous solution) :(NH4F aqueous solution) of from about 1 :4 to about 1 : 12, and the mineral acid is selected from the group consisting of H3PO4, H2SO4, HC1 and mixtures thereof, the concentration of the mineral acid in the mixed acid being in the range of about 10-40 vol%.

2. The method of claim 1, wherein the etchant mixture comprises a mixture of 1 : 10 buffered HF solution and 3.6M H3PO4.

3. The method of claim 1, wherein the etchant mixture comprises a mixture of 1 : 1 buffered HF solution diluted within a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

4. The method of claim 1, wherein the etchant mixture comprises a mixture of about 1 : 10 buffered HF solution and HC1 or H2SO4, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

5. The method of claim 1, wherein the etching is performed with an etchant mixture to glass article contact time in a range of from about 1 minute to about 10 minutes.

6. The method of claim 1, wherein the etching is performed with the etchant mixture at a temperature within the range of about 22-28° C.

7. The method of claim 5, wherein the etching is performed with the etchant mixture at a temperature within the range of about 22-28° C.

8. The method of claim 7, wherein the etching results in an etching rate that is equal to or greater than the etching rate achieved by etching a glass article with a 1 : 10 buffered HF solution for a contact time in a range of from about 1 minute to about 10 minutes at a temperature within the range of about 22-28° C.

9. The method of claim 1, wherein the etchant mixture comprises a mixture of 1 : 1 buffered HF solution diluted with about 1 :9 parts water on a volume basis.

10. The method of claim 1, wherein the etchant mixture comprises a mixture of about 1 : 10 buffered HF solution and HC1, the mixture diluted with a range of about 1 :4 to aboutl : 10 parts water on a volume basis.

11. The method of claim 1, wherein the etchant mixture comprises a mixture of about 1 : 10 buffered HF solution and H2SO4, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

12. The method of claim 1, the aluminosilicate glass article comprising, in mole percent on an oxide basis in ranges: S1O2 60.0-75.0, AI2O3 13.0-20.0, B2O3 0.01-2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01-4.5, and BaO 0.01-9.

13. A method of manufacturing a thin film transistor comprising:

etching an aluminosilicate glass sheet comprising barium and having a thickness in a range of from about 0.2 mm to about 1.7 mm and having a dielectric layer selected from SiOx or SiNx, the dielectric layer having a via therein, the etching comprising contacting the aluminosilicate glass sheet with an etchant mixture comprising a mixed acid diluted with water in a ratio of mixed acid : water in a range of from about 1 :3 to about 1 : 12 parts by volume, the mixed acid comprising mineral acid and a buffered HF solution, wherein the buffered HF solution corresponds to a volumetric mixture of a 47 vol% HF aqueous solution and 40 vol% NH4F aqueous solution in a volume ratio of (HF aqueous solution): (N¾F aqueous solution) of from about 1 :4 to about 1 : 12, and the mineral acid is selected from the group consisting of H3PO4, H2SO4, HC1 and mixtures thereof, the concentration of the mineral acid in the mixed acid being in the range of about 10-40 vol .

14. The method of claim 13, wherein the etchant mixture comprises a mixture of 1 : 10 buffered HF solution and 3.6M H₃P0₄.

15. The method of claim 13, wherein the etchant mixture comprises a mixture of 1 : 1 buffered HF solution diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

16. The method of claim 13, wherein the etchant mixture comprises a mixture of about 1 : 10 buffered HF solution and HCl or H2SO4, the mixture diluted with a range of about 1 :4 to about 1 : 10 parts water on a volume basis.

17. The method of claim 13, wherein the contacting is performed with an etchant mixture to glass sheet contact time of from about 1 minute to aboutlO minutes.

18. The method of claim 13, wherein the contacting is performed with the etchant mixture at a temperature within the range of about 22-28° C.

19. The method of claim 13, the glass sheet comprising, in mole percent on an oxide basis in ranges: S1O2 60.0-75.0, AI2O3 13.0-20.0, B₂0₃ 0.01-2.5, MgO 1.0-6.0, CaO 1.0-8.0, SrO 0.01-4.5, and BaO 0.01-9.