TWI431162B - Etchant composition for patterning circuits in thin film transistor-liquid crystal devices - Google Patents

Description

Etching composition for use in a circuit for patterning a thin film transistor-liquid crystal device Cross-references for related applications

The priority of Korean Patent No. 10-2007-009467, filed on Sep. 18, 2007, to the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

Field of invention

The present invention relates to an etching composition for etching a metal layer for forming a thin film transistor-liquid crystal device (TFT-LCD), and more particularly, the present invention relates to a separate program for forming a gate, a source, and a drain of a molybdenum (Mo) / yttrium aluminum (AlNd) double layer or a molybdenum / aluminum / molybdenum triple layer for wet etching without undercut or protrusion An excellent etch profile etching composition.

Background of the invention

Liquid crystal display devices (LCDs) have high resolution and are therefore capable of displaying sharp images. In addition, the LCD device has a low power consumption rate. In addition, the LCD device can be manufactured into a relatively thin product. Due to these advantages, among various flat panel display devices, LCD devices have received considerable attention. The LCD device is driven by a circuit such as a thin film transistor (TFT). In general, a TFT-LCD forms a pixel on a display screen. In the TFT-LCD, the function of a TFT is used as a switching device. The TFT-LCD is formed by filling a liquid material between a TFT substrate arranged in an array and a color filter substrate facing the TFT substrate. Method for manufacturing a TFT-LCD The method comprises forming a TFT substrate, a color filter, and a mold. To obtain accurate and clear images, it is important to accurately form the TFT substrate as well as the color filter system.

Generally, in forming a TFT substrate, aluminum or an aluminum alloy is used to form a gate, a source, and a drain of a TFT. Specifically, a combination of molybdenum, aluminum, or molybdenum aluminum, a molybdenum alloy, and an aluminum alloy is deposited on a substrate. For example, a double layer such as a molybdenum/yttrium aluminum layer or a metal layer of a molybdenum/aluminum/molybdenum triple layer is formed on a substrate. To form the desired circuitry in these metal layers, the metal layers must be etched according to the pattern of the circuitry. Since many film layers are formed on the TFT substrate, an undesired short circuit may occur between the films. To avoid short circuit current, one of the etched metal layers (i.e., an etched profile) should have a gradually push-out shape. A progressively pushed etch profile is referred to as a profile in which the layers are evenly inclined and the bottom portion is larger than the top portion. If an etched profile is gradually tilted and pushed out, the stepped condition between the metal layers can be slowed down. If the etching pattern of a gate metal layer is not uniform or accurate, the resolution of the TFT-LCD image will be reduced and the color will be distorted.

Examples of etching methods include wet etching and dry etching. Wet etching is an isotropic etching process in which etching is produced in all directions. Therefore, wet etching cannot form one substrate having a size of 3 μm or less. In addition, etchants for wet etching as well as deionized water systems are quite expensive. However, the wet etch process is inexpensive, does not require a high vacuum state, and provides superior etch selectivity for the mask and substrate. To form an aluminum alloy electrode, a mixed acid etch including phosphoric acid, nitric acid, and acetic acid is commonly used. Engraving agent. In the acidic mixed etchant, nitric acid oxidizes aluminum and forms aluminum oxide, and oxidizes molybdenum to form molybdenum oxide; acetic acid is used as a buffer solution to control the etching reaction rate; and phosphoric acid decomposes the aluminum. Oxides and molybdenum oxides. However, the phosphate system is quite expensive and has a high viscosity.

Dry etching is an anisotropic etch and can be used to form a substrate having a size of 3 microns or less. However, dry etching requires expensive vacuum equipment and has low selectivity.

In general, performing a wet etch does not result in a good etch profile, i.e., a push-out etch profile, in which no undercut occurs. The undercut phenomenon is referred to as, for example, the case where one of the bottom aluminum metal layers is etched more than the top molybdenum layer. To overcome the undercut phenomenon, further dry etching is required to etch the top molybdenum layer. However, this method lengthens the manufacturing process and increases the manufacturing cost, thereby reducing the yield. Therefore, a method of forming a good etching profile by performing only one wet etching process using a highly selective inexpensive etchant has been developed.

For example, Korean Patent Application No. 2003-70738 discloses an etchant for etching a double layer of molybdenum/niobium aluminum in a separate process, wherein the etchant comprises a nitric acid, iron nitrate, and a weight percentage of 1 to 4 Wt%, perchloric acid (HClO ₄ ) as an oxidizing agent. However, HClO ₄ emits chlorine radicals which destroy the ozone layer of the stratosphere and are therefore considered to be not environmentally friendly materials and are used only in a limited range of applications. In addition, HClO ₄ may precipitate unwanted materials such as residues on a substrate, and thus HClO ₄ cannot be used with other materials. Hydrogen peroxide has good oxidizing properties and is quite stable for etching an indium tin oxide layer. However, hydrogen peroxide can make the etchant unstable, reduce the life of the etchant, and thereby increase the manufacturing cost.

Korean Patent No. 598,418 discloses an etchant comprising 10 to 50 wt% of nitric acid, 5 to 30 wt% of acetic acid, 0.1 to 5 wt% of a fluorine-containing compound, and 0.1 to 5 wt% of a boron-containing compound. However, since it has a fluorine-containing compound, the glass used as a substrate is corroded, and since it has a compound mainly composed of iron, browning occurs.

Summary of invention

The present invention provides an etch composition that provides a superior push etch profile for a metal layer such as a molybdenum/yttrium aluminum double layer or a molybdenum/aluminum/molybdenum triple layer through a single wet etch process. a bismuth aluminum double layer or a molybdenum/aluminum/molybdenum triple layer for forming a gate, a source, and a drain, wherein the etch composition does not include any non-environmental material, any shortening of the etch composition An unstable component of lifetime, or a fluorine-based compound that etches glass used as a substrate, and is widely used to form a gate, a source, and a drain.

According to an aspect of the present invention, there is provided an etching composition comprising: 55 to 75 wt% of one phosphoric acid, 0.75 to 1.99 wt% of one nitric acid, 10 to 20 wt%, based on the total weight of the etching composition. One of acetic acid, 0.05 to 0.5 wt% of one molybdenum etch control agent, 0.02 to 3 wt% of one boron-containing compound, and the remainder is water.

The molybdenum etch control agent comprises at least one from MH ₂ PO ₄ , M ₂ HPO ₄ , M ₃ PO ₄ , MHSO ₄ , M ₂ SO ₄ , CH ₃ COOM, MHCO ₃ , M ₂ CO ₃ , MNO ₃ and M ₂ C a salt compound selected from the group consisting of ₂ O ₄ , wherein the M system is ammonium (NH ₄ ), sodium (Na) or potassium (K), specifically potassium nitrate (KNO ₃ ), potassium acetate ( CH ₃ COOK), ammonium nitrate (NH ₄ NO ₃ ), ammonium acetate (CH ₃ COONH ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), dihydrogen phosphate ((NH ₄ )H ₂ PO ₄ ) and sulfuric acid Potassium hydrogen (KHSO ₄ ). For example, the molybdenum etch control agent can be KNO ₃ or CH ₃ COONH ₄ .

The boron-containing compound may be a compound which decomposes in the etching composition and forms a boron ion or a boron-containing ion. The boron-containing compound includes at least one selected from the group consisting of boric acid (H ₃ BO ₃ ), diboron dioxide (B ₂ O ₂ ), boron trioxide (B ₂ O ₃ ), tetraboron trioxide (B ₄ O ₃ ), five Tetraboron (B ₄ O ₅ ), potassium metaborate (KBO ₂ ), metaboric acid (HBO ₂ ), tetraboric acid (H ₂ B ₄ O ₇ ), sodium tetraborate (Na ₂ B ₄ O ₇ -10H ₂ O ), potassium pentaborate (KB ₅ O ₈ -4H ₂ O), boron nitride (BN), boron trifluoride (BF ₃ ), boron trichloride (BCl ₃ ), and boron tribromide (BBr ₃ ) The selected compound in the group formed. For example, the boron-containing compound can be H ₃ BO ₃ .

Simple illustration

The above and other advantages of the present invention will become more apparent from the detailed description of the exemplary embodiments illustrated in the appended claims. The molybdenum triple layer is subjected to a wet etching process after the etching composition according to the present invention, and a scanning electron microscope (SEM) image before removing a photoresist; FIGS. 2 to 5 show a molybdenum/bismuth aluminum double The layer and a molybdenum/aluminum/molybdenum triple layer were subjected to a wet etching procedure after the etching compositions prepared according to Comparative Examples 1 to 4, and an SEM image before removal of a photoresist.

Detailed description of the preferred embodiment

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown in the drawings.

According to the present invention, an etching composition comprises 55 to 75 wt% of one phosphoric acid, 0.75 to 1.99 wt% of one nitric acid, 10 to 20 wt% of one of acetic acid, 0.05 to 0.5 wt%, based on the total weight of the etching composition. One molybdenum etch control agent, one 0.02 to 3 wt% of a boron-containing compound, and the remainder being water.

When etching a metal layer such as a molybdenum/yttrium aluminum double layer or a molybdenum/aluminum/molybdenum triple layer in a single etching process, the molybdenum etching control agent selectively controls the etching rate of the etching composition for molybdenum, Therefore, the difference in etching rate due to different oxidation characteristics of an aluminum layer and a molybdenum layer can be avoided, and an appropriate etching profile can be obtained. Examples of the molybdenum etching control agent include a monoammonium salt and an alkaline earth metal salt. Examples of alkaline earth metals include sodium, potassium and lithium. The mechanism of the molybdenum etching control agent will be described in detail below. The monovalent alkali ions of the monoammonium salt and the alkaline earth metal salt are easily reacted with molybdenum located on the surface of the molybdenum layer to form an insoluble molybdenum composite oxide. Examples of the insoluble molybdenum composite oxide include Mo, M ₂ O MoO ₃ , and M ₂ O 2MoO ₃ , wherein the M system is ammonium, sodium or potassium. As a result, the etching rate of the etching composition for molybdenum is lowered, that is, the oxidation rate of molybdenum to MoPO ₄ is lowered. In addition, the molybdenum etching control agent reduces the adhesion between the metal layer and the photoresist, and thus can obtain an excellent etching profile and form less residue.

If the amount of the molybdenum etching control agent is less than 0.05 wt%, the etching rate of the etching composition for molybdenum does not decrease, and thus for a molybdenum/niobium aluminum double For the layer, a molybdenum/aluminum/molybdenum triple layer, and a molybdenum/yttrium aluminum/molybdenum triple layer, a top molybdenum layer will have a first-order profile and a bottom molybdenum layer will have an undercut profile. If the amount of the molybdenum etching control agent is more than 0.5 wt%, the etching rate of the etching composition for molybdenum is too low, and thus for a molybdenum/yttrium aluminum double layer, a molybdenum/aluminum/molybdenum triple layer, and a molybdenum In the case of the bismuth/molybdenum triple layer, the top and bottom molybdenum layers will protrude.

The molybdenum etch control agent comprises at least one salt compound selected from the group consisting of ammonium salts, sodium salts, and potassium salts, specifically MH ₂ PO ₄ , M ₂ HPO ₄ , M ₃ PO ₄ , MHSO ₄ , M ₂ SO ₄ , CH ₃ COOM, MHCO ₃ , M ₂ CO ₃ , MNO ₃ and M ₂ C ₂ O ₄ , wherein the M system is ammonium, sodium or potassium. For example, the molybdenum etching control agent may be KNO ₃ , CH ₃ COOK, NH ₄ NO ₃ , CH ₃ COONH ₄ , KH ₂ PO ₄ , (NH ₄ )H ₂ PO ₄ and KHSO ₄ , and specifically KNO ₃ Or CH ₃ COONH ₄ .

Nitric acid oxidizes aluminum to aluminum oxide and etches molybdenum. If the amount of nitric acid is greater than 1.99 wt%, a top molybdenum layer will be significantly depressed for a molybdenum/niobium aluminum double layer, a molybdenum/aluminum/molybdenum triple layer, and a molybdenum/niobium aluminum/molybdenum triple layer. Thereby having a stepped profile, and a bottom molybdenum layer having an undercut profile. If the amount of nitric acid is less than 0.75 wt%, the top and bottom molybdenum layers will protrude for a molybdenum/niobium aluminum double layer, a molybdenum/aluminum/molybdenum triple layer, and a molybdenum/niobium/molybdenum triple layer. .

Phosphoric acid dissolves aluminum oxide. If the amount of phosphoric acid is less than 55 wt%, the etching rate of the etching composition for aluminum is lowered. For a molybdenum/aluminum/molybdenum triple layer and a molybdenum/yttrium aluminum/molybdenum triple layer, a top molybdenum layer is produced. A first-order profile, while a bottom molybdenum produces an undercut profile. If the amount of phosphoric acid is greater than 75 At wt%, the etch rate of the etchant for aluminum will be too high, and the top/bottom molybdenum layer will protrude. In addition, due to the high viscosity of phosphoric acid, the viscosity of the etching composition is lowered, and thus the etching uniformity is lowered. Acetic acid is used as a buffer solution to control the etching reaction rate. If the amount of acetic acid is less than 10% by weight, the etching composition lacks a buffer solution, and thus reduces the life of the etching composition; and increases the viscosity of the etching composition, and thus reduces the etching uniformity. On the other hand, if the amount of acetic acid is more than 20 wt%, the etching rate of the etching composition for molybdenum is too low, and for a molybdenum/yttrium aluminum double layer, a molybdenum/aluminum/molybdenum triple layer, and a molybdenum/ruthenium In the case of the aluminum/molybdenum triple layer, the top and bottom molybdenum layers will protrude.

The boron-containing compound reduces the etch rate of the etch composition to increase throughput and maintain processing margin. If the amount of the boron-containing compound is less than 0.02 wt%, the etching rate of the etching composition for aluminum is increased, and thus excessive etching is caused, and the etching profile is remarkably changed; and the processing margin cannot be maintained, thereby reducing the yield. If the amount of the boron-containing compound is more than 3 wt%, the solvency of the other components of the etching composition is lowered, and thus the etching rate of the etching composition for a metal layer is remarkably lowered. Examples of boron-containing compounds include H ₃ BO ₃ , B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₃ , B ₄ O ₅ , KBO ₂ , sodium perborate (NaBO ₂ ), HBO ₂ , H ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ -10H ₂ O, KB ₅ O ₈ -4H ₂ O, BN, BF ₃ , BCl ₃ and BBr ₃ . For example, the boron-containing compound can be H ₃ BO ₃ . The boron-containing compound can be any compound which decomposes in the etching composition and forms a boron ion or a boron ion.

In addition to this, the etching composition according to the present invention is an aqueous solution. That is, etching in accordance with the present invention, in addition to the above-mentioned essential components The composition necessarily includes the remainder of the water such that the etchant becomes 100% by weight. At this point, the water must be ultrapure water. Specifically, the etching composition contains 1 to 30% of water based on the total weight of the etching composition.

According to the present invention, a superior push-etch etching profile can be obtained by using an etching composition including those components.

The invention will be further described in detail with reference to the following examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[Example 1, Comparative Example 1~5]

An etching composition having the composition ratio shown in Table 1 was prepared. The molybdenum etching control agent is CH ₃ COONH ₄ and the boron-containing compound is H ₃ BO ₃ .

[Experimental example]

The etching properties of the etching compositions prepared according to Example 1 and Comparative Examples 1 to 5 were compared with each other. Specifically, each of a double layer of molybdenum/yttrium aluminum and a triple layer of molybdenum/aluminum/molybdenum are formed on a substrate having a size of 10 cm by 10 cm, and then each is sprayed with a mini-etcher, 10 The liter of etchant is sprayed on the substrate for 2 minutes to perform an etching process sequence. The etched substrate was identified by a scanning electron microscope (SEM) and individual etching performance was evaluated. Figs. 1 to 5 show SEM images of the substrate which were etched according to the etching compositions prepared in Example 1 and Comparative Examples 1 to 4.

Referring to FIG. 1, when a molybdenum/yttrium aluminum double layer and a molybdenum/aluminum/molybdenum triple layer are etched by the etching composition prepared according to the example 1, the molybdenum/yttrium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer are used. Has an excellent push etch profile. Specifically, in the molybdenum/yttrium aluminum double layer, a molybdenum layer is more etched than a tantalum aluminum layer, and the top molybdenum layer and the bottom aluminum layer have a suitable bevel; and in the molybdenum/aluminum/molybdenum triple layer, The top molybdenum layer etches more than the aluminum layer, and the other bottom molybdenum layer etches less than the aluminum layer.

Referring to Fig. 2, the molybdenum/niobium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer were etched with the etching composition prepared according to Comparative Example 1, wherein the amount of phosphoric acid was less than that of the example 1. As a result, the etching rate of the etching composition for aluminum is reduced by a small amount of phosphoric acid. Therefore, in the molybdenum/yttrium aluminum double layer, the molybdenum layer produces significant depressions; and in the molybdenum/aluminum/molybdenum triple layer, the top molybdenum layer has a first-order profile, and the bottom molybdenum has an undercut profile. This stepped etch profile results in an electrical short circuit and poor image quality of the TFT-LCD.

Referring to Fig. 3, the molybdenum/niobium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer were etched with the etching composition prepared according to Comparative Example 2, wherein the amount of nitric acid was larger than that in Example 1. As a result, the molybdenum layer of the molybdenum/yttrium aluminum double layer and the top molybdenum layer of the molybdenum/aluminum/molybdenum triple layer are significantly recessed and have a stepped profile, and the bottom molybdenum layer of the molybdenum/aluminum/molybdenum triple layer has an undercut profile. .

Referring to Figure 4, the molybdenum/yttrium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer are The etching composition prepared in Comparative Example 3 was etched, and the amount of acetic acid as a buffer solution was larger than that in Example 1. As a result, the etching rate of the etching composition for molybdenum is lowered. Therefore, the molybdenum layer of the molybdenum/yttrium aluminum double layer and the top and bottom molybdenum layers of the molybdenum/aluminum/molybdenum triple layer may protrude.

Referring to FIG. 5, the molybdenum/yttrium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer are etched by the etching composition prepared according to Comparative Example 4, wherein the amount of the molybdenum etching control agent is larger than that of the example 1. The etch rate of the etch composition for molybdenum is too low, and the molybdenum layer of the molybdenum/yttrium aluminum double layer and the top and bottom molybdenum layers of the molybdenum/aluminum/molybdenum triple layer may protrude.

Meanwhile, when the molybdenum/yttrium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer were etched by the etching composition prepared according to Comparative Example 5 and in which the amount of the boron-containing compound was more than that of the example 1, the etching composition was performed. The etch rate of the material is significantly reduced, as shown in Figure 2.

According to the present invention, an etching composition for a TFT-LCD is suitable for use in a separate process for forming a gate, a source and a drain of a molybdenum/bismuth aluminum double layer or a molybdenum/aluminum The molybdenum triple layer is wet etched without causing undercut or protrusion of bismuth aluminum, aluminum and molybdenum, and provides an excellent push etch profile. In addition, since the dry etching process is not used, the manufacturing cost can be simplified, the productivity can be increased, and the manufacturing cost can be reduced. In addition, Even if it does not include non-environmental materials such as perchlorate, an unstable material that shortens the service life of the etching composition, or a compound containing fluorine as a main component of the glass used as a substrate, only borrowing A good push profile can be obtained by performing a wet etching on the molybdenum/yttrium aluminum double layer and the molybdenum/aluminum/molybdenum triple layer.

Although the present invention has been particularly shown and described with respect to the exemplary embodiments thereof, it will be understood by those skilled in the art The scope of the following patent application scope is defined.

Figure 1 shows a molybdenum/niobium aluminum double layer and a molybdenum/aluminum/molybdenum triple layer after performing a wet etching procedure on the etching composition according to the present invention, and before scanning a photoresist (SEM) image; FIGS. 2 to 5 show a molybdenum/yttrium aluminum double layer and a molybdenum/aluminum/molybdenum triple layer after performing a wet etching process on the etching compositions prepared according to Comparative Examples 1 to 4, and The SEM image before removing a photoresist.

Claims (4)

An etching composition comprising: 55 to 75 wt% of one phosphoric acid, 0.75 to 1.99 wt% of one nitric acid, 10 to 20 wt% of one of acetic acid, 0.05 to 0.5 wt%, based on the total weight of the etching composition a molybdenum etch control agent, 0.02 to 3 wt% of one boron-containing compound, and the remainder being water, wherein the molybdenum etch control agent comprises at least one species from MH ₂ PO ₄ , M ₂ HPO ₄ , M ₃ PO ₄ , MHSO _{4, M 2 SO 4, CH} 3 COOM, MHCO 3, M 2 CO 3, a salt of the compound group MNO _3, and M ₂ C ₂ O ₄ formed in the selected, where M is an ammonium-based (NH ₄₎ Or sodium or potassium; wherein the boron-containing compound comprises at least one selected from the group consisting of boric acid (H ₃ BO ₃ ), diboron dioxide (B ₂ O ₂ ), boron trioxide (B ₂ O ₃ ), and tetraboron trioxide ( B ₄ O ₃ ), tetraboron pentoxide (B ₄ O ₅ ), potassium metaborate (KBO ₂ ), sodium metaborate (NaBO ₂ ), metaboric acid (HBO ₂ ), tetraboric acid (H ₂ B ₄ O ₇ ) , sodium tetraborate (Na ₂ B ₄ O ₇ -10H ₂ O), potassium pentaborate (KB ₅ O ₈ -4H ₂ O), boron nitride (BN), boron trifluoride (BF ₃ ), trichlorination A compound selected from the group consisting of boron (BCl ₃ ) and boron tribromide (BBr ₃ ). The etching composition of claim 1, wherein the molybdenum etching control agent comprises at least one selected from the group consisting of potassium nitrate (KNO ₃ ), potassium acetate (CH ₃ COOK), ammonium nitrate (NH ₄ NO ₃ ), ammonium acetate ( a salt selected from the group consisting of CH ₃ COONH ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), dihydrogen phosphate ((NH ₄ )H ₂ PO ₄ ) and potassium hydrogen sulfate (KHSO ₄ ) Compound. The etching composition of claim 1, wherein the molybdenum etching control agent is potassium nitrate (KNO ₃ ) or ammonium acetate (CH ₃ COONH ₄ ). The etching composition of claim 1, wherein the boron-containing compound is boric acid (H ₃ BO ₃ ).