TW201945520A - Etchant capable of suppressing damage to IGZO - Google Patents

Abstract

The present invention provides an etchant that suppresses damage to IGZO. The etchant of the present invention includes hydroxyethanediphosphonic acid (A), phosphonic acid (B), hydrogen peroxide (C), nitric acid (D), a fluorine compound (E), an azole (F), and an alkali (G), which is characterized in that the phosphonic acid (B) contains one or more phosphonic acids selected from the group consisting of diethylenetriaminepentamethylenephosphonic acid, N,N,N',N'-ethylenediaminetetrakismethylenephosphonic acid, and aminotrimethylenephosphonic acid, and that the proportion of the hydroxyethanediphosphonic acid (A) is in the range of 0.01-0.1 mass% and the proportion of the phosphonic acids (B) is in the range of 0.003-0.04 mass%.

Description

Etching solution

The present invention relates to semiconductor technology, and more particularly to a protective solution and an etching solution for IGZO.

Indium gallium zinc oxide (IGZO) has been discussed as an effective material as an oxide semiconductor material system. However, IGZO is easily etched by an acid or an alkali. Therefore, it is known that when these source solutions are used to form source-drain wiring, IGZO, which is a substrate, is corroded. In order to overcome this problem, an etch stopped structure (see FIG. 1) of a source-drain wiring is formed after forming a protective layer on IGZO, but the manufacturing becomes complicated, and the final result is cost. Increase. Therefore, in order to adopt a back channel etch type structure that does not require a protective layer (see FIG. 2), an etching solution capable of etching various wiring materials while suppressing damage to IGZO is expected (see Non-Patent Document 1). In recent years, as represented by 4K and 8K panels, high-resolution panels are rapidly progressing. If the resolution of the panel is advanced, the wiring patterns used to drive the pixels will become dense. In order to reduce the loss of light from the backlight, the wiring width must be made thinner. On the other hand, in order to ensure the amount of current flowing in the wiring, wiring processing capable of obtaining a shape that is preferable in obtaining the cross-sectional area of the wiring is required. That is, it is expected that the taper angle of the wiring can be processed to a higher etching solution. Currently, as for an etchant for suppressing damage to IGZO, a chemical solution characterized by a low pH described in Japanese Patent Application Laid-Open No. 2016-11342 (Patent Document 1) is known, but sufficient IGZO cannot be achieved Corrosion resistance and processability. [Prior Art Literature] [Patent Literature]

[Patent Document 1] JP 2016-11342 [Non-Patent Document]

[Non-Patent Document 1] Kobe Steel Technology Bulletin Vol.65, No.2, Sep.2015, Shinta Morita, etc. "BCE TFT Corresponding Oxide Semiconductor Materials"

[Problems to be Solved by the Invention]

Under such circumstances, it is desirable to provide an etchant that can etch wiring materials while suppressing damage to IGZO. [Means for solving problems]

The present invention is as follows: [1] An etching solution containing hydroxyethane diphosphonic acid (A), phosphonic acid (B), hydrogen peroxide (C), nitric acid (D), fluorine compound (E), and azole (F) and a base (G), the phosphonic acid (B) contains a material selected from the group consisting of diethylene glycol triamine pentamethylenephosphonic acid, N, N, N ', N'-ethylenediamine methylene phosphonic acid, and One or more of the group consisting of aminotrimethylenephosphonic acid, the proportion of the aforementioned hydroxyethanediphosphonic acid (A) is in the range of 0.01 to 0.1% by mass, and the proportion of the aforementioned phosphonic acid (B) is 0.003 to 0.04 Range of mass%.

[2] The etching solution according to [1], wherein the phosphonic acid (B) is diethylenetriaminepentamethylenephosphonic acid.

[3] The etching solution according to [1] or [2], wherein the fluorine compound (E) is ammonium fluoride or acid ammonium fluoride. [Effect of the invention]

According to an ideal aspect of the present invention, by using the etching solution of the present invention, IGZO can be prevented from being corroded by acids and alkalis, and a protective layer does not need to be formed on the IGZO, so the manufacturing cost can be greatly reduced. Therefore, a good substrate having a wiring structure having a high cone angle while preventing corrosion of IGZO in the etching step can be obtained. In particular, it has a multi-layer thin film structure including a copper layer and a titanium layer on IGZO, and can be processed by a particularly ideal etching process.

The etching solution of the present invention can have corrosion resistance to IGZO by containing hydroxyethane diphosphonic acid (A) and a specific phosphonic acid (B). In addition, by further containing hydrogen peroxide (C), nitric acid (D), fluorine compounds (E), azoles (F), and alkalis (G), it is possible to obtain corrosion resistance to IGZO, and to perform wiring material Etching composition.

Hereinafter, each component of the etching liquid of this invention is demonstrated in detail.

[Hydroxyethane diphosphonic acid (HEDP) (A)] The hydroxyethane diphosphonic acid (A) is a compound represented by the formula (1). [Chemical 1] ･ ･ ･ (1) The proportion of HEDP (A) in the etching solution is in the range of 0.01 to 0.1% by mass, and preferably in the range of 0.03 to 0.08% by mass. By setting the concentration range of HEDP (A) within this range, higher corrosion resistance of IGZO can be imparted, and the surface roughness of IGZO can be prevented.

[Phosphonic acid (B)] By using phosphonic acid (B) together with HEDP (A), high corrosion resistance of IGZO can be imparted, and the wiring shape can be processed into a high cone angle. The phosphonic acid (B) in the present invention is selected from the group consisting of diethylenetriaminepentamethylenephosphonic acid, N, N, N ', N'-ethylenediaminemethylidenephosphonic acid and aminotrimethylenephosphine One or more phosphonic acids in the group of acids. Among them, N, N, N ', N'-ethylenediamine methylenephosphonic acid has high corrosion resistance to IGZO, so it is preferable. The proportion of phosphonic acid (B) in the etching solution is in the range of 0.003 to 0.04 mass%, preferably 0.01 to 0.03 mass%, and more preferably 0.015 to 0.03 mass%. By setting the concentration range of the phosphonic acid (B) within this range, higher corrosion resistance of IGZO can be achieved.

[Hydrogen peroxide (C)] The hydrogen peroxide (C) has a function of oxidizing copper as an oxidizing agent. The proportion of hydrogen peroxide (C) in the etching solution is preferably in the range of 4.0 to 8.0% by mass, more preferably 4.5 to 7.5% by mass, and particularly preferably in the range of 5.0 to 6.5% by mass. When the concentration range of the hydrogen peroxide (C) is within this range, it is possible to appropriately implement the securing of the etching rate and the suppression of the local corrosion of the wiring.

[Nitric acid (D)] Nitric acid (D) has the effect of dissolving copper after the hydrogen peroxide has been used. The proportion of nitric acid (D) in the etching solution is preferably in the range of 0.8 to 7.0% by mass, more preferably 1.5 to 6.5% by mass, and particularly preferably in the range of 2.0 to 6.0% by mass. When the concentration range of the nitric acid (D) is within this range, a good etching rate can be ensured, and a good wiring shape can be obtained.

[Fluorine Compound (E)] The fluorine compound (E) has a function of etching a barrier layer made of a titanium-based metal. The type of the fluorine compound (E) is not limited as long as it generates fluorine ions. Specific examples include hydrofluoric acid, ammonium fluoride, and acid ammonium fluoride. Among them, ammonium fluoride and acid ammonium fluoride are preferable because they have low toxicity. The fluorine compound (E) may be used singly or in combination of two or more kinds. The proportion of the fluorine compound (E) in the etching solution is preferably in the range of 0.2 to 0.8% by mass, more preferably 0.2 to 0.6% by mass, and particularly preferably in the range of 0.2 to 0.5% by mass. When the concentration range of the fluorine compound (E) is within this range, a good etching rate for a barrier layer made of a titanium-based metal can be obtained.

[Azole (F)] The azole (F) is used for adjusting the etching rate by using pH. Specific examples of the azole (F) include 1,2,4-triazole, 1H-benzotriazole, 5-methyl-1H-benzotriazole, and 3-amino-1H-triazole. Triazoles such as azole; 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-amino-1H-tetrazole, and other tetrazoles; 1,3-thiazole , 4-thiazole and other thiazoles. Among them, tetrazoles are preferred, and from the viewpoint of not forming an insoluble salt with copper ions in the solution, 5-amino-1H-tetrazole is preferred. The azole (F) may be used singly or in combination of two or more kinds. The ratio of the azole (F) in the etching solution is preferably in the range of 0.05 to 0.35 mass%, more preferably 0.05 to 0.30 mass%, and particularly preferably 0.08 to 0.25% by mass. When the concentration range of the azole (F) is within this range, the etching rate can be appropriately adjusted, and a good wiring shape can be obtained.

[Base (G)] The base (G) is used for adjusting the etching rate by using pH. The base (G) is not limited as long as it is a type generally used to make an etching solution, and examples thereof include ammonia, potassium hydroxide, quaternary ammonium hydroxide, and amine compounds. Examples of the amine compound include alkylamines such as ethylamine and isopropylamine; alkanolamines represented by N-propanolamine and N-methylethanolamine; and diamines represented by ethylenediamine. Among them, quaternary ammonium hydroxide, N-propanolamine, and N-butylethanolamine are preferred from the viewpoint that the stability of hydrogen peroxide is not deteriorated. The base (G) may be used singly or in combination of two or more kinds. The proportion of alkali (G) in the etching solution is preferably in the range of 0.6 to 10% by mass, more preferably 1.0 to 9.0% by mass, and particularly preferably in the range of 2.0 to 8.0% by mass. By setting the concentration range within this range, the etching rate can be appropriately adjusted.

[Other components] The etching solution of the present invention may contain additives, hydrogen peroxide stabilizers, surfactants, colorants, and defoaming agents that have been used in etching solutions as long as the purpose of the present invention is not impaired. Agent.

[Preparation method of etching solution] The etching solution of the present invention is prepared by HEDP (A), phosphonic acid (B), hydrogen peroxide (C), nitric acid (D), fluorine compound (E), azole (F), The base (G) and other components as required are prepared by adding water (ideally ultrapure water) and stirring until uniform. The pH range of the composition liquid is not particularly limited, but is usually 1.5 to 2.8, and preferably 1.8 to 2.5. By setting it in this range, it is possible to appropriately resist corrosion to IGZO and etch the wiring material at the same time.

[Using method of etching solution] The object can be etched by bringing the etching solution of the present invention into contact with the object. The method for bringing the etching solution of the present invention into contact with the object is not particularly limited, and for example, a method of bringing the etching solution into contact with the object by means of dripping (single-piece rotation treatment) or spraying, or immersing the object in the object Invented method in etching solution. The temperature range in which the etching solution of the present invention is used is usually 10 to 70 ° C, preferably 20 to 50 ° C. The etching time is usually 0.2 to 60 minutes. As the rinse solution after the etching, any one of an organic solvent and water can be used.

[Semiconductor substrate] The substrate targeted for the etching solution of the present invention should preferably have IGZO. If IGZO is a semiconductor composed of indium, gallium, zinc, and oxygen, it is not particularly limited. The oxide may have an amorphous structure or may have crystallinity. When IGZO is used as an electronic element such as a thin film transistor (TFT: Thin Film Transistor), the IGZO is formed on a substrate such as glass using a film formation process such as a sputtering method. Then, an electrode pattern is formed by etching using a photoresist or the like as a mask. Then, copper (Cu), titanium (Ti), and the like are formed thereon by a film forming process such as a sputtering method, and then a source-drain electrode is formed by etching using a photoresist or the like as a mask.

FIG. 3 is an example of a schematic diagram of a wiring cross section when the etching solution of the present invention is used. As shown in FIG. 3, the IGZO layer (4) has a multilayer film structure with a barrier layer (3) such as a titanium layer containing titanium, and a wiring layer (2) composed of a copper layer containing copper. It is used for wiring of display devices such as flat panel displays, and the performance of the etching solution of the present invention is particularly effective. According to an ideal aspect of the present invention, by using the photoresist layer (1) as a mask and etching the multilayer film using the etching solution of the present invention, a desired wiring structure can be formed. In addition, in FIG. 3, twice the distance (a) from the end of the photoresist layer (1) to the end of the wiring layer (2) in contact with the photoresist layer (1) is called the top CD loss (a × 2), twice the distance (b) from the end of the photoresist layer (1) to the end of the wiring layer (2) in contact with the barrier layer (3) provided under the wiring (2) is called the bottom CD Loss (b × 2). In addition, twice (c × 2) the distance (c) from the end of the wiring layer (2) to the end of the barrier layer (3) is called tailing. The angle formed by the etched surface at the end of the wiring layer (2) and the lower IGZO layer (4) is called the cone angle (5). [Example]

Hereinafter, the present invention will be specifically described using examples. However, as long as the effects of the present invention can be exhibited, the embodiments can be appropriately changed. In addition, unless otherwise specified,% means mass%.

[Substrate for evaluation] <Substrate for evaluation of IGZO etching rate and surface state (1)> Indium (In), gallium (Ga), zinc was formed on a glass substrate by a sputtering method with a film thickness of 1000 Å (100 nm). IGZO (100 mm x 100 mm x 1 mm) having an element ratio of (Zn) and oxygen (O) of 1: 1: 1: 4.

<Substrate (2) for evaluating the etching performance of a multilayer film including a copper layer and a titanium layer> Titanium was sputtered on a glass substrate at a thickness of 25 nm to form a titanium layer, and then copper was sputtered at a thickness of 600 nm to laminate Copper layer for wiring materials. Then, a photoresist is applied, the pattern mask is exposed and transferred, and then developed to form a wiring pattern, and a multilayer film (100 mm × 100 mm × 1 mm) including a copper layer and a titanium layer is produced on a glass substrate.

[Evaluation method] [Etching rate of IGZO (ER (Å / sec))] The modulation is composed of (C), (D), (E), (F), and (G) component concentrations described in Table 1 or 2. After the composition, 6000 ppm of copper powder and 150 ppm of titanium powder were added, and the mixture was stirred until the metal was dissolved. After confirming that the metal is dissolved, the components (A) and (B) are added at a predetermined concentration to prepare an etching solution. Etching was performed by immersing the substrate (1) in a respective etching solution at 35 ° C for 20 seconds. After that, it was washed with water and dried with nitrogen. The film thickness after etching was measured using n & k Analyzer 1280 (n & k Technology Inc.), and the difference in film thickness was divided by the etching time to calculate the etching rate, and the following criteria were used for determination. E: Etching rate is less than 5 Å / sec G: Etching rate is 5 Å / sec or more and less than 8 Å / sec P: Etching rate is 8 Å / sec or more and less than 10 Å / sec B: Etching rate is more than 10 Å / sec Passed.

[IGZO surface state] Cut the IGZO film after measuring the IGZO etching rate, and use a scanning electron microscope (model: S5000H, manufactured by Hitachi, Ltd.) at a magnification of 50000 times (acceleration voltage 2kV, acceleration current 10μA) ) Observe the roughness of the surface and make a judgment using the following criteria. E: Smooth surface state G: The surface is slightly rough. When observing the IGZO section with a scanning electron microscope, the difference between the unevenness and the concavities and convexities is less than 25nm, or when the IGZO surface is observed with a scanning electron microscope, per unit area (1200nm × 1200nm) The number of voids is less than 20 B: The surface has significant roughness and voids. When the IGZO cross section is observed with a scanning electron microscope, the difference between the concave and convex portions is 25 nm or more, or when the surface of the IGZO is observed with a scanning electron microscope. The number of voids generated per unit area (1200 nm × 1200 nm) was 20 or more, and E and G were rated as acceptable. One example of cross-sectional observation of IGZO is shown in FIG. 4, and one example of surface observation is shown in FIG. 5.

[Etching performance for a multilayer film including a copper layer and a titanium layer] After preparing a composition composed of (C), (D), (E), (F), and (G) component concentrations described in Table 1 or 2 Add 6000 ppm of copper powder and 150 ppm of titanium powder, and stir until the metal is dissolved. After confirming that the metal is dissolved, the components (A) and (B) are added at a predetermined concentration to prepare an etching solution. The substrate (2) was immersed in each etching solution at 35 ° C for 150 seconds to perform etching, followed by washing with water and drying with nitrogen. The multilayer thin film sample including the copper layer and the titanium layer obtained by the above-mentioned etching method was cut, and a scanning electron microscope (type: S5000H, manufactured by Hitachi, Ltd.) was used at a rate of 50000 times (acceleration voltage 2kV, acceleration Current 10 μA) Observe the cross section. The cone angle 5 shown in FIG. 3 was measured based on the obtained SEM image, and the shape after etching was determined using the following criteria. Cone angle E: 60 ° or more and less than 70 ° G: 50 or more and less than 60 ° B: 50 or less or more than 70 ° E and G are rated as acceptable.

The evaluation results are shown in Tables 1 and 2.

【Table 1】

【Table 2】

The components in the table are as follows. B1: N, N, N ', N' ethylenediamine methylene phosphonic acid B2: ethylene diamine tripentamethylene phosphonic acid B3: aminotrimethylene phosphonic acid B4: phosphoric acid B5: phosphonic acid B6 : Ethylenepentamethylenephosphonic acid E1: Ammonium acid fluoride F1: 5-Amino-1H-tetrazole G1: Quaternary ammonium hydroxide G2: Potassium hydroxide G3: N-butylethanolamine G4: Ammonia G5: 1-amino-2 propanol [industrial availability]

The etching solution of the present invention can be ideally used for etching wiring materials in a substrate containing IGZO. According to an ideal aspect of the present invention, a substrate having a wiring structure having a high cone angle while preventing corrosion of IGZO can be manufactured.

1‧‧‧ photoresist layer

2‧‧‧ wiring layer

3‧‧‧ barrier layer

4‧‧‧IGZO layer

5‧‧‧ cone angle

a‧‧‧Top CD loss (a × 2)

b‧‧‧ bottom CD loss (b × 2)

c‧‧‧Tail (c × 2)

[Fig. 1] An example of a schematic view of a conventional etch-blocking structure TFT provided with a protective layer on IGZO. [Fig. 2] An example of a schematic diagram of a TFT of a back channel etching type structure without a protective layer. FIG. 3 is an example of a schematic diagram of a wiring cross section when the etching solution of the present invention is used. [Fig. 4] An example of a cross-sectional observation of IGZO when an etching solution of an example or a comparative example is used. FIG. 5 is an example of surface observation of IGZO when an etching solution of an example or a comparative example is used.

Claims (3)

An etching solution containing hydroxyethane diphosphonic acid (A), phosphonic acid (B), hydrogen peroxide (C), nitric acid (D), fluorine compound (E), azole (F), and base (G). Phosphonic acid (B) contains a group selected from the group consisting of diethylenetriaminepentamethylenephosphonic acid, N, N, N ', N'-ethylenediaminemethylidenephosphonic acid and aminotrimethylenephosphonic acid In one or more of the groups, the ratio of the hydroxyethanediphosphonic acid (A) is in the range of 0.01 to 0.1% by mass, and the ratio of the phosphonic acid (B) is in the range of 0.003 to 0.04% by mass. For example, the etching solution of the first item of the patent application scope, wherein the phosphonic acid (B) is diethylenetriaminepentamethylenephosphonic acid. For example, the etching solution in the scope of claims 1 or 2, wherein the fluorine compound (E) is ammonium fluoride or acid ammonium fluoride.