TW201906987A - Etchant Composition for Copper-Containing Metal - Google Patents

Abstract

An etchant composition for a copper-containing metal, including 1 wt% to 25 wt% of oxidant, 1 wt% to 30 wt% of acid, 0.1 wt% to 13 wt% of copper inhibitor, 0.5 ppm to 120 ppm of chloride ion, 0.1 wt% to 4 wt% of copper activator and the balance water. The etchant composition of the present invention can effectively remove the copper seed layer used in redistribution layer (RDL) process in wafer level chip scale packaging and can greatly reduce the RDL line width loss.

Description

Etchant composition for copper-containing metals

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an etchant composition for a copper-containing metal, and more particularly to an etchant composition for a copper-containing metal suitable for use in a metal rewiring process.

The metal repeating line process of the wafer level chip scale packaging process refers to forming a redistribution layer (RDL) on the surface of the wafer by electroplating. As shown in FIGS. 1(a) to 1(c), a seed layer 1 of copper is usually sputtered on the surface of the wafer 2 as a conductive layer during plating. Thereafter, a new wire pattern is defined by photoresist in the form of exposure and development, and then metal wire 3 is formed by electro-chemical deposition, and finally the photoresist is removed, and then the metal wire 3 is separated by an etching solution. The seed layer 1 is removed to obtain a complete redistribution line.

Since the materials of the seed layer 1 and the metal wires 3 are both copper-containing metals, the metal wires 3 are also etched simultaneously when the seed layer 1 is etched. Further, in order to ensure the uniformity of etching of the entire wafer 2 in order to completely remove the seed layer 1, over-etching is usually performed. For example, if the etching end point is 15 seconds, the over etching rate is 100%, which means that the etching time is 30 seconds.

Since the wet etching belongs to an isotropic etching, the etching thickness D of the seed layer 1 is proportional to the width of the line loss (CD loss) of the metal wire 3 after etching. As shown in FIG. 1(a), the width of the metal wire 3 before etching is W, and when the etching end point of the seed layer 1 is (refer to FIG. 1(b)), the width of the metal wire 3 becomes W1, at this time, the metal The line width loss width of the wire 3 is about twice the etching thickness D of the seed layer 1, that is, W-W1 = 2D. When the over etch rate is 100% (refer to FIG. 1(c)), the width of the metal wire 3 becomes W2, and the line width loss width of the metal wire 3 is about 4 times the etching thickness D of the seed layer 1, also That is, W-W2 = 4D. In other words, in order to completely etch and remove the seed layer 1, a serious loss of the line width of the metal wires 3 will be unduly caused.

As the wafer size shrinks and the demand for high-order wafer bandwidth increases, the line width of the redistribution line must also shrink. However, the etching liquid used in the etching process causes a serious loss of the line width of the metal wire, so that The heavy wiring has the defects of poor conductivity, low stability and easy fracture.

The main object of the present invention is to provide an etchant composition for a copper-containing metal which can not only completely remove the copper seed layer used in the redistribution process, but also greatly reduce the line width of the redistribution layer. The amount of loss.

For the purpose of the foregoing disclosure, an etchant composition for a copper-containing metal provided by the present invention comprises 1 wt% to 25 wt% of an oxidizing agent; 1 wt% to 30 wt% of an acid; 0.1 wt% to 13 wt%. Copper protectant; 0.5 ppm to 120 ppm chloride ion; 0.1 wt% to 4 wt% copper activator; and the balance of water. The copper protecting agent is a polyether polyol containing ethylene oxide, propylene oxide or a repeating unit of the foregoing; the copper activator is a sulfur-containing compound having the following chemical formula (I): Chemical formula (I) R ₂ -(X) _n R ₁ SO ₃ M

In the above formula (I), X is O, S or S=O; n is an integer from 1 to 6; M is hydrogen, an alkali metal or ammonium in accordance with the valence requirement of the compound; and R ₁ is a carbon number of 1 to 8. An alkylene group or a cyclic alkylene group, an aromatic hydrocarbon having 6 to 12 carbon atoms or an aliphatic aromatic hydrocarbon; R ₂ is hydrogen or carbon A hydroxyalkyl group of 1 to 8 or MO ₃ SR ₁ wherein M and R ₁ have the same definitions as described above.

An etchant composition for a copper-containing metal according to a preferred embodiment of the present invention, comprising 1 wt% to 15 wt% of the oxidizing agent. Further, the oxidizing agent is hydrogen peroxide, ammonium persulfate, potassium monopersulfate or a mixture of the foregoing.

An etchant composition for a copper-containing metal having a pH of up to about 3 in accordance with a preferred embodiment of the present invention. Further, the aforementioned copper-containing metal etchant composition contains 3 wt% to 15 wt% of the acid. Further, the acid is phosphoric acid, sulfuric acid, acetic acid, sulfonic acid or a mixture of the foregoing. Preferably, the sulfonic acid is preferably a methanesulfonic acid.

An etchant composition for a copper-containing metal according to a preferred embodiment of the present invention, comprising 0.5 wt% to 10 wt% of the copper protectant. Moreover, the copper protectant is polyethylene glycol (PEG), polypropylene glycol (PPG) or a mixture thereof.

An etchant composition for a copper-containing metal according to a preferred embodiment of the present invention, comprising 5 ppm to 100 ppm of the chloride ion.

An etchant composition for a copper-containing metal according to a preferred embodiment of the present invention, comprising 0.5 wt% to 3 wt% of the copper activator. Further, the copper activator is sodium bis(sodiumsulfopropyl disulfide, SPS), mercaptopropylsulfonic acid (MPS) or a mixture thereof.

According to a preferred embodiment of the present invention, the etchant composition for a copper-containing metal is copper or a copper alloy.

In order to more clearly understand the present invention, the present invention will be described in further detail by the following embodiments and examples.

The present invention provides an etchant composition suitable for use in a metal re-wiring process which is suitable for use in an etching process such as copper or a copper alloy.

The etchant composition for a copper-containing metal provided by the invention comprises an oxidizing agent, an acid, a copper protecting agent, a chloride ion, a copper activator and water.

The oxidizing agent used in the present invention is used for oxidizing copper metal (or copper alloy) into copper ions, and a specific example thereof is hydrogen peroxide or ammonium persulfate which is commonly used as an oxidizing agent in an etching liquid. ), potassium monopersulfate or a mixture of the foregoing. The oxidizing agent may be included in an amount ranging from 1 wt% to 25 wt%, preferably from 1 wt% to 15 wt%. When the content of the oxidizing agent is less than 1 wt%, the etching rate is too slow, resulting in a large increase in the total etching time, resulting in an increase in the line width loss of the redistributed wiring layer; when the content of the oxidizing agent is higher than 25 wt%, the etching rate is Too fast to accurately determine the end of the etch, affecting the subsequent over-etching.

The acid used in the present invention is used to maintain the copper metal (or copper alloy) oxidized by the oxidant in a copper ion state, and to prevent the copper metal (or copper alloy) from being present in the form of an oxide, which is advantageous for copper metal (or copper). Alloy) etching is carried out. Further, the pH of the etchant composition for a copper-containing metal of the present invention is preferably less than or equal to 3. When the pH of the etchant composition is greater than 3, the oxidized copper ions may produce a solid of copper oxide on the surface of the copper metal (or copper alloy), making the etching rate slow. The acid may be included in an amount ranging from 1 wt% to 30 wt%, preferably from 3 wt% to 15 wt%, and the pH of the etchant composition is maintained at 3 or less.

A specific example of the acid is phosphoric acid, sulfuric acid, acetic acid, sulfonic acid or a mixture of the foregoing, which is commonly used in an etching solution for pH adjustment. Further, it is preferred to use methanesulfonic acid as the sulfonic acid.

The copper protecting agent used in the present invention is a polyether polyol containing ethylene oxide, propylene oxide or a repeating unit of the foregoing, and a specific example thereof is polyethylene glycol (PEG), poly Polypropylene glycol (PPG) or a mixture of the foregoing. The copper protectant is adsorbed on the surface of the copper metal (or copper alloy) in the presence of an aqueous solution of chloride ions to achieve the effect of protecting the copper etching. The content of the copper protectant may range from 0.1 wt% to 13 wt%, preferably from 0.5 wt% to 10 wt%. When the content of the copper protective agent is less than 0.1 wt%, the etching of the surface of the metal wire and the seed layer is uneven, so that the yield of the redistributed circuit layer is lowered; when the content of the copper protective agent is higher than 13 wt%, Then, the etching rate is too slow, resulting in a large increase in the total etching time, resulting in an increase in the line width loss of the redistributed wiring layer.

The source of the chloride ion used in the present invention is not particularly limited, and for example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, chlorination can be used. Ammonium chloride, copper chloride, zinc chloride or other compound which can be dissociated into chloride ions in aqueous solution. The chloride ion may range from 0.5 ppm to 120 ppm, preferably from 5 ppm to 100 ppm. When the content of chloride ions is less than 0.5 ppm, the etching rate is too fast to accurately determine the etching end point, which affects the subsequent over-etching; when the content of chloride ions is higher than 120 ppm, the etching rate is too slow, resulting in metal wires. The etching with the surface of the seed layer is uneven, resulting in a decrease in the yield of the redistributed wiring layer.

The copper activator used in the present invention is a sulfur-containing compound having the following chemical formula (I): [Chemical Formula (I)] R ₂ -(X) _n R ₁ SO ₃ M

In the above formula (I), X is O, S or S=O; n is an integer from 1 to 6; M is hydrogen, an alkali metal or ammonium in accordance with the valence requirement of the compound; and R ₁ is a carbon number of 1 to 8. An alkylene group or a cyclic alkylene group, an aromatic hydrocarbon having 6 to 12 carbon atoms or an aliphatic aromatic hydrocarbon; R ₂ is hydrogen or carbon A hydroxyalkyl group of 1 to 8 or MO ₃ SR ₁ wherein M and R ₁ have the same definitions as described above.

The copper activator can compete with chloride ions and copper protectants for adsorption on the surface of the copper metal (or copper alloy) to reduce the adhesion of the copper protector to the surface of the copper metal (or copper alloy), thereby improving the copper metal (or copper alloy). Preferably, the etching rate is preferably sodium bis(sodiumsulfopropyl disulfide, SPS), mercaptopropylsulfonic acid (MPS) or a mixture of the foregoing. The copper activator may be included in an amount ranging from 0.1 wt% to 4 wt%, preferably from 0.5 wt% to 3 wt%. When the content of the copper activator is less than 0.1 wt%, the etching rate is too slow, resulting in a large increase in the total etching time, resulting in an increase in the line width loss of the redistributed wiring layer; when the content of the copper activator is higher than 4 wt% It will cause uneven etching of the surface of the metal wire and the seed layer, resulting in a decrease in the yield of the redistributed wiring layer.

The water used in the present invention may be pure water or deionized water in an amount such that the total weight of the etchant composition for the copper-containing metal is 100 wt%.

Hereinafter, the copper metal (or copper alloy) is etched by the etchant composition for a copper-containing metal of the present invention by the actual embodiment, and the amount of line loss of the formed copper metal wire is remarkably lowered.

[Preparation of test piece]

A 1000Å (ie 0.1 μm) thick layer of sputtered titanium is formed on the wafer, followed by a 250 Å (ie 0.2 μm) layer of sputtered copper, which is electrochemically deposited to a thickness of 3 μm and a line width of 3 μm. A plurality of copper metal wires having a line pitch of 3 μm between the copper metal wires. The wafer was cut into a size of 2 cm × 2 cm to complete the preparation of the test piece.

[experiment process]

A test piece having a copper metal wire was placed flat under 100 mL of the etchant composition shown in Table 1, and subjected to ultrasonic vibration at a temperature of 24 ° C to observe the color change of the test piece and record the etching end point. Thereafter, the etching time is doubled, that is, over-etching is performed (overetching rate is 100%). Next, the test piece was taken out and immediately washed with water and dried.

The test pieces before and after the etching were observed under a scanning electron microscope (SEM), and photographs were taken. The SEM photographs before and after the etching of the etchant composition of Example 1 are shown in FIG. 2; the SEM photographs before and after the etching of the etchant compositions of Comparative Example 1 and Comparative Example 2 are shown in FIG. 3, respectively. And Figure 4.

[Evaluation of line width loss of copper metal wires]

The line width before and after etching of the copper metal wires at the same position on the test piece was measured, and the line width loss was calculated. In this experiment, the line width of the copper metal wire in the middle of the three copper metal wires shown in the SEM photograph was measured to calculate the line width loss, and the results are reported in Table 2 below.

[Table 1] Note) 1. SPS is sodium polydithiodipropane sulfonate. 2. The compounds used in Table 1 are all reagent grades.

[Table 2] Note) * Remaining between the tracks: The copper seed layer between the copper metal wires remains and cannot be completely removed by etching.

It can be clearly seen from the results shown in FIGS. 2 to 4 and Table 2 that the etchant composition of the present invention can be etched using the etchant composition of the present invention and the etchant compositions of Comparative Examples 1 to 10 to etch the copper metal wires. Significantly reduce the line width loss of copper metal wires. Specifically, the comparative examples 1 to 4 lacking at least one of the copper protecting agent, the chloride ion or the copper activator, or the component having the etchant composition of the present invention, but the component content is not in the present invention In Comparative Examples 5 to 10 in the range of the component contents, the copper metal wires had a line width loss of more than 0.5 μm, and further, the etchant composition of Comparative Example 8 could not even completely etch and remove the copper seed layer. In contrast, the etchant composition of the present invention can greatly reduce the amount of line width loss of the copper metal wires (both line width loss is less than 0.16 μm).

Accordingly, the etchant composition for a copper-containing metal of the present invention is suitable for a metal rewiring process, and since the etchant composition of the present invention can greatly reduce the line width loss after etching of the copper metal wire, it is more capable In line with the demand for today's downsized wafers and high-order wafers, the redistribution lines have good electrical conductivity and stability by effectively reducing the line width loss of the metal wires during the etching process.

1‧‧‧ seed layer

2‧‧‧ wafer

3‧‧‧Metal wire

D‧‧‧thickness

W, W1, W2‧‧‧ width

Fig. 1(a) to Fig. 1(c) are schematic views showing the process of the metal redistribution line, showing the line width loss width of the metal wire; Fig. 2(a) to Fig. 2(b) are scanning electron microscope photographs showing the metal wire Before the etching and the etchant composition of the first embodiment of the present invention, the line width change after etching; FIG. 3(a) to FIG. 3(b) are scanning electron microscope photographs showing the metal wire before etching and using the comparative example 1. The line width change after etching of the etchant composition; and FIGS. 4(a) to 4(b) are scanning electron microscope photographs showing the line width before etching of the metal wire and after etching with the etchant composition of Comparative Example 2. Variety.

Claims (13)

An etchant composition for a copper-containing metal comprising: 1 wt% to 25 wt% of an oxidizing agent; 1 wt% to 30 wt% of an acid; 0.1 wt% to 13 wt% of a copper protectant comprising a ring Ethylene oxide, propylene oxide or a polyether polyol of the above-mentioned repeated repeating unit; 0.5 ppm to 120 ppm of chloride ion; 0.1 wt% to 4 wt% of copper activator, having the following chemical formula (I) Sulfur compound, Chemical formula (I) R ₂ -(X) _n R ₁ SO ₃ M wherein: X is O, S or S=O; n is an integer from 1 to 6; M is hydrogen and alkali in accordance with the valence requirement of the compound a metal, or an ammonium; R ₁ is an alkylene or cycloalkylene group having from 1 to 8 carbon atoms, an aromatic hydrocarbon or an aliphatic aromatic hydrocarbon having from 6 to 12 carbon atoms; R ₂ is hydrogen, and carbon number is from 1 to 8. Hydroxyalkyl, or MO ₃ SR ₁ , wherein M and R ₁ are as defined above; and the balance of water. The etchant composition for a copper-containing metal according to claim 1, which comprises 1 wt% to 15 wt% of the oxidizing agent. The etchant composition for a copper-containing metal according to claim 1, which comprises 3 wt% to 15 wt% of the acid. The etchant composition for a copper-containing metal according to claim 1, which comprises 0.5 wt% to 10 wt% of the copper protectant. The etchant composition for a copper-containing metal according to claim 1, which comprises 5 ppm to 100 ppm of the chloride ion. The etchant composition for a copper-containing metal according to claim 1, which comprises 0.5 wt% to 3 wt% of the copper activator. An etchant composition for a copper-containing metal according to claim 1, which has a pH of up to about 3. The etchant composition for a copper-containing metal according to claim 1, wherein the oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, ammonium persulfate, and potassium monopersulfate. The etchant composition for a copper-containing metal according to claim 1, wherein the acid is at least one selected from the group consisting of phosphoric acid, sulfuric acid, acetic acid, and sulfonic acid. The etchant composition for a copper-containing metal according to claim 9, wherein the sulfonic acid is methanesulfonic acid. The etchant composition for a copper-containing metal according to claim 1, wherein the copper protectant is polyethylene glycol, polypropylene glycol or a mixture thereof. The etchant composition for a copper-containing metal according to claim 1, wherein the copper activator is sodium polydithiodipropane sulfonate, 3-mercaptopropyl sulfonic acid or a mixture thereof. The etchant composition for a copper-containing metal according to claim 1, wherein the copper-containing metal is copper or a copper alloy.