TWI660030B - Etchant composition for copper-containing metal - Google Patents

Abstract

An etchant composition for a copper-containing metal, comprising 1 wt% to 25 wt% oxidant, 1 wt% to 30 wt% 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 etchant composition of the present invention can effectively etch and remove the copper seed layer used in the redistribution circuit process in wafer-level chip packaging, and can greatly reduce the line width loss of the redistribution circuit layer.

Description

Etchant composition for copper-containing metal

The present invention relates to an etchant composition for a copper-containing metal, and more particularly, to an etchant composition for a copper-containing metal that is suitable for use in a metal redistribution circuit process.

A metal redistribution circuit process in a wafer level chip scale packaging process refers to forming a redistribution layer (RDL) on a wafer surface through electroplating. As shown in FIGS. 1 (a) to (c), a seed layer 1 of copper is usually sputtered on the surface of the wafer 2 before electroplating as a conductive layer during electroplating. After that, a new wire pattern is defined by photoresist by way of exposure and development, and then electro-chemical deposition is used to form metal wires 3. Finally, the photoresist is removed, and an The seed layer 1 is removed to obtain a complete redistribution circuit.

Since the material of the seed layer 1 and the metal wire 3 are both copper-containing metals, the metal wire 3 is also etched at the same time when the seed layer 1 is etched. In addition, in order to ensure the etching uniformity of the entire wafer 2 so that the seed layer 1 can be completely removed, over etching is usually performed. For example, if the etching end point is 15 seconds, when the over etching rate is 100%, the etching time is 30 seconds.

Since the wet etching is an isotropic etching, the etching thickness D of the seed layer 1 is directly proportional to the CD loss width of the metal wire 3 after the etching. As shown in FIG. 1 (a), the width of the metal wire 3 before etching is W. When the seed layer 1 is etched at the end (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 lead 3 is about twice the etched thickness D of the seed layer 1, that is, W−W1 = 2D. When the overetch rate is 100% (refer to Figure 1 (c)), the width of the metal wire 3 becomes W2. At this time, the line width loss width of the metal wire 3 is about 4 times the etched thickness D of the seed layer 1. That is, W-W2 = 4D. In other words, in order to completely remove the seed layer 1 by etching, the line width of the metal wire 3 will be seriously lost.

As the size of wafers is shrinking and the demand for high-end wafer bandwidth is increasing, the line width of redistribution lines must also be tapered. However, the etchant used in the conventional etching process will cause serious loss of the line width of metal wires, making Redistribution lines have defects such as 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 circuit manufacturing process, but also can greatly reduce the line width of the redistribution circuit layer. Amount of loss.

In order to achieve the purpose of previous disclosure, an etchant composition for copper-containing metals provided by the present invention includes 1 wt% to 25 wt% oxidant; 1 wt% to 30 wt% acid; 0.1 wt% to 13 wt% Copper protection agent; 0.5 ppm to 120 ppm chloride ion; 0.1 wt% to 4 wt% copper activator; and the balance of water. The copper protective agent is a polyether polyol containing ethylene oxide, propylene oxide, or the above-mentioned mixed repeating unit; 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, alkali metal, or ammonium that meets the valence requirement of the compound; R ₁ is a carbon number of 1 to 8 Alkylene group or cyclic alkylene group, aromatic hydrocarbons with 6 to 12 carbon atoms, or aliphatic aromatic hydrocarbons; R ₂ is hydrogen, carbon A hydroxyalkyl group of 1 to 8 or MO ₃ SR ₁ , wherein M and R ₁ have the same definitions as the foregoing.

According to a preferred embodiment of the present invention, an etchant composition for a copper-containing metal includes 1 to 15 wt% of the oxidant. Moreover, the oxidant is hydrogen peroxide, ammonium persulfate, potassium monopersulfate, or a mixture thereof.

An etchant composition for a copper-containing metal according to a preferred embodiment of the present invention has a pH value of up to about 3. In addition, the aforementioned etchant composition of copper-containing metal contains 3 wt% to 15 wt% of the acid. In addition, the acid is phosphoric acid, sulfuric acid, acetic acid, sulfonic acid, or a mixture thereof. As the sulfonic acid, methanesulfonic acid is preferably used.

According to a preferred embodiment of the present invention, an etchant composition for a copper-containing metal includes 0.5 to 10 wt% of the copper protective agent. In addition, the copper protective agent is polyethylene glycol (PEG), polypropylene glycol (PPG), or a mixture thereof.

According to a preferred embodiment of the present invention, an etchant composition for a copper-containing metal includes 5 to 100 ppm of the chloride ion.

According to a preferred embodiment of the present invention, an etchant composition for a copper-containing metal includes 0.5 to 3 wt% of the copper activator. In addition, the copper activator is sodium bis (sodiumsulfopropyl) disulfide (SPS), 3-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 understand the present invention more clearly, the present invention is further described in detail through the following implementations and examples in conjunction with the drawings.

The invention provides an etchant composition suitable for a metal redistribution circuit process, which is suitable for an etching process such as copper or a copper alloy.

The invention provides an etchant composition for a copper-containing metal, including an oxidant, an acid, a copper protective agent, a chloride ion, a copper activator, and water.

The oxidant used in the present invention is used to oxidize copper metal (or copper alloy) to copper ions. Specific examples thereof are hydrogen peroxide, ammonium persulfate, which is often used as an oxidant in an etching solution. ), Potassium monopersulfate or a mixture thereof. The content of the oxidizing agent may range from 1 wt% to 25 wt%, preferably from 1 wt% to 15 wt%. When the content of oxidant is less than 1 wt%, the etching rate is too slow, resulting in a significant increase in the total etching time, which leads to an increase in the line width loss of the redistribution circuit layer. When the content of the oxidant exceeds 25 wt%, the etching rate Too fast to accurately determine the endpoint of the etch, which affects 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, to prevent the copper metal (or copper alloy) from being in the form of an oxide, and is beneficial to the copper metal (or copper). Alloy). In addition, the pH value of the etchant composition for a copper-containing metal of the present invention is preferably 3 or less. When the pH of the etchant composition is greater than 3, the oxidized copper ions may produce copper oxide solids on the surface of the copper metal (or copper alloy), making the etching rate slower. The content of the acid may range from 1 wt% to 30 wt%, preferably from 3 wt% to 15 wt%, so that the pH of the etchant composition is maintained at 3 or less.

Specific examples of the acid are phosphoric acid, sulfuric acid, acetic acid, sulfuric acid, or a mixture thereof, which is commonly used in etching solutions to adjust the pH. Furthermore, it is preferable to use methanesulfonic acid as the sulfonic acid.

The copper protective agent used in the present invention is a polyether polyol containing ethylene oxide, propylene oxide or the above-mentioned mixed repeating unit. Specific examples thereof are polyethylene glycol (PEG), poly (ethylene glycol) Propylene glycol (PPPG) or a mixture thereof. The copper protective agent is adsorbed on the surface of a copper metal (or a copper alloy) in an aqueous solution in which chloride ions are present, thereby achieving the effect of protecting copper etching. The content of the copper protective agent 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%, it will cause uneven etching of the surface of the metal wire and the seed layer, which will reduce the yield of the redistribution circuit layer. When the content of the copper protective agent is higher than 13 wt%, The etching rate is too slow, resulting in a significant increase in the total etching time, which results in an increase in the line width loss of the redistribution circuit layer.

The source of chloride ions used in the present invention is not particularly limited. For example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, and chloride can be used. Ammonium chloride, copper chloride, zinc chloride, or other compounds that dissociate into chloride ions in aqueous solution. The content of 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 end of the etching, which affects the subsequent over-etching. When the content of chloride ions is more than 120 ppm, the etching rate is too slow, resulting in metal wires. The uneven etching with the surface of the seed layer causes the yield of the redistribution circuit layer to decrease.

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, alkali metal, or ammonium that meets the valence requirement of the compound; R ₁ is a carbon number of 1 to 8 Alkylene group or cyclic alkylene group, aromatic hydrocarbons with 6 to 12 carbon atoms, or aliphatic aromatic hydrocarbons; R ₂ is hydrogen, carbon A hydroxyalkyl group of 1 to 8 or MO ₃ SR ₁ , wherein M and R ₁ have the same definitions as the foregoing.

The copper activator can compete with chloride ions and copper protective agents on the surface of copper metal (or copper alloy) to reduce the adsorption of copper protective agent on the surface of copper metal (or copper alloy), thereby improving copper metal (or copper alloy) The etching rate is preferably bis (sodiumsulfopropyl) disulfide (SPS), 3-mercaptopropylsulfonic acid (MPS) or a mixture thereof. The content of the copper activator may range from 0.1 wt% to 4 wt%, preferably from 0.5 wt% to 3 wt%. When the content of copper activator is less than 0.1 wt%, the etching rate is too slow, resulting in a significant increase in the total etching time, leading to an increase in the line width loss of the redistribution circuit layer. When the content of copper activator is more than 4 wt% , Will cause uneven etching of the surface of the metal wire and the seed layer, resulting in a reduction in the yield of the redistribution circuit layer.

The water used in the present invention may be pure water or deionized water, and its content range is such that the total weight of the etchant composition for copper-containing metals is 100 wt%.

Hereinafter, the copper metal (or copper alloy) is etched by the etchant composition for a copper-containing metal according to the present invention in more detail with actual examples, and the amount of line width loss of the copper metal wire formed is significantly reduced.

[Preparation of test piece]

On the silicon wafer, a sputtered titanium layer with a thickness of 1000 Å (that is, 0.1 μm) is formed, and then a sputtered copper layer with a thickness of 2000 Å (that is, 0.2 μm) is formed. For a plurality of copper metal wires, the space between the copper metal wires is 3 μm. The aforementioned wafer was cut into a size of 2 cm × 2 cm to complete the preparation of a test piece.

[experiment process]

Place the test piece with copper metal wire in the etchant composition shown in Table 1 below 100 mL, and match with ultrasonic vibration at a temperature of 24 ° C. Observe the color change of the test piece and record the end point of the etching. After that, the etching time is doubled, that is, over-etching is performed (over-etch rate is 100%). Then, immediately after taking out the test piece, it was washed with water and dried.

The test pieces before and after the etching were observed under a scanning electron microscope (SEM), and photos were taken. Among them, SEM photographs before and after the etching with the etchant composition of Example 1 are shown in FIG. 2; and SEM photographs before and after the etching with the etchant composition 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]

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

[Table 1] Note) 1. SPS is sodium polydithiopropane sulfonate. 2. The compounds used in Table 1 are reagent grade.

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

It is clear from the results shown in FIGS. 2 to 4 and Table 2 that the copper metal wire is etched by using the etchant composition of the present invention and the etchant composition of Comparative Examples 1 to 10, and the etchant composition of the present invention can Significantly reduces the line width loss of copper metal wires. Specifically, Comparative Examples 1 to 4 lacking at least one component of a copper protective agent, chloride ion, or copper activator, or components having the etchant composition of the present invention, but the content of the components did not fall within the present invention. In Comparative Examples 5 to 10 in the component content range, the line width loss of the copper metal wires was higher than 0.5 μm. Furthermore, the etchant composition of Comparative Example 8 could not even completely remove the copper seed layer by etching. In contrast, the etchant composition of the present invention can significantly reduce the line width loss of copper metal wires (all line width losses are less than 0.16 μm).

According to this, the etchant composition for copper-containing metal of the present invention is suitable for the metal redistribution circuit process, and because the etchant composition of the present invention can greatly reduce the line width loss after the copper metal wire is etched, it is more capable of It meets the needs of today's reduced-size wafers and high-end wafers. By effectively reducing the line width loss of the metal wires during the etching process, the redistribution lines have good conductivity and stability.

1‧‧‧ seed layer

2‧‧‧ wafer

3‧‧‧ metal wire

D‧‧‧thickness

W, W1, W2‧‧‧Width

Figures 1 (a) to 1 (c) are schematic diagrams of a metal redistribution circuit manufacturing process, showing the line width loss width of metal wires; Figures 2 (a) to 2 (b) are scanning electron microscope photographs showing metal wires Changes in line width before etching and after etching with the etchant composition of Example 1 of the present invention; Figures 3 (a) to 3 (b) are scanning electron microscope photographs showing the metal wire before etching and using Comparative Example 1 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 the metal wire is etched 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% oxidant; 1 wt% to 30 wt% acid; 0.1 wt% to 13 wt% copper protective agent, containing a ring Ethylene oxide, propylene oxide, or a mixed polyether polyol of the foregoing repeating unit; 0.5 ppm to 120 ppm of chloride ion; 0.1 wt% to 4 wt% of a copper activator, containing the following chemical formula (I) Sulfur compounds, chemical formula (I) R _2- (X) _n R ₁ SO ₃ M where: X is O, S or S = O; n is an integer from 1 to 6; M is hydrogen and alkali which meet the requirements of the valence of the compound Metal, or ammonium; R ₁ is an alkylene or cycloalkylene having 1 to 8 carbons, aromatic or aliphatic aromatic hydrocarbon having 6 to 12 carbons; R ₂ is hydrogen, 1 to 8 carbons Hydroxyalkyl, or MO ₃ SR ₁ , where M and R ₁ are the same as defined above; and the balance of water. The etchant composition for a copper-containing metal according to claim 1, comprising 1 wt% to 15 wt% of the oxidant. The etchant composition for a copper-containing metal according to claim 1, comprising 3 wt% to 15 wt% of the acid. The etchant composition for a copper-containing metal according to claim 1, comprising 0.5 to 10 wt% of the copper protective agent. The etchant composition for a copper-containing metal according to claim 1, comprising 5 to 100 ppm of the chloride ion. The etchant composition for a copper-containing metal according to claim 1, comprising 0.5 to 3 wt% of the copper activator. The etchant composition for a copper-containing metal according to claim 1, which has a pH value of up to about 3. The etchant composition for a copper-containing metal according to claim 1, wherein the oxidant is at least one peroxide 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 acid 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 protective agent 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 polydithiodipropanesulfonate, 3-mercaptopropylsulfonic 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.