TWI785591B - Copper surface microetch - Google Patents

Abstract

The invention relates to a copper surface microetchant, which is an aqueous solution prepared by an oxidant, an acid, and an oxyacid compound containing lanthanide elements, and is used for copper in printed circuit boards and semiconductor manufacturing processes. Surface treatment can quickly remove the oxide on the copper surface, and has a low amount of copper etching. It can prevent the stripping of the copper line with less side etching, which meets the application requirements of thinner printed circuit boards.

Description

Copper surface microetch

The invention relates to a metal surface treatment technology, in particular to a copper surface microetching agent.

In the production process of circuit board products, the pretreatment of many processes requires the use of microetches to treat the surface of the copper layer, so that the subsequent processing of circuit boards can achieve better results. For example, the chemical nickel-gold or nickel-palladium-gold process generally includes steps such as cleaning, microetching, pickling, pre-dip, activation, chemical nickel, chemical palladium, chemical gold, etc., where the role of microetching is to remove copper surface The oxide layer is used to enhance the bonding force between the electroless plating layer and the copper layer to meet the requirements of the electrical properties of the product.

In recent years, with the miniaturization and thinning of electronic products, the copper wiring on the circuit board is developing towards high density and miniaturization, and the distance between lines is obviously narrowed. Known microetches used in the production of circuit boards usually use sulfuric acid-hydrogen peroxide type etching solutions, persulfuric acid etching solutions, copper chloride etching solutions, ferric chloride etching solutions, and the like. However, these microetches can no longer meet the production requirements of high-precision circuit boards. They generally have the problem that the amount of copper etching on the copper layer or copper alloy layer is too high, which may easily cause the lines to be too thin or the side etching to be excessive, and even produce The possibility of breakage or peeling, open circuit and short circuit is greatly increased, which seriously affects the reliability of the circuit board, resulting in a decrease in product yield and a substantial increase in production costs.

Therefore, there is an urgent need to seek a copper surface microetch with higher reliability to solve the problems faced by this technical field today.

In view of this, the main purpose of the present invention is to provide a kind of micro-etching agent on copper surface, this micro-etching agent on copper surface can quickly remove the oxide on the surface of copper circuit, has lower copper etching amount simultaneously, can avoid the excessive corrosion of circuit, Conducive to the production of thin lines.

For reaching above-mentioned purpose, the present invention provides a kind of microetching agent on copper surface, and its composition comprises: the oxidizing agent of 0.1～20% by weight; The acid of 0.1～20% by weight; compounds; and the rest is water.

According to an embodiment of the present invention, the content of the oxidizing agent in the copper surface microetchant is 1.0-10% by weight.

According to an embodiment of the present invention, the content of the acid in the copper surface microetchant is 1.0-10% by weight.

According to an embodiment of the present invention, the content of the oxyacid compound containing lanthanide elements in the copper surface microetch agent is 0.1-3% by weight.

According to an embodiment of the present invention, the oxidizing agent in the copper surface microetching agent includes at least one of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide.

According to an embodiment of the present invention, the acid in the copper surface microetching agent includes at least one of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, citric acid, oxalic acid, lactic acid and tartaric acid.

According to an embodiment of the present invention, the oxoacid compound containing lanthanides in the aforementioned copper surface microetching agent includes lanthanum acetate, lanthanum oxalate, lanthanum sulfate, cerium sulfate, cerium ammonium sulfate, cerium ammonium nitrate, manganese nitrate, carbonic acid Chlorium, neodymium ammonium sulfate, manganese nitrate, samarium acetate, samarium sulfate, europium sulfate, europium carbonate, gadolinium sulfate, cerium phosphate, cerium sulfate, dysprosium acetate, dysprosium nitrate, sulfuric acid, nitric acid, erbium nitrate, erbium sulfate, striumium acetate , at least one of thulium sulfate and thulium carbonate.

Compared with the prior art, the present invention has the following advantages: (1) The copper surface microetchant provided by the present invention can quickly remove oxides on the surface of copper lines, so that the copper surface has a clean and fresh copper surface, and can improve the bonding force between the copper surface and the subsequent plating layer. (2) The copper surface microetchant provided by the present invention has a low amount of copper etching, which can prevent excessive corrosion of the copper layer of the line, reduce the occurrence of open circuit and short circuit, thereby increasing product reliability and improving product yield. Thereby reducing production costs.

In the following detailed description by means of specific embodiments, it will be easier to understand the purpose, technical content, characteristics and effects of the present invention.

The invention provides a copper surface microetching agent, which is composed of the following components and their weight percentages: 0.1-20% by weight of oxidizing agent, 0.1-20% by weight of acid, and 0.1-50% of oxyacid compound containing lanthanide elements % by weight, and the rest is water.

Among the present invention, the content of the oxidizing agent in the microetching agent on copper surface can preferably be 1.0～10% by weight, the content of acid can be preferably 1.0～10% by weight, and the content of the compound containing the oxyacid of lanthanide element is relatively high. Preferably, it may be 0.1 to 3% by weight.

Specifically, the oxidizing agent may include at least one of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide. The acid may include at least one of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, citric acid, oxalic acid, lactic acid, and tartaric acid. Compounds of oxyacids containing lanthanides may include lanthanum acetate, lanthanum oxalate, lanthanum sulfate, cerium sulfate, cerium ammonium sulfate, cerium ammonium nitrate, manganese nitrate, manganese carbonate, neodymium ammonium sulfate, manganese nitrate, samarium acetate, samarium sulfate , europium sulfate, europium carbonate, gadolinium sulfate, cerium phosphate, cerium sulfate, dysprosium acetate, dysprosium nitrate, sulfuric acid ', nitric acid ', erbium nitrate, erbium sulfate, thulium acetate, thulium sulfate and thulium carbonate.

The copper surface microetch agent of the present invention has the property of storing oxygen due to the oxyacid compound containing lanthanide elements, which helps to remove oxygen atoms and promote the reduction of copper oxide, so as to achieve the effect of removing copper oxide.

Further, in order to illustrate and verify the technical effect that the copper surface microetchant proposed by the present invention can achieve, adopt the following method to carry out experimental tests, and compare the copper surface microetchant of the present invention (embodiments 1-3) with the traditional microetch The micro-etching treatment ability of the etchant (Comparative Examples 1-3).

Example 1: The copper surface microetch agent is composed of 10 g/L potassium persulfate (KPS), 20 ml/L 98% (weight percent concentration) sulfuric acid (H ₂ SO ₄ ), 50 ml/L containing An aqueous solution prepared from a compound of oxoacids of lanthanide elements.

Example 2: The copper surface microetching agent is composed of 10 g/L sodium persulfate (SPS), 40 ml/L 98% (weight percent concentration) sulfuric acid (H ₂ SO ₄ ), 50 ml/L containing An aqueous solution prepared from a compound of oxoacids of lanthanide elements.

Example 3: The copper surface microetching agent is composed of 10 g/L potassium persulfate (KPS), 20 ml/L 98% (weight percent concentration) sulfuric acid (H ₂ SO ₄ ), 100 ml/L containing An aqueous solution prepared from a compound of oxoacids of lanthanide elements. The oxoacid compound containing lanthanide elements used in the above-mentioned Examples 1-3 is specifically ammonium cerium sulfate.

Comparative example 1: The copper surface microetching agent is prepared by 100 g/L sodium persulfate (SPS), 20 ml/L 98% (weight percent concentration) sulfuric acid, and 12 g/L copper sulfate aqueous solution.

Comparative Example 2: The copper surface microetching agent is composed of 20 ml/L of 98% sulfuric acid, 12g/L of copper sulfate, 20 ml/L of 50M tricalcium phosphate (TCP) and 40 ml/L of 35% (weight percent concentration) aqueous solution prepared by sulfuric acid.

Comparative Example 3: The copper surface microetching agent is a 10% sulfuric acid solution prepared by 100 ml/L of 98% sulfuric acid.

Copper oxide powder dissolution test:

The dissolution test of copper oxide powder is carried out by means of liquid medicine filtration. First, spread a fixed weight of copper oxide powder on the top of the filter paper, add pure water to spread the copper oxide powder evenly on the surface of the filter paper, and after standing for a period of time, turn on the pump to suck out the pure water. After the copper oxide powder is laid, start the comparison test of the dissolution rate of the microetchant on the copper oxide powder. Turn on the pump to pre-exhaust for 30 seconds, pour a fixed amount of microetch into the filter cup and observe and record that the microetch completely passes through the filter paper. Time to analyze the increase in copper concentration in the microetch and the time for the microetch to pass through the filter paper (equivalent to the rate at which copper oxide is dissolved).

Copper etching amount Analytical test:

Use a copper foil substrate with a 5 * 5 cm full copper surface, first clean the surface of the copper foil substrate, wash and dry it, and then weigh it. Take it out for a fixed time of 3 minutes, then wash and dry it, weigh it, record the weight loss of the copper foil substrate, and convert the specific gravity of copper to 8.9 to calculate the corrosion rate of copper corrosion (μm/min), that is, the copper corrosion rate.

Thin line bite analysis test:

In fact, the amount of erosion was compared with the thin line. The original line width of the thin line was 16 microns (μm), and the surface conditions after soaking in the microetching agent for 1 minute and 5 minutes were observed.

ENIG ( Electroless Nickel Gold ) Simulation test:

The test sample was subjected to ENIG simulation test under the conditions of severe oxidation and the same amount of copper corrosion. Among them, the condition of baking at 150°C for 8 hours was used to simulate the severe oxidation situation. The ENIG process includes the steps shown in Table 1 below.

Table I ENIG process Remark step potion temperature time to clean ACL-007 50℃ 5 minutes microetch Embodiment one 25°C 60 seconds Copper etching amount: 0.15 microns/min Comparative example one 25°C 10 seconds Copper etching amount: 1.07 microns/min pickling 5% sulfuric acid 25°C 1 minute Prepreg 1.5% sulfuric acid 25°C 30 seconds activation MFD-5 25°C 1 minute chemical nickel NPR-4 80°C 20 minutes chemical gold TRMT-20 85°C 3 minutes

test results :

(1) Copper oxide powder dissolution test:

The dissolution rate of copper oxide powder was compared by microetchant filtration. As shown in Figure 1, it can be found that the copper surface microetchant of Example 1 of the present invention has a faster dissolution rate for copper oxide.

(2) Copper corrosion analysis test:

As shown in Figure 2, it can be found that the microetchant on the copper surface of the first embodiment of the present invention has a lower copper etching rate for the fresh copper layer. Wherein, the copper etching rate of the microetchant on the copper surface of Comparative Example 1 is about 1.0 microns/minute (μm/min); the copper etching rate of the microetching agent on the copper surface of Example 1 is about 0.15 μm/min.

(3) Thin line bite analysis test:

The actual amount of erosion was compared with thin lines. As shown in Figure 3A to Figure 3C, it can be found that the copper surface microetch in Comparative Example 1 has a higher amount of copper etching, and the width of the line after soaking for 1 minute is reduced by 9.4%. (see Fig. 3B), and even after soaking for 5 minutes the line completely peeled off (see Fig. 3C). As shown in Figures 4A to 4C, it can be found that the copper surface microetch in Example 1 of the present invention has a lower amount of copper etching, and the line width is reduced by 0.9% after soaking for 1 minute (see Figure 4B). After 5 minutes the line width was reduced by 9.5% and the line was still intact (see Figure 4C).

(4) ENIG (chemical nickel gold) simulation test:

Figures 5A and 5B show the original surface of the test sample. Figure 6A and Figure 6B show that the surface of the test sample was baked at 150°C for 8 hours to simulate severe oxidation. Fig. 7A and Fig. 7B show the surface condition after 10 seconds of copper surface microetching in comparative example 1 in the ENIG process, and it can be found that electroless nickel gold has abnormal jump plating. Fig. 8A and Fig. 8B show the surface condition after using the copper surface microetch agent of embodiment 1 to process for 60 seconds in the ENIG process, and it can be found that under the same copper etching amount condition, the copper surface microetch agent of embodiment 1 can Effectively remove the oxide layer on the surface of the copper layer, which is beneficial to the subsequent electroless nickel-gold plating.

In summary, according to the copper surface microetchant disclosed in the present invention, the oxide on the surface of the copper circuit can be quickly removed, so that the copper surface has a clean fresh copper surface, and the bonding force between the copper surface and the subsequent plating layer can be improved. At the same time, there is a lower amount of copper corrosion for the fresh copper layer, and less side corrosion for the copper circuit, which can avoid excessive corrosion, breakage or floating of the circuit, reduce the occurrence of open circuit and short circuit, and effectively help the circuit board on the wet process surface. Plating on the treated chemical metal layer can improve product reliability and production yield. Therefore, the present invention is expected to provide effective micro-etching treatment for the miniaturization of copper circuit size in the future, and fully meet the needs of the industry in the future.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications based on the features and spirit described in the scope of the application of the present invention shall be included in the scope of the patent application of the present invention.

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Figure 1 is a comparison chart of the copper oxide dissolution rate of the copper oxide powder dissolution test using Examples 1-3 of the present invention and Comparative Examples 1-3. Fig. 2 is a comparison chart of copper corrosion rates in the copper corrosion analysis test using Examples 1 to 3 of the present invention and Comparative Examples 1 to 3. Figures 3A to 3C are microscopic observations of the surface of the thin line in the thin line erosion analysis test using Comparative Example 1; Figure 3A is the original surface, Figure 3B is the surface after microetching for 1 minute, and Figure 3 Figure 3C shows the surface after 5 minutes of microetching time. Figures 4A to 4C are microscopic observations of the surface of the thin line in the thin line erosion analysis test using Embodiment 1 of the present invention, wherein Figure 4A is the original surface, and Figure 4B is the surface after microetching for 1 minute , Figure 4C shows the surface after 5 minutes of microetching time. Fig. 5A and Fig. 5B are microscopic observation pictures and partial enlarged pictures of the original surface of the test sample subjected to the ENIG simulation test, respectively. Fig. 6A and Fig. 6B are microscopic observation pictures and partial enlarged pictures of test samples subjected to ENIG simulation test after being baked at 150°C for 8 hours. Fig. 7A and Fig. 7B are microscopic observation pictures and partial enlarged pictures of the test samples subjected to the ENIG simulation test after microetching treatment in Comparative Example 1, respectively. Fig. 8A and Fig. 8B are microscopic observation diagrams and partial enlarged diagrams of test samples subjected to ENIG simulation test after microetching treatment according to Embodiment 1 of the present invention.

Claims (6)

A copper surface microetching agent, the composition of which comprises: a) 0.1 to 20% by weight of an oxidizing agent; b) 0.1 to 20% by weight of an acid; c) 0.1 to 3% by weight of an oxyacid compound containing lanthanides; and d) the remainder is water. The copper surface microetch agent as described in Claim 1, wherein the content of the oxidizing agent is 1.0 to 10% by weight. The copper surface microetch agent as described in Claim 1, wherein the content of the acid is 1.0 to 10% by weight. The copper surface microetch agent as described in Claim 1, wherein the oxidizing agent comprises at least one of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide. The copper surface microetch agent as described in Claim 1, wherein the acid comprises at least one of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, citric acid, oxalic acid, lactic acid and tartaric acid. The copper surface microetch agent as described in claim item 1, wherein the compound of the oxyacid containing lanthanides comprises lanthanum acetate, lanthanum oxalate, lanthanum sulfate, cerium sulfate, cerium ammonium sulfate, cerium ammonium nitrate, manganese nitrate, carbonic acid Chlorium, neodymium ammonium sulfate, manganese nitrate, samarium acetate, samarium sulfate, europium sulfate, europium carbonate, gadolinium sulfate, cerium phosphate, cerium sulfate, dysprosium acetate, dysprosium nitrate, sulfuric acid, nitric acid, erbium nitrate, erbium sulfate, striumium acetate , at least one of thulium sulfate and thulium carbonate.

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