TWI414643B - Composition of copper electroplating solution - Google Patents

Abstract

A composition of a copper electroplating solution includes 0.6 - 1M copper compound, 0.1 -1M carboxylic acid, 10 - 100 ppm organic heterocyclic compound with nitrogen and 10 - 100 ppm halogen ion.

Description

Copper plating solution composition

This invention relates to a plating bath composition, and more particularly to a copper plating bath composition.

As the size of semiconductor components has shrunk, the popularity of copper metal wiring has gradually increased. Currently, most copper processes are performed by electroplating. When depositing copper in a blind hole or a via hole, it is necessary to control the deposition rate of copper ions at the bottom of the blind hole to be larger than the deposition rate on the outer surface of the blind hole, or it is necessary to control the deposition rate of copper ions in the center of the through hole to be larger than that of the through hole. The deposition rate on the outer surface of the hole, otherwise the hole current density is higher, resulting in a seam or a void in the center of the filled hole after the plating is completed. Cavities and gaps can affect the signal transfer rate and reduce the reliability of the chip.

Generally speaking, most of the electroplating solution formulations in the academic circles and the industry today use the addition of multiple additives, so that the copper deposition rate at the bottom of the blind hole is larger than that of the outer surface of the blind hole, and the phenomenon of the bottom of the hole is shifted upward, thereby improving the problem of voids and gaps. However, since each additive is individually affected by the ambient temperature, the interaction between the two or more additives, and even the additives and other components in the plating solution, affects the entire plating process. Furthermore, multiple additives often lead to difficulties in analysis and difficult to achieve stable quality control. In other words, once there are many types of additives, analysis and control are not easy. In addition, when the above copper plating solution is applied to a printed circuit board (PCB), it can only fill a blind hole, and cannot be used to fill a through hole.

Accordingly, the present invention is directed to a copper plating bath composition suitable for electroplating a substrate having micron or submicron vias or blind vias.

According to an embodiment of the present invention, a copper plating solution composition comprises 0.6-1 M of a copper-containing compound, 0.1-1 M of a carboxylic acid, 10 to 100 ppm of an organic nitrogen-containing heterocyclic compound, and 10 to 100 ppm of a halogen ion.

According to an embodiment of the present invention, the carboxylic acid does not simply mean a linear carboxylic acid, but also a branched saturated monocarboxylic acid having a carbon number of 1-10.

According to an embodiment of the present invention, the copper-containing compound is selected from the group consisting of anhydrous copper sulfate, aqueous copper sulfate, copper carbonate, and copper oxide. The above aqueous copper sulfate is copper sulfate pentahydrate.

According to an embodiment of the present invention, the halogen ion is a chloride ion, a bromide ion, and an iodide ion.

According to an embodiment of the present invention, the organic nitrogen-containing heterocyclic compound is an azole compound. The azole compound is, for example, blue tetrazolium chloride, Nitro blue tetrazolium chloride monohydrate or Tetranitro Blue Tetrazolium.

In an embodiment of the present invention, a copper plating solution composition comprising a copper-containing compound, a carboxylic acid, an organic nitrogen-containing heterocyclic compound, and a halogen ion is proposed. In the copper plating bath, the concentration of the copper-containing compound is 0.6-1 M, which is a source of copper ions. The copper-containing compound is selected from the group consisting of anhydrous copper sulfate, aqueous copper sulfate, copper carbonate, and copper oxide. According to an embodiment of the invention, the aqueous copper sulfate is copper sulfate pentahydrate (CuSO ₄ .5H ₂ O).

In the copper plating solution of the present invention, carboxylic acid is one of the sources of the electrolyte. According to one embodiment of the invention, the carboxylic acid is a linear or branched saturated monocarboxylic acid having a carbon number of from 1 to 10, such as formic acid, acetic acid, propionic acid or isobutyric acid. The concentration of the carboxylic acid in the copper plating bath is from 0.1 to 1 M.

Since the nitrogen atom of the organic nitrogen-containing heterocyclic compound is easily positively charged, it is preferentially aggregated and adsorbed in the high current density region of the plated surface during the electroplating process, thereby suppressing the copper deposition rate. Specifically, the current at the opening of the through hole or the blind hole is higher than the inside of the through hole or the blind hole, so that the adsorption concentration of the organic nitrogen-containing heterocyclic compound at the opening of the through hole or the blind hole is high to low. The distribution, in turn, controls the rate of copper deposition inside and outside the via or blind via to reduce the creation of voids or gaps. At the same time, the organic nitrogen-containing heterocyclic compound can also smooth the surface of the plated surface and can be used as a leveling agent in the electroplating process. An organic nitrogen-containing heterocyclic compound such as an Azole Compound.

In addition, since the carboxylic acid is an organic weak acid, it is difficult to react with the organic nitrogen-containing heterocyclic compound, which can improve the problem that the copper plating solution is easily precipitated, and can prevent the pinch plating phenomenon after the plating. The phenomenon of plate plating refers to the phenomenon of cracks or impurities in the hole filling or the peeling of the plate surface.

According to an embodiment of the present invention, the azole compound may be blue tetrazolium chloride, Nitro blue tetrazolium chloride monohydrate or Tetranitro Blue Tetrazolium. ). The individual chemical formulas are sequentially shown in the following formulas (i), (ii) and (iii).

The above halogen ions can help to form a coordination structure between the organic nitrogen-containing heterocyclic compound and the copper ion to stably adsorb on the copper layer, and the halogen ion The adsorption of the organic nitrogen-containing heterocyclic compound on the copper layer can be further enhanced. According to an embodiment of the invention, the halogen ion concentration is 10-100 ppm.

Next, the results of electroplating and filling with different copper plating solution compositions, and then observing the cross-section of the substrate and the surface of the substrate with an optical microscope (OM) will be described. The electroplating and filling steps are as follows.

First, before plating, the copper-containing compound, electrolyte and halogen ions are separately mixed, placed in a Haring cell, and the air pump is opened, and the temperature is maintained at 28 ° C using a cooling cycle machine. 30 minutes. A prepreg cup is also prepared containing an organic nitrogen-containing heterocyclic compound.

The test piece used was a 4 x 6 square centimeter printed circuit board. The test piece has a through hole having a diameter of 100 μm or 150 μm and a through hole depth of 230 μm, so the through hole aspect ratio is 2.3 or 1.53. Next, the test piece was washed with 0.54 M sulfuric acid to remove the contaminants on the surface of the plate, and the ultrasonic wave was shaken for 2 minutes to remove the residual air bubbles in the through hole of the test piece, and then rinsed with ultrapure water.

The test piece was placed in a Harlem test tank having an organic nitrogen-containing heterocyclic compound, and the plating solution in the bath was uniformly mixed and adsorbed on the test piece . It is supplied by direct current during electroplating.

Please refer to Table 1, which lists the copper plating solution compositions used in the respective experimental examples of the present invention.

Fig. 1 is a cross-sectional view showing a substrate after electroplating of copper in Experimental Example 1-3 of the present invention. (a) and (b) are cross-sectional views of the substrate after electroplating using formic acid as an electrolyte (Experimental Example 1). (c) and (d) are cross-sectional views of the substrate after electroplating using acetic acid as an electrolyte (Experimental Example 2). (e) and (f) are cross-sectional views of the substrate after electroplating using propionic acid as an electrolyte (Experimental Example 3). Among them, the magnifications of (a), (c), and (e) observed by an optical microscope were 50 times, and the magnifications of (b), (d), and (e) were 100 times. The plating time is 9 hours.

From Fig. 1, it is apparent that when a carboxylic acid is used as the electrolyte in the copper plating solution, no selenium plating occurs and the copper filling effect in the via holes is good.

Fig. 2 is a cross-sectional view showing the substrate at different plating times in the process of electroplating copper filling in Experimental Example 2 of the present invention. The test piece slicing at different plating time points was used to observe the effect of copper deposition when acetic acid was used as the electrolyte. The plating time of (a)-(c) was 5 hours, the plating time of (d)-(f) was 9 hours, and the plating time of (g)-(i) was 12 hours. The magnifications observed by optical microscopy are as follows: (a), (d), (g) are 50 times, (b), (e), (h) are 100 times, and (c), (f), i) is 200 times.

When the electroplating process is performed, the current density on both sides of the via opening is higher than the current density in the center of the via hole. Therefore, the concentration of the organic nitrogen-containing heterocyclic compound adsorbed on both sides of the opening of the via hole is higher, and the center of the through hole is higher. The lower the concentration. The organic nitrogen-containing heterocyclic compound inhibits the copper deposition rate, thus causing the copper metal to be deposited from the center of the via. It can be seen from the results in Fig. 2 that when acetic acid is used as the electrolyte, it does not affect the adsorption of the organic nitrogen-containing heterocyclic compound to a high The ability of the current density zone, copper metal also begins to deposit from the center of the via, thus reducing the voids created after filling the via.

Fig. 3 is a photograph of the surface of the substrate after the electroplating of the copper was carried out in Experimental Example 1-3 of the present invention. In Fig. 3, (a) - (c) are the substrate surfaces of Experimental Example 1-3. Carboxylic acid is used as the electrolyte in the copper plating solution, and there is no copper tumor on the surface of the substrate.

As is apparent from the above embodiments of the present invention, the copper plating solution composition to which the present invention is applied has the following advantages. First, since the acidity of the carboxylic acid is weak, it is not easy to interact with other components in the copper plating solution, which reduces the occurrence of copper plating precipitation. Secondly, the phenomenon of plate plating after plating can be improved, and no copper film is generated on the surface of the substrate, thereby improving the reliability of the printed circuit board. Third, since the acidity of the carboxylic acid is weak, the operating range of the inorganic acid used in the plating can be expanded.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; Sectional view.

Fig. 2 is a cross-sectional view showing the substrate at different plating times in the process of electroplating copper filling in Experimental Example 2 of the present invention.

Fig. 3 is a photograph of the surface of the substrate after the electroplating of the copper was carried out in Experimental Example 1-3 of the present invention.

Claims (7)

A copper plating composition comprising a 0.6-1 M copper-containing compound, 0.1-1 M carboxylic acid, 10-100 ppm of an organic nitrogen-containing heterocyclic compound, and 10-100 ppm of a halogen ion. The copper plating solution composition of claim 1, wherein the carboxylic acid has a carbon number of 1-10. The copper plating solution composition of claim 1, wherein the carboxylic acid is a linear saturated monocarboxylic acid. The copper plating solution composition of claim 1, wherein the carboxylic acid is a branched saturated monocarboxylic acid. The copper plating solution composition of claim 1, wherein the copper-containing compound is selected from the group consisting of anhydrous copper sulfate, aqueous copper sulfate, copper carbonate, and copper oxide. The copper plating solution composition of claim 5, wherein the aqueous copper sulfate is copper sulfate pentahydrate. The copper plating solution composition according to claim 1, wherein the organic nitrogen-containing heterocyclic compound is tetrazolium blue, nitrotetrazolium chloride or tetranitrotetrazolium blue.