TW201819684A - Etching solution for titanium-tungsten alloy - Google Patents

Abstract

An etching solution for a titanium-tungsten alloy is disclosed. The etching solution for the titanium-tungsten alloy includes (a) 10 to 32 wt. % of an oxidant, (b) 1.32 to 6.78 wt. % of a pH adjuster, (c) 0.1 to 14 wt. % of a copper corrosion inhibitor, (d) 2 to 14 wt. % of a pH buffer, and (e) 35 to 66 wt. % of water. The decrease of the pH value of the etching solution can be effectively slowed down during the etching of the titanium-tungsten alloy by adding the pH buffer into the etching solution for the titanium-tungsten alloy, and thus the etching solution will not corrode copper metal because the decrease of the pH value thereof.

Description

 Etching solution of titanium tungsten alloy  

This invention relates to an etchant, and more particularly to an etchant for a titanium-tungsten alloy.

Referring to FIG. 1 , in the conventional semiconductor chip bump process, a bump metallization (UBM) layer 10 is required to be used as a conductive layer when the bump 20 is plated. . The under bump metallization (UBM) layer 10 includes a sublayer 101 (made of copper) and an adhesion layer 102 (made of titanium or titanium tungsten alloy) in order from top to bottom. After the bumps 20 are plated, the under bump metallization (UBM) layer 10 of the electroless plating structure is removed by wet etching. First, the upper seed layer 101 is removed by etching, and the lower exposed adhesion layer 102 is removed.

The etching of a titanium-tungsten alloy is generally disclosed in the etchant containing 25 to 35 weight percent hydrogen peroxide and etching at a temperature between 35 ° C and 50 ° C as disclosed in the Republic of China Patent Publication No. I369724 ( Patent application Nos. 1, 9, 11 and 19), however, the etch rate is slow, even though the cost of the syrup is low but not conducive to operation.

The etchant of the further improved titanium-tungsten alloy adjusts the pH of the hydrogen peroxide to be greater than 4, and the etching rate is fast, but in the middle of the etching of the etching solution, the pH value thereof is dissolved in the etching solution with the titanium-tungsten alloy. The increase and decrease, which in turn causes corrosion of the seed layer 101 composed of copper metal, resulting in an increase in the undercut of the copper metal.

A method of controlling the amount of copper metal undercut in the prior art is to add a copper corrosion inhibitor to the etching solution of the titanium tungsten alloy. However, as the strength of the copper corrosion inhibitor increases, the etching rate of the titanium tungsten alloy also decreases.

Therefore, it is necessary to provide an improved etching solution for a titanium-tungsten alloy to solve the problems of the prior art.

In view of the above, an object of the present invention is to provide an etching solution for a titanium-tungsten alloy which can effectively slow the pH of the etching solution during the etching of the titanium-tungsten alloy by adding a pH buffer to the etching solution of the titanium-tungsten alloy. The value is lowered, so the etching solution does not corrode copper metal due to a decrease in pH.

In order to achieve the above object, the present invention provides an etching solution for a titanium-tungsten alloy for etching a titanium-tungsten alloy and effectively suppressing corrosion of copper metal during etching, the etching solution of the titanium-tungsten alloy comprising: 10 to 32% by weight The oxidizing agent; 1.32 to 6.78 weight percent of the pH adjusting agent; 0.1 to 14 weight percent of the copper corrosion inhibitor; 2 to 14 weight percent of the pH buffer; and 35 to 66 weight percent of the water.

In an embodiment of the invention, the pH buffer comprises: a pH buffer comprising potassium hydrogen phthalate, hydrogen chloride and sodium hydroxide; and a citrate acid; A pH buffer of hydrogen chloride and sodium hydroxide; a pH buffer containing acetic acid, hydrogen chloride, and sodium hydroxide; or a pH buffer containing acetic acid and sodium acetate, but the invention is not limited thereto.

In an embodiment of the invention, the copper corrosion inhibitor comprises poly(propylene glycol), PPG, 5-aminotetrazole (5-ATZ), polyethylene glycol (poly(ethylene) Glycol), PEG), Phenol Sulfonic Acid (PSA), Methylbenzotriazole (MBT), Tolyltriazole (TTA) or 1,2,3-benzotriazole (1, 2, 3-bezotriazol, BTA), but the invention is not limited thereto.

In an embodiment of the invention, the copper corrosion inhibitor is a copper corrosion inhibitor that does not affect the etch rate of the titanium tungsten alloy.

In an embodiment of the invention, the copper corrosion inhibitor comprises polyethylene glycol (PEG) or phenolsulfonic acid (PSA), but the invention is not limited thereto.

In an embodiment of the invention, the oxidizing agent comprises hydrogen peroxide (H ₂ O ₂ ), potassium peroxide (K ₂ O ₂ ), magnesium peroxide (MgO ₂ ) or potassium peroxymonosulfate (2KHSO ₅ .KHSO _4. K ₂ SO ₄ ; trade name Caroat), but the invention is not limited thereto.

In an embodiment of the invention, the pH adjusting agent comprises potassium hydroxide (KOH), sodium hydroxide (NaOH), hydrogen chloride (HCl), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) or acetic acid (CH) ₃ COOH), but the invention is not limited thereto.

In an embodiment of the invention, the pH of the etching solution of the titanium-tungsten alloy ranges from 3.5 to 7.0.

In an embodiment of the invention, the pH of the etching solution of the titanium-tungsten alloy ranges from 4.0 to 5.0.

Compared with the prior art, the present invention provides an etchant for a titanium-tungsten alloy which is effective for slowing down an etchant during etching of a titanium-tungsten alloy by adding a pH buffer to an etchant of a titanium-tungsten alloy. The pH is lowered, so the etching solution does not corrode copper metal due to a decrease in pH. Furthermore, since the contribution of the etching solution to the corrosion of the copper metal is reduced by effectively reducing the pH of the etching solution during the etching of the titanium-tungsten alloy, a protective copper corrosion inhibitor can be selected to protect The weak copper corrosion inhibitor has the advantage of not reducing the etching rate of the titanium tungsten alloy relative to the protective copper corrosion inhibitor, that is, the etching time of the titanium tungsten alloy can be reduced.

10‧‧‧ under bump metallization

20‧‧‧Bumps

101‧‧‧ seed layer

102‧‧‧Adhesive layer

201‧‧‧ solder layer

202‧‧‧ Nickel metal layer

Figure 1 is a partially enlarged schematic view of a wafer in a conventional semiconductor package bump process.

Figure 2 is a scanning electron image of a bump under metallization (UBM) layer after copper etching without etching of the titanium tungsten alloy.

Figure 3 is a scanning electron image of a titanium-tungsten alloy layer in a sub-bump metallization (UBM) layer etched using a conventional etchant of a titanium-tungsten alloy.

Figure 4 is a scanning electron image of a titanium-tungsten alloy layer in a sub-bump metallization (UBM) layer etched using an etchant of a titanium-tungsten alloy in accordance with a preferred embodiment of the present invention.

Fig. 5 is a pH chart of a preferred embodiment and a comparative example of the present invention.

In order to explain the technical content, structural features, objectives and effects of the present invention in detail, the following detailed description is given by way of example.

Hereinafter, a preferred embodiment and a comparative example of the present invention (that is, a conventional titanium-tungsten alloy etching solution) will be described in detail to explain the technical effects of the etching solution of the titanium-tungsten alloy of the present invention in detail.

Example

The etching solution of the titanium-tungsten alloy according to the preferred embodiment of the present invention is composed of the following components: 23.7 weight percent hydrogen peroxide; 4.47 weight percent potassium hydroxide; 6 weight percent polyethylene glycol (PEG); The weight percentage includes a pH buffer of potassium hydrogen phthalate, hydrogen chloride and sodium hydroxide; the rest is deionized water. Next, the titanium-tungsten alloy layer in the under bump metallization (UBM) layer was etched by the etching solution of the titanium-tungsten alloy of the example.

Comparative example

The etching solution of the titanium-tungsten alloy of the comparative example was the same as the etching solution of the titanium-tungsten alloy of the preferred embodiment of the present invention except that the hydrogen peroxide was 25.6 wt% and the pH buffer was not contained therein. Next, the titanium-tungsten alloy layer in the under bump metallization (UBM) layer was etched by the etching solution of the titanium-tungsten alloy of the comparative example. The results of the comparison between the examples and the comparative examples are shown in Table 1 below.

The thickness of the gold layer is 1000Å

In addition, please refer to Figures 2 to 5 at the same time. Figure 2 is a scanning electron image of a bump under metallization (UBM) layer which is etched by copper without etching of titanium tungsten alloy. Fig. 3 is a comparison An etchant of a titanium-tungsten alloy to etch a scan electron image of a titanium-tungsten alloy layer in a sub-bump metallization (UBM) layer; and FIG. 4 is an etch of a titanium-tungsten alloy in accordance with a preferred embodiment of the present invention; The liquid is used to etch a scanning electron image of a titanium-tungsten alloy layer in a sub-bump metallization (UBM) layer; FIG. 5 is a pH curve of a preferred embodiment and a comparative example of the present invention. The 0.58 μm in Fig. 2 is the undercut amount of electroplated nickel to copper.

It can be seen from the results of Table 1 and Figures 2 to 5 that the pH of the etching solution of the titanium-tungsten alloy of the comparative example decreases as the amount of dissolution of the titanium-tungsten alloy increases (the pH of the new acid is 5, the terminal acid The pH will drop below 2), the lower the pH, the stronger the attack on copper metal. Therefore, in the prior art, a strong copper corrosion inhibitor is often used to suppress the corrosion of copper metal, but a strong copper corrosion inhibitor can reduce the etching rate of the titanium tungsten alloy and prolong the etching time. .

However, in the etching solution of the titanium-tungsten alloy of the preferred embodiment of the present invention, a pH buffer is uniquely added to reduce the pH of the etching solution during etching (the pH of the new acid is 4.5, and the pH of the terminal acid is only reduced to 3.5 or so) and the use of a weakly protective copper corrosion inhibitor, in addition to the combination of the two, in addition to maintaining the protective copper corrosion inhibitor has the advantage of not affecting the etching rate of titanium tungsten alloy, The protective copper corrosion inhibitor can still exert the effect of protecting copper metal.

As described above, the etching solution of the titanium-tungsten alloy of the present invention is added to the etching solution of the titanium-tungsten alloy by the pH buffering agent, so that the etching solution can be effectively slowed down during the etching of the titanium-tungsten alloy. The etchant does not corrode copper metal due to a decrease in pH. Furthermore, since the contribution of the etching solution to the corrosion of the copper metal is reduced by effectively reducing the pH of the etching solution during the etching of the titanium-tungsten alloy, a protective copper corrosion inhibitor can be selected to protect The weak copper corrosion inhibitor has the advantage of not reducing the etching rate of the titanium-tungsten alloy relative to the protective copper corrosion inhibitor, that is, the etching time of the titanium-tungsten alloy can be reduced, thereby greatly reducing the production cost. .

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (9)

 An etching solution for a titanium-tungsten alloy for etching a titanium-tungsten alloy and suppressing corrosion of copper metal during etching, the etching solution of the titanium-tungsten alloy comprising: 10 to 32% by weight of an oxidizing agent; and 1.32 to 6.78% by weight of a pH adjusting agent 0.1 to 14 weight percent copper corrosion inhibitor; 2 to 14 weight percent pH buffer; and 35 to 66 weight percent water.    The etchant for a titanium-tungsten alloy according to claim 1, wherein the pH buffer comprises: a pH buffer comprising potassium hydrogen phthalate, hydrogen chloride and sodium hydroxide; a pH buffer for hydrogen chloride and sodium hydroxide; a pH buffer comprising acetic acid, hydrogen chloride and sodium hydroxide; or a pH buffer comprising acetic acid and sodium acetate.    An etching solution for a titanium tungsten alloy according to claim 1, wherein the copper corrosion inhibitor comprises polypropylene glycol (PPG), 5-aminotetrazole (5-ATZ), polyethylene glycol (PEG), phenol Sulfonic acid (PSA), methylbenzotriazole (MBT), tolyltriazole (TTA) or 1,2,3-benzotriazole (BTA).    An etching solution for a titanium tungsten alloy according to claim 1, wherein the copper corrosion inhibitor is a copper corrosion inhibitor that does not affect the etching rate of the titanium tungsten alloy.    An etching solution for a titanium tungsten alloy according to claim 4, wherein the copper corrosion inhibitor comprises polyethylene glycol (PEG) or phenolsulfonic acid (PSA).    An etching solution for a titanium tungsten alloy according to claim 1, wherein the oxidizing agent comprises hydrogen peroxide, potassium peroxide, magnesium peroxide or potassium peroxymonosulfate.    An etching solution for a titanium tungsten alloy according to claim 1, wherein the pH adjusting agent comprises potassium hydroxide, sodium hydroxide, hydrogen chloride, diammonium hydrogen phosphate or acetic acid.    The etching solution for a titanium-tungsten alloy according to claim 1, wherein the pH of the etching solution of the titanium-tungsten alloy ranges from 3.5 to 7.0.    The etching solution for a titanium-tungsten alloy according to claim 8, wherein the pH of the etching solution of the titanium-tungsten alloy ranges from 4.0 to 5.0.