JP4632038B2 - Copper wiring board manufacturing method - Google Patents

Description

  The present invention relates to a method for removing a seed layer by etching in the production of a copper wiring board by a semi-additive method.

In recent years, in the field of wiring boards for electronic devices, with increasing density mounting, copper wiring is rapidly becoming thinner and the wiring width and the distance between wirings are becoming extremely narrow. In order to cope with the thinning of copper wiring, the formation of copper wiring by a semi-additive method is the mainstream in the production of high-density wiring boards. In the semi-additive method, a metal thin film layer (seed layer) is provided on the insulating layer by a physical method such as electroless plating or sputtering, and a pattern resist is formed thereon by photolithography, followed by electrolytic copper plating. Then, the resist is removed and the unnecessary seed layer is removed by etching to form a copper wiring. The present inventors have proposed a system in which an azole is added to hydrogen peroxide-sulfuric acid as a copper etching solution for a seed layer in this semi-additive method (see Patent Document 1). The etching solution can be satisfactorily etched when the seed layer is electroless copper plating, but cannot be completely etched away when the seed layer is copper (sputtered copper) formed by a sputtering method. Sputtered copper is densely and physically formed on the insulating layer in the form of fine particles, so that it is more difficult to etch away than electroless copper plating. Therefore, the copper wiring width decreases when overetching is performed to completely remove the etching. A method of etching the copper of the seed layer by forming a metal film other than copper on the side or surface of the copper wiring has also been proposed, but if the seed layer is sputtered copper as in the case of the above chemical solution, it is completely removed Cannot be performed (see Patent Documents 2 and 3). For the nickel etchant for the seed layer in the semi-additive method, a peroxide-nitric acid-sulfuric acid system has been proposed, but in the case where the seed layer is nickel (sputtered nickel) formed by the sputtering method, the etching removal is complete. (See Patent Document 4). Accordingly, there is a demand for practical use of a method of etching and removing sputtered copper or sputtered nickel in the seed layer while suppressing a reduction in the wiring width of the copper wiring in the formation of the thin copper wiring by the semiadditive method.
Japanese Patent Laid-Open No. 2005-5341 JP-A-9-162523 JP 2003-78234 A JP 2001-140084

  The present invention suppresses a decrease in the wiring width of the copper wiring when etching and removing the sputtered copper or sputtered nickel in the seed layer in the formation of the thin-wire copper wiring by the semi-additive method, and there is no problem such as disconnection or short circuit. It is to provide a method for manufacturing a highly reliable substrate.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have formed a hydrogen peroxide-phosphoric acid when etching away sputtered copper or sputtered nickel in the seed layer in forming a thin copper wiring by the semi-additive method. It has been found that the reduction of the wiring width of the copper wiring can be suppressed by treating with this etching solution, and the present invention has been completed.

  That is, the present invention contains 0.1 to 10% by weight of hydrogen peroxide and 0.5 to 50% by weight of phosphoric acid as an etching solution for a metal thin film layer (seed layer) in the production of a copper wiring board by a semi-additive method. And a copper wiring board manufacturing method using an etching solution having a weight ratio of hydrogen peroxide / phosphoric acid of 0.02 to 0.2.

  With the etching method of the present invention, it is possible to suppress the reduction of the wiring width of the copper wiring and to remove the sputtered copper or sputtered nickel of the seed layer in the semi-additive thin-film copper wiring formation. This is useful for manufacturing electronic components such as wiring boards.

  The hydrogen peroxide concentration used in the etching solution of the copper wiring board manufacturing method of the present invention is 0.1 to 10% by weight, preferably 0.5 to 5% by weight. When the hydrogen peroxide concentration is less than 0.1% by weight, a sufficient etching rate cannot be obtained.

  The phosphoric acid concentration used in the etching solution of the copper wiring board manufacturing method of the present invention is 0.5 to 50% by weight, preferably 2.5 to 25% by weight. When the phosphoric acid concentration is less than 0.5% by weight, a sufficient etching rate cannot be obtained.

  The weight ratio of hydrogen peroxide to phosphoric acid (hydrogen peroxide / phosphoric acid) in the etching solution used in the present invention is 0.02 to 0.2. If the weight ratio of hydrogen peroxide to phosphoric acid is less than 0.02, the seed layer etching removability is not sufficient, and if it exceeds 0.2, the reduction in the wiring width of the copper wiring becomes remarkable.

  If even a small amount of chlorine ions is mixed in the etching solution used in the present invention, the etching removability of the seed layer is significantly inhibited. Therefore, when adjusting to the concentration of the present invention, adjustment is performed using pure water or ion-exchanged water. The chlorine ion concentration in the etching solution used in the present invention is preferably less than 1 ppm.

  The metal to be etched in the present invention is copper or nickel formed by a physical method such as sputtering, vacuum deposition, ion plating, or chemical vapor deposition. In particular, it is suitable for copper or nickel formed by sputtering.

  The contact method between the etching solution and the object in the present invention is not particularly limited, and can be performed by immersion treatment, spray treatment, or the like. The etching treatment temperature is preferably 20 to 60 ° C. When the treatment temperature exceeds 60 ° C., decomposition of hydrogen peroxide is accelerated, which is not preferable. As for the etching processing time, an optimal time is selected in accordance with the surface state and shape of the object, but practically 30 seconds to 120 seconds are preferable. If the etching solution is left as it is attached to the object after the etching process, the copper surface is oxidized and discolored, so that it is preferable to immediately wash with water after the etching process.

  In the management of the etching solution used in the present invention, the concentration of each component decreases as the metal dissolves. Moreover, since the etching rate decreases as the amount of dissolved metal increases, it is preferable to renew the solution when the amount of dissolved metal exceeds 15 g / L.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.
Example 1
An etching solution containing 1% by weight of hydrogen peroxide and 10% by weight of phosphoric acid was prepared. Next, a 0.5 μm-thick sputtered copper film is formed on the silicon wafer substrate, a pattern resist is formed thereon by photolithography, electrolytic copper plating is applied, and finally the resist is peeled off to form a copper wiring. A test substrate having a width / wiring space of 15 μm / 10 μm was prepared. The substrate was immersed in an etching solution at 30 ° C., and the time until the sputtered copper in the seed layer, which is a wiring space portion, was completely removed by etching was measured. Furthermore, the copper wiring width before and after the etching treatment was measured using an optical microscope, and the wiring width reduction amount was calculated. The results are shown in Table 1.

Example 2
The same procedure as in Example 1 was performed except that an etchant containing 0.5% by weight of hydrogen peroxide and 8% by weight of phosphoric acid was used as the etchant in Example 1, and the removal time and the reduction in wiring width were measured and calculated. . The results are shown in Table 1.

Comparative Example 1
In Example 1, except that an etching solution containing 1% by weight of hydrogen peroxide, 4% by weight of sulfuric acid, and 0.01% by weight of 1H-tetrazole was used as the etching solution, the removal time and the wiring width were obtained. The amount of decrease was measured and calculated. The results are shown in Table 1.

Comparative Example 2
In Example 1, except that an etching solution containing 3% by weight of hydrogen peroxide and 3% by weight of phosphoric acid was used as the etching solution, the removal time and the amount of decrease in wiring width were measured and calculated. The results are shown in Table 1.

Example 3
An etching solution containing 1.5% by weight of hydrogen peroxide and 15% by weight of phosphoric acid was prepared. Next, a sputtered nickel film having a thickness of 0.3 μm is formed on the polyimide substrate, a pattern resist is formed thereon by photolithography, electrolytic copper plating is performed, and finally the resist is peeled off to form a copper wiring width. / A test substrate having a wiring space of 15 μm / 10 μm was prepared. The substrate was sprayed with an etching solution at 30 ° C. (spray pressure 0.03 MPa), and the time until the sputtered nickel of the seed layer, which is a wiring space portion, was completely etched away was measured. Furthermore, the copper wiring width before and after the etching treatment was measured using an optical microscope, and the wiring width reduction amount was calculated. The results are shown in Table 1.

Comparative Example 3
In Example 3, an etching solution containing 0.3% by weight of hydrogen peroxide, 30% by weight of nitric acid, 6% by weight of sulfuric acid, 0.01% by weight of sodium chloride and 1% by weight of 2-chloro-pyridine was used as an etching solution. Was performed in the same manner as in Example 3, and the removal time and the amount of decrease in the wiring width were measured and calculated. The results are shown in Table 1.

Comparative Example 4
In Example 1, except that an etching solution containing 1.5% by weight of hydrogen peroxide, 15% by weight of phosphoric acid and 2 ppm of chlorine ions was used as the etching solution, the removal time and the amount of reduction in wiring width were reduced. Measurement was calculated. The results are shown in Table 1.

  As shown in Table 1, in the thin additive copper wiring formation by the semi-additive method by the etching method of the present invention, the reduction of the wiring width of the copper wiring can be suppressed and the sputtered copper or sputtered nickel of the seed layer can be removed by etching.

Claims (1)

In the production of a copper wiring board by the semi-additive method, 0.5 to 5 % by weight of hydrogen peroxide and 2.5 to 2.5 % phosphoric acid are used as an etching solution for a metal thin film layer (seed layer) that is copper or nickel formed by sputtering. A copper wiring board manufacturing method using an etching solution containing 25 % by weight, having a hydrogen peroxide / phosphoric acid weight ratio of 0.02 to 0.2, and having a chlorine ion of less than 1 ppm .